Stress intensity factors and weight functions for cracks in front of notches

International Nuclear Information System (INIS)

Fett, T.

1993-12-01

The knowledge of stress intensity factors for cracks at notch roots is important for the fracture mechanical treatment of real components. Stress intensity factor solutions are available only for special notches and externally applied loads. For the treatment of more complex loadings as thermal stresses near the notch root the weight function is needed in addition. In the first part of this report weight functions for cracks in front of internal notches are derived from stress intensity factor solutions under external loading available in the literature. The second part deals with cracks in front of edge notches. Limit cases of stress intensity factors are derived which allow to estimate stress intensity factors for cracks in front of internal elliptical notches with arbitrary aspect ratio of the ellipse and for external notches. (orig.) [de

Stress concentration factor and stress intensity factor on hard metals in connection with the wear characteristics

International Nuclear Information System (INIS)

Dawihl, W.; Altmeyer, G.

1977-01-01

Description of a method to determine stress intensity factors on hard metals by lapping in notches of different diameter. Dependence of the values of the stress intensity factors on the size of the notch base diameter. For tungsten carbide hard metals with 6% Co, determination of a final value of 250 Nmm -3 / 2 . Characterisation of the stress intensity factor governed by the surface roughness which is decisive for the assessment of the wear-resistant behaviour. (orig.) [de

Study on applicability of stress intensity factor solutions for flaw evaluation

International Nuclear Information System (INIS)

Miura, Naoki; Nagai, Masaki; Takahashi, Yukio

2014-01-01

Stress intensity factor is the quantity which characterizes the singularity of the stress field near a crack tip in the scheme of the linear elastic fracture mechanics, and is used for fatigue and/or SCC crack propagation evaluation. Stress intensity factor depends on the shape and the size of cracked structures, and is frequently prepared as the tabulated correction factors which are the functions of crack depth ratio, aspect ratio, etc. Some stress intensity factor solutions have been included in the JSME rules on fitness-for-service for nuclear power plants. Many of them have been significantly revised on the latest (2012) version of the rules, however, the validation of the revised solutions was not adequate so far. In this study, the implication of the revision was investigated together with its technical basis. A comprehensive comparison was made between available solutions including the 2008 and 2012 version of the rules. It was ascertained that the solutions in the 2012 version provided stress intensity factors consistent with the previous version and the referential stress intensity factors. (author)

Fathers' Stress in a Neonatal Intensive Care Unit

DEFF Research Database (Denmark)

Noergaard, Betty; Ammentorp, Jette; Garne, Ester

2018-01-01

BACKGROUND: Healthcare professionals in neonatal intensive care units (NICUs) tend to focus attention on the mothers and the newborn infants. Thus, fathers may find it difficult to establish an optimal father-child relationship and their stress may increase and persist during hospitalization...... and expect fathers to be involved, and support them to establish a father-child relationship, although they might become more stressed. IMPLICATIONS FOR RESEARCH: More adequate outcome measures are needed to determine the effect of interventions on paternal stress.This is an open-access article distributed....... PURPOSE: To investigate the impact of a more father-friendly NICU on paternal stress and their participation in childcare. METHODS: A quasiexperimental design was conducted on Danish-speaking fathers of newborn infants 28 or more weeks' gestational age. The Parental Stressor Scale: Neonatal Intensive Care...

Stressful life events and acute kidney injury in intensive and semi-intensive care unities.

Science.gov (United States)

Diniz, Denise Para; Marques, Daniella Aparecida; Blay, Sérgio Luis; Schor, Nestor

2012-03-01

Several studies point out that pathophysiological changes related to stress may influence renal function and are associated with disease onset and evolution. However, we have not found any studies about the influence of stress on renal function and acute kidney injury. To evaluate the association between stressful life events and acute kidney injury diagnosis, specifying the most stressful classes of events for these patients in the past 12 months. Case-control study. The study was carried out at Hospital São Paulo, in Universidade Federal de São Paulo and at Hospital dos Servidores do Estado de São Paulo, in Brazil. Patients with acute kidney injury and no chronic disease, admitted to the intensive or semi-intensive care units were included. Controls included patients in the same intensive care units with other acute diseases, except for the acute kidney injury, and also with no chronic disease. Out of the 579 patients initially identified, 475 answered to the Social Readjustment Rating Scale (SRRS) questionnaire and 398 were paired by age and gender (199 cases and 199 controls). The rate of stressful life events was statistically similar between cases and controls. The logistic regression analysis to detect associated effects of the independent variables to the stressful events showed that: increasing age and economic classes A and B in one of the hospitals (Hospital São Paulo - UNIFESP) increased the chance of a stressful life event (SLE). This study did not show association between the Acute Kidney Injury Group with a higher frequency of stressful life events, but that old age, higher income, and type of clinical center were associated.

Weight functions for the determination of stress intensity factor and T-stress for edge-cracked plates with built-in ends

International Nuclear Information System (INIS)

Li, J.; Wang, X.; Tan, C.L.

2004-01-01

This paper presents the weight functions for the determination of the stress intensity factor and T-stress solutions for edge-cracked plates with built-in ends under complex stress distributions. First, a compliance analysis approach is used to calculate stress intensity factor and T-stress for edge cracks in finite width plates with built-in ends with uniform or linear stress distributions acting on the crack face. The results serve as the reference solutions for the next step in which the approaches of deriving weight functions from reference stress intensity factor and T-stress solutions developed for stress boundary conditions are extended to obtain the corresponding weight functions for edge-cracked plates with built-in ends. Finite element analysis is conducted to validate the derived solutions. The weight functions derived are suitable for obtaining stress intensity factors and T-stress solutions under any complex stress field

Effects of overload on the threshold stress intensity factor for SCC

International Nuclear Information System (INIS)

Takahashi, Koji; Ando, Kotoji; Miyazaki, Yuji; Hashikura, Yasuaki

2009-01-01

The effects of overload on the threshold stress intensity factor for stress corrosion crack (K ISCC ) of stainless steel were studied. Tensile overload was applied to a wedge opening loaded (WOL) specimen of SUS316. Then, SCC tests were carried out to determine the resultant K ISCC . As a result, the apparent value of K ISCC increases as increasing a stress intensity factor by tensile overload (K OV ). The effects of tensile overload on K ISCC and the threshold stress intensity factor range for fatigue (ΔK th ) were compared. It was found that the effects of tensile overload on K ISCC were larger than that on ΔK th . (author)

The physical interpretation of the threshold-stress intensity range during fatigue loading

International Nuclear Information System (INIS)

Marci, G.; Bazant, E.

1977-01-01

Based on the experimental results, the threshold-stress intensity range is given the physical interpretation that it characterizes a range of effective tensile stresses which need to be exceeded during a loading cycle for stage II fatigue crack growth to occur. The threshold stress intensity range is independent from its relative position in the range of effective tensile stress, has always the same magnitude and, furthermore, is independent of the Ksub(Imax) which produced the active plastic zone. The experimental results available from previous threshold stress intensity determinations are in good agreement with the concept developed. (orig.) [de

[Post-traumatic stress disorder-related to intensive care stay: influence of sedation practices].

Science.gov (United States)

Bauerheim, Nadège; Masseret, Elodie; Mercier, Emmanuelle; Dequin, Pierre-François; El-Hage, Wissam

2013-03-01

The stay in intensive care unit can be potentially traumatic at the origin of post-traumatic stress symptoms. The severity of post-traumatic stress symptoms is linked to the intensity and the type of traumatic memories of the intensive care stay. Sedatives and analgesics given to ventilated patients in intensive care influence the traumatic memory. The level, the duration and the type of sedation-analgesia protocol are risk factors of post-traumatic stress symptoms. Links between sedation, dissociative symptoms, delirium and post-traumatic stress symptoms are documented. Environmental and pharmacological measures are to be considered to reduce the traumatic potential risk of the intensive care. Intensive care caregivers, liaison-psychiatrist and general practitioner have each a specific role to play in the screening of the post-traumatic stress symptoms. Copyright © 2012 Elsevier Masson SAS. All rights reserved.

Stress-intensity factor equations for cracks in three-dimensional finite bodies

Science.gov (United States)

Newman, J. C., Jr.; Raju, I. S.

1981-01-01

Empirical stress intensity factor equations are presented for embedded elliptical cracks, semi-elliptical surface cracks, quarter-elliptical corner cracks, semi-elliptical surface cracks at a hole, and quarter-elliptical corner cracks at a hole in finite plates. The plates were subjected to remote tensile loading. Equations give stress intensity factors as a function of parametric angle, crack depth, crack length, plate thickness, and where applicable, hole radius. The stress intensity factors used to develop the equations were obtained from three dimensional finite element analyses of these crack configurations.

Calculation of mixed mode stress intensity factors using an alternating method

International Nuclear Information System (INIS)

Sakai, Takayuki

1999-01-01

In this study, mixed mode stress intensity factors (K I and K II ) of a square plate with a notch were calculated using a finite element alternating method. The obtained results were compared with the ones by a finite element method, and it was shown that the finite element alternating method can accurately estimate mixed mode stress intensity factors. Then, using this finite element alternating method, mixed mode stress intensity factors were calculated as changing the size and position of the notch, and its simplified equations were proposed. (author)

Transient thermal stresses and stress intensity factors induced by thermal stratification in feedwater lines

International Nuclear Information System (INIS)

Sanchez Sarmiento, G.; Pardo, E.

1985-01-01

General analytical solutions for the thermal stresses and circumferential crack propagation in piping branches of nuclear power plants, that connect two circuits of the same fluid at different temperatures, are presented in this paper. Under certain conditions, two regions of the fluid possessing both temperatures with a separating layer of small thickness are formed ('flow stratification'). Dimensionless analytical expressions for the steady state temperature distribution in the pipe wall and the corresponding thermal stress are here derived, in terms of the basic geometrical and physical parameters. The position and thickness of the separating layer are considered as data of the model. Stress intensity ranges at any point of the tube wall are then determined. Finally, thermally induced stress intensity factors are calculated for hipothetically inside surface cracks. (orig.)

Local topology via the invariants of the velocity gradient tensor within vortex clusters and intense Reynolds stress structures in turbulent channel flow

International Nuclear Information System (INIS)

Buchner, Abel-John; Kitsios, Vassili; Atkinson, Callum; Soria, Julio; Lozano-Durán, Adrián

2016-01-01

Previous works have shown that momentum transfer in the wall–normal direction within turbulent wall–bounded flows occurs primarily within coherent structures defined by regions of intense Reynolds stress [1]. Such structures may be classified into wall–attached and wall–detached structures with the latter being typically weak, small–scale, and isotropically oriented, while the former are larger and carry most of the Reynolds stresses. The mean velocity fluctuation within each structure may also be used to separate structures by their dynamic properties. This study aims to extract information regarding the scales, kinematics and dynamics of these structures within the topological framework of the invariants of the velocity gradient tensor (VGT). The local topological characteristics of these intense Reynolds stress structures are compared to the topological characteristics of vortex clusters defined by the discriminant of the velocity gradient tensor. The alignment of vorticity with the principal strain directions within these structures is also determined, and the implications of these findings are discussed. (paper)

Transient Stress Intensity Factors of Functionally Graded Hollow Cylinders with Internal Circumferential Cracks

Directory of Open Access Journals (Sweden)

Iman Eshraghi

Full Text Available Abstract In this paper, transient thermomechanical stress intensity factors for functionally graded cylinders with complete internal circumferential cracks are obtained using the weight function method. The finite difference method is used to calculate the time dependent temperature distribution and thermal stresses along the cylinder thickness. Furthermore, finite element analysis is performed to determine the weight function coefficients and to investigate the accuracy of the predicted stress intensity factors from the weight functions. Variation of the stress intensity factors with time and effects of the material gradation on the results are investigated, as well. It is shown that the proposed technique can be used to accurately predict transient thermomechanical stress intensity factors for functionally graded cylinders with arbitrary material gradation.

Stress intensity factor analyses of surface cracks in three-dimensional structures

International Nuclear Information System (INIS)

Miyazaki, Noriyuki; Shibata, Katsuyuki; Watanabe, Takayuki; Tagata, Kazunori.

1983-11-01

The stress intensity factor analyses of surface cracks in various three-dimensional structures were performed using the finite element computer program EPAS-J1. The results obtained by EPAS-J1 were compared with other finite element solutions or results obtained by the simplified estimation methods. Among the simplified estimation methods, the equations proposed by Newman and Raju give the distributions of the stress intensity factor along a crack front, which were compared with the result obtained by EPAS-J1. It was confirmed by comparing the results that EPAS-J1 gives reasonable stress intensity factors of surface cracks in three-dimensional structures. (author)

Stress intensity factors for complete internal and external cracks in spherical shells

International Nuclear Information System (INIS)

Chao, Y.J.; Chen, H.

1989-01-01

Cracks or flows found in the nuclear structure must be fully evaluated to assure the safety of the plant. The weight function method has been widely used in the determination of stress intensity factors for cracks under stress gradient e.g. for thermal shock loading. The unique features of the weight function method is that once the weight function for a particular cracked geometry is determined the stress intensity factors at the crack tip for any loading applied to the flawed structure can be calculated by a simple integration. In this paper the stress intensity factors of the complete, part-through internal and external cracks in a spherical shell are determined. The finite element method was used to develop the weight functions for the flawed geometry. The approximate crack surface profile was used to derive the weight functions. The stress intensity factors associated with the cracks in spherical shells under internal pressure are determined by both the weight functions and the direct finite element method

Quantitative stress measurement of elastic deformation using mechanoluminescent sensor: An intensity ratio model

Science.gov (United States)

Cai, Tao; Guo, Songtao; Li, Yongzeng; Peng, Di; Zhao, Xiaofeng; Liu, Yingzheng

2018-04-01

The mechanoluminescent (ML) sensor is a newly developed non-invasive technique for stress/strain measurement. However, its application has been mostly restricted to qualitative measurement due to the lack of a well-defined relationship between ML intensity and stress. To achieve accurate stress measurement, an intensity ratio model was proposed in this study to establish a quantitative relationship between the stress condition and its ML intensity in elastic deformation. To verify the proposed model, experiments were carried out on a ML measurement system using resin samples mixed with the sensor material SrAl2O4:Eu2+, Dy3+. The ML intensity ratio was found to be dependent on the applied stress and strain rate, and the relationship acquired from the experimental results agreed well with the proposed model. The current study provided a physical explanation for the relationship between ML intensity and its stress condition. The proposed model was applicable in various SrAl2O4:Eu2+, Dy3+-based ML measurement in elastic deformation, and could provide a useful reference for quantitative stress measurement using the ML sensor in general.

Guideline for stress ulcer prophylaxis in the intensive care unit

DEFF Research Database (Denmark)

Madsen, Kristian Rørbaek; Lorentzen, Kristian; Clausen, Niels

2014-01-01

Stress ulcer prophylaxis (SUP) is commonly used in the intensive care unit (ICU), and is recommended in the Surviving Sepsis Campaign guidelines 2012. The present guideline from the Danish Society of Intensive Care Medicine and the Danish Society of Anesthesiology and Intensive Care Medicine sums...

Challenges in participatory primary stress management interventions in knowledge intensive SMEs

DEFF Research Database (Denmark)

Gish, Liv; Ipsen, Christine

2013-01-01

relevant change processes. This paper presents the outline of our research and development project on participatory primary stress management interventions in knowledge intensive SMEs, as well as the preliminary results and related implications. The research and development project is conducted in order...... to develop an operational model which SMEs can use when they want to initiate participatory primary stress management interventions in their company. The development project builds on a process model for participatory primary interventions in larger knowledge intensive companies and the premises behind......While knowledge intensive SMEs have recognized the need for change with respect to productivity and wellbeing, and to some extend have access to tools and methods for enabling this, they still lack process competences and are uncertain about how to approach primary stress interventions and initiate...

Dynamics stresses in pipelines and components

International Nuclear Information System (INIS)

Prates, C.L.M.; Stukart, R.N.L.; Halbritter, A.L.

1982-01-01

The procedure to generate the dynamic stresses caused by external events, necessary for the structural calculation of pipelines and components in nuclear power plants is presented. A special attention is given to the stress caused by the action of earthquakes and exterior explosions. In the dynamic analysis of pipeline and components is usually to show the stresses procedured by these events under the response spectra form. The methodology to obtain these response spectra is shown and discussed. Some pratical examples of spectra from nuclear power plant building are still shown. (E.G.) [pt

Post-traumatic stress disorder in intensive care unit patients.

Science.gov (United States)

Caiuby, Andrea Vannini Santesso; Andreoli, Paola Bruno de Araújo; Andreoli, Sergio Baxter

2010-03-01

Post-traumatic stress disorder has been detected in patients after treatment in intensive care unit. The main goal of this study is to review the psychological aspects and therapeutic interventions on those patients after their treatment on intensive care unit. Thirty eight articles have been included. The prevalence of post-traumatic stress disorder has varied from 17% up to 30% and the incidence from 14% to 24%. The risk factors were: previous anxiety historic, depression or panic, having delusional traumatic memories (derived from psychic formations as dreams and delirium), belief effects, depressive behavior, stressing experiences and mechanical ventilation. High doses of opiates, symptoms caused by sedation or analgesia reduction and the use of lorazepam were related with the increase of delirium and delusional memory. The disorder sintomatology can be reduced with hydrocortisone administration, with daily sedation interruption. No other effectiveness psychological intervention study was found.

Analysis of stress intensity factors for a new mechanical corrosion specimen

International Nuclear Information System (INIS)

Rassineux, B.; Crouzet, D.; Le Hong, S.

1996-03-01

Electricite de France is conducting a research program to determine corrosion cracking rates in the steam generators Alloy 600 tubes of the primary system. The objective is to correlate the cracking rates with the specimen stress intensity factor K I . One of the samples selected for the purpose of this study is the longitudinal notched specimen TEL (TEL: ''Tubulaire a Entailles Longitudinales''). This paper presents the analysis of the stress intensity factor and its experimental validation. The stress intensity factor has been evaluated for different loads using 3D finite element calculations with the Hellen-Parks and G(θ) methods. Both crack initiation and propagation are considered. As an assessment of the method, the numerical simulations are in good agreement with the fatigue crack growth rates measured experimentally for TEL and compact tension (CT) specimens. (authors). 8 refs., 6 figs., 2 tabs

Use of frozen stress in extracting stress intensity factor distributions in three dimensional cracked body problems

Science.gov (United States)

Smith, C. W.

1992-01-01

The adaptation of the frozen stress photoelastic method to the determination of the distribution of stress intensity factors in three dimensional problems is briefly reviewed. The method is then applied to several engineering problems of practical significance.

Calculation of stress intensity factors for circumferential semi-elliptical cracks with high aspect ratio in pipes

International Nuclear Information System (INIS)

Zareei, A.; Nabavi, S.M.

2016-01-01

In this paper, stress intensity factors are calculated at the deepest point of an internal circumferential semi-elliptical crack in a pipe subjected to any arbitrary load. Based on the three dimensional finite element analysis, a weight function is proposed for high aspect ratio semi-elliptical cracks in pipes. An effective expression is developed analytically to evaluate the stress intensity factor using the weight function method. For several crack face stress fields and welding residual stress distributions, the weight function is validated against finite element data and those in the literature. Based on the comparison results, it can be concluded that the solution proposed in this paper is effective in engineering applications. - Highlights: • Analysis of internal circumferential semi-elliptical cracks with high aspect ratio in pipes. • A weight function is proposed for the calculation of the stress intensity factors for the deepest point of the crack. • An effective closed form expression is proposed to evaluate the stress intensity factors. • Prediction of stress intensity factors for any applied stress gradients through the wall thickness without any limitations. • A three-dimensional finite element modeling employs to calculate the stress intensity factors for different geometries.

Numerical Determination of Crack Opening and Closure Stress Intensity Factors

DEFF Research Database (Denmark)

Ricardo, Luiz Carlos Hernandes

2009-01-01

The present work shows the numerical determination of fatigue crack opening and closure stress intensity factors of a C(T) specimen under variable amplitude loading using a finite element method. A half compact tension C(T) specimen, assuming plane stress constraint was used by finite element...

Neonatal Intensive Care Unit Nurses Working in an Open Ward: Stress and Work Satisfaction.

Science.gov (United States)

Lavoie-Tremblay, Mélanie; Feeley, Nancy; Lavigne, Geneviève L; Genest, Christine; Robins, Stéphanie; Fréchette, Julie

2016-01-01

There is some research on the impact of open-ward unit design on the health of babies and the stress experienced by parents and nurses in neonatal intensive care units. However, few studies have explored the factors associated with nurse stress and work satisfaction among nurses practicing in open-ward neonatal intensive care units. The purpose of this study was to examine what factors are associated with nurse stress and work satisfaction among nurses practicing in an open-ward neonatal intensive care unit. A cross-sectional correlational design was used in this study. Participants were nurses employed in a 34-bed open-ward neonatal intensive care unit in a major university-affiliated hospital in Montréal, Quebec, Canada. A total of 94 nurses were eligible, and 86 completed questionnaires (91% response rate). Descriptive statistics were computed to describe the participants' characteristics. To identify factors associated with nurse stress and work satisfaction, correlational analysis and multiple regression analyses were performed with the Nurse Stress Scale and the Global Work Satisfaction scores as the dependent variables. Different factors predict neonatal intensive care unit nurses' stress and job satisfaction, including support, family-centered care, performance obstacles, work schedule, education, and employment status. In order to provide neonatal intensive care units nurses with a supportive environment, managers can provide direct social support to nurses and influence the culture around teamwork.

Dynamic stresses, coulomb failure, and remote triggering: corrected

Science.gov (United States)

Hill, David P.

2012-01-01

Dynamic stresses associated with crustal surface waves with 15–30 s periods and peak amplitudes Coulomb failure models based on a frictional strength threshold offer one explanation for instances of rapid‐onset triggered seismicity that develop during the surface‐wave peak dynamic stressing. Evaluation of the triggering potential of surface‐wave dynamic stresses acting on critically stressed faults using a Mohr’s circle representation together with the Coulomb failure criteria indicates that Love waves should have a higher triggering potential than Rayleigh waves for most fault orientations and wave incidence angles. That (1) the onset of triggered seismicity often appears to begin during the Rayleigh wave rather than the earlier arriving Love wave, and (2) Love‐wave amplitudes typically exceed those for Rayleigh waves suggests that the explanation for rapid‐onset dynamic triggering may not reside solely with a simple static‐threshold friction mode. The results also indicate that normal faults should be more susceptible to dynamic triggering by 20‐s Rayleigh‐wave stresses than thrust faults in the shallow seismogenic crust (<10  km) while the advantage tips in favor of reverse faults greater depths. This transition depth scales with wavelength and coincides roughly with the transition from retrograde‐to‐prograde particle motion. Locally elevated pore pressures may have a role in the observed prevalence of dynamic triggering in extensional regimes and geothermal/volcanic systems. The result is consistent with the apparent elevated susceptibility of extensional or transtensional tectonic regimes to remote triggering by Rayleigh‐wave dynamic stresses than compressional or transpressional regimes.

Long-Range Coulomb Effect in Intense Laser-Driven Photoelectron Dynamics.

Science.gov (United States)

Quan, Wei; Hao, XiaoLei; Chen, YongJu; Yu, ShaoGang; Xu, SongPo; Wang, YanLan; Sun, RenPing; Lai, XuanYang; Wu, ChengYin; Gong, QiHuang; He, XianTu; Liu, XiaoJun; Chen, Jing

2016-06-03

In strong field atomic physics community, long-range Coulomb interaction has for a long time been overlooked and its significant role in intense laser-driven photoelectron dynamics eluded experimental observations. Here we report an experimental investigation of the effect of long-range Coulomb potential on the dynamics of near-zero-momentum photoelectrons produced in photo-ionization process of noble gas atoms in intense midinfrared laser pulses. By exploring the dependence of photoelectron distributions near zero momentum on laser intensity and wavelength, we unambiguously demonstrate that the long-range tail of the Coulomb potential (i.e., up to several hundreds atomic units) plays an important role in determining the photoelectron dynamics after the pulse ends.

Oxidative stress and antioxidant responses to progressive resistance exercise intensity in trained and untrained males

OpenAIRE

H Çakır-Atabek; F Özdemir; R Çolak

2015-01-01

The relationship between oxidative stress and some exercise components of resistance exercise (e.g. intensity, exercise volume) has not been clearly defined. Additionally, the oxidative stress markers may respond differently in various conditions. This study aims to determine the effects of progressive intensity of resistance exercise (RE) on oxidative stress and antioxidants in trained and untrained men, and also to investigate the possible threshold intensity required to evoke oxidative str...

Dynamics of neuroendocrine stress response: bistability, timing, and control of hypocortisolism

Science.gov (United States)

D'Orsogna, Maria; Chou, Tom; Kim, Lae

The hypothalamic-pituitary-adrenal (HPA) axis is a neuroendocrine system that regulates numerous physiological processes. Disruptions in its activity are correlated with stress-related diseases such as post-traumatic stress disorder (PTSD) and major depressive disorder. We characterize ``normal'' and ``diseased'' states of the HPA axis as basins of attraction of a dynamical system describing the inhibition of peptide hormones, corticotropin-releasing hormone (CRH) and adrenocorticotropic hormone (ACTH), by circulating glucocorticoids such as cortisol (CORT). Our model includes ultradian oscillations, CRH self-upregulation of CRH release, and distinguishes two components of negative feedback by cortisol on circulating CRH levels: a slow direct suppression of CRH synthesis and a fast indirect effect on CRH release. The slow regulation mechanism mediates external stress-driven transitions between the stable states in novel, intensity, duration, and timing-dependent ways. We find that the timing of traumatic events may be an important factor in determining if and how the hallmarks of depressive disorders will manifest. Our model also suggests a mechanism whereby exposure therapy of stress disorders may act to normalize downstream dysregulation of the HPA axis.

The impact of static stress change, dynamic stress change, and the background stress on aftershock focal mechanisms

Science.gov (United States)

Hardebeck, Jeanne L.

2014-01-01

The focal mechanisms of earthquakes in Southern California before and after four M ≥ 6.7 main shocks provide insight into how fault systems respond to stress and changes in stress. The main shock static stress changes have two observed impacts on the seismicity: changing the focal mechanisms in a given location to favor those aligned with the static stress change and changing the spatial distribution of seismicity to favor locations where the static stress change aligns with the background stress. The aftershock focal mechanisms are significantly aligned with the static stress changes for absolute stress changes of ≥ 0.02 MPa, for up to ~20 years following the main shock. The dynamic stress changes have similar, although smaller, effects on the local focal mechanisms and the spatial seismicity distribution. Dynamic stress effects are best observed at long periods (30–60 s) and for metrics based on repeated stress cycling in the same direction. This implies that dynamic triggering operates, at least in part, through cyclic shear stress loading in the direction of fault slip. The background stress also strongly controls both the preshock and aftershock mechanisms. While most aftershock mechanisms are well oriented in the background stress field, 10% of aftershocks are identified as poorly oriented outliers, which may indicate limited heterogeneity in the postmain shock stress field. The fault plane orientations of the outliers are well oriented in the background stress, while their slip directions are not, implying that the background stress restricts the distribution of available fault planes.

Numerical evaluation of stress intensity factor for vessel and pipe subjected to thermal shock

International Nuclear Information System (INIS)

Kim, Y.W.; Lee, H.Y.; Yoo, B.

1994-01-01

The thermal weight function method and the finite element method were employed in the numerical computation of the stress intensity factor for a cracked vessel and the cracked pipe subjected to thermal shock. A wall subjected to thermal shock was analyzed, and it has been shown that the effect of thermal shock on the stress intensity factor is dominant for the crack with small crack length to thickness ratio. Convection at the crack face had an influence on the stress intensity factor in the early stage of thermal shock. (Author)

Material properties under intensive dynamic loading

CERN Document Server

Cherne, Frank J; Zhernokletov, Mikhail V; Glushak, B L; Zocher, Marvin A

2007-01-01

Understanding the physical and thermomechanical response of materials subjected to intensive dynamic loading is a challenge of great significance in engineering today. This volume assumes the task of gathering both experimental and diagnostic methods in one place, since not much information has been previously disseminated in the scientific literature.

Implementation of intensity modulation with dynamic multileaf collimation

Energy Technology Data Exchange (ETDEWEB)

Wong, J W; Yu, C; Jaffray, D [William Beaumont Hospital, Royal Oak, MI (United States)

1995-12-01

The computer-controlled multileaf collimator (MLC) marks one of the most important advances in radiation therapy. The device efficiently replaces manual blocking to shape fields and can be used to modulate beam intensity. The results of a research programme at William Beaumont Hospital, aimed at bringing dynamic intensity modulation into clinical use, are discussed.

Dynamic forces on agglomerated particles caused by high-intensity ultrasound.

Science.gov (United States)

Knoop, Claas; Fritsching, Udo

2014-03-01

In this paper the acoustic forces on particles and agglomerates caused by high-intensity ultrasound in gaseous atmosphere are derived by means of computational fluid dynamics (CFD). Sound induced forces cause an oscillating stress scenario where the primary particles of an agglomerate are alternatingly pressed together and torn apart with the frequency of the applied wave. A comparison of the calculated acoustic forces with respect to the inter particle adhesion forces from Van-der-Waals and liquid bridge interactions reveals that the separation forces may reach the same order of magnitude for 80 μm sized SiO2-particles. Hence, with finite probability acoustically agitated gases may de-agglomerate/disperse solid agglomerate structures. This effect is confirmed by dispersion experiments in an acoustic particle levitation setup. Copyright © 2013 Elsevier B.V. All rights reserved.

Oxidative stress and antioxidant responses to progressive resistance exercise intensity in trained and untrained males

Directory of Open Access Journals (Sweden)

H Çakır-Atabek

2015-11-01

Full Text Available The relationship between oxidative stress and some exercise components of resistance exercise (e.g. intensity, exercise volume has not been clearly defined. Additionally, the oxidative stress markers may respond differently in various conditions. This study aims to determine the effects of progressive intensity of resistance exercise (RE on oxidative stress and antioxidants in trained and untrained men, and also to investigate the possible threshold intensity required to evoke oxidative stress. RE trained (N=8 and untrained (N=8 men performed the leg extension RE at progressive intensities standardized for total volume: 1x17 reps at 50% of one-repetition maximum (1RM; 1x14 reps at 60% of 1RM; 1x12 reps at 70% of 1RM; 2x5 reps at 80% of 1RM; and 3x3 reps at 90% of 1RM. Blood samples were drawn before (PRE and immediately after each intensity, and after 30 minutes, 60 minutes and 24 hours following the RE. Lipid-hydroperoxide (LHP significantly increased during the test and then decreased during the recovery in both groups (p0.05. Standardized volume of RE increased oxidative stress responses. Our study suggests that lower intensity (50% is enough to increase LHP, whereas higher intensity (more than 80% is required to evoke protein oxidation.

Guideline for stress ulcer prophylaxis in the intensive care unit

DEFF Research Database (Denmark)

Madsen, Kristian Rørbaek; Lorentzen, Kristian; Clausen, Niels

2014-01-01

Stress ulcer prophylaxis (SUP) is commonly used in the intensive care unit (ICU), and is recommended in the Surviving Sepsis Campaign guidelines 2012. The present guideline from the Danish Society of Intensive Care Medicine and the Danish Society of Anesthesiology and Intensive Care Medicine sums...... critically ill patients in the ICU outside the context of randomized controlled trials (GRADE 1C). No robust evidence supports recommendations for subpopulations in the ICU such as septic, burn, trauma, cardiothoracic or enterally fed patients. However, if SUP is considered clinically indicated in individual...

Physiologic stress interventions in cardiac imaging

International Nuclear Information System (INIS)

Buda, A.J.

1985-01-01

Physiologic stress interventions are designed to assess the reserve capability of coronary flow and myocardial function. In the normal individual, a sufficiently intense physiologic stress may increase coronary flow and cardiac output by 500% to 600%. However, in patients with cardiac disease, these reserve responses may be absent, or considerably blunted. Thus, physiologic stress testing has proved extremely helpful in detecting cardiac abnormalities when resting cardiac function appears normal. Although dynamic exercise remains the standard approach to physiologic stress testing, a number of other interventions have been used, including: (1) isometric exercise, (2) atrial pacing, (3) cold pressor testing, (4) postextrasystolic potentiation, (5) volume loading, and (6) negative intrathoracic pressure. Each of these may be considered an alternative physiologic intervention whenever dynamic exercise is not feasible. These alternative approaches are important since, in our experience, 20% to 30% of subjects are unable to perform dynamic exercise, or exercise inadequately to produce a sufficiently intense cardiac stress. This chapter reviews physiologic considerations, indications, contraindications, protocols, and results of these physiologic stress interventions when used in combination with cardiac radionuclide procedures

Ultrafast photoionization dynamics at high laser intensities in the xuv regime

Energy Technology Data Exchange (ETDEWEB)

Kaiser, B.; Vagov, A.; Axt, V. M.; Pietsch, U. [Institut fuer Theoretische Physik III, Universitaet Bayreuth, D-95440 Bayreuth (Germany); Institut fuer Festkoerperphysik, Universitaet Siegen, D-57068 Siegen (Germany)

2011-10-15

We study the ionization dynamics in the soft-x-ray regime for high intensities and short pulses for excitations near the ionization threshold. Using a one-dimensional helium atom model, we compare exact numerical solutions with time-dependent Hartree-Fock results in order to identify the role of electron-electron correlations. At moderate intensities but still in the x-ray and short-pulse regime, we find that the Hartree-Fock theory reproduces well the dynamics of the ground-state occupation, while at high intensities strong correlation effects occur for excitations close to the threshold. From their characteristic momentum distributions, we can identify contributions to the double ionization from sequential three-photon and nonsequential or sequential two-photon processes. At elevated intensities these contributions deviate from their usual intensity scaling due to saturation effects, even though the total double-ionization probability stays below 10%. Furthermore, analysis of the time evolution of the momentum distribution reveals signatures of the energy-time uncertainty which indicate a coherent regime of the dynamics.

Patient stress in intensive care: comparison between a coronary care unit and a general postoperative unit

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Dias, Douglas de Sá; Resende, Mariane Vanessa; Diniz, Gisele do Carmo Leite Machado

2015-01-01

Objective To evaluate and compare stressors identified by patients of a coronary intensive care unit with those perceived by patients of a general postoperative intensive care unit. Methods This cross-sectional and descriptive study was conducted in the coronary intensive care and general postoperative intensive care units of a private hospital. In total, 60 patients participated in the study, 30 in each intensive care unit. The stressor scale was used in the intensive care units to identify the stressors. The mean score of each item of the scale was calculated followed by the total stress score. The differences between groups were considered significant when p < 0.05. Results The mean ages of patients were 55.63 ± 13.58 years in the coronary intensive care unit and 53.60 ± 17.47 years in the general postoperative intensive care unit. For patients in the coronary intensive care unit, the main stressors were “being in pain”, “being unable to fulfill family roles” and “being bored”. For patients in the general postoperative intensive care unit, the main stressors were “being in pain”, “being unable to fulfill family roles” and “not being able to communicate”. The mean total stress scores were 104.20 ± 30.95 in the coronary intensive care unit and 116.66 ± 23.72 (p = 0.085) in the general postoperative intensive care unit. When each stressor was compared separately, significant differences were noted only between three items. “Having nurses constantly doing things around your bed” was more stressful to the patients in the general postoperative intensive care unit than to those in the coronary intensive care unit (p = 0.013). Conversely, “hearing unfamiliar sounds and noises” and “hearing people talk about you” were the most stressful items for the patients in the coronary intensive care unit (p = 0.046 and 0.005, respectively). Conclusion The perception of major stressors and the total stress score were similar between patients

Oxidative stress does not influence local sweat rate during high-intensity exercise.

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Meade, Robert D; Fujii, Naoto; Poirier, Martin P; Boulay, Pierre; Sigal, Ronald J; Kenny, Glen P

2018-02-01

What is the central question of this study? We evaluated whether oxidative stress attenuates the contribution of nitric oxide to sweating during high-intensity exercise. What is the main finding and its importance? In contrast to our previous report of an oxidative stress-mediated reduction in nitric oxide-dependent cutaneous vasodilatation in this cohort during intense exercise, we demonstrated no influence of local ascorbate administration on the sweating response during moderate- (∼51% peak oxygen uptake) or high-intensity exercise (∼72% peak oxygen uptake). These new findings provide important mechanistic insight into how exercise-induced oxidative stress impacts sudomotor activity. Nitric oxide (NO)-dependent sweating is diminished during high- but not moderate-intensity exercise. We evaluated whether this impairment stems from increased oxidative stress during high-intensity exercise. On two separate days, 11 young (24 ± 4 years) men cycled in the heat (35°C) at a moderate [500 W; 52 ± 6% peak oxygen uptake (V̇O2 peak )] or high (700 W; 71 ± 5% V̇O2 peak ) rate of metabolic heat production. Each session included two 30 min exercise bouts separated by a 20 min recovery period. Local sweat rate was monitored at four forearm skin sites continuously perfused via intradermal microdialysis with the following: (i) lactated Ringer solution (Control); (ii) 10 mm ascorbate (Ascorbate; non-selective antioxidant); (iii) 10 mm N G -nitro-l-arginine methyl ester (l-NAME; NO synthase inhibitor); or (iv) 10 mm ascorbate plus 10 mm l-NAME (Ascorbate + l-NAME). During moderate exercise, sweat rate was attenuated at the l-NAME and Ascorbate + l-NAME sites (both ∼1.0 mg min -1  cm -2 ; all P < 0.05) but not at the Ascorbate site (∼1.1 mg min -1  cm -2 ; both P ≥ 0.28) in comparison to the Control site (∼1.1 mg min -1  cm -2 ). However, no differences were observed between treatment sites (∼1.4 mg min -1  cm -2 ; P = 0

Experimental and numerical determination of critical stress intensity factor of aluminum curved thin sheets under tensile stress

Energy Technology Data Exchange (ETDEWEB)

Heidarvand, Majid; Soltani, Naser; Hajializadeh, Farshid [University of Tehran, Tehran (Iran, Islamic Republic of)

2017-05-15

We determined the fracture toughness of aluminum curved thin sheets using tensile stress tests and finite element method. We applied Linear elastic fracture mechanics (LEFM) and Feddersen procedure to evaluate stress intensity factor of the samples with central wire-cut cracks and fatigue cracks with different lengths to investigate the notch radius effect. Special fixture design was utilized to establish uniform stress distribution at the crack zone. Less than 9 % difference was found between the wire-cut and the fatigue cracked samples. Since generating central fatigue crack with different lengths required so much effort, wire-cut cracked samples were used to determine critical stress intensity factor. Finite element analysis was also performed on one-quarter of the specimen using both the singular Borsum elements and the regular isoparametric elements to further investigate fracture toughness of the samples. It was observed that the singular elements presented better results than the isoparametric ones. A slight difference was also found between the results obtained from finite element method using singular elements and the experimental results.

Stress level among intensive care nurses in the municipality of Paraná (Brazil

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Kelly Cristina Inoue

2014-04-01

Full Text Available Objective. To identify stress levels among intensive care nurses who work in the municipality of Western Paraná, Brazil. Methodology. This is a cross-sectional cohort study, carried out from May to July 2010, included 60 nurses from intensive care units (adult, pediatric, or neonatal of five hospitals. All participants completed the Bianchi Stress Scale. Results. The mean participant age was 31 years; 70% of the nurses were women, 33% had more than 15 years of experience, and 88% conducted care activities. The general level of stress was medium. Stress levels were low for relationships with other units and supervisors, activities related to adequate functioning of the unit and the coordination of activities of the unit. Levels were medium for the following domains: activities related to personnel management, labor conditions for the development of nursing activities, and delivery of care to patient; this last domain was related to the following stress factors: facing patient death, attending to emergencies in the unit, advising patients' family members, and conducting tasks in the minimal time available. Conclusion. Although the general stress level was medium, the identification of domains with a high score can be used to plan intervention strategies to preserve the health of intensive care nurses and, in turn, improve quality of care delivered to severely ill patients.

Resolved shear stress intensity coefficient and fatigue crack growth in large crystals

Science.gov (United States)

Chen, QI; Liu, Hao-Wen

1988-01-01

Fatigue crack growth in large grain Al alloy was studied. Fatigue crack growth is caused primarily by shear decohesion due to dislocation motion in the crack tip region. The crack paths in the large crystals are very irregular and zigzag. The crack planes are often inclined to the loading axis both in the inplane direction and the thickness direction. The stress intensity factors of such inclined cracks are approximated from the two dimensional finite element calculations. The plastic deformation in a large crystal is highly anisotropic, and dislocation motion in such crystals are driven by the resolved shear stress. The resolved shear stress intensity coefficient in a crack solid, RSSIC, is defined, and the coefficients for the slip systems at a crack tip are evaluated from the calculated stress intensity factors. The orientations of the crack planes are closely related to the slip planes with the high RSSIC values. If a single slip system has a much higher RSSIC than all the others, the crack will follow the slip plane, and the slip plane becomes the crack plane. If two or more slip systems have a high RSSIC, the crack plane is the result of the decohesion processes on these active slip planes.

Stress ulcer prophylaxis in the intensive care unit

DEFF Research Database (Denmark)

Krag, Morten Brøgger; Perner, A; Wetterslev, J

2013-01-01

Stress ulcer prophylaxis (SUP) is regarded as standard of care in the intensive care unit (ICU). However, recent randomized, clinical trials (RCTs) and meta-analyses have questioned the rationale and level of evidence for this recommendation. The aim of the present systematic review was to evaluate...... incidence of gastrointestinal (GI) bleeding varies considerably. Data on the incidence and severity of GI bleeding in general ICUs in the developed world as of today are lacking. The best intervention for SUP is yet to be settled by balancing efficacy and harm. In essence, it is unresolved if intensive care...... patients benefit overall from SUP. The following clinically research questions are unanswered: (1) What is the incidence of GI bleeding, and which interventions are used for SUP in general ICUs today?; (2) Which criteria are used to prescribe SUP?; (3) What is the best SUP intervention?; (4) Do intensive...

Further studies on stress intensity factors of semi-elliptical cracks in pressurized cylinders

International Nuclear Information System (INIS)

Kobayashi, A.S.; Emery, A.F.; Love, W.J.; Jain, A.

1979-01-01

The authors have used, in the past, the three-dimensional stress intensity magnification factor, Msub(KS), for a semi-elliptical surface crack in a flat plate with a curvature correction factor, Msub(C), to estimate the stress intensity magnification factor, Msub(K) = Msub(C) x Msub(KS), for unpressurized and pressurized inner semi-elliptical cracks and unpressurized outer semi-elliptical cracks in pressurized and thermally shocked cylinders. Recent papers by Atluri/Kathiresan, Welliot/Labbens/Pellissier-Tanon and McGowan/Raymund, however, showed that while this plate analogy with curvature correction provided reasonable estimates of the stress intensity factors at the deepest crack penetration, it underestimated the stress intensity factors at the cylindrical surface. The source of this discrepancy was traced to the curvature correction factor Msub(C), which was re-evaluated for various crack configurations and cylindrical geometries studied. Using the updated Msub(C) together with the previously derived Msub(KS), stress intensity factor magnification factor, Msub(K), was rederived for: (1) Pressurized and unpressurized inner semi-elliptical cracks of two crack aspects ratios of b/a = 0.2 and 0.98 at crack depth of b/(Rsub(o)-Rsub(i)) = 0.4, 0.6, and 0.8 in pressurized cylinders with outside-to-inside radius ratios of Rsub(o)/Rsub(i) = 3/2, 5/4, 7/6, and 10/9. (2) Unpressurized outer semi-elliptical cracks of two crack aspect ratios of b/a = 0.2 and 0.98 at crack depths of b/(Rsub(o)-Rsub(i)) = 0.4, 0.6, and 0.8 in pressurized cylinders with outside-to-inside radius ratio of Rsub(o)/Rsub(i) = 3/2, 5/4, 7/6, and 10/9. (orig.)

Effect of Couple Stresses on the Stress Intensity Factors for Two Parallel Cracks in an Infinite Elastic Medium under Tension

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Shouetsu Itou

2012-01-01

Full Text Available Stresses around two parallel cracks of equal length in an infinite elastic medium are evaluated based on the linearized couple-stress theory under uniform tension normal to the cracks. Fourier transformations are used to reduce the boundary conditions with respect to the upper crack to dual integral equations. In order to solve these equations, the differences in the displacements and in the rotation at the upper crack are expanded through a series of functions that are zero valued outside the crack. The unknown coefficients in each series are solved in order to satisfy the boundary conditions inside the crack using the Schmidt method. The stresses are expressed in terms of infinite integrals, and the stress intensity factors can be determined using the characteristics of the integrands for an infinite value of the variable of integration. Numerical calculations are carried out for selected crack configurations, and the effect of the couple stresses on the stress intensity factors is revealed.

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.

Thermal stress intensity factor for an axial crack in a clad cylinder

International Nuclear Information System (INIS)

Kuo, An Yu; Deardorf, A.F.; Riccardella, P.C.

1993-01-01

Many clad pressure vessels have been found to have cracks running through the inside surface cladding and into the base material. Although Young's moduli and Poisson's ratios of the clad and base materials are about the same for most of the industrial applications, coefficients of thermal expansion of the two dissimilar materials, clad and base materials, are usually quite different. For example, low alloy ferritic steel is a common base material for reactor pressure vessels (RPV) and the vessels are usually clad with austenitic stainless steel. Young's moduli for the low alloy steel and stainless steel at 350 F are 29,000 ksi and 28,000 ksi, respectively, while their coefficients of thermal expansion are 7.47x10 -6 in/in and 9.50x10 -6 in/in-degree F, respectively. The mismatch in coefficients of thermal expansion will cause high residual thermal stress even when the entire vessel is at a uniform temperature. This residual stress is one of the primary reasons why so many cracks have been found in the cladded components. In performing reactor pressure vessel integrity evaluation, such as computing probability of brittle fracture of the RPV, it is necessary to calculate stress intensity factors for cracks, which initiate from the clad material and run into the base metal. This paper presents a convenient method of calculating stress intensity factor for an axial crack emanating from the inside surface of a cladded cylinder under thermal loading. A J-integral like line integral was derived and used to calculate the stress intensity factors from finite element stress solutions of the problem

Blade dynamic stress analysis of rotating bladed disks

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Kellner J.

2007-10-01

Full Text Available The paper deals with mathematical modelling of steady forced bladed disk vibrations and with dynamic stress calculation of the blades. The blades are considered as 1D kontinuum elastic coupled with three-dimensional elastic disk centrally clamped into rotor rotating with constant angular speed. The steady forced vibrations are generated by the aerodynamic forces acting along the blade length. By using modal synthesis method the mathematical model of the rotating bladed disk is condensed to calculate steady vibrations. Dynamic stress analysis of the blades is based on calculation of the time dependent reduced stress in blade cross-sections by using Hubert-Misses-Hencky stress hypothesis. The presented method is applied to real turbomachinery rotor with blades connected on the top with shroud.

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)

High intensity and reduced volume training attenuates stress and recovery levels in elite swimmers

DEFF Research Database (Denmark)

Elbe, Anne-Marie; Rasmussen, Camilla P; Nielsen, Glen

2016-01-01

This study investigated the effect of increased high-intensity interval training (HIT) at the expense of total training volume on the stress and recovery levels of elite swimmers. Forty-one elite swimmers participated in the study and were randomly assigned to either a HIT or a control group (CON....... The Recovery Stress Questionnaire - Sport was used to measure the swimmers' stress and recovery levels. After the 12 week intervention, the general stress level was 16.6% (2.6-30.7%; mean and 95% CI) lower and the general recovery level was 6.5% (0.7-12.4%) higher in HIT compared to the CON, after adjusting...... for baseline values. No significant effects could be observed in sports-specific stress or sports-specific recovery. The results indicate that increasing training intensity and reducing training volume for 12 weeks can reduce general stress and increase general recovery levels in competitive swimmers....

Intermittent fasting modulates IgA levels in the small intestine under intense stress: a mouse model.

Science.gov (United States)

Lara-Padilla, Eleazar; Godínez-Victoria, Marycarmen; Drago-Serrano, Maria Elisa; Reyna-Garfias, Humberto; Arciniega-Martínez, Ivonne Maciel; Abarca-Rojano, Edgar; Cruz-Hernández, Teresita Rocío; Campos-Rodríguez, Rafael

2015-08-15

Intermittent fasting prolongs the lifespan and unlike intense stress provides health benefits. Given the role of the immunoglobulin A (IgA) in the intestinal homeostasis, the aim of this study was to assess the impact of intermittent fasting plus intense stress on secretory IgA (SIgA) production and other mucosal parameters in the duodenum and ileum. Two groups of six mice, with intermittent fasting or fed ad libitum for 12weeks, were submitted to a session of intense stress by a bout of forced swimming. Unstressed ad libitum fed or intermittently fasted groups were included as controls. After sacrifice, we evaluated intestinal SIgA and plasma adrenal hormones, lamina propria IgA+ plasma-cells, mRNA expression of polymeric immunoglobulin receptor, α- and J-chains in the liver and intestinal mucosa, as well as pro- (tumor necrosis factor-α, interleukin-6 and Interferon-γ) and anti- (interleukin-2, -4, -10 and transforming growth factor-β) inflammatory cytokines in mucosal samples. Under intense stress, intermittent fasting down- or up-modulated the levels of most parameters in the duodenum and ileum, respectively while up-regulated corticosterone levels without affecting epinephrine. Our data suggest intermittent fasting plus intense stress elicited neuroendocrine pathways that differentially controlled IgA and pIgR expression in duodenum and ileum. These findings provide experimental foundations for a presumable impact of intermittent fasting under intense stress on the intestinal homeostasis or inflammation by triggering or reducing the IgA production in ileum or duodenum respectively. Copyright © 2015 Elsevier B.V. All rights reserved.

A plastic stress intensity factor approach to turbine disk structural integrity assessment

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V. Shlyannikov

2016-07-01

Full Text Available This study based on a new fracture mechanics parameter is concerned with assessing the integrity of cracked steam turbine disk which operate under startup-shutdown cyclic loading conditions. Damage accumulation and growth in service have occurred on the inner surface of slot fillet of key. In order to determine elastic-plastic fracture mechanics parameters full-size stress-strain state analysis of turbine disk was performed for a quote-elliptical part-through cracks under considering loading conditions. As a result distributions of elastic and plastic stress intensity factors along crack front in slot fillet of key of turbine disk depending on surface crack form are defined. An engineering approach to the prediction of carrying capacity of cracked turbine disk which is sensitive to the loading history at maintenance is proposed. The predictions of the rate of crack growth and residual lifetime of steam turbine disk are compared for elastic and elastic-plastic solutions. It is shown that the previously proposed elastic crack growth models provide overestimate the lifetime with respect to the present one. An advantage to use the plastic stress intensity factor to characterize the fracture resistance as the self-dependent unified parameter for a variety of turbine disk configurations rather than the magnitude of the elastic stress intensity factors alone is discussed.

[Stress in parents of hospitalized newborns in a neonatal intensive care unit].

Science.gov (United States)

Palma I, Elisa; Von Wussow K, Fernanda; Morales B, Ignacia; Cifuentes R, Javier; Ambiado T, Sergio

2017-06-01

The birth of a child that requires hospitalization in a Neonatal Intensive Care Unit (NICU) can be very stressful for parents. To determine the stress level of parents of newborns (NB) hospitalized in a level III NICU in Santiago, and its association with clinical and sociodemographic variables. Descriptive cross-sectional study. 373 admissions were evaluated. The sampling was non-probabilistic and included parents of RN admitted to the UPCN between 7 and 21 days of hospitalization. Only parents which have visited the RN at least three times were included. i) Questionnaire to obtain data which could not be obtained from the medical record; ii) Parental Stress Scale: Neonatal Intensive Care Unit (PSS:NICU) which measures the perception of parents about stressors from the physical and psychological environment of the UPCN. 100 parents of 59 hospitalized NB participated in the study. The average parental stress was 2.87±0.69. The subscale scores got higher was “Relationship with the baby and parental role”. Complications in pregnancy, prenatal diagnosis or prenatal hospitalization, did not affect the stress level or the presence of prematurity, respiratory diseases, congenital malformations, genopathies or requirement of mechanical ventilation. Stress levels presented in parents are unrelated to gender and to the studied clinical variables.

New model for surface fracture induced by dynamical stress

OpenAIRE

Andersen, J. V.; Lewis, L. J.

1997-01-01

We introduce a model where an isotropic, dynamically-imposed stress induces fracture in a thin film. Using molecular dynamics simulations, we study how the integrated fragment distribution function depends on the rate of change and magnitude of the imposed stress, as well as on temperature. A mean-field argument shows that the system becomes unstable for a critical value of the stress. We find a striking invariance of the distribution of fragments for fixed ratio of temperature and rate of ch...

Computation of principal stresses and stress intensity of a nozzle on a spherical pressure vessel

International Nuclear Information System (INIS)

Sun, B.C.; Lyow, B.L.; Koplik, B.

1993-01-01

This paper presents a Stress Computation Table that systematically computes the local stresses at various locations of the sphere-nozzle intersection. The six components of external loading are: radial load, two overturning moments, two horizontal shear forces, and a torsional moment. The radial and overturning moments induce local membrane and bending stresses in both the circumferential and meridional directions of the sphere around the nozzle. The shear forces and torsional moment produce local shear stresses. In addition, the shear forces induce local membrane and bending stresses around the nozzle. The local stress factors from each external loading component are taken from recent publications by Lyow, Sun and Koplik who have studied this subject through the use of the finite element method. These factors are a function of the nozzle-sphere geometrical parameters, beta, β, (nozzle radius/sphere radius) and gamma, γ, (sphere radius/thickness), with the beta value ranging from 0.1 to 0.5, and the gamma value ranging from 10 to 100. The Stress Table summarizes all the normal and shear stresses at eight different locations around the nozzle, and finally the principal stresses and stress intensity are computed. The stress factor plots from previous publications are replotted in this paper to provide a handy reference as well as consistency. A numerical sample employing a FORTRAN program is also given. (author)

Stress ulcer prophylaxis in the intensive care unit trial

DEFF Research Database (Denmark)

Krag, M; Perner, A; Wetterslev, J

2017-01-01

BACKGROUND: In this statistical analysis plan, we aim to provide details of the pre-defined statistical analyses of the Stress Ulcer Prophylaxis in the Intensive Care Unit (SUP-ICU) trial. The aim of the SUP-ICU trial is to assess benefits and harms of stress ulcer prophylaxis with a proton pump......-year mortality, and a health economic analysis. Two formal interim analyses will be performed. The statistical analyses will be conducted according to the outlined pre-defined statistical analysis plan. The primary analysis will be a logistic regression analysis adjusted for stratification variables...... comparing the two intervention groups in the intention-to-treat population. In a secondary analysis, we will additionally adjust the primary outcome for potential random differences in baseline characteristics. The conclusion will be based on the intention-to-treat population. CONCLUSION: Stress ulcer...

