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1

TBC-Domain GAPs for Rab GTPases Accelerate GTP Hydrolysis by a Dual-Finger Mechanism  

SciTech Connect

Rab GTPases regulate membrane trafficking by cycling between inactive (GDP-bound) and active (GTP-bound) conformations. The duration of the active state is limited by GTPase-activating proteins (GAPs), which accelerate the slow intrinsic rate of GTP hydrolysis. Proteins containing TBC (Tre-2, Bub2 and Cdc16) domains are broadly conserved in eukaryotic organisms and function as GAPs for Rab GTPases as well as GTPases that control cytokinesis. An exposed arginine residue is a critical determinant of GAP activity in vitro and in vivo. It has been expected that the catalytic mechanism of TBC domains would parallel that of Ras and Rho family GAPs. Here we report crystallographic, mutational and functional analyses of complexes between Rab GTPases and the TBC domain of Gyp1p. In the crystal structure of a TBC-domain-Rab-GTPase-aluminium fluoride complex, which approximates the transition-state intermediate for GTP hydrolysis, the TBC domain supplies two catalytic residues in trans, an arginine finger analogous to Ras/Rho family GAPs and a glutamine finger that substitutes for the glutamine in the DxxGQ motif of the GTPase. The glutamine from the Rab GTPase does not stabilize the transition state as expected but instead interacts with the TBC domain. Strong conservation of both catalytic fingers indicates that most TBC-domain GAPs may accelerate GTP hydrolysis by a similar dual-finger mechanism.

Pan,X.; Eathiraj, S.; Lambright, D.

2006-01-01

2

Failure mechanisms in MEMS.  

SciTech Connect

MEMS components by their very nature have different and unique failure mechanisms than their macroscopic counterparts. This paper discusses failure mechanisms observed in various MEMS components and technologies. MEMS devices fabricated using bulk and surface micromachining process technologies are emphasized. MEMS devices offer uniqueness in their application, fabrication, and functionality. Their uniqueness creates various failure mechanisms not typically found in their bulk or IC counterparts. In ICs, electrical precautions are taken to mitigate failure. In MEMS, both electrical and mechanical precautions must be enacted to reduce the risk of failure and increased reliability. Unlike ICs, many MEMS components are designed to interact with their environment, making the fabrication, testing, and packaging processes critical for the success of the device.

Walraven, Jeremy Allen

2003-07-01

3

In Situ Observation of Creep and Fatigue Failure Behavior for Plasma-Sprayed Thermal Barrier Coating Systems  

Microsoft Academic Search

In order to investigate crack initiation sites and the crack propagation behavior in connection with the microstructure of thermal barrier coating (TBC) systems under creep and fatigue loadings, the failure behavior was observed in situ for plasma-sprayed TBC systems by optical microscopy, as a first step for elucidating the thermo-mechanical failure mechanism. Two types of TBC systems with differing top-coat

Satoru Takahashi; Yoshio Harada

2010-01-01

4

FAILURE MECHANISMS OF HENS' EGGS  

Microsoft Academic Search

The mechanics and mechanisms of failure of hens eggs have been examined experimentally under contact loading conditions. Eggs of known provenance were tested in compression between stiff platens, and the deformation modelled computationally as a Hertzian contact problem between a thin walled shell and a rigid plate. The associated contact damage was determined by scanning electron microscopy and by optical

N. MacLeod?; M. M. Bain; S. E. Solomon; J. W. Hancock?

5

TBC1D1 Regulates Insulin- and Contraction-Induced Glucose Transport in Mouse Skeletal Muscle  

PubMed Central

OBJECTIVE TBC1D1 is a member of the TBC1 Rab-GTPase family of proteins and is highly expressed in skeletal muscle. Insulin and contraction increase TBC1D1 phosphorylation on phospho-Akt substrate motifs (PASs), but the function of TBC1D1 in muscle is not known. Genetic linkage analyses show a TBC1D1 R125W missense variant confers risk for severe obesity in humans. The objective of this study was to determine whether TBC1D1 regulates glucose transport in skeletal muscle. RESEARCH DESIGN AND METHODS In vivo gene injection and electroporation were used to overexpress wild-type and several mutant TBC1D1 proteins in mouse tibialis anterior muscles, and glucose transport was measured in vivo. RESULTS Expression of the obesity-associated R125W mutant significantly decreased insulin-stimulated glucose transport in the absence of changes in TBC1D1 PAS phosphorylation. Simultaneous expression of an inactive Rab-GTPase (GAP) domain of TBC1D1 in the R125W mutant reversed this decrease in glucose transport caused by the R125W mutant. Surprisingly, expression of TBC1D1 mutated to Ala on four conserved Akt and/or AMP-activated protein kinase predicted phosphorylation sites (4P) had no effect on insulin-stimulated glucose transport. In contrast, expression of the TBC1D1 4P mutant decreased contraction-stimulated glucose transport, an effect prevented by concomitant disruption of TBC1D1 Rab-GAP activity. There was no effect of the R125W mutation on contraction-stimulated glucose transport. CONCLUSIONS TBC1D1 regulates both insulin- and contraction-stimulated glucose transport, and this occurs via distinct mechanisms. The R125W mutation of TBC1D1 impairs skeletal muscle glucose transport, which could be a mechanism for the obesity associated with this mutation.

An, Ding; Toyoda, Taro; Taylor, Eric B.; Yu, Haiyan; Fujii, Nobuharu; Hirshman, Michael F.; Goodyear, Laurie J.

2010-01-01

6

Failure mechanisms in viscoelastic films  

Microsoft Academic Search

This paper presents the results of tensile tests on viscoelastic films of two materials: a 100 pen bitumen and a commercial corn syrup. Experiments were performed using double-cantilever beam specimens, and butt-joint specimens, for a wide range of testing conditions. Failure by brittle fracture, voiding, and various viscous flow mechanisms was observed. The results are presented in the form of

J. A. F. Harvey; D. Cebon

2003-01-01

7

Metabolic Mechanisms in Heart Failure  

Microsoft Academic Search

Although neurohumoral antagonism has successfully reduced heart failure morbidity and mortality, the residual disability and death rate remains unacceptably high. Though abnormalities of myocardial metabolism are associated with heart failure, recent data suggest that heart failure may itself promote metabolic changes such as insulin resistance, in part through neurohumoral activation. A detrimental self-perpetuating cycle (heart failure 3 altered metabolism 3

Houman Ashrafian; Michael P. Frenneaux; Lionel H. Opie

8

TBC Experience in Land Based Gas Turbines.  

National Technical Information Service (NTIS)

Prior and on-going machine evaluations of TBC coatings for power generation applications are summarized. Rainbow testing of various TBC's on turbine nozzles, shrouds and buckets are described along with one test on combustor liners. GEPG has conducted ove...

W. A. Nelson R. M. Orenstein

1995-01-01

9

Diastolic heart failure: mechanisms and controversies  

Microsoft Academic Search

Epidemiological and experimental studies have documented both the rising burden of diastolic heart failure (DHF) and several mechanisms that distinguish this disease from systolic heart failure (SHF). Controversies continue to surround the term 'DHF' as well as its existence as a pathophysiological entity distinct from SHF. Approximately half of all patients who present with heart failure have near-normal systolic function

Maral Ouzounian; Douglas S Lee; Peter P Liu

2008-01-01

10

Heart Failure Recovery with Mechanical Circulatory Support  

Microsoft Academic Search

\\u000a An Expert Panel was convened in the Winnipeg 2001 Heart Congress to examine heart failure recovery mechanisms after mechanical\\u000a circulatory support. The Expert Panel consisted of leading researchers, and clinicians knowledgeable in the use of mechanical\\u000a circulatory support devices, and focused on heart failure recovery mechanisms at the gene, cell, organ and patient levels\\u000a after prolonged mechanical circulatory support. Views

Tofy Mussivand; Paul Heerdt; Kenneth B. Margulies; O. Howard Frazier; Gurmeet Singh; Hideo A. Baba

11

Mechanism of Procedural Failure Related to Wingspan  

PubMed Central

Purpose Wingspan is the only FDA approved self-expanding stent for intracranial artery and known to have better delivery compared to balloon expandable stent. However, some delivery failure has been reported but incidence and mechanism of the failure have not been completely elucidated. We present the cause and mechanism of Wingspan deployment failure experienced in our Institute. Materials and Methods We experienced deployment failure in seven patients (8.8%) out of 80 patients who underwent Wingspan stenting since 2007. Mean age of the patients was 62 (range 47~78) and male to female ratio was 6:1. We evaluated the cause and mechanism why the deployment was not successful and how we could manage it subsequently. Results We categorized failures occurred in seven patients into three categories: delivery failure (n = 3), deployment failure of stent (n = 3), retrieval failure of dual tapered (olive) tip of the inner body through the deployed the stent (n = 1). The technical failure in using Wingspan stent (delivery, deployment and retrieval failures) are related to tortuousness of the proximal (n =4) as well as distal (n =1) cerebral vessels to the stenotic lesion and bulky profile of the olive tip (n =2). Conclusion The technical failure in using Wingspan stent (delivery, deployment and retrieval failures) are related to tortuousness of the proximal as well as distal cerebral vessels to the stenotic lesion and bulky profile of the olive tip. To avoid device-related complication, complete understanding of the stent design is mandatory before using the stent.

Zhao, Lin-Bo; Park, Soonchan; Lee, Donggeun; Lee, Deok Hee

2012-01-01

12

Mechanisms of Hyperlipidemia in Chronic Renal Failure.  

National Technical Information Service (NTIS)

The mechanism of the hyperlipidemia of chronic renal failure involves either a defect in removal mechanisms or an accelerated synthesis. Analysis of the plasma lipoprotein spectrum of fasting uremic patients before scheduled dialysis has revealed some int...

J. M. Felts

1975-01-01

13

MEMS reliability from a failure mechanisms perspective  

Microsoft Academic Search

Over the last few years, considerable effort has gone into the study of the failure mechanisms and reliability of micro- electromechanical systems (MEMS). Although still very incomplete, our knowledge of the reliability issues relevant to MEMS is growing. This paper provides an overview of MEMS failure mechanisms that are commonly encountered. It focuses on the reliability issues of micro-scale devices,

W. Merlijn Van Spengen

2003-01-01

14

Assessment of Cyclic Lifetime of NiCoCrAlY/ZrO2-Based EB-PVD TBC Systems via Reactive Element Enrichment in the Mixed Zone of the TGO Scale  

NASA Astrophysics Data System (ADS)

The chemical composition of the alumina-zirconia mixed zone (MZ) of an electron beam physical vapor deposited thermal barrier coating (EB-PVD TBC) system is affected by service conditions and by the interdiffusion of elements from the substrate alloy below and the zirconia top coat. Three NiCoCrAlY bond-coated Ni-base substrates with YPSZ or CeSZ EB-PVD TBCs were subjected to a cyclic furnace oxidation test (FCT) at 1373 K (1100 °C) in order to provide experimental evidence of a link between chemistry of the MZ, the substrate alloy, the ceramic top coat, and the time in the FCT. Energy dispersive spectroscopy of the MZ revealed preferred accumulation of Cr, Zr, Y, and Ce. The concentration of the reactive elements (RE = Ce + Y + Zr) was related to the respective average lifetimes of the TBC systems at 1373 K (1100 °C). The RE content in the MZ turned out to be a life-limiting parameter for YPSZ and CeSZ TBC systems which can be utilized to predict their relative lifetimes on the individual substrates. Conversely, the TBC failure mechanisms of YPSZ and CeSZ TBC systems are dissimilar.

Fritscher, Klaus; Braue, Wolfgang; Schulz, Uwe

2013-05-01

15

High temperature failure mechanisms in ceramic polycrystals  

SciTech Connect

The high temperature failure of ceramics has been observed to occur by the nucleation, growth and coalescence of cracks. Each process involves diffusive cavity nucleation and growth, either within a damage zone or at microstructural heterogeneities. The specific cavitation and cracking mechanisms pertinent to ceramics are described and available models are presented. Particular emphasis is placed on continuous crack nucleation at microstructural heterogeneities and the crack coalescence process that causes eventual failure. Failure time data are also reviewed and correlated with models.

Evans, A.G.; Blumenthal, W.

1983-12-01

16

TBC experience in land- based gas turbines  

NASA Astrophysics Data System (ADS)

This paper summarizes prior and on-going machine evaluations of thermal barrier coatings (TBC) for power generation, that is large industrial gas turbine applications. Rainbow testing of TBCs on turbine nozzles, shrouds, and buckets are described along with a test of combustor liners. General Electric Power Generation has conducted more than IS machine tests on TBC turbine nozzles with various coatings. TBC performance has been quite good, and additional testing, including TBCs on shrouds and buckets, is continuing. Included is a brief comparison of TBC requirements for power generation and aircraft turbines.

Nelson, W. A.; Orenstein, R. M.

1997-06-01

17

Mechanisms of Hyperlipidemia in Chronic Renal Failure.  

National Technical Information Service (NTIS)

The mechanism of the hyperlipidemia of chronic renal failure is associated with a characteristic alteration of the lipoprotein spectrum regardless of the classification of the disease. Elevated very low density lipoproteins and reduced low density and hig...

J. M. Felts

1977-01-01

18

High temperature failure mechanisms in ceramics  

SciTech Connect

A statistical model of high temperature failure in ceramics, by the viscous or diffusive growth of cavities, has been developed. General expressions for the creep strain associated with cavitation and for the failure time have been derived, and shown to be in good agreement with available data. Specific models of cavity growth along grain facets, by diffusive and viscous mechanisms, have then been generated, and coupled with the statistical model: to provide specific predictions of the creep strain and the failure time. The predictions are in reasonable accord with experimental results.

Evans, A.G.; Rana, A.

1980-02-01

19

NON-DESTRUCTIVE TBC SPALLATION DETECTION BY A MICRO-INDENTATION METHOD  

SciTech Connect

In this research, a load-based depth-sensing micro-indentation method for spallation detection and damage assessment of thermal barrier coating (TBC) materials is presented. A non-destructive multiple loading/partial unloading testing methodology was developed where in stiffness responses of TBC coupons subjected to various thermal cyclic loading conditions were analyzed to predict the spallation site and assess TBC degradation state. The measured stiffness responses at various thermal loading cycles were used to generate time-series color maps for correlation with accumulation of TBC residual stress states. The regions with higher stiffness responses can be linked to a rise in out-of-plane residual stress located near or at the yttria stabilized zirconia (YSZ)/thermally grown oxide (TGO) interface, which is ultimately responsible for initiating TBC spallation failure. A TBC thermal exposure testing plan was carried out where time-series cross-sectional microstructural analyses of damage accumulation and spallation failure associated with the evolution of bond coat/TGO/top coat composite (e.g. thickness, ratcheting, localized oxidations, etc.) of air plasma sprayed (APS) TBCs were evaluated and correlated to the measured stiffness responses at various thermal cycles. The results show that the load-based micro-indentation test methodology is capable of identifying the spallation site(s) before actual occurrence. This micro-indentation technique can be viewed as a viable non-destructive evaluation (NDE) technique for determining as-manufactured and process-exposed TBCs. This technique also shows promise for the development of a portable instrument for on-line, in-situ spallation detection/prediction of industrial-size TBC turbine components.

J. M. Tannenbaum; B.S.-J. Kang; M.A. Alvin

2010-06-18

20

Noninvasive mechanical ventilation in acute respiratory failure  

Microsoft Academic Search

Mechanical ventilation (MV) has been indicated in the treatment of acute respiratory failure (ARF) if conservative treatment fails. Invasive MV is asso- ciated to a variety of complications. The recent innovations of noninvasive methods of MV (NMV) avoid the complications of invasive MV, whilst ensuring a similar degree of efficacy. A review of the literature from 1989 to 1995 shows

N. Ambrosino

1996-01-01

21

Drop impact test - mechanics & physics of failure  

Microsoft Academic Search

This paper deals with the mechanics and physics of board-level drop test with the intention of providing the fundamental understanding required to design and analyse the results of a drop test. Three finite element analyses were performed to understand the physics of failure in board-level drop impact: (i) velocity impact of a PCB - modeled as a beam; (ii) velocity

E. H. Wong; K. M. Lim; N. Lee; S. Seah; C. Hoe; J. Wang

2002-01-01

22

Mechanical circulatory support for advanced heart failure  

Microsoft Academic Search

Summary  BACKGROUND: Mechanical circulatory support with left ventricular assist devices (LVADs) offers a safe and effective alternative to medical therapy for patients with advanced heart failure. METHODS: Overview about LVAD therapy. RESULTS: LVAD therapy in this population may allow better optimization and more efficient implementation of medical therapy regimens. There is even evidence that in some cases LVAD therapy may prevent

B. Radovancevic; B. Vrtovec; R. Radovancevic; I. Gregoric

2004-01-01

23

In Situ Observation of Creep and Fatigue Failure Behavior for Plasma-Sprayed Thermal Barrier Coating Systems  

NASA Astrophysics Data System (ADS)

In order to investigate crack initiation sites and the crack propagation behavior in connection with the microstructure of thermal barrier coating (TBC) systems under creep and fatigue loadings, the failure behavior was observed in situ for plasma-sprayed TBC systems by optical microscopy, as a first step for elucidating the thermo-mechanical failure mechanism. Two types of TBC systems with differing top-coat (TC) microstructures were prepared by changing the processing conditions. The mechanical failure behavior of TBC system was found to depend strongly on the loading conditions. Under static creep loading, many segmentation cracks in the TC widened with increasing creep strain in the substrate. However, the propagation of these cracks into the bond-coat (BC) and alloy substrate was prevented due to the stress relief induced by plastic flow in the BC layer at elevated temperatures. As a result, the TBC system exhibited typical creep rupture behavior with nucleation and coalescence of microcracks in the alloy substrate interior regardless of the TC microstructure. Under dynamic fatigue loading, on the other hand, many fatigue cracks initiated not only from the tips of segmentation cracks in the TC layer but also from the TC/BC interface. Furthermore, it was found that the fatigue cracks propagated into the BC and alloy substrate even at elevated temperatures above the ductile-brittle transition temperature of the BC; the fatigue failure behavior under dynamic fatigue loading was dependent on the TC microstructure and the properties of the TC/BC interface.

Takahashi, Satoru; Harada, Yoshio

24

Hybrid expert system for the failure analysis of mechanical elements  

Microsoft Academic Search

An expert system for the failure analysis of metallic mechanical components is described, with emphasis on the structure and the solution strategy followed by the software. The system treats failure in common mechanical elements and is aimed to guide non-experts through the process of basic failure analysis. The system acts as a “virtual colleague”, providing guidance and experience during failure

V. H. Jacobo; A. Ortiz; Y. Cerrud; R. Schouwenaars

2007-01-01

25

PVD TBC experience on GE aircraft engines  

NASA Astrophysics Data System (ADS)

The higher performance levels of modern gas turbine engines present significant challenges in the reli-ability of materials in the turbine. The increased engine temperatures required to achieve the higher per-formance levels reduce the strength of the materials used in the turbine sections of the engine. Various forms of thermal barrier coatings have been used for many years to increase the reliability of gas turbine engine components. Recent experience with the physical vapor deposition process using ceramic material has demonstrated success in extending the service life of turbine blades and nozzles. Engine test results of turbine components with a 125 ?m (0.005 in.) PVD TBC have demonstrated component operating tem-peratures of 56 to 83 °C (100 to 150 °F) lower than non-PVD TBC components. Engine testing has also revealed that TBCs are susceptible to high angle particle impact damage. Sand particles and other engine debris impact the TBC surface at the leading edge of airfoils and fracture the PVD columns. As the impacting continues, the TBC erodes in local areas. Analysis of the eroded areas has shown a slight increase in temperature over a fully coated area ; however, a significant temperature reduc-tion was realized over an airfoil without TBC.

Maricocchi, A.; Bartz, A.; Wortman, D.

1997-06-01

26

Heart failure and mechanical circulatory assist devices.  

PubMed

During the last 20 years, the management of heart failure has significantly improved by means of new pharmacotherapies, more timely invasive treatments and device assisted therapies. Indeed, advances in mechanical support, namely with the development of more efficient left ventricular assist devices (LVAD), and the total artificial heart have reduced mortality and morbidity in patients with end-stage heart failure awaiting for transplantation. However, the transplant cannot be the only solution, due to an insufficient number of available donors, but also because of the high number of patients who are not candidates for severe comorbidities or advanced age. New perspectives are emerging in which the VAD is no longer conceived only as a "Bridge to Transplant", but is now seen as a destination therapy. In this review, the main VAD classification, current basic indications, functioning modalities, main limitations of surgical VAD and the total artificial heart development are described. PMID:23985102

La Franca, Eluisa; Iacona, Rosanna; Ajello, Laura; Sansone, Angela; Caruso, Marco; Assennato, Pasquale

2013-05-14

27

The mechanics and mechanisms of failure of hens’ eggs  

Microsoft Academic Search

The mechanics and mechanisms of failure of hens’ eggs have been examined experimentally under contact loading conditions relevant\\u000a to industrial conditions by testing eggs of known provenance in compression between stiff platens. Deformation was modelled\\u000a computationally as a Hertzian contact problem between a thin walled elastic shell and a rigid plate. Contact damage was determined\\u000a by scanning electron microscopy and

Niall Macleod; Maureen M. Bain; John W. Hancock

2006-01-01

28

Structure-sensitive mechanism of nanographene failure  

NASA Astrophysics Data System (ADS)

The quantum-mechanochemical-reaction-coordinate approach has disclosed atomically matched peculiarities that accompany the deformation-failure-rupture process occurring in nanographenes. The high stiffness of the graphene body is provided by the benzenoid unit. The anisotropy of the unit mechanical behavior in combination with different configurations of the unit packing with respect to the body C-C bond chains forms the ground for the structure-sensitive mechanism of the mechanical behavior that is drastically different for two different deformation modes. The zig-zag deformation mode is particularly manifested with the formation of one-atom chains. The approach allows tracing a deformation-stimulated change in the chemical reactivity of both the nanographene body and its individual atoms.

Sheka, E. F.; Popova, N. A.; Popova, V. A.; Nikitina, E. A.; Shaymardanova, L. H.

2011-04-01

29

Structure-sensitive mechanism of nanographene failure  

SciTech Connect

The quantum-mechanochemical-reaction-coordinate approach has disclosed atomically matched peculiarities that accompany the deformation-failure-rupture process occurring in nanographenes. The high stiffness of the graphene body is provided by the benzenoid unit. The anisotropy of the unit mechanical behavior in combination with different configurations of the unit packing with respect to the body C-C bond chains forms the ground for the structure-sensitive mechanism of the mechanical behavior that is drastically different for two different deformation modes. The zig-zag deformation mode is particularly manifested with the formation of one-atom chains. The approach allows tracing a deformation-stimulated change in the chemical reactivity of both the nanographene body and its individual atoms.

Sheka, E. F., E-mail: sheka@icp.ac.ru; Popova, N. A.; Popova, V. A.; Nikitina, E. A.; Shaymardanova, L. H. [Peoples' Friendship University of Russia (Russian Federation)

2011-04-15

30

Insulin Resistance and Heart Failure: Molecular Mechanisms  

PubMed Central

Insulin resistance and associated reductions in cardiac insulin metabolic signaling is emerging as a major factor for the development of heart failure and assumes more importance because of an epidemic increase in obesity and the cardiorenal metabolic syndrome and our aging population. Major factors contributing to the development of cardiac insulin resistance are oxidative stress, hyperglycemia, hyperlipidemia, dysregulated secretion of adipokines/cytokines and inappropriate activation of renin-angiotensin II-aldosterone system (RAAS) and the sympathetic nervous system. The effects of cardiac insulin resistance are exacerbated by metabolic, endocrine and cytokine alterations associated with systemic insulin resistance. The aggregate of these various alterations leads to an insulin resistant phenotype with metabolic inflexibility, impaired calcium handling, mitochondrial dysfunction and oxidative stress, dysregulated myocardial-endothelial interactions resulting in energy deficiency, impaired diastolic dysfunction, myocardial cell death and cardiac fibrosis. Therefore, understanding the molecular mechanisms linking insulin resistance and heart failure may help to design new and more effective mechanism-based drugs to improve myocardial and systemic insulin resistance.

Aroor, Annayya R.; Mandavia, Chirag H.; Sowers, James R.

2012-01-01

31

ESD failure modes: characteristics mechanisms, and process influences  

Microsoft Academic Search

Electrostatic discharge (ESD) failure modes in advanced CMOS processes have been electrically and physically characterized, and an analysis has been made of the mechanisms of each of the main failure modes. The physical failure modes have been related to the electrical degradation and, therefore, the electrical signatures of the damage mechanisms have been obtained. The distribution of the electrical characteristics

Ajith Amerasekera; Werner van den Abeelen; Leo van Roozendaal; Marcel Hannemann; Paul Schofield

1992-01-01

32

Mesh convergence differences based on failure mechanisms  

SciTech Connect

Material properties affect the deformation and failure modes in structural parts. When performing finite element analyses to compare response for different materials, different levels of mesh discretization may be necessary for each analyses because the failure mode changes, even through the part geometry and loading remain the same. Take, for example, strain localization, a material dependent phenomenon. When localization occurs, the mesh needs to be much finer to capture the steep strain gradients in the region of localization than in a case where localization does not occur. Although this requirement is almost intuitive once stated, it is often not used in practice because the effects are less pronounced when failure is not present, and also because failure modes are difficult to anticipate. The lack of availability of constitutive models for failure prediction is also a contributing factor. This paper describes a recent study regarding the effect of mesh refinement on failure prediction in a part modeled with two different materials.

Pilat, K.R. [Cornell Univ., Ithaca, NY (United States); Revelli, V.D. [Sandia National Labs., Livermore, CA (United States)

1994-04-01

33

Mechanical Circulatory Support for Advanced Heart Failure  

Microsoft Academic Search

Opinion statement  Both acute and chronic systolic heart failure can progress to an advanced phase, resulting in stage D heart failure and even\\u000a cardiogenic shock. Despite significant progress in the treatment of systolic heart failure using medical and device therapies,\\u000a this terminal phase continues to be prevalent and associated with unacceptably high morbidity and mortality. Given the inability\\u000a to offer cardiac

Chetan B. Patel; Kevin M. Alexander; Joseph G. Rogers

2010-01-01

34

An experiment on intermittent-failure mechanisms  

NASA Astrophysics Data System (ADS)

Intermittent failures are studied by stressing (temperature, supply voltage and extra loading) good parts. The behavior of the chips under stress is similar to that of a marginal chip under normal operating conditions. The experiments show that most intermittent failures are pattern-sensitive for both sequential and combinational circuits. The stuck-at fault model is shown to be inappropriate to describe intermittent failures. This paper presents a case where a single intermittent failure is not detected by a test set with 100% single stuck-at fault coverage. A stress-strength analysis is presented to explain the experimental results.

Cortes, Mario L.; McCluskey, Edward J.

1987-03-01

35

TBC1D3, a Hominoid-Specific Gene, Delays IRS-1 Degradation and Promotes Insulin Signaling by Modulating p70 S6 Kinase Activity  

PubMed Central

Insulin/IGF-1 signaling plays a pivotal role in the regulation of cellular homeostasis through its control of glucose metabolism as well as due to its effects on cell proliferation. Aberrant regulation of insulin signaling has been repeatedly implicated in uncontrolled cell growth and malignant transformations. TBC1D3 is a hominoid specific gene previously identified as an oncogene in breast and prostate cancers. Our efforts to identify the molecular mechanisms of TBC1D3-induced oncogenesis revealed the role of TBC1D3 in insulin/IGF-1 signaling pathway. We document here that TBC1D3 intensifies insulin/IGF-1-induced signal transduction through intricate, yet elegant fine-tuning of signaling mechanisms. We show that TBC1D3 expression substantially delayed ubiquitination and degradation of insulin receptor substrate-1 (IRS-1). This effect is achieved through suppression of serine phosphorylation at S636/639, S307 and S312 of IRS-1, which are key phosphorylation sites required for IRS-1 degradation. Furthermore, we report that the effect of TBC1D3 on IRS-1:S636/639 phosphorylation is mediated through TBC1D3-induced activation of protein phosphatase 2A (PP2A), followed by suppression of T389 phosphorylation on p70 S6 kinase (S6K). TBC1D3 specifically interacts with PP2A regulatory subunit B56?, indicating that TBC1D3 and PP2A B56? operate jointly to promote S6K:T389 dephosphorylation. These findings suggest that TBC1D3 plays an unanticipated and potentially unique role in the fine-tuning of insulin/IGF-1 signaling, while providing novel insights into the regulation of tumorigenesis by a hominoid-specific protein.

Kong, Chen; Srikanth, Priya; Samovski, Dmitri; Su, Xiong; Stahl, Philip D.

2012-01-01

36

Eastern European developments in failure mechanics  

Microsoft Academic Search

Evolution of Traditional Views on Failure Resistance. At the start of the 20th century, a simplified approach was used to evaluate the conditions for material failure. This was based on certain averaged characteristics of the material, which were identified by tension testing on smooth macroscopic specimens such as the yield point %, and the ultimate strength or temporary resistance %.

V. V. Panasyuk

1993-01-01

37

Electro-Thermomigration as an Electrical Overstress Failure Mechanism.  

National Technical Information Service (NTIS)

A critical review of electro-thermomigration as an EOS/ESD failure mechanism is presented. The paper focuses on the physical basis of the failure mechanism, the strength of the driving forces, and the effects of pulse attributes such as polarity on electr...

D. G. Pierce

1985-01-01

38

Electro-thermomigration as an electrical overstress failure mechanism  

NASA Astrophysics Data System (ADS)

A critical review of electrothermomigration as an EOS/ESD failure mechanism is presented. The paper focuses on the physical basis of the failure mechanism, the strength of the driving forces, and the effects of pulse attributes such as polarity on electrothermomigration. Recommendations or experiments to better understand this phenomenon are given.

Pierce, D. G.

1985-07-01

39

Failure-mechanism models for creep and creep rupture  

Microsoft Academic Search

This tutorial illustrates design situations where creep and creep rupture of components can compromise system performance over time, thereby acting as a wearout failure mechanism. Polycrystalline materials, such as metals and ceramics, and polymers are treated. Analytic microstructural creep mechanisms leading to failure of these materials are presented. Continuum microscale models for predicting long-term creep are explained for practical design

Junhui Li; Abhijit Dasgupta

1993-01-01

40

Failure Load Prediction of Mechanically Fastened Composite Joints  

Microsoft Academic Search

With the wide application of fiber-reinforced composite material in aero-structures and mechanical parts, the design of composite joints has become a very important research area because they are often the weakest regions in composite structures. In this paper, a failure area index method is proposed to predict failure loads of mechanically fastened composite joints under plane stress condition with the

Jin-Ho Choi; Young-Jun Chun

2003-01-01

41

High Temperature Failure Mechanisms in Ceramic Polycrystals.  

National Technical Information Service (NTIS)

The high temperature failure of ceramics has been observed to occur by the nucleation, growth and coalescence of cracks. Each process involves diffusive cavity nucleation and growth, either within a damage zone or at microstructural heterogeneities. The s...

A. G. Evans W. Blumenthal

1983-01-01

42

Manufacturing and failure mechanisms of syntactic foam under compression  

Microsoft Academic Search

Failure mechanisms of syntactic foams under compression were studied. The syntactic foams produced with a new manufacturing method involving buoyancy were made of glass hollow microspheres and epoxy resin. The foam density was varied from 0.09 to 0.15 g\\/cc, which resulted from variation of resin concentration. Two different failure modes were identified and these were attributed to different failure initiation

Ho Sung Kim; Pakorn Plubrai

2004-01-01

43

Failure mechanisms in lithium-ion batteries  

NASA Astrophysics Data System (ADS)

Lithium-ion batteries have become one of the leading candidates for energy storage in electric and hybrid-electric vehicles due to their high energy and power densities. However, the life of this class of rechargeable cells is limited, and is usually considerably shorter than the requirement for an economically feasible alternative to the internal combustion engine. The goal of this research is to explore specific mechanisms for cell failure via mathematical modeling of phenomena that occur in a broad assortment of lithium-ion cells. The theoretical framework of the models presented here is general enough to be applicable to most lithium-ion cells and even electrochemical cells that fall outside the realm of lithium-ion technology, but the properties and parameters that are used are specific enough that quantitative predictions can be made. Specifically, models for passive-film growth at the electrode/electrolyte interface and for particle fracture are presented. In addition, we discuss a framework for describing and understanding various types of capacity fade. Finally, we optimize the design of a lithium-titanate based cell using an existing full-cell model and compare its performance to that of a graphite based cell. The passive-film model indicates that the extent of film growth and impedance rise in a cell should depend strongly upon the state of charge (SOC) at which a battery is stored. We further show that current efficiency increases with the rate at which a cell is charged, although the cycling range of the cell decreases as the current is raised due to the impedance of the film. The particle-fracture model elucidates the conditions under which both graphitic and lithium-manganese-oxide particles surpass their yield strength, at which point cracking is initiated and particle fragmentation may occur. Higher rates of charge and larger particle size generally lead to a higher likelihood of fracture, although this dependence is absent in materials that undergo a two-phase transition. Pressure diffusion and nonidealities embodied in solid-state diffusion and the kinetics of lithium insertion are included in the model, and are shown to have significant impact on the results. Variations in the thermodynamic factor with lithium content result in local SOCs at which the stress in the material is much higher than would be predicted for an ideal solution. The implications of these variations, including the possibility of selecting SOC windows for battery operation that minimize stress, are examined in detail. The high-rate performance of cells with lithium-titanate negative electrodes can be enhanced, relative to cells with graphitic negative electrodes, through the selection of active material of small particle size. The high potential of the lithium-titanate electrode prevents many of the undesirable side reactions that occur in graphitic electrodes, including passive-film formation and lithium deposition. We conclude that the lithium-titanate electrode is probably the more attractive candidate for hybrid-electric-vehicle and other high-power applications.

Christensen, John Francis

44

Static strength and failure mechanism of CFRP under biaxial loadings  

Microsoft Academic Search

Tests of cross-ply composite tubes were performed under combined axial and torsional loading up to failure. Strength properties and failure mechanisms were evaluated with reference to the biaxiality ratio of the loading. The scattering of the biaxial strength data was analyzed using the Weibull distribution. The axial contraction of carbon fiber-reinforced plastic (CFRP) tubes under biaxial loading was investigated theoretically

C. S. Lee; W. Hwang; H. C. Park; K. S. Han

1998-01-01

45

Fatigue life prediction and failure mechanisms of composite materials  

Microsoft Academic Search

Fatigue life prediction and failure mechanisms of composite materials are studied based on the fatigue modulus concept and experimental results. Single-stress level fatigue life is predicted using generalized fatigue modulus degradation model and resultant strain failure criterion. Cumulative damage models defined by fatigue modulus and resultant strains are derived as functions of fatigue cycle and applied stress. This approach can

K. S. Han; W. Hwang

1992-01-01

46

Failure analysis for micro-electrical-mechanical systems (MEMS).  

National Technical Information Service (NTIS)

Micro-Electrical Mechanical Systems (MEMS) is an emerging technology with demonstrated potential for a wide range of applications including sensors and actuators for medical, industrial, consumer, military, automotive and instrumentation products. Failure...

K. A. Peterson P. Tangyunyong D. L. Barton

1997-01-01

47

Failure Mechanisms in Monolithic Integrated Circuits Fejlmekanismer I Monolitiske IC.  

National Technical Information Service (NTIS)

An informative description is presented of the most common failure mechanisms which occur in monolithic integrated circuits, particularly in plastic encapsulated components. There is also a brief description of the precautions already being applied, or th...

B. Schneider

1974-01-01

48

Prevent boiler tube failures -- Part 2: Waterside mechanisms  

Microsoft Academic Search

Boiler tubes can fail due to problems on either the fire-side or the water-side of the tube. Part 1 of this article discussed fire-side failure mechanisms and measures for preventing failures. Here the author focuses on the tubes' water-side. The term water-side mechanisms'' refers to damage on the water side of the boiler tube (as opposed to the fire side).

Colannino

1993-01-01

49

Failure mechanisms of fibrin-based surgical tissue adhesives  

NASA Astrophysics Data System (ADS)

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 stochastic in nature because the mean failure energy and burst pressure values were not predictive of locus and morphology. Instead, flow rate and fibrin concentration showed the most predictive value, with the outcome best described as a probability distribution rather than a specific deterministic outcome.

Sierra, David Hugh

50

Clinical Implication of Mechanical Dyssynchrony in Heart Failure  

PubMed Central

Mechanical dyssynchrony is a common phenomenon in patients with congestive heart failure, which usually identified by noninvasive cardiac imaging tools such as echocardiography. It demonstrates electromechanical delay in some regions of the failing heart which in turn contributes to further impairment of cardiac function. The diagnostic, therapeutic and prognostic values of mechanical dyssynchrony have been reported in a number of studies. Therefore, this review describes briefly the methods of measurement, but more importantly, explains the clinical implication of its assessment in heart failure related aspects including cardiac resynchronization therapy, functional mitral regurgitation, diastolic heart failure and mortality.

Zhang, Qing

2012-01-01

51

IMPERMEABLE THIN AL2O3 OVERLAY FOR TBC PROTECTION FROM SULFATE AND VANADATE ATTACK IN GAS TURBINES  

SciTech Connect

In order to improve the hot corrosion resistance of conventional YSZ TBC system, the overlay of Al{sub 2}O{sub 3} coating was deposited on the TBC by EB-PVD techniques. Hot corrosion tests were carried out on the TBC with and without Al{sub 2}O{sub 3} coating in molten salts mixtures (Na{sub 2}SO{sub 4} + 5%V{sub 2}O{sub 5}) at 950 C for 10h. The microstructures of TBC and overlay before and after exposure were examined by means of scanning electron microscopy (SEM), energy-dispersive X-ray spectrometer (EDX) and X-ray diffraction (XRD). It has been found that TBC will react with V{sub 2}O{sub 5} to form YVO{sub 4}. A substantial amount of M-phase was formed due to the leaching of Y{sub 2}O{sub 3} from YSZ. Al{sub 2}O{sub 3} overlay coating deposited by EB-PVD was dense, continues and adherent to the TBC. As a result, overlay Al{sub 2}O{sub 3} coating can prevent the YSZ from the attack by molten salts containing vanadium and arrest the penetration of salts into the YSZ along porous and cracks in the YSZ TBC, although there were some cracks in overlay Al{sub 2}O{sub 3} coating and at the interface between alumina and zirconia formed during hot corrosion tests due to the presence of tensile stress in the alumina coating. In the next reporting period, we will study the mechanisms of cracking of the overlay Al{sub 2}O{sub 3} layer and finish the hot corrosion tests of TBC with Al{sub 2}O{sub 3} coating deposited by high velocity oxy-fuel (HVOF) technique. The hot corrosion test of TBC with EB-PVD deposited Al{sub 2}O{sub 3} coating will be again performed. However before hot corrosion tests, a post-annealing will be carried out in vacuum (residual pressure 10{sup -3} Pa) at 1273K for 1h in order to transform the as-sputtered Al{sub 2}O{sub 3} overlay to crystalline {alpha}-Al{sub 2}O{sub 3} overlay.

Scott X. Mao

2002-01-31

52

Influence of EB-PVD TBC Microstructure on Thermal Barrier Coating System Performance Under Cyclic Conditions  

SciTech Connect

The lifetimes of electron beam physical vapor deposited (EB-PVD) thermal barrier coating systems (TBCs) with three different microstructures of the Y2O3-stabilized ZrO, YSZ) ceramic top layer were investigated in lh thermal cycles at 1100 and 1150°C in flowing oxygen. Single crystal alloys CMSX-4 and Rene N5 that had been coated with an EB-PVD NiCoCrAlY bond coat were chosen as substrate materials. At 1150°C all samples failed after 80-100, lh cycles, predominantly at the bond coat/alumina interface after cooling down from test temperature. The alumina scale remained adherent to the YSZ after spallation. Despite the different YSZ microstructures no clear tendency regarding differences in spallation behavior were observed at 1150°C. At 1100°C the minimum lifetime was 750 , lh cycles for CMSX-4, whereas the first Rene N5 specimen failed after 1750, lh cycles. The longest TBC lifetime on CMSX-4 substrates was 1250, lh cycles, whereas the respective Rene N5 specimens have not yet failed after 2300, lh cycles. The failure mode at 1100°C was identical to that at 115O?C, i.e. the TBC spalled off the surface exposing bare metal after cooling. Even though not all specimens have failed to date, the available results at 1100°C suggested that both, the substrate alloy chemistry and the YSZ microstructure significantly affect the spallation resistance of the TBC.

Leyens, C.; Pint, B.A.; Schulz, U.; Wright, I.G.

1999-04-12

53

PBFA-2 vacuum insulator stack failure mechanisms  

NASA Astrophysics Data System (ADS)

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.

Sweeney, M. A.

54

Ultraviolet photoelectron spectra of Tb@C 82  

NASA Astrophysics Data System (ADS)

Photoelectron spectra of the metallofullerene Tb@C 82 (I) were measured using a synchrotron radiation source. The band intensity of the Tb@C 82 (I) spectra was found to depend on the incident photon energy, as has been observed for other fullerenes. The spectral onset energy is 0.25 eV below the Fermi level. This value is nearly equal to that for La@C 82 (I) and is smaller than that for the empty C 82. The spectral shapes of Tb@C 82 (I) resemble those of La@C 82 (I).

Iwasaki, Kentaro; Wanita, Norihiko; Hino, Shojun; Yoshimura, Daisuke; Okazaki, Toshiya; Shinohara, Hisanori

2004-11-01

55

Mechanics concepts for failure in ferroelectric ceramics  

Microsoft Academic Search

The article reviews mechanics concepts suitable for analyzing defects (cracks, domain walls, etc.) in ferroelectric ceramics. Constitutive laws are summarized for dielectric, electrostrictive and piezoelectric ceramics. The formulation is based on an energy function of strain and induction, and a few experimental facts. Also summarized are the differential equations that govern stress and electric fields. Griffith's energy release rate is

Z. Suo

1991-01-01

56

Analysis of failure mechanism and stress influence on cylinder  

Microsoft Academic Search

Cylinder, which converts pressure of compressed gas into mechanical energy, is one of main pneumatic actuators in electromechan ical products. With application of cylinder becoming broader and broader, the demand on high reliability of cylinder gets more and more urgent. In order to improve the reliability of cylinder, it must be made clear the failure mechanism of it beforehand. This

Juan Chen; Xiaoye Qi; Bohong Liu; Deyi Wang

2011-01-01

57

Illuminating the functional and structural repertoire of human TBC\\/RABGAPs  

Microsoft Academic Search

The Tre2–Bub2–Cdc16 (TBC) domain-containing RAB-specific GTPase-activating proteins (TBC\\/RABGAPs) are characterized by the presence of highly conserved TBC domains and act as negative regulators of RABs. The importance of TBC\\/RABGAPs in the regulation of specific intracellular trafficking routes is now emerging, as is their role in different diseases. Importantly, TBC\\/RABGAPs act as key regulatory nodes, integrating signalling between RABs and other

Marieke A. M. Frasa; Katja T. Koessmeier; M. Reza Ahmadian; Vania M. M. Braga

2012-01-01

58

Mechanics concepts for failure in ferroelectric ceramics  

NASA Astrophysics Data System (ADS)

The article reviews mechanics concepts suitable for analyzing defects (cracks, domain walls, etc.) in ferroelectric ceramics. Constitutive laws are summarized for dielectric, electrostrictive and piezoelectric ceramics. The formulation is based on an energy function of strain and induction, and a few experimental facts. Also summarized are the differential equations that govern stress and electric fields. Griffith's energy release rate is examined for a body containing a defect under applied force and voltage, followed by applications to multilayer capacitors, conducting cracks, impermeable cracks and domain bands. A generalized Irwin-Kies relation is presented, explaining the peculiar results that the energy release rates are negative for non-conducting cracks but positive for conducting cracks. Singular fields around impermeable and conducting cracks axe contrasted. The possibility of using the energy release rate to correlate breakdown resistance of a ceramic is considered.

Suo, Z.

59

Survey on Failure Modes and Failure Mechanisms in Digital Components and Systems  

SciTech Connect

This paper presents the preliminary results of a survey on the operating experience of a broad range of digital components and systems deployed in various industries. The primary objective of this survey is to identify principal modes and mechanisms of failure in field-deployed digital systems. Earlier works have sought to determine the failure rates of various classes of digital devices with the intent to integrate this information into the risk analysis calculations though still immature for such systems. Failure rates of individual components or systems are not taken into account in this evaluation; only failure modes and their respective probabilistic distribution are considered. Preliminary results from two data sources, SPIDR and FARADIP, are presented.

Cetiner, Mustafa Sacit [ORNL; Korsah, Kofi [ORNL; Muhlheim, Michael David [ORNL

2009-01-01

60

Prevent boiler tube failures -- Part 2: Water-side mechanisms  

SciTech Connect

Boiler tubes can fail due to problems on either the fire-side or the water-side of the tube. Part 1 of this article discussed fire-side failure mechanisms and measures for preventing failures. Here the author focuses on the tubes' water-side. The term water-side mechanisms'' refers to damage on the water side of the boiler tube (as opposed to the fire side). However, the water itself is often not the culprit. Water-side corrosion mechanisms may be classified into two major categories: physical and chemical. Physical mechanisms include steam blanketing and overheating. Chemical mechanisms include: deposition; caustic, acidic, and chelant corrosion; oxidation; and hydrogen embrittlement.

Colannino, J. (Colannino Consultants, Oceanside, CA (United States))

1993-11-01

61

Failure mechanisms of flash cell in program\\/erase cycling  

Microsoft Academic Search

The impact of program\\/erase cycling on flash memory cell is reviewed considering both performance degradation of the typical bit and the evolution of the erase threshold voltage distribution of the whole memory array. Emphasis is given to the failure mechanisms which affect flash memory endurance: the erratic erase phenomenon is discussed with reference to the model recently reported in the

P. Cappelletti; R. Bez; D. Cantarelli; L. Fratin

1994-01-01

62

Popcorning: a failure mechanism in plastic-encapsulated microcircuits  

Microsoft Academic Search

Popcorning is a failure mechanism in plastic-encapsulated microcircuits. It occurs when the inherently hygroscopic encapsulant is rapidly exposed to high temperatures during reflow solder assembly of the component to a printed circuit card. At these temperatures the moisture absorbed by the molding compound vaporizes and rapidly expands leading to the development of high stresses. When these stresses exceed both the

Anthony A. Gallo; Ramesh Munamarty

1995-01-01

63

Failure analysis of deployment mechanism of a satellite solar array  

Microsoft Academic Search

The reliability issue of a solar array deployment mechanism was analyzed with FMECA and FTA. The main failure modes, their effects and criticalities were illustrated. A fault tree was built. Both qualitative analysis and the quantitative analysis of the fault tree were performed. The probability of the top event, the structural importance and the critical importance coefficients of different basic

Yi Yang; Shaoze Yan; Liyang Xie; Jianing Wu

2011-01-01

64

Failure Mechanisms for Ceramic Matrix Textile Composites at High Temperature  

SciTech Connect

OAK B188 Failure Mechanisms for Ceramic Matrix Textile Composites at High Temperature. This summary refers to work done in approximately the twelve months to the present in our contract ''Failure Mechanisms for Ceramic Matrix Textile Composites at High Temperature,'' which commenced in August, 1997. Our activities have consisted mainly of measurements of creep-controlled crack growth in ceramic matrix composites (CMCS) at high temperature; imaging of deformation fields in textile CMCS; the assessment of mechanisms of damage in textile composites, especially those with through-thickness reinforcement; the formulation of models of delamination crack growth under fatigue in textile composites; analytical models of the bridging traction law for creeping fibers in a CMC at high temperature; and an analytical model of a bridging fiber tow in a textile composite.

Cox, Brian

1999-03-01

65

Spontaneous thermal runaway as an ultimate failure mechanism of materials.  

PubMed

The first theoretical estimate of the shear strength of a perfect crystal was given by Frenkel [Z. Phys. 37, 572 (1926)10.1007/BF01397292]. By assuming that two rigid atomic rows in the crystal would move over each other along a slip plane, he derived the ultimate shear strength to be about one-tenth of the shear modulus. Here we present a theoretical study showing that catastrophic failure of viscoelastic materials may occur below Frenkel's ultimate limit as a result of thermal runaway. The thermal runaway failure mechanism exhibits progressive localization of the strain and temperature profiles in space, thereby producing a narrow region of highly deformed material, i.e., a shear band. We calculate the maximum shear strength sigma_{c} of materials and then demonstrate the relevance of this new concept for material failure known to occur at scales ranging from nanometers to kilometers. PMID:17359169

Braeck, S; Podladchikov, Y Y

2007-03-02

66

IMPERMEABLE THIN AL2O3 OVERLAY FOR TBC PROTECTION FROM SULFATE AND VANADATE ATTACK IN GAS TURBINES  

SciTech Connect

The project started on September 1, 2001. During last 4 months, one post-doctor has been hired for this project. We have received TBC samples (YSZ/CoNiCrAlY/ Inconel 601) from Tohoku University, Japan, while processing of the TBC samples was delayed in GE Corp. Research and Development. The TBC preparation in Japan was based on our technical requirement by plasma spray. Bond coat CoNiCrAlY and the YSZ was produced by low-pressure plasma spray and air plasma spray respectively. The morphology of the surface and the microstructure of cross-section of the sample was observed and analyzed by SEM and EDX. XRD was also used to detect the phases in the YSZ. Currently we are processing the overlay Al{sub 2}O{sub 3} on the TBC samples by EB-PVD and high velocity oxy-fuel (HVOF) spray techniques in collaboration with Penn State University and State University of New York at Stony Brook. We will finish comparing the hot corrosion behavior of the Al{sub 2}O{sub 3}/YSZ/CoNiCrAlY/superalloy system with the YSZ/CoNiCrAlY/superalloy system. The mechanism of hot corrosion will be investigated. The processing-structure-properties relationship of the overlays will be determined.

