Mode I Failure of Armor Ceramics: Experiments and Modeling

NASA Astrophysics Data System (ADS)

Meredith, Christopher; Leavy, Brian

2017-06-01

The pre-notched edge on impact (EOI) experiment is a technique for benchmarking the damage and fracture of ceramics subjected to projectile impact. A cylindrical projectile impacts the edge of a thin rectangular plate with a pre-notch on the opposite edge. Tension is generated at the notch tip resulting in the initiation and propagation of a mode I crack back toward the impact edge. The crack can be quantitatively measured using an optical method called Digital Gradient Sensing, which measures the crack-tip deformation by simultaneously quantifying two orthogonal surface slopes via measuring small deflections of light rays from a specularly reflective surface around the crack. The deflections in ceramics are small so the high speed camera needs to have a very high pixel count. This work reports on the results from pre-crack EOI experiments of SiC and B4 C plates. The experimental data are quantitatively compared to impact simulations using an advanced continuum damage model. The Kayenta ceramic model in Alegra will be used to compare fracture propagation speeds, bifurcations and inhomogeneous initiation of failure will be compared. This will provide insight into the driving mechanisms required for the macroscale failure modeling of ceramics.

Any way you look at it, successful obstacle negotiation needs visually guided on-line foot placement regulation during the approach phase.

PubMed

Patla, Aftab E; Greig, Michael

In the two experiments discussed in this paper we quantified obstacle avoidance performance characteristics carried out open loop (without vision) but with different initial visual sampling conditions and compared it to the full vision condition. The initial visual sampling conditions included: static vision (SV), vision during forward walking for three steps and stopping (FW), vision during forward walking for three steps and not stopping (FW-NS), and vision during backward walking for three steps and stopping (BW). In experiment 1, we compared performance during SV, FW and BW with full vision condition, while in the second experiment we compared performance during FW and FW-NS conditions. The questions we wanted to address are: Is ecologically valid dynamic visual sampling of the environment superior to static visual sampling for open loop obstacle avoidance task? What are the reasons for failure in performing open loop obstacle avoidance task? The results showed that irrespective of the initial visual sampling condition when open loop control is initiated from a standing posture, the success rate was only approximately 50%. The main reason for the high failure rates was not inappropriate limb elevation, but incorrect foot placement before the obstacle. The second experiment showed that it is not the nature of visual sampling per se that influences success rate, but the fact that the open loop obstacle avoidance task is initiated from a standing posture. The results of these two experiments clearly demonstrate the importance of on-line visual information for adaptive human locomotion.

A preliminary assessment of the effects of heat flux distribution and penetration on the creep rupture of a reactor vessel lower head

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chu, T.Y.; Bentz, J.; Simpson, R.

1997-02-01

The objective of the Lower Head Failure (LHF) Experiment Program is to experimentally investigate and characterize the failure of the reactor vessel lower head due to thermal and pressure loads under severe accident conditions. The experiment is performed using 1/5-scale models of a typical PWR pressure vessel. Experiments are performed for various internal pressure and imposed heat flux distributions with and without instrumentation guide tube penetrations. The experimental program is complemented by a modest modeling program based on the application of vessel creep rupture codes developed in the TMI Vessel Investigation Project. The first three experiments under the LHF programmore » investigated the creep rupture of simulated reactor pressure vessels without penetrations. The heat flux distributions for the three experiments are uniform (LHF-1), center-peaked (LHF-2), and side-peaked (LHF-3), respectively. For all the experiments, appreciable vessel deformation was observed to initiate at vessel wall temperatures above 900K and the vessel typically failed at approximately 1000K. The size of failure was always observed to be smaller than the heated region. For experiments with non-uniform heat flux distributions, failure typically occurs in the region of peak temperature. A brief discussion of the effect of penetration is also presented.« less

Association of Modality with Mortality among Canadian Aboriginals

PubMed Central

Hemmelgarn, Brenda; Rigatto, Claudio; Komenda, Paul; Yeates, Karen; Promislow, Steven; Mojica, Julie; Tangri, Navdeep

2012-01-01

Summary Background and objectives Previous studies have shown that Aboriginals and Caucasians experience similar outcome on dialysis in Canada. Using the Canadian Organ Replacement Registry, this study examined whether dialysis modality (peritoneal or hemodialysis) impacted mortality in Aboriginal patients. Design, setting, participants, & measurements This study identified 31,576 adult patients (hemodialysis: Aboriginal=1839, Caucasian=21,430; peritoneal dialysis: Aboriginal=554, Caucasian=6769) who initiated dialysis between January of 2000 and December of 2009. Aboriginal status was identified by self-report. Dialysis modality was determined 90 days after dialysis initiation. Multivariate Cox proportional hazards and competing risk models were constructed to determine the association between race and mortality by dialysis modality. Results During the study period, 939 (51.1%) Aboriginals and 12,798 (53.3%) Caucasians initiating hemodialysis died, whereas 166 (30.0%) and 2037 (30.1%), respectively, initiating peritoneal dialysis died. Compared with Caucasians, Aboriginals on hemodialysis had a comparable risk of mortality (adjusted hazards ratio=1.04, 95% confidence interval=0.96–1.11, P=0.37). However, on peritoneal dialysis, Aboriginals experienced a higher risk of mortality (adjusted hazards ratio=1.36, 95% confidence interval=1.13–1.62, P=0.001) and technique failure (adjusted hazards ratio=1.29, 95% confidence interval=1.03–1.60, P=0.03) than Caucasians. The risk of technique failure varied by patient age, with younger Aboriginals (<50 years old) more likely to develop technique failure than Caucasians (adjusted hazards ratio=1.76, 95% confidence interval=1.23–2.52, P=0.002). Conclusions Aboriginals on peritoneal dialysis experience higher mortality and technique failure relative to Caucasians. Reasons for this race disparity in peritoneal dialysis outcomes are unclear. PMID:22997343

Self-compassion increases self-improvement motivation.

PubMed

Breines, Juliana G; Chen, Serena

2012-09-01

Can treating oneself with compassion after making a mistake increase self-improvement motivation? In four experiments, the authors examined the hypothesis that self-compassion motivates people to improve personal weaknesses, moral transgressions, and test performance. Participants in a self-compassion condition, compared to a self-esteem control condition and either no intervention or a positive distraction control condition, expressed greater incremental beliefs about a personal weakness (Experiment 1); reported greater motivation to make amends and avoid repeating a recent moral transgression (Experiment 2); spent more time studying for a difficult test following an initial failure (Experiment 3); exhibited a preference for upward social comparison after reflecting on a personal weakness (Experiment 4); and reported greater motivation to change the weakness (Experiment 4). These findings suggest that, somewhat paradoxically, taking an accepting approach to personal failure may make people more motivated to improve themselves.

Two dimensional fall of granular columns controlled by slow horizontal withdrawal of a retaining wall

NASA Astrophysics Data System (ADS)

Mériaux, Catherine

2006-09-01

This paper describes a series of experiments designed to investigate the fall of granular columns in a quasi-static regime. Columns made of alternatively green and red sand layers were initially laid out in a box and then released when a retaining wall was set in slow motion with constant speed. The dependence of the dynamics of the fall on the initial aspect ratio of the columns, the velocity of the wall, and the material properties was investigated within the quasi-static regime. A change in the behavior of the columns was identified to be a function of the aspect ratio (height/length) of the initial sand column. Columns of high aspect ratio first subsided before sliding along failure planes, while columns of small aspect ratio were only observed to slide along failure planes. The transition between these two characteristic falls occurred regardless of the material and the velocity of the wall in the context of the quasi-static regime. When the final height and length of the piles were analyzed, we found power-law relations of the ratio of initial to final height and final run-out to initial length with the aspect ratio of the column. The dissipation of energy is also shown to increase with the run-out length of the pile until it reaches a plateau. Finally, we find that the structure of the slip planes that develop in our experiments are not well described by the failure of Coulomb's wedges for twin retaining rough walls.

A novel method for percutaneous insertion of a right ventricular assist device.

PubMed

Avgerinos, Dimitrios V; DeBois, William; Mongero, Linda; Krieger, Karl; Salemi, Arash

2013-06-01

Right heart failure is a rare but often fatal complication both in the pre- and postoperative setting. Right heart support with a ventricular assist device inserted in the operating room through median sternotomy can be a time-consuming procedure that requires a reoperation for removal. In cases of urgent need of right heart support, a percutaneous technique option may be of benefit. We present our initial experience with a percutaneously inserted right ventricular assist device (RVAD) in an elderly patient with severe right heart failure. An 81-year-old female patient underwent combined aortic and mitral valve replacement at our institution. During the first postoperative evening, the patient sustained sudden cardiovascular collapse and a bedside transesophageal echocardiogram revealed severe right heart failure. A coronary angiogram showed thrombosis of the right coronary artery, which was cleared with a suction device. As a result of the patient's critical condition, it was decided that an RVAD was needed as a bridge to recovery. The patient's condition improved significantly almost immediately. Her right heart function recovered over the next few days and the RVAD was removed at the bedside. She made a complete recovery and was discharged home. This patient is a prime example that a totally RVAD can be inserted in urgent situations easily and safely under fluoroscopic and echocardiographic guidance. More clinical experience with percutaneous RVADs is required to establish this technique as an alternative equivalent to the traditional open method. Right heart failure complicates many heart diseases both in the pre- and the postoperative setting. In cases of urgent need of right heart support, a percutaneous technique of a RVAD is needed for a successful outcome. We present our initial experience with a percutaneously inserted RVAD in an elderly patient with severe postoperative right heart failure.

Worsening heart failure in the setting of dronedarone initiation.

PubMed

Coons, James C; Plauger, Kara M; Seybert, Amy L; Sokos, George G

2010-09-01

To describe a challenging patient case in which dronedarone was selected for a patient with atrial fibrillation and heart failure; the drug may have been associated with worsening heart failure, leading to acute renal and hepatic failure. A 47-year-old male with a history of heart failure with New York Heart Association class III-IV symptoms presented to our institution with ventricular fibrillation and ventricular tachycardia storm. Torsade de pointes secondary to a combination of dofetilide and hypokalemia was determined to be the etiology. Upon stabilization, the patient was initiated on dronedarone 400 mg orally twice daily by the electrophysiology service for atrial fibrillation. The patient had a questionable history of amiodarone intolerance. By hospital day 9 (day 4 of dronedarone therapy), the patient demonstrated a clinical picture consistent with acute renal and hepatic failure possibly due to worsening heart failure. Dronedarone was discontinued on hospital day 10. He was subsequently transferred to an outside hospital where he required milrinone therapy for cardiogenic shock. Laboratory markers of renal and hepatic function improved over the remainder of his hospitalization and he was discharged on hospital day 20. Dronedarone is a newly approved antiarrhythmic agent with multichannel blocking properties similar to amiodarone. Use of the Naranjo probability scale determined that this patient's worsening heart failure leading to acute renal and hepatic failure was possibly caused by dronedarone. The implication from the ANDROMEDA trial as well as our experience in this case is that dronedarone should be used cautiously in patients with heart failure and avoided in patients specifically outlined in the product labeling. This case report, to our knowledge, represents the first published postmarketing report of worsening heart failure complicated by multiorgan dysfunction in the setting of dronedarone initiation. Dronedarone use must be approached with caution in patients with a history of heart failure.

Experimental Research on Fatigue Failure for 2219-T6 Aluminum Alloy Friction Stir-Welded Joints

NASA Astrophysics Data System (ADS)

Sun, Guo-Qin; Niu, Jiang-Pei; Chen, Ya-Jing; Sun, Feng-Yang; Shang, De-Guang; Chen, Shu-Jun

2017-08-01

The fatigue experiment was executed for the 2219-T6 aluminum alloy friction stir-welded joints at the rotation speed of 800 r/min and the welding velocity of 150 mm/min. Most fatigue failures occurred in the weld nugget zone (WNZ), the thermo-mechanical affected zone and the nearby areas. The experimental results demonstrated that the sudden hardness gradient increases sites corresponding to the fatigue failure locations. The high-angle grain boundaries with the highest concentration were scattered within the WNZ. The microcracks initiated at the intersection of the soft grains. More than one crack initiation site was observed within the WNZ and the thermo-mechanical affected zone, when the fracture occurred in these areas. The rough surface of the welding area should be one of the main reasons for the fatigue failure occurrence. The fatigue crack growth rate in the WNZ at the first stage was fastest in comparison with the fatigue crack growth rate in the other areas of the joint.

Matrix Dominated Failure of Fiber-Reinforced Composite Laminates Under Static and Dynamic Loading

NASA Astrophysics Data System (ADS)

Schaefer, Joseph Daniel

Hierarchical material systems provide the unique opportunity to connect material knowledge to solving specific design challenges. Representing the quickest growing class of hierarchical materials in use, fiber-reinforced polymer composites (FRPCs) offer superior strength and stiffness-to-weight ratios, damage tolerance, and decreasing production costs compared to metals and alloys. However, the implementation of FRPCs has historically been fraught with inadequate knowledge of the material failure behavior due to incomplete verification of recent computational constitutive models and improper (or non-existent) experimental validation, which has severely slowed creation and development. Noted by the recent Materials Genome Initiative and the Worldwide Failure Exercise, current state of the art qualification programs endure a 20 year gap between material conceptualization and implementation due to the lack of effective partnership between computational coding (simulation) and experimental characterization. Qualification processes are primarily experiment driven; the anisotropic nature of composites predisposes matrix-dominant properties to be sensitive to strain rate, which necessitates extensive testing. To decrease the qualification time, a framework that practically combines theoretical prediction of material failure with limited experimental validation is required. In this work, the Northwestern Failure Theory (NU Theory) for composite lamina is presented as the theoretical basis from which the failure of unidirectional and multidirectional composite laminates is investigated. From an initial experimental characterization of basic lamina properties, the NU Theory is employed to predict the matrix-dependent failure of composites under any state of biaxial stress from quasi-static to 1000 s-1 strain rates. It was found that the number of experiments required to characterize the strain-rate-dependent failure of a new composite material was reduced by an order of magnitude, and the resulting strain-rate-dependence was applicable for a large class of materials. The presented framework provides engineers with the capability to quickly identify fiber and matrix combinations for a given application and determine the failure behavior over the range of practical loadings cases. The failure-mode-based NU Theory may be especially useful when partnered with computational approaches (which often employ micromechanics to determine constituent and constitutive response) to provide accurate validation of the matrix-dominated failure modes experienced by laminates during progressive failure.

Assessment of compressive failure process of cortical bone materials using damage-based model.

PubMed

Ng, Theng Pin; R Koloor, S S; Djuansjah, J R P; Abdul Kadir, M R

2017-02-01

The main failure factors of cortical bone are aging or osteoporosis, accident and high energy trauma or physiological activities. However, the mechanism of damage evolution coupled with yield criterion is considered as one of the unclear subjects in failure analysis of cortical bone materials. Therefore, this study attempts to assess the structural response and progressive failure process of cortical bone using a brittle damaged plasticity model. For this reason, several compressive tests are performed on cortical bone specimens made of bovine femur, in order to obtain the structural response and mechanical properties of the material. Complementary finite element (FE) model of the sample and test is prepared to simulate the elastic-to-damage behavior of the cortical bone using the brittle damaged plasticity model. The FE model is validated in a comparative method using the predicted and measured structural response as load-compressive displacement through simulation and experiment. FE results indicated that the compressive damage initiated and propagated at central region where maximum equivalent plastic strain is computed, which coincided with the degradation of structural compressive stiffness followed by a vast amount of strain energy dissipation. The parameter of compressive damage rate, which is a function dependent on damage parameter and the plastic strain is examined for different rates. Results show that considering a similar rate to the initial slope of the damage parameter in the experiment would give a better sense for prediction of compressive failure. Copyright © 2016 Elsevier Ltd. All rights reserved.

Resilience of antagonistic networks with regard to the effects of initial failures and degree-degree correlations

NASA Astrophysics Data System (ADS)

Watanabe, Shunsuke; Kabashima, Yoshiyuki

2016-09-01

In this study we investigate the resilience of duplex networked layers α and β coupled with antagonistic interlinks, each layer of which inhibits its counterpart at the microscopic level, changing the following factors: whether the influence of the initial failures in α remains [quenched (case Q )] or not [free (case F )]; the effect of intralayer degree-degree correlations in each layer and interlayer degree-degree correlations; and the type of the initial failures, such as random failures or targeted attacks (TAs). We illustrate that the percolation processes repeat in both cases Q and F , although only in case F are nodes that initially failed reactivated. To analytically evaluate the resilience of each layer, we develop a methodology based on the cavity method for deriving the size of a giant component (GC). Strong hysteresis, which is ignored in the standard cavity analysis, is observed in the repetition of the percolation processes particularly in case F . To handle this, we heuristically modify interlayer messages for macroscopic analysis, the utility of which is verified by numerical experiments. The percolation transition in each layer is continuous in both cases Q and F . We also analyze the influences of degree-degree correlations on the robustness of layer α , in particular for the case of TAs. The analysis indicates that the critical fraction of initial failures that makes the GC size in layer α vanish depends only on its intralayer degree-degree correlations. Although our model is defined in a somewhat abstract manner, it may have relevance to ecological systems that are composed of endangered species (layer α ) and invaders (layer β ), the former of which are damaged by the latter whereas the latter are exterminated in the areas where the former are active.

Understanding Performance Decrements in a Letter-Canceling Task: Overcoming Habits or Inhibition of Reading.

PubMed

Myers, Larry; Downie, Steven; Taylor, Grant; Marrington, Jessica; Tehan, Gerald; Ireland, Michael J

2018-01-01

The importance of self-regulation in human behavior is readily apparent and diverse theoretical accounts for explaining self-regulation failures have been proposed. Typically, these accounts are based on a sequential task methodology where an initial task is presented to deplete self-regulatory resources, and carryover effects are then examined on a second outcome task. In the aftermath of high profile replication failures using a popular letter-crossing task as a means of depleting self-regulatory resources and subsequent criticisms of that task, current research into self-control is currently at an impasse. This is largely due to the lack of empirical research that tests explicit assumptions regarding the initial task. One such untested assumption is that for resource depletion to occur, the initial task must first establish an habitual response and then this habitual response must be inhibited, with behavioral inhibition being the causal factor in inducing depletion. This study reports on four experiments exploring performance on a letter-canceling task, where the rules for target identification remained constant but the method of responding differed (Experiment 1) and the coherence of the text was manipulated (Experiments 1-4). Experiment 1 established that habit forming and behavioral inhibition did not produce any performance decrement when the targets were embedded in random letter strings. Experiments 2-4 established that target detection was sensitive to language characteristics and the coherence of the background text, suggesting that participants' automatic reading processes is a key driver of performance in the letter-e task.

Detonation failure characterization of non-ideal explosives

NASA Astrophysics Data System (ADS)

Janesheski, Robert S.; Groven, Lori J.; Son, Steven

2012-03-01

Non-ideal explosives are currently poorly characterized, hence limiting the modeling of them. Current characterization requires large-scale testing to obtain steady detonation wave characterization for analysis due to the relatively thick reaction zones. Use of a microwave interferometer applied to small-scale confined transient experiments is being implemented to allow for time resolved characterization of a failing detonation. The microwave interferometer measures the position of a failing detonation wave in a tube that is initiated with a booster charge. Experiments have been performed with ammonium nitrate and various fuel compositions (diesel fuel and mineral oil). It was observed that the failure dynamics are influenced by factors such as chemical composition and confiner thickness. Future work is planned to calibrate models to these small-scale experiments and eventually validate the models with available large scale experiments. This experiment is shown to be repeatable, shows dependence on reactive properties, and can be performed with little required material.

Failure to obtain value enhancement by within-trial contrast in simultaneous and successive discriminations.

PubMed

Arantes, Joana; Grace, Randolph C

2008-02-01

The present research tested the generality of the "work ethic" effect described by Clement, Feltus, Kaiser, and Zentall (2000). In Experiment 1, we trained 10 pigeons on a pair of either simultaneous or successive discriminations. One discrimination followed a high-effort requirement (20 pecks to the center key) and the other followed a low-effort requirement (1 peck). Contrary to Clement et al.'s results, we found that preferences between the S+ and S- stimuli in transfer tests depended on the event that initiated the trial: Pigeons preferred the stimulus from the baseline discrimination whose initiating event was most dissimilar from that preceding the test trial. Preferences were similar but less extreme in the successive condition. In Experiment 2, we investigated whether test preferences depended on the amount of training. A total of 12 pigeons were trained on a pair of simultaneous discriminations, except that test sessions were scheduled after every three baseline sessions. Preferences increased across test sessions but were similar to those in Experiment 1. Together with Vasconcelos, Urcuioli, and Lionello-DeNolf (2007a), our study represents a second failure to replicate Clement et al.'s work ethic effect. The finding that preference depends on the event that initiates the test trial suggests that choice probes may not provide unambiguous assessments of stimulus value.

Snow fracture: From micro-cracking to global failure

NASA Astrophysics Data System (ADS)

Capelli, Achille; Reiweger, Ingrid; Schweizer, Jürg

2017-04-01

Slab avalanches are caused by a crack forming and propagating in a weak layer within the snow cover, which eventually causes the detachment of the overlying cohesive slab. The gradual damage process leading to the nucleation of the initial failure is still not entirely understood. Therefore, we studied the damage process preceding snow failure by analyzing the acoustic emissions (AE) generated by bond failure or micro-cracking. The AE allow studying the ongoing progressive failure in a non-destructive way. We performed fully load-controlled failure experiments on snow samples presenting a weak layer and recorded the generated AE. The size and frequency of the generated AE increased before failure revealing an acceleration of the damage process with increased size and frequency of damage and/or microscopic cracks. The AE energy was power-law distributed and the exponent (b-value) decreased approaching failure. The waiting time followed an exponential distribution with increasing exponential coefficient λ before failure. The decrease of the b-value and the increase of λ correspond to a change in the event distribution statistics indicating a transition from homogeneously distributed uncorrelated damage producing mostly small AE to localized damage, which cause larger correlated events which leads to brittle failure. We observed brittle failure for the fast experiment and a more ductile behavior for the slow experiments. This rate dependence was reflected also in the AE signature. In the slow experiments the b value and λ were almost constant, and the energy rate increase was moderate indicating that the damage process was in a stable state - suggesting the damage and healing processes to be balanced. On a shorter time scale, however, the AE parameters varied indicating that the damage process was not steady but consisted of a sum of small bursts. We assume that the bursts may have been generated by cascades of correlated micro-cracks caused by localization of stresses at a small scale. The healing process may then have prevented the self-organization of this small scale damage and, therefore, the total failure of the sample.

Experiences with Extra-Vehicular Activities in Response to Critical ISS Contingencies

NASA Technical Reports Server (NTRS)

Van Cise, Edward A.; Kelly, Brian J.; Radigan, Jeffery P.; Cranmer, Curtis W.

2016-01-01

Initial "Big 14" work was put to the test for the first time in 2010. Deficiencies were found in some of the planning and approaches to that work; Failure Response Assessment Team created in 2010 to address deficiencies -Identify and perform engineering analysis in operations products prior to failure; incorporate results into operations products -Identify actions for protecting ISS against a Next Worse Failure after the first failure occurs -Better document not only EVA products but also planning products, assumptions, and open actions; Pre-failure investments against critical failures best postures ISS for swift response and recovery -A type of insurance policy -Has proven effective in a number of contingency EVA cases since 2010. Planning for MBSU R&R in 2012, Second PM R&R in 2013, EXT MDM R&R in 2014; Current FRAT schedule projects completion of all analysis in 2018

LDEF electronic systems: Successes, failures, and lessons

NASA Technical Reports Server (NTRS)

Miller, Emmett; Porter, Dave; Smith, Dave; Brooks, Larry; Levorsen, Joe; Mulkey, Owen

1991-01-01

Following the Long Duration Exposure Facility (LDEF) retrieval, the Systems Special Investigation Group (SIG) participated in an extensive series of tests of various electronic systems, including the NASA provided data and initiate systems, and some experiment systems. Overall, these were found to have performed remarkably well, even though most were designed and tested under limited budgets and used at least some nonspace qualified components. However, several anomalies were observed, including a few which resulted in some loss of data. The postflight test program objectives, observations, and lessons learned from these examinations are discussed. All analyses are not yet complete, but observations to date will be summarized, including the Boeing experiment component studies and failure analysis results related to the Interstellar Gas Experiment. Based upon these observations, suggestions for avoiding similar problems on future programs are presented.

Rates of Initial Virological Suppression and Subsequent Virological Failure After Initiating Highly Active Antiretroviral Therapy: The Impact of Aboriginal Ethnicity and Injection Drug Use

PubMed Central

Martin, L.J.; Houston, S.; Yasui, Y.; Wild, T.C.; Saunders, L.D.

2010-01-01

Objectives: To compare rates of initial virological suppression and subsequent virological failure by Aboriginal ethnicity after starting highly active antiretroviral therapy (HAART). Methods: We conducted a retrospective cohort study of antiretroviral-naïve HIV-patients starting HAART in January 1999-June 2005 (baseline), followed until December 31, 2005 in Alberta, Canada. We compared the odds of achieving initial virological suppression (viral load <500 copies/mL) by Aboriginal ethnicity using logistic regression and, among those achieving suppression, rates of virological failure (the first of two consecutive viral loads > 1000 copies/mL) by Aboriginal ethnicity using cumulative incidence curves and Cox proportional hazards models. Sex, injection drug use as an HIV exposure category (IDU), baseline age, CD4 cell count, viral load, calendar year, and HAART regimen were considered as potential confounders. Results: Of 461 study patients, 37% were Aboriginal and 48% were IDUs; 71% achieved initial virological suppression and were followed for 730.4 person-years. After adjusting for confounding variables, compared to non-Aboriginals with other exposures, the odds of achieving initial virological suppression were lower for Aboriginal IDUs (odds ratio (OR)=0.33, 95% CI=0.19-0.60, p=0.0002), non-Aboriginal IDUs (OR=0.30, 95% CI=0.15-0.60, p=0.0006), and Aboriginals with other exposures (OR=0.38, 95% CI=0.21-0.67, p=0.0009). Among those achieving suppression, Aboriginals experienced higher virological failure rates ≥1 year after suppression (hazard ratio=3.35, 95% CI=1.68-6.65, p=0.0006). Conclusions: Future research should investigate adherence among Aboriginals and IDUs treated with HAART and explore their treatment experiences to assess ways to improve outcomes. PMID:21187007

Outcome of tacrolimus and vedolizumab after corticosteroid and anti-TNF failure in paediatric severe colitis.

PubMed

Hamel, Blaise; Wu, May; Hamel, Elizabeth O; Bass, Dorsey M; Park, K T

2018-01-01

Severe colitis flare from ulcerative colitis (UC) or Crohn's disease (CD) may be refractory to corticosteroids and antitumour necrosis factor (TNF) agents resulting in high colectomy rates. We aimed to describe the utility of tacrolimus to prevent colectomy during second-line vedolizumab initiation after corticosteroid and anti-TNF treatment failure in paediatric severe colitis. A retrospective cohort analysis was performed between 1 October 2014 and 31 October 2016 at a single tertiary care centre. Inclusion criteria were patients with severe colitis who received tacrolimus before or during vedolizumab induction and previous exposure to anti-TNF therapy with or without corticosteroids. The initiation of tacrolimus was clinician dependent based on an institutional protocol. Twelve patients (10 UC, two CD; median age 16 years; three female) received at least one dose of vedolizumab 10 mg/kg (max of 300 mg) due to anti-TNF therapy failure and persistent flare not responsive to corticosteroids. Of the 12 patients, eight (67%) and four (33%) had failed one or two anti-TNF agents, respectively. Tacrolimus was initiated for acute disease severity during hospitalisation (58%) or ongoing flare during outpatient care (42%). 9 (75%) of 12 patients avoided colectomy or inflammatory bowel disease-related surgery at 24 weeks and eight (68%) continued on vedolizumab maintenance with no adverse events out to 80 weeks. We report real-world data on the outcome of tacrolimus around vedolizumab initiation in paediatric UC or CD after corticosteroid and anti-TNF therapy treatment failure. Our pilot experience indicates a potential benefit of concomitant tacrolimus when initiating vedolizumab therapy.

Improving the Leader Development Experience in Army Units

DTIC Science & Technology

2013-04-01

conditions and creating a “ sweet spot” between order and chaos and simplicity and complexity, leaders can modify the experience to better align it with...subordinates to exercise initiative, overcome adversity, consider innovative solutions, or taste failure may not achieve maximum growth and are not...division commander’s behavior, preferences , and priorities become known down to battalion and lower levels.49 Some might view these techniques as

Fracture in Phenolic Impregnated Carbon Ablator

NASA Technical Reports Server (NTRS)

Agrawal, Parul; Chavez-Garcia, Jose F.

2011-01-01

The thermal protection materials used for spacecraft heat shields are subjected to various thermal-mechanical loads during an atmospheric reentry which can threaten the structural integrity of the system. This paper discusses the development of a novel technique to understand the failure mechanisms inside the thermal protection material, Phenolic Impregnated Carbon Ablator (PICA). PICA has successfully flown on the Stardust spacecraft and was the TPS material chosen for the Mars Science Laboratory (MSL), that will fly in 2011. Although PICA has good thermal properties, structurally, it is a weak material. To thoroughly understand failure in PICA, experiments were performed using FiberForm(Registered TradeMark) (precursor of PICA), virgin and furnace-charred PICA. Several small samples were tested inside an electron microscope to investigate the failure mechanisms. Micrographs were obtained before and after the failure in order to study crack initiation and growth. Videos were obtained to capture failure mechanisms in real time. Stress-strain data was obtained simultaneously for all the samples with the help of a data acquisition system, integrated to the mechanical stages. It was found that cracks initiated and grew in the FiberForm when a critical stress limit was reached such that the carbon fibers separated from the binder. However, both for virgin and charred PICA, crack initiation and growth occurred in the matrix (phenolic) phase. Both virgin and charred PICA showed greater strength values compared to FiberForm coupons, confirming that the presence of the porous matrix helps in absorbing the fracture energy.

The failure analysis, redesign, and final preparation of the Brilliant Eyes Thermal Storage Unit for flight testing

NASA Astrophysics Data System (ADS)

Lamkin, T.; Whitney, Brian

1995-09-01

This paper describes the engineering thought process behind the failure analysis, redesign, and rework of the flight hardware for the Brilliant Eyes Thermal Storage Unit (BETSU) experiment. This experiment was designed to study the zero-g performance of 2-methylpentane as a suitable phase change material. This hydrocarbon served as the cryogenic storage medium for the BETSU experiment which was flown 04 Mar 94 on board Shuttle STS-62. Ground testing had indicated satisfactory performance of the BETSU at the 120 Kelvin design temperature. However, questions remained as to the micro-gravity performance of this unit; potential deviations in ground (1 g) versus space flight (0 g) performance, and how the unit would operate in a realistic space environment undergoing cyclical operation. The preparations and rework performed on the BETSU unit, which failed initial flight qualification, give insight and lessons learned to successfully develop and qualify a space flight experiment.

Ventilatory support in critically ill hematology patients with respiratory failure

PubMed Central

2012-01-01

Introduction Hematology patients admitted to the ICU frequently experience respiratory failure and require mechanical ventilation. Noninvasive mechanical ventilation (NIMV) may decrease the risk of intubation, but NIMV failure poses its own risks. Methods To establish the impact of ventilatory management and NIMV failure on outcome, data from a prospective, multicenter, observational study were analyzed. All hematology patients admitted to one of the 34 participating ICUs in a 17-month period were followed up. Data on demographics, diagnosis, severity, organ failure, and supportive therapies were recorded. A logistic regression analysis was done to evaluate the risk factors associated with death and NIVM failure. Results Of 450 patients, 300 required ventilatory support. A diagnosis of congestive heart failure and the initial use of NIMV significantly improved survival, whereas APACHE II score, allogeneic transplantation, and NIMV failure increased the risk of death. The risk factors associated with NIMV success were age, congestive heart failure, and bacteremia. Patients with NIMV failure experienced a more severe respiratory impairment than did those electively intubated. Conclusions NIMV improves the outcome of hematology patients with respiratory insufficiency, but NIMV failure may have the opposite effect. A careful selection of patients with rapidly reversible causes of respiratory failure may increase NIMV success. PMID:22827955

Insomnia Self-Management in Heart Failure

ClinicalTrials.gov

2018-01-05

Cardiac Failure; Heart Failure; Congestive Heart Failure; Heart Failure, Congestive; Sleep Initiation and Maintenance Disorders; Chronic Insomnia; Disorders of Initiating and Maintaining Sleep; Fatigue; Pain; Depressive Symptoms; Sleep Disorders; Anxiety

Sleeve expansion of bolt holes in railroad rail. volume III - field experiment results

DOT National Transportation Integrated Search

1998-02-01

The bolt-hole cold-expansion process has been demonstrated by laboratory tests to significantly affect the initiation and propagation of fatigue cracks from rail bolt holes such that a reduction of the incidence of rail-bolt-holde failure in cold-exp...

Risk factors for eye bank preparation failure of Descemet membrane endothelial keratoplasty tissue.

PubMed

Vianna, Lucas M M; Stoeger, Christopher G; Galloway, Joshua D; Terry, Mark; Cope, Leslie; Belfort, Rubens; Jun, Albert S

2015-05-01

To assess the results of a single eye bank preparing a high volume of Descemet membrane endothelial keratoplasty (DMEK) tissues using multiple technicians to provide an overview of the experience and to identify possible risk factors for DMEK preparation failure. Cross-sectional study. setting: Lions VisionGift and Wilmer Eye Institute at Johns Hopkins Hospital. All 563 corneal tissues processed by technicians at Lions VisionGift for DMEK between October 2011 and May 2014 inclusive. Tissues were divided into 2 groups: DMEK preparation success and DMEK preparation failure. We compared donor characteristics, including past medical history. The overall tissue preparation failure rate was 5.2%. Univariate analysis showed diabetes mellitus (P = .000028) and its duration (P = .023), hypertension (P = .021), and hyperlipidemia or obesity (P = .0004) were more common in the failure group. Multivariate analysis showed diabetes mellitus (P = .0001) and hyperlipidemia or obesity (P = .0142) were more common in the failure group. Elimination of tissues from donors either with diabetes or with hyperlipidemia or obesity reduced the failure rate from 5.2% to 2.2%. Trends toward lower failure rates occurring with increased technician experience also were found. Our work showed that tissues from donors with diabetes mellitus (especially with longer disease duration) and hyperlipidemia or obesity were associated with higher failure rates in DMEK preparation. Elimination of tissues from donors either with diabetes mellitus or with hyperlipidemia or obesity reduced the failure rate. In addition, our data may provide useful initial guidelines and benchmark values for eye banks seeking to establish and maintain DMEK programs. Copyright © 2015 Elsevier Inc. All rights reserved.

Separation, failure and temporary relinquishment: women's experiences of early mothering in the context of emergency hysterectomy.

PubMed

Elmir, Rakime; Schmied, Virginia; Wilkes, Lesley; Jackson, Debra

2012-04-01

To describe the experiences of women who have had an emergency hysterectomy following a severe postpartum haemorrhage and the impact on their early mothering experiences. Postpartum haemorrhage and subsequent hysterectomy is a traumatic birth event. Traumatic birth experiences have the potential to impact on a woman's experience of motherhood and her initial relationship with her baby. The relative rarity of this event makes it easy to dismiss the experiences of women having a hysterectomy following childbirth. Little is known about a woman's early mothering experience in the context of having an emergency hysterectomy. Qualitative naturalistic inquiry approach. Data were collected through semi-structured qualitative interviews from 21 Australian women who had an emergency hysterectomy following a severe postpartum haemorrhage. Findings revealed three themes in relation to early mothering experiences in the context of having a hysterectomy following a severe postpartum haemorrhage. They were 'initial separation: lost bonding time', 'feelings of failure' and 'relinquishing care of the infant'. This paper highlights the ways undergoing emergency hysterectomy following childbirth can impact on the experience of early mothering in the postnatal period. Greater recognition and attention to the specific needs of women who have an emergency hysterectomy following childbirth is required. Providing women with an opportunity to talk, debrief and ask questions related to their birthing experiences, will help women to reconcile their feelings. Giving women the opportunity to have their infants with them in intensive care unit, together with ongoing emotional support and anticipatory guidance, may also be useful approaches in assisting women during this difficult and traumatic time. © 2011 Blackwell Publishing Ltd.

Micromechanical investigation of ductile failure in Al 5083-H116 via 3D unit cell modeling

NASA Astrophysics Data System (ADS)

Bomarito, G. F.; Warner, D. H.

2015-01-01

Ductile failure is governed by the evolution of micro-voids within a material. The micro-voids, which commonly initiate at second phase particles within metal alloys, grow and interact with each other until failure occurs. The evolution of the micro-voids, and therefore ductile failure, depends on many parameters (e.g., stress state, temperature, strain rate, void and particle volume fraction, etc.). In this study, the stress state dependence of the ductile failure of Al 5083-H116 is investigated by means of 3-D Finite Element (FE) periodic cell models. The cell models require only two pieces of information as inputs: (1) the initial particle volume fraction of the alloy and (2) the constitutive behavior of the matrix material. Based on this information, cell models are subjected to a given stress state, defined by the stress triaxiality and the Lode parameter. For each stress state, the cells are loaded in many loading orientations until failure. Material failure is assumed to occur in the weakest orientation, and so the orientation in which failure occurs first is considered as the critical orientation. The result is a description of material failure that is derived from basic principles and requires no fitting parameters. Subsequently, the results of the simulations are used to construct a homogenized material model, which is used in a component-scale FE model. The component-scale FE model is compared to experiments and is shown to over predict ductility. By excluding smaller nucleation events and load path non-proportionality, it is concluded that accuracy could be gained by including more information about the true microstructure in the model; emphasizing that its incorporation into micromechanical models is critical to developing quantitatively accurate physics-based ductile failure models.

Surgical management of early pregnancy failure: history, politics, and safe, cost-effective care.

PubMed

Harris, Lisa H; Dalton, Vanessa K; Johnson, Timothy R B

2007-05-01

Early pregnancy failure and induced abortion are often managed differently, even though safe uterine evacuation is the goal in both. Early pregnancy failure is commonly treated by curettage in operating room settings in anesthetized patients. Induced abortion is most commonly managed by office vacuum aspiration in awake or sedated patients. Medical evidence does not support routine operating room management of early pregnancy failure. This commentary reviews historical origins of these different care standards, explores political factors responsible for their perpetuation, and uses experience at University of Michigan to dramatize the ways in which history, politics, and biomedicine intersect to produce patient care. The University of Michigan initiated office uterine evacuations for early pregnancy failure treatment. Patients previously went to the operating room. These changes required faculty, staff, and resident education. Our efforts blurred the lines between spontaneous and induced abortion management, improved patient care and better utilized hospital resources.

FDIR Strategy Validation with the B Method

NASA Astrophysics Data System (ADS)

Sabatier, D.; Dellandrea, B.; Chemouil, D.

2008-08-01

In a formation flying satellite system, the FDIR strategy (Failure Detection, Isolation and Recovery) is paramount. When a failure occurs, satellites should be able to take appropriate reconfiguration actions to obtain the best possible results given the failure, ranging from avoiding satellite-to-satellite collision to continuing the mission without disturbance if possible. To achieve this goal, each satellite in the formation has an implemented FDIR strategy that governs how it detects failures (from tests or by deduction) and how it reacts (reconfiguration using redundant equipments, avoidance manoeuvres, etc.). The goal is to protect the satellites first and the mission as much as possible. In a project initiated by the CNES, ClearSy experiments the B Method to validate the FDIR strategies developed by Thales Alenia Space, of the inter satellite positioning and communication devices that will be used for the SIMBOL-X (2 satellite configuration) and the PEGASE (3 satellite configuration) missions and potentially for other missions afterward. These radio frequency metrology sensor devices provide satellite positioning and inter satellite communication in formation flying. This article presents the results of this experience.

A review for identification of initiating events in event tree development process on nuclear power plants

NASA Astrophysics Data System (ADS)

Riyadi, Eko H.

2014-09-01

Initiating event is defined as any event either internal or external to the nuclear power plants (NPPs) that perturbs the steady state operation of the plant, if operating, thereby initiating an abnormal event such as transient or loss of coolant accident (LOCA) within the NPPs. These initiating events trigger sequences of events that challenge plant control and safety systems whose failure could potentially lead to core damage or large early release. Selection for initiating events consists of two steps i.e. first step, definition of possible events, such as by evaluating a comprehensive engineering, and by constructing a top level logic model. Then the second step, grouping of identified initiating event's by the safety function to be performed or combinations of systems responses. Therefore, the purpose of this paper is to discuss initiating events identification in event tree development process and to reviews other probabilistic safety assessments (PSA). The identification of initiating events also involves the past operating experience, review of other PSA, failure mode and effect analysis (FMEA), feedback from system modeling, and master logic diagram (special type of fault tree). By using the method of study for the condition of the traditional US PSA categorization in detail, could be obtained the important initiating events that are categorized into LOCA, transients and external events.

Controls on shallow landslide initiation: Diverse hydrologic pathways, 3D failure geometries, and unsaturated soil suctions

NASA Astrophysics Data System (ADS)

Reid, Mark; Iverson, Richard; Brien, Dianne; Iverson, Neal; LaHusen, Richard; Logan, Matthew

2017-04-01

Shallow landslides and ensuing debris flows are a common hazard worldwide, yet forecasting their initiation at a specific site is challenging. These challenges arise, in part, from diverse near-surface hydrologic pathways under different wetting conditions, 3D failure geometries, and the effects of suction in partially saturated soils. Simplistic hydrologic models typically used for regional hazard assessment disregard these complexities. As an alterative to field studies where the effects of these governing factors can be difficult to isolate, we used the USGS debris-flow flume to conduct controlled, field-scale landslide initiation experiments. Using overhead sprinklers or groundwater injectors on the flume bed, we triggered failures using three different wetting conditions: groundwater inflow from below, prolonged moderate-intensity precipitation, and bursts of high-intensity precipitation. Failures occurred in 6 m3 (0.65-m thick and 2-m wide) prisms of loamy sand on a 31° slope; these field-scale failures enabled realistic incorporation of nonlinear scale-dependent effects such as soil suction. During the experiments, we monitored soil deformation, variably saturated pore pressures, and moisture changes using ˜50 sensors sampling at 20 Hz. From ancillary laboratory tests, we determined shear strength, saturated hydraulic conductivities, and unsaturated moisture retention characteristics. The three different wetting conditions noted above led to different hydrologic pathways and influenced instrumental responses and failure timing. During groundwater injection, pore-water pressures increased from the bed of the flume upwards into the sediment, whereas prolonged moderate infiltration wet the sediment from the ground surface downward. In both cases, pore pressures acting on the impending failure surface slowly rose until abrupt failure. In contrast, a burst of intense sprinkling caused rapid failure without precursory development of widespread positive pore pressures. Using coupled 2D variably saturated groundwater flow modeling and 3D limit-equilibrium analyses, we simulated the observed hydrologic behaviors and the time evolution of changes in factors of safety. Our measured parameters successfully reproduced pore pressure observations without calibration. We also quantified the mechanical effects of 3D geometry and unsaturated soil suction on stability. Although suction effects appreciably increased the stability of drier sediment, they were dampened (to <10% increase) in wetted sediment. 3D geometry effects from the lateral margins consistently increased factors of safety by >20% in wet or dry sediment. Importantly, both 3D and suction effects enabled more accurate simulation of failure times. Without these effects, failure timing and/or back-calculated shear strengths would be markedly incorrect. Our results indicate that simplistic models could not consistently predict the timing of slope failure given diverse hydrologic pathways. Moreover, high frequency monitoring (with sampling periods < ˜60 s) would be required to measure and interpret the effects of rapid hydrologic triggers, such as intense rain bursts.