Posttraumatic stress disorder in children and their parents following admission to the pediatric intensive care unit: a review.

Science.gov (United States)

Nelson, Lara P; Gold, Jeffrey I

2012-05-01

To evaluate posttraumatic stress disorder in children who have been admitted to the pediatric intensive care unit and their families. Studies were identified through PubMed, MEDLINE, and Ovid. All descriptive, observational, and controlled studies with a focus on posttraumatic stress disorder and the pediatric intensive care unit were included. Posttraumatic stress disorder rates in children following admission to the pediatric intensive care unit were between 5% and 28%, while rates of posttraumatic stress disorder symptoms were significantly higher, 35% to 62%. There have been inconsistencies noted across risk factors. Objective and subjective measurements of disease severity were intermittently positively associated with development of posttraumatic stress disorder. There was a positive relationship identified between the child's symptoms of posttraumatic stress disorder and their parents' symptoms.The biological mechanisms associated with the development of posttraumatic stress disorder in children admitted to the pediatric intensive care unit have yet to be explored. Studies in children following burn or other unintentional injury demonstrate potential relationships between adrenergic hormone levels and a diagnosis of posttraumatic stress disorder. Likewise genetic studies suggest the importance of the adrenergic system in this pathway.The rates of posttraumatic stress disorder in parents following their child's admission to the pediatric intensive care unit ranged between 10.5% and 21%, with symptom rates approaching 84%. It has been suggested that mothers are at increased risk for the development of posttraumatic stress disorder compared to fathers. Objective and subjective measures of disease severity yielded mixed findings with regard to the development of posttraumatic stress disorder. Protective parental factors may include education or the opportunity to discuss the parents' feelings during the admission. Following admission to the pediatric intensive

Effects of Exercise Intensity on Postexercise Endothelial Function and Oxidative Stress

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Conor McClean

2015-01-01

Full Text Available Purpose. To measure endothelial function and oxidative stress immediately, 90 minutes, and three hours after exercise of varying intensities. Methods. Sixteen apparently healthy men completed three exercise bouts of treadmill running for 30 minutes at 55% V˙O2max (mild; 20 minutes at 75% V˙O2max (moderate; or 5 minutes at 100% V˙O2max (maximal in random order. Brachial artery flow-mediated dilation (FMD was assessed with venous blood samples drawn for measurement of endothelin-1 (ET-1, lipid hydroperoxides (LOOHs, and lipid soluble antioxidants. Results. LOOH increased immediately following moderate exercise (P0.05. Conclusions. Acute exercise at different intensities elicits varied effects on oxidative stress, shear rate, and ET-1 that do not appear to mediate changes in endothelial function measured by FMD.

Mid-thickness studies of the stress intensity factor in the bulk of bainitic steel

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P. Lopez-Crespo

2017-07-01

Full Text Available The current work aims at estimating the stress intensity factor deep inside the bulk from elastic strain data measured by synchrotron X-ray diffraction. Key features affecting the evaluation of the stress intensity factor are the number of terms in the analytical model describing the crack tip field, the extension and position of the area of interest of the experimental data, the effect of the experimental data collected within the plastic zone and the number of elastic strain data points used. Here a parametric study of these features is presented in terms of their influence for the stress intensity factor determination. It was found that 3 or 4 terms in Williams’ expansion is often sufficient; the data should be collected from across the full range of angles around the crack tip; and the number of points/number of terms should be greater than 40.

Work stress, occupational burnout and depression levels: a clinical study of paediatric intensive care unit nurses in Taiwan.

Science.gov (United States)

Lin, Tzu-Ching; Lin, Huey-Shyan; Cheng, Su-Fen; Wu, Li-Min; Ou-Yang, Mei-Chen

2016-04-01

This study aimed to examine the relationship between work stress and depression; and investigate the mediating effect of occupational burnout among nurses in paediatric intensive care units. The relationships among work stress, occupational burnout and depression level have been explored, neither regarding occupational burnout as the mediating role that causes work stress to induce depression nor considering the paediatric intensive care unit context. A cross-sectional correlational design was conducted. One hundred and forty-four female paediatric intensive care unit nurses from seven teaching hospitals in southern Taiwan were recruited as the participants. Data were collected by structured questionnaires including individual demographics, the Nurse Stress Checklist, the Occupational Burnout Inventory and the Taiwan Depression Questionnaire. The results indicated that after controlling for individual demographic variables, the correlations of work stress with occupational burnout, as well as work stress and occupational burnout with depression level were all positive. Furthermore, occupational burnout may exert a partial mediating effect on the relationship between work stress and depression level. This study provides information about work stress, occupational burnout and depression level, and their correlations, as well as the mediating role of occupational burnout among paediatric intensive care unit nurses. It suggests government departments and hospital administrators when formulating interventions to prevent work stress and occupational burnout. These interventions can subsequently prevent episodes of depression in paediatric intensive care unit nurses, thereby providing patients with a safe and high-quality nursing environment. © 2016 John Wiley & Sons Ltd.

Dynamics of intense laser channel formation in an underdense plasma

International Nuclear Information System (INIS)

Davis, J.; Petrov, G.M.; Velikovich, A.L.

2005-01-01

Efficient guiding and propagation of multi-keV x-rays in plasmas can be achieved by dynamically modifying the media through plasma channel formation. The dynamics of plasma channel formation is studied in preformed underdense plasma irradiated by a high intensity laser. This is done by a two-dimensional model coupling laser propagation to a relativistic particle-in-cell model. For laser intensity of 10 20 W/cm 2 and a laser beam width of 5 μm the channel formation proceeds on a time scale of 60-70 fs in uniform plasma with density 10 18 cm -3 . The channel closes shortly after the rear of the laser pulse has passed due to Coulomb attraction from the ion core. Electron cavitation occurs only if the laser intensity is above a certain threshold intensity and the laser pulse duration exceeds 100 fs. X-ray generation and propagation is feasible for ultrarelativistic laser pulses with small beam width, less than ∼20 μm, and duration of more than 100 fs

Analysis of stress intensity factors for surface cracks in pre/post penetration

International Nuclear Information System (INIS)

Miyoshi, Toshiro; Yoshida, Yuichiro

1988-01-01

It is important to evaluate the penetration of surface cracks in a Leak-Before-Break analysis. Because the stress intensity factors for surface cracks in pre/post penetration had not yet been analyzed, the authors carried three-dimensional boundary element analyses in order to obtain them. First, the authors developed the technique of nodal breakdown appropriate for cracks with short ligament length in a two-dimensional boundary element analysis. Next, analyses of stress intensity factor for surface cracks in pre/post penetration were carried out using the technique of nodal breakdown for cracks with short ligament length and the three-dimensional boundary element code BEM 3 D which was designed for a supercomputer. (author)

Dynamic Initiation and Propagation of Multiple Cracks in Brittle Materials

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Xiaodan Ren

2013-07-01

Full Text Available Brittle materials such as rock and ceramic usually exhibit apparent increases of strength and toughness when subjected to dynamic loading. The reasons for this phenomenon are not yet well understood, although a number of hypotheses have been proposed. Based on dynamic fracture mechanics, the present work offers an alternate insight into the dynamic behaviors of brittle materials. Firstly, a single crack subjected to stress wave excitations is investigated to obtain the dynamic crack-tip stress field and the dynamic stress intensity factor. Second, based on the analysis of dynamic stress intensity factor, the fracture initiation sizes and crack size distribution under different loading rates are obtained, and the power law with the exponent of −2/3 is derived to describe the fracture initiation size. Third, with the help of the energy balance concept, the dynamic increase of material strength is directly derived based on the proposed multiple crack evolving criterion. Finally, the model prediction is compared with the dynamic impact experiments, and the model results agree well with the experimentally measured dynamic increasing factor (DIF.

A definition and evaluation procedure of generalized stress intensity factors at cracks and multi-material wedges

International Nuclear Information System (INIS)

Song Chongmin

2010-01-01

A definition of generalized stress intensity factors is proposed. It is based on a matrix function solution for singular stress fields obtained from the scaled boundary finite-element method. The dimensions of the matrix are equal to the number of singular terms. Not only real and complex power singularities but also power-logarithmic singularities are represented in a unified expression without explicitly determining the type of singularity. The generalized stress intensity factors are evaluated directly from the definition by following standard stress recovery procedures in the finite element method. Numerical examples are presented to valid the definition and evaluation procedure.

The Living, Dynamic and Complex Environment Care in Intensive Care Unit.

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Backes, Marli Terezinha Stein; Erdmann, Alacoque Lorenzini; Büscher, Andreas

2015-01-01

to understand the meaning of the Adult Intensive Care Unit environment of care, experienced by professionals working in this unit, managers, patients, families and professional support services, as well as build a theoretical model about the Adult Intensive Care Unit environment of care. Grounded Theory, both for the collection and for data analysis. Based on theoretical sampling, we carried out 39 in-depth interviews semi-structured from three different Adult Intensive Care Units. built up the so-called substantive theory "Sustaining life in the complex environment of care in the Intensive Care Unit". It was bounded by eight categories: "caring and continuously monitoring the patient" and "using appropriate and differentiated technology" (causal conditions); "Providing a suitable environment" and "having relatives with concern" (context); "Mediating facilities and difficulties" (intervenienting conditions); "Organizing the environment and managing the dynamics of the unit" (strategy) and "finding it difficult to accept and deal with death" (consequences). confirmed the thesis that "the care environment in the Intensive Care Unit is a living environment, dynamic and complex that sustains the life of her hospitalized patients".

Usefulness of creep work-time relation for determining stress intensity limit of high-temperature components

International Nuclear Information System (INIS)

Kim, Woo Gon; Ryu, Woo Seog; Lee, Kyung Yong

2003-01-01

In order to determine creep stress intensity limit of high-temperature components, the usefulness of the creep work and time equation, defined as W c t p = B (where W c = σ ε is the total creep work done during creep, and p and B are constants), was investigated using the experimental data. For this purpose, the creep tests for generating 1.0% strain for commercial type 316 stainless steel were conducted with different stresses; 160 MPa, 150 MPa, 145 MPa, 140 MPa and 135 MPa at 593 .deg. C. The plots of log W c - log t showed a good linear relation up to 10 5 hr, and the results of the creep work-time relation for p, B and stress intensity values showed good agreement to those of Isochronous Stress-Strain Curves (ISSC) presented in ASME BPV NH. The relation can be simply obtained with only several short-term 1% strain data without ISSC which can be obtained by long-term creep data. Particularly, this relation is useful in estimating stress intensity limit for new and emerging class of high-temperature creeping materials

Multibody Dynamic Stress Simulation of Rigid-Flexible Shovel Crawler Shoes

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Samuel Frimpong

2016-06-01

Full Text Available Electric shovels are used in surface mining operations to achieve economic production capacities. The capital investments and operating costs associated with the shovels deployed in the Athabasca oil sands formation are high due to the abrasive conditions. The shovel crawler shoes interact with sharp and abrasive sand particles, and, thus, are subjected to high transient dynamic stresses. These high stresses cause wear and tear leading to crack initiation, propagation and premature fatigue failure. The objective of this paper is to develop a model to characterize the crawler stresses and deformation for the P&H 4100C BOSS during propel and loading using rigid-flexible multi-body dynamic theory. A 3-D virtual prototype model of the rigid-flexible crawler track assembly and its interactions with oil sand formation is simulated to capture the model dynamics within multibody dynamics software MSC ADAMS. The modal and stress shapes and modal loads due to machine weight for each flexible crawler shoes are generated from finite element analysis (FEA. The modal coordinates from the simulation are combined with mode and stress shapes using modal superposition method to calculate real-time stresses and deformation of flexible crawler shoes. The results show a maximum von Mises stress value of 170 MPa occurring in the driving crawler shoe during the propel motion. This study provides a foundation for the subsequent fatigue life analysis of crawler shoes for extending crawler service life.

Stress Distribution in Graded Cellular Materials Under Dynamic Compression

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Peng Wang

Full Text Available Abstract Dynamic compression behaviors of density-homogeneous and density-graded irregular honeycombs are investigated using cell-based finite element models under a constant-velocity impact scenario. A method based on the cross-sectional engineering stress is developed to obtain the one-dimensional stress distribution along the loading direction in a cellular specimen. The cross-sectional engineering stress is contributed by two parts: the node-transitive stress and the contact-induced stress, which are caused by the nodal force and the contact of cell walls, respectively. It is found that the contact-induced stress is dominant for the significantly enhanced stress behind the shock front. The stress enhancement and the compaction wave propagation can be observed through the stress distributions in honeycombs under high-velocity compression. The single and double compaction wave modes are observed directly from the stress distributions. Theoretical analysis of the compaction wave propagation in the density-graded honeycombs based on the R-PH (rigid-plastic hardening idealization is carried out and verified by the numerical simulations. It is found that stress distribution in cellular materials and the compaction wave propagation characteristics under dynamic compression can be approximately predicted by the R-PH shock model.

Stress-intensity factor equations for cracks in three-dimensional finite bodies subjected to tension and bending loads

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Newman, J. C., Jr.; Raju, I. S.

1984-01-01

Stress intensity factor equations are presented for an embedded elliptical crack, a semielliptical surface crack, a quarter elliptical corner crack, a semielliptical surface crack along the bore of a circular hole, and a quarter elliptical corner crack at the edge of a circular hole in finite plates. The plates were subjected to either remote tension or bending loads. The stress intensity factors used to develop these equations were obtained from previous three dimensional finite element analyses of these crack configurations. The equations give stress intensity factors as a function of parametric angle, crack depth, crack length, plate thickness, and, where applicable, hole radius. The ratio of crack depth to plate thickness ranged from 0 to 1, the ratio of crack depth to crack length ranged from 0.2 to 2, and the ratio of hole radius to plate thickness ranged from 0.5 to 2. The effects of plate width on stress intensity variation along the crack front were also included.

The effect of couple-stresses on the stress concentration around a moving crack

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S. Itou

1981-01-01

Full Text Available The problem of a uniformly propagating finite crack in an infinite medium is solved within the linearized couple-stress theory. The self-equilibrated system of pressure is applied to the crack surfaces. The problem is reduced to dual integral equations and solved by a series-expansion method. The dynamic stress-intensity factor is computed numerically.

Effect of Magnetohydrodynamic Couple Stresses on Dynamic Characteristics of Exponential Slider Bearing

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N.B. Naduvinamani

2017-05-01

Full Text Available The effect of couple stresses on static and dynamic characteristics of exponential slider bearing in the presence of magnetic field considering squeeze action is theoretically analyzed in this paper. The modified magnetohydrodynamic couple stress Reynolds type equation is derived on the basis of Stokes couple stress model and closed form expressions are obtained for static and dynamic character coefficients. Comparing with bearing lubricated with non-conducting Newtonian lubricants, the magnetohydrodynamic couple stress lubrication provides the higher steady load carrying capacity, dynamic stiffness and damping coefficient. The exponential bearing shows higher efficiency for small film thickness at higher value of couple stress parameter and Hartmann number.

The dynamic functional capacity theory: A neuropsychological model of intense emotions

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Philip C. Klineburger

2015-12-01

Full Text Available The music-evoked emotion literature implicates many brain regions involved in emotional processing but is currently lacking a model that specifically explains how they temporally and dynamically interact to produce intensely pleasurable emotions. A conceptual model, the dynamic functional capacity theory (DFCT, is proposed and provides a foundation for the further understanding of how brain regions interact to produce intensely pleasurable emotions. The DFCT claims that brain regions mediating emotion and arousal regulation have a limited functional capacity that can be exceeded by intense stimuli. The prefrontal cortex is hypothesized to abruptly deactivate when this happens, resulting in the inhibitory release of sensory cortices, the limbic system, the reward-circuit, and the brainstem reticular activating system, causing “unbridled” activation of these areas. This process is hypothesized to produce extremely intense emotions. This theory may provide—music-evoked emotion researchers and music therapy researchers—a theoretical foundation for continued research and complement current theories of emotion.

Determination of Stress Intensity Factor K1 from Two Fringe Orders by Fringe Multiplication and Sharpening

International Nuclear Information System (INIS)

Chen, Lei; Baek, Tae Hyun

2007-01-01

Stress intensity factor is one of the most important parameters in fracture mechanics. Both the stress field distribution and the crack propagation are closely related to these parameters. Due to the complexity of actual engineering problems, it is difficult to calculate the stress intensity factor by theoretical formulation, so photoelasticity method is a good choice. In this paper, modified two parameter method is employed to calculate stress intensity factor for opening mode by using data from more than one photoelastic fringe loop. For getting accurate experiment results, the initial fringes are doubled and sharpened by digital image programs from the fringe patterns obtained by a CCD camera. Photoelastic results are compared with those obtained by the use of empirical equation and FEM. Good agreement shows that the methods utilized in experiments are considerably reliable. The photoelastic experiment can be used for bench mark in theoretical study and other experiments

The association between pregame snacks and exercise intensity, stress, and fatigue in children.

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Sacheck, Jennifer M; Rasmussen, Helen M; Hall, Meghan M; Kafka, Tamar; Blumberg, Jeffrey B; Economos, Christina D

2014-05-01

To investigate the association between pregame snacks varying in macronutrient content and exercise intensity, physiological stress, and fatigue in young soccer players. One hour before a 50-min soccer game, children (n = 79; 9.1 ± 0.8 y) were randomly assigned to consume a raisin-, peanut-butter-, or cereal-based snack. Body mass index, blood glucose, and salivary measures of stress (cortisol and immunoglobulin A-IgA) were measured pre- and post-game. Exercise intensity was measured by accelerometry. Self-administered questionnaires were used to assess diet quality and fatigue. Analysis of covariance was used to examine the relationship between pregame snacks and biochemical outcomes. Postgame glucose and cortisol increased [12.9 ± 21.3 mg/dL (p fatigue (p fatigue but not changes in blood sugar or stress biomarkers following a soccer game in children.

Gradually Increased Training Intensity Benefits Rehabilitation Outcome after Stroke by BDNF Upregulation and Stress Suppression

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Jing Sun

2014-01-01

Full Text Available Physical training is necessary for effective rehabilitation in the early poststroke period. Animal studies commonly use fixed training intensity throughout rehabilitation and without adapting it to the animals' recovered motor ability. This study investigated the correlation between training intensity and rehabilitation efficacy by using a focal ischemic stroke rat model. Eighty male Sprague-Dawley rats were induced with middle cerebral artery occlusion/reperfusion surgery. Sixty rats with successful stroke were then randomly assigned into four groups: control (CG, n=15, low intensity (LG, n=15, gradually increased intensity (GIG, n=15, and high intensity (HG, n=15. Behavioral tests were conducted daily to evaluate motor function recovery. Stress level and neural recovery were evaluated via plasma corticosterone and brain-derived neurotrophic factor (BDNF concentration, respectively. GIG rats significantly (P<0.05 recovered motor function and produced higher hippocampal BDNF (112.87 ± 25.18 ng/g. GIG and LG rats exhibited similar stress levels (540.63 ± 117.40 nM/L and 508.07 ± 161.30 nM/L, resp., which were significantly lower (P<0.05 than that (716.90 ± 156.48 nM/L of HG rats. Training with gradually increased intensity achieved better recovery with lower stress. Our observations indicate that a training protocol that includes gradually increasing training intensity should be considered in both animal and clinical studies for better stroke recovery.

The relation between intensity and complexity of coronary artery lesion and oxidative stress in patients with acute coronary syndrome.

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Turan, Turhan; Menteşe, Ümit; Ağaç, Mustafa Tarık; Akyüz, Ali Rıza; Kul, Selim; Aykan, Ahmet Çağrı; Bektaş, Hüseyin; Korkmaz, Levent; Öztaş Menteşe, Seda; Dursun, İhsan; Çelik, Şükrü

2015-10-01

Oxidative stress plays a major role in the development of atherosclerosis. However, the relationship between oxidative stress and complexity and intensity of coronary artery disease is less clear. The aim of this study is to assess the relationship between oxidative stress markers and the complexity and intensity of coronary artery disease in patients with acute coronary syndrome (ACS). Sixty-seven consecutive patients with an early phase of ACS (=22). Likewise patients were divided into two CAD severity groups according to the median Gensini score of 64: less intensive CAD with Gensini score (=64. Blood samples were taken in 1 hour within administration in order to measure total oxidative status (TOS) and total antioxidant capacity (TAC) levels determined by Erel method. Oxidative stress index (OSI) was calculated by TOS /TAC. There was no significant difference between the two SYNTAX groups for oxidative stress markers. Median TOS and OSI values were significantly high in the intensive CAD group (p=0.005, p=0.04, respectively). The Gensini score was positively correlated with TOS and OSI (p=0.003, p=0.02, respectively). Oxidative stress markers may be considered supportive laboratory parameters related to CAD intensity but not complexity in ACS patients.

Intensity approximation of random fluctuation in complex systems

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Yulmetyev, R. M.; Gafarov, F. M.; Yulmetyeva, D. G.; Emeljanova, N. A.

2002-01-01

The Markov and non-Markov processes in complex systems are examined with the help of dynamical information Shannon entropy method. Here we consider the essential role of two mutually independent channels of entropy involving creation of correlation and annihilation of correlation. The developed method has been used to analyze the intensity fluctuation of the complex systems of various nature: in psychology (to analyze numerical and pattern short-time human memory, to study the effect of stress on the parameters of the dynamical taping-test) and in cardiology (to analyze the random dynamics of RR-intervals in human ECG's and to diagnose various diseases of human cardiovascular systems). The received results show that the application of intensity approximation allows to improve essentially the diagnostics of parameters in the evolution of human dynamic states.

Stress intensities in flawed pressure vessels

International Nuclear Information System (INIS)

Smith, C.W.; Jolles, M.; Peters, W.H.

1977-01-01

A technique for determining the stess intensity factor (SIF) near pressure vessel flaws or cracks experimentally from photoelastic data for use in two-dimensional problems was developed in the 1950's. This technique was modified and extended to a variety of two-dimensional problems. The technique has been refined further and what has evolved may be regarded as a hybrid technique which affects a marriage between ''frozen stress'' photoelastic results and a simple least-squares digital computer program for estimating SIF values in three-dimensional problems. This technique, in its original modified form, has been shown to be applicable to a study of surface flaws and the applicability of the method to complex crack body geometries of current technological importance are discussed. The analytical foundations of the method are reviewed

The Living, Dynamic and Complex Environment Care in Intensive Care Unit

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Marli Terezinha Stein Backes

2015-06-01

Full Text Available OBJECTIVE: to understand the meaning of the Adult Intensive Care Unit environment of care, experienced by professionals working in this unit, managers, patients, families and professional support services, as well as build a theoretical model about the Adult Intensive Care Unit environment of care.METHOD: Grounded Theory, both for the collection and for data analysis. Based on theoretical sampling, we carried out 39 in-depth interviews semi-structured from three different Adult Intensive Care Units.RESULTS: built up the so-called substantive theory "Sustaining life in the complex environment of care in the Intensive Care Unit". It was bounded by eight categories: "caring and continuously monitoring the patient" and "using appropriate and differentiated technology" (causal conditions; "Providing a suitable environment" and "having relatives with concern" (context; "Mediating facilities and difficulties" (intervenienting conditions; "Organizing the environment and managing the dynamics of the unit" (strategy and "finding it difficult to accept and deal with death" (consequences.CONCLUSION: confirmed the thesis that "the care environment in the Intensive Care Unit is a living environment, dynamic and complex that sustains the life of her hospitalized patients".

Effect of stress hyperglycemia and intensive rehabilitation therapy in non-diabetic hemorrhagic stroke: Korean Stroke Cohort for Functioning and Rehabilitation.

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Yoon, J A; Kim, D Y; Sohn, M K; Lee, J; Lee, S-G; Lee, Y-S; Han, E Y; Joo, M C; Oh, G-J; Han, J; Lee, S W; Park, M; Chang, W H; Shin, Y-I; Kim, Y-H

2016-11-01

We investigated the effect of stress hyperglycemia on the functional outcomes of non-diabetic hemorrhagic stroke. In addition, we investigated the usefulness of intensive rehabilitation for improving functional outcomes in patients with stress hyperglycemia. Non-diabetic hemorrhagic stroke patients were recruited and divided into two groups: intracerebral hemorrhage (ICH) (n = 165) and subarachnoid hemorrhage (SAH) (n = 156). Each group was divided into non-diabetics with or without stress hyperglycemia. Functional assessments were performed at 7 days and 3, 6 and 12 months after stroke onset. The non-diabetic with stress hyperglycemia groups were again divided into two groups who either received or did not receive intensive rehabilitation treatment. Serial functional outcome was compared between groups. For the ICH group, patients with stress hyperglycemia had worse modified Rankin Scale, National Institutes of Health Stroke Scale, Functional Ambulatory Category and Korean Mini-Mental State Examination scores than patients without stress hyperglycemia. For the SAH group, patients with stress hyperglycemia had worse scores on all functional assessments than patients without stress hyperglycemia at all time-points. After intensive rehabilitation treatment of patients with stress hyperglycemia, the ICH group had better scores on Functional Ambulatory Category and the SAH group had better scores on all functional assessments than patients without intensive rehabilitation treatment. Stress hyperglycemia affects the long-term prognosis of non-diabetic hemorrhagic stroke patients. Among stress hyperglycemia patients, intensive rehabilitation can enhance functional improvement after stroke. © 2016 EAN.

Razlike med spoloma pri nekaterih simptomih stresa ter intenzivnost doživljanja stresnih simptomov = Gender Differences in Some Stress Symptoms and Intensity of Experiencing Stress Symptoms

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Maja Meško

2010-06-01

Full Text Available The aim of this study was to identify the symptoms of stress and to establishgender differences in stress symptoms. We tried to find out ifthere are gender differences in the stress level at work, if there aregender differences in terms of stress symptoms frequency, and if thereare gender differences in terms of the intensity of experiencing stresssymptoms. In this study 85 randomly selected managers from Slovenecompanies participated. The results of the study have shown that thereare gender differences in terms of all the above mentioned factors,namely a statistically higher level of stress in women. In terms of stresssymptoms occurrence there are gender differences in some stress symptomsas well as in the intensity of experiencing stress symptoms.

Measurement and interpretation of threshold stress intensity factors for steels in high-pressure hydrogen gas.

Energy Technology Data Exchange (ETDEWEB)

Dadfarnia, Mohsen (University of Illinois at Urbana-Champaign, Urbana, IL); Nibur, Kevin A.; San Marchi, Christopher W.; Sofronis, Petros (University of Illinois at Urbana-Champaign, Urbana, IL); Somerday, Brian P.; Foulk, James W., III; Hayden, Gary A. (CP Industries, McKeesport, PA)

2010-07-01

Threshold stress intensity factors were measured in high-pressure hydrogen gas for a variety of low alloy ferritic steels using both constant crack opening displacement and rising crack opening displacement procedures. The sustained load cracking procedures are generally consistent with those in ASME Article KD-10 of Section VIII Division 3 of the Boiler and Pressure Vessel Code, which was recently published to guide design of high-pressure hydrogen vessels. Three definitions of threshold were established for the two test methods: K{sub THi}* is the maximum applied stress intensity factor for which no crack extension was observed under constant displacement; K{sub THa} is the stress intensity factor at the arrest position for a crack that extended under constant displacement; and K{sub JH} is the stress intensity factor at the onset of crack extension under rising displacement. The apparent crack initiation threshold under constant displacement, K{sub THi}*, and the crack arrest threshold, K{sub THa}, were both found to be non-conservative due to the hydrogen exposure and crack-tip deformation histories associated with typical procedures for sustained-load cracking tests under constant displacement. In contrast, K{sub JH}, which is measured under concurrent rising displacement and hydrogen gas exposure, provides a more conservative hydrogen-assisted fracture threshold that is relevant to structural components in which sub-critical crack extension is driven by internal hydrogen gas pressure.

Dynamics of laser mass-limited foil interaction at ultra-high laser intensities

Energy Technology Data Exchange (ETDEWEB)

Yu, T. P., E-mail: tongpu@nudt.edu.cn [College of Science, National University of Defense Technology, Changsha 410073 (China); State Key Laboratory of High Performance Computing, National University of Defense Technology, Changsha 410073 (China); Sheng, Z. M. [Key Laboratory for Laser Plasmas (MoE) and Department of Physics, Shanghai Jiao Tong University, Shanghai 200240 (China); SUPA, Department of Physics, University of Strathclyde, Glasgow G4 0NG (United Kingdom); Yin, Y.; Zhuo, H. B.; Ma, Y. Y.; Shao, F. Q. [College of Science, National University of Defense Technology, Changsha 410073 (China); Pukhov, A. [Institut für Theoretische Physik I, Heinrich-Heine-Universität Düsseldorf, 40225 Düsseldorf (Germany)

2014-05-15

By using three-dimensional particle-in-cell simulations with synchrotron radiation damping incorporated, dynamics of ultra-intense laser driven mass-limited foils is presented. When a circularly polarized laser pulse with a peak intensity of ∼10{sup 22} W/cm{sup 2} irradiates a mass-limited nanofoil, electrons are pushed forward collectively and a strong charge separation field forms which acts as a “light sail” and accelerates the protons. When the laser wing parts overtake the foil from the foil boundaries, electrons do a betatron-like oscillation around the center proton bunch. Under some conditions, betatron-like resonance takes place, resulting in energetic circulating electrons. Finally, bright femto-second x rays are emitted in a small cone. It is also shown that the radiation damping does not alter the foil dynamics radically at considered laser intensities. The effects of the transverse foil size and laser polarization on x-ray emission and foil dynamics are also discussed.

Stress-intensity factors for a thick-walled cylinder containing an annular imbedded or external or internal surface crack

Science.gov (United States)

Erdol, R.; Erdogan, F.

1976-01-01

The elastostatic axisymmetric problem for a long thick-walled cylinder containing a ring-shaped internal or edge crack is considered. Using the standard transform technique the problem is formulated in terms of an integral equation which has a simple Cauchy kernel for the internal crack and a generalized Cauchy kernel for the edge crack as the dominant part. As examples the uniform axial load and the steady-state thermal stress problems have been solved and the related stress intensity factors have been calculated. Among other findings the results show that in the cylinder under uniform axial stress containing an internal crack the stress intensity factor at the inner tip is always greater than that at the outer tip for equal net ligament thicknesses and in the cylinder with an edge crack which is under a state of thermal stress the stress intensity factor is a decreasing function of the crack depth, tending to zero as the crack depth approaches the wall thickness.

The effect of massage therapy on occupational stress of Intensive Care Unit nurses.

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Nazari, Fateme; Mirzamohamadi, Mojtaba; Yousefi, Hojatollah

2015-01-01

One of the main causes of stress in the lives of people is their jobs. Occupational stress is causing a wide range of significant issues in health and community services. Nursing is the most stressful profession in the health services. Massage therapy is one way of coping with stress. This study was conducted to determine the effect of massage therapy on stress in nurses. This study was a clinical trial on 66 male and female nurses working in intensive care units (dialysis, ICU, and CCU) of Isfahan University of Medical Sciences, Iran, in 2013. Participants were selected according to the aims and inclusion criteria of the study. Then, they were randomly divided into experimental and control groups. The Occupational Stress Inventory (OSI) (Osipow and Spokane, 1987) was completed by participants of the two groups before, immediately after, and 2 weeks after the intervention. General Swedish massage was performed on participants of the experimental group for 25 min in each session, twice a week for 4 weeks. Data were analyzed by descriptive and inferential statistics [Chi-square, t-test, and repeated measures analysis of variance (ANOVA)] using SPSS software. Results showed that the difference in overall mean occupation stress scores between experimental and control groups 2 weeks after the intervention was significant (P < 0.001). According to the results, it is recommended that massage, as a valuable noninvasive method, be used for nurses in intensive care units to reduce their stress, promote mental health, and prevent the decrease in quality of nursing work life.

Point defects dynamics in a stress field

International Nuclear Information System (INIS)

Smetniansky de De Grande, Nelida.

1989-01-01

The dependence of anisotropic defect diffusion on stress is studied for a hexagonal close packed (hcp) material under irradiation and uniaxially stressed. The diffusion is described as a discrete process of thermally activated jumps. It is shown that the presence of an external stress field enhances the intrinsic anisotropic diffusion, being this variation determined by the defect dipole tensors' symmetry in the equilibrium and saddle point configurations. Also, the point defect diffusion equations to sinks, like edge dislocations and spherical cavities, are solved and the sink strengths are calculated. The conclusion is that the dynamics of the interaction between defects and sinks is controlled by the changes in diffusivity induced by stress fields. (Author) [es

Dissecting long-term adjustments of photoprotective and photo-oxidative stress acclimation occurring in dynamic light environments

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Shizue Matsubara

2016-11-01

Full Text Available Changes in light intensity directly affect the performance of the photosynthetic apparatus. Light energy absorbed in excess of cells’ needs leads to production of reactive oxygen species and photo-oxidative damage. Excess light in both constant and dynamic environments induces photoprotective acclimation in plants. Distinct sets of signals and regulatory mechanisms are involved in acclimatory adjustment of photoprotection and photosynthesis under constant and dynamic (fluctuating light conditions. We are still far away from drawing a comprehensive picture of acclimatory signal transduction pathways, particularly in dynamic environments. In this perspective article, we propose the use of Arabidopsis plants that produce H2O2 in chloroplasts (GO plants under atmospheric CO2 levels as a tool to study the mechanisms of long-term acclimation to photo-oxidative stress. In our opinion there are new avenues to future investigations on acclimatory adjustments and signal transduction occurring in plants under dynamic light environments.

Fatigue Crack Growth Rate and Stress-Intensity Factor Corrections for Out-of-Plane Crack Growth

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Forth, Scott C.; Herman, Dave J.; James, Mark A.

2003-01-01

Fatigue crack growth rate testing is performed by automated data collection systems that assume straight crack growth in the plane of symmetry and use standard polynomial solutions to compute crack length and stress-intensity factors from compliance or potential drop measurements. Visual measurements used to correct the collected data typically include only the horizontal crack length, which for cracks that propagate out-of-plane, under-estimates the crack growth rates and over-estimates the stress-intensity factors. The authors have devised an approach for correcting both the crack growth rates and stress-intensity factors based on two-dimensional mixed mode-I/II finite element analysis (FEA). The approach is used to correct out-of-plane data for 7050-T7451 and 2025-T6 aluminum alloys. Results indicate the correction process works well for high DeltaK levels but fails to capture the mixed-mode effects at DeltaK levels approaching threshold (da/dN approximately 10(exp -10) meter/cycle).

Low intensity aerobic exercise and oxidative stress markers in older adults.

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Bouzid, Mohamed A; Hammouda, Omar; Matran, Régis; Robin, Sophie; Fabre, Claudine

2014-10-01

This comparative study examined the effects of regular low intensity aerobic exercise on oxidative stress markers in older adults. The study was carried out on 15 sedentary subjects (age: 65.1 ± 3.5 years) versus 18 subjects performing fitness exercises (age: 65.8 ± 3.3 years). Before and after an incremental exercise test, oxidative stress markers were assessed. Superoxide dismutase was higher at rest and at the recovery for the physically active subjects compared with sedentary subjects (p aerobic exercise may be useful to prevent the decline of antioxidants linked with aging.

cHRV Uncovering Daily Stress Dynamics Using Bio-Signal from Consumer Wearables.

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Hao, Tian; Chang, Henry; Ball, Marion; Lin, Kun; Zhu, Xinxin

2017-01-01

Knowing the dynamics of one's daily stress is essential to effective stress management in the context of smart and connected health. However, there lacks a practical and unobtrusive means to obtain real-time and longitudinal stress information. In this paper, we attempt to derive a convenient HRV-based (heart rate variability) biomarker named cHRV, which can be used to reliably reflect stress dynamics. cHRV's key advantage lies in its low maintenance and high practicality. It can be efficiently calculated only using data from photoplethysmography (PPG) sensors, the mainstream heart rate sensor embedded in most of the consumer wearables like Apple Watch. Benefiting from the proliferation of wearables, cHRV is ideal for day-to-day stress monitoring. To evaluate its feasibility and performance, we have conducted 14 in-lab controlled experiments. The result shows that the proposed cHRV has strong correlation with the stress dynamics (r > 0.95), therefore exhibits great potential for continuous stress assessment.

Dynamical calculations for RHEED intensity oscillations

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Daniluk, Andrzej

2005-03-01

A practical computing algorithm working in real time has been developed for calculating the reflection high-energy electron diffraction from the molecular beam epitaxy growing surface. The calculations are based on the use of a dynamical diffraction theory in which the electrons are taken to be diffracted by a potential, which is periodic in the dimension perpendicular to the surface. The results of the calculations are presented in the form of rocking curves to illustrate how the diffracted beam intensities depend on the glancing angle of the incident beam. Program summaryTitle of program: RHEED Catalogue identifier:ADUY Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADUY Program obtainable from:CPC Program Library, Queen's University of Belfast, N. Ireland Computer for which the program is designed and others on which it has been tested: Pentium-based PC Operating systems or monitors under which the program has been tested: Windows 9x, XP, NT, Linux Programming language used: Borland C++ Memory required to execute with typical data: more than 1 MB Number of bits in a word: 64 bits Number of processors used: 1 Distribution format:tar.gz Number of lines in distributed program, including test data, etc.:982 Number of bytes in distributed program, including test data, etc.: 126 051 Nature of physical problem: Reflection high-energy electron diffraction (RHEED) is a very useful technique for studying growth and surface analysis of thin epitaxial structures prepared by the molecular beam epitaxy (MBE). Nowadays, RHEED is used in many laboratories all over the world where researchers deal with the growth of materials by MBE. The RHEED technique can reveal, almost instantaneously, changes either in the coverage of the sample surface by adsorbates or in the surface structure of a thin film. In most cases the interpretation of experimental results is based on the use of dynamical diffraction approaches. Such approaches are said to be quite useful in qualitative and

Hybrid determination of mixed-mode stress intensity factors on discontinuous finite-width plate by finite element and photoelasticity

International Nuclear Information System (INIS)

Baek, Tae Hyun; Chen, Lei; Hong, Dong Pyo

2011-01-01

For isotropic material structure, the stress in the vicinity of crack tip is generally much higher than the stress far away from it. This phenomenon usually leads to stress concentration and fracture of structure. Previous researches and studies show that the stress intensity factor is one of most important parameter for crack growth and propagation. This paper provides a convenient numerical method, which is called hybrid photoelasticity method, to accurately determine the stress field distribution in the vicinity of crack tip and mixed-mode stress intensity factors. The model was simulated by finite element method and isochromatic data along straight lines far away from the crack tip were calculated. By using the isochromatic data obtained from finite element method and a conformal mapping procedure, stress components and photoelastic fringes in the hybrid region were calculated. To easily compare calculated photoelastic fringes with experiment results, the fringe patterns were reconstructed, doubled and sharpened. Good agreement shows that the method presented in this paper is reliable and convenient. This method can then directly be applied to obtain mixed mode stress intensity factors from the experimentally measured isochromatic data along the straight lines

Coping With Staff Burnout and Work-Related Posttraumatic Stress in Intensive Care.

Science.gov (United States)

Colville, Gillian A; Smith, Jared G; Brierley, Joe; Citron, Kim; Nguru, Noreen M; Shaunak, Priyanka D; Tam, Olivia; Perkins-Porras, Linda

2017-07-01

To examine the associations with symptoms of 1) burnout and 2) work-related posttraumatic stress, in adult and pediatric intensive care staff, focusing on the particular contributions of resilience and coping strategies. Point prevalence cross-sectional study. Three adult ICUs and four PICUs. Three hundred seventy-seven ICU staff. None. Brief Resilience Scale, abbreviated Maslach Burnout Inventory, Trauma Screening Questionnaire, and Hospital Anxiety and Depression Scale. Prevalence of burnout (defined as high emotional exhaustion or high depersonalization) was 37%. Prevalence of clinically significant posttraumatic stress symptoms was 13%. There was a degree of overlap between burnout and other measures of distress, most notably for anxiety (odds ratio, 10.56; 95% CI, 4.12-27.02; p work-related distress (burnout: odds ratio, 0.52; 95% CI, 0.36-0.74; p stress: odds ratio, 0.28; 95% CI, 0.16-0.46; p stress were less if staff used talking to seniors (odds ratio, 0.43; 95% CI, 0.20-0.92; p = 0.029) or hobbies (odds ratio, 0.46; 95% CI, 0.23-0.93; p = 0.030) to cope with stress at work. Venting emotion (odds ratio, 1.92; 95% CI, 1.12-3.31; p = 0.018) and using alcohol (odds ratio, 2.30; 95% CI, 1.26-4.20; p = 0.006) were associated with a doubling in risk of reporting burnout. The use of particular coping strategies was systematically associated with symptoms of burnout and work-related posttraumatic stress in this group of intensive care staff, even after controlling for resilience and other factors. More research on how best to promote adaptive coping is needed in these challenging settings.

ORBIT : BEAM DYNAMICS CALCULATIONS FOR HIGH - INTENSITY RINGS

International Nuclear Information System (INIS)

HOLMES, J.A.; DANILOV, V.; GALAMBOS, J.; SHISHLO, A.; COUSINEAU, S.; CHOU, W.; MICHELOTTI, L.; OSTIGUY, F.; WEI, J.

2002-01-01

We are developing a computer code, ORBIT, specifically for beam dynamics calculations in high-intensity rings. Our approach allows detailed simulation of realistic accelerator problems. ORBIT is a particle-in-cell tracking code that transports bunches of interacting particles through a series of nodes representing elements, effects, or diagnostics that occur in the accelerator lattice. At present, ORBIT contains detailed models for strip-foil injection including painting and foil scattering; rf focusing and acceleration; transport through various magnetic elements; longitudinal and transverse impedances; longitudinal, transverse, and three-dimensional space charge forces; collimation and limiting apertures; and the calculation of many useful diagnostic quantities. ORBIT is an object-oriented code, written in C++ and utilizing a scripting interface for the convenience of the user. Ongoing improvements include the addition of a library of accelerator maps, BEAMLINE/MXYZPTLK the introduction of a treatment magnet errors and fringe fields; the conversion of the scripting interface to the standard scripting language, Python; and the parallelization of the computations using MPI. The ORBIT code is an open source, powerful, and convenient tool for studying beam dynamics in high-intensity rings

[The application of low-intensity electromagnetic radiation under immobilization stress conditions (an experimental study)].

Science.gov (United States)

Korolev, Iu N; Bobrovnitskiĭ, I P; Nikoulina, L A; Mikhaĭlik, L V; Geniatulina, M S; Bobkova, A S

2014-01-01

The experiments carried out on outbred male white rats with the use of optical, electron-microscopic, biochemical, and radioimmunological methods have demonstrated that the application of low-intensity electromagnetic radiation (LI-EMR) with a flow density of 1 mcW/cm2 and a frequency of around 1,000 MHz both in the primary prophylaxis regime and as the therapeuticpreventive modality arrested the development of post-stress disorders in the rat testicles, liver, and thymus; moreover, it promoted activation of the adaptive, preventive, and compensatory processes. The data obtained provide a rationale for the application of low-intensity electromagnetic radiation to protect the organism from negative effects of stressful factors.

Predicting the effects of organ motion on the dose delivered by dynamic intensity modulation

International Nuclear Information System (INIS)

Yu, C.X.; Jaffray, David; Martinez, A.A.; Wong, J.W.

1997-01-01

Purpose: Computer-optimized treatment plans, aimed to enhance tumor control and reduce normal tissue complication, generally require non-uniform beam intensities. One of the techniques for delivering intensity-modulated beams is the use of dynamic multileaf collimation, where the beam aperture and field shape change during irradiation. When intensity-modulated beams are delivered with dynamic collimation, intra-treatment organ motion may not only cause geometric misses at the field boundaries but also create hot and cold spots in the target. The mechanism for producing such effects has not been well understood. This study analyzes the dosimetric effects of intra-treatment organ motion on dynamic intensity modulation. A numerical method is developed for predicting the intensity distributions in a moving target before dose is delivered with dynamic intensity modulation. Material and Methods: In the numerical algorithm, the change in position and shape of the beam aperture with time were modeled as a three-dimensional 'tunnel', with the shape of the field aperture described in the x-y plane and its temporal position shown in the z-dimension. A point in the target had to be in the tunnel in order to receive irradiation and the dose to the point was proportional to the amount of time that this point stayed in the tunnel. Since each point in the target were analyzed separately, non-rigid body variations could easily be handled. The dependency of the dose variations on all parameters involved, including the speed of collimator motion, the frequency and amplitude of the target motion, and the size of the field segments, was analyzed. The algorithm was verified by irradiating moving phantoms with beams of dynamically modulated intensities. Predictions were also made for a treatment of a thoracic tumor using a dynamic wedge. The changes of target position with time were based on the MRI images of the chest region acquired using fast MRI scans in a cine fashion for a duration

Post-stress recovery of pituitary-adrenal hormones and glucose, but not the response during exposure to the stressor, is a marker of stress intensity in highly stressful situations.

Science.gov (United States)

Márquez, Cristina; Belda, Xavier; Armario, Antonio

2002-02-01

Acute immobilization in male rats elicited the same ACTH, corticosterone and glucose response as foot shock when measured immediately after stress. However, post-stress recovery of plasma ACTH, corticosterone and glucose levels were delayed in immobilized versus shocked rats. Similarly, stress-induced anorexia was much greater in the former animals. All these data suggest that post-stress speed of recovery of some physiological variables is positively related to stressor intensity and could be used to evaluate it.

Efficient computer program EPAS-J1 for calculating stress intensity factors of three-dimensional surface cracks

International Nuclear Information System (INIS)

Miyazaki, Noriyuki; Watanabe, Takayuki; Yagawa, Genki.

1982-03-01

A finite element computer program EPAS-J1 was developed to calculate the stress intensity factors of three-dimensional cracks. In the program, the stress intensity factor is determined by the virtual crack extension method together with the distorted elements allocated along the crack front. This program also includes the connection elements based on the Lagrange multiplier concept to connect such different kinds of elements as the solid and shell elements, or the shell and beam elements. For the structure including three-dimensional surface cracks, the solid elements are employed only at the neighborhood of a surface crack, while the remainder of the structure is modeled by the shell or beam elements due to the reason that the crack singularity is very local. Computer storage and computational time can be highly reduced with the application of the above modeling technique for the calculation of the stress intensity factors of the three-dimensional surface cracks, because the three-dimensional solid elements are required only around the crack front. Several numerical analyses were performed by the EPAS-J1 program. At first, the accuracies of the connection element and the virtual crack extension method were confirmed using the simple structures. Compared with other techniques of connecting different kinds of elements such as the tying method or the method using anisotropic plate element, the present connection element is found to provide better results than the others. It is also found that the virtual crack extension method provides the accurate stress intensity factor. Furthermore, the results are also presented for the stress intensity factor analyses of cylinders with longitudinal or circumferential surface cracks using the combination of the various kinds of elements together with the connection elements. (author)

The importance of physical activity and sleep for affect on stressful days: Two intensive longitudinal studies.

Science.gov (United States)

Flueckiger, Lavinia; Lieb, Roselind; Meyer, Andrea H; Witthauer, Cornelia; Mata, Jutta

2016-06-01

We investigated the potential stress-buffering effect of 3 health behaviors-physical activity, sleep quality, and snacking-on affect in the context of everyday life in young adults. In 2 intensive longitudinal studies with up to 65 assessment days over an entire academic year, students (Study 1, N = 292; Study 2, N = 304) reported stress intensity, sleep quality, physical activity, snacking, and positive and negative affect. Data were analyzed using multilevel regression analyses. Stress and positive affect were negatively associated; stress and negative affect were positively associated. The more physically active than usual a person was on a given day, the weaker the association between stress and positive affect (Study 1) and negative affect (Studies 1 and 2). The better than usual a person's sleep quality had been during the previous night, the weaker the association between stress and positive affect (Studies 1 and 2) and negative affect (Study 2). The association between daily stress and positive or negative affect did not differ as a function of daily snacking (Studies 1 and 2). On stressful days, increasing physical activity or ensuring high sleep quality may buffer adverse effects of stress on affect in young adults. These findings suggest potential targets for health-promotion and stress-prevention programs, which could help reduce the negative impact of stress in young adults. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

Internal dynamics of intense twin beams and their coherence

Czech Academy of Sciences Publication Activity Database

Peřina Jr., J.; Haderka, Ondřej; Allevi, A.; Bondani, M.

2016-01-01

Roč. 6, Feb (2016), 1-8, č. článku 22320. ISSN 2045-2322 R&D Projects: GA ČR GAP205/12/0382 Institutional support: RVO:68378271 Keywords : dynamics of intense * twin beams * pump-depleted parametric * down-conversion * coherence Subject RIV: BH - Optics, Masers, Lasers Impact factor: 4.259, year: 2016

Dynamics of Cavitation Clouds within a High-Intensity Focused Ultrasonic Beam

Science.gov (United States)

2012-03-01

the cloud size. I. INTRODUCTION High-intensity focused ultrasound (HIFU), along with the associated cavitation , is used in a variety of fields. The...Article 3. DATES COVERED (From - To) March 2012- May 2012 4. TITLE AND SUBTITLE Dynamics of Cavitation Clouds within a High-Intensity Focused...in initially quiescent water. The resulting pressure field and behavior of the cavitation bubbles are measured using high-speed digital in-line

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.

Effects of Light Intensity on Growth, Anti-Stress Ability and Immune Function in Yellow Feathered Broilers

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YL Guo

Full Text Available ABSTRACT An experiment was conducted to investigate the effects of light intensity on growth, anti-stress ability, and immune function of yellow feathered broilers. A total of 480 one-day-old male Lingnan yellow feathered broilers were randomly allocated to 4 treatments based on light intensity (1, 5, 20 and 80 lx with 8 replicates of 15 chicks each. The experiment lasted for 63 days. Compared with those under high light intensity, broilers exposed to low light intensity had higher (p<0.05 total antioxidant capacity (T-AOC, glutathione peroxidase (GSH-Px, a-Naphthylacetate esterase (ANAE+, antibody titer, but lower (p<0.05 malonaldehyde (MDA levels and heterophil/lymphocyte ratio (H/L. There was a linear effect for T-AOC(p=0.002, GSH-Px(p≤0.047, MDA (p=0.003, H/L(p≤0.014, ANAE+ (p≤0.044, and antibody titer (p≤0.021 with T-AOC, GSH-Px, ANAE+, and antibody titer increased significantly as light intensity decreased, whereas MDA and H/L were decreased with the decrease in light intensity. These results suggested that broilers under low light intensity could have similar performance, better anti-stress ability, stronger immune function, and more efficient in energy usage as compared with those exposed to high light intensity environment.

ITER vacuum vessel dynamic stress analysis of a disruption

International Nuclear Information System (INIS)

Riemer, B.W.; Conner, D.L.; Strickler, D.J.; Williamson, D.E.

1994-01-01

Dynamic stress analysis of the International Thermonuclear Experimental Reactor vacuum vessel loaded by disruption forces was performed. The deformation and stress results showed strong inertial effects when compared to static analyses. Maximum stress predicted dynamically was 300 MPa, but stress shown by static analysis from loads at the same point in time reached only 80 MPa. The analysis also provided a reaction load history in the vessel's supports which is essential in evaluating support design. The disruption forces were estimated by assuming a 25-MA plasma current decaying at 1 MA/ms while moving vertically. In addition to forces developed within the vessel, vertical loadings from the first wall/strong back assemblies and the divertor were applied to the vessel at their attachment points. The first 50 natural modes were also determined. The first mode's frequency was 6.0 Hz, and its shape is characterized by vertical displacement of the vessel inner leg. The predicted deformation of the vessel appeared similar to its first mode shape combined with radial contraction. Kinetic energy history from the analysis also correlated with the first mode frequency

Quantification of Protein Biomarker Using SERS Nano-Stress Sensing with Peak Intensity Ratiometry

Science.gov (United States)

Goh, Douglas; Kong, Kien Voon; Jayakumar, Perumal; Gong, Tianxun; Dinish, U. S.; Olivo, Malini

We report a surface enhanced Raman spectroscopy (SERS) ratiometry method based on peak intensity coupled in a nano-stress sensing platform to detect and quantify biological molecules. Herein, we employed an antibody-conjugated p-aminothiophenol (ATP) functionalized on a bimetallic-film-over-nanosphere (BMFON) substrate as a sensitive SERS platform to detect human haptoglobin (Hp) protein, which is an acute phase protein and a biomarker for various cancers. Correlation between change in the ATP spectral characteristics and concentration of Hp protein was established by examining the peak intensity ratio at 1572cm-1 and 1592cm-1 that reflects the degree of stress experienced by the aromatic ring of ATP during Hp protein-antibody interaction. Development of this platform shows the potential in developing a low-cost and sensitive SERS sensor for the pre-screening of various biomarkers.

Stress intensity magnification factors for fully circumferential cracks in valve bodies (thick cylinders)

International Nuclear Information System (INIS)

Toor, P.M.

