WorldWideScience

Sample records for mechanical failures prevention

  1. Burn prevention mechanisms and outcomes: pitfalls, failures and successes.

    Science.gov (United States)

    Atiyeh, Bishara S; Costagliola, Michel; Hayek, Shady N

    2009-03-01

    Burns are responsible for significant mortality and morbidity worldwide and are among the most devastating of all injuries, with outcomes spanning the spectrum from physical impairments and disabilities to emotional and mental consequences. Management of burns and their sequelae even in well-equipped, modern burn units of advanced affluent societies remains demanding and extremely costly. Undoubtedly, in most low and middle income countries (LMICs) with limited resources and inaccessibility to sophisticated skills and technologies, the same standard of care is obviously not possible. Unfortunately, over 90% of fatal fire-related burns occur in developing or LMICs with South-East Asia alone accounting for over half of these fire-related deaths. If burn prevention is an essential part of any integrated burn management protocol anywhere, focusing on burn prevention in LMICs rather than treatment cannot be over-emphasized where it remains the major and probably the only available way of reducing the current state of morbidity and mortality. Like other injury mechanisms, the prevention of burns requires adequate knowledge of the epidemiological characteristics and associated risk factors, it is hence important to define clearly, the social, cultural and economic factors, which contribute to burn causation. While much has been accomplished in the areas of primary and secondary prevention of fires and burns in many developed or high-income countries (HICs) such as the United States due to sustained research on the epidemiology and risk factors, the same cannot be said for many LMICs. Many health authorities, agencies, corporations and even medical personnel in LMICs consider injury prevention to have a much lower priority than disease prevention for understandable reasons. Consequently, burns prevention programmes fail to receive the government funding that they deserve. Prevention programmes need to be executed with patience, persistence, and precision, targeting high

  2. Fatigue damage mechanism and failure prevention in fiberglass reinforced plastic

    Directory of Open Access Journals (Sweden)

    Raimundo Carlos Silverio Freire Jr.

    2005-03-01

    Full Text Available Damaging of composite laminates was monitored during fatigue tests, revealing the formation and propagation stages for compressive, tensile, or alternate cyclic loading. Two different laminate stacking sequences, with different number of layers, were tested. The laminates consisted of E-glass fibers reinforced orthoftalic polyester resin (FGRP shaped as mats or (bi-direction woven fabric textile. Preliminary density, calcination tests and static compressive and tensile mechanical tests were carried out. Then, tensile (R = 0.1, compressive (R = 10 and alternate axial (R = - 1 fatigue tests were performed at different maximum stresses. Tensile cyclic loading resulted in crack formation and propagation confirming the findings reported in other studies. On the other hand, damage from alternate and compressive fatigue depicted peculiar features. Less extended damage and better fatigue resistance were observed for the laminate with symmetrically distributed layers.

  3. Focus on Mechanical Failures: Mechanisms and Detection. Proceedings of the Meeting (45th) of the Mechanical Failures Prevention Group Held in Annapolis, Maryland on April 9 - 11, 1999

    Science.gov (United States)

    1991-04-04

    of the applied strain rate. Except in the unusual case of a continuous reduction of area to rupture, separation during ductile fracture occurs by void...procedure in industry. As a general rule , all rotating elements over 2,000 lbs. usually have casing or foundation effects associated with them. Therefore...Analysis 195 P. Stumpff and W. B. Pinnell FAILURES IN METALS Analysis of a Failure of a Cu-Ni Fitting Used in a Ship Hydraulic System Application 207 D

  4. Creating incentives to prevent execution failures: an extension of VCG mechanisms

    NARCIS (Netherlands)

    Zhang, Y.; De Weerdt, M.M.

    2009-01-01

    When information or control in a multiagent system is private to the agents, they may misreport this information or refuse to execute an agreed outcome, in order to change the resulting end state of such a system to their benefit. In some domains this may result in an execution failure. We show that

  5. The use of failure mode and effects analysis to construct an effective disposal and prevention mechanism for infectious hospital waste.

    Science.gov (United States)

    Ho, Chao Chung; Liao, Ching-Jong

    2011-12-01

    In recent times, the quality of medical care has been continuously improving in medical institutions wherein patient-centred care has been emphasized. Failure mode and effects analysis (FMEA) has also been promoted as a method of basic risk management and as part of total quality management (TQM) for improving the quality of medical care and preventing mistakes. Therefore, a study was conducted using FMEA to evaluate the potential risk causes in the process of infectious medical waste disposal, devise standard procedures concerning the waste, and propose feasible plans for facilitating the detection of exceptional cases of infectious waste. The analysis revealed the following results regarding medical institutions: (a) FMEA can be used to identify the risk factors of infectious waste disposal. (b) During the infectious waste disposal process, six items were scored over 100 in the assessment of uncontrolled risks: erroneous discarding of infectious waste by patients and their families, erroneous discarding by nursing staff, erroneous discarding by medical staff, cleaning drivers pierced by sharp articles, cleaning staff pierced by sharp articles, and unmarked output units. Therefore, the study concluded that it was necessary to (1) provide education and training about waste classification to the medical staff, patients and their families, nursing staff, and cleaning staff; (2) clarify the signs of caution; and (3) evaluate the failure mode and strengthen the effects.

  6. Mechanics of Failure Mechanisms in Structures

    CERN Document Server

    Carlson, R L; Craig, J I

    2012-01-01

    This book focuses on the mechanisms and underlying mechanics of failure in various classes of materials such as metallic, ceramic, polymeric, composite and bio-material.  Topics include tensile and compressive fracture, crack initiation and growth, fatigue and creep rupture in metallic materials, matrix cracking and delamination and environmental degradation in polymeric composites, failure of bio-materials such as prosthetic heart valves and prosthetic hip joints, failure of ceramics and ceramic matrix composites, failure of metallic matrix composites, static and dynamic buckling failure, dynamic excitations and creep buckling failure in structural systems. Chapters are devoted to failure mechanisms that are characteristic of each of the materials.  The work also provides the basic elements of fracture mechanics and studies in detail several niche topics such as the effects of toughness gradients, variable amplitude loading effects in fatigue, small fatigue cracks, and creep induced brittleness. Furthe...

  7. Damage mechanics - failure modes

    Energy Technology Data Exchange (ETDEWEB)

    Krajcinovic, D.; Vujosevic, M. [Arizona State Univ., Tempe, AZ (United States)

    1996-12-31

    The present study summarizes the results of the DOE sponsored research program focused on the brittle failure of solids with disordered microstructure. The failure is related to the stochastic processes on the microstructural scale; namely, the nucleation and growth of microcracks. The intrinsic failure modes, such as the percolation, localization and creep rupture, are studied by emphasizing the effect of the micro-structural disorder. A rich spectrum of physical phenomena and new concepts that emerges from this research demonstrates the reasons behind the limitations of traditional, deterministic, and local continuum models.

  8. Detection, Diagnosis and Prognosis: Contribution to the energy challenge: Proceedings of the Meeting of the Mechanical Failures Prevention Group

    Science.gov (United States)

    Shives, T. R. (Editor); Willard, W. A. (Editor)

    1981-01-01

    The contribution of failure detection, diagnosis and prognosis to the energy challenge is discussed. Areas of special emphasis included energy management, techniques for failure detection in energy related systems, improved prognostic techniques for energy related systems and opportunities for detection, diagnosis and prognosis in the energy field.

  9. Current Practices and Trends in Mechanical Failure Prevention. Proceedings of the Meeting of the Mechanical Failures Prevention Group (44th) Held in Virginia Beach, Virginia 3-5 April 1990

    Science.gov (United States)

    1990-01-01

    DIGITAL DIAGNOSTICZii ~ b X ~ Figure 5 Oil System Screen 79Uater System Hea t I 17 AIR O1IL W TER ANALOG DGTLDANSI Figure 6 Water System Screen 302 Tap ...rupture Stress corrosion cracking, resonance, water -cutting 4. Generator failure Hydrogen embrittlement, catastrophic unbalance, retaining ring crackinq...become a sort of standard for the presence of microplasticity . What we have to realize is that both cleavage and MVC are larger scaled results of finer

  10. Experimental methods for identifying failure mechanisms

    Science.gov (United States)

    Daniel, I. M.

    1983-01-01

    Experimental methods for identifying failure mechanisms in fibrous composites are studied. Methods to identify failure in composite materials includes interferometry, holography, fractography and ultrasonics.

  11. Structural and failure mechanics of sandwich composites

    CERN Document Server

    Carlsson, LA; Carlsson, Leif A

    2011-01-01

    Focusing on important deformation and failure modes of sandwich structures, this volume describes the mechanics behind fracture processes. The text also reviews test methods developed for the cr, structural integrity, and failure mechanisms of sandwich structures.

  12. Mechanisms of heart failure in obesity.

    Science.gov (United States)

    Ebong, Imo A; Goff, David C; Rodriguez, Carlos J; Chen, Haiying; Bertoni, Alain G

    2014-01-01

    Heart failure is a leading cause of morbidity and mortality and its prevalence continues to rise. Because obesity has been linked with heart failure, the increasing prevalence of obesity may presage further rise in heart failure in the future. Obesity-related factors are estimated to cause 11% of heart failure cases in men and 14% in women. Obesity may result in heart failure by inducing haemodynamic and myocardial changes that lead to cardiac dysfunction, or due to an increased predisposition to other heart failure risk factors. Direct cardiac lipotoxicity has been described where lipid accumulation in the heart results in cardiac dysfunction inexplicable of other heart failure risk factors. In this overview, we discussed various pathophysiological mechanisms that could lead to heart failure in obesity, including the molecular mechanisms underlying cardiac lipotoxicity. We defined the obesity paradox and enumerated various premises for the paradoxical associations observed in the relationship between obesity and heart failure.

  13. Mechanical Failure in Colloidal Gels

    Science.gov (United States)

    Kodger, Thomas Edward

    When colloidal particles in a dispersion are made attractive, they aggregate into fractal clusters which grow to form a space-spanning network, or gel, even at low volume fractions. These gels are crucial to the rheological behavior of many personal care, food products and dispersion-based paints. The mechanical stability of these products relies on the stability of the colloidal gel network which acts as a scaffold to provide these products with desired mechanical properties and to prevent gravitational sedimentation of the dispersed components. Understanding the mechanical stability of such colloidal gels is thus of crucial importance to predict and control the properties of many soft solids. Once a colloidal gel forms, the heterogeneous structure bonded through weak physical interactions, is immediately subject to body forces, such as gravity, surface forces, such as adhesion to a container walls and shear forces; the interplay of these forces acting on the gel determines its stability. Even in the absence of external stresses, colloidal gels undergo internal rearrangements within the network that may cause the network structure to evolve gradually, in processes known as aging or coarsening or fail catastrophically, in a mechanical instability known as syneresis. Studying gel stability in the laboratory requires model colloidal system which may be tuned to eliminate these body or endogenous forces systematically. Using existing chemistry, I developed several systems to study delayed yielding by eliminating gravitational stresses through density matching and cyclic heating to induce attraction; and to study syneresis by eliminating adhesion to the container walls, altering the contact forces between colloids, and again, inducing gelation through heating. These results elucidate the varied yet concomitant mechanisms by which colloidal gels may locally or globally yield, but then reform due to the nature of the physical, or non-covalent, interactions which form

  14. Failure Mode/Mechanism Distributions

    Science.gov (United States)

    1991-09-01

    nsc. Modas /Mach Dist. Dist. Suurce(,%)/Detai19 Bolt, MahineSources :1 Brcikon 𔃺.1% 59.0% Broken Bolt(s) (25j01-(000,Qty:l) C25101-000,Qty:Ij., Part...Center (RAC) * 201 Mill St., Rome, NY 13440 * 315-337-0900 3-114 Failure Distribution Summaries FMD-91 ? art Failure Norm Fail Data Docm. Mode/Moch Dist... Deco . Mode/Mech Dist. Dist. Source(s)/Details Lamp,Bulb Sourcent 4 Lamp Failure 68.8% 53.8% Light Bulb Failure (23038-00l,Qty:3) (23038-004,Qty:l

  15. STATISTICAL EVALUATION OF HISTORICAL DIKE FAILURE MECHANISM

    Directory of Open Access Journals (Sweden)

    L. NAGY

    2012-12-01

    Full Text Available Statistical evaluation of historical dike failure mechanism The failure mechanism of flood protection dikes includes physical (geotechnical, seepage processes leading to a dike breach. An awareness of the failure mechanism is required directly in dike stability calculations and indirectly for risk calculations. Statistics of historical data indicate among others the distribution and frequency of failure mechanisms associated with dikes. These data may be used in estimations of the expected likelihood of occurrence of non-quantifiable failure mechanisms. In addition to a comparative evaluation of statistics collected in several countries, this publication also presents data for the Carpathian Basin. One of the most important conclusions drawn from statistical information suggests that most dike breaches develop as a consequence of poor safety strategy

  16. Mechanical circulatory treatment of advanced heart failure

    DEFF Research Database (Denmark)

    Løgstrup, Brian B; Vase, Henrik; Gjedsted, Jakob

    2016-01-01

    Heart failure is one of the most common causes of morbidity and mortality worldwide. When patients cease to respond adequately to optimal medical therapy mechanical circulatory support has been promising. The advent of mechanical circulatory support devices has allowed significant improvements...... in patient survival and quality of life for those with advanced or end-stage heart failure. We provide a general overview of current mechanical circulatory support devices encompassing options for both short- and long-term ventricular support....

  17. Field failure mechanisms for photovoltaic modules

    Science.gov (United States)

    Dumas, L. N.; Shumka, A.

    1981-01-01

    Beginning in 1976, Department of Energy field centers have installed and monitored a number of field tests and application experiments using current state-of-the-art photovoltaic modules. On-site observations of module physical and electrical degradation, together with in-depth laboratory analysis of failed modules, permits an overall assessment of the nature and causes of early field failures. Data on failure rates are presented, and key failure mechanisms are analyzed with respect to origin, effect, and prospects for correction. It is concluded that all failure modes identified to date are avoidable or controllable through sound design and production practices.

  18. Mechanisms for cachexia in heart failure.

    Science.gov (United States)

    Pureza, Vincent; Florea, Viorel G

    2013-12-01

    The combination of profound muscle wasting and severe weight loss that occurs in heart failure is a complex phenomenon that involves the interplay of numerous factors. In this article, we describe processes that contribute to cachexia, as part of the clinical sequelae of heart failure, and their potential underlying mechanisms. While multiple mechanisms of cardiac cachexia have been described, we propose a multifactorial etiology for this condition that includes, but is not limited to, nutritional and gastrointestinal alterations, immunological and neurohormonal activation, and anabolic and catabolic imbalance.

  19. Risky business: failure to prevent and failure to communicate.

    Science.gov (United States)

    Moore, Dorothy L; Ste-Marie, Micheline

    2009-01-01

    Healthcare-associated infections (HAIs), important threats to patient safety, are considered differently from other adverse events. Gardam and his colleagues discuss several reasons for this and outline approaches that may bring about changes in attitudes and enhance HAI prevention. We comment on the potential preventability of HAIs, the need for improved communication strategies and the different vision of the role of infection control personnel suggested by Gardam et al. Recent developments in infection control structure and management and patient safety in Quebec are summarized.

  20. Compressive Failure Mechanisms in Layered Materials

    DEFF Research Database (Denmark)

    Sørensen, Kim Dalsten

    Two important failure modes in fiber reinforced composite materials in cluding layers and laminates occur under loading conditions dominated by compression in the layer direction. These two distinctly different failure modes are 1. buckling driven delamination 2. failure by strain localization...... or on cylindrical substrates modeling the delamination as an interface fracture mechanical problem. Here attention is directed towards double-curved substrates, which introduces a new non-dimensional combination of geometric parameters. It is shown for a wide range of parameters that by choosing the two...... nondimensional parameters suitably, one of them plays a very insignificant role on the fracture mechanical parameters such as normalized energy release rate and mode mixity, which has obvious impact on the presentation of the results. In some cases, the local curvatures of the system is so high compared...

  1. Utility-scale system preventive and failure-related maintenance

    Energy Technology Data Exchange (ETDEWEB)

    Jennings, C.; Hutchinson, P.

    1995-11-01

    This paper describes the design and performance background on PVUSA utility-scale systems at Davis and Kerman, California, and reports on a preventative and failure-related maintenance approach and costs.

  2. Mechanical circulatory devices in acute heart failure.

    Science.gov (United States)

    Teuteberg, Jeffrey J; Chou, Josephine C

    2014-07-01

    Cardiogenic shock remains a leading cause of mortality despite advances in the treatment of myocardial infarction and advanced heart failure. Medical therapy can be inadequate, and patients may need mechanical circulatory support (MCS). The proper application of MCS requires knowledge of the underlying cause of acute heart failure, familiarity with the circulatory support devices, and the potential benefits and limitations of device therapy. This article describes the most commonly used temporary ventricular assist devices and their use in the various causes of cardiogenic shock.

  3. Creating incentives to prevent intentional execution failures

    NARCIS (Netherlands)

    Zhang, Y.; De Weerdt, M.M.

    2009-01-01

    When information or control in a multiagent system is private to the agents, they may misreport this information or refuse to execute an agreed outcome, in order to change the resulting end state of such a system to their benefit. This may result in execution failures. When only information is

  4. Principles of loads and failure mechanisms applications in maintenance, reliability and design

    CERN Document Server

    Tinga, T

    2013-01-01

    Failure of components or systems must be prevented by both designers and operators of systems, but knowledge of the underlying mechanisms is often lacking. Since the relation between the expected usage of a system and its failure behavior is unknown, unexpected failures often occur, with possibly serious financial and safety consequences. Principles of Loads and Failure Mechanisms.  Applications in Maintenance, Reliability and Design provides a complete overview of all relevant failure mechanisms, ranging from mechanical failures like fatigue and creep to corrosion and electric failures. Both qualitative and quantitative descriptions of the mechanisms and their governing loads enable a solid assessment of a system’s reliability in a given or assumed operational context. Moreover, a unique range of applications of this knowledge in the fields of maintenance, reliability and design are presented. The benefits of understanding the physics of failure are demonstrated for subjects like condition monitoring, pre...

  5. Recognition and Analysis of Corrosion Failure Mechanisms

    Directory of Open Access Journals (Sweden)

    Steven Suess

    2006-02-01

    Full Text Available Corrosion has a vast impact on the global and domestic economy, and currently incurs losses of nearly $300 billion annually to the U.S. economy alone. Because of the huge impact of corrosion, it is imperative to have a systematic approach to recognizing and mitigating corrosion problems as soon as possible after they become apparent. A proper failure analysis includes collection of pertinent background data and service history, followed by visual inspection, photographic documentation, material evaluation, data review and conclusion procurement. In analyzing corrosion failures, one must recognize the wide range of common corrosion mechanisms. The features of any corrosion failure give strong clues as to the most likely cause of the corrosion. This article details a proven approach to properly determining the root cause of a failure, and includes pictographic illustrations of the most common corrosion mechanisms, including general corrosion, pitting, galvanic corrosion, dealloying, crevice corrosion, microbiologically-influenced corrosion (MIC, corrosion fatigue, stress corrosion cracking (SCC, intergranular corrosion, fretting, erosion corrosion and hydrogen damage.

  6. Acute heart failure: Epidemiology, risk factors, and prevention.

    Science.gov (United States)

    Farmakis, Dimitrios; Parissis, John; Lekakis, John; Filippatos, Gerasimos

    2015-03-01

    Acute heart failure represents the first cause of hospitalization in elderly persons and is the main determinant of the huge healthcare expenditure related to heart failure. Despite therapeutic advances, the prognosis of acute heart failure is poor, with in-hospital mortality ranging from 4% to 7%, 60- to 90-day mortality ranging from 7% to 11%, and 60- to 90-day rehospitalization from 25% to 30%. Several factors including cardiovascular and noncardiovascular conditions as well as patient-related and iatrogenic factors may precipitate the rapid development or deterioration of signs and symptoms of heart failure, thus leading to an acute heart failure episode that usually requires patient hospitalization. The primary prevention of acute heart failure mainly concerns the prevention, early diagnosis, and treatment of cardiovascular risk factors and heart disease, including coronary artery disease, while the secondary prevention of a new episode of decompensation requires the optimization of heart failure therapy, patient education, and the development of an effective transition and follow-up plan. Copyright © 2014 Sociedad Española de Cardiología. Published by Elsevier España, S.L.U. All rights reserved.

  7. On-Board Particulate Filter Failure Prevention and Failure Diagnostics Using Radio Frequency Sensing

    Energy Technology Data Exchange (ETDEWEB)

    Sappok, Alex [Filter Sensing Technologies; Ragaller, Paul [Filter Sensing Technologies; Herman, Andrew [CTS Corporation; Bromberg, L. [Massachusetts Institute of Technology (MIT); Prikhodko, Vitaly Y [ORNL; Parks, II, James E [ORNL; Storey, John Morse [ORNL

    2017-01-01

    The increasing use of diesel and gasoline particulate filters requires advanced on-board diagnostics (OBD) to prevent and detect filter failures and malfunctions. Early detection of upstream (engine-out) malfunctions is paramount to preventing irreversible damage to downstream aftertreatment system components. Such early detection can mitigate the failure of the particulate filter resulting in the escape of emissions exceeding permissible limits and extend the component life. However, despite best efforts at early detection and filter failure prevention, the OBD system must also be able to detect filter failures when they occur. In this study, radio frequency (RF) sensors were used to directly monitor the particulate filter state of health for both gasoline particulate filter (GPF) and diesel particulate filter (DPF) applications. The testing included controlled engine dynamometer evaluations, which characterized soot slip from various filter failure modes, as well as on-road fleet vehicle tests. The results show a high sensitivity to detect conditions resulting in soot leakage from the particulate filter, as well as potential for direct detection of structural failures including internal cracks and melted regions within the filter media itself. Furthermore, the measurements demonstrate, for the first time, the capability to employ a direct and continuous monitor of particulate filter diagnostics to both prevent and detect potential failure conditions in the field.

  8. MECHANISMS OF RIGHT VENTRICULAR FAILURE AND BIVENTRICULAR MECHANICAL CIRCULATORY SUPPORT

    Directory of Open Access Journals (Sweden)

    G. P. Itkin

    2013-01-01

    Full Text Available The paper presents a review of the problems of mechanical circulatory support with left ventricular bypass in total cardiac failure. Dysfunction of right ventricular defines the high mortality on left ventricular device. One of the effective methods for solving this problem is the use of right ventricular assisted devices. There are considered of the basic physiological mechanisms of interaction between the right and left ventricles of the heart, affecting on the function of the right heart. Shows the need to assess right ventricular function before deciding on mechanical circulatory support. Provides examples of the estimation the predictors of the right ventricular failure. The basic methods and devices of biventricular circulatory support were con- sidered. 

  9. Preventing failure in distance learning: the use of Spector tool

    Directory of Open Access Journals (Sweden)

    Maciej Słomczyński

    2012-12-01

    Full Text Available In 2011 and 2012, University of Warsaw conducted a two-stage research which goals were: (1 to verify whether students’ access to information showing the characteristics of their learning organization is connected with a sense of efficacy, level of motivation, preferred learning forms and perceived teacher presence; (2 to examine the relations between organizational learning styles and the usage of Spector module. One of the means used in the project was introduction of a mechanism for teaching and learning management in an e-learning setting – Spector. This way, a support for prevention, diagnosis and learning failure therapy was introduced. The mechanism was implemented as a Moodle LMS extension. Its goal was to process activity reports gathered by Moodle and present them in an user-friendly way to both students and teachers. The first-stage research results did not confirm the correlation between mentioned variables, although the majority of students taking part in the research pointed out Spector’s importance to improving their motivation and planning their learning activities. Resolving of all the doubts set in the project required a further, more complex study (including organizational learning styles. The second stage of the research proved that students’ opinion about the usage of Spector is related to their current studies programme (Bachelor’s, Master’s or Doctoral.

  10. A Tool for Preventing Teamwork Failure: the TFP Questionnaire

    DEFF Research Database (Denmark)

    Qvist, Palle; Rebollar, Rubeén; Lidón, Iván

    2010-01-01

    This paper presents the process used to devise the Teamwork Failure Prevention Questionnaire (TFP Questionnaire), a tool that allows teams with problems in functioning to be detected early. The TFP Questionnaire was formulated in a project management course at the University of Zaragoza (Spain...

  11. A Tool for Preventing Teamwork Failure: the TFP Questionnaire

    DEFF Research Database (Denmark)

    Qvist, Palle; Rebollar, Rubeén; Lidón, Iván

    2010-01-01

    This paper presents the process used to devise the Teamwork Failure Prevention Questionnaire (TFP Questionnaire), a tool that allows teams with problems in functioning to be detected early. The TFP Questionnaire was formulated in a project management course at the University of Zaragoza (Spain...

  12. Preventing acute renal failure is crucial during acute tumor lysis syndrome

    Directory of Open Access Journals (Sweden)

    Darmon Michael

    2007-01-01

    Full Text Available Tumour Lysis syndrome (TLS is characterized by the massive destruction of tumoral cells and the release in the extracellular space of their content. While TLS may occur spontaneously before treatment, it usually develops shortly after the initiation of cytotoxic chemotherapy. These metabolites can overwhelm the homeostatic mechanisms and cause hyperuricemia, hyperkalemia, hyperphosphatemia and hypocalcemia. Moreover, TLS may lead to an acute renal failure (ARF. In addition to the hospital mortality induced by the acute renal failure itself, development of an ARF may preclude optimal cancer treatment. Therefore, prevention of the acute renal failure during acute tumor lysis syndrome is mandatory. The objective of this review is to describe pathophysiological mechanisms leading to acute tumor lysis syndrome, clinical and biological consequences of this syndrome and to provide up-to-date guidelines to ensure prevention and prompt management of this syndrome.

  13. Cardiac failure in β-thalassemia: diagnosis, prevention and management

    Directory of Open Access Journals (Sweden)

    A. Aessopos

    2011-12-01

    Full Text Available Heart failure always represented and still remains the leading cause of mortality in β (β-thalassemia, despite the therapeutic advances and the considerable amelioration of prognosis accomplished over the last decades. High cardiac output due to chronic anemia and myocardial iron overload due to repetitive blood transfusions are the two main pathogenetic mechanisms causing heart failure in β-thalassemia. In regularly treated thalassemia major patients, left ventricular dysfunction, resulting mainly from myocardial siderosis, is considered to be the primary cause of heart failure and thus the prevention, early recognition and effective management of iron overload is of key importance. However, the spectrum of cardiovascular complications that may ultimately lead to heart is wide and should be individually investigated in each one of the patients. Echocardiography is the main modality used for the regular follow-up and screening of asymptomatic patients and for the evaluation of patients with cardiac symptoms, while the T2* relaxation time provided by magnetic resonance imaging allows the accurate identification and quantification of myocardial iron burden and thus the proper guidance of iron chelation therapy. 近几十年来,尽管治疗方法取得进步和预断方法得到显著改进,但是心脏衰竭仍是引起β地中海贫血症患者死亡的主要原因。 慢性贫血导致的高心输出量和反复输血导致的心脏铁过载,是导致β地中海贫血患者心脏衰竭的两大发病机制。 在常规治疗的重型地中海贫血患者中,心脏铁质沉着病引起的可逆性左心室功能障碍,被认为是心脏衰竭的主要原因。因此,预防、早期确诊和有效控制铁过载至关重要。 然而,最终导致心脏衰竭的心血管并发症的症状繁多,应对每个患者单独进行检查。 超声心动图仪是用于无症状患者定期随访、筛查和诊断有心脏病症状患

  14. An Energy Model of a Failure Mechanism and its Application

    Institute of Scientific and Technical Information of China (English)

    MA Xiao-ning; LU Zhen-zhou

    2003-01-01

    The energy expression is presented for a failure mechanism, and it is applied in an Accelerated Life Test (ALT) and an Accelerated Reliability Growth Test (ARGT). The conditions of the common failure mechanism are obtained. The essential relationship between the conditions and the Accelerated Factor (Af) is proposed by using the energy model.

  15. Thesaurus of terms for information on mechanics of structural failure

    Science.gov (United States)

    Carpenter, J. L., Jr.; Moya, N.

    1973-01-01

    A Thesaurus of approximately 700 subject terms used to describe the six problem areas in the mechanics of structural failure is presented. The initial criteria for the selection of terms are their significance and frequency of use in the literature describing the mechanics of structural failure. The purpose of the Thesaurus is to provide the Aerospace Safety Research and Data Institute a list of key works and identifiers that afford effective retrieval of information regarding failure modes and mechanisms for aerospace structures. The Thesaurus includes both a conventional listing of subject terms and a Key Words In Context (KWIC) listing.

  16. Recognition and Analysis of Corrosion Failure Mechanisms

    OpenAIRE

    Steven Suess

    2006-01-01

    Corrosion has a vast impact on the global and domestic economy, and currently incurs losses of nearly $300 billion annually to the U.S. economy alone. Because of the huge impact of corrosion, it is imperative to have a systematic approach to recognizing and mitigating corrosion problems as soon as possible after they become apparent. A proper failure analysis includes collection of pertinent background data and service history, followed by visual inspection, photographic documentation, materi...

  17. Recognition and Analysis of Corrosion Failure Mechanisms

    OpenAIRE

    Steven Suess

    2006-01-01

    Corrosion has a vast impact on the global and domestic economy, and currently incurs losses of nearly $300 billion annually to the U.S. economy alone. Because of the huge impact of corrosion, it is imperative to have a systematic approach to recognizing and mitigating corrosion problems as soon as possible after they become apparent. A proper failure analysis includes collection of pertinent background data and service history, followed by visual inspection, photographic documentation, materi...

  18. ANALYSIS OF FAILURE MECHANISM IN MULTIPLE DISC WET BRAKES

    Institute of Scientific and Technical Information of China (English)

    1998-01-01

    By the numberical calculation of dynamic lining pressure distributions,temperature fields and thermal stress fields of steel plates,a method using nonlinear finite element techniques to analyze failure mechanism of a multiple disc wet brake is detailed ,and some measures for combatting these failures are provided.

  19. Failure Mechanism Analysis and Prevention of an Explosion Accident of Oxygen and Argon Balancing Tanks%氧气、氩气平衡罐爆炸事故失效机理分析与预防

    Institute of Scientific and Technical Information of China (English)

    李博; 吴兴华; 汤晓英; 黄文和

    2016-01-01

    用于向炼钢车间氩氧精炼炉供气的氧气平衡罐、氩气平衡罐发生爆炸事故。针对该事故展开技术分析与调查,在明确配气站概况、氧气及氩气装置技术参数、事故现场物损情况的基础上,通过罐体材料性能测试、断口检查、金相观察等手段展开失效分析,并对罐体相关气化器的气化能力计算审核,对汽化器的温度监控系统进行查验。结果表明:平衡罐罐体16MnR材料发生脆断是造成气化器下游的氧罐和氩罐最终发生爆裂的直接原因;整个装置系统缺乏低温保护系统,而气化器在气候条件恶劣情况下长时间连续、超负荷使用,导致翅片管表面结霜严重,诱发事故的产生。最后本文对材料组织碳化物偏析条件下的低温脆断机理进行揭示,并对该类事故的预防提出建议。%An explosion accident, which on an oxygen balance tank and an argon gas tank of the argon oxygen reifning furnace in the steelmaking plant, was investigated. The gas distribution proifles, oxygen and argon device technical parameters, the scene of the accident loss situation were investigated as the basis for the failure analysis through the shell material performance tests, fracture surface examination, and metallographic observation. The tank-related vaporizer vaporizing capacity was calculatied and veriifed. And the vaporizer temperature monitoring system was checked. The results showed that the brittle fracture of the 16MnR material of the balance tank is the cause of downstream of the gasiifer oxygen tank brust. The lack of low temperature protection system in the whole system, and the operation of gasiifer under the harsh climatic conditions for a long time resulted into serious frosting on the tube surface and induced the accident. Finally, the low temperature brittle fracture mechanism under the condition of carbide segregation was revealed. Then the the prevention of this kind of accident

  20. Failure mechanisms of fibrin-based surgical tissue adhesives

    Science.gov (United States)

    Sierra, David Hugh

    A series of studies was performed to investigate the potential impact of heterogeneity in the matrix of multiple-component fibrin-based tissue adhesives upon their mechanical and biomechanical properties both in vivo and in vitro. Investigations into the failure mechanisms by stereological techniques demonstrated that heterogeneity could be measured quantitatively and that the variation in heterogeneity could be altered both by the means of component mixing and delivery and by the formulation of the sealant. Ex vivo tensile adhesive strength was found to be inversely proportional to the amount of heterogeneity. In contrast, in vivo tensile wound-closure strength was found to be relatively unaffected by the degree of heterogeneity, while in vivo parenchymal organ hemostasis in rabbits was found to be affected: greater heterogeneity appeared to correlate with an increase in hemostasis time and amount of sealant necessary to effect hemostasis. Tensile testing of the bulk sealant showed that mechanical parameters were proportional to fibrin concentration and that the physical characteristics of the failure supported a ductile mechanism. Strain hardening as a function of percentage of strain, and strain rate was observed for both concentrations, and syneresis was observed at low strain rates for the lower fibrin concentration. Blister testing demonstrated that burst pressure and failure energy were proportional to fibrin concentration and decreased with increasing flow rate. Higher fibrin concentration demonstrated predominately compact morphology debonds with cohesive failure loci, demonstrating shear or viscous failure in a viscoelastic rubbery adhesive. The lower fibrin concentration sealant exhibited predominately fractal morphology debonds with cohesive failure loci, supporting an elastoviscous material condition. The failure mechanism for these was hypothesized and shown to be flow-induced ductile fracture. Based on these findings, the failure mechanism was

  1. Acute-on-chronic liver failure: terminology, mechanisms and management.

    Science.gov (United States)

    Sarin, Shiv K; Choudhury, Ashok

    2016-03-01

    Acute-on-chronic liver failure (ACLF) is a distinct clinical entity and differs from acute liver failure and decompensated cirrhosis in timing, presence of acute precipitant, course of disease and potential for unaided recovery. The definition involves outlining the acute and chronic insults to include a homogenous patient group with liver failure and an expected outcome in a specific timeframe. The pathophysiology of ACLF relates to persistent inflammation, immune dysregulation with initial wide-spread immune activation, a state of systematic inflammatory response syndrome and subsequent sepsis due to immune paresis. The disease severity and outcome can be predicted by both hepatic and extrahepatic organ failure(s). Clinical recovery is expected with the use of nucleoside analogues for hepatitis B, and steroids for severe alcoholic hepatitis and, possibly, severe autoimmune hepatitis. Artificial liver support systems help remove toxins and metabolites and serve as a bridge therapy before liver transplantation. Hepatic regeneration during ongoing liver failure, although challenging, is possible through the use of growth factors. Liver transplantation remains the definitive treatment with a good outcome. Pre-emptive antiviral agents for hepatitis B before chemotherapy to prevent viral reactivation and caution in using potentially hepatotoxic drugs can prevent the development of ACLF.

  2. PBFA-2 vacuum insulator stack failure mechanisms

    Science.gov (United States)

    Sweeney, M. A.

    The BPFA-II accelerator includes a large-radius, vertical-axis vacuum insulator stack. The possible failure of the acrylic rings in the stack from electron- or gamma-induced charge buildup is being evaluated. The induced static charges could remain for many hours, and either type of irradiation might cause dendrites to form. Aluminum grading rings sandwiched between the acrylic affect charge accumulation; the acrylic would preferentially break down to these grading rings. The charge buildup and the bremsstrahlung dose could depend critically upon the directionality and position of the electron loss. The effects of electron loss that occurs in the vicinity of the ion diode, where the electrons have energies of about 30 MeV are considered. Monte Carlo electron-photon transport calculations indicate that the bremsstrahlung dose expected in an acrylic ring once diode experiments begin in 1986 could be as much as 5 krads per shot, with roughly half of the photon energy above 5 MeV. Moreover, the calculation indicate that the charge deposition in an individual acrylic ring might exceed 2x10 to the 11 electrons/sq cm.

  3. Preoperative Prevention of Heart Failure in Noncardiac Surgery

    Directory of Open Access Journals (Sweden)

    V. V. Likhvantsev

    2016-01-01

    Full Text Available Congestive heart failure is consistently associated with adverse outcomes, and is characterized by a twofold increase in mortality in noncardiac surgery. In this regard, developing the methods aimed to prevent and treatacute heart failure (AHF in the intraoperative period remain a challenging problem.Objective. To evaluate the efficacy of preoperative levosimendan infusion in reduction both mortality and duration of treatment of elderly patients with reduced left ventricular ejection fraction in noncardiac surgery.Material and Methods. Design: Multicenter blind randomized placebocontrolled study. Patients: 81 patients operated on abdominal organs. The main endpoint of the study: The length of stay in the Intensive Care Unit (ICU and at the hospital were chosen as the primary endpoints. The secondary endpoints of the study were 30 day and annual mortality, the rate of acute myocardial infarction and stroke.Results. Levosimendan infusion at a rate of 0,05 μg/kg/min — 0,1 μg/kg/min to patients with low left ven tricular ejection fraction just before the surgery reduced the length of stay in ICU for 2 days and required hospital stay for 3 days. NTproBNP showed the best ratio of sensitivity/specificity in predicting 30day mortality in cumulative group: AUC=0,86 (90,77 to 0,93, P<0,0001. From other indicators the most informative were the Inotropes scoring, no change or decrease of a left ventricular ejection fraction, and cardiac index.Conclusion. To reduce perioperative mortality, the intravenous infusion of levosimendan at a rate of 0,05—0,1 μg/kg/min in elderly patients with low left ventricular ejection fraction is recommened as a preoperative preparation the day before the alleged noncardiac surgery.

  4. Diabetes mellitus and renal failure: Prevention and management

    Directory of Open Access Journals (Sweden)

    Hamid Nasri

    2015-01-01

    Full Text Available Nowadays, diabetes mellitus (DM and hypertension are considered as the most common causes of end-stage renal disease (ESRD. In this paper, other than presenting the role of DM in ESRD, glucose metabolism and the management of hyperglycemia in these patients are reviewed. Although in several large studies there was no significant relationship found between tight glycemic control and the survival of ESRD patients, it is recommended that glycemic control be considered as the main therapeutic goal in the treatment of these patients to prevent damage to other organs. Glycemic control is perfect when fasting blood sugar is less than 140 mg/dL, 1-h postprandial blood glucose is less than 200 mg/dL, and glycosylated hemoglobin (HbA1c is 6-7 in patients with type 1 diabetes and 7-8 in patients with type 2 diabetes. Administration of metformin should be avoided in chronic renal failure (CRF because of lactic acidosis, the potentially fatal complication of metformin, but glipizide and repaglinide seem to be good choices.

  5. [Hypercapnic respiratory failure. Pathophysiology, indications for mechanical ventilation and management].

    Science.gov (United States)

    Kreppein, U; Litterst, P; Westhoff, M

    2016-04-01

    Acute hypercapnic respiratory failure is mostly seen in patients with chronic obstructive pulmonary disease (COPD) and obesity hypoventilation syndrome (OHS). Depending on the underlying cause it may be associated with hypoxemic respiratory failure and places high demands on mechanical ventilation. Presentation of the current knowledge on indications and management of mechanical ventilation in patients with hypercapnic respiratory failure. Review of the literature. Important by the selection of mechanical ventilation procedures is recognition of the predominant pathophysiological component. In hypercapnic respiratory failure with a pH pathophysiological situation in patients with OHS or overlap syndrome. If severe respiratory acidosis and hypercapnia cannot be managed by mechanical ventilation therapy alone extracorporeal venous CO2 removal may be necessary. Reports on this approach in awake patients are available. The use of NIV is the predominant treatment in patients with hypercapnic respiratory failure but close monitoring is necessary in order not to miss the indications for intubation and invasive ventilation. Methods of extracorporeal CO2 removal especially in awake patients need further evaluation.

  6. Rockfall failure mechanisms in Yosemite Valley, California (USA)

    Science.gov (United States)

    Matasci, Battista; Guerin, Antoine; Carrea, Dario; Stock, Greg M.; Jaboyedoff, Michel; Collins, Brian

    2014-05-01

    Rockfall hazard is especially high in Yosemite Valley, with tens of rockfalls inventoried every year. A rockfall on 5 October 2013 from Ahwiyah Point consisted of a volume of 740 cubic meters and occurred within the perimeter of a larger event on 28 March 2009 that released 25'400 cubic meters of rock (Zimmer et al., 2012). In both events (2009 and 2013), the initial rockfall volumes dislodged a second one approximately equivalent in size by impacting the cliff below the source area during the fall. Rock fragments of up to several cubic meters were deposited on the talus slope, damaging a heavily used and recently reconstructed hiking path. We performed extensive mapping of structural features for several cliffs of Yosemite Valley to improve the assessment of the most susceptible rockfall areas. In particular we mapped and characterized the main brittle structures, the exfoliation joints and the failure mechanisms of the past rockfalls. Several failure mechanisms exist in Yosemite including the propagation of brittle structures that may lead to tensile, planar sliding, wedge sliding or toppling failures. Frequently, topographically-parallel exfoliation joints and topographically-oblique discontinuities coexist, resulting in complex failures. We also developed a methodology to examine how the distribution of joints within the cliff faces of Yosemite Valley affects overall stability with respect to the identified failure mechanisms. For these analyses, we used terrestrial laser scanning (TLS) to collect high resolution point clouds of the vertical and overhanging rock faces throughout the Valley. This provided the necessary 3D data to identify the main joint sets, perform spacing and trace length measurements, and calculate volumes of previous and potential rockfalls. We integrated this information with stability calculations to identify the likely failure mechanisms for each area of cliff and to obtain the number of potential failures per square meter of cliff face

  7. Failure mechanism and forming limit of tube axial compressive process

    Institute of Scientific and Technical Information of China (English)

    SUN Zhi-chao; YANG He

    2006-01-01

    Based on minimum energy principle for plastic forming,tearing and buckling failures mechanisms are explored and criteria for them are developed by theoretical analysis and experiment. Combined with finite element software developed forming limit and effects of process parameters on failures are investigated and proper parameters for stable forming are determined. The results show that: 1) The failures and forming limit are mainly determined by geometry and materials parameters of tube blank,fillet radius or half conical angle of die. For the process under fillet die,there exists a maximum fillet radius within which no tearing failure happens,and a maximum radius and a minimum radius range within which no buckling failure happens. For the process under conical die,there exists a maximum and minimum half conical angle range within which no tearing and buckling failures occur. 2) For both forming processes,the higher the value of material strain hardening exponent or the lower the value of relative thickness,the more impossible for tearing and buckling failures to occur,and the larger the ranges of fillet radius and half conical angle. The experiment results verify the reliability and practicability of this research.

  8. Li-ion Battery Separators, Mechanical Integrity and Failure Mechanisms Leading to Soft and Hard Internal Shorts

    Science.gov (United States)

    Zhang, Xiaowei; Sahraei, Elham; Wang, Kai

    2016-09-01

    Separator integrity is an important factor in preventing internal short circuit in lithium-ion batteries. Local penetration tests (nail or conical punch) often produce presumably sporadic results, where in exactly similar cell and test set-ups one cell goes to thermal runaway while the other shows minimal reactions. We conducted an experimental study of the separators under mechanical loading, and discovered two distinct deformation and failure mechanisms, which could explain the difference in short circuit characteristics of otherwise similar tests. Additionally, by investigation of failure modes, we provided a hypothesis about the process of formation of local “soft short circuits” in cells with undetectable failure. Finally, we proposed a criterion for predicting onset of soft short from experimental data.

  9. Electrical failure during cardiopulmonary bypass: an evaluation of incidence, causes, management and guidelines for preventative measures.

    LENUS (Irish Health Repository)

    Hargrove, M

    2012-02-03

    The incidence of electrical failure during cardiopulmonary bypass (CPB) has been reported to occur in approximately 1 per 1000 cases. While the resultant morbidity and mortality is low, electrical failure is a life-threatening scenario. We report three major electrical failures during CPB in a patient population of 3500 over a 15-year period. These cases involved mains failure and generator shut down, mains failure and generator power surge, and failure of the uninterruptable power supply (UPS), which caused protected sockets to shut down. Protocols for preventative maintenance, necessary equipment, battery backup and guidelines for the successful management of such accidents during CPB are discussed.

  10. Mechanical properties and failure mechanisms of carbon fiber reinforced epoxy laminated composites

    Energy Technology Data Exchange (ETDEWEB)

    Thissell, W.R.; Zurek, A.K.; Addessio, F.

    1995-09-01

    The mechanical behavior of quasi-isotropic and unidirectional epoxy-matrix carbon-fiber laminated composites subjected compressive loading at strain rates of 10{sup {minus}3} and 2000 s{sup {minus}1} are described. Failure in the studied composites was dominated by delamination which proceeded by brittle fracture of the epoxy-matrix. The matrix-fiber bonding in these composites is very strong and prevented the occurrence of significant fiber-pullout. The mode I delamination strain energy release rate of the unidirectional composites was determined using the double cantilever beam and hole in plate compression method. The DCB method indicated a significant R curve effect attributed to fiber bridging while the presently available hole in plate analytical methods show questionable validity for highly anisotropic materials.

  11. Mechanical properties, microscopy, and failure mechanisms of carbon fiber reinforced epoxy laminated composites

    Energy Technology Data Exchange (ETDEWEB)

    Thissell, W.R.; Zurek, A.K.; Addessio, F.

    1995-12-31

    The mechanical behavior of quasi-isotropic and unidirectional epoxy- matrix carbon-fiber laminated composites subjected to compressive loading at strain rates of 10{sup {minus}3} and 2000 s{sup {minus}1} are described. Failure in the studied composites was dominated by delamination which proceeded by brittle fracture of the epoxy matrix. The matrix-fiber bonding in these composites is very strong and prevented the occurrence of significant fiber-pullout. The mode I delamination strain energy release rate of the unidirectional composites was determined using the double cantilever beam and hole in plate compression methods. The DCB method indicated a significant R curve effect attributed to fiber bridging while the presently available hole in plate analytical methods show questionable validity for highly anisotropic materials.

  12. Numerical assessment of failure mechanisms in fibre metal laminates

    NARCIS (Netherlands)

    Hashagen, F.; De Borst, R.

    1998-01-01

    In this contribution numerical models are discussed for describing failure mechanisms in fibre metal laminates. Fibre metal laminates form a new class of materials which are considered for a possible application to the fuselage of future aircraft generations. The intensive experimental analyses of t

  13. Analysis of soft rock mineral components and roadway failure mechanism

    Institute of Scientific and Technical Information of China (English)

    CHEN Jie

    2001-01-01

    The mineral components and microstructure of soft rock sampled from ro adway floor in Xiagou pit are determined by X-ray diffraction and scanning elec t ron microscope. Combined with the test of expansion and water softening prop erty of the soft rock, the roadway failure mechanism is analyzed, and the reason able repair supporting principle of roadway is put forward.

  14. Mechanical modelling of transient- to- failure SFR fuel cladding

    Energy Technology Data Exchange (ETDEWEB)

    Feria, F.; Herranz, L. E.

    2014-07-01

    The response of Sodium Fast Reactor (SFR) fuel rods to transient accident conditions is an important safety concern. During transients the cladding strain caused by the stress due to pellet cladding mechanical interaction (PCMI) can lead to failure. Due to the fact that SFR fuel rods are commonly clad with strengthened material made of stainless steel (SS), cladding is usually treated as an elastic-perfectly-plastic material. However, viscoplastic behaviour can contribute to mechanical strain at high temperature (> 1000 K). (Author)

  15. Deformation and failure mechanisms in metal matrix composites

    Science.gov (United States)

    Newaz, G.; Majumdar, B. S.

    1991-01-01

    An investigation was undertaken to determine the key deformation mechanisms and their interaction leading to failure of both 0 degree and 90 degree Ti 15-3/SCS-6 laminae under monotonic loading. The experimental results suggest that inelastic deformation in the 0-degree lamina is dominated by plastic deformation and that in the 90-degree lamina is dominated by both fiber-matrix debonding and plasticity. The loading-unloading response, monitoring of Poisson's ratio and microscopy were utilized to identify the key deformation mechanisms. The sequence of deformation mechanisms leading to failure are identified for both the 0 and the 90-degree specimens. The threshold strains for plasticity or damage which are referred to as 'microdeformation' in the 0 deg and 90 deg laminae are approximately 0.004 and 0.002, respectively, at room temperature. These strain levels may be considered critical in initiation based structural design with these composites.

  16. Register of experts for information on mechanics of structural failure

    Science.gov (United States)

    Carpenter, J. L., Jr.; Stuhrke, W. F.

    1975-01-01

    This register is comprised of a list of approximately 300 experts from approximately 90 organizations who have published results of theoretical and/or experimental research related to six problem areas in the mechanics of structural failure: (1) life prediction for structural materials, (2) fracture toughness testing, (3) fracture mechanics analysis; (4) hydrogen embrittlement; (5) protective coatings; and (6) composite materials. The criteria for the selection of names for the register are recent contributions to the literature, participation in or support of relevant research programs, and referral by peers. Each author included is listed by organizational affiliation, address, and principal field of expertise. The purpose of the register is to present, in easy reference form, sources for dependable information regarding failure modes and mechanisms of aerospace structures. The register includes two indexes; an alphabetical listing of the experts and an alphabetical listing of the organizations with whom they are affiliated.

  17. Exercise-induced rhabdomyolysis mechanisms and prevention: A literature review

    Directory of Open Access Journals (Sweden)

    Jooyoung Kim

    2016-09-01

    Full Text Available Exercise-induced rhabdomyolysis (exRML, a pathophysiological condition of skeletal muscle cell damage that may cause acute renal failure and in some cases death. Increased Ca2+ level in cells along with functional degradation of cell signaling system and cell matrix have been suggested as the major pathological mechanisms associated with exRML. The onset of exRML may be exhibited in athletes as well as in general population. Previous studies have reported that possible causes of exRML were associated with excessive eccentric contractions in high temperature, abnormal electrolytes balance, and nutritional deficiencies possible genetic defects. However, the underlying mechanisms of exRML have not been clearly established among health professionals or sports medicine personnel. Therefore, we reviewed the possible mechanisms and correlated prevention of exRML, while providing useful and practical information for the athlete and general exercising population.

  18. Preventing school failure: the physician as child advocate.

    Science.gov (United States)

    Landman, G B

    1986-08-01

    Attending school heralds the end of the relative protection and nurture of home life. During the school day, a child experiences successes and failures that portend future feelings of self-worth and self-esteem. Usually children experiencing difficulty at school are identified by teachers, however, children are overlooked. When they are and subsequently experience chronic failure and frustration, long-term morbidity may ensue. Ideally, methods to identify potential learning problems should be available. Unfortunately, the state of the art does not allow accurate identification of problems before they occur. After any number of screening tests, we can accurately predict school successes, but predicting failure is elusive. Early school failure, however, like many maladies, can be diagnosed, particularly if a physician has a high index of suspicion and looks for signs and symptoms of ongoing failure and frustration. Family history, neonatal course, presence of minor congenital anomalies and soft neurological signs, attention problems and lack of age-appropriate processing skills in the preschool period should place a child at risk. Close observation should designate those children who fail to mobilize associated strengths that maintain development. Early intervention will reduce morbidity associated with academic difficulty. Longitudinally, reduction of chronic failure may be the most crucial intervention. The unfortunate cycle of developmental dysfunction leading to school failure and lowered self esteem with subsequent social pathology and delinquency is well known. To the extent that physicians are able to ensure appropriate school services for children experiencing failure, this cycle can be short circuited, adding significantly to the physician's traditional armamentarium.

  19. Failure Mechanisms of a Gold Microelectrode in Bioelectronics Applications

    Directory of Open Access Journals (Sweden)

    Jonghun Kim

    2015-01-01

    Full Text Available The generation, growth, and collapse of tiny bubbles are inevitable for a microelectrode working in aqueous environment, thus resulting in physical damages on the microelectrode. The failure mechanisms of a microelectrode induced by tiny bubble collapsing are investigated by generating tiny hydrogen bubbles on a gold microelectrode through deionized water electrolysis. The surface of the microelectrode is modified with a thiol-functionalized arginine-glycine-aspartic acid peptide to generate perfectly spherical bubbles in proximity of the surface. The failure of an Au microelectrode is governed by two damage mechanisms, depending on the thickness of the microelectrode: a water-hammer pressure due to the violent collapse of a single large bubble, formed through merging of small bubbles, for ultrathin Au microelectrodes of 40–60 nm in thickness, and an energy accumulation resulting from the repetitive collapse of tiny bubbles for thick Au microelectrodes of 100–120 nm.

  20. Deformation and failure mechanism of slope in three dimensions

    Directory of Open Access Journals (Sweden)

    Yingfa Lu

    2015-04-01

    Full Text Available Understanding three-dimensional (3D slope deformation and failure mechanism and corresponding stability analyses are crucially important issues in geotechnical engineering. In this paper, the mechanisms of progressive failure with thrust-type and pull-type landslides are described in detail. It is considered that the post-failure stress state and the pre-peak stress state may occur at different regions of a landslide body with deformation development, and a critical stress state element (or the soil slice block exists between the post-failure stress state and the pre-peak stress state regions. In this regard, two sorts of failure modes are suggested for the thrust-type and three sorts for pull-type landslides, based on the characteristics of shear stress and strain (or tensile stress and strain. Accordingly, a new joint constitutive model (JCM is proposed based on the current stability analytical theories, and it can be used to describe the mechanical behaviors of geo-materials with softening properties. Five methods, i.e. CSRM (comprehensive sliding resistance method, MTM (main thrust method, CDM (comprehensive displacement method, SDM (surplus displacement method, and MPM (main pull method, for slope stability calculation are proposed. The S-shaped curve of monitored displacement vs. time is presented for different points on the sliding surface during progressive failure process of landslide, and the relationship between the displacement of different points on the sliding surface and height of landslide body is regarded as the parabolic curve. The comparisons between the predicted and observed load–displacement and displacement–time relations of the points on the sliding surface are conducted. The classification of stable/unstable displacement–time curves is proposed. The definition of the main sliding direction of a landslide is also suggested in such a way that the failure body of landslide (simplified as “collapse body” is only

  1. Dispersed Trading and the Prevention of Market Failure

    DEFF Research Database (Denmark)

    Porter, David C.; Tanggaard, Carsten; G. Weaver, Daniel

    With augmented demands on power grids resulting in longer and larger blackouts combined with heightened concerns of terrorist attacks, trading institutions and policy makers have widened their search for systems that avoid market failure during these disturbing events. We provide insight into thi......With augmented demands on power grids resulting in longer and larger blackouts combined with heightened concerns of terrorist attacks, trading institutions and policy makers have widened their search for systems that avoid market failure during these disturbing events. We provide insight...... into this issue by examining trading behavior at the Copenhagen Stock Exchange during a major blackout. We find that although market quality declined, markets remained functional and some price discovery occurred during the blackout period suggesting that the NOREX structure of interlinked trading systems...... combined with widely dispersed trading locations may be a viable means of protection against market failure during massive power disruptions or terrorist attacks....

  2. Dispersed trading and the prevention of market failure

    DEFF Research Database (Denmark)

    Porter, David C.; Tanggaard, Carsten; Weaver, Daniel G.

    2008-01-01

    With augmented demands on power grids resulting in longer and larger blackouts combined with heightened concerns of terrorist attacks, trading institutions and policy makers have widened their search for systems that avoid market failure during these disturbing events. We provide insight...... into this issue by examining trading behaviour at the Copenhagen Stock Exchange during a major blackout. We find that although market quality declined, markets remained functional and some price discovery occurred during the blackout period suggesting that the NOREX structure of interlinked trading systems...... combined with widely dispersed trading locations may be a viable means of protection against market failure during massive power disruptions or terrorist attacks....

  3. Dispersed Trading and the Prevention of Market Failure

    DEFF Research Database (Denmark)

    Porter, David C.; Tanggaard, Carsten; G. Weaver, Daniel

    With augmented demands on power grids resulting in longer and larger blackouts combined with heightened concerns of terrorist attacks, trading institutions and policy makers have widened their search for systems that avoid market failure during these disturbing events. We provide insight...... into this issue by examining trading behavior at the Copenhagen Stock Exchange during a major blackout. We find that although market quality declined, markets remained functional and some price discovery occurred during the blackout period suggesting that the NOREX structure of interlinked trading systems...... combined with widely dispersed trading locations may be a viable means of protection against market failure during massive power disruptions or terrorist attacks....

  4. Dispersed trading and the prevention of market failure

    DEFF Research Database (Denmark)

    Porter, David C.; Tanggaard, Carsten; Weaver, Daniel G.

    2008-01-01

    With augmented demands on power grids resulting in longer and larger blackouts combined with heightened concerns of terrorist attacks, trading institutions and policy makers have widened their search for systems that avoid market failure during these disturbing events. We provide insight...... into this issue by examining trading behaviour at the Copenhagen Stock Exchange during a major blackout. We find that although market quality declined, markets remained functional and some price discovery occurred during the blackout period suggesting that the NOREX structure of interlinked trading systems...... combined with widely dispersed trading locations may be a viable means of protection against market failure during massive power disruptions or terrorist attacks....

  5. Failure Mechanisms of Ana Slide, Eivissa Channel, Western Mediterranean Sea

    Science.gov (United States)

    Lafuerza, S.; Sultan, N.; Canals, M.; Lastras, G.; Cattaneo, A.; Frigola, J.; Costa, S.; Berndt, C.

    2011-12-01

    Fluid seepage has been considered as the most plausible explanation to account for slope instabilities in the Eivissa Channel in between the Iberian Peninsula and the Balearic Islands, Western Mediterranean Sea. In situ geotechnical tests and sediment cores obtained in the Ana Slide area, on the Balearic slope of the Eivissa Channel, suggest that the development of the basal failure surface (BFS) was favoured by contrasting hydro-mechanical properties between a coarse unit (U7) charged with methane and a fine-grained unit above (U6). The presence of past methane seepage has been inferred from high magnetic susceptibility values found in sediments from the headwall area and is supported by seismic reflection data. Geotechnical data from piezocone tests, laboratory analyses and numerical calculations indicate degradation of the undrained shear strength generated by methane exsolution and expansion as the only plausible mechanism to explain the origin of Ana Slide. The probability of failure for different critical failure surfaces has been investigated by using the SAMU-3D slope stability model taking into account the role of free gas in the development of the landslide. According to SAMU-3D, the most probable failure surface is related to a minimum degradation of the undrained shear strength of units U6 and U7 of 95% and a basal failure surface developed at the base of U6, which acted as a weak layer. Wheeler's theory suggests that 9% of free-gas saturation in U7 is enough to reduce the undrained shear strength by 95%. However, using the theory of the undrained equilibrium behaviour of gassy sediments we conclude that the excess fluid pressure generated by gas exsolution and expansion is not relevant to bring the slope to fail.

  6. Dynamic tensile failure mechanics of the musculoskeletal neck using a cadaver model.

    Science.gov (United States)

    Yliniemi, Eno M; Pellettiere, Joseph A; Doczy, Erica J; Nuckley, David J; Perry, Chris E; Ching, Randal P

    2009-05-01

    Although the catapult phase of pilot ejections has been well characterized in terms of human response to compressive forces, the effect of the forces on the human body during the ensuing ejection phases (including windblast and parachute opening shock) has not been thoroughly investigated. Both windblast and parachute opening shock have been shown to induce dynamic tensile forces in the human cervical spine. However, the human tolerance to such loading is not well known. Therefore, the main objective of this research project was to measure human tensile neck failure mechanics to provide data for computational modeling, anthropometric test device development, and improved tensile injury criteria. Twelve human cadaver specimens, including four females and eight males with a mean age of 50.1+/-9 years, were subjected to dynamic tensile loading through the musculoskeletal neck until failure occurred. Failure load, failure strain, and tensile stiffness were measured and correlated with injury type and location. The mean failure load for the 12 specimens was 3100+/-645 N, mean failure strain was 16.7+/-5.4%, and mean tensile stiffness was 172+/-54.5 N/mm. The majority of injuries (8) occurred in the upper cervical spine (Oc-C3), and none took place in the midcervical region (C3-C5). The results of this study assist in filling the existing void in dynamic tensile injury data and will aid in developing improved neck injury prevention strategies.

  7. Failure and preventive costs of mastitis on Dutch dairy farms

    NARCIS (Netherlands)

    Soest, van Felix J.S.; Santman-Berends, Inge M.G.A.; Lam, Theo J.G.M.; Hogeveen, Henk

    2016-01-01

    Mastitis is an important disease from an economic perspective, but most cost assessments of mastitis include only the direct costs associated with the disease (e.g., production losses, culling, and treatment), which we call failure costs (FC). However, farmers also invest time and money in

  8. Failure and preventive costs of mastitis on Dutch dairy farms

    NARCIS (Netherlands)

    van Soest, Felix J S; Santman-Berends, Inge M G A; Lam, Theo J G M|info:eu-repo/dai/nl/14686820X; Hogeveen, Henk

    2016-01-01

    Mastitis is an important disease from an economic perspective, but most cost assessments of mastitis include only the direct costs associated with the disease (e.g., production losses, culling, and treatment), which we call failure costs (FC). However, farmers also invest time and money in

  9. Preventing Reading Failure: A Review of Five Effective Programs.

    Science.gov (United States)

    Pikulski, John J.

    1994-01-01

    Describes five programs of early intervention for the prevention of reading problems (Success for All, the Winston-Salem Project, Early Intervention in Reading, the Boulder Project, and Reading Recovery). Compares these five programs on a number of dimensions, identifying common features that seem related to preventing reading problems. Draws…

  10. Bibliography of information on mechanics of structural failure

    Science.gov (United States)

    Carpenter, J. L., Jr.; Moya, N.; Shaffer, R. A.; Smith, D. M.

    1973-01-01

    A bibliography of approximately 1500 reference citations related to six problem areas in the mechanics of failure in aerospace structures is presented. The bibliography represents a search of the literature published in the ten year period 1962-1972 and is largely limited to documents published in the United States. Listings are subdivided into the six problem areas: (1) life prediction of structural materials; (2) fracture toughness data; (3) fracture mechanics analysis; (4) hydrogen embrittlement; (5) protective coatings; and (6) composite materials. An author index is included.

  11. Failure mechanism and prevention measures of Majia potential unstable rock mass in Muping%穆坪镇马家危岩体破坏机制及治理措施研究

    Institute of Scientific and Technical Information of China (English)

    王宏益; 任鸿凌

    2011-01-01

    At present,Majia potential unstable rock masses seriously deformed and posed a great threat to the free flowing on S210 provincial slope road and residents' safty.It may result in even more serious harm.According to structure characteristics,signs of deformation and failure of potential unstable rock masses,this paper analyzes its two kinds of failure mechanisms: rip-slip failure mode and rip-dumping failure mode.On this basis,through energy conservation law and the laws of kinematics,the paper analyzes movement characteristic of falling rock mass,the largest height of bouncing of falling rock mass is 2.9 m and the largest kinetic energy is 1 289.54 kJ.Then,combined with the construction conditions,we use RXI-150 type passive protective net to ensure the free flowing of provincial road and the residents' safety.%马家危岩体目前变形加剧,已严重威胁坡脚省道S210的畅通和居民安全,可能造成更严重的危害。根据危岩体结构特征和变形破坏迹象,分析了危岩体的2种破坏机制:拉裂—滑移式和拉裂—倾倒式。在此基础上,运用能量守恒定律和运动学规律研究危岩体失稳落石运动特征,落石运动到坡脚的最大弹跳高度为2.9 m,最大动能为1 289.54 kJ。结合施工条件,采用RXI-150型被动网来拦截落石,确保省道畅通和居民安全。

  12. Priming as a means of preventing skill failure under pressure

    OpenAIRE

    Ashford, K; Jackson, RC

    2010-01-01

    Copyright @ 2010 Human Kinetics The present study examined the effectiveness of a priming paradigm in alleviating skill failure under stress. The priming intervention took the form of a scrambled sentence task. Experiment 1: Thirty-four skilled field-hockey players performed a dribbling task in low-and high-pressure situations under single task, skill-focused, and priming conditions. Results revealed a significant increase in performance time from low to high pressure. In addition, perform...

  13. Preventing Intelligence Failures in an Unpredictable 21st Century

    Science.gov (United States)

    2012-03-20

    environment. The IC must be both adaptable and flexible in the face of new external threats and inevitable internal change. In the words of Louis Pasteur ...NOTES 14. ABSTRACT Intelligence is a fundamental element of national security; however, history is littered with intelligence failures...Intelligence is about gathering information to inform our decisions and make better choices. Ultimately, intelligence will always be imperfect and, as history

  14. Octreotide May Prevent Ultrafiltration Failure in Experimental Peritonitis Model

    Directory of Open Access Journals (Sweden)

    Ender HÜR

    2011-01-01

    Full Text Available OBJECTIVE: Ultrafiltration (UF failure is a frequent complication of peritoneal dialysis peritonitis. Octreotide (OCT has antiproliferative effects on many cells. The present study aimed to investigate the effect of OCT (administered locally or systemically on peritoneal alterations induced by bacterial peritonitis. MATERIAL and METHODS: Forty-two non-uremic female rats, weighing 160-180 g, were divided into four groups receiving no treatment (Control, n=12, peritonitis group (received 1.5 ml suspension of E. coli (107 CFU/ml (E.coli, n=12, and two treatment groups that received E.coli + 50 mcg/kg OCT (local OCT, n=10 intraperitoneally (IP and (systemic OCT, n=8 subcutaneously. After six hours, a one-hour PET was performed with 20 ml 3.86% PD solution; the D1/D0 glucose, UF volume, dialysate cell count, dialysate protein, TGF-β1, VEGF and IL-1β levels were determined. RESULTS: Exposure to E. coli causes bacterial peritonitis with increase in peritoneal permeability leading to rapid dissipation of the glucose gradient and UF failure. IP administration of OCT led to attenuation of UF failure by inhibiting local TGF-β1 production. Both local and systemic administration of OCT decreased dialysate cell count and maintained UF. CONCLUSION: Local or systemic OCT administration may help to preserve peritoneal viability and UF capacity by inhibiting cell infiltration to the peritoneal cavity and decreasing dialysate cell count during peritonitis. In the long-term, it can decrease peritoneal fibrosis.

  15. Failure mechanisms and electromechanical coupling in semiconducting nanowires

    Directory of Open Access Journals (Sweden)

    Peng B.

    2010-06-01

    Full Text Available One dimensional nanostructures, like nanowires and nanotubes, are increasingly being researched for the development of next generation devices like logic gates, transistors, and solar cells. In particular, semiconducting nanowires with a nonsymmetric wurtzitic crystal structure, such as zinc oxide (ZnO and gallium nitride (GaN, have drawn immense research interests due to their electromechanical coupling. The designing of the future nanowire-based devices requires component-level characterization of individual nanowires. In this paper, we present a unique experimental set-up to characterize the mechanical and electromechanical behaviour of individual nanowires. Using this set-up and complementary atomistic simulations, mechanical properties of ZnO nanowires and electromechanical properties of GaN nanowires were investigated. In ZnO nanowires, elastic modulus was found to depend on nanowire diameter decreasing from 190 GPa to 140 GPa as the wire diameter increased from 5 nm to 80 nm. Inconsistent failure mechanisms were observed in ZnO nanowires. Experiments revealed a brittle fracture, whereas simulations using a pairwise potential predicted a phase transformation prior to failure. This inconsistency is addressed in detail from an experimental as well as computational perspective. Lastly, in addition to mechanical properties, preliminary results on the electromechanical properties of gallium nitride nanowires are also reported. Initial investigations reveal that the piezoresistive and piezoelectric behaviour of nanowires is different from bulk gallium nitride.

  16. Designing a safer process to prevent retained surgical sponges: a healthcare failure mode and effect analysis.

    Science.gov (United States)

    Steelman, Victoria M; Cullen, Joseph J

    2011-08-01

    A retained surgical sponge is a sentinel event that can result in serious negative outcomes for the patient. Current standards rely on manual counting, the accuracy of which may be suspect, yet little is known about why counting fails to prevent retained sponges. The objectives of this project were to describe perioperative processes to prevent retained sponges after elective abdominal surgery; to identify potential failures; and to rate the causes, probability, and severity of these failures. A total of 57 potential failures were identified, associated with room preparation, the initial count, adding sponges, removing sponges, the first closing count, and the final closing count. The most frequently identified causes of failures included distraction, multitasking, not following procedure, and time pressure. Most of the failures are not likely to be affected by an educational intervention, so additional technological controls should be considered in efforts to improve safety.

  17. [Early detection, prevention and management of renal failure in liver transplantation].

    Science.gov (United States)

    Castells, Lluís; Baliellas, Carme; Bilbao, Itxarone; Cantarell, Carme; Cruzado, Josep Maria; Esforzado, Núria; García-Valdecasas, Juan Carlos; Lladó, Laura; Rimola, Antoni; Serón, Daniel; Oppenheimer, Federico

    2014-10-01

    Renal failure is a frequent complication in liver transplant recipients and is associated with increased morbidity and mortality. A variety of risk factors for the development of renal failure in the pre- and post-transplantation periods have been described, as well as at the time of surgery. To reduce the negative impact of renal failure in this population, an active approach is required for the identification of those patients with risk factors, the implementation of preventive strategies, and the early detection of progressive deterioration of renal function. Based on published evidence and on clinical experience, this document presents a series of recommendations on monitoring RF in LT recipients, as well as on the prevention and management of acute and chronic renal failure after LT and referral of these patients to the nephrologist. In addition, this document also provides an update of the various immunosuppressive regimens tested in this population for the prevention and control of post-transplantation deterioration of renal function.

  18. Some Aspects of the Failure Mechanisms in BaTiO3-Based Multilayer Ceramic Capacitors

    Science.gov (United States)

    Liu, David Donhang; Sampson, Michael J.