Advanced Diagnostic System on Earth Observing One

NASA Technical Reports Server (NTRS)

Hayden, Sandra C.; Sweet, Adam J.; Christa, Scott E.; Tran, Daniel; Shulman, Seth

2004-01-01

In this infusion experiment, the Livingstone 2 (L2) model-based diagnosis engine, developed by the Computational Sciences division at NASA Ames Research Center, has been uploaded to the Earth Observing One (EO-1) satellite. L2 is integrated with the Autonomous Sciencecraft Experiment (ASE) which provides an on-board planning capability and a software bridge to the spacecraft's 1773 data bus. Using a model of the spacecraft subsystems, L2 predicts nominal state transitions initiated by control commands, monitors the spacecraft sensors, and, in the case of failure, isolates the fault based on the discrepant observations. Fault detection and isolation is done by determining a set of component modes, including most likely failures, which satisfy the current observations. All mode transitions and diagnoses are telemetered to the ground for analysis. The initial L2 model is scoped to EO-1's imaging instruments and solid state recorder. Diagnostic scenarios for EO-1's nominal imaging timeline are demonstrated by injecting simulated faults on-board the spacecraft. The solid state recorder stores the science images and also hosts: the experiment software. The main objective of the experiment is to mature the L2 technology to Technology Readiness Level (TRL) 7. Experiment results are presented, as well as a discussion of the challenging technical issues encountered. Future extensions may explore coordination with the planner, and model-based ground operations.

Performance Contracting - Accountability and the Michigan Education Program.

ERIC Educational Resources Information Center

Porter, John W.

1972-01-01

A report on the Michigan project in performance contracting is presented. In contrast to the Office of Economic Opportunity announcement that performance contracting is a failure, the Michigan program has been successful in the initial stage of a major experiment (Texarkana Project). The state legislature has appropriated $22.5 million for…

Module performance and failure analysis area: Flat-plate solar array project

NASA Technical Reports Server (NTRS)

Tornstrom, E.

1984-01-01

A redesign of the initial (Group I) Mobile Solar Block V module was done and documented. Manufacturing experience and accelerated test data from Group I formed the basis for the redesign. Ten Block V Group II modules were submitted for evaluation and the results are presented.

Prognostics of Power Electronics, Methods and Validation Experiments

NASA Technical Reports Server (NTRS)

Kulkarni, Chetan S.; Celaya, Jose R.; Biswas, Gautam; Goebel, Kai

2012-01-01

Abstract Failure of electronic devices is a concern for future electric aircrafts that will see an increase of electronics to drive and control safety-critical equipment throughout the aircraft. As a result, investigation of precursors to failure in electronics and prediction of remaining life of electronic components is of key importance. DC-DC power converters are power electronics systems employed typically as sourcing elements for avionics equipment. Current research efforts in prognostics for these power systems focuses on the identification of failure mechanisms and the development of accelerated aging methodologies and systems to accelerate the aging process of test devices, while continuously measuring key electrical and thermal parameters. Preliminary model-based prognostics algorithms have been developed making use of empirical degradation models and physics-inspired degradation model with focus on key components like electrolytic capacitors and power MOSFETs (metal-oxide-semiconductor-field-effect-transistor). This paper presents current results on the development of validation methods for prognostics algorithms of power electrolytic capacitors. Particularly, in the use of accelerated aging systems for algorithm validation. Validation of prognostics algorithms present difficulties in practice due to the lack of run-to-failure experiments in deployed systems. By using accelerated experiments, we circumvent this problem in order to define initial validation activities.

[The Predictive Factors of Stent Failure in the Treatment of Malignant Extrinsc Ureteral Obstruction Using Internal Ureteral Stents].

PubMed

Matsuura, Hiroshi; Arase, Shigeki; Hori, Yasuhide; Tochigi, Hiromi

2017-12-01

In this study, we retrospectively reviewed the experiences at our single institute in the treatment of malignant extrinsic ureteral obstruction (MUO) using ureteral stents to investigate the clinical outcomes and the predictive factors of stent failure. In 52 ureters of 38 patients who had radiologically significant hydronephrosis due to MUO, internal ureteral stents (The BARD(R) INLAY(TM) ureteral stent set) were inserted. The median follow-up interval after the initial stent insertion was 124.5 days (4-1,120). Stent failure occurred in 8 ureters (15.4%) of the 7 patients. The median interval from the first stent insertion to stent failure was 88 days (1-468). A Cox regression multivariate analysis showed that the significant predictors of stent failure were bladder invasion. Based on the possibility of stent failure, the adaptation of the internal ureteral stent placement should be considered especially in a patient with MUO combined with bladder invasion.

Prospective assessment of the occurrence of anemia in patients with heart failure: results from the Study of Anemia in a Heart Failure Population (STAMINA-HFP) Registry.

PubMed

Adams, Kirkwood F; Patterson, James H; Patterson, John H; Oren, Ron M; Mehra, Mandeep R; O'Connor, Christopher M; Piña, Ileana L; Miller, Alan B; Chiong, Jun R; Dunlap, Stephanie H; Cotts, William G; Felker, Gary M; Schocken, Douglas D; Schwartz, Todd A; Ghali, Jalal K

2009-05-01

Although a potentially important pathophysiologic factor in heart failure, the prevalence and predictors of anemia have not been well studied in unselected patients with heart failure. The Study of Anemia in a Heart Failure Population (STAMINA-HFP) Registry prospectively studied the prevalence of anemia and the relationship of hemoglobin to health-related quality of life and outcomes among patients with heart failure. A random selection algorithm was used to reduce bias during enrollment of patients seen in specialty clinics or clinics of community cardiologists with experience in heart failure. In this initial report, data on prevalence and correlates of anemia were analyzed in 1,076 of the 1,082 registry patients who had clinical characteristics and hemoglobin determined by finger-stick at baseline. Overall (n = 1,082), the registry patients were 41% female and 73% white with a mean age (+/-SD) of 64 +/- 14 years (68 +/- 13 years in community and 57 +/- 14 years in specialty sites, P < .001). Among the 1,076 patients in the prevalence analysis, mean hemoglobin was 13.3 +/- 2.1 g/dL (median 13.2 g/dL); and anemia (defined by World Health Organization criteria) was present in 34%. Age identified patients at risk for anemia, with 40% of patients >70 years affected. Initial results from the STAMINA-HFP Registry suggest that anemia is a common comorbidity in unselected outpatients with heart failure. Given the strong association of anemia with adverse outcomes in heart failure, this study supports further investigation concerning the importance of anemia as a therapeutic target in this condition.

The Benefits of Self-Set Goals: Is Ego Depletion Really a Result of Self-Control Failure?

PubMed Central

Zahn, Daniela; Rowland, Zarah; Kubiak, Thomas

2016-01-01

Research on ego depletion aims at explaining self-control failures in daily life. Both resource models and motivational accounts have been proposed for explanation. The aim of the present research was to test the different assumptions in two dual-task experiments where we operationalized ego depletion as a performance deviation from a self-set goal. In two experiments, we found evidence for this deviation contradicting motivational accounts of ego depletion: Participants experiencing ego depletion set themselves a stricter instead of a more lenient goal than controls, in that they chose to eat less cookies or wanted to perform better. Moreover, only participants without an initial self-control task could adhere to their self-set goal, whereas participants in the ego depletion condition in both experiments could not follow through with their more ambitious intentions. Taken together, our findings demonstrate the importance of goals in ego depletion research. PMID:27280531

Numerical and Experimental Validation of a New Damage Initiation Criterion

NASA Astrophysics Data System (ADS)

Sadhinoch, M.; Atzema, E. H.; Perdahcioglu, E. S.; van den Boogaard, A. H.

2017-09-01

Most commercial finite element software packages, like Abaqus, have a built-in coupled damage model where a damage evolution needs to be defined in terms of a single fracture energy value for all stress states. The Johnson-Cook criterion has been modified to be Lode parameter dependent and this Modified Johnson-Cook (MJC) criterion is used as a Damage Initiation Surface (DIS) in combination with the built-in Abaqus ductile damage model. An exponential damage evolution law has been used with a single fracture energy value. Ultimately, the simulated force-displacement curves are compared with experiments to validate the MJC criterion. 7 out of 9 fracture experiments were predicted accurately. The limitations and accuracy of the failure predictions of the newly developed damage initiation criterion will be discussed shortly.

Ignition and growth modeling of detonation reaction zone experiments on single crystals of PETN and HMX

NASA Astrophysics Data System (ADS)

White, Bradley W.; Tarver, Craig M.

2017-01-01

It has long been known that detonating single crystals of solid explosives have much larger failure diameters than those of heterogeneous charges of the same explosive pressed or cast to 98 - 99% theoretical maximum density (TMD). In 1957, Holland et al. demonstrated that PETN single crystals have failure diameters of about 8 mm, whereas heterogeneous PETN charges have failure diameters of less than 0.5 mm. Recently, Fedorov et al. quantitatively determined nanosecond time resolved detonation reaction zone profiles of single crystals of PETN and HMX by measuring the interface particle velocity histories of the detonating crystals and LiF windows using a PDV system. The measured reaction zone time durations for PETN and HMX single crystal detonations were approximately 100 and 260 nanoseconds, respectively. These experiments provided the necessary data to develop Ignition and Growth (I&G) reactive flow model parameters for the single crystal detonation reaction zones. Using these parameters, the calculated unconfined failure diameter of a PETN single crystal was 7.5 +/- 0.5 mm, close to the 8 mm experimental value. The calculated failure diameter of an unconfined HMX single crystal was 15 +/- 1 mm. The unconfined failure diameter of an HMX single crystal has not yet been determined precisely, but Fedorov et al. detonated 14 mm diameter crystals confined by detonating a HMX-based plastic bonded explosive (PBX) without initially overdriving the HMX crystals.

Compression failure of fibrous laminated composites in the presence of stress gradients : experiment and analysis

NASA Astrophysics Data System (ADS)

Waas, Anthony M.

A series of experiments were performed to determine the mechanism of failure in compressively loaded laminated plates in the presence of stress gradients generated by a circular cutout. Real time holographic interferometry and in-situ photomicrography of the hole surface, were used to observe the progression of failure.The test specimens are multi-layered composite flat plates, which are loaded in compression. The plates are made of two material systems, T300/BP907 and IM7/8551-7. Two different lay-ups of T300/BP907 and four different lay-ups of IM7/8551-7 are investigated.The load on the specimen is slowly increased and a series of interferograms are produced during the load cycle. These interferograms are video-recorded. The results obtained from the interferograms and photo-micrographs are substantiated by sectioning studies and ultrasonic C-scanning of some specimens which are unloaded prior to catastrophic failure, but beyond failure initiation. This is made possible by the servo-controlled loading mechanism that regulates the load application and offers the flexibility of unloading a specimen at any given instance in the loadtime history.An underlying objective of the present investigation is the identification of the physics of the failure initiation process. This required testing specimens with different stacking sequences, for a fixed hole diameter, so that consistent trends in the failure process could be identified.It is revealed that the failure is initiated as a localized instability in the 0? plies at the hole surface, approximately at right angles to the loading direction. This instability emanating at the hole edge and propagating into the interior of the specimen within the 0? plies is found to be fiber microbuckling. The microbuckling is found to occur at a local strain level of [...]8600 [mu]strain at the hole edge for the IM material system. This initial failure renders a narrow zone of fibers within the 0? plies to loose structural integrity. Subsequent to the 0?-ply failure, extensive delamination cracking is observed with increasing load. The through thickness location of these delaminations is found to depend on the position of the 0? plies.The delaminated portions spread to the undamaged areas of the laminate by a combination of delamination buckling and growth, the buckling further enhancing the growth. When the delaminated area reaches a critical size, about 75-100% of the hole radius in extent, an accelerated growth rate of the delaminated portions is observed. The culmination of this last event is the complete loss of flexural stiffness of each of the delaminated portions leading to catastrophic failure of the plate. The levels of applied load and the rate at which these events occur depend on the plate stacking sequence.A simple mechanical model is presented for the microbuckling problem. This model addresses the buckling instability of a semi-infinte layered half-plane alternatingly stacked with fibers and matrix, loaded parallel to the surface of the half-plane. The fibers are modelled using Bernoulli-Navier beam theory, and the matrix is assumed to be a linearly elastic foundation. The predicted buckling strains are found to overestimate the experimental result. However, the dependence of the buckling strain on parameters such as the fiber volume fraction, ratio of Youngs moduli of the constituents and Poisson's ratio of the matrix are obtained from the analysis. It is seen that a high fiber volume fraction, increased matrix stiffness, and perfect bonding between fiber and matrix are desirable properties for increasing the compressive strength.

Categorizing accident sequences in the external radiotherapy for risk analysis

PubMed Central

2013-01-01

Purpose This study identifies accident sequences from the past accidents in order to help the risk analysis application to the external radiotherapy. Materials and Methods This study reviews 59 accidental cases in two retrospective safety analyses that have collected the incidents in the external radiotherapy extensively. Two accident analysis reports that accumulated past incidents are investigated to identify accident sequences including initiating events, failure of safety measures, and consequences. This study classifies the accidents by the treatments stages and sources of errors for initiating events, types of failures in the safety measures, and types of undesirable consequences and the number of affected patients. Then, the accident sequences are grouped into several categories on the basis of similarity of progression. As a result, these cases can be categorized into 14 groups of accident sequence. Results The result indicates that risk analysis needs to pay attention to not only the planning stage, but also the calibration stage that is committed prior to the main treatment process. It also shows that human error is the largest contributor to initiating events as well as to the failure of safety measures. This study also illustrates an event tree analysis for an accident sequence initiated in the calibration. Conclusion This study is expected to provide sights into the accident sequences for the prospective risk analysis through the review of experiences. PMID:23865005

Role of HIV Infection Duration and CD4 Cell Level at Initiation of Combination Anti-Retroviral Therapy on Risk of Failure

PubMed Central

Lodi, Sara; Phillips, Andrew; Fidler, Sarah; Hawkins, David; Gilson, Richard; McLean, Ken; Fisher, Martin; Post, Frank; Johnson, Anne M.; Walker-Nthenda, Louise; Dunn, David; Porter, Kholoud

2013-01-01

Background The development of HIV drug resistance and subsequent virological failure are often cited as potential disadvantages of early cART initiation. However, their long-term probability is not known, and neither is the role of duration of infection at the time of initiation. Methods Patients enrolled in the UK Register of HIV seroconverters were followed-up from cART initiation to last HIV-RNA measurement. Through survival analysis we examined predictors of virologic failure (2HIV-RNA ≥400 c/l while on cART) including CD4 count and HIV duration at initiation. We also estimated the cumulative probabilities of failure and drug resistance (from the available HIV nucleotide sequences) for early initiators (cART within 12 months of seroconversion). Results Of 1075 starting cART at a median (IQR) CD4 count 272 (190,370) cells/mm3 and HIV duration 3 (1,6) years, virological failure occurred in 163 (15%). Higher CD4 count at initiation, but not HIV infection duration at cART initiation, was independently associated with lower risk of failure (p=0.033 and 0.592 respectively). Among 230 patients initiating cART early, 97 (42%) discontinued it after a median of 7 months; cumulative probabilities of resistance and failure by 8 years were 7% (95% CI 4,11) and 19% (13,25), respectively. Conclusion Although the rate of discontinuation of early cART in our cohort was high, the long-term rate of virological failure was low. Our data do not support early cART initiation being associated with increased risk of failure and drug resistance. PMID:24086588

Use of histamine H2 receptor antagonists and outcomes in patients with heart failure: a nationwide population-based cohort study.

PubMed

Adelborg, Kasper; Sundbøll, Jens; Schmidt, Morten; Bøtker, Hans Erik; Weiss, Noel S; Pedersen, Lars; Sørensen, Henrik Toft

2018-01-01

Histamine H 2 receptor activation promotes cardiac fibrosis and apoptosis in mice. However, the potential effectiveness of histamine H 2 receptor antagonists (H2RAs) in humans with heart failure is largely unknown. We examined the association between H2RA initiation and all-cause mortality among patients with heart failure. Using Danish medical registries, we conducted a nationwide population-based active-comparator cohort study of new users of H2RAs and proton pump inhibitors (PPIs) after first-time hospitalization for heart failure during the period 1995-2014. Hazard ratios (HRs) for all-cause mortality and hospitalization due to worsening of heart failure, adjusting for age, sex, and time between heart failure diagnosis and initiation of PPI or H2RA therapy, index year, comorbidity, cardiac surgery, comedications, and socioeconomic status were computed based on Cox regression analysis. Our analysis included 42,902 PPI initiators (median age 78 years, 46% female) and 3,296 H2RA initiators (median age 76 years, 48% female). Mortality risk was lower among H2RA initiators than PPI initiators after 1 year (26% vs 31%) and 5 years (60% vs 66%). In multivariable analyses, the 1-year HR was 0.80 (95% CI, 0.74-0.86) and the 5-year HR was 0.85 (95% CI, 0.80-0.89). These findings were consistent after propensity score matching and for ischemic and nonischemic heart failure, as for sex and age groups. The rate of hospitalization due to worsening of heart failure was lower among H2RA initiators than PPI initiators. In patients with heart failure, H2RA initiation was associated with 15%-20% lower mortality than PPI initiation.

Prediction Error Associated with the Perceptual Segmentation of Naturalistic Events

ERIC Educational Resources Information Center

Zacks, Jeffrey M.; Kurby, Christopher A.; Eisenberg, Michelle L.; Haroutunian, Nayiri

2011-01-01

Predicting the near future is important for survival and plays a central role in theories of perception, language processing, and learning. Prediction failures may be particularly important for initiating the updating of perceptual and memory systems and, thus, for the subjective experience of events. Here, we asked observers to make predictions…

Failure to Replicate the "Work Ethic" Effect in Pigeons

ERIC Educational Resources Information Center

Vasconcelos, Marco; Urcuioli, Peter J.; Lionello-DeNolf, Karen M.

2007-01-01

We report six unsuccessful attempts to replicate the "work ethic" phenomenon reported by Clement, Feltus, Kaiser, and Zentall (2000). In Experiments 1-5, pigeons learned two simultaneous discriminations in which the S+ and S- stimuli were obtained by pecking an initial stimulus once or multiple (20 or 40) times. Subsequent preference tests between…

[Perioperative management of a patient with myotonic dystrophy developing the cardiac symptoms initially prior to the neuromuscular symptoms].

PubMed

Wake, M; Matsushita, M; Aono, H; Matsumoto, M; Kohri, Y

1994-08-01

The authors anesthetized a 48-year-old woman with endometrial cancer and a large ovarian cyst. She developed cardiac failure initially followed by the sick sinus syndrome and A-V block from hypertrophic cardiomyopathy, prior to neuromuscular symptoms. Epidural anesthesia assisted by general anesthesia was carried out safely without intravenous administration of any muscle relaxants. From this experience, it is considered that epidural anesthesia assisted with some other proper methods is suitable for surgery of lower abdomen.

A review for identification of initiating events in event tree development process on nuclear power plants

DOE Office of Scientific and Technical Information (OSTI.GOV)

Riyadi, Eko H., E-mail: e.riyadi@bapeten.go.id

2014-09-30

Initiating event is defined as any event either internal or external to the nuclear power plants (NPPs) that perturbs the steady state operation of the plant, if operating, thereby initiating an abnormal event such as transient or loss of coolant accident (LOCA) within the NPPs. These initiating events trigger sequences of events that challenge plant control and safety systems whose failure could potentially lead to core damage or large early release. Selection for initiating events consists of two steps i.e. first step, definition of possible events, such as by evaluating a comprehensive engineering, and by constructing a top level logicmore » model. Then the second step, grouping of identified initiating event's by the safety function to be performed or combinations of systems responses. Therefore, the purpose of this paper is to discuss initiating events identification in event tree development process and to reviews other probabilistic safety assessments (PSA). The identification of initiating events also involves the past operating experience, review of other PSA, failure mode and effect analysis (FMEA), feedback from system modeling, and master logic diagram (special type of fault tree). By using the method of study for the condition of the traditional US PSA categorization in detail, could be obtained the important initiating events that are categorized into LOCA, transients and external events.« less

Perceptual, not memorial, disruption underlies emotion-induced blindness.

PubMed

Kennedy, Briana L; Most, Steven B

2012-04-01

Emotion-induced blindness refers to impaired awareness of stimuli appearing in the temporal wake of an emotionally arousing stimulus (S. B. Most, Chun, Widders, & Zald, 2005). In previous emotion-induced blindness experiments, participants withheld target responses until the end of a rapid stream of stimuli, even though each target appeared in the middle of the stream. The resulting interval between the targets' offset and participants' initiation of a response leaves open the possibility that emotion-induced blindness reflects a failure to encode or maintain target information in memory rather than a failure of perception. In the present study, participants engaged in a typical emotion-induced blindness task but initiated a response immediately upon seeing each target. Emotion-induced blindness was nevertheless robust. This suggests that emotion-induced blindness is not attributable to the delay between awareness of a target and the initiation of a response, but rather reflects the disruptive impact of emotional distractors on mechanisms driving conscious perception. (PsycINFO Database Record (c) 2012 APA, all rights reserved).

High burnup fuel behavior related to fission gas effects under reactivity initiated accidents (RIA) conditions

NASA Astrophysics Data System (ADS)

Lemoine, F.

1997-09-01

Specific aspects of irradiated fuel result from the increasing retention of gaseous and volatile fission products with burnup, which, under overpower conditions, can lead to solid fuel pressurization and swelling causing severe PCMI (pellet clad mechanical interaction). In order to assess the reliability of high burnup fuel under RIAs, experimental programs have been initiated which have provided important data concerning the transient fission gas behavior and the clad loading mechanisms. The importance of the rim zone is demonstrated based on three experiments resulting in clad failure at low enthalpy, which are explained by energetic considerations. High gas release in non-failure tests with low energy deposition underlines the importance of grain boundary and porosity gas. Measured final releases are strongly correlated to the microstructure evolution, depending on energy deposition, pulse width, initial and refabricated fuel rod design. Observed helium release can also increase internal pressure and gives hints to the gas behavior understanding.

Proposal for a functional classification system of heart failure in patients with end-stage renal disease: proceedings of the acute dialysis quality initiative (ADQI) XI workgroup.

PubMed

Chawla, Lakhmir S; Herzog, Charles A; Costanzo, Maria Rosa; Tumlin, James; Kellum, John A; McCullough, Peter A; Ronco, Claudio

2014-04-08

Structural heart disease is highly prevalent in patients with chronic kidney disease requiring dialysis. More than 80% of patients with end-stage renal disease (ESRD) are reported to have cardiovascular disease. This observation has enormous clinical relevance because the leading causes of death for patients with ESRD are of cardiovascular disease etiology, including heart failure, myocardial infarction, and sudden cardiac death. The 2 systems most commonly used to classify the severity of heart failure are the New York Heart Association (NYHA) functional classification and the American Heart Association (AHA)/American College of Cardiology (ACC) staging system. With rare exceptions, patients with ESRD who do not receive renal replacement therapy (RRT) develop signs and symptoms of heart failure, including dyspnea and edema due to inability of the severely diseased kidneys to excrete sodium and water. Thus, by definition, nearly all patients with ESRD develop a symptomatology consistent with heart failure if fluid removal by RRT is delayed. Neither the AHA/ACC heart failure staging nor the NYHA functional classification system identifies the variable symptomatology that patients with ESRD experience depending upon whether evaluation occurs before or after fluid removal by RRT. Consequently, the incidence, severity, and outcomes of heart failure in patients with ESRD are poorly characterized. The 11th Acute Dialysis Quality Initiative has identified this issue as a critical unmet need for the proper evaluation and treatment of heart failure in patients with ESRD. We propose a classification schema based on patient-reported dyspnea assessed both pre- and post-ultrafiltration, in conjunction with echocardiography. Copyright © 2014 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

Preoperative short hookwire placement for small pulmonary lesions: evaluation of technical success and risk factors for initial placement failure.

PubMed

Iguchi, Toshihiro; Hiraki, Takao; Matsui, Yusuke; Fujiwara, Hiroyasu; Masaoka, Yoshihisa; Tanaka, Takashi; Sato, Takuya; Gobara, Hideo; Toyooka, Shinichi; Kanazawa, Susumu

2018-05-01

To retrospectively evaluate the technical success of computed tomography fluoroscopy-guided short hookwire placement before video-assisted thoracoscopic surgery and to identify the risk factors for initial placement failure. In total, 401 short hookwire placements for 401 lesions (mean diameter 9.3 mm) were reviewed. Technical success was defined as correct positioning of the hookwire. Possible risk factors for initial placement failure (i.e., requirement for placement of an additional hookwire or to abort the attempt) were evaluated using logistic regression analysis for all procedures, and for procedures performed via the conventional route separately. Of the 401 initial placements, 383 were successful and 18 failed. Short hookwires were finally placed for 399 of 401 lesions (99.5%). Univariate logistic regression analyses revealed that in all 401 procedures only the transfissural approach was a significant independent predictor of initial placement failure (odds ratio, OR, 15.326; 95% confidence interval, CI, 5.429-43.267; p < 0.001) and for the 374 procedures performed via the conventional route only lesion size was a significant independent predictor of failure (OR 0.793, 95% CI 0.631-0.996; p = 0.046). The technical success of preoperative short hookwire placement was extremely high. The transfissural approach was a predictor initial placement failure for all procedures and small lesion size was a predictor of initial placement failure for procedures performed via the conventional route. • Technical success of preoperative short hookwire placement was extremely high. • The transfissural approach was a significant independent predictor of initial placement failure for all procedures. • Small lesion size was a significant independent predictor of initial placement failure for procedures performed via the conventional route.

Thermal barrier coating life prediction model

NASA Technical Reports Server (NTRS)

Hillery, R. V.; Pilsner, B. H.; Cook, T. S.; Kim, K. S.

1986-01-01

This is the second annual report of the first 3-year phase of a 2-phase, 5-year program. The objectives of the first phase are to determine the predominant modes of degradation of a plasma sprayed thermal barrier coating system and to develop and verify life prediction models accounting for these degradation modes. The primary TBC system consists of an air plasma sprayed ZrO-Y2O3 top coat, a low pressure plasma sprayed NiCrAlY bond coat, and a Rene' 80 substrate. Task I was to evaluate TBC failure mechanisms. Both bond coat oxidation and bond coat creep have been identified as contributors to TBC failure. Key property determinations have also been made for the bond coat and the top coat, including tensile strength, Poisson's ratio, dynamic modulus, and coefficient of thermal expansion. Task II is to develop TBC life prediction models for the predominant failure modes. These models will be developed based on the results of thermmechanical experiments and finite element analysis. The thermomechanical experiments have been defined and testing initiated. Finite element models have also been developed to handle TBCs and are being utilized to evaluate different TBC failure regimes.

Efficient 3-D finite element failure analysis of compression loaded angle-ply plates with holes

NASA Technical Reports Server (NTRS)

Burns, S. W.; Herakovich, C. T.; Williams, J. G.

1987-01-01

Finite element stress analysis and the tensor polynomial failure criterion predict that failure always initiates at the interface between layers on the hole edge for notched angle-ply laminates loaded in compression. The angular location of initial failure is a function of the fiber orientation in the laminate. The dominant stress components initiating failure are shear. It is shown that approximate symmetry can be used to reduce the computer resources required for the case of unaxial loading.

Operating Experience and Reliability Improvements on the 5 kW CW Klystron at Jefferson Lab

NASA Astrophysics Data System (ADS)

Nelson, R.; Holben, S.

1997-05-01

With substantial operating hours on the RF system, considerable information on reliability of the 5 kW CW klystrons has been obtained. High early failure rates led to examination of the operating conditions and failure modes. Internal ceramic contamination caused premature failure of gun potting material and ultimate tube demise through arcing or ceramic fracture. A planned course of repotting and reconditioning of approximately 300 klystrons, plus careful attention to operating conditions and periodic analysis of operational data, has substantially reduced the failure rate. It is anticipated that implementation of planned supplemental monitoring systems for the klystrons will allow most catastrophic failures to be avoided. By predicting end of life, tubes can be changed out before they fail, thus minimizing unplanned downtime. Initial tests have also been conducted on this same klystron operated at higher voltages with resultant higher output power. The outcome of these tests will provide information to be considered for future upgrades to the accelerator.

Factors Influencing Progressive Failure Analysis Predictions for Laminated Composite Structure

NASA Technical Reports Server (NTRS)

Knight, Norman F., Jr.

2008-01-01

Progressive failure material modeling methods used for structural analysis including failure initiation and material degradation are presented. Different failure initiation criteria and material degradation models are described that define progressive failure formulations. These progressive failure formulations are implemented in a user-defined material model for use with a nonlinear finite element analysis tool. The failure initiation criteria include the maximum stress criteria, maximum strain criteria, the Tsai-Wu failure polynomial, and the Hashin criteria. The material degradation model is based on the ply-discounting approach where the local material constitutive coefficients are degraded. Applications and extensions of the progressive failure analysis material model address two-dimensional plate and shell finite elements and three-dimensional solid finite elements. Implementation details are described in the present paper. Parametric studies for laminated composite structures are discussed to illustrate the features of the progressive failure modeling methods that have been implemented and to demonstrate their influence on progressive failure analysis predictions.

Initial experience with percutaneous selective embolization: A truly minimally invasive treatment of the adolescent varicocele with no risk of hydrocele development.

PubMed

Storm, Douglas W; Hogan, Mark J; Jayanthi, Venkata R

2010-12-01

Postoperative hydrocele development is a frustrating complication of varicocele surgical repair. To avoid this complication, we began to offer percutaneous embolization as a treatment option. We present our initial experience with this technique. A retrospective review of all patients who underwent percutaneous embolization and sclerotherapy of a varicocele at our institution was performed. There were 27 patients with a mean age of 16 years (range 13-19 years). Indications included pain (48%), varicocele size (30%) and persistent testicular asymmetry (22%). Four patients had experienced failure of a previous surgical repair. Follow-up data were available for 21 patients (mean 9 months). The varicocele resolved in 19 patients (91%) with no evidence of hydrocele formation in any of the boys. There was resolution of pain in all patients for whom this was the indication for the procedure. In the two failures, access to the lower spermatic vein was not possible owing to the number and tortuosity of the vessels. Percutaneous embolization and sclerotherapy represent a truly minimally invasive treatment with low morbidity, minimal pain and rapid recovery. In our early experience, since lymphatic channels are completely avoided, there appears to be no risk of hydrocele formation. Copyright © 2010 Journal of Pediatric Urology Company. Published by Elsevier Ltd. All rights reserved.

The National Heart Failure Project: a health care financing administration initiative to improve the care of Medicare beneficiaries with heart failure.

PubMed

Masoudi, F A; Ordin, D L; Delaney, R J; Krumholz, H M; Havranek, E P

2000-01-01

This is the second in a series describing Health Care Financing Administration (HCFA) initiatives to improve care for Medicare beneficiaries with heart failure. The first article outlined the history of HCFA quality-improvement projects and current initiatives to improve care in six priority areas: heart failure, acute myocardial infarction, stroke, pneumonia, diabetes, and breast cancer. This article details the objectives and design of the Medicare National Heart Failure Quality Improvement Project (NHF), which has as its goal the improvement of inpatient heart failure care. (c)2000 by CHF, Inc.

Overload cascading failure on complex networks with heterogeneous load redistribution

NASA Astrophysics Data System (ADS)

Hou, Yueyi; Xing, Xiaoyun; Li, Menghui; Zeng, An; Wang, Yougui

2017-09-01

Many real systems including the Internet, power-grid and financial networks experience rare but large overload cascading failures triggered by small initial shocks. Many models on complex networks have been developed to investigate this phenomenon. Most of these models are based on the load redistribution process and assume that the load on a failed node shifts to nearby nodes in the networks either evenly or according to the load distribution rule before the cascade. Inspired by the fact that real power-grid tends to place the excess load on the nodes with high remaining capacities, we study a heterogeneous load redistribution mechanism in a simplified sandpile model in this paper. We find that weak heterogeneity in load redistribution can effectively mitigate the cascade while strong heterogeneity in load redistribution may even enlarge the size of the final failure. With a parameter θ to control the degree of the redistribution heterogeneity, we identify a rather robust optimal θ∗ = 1. Finally, we find that θ∗ tends to shift to a larger value if the initial sand distribution is homogeneous.

Decision Makers Calibrate Behavioral Persistence on the Basis of Time-Interval Experience

ERIC Educational Resources Information Center

McGuire, Joseph T.; Kable, Joseph W.

2012-01-01

A central question in intertemporal decision making is why people reverse their own past choices. Someone who initially prefers a long-run outcome might fail to maintain that preference for long enough to see the outcome realized. Such behavior is usually understood as reflecting preference instability or self-control failure. However, if a…

Fault Damage Zone Permeability in Crystalline Rocks from Combined Field and Laboratory Measurements

NASA Astrophysics Data System (ADS)

Mitchell, T.; Faulkner, D.

2008-12-01

In nature, permeability is enhanced in the damage zone of faults, where fracturing occurs on a wide range of scales. Here we analyze the contribution of microfracture damage on the permeability of faults that cut through low porosity, crystalline rocks by combining field and laboratory measurements. Microfracture densities surrounding strike-slip faults with well-constrained displacements ranging over 3 orders of magnitude (~0.12 m - 5000 m) have been analyzed. The faults studied are excellently exposed within the Atacama Fault Zone, where exhumation from 6-10 km has occurred. Microfractures in the form of fluid inclusion planes (FIPs) show a log-linear decrease in fracture density with perpendicular distance from the fault core. Damage zone widths defined by the density of FIPs scale with fault displacement, and an empirical relationship for microfracture density distribution throughout the damage zone with displacement is derived. Damage zone rocks will have experienced differential stresses that were less than, but some proportion of, the failure stress. As such, permeability data from progressively loaded, initially intact laboratory samples, in the pre-failure region provide useful insights into fluid flow properties of various parts of the damage zone. The permeability evolution of initially intact crystalline rocks under increasing differential load leading to macroscopic failure was determined at water pore pressures of 50 MPa and effective pressure of 10 MPa. Permeability is seen to increase by up to, and over, two orders of magnitude prior to macroscopic failure. Further experiments were stopped at various points in the loading history in order to correlate microfracture density within the samples with permeability. By combining empirical relationships determined from both quantitative fieldwork and experiments we present a model that allows microfracture permeability distribution throughout the damage zone to be determined as function of increasing fault displacement.

Effects of Gas Pressure on the Failure Characteristics of Coal

NASA Astrophysics Data System (ADS)

Xie, Guangxiang; Yin, Zhiqiang; Wang, Lei; Hu, Zuxiang; Zhu, Chuanqi

2017-07-01

Several experiments were conducted using self-developed equipment for visual gas-solid coupling mechanics. The raw coal specimens were stored in a container filled with gas (99% CH4) under different initial gas pressure conditions (0.0, 0.5, 1.0, and 1.5 MPa) for 24 h prior to testing. Then, the specimens were tested in a rock-testing machine, and the mechanical properties, surface deformation and failure modes were recorded using strain gauges, an acoustic emission (AE) system and a camera. An analysis of the fractals of fragments and dissipated energy was performed to understand the changes observed in the stress-strain and crack propagation behaviour of the gas-containing coal specimens. The results demonstrate that increased gas pressure leads to a reduction in the uniaxial compression strength (UCS) of gas-containing coal and the critical dilatancy stress. The AE, surface deformation and fractal analysis results show that the failure mode changes during the gas state. Interestingly, a higher initial gas pressure will cause the damaged cracks and failure of the gas-containing coal samples to become severe. The dissipated energy characteristic in the failure process of a gas-containing coal sample is analysed using a combination of fractal theory and energy principles. Using the theory of fracture mechanics, based on theoretical analyses and calculations, the stress intensity factor of crack tips increases as the gas pressure increases, which is the main cause of the reduction in the UCS and critical dilatancy stress and explains the influence of gas in coal failure. More serious failure is created in gas-containing coal under a high gas pressure and low exterior load.

Meso-Scale Progressive Damage Behavior Characterization of Triaxial Braided Composites under Quasi-Static Tensile Load

NASA Astrophysics Data System (ADS)

Ren, Yiru; Zhang, Songjun; Jiang, Hongyong; Xiang, Jinwu

2018-04-01

Based on continuum damage mechanics (CDM), a sophisticated 3D meso-scale finite element (FE) model is proposed to characterize the progressive damage behavior of 2D Triaxial Braided Composites (2DTBC) with 60° braiding angle under quasi-static tensile load. The modified Von Mises strength criterion and 3D Hashin failure criterion are used to predict the damage initiation of the pure matrix and fiber tows. A combining interface damage and friction constitutive model is applied to predict the interface damage behavior. Murakami-Ohno stiffness degradation scheme is employed to predict the damage evolution process of each constituent. Coupling with the ordinary and translational symmetry boundary conditions, the tensile elastic response including tensile strength and failure strain of 2DTBC are in good agreement with the available experiment data. The numerical results show that the main failure modes of the composites under axial tensile load are pure matrix cracking, fiber and matrix tension failure in bias fiber tows, matrix tension failure in axial fiber tows and interface debonding; the main failure modes of the composites subjected to transverse tensile load are free-edge effect, matrix tension failure in bias fiber tows and interface debonding.

Effect of Initial Conditions on Reproducibility of Scientific Research

PubMed Central

Djulbegovic, Benjamin; Hozo, Iztok

2014-01-01

Background: It is estimated that about half of currently published research cannot be reproduced. Many reasons have been offered as explanations for failure to reproduce scientific research findings- from fraud to the issues related to design, conduct, analysis, or publishing scientific research. We also postulate a sensitive dependency on initial conditions by which small changes can result in the large differences in the research findings when attempted to be reproduced at later times. Methods: We employed a simple logistic regression equation to model the effect of covariates on the initial study findings. We then fed the input from the logistic equation into a logistic map function to model stability of the results in repeated experiments over time. We illustrate the approach by modeling effects of different factors on the choice of correct treatment. Results: We found that reproducibility of the study findings depended both on the initial values of all independent variables and the rate of change in the baseline conditions, the latter being more important. When the changes in the baseline conditions vary by about 3.5 to about 4 in between experiments, no research findings could be reproduced. However, when the rate of change between the experiments is ≤2.5 the results become highly predictable between the experiments. Conclusions: Many results cannot be reproduced because of the changes in the initial conditions between the experiments. Better control of the baseline conditions in-between the experiments may help improve reproducibility of scientific findings. PMID:25132705

Effect of initial conditions on reproducibility of scientific research.

PubMed

Djulbegovic, Benjamin; Hozo, Iztok

2014-06-01

It is estimated that about half of currently published research cannot be reproduced. Many reasons have been offered as explanations for failure to reproduce scientific research findings- from fraud to the issues related to design, conduct, analysis, or publishing scientific research. We also postulate a sensitive dependency on initial conditions by which small changes can result in the large differences in the research findings when attempted to be reproduced at later times. We employed a simple logistic regression equation to model the effect of covariates on the initial study findings. We then fed the input from the logistic equation into a logistic map function to model stability of the results in repeated experiments over time. We illustrate the approach by modeling effects of different factors on the choice of correct treatment. We found that reproducibility of the study findings depended both on the initial values of all independent variables and the rate of change in the baseline conditions, the latter being more important. When the changes in the baseline conditions vary by about 3.5 to about 4 in between experiments, no research findings could be reproduced. However, when the rate of change between the experiments is ≤2.5 the results become highly predictable between the experiments. Many results cannot be reproduced because of the changes in the initial conditions between the experiments. Better control of the baseline conditions in-between the experiments may help improve reproducibility of scientific findings.

Mitral Transcatheter Technologies

PubMed Central

Maisano, Francesco; Buzzatti, Nicola; Taramasso, Maurizio; Alfieri, Ottavio

2013-01-01

Mitral valve regurgitation (MR) is often diagnosed in patients with heart failure and is associated with worsening of symptoms and reduced survival. While surgery remains the gold standard treatment in low-risk patients with degenerative MR, in high-risk patients and in those with functional MR, transcatheter procedures are emerging as an alternative therapeutic option. MitraClip® is the device with which the largest clinical experience has been gained to date, as it offers sustained clinical benefit in selected patients. Further to MitraClip implantation, several additional approaches are developing, to better match with the extreme variability of mitral valve disease. Not only repair is evolving, initial steps towards percutaneous mitral valve implantation have already been undertaken, and initial clinical experience has just started. PMID:23908865

The Dynamic Flow and Failure Behavior of Magnesium and Magnesium Alloys

NASA Astrophysics Data System (ADS)

Eswar Prasad, K.; Li, B.; Dixit, N.; Shaffer, M.; Mathaudhu, S. N.; Ramesh, K. T.

2014-01-01

We review the dynamic behavior of magnesium alloys through a survey of the literature and a comparison with our own high-strain-rate experiments. We describe high-strain-rate experiments (at typical strain rates of 103 s-1) on polycrystalline pure magnesium as well as two magnesium alloys, AZ31B and ZK60. Both deformation and failure are considered. The observed behaviors are discussed in terms of the fundamental deformation and failure mechanisms in magnesium, considering the effects of grain size, strain rate, and crystallographic texture. A comparison of current results with the literature studies on these and other Mg alloys reveals that the crystallographic texture, grain size, and alloying elements continue to have a profound influence on the high-strain-rate deformation behavior. The available data set suggests that those materials loaded so as to initiate extension twinning have relatively rate-insensitive strengths up to strain rates of several thousand per second. In contrast, some rate dependence of the flow stress is observed for loading orientations in which the plastic flow is dominated by dislocation mechanisms.

Heart Failure Virtual Consultation: bridging the gap of heart failure care in the community - A mixed-methods evaluation.