Scott X. Mao

2002-01-31

67

Noninvasive mechanical ventilation in acute hypoxaemic respiratory failure  

Microsoft Academic Search

ABSTRACT: In acute hypoxaemic respiratory failure (HRF), oxygenation, reduction in the work,of breathing and in dyspnoea,may,be achieved by delivering noninvasive mechanical,ventilation (NIMV). Several uncontrolled and 13 randomized,controlled studies (RCS) were,reviewed. Uncontrolled studies confirmed,the feasibility and the possibility to improve,arterial blood oxygenation,with NIMV. The 13 RCS compared,NIMV versus a conventional approach,in a total of 720 patients with HRF. Endotracheal intubation was

M. Wysocki; M. Antonelli

2001-01-01

68

Evolution of Tre-2/Bub2/Cdc16 (TBC) Rab GTPase-activating proteins  

PubMed Central

Rab GTPases serve as major control elements in the coordination and definition of specific trafficking steps and intracellular compartments. Rab activity is modulated in part by GTPase-activating proteins (GAPs), and many RabGAPs share a Tre-2/Bub2/Cdc16 (TBC)–domain architecture, although the majority of TBC proteins are poorly characterized. We reconstruct the evolutionary history of the TBC family using ScrollSaw, a method for the phylogenetic analysis of pan-eukaryotic data sets, and find a sophisticated, ancient TBC complement of at least 10 members. Significantly, the TBC complement is nearly always smaller than the Rab cohort in any individual genome but also suggests Rab/TBC coevolution. Further, TBC-domain architecture has been well conserved in modern eukaryotes. The reconstruction also shows conservation of ancestral TBC subfamilies, continuing evolution of new TBCs, and frequent secondary losses. These patterns give additional insights into the sculpting of the endomembrane system.

Gabernet-Castello, Carme; O'Reilly, Amanda J.; Dacks, Joel B.; Field, Mark C.

2013-01-01

69

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

NASA Astrophysics Data System (ADS)

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.

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

2011-12-01

70

Effect of higher water vapor content on TBC performance  

SciTech Connect

Coal gasification, or IGCC (integrated gasification combined cycle), is one pathway toward cleaner use of coal for power generation with lower emissions. However, when coal-derived synthesis gas (i.e., syngas) is burned in turbines designed for natural gas, turbine manufacturers recommend 'derating,' or lowering the maximum temperature, which lowers the efficiency of the turbine, making electricity from IGCC more expensive. One possible reason for the derating is the higher water vapor contents in the exhaust gas. Water vapor has a detrimental effect on many oxidation-resistant high-temperature materials. In a turbine hot section, Ni-base superalloys are coated with a thermal barrier coating (TBC) allowing the gas temperature to be higher than the superalloy solidus temperature. TBCs have a low thermal conductivity ceramic top coating (typically Y{sub 2}O{sub 3}-stabilized ZrO{sub 2}, or YSZ) and an oxidation-resistant metallic bond coating. For land-based gas turbines, the industry standard is air plasma sprayed (APS) YSZ and high velocity oxygen fuel (HVOF) sprayed NiCoCrAlY bond coatings. To investigate the role of higher water vapor content on TBC performance and possible mitigation strategies, furnace cycling experiments were conducted in dry O{sub 2} and air with 10% (typical with natural gas or jet fuel) or 50 vol% water vapor. Cycle frequency and temperature were accelerated to one hour at 1100 C (with 10 minute cooling to {approx}30 C between each thermal cycle) to induce early failures in coatings that are expected to operate for several years with a metal temperature of {approx}900 C. Coupons (16 mm diameter x 2 mm thick) of commercial second-generation single crystal superalloy CMSX4 were HVOF coated on both sides with {approx}125 {micro}m of Ni-22wt%Co-17Cr-12Al either with 0.7Y or 0.7Y-0.3Hf-0.4Si. One side was then coated with 190-240 {micro}m of APS YSZ. Coatings were cycled until the YSZ top coating spalled. Figure 2 shows the results of the initial phase of experiments. Compared to dry O{sub 2}, the addition of 10% water vapor decreased the lifetime of MCrAlY by {approx}30% for the conventional CMSX4 substrates. Higher average lifetimes were observed with Hf in the bond coating, but a similar decrease in lifetime was observed when water vapor was added. The addition of Y and La to the superalloy substrate did not change the YSZ lifetime with 10% water vapor. However, increasing water vapor content from 10 to 50% did not further decrease the lifetime of either bond coating with the doped superalloy substrate. Thus, these results suggest that higher water vapor contents cannot explain the derating of syngas-fired turbines, and other factors such as sulfur and ash from imperfect syngas cleanup (or upset conditions) need to be explored. Researchers continue to study effects of water vapor on thermally grown alumina scale adhesion and growth rate, and are looking for bond coating compositions more resistant to oxidation in the presence of water vapor.

Pint, Bruce A [ORNL; Haynes, James A [ORNL

2012-01-01

71

Temporal patterns and mechanisms of epilepsy surgery failure.  

PubMed

Epilepsy surgery is an accepted treatment option in patients with medically refractory focal epilepsy. Despite various advances in recording and localization noninvasive and invasive techniques (including electroencephalography (EEG), magnetic resonance imaging (MRI), positron emission tomography (PET), single photon emission computed tomography (SPECT), magnetoencephalography (MEG), subdural grids, depth electrodes, and so on), the seizure outcome following surgical resection remains suboptimal in a significant number of patients. The availability of long-term outcome data on an increasing number of patients suggests two major temporal patterns of seizure recurrence (early vs. late) that implicate the following two different mechanisms for seizure recurrence: (1) a failure to either define/resect the epileptogenic zone, and (2) the nonstatic nature of epilepsy as a disease through the persistence of proepileptic cortical pathology. We describe the temporal patterns of epilepsy surgery failures and discuss their potential clinical, histopathologic, genetic, and molecular mechanisms. In addition, we review predictors of successful surgical interventions and analyze the natural history of epilepsy following surgical intervention. We hypothesize that the acute/early postoperative failures are due to errors in localizing and/or resecting the epileptic focus, whereas late recurrences are likely due to development/maturation of a new and active epileptic focus (de novo epileptogenesis). PMID:23586531

Najm, Imad; Jehi, Lara; Palmini, Andre; Gonzalez-Martinez, Jorge; Paglioli, Eliseu; Bingaman, William

2013-04-15

72

Failure analysis for micro-electrical-mechanical systems (MEMS)  

SciTech Connect

Micro-Electrical Mechanical Systems (MEMS) is an emerging technology with demonstrated potential for a wide range of applications including sensors and actuators for medical, industrial, consumer, military, automotive and instrumentation products. Failure analysis (FA) of MEMS is critically needed for the successful design, fabrication, performance analysis and reliability assurance of this new technology. Many devices have been examined using techniques developed for integrated circuit analysis, including optical inspection, scanning laser microscopy (SLM), scanning electron microscopy (SEM), focused ion beam (FIB) techniques, atomic force microscopy (AFM), infrared (IR) microscopy, light emission (LE) microscopy, acoustic microscopy and acoustic emission analysis. For example, the FIB was used to microsection microengines that developed poor performance characteristics. Subsequent SEM analysis clearly demonstrated the absence of wear on gear, hub, and pin joint bearing surfaces, contrary to expectations. Another example involved the use of infrared microscopy for thermal analysis of operating microengines. Hot spots were located, which did not involve the gear or hub, but indicated contact between comb structures which drive microengines. Voltage contrast imaging proved useful on static and operating MEMS in both the SEM and the FIB and identified electrostatic clamping as a potentially significant contributor to failure mechanisms in microengines. This work describes MEMS devices, FA techniques, failure modes, and examples of FA of MEMS.

Peterson, K.A.; Tangyunyong, P.; Barton, D.L.

1997-10-01

73

A fracture mechanics-based model for assessing the mechanical failure of nuclear fuel rods due to rock fall  

Microsoft Academic Search

One of the potential failure mechanisms of nuclear fuel rods that will be disposed in the proposed Yucca Mountain repository is mechanical failure of the degraded cladding tubes caused by rock fall impacting on waste packages. In this paper, the development of a fracture mechanics-based model for treating rock fall-induced failure of nuclear fuel cladding tubes is described. The rock

Kwai S. Chan; Yi-der Lee

2000-01-01

74

Damage and failure mechanisms associated with photoablation of biological tissues  

SciTech Connect

This paper aims to examine the processes associated with failure of the cornea and other collagenous tissues during photoablation. Two different constitutive models are applied to simulate a series of laser deposition experiments into porcine reticular dermis (1), a biological tissue similar to the cornea in composition and photoablation characteristics. The first of our constitutive models, DFRACT, is a physically motivated, micromechanical model based on the nucleation and growth of spherical voids (2). The second is a relatively simple model that allows the material to vaporize and thermally soften. The simulation results reproduce the prominent features observed experimentally thereby shedding a new light on the operative mechanisms during photoablation. The good qualitative agreement between the simulated stress histories and the stress histories measured during the experiments also demonstrates the effectiveness of micromechanical damage and failure modeling as a viable tool for optimizing existing laser surgery procedures and designing new ones. {copyright} {ital 1996 American Institute of Physics.}

Antoun, T.; Seaman, L.; Curran, D. [Poulter Laboratory, SRI International, 333 Ravenswood Avenue, Menlo Park, California 94025 (United States); Glinsky, M. [Lawrence Livermore National Laboratory, 7000 East Avenue, P.O. Box 808, Livermore, California 94551 (United States)

1996-05-01

75

49 CFR 191.12 - Distribution Systems: Mechanical Fitting Failure Reports  

Code of Federal Regulations, 2011 CFR

...Systems: Mechanical Fitting Failure Reports 191.12 Section 191.12...OTHER GAS BY PIPELINE; ANNUAL REPORTS, INCIDENT REPORTS, AND SAFETY-RELATED CONDITION...Mechanical Fitting Failure Report Form PHMSA F-7100.1-2. An...

2011-10-01

76

49 CFR 191.12 - Distribution Systems: Mechanical Fitting Failure Reports  

Code of Federal Regulations, 2012 CFR

...Systems: Mechanical Fitting Failure Reports 191.12 Section 191.12...OTHER GAS BY PIPELINE; ANNUAL REPORTS, INCIDENT REPORTS, AND SAFETY-RELATED CONDITION...Mechanical Fitting Failure Report Form PHMSA F-7100.1-2. An...

2012-10-01

77

Failure of cerebrospinal fluid shunts: part I: Obstruction and mechanical failure.  

PubMed

Ventricular shunts are commonly employed to treat children with hydrocephalus. Complications from shunts are common and can present with a variety of signs and symptoms. This pair of reviews discusses the common findings in patients with shunt malfunction, including physical examination and imaging findings. Part I of the series discusses obstruction and mechanical failure of shunts; Part II discusses overdrainage, loculation, and abdominal complications of shunts. An understanding of the presentation and etiology of shunt dysfunction is critical for neurologists and pediatricians who often are the first to evaluate and triage these children. PMID:16458818

Browd, Samuel R; Ragel, Brian T; Gottfried, Oren N; Kestle, John R W

2006-02-01

78

Failure mechanism of epoxy polymer: transition from ductile to brittle failure  

NASA Astrophysics Data System (ADS)

The failure processes of an epoxy polymer (Epicote 21506) were studied by using a high speed camera evolving over a range of strain rates from 0.0001s-1 to 668s-1. The front surface of the specimen was monitored by the high speed camera to capture the deformation and cracking processes. A split Hopkinson pressure bar (SHPB) was utilized to examine the dynamic response of the material, and the uniaxial compression test was applied for its quasi-static behavior. The microstructure of the specimen fracture surface after quasi-static and dynamic compression was also investigated by using a Scanning Electron Microscope (SEM) to look insight into the failure mechanism of the material. With the coupled analysis of stress-strain curves and captured images, the behaviors of the specimen under static and dynamic loading can be determined precisely with sufficient details. The specimen under static loading displayed ductile failure, while that under dynamic loading revealed different brittle damage behaviors.

Wu, Wei; Ma, Guowei

2009-12-01

79

Failure analysis and seal life prediction for contacting mechanical seals  

NASA Astrophysics Data System (ADS)

Fault tree analysis method was applied to quantitatively investigate the causes of the leakage failure of mechanical seals. It is pointed out that the change of the surface topography is the main reasons causing the leakage of mechanical seals under the condition of constant preloads. Based on the fractal geometry theory, the relationship between the surface topography and working time were investigated by experiments, and the effects of unit load acting on seal face on leakage path in a mechanical seal were analyzed. The model of predicting seal life of mechanical seals was established on the basis of the relationship between the surface topography and working time and allowable leakage. The seal life of 108 mechanical seal operating at the system of diesel fuel storage and transportation was predicted and the problem of the condition monitoring for the long-period operation of mechanical seal was discussed by this method. The research results indicate that the method of predicting seal life of mechanical seals is feasible, and also is foundation to make scheduled maintenance time and to achieve safe-reliability and low-cost operation for industrial devices.

Sun, J. J.; He, X. Y.; Wei, L.; Feng, X.

2008-11-01

80

Design and Environmental Factors Contributing to the Failure of Thermal Barrier Coating Systems  

NASA Astrophysics Data System (ADS)

Gas turbine engines are a staple of 21st century air and sea propulsion systems and are also a critical component in large-scale electricity generation. The hot-section components of these engines are protected by a complex ceramic and metal multi-layer coating called a thermal barrier coating (TBC) system. The failure of TBC systems occurs as a result of both thermo-chemical and thermo-mechanical degradation. This research involves exploring both of these mechanisms for two distinctly different issues. The United States Navy is currently making a push to implement the use of alternative fuels by 2012, but the use of these fuels (syngas, high hydrogen content, and alternatives to JP-8) presents significant materials durability challenges. Initial data suggests that high water vapor levels, high sulfur concentrations, and ash deposits from fuel impurities lead to unique, and severe, degradation modes. This research is aimed at addressing the effects of differing combustion environment characteristics on the corrosion and oxidation of TBC systems. On the industrial front, there is a constant driver to better understand and predict coating failure, particularly in air-plasma sprayed (APS) TBC systems. The morphology of the metal-ceramic interface is known to play a key role in the generation of compressive and tensile stresses that eventually cause coating failure in typical engine environments. Experimental evidence and field experience have shown that a tortuous interface is generally beneficial to coating lifetime. Nevertheless, for the past 40 years engineers have struggled to find a functional correlation between BC topology and coating system lifetime. This document also addresses the progress that has been made toward the establishment of this functional correlation.

Weeks, Matthew David

81

A neural mechanism underlying memory failure in older adults  

PubMed Central

Older adults have reduced memory, primarily for recall, but also for recognition (Craik and McDowd, 1987), particularly for unfamiliar faces (Bartlett et al., 1989). Behavioral studies have shown that age-related memory declines are due in part to distraction from impaired inhibition of task-irrelevant input during encoding (Healey et al., 2008). Functional magnetic resonance imaging (fMRI) has been used to uncover the sources of memory deficits associated with aging. To date, this work has focused on successful encoding, while the neural correlates of unsuccessful encoding are unknown. Here we provide novel evidence of a neural mechanism underlying memory failures exclusively affecting older adults. Whereas both younger and older adults showed reduced activation of brain regions important for encoding (e.g., hippocampus) during unsuccessful encoding, only older adults showed increased activity in brain regions mediating distraction (e.g., auditory cortex) and in left prefrontal cortex. Further, these regions were functionally connected with medial parietal areas, previously identified as default mode regions (Raichle and Snyder, 2007), which may reflect environmental monitoring. Our results suggest that increased distraction from task-irrelevant input (auditory in this case), associated with the unfamiliar and noisy fMRI environment, may increase environmental monitoring. This in turn could hinder suppression of default mode processing, resulting in memory failures in older adults. These findings provide novel evidence of a brain mechanism underlying the behavioral evidence that impaired inhibition of extraneous input during encoding leads to memory failure in older adults, and may have implications for the ubiquitous use of fMRI for investigating neurocognitive aging.

Stevens, W. Dale; Hasher, Lynn; Chiew, Kimberly S.; Grady, Cheryl L.

2008-01-01

82

Mechanisms and pathways of growth failure in primordial dwarfism.  

PubMed

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

Klingseisen, Anna; Jackson, Andrew P

2011-10-01

83

Non-destructive microwave evaluation of TBC delamination induced by acute angle laser drilling  

NASA Astrophysics Data System (ADS)

Laser drilling has been applied to the production of cooling holes of various size and angles in the modern aerospace gas turbine components such as turbine blades, nozzle guide vanes, combustion chambers and afterburner. These parts are usually made of heat resistant nickel superalloys. The superalloy substrate is coated with yttria-stabilized zirconia thermal barrier coatings (TBCs) to protect them from reaching excessive temperatures in hot engine environments. Drilling the parts at acute angles to the surface is complicated because (i) multiple layers are being drilled through, (ii) the melt ejection and heat flow patterns around the hole are non-symmetrical and (iii) the drilling distance is greater than when drilling normal to the surface. In a previous investigation by the authors, delamination of TBC was addressed as a main problem of angled drilling and mechanisms involved were discussed. Characterization of delamination cracks was normally performed via metallographic techniques. It involves sectioning the samples using an abrasive cutting machine, grinding with successively finer silicon carbide paper up to the centre of the hole and polishing to allow optical microscopic analysis of the cracks. However, clamping and sectioning process of thermal-spray-coated workpieces can introduce cracks in brittle coatings due to the drag of the cut-off wheels. Hence, it is not possible to decide if the delamination is caused as a result of post-process sectioning or laser drilling. In this paper, a microwave non-destructive testing (NDT) technique is employed to evaluate the integrity of TBC after acute angle laser drilling. An Agilent 8510 XF network analyser operating over the frequency range of 45 MHz to 110 GHz was used to measure the amplitude and phase variations of scattered waves. The results significantly indicated the existence of delamination of 1-1.5 mm long at the TBC/substrate interface on the leading edge part of an acute-angled hole laser drilled using a 400 W Nd:YAG laser.

Sezer, H. K.; Li, Lin; Wu, Z.; Anderson, B.; Williams, P.

2007-01-01

84

Deformation and failure mechanism in AISI 4340 steel under ballistic impact  

Microsoft Academic Search

Deformation and failure mechanism in quench-hardened AISI 4340 steel under ballistic impact is investigated. The influence of microstructure on damage evolution is also evaluated. Strain localization and shear failure along adiabatic shear bands are the dominant deformation and failure mechanisms. The time and critical strain for the commencement of strain localization is influenced by strain rate and microstructure. The microstructure

A. G. Odeshi; S. Al-ameeri; S. Mirfakhraei; F. Yazdani; M. N. Bassim

2006-01-01

85

Failure mechanisms and surface roughness statistics of fractured Fontainebleau sandstone.  

PubMed

In an effort to investigate the link between failure mechanisms and the geometry of fractures of compacted grains materials, a detailed statistical analysis of the surfaces of fractured Fontainebleau sandstones has been achieved. The roughness of samples of different widths W is shown to be self-affine with an exponent zeta=0.46+/-0.05 over a range of length scales ranging from the grain size d up to an upper cutoff length xi approximately =0.15 W. This low zeta value is in agreement with measurements on other sandstones and on sintered materials. The probability distributions pi delta z(delta h) of the variations of height over different distances delta z>d can be collapsed onto a single Gaussian distribution with a suitable normalization and do not display multiscaling features. The roughness amplitude, as characterized by the height-height correlation over fixed distances delta z, does not depend on the sample width, implying that no anomalous scaling of the type reported for other materials is present. It is suggested, in agreement with recent theoretical work, to explain these results by the occurrence of brittle fracture (instead of damage failure in materials displaying a higher value of zeta approximately =0.8 ). PMID:17930307

Ponson, L; Auradou, H; Pessel, M; Lazarus, V; Hulin, J P

2007-09-12

86

Mechanical Measurement of Gels: Pre-stress and Failure  

NASA Astrophysics Data System (ADS)

A recently developed technique, Cavitation Rheology (CR), provides a means of measuring the mechanical properties of soft materials on length scales from ˜0.1 ?m to mm at a specific location. CR involves inflation of a small bubble at the tip of a syringe needle which has been inserted into a material. After insertion, the pressure in the syringe is raised until a critical point where the material fails, resulting in rapid inflation of a cavity at the syringe tip. The critical pressure for failure can provide information about the materials properties of the system such as the elastic modulus, E, the critical strain energy release rate, Gc, and the surface energy, ?. Modulus measurements by CR have been made in many synthetic gels and biological tissues with similar accuracy to shear rheology. However, as CR requires insertion of a needle into the subject material, measurements are inherently made in a pre-stressed state. In this work, we have examined the pre-stress associated with needle insertion and the influence of this stress on failure in a synthetic gel of PMMA-PnBA-PMMA triblock copolymer in 2-ethylhexanol.

Fakhouri, Sami; Hutchens, Shelby; Crosby, Alfred

2013-03-01

87

On study of nonclassical problems of fracture and failure mechanics and related mechanisms  

Microsoft Academic Search

Nonclassical problems of fracture and failure mechanics that have been analyzed by the author and his collaborators at the\\u000a S. P. Timoshenko Institute of Mechanics (Kiev, National Academy of Sciences of Ukraine) during the past forty years are considered\\u000a in brief. The results of the analysis are presented in a form that would be quite informative for the majority of

Alexander N. Guz

2009-01-01

88

LIPID Abnormalities and Atherogenesis in Chronic Renal Failure. (Mechanism of Hyperlipidemia in Chronic Renal Failure).  

National Technical Information Service (NTIS)

The report presents the results of a project to test whether the hyperlipidemia of chronic renal failure is associated with altered hepatic lipogenesis or carbohydrate metabolism. The rates of lipogenesis are measured in animals with chronic renal failure...

L. M. Lowenstein D. Phil

1975-01-01

89

Failure mechanisms of flip chip DCA assembly using eutectic solder  

Microsoft Academic Search

Reliability performance is still the major concern for flip chip interconnection. While solder fatigue is believed to be the contributing factor for packaging failure and is the most widely studied for flip chip soldering, experimental work in this study find out solder fatigue itself is seldom the driving force for early failure. With the introduction of underfill, failures solely due

Qing Tan; Rebecca Cole; Addi Mistry; Craig Beddingfield

2000-01-01

90

Mechanisms of cell death in acute liver failure.  

PubMed

Acute liver failure (ALF) can be the consequence of various etiologies, that might vary between different geographic regions. Most frequent are intoxications with acetaminophen, viral hepatitis, or liver damage of unknown origin. ALF occurs when the extent of hepatocyte death exceeds the regenerative capacity of the liver. The mode of liver cell death that is predominantly induced in ALF, i.e., apoptosis or necrosis, is still controversial and presumably determined by the etiology, duration, and magnitude of liver injury. Severe liver damage involves oxidative stress and depletion of ATP resulting in necrosis. In contrast, maintenance of ATP stores is required for the execution of apoptosis. Recent data suggest that necrosis resulting from severe liver damage is associated with poor outcome of ALF patients. Discrimination between apoptosis and necrosis might be therefore useful for the identification of ALF patients requiring liver transplantation. Identification of the molecular cell death mechanisms remains an important issue not only for early prediction of ALF outcome, but also for therapeutic interventions. In view of the pleiotropic functions of critical mediators of cell death and tissue regeneration, a particular challenge will be to reduce hepatocellular death without inhibiting the regenerative capacity of the liver. Here, we review the molecular mechanisms of hepatocyte injury and the pathways leading to apoptosis and necrosis, which might represent potential diagnostic and therapeutic targets in ALF. PMID:22485095

Bantel, Heike; Schulze-Osthoff, Klaus

2012-04-02

91

Mechanisms of Cell Death in Acute Liver Failure  

PubMed Central

Acute liver failure (ALF) can be the consequence of various etiologies, that might vary between different geographic regions. Most frequent are intoxications with acetaminophen, viral hepatitis, or liver damage of unknown origin. ALF occurs when the extent of hepatocyte death exceeds the regenerative capacity of the liver. The mode of liver cell death that is predominantly induced in ALF, i.e., apoptosis or necrosis, is still controversial and presumably determined by the etiology, duration, and magnitude of liver injury. Severe liver damage involves oxidative stress and depletion of ATP resulting in necrosis. In contrast, maintenance of ATP stores is required for the execution of apoptosis. Recent data suggest that necrosis resulting from severe liver damage is associated with poor outcome of ALF patients. Discrimination between apoptosis and necrosis might be therefore useful for the identification of ALF patients requiring liver transplantation. Identification of the molecular cell death mechanisms remains an important issue not only for early prediction of ALF outcome, but also for therapeutic interventions. In view of the pleiotropic functions of critical mediators of cell death and tissue regeneration, a particular challenge will be to reduce hepatocellular death without inhibiting the regenerative capacity of the liver. Here, we review the molecular mechanisms of hepatocyte injury and the pathways leading to apoptosis and necrosis, which might represent potential diagnostic and therapeutic targets in ALF.

Bantel, Heike; Schulze-Osthoff, Klaus

2012-01-01

92

Failure mechanisms at the human dentin-resin interface: a fracture mechanics approach.  

PubMed

The present study reports on the failure mechanisms at the human dentin-resin interface, with special reference to two specific questions: (1) does failure at the human dentin-resin interface occur by a cohesive or an adhesive mechanism? (2) is the failure mechanism accompanied by a plastic deformation, and if so how important is it? The experimental design, computational analysis, and fractography were applied to two generically different bonding systems: Scotchbond-2 (SB2) and Scotchbond-multipurpose (SBM). The theoretical basis of the study required a three-dimensional finite element analysis for calibration of the new geometric factor coefficient. A minimum geometric factor coefficient (Ym) of 17.3 was then obtained which was vital for the determination of the interfacial fracture toughness. Accordingly, the dentin-resin interfacial fracture toughness (GIC), for the SB2 and for the SBM were 30.22 +/- 5.61 and 49.56 +/- 7.65 J m-2, respectively, which were significantly different (p < 0.01). Both SB2 and SBM interfaces with dentin displayed significant degrees of plasticity (0.15 and 0.19) which were beneficial to crack resistance. Thus, correcting for the plasticity, the GIC for SB2 and for SBM increased to 42.83 +/- 7.75 and 74.97 +/- 10.47 J m-2, respectively. The fractography of the two systems reflected these numeric differences. SB2 showed largely interfacial adhesive failure, while SBM showed adhesive-cohesive failure with occasional dentin adhesions attached to the composite interface and vice versa. PMID:8089158

Lin, C P; Douglas, W H

1994-08-01

93

Tbc1d15-17 regulates synaptic development at the Drosophila neuromuscular junction.  

PubMed

Members of the Tre-2/Bub2/Cdc16 (TBC) family of proteins are believed to function as GTPase-activating proteins (GAPs) for Rab GTPases, which play pivotal roles in intracellular membrane trafficking. Although membrane trafficking is fundamental to neuronal morphogenesis and function, the roles of TBC-family Rab GAPs have been poorly characterized in the nervous system. In this paper, we provide genetic evidence that Tbc1d15-17, the Drosophila homolog of mammalian Rab7-GAP TBC1d15, is required for normal presynaptic growth and postsynaptic organization at the neuromuscular junction (NMJ). A loss-of-function mutation in Tbc1d15-17 or its presynaptic knockdown leads to an increase in synaptic bouton number and NMJ length. Tbc1d15-17 mutants are also defective in the distribution of the postsynaptic scaffold Discs-large (Dlg) and in the level of the postsynaptic glutamate subunit GluRIIA. These postsynaptic phenotypes are recapitulated by postsynaptic knockdown of Tbc1d15-17. We also show that presynaptic overexpression of a constitutively active Rab7 mutant in a wild-type background causes a synaptic overgrowth phenotype resembling that of Tbc1d15-17 mutants, while a dominant-negative form of Rab7 has the opposite effect. Together, our findings establish a novel role for Tbc1d15-17 and its potential substrate Rab7 in regulating synaptic development. PMID:23812537

Lee, Min-Jung; Jang, Sooyeon; Nahm, Minyeop; Yoon, Jin-Ho; Lee, Seungbok

2013-06-27

94

Studies of Prevention, Treatment and Mechanisms of Heart Failure in the Aging Spontaneously Hypertensive Rat  

Microsoft Academic Search

The spontaneously hypertensive rat (SHR) is an animal model of genetic hypertension which develops heart failure with aging, similar to man. The consistent pattern of a long period of stable hypertrophy followed by a transition to failure provides a useful model to study mechanisms of heart failure with aging and test treatments at differing phases of the disease process. The

Oscar H. L. Bing; Chester H. Conrad; Marvin O. Boluyt; Kathleen G. Robinson; Wesley W. Brooks

2002-01-01

95

Accelerated life testing design based on wear failure mechanism for pneumatic cylinders  

Microsoft Academic Search

The piston and piston pole sealing ring are the weak units as well as leakage sources which easily result in the cylinders failure. The primary criterion for determining test acceleration factors is that the failure mode or failure mechanism should not change or be different from that expected from a non-accelerated test. Working temperature, frequency and motion velocity are chosen

Juan Chen; Qiang Wu; Guochang Bai; Jungong Ma; Zhanlin Wang

2009-01-01

96

Human reliability considerations in the analysis of mechanical failures  

SciTech Connect

Inclusion of human reliability consideration in the analysis of equipment failures is shown to produce pragmatic results while avoiding negative results often associated with human error and its connotation of placing blame. Human error is considered a subset of human reliability. Situational and human factors, including support systems, are the root cause of many failures which may otherwise appear to result from human error.

Smith, J.B.

1985-02-01

97

Mechanical Failure Properties of Composite Plastic Bonded >>>>>Explosives  

Microsoft Academic Search

The initial part of the uniaxial stress versus strain response in compression can be described in terms of a modulus, E, a peak stress, gammam (a failure stress) and a strain at the peak stress, ?m (a failure strain). gammam increases in proportion to E for smaller values of E and in proportion to E^1\\/2 for larger values with changes

Donald Wiegand

1997-01-01

98

Mechanisms by which exercise training benefits patients with heart failure  

Microsoft Academic Search

Clinical consequences of heart failure are fatigue, dyspnea, and progressive impairment of exercise tolerance. Regular exercise training is associated with health-improving effects. In patients with stable heart failure, exercise training can relieve symptoms, improve exercise capacity and quality of life, as well as reduce hospitalization and, to some extent, risk of mortality. Progressive exercise training is associated with pulmonary, cardiovascular,

Louis J. Ignarro; Francesco Cacciatore; Ettore Crimi; Claudio Napoli

2009-01-01

99

Failure mechanisms in blends of linear low-density polyethylene and polystyrene  

SciTech Connect

Mechanical models which describe the deformation and failure mechanisms for uncompatibilized blends of linear low-density polyethylene and polystyrene are described. A ductile to brittle transition was observed.

Li, T.; Topolkaraev, V.A.; Hiltner, A.; Baer, E. [Case Western Reserve Univ., Cleveland, OH (United States)

1996-12-31

100

IC failure mechanisms yesterday, today, tomorrow: implications from test to DFM  

Microsoft Academic Search

The failure mechanisms that occur on manufactured ICs affect yield or, worse, shipped product quality level. The difference between the two is in whether or not detection occurs at test. In this talk, we look at the types of failure mechanisms that occur, including random contamination-related defects, systematic defects and systematic parametric variations. We go through an evidence round-up looking

Anne E. Gattiker

2006-01-01

101

Anticipated transients without scram program: common mode failure analysis of control rod drive mechanism  

Microsoft Academic Search

As part of the Anticipated Transient Without Scram (ATWS) program, ; Diamond Power Specialty Corporation's control rod drive mechanism (CRDM) was ; evaluated to determine its susceptibility to common mode failure. This study ; qualitatively evaluates the credibility of mechanical failure of a significant ; number of control rods to insert into the reactor core by trip on loss of

C. W. Hammond; E. Oelkers; J. R. Penland; J. I. Schwartz; J. T. Williams

1975-01-01

102

Mechanical behavior and failure modes of aluminum\\/bamboo sandwich plates under quasi-static loading  

Microsoft Academic Search

Experimental investigations have been made on the quasi-static mechanical behavior and failure modes of aluminum\\/bamboo sandwich plates. Thermosetting epoxy resin and thermoplastic Polybond resin were used to bond the aluminum sheets and the bamboo. Tensile, compressive and flexural properties were evaluated. The effects of bond conditions on the mechanical behavior and failure modes were examined. The thermoplastic Polybond resin resulted

G. X. Sui; T. X. Yu; J. K. Kim; B. L. Zhou

2000-01-01

103

Identification of Deformation Mechanisms Responsible for Failure in Incremental Forming using a Damage Based Fracture Model  

Microsoft Academic Search

Single Point Incremental forming (SPIF) has generated significant interest recently due to its increased formability and greater process flexibility. However, the complicated deformation mechanisms involved in SPIF have prevented conclusive identification of the primary mechanisms responsible for failure. This work successfully predicts the forming forces and occurrence of failure in SPIF using explicit FEA with a damage based fracture model

Rajiv Malhotra; Liang Xue; Jian Cao; Ted Belytschko

2011-01-01

104

High-voltage failure mechanisms in liquid-filled, Fluorinert FC-40, capacitors  

SciTech Connect

The high-voltage electrical failure of a liquid-filled, FC-40 Fluorinert, capacitor occurred during a system random vibration test. This failure occurred between 1 and 5 hours of random vibration of the system in the longitudinal axis of the capacitor. The previous five hours of random vibration in the transverse direction left the capacitor functioning as designed. Similar failures were observed during component random vibration testing under high-voltage. This paper will describe the investigation of the above mentioned failures. The design and processing of this type of capacitor technology will also be reviewed. Both electrical and mechanical data will be provided. The results of this investigation revealed the cause of the above failures and the procedures necessary for avoiding such failures in the future. The interaction of the mechanical system, piece-part designs and the bellows temperature compensation system will be explained in connection with the electrical failures. Suggestions for future improved designs will be included.

McBrayer, J.D.; Richardson, C.B.; Jojola, A.A. [Sandia National Labs., Albuquerque, NM (United States); Pitre, L.J. [Martin Marietta Specialty Components, Largo, FL (United States)

1992-12-31

105

High-voltage failure mechanisms in liquid-filled, Fluorinert FC-40, capacitors  

SciTech Connect

The high-voltage electrical failure of a liquid-filled, FC-40 Fluorinert, capacitor occurred during a system random vibration test. This failure occurred between 1 and 5 hours of random vibration of the system in the longitudinal axis of the capacitor. The previous five hours of random vibration in the transverse direction left the capacitor functioning as designed. Similar failures were observed during component random vibration testing under high-voltage. This paper will describe the investigation of the above mentioned failures. The design and processing of this type of capacitor technology will also be reviewed. Both electrical and mechanical data will be provided. The results of this investigation revealed the cause of the above failures and the procedures necessary for avoiding such failures in the future. The interaction of the mechanical system, piece-part designs and the bellows temperature compensation system will be explained in connection with the electrical failures. Suggestions for future improved designs will be included.

McBrayer, J.D.; Richardson, C.B.; Jojola, A.A. (Sandia National Labs., Albuquerque, NM (United States)); Pitre, L.J. (Martin Marietta Specialty Components, Largo, FL (United States))

1992-01-01

106

Pressurized 3-piece steel container explosions and failure mechanisms  

Microsoft Academic Search

The design of 3-piece steel pressurized containers includes double seams that connect the bottom and top of the container\\u000a to the container body. These seams have some inherent design features, such as crevices, that can lead to corrosion and other\\u000a forms of failure. Since the 3-piece containers are pressurized with liquefied propellants, such as propane, failure can lead\\u000a to catastrophic

M. Fox; R. Hastings

2003-01-01

107

SPATIOTEMPORAL INHIBITION OF INNATE IMMUNITY SIGNALING BY THE TBC1D23 RAB-GAP1  

PubMed Central

We previously identified Tbc1d23 as a candidate novel regulator of innate immunity using comparative genomics RNAi screens in C. elegans and mouse macrophages. Using Tbc1d23 knockout mice and macrophages engineered to overexpress Tbc1d23, we now show that Tbc1d23 is a general inhibitor of innate immunity signaling, strongly inhibiting multiple Toll-like receptor (TLR) and Dectin signaling pathways. Tbc1d23 likely acts downstream of the TLR signaling adaptors MyD88 and Trif and upstream of the transcription factor XBP1. Importantly, like XBP1, Tbc1d23 affects the maintenance but not the initiation of inflammatory cytokine production induced by lipopolysaccharide (LPS). Tbc1d23 acts as a RAB-GAP to regulate innate immunity signaling. Thus, Tbc1d23 exerts its inhibitory effect on innate immunity signaling in spatiotemporal fashion. The identification of a novel spatiotemporal regulator of innate immunity signaling validates the comparative genomics approach for innate immunity gene discovery.

De Arras, Lesly; Yang, Ivana V.; Lackford, Brad; Riches, David W. H.; Prekeris, Rytis; Freedman, Jonathan H.; Schwartz, David A.; Alper, Scott

2012-01-01

108

Identification of Deformation Mechanisms Responsible for Failure in Incremental Forming using a Damage Based Fracture Model  

NASA Astrophysics Data System (ADS)

Single Point Incremental forming (SPIF) has generated significant interest recently due to its increased formability and greater process flexibility. However, the complicated deformation mechanisms involved in SPIF have prevented conclusive identification of the primary mechanisms responsible for failure. This work successfully predicts the forming forces and occurrence of failure in SPIF using explicit FEA with a damage based fracture model in which failure envelope depends on the hydrostatic pressure and the Lode angle. Furthermore it is shown that through-the-thickness shear is primarily responsible for failure in SPIF. Simulations are also performed to form the same component using SPIF and using a conventional punch and die, and a comparison is made between the dominant mechanisms of failure in the two processes. Furthermore, it is shown that reduction of tool-sheet friction can delay fracture in SPIF and the mechanism behind this effect is discussed as well.

Malhotra, Rajiv; Xue, Liang; Cao, Jian; Belytschko, Ted

2011-08-01

109

Unique failure mechanism of a femoral component after revision total hip arthroplasty.  

PubMed

As the prevalence of revision total hip arthroplasty increases, the mechanisms of failure of these revisions have become better delineated. Several studies have indicated infection, instability, and aseptic loosening to be the more common mechanisms of failure in revision surgery. However, with increasing numbers of revisions performed, unique mechanisms of failure are being seen, likely related to the implants that are used in the revision setting. Revision implants offer certain advantages over primary implants with the use of modular components. The revision implants allow the surgeon to increase offset and leg length with modular femoral bodies and necks. However, these modular junctions represent additional areas for implant failure. These new methods of failure associated with modular implants are slowly presenting as the use of these implants continues to increase. The authors recently encountered a mechanism of failure that, to their knowledge, has not been described in the literature. They report a 57-year-old man with dissociation of the proximal body from the diaphyseal component of a Wright Medical Link (Memphis, Tennessee) stem prosthesis. The patient presented with an audible click on physical examination, and radiographs confirmed dissociation of the proximal body. The intraoperative findings, treatment method, and proposed mechanisms for this type of failure are presented, as well as insight into potential ways to avoid this type of failure. PMID:24093712

Martin, J Ryan; Trousdale, Robert T

2013-10-01

110

Reverse remodeling in heart failure—mechanisms and therapeutic opportunities  

Microsoft Academic Search

Heart failure (HF) involves changes in cardiac structure, myocardial composition, myocyte deformation, and multiple biochemical and molecular alterations that impact heart function and reserve capacity. Collectively, these changes have been referred to as 'cardiac remodeling'. Understanding the components of this process with the goal of stopping or reversing its progression has become a major objective. This concept is often termed

Norimichi Koitabashi; David A. Kass

2011-01-01

111

Performance Impairment After Failure: Mechanism and Sex Differences  

Microsoft Academic Search

In two experiments, I replicated and extended previous research on performance impairment after failure. Children first completed 10 solvable or unsolvable matching-figures tasks. They then tried to solve 15 anagrams described as highly or moderately difficult. In the first study, the children did not have the option to give up on an anagram before the allotted time had elapsed. No

Arden Miller

1986-01-01

112

Failure mechanisms of aluminum bondpad peeling during thermosonic bonding  

Microsoft Academic Search

Aluminum bondpad peeling was observed in a newly developed thermosonic wirebonding process for chip-on-board assembly. Through detailed failure analysis and with the help of finite element analysis on stress simulation, the true root cause of the peeling is identified. It is found that the true root cause is the effect of skidding force as a result of the constrained movement

Cher Ming Tan; Zhenghao Gan

2003-01-01

113

PBFA-II Vacuum Insulator Stack Failure Mechanisms.  

National Technical Information Service (NTIS)

The PBFA-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 ma...

M. A. Sweeney

1985-01-01

114

Failure Modes and Mechanisms in Solid Tantalum Capacitors  

Microsoft Academic Search

Both the catastrophic and leakage current increase failure modes are directly associated with the current flickering phenomenon peculiar to the solid tantalum capacitor. These current bursts are themselves associated with imperfections in the tantalum oxide film. Imperfections or flaws can arise from several sources such as impurities (both metallic and gaseous) in the base metal, surface geometry of the metal,

E. J. Fresia; J. M. Eckfeldt

1963-01-01

115

Failure mechanisms and protection methods of spacecraft power system  

Microsoft Academic Search

Recent telecommunication satellites often have power larger than 10 kW. As the power level increases, so does the operational voltage that also exceeds 100 V for the recent high power satellites. As the power level and the voltage become higher, anomaly associated with failure of the power system has become a serious problem, which sometimes led to complete loss of

Mengu Cho

2005-01-01

116

Failure Mechanisms in PMMA\\/ATH Acrylic Casting Dispersion  

Microsoft Academic Search

Acrylic casting dispersion is used to fabricate particulate composites such as poly-methyl methacrylate (PMMA) filled with a fine dispersion alumina trihydrate (ATH). This composite is subjected to severe temperature variations during in-service conditions, giving rise to high thermal stresses which lead to failure by cracking. The influence of the interfacial bond strength between a particle and the matrix on the

Shihua Nie; Cemal Basaran; Clyde S. Hutchins; Hale Ergun

117

Flexural analysis of balsa core sandwich composite: Failure mechanisms, core grain orientation and padding effect  

Microsoft Academic Search

A comprehensive investigation was undertaken to study failure mechanisms of sandwich composites and their influence on flexural behavior (load-displacement curve). Sandwich composite panels were cured from compression thermoforming of E-glass\\/epoxy skins and a low density balsa wood core. Balsa core grain orientation is found to have major effect on flexural response and failure modes. Flexural behavior, failure mode and its

Avinash S Phadatare

2012-01-01

118

Flexural analysis of balsa core sandwich composite: failure mechanisms, core grain orientation and padding effect  

Microsoft Academic Search

A comprehensive investigation was undertaken to study failure mechanisms of sandwich composites and their influence on flexural behavior (load-displacement curve). Sandwich composite panels were cured from compression thermoforming of E-glass\\/epoxy skins and a low density balsa wood core. Balsa core grain orientation is found to have major effect on flexural response and failure modes. Flexural behavior, failure mode and its

Avinash S Phadatare

2012-01-01

119

Microstructures and failure mechanisms of friction stir spot welds of aluminum 6061-T6 sheets  

Microsoft Academic Search

Microstructures and failure mechanisms of friction stir spot welds in aluminum 6061-T6 lap-shear specimens are investigated based on experimental observations. Optical micrographs of the cross-sections of friction stir spot welds in lap-shear specimens before and after failure are examined. These friction stir spot welds show the failure mode of nugget pullout under lap-shear loading conditions. The experimental observations suggest that

D.-A. Wang; S.-C. Lee

2007-01-01

120

Failure modes and mechanisms in nickel alloys: Primarily austenitic stainless steel  

SciTech Connect

Austenitic stainless steels and higher nickel alloys such as the Inconels are used extensively in the chemical and nuclear industries. This review will concentrate on their behavior in nuclear reactors because of the availability of information to the author. Emphasis is given to the failure modes and mechanisms occurring in the context of causal mechanisms and the implications of alloy composition. Major use is made of the austenitic steels both AISI 304 and 316 in United States nuclear plants. This is true for both boiling water reactors (BWRs) and pressurized water reactors (PWRs). Over the years there have been many failures in these materials where failure is defined as cracking, leaking, and, rarely, catastrophic breakage. This review will examine failure mechanisms such as stress corrosion cracking, both transgranular and intergranular, fatigue, including vibrational and thermal, and other corrosion-related failures. 16 refs., 12 figs.

Bush, S.H.

1989-08-01

121

APPLICATION OF FAILURE EVENT DATA TO BENCHMARK PROBABILISTIC STRUCTURAL MECHANICS COMPUTER CODES  

SciTech Connect

This paper describes an application of data on cracking, leak and rupture events from nuclear power plant operating experience to estimate failure frequencies for piping components that had been previously evaluated using the PROLOCA and PRAISE probabilistic fracture mechanics (PFM) computer codes. The calculations had addressed the failure mechanisms of stress corrosion cracking, intergranular stress corrosion cracking and fatigue for materials and operating conditions that were known to have failed components. The first objective was to benchmark the calculations against field experience. A second objective was a review of uncertainties in the treatments of the data from observed failures and in the structural mechanics models. The database PIPExp-2006 was applied to estimate failure frequencies. Because the number of reported failure events was small, there were also statistical uncertainties in the estimates of frequencies. Comparisons of predicted and observed failure frequencies showed that PFM codes correctly predicted relatively high failure probabilities for components that had experienced field failures. However, the predicted frequencies tended to be significantly greater than those estimated from plant operating experience. A review of the PFM models and inputs to the models showed that uncertainties in the calculations were sufficiently large to explain the differences between the predicted and observed failure frequencies.

Simonen, Fredric A.; Gosselin, Stephen R.; Lydell, Bengt O.; Rudland, David L.; Wilkowski, Gery M.

2007-07-22

122

Impermeable thin AI2O3 overlay for TBC protection from sulfate and vanadate attack in gas turbines  

SciTech Connect

25 {micro}m and a 2 {micro}m thick Al{sub 2}O{sub 3} overlay were deposited by HVOF thermal spray and by sol-gel coating method, respectively, onto to the surface of YSZ coating. Indenter test was employed to investigate the spalling of YSZ with and without Al{sub 2}O{sub 3} overlay after hot corrosion. The results showed that Al{sub 2}O{sub 3} overlay acted as a barrier against the infiltration of the molten salt into the YSZ coating during exposure, thus significantly reduced the amount of M-phase of ZrO{sub 2} in YSZ coating. Thick Al{sub 2}O{sub 3} overlay will increase compressive stress and failure in TBC. During next reporting time, Al{sub 2}O{sub 3} overlay will be deposited on the YSZ surface by the composite-sol-gel route (CSG). Hot corrosion tests will be carried out on the TBC.

Scott X. Mao

2005-01-31

123

Safety impact of mechanical- and maintenance-induced seal failures of reactor coolant pumps  

Microsoft Academic Search

This paper presents an investigation of the safety impact resulting from mechanical- and maintenance-induced reactor coolant pump (RCP) seal failures in nuclear power plants. The intention of this study was to estimate the annual frequency for the spectrum of leak rates induced by RCP seal failures for the benefit of various pump designers and plant vendors; and to evaluate their

M. A. Azarm; J. L. Boccio

1985-01-01

124

Mechanism of failure in the treatment of type II endoleak with percutaneous coil embolization  

Microsoft Academic Search

Purpose: Type II endoleak after endovascular abdominal aortic aneurysm repair is a failure of aneurysm sac exclusion with unknown long-term consequences. Elevated aneurysm sac pressures documented in these patients have led us to aggressively treat type II endoleaks with percutaneous transluminal coil embolization (PTCE). The purpose of this study was to evaluate the results and the mechanisms of failure of

Maurice M. Solis; Juan Ayerdi; Gregory A. Babcock; Jose R. Parra; Robert B. McLafferty; Laura A. Gruneiro; Don E. Ramsey; Kim J. Hodgson

2002-01-01

125

Noninvasive mechanical ventilation in a patient with respiratory failure after hematopoietic progenitor transplantation  

Microsoft Academic Search

Respiratory failure requiring orotracheal intubation (OTI) and mechanical ventilation (MV) is almost always a fatal complication in patients who undergo hematopoietic progenitor transplantation (HPT). We present the case of a woman who suffered respiratory failure with bilateral infiltrates on a chest X-ray taken on day +14 following autologous bone marrow transplantation. We managed the patient satisfactorily with noninvasive ventilation, avoiding

D Marín; E González-Barca; E Domingo; J Berlanga; A Grañena

1998-01-01

126

Reverse remodeling of the extracellular matrix in heart failure after left ventricular mechanical support  

Microsoft Academic Search

This thesis describes a study of the changes in the extracellular matrix (ECM) of the myocardium, in patients with end stage heart failure and during mechanical support (Left Ventricular Assist Device support, LVAD) of the left ventricle. The changes during LVAD support may lead to recovery of the heart. Chapter 1 is a general introduction about heart failure, heart transplantation,

A. H. Bruggink

2008-01-01

127

Failure modes and fracture mechanisms in flexure of Kevlar-epoxy composites  

Microsoft Academic Search

The results of testing in three-point bending of aramid fibre-reinforced epoxy composites are described. This loading mode has been chosen in order to increase the variety of failure modes and of fracture mechanisms. The main failure modes observed are tensile and delamination, with a transition at a fibre volume fraction of about 46%. This mode transition is detectable by monitoring

M. Davidovitz; A. Mittelman; I. Roman; G. Marom

1984-01-01

128

Divalent ion metabolism in patients with acute renal failure: Studies on the mechanism of hypocalcemia  

Microsoft Academic Search

Divalent ion metabolism in patients with acute renal failure: Studies on the mechanism of hypocalcemia. Studies were carried out in ten patients with acute renal failure to characterize certain features of deranged divalent ion metabolism. During the oliguric period, the patients displayed hypocalcemia, hyperphosphatemia, hypermagnesemia and elevated levels of immunoreactive parathyroid hormone. Hypocalcemia and elevated levels of immunoreactive parathyroid hormone

Shaul G Massry; Allen I Arieff; Jack W Coburn; Genaro Palmieri; Charles R Kleeman

1974-01-01

129

Numerical analysis of fracture mechanisms and failure modes in bi-layered structural components  

Microsoft Academic Search

The problem of crack propagation in bi-layered structural components is addressed. Due to the presence of the bi-material interface and depending on the loading direction, a competition between different crack trajectories (failure modes) can take place. The quantification of the dominant failure mode and of the prevailing fracture mechanism is very often a challenging task, although it is crucial for

Alberto Carpinteri; Marco Paggi

2007-01-01

130

Mechanical support in acute and chronic heart failure  

Microsoft Academic Search

Heart failure (HF) is the leading cause of hospital admissions in the United States in people over the age of 65 years. Major\\u000a advancements in the medical therapy of HF, combined with automatic implantable cardioverterdefibrillators and cardiac resynchronization\\u000a therapy, have substantially reduced the mortality and morbidity of chronic HF, but mortality remains high, and the availability\\u000a of donor hearts for

Andreas Brieke; Joseph Cleveland Jr; JoAnn Lindenfeld

2008-01-01

131

Ultimate Strength and Failure Mechanism of Resistance Spot Weld Subjected to Tensile, Shear, or Combined Tensile\\/Shear Loads  

Microsoft Academic Search

Strength tests were performed to reveal the failure mechanisms of spot weld in lap-shear and cross tension test samples. It is shown the while the lap-shear (cross tension) sample is subjected to shear (normal) load at the structural level the failure mechanism at the spot weld is tensile (shear) mode at the materials level. Based on the observed failure mechanism,

Yuh J. Chao

2003-01-01

132

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

SciTech Connect

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.