    2012-01-01

    The objective of this presentation is to gain insight into possible failure mechanisms in BaTiO3-based ceramic capacitors that may be associated with the reliability degradation that accompanies a reduction in dielectric thickness, as reported by Intel Corporation in 2010. The volumetric efficiency (microF/cm3) of a multilayer ceramic capacitor (MLCC) has been shown to not increase limitlessly due to the grain size effect on the dielectric constant of ferroelectric ceramic BaTiO3 material. The reliability of an MLCC has been discussed with respect to its structure. The MLCCs with higher numbers of dielectric layers will pose more challenges for the reliability of dielectric material, which is the case for most base-metal-electrode (BME) capacitors. A number of MLCCs manufactured using both precious-metal-electrode (PME) and BME technology, with 25 V rating and various chip sizes and capacitances, were tested at accelerated stress levels. Most of these MLCCs had a failure behavior with two mixed failure modes: the well-known rapid dielectric wearout, and so-called 'early failures." The two failure modes can be distinguished when the testing data were presented and normalized at use-level using a 2-parameter Weibull plot. The early failures had a slope parameter of Beta >1, indicating that the early failures are not infant mortalities. Early failures are triggered due to external electrical overstress and become dominant as dielectric layer thickness decreases, accompanied by a dramatic reduction in reliability. This indicates that early failures are the main cause of the reliability degradation in MLCCs as dielectric layer thickness decreases. All of the early failures are characterized by an avalanche-like breakdown leakage current. The failures have been attributed to the extrinsic minor construction defects introduced during fabrication of the capacitors. A reliability model including dielectric thickness and extrinsic defect feature size is proposed in this

  19. Metformin prevents the development of chronic heart failure in the SHHF rat model.

    Science.gov (United States)

    Cittadini, Antonio; Napoli, Raffaele; Monti, Maria Gaia; Rea, Domenica; Longobardi, Salvatore; Netti, Paolo Antonio; Walser, Marion; Samà, Mariateresa; Aimaretti, Gianluca; Isgaard, Jörgen; Saccà, Luigi

    2012-04-01

    Insulin resistance is a recently identified mechanism involved in the pathophysiology of chronic heart failure (CHF). We investigated the effects of two insulin-sensitizing drugs (metformin and rosiglitazone) in a genetic model of spontaneously hypertensive, insulin-resistant rats (SHHF). Thirty SHHF rats were randomized into three treatment groups as follows: 1) metformin (100 mg/kg per day), 2) rosiglitazone (2 mg/kg per day), and 3) no drug. Ten Sprague-Dawley rats served as normal controls. At the end of the treatment period (12 months), the cardiac phenotype was characterized by histology, echocardiography, and isolated perfused heart studies. Metformin attenuated left ventricular (LV) remodeling, as shown by reduced LV volumes, wall stress, perivascular fibrosis, and cardiac lipid accumulation. Metformin improved both systolic and diastolic indices as well as myocardial mechanical efficiency, as shown by improved ability to convert metabolic energy into mechanical work. Metformin induced a marked activation of AMP-activated protein kinase, endothelial nitric oxide synthase, and vascular endothelial growth factor and reduced tumor necrosis factor-α expression and myocyte apoptosis. Rosiglitazone did not affect LV remodeling, increased perivascular fibrosis, and promoted further cardiac lipid accumulation. In conclusion, long-term treatment with metformin, but not with rosiglitazone, prevents the development of severe CHF in the SHHF model by a wide-spectrum interaction that involves molecular, structural, functional, and metabolic-energetic mechanisms.

  20. Brittle-Ductible Failure Mechanics of Concrete and Mortar

    Science.gov (United States)

    1988-10-14

    22c. OFF ICE SYMBOL (Include Arita Code, Dr. Spencer T. Wu ( 202) 767-6962 AFOSR/NA 00 FORM 1473, 83 APR EDITION OP I JAN 73 IS OBSOLETE. Ung...involves the analysis of discontinuities and is one of the 89 2 15 151 pressing issues of failure mechanics, see recent review by Bazant [I]. In the...29] Finney, J.L. (1979). "A Procedure for the Construction of Voronoi Polyhedra", J. Comp. Phyjsics, Vol. 32, pp. 137-143. [301 Bazant , Z.P., and

  1. Prevention from Dike Failure by Emergency Flood Control Measures

    Directory of Open Access Journals (Sweden)

    Koppe Baerbel

    2016-01-01

    Full Text Available The risk of failure of a flood protection system must always be taken into account. During flooding events, appropriate interim protection systems must be at hand and ready to be deployed to support weak and overloaded structures. Usually sandbags, eventually in combination with fascines and geotextiles, are in use to defend endangered dike stretches in case of emergency. Sandbags offer highly flexible employment, however the enormous personal, material and time consuming efforts required for installation and dismantling are problematic. Therefore, more effective constructions for emergency flood control are needed. Within the research projects HWS-Mobile, DeichSCHUTZ, and DeichKADE different constructions based on the use of flexible membranes have been developed or are in development to ensure easy and effective countermeasures to secure dike stretches, which are in risk of breakage. Successful applications of the developed systems have taken place during the catastrophic flood event at the river Elbe in Northern Germany in 2013.

  2. Knowledge Discovery Process for Characterization of Materials Failure Mechanism

    Science.gov (United States)

    Cios, Krzysztof J.

    1999-01-01

    It is the intent of this project to provide a platform to visualize the various data collected from stress-strain testing of composite ceramic matrix materials. The data collected from the stress-strain tests are acoustic emissions (AE). As a material is subjected to a stress-strain test, various failure mechanisms occur in the material. The recorded sounds emitted during the test may correspond to various failure mechanisms. This project, thus, will give a possible way to visualize the data and data derived from the recorded AE. The stress-strain testing was performed on several composite matrix material combinations. Each of these tests produced anywhere from 1000 to 10,000+ AE events. For each AE event recorded, several characteristics in both the time and frequency domains are created. This project has two goals. First, this project will provide a summation page for a selected waveform. This page will include all of the characteristics determined from the AE event waveform along with graphs of the AE event waveform and its corresponding Power Spectrum. The other function of this project is to retrieve and display selected AE event waveforms for comparison.

  3. Damage evolution and failure mechanisms in additively manufactured stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Carlton, Holly D., E-mail: carlton4@llnl.gov [Materials Engineering Division, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550 (United States); Haboub, Abdel [Lincoln University, Life and Physical Sciences Department, 820 Chestnut St, Jefferson City, MO 65101 (United States); Gallegos, Gilbert F. [Materials Engineering Division, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550 (United States); Parkinson, Dilworth Y.; MacDowell, Alastair A. [Advanced Light Source, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States)

    2016-01-10

    In situ tensile tests were performed on additively manufactured austenitic stainless steel to track damage evolution within the material. For these experiments Synchrotron Radiation micro-Tomography was used to measure three-dimensional pore volume, distribution, and morphology in stainless steel at the micrometer length-scale while tensile loading was applied. The results showed that porosity distribution played a larger role in affecting the fracture mechanisms than measured bulk density. Specifically, additively manufactured stainless steel specimens with large inhomogeneous void distributions displayed a flaw-dominated failure where cracks were shown to initiate at pre-existing voids, while annealed additively manufactured stainless steel specimens, which contained low porosity and randomly distributed pores, displayed fracture mechanisms that closely resembled wrought metal.

  4. Mechanisms and pathways of growth failure in primordial dwarfism

    Science.gov (United States)

    Klingseisen, Anna; Jackson, Andrew P.

    2011-01-01

    The greatest difference between species is size; however, the developmental mechanisms determining organism growth remain poorly understood. Primordial dwarfism is a group of human single-gene disorders with extreme global growth failure (which includes Seckel syndrome, microcephalic osteodysplastic primordial dwarfism I [MOPD] types I and II, and Meier-Gorlin syndrome). Ten genes have now been identified for microcephalic primordial dwarfism, encoding proteins involved in fundamental cellular processes including genome replication (ORC1 [origin recognition complex 1], ORC4, ORC6, CDT1, and CDC6), DNA damage response (ATR [ataxia-telangiectasia and Rad3-related]), mRNA splicing (U4atac), and centrosome function (CEP152, PCNT, and CPAP). Here, we review the cellular and developmental mechanisms underlying the pathogenesis of these conditions and address whether further study of these genes could provide novel insight into the physiological regulation of organism growth. PMID:21979914

  5. Mechanisms and pathways of growth failure in primordial dwarfism.

    Science.gov (United States)

    Klingseisen, Anna; Jackson, Andrew P

    2011-10-01

    The greatest difference between species is size; however, the developmental mechanisms determining organism growth remain poorly understood. Primordial dwarfism is a group of human single-gene disorders with extreme global growth failure (which includes Seckel syndrome, microcephalic osteodysplastic primordial dwarfism I [MOPD] types I and II, and Meier-Gorlin syndrome). Ten genes have now been identified for microcephalic primordial dwarfism, encoding proteins involved in fundamental cellular processes including genome replication (ORC1 [origin recognition complex 1], ORC4, ORC6, CDT1, and CDC6), DNA damage response (ATR [ataxia-telangiectasia and Rad3-related]), mRNA splicing (U4atac), and centrosome function (CEP152, PCNT, and CPAP). Here, we review the cellular and developmental mechanisms underlying the pathogenesis of these conditions and address whether further study of these genes could provide novel insight into the physiological regulation of organism growth.

  6. Mechanical Behavior and Failure Mechanism of Recycled Semi-lfexible Pavement Material

    Institute of Scientific and Technical Information of China (English)

    DING Qingjun; ZHAO Mingyu; SHEN Fan; ZHANG Xiaoqiang

    2015-01-01

    The mechanical behavior and failure mechanism of recycled semi-lfexible pavement material were investigated by different scales method. The macroscopic mechanical behavior of samples was studied by static and dynamic splitting tensile tests on mechanics testing system (MTS). The mechanical analysis in micro scale was carried out by material image analysis method and ifnite element analysis system. The strains of recycled semi-lfexible pavement material on samples surface and in each phase materials were obtained. The test results reveal that the performance of recovered asphalt binder was the major determinant on the structural stability of recycled semi-lfexible pavement material. The asphalt binder with high viscoelasticity could delay the initial cracking time and reduce the residual strain under cyclic loading conditions. The failure possibility order of each phase in recycled semi-flexible pavement material was asphalt binder, reclaimed aggregate, cement paste and virgin aggregate.

  7. An investigation of mechanical behavior and failure mechanisms of composite T-joints with transverse stitching

    Science.gov (United States)

    Stickler, Patrick Bickford

    2001-07-01

    A new low cost damage tolerant method of joining load-bearing composite structures using two-dimensional dry fabric preforms with transverse stitching and a novel fiber insertion process with resin transfer molding has recently been developed, however, knowledge of strength prediction and failure mechanisms is not well understood. In this investigation, fundamental knowledge of T-joint mechanical behavior was developed through detailed experimental, numerical, and post failure analyses. Experiments were conducted under flexure, tension, and shear loads and failed specimens were examined to discern failure modes. T-joint constituent elastic and strength properties were experimentally determined. Elastic properties were used as input to the finite element analysis and strength properties were used as limiting values in the T-joint failure analysis. Linear elastic, nonlinear elastic, and progressive damage finite element models were developed under each load condition. T-joint numerical models are shown to predict experimental behavior through ultimate load. Damage accumulation was characterized based on experimental, numerical, and post failure analyses. A parametric finite element analysis was conducted and design curves were derived to demonstrate the effect of varying key T-joint interface parameters on mechanical behavior under each load condition. Results of this research enable the application of T-joints with transverse stitching to future products and predictive finite element models developed herein reduce the structural testing required to validate these designs.

  8. Legal liability for failure to prevent pregnancy (wrongful pregnancy

    Directory of Open Access Journals (Sweden)

    Lodewicus Charl Coetzee

    2017-05-01

    Full Text Available Can the conception of a child ever constitute damage recoverable in law? This article considers the liability of healthcare practitioners for failing to prevent a pregnancy. Developments leading to the recognition of wrongful pregnancy as a cause of (legal action in South Africa (SA, are briefly outlined. The salient points of the relevant judgments by SA courts are set out to expose the rationale underlying the judgments and to highlight that recognition of liability for wrongful pregnancy resulted from an application of fair and equitable principles of general application. Conduct that could expose practitioners to liability is identified from reported cases and inferred from general principles laid down in case law.

  9. Failure of interpositional membrane to prevent recurrent arthrofibrosis.

    Science.gov (United States)

    Meehan, John P; Abbi, Gaurav

    2010-09-01

    Silicone has been used in numerous health care roles, from catheters to finger joint arthroplasties, with proven success. Its use as an interpositional membrane for the prevention of adhesions has been attempted in various anatomic sites with unpredictable results. We present a case report of a patient with recurrent arthrofibrosis requiring multiple operative procedures including manipulations under anesthesia, arthroscopies, and unicompartmental and eventual total knee replacement. After developing stiffness after total knee arthroplasty, the patient received placement of a silicone interpositional membrane with the goal of minimizing scar formation. Arthrofibrosis recurred, and only eventual removal of the membrane and correction of the underlying overstuffed patellofemoral compartment has allowed for maintained functional improvement in motion after 3 years.

  10. Failure Mechanisms in High Chrome Oxide Gasifier Refractories

    Science.gov (United States)

    Bennett, James P.; Kwong, Kyei-Sing

    2011-04-01

    Gasification is a high-temperature, high-pressure chemical process used to convert a carbon feedstock into CO and H2 (syngas) for use in power generation and the production of chemicals. It is also a leading candidate as a source of hydrogen in a hydrogen economy and is one of several technologies expected to see increased use in advanced fossil fuel power systems in the future. Gasification is being evaluated because of its high efficiency, its ability to capture CO2 for sequestration or reuse in other applications, and its potential for carbon feedstock fuel flexibility. At the heart of the gasification process is a gasifier, a high pressure chemical reaction vessel used to contain the interactions between carbon and water in a shortage of oxygen, producing syngas. The gasifier is lined with high chrome oxide materials to protect the containment vessel. Gasifiers are complex systems, and failure of the refractories used to line them was identified by industry as a limitation to their reliability and availability and to their increased use. NETL researchers have examined spent high-Cr2O3 (over 90 pct Cr2O3) refractories from numerous gasifiers to determine in-service failure mechanisms. This analysis revealed that premature failure of the high chrome oxide refractories was related to ash in the carbon feedstock, which liquefies during gasification and interacts with the refractories, leading to wear by chemical dissolution or spalling (structural and chemical). A discussion of this postmortem wear of spent refractory materials and of thermodynamic modeling used to explain microstructural changes leading to wear are explained in this article. This information will serve the basis to develop improved performance refractory materials.

  11. Periodic imperfect preventive maintenance with two categories of competing failure modes

    Energy Technology Data Exchange (ETDEWEB)

    Zequeira, R.I. [ISTIT FRE CNRS 2732-Equipe LM2S, Universite de Technologie de Troyes, 12 rue Marie Curie, BP 2060, 10010 Troyes (France)]. E-mail: romulo.zequeira@utt.fr; Berenguer, C. [ISTIT FRE CNRS 2732-Equipe LM2S, Universite de Technologie de Troyes, 12 rue Marie Curie, BP 2060, 10010 Troyes (France)]. E-mail: christophe.berenguer@utt.fr

    2006-04-15

    A maintenance policy is studied for a system with two types of failure modes: maintainable and non-maintainable. The quality of maintenance actions is modelled by its effect on the system failure rate. Preventive maintenance actions restore the system to a condition between as good as new and as bad as immediately before the maintenance action. The model presented permits to study the equipment condition improvement (improvement factor) as a function of the time of the preventive maintenance action. The determination of the maintenance policy, which minimizes the cost rate for an infinite time span, is examined. Conditions are given under which a unique optimal policy exists.

  12. Optical strain for monitoring of concrete failure mechanism with discontinuity.

    Science.gov (United States)

    Deb, Debasis; Bhattacharjee, Sudipta

    2015-12-10

    Finite-element-based digital image correlation (FEM-DIC) is one of the most widely used noncontact techniques in the field of experimental mechanics for measurement of deformation/strain. In this paper, the FEM-DIC method is refined by introducing the concept of multilevel extended digital image correlation (X-DIC), which also can capture deformation across discontinuity planes if they exist in images. Using regular and enhanced displacements at each node, strain tensors are estimated by applying the concept of smooth particle hydrodynamics (SPH). Numerical works are carried out to check the accuracy level of the developed algorithm by considering discrete discontinuity on the surface of a sample. Work is further extended to determine displacements and strains developed at the surface of several cubical concrete samples under uniaxial loading conditions. The tests are conducted until fractures are developed in the post-failure region. Using the concept of cumulative effective strain, a parameter is identified, which can be used as a precursor in the object failure process.

  13. A failure modes, mechanisms, and effects analysis (FMMEA) of lithium-ion batteries

    Science.gov (United States)

    Hendricks, Christopher; Williard, Nick; Mathew, Sony; Pecht, Michael

    2015-11-01

    Lithium-ion batteries are popular energy storage devices for a wide variety of applications. As batteries have transitioned from being used in portable electronics to being used in longer lifetime and more safety-critical applications, such as electric vehicles (EVs) and aircraft, the cost of failure has become more significant both in terms of liability as well as the cost of replacement. Failure modes, mechanisms, and effects analysis (FMMEA) provides a rigorous framework to define the ways in which lithium-ion batteries can fail, how failures can be detected, what processes cause the failures, and how to model failures for failure prediction. This enables a physics-of-failure (PoF) approach to battery life prediction that takes into account life cycle conditions, multiple failure mechanisms, and their effects on battery health and safety. This paper presents an FMMEA of battery failure and describes how this process enables improved battery failure mitigation control strategies.

  14. Public health and the prevention of obesity: failure or success?

    Directory of Open Access Journals (Sweden)

    Javier Aranceta Bartrina

    Full Text Available In recent decades, obesity has become a major public health problem in developed societies and economies in transition. Rapid social changes that have occurred since the mid 20th century prompted major changes in eating habits and lifestyles, with the gradual abandonment of traditional dietary patterns and culinary techniques, significant decrease in physical activity and increased sedentary time, giving as result in an imbalance in the energy balance. Obesity is a risk factor for many chronic diseases. There is evidence that childhood obesity influences adult health condition. Additionally, obesity in children affects their physical, emotional and social wellbeing. According to some estimates the cost of obesity may represent up to 12% of health cost in some countries. Many actions have been developed since around the year 2000 WHO alerted about the problem. The analysis of the factors involved in the origin of the problem have led to recognize the importance of creating supportive environments for healthier food choices and physical activity to be the easiest and accessible options in common everyday environments, such as schools, workplace or community environment. Evidence is long available that the most effective interventions to prevent childhood obesity should consider multiple strategies and last longer. Today it is also recognized the importance of implementing policies that encourage supportive friendly environments for physical activity and help decisions to opt for healthy eating habits.

  15. Public health and the prevention of obesity: failure or success?

    Science.gov (United States)

    Aranceta Bartrina, Javier

    2013-09-01

    In recent decades, obesity has become a major public health problem in developed societies and economies in transition. Rapid social changes that have occurred since the mid 20th century prompted major changes in eating habits and lifestyles, with the gradual abandonment of traditional dietary patterns and culinary techniques, significant decrease in physical activity and increased sedentary time, giving as result in an imbalance in the energy balance. Obesity is a risk factor for many chronic diseases. There is evidence that childhood obesity influences adult health condition. Additionally, obesity in children affects their physical, emotional and social wellbeing. According to some estimates the cost of obesity may represent up to 12% of health cost in some countries. Many actions have been developed since around the year 2000 WHO alerted about the problem. The analysis of the factors involved in the origin of the problem have led to recognize the importance of creating supportive environments for healthier food choices and physical activity to be the easiest and accessible options in common everyday environments, such as schools, workplace or community environment. Evidence is long available that the most effective interventions to prevent childhood obesity should consider multiple strategies and last longer. Today it is also recognized the importance of implementing policies that encourage supportive friendly environments for physical activity and help decisions to opt for healthy eating habits.

  16. Beneficial effects of Resveratrol, present in grapes in the prevention and treatment of heart disease and failure

    Directory of Open Access Journals (Sweden)

    Ali Movahed

    2015-04-01

    Full Text Available Resveratrol (3, 5, 4- trihydroxystilbene is one of the natural polyphenolic bioactive compounds synthesized by plants to serve many functions, especially defense against fungal infections, environmental stresses and UV radiation. It is found mainly in grapes, green tea, peanuts and berries. This compound has recently received increased attention in medical research, due to its effects on prevention and treatment of many diseases, including cancer, cardiovascular disease, and metabolic syndrome. Over the past two decades, researchers from all over the world studied the beneficial effects of resveratrol against cardiovascular diseases and heart failure in different animal models. Importantly, the results of these studies have been promising and recently this knowledge has been translated into examining the efficacy of resveratrol in humans with heart failure. Since heart failure continues to be a significant cause of cardiovascular mortality in the developed and also developing countries, and despite different medicines available for the treatment of such common chronic systemic diseases, preventive measures to be necessary to combat the incidence of heart problems. In this review article the protective effects of resveratrol and its mechanisms of action on different metabolic pathways with respect to heart disease and failure will be discussed.

  17. Investigation on multilayer failure mechanism of RPV with a high temperature gradient from core meltdown scenario

    Energy Technology Data Exchange (ETDEWEB)

    Jianfeng, Mao, E-mail: jianfeng-mao@163.com [Institute of Process Equipment and Control Engineering, Zhejiang University of Technology, Hangzhou, Zhejiang 310032 (China); Engineering Research Center of Process Equipment and Remanufacturing, Ministry of Education (China); Xiangqing, Li [Institute of Process Equipment and Control Engineering, Zhejiang University of Technology, Hangzhou, Zhejiang 310032 (China); Shiyi, Bao, E-mail: bsy@zjut.edu.cn [Institute of Process Equipment and Control Engineering, Zhejiang University of Technology, Hangzhou, Zhejiang 310032 (China); Engineering Research Center of Process Equipment and Remanufacturing, Ministry of Education (China); Lijia, Luo [Institute of Process Equipment and Control Engineering, Zhejiang University of Technology, Hangzhou, Zhejiang 310032 (China); Zengliang, Gao [Institute of Process Equipment and Control Engineering, Zhejiang University of Technology, Hangzhou, Zhejiang 310032 (China); Engineering Research Center of Process Equipment and Remanufacturing, Ministry of Education (China)

    2016-12-15

    Highlights: • The multilayer failure mechanism is investigated for RPV under CHF. • Failure time and location of RPV are predicted under various SA scenarios. • The structural behaviors are analyzed in depth for creep and plasticity. • The effect of internal pressure and temperature gradient is considered. • The structural integrity of RPV is secured within the required 72 creep hours. - Abstract: The Fukushima accident shows that in-vessel retention (IVR) of molten core debris has not been appropriately assessed, and a certain pressure (up to 8.0 MPa) still exists inside the reactor pressure vessel (RPV). In the traditional concept of IVR, the pressure is supposed to successfully be released, and the temperature distributed among the wall thickness is assumed to be uniform. However, this concept is seriously challenged by reality of Fukushima accident with regard to the existence of both internal pressure and high temperature gradient. Therefore, in order to make the IVR mitigation strategy succeed, the numerical investigation of the lower head behavior and its failure has been performed for several internal pressures under high temperature gradient. According to some requirements in severe accident (SA) management of RPV, it should be ensured that the IVR mitigation takes effect in preventing the failure of the structure within a period of 72 h. Subsequently, the failure time and location have to be predicted under the critical heat flux (CHF) loading condition for lower head, since the CHF is limit thermal boundary before the melt-through of RPV. In illustrating the so called ‘multilayer failure mechanism’, the structural behaviors of RPV are analyzed in terms of the stress, creep strain, deformation, damage on selected paths.

  18. Structural remodeling and mechanical function in heart failure.

    Science.gov (United States)

    Leonard, Bridget Louise; Smaill, Bruce Henry; LeGrice, Ian John

    2012-02-01

    The cardiac extracellular matrix (ECM) is the three-dimensional scaffold that defines the geometry and muscular architecture of the cardiac chambers and transmits forces produced during the cardiac cycle throughout the heart wall. The cardiac ECM is an active system that responds to the stresses to which it is exposed and in the normal heart is adapted to facilitate efficient mechanical function. There are marked differences in the short- and medium-term changes in ventricular geometry and cardiac ECM that occur as a result of volume overload, hypertension, and ischemic cardiomyopathy. Despite this, there is a widespread view that a common remodeling "phenotype" governs the final progression to end-stage heart failure in different forms of heart disease. In this review article, we make the case that this interpretation is not consistent with the clinical and experimental data on the topic. We argue that there is a need for new theoretical and experimental models that will enable stresses acting on the ECM and resultant deformations to be estimated more accurately and provide better spatial resolution of local signaling mechanisms that are activated as a result. These developments are necessary to link the effects of structural remodeling with altered cardiac mechanical function.

  19. Mechanical failure in amorphous solids: Scale-free spinodal criticality

    Science.gov (United States)

    Procaccia, Itamar; Rainone, Corrado; Singh, Murari

    2017-09-01

    The mechanical failure of amorphous media is a ubiquitous phenomenon from material engineering to geology. It has been noticed for a long time that the phenomenon is "scale-free," indicating some type of criticality. In spite of attempts to invoke "Self-Organized Criticality," the physical origin of this criticality, and also its universal nature, being quite insensitive to the nature of microscopic interactions, remained elusive. Recently we proposed that the precise nature of this critical behavior is manifested by a spinodal point of a thermodynamic phase transition. Demonstrating this requires the introduction of an "order parameter" that is suitable for distinguishing between disordered amorphous systems. At the spinodal point there exists a divergent correlation length which is associated with the system-spanning instabilities (known also as shear bands) which are typical to the mechanical yield. The theory, the order parameter used and the correlation functions which exhibit the divergent correlation length are universal in nature and can be applied to any amorphous solid that undergoes mechanical yield. The phenomenon is seen at its sharpest in athermal systems, as is explained below; in this paper we extend the discussion also to thermal systems, showing that at sufficiently high temperatures the spinodal phenomenon is destroyed by thermal fluctuations.

  20. The mechanisms of muscle wasting in COPD and heart failure

    Directory of Open Access Journals (Sweden)

    Giorgio Vescovo

    2012-10-01

    Full Text Available Many of the mechanisms leading to skeletal muscle wasting in COPD and heart failure are common to both conditions. These encompass neurohormonal activation and systemic inflammation. The mechanisms leading to muscle dysfunction are both qualitative and quantitative. Qualitative changes comprise the transition from aerobic metabolism and prevalent slow fibers composition toward anaerobic metabolism and fast fibers synthesis. Quantitative changes are mainly linked to muscle loss. These changes occur not only in the major muscles bulks of the body but also in respiratory muscles. The mechanisms leading to muscle wastage include cytokine-triggered skeletal muscle apoptosis and ubiquitin-proteasomeand non-ubiquitin-dependent pathways. The regulation of fiber type involves the growth hormone/insulin-like growth factor 1/calcineurin/transcriptional coactivator PGC1 cascade. The imbalance between protein synthesis and degradation plays an important role. Protein degradation can occur through ubiquitin-dependent and non-ubiquitin-dependent pathways. Very recently, two systems controlling ubiquitin-proteasome activation have been described: FOXO-ubiquitin ligase and NFkB ubiquitin ligase. These are triggered by TNFα and growth hormone/insulin-like growth factor 1. Moreover, apoptosis, which is triggered by tumor necrosis factor α, plays an important role. Another mechanism acting on muscle wastage is malnutrition, with an imbalance between catabolic and anabolic factors toward the catabolic component. Catabolism is also worsened by the activation of the adrenergic system and alteration of the cortisol/DEHA ratio toward cortisol production. Sarcomeric protein oxidation and its consequent contractile impairment can be another cause of skeletal muscle dysfunction in CHF.

  1. Prediction and prevention of failure: an early intervention to assist at-risk medical students

    NARCIS (Netherlands)

    Winston, K.A.; Vleuten, C.P.M. van der; Scherpbier, A.J.J.A.

    2014-01-01

    BACKGROUND: Consistent identification and prevention of failure for at-risk medical students is challenging, failing courses is costly to all stakeholders, and there is need for further research into duration, timing and structure of interventions to help students in difficulty. AIMS: To verify the

  2. [Electrical failure with nerve stimulation: cases report and check list for prevention].

    Science.gov (United States)

    Choquet, O; Feugeas, J-L; Capdevila, X; Manelli, J-C

    2007-03-01

    Functionality of the nerve stimulator and integrity of the electrical circuit should be verified and confirmed before performing peripheral nerve blockade. The clinical cases reported here demonstrate that electrical disconnection or malfunction during nerve localization can unpredictably occur and a checklist is described to prevent the unknown electrical circuit failure.

  3. Intralipid prevents and rescues fatal pulmonary arterial hypertension and right ventricular failure in rats.

    Science.gov (United States)

    Umar, Soban; Nadadur, Rangarajan D; Li, Jingyuan; Maltese, Federica; Partownavid, Parisa; van der Laarse, Arnoud; Eghbali, Mansoureh

    2011-09-01

    Pulmonary arterial hypertension (PAH) is characterized by pulmonary vascular remodeling leading to right ventricular (RV) hypertrophy and failure. Intralipid (ILP), a source of parenteral nutrition for patients, contains γ-linolenic acid and soy-derived phytoestrogens that are protective for lungs and heart. We, therefore, investigated the therapeutic potential of ILP in preventing and rescuing monocrotaline-induced PAH and RV dysfunction. PAH was induced in male rats with monocrotaline (60 mg/kg). Rats then received daily ILP (1 mL of 20% ILP per day IP) from day 1 to day 30 for prevention protocol or from day 21 to day 30 for rescue protocol. Other monocrotaline-injected rats were left untreated to develop severe PAH by day 21 or RV failure by approximately day 30. Saline or ILP-treated rats served as controls. Significant increase in RV pressure and decrease in RV ejection fraction in the RV failure group resulted in high mortality. Therapy with ILP resulted in 100% survival and prevented PAH-induced RV failure by preserving RV pressure and RV ejection fraction and preventing RV hypertrophy and lung remodeling. In preexisting severe PAH, ILP attenuated most lung and RV abnormalities. The beneficial effects of ILP in PAH seem to result from the interplay of various factors, among which preservation and/or stimulation of angiogenesis, suppression and/or reversal of inflammation, fibrosis and hypertrophy, in both lung and RV, appear to be major contributors. In conclusion, ILP not only prevents the development of PAH and RV failure but also rescues preexisting severe PAH.

  4. Deformation and Failure Mechanisms of Shape Memory Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Daly, Samantha Hayes [Univ. of Michigan, Ann Arbor, MI (United States)

    2015-04-15

    The goal of this research was to understand the fundamental mechanics that drive the deformation and failure of shape memory alloys (SMAs). SMAs are difficult materials to characterize because of the complex phase transformations that give rise to their unique properties, including shape memory and superelasticity. These phase transformations occur across multiple length scales (one example being the martensite-austenite twinning that underlies macroscopic strain localization) and result in a large hysteresis. In order to optimize the use of this hysteretic behavior in energy storage and damping applications, we must first have a quantitative understanding of this transformation behavior. Prior results on shape memory alloys have been largely qualitative (i.e., mapping phase transformations through cracked oxide coatings or surface morphology). The PI developed and utilized new approaches to provide a quantitative, full-field characterization of phase transformation, conducting a comprehensive suite of experiments across multiple length scales and tying these results to theoretical and computational analysis. The research funded by this award utilized new combinations of scanning electron microscopy, diffraction, digital image correlation, and custom testing equipment and procedures to study phase transformation processes at a wide range of length scales, with a focus at small length scales with spatial resolution on the order of 1 nanometer. These experiments probe the basic connections between length scales during phase transformation. In addition to the insights gained on the fundamental mechanisms driving transformations in shape memory alloys, the unique experimental methodologies developed under this award are applicable to a wide range of solid-to-solid phase transformations and other strain localization mechanisms.

  5. An orally active TRPV4 channel blocker prevents and resolves pulmonary edema induced by heart failure.

    Science.gov (United States)

    Thorneloe, Kevin S; Cheung, Mui; Bao, Weike; Alsaid, Hasan; Lenhard, Stephen; Jian, Ming-Yuan; Costell, Melissa; Maniscalco-Hauk, Kristeen; Krawiec, John A; Olzinski, Alan; Gordon, Earl; Lozinskaya, Irina; Elefante, Lou; Qin, Pu; Matasic, Daniel S; James, Chris; Tunstead, James; Donovan, Brian; Kallal, Lorena; Waszkiewicz, Anna; Vaidya, Kalindi; Davenport, Elizabeth A; Larkin, Jonathan; Burgert, Mark; Casillas, Linda N; Marquis, Robert W; Ye, Guosen; Eidam, Hilary S; Goodman, Krista B; Toomey, John R; Roethke, Theresa J; Jucker, Beat M; Schnackenberg, Christine G; Townsley, Mary I; Lepore, John J; Willette, Robert N

    2012-11-01

    Pulmonary edema resulting from high pulmonary venous pressure (PVP) is a major cause of morbidity and mortality in heart failure (HF) patients, but current treatment options demonstrate substantial limitations. Recent evidence from rodent lungs suggests that PVP-induced edema is driven by activation of pulmonary capillary endothelial transient receptor potential vanilloid 4 (TRPV4) channels. To examine the therapeutic potential of this mechanism, we evaluated TRPV4 expression in human congestive HF lungs and developed small-molecule TRPV4 channel blockers for testing in animal models of HF. TRPV4 immunolabeling of human lung sections demonstrated expression of TRPV4 in the pulmonary vasculature that was enhanced in sections from HF patients compared to controls. GSK2193874 was identified as a selective, orally active TRPV4 blocker that inhibits Ca(2+) influx through recombinant TRPV4 channels and native endothelial TRPV4 currents. In isolated rodent and canine lungs, TRPV4 blockade prevented the increased vascular permeability and resultant pulmonary edema associated with elevated PVP. Furthermore, in both acute and chronic HF models, GSK2193874 pretreatment inhibited the formation of pulmonary edema and enhanced arterial oxygenation. Finally, GSK2193874 treatment resolved pulmonary edema already established by myocardial infarction in mice. These findings identify a crucial role for TRPV4 in the formation of HF-induced pulmonary edema and suggest that TRPV4 blockade is a potential therapeutic strategy for HF patients.

  6. Reduced release probability prevents vesicle depletion and transmission failure at dynamin mutant synapses.

    Science.gov (United States)

    Lou, Xuelin; Fan, Fan; Messa, Mirko; Raimondi, Andrea; Wu, Yumei; Looger, Loren L; Ferguson, Shawn M; De Camilli, Pietro

    2012-02-21

    Endocytic recycling of synaptic vesicles after exocytosis is critical for nervous system function. At synapses of cultured neurons that lack the two "neuronal" dynamins, dynamin 1 and 3, smaller excitatory postsynaptic currents are observed due to an impairment of the fission reaction of endocytosis that results in an accumulation of arrested clathrin-coated pits and a greatly reduced synaptic vesicle number. Surprisingly, despite a smaller readily releasable vesicle pool and fewer docked vesicles, a strong facilitation, which correlated with lower vesicle release probability, was observed upon action potential stimulation at such synapses. Furthermore, although network activity in mutant cultures was lower, Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) activity was unexpectedly increased, consistent with the previous report of an enhanced state of synapsin 1 phosphorylation at CaMKII-dependent sites in such neurons. These changes were partially reversed by overnight silencing of synaptic activity with tetrodotoxin, a treatment that allows progression of arrested endocytic pits to synaptic vesicles. Facilitation was also counteracted by CaMKII inhibition. These findings reveal a mechanism aimed at preventing synaptic transmission failure due to vesicle depletion when recycling vesicle traffic is backed up by a defect in dynamin-dependent endocytosis and provide new insight into the coupling between endocytosis and exocytosis.

  7. Predictors of Prevention Failure in College Students Participating in Two Indicated Depression Prevention Programs

    Directory of Open Access Journals (Sweden)

    Vanessa Blanco

    2014-04-01

    Full Text Available The purpose of this study was to identify subgroups of university students with the highest likelihood of remaining at elevated levels of depressive symptoms six months following the receipt of a depressive prevention intervention on the basis of known risk factors and participation in one of two depression prevention programs. Data from a randomized controlled trial evaluating depression prevention among 133 college students with elevated depressive symptoms were analyzed. Participants were randomized to a cognitive-behavioral or relaxation training group preventive intervention. Classification tree analysis showed that older age was the strongest risk factor for persistently elevated depression. Additional risk factors were: (1 for younger students, fewer daily pleasant activities; (2 for those with higher level of pleasant activities, higher level of stressful events; and (3 for those with higher level of stressful events, lower assertiveness. Results offer directions for prevention foci, identify specific subgroups of college students to target for depression prevention efforts, and suggest that research aim to help older, non-traditional students or graduating students manage the transition from college to the work force.

  8. Predictors of prevention failure in college students participating in two indicated depression prevention programs.

    Science.gov (United States)

    Blanco, Vanessa; Rohde, Paul; Vázquez, Fernando L; Otero, Patricia

    2014-04-04

    The purpose of this study was to identify subgroups of university students with the highest likelihood of remaining at elevated levels of depressive symptoms six months following the receipt of a depressive prevention intervention on the basis of known risk factors and participation in one of two depression prevention programs. Data from a randomized controlled trial evaluating depression prevention among 133 college students with elevated depressive symptoms were analyzed. Participants were randomized to a cognitive-behavioral or relaxation training group preventive intervention. Classification tree analysis showed that older age was the strongest risk factor for persistently elevated depression. Additional risk factors were: (1) for younger students, fewer daily pleasant activities; (2) for those with higher level of pleasant activities, higher level of stressful events; and (3) for those with higher level of stressful events, lower assertiveness. Results offer directions for prevention foci, identify specific subgroups of college students to target for depression prevention efforts, and suggest that research aim to help older, non-traditional students or graduating students manage the transition from college to the work force.

  9. Development of Mechanical and Failure Properties in Sheep Cerebral Arteries.

    Science.gov (United States)

    Nye, Kevin S; Converse, Matthew I; Dahl, Mar Janna; Albertine, Kurt H; Monson, Kenneth L

    2017-04-01

    Traumatic brain injury (TBI) is a devastating problem for people of all ages, but the nature of the response to such injury is often different in children than in adults. Cerebral vessel damage and dysfunction are common following TBI, but age-dependent, large-deformation vessel response has not been characterized. Our objective was to investigate the mechanical properties of cerebral arteries as a function of development. Sheep middle cerebral arteries from four age groups (fetal, newborn, juvenile, and adult) were subjected to biaxial loading around physiological conditions and then to failure in the axial direction. Results show little difference among age groups under physiological loading conditions, but response varied significantly with age in response to large axial deformation. Vessels from all age groups reached the same ultimate stretch level, but the amount of stress carried at a given level of stretch increased significantly with age through the developmental period (fetal to juvenile). Our results are the first to identify changes in cerebral vessel response to large deformations with age and may lead to new insights regarding differences in response to TBI with age.

  10. Failure Criterion for Brick Masonry: A Micro-Mechanics Approach

    Directory of Open Access Journals (Sweden)

    Kawa Marek

    2015-02-01

    Full Text Available The paper deals with the formulation of failure criterion for an in-plane loaded masonry. Using micro-mechanics approach the strength estimation for masonry microstructure with constituents obeying the Drucker-Prager criterion is determined numerically. The procedure invokes lower bound analysis: for assumed stress fields constructed within masonry periodic cell critical load is obtained as a solution of constrained optimization problem. The analysis is carried out for many different loading conditions at different orientations of bed joints. The performance of the approach is verified against solutions obtained for corresponding layered and block microstructures, which provides the upper and lower strength bounds for masonry microstructure, respectively. Subsequently, a phenomenological anisotropic strength criterion for masonry microstructure is proposed. The criterion has a form of conjunction of Jaeger critical plane condition and Tsai-Wu criterion. The model proposed is identified based on the fitting of numerical results obtained from the microstructural analysis. Identified criterion is then verified against results obtained for different loading orientations. It appears that strength of masonry microstructure can be satisfactorily described by the criterion proposed.

  11. Experimental and Numerical Investigation on the Bearing and Failure Mechanism of Multiple Pillars Under Overburden

    Science.gov (United States)

    Zhou, Zilong; Chen, Lu; Zhao, Yuan; Zhao, Tongbin; Cai, Xin; Du, Xueming

    2017-04-01

    To reveal the mechanical response of a multi-pillar supporting system under external loads, compressive tests were carried out on single-pillar and double-pillar specimens. The digital speckle correlation method and acoustic emission technique were applied to record and analyse information of the deformation and failure processes. Numerical simulations with the software programme PFC2D were also conducted. In the compressive process of the double-pillar system, if both individual pillars have the same mechanical properties, each pillar deforms similarly and reaches the critical stable state almost simultaneously by sharing equal loads. If the two individual pillars have different mechanical properties, the pillar with higher elastic modulus or lower strength would be damaged and lose its bearing capacity firstly. The load would then be transferred to the other pillar under a load redistribution process. When the pillar with higher strength is strong enough, the load carried by the pillar system would increase again. However, the maximum bearing load of the double-pillar system is smaller than the sum of peak load of individual pillars. The study also indicates that the strength, elastic modulus, and load state of pillars all influence the supporting capacity of the pillar system. In underground space engineering, the appropriate choice of pillar dimensions and layout may play a great role in preventing the occurrence of cascading pillar failure.

  12. Core competencies and the prevention of school failure and early school leaving.

    Science.gov (United States)

    Bradshaw, Catherine P; O'Brennan, Lindsey M; McNeely, Clea A

    2008-01-01

    There is an increasing awareness that school failure and early school leaving are processes, rather than discrete events, that often co-occur and can have lasting negative effects on children's development. Most of the literature has focused on risk factors for failure and dropout rather than on the promotion of competencies that can increase youths' likelihood of successfully completing high school. This chapter applies the core competencies framework to the promotion of youths' success within the school environment. We conclude with a brief review of evidence-based prevention strategies that address the five competencies and identify avenues for future research.

  13. Identifying failure mechanisms in LDMOS transistors by analytical stability analysis

    NARCIS (Netherlands)

    Ferrara, A.; Steeneken, P.G.; Boksteen, B.K.; Heringa, A.; Scholten, A.J.; Schmitz, J.; Hueting, R.J.E.

    2014-01-01

    In this work, analytical stability equations are derived and combined with a physics-based model of an LDMOS transistor in order to identify the primary cause of failure in different operating and bias conditions. It is found that there is a gradual boundary between an electrical failure region at h

  14. Shale Failure Mechanics and Intervention Measures in Underground Coal Mines: Results From 50 Years of Ground Control Safety Research

    Science.gov (United States)

    Murphy, M. M.

    2016-02-01

    Ground control research in underground coal mines has been ongoing for over 50 years. One of the most problematic issues in underground coal mines is roof failures associated with weak shale. This paper will present a historical narrative on the research the National Institute for Occupational Safety and Health has conducted in relation to rock mechanics and shale. This paper begins by first discussing how shale is classified in relation to coal mining. Characterizing and planning for weak roof sequences is an important step in developing an engineering solution to prevent roof failures. Next, the failure mechanics associated with the weak characteristics of shale will be discussed. Understanding these failure mechanics also aids in applying the correct engineering solutions. The various solutions that have been implemented in the underground coal mining industry to control the different modes of failure will be summarized. Finally, a discussion on current and future research relating to rock mechanics and shale is presented. The overall goal of the paper is to share the collective ground control experience of controlling roof structures dominated by shale rock in underground coal mining.

  15. Statins in the prevention of cardiovascular events in patients with renal failure.

    Science.gov (United States)

    Buemi, Michele; Floccari, Fulvio; Nostro, Lorena; Campo, Susanna; Caccamo, Chiara; Sturiale, Alessio; Aloisi, Carmela; Giacobbe, Maria Stella; Frisina, Nicola

    2007-03-01

    HMG-CoA reductase inhibitors (statins) are among the most widely used hypolypemizing drugs with a pleiotropic activity. Numerous clinical trials have demonstrated that statins can have a significant effect in the prevention of cardiovascular diseases in the general population. In patients with renal failure, this drug preserves the hypolypemizing efficacy found in the general population without increasing their unwanted side-effects. The re-analysis of data from epidemiological studies conducted on the general population has confirmed that statins provide cardiovascular protection also in subjects with renal failure. These data have been partly confirmed by the findings made by 4D (Die Deutsche Diabetes Dialyse Studie) and Alert studies, conducted on diabetic patients on dialysis and patients with renal transplants, respectively. The results of other studies, such as AURORA, SHARP, REnal and Vascular End stage Disease, and ESPLANADE, clearly indicate that statins prevent cardiovascular disease in patients with renal insufficiency, just as they do in the general population.

  16. Failure Mechanism of Reflow Conductor Roll of Electroplating Tinning Line

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The surface roughness of reflow conductor roll was checked on membrane sample. The surface morphology of conductor roll was observed by microscope, and the composition of adhered layer on conductor roll surface was analyzed by X-ray spectroscope. The results show that tin adhesion is the main reason for failure of conductor roll, and the failure of conductor roll is accelerated by wear. The measures to decrease tin adhesion and improve wear resistance were put forward.

  17. Central Mechanisms of Abnormal Sympathoexcitation in Chronic Heart Failure

    Directory of Open Access Journals (Sweden)

    Takuya Kishi

    2012-01-01

    Full Text Available It has been recognized that the sympathetic nervous system is abnormally activated in chronic heart failure, and leads to further worsening chronic heart failure. In the treatment of chronic heart failure many clinical studies have already suggested that the inhibition of the abnormal sympathetic hyperactivity by beta blockers is beneficial. It has been classically considered that abnormal sympathetic hyperactivity in chronic heart failure is caused by the enhancement of excitatory inputs including changes in peripheral baroreceptor and chemoreceptor reflexes and chemical mediators that control sympathetic outflow. Recently, the abnormalities in the central regulation of sympathetic nerve activity mediated by brain renin angiotensin system-oxidative stress axis and/or proinflammatory cytokines have been focused. Central renin angiotensin system, proinflammatory cytokines, and the interaction between them have been determined as the target of the sympathoinhibitory treatment in experimental animal models with chronic heart failure. In conclusion, we must recognize that chronic heart failure is a syndrome with an abnormal sympathoexcitation, which is caused by the abnormalities in the central regulation of sympathetic nerve activity.

  18. Coupled Mechanical-Electrochemical-Thermal Analysis of Failure Propagation in Lithium-ion Batteries

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Chao; Santhanagopalan, Shriram; Pesaran, Ahmad

    2016-07-28

    This is a presentation given at the 12th World Congress for Computational Mechanics on coupled mechanical-electrochemical-thermal analysis of failure propagation in lithium-ion batteries for electric vehicles.

  19. Constitutive behavior and progressive mechanical failure of electrodes in lithium-ion batteries

    Science.gov (United States)

    Zhang, Chao; Xu, Jun; Cao, Lei; Wu, Zenan; Santhanagopalan, Shriram

    2017-07-01

    The electrodes of lithium-ion batteries (LIB) are known to be brittle and to fail earlier than the separators during an external crush event. Thus, the understanding of mechanical failure mechanism for LIB electrodes (anode and cathode) is critical for the safety design of LIB cells. In this paper, we present experimental and numerical studies on the constitutive behavior and progression of failure in LIB electrodes. Mechanical tests were designed and conducted to evaluate the constitutive properties of porous electrodes. Constitutive models were developed to describe the stress-strain response of electrodes under uniaxial tensile and compressive loads. The failure criterion and a damage model were introduced to model their unique tensile and compressive failure behavior. The failure mechanism of LIB electrodes was studied using the blunt rod test on dry electrodes, and numerical models were built to simulate progressive failure. The different failure processes were examined and analyzed in detail numerically, and correlated with experimentally observed failure phenomena. The test results and models improve our understanding of failure behavior in LIB electrodes, and provide constructive insights on future development of physics-based safety design tools for battery structures under mechanical abuse.

  20. Failure Mechanisms of Hollow Fiber Supported Ionic Liquid Membranes.

    Science.gov (United States)

    Zeh, Matthew; Wickramanayake, Shan; Hopkinson, David

    2016-03-23

    Hollow fiber supported ionic liquid membranes (SILMs) were tested using the bubble point method to investigate potential failure modes, including the maximum transmembrane pressure before loss of the ionic liquid from the support. Porous hollow fiber supports were fabricated with different pore morphologies using Matrimid(®) and Torlon(®) as the polymeric material and 1-hexyl-3-methylimidalzolium bis(trifluoromethylsulfonyl)imide ([C₆mim][Tf₂N]) as the ionic liquid (IL) component. Hollow fiber SILMs were tested for their maximum pressure before failure, with pressure applied either from the bore side or shell side. It was found that the membranes exhibited one or more of three different modes of failure when pressurized: liquid loss (occurring at the bubble point), rupture, and collapse.

  1. Numerical modeling of failure mechanisms in phyllite mine slopes in Brazil

    Institute of Scientific and Technical Information of China (English)

    Lana Milene Sabino

    2014-01-01

    This paper presents three case studies comprising failure mechanisms in phyllite mine slopes at Quadrilá-tero Ferrífero, State of Minas Gerais, Brazil. Numerical modeling techniques were used in this study. Fail-ure mechanisms involving discontinuities sub parallel to the main foliation are very common in these mines. Besides, failure through the rock material has also been observed due to the low strength of phyl-lites in this site. Results of this work permitted to establish unknown geotechnical parameters which have significant influence in failure processes, like the in situ stress field and the discontinuity stiffness.

  2. Steel Fibres: Effective Way to Prevent Failure of the Concrete Bonded with FRP Sheets

    Directory of Open Access Journals (Sweden)

    V. Gribniak

    2016-01-01

    Full Text Available Although the efficiency of steel fibres for improving mechanical properties (cracking resistance and failure toughness of the concrete has been broadly discussed in the literature, the number of studies dedicated to the fibre effect on structural behaviour of the externally bonded elements is limited. This experimental study investigates the influence of steel fibres on the failure character of concrete elements strengthened with external carbon fibre reinforced polymer sheets. The elements were subjected to different loading conditions. The test data of four ties and eight beams are presented. Different materials were used for the internal bar reinforcement: in addition to the conventional steel, high-grade steel and glass fibre reinforced polymer bars were also considered. The experimental results indicated that the fibres, by significantly increasing the cracking resistance, alter the failure character from splitting of the concrete to the bond loss of the external sheets and thus noticeably increase the load bearing capacity of the elements.

  3. Development of Overflow-Prevention Valve with Trigger Mechanism.

    Science.gov (United States)

    Ishino, Yuji; Mizuno, Takeshi; Takasaki, Masaya

    2016-09-01

    A new overflow-prevention valve for combustible fluid is developed which uses a trigger mechanism. Loading arms for combustible fluid are used for transferring oil from a tanker to tanks and vice versa. The loading arm has a valve for preventing overflow. Overflow- prevention valves cannot use any electric component to avoid combustion. Therefore, the valve must be constructed only by mechanical parts. The conventional overflow-prevention valve uses fluid and pneumatic forces. It consists of a sensor probe, a cylinder, a main valve for shutting off the fluid and a locking mechanism for holding an open state of the main valve. The proposed overflow-prevention valve uses the pressure due to the height difference between the fluid level of the tank and the sensor probe. However, the force of the cylinder produced by the pressure is too small to release the locking mechanism. Therefore, a trigger mechanism is introduced between the cylinder and the locking mechanism. The trigger mechanism produces sufficient force to release the locking mechanism and close the main valve when the height of fluid exceeds a threshold value. A trigger mechanism is designed and fabricated. The operation necessary for closing the main valve is conformed experimentally.

  4. Failure mechanisms in single-point incremental forming of metals

    DEFF Research Database (Denmark)

    Silva, Maria B.; Nielsen, Peter Søe; Bay, Niels

    2011-01-01

    The last years saw the development of two different views on how failure develops in single-point incremental forming (SPIF). Today, researchers are split between those claiming that fracture is always preceded by necking and those considering that fracture occurs with suppression of necking. Each...

  5. Ubiquitous protective effects of cyclosporine A in preventing cardiac arrest-induced multiple organ failure.

    Science.gov (United States)

    Cour, Martin; Abrial, Maryline; Jahandiez, Vincent; Loufouat, Joseph; Belaïdi, Elise; Gharib, Abdallah; Varennes, Annie; Monneret, Guillaume; Thibault, Hélène; Ovize, Michel; Argaud, Laurent

    2014-10-15

    Opening of the mitochondrial permeability transition pore (mPTP) appears to be a pivotal event in myocardial ischemia-reperfusion (I/R) injury. Resuscitated cardiac arrest (CA) leads to the post-CA syndrome that encompasses, not only myocardial dysfunction, but also brain injury, failure of other organs (kidney, liver, or lung), and systemic response to I/R. We aimed to determine whether cyclosporine A (CsA) might prevent multiple organ failure following CA through a ubiquitous mPTP inhibition in each distant vital organ. Anesthetized New Zealand White rabbits were subjected to 15 min of CA and 120 min of reperfusion. At the onset of resuscitation, the rabbits received CsA, its non-immunosuppressive derivative NIM811, or vehicle (controls). Survival, hemodynamics, brain damage, organ injuries, and systemic I/R response were analyzed. Fresh mitochondria were isolated from the brain, heart, kidney, liver, and lung to assess both oxidative phosphorylation and permeability transition. CsA analogs significantly improved short-term survival and prevented multiple organ failure, including brain damage and myocardial dysfunction (P ubiquitous mitochondrial protective effect at the level of each major distant organ.

  6. Traditional heart failure medications and sudden cardiac death prevention: a review.

    Science.gov (United States)

    Al Chekakie, M Obadah

    2013-09-01

    Sudden cardiac death (SCD) is still a major public health issue with an estimated annual incidence ranging from 184,000 to > 400,000 per year. The ACC/AHA/ESC 2006 guidelines define SCD as "death from an unexpected circulatory arrest, usually due to a cardiac arrhythmia occurring within an hour of the onset of symptoms". A recent study of sudden cardiac death using multiple sources of ascertainment found that coronary artery disease was present in more than 50% of patients older than 35 years who died suddenly and underwent autopsy. Antiarrhythmic drugs have failed to show any mortality benefit even when compared to placebo or implantable cardiovertor defibrillators (ICDs). While patients with systolic heart failure are at higher risk of dying suddenly, most of the patients experiencing sudden cardiac death have left ventricular ejection fraction (LVEF) > 50%. β-blockers, Angiotensin enzymes (ACE) inhibitors as well as aldosterone antagonists prevent ischemia and remodelling in the left ventricle especially in post myocardial infarction (MI) patients and in patients with systolic heart failure. This article will review the data on the effects of traditional heart failure medications, especially β-blockers, Renin Angiotensin system blockers, as well as Statin therapy on sudden cardiac death in post MI patients and in patients with systolic heart failure.

  7. Graphene coating for anti-corrosion and the investigation of failure mechanism

    Science.gov (United States)

    Zhu, Y. X.; Duan, C. Y.; Liu, H. Y.; Chen, Y. F.; Wang, Y.

    2017-03-01

    Graphene produced by chemical vapor deposition (CVD) methods has been considered as a promising corrosion prevention layer because of its exceptional structure and impermeability. However, the anti-corrosion performance and the failure mechanism are still controversial. In this study, graphene layers with different quality levels, crystallite sizes, and layer numbers were prepared on the surface of Cu by a CVD process. The effects of grain boundaries (GBs) on the failure of graphene layers to provide adequate protection were investigated in detail by combining graphene transfer techniques, computation, and anti-corrosion measurements. Our results reveal that corrosion rates decrease marginally upon the increase of graphene layer number, and this rather weak dependence on thickness likely arises from the aligned nature of the GBs in CVD-grown few-layer graphene. This problem can potentially be overcome by layer-by-layer graphene transfer technique, in which corrosion is found to be arrested locally when transferred graphene is present on top of the as-grown graphene. However, this advantage is not reflected in corrosion studies performed on large-scale samples, where cracks or imperfect interfaces could offset the advantages of GB misalignment. With improvements in technology, the layer-by-layer assembly technique could be used to develop an effective anti-corrosion barrier.

  8. Mechanisms of carcinogenesis prevention by flavonoids

    Directory of Open Access Journals (Sweden)

    G. A. Belitsky

    2014-01-01

    Full Text Available The mechanisms of anticancerogenic effects of flavanoids and isocyanates from the plants widely consumed in the midland belt of Russia were reviewed. Data of studies both in vitro and in vivo were analyzed. Special attention was paid to inhibition of targets responsible for carcinogen metabolic activation, carcinogenesis promotion and tumor progression as well as neoangiogenesis. Besides that the antioxidant properties of flavonoids and their effects on cell cycle regulation, apoptosis initiation and cell mobility were considered.

  9. A novel role of three dimensional graphene foam to prevent heater failure during boiling.

    Science.gov (United States)

    Ahn, Ho Seon; Kim, Ji Min; Park, Chibeom; Jang, Ji-Wook; Lee, Jae Sung; Kim, Hyungdae; Kaviany, Massoud; Kim, Moo Hwan

    2013-01-01

    We report a novel boiling heat transfer (NBHT) in reduced graphene oxide (RGO) suspended in water (RGO colloid) near critical heat flux (CHF), which is traditionally the dangerous limitation of nucleate boiling heat transfer because of heater failure. When the heat flux reaches the maximum value (CHF) in RGO colloid pool boiling, the wall temperature increases gradually and slowly with an almost constant heat flux, contrary to the rapid wall temperature increase found during water pool boiling. The gained time by NBHT would provide the safer margin of the heat transfer and the amazing impact on the thermal system as the first report of graphene application. In addition, the CHF and boiling heat transfer performance also increase. This novel boiling phenomenon can effectively prevent heater failure because of the role played by the self-assembled three-dimensional foam-like graphene network (SFG).

  10. Metal Dusting-Mechanisms and Preventions

    Institute of Scientific and Technical Information of China (English)

    J.Q.ZHANG; D.J.YOUNG

    2009-01-01

    Metal dusting attacks iron, low and high alloy steels and nickel-or cobalt-base alloys by disintegrating bulk metals and alloys into metal particles in a coke deposit. It occurs in strongly carburising gas atmospheres (carbon activity aC>1) at elevated temperatures (400℃~1000℃). This phenomenon has been studied for decades, but the detailed mechanism is still not well understood. Current methods of protection against metal dusting are either directed to the process conditions-temperature and gas composition-or to the development of a dense adherent oxide layer on the surface of the alloy by selective oxidation. However, metal dusting still occurs by carbon dissolving in the base metal via defects in the oxide scale. The research work at UNSW is aimed at determining the detailed mechanism of metal dusting of both ferritic and austenitic alloys, in particular the microprocesses of graphite deposition, nanoparticle formation and underlying metal destruction. This work was carried out using surface observation, cross-section analysis by focused ion beam and electron microscopic examination of coke deposits at different stages of the reaction. It was found that surface orientation affected carbon deposition and metal dusting at the initial stage of the reaction. Metal dusting occurred only when graphite grew into the metal interior where the volume expansion is responsible for metal disintegration and dusting. It was also found that the metal dusting process could be significantly changed by alterations in alloy chemistry. Germanium was found to affect the iron dusting process by destabilising FeC but increasing the rate of carbon deposition and dusting, which questions the role of cementite in ferritic alloy dusting. Whilst adding copper to iron did not change the carburisation kinetics, cementite formation and coke morphology, copper alloying reduced nickel and nickel-base alloy dusting rates significantly. Application of these fundamental results to the dusting

  11. A study of bonding and failure mechanisms in fuel pellets from different biomass resources

    DEFF Research Database (Denmark)

    Stelte, Wolfgang; Holm, Jens K.; Sanadi, Anand R.;

    2011-01-01

    higher for wood pellets than for straw pellets. Scanning electron microscopy of the beech pellets fracture surfaces, pressed at higher temperatures, showed areas of cohesive failure, indicating high energy failure mechanisms, likely due to lignin flow and inter-diffusion between adjacent wood particles...... the adhesion mechanism to van der Waals forces. Electron micrographs indicating interfacial failure mechanisms support these findings. Infrared spectra of the fracture surface of wood pellets, pressed at elevated temperatures, showed no signs of hydrophobic extractives. It has been shown that both temperature...

  12. Register of specialized sources for information on mechanics of structural failure

    Science.gov (United States)

    Carpenter, J. L., Jr.; Denny, F. J.

    1973-01-01

    Specialized information sources that generate information relative to six problem areas in aerospace mechanics of structural failure are identified. Selection for inclusion was based upon information obtained from the individual knowledge and professional contacts of Martin Marietta Aerospace staff members and the information uncovered by the staff of technical reviewers. Activities listed perform basic or applied research related to the mechanics of structural failure and publish the results of such research. The purpose of the register is to present, in easy reference form, original sources for dependable information regarding failure modes and mechanisms of aerospace structures.

  13. Exercise training in chronic heart failure: mechanisms and therapies

    OpenAIRE

    Piepoli, M. F.

    2012-01-01

    Decreased exercise capacity negatively affects the individuals’ ability to adequately perform activities required for normal daily life and, therefore, the independence and quality of life. Regular exercise training is associated with improved quality of life and survival in healthy individuals and in cardiovascular disease patients. Also in patients with stable heart failure, exercise training can relieve symptoms, improve exercise capacity and reduce disability, hospitalisation and probably...

  14. Seismic failure mechanisms for loaded slopes with associated and nonassociated flow rules

    Institute of Scientific and Technical Information of China (English)

    YANG Xiao-li; SUI Zhi-rong

    2008-01-01

    Seismic failure mechanisms were investigated for soil slopes subjected to strip load with upper bound method of limit analysis and finite difference method of numerical simulation, considering the influence of associated and nonassociated flow rules. Quasi-static representation of soil inertia effects using a seismic coefficient concept was adopted for seismic failure analysis. Numerical study was conducted to investigate the influences of dilative angle and earthquake on the seismic failure mechanisms for the loaded slope, and the failure mechanisms for different dilation angles were compared. The results show that dilation angle has influences on the seismic failure surfaces, that seismic maximum displacement vector decreases as the dilation angle increases, and that seismic maximum shear strain rate decreases as the dilation angle increases.

  15. Investigation of casing connection failure mechanisms in thermal wells

    Energy Technology Data Exchange (ETDEWEB)

    Xie, J. [C-FER Technologies, Edmonton, AB (Canada)

    2009-07-01

    Thermal well technologies use casing strings that consist of casing joints linked by threaded connections that are cemented over the wellbore's length in order to provide structural support and hydraulic isolation to the wellbore. Studies have demonstrated that over 80 per cent of uphole casing failures occur at the casing joint connections, and are caused by thread rupture or structural damage. This study discussed thermal well failures related to casing connection damage. Finite element analyses (FEA) were then conducted to consider various critical load conditions with a generic premium casing connection. The study considered structural integrity losses, fatigue, and leakage during connection installation. Results of the study were then used to optimize casing connection designs. The study showed that thermal cycle and curvature loading can have an impact on the structural and sealing performance of premium connections. Connection structural performance should be evaluated in order to determine appropriate designs for thermal well applications. It was concluded that the connection shoulder region is a critical area for material fatigue failure. 12 refs., 9 figs.

  16. High Strain-Rate and Quasi-Static Ductile Failure Mechanisms in Porous Materials

    Science.gov (United States)

    2007-11-02

    detailed understanding of the interrelated physical mechanisms that can result in ductile material failure in rate-dependent porous crystalline materials subjected...strains and slip-rates, and hydrostatic stresses on failure paths and ligament damage in face centered cubic (f.c.c.) crystalline materials have been

  17. Can we reduce preventable heart failure readmissions in patients enrolled in a Disease Management Programme?

    LENUS (Irish Health Repository)

    Phelan, D

    2012-02-01

    BACKGROUND: Disease Management Programmes (DMPs) are successful in reducing hospital readmissions in heart failure (HF). However, there remain a number of patients enrolled in a DMP who are readmitted with HF. The primary aim of the study was to determine the proportion of preventable readmissions (PR). The secondary aim was to recognise patient characteristics which would identify certain patients at risk of having a PR. METHODS: A retrospective chart search was performed on patients readmitted over a 1-year period. RESULTS: 38.5% of readmissions were classified as PR. None of these patients made prior contact with the DMP. Admission levels of BNP, potassium, urea and creatinine were significantly lower in the PR group. CONCLUSION: DMP have proven benefits in reducing hospital readmission nonetheless a significant proportion of these readmissions are preventable. Further work is required to prospectively analyse why these patients fail to contact the DMP.

  18. Is thrombosis a contributor to heart failure pathophysiology? Possible mechanisms, therapeutic opportunities, and clinical investigation challenges

    NARCIS (Netherlands)

    Zannad, F.; Stough, W.G.; Regnault, V.; Gheorghiade, M.; Deliargyris, E.; Gibson, C.M.; Agewall, S.; Berkowitz, S.D.; Burton, P.; Calvo, G.; Goldstein, S.; Verheugt, F.W.A.; Koglin, J.; O'Connor, C.M.

    2013-01-01

    Thrombotic events (coronary thrombosis, venous thromboembolism, intraventricular thrombosis, intracranial and systemic thromboembolism) occur frequently in patients with heart failure. These events may be precipitated by several mechanisms including hypercoagulability through enhancement of procoagu

  19. Sand Failure Mechanism and Sanding Parameters in Niger Delta Oil Reservoirs

    Directory of Open Access Journals (Sweden)

    Sunday Isehunwa,

    2010-05-01

    Full Text Available Sand production is a major issue during oil and gas production from unconsolidated reservoirs. In predicting the onset of sand production, it is important to accurately determine the failure mechanism and the contributing parameters. The aim of this study was to determine sand failure mechanism in the Niger-Delta, identify themajor contributing parameters and evaluate their effects on sanding.Completion and production data from 78 strings completed on 22 reservoirs in a Niger Delta oil Field were evaluated. Sand failure mechanisms and contributing parameters were identified and compared with published profiles. The results showed that cohesive stress is the predominant sand failure mechanism. Water cut, bean size and gas oil ratio (GOR impact sand production in the Niger Delta.

  20. Laboratory and 3-D-distinct element analysis of failure mechanism of slope under external surcharge

    Directory of Open Access Journals (Sweden)

    N. Li

    2014-09-01

    Full Text Available Landslide is a major disaster resulting in considerable loss of human lives and property damages in hilly terrain in Hong Kong, China and many other countries. The factor of safety and the critical slip surface for slope stabilization are the main considerations for slope stability analysis in the past, while the detailed post-failure conditions of the slopes have not been considered in sufficient details. There are however increasing interest on the consequences after the initiation of failure which includes the development and propagation of the failure surfaces, the amount of failed mass and runoff and the affected region. To assess the development of slope failure in more details and to consider the potential danger of slopes after failure has initiated, the slope stability problem under external surcharge is analyzed by the distinct element method (DEM and laboratory model test in the present research. A more refined study about the development of failure, microcosmic failure mechanism and the post-failure mechanism of slope will be carried out. The numerical modeling method and the various findings from the present work can provide an alternate method of analysis of slope failure which can give additional information not available from the classical methods of analysis.

  1. Cancer Therapy-Related Cardiac Dysfunction and Heart Failure: Part 2: Prevention, Treatment, Guidelines, and Future Directions.

    Science.gov (United States)

    Hamo, Carine E; Bloom, Michelle W; Cardinale, Daniela; Ky, Bonnie; Nohria, Anju; Baer, Lea; Skopicki, Hal; Lenihan, Daniel J; Gheorghiade, Mihai; Lyon, Alexander R; Butler, Javed

    2016-02-01

    Success with oncologic treatment has allowed cancer patients to experience longer cancer-free survival gains. Unfortunately, this success has been tempered by unintended and often devastating cardiac complications affecting overall patient outcomes. Cardiac toxicity, specifically the association of several cancer therapy agents with the development of left ventricular dysfunction and cardiomyopathy, is an issue of growing concern. Although the pathophysiologic mechanisms behind cardiac toxicity have been characterized, there is currently no evidence-based approach for monitoring and management of these patients. In the first of a 2-part review, we discuss the epidemiologic, pathophysiologic, risk factors, and imaging aspects of cancer therapy-related cardiac dysfunction and heart failure. In this second part, we discuss the prevention and treatment aspects in these patients and conclude with highlighting the evidence gaps and future directions for research in this area.

  2. A systematic review of discontinued trials suggested that most reasons for recruitment failure were preventable.

    Science.gov (United States)

    Briel, Matthias; Olu, Kelechi Kalu; von Elm, Erik; Kasenda, Benjamin; Alturki, Reem; Agarwal, Arnav; Bhatnagar, Neera; Schandelmaier, Stefan

    2016-12-01

    To collect and classify reported reasons for recruitment failure in discontinued randomized controlled trials (RCTs) and to assess reporting quality. We systematically searched MEDLINE and EMBASE (2010-2014) and a previous cohort of RCTs for published RCTs reporting trial discontinuation due to poor recruitment. Teams of two investigators selected eligible RCTs working independently and extracted information using standardized forms. We used an iterative approach to classify reasons for poor recruitment. We included 172 RCTs discontinued due to poor recruitment (including 26 conference abstracts and 63 industry-funded RCTs). Of those, 131 (76%) reported one or more reasons for discontinuation due to poor recruitment. We identified 28 different reasons for recruitment failure; most frequently mentioned were overestimation of prevalence of eligible participants and prejudiced views of recruiters and participants on trial interventions. Few RCTs reported relevant details about the recruitment process such as how eligible participants were identified, the number of patients assessed for eligibility, and who actually recruited participants. Our classification could serve as a checklist to assist investigators in the planning of RCTs. Most reasons for recruitment failure seem preventable with a pilot study that applies the planned informed consent procedure. Copyright © 2016 Elsevier Inc. All rights reserved.

  3. Distributed Monitoring for Prevention of Cascading Failures in Operational Power Grids

    CERN Document Server

    Warnier, Martijn; Koç, Yakup; Pauwels, Eric

    2015-01-01

    Electrical power grids are vulnerable to cascading failures that can lead to large blackouts. Detection and prevention of cascading failures in power grids is impor- tant. Currently, grid operators mainly monitor the state (loading level) of individual components in power grids. The complex architecture of power grids, with many interdependencies, makes it difficult to aggregate data provided by local compo- nents in a timely manner and meaningful way: monitoring the resilience with re- spect to cascading failures of an operational power grid is a challenge. This paper addresses this challenge. The main ideas behind the paper are that (i) a robustness metric based on both the topology and the operative state of the power grid can be used to quantify power grid robustness and (ii) a new proposed a distributed computation method with self-stabilizing properties can be used to achieving near real-time monitoring of the robustness of the power grid. Our con- tributions thus provide insight into the resilience wit...