PubMed

Gallagher, Joseph; James, Stephanie; Keane, Ciara; Fitzgerald, Annie; Travers, Bronagh; Quigley, Etain; Hecht, Christina; Zhou, Shuaiwei; Watson, Chris; Ledwidge, Mark; McDonald, Kenneth

2017-08-01

We undertook a mixed-methods evaluation of a Web-based conferencing service (virtual consult) between general practitioners (GPs) and cardiologists in managing patients with heart failure in the community to determine its effect on use of specialist heart failure services and acceptability to GPs. All cases from June 2015 to October 2016 were recorded using a standardized recording template, which recorded patient demographics, medical history, medications, and outcome of the virtual consult for each case. Quantitative surveys and qualitative interviewing of 17 participating GPs were also undertaken. During this time, 142 cases were discussed-68 relating to a new diagnosis of heart failure, 53 relating to emerging deterioration in a known heart failure patient, and 21 relating to therapeutic issues. Only 17% required review in outpatient department following the virtual consultation. GPs reported increased confidence in heart failure management, a broadening of their knowledge base, and a perception of overall better patient outcomes. These data from an initial experience with Heart Failure Virtual Consultation present a very positive impact of this strategy on the provision of heart failure care in the community and acceptability to users. Further research on the implementation and expansion of this strategy is warranted. © 2017 The Authors. ESC Heart Failure published by John Wiley & Sons Ltd on behalf of the European Society of Cardiology.

Extracorporeal membrane oxygenation: experience in an adult medical ICU.

PubMed

Hermans, G; Meersseman, W; Wilmer, A; Meyns, B; Bobbaers, H

2007-06-01

Extracorporeal membrane oxygenation (ECMO) is a technology that can provide extracorporeal gas exchange to patients with severe pulmonary or cardiac dysfunction. We report on our clinical experience with ECMO in critically ill patients. We performed a retrospective analysis of 23 patients treated with ECMO in a medical intensive care unit in a tertiary referral academic centre. 13 patients were considered immunocompetent and 10 were immunocompromised when extracorporeal membrane oxygenation was started. 16 patients presented with acute respiratory distress syndrome (ARDS), 2 patients had intractable cardiac failure, and 5 patients had combined respiratory and cardiac failure. In 16 patients, a veno-venous bypass was constructed; in 7 patients, the initial bypass was venoarterial. 11 patients survived. In 2 patients technical complications were fatal. Our data indicate that patients with community-acquired pneumonia and no underlying disease will benefit most from this technique. However, long-term survival is possible in immunocompromised patients. Venoarterial bypass can carry a higher risk for technical complications. Increasing experience apparently also reduces the risk of technical complications.

Evolution of wear and friction along experimental faults

USGS Publications Warehouse

Boneh, Yeval; Chang, Jefferson C.; Lockner, David A.; Reches, Zeev

2014-01-01

We investigate the evolution of wear and friction along experimental faults composed of solid rock blocks. This evolution is analyzed through shear experiments along five rock types, and the experiments were conducted in a rotary apparatus at slip velocities of 0.002–0.97 m/s, slip distances from a few millimeters to tens of meters, and normal stress of 0.25–6.9 MPa. The wear and friction measurements and fault surface observations revealed three evolution phases: A) An initial stage (slip distances <50 mm) of wear by failure of isolated asperities associated with roughening of the fault surface; B) a running-in stage of slip distances of 1–3 m with intense wear-rate, failure of many asperities, and simultaneous reduction of the friction coefficient and wear-rate; and C) a steady-state stage that initiates when the fault surface is covered by a gouge layer, and during which both wear-rate and friction coefficient maintain quasi-constant, low levels. While these evolution stages are clearly recognizable for experimental faults made from bare rock blocks, our analysis suggests that natural faults “bypass” the first two stages and slip at gouge-controlled steady-state conditions.

User-Defined Material Model for Progressive Failure Analysis

NASA Technical Reports Server (NTRS)

Knight, Norman F. Jr.; Reeder, James R. (Technical Monitor)

2006-01-01

An overview of different types of composite material system architectures and a brief review of progressive failure material modeling methods used for structural analysis including failure initiation and material degradation are presented. Different failure initiation criteria and material degradation models are described that define progressive failure formulations. These progressive failure formulations are implemented in a user-defined material model (or UMAT) for use with the ABAQUS/Standard1 nonlinear finite element analysis tool. The failure initiation criteria include the maximum stress criteria, maximum strain criteria, the Tsai-Wu failure polynomial, and the Hashin criteria. The material degradation model is based on the ply-discounting approach where the local material constitutive coefficients are degraded. Applications and extensions of the progressive failure analysis material model address two-dimensional plate and shell finite elements and three-dimensional solid finite elements. Implementation details and use of the UMAT subroutine are described in the present paper. Parametric studies for composite structures are discussed to illustrate the features of the progressive failure modeling methods that have been implemented.

Experimental analysis of quasi-static and dynamic fracture initiation toughness of gy4 armor steel material

NASA Astrophysics Data System (ADS)

Ren, Peng; Guo, Zitao

Quasi-static and dynamic fracture initiation toughness of gy4 armour steel material are investigated using three point bend specimen. The modified split Hopkinson pressure bar (SHPB) apparatus with digital image correlation (DIC) system is applied to dynamic loading experiments. Full-field deformation measurements are obtained by using DIC to elucidate on the strain fields associated with the mechanical response. A series of experiments are conducted at different strain rate ranging from 10-3 s-1 to 103 s-1, and the loading rate on the fracture initiation toughness is investigated. Specially, the scanning electron microscope imaging technique is used to investigate the fracture failure micromechanism of fracture surfaces. The gy4 armour steel material fracture toughness is found to be sensitive to strain rate and higher for dynamic loading as compared to quasi-static loading. This work is supported by National Nature Science Foundation under Grant 51509115.

Effect of porcelain and enamel thickness on porcelain veneer failure loads in vitro.

PubMed

Ge, Chunling; Green, Chad C; Sederstrom, Dalene; McLaren, Edward A; White, Shane N

2014-05-01

Bonded porcelain veneers are widely used esthetic restorations. Although high success and survival rates have been reported, failures occur. Fracture is the most common failure mode. Fractures range from incomplete cracks to the catastrophic. Minimally invasive or thin partial veneers have gained popularity. The aim of this study was to measure the influences of porcelain veneer thickness and enamel substrate thickness on the loads needed to cause the initial fracture and catastrophic failure of porcelain veneers. Model discoid porcelain veneer specimens of varying thickness were bonded to the flattened facial surfaces of incisors, artificially aged, and loaded to failure with a small sphere. Individual fracture events were identified and analyzed statistically and fractographically. Fracture events included initial Hertzian cracks, intermediate radial cracks, and catastrophic gross failure. Increased porcelain, enamel, and their combined thickness had like effects in substantially raising resistance to catastrophic failure but also slightly decreased resistance to initial Hertzian cracking. Fractographic and numerical data demonstrated that porcelain and tooth enamel behaved in a remarkably similar manner. As porcelain thickness, enamel thickness, and their combined thickness increased, the loads needed to produce initial fracture and catastrophic failure rose substantially. Porcelain veneers withstood considerable damage before catastrophic failure. Increased enamel thickness, increased porcelain thickness, and increased combined enamel and porcelain thickness all profoundly raised the failure loads necessary to cause catastrophic failure. Enamel and feldspathic porcelain behaved in a like manner. Surface contact damage occurred initially. Final catastrophic failure followed flexural radial cracking. Bonded porcelain veneers were highly damage tolerant. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Explosive Model Tarantula V1/JWL++ Calibration of LX-17: #2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Souers, P C; Vitello, P

2009-05-01

Tarantula V1 is a kinetic package for reactive flow codes that seeks to describe initiation, failure, dead zones and detonation simultaneously. The most important parameter is P1, the pressure between the initiation and failure regions. Both dead zone formation and failure can be largely controlled with this knob. However, V1 does failure with low settings and dead zones with higher settings, so that it cannot fulfill its purpose in the current format. To this end, V2 is under test. The derivation of the initiation threshold P0 is discussed. The derivation of the initiation pressure-tau curve as an output of Tarantulamore » shows that the initiation package is sound. A desensitization package is also considered.« less

SU-E-T-421: Failure Mode and Effects Analysis (FMEA) of Xoft Electronic Brachytherapy for the Treatment of Superficial Skin Cancers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hoisak, J; Manger, R; Dragojevic, I

Purpose: To perform a failure mode and effects analysis (FMEA) of the process for treating superficial skin cancers with the Xoft Axxent electronic brachytherapy (eBx) system, given the recent introduction of expanded quality control (QC) initiatives at our institution. Methods: A process map was developed listing all steps in superficial treatments with Xoft eBx, from the initial patient consult to the completion of the treatment course. The process map guided the FMEA to identify the failure modes for each step in the treatment workflow and assign Risk Priority Numbers (RPN), calculated as the product of the failure mode’s probability ofmore » occurrence (O), severity (S) and lack of detectability (D). FMEA was done with and without the inclusion of recent QC initiatives such as increased staffing, physics oversight, standardized source calibration, treatment planning and documentation. The failure modes with the highest RPNs were identified and contrasted before and after introduction of the QC initiatives. Results: Based on the FMEA, the failure modes with the highest RPN were related to source calibration, treatment planning, and patient setup/treatment delivery (Fig. 1). The introduction of additional physics oversight, standardized planning and safety initiatives such as checklists and time-outs reduced the RPNs of these failure modes. High-risk failure modes that could be mitigated with improved hardware and software interlocks were identified. Conclusion: The FMEA analysis identified the steps in the treatment process presenting the highest risk. The introduction of enhanced QC initiatives mitigated the risk of some of these failure modes by decreasing their probability of occurrence and increasing their detectability. This analysis demonstrates the importance of well-designed QC policies, procedures and oversight in a Xoft eBx programme for treatment of superficial skin cancers. Unresolved high risk failure modes highlight the need for non-procedural quality initiatives such as improved planning software and more robust hardware interlock systems.« less

Controls on the breach geometry and flood hydrograph during overtopping of non-cohesive earthen dams

USGS Publications Warehouse

Walder, Joseph S.; Iverson, Richard M.; Godt, Jonathan W.; Logan, Matthew; Solovitz, Stephen A.

2015-01-01

Overtopping failure of non-cohesive earthen dams was investigated in 13 large-scale experiments with dams built of compacted, damp, fine-grained sand. Breaching was initiated by cutting a notch across the dam crest and allowing water escaping from a finite upstream reservoir to form its own channel. The channel developed a stepped profile, and upstream migration of the steps, which coalesced into a headcut, led to the establishment of hydraulic control (critical flow) at the channel head, or breach crest, an arcuate erosional feature that functions hydraulically as a weir. Novel photogrammetric methods, along with underwater videography, revealed that the retreating headcut maintained a slope near the angle of friction of the sand, while the cross section at the breach crest maintained a geometrically similar shape through time. That cross-sectional shape was nearly unaffected by slope failures, contrary to the assumption in many models of dam breaching. Flood hydrographs were quite reproducible--for sets of dams ranging in height from 0.55 m to 0.98 m--when the time datum was chosen as the time that the migrating headcut intersected the breach crest. Peak discharge increased almost linearly as a function of initial dam height. Early-time variability between flood hydrographs for nominally identical dams is probably a reflection of subtle experiment-to-experiment differences in groundwater hydrology and the interaction between surface water and groundwater.

Failure prediction for the optimization of stretch forming aluminium-polymer laminate foils used for pharmaceutical packaging

NASA Astrophysics Data System (ADS)

Müller, Simon; Weygand, Sabine M.

2018-05-01

Axisymmetric stretch forming processes of aluminium-polymer laminate foils (e.g. consisting of PA-Al-PVC layers) are analyzed numerically by finite element modeling of the multi-layer material as well as experimentally in order to identify a suitable damage initiation criterion. A simple ductile fracture criterion is proposed to predict the forming limits. The corresponding material constants are determined from tensile tests and then applied in forming simulations with different punch geometries. A comparison between the simulations and the experimental results shows that the determined failure constants are not applicable. Therefore, one forming experiment was selected and in the corresponding simulation the failure constant was fitted to its measured maximum stretch. With this approach it is possible to predict the forming limit of the laminate foil with satisfying accuracy for different punch geometries.

Failure of Alzheimer's Aβ(1-40) amyloid nanofibrils under compressive loading

NASA Astrophysics Data System (ADS)

Paparcone, Raffaella; Buehler, Markus J.

2010-04-01

Amyloids are associated with severe degenerative diseases and show exceptional mechanical properties, in particular great stiffhess. Amyloid fibrils, forming protein nanotube structures, are elongated fibers with a diameter of ≈8 nm with a characteristic dense hydrogen-bond (H-bond)patterning in the form of beta-sheets (β-sheets). Here we report a series of molecular dynamics simulations to study mechanical failure properties of a twofold symmetric Aβ(l-40) amyloid fibril, a pathogen associated with Alzheimer’s disease. We carry out computational experiments to study the response of the amyloid fibril to compressive loading. Our investigations reveal atomistic details of the failure process, and confirm that the breakdown of H-bonds plays a critical role during the failure process of amyloid fibrils. We obtain a Young’s modulus of ≈12.43 GPa, in dose agreement with earlier experimental results. Our simulations show that failure by buck-ling and subsequent shearing in one of the layers initiates at ≈1% compressive strain, suggesting that amyloid fibrils can be rather brittle mechanical elements.

Virologic outcomes in early antiretroviral treatment: HPTN 052.

PubMed

Eshleman, Susan H; Wilson, Ethan A; Zhang, Xinyi C; Ou, San-San; Piwowar-Manning, Estelle; Eron, Joseph J; McCauley, Marybeth; Gamble, Theresa; Gallant, Joel E; Hosseinipour, Mina C; Kumarasamy, Nagalingeswaran; Hakim, James G; Kalonga, Ben; Pilotto, Jose H; Grinsztejn, Beatriz; Godbole, Sheela V; Chotirosniramit, Nuntisa; Santos, Breno Riegel; Shava, Emily; Mills, Lisa A; Panchia, Ravindre; Mwelase, Noluthando; Mayer, Kenneth H; Chen, Ying Q; Cohen, Myron S; Fogel, Jessica M

2017-05-01

The HIV Prevention Trials Network (HPTN) 052 trial demonstrated that early antiretroviral therapy (ART) prevented 93% of HIV transmission events in serodiscordant couples. Some linked infections were observed shortly after ART initiation or after virologic failure. To evaluate factors associated with time to viral suppression and virologic failure in participants who initiated ART in HPTN 052. 1566 participants who had a viral load (VL) > 400 copies/mL at enrollment were included in the analyses. This included 832 in the early ART arm (CD4 350-550 cells/mm 3 at ART initiation) and 734 in the delayed ART arm (204 with a CD4 < 250 cells/mm 3 at ART initiation; 530 with any CD4 at ART initiation). Viral suppression was defined as two consecutive VLs ≤ 400 copies/mL after ART initiation; virologic failure was defined as two consecutive VLs > 1000 copies/mL > 24 weeks after ART initiation. Overall, 93% of participants achieved viral suppression by 12 months. The annual incidence of virologic failure was 3.6%. Virologic outcomes were similar in the two study arms. Longer time to viral suppression was associated with younger age, higher VL at ART initiation, and region (Africa vs. Asia). Virologic failure was strongly associated with younger age, lower educational level, and lack of suppression by three months; lower VL and higher CD4 at ART initiation were also associated with virologic failure. Several clinical and demographic factors were identified that were associated with longer time to viral suppression and virologic failure. Recognition of these factors may help optimize ART for HIV treatment and prevention.

Virologic outcomes in early antiretroviral treatment: HPTN 052

PubMed Central

Eshleman, Susan H.; Wilson, Ethan A.; Zhang, Xinyi C.; Ou, San-San; Piwowar-Manning, Estelle; Eron, Joseph J.; McCauley, Marybeth; Gamble, Theresa; Gallant, Joel E.; Hosseinipour, Mina C.; Kumarasamy, Nagalingeswaran; Hakim, James G.; Kalonga, Ben; Pilotto, Jose H.; Grinsztejn, Beatriz; Godbole, Sheela V.; Chotirosniramit, Nuntisa; Santos, Breno Riegel; Shava, Emily; Mills, Lisa A.; Panchia, Ravindre; Mwelase, Noluthando; Mayer, Kenneth H.; Chen, Ying Q.; Cohen, Myron S.; Fogel, Jessica M.

2017-01-01

INTRODUCTION The HPTN 052 trial demonstrated that early antiretroviral therapy (ART) prevented 93% of HIV transmission events in serodiscordant couples. Some linked infections were observed shortly after ART initiation or after virologic failure. OBJECTIVE To evaluate factors associated with time to viral suppression and virologic failure in participants who initiated ART in HPTN 052. METHODS 1,566 participants who had a viral load (VL) >400 copies/mL at enrollment were included in the analyses. This included 832 in the early ART arm (CD4 350–550 cells/mm3 at ART initiation) and 734 in the delayed ART arm (204 with a CD4 <250 cells/mm3 at ART initiation; 530 with any CD4 at ART initiation). Viral suppression was defined as two consecutive VLs ≤400 copies/mL after ART initiation; virologic failure was defined as two consecutive VLs >1,000 copies/mL >24 weeks after ART initiation. RESULTS Overall, 93% of participants achieved viral suppression by 12 months. The annual incidence of virologic failure was 3.6%. Virologic outcomes were similar in the two study arms. Longer time to viral suppression was associated with younger age, higher VL at ART initiation, and region (Africa vs. Asia). Virologic failure was strongly associated with younger age, lower educational level, and lack of suppression by 3 months; lower VL and higher CD4 at ART initiation were also associated with virologic failure. CONCLUSIONS Several clinical and demographic factors were identified that were associated with longer time to viral suppression and virologic failure. Recognition of these factors may help optimize ART for HIV treatment and prevention. PMID:28385131

Cerebellar medulloblastoma: the importance of posterior fossa dose to survival and patterns of failure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Silverman, C.L.; Simpson, J.R.

1982-11-01

Fifty patients with biopsy-proven cerebellar medulloblastoma were retrospectively analyzed for prognostic factors, survival and patterns of failure. Five- and ten-year actuarial survivals for the entire group were 51% and 42%. Survival and local control were significantly better for the 21 patients who received doses greater than 5000 rad to the posterior fossa (85% and 80% respectively) than for the remaining patients (38% and 38%, respectively). Significant prognostic factors included achievement of local control in the posterior fossa (p = .0001) and dose to the posterior fossa (p = .0005). Sex, age, duration of symptoms, extent of surgery and initial T-stagemore » of disease were not significant. Posterior fossa was the predominant site of failure (71% of failures), but 10% of patients failed in the cerebrum and 12% outside the CNS. This experience confirms that survival rates of 70-80% are achievable with current treatment policies but accurate and consistent dose delivery to the posterior fossa is essential.« less

Cerebellar medulloblastoma: the importance of posterior fossa dose to survival and patterns of failure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Silverman, C.L.; Simpson, J.R.

1982-11-01

Fifty patients with biopsy-proven cerebellar medulloblastoma were retrospectively analyzed for prognostic factors, survival and patterns of failure. Five- and ten-year actuarial survivals for the entire group were 51% and 42%. Survival and local control were significantly better for the 21 patients who received doses greater that 5000 rad to the posterior fossa (85% and 80% respectively) than for the remaining patients (38% and 38%, respectively). Significant prognostic factors included achievement of local control in the posterior fossa (p = .0001) and dose to the posterior fossa (p = .0005). Sex, age, duration of symptoms, extent of surgery and initial T-stagemore » of disease were not significant. Posterior fossa was the predominant site of failure (71% of failures), but 10% of patients failed in the cerebrum and 12% outside the CNS. This experience confirms that survival rates of 70-80% are achievable with current treatment policies but accurate and consistent dose delivery to the posterior fossa is essential.« less

Reliability and performance experience with flat-plate photovoltaic modules

NASA Technical Reports Server (NTRS)

Ross, R. G., Jr.

1982-01-01

Statistical models developed to define the most likely sources of photovoltaic (PV) array failures and the optimum method of allowing for the defects in order to achieve a 20 yr lifetime with acceptable performance degradation are summarized. Significant parameters were the cost of energy, annual power output, initial cost, replacement cost, rate of module replacement, the discount rate, and the plant lifetime. Acceptable degradation allocations were calculated to be 0.0001 cell failures/yr, 0.005 module failures/yr, 0.05 power loss/yr, a 0.01 rate of power loss/yr, and a 25 yr module wear-out length. Circuit redundancy techniques were determined to offset cell failures using fault tolerant designs such as series/parallel and bypass diode arrangements. Screening processes have been devised to eliminate cells that will crack in operation, and multiple electrical contacts at each cell compensate for the cells which escape the screening test and then crack when installed. The 20 yr array lifetime is expected to be achieved in the near-term.

Reaction Times to Consecutive Automation Failures: A Function of Working Memory and Sustained Attention.

PubMed

Jipp, Meike

2016-12-01

This study explored whether working memory and sustained attention influence cognitive lock-up, which is a delay in the response to consecutive automation failures. Previous research has demonstrated that the information that automation provides about failures and the time pressure that is associated with a task influence cognitive lock-up. Previous research has also demonstrated considerable variability in cognitive lock-up between participants. This is why individual differences might influence cognitive lock-up. The present study tested whether working memory-including flexibility in executive functioning-and sustained attention might be crucial in this regard. Eighty-five participants were asked to monitor automated aircraft functions. The experimental manipulation consisted of whether or not an initial automation failure was followed by a consecutive failure. Reaction times to the failures were recorded. Participants' working-memory and sustained-attention abilities were assessed with standardized tests. As expected, participants' reactions to consecutive failures were slower than their reactions to initial failures. In addition, working-memory and sustained-attention abilities enhanced the speed with which participants reacted to failures, more so with regard to consecutive than to initial failures. The findings highlight that operators with better working memory and sustained attention have small advantages when initial failures occur, but their advantages increase across consecutive failures. The results stress the need to consider personnel selection strategies to mitigate cognitive lock-up in general and training procedures to enhance the performance of low ability operators. © 2016, Human Factors and Ergonomics Society.

Forgetting induced speeding: Can prospective memory failure account for drivers exceeding the speed limit?

PubMed

Bowden, Vanessa K; Visser, Troy A W; Loft, Shayne

2017-06-01

It is generally assumed that drivers speed intentionally because of factors such as frustration with the speed limit or general impatience. The current study examined whether speeding following an interruption could be better explained by unintentional prospective memory (PM) failure. In these situations, interrupting drivers may create a PM task, with speeding the result of drivers forgetting their newly encoded intention to travel at a lower speed after interruption. Across 3 simulated driving experiments, corrected or uncorrected speeding in recently reduced speed zones (from 70 km/h to 40 km/h) increased on average from 8% when uninterrupted to 33% when interrupted. Conversely, the probability that participants traveled under their new speed limit in recently increased speed zones (from 40 km/h to 70 km/h) increased from 1% when uninterrupted to 23% when interrupted. Consistent with a PM explanation, this indicates that interruptions lead to a general failure to follow changed speed limits, not just to increased speeding. Further testing a PM explanation, Experiments 2 and 3 manipulated variables expected to influence the probability of PM failures and subsequent speeding after interruptions. Experiment 2 showed that performing a cognitively demanding task during the interruption, when compared with unfilled interruptions, increased the probability of initially speeding from 1% to 11%, but that participants were able to correct (reduce) their speed. In Experiment 3, providing participants with 10s longer to encode the new speed limit before interruption decreased the probability of uncorrected speeding after an unfilled interruption from 30% to 20%. Theoretical implications and implications for road design interventions are discussed. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

What Drives a Successful E-Learning? An Empirical Investigation of the Critical Factors Influencing Learner Satisfaction

ERIC Educational Resources Information Center

Sun, Pei-Chen; Tsai, Ray J.; Finger, Glenn; Chen, Yueh-Yang; Yeh, Dowming

2008-01-01

E-Learning is emerging as the new paradigm of modern education. Worldwide, the e-Learning market has a growth rate of 35.6%, but failures exist. Little is known about why many users stop their online learning after their initial experience. Previous research done under different task environments has suggested a variety of factors affecting user…

Development, Implementation, and Evaluation of a Pre-Orientation Summer Virtual Acclimation and Academic Advising (SVA[superscript 3]) Initiative for First-Year, Traditional-Aged College Students

ERIC Educational Resources Information Center

Golubski, Pamela M.

2009-01-01

The high school to college transition is a difficult time for most first-time, traditional-aged students. Students experience changes in interpersonal and social adjustment, academic and career concerns, and personal adjustment (Bishop, Gallagher, & Cohen, 2000). Failure to successfully adjust and acclimate into their new college community can…

75 FR 35619 - Airworthiness Directives; Piper Aircraft, Inc. Models PA-32R-301T and PA-46-350P Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2010-06-23

... tighten to an July 28, 2010 (the initial torque of effective date of 40 in. lbs. Tap the this AD... installation than by a change in clamp design. Their experience shows proper installation, torque techniques, and pre-torque alignments of components go a long way in preventing clamp failures down the road. We...

Intralaminar and Interlaminar Progressive Failure Analysis of Composite Panels with Circular Cutouts

NASA Technical Reports Server (NTRS)

Goyal, Vinay K.; Jaunky, Navin; Johnson, Eric R.; Ambur, Damodar

2002-01-01

A progressive failure methodology is developed and demonstrated to simulate the initiation and material degradation of a laminated panel due to intralaminar and interlaminar failures. Initiation of intralaminar failure can be by a matrix-cracking mode, a fiber-matrix shear mode, and a fiber failure mode. Subsequent material degradation is modeled using damage parameters for each mode to selectively reduce lamina material properties. The interlaminar failure mechanism such as delamination is simulated by positioning interface elements between adjacent sublaminates. A nonlinear constitutive law is postulated for the interface element that accounts for a multi-axial stress criteria to detect the initiation of delamination, a mixed-mode fracture criteria for delamination progression, and a damage parameter to prevent restoration of a previous cohesive state. The methodology is validated using experimental data available in the literature on the response and failure of quasi-isotropic panels with centrally located circular cutouts loaded into the postbuckling regime. Very good agreement between the progressive failure analyses and the experimental results is achieved if the failure analyses includes the interaction of intralaminar and interlaminar failures.

Survey of Failure in Engineering Education and Industry

NASA Astrophysics Data System (ADS)

Arimitsu, Yutaka; Yagi, Hidetsugu

Students have failure experiences in the project-based learning but they do not profess their experiences. On the other hand, failures and accidents, in the industrial world, are analyzed frequently, and a knowledge data base on failure and QC activities have been introduced. To turn failure experience in education to advantage, the authors survey the properties of failures in project based learning and views of students, teachers and managers of design divisions in companies. Teachers and students regard failure experiences as instructive and acceptable. The typical causes of failure in educational institutions are luck of skill in manufacturing and inadequate planning, which are minor causes of failure in the industry. To establish a knowledge data base on failure in educational institutions, properties of failure in education should be taken into account.

Interest, Enjoyment and Pride after Failure Experiences? Predictors of Students' State-Emotions after Success and Failure during Learning in Mathematics

ERIC Educational Resources Information Center

Tulis, Maria; Ainley, Mary

2011-01-01

The current investigation was designed to identify emotion states students experience during mathematics activities, and in particular to distinguish emotions contingent on experiences of success and experiences of failure. Students' task-related emotional responses were recorded following experiences of success and failure while working with an…

Endovascular stent-graft repair of failed endovascular abdominal aortic aneurysm repair.

PubMed

Baril, Donald T; Silverberg, Daniel; Ellozy, Sharif H; Carroccio, Alfio; Jacobs, Tikva S; Sachdev, Ulka; Teodorescu, Victoria J; Lookstein, Robert A; Marin, Michael L

2008-01-01

Despite high initial technical success, the long-term durability of endovascular abdominal aortic aneurysm repair (EVAR) continues to be a concern. Following EVAR, patients can experience endoleaks, device migration, device fractures, or aneurysm growth that may require intervention. The purpose of this study was to review all patients treated with secondary endovascular devices at our institution for failed EVAR procedures. Over an 8-year period, 988 patients underwent EVAR, of whom 42 (4.3%) required secondary interventions involving placement of additional endovascular devices. Data regarding patient characteristics, aneurysm size, initial device type, time until failure, failure etiology, secondary interventions, and outcomes were reviewed. The mean time from initial operation until second operation was 34.1 months. Failures included type I endoleaks in 38 patients (90.5%), type III endoleaks in two patients (4.8%), and enlarging aneurysms without definite endoleaks in two patients (4.8%). The overall technical success rate for secondary repair was 92.9% (39/42). Perioperative complications occurred in nine patients (21.4%), including wound complications (n = 6), cerebrovascular accident (CVA) (n = 1), foot drop (n = 1), and death (n = 1). Mean follow-up following secondary repair was 16.4 months (range 1-50). Eighty-six percent of patients treated with aortouni-iliac devices had successful repairs compared to 45% of patients treated with proximal cuffs. Ten patients (23.8%) had persistent or recurrent type I or type III endoleaks following revision. Of these, four had tertiary interventions, including two patients who had additional devices placed. Failures following EVAR occur in a small but significant number of patients. When anatomically possible, endovascular revision offers a safe means of treating these failures. Aortouni-iliac devices appear to offer a more durable repair than the proximal cuff for treatment of proximal type I endoleaks. Midterm results indicate that these patients may require additional procedures but have a low rate of aneurysm-related mortality. Longer-term follow-up is necessary to determine the durability of these endovascular revisions.

Initial versus final fracture of metal-free crowns, analyzed via acoustic emission.

PubMed

Ereifej, Nadia; Silikas, Nick; Watts, David C

2008-09-01

To discriminate between initial and final fracture failure loads of four metal-free crown systems by the conjoint detection of acoustic emission signals during compressive loading. Teeth were prepared and used for crown construction with four crown systems; Vita Mark II (VM II) (Vita Zahnfabrik), IPS e.max Ceram/CAD (CAD) (Ivoclar-Vivadent), IPS e.max Ceram/ZirCAD (ZirCAD) (Ivoclar-Vivadent) and BelleGlass/EverStick (BGES) (Kerr/Stick Tech Ltd.). All samples were loaded in compression via a Co/Cr maxillary first molar tooth at 0.2mm/min and released acoustic signals were collected and analyzed. A minimum number of 15 crowns per group were loaded to final failure and values of loading at initial and final fracture were compared. Additional four samples per group were loaded till fracture initiation and were fractographically examined under the optical microscope. A lower threshold of 50dB was selected to exclude spurious background signals. Initial fracture forces were significantly lower than those of final fracture (p<0.05) in all groups and initial failure AE amplitudes were lower than those of final fracture. Mean initial fracture force of ZirCAD samples (1029.1N) was higher than those of VMII (744.4N), CAD (808.8 N) and BGES (979.7 N). Final fracture of ZirCAD also occurred at significantly higher force values (2091.7 N) than the rest of the groups; VMII (1120.9 N), CAD (1468.9 N) and BGES (1576.6 N). Significantly higher values of initial failure AE amplitude were found in VMII than CAD and BGES while those of final fracture were similar. All crowns observed under the microscope at initial fracture had signs of failure. Whereas the metal-free crowns examined showed significant variations in final failure loads, acoustic emission data showed that they all manifested initial failures at significantly lower load values.

Diameter Effect In Initiating Explosives, Numerical Simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lefrancois, A.; Benterou, J.; Roeske, F.

2006-02-10

The ability to safely machine small pieces of HE with the femtosecond laser allows diameter effect experiments to be performed in initiating explosives in order to study the failure diameter, the reduction of the detonation velocity and curvature versus the diameter. The reduced diameter configuration needs to be optimized, so that the detonation products of the first cylinder will not affect the measurement of the detonation velocity of the second cylinder with a streak camera. Different 2D axi-symmetrical configurations have been calculated to identify the best solution using the Ignition and Growth reactive flow model for LX16 Pellet with Ls-Dyna.

ROENTGEN: case-based reasoning and radiation therapy planning.

PubMed Central

Berger, J.

1992-01-01

ROENTGEN is a design assistant for radiation therapy planning which uses case-based reasoning, an artificial intelligence technique. It learns both from specific problem-solving experiences and from direct instruction from the user. The first sort of learning is the normal case-based method of storing problem solutions so that they can be reused. The second sort is necessary because ROENTGEN does not, initially, have an internal model of the physics of its problem domain. This dependence on explicit user instruction brings to the forefront representational questions regarding indexing, failure definition, failure explanation and repair. This paper presents the techniques used by ROENTGEN in its knowledge acquisition and design activities. PMID:1482869

Failure mechanisms of uni-ply composite plates with a circular hole under static compressive loading

NASA Technical Reports Server (NTRS)

Khamseh, A. R.; Waas, A. M.

1992-01-01

The objective of the study was to identify and study the failure mechanisms associated with compressive-loaded uniply graphite/epoxy square plates with a central circular hole. It is found that the type of compressive failure depends on the hole size. For large holes with the diameter/width ratio exceeding 0.062, fiber buckling/kinking initiated at the hole is found to be the dominant failure mechanism. In plates with smaller hole sizes, failure initiates away from the hole edge or complete global failure occurs. Critical buckle wavelengths at failure are presented as a function of the normalized hole diameter.

Mesoscale simulation of concrete spall failure

NASA Astrophysics Data System (ADS)

Knell, S.; Sauer, M.; Millon, O.; Riedel, W.

2012-05-01

Although intensively studied, it is still being debated which physical mechanisms are responsible for the increase of dynamic strength and fracture energy of concrete observed at high loading rates, and to what extent structural inertia forces on different scales contribute to the observation. We present a new approach for the three dimensional mesoscale modelling of dynamic damage and cracking in concrete. Concrete is approximated as a composite of spherical elastic aggregates of mm to cm size embedded in an elastic cement stone matrix. Cracking within the matrix and at aggregate interfaces in the μm range are modelled with adaptively inserted—initially rigid—cohesive interface elements. The model is applied to analyse the dynamic tensile failure observed in Hopkinson-Bar spallation experiments with strain rates up to 100/s. The influence of the key mesoscale failure parameters of strength, fracture energy and relative weakening of the ITZ on macromechanic strength, momentum and energy conservation is numerically investigated.

Failure of composite plates under static biaxial planar loading

NASA Technical Reports Server (NTRS)

Waas, Anthony M.; Khamseh, Amir R.

1992-01-01

The project involved detailed investigations into the failure mechanisms in composite plates as a function of hole size (holes centrally located in the plates) under static loading. There were two phases to the project, the first dealing with uniaxial loads along the fiber direction, and the second dealing with coplanar biaxial loading. Results for the uniaxial tests have been reported and published previously, thus this report will place emphasis on the second phase of the project, namely the biaxial tests. The composite plates used in the biaxial loading experiments, as well as the uniaxial, were composed of a single ply unidirectional graphite/epoxy prepreg sandwiched between two layers of transparent thermoplastic. This setup enabled us to examine the failure initiation and propagation modes nondestructively, during the test. Currently, similar tests and analysis of results are in progress for graphite/epoxy cruciform shaped flat laminates. The results obtained from these tests will be available at a later time.

Percutaneous treatment of symptomatic non-parasitic hepatic cysts. Initial experience with single-session sclerotherapy with polidocanol.

PubMed

Spârchez, Zeno; Radu, Pompilia; Zaharie, Florin; Al Hajjar, Nadim; Sparchez, Mihaela

2014-09-01

Hepatic cysts have a prevalence of 2.5-7% and most of them are asymptomatic. However, large cysts may cause complaints; in such cases an appropriate treatment is necessary (open surgery, laparoscopic deroofing, removal of cystic fluid and injection of a sclerosing agent. The aim of this study was to assess the efficacy and safety of a single session technique with polidocanol in the therapy of symptomatic non parasitic hepatic cysts. MATERIAL AND METHODS. The study included 13 patients with symptomatic liver cysts (range 4-10 cm). All patients underwent percutaneous aspiration of the liver cyst under ultrasound guidance followed by instillation of polidocanol (3%, 4-10 ml). The patients were followed up at 1, 3 and 12 months. The disappearance of the cyst or reduction in volume more than 90% was considered successful. If the fluid was accumulated at 1month the procedure was repeated. If after the second injection the fluid accumulation was more than 50% of the initial volume the case was considered a failure and a laparoscopic deroofing was performed. The procedure was successful in 10 patients, 9 after the first instillation and one after the second (76.9%). The mean initial volume of cysts was 228 ml, and the mean reduction in volume at 1, 3 and 12 months was 80.2%, 91.9% and 96.7%. The cyst resolution was gradual with clinically significant cyst reduction achievement within 1 year after therapy. In 3 patients the fluid reaccumulated at the same volume despite 2 instillations. Those 3 cases the procedure was considered failure and the patients were sent to surgery. In 2 patients (one successfully treated and one with treatment failure) bleeding during the first puncture and aspiration appeared and the therapy was postponed for 1 month. There were no significant adverse effects, and all the patients had relief of symptoms after therapy. This initial experience with percutaneous aspiration and polidocanol sclerosis of hepatic cysts demonstrated that the technique is efficient and safe.

2D fall of granular columns controlled by slow horizontal withdrawal of a retaining wall

NASA Astrophysics Data System (ADS)

Mériaux, C. A.

2006-12-01

This paper describes a series of experiments designed to investigate the fall of granular columns in quasi- static regime. Columns made of alternatively green and red sand layers were initially laid out in a box and then released when a retaining wall was set in slow motion with constant speed. The dependence of the dynamics of the fall on the initial aspect ratio of the columns, the velocity of the wall and the material properties was investigated within the quasi-static regime. A change in the behaviour of the columns was identified to be a function of the aspect ratio (height/length) of the initial sand column. Columns of high aspect ratio first subsided before sliding along failure planes, while columns of small aspect ratio were only observed to slide along failure planes. The transition between these two characteristic falls occurred regardless of the material and the velocity of the wall in the context of the quasi-static regime. When the final height and length of the piles were analyzed, we found power-law relations of the ratio of initial to final height and final run-out to initial length with the aspect ratio of the column. The dissipation of energy is also shown to increase with the run-out length of the pile until it reaches a plateau.

Multiscale Analysis of Nanocomposites and Their Use in Structural Level Applications

NASA Astrophysics Data System (ADS)

Hasan, Zeaid

This research focuses on the benefits of using nanocomposites in aerospace structural components to prevent or delay the onset of unique composite failure modes, such as delamination. Analytical, numerical, and experimental analyses were conducted to provide a comprehensive understanding of how carbon nanotubes (CNTs) can provide additional structural integrity when they are used in specific hot spots within a structure. A multiscale approach was implemented to determine the mechanical and thermal properties of the nanocomposites, which were used in detailed finite element models (FEMs) to analyze interlaminar failures in T and Hat section stringers. The delamination that first occurs between the tow filler and the bondline between the stringer and skin was of particular interest. Both locations are considered to be hot spots in such structural components, and failures tend to initiate from these areas. In this research, nanocomposite use was investigated as an alternative to traditional methods of suppressing delamination. The stringer was analyzed under different loading conditions and assuming different structural defects. Initial damage, defined as the first drop in the load displacement curve was considered to be a useful variable to compare the different behaviors in this study and was detected via the virtual crack closure technique (VCCT) implemented in the FE analysis. Experiments were conducted to test T section skin/stringer specimens under pull-off loading, replicating those used in composite panels as stiffeners. Two types of designs were considered: one using pure epoxy to fill the tow region and another that used nanocomposite with 5 wt. % CNTs. The response variable in the tests was the initial damage. Detailed analyses were conducted using FEMs to correlate with the experimental data. The correlation between both the experiment and model was satisfactory. Finally, the effects of thermal cure and temperature variation on nanocomposite structure behavior were studied, and both variables were determined to influence the nanocomposite structure performance.

Amnioinfusion to facilitate external cephalic version after initial failure.

PubMed

Adama van Scheltema, P N; Feitsma, A H; Middeldorp, J M; Vandenbussche, F P H A; Oepkes, D

2006-09-01

To evaluate the effectiveness of antepartum transabdominal amnioinfusion to facilitate external cephalic version after initial failure. Women with a structurally normal fetus in breech lie at term, with a failed external cephalic version and an amniotic fluid index (AFI) less than 15 cm, were asked to participate in our study. After tocolysis with indomethacin, a transabdominal amnioinfusion was performed with an 18G spinal needle. Lactated Ringers solution was infused until the AFI reached 15 cm, with a maximum of 1 L. External cephalic version was performed directly afterward. Seven women participated in the study. The gestational age of the women was between 36(+4) and 38(+3) weeks, and three women were primiparous. The AFI ranged from 4 cm to 13 cm. A median amount of 1,000 mL Ringers solution (range 700-1,000 mL) was infused per procedure. The repeat external cephalic versions after amnioinfusion were not successful in any of the patients. In our experience, amnioinfusion does not facilitate external cephalic version.

Like Fire to Water: Building Bridging Collaborations between Disability Service Providers and Course Instructors to Create User Friendly and Resource Efficient UDL Implementation Material

ERIC Educational Resources Information Center

Fovet, Frederic; Jarrett, Tynan; Mole, Heather; Syncox, David

2014-01-01

This study presents a post-secondary campus experience with systematic and global promotion of Universal Design for Learning. It analyzes data collected over a 24 months period, relating to course instructors' responses to the framework, through the lens of the initial hypothesis that successes and failures in adoption might be explained by the…

Dynamic Failure of Materials. Volume 1 - Experiments and Analyses

DTIC Science & Technology

1998-11-01

initial increments of voids do not lead to substantial relaxation of stress. In this case, the condition (8.1) gives Vv = Ao- aVv * ß=— (8.10) pc...enough strain steps to define the process accurately. At each strain step, a combined Newton-Raphson and regulafalsi solution technique (multiple trials ...laser surgery. Clinical studies have demonstrated that, for some applications, surgical lasers are superior to conventional surgical procedures

Redundant Design in Interdependent Networks

PubMed Central

2016-01-01

Modern infrastructure networks are often coupled together and thus could be modeled as interdependent networks. Overload and interdependent effect make interdependent networks more fragile when suffering from attacks. Existing research has primarily concentrated on the cascading failure process of interdependent networks without load, or the robustness of isolated network with load. Only limited research has been done on the cascading failure process caused by overload in interdependent networks. Redundant design is a primary approach to enhance the reliability and robustness of the system. In this paper, we propose two redundant methods, node back-up and dependency redundancy, and the experiment results indicate that two measures are effective and costless. Two detailed models about redundant design are introduced based on the non-linear load-capacity model. Based on the attributes and historical failure distribution of nodes, we introduce three static selecting strategies-Random-based, Degree-based, Initial load-based and a dynamic strategy-HFD (historical failure distribution) to identify which nodes could have a back-up with priority. In addition, we consider the cost and efficiency of different redundant proportions to determine the best proportion with maximal enhancement and minimal cost. Experiments on interdependent networks demonstrate that the combination of HFD and dependency redundancy is an effective and preferred measure to implement redundant design on interdependent networks. The results suggest that the redundant design proposed in this paper can permit construction of highly robust interactive networked systems. PMID:27764174

Early experience with influenza A H1N109 in an Australian intensive care unit.