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

1995-12-31

133

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

SciTech Connect

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.

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

1995-09-01

134

Application of dynamic fracture mechanics to the investigation of catastrophic failure in aircraft structures  

Microsoft Academic Search

A dynamic fracture mechanics approach to the estimation of the residual strength of aircraft structures is presented. The dependence of the dynamic crack initiation toughness of aluminum 2024-T3 on loading rate is first studied experimentally. Based on the experimental results and on established dynamic fracture mechanic concepts, a fracture mechanics based failure model is established and is used to estimate

Benjamin Bin Chow

2001-01-01

135

Mechanical failures detection by means of induction machine current analysis: a case history  

Microsoft Academic Search

This paper addresses the problem of the detection of the mechanical disturbances and failures in a mechanical system driven by asynchronous machines through motor's current signal. Since the load behavior modifies the motor's supply current, it is possible to use the machine itself through motor current signal analysis (MCSA), as a torque sensor to defect mechanical condition. In this paper

A. Bellini; F. Filippetti; G. Franceschini; C. Tassoni; R. Passaglia; M. Saottini; M. Giovannini

2003-01-01

136

Inelastic microstructural failure mechanisms in crystalline materials with high angle grain boundaries  

Microsoft Academic Search

Microstructurally-induced failure mechanisms in crystalline materials with coincident site-lattice (CSL) high angle grain boundaries (GBs) have been investigated. A multiple-slip rate-dependent crystalline constitutive formulation that is coupled to the evolution of mobile and immobile dislocation densities and specialized computational schemes have been developed to obtain a detailed understanding of the interrelated physical mechanisms that result in material failure. A transmission

M. A. Zikry; M. Kao

1996-01-01

137

Failure mechanism of urethane-elastomer-coated fabric collapsible fuel tanks. Technical report  

SciTech Connect

This report investigates the failure mechanism of urethane elastomer coated fabric collapsible fuel storage tanks. Past work has dealt with fuel degradation causing the tanks to fail but that work has met with failure. The mechanism that causes these tanks to fail is an extraction process whereby the protective ingredients in the polymer coating are removed by the fuel causing the elastomer to degrade by hydrolysis.

Feuer, H.O.; Touchet, P.

1990-03-01

138

Failure investigation of polymer and composite material structures in the mechanical engineering industry  

SciTech Connect

Despite efforts to process high-quality composite material parts, some untimely failures may occur because of defects introduced during manufacturing, because of data that were not taken into account during design, or because of a misuse of the materials` structure. A skilled postmortem failure analysis provides many pieces of information that shed light on the process and the design phase, improving the quality of the structures. The failure analysis of mechanical composite material parts follows the same system as for metals. It is based on different methods of investigation that complement each other and enable one to hypothesize and conceive different and gradually more and more precise ways of research to reach the most probable result. This work shows how failure problems involving composite materials in the mechanical industry may be solved. The authors also consider the economical aspects of failure in the industrial world with the skill and knowledge acquired by the personnel of CETIM.

Lemascon, A.; Castaing, P.; Mallard, H. [CETIM, Nantes (France). Polymers and Composite Materials Dept.

1996-04-01

139

Mechanism of TMI-1 steam-generator failures  

SciTech Connect

The low-temperature stress-corrosion cracking (SCC) of sensitized Inconel 600 was studied using various borated solutions of sulfur compounds. Sodium thiosulfate and sodium tetrathionate were equally aggressive provided that the alloy was sufficiently severely sensitized. Tetrathionate was more effective on marginally sensitized material. The threshold concentration of thiosulfate was below 10/sup -6/ M. LiOH additions inhibited SCC. Oxygen is necessary for SCC in these solutions. The relevance of the laboratory tests to the steam generator failures is discussed.

Newman, R.C.; Bandy, R.; Roberge, R.

1983-01-01

140

IMPERMEABLE THIN Al2O3 OVERLAY FOR TBC PROTECTION FROM SULFATE AND VANADATE ATTACK IN GAS TURBINES  

SciTech Connect

In order to improve the hot corrosion resistance of conventional YSZ TBC system, a thin and dense {alpha}-Al{sub 2}O{sub 3} overlay has been deposited on the YSZ surface by the composite-sol-gel route (CSG). The YSZ substrates were dipped with boehmite sol containing calcined {alpha}-Al{sub 2}O{sub 3} particles, dried to form a gel film and calcined at 1200 C to form {alpha}-Al{sub 2}O{sub 3} overlay. Hot corrosion tests were carried out on the TBCs with and without Al{sub 2}O{sub 3} coating in molten salt mixtures (Na{sub 2}SO{sub 4} + 5% V{sub 2}O{sub 5}) at 950 C for 10 hours. The results showed that besides a thin and dense alumina overlay with the thickness of about 100-500 nm formed on the YSZ surface, the microcracks and porous near the surface in YSZ was also occupied by alumina because of penetration of the low viscosity precursor. As a result, the Al{sub 2}O{sub 3} overlay remarkably refrained the infiltration of the molten salt into the YSZ coating. The amount of M-phase in the TBC coating with Al{sub 2}O{sub 3} overlay was substantially reduced comparing to that without alumina overlay. In the next reporting period, we will prepare the alumina overlay by CSG route with different thickness and study the hot corrosion mechanism of YSZ TBC with thin Al{sub 2}O{sub 3} overlay coating produced by CSG.

Scott X. Mao

2003-03-10

141

Pancreatic ?-Cell Dedifferentiation As Mechanism Of Diabetic ?-Cell Failure  

PubMed Central

Diabetes is associated with ?-cell failure. But it remains unclear whether the latter results from reduced ?-cell number or function. FoxO1 integrates ?-cell proliferation with adaptive ?-cell function. We interrogated the contribution of these two processes to ?-cell dysfunction, using mice lacking FoxO1 in ?-cells. FoxO1 ablation caused hyperglycemia with reduced ?-cell mass following physiologic stress, such as multiparity and aging. Surprisingly, lineage-tracing experiments demonstrated that loss of ?-cell mass was due to ?-cell dedifferentiation, not death. Dedifferentiated ?-cells reverted to progenitor-like cells expressing Neurogenin3, Oct4, Nanog, and L-Myc. A subset of FoxO1-deficient ?-cells adopted the ?-cell fate, resulting in hyperglucagonemia. Strikingly, we identify the same sequence of events as a feature of different models of murine diabetes. We propose that dedifferentiation trumps endocrine cell death in the natural history of ?-cell failure, and suggest that treatment of ?-cell dysfunction should restore differentiation, rather than promoting ?-cell replication.

Talchai, Chutima; Xuan, Shouhong; Lin, Hua V.; Sussel, Lori; Accili, Domenico

2012-01-01

142

Characterization of Tbc2, a nucleus-encoded factor specifically required for translation of the chloroplast psbC mRNA in Chlamydomonas reinhardtii  

Microsoft Academic Search

enetic analysis has revealed that the three nucleus- encoded factors Tbc1, Tbc2, and Tbc3 are involved in the translation of the chloroplast psbC mRNA of the eukaryotic green alga Chlamydomonas reinhardtii . In this study we report the isolation and phenotypic characterization of two new tbc2 mutant alleles and their use for cloning and characterizing the Tbc2 gene by genomic

Andrea H. Auchincloss; William Zerges; Karl Perron; Jacqueline Girard-Bascou; Jean-David Rochaix

143

Bearing failure analysis of mechanically fastened joints in composite laminates  

Microsoft Academic Search

An experimental investigation was performed to study the effects of stacking sequence and clamping force on delamination bearing strengths of mechanically fastened joints in carbon\\/epoxy composite laminates using acoustic emission (AE) technique. The experimental work of the study was presented in [H.J. Park, Effects of stacking sequence and clamping force on the bearing strengths of mechanically fastened joints in composite

Heung-Joon Park

2001-01-01

144

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

NASA Astrophysics Data System (ADS)

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-subroutine process simulation was able to capture the important aspects of the thermo-mechanical cycle that influence the thermal and stress gradients in the shell.

Penso Mula, Jorge Antonio

145

BIOMECHANICS OF THE FETAL MEMBRANE PRIOR TO MECHANICAL FAILURE: REVIEW AND IMPLICATIONS  

PubMed Central

Annually, premature birth is a major public health problem accounting for over 13,000 deaths and 30,000 surviving infants with life-long morbidity. Preterm premature rupture of the membranes is the initiating event leading to preterm birth of 40% of these premature infants. Fetal membrane (FM) rupture is a catastrophic tissue failure, a unique event in normal physiology; other tissue failures (bone breaks, aneurism ruptures) are pathological processes. The mechanisms which cause FM failure and thereby rupture are not understood. A full understanding of FM failure process requires a complete characterization of structural and biomechanical behavior at near/full term under sub-failure (forces well below that which induce rupture) and failure conditions as well as elucidating the biological factors which modulate its failure. The relatively, highly loaded stated of the FM in vivo may also facilitate its susceptibility to enzymatic degradation, which was shown to be augmented with increased load in collagenous tissues. Indeed, this last observation may help to provide the link between biomechanical degradation and premature mechanical failure in the FM. This integrated approach will further the understanding of this unique physiological event and thereby provide insight into how to anticipate and when appropriate, intervene to prevent preterm FM rupture.

Joyce, Erinn M.; Moore, John J.; Sacks, Michael S.

2009-01-01

146

Experimental Techniques for Predicting Fatigue Failure of Cannon Breech Mechanisms.  

National Technical Information Service (NTIS)

In this paper a technique for predicting thread fatigue behavior for full scale cannon breech mechanisms from small specimen tests is investigated. A thread load distribution factor is determined experimentally for the breech ring and breech block compone...

R. E. Weigle R. R. Lasselle

1965-01-01

147

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

NASA Astrophysics Data System (ADS)

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-central Nevada and regions with similar characteristics. Reference: Wesnousky, S., Barron, A., Briggs, R., Caskey, S., Kumar, S., and Owen, L., 2005, Paleoseismic Transect Across the Northern Great Basin, Journal of Geophysical Research, v. 110.

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

2008-12-01

148

Effects of creep and cyclic loading on the mechanical properties and failure of human Achilles tendons.  

PubMed

The Achilles tendon is one of the most frequently injured tendons in humans, and yet the mechanisms underlying its injury are not well understood. This study examines the ex vivo mechanical behavior of excised human Achilles tendons to elucidate the relationships between mechanical loading and Achilles tendon injury. Eighteen tendons underwent creep testing at constant stresses from 35 to 75 MPa. Another 25 tendons underwent sinusoidal cyclic loading at 1 Hz between a minimum stress of 10 MPa and maximum stresses of 30-80 MPa. For the creep specimens, there was no significant relationship between applied stress and time to failure, but time to failure decreased exponentially with increasing initial strain (strain when target stress is first reached) and decreasing failure strain. For the cyclically loaded specimens, secant modulus decreased and cyclic energy dissipation increased over time. Time and cycles to failure decreased exponentially with increasing applied stress, increasing initial strain (peak strain from first loading cycle), and decreasing failure strain. For both creep and cyclic loading, initial strain was the best predictor of time or cycles to failure, supporting the hypothesis that strain is the primary mechanical parameter governing tendon damage accumulation and injury. The cyclically loaded specimens failed faster than would be expected if only time-dependent damage occurred, suggesting that repetitive loading also contributes to Achilles tendon injuries. PMID:12797621

Wren, Tishya A L; Lindsey, Derek P; Beaupré, Gary S; Carter, Dennis R

2003-06-01

149

Delayed mechanical failure of the under-bump interconnects by bump shearing  

NASA Astrophysics Data System (ADS)

Packaging-induced stresses can cause mechanical failures of various forms in the Cu/low-k interconnects. Here we report a time-dependent failure mode of the interconnects underneath the copper pillar bump. Delayed catastrophic fracture is observed in the interconnect dielectrics when a sustained shear load is applied on the bump using a single bump shear setup. The time to failure is found to be highly sensitive to the load level and temperature, but not to the environmental humidity. However, moisture diffusion through intentionally broken moisture seal can accelerate the failure process. Quantitative analysis suggests the delayed failure can be well captured over a wide range of testing conditions by a model based on subcritical crack growth in the interconnect dielectrics.

Li, Han; Shaw, Thomas M.; Liu, Xiao-Hu; Bonilla, Griselda

2012-04-01

150

Porosity effects on machining direction -- Strength anisotropy and failure mechanisms  

SciTech Connect

The anisotropy in room-temperature flexural strength of ceramics as a result of machining test bar tensile surfaces parallel vs perpendicular to the bar axis was studied for various porous bodies. This shows that fine, relatively homogeneous porosity has no significant effect on such strength anisotropy, implying that such porosity has no significant effect on flaw sizes or shapes, which was also shown by fractography. However, as the size of pores or pore clusters (due to pore heterogeneity) increases, the strength anisotropy diminishes, becoming zero when the pores or pore clusters dominate failure. Logarithm of strength vs porosity (P) plots for the two machining directions followed nearly parallel lines for fine, homogeneous porosity, but have less separation and intersect at lower porosity as pore size or heterogeneity increases. Fracture toughnesses calculated from fractography data for Al[sub 2]O[sub 3] and B of varying porosity levels could be normalized to values at P [approximately] 0. Thus, extrapolation of strengths to P = 0 is clearly justified for bodies with fine, homogeneous porosity, but may be uncertain in bodies with coarser, or heterogeneous porosity.

Rice, R.W. (W.R. Grace and Co.-Conn., Columbia, MD (United States))

1994-08-01

151

Molecular mechanisms of deformation and failure in glassy materials  

Microsoft Academic Search

Understanding the molecular origins of macroscopic mechanical properties is a fundamental scientific challenge. Fracture of both amorphous and crystalline materials involves many length scales reaching from the continuum to atomic level processes near a crack tip. Using molecular simulations of simple models for amorphous glassy materials, we first study elastoplastic deformation and discuss the nature of the shear yield stress

Joerg Rottler

2004-01-01

152

Respiratory failure and mechanical ventilation: Pathophysiology and methods of promoting weaning  

Microsoft Academic Search

Respiratory failure may be manifested either by impaired gas exchange or by impaired ventilatory function. The latter results\\u000a in more severe problems in weaning patients from mechanical ventilation. Ventilatory failure may result from inadequate respiratory\\u000a drive, excessive respiratory workload, inadequate respiratory muscle endurance, or a combination of these factors.\\u000a \\u000a Simple bedside tests of ventilatory function are useful for evaluating the

Jill P. Karpel; Thomas K. Aldrich

1986-01-01

153

Solder failure mechanisms in single-sided insertion-mount printed wiring boards  

Microsoft Academic Search

This paper presents the defects that occur during the assembly and manufacturing of solder joints in single-sided insertion-mount printed wiring boards (PWBs). Each type of defect is discussed, with particular focus on how these defects are related to solderability issues, the mechanisms of failure due to defect-induced failure accelerators, and the effect of the defect on solder joint reliability.

C. Hillman; K. Rogers; A. Dasgupta; M. Pecht; R. Dusek; B. Lorence

1999-01-01

154

Mechanical circulatory support devices for acute heart failure syndromes: considerations for clinical trial design  

Microsoft Academic Search

Mechanical circulatory support (MCS) devices are a guideline-recommended treatment option for a small subset of advanced heart\\u000a failure patients. MCS has the potential to become more prominent in the management of Acute Heart Failure Syndromes (AHFS)\\u000a as device technology advances and as clinical trials consistently discover neutral or harmful effects with pharmacologic therapies\\u000a hypothesized to be beneficial in this population.

John B. O’Connell; Patrick M. McCarthy; George Sopko; Gerasimos S. Filippatos; Ileana L. Piña; Marvin A. Konstam; James B. Young; Leslie W. Miller; Mandeep R. Mehra; Edmond Roland; John E. A. Blair; David J. Farrar; Mihai Gheorghiade

2009-01-01

155

Role of Cytokines in the Mechanism of Action of Amlodipine: The PRAISE Heart Failure Trial  

Microsoft Academic Search

Objectives. We sought to determine whether the beneficial effects of amlodipine in heart failure may be mediated by a reduction in tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) levels. We postulated that TNF-alpha and IL-6 levels may also have predictive value in patients with congestive heart failure (CHF).Background. The molecular mechanism for progression of CHF may involve cytokine overexpression. The

Emile R Mohler; Leif C Sorensen; Jalal K Ghali; Douglas D Schocken; Park W Willis; John A Bowers; Anne B Cropp; Milton L Pressler

1997-01-01

156

Failure of latch mechanism for motion control of safety rods  

SciTech Connect

During safety rod tests in K-reactor prior to startup, one safety rod could not be lifted because the button'' broke off and became lodged in the mechanism. Examination of the failed latch assembly along with other assemblies from both K-Area and L-Area revealed several missing buttons as well as severely deformed jaw hanger extensions.'' We participated in the investigation of the damage by request of the Reactor Restart Section. Based on our study of the latch mechanism, the modifications to the safety rod extension,'' and the operating history of the machine, this memorandum describes the causes of the observed damage with experimental evidence and calculations to support the findings. 3 refs.

Yau, W.W.F.; Leader, D.R.

1992-01-16

157

Failure of latch mechanism for motion control of safety rods  

SciTech Connect

During safety rod tests in K-reactor prior to startup, one safety rod could not be lifted because the ``button`` broke off and became lodged in the mechanism. Examination of the failed latch assembly along with other assemblies from both K-Area and L-Area revealed several missing buttons as well as severely deformed ``jaw hanger extensions.`` We participated in the investigation of the damage by request of the Reactor Restart Section. Based on our study of the latch mechanism, the modifications to the ``safety rod extension,`` and the operating history of the machine, this memorandum describes the causes of the observed damage with experimental evidence and calculations to support the findings. 3 refs.

Yau, W.W.F.; Leader, D.R.

1992-01-16

158

Estradiol Stimulates Akt, AMPK* and TBC1D1/4, But Not Glucose Uptake in Rat Soleus  

PubMed Central

Post-menopausal women exhibit decreases in circulating estrogen levels and whole body insulin sensitivity, suggesting that estrogen regulates skeletal muscle glucose disposal. Thus, we assessed whether estrogen stimulates glucose uptake or enhances insulin sensitivity in skeletal muscle. Ex vivo muscle stimulation with 17?-estradiol (10 nM) resulted in a rapid (?10 min) increase in the phosphorylation of Akt, AMP-activated protein kinase (AMPK), and TBC1D1/4, key signaling proteins that regulate glucose uptake in muscle. Treatment with the estrogen receptor antagonist, ICI 182,780, only partly inhibited signaling, suggesting both an estrogen receptor-dependent and independent mechanism of estradiol action. 17?-Estradiol did not stimulate ex vivo muscle [3H]-2-deoxyglucose uptake or enhance insulin-induced glucose uptake, demonstrating discordance between the estradiol-induced stimulation of signaling proteins and muscle glucose uptake. This study is the first to demonstrate that estradiol stimulates Akt, AMPK, and TBC1D1/4 in intact skeletal muscle, but surprisingly, estradiol does not stimulate muscle glucose uptake.

Rogers, Nicole H; Witczak, Carol A; Hirshman, Michael F; Goodyear, Laurie J; Greenberg, Andrew S

2009-01-01

159

Investigation of the failure mechanism of thermal barrier coatings prepared by electron beam physical vapor deposition  

Microsoft Academic Search

Two-layer structure thermal barrier coatings (TBCs) (NiCoCrAlY [bond coat]+[6–8 wt.%] Y2O3-stabilized ZrO2 [YSZ top coat]) were deposited by electron beam physical vapor deposition (EB-PVD) on a Ni-base superalloy. Pre-treatments were carried out in a vacuum to improve the oxidation resistance of the bond coat, and the thermal cyclic life of the TBC system was investigated through thermal cyclic tests. It

Xiaofang Bi; Huibin Xu; Shengkai Gong

2000-01-01

160

Neurological events during long-term mechanical circulatory support for heart failure: The randomized evaluation of mechanical assistance for the treatment of congestive heart failure (REMATCH) experience  

Microsoft Academic Search

Background—Progression of heart failure can lead to cardiac transplantation, but when patients are ineligible, long-term mechanical circulatory support may improve survival. The REMATCH trial showed that left ventricular assist devices (LVADs) prolonged survival in patients with end-stage disease, but with a significant number of adverse events. We report on the neurological outcomes in the REMATCH trial. Methods and Results—We examined

Ronald M. Lazar; Peter A. Shapiro; Brian E. Jaski

2004-01-01

161

Molecular mechanics modeling of deformation and failure of super carbon nanotube networks  

NASA Astrophysics Data System (ADS)

A generalized molecular structure mechanics (MSM) model is proposed to investigate the deformation and failure behaviors of super carbon nanotubes (SCNTs) within the quasi-static approximation. The failure mechanism of the SCNTs with Y- and X-type junctions was examined by combining a failure criterion for the breakage of the carbon-carbon bonds in the CNT networks. The carbon-carbon bonds are modeled as elastic bars with equivalent stiffness and break as their elongation ratio reaches only 19%, which means that the broken carbon-carbon bonds are ineffective in terms of the Morse potential function. It is shown that the MSM method, combined with the failure criterion of the carbon-carbon bonds, is a powerful approach to simulate the deformation and failure of both Y junctions and X junctions with different chiralities and sizes. The deformation and failure modes of these junctions which involve rotation, bending and stretching of the CNT arms are predicted using the present model and the effects of various parameters of the junctions on their mechanical behaviors are discussed.

Liu, X.; Yang, Q.-S.; He, X.-Q.; Mai, Y.-W.

2011-11-01

162

Influence of Martensite Mechanical Properties on Failure Mode and Ductility of Dual Phase Steels  

SciTech Connect

In this paper, the effects of the mechanical properties of the martensite phase on the failure mode and ductility of dual phase (DP) steels are investigated using a micromechanics-based finite element method. Actual microstructures of DP sheet steels obtained from scanning electron microscopy are used as representative volume element (RVE) in two-dimensional plane-stress finite element calculations. Failure is predicted as plastic strain localization in the RVE during deformation. The mechanical properties of the ferrite and martensite phases in a commercial DP 980 steel are obtained based on the in-situ X-ray diffraction measurements of a uniaxial tensile test. Computations are then conducted on the RVE in order to investigate the influence of the martensite mechanical properties and volume fraction on the macroscopic behavior and failure mode of DP steels. The computations show that, as the strength and volume fraction of the martensite phase increase, the ultimate tensile strength (UTS) of DP steels increases but the UTS strain and failure strain decrease. These results agree well with the general experimental observations on DP steels. Additionally, shear dominant failure modes usually develop for DP steels with lower martensite strengths, whereas split failure modes typically develop for DP steels with higher martensite strengths.

Choi, Kyoo Sil; Liu, Wenning N.; Sun, Xin; Khaleel, Mohammad A.

2009-04-01

163

Evaluating heart failure after implantation of mechanical circulatory support devices.  

PubMed

The medical community has seen an explosive rise in the utilization of implantable mechanical circulatory support devices for late-stage cardiomyopathy. Care for these complex patients requires a basic understanding of device physiology and potential complications. This review focuses on an algorithm that incorporates a careful clinical history and examination with diagnostic modalities for the evaluation of a patient who is failing therapy with a continuous-flow left ventricular assist device, as well as the general management and optimization of patients implanted with an artificial heart. PMID:22135186

Shah, Keyur B; Tang, Daniel G; Cooke, Richard H; Kontos, Michael C; Lewis, Neil P; Katlaps, Gundars J; Hess, Michael L; Kasirajan, Vigneshwar

2012-03-01

164

On the isotropy of the dynamic mechanical and failure properties of swaged tungsten heavy alloys  

NASA Astrophysics Data System (ADS)

The quasi-static and dynamic mechanical and failure properties of a swaged tungsten-base heavy alloy rod have been investigated, with emphasis on the orientation of the specimens in the rod. Three orientations were considered, 0, 45, and 90 deg, with respect to the longitudinal axis of the rod. Compression, tension, and dominant shear tests were carried out. With the exception of the 0 deg orientation, all the orientations displayed quite similar mechanical characteristics in tension and compression. Dynamic shear revealed a critical strain for adiabatic shear failure of ? c ?0.13, independent of the orientation and quite inferior to the quasi-static ductility. The present study confirms previous results obtained for one (generally unspecified) orientation and extends them to three orientations. Failure mechanisms were thoroughly characterized and it appears that significant damage does not develop prior to final failure. It is concluded that, for practical purposes, the swaged heavy alloy considered here can be regarded as isotropic from a mechanical and failure point of view, in spite of its microstructural anisotropy resulting from the swaging process.

Rittel, D.; Levin, R.; Dorogoy, A.

2004-12-01

165

A study of failure in bonded lap joints using fracture mechanics  

NASA Astrophysics Data System (ADS)

Although adhesively bonded lap joint has already been widely applied in structures, the strength prediction of the joint is still a challenge. Among many parameters which affect the failure load of the lap joint, the adhesive layer thickness is a very important one. In this study, fracture mechanics is used to analyze the failure mechanism of the lap joint and evaluate the thickness effect on strength of the lap joint. Generally, the adhesive material is softer than the substrates and the crack in the adhesive layer is constrained by the rigid boundaries. The stress field is changed due to the effect of the rigid boundaries. For linear elastic material, the K-Dominance zone is highly reduced and the traditional constant stress intensity factor prediction over-predicts the failure load of the specimens. Constant effective fracture toughness is proposed for better strength prediction by considering of the non-singular stress term ahead of the crack tip. For elastic-plastic material, CTOA is proven to be insensitive to the constraining of the rigid boundaries and can be used as the failure criterion for fracture analysis. Both experimental and FEA simulation show that constant CTOA criterion well predicts the adhesive thickness effect on strength of the DCB specimens for mode I fracture failure. The failure initiation mode of single lap joint is analyzed and the constant CTOA criterion is also proven to be capable to prediction the strength of single lap joint.

Qian, Haiyang

166

The Influednce of Confinement on Mechanical Failure of Energetic Materials  

NASA Astrophysics Data System (ADS)

Several techniques are being used including confinement by a) a constant hydrostatic pressure and b) radial confinement by a thick walled steel cylinder surrounding the sample (negligible radial strain). In all cases the samples are cylindrical and are loaded along the cylinder axis. While many energetic materials fail by crack growth when unconfined (significant surface area free of stress), with both of these forms of confinement they appear to fail by yield and plastic flow. For crystalline explosives. e.g. TNT and composition B, the yield strength and the modulus are independent of confining pressure so that useful results can be obtained by use of the steel cylinder technique. However, for materials containing polymer binders such as plastic bonded explosives and many propellants a constant confining hydrostatic pressure is used because these same properties are found to significantly increase with confining pressure and are also functions of temperature and strain rate. These results indicate the very significant role of the polymer binders in determining the mechanical properties of these energetic materials.

Wiegand, Donald

1999-06-01

167

Effect of current reversal on the failure mechanism of Al-Cu-Si narrow interconnects  

SciTech Connect

The work reported here concerns the effect of a brief exposure to a reversed current on the electromigration failure of narrow Al-Cu thin-film conducting lines. While the precise mechanism by which Cu retards electromigration in Al-Cu alloys is not fully understood, the consistent observation that electromigration failure is preceded by the sweeping of Cu from the failure site can be used to improve electromigration resistance by stabilizing the distribution of Cu. One way of doing this is to expose the Al-Cu line to a reverse current for some period of time. The present work shows that this method is particularly effective in thin lines with `quasi-bamboo` microstructures. It has the effect of building a reservoir of Cu at the upstream ends of the polygranular segments that are the preferred failure sites, and significantly increases both the mean time of failure, and the time to first failure of a distribution of lines. It can be inferred from these results that Al-Cu lines that conduct alternating current should be exceptionally resistant to electromigration failure. 11 refs., 8 figs.

Kim, C.U.; Kang, S.H.; Morris, J.W. Jr. [Univ. of California, Berkeley, CA (United States)]|[Lawrence Berkeley Lab., CA (United States)

1996-02-01

168

IMPERMEABLE THIN Al{sub 2}O{sub 3} OVERLAY FOR TBC PROTECTION FROM SULFATE AND VANADATE ATTACK IN GAS TURBINES  

SciTech Connect

To improve the hot corrosion resistance of YSZ thermal barrier coatings, a 25 {micro}m thick Al{sub 2}O{sub 3} overlay were deposited by HVOF thermal spray, respectively, onto to the surface of YSZ coating. In the next reporting period, we will measure or calculate the residue stress within Al{sub 2}O{sub 3} overlay and YSZ coating to study the mechanism of effect of Al{sub 2}O{sub 3} overlay on spalling of YSZ coating. However, due to the thermal expansion mismatch between YSZ coating and Al{sub 2}O{sub 3} overlay, such surface modification using Al{sub 2}O{sub 3} overlay might deteriorate strain tolerance of the TBC. In the present work, in order to investigate the effect of Al{sub 2}O{sub 3} overlay on residual stress developed in the samples during cooling after hot corrosion at high temperature, Finite Element method (FEM) was employed to determine the detailed stress states in the test specimens after cooling. The results showed that there is no high stress concentration at the interface between the YSZ and the bond coat for TBCs system without Al{sub 2}O{sub 3} overlay. On the other hand, the maximum compressive stress with a value of approximately, -330 MPa occurred within the Al{sub 2}O{sub 3} overlay. The maximum tensile stress in YSZ coat near the Al{sub 2}O{sub 3} overlay is in the range of 10-133 MPa. The maximum compressive stress of approximately -160 MPa occurred near the YSZ-bond coat interface. X axis stress play a dominant role in influencing the coating failure and spalling. In the next reporting period, we will study the thickness of Al{sub 2}O{sub 3} overlay on hot corrosion resistance and spalling of YSZ coating.

Scott X. Mao

2004-03-31

169

On-Line Thermal Barrier Coating Monitoring for Real-Time Failure Protection and Life Maximization  

Microsoft Academic Search

Under the sponsorship of the U. S. Department of Energy's National Energy Laboratory, Siemens Westinghouse Power Corporation proposes a four year program titled, ''On-Line Thermal Barrier Coating (TBC) Monitor for Real-Time Failure Protection and Life Maximization'', to develop, build and install the first generation of an on-line TBC monitoring system for use on land-based advanced gas turbines (AGT). Federal deregulation

Dennis H. LeMieux

2005-01-01

170

ON-LINE THERMAL BARRIER COATING MONITORING FOR REAL-TIME FAILURE PROTECTION AND LIFE MAXIMIZATION  

Microsoft Academic Search

Under the sponsorship of the U. S. Department of Energy's National Energy Laboratory, Siemens Westinghouse Power Corporation proposes a four year program titled, ''On-Line Thermal Barrier Coating (TBC) Monitor for Real-Time Failure Protection and Life Maximization,'' to develop, build and install the first generation of an on-line TBC monitoring system for use on land-based advanced gas turbines (AGT). Federal deregulation

Dennis H. LeMieux

2003-01-01

171

ON-LINE THERMAL BARRIER COATING MONITORING FOR REAL-TIME FAILURE PROTECTION AND LIFE MAXIMIZATION  

Microsoft Academic Search

Under the sponsorship of the U. S. Department of Energy's National Energy Laboratory, Siemens Westinghouse Power Corporation proposes a four year program titled, ''On-Line Thermal Barrier Coating (TBC) Monitor for Real-Time Failure Protection and Life Maximization,'' to develop, build and install the first generation of an on-line TBC monitoring system for use on land-based advanced gas turbines (AGT). Federal deregulation

Dennis H. LeMieux

2002-01-01

172

On-Line Thermal Barrier Coating Monitoring for Real-Time Failure Protection and Life Maximization  

Microsoft Academic Search

Under the sponsorship of the U. S. Department of Energy's National Energy Laboratory, Siemens Westinghouse Power Corporation proposes a four year program titled, ''On-Line Thermal Barrier Coating (TBC) Monitor for Real-Time Failure Protection and Life Maximization'', to develop, build and install the first generation of an on-line TBC monitoring system for use on land -based advanced gas turbines (AGT). Federal

Dennis H. LeMieux

2004-01-01

173

On-Line Thermal Barrier Coating Monitoring for Real-Time Failure Protection and Life Maximization  

Microsoft Academic Search

Under the sponsorship of the U. S. Department of Energy's National Energy Laboratory, Siemens Power Generation, Inc proposed a four year program titled, ''On-Line Thermal Barrier Coating (TBC) Monitor for Real-Time Failure Protection and Life Maximization'', to develop, build and install the first generation of an on-line TBC monitoring system for use on land-based advanced gas turbines (AGT). Federal deregulation

Dennis H. LeMieux

2005-01-01

174

Dynamic Mechanical Behavior and Failure Mechanism of Polymer Composites Embedded with Tetraneedle-Shaped ZnO Whiskers  

NASA Astrophysics Data System (ADS)

Quasi-static and dynamic mechanical properties of glass-fiber reinforced polymer composites embedded with and without tetraneedle-shaped ZnO whiskers (T-ZnOw) in two loading directions are investigated by a split Hopkinson pressure bar. The stress-strain curves, ultimate strength, failure strain and elastic modulus are obtained and the failure mechanism of the composites is investigated by a high-speed camera and a scanning electron microscope. Strain rate effects on the mechanical behavior are discussed and the corresponding models are derived by fitting the experimental data. The experimental results show that the composites with T-ZnOw under dynamic loading have multiple failure modes and better mechanical properties. Finally, the strengthening and toughening mechanisms of T-ZnOw are analyzed. It is shown that T-ZnOw can improve mechanical properties of the composites, and can make the composites have some new features. The present results provide a reliable basis for advanced composite design and manufacture, and have broad applications in the field of aerospace.

Rong, Ji-Li; Wang, Dan; Wang, Xi; Li, Jian; Xu, Tian-Fu; Lu, Ming-Ming; Cao, Mao-Sheng

2013-01-01

175

Failure analysis of a graphite/epoxy laminate subjected to combined thermal and mechanical loading  

SciTech Connect

Quasi-static thermal stress response and failure behavior of graphite/epoxy laminated plates under combined intense thermal and mechanical loadings are investigated. The temperature field is obtained by using a one-dimensional finite difference code. The effects of ablation, degradation of thermophysical properties at elevated temperatures, and radiation and convective heat losses are included in the formulation. In the thermal stress and strength analyses, the temperature-dependent mechanical properties and temperature-dependent strengths are used. A nine-node isoparametric finite element is employed to calculate the structural responses. The maximum stress criterion is adopted for failure predictions. Numerical results include the temperature distribution over the thickness of the plate, structural responses, and time to failure. The analytical predictions are compared with experimental data. 17 references.

Chen, J.K.; Sun, C.T.; Chang, C.I.

1985-09-01

176

The microstructural mechanism of electromigration failure in narrow interconnects of Al alloys  

SciTech Connect

This thesis reports a study of the mechanism of electromigration failure in Al-2Cu-1Si thin-film conducting lines on Si. Samples were patterned from 0.5 {mu}m thick vapor-deposited films with various mean grain sizes (G), and had lines widths (W) of 1.3, 2, 4 and 6 {mu}m. The lines were aged at various conditions to change the Cu-precipitate distribution and were tested to failure at T = 225{degrees}C and j = 2.5 {times} 10{sup 6} A/cm{sup 2}. Some samples were tested over a range of substrate temperatures, current densities and current reversal times. Aging produces an initially dense distribution of metastable {Theta}{prime} (Al{sub 2}Cu; coherent) in the grain interiors, with stable {Theta} (Al{sub 2}Cu; incoherent) at the grain boundaries. The intragranular {theta}{prime} is gradually absorbed into the grain boundary precipitates. In the wide lines the mean time to failure increases slowly and monotonically with pre-aging time and current reversal time. The failure mode is the formation and coalescence of voids that form on grain boundaries with an apparent activation energy of 0.65 eV. In the narrow lines, the lines failed by a transgranular-slit mechanism with an activation energy near 0.93 eV. The distribution of the polygranular segments and the kinetics of failure varies with the linewidths. Failure occurs after Cu has been swept from the grains that fail. Pre-aging the line to create a more stable distribution of Cu significantly increases the time to failure. When the density of intragranular {Theta}-phase precipitates is maximized, the transgranular-slit failure mechanism is suppressed, and the bamboo grain fails by diffuse thinning to rupture. The results from the current reversal test indicate that the time to sweep Cu in the polygranular segments is longer for longer polygranular segments. Thus the time to first failure in an array of lines is much longer than predicted by a log-normal fit to the distribution of failure times.

Kim, Choongun

1993-04-01

177

SLOPE FAILURE MECHANISMS IN COHESIVE SOILS: INSIGHTS FROM THEORETICAL AND NUMERICAL ANALYSES OF FIELD AND LABORATORY-TRIGGERED EVENTS  

Microsoft Academic Search

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

J. Malet; A. Spickermann; T. van Asch

2009-01-01

178

The study on failure mechanisms of bond pad metal peeling: Part A--Experimental investigation  

Microsoft Academic Search

For the experimental investigation on failure mechanisms of bond pad metal peeling, 31 failed SDRAM chips after the pad peeling are gathered, and SEM and FIB are utilized. From the results of this study, the vertical tension loading transferred by the capillary to the deformed ball is recognized as the direct driving force for the pad peeling and the crack

Insu Jeon; Qwanho Chung

2003-01-01

179

An observer-based mechanical sensor failure fault tolerant controller structure in PMSM drive  

Microsoft Academic Search

This paper presents a specific controller architecture devoted to obtain a Permanent Magnet Synchronous Motor drive robust to mechanical sensor failure. In order to increase the reliability which is a key issue in industrial and transportation applications (Electric or Hybrid ground vehicle or aerospace actuators) two virtual sensors (a two stage Extended Kalman Filter and a back-emf adaptive observer) and

Ahmad Akrad; Mickaël Hilairet; Demba Diallo

2009-01-01

180

Mechanics-based statistics of failure risk of quasibrittle structures and size effect on safety factors  

Microsoft Academic Search

In mechanical design as well as protection from various natural hazards, one must ensure an extremely low failure probability such as 10-6. How to achieve that goal is adequately understood only for the limiting cases of brittle or ductile structures. Here we present a theory to do that for the transitional class of quasibrittle structures, having brittle constituents and characterized

Zdenek P. Bazant; Sze-Dai Pang

2006-01-01

181

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

National Technical Information Service (NTIS)

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 Co...

D. D. Liu M. J. Sampson

2012-01-01

182

Continuum damage mechanics analyses of type IV creep failure in ferritic steel crossweld specimens  

Microsoft Academic Search

A major high temperature failure mechanism for weldments in ferritic steel steam pipework is circumferential creep cracking within the region of the heat affected zone, adjacent to the parent material, that experiences the lowest temperatures during the welding process. This is commonly known as type IV cracking. In recent years a number of experimental studies have investigated the occurrence of

I. J Perrin; D. R Hayhurst

1999-01-01

183

STUDY OF THE MECHANISM OF FAILURE OF ROCKET MATERIALS AND MATERIALS RESEARCH  

Microsoft Academic Search

Rocket failure mechanisms in conjunction with the development of nozzle ; materials for solid propellant motors is discussed. Testing graphite in an oxy-; acetylene torch and the effects of purity, density, orientation, and ; microstructure on erosion-resistance were evaluated. Erosion decreased with ; greater purity. New graphite materials were developed and evaluated including ; hot pressed compositions and impregnated bodies.

Y. Baskin; D. C. Schell; W. K. Sumida

1962-01-01

184

Failure strain and mechanical property data for the Type IIIA waste tank liners  

SciTech Connect

The SRS Waste Tanks at the Savannah River Site to be employed in the In-Tank Precipitation (ITP) process are undergoing a structural evaluation in order to define their response to a hypothetical deflagration accident. This report provides mechanical property data to support the structural analyses, and characterizes the impact of mechanical property variability and materials degradation on the failure strain of the primary liner.

Thomas, J.K.

1992-06-01

185

Failure cause identification of tribo-mechanical systems using fault tree—a digraph approach  

Microsoft Academic Search

A procedure for the failure cause identification of tribo-mechanical systems is presented based on fault-tree using a digraph approach. A variable-event system digraph for a tribo-mechanical system is suggested which takes into account structure of the system. A top event or undesirable event for the system is then defined and the fault-tree for this top event is deduced from the

Rakesh Sehgal; O. P. Gandhi; S. Angra

2003-01-01

186

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

PubMed

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. PMID:19388771

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

2009-05-01

187

Failure mechanism analysis of electromigration dominated damage in TiSi2 nanowires  

NASA Astrophysics Data System (ADS)

Electromigration-induced damage has been an important concern in very large scale integrated circuit design for a long time and will be a major road block in the pursuit of nanoelectronics devices and next generation power electronics. In this letter, the failure mechanism analysis on two-terminal TiSi2 nanowire devices was reported. Electromigration dominant mass migration is observed and verified by energy dispersive spectroscopy. The contribution of thermomigration is discussed based on temperature simulation. This work provides useful reference for future devices and the failure analysis on nanostructures.

Zou, Chen-Xia; Xu, Jun; Zhang, Xin-Zheng; Song, Xue-Feng; Yu, Da-Peng

2009-06-01

188

Dynamic failure mechanisms in armor grade ceramics (the effect of lateral confinement and membrane restraint)  

NASA Astrophysics Data System (ADS)

Light weight ceramics such as SiC and Al2O3, have been used in impact related applications such as integrated armor for more than a decade and are an excellent prospect for the next-generation multi-functional armor systems. It is known that ceramics fail under a wide variety of failure modes ranging from brittle to ductile depending on the deformation conditions, such as the strain rate and the state of stress. The dynamic properties are dependent on the underlying failure mechanisms. The underpinning mechanisms of compression failure and their effect on the mechanical properties have been examined over a range of deformation rates from quasi-static to ballistic strain rates. Under moderate confining pressures [˜350 MPa] and at moderate deformation rates [strain-rates up to a few thousand per second], occurring during quasi-static and Hopkinson bar experiments, brittle failure involves initiation of micro-cracks at dominant micro-flaws and pre-existing micro-cracks and their subsequent interactive growth leading to axial splitting, faulting or a mixture of brittle-ductile failure. Experimental results relating to SiC have been compared to a wing-crack array model, developed by Nemat-Nasser and Deng, which describes the influence of microstructure on the dynamic behavior of materials. Under extreme conditions of stress, attained during shock impact, ceramics pulverize into fine powder. Classical crack-growth models seem inadequate for representing the actual failure initiation and evolution. Experiments have also been conducted to study the ballistic performance and failure of ceramic tiles. It has been observed that the defeat capability can be vastly improved by restraining the impact-face of ceramic tiles with a membrane of suitable tensile strength. The comparative effect of restraint by materials such as E-glass/epoxy pre-preg, carbon-fiber/epoxy pre-preg and Ti-3%Al-2.5%V alloy has been studied. Tungsten heavy alloy was used as the projectile material. The ballistic efficiency was improved by nearly 20% for a mere 2% increase in areal density. High-speed photography, flash radiography, microscopy and numerical simulations provide insight into the failure mechanisms.

Sarva, Sai Sushilkumar

189

Lifetimes and failure mechanisms of W/Re hairpin filaments. Technical report  

SciTech Connect

A life test of tungsten or tungsten alloys hairpin filaments used in a high-reliability electron beam instrument has been carried out to improve knowledge of filament life and failure mechanisms as a function of temperature. These filaments are made of non-sag tungsten/3% rhenium (W/3% Re) wire. A steep reduction in filament life is observed at 2760 K which is not predicted by models which assume thermal evaporation as the principal failure mechanism. Failure analysis of the filaments shows that the sudden loss of life at 2760 K is the result of localized formation of hot spots caused by the accumulation of voids at grain boundaries. Examination of the crystal growth rates indicates that the recrystallization temperature, occurs near 2760 K for the non-sag W/3% Re wire used in these filaments. This suggests that void accumulation acts as the principal life-limiting failure mechanism; spontaneous recrystallization at 2760 K increases the rate of voids growth and causes a severe reduction of filament life.

Luey, K.T.

1991-02-26

190

Impermeable Thin Al(2)O(3) overlay for TBC Protection from Sulfate and Vanadate Attack in Gas Turbines.  

National Technical Information Service (NTIS)

The project started on September 1, 2001. During last 4 months, one post-doctor has been hired for this project. We have received TBC samples (YSZ/ CoNiCrAlY/ Inconel 601) from Tohoku University, Japan, while processing of the TBC samples was delayed in G...

S. X. Mao

2002-01-01

191

Effect of beam angle on HAZ, recast and oxide layer characteristics in laser drilling of TBC nickel superalloys  

Microsoft Academic Search

Industrial applications of laser drilling include the production of cooling holes at acute angles in certain parts of the aero-engine components. These parts are often covered with ceramic thermal barrier coatings (TBC) to protect them from reaching excessive temperatures in hot engine environments. Acute angle TBC drilling brings three major simultaneous complications to the process. These are: (i) multi-layer drilling,

H. K. Sezer; L. Li; M. Schmidt; A. J. Pinkerton; B. Anderson; P. Williams

2006-01-01

192

Mechanisms and implications of vasodilator tolerance in the treatment of congestive heart failure.  

PubMed

Vasodilators play an important role in the treatment of the patient with severe heart failure and increased systemic vascular resistance. However, there are both clinical data and theoretic reasons to anticipate that some degree of tolerance may develop during the long-term use of most agents. The cause of the increased vascular resistance of heart failure is not completely understood, but it appears to be related to a number of neuroendocrine, molecular and physical mechanisms including increased activity of the sympathetic nervous and renin-angiotensin systems, and increased vascular stiffness due to intra- and extracellular sodium and fluid accumulation. Not surprisingly, a lowering of systemic vascular resistance either by direct smooth muscle relaxers or by blockade of specific neuroendocrine systems may result in a number of compensatory responses at the neuroendocrine and/or molecular level. The over-all effectiveness of a particular vasodilator is the net sum of its direct pharmacologic action, and the neuroendocrine and molecular responses to the drug. The specific compensatory mechanisms activated depend on several factors including the type of vasodilator used, the dose employed, the baseline neuroendocrine status of the patient, the severity of heart failure and the functional integrity of various reflex systems. Although not directly applicable to patients with heart failure, much information derived from the use of these agents to treat patients with hypertension and angina pectoris suggests several potential mechanisms by which tolerance may develop to virtually all classes of vasodilators. The major types of vasodilators are discussed with regard to their potential mechanisms of tolerance. Finally, the evidence currently available from long-term studies is reviewed in order to assess the potential relevance of vasodilator tolerance to the clinical management of the patient with heart failure. PMID:6166194

Colucci, W S; Williams, G H; Alexander, R W; Braunwald, E

1981-07-01

193

Tip cooling effect and failure mechanism of field-emitting carbon nanotubes.  

PubMed

The cooling effect accompanying field electron emission has been considered for a single carbon nanotube (CNT) used as a field emission (FE) electron source. An improved model for the failure mechanism of field emitting CNTs has been proposed and validated. Our model predicts a maximum temperature (T-max) located at an interior point rather than the tip of the CNTs, and the failure of the CNT emitters tends to take place at the T-max point, inducing a segment by segment breakdown process. A combination of Joule heating and electrostatic force effect is proposed responsible for initiating the failure of the field emitting CNT and validated by in situ FE observation. PMID:17212441

Wei, Wei; Liu, Yang; Wei, Yang; Jiang, Kaili; Peng, Lian-Mao; Fan, Shoushan

2007-01-01

194

The mechanism of electromigration failure of narrow Al-2Cu-1Si thin-film interconnects  

SciTech Connect

This work is principally concerned with the microstructure of electromigration failure in narrow Al-2Cu-1Si conducting lines on Si. Samples were patterned from 0.5-[mu]m-thick vapor-deposited films with mean grain size of 2.4 [mu]m, and had linewidths of 1.3 [mu]m ([ital W]/[ital G][approx]0.5), 2 [mu]m ([ital W]/[ital G][approx]0.8), and 6 [mu]m ([ital W]/[ital G][approx]2.5). The lines were tested to failure at [ital T]=226 [degree]C and [ital j]=2.5[times]10[sup 6] A/cm[sup 2]. Other samples were tested over a range of substrate temperatures and current densities to test the effect of these variables, and 1.3 [mu]m lines were tested after preaging at 226 [degree]C for various times to change the Cu-precipitate distribution prior to testing. Three failure modes were observed: The 6 [mu]m specimens failed by separation along grain boundaries with an apparent activation energy of 0.65 eV; the 1.3 [mu]m specimens that were preaged for 24 h failed after very long times by gradual thinning to rupture; all other narrow lines failed by the transgranular-slit mechanism with an activation energy near 0.93 eV. Microstructural studies suggest that the transgranular-slit failure mechanism is due to the accumulation of a supersaturation of vacancies in the bamboo grains that terminate polygranular segments in the line. Failure occurs after Cu has been swept from the grain that fails. Failure happens first at the end of the longest polygranular segment of the line, at a time that decreases exponentially with the polygranular segment length. Preaging the line to create a more stable distribution of Cu lengthens the time required to sweep Cu from the longest polygranular segment, and significantly increases the time to failure. In the optimal case the transgranular-slit failure mechanism is suppressed, and the bamboo grain fails by diffuse thinning to rupture.