1998-01-01

The stress intensity solutions presented herein were obtained using an energy method in conjunction with a two-dimensional finite element program in order to explicitly account for curvature effect for fully circumferential cracks. The magnification factors for a specific crack depth were calculated by successively loading the crack surface by a uniform, linear, quadratic, and a cubic loading distribution. The magnification factors can be used to calculate the stress intensity factors by superposition method. The functions for each load condition in terms of radius to thickness ratio (R/t) and a fractional distance in terms of crack depth to thickness ratio (a/t) were developed. The validity of these functions is R/t = 1.5 to 10.0 and for 0.0125 ≤ a/t ≤ 0.8125. The functions agree to within 1% of the finite elements solutions for most magnification factors

Low intensity microwave radiation induced oxidative stress, inflammatory response and DNA damage in rat brain.

Science.gov (United States)

Megha, Kanu; Deshmukh, Pravin Suryakantrao; Banerjee, Basu Dev; Tripathi, Ashok Kumar; Ahmed, Rafat; Abegaonkar, Mahesh Pandurang

2015-12-01

Over the past decade people have been constantly exposed to microwave radiation mainly from wireless communication devices used in day to day life. Therefore, the concerns over potential adverse effects of microwave radiation on human health are increasing. Until now no study has been proposed to investigate the underlying causes of genotoxic effects induced by low intensity microwave exposure. Thus, the present study was undertaken to determine the influence of low intensity microwave radiation on oxidative stress, inflammatory response and DNA damage in rat brain. The study was carried out on 24 male Fischer 344 rats, randomly divided into four groups (n=6 in each group): group I consisted of sham exposed (control) rats, group II-IV consisted of rats exposed to microwave radiation at frequencies 900, 1800 and 2450 MHz, specific absorption rates (SARs) 0.59, 0.58 and 0.66 mW/kg, respectively in gigahertz transverse electromagnetic (GTEM) cell for 60 days (2h/day, 5 days/week). Rats were sacrificed and decapitated to isolate hippocampus at the end of the exposure duration. Low intensity microwave exposure resulted in a frequency dependent significant increase in oxidative stress markers viz. malondialdehyde (MDA), protein carbonyl (PCO) and catalase (CAT) in microwave exposed groups in comparison to sham exposed group (pmicrowave exposed groups (pmicrowave exposed animal (pmicrowave exposed groups as compared to their corresponding values in sham exposed group (pmicrowave radiation induces oxidative stress, inflammatory response and DNA damage in brain by exerting a frequency dependent effect. The study also indicates that increased oxidative stress and inflammatory response might be the factors involved in DNA damage following low intensity microwave exposure. Copyright © 2015 Elsevier Inc. All rights reserved.

Prediction of flow- induced dynamic stress in an axial pump impeller using FEM

International Nuclear Information System (INIS)

Gao, J Y; Hou, Y S; Xi, S Z; Cai, Z H; Yao, P P; Shi, H L

2013-01-01

Axial pumps play an important role in water supply and flood control projects. Along with growing requirements for high reliability and large capacity, the dynamic stress of axial pumps has become a key problem. Unsteady flow is a significant reason which results structural dynamic stress of a pump. This paper reports on a flow-induced dynamic stress simulation in an axial pump impeller at three flow conditions by using FEM code. The pressure pulsation obtained from flow simulation using CFD code was set as the force boundary condition. The results show that the maximum stress of impeller appeared at joint between blade and root flange near trailing edge or joint between blade and root flange near leading edge. The dynamic stress of the two zones was investigated under three flow conditions (0.8Q d , 1.0Q d , 1.1Q d ) in time domain and frequency domain. The frequencies of stress at zones of maximum stress are 22.9Hz and 37.5Hz as the fundamental frequency and its harmonics. The fundamental frequencies are nearly equal to vane passing frequency (22.9 Hz) and 3 times blade passing frequency (37.5Hz). The first dominant frequency at zones of maximum stress is equal to the vane passing frequency due to rotor-stator interaction between the vane and the blade. This study would be helpful for axial pumps in reducing stress, improving structure design and fatigue life

Stress Intensity Factor for Interface Cracks in Bimaterials Using Complex Variable Meshless Manifold Method

Directory of Open Access Journals (Sweden)

Hongfen Gao

2014-01-01

Full Text Available This paper describes the application of the complex variable meshless manifold method (CVMMM to stress intensity factor analyses of structures containing interface cracks between dissimilar materials. A discontinuous function and the near-tip asymptotic displacement functions are added to the CVMMM approximation using the framework of complex variable moving least-squares (CVMLS approximation. This enables the domain to be modeled by CVMMM without explicitly meshing the crack surfaces. The enriched crack-tip functions are chosen as those that span the asymptotic displacement fields for an interfacial crack. The complex stress intensity factors for bimaterial interfacial cracks were numerically evaluated using the method. Good agreement between the numerical results and the reference solutions for benchmark interfacial crack problems is realized.

Comparison of erythrocyte dynamics in shear flow under different stress-free configurations

Science.gov (United States)

Cordasco, Daniel; Yazdani, Alireza; Bagchi, Prosenjit

2014-04-01

An open question that has persisted for decades is whether the cytoskeleton of a red blood cell is stress-free or under a stress. This question is important in the context of theoretical modeling of cellular motion under a flowing condition where it is necessary to make an assumption about the stress-free state. Here, we present a 3D numerical study to compare the cell dynamics in a simple shear flow under two different stress-free states, a biconcave discocyte representing the resting shape of the cell, and a nearly spherical oblate shape. We find that whether the stress-free states make a significant difference or not depends on the viscosity of the suspending medium. If the viscosity is close to that of blood plasma, the two stress-free states do not show any significant difference in cell dynamics. However, when the suspending medium viscosity is well above that of the physiological range, as in many in vitro studies, the shear rate separating the tank-treading and tumbling dynamics is observed to be higher for the biconcave stress-free state than the spheroidal state. The former shows a strong shape oscillation with repeated departures from the biconcave shape, while the latter shows a nearly stable biconcave shape. It is found that the cell membrane in the biconcave stress-free state is under a compressive stress and a weaker bending force density, leading to a periodic compression of the cell. The shape oscillation then leads to a higher energy barrier against membrane tank-tread leading to an early transition to tumbling. However, if the cells are released with a large off-shear plane angle, the oscillations can be suppressed due to an azimuthal motion of the membrane along the vorticity direction leading to a redistribution of the membrane points and lowering of the energy barrier, which again results in a nearly similar behavior of the cells under the two different stress-free states. A variety of off-shear plane dynamics is observed, namely, rolling

Intensive Research Program on Advances in Nonsmooth Dynamics 2016

CERN Document Server

Jeffrey, Mike; Lázaro, J; Olm, Josep

2017-01-01

This volume contains extended abstracts outlining selected talks and other selected presentations given by participants throughout the "Intensive Research Program on Advances in Nonsmooth Dynamics 2016", held at the Centre de Recerca Matemàtica (CRM) in Barcelona from February 1st to April 29th, 2016. They include brief research articles reporting new results, descriptions of preliminary work or open problems, and outlines of prominent discussion sessions. The articles are all the result of direct collaborations initiated during the research program. The topic is the theory and applications of Nonsmooth Dynamics. This includes systems involving elements of: impacting, switching, on/off control, hybrid discrete-continuous dynamics, jumps in physical properties, and many others. Applications include: electronics, climate modeling, life sciences, mechanics, ecology, and more. Numerous new results are reported concerning the dimensionality and robustness of nonsmooth models, shadowing variables, numbers of limit...

Relativistic classical and quantum dynamics in intense crossed laser beams of various polarizations

Directory of Open Access Journals (Sweden)

M. Verschl

2007-02-01

Full Text Available The dynamics of an electron in crossed laser fields is investigated analytically. Two different standing wave configurations are compared. The counterpropagating laser waves are either linearly or circularly polarized. Both configurations have in common that there are one-dimensional trajectories on which the electron can oscillate with vanishing Lorentz force. The dynamics is analyzed for the situations when the electron moves in the vicinity of these ideal axes. If the laser intensities imply nonrelativistic electron dynamics, the system is described quantum mechanically. A semiclassical treatment renders the strongly relativistic regime accessible as well. To describe relativistic wave packets, the results of the classical analysis are employed for a Monte Carlo ensemble. This allows for a comparison of the wave packet dynamics for both configurations in the strongly relativistic regime. It is found for certain cases that relativity slows down the dynamics, i.e., for higher laser intensities, wave packet spreading and the drift away from the ideal axis of vanishing Lorentz force are shown to be increasingly suppressed.

Conceptualizing the dynamics of workplace stress: a systems-based study of nursing aides

OpenAIRE

Jetha, Arif; Kernan, Laura; Kurowski, Alicia

2017-01-01

Background Workplace stress is a complex phenomenon that may often be dynamic and?evolving over time. Traditional linear modeling does not allow representation of recursive feedback loops among the implicated factors. The objective of this study was to develop a multidimensional system dynamics model (SDM) of workplace stress among nursing aides and conduct simulations to illustrate how changes in psychosocial perceptions and workplace factors might influence workplace stress over time. Metho...

Stress-intensity factors for surface cracks in pipes: a computer code for evaluation by use of influence functions. Final report

International Nuclear Information System (INIS)

Dedhia, D.D.; Harris, D.O.

1982-06-01

A user-oriented computer program for the evaluation of stress intensity factors for cracks in pipes is presented. Stress intensity factors for semi-elliptical, complete circumferential and long longitudinal cracks can be obtained using this computer program. The code is based on the method of influence functions which makes it possible to treat arbitrary stresses on the plane of the crack. The stresses on the crack plane can be entered as a mathematical or tabulated function. A user's manual is included in this report. Background information is also included

Review and synthesis of stress intensity factor solutions applicable to cracks in bolts

International Nuclear Information System (INIS)

James, L.A.; Mills, W.J.

1988-01-01

The available literature for stress intensity factor solutions for cracks in round bars, both threaded and unthreaded, subjected to either tension or bending, is reviewed. The results are synthesized into a form that is appropriate for the analysis of bolts and studs. (author)

The Effects of Aromatherapy on Intensive Care Unit Patients' Stress and Sleep Quality: A Nonrandomised Controlled Trial

Science.gov (United States)

Cho, Eun Hee; Lee, Mi-Young

2017-01-01

Background Stress has both physiological and psychological effects and can negatively impact patients' treatment and recovery. We examined whether the aromatherapy alleviated patients' stress and improved their sleep quality and provided data that can be utilized in clinical settings. Methods This was a nonrandomised controlled experimental study. Participants included lucid adult patients who were admitted to the intensive care unit and had spent more than two nights there. The experimental treatment required participants to engage in deep breathing with essential oils as part of the aromatherapy. The control group was instructed to go to sleep without receiving the lavender aroma oil. Results The experimental group and control group showed a significant difference in perceived stress (F = 60.11, p aromatherapy alleviated stress and improved sleep quality in intensive care unit patients after 2 days of the experimental treatment. These results demonstrate that aromatherapy affects stress and sleep quality, thus indicating its value in nursing interventions. This trial is registered with KCT0002344. PMID:29375641

Experimental Study on Wing Crack Behaviours in Dynamic-Static Superimposed Stress Field Using Caustics and High-Speed Photography

Directory of Open Access Journals (Sweden)

L.Y. Yang

2014-07-01

Full Text Available During the drill-and-blast progress in rock tunnel excavation of great deep mine, rock fracture is evaluated by both blasting load and pre-exiting earth stress (pre-compression. Many pre-existing flaws in the rock mass, like micro-crack, also seriously affect the rock fracture pattern. Under blasting load with pre-compression, micro-cracks initiate, propagate and grow to be wing cracks. With an autonomous design of static-dynamic loading system, dynamic and static loads were applied on some PMMA plate specimen with pre-existing crack, and the behaviour of the wing crack was tested by caustics corroding with a high-speed photography. Four programs with different static loading modes that generate different pre-compression fields were executed, and the length, velocity of the blasting wing crack and dynamic stress intensity factor (SIF at the wing crack tip were analyzed and discussed. It is found that the behaviour of blasting-induced wing crack is affected obviously by blasting and pre-compression. And pre-compression, which is vertical to the direction of the wing crack propagation, hinders the crack propagation. Furthermore, the boundary constraint condition plays an important role on the behaviour of blasting induced crack during the experiment.

Stress, coping and burnout among Intensive Care Unit nursing staff: associated factors.

Science.gov (United States)

Andolhe, Rafaela; Barbosa, Ricardo Luis; Oliveira, Elaine Machado de; Costa, Ana Lúcia Siqueira; Padilha, Katia Grillo

2015-02-01

Objective To investigate emotional stress, coping and burnout among nursing staff and their association with biosocial factors and characteristics of work in Intensive Care Units (ICU). Method This was a cross-sectional study, conducted in eight ICUs at a teaching hospital in the city of São Paulo, Brazil, in October 2012. Biosocial data and information about the professionals' work was gathered, and they were given the Scale of Occupational Stress, Scale of Occupational Coping, List of Signs and Symptoms of Stress and the Maslach Burnout Inventory. Results The study sample consisted of 287 subjects, predominately women, with partners and children. Most professionals presented moderate stress levels and control as a coping strategy (74.47% and 79.93%, respectively), and burnout was present among 12.54%. Factors associated with stress were related to working conditions. The most prevalent protective factors were having a partner, working in the clinical ICU and liking work, while adequate amount of sleep was a protective factor for burnout. Conclusion Control of the working environment and adequate sleep are decisive and protective factors in dealing with situations of occupational stress.

Functional Neuroimaging of Emotionally Intense Autobiographical Memories in Post-Traumatic Stress Disorder

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St. Jacques, Peggy L.; Botzung, Anne; Miles, Amanda; Rubin, David C.

2010-01-01

Post-traumatic stress disorder (PTSD) affects regions that support autobiographical memory (AM) retrieval, such as the hippocampus, amygdala and ventral medial prefrontal cortex (PFC). However, it is not well understood how PTSD may impact the neural mechanisms of memory retrieval for the personal past. We used a generic cue method combined with parametric modulation analysis and functional MRI (fMRI) to investigate the neural mechanisms affected by PTSD symptoms during the retrieval of a large sample of emotionally intense AMs. There were three main results. First, the PTSD group showed greater recruitment of the amygdala/hippocampus during the construction of negative versus positive emotionally intense AMs, when compared to controls. Second, across both the construction and elaboration phases of retrieval the PTSD group showed greater recruitment of the ventral medial PFC for negatively intense memories, but less recruitment for positively intense memories. Third, the PTSD group showed greater functional coupling between the ventral medial PFC and the amygdala for negatively intense memories, but less coupling for positively intense memories. In sum, the fMRI data suggest that there was greater recruitment and coupling of emotional brain regions during the retrieval of negatively intense AMs in the PTSD group when compared to controls. PMID:21109253

Role-based support for intensive care nursing : A designer's perspective

NARCIS (Netherlands)

Melles, M.

2011-01-01

Design goals and design directions are formulated for the (digital) support of non-technical nursing tasks and skills in the intensive care unit (ICU), such as organizing work, evaluating care, coping with stress and dealing with poor team dynamics. A conceptual framework for ICU nursing was

Transient electromagnetic and dynamic structural analyses of a blanket structure with coupling effects

Energy Technology Data Exchange (ETDEWEB)

Koganezawa, K. [Mitsubishi Atomic Power Industries, Inc., Yokohama (Japan); Kushiyama, M. [Mitsubishi Atomic Power Industries, Inc., Yokohama (Japan); Niikura, S. [Mitsubishi Atomic Power Industries, Inc., Yokohama (Japan); Kudough, F. [Mitsubishi Atomic Power Industries, Inc., Yokohama (Japan); Onozuka, M. [Mitsubishi Heavy Industries Ltd., Yokohama (Japan); Koizumi, K. [Japan Atomic Energy Research Inst., Ibaraki (Japan)

1995-12-31

Transient electromagnetic and dynamic structural analyses of a blanket structure in the fusion experimental reactor (FER) under a plasma disruption event and a vertical displacement event (VDE) have been performed to investigate the dynamic structural characteristics and the feasibility of the structure. Coupling effects between eddy currents and dynamic deflections have also been taken into account in these analyses. In this study, the inboard blanket was employed because of our computer memory limitation. A 1/192 segment model of a full torus was analyzed using the analytical code, EDDYCUFF. In the plasma disruption event, the maximum magnetic pressure caused by eddy currents and poloidal fields was 1.2MPa. The maximum stress intensity by this magnetic pressure was 114MPa. In the VDE, the maximum magnetic pressure was 2.4MPa and the maximum stress intensity was 253MPa. This stress was somewhat beyond the allowable stress limit. Therefore, the blanket structure and support design should be reviewed to reduce the stress to a suitable value. In summary, the dynamic structural characteristics and design issues of the blanket structure have been identified. (orig.).

Stress and Protists: No life without stress.

Science.gov (United States)

Slaveykova, Vera; Sonntag, Bettina; Gutiérrez, Juan Carlos

2016-08-01

We report a summary of the symposium "Stress and Protists: No life without stress", which was held in September 2015 on the VII European Congress of Protistology in partnership with the International Society of Protistologists (Seville, Spain). We present an overview on general comments and concepts on cellular stress which can be also applied to any protist. Generally, various environmental stressors may induce similar cell responses in very different protists. Two main topics are reported in this manuscript: (i) metallic nanoparticles as environmental pollutants and stressors for aquatic protists, and (ii) ultraviolet radiation - induced stress and photoprotective strategies in ciliates. Model protists such as Chlamydomonas reinhardtii and Tetrahymena thermophila were used to assess stress caused by nanoparticles while stress caused by ultraviolet radiation was tested with free living planktonic ciliates as well as with the symbiont-bearing model ciliate Paramecium bursaria. For future studies, we suggest more intensive analyses on protist stress responses to specific environmental abiotic and/or biotic stressors at molecular and genetic levels up to ecological consequences and food web dynamics. Copyright © 2016 Elsevier GmbH. All rights reserved.

Effect of ubiquinol supplementation on biochemical and oxidative stress indexes after intense exercise in young athletes.

Science.gov (United States)

Orlando, Patrick; Silvestri, Sonia; Galeazzi, Roberta; Antonicelli, Roberto; Marcheggiani, Fabio; Cirilli, Ilenia; Bacchetti, Tiziana; Tiano, Luca

2018-12-01

Physical exercise significantly impacts the biochemistry of the organism. Ubiquinone is a key component of the mitochondrial respiratory chain and ubiquinol, its reduced and active form, is an emerging molecule in sport nutrition. The aim of this study was to evaluate the effect of ubiquinol supplementation on biochemical and oxidative stress indexes after an intense bout of exercise. 21 male young athletes (26 + 5 years of age) were randomized in two groups according to a double blind cross-over study, either supplemented with ubiquinol (200 mg/day) or placebo for 1 month. Blood was withdrawn before and after a single bout of intense exercise (40 min run at 85% maxHR). Physical performance, hematochemical parameters, ubiquinone/ubiquinol plasma content, intracellular reactive oxygen species (ROS) level, mitochondrial membrane depolarization, paraoxonase activity and oxidative DNA damage were analyzed. A single bout of intense exercise produced a significant increase in most hematochemical indexes, in particular CK and Mb while, on the contrary, normalized coenzyme Q 10 plasma content decreased significantly in all subjects. Ubiquinol supplementation prevented exercise-induced CoQ deprivation and decrease in paraoxonase activity. Moreover at a cellular level, in peripheral blood mononuclear cells, ubiquinol supplementation was associated with a significant decrease in cytosolic ROS while mitochondrial membrane potential and oxidative DNA damage remained unchanged. Data highlights a very rapid dynamic of CoQ depletion following intense exercise underlying an increased demand by the organism. Ubiquinol supplementation minimized exercise-induced depletion and enhanced plasma and cellular antioxidant levels but it was not able to improve physical performance indexes or markers of muscular damage.

Intensive care diaries reduce new onset post traumatic stress disorder following critical illness

DEFF Research Database (Denmark)

Jones, Christina; Bäckman, Carl; Capuzzo, Maurizia

2010-01-01

Patients recovering from critical illness have been shown to be at risk of developing Post Traumatic Stress disorder (PTSD). This study was to evaluate whether a prospectively collected diary of a patient's intensive care unit (ICU) stay when used during convalescence following critical illness...

Posttraumatic stress in intensive care unit survivors - a prospective study

DEFF Research Database (Denmark)

Ratzer, Mette; Brink, Ole; Knudsen, Linda

2014-01-01

Aims: This study aimed to estimate the prevalence of severe Posttraumatic Stress Disorder (PTSD) symptoms and to identify factors associated with PTSD in survivors of intensive care unit (ICU) treatment following traumatic injury. Methods: Fifty-two patients who were admitted to an ICU through...... the emergency ward following traumatic injury were prospectively followed. Information on injury severity and ICU treatment were obtained through medical records. Demographic information and measures of acute stress symptoms, experienced social support, coping style, sense of coherence (SOC) and locus...... of control were assessed within one-month post-accident (T1). At the six months follow-up (T2), PTSD was assessed with the Harvard Trauma Questionnaire (HTQ). Results: In the six months follow-up, 10 respondents (19.2%) had HTQ total scores reaching a level suggestive of PTSD (N = 52), and 11 respondents (21...

Personality, stress and coping in intensive care nurses: a descriptive exploratory study.

Science.gov (United States)

Burgess, Lorraine; Irvine, Fiona; Wallymahmed, Akhtar

2010-01-01

The aim of the study was to investigate the relationship between personality traits, perception of workplace stress and coping among intensive care unit (ICU) nurses. Research has indicated that ICUs are stressful environments. There is a tendency for research studies to investigate causes of stress and ways of coping, but few studies, particularly in recent years, have considered the personality traits of the staff who thrive in this challenging environment, the work stress they perceive and the coping strategies they use. A convenience sample of critical care nurses (n = 46) completed three standardised questionnaires during September 2007: the revised NEO personality inventory (NEO-PI-R); the nurses stress scale (NSI) and the Brief Coping Orientations to Problems Experienced (COPE) scale. ICU nurses did not perceive their workplaces to be stressful. Certain personality traits, openness, agreeableness and conscientiousness, were associated with problem-solving coping strategies such as active planning and reframing. Openness and extraversion were associated with less perceived stress from the 'patients and relatives' dimension of the NSI; there were also negative correlations between conscientiousness and the 'workload stress' and stress from lack of 'confidence and competence' dimensions of the NSI. Certain personality traits may have a buffering effect on workplace stress. Pre-employment screening to identify staff that exhibit personality and coping traits associated with low perceived stress may be considered as part of the recruitment strategy to address problems relating to stress, sickness and retention. The retention and recruitment of staff who have lower perceived workplace stress and who utilise problem-focused coping may result in less reported absences and fewer critical incidents and errors.

Effect of Exercise Intensity on Neurotrophic Factors and Blood-Brain Barrier Permeability Induced by Oxidative-Nitrosative Stress in Male College Students.

Science.gov (United States)

Roh, Hee-Tae; Cho, Su-Youn; Yoon, Hyung-Gi; So, Wi-Young

2017-06-01

We investigated the effects of aerobic exercise intensity on oxidative-nitrosative stress, neurotrophic factor expression, and blood-brain barrier (BBB) permeability. Fifteen healthy men performed treadmill running under low-intensity (LI), moderate-intensity (MI), and high-intensity (HI) conditions. Blood samples were collected immediately before exercise (IBE), immediately after exercise (IAE), and 60 min after exercise (60MAE) to examine oxidative-nitrosative stress (reactive oxygen species [ROS]; nitric oxide [NO]), neurotrophic factors (brain-derived neurotrophic factor [BDNF]; nerve growth factor [NGF]), and blood-brain barrier (BBB) permeability (S-100β; neuron-specific enolase). ROS concentration significantly increased IAE and following HI (4.9 ± 1.7 mM) compared with that after LI (2.8 ± 1.4 mM) exercise (p exercise (p exercise (p exercise (p exercise (p .05). Moderate- and/or high-intensity exercise may induce higher oxidative-nitrosative stress than may low-intensity exercise, which can increase peripheral neurotrophic factor levels by increasing BBB permeability.

Estimation of flow stress of radiation induced F/M steels using molecular dynamics and discrete dislocation dynamics approach

International Nuclear Information System (INIS)

More, Ameya; Dutta, B.K.; Durgaprasad, P.V.; Arya, A.K.

2012-01-01

Fe-Cr based Ferritic/Martensitic (F/M) steels are the candidate structural materials for future fusion reactors. In this work, a multi-scale approach comprising atomistic Molecular Dynamics (MD) simulations and Discrete Dislocation Dynamics (DDD) simulations are used to model the effect of irradiation dose on the flow stress of F/M steels. At the atomic scale, molecular dynamics simulations are used to study the dislocation interaction with irradiation induced defects, i.e. voids and He bubbles. Whereas, the DDD simulations are used to estimate the change in flow stress of the material as a result of irradiation hardening. (author)

High-Intensity Exercise Induced Oxidative Stress and Skeletal Muscle Damage in Postpubertal Boys and Girls: A Comparative Study.

Science.gov (United States)

Pal, Sangita; Chaki, Biswajit; Chattopadhyay, Sreya; Bandyopadhyay, Amit

2018-04-01

Pal, S, Chaki, B, Chattopadhyay, S, and Bandyopadhyay, A. High-intensity exercise induced oxidative stress and skeletal muscle damage in post-pubertal boys and girls: a comparative study. J Strength Cond Res 32(4): 1045-1052, 2018-The purpose of this study was to examine the sex variation in high-intensity exercise induced oxidative stress and muscle damage among 44 sedentary postpubertal boys and girls through estimation of postexercise release pattern of muscle damage markers like creatine kinase, lactate dehydrogenase (LDH), alanine aminotransferase (ALT), aspartate aminotransferase (AST) and oxidative stress markers like extent of lipid peroxidation (thiobarbituric acid-reactive substances) and catalase activity. Muscle damage markers like creatine kinase, LDH, ALT, and AST were measured before, immediately after, and 24 and 48 hours after high-intensity incremental treadmill running. Oxidative stress markers like thiobarbituric acid-reactive substances and catalase activity were estimated before and immediately after the exercise. Lipid peroxidation and serum catalase activity increased significantly in both groups after exercise (p exercise level at 24 and 48 hours after exercise in both the sexes, (p exercise, the pattern of postexercise release of these markers were found to be similar in both the groups. Accordingly, it has been concluded from the present investigation that high-intensity exercise induces significant oxidative stress and increases indices of skeletal muscle damage in both postpubertal girls and boys. However, postpubertal girls are relatively better protected from oxidative stress and muscle damage as compared to the boys of similar age and physical activity level. It is further evident that sex difference may not be apparent for all the biomarkers of muscle damage in this age group.

Influences of sex, type and intensity of emotion in the ecognition of static and dynamic facial expressions*

Directory of Open Access Journals (Sweden)

Nelson Torro-Alves

2013-01-01

Full Text Available Ecological validity of static and intense facial expressions in emotional recognition has been questioned. Recent studies have recommended the use of facial stimuli more compatible to the natural conditions of social interaction, which involves motion and variations in emotional intensity. In this study, we compared the recognition of static and dynamic facial expressions of happiness, fear, anger and sadness, presented in four emotional intensities (25 %, 50 %, 75 % and 100 %. Twenty volunteers (9 women and 11 men, aged between 19 and 31 years, took part in the study. The experiment consisted of two sessions in which participants had to identify the emotion of static (photographs and dynamic (videos displays of facial expressions on the computer screen. The mean accuracy was submitted to an Anova for repeated measures of model: 2 sexes x [2 conditions x 4 expressions x 4 intensities]. We observed an advantage for the recognition of dynamic expressions of happiness and fear compared to the static stimuli (p < .05. Analysis of interactions showed that expressions with intensity of 25 % were better recognized in the dynamic condition (p < .05. The addition of motion contributes to improve recognition especially in male participants (p < .05. We concluded that the effect of the motion varies as a function of the type of emotion, intensity of the expression and sex of the participant. These results support the hypothesis that dynamic stimuli have more ecological validity and are more appropriate to the research with emotions.

Pulmonary artery wave propagation and reservoir function in conscious man: impact of pulmonary vascular disease, respiration and dynamic stress tests.

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Su, Junjing; Manisty, Charlotte; Simonsen, Ulf; Howard, Luke S; Parker, Kim H; Hughes, Alun D

2017-10-15

Wave travel plays an important role in cardiovascular physiology. However, many aspects of pulmonary arterial wave behaviour remain unclear. Wave intensity and reservoir-excess pressure analyses were applied in the pulmonary artery in subjects with and without pulmonary hypertension during spontaneous respiration and dynamic stress tests. Arterial wave energy decreased during expiration and Valsalva manoeuvre due to decreased ventricular preload. Wave energy also decreased during handgrip exercise due to increased heart rate. In pulmonary hypertension patients, the asymptotic pressure at which the microvascular flow ceases, the reservoir pressure related to arterial compliance and the excess pressure caused by waves increased. The reservoir and excess pressures decreased during Valsalva manoeuvre but remained unchanged during handgrip exercise. This study provides insights into the influence of pulmonary vascular disease, spontaneous respiration and dynamic stress tests on pulmonary artery wave propagation and reservoir function. Detailed haemodynamic analysis may provide novel insights into the pulmonary circulation. Therefore, wave intensity and reservoir-excess pressure analyses were applied in the pulmonary artery to characterize changes in wave propagation and reservoir function during spontaneous respiration and dynamic stress tests. Right heart catheterization was performed using a pressure and Doppler flow sensor tipped guidewire to obtain simultaneous pressure and flow velocity measurements in the pulmonary artery in control subjects and patients with pulmonary arterial hypertension (PAH) at rest. In controls, recordings were also obtained during Valsalva manoeuvre and handgrip exercise. The asymptotic pressure at which the flow through the microcirculation ceases, the reservoir pressure related to arterial compliance and the excess pressure caused by arterial waves increased in PAH patients compared to controls. The systolic and diastolic rate constants

Stress field control during large caldera-forming eruptions

Directory of Open Access Journals (Sweden)

Antonio Costa

2016-10-01

Full Text Available Crustal stress field can have a significant influence on the way magma is channelled through the crust and erupted explosively at the surface. Large Caldera Forming Eruptions (LCFEs can erupt hundreds to thousands of cubic kilometres of magma in a relatively short time along fissures under the control of a far-field extensional stress. The associated eruption intensities are estimated in the range 109 - 1011 kg/s. We analyse syn-eruptive dynamics of LCFEs, by simulating numerically explosive flow of magma through a shallow dyke conduit connected to a magma chamber that in turn is fed by a deeper magma reservoir, both under the action of an extensional far-field stress. Results indicate that huge amounts of high viscosity silicic magma can be erupted over timescales of a few to several hours. Our study provides answers to outstanding questions relating to the intensity and duration of catastrophic volcanic eruptions in the past. In addition, it presents far-reaching implications for the understanding of dynamics and intensity of large-magnitude volcanic eruptions on Earth and to highlight the necessity of a future research to advance our knowledge of these rare catastrophic events.

Effect of loading rate on dynamic fracture of reaction bonded silicon nitride

Science.gov (United States)

Liaw, B. M.; Kobayashi, A. S.; Emery, A. F.

1986-01-01

Wedge-loaded, modified tapered double cantilever beam (WL-MTDCB) specimens under impact loading were used to determine the room temperature dynamic fracture response of reaction bonded silicon nitride (RBSN). The crack extension history, with the exception of the terminal phase, was similar to that obtained under static loading. Like its static counterpart, a distinct crack acceleration phase, which was not observed in dynamic fracture of steel and brittle polymers, was noted. Unlike its static counterpart, the crack continued to propagate at nearly its terminal velocity under a low dynamic stress intensity factor during the terminal phase of crack propagation. These and previously obtained results for glass and RBSN show that dynamic crack arrest under a positive dynamic stress intensity factor is unlikely in static and impact loaded structural ceramics.

Characterizing the intra-urban spatiotemporal dynamics of High Heat Stress Zones (Hotspots)

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Shreevastava, A.; Rao, P. S.; McGrath, G. S.

2017-12-01

In this study, we present an innovative framework to characterize the spatio-temporal dynamics of High Heat Stress Zones (Hot spots) created within an Urban area in the event of a Heat Wave. Heat waves are one of the leading causes of weather-related human mortality in many countries, and cities receive its worst brunt. The extreme heat stress within urban areas is often a synergistic combination of large-scale meteorological events, and the locally exacerbated impacts due to Urban Heat Islands (UHI). UHI is typically characterized as the difference between mean temperature of the urban and rural area. As a result, it fails to capture the significant variability that exists within the city itself. This variability arises from the diverse and complex spatial geometries of cities. Previous studies that have attempted to quantify the heat stress at an intra-urban scale are labor intensive, expensive, and difficult to emulate globally as they rely on availability of extensive data and their assimilation. The proposed study takes advantage of the well-established notion of fractal properties of cities to make the methods scalable to other cities where in-situ observational data might not be available. As an input, land surface temperatures are estimated using Landsat data. Using clustering analysis, we probe the emergence of thermal hotspots. The probability distributions (PD) of these hotspots are found to follow a power-law distribution in agreement with fractal characteristics of the city. PDs of several archetypical cities are then investigated to compare the effect of different spatial structures (e.g. monocentric v/s polycentric, sprawl v/s compact). Further, the temporal variability of the distributions on a diurnal as well as a seasonal scale is discussed. Finally, the spatiotemporal dynamics of the urban hotspots under a heat-wave (E.g. Delhi Heat wave, 2015) are compared against the non-heat wave scenarios. In summary, a technique that is globally adaptive and

Communicating with parents in neonatal intensive care units: The impact on parental stress.

Science.gov (United States)

Enke, Christian; Oliva Y Hausmann, Andrés; Miedaner, Felix; Roth, Bernhard; Woopen, Christiane

2017-04-01

To analyse stress in parents whose infants with very low birth weight have just concluded high-level care in a Neonatal Intensive Care Unit (NICU). More specifically, we aimed 1) to identify groups of parents in the NICU who are particularly at risk of experiencing stress, and 2) to explore the effects of clinical staffś communication on parental stress. Our multi-center-study evaluated views from 1277 parents about care for 923 infants in 66 German NICUs. Answers were linked with separately evaluated medical outcomes of the infants. Separate generalised mixed models estimated the influence of personal, medical and communication-related characteristics on specific parental stress. Parents of a younger age and those of infants with severe prognoses were more likely to experience stress. While empathetic communication as one aspect of staffś communication was shown as appropriate in reducing parental stress, an initial introduction and the quantity of information were only slightly associated with lower levels of stress. Results provide evidence for the need to involve parents empathetically from the beginning of their child's stay in the NICU. Staff in the NICU should communicate empathetically and help to reduce stress in parents particularly at risk. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Oxidative stress and nitrite dynamics under maximal load in elite athletes: relation to sport type.

Science.gov (United States)

Cubrilo, Dejan; Djordjevic, Dusica; Zivkovic, Vladimir; Djuric, Dragan; Blagojevic, Dusko; Spasic, Mihajlo; Jakovljevic, Vladimir

2011-09-01

Maximal workload in elite athletes induces increased generation of reactive oxygen/nitrogen species (RONS) and oxidative stress, but the dynamics of RONS production are not fully explored. The aim of our study was to examine the effects of long-term engagement in sports with different energy requirements (aerobic, anaerobic, and aerobic/anaerobic) on oxidative stress parameters during progressive exercise test. Concentrations of lactates, nitric oxide (NO) measured through stabile end product-nitrites (NO(2) (-)), superoxide anion radical (O(2) (•-)), and thiobarbituric reactive substances (TBARS) as index of lipid peroxidation were determined in rest, after maximal workload, and at 4 and 10th min of recovery in blood plasma of top level competitors in rowing, cycling, and taekwondo. Results showed that sportmen had similar concentrations of lactates and O(2) (•-) in rest. Nitrite concentrations in rest were the lowest in taekwondo fighters, while rowers had the highest levels among examined groups. The order of magnitude for TBARS level in the rest was bicycling > taekwondo > rowing. During exercise at maximal intensity, the concentration of lactate significantly elevated to similar levels in all tested sportsmen and they were persistently elevated during recovery period of 4 and 10 min. There were no significant changes in O(2) (•-), nitrite, and TBARS levels neither at the maximum intensity of exercise nor during the recovery period comparing to the rest period in examined individuals. Our results showed that long term different training strategies establish different basal nitrites and lipid peroxidation levels in sportmen. However, progressive exercise does not influence basal nitrite and oxidative stress parameters level neither at maximal load nor during the first 10 min of recovery in sportmen studied.

Short-term intense exercise training reduces stress markers and alters the transcriptional response to exercise in skeletal muscle.

Science.gov (United States)

Hinkley, J Matthew; Konopka, Adam R; Suer, Miranda K; Harber, Matthew P

2017-03-01

The purpose of this investigation was to examine the influence of short-term intense endurance training on cycling performance, along with the acute and chronic signaling responses of skeletal muscle stress and stability markers. Ten recreationally active subjects (25 ± 2 yr, 79 ± 3 kg, 47 ± 2 ml·kg -1 ·min -1 ) were studied before and after a 12-day cycling protocol to examine the effects of short-term intense (70-100% V̇o 2max ) exercise training on resting and exercise-induced regulation of molecular factors related to skeletal muscle cellular stress and protein stability. Skeletal muscle biopsies were taken at rest and 3 h following a 20-km cycle time trial on days 1 and 12 to measure mRNA expression and protein content. Training improved ( P stress. The maintenance in the myocellular environment may be due to synthesis of cytoprotective markers, along with enhanced degradation of damage proteins, as training tended ( P short-term intense training enhances protein stability, creating a cellular environment capable of resistance to exercise-induced stress, which may be favorable for adaptation. Copyright © 2017 the American Physiological Society.

Intensive skills week for military medical students increases technical proficiency, confidence, and skills to minimize negative stress.

Science.gov (United States)

Mueller, Genevieve; Hunt, Bonnie; Wall, Van; Rush, Robert; Molof, Alan; Schoeff, Jonathan; Wedmore, Ian; Schmid, James; Laporta, Anthony

2012-01-01

The effects of stress induced cortisol on learning and memory is well documented in the literature.1-3 Memory and learning are enhanced at low levels while high levels are detrimental. Repetitive training in stressful situations enables management of the stress response4 as demonstrated by the high intensity training military members undergo to prepare for tactical situations. Appropriate management of one?s stress response is critical in the medical field, as the negative effects of stress can potentially hinder life-saving procedures and treatments. This also applies to physicians-in-training as they learn and practice triage, emergency medicine, and surgical skills prior to graduation. Rocky Vista University?s Military Medicine Honor?s Track (MMHT) held a week long high-intensity emergency medicine and surgical Intensive Skills Week (ISW), facilitated by military and university physicians, to advance students? skills and maximize training using the Human Worn Partial Surgical Task Simulator (Cut Suit). The short-term goal of the ISW was to overcome negative stress responses to increase confidence, technical and non-technical knowledge, and skill in surgery and emergency medicine in an effort to improve performance as third-year medical students. The long-term goal was to enhance performance and proficiency in residency and future medical practice. The metrics for the short-term goals were the focus of this pilot study. Results show an increase in confidence and decrease in perceived stress as well as statistically significant improvements in technical and non-technical skills and surgical instrumentation knowledge throughout the week. There is a correlative benefit to physician and non-physician military personnel, especially Special Operations Forces (SOF) medical personnel, from developing and implementing similar training programs when live tissue or cadaver models are unavailable or unfeasible. 2012.

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.

Dynamic energy release rate in couple-stress elasticity

International Nuclear Information System (INIS)

Morini, L; Piccolroaz, A; Mishuris, G

2013-01-01

This paper is concerned with energy release rate for dynamic steady state crack problems in elastic materials with microstructures. A Mode III semi-infinite crack subject to loading applied on the crack surfaces is considered. The micropolar behaviour of the material is described by the theory of couple-stress elasticity developed by Koiter. A general expression for the dynamic J-integral including both traslational and micro-rotational inertial contributions is derived, and the conservation of this integral on a path surrounding the crack tip is demonstrated

Dynamic jump intensities and risk premia : Evidence from S&P500 returns and options

NARCIS (Netherlands)

Christoffersen, P.; Jacobs, K.; Ornthanalai, C.

2012-01-01

We build a new class of discrete-time models that are relatively easy to estimate using returns and/or options. The distribution of returns is driven by two factors: dynamic volatility and dynamic jump intensity. Each factor has its own risk premium. The models significantly outperform standard

Time-course changes of oxidative stress response to high-intensity discontinuous training versus moderate-intensity continuous training in masters runners.

Directory of Open Access Journals (Sweden)

Alessandra Vezzoli

Full Text Available Beneficial systemic effects of regular physical exercise have been demonstrated to reduce risks of a number of age-related disorders. Antioxidant capacity adaptations are amongst these fundamental changes in response to exercise training. However, it has been claimed that acute physical exercise performed at high intensity (>60% of maximal oxygen uptake may result in oxidative stress, due to reactive oxygen species being generated excessively by enhanced oxygen consumption. The aim of this study was to evaluate the effect of high-intensity discontinuous training (HIDT, characterized by repeated variations of intensity and changes of redox potential, on oxidative damage. Twenty long-distance masters runners (age 47.8 ± 7.8 yr on the basis of the individual values of gas exchange threshold were assigned to a different 8-weeks training program: continuous moderate-intensity training (MOD, n = 10 or HIDT (n = 10. In both groups before (PRE and after (POST training we examined the following oxidative damage markers: thiobarbituric acid reactive substances (TBARS as marker of lipid peroxidation; protein carbonyls (PC as marker of protein oxidation; 8-hydroxy-2-deoxy-guanosine (8-OH-dG as a biomarker of DNA base modifications; and total antioxidant capacity (TAC as indicator of the overall antioxidant system. Training induced a significant (p<0.05 decrease in resting plasma TBARS concentration in both MOD (7.53 ± 0.30 and 6.46 ± 0.27 µM, PRE and POST respectively and HIDT (7.21 ± 0.32 and 5.85 ± 0.46 µM, PRE and POST respectively. Resting urinary 8-OH-dG levels were significantly decreased in both MOD (5.50 ± 0.66 and 4.16 ± 0.40 ng mg(-1creatinine, PRE and POST respectively and HIDT (4.52 ± 0.50 and 3.18 ± 0.34 ng mg(-1creatinine, PRE and POST respectively. Training both in MOD and HIDT did not significantly modify plasma levels of PC. Resting plasma TAC was reduced in MOD while no significant changes were observed in HIDT. In conclusion

Carbon and Nitrogen dynamics in deciduous and broad leaf trees under drought stress

Science.gov (United States)

Joseph, Jobin; Schaub, Marcus; Arend, Matthias; Saurer, Matthias; siegwolf, Rolf; Weiler, Markus; Gessler, Arthur

2017-04-01

Climate change is projected to lead to an increased frequency and duration of severe drought events in future. Already within the last twenty years, however, drought stress related forest mortality has been increasing across the globe. Tree and forest die off events have multiple adverse effects on ecosystem functioning and might convert previous carbon sinks to act as carbon sources instead and can thus intensify the effect of climate change and global warming. Current predictions of forest's functioning under drought and thus forest mortality under future climatic conditions are constrained by a still incomplete picture of the trees' physiological reactions that allows some trees to survive drought periods while others succumb. Concerning the effects of drought on the carbon balance and on tree hydraulics our picture is getting more complete, but still interactions between abiotic factors and pest and diseases as well as the interaction between carbon and nutrient balances as factors affecting drought induced mortality are not well understood. Reduced carbon allocation from shoots to roots might cause a lack of energy for root nutrient uptake and to a shortage of carbon skeletons for nitrogen assimilation and thus to an impaired nutrient status of trees. To tackle these points, we have performed a drought stress experiment with six different plant species, 3 broad leaf (maple, beech and oak) and 3 deciduous (pine, fir and spruce). Potted two-year-old seedlings were kept inside a greenhouse for 5 months and 3 levels of drought stress (no stress (control), intermediate and intensive drought stress) were applied by controlling water supply. Gas exchange measurements were performed periodically to monitor photosynthesis, transpiration, stomatal conductance. At the pinnacle of drought stress, we applied isotopic pulse labelling: On the one hand we exposed trees to 13CO2 to investigate on carbon dynamics and the allocation of new assimilates within the plant. Moreover

Burnout syndrome--assessment of a stressful job among intensive care staff.

Science.gov (United States)

Cubrilo-Turek, Mirjana; Urek, Roman; Turek, Stjepan

2006-03-01

The purpose of the study was to investigate the degree of burnout experienced by intensive care staff particularly, in Medical (MICU) and Surgical Intensive Care Units (SICU) General Hospital "Sveti Duh", Zagreb. A sample group of 41 emergency physicians and nurses from MICU and 30 from SICU was tested. The survey included demographic data and Maslach Burnout Inventory (MBI) scoring test identified by the three main components associated with burnout: emotional exhaustion (MBI-EE), depersonalization (MBI-DEP), and personal accomplishment (MBI-PA) were assessed using 22-item questionnaire. The degrees of burnout were stratified into low, moderate, and high range. Mean total MBI (X +/- SD) were high in both groups: higher for the MICU (65.5 +/- 6.7) than for SICU staff (55.7 +/- 3.8, p burnout represented in a moderate degree. The presence of burnout is a serious phenomenon, because it can lead to psychosomatic complaints, work-associated withdrawal behaviour, and a lower quality of care at intensive care units. Early recognition of burnout phenomenon as a result of prolonged stress and frustration among intensive care staff, contributes to better professional behavior, organizational structure changes in the work environment and better health care quality for critically ill patients.

Hole Defects Affect the Dynamic Fracture Behavior of Nearby Running Cracks

Directory of Open Access Journals (Sweden)

R. S. Yang

2018-01-01

Full Text Available Effects of defects on the dynamic fracture behavior of engineering materials cannot be neglected. Using the experimental system of digital laser dynamic caustics, the effects of defects on the dynamic fracture behavior of nearby running cracks are studied. When running cracks propagate near to defects, the crack path deflects toward the defect; the degree of deflection is greater for larger defect diameters. When the running crack propagates away from the defect, the degree of deflection gradually reduces and the original crack path is restored. The intersection between the caustic spot and the defect is the direct cause of the running crack deflection; the intersection area determines the degree of deflection. In addition, the defect locally inhibits the dynamic stress intensity factor of running cracks when they propagate toward the defect and locally promotes the dynamic stress intensity factor of running cracks when they propagate away from the defect.

Stress Intensity of Delamination in a Sintered-Silver Interconnection: Preprint

Energy Technology Data Exchange (ETDEWEB)

DeVoto, D. J.; Paret, P. P.; Wereszczak, A. A.

2014-08-01

In automotive power electronics packages, conventional thermal interface materials such as greases, gels, and phase-change materials pose bottlenecks to heat removal and are also associated with reliability concerns. The industry trend is toward high thermal performance bonded interfaces for large-area attachments. However, because of coefficient of thermal expansion mismatches between materials/layers and resultant thermomechanical stresses, adhesive and cohesive fractures could occur, posing a reliability problem. These defects manifest themselves in increased thermal resistance. This research aims to investigate and improve the thermal performance and reliability of sintered-silver for power electronics packaging applications. This has been experimentally accomplished by the synthesis of large-area bonded interfaces between metalized substrates and copper base plates that have subsequently been subjected to thermal cycles. A finite element model of crack initiation and propagation in these bonded interfaces will allow for the interpretation of degradation rates by a crack-velocity (V)-stress intensity factor (K) analysis. A description of the experiment and the modeling approach are discussed.

Noise, stress, and annoyance in a pediatric intensive care unit.

Science.gov (United States)

Morrison, Wynne E; Haas, Ellen C; Shaffner, Donald H; Garrett, Elizabeth S; Fackler, James C

2003-01-01

To measure and describe hospital noise and determine whether noise can be correlated with nursing stress measured by questionnaire, salivary amylase, and heart rate. Cohort observational study. Tertiary care center pediatric intensive care unit. Registered nurses working in the unit. None. Eleven nurse volunteers were recruited. An audiogram, questionnaire data, salivary amylase, and heart rate were collected in a quiet room. Each nurse was observed for a 3-hr period during patient care. Heart rate and sound level were recorded continuously; saliva samples and stress/annoyance ratings were collected every 30 mins. Variables assessed as potential confounders were years of nursing experience, caffeine intake, patients' Pediatric Risk of Mortality Score, shift assignment, and room assignment. Data were analyzed by random effects multiple linear regression using Stata 6.0. The average daytime sound level was 61 dB(A), nighttime 59 dB(A). Higher average sound levels significantly predicted higher heart rates (p =.014). Other significant predictors of tachycardia were higher caffeine intake, less nursing experience, and daytime shift. Ninety percent of the variability in heart rate was explained by the regression equation. Amylase measurements showed a large variability and were not significantly affected by noise levels. Higher average sound levels were also predictive of greater subjective stress (p =.021) and annoyance (p =.016). In this small study, noise was shown to correlate with several measures of stress including tachycardia and annoyance ratings. Further studies of interventions to reduce noise are essential.

The Effects of Aromatherapy on Intensive Care Unit Patients’ Stress and Sleep Quality: A Nonrandomised Controlled Trial

Directory of Open Access Journals (Sweden)

Eun Hee Cho

2017-01-01

Full Text Available Background. Stress has both physiological and psychological effects and can negatively impact patients’ treatment and recovery. We examined whether the aromatherapy alleviated patients’ stress and improved their sleep quality and provided data that can be utilized in clinical settings. Methods. This was a nonrandomised controlled experimental study. Participants included lucid adult patients who were admitted to the intensive care unit and had spent more than two nights there. The experimental treatment required participants to engage in deep breathing with essential oils as part of the aromatherapy. The control group was instructed to go to sleep without receiving the lavender aroma oil. Results. The experimental group and control group showed a significant difference in perceived stress (F=60.11, p<.001, objective stress index (F=25.65, p<.001, systolic blood pressure (F=9.09, p<.001, diastolic blood pressure (F=2.47, p=.046, heart rate (F=5.71, p<.001, and sleep quality (F=109.46, p<.001. Conclusions. The results revealed that aromatherapy alleviated stress and improved sleep quality in intensive care unit patients after 2 days of the experimental treatment. These results demonstrate that aromatherapy affects stress and sleep quality, thus indicating its value in nursing interventions. This trial is registered with KCT0002344.

Effect of Trailing Intensive Cooling on Residual Stress and Welding Distortion of Friction Stir Welded 2060 Al-Li Alloy

Science.gov (United States)

Ji, Shude; Yang, Zhanpeng; Wen, Quan; Yue, Yumei; Zhang, Liguo

2018-04-01

Trailing intensive cooling with liquid nitrogen has successfully applied to friction stir welding of 2 mm thick 2060 Al-Li alloy. Welding temperature, plastic strain, residual stress and distortion of 2060 Al-Li alloy butt-joint are compared and discussed between conventional cooling and trailing intensive cooling using experimental and numerical simulation methods. The results reveal that trailing intensive cooling is beneficial to shrink high temperature area, reduce peak temperature and decrease plastic strain during friction stir welding process. In addition, the reduction degree of plastic strain outside weld is smaller than that inside weld. Welding distortion presents an anti-saddle shape. Compared with conventional cooling, the reductions of welding distortion and longitudinal residual stresses of welding joint under intense cooling reach 47.7 % and 23.8 %, respectively.

Loss of parental role as a cause of stress in the neonatal intensive care unit.

Science.gov (United States)

Bouet, Kary M; Claudio, Norma; Ramirez, Verónica; García-Fragoso, Lourdes

2012-01-01

Having a baby in the Neonatal Intensive Care Unit (NICU) is a major source of stress for parents. The barriers to parenting and reactions to the environment may negatively influence the parent-infant relationship. To identify NICU-related parental stress and associated factors. Parents (N = 156) of newborns admitted to NICU completed the Parental Stressor Scale. Most of the parents (46%) rated the experience to be extremely stressful. The principal cause of stress was the alteration in parental role and being separated from their baby. Stress was not associated to education, marital status, infants' birth weight, gestational age, congenital anomalies or if the parents expected the baby to be in the NICU. Identification of areas associated to higher levels of stress in parents may help the NICU staff to establish strategies to help parents cope with the stress caused by being unable to start their parenting role immediately after their babies' birth.

Dynamic stress of impeller blade of shaft extension tubular pump device based on bidirectional fluid-structure interaction

Energy Technology Data Exchange (ETDEWEB)

Kan, Kan; Liu, Huiwen; Yang, Chunxia [Hohai University, Nanjing (China); Zheng, Yuan [National Engineering Research Center of Water Resources Efficient Utilization and Engineering Safety, Nanjing (China); Fu, Shifeng; Zhang, Xin [Power China Huadong Engineering Corporation, Hangzhou (China)

2017-04-15

Current research on the stability of tubular pumps is mainly concerned with the transient hydrodynamic characteristics. However, the structural response under the influence of fluid-structure interaction hasn't been taken fully into consideration. The instability of the structure can cause vibration and cracks, which may threaten the safety of the unit. We used bidirectional fluid-structure interaction to comprehensively analyze the dynamic stress characteristics of the impeller blades of the shaft extension tubular pump device. Furthermore, dynamic stress of impeller blade of shaft extension tubular pump device was solved under different lift conditions of 0° blade angle. Based on Reynolds-average N-S equation and SST k-ω turbulence model, numerical simulation was carried out for three-dimensional unsteady incompressible turbulent flow field of the pump device whole flow passage. Meanwhile, the finite element method was used to calculate dynamic characteristics of the blade structure. The blade dynamic stress distribution was obtained on the basis of fourth strength theory. The research results indicate that the maximum blade dynamic stress appears at the joint between root of inlet side of the blade suction surface and the axis. Considering the influence of gravity, the fluctuation of the blade dynamic stress increases initially and decreases afterwards within a rotation period. In the meantime, the dynamic stress in the middle part of inlet edge presents larger relative fluctuation amplitude. Finally, a prediction method for dynamic stress distribution of tubular pump considering fluid-structure interaction and gravity effect was proposed. This method can be used in the design stage of tubular pump to predict dynamic stress distribution of the structure under different operating conditions, improve the reliability of pump impeller and analyze the impeller fatigue life.