PubMed

Leen, Tim; Williams, Teresa A; Campbell, Lorraine; Chamberlain, Jenny; Gould, Andree; McEntaggart, Geraldine; Leslie, Gavin D

2010-08-01

Influenza is a common seasonal viral infection that affects large numbers of people. In early 2009, many people were admitted to hospitals in Mexico with severe respiratory failure following an influenza-like illness, subtyped as H1N1. An increased mortality rate was observed. By June 2009, H1N1 was upgraded to pandemic status. In June-July, Australian ICUs were experiencing increased activity due to the influenza pandemic. While hospitals implemented plans for the pandemic, the particularly heavy demand to provide critical care facilities to accommodate an influx of people with severe respiratory failure became evident and placed a great burden on provision of these services. This paper describes the initial experience (June to mid September) of the pandemic from the nursing perspective in a single Australian ICU. Patients were noted to be younger with a higher proportion of women, two of whom were pregnant. Two patients had APACHE III comorbidity. Of the 31 patients admitted during this period, three patients died in ICU and one patient died in hospital. Aerosol precautions were initiated for all patients. The requirement for single room accommodation placed enormous demands for bed management in ICU. Specific infection control procedures were developed to deal with this new pandemic influenza. Copyright 2010 Elsevier Ltd. All rights reserved.

Retrieval attempts enhance learning, but retrieval success (versus failure) does not matter.

PubMed

Kornell, Nate; Klein, Patricia Jacobs; Rawson, Katherine A

2015-01-01

Retrieving information from memory enhances learning. We propose a 2-stage framework to explain the benefits of retrieval. Stage 1 takes place as one attempts to retrieve an answer, which activates knowledge related to the retrieval cue. Stage 2 begins when the answer becomes available, at which point appropriate connections are strengthened and inappropriate connections may be weakened. This framework raises a basic question: Does it matter whether Stage 2 is initiated via successful retrieval or via an external presentation of the answer? To test this question, we asked participants to attempt retrieval and then randomly assigned items (which were equivalent otherwise) to be retrieved successfully or to be copied (i.e., not retrieved). Experiments 1, 2, 4, and 5 tested assumptions necessary for interpreting Experiments 3a, 3b, and 6. Experiments 3a, 3b, and 6 did not support the hypothesis that retrieval success produces more learning than does retrieval failure followed by feedback. It appears that retrieval attempts promote learning but retrieval success per se does not. PsycINFO Database Record (c) 2015 APA, all rights reserved.

Thanatos and massive psychic trauma: the impact of the death instinct on knowing, remembering, and forgetting.

PubMed

Laub, Dori; Lee, Susanna

2003-01-01

The connection between massive psychic trauma and the concept of the death instinct is explored using the basic assumptions that the death instinct is unleashed through and is in a sense characteristic of traumatic experience, and that the concept of the death instinct is indispensable to the understanding and treatment of trauma. Characteristics of traumatic experience, such as dissolution of the empathic bond, failure to assimilate experience into psychic representation and structure, a tendency to repeat traumatic experience, and a resistance to remembering and knowing, are considered as trauma-induced death instinct derivatives. An initial focus is on the individual, on how death instinct manifestations can be discerned in the survivors of trauma. Next the intergenerational force of trauma is examined; a clinical vignette illustrates how the death instinct acts on and is passed on to the children of survivors. Finally, the cultural or societal aspects of trauma are considered, with an eye to how death instinct derivatives permeate cultural responses (or failures to respond) to trauma. Because trauma causes a profound destructuring and decathexis, it is concluded that the concept of the death instinct is a clinical and theoretical necessity.

Evaluation of strength and failure of brittle rock containing initial cracks under lithospheric conditions

NASA Astrophysics Data System (ADS)

Li, Xiaozhao; Qi, Chengzhi; Shao, Zhushan; Ma, Chao

2018-02-01

Natural brittle rock contains numerous randomly distributed microcracks. Crack initiation, growth, and coalescence play a predominant role in evaluation for the strength and failure of brittle rocks. A new analytical method is proposed to predict the strength and failure of brittle rocks containing initial microcracks. The formulation of this method is based on an improved wing crack model and a suggested micro-macro relation. In this improved wing crack model, the parameter of crack angle is especially introduced as a variable, and the analytical stress-crack relation considering crack angle effect is obtained. Coupling the proposed stress-crack relation and the suggested micro-macro relation describing the relation between crack growth and axial strain, the stress-strain constitutive relation is obtained to predict the rock strength and failure. Considering different initial microcrack sizes, friction coefficients and confining pressures, effects of crack angle on tensile wedge force acting on initial crack interface are studied, and effects of crack angle on stress-strain constitutive relation of rocks are also analyzed. The strength and crack initiation stress under different crack angles are discussed, and the value of most disadvantaged angle triggering crack initiation and rock failure is founded. The analytical results are similar to the published study results. Rationality of this proposed analytical method is verified.

Prediction of Fracture Initiation in Hot Compression of Burn-Resistant Ti-35V-15Cr-0.3Si-0.1C Alloy

NASA Astrophysics Data System (ADS)

Zhang, Saifei; Zeng, Weidong; Zhou, Dadi; Lai, Yunjin

2015-11-01

An important concern in hot working of metals is whether the desired deformation can be accomplished without fracture of the material. This paper builds a fracture prediction model to predict fracture initiation in hot compression of a burn-resistant beta-stabilized titanium alloy Ti-35V-15Cr-0.3Si-0.1C using a combined approach of upsetting experiments, theoretical failure criteria and finite element (FE) simulation techniques. A series of isothermal compression experiments on cylindrical specimens were conducted in temperature range of 900-1150 °C, strain rate of 0.01-10 s-1 first to obtain fracture samples and primary reduction data. Based on that, a comparison of eight commonly used theoretical failure criteria was made and Oh criterion was selected and coded into a subroutine. FE simulation of upsetting experiments on cylindrical specimens was then performed to determine the fracture threshold values of Oh criterion. By building a correlation between threshold values and the deforming parameters (temperature and strain rate, or Zener-Hollomon parameter), a new fracture prediction model based on Oh criterion was established. The new model shows an exponential decay relationship between threshold values and Zener-Hollomon parameter (Z), and the relative error of the model is less than 15%. This model was then applied successfully in the cogging of Ti-35V-15Cr-0.3Si-0.1C billet.

Characterization of Mineralocorticoid Receptor Antagonist Therapy Initiation in High-Risk Patients With Heart Failure.

PubMed

Cooper, Lauren B; Hammill, Bradley G; Peterson, Eric D; Pitt, Bertram; Maciejewski, Matthew L; Curtis, Lesley H; Hernandez, Adrian F

2017-01-01

Heart failure guidelines recommend routine monitoring of serum potassium, and renal function in patients treated with a mineralocorticoid receptor antagonist (MRA). How these recommendations are implemented in high-risk patients or according to setting of drug initiation is poorly characterized. We conducted a retrospective cohort study of Medicare beneficiaries linked to laboratory data in 10 states with prevalent heart failure as of July 1, 2011, and incident MRA use between May 1 and September 30, 2011. Outcomes included laboratory testing before MRA initiation and in the early (days 1-10) and extended (days 11-90) post-initiation periods, based on setting of drug initiation and the presence of renal insufficiency. Additional outcomes included abnormal laboratory results and adverse events proximate to MRA initiation. Of 10 443 Medicare beneficiaries with heart failure started on an MRA, 19.7% were initiated during a hospitalization. Appropriate follow-up laboratory testing across all time periods occurred in 25.2% of patients with inpatient initiation compared with 2.8% of patients begun as an outpatient. Patients with chronic kidney disease had higher rates of both hyperkalemia and acute kidney failure in the early (1.3% and 2.7%, respectively) and extended (5.6% and 9.8%, respectively) post-initiation periods compared with those without chronic kidney disease. Patients initiated on MRA therapy as an outpatient had extremely poor rates of guideline indicated follow-up laboratory monitoring after drug initiation. In particular, patients with chronic kidney disease are at high risk for adverse events after MRA initiation. Quality improvement initiatives focused on systems to improve appropriate laboratory monitoring are needed. © 2017 American Heart Association, Inc.

Fatigue-Induced Damage in Zr-Based Bulk Metallic Glasses

PubMed Central

Chuang, Chih-Pin; Yuan, Tao; Dmowski, Wojciech; Wang, Gong-Yao; Freels, Matt; Liaw, Peter K.; Li, Ran; Zhang, Tao

2013-01-01

In the present work, we investigate the effect of “fatigue” on the fatigue behavior and atomic structure of Zr-based BMGs. Fatigue experiments on the failed-by-fatigue samples indicate that the remnants generally have similar or longer fatigue life than the as-cast samples. Meanwhile, the pair-distribution-function (PDF) analysis of the as-cast and post-fatigue samples showed very small changes of local atomic structures. These observations suggest that the fatigue life of the 6-mm in-diameter Zr-based BMG is dominated by the number of pre-existing crack-initiation sites in the sample. Once the crack initiates in the specimen, the fatigue-induced damage is accumulated locally on these initiated sites, while the rest of the region deforms elastically. The results suggest that the fatigue failure of BMGs under compression-compression fatigue experiments is a defect-controlled process. The present work indicates the significance of the improved fatigue resistance with decreasing the sample size. PMID:23999496

Two-year outcomes in initial survivors with acute liver failure: results from a prospective, multicentre study.

PubMed

Fontana, Robert J; Ellerbe, Caitlyn; Durkalski, Valerie E; Rangnekar, Amol; Reddy, Rajender K; Stravitz, Todd; McGuire, Brendan; Davern, Timothy; Reuben, Adrian; Liou, Iris; Fix, Oren; Ganger, Daniel R; Chung, Raymond T; Schilsky, Mike; Han, Steven; Hynan, Linda S; Sanders, Corron; Lee, William M

2015-02-01

The long-term clinical outcomes in initial survivors with acute liver failure (ALF) are not well known. The aim of this study was to provide an overview of the 2-year clinical outcomes among initial survivors and liver transplant (LT) recipients that were alive 3 weeks after enrolment in the Acute Liver Failure Study Group (ALFSG). Outcomes in adult ALFSG patients that were enrolled between 1998 and 2010 were reviewed. Two-year patient survival was significantly higher in the 262 LT recipients (92.4%) compared to the 306 acetaminophen (APAP) spontaneous survivors (SS) (89.5%) and 200 non-APAP SS (75.5%) (P < 0.0001). The causes of death were similar in the three groups but the time to death was significantly longer in the LT recipients (P < 0.0001). Independent predictors of 2-year mortality in the APAP group were a high serum phosphate level and patient age (c-statistic = 0.65 (0.54, 0.76)), patient age and days from jaundice to ALF onset in the non-APAP group (c-statistic = 0.69 (0.60, 0.78)), and patient age, days from jaundice, and higher coma grade in the LT recipients (c-statistic = 0.74 (0.61, 0.87)). The LT recipients were significantly more likely to be employed and have a higher educational level (P < 0.05). Two-year outcomes in initial survivors of ALF are generally good but non-APAP patients have a significantly lower survival which may relate to pre-existing medical comorbidities. Spontaneous survivors with APAP overdose experience substantial morbidity during follow-up from ongoing psychiatric and substance abuse issues. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Exploring gay couples' experience with sexual dysfunction after radical prostatectomy: a qualitative study.

PubMed

Hartman, Mary-Ellen; Irvine, Jane; Currie, Kristen L; Ritvo, Paul; Trachtenberg, Lianne; Louis, Alyssa; Trachtenberg, John; Jamnicky, Leah; Matthew, Andrew G

2014-01-01

This exploratory study examines the experience of three gay couples managing sexual dysfunction as a result of undergoing a radical prostatectomy. Semi-structured interviews were conducted as part of a larger study at an urban hospital in Toronto, Ontario, Canada. Interview transcripts were transcribed verbatim, and analyzed using interpretative phenomenological analysis. The authors clustered 18 subordinate themes under 3 superordinate themes: (a) acknowledging change in sexual experience (libido, erectile function, sexual activity, orgasmic function); (b) accommodating change in sexual experience (strategies: emphasizing intimacy, embracing plan B, focus on the other; barriers: side-effect concerns, loss of naturalness, communication breakdown, failure to initiate, trial and failure, partner confounds); and (c) accepting change in sexual experience (indicators: emphasizing health, age attributions, finding a new normal; barriers: uncertain outcomes, treatment regrets). Although gay couples and heterosexual couples share many similar challenges, we discovered that gay men have particular sexual roles and can engage in novel accommodation practices, such as open relationships, that have not been noted in heterosexual couples. All couples, regardless of their level of sexual functioning, highlighted the need for more extensive programming related to sexual rehabilitation. Equitable rehabilitative support is critical to assist homosexual couples manage distress associated with prostatectomy-related sexual dysfunction.

Coupled Fracture and Flow in Shale in Hydraulic Fracturing

NASA Astrophysics Data System (ADS)

Carey, J. W.; Mori, H.; Viswanathan, H.

2014-12-01

Production of hydrocarbon from shale requires creation and maintenance of fracture permeability in an otherwise impermeable shale matrix. In this study, we use a combination of triaxial coreflood experiments and x-ray tomography characterization to investigate the fracture-permeability behavior of Utica shale at in situ reservoir conditions (25-50 oC and 35-120 bars). Initially impermeable shale core was placed between flat anvils (compression) or between split anvils (pure shear) and loaded until failure in the triaxial device. Permeability was monitored continuously during this process. Significant deformation (>1%) was required to generate a transmissive fracture system. Permeability generally peaked at the point of a distinct failure event and then dropped by a factor of 2-6 when the system returned to hydrostatic failure. Permeability was very small in compression experiments (< 1 mD), possibly because of limited fracture connectivity through the anvils. In pure share experiments, shale with bedding planes perpendicular to shear loading developed complex fracture networks with narrow apertures and peak permeability of 30 mD. Shale with bedding planes parallel to shear loading developed simple fractures with large apertures and a peak permeability as high as 1 D. Fracture systems held at static conditions for periods of several hours showed little change in effective permeability at hydrostatic conditions as high as 140 bars. However, permeability of fractured systems was a function of hydrostatic pressure, declining in a pseudo-linear, exponential fashion as pressure increased. We also observed that permeability decreased with increasing fluid flow rate indicating that flow did not follow Darcy's Law, possibly due to non-laminar flow conditions, and conformed to Forscheimer's law. The coupled deformation and flow behavior of Utica shale, particularly the large deformation required to initiate flow, indicates the probable importance of activation of existing fractures in hydraulic fracturing and that these fractures can have adequate permeability for the production of hydrocarbon.

Risk factors for tuberculosis treatment failure, default, or relapse and outcomes of retreatment in Morocco

PubMed Central

2011-01-01

Background Patients with tuberculosis require retreatment if they fail or default from initial treatment or if they relapse following initial treatment success. Outcomes among patients receiving a standard World Health Organization Category II retreatment regimen are suboptimal, resulting in increased risk of morbidity, drug resistance, and transmission.. In this study, we evaluated the risk factors for initial treatment failure, default, or early relapse leading to the need for tuberculosis retreatment in Morocco. We also assessed retreatment outcomes and drug susceptibility testing use for retreatment patients in urban centers in Morocco, where tuberculosis incidence is stubbornly high. Methods Patients with smear- or culture-positive pulmonary tuberculosis presenting for retreatment were identified using clinic registries in nine urban public clinics in Morocco. Demographic and outcomes data were collected from clinical charts and reference laboratories. To identify factors that had put these individuals at risk for failure, default, or early relapse in the first place, initial treatment records were also abstracted (if retreatment began within two years of initial treatment), and patient characteristics were compared with controls who successfully completed initial treatment without early relapse. Results 291 patients presenting for retreatment were included; 93% received a standard Category II regimen. Retreatment was successful in 74% of relapse patients, 48% of failure patients, and 41% of default patients. 25% of retreatment patients defaulted, higher than previous estimates. Retreatment failure was most common among patients who had failed initial treatment (24%), and default from retreatment was most frequent among patients with initial treatment default (57%). Drug susceptibility testing was performed in only 10% of retreatment patients. Independent risk factors for failure, default, or early relapse after initial treatment included male gender (aOR = 2.29, 95% CI 1.10-4.77), positive sputum smear after 3 months of treatment (OR 7.14, 95% CI 4.04-13.2), and hospitalization (OR 2.09, 95% CI 1.01-4.34). Higher weight at treatment initiation was protective. Male sex, substance use, missed doses, and hospitalization appeared to be risk factors for default, but subgroup analyses were limited by small numbers. Conclusions Outcomes of retreatment with a Category II regimen are suboptimal and vary by subgroup. Default among patients receiving tuberculosis retreatment is unacceptably high in urban areas in Morocco, and patients who fail initial tuberculosis treatment are at especially high risk of retreatment failure. Strategies to address risk factors for initial treatment default and to identify patients at risk for failure (including expanded use of drug susceptibility testing) are important given suboptimal retreatment outcomes in these groups. PMID:21356062

Risk factors for tuberculosis treatment failure, default, or relapse and outcomes of retreatment in Morocco.

PubMed

Dooley, Kelly E; Lahlou, Ouafae; Ghali, Iraqi; Knudsen, Janine; Elmessaoudi, My Driss; Cherkaoui, Imad; El Aouad, Rajae

2011-02-28

Patients with tuberculosis require retreatment if they fail or default from initial treatment or if they relapse following initial treatment success. Outcomes among patients receiving a standard World Health Organization Category II retreatment regimen are suboptimal, resulting in increased risk of morbidity, drug resistance, and transmission.. In this study, we evaluated the risk factors for initial treatment failure, default, or early relapse leading to the need for tuberculosis retreatment in Morocco. We also assessed retreatment outcomes and drug susceptibility testing use for retreatment patients in urban centers in Morocco, where tuberculosis incidence is stubbornly high. Patients with smear- or culture-positive pulmonary tuberculosis presenting for retreatment were identified using clinic registries in nine urban public clinics in Morocco. Demographic and outcomes data were collected from clinical charts and reference laboratories. To identify factors that had put these individuals at risk for failure, default, or early relapse in the first place, initial treatment records were also abstracted (if retreatment began within two years of initial treatment), and patient characteristics were compared with controls who successfully completed initial treatment without early relapse. 291 patients presenting for retreatment were included; 93% received a standard Category II regimen. Retreatment was successful in 74% of relapse patients, 48% of failure patients, and 41% of default patients. 25% of retreatment patients defaulted, higher than previous estimates. Retreatment failure was most common among patients who had failed initial treatment (24%), and default from retreatment was most frequent among patients with initial treatment default (57%). Drug susceptibility testing was performed in only 10% of retreatment patients. Independent risk factors for failure, default, or early relapse after initial treatment included male gender (aOR = 2.29, 95% CI 1.10-4.77), positive sputum smear after 3 months of treatment (OR 7.14, 95% CI 4.04-13.2), and hospitalization (OR 2.09, 95% CI 1.01-4.34). Higher weight at treatment initiation was protective. Male sex, substance use, missed doses, and hospitalization appeared to be risk factors for default, but subgroup analyses were limited by small numbers. Outcomes of retreatment with a Category II regimen are suboptimal and vary by subgroup. Default among patients receiving tuberculosis retreatment is unacceptably high in urban areas in Morocco, and patients who fail initial tuberculosis treatment are at especially high risk of retreatment failure. Strategies to address risk factors for initial treatment default and to identify patients at risk for failure (including expanded use of drug susceptibility testing) are important given suboptimal retreatment outcomes in these groups.

Microseismic Signature of Magma Failure: Testing Failure Forecast in Heterogeneous Material

NASA Astrophysics Data System (ADS)

Vasseur, J.; Lavallee, Y.; Hess, K.; Wassermann, J. M.; Dingwell, D. B.

2012-12-01

Volcanoes exhibit a range of seismic precursors prior to eruptions. This range of signals derive from different processes, which if quantified, may tell us when and how the volcano will erupt: effusively or explosively. This quantification can be performed in laboratory. Here we investigated the signals associated with the deformation and failure of single-phase silicate liquids compare to mutli-phase magmas containing pores and crystals as heterogeneities. For the past decades, magmas have been simplified as viscoelastic fluids with grossly predictable failure, following an analysis of the stress and strain rate conditions in volcanic conduits. Yet it is clear that the way magmas fail is not unique and evidences increasingly illustrate the role of heterogeneities in the process of magmatic fragmentation. In such multi-phase magmas, failure cannot be predicted using current rheological laws. Microseismicity, as detected in the laboratory by analogous Acoustic Emission (AE), can be used to monitor fracture initiation and propagation, and thus provides invaluable information to characterise the process of brittle failure underlying explosive eruptions. Tri-axial press experiments on different synthetised and natural glass samples have been performed to investigate the acoustic signature of failure. We observed that the failure of single-phase liquids occurs without much strain and is preceded by the constant nucleation, propagation and coalescence of cracks as demonstrated by the monitored AE. In contrast, the failure of multi-phase magmas depends on the applied stress and is strain dependent. The path dependence of magma failure is nonetheless accompanied by supra exponential acceleration in released AEs. Analysis of the released AEs following material Failure Forecast Method (FFM) suggests that the predicability of failure is enhanced by the presence of heterogeneities in magmas. We discuss our observations in terms of volcanic scenarios.

The Role of Three-Dimensional Boundary Stresses in Limiting the Occurrence and Size of Experimental Landslides

NASA Astrophysics Data System (ADS)

Prancevic, Jeffrey P.; Lamb, Michael P.; Palucis, Marisa C.; Venditti, Jeremy G.

2018-01-01

The occurrence of seepage-induced shallow landslides on hillslopes and steep channel beds is important for landscape evolution and natural hazards. Infinite-slope stability models have been applied for seven decades, but sediment beds generally require higher water saturation levels than predicted for failure, and controlled experiments are needed to test models. We initiated 90 landslides in a 5 m long laboratory flume with a range in sediment sizes (D = 0.7, 2, 5, and 15 mm) and hillslope angles (θ = 20° to 43°), resulting in subsurface flow that spanned the Darcian and turbulent regimes, and failures that occurred with subsaturated and supersaturated sediment beds. Near complete saturation was required for failure in most experiments, with water levels far greater than predicted by infinite-slope stability models. Although 3-D force balance models predict that larger landslides are less stable, observed downslope landslide lengths were typically only several decimeters, not the entire flume length. Boundary stresses associated with short landslides can explain the increased water levels required for failure, and we suggest that short failures are tied to heterogeneities in granular properties. Boundary stresses also limited landslide thicknesses, and landslides progressively thinned on lower gradient hillslopes until they were one grain diameter thick, corresponding to a change from near-saturated to supersaturated sediment beds. Thus, landslides are expected to be thick on steep hillslopes with large frictional stresses acting on the boundaries, whereas landslides should be thin on low-gradient hillslopes or in channel beds with a critical saturation level that is determined by sediment size.

Bone Graft Substitute Provides Metaphyseal Fixation for a Stemless Humeral Implant.

PubMed

Kim, Myung-Sun; Kovacevic, David; Milks, Ryan A; Jun, Bong-Jae; Rodriguez, Eric; DeLozier, Katherine R; Derwin, Kathleen A; Iannotti, Joseph P

2015-07-01

Stemless humeral fixation has become an alternative to traditional total shoulder arthroplasty, but metaphyseal fixation may be compromised by the quality of the trabecular bone that diminishes with age and disease, and augmentation of the fixation may be desirable. The authors hypothesized that a bone graft substitute (BGS) could achieve initial fixation comparable to polymethylmethacrylate (PMMA) bone cement. Fifteen fresh-frozen human male humerii were randomly implanted using a stemless humeral prosthesis, and metaphyseal fixation was augmented with either high-viscosity PMMA bone cement (PMMA group) or a magnesium-based injectable BGS (OsteoCrete; Bone Solutions Inc, Dallas, Texas) (OC group). Both groups were compared with a control group with no augmentation. Initial stiffness, failure load, failure displacement, failure cycle, and total work were compared among groups. The PMMA and OC groups showed markedly higher failure loads, failure displacements, and failure cycles than the control group (P<.01). There were no statistically significant differences in initial stiffness, failure load, failure displacement, failure cycle, or total work between the PMMA and OC groups. The biomechanical properties of magnesium-based BGS fixation compared favorably with PMMA bone cement in the fixation of stemless humeral prostheses and may provide sufficient initial fixation for this clinical application. Future work will investigate the long-term remodeling characteristics and bone quality at the prosthetic-bone interface in an in vivo model to evaluate the clinical efficacy of this approach. Copyright 2015, SLACK Incorporated.

A Large-scale Finite Element Model on Micromechanical Damage and Failure of Carbon Fiber/Epoxy Composites Including Thermal Residual Stress

NASA Astrophysics Data System (ADS)

Liu, P. F.; Li, X. K.

2018-06-01

The purpose of this paper is to study micromechanical progressive failure properties of carbon fiber/epoxy composites with thermal residual stress by finite element analysis (FEA). Composite microstructures with hexagonal fiber distribution are used for the representative volume element (RVE), where an initial fiber breakage is assumed. Fiber breakage with random fiber strength is predicted using Monte Carlo simulation, progressive matrix damage is predicted by proposing a continuum damage mechanics model and interface failure is simulated using Xu and Needleman's cohesive model. Temperature dependent thermal expansion coefficients for epoxy matrix are used. FEA by developing numerical codes using ANSYS finite element software is divided into two steps: 1. Thermal residual stresses due to mismatch between fiber and matrix are calculated; 2. Longitudinal tensile load is further exerted on the RVE to perform progressive failure analysis of carbon fiber/epoxy composites. Numerical convergence is solved by introducing the viscous damping effect properly. The extended Mori-Tanaka method that considers interface debonding is used to get homogenized mechanical responses of composites. Three main results by FEA are obtained: 1. the real-time matrix cracking, fiber breakage and interface debonding with increasing tensile strain is simulated. 2. the stress concentration coefficients on neighbouring fibers near the initial broken fiber and the axial fiber stress distribution along the broken fiber are predicted, compared with the results using the global and local load-sharing models based on the shear-lag theory. 3. the tensile strength of composite by FEA is compared with those by the shear-lag theory and experiments. Finally, the tensile stress-strain curve of composites by FEA is applied to the progressive failure analysis of composite pressure vessel.

A Large-scale Finite Element Model on Micromechanical Damage and Failure of Carbon Fiber/Epoxy Composites Including Thermal Residual Stress

NASA Astrophysics Data System (ADS)

Liu, P. F.; Li, X. K.

2017-09-01

The purpose of this paper is to study micromechanical progressive failure properties of carbon fiber/epoxy composites with thermal residual stress by finite element analysis (FEA). Composite microstructures with hexagonal fiber distribution are used for the representative volume element (RVE), where an initial fiber breakage is assumed. Fiber breakage with random fiber strength is predicted using Monte Carlo simulation, progressive matrix damage is predicted by proposing a continuum damage mechanics model and interface failure is simulated using Xu and Needleman's cohesive model. Temperature dependent thermal expansion coefficients for epoxy matrix are used. FEA by developing numerical codes using ANSYS finite element software is divided into two steps: 1. Thermal residual stresses due to mismatch between fiber and matrix are calculated; 2. Longitudinal tensile load is further exerted on the RVE to perform progressive failure analysis of carbon fiber/epoxy composites. Numerical convergence is solved by introducing the viscous damping effect properly. The extended Mori-Tanaka method that considers interface debonding is used to get homogenized mechanical responses of composites. Three main results by FEA are obtained: 1. the real-time matrix cracking, fiber breakage and interface debonding with increasing tensile strain is simulated. 2. the stress concentration coefficients on neighbouring fibers near the initial broken fiber and the axial fiber stress distribution along the broken fiber are predicted, compared with the results using the global and local load-sharing models based on the shear-lag theory. 3. the tensile strength of composite by FEA is compared with those by the shear-lag theory and experiments. Finally, the tensile stress-strain curve of composites by FEA is applied to the progressive failure analysis of composite pressure vessel.

Experiments of thermomechanical fatigue of SMAs

NASA Astrophysics Data System (ADS)

Lagoudas, Dimitris C.; Miller, David A.

1999-07-01

As SMA wires are gaining in popularity for use as actuators, one constitutive parameter that remain unknown is the thermomechanical fatigue life. Even though the effect of thermal cycles on the transformation characteristics of SMAs has been studied, these teste have not been extended to high number of cycles. In this study, a novel test frame developed to study the thermomechanical fatigue life of SMAs is described. Additionally, a testing protocol is discussed necessary to fully establish the fatigue characteristics of SMAs under various conditions. Initial results of the initial test show a substantial increase in the number of cycles to failure as the applied stress level reduces to approximately 100 MPa.

Laser-driven mechanical fracture in fused silica

NASA Astrophysics Data System (ADS)

Dahmani, Faiz

1999-10-01

Fused silica, widely used as optical-window material in high-fluence requirements on glass and KrF lasers, experiences optical damage. Under fatigue conditions, the damage is initiated by slow crack growth and culminates, if not arrested, with catastrophic crack growth and implosive failure when the stress intensity approaches the critical value. Since laser-induced cracks cannot be eliminated entirely, the behavior of cracked structures under service conditions must be quantified to be predicted. Systematic scientific rules must be devised to characterize laser-induced cracks and their effects, and to predict if and when it may become necessary to replace the damaged components. This thesis makes a contribution toward this end. Measurements of fatigue failure strength of laser-cracked fused silica in air at room temperature for different number of laser pulses and laser fluences are presented. The failure-strength variability is found to be due mainly to the spectrum of crack depths. Agreement with theory suggests the incorporation of a residual term into the failure-strength equation. Experiments on residual stresses induced in fused silica by the presence of a laser-induced crack are carried out using two different techniques. Theoretical modelings show that this residual stress field is of shear nature and mouth-opening. A correlation between the reduction in fracture strength of fused silica and the increase of the residual-stress field is established, providing laser systems designers and operators with guidance on the rate of crack growth as well as on the stress-related ramifications such as laser-driven cracks entail. Specifically, a hoop-stress in the immediate vicinity of a crack growing along the beam propagation direction is identified as strongly coupling to both the laser fluence and the crack growth. This coupling prompted the question of whether or not breaking the hoop stress symmetry by some external perturbation will accelerate or stymie crack growth. Experimental results on stress-inhibited laser-driven crack growth and stress-delayed-laser-damage initiation thresholds in fused silica and borosilicate glass (BK7) are presented. The results obtained show that, for very low compressive stresses (<10 psi), the damage initiation threshold is raised by as much as 78%, while the crack growth is arrested by 70%. Different loading- geometries are tested, giving different crack growth rates and raising the distinction between uniaxial and biaxial states of stresses.

[Ethical attitudes of intensive care paediatricians as regards patients with spinal muscular atrophy type 1].

PubMed

Agra Tuñas, María Carmen; Hernández Rastrollo, Ramón; Hernández González, Arturo; Ramil Fraga, Carmen; Cambra Lasaosa, Francisco José; Quintero Otero, Sebastián; Ruiz Extremera, Angela; Rodríguez Núñez, Antonio

2017-03-01

Spinal muscular atrophy type 1 (SMA-1) is a progressive and fatal disease that leads to ethical problems for Paediatric professionals. Our objective was to determine the ethical options of Paediatric Intensive Care Unit (PICU) paediatricians as regards a child with SMA-1 and respiratory failure. A cross-sectional descriptive study was conducted using an anonymous questionnaire sent to PICUs in Spain (which can be accessed through the Spanish Society of Paediatric Critical Care web page). Of the 124 responses analysed, 70% were from women, 51% younger than 40 years, 54% from a PICU with more than 10 beds, 69% with prior experience in such cases, and 53% with religious beliefs. In the last patient cared for, most paediatricians opted for non-invasive mechanical ventilation (NIV) and limitation of therapeutic effort (LET) in case of NIV failure. Confronted with a future hypothetical case, half of paediatricians would opt for the same plan (NIV+LET), and 74% would support the family's decision, even in case of disagreement. Age, prior experience and sex were not related to the preferred options. Paediatricians with religious beliefs were less in favour of initial LET. Less than two-thirds (63%) scored the quality of life of a child with SMA-1 and invasive mechanical ventilation as very poor. Faced with child with SMA-1 and respiratory failure, most paediatricians are in favour of initiating NIV and LET when such support is insufficient, but they would accept the family's decision, even in case of disagreement. Copyright © 2015 Asociación Española de Pediatría. Publicado por Elsevier España, S.L.U. All rights reserved.

Spectral Characteristics of Continuous Acoustic Emission (AE) Data from Laboratory Rock Deformation Experiments

NASA Astrophysics Data System (ADS)

Flynn, J. William; Goodfellow, Sebastian; Reyes-Montes, Juan; Nasseri, Farzine; Young, R. Paul

2016-04-01

Continuous acoustic emission (AE) data recorded during rock deformation tests facilitates the monitoring of fracture initiation and propagation due to applied stress changes. Changes in the frequency and energy content of AE waveforms have been previously observed and were associated with microcrack coalescence and the induction or mobilisation of large fractures which are naturally associated with larger amplitude AE events and lower-frequency components. The shift from high to low dominant frequency components during the late stages of the deformation experiment, as the rate of AE events increases and the sample approaches failure, indicates a transition from the micro-cracking to macro-cracking regime, where large cracks generated result in material failure. The objective of this study is to extract information on the fracturing process from the acoustic records around sample failure, where the fast occurrence of AE events does not allow for identification of individual AE events and phase arrivals. Standard AE event processing techniques are not suitable for extracting this information at these stages. Instead the observed changes in the frequency content of the continuous record can be used to characterise and investigate the fracture process at the stage of microcrack coalescence and sample failure. To analyse and characterise these changes, a detailed non-linear and non-stationary time-frequency analysis of the continuous waveform data is required. Empirical Mode Decomposition (EMD) and Hilbert Spectral Analysis (HSA) are two of the techniques used in this paper to analyse the acoustic records which provide a high-resolution temporal frequency distribution of the data. In this paper we present the results from our analysis of continuous AE data recorded during a laboratory triaxial deformation experiment using the combined EMD and HSA method.

Thermal barrier coating life prediction model development

NASA Technical Reports Server (NTRS)

Hillery, R. V.; Pilsner, B. H.; Mcknight, R. L.; Cook, T. S.; Hartle, M. S.

1988-01-01

This report describes work performed to determine the predominat modes of degradation of a plasma sprayed thermal barrier coating system and to develop and verify life prediction models accounting for these degradation modes. The primary TBC system consisted of a low pressure plasma sprayed NiCrAlY bond coat, an air plasma sprayed ZrO2-Y2O3 top coat, and a Rene' 80 substrate. The work was divided into 3 technical tasks. The primary failure mode to be addressed was loss of the zirconia layer through spalling. Experiments showed that oxidation of the bond coat is a significant contributor to coating failure. It was evident from the test results that the species of oxide scale initially formed on the bond coat plays a role in coating degradation and failure. It was also shown that elevated temperature creep of the bond coat plays a role in coating failure. An empirical model was developed for predicting the test life of specimens with selected coating, specimen, and test condition variations. In the second task, a coating life prediction model was developed based on the data from Task 1 experiments, results from thermomechanical experiments performed as part of Task 2, and finite element analyses of the TBC system during thermal cycles. The third and final task attempted to verify the validity of the model developed in Task 2. This was done by using the model to predict the test lives of several coating variations and specimen geometries, then comparing these predicted lives to experimentally determined test lives. It was found that the model correctly predicts trends, but that additional refinement is needed to accurately predict coating life.

Early initiation of beta blockade in heart failure: issues and evidence.

PubMed

Williams, Randall E

2005-09-01

Despite clinical trials demonstrating that inhibitors of the renin-angiotensin and sympathetic nervous systems can reduce the mortality and morbidity risk associated with heart failure, these drugs have remained underutilized in general clinical practice. In particular, many patients with heart failure due to left ventricular systolic dysfunction fail to receive beta blockers, although this class of drugs, as well as other antihypertensive agents such as angiotensin-converting enzyme inhibitors or angiotensin receptor blockers, are recommended as part of routine heart failure therapy by national expert consensus guidelines. In-hospital initiation of beta-blocker therapy may improve long-term utilization by physicians and compliance by patients through obviating many of the misperceived dangers associated with beta blockade. The following review of the clinical trial data from the Randomized Evaluation of Strategies for Left Ventricular Dysfunction (RESOLVD) trial, the Metoprolol Controlled-Release Randomized Intervention Trial in Heart Failure (MERIT-HF), the Cardiac Insufficiency Bisoprolol Study II (CIBIS-II), the Carvedilol Prospective Randomized Cumulative Survival (COPERNICUS) trial, and the Initiation Management Predischarge Process for Assessment of Carvedilol Therapy for Heart Failure (IMPACT-HF) trial on the efficacy, safety, and tolerability of beta blockers indicates that early initiation can be safely achieved and can improve patient outcomes.

Coupled fluid and solid evolution in analogue volcanic vents

NASA Astrophysics Data System (ADS)

Solovitz, Stephen A.; Ogden, Darcy E.; Kim, Dave (Dae-Wook); Kim, Sang Young

2014-07-01

Volcanic eruptions emit rock particulates and gases at high speed and pressure, which change the shape of the surrounding rock. Simplified analytical solutions, field studies, and numerical models suggest that this process plays an important role in the behavior and hazards associated with explosive volcanic eruptions. Here we present results from a newly developed laboratory-scale apparatus designed to study this coupled process. The experiments used compressed air jets expanding into the laboratory through fabricated rock analogue material, which evolves through time during the experiment. The compressed air was injected at approximately 2.5 times atmospheric pressure. We fabricated rock analogues from sand and steel powder samples with a three-dimensional printing process. We studied the fluid development using phase-locked particle image velocimetry, while simultaneously observing the solid development via a video camera. We found that the fluid response was much more rapid than that of the solid, permitting a quasi-steady approximation. In most cases, the solid vent flared out rapidly, increasing its diameter by 20 to 100%. After the initial expansion, the vent and flow field achieved a near-steady condition for a long duration. The new expanded vent shapes permitted lower vent exit pressures and larger jet radii. In one experiment, after an initial vent shape development and establishment of steady flow behavior, rock failure occurred a second time, resulting in a new exit diameter and new steady state. This second failure was not precipitated by changes in the nozzle flow condition, and it radically changed the downstream flow dynamics. This experiment suggests that the brittle nature of volcanic host rock enables sudden vent expansion in the middle of an eruption without requiring a change in the conduit flow.

Micromechanics Based Failure Analysis of Heterogeneous Materials

NASA Astrophysics Data System (ADS)

Sertse, Hamsasew M.

In recent decades, heterogeneous materials are extensively used in various industries such as aerospace, defense, automotive and others due to their desirable specific properties and excellent capability of accumulating damage. Despite their wide use, there are numerous challenges associated with the application of these materials. One of the main challenges is lack of accurate tools to predict the initiation, progression and final failure of these materials under various thermomechanical loading conditions. Although failure is usually treated at the macro and meso-scale level, the initiation and growth of failure is a complex phenomena across multiple scales. The objective of this work is to enable the mechanics of structure genome (MSG) and its companion code SwiftComp to analyze the initial failure (also called static failure), progressive failure, and fatigue failure of heterogeneous materials using micromechanics approach. The initial failure is evaluated at each numerical integration point using pointwise and nonlocal approach for each constituent of the heterogeneous materials. The effects of imperfect interfaces among constituents of heterogeneous materials are also investigated using a linear traction-displacement model. Moreover, the progressive and fatigue damage analyses are conducted using continuum damage mechanics (CDM) approach. The various failure criteria are also applied at a material point to analyze progressive damage in each constituent. The constitutive equation of a damaged material is formulated based on a consistent irreversible thermodynamics approach. The overall tangent modulus of uncoupled elastoplastic damage for negligible back stress effect is derived. The initiation of plasticity and damage in each constituent is evaluated at each numerical integration point using a nonlocal approach. The accumulated plastic strain and anisotropic damage evolution variables are iteratively solved using an incremental algorithm. The damage analyses are performed for both brittle failure/high cycle fatigue (HCF) for negligible plastic strain and ductile failure/low cycle fatigue (LCF) for large plastic strain. The proposed approach is incorporated in SwiftComp and used to predict the initial failure envelope, stress-strain curve for various loading conditions, and fatigue life of heterogeneous materials. The combined effects of strain hardening and progressive fatigue damage on the effective properties of heterogeneous materials are also studied. The capability of the current approach is validated using several representative examples of heterogeneous materials including binary composites, continuous fiber-reinforced composites, particle-reinforced composites, discontinuous fiber-reinforced composites, and woven composites. The predictions of MSG are also compared with the predictions obtained using various micromechanics approaches such as Generalized Methods of Cells (GMC), Mori-Tanaka (MT), and Double Inclusions (DI) and Representative Volume Element (RVE) Analysis (called as 3-dimensional finite element analysis (3D FEA) in this document). This study demonstrates that a micromechanics based failure analysis has a great potential to rigorously and more accurately analyze initiation and progression of damage in heterogeneous materials. However, this approach requires material properties specific to damage analysis, which are needed to be independently calibrated for each constituent.

33 CFR 154.804 - Review, certification, and initial inspection.

Code of Federal Regulations, 2012 CFR

2012-07-01

..., property, and the environment if an accident were to occur; and (4) If a quantitative failure analysis is... quantitative failure analysis. (e) The certifying entity must conduct all initial inspections and witness all...

33 CFR 154.804 - Review, certification, and initial inspection.

Code of Federal Regulations, 2013 CFR

2013-07-01

..., property, and the environment if an accident were to occur; and (4) If a quantitative failure analysis is... quantitative failure analysis. (e) The certifying entity must conduct all initial inspections and witness all...

33 CFR 154.804 - Review, certification, and initial inspection.

Code of Federal Regulations, 2010 CFR

2010-07-01

..., property, and the environment if an accident were to occur; and (4) If a quantitative failure analysis is... quantitative failure analysis. (e) The certifying entity must conduct all initial inspections and witness all...

33 CFR 154.804 - Review, certification, and initial inspection.

Code of Federal Regulations, 2011 CFR

2011-07-01

..., property, and the environment if an accident were to occur; and (4) If a quantitative failure analysis is... quantitative failure analysis. (e) The certifying entity must conduct all initial inspections and witness all...

Fatigue Failure in Extra-Articular Proximal Tibia Fractures: Locking Intramedullary Nail Versus Double Locking Plates-A Biomechanical Study.