Kim, C.; Morris, J.W. Jr. (Center for Advanced Materials, Lawrence Berkeley Laboratory, and Department of Materials Science, University of California, Berkeley, California 94720 (United States))

1993-05-15

195

Serendipitous discovery of a novel protein signaling mechanism in heart failure  

PubMed Central

A number of protein signaling mechanisms are known to be involved in the progression of heart failure, yet the mechanism(s) by which the heart fails remains poorly understood. Therefore, we undertook a global approach to this question and used an antibody microarray to identify proteins differentially expressed in dysfunctional right ventricles in a bovine model of heart failure and the results were validated using cardiac tissue from both bovine and human heart failure. We found that protein disulfide isomerase 3, PDIA3, a protein that resides in the lumen of the endoplasmic reticulum, is significantly upregulated in both animal and human models of right and left heart failure. Altered expression of this protein has not previously been described in models of heart failure. In our initial microarray analysis, we found that CSK (c-Src kinase) was among the proteins upregulated in failing bovine ventricle. To further elucidate the role of CSK in heart failure we studied the expression of its downstream target, Src, and found that Src expression and phosphorylation were markedly upregulated in failing ventricles. However, we also noted a smaller immunologically reactive protein that was only seen in experimental animals. In order to positively identify the smaller, Src-reactive protein, we used 2-dimensional gel electrophoresis and mass spectrophotometry. Surprisingly, we identified this protein as PDIA3, a protein that did not belong to the Src family of proteins. Upon sequence examination we found that PDIA3 contains a short C-terminal sequence with strong homology to Src and that it was this short sequence to which the antibody was generated. PDIA3 participates in MHC class I presentation and is implicated in the progression of valvular dysfunction in rheumatic heart disease, as well as calcium modulation in the sarcoplasmic reticulum. The molecule resides in the lumen of the endoplasmic reticulum and participates in disulfide bond formation during protein folding by interacting with calnexin and calreticulin. This interaction may indirectly effect SERCA (sarco/endoplasmic reticulum Ca2+-transport ATPase) activity and by extension contribute to the calcium dysregulation that characterizes progressive heart failure. Further studies are needed to elucidate the role that PDIA3 may play in the progression of heart failure.

Vitello, Andrea M.; Du, Yanmei; Buttrick, Peter M.; Walker, Lori A.

2012-01-01

196

Serendipitous discovery of a novel protein signaling mechanism in heart failure.  

PubMed

A number of protein signaling mechanisms are known to be involved in the progression of heart failure, yet the mechanism(s) by which the heart fails remains poorly understood. Therefore, we undertook a global approach to this question and used an antibody microarray to identify proteins differentially expressed in dysfunctional right ventricles in a bovine model of heart failure and the results were validated using cardiac tissue from both bovine and human heart failure. We found that protein disulfide isomerase 3, PDIA3, a protein that resides in the lumen of the endoplasmic reticulum, is significantly upregulated in both animal and human models of right and left heart failure. Altered expression of this protein has not previously been described in models of heart failure. In our initial microarray analysis, we found that CSK (c-Src kinase) was among the proteins upregulated in failing bovine ventricle. To further elucidate the role of CSK in heart failure, we studied the expression of its downstream target, Src, and found that Src expression and phosphorylation were markedly upregulated in failing ventricles. However, we also noted a smaller immunologically reactive protein that was only seen in experimental animals. In order to positively identify the smaller, Src-reactive protein, we used 2-dimensional gel electrophoresis and mass spectrophotometry. Surprisingly, we identified this protein as PDIA3, a protein that did not belong to the Src family of proteins. Upon sequence examination we found that PDIA3 contains a short C-terminal sequence with strong homology to Src and that it was this short sequence to which the antibody was generated. PDIA3 participates in MHC class I presentation and is implicated in the progression of valvular dysfunction in rheumatic heart disease, as well as calcium modulation in the sarcoplasmic reticulum. The molecule resides in the lumen of the endoplasmic reticulum and participates in disulfide bond formation during protein folding by interacting with calnexin and calreticulin. This interaction may indirectly effect SERCA (sarco/endoplasmic reticulum Ca(2+)-transport ATPase) activity and by extension contribute to the calcium dysregulation that characterizes progressive heart failure. Further studies are needed to elucidate the role that PDIA3 may play in the progression of heart failure. PMID:22503978

Vitello, Andrea M; Du, Yanmei; Buttrick, Peter M; Walker, Lori A

2012-04-07

197

Turn-off failure mechanisms in large (2.2 kV, 20 A) MCT devices  

Microsoft Academic Search

In this paper we present the phenomenological mechanisms leading to turn-off failures for large size MCT devices under inductive loading. Depending on the device current and the clamping voltage two different mechanisms lead to turn-off failures. At lower clamping voltages or in soft switching conditions the SOA is limited by the MOSFET and cathode design rules. At higher voltages and

H. Lendenmann; W. Fichtnert

1994-01-01

198

Fundamentally Different Failure Mechanisms Around Boreholes in two High Porosity Sandstones  

NASA Astrophysics Data System (ADS)

We compare the shape and mechanism of failure around vertical boreholes drilled in blocks of two high-porosity sandstones subjected to unequal far-field principal stresses. Tablerock sandstone has a porosity of 28%, and is composed of 55% quartz and 37% weaker feldspar grains. Grain cementation is substantial through microcrystalline quartz. Critical far-field stresses induce failure around boreholes in the form of V-shaped (dog-eared) breakouts, the result of dilatant intra-and trans-granular microcracking subparallel to both the maximum horizontal far-field stress and to the borehole wall. No localized deformation ahead of the breakout tip is observed. On the other hand, boreholes in Mansfield sandstone, which has similar porosity (26%), but contains mainly quartz grains (90%) held together primarily by spot-sutured contacts, fail by developing fracture-like breakouts. These are long and very narrow (several grain diameters) tabular failure zones perpendicular to the maximum stress. Evidence provided mainly by SEM observations suggests a failure process initiated by localized grain-bond loosening along the least horizontal far-field stress springline, the packing of these grains into a lower porosity compaction band resembling those discovered in Navajo and Aztec sandstones, and the emptying of the loosened grains by the circulating drilling fluid starting from the borehole wall. Although the immediate several grain layers at the breakout tip often contain some cracked or even crushed grains, the failure mechanism enabled by the formation of the compaction band is largely non-dilatant, a major departure from the dilatant mechanism considered typical for rocks. The experimental results suggest that unlike our previous assertion, the type of grain bonding and mineral composition, and not the porosity, are major factors in the formation of compaction bands and the ensuing fracture-like breakouts.

Haimson, B.; Lee, H.

2003-12-01

199

Application of dynamic fracture mechanics to the investigation of catastrophic failure in aircraft structures  

NASA Astrophysics Data System (ADS)

A dynamic fracture mechanics approach to the estimation of the residual strength of aircraft structures is presented. The dependence of the dynamic crack initiation toughness of aluminum 2024-T3 on loading rate is first studied experimentally. Based on the experimental results and on established dynamic fracture mechanic concepts, a fracture mechanics based failure model is established and is used to estimate the residual strength of aircraft structures. A methodology to determine residual strength of dynamically loaded structures based on global structural analysis coupled with local finite element analysis is introduced. Local finite element calculations were performed for different loading rates to simulate the conditions encountered in an explosively loaded aircraft fuselage. The results from the analyses were then used in conjunction with the experimental results for the dynamic fracture toughness of a 2024-T3 aluminum alloy as a function of loading rate, KdIC vs. K?d(t), to determine the time to failure, tf, for a given loading rate. A failure envelope, sf vs. ? , based on the failure model and finite element analysis, is presented for the different cases and the implications for the residual strength of aircraft structures is discussed. Mixed mode dynamic crack initiation in aluminum 2024-T3 alloy is investigated by combining experiments with numerical simulations. The optical technique of coherent gradient sensing (CGS) and a strain gage method are employed to study the evolution of the mixed mode stress intensity factors. The dynamic mixed mode failure envelope is obtained using the crack initiation data from the experiments at a nominal loading rate of 7 x 105 MPam/s . Numerical simulations of the experiments are conducted to both help in designing the experiments and to validate the results of the experiments. The numerical simulations show good correlation with the experimental results.

Chow, Benjamin Bin

200

Investigation of a Limestone Pillar Failure Part 2: Stress History and Application of Fracture Mechanics Approach  

Microsoft Academic Search

Summary   Observed pillar failure could not be explained by comparing pillar strength with stresses on the pillar induced by mining\\u000a activities. Instead, the effects of the combined stress history of strata and pillar on the deformational response of rock\\u000a mass and rock were assessed. Application of the principles of fracture mechanics, i.e., extension strain and strain energy\\u000a release rate criteria

M. Alber; J. Heiland

2001-01-01

201

Stress and failure analysis of mechanically fastened joints in composite laminates  

Microsoft Academic Search

The literature published on single mechanically fastened joints in fiber-reinforced plastics is reviewed. A finite-element model is developed to predict the response of pin-loaded composite plates. The model takes into account contact at the pin–hole interface, progressive damage, large deformation theory, and a non-linear shear stress–strain relationship. To predict the progressive ply failure, the analysis combines Hashin and the maximum

Marie-Laure Dano; Guy Gendron; André Picard

2000-01-01

202

Deformation and failure mechanisms in titanium-aluminum-vanadium\\/titanium carbide particulate and layered composites  

Microsoft Academic Search

Composite materials are attractive for high performance applications due to their high specific strengths. The compressive deformation behavior of Ti-6Al-4V (Ti64) and Ti64\\/TiC particulate and layered composites was studied for ballistic applications at strain rates from 0.1 s-1 to 1000 s-1 and strengthening and failure mechanisms were identified. The behavior of Ti64 with the equiaxed and Widmanstatten microstructures was characterized

Amy Jaye Wagoner Johnson

2002-01-01

203

Sealing Mechanism and Failure Analysis of Automotive Engine Crankshaft Oil Seal  

Microsoft Academic Search

There are many factors that lead to the failure of automotive engine crankshaft back oil seal, these factors include seal working condition, seal`s material quality and seal`s technical parameters that directly affect the seal`s seal ability and service life. Aiming at the leakage problem of automotive engine crankshaft oil seal and basing on analysis of drain pump seal mechanism, I

Aifang Yan; Qingping Yan

2012-01-01

204

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

Microsoft Academic Search

Background. Due to the shortage of donor hearts, mechanical circulatory support is increasingly being used as a bridge to transplantation.\\u000a In order to allow for more widespread use of ventricular assist devices it is mandatory that patients are not continuously\\u000a hospitalised. We present the results of our experience with patients with end-stage heart failure, discharged from hospital\\u000a after implantation of

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

2007-01-01

205

Mechanisms Involved in Cardiac Enlargement and Congestive Heart Failure Development after Acute Myocardial Infarction  

Microsoft Academic Search

For 3 months, we followed up 40 patients with acute myocardial infarction, 20 were randomly assigned to treatment with captopril and 20 to placebo, to elucidate mechanisms inducing left ventricular volume enlargement and development of congestive heart failure. Echocardiographic follow-up could be obtained in 28 patients, 11 of whom showed more than a 10% increase in left ventricular systolic and\\/or

Franz X. Kleber; Jürg Nussberger; Lisa Niemöller; Wittich Doering

1992-01-01

206

Impact of interfacial solubility on penetration of metals into dielectrics and the mechanism of failure  

Microsoft Academic Search

Copper solubility in low-k dielectrics has been shown to be a major factor in decreasing the useful lifetime of an interconnect.\\u000a A number of groups have shown experimentally that increased surface oxygen concentration, increased moisture content in the\\u000a dielectric, and an increase in interfacial copper concentration from chemical–mechanical polishing all contribute to accelerated\\u000a failure. Here, we assumed that all these

Joel. L. Plawsky; William N. Gill; Ravi S. Achanta

207

Mechanisms of Cardiomyocyte Dysfunction in Heart Failure Following Myocardial Infarction in Rats  

Microsoft Academic Search

Available information regarding the cellular and molecular mechanisms for reduced myocardial function after myocardial infarction (MI) is scarce. In rats with congestive heart failure (CHF), we examined cardiomyocytes isolated from the non-infarcted region of the left ventricle 6 weeks after ligation of the left coronary artery. Systolic left-ventricular pressure was reduced and diastolic pressure was markedly increased in the CHF-rats.

Even Holt; Theis Tønnessen; Per K. Lunde; Svein O. Semb; J. Andrew Wasserstrom; Ole M. Sejersted; Geir Christensen

1998-01-01

208

Failure Mechanisms Associated with Die-to-Header Bonds of Planar Transistors  

Microsoft Academic Search

An investigation of failure mechanisms associated with die-to-header bonds in planar transistors was centered on five thermally induced physical processes that occur in these bonds. The five processes include solid-state diffusion of intermediate materials into the bonding layer and outgassing of materials on the header, both resulting in void formation; nickel-silicon intermetallic formation leading to cracking; thermal reordering of gold-silicon

J. D. Guttenplan; F. H. Stuckenberg

1965-01-01

209

Impermeable Thin Al2O3 Overlay for TBC Protection from Sulfate and Vanadate Attack in Gas Turbines  

SciTech Connect

Current advanced turbine system (ATS) requires thermal barrier coatings (TBCs) on turbine blades and vanes. The TBCs being specified, based on yttria stabilized zirconia (YSZ), have the limited durability for advanced industrial gas turbine applications that have longer durability requirements (30,000 hours versus <10,000 hours), particularly when dirty fuels are burned. Surface deposits (including molten sulfate and vanadate salts) can penetrate into porous TBCs and result in hot corrosion, leading to premature spalling. In the present project, it is planed to deposit a dense overlay Al2O3 on the surface of the YSZ coating to prevent YSZ coating from hot corrosion of deposits derived from combustion of low-grade fuel and air impurities. The dense overlay Al2O3 acts as a barrier to protect TBC and bond coat. The overlay Al2O3 will be deposited on the surface of the thermal barrier coating using physical vapor deposition (PVD) technique and solgel method, respectively. The hot corrosion resistance of the composite Al2O3/YSZ coating will be evaluated. The hot corrosion behavior of the Al2O3/YSZ/NiCrAlY/superalloy system will be compared with the YSZ/NiCrAlY/superalloy system. The corrosion behavior of the sol-gel-modified Al2O3/YSZ system will also be compared with that of the PVD-treated system. The mechanism of hot corrosion will be investigated. The processing-structure-properties relationship of the overlays will be determined. The implementation of the TBC technology is to improve the durability of turbine components and allow the service of turbines in fuels with impurity, which will contribute to the missions and goals of the DOE ''Vision 21'' R&D program in advanced materials, energy efficiency, environment stewardship and energy production.

Mao, Scott X.

2001-11-06

210

[Clinical evaluation of PFNA® and relationship between the tip-apex distance and mechanical failure].  

PubMed

The incidence of trochanteric fractures is increasing in Europe, and the economic impact and mortality is high. The aim of the study was to evaluate the PFNA® (proximal femoral nail antirotation) with respect to its clinical use and mechanical complications.All patients with a trochanteric fracture who had been treated with a PFNA® between 12/2004 and 12/2007 were identified and analysed regarding complications and radiological findings. The study included 195 patients; 61.2% of the patients were classified as Singh I und II. The mean duration of surgery was 57 min. In ten cases (5.1%) the blade migrated, four cases (2.1%) showed blade cut out and in one case the nail broke (0.5%). The mean TAD was 26.7 mm, in cases of cut out 41.3 mm and in blade migrations 38.6 mm. No failure could be documented when the TAD was less then 30 mm. There is a strong relationship between increasing TAD and mechanical failure (P<0.001); 84.6% of the patients have been followed up, and 30.2% died in the follow-up period.The PFNA® is an easy-to-use implant for the treatment of stable and instable proximal femur fractures. Mechanical failure depends on the TAD. PMID:21626197

Kraus, M; Krischak, G; Wiedmann, K; Riepl, C; Gebhard, F; Jöckel, J A; Scola, A

2011-06-01

211

Double deck bridge behavior and failure mechanism under seismic motions using nonlinear analyzes  

NASA Astrophysics Data System (ADS)

This paper investigates the behavior and the failure mechanism of a double deck bridge constructed in China through nonlinear time history analysis. A parametric study was conducted to evaluate the influence of different structural characteristics on the behavior of the double deck bridge under transverse seismic motions, and to detect the effect of bidirectional loading on the seismic response of this type of bridge. The results showed that some characteristics, such as the variable lateral stiffness, the foundation modelling, and the longitudinal reinforcement ratio of the upper and lower columns of the bridge pier bents have a major impact on the double deck bridge response and its failure mechanism under transverse seismic motions. It was found that the soft story failure mechanism is not unique to the double deck bridge and its occurrence is related to some conditions and structural characteristics of the bridge structure. The analysis also showed that the seismic vulnerability of the double deck bridge under bi-directional loading was severely increased compared to the bridge response under unidirectional transverse loading, and out-of-phase movements were triggered between adjacent girders.

Alali, Shirin; Li, Jianzhong; Guo, Guanzhong

2013-09-01

212

Prevent boiler tube failures--Part 1: Fire-side mechanisms  

SciTech Connect

A boiler tube fails when the structural integrity of the tube is compromised. For boilers that have been previously operating, some change must occur to effect tube failure. Usually this change is wrought through some combination of corrosion and erosion acting on the boiler tube to weaken it. Boiler tubes depend on a complex metal oxide layer for protection from the hot furnace environment. Fire-side corrosion and erosion remove or alter the oxide layer, rendering the tube vulnerable to attack. Corrosion and erosion are destructive mechanisms that ravage boiler tubes. They are distinguished by the cause of the destruction--corrosion is caused by chemical or electrochemical attack, whereas erosion is caused by abrasive action of a moving fluid or solid. Both mechanisms can and often do operate simultaneously. This article focuses on the fire side of the tube. It explains the major mechanisms responsible for fire-side boiler tube failures, how to recognize the underlying cause of the failure, and how to avoid such problems. Fuel oil, coal, and municipal solid waste boilers are discussed.

Colannino, J.

1993-10-01

213

Therapeutic efficacy of TBC3711 in monocrotaline-induced pulmonary hypertension  

PubMed Central

Background Endothelin-1 signalling plays an important role in pathogenesis of pulmonary hypertension. Although different endothelin-A receptor antagonists are developed, a novel therapeutic option to cure the disease is still needed. This study aims to investigate the therapeutic efficacy of the selective endothelin-A receptor antagonist TBC3711 in monocrotaline-induced pulmonary hypertension in rats. Methods Monocrotaline-injected male Sprague-Dawley rats were randomized and treated orally from day 21 to 35 either with TBC3711 (Dose: 30 mg/kg body weight/day) or placebo. Echocardiographic measurements of different hemodynamic and right-heart hypertrophy parameters were performed. After day 35, rats were sacrificed for invasive hemodynamic and right-heart hypertrophy measurements. Additionally, histologic assessment of pulmonary vascular and right-heart remodelling was performed. Results The novel endothelin-A receptor antagonist TBC3711 significantly attenuated monocrotaline-induced pulmonary hypertension, as evident from improved hemodynamics and right-heart hypertrophy in comparison with placebo group. In addition, muscularization and medial wall thickness of distal pulmonary vessels were ameliorated. The histologic evaluation of the right ventricle showed a significant reduction in fibrosis and cardiomyocyte size, suggesting an improvement in right-heart remodelling. Conclusion The results of this study suggest that the selective endothelin-A receptor antagonist TBC3711 demonstrates therapeutic benefit in rats with established pulmonary hypertension, thus representing a useful therapeutic approach for treatment of pulmonary hypertension.

2011-01-01

214

Effects of Al on the failure mechanism of the Sn-Ag-Zn eutectic solder  

Microsoft Academic Search

Tensile testing of Sn–3.7Ag–0.9Zn–xAl (x=0, 0.5 and 1.0wt.%) solders have been performed and the failure mechanism was investigated. The results suggest that the addition of Al in the Sn–3.7Ag–0.9Zn solder decreases both the tensile strength and ductility. Moreover, a brittle fracture occurs instead of a ductile fracture with increasing Al content. The fractographs suggest that the fracture mechanism of Sn–Ag–Zn

C. Wei; Y. C. Liu; L. M. Yu; H. Chen; X. Wang

2010-01-01

215

High Temperature Electrical Behaviour and Failure Mechanisms of Glass-Ceramic Dielectrics in Thick Film Multilayers.  

NASA Astrophysics Data System (ADS)

Glass-ceramics are polycrystalline materials obtained from glasses after an appropriate thermal treatment. They are of importance because they offer combinations of physical properties not available with other classes of materials. Recently, their technological importance has also been recognized in the field of microelectronics. Since the end of the eighties great effort has been spent in the development of glass-ceramics suitable as dielectrics in thick film multilayer systems. The construction of complex thick film multilayers can be seriously obstructed by the occurrence of failures during production at high temperatures, and therefore a reliable dielectric is needed. The most important high temperature failures in thick film multilayers are shorting and blistering of the dielectric in between two metal layers. The basic physico-chemical processes causing these failures are unsufficiently understood. In particular, the correlation between electrical properties of the glass -ceramic material and the occurrence of these failures is not clear. The temperature region of interest in the study of these failures ranges from room temperature up to 850 ^circC, which complicates the observation of the governing material properties. While other studies concerning these phenomena often concentrate on off-line results, here the study is mainly based on in-situ observation of the high temperature electrical behaviour of the given materials. Since ionic migration is believed to occur during failure formation, electrical conductivity is an interesting property for closer observation. In order to study the required property a new measurement method has been developed, termed as the in-situ leakage current measurement technique with voltage polarity switching. With this technique it has been possible to determine the conductivity in more detail and with less error. The submission of the obtained conductivity results to an Arrhenius analysis and the identification of the charge carriers with various analytical techniques have led to improved insights concerning the occurring conduction mechanisms. Appropriate test structures have been prepared for a set of eight different dielectric materials. Some of these materials are known to have an excellent failure resistance, while other rapidly fail. The various dielectrics are presented along with their microstructural properties obtained with several analytical techniques. The available variety of dielectric materials allows a systematic study of the corresponding high temperature electrical properties and the eventual relation with their predisposition to failure formation. Also the influence of the electrode material on the electrical properties and the occurrence of failures has been investigated. In this work two other techniques, impedance spectroscopy and e.m.f.'s-measurements, have been added to the available in-situ electrical measurement techniques. The in-situ impedance spectroscopy measurements have been performed in the first place to validate the results obtained with the leakage current measurement technique, but moreover deliver information about conduction mechanisms and interface reactions. The scope of the in-situ e.m.f.-measurements has been to investigate the existence of the 'battery effect' by measuring the eventual formation of galvanic effects in mixed metallurgy multilayers as postulated by Gilles et al in 1989. Related to these measurements some new experiments will be described which have led to a dispell of the fallacies concerning the true nature of the studied failure mechanisms.

Manca, Jean Vittorio

216

Conventional knockout of Tbc1d1 in mice impairs insulin- and AICAR-stimulated glucose uptake in skeletal muscle.  

PubMed

In the obesity-resistant SJL mouse strain, we previously identified a naturally occurring loss-of-function mutation in the gene for Tbc1d1. Characterization of recombinant inbred mice that carried the Tbc1d1(SJL) allele on a C57BL/6J background indicated that loss of TBC1D1 protects from obesity, presumably by increasing the use of fat as energy source. To provide direct functional evidence for an involvement of TBC1D1 in energy substrate metabolism, we generated and characterized conventional Tbc1d1 knockout mice. TBC1D1-deficient mice showed moderately reduced body weight, decreased respiratory quotient, and an elevated resting metabolic rate. Ex vivo analysis of intact isolated skeletal muscle revealed a severe impairment in insulin- and AICAR-stimulated glucose uptake in glycolytic extensor digitorum longus muscle and a substantially increased rate of fatty acid oxidation in oxidative soleus muscle. Our results provide direct evidence that TBC1D1 plays a major role in glucose and lipid utilization, and energy substrate preference in skeletal muscle. PMID:23892475

Dokas, Janine; Chadt, Alexandra; Nolden, Tobias; Himmelbauer, Heinz; Zierath, Juleen R; Joost, Hans-Georg; Al-Hasani, Hadi

2013-07-26

217

Failure mechanisms of polycrystalline diamond compact drill bits in geothermal environments  

SciTech Connect

Over the past few years the interest in polycrystalline diamond compact (PDC) drill bits has grown proportionately with their successful use in drilling oil and gas wells in the North Sea and the United States. This keen interest led to a research program at Sandia to develop PDC drill bits suitable for the severe drilling conditions encountered in geothermal fields. Recently, three different PDC drill bits were tested using either air or mud drilling fluids: one in the laboratory with hot air, one in the Geysers field with air, and one in the Geysers field with mud. All three tests were unsuccessful due to failure of the braze joint used to attach the PDC drill blanks to the tungsten carbide studs. A post-mortem failure analysis of the defective cutters identified three major failure mechanisms: peripheral nonbonding caused by braze oxidation during the brazing step, nonbonding between PDC drill blanks and the braze due to contamination prior to brazing, and hot shortness. No evidence was found to suggest that the braze failures in the Geysers field tests were caused by frictional heating. In addition, inspection of the PDC/stud cutter assemblies using ultrasonic techniques was found to be ineffective for detecting the presence of hot shortness in the braze joint.

Hoover, E.R.; Pope, L.E.

1981-09-01

218

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

PubMed

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 procoagulant reactions, impairment of the protein C pathway, protease activated receptor (PAR) activation, adenosine-mediated thrombosis, or neurohormonal activation; stasis secondary to low cardiac output; and endothelial dysfunction from neurohormonal activation or systemic inflammation. Pathophysiologic evidence and analyses of retrospective data support the hypothesis that antithrombotic agents may improve outcomes in patients with heart failure. Warfarin has not been shown to reduce clinical events in patients with heart failure, although several of the completed randomized trials were underpowered, and the most recent was not placebo-controlled. Many unanswered questions remain that justify continued research in this area. This paper examines the conceptual framework, opportunities, and challenges of clinical investigative approaches with the newer anti-thrombotic agents in patients with heart failure. Critical questions are raised with regard to clinical trial designs that warrant consideration as the field progresses. PMID:23298559

Zannad, Faiez; Stough, Wendy Gattis; Regnault, Véronique; Gheorghiade, Mihai; Deliargyris, Efthymios; Gibson, C Michael; Agewall, Stefan; Berkowitz, Scott D; Burton, Paul; Calvo, Gonzalo; Goldstein, Sidney; Verheugt, Freek W A; Koglin, Joerg; O'Connor, Christopher M

2013-01-06

219

Failure mechanisms of 3D woven composites in tension, compression, and bending  

SciTech Connect

Observations of failure mechanisms in monotonic loading are reported for graphite/epoxy composites containing three-dimensional (3D) interlock weave reinforcement. The key phenomena are delamination and kink band formation in compression, tow rupture and pullout in tension, and combinations of these in bending. The materials exhibit great potential for damage tolerance and notch insensitivity. This is partly due to the presence of geometrical flaws that are broadly distributed in strength and space; and partly to the coarseness of the reinforcing tows, which leads to extensive debonding and reduced stress intensification around sites of failure. Rules of mixture corrected for the effects of tow irregularity suffice to estimate elastic moduli. Rough estimates of the stress at which the first failure events occur in compression or tension can be made from existing micromechanical models. Ultimate tensile failure might be modeled by regarding failed tows that are being pulled out of the composite as a cohesive zone. The characteristic length estimated for this zone, which is a direct measure of damage tolerance and notch insensitivity, has very large values of order of magnitude 0.1--0.5 m.

Cox, B.N.; Dadkhah, M.S.; Morris, W.L.; Flintoff, J.G. (Rockwell International Science Center, Thousand Oaks, CA (United States))

1994-12-01

220

Cardiac arrhythmia mechanisms in rats with heart failure induced by pulmonary hypertension.  

PubMed

Pulmonary hypertension provokes right heart failure and arrhythmias. Better understanding of the mechanisms underlying these arrhythmias is needed to facilitate new therapeutic approaches for the hypertensive, failing right ventricle (RV). The aim of our study was to identify the mechanisms generating arrhythmias in a model of RV failure induced by pulmonary hypertension. Rats were injected with monocrotaline to induce either RV hypertrophy or failure or with saline (control). ECGs were measured in conscious, unrestrained animals by telemetry. In isolated hearts, electrical activity was measured by optical mapping and myofiber orientation by diffusion tensor-MRI. Sarcoplasmic reticular Ca(2+) handling was studied in single myocytes. Compared with control animals, the T-wave of the ECG was prolonged and in three of seven heart failure animals, prominent T-wave alternans occurred. Discordant action potential (AP) alternans occurred in isolated failing hearts and Ca(2+) transient alternans in failing myocytes. In failing hearts, AP duration and dispersion were increased; conduction velocity and AP restitution were steeper. The latter was intrinsic to failing single myocytes. Failing hearts had greater fiber angle disarray; this correlated with AP duration. Failing myocytes had reduced sarco(endo)plasmic reticular Ca(2+)-ATPase activity, increased sarcoplasmic reticular Ca(2+)-release fraction, and increased Ca(2+) spark leak. In hypertrophied hearts and myocytes, dysfunctional adaptation had begun, but alternans did not develop. We conclude that increased electrical and structural heterogeneity and dysfunctional sarcoplasmic reticular Ca(2+) handling increased the probability of alternans, a proarrhythmic predictor of sudden cardiac death. These mechanisms are potential therapeutic targets for the correction of arrhythmias in hypertensive, failing RVs. PMID:22427523

Benoist, David; Stones, Rachel; Drinkhill, Mark J; Benson, Alan P; Yang, Zhaokang; Cassan, Cecile; Gilbert, Stephen H; Saint, David A; Cazorla, Olivier; Steele, Derek S; Bernus, Olivier; White, Ed

2012-03-16

221

Cardiac arrhythmia mechanisms in rats with heart failure induced by pulmonary hypertension  

PubMed Central

Pulmonary hypertension provokes right heart failure and arrhythmias. Better understanding of the mechanisms underlying these arrhythmias is needed to facilitate new therapeutic approaches for the hypertensive, failing right ventricle (RV). The aim of our study was to identify the mechanisms generating arrhythmias in a model of RV failure induced by pulmonary hypertension. Rats were injected with monocrotaline to induce either RV hypertrophy or failure or with saline (control). ECGs were measured in conscious, unrestrained animals by telemetry. In isolated hearts, electrical activity was measured by optical mapping and myofiber orientation by diffusion tensor-MRI. Sarcoplasmic reticular Ca2+ handling was studied in single myocytes. Compared with control animals, the T-wave of the ECG was prolonged and in three of seven heart failure animals, prominent T-wave alternans occurred. Discordant action potential (AP) alternans occurred in isolated failing hearts and Ca2+ transient alternans in failing myocytes. In failing hearts, AP duration and dispersion were increased; conduction velocity and AP restitution were steeper. The latter was intrinsic to failing single myocytes. Failing hearts had greater fiber angle disarray; this correlated with AP duration. Failing myocytes had reduced sarco(endo)plasmic reticular Ca2+-ATPase activity, increased sarcoplasmic reticular Ca2+-release fraction, and increased Ca2+ spark leak. In hypertrophied hearts and myocytes, dysfunctional adaptation had begun, but alternans did not develop. We conclude that increased electrical and structural heterogeneity and dysfunctional sarcoplasmic reticular Ca2+ handling increased the probability of alternans, a proarrhythmic predictor of sudden cardiac death. These mechanisms are potential therapeutic targets for the correction of arrhythmias in hypertensive, failing RVs.

Benoist, David; Stones, Rachel; Drinkhill, Mark J.; Benson, Alan P.; Yang, Zhaokang; Cassan, Cecile; Gilbert, Stephen H.; Saint, David A.; Cazorla, Olivier; Steele, Derek S.; Bernus, Olivier

2012-01-01

222

Hexagon TB for the rapid diagnosis of lung TBC in praxis.  

PubMed

Hexagon TB is intended for the rapid diagnostics of tuberculosis. Tuberculosis is a contagious and epidemic disease. According to the data published by WHO, 3-4 millions of patients are diagnosed with this disease annually. In 2004, 107 new cases were discovered in the area of Tuzla Municipality. Annual incidence of this disease is 62,9 per 100 000 inhabitants in Bosnia and Herzegovina; 28,9 in Slovenia; 33,2 in FYRM; 48,5 in Croatia; 41,8 in Serbia and Montenegro. Western European countries have a rather low rate of the disease--5-10 cases per 100 000 inhabitants. Efficiency of Hexagon TB examination method was tested on 100 patients. The subjects were patients with clinical symptoms of active TBC infection, persons who were in contact with TBC patients and persons earlier cured of TBC. All the subjects were tested with Hexagon TB, and the results were compared against lungs X-rays and sputum test for BK and LOW. Hexagon TB is intended for rapid, qualitative detection of IgG, IgA, IgM antibodies against M. tuberculosis and mycobacterium in human serum, plasma or whole blood as an aid in the early diagnostics of tuberculosis infections for professional use. Hexagon TB was positive in 11 of the examined patients. 10 patients had changes suggesting TBC. 1 patient was directly positive for BK and 3 patients were positive for LOW. Of all the examined patients, 3 were positive for all tests positive. According to our results, Hexagon TB has significant importance in practice of rapid TBC diagnostics compared to lungs X-ray and examination of sputum for BK and LOW. PMID:17848145

As?eri?, Mensura; Nadarevi?, Alma; Avdi?, Sevleta; Vrabac-Mujcinagi?, Muamera; Nuki?, Sabrija; Mujcinovi?, Zulfo

2007-08-01

223

Failure mechanisms and assembly-process-based solution of FCBGA high lead C4 bump non-wetting  

NASA Astrophysics Data System (ADS)

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 chip-attach 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.

Wenqi, Li; Yiming, Qiu; Xing, Jin; Lei, Wang; Qidi, Wu

2012-05-01

224

Presence of intervertebral discs alters observed stiffness and failure mechanisms in the vertebra.  

PubMed

Ex vivo mechanical testing is an essential tool for study of vertebral mechanics. However, the common method of testing vertebral bodies in the absence of adjacent intervertebral discs (IVDs) may limit the physiological relevance of the results. The goal of this study was to determine the influence of IVDs on vertebral mechanical properties and failure mechanisms. Rabbit thoracic vertebral bodies were tested with and without IVDs in a stepwise fashion that incorporated a micro-computed tomography scan at each loading step. The image sequences were analyzed using digital volume correlation to quantify deformations throughout the vertebral body. The observed deformation patterns differed substantially between the groups. Specimens tested with IVDs exhibited a slow increase in strain in the inferior and posterior regions, followed by a sudden increase in strain in the anterior cortex right at the yield point. In contrast, the highest strains in the isolated vertebral bodies were in the posterior regions throughout the test. Specimens tested with IVDs had lower stiffness (507.49±184.73N/mm vs. 845.61±296.09N/mm; p=0.044), higher ultimate displacement (2.00±0.68mm vs. 1.17±0.54mm; p=0.043), and higher maximum shear strains (e.g. top 25th percentile: 0.19±0.11 vs. 0.06±0.07mm/mm; p<0.0458), and tended to have lower ultimate force (690.28±160.25N vs. 873.81±131.48N; p=0.056). Similar work to failure (648.15±317.86N-mm vs. 603.49±437.95 N-mm; p=0.844) was observed between the two groups. These results indicate that testing vertebral bodies in the absence of IVDs can elicit artifactual failure mechanisms. These artifacts may be more prominent than the effects on vertebral strength and toughness. PMID:23683319

Hussein, Amira I; Mason, Zachary D; Morgan, Elise F

2013-05-14

225

Ubiquitination and Degradation of the Hominoid-Specific Oncoprotein TBC1D3 Is Mediated by CUL7 E3 Ligase  

PubMed Central

Expression of the hominoid-specific TBC1D3 oncoprotein enhances growth factor receptor signaling and subsequently promotes cellular proliferation and survival. Here we report that TBC1D3 is degraded in response to growth factor signaling, suggesting that TBC1D3 expression is regulated by a growth factor-driven negative feedback loop. To gain a better understanding of how TBC1D3 is regulated, we studied the effects of growth factor receptor signaling on TBC1D3 post-translational processing and turnover. Using a yeast two-hybrid screen, we identified CUL7, the scaffolding subunit of the CUL7 E3 ligase complex, as a TBC1D3-interacting protein. We show that CUL7 E3 ligase ubiquitinates TBC1D3 in response to serum stimulation. Moreover, TBC1D3 recruits F-box 8 (Fbw8), the substrate recognition domain of CUL7 E3 ligase, in pull-down experiments and in an in vitro assay. Importantly, alkaline phosphatase treatment of TBC1D3 suppresses its ability to recruit Fbw8, indicating that TBC1D3 phosphorylation is critical for its ubiquitination and degradation. We conclude that serum- and growth factor-stimulated TBC1D3 ubiquitination and degradation are regulated by its interaction with CUL7-Fbw8.

Kong, Chen; Samovski, Dmitri; Srikanth, Priya; Wainszelbaum, Marisa J.; Charron, Audra J.; Liu, Jialiu; Lange, Jeffrey J.; Chen, Pin-I; Pan, Zhen-Qiang; Su, Xiong; Stahl, Philip D.

2012-01-01

226

The Primate-specific Protein TBC1D3 Is Required for Optimal Macropinocytosis in a Novel ARF6-dependent Pathway  

PubMed Central

The generation of novel genes and proteins throughout evolution has been proposed to occur as a result of whole genome and gene duplications, exon shuffling, and retrotransposition events. The analysis of such genes might thus shed light into the functional complexity associated with highly evolved species. One such case is represented by TBC1D3, a primate-specific gene, harboring a TBC domain. Because TBC domains encode Rab-specific GAP activities, TBC-containing proteins are predicted to play a major role in endocytosis and intracellular traffic. Here, we show that the TBC1D3 gene originated late in evolution, likely through a duplication of the RNTRE locus, and underwent gene amplification during primate speciation. Despite possessing a TBC domain, TBC1D3 is apparently devoid of Rab-GAP activity. However, TBC1D3 regulates the optimal rate of epidermal growth factor–mediated macropinocytosis by participating in a novel pathway involving ARF6 and RAB5. In addition, TBC1D3 binds and colocalize to GGA3, an ARF6-effector, in an ARF6-dependent manner, and synergize with it in promoting macropinocytosis, suggesting that the two proteins act together in this process. Accordingly, GGA3 siRNA-mediated ablation impaired TBC1D3-induced macropinocytosis. We thus uncover a novel signaling pathway that appeared after primate speciation. Within this pathway, a TBC1D3:GGA3 complex contributes to optimal propagation of signals, ultimately facilitating the macropinocytic process.

Frittoli, Emanuela; Palamidessi, Andrea; Pizzigoni, Alessandro; Lanzetti, Letizia; Garre, Massimiliano; Troglio, Flavia; Troilo, Albino; Fukuda, Mitsunori; Di Fiore, Pier Paolo

2008-01-01

227

Service failure of hot-stage turbine blades: The role and mechanisms of oxidation ratcheting  

SciTech Connect

Surface-connected porosity in current military aircraft hot-stage turbine engine blades is associated with blade failure. Oxidation ratcheting is suggested as the failure mechanism. Statistical comparison of new and used blade populations showed that for blades cast with an equiaxed structure, the porosity in new blades was associated with crack formation on the concave surface of the used blades. The pores did not tend to develop into cracks on the compressed (convex) surface of the blade. Insufficient suitable data on directionally solidified blades prevented similar statistical correlations. However, metallography of the directionally solidified blades showed that the in-service cracks were related to oxidation inside surface-connected pores and that the cracks were oriented in the same direction as the (axial) casting pores. Thus, the proposed failure mechanism through ratcheting is based on the following insights: (1) the blades are thermally cycled as a normal part of service; (2) the hot blades expand and the open pores are filled with oxide; (3) when the blade is cooled, thermal contraction of the metal is greater than the oxide, causing compressive stress and yield-, and (4) thermal expansion of the blades opens the pores again, since yield relaxed compressive stress at low temperature. These insights were supported by metallographic and computer-simulation studies which showed that the pores grow 20 to 50 pct in width per 100 missions (about 90 hours of operation) for a military aircraft on a typical mission profile.

Oldfield, W.; Oldfield, F.M. (MRCS Corp., St. Augustine, FL (United States))

1993-10-01

228

Investigation of moisture-induced delamination failure in a semiconductor package via multi-scale mechanics  

NASA Astrophysics Data System (ADS)

In this work, moisture-induced interfacial delamination in a semiconductor package was investigated by experiment and multi-scale numerical analysis. The interfacial adhesion strength between a silicon wafer and an epoxy adhesive layer was characterized by a die-shear test with respect to moisture concentration and temperature. Molecular dynamics simulation was performed to study the effect of moisture and temperature on the interfacial adhesion energy and strength at the Si/epoxy adhesive interface. Based on the molecular dynamics predicted interfacial adhesion strength, a numerical stress analysis was performed considering hygro-swelling stress and the thermo-mechanical stress during a solder reflow process to predict the moisture-induced delamination failure of the semiconductor package. The multi-scale simulation result was compared with the actual reliability test result. From this study, it was concluded that the proposed multi-scale simulation technique can be used successfully for the prediction of moisture-induced package failure.

Kim, Hak-Sung; Huh, Jeehyang; Ryu, Jongeun

2011-01-01

229

Early Use of Noninvasive Mechanical Ventilation in Patients with Acute Hypercapnic Respiratory Failure in a Respiratory Ward: A Prospective Study  

Microsoft Academic Search

BackgroundIn recent years, the optimal location for noninvasive mechanical ventilation (NIMV) has been a matter of debate. Our aim was to detect the effectiveness of NIMV in acute hypercapnic respiratory failure (AHRF) in respiratory ward and factors associated with failure.

Aydin Ciledag; Akin Kaya; Buket Basa Akdogan; Pinar Akin Kabalak; Zeynep P. Onen; Elif Seny Banu Gulbay

2010-01-01

230

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

Microsoft Academic Search

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

Jorge Antonio Penso Mula

2001-01-01

231

A mechanism based modeling approach to failure in fiber reinforced composites  

NASA Astrophysics Data System (ADS)

The increasing use of fiber reinforced polymer composites (FRPC) in civil and military applications has made it imperative that the behavior of FRPC be understood under a variety of loading conditions. It is known that the compressive load carrying capacity of FRPC is low compared to its tensile load carrying capacity. Thus, the compressive behavior of FRPC has been a limiting factor in the design of FRPC structures. In the current work, the compressive behavior of FRPC has been studied with an aim to identify and understand the important parameters affecting the compressive strength and failure mechanisms in FRPC, particularly under combined stress states. The purpose is to establish compressive strength degradation (or enhancement) in the presence of combined stress states. Results from experiments have led to the development of a mechanism based failure model, based on the principles of fracture mechanics for the splitting failure of FRPC. A mechanics model has been developed for both pure compression and combined compression-torsion loading. The predictions of the model were found to compare favorably with experimental data obtained from glass and carbon FRPC under pure compression and combined compression-torsion loading. A 3D finite element simulation of a representative cylindrical section of the composite was performed. The results indicated the importance of fiber diameter on the predicted compressive response of the composite. It also indicated the possibilities of fiber breakage under axial loading as a cause for the initiation of kinking in case of small diameter fiber reinforced composites. Pure compression tests were also conducted on hybrid (glass/carbon) composites under static and dynamic loading conditions. The static compressive strength of hybrid composites shows a non-monotonic behavior with respect to the hybrid ratio. The compressive strength first decreases and then increases as we approach either pure carbon or pure glass composites. The hybrid composites tested show an increase in strength with strain rate at all hybrid ratios. Based on the above experiments/analysis a non-dimensional number has been derived to a priori identify the composite failure mechanism, and thus aid the accurate prediction of composite compressive strength.

Yerramalli, Chandra Sekher

232

Memory Failure Has Different Mechanisms in Subcortical Stroke and Alzheimer's Disease  

PubMed Central

Patients with extensive subcortical cerebrovascular disease may have impaired memory, often despite the absence of medial temporal or diencephalic strokes. In this group, episodic memory failure may arise from frontal lobe dysfunction based on disruption of frontosubcortical loops caused by lacunae. We tested this idea by studying cognitively impaired subcortical stroke (CIS) patients and Alzheimer’s disease (AD) patients with [18F]-fluorodeoxyglucose positron emission tomography using a continuous verbal memory task during the period of tracer uptake. Patients were matched on severity of cognitive impairment and overall memory task performance. As hypothesized, we found a double dissociation in the relations between metabolism and memory in these groups, such that memory in CIS (but not in AD) correlates with prefrontal lobe metabolism, whereas in AD (but not in CIS), memory correlates with left hippocampal and temporal lobe metabolism. Analysis of memory subscores showed that CIS patients made more errors on short-delay trials, which is consistent with working memory failure. It seems that different pathogenic mechanisms underlie episodic memory failure in subcortical cerebrovascular disease and AD.

Reed, B. R.; Eberling, J. L.; Mungas, D.; Weiner, M. W.; Jagust, W. J.

2007-01-01

233

Failure mechanisms of lead-free chip scale package interconnections under fast mechanical loading  

Microsoft Academic Search

The reliability of chip scale package (CSP) components against mechanical shocks has been studied by employing statistical,\\u000a fractographic, and microstructural research methods. The components having high tin (Sn0.2Ag0.4Cu) solder bumps were reflow\\u000a soldered with the Sn3.8Ag0.7Cu (wt.%) solder paste on Ni(P)|Au- and organic solderability preservative (OSP)-coated multilayer\\u000a printed wiring boards (PWBs), and the assemblies were subjected to the standard drop

T. T. Mattila; J. K. Kivilahti

2005-01-01

234

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

SciTech Connect

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.

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

2008-10-24

235

Manipulating failure mechanism of rapid prototyped scaffolds by changing nodal connectivity and geometry of the pores.  

PubMed

The performance of cellular solids in biomedical applications relies strongly on a detailed understanding of the effects of pore topology on mechanical properties. This study aims at characterizing the failure mechanism of scaffolds based on nodal connectivity (number of struts that meet in joints) and geometry of the pores. Plastic models of scaffolds having the same relative density but different cubic and trigonal unit cells were designed and then fabricated via three dimensional (3-D) printing. Unit cells were repeated in different arrangements in 3-D space. An in-situ imaging technique was utilized to study the progressive deformation of the scaffold models. Different nodal connectivities resulted in a wide range of compressive behaviors in scaffold models, from elastic-plastic to fully brittle. The Maxwell necessary criterion for rigidity was used to explain mechanical behavior of the scaffolds. Nodal connectivity of 4 satisfied Maxwell's criterion for rigidity in the examined structures. In a stress-strain curve of scaffolds with cubic unit cells and nodal connectivities of 3 and 4, pore deformation was observed after yielding. On the other hand, scaffolds with trigonal unit cells and nodal connectivities of 4 and 6, exhibited brittle behavior in the absence of pore deformation. These results highlight the role of nodal connectivity on failure mechanism and subsequently mechanical performance of scaffolds. This study reveals that appropriate pore geometry can provide sufficient condition for rigidity when Maxwell's necessary condition is satisfied. In addition, this study demonstrates that Maxwell's criterion can be used in pre-designing of pore geometries for scaffolds with distinct nodal connectivities. PMID:22985476

Amirkhani, Soodeh; Bagheri, Reza; Zehtab Yazdi, Alireza

2012-09-15

236

Evaluation of the Rapid MGIT TBc Identification Test for Culture Confirmation of Mycobacterium tuberculosis Complex Strain Detection?  

PubMed Central

A culture confirmation test for the detection of Mycobacterium tuberculosis complex strains that uses a lateral-flow immunochromatographic assay to detect the MPB64 antigen, the MGIT TBc identification (TBc ID) test, has been developed. We evaluated the performance of the TBc ID test in the detection of the M. tuberculosis complex in 222 primary-positive liquid cultures. We compared these results to those of nucleic acid-based identification and conventional biochemical tests. The validity of the TBc ID test was determined, and all of the nontuberculous mycobacteria (NTM) and Nocardia species tested were found to be negative. The detection limit of the TBc ID test was 5 × 105 CFU/ml, and for IS6110 real-time PCR it was 5 CFU/ml. All of the M. tuberculosis and M. africanum cultures were found to be positive, while M. bovis and M. bovis BCG cultures were negative. With the exception of 1 contaminated culture, the 221 culture-positive isolates contained 171 (77.5%) M. tuberculosis isolates, 39 (17.6%) NTM species, and 11 (5.0%) unidentified species. Two culture-positive isolates harbored a 63-bp deletion at position 196 of the mpb64 gene. The sensitivity, specificity, positive predictive values, and negative predictive values of the TBc ID test were 98.8, 100, 100, and 95.1%, respectively. Furthermore, the approximate turnaround time for real-time PCR was 4 h (including buffer and sample preparation), while for the TBc ID test it was less than 1 h. We suggest an algorithm for the primary identification of M. tuberculosis in liquid culture using the TBc ID test as an alternative to conventional subculture followed by identification using biochemical methods.

Yu, Ming-Chih; Chen, Huang-Yao; Wu, Mei-Hua; Huang, Wei-Lun; Kuo, Yuh-Min; Yu, Fang-Lan; Jou, Ruwen

2011-01-01

237

DEFORMATION AND FRACTURE OF POORLY CONSOLIDATED MEDIA - Borehole Failure Mechanisms in High-Porosity Sandstone  

SciTech Connect

We investigated failure mechanisms around boreholes and the formation of borehole breakouts in high-porosity sandstone, with particular interest to grain-scale micromechanics of failure leading to the hitherto unrecognized fracture-like borehole breakouts and apparent compaction band formation in poorly consolidated granular materials. We also looked at a variety of drilling-related factors that contribute to the type, size and shape of borehole breakouts. The objective was to assess their effect on the ability to establish correlations between breakout geometry and in situ stress magnitudes, as well as on borehole stability prediction, and hydrocarbon/water extraction in general. We identified two classes of medium to high porosity (12-30%) sandstones, arkosic, consisting of 50-70% quartz and 15 to 50% feldspar, and quartz-rich sandstones, in which quartz grain contents varied from 90 to 100%. In arkose sandstones critical far-field stress magnitudes induced compressive failure around boreholes in the form of V-shaped (dog-eared) breakouts, the result of dilatant intra-and trans-granular microcracking subparallel to both the maximum horizontal far-field stress and to the borehole wall. On the other hand, boreholes in quartz-rich sandstones failed by developing fracture-like breakouts. These are long and very narrow (several grain diameters) tabular failure zones perpendicular to the maximum stress. Evidence provided mainly by SEM observations suggests a failure process initiated by localized grain-bond loosening along the least horizontal far-field stress springline, the packing of these grains into a lower porosity compaction band resembling those discovered in Navajo and Aztec sandstones, and the emptying of the loosened grains by the circulating drilling fluid starting from the borehole wall. Although the immediate several grain layers at the breakout tip often contain some cracked or even crushed grains, the failure mechanism enabled by the formation of the compaction band is largely non-dilatant, a major departure from the dilatant mechanism observed in Tablerock sandstone. The experimental results suggest that unlike our previous assertion, the strength of grain bonding and the mineral composition, rather than the porosity, are major factors in the formation of compaction bands and the ensuing fracture-like breakouts. Some breakout dimensions in all rocks were correlatable to the far-field principal stresses, and could potentially be used (in conjunction with other information) as indicators of their magnitudes. However, we found that several factors can significantly influence breakout geometry. Larger boreholes and increased drilling-fluid flow rates produce longer fracture-like breakouts, suggesting that breakouts in field-scale wellbores could reach considerable lengths. On the other hand, increased drilling-fluid weight and increased drill-bit penetration rate resulted in a decrease in breakout length. These results indicate that breakout growth can be controlled to some degree by manipulating drilling variables. Realizing how drilling variables impact borehole breakout formation is important in understanding the process by which breakouts form and their potential use as indicators of the far-field in situ stress magnitudes and as sources of sand production. As our research indicates, the final breakout size and mechanism of formation can be a function of several variables and conditions, meaning there is still much to be understood about this phenomenon.