  4. Tools for in service monitoring and testing of riser to prevent failure and extend service life

    Energy Technology Data Exchange (ETDEWEB)

    Ward, Haakon; Bondevik, Jon Olav; Skjerve, Haavard; Tveit, Oeyvind [SeaFlex AS, Asker (Norway)

    2005-07-01

    Exploration and development of new oil and gas fields is heavily dependant on use of flexible pipes and many field developments would not have been possible without them. The number of flexible risers in service is constantly increasing since relatively few offshore projects have reached the estimated operational life and the operational lifetime of several fields in-service has been extended due to new and improved technology. Many risers have been in service over a large number of years. Some risers have been operated under demanding conditions such as severe dynamic loads, high pressure and temperatures. One may in some cases find that risers actually have shorter service life than estimated in the design phase due to the severe operational conditions. In order to extend the use of the riser, some risers may have to be modified and re-terminated and prepared for a new and less demanding application. In order to operate risers safely, it is important to re-assess the fatigue life in order to prevent potential riser failure. The operator should implement methods and tools for in-service monitoring and testing. This paper addresses efficient and reliable methods and tools for monitoring of critical operational parameters as well as in-service riser testing. A brief description of structural failure modes will also be given in order to understand how to interpret test results in view of potential failure modes. (author)

  5. Computational investigations of mechanical failures of internal plate fixation.

    Science.gov (United States)

    Chen, G; Schmutz, B; Wullschleger, M; Pearcy, M J; Schuetz, M A

    2010-01-01

    This paper investigated the biomechanics of two clinical cases of bone fracture treatments. Both fractures were treated with the same locking compression plate but with different numbers of screws as well as different plate materials. The fracture treated with 12 screws (rigid fixation) failed at 7 weeks with the plate breaking; the fracture with six screws (flexible fixation) endured the entire healing process. It was hypothesized that the plate failure in the unsuccessful case was due to the material fatigue induced by stress concentration in the plate. As the two clinical cases had different fracture locations and different plate materials, finite element simulations were undertaken for each fractured bone fixed by both a rigid and a flexible method. This enabled comparisons to be made between the rigid and flexible fixation methods. The fatigue life was assessed for each fixation method. The results showed that the stress in the rigid fixation methods could be significantly higher than that in flexible fixation methods. The fatigue analyses showed that, with the stress level in flexible fixation (i.e. with fewer screws), the plate was able to endure 2000 days, and that the plate in rigid fixation could fail by fatigue fracture in 20 days. The paper concludes that the rigid fixation method resulted in serious stress concentrations in the plate, which induced fatigue failure. The flexible fixation gave sufficient stability and was better for fracture healing.

  6. Sand Failure Mechanism and Sanding Parameters in Niger Delta Oil Reservoirs

    OpenAIRE

    Sunday Isehunwa,; Andrew Farotade

    2010-01-01

    Sand production is a major issue during oil and gas production from unconsolidated reservoirs. In predicting the onset of sand production, it is important to accurately determine the failure mechanism and the contributing parameters. The aim of this study was to determine sand failure mechanism in the Niger-Delta, identify themajor contributing parameters and evaluate their effects on sanding.Completion and production data from 78 strings completed on 22 reservoirs in a Niger Delta oil Field ...

  7. Friction Stir Weld Failure Mechanisms in Aluminum-Armor Structures Under Ballistic Impact Loading Conditions

    Science.gov (United States)

    2013-01-01

    Sheet) Continuation for Block 13 ARO Report Number Friction Stir Weld Failure Mechanisms in Alumin Block 13: Supplementary Note © 2013 . Published in...nose, steel jacketed, hard tungsten core (1400 Hv), armor piercing (AP) projectile (Ref 1). As mentioned above, this failure mechanism is often...zones being impacted with blunt, lower hardness projectiles [e.g., 20-mm caliber, 53 g, blunt, chamfered right circular cylindrical steel fragment

  8. Numerical Simulation of the Mechanical Properties and Failure of Heterogeneous Elasto-Plastic Materials

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A general numerical approach was developed to simulate the mechanical properties and the failure of heterogeneous elasto-plastic materials using statistical distributions of the material properties. An appropriate elastic-plastic constitutive relation is used to describe the material behavior and failure in each element, with a two-parameter Weibull distribution used to produce the initial heterogeneous material property variations. An adaptive incremental load-step is applied so that only one or a few elements (or integration points) change their status (i.e., from elastic to plastic, or from plastic to strain failure) within one load step. A failed element is then assigned a very small modulus to simulate the failure rather than removing it from the model, which keeps the continuity of the geometric mesh. The numerical results show that the model is suitable for simulating the effective mechanical properties and failure of heterogeneous materials with local elasto-plastic constitutive relations.

  9. Agent autonomy approach to probabilistic physics-of-failure modeling of complex dynamic systems with interacting failure mechanisms

    Science.gov (United States)

    Gromek, Katherine Emily

    A novel computational and inference framework of the physics-of-failure (PoF) reliability modeling for complex dynamic systems has been established in this research. The PoF-based reliability models are used to perform a real time simulation of system failure processes, so that the system level reliability modeling would constitute inferences from checking the status of component level reliability at any given time. The "agent autonomy" concept is applied as a solution method for the system-level probabilistic PoF-based (i.e. PPoF-based) modeling. This concept originated from artificial intelligence (AI) as a leading intelligent computational inference in modeling of multi agents systems (MAS). The concept of agent autonomy in the context of reliability modeling was first proposed by M. Azarkhail [1], where a fundamentally new idea of system representation by autonomous intelligent agents for the purpose of reliability modeling was introduced. Contribution of the current work lies in the further development of the agent anatomy concept, particularly the refined agent classification within the scope of the PoF-based system reliability modeling, new approaches to the learning and the autonomy properties of the intelligent agents, and modeling interacting failure mechanisms within the dynamic engineering system. The autonomous property of intelligent agents is defined as agent's ability to self-activate, deactivate or completely redefine their role in the analysis. This property of agents and the ability to model interacting failure mechanisms of the system elements makes the agent autonomy fundamentally different from all existing methods of probabilistic PoF-based reliability modeling. 1. Azarkhail, M., "Agent Autonomy Approach to Physics-Based Reliability Modeling of Structures and Mechanical Systems", PhD thesis, University of Maryland, College Park, 2007.

  10. An Enhanced Preventive Maintenance Optimization Model Based on a Three-Stage Failure Process

    Directory of Open Access Journals (Sweden)

    Ruifeng Yang

    2015-01-01

    Full Text Available Nuclear power plants are highly complex systems and the issues related to their safety are of primary importance. Probabilistic safety assessment is regarded as the most widespread methodology for studying the safety of nuclear power plants. As maintenance is one of the most important factors for affecting the reliability and safety, an enhanced preventive maintenance optimization model based on a three-stage failure process is proposed. Preventive maintenance is still a dominant maintenance policy due to its easy implementation. In order to correspond to the three-color scheme commonly used in practice, the lifetime of system before failure is divided into three stages, namely, normal, minor defective, and severe defective stages. When the minor defective stage is identified, two measures are considered for comparison: one is that halving the inspection interval only when the minor defective stage is identified at the first time; the other one is that if only identifying the minor defective stage, the subsequent inspection interval is halved. Maintenance is implemented immediately once the severe defective stage is identified. Minimizing the expected cost per unit time is our objective function to optimize the inspection interval. Finally, a numerical example is presented to illustrate the effectiveness of the proposed models.

  11. Emerging drugs for prevention of graft failure after allogeneic hematopoietic stem cell transplantation.

    Science.gov (United States)

    Servais, Sophie; Beguin, Yves; Baron, Frédéric

    2013-06-01

    Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the treatment of choice for many patients suffering from hematological malignancies, severe hemoglobinopathies, bone marrow failures or severe primary immunodeficiencies. Graft rejection/failure (GF) is a life-threatening complication following allo-HSCT that is most commonly caused by the reactivity of recipient T cells, natural killer (NK) cells or antibodies against donor grafted hematopoietic cells. The increasing use of allo-HSCT following reduced-intensity conditioning (RIC) and the increasing use of alternative donors (unrelated cord blood and human leukocyte antigen (HLA)-mismatched donor) have resulted in higher frequency of GF. This review describes the pathogenesis and current prevention and treatment of GF as well as agents in development for GF prevention or treatment. The risk of GF may be reduced in the future by optimizing the conditioning regimens and post-grafting immunosuppression, increasing the number of hematopoietic stem cells (HSCs) and/or immune cells transplanted, optimizing HSC homing and better detecting patients at high risk of GF by searching for pre-transplant donor-specific anti-HLA antibodies in patients given grafts from HLA-mismatched donors, or by closely monitoring donor T- and/or NK-cell chimerism after allo-HSCT following RIC.

  12. New Graduate Nurses' Preparation for Recognition and Prevention of Failure to Rescue: A Qualitative Study.

    Science.gov (United States)

    Herron, Elizabeth K

    2017-08-17

    To explore new graduate nurses' experiences with recognition and prevention of failure to rescue. Failure to rescue is recognized as a quality of care indicator, a core measure of nursing care in hospitals, and a determinant for staffing in acute care facilities. Clinical reasoning is an essential component in preventing failure to rescue and should be emphasized in nursing education and new graduate orientation. Many nurses graduate without the ability to use clinical reasoning in providing patient care which can lead to adverse patient outcomes. A descriptive phenomenological design was used. A purposive sample of 14 new graduate nurses from a nursing program in the Southeastern United States, in practice for no more than eighteen months, was recruited. Individual one on one interviews were conducted from January to June 2016 and audio recorded for accuracy. Data were evaluated using the consolidated criteria for reporting qualitative research (COREQ) guidelines. Recordings were professionally transcribed and reviewed. Using Giorgi's methods for data analysis, five main themes were discerned in the data: clinical preparation in school; experience with emergent situations; development of clinical reasoning; low confidence as a new graduate; and responding to emergencies. Within each theme, subthemes emerged. The words of the participants provided rich detail into the preparation of new graduate nurses and how nurse educators, managers, and preceptors can better focus learning opportunities to prepare them for practice. Experiential learning combined with collaboration among education stakeholders will lead to a better prepared and more confident nursing work force. Better preparation and continued support of new graduate nurses leads to positive patient outcomes and more satisfaction with their choice of nursing as a profession. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

  13. Left ventricular mechanics in advanced heart failure patients

    NARCIS (Netherlands)

    Bertini, Matteo

    2015-01-01

    The general introduction of the thesis outlines the role of cardiac mechanics assessment in the evaluation and risk stratification of HF patients. Part I This part of the thesis summarizes current imaging techniques to assess various aspects of LV mechanics in HF patients (Chapter 2),

  14. [Nutritional management of intestinal failure and potential stimulation mechanisms].

    Science.gov (United States)

    Pérez de la Cruz, A J; Moreno-Torres Herrera, R; Pérez Roca, C

    2007-05-01

    Severe forms of intestinal failure represent one of the most complex pathologies to manage, in both children and adults. In adults, the most common causes are chronic intestinal pseudo-obstruction and severe short bowel syndrome following large intestinal resections, particularly due to massive mesenteric ischemic, within the context of cardiopathies occurring with atrial fibrillation. The essential management after stabilizing the patient consists in nutritional support, either by parenteral or enteral routes, with tolerance to oral diet being the final goal of intestinal adaptation in these pathologies. Surgery may be indicated in some cases to increase the absorptive surface area. Parenteral nutrition is an essential support measure that sometimes has to be maintained for long time, even forever, except for technique-related complications or unfavorable clinical course that would lead to extreme surgical alternatives such as intestinal transplantation. Hormonal therapy with trophism-stimulating factors opens new alternatives that are already being tried in humans.

  15. Non-invasive mechanic ventilation in treating acute respiratory failure

    Directory of Open Access Journals (Sweden)

    Federico Lari

    2009-12-01

    Full Text Available Non invasive ventilation (NIV in acute respiratory failure (ARF improve clinical parameters, arterial blood gases, decrease mortality and endo tracheal intubation (ETI rate also outside the intensive care units (ICUs. Objective of this study is to verify applicability of NIV in a general non respiratory medical ward. We enrolled 68 consecutive patients (Pts with Hypoxemic or Hyper capnic ARF: acute cardiogenic pulmonary edema (ACPE, exacerbation of chronic obstructive pulmonary disease (COPD, Pneu - monia, acute lung injury / acute respiratory distress syndrome (ALI/ARDS. NIV treatment was CPAP or PSV + PEEP. 12 Pts (18,5% met primary endpoint (NIV failure: 11 Pts (17% needed ETI (5ALI/ARDS p < 0,0001, 6COPD 16,6%, 1 Patient (1,5% died (Pneumonia. No Pts with ACPE failed (p = 0,0027. Secondary endpoints: significant improvement in Respiratory Rate (RR, Kelly Score, pH, PaCO2, PaO2 vs baseline. Median duration of treatment: 16:06 hours: COPD 18:54, ACPE 4:15. Mean length of hospitalisation: 8.66 days. No patients discontinued NIV, no side effects. Results are consistent with literature. Hypoxemic ARF related to ALI/ARDS and pneumonia show worst outcome: it is not advisable to manage these conditions with NIV outside the ICU. NIV for ARF due to COPD and ACPE is feasible, safe and effective in a general medical ward if selection of Pts, staff’s training and monitoring are appropriate. This should encourage the diffusion of NIV in this specific setting. According to strong evidences in literature, NIV should be considered a first line and standard treatment in these clinical conditions irrespective of the setting.

  16. Intestinal endotoxemia as a pathogenetic mechanism in liver failure

    Institute of Scientific and Technical Information of China (English)

    De-WuHan

    2002-01-01

    Liver injury induced by various pathogenic factors(such as hepatitis virus,ethanol,drugs and hepatotoxicants,etc.)through their respective special pathogenesis is referred to as“primary liver injury”(LPS)and the activation of kupffer cells by LPS while intestinal endotoxemia(IETM)occurted during the occurrence and development of hepatitis is named the“secondary liver injury”(SLI).The latter which has lost their own specificities of primary pathogenic factors is ascribed to IETM.The“secondary liver injury”is of important action and impact on development and prognosis of hepatitis.More severe IETM commonly results in excessive inflammatory responses,with serious hepatic necrosis,further severe hepatitis and even induces acute liver failure.The milder IETM successively precipitates a cascade,including repeated and persistent hepatocytic impairment accompanied by infiltration of inflammatory cells,hepatic fibrosis,cirrhosis and hepatocarcinoma.Generally,the milder IETM ends with chronic hepatic failure.If PLI caused by various pathogenic factors through their independent specific mechanismis regarded as“the first hit”on liver,then SLI mediated by different chemical mediators from KC,activated by IETMin the course of hepatitis is “the second hit”on liver.Thus,fusing and overlapping of the primary and scorndary liver injunies determine and influeuce the complexity of the illness and outcome of the patient with hepatitis.For this reason,the viewpoint of “SLI”induced by the “second hit”on liver inflicted by IETM suggests that medical professionals should attach great importance to both“PLI”and“SLI”caused by IETM.That is,try to adjust the function of KS,and eliminate endotoxemia ofthe patient.

  17. Intestinal endotoxemia as a pathogenetic mechanism in liver failure

    Institute of Scientific and Technical Information of China (English)

    De-Wu Han

    2002-01-01

    Liver injury induced by various pathogenic factors (such as hepatitis virus, ethanol, drugs and hepatotoxicants, etc.)through their respective special pathogenesis is referred to as "primary liver injury" (PLI). Liver injury resultedfrom endotoxin (lipopolysaccharide, LPS) and the activation of Kupffer cells by LPS while intestinal endotoxemia (IETM) occurred during the occurrence and development of hepatitis is named the "secondary liver injury" (SLI).The latter which has lost their own specificities of primary pathogenic factors is ascribed to IETM. The "secondary liver injury" is of important action and impact on development and prognosis of hepatitis. More severe IETM commonly results in excessive inflammatory responses, with serious hepatic necrosis,further severe hepatitis and even induces acute liver failure.The milder IETM successively precipitates a cascade,including repeated and persistent hepatocytic impairment accompanied by infiltration of inflammatory cells, hepatic fibrosis, cirrhosis and hepatocarcinoma. Generally, the milder IETM ends with chronic hepatic failure. If PLI caused by various pathogenic factors through their independent specific mechanismis regarded as "the first hit" on liver, then SLI mediated by different chemical mediators from KCs activated by IETM in the course of hepatitis is "the second hit" on liver. Thus, fusing and overlapping of the primary and scondary liver injuries determine and influeuce the complexity of the illness and outcome of the patient with hepatitis. For this reason, the viewpoint of "SLI" induced by the "second hit" on liver inflicted by IFTM suggests that medical professionals should attach great importance to both "PLI"and "SLI" caused by IETM. That is, try to adjust the function of KSs and eliminate endotoxemia of the patient.

  18. Fundamental study of failure mechanisms of pressure vessels under thermo-mechanical cycling in multiphase environments

    Science.gov (United States)

    Penso Mula, Jorge Antonio

    Cracking and bulging in welded and internally lined pressure vessels that work in thermal-mechanical cycling services have been well known problems in the petrochemical, power and nuclear industries. Published literature and industry surveys show that similar problems have been occurring during the last 50 years. Understanding the causes of cracking and bulging would lead to improvements in the reliability of these pressure vessels. This study attempts to add information required for improving the knowledge and fundamental understanding of these problems. Cracking and bulging, most often in the weld areas, commonly experienced in delayed coking units (e.g. coke drums) in oil refineries are typical examples. The coke drum was selected for this study because of the existing field experience and past industrial investigation results that were available to serve as the baseline references for the analytical studies performed for this dissertation. Another reason for selecting the delayed coking units for this study was due to their high economical yields. Shutting down these units would cause a high negative economic impact on the refinery operations. Several failure mechanisms were hypothesized. The finite element method was used to analyze these significant variables and to verify the hypotheses. In conclusion, a fundamental explanation of the occurrence of bulging and cracking in pressure vessels in multiphase environments has been developed. Several important factors have been identified, including the high convection coefficient of the boiling layer during filling and quenching, the mismatch in physical, thermal and mechanical properties in the dissimilar weld of the clad plates and process conditions such as heating and quenching rate and warming time. Material selection for coke drums should consider not only fatigue strength but also corrosion resistance at high temperatures and low temperatures. Cracking occurs due to low cycle fatigue and corrosion. The FEA

  19. Ventricular assist devices in heart failure: how to support the heart but prevent atrophy?

    Science.gov (United States)

    Pokorný, M; Cervenka, L; Netuka, I; Pirk, J; Koňařík, M; Malý, J

    2014-01-01

    Ventricular assist devices (VAD) have recently established themselves as an irreplaceable therapeutic modality of terminal heart failure. Because of the worldwide shortage of donors, ventricular assist devices play a key role in modern heart failure therapy. Some clinical data have revealed the possibility of cardiac recovery during VAD application. On the other hand, both clinical and experimental studies indicate the risk of the cardiac atrophy development, especially after prolonged mechanical unloading. Little is known about the specific mechanisms governing the unloading-induced cardiac atrophy and about the exact ultrastructural changes in cardiomyocytes, and even less is known about the ways in which possible therapeutical interventions may affect heart atrophy. One aim of this review was to present important aspects of the development of VAD-related cardiac atrophy in humans and we also review the most significant observations linking clinical data and those derived from studies using experimental models. The focus of this article was to review current methods applied to alleviate cardiac atrophy which follows mechanical unloading of the heart. Out of many pharmacological agents studied, only the selective beta2 agonist clenbuterol has been proved to have a significantly beneficial effect on unloading-induced atrophy. Mechanical means of atrophy alleviation also seem to be effective and promising.

  20. Deformation and failure mechanisms of graphite/epoxy composites under static loading

    Science.gov (United States)

    Clements, L. L.

    1981-01-01

    The mechanisms of deformation and failure of graphite epoxy composites under static loading were clarified. The influence of moisture and temperature upon these mechanisms were also investigated. Because the longitudinal tensile properties are the most critical to the performance of the composite, these properties were investigated in detail. Both ultimate and elastic mechanical properties were investigated, but the study of mechanisms emphasized those leading to failure of the composite. The graphite epoxy composite selected for study was the system being used in several NASA sponsored flight test programs.

  1. Detection of mechanical failures in induction motors by current spectrum analysis

    Energy Technology Data Exchange (ETDEWEB)

    Sokansky, K.; Novak, P.; Bilos, J.; Labaj, J. [Technical University Ostrava, Moraviasilesian Power Stations s.h.c. (Czech Republic)

    1997-12-31

    From the diagnostic point of view, an electric machine can be understood as an electromechanical system. It means that any manifestations of mechanical failures do not have to show themselves only in mechanical quantities, i.e. vibration in our case. Mechanical failures can also manifest themselves in electrical quantities, namely in electric current in our case. This statement is valid inversely too, which means that faults occurring in electric circuits can be measured through mechanical quantities. This presentation deals with measuring the current spectra of induction motors with short circuited armatures that are drives used in the industries most. (orig.) 3 refs.

  2. Effect of flexural crack on plain concrete beam failure mechanism A numerical simulation

    Directory of Open Access Journals (Sweden)

    Abdoullah Namdar

    2016-03-01

    Full Text Available The flexural failure of plain concrete beam occurs along with development of flexural crack on beam. In this paper by using ABAQUS, mechanism failure of plain concrete beam under three steps have been simulated. The cracking moment has been analytically calculated and applied on the both sides of the fixed beam, and flexural crack has been simulated on beam. Displacement, von Mises, load reaction, displacementcrack length, von Mises-crack length and von Mises-displacement of beams have been graphical depicted. Results indicated that, the flexural crack governs beam mechanism failure and its effects on beam resistance failure. It has been found that the flexural crack in initial stage it developed slowly and changes to be fast at the final stage of collapsing beam due to reduction of the flexural resistance of beam. Increasing mechanical properties of concrete, collapse displacement is reduced.

  3. Evaluating Failure Mechanics of the Malpais Landslide, Eureka County, Nevada

    Science.gov (United States)

    Wilhite, C. P.; Carr, J. R.; Wallace, A. R.; Watters, R. J.

    2008-12-01

    The Malpais Landslide is located on the northeast end of the Shoshone Mountains in north-central Nevada. The 2.3 square kilometer slide originated near the crest of the Malpais Rim and flowed north into Whirlwind Valley. Given the proximity to Holocene faulting and active geothermal conditions, destabilizing forces include seismic activity, hydrothermal alteration, and changes in groundwater conditions. Approximately 3 km west of the slide is the Beowawe Geothermal Field, which is partially recharged along local faults and has altered geologic units throughout the slide area. The area contains two major normal faults (the approximately east striking Malpais Fault and the approximately north striking Dunphy Pass Fault) and numerous smaller faults. The most recent offset along the Malpais fault was approximately 7450 years B.P. (Wesnousky et al., 2005). The resulting scarp cannot be traced through the slide, therefore sliding occurred after that time (though previous sliding has not been ruled out). The stratigraphy in the slide area consists of a basal Paleozoic quartzite, unconformably overlain by Oligocene to Miocene conglomeratic to tuffaceous sediments with interbedded volcanic flows, capped by a sequence of mafic flow units. Except for the lowest sedimentary unit, Tts, all units dip approximately 25 degrees southeast. Tts was measured in outcrops east of the site and dips approximately 20 degrees north; since these outcrops could not be traced into the slide area, the dip of Tts at the slide is unknown. Point-load testing showed Tts to have a tensile strength of 3.12 MPa which is 55% weaker than the next weakest unit in the area. These factors, as well as Tts" semiconsolidated nature, suggest that Tts was the unit of failure. Further testing of the Malpais Landslide, as well as computer simulation, will be used to determine the cause of failure. This information and the examination of other nearby landslides may be helpful in assessing landslide risk in north

  4. Risk Analysis and Prediction of Floor Failure Mechanisms at Longwall Face in Parvadeh-I Coal Mine using Rock Engineering System (RES)

    Science.gov (United States)

    Aghababaei, Sajjad; Saeedi, Gholamreza; Jalalifar, Hossein

    2016-05-01

    The floor failure at longwall face decreases productivity and safety, increases operation costs, and causes other serious problems. In Parvadeh-I coal mine, the timber is used to prevent the puncture of powered support base into the floor. In this paper, a rock engineering system (RES)-based model is presented to evaluate the risk of floor failure mechanisms at the longwall face of E 2 and W 1 panels. The presented model is used to determine the most probable floor failure mechanism, effective factors, damaged regions and remedial actions. From the analyzed results, it is found that soft floor failure is dominant in the floor failure mechanism at Parvadeh-I coal mine. The average of vulnerability index (VI) for soft, buckling and compressive floor failure mechanisms was estimated equal to 52, 43 and 30 for both panels, respectively. By determining the critical VI for soft floor failure mechanism equal to 54, the percentage of regions with VIs beyond the critical VI in E 2 and W 1 panels is equal to 65.5 and 30, respectively. The percentage of damaged regions showed that the excess amount of used timber to prevent the puncture of weak floor below the powered support base is equal to 4,180,739 kg. RES outputs and analyzed results showed that setting and yielding load of powered supports, length of face, existent water at face, geometry of powered supports, changing the cutting pattern at longwall face and limiting the panels to damaged regions with supercritical VIs could be considered to control the soft floor failure in this mine. The results of this research could be used as a useful tool to identify the damaged regions prior to mining operation at longwall panel for the same conditions.

  5. A New Rock Strength Criterion from Microcracking Mechanisms Which Provides Theoretical Evidence of Hybrid Failure

    Science.gov (United States)

    Zhu, Qi-Zhi

    2017-02-01

    A proper criterion describing when material fails is essential for deep understanding and constitutive modeling of rock damage and failure by microcracking. Physically, such a criterion should be the global effect of local mechanical response and microstructure evolution inside the material. This paper aims at deriving a new mechanisms-based failure criterion for brittle rocks, based on micromechanical unilateral damage-friction coupling analyses rather than on the basic results from the classical linear elastic fracture mechanics. The failure functions respectively describing three failure modes (purely tensile mode, tensile-shear mode as well as compressive-shear mode) are achieved in a unified upscaling framework and illustrated in the Mohr plane and also in the plane of principal stresses. The strength envelope is proved to be continuous and smooth with a compressive to tensile strength ratio dependent on material properties. Comparisons with experimental data are finally carried out. By this work, we also provide a theoretical evidence on the hybrid failure and the smooth transition from tensile failure to compressive-shear failure.

  6. Mechanism for Corrosion Prevention by a Mechanical Plating of Uniform Zinc-Iron Alloy

    Science.gov (United States)

    Kasai, Naoya; Kaku, Yoshihiko; Okazaki, Shinji; Hirai, Kuninori

    2016-09-01

    In situ electrochemical monitoring with a three-electrode cell was applied to investigate the anti-corrosion properties of a mechanical zinc-iron alloy plating. Several electron probe microanalyses were also conducted to identify the chemical elements in the plating. The results indicated the formation of a Zn-Fe intermetallic compound, which allowed a mechanism for corrosion prevention to be proposed. In the proposed mechanism, Zn(OH)2 plays a significant role in the corrosion prevention of steel alloys.

  7. Mechanical properties and failure behavior of unidirectional porous ceramics

    Science.gov (United States)

    Seuba, Jordi; Deville, Sylvain; Guizard, Christian; Stevenson, Adam J.

    2016-04-01

    We show that the honeycomb out-of-plane model derived by Gibson and Ashby can be applied to describe the compressive behavior of unidirectional porous materials. Ice-templating allowed us to process samples with accurate control over pore volume, size, and morphology. These samples allowed us to evaluate the effect of this microstructural variations on the compressive strength in a porosity range of 45-80%. The maximum strength of 286 MPa was achieved in the least porous ice-templated sample (P(%) = 49.9), with the smallest pore size (3 μm). We found that the out-of-plane model only holds when buckling is the dominant failure mode, as should be expected. Furthermore, we controlled total pore volume by adjusting solids loading and sintering temperature. This strategy allows us to independently control macroporosity and densification of walls, and the compressive strength of ice-templated materials is exclusively dependent on total pore volume.

  8. Mechanical properties and failure behavior of unidirectional porous ceramics.

    Science.gov (United States)

    Seuba, Jordi; Deville, Sylvain; Guizard, Christian; Stevenson, Adam J

    2016-04-14

    We show that the honeycomb out-of-plane model derived by Gibson and Ashby can be applied to describe the compressive behavior of unidirectional porous materials. Ice-templating allowed us to process samples with accurate control over pore volume, size, and morphology. These samples allowed us to evaluate the effect of this microstructural variations on the compressive strength in a porosity range of 45-80%. The maximum strength of 286 MPa was achieved in the least porous ice-templated sample (P(%) = 49.9), with the smallest pore size (3 μm). We found that the out-of-plane model only holds when buckling is the dominant failure mode, as should be expected. Furthermore, we controlled total pore volume by adjusting solids loading and sintering temperature. This strategy allows us to independently control macroporosity and densification of walls, and the compressive strength of ice-templated materials is exclusively dependent on total pore volume.

  9. Exogenous midkine administration prevents cardiac remodeling in pacing-induced congestive heart failure of rabbits.

    Science.gov (United States)

    Harada, Masahide; Hojo, Mayumi; Kamiya, Kaichiro; Kadomatsu, Kenji; Murohara, Toyoaki; Kodama, Itsuo; Horiba, Mitsuru

    2016-01-01

    Midkine (MK), a heparin-binding growth factor, has been shown to prevent cardiac remodeling after ischemic injury through its anti-apoptotic effect. Cell apoptosis is central to the pathophysiology of cardiac remodeling in congestive heart failure (CHF) of ischemic as well as non-ischemic origin. We hypothesized that MK exerts the anti-apoptotic cardioprotective effect in CHF of non-ischemic etiology. MK protein or vehicle (normal saline) was subcutaneously administered in tachycardia-induced CHF rabbits (right ventricular pacing, 350 beats/min, 4 weeks). The vehicle-treated rabbits (n = 19, control) demonstrated severe CHF and high mortality rate, whereas MK (n = 16) demonstrated a well-compensated state and a lower mortality rate. In echocardiography, left ventricular (LV) end-diastolic dimension decreased in MK versus control, whereas LV systolic function increased. In histological analysis (picrosirius red staining), MK decreased collagen deposition area compared with control. TUNEL staining showed that MK prevented cell apoptosis and minimized myocyte loss in the CHF rabbit ventricle, associated with activation of PI3-K/Akt signaling, producing a parallel decrease of Bax/Bcl-2 ratio. MK prevented progression of cardiac remodeling in the CHF rabbit, likely by activation of anti-apoptotic signaling. Exogenous MK application might be a novel therapeutic strategy for CHF due to non-ischemic origin.

  10. Regional cerebral blood flow during mechanical hyperventilation in patients with fulminant hepatic failure

    DEFF Research Database (Denmark)

    Strauss, Gitte Irene; Høgh, Peter; Møller, Kirsten;

    1999-01-01

    Hyperventilation is frequently used to prevent or postpone the development of cerebral edema and intracranial hypertension in patients with fulminant hepatic failure (FHF). The influence of such therapy on regional cerebral blood flow (rCBF) remains, however, unknown. In this study the CBF...

  11. Heart failure-inducible gene therapy targeting protein phosphatase 1 prevents progressive left ventricular remodeling.

    Directory of Open Access Journals (Sweden)

    Yosuke Miyazaki

    Full Text Available BACKGROUND: The targeting of Ca(2+ cycling has emerged as a potential therapy for the treatment of severe heart failure. These approaches include gene therapy directed at overexpressing sarcoplasmic reticulum (SR Ca(2+ ATPase, or ablation of phospholamban (PLN and associated protein phosphatase 1 (PP1 protein complexes. We previously reported that PP1β, one of the PP1 catalytic subunits, predominantly suppresses Ca(2+ uptake in the SR among the three PP1 isoforms, thereby contributing to Ca(2+ downregulation in failing hearts. In the present study, we investigated whether heart-failure-inducible PP1β-inhibition by adeno-associated viral-9 (AAV9 vector mediated gene therapy is beneficial for preventing disease progression in genetic cardiomyopathic mice. METHODS: We created an adeno-associated virus 9 (AAV9 vector encoding PP1β short-hairpin RNA (shRNA or negative control (NC shRNA. A heart failure inducible gene expression system was employed using the B-type natriuretic protein (BNP promoter conjugated to emerald-green fluorescence protein (EmGFP and the shRNA sequence. AAV9 vectors (AAV9-BNP-EmGFP-PP1βshRNA and AAV9-BNP-EmGFP-NCshRNA were injected into the tail vein (2×10(11 GC/mouse of muscle LIM protein deficient mice (MLPKO, followed by serial analysis of echocardiography, hemodynamic measurement, biochemical and histological analysis at 3 months. RESULTS: In the MLPKO mice, BNP promoter activity was shown to be increased by detecting both EmGFP expression and the induced reduction of PP1β by 25% in the myocardium. Inducible PP1βshRNA delivery preferentially ameliorated left ventricular diastolic function and mitigated adverse ventricular remodeling. PLN phosphorylation was significantly augmented in the AAV9-BNP-EmGFP-PP1βshRNA injected hearts compared with the AAV9-BNP-EmGFP-NCshRNA group. Furthermore, BNP production was reduced, and cardiac interstitial fibrosis was abrogated at 3 months. CONCLUSION: Heart failure

  12. Study of the failure mechanism for fiber composite materials taking account of physicochemical interaction of components

    Energy Technology Data Exchange (ETDEWEB)

    Zabolotskii, A.A.; Ignatova, N.P.

    1985-11-01

    An analytical approach is presented to study the failure process for fiber composite materials (CM). Failure processes are modelled in a computer, including a stage for model construction and a loading and failure stage for the model CM as a simulation of CM behavior. Three composite materials were considered with an aluminum matrix reinforced with fibers of carbon, boron (coated with B/sub 4/C), and silicon carbide. The authors found that failure of a CM develops by one of three micromechanisms depending on the ratio of mechanical characteristics of interaction, i.e., retention in the CM of fiber strength and matrix ductility and creation of strong component bonds. The sequence of elementary acts forming one or another failure macromechanism is presented.

  13. Preventive strategy in response to climate change and infrastructural failures for Jakarta slum dwellers

    Directory of Open Access Journals (Sweden)

    V. Pooroe

    2012-08-01

    Full Text Available Jakarta is a city with unpredictable yet annual water shortages, both during the dry and wet season, which disproportionately affect the urban poor. One possible solution is to redevelop the existing water supply system which is now working in one of the largest slum area in Penjaringan, North Jakarta. This system is equipped with a large meter, the Master Meter, to record the communal water consumption and individual meters to record household consumptions. The Community Based Organization uses, operates, and maintains the system based on agreement with water users. Improvement of the Master Meter is achieved by harvesting uncollected rain water during the wet season with its high rainfall intensity, modifying the water storage system and improving the influent water quality. This paper aims to provide a preventive strategy in response to climate change and infrastructural failures based on a case study of community-based water supply project in Penjaringan, Jakarta.

  14. New tool aims to standardize handoffs in the ED, boosting safety and preventing communication failures.

    Science.gov (United States)

    2013-08-01

    To address identified patient safety risks in the handoff process, a group of emergency providers developed Safer Sign Out, a paper-based template that prompts clinicians to jointly review issues of concern on patients who are being passed from one clinician to another at the end of a shift. Already in practice at 12 hospitals in the Mid-Atlantic region, the approach is now being disseminated nationwide with the help of the non-profit Emergency Medicine Patient Safety Foundation. Advocates of the new tool say very few EDs have a clear, agreed-upon process for how to conduct handoffs. Safer Sign Out seeks to prevent communications failures by putting structure into the handoff process. In addition to prompting incoming and outgoing physicians to discuss each patient being handed off, the approach involves having both physicians round at the bedside of these patients so that patients fully understand when their care is being transitioned to a new provider.

  15. Effect of gomisin A in the prevention of acute hepatic failure induction.

    Science.gov (United States)

    Mizoguchi, Y; Kawada, N; Ichikawa, Y; Tsutsui, H

    1991-08-01

    Nearly all rats develop massive hepatic cell necrosis and die upon intravenous administration of heat-killed Propionibacterium acnes followed by a small amount of Gram-negative lipopolysaccharide 7 days later. However, when such an experimental liver disorder is induced in rats raised for 4 or more weeks on food containing 0.06% of gomisin A extracted and purified from Schizandra chinensis, the survival rate rises, histological changes of the liver improve remarkably, and splenocyte reactivity to phytohemagglutinin and pokeweed mitogen as well as splenocyte interleukin 1 productivity are retained. These results suggested the possibility that the development of acute hepatic failure may be prevented with the oral administration of gomisin A.

  16. Expectations and high school change: teacher-researcher collaboration to prevent school failure.

    Science.gov (United States)

    Weinstein, R S; Soulé, C R; Collins, F; Cone, J; Mehlhorn, M; Simontacchi, K

    1991-06-01

    Describes the multilevel outcomes of a collaborative preventive intervention for ninth-graders at risk for school failure using qualitative and quasi-experimental methods. Teachers, administrators, and researchers implemented innovative practices communicating positive expectations for low-achieving adolescents in their transition to high school. Changes were made in the practices of curriculum, grouping, evaluation, motivation, student responsibility, and relationships (in the classroom, with parents, and in the school). Both implementation and evaluation evolved as a function of collaboration. Change was promising but not uniform. Project teachers became more positive about students and colleagues, expanded their roles, and changed school tracking policies. The 158 project students, in contrast to the 154 comparison students showed improved grades and disciplinary referrals post-intervention and increased retention in school 1 year later, but their absences rose and improved performance was not maintained. The implications of this analysis for school-based interventions and its evaluation are discussed.

  17. Hepatocyte Growth Factor Prevents Acute Renal Failure of Accelerates Renal Regeneration in mice

    Science.gov (United States)

    Kawaida, Kouichi; Matsumoto, Kunio; Shimazu, Hisaaki; Nakamura, Toshikazu

    1994-05-01

    Although acute renal failure is encountered with administration of nephrotoxic drugs, ischemia, or unilateral nephrectomy, there has been no effective drug which can be used in case of acute renal failure. Hepatocyte growth factor (HGF) is a potent hepatotropic factor for liver regeneration and is known to have mitogenic, motogenic, and morphogenic activities for various epithelial cells, including renal tubular cells. Intravenous injection of recombinant human HGF into mice remarkably suppressed increases in blood urea nitrogen and serum creatinine caused by administration of cisplatin, a widely used antitumor drug, or HgCl_2, thereby indicating that HGF strongly prevented the onset of acute renal dysfunction. Moreover, exogenous HGF stimulated DNA synthesis of renal tubular cells after renal injuries caused by HgCl_2 administration and unilateral nephrectomy and induced reconstruction of the normal renal tissue structure in vivo. Taken together with our previous finding that expression of HGF was rapidly induced after renal injuries, these results allow us to conclude that HGF may be the long-sought renotropic factor for renal regeneration and may prove to be effective treatment for patients with renal dysfunction, especially that caused by cisplatin.

  18. Early diagnosis of the urofacial syndrome is essential to prevent irreversible renal failure

    Directory of Open Access Journals (Sweden)

    Francisco A. Nicanor

    2005-10-01

    Full Text Available INTRODUCTION: The urofacial or Ochoa syndrome is a rare disease characterized by the presence of functional obstructive uropathy associated with peculiar facial features when patients attempt to smile or laugh. Unfortunately, many of these patients remain without proper diagnosis or adequate treatment due to lack of recognition of the disease. This can ultimately result in upper tract deterioration and eventual renal failure. We present our experience with this rare syndrome. MATERIALS AND METHODS: We identified 3 patients who presented initially with acute renal failure, urinary tract infection (UTI and severe dysfunctional elimination. All patients were thoroughly evaluated, including screening for spinal cord anomalies, and were subsequently diagnosed with urofacial syndrome. RESULTS: At the outset, the two older patients (aged 4 and 9 years presented with the typical facial features when attempting to smile or laugh. One patient in the newborn period presented with urinary and fecal retention and septicemia and, to our knowledge, represents the youngest case of urofacial syndrome reported so far. All patients were evaluated with ultrasonography, renal scan, voiding cystourethrogram (VCUG and urodynamics. Findings included hydronephrosis and a thick-walled, trabeculated bladder with poor compliance and detrusor hypereflexia respectively in each patient. All were subsequently treated with clean intermittent catheterization (CIC, antibiotic prophylaxis and anticholinergic therapy. One patient required appendicovesicostomy for CIC due to discomfort secondary to a sensate urethra. CONCLUSIONS: Our series demonstrates that early recognition of this rare syndrome is necessary to adequately treat and prevent upper tract deterioration in these unique individuals. Although the urofacial is difficult to diagnose in infants, cognizance must be maintained in order to prevent severe subsequent sequalae.

  19. Interface failure modes explain non-monotonic size-dependent mechanical properties in bioinspired nanolaminates

    Science.gov (United States)

    Song, Z. Q.; Ni, Y.; Peng, L. M.; Liang, H. Y.; He, L. H.

    2016-03-01

    Bioinspired discontinuous nanolaminate design becomes an efficient way to mitigate the strength-ductility tradeoff in brittle materials via arresting the crack at the interface followed by controllable interface failure. The analytical solution and numerical simulation based on the nonlinear shear-lag model indicates that propagation of the interface failure can be unstable or stable when the interfacial shear stress between laminae is uniform or highly localized, respectively. A dimensionless key parameter defined by the ratio of two characteristic lengths governs the transition between the two interface-failure modes, which can explain the non-monotonic size-dependent mechanical properties observed in various laminate composites.

  20. The contribution of inspiratory muscles function to exercise limitation in heart failure: pathophysiological mechanisms

    OpenAIRE

    Jorge P. Ribeiro; Chiappa, Gaspar R.; Carine C. Callegaro

    2012-01-01

    BACKGROUND: Heart failure induces histological, metabolic and functional adaptations in the inspiratory muscles. This inspiratory muscle weakness, which occurs in 30% to 50% of the heart failure patients, is associated with reduction in the functional capacity, reduction in the quality of life and with a poor prognosis in these individuals. OBJECTIVES: The objective of this review was to discuss the pathophysiological mechanisms that may explain the role of the inspiratory muscles in the exer...

  1. Brittleness Generation Mechanism and Failure Model of High Strength Lightweight Aggregate Concrete

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The brittleness generation mechanism of high strength lightweight aggregate concrete(HSLWAC) was presented, and it was indicated that lightweight aggregate was the vulnerable spot,initiating brittleness. Based on the analysis of the brittleness failure by the load-deflection curve, the brittleness presented by HSLWAC was more prominent compared with ordinary lightweight aggregate concrete of the same strength grade. The model of brittleness failure was also established.

  2. An autonomous recovery mechanism against optical distribution network failures in EPON

    Science.gov (United States)

    Liem, Andrew Tanny; Hwang, I.-Shyan; Nikoukar, AliAkbar

    2014-10-01

    Ethernet Passive Optical Network (EPON) is chosen for servicing diverse applications with higher bandwidth and Quality-of-Service (QoS), starting from Fiber-To-The-Home (FTTH), FTTB (business/building) and FTTO (office). Typically, a single OLT can provide services to both residential and business customers on the same Optical Line Terminal (OLT) port; thus, any failures in the system will cause a great loss for both network operators and customers. Network operators are looking for low-cost and high service availability mechanisms that focus on the failures that occur within the drop fiber section because the majority of faults are in this particular section. Therefore, in this paper, we propose an autonomous recovery mechanism that provides protection and recovery against Drop Distribution Fiber (DDF) link faults or transceiver failure at the ONU(s) in EPON systems. In the proposed mechanism, the ONU can automatically detect any signal anomalies in the physical layer or transceiver failure, switching the working line to the protection line and sending the critical event alarm to OLT via its neighbor. Each ONU has a protection line, which is connected to the nearest neighbor ONU, and therefore, when failure occurs, the ONU can still transmit and receive data via the neighbor ONU. Lastly, the Fault Dynamic Bandwidth Allocation for recovery mechanism is presented. Simulation results show that our proposed autonomous recovery mechanism is able to maintain the overall QoS performance in terms of mean packet delay, system throughput, packet loss and EF jitter.

  3. Exertional dyspnoea in chronic heart failure: the role of the lung and respiratory mechanical factors

    Directory of Open Access Journals (Sweden)

    Bruno-Pierre Dubé

    2016-09-01

    Full Text Available Exertional dyspnoea is among the dominant symptoms in patients with chronic heart failure and progresses relentlessly as the disease advances, leading to reduced ability to function and engage in activities of daily living. Effective management of this disabling symptom awaits a better understanding of its underlying physiology. Cardiovascular factors are believed to play a major role in dyspnoea in heart failure patients. However, despite pharmacological interventions, such as vasodilators or inotropes that improve central haemodynamics, patients with heart failure still complain of exertional dyspnoea. Clearly, dyspnoea is not determined by cardiac factors alone, but likely depends on complex, integrated cardio-pulmonary interactions. A growing body of evidence suggests that excessively increased ventilatory demand and abnormal “restrictive” constraints on tidal volume expansion with development of critical mechanical limitation of ventilation, contribute to exertional dyspnoea in heart failure. This article will offer new insights into the pathophysiological mechanisms of exertional dyspnoea in patients with chronic heart failure by exploring the potential role of the various constituents of the physiological response to exercise and particularly the role of abnormal ventilatory and respiratory mechanics responses to exercise in the perception of dyspnoea in patients with heart failure.

  4. Evidence of an emerging levee failure mechanism causing disastrous floods in Italy

    Science.gov (United States)

    Orlandini, Stefano; Moretti, Giovanni; Albertson, John

    2017-04-01

    A levee failure occurred along the Secchia River, Northern Italy, on January 19, 2014, resulting in flood damage in excess of 500 Million. In response to this failure, immediate surveillance of other levees in the region led to the identification of a second breach developing on the neighboring Panaro River, where rapid mitigation efforts were successful in averting a full levee failure. The paired breach events that occurred along the Secchia and Panaro Rivers provided an excellent window on an emerging levee failure mechanism. In the Secchia River, by combining the information content of photographs taken from helicopters in the early stage of breach development and 10-cm resolution aerial photographs taken in 2010 and 2012, animal burrows were found to exist in the precise levee location where the breach originated. In the Panaro River, internal erosion was observed to occur at a location where a crested porcupine den was known to exist and this erosion led to the collapse of the levee top. This paper uses detailed numerical modeling of rainfall, river flow, and variably saturated flow in the levee to explore the hydraulic and geotechnical mechanisms that were triggered along the Secchia and Panaro Rivers by activities of burrowing animals leading to levee failures. As habitats become more fragmented and constrained along river corridors it is possible that this failure mechanism could become more prevalent and, therefore, will demand greater attention in both the design and maintenance of earthen hydraulic structures as well as in wildlife management.

  5. Original mechanism of failure initiation revealed through modelling of naturally occurring microstructures

    Science.gov (United States)

    Gorbatikh, Larissa; Lomov, Stepan V.; Verpoest, Ignaas

    2010-05-01

    Motivated to reveal original mechanisms of failure resistance, we developed a material model that encompasses most reoccurring microstructural features of natural composites. The interesting result of the work is a notion that material failure is governed by the quality of interactions between hierarchical levels in the material microstructure. With intelligent use of the structure, these interactions can be tuned to create a powerful synergetic effect on the material failure behaviour. For example, while exploring different mechanisms of failure initiation in composites with bimodal size reinforcements (an indirect way to model two levels of hierarchy simultaneously) we found that failure initiation could be shifted from stress concentration sites of the higher level to the lower level. One could say that the material behaviour became insensitive to the presence of reinforcements on the higher level—a phenomenon that is counterintuitive to what is commonly known. The new mechanism of failure initiation could only be activated in composites with a highly controlled structural organization—in the studied case, reinforcements of the lower level needed to establish lamellar pathways between reinforcements of the higher level. These pathways lead to formation of an intriguing network-like microstructure. Intelligent communication between reinforcements in such a network created the necessary synergy to change the failure initiation mechanism in a discontinuous fashion. Another finding was that by establishing such a network, tensile stresses near dangerous stress concentration sites were locally transformed into compressive stresses. Resemblance of the revealed mechanism to phenomena on the nano-scale was also discussed. In the course of this work a new method was developed to investigate interactions between reinforcements and their collective input into effective and local properties of a composite. The reinforcement phase was modelled with the use of rigid

  6. Influence of metabolic dysfunction on cardiac mechanics in decompensated hypertrophy and heart failure.

    Science.gov (United States)

    Tewari, Shivendra G; Bugenhagen, Scott M; Vinnakota, Kalyan C; Rice, J Jeremy; Janssen, Paul M L; Beard, Daniel A

    2016-05-01

    Alterations in energetic state of the myocardium are associated with decompensated heart failure in humans and in animal models. However, the functional consequences of the observed changes in energetic state on mechanical function are not known. The primary aim of the study was to quantify mechanical/energetic coupling in the heart and to determine if energetic dysfunction can contribute to mechanical failure. A secondary aim was to apply a quantitative systems pharmacology analysis to investigate the effects of drugs that target cross-bridge cycling kinetics in heart failure-associated energetic dysfunction. Herein, a model of metabolite- and calcium-dependent myocardial mechanics was developed from calcium concentration and tension time courses in rat cardiac muscle obtained at different lengths and stimulation frequencies. The muscle dynamics model accounting for the effect of metabolites was integrated into a model of the cardiac ventricles to simulate pressure-volume dynamics in the heart. This cardiac model was integrated into a simple model of the circulation to investigate the effects of metabolic state on whole-body function. Simulations predict that reductions in metabolite pools observed in canine models of heart failure can cause systolic dysfunction, blood volume expansion, venous congestion, and ventricular dilation. Simulations also predict that myosin-activating drugs may partially counteract the effects of energetic state on cross-bridge mechanics in heart failure while increasing myocardial oxygen consumption. Our model analysis demonstrates how metabolic changes observed in heart failure are alone sufficient to cause systolic dysfunction and whole-body heart failure symptoms.

  7. Investigating Deformation and Failure Mechanisms in Nanoscale Multilayer Metallic Composites

    Energy Technology Data Exchange (ETDEWEB)

    Zbib, Hussein M. [Washington State Univ., Pullman, WA (United States); Bahr, David F. [Purdue Univ., West Lafayette, IN (United States)

    2014-10-22

    Over the history of materials science there are many examples of materials discoveries that have made superlative materials; the strongest, lightest, or toughest material is almost always a goal when we invent new materials. However, often these have been a result of enormous trial and error approaches. A new methodology, one in which researchers design, from the atoms up, new ultra-strong materials for use in energy applications, is taking hold within the science and engineering community. This project focused on one particular new classification of materials; nanolaminate metallic composites. These materials, where two metallic materials are intimately bonded and layered over and over to form sheets or coatings, have been shown over the past decade to reach strengths over 10 times that of their constituents. However, they are not yet widely used in part because while extremely strong (they don’t permanently bend), they are also not particularly tough (they break relatively easily when notched). Our program took a coupled approach to investigating new materials systems within the laminate field. We used computational materials science to explore ways to institute new deformation mechanisms that occurred when a tri-layer, rather than the more common bi-layer system was created. Our predictions suggested that copper-nickel or copper-niobium composites (two very common bi-layer systems) with layer thicknesses on the order of 20 nm and then layered 100’s of times, would be less tough than a copper-nickel-niobium metallic composite of similar thicknesses. In particular, a particular mode of permanent deformation, cross-slip, could be activated only in the tri-layer system; the crystal structure of the other bi-layers would prohibit this particular mode of deformation. We then experimentally validated this predication using a wide range of tools. We utilized a DOE user facility, the Center for Integrated Nanotechnology (CINT), to fabricate, for the first time, these

  8. Influence of Fabric Parameters on Microstructure, Mechanical Properties and Failure Mechanisms in Carbon-Fibre Reinforced Composites

    Institute of Scientific and Technical Information of China (English)

    B.Wielage; D.Richter; H.Mucha; Th.Lampke

    2008-01-01

    The effects of fibre/matrix bonding,fabric density,fibre volume fraction and bundle size on microstructure,mechanical properties and failure mechanisms in carbon fibre reinforced composites (plastic and carbon matrix) have been investigated.The microstructure of unloaded and cracked samples was studied by optical microscopy and scanning electron microscopy (SEM),respectively whereas the mechanical behaviour was examined by 3-point bending experiments.Exclusively one type of experimental resole type phenolic resin was applied.A strong fibre/matrix bonding,which is needed for high strength of carbon fibre reinforced plastic (CFRP) materials leads to severe composite damages during the pyrolysis resulting in low strength,brittle failure and a very low utilisation of the fibres strain to failure in C/C composites.Inherent fabric parameters such as an increasing fabric density or bundle size or a reduced fibre volume fraction introduce inhomogenities to the CFRP's microstructure.Results are lower strength and stiffness whereas the strain to failure increases or remains unchanged.Toughness is almost not affected.In C/C composites inhomogenities due to a reduced bundle size reduce strain to failure,strength,stiffness and toughness.Vice versa a declining fibre volume fraction leads to exactly the opposite behaviour.Increasing the fabric density (weight per unit area) causes similar effects as in CFRPs.

  9. The SAFE project: community-driven partnerships in health, mental health, and education to prevent early school failure.

    Science.gov (United States)

    Poole, D L

    1997-11-01

    This article presents a case study of an innovative school-based health and mental health project that prevents early school failure in one county in Oklahoma. Success is attributed to social work development of broad-based partnerships involving families, schools, communities, and public policy officials. Citizen-driven, these partnerships have meshed previously fixed institutional boundaries in health, mental health, and education to prevent early school failure. The article describes school-family partnerships that form the core of the project's service intervention model. Statistics on service activities and outcomes are presented, along with a discussion of lessons learned for implementation of the project.

  10. New Therapeutic Approaches to Prevent or Delay Beta-Cell Failure in Diabetes

    Directory of Open Access Journals (Sweden)

    Ionica Floriana Elvira

    2015-09-01

    Full Text Available Background and aims: The most recent estimates of International Diabetes Federation indicate that 382 million people have diabetes, and the incidence of this disease is increasing. While in type 1 diabetes mellitus (T1DM beta-cell death is autoimmunemediated, type 2 diabetes mellitus (T2DM results from an interaction between genetic and environmental factors that impair beta-cell function and insulin action. Many people with T2DM remain unaware of their illness for a long time because symptoms may take years to appear or be recognized, while the body is affected by excess blood glucose. These patients are often diagnosed only when diabetes complications have already developed. The aim of this article was to perform a review based on literature data on therapeutic modalities to prevent/delay beta cell function decline. Material and Methods: We searched MEDLINE from 2000 to the present to identify the therapeutic approaches to prevent or delay beta-cell failure in patients with T2DM. Results and conclusions: Several common polymorphisms in genes linked to monogenic forms of diabetes appear to influence the response to T2DM pharmacotherapy. Recent studies report the role of the G protein coupled receptor 40 (GPR40, also known as Free Fatty Acids Receptor 1 (FFAR1 in the regulation of beta-cell function- CNX-011-67 (a GPR40 agonist has the potential to provide good and durable glycemic control in T2DM patients.

  11. Mechanical Properties and Failure of Biopolymers: Atomistic Reactions to Macroscale Response.

    Science.gov (United States)

    Jung, GangSeob; Qin, Zhao; Buehler, Markus J

    2015-01-01

    The behavior of chemical bonding under various mechanical loadings is an intriguing mechanochemical property of biological materials, and the property plays a critical role in determining their deformation and failure mechanisms. Because of their astonishing mechanical properties and roles in constituting the basis of a variety of physiologically relevant materials, biological protein materials have been intensively studied. Understanding the relation between chemical bond networks (structures) and their mechanical properties offers great possibilities to enable new materials design in nanotechnology and new medical treatments for human diseases. Here we focus on how the chemical bonds in biological systems affect mechanical properties and how they change during mechanical deformation and failure. Three representative cases of biomaterials related to the human diseases are discussed in case studies, including: amyloids, intermediate filaments, and collagen, each describing mechanochemical features and how they relate to the pathological conditions at multiple scales.

  12. A preliminary study of the failure mechanisms of cascading landslide dams

    Institute of Scientific and Technical Information of China (English)

    Gordon GD Zhou; Peng Cui; Xinghua Zhu; Jinbo Tang; Huayong Chen; Qicheng Sun

    2015-01-01

    abstract Landslide dams commonly form when mass earth or rock movements reach a river channel and cause a complete or partial blockage of the channel. Intense rainfalls can induce upstream flows along a sloping channel that significantly affect downstream landslide dams. If a series of landslide dams are collapsed by incoming mountain torrents (induced by intense rainfall), large debris flows can form in a very short period. Furthermore, the failure of these dams can amplify the magnitude and scale of debris flows in the flow direction. The catastrophic debris flows that occurred in Zhouqu County, China on 8 August 2010 were caused by intense rainfall and the upstream cascading failure of landslide dams along the gullies. Incorporating the role of outburst floods associated with the complete or partial failure of landslide dams is an interesting problem usually beyond the scope of analysis because of the inherent modeling complexity. To understand the cascading failure modes of a series of landslide dams, and the dynamic effect these failures have on the enlargement of debris flow scales, experimental tests are conducted in sloping channels mimicking field conditions, with the modeled landslide dams distributed along a sloping channel and crushed by different upstream flows. The failure modes of three different cascades of landslide dams fully or partially blocking a channel river are parametrically studied. This study illustrates that upstream flows can induce a cascading failure of the landslide dams along a channel. Overtopping is the primary failure mechanism, while piping and erosion can also induce failures for different constructed landslide dams. A cascading failure of landslide dams causes a gradually increasing flow velocity and discharge of the front flow, resulting in an increase in both diameter and percentage of the entrained coarse particles. Furthermore, large landslide blockages can act to enhance the efficiency of river incision, or conversely to

  13. Mechanisms of compressive deformation and failure of porous bulk metallic glasses

    Science.gov (United States)

    Gouripriya, S.; Tandaiya, Parag

    2017-06-01

    Bulk metallic glasses (BMGs) are a new class of engineering materials having strengths as high as 10 times that of conventional steels, but show no significant plastic strain at fracture. By introducing pores, their strain to failure has been shown to improve under uniaxial compression. In this work, three-dimensional finite element simulations of uniaxial compression are carried out on Pd-based porous BMGs having a wide range of pore volume fraction (1.9%-60%) with emphasis on understanding the underlying deformation and failure mechanisms. The resulting stress-strain curves agree reasonably well with existing experimental results. The simulations clearly bring out different failure mechanisms in low porosity BMGs and high porosity BMG foams. For low porosity BMGs (below 20%), the deformation and failure involves nucleation of shear bands around the pore diameter, linking of the shear bands with adjacent pores finally leading to initiation of ductile cracking within the shear bands. For high porosity BMG foams, the mechanism of deformation involves reduction in porosity of the material, self-contact of the pores, and their collapse on themselves causing densification of the material leading to apparent hardening in the stress strain behavior. The effect of pore geometry is also studied by considering ellipsoidal pores of volume fraction 3% and 11%. For ellipsoidal pores, the failure mechanisms are found to differ significantly when the orientation of the major axis of the pore vis-a-vis the loading axis is changed.

  14. Load redistribution rules for progressive failure in shallow landslides: Threshold mechanical models

    Science.gov (United States)

    Fan, Linfeng; Lehmann, Peter; Or, Dani

    2017-01-01

    Rainfall-induced landslides are often preceded by progressive failures that culminate in abrupt mass release. Local failure progression is captured by a landslide hydro-mechanical triggering model that represents the soil mantle as interacting columns linked by tensile and compressive mechanical "bonds." Mechanical bonds may fail at a prescribed threshold leaving a modeling challenge of how to redistribute their load to neighboring intact soil columns. We employed an elastic spring-block model to analytically derive redistribution rules defined by the stiffness ratio of compressive to tensile bonds. These linear-elastic rules were generalized to real soil using measurable Young's modulus and Poisson's ratio. Results indicate that "local" failure characteristics of ductile-like soils (e.g., clay) are reproduced by low stiffness ratios, whereas "global" failure of brittle sandy soils corresponds to large stiffness ratios. Systematic analyses yield guidelines for selecting load redistribution rules for failure of geological materials and mass-movement phenomena represented by discrete threshold-mechanics.

  15. Product Reliability Trends, Derating Considerations and Failure Mechanisms with Scaled CMOS

    Science.gov (United States)

    White, Mark; Vu, Duc; Nguyen, Duc; Ruiz, Ron; Chen, Yuan; Bernstein, Joseph B.

    2006-01-01

    As microelectronics is scaled into the deep sub-micron regime, space and aerospace users of advanced technology CMOS are reassessing how scaling effects impact long-term product reliability. The effects of electromigration (EM), time-dependent-dielectric-breakdown (TDDB) and hot carrier degradation (HCI and NBTI) wearout mechanisms on scaled technologies and product reliability are investigated, accelerated stress testing across several technology nodes is performed, and FA is conducted to confirm the failure mechanism(s).

  16. Exercise-induced rhabdomyolysis mechanisms and prevention:A literature review

    Institute of Scientific and Technical Information of China (English)

    Jooyoung Kim; Joohyung Lee; Sojung Kim; Ho Young Ryu; Kwang Suk Cha; Dong Jun Sung

    2016-01-01

    Exercise-induced rhabdomyolysis (exRML), a pathophysiological condition of skeletal muscle cell damage that may cause acute renal failure and in some cases death. Increased Ca2+ level in cells along with functional degradation of cell signaling system and cell matrix have been suggested as the major pathological mechanisms associated with exRML. The onset of exRML may be exhibited in athletes as well as in general population. Previous studies have reported that possible causes of exRML were associated with excessive eccentric contractions in high temperature, abnormal electrolytes balance, and nutritional deficiencies possible genetic defects. However, the underlying mechanisms of exRML have not been clearly established among health professionals or sports medicine personnel. Therefore, we reviewed the possible mechanisms and correlated prevention of exRML, while providing useful and practical information for the athlete and general exercising population.

  17. Failure mechanism of hollow tree trunks due to cross-sectional flattening.

    Science.gov (United States)

    Huang, Yan-San; Hsu, Fu-Lan; Lee, Chin-Mei; Juang, Jia-Yang

    2017-04-01

    Failure of hollow trees in urban areas is a worldwide concern, and it can be caused by different mechanisms, i.e. bending stresses or flattening-related failures. Here we derive a new analytical expression for predicting the bending moment for tangential cracking, and compare the breaking moment of various failure modes, including Brazier buckling, tangential cracking, shear failure and conventional bending failure, as a function of t/R ratio, where t and R are the trunk wall thickness and trunk radius, respectively, of a hollow tree. We use Taiwan red cypress as an example and show that its failure modes and the corresponding t/R ratios are: Brazier buckling (Mode I), tangential cracking followed by longitudinal splitting (Mode II) and conventional bending failure (Mode III) for 0 bending moments. Hence, we conclude that tangential cracking due to cross-sectional flattening, followed by longitudinal splitting, is dominant for hollow trunks. Our equations are applicable to analyse straight hollow tree trunks and plant stems, but are not applicable to those with side openings or those with only heart decay. Our findings provide insights for those managing trees in urban situations and those managing for conservation of hollow-dependent fauna in both urban and rural settings.

  18. Failure Mechanisms and Structural Optimization of Shredder Hammer for Metal Scraps

    Institute of Scientific and Technical Information of China (English)

    ZHOU Xianyan; HU Zhili; TAO Yijun; QIN Xunpeng; HUA Lin

    2016-01-01

    Recycling retired cars can relieve the environmental pollution and resource waste efficiently. However, a few publications can be found on the failure mechanisms and optimization method of recycling equipment, shredders. Thus, the failure mechanisms and structural optimization of shredder hammers for retired cars are studied aiming improving shredding efficiency and reducing cost. Failure types of shredder hammer are studied theoretically, and it is found that wear failure and fatigue failure are the two main failure types of shredder hammer. The shredding process of metal scraps is analyzed by finite element method, and it can be divided into four stages based on the stress states: initial stage, collision stage, grinding stage and separation stage. It is proved that the shredding efficiency can be improved by increasing cutouts on the hammer head. Finally, it is determined that the hammer with two cutouts is the optimal structure for metal scraps, which can improve the shredding efficiency by 20% and lengthen the hammer life by 15%. This study provides scientific basis for the industry application and theoretical foundation for further research.

  19. Failure mechanisms and structural optimization of shredder hammer for metal scraps

    Science.gov (United States)

    Zhou, Xianyan; Hu, Zhili; Tao, Yijun; Qin, Xunpeng; Hua, Lin

    2016-07-01

    Recycling retired cars can relieve the environmental pollution and resource waste efficiently. However, a few publications can be found on the failure mechanisms and optimization method of recycling equipment, shredders. Thus, the failure mechanisms and structural optimization of shredder hammers for retired cars are studied aiming improving shredding efficiency and reducing cost. Failure types of shredder hammer are studied theoretically, and it is found that wear failure and fatigue failure are the two main failure types of shredder hammer. The shredding process of metal scraps is analyzed by finite element method, and it can be divided into four stages based on the stress states: initial stage, collision stage, grinding stage and separation stage. It is proved that the shredding efficiency can be improved by increasing cutouts on the hammer head. Finally, it is determined that the hammer with two cutouts is the optimal structure for metal scraps, which can improve the shredding efficiency by 20% and lengthen the hammer life by 15%. This study provides scientific basis for the industry application and theoretical foundation for further research.

  20. Hydraulic mechanism and time-dependent characteristics of loose gully deposits failure induced by rainfall

    Institute of Scientific and Technical Information of China (English)

    Yong Wu; Siming He

    2015-01-01

    Failure of loose gully deposits under the effect of rainfall contributes to the potential risk of debris flow. In the past decades, researches on hydraulic mechanism and time-dependent characteristics of loose deposits failure are frequently reported, however adequate measures for reducing debris flow are not available practically. In this context, a time-dependent model was established to determine the changes of water table of loose deposits using hydraulic and topographic theories. In addition, the variation in water table with elapsed time was analyzed. The formulas for calculating hydrodynamic and hydrostatic pressures on each strip and block unit of deposit were proposed, and the slope stability and failure risk of the loose deposits were assessed based on the time-dependent hydraulic characteristics of established model. Finally, the failure mechanism of deposits based on infinite slope theory was illustrated, with an example, to calculate sliding force, anti-sliding force and residual sliding force applied to each slice. The results indicate that failure of gully deposits under the effect of rainfall is the result of continuously increasing hydraulic pressure and water table. The time-dependent characteristics of loose deposit failure are determined by the factors of hydraulic properties, drainage area of interest, rainfall pattern, rainfall duration and intensity.

  1. Numerical Analysis on Failure Modes and Mechanisms of Mine Pillars under Shear Loading

    Directory of Open Access Journals (Sweden)

    Tianhui Ma

    2016-01-01

    Full Text Available Severe damage occurs frequently in mine pillars subjected to shear stresses. The empirical design charts or formulas for mine pillars are not applicable to orebodies under shear. In this paper, the failure process of pillars under shear stresses was investigated by numerical simulations using the rock failure process analysis (RFPA 2D software. The numerical simulation results indicate that the strength of mine pillars and the corresponding failure mode vary with different width-to-height ratios and dip angles. With increasing dip angle, stress concentration first occurs at the intersection between the pillar and the roof, leading to formation of microcracks. Damage gradually develops from the surface to the core of the pillar. The damage process is tracked with acoustic emission monitoring. The study in this paper can provide an effective means for understanding the failure mechanism, planning, and design of mine pillars.

  2. Blocking NMDA receptors delays death in rats with acute liver failure by dual protective mechanisms in kidney and brain.

    Science.gov (United States)

    Cauli, Omar; González-Usano, Alba; Cabrera-Pastor, Andrea; Gimenez-Garzó, Carla; López-Larrubia, Pilar; Ruiz-Sauri, Amparo; Hernández-Rabaza, Vicente; Duszczyk, Malgorzata; Malek, Michal; Lazarewicz, Jerzy W; Carratalá, Arturo; Urios, Amparo; Miguel, Alfonso; Torregrosa, Isidro; Carda, Carmen; Montoliu, Carmina; Felipo, Vicente

    2014-06-01

    Treatment of patients with acute liver failure (ALF) is unsatisfactory and mortality remains unacceptably high. Blocking NMDA receptors delays or prevents death of rats with ALF. The underlying mechanisms remain unclear. Clarifying these mechanisms will help to design more efficient treatments to increase patient's survival. The aim of this work was to shed light on the mechanisms by which blocking NMDA receptors delays rat's death in ALF. ALF was induced by galactosamine injection. NMDA receptors were blocked by continuous MK-801 administration. Edema and cerebral blood flow were assessed by magnetic resonance. The time course of ammonia levels in brain, muscle, blood, and urine; of glutamine, lactate, and water content in brain; of glomerular filtration rate and kidney damage; and of hepatic encephalopathy (HE) and intracranial pressure was assessed. ALF reduces kidney glomerular filtration rate (GFR) as reflected by reduced inulin clearance. GFR reduction is due to both reduced renal perfusion and kidney tubular damage as reflected by increased Kim-1 in urine and histological analysis. Blocking NMDA receptors delays kidney damage, allowing transient increased GFR and ammonia elimination which delays hyperammonemia and associated changes in brain. Blocking NMDA receptors does not prevent cerebral edema or blood-brain barrier permeability but reduces or prevents changes in cerebral blood flow and brain lactate. The data show that dual protective effects of MK-801 in kidney and brain delay cerebral alterations, HE, intracranial pressure increase and death. NMDA receptors antagonists may increase survival of patients with ALF by providing additional time for liver transplantation or regeneration.

  3. Cardiac nuclear high mobility group box 1 prevents the development of cardiac hypertrophy and heart failure.

    Science.gov (United States)

    Funayama, Akira; Shishido, Tetsuro; Netsu, Shunsuke; Narumi, Taro; Kadowaki, Shinpei; Takahashi, Hiroki; Miyamoto, Takuya; Watanabe, Tetsu; Woo, Chang-Hoon; Abe, Jun-ichi; Kuwahara, Koichiro; Nakao, Kazuwa; Takeishi, Yasuchika; Kubota, Isao

    2013-09-01

    High mobility group box 1 (HMGB1) is an abundant and ubiquitous nuclear DNA-binding protein that has multiple functions dependent on its cellular location. HMGB1 binds to DNA, facilitating numerous nuclear functions including maintenance of genome stability, transcription, and repair. However, little is known about the effects of nuclear HMGB1 on cardiac hypertrophy and heart failure. The aim of this study was to examine whether nuclear HMGB1 plays a role in the development of cardiac hypertrophy induced by pressure overload. Analysis of human biopsy samples by immunohistochemistry showed decreased nuclear HMGB1 expression in failing hearts compared with normal hearts. Nuclear HMGB1 decreased in response to both endothelin-1 (ET-1) and angiotensin II (Ang II) stimulation in neonatal rat cardiomyocytes, where nuclear HMGB1 was acetylated and translocated to the cytoplasm. Overexpression of nuclear HMGB1 attenuated ET-1 induced cardiomyocyte hypertrophy. Thoracic transverse aortic constriction (TAC) was performed in transgenic mice with cardiac-specific overexpression of HMGB1 (HMGB1-Tg) and wild-type (WT) mice. Cardiac hypertrophy after TAC was attenuated in HMGB1-Tg mice and the survival rate after TAC was higher in HMGB1-Tg mice than in WT mice. Induction of foetal cardiac genes was decreased in HMGB1-Tg mice compared with WT mice. Nuclear HMGB1 expression was preserved in HMGB1-Tg mice compared with WT mice and significantly attenuated DNA damage after TAC was attenuated in HMGB1-TG mice. These results suggest that the maintenance of stable nuclear HMGB1 levels prevents hypertrophy and heart failure by inhibiting DNA damage.