Stress and Systemic Inflammation: Yin-Yang Dynamics in Health and Diseases.

Science.gov (United States)

Yan, Qing

2018-01-01

Studies in psychoneuroimmunology (PNI) would provide better insights into the "whole mind-body system." Systems biology models of the complex adaptive systems (CASs), such as a conceptual framework of "Yin-Yang dynamics," may be helpful for identifying systems-based biomarkers and targets for more effective prevention and treatment. The disturbances in the Yin-Yang dynamical balance may result in stress, inflammation, and various disorders including insomnia, Alzheimer's disease, obesity, diabetes, cardiovascular diseases, skin disorders, and cancer. At the molecular and cellular levels, the imbalances in the cytokine pathways, mitochondria networks, redox systems, and various signaling pathways may contribute to systemic inflammation. In the nervous system, Yin and Yang may represent the dynamical associations between the progressive and regressive processes in aging and neurodegenerative diseases. In response to the damages to the heart, the Yin-Yang dynamical balance between proinflammatory and anti-inflammatory cytokine networks is crucial. The studies of cancer have revealed the importance of the Yin-Yang dynamics in the tumoricidal and tumorigenic activities of the immune system. Stress-induced neuroimmune imbalances are also essential in chronic skin disorders including atopic dermatitis and psoriasis. With the integrative framework, the restoration of the Yin-Yang dynamics can become the objective of dynamical systems medicine.

Effects of upper mantle heterogeneities on the lithospheric stress field and dynamic topography

Science.gov (United States)

Osei Tutu, Anthony; Steinberger, Bernhard; Sobolev, Stephan V.; Rogozhina, Irina; Popov, Anton A.

2018-05-01

The orientation and tectonic regime of the observed crustal/lithospheric stress field contribute to our knowledge of different deformation processes occurring within the Earth's crust and lithosphere. In this study, we analyze the influence of the thermal and density structure of the upper mantle on the lithospheric stress field and topography. We use a 3-D lithosphere-asthenosphere numerical model with power-law rheology, coupled to a spectral mantle flow code at 300 km depth. Our results are validated against the World Stress Map 2016 (WSM2016) and the observation-based residual topography. We derive the upper mantle thermal structure from either a heat flow model combined with a seafloor age model (TM1) or a global S-wave velocity model (TM2). We show that lateral density heterogeneities in the upper 300 km have a limited influence on the modeled horizontal stress field as opposed to the resulting dynamic topography that appears more sensitive to such heterogeneities. The modeled stress field directions, using only the mantle heterogeneities below 300 km, are not perturbed much when the effects of lithosphere and crust above 300 km are added. In contrast, modeled stress magnitudes and dynamic topography are to a greater extent controlled by the upper mantle density structure. After correction for the chemical depletion of continents, the TM2 model leads to a much better fit with the observed residual topography giving a good correlation of 0.51 in continents, but this correction leads to no significant improvement of the fit between the WSM2016 and the resulting lithosphere stresses. In continental regions with abundant heat flow data, TM1 results in relatively small angular misfits. For example, in western Europe the misfit between the modeled and observation-based stress is 18.3°. Our findings emphasize that the relative contributions coming from shallow and deep mantle dynamic forces are quite different for the lithospheric stress field and dynamic

Strain-rate effect on initial crush stress of irregular honeycomb under dynamic loading and its deformation mechanism

Science.gov (United States)

Wang, Peng; Zheng, Zhijun; Liao, Shenfei; Yu, Jilin

2018-02-01

The seemingly contradictory understandings of the initial crush stress of cellular materials under dynamic loadings exist in the literature, and a comprehensive analysis of this issue is carried out with using direct information of local stress and strain. Local stress/strain calculation methods are applied to determine the initial crush stresses and the strain rates at initial crush from a cell-based finite element model of irregular honeycomb under dynamic loadings. The initial crush stress under constant-velocity compression is identical to the quasi-static one, but less than the one under direct impact, i.e. the initial crush stresses under different dynamic loadings could be very different even though there is no strain-rate effect of matrix material. A power-law relation between the initial crush stress and the strain rate is explored to describe the strain-rate effect on the initial crush stress of irregular honeycomb when the local strain rate exceeds a critical value, below which there is no strain-rate effect of irregular honeycomb. Deformation mechanisms of the initial crush behavior under dynamic loadings are also explored. The deformation modes of the initial crush region in the front of plastic compaction wave are different under different dynamic loadings.

High-intensity stress elicits robust cortisol increases, and impairs working memory and visuo-spatial declarative memory in Special Forces candidates: A field experiment.

Science.gov (United States)

Taverniers, John; Van Ruysseveldt, Joris; Smeets, Tom; von Grumbkow, Jasper

2010-07-01

While running a selection procedure, 27 male Belgian Special Forces candidates, with a mean age of 27.4 years (SD = 5.1), were randomly assigned to a no-stress control (n = 14) or a high-intensity stress group (n = 13). Participants in the latter group were exposed to an extremely strenuous mock prisoner of war (POW) exercise. Immediately after stress or control treatment, working memory and visuo-spatial declarative memory performances were measured by the digit span (DS) test and the Rey-Osterrieth complex figure (ROCF), respectively. Concurrently, stress levels were assessed by obtaining salivary cortisol measurements and subjectively by the NASA Task Load Index (TLX). As expected, exposure to high-intensity stress led to both robust cortisol increases and significant differences in TLX scores. Stress induction also significantly impaired DS and ROCF performances. Moreover, delta cortisol increases and ROCF performance in the POW stress group showed a significant negative correlation, while DS performances followed the same tendency. Summarizing, the current findings complement and extend previous work on hormonal stress effects, and the subsequent performance deterioration on two memory tests in a unique high-intensity stress environment.

Stress ulcer prophylaxis in the intensive care unit

DEFF Research Database (Denmark)

Krag, M; Perner, A; Wetterslev, J

2015-01-01

BACKGROUND: Stress ulcer prophylaxis (SUP) may decrease the incidence of gastrointestinal bleeding in patients in the intensive care unit (ICU), but the risk of infection may be increased. In this study, we aimed to describe SUP practices in adult ICUs. We hypothesised that patient selection...... for SUP varies both within and between countries. METHODS: Adult ICUs were invited to participate in the survey. We registered country, type of hospital, type and size of ICU, preferred SUP agent, presence of local guideline, reported indications for SUP, criteria for discontinuing SUP, and concerns about...... adverse effects. Fisher's exact test was used to assess differences between groups. RESULTS: Ninety-seven adult ICUs in 11 countries participated (eight European). All but one ICU used SUP, and 64% (62/97) reported having a guideline for the use of SUP. Proton pump inhibitors were the most common SUP...

Dynamic Response in Transient Stress-Field Behavior Induced by Hydraulic Fracturing

Science.gov (United States)

Jenkins, Andrew

Hydraulic fracturing is a technique which is used to exploit geologic features and subsurface properties in an effort to increase production in low-permeability formations. The process of hydraulic fracturing provides a greater surface contact area between the producing formation and the wellbore and thus increases the amount of recoverable hydrocarbons from within the reservoir. The use of this stimulation technique has brought on massive applause from the industry due to its widespread success and effectiveness, however the dynamic processes that take part in the development of hydraulic fractures is a relatively new area of research with respect to the massive scale operations that are seen today. The process of hydraulic fracturing relies upon understanding and exploiting the in-situ stress distribution throughout the area of study. These in-situ stress conditions are responsible for directing fracture orientation and propagation paths throughout the period of injection. The relative magnitude of these principle stresses is key in developing a successful stimulation plan. In horizontal well plan development the interpretation of stress within the reservoir is required for determining the azimuth of the horizontal well path. These horizontal laterals are typically oriented in a manner such that the well path lies parallel to the minimum horizontal stress. This allows for vertical fractures to develop transversely to the wellbore, or normal to the least principle stress without the theoretical possibility of fractures overlapping, creating the most efficient use of the fluid energy during injection. The orientation and magnitude of these in-situ stress fields however can be dynamic, controlled by the subsequent fracture propagation and redistribution of the surrounding stresses. That is, that as the fracture propagates throughout the reservoir, the relative stress fields surrounding the fractures may see a shift and deviate from their original direction or

Specific features of peroxide stress in children permanently exposed to low-intensity radiation

International Nuclear Information System (INIS)

Durnov, L.A.; Bajkova, V.N.; Mayakova, S.A.; Polyakov, V.G.; Kolosov, E.A.; Dumbrajs, K.O.; Gracheva, I.V.; Zakharova, N.V.; Leonidova, Yu.A.; Romanova, L.F.

2000-01-01

To study the peculiarities of peroxide stress in children residing at the territories with chronic low-intensity radiation effects, the investigation was performed of tyrosine level, indices of the intensity of free radical lipid peroxidation and antioxidant system status in children and teenagers living in Sverdlovsk and Kolpnyansk districts of the Orel region contaminated due to the Chernobyl accident. Regions mentioned are characterized by low-intensity contamination with radionuclides (mainly 90 Sr, 131 I, 137 Cs), 25% an increase in tyrosine content, 1.8 times in malonic dial, 25-40 % in catalase and superoxide dismutase activity was revealed in blood plasma. Contents of A and E vitamins, glutathione and glutathione-depending enzymes are decreased. It is recommended to observe children health in regions contaminated as a result of the Chernobyl accident and correct failed redox processes using antioxidative vitamins [ru

Dynamics for a two-atom two-mode intensity-dependent Raman coupled model

Energy Technology Data Exchange (ETDEWEB)

Singh, S., E-mail: vasudha-rnc1@rediffmail.com, E-mail: sudhhasingh@gmail.com; Gilhare, K. [Ranchi University, Department of Physics (India)

2016-06-15

We study the quantum dynamics of a two-atom Raman coupled model interacting with a quantized bimodal field with intensity-dependent coupling terms in a lossless cavity. The unitary transformation method used to solve the time-dependent problem also gives the eigensolutions of the interaction Hamiltonian. We study the atomic-population dynamics and dynamics of the photon statistics in the two cavity modes, and present evidence of cooperative effects in the production of antibunching and anticorrelations between the modes. We also investigate the effect of detuning on the evolution of second-order correlation functions and observe that the oscillations become more rapid for large detuning.

Influence of acute exercise of varying intensity and duration on postprandial oxidative stress.

Science.gov (United States)

Canale, Robert E; Farney, Tyler M; McCarthy, Cameron G; Bloomer, Richard J

2014-09-01

Aerobic exercise can reduce postprandial lipemia, and possibly oxidative stress, when performed prior to a lipid-rich meal. To compare the impact of acute exercise on postprandial oxidative stress. We compared aerobic and anaerobic exercise bouts of different intensities and durations on postprandial blood triglycerides (TAG), oxidative stress biomarkers (malondialdehyde, hydrogen peroxide, advanced oxidation protein products), and antioxidant status (trolox equivalent antioxidant capacity, superoxide dismutase, catalase, glutathione peroxidase). Twelve trained men (21-35 years) underwent four conditions: (1) No exercise rest; (2) 60-min aerobic exercise at 70% heart rate reserve; (3) five 60-s sprints at 100% max capacity; and (4) ten 15-s sprints at 200% max capacity. All exercise bouts were performed on a cycle ergometer. A high-fat meal was consumed 1 h after exercise cessation. Blood samples were collected pre-meal and 2 and 4 h post-meal and analyzed for TAG, oxidative stress biomarkers, and antioxidant status. No significant interaction or condition effects were noted for any variable (p > 0.05), with acute exercise having little to no effect on the magnitude of postprandial oxidative stress. In a sample of healthy, well-trained men, neither aerobic nor anaerobic exercise attenuates postprandial oxidative stress in response to a high-fat meal.

Development of a screening measure of stress for parents of children hospitalised in a Paediatric Intensive Care Unit.

Science.gov (United States)

Rodríguez-Rey, Rocío; Alonso-Tapia, Jesús

2016-08-01

Having a child admitted to intensive care is a highly stressful experience for parents; however there is a lack of screening instruments of parental stress in that context, which would be useful for both, research and clinical purposes. (1) To validate a brief measure of parental stress based on the Parental Stressor Scale: Paediatric Intensive Care Unit (PSS:PICU), (2) to study which environmental factors of the PICU are more stressful in a sample of Spanish parents, and (3) to study which variables are related to higher levels of stress among this group. 196 Spanish parents completed the Abbreviated PSS: PICU (A-PSS:PICU) and a general stress scale (the Perceived Stress Scale) upon their child's discharge to test the convergent validity of the tool. Three months later, they were assessed anxiety and depression using the Hospital Anxiety and Depression Scale, and posttraumatic stress with the Davidson Trauma Scale in order to test the predictive validity of the A-PSS:PICU. Two factors emerged from Confirmatory Factor Analyses, (1) stress due to child's condition and (2) stress related to PICU's staff. The A-PSS:PICU showed adequate reliability and convergent and predictive validity. The most stressful aspects were the behaviours and emotional responses of their child and the loss of their parental role. Age, gender, child's condition, length of admission, spiritual beliefs, and mechanical ventilation were associated to parental stress scores. The A-PSS:PICU is a reliable and valid measure. Parental stress should be screened during a child's PICU admission to identify parents at risk of post-discharge distress. Copyright © 2016 Australian College of Critical Care Nurses Ltd. Published by Elsevier Ltd. All rights reserved.

Dynamic strain aging of zircaloy-4 PWR fuel cladding in biaxial stress state

International Nuclear Information System (INIS)

Park, Ki Seong; Lee, Byong Whi

1989-01-01

The expanding copper mandrel test performed at three strain rates (3.2x10E-5/s,2.0x10E-6/s and 1.2x10E-7/s) over 553-873 K temperature range by varying the heating rates (8-10deg C/s,1-2deg C/s and 0.5deg C/s) in air and in vacuum (5x10E-5 torr). The yield stress peak, the strain rate sensitivity minimum and the activation volume peaks could be explained in terms of the dynamic strain aging. The activation energy for dynamic strain aging obtained from the yield stress peak temperature and strain rate was 196 KJ/mol and this value was in good agreement with the activation energy for oxygen diffusion in α-zirconium and Zircaloy-2 (207-220KJ/mol). Therefore, oxygen atoms are responsible for the dynamic strain aging which appeared between 573K and 673K. The yield stress increase due to the oxidation was obtained by comparing the yield stress in air with that in vacuum and represented by the percentage increase of yield stress (σ y a -σ y v /σ y v ). The slower the strain rate, the greater the percentage increase occurs. In order to estimate the yield stress of PWR fuel cladding material under the service environment, the yield stress in water was obtained by comparing the oxidation rate in air that in water assuming the relationship between the oxygen pick-up amount and the yield stress increase. (Author)

Reconstructing a Network of Stress-Response Regulators via Dynamic System Modeling of Gene Regulation

Directory of Open Access Journals (Sweden)

Wei-Sheng Wu

2008-01-01

Full Text Available Unicellular organisms such as yeasts have evolved mechanisms to respond to environmental stresses by rapidly reorganizing the gene expression program. Although many stress-response genes in yeast have been discovered by DNA microarrays, the stress-response transcription factors (TFs that regulate these stress-response genes remain to be investigated. In this study, we use a dynamic system model of gene regulation to describe the mechanism of how TFs may control a gene’s expression. Then, based on the dynamic system model, we develop the Stress Regulator Identification Algorithm (SRIA to identify stress-response TFs for six kinds of stresses. We identified some general stress-response TFs that respond to various stresses and some specific stress-response TFs that respond to one specifi c stress. The biological significance of our findings is validated by the literature. We found that a small number of TFs is probably suffi cient to control a wide variety of expression patterns in yeast under different stresses. Two implications can be inferred from this observation. First, the response mechanisms to different stresses may have a bow-tie structure. Second, there may be regulatory cross-talks among different stress responses. In conclusion, this study proposes a network of stress-response regulators and the details of their actions.

Cardiorespiratory Dynamic Response to Mental Stress: A Multivariate Time-Frequency Analysis

Directory of Open Access Journals (Sweden)

Devy Widjaja

2013-01-01

out continuously in time to evaluate the dynamic response to mental stress and attention. The results show an increased heart and respiratory rate during stress and attention, compared to a resting condition. Also a fast reduction in vagal activity is noted. The partial TF analysis reveals a faster reduction of RRV power related to (3 s than unrelated to (30 s respiration, demonstrating that the autonomic response to mental stress is driven by mechanisms characterized by different temporal scales.

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

Suppression of Helicobacter pylori infection during intensive care stay: related to stress ulcer bleeding incidence?

NARCIS (Netherlands)

van der Voort, P. H.; van der Hulst, R. W.; Zandstra, D. F.; Geraedts, A. A.; van der Ende, A.; Tytgat, G. N.

2001-01-01

PURPOSE: To assess the prevalence of active Helicobacter pylori infection in patients admitted to the intensive care unit, to determine the effect of selective gut decontamination on the persistence of this organism, and to explore the possible relationship between H. pylori infection and stress

Measurement accuracy of weighing and tipping-bucket rainfall intensity gauges under dynamic laboratory testing

Science.gov (United States)

Colli, M.; Lanza, L. G.; La Barbera, P.; Chan, P. W.

2014-07-01

The contribution of any single uncertainty factor in the resulting performance of infield rain gauge measurements still has to be comprehensively assessed due to the high number of real world error sources involved, such as the intrinsic variability of rainfall intensity (RI), wind effects, wetting losses, the ambient temperature, etc. In recent years the World Meteorological Organization (WMO) addressed these issues by fostering dedicated investigations, which revealed further difficulties in assessing the actual reference rainfall intensity in the field. This work reports on an extensive assessment of the OTT Pluvio2 weighing gauge accuracy when measuring rainfall intensity under laboratory dynamic conditions (time varying reference flow rates). The results obtained from the weighing rain gauge (WG) were also compared with a MTX tipping-bucket rain gauge (TBR) under the same test conditions. Tests were carried out by simulating various artificial precipitation events, with unsteady rainfall intensity, using a suitable dynamic rainfall generator. Real world rainfall data measured by an Ogawa catching-type drop counter at a field test site located within the Hong Kong International Airport (HKIA) were used as a reference for the artificial rain generation system. Results demonstrate that the differences observed between the laboratory and field performance of catching-type gauges are only partially attributable to the weather and operational conditions in the field. The dynamics of real world precipitation events is responsible for a large part of the measurement errors, which can be accurately assessed in the laboratory under controlled environmental conditions. This allows for new testing methodologies and the development of instruments with enhanced performance in the field.

Dynamic behaviour of the icosahedral Al–Pd–Mn quasicrystal with a Griffith crack

International Nuclear Information System (INIS)

Xiao-Fang, Wang; Ai-Yu, Zhu; Tian-You, Fan

2009-01-01

The dynamic response of an icosahedral Al–Pd–Mn quasicrystal with a Griffith crack to impact loading is investigated in this paper. The elastohydrodynamic model for the wave propagation and diffusion together with their interaction is adopted. Numerical results of stress, displacement and dynamic stress intensity factors are obtained by using the finite difference method. The effects of wave propagation, diffusion and phonon–phason coupling on the quasicrystal in the dynamic process are discussed in detail, where the phason dynamics is explored particularly. (condensed matter: structure, thermal and mechanical properties)

Evaluation of stress intensity factor for craks in surface of tubes with internal pressure

International Nuclear Information System (INIS)

Cesari, F.; Hellen, T.K.

1977-01-01

In this report the authors have examined the different methods for calculation of the stress intensity factor in tubes subject at internal pressure with surface cracks. The analysis includes cracks in 2-D axialsymmetric and 3-D. Moreover the authors have clarified the difference between the ASME Sec.11 and the procedure more rigorous

Stress intensity factors for underclad and through clad defects in a reactor pressure vessel submitted to a pressurised thermal shock

International Nuclear Information System (INIS)

Marie, S.; Menager, Y.; Chapuliot, S.

2005-01-01

CEA has launched important work on the development of a Stress Intensity Factors compendium for cracks in a Reactor Pressure Vessel (RPV) taking into account the cladding. The work is performed by Finite Element analysis with a parametric mesh for two types of defects (under clad defect and through clad defect) and a wide range of geometrical and material parameters. In addition, an analytical stress solution for Pressurised Thermal Shock (PTS) on the RPV is proposed to allow a complete analytical estimation of the stress intensity factor K I for the PTS problem. The results are validated by comparison with a complete 3D finite element calculation performed on a complex and realistic case study

The dynamics of stress and fatigue across menopause: attractors, coupling, and resilience.

Science.gov (United States)

Taylor-Swanson, Lisa; Wong, Alexander E; Pincus, David; Butner, Jonathan E; Hahn-Holbrook, Jennifer; Koithan, Mary; Wann, Kathryn; Woods, Nancy F

2018-04-01

The objective of this study was to evaluate the regulatory dynamics between stress and fatigue experienced by women during the menopausal transition (MT) and early postmenopause (EPM). Fatigue and perceived stress are commonly experienced by women during the MT and EPM. We sought to discover relationships between these symptoms and to employ these symptoms as possible markers for resilience. Participants were drawn from the longitudinal Seattle Midlife Women's Health Study. Eligible women completed questionnaires on 60+ occasions (annual health reports and monthly health diaries) (n = 56 women). The total number of observations across the sample was 4,224. STRAW+10 criteria were used to stage women in either in late reproductive, early or late transition, or EPM stage. Change values were generated for fatigue and stress and analyzed with a multilevel structural equation model; slopes indicate how quickly a person returns to homeostasis after a perturbation. Coupling of stress and fatigue was modeled to evaluate resilience, the notion of maintaining stability during change. Eligible women were on average 35 years old (SD = 4.71), well educated, employed, married or partnered, and white. Fit indices suggested the model depicts the relationships of stress and fatigue (χ(9 df) = 7.638, P = 0.57, correction factor = 4.9244; root mean square error of approximation (RMSEA) 90% CI = 0.000 ≤ 0.000 ≤ 0.032; comparative fit index (CFI) = 1.00). A loss in model fit across stages suggests that the four stages differed in their dynamics (χΔ(12 df) = 21.181, P = .048). All stages showed fixed-point attractor dynamics: fatigue became less stable over time; stress generally became more stable over time. Coupling relationships of stress on fatigue show evidence for shifts in regulatory relationships with one another across the MT. Results are suggestive of general dysregulation via disruptions to coupling relationships of stress and

ORBIT: A CODE FOR COLLECTIVE BEAM DYNAMICS IN HIGH INTENSITY RINGS

International Nuclear Information System (INIS)

HOLMES, J.A.; DANILOV, V.; GALAMBOS, J.; SHISHLO, A.; COUSINEAU, S.; CHOU, W.; MICHELOTTI, L.; OSTIGUY, J.F.; WEI, J.

2002-01-01

We are developing a computer code, ORBIT, specifically for beam dynamics calculations in high-intensity rings. Our approach allows detailed simulation of realistic accelerator problems. ORBIT is a particle-in-cell tracking code that transports bunches of interacting particles through a series of nodes representing elements, effects, or diagnostics that occur in the accelerator lattice. At present, ORBIT contains detailed models for strip-foil injection, including painting and foil scattering; rf focusing and acceleration; transport through various magnetic elements; longitudinal and transverse impedances; longitudinal, transverse, and three-dimensional space charge forces; collimation and limiting apertures; and the calculation of many useful diagnostic quantities. ORBIT is an object-oriented code, written in C++ and utilizing a scripting interface for the convenience of the user. Ongoing improvements include the addition of a library of accelerator maps, BEAMLINE/MXYZPTLK, the introduction of a treatment of magnet errors and fringe fields; the conversion of the scripting interface to the standard scripting language, Python; and the parallelization of the computations using MPI. The ORBIT code is an open source, powerful, and convenient tool for studying beam dynamics in high-intensity rings

ORBIT: A Code for Collective Beam Dynamics in High-Intensity Rings

Science.gov (United States)

Holmes, J. A.; Danilov, V.; Galambos, J.; Shishlo, A.; Cousineau, S.; Chou, W.; Michelotti, L.; Ostiguy, J.-F.; Wei, J.

2002-12-01

We are developing a computer code, ORBIT, specifically for beam dynamics calculations in high-intensity rings. Our approach allows detailed simulation of realistic accelerator problems. ORBIT is a particle-in-cell tracking code that transports bunches of interacting particles through a series of nodes representing elements, effects, or diagnostics that occur in the accelerator lattice. At present, ORBIT contains detailed models for strip-foil injection, including painting and foil scattering; rf focusing and acceleration; transport through various magnetic elements; longitudinal and transverse impedances; longitudinal, transverse, and three-dimensional space charge forces; collimation and limiting apertures; and the calculation of many useful diagnostic quantities. ORBIT is an object-oriented code, written in C++ and utilizing a scripting interface for the convenience of the user. Ongoing improvements include the addition of a library of accelerator maps, BEAMLINE/MXYZPTLK; the introduction of a treatment of magnet errors and fringe fields; the conversion of the scripting interface to the standard scripting language, Python; and the parallelization of the computations using MPI. The ORBIT code is an open source, powerful, and convenient tool for studying beam dynamics in high-intensity rings.

ORBIT: A code for collective beam dynamics in high-intensity rings

International Nuclear Information System (INIS)

Holmes, J.A.; Danilov, V.; Galambos, J.; Shishlo, A.; Cousineau, S.; Chou, W.; Michelotti, L.; Ostiguy, J.-F.; Wei, J.

2002-01-01

We are developing a computer code, ORBIT, specifically for beam dynamics calculations in high-intensity rings. Our approach allows detailed simulation of realistic accelerator problems. ORBIT is a particle-in-cell tracking code that transports bunches of interacting particles through a series of nodes representing elements, effects, or diagnostics that occur in the accelerator lattice. At present, ORBIT contains detailed models for strip-foil injection, including painting and foil scattering; rf focusing and acceleration; transport through various magnetic elements; longitudinal and transverse impedances; longitudinal, transverse, and three-dimensional space charge forces; collimation and limiting apertures; and the calculation of many useful diagnostic quantities. ORBIT is an object-oriented code, written in C++ and utilizing a scripting interface for the convenience of the user. Ongoing improvements include the addition of a library of accelerator maps, BEAMLINE/MXYZPTLK; the introduction of a treatment of magnet errors and fringe fields; the conversion of the scripting interface to the standard scripting language, Python; and the parallelization of the computations using MPI. The ORBIT code is an open source, powerful, and convenient tool for studying beam dynamics in high-intensity rings

Calculations of the stress intensity factor on a specimen for a four-point bend

International Nuclear Information System (INIS)

Lauerova, D.

1995-02-01

The stress intensity factor K I was calculated in dependence on the crack length in a sample for a (non-standard) four-point bend assuming elastic properties of the material. It is shown that the SYSTUS code gives the best results when calculating the K I value from the J-integral. 4 tabs., 12 figs., 4 refs

Population Dynamics and Transcriptomic Responses of Chorthippus albonemus (Orthoptera: Acrididae to Herbivore Grazing Intensity

Directory of Open Access Journals (Sweden)

Xinghu Qin

2017-11-01

Full Text Available Livestock grazing can trigger outbreaks of insect pests in steppe ecosystems of Inner Mongolia in China. However, the physiological responses of the grasshopper Chorthippus albonemus to grazing are not well-understood. Here we investigated the effects of sheep grazing on the population dynamics and transcriptomic response of C. albonemus. We collected the insects three times (about 20 days apart in 1.33-ha plots in which there were no grazing, light grazing, moderate grazing, heavy grazing, or overgrazing. Our results showed that continuous grazing significantly decreased plant biomass and influenced plant succession. Total insect species diversity significantly declined along the grazing intensity gradient and over time. Results of the first two collections of C. albonemus indicated that moderate grazing significantly increased the abundance of C. albonemus. However, abundance was significantly decreased in plots that were overgrazed, possibly because of food stress and environmental pressures. Under moderate grazing, betA and CHDH genes were significantly upregulated in C. albonemus. In response to higher grazing intensity, upregulated genes included those involved in serine-type peptidase activity, anatomical structure development, and sensory organ development; downregulated genes included those involved in the structural constituents of the ribosome and ribosome processes. Genes strongly upregulated in response to heavy grazing pressure included adaptive genes such as those encoding ankyrin repeat domain-containing protein and HSP. These findings improve our understanding of the role of the transcriptome in C. albonemus population response to livestock grazing and may provide useful targets for grasshopper control.

Dynamic functional connectivity and individual differences in emotions during social stress.

Science.gov (United States)

Tobia, Michael J; Hayashi, Koby; Ballard, Grey; Gotlib, Ian H; Waugh, Christian E

2017-12-01

Exposure to acute stress induces multiple emotional responses, each with their own unique temporal dynamics. Dynamic functional connectivity (dFC) measures the temporal variability of network synchrony and captures individual differences in network neurodynamics. This study investigated the relationship between dFC and individual differences in emotions induced by an acute psychosocial stressor. Sixteen healthy adult women underwent fMRI scanning during a social evaluative threat (SET) task, and retrospectively completed questionnaires that assessed individual differences in subjectively experienced positive and negative emotions about stress and stress relief during the task. Group dFC was decomposed with parallel factor analysis (PARAFAC) into 10 components, each with a temporal signature, spatial network of functionally connected regions, and vector of participant loadings that captures individual differences in dFC. Participant loadings of two networks were positively correlated with stress-related emotions, indicating the existence of networks for positive and negative emotions. The emotion-related networks involved the ventromedial prefrontal cortex, cingulate cortex, anterior insula, and amygdala, among other distributed brain regions, and time signatures for these emotion-related networks were uncorrelated. These findings demonstrate that individual differences in stress-induced positive and negative emotions are each uniquely associated with large-scale brain networks, and suggest that dFC is a mechanism that generates individual differences in the emotional components of the stress response. Hum Brain Mapp 38:6185-6205, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

The interplay of stress and mowing disturbance for the intensity and importance of plant interactions in dry calcareous grasslands.

Science.gov (United States)

Maalouf, Jean-Paul; Le Bagousse-Pinguet, Yoann; Marchand, Lilian; Touzard, Blaise; Michalet, Richard

2012-09-01

There is still debate regarding the direction and strength of plant interactions under intermediate to high levels of stress. Furthermore, little is known on how disturbance may interact with physical stress in unproductive environments, although recent theory and models have shown that this interplay may induce a collapse of plant interactions and diversity. The few studies assessing such questions have considered the intensity of biotic interactions but not their importance, although this latter concept has been shown to be very useful for understanding the role of interactions in plant communities. The objective of this study was to assess the interplay between stress and disturbance for plant interactions in dry calcareous grasslands. A field experiment was set up in the Dordogne, southern France, where the importance and intensity of biotic interactions undergone by four species were measured along a water stress gradient, and with and without mowing disturbance. The importance and intensity of interactions varied in a very similar way along treatments. Under undisturbed conditions, plant interactions switched from competition to neutral with increasing water stress for three of the four species, whereas the fourth species was not subject to any significant biotic interaction along the gradient. Responses to disturbance were more species-specific; for two species, competition disappeared with mowing in the wettest conditions, whereas for the two other species, competition switched to facilitation with mowing. Finally, there were no significant interactions for any species in the disturbed and driest conditions. At very high levels of stress, plant performances become too weak to allow either competition or facilitation and disturbance may accelerate the collapse of interactions in dry conditions. The results suggest that the importance and direction of interactions are more likely to be positively related in stressful environments.

Plants in water-controlled ecosystems: active role in hydrologic processes and response to water stress. III. Vegetation water stress

Science.gov (United States)

Porporato, A.; Laio, F.; Ridolfi, L.; Rodriguez-Iturbe, I.

The reduction of soil moisture content during droughts lowers the plant water potential and decreases transpiration; this in turn causes a reduction of cell turgor and relative water content which brings about a sequence of damages of increasing seriousness. A review of the literature on plant physiology and water stress shows that vegetation water stress can be assumed to start at the soil moisture level corresponding to incipient stomatal closure and reach a maximum intensity at the wilting point. The mean crossing properties of these soil moisture levels crucial for water stress are derived analytically for the stochastic model of soil moisture dynamics described in Part II (F. Laio, A. Porporato, L. Ridolfi, I. Rodriguez-Iturbe. Adv. Water Res. 24 (7) (2001) 707-723). These properties are then used to propose a measure of vegetation water stress which combines the mean intensity, duration, and frequency of periods of soil water deficit. The characteristics of vegetation water stress are then studied under different climatic conditions, showing how the interplay between plant, soil, and environment can lead to optimal conditions for vegetation.

Simultaneous analysis of residual stress and stress intensity factor in a resist after UV-nanoimprint lithography based on electron moiré fringes

International Nuclear Information System (INIS)

Wang, Qinghua; Kishimoto, Satoshi

2012-01-01

In this study, the residual stress in a resist (PAK01) film and the stress intensity factor (SIF) of an induced crack are simultaneously estimated during ultraviolet nanoimprint lithography (UV-NIL) based on electron moiré fringes. A micro grid in a triangular arrangement on the resist film fabricated by UV-NIL is directly used as the model grid. Electron moiré fringes formed by the interference between the fabricated grid and the electron scan beam are used to measure the displacement distribution around the tip of a crack induced by the residual stress in the resist. The SIF of the crack is estimated using a displacement extrapolation method. The residual strain fields and the corresponding residual stress in the resist film far from the crack are determined and analyzed. This method is effective for evaluating the grid quality fabricated by the UV-NIL technique. (paper)

Spatio-temporal Dynamics and Mechanisms of Stress Granule Assembly.

Directory of Open Access Journals (Sweden)

Daisuke Ohshima

2015-06-01

Full Text Available Stress granules (SGs are non-membranous cytoplasmic aggregates of mRNAs and related proteins, assembled in response to environmental stresses such as heat shock, hypoxia, endoplasmic reticulum (ER stress, chemicals (e.g. arsenite, and viral infections. SGs are hypothesized as a loci of mRNA triage and/or maintenance of proper translation capacity ratio to the pool of mRNAs. In brain ischemia, hippocampal CA3 neurons, which are resilient to ischemia, assemble SGs. In contrast, CA1 neurons, which are vulnerable to ischemia, do not assemble SGs. These results suggest a critical role SG plays in regards to cell fate decisions. Thus SG assembly along with its dynamics should determine the cell fate. However, the process that exactly determines the SG assembly dynamics is largely unknown. In this paper, analyses of experimental data and computer simulations were used to approach this problem. SGs were assembled as a result of applying arsenite to HeLa cells. The number of SGs increased after a short latent period, reached a maximum, then decreased during the application of arsenite. At the same time, the size of SGs grew larger and became localized at the perinuclear region. A minimal mathematical model was constructed, and stochastic simulations were run to test the modeling. Since SGs are discrete entities as there are only several tens of them in a cell, commonly used deterministic simulations could not be employed. The stochastic simulations replicated observed dynamics of SG assembly. In addition, these stochastic simulations predicted a gamma distribution relative to the size of SGs. This same distribution was also found in our experimental data suggesting the existence of multiple fusion steps in the SG assembly. Furthermore, we found that the initial steps in the SG assembly process and microtubules were critical to the dynamics. Thus our experiments and stochastic simulations presented a possible mechanism regulating SG assembly.

Fear conditioning and shock intensity: the choice between minimizing the stress induced and reducing the number of animals used

NARCIS (Netherlands)

Pietersen, C.Y.; Bosker, F.J; Posterna, F.; Den Boer, J.A.

2006-01-01

Many fear conditioning studies use electric shock as the aversive stimulus. The intensity of shocks varies throughout the literature. In this study, shock intensities ranging from 0 to 1.5 mA were used, and the effects on the rats assessed by both behavioural and biochemical stress parameters.

Fear conditioning and shock intensity : the choice between minimizing the stress induced and reducing the number of animals used

NARCIS (Netherlands)

Pietersen, CY; Bosker, FJ; Posterna, F; den Boer, JA

Many fear conditioning studies use electric shock as the aversive stimulus. The intensity of shocks varies throughout the literature. In this study, shock intensities ranging from 0 to 1.5 mA were used, and the effects on the rats assessed by both behavioural and biochemical stress parameters.

Intense field stabilization in circular polarization: Three-dimensional time-dependent dynamics

International Nuclear Information System (INIS)

Choi, Dae-Il; Chism, Will

2002-01-01

We investigate the stabilization of hydrogen atoms in a circularly polarized laser field. We use a three-dimensional, time-dependent approach to study the quantum dynamics of hydrogen atoms subject to high-intensity, short-wavelength, laser pulses. We find an enhanced survival probability as the field is increased under fixed envelope conditions. We also confirm wave packet behaviors previously seen in two-dimensional time-dependent computations

Iranian parent-staff communication and parental stress in the neonatal Intensive Care Unit.

Science.gov (United States)

Hasanpour, Marzieh; Alavi, Mousa; Azizi, Fatemeh; Als, Heidelise; Armanian, Amir Mohmmad

2017-01-01

The birth of an infant requiring hospitalization in the neonatal Intensive Care Unit (NICU) uniformly is reported to be stressful for parents and family members. This study aimed to determine parent-staff communication in the NICU and its relationship to parent stress. Two hundred and three Iranian parents with preterm infants hospitalized in the NICU participated in this descriptive-correlational study. The participants were selected by the quota sampling method. Data collected included a three-part: questionnaire, the first part covered demographic parent and infant information, the second was the Parent-Staff Communication Scale (the score of which ranged from 0 to 180), and the third was the Parental Stress Scale (the score of which ranged from 0 to 102). Descriptive and inferential statistics including the Pearson's correlation coefficient test were applied to the data, using SPSS software Version 16. This study revealed that fathers and mothers' stress and communication scores were almost comparable and both higher than expected. The total mean score of the two main variables, i.e., parent-staff communication and parental stress were, respectively, 100.72 ± 18.89 and 75.26 ± 17.6. A significant inverse correlation was found between parental stress and parent-staff communication scores ( r = -0.144, P = 0.041). Based on this study finding showed that better parent-staff communication is related to lower parent stress scores, it is recommended that nurses and physicians receive specific skill training for the establishment of effective parent-staff communication. It is anticipated that such improved staff skills will help decrease parent stress and therewith likely promote parent and infant health in the NICU.

Label-free nanoscale characterization of red blood cell structure and dynamics using single-shot transport of intensity equation

Science.gov (United States)

Poola, Praveen Kumar; John, Renu

2017-10-01

We report the results of characterization of red blood cell (RBC) structure and its dynamics with nanometric sensitivity using transport of intensity equation microscopy (TIEM). Conventional transport of intensity technique requires three intensity images and hence is not suitable for studying real-time dynamics of live biological samples. However, assuming the sample to be homogeneous, phase retrieval using transport of intensity equation has been demonstrated with single defocused measurement with x-rays. We adopt this technique for quantitative phase light microscopy of homogenous cells like RBCs. The main merits of this technique are its simplicity, cost-effectiveness, and ease of implementation on a conventional microscope. The phase information can be easily merged with regular bright-field and fluorescence images to provide multidimensional (three-dimensional spatial and temporal) information without any extra complexity in the setup. The phase measurement from the TIEM has been characterized using polymeric microbeads and the noise stability of the system has been analyzed. We explore the structure and real-time dynamics of RBCs and the subdomain membrane fluctuations using this technique.

Death and population dynamics affect mutation rate estimates and evolvability under stress in bacteria.

Science.gov (United States)

Frenoy, Antoine; Bonhoeffer, Sebastian

2018-05-01

The stress-induced mutagenesis hypothesis postulates that in response to stress, bacteria increase their genome-wide mutation rate, in turn increasing the chances that a descendant is able to better withstand the stress. This has implications for antibiotic treatment: exposure to subinhibitory doses of antibiotics has been reported to increase bacterial mutation rates and thus probably the rate at which resistance mutations appear and lead to treatment failure. More generally, the hypothesis posits that stress increases evolvability (the ability of a population to generate adaptive genetic diversity) and thus accelerates evolution. Measuring mutation rates under stress, however, is problematic, because existing methods assume there is no death. Yet subinhibitory stress levels may induce a substantial death rate. Death events need to be compensated by extra replication to reach a given population size, thus providing more opportunities to acquire mutations. We show that ignoring death leads to a systematic overestimation of mutation rates under stress. We developed a system based on plasmid segregation that allows us to measure death and division rates simultaneously in bacterial populations. Using this system, we found that a substantial death rate occurs at the tested subinhibitory concentrations previously reported to increase mutation rate. Taking this death rate into account lowers and sometimes removes the signal for stress-induced mutagenesis. Moreover, even when antibiotics increase mutation rate, we show that subinhibitory treatments do not increase genetic diversity and evolvability, again because of effects of the antibiotics on population dynamics. We conclude that antibiotic-induced mutagenesis is overestimated because of death and that understanding evolvability under stress requires accounting for the effects of stress on population dynamics as much as on mutation rate. Our goal here is dual: we show that population dynamics and, in particular, the

Propagating stress-pulses and wiggling transition revealed in string dynamics

Science.gov (United States)

Yao, Zhenwei

2018-02-01

Understanding string dynamics yields insights into the intricate dynamic behaviors of various filamentary thin structures in nature and industry covering multiple length scales. In this work, we investigate the planar dynamics of a flexible string where one end is free and the other end is subject to transverse and longitudinal motions. Under transverse harmonic motion, we reveal the propagating pulse structure in the stress profile over the string, and analyze its role in bringing the system into a chaotic state. For a string where one end is under longitudinal uniform acceleration, we identify the wiggling transition, derive the analytical wiggling solution from the string equations, and present the phase diagram.

No Time Like the Present : Discovering the Hidden Dynamics in Intensive Longitudinal Data

NARCIS (Netherlands)

Hamaker, Ellen L.|info:eu-repo/dai/nl/208146660; Wichers, Marieke

2017-01-01

There has been a strong increase in the number of studies based on intensive longitudinal data, such as those obtained with experience sampling and daily diaries. These data contain a wealth of information regarding the dynamics of processes as they unfold within individuals over time. In this

Preventing overtraining in athletes in high-intensity sports and stress/recovery monitoring.

Science.gov (United States)

Kellmann, M

2010-10-01

In sports, the importance of optimizing the recovery-stress state is critical. Effective recovery from intense training loads often faced by elite athletes can often determine sporting success or failure. In recent decades, athletes, coaches, and sport scientists have been keen to find creative, new methods for improving the quality and quantity of training for athletes. These efforts have consistently faced barriers, including overtraining, fatigue, injury, illness, and burnout. Physiological and psychological limits dictate a need for research that addresses the avoidance of overtraining, maximizes recovery, and successfully negotiates the fine line between high and excessive training loads. Monitoring instruments like the Recovery-Stress Questionnaire for Athletes can assist with this research by providing a tool to assess their perceived state of recovery. This article will highlight the importance of recovery for elite athletes and provide an overview of monitoring instruments. © 2010 John Wiley & Sons A/S.

Motor intensive anti-gravity training improves performance in dynamic balance related tasks in persons with Parkinson's disease

DEFF Research Database (Denmark)

Malling, Anne Sofie Bøgh; Jensen, Bente Rona

2016-01-01

, the aim was to study the effect of motor intensive training performed in a safe anti-gravity environment using lower-body positive pressure (LBPP) technology on performance during dynamic balance related tasks. Thirteen male PDP went through an 8-week control period followed by 8 weeks of motor intensive...... antigravity training. Seventeen healthy males constituted a control group (CON). Performance during a five repetition sit-to-stand test (STS; sagittal plane) and a dynamic postural balance test (DPB; transversal plane) was evaluated. Effect measures were completion time, functional rates of force development...

MRI intensity inhomogeneity correction by combining intensity and spatial information

International Nuclear Information System (INIS)

Vovk, Uros; Pernus, Franjo; Likar, Bostjan

2004-01-01

We propose a novel fully automated method for retrospective correction of intensity inhomogeneity, which is an undesired phenomenon in many automatic image analysis tasks, especially if quantitative analysis is the final goal. Besides most commonly used intensity features, additional spatial image features are incorporated to improve inhomogeneity correction and to make it more dynamic, so that local intensity variations can be corrected more efficiently. The proposed method is a four-step iterative procedure in which a non-parametric inhomogeneity correction is conducted. First, the probability distribution of image intensities and corresponding second derivatives is obtained. Second, intensity correction forces, condensing the probability distribution along the intensity feature, are computed for each voxel. Third, the inhomogeneity correction field is estimated by regularization of all voxel forces, and fourth, the corresponding partial inhomogeneity correction is performed. The degree of inhomogeneity correction dynamics is determined by the size of regularization kernel. The method was qualitatively and quantitatively evaluated on simulated and real MR brain images. The obtained results show that the proposed method does not corrupt inhomogeneity-free images and successfully corrects intensity inhomogeneity artefacts even if these are more dynamic

TH-A-18C-10: Dynamic Intensity Weighted Region of Interest Imaging

International Nuclear Information System (INIS)

Pearson, E; Pan, X; Pelizzari, C

2014-01-01

Purpose: For image guidance tasks full image quality is not required throughout the entire image. With dynamic filtration of the kV imaging beam the noise properties of the CT image can be locally controlled, providing a high quality image around the target volume with a lower quality surrounding region while providing substantial dose sparing to the patient as well as reduced scatter fluence on the detector. Methods: A dynamic collimation device with 3mm copper blades has been designed to mount in place of the bowtie filter on the On-Board Imager (Varian Medical Systems). The beam intensity is reduced by 95% behind the copper filters and the aperture is controlled dynamically to conformally illuminate a given ROI during a standard cone-beam CT scan. A data correction framework to account for the physical effects of the collimator prior to reconstruction was developed. Furthermore, to determine the dose savings and scatter reduction a monte carlo model was built in BEAMnrc with specifics from the Varian Monte Carlo Data Package. The MC model was validated with Gafchromic film. Results: The reconstructed image shows image quality comparable to a standard scan in the specified ROI, with higher noise and streaks in the outer region but still sufficient information for alignment to high contrast structures. The monte carlo modeling showed that the scatter-to-primary ratio was reduced from 1.26 for an unfiltered scan to 0.45 for an intensity weighted scan, suggesting that image quality may be improved in the inner ROI. Dose in the inner region was reduced 10–15% due to reduced scatter and by as much as 75% in the outer region. Conclusion: Dynamic intensity-weighted ROI imaging allows reduction of imaging dose to sensitive organs away from the target region while providing images that retain their utility for patient setup and procedure guidance. Funding was provided in part by Varian Medical Systems and NIH Grants 1RO1CA120540, T32EB002103, S10 RR021039 and P30 CA

Computational Psychometrics for Modeling System Dynamics during Stressful Disasters

Directory of Open Access Journals (Sweden)

Pietro Cipresso

2017-08-01

Full Text Available Disasters can be very stressful events. However, computational models of stress require data that might be very difficult to collect during disasters. Moreover, personal experiences are not repeatable, so it is not possible to collect bottom-up information when building a coherent model. To overcome these problems, we propose the use of computational models and virtual reality integration to recreate disaster situations, while examining possible dynamics in order to understand human behavior and relative consequences. By providing realistic parameters associated with disaster situations, computational scientists can work more closely with emergency responders to improve the quality of interventions in the future.

Dynamic Stress Concentration at the Boundary of an Incision at the Plate Under the Action of Weak Shock Waves

Directory of Open Access Journals (Sweden)

Mikulich Olena

2017-09-01

Full Text Available This paper proposes the novel technique for analysis of dynamic stress state of multi-connected infinite plates under the action of weak shock waves. For solution of the problem it uses the integral and discrete Fourier transforms. Calculation of transformed dynamic stresses at the incisions of plates is held using the boundary-integral equation method and the theory of complex variable functions. The numerical implementation of the developed algorithm is based on the method of mechanical quadratures and collocation technique. For calculation of originals of the dynamic stresses it uses modified discrete Fourier transform. The algorithm is effective in the analysis of the dynamic stress state of defective plates.

Proposal of a relationship between dynamic aperture adn intensity evolution in a storage ring

CERN Document Server

Giovannozzi, M

2010-01-01

A scaling law for the time-dependence of the dynamic aperture, i.e., the region of phase space where stable motion occurs, was proposed in previous papers, about ten years ago. The use of fundamental theorems of the theory of dynamical systems allowed showing that the dynamic aperture has a logarithmic dependence on time. In this paper this result, proved by mean of numerical simulations, is used as a basis for deriving a scaling law for the intensity evolution in a storage ring. The proposed scaling law is also tested against experimental data showing a remarkable agreement.

Predictors of stress among parents in pediatric intensive care unit: a prospective observational study.

Science.gov (United States)

Aamir, Mohd; Mittal, Kundan; Kaushik, Jaya Shankar; Kashyap, Haripal; Kaur, Gurpreet

2014-11-01

To determine the sociodemographic and clinical factors leading to stress among parents whose children are admitted in pediatric intensive care unit (PICU). A prospective observational study was conducted in PICU of a tertiary care hospital of north India. Parents of children admitted to PICU for at least 48 h duration were eligible for participation. At the end of 48 h, parental stress was assessed using parental stress scale (PSS:PICU) questionnaire which was administered to the parents. Baseline demographic and clinical parameters of children admitted to PICU were recorded. The parental stress was compared with demographic and clinical characteristics of children using appropriate statistical methods. A total of 49 parents were finally eligible for participation. Mean (SD) parental stress scores was highest in domains of procedures [1.52 (0.66)] and behavior and emotional [1.32 (0.42)] subscales. Mean (SD) total parental stress score among intubated children [1.31 (0.25)] was significantly more than among non intubated children [0.97 (0.26)] (p parental stress score were comparable in terms of gender (p = 0.15) and socioeconomic status (p = 0.32). On subscale analysis, it was found that professional communication is a significant stressor in age groups 0-12 mo [0.61(0.41)] (p = 0.02). It was observed that parents of intubated children were significantly stressed by the physical appearance of their children (p parental role (p = 0.002). Total parental stress score had a positive correlation with PRISM score (r = 0.308). Indian parents are stressed maximally with environment of PICU. Factor leading to parental stress was intubation status of the child and was not affected by gender or socio demographic profile of the parents.

Dynamics of a collisionless plasma interacting with an ultra-intense laser pulse

International Nuclear Information System (INIS)

Capdessus, Remi

2013-01-01

The interaction of a plasma with an ultra-intense laser pulse becomes more and more interesting as a result of the advances made in terms of numerical tools laser technology. The radiation reaction impacts the electrons dynamics, those of the synchrotron radiation as well as those of the ions by means of charge separation field, for laser intensities above 10 22 W/cm 2 . The kinetic equations governing the particles transport at ultra-high intensity have been obtained. The radiation reaction involves the shrinkage of the space volume of the electrons phases. It has been shown with numerical simulations the strong retro-action that the collective effects induce on the synchrotron radiation generated by the accelerated electrons. The importance of the collective effects depends strongly on the ions mass and of the thickness of the considered plasma. These effects could be verified experimentally with hydrogen cryogenic targets. (author) [fr

Field Measurement of Dynamic Compressive Stress Response of Pavement-Subgrade Induced by Moving Heavy-Duty Trucks

Directory of Open Access Journals (Sweden)

Lingshi An

2018-01-01

Full Text Available This paper presents the dynamic compressive stress response of pavement-subgrade induced by moving heavy-duty trucks. In order to study the distribution characteristic of dynamic pressure of pavement-subgrade in more detail, truck loadings, truck speeds, and dynamic pressure distributions at different depths were monitored under twenty-five working conditions on the section of Qiqihar-Nenjiang Highway in Heilongjiang Province, China. The effects of truck loading, truck speed, and depth on dynamic compressive stress response can be concluded as follows: (1 increasing truck loading will increase the dynamic pressure amplitude of subgrade-pavement and dominant frequencies are close to the characteristic frequencies caused by heavy-duty trucks at the speed of 70 km/h; (2 as truck speed increases, the dynamic pressure amplitudes of measuring points have an increasing tendency; the dynamic pressure spectrums are also significantly influenced by truck speed: the higher the truck speed, the wider the spectrum and the higher the dominant frequencies; (3 as depth increases, the dynamic pressure amplitudes of measuring points decrease rapidly. The influence of the front axle decreases gradually until disappearing and the compressive stress superposition phenomenon caused by rear double axles can be found with increasing depth.

Stress-intensity factors for cracks emanating from the loaded fastener hole

Science.gov (United States)

Shivakumar, V.; Hsu, Y. C.

1977-01-01

Using a series approach and the Muskhelishvili formulation in the two-dimensional theory of elasticity, stress-intensity factors K are derived for problems in which cracks emanate radially from the boundary of an arbitrarily loaded internal circular hole in an infinite plate. Numerical values are obtained for K(I) and K(II) for radial cracks from a hole containing a loose-fitted pin or rivet that is pulled perpendicular to the crack direction in the plane of the plate. The method is a general one for determining K for a set of symmetrically emanating radial cracks for a variety of concentrated or distributed tractions on the circular hole.

Gene Expression Dynamics Accompanying the Sponge Thermal Stress Response.

Science.gov (United States)

Guzman, Christine; Conaco, Cecilia

2016-01-01

Marine sponges are important members of coral reef ecosystems. Thus, their responses to changes in ocean chemistry and environmental conditions, particularly to higher seawater temperatures, will have potential impacts on the future of these reefs. To better understand the sponge thermal stress response, we investigated gene expression dynamics in the shallow water sponge, Haliclona tubifera (order Haplosclerida, class Demospongiae), subjected to elevated temperature. Using high-throughput transcriptome sequencing, we show that these conditions result in the activation of various processes that interact to maintain cellular homeostasis. Short-term thermal stress resulted in the induction of heat shock proteins, antioxidants, and genes involved in signal transduction and innate immunity pathways. Prolonged exposure to thermal stress affected the expression of genes involved in cellular damage repair, apoptosis, signaling and transcription. Interestingly, exposure to sublethal temperatures may improve the ability of the sponge to mitigate cellular damage under more extreme stress conditions. These insights into the potential mechanisms of adaptation and resilience of sponges contribute to a better understanding of sponge conservation status and the prediction of ecosystem trajectories under future climate conditions.

Response of coral assemblages to thermal stress: are bleaching intensity and spatial patterns consistent between events?