Bezalel c. Haimson

2005-06-10

238

Accurate in vitro identification of fracture onset in bones: failure mechanism of the proximal human femur.  

PubMed

Bone fractures have extensively been investigated, especially for the proximal femur. While failure load can easily be recorded, and the fracture surface is readily accessible, identification of the point of fracture initiation is difficult. Accurate location of fracture initiation is extremely important to understand the multi-scale determinants of bone fracture. In this study, a recently developed technique based on electro-conductive lines was applied to the proximal femoral metaphysis to elucidate the fracture mechanism. Eight cadaveric femurs were prepared with 15-20 electro-conductive lines (crack-grid) covering the proximal region. The crack-grid was connected to a dedicated data-logger that monitored electrical continuity of each line at 700 kHz. High-speed videos (12,000 frames/s, 0.1-0.2 mm pixel size) of the destructive tests were acquired. Most crack-grid-lines failed in a time-span of 0.08-0.50 ms, which was comparable to that identified in the high-speed videos, and consistent with previous video recordings. However, on all specimens 1-3 crack-grid-lines failed significantly earlier (2-200 ms) than the majority of the crack-grid-lines. The first crack-grid-line to fail was always the closest one to the point of fracture initiation identified in the high-speed videos (superior-lateral neck region). Then the crack propagated simultaneously, at comparable velocity on the anterior and posterior sides of the neck. Such a failure pattern has never been observed before, as spatial resolution of the high-speed videos prevented from observing the initial opening of a crack. This mechanism (fracture onset, time-lag, followed by catastrophic failure) can be explained with a transfer of load to the internal trabecular structure caused by the initial fracture of the thin cortical shell. This study proves the suitability of the crack-grid method to investigate bone fractures associated to tensile stress. The crack-grid method enables significantly faster sampling than high-speed cameras. The present findings elucidate some aspects of the failure mechanism of the proximal human femoral metaphysis. PMID:23218142

Juszczyk, Mateusz Maria; Cristofolini, Luca; Salvà, Marco; Zani, Lorenzo; Schileo, Enrico; Viceconti, Marco

2012-12-04

239

Epidemiology of noninvasive mechanical ventilation in acute respiratory failure - a retrospective population-based study  

PubMed Central

Background Noninvasive mechanical ventilation (NIV) is a front-line therapy for the management of acute respiratory failure (ARF) in the intensive care units. However, the data on factors and outcomes associated with the use of NIV in ARF patients is lacking. Therefore, we aimed to determine the utilization of NIV for ARF in a population-based study. Methods We conducted a populated-based retrospective cohort study, where in all consecutively admitted adults (?18?years) with ARF from Olmsted County, Rochester, MN, at the Mayo Clinic medical and surgical ICUs, during 2006 were included. Patients without research authorization or on chronic NIV use for sleep apnea were excluded. Results Out of 1461 Olmsted County adult residents admitted to the ICUs in 2006, 364 patients developed ARF, of which 146 patients were initiated on NIV. The median age in years was 75 (interquartile range, 60–84), 48% females and 88.7% Caucasians. Eighteen patients (12%) were on Continuous Positive Airway Pressure (CPAP) mode and 128 (88%) were on noninvasive intermittent positive-pressure ventilation (NIPPV) mode. Forty-six (10%) ARF patients were put on NIV for palliative strategy to alleviate dyspnea. Seventy-six ARF patients without treatment limitation were given a trial of NIV and 49 patients succeeded, while 27 had to be intubated. Mortality was similar between the patients initially supported with NIV versus invasive mechanical ventilation (33% vs 22%, P=0.289). In the multivariate analysis, the development of acute respiratory distress syndrome (ARDS) and higher APACHE III scores were associated with the failure of initial NIV treatment. Conclusions Our results have important implications for a future planning of NIV in a suburban US community with high access to critical care services. The higher APACHE III scores and the development of ARDS are associated with the failure of initial NIV treatment.

2013-01-01

240

To Err is Human Case Reports of Two Military Aircraft Accidents: Possible mechanisms of human failure.  

PubMed

It has been postulated that pilot error or in-flight incapacitation may be the main contributory factors to 70-80% of aircraft accidents. Two fatal aircraft accidents are presented in which either of the above possibilities may have played a role. The first case report describes an erroneous decision by a fighter pilot to use a seat position adjustment of the ejection seat leading to fatal injuries when he had to eject from his aircraft. Injuries to the body of the pilot, and observations on the state of his flying clothing and the ejection seat were used to postulate the mechanism of fatal injury and establish the cause of the accident. The second case report describes the sequence of events which culminated in the incapacitation of a fighter pilot while executing a routine manouevre. This resulted in a fatal air crash. Possible contributions of environmental factors which may have resulted in failure of his physiological mechanisms are discussed. PMID:21509093

Dikshit, Mohan B

2010-04-17

241

Gorham syndrome with postoperative respiratory failure and requiring prolonged mechanical ventilation.  

PubMed

Gorham syndrome is a rare disease that presents as progressive osteolysis, and may affect any part of the skeleton. The pathologic process involves the replacement of normal bone by aggressively expanding but non-neoplastic vascular tissue, resulting in massive osteolysis of the adjacent bone. If the spine and ribs are affected, the subsequent kyphosis and chest wall deformity may cause severe restrictive ventilatory impairment. We report a 34-year-old male with Gorham syndrome presenting as progressive kyphosis, severe back pain, unstable gait, and exertional dyspnea. Pulmonary function testing revealed severe restrictive ventilatory impairment. He underwent spinal surgery but could not be extubated after surgery. Postoperative left lower lung pneumonia and respiratory failure required prolonged mechanical ventilation. After a weaning program of pressure support ventilation and T-piece spontaneous breathing trials, he was successfully weaned from mechanical ventilation. PMID:23550170

Huang, Shiang-Yu; Lee, Ying-Min; Tzeng, Shiau-Tzu; Su, Chiu-Ping; Huang, Shiu-Feng; Wu, Yao-Kuang; Lan, Chou-Chin

2013-04-02

242

Mechanisms of Disease: detrimental adrenergic signaling in acute decompensated heart failure  

PubMed Central

SUMMARY Acute decompensated heart failure (ADHF) is responsible for more than 1 million hospital admissions each year in the US. Clinicians and scientists have developed therapeutic strategies that reduce mortality in patients with chronic heart failure (HF). Despite the widely appreciated magnitude of the ADHF problem, there is still a critical gap in our understanding of the cellular mechanisms involved and effective treatment strategies for hospitalized patients. Irrespective of the etiology, patients with ADHF present with similar symptoms (e.g. edema, altered hemodynamics and congestion) as multiple signaling pathways converge in a common phenotypic presentation. Investigations have shown that patients with ADHF have increased catecholamine levels, which cause chronic stimulation of ?-adrenergic receptors. This overstimulation leads to chronic G-protein activation and perturbations in myocyte signaling, as the patient’s heart attempts to adapt to progressive HF. Over time, these compensatory signaling mechanisms ultimately fail, and maladaptive signaling prevails with progressive worsening of symptoms. This Review summarizes some of the changes that occur during chronic adrenergic stimulation, and examines how downstream contractile dysfunction and myocyte death can alter the prognosis of patients with HF hospitalized for acute events.

Feldman, David S; Elton, Terry S; Sun, Benjamin; Martin, Mickey M; Ziolo, Mark T

2008-01-01

243

Mechanical Circulatory Support for End-Stage Heart Failure in Repaired and Palliated Congenital Heart Disease  

PubMed Central

Approximately one in one hundred children is born with congenital heart disease. Most can be managed with corrective or palliative surgery but a small group will develop severe heart failure, leaving cardiac transplantation as the ultimate treatment option. Unfortunately, due to the inadequate number of available donor organs, only a small number of patients can benefit from this therapy, and mortality remains high for pediatric patients awaiting heart transplantation, especially compared to adults. The purpose of this review is to describe the potential role of mechanical circulatory support in this context and to review current experience. For patients with congenital heart disease, ventricular assist devices are most commonly used as a bridge to cardiac transplantation, an application which has been shown to have several important advantages over medical therapy alone or support with extracorporeal membrane oxygenation, including improved survival to transplant, less exposure to blood products with less immune sensitization, and improved organ function. While these devices may improve wait list mortality, the chronic shortage of donor organs for children is likely to remain a problem into the foreseeable future. Therefore, there is great interest in the development of mechanical ventricular assist devices as potential destination therapy for congenital heart disease patients with end-stage heart failure. This review first discusses the experience with the currently available ventricular assist devices in children with congenital heart disease, and then follows to discuss what devices are under development and may reach the bedside soon.

Clark, Joseph B; Pauliks, Linda B; Myers, John L; Undar, Akif

2011-01-01

244

Characterization of rupture and fatigue resistance of TBC superalloy for combustion liners  

Microsoft Academic Search

High-temperature, high-cycle fatigue and accelerated creep properties of thermal barrier coated (TBC) Superni C263 alloy used as a candidate material in combustor liners of aero engines are highlighted in this paper. An acoustic emission technique has been utilised to detect the ductile–brittle transition temperature of the bond coat. Results revealed that the ductile-to-brittle transition temperature (DBTT) of this bond coat

A. K. Ray; D. K. Das; B. Venkataraman; P. K. Roy; B. Goswami; N. Roy; S. K. Das; N. Parida; S. Tarafder; S. Chaudhuri; S. K. Sahay; R. N. Ghosh

2005-01-01

245

Microstructural characteristics and technological properties of YSZ-type powders designed for thermal spraying of TBC  

Microsoft Academic Search

This paper presents the experimental results relating to the microstructural characteristics and selected technological properties of yttria and partially stabilized zirconia (YSZ)-type powders designed for spraying thermal barrier coating (TBC) layers with the atmospheric plasma spraying (APS) method. Three types of powders with the following chemical compositions - ZrO2 × 8Y2O3, ZrO2 × 20Y2O3, and \\

G. Moskal

2010-01-01

246

Failure characteristics during cyclic oxidation of yttria stabilized zirconia thermal barrier coatings deposited via electron beam physical vapor deposition on platinum aluminide and on NiCoCrAlY bond coats with processing modifications for improved performances  

Microsoft Academic Search

In this study, the cyclic oxidation lives of the current state-of-the-art thermal barrier coating (TBC) systems (heavy grit-blasted\\u000a Pt aluminide and NiCoCrAlY bond coats with EBPVD TBCs) were investigated first, followed by TBC systems that were modified\\u000a based on the results obtained on the failure of the state-of-the-art TBC systems. The specimens were subjected to cyclic oxidation\\u000a testing, mostly at

N. M. Yanar; F. S. Pettit; G. H. Meier

2006-01-01

247

How mechanical circulatory support helps not to need it--new strategies in pediatric heart failure.  

PubMed

During the past 3 years, seven potential candidates for mechanical circulatory support (MCS) were treated at our center. Ultimately, only one of them needed MCS (extracorporeal membrane oxygenation [ECMO] for 16 days), although 5 years earlier, all would have been considered for MCS at our center. Seven consecutive patients were seen in this period: four toddlers (three suffering from fulminant myocarditis and one with dilated cardiomyopathy associated with spongy myocardium) and three adolescents (two with postmyocarditis cardiomyopathy and one with hypertrophic cardiomyopathy and severe restrictive dysfunction after an ischemic event with cardiopulmonary resuscitation [stunned heart]). All patients presented in acute cardiocirculatory decompensation. All were admitted to the intensive care unit (ICU); all but one were sedated and intubated. A combination of levosimendan, milrinone, and nesiritide was administered to all patients. Use of catecholamines was kept short (<48 h in six individuals). MCS (ECMO, Berlin Heart Excor Pediatric, and Heartware) was always available. MCS initiation was indicated in only one patient, who was developing progressive multiorgan failure (MOF). The three toddlers with myocarditis recovered with complete normalization of myocardial function within 6 months. The fourth toddler is still at the ICU while waiting for transplantation. The three adolescents were listed with high urgency for heart transplantation, and all received a graft within 3 weeks. The adolescent with the stunned heart developed progressive MOF and was successfully supported with ECMO until transplantation. All six patients with completed course were discharged home in New York Heart Association Heart Failure Functional Classification System I condition without neurological deficits. Combined use of levosimendan, milrinone, and nesiritide, avoidance of catecholamines as much as possible, and MCS as backup are the new strategies at our center. This cardioprotective approach gives excellent outcome at lower risk and better cost-effectiveness in our pediatric patients with acute heart failure. Pediatric trials are recommended to evaluate combined use of newer cardioprotective drugs. PMID:21954874

Schweigmann, Ulrich; Velik-Salchner, Corinna; Kilo, Juliane; Schermer, Elisabeth

2011-09-29

248

Effects of mechanical insufflation-exsufflation in preventing respiratory failure after extubation: a randomized controlled trial  

PubMed Central

Introduction Weaning protocols that include noninvasive ventilation (NIV) decrease re-intubation rates and ICU length of stay. However, impaired airway clearance is associated with NIV failure. Mechanical insufflation-exsufflation (MI-E) has been proven to be very effective in patients receiving NIV. We aimed to assess the efficacy of MI-E as part of an extubation protocol. Method Patients with mechanical ventilation (MV) for more than 48 hours with specific inclusion criteria, who successfully tolerated a spontaneous breathing trial (SBT), were randomly allocated before extubation, either for (A) a conventional extubation protocol (control group), or (B) the MI-E extubation protocol (study group). During the postextubation period (48 hours), group A patients received standard medical treatment (SMT), including NIV in case of specific indications, whereas group B received the same postextubation approach plus three daily sessions of mechanical in-exsufflation (MI-E). Reintubation rates, ICU length of stay, and NIV failure rates were analyzed. Results Seventy-five patients (26 women) with a mean age of 61.8 ± 17.3 years were randomized to a control group (n = 40; mean SAPS II, 47.8 ± 17.7) and to a study group (n = 35; mean SAPS II, 45.0 ± 15.0). MV time before enrollment was 9.4 ± 4.8 and 10.5 ± 4.1 days for the control and the study group, respectively. In the 48 hours after extubation, 20 control patients (50%) and 14 study patients (40%) used NIV. Study group patients had a significant lower reintubation rate than did controls; six patients (17%) versus 19 patients (48%), P < 0.05; respectively, and a significantly lower time under MV; 17.8 ± 6.4 versus 11.7 ± 3.5 days; P < 0.05; respectively. Considering only the subgroup of patients that used NIV, the reintubation rates related to NIV failure were significantly lower in the study group when compared with controls; two patients (6%) versus 13 (33%); P < 0.05, respectively. Mean ICU length of stay after extubation was significantly lower in the study group when compared with controls (3.1 ± 2.5 versus 9.8 ± 6.7 days; P < 0.05). No differences were found in the total ICU length of stay. Conclusion Inclusion of MI-E may reduce reintubation rates with consequent reduction in postextubation ICU length of stay. This technique seems to be efficient in improving the efficacy of NIV in this patient population.

2012-01-01

249

Compariso of two different modes for noninvasive mechanical ventilation in chronic respiratory failure: volume versus pressure controlled device  

Microsoft Academic Search

Comparison of two different modes for noninvasive mechanical ventilation in chronic respiratory failure: volume versus pressure controlled device. B. Schönhofer, M. Sonneborn, P. Haidl, H. Böhrer, D. Köhler. ©ERS Journals Ltd 1997. ABSTRACT: The most commonly used mode of noninvasive mechanical ventila- tion (NMV) is volume-controlled intermittent positive pressure ventilation (IPPV). Pressure support ventilation has recently become increasingly popular, but

B. Schönhofer; M. Sonneborn; P. Haidl; H. Böhrer; D. Köhler

1997-01-01

250

Wear and failure mechanisms of multilayered PVD TiN\\/TaN coated tools when milling austenitic stainless steel  

Microsoft Academic Search

As compared to today's single layered coatings, multilayered PVD coatings offer improved mechanical and tribological properties. This work reports on milling austenitic stainless steel with cemented carbide tools coated with multilayered coatings. The purpose was to increase the understanding of wear and failure mechanisms during milling of austenitic stainless steel. Multilayered PVD TiN\\/TaN coatings deposited on cemented carbide substrates are

M Nordin; R Sundström; T. I Selinder; S Hogmark

2000-01-01

251

Evaluation of the Bactec MGIT 960 System in Combination with the MGIT TBc Identification Test for Detection of Mycobacterium tuberculosis Complex in Respiratory Specimens?  

PubMed Central

The sensitivity and specificity of the MGIT TBc identification (TBc ID) test for Mycobacterium tuberculosis complex (MTC) detection in positive Bactec MGIT cultures were 95.2% and 99.2%, respectively. When MTC-positive results obtained from two additional molecular methods were included, the sensitivity of the MGIT TBc ID test was 85.4%, while that of culture was 95.7%.

Lu, Po-Liang; Yang, Yuan-Chieh; Huang, Su Chiao; Jenh, Yi-Shan; Lin, Yao-Cheng; Huang, Hsin-Hui; Chang, Tsung Chain

2011-01-01

252

Mechanics-based statistics of failure risk of quasibrittle structures and size effect on safety factors.  

PubMed

In mechanical design as well as protection from various natural hazards, one must ensure an extremely low failure probability such as 10(-6). How to achieve that goal is adequately understood only for the limiting cases of brittle or ductile structures. Here we present a theory to do that for the transitional class of quasibrittle structures, having brittle constituents and characterized by nonnegligible size of material inhomogeneities. We show that the probability distribution of strength of the representative volume element of material is governed by the Maxwell-Boltzmann distribution of atomic energies and the stress dependence of activation energy barriers; that it is statistically modeled by a hierarchy of series and parallel couplings; and that it consists of a broad Gaussian core having a grafted far-left power-law tail with zero threshold and amplitude depending on temperature and load duration. With increasing structure size, the Gaussian core shrinks and Weibull tail expands according to the weakest-link model for a finite chain of representative volume elements. The model captures experimentally observed deviations of the strength distribution from Weibull distribution and of the mean strength scaling law from a power law. These deviations can be exploited for verification and calibration. The proposed theory will increase the safety of concrete structures, composite parts of aircraft or ships, microelectronic components, microelectromechanical systems, prosthetic devices, etc. It also will improve protection against hazards such as landslides, avalanches, ice breaks, and rock or soil failures. PMID:16769888

Bazant, Zden?k P; Pang, Sze-Dai

2006-06-12

253

[Mechanisms of development of secondary axonal failure in diffuse and local demyelinating neuropathies].  

PubMed

To estimate a qualitative and quantitative effects of axonal failure on the clinical and electromyographic (EMG) picture of diffuse and local demyelination, 24 patients with Guillain-Barre syndrome (GBS), 144 with chronic inflammatory demyelinating polyneuropathy (CIDP) and 27 patients with multifocal motor neuropathy (MMN) have been studied. All the patients underwent a complex clinical neurological and EMG examination. Along with significant association between muscular hypotrophies and weakness in the majority of patients (tau=0,51; p<0,001), in some cases weakness in extremities was found in the absence of amyotrophic syndrome specifying a "functional" axonopathy due to the disturbance of ionic transport and the blockade of potassium channels. The formation of persisting conduction block in 100% of MMN cases and in up to 75% of GBS and CIDP cases revealed the additional special mechanism of axonopathy. The primary autoimmune affection of axonal membrane in a case of acute motor axonal neuropathy is described. The data obtained suggest that secondary axonal pathology underlies formation of the pathological system manifesting with failure of neurotrophic influence of the affected axons in relation to muscles and leading to neurological plastic deficiency at a level of self-supporting dysregulation pathology. PMID:17310795

Merkulov, Iu A; Kryzhanovski?, G N; Zavalishin, I A; Merkulova, D M

2007-01-01

254

Evaluation of TBc Identification Immunochromatographic Assay for Rapid Identification of Mycobacterium tuberculosis Complex in Samples from Broth Cultures?  

PubMed Central

Tuberculosis (TB) is a disease of major public health concern worldwide, especially in developing countries. In addition, the human immunodeficiency virus (HIV) epidemic has increased the incidence of infection with nontuberculous mycobacteria (NTM). Rapid, accurate, and simple methods for differentiation of Mycobacterium tuberculosis complex (MTBC) isolates from NTM is greatly needed for successful control of the TB epidemic. This study was done to evaluate the clinical performance of the BD MGIT TBc identification test (TBc ID) for rapid identification of MTBC in samples from broth cultures. A total of 229 Ziehl-Neelsen (ZN) stain-positive MGIT cultures were tested using the TBc ID test, and the results were compared with those of the AccuProbe MTBC identification test (GenProbe, San Diego, CA). The agreement between the TBc ID test and the AccuProbe assay was 96% (kappa = 0.92; confidence interval [CI] = 0.869 to 0.971). The sensitivity, specificity, and negative and positive predictive values of the TBc ID test compared to the AccuProbe assay were 100%, 92.4%, 100%, and 92.2%, respectively. After additional molecular testing, the agreement between the two methods increased to 97.8% (kappa = 0.96; CI = 0.917 to 0.994), and the specificity and positive predictive value increased to 95.6% and 95.7%, respectively. The TBc ID test is a simple, sensitive, and specific test for identification of MTBC in samples from acid-fast bacillus (AFB) smear-positive cultures. The TBc ID test could be a good alternative to the AccuProbe test in TB diagnostic laboratories.

Said, Halima M.; Ismail, Nazir; Osman, Ayman; Velsman, Chrisna; Hoosen, A. A.

2011-01-01

255

Expanding cardiac resynchronization for systolic heart failure to patients with mechanical dyssynchrony and atrial fibrillation.  

PubMed

Despite progress in the management of heart failure (HF) using pharmacotherapy, the mortality and morbidity associated with this condition remain unacceptably high. Cardiac resynchronization therapy (CRT), a left-sided pacing therapy for drug-refractory and highly symptomatic HF patients with ventricular conduction delay, has been shown to improve left ventricular (LV) systolic function, myocardial oxygen consumption, and New York Heart Association functional class and to inhibit or reverse LV chamber dilation and remodeling. Atrial fibrillation is common in patients with HF and is associated with significant worsening of HF and myocardial function. Only recently have trials been designed to specifically study CRT in patients with HF and chronic atrial fibrillation. These studies have shown that CRT with biventricular or univentricular LV pacing in patients with atrial fibrillation corrects mechanical dyssynchrony and results in significant and sustained improvement in functional capacity, LV ejection fraction, quality of life, and QRS duration. PMID:16195687

Ghanbari, Hamid; Hassunizadeh, Bischan; Machado, Christian

2005-01-01

256

Mechanisms of non-apoptotic programmed cell death in diabetes and heart failure  

PubMed Central

Programmed cell elimination is an important pathological mediator of disease. Multiple pathways to programmed cell death have been delineated, including apoptosis, autophagy and programmed necrosis. Cross-talk between the signaling pathways mediating each process has made it difficult to define specific mechanisms of in vivo programmed cell death. For this reason, many “apoptotic” diseases may involve other death signaling pathways. Recent advances in genetic complementation using mouse knockout models are helping to dissect apoptotic and necrotic cell death in different pathological states. The current state of research in this area is reviewed, focusing upon new findings describing the role of programmed necrosis induced by the mitochondrial permeability transition in mouse models of heart failure and diabetes.

2010-01-01

257

Thermal Cycling Reliability of Sn-Ag-Cu Solder Interconnections—Part 2: Failure Mechanisms  

NASA Astrophysics Data System (ADS)

Part 1 of this study focused on identifying the effects of (i) temperature difference (? T), (ii) lower dwell temperature and shorter dwell time, (iii) mean temperature, (iv) dwell time, and (v) ramp rate on the lifetime of ball grid array (with 144 solder balls) component boards. Based on the characteristic lifetime, the studied thermal cycling profiles were categorized into three groups: (i) highly accelerated conditions, (ii) moderately accelerated conditions, and (iii) mildly/nonaccelerated conditions. In this work, the observed differences in component board lifetime are explained by studying the failure mechanisms and microstructural changes that take place in the three groups of loading conditions. It was observed that, under the standardized thermal cycling conditions (highly accelerated conditions), the networks of grain boundaries formed by recrystallization provided favorable paths for cracks to propagate intergranularly. It is noteworthy that the coarsening of intermetallic particles was strong in the recrystallized regions (the cellular structure had disappeared completely in the crack region). However, under real-use conditions (mildly/nonaccelerated conditions), recrystallization was not observed in the solder interconnections and cracks had propagated transgranularly in the bulk solder or between the intermetallic compound (IMC) layer and the bulk solder. The real-use conditions showed slight coarsening of the microstructure close to the crack region, but the solder bulk still included finer IMC particles and ?-Sn cells characteristic of the as-solidified microstructures. These findings suggest that standardized thermal cycling tests used to assess the solder interconnection reliability of BGA144 component boards create failure mechanisms that differ from those seen in conditions representing real-use operation.

Hokka, Jussi; Mattila, Toni T.; Xu, Hongbo; Paulasto-Kröckel, Mervi

2013-06-01

258

Effect of Superalloy Substrate and Bond Coating on TBC Lifetime  

SciTech Connect

Several different single-crystal superalloys were coated with different bond coatings to study the effect of composition on the cyclic oxidation lifetime of an yttria-stabilized zirconia (YSZ) top coating deposited by electron beam physical vapor deposition from a commercial source. Three different superalloys were coated with a 7 {micro}m Pt layer that was diffused into the surface prior to YSZ deposition. One of the superalloys, N5, was coated with a low activity, Pt-modified aluminide coating and Pt-diffusion coatings with 3 and 7 {micro}m of Pt. Three coatings of each type were furnace cycled to failure in 1 h cycles at 1150 C to assess average coating lifetime. The 7 {micro}m Pt diffusion coating on N5 had an average YSZ coating lifetime >50% higher than a Pt-modified aluminide coating on N5. Without a YSZ coating, the Pt-modified aluminide coating on N5 showed the typical surface deformation during cycling, however, the deformation was greatly reduced when constrained by the YSZ coating. The 3 {micro}m Pt diffusion coating had a similar average lifetime as the Pt-modified aluminide coating but a much wider scatter. The Pt diffusion bond coating on superalloy X4 containing Ti exhibited the shortest YSZ coating lifetime, this alloy-coating combination also showed the worst alumina scale adhesion without a YSZ coating. The third generation superalloy N6 exhibited the longest coating lifetime with a 7 {micro}m Pt diffusion coating.

Pint, Bruce A [ORNL; Haynes, James A [ORNL; Zhang, Ying [Tennessee Technological University

2010-01-01

259

Mechanical support for isolated right ventricular failure in patients after cardiotomy  

Microsoft Academic Search

BackgroundPatients with acute right ventricular (RV) failure after cardiotomy have a poor prognosis. We evaluated the surgical and long-term outcomes of patients with isolated RV failure that required right ventricular assist device (RVAD) support.

Nader Moazami; Michael K. Pasque; Marc R. Moon; Rachel L. Herren; Marci S. Bailey; Jennifer S. Lawton; Ralph J. Damiano

2004-01-01

260

IMPERMEABLE THIN AL2O3 OVERLAY FOR TBC PROTECTION FROM SULFATE AND VANADATE ATTACK IN GAS TURBINES  

SciTech Connect

To improve the hot corrosion resistance of YSZ thermal barrier coatings, a 25 {micro}m and a 2 {micro}m thick Al{sub 2}O{sub 3} overlay were deposited by HVOF thermal spray and by sol-gel coating method, respectively, onto to the surface of YSZ coating. Indenter test was employed to investigate the spalling of YSZ with and without Al{sub 2}O{sub 3} overlay after hot corrosion. The results showed that Al{sub 2}O{sub 3} overlay acted as a barrier against the infiltration of the molten salt into the YSZ coating during exposure, thus significantly reduced the amount of M-phase of ZrO{sub 2} in YSZ coating. However, a thick Al{sub 2}O{sub 3} overlay was harmful for TBC by increasing compressive stress which causes crack and spalling of YSZ coating. As a result, a dense and thin Al{sub 2}O{sub 3} overlay is critical for simultaneously preventing YSZ from hot corrosion and spalling. In the next reporting period, we will measure or calculate the residue stress within Al{sub 2}O{sub 3} overlay and YSZ coating to study the mechanism of effect of Al{sub 2}O{sub 3} overlay on spalling of YSZ coating.

Scott X. Mao

2003-12-16

261

Variation in Geologic and Topographic Setting Cause Spatial Correlations Between Hillslope Failure Mechanisms in the Ridge Basin, California  

NASA Astrophysics Data System (ADS)

A large number of mass movements driven by various failure mechanisms exist within the Ridge Basin region of Southern California. These landslides pose a risk to important transportation and utility corridors as well as residential areas. The field area is also directly within the restraining bend of the San Andreas Fault, and thus subject to high rock uplift rates and seismic activity. Bedrock is composed of terrigeneous clastic sediments deposited in a Late Neogene trans-extensional basin. These units are weakly lithified and have been tilted during syn- and post-depositional folding, creating a steep ridge and valley topography. Previous landslide studies in the area have focused on understanding the mechanics of individual slides or developing static landslide inventories along selected corridors. Studies up to now have not provided a regional synthesis of the how the variable failure mechanisms and triggers could be spatially correlated. In this study, we use a LiDAR derived DEM and low-altitude aerial photography collected in the fall of 2007 to map landslide features in a GIS. The position and morphologic attributes of ~2500 slides are identified. We combine field evidence and topographic form to infer failure mechanism. These mechanisms are then spatially correlated with forcing factors such as lithologic units, soil properties, geologic structures, topographic form and human disturbances. These spatial controls will be used in developing a hillslope stability model for each failure mechanism as well as creating an integrated hillslope stability model for the region.

Whitehead, K.; Crosby, B. T.; Mahar, J.

2008-12-01

262

Structurally Distinct Bacterial TBC-like GAPs Link Arf GTPase to Rab1 Inactivation to Counteract Host Defenses  

SciTech Connect

Rab GTPases are frequent targets of vacuole-living bacterial pathogens for appropriate trafficking of the vacuole. Here we discover that bacterial effectors including VirA from nonvacuole Shigella flexneri and EspG from extracellular Enteropathogenic Escherichia coli (EPEC) harbor TBC-like dual-finger motifs and exhibits potent RabGAP activities. Specific inactivation of Rab1 by VirA/EspG disrupts ER-to-Golgi trafficking. S. flexneri intracellular persistence requires VirA TBC-like GAP activity that mediates bacterial escape from autophagy-mediated host defense. Rab1 inactivation by EspG severely blocks host secretory pathway, resulting in inhibited interleukin-8 secretion from infected cells. Crystal structures of VirA/EspG-Rab1-GDP-aluminum fluoride complexes highlight TBC-like catalytic role for the arginine and glutamine finger residues and reveal a 3D architecture distinct from that of the TBC domain. Structure of Arf6-EspG-Rab1 ternary complex illustrates a pathogenic signaling complex that rewires host Arf signaling to Rab1 inactivation. Structural distinctions of VirA/EspG further predict a possible extensive presence of TBC-like RabGAP effectors in counteracting various host defenses.

Dong, Na; Zhu, Yongqun; Lu, Qiuhe; Hu, Liyan; Zheng, Yuqing; Shao, Feng (NIBS-China); (Zhejiang)

2012-10-10

263

Structurally distinct bacterial TBC-like GAPs link Arf GTPase to Rab1 inactivation to counteract host defenses.  

PubMed

Rab GTPases are frequent targets of vacuole-living bacterial pathogens for appropriate trafficking of the vacuole. Here we discover that bacterial effectors including VirA from nonvacuole Shigella flexneri and EspG from extracellular Enteropathogenic Escherichia coli (EPEC) harbor TBC-like dual-finger motifs and exhibits potent RabGAP activities. Specific inactivation of Rab1 by VirA/EspG disrupts ER-to-Golgi trafficking. S. flexneri intracellular persistence requires VirA TBC-like GAP activity that mediates bacterial escape from autophagy-mediated host defense. Rab1 inactivation by EspG severely blocks host secretory pathway, resulting in inhibited interleukin-8 secretion from infected cells. Crystal structures of VirA/EspG-Rab1-GDP-aluminum fluoride complexes highlight TBC-like catalytic role for the arginine and glutamine finger residues and reveal a 3D architecture distinct from that of the TBC domain. Structure of Arf6-EspG-Rab1 ternary complex illustrates a pathogenic signaling complex that rewires host Arf signaling to Rab1 inactivation. Structural distinctions of VirA/EspG further predict a possible extensive presence of TBC-like RabGAP effectors in counteracting various host defenses. PMID:22939626

Dong, Na; Zhu, Yongqun; Lu, Qiuhe; Hu, Liyan; Zheng, Yuqing; Shao, Feng

2012-08-31

264

Interdependency of mechanical failure rate of encapsulated solar cells and module design parameters  

NASA Astrophysics Data System (ADS)

In recent studies the mechanical reliability of encapsulated solar cells was numerically investigated. A finite element model of a solar module with all essential components, such as cells, polymer layers and frame was created. The principle stress field in each solar cell was calculated by exposing the module to distributed pressure loads on the glass surface. By means of a probabilistic approach based on the Weibull distribution function and the size effect the stress field was evaluated and the probability of failure of each solar cell was calculated. This approach is new in the reliability evaluation of encapsulated solar cells and can enhance the module design process. Two fundamental studies were carried out varying the mounting and frame as well as the encapsulant and its thickness. The results show that there is an interdependency between the stiffness of the frame section and the type of mounting. Furthermore the recommendation for an appropriate frame and mounting selection can change if the magnitude of the load changes. It was found that there is a correlation between the stiffness of the encapsulant and the fundamental mechanical behavior of the module laminate. For high stiffness values a sandwich behavior is dominant whereas for small stiffness values a laminate behavior with shear deformation is dominant. This results in contrary thickness recommendations for different encapsulants as well as temperatures. For high stiffness values respectively low temperatures a thin encapsulant is advantageous whereas for low stiffness values at high temperatures a thick encapsulant would be better.

Dietrich, Sascha; Sander, Martin; Pander, Matthias; Ebert, Matthias

2012-10-01

265

Interferometry of AlN-based microcantilevers to determine the material properties and failure mechanisms  

NASA Astrophysics Data System (ADS)

Micro-electro-mechanical systems are exposed to a variety of environmental stimuli, making a prediction of operational reliability difficult. Here, we investigate environmental effects on properties of piezoelectrically actuated microcantilevers, where AlN is used as actuation material. The environmental effects to be considered include thermal and humid cycling, as well as harsh electrical loading performed under normal conditions. Investigated properties are defined for the static and dynamic behavior of microcantilevers. A Twyman-Green interferometer, operating in both stroboscopic regime and time-average interferometry mode, is used as a metrology tool. The initial deflection and frequency changes of the first resonance mode of the microcantilevers are monitored during accelerated thermal aging tests, humidity tests, as well as harsh electrical loading and fatigue tests. Finally, the resonant fatigue tests accelerated by application of a high voltage are accomplished to evaluate a lifetime of microcantilevers. Monitoring the micromechanical behaviors of devices driven by AlN during the lifetime tests assists monitoring of their long-term stability. FEM calculation is used to identify critical areas of stress concentration in the cantilever structure and to further explain various failure mechanisms.

Gorecki, Christophe; Krupa, Katarzyna; Józwik, Micha?

2012-05-01

266

Mechanical behavior and localized failure modes in a porous basalt from the Azores  

NASA Astrophysics Data System (ADS)

Basaltic rocks are the main component of the oceanic upper crust, thus of potential interest for water and geothermal resources, storage of CO2 and volcanic edifice stability. In this work, we investigated experimentally the mechanical behavior and the failure modes of a porous basalt, with an initial connected porosity of 18%. Results were acquired under triaxial compression experiments at confining pressure in the range of 25-200 MPa on water saturated samples. In addition, a purely hydrostatic test was also performed to reach the pore collapse critical pressure P*. During hydrostatic loading, our results show that the permeability is highly pressure dependent, which suggests that the permeability is mainly controlled by pre-existing cracks. When the sample is deformed at pressure higher than the pore collapse pressure P*, some very small dilatancy develops due to microcracking, and an increase in permeability is observed. Under triaxial loading, two modes of deformation can be highlighted. At low confining pressure (Pc < 50 MPa), the samples are brittle and shear localization occurs. For confining pressure > 50 MPa, the stress-strain curves are characterized by strain hardening and volumetric compaction. Stress drops are also observed, suggesting that compaction may be localized. The presence of compaction bands is confirmed by our microstructure analysis. In addition, the mechanical data allows us to plot the full yield surface for this porous basalt, which follows an elliptic cap as previously observed in high porosity sandstones and limestones.

Loaiza, S.; Fortin, J.; Schubnel, A.; Gueguen, Y.; Vinciguerra, S.; Moreira, M.

2012-10-01

267

SLOPE FAILURE MECHANISMS IN COHESIVE SOILS: INSIGHTS FROM THEORETICAL AND NUMERICAL ANALYSES OF FIELD AND LABORATORY-TRIGGERED EVENTS  

NASA Astrophysics Data System (ADS)

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 flume experiments. Finally, tentative modeling is discussed and the observed failure modes and possible mechanisms leading to failure are summarized.

Malet, J.; Spickermann, A.; van Asch, T.

2009-12-01

268

The mechanics of harmonic gas pressurization and failure of lava domes  

NASA Astrophysics Data System (ADS)

Solutions are developed for the harmonic interior pressurization of idealized hemispherical lava domes to determine the evolution of instability with time. Integrated gas pressure distributions are evaluated to determine uplift on inclined planes of potential detachment that traverse the dome, and to evaluate the limit-equilibrium stability of blocks isolated by these planes. Average pressure distributions show an initial transient rise to peak dynamic gas pressures that corresponds to a harmonic steady state. Progress towards potential instability mirrors this rise, and oscillates with the harmonic steady state. The timing of pressurization of the dome lavas is modulated by a diffusive time. The magnitude of this pressurization is modulated by dome geometry and the magnitude and non-dimensional frequency of the interior inflation. Two distinct pressurization behaviours are apparent: the first, at high relative inflation frequencies, is where the dynamic steady state corresponds to static pressurization at the mean interior pressure; and the second, at low relative inflation frequencies, is where the dynamic state synchronously responds to the oscillating interior-pressure boundary condition, and peak uplift is proportional to the mean pressure plus the maximum harmonic overpressure. These two conditions are separated by a frequency shift, or change in fluid diffusivity, of only two orders of magnitude, and are significant because the destabilizing uplift force may increase by a factor of two, where all other parameters, except excitation frequency or diffusivity, remain fixed. These results are applied to stability evaluations of the lava dome at the Soufriere Hills volcano, to examine failure mechanisms potentially consistent with the observed delay in collapse. Linear models incorporating time-invariant strength and transport parameters are only able to represent collapse for interior gas pressures at the upper limit of observed magnitudes. Conversely, behaviours incorporating fatigue-weakening, or hysteretic permeability enhancement, of the dome rocks are able to approach failure for modest pressurization magnitudes, to match observed delays in collapse and potentially to explain why some domes collapse explosively whereas others do not.

Elsworth, Derek; Voight, Barry

2001-04-01

269

Mechanical failure begins preferentially near resorption cavities in human vertebral cancellous bone under compression.  

PubMed

The amount of bone turnover in the body has been implicated as a factor that can influence fracture risk and bone strength. Here we test the idea that remodeling cavities promote local tissue failure by determining if microscopic tissue damage (microdamage) caused by controlled loading in vitro is more likely to form near resorption cavities. Specimens of human vertebral cancellous bone (L4, 7 male and 2 female, age 70±10, mean±SD) were loaded in compression to the yield point, stained for microscopic tissue damage and submitted to three-dimensional fluorescent imaging using serial milling (image voxel size 0.7×0.7×5.0 ?m). We found the resulting damage volume per bone volume (DV/BV) was correlated with percent eroded surface (p<0.01, r(2)=0.65), demonstrating that whole specimen measures of resorption cavities and microdamage are related. Locations of microdamage were more than two times as likely to have a neighboring resorption cavity than randomly selected sites without microdamage (relative risk 2.39, 95% confidence interval of relative risk: 2.09-2.73), indicating a spatial association between resorption cavities and microdamage at the local level. Individual microdamage sites were 48,700 (40,100; 62,700) ?m(3) in size (median, 25th and 75th percentiles). That microdamage was associated with resorption cavities when measured at the whole specimen level as well as at the local level provides strong evidence that resorption cavities play a role in mechanical failure processes of cancellous bone and therefore have the potential to influence resistance to clinical fracture. PMID:22426306

Slyfield, C R; Tkachenko, E V; Fischer, S E; Ehlert, K M; Yi, I H; Jekir, M G; O'Brien, R G; Keaveny, T M; Hernandez, C J

2012-03-09

270

Therapeutic efficacy of TBC3711 in monocrotaline-induced pulmonary hypertension  

Microsoft Academic Search

Background  Endothelin-1 signalling plays an important role in pathogenesis of pulmonary hypertension. Although different endothelin-A\\u000a receptor antagonists are developed, a novel therapeutic option to cure the disease is still needed. This study aims to investigate\\u000a the therapeutic efficacy of the selective endothelin-A receptor antagonist TBC3711 in monocrotaline-induced pulmonary hypertension\\u000a in rats.\\u000a \\u000a \\u000a \\u000a \\u000a Methods  Monocrotaline-injected male Sprague-Dawley rats were randomized and treated orally from

Djuro Kosanovic; Baktybek Kojonazarov; Himal Luitel; Bhola K Dahal; Akylbek Sydykov; Teodora Cornitescu; Wiebke Janssen; Ralf P Brandes; Neil Davie; Hossein A Ghofrani; Norbert Weissmann; Friedrich Grimminger; Werner Seeger; Ralph T Schermuly

2011-01-01

271

High levels of B-type natriuretic peptide predict weaning failure from mechanical ventilation in adult patients after cardiac surgery  

PubMed Central

OBJECTIVE: The failure to wean from mechanical ventilation is related to worse outcomes after cardiac surgery. The aim of this study was to evaluate whether the serum level of B-type natriuretic peptide is a predictor of weaning failure from mechanical ventilation after cardiac surgery. METHODS: We conducted a prospective, observational cohort study of 101 patients who underwent on-pump coronary artery bypass grafting. B-type natriuretic peptide was measured postoperatively after intensive care unit admission and at the end of a 60-min spontaneous breathing test. The demographic data, hemodynamic and respiratory parameters, fluid balance, need for vasopressor or inotropic support, and length of the intensive care unit and hospital stays were recorded. Weaning failure was considered as either the inability to sustain spontaneous breathing after 60 min or the need for reintubation within 48 h. RESULTS: Of the 101 patients studied, 12 patients failed the weaning trial. There were no differences between the groups in the baseline or intraoperative characteristics, including left ventricular function, EuroSCORE and lengths of the cardiac procedure and cardiopulmonary bypass. The B-type natriuretic peptide levels were significantly higher at intensive care unit admission and at the end of the breathing test in the patients with weaning failure compared with the patients who were successfully weaned. In a multivariate model, a high B-type natriuretic peptide level at the end of a spontaneous breathing trial was the only independent predictor of weaning failure from mechanical ventilation. CONCLUSIONS: A high B-type natriuretic peptide level is a predictive factor for the failure to wean from mechanical ventilation after cardiac surgery. These findings suggest that optimizing ventricular function should be a goal during the perioperative period.

Lara, Thiago Martins; Hajjar, Ludhmila Abrahao; de Almeida, Juliano Pinheiro; Fukushima, Julia Tizue; Barbas, Carmem Silvia Valente; Rodrigues, Adriano Rogerio Baldacin; Nozawa, Emilia; Feltrim, Maria Ignes Zanetti; Almeida, Elisangela; Coimbra, Vera; Osawa, Eduardo; de Moraes Ianotti, Rafael; Leme, Alcino Costa; Jatene, Fabio Biscegli; Auler-Jr., Jose Otavio Costa; Galas, Filomena Regina Barbosa Gomes

2013-01-01

272

TBC1D13 IS A RAB35 SPECIFIC GAP THAT PLAYS AN IMPORTANT ROLE IN GLUT4 TRAFFICKING IN ADIPOCYTES  

PubMed Central

Insulin stimulates glucose transport in adipocytes by triggering translocation of GLUT4 glucose transporters to the plasma membrane (PM) and several Rabs including Rab10 have been implicated in this process. To delineate the molecular regulation of this pathway, we conducted a TBC/RabGAP overexpression screen in adipocytes. This identified TBC1D13 as a potent inhibitor of insulin-stimulated GLUT4 translocation without affecting other trafficking pathways. To determine the potential Rab substrate for TBC1D13 we conducted a yeast two-hybrid screen and found that the GTP bound forms of Rabs 1 and 10 specifically interacted with TBC1D13 but not with eight other TBC proteins. Surprisingly, a comprehensive in vitro> screen for TBC1D13 GAP activity revealed Rab35 but not Rab10 as a specific substrate. TBC1D13 also displayed in vivo GAP activity towards Rab35. Overexpression of constitutively active Rab35 but not constitutively active Rab10 reversed the block in insulin-stimulated GLUT4 translocation observed with TBC1D13 overexpression. These studies implicate an important role for Rab35 in insulin-stimulated GLUT4 translocation in adipocytes.

Davey, Jonathan R; Humphrey, Sean J; Junutula, Jagath R; Mishra, Ashwini K; Lambright, David G; James, David E; Stockli, Jacqueline

2012-01-01

273

Noninvasive mechanical ventilation as a palliative treatment of acute respiratory failure in patients with end-stage solid cancer  

Microsoft Academic Search

Noninvasive ventilation (NIV) is widely used in the treatment of acute respiratory failure (ARF), but not in patients with end-stage solid cancer in whom any form of mechanical ventilation tends to be avoided. In a prospective study, we investigated the use of NIV in 23 patients with solid malignancies receiving palliative care and who were affected by severe hypoxic or

Annamaria Cuomo; Monica Delmastro; Piero Ceriana; Stefano Nava; Giorgio Conti; Massimo Antonelli; Emanuele Iacobone

2004-01-01

274

Mechanical Circulatory Support Devices Improve Tissue Perfusion in Patients With End-Stage Heart Failure or Cardiogenic Shock  

Microsoft Academic Search

Objectives: This study evaluated the effects of mechanical circulatory support (MCS) on sub-lingual microcirculation as a surrogate for splanchnic microvascular perfusion. Methods: Between May 2008 and April 2009, 10 consecutive patients received an MCS device or extracorporeal membrane oxygenation for end-stage chronic heart failure (n = 6) or cardiogenic shock (n = 4). Microcirculation was investigated using a hand-held Sidestream

Corstiaan A. den Uil; Alexander P. Maat; Wim K. Lagrand; Martin van der Ent; Lucia S. D. Jewbali; Robert J. van Thiel; Peter E. Spronk; Maarten L. Simoons

2009-01-01

275

Life tests and failure mechanisms of GaN-AlGaN-InGaN light emitting diodes  

Microsoft Academic Search

Our studies of device lifetime and the main degradation mechanisms in Nichia blue LEDs date back to Spring 1994. Following the initial studies of rapid failures under high current electrical pulses, where metal migration was identified as the cause of degradation, we have placed a number of Nichia NLPB-500 LEDs on a series of cw life tests. This work reviews

D. L. Barton; Marek Osinski; Piotr Perlin; Christopher J. Helms; Niel H. Berg

1998-01-01

276

Kinetics and mechanism of failure of carbides of refractory metals under the effect of internal stresses in neutron irradiation  

Microsoft Academic Search

The problems of analysis of the kinetics of failure of brittle materials in the conditions with the effect of external constant and alternating stresses have been studied extensively since it is necessary to determine the endurance of materials with the accuracy required for practice. In fracture mechanics, the endurance is predicted on the basis of analysis of the diagrams constructed

L. M. Murzin; V. V. Ogorodnikov

1988-01-01

277

Intravenous Allopurinol Decreases Myocardial Oxygen Consumption and Increases Mechanical Efficiency in Dogs With Pacing-Induced Heart Failure  

Microsoft Academic Search

Allopurinol, an inhibitor of xanthine oxidase, increases myofilament calcium responsiveness and blunts calcium cycling in isolated cardiac muscle. We sought to extend these observations to conscious dogs with and without pacing-induced heart failure and tested the prediction that allopurinol would have a positive inotropic effect without increasing energy expenditure, thereby increasing mechanical efficiency. In control dogs (n 510), allopurinol (200

Ulf E. G. Ekelund; Robert W. Harrison; Ori Shokek; Rajiv N. Thakkar; Richard S. Tunin; Hideaki Senzaki; David A. Kass; Eduardo Marban; Joshua M. Hare

2010-01-01

278

Failure mechanism of the interturn insulation of low voltage electric machines fed by pulse-controlled inverters  

Microsoft Academic Search

Partial discharges (PDs) occur in the air-filled gaps of enameled wires that are touching. They erode the insulation and consequently lead to an interturn breakdown. This paper describes the failure mechanism of low voltage interturn insulation as a consequence of PDs and shows why and how it is influenced by the insulation design, temperature, and the applied voltage. Understanding the

M. Kaufhold; G. Borner; M. Eberhardt; J. Speck

1996-01-01

279

High-voltage failure mechanisms in liquid-filled, Fluorinert FC40, capacitors  

Microsoft Academic Search

The high-voltage electrical failure of a liquid-filled, FC-40 Fluorinert, capacitor occurred during a system random vibration test. This failure occurred between 1 and 5 hours of random vibration of the system in the longitudinal axis of the capacitor. The previous five hours of random vibration in the transverse direction left the capacitor functioning as designed. Similar failures were observed during

J. D. McBrayer; C. B. Richardson; A. A. Jojola; L. J. Pitre

1992-01-01

280

TBC1D24 mutation associated with focal epilepsy, cognitive impairment and a distinctive cerebro-cerebellar malformation.  