PubMed

Kandemir, Utku; Herfat, Safa; Herzog, Mary; Viscogliosi, Paul; Pekmezci, Murat

2017-02-01

The goal of this study is to compare the fatigue strength of a locking intramedullary nail (LN) construct with a double locking plate (DLP) construct in comminuted proximal extra-articular tibia fractures. Eight pairs of fresh frozen cadaveric tibias with low bone mineral density [age: 80 ± 7 (SD) years, T-score: -2.3 ± 1.2] were used. One tibia from each pair was fixed with LN, whereas the contralateral side was fixed with DLP for complex extra-articular multifragmentary metaphyseal fractures (simulating OTA 41-A3.3). Specimens were cyclically loaded under compression simulating single-leg stance by staircase method out to 260,000 cycles. Every 2500 cycles, localized gap displacements were measured with a 3D motion tracking system, and x-ray images of the proximal tibia were acquired. To allow for mechanical settling, initial metrics were calculated at 2500 cycles. The 2 groups were compared regarding initial construct stiffness, initial medial and lateral gap displacements, stiffness at 30,000 cycles, medial and lateral gap displacements at 30,000 cycles, failure load, number of cycles to failure, and failure mode. Failure metrics were reported for initial and catastrophic failures. DLP constructs exhibited higher initial stiffness and stiffness at 30,000 cycles compared with LN constructs (P < 0.03). There were no significant differences between groups for loads at failure or cycles to failure. For the fixation of extra-articular proximal tibia fractures, a LN provides a similar fatigue performance to double locked plates. The locked nail could be safely used for fixation of proximal tibia fractures with the advantage of limited extramedullary soft tissue damage.

Acute renal failure as a form of presentation of sarcoidosis in a young adult: a case report

PubMed Central

2014-01-01

Introduction Sarcoidosis is a systemic granulomatous disease. Renal involvement is a rare initial presentation of this disease. Few articles on renal involvement as an initial presentation of sarcoidosis have been published in the literature. Case presentation A 26-year-old Caucasian woman presented with acute renal failure as an initial manifestation of sarcoidosis. Conclusions Renal involvement is an uncommon feature of sarcoidosis and it is essential to establish a fast and correct diagnosis because early therapy avoids progression to terminal renal failure. PMID:25124289

CRYOGENIC UPPER STAGE SYSTEM SAFETY

NASA Technical Reports Server (NTRS)

Smith, R. Kenneth; French, James V.; LaRue, Peter F.; Taylor, James L.; Pollard, Kathy (Technical Monitor)

2005-01-01

NASA s Exploration Initiative will require development of many new systems or systems of systems. One specific example is that safe, affordable, and reliable upper stage systems to place cargo and crew in stable low earth orbit are urgently required. In this paper, we examine the failure history of previous upper stages with liquid oxygen (LOX)/liquid hydrogen (LH2) propulsion systems. Launch data from 1964 until midyear 2005 are analyzed and presented. This data analysis covers upper stage systems from the Ariane, Centaur, H-IIA, Saturn, and Atlas in addition to other vehicles. Upper stage propulsion system elements have the highest impact on reliability. This paper discusses failure occurrence in all aspects of the operational phases (Le., initial burn, coast, restarts, and trends in failure rates over time). In an effort to understand the likelihood of future failures in flight, we present timelines of engine system failures relevant to initial flight histories. Some evidence suggests that propulsion system failures as a result of design problems occur shortly after initial development of the propulsion system; whereas failures because of manufacturing or assembly processing errors may occur during any phase of the system builds process, This paper also explores the detectability of historical failures. Observations from this review are used to ascertain the potential for increased upper stage reliability given investments in integrated system health management. Based on a clear understanding of the failure and success history of previous efforts by multiple space hardware development groups, the paper will investigate potential improvements that can be realized through application of system safety principles.

Implicit Behavioral Change in Response to Cognitive Tasks in Alzheimer Disease.

PubMed

Bomilcar, Iris; Morris, Robin G; Brown, Richard G; Mograbi, Daniel C

2018-03-01

Lack of awareness about impairments is commonly found in Alzheimer disease (AD), but recent evidence suggests that patients may respond to the experience of illness despite limited awareness. In this study, we explored whether implicit emotional responses to experiences of failure in cognitive tasks would result in longer-term change in behavior. Twenty-two patients with AD were seen 1 week after a previous session in which they performed computer tasks that had been manipulated to be either too difficult (failure condition) or very easy (success condition) for them. At the second session, both types of tasks were set to have medium difficulty and were administered so that the participants decided how long to persist on each task. Task persistence was determined by relative time spent doing the tasks, considering that participants would be more likely to stop performing tasks in which they had experienced failure during the first session. Task persistence in the second session was not affected by performance in the first session. However, when participants' awareness of performance in the first session was taken into account, differences were found in persistence between tasks in the second session. During the second session, participants stopped performing tasks after a sequence of errors. There were no self-reported changes in motivation or enjoyment in response to task failure. These findings suggest that implicit learning of task valence may be compromised in AD, but that initial moments of awareness of performance may influence long-term adaptation in unaware patients.

 Early initiation of MARS® dialysis in Amanita phalloides-induced acute liver injury prevents liver transplantation.

PubMed

Pillukat, Mike Hendrik; Schomacher, Tina; Baier, Peter; Gabriëls, Gert; Pavenstädt, Hermann; Schmidt, Hartmut H J

2016-01-01

 Amanita phalloides is the most relevant mushroom intoxication leading to acute liver failure. The two principal groups of toxins, the amatoxins and the phallotoxins, are small oligopeptides highly resistant to chemical and physical influences. The amatoxins inhibit eukaryotic RNA polymerase II causing transcription arrest affecting mainly metabolically highly active cells like hepatocytes and renal cells. The clinically most characteristic symptom is a 6-40 h lag phase before onset of gastrointestinal symptoms and the rapid progression of acute liver failure leading to multi-organ failure and death within a week if left untreated. Extracorporeal albumin dialysis (ECAD) was reported to improve patient's outcome or facilitate bridging to transplantation. In our tertiary center, out of nine intoxicated individuals from five non-related families six patients presented with acute liver injury; all of them were treated with ECAD using the MARS® system. Four of them were listed on admission for high urgency liver transplantation. In addition to standard medical treatment for Amanita intoxication we initiated ECAD once patients were admitted to our center. Overall 16 dialysis sessions were performed. All patients survived with full native liver recovery without the need for transplantation. ECAD was well tolerated; no severe adverse events were reported during treatment. Coagulopathy resolved within days in all patients, and acute kidney injury in all but one individual. In conclusion, ECAD is highly effective in treating intoxication with Amanita phalloides. Based on these experiences we suggest early initiation and repeated sessions depending on response to ECAD with the chance of avoiding liver transplantation.

42 CFR 433.113 - Reduction of FFP for failure to operate a system and obtain initial approval.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 42 Public Health 4 2010-10-01 2010-10-01 false Reduction of FFP for failure to operate a system... ADMINISTRATION Mechanized Claims Processing and Information Retrieval Systems § 433.113 Reduction of FFP for failure to operate a system and obtain initial approval. (a) Except as waived under § 433.130 or 433.131...

Tectonic lineations and frictional faulting on a relatively simple body (Ariel)

NASA Astrophysics Data System (ADS)

Nyffenegger, Paul; Davis, Dan M.; Consolmagno, Guy J.

1997-09-01

Anderson's model of faulting and the Mohr-Coulomb failure criterion can predict the orientations of faults generated in laboratory triaxial compression experiments, but do a much poorer job of explaining the orientations of outcrop- and map-scale faults on Earth. This failure may be due to the structural complexity of the Earth's lithosphere, the failure of laboratory experiments to predict accurately the strength of natural faults, or some fundamental flaw in the model. A simpler environment, such as the lithosphere of an icy satellite, allows us to test whether this model can succeed in less complex settings. A mathematical method is developed to analyze patterns in fracture orientations that can be applied to fractures in the lithospheres of icy satellites. In a initial test of the method, more than 300 lineations on Uranus' satellite Ariel are examined. A nonrandom pattern of lineations is looked for, and the source of the stresses that caused those features and the strength of the material in which they occur are constrained. It is impossible to observe directly the slip on these fractures. However, their orientations are clearly nonrandom and appear to be consistent with Andersonian strike-slip faulting in a relatively weak frictional lithosphere during one or more episodes of tidal flexing.

Age and treatment of kidney failure.

PubMed

Elliott, Meghan J; Tam-Tham, Helen; Hemmelgarn, Brenda R

2013-05-01

This review discusses issues related to treatment of chronic kidney disease, and kidney failure in particular, among older adults. A substantial proportion of older adults have chronic kidney disease and progress to kidney failure. There is considerable variability in treatment practices for advanced kidney disease among older adults, and evidence that treatment decisions such as dialysis initiation may be made without adequate preparation. When initiated, survival among older adults on chronic dialysis remains poor, and is associated with a significant decline in functional status. There is also evidence to suggest that dialysis initiation may not reflect overall treatment goals of elderly patients, but rather a lack of clear communication between patients and health practitioners, and underdeveloped conservative care programs in many centers. Kidney failure is common among older adults. When considering treatment options for kidney failure, patient priorities, preferences, and symptoms should be taken into account, using a shared decision-making approach.

Investigation of heat transfer in zirconium potassium perchlorate at low temperature: A study of the failure mechanism of the NASA standard initiator

NASA Technical Reports Server (NTRS)

Varghese, Philip L.

1989-01-01

The objective of this work was to study the reasons for the failure of pyrotechnic initiators at very low temperatures (10 to 100 K). A two-dimensional model of the NASA standard initiator was constructed to model heat transfer from the electrically heated stainless steel bridgewire to the zirconium potassium perchlorate explosive charge and the alumina charge cup. Temperature dependent properties were used in the model to simulate initiator performance over a wide range of initial temperatures (10 to 500 K). A search of the thermophysical property data base showed that pure alumina has a very high thermal conductivity at low temperatures. It had been assumed to act as a thermal insulator in all previous analyses. Rapid heat transfer from the bridgewire to the alumina at low initial temperatures was shown to cause failure of the initiators if the wire did not also make good contact with the zirconium potassium perchlorate charge. The mode is able to reproduce the results of the tests that had been conducted to investigate the cause for failure. It also provides an explanation for previously puzzling results and suggests simple design changes that will increase reliability at very low initial temperatures.

Cost of a recall of a single-center experience managing the Riata defibrillator lead.

PubMed

Hussain, Sarah; Moorman, Liza; Moorman, J Randall; DiMarco, John P; Malhotra, Rohit; Darby, Andrew; Bilchick, Kenneth; Mangrum, J Michael; Ferguson, John D; Mason, Pamela K

2015-01-15

Riata and Riata ST defibrillator leads (St. Jude Medical, Sylmar, California) were recalled in 2011 due to increased risk of insulation failure leading to externalized cables. Fluoroscopic screening can identify insulation failure, although the relation between mechanical failure and electrical failure is unclear. At the time of the recall, the University of Virginia developed a screening program, including fluoroscopic evaluation, education sessions, device interrogation, and remote monitoring for patients with this defibrillator lead. The aim of this study was to review the outcomes of the screening program, including costs, which were absorbed by our institution. Costs were calculated using Medicare reimbursement estimates. Forty-eight patients participated in the screening program. At initial screening, 31% were found to have evidence of insulation failure but electrical function was normal in all leads. The cost of this program was $35,358.72. The cost per diagnosis of mechanical lead failure was $2,357.25. During 2 years of follow-up, 1 patient experienced Riata lead electrical failure without fluoroscopic evidence of insulation failure. Patients were more likely to have a lead revision if there was evidence of insulation failure. Lead revisions occurred at the time of generator change in 88% of patients with insulation failure but in only 14% of patients with a fluoroscopically normal lead (p = 0.04). The cost of recall-related defibrillator lead revisions was $81,704.55. In conclusion, our Riata screening program added expense without clear benefit to patients. In fact, patients may have been put at more risk by undergoing defibrillator lead revisions based solely on the results of the fluoroscopic screening. Copyright © 2015 Elsevier Inc. All rights reserved.

A Unified Constitutive Model for Subglacial Till, Part I: The Disturbed State Concept

NASA Astrophysics Data System (ADS)

Jenson, J. W.; Desai, C. S.; Clark, P. U.; Contractor, D. N.; Sane, S. M.; Carlson, A. E.

2006-12-01

Classical plasticity models such as Mohr-Coulomb may not adequately represent the full range of possible motion and failure in tills underlying ice sheets. Such models assume that deformations are initially elastic, and that when a peak or failure stress level is reached the system experiences sudden failure, after which the stress remains constant and the deformations can tend to infinite magnitudes. However, theory suggests that the actual behavior of deforming materials, including granular materials such as glacial till, can involve plastic or irreversible strains almost from the beginning, in which localized zones of microcracking and "failure" can be distributed over the material element. As the loading increases, and with associated plastic and creep deformations, the distributed failure zones coalesce. When the extent of such coalesced zones reaches critical values of stresses and strains, the critical condition (failure) can occur in the till, which would cause associated movements of the ice sheet. Failure or collapse then may occur at much larger strain levels. Classical models (e.g., Mohr-Coulomb) may therefore not be able to fully and realistically characterize deformation behavior and the gradual developments of localized failures tending to the global failure and movements. We present and propose the application of the Disturbed State Concept (DSC), a unified model that incorporates the actual pre- and post-failure behavior, for characterizing the behavior of subglacial tills. In this presentation (Part I), we describe the DSC and propose its application to subglacial till. Part II (Desai et al.) describes our application of the DSC with laboratory testing, model calibration, and validations to evaluate the mechanical properties of two regionally significant Pleistocene tills.

[Transcatheter aortic valve implantation for aortic stenosis. Initial experience].

PubMed

Careaga-Reyna, Guillermo; Lázaro-Castillo, José Luis; Lezama-Urtecho, Carlos Alberto; Macías-Miranda, Enriqueta; Dosta-Herrera, Juan José; Galván Díaz, José

Aortic stenosis is a frequent disease in the elderly, and is associated with other systemic pathologies that may contraindicate the surgical procedure. Another option for these patients is percutaneous aortic valve implantation, which is less invasive. We present our initial experience with this procedure. Patients with aortic stenosis were included once selection criteria were accomplished. Under general anaesthesia and echocardiographic and fluosocopic control, a transcatheter aortic valve was implanted following s valvuloplasty. Once concluded the procedure, angiographic and pressure control was realized in order to confirm the valve function. Between November 2014 and May 2015, 6 patients were treated (4 males and 2 females), with a mean age of 78.83±5.66 years-old. The preoperative transvalvular gradient was 90.16±28.53mmHg and posterior to valve implant was 3.33±2.92mmHg (P<.05). Two patients had concomitant coronary artery disease which had been treated previously. One patient presented with acute right coronary artery occlusion which was immediately treated. However due to previous renal failure, postoperative sepsis and respiratory failure, the patient died one month later. It was concluded that our preliminary results showed that in selected patients percutaneous aortic valve implantation is a safe procedure with clinical improvement for treated patients. Copyright © 2016 Academia Mexicana de Cirugía A.C. Publicado por Masson Doyma México S.A. All rights reserved.

Appropriate evaluation and treatment of heart failure patients after implantable cardioverter-defibrillator discharge: time to go beyond the initial shock.

PubMed

Mishkin, Joseph D; Saxonhouse, Sherry J; Woo, Gregory W; Burkart, Thomas A; Miles, William M; Conti, Jamie B; Schofield, Richard S; Sears, Samuel F; Aranda, Juan M

2009-11-24

Multiple clinical trials support the use of implantable cardioverter-defibrillators (ICDs) for prevention of sudden cardiac death in patients with heart failure (HF). Unfortunately, several complicating issues have arisen from the universal use of ICDs in HF patients. An estimated 20% to 35% of HF patients who receive an ICD for primary prevention will experience an appropriate shock within 1 to 3 years of implant, and one-third of patients will experience an inappropriate shock. An ICD shock is associated with a 2- to 5-fold increase in mortality, with the most common cause being progressive HF. The median time from initial ICD shock to death ranges from 168 to 294 days depending on HF etiology and the appropriateness of the ICD therapy. Despite this prognosis, current guidelines do not provide a clear stepwise approach to managing these high-risk patients. An ICD shock increases HF event risk and should trigger a thorough evaluation to determine the etiology of the shock and guide subsequent therapeutic interventions. Several combinations of pharmacologic and device-based interventions such as adding amiodarone to baseline beta-blocker therapy, adjusting ICD sensitivity, and employing antitachycardia pacing may reduce future appropriate and inappropriate shocks. Aggressive HF surveillance and management is required after an ICD shock, as the risk of sudden cardiac death is transformed to an increased HF event risk.

The Response of Simple Polymer Structures Under Dynamic Loading

NASA Astrophysics Data System (ADS)

Proud, William; Ellison, Kay; Yapp, Su; Cole, Cloe; Galimberti, Stefano; Institute of Shock Physics Team

2017-06-01

The dynamic response of polymeric materials has been widely studied with the effects of degree of crystallinity, strain rate, temperature and sample size being commonly reported. This study uses a simple PMMA structure, a right cylindrical sample, with structural features such as holes. The features are added an varied in a systematic fashion. Samples were dynamically loaded using a Split Hopkinson Pressure Bar up to failure. The resulting stress-strain curves are presented showing the change in sample response. The strain to failure is shown to increase initially with the presence of holes, while failure stress is relatively unaffected. The fracture patterns seen in the failed samples change, with tensile cracks, Hertzian cones, shear effects being dominant for different holes sizes and geometries. The sample were prepared by laser cutting and checked for residual stress before experiment. The data is used to validate predictive model predictions where material, structure and damage are included.. The Institute of Shock Physics acknowledges the support of Imperial College London and the Atomic Weapons Establishment.

'As many options as there are, there are just not enough for me': contraceptive use and barriers to access among Australian women.

PubMed

Dixon, Suzanne C; Herbert, Danielle L; Loxton, Deborah; Lucke, Jayne C

2014-10-01

A comprehensive life course perspective of women's experiences in obtaining and using contraception in Australia is lacking. This paper explores free-text comments about contraception provided by women born between 1973 and 1978 who participated in the Australian Longitudinal Study on Women's Health (ALSWH). The ALSWH is a national population-based cohort study involving over 40,000 women from three age groups, who are surveyed every three years. An initial search identified 1600 comments from 690 women across five surveys from 1996 (when they were aged 18-23 years) to 2009 (31-36 years). The analysis included 305 comments from 289 participants. Factors relating to experiences of barriers to access and optimal contraceptive use were identified and explored using thematic analysis. Five themes recurred across the five surveys as women aged: (i) side effects affecting physical and mental health; (ii) lack of information about contraception; (iii) negative experiences with health services; (iv) contraceptive failure; and (v) difficulty with accessing contraception. Side effects of hormonal contraception and concerns about contraceptive failure influence women's mental and physical health. Many barriers to effective contraception persist throughout women's reproductive lives. Further research is needed into reducing barriers and minimising negative experiences, to ensure optimal contraceptive access for Australian women.

Heart Failure Epidemiology: European Perspective

PubMed Central

Guha, K; McDonagh, T

2013-01-01

Heart failure poses an increasing problem for global healthcare systems. The epidemiological data which has been accrued over the last thirty years has predominantly been accumulated from experience within North America and Europe. Initial large cohort, prospective longitudinal studies produced the first publications; however latterly the focus has shifted onto epidemiological data governing hospitalisation and mortality. The emphasis behind this shift has been the resource implications with regards to repetitive, costly and prolonged hospitalisation. The European experience in heart failure, though similar to North America has recently demonstrated differences in hospitalisation which may underlie the differences between healthcare system configuration. Heart failure however remains an increasing global problem and the endpoint of a variety of cardiovascular diseases. Allied with the fact of increasingly elderly populations and prior data demonstrating a steep rise in prevalent cases within more elderly populations, it is likely that the increasing burden of disease will continue to pose challenges for modern healthcare. Despite the predicted increase in the number of patients affected by heart failure, over the last thirty years, a clear management algorithm has evolved for the use of pharmacotherapies (neuro-hormonal antagonists), device based therapies (Implantable Cardioverting Defibrillator (ICD) and Cardiac Resynchronisation Therapy (CRT)) and mechanical therapies including left ventricular assist devices and cardiac transplantation. Though the management of such patients has been clearly delineated in national and international guidelines, the underuse of all available and appropriate therapies remains a significant problem. When comparing various epidemiological studies from different settings and timepoints, it should be remembered that rates of prevalence and incidence may vary depending upon the definition used, methods of accumulating information (with the possibility of bias) and the chosen cut point of defining left ventricular systolic dysfunction (LVSD). PMID:23597298

Medical results of the Skylab program

NASA Technical Reports Server (NTRS)

Johnston, R. S.; Dietlein, L. F.

1974-01-01

The Skylab food system, waste management system, operational bioinstrumentation, personal hygiene provisions, in-flight medical support system, and the cardiovascular counterpressure garment worn during reentry are described. The medical experiments program provided scientific data and also served as the basis for real-time decisions on flight duration. Premission support, in-flight operational support, and postflight medical activities are surveyed. Measures devised to deal with possible food spoilage, medical instrument damage, and toxic atmosphere caused by the initial failures on the Orbital Workshop (OWS) are discussed. The major medical experiments performed in flight allowed the study of physiological changes as a function of exposure to weightless flight. The experiments included studies of the cardiovascular system, musculoskeletal and fluid/electrolyte balance, sleep, blood, vestibular system, and time and motion studies.

DOE Office of Scientific and Technical Information (OSTI.GOV)

McAdams, Brian J.; Pearson, Raymond A.

With the continuing trend of decreasing feature sizes in flip-chip assemblies, the reliability tolerance to interfacial flaws is also decreasing. Small-scale disbonds will become more of a concern, pointing to the need for a better understanding of the initiation stage of interfacial delamination. With most accepted adhesion metric methodologies tailored to predict failure under the prior existence of a disbond, the study of the initiation phenomenon is open to development and standardization of new testing procedures. Traditional fracture mechanics approaches are not suitable, as the mathematics assume failure to originate at a disbond or crack tip. Disbond initiation is believedmore » to first occur at free edges and corners, which act as high stress concentration sites and exhibit singular stresses similar to a crack tip, though less severe in intensity. As such, a 'fracture mechanics-like' approach may be employed which defines a material parameter--a critical stress intensity factor (K{sub c})--that can be used to predict when initiation of a disbond at an interface will occur. The factors affecting the adhesion of underfill/polyimide interfaces relevant to flip-chip assemblies were investigated in this study. The study consisted of two distinct parts: a comparison of the initiation and propagation phenomena and a comparison of the relationship between sub-critical and critical initiation of interfacial failure. The initiation of underfill interfacial failure was studied by characterizing failure at a free-edge with a critical stress intensity factor. In comparison with the interfacial fracture toughness testing, it was shown that a good correlation exists between the initiation and propagation of interfacial failures. Such a correlation justifies the continuing use of fracture mechanics to predict the reliability of flip-chip packages. The second aspect of the research involved fatigue testing of tensile butt joint specimens to determine lifetimes at sub-critical load levels. The results display an interfacial strength ranking similar to that observed during monotonic testing. The fatigue results indicate that monotonic fracture mechanics testing may be an adequate screening tool to help predict cyclic underfill failure; however lifetime data is required to predict reliability.« less

IMU-based Real-time Pose Measurement system for Anterior Pelvic Plane in Total Hip Replacement Surgeries.

PubMed

Zhe Cao; Shaojie Su; Hao Tang; Yixin Zhou; Zhihua Wang; Hong Chen

2017-07-01

With the aging of population, the number of Total Hip Replacement Surgeries (THR) increased year by year. In THR, inaccurate position of the implanted prosthesis may lead to the failure of the operation. In order to reduce the failure rate and acquire the real-time pose of Anterior Pelvic Plane (APP), we propose a measurement system in this paper. The measurement system includes two parts: Initial Pose Measurement Instrument (IPMI) and Real-time Pose Measurement Instrument (RPMI). IPMI is used to acquire the initial pose of the APP, and RPMI is used to estimate the real-time pose of the APP. Both are composed of an Inertial Measurement Unit (IMU) and magnetometer sensors. To estimate the attitude of the measurement system, the Extended Kalman Filter (EKF) is adopted in this paper. The real-time pose of the APP could be acquired together with the algorithm designed in the paper. The experiment results show that the Root Mean Square Error (RMSE) is within 1.6 degrees, which meets the requirement of THR operations.

Working session 5: Operational aspects and risk analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cizelj, L.; Donoghue, J.

1997-02-01

A general observation is that both operational aspects and risk analysis cannot be adequately discussed without information presented in other sessions. Some overlap of conclusions and recommendations is therefore to be expected. Further, it was assumed that recommendations concerning improvements in some related topics were generated by other sessions and are not repeated here. These include: (1) Knowledge on degradation mechanisms (initiation, progression, and failure). (2) Modeling of degradation (initiation, progression, and failure). (3) Capabilities of NDE methods. (4) Preventive maintenance and repair. One should note here, however, that all of these directly affect both operational and risk aspects ofmore » affected plants. A list of conclusions and recommendations is based on available presentations and discussions addressing risk and operational experience. The authors aimed at reaching as broad a consensus as possible. It should be noted here that there is no strict delineation between operational and safety aspects of degradation of steam generator tubes. This is caused by different risk perceptions in different countries/societies. The conclusions and recommendations were divided into four broad groups: human reliability; leakage monitoring; risk impact; and consequence assessment.« less

[Consensus on improving the care integrated of patients with acute heart failure].

PubMed

Llorens, Pere; Manito Lorite, Nicolás; Manzano Espinosa, Luis; Martín-Sánchez, Francisco Javier; Comín Colet, Josep; Formiga, Francesc; Jacob, Javier; Delgado Jiménez, Juan; Montero-Pérez-Barquero, Manuel; Herrero, Pablo; López de Sá Areses, Esteban; Pérez Calvo, Juan Ignacio; Masip, Josep; Miró, Òscar

2015-01-01

Acute heart failure (AHF) requires considerable use of resources, is an economic burden, and is associated with high complication and mortality rates in emergency departments, on hospital wards, or outpatient care settings. Diagnosis, treatment, and continuity of care are variable at present, leading 3 medical associations (for cardiology, internal medicine, and emergency medicine) to undertake discussions and arrive at a consensus on clinical practice guidelines to support those who manage AHF and encourage standardized decision making. These guidelines, based on a review of the literature and clinical experience with AHF, focus on critical points in the care pathway. Regarding emergency care, the expert participants considered the initial evaluation of patients with signs and symptoms that suggest AHF, the initial diagnosis, first decisions about therapy, monitoring, assessment of prognosis, and referral criteria. For care of the hospitalized patient, the group developed a protocol for essential treatment. Objectives for the management and treatment of AHF on discharge were also covered through the creation or improvement of multidisciplinary care systems to provide continuity of care.

Characteristics of solder joints under fatigue loads using piezomechanical actuation

NASA Astrophysics Data System (ADS)

Shim, Dong-Jin; Spearing, S. Mark

2003-07-01

Crack initiation and growth characteristics of solder joints under fatigue loads are investigated using piezomechanical actuation. Cracks in solder joints, which can cause failure in microelectronics components, are induced via piezoelectricity in piezo-ceramic bonded joints. Lead-zirconate-titanate ceramic plates and eutectic Sn-Pb solder bonded in a double-lap shear configuration are used in the investigation. Electric field across each piezo-ceramic plate is applied such that shear stresses/strains are induced in the solder joints. The experiments show that cracks initiate in the solder joints around defects such as voids and grow in length until they coalesce with other cracks from adjacent voids. These observations are compared with the similar thermal cycling tests from the literature to show feasibility and validity of the current method in investigating the fatigue characteristics of solder joints. In some specimens, cracks in the piezo-ceramic plates are observed, and failure in the specimens generally occurred due to piezo-ceramic plate fracture. The issues encountered in implementing this methodology such as low actuation and high processing temperatures are further discussed.

A Framework for Creating a Function-based Design Tool for Failure Mode Identification

NASA Technical Reports Server (NTRS)

Arunajadai, Srikesh G.; Stone, Robert B.; Tumer, Irem Y.; Clancy, Daniel (Technical Monitor)

2002-01-01

Knowledge of potential failure modes during design is critical for prevention of failures. Currently industries use procedures such as Failure Modes and Effects Analysis (FMEA), Fault Tree analysis, or Failure Modes, Effects and Criticality analysis (FMECA), as well as knowledge and experience, to determine potential failure modes. When new products are being developed there is often a lack of sufficient knowledge of potential failure mode and/or a lack of sufficient experience to identify all failure modes. This gives rise to a situation in which engineers are unable to extract maximum benefits from the above procedures. This work describes a function-based failure identification methodology, which would act as a storehouse of information and experience, providing useful information about the potential failure modes for the design under consideration, as well as enhancing the usefulness of procedures like FMEA. As an example, the method is applied to fifteen products and the benefits are illustrated.

Think Again: First Do No Harm: A Case of Munchausen Syndrome by Proxy.

PubMed

Yalndağ-Öztürk, Nilüfer; Erkek, Nilgün; Şirinoğlu, Melis Bayram

2015-10-01

Apparent life-threatening events caused by Munchausen syndrome by proxy (MSP) are rare but difficult to resolve medically. Failure to properly diagnose MSP can lead to further abuse by the caregiver and increase the risk of complications due to long hospital stays and invasive tests. In this paper, we describe our experiences with a baby who ended up being diagnosed with MSP, including our initial failure to find a pathology, delay of MSP diagnosis, our growing suspicion of MSP despite technical setbacks, our actions after we confirmed MSP as the cause of his hospitalizations. We also describe the difficulties of diagnosing MSP compared to more traditional problems and explain a series of precautions and guidelines to help detect it in a timely manner.

Skin Effect Simulation for Area 11 Dense Plasma Focus Hot Plate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meehan, B. Timothy

Two arc flashover events occurred at the DPF Area 11 facility. These flashover events happened in the same location on the bank current delivery plates. The damage from one of these events can be seen on the left-hand side of Figure 1. Since the flashovers occurred in the same area of the bank, and the reliability of the bank is important for future DPF experiments, a failure analysis effort was initiated. Part of this failure analysis effort was an effort to understand the physical reasons behind why the flashover happened, and why it happened in the same place twice. Thismore » paper summarizes an effort to simulate the current flow in the bank in order to understand the reasons for the flashover.« less

Research on computer aided testing of pilot response to critical in-flight events

NASA Technical Reports Server (NTRS)

Giffin, W. C.; Rockwell, T. H.; Smith, P. J.

1984-01-01

Experiments on pilot decision making are described. The development of models of pilot decision making in critical in flight events (CIFE) are emphasized. The following tests are reported on the development of: (1) a frame system representation describing how pilots use their knowledge in a fault diagnosis task; (2) assessment of script norms, distance measures, and Markov models developed from computer aided testing (CAT) data; and (3) performance ranking of subject data. It is demonstrated that interactive computer aided testing either by touch CRT's or personal computers is a useful research and training device for measuring pilot information management in diagnosing system failures in simulated flight situations. Performance is dictated by knowledge of aircraft sybsystems, initial pilot structuring of the failure symptoms and efficient testing of plausible causal hypotheses.

[Therapy of heart failure with beta-blockers?].

PubMed

Osterziel, K J; Dietz, R

1997-01-01

In heart failure the chronic sympathetic stimulation alters the cardiac beta-adrenergic pathway. This alteration leads to a diminished contractile response to stimulation of the cardiac beta 1 receptor. A blockade of the beta 1 receptor partly restores the physiologic response to sympathetic stimulation at rest and during exercise. Several mechanisms resulting from the competitive blockade of the beta 1 receptor may be important. The major effect of beta-blockers seems to be triggered by a reduction of the heart rate at rest resulting in an increase of the left ventricular ejection fraction on the average by 7-8%. Patients with heart failure who are treated with a beta-blocker experience initially a slight decrease of the left ventricular function. beta-blocker therapy should therefore be initiated only in patients with stable heart failure. The starting dose of the beta-blocker has to be very small, e.g, 5 mg Metoprolol, 1.25 mg Bisoprolol or 3.125 mg Carvedilol. In a stepwise fashion the dose has to be increased to a full beta blocking effect over a period of 4-8 weeks. Despite a careful dose titration only 90% of the patients tolerate this regimen. Patients with high resting heart rates and/or dilated cardiomyopathy will have the greatest benefit. The two main reasons for withdrawal of the beta-blocker are deterioration of heart failure or symptomatic hypotension. Symptomatic improvement and a significant increase of exercise capacity appear gradually and can be measured only after more than 1 month duration of therapy. Three multicenter studies (MDC. CIBIS I, Carvedilol) evaluated the influence of beta-blockers on prognosis of heart failure. The MDC trial demonstrated a slower progression of heart failure with Metoprolol. The MDC and the CIBIS I trial could not show a significant improvement of prognosis. The larger trial with carvedilol was the first study to demonstrate a decreased mortality in patients who initially tolerate the beta-blocker therapy. One major concern in that study is the evaluation and classification of patients in the run-in phase who do not tolerate the beta-blocker. Definite studies (BEST, CIBIS II; COMET; RESOLVED; MERIT) are designed to answer these problems and to evaluate the effect of beta-blockers on mortality. Until the results of these studies are available the main goal of treatment with beta-blockers remains symptomatic improvement. Further, there is good evidence for an additional increase in life expectancy. In order to achieve optimal medical treatment and to avoid side-effects careful clinical evaluation and management of the patients is mandatory during therapy with beta-blockers.

Two case reports of severe myocarditis associated with the initiation of dolutegravir treatment in HIV patients

PubMed Central

Mahlab-Guri, Keren; Asher, Ilan; Rosenberg-Bezalel, Shira; Elbirt, Daniel; Burke, Michael; Sthoeger, Zev M.

2016-01-01

Abstract Rationale: The integrase inhibitor dolutegravir is now recommended as first-line treatment for HIV. A single case of myocarditis after treatment with dolutegravir was reported in the FLAMINGO trial. We present here 2 cases of severe myocarditis that occurred shortly after the initiation of dolutegravir treatment. Patients concerns: The first case is a 45-year-old female who developed severe congestive heart failure and died, weeks after the initiation of dolutegravir treatment (for simplification of her antiretroviral regimen). The second case was a 51-year-old male who presented with effort dyspnea 3 weeks after the initiation of dolutegravir treatment and was later diagnosed as severe congestive heart failure. The treatment was changed and the patient survived, but he still suffers from severe heart failure with functional impairment. Diagnosis and Outcome: Patient 1 died, patient 2 suffers from severe heart failure. Lessons: We discuss here the possible relationship between the initiation of dolutegravir treatment and the development of lymphocytic myocarditis in our patients, and we suggest a possible mechanism. PMID:27893693

Ten year experience with antiretroviral treatment in Cambodia: Trends in patient characteristics and treatment outcomes.

PubMed

Lay, Phirum; An, Sokkab; Soeung, Sunpiseth; Srey, Pich Sovannary; Thai, Sopheak; Lynen, Lutgarde; Griensven, Johan van

2017-01-01

Although HIV disease stage at ART initiation critically determines ART outcomes, few reports have longitudinally monitored this within Asia. Using prospectively collected data from a large ART program at Sihanouk Hospital Center of Hope in Cambodia, we report on the change in patient characteristics and outcomes over a ten-year period. We conducted a retrospective analysis including all adults (≥ 18 years old) starting ART from March 2003-March 2013 in a non-governmental hospital in Phnom Penh, Cambodia. The cumulative incidence of death, lost to follow-up (LTFU), attrition (death or LTFU) and first line treatment failure were calculated using Kaplan-Meier methods. Independent risk factors for these outcomes were determined using Cox regression modeling. Over the ten-year period, 3581 patients initiated ART with a median follow-up time of 4.8 years (IQR 2.8-7.2). The median age was 35 years (IQR 30-41), 54% were female. The median CD4 count at ART initiation increased from 22 cells/μL (IQR 4-129) in 2003 to 218 (IQR 57-302) in 2013. Over the 10 year period, a total of 282 (7.9%) individuals died and 433 (12.1%) were defined LTFU. Program attrition (died or LTFU) was 11.1% (95% CI: 10.1%- 12.4%) at one year, 16.3% (95% CI: 15.1%-17.6%) at three years, 19.8% (95% CI: 18.5%-21.2%) at five years and 23.3% (95% CI: 21.6-25.1) at ten years. Male sex and low baseline body mass index (BMI) were associated with increased attrition. Factors independently associated with mortality included a low baseline CD4 count, older age, male sex, low baseline BMI and hepatitis B co-infection. Individuals aged above 40 years old had an increased risk of mortality but were less likely to LTFU. There were a total of 137 individuals with first line ART failure starting second line treatment. The probability of first line failure was estimated at 2.8% (95% CI: 2.3%-3.4%) at 3 years, 4.6% (95% CI: 3.9%-5.5%) at 5 years and 7.8% (95% CI 4.8%-12.5%) at ten years of ART. The probability was particularly high in the first few program years. A lower risk was observed among individuals starting ART during the 2006-2008 period. Factors independently associated with an increased risk of treatment failure included ART-experience, NVP-based ART and a baseline CD4 count below 200 cells/μL. Overall program outcomes were fair, and generally compare well to other reports from the region. Despite gradually earlier initiation of ART over the ten year period, ART is still initiated at too low CD4 count levels, warranting increased efforts for early HIV diagnosis and enrolment/retention into HIV care. Tailored strategies for poor prognostic groups (older age, male, low BMI) should be designed and evaluated.

A parametric study of the dynamic failure of energetic composites

NASA Astrophysics Data System (ADS)

Tanasoiu, Bogdan; Koslowski, Marisol

2017-09-01

Heating by frictional sliding of cracks is often considered to be one of the most important causes of localized melting and ignition in solid explosives. Furthermore, recent high speed X-ray phase contrast experiments on energetic composites under dynamic compression [Parab et al., Appl. Phys. Lett. 109(13) (2016)] show that most fracture events appear inside the particles. Initial cracks develop in regions where particles are close, and widespread fragmentation is observed in the interior of the particles as the stress waves propagate through the sample. However, most simulations have focused on interface debonding of energetic composites and, in general, do not include fracture of the particles explicitly. A phase field damage approach is used to model the dynamic response of a system of cyclotetramethylene-tetranitramine particles embedded in a Sylgard matrix. The simulations show several damage mechanisms observed in the experiments. The effects of the energy release rate and the initial crack distribution on the energy dissipation due to fracture are studied. The numerical results confirm that initial cracks play an important role in the evolution of damage, energy dissipation and consequently, the formation of hot-spots.

Outcomes after an excisional procedure for cervical intraepithelial neoplasia in HIV-infected women

PubMed Central

Reimers, Laura L.; Sotardi, Susan; Daniel, David; Chiu, Lydia G.; Arsdale, Anne Van; Wieland, Daryl L.; Leider, Jason M.; Xue, Xiaonan; Strickler, Howard D.; Garry, David J.; Goldberg, Gary L.; Einstein, Mark H.

2011-01-01

Objective To determine predictors of treatment failure and recurrence after surgical excisional procedures for CIN in HIV-infected women. Methods A retrospective cohort study was conducted in which 136 eligible HIV-infected women treated for CIN between 1999 and 2005 were included. Data were abstracted from charts and computer databases. Treatment failures were defined as the presence of CIN 1+ at initial follow-up. Recurrences were defined as the presence of CIN 1+ subsequent to initial normal follow-up. Results Treatment failure at initial follow-up was common, occurring in 51% of CIN 1 and 55% of CIN 2+. Most lesions detected at treatment failure were high grade (>70%), regardless of the grade of initial lesion. Significant risk factors for treatment failure were loop electrosurgical excision procedure (LEEP) compared to cold knife conization (RR=1.76; 95% CI: 1.15–2.64), and low CD4+ count (p = 0.04). Among those with an initial normal clinical evaluation, 55% eventually recurred. As with treatment failure, most lesions detected at recurrence were high grade. Risk factors for recurrence included use of LEEP (hazard ratio [HR] = 3.38; 95% CI: 1.55–7.39), higher HIV RNA level, and the presence of positive margins at treatment (HR = 6.12; 95% CI: 1.90–19.73). Conclusions Most CIN treatment of HIV-infected women studied either failed or resulted in recurrence. Of particular concern, many of these subsequent lesions were high grade. Conization, however, was associated with significantly less failure/recurrence than LEEP. Clinicians treating CIN in HIV-infected women should avoid raising expectations of cure and instead focus on the achievable goal of cancer prevention until there are better therapies for this patient population. PMID:20605046

Correlation between failure and local material property in chopped carbon fiber chip-reinforced sheet molding compound composites under tensile load

DOE PAGES

Tang, Haibin; Chen, Zhangxing; Zhou, Guowei; ...

2018-02-06

To develop further understanding towards the role of a heterogeneous microstructure on tensile crack initiation and failure behavior in chopped carbon fiber chip-reinforced composites, uni-axial tensile tests are performed on coupons cut from compression molded plaque with varying directions. Our experimental results indicate that failure initiation is relevant to the strain localization, and a new criterion with the nominal modulus to predict the failure location is proposed based on the strain analysis. Furthermore, optical microscopic images show that the nominal modulus is determined by the chip orientation distribution. At the area with low nominal modulus, it is found that chipsmore » are mostly aligning along directions transverse to loading direction and/or less concentrated, while at the area with high nominal modulus, more chips are aligning to tensile direction. On the basis of failure mechanism analysis, it is concluded that transversely-oriented chips or resin-rich regions are easier for damage initiation, while longitudinally-oriented chips postpone the fracture. Good agreement is found among failure mechanism, strain localization and chip orientation distribution.« less

Correlation between failure and local material property in chopped carbon fiber chip-reinforced sheet molding compound composites under tensile load

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang, Haibin; Chen, Zhangxing; Zhou, Guowei

To develop further understanding towards the role of a heterogeneous microstructure on tensile crack initiation and failure behavior in chopped carbon fiber chip-reinforced composites, uni-axial tensile tests are performed on coupons cut from compression molded plaque with varying directions. Our experimental results indicate that failure initiation is relevant to the strain localization, and a new criterion with the nominal modulus to predict the failure location is proposed based on the strain analysis. Furthermore, optical microscopic images show that the nominal modulus is determined by the chip orientation distribution. At the area with low nominal modulus, it is found that chipsmore » are mostly aligning along directions transverse to loading direction and/or less concentrated, while at the area with high nominal modulus, more chips are aligning to tensile direction. On the basis of failure mechanism analysis, it is concluded that transversely-oriented chips or resin-rich regions are easier for damage initiation, while longitudinally-oriented chips postpone the fracture. Good agreement is found among failure mechanism, strain localization and chip orientation distribution.« less

Timing of pregnancy, postpartum risk of virologic failure and loss to follow-up among HIV-positive women

PubMed Central

Onoya, Dorina; Sineke, Tembeka; Brennan, Alana T.; Long, Lawrence; Fox, Matthew P.