Science.gov (United States)

Penin, Lucie; Vidal-Dupiol, Jeremie; Adjeroud, Mehdi

2013-06-01

Mass bleaching events resulting in coral mortality are among the greatest threats to coral reefs, and are projected to increase in frequency and intensity with global warming. Achieving a better understanding of the consistency of the response of coral assemblages to thermal stress, both spatially and temporally, is essential to determine which reefs are more able to tolerate climate change. We compared variations in spatial and taxonomic patterns between two bleaching events at the scale of an island (Moorea Island, French Polynesia). Despite similar thermal stress and light conditions, bleaching intensity was significantly lower in 2007 (approximately 37 % of colonies showed signs of bleaching) than in 2002, when 55 % of the colonies bleached. Variations in the spatial patterns of bleaching intensity were consistent between the two events. Among nine sampling stations at three locations and three depths, the stations at which the bleaching response was lowest in 2002 were those that showed the lowest levels of bleaching in 2007. The taxonomic patterns of susceptibility to bleaching were also consistent between the two events. These findings have important implications for conservation because they indicate that corals are capable of acclimatization and/or adaptation and that, even at small spatial scales, some areas are consistently more susceptible to bleaching than others.

Combined centroid-envelope dynamics of intense, magnetically focused charged beams surrounded by conducting walls

International Nuclear Information System (INIS)

Fiuza, K.; Rizzato, F.B.; Pakter, R.

2006-01-01

In this paper we analyze the combined envelope-centroid dynamics of magnetically focused high-intensity charged beams surrounded by conducting walls. Similar to the case where conducting walls are absent, it is shown that the envelope and centroid dynamics decouple from each other. Mismatched envelopes still decay into equilibrium with simultaneous emittance growth, but the centroid keeps oscillating with no appreciable energy loss. Some estimates are performed to analytically obtain characteristics of halo formation seen in the full simulations

Temporal changes in vegetation of a virgin beech woodland remnant: stand-scale stability with intensive fine-scale dynamics governed by stand dynamic events

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Tibor Standovár

2017-03-01

Full Text Available The aim of this resurvey study is to check if herbaceous vegetation on the forest floor exhibits overall stability at the stand-scale in spite of intensive dynamics at the scale of individual plots and stand dynamic events (driven by natural fine scale canopy gap dynamics. In 1996, we sampled a 1.5 ha patch using 0.25 m² plots placed along a 5 m × 5 m grid in the best remnant of central European montane beech woods in Hungary. All species in the herbaceous layer and their cover estimates were recorded. Five patches representing different stand developmental situations (SDS were selected for resurvey. In 2013, 306 plots were resurveyed by using blocks of four 0.25 m² plots to test the effects of imperfect relocation. We found very intensive fine-scale dynamics in the herbaceous layer with high species turnover and sharp changes in ground layer cover at the local-scale (< 1 m2. A decrease in species richness and herbaceous layer cover, as well as high species turnover, characterized the closing gaps. Colonization events and increasing species richness and herbaceous layer cover prevailed in the two newly created gaps. A pronounced decrease in the total cover, but low species turnover and survival of the majority of the closed forest specialists was detected by the resurvey at the stand-scale. The test aiming at assessing the effect of relocation showed a higher time effect than the effect of imprecise relocation. The very intensive fine-scale dynamics of the studied beech forest are profoundly determined by natural stand dynamics. Extinction and colonisation episodes even out at the stand-scale, implying an overall compositional stability of the herbaceous vegetation at the given spatial and temporal scale. We argue that fine-scale gap dynamics, driven by natural processes or applied as a management method, can warrant the survival of many closed forest specialist species in the long-run. Nomenclature: Flora Europaea (Tutin et al. 2010 for

Role of Reynolds stress and toroidal momentum transport in the dynamics of internal transport barriers

International Nuclear Information System (INIS)

Kim, S. S.; Jhang, Hogun; Diamond, P. H.

2012-01-01

We study the interplay between intrinsic rotation and internal transport barrier (ITB) dynamics through the dynamic change of the parallel Reynolds stress. Global flux-driven gyrofluid simulations are used for this study. In particular, we investigate the role of parallel velocity gradient instability (PVGI) in the ITB formation and the back transition. It is found that the excitation of PVGI is followed by a change in the Reynolds stress which drives a momentum redistribution. This significantly influences E×B shear evolution and subsequent ITB dynamics. Nonlocal interactions among fluctuations are also observed during the PVGI excitation, resulting in turbulence suppression at the ITB.

Dynamic characteristic of intense short microwave propagation in an atmosphere

International Nuclear Information System (INIS)

Yee, J.H.; Alvarez, R.A.; Mayhall, D.J.; Madsen, N.K.; Cabayan, H.S.

1983-07-01

The dynamic behavior of an intense microwave pulse which propagates through the atmosphere will be presented. Our theoretical results are obtained by solving Maxwell's equations, together with the electron fluid equations. Our calculations show that although large portions of the initial energy are absorbed by the electrons that are created through the avalanche process, a significant amount of energy is still able to reach the earth's surface. The amount of energy that reaches the earth's surface as a function of initial energy and wave shape after having propagated through 100 km in the atmosphere are investigated. Results for the air breakdown threshold intensity as a function of the pressure for different pulse widths and different frequencies will also be presented. In addition, we will present a comparison between the theoretical and the experimental results for the pulse shape of a short microwave pulse after it has traveled through a rectangular wave guide which contains a section of air. 23 references, 9 figures

Posttraumatic Stress Disorder's Frequency and Intensity Ratings Are Associated with Factor Structure Differences in Military Veterans

Science.gov (United States)

Elhai, Jon D.; Palmieri, Patrick A.; Biehn, Tracey L.; Frueh, B. Christopher; Magruder, Kathryn M.

2010-01-01

We examined possible differences in the factor structure of posttraumatic stress disorder (PTSD) on the basis of whether frequency or intensity symptom response formats were used to assess PTSD. Participants included 669 veterans recruited from an epidemiological study of four Veterans Affairs Medical Centers' primary care clinics in the…

The stress and stress intensity factors computation by BEM and FEM combination for nozzle junction under pressure and thermal loads

International Nuclear Information System (INIS)

Du, Q.; Cen, Z.; Zhu, H.

1989-01-01

This paper reports linear elastic fracture analysis based upon the stress intensity factor evaluation successfully applied to safety assessments of cracked structures. The nozzle junction are usually subjected to high pressure and thermal loads simultaneously. In validity of linear elastic fracture analysis, K can be decomposed into K P (caused by mechanic loads) and K τ (caused by thermal loads). Under thermal transient loading, explicit analysis (say by the FEM or BEM) of K tracing an entire history respectively for a range of crack depth may be much more time consuming. The techniques of weight function provide efficient means for transforming the problem into the stress computation of the uncracked structure and generation of influence function (for the given structure and size of crack). In this paper, a combination of BE-FEM has been used for the analysis of the cracked nozzle structure by techniques of weight function. The influence functions are obtained by coupled BE-FEM and the uncracked structure stress are computed by finite element methods

Dynamic energy spectrum and energy deposition in solid target by intense pulsed ion beams

Institute of Scientific and Technical Information of China (English)

Xiao Yu; Xiao-Yun Le; Zheng Liu; Jie Shen; Yu I.Isakova; Hao-Wen Zhong; Jie Zhang; Sha Yan; Gao-Long Zhang; Xiao-Fu Zhang

2017-01-01

A method for analyzing the dynamic energy spectrum of intense pulsed ion beam (IPIB) was proposed.Its influence on beam energy deposition in metal target was studied with IPIB produced by two types of magnetically insulated diodes (MID).The emission of IPIB was described with space charge limitation model,and the dynamic energy spectrum was further analyzed with time-of-flight method.IPIBs generated by pulsed accelerators of BIPPAB-450 (active MID) and TEMP-4M (passive MID) were studied.The dynamic energy spectrum was used to deduce the power density distribution of IPIB in the target with Monte Carlo simulation and infrared imaging diagnostics.The effect on the distribution and evolution of thermal field induced by the characteristics of IPIB dynamic energy spectrum was discussed.

Comparison of dynamic ultrasound and stress radiology for assessment of inferior glenohumeral laxity in asymptomatic shoulders

International Nuclear Information System (INIS)

Cheng, S.C.; Wallace, W.A.; Hulse, D.; Fairbairn, K.J.; Clarke, M.

2008-01-01

To determine the level of agreement between dynamic ultrasound imaging and stress radiography used for the measurement of inferior glenohumeral laxity in asymptomatic shoulders, and to determine the repeatability of the dynamic ultrasound technique. Using a custom-made stress device to apply an inferior displacement force of 90 N, we assessed 20 asymptomatic male subjects for inferior glenohumeral laxity, using stress radiography and dynamic ultrasound. Paired differences between the two methods were evaluated by the 95% limits of agreement method. At a separate session, 19 subjects had inferior glenohumeral laxity assessed by two observers, using dynamic ultrasound. Inter- and intra-observer repeatability was determined for the ultrasound technique. The mean [± standard deviation (SD)] inferior translation was 4.7 ± 4.1 mm by stress radiography and 4.4 ± 2.3 mm by dynamic ultrasound. The 95% limits of agreement showed good agreement between the two methods. The paired difference between the two measurement methods varied with the magnitude of the measurement (P < 0.001). Intra-observer repeatability of dynamic ultrasound was determined by the use of intra-class correlation coefficients and was 0.94 and 0.89 for the two investigators. Inter-observer repeatability was 0.85. The standard error of the measurement was 0.60 mm and 0.66 mm, for repeated measurements by the two investigators, and 0.85 mm between investigators. Repeatability coefficients demonstrated excellent consistency of measurement between sessions and good consistency between observers. Dynamic ultrasound is a valid and reproducible method for the assessment and quantification of inferior glenohumeral laxity. (orig.)

Investigating the running abilities of Tyrannosaurus rex using stress-constrained multibody dynamic analysis

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William I. Sellers

2017-07-01

Full Text Available The running ability of Tyrannosaurus rex has been intensively studied due to its relevance to interpretations of feeding behaviour and the biomechanics of scaling in giant predatory dinosaurs. Different studies using differing methodologies have produced a very wide range of top speed estimates and there is therefore a need to develop techniques that can improve these predictions. Here we present a new approach that combines two separate biomechanical techniques (multibody dynamic analysis and skeletal stress analysis to demonstrate that true running gaits would probably lead to unacceptably high skeletal loads in T. rex. Combining these two approaches reduces the high-level of uncertainty in previous predictions associated with unknown soft tissue parameters in dinosaurs, and demonstrates that the relatively long limb segments of T. rex—long argued to indicate competent running ability—would actually have mechanically limited this species to walking gaits. Being limited to walking speeds contradicts arguments of high-speed pursuit predation for the largest bipedal dinosaurs like T. rex, and demonstrates the power of multiphysics approaches for locomotor reconstructions of extinct animals.

Dynamic regulation of NMDAR function in the adult brain by the stress hormone corticosterone

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Yiu Chung eTse

2012-03-01

Full Text Available Stress and corticosteroids dynamically modulate the expression of synaptic plasticity at glutamatergic synapses in the developed brain. Together with alpha-amino-3-hydroxy-methyl-4-isoxazole propionic acid receptors (AMPAR, N-methyl-D-aspartate receptors (NMDAR are critical mediators of synaptic function and are essential for the induction of many forms of synaptic plasticity. Regulation of NMDAR function by cortisol/corticosterone (CORT may be fundamental to the effects of stress on synaptic plasticity. Recent reports of the efficacy of NMDAR antagonists in treating certain stress-associated psychopathologies further highlight the importance of understanding the regulation of NMDAR function by CORT. Knowledge of how corticosteroids regulate NMDAR function within the adult brain is relatively sparse, perhaps due to a common belief that NMDAR function is relatively stable in the adult brain. We review recent results from our laboratory and others demonstrating dynamic regulation of NMDAR function by CORT in the adult brain. In addition, we consider the issue of how differences in the early life environment may program differential sensitivity to modulation of NMDAR function by CORT and how this may influence synaptic function during stress. Findings from these studies demonstrate that NMDAR function in the adult hippocampus remains sensitive to even brief exposures to CORT and that the capacity for modulation of NMDAR may be programmed, in part, by the early life environment. Modulation of NMDAR function may contribute to dynamic regulation of synaptic plasticity and adaptation in the face of stress, however enhanced NMDAR function may be implicated in mechanisms of stress related psychopathologies including depression.

Demographic and occupational predictors of stress and fatigue in French intensive-care registered nurses and nurses' aides: a cross-sectional study.

Science.gov (United States)

Jones, Gabrielle; Hocine, Mounia; Salomon, Jérôme; Dab, William; Temime, Laura

2015-01-01

Healthcare workers (HCWs) working in intensive-care units (ICUs) are exposed to high physical and mental demands potentially affecting their health or having repercussions on patient care. Although several studies have explored the links between some aspects of working conditions in hospitals and HCW health, the complex dynamics at play are not fully understood. This study aimed to explore the impact of a wide array of demographic, employment and organizational factors related to fatigue and stress of French ICU HCWs. A cross-sectional study was conducted in ICUs of Paris-area hospitals between January 18, 2013 and April 2, 2013. All types of adult ICUs were included (medical, surgical and polyvalent). Included in the study were HCWs with patient contact (doctors, residents, registered nurses, nurse's aides and physical therapists). Participation was proposed to all eligible HCWs present during on-site visits. Temporary staff not typically assigned to the given ICU was excluded. Data were collected using an individual questionnaire administered in interviews during day and night shifts (N=682). Stress and fatigue outcomes included the 10-item Perceived Stress Scale (PSS10), the Nottingham Health Profile sleep and energy level rubrics and the current fatigue state at the interview. Multivariate analysis was restricted to nurse and nurse's aide data (n=536). Doctors and residents reported fewer sleep difficulties but were more likely to report a tired current state. Female gender was associated with higher stress levels and greater fatigue for all outcomes, while greater social support of supervisor or colleagues decreased stress and fatigue. At the organizational level, longer shifts (12 h vs. 8 h) were associated with tired current state and greater sleep difficulties. Personnel on rotating shifts had lower stress and a better current state, while those on night shifts had greater sleep and energy level difficulties. Even when controlling for demographic factors

Effect of Schisandrae on stress system of soldiers undergone high-intensity military training

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Nan XIA

2014-03-01

Full Text Available Objective　To explore the changes in basic serum levels of hypothalamus-pituitrin-adrenal (HPA axis, hypothalamus-pituitrin-gonad (HPG axis and proinflammatory cytokines IL-1, IL-2 and IL-6 in repeated acute stress caused by one-week intensive training, and study the effects of oral administration of Schisandrae, salidroside and Schisandrae compound on the contents of those stress hormones and cytokines mentioned above. Methods　One hundred and twenty healthy soldiers chosen from junior infantry combat troops who had never received long-term amphibious training were randomly divided into four groups (30 each: group A (Schisandrae compound group, group B (Schisandrae group, group C (salidroside group and group D (control group. Each and every soldier of all the groups underwent high-intensity composite military training, 8 hours per day, for a week. Venous blood sampling was collected at 7:00-8:00 a.m. before and after the training, respectively. Levels of cortisol (CORT, adrenocorticotropic hormone (ACTH, testosterone (T, IL-1, IL-2 and IL-6 in different groups were measured by radioimmunoassay (RIA. The changes in the levels of all the above mentioned hormones and cytokines in every group were observed and compared. Results　In group D, as compared with the pre-stress levels, no marked difference was found in the levels of serum CORT and ACTH (P>0.05, but the levels of T and IL-6 significantly decreased (P0.05. In group C, the levels of T and IL-6 significantly decreased (P0.05. In group A, the serum levels of CORT, ACTH, T, IL-1 and IL-6 significantly decreased, while that of IL-2 significantly increased (P<0.01. As compared with group D, the level of ACTH in group A and group B, the level of IL-2 in group C significantly decreased (P<0.05. Conclusions　 Schisandrae and Schisandrae compound have a marked and lasting inhibitory effect on the activation of HPA axis and the elevation of serum CORT levels induced by stress, while the similar

Development of crankshaft dynamic stress prediction; Jitsudoji crankshaft oryoku yosoku shuho no kaihatsu

Energy Technology Data Exchange (ETDEWEB)

Takahashi, S; Iwamoto, A; Miyazawa, H; Sato, K; Ozaki, H [Honda R and D Co. Ltd., Tokyo (Japan)

1997-10-01

In this paper, the development of the simulation model which predicts the stress of the crankshaft under running condition precisely is described. This simulation model considers about the nonlinearity of the oil film stiffness in the main bearing, the dynamic characteristic of the crankshaft system including resonance and the cylinder block stiffness. By the development of this stress analysis simulation, the stress m each part of the crankshaft during durability testing could be precisely predicted. 1 ref., 10 figs.

Love-type wave propagation in a pre-stressed viscoelastic medium influenced by smooth moving punch

Science.gov (United States)

Singh, A. K.; Parween, Z.; Chatterjee, M.; Chattopadhyay, A.

2015-04-01

In the present paper, a mathematical model studying the effect of smooth moving semi-infinite punch on the propagation of Love-type wave in an initially stressed viscoelastic strip is developed. The dynamic stress concentration due to the punch for the force of a constant intensity has been obtained in the closed form. Method based on Weiner-hopf technique which is indicated by Matczynski has been employed. The study manifests the significant effect of various affecting parameters viz. speed of moving punch associated with Love-type wave speed, horizontal compressive/tensile initial stress, vertical compressive/tensile initial stress, frequency parameter, and viscoelastic parameter on dynamic stress concentration due to semi-infinite punch. Moreover, some important peculiarities have been traced out and depicted by means of graphs.

Dynamic stresses in a Francis model turbine at deep part load

Science.gov (United States)

Weber, Wilhelm; von Locquenghien, Florian; Conrad, Philipp; Koutnik, Jiri

2017-04-01

A comparison between numerically obtained dynamic stresses in a Francis model turbine at deep part load with experimental ones is presented. Due to the change in the electrical power mix to more content of new renewable energy sources, Francis turbines are forced to operate at deep part load in order to compensate stochastic nature of wind and solar power and to ensure grid stability. For the extension of the operating range towards deep part load improved understanding of the harsh flow conditions and their impact on material fatigue of hydraulic components is required in order to ensure long life time of the power unit. In this paper pressure loads on a model turbine runner from unsteady two-phase computational fluid dynamics simulation at deep part load are used for calculation of mechanical stresses by finite element analysis. Therewith, stress distribution over time is determined. Since only few runner rotations are simulated due to enormous numerical cost, more effort has to be spent to evaluation procedure in order to obtain objective results. By comparing the numerical results with measured strains accuracy of the whole simulation procedure is verified.

Conceptualizing the dynamics of workplace stress: a systems-based study of nursing aides.

Science.gov (United States)

Jetha, Arif; Kernan, Laura; Kurowski, Alicia

2017-01-05

Workplace stress is a complex phenomenon that may often be dynamic and evolving over time. Traditional linear modeling does not allow representation of recursive feedback loops among the implicated factors. The objective of this study was to develop a multidimensional system dynamics model (SDM) of workplace stress among nursing aides and conduct simulations to illustrate how changes in psychosocial perceptions and workplace factors might influence workplace stress over time. Eight key informants with prior experience in a large study of US nursing home workers participated in model building. Participants brainstormed the range of components related to workplace stress. Components were grouped together based on common themes and translated into feedback loops. The SDM was parameterized through key informant insight on the shape and magnitude of the relationship between model components. Model construction was also supported utilizing survey data collected as part of the larger study. All data was entered into the software program, Vensim. Simulations were conducted to examine how adaptations to model components would influence workplace stress. The SDM included perceptions of organizational conditions (e.g., job demands and job control), workplace social support (i.e., managerial and coworker social support), workplace safety, and demands outside of work (i.e. work-family conflict). Each component was part of a reinforcing feedback loop. Simulations exhibited that scenarios with increasing job control and decreasing job demands led to a decline in workplace stress. Within the context of the system, the effects of workplace social support, workplace safety, and work-family conflict were relatively minor. SDM methodology offers a unique perspective for researchers and practitioners to view workplace stress as a dynamic process. The portrayal of multiple recursive feedback loops can guide the development of policies and programs within complex organizational contexts

Parasitism and Physiological Trade-Offs in Stressed Capybaras

Science.gov (United States)

Eberhardt, Ayelen T.; Costa, Sebastián A.; Marini, M. Rocío; Racca, Andrea; Baldi, Cecilia J.; Robles, M. Rosario; Moreno, Pablo G.; Beldomenico, Pablo M.

2013-01-01

Parasites play a key role in regulating wildlife population dynamics, but their impact on the host appears to be context-dependent. Evidence indicates that a synergistic interaction between stress, host condition and parasites is implicated in this phenomenon, but more studies are needed to better understand this context-dependency. With the goal to assess the net effect of two types of chronic stress on various host-parasite interactions, we conducted an experiment in capybaras to evaluate the impact of food restriction and physical restraint on the infection intensity of specific gastrointestinal nematodes and coccidia, and how these stressors affected the growth, body condition, and some immuno-physiological parameters. Our hypothesis was that both forms of stress would result in an alteration in the host-parasite interactions, with deteriorated condition and reduced immunological investment leading to high parasite burdens and vice versa. Stressed capybaras had significantly higher coccidia infection intensities; but among individuals that were smaller, those stressed consistently showed lower helminth burdens than controls. Both stress treatments had a marked negative impact on growth and body condition, but concomitantly they had a significant positive effect on some components of the immune system. Our results suggest, on the one hand, that during prolonged periods of stress capybaras preventatively invest in some components of their immunity, such as innate humoural defenses and cells that combat helminths, which could be considered a stress-dependent prophylaxis. On the other hand, stress was found to cause greater infection intensities of protozoans but lower burdens of nematodes, indicating that the relationship between stress, physiological trade-offs and infection depends on the type of parasite in question. Moreover, both findings might be related in a causal way, as one of the immunological parameters enhanced in stressed capybaras is associated with

Comparing of Normal Stress Distribution in Static and Dynamic Soil-Structure Interaction Analyses

International Nuclear Information System (INIS)

Kholdebarin, Alireza; Massumi, Ali; Davoodi, Mohammad; Tabatabaiefar, Hamid Reza

2008-01-01

It is important to consider the vertical component of earthquake loading and inertia force in soil-structure interaction analyses. In most circumstances, design engineers are primarily concerned about the analysis of behavior of foundations subjected to earthquake-induced forces transmitted from the bedrock. In this research, a single rigid foundation with designated geometrical parameters located on sandy-clay soil has been modeled in FLAC software with Finite Different Method and subjected to three different vertical components of earthquake records. In these cases, it is important to evaluate effect of footing on underlying soil and to consider normal stress in soil with and without footing. The distribution of normal stress under the footing in static and dynamic states has been studied and compared. This Comparison indicated that, increasing in normal stress under the footing caused by vertical component of ground excitations, has decreased dynamic vertical settlement in comparison with static state

Investigation into Mechanism of Floor Dynamic Rupture by Evolution Characteristics of Stress and Mine Tremors: A Case Study in Guojiahe Coal Mine, China

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Guangjian Liu

2018-01-01

Full Text Available In order to explore the mechanism of floor dynamic rupture, the current study adopts a thin plate model to further investigate the condition of floor failure. One of the possible explanations could be floor buckling due to high horizontal stress and dynamic disturbance ultimately leading to rapid and massive release of elastic energy thus inducing dynamic rupture. Seismic computed tomography and 3D location were employed to explore the evolution characteristics of floor stress distribution and positions of mine tremors. In the regions of floor dynamic rupture, higher P-wave velocity was recorded prior to the dynamic rupture. On the contrary, relatively lower reading was observed after the dynamic rupture thus depicting a high stress concentration condition. Meanwhile, evolution of mine tremors revealed the accumulation and subsequent release of energy during the dynamic rupture process. It was further revealed that dynamic rupture was induced due to the superposition of static and dynamic stresses: (i the high static stress concentration due to frontal and lateral abutment stress from coal pillar and (ii dynamic stress from the fracture and caving of coal pillar, hard roof, and key stratum. In the later part of this study, the floor dynamic rupture occurrence process would be reproduced through numerical simulations within a 0.6 sec time frame. The above-mentioned findings would be used to propose a feasible mechanism for prewarning and prevention of floor dynamic rupture using seismic computed tomography and mine tremors 3D location.

Dynamic Jump Intensities and Risk Premiums in Crude Oil Futures and Options Markets

DEFF Research Database (Denmark)

Christoffersen, Peter; Jacobs, Kris; Li, Bingxin

2016-01-01

Options on crude oil futures are the most actively traded commodity options. We develop a class of computationally efficient discrete-time jump models that allow for closed-form option valuation, and we use crude oil futures and options data to investigate the economic importance of jumps...... and dynamic jump intensities in these markets. Allowing for jumps is crucial for modeling crude oil futures and futures options, and we find evidence in favor of time-varying jump intensities. During crisis periods, jumps occur more frequently. The properties of the jump processes implied by the option data...... differ from those implied by the futures data, which may be due to improved parameter identification....

Effect of elastic anisotropy of crystal grain on stress intensity factor

Energy Technology Data Exchange (ETDEWEB)

Kamaya, Masayuki [Inst. of Nuclear Safety System Inc., Mihama, Fukui (Japan)

2002-09-01

The stress intensity factor (SIF) is used widely for evaluating integrity of cracked components. Usually, the SIF obtained under isotropic elastic conditions is used for the evaluations. Although, macroscopic elastic behaviors of polycrystal materials can be considered isotropic, each crystal has anisotropic elastic properties. This implies that if the crack size is small and the influence of anisotropic elastic properties on the stress around cracks is significant, the SIF evaluated under anisotropic elastic conditions may differ from the SIF obtained under isotropic elastic conditions. In the present study, the effect of anisotropic elasticity on the SIF was evaluated by using the finite element analysis (FEA). First, the SIF of semi-circular cracks located in a single crystal was evaluated. It was found that the SIF is affected crystal orientation. Secondly, FEA using a polycrystal model was performed. It was found that the change in the SIF was caused by crack tip crystal orientation as well as the deformation constraint from neighboring crystals. Finally, the statistical tendency of change in the SIF caused by the anisotropic elastic properties and the relationship with crack size were examined. The influence of the local SIF on crack growth behavior is also discussed. (author)

Effect of elastic anisotropy of crystal grain on stress intensity factor

International Nuclear Information System (INIS)

Kamaya, Masayuki

2002-01-01

The stress intensity factor (SIF) is used widely for evaluating integrity of cracked components. Usually, the SIF obtained under isotropic elastic conditions is used for the evaluations. Although, macroscopic elastic behaviors of polycrystal materials can be considered isotropic, each crystal has anisotropic elastic properties. This implies that if the crack size is small and the influence of anisotropic elastic properties on the stress around cracks is significant, the SIF evaluated under anisotropic elastic conditions may differ from the SIF obtained under isotropic elastic conditions. In the present study, the effect of anisotropic elasticity on the SIF was evaluated by using the finite element analysis (FEA). First, the SIF of semi-circular cracks located in a single crystal was evaluated. It was found that the SIF is affected crystal orientation. Secondly, FEA using a polycrystal model was performed. It was found that the change in the SIF was caused by crack tip crystal orientation as well as the deformation constraint from neighboring crystals. Finally, the statistical tendency of change in the SIF caused by the anisotropic elastic properties and the relationship with crack size were examined. The influence of the local SIF on crack growth behavior is also discussed. (author)

The physiological stress response to high-intensity sprint exercise following the ingestion of sodium bicarbonate.

Science.gov (United States)

Peart, Daniel J; Kirk, Richard J; Hillman, Angela R; Madden, Leigh A; Siegler, Jason C; Vince, Rebecca V

2013-01-01

The purpose of this study was to investigate the effects of pre-exercise alkalosis on the physiological stress response to high-intensity exercise. Seven physically active males (age 22 ± 3 years, height 1.82 ± 0.06 m, mass 81.3 ± 8.4 kg and peak power output 300 ± 22 W) performed a repeated sprint cycle exercise following a dose of 0.3 g kg(-1) body mass of sodium bicarbonate (NaHCO(3)) (BICARB), or a placebo of 0.045 g kg(-1) body mass of sodium chloride (PLAC). Monocyte-expressed heat shock protein 72 (HSP72) and plasma thiobarbituric acid reactive substances (TBARS) were significantly attenuated in BICARB compared to PLAC (p = 0.04 and p = 0.039, respectively), however total anti-oxidant capacity, the ratio of oxidised to total glutathione, cortisol, interleukin 6 and interleukin 8 were not significantly induced by the exercise. In conclusion, monocyte-expressed HSP72 is significantly increased following high-intensity anaerobic exercise, and its attenuation following such exercise with the ingestion of NaHCO(3) is unlikely to be due to a decreased oxidative stress.

Effects of moving dynamic tyre loads on tyre-pavement contact stresses

CSIR Research Space (South Africa)

Steyn, WJvdM

2002-01-01

Full Text Available The purpose of this paper is to indicate the effect that moving dynamic tyre loads has on the tyre-pavement contact stresses used in pavement analysis. Traditionally tyre loads (in pavement analysis) are modelled as constant loads applied through...

Risk factors for the development of post-traumatic stress disorder and coping strategies in mothers and fathers following infant hospitalisation in the neonatal intensive care unit.

Science.gov (United States)

Aftyka, Anna; Rybojad, Beata; Rosa, Wojciech; Wróbel, Aleksandra; Karakuła-Juchnowicz, Hanna

2017-12-01

The aim of this study was to identify the potential risk factors for the development of post-traumatic stress disorder in mothers and fathers following infant hospitalisation in the neonatal intensive care unit. The development of neonatal intensive care units has increased the survival rate of infants. However, one of the major parental problems is post-traumatic stress disorder. An observational study covered 125 parents (72 mothers and 53 fathers) of infants aged 3-12 months who were hospitalised in the neonatal intensive care unit during the neonatal period. Third-referral neonatal intensive care unit. Several standardised and self-reported research tools were used to estimate the level of post-traumatic stress symptoms (Impact Event Scale-Revised), perceived stress (Perceived Stress Scale) and coping strategies (COPE Inventory). The respondents also completed a Parent and Infant Characteristic Questionnaire. The mothers and fathers did not differ in their parental and infant characteristics. Post-traumatic stress disorder was present in 60% of the mothers and 47% of the fathers. Compared to the fathers, the mothers felt greater stress (p = .020) and presented a higher severity of post-traumatic stress disorder (p stress disorder in the mothers. In the fathers, an Apgar test at 1 min after birth (p = .030) and a partner's post-traumatic stress disorder (p = .038) were related to post-traumatic stress disorder. The mothers compared to the fathers were more likely to use strategies such as: positive reinterpretation and growth, focusing on and venting of emotions, instrumental social support, religious coping and acceptance. In the fathers, the predictors included an Apgar score at 1 min after birth, a lack of congenital anomalies in the child and mental disengagement. Risk factors for post-traumatic stress disorder, as well as coping strategies, differ in women compare to men. Knowledge of risk factors for post-traumatic stress disorder, specific to

Stress, strain, and structural dynamics an interactive handbook of formulas, solutions, and Matlab toolboxes

CERN Document Server

Yang, Bingen

2005-01-01

Stress, Strain, and Structural Dynamics is a comprehensive and definitive reference to statics and dynamics of solids and structures, including mechanics of materials, structural mechanics, elasticity, rigid-body dynamics, vibrations, structural dynamics, and structural controls. This text integrates the development of fundamental theories, formulas and mathematical models with user-friendly interactive computer programs, written in the powerful and popular MATLAB. This unique merger of technical referencing and interactive computing allows instant solution of a variety of engineering problems

Simulation Analysis of the Mutual Influence of the Stress Intensity Factor on the Multiple Blisters Caused by Hydrogen Induced Damage

Science.gov (United States)

Ji, Congwei; Zhang, Shaojie; Wang, Hehui

2018-03-01

Hydrogen blisters are taken as the research object by using the finite element software ABAQUS. The stress intensity factors of blister cracks are numerically calculated at varying depths and different edge distances for established three-dimensional finite element models of single-blister and double-blisters, respectively. The mutual influence of the stress intensity factors of the multiple blisters is obtained. It shows that the blister crack is easier to expand when the crack is closer to inner wall of the cylinder. What’s more, the crack growth rate increases firstly and then decreases as the increasing of the distance between two blisters cracks. The investigated result is of great reference value for predicting the trend of blister crack growth.

Does urbanization affect energy intensities across provinces in China?Long-run elasticities estimation using dynamic panels with heterogeneous slopes

International Nuclear Information System (INIS)

Ma, Ben

2015-01-01

Although there has been extensive debate in the literature that addresses the impact of urbanization on total energy use, the relative magnitude of each impact channel has not been empirically examined and urbanization's effects on energy transition dynamics in China remains unknown. Using panel datasets at the provincial level from 1986 to 2011, this paper employs dynamic models to investigate both the long-run and short-run elasticities of urbanization on energy intensities and the most significant impact channel is identified. Coal intensity and electricity intensity are also modeled to reveal energy transition dynamics driven by urbanization. A set of newly developed regression techniques, namely well-performed common correlated effects mean group (CCEMG) and augmented mean group (AMG) estimators, are used to treat residual cross-sectional dependence, nonstationary residuals, and unlikely-to-hold homogeneous slope assumptions. The results obtained verify that the net effects of urbanization on overall energy intensity and electricity intensity are statistically positive, with long-run elasticities of 0.14% to 0.37% and 0.23% to 0.29%, respectively, whereas China's urbanization does not significantly increase coal intensity. The fact that short-run elasticities account for a majority of corresponding long-run values indicates that the short-run effect, that is, indirect energy use induced by urban infrastructures is the most significant impact channel of urbanization on energy use in China. An energy transition from high-pollution coal to clean electricity is also present in China, although the fundamental transition to renewable energy is still in its infancy. From a regional perspective, urbanization exerts asymmetric impacts on provincial energy use so that energy policies associated with urbanization should be province-specific. The findings also illustrate that for a panel dataset on regional dimension within large and fast-growing economies such

The Role of Molecular Microtubule Motors and the Microtubule Cytoskeleton in Stress Granule Dynamics

Directory of Open Access Journals (Sweden)

Kristen M. Bartoli

2011-01-01

Full Text Available Stress granules (SGs are cytoplasmic foci that appear in cells exposed to stress-induced translational inhibition. SGs function as a triage center, where mRNAs are sorted for storage, degradation, and translation reinitiation. The underlying mechanisms of SGs dynamics are still being characterized, although many key players have been identified. The main components of SGs are stalled 48S preinitiation complexes. To date, many other proteins have also been found to localize in SGs and are hypothesized to function in SG dynamics. Most recently, the microtubule cytoskeleton and associated motor proteins have been demonstrated to function in SG dynamics. In this paper, we will discuss current literature examining the function of microtubules and the molecular microtubule motors in SG assembly, coalescence, movement, composition, organization, and disassembly.

Utilization of the molecular dynamic to study the effect of hydrogen in the stress corrosion

International Nuclear Information System (INIS)

Arnoux, P.

2007-01-01

Many microscopic and theoretical models of stress corrosion have been proposed, in particularly to explain the grain boundary cracking of stainless steels and nickel base. In this work calculus of molecular dynamic have been used to propose a mechanism of stress corrosion at the atomic scale. The author aims to reproduce, by molecular dynamic, the mechanism of an open crack in irradiated stainless steel in PWR reactor and show that the growth of the oxide at the crack back produce hydrogen. (A.L.B.)

Short-term salt stress strongly affects dynamic photosynthesis, but not steady-state photosynthesis, in tomato (Solanum lycopersicum)

NARCIS (Netherlands)

Zhang, Yuqi; Kaiser, Elias; Zhang, Yating; Yang, Qichang; Li, Tao

2018-01-01

Salt stress occurs worldwide due to widespread soil salinization. Also, plants are often subjected to rapidly alternating periods of sun and shade (sunflecks). Despite this combined occurrence of salt stress and sunflecks, dynamic photosynthetic responses to sunflecks under salt stress remain

Effects of water stress and light intensity on chlorophyll fluorescence parameters and pigments of Aloe vera L.

Science.gov (United States)

Hazrati, Saeid; Tahmasebi-Sarvestani, Zeinolabedin; Modarres-Sanavy, Seyed Ali Mohammad; Mokhtassi-Bidgoli, Ali; Nicola, Silvana

2016-09-01

Aloe vera L. is one of the most important medicinal plants in the world. In order to determine the effects of light intensity and water deficit stress on chlorophyll (Chl) fluorescence and pigments of A. vera, a split-plot in time experiment was laid out in a randomized complete block design with four replications in a research greenhouse. The factorial combination of three light intensities (50, 75 and 100% of sunlight) and four irrigation regimes (irrigation after depleting 20, 40, 60 and 80% of soil water content) were considered as main factors. Sampling time was considered as sub factor. The first, second and third samplings were performed 90, 180 and 270 days after imposing the treatments, respectively. The results demonstrated that the highest light intensity and the severe water stress decreased maximum fluorescence (Fm), variable fluorescence (Fv)/Fm, quantum yield of PSII photochemistry (ФPSII), Chl and photochemical quenching (qP) but increased non-photochemical quenching (NPQ), minimum fluorescence (F0) and Anthocyanin (Anth). Additionally, the highest Fm, Fv/Fm, ФPSII and qP and the lowest NPQ and F0 were observed when 50% of sunlight was blocked and irrigation was done after 40% soil water depletion. Irradiance of full sunlight and water deficit stress let to the photoinhibition of photosynthesis, as indicated by a reduced quantum yield of PSII, ФPSII, and qP, as well as higher NPQ. Thus, chlorophyll florescence measurements provide valuable physiological data. Close to half of total solar radiation and irrigation after depleting 40% of soil water content were selected as the most efficient treatments. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

Mixed-mode stress intensity factors for kink cracks with finite kink length loaded in tension and bending: application to dentin and enamel.

Science.gov (United States)

Bechtle, Sabine; Fett, Theo; Rizzi, Gabriele; Habelitz, Stefan; Schneider, Gerold A

2010-05-01

Fracture toughness resistance curves describe a material's resistance against crack propagation. These curves are often used to characterize biomaterials like bone, nacre or dentin as these materials commonly exhibit a pronounced increase in fracture toughness with crack extension due to co-acting mechanisms such as crack bridging, crack deflection and microcracking. The knowledge of appropriate stress intensity factors which depend on the sample and crack geometry is essential for determining these curves. For the dental biomaterials enamel and dentin it was observed that, under bending and tensile loading, crack propagation occurs under certain constant angles to the initial notch direction during testing procedures used for fracture resistance curve determination. For this special crack geometry (a kink crack of finite length in a finite body) appropriate geometric function solutions are missing. Hence, we present in this study new mixed-mode stress intensity factors for kink cracks with finite kink length within samples of finite dimensions for two loading cases (tension and bending) which were derived from a combination of mixed-mode stress intensity factors of kink cracks with infinitely small kinks and of slant cracks. These results were further applied to determine the fracture resistance curves of enamel and dentin by testing single edge notched bending (SENB) specimens. It was found that kink cracks with finite kink length exhibit identical stress fields to slant cracks as soon as the kink length exceeds 0.15 times the initial straight crack or notch length. The use of stress intensity factor solutions for infinitely small kink cracks for the determination of dentin fracture resistance curves (as was done by other researchers) leads to an overestimation of dentin's fracture resistance of up to 30%. Copyright 2010 Elsevier Ltd. All rights reserved.

Photoelastic investigations on dynamic fracture propagation by models

International Nuclear Information System (INIS)

Kuske, A.; Schlonski, A.

1977-01-01

Given the existence of a linear elastic type of fracture behavior, stress conditions at tips of cracks occurring in disks or disk shaped components dynamically stressed by impact, vibration or explosion can be studied by model investigations using stress optics. The levels of the stress intensity factor Ksub(I) as determined in such experiments can be extrapolated to full size components under certain conditions, In crack problems in disks in which there are no major mass forces, Ksub(I) can be determined from the distribution of isochromats. Stress distributions in tips of cracks occurring in disks where stress conditions at the tips are influenced by mass forces (e.g., mass force of inertial) can be described by means of isochromat and isocline images. (orig.) [de

Using Mouse and Keyboard Dynamics to Detect Cognitive Stress During Mental Arithmetic

OpenAIRE

Ayesh, Aladdin, 1972-; Stacey, Martin; Lim, Yee Mei

2015-01-01

To build a personalized e-learning system that can deliver adaptive learning content based on student’s cognitive effort and efficiency, it is important to develop a construct that can help measuring perceived mental state, such as stress and cognitive load. The construct must be able to be quantified, computerized and automated. Our research investigates how mouse and keyboard dynamics analyses could be used to detect cognitive stress, which is induced by high mental arithmetic demand with t...

Dynamics of Mount Somma-Vesuvius edifice: from stress field inversion to analogue and numerical modelling

Science.gov (United States)

De Matteo, Ada; Massa, Bruno; D'Auria, Luca; Castaldo, Raffaele

2017-04-01

Geological processes are generally very complex and too slow to be directly observed in their completeness; modelling procedures overcome this limit. The state of stress in the upper lithosphere is the main responsible for driving geodynamical processes; in order to retrieve the active stress field in a rock volume, stress inversion techniques can be applied on both seismological and structural datasets. This approach has been successfully applied to active tectonics as well as volcanic areas. In this context the best approach in managing heterogeneous datasets in volcanic environments consists in the analysis of spatial variations of the stress field by applying robust techniques of inversion. The study of volcanic seismicity is an efficient tool to retrieve spatial and temporal pattern of the pre-, syn- and inter-eruptive stress field: magma migration as well as dynamics of magma chamber and hydrothermal system are directly connected to the volcanic seismicity. Additionally, analysis of the temporal variations of stress field pattern in volcanoes could be a useful monitoring tool. Recently the stress field acting on several active volcanoes has been investigated by using stress inversion techniques on seismological datasets (Massa et al., 2016). The Bayesian Right Trihedra Method (BRTM; D'Auria and Massa, 2015) is able to successfully manage heterogeneous datasets allowing the identification of regional fields locally overcame by the stress field due to volcano specific dynamics. In particular, the analysis of seismicity and stress field inversion at the Somma-Vesuvius highlighted the presence of two superposed volumes characterized by different behaviour and stress field pattern: a top volume dominated by an extensional stress field, in accordance with a gravitational spreading-style of deformation, and a bottom volume related to a regional extensional stress field. In addition, in order to evaluate the dynamics of deformation, both analogue and numerical

Photobiomodulation Leads to Reduced Oxidative Stress in Rats Submitted to High-Intensity Resistive Exercise

Directory of Open Access Journals (Sweden)

Helenita Antonia de Oliveira

2018-01-01

Full Text Available The aim of this study was to determine whether oxidative stress markers are influenced by low-intensity laser therapy (LLLT in rats subjected to a high-intensity resistive exercise session (RE. Female Wistar rats divided into three experimental groups (Ctr: control, 4J: LLLT, and RE and subdivided based on the sampling times (instantly or 24 h postexercise underwent irradiation with LLLT using three-point transcutaneous method on the hind legs, which was applied to the gastrocnemius muscle at the distal, medial, and proximal points. Laser (4J or placebo (device off were carried out 60 sec prior to RE that consisted of four climbs bearing the maximum load with a 2 min time interval between each climb. Lipoperoxidation levels and antioxidant capacity were obtained in muscle. Lipoperoxidation levels were increased (4-HNE and CL markers instantly post-RE. LLLT prior to RE avoided the increase of the lipid peroxidation levels. Similar results were also notified for oxidation protein assays. The GPx and FRAP activities did not reduce instantly or 24 h after RE. SOD increased 24 h after RE, while CAT activity did not change with RE or LLLT. In conclusion, LLLT prior to RE reduced the oxidative stress markers, as well as, avoided reduction, and still increased the antioxidant capacity.

Research on Formation Mechanism of Dynamic Response and Residual Stress of Sheet Metal Induced by Laser Shock Wave

Science.gov (United States)

Feng, Aixin; Cao, Yupeng; Wang, Heng; Zhang, Zhengang

2018-01-01

In order to reveal the quantitative control of the residual stress on the surface of metal materials, the relevant theoretical and experimental studies were carried out to investigate the dynamic response of metal thin plates and the formation mechanism of residual stress induced by laser shock wave. In this paper, the latest research trends on the surface residual stress of laser shock processing technology were elaborated. The main progress of laser shock wave propagation mechanism and dynamic response, laser shock, and surface residual stress were discussed. It is pointed out that the multi-scale characterization of laser and material, surface residual stress and microstructure change is a new hotspot in laser shock strengthening technology.

Stress intensities for nozzle cracks in reactor vessels. Reporting period, January 1, 1976--October 31, 1976

International Nuclear Information System (INIS)

Smith, C.W.; Jolles, M.; Peters, W.H.

1976-11-01

A series of six frozen stress photoelastic tests was conducted to investigate the distribution of stress intensity factor (SIF) along a crack which occurred at the juncture of a pipe (nozzle) with a cylindrical pressure vessel. Typical photoelastic fringe patterns are shown for slices which were taken mutually orthogonal to the flaw border and the flaw surface. A typical plot of normalized apparent SIF versus square root of normalized distance from the crack tip is presented. The variation in SIF along the flaw border is given for all six different crack geometries and also the variation of SIF with varying a/T is presented. 40 references

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.

Analysis of stress intensity factor for a Griffith crack opened under constant pressure in a plate with temperature dependent properties

International Nuclear Information System (INIS)

Hata, Toshiaki

1982-01-01

Recently, the research on the thermal stress of structural materials has become important with the progress of nuclear reactor technology. In the case of large temperature gradient, the change of the physical properties of materials must be taken into account. The thermal stress analysis for the things with cracks taking the temperature dependence of properties into account has scarcely been carried out. In this report, the general method of solution of three-dimensional problems using perturbation method and the extension of thermo-elastic displacement potential method is shown for the case in which Young's modulus changes according to the exponential function of temperature. Moreover, using this method, the effect of the temperature dependence of properties on the stress intensity factor of the cracks subjected to internal pressure in a strip exposed to linear thermal flow was clarified. In the analysis, Young's modulus, the coefficient of linear thermal expansion and thermal conductivity were assumed to be dependent on temperature. The method of solution, the analysis of stress intensity factor considering the change of properties due to temperature, and the numerical calculation for a square plate with a crack are explained. (Kako, I.)

Round Robin Analyses on Stress Intensity Factors of Inner Surface Cracks in Welded Stainless Steel Pipes

Directory of Open Access Journals (Sweden)

Chang-Gi Han

2016-12-01

Full Text Available Austenitic stainless steels (ASSs are widely used for nuclear pipes as they exhibit a good combination of mechanical properties and corrosion resistance. However, high tensile residual stresses may occur in ASS welds because postweld heat treatment is not generally conducted in order to avoid sensitization, which causes a stress corrosion crack. In this study, round robin analyses on stress intensity factors (SIFs were carried out to examine the appropriateness of structural integrity assessment methods for ASS pipe welds with two types of circumferential cracks. Typical stress profiles were generated from finite element analyses by considering residual stresses and normal operating conditions. Then, SIFs of cracked ASS pipes were determined by analytical equations represented in fitness-for-service assessment codes as well as reference finite element analyses. The discrepancies of estimated SIFs among round robin participants were confirmed due to different assessment procedures and relevant considerations, as well as the mistakes of participants. The effects of uncertainty factors on SIFs were deducted from sensitivity analyses and, based on the similarity and conservatism compared with detailed finite element analysis results, the R6 code, taking into account the applied internal pressure and combination of stress components, was recommended as the optimum procedure for SIF estimation.

Round robin analysis on stress intensity factor of inner surface cracks in welded stainless steel pipes

Energy Technology Data Exchange (ETDEWEB)

Han, Chang Gi; Chang, Yoon Suk [Dept. of Nuclear Engineering, College of Engineering, Kyung Hee University, Yongin (Korea, Republic of); Kim, Jong Sung [Dept. of Mechanical Engineering, Sunchon National University, Sunchon (Korea, Republic of); Kim, Maan Won [Central Research Institute, Korea Hydro and Nuclear Power Company, Daejeon (Korea, Republic of)

2016-12-15

Austenitic stainless steels (ASSs) are widely used for nuclear pipes as they exhibit a good combination of mechanical properties and corrosion resistance. However, high tensile residual stresses may occur in ASS welds because postweld heat treatment is not generally conducted in order to avoid sensitization, which causes a stress corrosion crack. In this study, round robin analyses on stress intensity factors (SIFs) were carried out to examine the appropriateness of structural integrity assessment methods for ASS pipe welds with two types of circumferential cracks. Typical stress profiles were generated from finite element analyses by considering residual stresses and normal operating conditions. Then, SIFs of cracked ASS pipes were determined by analytical equations represented in fitness-for-service assessment codes as well as reference finite element analyses. The discrepancies of estimated SIFs among round robin participants were confirmed due to different assessment procedures and relevant considerations, as well as the mistakes of participants. The effects of uncertainty factors on SIFs were deducted from sensitivity analyses and, based on the similarity and conservatism compared with detailed finite element analysis results, the R6 code, taking into account the applied internal pressure and combination of stress components, was recommended as the optimum procedure for SIF estimation.

Cardiorespiratory dynamic response to mental stress: a multivariate time-frequency analysis.

Science.gov (United States)

Widjaja, Devy; Orini, Michele; Vlemincx, Elke; Van Huffel, Sabine

2013-01-01

Mental stress is a growing problem in our society. In order to deal with this, it is important to understand the underlying stress mechanisms. In this study, we aim to determine how the cardiorespiratory interactions are affected by mental arithmetic stress and attention. We conduct cross time-frequency (TF) analyses to assess the cardiorespiratory coupling. In addition, we introduce partial TF spectra to separate variations in the RR interval series that are linearly related to respiration from RR interval variations (RRV) that are not related to respiration. The performance of partial spectra is evaluated in two simulation studies. Time-varying parameters, such as instantaneous powers and frequencies, are derived from the computed spectra. Statistical analysis is carried out continuously in time to evaluate the dynamic response to mental stress and attention. The results show an increased heart and respiratory rate during stress and attention, compared to a resting condition. Also a fast reduction in vagal activity is noted. The partial TF analysis reveals a faster reduction of RRV power related to (3 s) than unrelated to (30 s) respiration, demonstrating that the autonomic response to mental stress is driven by mechanisms characterized by different temporal scales.

Infants born preterm, stress, and neurodevelopment in the neonatal intensive care unit: might music have an impact?

Science.gov (United States)

Anderson, Dane E; Patel, Aniruddh D

2018-03-01

The neonatal intensive care unit (NICU) provides life-saving medical care for an increasing number of newborn infants each year. NICU care, while lifesaving, does have attendant consequences which can include repeated activation of the stress response and reduced maternal interaction, with possible negative long-term impacts on brain development. Here we present a neuroscientific framework for considering the impact of music on neurodevelopment in the NICU of infants born preterm and evaluate current literature on the use of music with this population to determine what is most reliably known of the physiological effects of music interventions. Using online academic databases we collected relevant, experimental studies aimed at determining effects of music listening in infants in the NICU. These articles were evaluated for methodological rigor, ranking the 10 most experimentally stringent as a representative sample. The selected literature seems to indicate that effects are present on the cardio-pulmonary system and behavior of neonates, although the relative effect size remains unclear. These findings indicate a need for more standardized longitudinal studies aimed at determining not only whether NICU music exposure has beneficial effects on the cardio-pulmonary system, but also on the hypothalamic-pituitary-adrenal axis, brain structures, and cognitive behavioral status of these children as well. Provides a neuroscience framework for considering how music might attenuate stress in neonatal intensive care unit (NICU) infants. Considers how repeated stress may cause negative neurodevelopmental impacts in infants born preterm. Posits epigenetics can serve as a mechanistic pathway for music moderating the stress response. © 2018 Mac Keith Press.

Reduced Insulin/IGF-1 Signaling Restores the Dynamic Properties of Key Stress Granule Proteins during Aging

Directory of Open Access Journals (Sweden)

Marie C. Lechler

2017-01-01

Full Text Available Summary: Low-complexity “prion-like” domains in key RNA-binding proteins (RBPs mediate the reversible assembly of RNA granules. Individual RBPs harboring these domains have been linked to specific neurodegenerative diseases. Although their aggregation in neurodegeneration has been extensively characterized, it remains unknown how the process of aging disturbs RBP dynamics. We show that a wide variety of RNA granule components, including stress granule proteins, become highly insoluble with age in C. elegans and that reduced insulin/insulin-like growth factor 1 (IGF-1 daf-2 receptor signaling efficiently prevents their aggregation. Importantly, stress-granule-related RBP aggregates are associated with reduced fitness. We show that heat shock transcription factor 1 (HSF-1 is a main regulator of stress-granule-related RBP aggregation in both young and aged animals. During aging, increasing DAF-16 activity restores dynamic stress-granule-related RBPs, partly by decreasing the buildup of other misfolded proteins that seed RBP aggregation. Longevity-associated mechanisms found to maintain dynamic RBPs during aging could be relevant for neurodegenerative diseases. : Lechler et al. show that RNA-binding proteins (RBPs including stress granule proteins are prone to aggregate with age in C. elegans. Aggregation of stress granule RBPs with “prion-like” domains is associated with reduced fitness. Their aggregation is prevented by longevity pathways and promoted by the aggregation of other misfolded proteins. Keywords: neurodegenerative diseases, Caenorhabditis elegans, protein aggregation, aging, RNA-binding proteins, stress granules, HSF-1, DAF-2, longevity

Modeling Coupled Landscape Evolution and Soil Organic Carbon Dynamics in Intensively Management Landscapes

Science.gov (United States)

Yan, Q.; Kumar, P.