  4. Research on failure criterion of composite based on unified macro-and micro-mechanical model

    Institute of Scientific and Technical Information of China (English)

    Sun Zhigang; Zhao Long; Chen Lei; Song Yingdong

    2013-01-01

    A new unified macro-and micro-mechanics failure analysis method for composite structures was developed in order to take the effects of composite micro structure into consideration.In this method,the macro stress distribution of composite structure was calculated by commercial finite element analysis software.According to the macro stress distribution,the damage point was searched and the micro-stress distribution was calculated by reformulated finite-volume direct averaging micromechanics (FVDAM),which was a multi-scale finite element method for composite.The micro structure failure modes were estimated with the failure strength of constituents.A unidirectional composite plate with a circular hole in the center under two kinds of loads was analyzed with the traditional macro-mechanical failure analysis method and the unified macro-and micro-mechanics failure analysis method.The results obtained by the two methods are consistent,which show this new method's accuracy and efficiency.

  5. Bone Fragility in Turner Syndrome: Mechanisms and Prevention Strategies.

    Science.gov (United States)

    Faienza, Maria Felicia; Ventura, Annamaria; Colucci, Silvia; Cavallo, Luciano; Grano, Maria; Brunetti, Giacomina

    2016-01-01

    Bone fragility is recognized as one of the major comorbidities in Turner syndrome (TS). The mechanisms underlying bone impairment in affected patients are not clearly elucidated, but estrogen deficiency and X-chromosomal abnormalities represent important factors. Moreover, although many girls with TS undergo recombinant growth hormone therapy to treat short stature, the efficacy of this treatment on bone mineral density is controversial. The present review will focus on bone fragility in subjects with TS, providing an overview on the pathogenic mechanisms and some prevention strategies.

  6. BONE FRAGILITY IN TURNER SYNDROME: MECHANISMS AND PREVENTION STRATEGIES

    Directory of Open Access Journals (Sweden)

    Maria Felicia Faienza

    2016-04-01

    Full Text Available Bone fragility is recognized as one of major comorbidities in Turner Syndrome (TS. The mechanisms underlying bone impairment in affected patients are not clearly elucidated, but estrogen deficiency and X-chromosomal abnormalities represent important factors. Moreover, although many girls with TS undergo recombinant growth hormone (rGH therapy to treat short stature, the efficacy of this treatment on BMD is controversial. The present review will focus on bone fragility in subjects with TS, providing an overview on the pathogenic mechanisms and some prevention strategies.

  7. Mechanisms linking dietary fiber, gut microbiota and colon cancer prevention.

    Science.gov (United States)

    Zeng, Huawei; Lazarova, Darina L; Bordonaro, Michael

    2014-02-15

    Many epidemiological and experimental studies have suggested that dietary fiber plays an important role in colon cancer prevention. These findings may relate to the ability of fiber to reduce the contact time of carcinogens within the intestinal lumen and to promote healthy gut microbiota, which modifies the host's metabolism in various ways. Elucidation of the mechanisms by which dietary fiber-dependent changes in gut microbiota enhance bile acid deconjugation, produce short chain fatty acids, and modulate inflammatory bioactive substances can lead to a better understanding of the beneficial role of dietary fiber. This article reviews the current knowledge concerning the mechanisms via which dietary fiber protects against colon cancer.

  8. Self-Regulation, Cooperative Learning, and Academic Self-Efficacy: Interactions to Prevent School Failure

    Science.gov (United States)

    Fernandez-Rio, Javier; Cecchini, Jose A.; Méndez-Gimenez, Antonio; Mendez-Alonso, David; Prieto, Jose A.

    2017-01-01

    Learning to learn and learning to cooperate are two important goals for individuals. Moreover, self regulation has been identified as fundamental to prevent school failure. The goal of the present study was to assess the interactions between self-regulated learning, cooperative learning and academic self-efficacy in secondary education students experiencing cooperative learning as the main pedagogical approach for at least one school year. 2.513 secondary education students (1.308 males, 1.205 females), 12–17 years old (M = 13.85, SD = 1.29), enrolled in 17 different schools belonging to the National Network of Schools on Cooperative Learning in Spain agreed to participate. They all had experienced this pedagogical approach a minimum of one school year. Participants were asked to complete the cooperative learning questionnaire, the strategies to control the study questionnaire and the global academic self-efficacy questionnaire. Participants were grouped based on their perceptions on cooperative learning and self-regulated learning in their classes. A combination of hierarchical and κ-means cluster analyses was used. Results revealed a four-cluster solution: cluster one included students with low levels of cooperative learning, self-regulated learning and academic self-efficacy, cluster two included students with high levels of cooperative learning, self-regulated learning and academic self-efficacy, cluster three included students with high levels of cooperative learning, low levels of self-regulated learning and intermediate-low levels of academic self-efficacy, and, finally, cluster four included students with high levels of self-regulated learning, low levels of cooperative learning, and intermediate-high levels of academic self-efficacy. Self-regulated learning was found more influential than cooperative learning on students’ academic self-efficacy. In cooperative learning contexts students interact through different types of regulations: self, co, and

  9. Self-Regulation, Cooperative Learning, and Academic Self-Efficacy: Interactions to Prevent School Failure.

    Science.gov (United States)

    Fernandez-Rio, Javier; Cecchini, Jose A; Méndez-Gimenez, Antonio; Mendez-Alonso, David; Prieto, Jose A

    2017-01-01

    Learning to learn and learning to cooperate are two important goals for individuals. Moreover, self regulation has been identified as fundamental to prevent school failure. The goal of the present study was to assess the interactions between self-regulated learning, cooperative learning and academic self-efficacy in secondary education students experiencing cooperative learning as the main pedagogical approach for at least one school year. 2.513 secondary education students (1.308 males, 1.205 females), 12-17 years old (M = 13.85, SD = 1.29), enrolled in 17 different schools belonging to the National Network of Schools on Cooperative Learning in Spain agreed to participate. They all had experienced this pedagogical approach a minimum of one school year. Participants were asked to complete the cooperative learning questionnaire, the strategies to control the study questionnaire and the global academic self-efficacy questionnaire. Participants were grouped based on their perceptions on cooperative learning and self-regulated learning in their classes. A combination of hierarchical and κ-means cluster analyses was used. Results revealed a four-cluster solution: cluster one included students with low levels of cooperative learning, self-regulated learning and academic self-efficacy, cluster two included students with high levels of cooperative learning, self-regulated learning and academic self-efficacy, cluster three included students with high levels of cooperative learning, low levels of self-regulated learning and intermediate-low levels of academic self-efficacy, and, finally, cluster four included students with high levels of self-regulated learning, low levels of cooperative learning, and intermediate-high levels of academic self-efficacy. Self-regulated learning was found more influential than cooperative learning on students' academic self-efficacy. In cooperative learning contexts students interact through different types of regulations: self, co, and shared

  10. Degradation and corresponding failure mechanism for GaN-based LEDs

    Science.gov (United States)

    Fu, Jiajia; Zhao, Lixia; Cao, Haicheng; Sun, Xuejiao; Sun, Baojuan; Wang, Junxi; Li, Jinmin

    2016-05-01

    The degradation behaviors of high power GaN-based vertical blue LEDs on Si substrates were measured using in-situ accelerated life test. The results show that the dominant failure mechanism would be different during the operation. Besides that, the corresponding associated failure mechanisms were investigated systematically by using different analysis technologies, such as Scan Electron Microscopy, Reflectivity spectroscopy, Transient Thermal Analysis, Raman Spectra, etc. It is shown that initially, the failure modes were mainly originated from the semiconductor die and interconnect, while afterwards, the following serious deterioration of the radiant fluxes was attributed to the package. The interface material and quality, such as die attach and frame, play an important role in determining the thermal performance and reliability. In addition, the heating effect during the operation will also release the compressive strain in the chip. These findings will help to improve the reliability of GaN-based LEDs, especially for the LEDs with vertical structure.

  11. Progressive failure analysis of composite structure based on micro- and macro-mechanics models

    Institute of Scientific and Technical Information of China (English)

    孙志刚; 阮绍明; 陈磊; 宋迎东

    2015-01-01

    Based on parameter design language, a program of progressive failure analysis in composite structures is proposed. In this program, the relationship between macro- and micro-mechanics is established and the macro stress distribution of the composite structure is calculated by commercial finite element software. According to the macro-stress, the damaged point is found and the micro-stress distribution of representative volume element is calculated by finite-volume direct averaging micromechanics (FVDAM). Compared with the results calculated by failure criterion based on macro-stress field (the maximum stress criteria and Hashin criteria) and micro-stress field (Huang model), it is proven that the failure analysis based on macro- and micro-mechanics model is feasible and efficient.

  12. A comparison of electromigration failure of metal lines with fracture mechanics

    Institute of Scientific and Technical Information of China (English)

    Hiroyuki Abé; Mikio Muraoka; Kazuhiko Sasagawa; Masumi Saka

    2012-01-01

    Atoms constructing an interconnecting metal line in a semiconductor device are transported by electron flow in high density.This phenomenon is called electromigration,which may cause the line failure.In order to characterize the electromigration failure,a comparison study is carried out with some typical phenomena treated by fracture mechanics for thin and large structures.An example of thin structures,which have been treated by fracture mechanics,is silica optical fibers for communication systems.The damage growth in a metal line by electromigration is characterized in comparison with the crack growth in a silica optical fiber subjected to static fatigue.Also a brief comparison is made between the electromigration failure and some fracture phenomena in large structures.

  13. Countermeasures to prevent detection failure of a vehicle approaching on collision course

    NARCIS (Netherlands)

    Uchida, Nobuyuki; de Waard, Dick; Brookhuis, Karel A.

    2011-01-01

    Objective: This study investigated causal factor of perceptual failure and possible countermeasure of crossing path crashes at clear-sighted unsignalised intersections. Background: Crossing path crashes involving two vehicles at intersections are a common and serious problem, and perceptual failure

  14. Relations between a micro-mechanical model and a damage model for ductile failure in shear

    Science.gov (United States)

    Tvergaard, Viggo; Nielsen, Kim Lau

    2010-09-01

    Gurson type constitutive models that account for void growth to coalescence are not able to describe ductile fracture in simple shear, where there is no hydrostatic tension in the material. But recent micro-mechanical studies have shown that in shear the voids are flattened out to micro-cracks, which rotate and elongate until interaction with neighbouring micro-cracks gives coalescence. Thus, the failure mechanism is very different from that under tensile loading. Also, the Gurson model has recently been extended to describe failure in shear, by adding a damage term to the expression for the growth of the void volume fraction, and it has been shown that this extended model can represent experimental observations. Here, numerical studies are carried out to compare predictions of the shear-extended Gurson model with the shear failures predicted by the micro-mechanical cell model. Both models show a strong dependence on the level of hydrostatic tension. Even though the reason for this pressure dependence is different in the two models, as the shear-extended Gurson model does not describe voids flattening out and the associated failure mechanism by micro-cracks interacting with neighbouring micro-cracks, it is shown that the trends of the predictions are in good agreement.

  15. The Weakest Link: Spatial Variability in the Piping Failure Mechanism of Dikes

    NARCIS (Netherlands)

    Kanning, W.

    2012-01-01

    Piping is an important failure mechanism of flood defense structures. A dike fails due to piping when a head difference causes first the uplift of an inland blanket layer, and subsequently soil erosion due to a ground water flow. Spatial variability of subsoil parameters causes the probability of pi

  16. Relative Damage Stress: Dominant Mechanical Factor for the Failure of Soldered Joints under Temperature Cycling

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    By temperature normalization of the concept of equivalent damage stress proposed by Lemaitre,a new concept of relative damage stress has been put forward as the dominant mechanical factor for the failure of soldered joints under temperature cycling. Finite element numerical simulation results showed that the highest value of relative damage stress occurred at the high temperaturehold time during temperature cycling history.

  17. Wear and Failure Mechanism of PTFE/SiO2/Epoxy Composites

    NARCIS (Netherlands)

    Shen, J.T.; Pei, Y.T.; De Hosson, J.Th.M.

    2016-01-01

    In this work, the wear and failure mechanism of polytetrafluoroethylene (PTFE)/SiO2/epoxy composites with a high concentration of SiO2 particles under dry sliding is examined. In the composite with 12.5 wt.% PTFE, a significant rise of the coefficient of friction (COF) appears after sliding over

  18. Basic failure mechanisms in advanced composites. [composed of epoxy resins reinforced with carbon fibers

    Science.gov (United States)

    Mazzio, V. F.; Mehan, R. L.; Mullin, J. V.

    1973-01-01

    The fundamental failure mechanisms which result from the interaction of thermal cycling and mechanical loading of carbon-epoxy composites were studied. This work was confined to epoxy resin uniderictionally reinforced with HTS carbon fibers, and consists of first identifying local fiber, matrix and interface failure mechanisms using the model composite specimen containing a small number of fibers so that optical techniques can be used for characterization. After the local fracture process has been established for both mechanical loading and thermal cycling, engineering composite properties and gross fracture modes are then examined to determine how the local events contribute to real composite performance. Flexural strength in high fiber content specimens shows an increase in strength with increased thermal cycling. Similar behavior is noted for 25 v/o material up to 200 cycles; however, there is a drastic reduction after 200 cycles indicating a major loss of integrity probably through the accumulation of local cleavage cracks in the tensile region.

  19. Netrin-1 prevents the development of cardiac hypertrophy and heart failure.

    Science.gov (United States)

    Wang, Nan; Cao, Yunshan; Zhu, Yan

    2016-03-01

    The aim of the present study was to examine whether netrin-1 is involved in the development of cardiac hypertrophy, induced by pressure overload. For this investigation, thoracic transverse aortic constriction (TAC) was performed in mice. A total of 18 mice were divided into three groups (n=6 per group): Sham, TAC and TAC + recombinant netrin-1. Neonatal rat cardiomyocytes were stimulated with endothelin-1 (ET-1), and samples were collected to examine the expression levels of netrin‑1 by western blot analysis and the mRNA expression of A‑type natriuretic peptide by reverse transcription‑quantitative polymerase chain reaction. It was found that the expression of netrin‑1 was decreased in the TAC mice and in the neonatal rat cardiomyocytes in response to ET‑1 stimulation. Netrin‑1 eliminated ventricular remodeling, cardiac dysfunction and DNA damage during pressure overload. Furthermore, analysis of the signaling events indicated that netrin‑1‑mediated protection against cardiac hypertrophy was attributed to interruption of the activation of mitogen‑activated protein kinase kinase (MEK) kinase‑1 (K1)‑dependent MEK‑extracellular signal‑regulated protein kinase 1/2 (ERK1/2) and c‑Jun N‑terminal kinase 1/2 (JNK1/2). Therefore, netrin‑1 prevented cardiac hypertrophy and heart failure through the negative regulation of the MEKK1-dependent MEK‑ERK1/2 and JNK1/2 signaling pathways.

  20. Early failure mechanisms of constrained tripolar acetabular sockets used in revision total hip arthroplasty.

    Science.gov (United States)

    Cooke, Christopher C; Hozack, William; Lavernia, Carlos; Sharkey, Peter; Shastri, Shani; Rothman, Richard H

    2003-10-01

    Fifty-eight patients received an Osteonics constrained acetabular implant for recurrent instability (46), girdlestone reimplant (8), correction of leg lengthening (3), and periprosthetic fracture (1). The constrained liner was inserted into a cementless shell (49), cemented into a pre-existing cementless shell (6), cemented into a cage (2), and cemented directly into the acetabular bone (1). Eight patients (13.8%) required reoperation for failure of the constrained implant. Type I failure (bone-prosthesis interface) occurred in 3 cases. Two cementless shells became loose, and in 1 patient, the constrained liner was cemented into an acetabular cage, which then failed by pivoting laterally about the superior fixation screws. Type II failure (liner locking mechanism) occurred in 2 cases. Type III failure (femoral head locking mechanism) occurred in 3 patients. Seven of the 8 failures occurred in patients with recurrent instability. Constrained liners are an effective method for treatment during revision total hip arthroplasty but should be used in select cases only.

  1. Analysis of health promotion and prevention financing mechanisms in Thailand.

    Science.gov (United States)

    Watabe, Akihito; Wongwatanakul, Weranuch; Thamarangsi, Thaksaphon; Prakongsai, Phusit; Yuasa, Motoyuki

    2016-03-17

    In the transition to the post-2015 agenda, many countries are striving towards universal health coverage (UHC). Achieving this, governments need to shift from curative care to promotion and prevention services. This research analyses Thailand's financing system for health promotion and prevention, and assesses policy options for health financing reforms. The study employed a mixed-methods approach and integrates multiple sources of evidence, including scientific and grey literature, expenditure data, and semi-structured interviews with key stakeholders in Thailand. The analysis was underpinned by the use of a well-known health financing framework. In Thailand, three agencies plus local governments share major funding roles for health promotion and prevention services: the Ministry of Public Health (MOPH), the National Health Security Office, the Thai Health Promotion Foundation and Tambon Health Insurance Funds. The total expenditure on prevention and public health in 2010 was 10.8% of the total health expenditure, greater than many middle-income countries that average 7.0-9.2%. MOPH was the largest contributor at 32.9%, the Universal Coverage scheme was the second at 23.1%, followed by the local governments and ThaiHealth at 22.8 and 7.3%, respectively. Thailand's health financing system for promotion and prevention is strategic and innovative due to the three complementary mechanisms in operation. There are several methodological limitations to determine the adequate level of spending. The health financing reforms in Thailand could usefully inform policymakers on ways to increase spending on promotion and prevention. Further comparative policy research is needed to generate evidence to support efforts towards UHC.

  2. Bridging the gap in heart failure prevention: rationale and design of the Nurse-led Intervention for Less Chronic Heart Failure (NIL-CHF) Study

    DEFF Research Database (Denmark)

    Carrington, Melinda J; Stewart, Simon; de Courten, Barbora

    2010-01-01

    AIMS: The primary objective of the Nurse-led Intervention for Less Chronic Heart Failure (NIL-CHF) Study is to develop a programme of care that cost-effectively prevents the development of chronic heart failure (CHF). Methods NIL-CHF is a randomized controlled trial of a hybrid, home- and clinic......-based, nurse-led multidisciplinary intervention targeting hospitalized patients at risk of developing CHF. A target of 750 patients aged >/=45 years will be exposed to usual post-discharge care or the NIL-CHF intervention. The composite primary endpoint is all-cause mortality or CHF-related admission during 3......-5 years of follow-up. After 12 months recruitment, approximately 300 eligible patients (40% of target) have been randomized. Overall, 73% are male and the mean age is 65 +/- 10 years. The most common antecedents for CHF thus far are hypertension (70%, 95% CI, 64-75%), coronary artery disease (51%, 95% CI...

  3. Electrochemical stabilization as a means of preventing ground failure in railroads

    Science.gov (United States)

    Solntzev, D.I.; Sorkov, V.S.; Sokoloff, V.P.

    1947-01-01

    Laboratory and field data on electrochemical stabilization of clays, by three Russian authors, are here presented in translation. Abstracts of the Russian papers were published in May 1947 issue of the Engineering News Record (pp. 100-101). There exists also a small body of literature, in German and English, dealing with the electrochemical stabilization and related subjects. Elements of the electrochemical process were patented by Casagrande in Germany, shortly before the last war. Results of the Russians and of others, including the German patent, appear to be sound and interesting accordingly. Mechanism of the electrochemical stabilization, however, appears to be surmised rather than established. Unless the mechanism of such stabilization is understood in detail, little progress may be expected in field applications of the electrochemical method. Electroosmosis, a poorly reversible coagulation of the soil colloids, and introduction of exchangeable aluminum into the clay complex have been given credit for the ground-stabilizing effects of direct electrical current. Much remains to be done, as the reader may see, in developing further the theory of the method. A critical study is indicated, in this connection, by agencies or individuals qualified and equipped for basic research in soil physics. Optimum schedules for field treatments need be ascertained with particular care, to suit any given kind of material and environment. A wide range of variation in such schedules, is most certainly to be encountered in dealing with materials as diverse in their composition and properties as are clays. Any generalization on relationships between soil, electrolytes, moisture, and current could be premature if based on the Russian work alone. Stabilization of ground is a major engineering geologic problem of national interest. Needless to say, perhaps, that failures are to be expected, in laboratory and in the field, in this as well as in any other kind of research. To minimize

  4. Electrochemical stabilization as a means of preventing ground failure in railroads

    Science.gov (United States)

    Solntzev, D.I.; Sorkov, V.S.; Sokoloff, V.P.

    1947-01-01

    Laboratory and field data on electrochemical stabilization of clays, by three Russian authors, are here presented in translation. Abstracts of the Russian papers were published in May 1947 issue of the Engineering News Record (pp. 100-101). There exists also a small body of literature, in German and English, dealing with the electrochemical stabilization and related subjects. Elements of the electrochemical process were patented by Casagrande in Germany, shortly before the last war. Results of the Russians and of others, including the German patent, appear to be sound and interesting accordingly. Mechanism of the electrochemical stabilization, however, appears to be surmised rather than established. Unless the mechanism of such stabilization is understood in detail, little progress may be expected in field applications of the electrochemical method. Electroosmosis, a poorly reversible coagulation of the soil colloids, and introduction of exchangeable aluminum into the clay complex have been given credit for the ground-stabilizing effects of direct electrical current. Much remains to be done, as the reader may see, in developing further the theory of the method. A critical study is indicated, in this connection, by agencies or individuals qualified and equipped for basic research in soil physics. Optimum schedules for field treatments need be ascertained with particular care, to suit any given kind of material and environment. A wide range of variation in such schedules, is most certainly to be encountered in dealing with materials as diverse in their composition and properties as are clays. Any generalization on relationships between soil, electrolytes, moisture, and current could be premature if based on the Russian work alone. Stabilization of ground is a major engineering geologic problem of national interest. Needless to say, perhaps, that failures are to be expected, in laboratory and in the field, in this as well as in any other kind of research. To minimize

  5. Experimental and numerical study of the micro-mechanical failure in composites

    DEFF Research Database (Denmark)

    Ashouri Vajari, Danial; Martyniuk, Karolina; Sørensen, Bent F.;

    2013-01-01

    . This study is based on the comparison between the results of numerical modeling and those corresponding to the experimental tests by employing two parameters: The angle from the load direction to the crack tip and the crack normal opening. This comparison aims to investigate the interfacial properties......The fibre/matrix interfacial debonding is found to be the first microscale failure mechanism leading to subsequent macroscale transverse cracks in composite materials under tensile load. In this paper, the micromechanical interface failure in fiber-reinforced composites is studied experimentally...

  6. Percutaneous mechanical assist for severe cardiogenic shock due to acute right ventricular failure.

    Science.gov (United States)

    Kipp, Ryan; Raval, Amish N

    2015-05-01

    Acute right ventricular failure can lead to severe cardiogenic shock and death. Recovery may be achieved with early supportive measures. In many patients, intravenous fluid and inotropic resuscitation is inadequate to improve cardiac output. In these cases, percutaneous mechanical assist may provide a non-surgical bridge to recovery. Herein, we describe a case series of patients with severe, refractory cardiogenic shock due to acute right ventricular failure who received a continuous flow percutaneous ventricular device primarily utilizing the right internal jugular vein for out flow cannula placement.

  7. Continuum Damage Mechanics Models for the Analysis of Progressive Failure in Open-Hole Tension Laminates

    Science.gov (United States)

    Song, Kyonchan; Li, Yingyong; Rose, Cheryl A.

    2011-01-01

    The performance of a state-of-the-art continuum damage mechanics model for interlaminar damage, coupled with a cohesive zone model for delamination is examined for failure prediction of quasi-isotropic open-hole tension laminates. Limitations of continuum representations of intra-ply damage and the effect of mesh orientation on the analysis predictions are discussed. It is shown that accurate prediction of matrix crack paths and stress redistribution after cracking requires a mesh aligned with the fiber orientation. Based on these results, an aligned mesh is proposed for analysis of the open-hole tension specimens consisting of different meshes within the individual plies, such that the element edges are aligned with the ply fiber direction. The modeling approach is assessed by comparison of analysis predictions to experimental data for specimen configurations in which failure is dominated by complex interactions between matrix cracks and delaminations. It is shown that the different failure mechanisms observed in the tests are well predicted. In addition, the modeling approach is demonstrated to predict proper trends in the effect of scaling on strength and failure mechanisms of quasi-isotropic open-hole tension laminates.

  8. Potential Mechanisms of Cancer Prevention by Weight Control

    Science.gov (United States)

    Jiang, Yu; Wang, Weiqun

    Weight control via dietary caloric restriction and/or physical activity has been demonstrated in animal models for cancer prevention. However, the underlying mechanisms are not fully understood. Body weight loss due to negative energy balance significantly reduces some metabolic growth factors and endocrinal hormones such as IGF-1, leptin, and adiponectin, but enhances glucocorticoids, that may be associated with anti-cancer mechanisms. In this review, we summarized the recent studies related to weight control and growth factors. The potential molecular targets focused on those growth factors- and hormones-dependent cellular signaling pathways are further discussed. It appears that multiple factors and multiple signaling cascades, especially for Ras-MAPK-proliferation and PI3K-Akt-anti-apoptosis, could be involved in response to weight change by dietary calorie restriction and/or exercise training. Considering prevalence of obesity or overweight that becomes apparent over the world, understanding the underlying mechanisms among weight control, endocrine change and cancer risk is critically important. Future studies using "-omics" technologies will be warrant for a broader and deeper mechanistic information regarding cancer prevention by weight control.

  9. WEAR FAILURE MECHANISM AND MULTI-IMPACT PROPERTY OF AUTOMOTIVE ENGINE CHAIN

    Institute of Scientific and Technical Information of China (English)

    Meng Fanzhong; Wang Shukun; Lan Hong; Xu Rongjin; Xu Hanxue

    2005-01-01

    The multi-impact characteristics and failure mechanism of two kinds of automotive engine chain made in China are studied through engine assembly and road-drive tests. The worn surface morphologies of rubbing area between pin, bush and roller are also analyzed based on scanning electron microscope. The results show that the main wear mechanism of automotive engine chain is fatigue wear, and its failure mechanism is the forming, extending and flaking of cracks on top layer of pin and bush. In addition, the material, hot-treatment method and shaping technique for roller have a great influence upon the resistance to multi-impact. Ensuring sufficient strength and plasticity of roller, as well as adopting suitable shaping technique are the effective method to increase its resistance to multi-impact.

  10. Deformation and failure mechanisms of 18650 battery cells under axial compression

    Science.gov (United States)

    Zhu, Juner; Zhang, Xiaowei; Sahraei, Elham; Wierzbicki, Tomasz

    2016-12-01

    An important deformation mode during ground impacts of battery packs made of cylindrical battery cells is axial compression. This type of loading subjects the cell to a complex deformation pattern and failure mechanism. The design of endcaps plays an important role in such deformations. To explore the sequence of deformation and the underlying failure mechanisms, a combined experimental/numerical study was carried out. Tests were conducted on 18650 cells, and the deformation of each component was carefully investigated and documented. There are four different stages in the force-displacement curve, corresponding with deformation of various components in the endcap assembly. A short circuit happens at a displacement of 4 mm. To clarify these observations, a detailed Finite Element model was set up, covering the geometry and the mechanical property of almost all the components of the cell. Using the simulation results, the sequence of the axial compression was revealed, which was subsequently validated by Micro CT scans as well as analytical solutions. Based on the precise analysis of the mechanical behavior, the cause of the short circuit during axial loading was clarified. Two failure mechanisms in the separator at the top section of the cell explain the possible causes of short circuit.

  11. Preventing proximal junctional failure in long segmental instrumented cases of adult degenerative scoliosis using a multilevel stabilization screw technique

    Directory of Open Access Journals (Sweden)

    Lee Sandquist

    2015-01-01

    Conclusion: PJK and failure are well-recognized suboptimal outcomes of long-segmental fusions of the thoracolumbar spine that can lead to significant neurological morbidity and costly revision surgeries. With no known proximal junction failures to date, the MLSS technique has shown promising results in preventing adverse proximal junctional conditions and can be safely performed under fluoroscopy guidance. Future direction includes a comparative study establishing the relative risk of developing PJK with this novel technique versus a traditional long-segmental thoracolumbar fusion.

  12. Tensile Properties and Failure Mechanism of 3D Woven Hollow Integrated Sandwich Composites

    Science.gov (United States)

    Liu, Chang; Cai, Deng'an; Zhou, Guangming; Lu, Fangzhou

    2017-01-01

    Tensile properties and failure mechanism of 3D woven hollow integrated sandwich composites are investigated experimentally, theoretically and numerically in this paper. Firstly, the tensile properties are obtained by quasi-static tensile tests on the specimens in two principal directions of the sandwich panels, called warp and weft. The experimental results shows that the tensile performances of the warp are better than that of the weft. By observing the broken specimens, it is found that the touch parts between yarns are the main failure regions under tension. Then, a theoretical method is developed to predict the tensile properties. By comparing with the experimental data, the accuracy of the theoretical method is verified. Simultaneously, a finite element model is established to predict the tensile behavior of the composites. The numerical results agree well with the experimental data. Moreover, the simulated progressive damages show that the contact regions in the warp and weft tension are both the initial failure areas.

  13. Compression failure mechanisms of single-ply, unidirectional, carbon-fiber composites

    Science.gov (United States)

    Ha, Jong-Bae; Nairn, John A.

    1992-01-01

    A single-ply composite compression test was used to study compression failure mechanisms as a function of fiber type, matrix type, and interfacial strength. Composites made with low- and intermediate-modulus fibers (Hercules AS4 and IM7) in either an epoxy (Hercules 3501-6) or a thermoplastic (ULTEM and LARC-TPI) matrix failed by kink banding and out-of-plane slip. The failures proceeded by rapid and catastrophic damage propagation across the specimen width. Composites made with high-modulus fibers (Hercules HMS4/3501-6) had a much lower compression strength. Their failures were characterized by kink banding and longitudinal splitting. The damage propagated slowly across the specimen width. Composites made with fibers treated to give low interfacial strength had low compression strength. These composites typically failed near the specimen ends and had long kink bands.

  14. Upper bound analysis for deep tunnel face with joined failure mechanism of translation and rotation

    Institute of Scientific and Technical Information of China (English)

    许敬叔; 杜佃春; 杨子汉

    2015-01-01

    A joined failure mechanism of translation and rotation was proposed for the stability analysis of deep tunnel face, and the upper bound solution of supporting force of deep tunnel was calculated under pore water pressure. The calculations were based on limit analysis method of upper bound theory, with the employment of non-associated Mohr-Coulomb flow rule. Nonlinear failure criterion was adopted. Optimized analysis was conducted for the effects of the tunnel depth, pore water pressure coefficient, the initial cohesive force and nonlinear coefficient on supporting force. The upper bound solutions are obtained by optimum method. Results are listed and compared with the previously published solutions for the verification of correctness and effectiveness. The failure shapes are presented, and results are discussed for different pore water pressure coefficients and nonlinear coefficients of tunnel face.

  15. Postsurgical intrapericardial adhesions: mechanisms of formation and prevention.

    Science.gov (United States)

    Cannata, Aldo; Petrella, Duccio; Russo, Claudio Francesco; Bruschi, Giuseppe; Fratto, Pasquale; Gambacorta, Marcello; Martinelli, Luigi

    2013-05-01

    Postsurgical intrapericardial adhesions are still considered an unavoidable consequence of cardiothoracic operations. They increase the technical difficulty and the risk of reoperations. The pathogenesis of postsurgical adhesions is a multistep process, and the main key players are (1) loss of mesothelial cells, (2) accumulation of fibrin in areas devoid of mesothelial cells, (3) loss of normal pericardial fibrinolysis, and (4) local inflammation. Today, very promising methods to reduce adhesions are available for clinical use. This report reviews the process of formation of adhesions and the methods to prevent them, classified according to the mechanism of action.

  16. Failure mechanism and coupled static-dynamic loading theory in deep hard rock mining: A review

    Directory of Open Access Journals (Sweden)

    Xibing Li

    2017-08-01

    Full Text Available Rock failure phenomena, such as rockburst, slabbing (or spalling and zonal disintegration, related to deep underground excavation of hard rocks are frequently reported and pose a great threat to deep mining. Currently, the explanation for these failure phenomena using existing dynamic or static rock mechanics theory is not straightforward. In this study, new theory and testing method for deep underground rock mass under coupled static-dynamic loading are introduced. Two types of coupled loading modes, i.e. “critical static stress + slight disturbance” and “elastic static stress + impact disturbance”, are proposed, and associated test devices are developed. Rockburst phenomena of hard rocks under coupled static-dynamic loading are successfully reproduced in the laboratory, and the rockburst mechanism and related criteria are demonstrated. The results of true triaxial unloading compression tests on granite and red sandstone indicate that the unloading can induce slabbing when the confining pressure exceeds a certain threshold, and the slabbing failure strength is lower than the shear failure strength according to the conventional Mohr-Column criterion. Numerical results indicate that the rock unloading failure response under different in situ stresses and unloading rates can be characterized by an equivalent strain energy density. In addition, we present a new microseismic source location method without premeasuring the sound wave velocity in rock mass, which can efficiently and accurately locate the rock failure in hard rock mines. Also, a new idea for deep hard rock mining using a non-explosive continuous mining method is briefly introduced.

  17. Hydrological Effects on Failure Mechanism of the Shiaolin Landslide, Taiwan Induced by Typhoon Morakot

    Science.gov (United States)

    Lin, Meei-Ling; Chou, Li-Sheng

    2016-04-01

    In 2009 Typhoon Morakot struck southern Taiwan and induced a catastrophic landslide in Shiaolin Village, Kaoshiung City, and more than 400 people were killed. This research focused on the hydrological condition and its effect on the failure mechanism of the catastrophic Shiaolin Landslide. The topographic analysis was conducted using the DEM before and LiDAR derived DEM after the landslide. Based on results of the topographic analysis, a wedge type failure mode was deduced. In order to determine the critical sliding condition and geometry of the failure wedge, the PIV analysis, slope & aspect analysis and attitude analysis were conducted, and comparisons of results were made to finalize the geometry and attitude of the critical sliding condition of the Shiaolin Landslide. The stability analysis was conducted accordingly using material properties from laboratory test and estimation from the similar formation. The effects of ground water variation, possible effect of fault gouge on seepage water table, and the strength reduction of rock mass material were considered in the detailed analysis. The results suggested that the Shiaolin Landslide has a wedge type failure mode, and the ground water variation played an important role of the landslide, and the existence of fault gouge affected the ground hydrology significantly, which could lead to the critical failure of the Shiaolin Landslide.

  18. Genistein, a soy phytoestrogen, reverses severe pulmonary hypertension and prevents right heart failure in rats.

    Science.gov (United States)

    Matori, Humann; Umar, Soban; Nadadur, Rangarajan D; Sharma, Salil; Partow-Navid, Rod; Afkhami, Michelle; Amjedi, Marjan; Eghbali, Mansoureh

    2012-08-01

    Pretreatment with a phytoestrogen genistein has been shown to attenuate the development of pulmonary hypertension (PH). Because PH is not always diagnosed early, we examined whether genistein could also reverse preexisting established PH and prevent associated right heart failure (RHF). PH was induced in male rats by 60 mg/kg of monocrotaline. After 21 days, when PH was well established, rats received daily injection of genistein (1 mg/kg per day) for 10 days or were left untreated to develop RHF by day 30. Effects of genistein on human pulmonary artery smooth muscle cell and endothelial cell proliferation and neonatal rat ventricular myocyte hypertrophy were assessed in vitro. Severe PH was evident 21 days after monocrotaline, as peak systolic right ventricular pressure increased to 66.35±1.03 mm Hg and right ventricular ejection fraction reduced to 41.99±1.27%. PH progressed to RHF by day 30 (right ventricular pressure, 72.41±1.87 mm Hg; RV ejection fraction, 29.25±0.88%), and mortality was ≈75% in RHF rats. Genistein therapy resulted in significant improvement in lung and heart function as right ventricular pressure was significantly reduced to 43.34±4.08 mm Hg and right ventricular ejection fraction was fully restored to 65.67±1.08% similar to control. Genistein reversed PH-induced pulmonary vascular remodeling in vivo and inhibited human pulmonary artery smooth muscle cell proliferation by ≈50% in vitro likely through estrogen receptor-β. Genistein also reversed right ventricular hypertrophy (right ventricular hypertrophy index, 0.35±0.029 versus 0.70±0.080 in RHF), inhibited neonatal rat ventricular myocyte hypertrophy, and restored PH-induced loss of capillaries in the right ventricle. These improvements in cardiopulmonary function and structure resulted in 100% survival by day 30. Genistein restored PH-induced downregulation of estrogen receptor-β expression in the right ventricle and lung. In conclusion, genistein therapy not only rescues

  19. Failure of fragmented parathyroid gland autotransplantation to prevent permanent hypoparathyroidism after total thyroidectomy.

    Science.gov (United States)

    Lorente-Poch, Leyre; Sancho, Juan; Muñoz, Jose Luis; Gallego-Otaegui, Lander; Martínez-Ruiz, Carlos; Sitges-Serra, Antonio

    2017-03-01

    Parathyroid autotransplantation during total thyroidectomy leads to higher rates of postoperative hypocalcaemia. It has been argued, however, that it prevents permanent hypoparathyroidism. The impact of autografted normal parathyroid gland fragments on long-term parathyroid status has not been assessed properly. To clarify this, the short- and long-term parathyroid function was assessed in patients with three glands remaining in situ after total thyroidectomy, in whom the fourth gland was either autotransplanted (Tx) or accidentally resected (AR). Consecutive patients (n = 669) undergoing first-time total thyroidectomy were prospectively studied recording the number of parathyroid glands remaining in situ: PGRIS =4-(glands autografted + glands in the specimen). The study was focused on the subgroup of 186 patients with three parathyroid glands remaining in situ as a result of either accidental resection (AR, n = 76) or autotransplantation into the sternocleidomastoid muscle (Tx, n = 110). Prevalence of postoperative hypocalcaemia, protracted, and permanent hypoparathyroidism were compared between the two groups. Demographic, disease-related, laboratory, and surgical variables were recorded. All patients were followed for at least 1 year. Both groups were comparable in terms of disease and extent of surgery. Mean postoperative serum calcium was the same (AR: 1.97 ± 0.2 vs Tx: 1.97 ± 0.22 mmol/L). Rates of protracted (AR: 24% vs Tx: 25.5%) and permanent hypoparathyroidism (AR: 5.3% vs Tx: 7.3%) were similar in both groups. The prevalence of parathyroid failure syndromes after total thyroidectomy was similar whether a parathyroid gland was inadvertently excised or autotransplanted. Autotransplantation did not influence the permanent hypoparathyroidism rate.

  20. Chromatin resetting mechanisms preventing trangenerational inheritance of epigenetic states

    Directory of Open Access Journals (Sweden)

    Mayumi eIwasaki

    2015-05-01

    Full Text Available Epigenetic regulation can be altered by environmental cues including abiotic and biotic stresses. In most cases, environmentally-induced epigenetic changes are transient, but in some cases they are maintained for extensive periods of time and may even be transmitted to the next generation. However, the underlying mechanisms of transgenerational transmission of environmentally-induced epigenetic states remain largely unknown. Such traits can be adaptive, but also can have negative consequences if the parentally inherited epigenetic memory interferes with canonical environmental responses of the progeny. This review highlights recent insights into the mechanisms preventing transgenerational transmission of environmentally-induced epigenetic states in plants, which resemble those of germline reprogramming in mammals.

  1. Relations between a micro-mechanical model and a damage model for ductile failure in shear

    DEFF Research Database (Denmark)

    Tvergaard, Viggo; Nielsen, Kim Lau

    2010-01-01

    Gurson type constitutive models that account for void growth to coalescence are not able to describe ductile fracture in simple shear, where there is no hydrostatic tension in the material. But recent micro-mechanical studies have shown that in shear the voids are flattened out to micro-cracks, w......Gurson type constitutive models that account for void growth to coalescence are not able to describe ductile fracture in simple shear, where there is no hydrostatic tension in the material. But recent micro-mechanical studies have shown that in shear the voids are flattened out to micro......-cracks, which rotate and elongate until interaction with neighbouring micro-cracks gives coalescence. Thus, the failure mechanism is very different from that under tensile loading. Also, the Gurson model has recently been extended to describe failure in shear, by adding a damage term to the expression...... for the growth of the void volume fraction, and it has been shown that this extended model can represent experimental observations. Here, numerical studies are carried out to compare predictions of the shear-extended Gurson model with the shear failures predicted by the micro-mechanical cell model. Both models...

  2. Non-invasive versus invasive mechanical ventilation for respiratory failure in severe acute respiratory syndrome

    Institute of Scientific and Technical Information of China (English)

    Loretta YC Yam; Alfred YF Chan; Thomas MT Cheung; Eva LH Tsui; Jane CK Chan; Vivian CW Wong

    2005-01-01

    Background Severe acute respiratory syndrome is frequently complicated by respiratory failure requiring ventilatory support. We aimed to compare the efficacy of non-invasive ventilation against invasive mechanical ventilation treating respiratory failure in this disease. Methods Retrospective analysis was conducted on all respiratory failure patients identified from the Hong Kong Hospital Authority Severe Acute Respiratory Syndrome Database. Intubation rate, mortality and secondary outcome of a hospital utilizing non-invasive ventilation under standard infection control conditions (NIV Hospital) were compared against 13 hospitals using solely invasive ventilation (IMV Hospitals). Multiple logistic regression analyses with adjustments for confounding variables were performed to test for association between outcomes and hospital groups. Results Both hospital groups had comparable demographics and clinical profiles, but NIV Hospital (42 patients) had higher lactate dehydrogenase ratio and worse radiographic score on admission and ribavirin-corticosteroid commencement. Compared to IMV Hospitals (451 patients), NIV Hospital had lower adjusted odds ratios for intubation (0.36, 95% CI 0.164-0.791, P=0.011) and death (0.235, 95% CI 0.077-0.716, P=0.011), and improved earlier after pulsed steroid rescue. There were no instances of transmission of severe acute respiratory syndrome among health care workers due to the use of non-invasive ventilation.Conclusion Compared to invasive mechanical ventilation, non-invasive ventilation as initial ventilatory support for acute respiratory failure in the presence of severe acute respiratory syndrome appeared to be associated with reduced intubation need and mortality.

  3. A novel approach of testability modeling and analysis for PHM systems based on failure evolution mechanism

    Institute of Scientific and Technical Information of China (English)

    Tan Xiaodong; Qiu Jing; Liu Guanjun; Lv Kehong; Yang Shuming; Wang Chao

    2013-01-01

    Prognostics and health management (PHM) significantly improves system availability and reliability,and reduces the cost of system operations.Design for testability (DFT) developed concurrently with system design is an important way to improve PHM capability.Testability modeling and analysis are the foundation of DFT.This paper proposes a novel approach of testability modeling and analysis based on failure evolution mechanisms.At the component level,the fault progression-related information of each unit under test (UUT) in a system is obtained by means of failure modes,evolution mechanisms,effects and criticality analysis (FMEMECA),and then the failure-symptom dependency can be generated.At the system level,the dynamic attributes of UUTs are assigned by using the bond graph methodology,and then the symptom-test dependency can be obtained by means of the functional flow method.Based on the failure-symptom and symptom-test dependencies,testability analysis for PHM systems can be realized.A shunt motor is used to verify the application of the approach proposed in this paper.Experimental results show that this approach is able to be applied to testability modeling and analysis for PHM systems very well,and the analysis results can provide a guide for engineers to design for testability in order to improve PHM performance.

  4. Analysis of seismic disaster failure mechanism and dam-break simulation of high arch dam

    Science.gov (United States)

    Zhang, Jingkui; Zhang, Liaojun

    2014-06-01

    Based on a Chinese national high arch dam located in a meizoseismal region, a nonlinear numerical analysis model of the damage and failure process of a dam-foundation system is established by employing a 3-D deformable distinct element code (3DEC) and its re-development functions. The proposed analysis model considers the dam-foundation-reservoir coupling effect, influence of nonlinear contact in the opening and closing of the dam seam surface and abutment rock joints during strong earthquakes, and radiation damping of far field energy dissipation according to the actual workability state of an arch dam. A safety assessment method and safety evaluation criteria is developed to better understand the arch dam system disaster process from local damage to ultimate failure. The dynamic characteristics, disaster mechanism, limit bearing capacity and the entire failure process of a high arch dam under a strong earthquake are then analyzed. Further, the seismic safety of the arch dam is evaluated according to the proposed evaluation criteria and safety assessment method. As a result, some useful conclusions are obtained for some aspects of the disaster mechanism and failure process of an arch dam. The analysis method and conclusions may be useful in engineering practice.

  5. Mechanism of preventing coal and gas compression disseminated values outburst with stress pre-released hydraulically

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Zhong-fei; Yu, Qi-xiang [Jiangsu University, Zhenjiang (China). Center of Safety Engineering

    2007-01-15

    Based on the conditions of coal and gas outburst, the action mechanism for preventing coal and gas compression disseminated values outburst with stress pre-released hydraulically was analyzed. The accuracy of this mechanism was validated by measuring the gas emission before and after pre-releasing stress hydraulically, measuring the rupture failure by the electromagnetic radiation technique and the correlative practical datum. The results show that the electromagnetic radiation intensity and pulse count are increscent when taking the measure of stress pre-released hydraulically, which is propitious to prevent the coal and gas outburst. The action mechanism consists of three aspects: 1) Pre-releasing gas and increasing tangential stress and disseminated values friction resistance; 2) Pre-releaseing the radial effective geostress on high-tension side and reducing the radial stress difference of disseminated values chop motion for enhancing coal displacement; 3) Making the disseminated values and adjacent coal and rock felting by flooding water and increasing the disseminated values' friction resistance coefficients. 9 refs., 2 figs.

  6. Core Competencies and the Prevention of School Failure and Early School Leaving

    Science.gov (United States)

    Bradshaw, Catherine P.; O'Brennan, Lindsey M.; McNeely, Clea A.

    2008-01-01

    There is an increasing awareness that school failure and early school leaving are processes, rather than discrete events, that often co-occur and can have lasting negative effects on children's development. Most of the literature has focused on risk factors for failure and dropout rather than on the promotion of competencies that can increase…

  7. Core Competencies and the Prevention of School Failure and Early School Leaving

    Science.gov (United States)

    Bradshaw, Catherine P.; O'Brennan, Lindsey M.; McNeely, Clea A.

    2008-01-01

    There is an increasing awareness that school failure and early school leaving are processes, rather than discrete events, that often co-occur and can have lasting negative effects on children's development. Most of the literature has focused on risk factors for failure and dropout rather than on the promotion of competencies that can increase…

  8. Failures of the State”: Factors of Formation and Mechanisms of Influence on Economic Processes

    Directory of Open Access Journals (Sweden)

    Gontar Nikolay Vladimirovich

    2014-11-01

    Full Text Available The article is devoted to the problem of genesis and influence on real economic processes of “failures of the state”. The article designates the objective functions inherent in the state the realization of which can increase the efficiency of economic interactions reducing transaction expenses. Besides, the key factors of non-optimal activity of the state as well as actual “failures of the state” are considered. The approaches to the definition of “failures of the state” are analyzed. Taking into account functional approach the author proposes the model definition allowing to separate “failures of the state” from factors and conditions of their emergence. Among the emergence factors of “failures of the state” the author analyzes in detail the key division of economy subjects to net-payers and net-recipients of the income, the fact of distribution of consequences of state regulation to the sectors which are not direct objects of regulation as well as the influence of short-term decisions for long-term prospects are designated. The author also analyzes the range of “failures of the state”, including such as formation of monopolies, tax discouraging, failures of social security, nature of “state business”, derivation of resources and workers from economy, formation of an inequality and calculational (price chaos in economy. The key consequences and volume of the economic damage formed by “failures of the state” are considered, the corresponding quantitative estimates are given. The most important vectors of optimization of activity of the state which provide minimization of “failures of the state” and the related economic damage are designated. According to the author, such vectors include the priority of market self-regulation under the condition of refusal from substitutes in the form of “approach” of public sector to market standards. The minimization of public sector activity aimed at the exclusion of

  9. A mechanism for the early detection and management of physical asset management strategy execution failure

    Directory of Open Access Journals (Sweden)

    Stimie, Johann

    2016-11-01

    Full Text Available The purpose of this paper is to present a mechanism that can assist physical asset management (PAM practitioners and academics with the early detection and management of PAM strategy execution failure. In the pursuit of this objective, case studies were applied to develop the theory related to this topic the methodologies involved in the development of theory through case studies was were applied. The paper commences with a brief literature review of the contemporary literature on general business strategy, strategy execution, and, more specifically, PAM strategy execution failure (PAMSEF. The physical asset management strategy execution enforcement mechanism (PAMSEEM is presented next. Validation of each one of the components of the PAMSEEM takes place within the context of an organisation that is highly dependent on physical assets (PA dependent organization. The conclusion reached is that the PAMSEEM, can indeed assist organisations with the early detection and management of PAMSEF.

  10. Parametric Studies Of Failure Mechanisms In Thermal Barrier Coatings During Thermal Cycling Using FEM

    Directory of Open Access Journals (Sweden)

    Srivathsa B.

    2015-12-01

    Full Text Available Thermal barrier coatings (TBCs are widely used on different hot components of gas turbine engines such as blades and vanes. Although, several mechanisms for the failure of the TBCs have been suggested, it is largely accepted that the durability of these coatings is primarily determined by the residual stresses that are developed during the thermal cycling. In the present study, the residual stress build-up in an electron beam physical vapour deposition (EB-PVD based TBCs on a coupon during thermal cycling has been studied by varying three parameters such as the cooling rate, TBC thickness and substrate thickness. A two-dimensional thermomechanical generalized plane strain finite element simulations have been performed for thousand cycles. It was observed that these variations change the stress profile significantly and the stress severity factor increases non-linearly. Overall, the predictions of the model agree with reported experimental results and help in predicting the failure mechanisms.

  11. Atomistic Failure Mechanism of Single Wall Carbon Nanotubes with Small Diameters

    Institute of Scientific and Technical Information of China (English)

    JI Dong; GAO Xiang; KONG Xiang-Yang; LI Jia-Ming

    2007-01-01

    @@ Single wall carbon nanotubes with small diameters (< 5.0 (A)) subjected to bending deformation are simulated by orthogonal tight-binding molecular dynamics approach. Based on the calculations of C-C bond stretching and breaking in the bending nanotubes, we elucidate the atomistic failure mechanisms of nanotube with small diameters. In the folding zone of bending nanotube, a large elongation of C-C bonds occurs, accounting for the superelastic behaviour.

  12. Failure mechanisms of additively manufactured porous biomaterials: Effects of porosity and type of unit cell.

    Science.gov (United States)

    Kadkhodapour, J; Montazerian, H; Darabi, A Ch; Anaraki, A P; Ahmadi, S M; Zadpoor, A A; Schmauder, S

    2015-10-01

    Since the advent of additive manufacturing techniques, regular porous biomaterials have emerged as promising candidates for tissue engineering scaffolds owing to their controllable pore architecture and feasibility in producing scaffolds from a variety of biomaterials. The architecture of scaffolds could be designed to achieve similar mechanical properties as in the host bone tissue, thereby avoiding issues such as stress shielding in bone replacement procedure. In this paper, the deformation and failure mechanisms of porous titanium (Ti6Al4V) biomaterials manufactured by selective laser melting from two different types of repeating unit cells, namely cubic and diamond lattice structures, with four different porosities are studied. The mechanical behavior of the above-mentioned porous biomaterials was studied using finite element models. The computational results were compared with the experimental findings from a previous study of ours. The Johnson-Cook plasticity and damage model was implemented in the finite element models to simulate the failure of the additively manufactured scaffolds under compression. The computationally predicted stress-strain curves were compared with the experimental ones. The computational models incorporating the Johnson-Cook damage model could predict the plateau stress and maximum stress at the first peak with less than 18% error. Moreover, the computationally predicted deformation modes were in good agreement with the results of scaling law analysis. A layer-by-layer failure mechanism was found for the stretch-dominated structures, i.e. structures made from the cubic unit cell, while the failure of the bending-dominated structures, i.e. structures made from the diamond unit cells, was accompanied by the shearing bands of 45°.

  13. Bibliography of information on mechanics of structural failure (hydrogen embrittlement, protective coatings, composite materials, NDE)

    Science.gov (United States)

    Carpenter, J. L., Jr.

    1976-01-01

    This bibliography is comprised of approximately 1,600 reference citations related to four problem areas in the mechanics of failure in aerospace structures. The bibliography represents a search of the literature published in the period 1962-1976, the effort being largely limited to documents published in the United States. Listings are subdivided into the four problem areas: Hydrogen Embrittlement; Protective Coatings; Composite Materials; and Nondestructive Evaluation. An author index is included.

  14. Increased Dicarbonyl Stress as a Novel Mechanism of Multi-Organ Failure in Critical Illness

    Science.gov (United States)

    van Bussel, Bas C. T.; van de Poll, Marcel C. G.; Schalkwijk, Casper G.; Bergmans, Dennis C. J. J.

    2017-01-01

    Molecular pathological pathways leading to multi-organ failure in critical illness are progressively being unravelled. However, attempts to modulate these pathways have not yet improved the clinical outcome. Therefore, new targetable mechanisms should be investigated. We hypothesize that increased dicarbonyl stress is such a mechanism. Dicarbonyl stress is the accumulation of dicarbonyl metabolites (i.e., methylglyoxal, glyoxal, and 3-deoxyglucosone) that damages intracellular proteins, modifies extracellular matrix proteins, and alters plasma proteins. Increased dicarbonyl stress has been shown to impair the renal, cardiovascular, and central nervous system function, and possibly also the hepatic and respiratory function. In addition to hyperglycaemia, hypoxia and inflammation can cause increased dicarbonyl stress, and these conditions are prevalent in critical illness. Hypoxia and inflammation have been shown to drive the rapid intracellular accumulation of reactive dicarbonyls, i.e., through reduced glyoxalase-1 activity, which is the key enzyme in the dicarbonyl detoxification enzyme system. In critical illness, hypoxia and inflammation, with or without hyperglycaemia, could thus increase dicarbonyl stress in a way that might contribute to multi-organ failure. Thus, we hypothesize that increased dicarbonyl stress in critical illness, such as sepsis and major trauma, contributes to the development of multi-organ failure. This mechanism has the potential for new therapeutic intervention in critical care. PMID:28178202

  15. Increased Dicarbonyl Stress as a Novel Mechanism of Multi-Organ Failure in Critical Illness.

    Science.gov (United States)

    van Bussel, Bas C T; van de Poll, Marcel C G; Schalkwijk, Casper G; Bergmans, Dennis C J J

    2017-02-07

    Molecular pathological pathways leading to multi-organ failure in critical illness are progressively being unravelled. However, attempts to modulate these pathways have not yet improved the clinical outcome. Therefore, new targetable mechanisms should be investigated. We hypothesize that increased dicarbonyl stress is such a mechanism. Dicarbonyl stress is the accumulation of dicarbonyl metabolites (i.e., methylglyoxal, glyoxal, and 3-deoxyglucosone) that damages intracellular proteins, modifies extracellular matrix proteins, and alters plasma proteins. Increased dicarbonyl stress has been shown to impair the renal, cardiovascular, and central nervous system function, and possibly also the hepatic and respiratory function. In addition to hyperglycaemia, hypoxia and inflammation can cause increased dicarbonyl stress, and these conditions are prevalent in critical illness. Hypoxia and inflammation have been shown to drive the rapid intracellular accumulation of reactive dicarbonyls, i.e., through reduced glyoxalase-1 activity, which is the key enzyme in the dicarbonyl detoxification enzyme system. In critical illness, hypoxia and inflammation, with or without hyperglycaemia, could thus increase dicarbonyl stress in a way that might contribute to multi-organ failure. Thus, we hypothesize that increased dicarbonyl stress in critical illness, such as sepsis and major trauma, contributes to the development of multi-organ failure. This mechanism has the potential for new therapeutic intervention in critical care.

  16. Scaling of the Transient Hydroelastic Response and Failure Mechanisms of Self-Adaptive Composite Marine Propellers

    Directory of Open Access Journals (Sweden)

    Michael R. Motley

    2012-01-01

    Full Text Available The load dependent deformation responses and complex failure mechanisms of self-adaptive composite propeller blades make the design, analysis, and scaling of these structures nontrivial. The objective of this work is to investigate and verify the dynamic similarity relationships for the hydroelastic response and potential failure mechanisms of self-adaptive composite marine propellers. A fully coupled, three-dimensional boundary element method-finite element method is used to compare the model and full-scale responses of a self-adaptive composite propeller. The effects of spatially varying inflow, transient sheet cavitation, and load-dependent blade deformation are considered. Three types of scaling are discussed: Reynolds scale, Froude scale, and Mach scale. The results show that Mach scaling, which requires the model inflow speed to be the same as the full scale, will lead to discrepancies in the spatial load distributions at low speeds due to differences in Froude number, but the differences between model and full-scale results become negligible at high speeds. Thus, Mach scaling is recommended for a composite marine propeller because it allows the same material and layering scheme to be used between the model and the full scale, leading to similar 3D stress distributions, and hence similar failure mechanisms, between the model and the full scale.

  17. Economic Statistical Design of integrated X-bar-S control chart with Preventive Maintenance and general failure distribution.

    Science.gov (United States)

    Caballero Morales, Santiago Omar

    2013-01-01

    The application of Preventive Maintenance (PM) and Statistical Process Control (SPC) are important practices to achieve high product quality, small frequency of failures, and cost reduction in a production process. However there are some points that have not been explored in depth about its joint application. First, most SPC is performed with the X-bar control chart which does not fully consider the variability of the production process. Second, many studies of design of control charts consider just the economic aspect while statistical restrictions must be considered to achieve charts with low probabilities of false detection of failures. Third, the effect of PM on processes with different failure probability distributions has not been studied. Hence, this paper covers these points, presenting the Economic Statistical Design (ESD) of joint X-bar-S control charts with a cost model that integrates PM with general failure distribution. Experiments showed statistically significant reductions in costs when PM is performed on processes with high failure rates and reductions in the sampling frequency of units for testing under SPC.

  18. Analysis of potential failure modes and failure mechanisms in spacecrafts%航天机构潜在故障模式与故障机理分析

    Institute of Scientific and Technical Information of China (English)

    马明臻; 张新宇; 谭春林; 刘日平

    2014-01-01

    空间环境效应、制造加工质量以及所承受的工作载荷是诱发航天机构在轨服役过程中潜在故障的影响因素,对其服役寿命和可靠性将产生重要的影响。因此,开展航天机构潜在故障模式与故障机理分析具有重要科学意义和工程价值。本文对航天机构潜在故障的成因、故障模式、故障机理与影响因素之间的关系以及故障的种类进行了论述,梳理了3类15种可能引发航天机构潜在故障的因素,指出由润滑失效引起的摩擦磨损和载荷作用引起的疲劳失效是导致航天机构潜在故障的两个重要原因,并提出了故障机理的分析程序和方法。%The factors for potential failures in spacecrafts include the effects of the harsh space environment on it during the on-orbit servicing, manufacturing quality as well as the work load during service, which all have significant impacts on its service life and reliability. Therefore, it is of great scientific and technical importance to analyze potential failure mechanism and failure modes in the spacecrafts. In this paper, the types of failures and the relationship of the causes of potential failures, failure modes, failure mechanism and influencing factors for a space structure are discussed. Additionally, fifteen factors classified as three categories that could lead to potential failures of the spacecrafts are presented. It is concluded that the friction and wear phenomena resulted from lubrication failure and fatigue failure related to the loading are two major potential causes of failure in space structure. Pro-cedures and strategies for the analysis of failure mechanism are proposed.

  19. Success in Prevention of Casing Failures Opposite Salts, Little Knife Field, ND

    Energy Technology Data Exchange (ETDEWEB)

    Rilke, E.A.

    1984-05-01

    Early in 1981, Gulf became aware of a severe problem with casing failures opposite salts in the Little Knife Field. A concerted effort was initiated at that time to isolate and remedy the cause of failures. By properly designing tubulars, utilizing a relaxed invert oil emulsion drilling fluid, and properly designing cementing programs, the problem has been arrested. In the 22 wells drilled in the Little Knife Field since initiation of this drilling program in 1981, there have been no instances of casing failure.

  20. A molecular-dynamics study of defects and failure mechanisms in strained heteroepitaxial interfaces

    Science.gov (United States)

    Schiffbauer, Jarrod E.; Bachlechner, Martina E.

    2006-03-01

    The formation and growth of pits and pit-like structures through a delamination-driven mechanism have been observed in the analysis of comprehensive molecular dynamics simulations of a laterally strained Si(111)/Si3N4(0001) interfacial system. These phenomena contribute to the ultimate mechanical failure of the simulated samples. Several factors play a key role the nucleation and growth of the pits including temperature and strain rate. Here we present an overview of the dependence of pit nucleation and morphology on both global and local conditions for a representative range of temperatures and applied strain rates.

  1. Oxime and atropine failure to prevent intermediate syndrome development in acute organophosphate poisoning

    Directory of Open Access Journals (Sweden)

    Vučinić Slavica

    2013-01-01

    Full Text Available Introduction. Intermediate syndrome (IMS was described a few decades ago, however, there is still a controversy regarding its exact etiology, risk factors, diagnostic parameters and required therapy. Considering that acute poisonings are treated in different types of medical institutions this serious complication of organophosphate insecticide (OPI poisoning is frequently overlooked. The aim of this paper was to present a case of IMS in organophosphate poisoning, which, we believe, provides additional data on the use of oxime or atropine. Case report. After a well-resolved cholinergic crisis, the patient developed clinical presentation of IMS within the first 72 h from deliberate malathion ingestion. The signs of IMS were weakness of proximal limb muscles and muscles innervated by motor cranial nerves, followed by the weakness of respiratory muscles and serious respiratory insufficiency. Malathion and its active metabolite were confirmed by analytical procedure (liquid chromatography-mass spectrometry. Pralidoxime methylsulphate, adiministered as a continuous infusion until day 8 (total dose 38.4 g, and atropine until the day 10 (total dose 922 mg did not prevent the development of IMS, hence the mechanical ventilation that was stopped after 27 h had to be continued until the day 10. Conclusion. Continuous pralidoxime methylsulphate infusion with atropine did not prevent the development of IMS, most likely due to the delayed treatment and insufficient oxime dose but also because of chemical structure and lipophilicity of ingested OPI. A prolonged intensive care monitoring and respiratory care are the key management for the intermediate syndrome. [Projekat Ministarstva nauke Republike Srbije, br. OI 176018, No. 46009

  2. Relationship Between Pre-failure and Post-failure Mechanical Properties of Rock Material of Different Origin

    Science.gov (United States)

    Tutluoğlu, Levent; Öge, İbrahim Ferid; Karpuz, Celal

    2015-01-01

    Under compression, gathering data related to the post-failure part of the stress-strain curve requires stiff servo-controlled testing systems. In unconfined conditions, data related to the post-peak region of the intact rock parameters are not common as pre-peak and peak state parameters of stress-strain behavior. For problems involving rock in the failed state around structures, proper choice of plastic constitutive laws and post-failure parameters is important for the modeling of the failed state. The aim is to relate commonly used intact rock parameters of pre-failure (tangent modulus E i and secant modulus E s) and peak strength ( σ ci) states to parameters of the post-failure state under unconfined compression. Post-failure parameters are the drop modulus ( D pf), representing the slope of the falling portion in brittle state, residual strength ( σ cr), and dilatancy angle ( ψ°). Complete stress-strain curves were generated for various intact rock of different origin. Seventy-three post-failure tests were conducted. Samples included in the testing program were chosen to represent rocks of different origin. Specimens of granite, rhyodacite, dunite, quartzite series, glauberite, argillite, marl, and lignite were used in the tests. The results from the pre-failure and peak state testing parts were processed and compared to the post-failure stress-strain parameters. For the estimation of post-failure parameters in terms of the pre-peak and peak states, the functional relations were assessed. It was found that the drop modulus D pf increases with rock strength σ ci, following a power function with an approximate power of two. With an exponential trend, the D pf/ E s ratio increases with decreasing E i/ σ ci ratio. Relations estimating the residual strength and dilatancy from the pre-peak and peak state parameters are in logarithmic and exponential functional forms, respectively.

  3. Role of long-term mechanical circulatory support in patients with advanced heart failure.

    Science.gov (United States)

    Stokes, M B; Bergin, P; McGiffin, D

    2016-05-01

    Advanced heart failure represents a small proportion of patients with heart failure that possess high-risk features associated with high hospital readmission rates, significant functional impairment and mortality. Identification of those who have progressed to, or are near a state of advanced heart failure should prompt referral to a service that offers therapies in mechanical circulatory support (MCS) and cardiac transplantation. MCS has grown as a management strategy in the care of these patients, most commonly as a bridge to cardiac transplantation. The predominant utilisation of MCS is implantation of left ventricular assist devices (LVAD), which have evolved significantly in their technology and application over the past 15-20 years. The technology has evolved to such an extent that Destination Therapy is now being utilised as a strategy in management of advanced heart failure in appropriately selected patients. Complication rates have decreased with VAD implantation, but remain a significant consideration in the decision to implant a device, and in the follow up of these patients.

  4. Mechanisms That Modulate Peripheral Oxygen Delivery during Exercise in Heart Failure.

    Science.gov (United States)

    Kisaka, Tomohiko; Stringer, William W; Koike, Akira; Agostoni, Piergiuseppe; Wasserman, Karlman

    2017-07-01

    Oxygen uptake ([Formula: see text]o2) measured at the mouth, which is equal to the cardiac output (CO) times the arterial-venous oxygen content difference [C(a-v)O2], increases more than 10- to 20-fold in normal subjects during exercise. To achieve this substantial increase in oxygen uptake [[Formula: see text]o2 = CO × C(a-v)O2] both CO and the arterial-venous difference must simultaneously increase. Although this occurs in normal subjects, patients with heart failure cannot achieve significant increases in cardiac output and must rely primarily on changes in the arterial-venous difference to increase [Formula: see text]o2 during exercise. Inadequate oxygen delivery to the tissue during exercise in heart failure results in tissue anaerobiosis, lactic acid accumulation, and reduction in exercise tolerance. H(+) is an important regulatory and feedback mechanism to facilitate additional oxygen delivery to the tissue (Bohr effect) and further aerobic production of ATP when tissue anaerobic metabolism increases the production of lactate (anaerobic threshold). This H(+) production in the muscle capillary promotes the continued unloading of oxygen (oxyhemoglobin desaturation) while maintaining the muscle capillary Po2 (Fick principle) at a sufficient level to facilitate aerobic metabolism and overcome the diffusion barriers from capillary to mitochondria ("critical capillary Po2," 15-20 mm Hg). This mechanism is especially important during exercise in heart failure where cardiac output increase is severely constrained. Several compensatory mechanisms facilitate peripheral oxygen delivery during exercise in both normal persons and patients with heart failure.

  5. Reliability technology principles and practice of failure prevention in electronic systems

    CERN Document Server

    Pascoe, Norman

    2011-01-01

    A unique book that describes the practical processes necessary to achieve failure free equipment performance, for quality and reliability engineers, design, manufacturing process and environmental test engineers. This book studies the essential requirements for successful product life cycle management. It identifies key contributors to failure in product life cycle management and particular emphasis is placed upon the importance of thorough Manufacturing Process Capability reviews for both in-house and outsourced manufacturing strategies. The readers? attention is also drawn to the ma

  6. In-Built Customised Mechanical Failure of 316L Components Fabricated Using Selective Laser Melting

    Directory of Open Access Journals (Sweden)

    Andrei Ilie

    2017-02-01

    Full Text Available The layer-by-layer building methodology used within the powder bed process of Selective Laser Melting facilitates control over the degree of melting achieved at every layer. This control can be used to manipulate levels of porosity within each layer, effecting resultant mechanical properties. If specifically controlled, it has the potential to enable customisation of mechanical properties or design of in-built locations of mechanical fracture through strategic void placement across a component, enabling accurate location specific predictions of mechanical failure for fail-safe applications. This investigation examined the process parameter effects on porosity formation and mechanical properties of 316L samples whilst maintaining a constant laser energy density without manipulation of sample geometry. In order to understand the effects of customisation on mechanical properties, samples were manufactured with in-built porosity of up to 3% spanning across ~1.7% of a samples’ cross-section using a specially developed set of “hybrid” processing parameters. Through strategic placement of porous sections within samples, exact fracture location could be predicted. When mechanically loaded, these customised samples exhibited only ~2% reduction in yield strength compared to samples processed using single set parameters. As expected, microscopic analysis revealed that mechanical performance was closely tied to porosity variations in samples, with little or no variation in microstructure observed through parameter variation. The results indicate that there is potential to use SLM for customising mechanical performance over the cross-section of a component.

  7. Failure mechanism of shear-wall dominant multi-story buildings

    Science.gov (United States)

    Yuksel, S.B.; Kalkan, E.

    2008-01-01

    The recent trend in the building industry of Turkey as well as in many European countries is towards utilizing the tunnel form (shear-wall dominant) construction system for development of multi-story residential units. The tunnel form buildings diverge from other conventional reinforced concrete (RC) buildings due to the lack of beams and columns in their structural integrity. The vertical load-carrying members of these buildings are the structural-walls only, and the floor system is a flat plate. Besides the constructive advantages, tunnel form buildings provide superior seismic performance compared to conventional RC frame and dual systems as observed during the recent devastating earthquakes in Turkey (1999 Mw 7.4 Kocaeli, Mw 7.2 Duzce, and 2004 Mw 6.5 Bingol). With its proven earthquake performance, the tunnel form system is becoming the primary construction technique in many seismically active regions. In this study, a series of nonlinear analyses were conducted using finite element (FE) models to augment our understanding on their failure mechanism under lateral forces. In order to represent the nonlinear behavior adequately, The FE models were verified with the results of experimental studies performed on three dimensional (3D) scaled tunnel form building specimens. The results of this study indicate that the structural walls of tunnel form buildings may exhibit brittle flexural failure under lateral loading, if they are not properly reinforced. The global tension/compression couple triggers this failure mechanism by creating pure axial tension in the outermost shear-walls.