2017-01-01

Objectives: We assessed the association between the timing of pregnancy with the risk of postpartum virologic failure and loss from HIV care in South Africa. Design: This is a retrospective cohort study of 6306 HIV-positive women aged 15–49 at antiretroviral therapy (ART) initiation, initiated on ART between January 2004 and December 2013 in Johannesburg, South Africa. Methods: The incidence of virologic failure (two consecutive viral load measurements of >1000 copies/ml) and loss to follow-up (>3 months late for a visit) during 24 months postpartum were assessed using Cox proportional hazards modelling. Results: The rate of postpartum virologic failure was higher following an incident pregnancy on ART [adjusted hazard ratio 1.8, 95% confidence interval (CI): 1.1–2.7] than among women who initiated ART during pregnancy. This difference was sustained among women with CD4+ cell count less than 350 cells/μl at delivery (adjusted hazard ratio 1.8, 95% CI: 1.1–3.0). Predictors of postpartum virologic failure were being viremic, longer time on ART, being 25 or less years old and low CD4+ cell count and anaemia at delivery, as well as initiating ART on stavudine-containing or abacavir-containing regimen. There was no difference postpartum loss to follow-up rates between the incident pregnancies group (hazard ratio 0.9, 95% CI: 0.7–1.1) and those who initiated ART in pregnancy. Conclusion: The risk of virologic failure remains high among postpartum women, particularly those who conceive on ART. The results highlight the need to provide adequate support for HIV-positive women with fertility intention after ART initiation and to strengthen monitoring and retention efforts for postpartum women to sustain the benefits of ART. PMID:28463877

Timing of pregnancy, postpartum risk of virologic failure and loss to follow-up among HIV-positive women.

PubMed

Onoya, Dorina; Sineke, Tembeka; Brennan, Alana T; Long, Lawrence; Fox, Matthew P

2017-07-17

We assessed the association between the timing of pregnancy with the risk of postpartum virologic failure and loss from HIV care in South Africa. This is a retrospective cohort study of 6306 HIV-positive women aged 15-49 at antiretroviral therapy (ART) initiation, initiated on ART between January 2004 and December 2013 in Johannesburg, South Africa. The incidence of virologic failure (two consecutive viral load measurements of >1000 copies/ml) and loss to follow-up (>3 months late for a visit) during 24 months postpartum were assessed using Cox proportional hazards modelling. The rate of postpartum virologic failure was higher following an incident pregnancy on ART [adjusted hazard ratio 1.8, 95% confidence interval (CI): 1.1-2.7] than among women who initiated ART during pregnancy. This difference was sustained among women with CD4 cell count less than 350 cells/μl at delivery (adjusted hazard ratio 1.8, 95% CI: 1.1-3.0). Predictors of postpartum virologic failure were being viremic, longer time on ART, being 25 or less years old and low CD4 cell count and anaemia at delivery, as well as initiating ART on stavudine-containing or abacavir-containing regimen. There was no difference postpartum loss to follow-up rates between the incident pregnancies group (hazard ratio 0.9, 95% CI: 0.7-1.1) and those who initiated ART in pregnancy. The risk of virologic failure remains high among postpartum women, particularly those who conceive on ART. The results highlight the need to provide adequate support for HIV-positive women with fertility intention after ART initiation and to strengthen monitoring and retention efforts for postpartum women to sustain the benefits of ART.

Does short-term virologic failure translate to clinical events in antiretroviral-naïve patients initiating antiretroviral therapy in clinical practice?

PubMed

Mugavero, Michael J; May, Margaret; Harris, Ross; Saag, Michael S; Costagliola, Dominique; Egger, Matthias; Phillips, Andrew; Günthard, Huldrych F; Dabis, Francois; Hogg, Robert; de Wolf, Frank; Fatkenheuer, Gerd; Gill, M John; Justice, Amy; D'Arminio Monforte, Antonella; Lampe, Fiona; Miró, Jose M; Staszewski, Schlomo; Sterne, Jonathan A C

2008-11-30

To determine whether differences in short-term virologic failure among commonly used antiretroviral therapy (ART) regimens translate to differences in clinical events in antiretroviral-naïve patients initiating ART. Observational cohort study of patients initiating ART between January 2000 and December 2005. The Antiretroviral Therapy Cohort Collaboration (ART-CC) is a collaboration of 15 HIV cohort studies from Canada, Europe, and the United States. A total of 13 546 antiretroviral-naïve HIV-positive patients initiating ART with efavirenz, nevirapine, lopinavir/ritonavir, nelfinavir, or abacavir as third drugs in combination with a zidovudine and lamivudine nucleoside reverse transcriptase inhibitor backbone. Short-term (24-week) virologic failure (>500 copies/ml) and clinical events within 2 years of ART initiation (incident AIDS-defining event, death, and a composite measure of these two outcomes). Compared with efavirenz as initial third drug, short-term virologic failure was more common with all other third drugs evaluated; nevirapine (adjusted odds ratio = 1.87, 95% confidence interval (CI) = 1.58-2.22), lopinavir/ritonavir (1.32, 95% CI = 1.12-1.57), nelfinavir (3.20, 95% CI = 2.74-3.74), and abacavir (2.13, 95% CI = 1.82-2.50). However, the rate of clinical events within 2 years of ART initiation appeared higher only with nevirapine (adjusted hazard ratio for composite outcome measure 1.27, 95% CI = 1.04-1.56) and abacavir (1.22, 95% CI = 1.00-1.48). Among antiretroviral-naïve patients initiating therapy, between-ART regimen, differences in short-term virologic failure do not necessarily translate to differences in clinical outcomes. Our results should be interpreted with caution because of the possibility of residual confounding by indication.

Pyogenic liver abscess: An audit of 10 years’ experience

PubMed Central

Pang, Tony CY; Fung, Thomas; Samra, Jaswinder; Hugh, Thomas J; Smith, Ross C

2011-01-01

AIM: To describe our own experience with pyogenic liver abscesses over the past 10 years and investigate the risk factors associated with failure of initial percutaneous therapy. METHODS: A retrospective study of records of 63 PLA patients presenting between 1998 and 2008 to Australian tertiary referral centre, were reviewed. Amoebic and hydatid abscesses were excluded. Demographic, clinical, radiological, and microbiological characteristics, as well as surgical/radiological interventions, were recorded. RESULTS: Sixty-three patients (42 males, 21 females) aged 65 (± 14) years [mean ± (SD)] had prodromal symptoms for a median (interquartile range; IQR) of 7 (5-14) d. Only 59% of patients were febrile at presentation; however, the serum C-reactive protein was elevated in all 47 in whom it was measured. Liver function tests were non-specifically abnormal. 67% of patients had a solitary abscess, while 32% had > 3 abscesses with a median (IQR) diameter of 6.3 (4-9) cm. Causative organisms were: Streptococcus milleri 25%, Klebsiella pneumoniae 21%, and Escherichia coli 16%. A presumptive cryptogenic cause was most common (34%). Four patients died in this series: one from sepsis, two from advanced cancer, and one from acute myocardial infarction. The initial procedure was radiological aspiration ± drainage in 54 and surgery in two patients. 17% underwent surgical management during their hospitalization. Serum hypoalbuminaemia [mean (95% CI): 32 (29-35) g/L vs 28 (25-31) g/L, P = 0.045] on presentation was found to be the only factor related to failure of initial percutaneous therapy on univariate analysis. CONCLUSION: PLA is a diagnostic challenge, because the presentation of this condition is non-specific. Intravenous antibiotics and radiological drainage in the first instance allows resolution of most PLAs; However, a small proportion of patients still require surgical drainage. PMID:21472130

Influence of High Cycle Thermal Loads on Thermal Fatigue Behavior of Thick Thermal Barrier Coatings

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Miller, Robert A.

1997-01-01

Thick thermal barrier coating systems in a diesel engine experience severe thermal Low Cycle Fatigue (LCF) and High Cycle Fatigue (HCF) during engine operation. In the present study, the mechanisms of fatigue crack initiation and propagation, as well as of coating failure, under thermal loads which simulate engine conditions, are investigated using a high power CO2 laser. In general, surface vertical cracks initiate early and grow continuously under LCF and HCF cyclic stresses. It is found that in the absence of interfacial oxidation, the failure associated with LCF is closely related to coating sintering and creep at high temperatures, which induce tensile stresses in the coating after cooling. Experiments show that the HCF cycles are very damaging to the coating systems. The combined LCF and HCF tests produced more severe coating surface cracking, microspallation and accelerated crack growth, as compared to the pure LCF test. It is suggested that the HCF component cannot only accelerate the surface crack initiation, but also interact with the LCF by contributing to the crack growth at high temperatures. The increased LCF stress intensity at the crack tip due to the HCF component enhances the subsequent LCF crack growth. Conversely, since a faster HCF crack growth rate will be expected with lower effective compressive stresses in the coating, the LCF cycles also facilitate the HCF crack growth at high temperatures by stress relaxation process. A surface wedging model has been proposed to account for the HCF crack growth in the coating system. This mechanism predicts that HCF damage effect increases with increasing temperature swing, the thermal expansion coefficient and the elastic modulus of the ceramic coating, as well as the HCF interacting depth. A good agreement has been found between the analysis and experimental evidence.

Fear of failure and student athletes' interpersonal antisocial behaviour in education and sport.

PubMed

Sagar, Sam S; Boardley, Ian D; Kavussanu, Maria

2011-09-01

BACKGROUND. The link between fear of failure and students' antisocial behaviour has received scant research attention despite associations between fear of failure, hostility, and aggression. Also, the effect of sport experience on antisocial behaviour has not been considered outside of the sport context in adult populations. Further, to date, sex differences have not been considered in fear of failure research. AIMS. To examine whether (a) fear of failure and sport experience predict antisocial behaviour in the university and sport contexts in student athletes, and whether this prediction is the same in males and females; and (b) sex differences exist in antisocial behaviour and fear of failure. SAMPLE. British university student athletes (n= 176 male; n= 155 female; M(age) = 20.11 years). METHOD. Participants completed questionnaires assessing fear of failure, sport experience, and antisocial behaviour in both contexts. RESULTS. (a) Fear of failure and sport experience positively predicted antisocial behaviour in university and sport and the strength of these predictions did not differ between males and females; (b) females reported higher levels of fear of devaluing one's self-estimate than males whereas males reported higher levels of fear of important others losing interest than females. Males engaged more frequently than females in antisocial behaviour in both contexts. CONCLUSIONS. Fear of failure and sport experience may be important considerations when trying to understand antisocial behaviour in student athletes in education and sport; moreover, the potential effect of overall fear of failure and of sport experience on this frequency does not differ by sex. The findings make an important contribution to the fear of failure and morality literatures. ©2010 The British Psychological Society.

Fault Damage Zone Permeability in Crystalline Rocks from Combined Field and Laboratory Measurements: Can we Predict Damage Zone Permeability?

NASA Astrophysics Data System (ADS)

Mitchell, T. M.; Faulkner, D. R.

2009-04-01

Models predicting crustal fluid flow are important for a variety of reasons; for example earthquake models invoking fluid triggering, predicting crustal strength modelling flow surrounding deep waste repositories or the recovery of natural resources. Crustal fluid flow is controlled by both the bulk transport properties of rocks as well as heterogeneities such as faults. In nature, permeability is enhanced in the damage zone of faults, where fracturing occurs on a wide range of scales. Here we analyze the contribution of microfracture damage on the permeability of faults that cut through low porosity, crystalline rocks by combining field and laboratory measurements. Microfracture densities surrounding strike-slip faults with well-constrained displacements ranging over 3 orders of magnitude (~0.12 m - 5000 m) have been analyzed. The faults studied are excellently exposed within the Atacama Fault Zone, where exhumation from 6-10 km has occurred. Microfractures in the form of fluid inclusion planes (FIPs) show a log-linear decrease in fracture density with perpendicular distance from the fault core. Damage zone widths defined by the density of FIPs scale with fault displacement, and an empirical relationship for microfracture density distribution throughout the damage zone with displacement is derived. Damage zone rocks will have experienced differential stresses that were less than, but some proportion of, the failure stress. As such, permeability data from progressively loaded, initially intact laboratory samples, in the pre-failure region provide useful insights into fluid flow properties of various parts of the damage zone. The permeability evolution of initially intact crystalline rocks under increasing differential load leading to macroscopic failure was determined at water pore pressures of 50 MPa and effective pressure of 10 MPa. Permeability is seen to increase by up to, and over, two orders of magnitude prior to macroscopic failure. Further experiments were stopped at various points in the loading history in order to correlate microfracture density within the samples with permeability. By combining empirical relationships determined from both quantitative fieldwork and experiments we present a new model that allows microfracture permeability distribution throughout the damage zone to be determined as function of increasing fault displacement.

Electrophysiological diagnosis and patterns of response to treatment of botulism with neuromuscular respiratory failure.

PubMed

Kongsaengdao, Subsai; Samintarapanya, Kanoksri; Rusmeechan, Siwarit; Sithinamsuwan, Pasiri; Tanprawate, Surat

2009-08-01

In this study we describe the electrophysiological findings in botulism patients with neuromuscular respiratory failure from major botulism outbreaks in Thailand. High-rate repetitive nerve stimulation testing (RNST) of the abductor digiti minimi (ADM) muscle of 17 botulism patients with neuromuscular respiratory failure showed mostly incremental responses, especially in response to >20-HZ stimulation. In the most severe stage of neuromuscular respiratory failure, RNST failed to elicit a compound muscle action potential (CMAP) of the ADM muscle. In the moderately severe stage, the initial CMAPs were of very low amplitude, and a 3-HZ RNST elicited incremental or decremental responses. A 10-HZ RNST elicited mainly decremental responses. In the early recovery stage, the initial CMAP amplitudes of the ADM muscle improved, with initially low amplitudes and an incremental response to 3- and 10-HZ RNSTs. Improved electrophysiological patterns of the ADM muscle correlated with improved respiratory muscle function. Incremental responses to 20-HZ RNST were most useful for diagnosis. The initial electrodiagnostic sign of recovery following treatment of neuromuscular respiratory failure was an increased CMAP amplitude and an incremental response to 10-20-HZ RNST. Muscle Nerve 40: 271-278, 2009.

Failure prediction of thin beryllium sheets used in spacecraft structures

NASA Technical Reports Server (NTRS)

Roschke, Paul N.; Mascorro, Edward; Papados, Photios; Serna, Oscar R.

1991-01-01

The primary objective of this study is to develop a method for prediction of failure of thin beryllium sheets that undergo complex states of stress. Major components of the research include experimental evaluation of strength parameters for cross-rolled beryllium sheet, application of the Tsai-Wu failure criterion to plate bending problems, development of a high order failure criterion, application of the new criterion to a variety of structures, and incorporation of both failure criteria into a finite element code. A Tsai-Wu failure model for SR-200 sheet material is developed from available tensile data, experiments carried out by NASA on two circular plates, and compression and off-axis experiments performed in this study. The failure surface obtained from the resulting criterion forms an ellipsoid. By supplementing experimental data used in the the two-dimensional criterion and modifying previously suggested failure criteria, a multi-dimensional failure surface is proposed for thin beryllium structures. The new criterion for orthotropic material is represented by a failure surface in six-dimensional stress space. In order to determine coefficients of the governing equation, a number of uniaxial, biaxial, and triaxial experiments are required. Details of these experiments and a complementary ultrasonic investigation are described in detail. Finally, validity of the criterion and newly determined mechanical properties is established through experiments on structures composed of SR200 sheet material. These experiments include a plate-plug arrangement under a complex state of stress and a series of plates with an out-of-plane central point load. Both criteria have been incorporated into a general purpose finite element analysis code. Numerical simulation incrementally applied loads to a structural component that is being designed and checks each nodal point in the model for exceedance of a failure criterion. If stresses at all locations do not exceed the failure criterion, the load is increased and the process is repeated. Failure results for the plate-plug and clamped plate tests are accurate to within 2 percent.

Heart Failure and Frailty in the Community-Living Elderly Population: What the UFO Study Will Tell Us.

PubMed

Fung, Erik; Hui, Elsie; Yang, Xiaobo; Lui, Leong T; Cheng, King F; Li, Qi; Fan, Yiting; Sahota, Daljit S; Ma, Bosco H M; Lee, Jenny S W; Lee, Alex P W; Woo, Jean

2018-01-01

Heart failure and frailty are clinical syndromes that present with overlapping phenotypic characteristics. Importantly, their co-presence is associated with increased mortality and morbidity. While mechanical and electrical device therapies for heart failure are vital for select patients with advanced stage disease, the majority of patients and especially those with undiagnosed heart failure would benefit from early disease detection and prompt initiation of guideline-directed medical therapies. In this article, we review the problematic interactions between heart failure and frailty, introduce a focused cardiac screening program for community-living elderly initiated by a mobile communication device app leading to the Undiagnosed heart Failure in frail Older individuals (UFO) study, and discuss how the knowledge of pre-frailty and frailty status could be exploited for the detection of previously undiagnosed heart failure or advanced cardiac disease. The widespread use of mobile devices coupled with increasing availability of novel, effective medical and minimally invasive therapies have incentivized new approaches to heart failure case finding and disease management.

Initial clinical experience with the first drug (sacubitril/valsartan) in a new class - angiotensin receptor neprilysin inhibitors in patients with heart failure with reduced left ventricular ejection fraction in Poland.

PubMed

Kałużna-Oleksy, Marta; Kolasa, Jolanta; Migaj, Jacek; Pawlak, Agnieszka; Lelonek, Małgorzata; Nessler, Jadwiga; Straburzyńska-Migaj, Ewa

2018-01-01

Sacubitril/valsartan is the first drug from a new class of angiotensin receptor neprilysin inhibitors (ARNIs) recommended in the new European Society of Cardiology guidelines instead of angiotensin converting enzyme inhibitors (ACEI), or angiotensin receptor blockers (ARB) that are used if ACEI are not tolerated. Sacubitril/valsartan is recommended for further reduction in the risk of hospitalisation or death in outpatients with heart failure with reduced ejection fraction (HFrEF) if symptoms continue despite optimal treatment with ACEI/ARB, beta-blockers, and mineralocorticoid antagonists. The aim of this study is to present the initial experience with regard to the effectiveness, tolerance, and safety of sacubitril/valsartan in the outpatient cardiology practice in Poland. The study is a retrospective analysis of data obtained through a questionnaire filled in by the physicians who initiated the sacubitril/valsartan treatment in patients with HFrEF between 1 June 2016 and 30 September 2016. Patients were followed-up for three months. The analysis included data on 28 patients aged 61 ± 16 years, of whom 85.7% were males. The drug was used in patients in New York Heart Association (NYHA) class I-III. In 25 (89.2%) patients sacubitril/valsartan was started at the lowest dose (24/26 mg BID). During follow-up the sacubitril/valsartan-treated patients had a reduction in HF symptoms assessed using the NYHA functional class (p = 0.001), a significant drop in N-terminal-pro B-type natriuretic peptide levels (mean, from 2900 to 2270 pg/mL; p = 0.008), and improved exercise tolerance, which occurred shortly after treatment initiation - after a mean of 28 days. It was demonstrated that the use of sacubitril/valsartan in outpatients with HFrEF is safe and is associated with a significant clinical improvement.

Engineering sciences area and module performance and failure analysis area

NASA Technical Reports Server (NTRS)

Ross, R. G., Jr.; Runkle, L. D.

1982-01-01

Photovoltaic-array/power-conditioner interface studies are updated. An experiment conducted to evaluate different operating-point strategies, such as constant voltage and pilot cells, and to determine array energy losses when the array is operated off the maximum power points is described. Initial results over a test period of three and a half weeks showed a 2% energy loss when the array is operated at a fixed voltage. Degraded-array studies conducted at NE RES that used a range of simulated common types of degraded I-V curves are reviewed. The instrumentation installed at the JPL field-test site to obtain the irradiance data was described. Experiments using an optical filter to adjust the spectral irradiance of the large-area pulsed solar simulator (LAPSS) to AM1.5 are described. Residential-array research activity is reviewed. Voltage isolation test results are described. Experiments performed on one type of module to determine the relationship between leakage current and temperature are reviewed. An encapsulated-cell testing approach is explained. The test program, data reduction methods, and initial results of long-duration module testing are described.

Hypervitaminosis a in pediatric hematopoietic stem cell patients requiring renal replacement therapy.

PubMed

Lipkin, Ann Connell; Lenssen, Polly

Chronic renal failure patients have been known to develop vitamin A toxicity, but a descriptive study of hypervitaminosis A in patients with acute renal failure (ARF) has not yet been published. The authors observed hypervitaminosis A in pediatric hematopoietic stem cell transplant (HSCT) patients. All HSCT patients admitted between January 2001 and May 2006 who experienced ARF, received renal replacement therapy (RRT), and had a vitamin A level drawn were included in this retrospective, descriptive study. Molar ratios of vitamin A and retinol-binding protein (RBP) were calculated to more accurately assess vitamin A status. Nineteen patients met the criteria for this study. At initial testing (generally between days 6 and 10 after initiation of RRT), 17 of the 19 patients had abnormally elevated vitamin A levels for their age. Molar ratios of vitamin A to RBP were elevated in 6 patients at initial testing. Prescribed vitamin A intake information (parenteral and enteral) was available for most patients; all but 3 had an average daily intake greater than 2000 IU/kg over the 30 days prior to RRT initiation. Many patients had symptoms possibly related to vitamin A toxicity, although interpretation of hair, skin, and liver abnormalities are difficult to ascertain in HSCT patients. Seven patients had other findings that may have been associated with vitamin A toxicity. Children undergoing HSCT who receive nutrition support (predominantly parenteral nutrition), experience ARF, and require RRT are at risk for hypervitaminosis A and toxicity.

Automated inhaled nitric oxide alerts for adult extracorporeal membrane oxygenation patient identification.

PubMed

Belenkiy, Slava M; Batchinsky, Andriy I; Park, Timothy S; Luellen, David E; Serio-Melvin, Maria L; Cancio, Leopoldo C; Pamplin, Jeremy C; Chung, Kevin K; Salinas, Josè; Cannon, Jeremy W

2014-09-01

Recently, automated alerts have been used to identify patients with respiratory failure based on set criteria, which can be gleaned from the electronic medical record (EMR). Such an approach may also be useful for identifying patients with severe adult respiratory distress syndrome (ARDS) who may benefit from extracorporeal membrane oxygenation (ECMO). Inhaled nitric oxide (iNO) is a common rescue therapy for severe ARDS which can be easily tracked in the EMR, and some patients started on iNO may have indications for initiating ECMO. This case series summarizes our experience with using automated electronic alerts for ECMO team activation focused particularly on an alert triggered by the initiation of iNO. After a brief trial evaluation, our Smart Alert system generated an automated page and e-mail alert to ECMO team members whenever a nonzero value for iNO appeared in the respiratory care section of our EMR. If iNO was initiated for severe respiratory failure, a detailed evaluation by the ECMO team determined if ECMO was indicated. For those patients managed with ECMO, we tabulated baseline characteristics, indication for ECMO, and outcomes. From September 2012 to July 2013, 45 iNO alerts were generated on 42 unique patients. Six patients (14%) met criteria for ECMO. Of these, four were identified exclusively by the iNO alert. At the time of the alert, the median PaO₂-to-FIO₂ ratio was 64 mm Hg (range, 55-107 mm Hg), the median age-adjusted oxygenation index was 73 (range, 51-96), and the median Murray score was 3.4 (range, 3-3.75), indicating severe respiratory failure. Median time from iNO alert to ECMO initiation was 81 hours (range, -2-292 hours). Survival to hospital discharge was 83% in those managed with ECMO. Automated alerts may be useful for identifying patients with severe ARDS who may be ECMO candidates. Diagnostic test, level V.

Austerity: a failed experiment on the people of Europe.

PubMed

McKee, Martin; Karanikolos, Marina; Belcher, Paul; Stuckler, David

2012-08-01

Many governments in Europe, either of their own volition or at the behest of the international financial institutions, have adopted stringent austerity policies in response to the financial crisis. By contrast, the USA launched a financial stimulus. The results of these experiments are now clear: the American economy is growing and those European countries adopting austerity, including the UK, Ireland, Greece, Portugal and Spain, are stagnating and struggling to repay rising debts. An initial recovery in the UK was halted once austerity measures hit. However, austerity has been not only an economic failure, but also a health failure, with increasing numbers of suicides and, where cuts in health budgets are being imposed, increasing numbers of people being unable to access care. Yet their stories remain largely untold. Here, we argue that there is an alternative to austerity, but that ideology is triumphing over evidence. Our paper was written to contribute to discussions among health policy leaders in Europe that will take place at the 15th European Health Forum at Gastein in October 2012, as its theme 'Crisis and Opportunity - Health in an Age of Austerity'.

The embodiment of success and failure as forward versus backward movements.

PubMed

Robinson, Michael D; Fetterman, Adam K

2015-01-01

People often speak of success (e.g., "advance") and failure (e.g., "setback") as if they were forward versus backward movements through space. Two experiments sought to examine whether grounded associations of this type influence motor behavior. In Experiment 1, participants categorized success versus failure words by moving a joystick forward or backward. Failure categorizations were faster when moving backward, whereas success categorizations were faster when moving forward. Experiment 2 removed the requirement to categorize stimuli and used a word rehearsal task instead. Even without Experiment 1's response procedures, a similar cross-over interaction was obtained (e.g., failure memorizations sped backward movements relative to forward ones). The findings are novel yet consistent with theories of embodied cognition and self-regulation.

An Exploration of Teachers' Perceptions of the Change Process for School Improvement in Four High Schools in the State of Illinois

ERIC Educational Resources Information Center

Hurlburt, Thomas A.

2012-01-01

Many procedures are used by school districts to initiate change that are integral to the success or failure of that initiative. Many initiatives have failed because they were not implemented successfully. Too often, the failure is attributed to the inability of the administration to get the necessary buy-in from the teaching and support staff. The…

The tether inspection and repair experiment (TIRE)

NASA Technical Reports Server (NTRS)

Wood, George M.; Loria, Alberto; Harrison, James K.

1988-01-01

The successful development and deployment of reusable tethers for space applications will require methods for detecting, locating, and repairing damage to the tether. This requirement becomes especially important whenever the safety of the STS or the Space Station may be diminished or when critical supplies or systems would be lost in the event of a tether failure. A joint NASA/PSN study endeavor has recently been initiated to evaluate and address the problems to be solved for such an undertaking. The objectives of the Tether Inspection and Repair Experiment (TIRE) are to develop instrumentation and repair technology for specific classes of tethers defined as standards, and to demonstrate the technologies in ground-based and in-flight testing on the STS.

Driving and latching of the Starlab pointing mirror doors

NASA Technical Reports Server (NTRS)

Beaven, Herbert R., Jr.; Avina, Raymond R.

1990-01-01

The Starlab Experiment, a major SDIO technology initiative, is an attached payload which will be delivered into Earth orbit aboard NASA's Space Shuttle in 1991. Starlab will generate and aim an 80 cm diameter laser beam into space through a large opening in the structure which houses the pointing mirror. Two doors, each somewhat larger than a desktop, cover the opening when the laser optics system is nonoperational. Latch Mechanism Assemblies hold the doors shut during liftoff and ascent and, again, during Orbiter reentry. Each door is powered by a Door Drive System during the many open/close cycles between various experiments. The design, testing, and resultant failure modes of these mechanisms are examined.

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

NASA Astrophysics Data System (ADS)

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

2016-04-01

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

Initial flight results of the TRMM Kalman filter

NASA Technical Reports Server (NTRS)

Andrews, Stephen F.; Morgenstern, Wendy M.

1998-01-01

The Tropical Rainfall Measuring Mission (TRMM) spacecraft is a nadir pointing spacecraft that nominally controls attitude based on the Earth Sensor Assembly (ESA) output. After a potential single point failure in the ESA was identified, the contingency attitude determination method chosen to backup the ESA-based system was a sixth-order extended Kalman filter that uses magnetometer and digital sun sensor measurements. A brief description of the TRMM Kalman filter will be given, including some implementation issues and algorithm heritage. Operational aspects of the Kalman filter and some failure detection and correction will be described. The Kalman filter was tested in a sun pointing attitude and in a nadir pointing attitude during the in-orbit checkout period, and results from those tests will be presented. This paper will describe some lessons learned from the experience of the TRMM team.

Initial Flight Results of the TRMM Kalman Filter

NASA Technical Reports Server (NTRS)

Andrews, Stephen F.; Morgenstern, Wendy M.

1998-01-01

The Tropical Rainfall Measuring Mission (TRMM) spacecraft is a nadir pointing spacecraft that nominally controls attitude based on the Earth Sensor Assembly (ESA) output. After a potential single point failure in the ESA was identified, the contingency attitude determination method chosen to backup the ESA-based system was a sixth-order extended Kalman filter that uses magnetometer and digital sun sensor measurements. A brief description of the TRMM Kalman filter will be given, including some implementation issues and algorithm heritage. Operational aspects of the Kalman filter and some failure detection and correction will be described. The Kalman filter was tested in a sun pointing attitude and in a nadir pointing attitude during the in-orbit checkout period, and results from those tests will be presented. This paper will describe some lessons learned from the experience of the TRMM team.

Attributional processes in the learned helplessness paradigm: behavioral effects of global attributions.

PubMed

Mikulincer, M

1986-12-01

Following the learned helplessness paradigm, I assessed in this study the effects of global and specific attributions for failure on the generalization of performance deficits in a dissimilar situation. Helplessness training consisted of experience with noncontingent failures on four cognitive discrimination problems attributed to either global or specific causes. Experiment 1 found that performance in a dissimilar situation was impaired following exposure to globally attributed failure. Experiment 2 examined the behavioral effects of the interaction between stable and global attributions of failure. Exposure to unsolvable problems resulted in reduced performance in a dissimilar situation only when failure was attributed to global and stable causes. Finally, Experiment 3 found that learned helplessness deficits were a product of the interaction of global and internal attribution. Performance deficits following unsolvable problems were recorded when failure was attributed to global and internal causes. Results were discussed in terms of the reformulated learned helplessness model.

EARLY-ESLI study: Long-term experience with eslicarbazepine acetate after first monotherapy failure.

PubMed

Villanueva, V; Bermejo, P; Montoya, J; Toledo, M; Gómez-Ibáñez, A; Garcés, M; Vilella, L; López-González, F J; Rodriguez-Osorio, X; Campos, D; Martínez, P; Giner, P; Zurita, J; Rodríguez-Uranga, J; Ojeda, J; Mauri, J A; Camacho, J L; Ruiz-Giménez, J; Poza, J J; Massot-Tarrús, A; Galiano, M L; Bonet, M

2017-09-01

Evaluate real-life experience with eslicarbazepine acetate (ESL) after first monotherapy failure in a large series of patients with focal epilepsy. Multicentre, retrospective, 1-year, observational study in patients older than 18 years, with focal epilepsy, who had failed first antiepileptic drug monotherapy and who received ESL. Data from clinical records were analysed at baseline, 3, 6 and 12 months to assess effectiveness and tolerability. Eslicarbazepine acetate was initiated in 253 patients. The 1-year retention rate was 92.9%, and the final median dose of ESL was 800 mg. At 12 months, 62.3% of patients had been seizure free for 6 months; 37.3% had been seizure free for 1 year. During follow-up, 31.6% of the patients reported ESL-related adverse events (AEs), most commonly somnolence (8.7%) and dizziness (5.1%), and 3.6% discontinued due to AEs. Hyponatraemia was observed in seven patients (2.8%). After starting ESL, 137 patients (54.2%) withdrew the prior monotherapy and converted to ESL monotherapy; 75.9% were seizure free, 87.6% were responders, 4.4% worsened, and 23.4% reported ESL-related AEs. Use of ESL after first monotherapy failure was associated with an optimal seizure control and tolerability profile. Over half of patients were converted to ESL monotherapy during follow-up. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Clinical and Virologic Outcomes After Changes in First Antiretroviral Regimen at 7 Sites in the Caribbean, Central and South America Network.

PubMed

Wolff, Marcelo; Shepherd, Bryan E; Cortés, Claudia; Rebeiro, Peter; Cesar, Carina; Wagner Cardoso, Sandra; Pape, Jean W; Padgett, Denis; Sierra-Madero, Juan; Echevarria, Juan; McGowan, Catherine C

2016-01-01

HIV-infected persons in resource-limited settings may experience high rates of antiretroviral therapy (ART) change, particularly because of toxicity or other nonfailure reasons. Few reports address patient outcomes after these modifications. HIV-infected adults from the 7 Caribbean, Central and South America network clinical cohorts who modified >1 drug from the first ART regimen (ART-1) for any reason thereby starting a second regimen (ART-2) were included. We assessed cumulative incidence of, and factors associated with, death, virologic failure (VF), and regimen change after starting ART-2. Five thousand five hundred sixty-five ART-naive highly active ART initiators started ART-2 after a median of 9.8 months on ART-1; 39% changed to ART-2 because of toxicity and 11% because of failure. Median follow-up after starting ART-2 was 2.9 years; 45% subsequently modified ART-2. Cumulative incidences of death at 1, 3, and 5 years after starting ART-2 were 5.1%, 8.4%, and 10.5%, respectively. In adjusted analyses, death was associated with older age, clinical AIDS, lower CD4 at ART-2 start, earlier calendar year, and starting ART-2 because of toxicity (adjusted hazard ratio = 1.5 vs. failure, 95% confidence interval: 1.0 to 2.1). Cumulative incidences of VF after 1, 3, and 5 years were 9%, 19%, and 25%. In adjusted analyses, VF was associated with younger age, earlier calendar year, lower CD4 at the start of ART-2, and starting ART-2 because of failure (adjusted hazard ratio = 2.1 vs. toxicity, 95% confidence interval: 1.5 to 2.8). Among patients modifying the first ART regimen, risks of subsequent modifications, mortality, and virologic failure were high. Access to improved antiretrovirals in the region is needed to improve initial treatment success.

Failure modes for compression loaded angle-ply plates with holes

NASA Technical Reports Server (NTRS)

Burns, S. W.; Herakovich, C. T.; Williams, J. G.

1987-01-01

A combined theoretical-experimental investigation of failure in notched, graphite-epoxy, angle-ply laminates subjected to far-field compression loading indicates that failure generally initiates on the hole boundary and propagates along a line parallel to the fiber orientation of the laminate. The strength of notched laminates with specimen width-to-hole diameter ratios of 5 and 10 are compared to the strength of unnotched laminates. The experimental results are complemented by a three-dimensional finite element stress analysis that includes interlaminar stresses around holes in (+/- theta)s laminates. The finite element predictions indicate that failure is initiated by shear stresses at the hole boundary.

The segment as the minimal planning unit in speech production: evidence based on absolute response latencies.

PubMed

Kawamoto, Alan H; Liu, Qiang; Lee, Ria J; Grebe, Patricia R

2014-01-01

A minimal amount of information about a word must be phonologically and phonetically encoded before a person can begin to utter that word. Most researchers assume that the minimum is the complete word or possibly the initial syllable. However, there is some evidence that the initial segment is sufficient based on longer durations when the initial segment is primed. In two experiments in which the initial segment of a monosyllabic word is primed or not primed, we present additional evidence based on very short absolute response times determined on the basis of acoustic and articulatory onset relative to presentation of the complete target. We argue that the previous failures to find very short absolute response times when the initial segment is primed are due in part to the exclusive use of acoustic onset as a measure of response latency, the exclusion of responses with very short acoustic latencies, the manner of articulation of the initial segment (i.e., plosive vs. nonplosive), and individual differences. Theoretical implications of the segment as the minimal planning unit are considered.

Informed renesting decisions: the effect of nest predation risk.

PubMed

Pakanen, Veli-Matti; Rönkä, Nelli; Thomson, Robert L; Koivula, Kari

2014-04-01

Animals should cue on information that predicts reproductive success. After failure of an initial reproductive attempt, decisions on whether or not to initiate a second reproductive attempt may be affected by individual experience and social information. If the prospects of breeding success are poor, long-lived animals in particular should not invest in current reproductive success (CRS) in case it generates costs to future reproductive success (FRS). In birds, predation risk experienced during breeding may provide a cue for renesting success. Species having a high FRS potential should be flexible and take predation risk into account in their renesting decisions. We tested this prediction using breeding data of a long-lived wader, the southern dunlin Calidris alpina schinzii. As predicted, dunlin cued on predation risk information acquired from direct experience of nest failure due to predation and ambient nest predation risk. While the overall renesting rate was low (34.5%), the early season renesting rate was high but declined with season, indicating probable temporal changes in the costs and benefits of renesting. We develop a conceptual cost-benefit model to describe the effects of the phase and the length of breeding season on predation risk responses in renesting. We suggest that species investing in FRS should not continue breeding in short breeding seasons in response to predation risk but without time constraints, their response should be similar to species investing in CRS, e.g. within-season dispersal and increased nest concealment.

Level of Automation and Failure Frequency Effects on Simulated Lunar Lander Performance

NASA Technical Reports Server (NTRS)

Marquez, Jessica J.; Ramirez, Margarita

2014-01-01

A human-in-the-loop experiment was conducted at the NASA Ames Research Center Vertical Motion Simulator, where instrument-rated pilots completed a simulated terminal descent phase of a lunar landing. Ten pilots participated in a 2 x 2 mixed design experiment, with level of automation as the within-subjects factor and failure frequency as the between subjects factor. The two evaluated levels of automation were high (fully automated landing) and low (manual controlled landing). During test trials, participants were exposed to either a high number of failures (75% failure frequency) or low number of failures (25% failure frequency). In order to investigate the pilots' sensitivity to changes in levels of automation and failure frequency, the dependent measure selected for this experiment was accuracy of failure diagnosis, from which D Prime and Decision Criterion were derived. For each of the dependent measures, no significant difference was found for level of automation and no significant interaction was detected between level of automation and failure frequency. A significant effect was identified for failure frequency suggesting failure frequency has a significant effect on pilots' sensitivity to failure detection and diagnosis. Participants were more likely to correctly identify and diagnose failures if they experienced the higher levels of failures, regardless of level of automation

Taming Test Anxiety: The Activation of Failure-Related Concepts Enhances Cognitive Test Performance of Test-Anxious Students

ERIC Educational Resources Information Center

Tempel, Tobias; Neumann, Roland

2016-01-01

We investigated processes underlying performance decrements of highly test-anxious persons. Three experiments contrasted conditions that differed in the degree of activation of concepts related to failure. Participants memorized a list of words either containing words related to failure or containing no words related to failure in Experiment 1. In…

Failure Wave in DEDF and Soda-Lime Glass during Rod Impact

DOE Office of Scientific and Technical Information (OSTI.GOV)

Orphal, D. L.; Behner, Th.; Hohler, V.

2006-07-28

Investigations of glass by planar, and classical and symmetric Taylor impact experiments reveal that failure wave velocity vF depends on impact velocity, geometry, and type of glass. vF typically increases with impact velocity vP to between cS and cL or to {radical}2cS (shear and longitudinal wave velocity). This paper reports initial results of an investigation of failure waves associated with gold rod impact on high-density (DEDF) glass and soda-lime glass. Data are obtained by visualizing simultaneously the failure propagation in the glass with a high-speed camera and the rod penetration velocity u with flash radiography. Results for DEDF glass aremore » reported for vP between 1.2 and 2.0 km/s, those for soda-lime glass with vP {approx_equal}1.3 km/s. It is shown that vF > u, and that in the case of DEDF glass vF/u decreases from ; 1.38 to 1.13 with increasing vp. In addition, several Taylor tests were performed. For both DEDF and soda-lime glass the vF-values, found here as well as vF- data reported in the literature, reveal that--for equal pressures--the failure wave velocities determined from Taylor tests or planar-impact tests are distinctly greater than those observed during steady-state rod penetration.« less

Hydraulic limits preceding mortality in a piñon-juniper woodland under experimental drought.

PubMed

Plaut, Jennifer A; Yepez, Enrico A; Hill, Judson; Pangle, Robert; Sperry, John S; Pockman, William T; McDowell, Nate G

2012-09-01

Drought-related tree mortality occurs globally and may increase in the future, but we lack sufficient mechanistic understanding to accurately predict it. Here we present the first field assessment of the physiological mechanisms leading to mortality in an ecosystem-scale rainfall manipulation of a piñon-juniper (Pinus edulis-Juniperus monosperma) woodland. We measured transpiration (E) and modelled the transpiration rate initiating hydraulic failure (E(crit) ). We predicted that isohydric piñon would experience mortality after prolonged periods of severely limited gas exchange as required to avoid hydraulic failure; anisohydric juniper would also avoid hydraulic failure, but sustain gas exchange due to its greater cavitation resistance. After 1 year of treatment, 67% of droughted mature piñon died with concomitant infestation by bark beetles (Ips confusus) and bluestain fungus (Ophiostoma spp.); no mortality occurred in juniper or in control piñon. As predicted, both species avoided hydraulic failure, but safety margins from E(crit) were much smaller in piñon, especially droughted piñon, which also experienced chronically low hydraulic conductance. The defining characteristic of trees that died was a 7 month period of near-zero gas exchange, versus 2 months for surviving piñon. Hydraulic limits to gas exchange, not hydraulic failure per se, promoted drought-related mortality in piñon pine. © 2012 Blackwell Publishing Ltd.

Informal Caregivers' Experiences and Needs When Caring for a Relative With Heart Failure: An Interview Study.

PubMed

Gusdal, Annelie K; Josefsson, Karin; Adolfsson, Eva Thors; Martin, Lene

2016-01-01

Informal caregivers play an important role for persons with heart failure in strengthening medication adherence, encouraging self-care, and identifying deterioration in health status. Caring for a relative with heart failure can affect informal caregivers' well-being and cause caregiver burden. The objective of this study was to explore informal caregivers' experiences and needs when caring for a relative with heart failure living in their own home. The study has a qualitative design with an inductive approach. Interviews were conducted with 14 informal caregivers. Data were analyzed using qualitative content analysis. Two themes emerged: "living in a changed existence" and "struggling and sharing with healthcare." The first theme describes informal caregivers' experiences, needs, and ways of moving forward when living in a changed existence with their relative. Informal caregivers were responsible for the functioning of everyday life, which challenged earlier established roles and lifestyle. They experienced an ever-present uncertainty related to the relative's impending sudden deterioration and to lack of knowledge about the condition. Incongruence was expressed between their own and their relative's understanding and acceptance of the heart failure condition. They also expressed being at peace with their relative and managed to restore new strength and motivation to care. The second theme describes informal caregivers' experiences, needs, and ways in which they handled the healthcare. They felt counted upon but not accounted for, as their care was taken for granted while their need to be seen and acknowledged by healthcare professionals was not met. Informal caregivers experienced an ever-present uncertainty regarding their lack of involvement with healthcare. The lack of involvement with healthcare had a negative impact on the relationship between informal caregivers and their relative due to the mutual loss of important information about changes in medication regimens and the relative's symptoms and well-being. Another cause of negative impact was the lack of opportunity to talk with healthcare professionals about the emotional and relational consequences of heart failure. Healthcare professionals had provided them neither with knowledge on heart failure nor with information on support groups in the municipality. Informal caregivers captured their own mandate through acting as deputies for their relative and claiming their rights of involvement in their relative's healthcare. They also felt confident despite difficult circumstances. The direct access to the medical clinic was a source of relief and they appreciated the contacts with the registered nurses specialized in heart failure. Informal caregivers' own initiatives to participate in meetings were positively received by healthcare professionals. Informal caregivers' daily life involves decisive changes that are experienced as burdensome. They handled their new situations using different strategies to preserve a sense of "self" and of "us." Informal caregivers express a need for more involvement with healthcare professionals, which may facilitate informal caregivers' situation and improve the dyadic congruence in the relation with their relative.