PubMed

We describe the clinical and radiological features of a family with a homozygous mutation in TBC1D24. The phenotype comprised onset of focal seizures at 2 months with prominent eye-blinking, facial and limb jerking with an oral sensory aura. These were controllable with medication but persisted into adult life. Associated features were mild to moderate intellectual disability and cerebellar features. MRI showed subtle cortical thickening with cerebellar atrophy and high signal confined to the ansiform lobule. The disorder is allelic with familial infantile myoclonic epilepsy, where intellect and neurologic examination are normal, highlighting the phenotypic variation with mutations of TBC1D24. PMID:23517570

Afawi, Zaid; Mandelstam, Simone; Korczyn, Amos D; Kivity, Sara; Walid, Simri; Shalata, Adel; Oliver, Karen L; Corbett, Mark; Gecz, Jozef; Berkovic, Samuel F; Jackson, Graeme D

2013-03-19

281

Mechanical Strength and Failure Characterization of Sn-Ag-Cu Intermetallic Compound Joints at the Microscale  

NASA Astrophysics Data System (ADS)

Continuous miniaturization of microelectronic devices has led the industry to develop interconnects on the order of a few microns for advanced superhigh-density and three-dimensional integrated circuits (3D ICs). At this scale, interconnects that conventionally consist of solder material will completely transform to intermetallic compounds (IMCs) such as Cu6Sn5. IMCs are brittle, unlike conventional solder materials that are ductile in nature; therefore, IMCs do not experience large amounts of plasticity or creep before failure. IMCs have not been fully characterized, and their mechanical and thermomechanical reliability is questioned. This study presents experimental efforts to characterize such material. Sn-based microbonds are fabricated in a controlled environment to assure complete transformation of the bonds to Cu6Sn5 IMC. Microstructural analysis including scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDS), and x-ray diffraction (XRD) is utilized to determine the IMC material composition and degree of copper diffusion into the bond area. Specimens are fabricated with different bond thicknesses and in different configurations for various tests. Normal strength of the bonds is measured utilizing double cantilever beam and peeling tests. Shear tests are conducted to quantify the shear strength of the material. Four-point bending tests are conducted to measure the fracture toughness and critical energy release rate. Bonds are fabricated in different sizes, and the size effect is investigated. The shear strength, normal strength, critical energy release rate, and effect of bond size on bond strength are reported.

Ladani, Leila; Razmi, Jafar

2012-03-01

282

Application of a Fracture Methodology for Studying the Mechanics that Govern Failure of Aluminum Structures  

NASA Astrophysics Data System (ADS)

The existence of cracks besides the effect of structural degradation can cause partial or total failure of a structure. Usually, structures are designed to resist yielding, buckling and fatigue, but not fracture due to limited existing data on large scalemodels. As a result, robust methods and procedures to design structures against fracture have not been developed, although the industry is seeking to achieve more efficient concepts and designs with advanced safety and performance using optimized structural design. The rapidly increasing application of lightweight materials and thin-walled structures in several industries requires fundamental understanding of the mechanisms and mechanics of fracture that govern stiffened panels. A methodology consisting of the application of advanced fracture models, material calibration, and validation through component testing is provided that will increase the survivability envelope of new structures. This paper presents its application that will enable designers to evaluate critical areas within a structure with respect to crack initiation, propagation, optimum material usage, and computational cost. It is based on the effect of stiffening configurations on fracture of aluminum marine structures by studying the structural response of various stiffened plates, represented by small-scale compact tension (CT) and intermediate-scale specimens, which are compared with unstiffened plates. It is shown that mapping of crack patterns in stiffened plates is feasible. Numerical modeling and analyses of ductile fracture initiation and propagation on a precracked geometry using a commercial finite element code (ABAQUS), taking into account the behavior of simple uncracked material, has been performed showing a very good agreement with small and intermediate scale tests.

Galanis, Konstantinos Panagiotis; Wierzbicki, Tomasz; Papazoglou, Vassilios John

283

Perioperative risk factors for prolonged mechanical ventilation after liver transplantation due to acute liver failure  

PubMed Central

Background Acute liver failure (ALF) is a rapidly progressing and fatal disease for which liver transplantation (LT) is the only treatment. Posttransplant mechanical ventilation tends to be more prolonged in patients with ALF than in other LT patients. The present study examined the clinical effects of prolonged posttransplant mechanical ventilation (PMV), and identified risk factors for PMV following LT for ALF. Methods We reviewed data of patients undergoing LT for ALF between January 2005 and June 2011. After grouping patients according to administration of PMV (? 24 h), donor and recipient perioperative variables were compared between the groups with and without PMV. Potentially significant factors (P < 0.1) from the univariate intergroup comparison were entered into a multivariate logistic regression to establish a predictive model for PMV. Results Twenty-four (25.3%) of 95 patients with ALF who received PMV had a higher mortality rate (29.2% vs 11.3%, P = 0.038) and longer intensive care unit stay (12.9 ± 10.4 vs 7.1 ± 2.7 days, P = 0.012) than patients without PMV. The intergroup comparisons revealed worse preoperative hepatic conditions, more supportive therapy, and more intraoperative fluctuations in vital signs and less urine output in the with- compared with the without-PMV group. The multivariate analysis revealed that preoperative hepatic encephalopathy (? grade III), intraoperative blood pressure fluctuation, and oliguria (< 0.5 ml/kg/h) were independent risk factors for PMV. Conclusions PMV was associated with deleterious outcomes. Besides care for known risk factors including hepatic encephalopathy, meticulous attention to managing intraoperative hemodynamic circulatory status is required to avoid PMV and improve the posttransplant prognosis in ALF patients.

Lee, Serin; Jung, Hyun Sik; Choi, Jong Ho; Lee, Jaemin; Hong, Sang Hyun; Lee, Sung Hyun

2013-01-01

284

Mechanism of augmented exercise hyperpnea in chronic heart failure and dead space loading.  

PubMed

Patients with chronic heart failure (CHF) suffer increased alveolar VD/VT (dead-space-to-tidal-volume ratio), yet they demonstrate augmented pulmonary ventilation such that arterial [Formula: see text] ( [Formula: see text] ) remains remarkably normal from rest to moderate exercise. This paradoxical effect suggests that the control law governing exercise hyperpnea is not merely determined by metabolic CO2 production ( [Formula: see text] ) per se but is responsive to an apparent (real-feel) metabolic CO2 load ( [Formula: see text] ) that also incorporates the adverse effect of physiological VD/VT on pulmonary CO2 elimination. By contrast, healthy individuals subjected to dead space loading also experience augmented ventilation at rest and during exercise as with increased alveolar VD/VT in CHF, but the resultant response is hypercapnic instead of eucapnic, as with CO2 breathing. The ventilatory effects of dead space loading are therefore similar to those of increased alveolar VD/VT and CO2 breathing combined. These observations are consistent with the hypothesis that the increased series VD/VT in dead space loading adds to [Formula: see text] as with increased alveolar VD/VT in CHF, but this is through rebreathing of CO2 in dead space gas thus creating a virtual (illusory) airway CO2 load within each inspiration, as opposed to a true airway CO2 load during CO2 breathing that clogs the mechanism for CO2 elimination through pulmonary ventilation. Thus, the chemosensing mechanism at the respiratory controller may be responsive to putative drive signals mediated by within-breath [Formula: see text] oscillations independent of breath-to-breath fluctuations of the mean [Formula: see text] level. Skeletal muscle afferents feedback, while important for early-phase exercise cardioventilatory dynamics, appears inconsequential for late-phase exercise hyperpnea. PMID:23274121

Poon, Chi-Sang; Tin, Chung

2012-12-27

285

High-voltage failure mechanisms in liquid-filled, Fluorinert FC-40, capacitors.  

National Technical Information Service (NTIS)

The high-voltage electrical failure of a liquid-filled, FC-40 Fluorinert, capacitor occurred during a system random vibration test. This failure occurred between 1 and 5 hours of random vibration of the system in the longitudinal axis of the capacitor. Th...

J. D. McBrayer C. B. Richardson A. A. Jojola L. J. Pitre

1992-01-01

286

Deformation and failure in polyethylene: correlation between mechanisms of creep and fatigue  

Microsoft Academic Search

Fatigue and creep tests have been conducted on medium density gas- and water-grade pipe materials using a longitudinally notched pipe geometry with internal pressurization. The failure in both types of test was brittle compared to the failure occurring when the unnotched pipe is exposed to a constant intense pressure. Further to this superficial similarity, fractographic studies revealed creep and fatigue

P. T. Reynolds; C. C. Lawrence

1991-01-01

287

Investigation of failure mechanisms in high-power microwave transmission windows  

Microsoft Academic Search

Thermal runaway and window failure restrict the power output of high power (˜1 MW), long pulse length (˜10 sec) gyrotrons used for plasma heating in magnetic confinement fusion experiments. Chemical vapor deposition diamond is used as window material due to its low loss tangent and high thermal conductivity, but still suffers from occasional, unpredictable failure. With the use of a

Herman L. Bosman

2004-01-01

288

Mechanical failure of prosthetic human implants: A 10-year experience with aortic stent graft devices  

Microsoft Academic Search

Objective: The first endovascular stent graft was implanted to treat an abdominal aortic aneurysm more than a decade ago. This technique has evolved dramatically with the growing understanding of metallurgic and fabric sciences and improved device designs. However the potential for stent graft material failure remains. This investigation describes the incidence of material failure, potential modes of device fatigue, and

Tikva S. Jacobs; Jamie Won; Edwin C. Gravereaux; Peter L. Faries; Nicholas Morrissey; Victoria J. Teodorescu; Larry H. Hollier; Michael L. Marin

2003-01-01

289

TBC costing  

NASA Astrophysics Data System (ADS)

Procedures to be used in determining the cost of producing and installing a parabolic dish collector in annual production volumes of 10,000, 50,000, 100,000, and 1,000,000 units include (1) evaluating each individual part for material cost and for the type and number of operations required to work the raw material into the finished part; (2) costing labor, burden, tooling, gaging, machinery, and equipment; (3) estimating facilities requirements for each production volume; and (4) considering suggestions for design and material alterations that could result in cost reduction.

Kaminski, H. L.

1980-05-01

290

Mechanisms of desensitization to a PDE inhibitor (milrinone) in conscious dogs with heart failure.  

PubMed

The goal of this study was to determine the extent to which the effects of milrinone were desensitized in heart failure (HF) and to determine the mechanisms, i.e., whether these effects could be ascribed to changes in cAMP or phosphodiesterase (PDE) activity in HF. Accordingly, we examined the effects of milrinone in seven conscious dogs before and after HF was induced by rapid ventricular pacing at 240 beats/min. The dogs were chronically instrumented for measurements of left ventricular (LV) pressure and first derivative of LV pressure (dP/dt), arterial pressure, LV internal diameter, and wall thickness. Milrinone (10 micrograms . kg-1. min-1 iv) increased LV dP/dt by 1,854 +/- 157 from 2,701 +/- 105 mmHg/s (P < 0.05) before HF. After HF the increase in LV dP/dt in response to milrinone was attenuated significantly (P < 0.05); it increased by 615 +/- 67 from 1,550 +/- 107 mmHg/s, indicating marked desensitization. In the presence of ganglionic blockade the increases in LV dP/dt (+445 +/- 65 mmHg/s) in response to milrinone were markedly less (P < 0.01), and milrinone increased LV dP/dt even less in HF (+240 +/- 65 mmHg/s). cAMP and PDE activity were measured in endocardial and epicardial layers in normal and failing myocardium. cAMP was decreased significantly (P < 0.05) in LV endocardium (-26%) but not significantly in LV epicardium (-14%). PDE activity was also decreased significantly (P < 0.05) in LV endocardium (-18%) but not in LV epicardium (-4%). Thus significant desensitization to milrinone was observed in conscious dogs with HF. The major effect was autonomically mediated. The biochemical mechanism appears to be due in part to the modest reductions in PDE activity in failing myocardium, which, in turn, may be a compensatory mechanism to maintain cAMP levels in HF. Reductions in cAMP and PDE levels were restricted to the subendocardium, suggesting that the increased wall stress and reduced coronary reserve play a role in mediating these changes. PMID:10330256

Sato, N; Asai, K; Okumura, S; Takagi, G; Shannon, R P; Fujita-Yamaguchi, Y; Ishikawa, Y; Vatner, S F; Vatner, D E

1999-05-01

291

Comparison of High Frequency Positive Pressure Mechanical Ventilation (HFPPV) With Conventional Method in the Treatment of Neonatal Respiratory Failure  

PubMed Central

Background Respiratory failure is a major problem in neonatal medicine in all over the world and has different causes. Using mechanical ventilation is one of its major treatments. Objectives Different strategies have been expressed in this context, including high frequency mechanical ventilation. Patients and Methods This study is a prospective randomized clinical trial conducted on all newborns with respiratory failure hospitalized in the NICU of Tehran vali-asr Hospital during 2009.These patients were divided in to two groups through block Randomization method; conventional mechanical ventilation group and high frequency ventilation group. Results Intraventricular hemorrhage (IVH) and air leak (e.g. pneumothorax) were less in HFPPV group than conventional group (P = 0.012 and P = 0.038). The mean time needed for mechanical ventilation was lower in HFPPV group, but this difference was not statistically significant (P = 0.922). Needing to O2 in 28 days of age was almost equal in both groups (P = 0. 99). Mortality, and refractory hypoxia and PVL were lower in HFPPV group, but the difference was not statistically significant (P = 0.301, P = 0. 508, P = 0. 113). Conclusions Treatment of neonatal respiratory failure with high rate mechanical ventilation may reduce some complications.

Amini, Elahe; Nayeri, Fatemeh Sadat; Hemati, Arezu; Esmaeilinia, Tahere; Nili, Firuzeh; Dalili, Hossein; Aminnejad, Majid

2013-01-01

292

Mode II electromigration failure mechanism in Sn-based Pb-free solder joints with Ni under-bump metallization  

NASA Astrophysics Data System (ADS)

Early electromigration (EM) failure mechanism, also known as Mode II EM failure in Sn-based Pb-free solder joints with Ni under-bump metallization (UBM) is studied. A numerical model was built to incorporate interdiffusion and EM, and to investigate the effect of Sn crystal orientation. Results show that when the c axis of Sn has a close alignment to the current direction, intermetallic compound (IMC) growth is enhanced by both EM and extremely fast interstitial diffusion of Ni in the solder. The combined process results in IMC dissolution from the cathode side of the solder joint and causes EM failure by UBM depletion. Theoretical predictions are consistent with experimental observations.

Wang, Yiwei; Ho, Paul S.

2013-09-01

293

Separate mechanisms cause anemia in ischemic vs. nonischemic murine heart failure.  

PubMed

In ischemic congestive heart failure (CHF), anemia is associated with poor prognosis. Whether anemia develops in nonischemic CHF is uncertain. The hematopoietic inhibitors TNF-alpha and nitric oxide (NO) are activated in ischemic CHF. We examined whether mice with ischemic or nonischemic CHF develop anemia and whether TNF-alpha and NO are involved. We studied mice (n = 7-9 per group) with CHF either due to myocardial infarction (MI) or to overexpression of the Ca(2+)-binding protein calsequestrin (CSQ) or to induced cardiac disruption of the sarcoplasmic reticulum Ca(2+)-ATPase 2 gene (SERCA2 KO). Hematopoiesis was analyzed by colony formation of CD34(+) bone marrow cells. Hemoglobin concentration was 14.0 +/- 0.4 g/dl (mean +/- SD) in controls, while it was decreased to 10.1 +/- 0.4, 9.7 +/- 0.4, and 9.6 +/- 0.3 g/dl in MI, CSQ, and SERCA2 KO, respectively (P < 0.05). Colony numbers per 100,000 CD34(+) cells in the three CHF groups were reduced to 33 +/- 3 (MI), 34 +/- 3 (CSQ), and 39 +/- 3 (SERCA2 KO) compared with 68 +/- 4 in controls (P < 0.05). Plasma TNF-alpha nearly doubled in MI, and addition of anti-TNF-alpha antibody normalized colony formation. Inhibition of colony formation was completely abolished with blockade of endothelial NO synthase in CSQ and SERCA2 KO, but not in MI. In conclusion, the mechanism of anemia in CHF depends on the etiology of cardiac disease; whereas TNF-alpha impairs hematopoiesis in CHF following MI, NO inhibits blood cell formation in nonischemic murine CHF. PMID:20032264

Iversen, Per O; Andersson, Kristin B; Finsen, Alexandra V; Sjaastad, Ivar; von Lueder, Thomas G; Sejersted, Ole M; Attramadal, Havard; Christensen, Geir

2009-12-23

294

Hill Slope Failure as a Mechanism to Resurface Asteroids During Planetary Flybys  

NASA Astrophysics Data System (ADS)

Laboratory measurements of meteorite reflectance spectra rarely match telescopic observations of asteroid reflectance spectra. This difference is likely due to the process(es) of space weathering, which rapidly redden asteroid surfaces on million year timescales (e.g. Chapman 2004, Annu. Rev. Earth Planet. Sci. 32, 539). While nearly all Main Belt asteroids are “weathered,” many asteroids on terrestrial planet crossing orbits appear “unweathered” (Marchi et al., 2006, MNRAS 368, L39). Numerical integration of the orbits of these unweathered asteroids suggest that close approaches within 16 Earth radii may reset the surfaces of asteroids, and erase the signatures of space weathering (Binzel et al. 2010, Nature 463, 331; Nesvorny et al. 2010, Icarus 209, 510). Despite the evidence that close approaches may play a role in resurfacing asteroids, the specific resurfacing mechanism is unknown. I hypothesize that tidal perturbations during planetary close approaches trigger debris flows, which resurface portions of the asteroid. I have developed an original numerical model for evaluating the stability of hill slopes on rigid asteroids of arbitrary shape, density, and spin during planetary flybys. I present preliminary results for a limited range of asteroid and flyby parameters, which suggest that significant fractions of the asteroid surface (a few percent) can become unstable to hill slope failure during flybys with close approach distances out to ~10 Earth radii. In future work, I will explore a range of asteroid and flyby parameters, in order to better constrain the critical distance required for resetting asteroid surfaces. By characterizing this critical distance, it may be possible to better constrain the space weathering rate on asteroids.

Keane, James; Matsuyama, I.

2013-10-01

295

Efficacy of noninvasive mechanical ventilation in obese patients with chronic respiratory failure.  

PubMed

Chronic respiratory failure (CRF) develops in a minority of obese patients. Noninvasive mechanical ventilation (NIMV) is a new optional treatment for such patients. The aim of this study was to evaluate the effectiveness of NIMV in obese patients with CRF. The material of the study consisted of 34 obese patients (body mass index 47.3 ± 7.9 kg/m(2)) with CRF (PaO2 = 6.40 ± 0.93 kPa and PaCO2 = 8.67 ± 2.13 kPa) who were hypoxemic despite an optimal therapy. Thirteen patients had an overlap syndrome (OS) - chronic obstructive pulmonary disease (COPD) coexisting with obstructive sleep apnea syndrome (OSAS) and 21 patients had obesity-hypoventilation syndrome (OHS). Ventilation parameters were determined during polysomnography. The efficacy of NIMV was evaluated on the fifth day and after 1 year's home treatment. We observed a significant increase in the mean blood oxygen saturation during sleep in all patients; the increase was greater in patients with OHS (92.6 ± 1.4 %) than in patients with OS (90.4 ± 1.8 %). There was a significant improvement of diurnal PaO2 and PaCO2 on the fifth day of NIMV (mean PaO2 increase 2.1 kPa and PaCO2 decrease 0.9 kPa) and also after 1 year of home NIMV (mean PaO2 increase 1.9 kPa and PaCO2 decrease 2.4 kPa). Only one patient stopped treatment because of lack of tolerance during the observation period (1-3 years). In conclusion, NIMV is an effective and well tolerated treatment option in obese patients with CRF resulting in a rapid relief of respiratory disorders during sleep and a gradual, long-term improvement of gas exchange during the day, particularly in patients with OHS. PMID:23835975

Piesiak, P; Brzecka, A; Kosacka, M; Jankowska, R

2013-01-01

296

On the mechanism of impaired insulin secretion in chronic renal failure.  

PubMed Central

It has been suggested that a sustained rise in resting levels of cytosolic calcium [Ca2+]i of pancreatic islets is responsible for impaired insulin secretion in chronic renal failure (CRF). Evidence for such an event is lacking and the mechanisms through which it may affect insulin secretion are not known. Studies were conducted in normal, CRF, and normocalcemic, parathyroidectomized (PTX) CRF rats to answer these questions. Resting levels of [Ca2+]i of islets from CRF rats were higher (P less than 0.01) than in control of CRF-PTX rats. [3H]2-deoxyglucose uptake and cAMP production by islets were not different in the three groups. Insulin content of, and glucose-induced insulin secretion by islets from CRF rats was lower (P less than 0.01) than in control and CRF-PTX rats. In contrast, glyceraldehyde-induced insulin release by CRF islets was normal. Basal ATP content, both glucose-stimulated ATP content and ATP/ADP ratio, net lactic acid output, Vmax of phosphofructokinase-1, and Ca2+ ATPase of islets from CRF rats were lower (P less than 0.02-less than 0.01) than in normal or CRF-PTX animals. Data show that: (a) Glucose but not glyceraldehyde-induced insulin secretion is impaired in CRF; (b) the impairment in glucose-induced insulin release in CRF is due to a defect in the metabolism of glucose; (c) this latter defect is due to reduced ATP content induced partly by high [Ca2+]i of islets; and (d) the high [Ca2+]i in islets of CRF rats is due to augmented PTH-induced calcium entry into cells and decreased calcium extrusion from the islets secondary to reduced activity of the Ca2+ ATPase. Images

Fadda, G Z; Hajjar, S M; Perna, A F; Zhou, X J; Lipson, L G; Massry, S G

1991-01-01

297

Mitigation of SCC and Corrosion Fatigue Failures in 300M Landing Gear Steel Using Mechanical Suppression.  

National Technical Information Service (NTIS)

300M steel is widely used in landing gear because of its unique combination of ultrahigh strength with high fracture toughness. However, 300M is vulnerable to both corrosion fatigue and stress corrosion cracking (SCC) failures with catastrophic consequenc...

P. S. Prevey N. Jayaraman N. Ontko M. Shepard R. Ware

2004-01-01

298

Structural and population-based evaluations of TBC1D1 p.Arg125Trp.  

PubMed

Obesity is now a leading cause of preventable death in the industrialised world. Understanding its genetic influences can enhance insight into molecular pathogenesis and potential therapeutic targets. A non-synonymous polymorphism (rs35859249, p.Arg125Trp) in the N-terminal TBC1D1 phosphotyrosine-binding (PTB) domain has shown a replicated association with familial obesity in women. We investigated these findings in the Avon Longitudinal Study of Parents and Children (ALSPAC), a large European birth cohort of mothers and offspring, and by generating a predicted model of the structure of this domain. Structural prediction involved the use of three separate algorithms; Robetta, HHpred/MODELLER and I-TASSER. We used the transmission disequilibrium test (TDT) to investigate familial association in the ALSPAC study cohort (N?=?2,292 mother-offspring pairs). Linear regression models were used to examine the association of genotype with mean measurements of adiposity (Body Mass Index (BMI), waist circumference and Dual-energy X-ray absorptiometry (DXA) assessed fat mass), and logistic regression was used to examine the association with odds of obesity. Modelling showed that the R125W mutation occurs in a location of the TBC1D1 PTB domain that is predicted to have a function in a putative protein:protein interaction. We did not detect an association between R125W and BMI (mean per allele difference 0.27 kg/m(2) (95% Confidence Interval: 0.00, 0.53) P?=?0.05) or obesity (odds ratio 1.01 (95% Confidence Interval: 0.77, 1.31, P?=?0.96) in offspring after adjusting for multiple comparisons. Furthermore, there was no evidence to suggest that there was familial association between R125W and obesity (?(2)?=?0.06, P?=?0.80). Our analysis suggests that R125W in TBC1D1 plays a role in the binding of an effector protein, but we find no evidence that the R125W variant is related to mean BMI or odds of obesity in a general population sample. PMID:23667688

Richardson, Tom G; Thomas, Elaine C; Sessions, Richard B; Lawlor, Debbie A; Tavaré, Jeremy M; Day, Ian N M

2013-05-07

299

Failure mechanisms of silver and aluminum on titanium nitride under high current stress  

Microsoft Academic Search

The effects of high-current stress (3–10 A) on single-line structures of aluminum (Al) and silver (Ag) of different widths (2.5–10 ?m) and on titanium nitride (TiN) as barrier are reported in this paper. As the applied current-densities were increased, the lines experienced catastrophic failure. In the cases of Al\\/TiN\\/SiO2 and Ag\\/TiN\\/Si, failure occurred at individual sites that were distributed over

E. Misra; C. Marenco; N. D. Theodore; T. L. Alford

2005-01-01

300

Failure of carbon composite-to-aluminum joints with combined mechanical fastening and adhesive bonding  

Microsoft Academic Search

Composite-to-aluminum double lap joints were tested to obtain the failure loads and modes for three types of joints: adhesive bonding, bolt fastening and adhesive-bolt hybrid joining. A film type adhesive FM73 and a paste type adhesive EA9394S were used for aluminum and composite bonding. A digital microscope camcorder was used to monitor the failure of the joints. It was found

Jin-Hwe Kweon; Jae-Woo Jung; Tae-Hwan Kim; Jin-Ho Choi; Dong-Hyun Kim

2006-01-01

301

TBC1D7 is a third subunit of the TSC1-TSC2 complex upstream of mTORC1  

PubMed Central

SUMMARY The tuberous sclerosis complex (TSC) tumor suppressors form the TSC1-TSC2 complex, which limits cell growth in response to poor growth conditions. Through its GTPase-activating protein (GAP) activity toward Rheb, this complex inhibits the mechanistic target of rapamycin (mTOR) complex 1 (mTORC1), a key promoter of cell growth. Here, we identify and biochemically characterize TBC1D7 as a stably-associated and ubiquitous third core subunit of the TSC1-TSC2 complex. We demonstrate that the TSC1-TSC2-TBC1D7 (TSC-TBC) complex is the functional complex that senses specific cellular growth conditions and possesses Rheb-GAP activity. Sequencing analyses of samples from TSC patients suggest that TBC1D7 is unlikely to represent TSC3. TBC1D7 knockdown decreases the association of TSC1 and TSC2 leading to decreased Rheb-GAP activity, without effects on the localization of TSC2 to the lysosome. Like the other TSC-TBC components, TBC1D7 knockdown results in increased mTORC1 signaling, delayed induction of autophagy, and enhanced cell growth under poor growth conditions.

Dibble, Christian C.; Elis, Winfried; Menon, Suchithra; Qin, Wei; Klekota, Justin; Asara, John M.; Finan, Peter M.; Kwiatkowski, David J.; Murphy, Leon O.; Manning, Brendan D.

2013-01-01

302

Failure mechanism of thin Al 2O 3 coatings grown by atomic layer deposition for corrosion protection of carbon steel  

Microsoft Academic Search

Combined analysis by electrochemical impedance spectroscopy (EIS), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and field emission scanning electron microscopy (FESEM) of the corrosion protection provided to carbon steel by thin (50nm) Al2O3 coatings grown by atomic layer deposition (ALD) and its failure mechanism is reported. In spite of excellent sealing properties, the results show an average dissolution rate of the

Belén Díaz; Emma Härkönen; Vincent Maurice; Jolanta ?wiatowska; Antoine Seyeux; Mikko Ritala; Philippe Marcus

2011-01-01

303

Negative pressure ventilation versus conventional mechanical ventilation in the treatment of acute respiratory failure in COPD patients  

Microsoft Academic Search

This case-control study was aimed to evaluate the effectiveness of nega- tive pressure ventilation (NPV) versus conventional mechanical ventilation (CMV) for the treatment of acute respiratory failure (ARF) in patients with chronic obstructive pulmonary disease (COPD) admitted to a respiratory intermediate intensive care unit (RIICU) and four general intensive care units (ICU). Twenty-six COPD patients in ARF admitted in 1994-95

A. Corrado; M. Gorini; R. Ginanni; C. Pelagatti; G. Villella; U. Buoncristiano; F. Guidi; E. Pagni; A. Peris; E. De Paola

1998-01-01

304

Protection of steel by inhibitors from corrosion, hydrogen absorption, and corrosion-mechanical failure in a hydrogen sulfide medium  

Microsoft Academic Search

The effectiveness of the inhibitors in retarding corrosion, hydrogen impregnation, and corrosion-mechanical failure of steelwas determined in a 3% NaCI solution saturated with hy- drogen sulfide at atmospheric pressure and a temperature of 30~ The concentration of~the additions was 1.5 g\\/liter (selected for a comparative characteristic of the protective effec- tiveness of the inhibitors, the maximum of which appears at

E. I. Svist; V. M. Zhovnirchuk; A. K. Mindyuk; Yu. I. Babei

1983-01-01

305

The failure mechanism of ZrB 2–SiC–graphite composite heated by high electric current  

Microsoft Academic Search

The failure mechanism of the ZrB2–SiC–graphite composite heated by high electric current was investigated. The results indicated that a large numbers of graphite flake was torn along their basal planes, which was attributed to that the thermal stress is perpendicular to graphite flake. The thermal stress resulted from the thermal expansion mismatch during rapid heating was calculated to be above

Hongbo Chen; Zhi Wang; Songhe Meng; Guanghui Bai; Wei Qu

2009-01-01

306

KhOD-1, a highly effective inhibitor of acid corrosion and corrosion-mechanical failure of steel  

Microsoft Academic Search

Below are given results of investigations of the protective capacity of KhOD-I inhibitor, which does not form foam in acid solutions (developed by the Physicomechanical Institute of the Academy of Sciences of the Ukrainian SSR together with the LvovMedical Institute), and also of the inhibitors KhOSP-10, KI-I, PB-5, BA-6, and urotropin (concentrations 1.5 g\\/liter) in retarding corrosion and corrosion-mechanical failure

A. K. Mindyuk; O. P. Savitskaya; A. D. Tkach

1983-01-01

307

Application of non-invasive mechanical ventilation in an asthmatic pregnant woman in respiratory failure: a case report  

PubMed Central

The use of non-invasive mechanical ventilation (NIV) during an asthma attack is controversial. We report a case of a 28-year-old female patient in her 16th week of pregnancy with community-acquired pneumonia who presented during an asthma attack, which led to hypoxic respiratory failure. She was successfully treated using NIV. This case is worth discussing as it includes two clinical conditions in which NIV is often considered contraindicated.

Caner, Hanife; Eryuksel, Emel; Kosar, Filiz

2013-01-01

308

Fracture toughness and failure mechanisms in unreinforced and long-glass-fibre-reinforced PA66\\/PP blends  

Microsoft Academic Search

In this paper unreinforced and long-glass-fibre-reinforced PA66\\/PP blends with different glass-fibre sizing were studied with respect to their fracture toughness determined by the typical Kc method. The fracture surfaces of these blends were studied by scanning electron microscopy in order to characterize the failure mechanisms. For the unreinforced blends a decrease in fracture toughness was observed when 25 wt% of

T. Harmia; K. Friedrich

1995-01-01

309

Akt substrate TBC1D1 regulates GLUT1 expression through the mTOR pathway in 3T3-L1 adipocytes  

PubMed Central

Multiple studies have suggested that the protein kinase Akt/PKB (protein kinase B) is required for insulin-stimulated glucose transport in skeletal muscle and adipose cells. In an attempt to understand links between Akt activation and glucose transport regulation, we applied mass spectrometry-based proteomics and bioinformatics approaches to identify potential Akt substrates containing the phospho-Akt substrate motif RXRXXpS/T. The present study describes the identification of the Rab GAP (GTPase-activating protein)-domain containing protein TBC1D1 [TBC (Tre-2/Bub2/Cdc16) domain family, member 1], which is closely related to TBC1D4 [TBC domain family, member 4, also denoted AS160 (Akt substrate of 160 kDa)], as an Akt substrate that is phosphorylated at Thr590. RNAi (RNA interference)-me-diated silencing of TBC1D1 elevated basal deoxyglucose uptake by approx. 61% in 3T3-L1 mouse embryo adipocytes, while the suppression of TBC1D4 and RapGAP220 under the same conditions had little effect on basal and insulin-stimulated deoxy-glucose uptake. Silencing of TBC1D1 strongly increased expression of the GLUT1 glucose transporter but not GLUT4 in cultured adipocytes, whereas the decrease in TBC1D4 had no effect. Remarkably, loss of TBC1D1 in 3T3-L1 adipocytes activated the mTOR (mammalian target of rapamycin)-p70 S6 protein kinase pathway, and the increase in GLUT1 expression in the cells treated with TBC1D1 siRNA (small interfering RNA) was blocked by the mTOR inhibitor rapamycin. Furthermore, overexpression of the mutant TBC1D1-T590A, lacking the putative Akt/PKB phosphorylation site, inhibited insulin stimulation of p70 S6 kinase phosphorylation at Thr389, a phosphorylation induced by mTOR. Taken together, our data suggest that TBC1D1 may be involved in controlling GLUT1 glucose transporter expression through the mTOR-p70 S6 kinase pathway.

Zhou, Qiong L.; Jiang, Zhen Y.; Holik, John; Chawla, Anil; Hagan, G. Nana; Leszyk, John; Czech, Michael P.

2010-01-01

310

Market failure in the pharmaceutical industry and how it can be overcome: the CureShare mechanism.  

PubMed

Allowing patients to take part in the initial investment for the development of cures for their illnesses can, under certain conditions, lead to the development of drugs that would have otherwise not been developed and to a dramatic welfare increase. We theoretically analyze these conditions. The suggested patient investment mechanism, which we call CureShare, does not involve any philanthropy or government subsidies. It is simply a way to overcome market failure. Based on empirical data, we estimate that applying this mechanism may save thousands of lives annually and may dramatically improve the quality of many others. PMID:23417217

Levy, Moshe; Rizansky, Adi

2013-02-17

311

Active wear and failure mechanisms of TiN-Coated high speed steel and tin-coated cemented carbide tools when machining powder metallurgically made stainless steels  

Microsoft Academic Search

In this study, active wear and failure mechanisms of both TiN-coated high speed steel and TiN-coated cemented carbide tools\\u000a when machining stainless steels made by powder metallurgy in low and high cutting speed ranges, respectively, have been investigated.\\u000a Abrasive wear mechanisms, fatigue-induced failure, and adhesive and diffusion wear mechanisms mainly affected the tool life\\u000a of TiN-coated high speed steel tools

Laizhu Jiang; Hannu Hänninen; Jukka Paro; Veijo Kauppinen

1996-01-01

312

Mechanism of electromigration-induced failure in the 97Pb-3Sn and 37Pb-63Sn composite solder joints  

NASA Astrophysics Data System (ADS)

The electromigration-induced failure in the composite solder joints consisting of 97Pb-3Sn on the chip side and 37Pb-63Sn on the substrate side was studied. The under-bump metallization (UBM) on the chip side was 5 ?m thick electroplated Cu coated on sputtered TiW/Cu and on the substrate side was electroless Ni/Au. It was observed that failure occurred in joints in a downward electron flow (from chip to substrate), while those joints having the opposite current polarity showed only minor changes. During electromigration, in addition to the compositional change by the moving of Pb atoms in the same direction as the electrons, current crowding was observed inside the UBM and it enhanced the phase transformation of Cu to Cu3Sn and to Cu6Sn5 at the UBM/solder interface. Due to the growth of Cu6Sn5, the Cu UBM was consumed rapidly, resulting in void formation-induced failure at the cathode side. The Cu6Sn5 intermetallic compound and void were first initiated from the upper left-hand side corner of the contact window which matches the current crowding region. The sequence of Cu UBM consumption and void formation is presented. The current crowding has been confirmed by simulation. The mechanism of electromigration-induced failure in the composite solder joint structure is discussed.

Nah, J. W.; Paik, K. W.; Suh, J. O.; Tu, K. N.

2003-12-01

313

Impermeable thin AI2O3 overlay for TBC protection from sulfate and vanadate attack in gas turbines  

SciTech Connect

In order to improve the hot corrosion resistance of conventional YSZ TBC system, a dense and continues overlay of Al{sub 2}O{sub 3} coating of about 0.1-25 {micro}m thick was deposited on the surface of TBC by EB-PVD, high velocity oxy-fuel (HVOF) spray and composite-sol-gel (CSG) techniques. Hot corrosion tests were carried out on the TBC with and without Al{sub 2}O{sub 3} coating in molten salts mixtures (Na{sub 2}SO{sub 4} + 5%V{sub 2}O{sub 5}) at 950 C for 10h. The microstructures of TBC and overlay before and after exposure were examined by means of scanning electron microscopy (SEM), energy-dispersive X-ray spectrometer (EDX), X-ray diffraction (XRD) and secondary ion mass spectrometry (SIMS). In order to investigate the effect of Al{sub 2}O{sub 3} overlay on degradation and spalling of the TBC, indentation test has been employed to study spallation behaviors of YSZ coating with and without Al{sub 2}O{sub 3} overlay. It has been found that TBC will react with V{sub 2}O5 to form YVO{sub 4} in hot corrosion tests. A substantial amount of M-phase of ZrO{sub 2} was formed due to the leaching of Y{sub 2}O{sub 3} from YSZ. During hot corrosion test, there were no significant interactions between overlay Al{sub 2}O{sub 3} coating and molten salts. After exposure, the alumina coating, especially produced by HVOF, was still very dense and cover the surface of YSZ, although they had been translated to {alpha} - Al{sub 2}O{sub 3} from original {gamma} - Al{sub 2}O{sub 3}. As a result, Al{sub 2}O{sub 3} overlay coating decreased the penetration of salts into the YSZ and prevented the YSZ from the attack by molten salts containing vanadium. Accordingly, only a few M-phase was formed in YSZ TBC, compared with TBC without overlay coating. The penetration of salts into alumina coating was thought to be through microcracks formed in overlay Al{sub 2}O{sub 3} coating and at the interface between alumina and zirconia due to the presence of tensile stress in the alumina coating. Al{sub 2}O{sub 3} overlay acted as a barrier against the infiltration of the molten salt into the YSZ coating during exposure, thus significantly reduced the amount of M-phase of ZrO{sub 2} in YSZ coating. However, a thick Al{sub 2}O{sub 3} overlay was harmful for TBC by increasing compressive stress which causes crack and spalling of YSZ coating. As a result, a dense and thin Al{sub 2}O{sub 3} overlay is critical for simultaneously preventing YSZ from hot corrosion and spalling.

Scott X. Mao

2005-10-30

314

355 nm diffractive beam shaper: modes and mechanism of failure and its impact on operational lifetime  

Microsoft Academic Search

One of the key tasks of a laser systems field service engineer is to determine where and why an optical system is not performing to specification or why it has failed prematurely. On most occasions, the field service engineer is faced with a completely failed optical system and is left to isolate how and where the failure occurred and if

Todd E. Lizotte

2009-01-01

315

Creep mechanism fractography analysis on SnPb eutectic solder joint failure  

Microsoft Academic Search

Microstructural fracture mode observed in creep can be divided into intergranular and transgranular fracture. Depending on temperature and stress condition, creep fracture mode is decided. To design an accelerated life test, it should be confirmed that the failure mode in the accelerated test is identical to the mode in real field condition. Selecting optimal conditions of temperature and stress in

Chulmin Oh; Changwoon Han; Byungsuk Song; Wonsik Hong

2009-01-01

316

Drop impact life prediction models with solder joint failure modes and mechanisms  

Microsoft Academic Search

Drop impact performance of solder joints of IC packages becomes a great concern for handheld products, such as mobile phones and PDA. Failure modes of solder joints under drop impact depend on solder alloys, interfacial strength, intermetallic formulation, and etc. Submodeling technique is applied to model detailed structure of critical solder joint. The stress and strain concentration at different locations

Jing-en Luana; Tong Yan Tee; Xueren Zhanga; E. Hussa; Jason Wang; C. Ford; K. C. Jend

2005-01-01

317

A comparative study of the failure mechanisms encountered in drop and large amplitude vibration tests  

Microsoft Academic Search

Drop tests are commonly used to study the reliability of components under shock loading conditions. However, to overcome some of the drawbacks inherent to drop testing systems, the applicability of large amplitude vibration test to reliability assessment has been investigated by comparing the vibration behaviors and failure modes of component boards in the two tests. The component boards and the

P. Marjamaki; T. T. Mattila; J. K. Kivilahti

2006-01-01

318

Myocyte Recovery After Mechanical Circulatory Support in Humans With End-Stage Heart Failure  

Microsoft Academic Search

Background—The failing myocardium is characterized by decreased force production, slowed relaxation, and depressed responses to b-adrenergic stimulation. In some heart failure patients, heart function is so poor that a left ventricular assist device (LVAD) is inserted as a bridge to transplantation. In the present research, we investigated whether circulatory support with an LVAD influenced the functional properties of myocytes from

Konstantina Dipla; Julian A. Mattiello; Valluvan Jeevanandam; Steven R. Houser; Kenneth B. Margulies

319

Mechanical circulatory support for advanced heart failure: effect of patient selection on outcome  

Microsoft Academic Search

Background—Use of wearable left ventricular assist systems (LVAS) in the treatment of advanced heart failure has steadily increased since 1993, when these devices became generally available in Europe. The aim of this study was to identify in an unselected cohort of LVAS recipients those aspects of patient selection that have an impact on postimplant survival. Methods and Results—Data were obtained

Mario C. Deng; Matthias Loebe; Aly El-Banayosy

2001-01-01

320

Mechanical circulatory support in severe heart failure: single-center experience  

Microsoft Academic Search

Ventricular assist devices (VADs) have become important therapeutic tools to treat patients with end-stage cardiac failure. VADs are an essential component of transplantation programs as they successfully bridge individuals who would otherwise die. Recently left ventricular VAD (LVAD) therapy has been proposed as alternative to heart transplantation (HTx) for patients who are not transplant candidates. Other indications have now expanded

E Vitali; M Lanfranconi; G Bruschi; E Ribera; A Garatti; T Colombo; C. F Russo

2004-01-01

321

Failure mechanisms governing reinforcement length of geogrid reinforced soil retaining walls  

Microsoft Academic Search

Current design practice of reinforced soil retaining walls is based on the limit equilibrium approach. The walls are designed for both external and internal stability criteria. Design reinforcement length should be such that minimum required safety factors are fulfilled for all failure modes. Most agencies require minimum reinforcement length equal to 70 percent of wall height. However, it is not

Ömer Bilgin

2009-01-01

322

Root-soil mechanical interactions during pullout and failure of root bundles  

Microsoft Academic Search

Roots play a major role in reinforcing and stabilizing steep hillslopes. Most studies in slope stability implement root reinforcement as an apparent cohesion by upscaling the behavior of static individual roots. Recent studies, however, have shown that much better predictions of slope stability can be made if the progressive failure of bundles of roots are considered. The characteristics of progressive

M. Schwarz; D. Cohen; D. Or

2010-01-01

323

A finite element analysis of dynamic fracture initiation by ductile failure mechanisms in a 4340 steel  

Microsoft Academic Search

In some recent dropweight impact experiments [5] with pre-notched bend specimens of 4340 steel, it was observed that considerable crack tunneling occurred in the interior of the specimen prior to gross fracture initiation on the free surfaces. The final failure of the side ligaments happened because of shear lip formation. The tunneled region is characterized by a flat, fibrous fracture

M. Jha; R. Narasimhan

1992-01-01

324

Failure loads of mechanical fastened pinned and bolted composite joints with two serial holes  

Microsoft Academic Search

An experimental and numerical study has been carried out to investigate the first failure load and the bearing strength behavior of pinned joints of glass fiber reinforced woven epoxy composite prepregs with two serial holes subjected to traction forces by two serial rigid pins. In the experiments, a number of parameters such as the edge distance-to- upper hole diameter (E\\/D),

Mustafa Ozen; Onur Sayman

2011-01-01

325

Prevent boiler tube failures--Part 1: Fire-side mechanisms  

Microsoft Academic Search

A boiler tube fails when the structural integrity of the tube is compromised. For boilers that have been previously operating, some change must occur to effect tube failure. Usually this change is wrought through some combination of corrosion and erosion acting on the boiler tube to weaken it. Boiler tubes depend on a complex metal oxide layer for protection from

Colannino

1993-01-01

326

A Study on Wire Ball\\/Pad Open Failure Mechanism of a Multi-Stack Package (MSP) under High Temperature Storage (HTS) Condition  

Microsoft Academic Search

The mechanism of a wire ball\\/pad open failure at a gold wire and bonding pad interface of a multi-stack package (MSP) under high temperature storage (HTS) condition, 150 degC, is studied. Failure analysis using FE-SEM (field emission) and FIB-SEM (focused ion beam) was conducted. The analysis revealed that the main factors that contribute to a ball\\/pad failure were the tensile

Se Young Yang; Hyeong-Jik Byun; Sang-Wook Park; Wang-Joo Lee

2007-01-01

327

On-Line Thermal Barrier Coating Monitoring for Real-Time Failure Protection and Life Maximization  

SciTech Connect

Under the sponsorship of the U. S. Department of Energy's National Energy Laboratory, Siemens Westinghouse Power Corporation proposes a four year program titled, ''On-Line Thermal Barrier Coating (TBC) Monitor for Real-Time Failure Protection and Life Maximization'', to develop, build and install the first generation of an on-line TBC monitoring system for use on land -based advanced gas turbines (AGT). Federal deregulation in electric power generation has accelerated power plant owner's demand for improved reliability availability maintainability (RAM) of the land-based advanced gas turbines. As a result, firing temperatures have been increased substantially in the advanced turbine engines, and the TBCs have been developed for maximum protection and life of all critical engine components operating at these higher temperatures. Losing TBC protection can therefore accelerate the degradation of substrate components materials and eventually lead to a premature failure of critical component and costly unscheduled power outages. This program seeks to substantially improve the operating life of high cost gas turbine components using TBC; thereby, lowering the cost of maintenance leading to lower cost of electricity. Siemens Westinghouse Power Corporation has teamed with Indigo Systems; a supplier of state-of-the-art infrared camera systems, and Wayne State University, a leading research organization.

Dennis H. LeMieux

2004-10-01

328

On-Line Thermal Barrier Coating Monitoring for Real-Time Failure Protection and Life Maximization  

SciTech Connect

Under the sponsorship of the U. S. Department of Energy's National Energy Laboratory, Siemens Westinghouse Power Corporation proposes a four year program titled, ''On-Line Thermal Barrier Coating (TBC) Monitor for Real-Time Failure Protection and Life Maximization'', to develop, build and install the first generation of an on-line TBC monitoring system for use on land-based advanced gas turbines (AGT). Federal deregulation in electric power generation has accelerated power plant owner's demand for improved reliability availability maintainability (RAM) of the land-based advanced gas turbines. As a result, firing temperatures have been increased substantially in the advanced turbine engines, and the TBCs have been developed for maximum protection and life of all critical engine components operating at these higher temperatures. Losing TBC protection can therefore accelerate the degradation of substrate components materials and eventually lead to a premature failure of critical component and costly unscheduled power outages. This program seeks to substantially improve the operating life of high cost gas turbine components using TBC; thereby, lowering the cost of maintenance leading to lower cost of electricity. Siemens Westinghouse Power Corporation has teamed with Indigo Systems, a supplier of state-of-the-art infrared camera systems, and Wayne State University, a leading research organization in the field of infrared non-destructive examination (NDE), to complete the program.

Dennis H. LeMieux

2005-04-01

329

Ibuprofen-associated renal dysfunction. Pathophysiologic mechanisms of acute renal failure, hyperkalemia, tubular necrosis, and proteinuria.  

PubMed

Ibuprofen-associated, acute, reversible renal failure with hyperkalemia, tubular necrosis, and proteinuria developed in a patient who had no predisposing underlying disease. A renal biopsy specimen revealed mesangial hypercellularity without glomerular crescent formation. A profound interstitial nephritis with focal inflammatory cell infiltrates of predominantly mononuclear cells and neutrophils as well as focal tubular destruction was seen. Vasculitis was not observed. Ultrastructural studies confirmed the light microscopic diagnosis of a tubulointerstitial nephritis and, in addition, indicated the presence of electron-dense mesangial and subepithelial deposits. Direct immunofluorescence examination showed diffuse mesangial IgM and C3 deposition as well as vascular C3 deposition. Renal failure rapidly resolved after discontinuation of ibuprofen therapy and initiation of steroid therapy, with return to normal levels of serum creatinine, urea nitrogen, potassium, and sodium. Proteinuria also resolved. PMID:3689062

Marasco, W A; Gikas, P W; Azziz-Baumgartner, R; Hyzy, R; Eldredge, C J; Stross, J

1987-12-01

330

Femoral stem failures in total hip arthroplasty: an unusual causal mechanism.  

PubMed

Femoral stem failure in a 55-year-old man and a 33-year-old woman who had a Charnley and T28 stainless steel total hip arthroplasty, respectively, at the level of the transmedullar horizontal trochanteric wire, possibly resulted from intraoperative damage to the lateral aspect of the stem of the femoral component. The damage was inflicted by either the drill or the wire itself. After three and two years' follow-up there were no signs of cement loosening; yet, this component failure demonstrates that there was constant motion within the cement. The stem broke before there was any radiographic evidence of cement loosening, and the patients were basically asymptomatic. It is also clear from this experience that horizontal transmedullary transtrochanteric wiring should be viewed with concern for fear of initiating stress fracture in the femoral prosthetic stem if drilling is performed after the component is cemented. PMID:7075056

Ritter, M A; Kiester, P D

1982-05-01

331

Mechanism of electromigration failure in Al thin film interconnects containing Sc  

SciTech Connect

In order to understand the role of Sc on electromigration (EM) failure, Al interconnects with 0.1 and 0.3 wt.% Sc sere tested as a function of post-pattern annealing time. In response to the evolution of the line structure, the statistics of lifetime evolved. While the addition of Sc greatly reduces the rate of evolution of the failure statistics because the grain growth rate decreases, the MTF variation was found to be very similar to that of pure Al. These observations seem to show that Sc has little influence on the kinetics of Al EM; however, it has some influence on the EM resistance of the line since it is an efficient grain refiner. Unlike Cu in Al, Sc does not seem to migrate, which may explain its lack of influence on the kinetics of Al EM.