  8. THEORETICAL MODEL ON INTERFACE FAILURE MECHANISM OF REINFORCED CONCRETE CONTINUOUS BEAM STRENGTHENED BY FRP

    Institute of Scientific and Technical Information of China (English)

    Hong Yuan; Zifeng Lin

    2009-01-01

    Fiber reinforced polymer (FRP) composites are increasingly being used for the re-pair and strengthening of deteriorated concrete structural components through adhesive bonding of prefabricated strips/plates and the wet lay-up of fabric. Interracial bond failure modes have at-tracted the attention of researchers because of the importance. The objective of the present study is to analyse the interface failure mechanism of reinforced concrete continuous beam strength-ened by FRP. An analytical solution has been firstly presented to predict the entire debonding process of the model. The realistic bi-linear bond-slip interfacial law was adopted to study this problem. The crack propagation process of the loaded model was divided into four stages (elastic, elastic-softening, elastic-softening-debonded and softening-debonded stage). Among them, elastic-softening-debonded stage has four sub-stages. The equations are solved by adding suitable stress and displacement boundary conditions. Finally, critical value of bond length is determined to make the failure mechanism in the paper effective by solving the simultaneously linear algebraic equations. The interaction between the upper and lower FRP plates can be neglected if axial stiffness ratio of the concrete-to-plate prism is large enough.

  9. Failure Mechanism of Fast-Charged Lithium Metal Batteries in Liquid Electrolyte

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Dongping; Shao, Yuyan; Lozano, Terence J.; Bennett, Wendy D.; Graff, Gordon L.; Polzin, Bryant; Zhang, Jiguang; Engelhard, Mark H.; Saenz, Natalio T.; Henderson, Wesley A.; Bhattacharya, Priyanka; Liu, Jun; Xiao, Jie

    2015-02-01

    In recent years, lithium anode has re-attracted broad interest because of the necessity of employing lithium metal in the next-generation battery technologies such as lithium sulfur (Li-S) and lithium oxygen (Li-O2) batteries. Fast capacity degradation and safety issue associated with rechargeable lithium metal batteries have been reported, although the fundamental understanding on the failure mechanism of lithium metal at high charge rate is still under debate due to the complicated interfacial chemistry between lithium metal and electrolyte. Herein, we demonstrate that, at high current density, the quick growth of porous solid electrolyte interphase towards bulk lithium, instead of towards the separator, dramatically builds up the cell impedance that directly leads to the cell failure. Understanding the lithium metal failure mechanism is very critical to gauge the various approaches used to address the stability and safety issues associated with lithium metal anode. Otherwise, all cells will fail quickly at high rates before the observation of any positive effects that might be brought from adopting the new strategies to protect lithium.

  10. Failure and deformation mechanisms at macro- and nano-scales of alkali activated clay

    Science.gov (United States)

    Sekhar Das, Pradip; Bhattacharya, Manjima; Chanda, Dipak Kr; Dalui, Srikanta; Acharya, Saikat; Ghosh, Swapankumar; Mukhopadhyay, Anoop Kumar

    2016-06-01

    Here we report two qualitative models on failure and deformation mechanisms at macro- and nano-scales of alkali activated clay (AACL), a material of extraordinary importance as a low cost building material. The models were based on experimental data of compressive failure and nanoindentation response of the AACL materials. A 420% improvement in compressive strength (σ c) of the AACL was achieved after 28 days (d) of curing at room temperature and it correlated well with the decrements in the residual alkali and pH concentrations with the increase in curing time. Based on extensive post-mortem FE-SEM examinations, a schematic model for the compressive failure mechanism of AACL was proposed. In addition, the nanoindentation results of AACL provided the first ever experimental evidence of the presence of nano-scale plasticity and a nano-scale contact deformation resistance that increased with the applied load. These results meant the development of a unique strain tolerant microstructure in the AACL of Indian origin. The implications of these new observations were discussed in terms of a qualitative model based on the deformation of layered clay structure.

  11. Radiation health consequences for astronauts: mechanisms, monitoring and prevention

    Science.gov (United States)

    Neyfakh, E.

    During space flights crews are exposed chronically to uneven irradiation of enhanced bioefficiency following with significant elevation for chromosomal aberrations as minimum. To protect in space rationally monitoring and preventing of health radiogenic individual primary consequences for astronauts are of high importance. Majority of Chernobyl-touched population has some common etiologic radiogenic mechanisms and radioloads with astronauts ones during long-term missions and former is able to be used well as the close ground-level model. Primary radiogenic deviations. Two radiogenic pathologies as lipoperoxic ( LP ) stress with coupled deficits for essential bioantioxidants ( BAO ) were typical for chronic low-dose Chernobyl-touched contingents. When BAO expenditure had led to their subnormal levels, radiogenic free radical chain -b ranched LP processes occurred in vivo hyperbolically. Catabolites and their free radicals of the abnormal LP cascade are known to be toxic, mutagenic / carcinogenic and teratogenic factors as such, as they are for retinol and tocopherol deficiencies. Both coupled pathogenic factors interrelated synergistically. Simultaneous dysbalances for LP and / or BAO systems were evaluated as the cause and markers for metabolic disregulations. Human LP stress was proved to be the most radiosensible known marker to mo nitor least invasively of blood microsamples in a ground lab via the developed PC Program. But for capsule conditions the best approach is assumed to be LP monitoring via skin ultraweak green-blue chemiluminescence ( CL ) caused by recombination of peroxyl radicals. CL from surfaces of organs was embedded first ( E. Neyfakh, 1964 - 71 ) to reflect their internal LP velocities in vivo and it is the non-invasive on-line simple method of the highest sensitivity, supplying with data transmissible to the ground directly. Related deviations. a) Radiogenic hypermutagenesis: LP catabolites and their free radicals are responsible for direct DNA

  12. Cortical and spinal mechanisms of task failure of sustained submaximal fatiguing contractions.

    Directory of Open Access Journals (Sweden)

    Petra S Williams

    Full Text Available In this and the subsequent companion paper, results are presented that collectively seek to delineate the contribution that supraspinal circuits have in determining the time to task failure (TTF of sustained submaximal contractions. The purpose of this study was to compare adjustments in supraspinal and spinal excitability taken concurrently throughout the performance of two different fatigue tasks with identical mechanical demands but different TTF (i.e., force-matching and position-matching tasks. On separate visits, ten healthy volunteers performed the force-matching or position-matching task at 15% of maximum strength with the elbow flexors to task failure. Single-pulse transcranial magnetic stimulation (TMS, paired-pulse TMS, paired cortico-cervicomedullary stimulation, and brachial plexus electrical stimulation were delivered in a 6-stimuli sequence at baseline and every 2-3 minutes throughout fatigue-task performance. Contrary to expectations, the force-matching task TTF was 42% shorter (17.5 ± 7.9 min than the position-matching task (26.9 ± 15.11 min; p0.05. Therefore, failure occurred after a similar mean decline in motorneuron excitability developed (p0.10 and an index of upstream excitation of the motor cortex remained constant (p>0.40. Together, these results suggest that as fatigue develops prior to task failure, the increase in corticospinal excitability observed in relationship to the decrease in spinal excitability results from a combination of decreasing intracortical inhibition with constant levels of intracortical facilitation and upstream excitability that together eventually fail to provide the input to the motor cortex necessary for descending drive to overcome the spinal cord resistance, thereby contributing to task failure.

  13. FAILURE MECHANISMS OF THERMAL BARRIER COATINGS INTERNAL COMBUSTION ENGINES AND llMPROVEMENTS

    Directory of Open Access Journals (Sweden)

    ADNAN PARLAK

    2003-04-01

    Full Text Available MechanicaJ properties of high performance ceramics have been improved to the point where their use in heat engines is possible. The high temperature strength and low thermal expansion properties of bigh performance ceramics offer an advantage over metals in the development of non-water cooling engine. However, because bard environment in diesel engine combustion chamber, solving the problem of durabiUty of TBC is important. DurabiUty of thermal barrier coatings(TBC is liınited by two main failure mechanisms: Therınal expansion nlİsmatch betwcen bond coat and top coat and bond coat oxidation. Both of these can cause failure of the ceramic top coat. Developments of recent years sholv that bond coats \\Vith higher oxidation resistance tend to have better coating system cyclic lives

  14. A numerical study on intended and unintended failure mechanisms in blanking of sandwich plates

    Science.gov (United States)

    Chen, L.; Soyarslan, C.; Tekkaya, A. E.

    2013-05-01

    Metal-polymer-metal sandwich plates are widely used in the automotive and aerospace industry. As for different applications the sandwich plates can be divided into two types. They are sound-damping laminates with a polymer core much thinner than the metallic faces and low-density laminates with a core thickness of approximately 40-60% of the total thickness. One frequent process step in production of parts made of these plates is the blanking process whose hereditary effects draw the limits of further forming stages or service performance and life; e.g. the failure of the adhesive in the thermoplastic polymer interface affects the sound-damping efficiency intensively. With this motivation, we present FE simulation of an axi-symmetric blanking process of steel/polyethylene/steel sound-damping laminates. The mechanical behavior of the metallic layers was characterized by finite strain rate independent elasto-plasticity where progressive material deterioration and fracture are given account for using continuum damage mechanics (CDM). This material model is made accessible via implementations as VUMAT subroutines for ABAQUS/Explicit. Possible failure of the thermoplastic polymer which may lead to delamination of the metallic layers is modeled using ABAQUS built-in cohesive zone elements. The results show that existing intended and unintended failure modes, e.g. blanking of the metallic and thermoplastic polymer constituents as well as failure of polymer layer under shear and compression, can be effectively studied with the proposed framework for process enhancement. As a future work, a damage coupled nonlinear visco-elastic constitutive model will be devised for the simulation of the thermoplastic layer in low-density laminates.

  15. The effect of carbon content on mechanical properties, failure and corrosion resistance of deposited chromium metal

    Directory of Open Access Journals (Sweden)

    Леонід Кімович Лещинськiй

    2017-06-01

    Full Text Available It has been shown that if choosing a metal composition for surfacing rolls and rollers of continuous casting machines, both the carbon impact on the mechanical and functional properties and the critical values of the chromium concentration, which determine the corrosion resistance of the metal with regard to electrochemical corrosion theory, should be considered as well. The paper studied the effect of chromium and carbon steel the X5-X12 type on the structure, technological strength, mechanical properties, fracturing resistance and corrosion resistance of the weld metal. The composition of chromium tool steels (deposited metal (X5-used for the rolls of hot rolling mills and (X12-used for continuous casting machines rollers correspond to these values. The impact of carbon on the properties of the deposited metal containing chromium was considered by comparing the data for both types of the deposited metal. It was found that for both types of the deposited metal (X5 and X12, the limiting value of the carbon content, providing an optimal combination of strength, ductility, failure resistance is the same. If the carbon content is more than the limiting value – (0,25% the technological strength and failure resistance of the deposited metal significantly reduce. With increasing carbon content from 0,18 to 0,25% the martensite structure has a mixed morphology – lath and plate. The strength and toughness of the deposited metal grow. Of particular interest is simultaneous increase in the specific work of failure resulted from crack inhibition at the boundary with far less solid and more ductile ferrite. As for the 5% chromium metal, the X12 type composition with 0,25% C, is borderline. With a further increase in the carbon content of the metal both ductility and failure resistance sharply decrease and with 0,40% C the growth rate of fatigue crack increases by almost 1,5 times

  16. Predicting and preventing peripheral intravenous cannula insertion failure in the emergency department: Clinician 'gestalt' wins again.

    Science.gov (United States)

    Rippey, James Cr; Carr, Peter J; Cooke, Marie; Higgins, Niall; Rickard, Claire M

    2016-12-01

    Failed attempts at peripheral i.v. cannula (PIVC) insertion in the ED are common. The psychological, physical and economic impact of these failures is significant. We sought to explore whether clinicians of differing experience levels can predict their own likelihood (clinician 'gestalt') of first-time cannula insertion success on any given patient. Data analyses from a prospective self-reported study assessing risk factors for first-time insertion success in a tertiary adult ED. We constructed and compared two simple theoretical clinical decision algorithms in an attempt to improve first-time PIVC insertion success rates. This best algorithm identified a subgroup of 18% of the total PIVC population at higher risk of failure. This 18% comprised 57% of all PIVC failures, and implementation would result in a relative risk reduction of PIVC failure by 31%. When applied to our sample population, an algorithm relying on clinician gestalt to identify patients at high risk of PIVC failure had the greatest potential impact. These patients would be referred to expert PIVC inserters prior to, rather than after, failed attempts. © 2016 Australasian College for Emergency Medicine and Australasian Society for Emergency Medicine.

  17. Effect of fluid therapy on prevention of acute renal failure in Bam earthquake crush victims.

    Science.gov (United States)

    Sagheb, Mohammad Mahdi; Sharifian, Maryam; Roozbeh, Jamshid; Moini, Maryam; Gholami, Khodakaram; Sadeghi, Hossein

    2008-01-01

    At 5:28 a.m. (local time) on December 26, 2003, an earthquake measuring 6.51 on the Richter scale struck the city of Bam in the Kerman Province in southeastern Iran. Among the most important morbid events in survivors were acute renal problems. Clinical findings, laboratory data, and management of the renal victims, all of whom were transferred to Shiraz Hospitals, have been the subject of this analysis. Medical records of twenty patients with acute renal failure admitted to three university hospitals and one community hospital were reviewed. Overall, 801 patients were transferred to Shiraz hospitals, of whom 20 (mean age 36.2 +/- 14.8 years, 15 males) developed acute renal failure with mean duration of 14.5 +/- 9.6 days. Total mortality was 21 (2.6%) and acute renal failure mortality was 3 (15%). Seven patients received standard fluid therapy and 13 patients received variable volume treatment. In total, 79 dialysis sessions were performed in 15 patients (mean 5.2, 3.3 +/- 1 sessions per patients). There was a positive correlation between time spent under rubble and peak serum CK (creatine phosphokinase) level (p = 0.035), acute renal failure duration (p = 0.047), and admission potassium levels (p = 0.033). Serum CK level was positively correlated with acute renal failure duration (p = 0.008). Patients who had received standard treatment had significantly shorter duration of acute renal failure (7.1 versus 9.4 days, p = 0.008) and less need for dialysis (1 versus 6, p = 0.007) than patients who were treated variably. In victims of earthquake, time spent under rubble and peak serum CK level can serve to estimate morbidity, and early standard treatment may decrease renal morbidity.

  18. Mechanics and complications of reverse shoulder arthroplasty: morse taper failure analysis and prospective rectification

    Science.gov (United States)

    Hoskin, HLD; Furie, E.; Collins, W.; Ganey, TM; Schlatterer, DR

    2017-05-01

    and O are used as stabilizers that help raise the temperature at which titanium can be cast. Since the presence of stabilizers reduces ductility and fatigue strength, all interstitial elements are removed after casting. Considering this, the presence of C and O suggests that not all of the interstitials were removed during the manufacturing process, resulting in decreased fatigue strength. Further destructive analytical testing would verify weld quality and failure mode. RTSSs are quite successful in select patients not amenable to traditional shoulder arthroplasty options. This case report highlights how an implant may function well for several years and then suddenly fail without warning. SEM and EDS analysis suggest that residual C and O in the taper lowered the metal implant’s integrity, leading to torsional cracking at the weld junction of the humeral tray and the taper. The elevated levels of C and O measured at fracture sites on both the tray and the taper suggest poor quality filler metal or failure to remove all interstitial elements after casting. In both cases, the results would be decreased fatigue strength and overall toughness, leading to mechanical failure. A manufacturer’s recall of all implants soon followed the reporting of this implant failure; subsequently, the metal materials were changed from Ti6Al4V to both titanium alloy and cobalt-chrome alloy (Co-Cr-Mo). Time will tell if the alterations were sufficient.

  19. In Situ Observation of Failure Mechanisms Controlled by Rock Masses with Weak Interlayer Zones in Large Underground Cavern Excavations Under High Geostress

    Science.gov (United States)

    Duan, Shu-Qian; Feng, Xia-Ting; Jiang, Quan; Liu, Guo-Feng; Pei, Shu-Feng; Fan, Yi-Lin

    2017-09-01

    A weak interlayer zone (WIZ) is a poor rock mass system with loose structure, weak mechanical properties, variable thickness, random distribution, strong extension, and high risk due to the shear motion of rock masses under the action of tectonism, bringing many stability problems and geological hazards, especially representing a potential threat to the overall stability of rock masses with WIZs in large underground cavern excavations. Focusing on the deformation and failure problems encountered in the process of excavation unloading, this research proposes comprehensive in situ observation schemes for rock masses with WIZs in large underground cavern on the basis of the collection of geological, construction, monitoring, and testing data. The schemes have been fully applied in two valuable project cases of an underground cavern group under construction in the southwest of China, including the plastic squeezing-out tensile failure and the structural stress-induced collapse of rock masses with WIZs. In this way, the development of rock mass failure, affected by the step-by-step excavations along the cavern's axis and the subsequent excavation downward, could be observed thoroughly. Furthermore, this paper reveals the preliminary analyses of failure mechanism of rock masses with WIZs from several aspects, including rock mass structure, strength, high stress, ground water effects, and microfracture mechanisms. Finally, the failure particularities of rock masses with WIZs and rethink on prevention and control of failures are discussed. The research results could provide important guiding reference value for stability analysis, as well as for rethinking the excavation and support optimization of rock masses with WIZs in similar large underground cavern under high geostress.

  20. An atypical presentation of mechanical failure of eruption of a mandibular permanent molar: diagnosis and treatment case report.

    LENUS (Irish Health Repository)

    Smith, C P

    2012-06-01

    Failure of eruption of mandibular permanent molars occurs infrequently but is a difficult clinical problem. It can be due to local or systemic factors or failure of the eruption process. Primary failure of eruption (PFE) is a rare condition that can result in severe posterior open bite, requires complex treatment strategies and has unfavourable outcomes. Mechanical failure of eruption (MFE) is more unusual but can respond positively to treatment. Differentiating between the two is crucial in making the correct diagnosis and managing the case successfully.

  1. Aircraft Loss-of-Control Accident Prevention: Switching Control of the GTM Aircraft with Elevator Jam Failures

    Science.gov (United States)

    Chang, Bor-Chin; Kwatny, Harry G.; Belcastro, Christine; Belcastro, Celeste

    2008-01-01

    Switching control, servomechanism, and H2 control theory are used to provide a practical and easy-to-implement solution for the actuator jam problem. A jammed actuator not only causes a reduction of control authority, but also creates a persistent disturbance with uncertain amplitude. The longitudinal dynamics model of the NASA GTM UAV is employed to demonstrate that a single fixed reconfigured controller design based on the proposed approach is capable of accommodating an elevator jam failure with arbitrary jam position as long as the thrust control has enough control authority. This paper is a first step towards solving a more comprehensive in-flight loss-of-control accident prevention problem that involves multiple actuator failures, structure damages, unanticipated faults, and nonlinear upset regime recovery, etc.

  2. Mechanical strength, fatigue life, and failure analysis of two prototypes and five conventional tibial locking screws.

    Science.gov (United States)

    Hou, Sheng-Mou; Wang, Jaw-Lin; Lin, Jinn

    2002-01-01

    To investigate the effects of the design and microstructure on the mechanical strength of tibial locking devices. The mechanical strength of two prototypes of specially developed locking devices (a both-ends-threaded screw and an unthreaded bolt) was tested and compared with that of five types of commercially available tibial locking screws (Synthes, Howmedica, Richards, Osteo AG, and Zimmer) with similar dimensions. The devices were inserted into a polyethylene tube and loaded at their midpoint by a materials testing machine to simulate a three-point bending test. Single-loading yielding strength and cyclic-loading fatigue life were then measured. Failure analysis of the fractured screws was performed to investigate the microstructure and potential causes of the fatigue fracture. Test results showed that both yielding strength and fatigue life were closely related to the section modulus of the inner diameter of screws. Among the threaded screws, the both-ends-threaded screws had a higher yielding strength and longer fatigue life than the Osteo AG, Howmedica, Richards, and Zimmer screws. The unthreaded bolts had a lower yielding strength than Synthes screws, but they demonstrated the longest fatigue life among all. In failure analysis of broken screws, no metallurgical or manufacturing defects were found except for surface microimperfections. The implants investigated in this study are manufactured with high-quality materials and manufacturing processes. The main cause of hardware failure was mechanical overloading. The five commercially used tibial locking screws had a relatively short fatigue life under high loading. Removing the screw threads might substantially increase the fatigue life of the locking devices. In unthreaded bolts, this increase might be tenfold to a hundredfold.

  3. Mechanical Ventilation during Extracorporeal Membrane Oxygenation in Patients with Acute Severe Respiratory Failure

    Directory of Open Access Journals (Sweden)

    Zhongheng Zhang

    2017-01-01

    Full Text Available Conventionally, a substantial number of patients with acute respiratory failure require mechanical ventilation (MV to avert catastrophe of hypoxemia and hypercapnia. However, mechanical ventilation per se can cause lung injury, accelerating the disease progression. Extracorporeal membrane oxygenation (ECMO provides an alternative to rescue patients with severe respiratory failure that conventional mechanical ventilation fails to maintain adequate gas exchange. The physiology behind ECMO and its interaction with MV were reviewed. Next, we discussed the timing of ECMO initiation based on the risks and benefits of ECMO. During the running of ECMO, the protective ventilation strategy can be employed without worrying about catastrophic hypoxemia and carbon dioxide retention. There is a large body of evidence showing that protective ventilation with low tidal volume, high positive end-expiratory pressure, and prone positioning can provide benefits on mortality outcome. More recently, there is an increasing popularity on the use of awake and spontaneous breathing for patients undergoing ECMO, which is thought to be beneficial in terms of rehabilitation.

  4. Mechanical Ventilation during Extracorporeal Membrane Oxygenation in Patients with Acute Severe Respiratory Failure

    Science.gov (United States)

    Gu, Wan-Jie; Chen, Kun; Ni, Hongying

    2017-01-01

    Conventionally, a substantial number of patients with acute respiratory failure require mechanical ventilation (MV) to avert catastrophe of hypoxemia and hypercapnia. However, mechanical ventilation per se can cause lung injury, accelerating the disease progression. Extracorporeal membrane oxygenation (ECMO) provides an alternative to rescue patients with severe respiratory failure that conventional mechanical ventilation fails to maintain adequate gas exchange. The physiology behind ECMO and its interaction with MV were reviewed. Next, we discussed the timing of ECMO initiation based on the risks and benefits of ECMO. During the running of ECMO, the protective ventilation strategy can be employed without worrying about catastrophic hypoxemia and carbon dioxide retention. There is a large body of evidence showing that protective ventilation with low tidal volume, high positive end-expiratory pressure, and prone positioning can provide benefits on mortality outcome. More recently, there is an increasing popularity on the use of awake and spontaneous breathing for patients undergoing ECMO, which is thought to be beneficial in terms of rehabilitation. PMID:28127231

  5. Failure Predictions for VHTR Core Components using a Probabilistic Contiuum Damage Mechanics Model

    Energy Technology Data Exchange (ETDEWEB)

    Fok, Alex

    2013-10-30

    The proposed work addresses the key research need for the development of constitutive models and overall failure models for graphite and high temperature structural materials, with the long-term goal being to maximize the design life of the Next Generation Nuclear Plant (NGNP). To this end, the capability of a Continuum Damage Mechanics (CDM) model, which has been used successfully for modeling fracture of virgin graphite, will be extended as a predictive and design tool for the core components of the very high- temperature reactor (VHTR). Specifically, irradiation and environmental effects pertinent to the VHTR will be incorporated into the model to allow fracture of graphite and ceramic components under in-reactor conditions to be modeled explicitly using the finite element method. The model uses a combined stress-based and fracture mechanics-based failure criterion, so it can simulate both the initiation and propagation of cracks. Modern imaging techniques, such as x-ray computed tomography and digital image correlation, will be used during material testing to help define the baseline material damage parameters. Monte Carlo analysis will be performed to address inherent variations in material properties, the aim being to reduce the arbitrariness and uncertainties associated with the current statistical approach. The results can potentially contribute to the current development of American Society of Mechanical Engineers (ASME) codes for the design and construction of VHTR core components.

  6. Blockage of the Ryanodine Receptor via Azumolene Does Not Prevent Mechanical Ventilation-Induced Diaphragm Atrophy.

    Directory of Open Access Journals (Sweden)

    Erin E Talbert

    Full Text Available Mechanical ventilation (MV is a life-saving intervention for patients in respiratory failure. However, prolonged MV causes the rapid development of diaphragm muscle atrophy, and diaphragmatic weakness may contribute to difficult weaning from MV. Therefore, developing a therapeutic countermeasure to protect against MV-induced diaphragmatic atrophy is important. MV-induced diaphragm atrophy is due, at least in part, to increased production of reactive oxygen species (ROS from diaphragm mitochondria and the activation of key muscle proteases (i.e., calpain and caspase-3. In this regard, leakage of calcium through the ryanodine receptor (RyR1 in diaphragm muscle fibers during MV could result in increased mitochondrial ROS emission, protease activation, and diaphragm atrophy. Therefore, these experiments tested the hypothesis that a pharmacological blockade of the RyR1 in diaphragm fibers with azumolene (AZ would prevent MV-induced increases in mitochondrial ROS production, protease activation, and diaphragmatic atrophy. Adult female Sprague-Dawley rats underwent 12 hours of full-support MV while receiving either AZ or vehicle. At the end of the experiment, mitochondrial ROS emission, protease activation, and fiber cross-sectional area were determined in diaphragm muscle fibers. Decreases in muscle force production following MV indicate that the diaphragm took up a sufficient quantity of AZ to block calcium release through the RyR1. However, our findings reveal that AZ treatment did not prevent the MV-induced increase in mitochondrial ROS emission or protease activation in the diaphragm. Importantly, AZ treatment did not prevent MV-induced diaphragm fiber atrophy. Thus, pharmacological inhibition of the RyR1 in diaphragm muscle fibers is not sufficient to prevent MV-induced diaphragm atrophy.

  7. Blockage of the Ryanodine Receptor via Azumolene Does Not Prevent Mechanical Ventilation-Induced Diaphragm Atrophy.

    Science.gov (United States)

    Talbert, Erin E; Smuder, Ashley J; Kwon, Oh Sung; Sollanek, Kurt J; Wiggs, Michael P; Powers, Scott K

    2016-01-01

    Mechanical ventilation (MV) is a life-saving intervention for patients in respiratory failure. However, prolonged MV causes the rapid development of diaphragm muscle atrophy, and diaphragmatic weakness may contribute to difficult weaning from MV. Therefore, developing a therapeutic countermeasure to protect against MV-induced diaphragmatic atrophy is important. MV-induced diaphragm atrophy is due, at least in part, to increased production of reactive oxygen species (ROS) from diaphragm mitochondria and the activation of key muscle proteases (i.e., calpain and caspase-3). In this regard, leakage of calcium through the ryanodine receptor (RyR1) in diaphragm muscle fibers during MV could result in increased mitochondrial ROS emission, protease activation, and diaphragm atrophy. Therefore, these experiments tested the hypothesis that a pharmacological blockade of the RyR1 in diaphragm fibers with azumolene (AZ) would prevent MV-induced increases in mitochondrial ROS production, protease activation, and diaphragmatic atrophy. Adult female Sprague-Dawley rats underwent 12 hours of full-support MV while receiving either AZ or vehicle. At the end of the experiment, mitochondrial ROS emission, protease activation, and fiber cross-sectional area were determined in diaphragm muscle fibers. Decreases in muscle force production following MV indicate that the diaphragm took up a sufficient quantity of AZ to block calcium release through the RyR1. However, our findings reveal that AZ treatment did not prevent the MV-induced increase in mitochondrial ROS emission or protease activation in the diaphragm. Importantly, AZ treatment did not prevent MV-induced diaphragm fiber atrophy. Thus, pharmacological inhibition of the RyR1 in diaphragm muscle fibers is not sufficient to prevent MV-induced diaphragm atrophy.

  8. A multicentre randomized controlled trial of moderate hypothermia to prevent intracranial hypertension in acute liver failure

    DEFF Research Database (Denmark)

    Bernal, William; Murphy, Nicholas; Brown, Sarah

    2016-01-01

    BACKGROUND & AIMS: Animal models and human case series of acute liver failure (ALF) suggest moderate hypothermia (MH) to have protective effects against cerebral oedema (CO) development and intracranial hypertension (ICH). However, the optimum temperature for patient management is unknown. In a p...

  9. High saturated fat feeding prevents left ventricular dysfunction and enhances mitochondrial function in heart failure

    Science.gov (United States)

    Accumulation of lipids in the heart is associated with contractile dysfunction, and has been proposed to be a causative factor in mitochondrial dysfunction. We have previously shown that administration of a high saturated fat diet in heart failure (HF) increased mitochondrial respiration and ETC com...

  10. Prevention and management of brain edema in patients with acute liver failure

    DEFF Research Database (Denmark)

    Wendon, J.; Larsen, Finn Stolze

    2008-01-01

    1. Intracranial pressure is the pressure exerted by the cranial contents on the dural envelope and consists of the partial pressures of the brain, blood, and cerebrospinal fluid. 2. Severe cases of acute liver failure are frequently complicated by brain edema (due to cytotoxic edema...

  11. Primary Prevention of Reading Failure: Effect of Universal Peer Tutoring in the Early Grades

    Science.gov (United States)

    Jones, Giavana; Ostojic, Dragana; Menard, Jessica; Picard, Erin; Miller, Carlin J.

    2017-01-01

    Reading is typically considered a survival skill in our technology- and literacy-bound culture. Individuals who struggle with learning to read are at significantly elevated risk for a number of negative outcomes, including school failure, under- and unemployment, and special education placement. Thus, those who do not learn to read fluently will…

  12. [Right-sided mechanical circulatory support in acute right ventricular failure in the dog].

    Science.gov (United States)

    Gabauer, I; Okolicány, J; Styk, J; Pancza, D; Holec, V

    1991-05-01

    The technique of surgically induced acute progressive right ventricular failure in experimental animals is described. It sumultates the hemodynamic situation of right ventricular failure in some patients after termination of extracorporeal circulation applied for carrying out procedures on the left ventricle. The described technique consists of rightsided longitudinal ventriculotomy, destruction of the tricuspid valve, and ligation of the right coronary artery. Nine control dogs died within two hours after induction of failure due to low stroke volume caused by low pulmonary and left atrial pressure. The use of rightsided support appliance draining blood from the right atrium in systole and pumping it into the trunk of the pulmonary artery in diastole by means of a membrane pump resulted in further 12 dogs in the restoration of left ventricular diastolic pressure, significant increase of aortal pressure (p less than 0.003) and stroke volume (p less than 0.003) and in a decrease of right atrial pressure (p less than 0.003). The study demonstrated that by using the described mechanical support the circulation can be adequately assisted so that the failing right side of the heart can get restored. (Tab.1,Fig.5,Ref.25.).

  13. Failure Mechanisms of Air Entrainment in Drop Impact on Lubricated Surfaces

    Science.gov (United States)

    Pack, Min; Hu, Han; Kim, Dong-Ook; Zheng, Zhong; Stone, Howard; Sun, Ying; Drexel University Team; Princeton University Team

    2016-11-01

    Lubricated surfaces have recently been introduced and studied due to their potential benefit in various applications. Combining the techniques of total internal reflection microscopy and reflection interference microscopy, we examine the dynamics of an underlying air film upon drop impact on a lubricated substrate. In contrast to drop impact on solid surfaces where asperities cause random breakup of the entraining air film, we report two air film failure mechanisms on lubricated surfaces. In particular, using thin liquid films of high viscosity, we show that air film rupture shifts from a randomly driven to a controlled event. At low Weber numbers (We) the droplet bounces. At intermediate We, the air film fails at the center as the drop top surface crashes downward owing to impact-induced capillary waves; the resulting liquid-liquid contact time is found to be independent of We. In contrast, at high We, the air film failure occurs much earlier in time at the first inflection point of the air film shape away from the drop center, where the liquid-liquid van der Waals interactions become important. The predictable failure modes of the air film upon drop impact sheds light on droplet deposition in applications such as lubricant-infused self-cleaning surfaces. Support for this work was provided by the National Science Foundation under Grant No. CMMI-1401438 to Y.S.

  14. Analysis of electrolyte abnormalities and the mechanisms leading to arrhythmias in heart failure. A literature review.

    Science.gov (United States)

    Urso, C; Canino, B; Brucculeri, S; Firenze, A; Caimi, G

    2016-01-01

    About 50% of deaths from heart failure (HF) are sudden, presumably referable to arrhythmias. Electrolyte and acid-base abnormalities are a frequent and potentially dangerous complication in HF patients. Their incidence is almost always correlated with the severity of cardiac dysfunction; furthermore leading to arrhythmias, these imbalances are associated with a poor prognosis. The frequency of ventricular ectopic beats and sudden cardiac death correlate with both plasma and whole body levels of potassium, especially in alkalemia. The early recognition of these alterations and the knowledge of the pathophysiological mechanisms are useful for the management of these HF patients.

  15. User-defined Material Model for Thermo-mechanical Progressive Failure Analysis

    Science.gov (United States)

    Knight, Norman F., Jr.

    2008-01-01

    Previously a user-defined material model for orthotropic bimodulus materials was developed for linear and nonlinear stress analysis of composite structures using either shell or solid finite elements within a nonlinear finite element analysis tool. Extensions of this user-defined material model to thermo-mechanical progressive failure analysis are described, and the required input data are documented. The extensions include providing for temperature-dependent material properties, archival of the elastic strains, and a thermal strain calculation for materials exhibiting a stress-free temperature.

  16. Analysis of the failure mechanism for a stable organic photovoltaic during 10 000 h of testing

    DEFF Research Database (Denmark)

    Krebs, Frederik C; Norrman, Kion

    2007-01-01

    The degradation and failure mechanisms of a stable photovoltaic device comprising a bilayer heterojunction formed between poly(3-carboxythiophene-2,5-diyl-co-thiophene-2,5-diyl) (P3CT) and Buckminsterfullerene (C-60) sandwiched between indium tin oxide (ITO) and aluminium (Al) electrodes were...... of the device under accelerated testing conditions. The cell was subjected to continuous illumination with an incident light intensity of 1000 W m(-2) (AM1.5) at 72 +/- 2 degrees C under a vacuum of...

  17. Body habitus in heart failure: understanding the mechanisms and clinical significance of the obesity paradox.

    Science.gov (United States)

    Parto, Parham; Lavie, Carl J; Arena, Ross; Bond, Samantha; Popovic, Dejana; Ventura, Hector O

    2016-11-01

    The prevalence of obesity among adults and children worldwide has reached epic proportions and has become a major independent risk factor for the development of heart failure (HF), in addition to a contributor of hypertension and cardiovascular disease. The implications of obesity in the development of HF involve adverse effects on cardiac structure and function. Despite all of this, in the setting of chronic HF, excess body mass is associated with improved clinical outcomes, demonstrating the presence of an obesity paradox. In this review, we will discuss the gender differences, global application, potential mechanisms and role of interventions based on fitness and purposeful weight loss as potential therapeutic strategies.

  18. A unified phase-field theory for the mechanics of damage and quasi-brittle failure

    Science.gov (United States)

    Wu, Jian-Ying

    2017-06-01

    Being one of the most promising candidates for the modeling of localized failure in solids, so far the phase-field method has been applied only to brittle fracture with very few exceptions. In this work, a unified phase-field theory for the mechanics of damage and quasi-brittle failure is proposed within the framework of thermodynamics. Specifically, the crack phase-field and its gradient are introduced to regularize the sharp crack topology in a purely geometric context. The energy dissipation functional due to crack evolution and the stored energy functional of the bulk are characterized by a crack geometric function of polynomial type and an energetic degradation function of rational type, respectively. Standard arguments of thermodynamics then yield the macroscopic balance equation coupled with an extra evolution law of gradient type for the crack phase-field, governed by the aforesaid constitutive functions. The classical phase-field models for brittle fracture are recovered as particular examples. More importantly, the constitutive functions optimal for quasi-brittle failure are determined such that the proposed phase-field theory converges to a cohesive zone model for a vanishing length scale. Those general softening laws frequently adopted for quasi-brittle failure, e.g., linear, exponential, hyperbolic and Cornelissen et al. (1986) ones, etc., can be reproduced or fit with high precision. Except for the internal length scale, all the other model parameters can be determined from standard material properties (i.e., Young's modulus, failure strength, fracture energy and the target softening law). Some representative numerical examples are presented for the validation. It is found that both the internal length scale and the mesh size have little influences on the overall global responses, so long as the former can be well resolved by sufficiently fine mesh. In particular, for the benchmark tests of concrete the numerical results of load versus displacement

  19. Mechanical behavior and failure mechanism of pre-cracked specimen under uniaxial compression

    Science.gov (United States)

    Liu, Ting; Lin, Baiquan; Yang, Wei

    2017-08-01

    As a desirable permeability enhancement method, hydraulic slotting has been widely used for enhanced coal bed methane (ECBM) recovery in China. Aiming at the problem that the action mechanism of the slot on the mechanical properties of the slotted coal is still unclear, this paper investigates the effects of flaw inclination on the strength, deformation and cracking process of the pre-cracked specimens. The result shows that the stress-strain curves can be divided into three categories based on the stress behaviors, dropping step by step or dropping sharply, after the peak. With an increase of the flaw inclination, the strength and elastic modulus of the pre-cracked specimen increases gradually, which is verified by the numerical simulation and theoretical results. Analysis of the cracking processes indicates that the initiation position of the first crack in specimens with various flaw inclinations is different, which is caused by the various distributions of tensile and compressive stress concentration zones. The distribution of the stress field controls the cracking process which will in turn affect the stress field distribution. With the propagation of the cracks, the tensile stress concentration zones expand and the concentration degree lowers gradually, while the compressive stress concentration zones show the opposite variation trend. Based on the above results, an optimized slot arrangement method has been proposed for the field application of hydraulic slotting.

  20. A 3D Analysis of Rock Block Deformation and Failure Mechanics Using Terrestrial Laser Scanning

    Science.gov (United States)

    Rowe, Emily; Hutchinson, D. Jean; Kromer, Ryan A.; Edwards, Tom

    2017-04-01

    planes on the slope that were confining the block. It is concluded that rock blocks in White Canyon may be classified as one of five main failure mechanisms based on their pre-failure deformation and structure: planar slide, topple, rotation, wedge, and overhang, with overhang failures representing a large portion of rockfalls in this area. Overhang rockfalls in the White Canyon are characterized by blocks that (a) are not supported by an underlying discontinuity plane, and (b) generally do not exhibit pre-failure deformation. Though overhanging rock blocks are a structural subset of toppling failure, their behavior suggests a different mechanism of detachment. Future work will further populate the present database of rockfalls in White Canyon and will expand the study to include other sites along this corridor. The ultimate goal of this research is to establish warning thresholds based on deformation magnitudes for rockfalls in White Canyon to assist Canadian railways in better understanding and managing these slopes.

  1. Genetic deletion of myostatin from the heart prevents skeletal muscle atrophy in heart failure.

    Science.gov (United States)

    Heineke, Joerg; Auger-Messier, Mannix; Xu, Jian; Sargent, Michelle; York, Allen; Welle, Stephen; Molkentin, Jeffery D

    2010-01-26

    Cardiac cachexia is characterized by an exaggerated loss of skeletal muscle, weakness, and exercise intolerance, although the cause of these effects remains unknown. Here, we hypothesized that the heart functions as an endocrine organ in promoting systemic cachexia by secreting peptide factors such as myostatin. Myostatin is a cytokine of the transforming growth factor-beta superfamily that is known to control muscle wasting. We used a Cre/loxP system to ablate myostatin (Mstn gene) expression in a cell type-specific manner. As expected, elimination of Mstn selectively in skeletal muscle with a myosin light chain 1f (MLC1f)-cre allele induced robust hypertrophy in all skeletal muscle. However, heart-specific deletion of Mstn with an Nkx2.5-cre allele did not alter baseline heart size or secondarily affect skeletal muscle size, but the characteristic wasting and atrophy of skeletal muscle that typify heart failure were not observed in these heart-specific null mice, indicating that myocardial myostatin expression controls muscle atrophy in heart failure. Indeed, myostatin levels in the plasma were significantly increased in wild-type mice subjected to pressure overload-induced cardiac hypertrophy but not in Mstn heart-specific deleted mice. Moreover, cardiac-specific overexpression of myostatin, which increased circulating levels of myostatin by 3- to 4-fold, caused a reduction in weight of the quadriceps, gastrocnemius, soleus, and even the heart itself. Finally, to investigate myostatin as a potential therapeutic target for the treatment of muscle wasting in heart failure, we infused a myostatin blocking antibody (JA-16), which promoted greater maintenance of muscle mass in heart failure. Myostatin released from cardiomyocytes induces skeletal muscle wasting in heart failure. Targeted inhibition of myostatin in cardiac cachexia might be a therapeutic option in the future.

  2. A damage mechanics approach for quantifying stress changes due to brittle failure of porous rocks

    Science.gov (United States)

    Jacquey, Antoine B.; Cacace, Mauro; Blöcher, Guido; Milsch, Harald; Scheck-Wenderoth, Magdalena

    2016-04-01

    Natural fault zones or man-made injection or production of fluid impact the regional stress distribution in Earth's crust and can be responsible for localized stress discontinuities. Understanding the processes controlling fracturing of the porous rocks and mechanical behaviour of fault zones is therefore of interest for several applications including geothermal energy production. In this contribution, we will present a thermodynamically consistent visco-poroelastic damage model which can deal with the multi-scale and multi-physics nature of the physical processes controlling the deformation of porous rocks during and after brittle failure. Deformation of a porous medium is crucially influenced by the changes in the effective stress. Considering a strain-formulated yield cap and the compaction-dilation transition, three different regimes can be identified: quasi-elastic deformation, cataclastic compaction with microcracking (damage accumulation) and macroscopic brittle failure with dilation. The governing equations for deformation, damage accumulation/healing and fluid flow have been implemented in a fully-coupled finite-element-method based framework (MOOSE). The MOOSE framework provides a powerful and flexible platform to solve multiphysics problems implicitly and in a tightly coupled manner on unstructured meshes which is of interest for such non-linear context. To illustrate the model, simulation of a compaction experiment of a sandstone leading to shear failure will be presented which allows to quantify the stress drop accompanying the failure. Finally, we will demonstrate that this approach can also be used at the field scale to simulate hydraulic fracturing and assess the resulting changes in the stress field.

  3. Failure mechanisms in cobalt welded with a silver–copper filler

    Energy Technology Data Exchange (ETDEWEB)

    Criss, Everett M., E-mail: ecriss@ucsd.edu [Department of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla (United States); Smith, Richard J. [Electrical Systems and Optics Research Division, Faculty of Engineering, University of Nottingham, Nottingham, Nottinghamshire (United Kingdom); Meyers, Marc A. [Department of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla (United States); Materials Science and Engineering Program, University of California, San Diego, La Jolla (United States); Department of Nanoengineering, University of California, San Diego, La Jolla (United States)

    2015-10-01

    Cobalt silver–copper (Co–AgCu) weldments approximate the stresses and failure mechanisms of beryllium aluminum–silicon (Be–AlSi) welds, which have strategic importance but are hazardous to study. Failure tests of these surrogate Co–AgCu welds, examined in tension and four-point bending, show that residual stresses and post-welding heat treatment have little or no effect on strength, whereas weld quality and geometry are extremely important. Scanning electron microscopy images reveal abundant defects in poor welds, which usually fail through propagation of preexisting cracks. Fracture surfaces show a variety of morphologies, ranging from dimples in the AgCu filler, to cleavage steps in the CoCu peritectic, and suspected intergranular fracture in the cobalt base. Spatially resolved acoustic spectroscopy reveals significant changes in microstructure near the base–filler interface, whereas wavelength dispersive analysis shows high Cu concentrations in this area.. Contrary to finite element predictions, these welds were found to be stronger during face bending than root bending, likely resulting from the increased number of cracks and imperfections in the Co base. These computations correctly predict that weld strength depends on geometry and that welds fail either in the cobalt base, or along the base–filler interface. Crack compliance measurements show that the largest residual stresses are located along this interface. However, these stresses are unlikely to influence failure due to their direction, whereas stresses in the weld root are too small to have observable effects on failure. The strength of Co–AgCu welds depends strongly on geometry, penetration, and weld quality, but little on residual stresses, and this conclusion is tentatively extended to Be–AlSi welds.

  4. Dynamical mechanism of antifreeze proteins to prevent ice growth

    CERN Document Server

    Kutschan, B; Thoms, S

    2014-01-01

    The fascinating ability of algae, insects and fishes to survive at temperatures below normal freezing is realized by antifreeze proteins (AFPs). Antifreeze proteins (AFPs) are surface-active molecules and interact with the diffusive water/ice interface preventing a complete solidification. A new dynamical mechanism is proposed how these proteins inhibit the freezing of water. We apply a Ginzburg-Landau type approach to describe the phase separation in the two-component system (ice, AFP). The free energy density involves two fields: one for the ice phase with low AFP concentration, and one for the liquid water with high AFP concentration. The time evolution of the ice reveals microstructures as a result of phase separation in the presence of AFPs. We observe a faster clustering of pre-ice structure connected with a locking of grain size by the action of AFP which is an essentially dynamical process. The adsorption of additional water molecules are inhibited and the further growth of ice grains are stopped. The...

  5. Mechanical Consequences of Molecular Composition on Failure in Polyolefin Composites Containing Glassy, Elastomeric, and Semicrystalline Components

    Energy Technology Data Exchange (ETDEWEB)

    Mahanthappa, Mahesh K.; Hillmyer, Marc A.; Bates, Frank S. (UMM)

    2008-10-24

    In order to gain insights into the mechanisms of deformation and ultimate failure in a homologous series of lamellae-forming polyolefin block copolymers comprised of glassy poly(cyclohexylethylene) (C), elastomeric poly(ethylene-alt-propylene) (P), and semicrystalline poly(ethylene) (E), the anisotropic tensile properties of samples in which the microphase separate structure is oriented on a macroscopic length scale were probed. Reciprocating shear processing of monodisperse CPCPC and CPEPC-{xi} polymers having mass fraction w{sub c} 0.39--0.44 and 0 {<=} {xi} {<=} 1, where {xi} = w{sub E}/(w{sub E} + w{sub P}), produces 'single-grain' polymer samples with perpendicular-oriented lamellae. Tensile deformation studies in which the strain axis coincides with the lamellar normal direction yield varied mechanical responses ranging from brittle fracture for CEC ({xi} = 0) to ductile behavior for CPEPC ({xi} > 0) and CPCPC. Tandem small- and wide-angle X-ray scattering analysis of samples undergoing deformation shows that application of strain along the lamellar normal in the CPEPC materials results in formation of a folded lamellar structure or 'chevron' morpohology within which the E crystals cant relative to the strain direction. Since the ultimate failure mechanism for materials strained in this direction is chain pullout in the glassy domains, a simple mechanical model applied to the data enables quantitation of the stress required for chain pullout at {approx}4 MPa. Additionally, the mechanical properties of miscible blends of CEC and CPC polymers with matched segregation strengths are shown to mimic those of the covalently linked CPEPC pentablock copolymer.

  6. Preventing school failure, drug use, and delinquency among low-income children: long-term intervention in elementary schools.

    Science.gov (United States)

    O'Donnell, J; Hawkins, J D; Catalano, R F; Abbott, R D; Day, L E

    1995-01-01

    A six-year, school-based prevention program, which modified classroom teacher practices, offered parent training, and provided child social skills training, was evaluated for its effects on school failure, drug abuse, and delinquency among low-income urban children. Compared to a low-income control group, children in the intervention group showed enhanced school commitment and class participation. The girls in the group also evidenced lower rates of substance use initiation, while the boys exhibited increased social and school work skills.

  7. Sensitivity of stresses and failure mechanisms in SOFCs to the mechanical properties and geometry of the constitutive layers

    Energy Technology Data Exchange (ETDEWEB)

    Nakajo, A.; Van herle, J.; Favrat, D. [Laboratoire d' Energetique Industrielle (LENI), Institut de Genie Mecanique, Ecole Polytechnique Federale de Lausanne, 1015 Lausanne (Switzerland)

    2011-08-15

    A model based on the Euler-Bernoulli theory is used to assess the sensitivity of residual stresses in solid oxide fuel cells to the mechanical properties and geometry of the constituents. It considers different cell configurations, characterised by the presence or not of a compensating layer, and a cathode based on either lanthanum strontium manganite (LSM) or lanthanum strontium cobaltite ferrite (LSCF). The implementation of creep in the model provides insights into the parameters that affect the zero-stress temperature and behaviour during ageing. The amount of irreversible deformation generated in the cell layers after the sintering step depends on the mechanical properties of the layers, type of cell and to some extent, cooling rate. X-ray diffraction measurements from literature are used to verify the prediction. Depending on the mechanical properties, the stress state in the LSM cathode changes from tensile to compressive with respect to temperature. During combined ageing and thermal cycling, tensile stress might arise in the compatibility layer of LSCF-based cells, due to the relief of the initial compressive stress at operating temperature. The Weibull analysis provides the assessment of mechanical failure. A simplified approach is used for buckling-driven delamination, but the propagation of cracks is predicted for unlikely large pre-existing defects. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. Sequential non-invasive mechanical ventilation following short-term invasive mechanical ventilation in COPD induced hypercapnic respiratory failure

    Institute of Scientific and Technical Information of China (English)

    王辰; 商鸣宇; 黄克武; 童朝晖; 孔维民; 姜超美; 代华平; 张洪玉; 翁心植

    2003-01-01

    Objective To estimate the feasibility and the efficacy of early extubation and sequential non-invasive mechanical ventilation (MV) in chronic obstructive pulmonary disease (COPD) with exacerbated hypercapnic respiratory failure.Methods Twenty-two intubated COPD patients with severe hypercapnic respiratory failure due to pulmonary infection (pneumonia or purulent bronchitis) were involved in the study. At the time of pulmonary infection control window (PIC window) appeared, when pulmonary infection had been significantly controlled (resolution of fever and decrease in purulent sputum, radiographic infiltrations, and leukocytosis) after the antibiotic and the comprehensive therapy, the early extubation was conducted and followed by non-invasive MV via facial mask immediately in 11 cases (study group). Other 11 COPD cases with similar clinical characteristics who continuously received invasive MV after PIC window were recruited as control group.Results All patients had similar clinical characteristics and gas exchange before treatment, as well as the initiating time and all indices at the time of the PIC window. For study group and control group, the duration of invasive MV was (7.1±2.9) vs (23.0±14.0) days, respectively, P<0.01. The total duration of ventilatory support was (13±7) vs (23±14) days, respectively, P<0.05. The incidence of ventilator associated pneumonia (VAP) were 0/11 vs 6/11, respectively, P<0.01. The duration of intensive care unit (ICU) stay was (13±7) vs (26±14) days, respectively, P<0.05. Conclusions In COPD patients requiring intubation and MV for pulmonary infection and hypercapnic respiratory failure, early extubation followed by non-invasive MV initiated at the point of PIC window significantly decreases the invasive and total durations of ventilatory support, the risk of VAP, and the duration of ICU stay.

  9. Success, Failure, and Unfinished Business of Education, Prevention, Policy, and Intervention Programs on Substance Misuse in Brazilian Sport.

    Science.gov (United States)

    Santos, Azenildo M

    2015-01-01

    The current Brazilian situation is such that it is difficult to obtain a worldwide evaluation of failure in education, intervention, or prevention programs. How fragile Brazil's anti-doping system is, its appropriateness as well as its relevance, with needed policy infrastructures for achieving the selected goals, and how wide the gap is between education and prevention program effectiveness between high-performance athletes and recreational practitioners who just want to look good. An additional concern, and ever present flaw regarding Brazil's "common sportsman" in day-to-day society is their not receiving known and necessary "sports education," enabling the development of an "at-risk" population for self-harm. Reflections on public health policy are noted.

  10. Reducing risk of Anthracycline-related heart failure after childhood cancer | Division of Cancer Prevention

    Science.gov (United States)

    DESCRIPTION (provided by applicant): Childhood cancer survivors are at a 15-fold risk of developing heart failure (HF) compared to age-matched controls. There is a strong dose-dependent association between anthracyclines and risk of HF;the incidence approaches 20% at cumulative doses between 300-600 mg/m2, and exceeds 30% for doses >600 mg/m2. Outcome following HF is poor;5-year survival rate is |

  11. Reliability analysis of supporting pressure in tunnels based on three-dimensional failure mechanism

    Institute of Scientific and Technical Information of China (English)

    罗卫华; 李闻韬

    2016-01-01

    Based on nonlinear failure criterion, a three-dimensional failure mechanism of the possible collapse of deep tunnel is presented with limit analysis theory. Support pressure is taken into consideration in the virtual work equation performed under the upper bound theorem. It is necessary to point out that the properties of surrounding rock mass plays a vital role in the shape of collapsing rock mass. The first order reliability method and Monte Carlo simulation method are then employed to analyze the stability of presented mechanism. Different rock parameters are considered random variables to value the corresponding reliability index with an increasing applied support pressure. The reliability indexes calculated by two methods are in good agreement. Sensitivity analysis was performed and the influence of coefficient variation of rock parameters was discussed. It is shown that the tensile strength plays a much more important role in reliability index than dimensionless parameter, and that small changes occurring in the coefficient of variation would make great influence of reliability index. Thus, significant attention should be paid to the properties of surrounding rock mass and the applied support pressure to maintain the stability of tunnel can be determined for a given reliability index.

  12. Reasons of PEG failure to eliminate gastroesophageal reflux in mechanically ventilated patients

    Institute of Scientific and Technical Information of China (English)

    Emmanuel E Douzinas; Ilias Andrianakis; Olga Livaditi; Dimitrios Bakos; Katerina Flevari; Nikos Goutas; Dimitrios Vlachodimitropoulos; Marios-Konstantinos Tasoulis; Alex P Betrosian

    2009-01-01

    AIM: To investigate factors predicting failure of percutaneous endoscopic gastrostomy (PEG) to eliminate gastroesophageal reflux (GER).METHODS: Twenty-nine consecutive mechanically ventilated patients were investigated.Patients were evaluated for GER by pH-metry pre-PEG and on the 7th post-PEG day.Endoscopic and histologic evidence of reflux esophagitis was also carried out.A beneficial response to PEG was considered when pH-metry on the 7th post-PEG day showed that GER was below 4%.RESULTS: Seventeen patients responded (RESP group) and 12 did not respond (N-RESP) to PEG.The mean age, sex, weight and APACHE Ⅱ score were similar in both groups.GER (%) values were similar in both groups at baseline, but were significantly reduced in the RESP group compared with the N-RESP group on the 7th post-PEG day [2.5 (0.6-3.8) vs 8.1 (7.4-9.2, P < 0.001)].Reflux esophagitis and the gastroesophageal flap valve (GEFV) grading differed significantly between the two groups ( P = 0.031 and P = 0.020, respectively).Histology revealed no significant differences between the two groups.CONCLUSION: Endoscopic grading of GEFV and the presence of severe reflux esophagitis are predisposing factors for failure of PEG to reduce GER in mechanically ventilated patients.

  13. Failure Mechanism for Fast-Charged Lithium Metal Batteries with Liquid Electrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Lv, DP; Shao, YY; Lozano, T; Bennett, WD; Graff, GL; Polzin, B; Zhang, JG; Engelhard, MH; Saenz, NT; Henderson, WA; Bhattacharya, P; Liu, J; Xiao, J

    2014-09-11

    In recent years, the Li metal anode has regained a position of paramount research interest because of the necessity for employing Li metal in next-generation battery technologies such as Li-S and Li-O-2. Severely limiting this utilization, however, are the rapid capacity degradation and safety issues associated with rechargeable Li metal anodes. A fundamental understanding of the failure mechanism of Li metal at high charge rates has remained elusive due to the complicated interfacial chemistry that occurs between Li metal and liquid electrolytes. Here, it is demonstrated that at high current density the quick formation of a highly resistive solid electrolyte interphase (SEI) entangled with Li metal, which grows towards the bulk Li, dramatically increases up the cell impedance and this is the actual origin of the onset of cell degradation and failure. This is instead of dendritic or mossy Li growing outwards from the metal surface towards/through the separator and/or the consumption of the Li and electrolyte through side reactions. Interphase, in this context, refers to a substantive layer rather than a thin interfacial layer. Discerning the mechanisms and consequences for this interphase formation is crucial for resolving the stability and safety issues associated with Li metal anodes.

  14. Heart Transplant and Mechanical Circulatory Support in Patients With Advanced Heart Failure.

    Science.gov (United States)

    Sánchez-Enrique, Cristina; Jorde, Ulrich P; González-Costello, José

    2017-05-01

    Patients with advanced heart failure have a poor prognosis and heart transplant is still the best treatment option. However, the scarcity of donors, long waiting times, and an increasing number of unstable patients have favored the development of mechanical circulatory support. This review summarizes the indications for heart transplant, candidate evaluation, current immunosuppression strategies, the evaluation and treatment of rejection, infectious prophylaxis, and short and long-term outcomes. Regarding mechanical circulatory support, we distinguish between short- and long-term support and the distinct strategies that can be used: bridge to decision, recovery, candidacy, transplant, and destination therapy. We then discuss indications, risk assessment, management of complications, especially with long-term support, and outcomes. Finally, we discuss future challenges and how the widespread use of long-term support for patients with advanced heart failure will only be viable if their complications and costs are reduced. Copyright © 2017 Sociedad Española de Cardiología. Published by Elsevier España, S.L.U. All rights reserved.

  15. Development, Testing, and Failure Mechanisms of a Replicative Ice Phase Change Material Heat Exchanger

    Science.gov (United States)

    Leimkuehler, Thomas O.; Hansen, Scott; Stephan, Ryan A.

    2010-01-01

    Phase change materials (PCM) may be useful for thermal control systems that involve cyclical heat loads or cyclical thermal environments such as Low Earth Orbit (LEO) and Low Lunar Orbit (LLO). Thermal energy can be stored in the PCM during peak heat loads or in adverse thermal environments. The stored thermal energy can then be released later during minimum heat loads or in more favorable thermal environments. One advantage that PCM's have over evaporators in this scenario is that they do not use a consumable. Wax PCM units have been baselined for the Orion thermal control system and also provide risk mitigation for the Altair Lander. However, the use of water as a PCM has the potential for significant mass reduction since the latent heat of formation of water is approximately 70% greater than that of wax. One of the potential drawbacks of using ice as a PCM is its potential to rupture its container as water expands upon freezing. In order to develop a space qualified ice PCM heat exchanger, failure mechanisms must first be understood. Therefore, a methodical experimental investigation has been undertaken to demonstrate and document specific failure mechanisms due to ice expansion in the PCM. An ice PCM heat exchanger that replicates the thermal energy storage capacity of an existing wax PCM unit was fabricated and tested. Additionally, methods for controlling void location in order to reduce the risk of damage due to ice expansion are investigated. This paper presents the results to date of this investigation. Nomenclature

  16. Testing and Failure Mechanisms of Ice Phase Change Material Heat Exchangers

    Science.gov (United States)

    Leimkuehler, Thomas O.; Stephan, Ryan A.; Hawkins-Reynolds, Ebony

    2011-01-01

    Phase change materials (PCM) may be useful for thermal control systems that involve cyclical heat loads or cyclical thermal environments such as specific spacecraft orientations in Low Earth Orbit (LEO) and low beta angle Low Lunar Orbit (LLO). Thermal energy can be stored in the PCM during peak heat loads or in adverse thermal environments. The stored thermal energy can then be released later during minimum heat loads or in more favorable thermal environments. One advantage that PCM s have over evaporators in this scenario is that they do not use a consumable. The use of water as a PCM rather than the more traditional paraffin wax has the potential for significant mass reduction since the latent heat of formation of water is approximately 70% greater than that of wax. One of the potential drawbacks of using ice as a PCM is its potential to rupture its container as water expands upon freezing. In order to develop a space qualified ice PCM heat exchanger, failure mechanisms must first be understood. Therefore, a methodical experimental investigation has been undertaken to demonstrate and document specific failure mechanisms due to ice expansion in the PCM. A number of ice PCM heat exchangers were fabricated and tested. Additionally, methods for controlling void location in order to reduce the risk of damage due to ice expansion were investigated. This paper presents the results of testing that occurred from March through September of 2010 and builds on testing that occurred during the previous year.

  17. Heart failure with normal ejection fraction: consideration of mechanisms other than diastolic dysfunction.

    Science.gov (United States)

    Bench, Travis; Burkhoff, Daniel; O'Connell, John B; Costanzo, Maria Rosa; Abraham, William T; St John Sutton, Martin; Maurer, Mathew S

    2009-03-01

    More than half of patients with heart failure (HF) have a normal ejection fraction (EF). These patients are typically elderly, are predominantly female, and have a high incidence of multiple comorbid conditions associated with development of ventricular hypertrophy and/or interstitial fibrosis. Thus, the cause of HF has been attributed to diastolic dysfunction. However, the same comorbidities may also impact myocardial systolic, ventricular, vascular, renal, and extracardiovascular properties in ways that can also contribute to symptoms of HF by way of mechanisms not related to diastolic dysfunction. Accordingly, the descriptive term HF with normal EF has been suggested as an alternative to the mechanistic term diastolic HF. In this article, we review the current understanding of nondiastolic mechanisms that may contribute to the HF with normal EF syndrome to highlight potential pathways for research that may lead to new targets for therapy.

  18. Failure of EB-PVD Thermal Barrier Coatings Subjected to Thermo-Mechanical Loading

    Institute of Scientific and Technical Information of China (English)

    CHEN Chen; ZHANG Chun-xia; GUO Hong-bo; GONG Sheng-kai; ZHANG Yue

    2006-01-01

    Thermal barrier coatings (TBCs) were developed to protect metallic blades and vanes working in turbo-engines. The two-layered structure TBCs, consisting of NiCoCrAlY bond coat and yttria stabilized zirconia (YSZ), were deposited on a cylinder of superalloy substrate by the electron beam-physical vapor deposition (EB-PVD). The failure mechanism of the TBCs was investigated with a thermo-mechanical fatigue testing system under the service condition similar to that for turbine blades. Non-destructive evaluation of the coated specimens was conducted through the impedance spectroscopy. It is found that the crack initiation mainly takes place on the top coat at the edge of the heated zones.

  19. Are calcium oxalate crystals involved in the mechanism of acute renal failure in ethylene glycol poisoning?

    Science.gov (United States)

    McMartin, Kenneth

    2009-11-01

    Ethylene glycol (EG) poisoning often results in acute renal failure, particularly if treatment with fomepizole or ethanol is delayed because of late presentation or diagnosis. The mechanism has not been established but is thought to result from the production of a toxic metabolite. A literature review utilizing PubMed identified papers dealing with renal toxicity and EG or oxalate. The list of papers was culled to those relevant to the mechanism and treatment of the renal toxicity associated with either compound. ROLE OF METABOLITES: Although the "aldehyde" metabolites of EG, glycolaldehyde, and glyoxalate, have been suggested as the metabolites responsible, recent studies have shown definitively that the accumulation of calcium oxalate monohydrate (COM) crystals in kidney tissue produces renal tubular necrosis that leads to kidney failure. In vivo studies in EG-dosed rats have correlated the severity of renal damage with the total accumulation of COM crystals in kidney tissue. Studies in cultured kidney cells, including human proximal tubule (HPT) cells, have demonstrated that only COM crystals, not the oxalate ion, glycolaldehyde, or glyoxylate, produce a necrotic cell death at toxicologically relevant concentrations. COM CRYSTAL ACCUMULATION: In EG poisoning, COM crystals accumulate to high concentrations in the kidney through a process involving adherence to tubular cell membranes, followed by internalization of the crystals. MECHANISM OF TOXICITY: COM crystals have been shown to alter membrane structure and function, to increase reactive oxygen species and to produce mitochondrial dysfunction. These processes are likely to be involved in the mechanism of cell death. Accumulation of COM crystals in the kidney is responsible for producing the renal toxicity associated with EG poisoning. The development of a pharmacological approach to reduce COM crystal adherence to tubular cells and its cellular interactions would be valuable as this would decrease the renal

  20. A novel intrinsic analgesic mechanism: the enhancement of the conduction failure along polymodal nociceptive C-fibers.

    Science.gov (United States)

    Wang, Xiuchao; Wang, Shan; Wang, Wenting; Duan, Jianhong; Zhang, Ming; Lv, Xiaohua; Niu, Chunxiao; Tan, Chao; Wu, Yuanbin; Yang, Jing; Hu, Sanjue; Xing, Junling

    2016-10-01

    Although conduction failure has been observed in nociceptive C-fibers, little is known regarding its significance or therapeutic potential. In a previous study, we demonstrated that C-fiber conduction failure, which is regarded as an intrinsic self-inhibition mechanism, was reduced in circumstances of painful diabetic neuropathy. In this study, we extend this finding in the complete Freund's adjuvant model of inflammatory pain and validate that the degree of conduction failure decreased and led to a greater amount of pain signals conveyed to the central nervous system. In complete Freund's adjuvant-injected animals, conduction failure occurred in a C-fiber-selective, activity-dependent manner and was associated with an increase in the rising slope of the C-fiber after-hyperpolarization potential. To target conduction failure in a therapeutic modality, we used ZD7288, an antagonist of hyperpolarization-activated, cyclic nucleotide-modulated channels which are activated by hyperpolarization and play a pivotal role in both inflammatory and neuropathic pain. ZD7288 promoted conduction failure by suppressing Ih as a mechanism to reduce the rising slope of the after-hyperpolarization potential. Moreover, perineuronal injection of ZD7288 inhibited abnormal mechanical allodynia and thermal hyperalgesia without affecting motor function or heart rate. Our data highlight the analgesic potential of local ZD7288 application and identify conduction failure as a novel target for analgesic therapeutic development.

  1. How can health literacy influence outcomes in heart failure patients? Mechanisms and interventions.

    Science.gov (United States)

    Westlake, Cheryl; Sethares, Kristen; Davidson, Patricia

    2013-09-01

    Health literacy is discussed in papers from 25 countries where findings suggest that approximately a third up to one half of the people in developed countries have low health literacy. Specifically, health literacy is the mechanism by which individuals obtain and use health information to make health decisions about individual treatments in the home, access care in the community, promote provider-patient interactions, structure self-care, and navigate health care programs both locally and nationally. Further, health literacy is a key determinant of health and a critical dimension for assessing individuals' needs, and, importantly, their capacity for self-care. Poorer health knowledge/status, more medication errors, costs, and higher rates of morbidity, readmissions, emergency room visits, and mortality among patients with health illiteracy have been demonstrated. Individuals at high risk for low health literacy include the elderly, disabled, Blacks, those with a poverty-level income, some or less high school education, either no insurance or Medicare or Medicaid, and those for whom English is a second language. As a consequence, health literacy is a complex, multifaceted, and evolving construct including aspects of social, psychological, cultural and economic circumstances. The purpose of this paper is to describe the mechanisms and consequences of health illiteracy. Specifically, the prevalence, associated demographics, and models of health literacy are described. The mechanism of health illiteracy's influence on outcomes in heart failure is proposed. Tools for health literacy assessment are described and compared. Finally, the health outcomes and general interventions to enhance the health outcomes in heart failure are discussed.

  2. Failure analysis of porcupine quills under axial compression reveals their mechanical response during buckling.

    Science.gov (United States)

    Torres, Fernando G; Troncoso, Omar P; Diaz, John; Arce, Diego

    2014-11-01

    Porcupine quills are natural structures formed by a thin walled conical shell and an inner foam core. Axial compression tests, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FT-IR) were all used to compare the characteristics and mechanical properties of porcupine quills with and without core. The failure mechanisms that occur during buckling were analyzed by scanning electron microscopy (SEM), and it was found that delamination buckling is mostly responsible for the decrease in the measured buckling stress of the quills with regard to predicted theoretical values. Our analysis also confirmed that the foam core works as an energy dissipater improving the mechanical response of an empty cylindrical shell, retarding the onset of buckling as well as producing a step wise decrease in force after buckling, instead of an instantaneous decrease in force typical for specimens without core. Cell collapse and cell densification in the inner foam core were identified as the key mechanisms that allow for energy absorption during buckling.

  3. End-stage heart failure and mechanical circulatory support: feasibility of discharge from hospital.

    Science.gov (United States)

    Oosterom, A; de Jonge, N; Kirkels, J H; Rodermans, B F M; Sukkel, E; Klöpping, C; Ramjankhan, F; Lahpor, J R

    2007-01-01

    BACKGROUND.: Due to the shortage of donor hearts, mechanical circulatory support is increasingly being used as a bridge to transplantation. In order to allow for more widespread use of ventricular assist devices it is mandatory that patients are not continuously hospitalised. We present the results of our experience with patients with end-stage heart failure, discharged from hospital after implantation of a ventricular assist device and followed in an outpatient setting. METHODS.: After an intensive training and education programme, focusing on the management of the percutaneous driveline and instructions on how to handle in case of an alarm or malfunction of the device, patients were discharged. They were followed in the outpatient department. All regular and unplanned visits were registered, including readmissions. RESULTS.: Twenty-seven patients treated with a ventricular assist device were discharged from hospital. There were 37 extra visits, of these, 27 were device related resulting in 21 readmissions (0.78/patient). We treated eight infectious episodes in four patients, all device related. Furthermore seven thromboembolic episodes occurred in four patients. One patient died because of multiorgan failure seven weeks after he was readmitted with an urosepsis. In our experience of 11.4 patient years at home while on the device, only 5% of the time was spent in hospital for complications. In comparison with patients on an assist device who stayed in hospital until transplantation, there were no more complications. CONCLUSION.: This study demonstrates that patients with end-stage heart failure, treated with a ventricular assist device, can be safely discharged from hospital, with an acceptable rate of readmissions. It results in a fair quality of life, with a high degree of independence of the patient. (Neth Heart J 2007;15:45-50.).