Collapse of Composite Cylinders in Bending

NASA Technical Reports Server (NTRS)

Fuchs, Hannes P.; Starnes, James H., Jr.; Hyer, Michael W.

1998-01-01

This paper summarizes the results of a numerical and experimental study of the collapse behavior of small-scale graphite-epoxy cylindrical shells subjected to overall bending loads, and in one case, an initial internal pressure. Shells with quasi-isotropic and orthotropic inplane stiffness properties are studied. Numerical results from geometrically nonlinear finite element analyses and results from experiments using a specially-built apparatus indicate that extensive stable postbuckling responses occur. Orthotropy influences the buckling values and the extent to which the bending moment decreases after buckling. Material damage is observed to initiate in the vicinity of the nodal lines of the postbuckled deflection patterns. Numerical results indicate that the magnitudes of the shear stress resultants are greatest in these nodal regions. Failure of the internally pressurized cylinder is catastrophic.

Flight Validation of a Metrics Driven L(sub 1) Adaptive Control

NASA Technical Reports Server (NTRS)

Dobrokhodov, Vladimir; Kitsios, Ioannis; Kaminer, Isaac; Jones, Kevin D.; Xargay, Enric; Hovakimyan, Naira; Cao, Chengyu; Lizarraga, Mariano I.; Gregory, Irene M.

2008-01-01

The paper addresses initial steps involved in the development and flight implementation of new metrics driven L1 adaptive flight control system. The work concentrates on (i) definition of appropriate control driven metrics that account for the control surface failures; (ii) tailoring recently developed L1 adaptive controller to the design of adaptive flight control systems that explicitly address these metrics in the presence of control surface failures and dynamic changes under adverse flight conditions; (iii) development of a flight control system for implementation of the resulting algorithms onboard of small UAV; and (iv) conducting a comprehensive flight test program that demonstrates performance of the developed adaptive control algorithms in the presence of failures. As the initial milestone the paper concentrates on the adaptive flight system setup and initial efforts addressing the ability of a commercial off-the-shelf AP with and without adaptive augmentation to recover from control surface failures.

Explosive Model Tarantula 4d/JWL++ Calibration of LX-17

DOE Office of Scientific and Technical Information (OSTI.GOV)

Souers, P C; Vitello, P A

2008-09-30

Tarantula is an explosive kinetic package intended to do detonation, shock initiation, failure, corner-turning with dead zones, gap tests and air gaps in reactive flow hydrocode models. The first, 2007-2008 version with monotonic Q is here run inside JWL++ with square zoning from 40 to 200 zones/cm on ambient LX-17. The model splits the rate behavior in every zone into sections set by the hydrocode pressure, P + Q. As the pressure rises, we pass through the no-reaction, initiation, ramp-up/failure and detonation sections sequentially. We find that the initiation and pure detonation rate constants are largely insensitive to zoning butmore » that the ramp-up/failure rate constant is extremely sensitive. At no time does the model pass every test, but the pressure-based approach generally works. The best values for the ramp/failure region are listed here in Mb units.« less

Mixed-method exploratory study of general practitioner and nurse perceptions of a new community based nurse-led heart failure service.

PubMed

MacKenzie, Emma; Smith, Amanda; Angus, Neil; Menzies, Sue; Brulisauer, Franz; Leslie, Stephen J

2010-01-01

The treatment of patients with chronic heart failure (CHF) remains sub-optimal. Specialist CHF nurses are proven to improve care and reduce admission but developing such services, especially in remote areas, can be difficult. This study aimed: first, to assess the perceived acceptability and effectiveness of a new community based nurse-led heart failure service by general practitioners (GPs) in an area with a dispersed population; second, to assess the knowledge and learning needs of GPs; and third, to assess perceptions of the use of national guidelines and telehealth on heart failure management. The study was conducted in the Scottish Highlands, a large geographical area in the north of the UK which includes both rural and urban populations. The area has a total population of 240 000, approximately 60% of whom are within 1 hour travel time of the largest urban centre. A postal survey of all GPs (n = 260) and structured email survey of all CHF specialist nurses (n = 3) was performed. All responses were entered into a Microsoft Excel spreadsheet, summarised and subjected to thematic analysis. Differences between GPs in 'rural', 'urban' or both 'urban & rural' was investigated using an F-test for continuous variables and a three-sample test for equality of proportions for nominal data. Questionnaires were returned from 83 GPs (32%) and all three CHF specialist nurses. In this sample there were only a few differences between GPs from 'rural', 'urban' and 'urban & rural'. There also appeared to be little difference in responses between those who had the experience of the CHF nurse service and those who had not. Overall, 32 GPs (39%) wished better, local access to echocardiography, while 63 (76%) wished access to testing for brain natriuretic peptide (BNP). Only 27 GPs (33%) referred all patients with CHF to hospital. A number of GPs stated that this was dependant on individual circumstances and the patient's ability to travel. The GPs were confident to initiate standard heart failure drugs although only 54 (65%) were confident in the initiation of beta-blockers. Most GPs (69%) had had experience of the CHF specialist nurse service and the responses were mixed. The GPs who had experienced the service appeared less confident that it would lead to reduced admission of patients to hospital (51% vs 77%, p = 0.046). Three main themes emerged from the nurse responses: service planning, communication and attitudinal changes after service embedment. This study demonstrates that a community based heart failure nurse service was not universally valued. Differences between urban and rural localities (communication) suggest that models of care derived from evidence based practice in urban areas may not be directly transferable to remote areas. Clearly, good communication among staff groups at all stages of implementation is important; however, despite best efforts and clinical trial evidence, specialist nurse services will not be welcomed by all doctors. Service providers and commissioners should be cognisant of the different roles of urban and rural GPs when designing such services. Among GPs there was a high degree of confidence with initiation and titration of drugs for heart failure with the exception of beta-blockers so clearly this is an area of ongoing educational need and support. Education and support should focus on ensuring that all doctors who care for patients with CHF have the skills and confidence to use medical therapies and specialist services as appropriate.

Failure analysis of aluminum alloy components

NASA Technical Reports Server (NTRS)

Johari, O.; Corvin, I.; Staschke, J.

1973-01-01

Analysis of six service failures in aluminum alloy components which failed in aerospace applications is reported. Identification of fracture surface features from fatigue and overload modes was straightforward, though the specimens were not always in a clean, smear-free condition most suitable for failure analysis. The presence of corrosion products and of chemically attacked or mechanically rubbed areas here hindered precise determination of the cause of crack initiation, which was then indirectly inferred from the scanning electron fractography results. In five failures the crack propagation was by fatigue, though in each case the fatigue crack initiated from a different cause. Some of these causes could be eliminated in future components by better process control. In one failure, the cause was determined to be impact during a crash; the features of impact fracture were distinguished from overload fractures by direct comparisons of the received specimens with laboratory-generated failures.

The Embodiment of Success and Failure as Forward versus Backward Movements

PubMed Central

Robinson, Michael D.; Fetterman, Adam K.

2015-01-01

People often speak of success (e.g., “advance”) and failure (e.g., “setback”) as if they were forward versus backward movements through space. Two experiments sought to examine whether grounded associations of this type influence motor behavior. In Experiment 1, participants categorized success versus failure words by moving a joystick forward or backward. Failure categorizations were faster when moving backward, whereas success categorizations were faster when moving forward. Experiment 2 removed the requirement to categorize stimuli and used a word rehearsal task instead. Even without Experiment 1’s response procedures, a similar cross-over interaction was obtained (e.g., failure memorizations sped backward movements relative to forward ones). The findings are novel yet consistent with theories of embodied cognition and self-regulation. PMID:25658923

Very High Cycle Fatigue Failure Analysis and Life Prediction of Cr-Ni-W Gear Steel Based on Crack Initiation and Growth Behaviors.

PubMed

Deng, Hailong; Li, Wei; Sakai, Tatsuo; Sun, Zhenduo

2015-12-02

The unexpected failures of structural materials in very high cycle fatigue (VHCF) regime have been a critical issue in modern engineering design. In this study, the VHCF property of a Cr-Ni-W gear steel was experimentally investigated under axial loading with the stress ratio of R = -1, and a life prediction model associated with crack initiation and growth behaviors was proposed. Results show that the Cr-Ni-W gear steel exhibits the constantly decreasing S-N property without traditional fatigue limit, and the fatigue strength corresponding to 10⁸ cycles is around 485 MPa. The inclusion-fine granular area (FGA)-fisheye induced failure becomes the main failure mechanism in the VHCF regime, and the local stress around the inclusion play a key role. By using the finite element analysis of representative volume element, the local stress tends to increase with the increase of elastic modulus difference between inclusion and matrix. The predicted crack initiation life occupies the majority of total fatigue life, while the predicted crack growth life is only accounts for a tiny fraction. In view of the good agreement between the predicted and experimental results, the proposed VHCF life prediction model involving crack initiation and growth can be acceptable for inclusion-FGA-fisheye induced failure.

EIGHTH INTERIM STATUS REPORT: MODEL 9975 PCV O-RING FIXTURE LONG-TERM LEAK PERFORMANCE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Daugherty, W. L.

2013-09-03

A series of experiments to monitor the aging performance of Viton® GLT O-rings used in the Model 9975 package has been ongoing since 2004 at the Savannah River National Laboratory. Seventy tests using mock-ups of 9975 Primary Containment Vessels (PCVs) were assembled and heated to temperatures ranging from 200 to 450 ºF. They were leak-tested initially and have been tested periodically to determine if they meet the criterion of leak-tightness defined in ANSI standard N14.5-97. Fourteen additional tests were initiated in 2008 with GLT-S O-rings heated to temperatures ranging from 200 to 400 ºF. High temperature aging continues for 23more » GLT O-ring fixtures at 200 – 270 ºF. Room temperature leak test failures have been experienced in all of the GLT O-ring fixtures aging at 350 ºF and higher temperatures, and in 8 fixtures aging at 300 ºF. The remaining GLT O-ring fixtures aging at 300 ºF have been retired from testing following more than 5 years at temperature without failure. No failures have yet been observed in GLT O-ring fixtures aging at 200 ºF for 61 - 85 months, which is still bounding to O-ring temperatures during storage in KArea Complex (KAC). Based on expectations that the fixtures aging at 200 ºF will remain leaktight for a significant period yet to come, 2 additional fixtures began aging in 2011 at an intermediate temperature of 270 ºF, with hopes that they may reach a failure condition before the 200 ºF fixtures. High temperature aging continues for 6 GLT-S O-ring fixtures at 200 – 300 ºF. Room temperature leak test failures have been experienced in all 8 of the GLT-S O-ring fixtures aging at 350 and 400 ºF. No failures have yet been observed in GLT-S O-ring fixtures aging at 200 - 300 ºF for 41 - 45 months. Aging and periodic leak testing will continue for the remaining PCV fixtures.« less

Application of Interface Technology in Progressive Failure Analysis of Composite Panels

NASA Technical Reports Server (NTRS)

Sleight, D. W.; Lotts, C. G.

2002-01-01

A progressive failure analysis capability using interface technology is presented. The capability has been implemented in the COMET-AR finite element analysis code developed at the NASA Langley Research Center and is demonstrated on composite panels. The composite panels are analyzed for damage initiation and propagation from initial loading to final failure using a progressive failure analysis capability that includes both geometric and material nonlinearities. Progressive failure analyses are performed on conventional models and interface technology models of the composite panels. Analytical results and the computational effort of the analyses are compared for the conventional models and interface technology models. The analytical results predicted with the interface technology models are in good correlation with the analytical results using the conventional models, while significantly reducing the computational effort.

DOE Office of Scientific and Technical Information (OSTI.GOV)

English, Shawn Allen; Nelson, Stacy Michelle; Briggs, Timothy

Presented is a model verification and validation effort using low - velocity impact (LVI) of carbon fiber reinforced polymer laminate experiments. A flat cylindrical indenter impacts the laminate with enough energy to produce delamination, matrix cracks and fiber breaks. Included in the experimental efforts are ultrasonic scans of the damage for qualitative validation of the models. However, the primary quantitative metrics of validation are the force time history measured through the instrumented indenter and initial and final velocities. The simulations, whi ch are run on Sandia's Sierra finite element codes , consist of all physics and material parameters of importancemore » as determined by a sensitivity analysis conducted on the LVI simulation. A novel orthotropic damage and failure constitutive model that is cap able of predicting progressive composite damage and failure is described in detail and material properties are measured, estimated from micromechanics or optimized through calibration. A thorough verification and calibration to the accompanying experiment s are presented. Specia l emphasis is given to the four - point bend experiment. For all simulations of interest, the mesh and material behavior is verified through extensive convergence studies. An ensemble of simulations incorporating model parameter unc ertainties is used to predict a response distribution which is then compared to experimental output. The result is a quantifiable confidence in material characterization and model physics when simulating this phenomenon in structures of interest.« less

Drug choice as a self-handicapping strategy in response to noncontingent success.

PubMed

Berglas, S; Jones, E E

1978-04-01

In two closely related experiments, college student subjects were instructed to choose between a drug that allegedly interfered with performance and a drug that allegedly enhanced performance. This choice was the main dependent measure of the experiment. The drug choice intervened between work on soluble or insoluble problems and a promised retest on similar problems. In Experiment 1, all subjects received success feedback after their initial problem-solving attempts, thus creating one condition in which the success appeared to be accidental (noncontingent on performance) and one in which the success appeared to be contingent on appropriate knowledge. Males in the noncontingent-success condition were alone in preferring the performance-inhibiting drug, presumably because they wished to externalize probable failure on the retest. The predicted effect, however, did not hold for female subjects. Experiment 2 replicated the unique preference shown by males after noncontingent success and showed the critical importance of success feedback.

Nonlinear analysis for the response and failure of compression-loaded angle-ply laminates with a hole

NASA Technical Reports Server (NTRS)

Mathison, Steven R.; Herakovich, Carl T.; Pindera, Marek-Jerzy; Shuart, Mark J.

1987-01-01

The objective was to determine the effect of nonlinear material behavior on the response and failure of unnotched and notched angle-ply laminates under uniaxial compressive loading. The endochronic theory was chosen as the constitutive theory to model the AS4/3502 graphite-epoxy material system. Three-dimensional finite element analysis incorporating the endochronic theory was used to determine the stresses and strains in the laminates. An incremental/iterative initial strain algorithm was used in the finite element program. To increase computational efficiency, a 180 deg rotational symmetry relationship was utilized and the finite element program was vectorized to run on a supercomputer. Laminate response was compared to experimentation revealing excellent agreement for both the unnotched and notched angle-ply laminates. Predicted stresses in the region of the hole were examined and are presented, comparing linear elastic analysis to the inelastic endochronic theory analysis. A failure analysis of the unnotched and notched laminates was performed using the quadratic tensor polynomial. Predicted fracture loads compared well with experimentation for the unnotched laminates, but were very conservative in comparison with experiments for the notched laminates.

Experimental and Computational Studies of Coupled Geomechanical and Hydrologic Processes in Wellbore Systems (Invited)

NASA Astrophysics Data System (ADS)

Carey, J. W.; Mori, H.; Porter, M. L.; Lewis, K. C.; Kelkar, S.

2013-12-01

Potential leakage from wells is an important issue in the protection of groundwater resources, CO2 sequestration, and hydraulic fracturing. The first defense in all of these applications is a properly constructed well with adequate Portland cement that effectively isolates the subsurface. The chief threat for such wells is mechanical disruption of the cement, cement/steel, or cement/caprock interfaces. This can occur through wellbore operations that pressurize/depressurize the steel tubing or create temperature transients (e.g., injection, production, hydraulic fracturing, and mechanical testing) as well as reservoir-scale stresses (e.g., filling or depletion of the reservoir) and tectonic stresses (e.g., the mobility of salt). However, there is relatively limited information available on the hydrologic consequences of such processes. Toward this end, we discuss recent experiments and computational models of coupled geomechanical and hydrologic processes in wellbore systems. Triaxial coreflood experiments with tomography were conducted on synthetic wellbore systems including cement-steel, rock-cement and rock-cement-steel composites. The aim of the experiments was to induce stresses through application of axial loads in order to create defects within the cement or at the cement/steel or cement/rock interface. High injection fluid pressures (supercritical CO2 × brine) were applied to the base of the initially impermeable composites. Mechanical failure resulted in creation of permeability, which was measured as a function of time (allowing for the possibility of Portland cement to deform and modify permeability). In addition, fracture patterns were characterized using x-ray tomography. We used the computer code FEHM to study coupled hydrologic and mechanical processes in the near-wellbore environment. The wellbore model was developed as a wedge within a radially symmetric 3D volume. The grid elements consist of the steel casing, the casing-cement interface, the cement, the cement-rock interface, caprock, and reservoir rock. We used a model that is 1 m in radius, and extends 5 m along the wellbore. The model consisted of a lower storage aquifer, a caprock and an upper aquifer that received leaking fluids. We coupled flow and geomechanics using a shear-failure model that represents shear-induced damage and is similar to a Mohr-Coulomb slip mechanism. In this model, damage occurs for any excess shear stress with permeability enhancement a function of stress with a maximum magnitude set by the user. Stresses were induced by application of an elevated constant pressure within the injection reservoir representing a far-field injection process. The initial permeability of the cement was 1 mD and stress-enhanced permeability was limited to an increase by a factor of 10-100. The simulations show that shear-failure modes lead to enhanced permeability of the wellbore system. Continuing work will examine sensitivity of the results to mechanical properties and initial permeability distributions, the impact of relative permeability models, and the development of permeability-stress models including an aperture-opening tensile-failure model.

Testing and Analysis of Composite Skin/Stringer Debonding Under Multi-Axial Loading

NASA Technical Reports Server (NTRS)

Krueger, Ronald; Cvitkovich, Michael K.; O'Brien, T. Kevin; Minguet, Pierre J.

2000-01-01

A consistent step-wise approach is presented to investigate the damage mechanism in composite bonded skin/stringer constructions under uniaxial and biaxial (in-plane/out-of-plane) loading conditions. The approach uses experiments to detect the failure mechanism, computational stress analysis to determine the location of first matrix cracking and computational fracture mechanics to investigate the potential for delamination growth. In a first step, tests were performed on specimens, which consisted of a tapered composite flange, representing a stringer or frame, bonded onto a composite skin. Tests were performed under monotonic loading conditions in tension, three-point bending, and combined tension/bending to evaluate the debonding mechanisms between the skin and the bonded stringer. For combined tension/bending testing, a unique servohydraulic load frame was used that was capable of applying both in-plane tension and out-of-plane bending loads simultaneously. Specimen edges were examined on the microscope to document the damage occurrence and to identify typical damage patterns. For all three load cases, observed failure initiated in the flange, near the flange tip, causing the flange to almost fully debond from skin. In a second step, a two dimensional plane-strain finite element model was developed to analyze the different test cases using a geometrically nonlinear solution. For all three loading conditions, computed principal stresses exceeded the transverse strength of the material in those areas of the flange where the matrix cracks had developed during the tests. In a third step, delaminations of various lengths were simulated in two locations where delaminations were observed during the tests. The analyses showed that at the loads corresponding to matrix ply crack initiation computed strain energy release rates exceeded the values obtained from a mixed mode failure criterion in one location, Hence. Unstable delamination propagation is likely to occur as observed in the experiments.

Testing and Analysis of Composite Skin/Stringer Debonding under Multi-Axial Loading

NASA Technical Reports Server (NTRS)

Krueger, Ronald; Cvitkovich, Michael; OBrien, Kevin; Minguet, Pierre J.

2000-01-01

A consistent step-wise approach is presented to investigate the damage mechanism in composite bonded skin/stringer constructions under uniaxial and biaxial (in-plane/out-of-plane) loading conditions. The approach uses experiments to detect the failure mechanism, computational stress analysis to determine the location of first matrix cracking and computational fracture mechanics to investigate the potential for delamination growth. In a first step, tests were performed on specimens, which consisted of a tapered composite flange, representing a stringer or frame, bonded onto a composite skin. Tests were performed under monotonic loading conditions in tension, three-point bending, and combined tension/bending to evaluate the debonding mechanisms between the skin and the bonded stringer. For combined tension/bending testing, a unique servohydraulic load frame was used that was capable of applying both in-plane tension and out-of-plane bending loads simultaneously. Specimen edges were examined on the microscope to document the damage occurrence and to identify typical damage patterns. For all three load cases, observed failure initiated in the flange, near the flange tip, causing the flange to almost fully debond from the skin. In a second step, a two-dimensional plane-strain finite element model was developed to analyze the different test cases using a geometrically nonlinear solution. For all three loading conditions, computed principal stresses exceeded the transverse strength of the material in those areas of the flange where the matrix cracks had developed during the tests. In a third step, delaminations of various lengths were simulated in two locations where delaminations were observed during the tests. The analyses showed that at the loads corresponding to matrix ply crack initiation computed strain energy release rates exceeded the values obtained from a mixed mode failure criterion in one location. Hence, unstable delamination propagation is likely to occur as observed in the experiments.

Medical costs associated with non-Hodgkin's lymphoma in the United States during the first two years of treatment.

PubMed

Kutikova, Lucie; Bowman, Lee; Chang, Stella; Long, Stacey R; Arning, Michael; Crown, William H

2006-08-01

To determine the direct costs of medical care associated with aggressive and indolent non-Hodgkin's lymphoma (NHL) in the United States; to show how costs for aggressive NHL change over time by examining costs related to initial, secondary and palliative treatment phases; and to evaluate the economic consequences of treatment failure in aggressive NHL. A retrospective cohort analysis of 1999 - 2000 direct costs in newly diagnosed NHL patients and controls (subjects without any cancer) was conducted using the MarketScan medical and drug claims database of large employers across the United States. Treatment failure analysis was conducted for aggressive NHL patients, and was defined by the need for secondary treatment or palliative care after initial therapy. Cost of treatment failure was calculated as difference in regression-adjusted costs between patients with initial therapy only and patients experiencing initial treatment failure. Patients with aggressive (n = 356) and indolent (n = 698) NHL had significantly greater health service utilization and associated costs (all P < 05) than controls (n = 1068 for aggressive, n = 2094 for indolent). Mean monthly costs were 5871 dollars for aggressive NHL vs. 355 dollars for controls (P < 0001) and 3833 dollars for indolent NHL vs. 289 dollars for controls (P < 0001). The primary cost drivers were hospitalization (aggressive NHL = 44% of total costs, indolent NHL = 50%) and outpatient office visits (aggressive NHL = 39%, indolent NHL = 34%). For aggressive NHL, mean monthly initial treatment phase costs (10,970 dollars) and palliative care costs (9836 dollars) were higher than costs incurred during secondary phase (3302 dollars). The mean cost of treatment failure in aggressive NHL was 14,174 dollars per month, and 85,934 dollars over the study period. The treatment of NHL was associated with substantial health care costs. Patients with aggressive lymphomas tended to accrue higher costs, compared with those with indolent lymphomas. These costs varied over time, with the highest costs occurring during the initial treatment and palliative care phases. Treatment failure was the most expensive treatment pattern. New strategies to prevent or delay treatment failure in aggressive NHL could help reduce the economic burden of NHL.

Changing scenes: memory for naturalistic events following change blindness.

PubMed

Mäntylä, Timo; Sundström, Anna

2004-11-01

Research on scene perception indicates that viewers often fail to detect large changes to scene regions when these changes occur during a visual disruption such as a saccade or a movie cut. In two experiments, we examined whether this relative inability to detect changes would produce systematic biases in event memory. In Experiment 1, participants decided whether two successively presented images were the same or different, followed by a memory task, in which they recalled the content of the viewed scene. In Experiment 2, participants viewed a short video, in which an actor carried out a series of daily activities, and central scenes' attributes were changed during a movie cut. A high degree of change blindness was observed in both experiments, and these effects were related to scene complexity (Experiment 1) and level of retrieval support (Experiment 2). Most important, participants reported the changed, rather than the initial, event attributes following a failure in change detection. These findings suggest that attentional limitations during encoding contribute to biases in episodic memory.

Association Between Efavirenz-Based Compared With Nevirapine-Based Antiretroviral Regimens and Virological Failure in HIV-Infected Children

PubMed Central

Lowenthal, Elizabeth D.; Ellenberg, Jonas H.; Machine, Edwin; Sagdeo, Aditi; Boiditswe, Sefelani; Steenhoff, Andrew P.; Rutstein, Richard; Anabwani, Gabriel; Gross, Robert

2013-01-01

Importance Worldwide, the nonnucleoside reverse transcriptase inhibitors (NNRTIs) efavirenz and nevirapine are commonly used in first-line antiretroviral regimens in both adults and children with human immunodeficiency virus (HIV) infection. Data on the comparative effectiveness of these medications in children are limited. Objective To investigate whether virological failure is more likely among children who initiated 1 or the other NNRTI-based HIV treatment. Design, Setting, and Participants Retrospective cohort study of children (aged 3–16 years) who initiated efavirenz-based (n=421) or nevirapine-based (n=383) treatment between April 2002 and January 2011 at a large pediatric HIV care setting in Botswana. Main Outcomes and Measures The primary outcome was time from initiation of therapy to virological failure. Virological failure was defined as lack of plasma HIV RNA suppression to less than 400 copies/mL by 6 months or confirmed HIV RNA of 400 copies/mL or greater after suppression. Cox proportional hazards regression analysis compared time to virological failure by regimen. Multivariable Cox regression controlled for age, sex, baseline immunologic category, baseline clinical category, baseline viral load, nutritional status, NRTIs used, receipt of single-dose nevirapine, and treatment for tuberculosis. Results With a median follow-up time of 69 months (range, 6–112 months; interquartile range, 23–87 months), 57 children (13.5%; 95% CI, 10.4%–17.2%) initiating treatment with efavirenz and 101 children (26.4%; 95% CI, 22.0%–31.1%) initiating treatment with nevirapine had virological failure. There were 11 children (2.6%; 95% CI, 1.3%–4.6%) receiving efavirenz and 20 children (5.2%; 95% CI, 3.2%–7.9%) receiving nevirapine who never achieved virological suppression. The Cox proportional hazard ratio for the combined virological failure end point was 2.0 (95% CI, 1.4–2.7; log rank P<.001, favoring efavirenz). None of the measured covariates affected the estimated hazard ratio in the multivariable analyses. Conclusions and Relevance Among children aged 3 to 16 years infected with HIV and treated at a clinic in Botswana, the use of efavirenz compared with nevirapine as initial antiretroviral treatment was associated with less virological failure. These findings may warrant additional research evaluating the use of efavirenz and nevirapine for pediatric patients. PMID:23632724

Effect of tooth substrate and porcelain thickness on porcelain veneer failure loads in vitro.

PubMed

Ge, Chunling; Green, Chad C; Sederstrom, Dalene A; McLaren, Edward A; Chalfant, James A; White, Shane N

2017-12-19

Bonded porcelain veneers are widely used esthetic restorations. High success and survival rates have been reported, but failures do occur. Fractures are the commonest failure mode. Minimally invasive or thin veneers have gained popularity. Increased enamel and porcelain thickness improve the strength of veneers bonded to enamel, but less is known about dentin or mixed substrates. The purpose of this in vitro study was to measure the influences of tooth substrate type (all-enamel, all-dentin, or half-dentin-half-enamel) and veneer thickness on the loads needed to cause initial and catastrophic porcelain veneer failure. Model discoid porcelain veneer specimens of varying thicknesses were bonded to the flattened facial surfaces of incisors with different enamel and dentin tooth substrates, artificially aged, and loaded to failure with a small sphere. Initial and catastrophic fracture events were identified and analyzed statistically and fractographically. Fracture events included initial Hertzian cracks, intermediate radial cracks, and catastrophic gross failure. All specimens retained some porcelain after catastrophic failure. Cement failure occurred at the cement-porcelain interface not at the cement-tooth interface. Porcelain veneers bonded to enamel were substantially stronger and more damage-tolerant than those bonded to dentin or mixed substrates. Increased porcelain thickness substantially raised the loads to catastrophic failure on enamel substrates but only moderately raised the loads to catastrophic failure on dentin or mixed substrates. The veneers bonded to half-dentin-half-enamel behaved remarkably like those bonded wholly to dentin. Porcelain veneers bonded to enamel were substantially stronger and more damage-tolerant than those bonded to dentin or half-enamel-half dentin. Copyright © 2017 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Heart Failure and Frailty in the Community-Living Elderly Population: What the UFO Study Will Tell Us

PubMed Central

Fung, Erik; Hui, Elsie; Yang, Xiaobo; Lui, Leong T.; Cheng, King F.; Li, Qi; Fan, Yiting; Sahota, Daljit S.; Ma, Bosco H. M.; Lee, Jenny S. W.; Lee, Alex P. W.; Woo, Jean

2018-01-01

Heart failure and frailty are clinical syndromes that present with overlapping phenotypic characteristics. Importantly, their co-presence is associated with increased mortality and morbidity. While mechanical and electrical device therapies for heart failure are vital for select patients with advanced stage disease, the majority of patients and especially those with undiagnosed heart failure would benefit from early disease detection and prompt initiation of guideline-directed medical therapies. In this article, we review the problematic interactions between heart failure and frailty, introduce a focused cardiac screening program for community-living elderly initiated by a mobile communication device app leading to the Undiagnosed heart Failure in frail Older individuals (UFO) study, and discuss how the knowledge of pre-frailty and frailty status could be exploited for the detection of previously undiagnosed heart failure or advanced cardiac disease. The widespread use of mobile devices coupled with increasing availability of novel, effective medical and minimally invasive therapies have incentivized new approaches to heart failure case finding and disease management. PMID:29740330

What can NSC tell us about tree drought mortality mechanism?: An meta-analysis of results from several experiments on southwest US species

NASA Astrophysics Data System (ADS)

Adams, H. D.; Dickman, L. T.; Sevanto, S.; McDowell, N. G.; Pockman, W.; Breshears, D. D.; Huxman, T. E.

2012-12-01

Widespread increases in tree mortality are now a well-documented global phenomenon that has been linked to drought, increased temperatures, and pest/pathogen outbreaks. Since forests play an important regulatory role in planetary carbon, water, and energy budgets, further widespread tree mortality could disrupt biosphere-atmosphere feedbacks with additional effects on climate. Despite these threats, few vegetation models exist that predict drought-induced tree mortality in response to climate due, in part, to uncertainty surrounding the physiological mechanism of mortality in trees. Several mechanisms for drought mortality have been proposed, relating to tree carbohydrate balance, xylem stress, and their interaction with each other and tree pests and pathogens. Carbon starvation could occur if stomatal closure in response to drought inhibits carbon assimilation and carbohydrate resources are depleted below a critical threshold for survival. Hydraulic failure could occur if excessive xylem tension during drought causes complete and irreversible cavitation and subsequent desiccation of the canopy. Here we present results from three recent experiments with trees from the southwest US, two conducted in the glasshouse with transplanted piñon pine, and one in the field with piñon pine and juniper, where non-structural carbohydrates (NSC) and hydraulic function were assessed during drought through mortality to distinguish the relative contribution of these mechanisms to mortality. In all three experiments, piñon leaf and twig NSC declined by ~30-40% from initial values to measurement at mortality and trees experienced some hydraulic failure. In the first glasshouse study the piñon leaf NSC decline of ~30%, was driven by a ~50% decline in sugar concentration despite a 100% increase in starch concentration. Surprisingly, in this experiment NSC did not decline faster for trees that died under elevated (+4.3°C) temperatures, although starch increased earlier in these trees. In the field experiment, juniper leaf and twig NSC did not decline as mortality approached, but was lower than non-drought controls. Hydraulic failure did not occur with mortality for juniper in the field experiment. In an additional treatment in the second glasshouse experiment, well-watered piñon pines that were shaded to prevent photosynthesis experienced a ~70% decline in leaf and twig NSC at mortality, without hydraulic failure. Considering the ~70% NSC reduction in this shaded treatment as a survival threshold, piñon pine in all three drought experiments appear to have died from a combination of carbon starvation and hydraulic failure, while juniper appears to have died from carbon starvation alone. These results demonstrate that proposed tree drought mortality mechanisms are often interrelated, but can act independently. Future models of tree drought mortality should include flexibility, predicting death from mechanisms acting either independently or in combination.

A risk assessment method for multi-site damage

NASA Astrophysics Data System (ADS)

Millwater, Harry Russell, Jr.

This research focused on developing probabilistic methods suitable for computing small probabilities of failure, e.g., 10sp{-6}, of structures subject to multi-site damage (MSD). MSD is defined as the simultaneous development of fatigue cracks at multiple sites in the same structural element such that the fatigue cracks may coalesce to form one large crack. MSD is modeled as an array of collinear cracks with random initial crack lengths with the centers of the initial cracks spaced uniformly apart. The data used was chosen to be representative of aluminum structures. The structure is considered failed whenever any two adjacent cracks link up. A fatigue computer model is developed that can accurately and efficiently grow a collinear array of arbitrary length cracks from initial size until failure. An algorithm is developed to compute the stress intensity factors of all cracks considering all interaction effects. The probability of failure of two to 100 cracks is studied. Lower bounds on the probability of failure are developed based upon the probability of the largest crack exceeding a critical crack size. The critical crack size is based on the initial crack size that will grow across the ligament when the neighboring crack has zero length. The probability is evaluated using extreme value theory. An upper bound is based on the probability of the maximum sum of initial cracks being greater than a critical crack size. A weakest link sampling approach is developed that can accurately and efficiently compute small probabilities of failure. This methodology is based on predicting the weakest link, i.e., the two cracks to link up first, for a realization of initial crack sizes, and computing the cycles-to-failure using these two cracks. Criteria to determine the weakest link are discussed. Probability results using the weakest link sampling method are compared to Monte Carlo-based benchmark results. The results indicate that very small probabilities can be computed accurately in a few minutes using a Hewlett-Packard workstation.

Compression Fracture of CFRP Laminates Containing Stress Intensifications.

PubMed

Leopold, Christian; Schütt, Martin; Liebig, Wilfried V; Philipkowski, Timo; Kürten, Jonas; Schulte, Karl; Fiedler, Bodo

2017-09-05

For brittle fracture behaviour of carbon fibre reinforced plastics (CFRP) under compression, several approaches exist, which describe different mechanisms during failure, especially at stress intensifications. The failure process is not only initiated by the buckling fibres, but a shear driven fibre compressive failure beneficiaries or initiates the formation of fibres into a kink-band. Starting from this kink-band further damage can be detected, which leads to the final failure. The subject of this work is an experimental investigation on the influence of ply thickness and stacking sequence in quasi-isotropic CFRP laminates containing stress intensifications under compression loading. Different effects that influence the compression failure and the role the stacking sequence has on damage development and the resulting compressive strength are identified and discussed. The influence of stress intensifications is investigated in detail at a hole in open hole compression (OHC) tests. A proposed interrupted test approach allows identifying the mechanisms of damage initiation and propagation from the free edge of the hole by causing a distinct damage state and examine it at a precise instant of time during fracture process. Compression after impact (CAI) tests are executed in order to compare the OHC results to a different type of stress intensifications. Unnotched compression tests are carried out for comparison as a reference. With this approach, a more detailed description of the failure mechanisms during the sudden compression failure of CFRP is achieved. By microscopic examination of single plies from various specimens, the different effects that influence the compression failure are identified. First damage of fibres occurs always in 0°-ply. Fibre shear failure leads to local microbuckling and the formation and growth of a kink-band as final failure mechanisms. The formation of a kink-band and finally steady state kinking is shifted to higher compressive strains with decreasing ply thickness. Final failure mode in laminates with stress intensification depends on ply thickness. In thick or inner plies, damage initiates as shear failure and fibre buckling into the drilled hole. The kink-band orientation angle is changing with increasing strain. In outer or thin plies shear failure of single fibres is observed as first damage and the kink-band orientation angle is constant until final failure. Decreasing ply thickness increases the unnotched compressive strength. When stress intensifications are present, the position of the 0°-layer is critical for stability under compression and is thus more important than the ply thickness. Central 0°-layers show best results for OHC and CAI strength due to higher bending stiffness and better supporting effect of the adjacent layers.

Compression Fracture of CFRP Laminates Containing Stress Intensifications

PubMed Central

Schütt, Martin; Philipkowski, Timo; Kürten, Jonas; Schulte, Karl

2017-01-01

For brittle fracture behaviour of carbon fibre reinforced plastics (CFRP) under compression, several approaches exist, which describe different mechanisms during failure, especially at stress intensifications. The failure process is not only initiated by the buckling fibres, but a shear driven fibre compressive failure beneficiaries or initiates the formation of fibres into a kink-band. Starting from this kink-band further damage can be detected, which leads to the final failure. The subject of this work is an experimental investigation on the influence of ply thickness and stacking sequence in quasi-isotropic CFRP laminates containing stress intensifications under compression loading. Different effects that influence the compression failure and the role the stacking sequence has on damage development and the resulting compressive strength are identified and discussed. The influence of stress intensifications is investigated in detail at a hole in open hole compression (OHC) tests. A proposed interrupted test approach allows identifying the mechanisms of damage initiation and propagation from the free edge of the hole by causing a distinct damage state and examine it at a precise instant of time during fracture process. Compression after impact (CAI) tests are executed in order to compare the OHC results to a different type of stress intensifications. Unnotched compression tests are carried out for comparison as a reference. With this approach, a more detailed description of the failure mechanisms during the sudden compression failure of CFRP is achieved. By microscopic examination of single plies from various specimens, the different effects that influence the compression failure are identified. First damage of fibres occurs always in 0°-ply. Fibre shear failure leads to local microbuckling and the formation and growth of a kink-band as final failure mechanisms. The formation of a kink-band and finally steady state kinking is shifted to higher compressive strains with decreasing ply thickness. Final failure mode in laminates with stress intensification depends on ply thickness. In thick or inner plies, damage initiates as shear failure and fibre buckling into the drilled hole. The kink-band orientation angle is changing with increasing strain. In outer or thin plies shear failure of single fibres is observed as first damage and the kink-band orientation angle is constant until final failure. Decreasing ply thickness increases the unnotched compressive strength. When stress intensifications are present, the position of the 0°-layer is critical for stability under compression and is thus more important than the ply thickness. Central 0°-layers show best results for OHC and CAI strength due to higher bending stiffness and better supporting effect of the adjacent layers. PMID:28872623

Evaluation of a Progressive Failure Analysis Methodology for Laminated Composite Structures

NASA Technical Reports Server (NTRS)

Sleight, David W.; Knight, Norman F., Jr.; Wang, John T.

1997-01-01

A progressive failure analysis methodology has been developed for predicting the nonlinear response and failure of laminated composite structures. The progressive failure analysis uses C plate and shell elements based on classical lamination theory to calculate the in-plane stresses. Several failure criteria, including the maximum strain criterion, Hashin's criterion, and Christensen's criterion, are used to predict the failure mechanisms. The progressive failure analysis model is implemented into a general purpose finite element code and can predict the damage and response of laminated composite structures from initial loading to final failure.

Development of an Electronic Medical Record Based Alert for Risk of HIV Treatment Failure in a Low-Resource Setting

PubMed Central

Puttkammer, Nancy; Zeliadt, Steven; Balan, Jean Gabriel; Baseman, Janet; Destiné, Rodney; Domerçant, Jean Wysler; France, Garilus; Hyppolite, Nathaelf; Pelletier, Valérie; Raphael, Nernst Atwood; Sherr, Kenneth; Yuhas, Krista; Barnhart, Scott

2014-01-01

Background The adoption of electronic medical record systems in resource-limited settings can help clinicians monitor patients' adherence to HIV antiretroviral therapy (ART) and identify patients at risk of future ART failure, allowing resources to be targeted to those most at risk. Methods Among adult patients enrolled on ART from 2005–2013 at two large, public-sector hospitals in Haiti, ART failure was assessed after 6–12 months on treatment, based on the World Health Organization's immunologic and clinical criteria. We identified models for predicting ART failure based on ART adherence measures and other patient characteristics. We assessed performance of candidate models using area under the receiver operating curve, and validated results using a randomly-split data sample. The selected prediction model was used to generate a risk score, and its ability to differentiate ART failure risk over a 42-month follow-up period was tested using stratified Kaplan Meier survival curves. Results Among 923 patients with CD4 results available during the period 6–12 months after ART initiation, 196 (21.2%) met ART failure criteria. The pharmacy-based proportion of days covered (PDC) measure performed best among five possible ART adherence measures at predicting ART failure. Average PDC during the first 6 months on ART was 79.0% among cases of ART failure and 88.6% among cases of non-failure (p<0.01). When additional information including sex, baseline CD4, and duration of enrollment in HIV care prior to ART initiation were added to PDC, the risk score differentiated between those who did and did not meet failure criteria over 42 months following ART initiation. Conclusions Pharmacy data are most useful for new ART adherence alerts within iSanté. Such alerts offer potential to help clinicians identify patients at high risk of ART failure so that they can be targeted with adherence support interventions, before ART failure occurs. PMID:25390044

Development of an electronic medical record based alert for risk of HIV treatment failure in a low-resource setting.

PubMed

Puttkammer, Nancy; Zeliadt, Steven; Balan, Jean Gabriel; Baseman, Janet; Destiné, Rodney; Domerçant, Jean Wysler; France, Garilus; Hyppolite, Nathaelf; Pelletier, Valérie; Raphael, Nernst Atwood; Sherr, Kenneth; Yuhas, Krista; Barnhart, Scott

2014-01-01

The adoption of electronic medical record systems in resource-limited settings can help clinicians monitor patients' adherence to HIV antiretroviral therapy (ART) and identify patients at risk of future ART failure, allowing resources to be targeted to those most at risk. Among adult patients enrolled on ART from 2005-2013 at two large, public-sector hospitals in Haiti, ART failure was assessed after 6-12 months on treatment, based on the World Health Organization's immunologic and clinical criteria. We identified models for predicting ART failure based on ART adherence measures and other patient characteristics. We assessed performance of candidate models using area under the receiver operating curve, and validated results using a randomly-split data sample. The selected prediction model was used to generate a risk score, and its ability to differentiate ART failure risk over a 42-month follow-up period was tested using stratified Kaplan Meier survival curves. Among 923 patients with CD4 results available during the period 6-12 months after ART initiation, 196 (21.2%) met ART failure criteria. The pharmacy-based proportion of days covered (PDC) measure performed best among five possible ART adherence measures at predicting ART failure. Average PDC during the first 6 months on ART was 79.0% among cases of ART failure and 88.6% among cases of non-failure (p<0.01). When additional information including sex, baseline CD4, and duration of enrollment in HIV care prior to ART initiation were added to PDC, the risk score differentiated between those who did and did not meet failure criteria over 42 months following ART initiation. Pharmacy data are most useful for new ART adherence alerts within iSanté. Such alerts offer potential to help clinicians identify patients at high risk of ART failure so that they can be targeted with adherence support interventions, before ART failure occurs.