2017-12-01

Soil is the largest reservoir of carbon in the biosphere but in agricultural areas it is going through rapid erosion due disturbance arising from crop harvest, tillage, and tile drainage. Identifying whether the production of soil organic carbon (SOC) from the crops can compensate for the loss due to erosion is critical to ensure our food security and adapt to climate change. In the U.S. Midwest where large areas of land are intensively managed for agriculture practices, predicting soil quantity and quality are critical for maintaining crop yield and other Critical Zone services. This work focuses on modeling the coupled landscape evolutions soil organic carbon dynamics in agricultural fields. It couples landscape evolution, surface water runoff, organic matter transformation, and soil moisture dynamics to understand organic carbon gain and loss due to natural forcing and farming practices, such as fertilizer application and tillage. A distinctive feature of the model is the coupling of surface ad subsurface processes that predicts both surficial changes and transport along with the vertical transport and dynamics. Our results show that landscape evolution and farming practices play dominant roles in soil organic carbon (SOC) dynamics both above- and below-ground. Contrary to the common assumption that a vertical profile of SOC concentration decreases exponentially with depth, we find that in many situations SOC concentration below-ground could be higher than that at the surface. Tillage plays a complex role in organic matter dynamics. On one hand, tillage would accelerate the erosion rate, on the other hand, it would improve carbon storage by burying surface SOC into below ground. Our model consistently reproduces the observed above- and below-ground patterns of SOC in the field sites of Intensively Managed Landscapes Critical Zone Observatory (IMLCZO). This model bridges the gaps between the landscape evolution, below- and above-ground hydrologic cycle, and

Correlation between electron-irradiation defects and applied stress in graphene: A molecular dynamics study

Energy Technology Data Exchange (ETDEWEB)

Kida, Shogo; Yamamoto, Masaya; Kawata, Hiroaki; Hirai, Yoshihiko; Yasuda, Masaaki, E-mail: yasuda@pe.osakafu-u.ac.jp [Department of Physics and Electronics, Osaka Prefecture University, Sakai, Osaka 599-8531 (Japan); Tada, Kazuhiro [Department of Electrical and Control Systems Engineering, National Institute of Technology, Toyama College, Toyama 939-8630 (Japan)

2015-09-15

Molecular dynamics (MD) simulations are performed to study the correlation between electron irradiation defects and applied stress in graphene. The electron irradiation effect is introduced by the binary collision model in the MD simulation. By applying a tensile stress to graphene, the number of adatom-vacancy (AV) and Stone–Wales (SW) defects increase under electron irradiation, while the number of single-vacancy defects is not noticeably affected by the applied stress. Both the activation and formation energies of an AV defect and the activation energy of an SW defect decrease when a tensile stress is applied to graphene. Applying tensile stress also relaxes the compression stress associated with SW defect formation. These effects induced by the applied stress cause the increase in AV and SW defect formation under electron irradiation.

Analysis of stress intensity factors for a new mechanical corrosion specimen; Analyse du facteur d`intensite de contrainte pour une nouvelle eprouvette de mecanique corrosion

Energy Technology Data Exchange (ETDEWEB)

Rassineux, B; Crouzet, D; Le Hong, S

1996-03-01

Electricite de France is conducting a research program to determine corrosion cracking rates in the steam generators Alloy 600 tubes of the primary system. The objective is to correlate the cracking rates with the specimen stress intensity factor K{sub I}. One of the samples selected for the purpose of this study is the longitudinal notched specimen TEL (TEL: ``Tubulaire a Entailles Longitudinales``). This paper presents the analysis of the stress intensity factor and its experimental validation. The stress intensity factor has been evaluated for different loads using 3D finite element calculations with the Hellen-Parks and G({theta}) methods. Both crack initiation and propagation are considered. As an assessment of the method, the numerical simulations are in good agreement with the fatigue crack growth rates measured experimentally for TEL and compact tension (CT) specimens. (authors). 8 refs., 6 figs., 2 tabs.

Global intensity correction in dynamic scenes

NARCIS (Netherlands)

Withagen, P.J.; Schutte, K.; Groen, F.C.A.

2007-01-01

Changing image intensities causes problems for many computer vision applications operating in unconstrained environments. We propose generally applicable algorithms to correct for global differences in intensity between images recorded with a static or slowly moving camera, regardless of the cause

Effect of the R dependence of laser-induced polarizability on molecular dynamic alignment in an intense femtosecond laser field

International Nuclear Information System (INIS)

Chen Jianxin; Cui Xiaomei; Huang Bomin; Wu Hongchun; Zhuo Shuangmu

2006-01-01

In the rotation equation of the angle θ between the molecular axis and the laser polarization direction, the dependence of laser-induced polarizability on the molecular internuclear distance R is considered. The effect of the R dependence of laser-induced polarizability on molecular dynamic alignment in an intense femtosecond laser field is investigated with 20 and 100 fs laser pulses for N 2 molecules and with 60 and 100 fs laser pulses for Br 2 molecules at intensities of 5x10 14 W cm -2 and 5x10 15 W cm -2 . This effect exists and only occurs during the dissociative process after the molecule is ionized. It enhances the degrees of molecular dynamic alignment and is more significant in reorienting the angular distributions of molecules towards the laser polarization direction in the conditions of high laser intensity and short pulse length. Compared with the N 2 molecule, the effect of the R dependence of laser-induced polarizability on molecular dynamic alignment for Br 2 is stronger. The reasons are presented and discussed

Impact of intensive insulin treatment on the development and consequences of oxidative stress in insulin-dependent diabetes mellitus

Directory of Open Access Journals (Sweden)

Kocić Radivoj

2007-01-01

Full Text Available Background/Aim. The aim of this study, which included patients with insulin-dependent diabetes mellitus, was to determine the influence of the application of various treatment modalities (intensive or conventional on the total plasma antioxidative capacity and lipid peroxidation intensity expressed as malondialdehyde (MDA level, catalase and xanthine oxidase activity, erythrocyte glutatione reduced concentration (GSH RBC, erythrocyte MDA level (MDA RBC, as well as susceptibility of erythrocyte to H2O2-induced oxidative stress. Methods. This study included 42 patients with insulin-dependent diabetes mellitus. In 24 of the patients intensive insulin treatment was applied using the model of short-acting insulin in each meal and medium- acting insulin before going to bed, while in 18 of the patients conventional insulin treatment was applied in two (morning and evening doses. In the examined patients no presence of diabetes mellitus complications was recorded. The control group included 20 healthy adults out of a blood doner group. The plasma and erythrocytes taken from the blood samples were analyzed immediately. Results. This investigation proved that the application of intensive insulin treatment regime significantly improves total antioxidative plasma capacity as compared to the application of conventional therapy regime. The obtained results showed that the both plasma and lipoproteines apo B MDA increased significantly more in the patients on conventional therapy than in the patients on intensive insulin therapy, most probably due to intensified xanthine oxidase activity. The level of the MDA in fresh erythrocytes did not differ significantly between the groups on intensive and conventional therapy. The level of GSH and catalase activity, however, were significantly reduced in the patients on conventional therapy due to the increased susceptibility to H2O2-induced oxidative stress . Conclusion. The presented study confirmed positive effect of

THE EFFECTS OF ACUTE AND CHRONIC STRESS ON ERYTHROCYTE DYNAMIC IN COMBINATION WITH ß–ADRENERGIC RECEPTORS BLOCKADE IN RATS

Directory of Open Access Journals (Sweden)

Lucian Hritcu

2005-08-01

Full Text Available : 3 consecutive days propranolol hydrochloride administration (5 mg/kg b.w., subcutaneous injections under acute and chronic stress conditions causes changes of peripheral erythrocyte distribution in rats. The effects of acute stress and its combination with ȕ-adrenergic receptor blockade on erythrocyte dynamic were more pregnant beside the effects of chronic stress and its combination with ȕ-adrenergic receptor blockade, respectively. ȕ-adrenergic mechanisms were shown to be involved in regulation of erythrocyte dynamic in acute and chronic stress response.

Stress intensity factors of three parallel edge cracks under bending moments

International Nuclear Information System (INIS)

Ismail, A E

2013-01-01

This paper reports the study of stress intensity factors (SIF) of three edge cracks in a finite plate under bending moments. The goal of this paper was to analyze the three edge crack interactions under such loading. Several studies can be found in literature discussing on mode I SIF. However, most of these studies obtained the SIFs using tensile force. Lack of SIF reported discussing on the SIFs obtained under bending moments. ANSYS finite element program was used to develop the finite element model where singular elements were used to model the cracks. Different crack geometries and parameters were utilized in order to characterize the SIFs. According to the present results, crack geometries played a significant role in determining the SIFs and consequently induced the crack interaction mechanisms

Neonatal Intensive Care and Child Psychiatry Inpatient Care: Do Different Working Conditions Influence Stress Levels?

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Evalotte Mörelius

2013-01-01

Full Text Available Introduction. Nurses often experience work-related stress. High stress can negatively affect job satisfaction and lead to emotional exhaustion with risk of burnout. Aim. To analyse possible differences in biological stress markers, psychosocial working conditions, health, and well-being between nurses working in two different departments. Methods. Stress was evaluated in nurses working in a neonatal intensive care unit (NICU (n=33 and nurses working in a child and adolescent psychiatry inpatient ward (CAP (n=14 using salivary cortisol and HbA1c. Salivary cortisol was measured three times a day on two consecutive days during two one-week periods, seven weeks apart (= 12 samples/person. Psychosocial working conditions, health, and well-being were measured once. Results. NICU nurses had better social support and more self-determination. CAP nurses had a lower salivary cortisol quotient, poorer general health, and higher client-related burnout scores. Conclusion. When comparing these nurses with existing norm data for Sweden, as a group their scores reflect less work-related stress than Swedes overall. However, the comparison between NICU and CAP nurses indicates a less healthy work situation for CAP nurses. Relevance to Clinical Practice. Healthcare managers need to acknowledge the less healthy work situation CAP nurses experience in order to provide optimal support and promote good health.

Simulation Based Exploration of Critical Zone Dynamics in Intensively Managed Landscapes

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Kumar, P.

2017-12-01

The advent of high-resolution measurements of topographic and (vertical) vegetation features using areal LiDAR are enabling us to resolve micro-scale ( 1m) landscape structural characteristics over large areas. Availability of hyperspectral measurements is further augmenting these LiDAR data by enabling the biogeochemical characterization of vegetation and soils at unprecedented spatial resolutions ( 1-10m). Such data have opened up novel opportunities for modeling Critical Zone processes and exploring questions that were not possible before. We show how an integrated 3-D model at 1m grid resolution can enable us to resolve micro-topographic and ecological dynamics and their control on hydrologic and biogeochemical processes over large areas. We address the computational challenge of such detailed modeling by exploiting hybrid CPU and GPU computing technologies. We show results of moisture, biogeochemical, and vegetation dynamics from studies in the Critical Zone Observatory for Intensively managed Landscapes (IMLCZO) in the Midwestern United States.

High- but not low-intensity light leads to oxidative stress and quality loss of cold-stored baby leaf spinach.

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Glowacz, Marcin; Mogren, Lars M; Reade, John P H; Cobb, Andrew H; Monaghan, James M

2015-07-01

Quality management in the fresh produce industry is an important issue. Spinach is exposed to various adverse conditions (temperature, light, etc.) within the supply chain. The present experiments were conducted to investigate the effect of light conditions (dark, low-intensity light (LL) and high-intensity light (HL)) and photoperiod (6 h HL and 18 h dark) on the quality changes of cold-stored spinach. HL exposure resulted in oxidative stress, causing tissue damage and quality loss as evidenced by increased membrane damage and water loss. The content of total ascorbic acid was reduced under HL conditions. On the other hand, storage of spinach under LL conditions gave promising results, as nutritional quality was not reduced, while texture maintenance was improved. No significant differences, with the exception of nutritional quality, were found between spinach leaves stored under continuous (24 h) low-intensity light (30-35 µmol m(-2) s(-1)) and their counterparts stored under the same light integral over 6 h (130-140 µmol m(-2) s(-1)). LL extended the shelf-life of spinach. The amount of light received by the leaves was the key factor affecting produce quality. Light intensity, however, has to be low enough not to cause excess oxidative stress and lead to accelerated senescence. © 2014 Society of Chemical Industry.

Plasma Hsp72 (HSPA1A) and Hsp27 (HSPB1) expression under heat stress: influence of exercise intensity.

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Périard, Julien D; Ruell, Patricia; Caillaud, Corinne; Thompson, Martin W

2012-05-01

Extracellular heat-shock protein 72 (eHsp72) expression during exercise-heat stress is suggested to increase with the level of hyperthermia attained, independent of the rate of heat storage. This study examined the influence of exercise at various intensities to elucidate this relationship, and investigated the association between eHsp72 and eHsp27. Sixteen male subjects cycled to exhaustion at 60% and 75% of maximal oxygen uptake in hot conditions (40°C, 50% RH). Core temperature, heart rate, oxidative stress, and blood lactate and glucose levels were measured to determine the predictor variables associated with eHsp expression. At exhaustion, heart rate exceeded 96% of maximum in both conditions. Core temperature reached 39.7°C in the 60% trial (58.9 min) and 39.0°C in the 75% trial (27.2 min) (P exercise may relate to the duration (i.e., core temperature attained) and intensity (i.e., rate of increase in core temperature) of exercise. Thus, the immuno-inflammatory release of eHsp72 and eHsp27 in response to exercise in the heat may be duration and intensity dependent.

Perceived Stress and Professional Quality of Life in Neonatal Intensive Care Unit Nurses in Gujarat, India.

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Amin, Amee A; Vankar, Jagdish R; Nimbalkar, Somashekhar M; Phatak, Ajay G

2015-11-01

To study the levels of perceived stress in Neonatal Intensive Care Unit (NICU) nurses and its association with professional quality of life domains viz. compassion satisfaction, burnout and secondary trauma. In this multicenter, cross sectional study, data was collected by surveying 129 nurses from nine NICUs across six cities of Gujarat, India using demographic questionnaire, Perceived Stress Scale (PSS14) and Professional Quality of Life Scale (ProQOL5) during July to September 2013. Descriptive statistics, correlation coefficient and multiple regression were used for analysis. The mean (SD) age of participants was 28.37 (8.20) y. Most were single, satisfied with salary benefits and reported 'good' to 'excellent' relationships at work. The mean (SD) duration of duty hours was 8.12 (0.76) h and 43.6% were attending to more than 4 patients/shift. The mean (SD) perceived stress level was 22.19 (7.17) [Range: 3 to 39]. High compassion satisfaction, high burnout, and high secondary traumatic stress were reported by 25 (19.4%), 30 (23.3%) and 30 (23.3%) nurses respectively. PSS14 was negatively correlated with compassion satisfaction (r = -0.28) and positively correlated with burnout (r = 0.43) and secondary traumatic stress (r = 0.24). Most of the nurses (91, 70.5%) were identified as perceiving moderate to high stress. Professional quality of life domains correlated with perceived stress. There is further need to study domains influencing NICU nurses' professional QOL. Identifying stress and QOL issues in NICU nurses can help formulate relevant policies.

A tailored relocation stress intervention programme for family caregivers of patients transferred from a surgical intensive care unit to a general ward.

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Lee, Seul; Oh, HyunSoo; Suh, YeonOk; Seo, WhaSook

2017-03-01

To develop and examine a relocation stress intervention programme tailored for the family caregivers of patients scheduled for transfer from a surgical intensive care unit to a general ward. Family relocation stress syndrome has been reported to be similar to that exhibited by patients, and investigators have emphasised that nurses should make special efforts to relieve family relocation stress to maximise positive contributions to the well-being of patients by family caregivers. A nonequivalent control group, nonsynchronised pretest-post-test design was adopted. The study subjects were 60 family caregivers of patients with neurosurgical or general surgical conditions in the surgical intensive care unit of a university hospital located in Incheon, South Korea. Relocation stress and family burden were evaluated at three times, that is before intervention, immediately after transfer and four to five days after transfer. This relocation stress intervention programme was developed for the family caregivers based on disease characteristics and relocation-related needs. In the experimental group, relocation stress levels significantly and continuously decreased after intervention, whereas in the control group, a slight nonsignificant trend was observed. Family burden levels in the control group increased significantly after transfer, whereas burden levels in the experimental group increased only marginally and nonsignificantly. No significant between-group differences in relocation stress or family burden levels were observed after intervention. Relocation stress levels of family caregivers were significantly decreased after intervention in the experimental group, which indicates that the devised family relocation stress intervention programme effectively alleviated family relocation stress. The devised intervention programme, which was tailored to disease characteristics and relocation-related needs, may enhance the practicality and efficacy of relocation stress

Correlations of the glycemic variability with oxidative stress and erythrocytes membrane stability in patients with type 1 diabetes under intensive treatment.

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Rodrigues, Ricardo; Alves de Medeiros, Luciana; Moreira Cunha, Lucas; da Silva Garrote-Filho, Mario; Bernardino Neto, Morun; Tannus Jorge, Paulo; Santos Resende, Elmiro; Penha-Silva, Nilson

2018-02-07

This study aimed to evaluate the correlations of glycemic variability with erythrocyte membrane stability parameters and oxidative stress markers in patients with DM1 under intensive treatment. 90 patients with DM1 and under intensive treatment of the disease were evaluated in relation to anthropometric indices, records of glycemic averages and parameters of glycemic variability, biochemical dosages (glucose, uric acid, lipidogram, glycated hemoglobin, microalbuminuria, creatinine and iron) reticulocyte count, erythrocyte membrane stability parameters and oxidative stress markers (thiobarbituric acid reactive substances, TBARS, and glutathione reductase, GR). Indicators of glycemic variability in the short and long term showed correlations with parameters of membrane stability and markers of oxidative stress (GR). In addition, the comparison of these same parameters between the subgroups consisting of quartiles of GV or glycemic control also showed significant differences. In the DM1 patients studied here, glycemic variability showed correlations with oxidative stress and erythrocyte membrane stability variables. This corroborates the hypothesis that glycemic fluctuations interfere with lipid peroxidation and cell membrane behavior, emphasizing its participation in mechanisms related to the development of chronic complications of diabetes. Copyright © 2018 Elsevier B.V. All rights reserved.

Preoperative diagnosis of breast diseases by dynamic MR mammography. Cut off point establishment for signal intensity ratio

International Nuclear Information System (INIS)

Tsuchiya, Juji; Nagata, Takayasu; Kawagoe, Hajime; Tachibana, Susumu; Kajima, Toshihiko; Hoshino, Mutsuo; Uno, Takashi; Shimokawa, Kuniyasu.

1997-01-01

We have revealed that a dynamic study of the breast using MR imaging technique can estimate objectively benign-malignant differentiative diagnosis. Subjects were 41 cases of breast lesion, including 13 cases of breast cancer, 21 cases of mastopathy, six cases of fibroadenoma and one case of intraductal papillomatosis and the results of them were investigated in comparison with histopathological diagnosis. As so the method, we drew up time-signal intensity ratio curve plotting signal intensity ratio at each 30 second of dynamic MR mammography after Gd-DTPA administration. We found a especially high significant difference between cancer and mastopathy, within 90 second after Gd-DTPA administration (p=0.0000). Still more, we established cut off point concerning with establishment of 95% confidence interval, that is, at 30 second after Gd-DTPA administration of point equivalent 1.53 at 60 second equivalent 2.00, at 90 second equivalent 2.47, and about this estimating maneuver using the cut off point we named Dynamic ratio method. We can estimate preoperatively not only benign-malignant differentiative diagnosis with breast tumor, but also neighboring infiltration and lymph node metastasis of breast cancer using this Dynamic ratio method. Over again, Dynamic ratio method provides fine information to preoperative decision of resecting region for breast conserving surgery. The efficiency of this method is sensitivity=92.3%, specificity=89.3% and positive predictive value=80.0%. (author)

Preoperative diagnosis of breast diseases by dynamic MR mammography. Cut off point establishment for signal intensity ratio

Energy Technology Data Exchange (ETDEWEB)

Tsuchiya, Juji; Nagata, Takayasu; Kawagoe, Hajime; Tachibana, Susumu; Kajima, Toshihiko; Hoshino, Mutsuo [Ibi General Hospital, Gifu (Japan); Uno, Takashi; Shimokawa, Kuniyasu

1997-12-01

We have revealed that a dynamic study of the breast using MR imaging technique can estimate objectively benign-malignant differentiative diagnosis. Subjects were 41 cases of breast lesion, including 13 cases of breast cancer, 21 cases of mastopathy, six cases of fibroadenoma and one case of intraductal papillomatosis and the results of them were investigated in comparison with histopathological diagnosis. As so the method, we drew up time-signal intensity ratio curve plotting signal intensity ratio at each 30 second of dynamic MR mammography after Gd-DTPA administration. We found a especially high significant difference between cancer and mastopathy, within 90 second after Gd-DTPA administration (p=0.0000). Still more, we established cut off point concerning with establishment of 95% confidence interval, that is, at 30 second after Gd-DTPA administration of point equivalent 1.53 at 60 second equivalent 2.00, at 90 second equivalent 2.47, and about this estimating maneuver using the cut off point we named Dynamic ratio method. We can estimate preoperatively not only benign-malignant differentiative diagnosis with breast tumor, but also neighboring infiltration and lymph node metastasis of breast cancer using this Dynamic ratio method. Over again, Dynamic ratio method provides fine information to preoperative decision of resecting region for breast conserving surgery. The efficiency of this method is sensitivity=92.3%, specificity=89.3% and positive predictive value=80.0%. (author)

Dynamics of seed germination, seedling growth and physiological responses of sweet corn under peg-induced water stress

International Nuclear Information System (INIS)

Li, W.; Zhang, X.; Li, G.; Suo, H.; Ashraf, U.; Mo, Z.

2017-01-01

Stress induced variations in seed germination of various crops has been well reported but germination potential of sweet corn seeds under osmotic stress with relation to time dynamics is still elusive. Present study explored the water absorption, germination potential and physiological indices and of sweet corn seeds exposed to five different levels of PEG-induced water stress i.e., 0, -0.3, -0.6, -0.9 and -1.2 M Pa water potential (Psi /sub w/) with respect to time dynamics. Results showed that enhanced water stress for prolonged time period (96 h) led to substantial reduction in water absorption and seed moisture contents, seed germination and vigor index as well as seedlings growth and fresh and dry biomass. Osmotic stress triggered antioxidant defense system like super-oxide dismutase (SOD), peroxidase (POD) and catalase (CAT) and accumulation of soluble sugars, proline and protein contents considerably. Initially, activities of SOD and CAT were higher but then reduced as stress persisted, however, POD showed a linear increase with respect to stress exposure time. Water stress also increased MDA contents up to 36 h then declined. Further, alpha-amylase activity and soluble protein showed significant correlations with maize seed germination. Overall, germination potential decreased with increase in osmotic stress in sweet corn seeds. (author)

Threshold intensity factors as lower boundaries for crack propagation in ceramics

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Walter Per-Ole

2004-11-01

Full Text Available Abstract Background Slow crack growth can be described in a v (crack velocity versus KI (stress intensity factor diagram. Slow crack growth in ceramics is attributed to corrosion assisted stress at the crack tip or at any pre-existing defect in the ceramic. The combined effect of high stresses at the crack tip and the presence of water or body fluid molecules (reducing surface energy at the crack tip induces crack propagation, which eventually may result in fatigue. The presence of a threshold in the stress intensity factor, below which no crack propagation occurs, has been the subject of important research in the last years. The higher this threshold, the higher the reliability of the ceramic, and consequently the longer its lifetime. Methods We utilize the Irwin K-field displacement relation to deduce crack tip stress intensity factors from the near crack tip profile. Cracks are initiated by indentation impressions. The threshold stress intensity factor is determined as the time limit of the tip stress intensity when the residual stresses have (nearly disappeared. Results We determined the threshold stress intensity factors for most of the all ceramic materials presently important for dental restorations in Europe. Of special significance is the finding that alumina ceramic has a threshold limit nearly identical with that of zirconia. Conclusion The intention of the present paper is to stress the point that the threshold stress intensity factor represents a more intrinsic property for a given ceramic material than the widely used toughness (bend strength or fracture toughness, which refers only to fast crack growth. Considering two ceramics with identical threshold limits, although with different critical stress intensity limits, means that both ceramics have identical starting points for slow crack growth. Fast catastrophic crack growth leading to spontaneous fatigue, however, is different. This growth starts later in those ceramic materials

A virtual crack-closure technique for calculating stress intensity factors for cracked three dimensional bodies

Science.gov (United States)

Shivakumar, K. N.; Tan, P. W.; Newman, J. C., Jr.

1988-01-01

A three-dimensional virtual crack-closure technique is presented which calculates the strain energy release rates and the stress intensity factors using only nodal forces and displacements from a standard finite element analysis. The technique is an extension of the Rybicki-Kanninen (1977) method, and it assumes that any continuous function can be approximated by a finite number of straight line segments. Results obtained by the method for surface cracked plates with and without notches agree favorably with previous results.

The Role of Musculoskeletal Dynamics and Neuromuscular Control in Stress Development in Bone

Science.gov (United States)

DeWoody, Yssa

1996-01-01

The role of forces produced by the musculotendon units in the stress development of the long bones during gait has not been fully analyzed. It is well known that the musculotendons act as actuators producing the joint torques which drive the body. Although the joint torques required to perform certain motor tasks can be recovered through a kinematic analysis, it remains a difficult problem to determine the actual forces produced by each muscle that resulted in these torques. As a consequence, few studies have focused on the role of individual muscles in the development of stress in the bone. This study takes a control theoretic approach to the problem. A seven-link, eight degrees of freedom model of the body is controlled by various muscle groups on each leg to simulate gait. The simulations incorporate Hill-type models of muscles with activation and contraction dynamics controlled through neural inputs. This direct approach allows one to know the exact muscle forces exerted by each musculotendon throughout the gait cycle as well the joint torques and reaction forces at the ankle and knee. Stress and strain computed by finite element analysis on skeletal members will be related to these derived loading conditions. Thus the role of musculoskeletal dynamics and neuromuscular control in the stress development of the tibia during gait can be analyzed.

Validation of the Amsterdam Dynamic Facial Expression Set--Bath Intensity Variations (ADFES-BIV: A Set of Videos Expressing Low, Intermediate, and High Intensity Emotions.

Directory of Open Access Journals (Sweden)

Tanja S H Wingenbach

Full Text Available Most of the existing sets of facial expressions of emotion contain static photographs. While increasing demand for stimuli with enhanced ecological validity in facial emotion recognition research has led to the development of video stimuli, these typically involve full-blown (apex expressions. However, variations of intensity in emotional facial expressions occur in real life social interactions, with low intensity expressions of emotions frequently occurring. The current study therefore developed and validated a set of video stimuli portraying three levels of intensity of emotional expressions, from low to high intensity. The videos were adapted from the Amsterdam Dynamic Facial Expression Set (ADFES and termed the Bath Intensity Variations (ADFES-BIV. A healthy sample of 92 people recruited from the University of Bath community (41 male, 51 female completed a facial emotion recognition task including expressions of 6 basic emotions (anger, happiness, disgust, fear, surprise, sadness and 3 complex emotions (contempt, embarrassment, pride that were expressed at three different intensities of expression and neutral. Accuracy scores (raw and unbiased (Hu hit rates were calculated, as well as response times. Accuracy rates above chance level of responding were found for all emotion categories, producing an overall raw hit rate of 69% for the ADFES-BIV. The three intensity levels were validated as distinct categories, with higher accuracies and faster responses to high intensity expressions than intermediate intensity expressions, which had higher accuracies and faster responses than low intensity expressions. To further validate the intensities, a second study with standardised display times was conducted replicating this pattern. The ADFES-BIV has greater ecological validity than many other emotion stimulus sets and allows for versatile applications in emotion research. It can be retrieved free of charge for research purposes from the

Validation of the Amsterdam Dynamic Facial Expression Set--Bath Intensity Variations (ADFES-BIV): A Set of Videos Expressing Low, Intermediate, and High Intensity Emotions.

Science.gov (United States)

Wingenbach, Tanja S H; Ashwin, Chris; Brosnan, Mark

2016-01-01

Most of the existing sets of facial expressions of emotion contain static photographs. While increasing demand for stimuli with enhanced ecological validity in facial emotion recognition research has led to the development of video stimuli, these typically involve full-blown (apex) expressions. However, variations of intensity in emotional facial expressions occur in real life social interactions, with low intensity expressions of emotions frequently occurring. The current study therefore developed and validated a set of video stimuli portraying three levels of intensity of emotional expressions, from low to high intensity. The videos were adapted from the Amsterdam Dynamic Facial Expression Set (ADFES) and termed the Bath Intensity Variations (ADFES-BIV). A healthy sample of 92 people recruited from the University of Bath community (41 male, 51 female) completed a facial emotion recognition task including expressions of 6 basic emotions (anger, happiness, disgust, fear, surprise, sadness) and 3 complex emotions (contempt, embarrassment, pride) that were expressed at three different intensities of expression and neutral. Accuracy scores (raw and unbiased (Hu) hit rates) were calculated, as well as response times. Accuracy rates above chance level of responding were found for all emotion categories, producing an overall raw hit rate of 69% for the ADFES-BIV. The three intensity levels were validated as distinct categories, with higher accuracies and faster responses to high intensity expressions than intermediate intensity expressions, which had higher accuracies and faster responses than low intensity expressions. To further validate the intensities, a second study with standardised display times was conducted replicating this pattern. The ADFES-BIV has greater ecological validity than many other emotion stimulus sets and allows for versatile applications in emotion research. It can be retrieved free of charge for research purposes from the corresponding author.

Nonlinear dynamics of a flexible rotor supported by turbulent journal bearings with couple stress fluid

International Nuclear Information System (INIS)

Lo, C.-Y.; Chang-Jian, C.-W.

2008-01-01

This study presents a dynamic analysis of a rotor supported by two turbulent flow model journal bearings and lubricated with couple stress fluid under nonlinear suspension. The dynamics of the rotor center and bearing center is studied. The dynamic equations are solved using the Runge-Kutta method. The analysis methods employed in this study is inclusive of the dynamic trajectories of the rotor center and bearing center, power spectra, Poincare maps and bifurcation diagrams. The maximum Lyapunov exponent analysis is also used to identify the onset of chaotic motion. The results show that the values of dimensionless parameters l* strongly influence dynamic motions of bearing and rotor centre. It is found that couple stress fluid improve the stability of the system when l* > 0.4 even if the flow of this system is turbulent. We also demonstrated that the dimensionless rotational speed ratios s and the dimensionless unbalance parameter β are also significant system parameters. The modeling results thus obtained by using the method proposed in this paper can be employed to predict the stability of the rotor-bearing system and the undesirable behavior of the rotor and bearing center can be avoided

Delayed memory effects after intense stress in Special Forces candidates: exploring path processes between cortisol secretion and memory recall.

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Taverniers, John; Taylor, Marcus K; Smeets, Tom

2013-05-01

The aim of this paper is twofold. First, it explores delayed effects of high endogenously evoked cortisol concentrations on visuo-spatial declarative memory. Subsequently, it applies multiple mediation (MM) analyses to reveal path processes between stress and cognitive performance in a sample of 24 male Special Forces (SF) candidates (mean age = 27.0 years, SD = 4.1). The SF candidates were randomly assigned to a control (n = 12) or an intense stress group (n = 12), and cortisol secretion for the intense stress condition was triggered by a brusque 60 min prisoner of war exercise. Stress exposure provoked robust increases in cortisol concentrations and a significant decline in immediate recall performance, measured with the Rey-Osterrieth Complex Figure (ROCF). The relative retrieval differences in regard to the ROCF persisted even after a recovery period of 24 h, as both groups showed similar levels of memory decline over 24 h. Next, the study applied a MM design that involved distribution-independent asymptotic and resampling strategies to extend traditional bivariate analyses. MM results showed that ROCF performance was mediated by increases in cortisol concentrations. Considering the studied variables, the current analysis was the first to provide statistical support for the generally accepted thesis that cortisol secretion in itself, rather than subjective strain or the experimental treatment, affects cognitive performance. The revelation of such path processes is important because it establishes process identification and may refine existing paradigms.

Target Surface Area Effects on Hot Electron Dynamics from High Intensity Laser-Plasma Interactions

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2016-08-19

Science, University ofMichigan, AnnArbor,MI 48109-2099, USA E-mail: czulick@umich.edu Keywords: laser- plasma ,mass-limited, fast electrons , sheath...New J. Phys. 18 (2016) 063020 doi:10.1088/1367-2630/18/6/063020 PAPER Target surface area effects on hot electron dynamics from high intensity laser... plasma interactions CZulick, ARaymond,AMcKelvey, VChvykov, AMaksimchuk, AGRThomas, LWillingale, VYanovsky andKKrushelnick Center forUltrafast Optical

Pain-related stress in the Neonatal Intensive Care Unit and salivary cortisol reactivity to socio-emotional stress in 3-month-old very preterm infants.

Science.gov (United States)

Provenzi, Livio; Giusti, Lorenzo; Fumagalli, Monica; Tasca, Hilarj; Ciceri, Francesca; Menozzi, Giorgia; Mosca, Fabio; Morandi, Francesco; Borgatti, Renato; Montirosso, Rosario

2016-10-01

Very preterm (VPT) infants are hospitalized in the Neonatal Intensive Care Unit (NICU) and exposed to varying levels of skin-breaking procedures (pain-related stress), even in absence of severe clinical conditions. Repeated and prolonged pain exposure may alter hypothalamic-pituitary-adrenal (HPA) axis reactivity in VPT infants. During the post-discharge period, altered HPA axis reactivity has been documented in response to non-social stressors, using salivary cortisol as a biomarker. However, little is known about the effects of NICU pain-related stress on subsequent HPA axis reactivity to socio-emotional stress in infants. We examined the relationship between pain-related stress in NICU and HPA axis reactivity (i.e., salivary cortisol reactivity) to an age-appropriate socio-emotional condition in 37 healthy VPT infants compared to 53 full-term (FT) controls. The number of skin-breaking procedures was obtained across NICU stay for VPT infants. At 3 months (corrected age for prematurity), all infants participated in the maternal Face-to-Face Still-Face (FFSF) procedure, in order to assess HPA axis reactivity to socio-emotional stress (i.e., maternal unresponsiveness). VPT infants exhibited a blunted salivary cortisol reactivity, which was associated with the amount of skin-breaking procedures during NICU: greater pain-related stress predicted lower salivary cortisol reactivity, adjusting for neonatal confounders. These findings further advance our knowledge of how early exposure to pain-related stress in NICU contributes to the programming of an altered HPA axis reactivity to socio-emotional stress in 3-month-old VPT infants, even in the absence of major perinatal complications. Copyright © 2016 Elsevier Ltd. All rights reserved.

Effects of fluid dynamic stress on fracturing of cell-aggregated tissue during purification for islets of Langerhans transplantation

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Shintaku, H; Kawano, S [Department of Mechanical Science and Bioengineering, Graduate School of Engineering Science, Osaka University, Machikaneyama-cho, Toyonaka, Osaka 560-8531 (Japan); Okitsu, T [Transplantation Unit, Kyoto University Hospital, Kawara-cho Shogoin, Sakyo-ku, Kyoto 606-8507 (Japan); Matsumoto, S [Baylor Research Institute Islet Cell Laboratory, 1400 Eight Avenue, Fort Worth, TX 76104 (United States); Suzuki, T; Kanno, I; Kotera, H [Department of Microengineering, Kyoto University, Yoshida-Honmachi, Sakyo-ku, Kyoto 606-8501 (Japan)], E-mail: shintaku@me.es.osaka-u.ac.jp

2008-06-07

Among clinical treatments for type 1 diabetes mellitus, the transplantation of islets of Langerhans to the portal vein of the hepar is a commonly used treatment for glucose homeostasis. Islet purification using the density gradient of a solution in a centrifuge separator is required for safety and efficiency. In the purification, the number of tissues to be transplanted is reduced by removing the acinar tissue and gathering the islet from the digest of pancreas. However, the mechanical effects on the fracture of islets in the centrifuge due to fluid dynamic stress are a serious problem in the purification process. In this study, a preliminary experiment using a cylindrical rotating viscometer with a simple geometry is conducted in order to systematically clarify the effect of fluid dynamic stress on the fracture of islets. The effects of fluid dynamic stress on the islet configuration is quantitatively measured for various flow conditions, and a predictive fracture model is developed based on the experimental results. Furthermore, in the practical purification process in the COBE (Gambro BCT), which is widely used in clinical applications, we perform a numerical analysis of the fluid dynamic stress based on Navier-Stokes equations to estimate the stress conditions for islets. Using the fracture model and numerical analysis, the islet fracture characteristics using the COBE are successfully investigated. The results obtained in this study provide crucial information for the purification of islets by centrifuge in practical and clinical applications.

Effects of fluid dynamic stress on fracturing of cell-aggregated tissue during purification for islets of Langerhans transplantation

International Nuclear Information System (INIS)

Shintaku, H; Kawano, S; Okitsu, T; Matsumoto, S; Suzuki, T; Kanno, I; Kotera, H

2008-01-01

Among clinical treatments for type 1 diabetes mellitus, the transplantation of islets of Langerhans to the portal vein of the hepar is a commonly used treatment for glucose homeostasis. Islet purification using the density gradient of a solution in a centrifuge separator is required for safety and efficiency. In the purification, the number of tissues to be transplanted is reduced by removing the acinar tissue and gathering the islet from the digest of pancreas. However, the mechanical effects on the fracture of islets in the centrifuge due to fluid dynamic stress are a serious problem in the purification process. In this study, a preliminary experiment using a cylindrical rotating viscometer with a simple geometry is conducted in order to systematically clarify the effect of fluid dynamic stress on the fracture of islets. The effects of fluid dynamic stress on the islet configuration is quantitatively measured for various flow conditions, and a predictive fracture model is developed based on the experimental results. Furthermore, in the practical purification process in the COBE (Gambro BCT), which is widely used in clinical applications, we perform a numerical analysis of the fluid dynamic stress based on Navier-Stokes equations to estimate the stress conditions for islets. Using the fracture model and numerical analysis, the islet fracture characteristics using the COBE are successfully investigated. The results obtained in this study provide crucial information for the purification of islets by centrifuge in practical and clinical applications

The Effects of a Korean Ginseng, GINST15, on Hypo-Pituitary-Adrenal and Oxidative Activity Induced by Intense Work Stress.

Science.gov (United States)

Flanagan, Shawn D; DuPont, William H; Caldwell, Lydia K; Hardesty, Vincent H; Barnhart, Emily C; Beeler, Matthew K; Post, Emily M; Volek, Jeff S; Kraemer, William J

2018-01-01

The effect of GINST15, an enzyme fermented ginseng supplement, on hormonal and inflammatory responses to physical stress in humans is unknown. The purpose of this investigation was to examine the constitutive and stress-induced effects of GINST15 supplement on hypo-pituitary-adrenal (HPA) and antioxidant activity in addition to muscle damage. Ten women (age: 38.7 ± 7.8 years; height: 163.81 ± 4.4 cm; body mass 76.0 ± 11.6 kg) and nine men (age: 41.2. ± 9.7 years; height: 177.4 ± 5.3 cm; body mass: 88.5 ± 5.0 kg) participated in a double-blinded, placebo-controlled, counterbalanced within-group study. Participants completed three 14-day treatment cycles with different doses (high: 960 mg; low: 160 mg; placebo: 0 mg) separated by a 1-week washout period. At the end of treatment, physical stress was imposed with intense resistance exercise work stress. Participants provided blood at rest and various time points after exercise (immediately [IP], 30 min [30], 60 min [60], 24 h [+24HR]). Cortisol (CORT), superoxide dismutase (SOD), total glutathione, nonspecific antioxidant activity, total antioxidant power (TAP), and creatine kinase were measured. GINST15 supplementation produced stress-inducible dose-dependent reductions in circulating cortisol and increased enzymatic and nonspecific antioxidant activity. Twenty-four hours after intense exercise, a high dose GINST15, a bioactive ginsenoside metabolite, significantly reduces muscle damage and HPA responses to physical stress in humans; these effects may result from increased antioxidant expression.

Analysis of the dynamic behavior of an intense charged particle beam using the semigroup approach

International Nuclear Information System (INIS)

Stafford, M.A.

1984-01-01

Dynamic models of a charged particle beam subject to external electromagnetic fields are cast into the abstract Cauchy problem form. Various applications of intense charged particle beams, i.e., beams whose self electromagnetic fields are significant, might require, or be enhanced by, the use of dynamic control constructed from suitably processed measurements of the state of the beam. This research provides a mathematical foundation for future engineering development of estimation and control designs for such beams. Beginning with the Vlasov equation, successively simpler models of intense beams are presented, along with their corresponding assumptions. Expression of a model in abstract Cauchy problem form is useful in determining whether the model is well posed. Solutions of well-posed problems can be expressed in terms of a one-parameter semigroup of linear operators. The semigroup point of view allows the application of the rapidly maturing modern control theory of infinite dimensional system. An appropriate underlying Banach space is identified for a simple, but nontrivial, single degree of freedom model (the electrostatic approximation model), and the associated one-parameter semigroup of linear operators is characterized

Velocity and stress autocorrelation decay in isothermal dissipative particle dynamics

Science.gov (United States)

Chaudhri, Anuj; Lukes, Jennifer R.

2010-02-01

The velocity and stress autocorrelation decay in a dissipative particle dynamics ideal fluid model is analyzed in this paper. The autocorrelation functions are calculated at three different friction parameters and three different time steps using the well-known Groot/Warren algorithm and newer algorithms including self-consistent leap-frog, self-consistent velocity Verlet and Shardlow first and second order integrators. At low friction values, the velocity autocorrelation function decays exponentially at short times, shows slower-than exponential decay at intermediate times, and approaches zero at long times for all five integrators. As friction value increases, the deviation from exponential behavior occurs earlier and is more pronounced. At small time steps, all the integrators give identical decay profiles. As time step increases, there are qualitative and quantitative differences between the integrators. The stress correlation behavior is markedly different for the algorithms. The self-consistent velocity Verlet and the Shardlow algorithms show very similar stress autocorrelation decay with change in friction parameter, whereas the Groot/Warren and leap-frog schemes show variations at higher friction factors. Diffusion coefficients and shear viscosities are calculated using Green-Kubo integration of the velocity and stress autocorrelation functions. The diffusion coefficients match well-known theoretical results at low friction limits. Although the stress autocorrelation function is different for each integrator, fluctuates rapidly, and gives poor statistics for most of the cases, the calculated shear viscosities still fall within range of theoretical predictions and nonequilibrium studies.

Effects of stress-shielding on the dynamic viscoelasticity and ordering of the collagen fibers in rabbit Achilles tendon.

Science.gov (United States)

Ikoma, Kazuya; Kido, Masamitsu; Nagae, Masateru; Ikeda, Takumi; Shirai, Toshiharu; Ueshima, Keiichiro; Arai, Yuji; Oda, Ryo; Fujiwara, Hiroyoshi; Kubo, Toshikazu

2013-11-01

We investigated the effects of stress-shielding on both viscoelastic properties and microstructure of collagen fibers in the Achilles tendon by proton double-quantum filtered ((1) H-DQF) NMR spectroscopy. The right hind-limbs of 20 Japanese white rabbits were immobilized for 4 weeks in a cast with the ankle in plantarflexion. Dynamic viscoelasticity of the Achilles tendons was measured using a viscoelastic spectrometer. Proton DQF NMR signals were analyzed to determine the residual dipolar coupling of bound water molecules in the Achilles tendons. Both the dynamic storage modulus (E') and dynamic loss modulus (E″) decreased significantly in the Achilles tendons of the stress-shielding group. The results of the (1) H-DQF NMR examination demonstrated significantly reduced residual dipolar coupling in the Achilles tendons of this same group. The disorientation of collagen fibers by stress-shielding should contribute to degradation of the dynamic storage and loss moduli. The alterations of the collagen fiber orientation that contributed to the function of tendinous tissue can be evaluated by performing an analysis of (1) H DQF NMR spectroscopy. © 2013 Orthopaedic Research Society.

Social, psychological and psychosomatic disorders in the people with combat stress in their medical histories

Directory of Open Access Journals (Sweden)

L. V. Gracheva

2013-01-01

Full Text Available The authors examined three groups of patients – military men (40 men in each group with combat stress of different intensity in their medical histories (two main groups and a  control group – without combat stress. The results showed that the military men with a high level combat stress in the past (more than 5 years ago more frequently demonstrated socialmental disadaptation against the background of subclinical chronic posttraumatic stress disorder (PTSD. The conclusion is that this group of people requires dynamic followup and adequate medicopsychological aid.

Unsteady exergy destruction of the neuron under dynamic stress conditions

International Nuclear Information System (INIS)

Genc, S.; Sorguven, E.; Ozilgen, M.; Aksan Kurnaz, I.

2013-01-01

Just like all physical systems, biological systems also obey laws of thermodynamics, and as such the useful work potential of a biological system is its exergy. In some studies, exergy of living systems is considered with respect to work performance of humans in offices or buildings; however the exergy analysis of biochemical reactions in a cell as a closed system goes largely untouched. In this study, exergy analysis was applied to glucose metabolism of a model neuron, and dynamic exergy destructions were calculated for four different conditions, namely normoxia, hypoxia, glucose starvation and excess glucose. Our results showed that neuronal metabolism achieved a new steady state under each condition within 5 min. This dynamic model predicts that, both exergy destruction and work potential rates increase with increasing blood glucose concentration. The ratio of exergy destruction rate to work potential rate increases logarithmically with increasing blood glucose concentration. The neuronal metabolism is thus found to function in an efficient way and switches to lower exergy destruction under stress conditions such as glucose starvation. This behavior seen in this exergy analysis study confirms the assumption of minimum entropy production in living systems. - Highlights: • Unsteady exergy analysis of glucose metabolism of a model neuron is performed. • Dynamic exergy losses were calculated for four different conditions: normoxia, hypoxia, glucose starvation and excess glucose. • Neuronal metabolism achieved a new steady state under each condition within 5 min. • Both exergy loss and work potential rates increase with increasing blood glucose concentration. • Neuronal metabolism functions in an efficient way and switches to lower exergy loss under stress conditions

Stress in parents of very low birth weight preterm infants hospitalized in neonatal intensive care units. A multicenter study.

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Wormald, Francisca; Tapia, José L; Torres, Gabriela; Cánepa, Paula; González, María Aurelia; Rodríguez, Diana; Escobar, Marisol; Reyes, Bernardita; Capelli, Carola; Menéndez, Laura; Delgado, Patricia; Treuer, Sergio; Ramírez, Rodrigo; Borja, Norma; Domínguez, Angélica

2015-08-01

The birth of a premature baby is a stressful event for parents. The objective of this study was to determine early stress in parents of very low birth weight infants (VLBWIs) hospitalized in 12 neonatal intensive care units from a South American Neonatal Network, to identify associated factors, and to compare the level of parental stress in public versus private healthcare facilities. Cross-sectional study in mothers/fathers of VLBWIs (500 to 1500 g). Early parental stress was measured using the Parental Stressor Scale, with a score from 1 (low stress) to 5 (high stress). The sociodemographic characteristics of parents and newborn infants were collected and associated with levels of parental stress. The study included 273 fathers/mothers of a total of 218 VLBW preterm infants. The survey was administered at 5.9 ± 2.0 days of life. The average total parental stress was 3.1 ± 0.8, and the highest score was obtained for the parental role subscale (3.6). A lower education level, unemployment, not having held the newborn infant, and respiratory support requirement were associated with higher parental stress levels. Stress was higher among mothers than fathers, and at public facilities versus private ones. Among parents of VLBWIs, a moderate early parental stress was observed. Parental role alteration was the most relevant factor. Parental stress was higher among mothers and at public healthcare facilities. A greater sensitization, further research and interventions in this area are required.

The nonequilibrium molecular dynamics

International Nuclear Information System (INIS)

Hoover, W.G.

1992-03-01

MOLECULAR DYNAMICS has been generalized in order to simulate a variety of NONEQUILIBRIUM systems. This generalization has been achieved by adopting microscopic mechanical definitions of macroscopic thermodynamic and hydrodynamic variables, such as temperature and stress. Some of the problems already treated include rapid plastic deformation, intense heat conduction, strong shockwaves simulation, and far-from-equilibrium phase transformations. Continuing advances in technique and in the modeling of interatomic forces, coupled with qualitative improvements in computer hardware, are enabling such simulations to approximate real-world microscale and nanoscale experiments

High-intensity training reduces intermittent hypoxia-induced ER stress and myocardial infarct size.

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Bourdier, Guillaume; Flore, Patrice; Sanchez, Hervé; Pepin, Jean-Louis; Belaidi, Elise; Arnaud, Claire

2016-01-15

Chronic intermittent hypoxia (IH) is described as the major detrimental factor leading to cardiovascular morbimortality in obstructive sleep apnea (OSA) patients. OSA patients exhibit increased infarct size after a myocardial event, and previous animal studies have shown that chronic IH could be the main mechanism. Endoplasmic reticulum (ER) stress plays a major role in the pathophysiology of cardiovascular disease. High-intensity training (HIT) exerts beneficial effects on the cardiovascular system. Thus, we hypothesized that HIT could prevent IH-induced ER stress and the increase in infarct size. Male Wistar rats were exposed to 21 days of IH (21-5% fraction of inspired O2, 60-s cycle, 8 h/day) or normoxia. After 1 wk of IH alone, rats were submitted daily to both IH and HIT (2 × 24 min, 15-30m/min). Rat hearts were either rapidly frozen to evaluate ER stress by Western blot analysis or submitted to an ischemia-reperfusion protocol ex vivo (30 min of global ischemia/120 min of reperfusion). IH induced cardiac proapoptotic ER stress, characterized by increased expression of glucose-regulated protein kinase 78, phosphorylated protein kinase-like ER kinase, activating transcription factor 4, and C/EBP homologous protein. IH-induced myocardial apoptosis was confirmed by increased expression of cleaved caspase-3. These IH-associated proapoptotic alterations were associated with a significant increase in infarct size (35.4 ± 3.2% vs. 22.7 ± 1.7% of ventricles in IH + sedenary and normoxia + sedentary groups, respectively, P < 0.05). HIT prevented both the IH-induced proapoptotic ER stress and increased myocardial infarct size (28.8 ± 3.9% and 21.0 ± 5.1% in IH + HIT and normoxia + HIT groups, respectively, P = 0.28). In conclusion, these findings suggest that HIT could represent a preventive strategy to limit IH-induced myocardial ischemia-reperfusion damages in OSA patients. Copyright © 2016 the American Physiological Society.

Intensity of anxiety is modified via complex integrative stress circuitries.

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Smith, Justin P; Prince, Melissa A; Achua, Justin K; Robertson, James M; Anderson, Raymond T; Ronan, Patrick J; Summers, Cliff H

2016-01-01

Escalation of anxious behavior while environmentally and socially relevant contextual events amplify the intensity of emotional response produces a testable gradient of anxiety shaped by integrative circuitries. Apprehension of the Stress-Alternatives Model apparatus (SAM) oval open field (OF) is measured by the active latency to escape, and is delayed by unfamiliarity with the passageway. Familiar OF escape is the least anxious behavior along the continuum, which can be reduced by anxiolytics such as icv neuropeptide S (NPS). Social aggression increases anxiousness in the SAM, reducing the number of mice willing to escape by 50%. The apprehension accompanying escape during social aggression is diminished by anxiolytics, such as exercise and corticotropin releasing-factor receptor 1 (CRF1) antagonism, but exacerbated by anxiogenic treatment, like antagonism of α2-adrenoreceptors. What is more, the anxiolytic CRF1 and anxiogenic α2-adrenoreceptor antagonists also modify behavioral phenotypes, with CRF1 antagonism allowing escape by previously submissive animals, and α2-adrenoreceptor antagonism hindering escape in mice that previously engaged in it. Gene expression of NPS and brain-derived neurotrophic factor (BDNF) in the central amygdala (CeA), as well as corticosterone secretion, increased concomitantly with the escalating anxious content of the mouse-specific anxiety continuum. The general trend of CeA NPS and BDNF expression suggested that NPS production was promoted by increasing anxiousness, and that BDNF synthesis was associated with learning about ever-more anxious conditions. The intensity gradient for anxious behavior resulting from varying contextual conditions may yield an improved conceptualization of the complexity of mechanisms producing the natural continuum of human anxious conditions, and potential therapies that arise therefrom. Copyright © 2015 Elsevier Ltd. All rights reserved.

Intensity-modulated stereotactic radiosurgery using dynamic micro-multileaf collimation

International Nuclear Information System (INIS)

Benedict, Stanley H.; Cardinale, Robert M.; Wu Qiuwen; Zwicker, Robert D.; Broaddus, William C.; Mohan, Radhe

2001-01-01

Purpose: The implementation of dynamic leaf motion on a micro-multileaf collimator system provides the capability for intensity-modulated stereotactic radiosurgery (IMSRS), and the consequent potential for improved dose distributions for irregularly shaped tumor volumes adjacent to critical organs. This study explores the use of IMSRS to provide improved tumor coverage and normal tissue sparing for small cranial tumors relative to plans based on multiple fixed uniform-intensity beams or traditional circular collimator arc-based stereotactic techniques. Methods and Materials: Four patient cases involving small brain lesions are presented and analyzed. The cases were chosen to include a representative selection of target shapes, number of targets, and adjacent critical areas. Patient plans generated for these comparisons include standard arcs with multiple circular collimators, and fixed noncoplanar static fields with uniform-intensity beams and IMSRS. Parameters used for evaluation of the plans include the percentage of irradiated volume to tumor volume (PITV), normal tissue dose-volume histograms, and dose-homogeneity ratios. All IMSRS plans were computed using previously established IMRT techniques adapted for use with the BrainLAB M3 micro-multileaf collimator. The algorithms comprising the IMRT system for optimization of intensity distributions and conversion into leaf trajectories of the BrainLab M3 were developed at our institution. The ADAC Pinnacle 3 radiation treatment-planning system was used for dose calculations and for input of contours for target volumes and normal critical structures. Results: For all cases, the IMSRS plans showed a high degree of conformity of the dose distribution with the target shape. The IMSRS plans provided either (1) a smaller volume of normal tissue irradiated to significant dose levels, generally taken as doses greater than 50% of the prescription, or (2) a lower dose to an important adjacent critical organ. The reduction in

Effect of the low- versus high-intensity exercise training on endoplasmic reticulum stress and GLP-1 in adolescents with type 2 diabetes mellitus.