  4. Impact of mechanical- and maintenance-induced failures of main reactor coolant pump seals on plant safety

    Energy Technology Data Exchange (ETDEWEB)

    Azarm, M A; Boccio, J L; Mitra, S

    1985-12-01

    This document presents an investigation of the safety impact resulting from mechanical- and maintenance-induced reactor coolant pump (RCP) seal failures in nuclear power plants. A data survey of the pump seal failures for existing nuclear power plants in the US from several available sources was performed. The annual frequency of pump seal failures in a nuclear power plant was estimated based on the concept of hazard rate and dependency evaluation. The conditional probability of various sizes of leak rates given seal failures was then evaluated. The safety impact of RCP seal failures, in terms of contribution to plant core-melt frequency, was also evaluated for three nuclear power plants. For leak rates below the normal makeup capacity and the impact of plant safety were discussed qualitatively, whereas for leak rates beyond the normal make up capacity, formal PRA methodologies were applied. 22 refs., 17 figs., 19 tabs.

  5. High rate of failure of allograft reconstruction of the extensor mechanism after total knee arthroplasty.

    Science.gov (United States)

    Leopold, S S; Greidanus, N; Paprosky, W G; Berger, R A; Rosenberg, A G

    1999-11-01

    Disruption of the extensor mechanism is an uncommon but devastating complication of total knee arthroplasty. Several techniques for reconstruction of the extensor mechanism after total knee arthroplasty have been reported, but we do not know of any study in which the results of one group's method were corroborated by a second group using the same technique. In the present series, we evaluated the results of reconstruction of the extensor mechanism with use of allograft according to the method described by Emerson et al. Seven reconstructions of the extensor mechanism with use of a bone-tendon-bone allograft were performed with the technique of Emerson et al. in six patients. The patients were evaluated before and after the operation. The knee score according to the system of The Hospital for Special Surgery, evidence of an extensor lag, use of walking aids, and the ambulatory status of each patient were recorded. The patients were also asked about, and the medical records were reviewed for, episodes of falling related to weakness of the quadriceps after the reconstruction. The mean duration of follow-up was thirty-nine months (range, six to 115 months). As these reconstructions often fail early, the minimum duration of follow-up was six months. All seven reconstructions were rated as clinical failures on the basis of a persistent or recurrent extensor lag of more than 30 degrees. All but one patient needed an assistive device full time for walking, and four patients (five knees) had at least one documented episode of falling that was due to giving-way of the affected knee. Four of the reconstructions were revised; one revision was performed with use of another extensor mechanism allograft and three were performed with use of a medial gastrocnemius rotation flap. The other three clinical failures had not been revised at the time of writing. At the time of the most recent follow-up (or at the time of revision of the extensor reconstruction), the mean extensor lag was

  6. Failure of fluid-saturated granular materials: a unified approach to capture diffuse and localized instability mechanisms

    Science.gov (United States)

    Mihalache, Constance; Buscarnera, Giuseppe

    2013-04-01

    Granular materials are susceptible to a wide variety of failure and deformation mechanisms, especially because of their interaction with the pore fluids and the surrounding environment. An adequate modeling of their mechanical response is therefore essential for understanding a number of geological processes, such as the onset of rapid landslides, hillslope denudation and sediment transport, or even the mechanics of fault gauges. Depending on the type of material, the groundwater conditions and the surrounding kinematic constraints, both diffuse and localized mechanisms are possible, and these may occur under either drained or undrained conditions. In the geomechanics literature, failure modes are usually explained and modeled with the tools of continuum mechanics, such as the mathematical theory of plasticity. Due to the complexity of granular material behavior, however, most classical models for frictional strength are unable to capture the variety of instability mechanisms observed for such class of geomaterials (e.g., liquefaction, shear banding, etc.). Sophisticated strain-hardening plasticity models are therefore required for numerical modeling purposes, thus making the evaluation of critical failure conditions less straightforward than in perfect plasticity theories. Here we propose a mathematical strategy that can be adapted to any elastoplastic model and allows the onset of failure in elastoplastic geomaterials to be expressed in a more general manner. More specifically, our theory expresses the failure conditions as a function of local kinematics and solid-fluid interactions. The stability criterion used in this study is based on the so-called stability modulus, a scalar index of failure that was formulated by linking the physical concept controllability to the mathematical notion of plastic admissibility upon an incremental loading path [Buscarnera et al, 2011]. In this contribution, different loading constraints are considered, accounting for the

  7. Capacity and failure mechanism of laterally loaded jet-grouting reinforced piles: Field and numerical investigation

    Institute of Scientific and Technical Information of China (English)

    HE Ben; WANG LiZhong; HONG Yi

    2016-01-01

    This study presents the results of field and numerical investigations of lateral stiffness,capacity,and failure mechanisms for plain piles and reinforced concrete piles in soft clay.A plastic-damage model is used to simulate concrete piles and jet-grouting in the numerical analyses.The field study and numerical investigations show that by applying jet-grouting surrounding the upper 7.5D (D =pile diameter) of a pile,lateral stiffness and bearing capacity of the pile are increased by about 110% and 100%,respectively.This is partially because the jet-grouting increases the apparent diameter of the pile,so as to enlarge the extent of failure wedge and hence passive resistance in front of the reinforced pile.Moreover,the jet-grouting provides a circumferential confinement to the concrete pile,which suppresses development of tensile stress in the pile.Correspondingly,tension-induced plastic damage in the concrete pile is reduced,causing less degradation of stiffness and strength of the pile than that of a plain pile.Effectiveness of the circumferential confinement provided by the jet-grouting,however,diminishes once the grouting cracks because of the significant vertical and circumferential tensile stress near its mid-depth.The lateral capacity of the jet-grouting reinforced pile is,therefore,governed by mobilized passive resistance of soil and plastic damage of jet-grouting.

  8. Deformation and Failure Mechanism of Roadway Sensitive to Stress Disturbance and Its Zonal Support Technology

    Directory of Open Access Journals (Sweden)

    Qiangling Yao

    2016-01-01

    Full Text Available The 6163 haulage roadway in the Qidong coal mine passes through a fault zone, which causes severe deformation in the surrounding rock, requiring repeated roadway repairs. Based on geological features in the fault area, we analyze the factors affecting roadway deformation and failure and propose the concept of roadway sensitive to stress disturbance (RSSD. We investigate the deformation and failure mechanism of the surrounding rocks of RSSD using field monitoring, theoretical analysis, and numerical simulation. The deformation of the surrounding rocks involves dilatation of shallow rocks and separation of deep rocks. Horizontal and longitudinal fissures evolve to bed separation and fracture zones; alternatively, fissures can evolve into fracture zones with new fissures extending to deeper rock. The fault affects the stress field of the surrounding rock to ~27 m radius. Its maximum impact is on the vertical stress of the rib rock mass and its minimum impact is on the vertical stress of the floor rock mass. Based on our results, we propose a zonal support system for a roadway passing through a fault. Engineering practice shows that the deformation of the surrounding rocks of the roadway can be effectively controlled to ensure normal and safe production in the mine.

  9. Protective effect of telmisartan on rats with renal failure and its mechanism

    Institute of Scientific and Technical Information of China (English)

    Zhi-Kui Wang; Zhen-Ying Liu; Hai-Bo Yu

    2015-01-01

    Objective:To study the protective effect of telmisartan on rats with renal failure and its mechanism. Methods:60 Wistar rats were chosen as study objective, and were divided into 4 groups randomly:15 in group A (sham operation group), 15 in group B (model group), 15 in group C (telmisartan group) and 15 in group D (telmisartan+GW9962 group). The difference of survival rate, blood-urine biochemical indexes, renal pathological change, and the expression level of PPARγ and nNOS were compared. Results:After 12 weeks, the survival rate of group A was 93.33%(14/15), that of group B was 46.67%(7/15), that of group C was 86.67%(13/15), that of group D was 60.00%(9/15), and the difference among 4 groups had statistical significance (P0.05);after 3 weeks, 6 weeks and 12 weeks, these difference was statistical significant (P<0.05). The difference of blood-urine biochemical indexes, that of renal pathological change, and that of the expression level of PPAR毭and nNOS was statistical significant (P<0.05). Conclusions:Telmisartan has protective effect on renal failure caused by 5/6 nephrectomy, which might be relative to the expression level of PPARγ and nNOS.

  10. Failure mechanism of Mesozoic soft rock roadway in Shajihai coal mine and its surrounding rock control

    Institute of Scientific and Technical Information of China (English)

    Yuan Yue; Zhu Yongjian; Wang Weijun; Yu Weijian

    2014-01-01

    In view of the buckling failure caused by large deformation of Mesozoic soft rock roadway in Shajihai mining area, such as serious roof fall, rib spalling, floor heave, etc., based on the detail site investigation, theoretical analysis, mineral composition test, microstructure test, water-physical property test and field experiments were carried out. And we revealed the compound failure mechanism of Mesozoic soft rock roadway in Shajihai mining area, namely the molecule expansion-shear slip of weak structural plane-construction disturbance. On this basis, the coupling support technology whose core is constant resistance with large deformation bolt was proposed. The feature of this supporting technology is that a new type of structural composite material was used, which makes the supporting system not only has the ideal deformation characteristics, but also has high supporting resistance. Thus the fully release of plastic energy within surrounding rock and reasonable control of the thickness of the plastic ring were realized. Then the differential deformation between the surrounding rock and support was eliminated by the secondary coupling support of bolt–mesh–cable, and the bolt with high strength was applied in the base angle to control floor. Eventually the collaborative bearing system of surrounding rock–support was formed. Through field tests the validity and rationality of support was also verified.

  11. Linking Seismicity at Depth to the Mechanics of a Lava Dome Failure - a Forecasting Approach

    Science.gov (United States)

    Salvage, R. O.; Neuberg, J. W.; Murphy, W.

    2014-12-01

    Soufriere Hills volcano (SHV), Montserrat has been in a state of ongoing unrest since 1995. Prior to eruptions, an increase in the number of seismic events has been observed. We use the Material Failure Law (MFL) (Voight, 1988) to investigate how an accelerating number of low frequency seismic events are related to the timing of a large scale dome collapse in June 1997. We show that although the forecasted timing of a dome collapse may coincide with the known timing, the accuracy of the application of the MFL to the data is poor. Using a cross correlation technique we show how characterising seismicity into similar waveform "families'' allows us to focus on a single process at depth and improve the reliability of our forecast. A number of families are investigated to assess their relative importance. We show that despite the timing of a forecasted dome collapse ranging between several hours of the known timing of collapse, each of the families produces a better forecast in terms of fit to the seismic acceleration data than when using all low frequency seismicity. In addition, we investigate the stability of such families between major dome collapses (1997 and 2003), assessing their potential for use in real-time forecasting. Initial application of Grey's Incidence Analysis suggests that a key parameter influencing the potential for a large scale slumping on the dome of SHV is the rate of low frequency seismicity associated with magma movement and dome growth. We undertook numerical modelling of an andesitic dome with a hydrothermally altered layer down to 800m. The geometry of the dome is based on SHV prior to the collapse of 2003. We show that a critical instability is reached once slope angles exceed 25°, corresponding to a summit height of just over 1100m a.s.l.. The geometry of failure is in close agreement with the identified failure plane suggesting that the input mechanical properties are broadly consistent with reality. We are therefore able to compare

  12. Study on Contact Fatigue Life and Failure Mechanism of Subquenched 42CrMo Steel

    Institute of Scientific and Technical Information of China (English)

    HE Bo-lin; YU Ying-xia; SHAO Er-yu

    2004-01-01

    The effect of undissolved ferrite amount in subcritically quenched 42CrMo steel on contact fatigue properties and failure mechanism were studied. The amount of undissolved ferrite in the steel were 0%,3%,10%,15% and 20% in volume fraction, respectively. The experimental results show that the existence of undissolved ferrite can increase the contact fatigue life The contact fatigue life can be prolonged with increasing the amounts of undissolved ferrite The grain size can be fined by using subcritical quenching process and the area of phase boundaries can also be greatly increased. The stress relaxation and grain refinement due to occurring of plastic deformation are main reasons for improving the fatigue life. The existence of undissolved ferrite can increase the crack initiation period. Under the experiment conditions, when the amount of undissolved ferrite is 10%, the longest contact fatigue life can be the obtained.

  13. The Effect of Rainfall Patterns on the Mechanisms of Shallow Slope Failure

    Directory of Open Access Journals (Sweden)

    Muhammad Suradi

    2014-04-01

    Full Text Available This paper examines how rainfall patterns affect the mechanisms of shallow slope failure. Numerical modelling, utilising the commercial software SVFlux and SVSlope, was carried out for a coupled analysis of rainfall-induced slope seepage and instability, with reference to a shallow landslide took place in Jabiru, Northern Territory (NT Australia in 2007. Rainfall events were varied in terms of pattern in this analysis. The results revealed that slopes are sensitive to rainfall pattern when the rainfall intensity has a high degree of fluctuation at around the same value as that of saturated hydraulic conductivity. Average rainfall intensity at the beginning of a rainfall period plays a primary role in determining the rate of decrease in initial factor of safety (Fi towards minimum factor of safety (Fmin. The effect of rainfall events on the slope instability is attributed to the amount of rainwater infiltration into slope associated with rainfall pattern.

  14. Cognitive mechanisms in chronic tinnitus: Psychological markers of a failure to switch attention

    Directory of Open Access Journals (Sweden)

    Krysta Jannaya Trevis

    2016-08-01

    Full Text Available The cognitive mechanisms underpinning chronic tinnitus (phantom auditory perceptions are underexplored but may reflect a failure to switch attention away from a tinnitus sound. Here, we investigated a range of components that influence the ability to switch attention, including cognitive control, inhibition, working memory and mood, on the presence and severity of chronic tinnitus. Our participants with tinnitus showed significant impairments in cognitive control and inhibition as well as lower levels of emotional wellbeing, compared to healthy-hearing participants. Moreover, the subjective cognitive complaints of tinnitus participants correlated with their emotional wellbeing whereas complaints in healthy participants correlated with objective cognitive functioning. Combined, cognitive control and depressive symptoms correctly classified 67% of participants. These results demonstrate the core role of cognition in chronic tinnitus. They also provide the foundations for a neurocognitive account of the maintenance of tinnitus, involving impaired interactions between the neurocognitive networks underpinning attention-switching and mood.

  15. Acute respiratory failure and mechanical ventilation in pregnant patient: A narrative review of literature

    Directory of Open Access Journals (Sweden)

    Pradeep Kumar Bhatia

    2016-01-01

    Full Text Available Physiological changes of pregnancy imposes higher risk of acute respiratory failure (ARF with even a slight insult and remains an important cause of maternal and fetal morbidity and mortality. Although pregnant women have different respiratory physiology and different causes of ARF, guidelines specific to ventilatory settings, goals of oxygenation and weaning process could not be framed due to lack of large-scale randomized controlled trials. During the 2009 H1N1 pandemic, pregnant women had higher morbidity and mortality compared to nonpregnant women. During this period, alternative strategies of ventilation such as high-frequency oscillatory ventilation, inhalational of nitric oxide, prone positioning, and extra corporeal membrane oxygenation were increasingly used as a desperate measure to rescue pregnant patients with severe hypoxemia who were not improving with conventional mechanical ventilation. This article highlights the causes of ARF and recent advances in invasive, noninvasive and alternative strategies of ventilation used during pregnancy.

  16. Nutritional status in patients with chronic respiratory failure receiving home mechanical ventilation: impact on survival.

    Science.gov (United States)

    Hitzl, Andre P; Jörres, Rudolf A; Heinemann, Frank; Pfeifer, Michael; Budweiser, Stephan

    2010-02-01

    In patients with chronic respiratory diseases body mass index (BMI) is a predictor of long-term survival, whereas the prognostic value of body composition, especially fat-free mass index (FFMI), is unknown. In a prospectively collected cohort of 131 patients (50 females, 81 males; 71% chronic obstructive pulmonary disease, 29% severe restrictive disorders) undergoing home mechanical ventilation (HMV) due to chronic hypercapnic respiratory failure (CHRF), the prognostic value of nutritional composition assessed by bioelectrical impedance analysis was evaluated during a 4-year follow-up and compared to that of BMI, anthropometrics, and functional parameters. After follow-up, 53 patients (40.5%) had died. Regarding all-cause mortality cumulative survival percentages after 1, 2 and 3 years were 89.3, 76.3 and 67.9%, respectively. In univariate analyses, FFMI, BMI, sex, age, leukocyte number, FEV1 and 6-min walking distance were associated with survival (pNutrition and Metabolism. All rights reserved.

  17. Failure mechanism and supporting measures for large deformation of Tertiary deep soft rock

    Institute of Scientific and Technical Information of China (English)

    Guo Zhibiao; Wang Jiong; Zhang Yuelin

    2015-01-01

    The Shenbei mining area in China contains typical soft rock from the Tertiary Period. As mining depths increase, deep soft rock roadways are damaged by large deformations and constantly need to be repaired to meet safety requirements, which is a great security risk. In this study, the characteristics of deformation and failure of typical roadway were analyzed, and the fundamental reason for the roadway deformation was that traditional support methods and materials cannot control the large deformation of deep soft rock. Deep soft rock support technology was developed based on constant resistance energy absorption using constant resistance large deformation bolts. The correlative deformation mechanisms of surrounding rock and bolt were analyzed to understand the principle of constant resistance energy absorption. The new technology works well on-site and provides a new method for the excavation of roadways in Tertiary deep soft rock.

  18. Initiation of vacuum breakdown and failure mechanism of the carbon nanotube during thermal field emission

    Science.gov (United States)

    Dan, Cai; Lie, Liu; Jin-Chuan, Ju; Xue-Long, Zhao; Hong-Yu, Zhou; Xiao, Wang

    2016-04-01

    The carbon nanotube (CNT)-based materials can be used as vacuum device cathodes. Owing to the excellent field emission properties of CNT, it has great potentials in the applications of an explosive field emission cathode. The falling off of CNT from the substrate, which frequently appears in experiments, restricts its application. In addition, the onset time of vacuum breakdown limits the performance of the high-power explosive-emission-cathode-based diode. In this paper, the characteristics of the CNT, electric field strength, contact resistance and the kind of substrate material are varied to study the parameter effects on the onset time of vacuum breakdown and failure mechanism of the CNT by using the finite element method. Project supported by the National Natural Science Foundation of China (Grant Nos. 11305263 and 61401484).

  19. Failure Mechanisms and Life Prediction of Thermal and Environmental Barrier Coatings under Thermal Gradients

    Science.gov (United States)

    Zju, Dongming; Ghosn, Louis J.; Miller, Robert A.

    2008-01-01

    Ceramic thermal and environmental barrier coatings (TEBCs) will play an increasingly important role in gas turbine engines because of their ability to further raise engine temperatures. However, the issue of coating durability is of major concern under high-heat-flux conditions. In particular, the accelerated coating delamination crack growth under the engine high heat-flux conditions is not well understood. In this paper, a laser heat flux technique is used to investigate the coating delamination crack propagation under realistic temperature-stress gradients and thermal cyclic conditions. The coating delamination mechanisms are investigated under various thermal loading conditions, and are correlated with coating dynamic fatigue, sintering and interfacial adhesion test results. A coating life prediction framework may be realized by examining the crack initiation and propagation driving forces for coating failure under high-heat-flux test conditions.

  20. Assessing cell fusion and cytokinesis failure as mechanisms of clone 9 hepatocyte multinucleation in vitro.

    Science.gov (United States)

    Simic, Damir; Euler, Catherine; Thurby, Christina; Peden, Mike; Tannehill-Gregg, Sarah; Bunch, Todd; Sanderson, Thomas; Van Vleet, Terry

    2012-08-01

    In this in vitro model of hepatocyte multinucleation, separate cultures of rat Clone 9 cells are labeled with either red or green cell tracker dyes (Red Cell Tracker CMPTX or Vybrant CFDA SE Cell Tracer), plated together in mixed-color colonies, and treated with positive or negative control agents for 4 days. The fluorescent dyes become cell-impermeant after entering cells and are not transferred to adjacent cells in a population, but are inherited by daughter cells after fusion. The mixed-color cultures are then evaluated microscopically for multinucleation and analysis of the underlying mechanism (cell fusion/cytokinesis). Multinucleated cells containing only one dye have undergone cytokinesis failure, whereas dual-labeled multinucleated cells have resulted from fusion.

  1. Structural analysis of SiC Schottky diodes failure mechanism under current overload

    Science.gov (United States)

    León, J.; Berthou, M.; Perpiñà, X.; Banu, V.; Montserrat, J.; Vellvehi, M.; Godignon, P.; Jordà, X.

    2014-02-01

    1.2 kV-10 A tungsten Schottky diodes (W-SBD) have been aged and tested at limit under current overload (surge current pulses) to determine their structural weakest spots. All devices showed no ageing at 40 A amplitudes and a surge current capability higher than 60 A. Infrared lock-in measurements have located the weakest spots on the surface of failed chips and allowed us to non-invasively infer their origin: Schottky barrier modification by metal contact change. After, a focused ion beam coupled with scanning electron microscope has been used to analyse the physical signature at these locations. These inspections have revealed that the destruction mechanism responsible for their failure was the electromigration and thermomigration of tungsten into aluminum, locally modifying the electrical behaviour of the Schottky barrier (loss of blocking capability).

  2. Durable mechanical circulatory support in advanced heart failure: a critical care cardiology perspective.

    Science.gov (United States)

    Lala, Anuradha; Mehra, Mandeep R

    2013-11-01

    Though cardiac transplantation for advanced heart disease patients remains definitive therapy for patients with advanced heart failure, it is challenged by inadequate donor supply, causing durable mechanical circulatory support (MCS) to slowly become a new primary standard. Selecting appropriate patients for MCS involves meeting a number of prespecifications as is required in evaluation for cardiac transplant candidacy. As technology evolves to bring forth more durable smaller devices, selection criteria for appropriate MCS recipients will likely expand to encompass a broader, less sick population. The "Holy Grail" for MCS will be a focus on clinical recovery and explantation of devices rather than the currently more narrowly defined indications of bridge to transplantation or lifetime device therapy. Copyright © 2013 Elsevier Inc. All rights reserved.

  3. Immunotherapeutics to prevent the replication of Brucella in a treatment failure mouse model.

    Science.gov (United States)

    Jain-Gupta, N; Contreras-Rodriguez, A; Smith, G P; Garg, V K; Witonsky, S G; Isloor, S; Vemulapalli, R; Boyle, S M; Sriranganathan, N

    2014-02-12

    Outer membrane vesicles (OMVs) from Brucella melitensis and irradiated Brucella neotomae have been shown to be effective vaccines against a B. melitensis challenge in a mouse model. The present study evaluates the efficacy of these two vaccines as immuno-therapeutics in combination with conventional antibiotics against a B. melitensis infection. BALB/c mice chronically infected with B. melitensis were treated for 4 weeks with doxycycline and gentamicin and vaccinated twice during the course of therapy. Antibiotics in sub-therapeutic concentrations were chosen in such a way that the treatment would result in a therapeutic failure in mice. Although no additive effect of vaccines and antibiotics was seen on the clearance of B. melitensis, mice receiving vaccines along with antibiotics exhibited no Brucella replication post-treatment compared to mice treated only with antibiotics. Administration of irradiated B. neotomae along with antibiotics led to higher production of IFN-γ ex vivo by splenocytes upon stimulation with heat inactivated B. melitensis while no such effect was seen by splenocytes from mice vaccinated with OMVs. OMV vaccinated mice developed significantly higher anti-Brucella IgG antibody titers at the end of the treatment compared to the mice that received only antibiotics. The mice that received only vaccines did not show any significant clearance of Brucella from spleens and livers compared to non-treated control mice. This study suggests that incorporating OMVs or irradiated B. neotomae along with conventional antibiotics might be able to improve therapeutic efficacy and control the progression of disease in treatment failure cases.

  4. PREDICTION AND PREVENTION OF LIVER FAILURE AFTER MAJOR LIVER PRIMARY AND METASTATIC TUMORS RESECTION

    Directory of Open Access Journals (Sweden)

    A. D. Kaprin

    2016-01-01

    Full Text Available Abstract Purpose of the study. Improvement of results of treatment in patients with primary and metastatic liver cancer by decreasing the risk of post-resection liver failure on the basis of the evaluation of the functional reserves of the liver.Materials and Methods. The study included two independent samples of patients operated about primary or metastatic lesions of the liver at the Department of abdominal Oncology, P. A. Hertsen MORI. The first group included 53 patients who carried out 13C-breath test metallimovie and dynamic scintigraphy of the liver in the preoperative stage in addition to the standard algorithm of examination. Patients of the 2nd group (n=35 had a standard clinical and laboratory examination, the patients were not performed the preoperative evaluation of the functional reserve of the liver, the incidences of total bilirubin, albumin and prothrombin time did not reveal a reduction of liver function. Post-resection liver failure have been established on the basis of the 50/50 criterion in the evaluation on day 5 after surgery.Results. Analysis of operating characteristics of the functional tests showed the absolute methacin breath test sensitivity (SE≥100%, high specificity (SP≥67% of scintigraphy of the liver and the negative predictive value of outcome (VP≥100% at complex use of two diagnostic methods. The incidence of PROPS in the study group was significantly 2 times higher in the control group –15,1% and 26.8%, respectively (p<0.001.Conclusion. The combination of preoperative dynamic scintigraphy of the liver with carrying out 13C-breath methacin test allows you to conduct a comprehensive evaluation of the liver functional reserve and can significantly improve preoperative evaluation and postoperative results of anatomic resection in patients with primary and metastatic liver lesions.

  5. Role of Physiotherapy in Preventing Failure of Primary Anterior Cruciate Ligament Reconstruction

    OpenAIRE

    Yu, Pak-him Vincent; Wun, Yiu-Chung; Yung, Shu-Hang Patrick

    2017-01-01

    Background/Purpose: Anterior cruciate ligament (ACL) reconstruction is routinely performed in sports medicine. We aimed to determine if there is any protective effect of postoperative physiotherapy in preventing graft rupture after primary ACL reconstruction (ACLR). Methods: A retrospective case–control study was carried out, with demographic data, concomitant meniscal injury, and intraoperative fixation methods matched. The number of sessions of physiotherapy attended by the rupture group...

  6. Mechanisms of improvement of respiratory failure in patients with COPD treated with NIV.

    Science.gov (United States)

    Nickol, Annabel H; Hart, Nicholas; Hopkinson, Nicholas S; Hamnegård, Carl-Hugo; Moxham, John; Simonds, Anita; Polkey, Michael I

    2008-01-01

    Noninvasive ventilation (NIV) improves gas-exchange and symptoms in selected chronic obstructive pulmonary disease (COPD) patients with hypercapnic respiratory failure. We hypothesized NIV reverses respiratory failure by one or all of increased ventilatory response to carbon-dioxide, reduced respiratory muscle fatigue, or improved pulmonary mechanics. Nineteen stable COPD patients (forced expiratory volume in one second 35% predicted) were studied at baseline (DO), 5-8 days (D5) and 3 months (3M) after starting NIV. Ventilator use was 6.2 (3.7) hours per night at D5 and 3.4 (1.6) at 3M (p = 0.12). Mean (SD) daytime arterial carbon-dioxide tension (PaCO2) was reduced from 7.4 (1.2) kPa to 7.0 (1.1) kPa at D5 and 6.5 (1.1) kPa at 3M (p = 0.001). Total lung capacity decreased from 107 (28) % predicted to 103 (28) at D5 and 103 (27) % predicted at 3M (p = 0.035). At D5 there was an increase in the hypercapnic ventilatory response and some volitional measures of inspiratory and expiratory muscle strength, but not isolated diaphragmatic strength whether assessed by volitional or nonvolitional methods. These findings suggest decreased gas trapping and increased ventilatory sensitivity to CO2 are the principal mechanism underlying improvements in gas-exchange in patients with COPD following NIV. Changes in some volitional but not nonvolitional muscle strength measures may reflect improved patient effort.

  7. Failure mechanisms of single-crystal silicon electrodes in lithium-ion batteries

    Science.gov (United States)

    Shi, Feifei; Song, Zhichao; Ross, Philip N.; Somorjai, Gabor A.; Ritchie, Robert O.; Komvopoulos, Kyriakos

    2016-06-01

    Long-term durability is a major obstacle limiting the widespread use of lithium-ion batteries in heavy-duty applications and others demanding extended lifetime. As one of the root causes of the degradation of battery performance, the electrode failure mechanisms are still unknown. In this paper, we reveal the fundamental fracture mechanisms of single-crystal silicon electrodes over extended lithiation/delithiation cycles, using electrochemical testing, microstructure characterization, fracture mechanics and finite element analysis. Anisotropic lithium invasion causes crack initiation perpendicular to the electrode surface, followed by growth through the electrode thickness. The low fracture energy of the lithiated/unlithiated silicon interface provides a weak microstructural path for crack deflection, accounting for the crack patterns and delamination observed after repeated cycling. On the basis of this physical understanding, we demonstrate how electrolyte additives can heal electrode cracks and provide strategies to enhance the fracture resistance in future lithium-ion batteries from surface chemical, electrochemical and material science perspectives.

  8. Fatigue degradation and failure of rotating composite structures - Materials characterisation and underlying mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Gamstedt, E.K.; Andersen, S.I.

    2001-03-01

    The present review concerns rotating composite structures, in which fatigue degradation is of key concern for in-service failure. Such applications are for instance rotor blades in wind turbines, helicopter rotor blades, flywheels for energy storage, marine and aeronautical propellers, and rolls for paper machines. The purpose is to identify areas where impending efforts should be made to make better use of composite materials in these applications. In order to obtain better design methodologies, which would allow more reliable and slender structures, improved test methods are necessary. Furthermore, the relation between structural, component and specimen test results should be better understood than what is presently the case. Improved predictive methods rely on a better understanding of the underlying damage mechanisms. With mechanism-based models, the component substructure or even the material microstructure could be optimised for best possible fatigue resistance. These issues are addressed in the present report, with special emphasis on test methods, and scaling from damage mechanisms to relevant material properties. (au)

  9. The unsteady nature of sea cliff retreat due to mechanical abrasion, failure and comminution feedbacks

    Science.gov (United States)

    Kline, Shaun W.; Adams, Peter N.; Limber, Patrick W.

    2014-08-01

    Sea cliff retreat is often linked to large waves, heavy precipitation and seismic events, but the specific operative mechanics have not been well constrained. In particular, what is the role of mechanical abrasion by beach sediments in cliff/platform evolution and how does it relate to the episodic nature of cliff retreat observed at certain locations? Here we present a simple, numerical model of sea cliff retreat that incorporates mechanical abrasion of a basal notch, threshold-controlled failure of the cantilevered block, and a feedback mechanism wherein retreat is dependent on the rate of sediment comminution within the surf zone. Using shore platform and cliff characteristics found in two coastal settings (the central California coast and the English North Sea coast), the model produces retreat rates comparable to those observed via field measurements. The highest retreat rates coincide with the steepest shore platforms and increasing wave height. Steeper platforms promote wave access to the cliff toe and, correspondingly, the receding cliff face produces additional accommodation space for the platform beach, preserving the erosive efficacy of the beach sediments. When exposed to energetic wave forcing, the slope of the inner platform segment controls retreat rates for concave platforms, whereas the slope of the outer platform segment exerts greater control for convex platforms. Platform beaches approached a long-term dynamic equilibrium on the concave profiles, leading to more consistent and steady retreat. Platform beaches were ephemeral on convex profiles, mirroring observed sand wave (Ord) migration on the Holderness coast, UK. These findings agree with previous field observations and support mechanical abrasion as a viable cause of temporal heterogeneity in cliff retreat rate for both coastlines.

  10. Edema mechanisms in the patient with heart failure and treatment options.

    Science.gov (United States)

    Sica, Domenic A

    2008-10-01

    Volume overload is a common accompanying feature of heart failure. The mechanistic basis for volume overload in heart failure is incompletely worked out. An important component of heart failure treatment remains diuretic therapy. Diuretic dosing remains as much an art as a science with multiple environmental and disease state-related factors influencing the efficiency with which a diuretic works. In heart failure, diuretics should always be given in the lowest possible dose with careful attention to reducing dietary sodium intake.

  11. Failure Mechanism of Laminated Damping Steel Sheet during Tensile-Shearing

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The tensile-shear failure zone of the laminated damping steel sheet was investigated by scanning electron microscopyand X-ray photoelectron spectroscopy. It is found that there exists cohesive failure in polymer sandwich and sub-boundary failure between the steel sheet and the polymer. The sub-boundary layer is dominantly polymer material.The tensile-shear failure of the laminated damping steel sheet is a process during which the crazes form, grow upand merge into cracks.

  12. Failure mode and effect analysis: a technique to prevent chemotherapy errors.

    Science.gov (United States)

    Sheridan-Leos, Norma; Schulmeister, Lisa; Hartranft, Steve

    2006-06-01

    Complex, multidrug chemotherapy protocols commonly are administered to patients with cancer. At every step of the chemotherapy administration process, from the point that chemotherapy is ordered to the point that it is infused and beyond, potential for error exists. FMEA, a proactive process that promotes systematic thinking about the safety of patient care, is a risk analysis technique that can be used to evaluate the process of chemotherapy administration. Error prevention is an ongoing quality improvement process that requires institutional commitment and support, and nurses play a vital role in the process.

  13. Anemia and iron deficiency in heart failure: mechanisms and therapeutic approaches.

    Science.gov (United States)

    van Veldhuisen, Dirk J; Anker, Stefan D; Ponikowski, Piotr; Macdougall, Iain C

    2011-05-31

    Anemia and iron deficiency are common in patients with heart failure (HF), and are associated with worse symptoms and adverse outcomes in this population. Although the two can occur together, anemia in HF is often not caused by iron deficiency, and iron deficiency can be present without causing anemia. Erythropoiesis-stimulating agents have been investigated extensively in the past few years and might be of benefit in patients with HF and anemia. However, concerns have arisen regarding the safety of erythropoiesis-stimulating agents in patients with chronic kidney disease and so the results of a large mortality trial are eagerly awaited to provide information on safety in patients with HF. Iron supplementation or replacement is a much older treatment option for patients with HF and anemia, but questions about the safety of intravenous iron, and absorption problems with oral formulations have prevented its widespread use to date. In the past few years, however, new data on the importance of iron deficiency in HF have become available, and a number of studies with intravenous iron have shown promising results. Therefore, this treatment approach is likely to become an attractive option for patients with HF and iron deficiency, both with and without anemia.

  14. Can intracytoplasmic sperm injection prevent total fertilization failure and enhance embryo quality in patients with non-male factor infertility?

    Science.gov (United States)

    Kim, Ju Yeong; Kim, Jee Hyun; Jee, Byung Chul; Lee, Jung Ryeol; Suh, Chang Suk; Kim, Seok Hyun

    2014-07-01

    To determine whether intracytoplasmic sperm injection (ICSI) could prevent total fertilization failure (TFF) and enhance the embryo quality in patients with non-male factor infertility. A total of 296 in vitro fertilization (IVF) cycles performed in patients with non-male factor infertility between April 2009 and March 2013 were included in this retrospective study. During the period, ICSI and conventional IVF were performed in 142 and 154 cycles, respectively. The usual indications for ICSI were in the cycles of patients with (1) known low fertilization rate, (2) repetitive implantation failure, (3) advanced maternal age, (4) presence of endometrioma, (5) low oocyte yield (number of oocytes ≤3), or (6) poor quality oocytes. The rate of TFF, normal fertilization, abnormal pronuclei (PN) formation, embryo quality, and pregnancy outcomes between the patients treated with ICSI and conventional IVF cycles were compared. The patients treated with ICSI (ICSI group, n=142) presented fewer number of oocytes than patients treated with conventional IVF cycles (n=154). The TFF rate was not different (4.2% vs. 0.6%, P=0.059), but the ICSI group presented a significantly higher rate of normal fertilization (83.4% vs. 79.1%, P=0.04) and lower rate of abnormal PN formation (3.9% vs. 13.3%, Pfertilization rate and the embryo quality. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  15. Becoming a first-class noticer. How to spot and prevent ethical failures in your organization.

    Science.gov (United States)

    Bazerman, Max H

    2014-01-01

    We'd like to think that no smart, upstanding manager would ever overlook or turn a blind eye to threats or wrongdoing that ultimately imperil his or her business. Yet it happens all the time. We fall prey to obstacles that obscure or drown out important signals that things are amiss. Becoming a "first-class noticer," says Max H. Bazerman, a professor at Harvard Business School, requires conscious effort to fight ambiguity, motivated blindness, conflicts of interest, the slippery slope, and efforts of others to mislead us. As a manager, you can develop your noticing skills by acknowledging responsibility when things go wrong rather than blaming external forces beyond your control. Bazerman also advises taking an outsider's view to challenge the status quo. Given the string of ethical failures of corporations around the world in recent years--from BP to GM to JP Morgan Chase--it's clear that leaders not only need to act more responsibly themselves but also must develop keen noticing skills in their employees and across their organizations.

  16. Prevention of liver cancer cachexia-induced cardiac wasting and heart failure

    Science.gov (United States)

    Springer, Jochen; Tschirner, Anika; Haghikia, Arash; von Haehling, Stephan; Lal, Hind; Grzesiak, Aleksandra; Kaschina, Elena; Palus, Sandra; Pötsch, Mareike; von Websky, Karoline; Hocher, Berthold; Latouche, Celine; Jaisser, Frederic; Morawietz, Lars; Coats, Andrew J.S.; Beadle, John; Argiles, Josep M.; Thum, Thomas; Földes, Gabor; Doehner, Wolfram; Hilfiker-Kleiner, Denise; Force, Thomas; Anker, Stefan D.

    2014-01-01

    Aims Symptoms of cancer cachexia (CC) include fatigue, shortness of breath, and impaired exercise capacity, which are also hallmark symptoms of heart failure (HF). Herein, we evaluate the effects of drugs commonly used to treat HF (bisoprolol, imidapril, spironolactone) on development of cardiac wasting, HF, and death in the rat hepatoma CC model (AH-130). Methods and results Tumour-bearing rats showed a progressive loss of body weight and left-ventricular (LV) mass that was associated with a progressive deterioration in cardiac function. Strikingly, bisoprolol and spironolactone significantly reduced wasting of LV mass, attenuated cardiac dysfunction, and improved survival. In contrast, imidapril had no beneficial effect. Several key anabolic and catabolic pathways were dysregulated in the cachectic hearts and, in addition, we found enhanced fibrosis that was corrected by treatment with spironolactone. Finally, we found cardiac wasting and fibrotic remodelling in patients who died as a result of CC. In living cancer patients, with and without cachexia, serum levels of brain natriuretic peptide and aldosterone were elevated. Conclusion Systemic effects of tumours lead not only to CC but also to cardiac wasting, associated with LV-dysfunction, fibrotic remodelling, and increased mortality. These adverse effects of the tumour on the heart and on survival can be mitigated by treatment with either the β-blocker bisoprolol or the aldosterone antagonist spironolactone. We suggest that clinical trials employing these agents be considered to attempt to limit this devastating complication of cancer. PMID:23990596

  17. Mechanisms linking dietary fiber, gut microbiota and colon cancer prevention

    Science.gov (United States)

    Many epidemiological and experimental studies have suggested that dietary fiber plays an important role in colon cancer prevention. These findings may relate to the ability of fiber to reduce the contact time of carcinogens within the intestinal lumen and to promote healthy gut microbiota, which mod...

  18. Molecular Mechanism by Which Retinoids Prevent Breast Cancer Development

    Science.gov (United States)

    2007-06-01

    clinicians to conquer this disease is to prevent the incidence, detect early and treat breast cancer with effective therapy resulting in long overall... biological functions such as embryogenesis, growth, differentiation, vision and reproduction (3-6). Retinoids also contain anti- proliferative...and are currently available to treat psoriasis , acne, photoaging, actinic keratosis or cancers such as acute promelocytic leukemia, cutaneous T-cell

  19. Pretreatment of Sialic Acid Efficiently Prevents Lipopolysaccharide-Induced Acute Renal Failure and Suppresses TLR4/gp91-Mediated Apoptotic Signaling

    Directory of Open Access Journals (Sweden)

    Shih-Ping Hsu

    2016-05-01

    Full Text Available Background/Aims: Lipopolysaccharides (LPS binding to Toll-like receptor 4 (TLR4 activate NADPH oxidase gp91 subunit-mediated inflammation and oxidative damage. Recognizing the high binding affinity of sialic acid (SA with LPS, we further explored the preventive potential of SA pretreatment on LPS-evoked acute renal failure (ARF. Methods: We determined the effect of intravenous SA 30 min before LPS-induced injury in urethane-anesthetized female Wistar rats by evaluating kidney reactive oxygen species (ROS responses, renal and systemic hemodynamics, renal function, histopathology, and molecular mechanisms. Results: LPS time-dependently reduced arterial blood pressure, renal microcirculation, and increased blood urea nitrogen and creatinine in the rats. LPS enhanced monocyte/macrophage infiltration and ROS production, and subsequently impaired kidneys with the enhancement of TLR4/NADPH oxidase gp91/Caspase 3/poly-(ADP-ribose-polymerase (PARP-mediated apoptosis in the kidneys. SA pretreatment effectively alleviated LPS-induced ARF. The levels of LPS-increased ED-1 infiltration and ROS production in the kidney were significantly depressed by SA pretreatment. Furthermore, SA pretreatment significantly depressed TLR4 activation, gp91 expression, and Caspase 3/PARP induced apoptosis in the kidneys. Conclusion: We suggest that pretreatment of SA significantly and preventively attenuated LPS-induced detrimental effects on systemic and renal hemodynamics, renal ROS production and renal function, as well as, LPS-activated TLR4/gp91/Caspase3 mediated apoptosis signaling.

  20. Mechanisms of decompensation and organ failure in cirrhosis: From peripheral arterial vasodilation to systemic inflammation hypothesis.

    Science.gov (United States)

    Bernardi, Mauro; Moreau, Richard; Angeli, Paolo; Schnabl, Bernd; Arroyo, Vicente

    2015-11-01

    The peripheral arterial vasodilation hypothesis has been most influential in the field of cirrhosis and its complications. It has given rise to hundreds of pathophysiological studies in experimental and human cirrhosis and is the theoretical basis of life-saving treatments. It is undisputed that splanchnic arterial vasodilation contributes to portal hypertension and is the basis for manifestations such as ascites and hepatorenal syndrome, but the body of research generated by the hypothesis has revealed gaps in the original pathophysiological interpretation of these complications. The expansion of our knowledge on the mechanisms regulating vascular tone, inflammation and the host-microbiota interaction require a broader approach to advanced cirrhosis encompassing the whole spectrum of its manifestations. Indeed, multiorgan dysfunction and failure likely result from a complex interplay where the systemic spread of bacterial products represents the primary event. The consequent activation of the host innate immune response triggers endothelial molecular mechanisms responsible for arterial vasodilation, and also jeopardizes organ integrity with a storm of pro-inflammatory cytokines and reactive oxygen and nitrogen species. Thus, the picture of advanced cirrhosis could be seen as the result of an inflammatory syndrome in contradiction with a simple hemodynamic disturbance.

  1. Stress State Analysis and Failure Mechanisms of Masonry Columns Reinforced with FRP under Concentric Compressive Load

    Directory of Open Access Journals (Sweden)

    Jiří Witzany

    2016-04-01

    Full Text Available The strengthening and stabilization of damaged compressed masonry columns with composites based on fabrics of high-strength fibers and epoxy resin, or polymer-modified cement mixtures, belongs to novel, partially non-invasive and reversible progressive methods. The stabilizing and reinforcing effect of these fabrics significantly applies to masonry structures under concentric compressive loading whose failure mechanism is characterized by the appearance and development of vertical tensile cracks accompanied by an increase in horizontal masonry strain. During the appearance of micro and hairline cracks (10−3 to 10−1 mm, the effect of non-pre-stressed wrapping composite is very small. The favorable effect of passive wrapping is only intensively manifested after the appearance of cracks (10−1 mm and bigger at higher loading levels. In the case of “optimum” reinforcement of a masonry column, the experimental research showed an increase in vertical displacements δy (up to 247%, horizontal displacements δx (up to 742% and ultimate load-bearing capacity (up to 136% compared to the values reached in unreinforced masonry columns. In the case of masonry structures in which no intensive “bed joint filler–masonry unit” interaction occurs, e.g., in regular coursed masonry with little differences in the mechanical characteristics of masonry units and the binder, the reinforcing effect of the fabric applies only partially.

  2. Mechanisms of renal cell repair and regeneration after acute renal failure.

    Science.gov (United States)

    Nony, Paul A; Schnellmann, Rick G

    2003-03-01

    In many cases, acute renal failure (ARF) is the result of proximal tubular cell injury and death and can arise in a variety of clinical situations, especially following renal ischemia and drug or toxicant exposure. Although much research has focused on the cellular events leading to ARF, less emphasis has been placed on the mechanisms of renal cell repair and regeneration, although ARF is reversed in over half of those who acquire it. Studies using in vivo and in vitro models have demonstrated the importance of proliferation, migration, and repair of physiological functions of injured renal proximal tubular cells (RPTC) in the reversal of ARF. Growth factors have been shown to produce migration and proliferation of injured RPTC, although the specific mechanisms through which growth factors promote renal regeneration in vivo are unclear. Recently, interactions between integrins and extracellular matrix proteins such as collagen IV were shown to promote the repair of physiological functions in injured RPTC. Specifically, collagen IV synthesis and deposition following cellular injury restored integrin polarity and promoted repair of mitochondrial function and active Na(+) transport. Furthermore, exogenous collagen IV, but not collagen I, fibronectin, or laminin, promoted the repair of physiological functions without stimulating proliferation. These findings suggest the importance of establishing and/or maintaining collagen IV-integrin interactions in the stimulation of repair of physiological functions following sublethal cellular injury. Furthermore, the pathway that stimulates repair is distinct from that of proliferation and migration and may be a viable target for pharmacological intervention.

  3. Failure mechanism of coated biomaterials under high impact-sliding contact stresses

    Science.gov (United States)

    Chen, Ying

    This study uses a newly developed testing method--- inclined cyclic impact-sliding test to investigate the failure behaviors of different types of biomaterials, (SS316L, Ti6Al4V and CoCr) coated by different coatings (TiN, DLC and PEO), under extremely high dynamic contact stress conditions. This test method can simulate the combined impact and sliding/rolling loading conditions, which is very practical in many aspects of commercial usages. During the tests, fatigue cracking, chipping, peeling and material transferring were observed in damaged area. This research is mainly focused on the failure behaviors of load-bearing materials which cyclic impacting and sliding are always involved. This purpose was accomplished in the three stages: First, impact-sliding test was carried out on TiN coated unhardened M2. It was found that soft substrate can cause early failure of coating due to the considerable plastic deformation in the substrate. In this case, stronger substrate is required to support coating better when tested under high contact stresses. Second, PEO coated Ti-6Al-4V was tested under pure sliding and impact-sliding wear conditions. PEO coating was found not strong enough to afford the high contact pressure under cyclic impact-sliding wear test due to its porous surface structure. However, the wear performance of PEO coating was enhanced due to the sub-stoichiometric oxide. To sum up, for load-bearing biomedical implants involved in high impacting movement, PEO coating may not be a promising surface protection. Third, the dense, smooth PVD/CVD bio-inert coatings were reconsidered. DLC and TiN coatings, combined by different substrates together with different interface materials were tested under the cyclic impact-sliding test using a set of proper loading. The results show that to choose a proper combination of coating, interface and substrate based on their mechanical properties is of great importance under the test condition. Hard substrates provide support

  4. Failure mechanisms and assembly-process-based solution of FCBGA high lead C4 bump non-wetting

    Institute of Scientific and Technical Information of China (English)

    Li Wenqi; Qiu Yiming; Jin Xing; Wang Lei; Wu Qidi

    2012-01-01

    This paper studies the typical failure modes and failure mechanisms of non-wetting in an FCBGA (flip chip ball grid array) assembly.We have identified that the residual lead and tin oxide layer on the surface of the die bumps as the primary contributor to non-wetting between die bumps and substrate bumps during the chipattach reflow process.Experiments with bump reflow parameters revealed that an optimized reflow dwell time and H2 flow rate in the reflow oven can significantly reduce the amount of lead and tin oxides on the surface of the die bumps,thereby reducing the non-wetting failure rate by about 90%.Both failure analysis results and mass production data validate the non-wetting failure mechanisms identified by this study.As a result of the reflow process optimization,the failure rate associated with non-wetting is significantly reduced,which further saves manufacturing cost and increases capacity utilization.

  5. Soft Roof Failure Mechanism and Supporting Method for Gob-Side Entry Retaining

    Directory of Open Access Journals (Sweden)

    Hongyun Yang

    2015-10-01

    Full Text Available To study the soft roof failure mechanism and the supporting method for a gateway in a gently inclined coal seam with a dip angle of 16° kept for gob-side entry retaining, and through the methodology of field investigation and numerical and analytical modeling, this paper analyzed the stress evolution law of roof strata at the working face end and determined that the sharp horizontal stress unloading phenomenon along the coal wall side did not appear after the working face advanced. Conversely, the horizontal stress along the gob side instantly decreased and the tensile stress produced, and the vertical stress in the central part of the roof had a higher reduction magnitude as well. An in-depth study indicates that the soft roof of the working face end subsided and seriously separated due to the effect of the front abutment pressure and the roof hanging length above the gob line, as well as certain other factors, including the rapid unloading of the lateral stress, tension and shear on the lower roof rock layer and dynamic disturbance. Those influencing factors also led to rapid crack propagation on a large scale and serious fracturing in the soft roof of the working face end. However, in the gob stress stabilized zone, the soft roof in the gob-side entry retaining has a shearing failure along the filling wall inside affected by the overburden pressure, rock bulking pressure, and roof gravity. To maintain the roof integrity, decrease the roof deformation, and enable the control of the working face end soft roof and the stabilization of the gob-side entry retaining roof, this study suggests that the preferred bolt installation angle for the soft roof situation is 70° based on the rock bolt extrusion strengthening theory.

  6. Early successes and late failures in the prevention of post endoscopic retrograde cholangiopancreatography

    Institute of Scientific and Technical Information of China (English)

    John G Lieb II; Peter V Draganov

    2007-01-01

    Acute pancreatitis is the most common complication of endoscopic retrograde cholangiopancreatography (ERCP).The only way to prevent this complication is to avoid an ERCP all together. Because of the risks involved, a careful consideration should be given to the indication for ERCP and the potential risk/benefit ratio of the test. Once a decision to perform an ERCP is made, the procedure should be carried out with meticulous care by an experienced endoscopist, and with a minimum of pancreatic duct opacification. Several pharmacologic agents have been tested, but to date the most important method of reducing post ERCP pancreatitis is the placement of pancreatic stent. Pancreatic stents should be placed in all patients at high risk of this complication such as those undergoing pancreatic sphincterotomy,pancreatic duct manipulation and intervention, and patients with suspected sphincter of Oddi dysfunction.Pancreatic stents should be also considered in patients requiring precut sphincterotomy to gain biliary access.

  7. Intraportal mesenchymal stem cell transplantation prevents acute liver failure through promoting cell proliferation and inhibiting apoptosis

    Institute of Scientific and Technical Information of China (English)

    Jian-Feng Sang; Xiao-Lei Shi; Bin Han; Tao Huang; Xu Huang; Hao-Zhen Ren; Yi-Tao Ding

    2016-01-01

    BACKGROUND: Transplantation of mesenchymal stem cells (MSCs) has been regarded as a potential treatment for acute liver failure (ALF), but the optimal route was unknown. The present study aimed to explore the most effective MSCs trans-plantation route in a swine ALF model. METHODS: The swine ALF model induced by intravenous injection of D-Gal was treated by the transplantation of swine MSCs through four routes including intraportal injection (InP group), hepatic intra-arterial injection (AH group), pe-ripheral intravenous injection (PV group) and intrahepatic injection (IH group). The living conditions and survival time were recorded. Blood samples before and after MSCs trans-plantation were collected for the analysis of hepatic function. The histology of liver injury was interpreted and scored in terminal samples. Hepatic apoptosis was detected by TUNEL assay. Apoptosis and proliferation related protein expressions including cleaved caspase-3, survivin, AKT, phospho-AKT (Ser473), ERK and phospho-ERK (Tyr204) were analyzed by Western blotting. RESULTS: The average survival time of each group was 10.7 ± 1.6 days (InP), 6.0±0.9 days (AH), 4.7±1.4 days (PV), 4.3± 0.8 days (IH), respectively, when compared with the average survival time of 3.8±0.8 days in the D-Gal group. The sur-vival rates between the InP group and D-Gal group revealed a statistically signiifcant difference (P CONCLUSIONS: Intraportal injection was superior to other pathways for MSC transplantation. Intraportal MSC trans-plantation could improve liver function, inhibit apoptosis and prolong the survival time of swine with ALF. The transplanted MSCs may participate in liver regeneration via promoting cell proliferation and suppressing apoptosis during the initial stage of ALF.

  8. SLOPE FAILURE MECHANISMS IN COHESIVE SOILS: INSIGHTS FROM THEORETICAL AND NUMERICAL ANALYSES OF FIELD AND LABORATORY-TRIGGERED EVENTS

    Science.gov (United States)

    Malet, J.; Spickermann, A.; van Asch, T.

    2009-12-01

    A landslide can show a variety of failure modes which depends on the given conditions of the slope such as geometry, material characteristics and presence of discontinuities. Besides the gravity as main loading factor, it is assumed that slope failures are often caused by hydrological processes. The identification and modelling of failure modes and triggering mechanisms are essential requirements in landslide forecasting and in the design of reliable early warning systems. This work is an attempt to get a better understanding of the mode of failure and possible failure mechanisms taking place in cohesive slopes. Theoretical analysis has been carried out on the basis of (1) field observations of two failure events of the clay-rich Super-Sauze mudslide (Southeast France) and (2) small-scale landslides triggered in a flume using clay from Zoelen (Netherlands) and reworked black marls from Super-Sauze. To investigate the failure behaviour numerically a simple analytical model, named 2LM (Landslide Liquefaction Model) (van Asch et al. 2006; van Asch & Malet, in press) is used. The model assumes that liquefaction is related to previous development of slip surfaces, i.e. deformation of the landslide body (sliding blocks, slumps) during motion leading to the generation of excess pore water pressure and thus to fluidization. The model is based on the theory of limiting equilibrium dividing the area above an estimated slip surface into slices of constant width. Immediately after failure, the difference in movement for each slice is calculated assuming a viscous shear band and using the Coulomb-viscous model. The differential movements conduct to differential strains which are transferred to excess pore water pressures. The potential fluidization is then evaluated for each slice in relation to the displacements. Results from an application of this model on the two slump-type failures that occurred in the Super-Sauze mudslide are presented. Then the model is applied to the

  9. Living with Heart Failure

    Science.gov (United States)

    ... page from the NHLBI on Twitter. Living With Heart Failure Currently, heart failure has no cure. You'll ... avoid harmful side effects. Take Steps To Prevent Heart Failure From Getting Worse Certain actions can worsen your ...

  10. Exercise intolerance in patients with heart failure and preserved left ventricular systolic function: failure of the Frank-Starling mechanism.

    Science.gov (United States)

    Kitzman, D W; Higginbotham, M B; Cobb, F R; Sheikh, K H; Sullivan, M J

    1991-04-01

    Invasive cardiopulmonary exercise testing was performed in 7 patients who presented with congestive heart failure, normal left ventricular ejection fraction and no significant coronary or valvular heart disease and in 10 age-matched normal subjects. Compared with the normal subjects, patients demonstrates severe exercise intolerance with a 48% reduction in peak oxygen consumption (11.6 +/- 4.0 versus 22.7 +/- 6.1 ml/kg per min; p less than 0.001), primarily due to a 41% reduction in peak cardiac index (4.2 +/- 1.4 versus 7.1 +/- 1.1 liters/min per m2; p less than 0.001). In patients compared with normal subjects, peak left ventricular stroke volume index (34 +/- 9 versus 46 +/- 7 ml/min per m2; p less than 0.01) and end-diastolic volume index (56 +/- 14 versus 68 +/- 12 ml/min per m2; p less than 0.08) were reduced, whereas peak ejection fraction and end-systolic volume index were not different. In patients, the change in end-diastolic volume index during exercise correlated strongly with the change in stroke volume index (r = 0.97; p less than 0.0001) and cardiac index (r = 0.80; p less than 0.03). Pulmonary wedge pressure was markedly increased at peak exercise in patients compared with normal subjects (25.7 +/- 9.1 versus 7.1 +/- 4.4 mm Hg; p less than 0.0001). Patients demonstrated a shift of the left ventricular end-diastolic pressure-volume relation upward and to the left at rest. Increases in left ventricular filling pressure during exercise were not accompanied by increases in end-diastolic volume, indicating a limitation to left ventricular filling.(ABSTRACT TRUNCATED AT 250 WORDS)

  11. Influence of bone volume fraction and architecture on computed large-deformation failure mechanisms in human trabecular bone.

    Science.gov (United States)

    Bevill, Grant; Eswaran, Senthil K; Gupta, Atul; Papadopoulos, Panayiotis; Keaveny, Tony M

    2006-12-01

    Large-deformation bending and buckling have long been proposed as failure mechanisms by which the strength of trabecular bone can be affected disproportionately to changes in bone density, and thus may represent an important aspect of bone quality. We sought here to quantify the contribution of large-deformation failure mechanisms on strength, to determine the dependence of these effects on bone volume fraction and architecture, and to confirm that the inclusion of large-deformation effects in high-resolution finite element models improves predictions of strength versus experiment. Micro-CT-based finite element models having uniform hard tissue material properties were created from 54 cores of human trabecular bone taken from four anatomic sites (age = 70+/-11; 24 male, 27 female donors), which were subsequently biomechanically tested to failure. Strength predictions were made from the models first including, then excluding, large-deformation failure mechanisms, both for compressive and tensile load cases. As expected, strength predictions versus experimental data for the large-deformation finite element models were significantly improved (p deformation models in both tension and compression. Below a volume fraction of about 0.20, large-deformation failure mechanisms decreased trabecular strength from 5-80% for compressive loading, while effects were negligible above this volume fraction. Step-wise nonlinear multiple regression revealed that structure model index (SMI) and volume fraction (BV/TV) were significant predictors of these reductions in strength (R2 = 0.83, p deformation failure mechanisms on trabecular bone strength is highly heterogeneous and is not well explained by standard architectural metrics.

  12. Numerical simulation of mechanisms of deformation,failure and energy dissipation in porous rock media subjected to wave stresses

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The pore characteristics,mineral compositions,physical and mechanical properties of the subarkose sandstones were acquired by means of CT scan,X-ray diffraction and physical tests.A few physical models possessing the same pore characteristics and matrix properties but different porosities compared to the natural sandstones were developed.The 3D finite element models of the rock media with varied porosities were established based on the CT image processing of the physical models and the MIMICS software platform.The failure processes of the porous rock media loaded by the split Hopkinson pressure bar(SHPB) were simulated by satisfying the elastic wave propagation theory.The dynamic responses,stress transition,deformation and failure mechanisms of the porous rock media subjected to the wave stresses were analyzed.It is shown that an explicit and quantitative analysis of the stress,strain and deformation and failure mechanisms of porous rocks under the wave stresses can be achieved by using the developed 3D finite element models.With applied wave stresses of certain amplitude and velocity,no evident pore deformation was observed for the rock media with a porosity less than 15%.The deformation is dominantly the combination of microplasticity(shear strain),cracking(tensile strain) of matrix and coalescence of the cracked regions around pores.Shear stresses lead to microplasticity,while tensile stresses result in cracking of the matrix.Cracking and coalescence of the matrix elements in the neighborhood of pores resulted from the high transverse tensile stress or tensile strain which exceeded the threshold values.The simulation results of stress wave propagation,deformation and failure mechanisms and energy dissipation in porous rock media were in good agreement with the physical tests.The present study provides a reference for analyzing the intrinsic mechanisms of the complex dynamic response,stress transit mode,deformation and failure mechanisms and the disaster

  13. Asbestos contamination in feldspar extraction sites: a failure of prevention? Commentary.

    Science.gov (United States)

    Cavariani, Fulvio

    2016-01-01

    Fibrous tremolite is a mineral species belonging to the amphibole group. It is present almost everywhere in the world as a natural contaminant of other minerals, like talc and vermiculite. It can be also found as a natural contaminant of the chrysotile form of asbestos. Tremolite asbestos exposures result in respiratory health consequences similar to the other forms of asbestos exposure, including lung cancer and mesothelioma. Although abundantly distributed on the earth's surface, tremolite is only rarely present in significant deposits and it has had little commercial use. Significant presence of amphibole asbestos fibers, characterized as tremolite, was identified in mineral powders coming from the milling of feldspar rocks extracted from a Sardinian mining site (Italy). This evidence raises several problems, in particular the prevention of carcinogenic risks for the workers. Feldspar is widespread all over the world and every year it is produced in large quantities and it is used for several productive processes in many manufacturing industries (over 21 million tons of feldspar mined and marketed every year). Until now the presence of tremolite asbestos in feldspar has not been described, nor has the possibility of such a health hazard for workers involved in mining, milling and handling of rocks from feldspar ores been appreciated. Therefore the need for a wider dissemination of knowledge of these problems among professionals, in particular mineralogists and industrial hygienists, must be emphasized. In fact both disciplines are necessary to plan appropriate environmental controls and adequate protections in order to achieve safe working conditions.

  14. A failure of matrix metalloproteinase inhibition in the prevention of rat intracranial aneurysm formation

    Energy Technology Data Exchange (ETDEWEB)

    Kaufmann, T.J.; Kallmes, D.F. [Mayo Clinic and Foundation, Department of Radiology, Rochester, MN (United States); Marx, W.F. [Asheville Radiology Associates, Asheville, NC (United States)

    2006-03-15

    We tested the hypothesis that nonspecific matrix metalloproteinase (MMP) inhibition with doxycycline would decrease the incidence of intracranial aneurysm formation in a rat aneurysm model. We performed common carotid artery ligation on 96 Long-Evans rats. A treatment group of 48 animals was chosen at random to receive oral doxycycline (3 mg/kg) in addition to standard rat chow, and the control group of 48 animals received standard rat chow only. The major circle of Willis arteries was dissected at 1 year following carotid ligation, and the proportions of animals with aneurysms were compared between groups using Fisher's exact test. Four animals given oral doxycycline and ten control animals expired before 1 year. Of the examined animals, eight saccular intracranial aneurysms were found in 8 of 45 animals which had received doxycycline (17.8%) and seven saccular intracranial aneurysms were found in 7 of 37 control animals (18.9%). There was no significant difference in aneurysm formation between the doxycycline-treated and control groups (P=0.894). Nonspecific MMP inhibition with doxycycline is not effective in preventing intracranial aneurysm formation in a rat model. (orig.)

  15. The performance efficiency of bioaugmentation to prevent anaerobic digestion failure from ammonia and propionate inhibition.

    Science.gov (United States)

    Li, Ying; Zhang, Yue; Sun, Yongming; Wu, Shubiao; Kong, Xiaoying; Yuan, Zhenhong; Dong, Renjie

    2017-05-01

    This study aims to investigate the effect of bioaugmentation with enriched methanogenic propionate degrading microbial consortia on propionate fermentation under ammonia stress from total ammonia nitrogen concentration (TAN) of 3.0gNL(-1). Results demonstrated that bioaugmentation could prevent unstable digestion against further deterioration. After 45days of 1dosage (0.3g dry cell weight L(-1)d(-1), DCW L(-1)d(-1)) of bioaugmentation, the average volumetric methane production (VMP), methane recovery rate and propionic acid (HPr) degradation rate was enhanced by 70mLL(-1)d(-1), 21% and 51%, respectively. In contrast, the non-bioaugmentation reactor almost failed. Routine addition of a double dosage (0.6g DCW L(-1)d(-1)) of bioaugmentation culture was able to effectively recover the failing digester. The results of FISH suggested that the populations of Methanosaetaceae increased significantly, which could be a main contributor for the positive effect on methane production. Copyright © 2017 Elsevier Ltd. All rights reserved.

  16. Development of a new code to solve hydro-mechanical coupling, shear failure and tensile failure due to hydraulic fracturing operations.

    Science.gov (United States)

    María Gómez Castro, Berta; De Simone, Silvia; Carrera, Jesús

    2016-04-01

    Nowadays, there are still some unsolved relevant questions which must be faced if we want to proceed to the hydraulic fracturing in a safe way. How much will the fracture propagate? This is one of the most important questions that have to be solved in order to avoid the formation of pathways leading to aquifer targets and atmospheric release. Will the fracture failure provoke a microseismic event? Probably this is the biggest fear that people have in fracking. The aim of this work (developed as a part of the EU - FracRisk project) is to understand the hydro-mechanical coupling that controls the shear of existing fractures and their propagation during a hydraulic fracturing operation, in order to identify the key parameters that dominate these processes and answer the mentioned questions. This investigation focuses on the development of a new C++ code which simulates hydro-mechanical coupling, shear movement and propagation of a fracture. The framework employed, called Kratos, uses the Finite Element Method and the fractures are represented with an interface element which is zero thickness. This means that both sides of the element lie together in the initial configuration (it seems a 1D element in a 2D domain, and a 2D element in a 3D domain) and separate as the adjacent matrix elements deform. Since we are working in hard, fragile rocks, we can assume an elastic matrix and impose irreversible displacements in fractures when rock failure occurs. The formulation used to simulate shear and tensile failures is based on the analytical solution proposed by Okada, 1992 and it is part of an iterative process. In conclusion, the objective of this work is to employ the new code developed to analyze the main uncertainties related with the hydro-mechanical behavior of fractures derived from the hydraulic fracturing operations.

  17. Aerobic exercise training prevents heart failure-induced skeletal muscle atrophy by anti-catabolic, but not anabolic actions.

    Science.gov (United States)

    Souza, Rodrigo W A; Piedade, Warlen P; Soares, Luana C; Souza, Paula A T; Aguiar, Andreo F; Vechetti-Júnior, Ivan J; Campos, Dijon H S; Fernandes, Ana A H; Okoshi, Katashi; Carvalho, Robson F; Cicogna, Antonio C; Dal-Pai-Silva, Maeli

    2014-01-01

    Heart failure (HF) is associated with cachexia and consequent exercise intolerance. Given the beneficial effects of aerobic exercise training (ET) in HF, the aim of this study was to determine if the ET performed during the transition from cardiac dysfunction to HF would alter the expression of anabolic and catabolic factors, thus preventing skeletal muscle wasting. We employed ascending aortic stenosis (AS) inducing HF in Wistar male rats. Controls were sham-operated animals. At 18 weeks after surgery, rats with cardiac dysfunction were randomized to 10 weeks of aerobic ET (AS-ET) or to an untrained group (AS-UN). At 28 weeks, the AS-UN group presented HF signs in conjunction with high TNF-α serum levels; soleus and plantaris muscle atrophy; and an increase in the expression of TNF-α, NFκB (p65), MAFbx, MuRF1, FoxO1, and myostatin catabolic factors. However, in the AS-ET group, the deterioration of cardiac function was prevented, as well as muscle wasting, and the atrophy promoters were decreased. Interestingly, changes in anabolic factor expression (IGF-I, AKT, and mTOR) were not observed. Nevertheless, in the plantaris muscle, ET maintained high PGC1α levels. Thus, the ET capability to attenuate cardiac function during the transition from cardiac dysfunction to HF was accompanied by a prevention of skeletal muscle atrophy that did not occur via an increase in anabolic factors, but through anti-catabolic activity, presumably caused by PGC1α action. These findings indicate the therapeutic potential of aerobic ET to block HF-induced muscle atrophy by counteracting the increased catabolic state.

  18. Aerobic exercise training prevents heart failure-induced skeletal muscle atrophy by anti-catabolic, but not anabolic actions.

    Directory of Open Access Journals (Sweden)

    Rodrigo W A Souza

    Full Text Available BACKGROUND: Heart failure (HF is associated with cachexia and consequent exercise intolerance. Given the beneficial effects of aerobic exercise training (ET in HF, the aim of this study was to determine if the ET performed during the transition from cardiac dysfunction to HF would alter the expression of anabolic and catabolic factors, thus preventing skeletal muscle wasting. METHODS AND RESULTS: We employed ascending aortic stenosis (AS inducing HF in Wistar male rats. Controls were sham-operated animals. At 18 weeks after surgery, rats with cardiac dysfunction were randomized to 10 weeks of aerobic ET (AS-ET or to an untrained group (AS-UN. At 28 weeks, the AS-UN group presented HF signs in conjunction with high TNF-α serum levels; soleus and plantaris muscle atrophy; and an increase in the expression of TNF-α, NFκB (p65, MAFbx, MuRF1, FoxO1, and myostatin catabolic factors. However, in the AS-ET group, the deterioration of cardiac function was prevented, as well as muscle wasting, and the atrophy promoters were decreased. Interestingly, changes in anabolic factor expression (IGF-I, AKT, and mTOR were not observed. Nevertheless, in the plantaris muscle, ET maintained high PGC1α levels. CONCLUSIONS: Thus, the ET capability to attenuate cardiac function during the transition from cardiac dysfunction to HF was accompanied by a prevention of skeletal muscle atrophy that did not occur via an increase in anabolic factors, but through anti-catabolic activity, presumably caused by PGC1α action. These findings indicate the therapeutic potential of aerobic ET to block HF-induced muscle atrophy by counteracting the increased catabolic state.

  19. Preventing low birth weight, child abuse, and school failure: the need for comprehensive, community-wide approaches.

    Science.gov (United States)

    Chamberlin, R W

    1992-02-01

    Based on numerous examples from this country and abroad, we now have a reasonable idea of how we can reduce substantially the incidence of low-weight births, child abuse, adolescent pregnancy, school failure, and school dropout. The most effective long-term strategy appears to be the development of a comprehensive, coordinated, community-wide approach focused on preventing low- and medium-risk families from becoming high-risk as well as providing intensive services to those who already have reached a high-risk status. The best results can be obtained when all levels of government and the private sector work together. In this partnership, the best outcomes appear to result when the state and federal governments, private corporations, or both provide technical assistance, additional funding as needed, and help in setting program standards, and when the community maintains local control over establishing priorities and implementation strategies. However, to reach these goals and to maintain program support over the long time periods needed to show positive results (4 to 8 years), it is necessary to become skilled in social marketing techniques to turn program need into demand and to develop a strong local and statewide advocacy group to facilitate passage of needed legislation and prevent funding cutbacks. Pediatricians can modify their practices to make them more supportive to families and can work with other community leaders to bring about the changes in attitudes and about the changes in attitudes and funding priorities at the state and community levels that will be necessary to develop more effective preventive programs.