Kim, Choong-un; Kang, S.H.; Morris, J.W. Jr. [Lawrence Berkeley Lab., CA (United States); Genin, F.Y. [Lawrence Livermore National Lab., CA (United States)

1995-05-01

332

Metabolic encephalopathy as a complication of renal failure: mechanisms and mediators.  

PubMed

Among patients with end-stage renal disease, nervous system dysfunction remains a major cause of disability. Patients with chronic renal failure who have not yet received dialysis may develop symptoms ranging from mild sensorial clouding to delirium and coma. Dialysis itself is associated with at least three distinct disorders of the CNS: dialysis disequilibrium syndrome; dialysis dementia; and progressive intellectual dysfunction. Peripheral neuropathy is also a major cause of disability in uremic subjects. It is believed that aluminum contributes to the pathogenesis of dialysis dementia. Biochemically, brain calcium is elevated in patients with renal failure, probably because of actions of parathyroid hormone on the brain. The diagnosis of dialysis disequilibrium syndrome, intellectual dysfunction, dialysis dementia, and uremic neuropathy can be made by the characteristic clinical pictures of these syndromes and the exclusion of other causes of nervous system dysfunction. PMID:7804801

Fraser, C L; Arieff, A I

1994-11-01

333

Drug Insight: statins for nonischemic heart failure—evidence and potential mechanisms  

Microsoft Academic Search

While 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors, also known as statins, have a well-established in role in the treatment and prevention of ischemic coronary artery disease, their utility in the setting of heart failure (HF) and left ventricular (LV) dysfunction remains under investigation. Although a reduction in LDL is the major effect of statin therapy, pleiotropic effects have been demonstrated, which could

Antonio Abbate; Valentin Fuster; George W Vetrovec; Michael J Lipinski

2007-01-01

334

Failure analysis mechanisms of miniaturized multilayer ceramic capacitors under normal service conditions  

Microsoft Academic Search

The authors report on failure analysis results on miniaturized multilayer ceramic capacitors (`0402', `0603', `0805', and `1206' sizes) which have been subjected to various degrees of thermal shock up to 450°C by ice-water or dry-ice quenching. The thermal shock resistance of `0402' multilayer ceramic capacitors is found to be about 400°C and considerably better than that of the larger ones.

Y. C. Chan; F. Yeung

1993-01-01

335

Screening for target Rabs of TBC (Tre-2/Bub2/Cdc16) domain-containing proteins based on their Rab-binding activity.  

PubMed

It has recently been proposed that the TBC (Tre2/Bub2/Cdc16) domain functions as a GAP (GTPase-activating protein) domain for small GTPase Rab. Because of the large number of Rab proteins in mammals, however, most TBC domains have never been investigated for Rab-GAP activity. In this study we established panels of the GTP-fixed form of 60 different Rabs constructed in pGAD-C1, a yeast two-hybrid bait vector. We also constructed a yeast two-hybrid prey vector (pGBDU-C1) that harbors the cDNA of 40 distinct TBC proteins. Systematic investigation of 2400 combinations of 60 GTP-fixed Rabs and 40 TBC proteins by yeast two-hybrid screening revealed that seven TBC proteins specifically and differentially interact with specific Rabs (e.g. OATL1 interacts with Rab2A; FLJ12085 with Rab5A/B/C; and Evi5-like with Rab10). Measurement of in vitro Rab-GAP activity revealed that OATL1 and Evi5-like actually possess significant Rab2A- and Rab10-GAP activity, respectively, but that FLJ12085 do not display Rab5A-GAP activity at all. These results indicate that specific interaction between TBC protein and Rab would be a useful indicator for screening for the target Rabs of some TBC/Rab-GAP domains, but that there is little correlation between the Rab-binding activity and Rab-GAP activity of other TBC proteins. PMID:16923123

Itoh, Takashi; Satoh, Megumi; Kanno, Eiko; Fukuda, Mitsunori

2006-09-01

336

Multidisciplinary analysis of the operational temperature increase of turbine blades in combustion engines by application of the ceramic thermal barrier coatings (TBC)  

Microsoft Academic Search

The improvement of the temperature resistance of the aircraft engine elements can be obtained by application of a single ceramic thermal barrier coating (TBC) (e.g. Noda [1]) or several composite layers (e.g. Sadowski [2]). Engine elements protected by TBC can work safely in elevated temperature range above 1000°C. Continuous endeavour to increase thermal resistance of engine the elements requires, apart

T. Sadowski; P. Golewski

2011-01-01

337

Understanding the failure mechanisms of microwave bipolar transistors caused by electrostatic discharge  

NASA Astrophysics Data System (ADS)

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.

Jin, Liu; Yongguang, Chen; Zhiliang, Tan; Jie, Yang; Xijun, Zhang; Zhenxing, Wang

2011-10-01

338

Practical method of control of TBC in a population of tudents belonging to the Sapienza University of Rome, Italy.  

PubMed

Aim: To describe the surveillance and control protocol for tuberculosis in healthcare students in use at the CMO of University "Sapienza" and founded on a dedicated database. Methods: Analysis of health certificates through a dedicated data storage software based on Microsoft Access 2007. Results: Students resulting positive to Mantoux test who did not undergo second-level examination (chest X-ray, TB Gold, prophylaxis) are invited to refer themselves within ten days to the infectious disease specialist. Conclusion: the methodological analysis, refined over the years by the CMO staff of the Sapienza University of Rome, allowed to match clinical certification data, to rapidly focus upon TBC spread control among healthcare settings, to register new students time zero before their admission to courses and potential professional exposure, to perform epidemiological studies aimed to increase TBC control through healthcare system released clinical certification confirmation. PMID:24048180

Sernia, S; Antoniozzi, T; Ortis, M

339

Fis1 acts as a mitochondrial recruitment factor for TBC1D15 that is involved in regulation of mitochondrial morphology.  

PubMed

In yeast, C-tail-anchored mitochondrial outer membrane protein Fis1 recruits the mitochondrial-fission-regulating GTPase Dnm1 to mitochondrial fission sites. However, the function of its mammalian homologue remains enigmatic because it has been reported to be dispensable for the mitochondrial recruitment of Drp1, a mammalian homologue of Dnm1. We identified TBC1D15 as a Fis1-binding protein in HeLa cell extracts. Immunoprecipitation revealed that Fis1 efficiently interacts with TBC1D15 but not with Drp1. Bacterially expressed Fis1 and TBC1D15 formed a direct and stable complex. Exogenously expressed TBC1D15 localized mainly in cytoplasm in HeLa cells, but when coexpressed with Fis1 it localized to mitochondria. Knockdown of TBC1D15 induced highly developed mitochondrial network structures similar to the effect of Fis1 knockdown, suggesting that the TBC1D15 and Fis1 are associated with the regulation of mitochondrial morphology independently of Drp1. These data suggest that Fis1 acts as a mitochondrial receptor in the recruitment of mitochondrial morphology protein in mammalian cells. PMID:23077178

Onoue, Kenta; Jofuku, Akihiro; Ban-Ishihara, Reiko; Ishihara, Takaya; Maeda, Maki; Koshiba, Takumi; Itoh, Takashi; Fukuda, Mitsunori; Otera, Hidenori; Oka, Toshihiko; Takano, Hiroyoshi; Mizushima, Noboru; Mihara, Katsuyoshi; Ishihara, Naotada

2012-10-17

340

Investigation of meso-failure behavior of rock under thermal-mechanical coupled effects based on high temperature SEM  

NASA Astrophysics Data System (ADS)

It is extremely important to study and understand the deformation behavior and strength characteristics of rocks under thermal-mechanical (TM) coupling effects. Failure behavior and strength characteristics of Pingdingshan sandstone were investigated at room temperatures up to 300°C in an internally heated apparatus and tensile load through meso-scale laboratory experiments in this work. 33 experiments have successfully been conducted for Pingdingshan sandstone. Experimental results indicated that the tensile strength increased slowly with temperatures from 25°C to 100°C, and then sharply jumped from 100°C to 150°C, and finally decreased slightly with temperatures from 150°C to 300°C. And about 150°C is the threshold temperature of strength and thermal cracking. At low temperatures (25°C-150°C), sandstone strength is determined by relatively weak clay cement. However, at higher temperatures (150°C-300°C), because of the strength enhancement of clay cement, sandstone strength is controlled by both mineral particles and clay cement. The effects of cement clay, micro-cracks closing, and thermal cracking were the possible reasons for our detailed analysis. In addition, the typical fracture position maps and nominal stress-strain curves indicated that the temperature had strong effects on the failure mechanism of sandstone. The fractograph implied that the dominant fracture mechanism tended to transform from brittle at low temperatures to ductile at high temperatures.

Zuo, JianPing; Xie, HePing; Zhou, HongWei

2012-10-01

341

Identification of failure modes in portable electronics subjected to mechanical-shock using supervised learning of damage progression  

Microsoft Academic Search

An anomaly detection and failure mode classification method has been developed for electronic assemblies with multiple failure modes. The presented prognostic health management method targets the pre-failure space of the electronic assembly life to trigger repair or replacement of impending failures. Presently, health monitoring systems focus on reactive diagnostic detection of failure modes. Examples of diagnostic detection include the built

Pradeep Lall; Prashant Gupta; Kai Goebel

2011-01-01

342

Improved Outcomes of Patients with End-stage Cystic Fibrosis Requiring Invasive Mechanical Ventilation for Acute Respiratory Failure  

Microsoft Academic Search

Study Objectives  The aim of this study was to determine the effects of an antibiotic strategy with intravenous (IV) continuous infusion of\\u000a a ?-lactam (CIBL) antibiotic and high-dose extended-interval (HDEI) tobramycin upon outcomes in patients with cystic fibrosis\\u000a (CF) requiring invasive mechanical ventilation (IMV) for acute respiratory failure.\\u000a \\u000a \\u000a \\u000a \\u000a Design  The study was a retrospective review from June 1, 2006, to December 1,

Don Hayes Jr; Heidi M. Mansour

343

Formation Mechanism of Type IV Failure in High Cr Ferritic Heat-Resistant Steel-Welded Joint  

NASA Astrophysics Data System (ADS)

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.

Liu, Y.; Tsukamoto, S.; Shirane, T.; Abe, F.

2013-10-01

344

Distribution of coastal cliffs in Kerala, India: their mechanisms of failure and related human engineering response  

NASA Astrophysics Data System (ADS)

The 560-km-long Kerala coast is characterised by long barriers with narrow beaches and steep cliffs. Distribution of cliffs from nine sections measuring a cumulative length of 63.5 km is evaluated in ArcGIS Software using topomaps and field survey data. The cliff sections in the southern coast comprise both permeable and impermeable rocks, whereas those along northern coast are comprised of either Precambrian crystalline and/or Tertiary formations. Notches, caves and even small arches are developed in Cannanore, Dharmadam and Kadalundi cliffs, where only primary laterites are exposed to wave attack. Stacks composed of laterite and Precambrian crystallines found in nearshore of cliffed coast indicate recession of shoreline. Mass wasting, mudslide and mudflow type of cliff failures are common in permeable to semi-permeable rocks, whereas rotational sliding, rockfall and toppling failure are found in hard rock cliffs. Retreat of cliff sections are induced by natural or anthropogenic activities or both. Rate of recession vary from a few centimetres to one metre/year depending upon the nature of lithology, structures and recession agents acting upon the cliffs. Various methods of cliff protection for e.g. hard structures—revetments, groins, seawalls, breakwater and jetties—and soft measures—artificial reefs/marsh creation, floating breakwaters, beach nourishment, beach scraping and vegetation planting—are suggested.

Kumar, Avinash; Seralathan, P.; Jayappa, K. S.

2009-08-01

345

Failure prediction analysis of an ACCC conductor subjected to thermal and mechanical stresses  

Microsoft Academic Search

In this work, the Aluminum Conductor Composite Core¿ (ACCC) was numerically investigated to evaluate stress distributions when subjected to thermal and mechanical loads. The thermal analysis was conducted to simulate the cooling cycle of the rod from 250°C to room temperature. Three types of mechanical loads were considered, namely axial tension, small bending, and large bending conditions. This was done

B. Burks; D. L. Armentrout; M. Kumosa

2010-01-01

346

Mechanical failure in COB-technology using glob-top encapsulation  

Microsoft Academic Search

There are several reasons for mechanical stresses in “globbed” assemblies. For example: cure shrinkage; thermal gradients; and moisture diffusion. Thermal mismatch between substrate, silicon die, and encapsulant represent a main reason for thermally induced stresses and is investigated in detail. The filled polymers used have shown temperature, time, and moisture dependent mechanical characteristics. The viscoelastic properties of the encapsulant below

Rainer Dudek; Dietmar Vogel; Bernd Michel

1996-01-01

347

Exercise-induced TBC1D1 Ser237 phosphorylation and 14-3-3 protein binding capacity in human skeletal muscle  

PubMed Central

TBC1D1 is a Rab-GTPase activating protein involved in regulation of GLUT4 translocation in skeletal muscle. We here evaluated exercise-induced regulation of TBC1D1 Ser237 phosphorylation and 14-3-3 protein binding capacity in human skeletal muscle. In separate experiments healthy men performed all-out cycle exercise lasting either 30 s, 2 min or 20 min. After all exercise protocols, TBC1D1 Ser237 phosphorylation increased (?70–230%, P < 0.005), with the greatest response observed after 20 min of cycling. Interestingly, capacity of TBC1D1 to bind 14-3-3 protein showed a similar pattern of regulation, increasing 60–250% (P < 0.001). Furthermore, recombinant 5?AMP-activated protein kinase (AMPK) induced both Ser237 phosphorylation and 14-3-3 binding properties on human TBC1D1 when evaluated in vitro. To further characterize the role of AMPK as an upstream kinase regulating TBC1D1, extensor digitorum longus muscle (EDL) from whole body ?1 or ?2 AMPK knock-out and wild-type mice were stimulated to contract in vitro. In wild-type and ?1 knock-out mice, contractions resulted in a similar ?100% increase (P < 0.001) in Ser237 phosphorylation. Interestingly, muscle of ?2 knock-out mice were characterized by reduced protein content of TBC1D1 (?50%, P < 0.001) as well as in basal and contraction-stimulated (?60%, P < 0.001) Ser237 phosphorylation, even after correction for the reduced TBC1D1 protein content. This study shows that TBC1D1 is Ser237 phosphorylated and 14-3-3 protein binding capacity is increased in response to exercise in human skeletal muscle. Furthermore, we show that the catalytic ?2 AMPK subunit is the main (but probably not the only) donor of AMPK activity regulating TBC1D1 Ser237 phosphorylation in mouse EDL muscle.

Fr?sig, Christian; Pehm?ller, Christian; Birk, Jesper B; Richter, Erik A; Wojtaszewski, J?rgen F P

2010-01-01

348

Mechanisms of reduced contractility in an animal model of hypertensive heart failure.  

PubMed

1. Alterations in intracellular Ca(2+) homeostasis have frequently been implicated as underlying the contractile dysfunction of failing hearts. Contraction in cardiac muscle is due to a balance between sarcolemmal (SL) and sarcoplasmic reticulum (SR) Ca(2+) transport, which has been studied in single cells and small tissue samples. However, many studies have not used physiological temperatures and pacing rates, and this could be problematic given different temperature dependencies and kinetics for transport processes. 2. Spontaneously-hypertensive rats (SHR) and their age-matched Wistar Kyoto controls (WKY) provide an animal model of hypertensive failure with many features in common to heart failure in humans. Steady-state measurements of Ca(2+) and force showed that peak stress was reduced in trabeculae from failing SHR hearts in comparison to WKY, although the Ca(2+) transients were bigger and decayed more slowly. 3. Dynamic Ca(2+) cycling was investigated by determining the recirculation fraction (RF) of activator Ca(2+) through the SR between beats during recovery from experimental protocols that potentiated twitch force. No difference in RF between rat strains was found, although the RF was dependent on the potentiation protocol used. 4.?Superfusion with 10 mmol/L caffeine and 0 mmol/L [Ca(2+)](o) was used to measure SL Ca(2+) extrusion. The caffeine-induced [Ca(2+)](i) transient decayed more slowly in SHR trabeculae, suggesting that SL Ca(2+) extrusion was slower in SHR. 5. An ultrastructural immunohistochemical analysis of left ventricular free wall sections using confocal microscopy showed that t-tubule organization was disrupted in myocytes from SHR, with reduced labelling of the SR Ca(2+) -ATPase and Na(+) -Ca(2+) exchanger in comparison to WKY, with the latter possibly related to a lower fraction of t-tubules per unit cell volume. 6. We suggest that although Ca(2+) transport is altered in the progression to heart failure, force development is not limited by the amplitude of the Ca(2+) transient. Despite slower SR Ca(2+) transport, the recirculation fraction and dynamic response to a change of inotropic state minimally altered changes in the SHR model because there was a similar slowing in Ca(2+) extrusion across the surface membrane. PMID:21711381

Ward, Marie-Louise; Crossman, David J; Cannell, Mark B

2011-10-01

349

Direct correlation between mechanical failure and metallurgical reaction in flip chip solder joints  

NASA Astrophysics Data System (ADS)

We tested flip chip solder bonded Si samples under tensile and shear loading as a function of annealing time at 200 °C. The solder bump was eutectic SnPb and the underbump thin film metallization was Cu/Cr deposited on oxidized Si. We found that the failure mode is interfacial fracture and the fracture strength decreases rapidly with annealing time. From scanning electric microscope observations, the fracture occurs at the Cu-Sn/Cr interface. We conclude that it is the metallurgical reaction that has brought the solder into direct contact with the Cr surface. The weak joint is due to the spalling of Cu-Sn compound grains from the Cr surface, especially near the edges and corners of the joint.

Liu, C. Y.; Chen, Chih; Mal, A. K.; Tu, K. N.

1999-04-01

350

Tolerance Limits and Mechanisms of Failure of the Skeletal System under Impact Conditions.  

National Technical Information Service (NTIS)

This report is a summary of a statistical analysis of data obtained in several related studies on the mechanical, chemical, and histological properties of primate long bones before and after total body immobilization in plaster casts. Statistical correlat...

G. A. Graves A. A. Wolff

1983-01-01

351

Analysis of GaAs HBT failure mechanisms: impact on life test strategy  

Microsoft Academic Search

A field-induced degradation mechanism responsible for the surface current drift in GaAs HBT is identified on the basis of accelerated ageing tests under bias. Degradations of ohmic contact and metallisation are highlighted under high temperature storage. These results bring further evidence of both bias and temperature-induced degradation mechanisms in GaAs HBTs. As a consequence, a specific life test strategy similar

C. Maneux; N. Labat; N. Saysset; A. Touboul; Y. Danto; J.-M. Dumas; P. Launay; J. Dangla

1997-01-01

352

Dynamic Failure of a Lamina Meshwork in Cell Nuclei under Extreme Mechanical Deformation  

Microsoft Academic Search

The nuclear lamina is a structural protein meshwork at the inner nuclear membrane. It confers mechanical strength to the cell’s\\u000a nucleus and also sustains the overall structural integrity of the cell. The rupture of nuclear lamina is involved in many\\u000a physiologically extreme conditions, such as cell division, genetic disease, and injury. Yet, its rupture mechanisms and processes\\u000a are largely unknown

Zhao Qin; Markus J. Buehler

2011-01-01

353

Mechanical properties of coagulated albumin and failure mechanisms of liver repaired with the use of an argon-beam coagulator with albumin.  

PubMed

Hemostasis in the traumatized liver has been achieved by thermally denaturing topically applied albumin. In this article, the mechanical properties of liver and denatured albumin (solder) were measured, and the failure methods of liver repaired with albumin were identified. The ultimate tensile strength and Young's modulus were measured for healthy liver (N = 20) and thermally damaged liver (N = 20). The ultimate tensile strength and Young's modulus were measured for three concentrations of coagulated albumin (25, 38, and 53%) in a single layer and for two layers of denatured 38% albumin. Failure under tension of argon-beam coagulator soldered liver on the parenchymal surface (N = 30) with 38% albumin in two layers had a 70% occurrence for tearing at a mean stress of 39 kPa and a 23% occurrence for shearing at a mean stress of 7 kPa. Liver repaired on the interior surface (N = 11) failed in tension by tearing (64%) at a mean stress of 34 kPa and by shearing (36%) at a mean stress of 6 kPa. Argon-beam coagulator soldering with 38% albumin took 6 s/cm(2) for two layers of solder and gave the best balance of usability, strength, and matching of mechanical properties with those of the liver. PMID:12418016

Moffitt, T P; Baker, D A; Kirkpatrick, S J; Prahl, S A

2002-01-01

354

Mechanical support as failure intervention in patients with cavopulmonary shunts (MFICS): rationale and aims of a new registry of mechanical circulatory support in single ventricle patients.  

PubMed

It is now recognized that a majority of single ventricle patients, those with functionally univentricular hearts, who have survived palliative cavopulmonary connection will experience circulatory failure and end-organ dysfunction due to intrinsic inadequacies of a circulation supported by a single ventricle. Thus, there are an increasing number of patients with functional single ventricles presenting with failing circulations that may benefit from mechanical circulatory support (MCS). The paucity of experience with MCS in this population, even at high volume cardiac centers, contributes to limited available data to guide MCS device selection and management. Thus, a registry of MCS in this population would be beneficial to the field. A conference was convened in January 2012 of pediatric and adult cardiologists, pediatric cardiac intensivists, congenital heart surgeons, and adult cardiothoracic surgeons to discuss the current state of MCS, ventricular assist device, and total artificial heart therapy for patients who have undergone cavopulmonary connection, either superior cavopulmonary connection or total cavopulmonary connection. Specifically, individual experience and challenges with VAD therapy in this population was reviewed and creation of a multiinstitutional registry of MCS/ventricular assist device in this population was proposed. This document reflects the consensus from the meeting and provides a descriptive overview of the registry referred to as Mechanical Support as Failure Intervention in Patients with Cavopulmonary Shunts. PMID:23510301

Rossano, Joseph W; Woods, Ronald K; Berger, Stuart; Gaynor, J William; Ghanayem, Nancy; Morales, David L S; Ravishankar, Chitra; Mitchell, Michael E; Shah, Tejas K; Mahr, Claudius; Tweddell, James S; Adachi, Iki; Zangwill, Steven; Wearden, Peter D; Icenogle, Timothy B; Jaquiss, Robert D; Rychik, Jack

2013-03-20

355

Spatial and Temporal Mode-Of-Failure Transitions in Faulted Earth Materials: A Link Between Mechanics and Hydrology  

NASA Astrophysics Data System (ADS)

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 by the fault, the magnitude of displacement, and fluid-rock interactions. In faulted ignimbrite sequences, for example, faults vary laterally and vertically between deformation-band shear zones and faults with fractures; they are mechanically and hydraulically heterogeneous systems.

Goodwin, L. B.; Wilson, J. E.; Rawling, G. C.; Tobin, H.; Mozley, P. S.; Wilson, J. L.

2002-12-01

356

Relation of Carotid Artery Diameter With Cardiac Geometry and Mechanics in Heart Failure With Preserved Ejection Fraction  

PubMed Central

Background Central artery dilation and remodeling are associated with higher heart failure and cardiovascular risks. However, data regarding carotid artery diameter from hypertension to heart failure have remained elusive. We sought to investigate this issue by examining the association between carotid artery diameter and surrogates of ventricular dysfunction. Methods and Results Two hundred thirteen consecutive patients including 49 with heart failure and preserved ejection fraction (HFpEF), 116 with hypertension, and an additional 48 healthy participants underwent comprehensive echocardiography and tissue Doppler imaging. Ultrasonography of the common carotid arteries was performed for measurement of intima?media thickness and diameter (CCAD). Cardiac mechanics, including LV twist, were assessed by novel speckle?tracking software. A substantial graded enlargement of CCAD was observed across all 3 groups (6.8±0.6, 7.7±0.73, and 8.7±0.95 mm for normal, hypertension, and HFpEF groups, respectively; ANOVA P<0.001) and correlated with serum brain natriuretic peptide level (R2=0.31, P<0.001). Multivariable models showed that CCAD was associated with increased LV mass, LV mass?to?volume ratio (??coefficient=10.9 and 0.11, both P<0.001), reduced LV longitudinal and radial strain (??coeffficient=0.81 and ?3.1, both P<0.05), and twist (??coefficient=?0.84, P<0.05). CCAD set at 8.07 mm as a cut?off had a 77.6% sensitivity, 82.3% specificity, and area under the receiver operating characteristic curves (AUROC) of 0.86 (95% CI 0.80 to 0.92) in discriminating HFpEF. In addition, CCAD superimposed on myocardial deformation significantly expanded AUROC (for longitudinal strain, from 0.84 to 0.90, P of ?AUROC=0.02) in heart failure discrimination models. Conclusions Increased carotid artery diameter is associated with worse LV geometry, higher brain natriuretic peptide level, and reduced contractile mechanics in individuals with HFpEF.

Liao, Zhen-Yu; Peng, Ming-Cheng; Yun, Chun-Ho; Lai, Yau-Huei; Po, Helen L.; Hou, Charles Jia-Yin; Kuo, Jen-Yuan; Hung, Chung-Lieh; Wu, Yih-Jer; Bulwer, Bernard E.; Yeh, Hung-I; Tsai, Cheng-Ho

2012-01-01

357

Geophysical Survey To Understand Failure Mechanisms Involved On Deep Seated Landslides  

Microsoft Academic Search

The understanding of rupture processes involve on deep seated landslides and hence the prediction of such phenomenon is difficult for two main reasons. The first one, arise from the difficulty in estimating the mechanical behaviour of the whole mountain which is very different from that of a rock sample we can study on laboratory. This is mainly true in the

T. Lebourg; E. Tric; Y. Guglielmi; F. Cappa; A. Charmoille; S. Bouissou

2003-01-01

358

Fracture surfaces and the associated failure mechanisms in ductile iron with different matrices and load bearing  

Microsoft Academic Search

Ductile iron (DI) is a family of cast alloys that covers a wide range of mechanical properties, depending on its matrix microstructure. For instance, ferritic matrices used in parts, such as automotive suspension components, demand high impact properties and ductility among some of their main requirements. On the other hand, pearlitic and martensitic matrices are used when hardness, strength and

Ricardo A. Martínez

2010-01-01

359

Mechanisms of High-Temperature Fatigue Failure in Alloy 800H.  

National Technical Information Service (NTIS)

The damage mechanisms influencing the axial strain-controlled Low-Cycle Fatigue (LCF) behavior of alloy 800H at 850 C have been evaluated under conditions of equal tension/compression ramp rates (Fast-Fast (F-F): 4 X 10(sup -3)/s and Slow-Slow (S-S): 4 X ...

K. BhanuSankaraRao H. Schuster G. R. Halford

1996-01-01

360

Mechanisms of bioprosthetic heart valve failure: Fatigue causes collagen denaturation and glycosaminoglycan loss  

Microsoft Academic Search

Bioprosthetic heart valve (BPHV) degeneration, characterized by extracellular matrix deterioration, remod- eling, and calcification, is an important clinical problem ac- counting for thousands of surgeries annually. Here we re- port for the first time, in a series of in vitro accelerated fa- tigue studies (5-500 million cycles) with glutaraldehyde fixed porcine aortic valve bioprostheses, that the mechanical function of cardiac

Narendra Vyavahare; Matthew Ogle; Frederick J. Schoen; Robert Zand; D. Claire Gloeckner; Michael Sacks; Robert J. Levy

1999-01-01

361

Application of bimaterial interface corner failure mechanics to silicon\\/glass anodic bonds  

Microsoft Academic Search

Motivated by the existence of a universal singular stress field at bimaterial interface corners, a fair amount of work has been performed to support the use of the corresponding critical stress intensities to correlate fracture initiation. The approach is in the spirit of interface fracture mechanics but applicable to a different class of problems, specifically, when a crack does not

Paul E. W. Labossiere; Martin L. Dunn; Shawn J. Cunningham

2002-01-01

362

Noninvasive Mechanical Ventilation in the Weaning of Patients with Respiratory Failure Due to Chronic Obstructive Pulmonary Disease A Randomized, Controlled Trial  

Microsoft Academic Search

Background: In patients with acute exacerbations of chronic obstructive pulmonary disease, mechanical venti­ lation is often needed. The rate of weaning failure is high in these patients, and prolonged mechanical ventilation increases intubation-associated complications. Objective: To determine whether noninvasive ventila­ tion improves the outcome of weaning from invasive me­ chanical ventilation. Design: Multicenter, randomized trial. Setting: Three respiratory intensive care

Stefano Nava; Nicolino Ambrosino; Enrico Clini; Maurizio Prato; Giacomo Orlando; Michele Vitacca; Paolo Brigada; Claudio Fracchia; Fiorenzo Rubini

363

IMPERMEABLE THIN Al{sub 2}O{sub 3} OVERLAY FOR TBC PROTECTION FROM SULFATE AND VANADATE ATTACK IN GAS TURBINES  

SciTech Connect

To improve the hot corrosion resistance of YSZ thermal barrier coatings, a 25 {micro}m and a 2 {micro}m thick Al{sub 2}O{sub 3} overlay were deposited by HVOF thermal spray and by sol-gel coating method, respectively, onto to the surface of YSZ coating. Indenter test was employed to investigate the spalling of YSZ with and without Al{sub 2}O{sub 3} overlay after hot corrosion. The results showed that Al{sub 2}O{sub 3} overlay acted as a barrier against the infiltration of the molten salt into the YSZ coating during exposure, thus significantly reduced the amount of M-phase of ZrO{sub 2} in YSZ coating. However, a thick Al{sub 2}O{sub 3} overlay was harmful for TBC by increasing compressive stress which causes crack and spalling of YSZ coating. As a result, a dense and thin Al{sub 2}O{sub 3} overlay is critical for simultaneously preventing YSZ from hot corrosion and spalling. In the next reporting period, we will measure or calculate the residue stress within Al{sub 2}O{sub 3} overlay and YSZ coating to study the mechanism of effect of Al{sub 2}O{sub 3} overlay on spalling of YSZ coating.

Scott X. Mao

2003-12-16

364

Erythrocytosis in patients with renal failure on hemodialysis: study of underlying mechanism by in vitro erythroid culture assay.  

PubMed

Five patients with erythrocytosis associated with renal failure on maintenance hemodialysis were investigated for in vitro erythroid progenitor growth and the effect of their uremic sera on normal erythropoiesis. The duration of hemodialysis prior to discovery of erythrocytosis ranged from 1 week to 96 months. None had acquired cystic disease and no other known cause of increased erythropoietin (Epo) production was identified. With the presence of Epo in cultures, all five patients grew erythroid colonies within normal or higher than normal ranges. Three patients formed spontaneous erythroid colonies in the absence of added Epo; all three fulfilled the clinical diagnosis of polycythemia vera (PV). The uremic sera from patients with PV lacked either a stimulating or an inhibiting effect on normal erythropoiesis. The association between renal failure and PV was coincidental. The other two patients without endogenous erythroid colony formation had enhanced erythropoietic activity in their sera, which increasingly stimulated the erythroid colony growth by normal bone marrow cells as the concentration of the uremic serum was increased. The etiology of increased Epo production in these 2 patients remained undefined during long-term follow-up. The present study on five uremic patients with polycythemia showed two different underlying mechanisms of erythrocytosis--characteristic autonomous erythroid proliferation for PV in three patients and inappropriate idiopathic Epo production in two patients. PMID:8330648

Shih, L Y; Leu, M L

1993-08-01

365

Microstructural characteristics and technological properties of YSZ-type powders designed for thermal spraying of TBC  

NASA Astrophysics Data System (ADS)

This paper presents the experimental results relating to the microstructural characteristics and selected technological properties of yttria and partially stabilized zirconia (YSZ)-type powders designed for spraying thermal barrier coating (TBC) layers with the atmospheric plasma spraying (APS) method. Three types of powders with the following chemical compositions - ZrO2 × 8Y2O3, ZrO2 × 20Y2O3, and "nano" ZrO2 × 8Y2O3 - were subjected to analysis. Assessment of the surface morphology and inner structure of the powder particles was performed by scanning electron microscopy. The chemical composition of the powders was determined by energy-dispersive X-ray spectroscopy and inductively coupled plasma-optical emission spectroscopy (EDS and ICP-OES, respectively), with special attention focussed on the degree of uniformity in the arrangement of the alloy elements and the contents of carbon, sulphur, oxygen and nitrogen. The phase compositions were also analysed by using X-ray diffraction (XRD) and electron backscattered diffraction (EBSD). The technological properties describing density and friability of the analysed powders were assessed. The study showed that the analyzed conventional powders were predominantly characterized by spherical-shaped particles and single deformed particles. The surface of the conventional powder (8YSZ) was smooth with no porosity. The inner structure had a solid and clear grain structure with single voids. The 20YSZ-type powder showed a structure that typically arose from the agglomeration process. The surface was rough with noticeable voids, and the powder inner structure had a similar appearance. The nanostructured powder particles had a polyhedral shape that was typical of the grinding process. From the chemical composition analysis the powder materials had high metallurgical purity, and the alloy elements were uniformly arranged. The XRD phase composition analysis and the EBSD microanalysis confirmed the predominant presence of the ZrO2 tetragonal phase in the YSZ powders and the cubic phase in the 20YSZ powder.

Moskal, G.

2010-02-01

366

Microstructure and hydrogen induced failure mechanisms in iron-nickel weldments  

NASA Astrophysics Data System (ADS)

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 difference in the weld metal interfaces was the presence of M 7C3 precipitates in the planar solidification region. The formation of these precipitates, which were found in what was previously referred to as the "featureless-zone," were determined to be dependent on the carbon content of the Fe-base metal and the duration of the post-weld heat treatment. A high density of these ordered 100 nm-long by 10 nm-wide needle-like precipitates were found in the AISI 8630-IN 625 weldment in the 10 hour post-weld heat treatment condition while only the initial stages of their nucleation were evident in the F22-IN 625 15 hour post-weld heat treatment specimen. The study of the fractured specimens revealed that the M7C 3 carbides play a key role in the susceptibility to hydrogen embrittlement of the Fe-Ni butter weldments. The fractures initially nucleate along the isolated Fe-base metal -- discontinuous partially mixed zone interfaces. The M7C3 carbides accumulate hydrogen and then provide a low energy fracture path between the discontinuous partially mixed zones leading to catastrophic failure. The result is a fracture morphology that alternates between flat regions produced by fracture along the discontinuous partially mixed zones and cleavage-like fracture regions produced by fracture along the ordered carbide matrix interfaces.

Fenske, Jamey Alan

367

Nicorandil ameliorates mitochondrial dysfunction in doxorubicin-induced heart failure in rats: Possible mechanism of cardioprotection.  

PubMed

Despite of its known cardiotoxicity, doxorubicin is still a highly effective anti-neoplastic agent in the treatment of several cancers. In the present study, the cardioprotective effect of nicorandil was investigated on hemodynamic alterations and mitochondrial dysfunction induced by cumulative administration of doxorubicin in rats. Doxorubicin was injected i.p. over 2 weeks to obtain a cumulative dose of 18mg/kg. Nicorandil (3mg/kg/day) was given orally with or without doxorubicin treatment. Heart rate and aortic blood flow were recorded 24h after receiving the last dose of doxorubicin. Rats were then sacrificed and hearts were rapidly excised for estimation of caspase-3 activity, phosphocreatine and adenine nucleotides contents in addition to cytochrome c, Bcl2, Bax and caspase 3 expression. Moreover, mitochondrial oxidative phosphorylation capacity, creatine kinase activity and oxidative stress markers were measured together with the examination of DNA fragmentation and ultrastructural changes. Nicorandil was effective in alleviating the decrement of heart rate and aortic blood flow and the state of mitochondrial oxidative stress induced by doxorubicin cardiotoxicity. Nicorandil also preserved phosphocreatine and adenine nucleotides contents by restoring mitochondrial oxidative phosphorylation capacity and creatine kinase activity. Moreover, nicorandil provided a significant cardioprotection via inhibition of apoptotic signaling pathway, DNA fragmentation and mitochondrial ultrastructural changes. Interestingly, nicorandil did not interfere with cytotoxic effect of doxorubicin against the growth of solid Ehrlich carcinoma. In conclusion, nicorandil was effective against the development of doxorubicin-induced heart failure in rats as indicated by improvement of hemodynamic perturbations, mitochondrial dysfunction and ultrastructural changes without affecting its antitumor activity. PMID:23872193

Ahmed, Lamiaa A; El-Maraghy, Shohda A

2013-07-17

368

Effect of surface finish on the failure mechanisms of flip-chip solder joints under electromigration  

NASA Astrophysics Data System (ADS)

Two substrate surface finishes, Au/Ni and organic solderable preservative (OSP), were used to study the effect of the surface finish on the reliability of flip-chip solder joints under electromigration at 150°C ambient temperature. The solder used was eutectic PbSn, and the applied current density was 5×103 A/cm2 at the contact window of the chip. The under bump metallurgy (UBM) on the chip was sputtered Cu/Ni. It was found that the mean-time-to-failure (MTTF) of the OSP joints was six times better than that of the Au/Ni joints (3080 h vs. 500 h). Microstructure examinations uncovered that the combined effect of current crowding and the accompanying local Joule heating accelerated the local Ni UBM consumption near the point of electron entrance. Once Ni was depleted at a certain region, this region became nonconductive, and the flow of the electrons was diverted to the neighboring region. This neighboring region then became the place where electrons entered the joint, and the local Ni UBM consumption was accelerated. This process repeated itself, and the Ni-depleted region extended further on, creating an ever-larger nonconductive region. The solder joint eventually, failed when the nonconductive region became too large, making the effective current density very high. Accordingly, the key factor determining the MTTF was the Ni consumption rate. The joints with the OSP surface finish had a longer MTTF because Cu released from the substrate was able to reduce the Ni consumption rate.

Lin, Y. L.; Lai, Y. S.; Tsai, C. M.; Kao, C. R.

2006-12-01

369

[Bullectomy as emergency intervention in a mechanically ventilated patient with refractory type II respiratory failure due to chronic obstructive lung disease (COPD)].  

PubMed

A 44-year-old female patient presented with an extensive exacerbation of severe chronic obstructive lung disease (COPD) and bullous emphysema. Because of a severe type II respiratory failure, the patient was intubated and mechanically ventilated. Respiratory failure was refractory despite appropriate ventilation regimes and pCO2 values ranged from 110 mm Hg to 180 mm Hg. Chest radiography revealed hyperinflation of two giant bullae with mediastinal shifting to the left lung. We describe a successful rescue bullectomy. PMID:18264895

Bastian, A; Khanavkar, B; Scherff, A; Witte, K; Behn, M; Schulte, E; Linder, A; Bollow, M; Ewig, S

2008-02-11

370

On fibre debonding effects and the mechanism of transverse-ply failure in cross-ply laminates of glass fibre\\/thermoset composites  

Microsoft Academic Search

The mechanism of transverse-ply failure in cross-ply laminates of glass fibre thermoset composites has been investigated.\\u000a It is shown that fibre debonding initiates failure, the debonds subsequently joining up to form a transverse crack nucleus.\\u000a In the epoxy system investigated fibre debonding causes an observable whitening effect and small modulus change; this effect\\u000a is reversible in that rebonding can be

J. E. Bailey; A. Parvizi

1981-01-01

371

Failure Mechanisms in a Fatigue-Loaded High-Performance Powder Metallurgical Tool Steel  

NASA Astrophysics Data System (ADS)

High-performance powder metallurgical (PM) produced tool steels are often subjected to fatigue loading. The lifetime of such components can be dominated by fatigue damage. Hence fatigue crack growth curves were determined for different heat treatments at positive and negative stress ratios. The fracture processes are analyzed by fractographic methods. Despite the brittleness of the investigated material the fatigue crack propagation behavior in the lower Paris regime is similar to the behavior of ductile alloys. The fatigue crack growth mechanisms in the upper Paris regime were examined by single overload experiments. On the basis of these investigations, a schematic model is proposed for the different fracture mechanisms in a fatigue-loaded PM tool steel for two different heat-treatment conditions.

Jesner, G.; Pippan, R.

2009-04-01

372

Fatigue failure kinetics and structural changes in lead-free interconnects due to mechanical and thermal cycling  

NASA Astrophysics Data System (ADS)

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 the interface was found to be caused by dislocation pile-ups at the IMC when the plastic zone ahead of the crack tip reached this interface. In temperature cycling testing, strains arose within the interconnect due to CTE mismatch between the solder and IMC. The substrates had matched CTE for all specimens in this research. Because of this, all the temperature cycling cracks were observed at interfaces, generally between the solder and IMC. Additionally, real-time electrical resistance may be a useful non-destructive evaluation (NDE) tool for the empirical observation of fatigue cracking in ball-grid arrays (BGA) during both mechanical and temperature cycling tests.

Fiedler, Brent Alan

373

Failure and switching mechanism in semiconductor p-n junction devices  

NASA Astrophysics Data System (ADS)

Theoretical results obtained with computer models were used to interpret existing experimental data related to second breakdown mechanisms. If you solve the complete set of transport equations for electrons, holes, and heat, three kinds of second breakdown phenomena can be modelled: current mode (CSB), thermal mode (TSB), and current-thermal (CSB-TSB) mode second breakdown. The effect of the input voltage pulse shape on the current switching time of a p-n junction device is also discussed.

Yee, J. H.; Orvis, W. J.; Khanaka, G. H.; Lair, D. L.

1983-03-01

374

Electrophysiological Alterations After Mechanical Circulatory Support in Patients With Advanced Cardiac Failure  

Microsoft Academic Search

Background—Recognizing that mechanical circulatory support with a left ventricular assist device (LVAD) induces changes in myocardial structure and contractile function, we examined whether there are changes in ventricular conduction and\\/or repolarization among failing human hearts after LVAD implantation. Methods and Results—We examined 12-lead electrocardiograms before surgery, immediately after LVAD placement, and at a delayed (.1 week) postoperative time point in

John D. Harding; Valentino Piacentino; John P. Gaughan; Steven R. Houser; Kenneth B. Margulies

375

Investigations of failure mechanisms of TAB-bonded chips during thermal aging  

Microsoft Academic Search

Eutectic soldering and thermocompression bonding were investigated with regard to thermal aging mechanisms in tape automated bonding (TAB) chips. These methods require two different metallurgies: Cu-Sn-Au and Cu-Au. Effects such as pore formation which are due to the Kirkendall effect and the formation of ternary phases were investigated. The influence of the lead roughness and of copper recrystallization was shown

ELKE ZAKEL; HERBERT REICHL

1990-01-01

376

Investigations of failure mechanisms of TAB-bonded chips during thermal aging  

Microsoft Academic Search

Eutectic soldering and thermocompression bonding were investigated with regard to thermal aging mechanisms. These methods require two different metallurgies: Cu-Sn-Au and Cu-Au. Effects like pore formation due to the Kirkendall effect and the formation of ternary phases were investigated. The influence of the lead roughness and of copper recrystallization is shown by the use of ED (electrodeposited) copper and RA

E. Zakel; H. Reichl

1990-01-01

377

Development of a rule-based software system for the fabrication of a contoured EB-PVD TBC on a PW4000 second-stage blade  

NASA Astrophysics Data System (ADS)

A rule-based software system capable of predicting the manufacturing process parameters required to apply any reasonable contoured electron beam physical vapor deposition (EB-PVD) thermal barrier coating (TBC) to a gas turbine blade has been developed and tested. This system is based upon an experimentally verified TBC thickness prediction model for ytria partially stabilized zirconia (YPSZ) TBCs applied using EB-PVD. The following three goals were set at the outset of the work and have been accomplished. First, an experimentally verified model capable of predicting TBC coating thickness as a function of position in the EB-PVD coater was created. Nearly seventeen hundred flat samples, seven twelve inch long cylinders, and four PW4000 gas turbine blades were coated and analyzed during the verification of the model. The correlation coefficients between the improved model and the experimental data ranged between 0.8 and 0.95. Second, a model was developed that was proven capable of predicting the effects of vapor shadowing and angular rotation on TBC coating thickness on a PW4000 turbine blade. Third, the model was run to populate a knowledge base for the rule-based software system. The system and its graphical user interface are designed to allow a coating engineer to select the EB-PVD process parameters that best fit the designer's requested TBC profile.

Weir, William Charles Stuart

2002-09-01

378

Spatial distribution and inter-year variation of hexabromocyclododecane (HBCD) and tris-(2,3-dibromopropyl) isocyanurate (TBC) in farm soils at a peri-urban region.  

PubMed

Hexabromocyclododecane (HBCD) is a high production volume brominated flame retardant (BFR) which has been of increasing environmental and public health concern due to its potential environmental persistency, bioaccumulation and toxicity. Tris-(2,3-dibromopropyl) isocyanurate (TBC) is another BFR which has recently been found in environmental matrices near a manufacturing plant, but its production volume and environmental distribution is currently not well known. This study was conducted to investigate the presence and distribution of these two BFRs in farm soils at a region in southeast Beijing. Total HBCD levels ranged from 0.17 to 34.5 ng g(-1) on a dry weight basis (dw) with a median level of 2.97 ng g(-1)dw. The composition profile of HBCD diastereoisomers was, on average, 28%, 13% and 59% for ?-, ?- and ?-HBCD, respectively. Detection frequency of TBC was only 25% in 2010 but was detected in all soil samples in 2011, and the median level was 0.19 ng g(-1)dw with the range between below detection limit to 1.62 ng g(-1) dw. There were no significant differences of HBCD and TBC levels among different irrigation sources in the region. The soil HBCD and TBC levels in samples collected in 2011 were significantly higher than in 2010. The increasing short-term temporal levels in farm soil might be due to the rapid urbanization in this region or could also reflect the increasing usage of HBCD and TBC after the phase out of other BFRs. PMID:22818088

Wang, Thanh; Han, Shanlong; Ruan, Ting; Wang, Yawei; Feng, Jiayong; Jiang, Guibin

2012-07-19

379

Molecular structure, mechanical behavior and failure mechanism of the C-terminal cross-link domain in type I collagen.  

PubMed

Collagen is a key constituent in structural materials found in biology, including bone, tendon, skin and blood vessels. Here we report a first molecular level model of an entire overlap region of a C-terminal cross-linked type I collagen assembly and carry out a nanomechanical characterization based on large-scale molecular dynamics simulation in explicit water solvent. Our results show that the deformation mechanism and strength of the structure are greatly affected by the presence of the cross-link, and by the specific loading condition of how the stretching is applied. We find that the presence of a cross-link results in greater strength during deformation as complete intermolecular slip is prevented, and thereby particularly affects larger deformation levels. Conversely, the lack of a cross-link results in the onset of intermolecular sliding during deformation and as a result an overall weaker structure is obtained. Through a detailed analysis of the distribution of deformation by calculating the molecular strain we show that the location of largest strains does not occur around the covalent bonding region, but is found in regions further away from this location. The insight developed from understanding collagenous materials from a fundamental molecular level upwards could play a role in advancing our understanding of physiological and disease states of connective tissues, and also enable the development of new scaffolding material for applications in regenerative medicine and biologically inspired materials. PMID:21262493

Uzel, Sebastien G M; Buehler, Markus J

2010-07-16

380

Mechanisms of improvement of respiratory failure in patients with restrictive thoracic disease treated with non-invasive ventilation  

PubMed Central

Background: Nocturnal non-invasive ventilation (NIV) is an effective treatment for hypercapnic respiratory failure in patients with restrictive thoracic disease. We hypothesised that NIV may reverse respiratory failure by increasing the ventilatory response to carbon dioxide, reducing inspiratory muscle fatigue, or enhancing pulmonary mechanics. Methods: Twenty patients with restrictive disease were studied at baseline (D0) and at 5–8 days (D5) and 3 months (3M). Results: Mean (SD) daytime arterial carbon dioxide tension (PaCO2) was reduced from 7.1 (0.9) kPa to 6.6 (0.8) kPa at D5 and 6.3 (0.9) kPa at 3M (p = 0.004), with the mean (SD) hypercapnic ventilatory response increasing from 2.8 (2.3) l/min/kPa to 3.6 (2.4) l/min/kPa at D5 and 4.3 (3.3) l/min/kPa at 3M (p = 0.044). No increase was observed in measures of inspiratory muscle strength including twitch transdiaphragmatic pressure, nor in lung function or respiratory system compliance. Conclusions: These findings suggest that increased ventilatory response to carbon dioxide is the principal mechanism underlying the long term improvement in gas exchange following NIV in patients with restrictive thoracic disease. Increases in respiratory muscle strength (sniff oesophageal pressure and sniff nasal pressure) correlated with reductions in the Epworth sleepiness score, possibly indicating an increase in the ability of patients to activate inspiratory muscles rather than an improvement in contractility.

Nickol, A; Hart, N; Hopkinson, N; Moxham, J; Simonds, A; Polkey, M

2005-01-01

381

Monitoring of temperature fatigue failure mechanism for polyvinyl alcohol fiber concrete using acoustic emission sensors.  

PubMed

The applicability of acoustic emission (AE) techniques to monitor the mechanism of evolution of polyvinyl alcohol (PVA) fiber concrete damage under temperature fatigue loading is investigated. Using the temperature fatigue test, real-time AE monitoring data of PVA fiber concrete is achieved. Based on the AE signal characteristics of the whole test process and comparison of AE signals of PVA fiber concretes with different fiber contents, the damage evolution process of PVA fiber concrete is analyzed. Finally, a qualitative evaluation of the damage degree is obtained using the kurtosis index and b-value of AE characteristic parameters. The results obtained using both methods are discussed. PMID:23012555

Li, Dongsheng; Cao, Hai

2012-07-11

382

IMPERMEABLE THIN Al2O3 OVERLAY FOR TBC PROTECTION FROM SULFATE AND VANADATE ATTACK IN GAS TURBINES  

SciTech Connect

In order to improve the hot corrosion resistance of conventional YSZ TBC system, the Al{sub 2}O{sub 3} overlay coating has been successfully produced on the surface of YSZ by the Sol-gel route. The YSZ substrates were coated with boehmite sol by dip coating process, dried to form a gel film and calcined at 1200 C to form {alpha}-Al{sub 2}O{sub 3} overlay. The microstructures of TBC and Al{sub 2}O{sub 3} overlay were examined by scanning electron microscopy (SEM). The results showed that micro-pores ranged from 3 {micro}m to 20 {micro}m and micro-cracks could be clearly seen on the surface of APS YSZ coating. The thickness of alumina overlay increased with increasing the number of dip coating circles. The small microcracks (0.5-1.0 {micro}m width) on the YSZ surface could be filled and blocked by calcined alumina particles, whereas large pores remained empty and the alumina overlay was un-continuous after one time dip coating circle. Alumina overlay thicker than 5 m m obtained by five times dip coating circles largely cracked after calcinations. As a result, multiple dip coatings up to three times were ideal for getting high quality, crack- free and continuous overlay. The optimal thickness of alumina overlay was in the range of 2.5-3.5 {micro}m. In the next reporting period, we will study the hot corrosion behaviors of YSZ TBC with Al{sub 2}O{sub 3} overlay coating produced by sol gel route by exposure the samples to molten salts mixtures (Na{sub 2}SO{sub 4} + 5%V{sub 2}O{sub 5}) at 950 C.