Science.gov (United States)

Lee, Sung Soo; Yoo, Jae Ho; So, Yong Seok

2015-10-01

[Purpose] The primary objective of this study was to investigate the effect of low-intensity exercise training compare with high-intensity exercise training on endoplasmic reticulum stress and glucagon-like peptide-1 in adolescents with type 2 diabetes mellitus. [Subjects and Methods] The low-intensity exercise training group performed aerobic exercise training at an intensity of ≤ 45% of the heart rate reserve. The high-intensity interval exercise training group performed interval exercise training at an intensity of ≥ 80% of the heart rate reserve. The exercise-related energy consumption was determined for both groups on a per-week basis (1,200 kcal/week). [Results] Both groups showed improvement in the glucose-regulated protein 78 and dipeptidyl peptidase-4, but the size of the between-group effect was not statistically significant. The high-intensity interval exercise training group showed a significant reduction in percentage body fat. The C-peptide level increased after the 12-weeks programs and was significantly different, between the groups. Fasting glucose, insulin resistance in the fasting state according to homeostasis model assessment, and leptin decreased after the 12-weeks exercise program and were significantly different between the groups, and glucagon-like peptide-1 increased after the 12-week exercise programs and was significantly different between the groups. [Conclusion] In conclusion high-intensity interval exercise training, as defined in this study, may lead to improvements in body composition, glycemic control, endoplasmic reticulum stress, and the glucagon-like peptide-1 in adolescents with type 2 diabetes mellitus.

Validation of the Amsterdam Dynamic Facial Expression Set – Bath Intensity Variations (ADFES-BIV): A Set of Videos Expressing Low, Intermediate, and High Intensity Emotions

Science.gov (United States)

Wingenbach, Tanja S. H.

2016-01-01

Most of the existing sets of facial expressions of emotion contain static photographs. While increasing demand for stimuli with enhanced ecological validity in facial emotion recognition research has led to the development of video stimuli, these typically involve full-blown (apex) expressions. However, variations of intensity in emotional facial expressions occur in real life social interactions, with low intensity expressions of emotions frequently occurring. The current study therefore developed and validated a set of video stimuli portraying three levels of intensity of emotional expressions, from low to high intensity. The videos were adapted from the Amsterdam Dynamic Facial Expression Set (ADFES) and termed the Bath Intensity Variations (ADFES-BIV). A healthy sample of 92 people recruited from the University of Bath community (41 male, 51 female) completed a facial emotion recognition task including expressions of 6 basic emotions (anger, happiness, disgust, fear, surprise, sadness) and 3 complex emotions (contempt, embarrassment, pride) that were expressed at three different intensities of expression and neutral. Accuracy scores (raw and unbiased (Hu) hit rates) were calculated, as well as response times. Accuracy rates above chance level of responding were found for all emotion categories, producing an overall raw hit rate of 69% for the ADFES-BIV. The three intensity levels were validated as distinct categories, with higher accuracies and faster responses to high intensity expressions than intermediate intensity expressions, which had higher accuracies and faster responses than low intensity expressions. To further validate the intensities, a second study with standardised display times was conducted replicating this pattern. The ADFES-BIV has greater ecological validity than many other emotion stimulus sets and allows for versatile applications in emotion research. It can be retrieved free of charge for research purposes from the corresponding author

The Development of Dynamic Facial Expression Recognition at Different Intensities in 4- to 18-Year-Olds

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Montirosso, Rosario; Peverelli, Milena; Frigerio, Elisa; Crespi, Monica; Borgatti, Renato

2010-01-01

The primary purpose of this study was to examine the effect of the intensity of emotion expression on children's developing ability to label emotion during a dynamic presentation of five facial expressions (anger, disgust, fear, happiness, and sadness). A computerized task (AFFECT--animated full facial expression comprehension test) was used to…

A Randomized Double-Blind Controlled Trial Comparing Davanloo Intensive Short-Term Dynamic Psychotherapy as Internet-Delivered Vs Treatment as Usual for Medically Unexplained Pain: A 6-Month Pilot Study.

Science.gov (United States)

Chavooshi, Behzad; Mohammadkhani, Parvaneh; Dolatshahi, Behrouz

2016-01-01

Research has shown that Intensive Short-Term Dynamic Psychotherapy (ISTDP) can effectively decrease pain intensity and improve quality of life in patients with medically unexplained pain. Understanding that not all patients with medically unexplained pain have access to in-person ISTDP, this study aims to investigate the efficacy of an Internet-delivered ISTDP for individuals with medically unexplained pain using Skype in comparison with treatment as usual. In this randomized controlled trial, 100 patients were randomly allocated into Internet-delivered ISTDP (n = 50) and treatment-as- usual (n = 50) groups. Treatment intervention consisted of 16 weekly, hour-long therapy sessions. The primary outcome was perceived pain assessed using the Numeric Pain Rating Scale. The secondary outcome included Depression Anxiety Stress Scale-21, Emotion Regulation Questionnaire, Mindful Attention Awareness Scale, and Quality-of-Life Inventory. Blind assessments were conducted at the baseline, posttreatment, and at a 6-month follow-up. In the intention-to-treat analysis, pain symptoms in the intervention group were significantly reduced (p Skype can significantly improve pain intensity and clinical symptoms of medically unexplained pain. Copyright © 2016 The Academy of Psychosomatic Medicine. Published by Elsevier Inc. All rights reserved.

Viscoplasticity and the dynamics of brittle fracture

International Nuclear Information System (INIS)

Langer, J. S.

2000-01-01

I propose a model of fracture in which the curvature of the crack tip is a relevant dynamical variable and crack advance is governed solely by plastic deformation of the material near the tip. This model is based on a rate-and-state theory of plasticity introduced in earlier papers by Falk, Lobkovsky, and myself. In the approximate analysis developed here, fracture is brittle whenever the plastic yield stress is nonzero. The tip curvature finds a stable steady-state value at all loading strengths, and the tip stress remains at or near the plastic yield stress. The crack speed grows linearly with the square of the effective stress intensity factor above a threshold that depends on the surface tension. This result provides a possible answer to the fundamental question of how breaking stresses are transmitted through plastic zones near crack tips. (c) 2000 The American Physical Society

Elevated nonlinearity as an indicator of shifts in the dynamics of populations under stress.

Science.gov (United States)

Dakos, Vasilis; Glaser, Sarah M; Hsieh, Chih-Hao; Sugihara, George

2017-03-01

Populations occasionally experience abrupt changes, such as local extinctions, strong declines in abundance or transitions from stable dynamics to strongly irregular fluctuations. Although most of these changes have important ecological and at times economic implications, they remain notoriously difficult to detect in advance. Here, we study changes in the stability of populations under stress across a variety of transitions. Using a Ricker-type model, we simulate shifts from stable point equilibrium dynamics to cyclic and irregular boom-bust oscillations as well as abrupt shifts between alternative attractors. Our aim is to infer the loss of population stability before such shifts based on changes in nonlinearity of population dynamics. We measure nonlinearity by comparing forecast performance between linear and nonlinear models fitted on reconstructed attractors directly from observed time series. We compare nonlinearity to other suggested leading indicators of instability (variance and autocorrelation). We find that nonlinearity and variance increase in a similar way prior to the shifts. By contrast, autocorrelation is strongly affected by oscillations. Finally, we test these theoretical patterns in datasets of fisheries populations. Our results suggest that elevated nonlinearity could be used as an additional indicator to infer changes in the dynamics of populations under stress. © 2017 The Author(s).

Posttraumatic stress disorder (PTSD) in children after paediatric intensive care treatment compared to children who survived a major fire disaster

NARCIS (Netherlands)

Bronner, M.B.; Knoester, H.; Bos, AP; Last, B.F.; Grootenhuis, M.A.

2008-01-01

Background: The goals were to determine the presence of posttraumatic stress disorder (PTSD) in children after paediatric intensive care treatment, to identify risk factors for PTSD, and to compare this data with data from a major fire disaster in the Netherlands. Methods: Children completed the

The five-factor model of personality, work stress and professional quality of life in neonatal intensive care unit nurses.

Science.gov (United States)

Barr, Peter

2018-06-01

The study aim was to determine the direct and indirect relations of the five-factor model of personality traits and work stress with professional quality of life in neonatal nurses. Neonatal intensive care nursing has positive and negative effects on neonatal nurses' psychological well-being. Although individual and situational factors interact to influence professional quality of life, there have been few studies of these relationships in neonatal nurses. A cross-sectional study conducted in 2016. Self-report questionnaires were used to measure professional quality of life (burnout, secondary traumatic stress and compassion satisfaction), five-factor model of personality traits (neuroticism, agreeableness, extraversion, conscientiousness and openness) and work stress (role ambiguity, role conflict and role overload). One hundred and forty (34%) of 405 eligible neonatal nurses provided the data. After controlling for work stress, neuroticism and agreeableness were related to burnout, neuroticism was related to secondary traumatic stress, and extraversion was related to compassion satisfaction. Work stress controlled for personality traits was related to burnout and secondary traumatic stress, but not to compassion satisfaction. Neuroticism moderated the effect of work stress on secondary traumatic stress and agreeableness and openness moderated the effect of work stress on compassion satisfaction. Work stress mediated the effect of neuroticism and extraversion on burnout and the effects of extraversion and conscientiousness on compassion satisfaction. Strategies to reduce work stress may not lessen burnout and secondary traumatic stress or increase compassion satisfaction in neonatal nurses who are prone to high neuroticism, low agreeableness and low extraversion. © 2018 John Wiley & Sons Ltd.

Calculation of stress intensity factors using the UNCLE finite element system and their application in fracture mechanics

International Nuclear Information System (INIS)

Pearce, J.H.B.

1978-02-01

The behaviour of crack-like defects in loaded structures is in many cases characterised by the stress intensity factor, K, which describes the spatial distribution around the crack tip. Analytical evaluation of K for generalised loading and geometry would be extremely complex. A finite element approach is described which utilises the existing UNCLE system of the UKAEA. The interpretation of the results for a fracture mechanics analysis is briefly reviewed. (author)

Numerical methods in dynamic fracture mechanics

International Nuclear Information System (INIS)

Beskos, D.E.

1987-01-01

A review of numerical methods for the solution of dynamic problems of fracture mechanics is presented. Finite difference, finite element and boundary element methods as applied to linear elastic or viscoelastic and non-linear elastoplastic or elastoviscoplastic dynamic fracture mechanics problems are described and critically evaluated. Both cases of stationary cracks and rapidly propagating cracks of simple I, II, III or mixed modes are considered. Harmonically varying with time or general transient dynamic disturbances in the form of external loading or incident waves are taken into account. Determination of the dynamic stress intensity factor for stationary cracks or moving cracks with known velocity history as well as determination of the crack-tip propagation history for given dynamic fracture toughness versus crack velocity relation are described and illustrated by means of certain representative examples. Finally, a brief assessment of the present state of knowledge is made and research needs are identified

Finite-size effect on the dynamic and sensing performances of graphene resonators: the role of edge stress.

Science.gov (United States)

Kim, Chang-Wan; Dai, Mai Duc; Eom, Kilho

2016-01-01

We have studied the finite-size effect on the dynamic behavior of graphene resonators and their applications in atomic mass detection using a continuum elastic model such as modified plate theory. In particular, we developed a model based on von Karman plate theory with including the edge stress, which arises from the imbalance between the coordination numbers of bulk atoms and edge atoms of graphene. It is shown that as the size of a graphene resonator decreases, the edge stress depending on the edge structure of a graphene resonator plays a critical role on both its dynamic and sensing performances. We found that the resonance behavior of graphene can be tuned not only through edge stress but also through nonlinear vibration, and that the detection sensitivity of a graphene resonator can be controlled by using the edge stress. Our study sheds light on the important role of the finite-size effect in the effective design of graphene resonators for their mass sensing applications.

Flow stress and dynamic strain-ageing of β-transformed Zircaloy-4

International Nuclear Information System (INIS)

Woo, O.T.; Tseng, D.; Tangri, K.; MacEwen, S.R.

1979-01-01

The 0.2% yield stress of β-transformed Zircaloy-4 was found to be independent of prior-β grain size but varied as the inverse of the transformed β plate width. A dislocation loop expansion model originally proposed by Langford and Cohen (1969) for cold-drawn iron wires is used to explain the inverse plate width dependence. Both air-cooled and water-quenched samples exhibited dynamic strain-ageing effects in approximately the same temperature range of 573 to 673 K: (a) a local minimum in strain-rate sensitivity is associated with a peak or an inflection point in the temperature dependence of the 0.2% yield stress for water-quenched or air-cooled samples respectively, and (b) yield drops were observed in strain rate change tests. (Auth.)

Growing up with stress - carbon sequestration and allocation dynamics of a broadleaf evergreen forest

Science.gov (United States)

Griebel, Anne; Bennett, Lauren T.; Arndt, Stefan K.

2016-04-01

Evergreen forests have the potential to sequester carbon year-round due to the presence of leaves with a multi-year lifespan. Eucalypt forests occur in warmer climates where temperature and radiation are not imposing a strong seasonality. Thus, unlike deciduous or many coniferous trees, many eucalypts grow opportunistically as conditions allow. As such, many eucalypts do not produce distinct growth rings, which present challenges to the implementation of standard methods and data interpretation approaches for monitoring and explaining carbon allocation dynamics in response to climatic stress. As a consequence, there is a lack of detailed understanding of seasonal growth dynamics of evergreen forests as a whole, and, in particular, of the influence of climatic drivers on carbon allocation to the various biomass pools. We used a multi-instrument approach in a mixed species eucalypt forest to investigate the influence of climatic drivers on the seasonal growth dynamics of a predominantly temperate and moisture-regulated environment in south-eastern Australia. Ecosystem scale observations of net ecosystem exchange (NEE) from a flux tower in the Wombat forest near Melbourne indicated that the ecosystem is a year-round carbon sink, but that intra-annual variations in temperature and moisture along with prolonged heat waves and dry spells resulted in a wide range of annual sums over the past three years (NEE ranging from ~4 to 12 t C ha-1 yr-1). Dendrometers were used to monitor stem increments of the three dominant eucalypt species. Stem expansion was generally opportunistic with the greatest increments under warm but moist conditions (often in spring and autumn), and the strongest indicators of stem growth dynamics being radiation, vapour pressure deficit and a combined heat-moisture index. Differences in the seasonality of stem increments between species were largely due to differences in the canopy position of sampled individuals. The greatest stem increments were

The effect of Residual Stress on the Stress Intensity Factor of Nuclear Material

International Nuclear Information System (INIS)

Song, Taek Ho

2008-01-01

As NPP (Nuclear Power Plant) gets aged, the importance of the pressure boundary integrity increases very much to those who are trying to operate their plant beyond its design life. Not long ago, Boric acid crystal was found at the RPV outlet nozzle of V.C. Summer plant during the visual examination in 2000. After this finding, non-destructive examination was taken to find out what's taken place. As a result of this examination, circumferential and axial cracks were found. With Metallurgical structure examination, it was shown that crack had been developed at the mid-point between Inco-alloy buttering and weld metal. It was turned out that high welding residual stress was the main cause of the cracking. Because of the through wall crack, nozzle and welding parts were replaced. Many other nuclear power plants experienced similar pressure boundary stress corrosion cracks (SCCs). KEPRI (Korea Electric Power Research Institute) has carried out research projects for managing and preventing these kinds of cracks in nuclear power plants (NPPs). The titles of these research projects are 'Development of Stress Corrosion Cracking Management Technology and Aging Monitor for NPP Main Components' and 'Development of Analysis Technology for Crack Management of Dissimilar Metal Weld'. Through these projects, residual stress measurement techniques have been exercised at various points in mock-up test specimens to simulate nuclear power plant dissimilar base metal and weldment residual stress. X-ray test and hole drilling method have been reviewed to measure residual stresses of the dissimilar metal welds. This paper shows some point of view in residual stress measurement. Fracture mechanics analysis has been performed to explain the importance of residual stress measurement in association with nuclear power plant safety

[The combined action of drinking mineral water and low-intensity electromagnetic radiation under the immobilization stress conditions (an experimental study)].

Science.gov (United States)

Korolev, Yu N; Bobrovnitsky, I P; Geniatulina, M S; Mikhailik, L V; Nikulina, L A; Bobkova, A S; Yakovlev, M Yu

2015-01-01

The present study carried out on white male rats in experiments with the use of biochemical, radioimmunological, and electron- microscopic methods. It was shown that the combined treatment with potable mineral water (MV) and low-intensity electromagnetic radiation (LIEMR) of ultrahigh frequency (power density less than 1 pW/cm2, the frequency about 1000 MHz) facilitated the activation of metabolic and intracellular regenerative processes in the liver and testes. One of the advantages of the combined application of MV and LIEMR over the single-factor treatment manifested itself as the weakening of stress reactions, the increase in the frequency of the plastic processes, and the more harmonious development of different forms of intracellular regeneration. The results of the study provide a deeper insight ino the mechanisms underlying the combined actions of drinking mineral water and low-intensity electromagnetic radiation; also, they justify the application of these factors for the protection of the reproductive system and the entire body from stress-induced disorders.

Mode I Stress Intensity Factors for triangular corner crack nearby intersecting of cylindrical holes

Directory of Open Access Journals (Sweden)

E. Salvati

2013-10-01

Full Text Available In this paper triangular flaws has been taken into account at the intersection of two holes inside a specified specimen. Influence of bore hole D1/D2 and angle between their axes α are examined. Numerical analysis are performed to determine Stress Intensity factors (SIF in many geometric configurations. Afterwards, fitting weight function’s parameters with FEM results, new SIF analytics expression are shown. Finally, the accuracy of weight functions in SIF predictions for different inner pressure, has been checked as well as the comparison between the SIF of a triangular crack and that of an actual crack shape obtained through a fatigue test.

Whole-body heat stress and exercise stimulate the appearance of platelet microvesicles in plasma with limited influence of vascular shear stress.

Science.gov (United States)

Wilhelm, Eurico N; González-Alonso, José; Chiesa, Scott T; Trangmar, Steven J; Kalsi, Kameljit K; Rakobowchuk, Mark

2017-11-01

Intense, large muscle mass exercise increases circulating microvesicles, but our understanding of microvesicle dynamics and mechanisms inducing their release remains limited. However, increased vascular shear stress is generally thought to be involved. Here, we manipulated exercise-independent and exercise-dependent shear stress using systemic heat stress with localized single-leg cooling (low shear) followed by single-leg knee extensor exercise with the cooled or heated leg (Study 1, n  = 8) and whole-body passive heat stress followed by cycling (Study 2, n  = 8). We quantified femoral artery shear rates (SRs) and arterial and venous platelet microvesicles (PMV-CD41 + ) and endothelial microvesicles (EMV-CD62E + ). In Study 1, mild passive heat stress while one leg remained cooled did not affect [microvesicle] ( P  ≥ 0.05). Single-leg knee extensor exercise increased active leg SRs by ~12-fold and increased arterial and venous [PMVs] by two- to threefold, even in the nonexercising contralateral leg ( P  body passive heat stress increased arterial [PMV] compared with baseline (mean±SE, from 19.9 ± 1.5 to 35.5 ± 5.4 PMV . μ L -1. 10 3 , P  stress increased [PMV] further in the venous circulation (from 27.5 ± 2.2 at baseline to 57.5 ± 7.2 PMV . μ L -1. 10 3 during cycling with heat stress, P  body heat stress may increase arterial [PMV], and intense exercise engaging either large or small muscle mass promote PMV formation locally and systemically, with no influence upon [EMV]. Local shear stress, however, does not appear to be the major stimulus modulating PMV formation in healthy humans. © 2017 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.

The Effects of Emotional Intelligence (EI Items Education on Job Related Stress in Physicians and Nurses who Work in Intensive Care Units

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Kh Nooryan

2011-12-01

Full Text Available Background & Aim: Intensive care units (ICUs are recognized as stressful environments. The objective of this study was to determine the effects of emotional intelligence education items on job related stress on physicians and nurses who work in intensive care units at hospitals of Yerevan, Armenia. Methods: A interventional study design was implemented with 106 registered hospital physicians and nurses, who were widely distributed all the way through. Case group was taught about 15 E.I items. For data collection, the 20-question Berger situational (overt anxiety questionnaire, the 20-item personality (covert anxiety questionnaire, and the Bar-on emotional intelligence questionnaire with 133 questions were used. Statistical descriptive methods, chi-square (X2 and t-tests were used to analyze data. Results: The research achievements revealed that the average score of the case group`s situational anxiety was 46.59 before intervention, which decreased to 39.95 after the training of the items of emotional intelligence. The average score of situational anxiety of control group was 44.32 before intervention which increased to 44.76 after examination. There was a meaningful statistical difference between case and control group after education of emotional intelligence`s items (p=0.001. Conclusion: Results of the current study showed that physicians and nurses experience high level of stress. The ability to effectively deal with emotion intelligence and emotional information in the workplace assists employees in coping with occupational stress and should be developed in stress managing trainings.

Two-dimensional simulation of the thermal stress effect on static and dynamic VDMOS characteristics

International Nuclear Information System (INIS)

Alwan, M.; Beydoun, B.; Ketata, K.; Zoaeter, M.

2005-01-01

Using a two-dimensional simulator, the effect of the thermal stress on static and dynamic vertical double-diffusion metal oxide semiconductor (VDMOS) characteristics have been investigated. The use of the device under certain thermal stress conditions can produce modifications of its physical and electrical properties. Based on physics and 2D simulations, this paper proposes an analysis of this stress effect observed on the electrical characteristics of the device. Parameters responsible of these modifications are determined. Approximate expressions of the ionization coefficients and breakdown voltage in terms of temperature are proposed. Non-punch-through junction theory is used to express the breakdown voltage and the space charge extension with respect to the impurity concentration and the temperature. The capacitances of the device have been also studied. The effect of the stress on C-V characteristics is observed and analyzed. We notice that the drain-gate, drain-source and gate-source capacitances are shifted due to the degradation of device physical properties versus thermal stress

Dynamic characteristics of rotating pretwisted clamped-clamped beam under thermal stress

International Nuclear Information System (INIS)

Zhang, Bo; Li, Yueming; Lu, Wei Zhen

2016-01-01

Effects of thermal stress on the vibration characteristics, buckling limit and critical speed of a rotating pretwisted beam clamped to rigid hub at a stagger angle were investigated. By considering the work done by thermal stress, the thermal influence on stiffness matrix was introduced in the dynamic model. The motion equations were derived based on Lagrange equation by employing three pure Cartesian deformation variables combined with nonlinear von Karman strain formula. Numerical investigations studied the modal characteristics of the beam. Numerical results calculated from a commercial finite element code and obtained with the present modeling method were in good agreement with the previous results reported in the literature. The combined softening effects due to the thermal stress and the rotation motion were observed. Furthermore, it is shown that the inclusion of thermal stress is necessary for blades operating under a high temperature field. Buckling thermal loads and the critical rotating speed were calculated through solving the corresponding nonlinear equations numerically, and some pertinent conclusions are outlined. It is also found that the peak value position of the first mode shape approaches to the tip of blade with the increment of rotating speed and hub radius. However, the variation in the environment temperature causes only a slight alteration in the mode shape

Dynamic characteristics of rotating pretwisted clamped-clamped beam under thermal stress

Energy Technology Data Exchange (ETDEWEB)

Zhang, Bo; Li, Yueming [State Key Laboratory for Strength and Vibration of Mechanical Structures, Shaanxi Key Laboratory of Environment and Control for Flight Vehicle, School of Aerospace, Xi' an Jiaotong UniversityXi' an (China); Lu, Wei Zhen [Dept. of Civil and Architectural Engineering, City University of Hong Kong, Hong Kong (China)

2016-09-15

Effects of thermal stress on the vibration characteristics, buckling limit and critical speed of a rotating pretwisted beam clamped to rigid hub at a stagger angle were investigated. By considering the work done by thermal stress, the thermal influence on stiffness matrix was introduced in the dynamic model. The motion equations were derived based on Lagrange equation by employing three pure Cartesian deformation variables combined with nonlinear von Karman strain formula. Numerical investigations studied the modal characteristics of the beam. Numerical results calculated from a commercial finite element code and obtained with the present modeling method were in good agreement with the previous results reported in the literature. The combined softening effects due to the thermal stress and the rotation motion were observed. Furthermore, it is shown that the inclusion of thermal stress is necessary for blades operating under a high temperature field. Buckling thermal loads and the critical rotating speed were calculated through solving the corresponding nonlinear equations numerically, and some pertinent conclusions are outlined. It is also found that the peak value position of the first mode shape approaches to the tip of blade with the increment of rotating speed and hub radius. However, the variation in the environment temperature causes only a slight alteration in the mode shape.

ALS mutant SOD1 interacts with G3BP1 and affects stress granule dynamics.

Science.gov (United States)

Gal, Jozsef; Kuang, Lisha; Barnett, Kelly R; Zhu, Brian Z; Shissler, Susannah C; Korotkov, Konstantin V; Hayward, Lawrence J; Kasarskis, Edward J; Zhu, Haining

2016-10-01

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease. Mutations in Cu/Zn superoxide dismutase (SOD1) are responsible for approximately 20 % of the familial ALS cases. ALS-causing SOD1 mutants display a gain-of-toxicity phenotype, but the nature of this toxicity is still not fully understood. The Ras GTPase-activating protein-binding protein G3BP1 plays a critical role in stress granule dynamics. Alterations in the dynamics of stress granules have been reported in several other forms of ALS unrelated to SOD1. To our surprise, the mutant G93A SOD1 transgenic mice exhibited pathological cytoplasmic inclusions that co-localized with G3BP1-positive granules in spinal cord motor neurons. The co-localization was also observed in fibroblast cells derived from familial ALS patient carrying SOD1 mutation L144F. Mutant SOD1, unlike wild-type SOD1, interacted with G3BP1 in an RNA-independent manner. Moreover, the interaction is specific for G3BP1 since mutant SOD1 showed little interaction with four other RNA-binding proteins implicated in ALS. The RNA-binding RRM domain of G3BP1 and two particular phenylalanine residues (F380 and F382) are critical for this interaction. Mutant SOD1 delayed the formation of G3BP1- and TIA1-positive stress granules in response to hyperosmolar shock and arsenite treatment in N2A cells. In summary, the aberrant mutant SOD1-G3BP1 interaction affects stress granule dynamics, suggesting a potential link between pathogenic SOD1 mutations and RNA metabolism alterations in ALS.

Dynamics of intense pulsed proton beam in the Nagaoka ETIGO-I

International Nuclear Information System (INIS)

Tanaka, Hajime; Konno, Kohji; Masugata, Katsumi; Yatsui, Kiyoshi; Matsui, Masao

1982-01-01

Dynamics of an intense pulsed proton beam have been studied by measuring nuclear reactions as well as by a biased ion-collector (BIC). When the ion-current density (Jsub(i)) is small such that Jsub(i) lt 30 A/cm 2 , the proton numer measured by BIC is in good agreement with that by nuclear activation. Good linearity exists between time integrated gamma -ray signal and proton number measured by the activation. Hence, it would be possible to obtain the proton number quantitatively even when a target ''blow-off'' takes place at Jsub(i) gt 1 kA/cm 2 . Prompt gamma -ray is also measured by the time-of-flight method to yield reasonable agreement with the applied peak potential. (author)

Distribution of Side Abutment Stress in Roadway Subjected to Dynamic Pressure and Its Engineering Application

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Yao Qiangling

2015-01-01

Full Text Available The borehole stress-meter was employed in this study to investigate the distribution of the side abutment stress in roadway subjected to dynamic pressure. The results demonstrate that the side abutment stress of the mining roadway reaches a peak value when the distance to the gob is 8 m and the distribution curve of the side abutment stress can be divided into three zones: stress rising zone, stress stabilizing zone, and stress decreasing zone. Further numerical investigation was carried out to study the effect of the coal mass strength, coal seam depth, immediate roof strength, and thickness on the distribution of the side abutment stress. Based on the research results, we determined the reasonable position of the mining roadway and the optimal width of the barrier pillar. The engineering application demonstrates that the retention of the barrier pillar with a width of 5 m along the gob as the haulage roadway for the next panel is feasible, which delivers favorable technological and economic benefits.

Gene expression dynamics in the oxidative stress response of fission yeast

DEFF Research Database (Denmark)

Papadakis, Emmanouil

Changes in the environment continuously challenge living organisms during their lifetime. A cell’s survival depends on its ability to coordinate a rapid and successful stress response when exposed to acute doses of damaging agents. Oxidative stress caused by an excess of reactive oxygen species......, especially using model organisms. The fission yeast Schizosaccharomyces pombe is a unicellular eukaryotic organism that possesses genome features and molecular pathways that are highly conserved in humans. Moreover, the limited redundancy of its genome make S. pombe well suited for phenotypic studies...... (HP, 0.5 mM). The applied experimental design allowed us to measure both the activation and recovery phases of the response at a sufficiently high time resolution to model transcription and translation dynamics. Absolute expression levels (copies per cell) and time-resolved expression profiles for 4...

Static Tensile and Transient Dynamic Response of Cracked Aluminum Plate Repaired with Composite Patch - Numerical Study

Science.gov (United States)

Khalili, S. M. R.; Shariyat, M.; Mokhtari, M.

2014-06-01

In this study, the central cracked aluminum plates repaired with two sided composite patches are investigated numerically for their response to static tensile and transient dynamic loadings. Contour integral method is used to define and evaluate the stress intensity factors at the crack tips. The reinforcement for the composite patches is carbon fibers. The effect of adhesive thickness and patch thickness and configuration in tensile loading case and pre-tension, pre-compression and crack length effect on the evolution of the mode I stress intensity factor (SIF) (KI) of the repaired structure under transient dynamic loading case are examined. The results indicated that KI of the central cracked plate is reduced by 1/10 to 1/2 as a result of the bonded composite patch repair in tensile loading case. The crack length and the pre-loads are more effective in repaired structure in transient dynamic loading case in which, the 100 N pre-compression reduces the maximum KI for about 40 %, and the 100 N pre-tension reduces the maximum KI after loading period, by about 196 %.

Stress Intensity Factors of Slanted Cracks in Bi-Material Plates

Science.gov (United States)

Ismail, Al Emran; Azhar Kamarudin, Kamarul; Nor, Nik Hisyamudin Muhd

2017-10-01

In this study, the stress intensity factors (SIF) of slanted cracks in bi-material plates subjected to mode I loading is numerically solved. Based on the literature survey, tremendous amount of research works are available studying the normal cracks in both similar and dissimilar plates. However, lack of SIF behavior for slanted cracks especially when it is embedded in bi-material plates. The slanted cracks are then modelled numerically using ANSYS finite element program. Two plates of different in mechanical properties are firmly bonded obliquely and then slanted edge cracks are introduced at the lower inclined edge. Isoparametric singular element is used to model the crack tip and the SIF is determined which is based on the domain integral method. Three mechanical mismatched and four slanted angles are used to model the cracks. According to the present results, the effects of mechanical mismatch on the SIF for normal cracks are not significant. However, it is played an important role when slanted angles are introduced. It is suggested that higher SIF can be obtained when the cracks are inclined comparing with the normal cracks. Consequently, accelerating the crack growth at the interface between two distinct materials.

Clinical and epidemiological study of stress hyperglycemia among medical intensive care unit patients in Central India

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Jitendra Sharma

2017-01-01

Full Text Available Background: Stress hyperglycemia is common in patients presenting at the emergency medical ward and is associated with poor prognosis and increased risk of mortality. Aims and Objective: To study and determine the prevalence and factors associated with stress hyperglycemia. Materials and Methods: A cross-sectional observational study was performed on 536 nondiabetic patients presented to the Intensive Care Unit (ICU at Gandhi Medical College and allied Hamidia Hospital, Bhopal, between March 31, 2015, and May 28, 2015. A detailed history including demographic profile, presence of chronic disease, history of hospitalization and ICU admission, surgical status, and major reason for ICU admission (i.e., predominant diagnostic category was collected. Hematological and other parameters based on profile of study population were also analyzed. Results: Out of 536 patients, 109 (20.33% had stress hyperglycemia. Out of 109 patients with stress hyperglycemia, 87 (16.23% patients had glycated hemoglobin (HbA1c <5.7% and 22 (4.10% patients had HbA1c between 5.7% and 6.4%. Mean age of the study population was 40.27 ± 1.44 years, with male dominance. Mean random blood glucose level was 181.46 ± 3.80 mg/dl. Frequency of stress hyperglycemia was 24.13% in stroke, 19.54% in multiple organ dysfunction syndrome (MODS, 17.24% in chronic kidney disease (CKD, 12.64% in central nervous system (CNS infection, 8.05% in chronic liver disease (CLD, and 8.05% in seizure patients. Association between stroke and stress hyperglycemia was significant (P = 0.036. Association between hospital stay more than 7 days and stress hyperglycemia was significant in stroke patients (P = 0.0029, CKD patients (P = 0.0036, CLD (P = 0.0099, and MODS patients (P = 0.0328. Conclusions: The factors associated with stress hyperglycemia were stroke, MODS, CKD, CNS infection, CLD, seizure patients, with prolonged hospital stay and expected proportion.

Application of the virtual crack closure technique to calculate stress intensity factors for through cracks with an oblique elliptical crack front

NARCIS (Netherlands)

Fawaz, S.

1998-01-01

Fractographic observations on fatigue tested 2024 T3 clad aluminium riveted lap-splice joints indicate oblique fronts after the initial surface or corner crack at a rivet hole has penetrated through the sheet thichness. No stress intensity factor solutions are available for this geometry subjected

The lipid peroxidation intensity of fungi strains from the orders Agaricales and Polyporales

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O. V. Fedotov

2016-07-01

Full Text Available This article is devoted to investigation of the dynamics of growth and level of spontaneous and induced lipid peroxidation intensity of Basidiomycetes strains grown by surface cultivation on a glucose-peptone medium. The materials of the research are mycelium and culture filtrates (CF of 57 strains (5 belong to 5 species from the order Polyporales s.l., and 52 belong to 7 species of the order Agaricales s.l.. To study the dynamics of growth we used a weighing method for determining the accumulation of absolutely dry biomass. Intensity of lipid peroxidation was determined by a modified spectrophotometric method for content of active to thiobarbituric acid products. It was found that the most productive in absolutely dry biomass accumulation were the strains Flammulina velutipes (Curt.: Fr. Sing. F-610 and Pleurotus eryngii (DC.: Fr. Quél. P-er. The level of spontaneous and induced LPO intensity in mycelia of all strains was higher than this figure in the culture filtrate and increased with the duration of cultivation. Dependencies between the content of lipid peroxidation products in the mycelia and CF were not established. The lowest values were recorded for biomass accumulation by the strains Pleurotus ostreatus (Jacq.: Fr. P. Kumm. P-14, P-192 and P. citrinopileatus Singer. Р-сіtr. Groups of basidiomycete cultures with different levels of TBA-AP were identified. Spontaneous and induced intensivity of lipid peroxidation in all studied strains of mycelia was higher than the figure in the culture filtrate. The intensity of lipid peroxidation in both mycelia and culture filtrate constantly increased, which can be explained by the growing shortage of certain nutrients (primarily carbon and increased concentration of metabolic products in the medium. The ratio of spontaneous and induced lipid peroxidation intensity is specific to each strain and is independent of its systematic position. Shifting of prooxidant-antioxidant balance to a

Sustained, Low?Intensity Exercise Achieved by a Dynamic Feeding System Decreases Body Fat in Ponies

OpenAIRE

de Laat, M.A.; Hampson, B.A.; Sillence, M.N.; Pollitt, C.C.

2016-01-01

Background Obesity in horses is increasing in prevalence and can be associated with insulin insensitivity and laminitis. Current treatment strategies for obesity include dietary restriction and exercise. However, whether exercise alone is effective for decreasing body fat is uncertain. Hypothesis Our hypothesis was that twice daily use of a dynamic feeding system for 3 months would induce sustained, low?intensity exercise thereby decreasing adiposity and improving insulin sensitivity (SI). An...

The Dynamics of Migration-Related Stress and Coping of Female Domestic Workers from the Philippines: An Exploratory Study

NARCIS (Netherlands)

van der Ham, A.J.; Ujano-Batangan, M.T.; Ignacio, R.; Wolffers, I.N.

2015-01-01

Female domestic workers face many migration-related stressors that affect their mental health, but we know little about the dynamics of stress and coping in different migration phases. This exploratory study aims to assess stress and coping of female migrant domestic workers from the Philippines in

Calculation of dynamic stresses in viscoelastic sandwich beams using oma

DEFF Research Database (Denmark)

Pelayo, F.; Aenlle, M. L.; Ismael, G.

2017-01-01

The mechanical response of sandwich elements with viscoelastic core is time and temperature dependent. Laminated glass is a sandwich element where the mechanical behavior of the glass layers is usually considered linear-elastic material whereas the core is made of an amorphous thermoplastic which...... data. In simple structures, analytical mode shapes can be used alternatively to the numerical ones. In this paper, the dynamic stresses on the glass layers of a laminated glass beam have estimated using the experimental acceleration responses measured at 7 points of the beam, and the experimental mode...

Dynamics of final sectoral energy demand and aggregate energy intensity

International Nuclear Information System (INIS)

Lescaroux, Francois

2011-01-01

This paper proposes a regional and sectoral model of global final energy demand. For the main end-use sectors of consumption (industrial, commercial and public services, residential and road transportation), per-capita demand is expressed as an S-shaped function of per-capita income. Other variables intervene as well, like energy prices, temperatures and technological trends. This model is applied on a panel of 101 countries and 3 aggregates (covering the whole world) and it explains fairly well past variations in sectoral, final consumption since the beginning of the 2000s. Further, the model is used to analyze the dynamics of final energy demand, by sector and in total. The main conclusion concerns the pattern of change for aggregate energy intensity. The simulations performed show that there is no a priori reason for it to exhibit a bell-shape, as reported in the literature. Depending on initial conditions, the weight of basic needs in total consumption and the availability of modern commercial energy resources, various forms might emerge. - Research Highlights: → The residential sector accounts for most of final energy consumption at low income levels. → Its share drops at the benefit of the industrial, services and road transportation sectors in turn. → Sectoral shares' pattern is affected by changes in geographic, sociologic and economic factors. → Final energy intensity may show various shapes and does not exhibit necessarily a bell-shape.

Regular moderate or intense exercise prevents depression-like behavior without change of hippocampal tryptophan content in chronically tryptophan-deficient and stressed mice.

Directory of Open Access Journals (Sweden)

Hosung Lee

Full Text Available Regular exercise has an antidepressant effect in human subjects. Studies using animals have suggested that the antidepressant effect of exercise is attributable to an increase of brain 5-hydroxytryptamine (5-HT; however, the precise mechanism underlying the antidepressant action via exercise is unclear. In contrast, the effect of 5-HT on antidepressant activity has not been clarified, in part because the therapeutic response to antidepressant drugs has a time lag in spite of the rapid increase of brain 5-HT upon administration of these drugs. This study was designed to investigate the contribution of brain 5-HT to the antidepressant effect of exercise. Mice were fed a tryptophan-deficient diet and stressed using chronic unpredictable stress (CUS for 4 weeks with or without the performance of either moderate or intense exercise on a treadmill 3 days per week. The findings demonstrated that the onset of depression-like behavior is attributable not to chronic reduction of 5-HT but to chronic stress. Regular exercise, whether moderate or intense, prevents depression-like behavior with an improvement of adult hippocampal cell proliferation and survival and without the recovery of 5-HT. Concomitantly, the mice that exercised showed increased hippocampal noradrenaline. Regular exercise prevents the impairment of not long-term memory but short-term memory in a 5-HT-reduced state. Together, these findings suggest that: (1 chronic reduction of brain 5-HT may not contribute to the onset of depression-like behavior; (2 regular exercise, whether moderate or intense, prevents the onset of chronic stress-induced depression-like behavior independent of brain 5-HT and dependent on brain adrenaline; and (3 regular exercise prevents chronic tryptophan reduction-induced impairment of not long-term but short-term memory.

Sub-nanometer glass surface dynamics induced by illumination

International Nuclear Information System (INIS)

Nguyen, Duc; Nienhaus, Lea; Haasch, Richard T.; Lyding, Joseph; Gruebele, Martin

2015-01-01

Illumination is known to induce stress and morphology changes in opaque glasses. Amorphous silicon carbide (a-SiC) has a smaller bandgap than the crystal. Thus, we were able to excite with 532 nm light a 1 μm amorphous surface layer on a SiC crystal while recording time-lapse movies of glass surface dynamics by scanning tunneling microscopy (STM). Photoexcitation of the a-SiC surface layer through the transparent crystal avoids heating the STM tip. Up to 6 × 10 4 s, long movies of surface dynamics with 40 s time resolution and sub-nanometer spatial resolution were obtained. Clusters of ca. 3-5 glass forming units diameter are seen to cooperatively hop between two states at the surface. Photoexcitation with green laser light recruits immobile clusters to hop, rather than increasing the rate at which already mobile clusters hop. No significant laser heating was observed. Thus, we favor an athermal mechanism whereby electronic excitation of a-SiC directly controls glassy surface dynamics. This mechanism is supported by an exciton migration-relaxation-thermal diffusion model. Individual clusters take ∼1 h to populate states differently after the light intensity has changed. We believe the surrounding matrix rearranges slowly when it is stressed by a change in laser intensity, and clusters serve as a diagnostic. Such cluster hopping and matrix rearrangement could underlie the microscopic mechanism of photoinduced aging of opaque glasses

Finite-element analysis of dynamic fracture

Science.gov (United States)

Aberson, J. A.; Anderson, J. M.; King, W. W.

1976-01-01

Applications of the finite element method to the two dimensional elastodynamics of cracked structures are presented. Stress intensity factors are computed for two problems involving stationary cracks. The first serves as a vehicle for discussing lumped-mass and consistent-mass characterizations of inertia. In the second problem, the behavior of a photoelastic dynamic tear test specimen is determined for the time prior to crack propagation. Some results of a finite element simulation of rapid crack propagation in an infinite body are discussed.

Using the Dynamic Model of Affect (DMA) to examine leisure time as a stress coping resource: Taking into account stress severity and gender difference

Science.gov (United States)

Qian, Xinyi Lisa; Yarnal, Careen M.; Almeida, David M.

2014-01-01

Affective complexity (AC) is a marker of psychological well-being. According to the Dynamic Model of Affect (DMA), stressful experiences reduce AC while positive events increase AC. One type of positive events is leisure, which was also identified as a coping resource. This study extended the DMA and leisure coping research by assessing gender difference in how daily stress severity and leisure time influence AC. Analyzing eight-day diary data, we found that females, compared to males, experienced greater decrease in AC with increase in stress severity but also bigger increase in AC with increase in leisure time. The finding highlights gender difference in affective reactivity to and coping with daily stress, the value of the DMA, and the importance of severity appraisal. PMID:25242824

Manipulating the magnetic anisotropy and magnetization dynamics by stress: Numerical calculation and experiment

Science.gov (United States)

Correa, M. A.; Bohn, F.

2018-05-01

We perform a theoretical and experimental investigation of the magnetic properties and magnetization dynamics of a ferromagnetic magnetostrictive multilayer grown onto a flexible substrate and submitted to external stress. We calculate the magnetic behavior and magnetoimpedance effect for a trilayered system from an approach that considers a magnetic permeability model for planar geometry and a magnetic free energy density which takes into account induced uniaxial and magnetoelastic anisotropy contributions. We verify remarkable modifications of the magnetic anisotropy with external stress, as well as we show that the dynamic magnetic response is strongly affected by these changes. We discuss the magnetic features that lead to modifications of the frequency limits where distinct mechanisms are responsible by the magnetoimpedance variations, enabling us to manipulate the resonance fields. To test the robustness of the approach, we directly compare theoretical results with experimental data. Thus, we provide experimental evidence to confirm the validity of the theoretical approach, as well as to manipulate the resonance fields to tune the MI response according to real applications in devices.

Intensity of heat stress in winter wheat—phenology compensates for the adverse effect of global warming

Science.gov (United States)

Eyshi Rezaei, Ehsan; Siebert, Stefan; Ewert, Frank

2015-02-01

Higher temperatures during the growing season are likely to reduce crop yields with implications for crop production and food security. The negative impact of heat stress has also been predicted to increase even further for cereals such as wheat under climate change. Previous empirical modeling studies have focused on the magnitude and frequency of extreme events during the growth period but did not consider the effect of higher temperature on crop phenology. Based on an extensive set of climate and phenology observations for Germany and period 1951-2009, interpolated to 1 × 1 km resolution and provided as supplementary data to this article (available at stacks.iop.org/ERL/10/024012/mmedia), we demonstrate a strong relationship between the mean temperature in spring and the day of heading (DOH) of winter wheat. We show that the cooling effect due to the 14 days earlier DOH almost fully compensates for the adverse effect of global warming on frequency and magnitude of crop heat stress. Earlier heading caused by the warmer spring period can prevent exposure to extreme heat events around anthesis, which is the most sensitive growth stage to heat stress. Consequently, the intensity of heat stress around anthesis in winter crops cultivated in Germany may not increase under climate change even if the number and duration of extreme heat waves increase. However, this does not mean that global warning would not harm crop production because of other impacts, e.g. shortening of the grain filling period. Based on the trends for the last 34 years in Germany, heat stress (stress thermal time) around anthesis would be 59% higher in year 2009 if the effect of high temperatures on accelerating wheat phenology were ignored. We conclude that climate impact assessments need to consider both the effect of high temperature on grain set at anthesis but also on crop phenology.

Hot carrier injection degradation under dynamic stress

International Nuclear Information System (INIS)

Ma Xiao-Hua; Cao Yan-Rong; Hao Yue; Zhang Yue

2011-01-01

In this paper, we have studied hot carrier injection (HCI) under alternant stress. Under different stress modes, different degradations are obtained from the experiment results. The different alternate stresses can reduce or enhance the HC effect, which mainly depends on the latter condition of the stress cycle. In the stress mode A (DC stress with electron injection), the degradation keeps increasing. In the stress modes B (DC stress and then stress with the smallest gate injection) and C (DC stress and then stress with hole injection under V g = 0 V and V d = 1.8 V), recovery appears in the second stress period. And in the stress mode D (DC stress and then stress with hole injection under V g = −1.8 V and V d = 1.8 V), as the traps filled in by holes can be smaller or greater than the generated interface states, the continued degradation or recovery in different stress periods can be obtained. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Extension to linear dynamics for hybrid stress finite element formulation based on additional displacements

Science.gov (United States)

Sumihara, K.

Based upon legitimate variational principles, one microscopic-macroscopic finite element formulation for linear dynamics is presented by Hybrid Stress Finite Element Method. The microscopic application of Geometric Perturbation introduced by Pian and the introduction of infinitesimal limit core element (Baby Element) have been consistently combined according to the flexible and inherent interpretation of the legitimate variational principles initially originated by Pian and Tong. The conceptual development based upon Hybrid Finite Element Method is extended to linear dynamics with the introduction of physically meaningful higher modes.

Negative Affect Intensity and Hostility in Individuals with Alcohol Use Disorder with or without Post-Traumatic Stress Disorder.

Science.gov (United States)

Gandelman, Erin; Petrakis, Ismene; Kachadourian, Lorig; Ralevski, Elizabeth

2018-02-20

Negative affect intensity and hostility have both been implicated in alcohol use disorders (AUD) and post-traumatic stress disorder (PTSD) when they occur separately, but have neither been compared nor explored among those with dual diagnosis AUD and PTSD. This study is a secondary analysis designed to compare levels of negative affect intensity and hostility among those with AUD to those with dual diagnosis AUD and PTSD. Participants (n = 113) were recruited from the placebo-controlled groups of two distinct 12-week clinical trials (NCT00342563 and NCT00744055). The Short Affect Intensity Scale and Buss-Durkee Hostility Inventory were administered at weeks 0, 4, 8 and 12 to all study participants to assess negative affect intensity and hostility levels, respectively. Dual diagnosis AUD and PTSD individuals showed significantly higher levels of negative affect intensity and hostility than individuals with single diagnosis AUD. These levels remained relatively stable over the course of the study in spite of all study participants showing clinically significant improvements in AUD severity and PTSD symptomology (for those with dual diagnosis). Our results indicate that individuals with dual diagnosis AUD and PTSD have higher levels of negative affect and higher levels of hostility compared to individuals with single diagnosis AUD. In addition, these heightened levels of negative affect intensity and hostility appear to function somewhat independently of diagnosis severity and symptomology improvement. To our knowledge, this is the first study to compare negative affect intensity and hostility levels between single diagnosis AUD and dual diagnosis AUD and PTSD individuals.

Fatigue threshold studies in Fe, Fe-Si, and HSLA steel: Part II. thermally activated behavior of the effective stress intensity at threshold

Science.gov (United States)

Yu, W.; Esaklul, K.; Gerberich, W. W.

1984-05-01

It is shown that closure mechanisms alone cannot fully explain increasing fatigue thresholds with decreasing test temperature for a sequence of Fe-Si binary alloys and an HSLA steel. Implications are that fatigue crack propagation near threshold is a thermally activated process. The effective threshold stress intensity, which was obtained by subtracting the closure portion from the fatigue threshold, was examined. This effective stress intensity was found to correlate very well to the thermal component of the flow stress. A detailed fractographic study of the fatigue surface was performed. Water vapor in the room air was found to promote the formation of oxide and intergranular crack growth. At lower temperature, a brittle-type cyclic cleavage fatigue surface was observed but the ductile process persisted even at 123 K. Arrest marks were found on all three modes of fatigue crack growth. The regular spacings between these lines and dislocation modeling suggested that fatigue crack growth was controlled by the subcell structure near threshold. A model based on the slip-off of dislocations was examined. From this, it is shown that the effective fatigue threshold may be related to the square root of (one plus the strain rate sensitivity).

How does stress affect human being—a molecular dynamic simulation study on cortisol and its glucocorticoid receptor

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Dan Zhang

2017-03-01

Full Text Available Stress can be either positive or negative to human beings. Under stressful conditions, the mental and physical conditions of human can be affected. There exists certain relation between stress and illness. The cortisol and other glucocorticoids bind to the same receptor, which is called glucocorticoid receptor. Some evidences indicated that cortisol molecule binding to its glucocorticoid receptor was necessary for the stress response. Up to now, the structure–function relationships between cortisol molecule and its glucocorticoid receptor have not been deliberated from the atomic-level. In order to get a detailed understanding of the structure–function relationships between the cortisol molecule and glucocorticoids receptor, we have carried out molecular dynamic (MD simulations on glucocorticoid receptor (Apo system and cortisol with its glucocorticoid receptor complex (HCY system. On the basis of molecular dynamic simulations, a couple of key residues were identified, which were crucial for the binding of cortisol molecule. The results of binding free energy calculations are in good agreement with the experiment data. Our research gives clear insights from atomic-level into the structural–functional aspects of cortisol molecule and its glucocorticoid receptor, and also provides valuable information for the design of drug which can treat stress related illnesses.

Dynamic response of plant genome to ultraviolet radiation and other genotoxic stresses

International Nuclear Information System (INIS)

Molinier, Jean; Oakeley, Edward J.; Niederhauser, Olivier; Kovalchuk, Igor; Hohn, Barbara

2005-01-01

Oligonucleotide microarray technology was used to identify genes, which are responding after exposure to UV-C radiation and to other agents causing genotoxic stress. The effect of these conditions on recombinational DNA repair was monitored in parallel. Global changes in gene expression were investigated in Arabidopsis wild-type plants challenged with UV-C, bleomycin, another abiotic agent and xylanase, a biotic factor, all leading to elevated homologous recombination frequencies. The comparison of the expression profile of each treatment allowed defining genes specifically involved in the dynamic response to UV. In the future, the potential roles of such genes in the different forms of stress recognition, signal transduction, and their roles in DNA repair processes will be assessed by using reverse genetic tools available for Arabidopsis thaliana

Internal stress evolution in Fe laths deformed at low temperature analysed by dislocation dynamics simulations

International Nuclear Information System (INIS)

Chaussidon, Julien; Fivel, Marc; Robertson, Christian; Marini, Bernard

2010-01-01

Stress evolution in Fe laths undergoing plastic deformation is investigated using three-dimensional dislocation dynamics simulations adapted to body centred cubic crystals, in the ductile to brittle transition temperature range. The selected boundary conditions, applied stress tensor and initial dislocation structures account for the realistic microstructure observed in bainitic steels. The effective stress field projected in the three different {1 0 0}cleavage planes is calculated for two different temperatures (50 and 200 K) and presented quantitatively, in the form of stress/frequency diagrams. It is shown that plastic activity tends to relax the stress acting in certain cleavage planes (the (0 1 0) and (0 0 1) planes) while, at the same time, amplifying the stress acting in other cleavage planes (the (1 0 0) planes). The selective stress amplification in the latter planes depends on the applied load direction, in combination with the limited set of available slip systems and the lath geometry. In the examined configuration, this selection effect is more pronounced with decreasing temperature, emphasizing the role of thermally activated plasticity on deformation-induced stress concentrations

Quantitative phase microscopy for cellular dynamics based on transport of intensity equation.

Science.gov (United States)

Li, Ying; Di, Jianglei; Ma, Chaojie; Zhang, Jiwei; Zhong, Jinzhan; Wang, Kaiqiang; Xi, Teli; Zhao, Jianlin

2018-01-08

We demonstrate a simple method for quantitative phase imaging of tiny transparent objects such as living cells based on the transport of intensity equation. The experiments are performed using an inverted bright field microscope upgraded with a flipping imaging module, which enables to simultaneously create two laterally separated images with unequal defocus distances. This add-on module does not include any lenses or gratings and is cost-effective and easy-to-alignment. The validity of this method is confirmed by the measurement of microlens array and human osteoblastic cells in culture, indicating its potential in the applications of dynamically measuring living cells and other transparent specimens in a quantitative, non-invasive and label-free manner.