  20. A Study of Pull-Through Failures of Mechanically Fastened Joints.

    Science.gov (United States)

    1977-09-01

    are available and a great deal is known about the behavior of metals at failure. Theories of failure have been tested time and again and failure...assumptions were made. First, the dynamic effects of the hydraulic ram were not addressed, although it is known that they are of great importance in...as suggested by Figure 5C, a devide was constructed in the Naval Postgraduate School Machine Shop. The simple support condition was provided by

  1. Mechanical properties and failure characteristics of fractured sandstone with grouting and anchorage

    Institute of Scientific and Technical Information of China (English)

    Zong Yijiang; Han Lijun; Qu Tao; Yang Shengqi

    2014-01-01

    Based on uniaxial compression experimental results on fractured sandstone with grouting and anchorage, we studied the strength and deformation properties, the failure model, crack formation and evolution laws of fractured sandstone under different conditions of anchorage. The experimental results show that the strength and elastic modulus of fractured sandstone with different fracture angles are sig-nificantly lower than those of intact sandstone. Compared with the fractured samples without anchorage, the peak strength, residual strength, peak and ultimate axial strain of fractured sandstone under different anchorage increase by 64.5-320.0%, 62.8-493.0%, and 31.6-181.4%, respectively. The number of bolts and degree of pre-stress has certain effects on the peak strength and failure model of fractured sandstone. The peak strength of fractured sandstone under different anchorage increases to some extent, and the failure model of fractured sandstone also transforms from tensile failure to tensile-shear mixed failure with the number of bolts. The pre-stress can restrain the formation and evolution process of tensile cracks, delay the failure process of fractured sandstone under anchorage and impel the transformation of failure model from brittle failure to plastic failure.

  2. The behavior of the micro-mechanical cement-bone interface affects the cement failure in total hip replacement

    NARCIS (Netherlands)

    Waanders, D.; Janssen, D.; Mann, K.A.; Verdonschot, N.J.J.

    2011-01-01

    In the current study, the effects of different ways to implement the complex micro-mechanical behavior of the cement-bone interface on the fatigue failure of the cement mantle were investigated. In an FEA-model of a cemented hip reconstruction the cement-bone interface was modeled and numerically im

  3. Test selection and optimization for PHM based on failure evolution mechanism model

    Institute of Scientific and Technical Information of China (English)

    Jing Qiu; Xiaodong Tan; Guanjun Liu; Kehong LÜ

    2013-01-01

    The test selection and optimization (TSO) can improve the abilities of fault diagnosis, prognosis and health-state evalua-tion for prognostics and health management (PHM) systems. Tra-ditional y, TSO mainly focuses on fault detection and isolation, but they cannot provide an effective guide for the design for testa-bility (DFT) to improve the PHM performance level. To solve the problem, a model of TSO for PHM systems is proposed. Firstly, through integrating the characteristics of fault severity and propa-gation time, and analyzing the test timing and sensitivity, a testabi-lity model based on failure evolution mechanism model (FEMM) for PHM systems is built up. This model describes the fault evolution-test dependency using the fault-symptom parameter matrix and symptom parameter-test matrix. Secondly, a novel method of in-herent testability analysis for PHM systems is developed based on the above information. Having completed the analysis, a TSO model, whose objective is to maximize fault trackability and mini-mize the test cost, is proposed through inherent testability analysis results, and an adaptive simulated annealing genetic algorithm (ASAGA) is introduced to solve the TSO problem. Final y, a case of a centrifugal pump system is used to verify the feasibility and effectiveness of the proposed models and methods. The results show that the proposed technology is important for PHM systems to select and optimize the test set in order to improve their perfor-mance level.

  4. Failure Mechanism of a Stellite Coating on Heat-Resistant Steel

    Science.gov (United States)

    Wang, Dong; Zhao, Haixing; Wang, Huang; Li, Yuyan; Liu, Xia; He, Guo

    2017-09-01

    The Stellite 21 coating on the heat-resistant steel X12CrMoWVNbN10-1-1 (so-called COSTE) used in a steam turbine valve was found to be fatigue broken after service at around 873 K (600 °C) for about 8 years. In order to investigate the failure mechanism, a fresh Stellite 21 coating was also prepared on the same COSTE steel substrate by using the similar deposition parameters for comparison. It was found that the Stellite 21 coating was significantly diluted by the steel, resulting in a thin Fe-rich layer in the coating close to the fusion line. Such high Fe concentration together with the incessant Fe diffusion from the steel substrate to the coating during the service condition (about 873 K (600 °C) for long time) induced the eutectoid decomposition of the fcc α-Co(Fe,Cr,Mo) solid solution, forming an irregular eutectoid microstructure that was composed of the primitive cubic α'-FeCo(Cr,Mo) phase and the tetragonal σ-CrCo(Fe,Mo) phase. The brittle nature of such α'/ σ eutectoid microstructure contributed to the fatigue fracture of the Stellite 21 coating, resulting in an intergranular rupture mode.

  5. The Mean Failure Cost Cybersecurity Model toward Security Measures and Associated Mechanisms

    Directory of Open Access Journals (Sweden)

    Neila Rjaibi

    2015-05-01

    Full Text Available This paper presents results of the quantification of security threats of e-learning system using an economic measure abridged by MFC (Mean Failure Cost. We study means to optimize this measure and to make it more precise, more useful in practice. First we develop basic security requirements taxonomy adapted to all context and systems because security requirements lacks a clear basic taxonomy. Then our hierarchical model is used to enrich the first matrix (stake matrix of the MFC cyber security measure. The stake matrix defines the list of system’s stakeholders and the list of security requirements, it is used to express each cell in dollar monetary terms, it represents loss incurred and/or premium placed on requirement. Then we present a survey of known relationships among security sub-factors and measures as well as common mechanisms. Also we provide a control of the MFC using a classification of security measures. This information is useful in the design of decisions to requirements.

  6. Mitigating mechanical failure of crystalline silicon electrodes for lithium batteries by morphological design.

    Science.gov (United States)

    An, Yonghao; Wood, Brandon C; Ye, Jianchao; Chiang, Yet-Ming; Wang, Y Morris; Tang, Ming; Jiang, Hanqing

    2015-07-21

    Although crystalline silicon (c-Si) anodes promise very high energy densities in Li-ion batteries, their practical use is complicated by amorphization, large volume expansion and severe plastic deformation upon lithium insertion. Recent experiments have revealed the existence of a sharp interface between crystalline Si (c-Si) and the amorphous LixSi alloy during lithiation, which propagates with a velocity that is orientation dependent; the resulting anisotropic swelling generates substantial strain concentrations that initiate cracks even in nanostructured Si. Here we describe a novel strategy to mitigate lithiation-induced fracture by using pristine c-Si structures with engineered anisometric morphologies that are deliberately designed to counteract the anisotropy in the crystalline/amorphous interface velocity. This produces a much more uniform volume expansion, significantly reducing strain concentration. Based on a new, validated methodology that improves previous models of anisotropic swelling of c-Si, we propose optimal morphological designs for c-Si pillars and particles. The advantages of the new morphologies are clearly demonstrated by mesoscale simulations and verified by experiments on engineered c-Si micropillars. The results of this study illustrate that morphological design is effective in improving the fracture resistance of micron-sized Si electrodes, which will facilitate their practical application in next-generation Li-ion batteries. The model and design approach present in this paper also have general implications for the study and mitigation of mechanical failure of electrode materials that undergo large anisotropic volume change upon ion insertion and extraction.

  7. Embryo malposition as a potential mechanism for mercury-induced hatching failure in bird eggs

    Science.gov (United States)

    Herring, G.; Ackerman, J.T.; Eagles-Smith, C. A.

    2010-01-01

    We examined the prevalence of embryo malpositions and deformities in relation to total mercury (THg) and selenium (Se) concentrations in American avocet (Recurvirostra americana), black-necked stilt (Himantopus mexicanus), and Forster's tern (Sterna forsteri) eggs in San Francisco Bay (CA, USA) during 2005 to 2007. Overall, 11% of embryos were malpositioned in eggs ???18 d of age (n=282) and 2% of embryos were deformed in eggs ???13 d of age (n=470). Considering only those eggs that failed to hatch (n=62), malpositions occurred in 24% of eggs ???18 d of age and deformities occurred in 7% of eggs ???13 d of age. The probability of an embryo being malpositioned increased with egg THg concentrations in Forster's terns, but not in avocets or stilts. The probability of embryo deformity was not related to egg THg concentrations in any species. Using a reduced dataset with both Se and THg concentrations measured in eggs (n=87), we found no interaction between Se and THg on the probability of an embryo being malpositioned or deformed. Results of the present study indicate that embryo malpositions were prevalent in waterbird eggs that failed to hatch and the likelihood of an embryo being malpositioned increased with egg THg concentrations in Forster's terns. We hypothesize that malpositioning of avian embryos may be one reason for mercury-related hatching failure that occurs late in incubation, but further research is needed to elucidate this potential mechanism. ?? 2010 SETAC.

  8. Exhaustion of the Frank-Starling mechanism in conscious dogs with heart failure induced by chronic coronary microembolization.

    Science.gov (United States)

    Gill, Robert M; Jones, Bonita D; Corbly, Angela K; Ohad, Dan G; Smith, Gerald D; Sandusky, George E; Christe, Michael E; Wang, Jie; Shen, Weiqun

    2006-07-04

    The role of the Frank-Starling mechanism in the regulation of cardiac systolic function in the ischemic failing heart was examined in conscious dogs. Left ventricular (LV) dimension, pressure and systolic function were assessed using surgically implanted instrumentations and non-invasive echocardiogram. Heart failure was induced by daily intra-coronary injections of microspheres for 3-4 weeks via implanted coronary catheters. Chronic coronary embolization resulted in a progressive dilation of the left ventricle (12+/-3%), increase in LV end-diastolic pressure (118+/-19%), depression of LV dP/dt(max) (-19+/-4%), fractional shortening (-36+/-7%), and cardiac work (-60+/-9%), and development of heart failure, while the LV contractile response to dobutamine was depressed. A brief inferior vena caval occlusion in dogs with heart failure decreased LV preload to match the levels attained in their control state and caused a further reduction of LV dP/dt(max), fractional shortening, stroke work and cardiac work. Moreover, in response to acute volume loading, the change in the LV end-diastolic dimension-pressure (DeltaLVEDD-DeltaLVEDP) curve in the failing heart became steeper and shifted significantly to the left, while the increases in LV stroke work and cardiac work were blunted. Thus, our results suggest that the Frank-Starling mechanism is exhausted in heart failure and unable to further respond to increasing volume while it plays an important compensatory role in adaptation to LV dysfunction in heart failure.

  9. Vitamin D Biology in Heart Failure : Molecular Mechanisms and Systematic Review

    NARCIS (Netherlands)

    Meems, Laura M. G.; van der Harst, P.; van Gilst, W. H.; de Boer, R. A.

    Vitamin D has recently been suggested as an important mediator of blood pressure and cardiovascular disease, including heart failure. In patients with heart failure, low vitamin D levels are associated with adverse outcome and correlate with established clinical correlates and biomarkers. Many

  10. Vitamin D Biology in Heart Failure : Molecular Mechanisms and Systematic Review

    NARCIS (Netherlands)

    Meems, Laura M. G.; van der Harst, P.; van Gilst, W. H.; de Boer, R. A.

    2011-01-01

    Vitamin D has recently been suggested as an important mediator of blood pressure and cardiovascular disease, including heart failure. In patients with heart failure, low vitamin D levels are associated with adverse outcome and correlate with established clinical correlates and biomarkers. Many precu

  11. Vitamin D Biology in Heart Failure : Molecular Mechanisms and Systematic Review

    NARCIS (Netherlands)

    Meems, Laura M. G.; van der Harst, P.; van Gilst, W. H.; de Boer, R. A.

    2011-01-01

    Vitamin D has recently been suggested as an important mediator of blood pressure and cardiovascular disease, including heart failure. In patients with heart failure, low vitamin D levels are associated with adverse outcome and correlate with established clinical correlates and biomarkers. Many precu

  12. Analysis and Prevention for Oscillation Failure of Capacitive Micro-accelerometers

    Institute of Scientific and Technical Information of China (English)

    WAN Caixin; DONG Jingxin; HAN Fengtian

    2010-01-01

    As actuator of the force-rebalanced servo loop, the electrostatic force generator of the micro-accelerometer shows high nonlinearity while the interpole of the micro-electro-mechanical system(MEMS) sensor is far away from its balance position. The control system cannot rebalance itself with the limited bandwidth after an external long overload, because the characteristics of the force generator differ from normal case. Although for similar problems, solutions with cascading lead-lag blocks, with the anti-windup(AW) technology, or with the sliding-mode control, are widely reported, the problems such as performance loss or difficulty to synthesize a digital controller still remain. Based on existing researches, remedies are developed by analyzing the characteristic of the system not only near the balance position, but also corresponding to the whole moveable range of the interpole, and a new controller is proposed. The solution is compared with the common solutions of cascading lead-lag blocks method, AW methods, and sliding mode methods. Comparison results show that the proposed solution avoid performance loss, compared to cascading lead-lag blocks solution; the proposed solution is easily synthesized and implemented in the analog servo loop of the micro-accelerometer, compared to digital AW methods; at the same time, the proposed solution avoids suffering the chattering effect problem but just utilize it, compared to the sliding-mode control solution. Nevertheless, comparison results show the solution is lack of commonality, since the solution is only more suitable to micro electrostatic force-rebalance system. The SIMULINK models with and without the proposed solution, taking typical micro-accelerometer parameters, have been set up for simulation; corresponding experiments utilizing electrometric method are also conducted after the successful simulations. Simulation and experiment results verify that the micro-accelerometer will reliably return to normal operation

  13. Dynamic analysis method for prevention of failure in the first-stage low-pressure turbine blade with two-finger root

    Science.gov (United States)

    Park, Jung-Yong; Jung, Yong-Keun; Park, Jong-Jin; Kang, Yong-Ho

    2002-05-01

    Failures of turbine blades are identified as the leading causes of unplanned outages for steam turbine. Accidents of low-pressure turbine blade occupied more than 70 percent in turbine components. Therefore, the prevention of failures for low pressure turbine blades is certainly needed. The procedure is illustrated by the case study. This procedure is used to guide, and support the plant manager's decisions to avoid a costly, unplanned outage. In this study, we are trying to find factors of failures in LP turbine blade and to make three steps to approach the solution of blade failure. First step is to measure natural frequency in mockup test and to compare it with nozzle passing frequency. Second step is to use FEM and to calculate the natural frequencies of 7 blades and 10 blades per group in BLADE code. Third step is to find natural frequencies of grouped blade off the nozzle passing frequency.

  14. Potential synergy of phytochemicals in cancer prevention: mechanism of action.

    Science.gov (United States)

    Liu, Rui Hai

    2004-12-01

    Epidemiological studies have consistently shown that regular consumption of fruits and vegetables is strongly associated with reduced risk of developing chronic diseases, such as cancer and cardiovascular disease. It is now widely believed that the actions of the antioxidant nutrients alone do not explain the observed health benefits of diets rich in fruits and vegetables, because taken alone, the individual antioxidants studied in clinical trials do not appear to have consistent preventive effects. Work performed by our group and others has shown that fruits and vegetable phytochemical extracts exhibit strong antioxidant and antiproliferative activities and that the major part of total antioxidant activity is from the combination of phytochemicals. We proposed that the additive and synergistic effects of phytochemicals in fruits and vegetables are responsible for these potent antioxidant and anticancer activities and that the benefit of a diet rich in fruits and vegetables is attributed to the complex mixture of phytochemicals present in whole foods. This explains why no single antioxidant can replace the combination of natural phytochemicals in fruits and vegetables to achieve the health benefits. The evidence suggests that antioxidants or bioactive compounds are best acquired through whole-food consumption, not from expensive dietary supplements. We believe that a recommendation that consumers eat 5 to 10 servings of a wide variety of fruits and vegetables daily is an appropriate strategy for significantly reducing the risk of chronic diseases and to meet their nutrient requirements for optimum health.

  15. Lactulose and renal failure.

    Science.gov (United States)

    Vogt, B; Frey, F J

    1997-01-01

    The introduction of lactulose as a new therapeutic agent for treatment of hepatic encephalopathy was a major breakthrough in this field. It was hypothesized that lactulose might prevent postoperative renal impairment after biliary surgery in patients with obstructive jaundice. The presumable mechanism purported was the diminished endotoxinemia by lactulose. Unfortunately, such a reno-protective effect has not been shown conclusively until now in clinical studies. In chronic renal failure lactulose is known to promote fecal excretion of water, sodium, potassium, amonium, urea, creatinine and protons. Thus, lactulose could be useful for the treatment of chronic renal failure. However, compliance to the therapy represents a major problem.

  16. Mechanisms of Biliary Plastic Stent Occlusion and Efforts at Prevention

    Science.gov (United States)

    Kwon, Chang-Il; Lehman, Glen A.

    2016-01-01

    Biliary stenting via endoscopic retrograde cholangiopancreatography has greatly improved the quality of patient care over the last 30 years. Plastic stent occlusion limits the life span of such stents. Attempts to improve plastic stent patency duration have mostly failed. Metal stents (self-expandable metal stents [SEMSs]) have therefore replaced plastic stents, especially for malignant biliary strictures. SEMS are at least 10 times more expensive than plastic stents. In this focused review, we will discuss basic mechanisms of plastic stent occlusion, along with a systematic summary of previous efforts and related studies to improve stent patency and potential new techniques to overcome existing limitations. PMID:27000422

  17. Failure mechanisms of lead/acid automotive batteries in service in the U.S.A.

    Science.gov (United States)

    Hoover, John H.; Boden, David P.

    Discarded lead/acid batteries were selected at random without regard to brand or condition and these were inspected and tested to determine the causes of failure. Samples were limited to 12-V automotive passenger-car batteries. Their age was determined from the manufacturing code and shipping date. In addition to the cause of failure, information on battery components and construction was also noted. Data are presented showing the principal modes of failure, the effect of geographical location, and the influence of grid alloy on life. In particular, the differences observed between those batteries utilizing calcium alloy for the positive grids and those using antimony alloy are discussed.

  18. Prevention and treatment of skin lesions associated with non-invasive mechanical ventilation. Recommendations of experts.

    Science.gov (United States)

    Raurell-Torredà, M; Romero-Collado, A; Rodríguez-Palma, M; Farrés-Tarafa, M; Martí, J D; Hurtado-Pardos, B; Peñarrubia-San Florencio, L; Saez-Paredes, P; Esquinas, A M

    In the last two decades, non-invasive mechanical ventilation (NIV) has been consolidated as an initial strategy for the management of respiratory failure in critical adult and paediatric patients. To identify risk factors and preventive strategies to reduce the incidence of skin lesions associated with clinical devices (LESADIC) related to NIV, as well as the most effective treatment for injuries that cannot be avoided. Review in the MEDLINE, CINAHL and Cochrane databases of studies published in the last 10years to reach consensus through an expert panel. Knowledge about how to measure correct mask size and protection of the skin with foam or hydrocolloids dressings are factors related to the incidence of LESADIC, as it conditions the degree of pressure-friction and shear that the interface exerts on the skin. The interface that causes fewer LESADIC and is better tolerated is the face mask. When there are injuries, the first thing is to remove the interface that causes pressure on damaged skin, recommending a Helmet(®) hood as an alternative, treating the infection, managing the exudate and stimulating perilesional skin. The mask of choice is the facial, always using foam or hydrocolloid dressings on the nasal bridge. Evaluate the condition of the skin under the interface and harness every 4hours (recommended) and 11hours (maximum). Evaluate the rotation strategy of the interface at 24hours if the NIV is still needed on an ongoing basis. Copyright © 2017 Sociedad Española de Enfermería Intensiva y Unidades Coronarias (SEEIUC). Publicado por Elsevier España, S.L.U. All rights reserved.

  19. Saying 'No' to PrEP research in Malawi: what constitutes 'failure' in offshored HIV prevention research?

    Science.gov (United States)

    Peterson, Kristin; Folayan, Morenike Oluwatoyin; Chigwedere, Edward; Nthete, Evaristo

    2015-12-01

    Between 2004 and 2005, the first multi-sited clinical trial tested whether an existing, marketed antiretroviral drug, Tenofovir (TDF), could prevent HIV transmission. Referred to as pre-exposure prophylaxis (PrEP), most of these trial sites prematurely closed down. Two sites located in Cambodia and Cameroon received international media attention. But little attention was drawn to sites in Malawi and Nigeria, where university ethicists and research scientists extensively debated PrEP. This article focuses on events that took place in Malawi where there was a prolonged dispute over the scientific rationales of PrEP and not trial specific ethics referred to as 'bioethics'. Specifically, the article discusses debates pertaining to three PrEP trial protocols that were refused ethics approval in Malawi between 2004 and 2009. It is argued that HIV science debates in Malawi are embedded in postcolonial politics--geopolitical histories and state and household economic dispossessions that have created the structural possibilities for Malawi to become an offshore destination for HIV clinical research. As such, ethics in this case does not pertain to trial or bioethical 'failures'. Rather, ethics is located at the scale of imperial relations that give rise to multiple, often invisible, research concerns and constraints.

  20. Bactericidal Immunity to Salmonella in Africans and Mechanisms Causing Its Failure in HIV Infection.

    Science.gov (United States)

    Goh, Yun Shan; Necchi, Francesca; O'Shaughnessy, Colette M; Micoli, Francesca; Gavini, Massimiliano; Young, Stephen P; Msefula, Chisomo L; Gondwe, Esther N; Mandala, Wilson L; Gordon, Melita A; Saul, Allan J; MacLennan, Calman A

    2016-04-01

    Nontyphoidal strains of Salmonella are a leading cause of death among HIV-infected Africans. Antibody-induced complement-mediated killing protects healthy Africans against Salmonella, but increased levels of anti-lipopolysaccharide (LPS) antibodies in some HIV-infected African adults block this killing. The objective was to understand how these high levels of anti-LPS antibodies interfere with the killing of Salmonella. Sera and affinity-purified antibodies from African HIV-infected adults that failed to kill invasive S. Typhimurium D23580 were compared to sera from HIV-uninfected and HIV-infected subjects with bactericidal activity. The failure of sera from certain HIV-infected subjects to kill Salmonella was found to be due to an inherent inhibitory effect of anti-LPS antibodies. This inhibition was concentration-dependent and strongly associated with IgA and IgG2 anti-LPS antibodies (peffect of high concentrations of anti-LPS antibodies is seen with IgM as well as IgG and IgA. No correlation was found between affinity or avidity, or complement deposition or consumption, and inhibition of killing. IgG and IgM classes of anti-S. Typhimurium LPS antibodies from HIV-infected and HIV-uninfected individuals are bactericidal, while at very high concentrations, anti-LPS antibodies of all classes inhibit in vitro killing of Salmonella. This could be due to a variety of mechanisms relating to the poor ability of IgA and IgG2 to activate complement, and deposition of complement at sites where it cannot insert in the bacterial membrane. Vaccine trials are required to understand the significance of lack of in vitro killing by anti-LPS antibodies from a minority of HIV-infected individuals with impaired immune homeostasis.

  1. Platelet aggregation measurement for assessment of hemostasis failure mechanisms in patients with gastroduodenal ulcer bleeding

    Science.gov (United States)

    Barinov, Edward; Sulaieva, Oksana; Lyakch, Yuriy; Guryanov, Vitaliy; Kondratenko, Petr; Radenko, Yevgeniy

    2013-01-01

    Background The purpose of this study was to identify factors associated with the risk of unsustainable hemostasis in patients with gastric and duodenal ulcer bleeding by in vitro assessment of platelet reactivity using artificial neural networks. Methods Patients with gastroduodenal ulcers complicated by bleeding were studied. Platelet aggregation was measured using aggregometry with adenosine diphosphate 5 μM, epinephrine 2.5 μM, 5-hydroxytryptophan 10 μM, collagen 1 μM, and thrombin 0.06 NIH Unit/mL as agonists. Multiple logistic regression was used to evaluate the independent relationship between demographic, clinical, endoscopic, and laboratory data and in vitro assessment of platelet reactivity and local parameters of hemostasis in patients with ulcer bleeding. Results Analysis of platelet aggregation in patients with gastroduodenal ulcer bleeding allowed the variability of platelet response to different agonists used in effective concentration which induces 50% platelet aggregation (EC50) to be established. The relationship between platelet aggregation and the spatial-temporal characteristics of ulcers complicated by bleeding was demonstrated. Adrenoreactivity of platelets was associated with time elapsed since the start of ulcer bleeding and degree of hemorrhage. The lowest platelet response to collagen and thrombin was detected in patients with active bleeding (P < 0.001) and unsustainable recent bleeding (P < 0.01). Decreased adenosine diphosphate-induced platelet aggregation in patients with ulcer bleeding was correlated with the platelet response to thrombin (r = 0.714, P < 0.001) and collagen (r = 0.584, P < 0.01). Conclusion Estimation of platelet reactivity in vitro indicates the key mechanisms of failure of hemostasis in patients with ulcer bleeding. In addition to gender, an important determinant of unsustainable hemostasis was a decreased platelet response to thrombin and adenosine diphosphate. PMID:23950655

  2. Exhaustion of Frank-Starling mechanism in conscious dogs with heart failure.

    Science.gov (United States)

    Komamura, K; Shannon, R P; Ihara, T; Shen, Y T; Mirsky, I; Bishop, S P; Vatner, S F

    1993-10-01

    The goal of this study was to elucidate the ability of the left ventricle to accommodate an increase in preload (Frank-Starling mechanism) in the presence of congestive heart failure (CHF) but in the absence of the complicating effects of hypertrophy and fibrosis. To accomplish this, the effects of volume loading were examined in eight conscious dogs during the control state and after 3 wk of right ventricular pacing (240 beats/min). CHF increased heart rate (by 16 +/- 5 from 92 +/- 5 beats/min), left ventricular (LV) end-diastolic pressure (by 17 +/- 2 from 10 +/- 1 mmHg), and LV end-diastolic volume (EDV; by 23 +/- 4 from 57 +/- 3 ml). Despite reduced LV ejection fraction (from 54 +/- 3 to 31 +/- 3%), there was no significant change in cardiac output (2.5 +/- 0.3 l/min) compared with control (2.7 +/- 0.2 l/min). Stroke volume was preserved (control 19 +/- 2 ml; CHF 18 +/- 2 ml) at a constant heart rate by a shift to the right in the relationship between LV stroke volume and EDV, indicating the importance of chronic ventricular dilatation in maintaining pump performance. In the control state, acute volume load increased LV EDV (by 17 +/- 2 ml) and stroke volume (by 11 +/- 2 ml), whereas in CHF it did not increase LV EDV or stroke volume. Scanning electron microscopy revealed areas of reduced collagen weave pattern surrounding myofibers. Myocyte cross-sectional area by transmission electron microscopy was significantly reduced, and there were multiple electron-dense expansions of the Z lines with disruption of the normal lateral sarcomere alignment. These morphological findings suggest that chronic ventricular dilatation utilized in CHF results from myocyte stretch and morphological intracellular rearrangement. Furthermore, the failing heart cannot further augment stroke volume by acutely increasing EDV in CHF, suggesting that the Frank-Starling reserve is essentially exhausted.

  3. Prevention of disabling back injuries in nurses by the use of mechanical patient lift systems.

    Science.gov (United States)

    Edlich, Richard F; Winters, Kathryne L; Hudson, Mary Anne; Britt, L D; Long, William B

    2004-01-01

    Occupational back pain in nurses (OBPN) constitutes a major source of morbidity in the health care environment. According to the National Institute for Occupational Safety and Health (NIOSH), occupational back injury is the second leading occupational injury in the United States. Among health care personnel, nurses have the highest rate of back pain, with an annual prevalence of 40-50% and a lifetime prevalence of 35-80%. The American Nursing Association believes that manual patient handling is unsafe and is directly responsible for musculoskeletal disorders encountered in nurses. It has been well documented that patient handling can be done safely with the use of assistive equipment and devices that eliminate these hazards to nurses that invite serious back injuries. The benefit of assistive patient handling equipment is characterized by the simultaneous reduction of the risk of musculoskeletal injury to the nursing staff and improvement in the quality of care for patient populations. To understand the cause of disabling injuries in health care workers, several factors must be considered, including the following: (1) anatomy/physiology of the back, (2) risk factors, (3) medical legal implications, and (4) prevention. Among nurses, back, neck, and shoulder injuries are commonly noted as the most prevalent and debilitating. While mostly associated with dependant patient care, the risk for musculoskeletal injury secondary to manual patient handling crosses all specialty areas of nursing. The skeletal defects of an abnormal back make the back more susceptible to occupational injury, even under normal stress conditions. Workers compensation guidelines for occupational back injury differ in public and private health care sectors from state to state. Nursing personnel should be reminded that the development of back pain following occupational activities in the hospital should be reported immediately to the Occupational Health Department. A nurse's failure to report OBPN

  4. The impact of stylolites on brittle failure of carbonates: mechanical data and numerical simulations

    Science.gov (United States)

    Baud, Patrick; Heap, Michael; Xu, Tao; Rolland, Alexandra; Ferrand, Thomas; Nicolé, Marion; Reuschlé, Thierry; Conil, Nathalie

    2015-04-01

    orthogonal to the loading, microcracks clearly appeared to nucleate from the stylolite. Whatever the stylolite orientation, the macroscopic fracture appeared to follow only small parts of the tortuous stylolite path. Numerical simulations were performed using stochastic modelling and the Failure and Process Analysis Code (RPFA). Two dimensional numerical samples (40 mm x 20 mm) consisted of 51200 (320 x 120) square elements were deformed uniaxially. To reflect material heterogeneity on the microscale, each square was assigned a value of strength (tensile and compressive) and Young's modulus using a Weibull probability density function. The model parameters were first set to reproduce the mechanical behavior of the stylolite-free material. Guided by our microstructural analysis we then introduced a weaker layer in several orientations in the numerical samples. The simulations showed good qualitative agreement with the experiments performed on samples with stylolites. Our study showed that stylolites have more impact of the mechanical properties than on fluid flow in the limestone from Bure.

  5. Andreas Acrivos Dissertation Award: Onset of Dynamic Wetting Failure - The Mechanics of High-Speed Fluid Displacement

    Science.gov (United States)

    Vandre, Eric

    2014-11-01

    Dynamic wetting is crucial to processes where a liquid displaces another fluid along a solid surface, such as the deposition of a coating liquid onto a moving substrate. Dynamic wetting fails when process speed exceeds some critical value, leading to incomplete fluid displacement and transient phenomena that impact a variety of applications, such as microfluidic devices, oil-recovery systems, and splashing droplets. Liquid coating processes are particularly sensitive to wetting failure, which can induce air entrainment and other catastrophic coating defects. Despite the industrial incentives for careful control of wetting behavior, the hydrodynamic factors that influence the transition to wetting failure remain poorly understood from empirical and theoretical perspectives. This work investigates the fundamentals of wetting failure in a variety of systems that are relevant to industrial coating flows. A hydrodynamic model is developed where an advancing fluid displaces a receding fluid along a smooth, moving substrate. Numerical solutions predict the onset of wetting failure at a critical substrate speed, which coincides with a turning point in the steady-state solution path for a given set of system parameters. Flow-field analysis reveals a physical mechanism where wetting failure results when capillary forces can no longer support the pressure gradients necessary to steadily displace the receding fluid. Novel experimental systems are used to measure the substrate speeds and meniscus shapes associated with the onset of air entrainment during wetting failure. Using high-speed visualization techniques, air entrainment is identified by the elongation of triangular air films with system-dependent size. Air films become unstable to thickness perturbations and ultimately rupture, leading to the entrainment of air bubbles. Meniscus confinement in a narrow gap between the substrate and a stationary plate is shown to delay air entrainment to higher speeds for a variety of

  6. Mechanical assessment of local bone quality to predict failure of locked plating in a proximal humerus fracture model.

    Science.gov (United States)

    Röderer, Götz; Brianza, Stefano; Schiuma, Damiano; Schwyn, Ronald; Scola, Alexander; Gueorguiev, Boyko; Gebhard, Florian; Tami, Andrea

    2013-09-01

    The importance of osteoporosis in proximal humerus fractures is well recognized. However, the local distribution of bone quality in the humeral head may also have a significant effect because it remains unclear in what quality of bone screws of standard implants purchase. The goal of this study was to investigate whether the failure of proximal humerus locked plating can be predicted by the DensiProbe (ARI, Davos, Switzerland). A 2-part fracture with metaphyseal impaction was simulated in 12 fresh-frozen human cadaveric humeri. Using the DensiProbe, local bone quality was determined in the humeral head in the course of 6 proximal screws of a standard locking plate (Philos; Synthes GmbH, Solothurn, Switzerland). Cyclic mechanical testing with increasing axial loading until failure was performed. Bone mineral density (BMD) significantly correlated with cycles until failure. Head migration significantly increased between 1000 and 2000 loading cycles and significantly correlated with BMD after 3000 cycles. DensiProbe peak torque in all screw positions and their respective mean torque correlated significantly with the BMD values. In 3 positions, the peak torque significantly correlated with cycles to failure; here BMD significantly influenced mechanical stability. The validity of the DensiProbe was proven by the correlation between its peak torque measurements and BMD. The correlation between the peak torque and cycles to failure revealed the potential of the DensiProbe to predict the failure of locked plating in vitro. This method provides information about local bone quality, potentially making it suitable for intraoperative use by allowing the surgeon to take measures to improve stability.

  7. Failure Mechanical Behavior of Australian Strathbogie Granite at High Temperatures: Insights from Particle Flow Modeling

    Directory of Open Access Journals (Sweden)

    Sheng-Qi Yang

    2017-05-01

    Full Text Available Thermally induced damage has an important influence on rock mechanics and engineering, especially for high-level radioactive waste repositories, geological carbon storage, underground coal gasification, and hydrothermal systems. Additionally, the wide application of geothermal heat requires knowledge of the geothermal conditions of reservoir rocks at elevated temperature. However, few methods to date have been reported for investigating the micro-mechanics of specimens at elevated temperatures. Therefore, this paper uses a cluster model in particle flow code in two dimensions (PFC2D to simulate the uniaxial compressive testing of Australian Strathbogie granite at various elevated temperatures. The peak strength and ultimate failure mode of the granite specimens at different elevated temperatures obtained by the numerical methods are consistent with those obtained by experimentation. Since the tensile force is always concentrated around the boundary of the crystal, cracks easily occur at the intergranular contacts, especially between the b-b and b-k boundaries where less intragranular contact is observed. The intergranular and intragranular cracking of the specimens is almost constant with increasing temperature at low temperature, and then it rapidly and linearly increases. However, the inflection point of intergranular micro-cracking is less than that of intragranular cracking. Intergranular cracking is more easily induced by a high temperature than intragranular cracking. At an elevated temperature, the cumulative micro-crack counts curve propagates in a stable way during the active period, and it has no unstable crack propagation stage. The micro-cracks and parallel bond forces in the specimens with elevated temperature evolution and axial strain have different characteristics than those at lower temperature. More branch fractures and isolated wider micro-cracks are generated with increasing temperature when the temperature is over 400

  8. Anterior cruciate ligament injuries in soccer: Loading mechanisms, risk factors, and prevention programs

    Directory of Open Access Journals (Sweden)

    Boyi Dai

    2014-12-01

    Full Text Available Anterior cruciate ligament (ACL injuries are common in soccer. Understanding ACL loading mechanisms and risk factors for ACL injury is critical for designing effective prevention programs. The purpose of this review is to summarize the relevant literature on ACL loading mechanisms, ACL injury risk factors, and current ACL injury prevention programs for soccer players. Literature has shown that tibial anterior translation due to shear force at the proximal end of tibia is the primary ACL loading mechanism. No evidence has been found showing that knee valgus moment is the primary ACL loading mechanism. ACL loading mechanisms are largely ignored in previous studies on risk factors for ACL injury. Identified risk factors have little connections to ACL loading mechanisms. The results of studies on ACL injury prevention programs for soccer players are inconsistent. Current ACL injury prevention programs for soccer players are clinically ineffective due to low compliance. Future studies are urgently needed to identify risk factors for ACL injury in soccer that are connected to ACL loading mechanisms and have cause-and-effect relationships with injury rate, and to develop new prevention programs to improve compliance.

  9. Influence of intermediate principal stress on failure mechanism of hard rock with a pre-existing circular opening

    Institute of Scientific and Technical Information of China (English)

    张社荣; 孙博; 王超; 严磊

    2014-01-01

    Based on particle flow theory, the influences of the magnitude and direction of the intermediate principal stress on failure mechanism of hard rock with a pre-existing circular opening were studied by carrying out true triaxial tests on siltstone specimen. It is shown that peak strength of siltstone specimen increases firstly and subsequently decreases with the increase of the intermediate principal stress. And its turning point is related to the minimum principal stress and the direction of the intermediate principal stress. Failure characteristic (brittleness or ductility) of siltstone is determined by the minimum principal stress and the difference between the intermediate and minimum principal stress. The intermediate principal stress has a significant effect on the types and distributions of microcracks. The failure modes of the specimen are determined by the magnitude and direction of the intermediate principal stress, and related to weakening effect of the opening and inhibition effect of confining pressure in essence:when weakening effect of the opening is greater than inhibition effect of confining pressure, the failure surface is parallel to the x axis (such as σ2=σ3=0 MPa);conversely, the failure surface is parallel to the z axis (such asσ2=20 MPa,σ3=0 MPa).

  10. Exertional dyspnoea in chronic heart failure: the role of the lung and respiratory mechanical factors

    OpenAIRE

    Bruno-Pierre Dubé; Piergiuseppe Agostoni; Pierantonio Laveneziana

    2016-01-01

    Exertional dyspnoea is among the dominant symptoms in patients with chronic heart failure and progresses relentlessly as the disease advances, leading to reduced ability to function and engage in activities of daily living. Effective management of this disabling symptom awaits a better understanding of its underlying physiology. Cardiovascular factors are believed to play a major role in dyspnoea in heart failure patients. However, despite pharmacological interventions, such as vasodilators o...

  11. Innovation in Bio-disaster Prevention and Control Mechanism after Forest Tenure Reform at County Level

    Institute of Scientific and Technical Information of China (English)

    ZHAN Zu-ren

    2012-01-01

    Taking Youxi County of Fujian Province as an example,the author introduced basic situations of new bio-disaster prevention and control mechanism for forest resource protection and social service works after the forest tenure reform.Then,the author analyzed new problems faced by bio-disaster prevention and control in forestry.Finally,the author present the existing problems of bio-disaster prevention and control at the county level from five aspects:innovating upon plant quarantine management mechanism;innovation upon survey methods and service modes of bio-disaster monitoring;strengthening and improving construction of bio-disaster monitoring and forecasting network;innovating upon management system for bio-disaster prevention and control;speeding up construction of service system for social prevention and control of bio-disasters.

  12. Preventive and Prophylactic Mechanisms of Action of Pomegranate Bioactive Constituents

    Directory of Open Access Journals (Sweden)

    Monica Viladomiu

    2013-01-01

    Full Text Available Pomegranate fruit presents strong anti-inflammatory, antioxidant, antiobesity, and antitumoral properties, thus leading to an increased popularity as a functional food and nutraceutical source since ancient times. It can be divided into three parts: seeds, peel, and juice, all of which seem to have medicinal benefits. Several studies investigate its bioactive components as a means to associate them with a specific beneficial effect and develop future products and therapeutic applications. Many beneficial effects are related to the presence of ellagic acid, ellagitannins (including punicalagins, punicic acid and other fatty acids, flavonoids, anthocyanidins, anthocyanins, estrogenic flavonols, and flavones, which seem to be its most therapeutically beneficial components. However, the synergistic action of the pomegranate constituents appears to be superior when compared to individual constituents. Promising results have been obtained for the treatment of certain diseases including obesity, insulin resistance, intestinal inflammation, and cancer. Although moderate consumption of pomegranate does not result in adverse effects, future studies are needed to assess safety and potential interactions with drugs that may alter the bioavailability of bioactive constituents of pomegranate as well as drugs. The aim of this review is to summarize the health effects and mechanisms of action of pomegranate extracts in chronic inflammatory diseases.

  13. Preventive and prophylactic mechanisms of action of pomegranate bioactive constituents.

    Science.gov (United States)

    Viladomiu, Monica; Hontecillas, Raquel; Lu, Pinyi; Bassaganya-Riera, Josep

    2013-01-01

    Pomegranate fruit presents strong anti-inflammatory, antioxidant, antiobesity, and antitumoral properties, thus leading to an increased popularity as a functional food and nutraceutical source since ancient times. It can be divided into three parts: seeds, peel, and juice, all of which seem to have medicinal benefits. Several studies investigate its bioactive components as a means to associate them with a specific beneficial effect and develop future products and therapeutic applications. Many beneficial effects are related to the presence of ellagic acid, ellagitannins (including punicalagins), punicic acid and other fatty acids, flavonoids, anthocyanidins, anthocyanins, estrogenic flavonols, and flavones, which seem to be its most therapeutically beneficial components. However, the synergistic action of the pomegranate constituents appears to be superior when compared to individual constituents. Promising results have been obtained for the treatment of certain diseases including obesity, insulin resistance, intestinal inflammation, and cancer. Although moderate consumption of pomegranate does not result in adverse effects, future studies are needed to assess safety and potential interactions with drugs that may alter the bioavailability of bioactive constituents of pomegranate as well as drugs. The aim of this review is to summarize the health effects and mechanisms of action of pomegranate extracts in chronic inflammatory diseases.

  14. Sequential mechanical ventilation improves hemodynamics, cardiac function and neurohumoral status in elderly patients with acute left heart failure

    Institute of Scientific and Technical Information of China (English)

    Xing-Hong Zeng; Ming Chen; Qi Cao; Yan-Xia Chen

    2016-01-01

    Objective:To analyze the effect of sequential mechanical ventilation on improving hemodynamics, cardiac function and neurohumoral status in elderly patients with acute left heart failure.Methods:A total of 90 cases of elderly patients with acute left heart failure were randomly divided into observation group and control group, control group received conventional mechanical ventilation therapy, observation group received sequential mechanical ventilation, and then differences in hemodynamics, cardiac function and neurohumoral status were compared between two groups after treatment.Results:24 h after treatment, mPAP, PCWP and RAP levels of observation group after treatment were lower than those of control group, and CO level was higher than that of control group; LVEF value was higher than that of control group, and SVR, LVEDV and LVESV values were lower than those of control group; 12 h and 24 h after treatment, plasma Nt-proBNP, ANP, R, AngⅡ and ALD levels of observation group were significantly lower than those of control group.Conclusion:Sequential mechanical ventilation can optimize the illness in elderly patients with acute left heart failure, and plays a positive role in promoting patients' cardiac function recovery, restoring homeostasis and other aspects.

  15. The EARLY ALLIANCE prevention trial: a dual design to test reduction of risk for conduct problems, substance abuse, and school failure in childhood.

    Science.gov (United States)

    Prinz, R J; Dumas, J E; Smith, E P; Laughlin, J E

    2000-06-01

    This paper describes a preventive intervention trial called EARLY ALLIANCE which is aimed at reducing risk for three adverse outcomes in childhood and adolescence: conduct problems, substance abuse, and school failure. The structure of the prevention trial is unique because two linked designs are being implemented concurrently. The primary design focuses on children at elevated risk for adverse outcomes, and compares a targeted, multicontextual preventive intervention with family, classroom, peer relational, and academic components to a universal, schoolwide preventive intervention that emphasizes peaceful conflict management and serves as a "usual care" control condition. The secondary design focuses on children at lower risk for adverse outcomes and compares a universally administered classroom program to the control condition. The paper describes the theoretical foundation for EARLY ALLIANCE, the goals of the prevention trial, the rationale for design choices, and the methods employed.

  16. Investigation of wrinkling failure mechanics in metal spinning by Box-Behnken design of experiments using finite element method

    OpenAIRE

    Watson, M.; Van Long, H.; Lu, B

    2014-01-01

    An investigation into material wrinkling failure mechanics of conventional metal spinning and the effects of process parameters and material properties are presented in this paper. By developing finite element (FE) models using the Box-Behnken design of experiments, the effects of six key process and material parameters on the start of material wrinkling have been investigated. These key factors include roller feed per pass, feed rate, blank thickness, tool path profile, material Young’s modu...

  17. Bactericidal Immunity to Salmonella in Africans and Mechanisms Causing Its Failure in HIV Infection.

    Directory of Open Access Journals (Sweden)

    Yun Shan Goh

    2016-04-01

    Full Text Available Nontyphoidal strains of Salmonella are a leading cause of death among HIV-infected Africans. Antibody-induced complement-mediated killing protects healthy Africans against Salmonella, but increased levels of anti-lipopolysaccharide (LPS antibodies in some HIV-infected African adults block this killing. The objective was to understand how these high levels of anti-LPS antibodies interfere with the killing of Salmonella.Sera and affinity-purified antibodies from African HIV-infected adults that failed to kill invasive S. Typhimurium D23580 were compared to sera from HIV-uninfected and HIV-infected subjects with bactericidal activity. The failure of sera from certain HIV-infected subjects to kill Salmonella was found to be due to an inherent inhibitory effect of anti-LPS antibodies. This inhibition was concentration-dependent and strongly associated with IgA and IgG2 anti-LPS antibodies (p<0.0001 for both. IgG anti-LPS antibodies, from sera of HIV-infected individuals that inhibit killing at high concentration, induced killing when diluted. Conversely, IgG, from sera of HIV-uninfected adults that induce killing, inhibited killing when concentrated. IgM anti-LPS antibodies from all subjects also induced Salmonella killing. Finally, the inhibitory effect of high concentrations of anti-LPS antibodies is seen with IgM as well as IgG and IgA. No correlation was found between affinity or avidity, or complement deposition or consumption, and inhibition of killing.IgG and IgM classes of anti-S. Typhimurium LPS antibodies from HIV-infected and HIV-uninfected individuals are bactericidal, while at very high concentrations, anti-LPS antibodies of all classes inhibit in vitro killing of Salmonella. This could be due to a variety of mechanisms relating to the poor ability of IgA and IgG2 to activate complement, and deposition of complement at sites where it cannot insert in the bacterial membrane. Vaccine trials are required to understand the significance of

  18. Platelet aggregation measurement for assessment of hemostasis failure mechanisms in patients with gastroduodenal ulcer bleeding

    Directory of Open Access Journals (Sweden)

    Barinov E

    2013-08-01

    = 0.584, P < 0.01. Conclusion: Estimation of platelet reactivity in vitro indicates the key mechanisms of failure of hemostasis in patients with ulcer bleeding. In addition to gender, an important determinant of unsustainable hemostasis was a decreased platelet response to thrombin and adenosine diphosphate. Keywords: ulcer, hemostasis, blood platelets

  19. Bactericidal Immunity to Salmonella in Africans and Mechanisms Causing Its Failure in HIV Infection

    Science.gov (United States)

    Goh, Yun Shan; Necchi, Francesca; O’Shaughnessy, Colette M.; Micoli, Francesca; Gavini, Massimiliano; Young, Stephen P.; Msefula, Chisomo L.; Gondwe, Esther N.; Mandala, Wilson L.; Gordon, Melita A.; Saul, Allan J.; MacLennan, Calman A.

    2016-01-01

    Background Nontyphoidal strains of Salmonella are a leading cause of death among HIV-infected Africans. Antibody-induced complement-mediated killing protects healthy Africans against Salmonella, but increased levels of anti-lipopolysaccharide (LPS) antibodies in some HIV-infected African adults block this killing. The objective was to understand how these high levels of anti-LPS antibodies interfere with the killing of Salmonella. Methodology/Principal Findings Sera and affinity-purified antibodies from African HIV-infected adults that failed to kill invasive S. Typhimurium D23580 were compared to sera from HIV-uninfected and HIV-infected subjects with bactericidal activity. The failure of sera from certain HIV-infected subjects to kill Salmonella was found to be due to an inherent inhibitory effect of anti-LPS antibodies. This inhibition was concentration-dependent and strongly associated with IgA and IgG2 anti-LPS antibodies (p<0.0001 for both). IgG anti-LPS antibodies, from sera of HIV-infected individuals that inhibit killing at high concentration, induced killing when diluted. Conversely, IgG, from sera of HIV-uninfected adults that induce killing, inhibited killing when concentrated. IgM anti-LPS antibodies from all subjects also induced Salmonella killing. Finally, the inhibitory effect of high concentrations of anti-LPS antibodies is seen with IgM as well as IgG and IgA. No correlation was found between affinity or avidity, or complement deposition or consumption, and inhibition of killing. Conclusion/Significance IgG and IgM classes of anti-S. Typhimurium LPS antibodies from HIV-infected and HIV-uninfected individuals are bactericidal, while at very high concentrations, anti-LPS antibodies of all classes inhibit in vitro killing of Salmonella. This could be due to a variety of mechanisms relating to the poor ability of IgA and IgG2 to activate complement, and deposition of complement at sites where it cannot insert in the bacterial membrane. Vaccine trials

  20. Race, Gender, and Age Differences in Heart Failure-Related Hospitalizations in a Southern State: Implications for Prevention

    Science.gov (United States)

    Husaini, Baqar A.; Mensah, George A.; Sawyer, Douglas; Cain, Van A.; Samad, Zahid; Hull, Pamela C.; Levine, Robert S.; Sampson, Uchechukwu K. A.

    2011-01-01

    Background Since heart failure (HF) is the final common pathway for most heart diseases, we examined its 10-year prevalence trend by race, gender, and age in Tennessee. Methods and Results HF hospitalization data from the Tennessee Hospital Discharge Data System were analyzed by race, gender and age. Rates were directly age-adjusted using the Year 2000 standard population. Adult (age 20+) in-patient hospitalization for primary diagnosis of HF (HFPD) increased from 4.2% in 1997 to 4.5% in 2006. Age-adjusted hospitalization for HF (per 10,000 population) rose by 11.3% (from 29.3 in 1997 to 32.6 in 2006). Parallel changes in secondary HF admissions were also noted. Age-adjusted rates were higher among blacks than whites and higher among men than women. The ratios of black to white by gender admitted with HFPD in 2006 were highest (9:1) among the youngest age categories (20-34 and 35-44 years). Furthermore, for each age category of black men below 65 years, there were higher HF admission rates than for white men in the immediate older age category. In 2006, the adjusted rate ratios for HFPD in black to white men aged 20-34 and 35-44 years were OR=4.75, CI (3.29-6.86) and OR 5.10, CI (4.15-6.25) respectively. Hypertension was the independent predictor of HF admissions in black men age 20-34 years. Conclusions The higher occurrence of HF among young adults in general, particularly among young black men, highlights the need for prevention by identifying modifiable biological and social determinants in order to reduce cardiovascular health disparities in this vulnerable group. PMID:21178017

  1. Effects of Service Condition on Rolling Contact Fatigue Failure Mechanism and Lifetime of Thermal Spray Coatings-A Review

    Institute of Scientific and Technical Information of China (English)

    CUI Huawei; CUI Xiufang; WANG Haidou; XING Zhiguo; JIN Guo

    2015-01-01

    The service condition determines the Rolling Contact Fatigue(RCF) failure mechanism and lifetime under ascertain material structure integrity parameter of thermal spray coating. The available literature on the RCF testing of thermal spray coatings under various condition services is considerable;it is generally difficult to synthesize all of the result to obtain a comprehensive understanding of the parameters which has a great effect on a thermal spray coating’s resistance of RCF. The effects of service conditions(lubrication states, contact stresses, revolve speed, and slip ratio) on the changing of thermal spray coatings’ contact fatigue lifetime is introduced systematically. The effects of different service condition on RCF failure mechanism of thermal spray coating from the change of material structure integrity are also summarized. Moreover, In order to enhance the RCF performance, the parameter optimal design formula of service condition and material structure integrity is proposed based on the effect of service condition on thermal spray coatings’ contact fatigue lifetime and RCF failure mechanism. The shortage of available literature and the forecast focus in future researches are discussed based on available research. The explicit result of RCF lifetime law and parameter optimal design formula in term of lubrication states, contact stresses, revolve speed, and slip ratio, is significant to improve the RCF performance on the engineering application.

  2. Adaptive coupling between damage mechanics and peridynamics: A route for objective simulation of material degradation up to complete failure

    Science.gov (United States)

    Han, Fei; Lubineau, Gilles; Azdoud, Yan

    2016-09-01

    The objective (mesh-independent) simulation of evolving discontinuities, such as cracks, remains a challenge. Current techniques are highly complex or involve intractable computational costs, making simulations up to complete failure difficult. We propose a framework as a new route toward solving this problem that adaptively couples local-continuum damage mechanics with peridynamics to objectively simulate all the steps that lead to material failure: damage nucleation, crack formation and propagation. Local-continuum damage mechanics successfully describes the degradation related to dispersed microdefects before the formation of a macrocrack. However, when damage localizes, it suffers spurious mesh dependency, making the simulation of macrocracks challenging. On the other hand, the peridynamic theory is promising for the simulation of fractures, as it naturally allows discontinuities in the displacement field. Here, we present a hybrid local-continuum damage/peridynamic model. Local-continuum damage mechanics is used to describe "volume" damage before localization. Once localization is detected at a point, the remaining part of the energy is dissipated through an adaptive peridynamic model capable of the transition to a "surface" degradation, typically a crack. We believe that this framework, which actually mimics the real physical process of crack formation, is the first bridge between continuum damage theories and peridynamics. Two-dimensional numerical examples are used to illustrate that an objective simulation of material failure can be achieved by this method.

  3. Adaptive coupling between damage mechanics and peridynamics: a route for objective simulation of material degradation up to complete failure

    KAUST Repository

    Han, Fei

    2016-05-17

    The objective (mesh-independent) simulation of evolving discontinuities, such as cracks, remains a challenge. Current techniques are highly complex or involve intractable computational costs, making simulations up to complete failure difficult. We propose a framework as a new route toward solving this problem that adaptively couples local-continuum damage mechanics with peridynamics to objectively simulate all the steps that lead to material failure: damage nucleation, crack formation and propagation. Local-continuum damage mechanics successfully describes the degradation related to dispersed microdefects before the formation of a macrocrack. However, when damage localizes, it suffers spurious mesh dependency, making the simulation of macrocracks challenging. On the other hand, the peridynamic theory is promising for the simulation of fractures, as it naturally allows discontinuities in the displacement field. Here, we present a hybrid local-continuum damage/peridynamic model. Local-continuum damage mechanics is used to describe “volume” damage before localization. Once localization is detected at a point, the remaining part of the energy is dissipated through an adaptive peridynamic model capable of the transition to a “surface” degradation, typically a crack. We believe that this framework, which actually mimics the real physical process of crack formation, is the first bridge between continuum damage theories and peridynamics. Two-dimensional numerical examples are used to illustrate that an objective simulation of material failure can be achieved by this method.

  4. Mitigating Link Failures & Implementing Security Mechanism in Multipath Flows for Data Plane Resources

    Directory of Open Access Journals (Sweden)

    Ramya M

    2016-03-01

    Full Text Available The transmission of a traffic flows with a certain bandwidth demand over a single network path is either not possible or not cost-effective. In these cases, it is veritably periodic usable to improve focus the network's bandwidth appliance by breaking the traffic flow upon multiple qualified paths. Using multiple paths for the equivalent traffic flow increases the certainty of the network, it absorbs deluxe forwarding resources from the network nodes and also it overcomes link failure provide security. In this paper, we illustrate several problems related to splitting a traffic flow over multiple paths while minimizing the absorption of forwarding resources mitigates failures and implementing security.

  5. 3D constitutive model of anisotropic damage for unidirectional ply based on physical failure mechanisms

    DEFF Research Database (Denmark)

    Qing, Hai; Mishnaevsky, Leon

    2010-01-01

    A 3D anisotropic continuum damage model is developed for the computational analysis of the elastic–brittle behaviour of fibre-reinforced composite. The damage model is based on a set of phenomenological failure criteria for fibre-reinforced composite, which can distinguish the matrix and fibre...... failure under tensile and compressive loading. The homogenized continuum theory is adopted for the anisotropic elastic damage constitutive model. The damage modes occurring in the longitudinal and transverse directions of a ply are represented by a damage vector. The elastic damage model is implemented...

  6. A low-carbohydrate diet may prevent end-stage renal failure in type 2 diabetes. A case report

    Directory of Open Access Journals (Sweden)

    Westerlund Per

    2006-06-01

    Full Text Available Abstract An obese patient with type 2 diabetes whose diet was changed from the recommended high-carbohydrate, low-fat type to a low-carbohydrate diet showed a significant reduction in bodyweight, improved glycemic control and a reversal of a six year long decline of renal function. The reversal of the renal function was likely caused by both improved glycemic control and elimination of the patient's obesity. Insulin treatment in type 2 diabetes patients usually leads to weight increase which may cause further injury to the kidney. Although other unknown metabolic mechanisms cannot be excluded, it is likely that the obesity caused by the combination of high-carbohydrate diet and insulin in this case contributed to the patient's deteriorating kidney function. In such patients, where control of bodyweight and hyperglycemia is vital, a trial with a low-carbohydrate diet may be appropriate to avoid the risk of adding obesity-associated renal failure to already failing kidneys.

  7. Oral administration of both tetrahydrobiopterin and L-arginine prevents endothelial dysfunction in rats with chronic renal failure.

    Science.gov (United States)

    Yamamizu, Kohei; Shinozaki, Kazuya; Ayajiki, Kazuhide; Gemba, Munekazu; Okamura, Tomio

    2007-03-01

    We examined the mechanism of endothelial dysfunction in chronic renal failure (CRF), with reference to NO synthase. CRF was induced by 5/6 nephrectomy in rats. Either L-arginine (1.25 g/L in drinking water), tetrahydrobiopterin (BH4, 10 mg/kg per day in food), or a combination of the 2 were orally administered to CRF rats for 9 weeks. CRF rats showed elevation of systolic blood pressure compared with sham-operated rats. Endothelium-dependent relaxation induced by acetylcholine or A23187 in the isolated aorta was significantly reduced, and in vitro treatment with L-arginine, BH4, or superoxide dismutase restored the relaxation. Aortic segments from CRF rats showed significantly higher superoxide production in response to A23187, which was inhibited by L-NAME. Plasma concentrations of asymmetric dimethylarginine and symmetric dimethylarginine were higher in CRF rats. These changes in CRF rats were totally or partially decreased by L-arginine or BH4 supplementation in vivo. Interestingly, the combined treatment showed additive effects in certain parameters. These results suggest that vascular disorders in CRF rats may be partly due to NOS uncoupling caused by a relative deficiency of BH4 and partially due to accumulation of endogenous inhibitors of NOS and L-arginine uptake, resulting in the decrease of NO production and the increase of reactive oxygen species.

  8. Tribocorrosion Failure Mechanism of TiN/SiOx Duplex Coating Deposited on AISI304 Stainless Steel

    Directory of Open Access Journals (Sweden)

    Qiang Chen

    2016-11-01

    Full Text Available TiN/SiOx duplex coatings were synthesized on AISI304 stainless steel by plasma immersion ion implantation and deposition (PIIID followed by radio frequency magnetron sputtering (RFMS. The microstructure and tribocorrosion failure behaviors of the duplex coatings were investigated by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, atomic force microscopy, reciprocating-sliding tribometer, and electrochemical tests. The as-deposited duplex coating had a two-layered columnar growth structure consisting of face-centered cubic TiN and amorphous SiOx. Sliding tests showed that the TiN interlayer had good adhesion with the substrate, but the SiOx layer suffered from severe delamination failure. Friction force induced a number of micro-cracks in the coating, which provided channels for the diffusion of NaCl solution. The tribocorrosion test showed that the duplex coating exhibited a lower wear-performance in NaCl solution than in ambient atmosphere. Multi-scale chloride ion corrosion occurred simultaneously and substantially degraded the bonding strength of the columnar crystals or neighboring layers. Force-corrosion synergy damage eventually led to multi-degradation failure of the duplex coating. The presented results provide a comprehensive understanding of the tribocorrosion failure mechanism in coatings with duplex architecture.

  9. Seepage and piping: Solitary and integrated mechanisms of streambank erosion and failure

    Science.gov (United States)

    Recent work has shown that a majority of the sediment entering streams and rivers now comes from streambanks. We lack the understanding of the processes controlling streambank failure to be able to predict how erosion control methods will work for all conditions. Research underway at Oklahoma State...

  10. Fatigue degradation and failure of rotating composite structures - Materials characterisation and underlying mechanisms

    DEFF Research Database (Denmark)

    Gamstedt, Kristofer; Andersen, Svend Ib Smidt

    2001-01-01

    The present review concerns rotating composite structures, in which fatigue degradation is of key concern for in-service failure. Such applications are for instance rotor blades in wind turbines, helicopter rotor blades, flywheels for energy storage,marine and aeronautical propellers, and rolls...

  11. Full-Field Strain Methods for Investigating Failure Mechanisms in Triaxial Braided Composites

    Science.gov (United States)

    Littell, Justin D.; Binienda, Wieslaw K.; Goldberg, Robert K.; Roberts, Gary D.

    2008-01-01

    Recent advancements in braiding technology have led to commercially viable manufacturing approaches for making large structures with complex shape out of triaxial braided composite materials. In some cases, the static load capability of structures made using these materials has been higher than expected based on material strength properties measured using standard coupon tests. A more detailed investigation of deformation and failure processes in large-unit-cell-size triaxial braid composites is needed to evaluate the applicability of standard test methods for these materials and to develop alternative testing approaches. This report presents some new techniques that have been developed to investigate local deformation and failure using digital image correlation techniques. The methods were used to measure both local and global strains during standard straight-sided coupon tensile tests on composite materials made with 12- and 24-k yarns and a 0 /+60 /-60 triaxial braid architecture. Local deformation and failure within fiber bundles was observed and correlations were made between these local failures and global composite deformation and strength.

  12. Acute heart failure : Multiple clinical profiles and mechanisms require tailored therapy

    NARCIS (Netherlands)

    Metra, Marco; Felker, G. Michael; Zaca, Valerio; Bugatti, Silvia; Lombardi, Carlo; Bettari, Luca; Voors, Adrian A.; Gheorghiade, Mihai; Cas, Livio Dei

    2010-01-01

    Acute heart failure (HF) is the most common diagnosis at discharge in patients aged >65 years. It carries a dismal prognosis with a high in-hospital mortality and very high post-discharge mortality and re-hospitalization rates. It is a complex clinical syndrome that cannot be described as a single

  13. Anemia and iron deficiency in heart failure : mechanisms and therapeutic approaches

    NARCIS (Netherlands)

    van Veldhuisen, Dirk J.; Anker, Stefan D.; Ponikowski, Piotr; Macdougall, Iain C.

    Anemia and iron deficiency are common in patients with heart failure (HF), and are associated with worse symptoms and adverse outcomes in this population. Although the two can occur together, anemia in HF is often not caused by iron deficiency, and iron deficiency can be present without causing

  14. Anemia and iron deficiency in heart failure : mechanisms and therapeutic approaches

    NARCIS (Netherlands)

    van Veldhuisen, Dirk J.; Anker, Stefan D.; Ponikowski, Piotr; Macdougall, Iain C.

    2011-01-01

    Anemia and iron deficiency are common in patients with heart failure (HF), and are associated with worse symptoms and adverse outcomes in this population. Although the two can occur together, anemia in HF is often not caused by iron deficiency, and iron deficiency can be present without causing anem

  15. Biophysical Approach to Mechanisms of Cancer Prevention and Treatment with Green Tea Catechins

    OpenAIRE

    Masami Suganuma; Atsushi Takahashi; Tatsuro Watanabe; Keisuke Iida; Takahisa Matsuzaki; Yoshikawa, Hiroshi Y.; Hirota Fujiki

    2016-01-01

    Green tea catechin and green tea extract are now recognized as non-toxic cancer preventives for humans. We first review our brief historical development of green tea cancer prevention. Based on exciting evidence that green tea catechin, (−)-epigallocatechin gallate (EGCG) in drinking water inhibited lung metastasis of B16 melanoma cells, we and other researchers have studied the inhibitory mechanisms of metastasis with green tea catechins using biomechanical tools, atomic force microscopy (AF...

  16. Improvement of the safety of a clinical process using failure mode and effects analysis: Prevention of venous thromboembolic disease in critical patients.

    Science.gov (United States)

    Viejo Moreno, R; Sánchez-Izquierdo Riera, J Á; Molano Álvarez, E; Barea Mendoza, J A; Temprano Vázquez, S; Díaz Castellano, L; Montejo González, J C

    2016-11-01

    To improve critical patient safety in the prevention of venous thromboembolic disease, using failure mode and effects analysis as safety tool. A contemporaneous cohort study covering the period January 2014-March 2015 was made in 4 phases: phase 1) prior to failure mode and effects analysis; phase 2) conduction of mode analysis and implementation of the detected improvements; phase 3) evaluation of outcomes, and phase 4) (post-checklist introduction impact. Patients admitted to the adult polyvalent ICU of a third-level hospital center. A total of 196 patients, older than 18 years, without thromboembolic disease upon admission to the ICU and with no prior anticoagulant treatment. A series of interventions were implemented following mode analysis: training, and introduction of a protocol and checklist to increase preventive measures in relation to thromboembolic disease. Indication and prescription of venous thrombosis prevention measures before and after introduction of the measures derived from the failure mode and effects analysis. A total of 59, 97 and 40 patients were included in phase 1, 3 and 4, respectively, with an analysis of the percentage of subjects who received thromboprophylaxis. The failure mode and effects analysis was used to detect potential errors associated to a lack of training and protocols referred to thromboembolic disease. An awareness-enhancing campaign was developed, with staff training and the adoption of a protocol for the prevention of venous thromboembolic disease. The prescription of preventive measures increased in the phase 3 group (91.7 vs. 71.2%, P=.001). In the post-checklist group, prophylaxis was prescribed in 97.5% of the patients, with an increase in the indication of dual prophylactic measures (4.7, 6.7 and 41%; P<.05). There were no differences in complications rate associated to the increase in prophylactic measures. The failure mode and effects analysis allowed us to identify improvements in the prevention of

  17. Failure Mechanisms and Color Stability in Light-Emitting Diodes during Operation in High- Temperature Environments in Presence of Contamination

    Energy Technology Data Exchange (ETDEWEB)

    Lall, Pradeep; Zhang, Hao; Davis, J Lynn

    2015-05-26

    The energy efficiency of light-emitting diode (LED) technology compared to incandescent light bulbs has triggered an increased focus on solid state luminaries for a variety of lighting applications. Solid-state lighting (SSL) utilizes LEDs, for illumination through the process of electroluminescence instead of heating a wire filament as seen with traditional lighting. The fundamental differences in the construction of LED and the incandescent lamp results in different failure modes including lumen degradation, chromaticity shift and drift in the correlated color temperature. The use of LED-based products for safety-critical and harsh environment applications necessitates the characterization of the failure mechanisms and modes. In this paper, failure mechanisms and color stability has been studied for commercially available vertical structured thin film LED (VLED) under harsh environment conditions with and without the presence of contaminants. The VLED used for the study was mounted on a ceramic starboard in order to connect it to the current source. Contamination sources studied include operation in the vicinity of vulcanized rubber and adhesive epoxies in the presence of temperature and humidity. Performance of the VLEDs has been quantified using the measured luminous flux and color shift of the VLEDs subjected to both thermal and humidity stresses under a forward current bias of 350 mA. Results indicate that contamination can result in pre-mature luminous flux degradation and color shift in LEDs.

  18. Prevention

    Science.gov (United States)

    ... Error processing SSI file About Heart Disease & Stroke Prevention Heart disease and stroke are an epidemic in ... secondhand smoke. Barriers to Effective Heart Disease & Stroke Prevention Many people with key risk factors for heart ...

  19. Forensic engineering: applying materials and mechanics principles to the investigation of product failures.

    Science.gov (United States)

    Hainsworth, S V; Fitzpatrick, M E

    2007-06-01

    Forensic engineering is the application of engineering principles or techniques to the investigation of materials, products, structures or components that fail or do not perform as intended. In particular, forensic engineering can involve providing solutions to forensic problems by the application of engineering science. A criminal aspect may be involved in the investigation but often the problems are related to negligence, breach of contract, or providing information needed in the redesign of a product to eliminate future failures. Forensic engineering may include the investigation of the physical causes of accidents or other sources of claims and litigation (for example, patent disputes). It involves the preparation of technical engineering reports, and may require giving testimony and providing advice to assist in the resolution of disputes affecting life or property.This paper reviews the principal methods available for the analysis of failed components and then gives examples of different component failure modes through selected case studies.

  20. Probabilistic Approach to System Reliability of Mechanism with Correlated Failure Models

    Directory of Open Access Journals (Sweden)

    Xianzhen Huang

    2012-01-01

    Full Text Available In this paper, based on the kinematic accuracy theory and matrix-based system reliability analysis method, a practical method for system reliability analysis of the kinematic performance of planar linkages with correlated failure modes is proposed. The Taylor series expansion is utilized to derive a general expression of the kinematic performance errors caused by random variables. A proper limit state function (performance function for reliability analysis of the kinematic performance of planar linkages is established. Through the reliability theory and the linear programming method the upper and lower bounds of the system reliability of planar linkages are provided. In the course of system reliability analysis, the correlation of different failure modes is considered. Finally, the practicality, efficiency, and accuracy of the proposed method are shown by a numerical example.

  1. Study on Mechanism of Concrete Failure Induced by Steel Corrosion under Externally Applied Direct Current

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    With the combination of electrochemical corrosion due to straycurrent in running tunnels of metro, the formula to determine the corrosion products of rebars in reinforced concrete subjected to externally applied direct current is proposed, and the influence of corrosion on stress in concrete is also discussed. Meanwhile, the concept of corrosion stress field and its mathematical formula are presented in the paper. Finally the failure mode of concrete and its shortest breaking time are also analyzed.