Scott X. Mao

2002-11-30

383

Mechanical deformation and failure of electrospun polyacrylonitrile nanofibers as a function of strain rate  

NASA Astrophysics Data System (ADS)

The mechanical deformation of 12 ?m long electrospun polyacrylonitrile (PAN) nanofibers with diameters of 300-600 nm was investigated. The nanofibers were subjected to cold drawing in atmospheric conditions and at strain rates between 10-2 and 10-4 s-1. The ultimate strain of the PAN nanofibers was 60%-130% varying monotonically with the strain rate. On the contrary, the fiber tensile strength, ranging between 30 and 130 MPa, varied nonmonotonically with the slowest drawing rate resulting in the largest ductilities and fiber strengths. At the two faster rates, the large fiber ductilities originated in the formation of a cascade of ripples (necks), while at the slowest strain rate, the nanofibers deformed homogeneously allowing for the largest engineering strengths and extension ratios.

Naraghi, Mohammad; Chasiotis, Ioannis; Kahn, Harold; Wen, Yongkui; Dzenis, Yuris

2007-10-01

384

Exercise alleviates lipid-induced insulin resistance in human skeletal muscle-signaling interaction at the level of TBC1 domain family member 4.  

PubMed

Excess lipid availability causes insulin resistance. We examined the effect of acute exercise on lipid-induced insulin resistance and TBC1 domain family member 1/4 (TBCD1/4)-related signaling in skeletal muscle. In eight healthy young male subjects, 1 h of one-legged knee-extensor exercise was followed by 7 h of saline or intralipid infusion. During the last 2 h, a hyperinsulinemic-euglycemic clamp was performed. Femoral catheterization and analysis of biopsy specimens enabled measurements of leg substrate balance and muscle signaling. Each subject underwent two experimental trials, differing only by saline or intralipid infusion. Glucose infusion rate and leg glucose uptake was decreased by intralipid. Insulin-stimulated glucose uptake was higher in the prior exercised leg in the saline and the lipid trials. In the lipid trial, prior exercise normalized insulin-stimulated glucose uptake to the level observed in the resting control leg in the saline trial. Insulin increased phosphorylation of TBC1D1/4. Whereas prior exercise enhanced TBC1D4 phosphorylation on all investigated sites compared with the rested leg, intralipid impaired TBC1D4 S341 phosphorylation compared with the control trial. Intralipid enhanced pyruvate dehydrogenase (PDH) phosphorylation and lactate release. Prior exercise led to higher PDH phosphorylation and activation of glycogen synthase compared with resting control. In conclusion, lipid-induced insulin resistance in skeletal muscle was associated with impaired TBC1D4 S341 and elevated PDH phosphorylation. The prophylactic effect of exercise on lipid-induced insulin resistance may involve augmented TBC1D4 signaling and glycogen synthase activation. PMID:22851577

Pehmøller, Christian; Brandt, Nina; Birk, Jesper B; Høeg, Louise D; Sjøberg, Kim A; Goodyear, Laurie J; Kiens, Bente; Richter, Erik A; Wojtaszewski, Jørgen F P

2012-07-30

385

A study of the failure mechanism of a titanium nitride diffusion barrier  

NASA Astrophysics Data System (ADS)

TiN has been popularly used as a diffusion barrier between Al and Si to prevent ``spiking.'' It has, however, been reported that spiking still occurs through TiN at temperatures higher than 500 °C. In this study, we investigated the mechanism of spiking through TiN using high resolution transmission electron microscopy and electron dispersive spectroscopy (EDS). We found TiN to be saturated with Al upon annealing at 550 °C. Si also diffuses through TiN and dissolves into Al. Spikes form upon 550 °C annealing at the Si substrate. EDS analysis revealed the phase of the spikes to be Al3Ti containing a considerable amount of Si. These results indicate that spiking through TiN is due to the formation and growth of Al3Ti after the Al saturation at the bottom of TiN. We discuss these results based on the Al-Ti-Si and Al-Ti-N ternary phase diagrams.

Lee, Hoo-Jeong; Sinclair, Robert; Li, Pamela; Roberts, Bruce

1999-09-01

386

Electromigration-induced UBM consumption and the resulting failure mechanisms in flip-chip solder joints  

NASA Astrophysics Data System (ADS)

Eutectic PbSn flip chip solder joint was subjected to 5×103 A/cm2 current stressing at 150°C and 3.5 × 104 A/cm2 current stressing at 30°C. The under bump metallurgy (UBM) on the chip was sputtered Ni/Cu, and the substrate side was a thick Cu trace. It was shown through in-situ observation that the local temperature near the entrance of electrons from the Al interconnect to the solder became higher than the rest of the joint. The accelerated local Ni UBM consumption near the entrance was also observed. Once the Ni was consumed at a location, a porous structure formed, and the flow of the electrons was blocked there. It was found that the formation of the void and the formation of the porous structure were competing with each other. If the porous structure formed first, then the void would not be able to nucleate there. On the other hand, if the void could nucleate before the UBM above lost its conductivity, then the joint would fail by the void formation-and-propagation mechanism.

Lin, Y. L.; Chang, C. W.; Tsai, C. M.; Lee, C. W.; Kao, C. R.

2006-05-01

387

Treatment resistant depression as a failure of brain homeostatic mechanisms: implications for deep brain stimulation.  

PubMed

Given the profound negative public health effects of major depressive disorder (MDD), and data suggesting only modest effectiveness of existing psychological and pharmacological treatments for this condition, there has been increasing interest in exploring the antidepressant potential of non-pharmacological, brain-based interventions, such as deep brain stimulation (DBS). The use of the DBS for psychiatric indications follows a decade of data suggesting that DBS is an effective, evidence-based strategy for the treatment of movement disorders such as Parkinson's disease. At the present time there is open-label case series data to suggest that DBS in the subgenual cingulate gyrus, ventral caudate/ventral striatum, and the nucleus accumbens, is associated with antidepressant effects in individuals who fail to respond to conventional treatments for MDD. However a number of unresolved issues about the optimal use of DBS for MDD remain, such as the optimal anatomical placement of the electrodes and the mechanisms of its antidepressant effects. This review summarizes the clinical experience of DBS for treatment resistant depression (TRD). The rationale for the use of DBS for TRD is reviewed in the context of the growing neuroimaging literatures exploring the biomarkers of antidepressant response, and the neural substrates of emotional regulation in both normal and pathological states. PMID:19426730

Giacobbe, Peter; Mayberg, Helen S; Lozano, Andres M

2009-05-06

388

What is the optimal mode of mechanical support in transplanted patients with acute graft failure?  

PubMed

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was: is extracorporeal membrane oxygenation (ECMO) superior to dedicated ventricular assist device (VAD) in patients with acutely failing allograft following transplantation. Altogether, 162 papers were found using the reported search, of which 8 represented the best evidence to answer the clinical question. The authors, journal, date and country of publication, patient group studied, study type, relevant outcomes and results of these papers are tabulated. Two studies provide data only for ECMO-treated patients, in three, the authors describe their experiences with Levitronix CentriMag and three studies directly compare the outcomes of ECMO and VAD support. The survival ranges from 40 to 74% in patients rescued with ECMO compared with 33-60% in patients supported with dedicated VAD. We conclude that there is insufficient evidence to prefer ECMO over VAD and the optimal modality of mechanical circulatory support (MCS) following heart transplantation should be determined by the surgeon and institutional experience and dependent on the extent and severity of myocardial dysfunction and the presence or absence of associated respiratory insufficiency. PMID:23277596

Urban, Marian; Szarszoi, Ondrej; Pirk, Jan; Netuka, Ivan

2012-12-30

389

Failure mechanisms of fuel particle coating for high-temperature gas-cooled reactors during the coating processes  

SciTech Connect

The high-temperature engineering test reactor (HTTR), a 30-MW(thermal) high-temperature gas-cooled reactor, is being constructed by the Japan Atomic Energy Research Institute. The HTTR uses TRISO-coated fuel particles: UO{sub 2} microspheres coated with layers of porous pyrolytic carbon (PyC), inner dense PyC (IPyC), silicon carbide (SiC), and outer dense PyC (OPyC). To reduce the defective coating fraction of TRISO-coated UO{sub 2} particles, failure mechanisms of fuel particle coating during the coating processes have been studied. Examinations of the coated fuel particles at every coating stage revealed two kinds of silicon carbide (SiC)-defective particles. The SiC-defective particles with partly carbonized kernels were formed by chemical reactions during SiC deposition when the coating layer of inner dense pyrolytic carbon was defective. The SiC-defective particles with nonreacted kernels were formed by mechanical shocks during unloading of SiC-coated particles from the coater. The coating processes were improved by controlling particle fluidization modes in the coater and by adopting a coating process without unloading and loading of the particles at intermediate coating stages.

Minato, Kazuo; Kikuchi, Hironobu; Fukuda, Kousaku [Japan Atomic Energy Research Inst., Tokai (Japan). Dept. of Chemistry and Fuel Research; Suzuki, Nobuyuki; Tomimoto, Hiroshi; Kitamura, Nobu; Kaneko, Mitsunobu [Nuclear Fuel Industries, Ltd., Tokai (Japan). Advanced Reactor Fuel Dept.

1995-08-01

390

Impact induced failure of cartilage-on-bone following creep loading: a microstructural and fracture mechanics study.  

PubMed

Cartilage-on-bone samples obtained from healthy bovine patellae, with or without prior static compression (i.e. creep) at 2MPa for 3h, were delivered a single impact via an instrumented pendulum indenter at a velocity of 1.13m/s and an energy of 2.2J. Mechanical data was obtained and microstructural assessment of the region of failure was carried out using differential interference contrast (DIC) optical imaging. In addition, a fibrillar-level structural analysis using scanning electron microscopy (SEM) was conducted on a control batch of non-impacted samples that were subjected to either creep or non-creep loading protocols. Arising from the impact event the deepest levels of crack penetration into the articular cartilage occurred in those samples subjected to prior creep loading. Further the crack depth was inversely proportional to the rebound velocity of the indenter. By contrast, those impacted samples not subjected to prior creep loading had only short obliquely patterned microcracks confined to the upper one-third of the full cartilage depth. Ultrastructurally the creep-loaded cartilage matrix exhibited a substantial radial collapse or compaction of the fibrillar network in its primary radial zone. The increase in crack length in the prior creep-loaded cartilage is consistent with a reduction in its dissipative properties as indicated by a reduction in rebound velocity. An interpretation is offered in terms of classical fracture mechanics theory. PMID:22784816

Thambyah, Ashvin; Zhang, Geran; Kim, Woong; Broom, Neil D

2012-06-20

391

Impact of defects on the electrical transport, optical properties and failure mechanisms of GaN nanowires.  

SciTech Connect

We present the results of a three year LDRD project that focused on understanding the impact of defects on the electrical, optical and thermal properties of GaN-based nanowires (NWs). We describe the development and application of a host of experimental techniques to quantify and understand the physics of defects and thermal transport in GaN NWs. We also present the development of analytical models and computational studies of thermal conductivity in GaN NWs. Finally, we present an atomistic model for GaN NW electrical breakdown supported with experimental evidence. GaN-based nanowires are attractive for applications requiring compact, high-current density devices such as ultraviolet laser arrays. Understanding GaN nanowire failure at high-current density is crucial to developing nanowire (NW) devices. Nanowire device failure is likely more complex than thin film due to the prominence of surface effects and enhanced interaction among point defects. Understanding the impact of surfaces and point defects on nanowire thermal and electrical transport is the first step toward rational control and mitigation of device failure mechanisms. However, investigating defects in GaN NWs is extremely challenging because conventional defect spectroscopy techniques are unsuitable for wide-bandgap nanostructures. To understand NW breakdown, the influence of pre-existing and emergent defects during high current stress on NW properties will be investigated. Acute sensitivity of NW thermal conductivity to point-defect density is expected due to the lack of threading dislocation (TD) gettering sites, and enhanced phonon-surface scattering further inhibits thermal transport. Excess defect creation during Joule heating could further degrade thermal conductivity, producing a viscous cycle culminating in catastrophic breakdown. To investigate these issues, a unique combination of electron microscopy, scanning luminescence and photoconductivity implemented at the nanoscale will be used in concert with sophisticated molecular-dynamics calculations of surface and defect-mediated NW thermal transport. This proposal seeks to elucidate long standing material science questions for GaN while addressing issues critical to realizing reliable GaN NW devices.

Armstrong, Andrew M.; Aubry, Sylvie; Shaner, Eric Arthur; Siegal, Michael P.; Li, Qiming; Jones, Reese E.; Westover, Tyler; Wang, George T.; Zhou, Xiao Wang; Talin, Albert Alec; Bogart, Katherine Huderle Andersen; Harris, C. Thomas; Huang, Jian Yu

2010-09-01

392

Molecular Mechanisms of Microvascular Failure in CNS Injury - Synergistic Roles of NKCC1 and SUR1/TRPM4  

PubMed Central

Microvascular failure largely underlies the damaging secondary events that accompany traumatic brain injury (TBI). Changes in capillary permeability result in the extravasation of extracellular fluid, inflammatory cells, and blood, thereby producing cerebral edema, inflammation, and progressive secondary hemorrhage (PSH). Recent work in rat models of TBI and stroke have implicated two ion transport proteins expressed in brain endothelial cells as critical mediators of edema formation: the constitutively-expressed Na+-K+-2Cl? cotransporter, NKCC1, and the trauma/ischemia-induced SUR1-regulated NCCa-ATP (SUR1/TRPM4) channel. Whereas NKCC1 function requires ATP, activation of SUR1/TRPM4 occurs only after ATP depletion. This opposite dependence on intracellular ATP levels implies that one or the other mechanism will activate/deactivate as ATP concentrations rise and fall during periods of ischemia/reperfusion, resulting in continuous edema formation regardless of cellular energy status. Moreover, with critical ATP depletion, sustained opening of SUR1/TRPM4 channels results in the oncotic death of endothelial cells, leading to capillary fragmentation and secondary hemorrhage. Bumetanide and glibenclamide are two well-characterized, safe, FDA-approved drugs that inhibit NKCC1 and the SUR1/TRPM4 channel, respectively. When used alone, these drugs have documented beneficial effects in animal models of TBI-and ischemia-associated cerebral edema and PSH. Given the mechanistic and temporal differences by which NKCC1 and the SUR1/TRPM4 channel contribute to the pathophysiology of these events, combination therapy with bumetanide and glibenclamide may yield critical synergy in preventing injury-associated capillary failure.

Kahle, Kristopher T.; Gerzanich, Volodymyr; Simard, J. Marc

2011-01-01

393

Inventory of landslides in southern Illinois near the New Madrid Seismic Zone and the possible failure mechanism at three sites  

SciTech Connect

A total of 221 landslides was inventoried along a 200-kilometer reach of the Ohio and the Mississippi Rivers from Olmsted to Chester, IL using Side-Looking Airborne Radar imagery, vertical, stereoscopic, black and white aerial photography at various scales, and low altitude, oblique color and color infrared photography. Features observed on aerial photographs were used to classify landslides into three types (rock/debris fall, block slide, and rotational/translational slide) at three levels of confidence: certain, probable, or possible. Some landslides combined two or more types at a single site. Only a few of the landslides showed evidence of repeated activity; most are ancient landforms. Most of the landslides were developed in the loess, alluvium, colluvium, and weak clay layers of the Chesterian Series or in the Porter's Creek Clay and McNairy Formation. Failure of three representative landslides was modeled under static (aseismic) and dynamic (seismic) situations using three different sliding mechanisms. Both the pseudo-static method and a simplified method of the Newmark displacement analysis were used to determine the stability of the slope under earthquake conditions. The three representative landslides selected for detailed slope stability analysis were the Ford Hill, Jones Ridge, and Olmsted landslides. The Ford Hill and Jones Ridge landslides have similar slope geometries. Their modes of failure were recognized as a translational block slide on a weak clay layer. The Olmsted landslide is a complex of several rotational slides of different ages and a mega block slide on weak clay layers. The stability analyses of these three landslides suggest that they would not have occurred under aseismic conditions. However, under earthquake loadings similar to those generated by the 1811-12 earthquakes, most of the slopes could have experienced large displacements leading to landslide initiation.

Su, Wen June (Illinois State Geological Survey, Champaign, IL (United States). Engineering Geology Section)

1992-01-01

394

Mathematical model of cardiovascular mechanics for diagnostic analysis and treatment of heart failure: Part 2. Analysis of vasodilator therapy and planning of optimal drug therapy.  

PubMed

Using a mathematical model of cardiovascular mechanics, various complicated responses to vasodilator therapy for heart failure have been well accounted for through common logic: (i) the differential effects of various vasodilators on cardiac output; (ii) the opposite response of cardiac output to sodium nitroprusside in a normal state and heart failure state; (iii) the different responses of cardiac index, arterial pressure and left ventricular end-diastolic pressure to hydralazine in different types of heart failure. The response to combined vasodilator-inotropic agent therapy was simulated well by the model. The optimal therapeutic regimen was then formulated to simultaneously control the cardiac output, systemic and pulmonary arterial and venous pressures, and the degree of coronary ischaemia by multiple drug delivery, and the problem was solved using the model. We conclude that the model provides a useful basis for obtaining a guidance for more appropriate therapeutic regimen in heart failure. PMID:8182956

Tsuruta, H; Sato, T; Ikeda, N

1994-01-01

395

Mechanisms of excitation-contraction coupling failure during metabolic inhibition in guinea-pig ventricular myocytes.  

PubMed Central

1. The effects of complete metabolic inhibition on excitation-contraction coupling in heart were studied by exposing patch-clamped guinea-pig ventricular myocytes, loaded via the patch pipette with the Ca2+ indicator Fura-2 (0.1 mM), to carbonyl cyanide-p-trifluoromethoxyphenylhydrazone (FCCP, 1 microM) and 2-deoxyglucose (2-DG, 10 mM) while simultaneously recording membrane current, Fura-2 fluorescence, and cell motion. The patch pipette solution contained Cs+ and TEA (tetraethylammonium) to partially block K+ currents. 2. During voltage clamps from a holding potential of -40 mV to a test potential of 0 mV, complete metabolic inhibition decreased the Ca2+ current (ICa), activated the ATP-sensitive K+ current, modestly elevated diastolic [Ca2+]i and markedly reduced the [Ca2+]i transient without altering its voltage dependence. Active shortening was impaired and diastolic cell length decreased prior to large increases in diastolic [Ca2+]i, consistent with rigor induced by ATP depletion. Return of the [Ca2+]i transient to baseline and relaxation upon repolarization were also delayed. 3. Despite the depression of the peak [Ca2+]i transient induced by membrane depolarization during metabolic inhibition, the [Ca2+]i transient induced by a rapid exposure to 5 mM-caffeine was greater than control. The Na(+)-Ca2+ exchange current during the caffeine-induced [Ca2+]i transient was not affected by metabolic inhibition. 4. [Ca2+]i transients depressed by metabolic inhibition could be enhanced by augmenting ICa with elevated [Ca2+]o (10 mM) and Bay K 8644 (5 microM). 5. To study the relationship between the magnitude of ICa and the amplitude of the [Ca2+]i transient, ICa was modulated either by (a) voltage clamping the cell to different membrane potentials at constant [Ca2+]o or by (b) rapidly altering [Ca2+]o immediately prior to a voltage clamp to a fixed membrane potential. Under control conditions, the relationship between the size of ICa and the magnitude of the [Ca2+]i transient was the same whether ICa was modulated by altering membrane potential or [Ca2+]o, suggesting that membrane potential does not significantly modulate the Ca(2+)-induced Ca2+ release mechanism of cardiac excitation-contraction coupling. 6. After metabolic inhibition, however, the same ICa released less Ca2+ than under control conditions, consistent with some impairment of the Ca2+ release mechanism. 7. These results suggest that under conditions in which excitability is maintained by controlling membrane voltage and minimizing metabolically sensitive K+ currents, the decreased [Ca2+]i transient observed during metabolic inhibition severe enough to induce rigor is caused primarily by depression of ICa and not by depletion of intracellular Ca2+ stores. Additional factors also modestly hinder Ca2+ release from intracellular stores during metabolic inhibition.

Goldhaber, J I; Parker, J M; Weiss, J N

1991-01-01

396

Mechanisms of high-temperature fatigue failure in alloy 800H  

SciTech Connect

The damage mechanisms influencing the axial strain-controlled low-cycle fatigue (LCF) behavior of alloy 800H at 850C have been evaluated under conditions of equal tension/compression ramp rates (fast-fast (F-F): 4 {times} 10{sup {minus}3} s{sup {minus}1} and slow-slow (S-S): 4 {times} 10{sup {minus}5} s{sup {minus}1}) and asymmetrical ramp rates (fast-slow (F-S): 4 {times} 10{sup {minus}3} s{sup {minus}1}/4 {times} 10{sup {minus}5}s{sup {minus}1} and slow-fast (S-F): 4 {times} 10{sup {minus}5}/4 {times} 10{sup {minus}3} s{sup {minus}1}) in tension and compression. The fatigue life, cyclic stress response, and fracture modes were significantly influenced by the waveform shape. The fatigue lives displayed by different loading conditions were in the following order: F-F > S-S > F-S > S-F. The fracture mode was dictated by the ramp rate adopted in the tensile direction. The fast ramp rate in the tensile direction led to the occurrence of transgranular crack initiation and propagation, whereas the slow ramp rate caused intergranular initiation and propagation. The time-dependent processes and their synergistic interactions, which were at the basis of observed changes in cyclic stress response and fatigue life, were identified. Oxidation, creep damage, dynamic strain aging, massive carbide precipitation, time-dependent creep deformation, and deformation ratcheting were among the several factors influencing cyclic life. Irrespective of the loading condition, the largest effect on life was exerted by oxidation processes. Deformation ratcheting had its greatest influence on life under asymmetrical loading conditions. Creep damage accumulated the greatest amount during the slow tensile ramp under S-F conditions.

Rao, K.B.S.; Halford, G.R. [NASA-Lewis Research Center, Cleveland, OH (United States); Schuster, H. [Inst. for Materials in Energy Systems Research Centre, Juelich (Germany)

1996-04-01

397

Mechanical properties and shear failure surfaces of two alumina powders in triaxial compression  

SciTech Connect

In the manufacture of ceramic components, near-net-shape parts are commonly formed by uniaxially pressing granulated powders in rigid dies. Density gradients that are introduced into a powder compact during press-forming often increase the cost of manufacturing, and can degrade the performance and reliability of the finished part. Finite element method (FEM) modeling can be used to predict powder compaction response, and can provide insight into the causes of density gradients in green powder compacts; however, accurate numerical simulations require accurate material properties and realistic constitutive laws. To support an effort to implement an advanced cap plasticity model within the finite element framework to realistically simulate powder compaction, the authors have undertaken a project to directly measure as many of the requisite powder properties for modeling as possible. A soil mechanics approach has been refined and used to measure the pressure dependent properties of ceramic powders up to 68.9 MPa (10,000 psi). Due to the large strains associated with compacting low bulk density ceramic powders, a two-stage process was developed to accurately determine the pressure-density relationship of a ceramic powder in hydrostatic compression, and the properties of that same powder compact under deviatoric loading at the same specific pressures. Using this approach, the seven parameters that are required for application of a modified Drucker-Prager cap plasticity model were determined directly. The details of the experimental techniques used to obtain the modeling parameters and the results for two different granulated alumina powders are presented.

ZEUCH,DAVID H.; GRAZIER,J. MARK; ARGUELLO JR.,JOSE G.; EWSUK,KEVIN G.

2000-04-24

398

Down regulation of kidney neutral endopeptidase mRNA, protein and activity during acute renal failure: Possible mechanism for ischemia-induced acute renal failure in rats?  

Microsoft Academic Search

Neutral endopeptidase (NEP, 24.11) is an ectoenzyme involved in the degradation of peptide hormones such as endothelin (ET), atrial natriuretic factor and enkephalins. The current study was designed to assess the involvement of NEP in ischemia-induced acute renal failure (ARF). In unilaterally nephrectomized Sprague-Dawley rats, the left renal artery was occluded for 30 min under pentobarbital anesthesia (40 mg\\/kg, i.p.)

Ponnal Nambi; Hsiao-Ling Wu; Uma Prabhakar; Louis Hersh; Mikios Gellai

1999-01-01

399

Computational assessment of the effect of polyethylene wear rate, mantle thickness, and porosity on the mechanical failure of the acetabular cement mantle.  

PubMed

Clinical studies have revealed that aseptic loosening is the dominant cause of failure in total hip arthroplasty, particularly for the acetabular component. For a cemented polyethylene cup, failure is generally accompanied by the formation of fibrous tissue at the cement-bone interface. A variety of reasons for the formation of this tissue have been suggested, including osteolysis and mechanical overload at the cement-bone interface. In this study, a computational cement damage accumulation method was used to investigate the effect of polyethylene cup penetration, cement mantle thickness, and cement porosity on the number of cycles required to achieve mechanical fatigue failure of the cement mantle. Cup penetration was found to increase cement mantle stresses, resulting in a reduction in cement mantle fatigue life of 9% to 11% for a high cup penetration rate. The effect of using a thin (2 mm) over a thick (4 mm) cement mantle also reduced cement mantle fatigue life between 9% and 11%, and greatly raised cancellous bone stresses. Cement porosity was found to have very little effect on cement mantle fatigue life. Failure modes and cement stresses involved suggest that only extreme combinations of a thin cement mantle and high cup penetration may lead to mechanical failure of the cement mantle, thereby allowing wear debris access to the cement-bone interface. A thin cement mantle may also lead to the mechanical overload of the cement-bone interface. In this manner, the authors suggest that the mechanical factors may contribute to the failure mode of cemented polyethylene cups. PMID:19950359

Coultrup, Oliver J; Hunt, Chris; Wroblewski, B Michael; Taylor, Mark

2010-05-01

400

Active wear and failure mechanisms of TiN-Coated high speed steel and tin-coated cemented carbide tools when machining powder metallurgically made stainless steels  

NASA Astrophysics Data System (ADS)

In this study, active wear and failure mechanisms of both TiN-coated high speed steel and TiN-coated cemented carbide tools when machining stainless steels made by powder metallurgy in low and high cutting speed ranges, respectively, have been investigated. Abrasive wear mechanisms, fatigue-induced failure, and adhesive and diffusion wear mechanisms mainly affected the tool life of TiN-coated high speed steel tools at cutting speeds below 35 m/min, between 35 and 45 m/min, and over 45 m/min, respectively. Additionally, fatigue-induced failure was active at cutting speeds over 45 m/min in the low cutting speed range when machining powder metallurgically made duplex stainless steel 2205 and austenitic stainless steel 316L. In the high cutting speed range, from 100 to 250 m/min, fatigue-induced failure together with diffusion wear mechanism, affected the tool life of TiN-coated cemented carbide tools when machining both 316L and 2205 stainless steels. It was noticed that the tool life of TiN-coated high speed steel tools used in the low cutting speed range when machining 2205 steel was longer than that when machining 316L steel, whereas the tool life of TiN-coated cemented carbide tools used in the high cutting speed range when machining 316L steel was longer than that when machining 2205 steel.

Jiang, Laizhu; Hänninen, Hannu; Paro, Jukka; Kauppinen, Veijo

1996-09-01

401

Active wear and failure mechanisms of TiN-coated high speed steel and TiN-coated cemented carbide tools when machining powder metallurgically made stainless steels  

SciTech Connect

In this study, active wear and failure mechanisms of both TiN-coated high speed steel and TiN-coated cemented carbide tools when machining stainless steels made by powder metallurgy in low and high cutting speed ranges, respectively, have been investigated. Abrasive wear mechanisms, fatigue-induced failure, and adhesive and diffusion wear mechanisms mainly affected the tool life of TiN-coated high speed steel tools at cutting speeds below 35 m/min, between 35 and 45 m/min, and over 45 m/min, respectively. Additionally, fatigue-induced failure was active at cutting speeds over 45 m/min in the low cutting speed range when machining powder metallurgically made duplex stainless steel 2205 and austenitic stainless steel 316L. In the high cutting speed range, from 100 to 250 m/min, fatigue-induced failure together with diffusion wear mechanism, affected the tool life of TiN-coated cemented carbide tools when machining both 316L and 2205 stainless steels. It was noticed that the tool life of TiN-coated high speed steel tools used in the low cutting speed range when machining 2205 steel was longer than that when machining 316L steel, whereas the tool life of TiN-coated cemented carbide tools used in the high cutting speed range when machining 316L steel was longer than that when machining 2205 steel.

Jiang, L.; Haenninen, H.; Paro, J.; Kauppinen, V. [Helsinki Univ. of Technology, Espoo (Finland)

1996-09-01

402

ACCF\\/AHA\\/HFSA 2011 Survey Results: Current Staffing Profile of Heart Failure Programs, Including Programs That Perform Heart Transplant and Mechanical Circulatory Support Device Implantation  

Microsoft Academic Search

ObjectivesThere have been no published recommendations about staffing needs for a heart failure (HF) clinic or an office setting focused on heart transplant. The goal of this survey was to understand the current staffing environment of HF, transplant, and mechanical circulatory support device (MCSD) programs in the United States and abroad. This report identifies current staffing patterns but does not

Mariell Jessup; Nancy M. Albert; David E. Lanfear; JoAnn Lindenfeld; Barry M. Massie; Mary Norine Walsh; Mark J. Zucker

2011-01-01

403

Sequential Oxygenation Index and Organ Dysfunction Assessment within the First 3 Days of Mechanical Ventilation Predict the Outcome of Adult Patients with Severe Acute Respiratory Failure  

PubMed Central

Objective. To determine early predictors of outcomes of adult patients with severe acute respiratory failure. Method. 100 consecutive adult patients with severe acute respiratory failure were evaluated in this retrospective study. Data including comorbidities, Sequential Organ Failure Assessment (SOFA) score, Acute Physiological Assessment and Chronic Health Evaluation II (APACHE II) score, PaO2, FiO2, PaO2/FiO2, PEEP, mean airway pressure (mPaw), and oxygenation index (OI) on the 1st and the 3rd day of mechanical ventilation, and change in OI within 3 days were recorded. Primary outcome was hospital mortality; secondary outcome measure was ventilator weaning failure. Results. 38 out of 100 (38%) patients died within the study period. 48 patients (48%) failed to wean from ventilator. Multivariate analysis showed day 3 OI (P = 0.004) and SOFA (P = 0.02) score were independent predictors of hospital mortality. Preexisting cerebrovascular accident (CVA) (P = 0.002) was the predictor of weaning failure. Results from Kaplan-Meier method demonstrated that higher day 3 OI was associated with shorter survival time (log-Rank test, P < 0.001). Conclusion. Early OI (within 3 days) and SOFA score were predictors of mortality in severe acute respiratory failure. In the future, prospective studies measuring serial OIs in a larger scale of study cohort is required to further consolidate our findings.

Lai, Ting-Yu; Hung, Heui-Ling; Chen, Yu-Mu; Chou, Po-An; Wang, Chin-Chou; Lin, Meng-Chih; Fang, Wen-Feng

2013-01-01

404

A novel mechanism of NALP3 inducing ischemia reperfusion injury by activating MAPK pathway in acute renal failure.  

PubMed

Acute renal failure (ARF) is a rapid loss of kidney function. The reasons and mechanism by which this occurs has not been clarified so far thus creating obstacles to management of this disease. Presently, the experimental research using the accepted renal ischemia reperfusion injury (I/R injury) model represented for ARF focuses on several possible relevant factors such as reactive oxygen species, no-reflow phenomenon, apoptosis and extensive inflammatory response. The latter is much talked about currently. Some intracellular danger sensing proteins, such as the nucleotide binding domain leucine rich repeats-containing family proteins known as NLRs, adjust the inflammatory response through the formation of a multi-protein complex known as an inflammasome. The most classic family member of this complex is NALP3 confirmed to serve as a contributor to I/R injury. However, how it contributes to the pathology remains obscure. The extensive inflammatory response is considered to be modulated by the mitogen-activated protein kinases (MAPK) signaling pathway. NOD2, another family member of NLR, which shares similar structure with NALP3, indicated that it induced the activation of MAPK in response to a pathogen, thus we assumed that NALP3 performed the harmful process of I/R injury, resulting probably from the activation of the MAPK signaling pathway. If this hypothesis proves to be correct, it might benefit the management of ARF. PMID:23399110

Hao, J L; Li, Y F; Li, R S

2013-02-08

405

Micromechanics - Failure Mechanism Studies.  

National Technical Information Service (NTIS)

The objective of the program was to investigate the micromechanical behavior of a fiber reinforced composite under static tension, bending, shear loading, and also under fatigue loading. The approach used for the investigation was both analytical and expe...

V. G. Grinius

1966-01-01

406

Thermal cycling behavior of EBPVD TBC systems deposited on doped Pt-rich ?–?? bond coatings made by Spark Plasma Sintering (SPS)  

Microsoft Academic Search

In the last decade, an increasing interest was given to Pt-rich ?–?? alloys and coatings as they have shown good oxidation and corrosion properties. In our previous work, Spark Plasma Sintering (SPS) has been proved to be a fast and efficient tool to fabricate coatings on superalloys including entire thermal barrier coating systems (TBC). In the present study, this technique

S. Selezneff; M. Boidot; J. Hugot; D. Oquab; C. Estournès; D. Monceau

407

Three-dimensional stability analysis of the Kettleman Hills landfill slope failure based on observed sliding-block mechanism  

Microsoft Academic Search

Previous studies of the Kettleman landfill slope failure of 1988 had concluded that the failure, which slid along the underlying liner interfaces with low shearing resistance, occurred as a result of attaining the critical waste fill height. These studies showed, however, some discrepancies in regard to the adopted material strength data as well as the computed factors of safety. Based

Muhsiung Chang

2005-01-01

408

Cobalt-alloy implant debris induce HIF-1? hypoxia associated responses: a mechanism for metal-specific orthopedic implant failure.  

PubMed

The historical success of orthopedic implants has been recently tempered by unexpected pathologies and early failures of some types of Cobalt-Chromium-Molybdenum alloy containing artificial hip implants. Hypoxia-associated responses to Cobalt-alloy metal debris were suspected as mediating this untoward reactivity at least in part. Hypoxia Inducible Factor-1? is a major transcription factor involved in hypoxia, and is a potent coping mechanism for cells to rapidly respond to changing metabolic demands. We measured signature hypoxia associated responses (i.e. HIF-1?, VEGF and TNF-?) to Cobalt-alloy implant debris both in vitro (using a human THP-1 macrophage cell line and primary human monocytes/macrophages) and in vivo. HIF-1? in peri-implant tissues of failed metal-on-metal implants were compared to similar tissues from people with metal-on-polymer hip arthroplasties, immunohistochemically. Increasing concentrations of cobalt ions significantly up-regulated HIF-1? with a maximal response at 0.3 mM. Cobalt-alloy particles (1 um-diameter, 10 particles/cell) induced significantly elevated HIF-1?, VEGF, TNF-? and ROS expression in human primary macrophages whereas Titanium-alloy particles did not. Elevated expression of HIF-1? was found in peri-implant tissues and synovial fluid of people with failing Metal-on-Metal hips (n?=?5) compared to failed Metal-on-Polymer articulating hip arthroplasties (n?=?10). This evidence suggests that Cobalt-alloy, more than other metal implant debris (e.g. Titanium alloy), can elicit hypoxia-like responses that if unchecked can lead to unusual peri-implant pathologies, such as lymphocyte infiltration, necrosis and excessive fibrous tissue growths. PMID:23840602

Samelko, Lauryn; Caicedo, Marco S; Lim, Seung-Jae; Della-Valle, Craig; Jacobs, Joshua; Hallab, Nadim J

2013-06-20

409

Combined noninvasive ventilation and mechanical in-exsufflator in the treatment of pediatric acute neuromuscular respiratory failure.  

PubMed

OBJECTIVES: The present study aims to evaluate the efficacy and complications of combined noninvasive ventilation (NIV) and assisted coughing by mechanical in-exsufflator (MIE) for acute respiratory failure (ARF) in children with neuromuscular disease (NMD). METHODS: A prospective study was conducted in the pediatric intensive care unit. Children with NMD and ARF treated by combined NIV and MIE were included. Treatment success was defined as freedom from tracheal intubation during the hospital stay. Physiologic indices including PaO2 , PaCO2 , pH, and PaO2 /FiO2 were recorded before and 12, 24?hr after the use of NIV/MIE. RESULTS: Combined NIV/MIE was used in 15 NMD children (mean: 8.1 years, range: 3 months to 18 years) with 16 cases of ARF. There was no mortality in this cohort. Treatment success was achieved in 12 cases (75%), including six cases (38%) demanding "Do Not Intubate." ARF was due to pneumonia, with a mean baseline PaCO2 of 73.2?±?19.0?mmHg. In the success group, hypercarbia and acidosis improved after use of NIV/MIE for 24?hr (PaCO2 : 71.7?±?18.6?mmHg vs. 55.8?±?11.6?mmHg, P?

Chen, Tai-Heng; Hsu, Jong-Hau; Wu, Jiunn-Ren; Dai, Zen-Kong; Chen, I-Chen; Liang, Wen-Chen; Yang, San-Nan; Jong, Yuh-Jyh

2013-06-18

410

The Mechanism Responsible for a Low Electrostatic Discharge Failure Threshold of an Output Buffer Circuit with Low Current Drive Capability  

Microsoft Academic Search

The electrostatic discharge (ESD) failure threshold of an output buffer is observed to be sensitive to the used-gate finger number. It is found that the lower the current drive capability, the lower the ESD failure threshold, and the damage sites of the output buffer are always located at the used gate n-channel metal-oxide semiconductor (NMOS) transistors. This observation can only

Jiaw-Ren Shih; Jian-Hsing Lee; Yi-Hsun Wu; Scott Liao; Boon-Khim Liew; Ruey-Yun Shiue; Huey-Liang Hwang; John Yue

2000-01-01

411

Failure mechanisms of TiB 2 particle and SiC whisker reinforced Al 2O 3 ceramic cutting tools when machining nickel-based alloys  

Microsoft Academic Search

In this paper, Al2O3\\/TiB2\\/SiCw ceramic cutting tools with different volume fraction of TiB2 particles and SiC whiskers were produced by hot pressing. The fundamental properties of these composite tool materials were examined. Machining tests with these ceramic tools were carried out on the Inconel718 nickel-based alloys. The tool wear rates and the cutting temperature were measured. The failure mechanisms of

Deng Jianxin; Liu Lili; Liu Jianhua; Zhao Jinlong; Yang Xuefeng

2005-01-01

412

An energy-based fatigue failure model for super-elastic NiTi alloys under pure mechanical cyclic loading  

NASA Astrophysics Data System (ADS)

The fatigue failure of a super-elastic NiTi alloy was observed by uniaxial stress-controlled cyclic tests. During the cyclic loading a hysteresis loop with a varied but stabilized size after certain cycles was obtained, which is similar to plastic shakedown. The material exhibits unique brittle fracture with a large transformation strain. The fatigue life of the material greatly depends on the applied peak nominal stress, the nominal stress amplitude and the mean nominal stress. A relation between the dissipation energy at the stabilized stage of cyclic loading and the number of cycles at failure was derived from the experimental results. Based on the obtained experimental results, a uniaxial fatigue failure model based on the energy approach was proposed to predict the fatigue life. It was shown that the proposed model provides good predictions to the uniaxial fatigue lives of super-elastic NiTi alloys with different types of cyclic stressing.

Kan, Qianhua; Kang, Guozheng; Yan, Wenyi; Dong, Yawei; Yu, Chao

2011-11-01

413

Solder joint failure modes, mechanisms, and life prediction models of IC packages under board level drop impact  

Microsoft Academic Search

Drop impact performance of solder joints of IC packages becomes a great concern for handheld products, such as mobile phones and PDA. Failure modes of solder joints under drop impact depend on solder alloys, interfacial strength, intermetallic formulation, and etc. Submodeling technique is applied to model detailed structure of critical solder joint. The stress and strain concentration at different locations

Jing-en Luan; Tong Yan Tee; Xueren Zhang; E. Hussab

2005-01-01

414

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

Microsoft Academic Search

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

Chao Chung Ho; Ching-Jong Liao

2011-01-01

415

A three-dimensional numerical investigation of fracture initiation by ductile failure mechanisms in a 4340 steel  

Microsoft Academic Search

Fracture initiation in ductile metal plates occurs due to substantial tunneling of the crack in the interior of the specimen followed by final failure of side ligaments by shear lip formation. The tunneled region is characterized by a flat, fibrous fracture surface. This phenomenon is clearly exhibited in a recent experimental investigation [8] performed on pre-notched plates of a ductile

R. Narasimhan; A. J. Rosakis; B. Moran

1992-01-01

416

Weld crack assessments in API X65 pipeline: failure assessment diagrams with variations in representative mechanical properties  

Microsoft Academic Search

Applying accurate material properties to failure assessment diagrams (FAD) for flaw assessment has been problematic, particularly for welded joints in structures such as natural gas pipeline. In a study of API X65-graded natural gas pipeline, we evaluated material properties such as tensile properties and fracture toughness for the base metal, weld metal and heat-affected zone (HAZ), and investigated the influence

Jung-Suk Lee; Jang-Bog Ju; Jae-il Jang; Woo-Sik Kim; Dongil Kwon

2004-01-01

417

Effect of Crosslinking on the Structure, Properties and Failure Mechanisms of XLPE and Crosslinked Butyl Elastomer Blends  

Microsoft Academic Search

The polyblend systems consisting of crosslinkable polyethylene (XLPE) and the crosslinked butyl rubbers were studied. Two types of crosslinked butyl rubbers viz XL-20 (80% crosslinked) and XL-50 (50% crosslinked) were considered in order to find out the effect of crosslinking of the elastomer on the structure, properties and mode of failure of the blends. Properties are correlated with the crystallinity

Prithu Mukhopadhyay; C. K. Das

1991-01-01

418

Mechanisms of Disease: cell death in acute renal failure and emerging evidence for a protective role of erythropoietin  

Microsoft Academic Search

Acute renal failure—characterized by a sudden loss of the ability of the kidneys to excrete nitrogenous waste, and to maintain electrolyte homeostasis and fluid balance—is a frequently encountered clinical problem, particularly in the intensive care unit. Unfortunately, advances in supportive interventions have done little to reduce the high mortality associated with this condition. Might erythropoietin (EPO) have utility as a

Christoph Thiemermann; Magdi M Yaqoob; Edward J Sharples

2005-01-01

419

Implant size and mechanical properties influence the failure of the adhesive bond between cartilage implants and native tissue in a finite element analysis.  

PubMed

Implanted cartilage replacements (ICRs) are a promising approach to restore the functionality of joints with partial- and full-thickness articular cartilage lesions. Two major hurdles hindering successful repair of cartilage injuries with ICRs are their inadequate mechanical properties and fixation into the defect area. While the ICR geometry and mechanical properties are expected to affect the loads and deformations at the adhesive interface between the implant and native cartilage, little is known about the relationship between these implant characteristics and the quality of the fixation. The objective of this study was to evaluate the effect of implant size, thickness, modulus, surface coefficient of friction and Poisson's ratio on the failure of a fibrin adhesive interface. These factors were evaluated in an idealized finite element model of the medial compartment of the human knee with the damage and failure of fibrin at the implant/cartilage interface represented by a cohesive zone model. Both axial compression and sliding were included in the loading conditions. The results demonstrated that ICR size and material properties have a significant effect on the failure of the fibrin that adheres the implant to the native tissue. Lack of anchorage to underlying bone, larger implant sizes, higher surface coefficient of friction and higher compliance of the implant can increase the chance of implant loosening and delamination. In the future, these results may guide implant design and cartilage repair techniques. PMID:23618130

Vahdati, Ali; Wagner, Diane R

2013-04-22

420

The Role of Coatings in the Prevention of Mechanical Failures. Proceedings of the Meeting of the Mechanical Failures Prevention Group (23rd) Held at the National Bureau of Standards, Gaithersburg, Maryland, October 29-31, 1975.  

National Technical Information Service (NTIS)

Contents: Polymer coatings--The friction and wear of polymeric coatings on metal, Performance studies of polymer processed mechanical and structural components, Nylon II as a lubricant and corrosion preventative coating, Mechanical design concepts for coa...

T. R. Shives W. A. Willard

1976-01-01

421

Interfacial fracture toughness of APS bond coat\\/substrate under high temperature  

Microsoft Academic Search

Thermal barrier coating (TBC) is an essential requirement of a modern gas turbine engine. The TBC failure is the delamination\\u000a and spallation. The failure mechanism is interfacial expansion mismatch and oxidation of bond coat (BC). The oxidation damage\\u000a under high temperature results in the reduction of interfacial adhesion. The interfacial fracture toughness is an important\\u000a property to analyze the TBC

Qi Hongyu; Yang Xiaoguang; Wang Yamei

2009-01-01

422

Affinity between TBC1D4 (AS160) phosphotyrosine-binding domain and insulin-regulated aminopeptidase cytoplasmic domain measured by isothermal titration calorimetry.  

PubMed

Uptake of circulating glucose into the cells happens via the insulin- mediated signalling pathway, which translocates the glucose transporter 4 (GLUT4) vesicles from the intracellular compartment to the plasma membrane. Rab?GTPases are involved in this vesicle trafficking, where Rab?GTPase-activating proteins (RabGAP) enhance the GTP to GDP hydrolysis. TBC1D4 (AS160) and TBC1D1 are functional RabGAPs in the adipocytes and the skeletonal myocytes, respectively. These proteins contain two phosphotyrosine-binding domains (PTBs) at the amino-terminus of the catalytic RabGAP domain. The second PTB has been shown to interact with the cytoplasmic region of the insulin-regulated aminopeptidase (IRAP) of the GLUT4 vesicle. In this study, we quantitatively measured the ??M affinity (KD) between TBC1D4 PTB and IRAP using isothermal titration calorimetry, and further showed that IRAP residues 1-49 are the major region mediating this interaction. We also demonstrated that the IRAP residues 1-15 are necessary but not sufficient for the PTB interaction. PMID:22732222

Park, SangYoun; Kim, Keon Young; Kim, Sunmin; Yu, Young Seok

2012-06-01

423

The dual role of fission yeast Tbc1/cofactor C orchestrates microtubule homeostasis in tubulin folding and acts as a GAP for GTPase Alp41/Arl2  

PubMed Central

Supplying the appropriate amount of correctly folded ?/?-tubulin heterodimers is critical for microtubule dynamics. Formation of assembly-competent heterodimers is remarkably elaborate at the molecular level, in which the ?- and ?-tubulins are separately processed in a chaperone-dependent manner. This sequential step is performed by the tubulin-folding cofactor pathway, comprising a specific set of regulatory proteins: cofactors A–E. We identified the fission yeast cofactor: the orthologue of cofactor C, Tbc1. In addition to its roles in tubulin folding, Tbc1 acts as a GAP in regulating Alp41/Arl2, a highly conserved small GTPase. Of interest, the expression of GDP- or GTP-bound Alp41 showed the identical microtubule loss phenotype, suggesting that continuous cycling between these forms is important for its functions. In addition, we found that Alp41 interacts with Alp1D, the orthologue of cofactor D, specifically when in the GDP-bound form. Intriguingly, Alp1D colocalizes with microtubules when in excess, eventually leading to depolymerization, which is sequestered by co-overproducing GDP-bound Alp41. We present a model of the final stages of the tubulin cofactor pathway that includes a dual role for both Tbc1 and Alp1D in opposing regulation of the microtubule.

Mori, Risa; Toda, Takashi

2013-01-01

424

The remote sensing observation in experiments of rock failure and the beginning of remote sensing rock mechanics  

Microsoft Academic Search

The remote sensing observational study for infrared radiation of rocks was proceeded during the loading on rocks until failure.\\u000a The major instruments used in experiments were transient spectrum apparatus, intelligent spectrum apparatus, infrared radiation\\u000a thermometer, infrared spectrum radiometer, and infrared thermal imaging system. The experiments for 26 kinds of rocks were\\u000a made. The studies show that infrared radiation temperature of

Nai-Guang Geng; Cheng-Yu Cui; Ming-De Deng

1993-01-01

425

Failure Rate - A Unified Approach.  

National Technical Information Service (NTIS)

Aging, of biological and mechanical systems, is well described as 'deterioration of the power to withstand destruction.' The failure rate concept is the mathematical way of describing aging. Failure rates have been defined for discrete and continuous time...

L. Lee W. A. Thompson

1975-01-01

426

Mechanical Properties and Tensile Failure Analysis of Novel Bio-absorbable Mg-Zn-Cu and Mg-Zn-Se Alloys for Endovascular Applications.  

PubMed

In this paper, the mechanical properties and tensile failure mechanism of two novel bio-absorbable as-cast Mg-Zn-Se and Mg-Zn-Cu alloys for endovascular medical applications are characterized. Alloys were manufactured using an ARC melting process and tested as-cast with compositions of Mg-Zn-Se and Mg-Zn-Cu, being 98/1/1 wt.% respectively. Nanoindentation testing conducted at room temperature was used to characterize the elastic modulus (E) and surface hardness (H) for both the bare alloys and the air formed oxide layer. As compared to currently available shape memory alloys and degradable as-cast alloys, these experimental alloys possess superior as-cast mechanical properties that can increase their biocompatibility, degradation kinetics, and the potential for medical device creation. PMID:23543822

Persaud-Sharma, Dharam; Budiansky, Noah; McGoron, Anthony J

2012-12-21