Determination of the Critical Stress Associated with Dynamic Phase Transformation in Steels by Means of Free Energy Method

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Clodualdo Aranas

2018-05-01

Full Text Available The double differentiation method overestimates the critical stress associated with the initiation of dynamic transformation (DT because significant amounts of the dynamic phase must be present in order for its effect on the work hardening rate to be detectable. In this work, an alternative method (referred to here as the free energy method is presented based on the thermodynamic condition that the driving force is equal to the total energy obstacle during the exact moment of transformation. The driving force is defined as the difference between the DT critical stress (measured in the single-phase austenite region and the yield stress of the fresh ferrite that takes its place. On the other hand, the energy obstacle consists of the free energy difference between austenite and ferrite, and the work of shear accommodation and dilatation associated with the phase transformation. Here, the DT critical stresses in a C-Mn steel were calculated using the free energy method at temperatures ranging from 870 °C to 1070 °C. The results show that the calculated critical stress using the present approach appears to be more accurate than the values measured by the double differentiation method.

A Dynamic Model of the Tragedy of the Commons in Marketing-Intensive Industries

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Dohoon Kim

2014-01-01

Full Text Available This study provides a dynamic model and analyzes its process that may plunge the business ecosystem into ToC (the Tragedy of the Commons. When developing the model, we have in mind some industries where the marketing competition to secure a large installed base is intense. The social commerce industry is a representative example of this type of industries, but the scope of this study is not limited to the industry. We first introduce a previous study focusing on the static Nash equilibrium, and then present an extended version of the basic model in a dynamic perspective. According to our analyses on the dynamic equilibria together with their stability, there may be a unique interior equilibrium, but it is highly likely unstable. In addition, possible (near boundary equilibria are also unstable for a wide range of parameter values. We also conduct some numerical experiments and discover cycles as solutions to some particular instances. Since those cycles contain the ToC traps, a policy measure or regulation may need to be employed. Our approach and results will help to figure out a clue to escape from the ToC trap, thereby shedding new light on the sustainable growth of the business ecosystem, which is prone to excessive marketing competition.

Stress map for ion irradiation: Depth-resolved dynamic competition between radiation-induced viscoelastic phenomena in SiO2

International Nuclear Information System (INIS)

Dillen, T. van; Siem, M.Y.S.; Polman, A.

2004-01-01

The dynamic competition between structural transformation, Newtonian viscous flow, and anisotropic strain generation during ion irradiation of SiO 2 , leads to strongly depth-dependent evolution of the mechanical stress, ranging between compressive and tensile. From independent in situ stress measurements during irradiation, generic expressions are derived of the nuclear stopping dependence of both the structural transformation rate and the radiation-induced viscosity. Using these data we introduce and demonstrate the concept of a 'stress map' that predicts the depth-resolved saturation stress in SiO 2 for any irradiation up to several MeV

The tensile effect on crack formation in single crystal silicon irradiated by intense pulsed ion beam

Science.gov (United States)

Liang, Guoying; Shen, Jie; Zhang, Jie; Zhong, Haowen; Cui, Xiaojun; Yan, Sha; Zhang, Xiaofu; Yu, Xiao; Le, Xiaoyun

2017-10-01

Improving antifatigue performance of silicon substrate is very important for the development of semiconductor industry. The cracking behavior of silicon under intense pulsed ion beam irradiation was studied by numerical simulation in order to understand the mechanism of induced surface peeling observed by experimental means. Using molecular dynamics simulation based on Stillinger Weber potential, tensile effect on crack growth and propagation in single crystal silicon was investigated. Simulation results reveal that stress-strain curves of single crystal silicon at a constant strain rate can be divided into three stages, which are not similar to metal stress-strain curves; different tensile load velocities induce difference of single silicon crack formation speed; the layered stress results in crack formation in single crystal silicon. It is concluded that the crack growth and propagation is more sensitive to strain rate, tensile load velocity, stress distribution in single crystal silicon.

Hemodynamic Changes After Static and Dynamic Exercises and Treadmill Stress Test; Different Patterns in Patients with Primary Benign Exertional Headache?

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Mohsen Rostami

2012-06-01

Full Text Available The pathophysiology of primary benign exertional headache (EH is not still clearly defined. Some researchers have suggested an impaired vascular response as the etiology of this disorder. In this study we investigated whether there are any differences in blood pressure (BP and heart rate (HR of the subjects in course of the static and dynamic exercises and the treadmill stress test between those with and without EH. From university students, 22 patients with EH (mean age: 19.8 ± 2.10, Female to Male: 7:15 and 20 normal subjects (mean age: 19.3 ± 1.97, Female: Male: 8:12 were recruited. All the subjects performed the static and dynamic exercises at 30 and 20 percent of the maximal voluntary contraction (MVC and Bruce treadmill stress test according to the standard protocols. HR and BP of all the cases at the baseline and during and immediately after each test were measured. No significant difference was found between the mean rise of HR, systolic and diastolic BP of the subjects with and without EH in static and dynamic exercises and also treadmill stress test. It seems that between those with and without EH, there is no significant difference in rise of HR and BP response to static and dynamic exercises and treadmill stress test. Further studies are required to find the pathophysiology and risk factors of EH.

Hemodynamic changes after static and dynamic exercises and treadmill stress test; different patterns in patients with primary benign exertional headache?

Science.gov (United States)

Kordi, Ramin; Mazaheri, Reza; Rostami, Mohsen; Mansournia, Mohammad Ali

2012-01-01

The pathophysiology of primary benign exertional headache (EH) is not still clearly defined. Some researchers have suggested an impaired vascular response as the etiology of this disorder. In this study we investigated whether there are any differences in blood pressure (BP) and heart rate (HR) of the subjects in course of the static and dynamic exercises and the treadmill stress test between those with and without EH. From university students, 22 patients with EH (mean age: 19.8 ± 2.10, Female to Male: 7:15) and 20 normal subjects (mean age: 19.3 ± 1.97, Female: Male: 8:12) were recruited. All the subjects performed the static and dynamic exercises at 30 and 20 percent of the maximal voluntary contraction (MVC) and Bruce treadmill stress test according to the standard protocols. HR and BP of all the cases at the baseline and during and immediately after each test were measured. No significant difference was found between the mean rise of HR, systolic and diastolic BP of the subjects with and without EH in static and dynamic exercises and also treadmill stress test. It seems that between those with and without EH, there is no significant difference in rise of HR and BP response to static and dynamic exercises and treadmill stress test. Further studies are required to find the pathophysiology and risk factors of EH.

Effects of heat stress on dynamic absorption process, tissue distribution and utilization efficiency of vitamin C in broilers

International Nuclear Information System (INIS)

Liu Guohua; Chen Guosheng; Cai Huiyi

1998-01-01

The experiment was conducted to determine the effects of heat stress on ascorbic acid nutritional physiology of broilers with radioisotope technology. 3 H-Vc was fed to broilers and then the blood, liver, kidney, breast muscle, and excreta were sampled to determine the dynamic absorption process, the tissue distribution and the utilization efficiency of vitamin C. The results indicated that the absorption, metabolism and mobilization of supplemented vitamin C in broilers with heat stress was faster than that in broilers without heat stress. However, the utilization efficiency of supplemented vitamin C in broilers with heat stress was not higher than that of broilers without heat stress

Low Intensity Physical Exercise Attenuates Cardiac Remodeling and Myocardial Oxidative Stress and Dysfunction in Diabetic Rats

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C. Gimenes

2015-01-01

Full Text Available We evaluated the effects of a low intensity aerobic exercise protocol on cardiac remodeling and myocardial function in diabetic rats. Wistar rats were assigned into four groups: sedentary control (C-Sed, exercised control (C-Ex, sedentary diabetes (DM-Sed, and exercised diabetes (DM-Ex. Diabetes was induced by intraperitoneal injection of streptozotocin. Rats exercised for 9 weeks in treadmill at 11 m/min, 18 min/day. Myocardial function was evaluated in left ventricular (LV papillary muscles and oxidative stress in LV tissue. Statistical analysis was given by ANOVA or Kruskal-Wallis. Echocardiogram showed diabetic groups with higher LV diastolic diameter-to-body weight ratio and lower posterior wall shortening velocity than controls. Left atrium diameter was lower in DM-Ex than DM-Sed (C-Sed: 5.73±0.49; C-Ex: 5.67±0.53; DM-Sed: 6.41±0.54; DM-Ex: 5.81±0.50 mm; P<0.05 DM-Sed vs C-Sed and DM-Ex. Papillary muscle function was depressed in DM-Sed compared to C-Sed. Exercise attenuated this change in DM-Ex. Lipid hydroperoxide concentration was higher in DM-Sed than C-Sed and DM-Ex. Catalase and superoxide dismutase activities were lower in diabetics than controls and higher in DM-Ex than DM-Sed. Glutathione peroxidase activity was lower in DM-Sed than C-Sed and DM-Ex. Conclusion. Low intensity exercise attenuates left atrium dilation and myocardial oxidative stress and dysfunction in type 1 diabetic rats.

Intensive meditation for refractory pain and symptoms.

Science.gov (United States)

Goyal, Madhav; Haythornthwaite, Jennifer; Levine, David; Becker, Diane; Vaidya, Dhananjay; Hill-Briggs, Felicia; Ford, Daniel

2010-06-01

The objective of this study was to assess patient interest in intensive meditation training for chronic symptoms. This was a cross-sectional anonymous survey among six chronic disease clinics in Baltimore including Chronic Kidney Disease, Crohn's Disease, Headache, Renal Transplant Recipients, General Rheumatology, and lupus clinic. Subjects were 1119 consecutive patients registering for their appointments at these clinics. Outcome measures were 6-month pain, global symptomatology, four-item perceived stress scale, use of complementary and alternative medicine (CAM) therapies, and attitudes toward use of meditation for managing symptoms. We then gave a scripted description of an intensive, 10-day meditation training retreat. Patient interest in attending such a retreat was assessed. Seventy-seven percent (77%) of patients approached completed the survey. Fifty-three percent (53%) of patients reported moderate to severe pain over the past 6 months. Eighty percent (80%) reported use of some CAM therapy in the past. Thirty-five percent (35%) thought that learning meditation would improve their health, and 49% thought it would reduce stress. Overall, 39% reported interest in attending the intensive 10-day meditation retreat. Among those reporting moderate to severe pain or stress, the percentages were higher (48% and 59%). In a univariate analysis, higher education, nonworking/disabled status, female gender, higher stress, higher pain, higher symptomatology, and any CAM use were all associated with a greater odds of being moderately to very interested in an intensive 10-day meditation retreat. A multivariate model that included prior use of CAM therapies as predictors of interest in the program fit the data significantly better than a model not including CAM therapies (p = 0.0013). Over 50% of patients followed in chronic disease clinics complain of moderate to severe pain. Patients with persistent pain or stress are more likely to be interested in intensive meditation.

Dynamic Fungal Cell Wall Architecture in Stress Adaptation and Immune Evasion.

Science.gov (United States)

Hopke, Alex; Brown, Alistair J P; Hall, Rebecca A; Wheeler, Robert T

2018-04-01

Deadly infections from opportunistic fungi have risen in frequency, largely because of the at-risk immunocompromised population created by advances in modern medicine and the HIV/AIDS pandemic. This review focuses on dynamics of the fungal polysaccharide cell wall, which plays an outsized role in fungal pathogenesis and therapy because it acts as both an environmental barrier and as the major interface with the host immune system. Human fungal pathogens use architectural strategies to mask epitopes from the host and prevent immune surveillance, and recent work elucidates how biotic and abiotic stresses present during infection can either block or enhance masking. The signaling components implicated in regulating fungal immune recognition can teach us how cell wall dynamics are controlled, and represent potential targets for interventions designed to boost or dampen immunity. Copyright © 2018 Elsevier Ltd. All rights reserved.

On the relation between quasi-static and dynamic stress induced reversible structural relaxation of amorphous alloys

International Nuclear Information System (INIS)

Krueger, P.; Stucky, T.; Boewe, M.; Neuhaeuser, H.

1993-01-01

Quasi-static stress relaxation and dynamic internal friction measurements of stress induced reversible structural relaxation were performed on the amorphous alloy Fe 40 Ni 40 B 20 . The kinetics can be well described by a stretched exponential Kohlrausch-Williams-Watts quasi-static relaxation. The thermally activated part of the internal friction shows an Arrhenius temperature behaviour for a fixed vibration frequency and an inverse power frequency behaviour for a fixed temperature. The activation energies calculated from the Arrhenius equation and from the frequency shift method are significantly different. In order to explain this discrepancy the relation between the quasi-static and the dynamic descriptions of the reversible relaxation is reexamined. In particular it is shown that these two activation energies are connected by the Kohlrausch exponent of the quasi-static relaxation. (orig.)

Non-Destructive Evaluation Method Based On Dynamic Invariant Stress Resultants

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Zhang Junchi

2015-01-01

Full Text Available Most of the vibration based damage detection methods are based on changes in frequencies, mode shapes, mode shape curvature, and flexibilities. These methods are limited and typically can only detect the presence and location of damage. Current methods seldom can identify the exact severity of damage to structures. This paper will present research in the development of a new non-destructive evaluation method to identify the existence, location, and severity of damage for structural systems. The method utilizes the concept of invariant stress resultants (ISR. The basic concept of ISR is that at any given cross section the resultant internal force distribution in a structural member is not affected by the inflicted damage. The method utilizes dynamic analysis of the structure to simulate direct measurements of acceleration, velocity and displacement simultaneously. The proposed dynamic ISR method is developed and utilized to detect the damage of corresponding changes in mass, damping and stiffness. The objectives of this research are to develop the basic theory of the dynamic ISR method, apply it to the specific types of structures, and verify the accuracy of the developed theory. Numerical results that demonstrate the application of the method will reflect the advanced sensitivity and accuracy in characterizing multiple damage locations.

Probing ultrafast dynamics of solid-density plasma generated by high-contrast intense laser pulses

Science.gov (United States)

Jana, Kamalesh; Blackman, David R.; Shaikh, Moniruzzaman; Lad, Amit D.; Sarkar, Deep; Dey, Indranuj; Robinson, Alex P. L.; Pasley, John; Ravindra Kumar, G.

2018-01-01

We present ultrafast dynamics of solid-density plasma created by high-contrast (picosecond contrast ˜10-9), high-intensity (˜4 × 1018 W/cm2) laser pulses using time-resolved pump-probe Doppler spectrometry. Experiments show a rapid rise in blue-shift at early time delay (2-4.3 ps) followed by a rapid fall (4.3-8.3 ps) and then a slow rise in blue-shift at later time delays (>8.3 ps). Simulations show that the early-time observations, specifically the absence of any red-shifting of the reflected probe, can only be reproduced if the front surface is unperturbed by the laser pre-pulse at the moment that the high intensity pulse arrives. A flexible diagnostic which is capable of diagnosing the presence of low-levels of pre-plasma formation would be useful for potential applications in laser-produced proton and ion production, such as cancer therapy and security imaging.

Counterbalancing work-related stress? Work engagement among intensive care professionals.

Science.gov (United States)

van Mol, Margo M C; Nijkamp, Marjan D; Bakker, Jan; Schaufeli, Wilmar B; Kompanje, Erwin J O

2018-07-01

Working in an Intensive Care Unit (ICU) is increasingly complex and is also physically, cognitively and emotionally demanding. Although the negative emotions of work-related stress have been well studied, the opposite perspective of work engagement might also provide valuable insight into how these emotional demands may be countered. This study focused on the work engagement of ICU professionals and explored the complex relationship between work engagement, job demands and advantageous personal resources. This was a cross-sectional survey study among ICU professionals in a single-centre university hospital. Work engagement was measured by the Utrecht Work Engagement Scale, which included items about opinions related to the respondent's work environment. Additionally, 14 items based on the Jefferson Scale of Physician Empathy were included to measure empathic ability. A digital link to the questionnaire was sent in October 2015 to a population of 262 ICU nurses and 53 intensivists. The overall response rate was 61% (n=193). Work engagement was negatively related both to cognitive demands among intensivists and to emotional demands among ICU nurses. No significant relationship was found between work engagement and empathic ability; however, agreeableness, conscientiousness, and emotional stability were highly correlated with work engagement. Only the number of hours worked per week remained as a confounding factor, with a negative effect of workload on work engagement after controlling for the effect of weekly working hours. Work engagement counterbalances work-related stress reactions. The relatively high workload in ICUs, coupled with an especially heavy emotional burden, may be acknowledged as an integral part of ICU work. This workload does not affect the level of work engagement, which was high for both intensivists and nurses despite the known high job demands. Specific factors that contribute to a healthy and successful work life among ICU professionals need

Adaptação cultural e validação para a língua portuguesa da Parental Stress Scale: Neonatal Intensive Care Unit (PSS:NICU Adaptación cultural y validación al idioma português del Parental Stress Scale: Neonatal Intensive Care Unit (PSS:NICU Cultural adaptation and validation for the portuguese language of the Parental Stress Scale: Neonatal Intensive Care Unit (PSS:NICU

Directory of Open Access Journals (Sweden)

Sandra Regina de Souza

2012-01-01

Full Text Available OBJETIVO: Traduzir, realizar a adaptação cultural e validar a escala Parental Stress Scale:Neonatal Intensive Care Unit (PSS:NICU para a língua portuguesa. MÉTODOS: Utilizou-se o método descritivo de validação de instrumentos de medida, baseado nas etapas propostas por Guillemin et al. A análise da confiabilidade foi realizada por meio dos testes e retestes e da consistência interna. Na validação clínica, participaram 163 pais de recém-nascidos internados em Unidade de Terapia Intensiva Neonatal (UTIN. RESULTADOS: Os coeficientes de correlação intraclasse ficaram em torno de 0,70 mostrando boa estabilidade entre as duas avaliações. A análise fatorial pelo método de componentes principais utilizou os mesmos critérios da escala original, com rotação Varimax, com grau de variância adequado de 57,9%. Os maiores níveis de estresse dos pais foram obtidos na subescala "alteração do papel de pais". CONCLUSÃO: A PSS:NICU na versão em português é uma ferramenta válida e confiável para avaliação do estresse de pais com filho internado na UTIN.OBJETIVO: Traducir, realizar la adaptación cultural y validar la escala Parental Stress Scale:Neonatal Intensive Care Unit (PSS:NICU al idioma portugués. MÉTODOS: Se utilizó el método descriptivo de validación de instrumentos de medida, basado en las etapas propuestas por Guillemin et al. El análisis de la confiabilidad fue realizado por medio de los tests y retests y de la consistencia interna. En la validación clínica, participaron 163 padres de recién nacidos internados en una Unidad de Cuidados Intensivos Neonatal (UCIN. RESULTADOS: Los coeficientes de correlación intraclase quedaron alrededor de 0,70 mostrando buena estabilidad entre las dos evaluaciones El análisis factorial por el método de componentes principales utilizó los mismos criterios de la escala original, con rotación Varimax, con grado de varianza adecuado de 57,9%. Los mayores niveles de estrés de

Development of stress ulcers assessed by gastric electrical potential difference, pH of gastric juice, and endoscopy in patients in the intensive care unit

DEFF Research Database (Denmark)

Rubinstein, E; Gjørup, I; Schulze, S

1992-01-01

OBJECTIVE: To assess measurement of gastric electrical potential difference, pH of gastric mucosa, and endoscopic findings in patients in intensive care units who are at risk of developing stress ulcers. DESIGN: Open comparison with age- and sex-matched control subjects. SETTING: Herlev Hospital......, Denmark. SUBJECTS: Sixteen consecutive patients with no history of gastrointestinal haemorrhage, coagulopathy, or ulcer disease who had been admitted to the intensive care unit, and 16 age- and sex-matched outpatients with normal endoscopic findings. INTERVENTIONS: Upper gastrointestinal endoscopy, during...... which any lesions that were found were scored according to severity, the gastric potential difference, and the pH of gastric juice were measured. OUTCOME MEASURES: Correlation between the incidence of stress ulceration found at endoscopy, gastric potential difference, and gastric pH. RESULTS: Gastric...

Project of integrity assessment of flawed components with structural discontinuity (IAF). Data book for estimation stress intensity factor. Surface crack on ICM housing for penetration in reactor vessel

International Nuclear Information System (INIS)

2012-12-01

The project of Integrity Assessment of Flawed Components with Structural Discontinuity (IAF) was entrusted to Japan Power Engineering and Inspection Corporation (JAPEIC) from Nuclear and Industrial Safety Agency (NISA) and started from FY 2001. And then, it was taken over to Japan Nuclear Energy Safety Organization (JNES) which was established in October 2003 and carried out until FY 2007. In the IAF project, weld joints between nickel based alloys and low alloy steels around penetrations in reactor vessel, safe-end of nozzles and shroud supports were selected from among components and pipe arrangements in nuclear power plants, where high residual stresses were generated due to welding and complex structure. Residual stresses around of the weld joints were estimated by finite element analysis method (FEM) with a general modeling method, then the reasonability and the conservativeness was evaluated. In addition, for postulated surface crack of stress corrosion cracking (SCC), a simple calculation method of stress intensity factor (K) required to estimate the crack growth was proposed and the effectiveness was confirmed. JNES compiled results of the IAF project into Data Books of Residual Stress Analysis of Weld Joint, and Data Book of Simplified Stress Intensity Factor Calculation for Penetration of Reactor as typical Structure Discontinuity, respectively. Data Books of Residual Stress Analysis in Weld Joint. 1. Butt Weld Joint of Small Diameter Cylinder (4B Sch40) (JNES-RE-2012-0005), 2. Dissimilar Metal Weld Joint in Safe End (One-Side Groove Joint (JNES-RE-2012-0006), 3. Dissimilar Metal Weld Joint in Safe End (Large Diameter Both-Side Groove Joint) (JNES-RE-2012-0007), 4. Weld Joint around Penetrations in Reactor Vessel (Insert Joint) (JNES-RE-2012-0008), 5. Weld Joint in Shroud Support (H8, H9, H10 and H11 Welds) (JNES-RE-2012-0009), 6. Analysis Model of Dissimilar Metal Weld Joint Applied Post Weld Heat Treatment (PWHT) (JNES-RE-2012-0010). Data Book of

Is Less Noise, Light and Parental/Caregiver Stress in the Neonatal Intensive Care Unit Better for Neonates?

Science.gov (United States)

Venkataraman, Rohini; Kamaluddeen, Majeeda; Amin, Harish; Lodha, Abhay

2018-01-15

In utero sensory stimuli and interaction with the environment strongly influence early phases of fetal and infant development. Extremely premature infants are subjected to noxious procedures and routine monitoring, in addition to exposure to excessive light and noise, which disturb the natural sleep cycle and induce stress. Non-invasive ventilation, measures to prevent sepsis, and human milk feeding improve short-term and long-term neurodevelopmental outcomes in premature infants. To preserve brain function, and to improve quality of life and long-term neurodevelopmental outcomes, the focus now is on the neonatal intensive care unit (NICU) environment and its impact on the infant during hospital stay. The objectives of this write-up are to understand the effects of environmental factors, including lighting and noise in the NICU, on sensory development of the infant, the need to decrease parental and caregiver stress, and to review existing literature, local policies and recommendations.

Effect of exercise training intensity on mitochondrial dynamics and mitophagy in post myocardial infarction rats

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Babak Ebadi

2018-06-01

Full Text Available Myocardial infarction (MI is the most common type of heart disease. According to recent studies, mitochondrial dysfunction has been suggested as a central player in cardiac disease and evidences point out the association of mitochondrial morphology with development of heart diseases. Exercise training plays a protective role against cardiovascular disease. However, the role of exercise training on proteins involved in mitochondrial dynamics and mitophagy system are not well understood. Therefore, the aim of the present study was to investigate these on cardiac mitochondrial dynamic and mitophagy proteins in rats with myocardial infarction. The present study was post-test design experiment with the control group. after MI with ligation of the left anterior descending coronary artery (LAD and ensuring the creation of MI by echocardiography, male rats were subjected to high intensity interval training (HIIT, moderate (MIIT, low (LIIT, sedentary myocardial infarction (SED-MI and healthy control groups. After six weeks exercise, the levels of MFN2, DRP1, Parkin, P62 and PGC-1α proteins were measured by ELISA method. Data analysis showed that proteins levels of MFN2, PGC-1α, Parkin and P62 decreased significantly in SED-MI group compared to healthy control while DRP1 protein levels increased significantly (P≤0.05. Also, MFN2 and PGC-1α proteins increased in MIIT group compared with SED-MI group and DRP1 protein levels were significantly decreased (P≤0.05. Moderate-intensity interval training (MIIT resulted to improve mitochondrial fusion and fusion proteins in rats with myocardial infarction. While high and low intensity interval training (HIIT, LIIT, despite increasing MFN2 and PGC-1α and reducing DRP1, failed to improve fusion and mitochondrial fission

Organizational Stressors and Related Stress Intensities in Tehran\\'s Comprehensive Rehabilitation Centers: From the Employees\\' Point of View

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Nayyereh Tavafi

2007-01-01

Full Text Available Objective: Rehabilitation services employees are exposed to stressors at everyday work because they are in touch with people who disability and problems have associated with. Inappropriate policies and processes in work place aggravate stress and would adversely affect mental and physical health of this population which in turn would affect their quality of work. Materials & Methods: In order to determine the status of inappropriate organizational policies and processes as organizational stressors and related stress intensities in Tehran’s comprehensive rehabilitation centers, in a descriptive study all of the personnel were asked to fill a questionnaire which consisted of 32 questions. Content validity was approved by expertise people and reliability was 0.83. Results: Revealed that misevaluation of employees (%98 and using unclear and inappropriate criteria for evaluating personal (%95 were the most prevalent inappropriate organizational policy and process that personnel confronted with. Also we found that exposure to "inequality of payment for similar jobs" and "invalidity of criteria which were used for personnel evaluation", induced highest degree of stress on employees (2.64 from 4 & 1.71from 4 respectively. Conclusion: We conclude that as the most prevalent factor which induced stress in personnel is misevaluation, correction of personnel evaluation system should be over emphasized.

Exercise-induced shear stress is associated with changes in plasma von Willebrand factor in older humans

OpenAIRE

Gonzales, Joaquin U.; Thistlethwaite, John R.; Thompson, Benjamin C.; Scheuermann, Barry W.

2009-01-01

Shear stress is the frictional force of blood against the endothelium, a stimulus for endothelial activation and the release of von Willebrand factor (vWF). This study tested the hypothesis that the increase in shear stress associated with exercise correlates with plasma vWF. Young (n = 14, 25.7 ± 5.4 y) and older (n = 13, 65.6 ± 10.7 y) individuals participated in 30 min of dynamic handgrip exercise at a moderate intensity. Brachial artery diameter and blood flow were measured using ultrasou...

Adenosine-stress dynamic real-time myocardial perfusion CT and adenosine-stress first-pass dual-energy myocardial perfusion CT for the assessment of acute chest pain: Initial results

Energy Technology Data Exchange (ETDEWEB)

Weininger, Markus [Medical University of South Carolina, Department of Radiology and Radiological Science, Charleston, SC (United States); Schoepf, U. Joseph, E-mail: schoepf@musc.edu [Medical University of South Carolina, Department of Radiology and Radiological Science, Charleston, SC (United States); Department of Medicine, Division of Cardiology, Medical University of South Carolina, Charleston, SC (United States); Ramachandra, Ashok [Medical University of South Carolina, Department of Radiology and Radiological Science, Charleston, SC (United States); Fink, Christian [Institute of Clinical Radiology and Nuclear Medicine, University Medical Center Mannheim, Medical Faculty Mannheim, Heidelberg University (Germany); Rowe, Garrett W.; Costello, Philip [Medical University of South Carolina, Department of Radiology and Radiological Science, Charleston, SC (United States); Henzler, Thomas [Medical University of South Carolina, Department of Radiology and Radiological Science, Charleston, SC (United States); Institute of Clinical Radiology and Nuclear Medicine, University Medical Center Mannheim, Medical Faculty Mannheim, Heidelberg University (Germany)

2012-12-15

Purpose: Recent innovations in CT enable the evolution from mere morphologic imaging to dynamic and functional testing. We describe our initial experience performing myocardial stress perfusion CT in a clinical population with acute chest pain. Methods and materials: Myocardial stress perfusion CT was performed on twenty consecutive patients (15 men, 5 women; mean age 65 ± 8 years) who presented with acute chest pain and were clinically referred for stress/rest SPECT and cardiac MRI. Prior to CT each patient was randomly assigned either to Group A or to Group B in a consecutive order (10 patients per group). Group A underwent adenosine-stress dynamic real-time myocardial perfusion CT using a novel “shuttle” mode on a 2nd generation dual-source CT. Group B underwent adenosine-stress first-pass dual-energy myocardial perfusion CT using the same CT scanner in dual-energy mode. Two experienced observers visually analyzed all CT perfusion studies. CT findings were compared with MRI and SPECT. Results: In Group A 149/170 myocardial segments (88%) could be evaluated. Real-time perfusion CT (versus SPECT) had 86% (84%) sensitivity, 98% (92%) specificity, 94% (88%) positive predictive value, and 96% (92%) negative predictive value in comparison with perfusion MRI for the detection of myocardial perfusion defects. In Group B all myocardial segments were available for analysis. Compared with MRI, dual-energy myocardial perfusion CT (versus SPECT) had 93% (94%) sensitivity, 99% (98%) specificity, 92% (88%) positive predictive value, and 96% (94%) negative predictive value for detecting hypoperfused myocardial segments. Conclusion: Our results suggest the clinical feasibility of myocardial perfusion CT imaging in patients with acute chest pain. Compared to MRI and SPECT both, dynamic real-time perfusion CT and first-pass dual-energy perfusion CT showed good agreement for the detection of myocardial perfusion defects.

Adenosine-stress dynamic real-time myocardial perfusion CT and adenosine-stress first-pass dual-energy myocardial perfusion CT for the assessment of acute chest pain: Initial results

International Nuclear Information System (INIS)

Weininger, Markus; Schoepf, U. Joseph; Ramachandra, Ashok; Fink, Christian; Rowe, Garrett W.; Costello, Philip; Henzler, Thomas

2012-01-01

Purpose: Recent innovations in CT enable the evolution from mere morphologic imaging to dynamic and functional testing. We describe our initial experience performing myocardial stress perfusion CT in a clinical population with acute chest pain. Methods and materials: Myocardial stress perfusion CT was performed on twenty consecutive patients (15 men, 5 women; mean age 65 ± 8 years) who presented with acute chest pain and were clinically referred for stress/rest SPECT and cardiac MRI. Prior to CT each patient was randomly assigned either to Group A or to Group B in a consecutive order (10 patients per group). Group A underwent adenosine-stress dynamic real-time myocardial perfusion CT using a novel “shuttle” mode on a 2nd generation dual-source CT. Group B underwent adenosine-stress first-pass dual-energy myocardial perfusion CT using the same CT scanner in dual-energy mode. Two experienced observers visually analyzed all CT perfusion studies. CT findings were compared with MRI and SPECT. Results: In Group A 149/170 myocardial segments (88%) could be evaluated. Real-time perfusion CT (versus SPECT) had 86% (84%) sensitivity, 98% (92%) specificity, 94% (88%) positive predictive value, and 96% (92%) negative predictive value in comparison with perfusion MRI for the detection of myocardial perfusion defects. In Group B all myocardial segments were available for analysis. Compared with MRI, dual-energy myocardial perfusion CT (versus SPECT) had 93% (94%) sensitivity, 99% (98%) specificity, 92% (88%) positive predictive value, and 96% (94%) negative predictive value for detecting hypoperfused myocardial segments. Conclusion: Our results suggest the clinical feasibility of myocardial perfusion CT imaging in patients with acute chest pain. Compared to MRI and SPECT both, dynamic real-time perfusion CT and first-pass dual-energy perfusion CT showed good agreement for the detection of myocardial perfusion defects.

Quantitative analysis of localized stresses in irradiated stainless steels using high resolution electron backscatter diffraction and molecular dynamics modeling

International Nuclear Information System (INIS)

Johnson, D.C.; Kuhr, B.; Farkas, D.; Was, G.S.

2016-01-01

Quantitative measurements of stress near dislocation channel–grain boundary (DC–GB) interaction sites were made using high resolution electron backscatter diffraction (HREBSD) and have been compared with molecular dynamics (MD) simulations. Tensile stress normal to the grain boundary was significantly elevated at discontinuous DC–GB intersections with peak magnitudes roughly an order of magnitude greater than at sites where slip transfer occurred. These results constitute the first measurement of stress amplification at DC–GB intersections and provide support to the theory that high normal stress at the grain boundary may be a key driver for the initiation of irradiation assisted stress corrosion cracks.

SAP-4, Static and Dynamic Linear System Stress Analysis for Various Structures

International Nuclear Information System (INIS)

Zawadzki, S.

1984-01-01

1 - Description of problem or function: SAP4 is a structural analysis program for determining the static and dynamic response of linear systems. The structural systems to be analyzed may be composed of combinations of a number of different structural elements. Currently the program contains the following element types - (a) three-dimensional truss element, (b) three-dimensional beam element, (c) plane stress and plane strain element, (d) two-dimensional axisymmetric solid, (e) three-dimensional solid, (f) variable-number nodes thick shell and three-dimensional element, (g) thin-plate or thin-shell element, (h) boundary element, and (i) pipe element (tangent and bend). 2 - Method of solution: The formation of the structure matrices is carried out in the same way in a static or dynamic analysis. The static analysis is continued by solving the equations of equilibrium followed by the computation of element stresses. In a dynamic analysis the choice is between frequency calculations only, frequency calculations followed by response history analysis, frequency calculations followed by response spectrum analysis, or response history analysis by direct integration. To obtain the frequencies and vibration mode shapes, solution routines are used which calculate the required eigenvalues and eigenvectors directly without a transformation of the structure stiffness matrix and mass matrix to a reduced form. To perform the direct integration an unconditionally stable scheme is used, which also operates on the original structure stiffness matrix and mass matrix. In this manner the program operation and input data required for a dynamic analysis are simple extensions of those needed for a static analysis. 3 - Restrictions on the complexity of the problem: The capacity of the program depends mainly on the total number of nodal points in the system, the number of eigenvalues needed in the dynamic analysis, and the computer used. There is practically no restriction on the number of

Hepatoprotective Effect of Quercetin on Endoplasmic Reticulum Stress and Inflammation after Intense Exercise in Mice through Phosphoinositide 3-Kinase and Nuclear Factor-Kappa B

Directory of Open Access Journals (Sweden)

Yuhan Tang

2016-01-01

Full Text Available The mechanisms underlying intense exercise-induced liver damage and its potential treatments remain unclear. We explored the hepatoprotection and mechanisms of quercetin, a naturally occurring flavonoid, in strenuous exercise-derived endoplasmic reticulum stress (ERS and inflammation. Intense exercise (28 m/min at a 5° slope for 90 min resulted in the leakage of aminotransferases in the BALB/C mice. The hepatic ultrastructural malformations and oxidative stress levels were attenuated by quercetin (100 mg/kg·bw. Intense exercise and thapsigargin- (Tg- induced ERS (glucose-regulated protein 78, GRP78 and inflammatory cytokines levels (IL-6 and TNF-α were decreased with quercetin. Furthermore, quercetin resulted in phosphoinositide 3-kinase (PI3K induction, Ca2+ restoration, and blockade of the activities of Jun N-terminal kinase (JNK, activating transcription factor 6 (ATF6 and especially NF-κB (p65 and p50 nuclear translocation. A PI3K inhibitor abrogated the protection of quercetin on ERS and inflammation of mouse hepatocytes. SP600125 (JNK inhibitor, AEBSF (ATF6 inhibitor, and especially PDTC (NF-κB inhibitor enhanced the quercetin-induced protection against Tg stimulation. Collectively, intense exercise-induced ERS and inflammation were attenuated by quercetin. PI3K/Akt activation and JNK, ATF6, and especially NF-κB suppression were involved in the protection. Our results highlight a novel preventive strategy for treating ERS and inflammation-mediated liver damage induced by intense exercise using natural phytochemicals.

Three dimensional viscoelastic simulation on dynamic evolution of stress field in North China induced by the 1966 Xingtai earthquake

Science.gov (United States)

Chen, Lian-Wang; Lu, Yuan-Zhong; Liu, Jie; Guo, Ruo-Mei

2001-09-01

Using three dimensional (3D) viscoelastic finite element method (FEM) we study the dynamic evolution pattern of the coseismic change of Coulomb failure stress and postseismic change, on time scale of hundreds years, of rheological effect induced by the M S=7.2 Xingtai earthquake on March 22, 1966. Then, we simulate the coseismic disturbance in stress field in North China and dynamic change rate on one-year scale caused by the Xingtai earthquake and Tangshan earthquake during 15 years from 1966 to 1980. Finally, we discuss the triggering of a strong earthquake to another future strong earthquake.

Heavy metal dynamics in the soil-leaf-fruit system under intensive apple cultivation

Directory of Open Access Journals (Sweden)

Murtić Senad

2014-01-01

Full Text Available One of the major problems confronting agricultural production is heavy metal contamination of agricultural soils, which imposes considerable limitations on productivity and leads to great consumer health and safety concerns about the products obtained on these soils. The objective of this study was to evaluate heavy metal dynamics in the soil-leaf-fruit system in an intensive apple cv. 'Idared' planting located in the Municipality of Goražde. Heavy metal contents in the soil samples and plant material were determined by atomic absorption spectrophotometry using a Shimadzu 7000 AA device, according to the instructions specified in the ISO 11047 method. The dynamics of the heavy metals analyzed, excepting zinc, in the soil-leaf-fruit system was characterized by relatively high total levels of heavy metals in the soil and a very low degree of their accumulation in the leaves and in particular the fruits. No fruit sample was found to have toxic levels of any of the heavy metals analyzed. In terms of soil contamination, this suggests the suitability of the study location for safe apple fruit production.

Effects of high-intensity interval versus continuous moderate-intensity aerobic exercise on apoptosis, oxidative stress and metabolism of the infarcted myocardium in a rat model.

Science.gov (United States)

Lu, Kai; Wang, Li; Wang, Changying; Yang, Yuan; Hu, Dayi; Ding, Rongjing

2015-08-01

The optimal aerobic exercise training (AET) protocol for patients following myocardial infarction (MI) has remained under debate. The present study therefore aimed to compare the effects of continuous moderate-intensity training (CMT) and high-intensity interval training (HIT) on cardiac functional recovery, and to investigate the potential associated mechanisms in a post-MI rat model. Female Sprague Dawley rats (8-10 weeks old) undergoing MI or sham surgery were subsequently submitted to CMT or HIT, or kept sedentary for eight weeks. Prior to and following AET, echocardiographic parameters and exercise capacity of the rats were measured. Western blotting was used to evaluate the levels of apoptosis and associated signaling pathway protein expression. The concentrations of biomarkers of oxidative stress were also determined by ELISA assay. Messenger (m)RNA levels and activity of the key enzymes for glycolysis and fatty acid oxidation, as well as the rate of adenosine triphosphate (ATP) synthesis, were also measured. Compared with the MI group, exercise capacity and cardiac function were significantly improved following AET, particularly following HIT. Left ventricular ejection fraction and fraction shortening were further improved in the MI-HIT group in comparison to that of the MI-CMT group. The two forms of AET almost equally attenuated apoptosis of the post-infarction myocardium. CMT and HIT also alleviated oxidative stress by decreasing the concentration of malondialdehyde and increasing the concentration of superoxide dismutase and glutathione peroxidase (GPx). In particular, HIT induced a greater increase in the concentration of GPx than that of CMT. AET, and HIT in particular, significantly increased the levels of mRNA and the maximal activity of phosphofructokinase-1 and carnitine palmitoyl transferase-1, as well as the maximal ratio of ATP synthesis. In addition, compared with the MI group, the expression of signaling proteins PI3K, Akt, p38mapk and AMPK

Stochastic conditional intensity processes

DEFF Research Database (Denmark)

Bauwens, Luc; Hautsch, Nikolaus

2006-01-01

model allows for a wide range of (cross-)autocorrelation structures in multivariate point processes. The model is estimated by simulated maximum likelihood (SML) using the efficient importance sampling (EIS) technique. By modeling price intensities based on NYSE trading, we provide significant evidence......In this article, we introduce the so-called stochastic conditional intensity (SCI) model by extending Russell’s (1999) autoregressive conditional intensity (ACI) model by a latent common dynamic factor that jointly drives the individual intensity components. We show by simulations that the proposed...... for a joint latent factor and show that its inclusion allows for an improved and more parsimonious specification of the multivariate intensity process...

Dynamic fracture initiation in brittle materials under combined mode I/II loading

International Nuclear Information System (INIS)

Nakano, M.; Kishida, K.; Yamauchi, Y.; Sogabe, Y.

1994-01-01

A new test method has been developed to measure the resistance of dynamic fracture initiation in brittle materials under combined mode I/II loadings. The Brazilian disks with center-cracks have been fractured under oblique impact loadings in diametral-compression. The dynamic stress intensity factors of mode I and II are evaluated from the superposition integrals of the step response functions for the cracked disk. The experimental results are presented to elucidate the influence of loading rate on the combined mode fracture toughness for ceramics and glasses. (orig.)

Sustained, Low-Intensity Exercise Achieved by a Dynamic Feeding System Decreases Body Fat in Ponies.

Science.gov (United States)

de Laat, M A; Hampson, B A; Sillence, M N; Pollitt, C C

2016-09-01

Obesity in horses is increasing in prevalence and can be associated with insulin insensitivity and laminitis. Current treatment strategies for obesity include dietary restriction and exercise. However, whether exercise alone is effective for decreasing body fat is uncertain. Our hypothesis was that twice daily use of a dynamic feeding system for 3 months would induce sustained, low-intensity exercise thereby decreasing adiposity and improving insulin sensitivity (SI). Eight, university-owned, mixed-breed, adult ponies with body condition scores (BCS) ≥5/9 were used. Two treatments ("feeder on" or "feeder off") were administered for a 3-month period by a randomized, crossover design (n = 4/treatment). An interim equilibration period of 6 weeks at pasture separated the 2 study phases. Measurements of body mass (body weight, BCS, cresty neck score [CrNS], and morphometry), body fat (determined before and after the "feeder on" treatment only), triglycerides, and insulin sensitivity (SI; combined glucose-insulin test) were undertaken before and after treatments. The dynamic feeding system induced a 3.7-fold increase in the daily distance travelled (n = 6), compared to with a stationary feeder, which significantly decreased mean BCS (6.53 ± 0.94 to 5.38 ± 1.71), CrNS (2.56 ± 1.12 to 1.63 ± 1.06) and body fat (by 4.95%). An improvement in SI did not occur in all ponies. A dynamic feeding system can be used to induce sustained (daily), low-intensity exercise that promotes weight loss in ponies. However, this exercise may not be sufficient to substantially improve SI. Copyright © 2016 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals, Inc. on behalf of the American College of Veterinary Internal Medicine.

MALDI-TOF Mass Spectrometry Enables a Comprehensive and Fast Analysis of Dynamics and Qualities of Stress Responses of Lactobacillus paracasei subsp. paracasei F19

Science.gov (United States)

Schott, Ann-Sophie; Behr, Jürgen; Quinn, Jennifer; Vogel, Rudi F.

2016-01-01

Lactic acid bacteria (LAB) are widely used as starter cultures in the manufacture of foods. Upon preparation, these cultures undergo various stresses resulting in losses of survival and fitness. In order to find conditions for the subsequent identification of proteomic biomarkers and their exploitation for preconditioning of strains, we subjected Lactobacillus (Lb.) paracasei subsp. paracasei TMW 1.1434 (F19) to different stress qualities (osmotic stress, oxidative stress, temperature stress, pH stress and starvation stress). We analysed the dynamics of its stress responses based on the expression of stress proteins using MALDI-TOF mass spectrometry (MS), which has so far been used for species identification. Exploiting the methodology of accumulating protein expression profiles by MALDI-TOF MS followed by the statistical evaluation with cluster analysis and discriminant analysis of principle components (DAPC), it was possible to monitor the expression of low molecular weight stress proteins, identify a specific time point when the expression of stress proteins reached its maximum, and statistically differentiate types of adaptive responses into groups. Above the specific result for F19 and its stress response, these results demonstrate the discriminatory power of MALDI-TOF MS to characterize even dynamics of stress responses of bacteria and enable a knowledge-based focus on the laborious identification of biomarkers and stress proteins. To our knowledge, the implementation of MALDI-TOF MS protein profiling for the fast and comprehensive analysis of various stress responses is new to the field of bacterial stress responses. Consequently, we generally propose MALDI-TOF MS as an easy and quick method to characterize responses of microbes to different environmental conditions, to focus efforts of more elaborate approaches on time points and dynamics of stress responses. PMID:27783652

MALDI-TOF Mass Spectrometry Enables a Comprehensive and Fast Analysis of Dynamics and Qualities of Stress Responses of Lactobacillus paracasei subsp. paracasei F19.

Directory of Open Access Journals (Sweden)

Ann-Sophie Schott

Full Text Available Lactic acid bacteria (LAB are widely used as starter cultures in the manufacture of foods. Upon preparation, these cultures undergo various stresses resulting in losses of survival and fitness. In order to find conditions for the subsequent identification of proteomic biomarkers and their exploitation for preconditioning of strains, we subjected Lactobacillus (Lb. paracasei subsp. paracasei TMW 1.1434 (F19 to different stress qualities (osmotic stress, oxidative stress, temperature stress, pH stress and starvation stress. We analysed the dynamics of its stress responses based on the expression of stress proteins using MALDI-TOF mass spectrometry (MS, which has so far been used for species identification. Exploiting the methodology of accumulating protein expression profiles by MALDI-TOF MS followed by the statistical evaluation with cluster analysis and discriminant analysis of principle components (DAPC, it was possible to monitor the expression of low molecular weight stress proteins, identify a specific time point when the expression of stress proteins reached its maximum, and statistically differentiate types of adaptive responses into groups. Above the specific result for F19 and its stress response, these results demonstrate the discriminatory power of MALDI-TOF MS to characterize even dynamics of stress responses of bacteria and enable a knowledge-based focus on the laborious identification of biomarkers and stress proteins. To our knowledge, the implementation of MALDI-TOF MS protein profiling for the fast and comprehensive analysis of various stress responses is new to the field of bacterial stress responses. Consequently, we generally propose MALDI-TOF MS as an easy and quick method to characterize responses of microbes to different environmental conditions, to focus efforts of more elaborate approaches on time points and dynamics of stress responses.

Intensity of heat stress in winter wheat—phenology compensates for the adverse effect of global warming

International Nuclear Information System (INIS)

Rezaei, Ehsan Eyshi; Siebert, Stefan; Ewert, Frank

2015-01-01

Higher temperatures during the growing season are likely to reduce crop yields with implications for crop production and food security. The negative impact of heat stress has also been predicted to increase even further for cereals such as wheat under climate change. Previous empirical modeling studies have focused on the magnitude and frequency of extreme events during the growth period but did not consider the effect of higher temperature on crop phenology. Based on an extensive set of climate and phenology observations for Germany and period 1951–2009, interpolated to 1 × 1 km resolution and provided as supplementary data to this article (available at stacks.iop.org/ERL/10/024012/mmedia), we demonstrate a strong relationship between the mean temperature in spring and the day of heading (DOH) of winter wheat. We show that the cooling effect due to the 14 days earlier DOH almost fully compensates for the adverse effect of global warming on frequency and magnitude of crop heat stress. Earlier heading caused by the warmer spring period can prevent exposure to extreme heat events around anthesis, which is the most sensitive growth stage to heat stress. Consequently, the intensity of heat stress around anthesis in winter crops cultivated in Germany may not increase under climate change even if the number and duration of extreme heat waves increase. However, this does not mean that global warning would not harm crop production because of other impacts, e.g. shortening of the grain filling period. Based on the trends for the last 34 years in Germany, heat stress (stress thermal time) around anthesis would be 59% higher in year 2009 if the effect of high temperatures on accelerating wheat phenology were ignored. We conclude that climate impact assessments need to consider both the effect of high temperature on grain set at anthesis but also on crop phenology. (letter)

Heat Shock Protein Genes Undergo Dynamic Alteration in Their Three-Dimensional Structure and Genome Organization in Response to Thermal Stress.

Science.gov (United States)

Chowdhary, Surabhi; Kainth, Amoldeep S; Gross, David S

2017-12-15

Three-dimensional (3D) chromatin organization is important for proper gene regulation, yet how the genome is remodeled in response to stress is largely unknown. Here, we use a highly sensitive version of chromosome conformation capture in combination with fluorescence microscopy to investigate Heat Shock Protein ( HSP ) gene conformation and 3D nuclear organization in budding yeast. In response to acute thermal stress, HSP genes undergo intense intragenic folding interactions that go well beyond 5'-3' gene looping previously described for RNA polymerase II genes. These interactions include looping between upstream activation sequence (UAS) and promoter elements, promoter and terminator regions, and regulatory and coding regions (gene "crumpling"). They are also dynamic, being prominent within 60 s, peaking within 2.5 min, and attenuating within 30 min, and correlate with HSP gene transcriptional activity. With similarly striking kinetics, activated HSP genes, both chromosomally linked and unlinked, coalesce into discrete intranuclear foci. Constitutively transcribed genes also loop and crumple yet fail to coalesce. Notably, a missense mutation in transcription factor TFIIB suppresses gene looping, yet neither crumpling nor HSP gene coalescence is affected. An inactivating promoter mutation, in contrast, obviates all three. Our results provide evidence for widespread, transcription-associated gene crumpling and demonstrate the de novo assembly and disassembly of HSP gene foci. Copyright © 2017 American Society for Microbiology.

Investigation of the yearly dynamics of the intensity of reciprocal feeding among honey bees Apis mellifica L. by means of I131

International Nuclear Information System (INIS)

Skirkevicius, A.V.; Bagdonas, J.-S.A.

1978-01-01

The results of the investigation show that the early change of the intensity of reciprocal feeding among honey bees makes up a circle consisting of 4 phases, 2 of them being with a more frequent and 2 with a less frequent reciprocal feeding. The duration of one phase varies from 1 to 6 months. The intensity of the reciprocal feeding is the same during both phases with the less frequent reciprocal feeding, while significantly unequal in the phases with the more frequent reciprocal feeding (on the average by 2.6 times greater in the 2nd phase than in the 4th). There is a positive correlation between the yearly dynamics of the intensity of reciprocal feeding and the quantity of feed given by the nurse bee. The average radioactivity per 1 bee (from those who got radioactive feed) is constant and depends neither upon season nor the period worker bees were kept in the group. Here is a positive correlation between the yearly dynamics of the intensity of reciprocal feeding among worker bees and the extent of variability of the quantity of feed they receive

Stress Management and Gifted Children

Science.gov (United States)

Patel, Vidisha A.

2009-01-01

Stress can affect anyone, and gifted children are no exception. Giftedness can sometimes be the cause of the stress. Perfectionism, sensitivity, and intensity are characteristics of gifted children that may exacerbate stress. Stress can be constructive. Prolonged stress, however, with no time to recover becomes detrimental. Continued stress upsets…

Standard test method for determining a threshold stress intensity factor for environment-assisted cracking of metallic materials

CERN Document Server

American Society for Testing and Materials. Philadelphia

2003-01-01

1.1 This test method covers the determination of the environment-assisted cracking threshold stress intensity factor parameters, KIEAC and KEAC, for metallic materials from constant-force testing of fatigue precracked beam or compact fracture specimens and from constant-displacement testing of fatigue precracked bolt-load compact fracture specimens. 1.2 This test method is applicable to environment-assisted cracking in aqueous or other aggressive environments. 1.3 Materials that can be tested by this test method are not limited by thickness or by strength as long as specimens are of sufficient thickness and planar size to meet the size requirements of this test method. 1.4 A range of specimen sizes with proportional planar dimensions is provided, but size may be variable and adjusted for yield strength and applied force. Specimen thickness is a variable independent of planar size. 1.5 Specimen configurations other than those contained in this test method may be used, provided that well-established stress ...

A database to evaluate stress intensity factors of elbows with throughwall flaws under combined internal pressure and bending moment

International Nuclear Information System (INIS)

Chattopadhyay, J.; Dutta, B.K.; Kushwaha, H.S.; Mahajan, S.C.; Kakodkar, A.

1993-01-01

The advent of Leak-Before-Break (LBB) concept has replaced the traditional design basis event of Double Ended Guillotine Break (DEGB) in the design of primary heat transport (PHT) piping. The use of LBB concept requires postulation of largest credible cracks at highly stressed locations and demonstration of its stability under the maximum credible loading conditions. Stress analysis of PHT piping in nuclear power plants shows that the highly stressed piping components are normally elbows and branch tees. This necessitates detailed fracture mechanics evaluation of piping connections by computing Stress Intensity Factor (SIF) and/or J-integral. Simple analytical solutions for evaluation of SIF and J-integral for cracks in straight pipes are readily available in literature. However, the same type of solutions for elbows and tees are limited in open literature. In the present work, a database is generated to evaluate SIF for throughwall circumferential and longitudinal cracks under combined internal pressure and bending moment. Different parameters to characterise a cracked elbow are pipe factor (h), pipe bore radius to thickness ratio (r/t) and crack length. Another parameter (σ) is used to consider the relative magnitude of stresses due to internal pressure and remote bending moment. The database has been used to derive closed form expressions to evaluate SIF for elbow with cracks in terms of the aforementioned parameters. (author). 8 refs., 12 figs., 3 tabs

Dynamic Stresses in the LHC TCDS Diluter from 7 TeV Beam Loading

CERN Document Server

Goddard, B; Presland, A; Weterings, W

2006-01-01

In the event of an unsynchronised beam abort, the MSD extraction septum of the LHC beam dumping system is protected from damage by the TCDS diluter. The simultaneous constraints of obtaining sufficient beam dilution while ensuring the survival of the TCDS make the design difficult, with high thermally induced dynamic stresses occurring in the material needed to attenuate the particle showers induced by the primary beam impact. In this paper, full 3D simulations are described where the worst-case beam loading has been used to generate the local temperature rise and to follow the resulting time evolution of the mechanical stresses. The results and the accompanying design changes for the TCDS, to provide an adequate performance margin, are detailed.