  2. Understanding the failure mechanisms of microwave bipolar transistors caused by electrostatic discharge

    Institute of Scientific and Technical Information of China (English)

    Liu Jin; Chen Yongguang; Tan Zhiliang; Yang Jie; Zhang Xijun; Wang Zhenxing

    2011-01-01

    Electrostatic discharge (ESD) phenomena involve both electrical and thermal effects,and a direct electrostatic discharge to an electronic device is one of the most severe threats to component reliability.Therefore,the electrical and thermal stability of multifinger microwave bipolar transistors (BJTs) under ESD conditions has been investigated theoretically and experimentally.100 samples have been tested for multiple pulses until a failure occurred.Meanwhile,the distributions of electric field,current density and lattice temperature have also been analyzed by use of the two-dimensional device simulation tool Medici.There is a good agreement between the simulated results and failure analysis.In the case of a thermal couple,the avalanche current distribution in the fingers is in general spatially unstable and results in the formation of current crowding effects and crystal defects.The experimental results indicate that a collector-base junction is more sensitive to ESD than an emitter-base junction based on the special device structure.When the ESD level increased to 1.3 kV,the collector-base junction has been burnt out first.The analysis has also demonstrated that ESD failures occur generally by upsetting the breakdown voltage of the dielectric or overheating of the aluminum-silicon eutectic.In addition,fatigue phenomena are observed during ESD testing,with devices that still function after repeated low-intensity ESDs but whose performances have been severely degraded.

  3. Understanding the failure mechanisms of microwave bipolar transistors caused by electrostatic discharge

    Science.gov (United States)

    Jin, Liu; Yongguang, Chen; Zhiliang, Tan; Jie, Yang; Xijun, Zhang; Zhenxing, Wang

    2011-10-01

    Electrostatic discharge (ESD) phenomena involve both electrical and thermal effects, and a direct electrostatic discharge to an electronic device is one of the most severe threats to component reliability. Therefore, the electrical and thermal stability of multifinger microwave bipolar transistors (BJTs) under ESD conditions has been investigated theoretically and experimentally. 100 samples have been tested for multiple pulses until a failure occurred. Meanwhile, the distributions of electric field, current density and lattice temperature have also been analyzed by use of the two-dimensional device simulation tool Medici. There is a good agreement between the simulated results and failure analysis. In the case of a thermal couple, the avalanche current distribution in the fingers is in general spatially unstable and results in the formation of current crowding effects and crystal defects. The experimental results indicate that a collector-base junction is more sensitive to ESD than an emitter-base junction based on the special device structure. When the ESD level increased to 1.3 kV, the collector-base junction has been burnt out first. The analysis has also demonstrated that ESD failures occur generally by upsetting the breakdown voltage of the dielectric or overheating of the aluminum-silicon eutectic. In addition, fatigue phenomena are observed during ESD testing, with devices that still function after repeated low-intensity ESDs but whose performances have been severely degraded.

  4. Tissue factor pathway inhibitor prevents airway obstruction, respiratory failure and death due to sulfur mustard analog inhalation

    Energy Technology Data Exchange (ETDEWEB)

    Rancourt, Raymond C., E-mail: raymond.rancourt@ucdenver.edu; Veress, Livia A., E-mail: livia.veress@ucdenver.edu; Ahmad, Aftab, E-mail: aftab.ahmad@ucdenver.edu; Hendry-Hofer, Tara B., E-mail: tara.hendry-hofer@ucdenver.edu; Rioux, Jacqueline S., E-mail: jacqueline.rioux@ucdenver.edu; Garlick, Rhonda B., E-mail: rhonda.garlick@ucdenver.edu; White, Carl W., E-mail: carl.w.white@ucdenver.edu

    2013-10-01

    Sulfur mustard (SM) inhalation causes airway injury, with enhanced vascular permeability, coagulation, and airway obstruction. The objective of this study was to determine whether recombinant tissue factor pathway inhibitor (TFPI) could inhibit this pathogenic sequence. Methods: Rats were exposed to the SM analog 2-chloroethyl ethyl sulfide (CEES) via nose-only aerosol inhalation. One hour later, TFPI (1.5 mg/kg) in vehicle, or vehicle alone, was instilled into the trachea. Arterial O{sub 2} saturation was monitored using pulse oximetry. Twelve hours after exposure, animals were euthanized and bronchoalveolar lavage fluid (BALF) and plasma were analyzed for prothrombin, thrombin–antithrombin complex (TAT), active plasminogen activator inhibitor-1 (PAI-1) levels, and fluid fibrinolytic capacity. Lung steady-state PAI-1 mRNA was measured by RT-PCR analysis. Airway-capillary leak was estimated by BALF protein and IgM, and by pleural fluid measurement. In additional animals, airway cast formation was assessed by microdissection and immunohistochemical detection of airway fibrin. Results: Airway obstruction in the form of fibrin-containing casts was evident in central conducting airways of rats receiving CEES. TFPI decreased cast formation, and limited severe hypoxemia. Findings of reduced prothrombin consumption, and lower TAT complexes in BALF, demonstrated that TFPI acted to limit thrombin activation in airways. TFPI, however, did not appreciably affect CEES-induced airway protein leak, PAI-1 mRNA induction, or inhibition of the fibrinolytic activity present in airway surface liquid. Conclusions: Intratracheal administration of TFPI limits airway obstruction, improves gas exchange, and prevents mortality in rats with sulfur mustard-analog-induced acute lung injury. - Highlights: • TFPI administration to rats after mustard inhalation reduces airway cast formation. • Inhibition of thrombin activation is the likely mechanism for limiting casts. • Rats given TFPI

  5. Mechanics behind breast cancer prevention - focus on obesity, exercise and dietary fat.

    Science.gov (United States)

    Alegre, Melissa Marie; Knowles, McKay Hovis; Robison, Richard A; O'Neill, Kim Leslie

    2013-01-01

    Cancer prevention is rapidly emerging as a major strategy to reduce cancer mortality. In the field of breast cancer, significant strides have recently been made in the understanding of underlying preventive mechanisms. Currently, three major strategies have been linked to an increase in breast cancer risk: obesity, lack of physical exercise, and high levels of saturated dietary fat. As a result, prevention strategies for breast cancer are usually centered on these lifestyle factors. Unfortunately, there remains controversy regarding epidemiological studies that seek to determine the benefit of these lifestyle changes. We have identified crucial mechanisms that may help clarify these conflicting studies. For example, recent reports with olive oil have demonstrated that it may influence crucial transcription factors and reduce breast tumor aggressiveness by targeting HER2. Similarly, physical exercise reduces sex hormone levels, which may help protect against breast cancer. Obesity promotes tumor cell growth and cell survival through upregulation of leptin and insulin-like growth factors. This review seeks to discuss these underlying mechanisms, and more behind the three major prevention strategies, as a means of understanding how breast cancer can be prevented.

  6. Interpretation of Simultaneous Mechanical-Electrical-Thermal Failure in a Lithium-Ion Battery Module: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Chao; Santhanagopalan, Shriram; Stock, Mark J.; Brunhart-Lupo, Nicholas; Gruchalla, Kenny

    2016-12-01

    Lithium-ion batteries are currently the state-of- the-art power sources for electric vehicles, and their safety behavior when subjected to abuse, such as a mechanical impact, is of critical concern. A coupled mechanical-electrical-thermal model for simulating the behavior of a lithium-ion battery under a mechanical crush has been developed. We present a series of production-quality visualizations to illustrate the complex mechanical and electrical interactions in this model.

  7. Evaluation of left ventricular mechanical dyssynchrony in chronic heart failure patients by two-dimensional speckle tracking imaging.

    Science.gov (United States)

    Jiang, Feng-Xia; Guo, Rui-Qiang; Chen, Jin-Ling

    2013-07-01

    The purpose of this study was to evaluate left ventricular mechanical dyssynchrony (LVMD) in chronic heart failure (CHF) patients using two-dimensional speckle tracking imaging (2D-STI), and also to compare the usefulness of three patterns of myocardial deformation in mechanical dyssynchrony assessment. Furthermore, the relationships between left ventricular ejection fraction (LVEF), QRS duration (QRSd), and LVMD were explored. In total, 78 patients and 60 healthy individuals (group 3) were enrolled. The patients were classified into two subgroups: LVEF≤35% (group 1), 35%0.05). CHF patients have different extents of LVMD. Longitudinal deformation shows the best detectability of dyssynchrony motion. Left ventricular systolic function was closely related to mechanical dyssynchrony, whereas QRSd showed no significant correlation.

  8. Neural mechanisms underlying catastrophic failure in human-machine interaction during aerial navigation

    Science.gov (United States)

    Saproo, Sameer; Shih, Victor; Jangraw, David C.; Sajda, Paul

    2016-12-01

    Objective. We investigated the neural correlates of workload buildup in a fine visuomotor task called the boundary avoidance task (BAT). The BAT has been known to induce naturally occurring failures of human-machine coupling in high performance aircraft that can potentially lead to a crash—these failures are termed pilot induced oscillations (PIOs). Approach. We recorded EEG and pupillometry data from human subjects engaged in a flight BAT simulated within a virtual 3D environment. Main results. We find that workload buildup in a BAT can be successfully decoded from oscillatory features in the electroencephalogram (EEG). Information in delta, theta, alpha, beta, and gamma spectral bands of the EEG all contribute to successful decoding, however gamma band activity with a lateralized somatosensory topography has the highest contribution, while theta band activity with a fronto-central topography has the most robust contribution in terms of real-world usability. We show that the output of the spectral decoder can be used to predict PIO susceptibility. We also find that workload buildup in the task induces pupil dilation, the magnitude of which is significantly correlated with the magnitude of the decoded EEG signals. These results suggest that PIOs may result from the dysregulation of cortical networks such as the locus coeruleus (LC)—anterior cingulate cortex (ACC) circuit. Significance. Our findings may generalize to similar control failures in other cases of tight man-machine coupling where gains and latencies in the control system must be inferred and compensated for by the human operators. A closed-loop intervention using neurophysiological decoding of workload buildup that targets the LC-ACC circuit may positively impact operator performance in such situations.

  9. Protein kinase C epsilon induces systolic cardiac failure marked by exhausted inotropic reserve and intact Frank-Starling mechanism.

    Science.gov (United States)

    Montgomery, David E; Rundell, Veronica L M; Goldspink, Paul H; Urboniene, Dalia; Geenen, David L; de Tombe, Pieter P; Buttrick, Peter M

    2005-11-01

    Myofilament dysfunction is a common point of convergence for many forms of heart failure. Recently, we showed that cardiac overexpression of PKC epsilon initially depresses myofilament activity and then leads to a progression of changes characteristic of human heart failure. Here, we examined the effects of PKC epsilon on contractile reserve, Starling mechanism, and myofilament activation in this model of end-stage dilated cardiomyopathy. Pressure-volume loop analysis and echocardiography showed that the PKC epsilon mice have markedly compromised systolic function and increased end-diastolic volumes. Dobutamine challenge resulted in a small increase in contractility in PKC epsilon mice but failed to enhance cardiac output. The PKC epsilon mice showed a normal length-dependent tension development in skinned cardiac muscle preparations, although Frank-Starling mechanism appeared to be compromised in the intact animal. Simultaneous measurement of tension and ATPase demonstrated that the maximum tension and ATPase were markedly lower in the PKC epsilon mice at any length or Ca2+ concentration. However, the tension cost was also lower indicating less energy expenditure. We conclude 1) that prolonged overexpression of PKC epsilon ultimately leads to a dilated cardiomyopathy marked by exhausted contractile reserve, 2) that PKC epsilon does not compromise the Frank-Starling mechanism at the myofilament level, and 3) that the Starling curve excursion is limited by the inotropic state of the heart. These results reflect the significance of the primary myofilament contractilopathy induced by phosphorylation and imply a role for PKC epsilon-mediated phosphorylation in myofilament physiology and the pathophysiology of decompensated cardiac failure.

  10. Electrochemical and Mechanical Failure of Graphite-Based Anode Materials in Li-Ion Batteries for Electric Vehicles

    Directory of Open Access Journals (Sweden)

    Cheng Lin

    2016-01-01

    Full Text Available Graphite-based anode materials undergo electrochemical reactions, coupling with mechanical degradation during battery operation, can affect or deteriorate the performance of Li-ion batteries dramatically, and even lead to the battery failure in electric vehicle. First, a single particle model (SPM based on kinetics of electrochemical reactions was built in this paper. Then the Li-ion concentration and evolution of diffusion induced stresses (DISs within the SPM under galvanostatic operating conditions were analyzed by utilizing a mathematical method. Next, evolution of stresses or strains in the SPM, together with mechanical degradation of anode materials, was elaborated in detail. Finally, in order to verify the hypothesis aforementioned surface and morphology of the graphite-based anode dismantled from fresh and degraded cells after galvanostatic charge/discharge cycling were analyzed by X-ray diffraction (XRD, field-emission scanning electron microscopy (SEM, and transmission electron microscopy (TEM. The results show that large volume changes of anode materials caused DISs during Li-ion insertion and extraction within the active particles. The continuous accumulations of DISs brought about mechanical failure of the anode eventually.

  11. Late sodium current: A mechanism for angina, heart failure, and arrhythmia.

    Science.gov (United States)

    Makielski, Jonathan C

    2016-02-01

    The peak sodium current underlies excitability and conduction in heart muscle, but a late sodium current flowing after the peak contributes to maintaining and prolonging the action potential plateau, and also to intracellular sodium loading, which in turn increases intracellular calcium with consequent effects on arrhythmia and diastolic function. Late sodium current is pathologically increased in both genetic and acquired heart disease, making it an attractive target for therapy to treat arrhythmia, heart failure, and angina. This review provides an overview of the underlying bases for the clinical implications of late sodium current block.

  12. Perioperative acute renal failure.

    LENUS (Irish Health Repository)

    Mahon, Padraig

    2012-02-03

    PURPOSE OF REVIEW: Recent biochemical evidence increasingly implicates inflammatory mechanisms as precipitants of acute renal failure. In this review, we detail some of these pathways together with potential new therapeutic targets. RECENT FINDINGS: Neutrophil gelatinase-associated lipocalin appears to be a sensitive, specific and reliable biomarker of renal injury, which may be predictive of renal outcome in the perioperative setting. For estimation of glomerular filtration rate, cystatin C is superior to creatinine. No drug is definitively effective at preventing postoperative renal failure. Clinical trials of fenoldopam and atrial natriuretic peptide are, at best, equivocal. As with pharmacological preconditioning of the heart, volatile anaesthetic agents appear to offer a protective effect to the subsequently ischaemic kidney. SUMMARY: Although a greatly improved understanding of the pathophysiology of acute renal failure has offered even more therapeutic targets, the maintenance of intravascular euvolaemia and perfusion pressure is most effective at preventing new postoperative acute renal failure. In the future, strategies targeting renal regeneration after injury will use bone marrow-derived stem cells and growth factors such as insulin-like growth factor-1.

  13. Failure Mechanisms of Ni-H2 and Li-Ion Batteries Under Hypervelocity Impacts

    Science.gov (United States)

    Miller, J. E.; Lyons, F.; Christiansen, E. L.; Lear, D. M.

    2017-01-01

    Lithium-Ion (Li-Ion) batteries have yielded significant performance advantages for many industries, including the aerospace industry, and have been selected to replace nickel hydrogen (Ni-H2) batteries for the International Space Station (ISS) program to meet the energy storage demands. As the ISS uses its vast solar arrays to generate its power, the solar ar-rays meet their sunlit power demands and supply excess power to battery packs for power de-livery on the sun obscured phase of the approximate 90 minute low Earth orbit. These large battery packs are located on the exterior of the ISS, and as such, the battery packs are ex-posed to external environment threats like naturally occurring meteoroids and artificial orbital debris (MMOD). While the risks from these solid particle environments has been known and addressed to an acceptable risk of failure through shield design, it is not possible to completely eliminate the risk of loss of these assets on orbit due to MMOD, and as such, failure consequences to the ISS have been considered.

  14. Formation Mechanism of Type IV Failure in High Cr Ferritic Heat-Resistant Steel-Welded Joint

    Science.gov (United States)

    Liu, Y.; Tsukamoto, S.; Shirane, T.; Abe, F.

    2013-10-01

    The mechanism of type IV failure has been investigated by using a conventional 9Cr ferritic heat-resistant steel Gr.92. In order to clarify the main cause of type IV failure, different heat treatments were performed on the base metal in order to change the prior austenite grain (PAG) size and precipitate distribution after applying the heat-affected zone (HAZ) simulated thermal cycle at the peak temperature of around A c3 ( A c3 HAZ thermal cycle) and postweld heat treatment (PWHT). The microstructural evolution during the A c3 HAZ thermal cycle and PWHT was investigated by means of scanning electron microscope (SEM), electron backscatter diffraction (EBSD), electron probe microanalysis (EPMA), and transmission electron microscope (TEM). It was found that M23C6 carbides were scarcely precipitated at the newly formed fine PAG, block, and lath boundaries in A c3 HAZ-simulated Gr.92, because the carbide forming elements such as Cr and C were segregated at the former PAG and block boundaries of the base metal. On the other hand, if all the boundaries were covered by sufficient M23C6 carbides by homogenization of the alloying elements prior to applying the HAZ thermal cycle, the creep strength was much improved even if the fine PAG was formed. From these results, it is concluded that fine-grained microstructure cannot account for the occurrence of type IV failure, and it only has a small effect during long-term creep. The most important factor is the precipitate formation behavior at various boundaries. Without sufficient boundary strengthening by precipitates, the microstructure of A c3 HAZ undergoes severe changes even during PWHT and causes premature failure during creep.

  15. Prevention

    DEFF Research Database (Denmark)

    Halken, S; Høst, A

    2001-01-01

    , breastfeeding should be encouraged for 4-6 months. In high-risk infants a documented extensively hydrolysed formula is recommended if exclusive breastfeeding is not possible for the first 4 months of life. There is no evidence for preventive dietary intervention neither during pregnancy nor lactation....... Preventive dietary restrictions after the age of 4-6 months are not scientifically documented....

  16. Use of Mechanical Circulatory Support in Isolated Right Heart Failure: A Bridge to Transplantation.

    Science.gov (United States)

    Beissel, Daniel J; Birnbaum, Brian F; Barnes, Aliessa P; O'Brien, James E; Turk, Elizabeth M; St Louis, James D

    2017-08-01

    Acute myocarditis may lead to left ventricular dysfunction and subsequent need for cardiac transplantation. We describe a 15-month-old child who presented with right heart failure of unclear cause. Echocardiography showed normal left ventricular function; however, right ventricular function was markedly reduced. The patient required extracorporeal membrane oxygenation followed by placement of a right-sided Berlin EXCOR ventricular assist device. There was little recovery, and the child underwent cardiac transplantation. Subsequent pathologic examination revealed lymphocytic myocarditis. We believe this is the first use of an isolated right ventricular assist device as a bridge to heart transplantation. Copyright © 2017 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.

  17. Biofilms: An Underappreciated Mechanism of Treatment Failure and Recurrence in Vaginal Infections.

    Science.gov (United States)

    Muzny, Christina A; Schwebke, Jane R

    2015-08-15

    Biofilms are microbial communities of surface-attached cells embedded in a self-produced extracellular matrix. They are of major medical significance because they decrease susceptibility to antimicrobial agents and enhance the spread of antimicrobial resistance. Biofilm-associated bacterial and fungal microorganisms have increasingly been recognized to play a role in multiple infectious diseases, particularly in their persistence and recurrence. More recently, biofilms have also been implicated in vaginal infections, notably bacterial vaginosis (BV) and vulvovaginal candidiasis (VVC), particularly in the setting of treatment failure and recurrence. The purpose of this review is to discuss the impact of biofilms on the management and treatment of BV and recurrent VVC and highlight the need for additional research and development of novel therapeutics targeting pathogenic vaginal biofilms. © The Author 2015. Published by Oxford University Press on behalf of the Infectious Diseases Society of America. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

  18. 压力机轴杆件断裂失效分析及预防%Analysis and Prevention of Fracture Failure of Axostyle of Press

    Institute of Scientific and Technical Information of China (English)

    胡明杰

    2015-01-01

    The application and function of axostyle for press were introduced. By combined with examples, the fracture failure of the crankshafts and the columns of press were analyzed. On the basis of this, the causes of the axostyle’ s fracture failure for the press’ s life cycle were analyzed. The corresponding preventive measures are proposed.%介绍了轴杆件在压力机上的应用及其作用,并结合实例,对压力机曲轴和立柱断裂失效进行了分析,在此基础上分析了在压力机生命周期内导致压力机轴杆件断裂失效的原因,并提出了相应的预防措施。

  19. Mechanism and prediction of failure of diamond films deposited on various substrates by HFCVD

    Institute of Scientific and Technical Information of China (English)

    ZHOU Ling-ping; SUN Xin-yuan; LI Shao-lu; LI De-yi; CHEN Xiao-hua

    2004-01-01

    Diamond films were deposited on the WC-Co cemented carbide and Si3N4 ceramic cutting tool substrates by hot-filament-assisted chemical vapour deposition. The adherence property of diamond films was estimated using the critical load (Pcr) in the indentation test. The adhesive strength of diamond films is related to the intermediate layer between the film and the substrate. Poor adhesion of diamond films to polished cemented carbide substrate is owing to the formation of graphite phase in the interface. The adhesion of diamond films deposited on acid etched cemented carbide substrate is improved, and the peeling-off of the films often happens in the loosen layer of WC particles where the cobalt element is nearly removed. The diamond films' adhesion to cemented carbide substrate whose surface layer is decarbonizated is strengthened dramatically because WC phase forms by reaction between the deposited carbon and tungsten in the surface layer of substrates during the deposition of diamond, which results in chemical combination in the film-substrate interface. The adhesion of diamond films to silicon nitride substrate is the firmest due to the formation of chemical combination of the SiC intermediate layer in the interfaces. In the piston-turning application, the diamond-coated Si3N4 ceramic and the cemented carbide cutting tools usually fail in the form of collapsing of edge and cracking or flaking respectively. They have no built-up edge(BUE) as long as coating is intact.As it wears through, BUE develops and the cutting force on it increases 1 - 3 times than that prior to failure. This can predict the failure of diamond-coated cutting tools.

  20. Geo Mechanical Analysis of Casing Failure in Bedded Rock Salt Formation

    Directory of Open Access Journals (Sweden)

    Tongtao Wang

    2012-08-01

    Full Text Available There are many bedded rock salt resources in China which are serviced as the hosts of underground natural gas storages. For the relatively thin nature of bedded rock salt and the local presence of other sedimentary rock formations, the design and safety evaluation of well completion casing take greater challenges to the engineers than that of casing in other type formations, i.e., limestone and carbonatite. The 2D and 3D geomechanical models of casing-cement sheath-rock salt are established in the paper based on the field data to obtain the creep loads in casing and find the main reasons causing casing failure. In addition, the effects of non-salt layer dip angle, friction factor between salt and non-salt layers and non-salt layer thickness, etc., on the stresses and deformations of casing are studied. The comprehensive results show hoop creep loads are the main reasons causing casing failure rather than radial creep loads. The cement sheath can improve the safety and optimize force state of casing even in perfect wellbore, which disagrees with Willson’s view that the cement sheath can be neglected in a salt formation wellbore with high quality. The non-uniform factor of radial creep loads in cement sheath is slightly smaller than that of original in-situ stresses, while that of radial creep loads in casing is greatly smaller than it. The stresses and deformations of casing increase with increasing thickness of non-salt layer and decrease with the increase of friction factor. When the non-salt layer dip angle is with a value of 50 deg, the stresses and deformations achieve the max and subsequently decrease.

  1. Marine omega-3 highly unsaturated fatty acids: From mechanisms to clinical implications in heart failure and arrhythmias.

    Science.gov (United States)

    Glück, Tobias; Alter, Peter

    2016-07-01

    Therapeutic implications of marine omega-3 highly unsaturated fatty acids (HUFA) in cardiovascular disease are still discussed controversially. Several clinical trials report divergent findings and thus leave ambiguity on the meaning of oral omega-3 therapy. Potential prognostic indications of HUFA treatment have been predominantly studied in coronary artery disease, sudden cardiac death, ventricular arrhythmias, atrial fibrillation and heart failure of various origin. It is suspected that increased ventricular wall stress is crucially involved in the prognosis of heart failure. Increased wall stress and an unfavorable myocardial remodeling is associated with an increased risk of arrhythmias by stretch-activated membrane ion channels. Integration of HUFA into the microenvironment of cardiomyocyte ion channels lead to allosteric changes and increase the electrical stability. Increased ventricular wall stress appears to be involved in the local myocardial as well as in the hepatic fatty acid metabolism, i.e. a cardio-hepatic syndrome. Influences of an altered endogenous HUFA metabolism and an inverse shift of the fatty acid profile was underrated in the past. A better understanding of these interacting endogenous mechanisms appears to be required for interpreting the findings of recent experimental and clinical studies. The present article critically reviews major studies on basic pathophysiological mechanisms and treatment effects in clinical trials.

  2. Fracture Mechanics Models for Brittle Failure of Bottom Rails due to Uplift in Timber Frame Shear Walls

    Directory of Open Access Journals (Sweden)

    Joergen L. Jensen

    2016-01-01

    Full Text Available In partially anchored timber frame shear walls, hold-down devices are not provided; hence the uplift forces are transferred by the fasteners of the sheathing-to-framing joints into the bottom rail and via anchor bolts from the bottom rail into the foundation. Since the force in the anchor bolts and the sheathing-to-framing joints do not act in the same vertical plane, the bottom rail is subjected to tensile stresses perpendicular to the grain and splitting of the bottom rail may occur. This paper presents simple analytical models based on fracture mechanics for the analysis of such bottom rails. An existing model is reviewed and several alternative models are derived and compared qualitatively and with experimental data. It is concluded that several of the fracture mechanics models lead to failure load predictions which seem in sufficiently good agreement with the experimental results to justify their application in practical design.

  3. Respiratory muscle training improves hemodynamics, autonomic function, baroreceptor sensitivity, and respiratory mechanics in rats with heart failure.

    Science.gov (United States)

    Jaenisch, Rodrigo B; Hentschke, Vítor S; Quagliotto, Edson; Cavinato, Paulo R; Schmeing, Letiane A; Xavier, Léder L; Dal Lago, Pedro

    2011-12-01

    Respiratory muscle training (RMT) improves functional capacity in chronic heart-failure (HF) patients, but the basis for this improvement remains unclear. We evaluate the effects of RMT on the hemodynamic and autonomic function, arterial baroreflex sensitivity (BRS), and respiratory mechanics in rats with HF. Rats were assigned to one of four groups: sedentary sham (n = 8), trained sham (n = 8), sedentary HF (n = 8), or trained HF (n = 8). Trained animals underwent a RMT protocol (30 min/day, 5 day/wk, 6 wk of breathing through a resistor), whereas sedentary animals did not. In HF rats, RMT had significant effects on several parameters. It reduced left ventricular (LV) end-diastolic pressure (P RMT (P RMT (P RMT (P RMT protocol in HF rats promotes an improvement in hemodynamic function, sympathetic and vagal heart modulation, arterial BRS, and respiratory mechanics, all of which are benefits associated with improvements in cardiopulmonary interaction.

  4. beta-blockade with nebivolol for prevention of acute ischaemic events in elderly patients with heart failure

    NARCIS (Netherlands)

    Ambrosio, G.; Flather, M. D.; Boehm, M.; Cohen-Solal, A.; Murrone, A.; Mascagni, F.; Spinucci, G.; Conti, M. G.; van Veldhuisen, D. J.; Tavazzi, L.; Coats, A. J. S.

    2011-01-01

    Aim. This subanalysis of the Study of the Effects of Nebivolol Intervention on Outcomes and Hospitalisation in Seniors with Heart Failure (SENIORS) investigates whether treatment with nebivolol, a p-blocker with nitric oxide-releasing properties, can provide additional benefits besides its effects o

  5. beta-blockade with nebivolol for prevention of acute ischaemic events in elderly patients with heart failure

    NARCIS (Netherlands)

    Ambrosio, Giuseppe; Flather, Marcus D.; Boehm, Michael; Cohen-Solal, Alain; Murrone, Adriano; Mascagni, Flavio; Spinucci, Giulio; Conti, Maria Giovanna; van Veldhuisen, Dirk J.; Tavazzi, Luigi; Coats, Andrew J. S.

    2011-01-01

    Objectives This subanalysis of the Study of the Effects of Nebivolol Intervention on Outcomes and Hospitalisation in Seniors with Heart Failure (SENIORS) investigates whether treatment with nebivolol, a beta-blocker with nitric oxide-releasing properties, can provide additional benefits besides its

  6. Large Deformation Mechanisms, Plasticity, and Failure of an Individual Collagen Fibril With Different Mineral Content.

    Science.gov (United States)

    Depalle, Baptiste; Qin, Zhao; Shefelbine, Sandra J; Buehler, Markus J

    2016-02-01

    Mineralized collagen fibrils are composed of tropocollagen molecules and mineral crystals derived from hydroxyapatite to form a composite material that combines optimal properties of both constituents and exhibits incredible strength and toughness. Their complex hierarchical structure allows collagen fibrils to sustain large deformation without breaking. In this study, we report a mesoscale model of a single mineralized collagen fibril using a bottom-up approach. By conserving the three-dimensional structure and the entanglement of the molecules, we were able to construct finite-size fibril models that allowed us to explore the deformation mechanisms which govern their mechanical behavior under large deformation. We investigated the tensile behavior of a single collagen fibril with various intrafibrillar mineral content and found that a mineralized collagen fibril can present up to five different deformation mechanisms to dissipate energy. These mechanisms include molecular uncoiling, molecular stretching, mineral/collagen sliding, molecular slippage, and crystal dissociation. By multiplying its sources of energy dissipation and deformation mechanisms, a collagen fibril can reach impressive strength and toughness. Adding mineral into the collagen fibril can increase its strength up to 10 times and its toughness up to 35 times. Combining crosslinks with mineral makes the fibril stiffer but more brittle. We also found that a mineralized fibril reaches its maximum toughness to density and strength to density ratios for a mineral density of around 30%. This result, in good agreement with experimental observations, attests that bone tissue is optimized mechanically to remain lightweight but maintain strength and toughness.

  7. Intravenous Versus Oral Antibiotics for the Prevention of Treatment Failure in Children With Complicated Appendicitis: Has the Abandonment of Peripherally Inserted Catheters Been Justified?

    Science.gov (United States)

    Rangel, Shawn J; Anderson, Brett R; Srivastava, Rajendu; Shah, Samir S; Ishimine, Paul; Srinivasan, Mythili; Bryan, Matthew; Gong, Wu; Hall, Matt; Localio, Russell; Luan, Xianqun; Anandalwar, Seema; Keren, Ron

    2017-08-01

    To compare treatment failure leading to hospital readmission in children with complicated appendicitis who received oral versus intravenous antibiotics after discharge. Antibiotics are often employed after discharge to prevent treatment failure in children with complicated appendicitis, although existing studies comparing intravenous and oral antibiotics for this purpose are limited. We identified all patients aged 3 to 18 years undergoing appendectomy for complicated appendicitis, who received postdischarge antibiotics at 35 childrens hospitals from 2009 to 2012. Discharge codes were used to identify study subjects from the Pediatric Health Information System database, and chart review confirmed eligibility, treatment assignment, and outcomes. Exposure status was based on outpatient antibiotic therapy, and analysis used optimal and full matching methods to adjust for demographic and clinical characteristics. Treatment failure (defined as an organ-space infection) requiring inpatient readmission was the primary outcome. Secondary outcomes included revisits from any cause to either the inpatient or emergency department setting. In all, 4579 patients were included (median: 99/hospital), and utilization of intravenous antibiotics after discharge ranged from 0% to 91.7% across hospitals. In the matched analysis, the rate of treatment failure was significantly higher for the intravenous group than the oral group [odds ratio (OR) 1.74, 95% confidence interval (CI) 1.05-2.88; risk difference: 4.0%, 95% CI 0.4-7.6%], as was the rate of all-cause revisits (OR 2.11, 95% CI 1.44-3.11; risk difference: 9.4%, 95% CI 4.7-14.2%). The rate of peripherally inserted central catheter line complications was 3.2% in the intravenous group, and drug reactions were rare in both groups (intravenous: 0.7%, oral: 0.5%). Compared with oral antibiotics, use of intravenous antibiotics after discharge in children with complicated appendicitis was associated with higher rates of both treatment

  8. Spatial and Temporal Mode-Of-Failure Transitions in Faulted Earth Materials: A Link Between Mechanics and Hydrology

    Science.gov (United States)

    Goodwin, L. B.; Wilson, J. E.; Rawling, G. C.; Tobin, H.; Mozley, P. S.; Wilson, J. L.

    2002-12-01

    Research into fluid-fault interactions generally falls into two categories: 1) work that considers fault impacts on fluid flow (typically based on static conceptual models of fault-zone architecture) and 2) studies that address fluid impacts on fault-zone mechanics (in which dynamic mechanical processes are considered in detail but the hydrology of the fault-protolith system is not quantified). Bridging the gap between these end-member approaches, and considering dynamic fluid-rock interactions, requires consideration of three-dimensional spatial and temporal variations in fault-zone character, and their resulting impact on both the hydrology and mechanics of fault-protolith systems. We argue that understanding how spatial and temporal mode-of-failure transitions are controlled by the evolving petrophysical characteristics of both protolith and fault rock is a key part of this analysis. Examples of spatial transitions in faulted ignimbrites (Los Alamos, NM and Nevada Test Site, NV) and temporal transitions in faulted sedimentary sequences (Sand Hill fault zone, NM and San Gregorio fault, CA) illustrate this point. In all cases, the primary control on mode of failure at a given location and time appears to be the strength and number of contacts between clasts in the faulted material. Contact area increases with increasing consolidation (which increases with overburden and by particulate flow in a fault zone), cementation (a record of fluid-rock interaction), and welding, and is inversely proportional to porosity. In the weakest, highest porosity materials, failure is accomplished by particulate flow with minor cataclasis. With increasing contact area, sand and non-welded tuff fail through formation of deformation bands. In the strongest materials (fully lithified sedimentary rock and welded tuff), the rocks fail by fracture. The 3-D distribution of structures within a given fault zone will therefore reflect the petrophysical features of the geomaterials intersected

  9. An Empirical Study of Spam and Prevention Mechanisms in Online Video Chat Services

    CERN Document Server

    Xing, Xinyu; Lee, Wenke; Han, Richard; Mishra, Shivakant

    2012-01-01

    Recently, online video chat services are becoming increasingly popular. While experiencing tremendous growth, online video chat services have also become yet another spamming target. Unlike spam propagated via traditional medium like emails and social networks, we find that spam propagated via online video chat services is able to draw much larger attention from the users. We have conducted several experiments to investigate spam propagation on Chatroulette - the largest online video chat website. We have found that the largest spam campaign on online video chat websites is dating scams. Our study indicates that spam carrying dating or pharmacy scams have much higher clickthrough rates than email spam carrying the same content. In particular, dating scams reach a clickthrough rate of 14.97%. We also examined and analysed spam prevention mechanisms that online video chat websites have designed and implemented. Our study indicates that the prevention mechanisms either harm legitimate user experience or can be e...

  10. MASK: An efficient mechanism to extend inter-domain IP spoofing preventions

    Institute of Scientific and Technical Information of China (English)

    LU XiCheng; L(U) GaoFeng; ZHU PeiDong; CHEN YiJiao

    2008-01-01

    IP spoofing hinders the efficiency of DDoS defenses. While recent proposals of IP spoofing prevention mechanisms are weak at filtering spoofing packets due to the complexity in maintaining source IP spaces and the Iow incentive of deployments.To address this problem, we propose an efficient mechanism to extend the range of inter-domain IP spoofing prevention called MASK. Source MASK nodes inform destination MASK nodes about the source IP spaces and labels of their neighbor Stub-ASes in order to implement the marking and verification of packets towards the Stub-ASes, and limit the number of MASK peers through the propagation of BGP updates so as to reduce the overheads of computing and storing of labels. By utilizing the method of extending the spoofing prevention to Stub-ASes, MASK can not only enlarge the domain of the spoofing prevention service, but also filter spoofing packets in advance. Through analysis and simulations, we demonstrate MASK's accuracy and effectiveness.

  11. Effect of heat treatments on failure mechanism of SiCp/2124 Al composite

    Institute of Scientific and Technical Information of China (English)

    M.Murato(g)lu

    2005-01-01

    The mechanical response of a 17% (volume fraction) silicon carbide particles reinforced 2124 Al composite prepared by powder metallurgy techniques was studied by altering the matrix strength with different heat treatments. The fracture mechanisms and the deformation microstructure were examined by scanning electron microscopy. The results show that matrix strength appears to play an important role in influcing the behaviour of the composite under hardness and tensile loading conditions and also fracture mechanisms. The high matrix strength results in a larger decrease in yield strength due to the increasing damage probability. The tensile yield strength values decrease under peak aged and overaged condition whereas under the solutinized condition the opposite effect can be seen.

  12. MRI patterns of Nissen fundoplication: normal appearance and mechanisms of failure

    Energy Technology Data Exchange (ETDEWEB)

    Kulinna-Cosentini, Christiane; Ba-Ssalamah, Ahmed [Medical University of Vienna, Department of Biomedical Imaging and Image-guided Therapy, Vienna (Austria); Schima, Wolfgang [Krankenhaus der Barmherzigen Schwestern Wien und Sankt Josef Krankenhaus, Department of Radiology, Krankenhaus Goettlicher Heiland, Vienna (Austria); Cosentini, Enrico P. [Medical University of Vienna, Department of Surgery, Vienna (Austria)

    2014-09-15

    The purpose of the study was to assess the role of MR fluoroscopy in the evaluation of post-surgical conditions of Nissen fundoplication due to gastro-oesophageal reflux disease (GERD). A total of 29 patients (21 patients with recurrent/persistent symptoms and eight asymptomatic patients as the control group) underwent MRI of the oesophagus and gastro-oesophageal junction (GEJ) at 1.5 T. Bolus transit of a buttermilk-spiked gadolinium mixture was evaluated with T2-weighted half-Fourier acquisition single-shot turbo spin-echo (HASTE) and dynamic gradient echo sequences (B-FFE) in three planes. The results of MRI were compared with intraoperative findings, or, if the patients were treated conservatively, with endoscopy, manometry, pH-metry and barium swallow. MRI was able to determine the position of fundoplication wrap in 27/29 cases (93 % overall accuracy) and to correctly identify 4/6 malpositions (67 %), as well as all four wrap disruptions. All five stenoses in the GEJ were identified and could be confirmed intraoperatively or during dilatation. MRI correctly visualized three cases with motility disorders, which were manometrically confirmed as secondary achalasia. Three patients showed signs of recurrent reflux without anatomical failure. MRI is a promising diagnostic method to evaluate morphologic integrity of Nissen fundoplication and functional disorders after surgery. (orig.)

  13. Mechanical failure of zigzag graphene nanoribbons under tensile strain induced by edge reconstruction

    KAUST Repository

    Cheng, Yingchun

    2012-10-01

    The structural and mechanical properties of graphene nanoribbons (GNRs) under uniaxial tensile strain are studied by density functional theory. The ideal strength of a zigzag GNR (120 GPa) is close to that of pristine graphene. However, for a GNR with both edges reconstructed to pentagon–heptagon pairs (from hexagon–hexagon pairs) it decreases to 94 GPa and the maximum tensile strain is reduced to 15%. Our results constitute a comprehensive picture of the edge structure effect on the mechanical properties of GNRs.

  14. Chronic post-thoracotomy pain: a critical review of pathogenic mechanisms and strategies for prevention

    DEFF Research Database (Denmark)

    Wildgaard, Kim; Ravn, Jesper; Kehlet, Henrik

    2009-01-01

    Chronic pain complaints after thoracic surgery represent a significant clinical problem in 25-60% of patients. Results from thoracic and other surgical procedures suggest multiple pathogenic mechanisms that include pre-, intra-, and postoperative factors. This review attempts to analyse the metho...... as preventive and treatment strategies. However, intercostal nerve injury seems to be the most important pathogenic factor. Since there is a general agreement on the clinical relevance of PTPS, a proposal for design of future trials is presented....

  15. Mechanical analysis of congestive heart failure caused by bundle branch block based on an electromechanical canine heart model

    Energy Technology Data Exchange (ETDEWEB)

    Dou Jianhong; Xia Ling; Zhang Yu; Shou Guofa [Department of Biomedical Engineering, Zhejiang University, Hangzhou 310027 (China); Wei Qing; Liu Feng; Crozier, Stuart [School of Information Technology and Electrical Engineering, University of Queensland, St Lucia, Brisbane, Queensland 4072 (Australia)], E-mail: xialing@zju.edu.cn

    2009-01-21

    understanding of the mechanical implications of congestive heart failure (CHF) caused by BBB.

  16. Mechanical analysis of congestive heart failure caused by bundle branch block based on an electromechanical canine heart model

    Science.gov (United States)

    Dou, Jianhong; Xia, Ling; Zhang, Yu; Shou, Guofa; Wei, Qing; Liu, Feng; Crozier, Stuart

    2009-01-01

    understanding of the mechanical implications of congestive heart failure (CHF) caused by BBB.

  17. Local anesthetic failure associated with inflammation: verification of the acidosis mechanism and the hypothetic participation of inflammatory peroxynitrite

    Directory of Open Access Journals (Sweden)

    Takahiro Ueno

    2008-11-01

    Full Text Available Takahiro Ueno1, Hironori Tsuchiya2, Maki Mizogami1, Ko Takakura11Department of Anesthesiology, Asahi University School of Dentistry, Mizuho, Gifu, Japan; 2Department of Dental Basic Education, Asahi University School of Dentistry, Mizuho, Gifu, JapanAbstract: The presence of inflammation decreases local anesthetic efficacy, especially in dental anesthesia. Although inflammatory acidosis is most frequently cited as the cause of such clinical phenomena, this has not been experimentally proved. We verified the acidosis mechanism by studying the drug and membrane lipid interaction under acidic conditions together with proposing an alternative hypothesis. Liposomes and nerve cell model membranes consisting of phospholipids and cholesterol were treated at different pH with lidocaine, prilocaine and bupivacaine (0.05%–0.2%, w/v. Their membrane-interactive potencies were compared by the induced-changes in membrane fluidity. Local anesthetics fluidized phosphatidylcholine membranes with the potency being significantly lower at pH 6.4 than at pH 7.4 (p < 0.01, supporting the acidosis theory. However, they greatly fluidized nerve cell model membranes even at pH 6.4 corresponding to inflamed tissues, challenging the conventional mechanism. Local anesthetics acted on phosphatidylserine liposomes, as well as nerve cell model membranes, at pH 6.4 with almost the same potency as that at pH 7.4, but not on phosphatidylcholine, phosphatidylethanolamine and sphingomyelin liposomes. Since the positively charged anesthetic molecules are able to interact with nerve cell membranes by ion-paring with anionic components like phosphatidylserine, tissue acidosis is not essentially responsible for the local anesthetic failure associated with inflammation. The effects of local anesthetics on nerve cell model membranes were inhibited by treating with peroxynitrite (50 μM, suggesting that inflammatory cells producing peroxynitrite may affect local anesthesia

  18. The EARLY ALLIANCE prevention trial: an integrated set of interventions to promote competence and reduce risk for conduct disorder, substance abuse, and school failure.

    Science.gov (United States)

    Dumas, J E; Prinz, R J; Smith, E P; Laughlin, J

    1999-03-01

    Describes the EARLY ALLIANCE interventions, an integrated set of four programs designed to promote competence and reduce risk for early-onset conduct disorder, substance abuse, and school failure. These interventions are evaluated as part of a prevention trial that begins at school entry and targets child functioning and socializing practices across multiple contexts (school, peer group, family) and multiple domains (affective, social, and achievement coping-competence). The paper presents the conceptual foundation of the four interventions, including a synopsis of the risk and protective factors associated with conduct disorder and related outcomes, and of the coping-competence model driving EARLY ALLIANCE. The developmental rationale, intended impact, and procedures are described for each intervention: a universally administered classroom program and indicated, peer, reading-mentoring, and family programs. Interventions are currently being tested in a prevention trial, which is briefly summarized.

  19. Computational Modeling of Dynamic Failure Mechanisms in Armor/Anti-Armor Materials

    Science.gov (United States)

    1991-02-01

    Costa, C.R.C., "A Study of the Mechanical Behavior in Ballistic Impact of Alumina Plates," Ceramica , Vol 30, No. 175, July 1984. 5 Table 2 USEFUL...Behavior in Ballistic Impact of Alumina Plates). Ceramica , v175 n30, July 1984. Information Services 56 Yaziv, D.; Bless, S.J.; Rosenberg, Z. Study of

  20. Regulatory mechanisms of immune tolerance in type 1 diabetes and their failures.

    Science.gov (United States)

    Kuhn, Chantal; Besançon, Alix; Lemoine, Sébastien; You, Sylvaine; Marquet, Cindy; Candon, Sophie; Chatenoud, Lucienne

    2016-07-01

    In this brief review we propose to discuss salient data showing the importance of immune regulatory mechanisms, and in particular of Treg, for the control of pathogenic anti-β-cell response in autoimmune diabetes. Disease progression that culminates with the massive destruction of insulin-secreting β-cells and advent of hyperglycemia and glycosuria tightly correlates with a functional deficit in immune regulation. Better dissection of the cellular and molecular mechanisms through which the immune system normally sustains tolerance to "self", and which become defective when autoimmune aggression is overt, is the only direct and robust way to learn how to harness these effectively, so as to restore immune tolerance in patients with insulin-dependent type 1 diabetes. No doubt that regulatory T cells are a privileged mechanism underlying this self-tolerance in the periphery. The discovery of the key role of the transcription factor FoxP3, represented the cornerstone leading to the great advances in the field we are witnessing today. Type 1 diabetes is certainly one of the prototypic T cell-mediated autoimmune diseases where immune regulatory mechanisms relying on specialized subsets of T cells have been the most thoroughly analyzed from the fundamental point of view and also largely exploited in a translational therapeutic perspective.

  1. When Public Acts Like Private: The Failure of Estonia's School Choice Mechanism

    Science.gov (United States)

    Poder, Kaire; Lauri, Triin

    2014-01-01

    This article aims to show the segregating effect of the market-like matching of students and schools at the basic school level. The natural experiment case is Tallinn, the capital of Estonia. The current school choice mechanism applied in this case is based on entrance tests. There are increasingly over-subscribed intra-catchment area public…

  2. REM sleep pathways and anticholinesterase intoxication: A mechanism for nerve agent-induced, central respiratory failure.

    NARCIS (Netherlands)

    Kok, A.

    1993-01-01

    The mechanism of death following exposure to anticholinesterases, such as the highly toxic nerve agents soman and VX, and other organophosphate anticholinesterases such as the insecticide parathion, remains unclear, although evidence from nerve agent research suggests that death occurs by an atropin

  3. Acoustic Emission Determination of Deformation Mechanisms Leading to Failure of Naval Alloys. Volume 2

    Science.gov (United States)

    1983-05-01

    Emission Laser Beam Interferometer HY80 , 100, 130 Steels Mechanical Deformation Nondestructive Evaluation 2. ABSTRACT (Conetnue an rovere eli if necoo y...publication, J. Applied Phys.). 43. A. Peterlin, B.B. Djordjvic, J.C. Murphy, R.E. Green, "Acoustic Emission During Craze Forma- tion in Polymers

  4. Overall Quality of Life Improves to Similar Levels after Mechanical Circulatory Support Regardless of Severity of Heart Failure before Implantation

    Science.gov (United States)

    Grady, Kathleen L; Naftel, David; Stevenson, Lynne; Dew, Mary Amanda; Weidner, Gerdi; Pagani, Francis D.; Kirklin, James K; Myers, Susan; Baldwin, Timothy; Young, James

    2014-01-01

    Background Pre implant heart failure severity may affect post implant health-related quality of life (HRQOL). The purpose of our study was to examine differences in HRQOL from before mechanical circulatory support (MCS) through 1 year after surgery, by INTERMACS patient profiles. Methods Data from adult patients with advanced heart failure who received primary continuous flow pumps between 6/23/06 – 3/31/10 and were enrolled in INTERMACS (n=1,559) were analyzed. HRQOL data were collected using the EQ-5D-3L survey pre implant and at 3, 6 and 12 months after implant. Statistical analyses included chi square and t-tests, using all available data for each time period. Paired ttests and sensitivity analyses were also conducted. Results Quality of life was poor before MCS implant among patients with INTERMACS profiles 1–7 and significantly improved after MCS for all profiles. Stratified by INTERMACS profile, problems within each of the five dimensions of HRQOL (i.e., mobility, self-care, usual activities, pain, and anxiety / depression) generally decreased from before to after implant. By six months after implant, patients with all INTERMACS profiles reported similar frequencies of problems for all HRQOL dimensions. Paired ttests and sensitivity analyses supported the vast majority of our findings. Conclusions HRQOL is poor among advanced heart failure patients with INTERMACS profiles 1–7 before MCS implantation and improves to similar levels for patients who remained on MCS 1 year after surgery. Patients have problems in HRQOL dimensions before and after MCS; the frequency of reporting problems decreases for all dimensions within most profiles across time. PMID:24360203

  5. Microstructure and hydrogen induced failure mechanisms in iron-nickel weldments

    Science.gov (United States)

    Fenske, Jamey Alan

    A recent series of inexplicable catastrophic failures of specific subsea dissimilar metal Fe-Ni butter welds has illuminated a fundamental lack of understanding of both the microstructure created along the fusion line as well as its impact on the hydrogen susceptibility of these interfaces. In order to remedy this, the present work compares and contrasts the microstructure and hydrogen-induced fracture morphology of AISI 8630-IN 625 and F22-IN 625 dissimilar metal weld interfaces as a function of post-weld heat treatment duration. A variety of techniques were used to study details of both the microstructure and fracture morphology including optical microscopy, scanning electron microscopy, secondary ion mass spectrometry, transmission electron microscopy, electron backscatter diffraction, and energy dispersive x-ray spectroscopy. For both systems, the microstructure along the weld interface consisted of a coarse grain heat-affected zone in the Fe-base metal followed by discontinuous martensitic partially-mixed zones and a continuous partially-mixed zone on the Ni-side of the fusion line. Within the partially mixed zone on the Ni-side there exists a 200 nm-wide transition zone within a 20 mum-wide planar solidification region followed by a cellular dendritic region with Nb-Mo rich carbides decorating the dendrite boundaries. The size, area fraction and composition of the discontinuous PMZ were determined to be controlled by uneven mixing in the liquid weld pool influenced by convection currents produced from the welding procedure. The virgin martensitic microstructure produced in these regions is formed as consequence of a both the local composition and the post-weld heat treatment. The local higher Ni content results in these regions being retransformed into austenite during the post-weld heat treatment and then virgin martensite while cooling to room temperature. Although there were differences in the volume of the discontinuous partially mixed-zones, the major

  6. INVESTIGATION OF GLASS PLATE FAILURE MECHANISM SUBJECTED TO COPPER AND STEEL PROJECTILE IMPACTS

    Directory of Open Access Journals (Sweden)

    Qasim H. Shah

    2014-05-01

    Full Text Available Normal 0 false false false EN-US JA X-NONE ABSTRACT: A glass plate was subjected to impact by spherical copper and steel projectiles at low velocities. The glass failure features consisted of a central Hertzian cone made up of comminuted glass and a spider web like cracking pattern around the cone with circumferential and radial cracks. The objective of the investigation was to determine if the damage caused by copper projectile impact compared to steel projectile impact was higher for the same kinetic energy (K.E. projectiles and the reason for this phenomenon. For the constant K.E. impact, copper projectile apparently caused higher damage in glass plate. Higher damage was attributed to projectile contact duration and the contact area between the projectile and the glass plate. Finite element analysis using LS-DYNA based upon maximum principal strain failure criterion for laminated glass model was able to predict the failed material under the impact location and the cracking pattern in the glass plate for a biased meshing scheme. Radial cracks in glass target were reported to be 15% higher for copper projectile impact than the steel projectile impact. ABSTRAK: Kepingan kaca dikenakan impak oleh projektil kuprum dan keluli berbentuk sfera pada halaju rendah. Ciri-ciri kegagalan kaca terdiri daripada kon berpusat Hertzian yang melibatkan kaca yang hancur dan corak pecahan berbentuk sesawang lelabah pada keliling kon dengan retakan lilitan dan jejarian. Tujuan penyelidikan adalah untuk menentukan sebab bagaimana  dengan projektil tenaga kinetik yang sama, kerosakan yang diakibatkan oleh impak projektil kuprum berbanding dengan impak projektil keluli adalah lebih tinggi. Untuk impak tenaga kinetik yang malar, projektil kuprum didapati menyebabkan kerosakan yang lebih ke atas kepingan kaca. Kerosakan lebih disebabkan oleh tempoh sentuhan projektil dan kawasan sentuhan di antara projektil dan kepingan kaca. Analisis unsur terhingga menggunakan LS

  7. Failure Mechanism and Material Requirements for Coal Lance in Blast Furnace

    Institute of Scientific and Technical Information of China (English)

    XIONG Wei; JIA Juan; CHEN Jia-chao; SHANG He-ming

    2012-01-01

    Pulverized coal injection(PCI) is a key technology in modern ironmaking by blast furnace(BF) and the life of injection lance has a great influence on PCI operation and on normal running of blast furnace.It is found that the main reasons for the failure of the lances are their outer surface oxidation and the inner surface erosion through monitoring some lances used in BF.The outer surface oxidation of the lances made of lCr18Ni9Ti is inevitable under high hot blast temperature condition through thermodynamics analysis.A mathematical model for calculating the temperature of common monocular coal lance had been developed according to the principles of mass and energy balance.Increasing temperature and flow velocity of the hot blast would cause a rise in the lance temperature.The influence of hot blast temperature is more obvious.The lance temperature would decline when compressed air flux increases.Conveying technology of dense phase pulverized coal is beneficial to extending lance’s life because decreasing solid-gas ratio would intensify erosion and burning loss.The anti-oxidation temperature of lance materials needs to be over 1000 ℃ for BF intensified smelting.In order to increase the resistance to oxidation of the coal lance’s outer surface,oxidation-resistant steel or Al coating stainless steel is the appropriate material for BF use.Employing the metal surface treatment technology to enhance the hardness of the coal lance’s internal surface could prolong the service life of coal lance

  8. A Prevention of Pre-eclampsia with the Use of Acetylsalicylic Acid and Low-molecular Weight Heparin - Molecular Mechanisms.

    Science.gov (United States)

    Darmochwal-Kolarz, Dorota; Kolarz, Bogdan; Korzeniewski, Michal; Kimber-Trojnar, Zaneta; Patro-Malysza, Jolanta; Mierzynski, Radzisław; Przegalinska-Kałamucka, Monika; Oleszczuk, Jan

    Pre-eclampsia appears to be the main cause for the maternal and fetal morbidity and mortality. Pregnant women with pre-eclampsia are more likely to be threatened with conditions which potentially may be lethal, such as: disseminated intravascular coagulation, cerebral hemorrhage, liver and renal failure. Pregnancy complicated with pre-eclampsia is also associated with a greater risk for iatrogenic prematurity, intrauterine growth retardation, premature abruption of placenta, and even intrauterine fetal death. In the majority of cases the reasons for arterial hypertension among pregnant women remain obscure. For the past decades, there were many abortive attempts in the use of some microelements, vitamins or specific diets, such as polyunsaturated fatty acids, for the prophylaxis of pre-eclampsia. Recently, it has been shown that a prevention of pre-eclampsia with the use of a lowmolecular- weight heparins (LMWHs) and acetylsalicylic acid (ASA) could considerably reduce the frequency of preeclampsia. In this review, we present the studies concerning the applications of LMWHs and aspirin in the prophylaxis of pre-eclampsia and some important data about the mechanisms of anti-inflammatory actions of LMWHs and ASA.

  9. Procalcitonin Impairs Liver Cell Viability and Function In Vitro: A Potential New Mechanism of Liver Dysfunction and Failure during Sepsis?

    Science.gov (United States)

    Ehler, Johannes; Wagner, Nana-Maria

    2017-01-01

    Purpose. Liver dysfunction and failure are severe complications of sepsis and result in poor outcome and increased mortality. The underlying pathologic mechanisms of hepatocyte dysfunction and necrosis during sepsis are only incompletely understood. Here, we investigated whether procalcitonin, a biomarker of sepsis, modulates liver cell function and viability. Materials and Methods. Employing a previously characterized and patented biosensor system evaluating hepatocyte toxicity in vitro, human hepatocellular carcinoma cells (HepG2/C3A) were exposed to 0.01–50 ng/mL procalcitonin for 2 × 72 h and evaluated for proliferation, necrosis, metabolic activity, cellular integrity, microalbumin synthesis, and detoxification capacity. Acetaminophen served as positive control. For further standardization, procalcitonin effects were confirmed in a cellular toxicology assay panel employing L929 fibroblasts. Data were analyzed using ANOVA/Tukey's test. Results. Already at concentrations as low as 0.25 ng/mL, procalcitonin induced HepG2/C3A necrosis (P < 0.05) and reduced metabolic activity, cellular integrity, synthesis, and detoxification capacity (all P < 0.001). Comparable effects were obtained employing L929 fibroblasts. Conclusion. We provide evidence for procalcitonin to directly impair function and viability of human hepatocytes and exert general cytotoxicity in vitro. Therapeutical targeting of procalcitonin could thus display a novel approach to reduce incidence of liver dysfunction and failure during sepsis and lower morbidity and mortality of septic patients. PMID:28255555

  10. Topical Report ''Corrosion Evaluation of LLW2 Skid-B Weld Failure Mechanisms (44139-92)

    Energy Technology Data Exchange (ETDEWEB)

    JI Young Chang

    2001-05-31

    An independent investigation of pipe welding leaks from the Low-Level Waste 2 (LLW2) Skid-B System for the possibilities of improper welding (IW), microbiologically influenced corrosion (MIC), sensitization, chloride pitting corrosion (CPC), and intergranular stress corrosion cracking (IGSCC) was conducted. The results show the prevailing mechanisms that caused the leaks are identified as IW, CPC, and the improper selection of weld filler material for the base metals in an environment of the North Plateau underground water. These is no evidence of MIC, sensitization, or IGSCC. The chloride pitting corrosion mechanism that took place at all the welds are also described. All the pipelines were replaced with polyvinyl chloride (PVC) for cost saving and the LLW2 Skid B System has been successfully operating since 1999. This report summarizes the findings and recommendations associated with preventive measures for future operations. The LLW2 Facility is a replacement for an existing waste treatment system. The Facility processes two different waste streams through two different ''skids.'' After seven months of operation, one of the two skids began to leak. Extensive evaluation of the corrosion mechanisms and the contributing factors are documented in this report. This report principally evaluates the physical and chemical configurations that led to the corrosion and leaks. Chloride pitting corrosion, exacerbated by weld defects, is the corrosion mechanism. The report also discusses fabrication and Quality Assurance (QA)/Quality Control (QC) actions that would have prevented their occurrence. It is believed that in the absence of either the defects or the chloride concentrations, corrosion would not have occurred. In developing the specification for processing skids to be used in the Facility, high chloride was not identified as a parameter of concern. As such, piping fabrication and inspection standards for the system did not identify more rigorous

  11. Role of the Renin–Angiotensin System in the Pathogenesis of Intimal Hyperplasia: Therapeutic Potential for Prevention of Vein Graft Failure?

    Science.gov (United States)

    Osgood, Michael J.; Harrison, David G.; Sexton, Kevin W.; Hocking, Kyle M.; Voskresensky, Igor V.; Komalavilas, Padmini; Cheung-Flynn, Joyce; Guzman, Raul J.; Brophy, Colleen M.

    2014-01-01

    The saphenous vein remains the most widely used conduit for peripheral and coronary revascularization despite a high rate of vein graft failure. The most common cause of vein graft failure is intimal hyperplasia. No agents have been proven to be successful for the prevention of intimal hyperplasia in human subjects. The rennin–angiotensin system is essential in the regulation of vascular tone and blood pressure in physiologic conditions. However, this system mediates cardiovascular remodeling in pathophysiologic states. Angiotensin II is becoming increasingly recognized as a potential mediator of intimal hyperplasia. Drugs modulating the renin–angiotensin system include angiotensin-converting enzyme inhibitors and angiotensin receptor blockers. These drugs are powerful inhibitors of atherosclerosis and cardiovascular remodeling, and they are first-line agents for management of several medical conditions based on class I evidence that they delay progression of cardiovascular disease and improve survival. Several experimental models have demonstrated that these agents are capable of inhibiting intimal hyperplasia. However, there are no data supporting their role in prevention of intimal hyperplasia in patients with vein grafts. This review summarizes the physiology of the rennin–angiotensin system, the role of angiotensin II in the pathogenesis of cardiovascular remodeling, the medical indications for these agents, and the experimental data supporting an important role of the rennin–angiotensin system in the pathogenesis of intimal hyperplasia. PMID:22445245

  12. Real-Time Smart Grids Control for Preventing Cascading Failures and Blackout using Neural Networks: Experimental Approach for N-1-1 Contingency

    Science.gov (United States)

    Zarrabian, Sina; Belkacemi, Rabie; Babalola, Adeniyi A.

    2016-12-01

    In this paper, a novel intelligent control is proposed based on Artificial Neural Networks (ANN) to mitigate cascading failure (CF) and prevent blackout in smart grid systems after N-1-1 contingency condition in real-time. The fundamental contribution of this research is to deploy the machine learning concept for preventing blackout at early stages of its occurrence and to make smart grids more resilient, reliable, and robust. The proposed method provides the best action selection strategy for adaptive adjustment of generators' output power through frequency control. This method is able to relieve congestion of transmission lines and prevent consecutive transmission line outage after N-1-1 contingency condition. The proposed ANN-based control approach is tested on an experimental 100 kW test system developed by the authors to test intelligent systems. Additionally, the proposed approach is validated on the large-scale IEEE 118-bus power system by simulation studies. Experimental results show that the ANN approach is very promising and provides accurate and robust control by preventing blackout. The technique is compared to a heuristic multi-agent system (MAS) approach based on communication interchanges. The ANN approach showed more accurate and robust response than the MAS algorithm.

  13. Fatigue failure kinetics and structural changes in lead-free interconnects due to mechanical and thermal cycling

    Science.gov (United States)

    Fiedler, Brent Alan

    Environmental and human health concerns drove European parliament to mandate the Reduction of Hazardous Substances (RoHS) for electronics. This was enacted in July 2006 and has practically eliminated lead in solder interconnects. There is concern in the electronics packaging community because modern lead-free solder is rich in tin. Presently, near-eutectic tin-silver-copper solders are favored by industry. These solders are stiffer than the lead-tin near-eutectic alloys, have a higher melting temperature, fewer slip systems, and form intermetallic compounds (IMC) with Cu, Ni and Ag, each of which tend to have a negative effect on lifetime. In order to design more reliable interconnects, the experimental observation of cracking mechanisms is necessary for the correct application of existing theories. The goal of this research is to observe the failure modes resulting from mode II strain and to determine the damage mechanisms which describe fatigue failures in 95.5 Sn- 4.0 Ag - 0.5 Cu wt% (SAC405) lead-free solder interconnects. In this work the initiation sites and crack paths were characterized for SAC405 ball-grid array (BGA) interconnects with electroless-nickel immersion-gold (ENIG) pad-finish. The interconnects were arranged in a perimeter array and tested in fully assembled packages. Evaluation methods included monotonic and displacement controlled mechanical shear fatigue tests, and temperature cycling. The specimens were characterized using metallogaphy, including optical and electron microscopy as well as energy dispersive spectroscopy (EDS) and precise real-time electrical resistance structural health monitoring (SHM). In mechanical shear fatigue tests, strain was applied by the substrates, simulating dissimilar coefficients of thermal expansion (CTE) between the board and chip-carrier. This type of strain caused cracks to initiate in the soft Sn-rich solder and grow near the interface between the solder and intermetallic compounds (IMC). The growth near

  14. Severe acute respiratory failure secondary to acute fibrinous and organizing pneumonia requiring mechanical ventilation: a case report and literature review.

    Science.gov (United States)

    López-Cuenca, Sonia; Morales-García, Silvia; Martín-Hita, Ana; Frutos-Vivar, Fernando; Fernández-Segoviano, Pilar; Esteban, Andrés

    2012-08-01

    A 27-year-old woman was admitted to our ICU with acute hypoxemic respiratory failure and criteria for ARDS. Despite an F(IO(2)) of 1.0 and a lung protective strategy, the patient died on day 15 without any improvement. The relatives gave consent for post-mortem analysis. The histopathologic study of the lung showed findings typical of an acute fibrinous and organizing pneumonia. Apropos of this case we performed a PubMed search. We found 13 articles, including a total of 29 patients. Acute fibrinous and organizing pneumonia is an unusual cause of acute lung injury. The diagnostic criterion is histopathologic. There is little information regarding the pathophysiology of this illness. Important questions remain regarding this disease, including predisposing factors and management. Patients who require mechanical ventilation have poor outcomes.

  15. Physiologic benefits of pulsatile perfusion during mechanical circulatory support for the treatment of acute and chronic heart failure in adults.

    Science.gov (United States)

    Guan, Yulong; Karkhanis, Tushar; Wang, Shigang; Rider, Alan; Koenig, Steven C; Slaughter, Mark S; El Banayosy, Aly; Undar, Akif

    2010-07-01

    A growing population experiencing heart failure (100,000 patients/year), combined with a shortage of donor organs (less than 2200 hearts/year), has led to increased and expanded use of mechanical circulatory support (MCS) devices. MCS devices have successfully improved clinical outcomes, which are comparable with heart transplantation and result in better 1-year survival than optimal medical management therapies. The quality of perfusion provided during MCS therapy may play an important role in patient outcomes. Despite demonstrated physiologic benefits of pulsatile perfusion, continued use or development of pulsatile MCS devices has been widely abandoned in favor of continuous flow pumps owing to the large size and adverse risks events in the former class, which pose issues of thrombogenic surfaces, percutaneous lead infection, and durability. Next-generation MCS device development should ideally implement designs that offer the benefits of rotary pump technology while providing the physiologic benefits of pulsatile end-organ perfusion.

  16. Effect of Residual Stresses and Prediction of Possible Failure Mechanisms on Thermal Barrier Coating System by Finite Element Method

    Science.gov (United States)

    Ranjbar-Far, M.; Absi, J.; Mariaux, G.; Shahidi, S.

    2010-09-01

    This work is focused on the effect of the residual stresses resulting from the coating process and thermal cycling on the failure mechanisms within the thermal barrier coating (TBC) system. To reach this objective, we studied the effect of the substrate preheating and cooling rate on the coating process conditions. A new thermomechanical finite element model (FEM) considering a nonhomogeneous temperature distribution has been developed. In the results, we observed a critical stress corresponding to a low substrate temperature and high cooling rate during spraying of the top-coat material. Moreover, the analysis of the stress distribution after service shows that more critical stresses are obtained in the case where residual stresses are taken into account.

  17. Improvement of a Genetic Back Propagation Algorithm and Its Application to Diagnosis in Mechanical Failure

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A new improved genetic BP algorithm was put forward in the paper. To deter-mine whether the network falls into local minimum point, a discriminant of local minimum was put forth in the training process of a neural network. A genetic algorithm was used to revise the weights of the neural network if the BP algorithm fell into minimums. The me-chanical faults were diagnosed using the algorithm put forward in the paper, which veri-fied the validity of this improved genetic BP algorithm.

  18. Preoperative prediction and prevention of intraoperative acute liver failure after major liver resection for metastatic colorectal cancer

    Directory of Open Access Journals (Sweden)

    A. D. Kaprin

    2016-01-01

    Full Text Available Objective: improve the results of treatment of patients with metastatic cancer of liver by reducing the risk of post-resection liver failure based on the assessment of liver functional reserve.Materials and methods. The study included 2 independent samples of patients underwent surgery for liver metastases in the department of abdominal oncology at the P. A. Herzen Moscow Oncological Research Institute. Group 1 included 47 patients: in addition to the standard treatment algorithm they underwent 13C methacetin breath test and dynamic scintigraphy of liver in the preoperative stage. Patients from the group 2 (n = 30 underwent standard clinical and laboratory examination, without preoperative evaluation of liver functional reserves; the level of total bilirubin, albumin and prothrombin time showed no decrease in liver function. Post-resection liver failure was established based on 50/50 criterion when evaluated on the 5th postoperative day.Results. The analysis of operational characteristics of functional tests showed absolute sensitivity of 13C methacetin breath test (SE ≥ 100 % and negative predictive value (–VP ≥ 100 % in case of integrated application of 2 diagnostic methods. An incidence of post-resection acute liver failure in the study group was significantly 2.2-fold lower than in the control group – 10.6 % and 23.3 %, respectively (p < 0.001.Conclusion. Combination of preoperative dynamic scintigraphy of liver with 13C methacetin breath test allows to perform comprehensive assessment of liver functional reserves, and it can greatly improve preoperative assessment and postoperative results of anatomic resections in patients with liver metastases.

  19. Heart failure overview

    Science.gov (United States)

    ... symptoms) You feel a severe crushing chest pain Prevention Most cases of heart failure can be prevented by living a healthy lifestyle and taking steps aimed at reducing your risk for heart disease . . Alternative Names CHF; Congestive heart failure; Left-sided ...

  20. [Clinical experience of mechanical ventricular support with centrifugal pump for severe ventricular failure after open heart surgery].

    Science.gov (United States)

    Matsuwaka, R; Matsuda, H; Kaneko, M; Masai, T; Fudemoto, Y; Kobayashi, T; Imagawa, H; Miyamoto, K; Morisaki, H; Kawashima, Y

    1990-09-01

    Five adult patients (pts) with age 15-67 (mean 43) received mechanical circulatory support with centrifugal pump (Biomedicus, BP-80, Sarns centrifugal pump) for postcardiotomy profound shock. Three pts underwent left ventricular support (LVS) alone, and the other 2 required biventricular support (BVS). Duration of the LVS ranged from 33 to 240 hours (mean 126 hours) and the right ventricular support 92, 120 hrs. Pump flow rate was 1.1 to 2.5 (mean 1.9) L/min/m2. Sixteen pumps were used and the pump exchange was performed 9 times in five pts and an average perfusion time per pump was 57 hrs. Two of 3 pts with LVS alone survived and one died of multiorgan failure associated with right heart dysfunction. In two pts with BVS, one survived and the other died of persistent low cardiac output early after pump removal. As the complication during mechanical support, bleeding was seen in 3 pts and cerebral infarction in one. Although centrifugal pump has potential limitation in antithrombogenicity and durability, this device provides a simple and effective mechanical circulatory support.