An improved approach for flight readiness certification: Methodology for failure risk assessment and application examples. Volume 2: Software documentation

NASA Technical Reports Server (NTRS)

Moore, N. R.; Ebbeler, D. H.; Newlin, L. E.; Sutharshana, S.; Creager, M.

1992-01-01

An improved methodology for quantitatively evaluating failure risk of spaceflight systems to assess flight readiness and identify risk control measures is presented. This methodology, called Probabilistic Failure Assessment (PFA), combines operating experience from tests and flights with engineering analysis to estimate failure risk. The PFA methodology is of particular value when information on which to base an assessment of failure risk, including test experience and knowledge of parameters used in engineering analyses of failure phenomena, is expensive or difficult to acquire. The PFA methodology is a prescribed statistical structure in which engineering analysis models that characterize failure phenomena are used conjointly with uncertainties about analysis parameters and/or modeling accuracy to estimate failure probability distributions for specific failure modes, These distributions can then be modified, by means of statistical procedures of the PFA methodology, to reflect any test or flight experience. Conventional engineering analysis models currently employed for design of failure prediction are used in this methodology. The PFA methodology is described and examples of its application are presented. Conventional approaches to failure risk evaluation for spaceflight systems are discussed, and the rationale for the approach taken in the PFA methodology is presented. The statistical methods, engineering models, and computer software used in fatigue failure mode applications are thoroughly documented.

An improved approach for flight readiness certification: Methodology for failure risk assessment and application examples, volume 1

NASA Technical Reports Server (NTRS)

Moore, N. R.; Ebbeler, D. H.; Newlin, L. E.; Sutharshana, S.; Creager, M.

1992-01-01

An improved methodology for quantitatively evaluating failure risk of spaceflight systems to assess flight readiness and identify risk control measures is presented. This methodology, called Probabilistic Failure Assessment (PFA), combines operating experience from tests and flights with engineering analysis to estimate failure risk. The PFA methodology is of particular value when information on which to base an assessment of failure risk, including test experience and knowledge of parameters used in engineering analyses of failure phenomena, is expensive or difficult to acquire. The PFA methodology is a prescribed statistical structure in which engineering analysis models that characterize failure phenomena are used conjointly with uncertainties about analysis parameters and/or modeling accuracy to estimate failure probability distributions for specific failure modes. These distributions can then be modified, by means of statistical procedures of the PFA methodology, to reflect any test or flight experience. Conventional engineering analysis models currently employed for design of failure prediction are used in this methodology. The PFA methodology is described and examples of its application are presented. Conventional approaches to failure risk evaluation for spaceflight systems are discussed, and the rationale for the approach taken in the PFA methodology is presented. The statistical methods, engineering models, and computer software used in fatigue failure mode applications are thoroughly documented.

A failure of conflict to modulate dual-stream processing may underlie the formation and maintenance of delusions.

PubMed

Speechley, W J; Murray, C B; McKay, R M; Munz, M T; Ngan, E T C

2010-03-01

Dual-stream information processing proposes that reasoning is composed of two interacting processes: a fast, intuitive system (Stream 1) and a slower, more logical process (Stream 2). In non-patient controls, divergence of these streams may result in the experience of conflict, modulating decision-making towards Stream 2, and initiating a more thorough examination of the available evidence. In delusional schizophrenia patients, a failure of conflict to modulate decision-making towards Stream 2 may reduce the influence of contradictory evidence, resulting in a failure to correct erroneous beliefs. Delusional schizophrenia patients and non-patient controls completed a deductive reasoning task requiring logical validity judgments of two-part conditional statements. Half of the statements were characterized by a conflict between logical validity (Stream 2) and content believability (Stream 1). Patients were significantly worse than controls in determining the logical validity of both conflict and non-conflict conditional statements. This between groups difference was significantly greater for the conflict condition. The results are consistent with the hypothesis that delusional schizophrenia patients fail to use conflict to modulate towards Stream 2 when the two streams of reasoning arrive at incompatible judgments. This finding provides encouraging preliminary support for the Dual-Stream Modulation Failure model of delusion formation and maintenance. 2009 Elsevier Masson SAS. All rights reserved.

Intervention Mapping Approach in the Design of an Interactive Mobile Health Application to Improve Self-care in Heart Failure.

PubMed

Athilingam, Ponrathi; Clochesy, John M; Labrador, Miguel A

2018-02-01

Heart failure is a complex syndrome among older adults who may experience and interpret symptoms differently. These differences in symptom interpretation may influence decision-making in symptom management. A well-informed and motivated person may develop the knowledge and skills needed to successfully manage symptoms. Therefore, the patient-centered mobile health application HeartMapp was designed to engage patients with heart failure in self-care management by offering tailored alerts and feedback using mobile phones. The main objective of this article is to describe the six-step intervention mapping approach including (1) the initial needs assessment, (2) proximal program objective, (3) selection of theory-based methods, (4) the translation of objectives into an actual program plan for mobile health intervention, (5) adaptation and implementation plan, and (6) evaluation plan that assisted the team in the development of a conceptual framework and intervention program matrix during the development of HeartMapp. The HeartMapp intervention takes the information, motivation, and behavioral skills model as the theoretical underpinning, with "patient engagement" as the key mediator in achieving targeted and persistent self-care behavioral changes in patients with heart failure. The HeartMapp intervention is proposed to improve self-care management and long-term outcomes.

High-Dose Methylprednisolone for Veno-Occlusive Disease of the Liver in Pediatric Hematopoietic Stem Cell Transplantation Recipients

PubMed Central

Myers, Kasiani C.; Lawrence, Julia; Marsh, Rebecca A.; Davies, Stella M.; Jodele, Sonata

2017-01-01

Veno-occlusive disease (VOD) of the liver is a well-recognized serious complication of hematopoietic stem cell transplantation (HSCT), with few successful treatment modalities available for severe disease. Some reports have demonstrated success in adults with the use of high-dose steroid therapy, but experience in the pediatric population is lacking. We retrospectively reviewed HSCT patients treated at our institution since 2003 and identified 15 (2.4%) who developed VOD. Of these, nine (60%) were treated with intravenous high-dose methylprednisolone (500 mg/m2 per dose every 12 hours for six doses). Steroid therapy was initiated at or before first ultrasound evidence of reversal of portal venous flow and before meeting criteria for initiation of defibrotide therapy. Four patients were also treated with defibrotide starting 2 to 5 days after initiation of steroids. Eight of nine patients (88%) with VOD were diagnosed with multiorgan failure. Response to high-dose steroid therapy as defined by decrease in bilirubin by 50% in 10 days from therapy initiation was noted in six of nine patients (67%), occurring within 3 to 6 days of steroid therapy. Two patients died from multiorgan failure due to VOD. Seven survivors of VOD recovered at the median 6 days (range, 5 to 38) from VOD diagnosis. Overall, VOD survival as a group was 78%; however, survival among responders was 100%. No serious toxicities related to high-dose steroid therapy were observed. We conclude that high-dose steroid therapy if initiated early may reverse VOD of the liver in pediatric HSCT patients, abrogating the need for defibrotide therapy with its associated toxicities and regulatory difficulties. PMID:23211838

Nonlinear fracture mechanics-based analysis of thin wall cylinders

NASA Technical Reports Server (NTRS)

Brust, Frederick W.; Leis, Brian N.; Forte, Thomas P.

1994-01-01

This paper presents a simple analysis technique to predict the crack initiation, growth, and rupture of large-radius, R, to thickness, t, ratio (thin wall) cylinders. The method is formulated to deal both with stable tearing as well as fatigue mechanisms in applications to both surface and through-wall axial cracks, including interacting surface cracks. The method can also account for time-dependent effects. Validation of the model is provided by comparisons of predictions to more than forty full scale experiments of thin wall cylinders pressurized to failure.

Predicatbility of windstorm Klaus; sensitivity to PV perturbations

NASA Astrophysics Data System (ADS)

Arbogast, P.; Maynard, K.

2010-09-01

It appears that some short-range weather forecast failures may be attributed to initial conditions errors. In some cases it is possible to anticipate the behavior of the model by comparison between observations and model analyses. In the case of extratropical cyclone development one may qualify the representation of the upper-level precursors described in terms of PV in the initial conditions by comparison with either satellite ozone or water-vapor. A step forward has been made in developing a tool based upon manual modifications of dynamical tropopause (i.e. height of 1.5 PV units) and PV inversion. After five years of experimentations it turns out that the forecasters eventually succeed in improving the forecast of some strong cyclone development. However the present approach is subjective per se. To measure the subjectivity of the procedure a set of 15 experiments has been performed provided by 7 different people (senior forecasters and scientists involved in dynamical meteorology) in order to improve an initial state of the global model ARPEGE leading to a poor forecast of the wind storm Klaus (24 January 2009). This experiment reveals that the manually defined corrections present common features but also a large spread.

Numerical investigation of contact stresses for fretting fatigue damage initiation

NASA Astrophysics Data System (ADS)

Bhatti, N. A.; Abdel Wahab, M.

2017-05-01

Fretting fatigue phenomena occurs due to interaction between contacting bodies under application of cyclic and normal loads. In addition to environmental conditions and material properties, the response at the contact interface highly depends on the combination of applied loads. High stress concentration is present at the contact interface, which can start the damage nucleation process. At the culmination of nucleation process several micro cracks are initiated, ultimately leading to the structural failure. In this study, effect of ratio of tangential to normal load on contact stresses, slip amplitude and damage initiation is studied using finite element analysis. The results are evaluated for Ruiz parameter as it involves the slip amplitude which in an important factor in fretting fatigue conditions. It is observed that tangential to normal load ratio influences the stick zone size and damage initiation life. Furthermore, it is observed that tensile stress is the most important factor that drives the damage initiation to failure for the cases where failure occurs predominantly in mode I manner.

Experimental Durability Testing of 4H SiC JFET Integrated Circuit Technology at 727 C

NASA Technical Reports Server (NTRS)

Spry, David; Neudeck, Phil; Chen, Liangyu; Chang, Carl; Lukco, Dorothy; Beheim, Glenn M

2016-01-01

We have reported SiC integrated circuits (IC's) with two levels of metal interconnect that have demonstrated prolonged operation for thousands of hours at their intended peak ambient operational temperature of 500 C [1, 2]. However, it is recognized that testing of semiconductor microelectronics at temperatures above their designed operating envelope is vital to qualification. Towards this end, we previously reported operation of a 4H-SiC JFET IC ring oscillator on an initial fast thermal ramp test through 727 C [3]. However, this thermal ramp was not ended until a peak temperature of 880 C (well beyond failure) was attained. Further experiments are necessary to better understand failure mechanisms and upper temperature limit of this extreme-temperature capable 4H-SiC IC technology. Here we report on additional experimental testing of custom-packaged 4H-SiC JFET IC devices at temperatures above 500 C. In one test, the temperature was ramped and then held at 727 C, and the devices were periodically measured until electrical failure was observed. A 4H-SiC JFET on this chip electrically functioned with little change for around 25 hours at 727 C before rapid increases in device resistance caused failure. In a second test, devices from our next generation 4H-SiC JFET ICs were ramped up and then held at 700 C (which is below the maximum deposition temperature of the dielectrics). Three ring oscillators functioned for 8 hours at this temperature before degradation. In a third experiment, an alternative die attach of gold paste and package lid was used, and logic circuit operation was demonstrated for 143.5 hours at 700 C.

Experimental Durability Testing of 4H SiC JFET Integrated Circuit Technology at 727 Degrees Centigrade

NASA Technical Reports Server (NTRS)

Spry, David J.; Neudeck, Philip G.; Chen, Liangyu; Chang, Carl W.; Lukco, Dorothy; Beheim, Glenn M.

2016-01-01

We have reported SiC integrated circuits (ICs) with two levels of metal interconnect that have demonstrated prolonged operation for thousands of hours at their intended peak ambient operational temperature of 500 degrees Centigrade. However, it is recognized that testing of semiconductor microelectronics at temperatures above their designed operating envelope is vital to qualification. Towards this end, we previously reported operation of a 4H-SiC JFET IC ring oscillator on an initial fast thermal ramp test through 727 degrees Centigrade. However, this thermal ramp was not ended until a peak temperature of 880 degrees Centigrade (well beyond failure) was attained. Further experiments are necessary to better understand failure mechanisms and upper temperature limit of this extreme-temperature capable 4H-SiC IC technology.Here we report on additional experimental testing of custom-packaged 4H-SiC JFET IC devices at temperatures above 500 degrees Centigrade. In one test, the temperature was ramped and then held at 727 degrees Centigrade, and the devices were periodically measured until electrical failure was observed. A 4H-SiC JFET on this chip electrically functioned with little change for around 25 hours at 727 degrees Centigrade before rapid increases in device resistance caused failure. In a second test, devices from our next generation 4H-SiC JFET ICs were ramped up and then held at 700 degrees Centigrade (which is below the maximum deposition temperature of the dielectrics). Three ring oscillators functioned for 8 hours at this temperature before degradation. In a third experiment, an alternative die attach of gold paste and package lid was used, and logic circuit operation was demonstrated for 143.5 hours at 700 degrees Centigrade.

Liver transplantation in Greek children: 15 years experience

PubMed Central

Xinias, Ioannis; Mavroudi, Antigoni; Vrani, Olga; Imvrios, Georgios; Takoudas, Dimitrios; Spiroglou, Kleomenis

2010-01-01

Liver transplantation (LT) is the only available live-saving procedure for children with irreversible liver failure. This paper reports our experience from the follow-up of 16 Greek children with end-stage liver failure who underwent a LT. Over a period of 15 years, 16 pediatric liver recipients received follow up after being subjected to OLT (orthotopic liver transplantation) due to end-stage liver failure. Nine children initially presented with extrahepatic biliary atresia, 2 with acute liver failure after toxic mushroom ingestion, 2 with intrahepatic cholestasis, 2 with metabolic diseases and one with hepatoblastoma. Ten children received a liver transplant in the Organ Transplantation Unit of Aristotle University of Thessaloniki and the rest in other transplant centers. Three transplants came from a living-related donor and 13 from a deceased donor. Six children underwent immunosuppressive treatment with cyclosporine, mycophenolate mofetil and corticosteroids, and 7 with tacrolimus, mycophenolate mofetil and corticosteroids. Three out of 16 children died within the first month after the transplantation due to post-transplant complications. Three children presented with acute rejection and one with chronic organ rejection which was successfully managed. Five children presented with cytomegalovirus infection, 5 with Epstein-Barr virus, 2 with HSV1,2, 2 with ParvoB19 virus, 2 with varicella-zoster virus and one with C. Albicans infection. One child presented with upper gastrointestinal hemorrhage and one with small biliary paucity. A satisfying outcome was achieved in most cases, with good graft function, except for the patient with small biliary paucity who required re-transplantation. The long-term clinical course of liver transplanted children is good under the condition that they are attended in specialized centers. PMID:21589827

Epicure: a European epidemiological study of patients with an advanced or metastatic Urothelial Carcinoma (UC) having progressed to a platinum-based chemotherapy.

PubMed

Houédé, N; Locker, G; Lucas, C; Parra, H Soto; Basso, U; Spaeth, D; Tambaro, R; Basterretxea, L; Morelli, F; Theodore, C; Lusuardi, L; Lainez, N; Guillot, A; Tonini, G; Bielle, J; Del Muro, X Garcia

2016-09-23

Platinum-based systemic chemotherapy is considered the backbone for management of advanced urothelial carcinomas. However there is a lack of real world data on the use of such chemotherapy regimens, on patient profiles and on management after treatment failure. Fifty-one randomly selected physicians from 4 European countries registered 218 consecutive patients in progression or relapse following a first platinum-based chemotherapy. Patient characteristics, tumor history and treatment regimens, as well as the considerations of physicians on the management of urothelial carcinoma were recorded. A systemic platinum-based regimen had been administered as the initial chemotherapy in 216 patients: 15 in the neoadjuvant setting, 61 in adjuvant therapy conditions, 137 in first-line advanced setting and 3 in other conditions. Of these patients, 76 (35 %) were initially considered as cisplatin-unfit, mainly because of renal impairment (52 patients). After platinum failure, renal impairment was observed in 44 % of patients, ECOG Performance Status ≥ 2 in 17 %, hemoglobinemia < 10 g/dL in 16 %, hepatic metastases in 13 %. 80 % of these patients received further anticancer therapy. Immediately after failure of adjuvant/neoadjuvant chemotherapy, most subsequent anticancer treatments were chemotherapy doublets (35/58), whereas after therapy failure in the advanced setting most patients receiving further anticancer drugs were treated with a single agent (80/114). After first progression to chemotherapy, treatment decisions were mainly driven by Performance Status and prior response to chemotherapy (>30 % patients). The most frequent all-settings second anticancer therapy regimen was vinflunine (70 % of single-agent and 42 % of all subsequent treatments), the main reasons evoked by physicians (>1 out of 4) being survival benefit, safety and phase III evidence. In this daily practice experience, a majority of patients with urothelial carcinoma previously treated with a platinum-based therapy received a second chemotherapy regimen, most often a single agent after an initial chemotherapy in the advanced setting and preferably a cytotoxic combination after a neoadjuvant or adjuvant chemotherapy. Performance Status and prior response to chemotherapy were the main drivers of further treatment decisions.

Earthquake Prediction in Large-scale Faulting Experiments

NASA Astrophysics Data System (ADS)

Junger, J.; Kilgore, B.; Beeler, N.; Dieterich, J.

2004-12-01

We study repeated earthquake slip of a 2 m long laboratory granite fault surface with approximately homogenous frictional properties. In this apparatus earthquakes follow a period of controlled, constant rate shear stress increase, analogous to tectonic loading. Slip initiates and accumulates within a limited area of the fault surface while the surrounding fault remains locked. Dynamic rupture propagation and slip of the entire fault surface is induced when slip in the nucleating zone becomes sufficiently large. We report on the event to event reproducibility of loading time (recurrence interval), failure stress, stress drop, and precursory activity. We tentatively interpret these variations as indications of the intrinsic variability of small earthquake occurrence and source physics in this controlled setting. We use the results to produce measures of earthquake predictability based on the probability density of repeating occurrence and the reproducibility of near-field precursory strain. At 4 MPa normal stress and a loading rate of 0.0001 MPa/s, the loading time is ˜25 min, with a coefficient of variation of around 10%. Static stress drop has a similar variability which results almost entirely from variability of the final (rather than initial) stress. Thus, the initial stress has low variability and event times are slip-predictable. The variability of loading time to failure is comparable to the lowest variability of recurrence time of small repeating earthquakes at Parkfield (Nadeau et al., 1998) and our result may be a good estimate of the intrinsic variability of recurrence. Distributions of loading time can be adequately represented by a log-normal or Weibel distribution but long term prediction of the next event time based on probabilistic representation of previous occurrence is not dramatically better than for field-observed small- or large-magnitude earthquake datasets. The gradually accelerating precursory aseismic slip observed in the region of nucleation in these experiments is consistent with observations and theory of Dieterich and Kilgore (1996). Precursory strains can be detected typically after 50% of the total loading time. The Dieterich and Kilgore approach implies an alternative method of earthquake prediction based on comparing real-time strain monitoring with previous precursory strain records or with physically-based models of accelerating slip. Near failure, time to failure t is approximately inversely proportional to precursory slip rate V. Based on a least squares fit to accelerating slip velocity from ten or more events, the standard deviation of the residual between predicted and observed log t is typically 0.14. Scaling these results to natural recurrence suggests that a year prior to an earthquake, failure time can be predicted from measured fault slip rate with a typical error of 140 days, and a day prior to the earthquake with a typical error of 9 hours. However, such predictions require detecting aseismic nucleating strains, which have not yet been found in the field, and on distinguishing earthquake precursors from other strain transients. There is some field evidence of precursory seismic strain for large earthquakes (Bufe and Varnes, 1993) which may be related to our observations. In instances where precursory activity is spatially variable during the interseismic period, as in our experiments, distinguishing precursory activity might be best accomplished with deep arrays of near fault instruments and pattern recognition algorithms such as principle component analysis (Rundle et al., 2000).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kashiwa, Bryan Andrew; Hull, Lawrence Mark

Highlights of recent phenomenological studies of metal failure are given. Failure leading to spallation and fragmentation are typically of interest. The current ‘best model’ includes the following; a full history stress in tension; nucleation initiating dynamic relaxation; toward a tensile yield function; failure dependent on strain, strain rate, and temperature; a mean-preserving ‘macrodefect’ is introduced when failure occurs in tension; and multifield theoretical refinements

Da Vinci robot error and failure rates: single institution experience on a single three-arm robot unit of more than 700 consecutive robot-assisted laparoscopic radical prostatectomies.

PubMed

Zorn, Kevin C; Gofrit, Ofer N; Orvieto, Marcelo A; Mikhail, Albert A; Galocy, R Matthew; Shalhav, Arieh L; Zagaja, Gregory P

2007-11-01

Previous reports have suggested that a 2% to 5% device failure rate (FR) be quoted when counseling patients about robot-assisted laparoscopic radical prostatectomy (RLRP). We sought to evaluate our FR on the da Vinci system. Since February 2003, more than 800 RLRPs have been performed at our institution using a single three-armed robotic unit. A prospective database was analyzed to determine the device FR and whether it resulted in case abortion or open conversion. Intuitive Surgical Systems provided data concerning the system's performance, including its fault rate. Error messages were classified as recoverable and non-recoverable faults. Between February 2003 and November 2006, 725 RLRP cases were available for evaluation. There were no intraoperative device failures that resulted in a case conversion. Technical errors resulting in surgeon handicap occurred in 3 cases (0.4%). Four patients (0.5%) had their procedures aborted secondary to system failure at initial set-up prior to patient entrance to the operating room. Data analysis retrieved from the da Vinci console reported on a total of 807 procedures since 2003. Only 4 cases (0.4%) were reported from the Intuitive Surgical database to result in either an aborted or a converted case, which compares favorably with our results. Since the last computer system upgrade (September 2005), the mean recoverable and non-recoverable fault rates per procedure were 0.21 and 0.05, respectively. For all the advanced features the da Vinci system offers, it is surprisingly reliable. Throughout our RLRP experience, device failure resulted in case conversion, procedure abortion, and surgeon handicap in 0, 0.5%, and 0.4% of procedures, respectively. As such, a lowered device FR of 0.5% should be used when counseling patients undergoing RLRP. To avoid futile general anesthesia, a policy should be enforced to ensure that the da Vinci system is completely set up before the patient enters the operating room.

Laboratory and 3-D distinct element analysis of the failure mechanism of a slope under external surcharge

NASA Astrophysics Data System (ADS)

Li, N.; Cheng, Y. M.

2015-01-01

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

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

NASA Astrophysics Data System (ADS)

Li, N.; Cheng, Y. M.

2014-09-01

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

Combined mechanical loading of composite tubes

NASA Technical Reports Server (NTRS)

Derstine, Mark S.; Pindera, Marek-Jerzy; Bowles, David E.

1988-01-01

An analytical/experimental investigation was performed to study the effect of material nonlinearities on the response of composite tubes subjected to combined axial and torsional loading. The effect of residual stresses on subsequent mechanical response was included in the investigation. Experiments were performed on P75/934 graphite-epoxy tubes with a stacking sequence of (15/0/ + or - 10/0/ -15), using pure torsion and combined axial/torsional loading. In the presence of residual stresses, the analytical model predicted a reduction in the initial shear modulus. Experimentally, coupling between axial loading and shear strain was observed in laminated tubes under combined loading. The phenomenon was predicted by the nonlinear analytical model. The experimentally observed linear limit of the global shear response was found to correspond to the analytically predicted first ply failure. Further, the failure of the tubes was found to be path dependent above a critical load level.

Elasticity, strength, and toughness of single crystal silicon carbide, ultrananocrystalline diamond, and hydrogen-free tetrahedral amorphous carbon

NASA Astrophysics Data System (ADS)

Espinosa, H. D.; Peng, B.; Moldovan, N.; Friedmann, T. A.; Xiao, X.; Mancini, D. C.; Auciello, O.; Carlisle, J.; Zorman, C. A.; Merhegany, M.

2006-08-01

In this work, the authors report the mechanical properties of three emerging materials in thin film form: single crystal silicon carbide (3C-SiC), ultrananocrystalline diamond, and hydrogen-free tetrahedral amorphous carbon. The materials are being employed in micro- and nanoelectromechanical systems. Several reports addressed some of the mechanical properties of these materials but they are based in different experimental approaches. Here, they use a single testing method, the membrane deflection experiment, to compare these materials' Young's moduli, characteristic strengths, fracture toughnesses, and theoretical strengths. Furthermore, they analyze the applicability of Weibull theory [Proc. Royal Swedish Inst. Eng. Res. 153, 1 (1939); ASME J. Appl. Mech. 18, 293 (1951)] in the prediction of these materials' failure and document the volume- or surface-initiated failure modes by fractographic analysis. The findings are of particular relevance to the selection of micro- and nanoelectromechanical systems materials for various applications of interest.

Development of a Distributed Crack Sensor Using Coaxial Cable.

PubMed

Zhou, Zhi; Jiao, Tong; Zhao, Peng; Liu, Jia; Xiao, Hai

2016-07-29

Cracks, the important factor of structure failure, reflect structural damage directly. Thus, it is significant to realize distributed, real-time crack monitoring. To overcome the shortages of traditional crack detectors, such as the inconvenience of installation, vulnerability, and low measurement range, etc., an improved topology-based cable sensor with a shallow helical groove on the outside surface of a coaxial cable is proposed in this paper. The sensing mechanism, fabrication method, and performances are investigated both numerically and experimentally. Crack monitoring experiments of the reinforced beams are also presented in this paper, illustrating the utility of this sensor in practical applications. These studies show that the sensor can identify a minimum crack width of 0.02 mm and can measure multiple cracks with a spatial resolution of 3 mm. In addition, it is also proved that the sensor performs well to detect the initiation and development of cracks until structure failure.

Development of a Distributed Crack Sensor Using Coaxial Cable

PubMed Central

Zhou, Zhi; Jiao, Tong; Zhao, Peng; Liu, Jia; Xiao, Hai

2016-01-01

Cracks, the important factor of structure failure, reflect structural damage directly. Thus, it is significant to realize distributed, real-time crack monitoring. To overcome the shortages of traditional crack detectors, such as the inconvenience of installation, vulnerability, and low measurement range, etc., an improved topology-based cable sensor with a shallow helical groove on the outside surface of a coaxial cable is proposed in this paper. The sensing mechanism, fabrication method, and performances are investigated both numerically and experimentally. Crack monitoring experiments of the reinforced beams are also presented in this paper, illustrating the utility of this sensor in practical applications. These studies show that the sensor can identify a minimum crack width of 0.02 mm and can measure multiple cracks with a spatial resolution of 3 mm. In addition, it is also proved that the sensor performs well to detect the initiation and development of cracks until structure failure. PMID:27483280

High Pressure Coolant Injection (HPCI) System Risk-Based Inspection Guide for Browns Ferry Nuclear Power Station

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wong, S.; DiBiasio, A.; Gunther, W.

1993-09-01

The High Pressure Coolant Injection (HPCI) system has been examined from a risk perspective. A System Risk-Based Inspection Guide (S-RIG) has been developed as an aid to HPCI system inspections at the Browns Ferry Nuclear Power Plant, Units 1, 2 and 3. The role of. the HPCI system in mitigating accidents is discussed in this S-RIG, along with insights on identified risk-based failure modes which could prevent proper operation of the system. The S-RIG provides a review of industry-wide operating experience, including plant-specific illustrative examples to augment the PRA and operational considerations in identifying a catalogue of basic PRA failuremore » modes for the HPCI system. It is designed to be used as a reference for routine inspections, self-initiated safety system functional inspections (SSFIs), and the evaluation of risk significance of component failures at the nuclear power plant.« less

The Oxford unicompartmental knee fails at a high rate in a high-volume knee practice.

PubMed

Schroer, William C; Barnes, C Lowry; Diesfeld, Paul; LeMarr, Angela; Ingrassia, Rachel; Morton, Diane J; Reedy, Mary

2013-11-01

The Oxford knee is a unicompartmental implant featuring a mobile-bearing polyethylene component with excellent long-term survivorship results reported by the implant developers and early adopters. By contrast, other studies have reported higher revision rates in large academic practices and in national registries. Registry data have shown increased failure with this implant especially by lower-volume surgeons and institutions. In the setting of a high-volume knee arthroplasty practice, we sought to determine (1) the failure rate of the Oxford unicompartmental knee implant using a failure definition for aseptic loosening that combined clinical features, plain radiographs, and scintigraphy, and (2) whether increased experience with this implant would decrease failure rate, if there is a learning curve effect. Eighty-three Oxford knee prostheses were implanted between September 2005 and July 2008 by the principal investigator. Radiographic and clinical data were available for review for all cases. A failed knee was defined as having recurrent pain after an earlier period of recovery from surgery, progressive radiolucent lines compared with initial postoperative radiographs, and a bone scan showing an isolated area of uptake limited to the area of the replaced compartment. Eleven knees in this series failed (13%); Kaplan-Meier survivorship was 86.5% (95% CI, 78.0%-95.0%) at 5 years. Failure occurrences were distributed evenly over the course of the study period. No learning curve effect was identified. Based on these findings, including a high failure rate of the Oxford knee implant and the absence of any discernible learning curve effect, the principal investigator no longer uses this implant.

Implementing quality initiatives in healthcare organizations: drivers and challenges.

PubMed

Abdallah, Abdallah

2014-01-01

Various quality initiatives seem to have successful implementation in some healthcare organizations yet fail in others. This paper sets out to study the literature trying to understand drivers and challenges facing quality initiatives implementation in healthcare organizations then compare findings from literature with those of a structured questionnaire answered by 60 representatives from 18 hospitals. Finally it proposes a framework that mitigates challenges and utilizes drivers to ensure best implementation results. Literature regarding implementing various quality initiatives in the healthcare sector was reviewed. Representatives from several healthcare organizations were surveyed. Results from both approaches are compared to highlight the key challenges and drivers facing implementers. This research reveals that internal factors related to leadership and employees greatly affect quality initiative success or failure. Design and relevance play a major role in successful implementation. PRACTICAL IMPLICATIONs: This research offers healthcare professionals greater success when implementing certain quality initiatives by taking success/failure factors into consideration. A general framework for successful implementation in the healthcare sector is provided. This article uncovers reasons behind success or failure in a comprehensive and practical way. It also explores how most popular quality initiatives are applied in hospitals.

Continuing Climate Warming Will Result in Failure of Post-Harvest Natural Regeneration across the Landscape in Interior Alaska

NASA Astrophysics Data System (ADS)

Morimoto, M.; Juday, G. P.; Huettmann, F.

2016-12-01

Following forest disturbance, the stand initiation stage decisively influences future forest structure. Understanding post-harvest regeneration, especially under climate change, is essential to predicting future carbon stores in this extensive forest biome. We apply IPCC B1, A1B, and A2 climate scenarios to generate plausible future forest conditions under different management. We recorded presence of white spruce, birch, and aspen in 726 plots on 30 state forest white spruce harvest units. We built spatially explicit models and scenarios of species presence/absence using TreeNet (Stochastic Gradient Boosting). Post-harvest tree regeneration predictions in calibration data closely matched the validation set, indicating tree regeneration scenarios are reliable. Early stage post-harvest regeneration is similar to post-fire regeneration and matches the pattern of long-term natural vegetation distribution, confirming that site environmental factors are more important than management practices. Post-harvest natural regeneration of tree species increases under moderate warming scenarios, but fails under strong warming scenarios in landscape positions with high temperatures and low precipitation. Under all warming scenarios, the most successful regenerating species following white spruce harvest is white spruce. Birch experiences about 30% regeneration failure under A2 scenario by 2050. White spruce and aspen are projected to regenerate more successfully when site preparation is applied. Although white spruce has been the major managed species, birch may require more intensive management. Sites likely to experience regeneration failure of current tree species apparently will experience biome shift, although adaptive migration of existing or new species might be an option. Our scenario modeling tool allows resource managers to forecast tree regeneration on productive managed sites that have made a disproportionate contribution to carbon flux in a critical region.

A prospective observational cohort study in primary care practices to identify factors associated with treatment failure in Staphylococcus aureus skin and soft tissue infections.

PubMed

Lee, Grace C; Hall, Ronald G; Boyd, Natalie K; Dallas, Steven D; Du, Liem C; Treviño, Lucina B; Treviño, Sylvia B; Retzloff, Chad; Lawson, Kenneth A; Wilson, James; Olsen, Randall J; Wang, Yufeng; Frei, Christopher R

2016-11-22

The incidence of outpatient visits for skin and soft tissue infections (SSTIs) has substantially increased over the last decade. The emergence of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has made the management of S. aureus SSTIs complex and challenging. The objective of this study was to identify risk factors contributing to treatment failures associated with community-associated S. aureus skin and soft tissue infections SSTIs. This was a prospective, observational study among 14 primary care clinics within the South Texas Ambulatory Research Network. The primary outcome was treatment failure within 90 days of the initial visit. Univariate associations between the explanatory variables and treatment failure were examined. A generalized linear mixed-effect model was developed to identify independent risk factors associated with treatment failure. Overall, 21% (22/106) patients with S. aureus SSTIs experienced treatment failure. The occurrence of treatment failure was similar among patients with methicillin-resistant S. aureus and those with methicillin-susceptible S. aureus SSTIs (19 vs. 24%; p = 0.70). Independent predictors of treatment failure among cases with S. aureus SSTIs was a duration of infection of ≥7 days prior to initial visit [aOR, 6.02 (95% CI 1.74-19.61)] and a lesion diameter size ≥5 cm [5.25 (1.58-17.20)]. Predictors for treatment failure included a duration of infection for ≥7 days prior to the initial visit and a wound diameter of ≥5 cm. A heightened awareness of these risk factors could help direct targeted interventions in high-risk populations.

Methicillin-Resistant Staphylococcus aureus in Foot Osteomyelitis.

PubMed

Ashong, Chester N; Raheem, Shazia A; Hunter, Andrew S; Mindru, Cezarina; Barshes, Neal R

Conflicting studies exist regarding the impact of methicillin-resistant Staphylococcus aureus (MRSA) on increased time to wound healing, future need for surgical procedures, and likelihood of treatment failure in patients with diabetic foot osteomyelitis. The purpose of this study is to determine the overall significance of MRSA in predicting treatment failure in bone infections of the foot and to determine an appropriate pre-operative and empiric post-operative antibiotic regimen. Patients presenting with an initial episode of "probable" or "definite" foot osteomyelitis were included for review and analysis if the following criteria were met: (1) Osteomyelitis occurred in the foot (i.e., distal to the malleoli of the ankle); episodes occurring above the ankle were excluded. (2) Patients received either no antibiotics or only oral antibiotics for long-term treatment; episodes managed with long-term parenteral antibiotics were excluded. (3) The infection was managed initially with medical therapy or conservative surgical therapy; episodes managed with major (above-ankle) amputation as the initial treatment were excluded. The primary objective of this study was to assess whether episodes of foot osteomyelitis associated with MRSA resulted in treatment failure more frequently than not. Of 178 episodes included in the study, 50 (28.1%) episodes had treatment failure. Median time-to-treatment failure was 60 days (range 7-598 days). In 28.1% (9/32 episodes) in which treatment failure occurred and 39.0% (41/105) episodes in which no treatment failure occurred, MRSA was present. The presence of MRSA was not significantly associated with treatment failure (p = 0.99). The presence of MRSA in bone culture and whether antibiotic use had anti-MRSA activity was not associated with increased treatment failure of diabetic foot osteomyelitis in our institution. Empiric antibiotic coverage of MRSA may not be necessary for many patients presenting with foot osteomyelitis.

Reactive flow calibration for diaminoazoxyfurazan (DAAF) and comparison with experiment

NASA Astrophysics Data System (ADS)

Johnson, Carl; Francois, Elizabeth Green; Morris, John

2012-03-01

Diaminoazoxyfurazan (DAAF) has a number of desirable properties; it is sensitive to shock while being insensitive to initiation by low level impact or friction, it has a small failure diameter, and its manufacturing process is inexpensive with minimal environmental impact. In light of its unique properties, DAAF based materials have gained interest for possible applications in insensitive munitions. In order to facilitate hydrocode modeling of DAAF and DAAF based formulations, we have developed a set of reactive flow parameters which were calibrated using published experimental data as well as recent experiments at LANL. Hydrocode calculations using the DAAF reactive flow parameters developed in the course of this work were compared to rate stick experiments, small scale gap tests, as well as the Onionskin experiment. Hydrocode calculations were compared directly to streak image results using numerous tracer points in conjunction with an external algorithm to match the data sets. The calculations display a reasonable agreement with experiment with the exception of effects related to shock desensitization of explosive.

Dynamic Response of Monolithic and Laminate/Particulate Reactive Mixtures

NASA Astrophysics Data System (ADS)

Wei, Chung-Ting

Two dynamic compression methods were applied to a monolithic metal and reactive mixtures to investigate their responses: (a) Dynamic experiments using a split Hopkinson pressure bar were applied to reactive mixtures densified by explosive consolidation in order to establish their mechanical response and failure mechanisms. (b) Laser compression and release, which can impart high stresses, up to hundreds GPa, in times of nanoseconds and fractions thereof, was applied to establish the spalling strength of vanadium and the reaction threshold for Ni/Al laminates. The spallation and fragmentation exhibited by recovered mono- and poly-crystalline vanadium prove that the laser intensities and crystal structure play important roles in determining spall strength, fragmentation, and microstructural processes. Densified reactive mixtures with different microstructures (Ni, Mo, W, Nb and Ta with Al) were subjected to the quasi-static and dynamic strain rates. Two distinct failure mechanisms, axial splitting and shear failure, were observed in the recovered specimens. Axial splitting occurred when the bonding between the powders was poor; shear failure was primarily associated with extensive deformation of continuous Ta and Nb phases. Finite element simulations provided valuable information in interpreting the experimental results and predicting failure mechanisms akin to those observed. Ni/Al laminates were subjected to laser compression. The strain rates varied from 105 to 108 s-1, and the initial stress varied from 30 to ˜300 GPa. It is found the thickness of the lamellar and the interlaminar bonding strength are the two critical factors in determining mechanical failure. The intermetallic reaction leading to Ni3Al and NiAl were produced by the laser energies and laser pulse durations in direct laser shock experiments. Laser-driven compression was also applied to study the high temperature synthesis in nano-scale Ni/Al laminates with bilayer thickness 54 nm. Intermetallic phases, NiAl and NiAl 3, were found on the plasma stagnated laminates. However, the self-propagating high temperature synthesis (SHS) did not self-sustain in the micro-scale laminate because of the short duration of the pulse.

MEMS ultrasonic transducer for monitoring of steel structures

NASA Astrophysics Data System (ADS)

Jain, Akash; Greve, David W.; Oppenheim, Irving J.

2002-06-01

Ultrasonic methods can be used to monitor crack propagation, weld failure, or section loss at critical locations in steel structures. However, ultrasonic inspection requires a skilled technician, and most commonly the signal obtained at any inspection is not preserved for later use. A preferred technology would use a MEMS device permanently installed at a critical location, polled remotely, and capable of on-chip signal processing using a signal history. We review questions related to wave geometry, signal levels, flaw localization, and electromechanical design issues for microscale transducers, and then describe the design, characterization, and initial testing of a MEMS transducer to function as a detector array. The device is approximately 1-cm square and was fabricated by the MUMPS process. The chip has 23 sensor elements to function in a phased array geometry, each element containing 180 hexagonal polysilicon diaphragms with a typical leg length of 49 microns and an unloaded natural frequency near 3.5 MHz. We first report characterization studies including capacitance-voltage measurements and admittance measurements, and then report initial experiments using a conventional piezoelectric transducer for excitation, with successful detection of signals in an on-axis transmission experiment and successful source localization from phased array performance in an off-axis transmission experiment.

Structural tests on space shuttle thermal protection system constructed with nondensified and densified Li 900 and LI 2200 tile

NASA Technical Reports Server (NTRS)

Williams, J. G.

1981-01-01

Structural tests were conducted on thermal protection systems (TPS) LI 900 and LI 2200 tiles and .41 cm and .23 cm thick strain isolation pads. The bond surface of selected tiles was densified to obtain improved strength. Four basic types of experiments were conducted including tension tests, substrate mismatch (initial imperfection) tests, tension loads eccentrically applied, and pressure loads applied rapidly to the tile top surface. A small initial imperfection mismatch (2.29 m spherical radius on the substrate) did not influence significantly the ultimate failure strength. Densification of the tile bond region improved the strength of TPS constructed both of LI 900 tile and of LI 2200 tile. Pressure shock conditions studied did not significantly affect the TPS strength.

When does a strategy intervention overcome a failure of inhibition? Evidence from two left frontal brain tumour cases.

PubMed

Robinson, Gail A; Walker, David G; Biggs, Vivien; Shallice, Tim

2016-06-01

Initiation and inhibition of responses are crucial for appropriate behaviour across different settings. Initiation and inhibition difficulties are well documented following frontal damage, although task differences have limited our understanding. The Hayling Sentence Completion Test was designed to assess verbal initiation and inhibition within the same task. This study investigates the ability of two patients with left frontal tumours (KI: high grade glioma; PM: meningioma) to use a strategy to overcome profound suppression failures on the Hayling Test. KI and PM completed the Hayling Test and two experimental tasks. The Selection Investigation assessed verbal initiation on a sentence completion task that varied selection demands (high/low). The Suppression and Strategy Investigation assessed ability to implement four strategies aimed to override a suppression failure and facilitate production of an unconnected word. On the Hayling Test, KI and PM initiated responses to complete high constraint sentences, in contrast to impaired suppression. KI benefitted minimally from strategies to overcome suppression failure although one strategy (object naming) was partially successful. KI's errors revealed fast suppression errors, in contrast to slow no responses, and selection ability was also impaired for verbal initiation. PM, however, implemented each strategy 100% to overcome a suppression failure and had no difficulty completing sentences meaningfully, regardless of selection demands. This first investigation of strategy implementation to overcome profound suppression impairments provides insights into verbal initiation, inhibition, selection and strategy mechanisms, which has implications for neurorehabilitation. Specifically, both patients had profound inhibition deficits but KI also presented with a selection deficit and was unable to implement a strategy. By contrast, PM's selection ability was intact but she was unable to generate, rather than implement, a strategy. We suggest that KI has both fast, uncontrolled semantic output and response inhibition difficulty, whereas PM's difficulty is underpinned by motivational factors. Copyright © 2016 Elsevier Ltd. All rights reserved.

An experimental study of compression failure of fibrous laminated composites in the presence of stress gradients

NASA Technical Reports Server (NTRS)

Waas, A. M.; Knauss, W. G.; Babcock, C. D., Jr.

1990-01-01

Mechanisms of failure in laminates in the presence of a stress raiser were experimentally studied. The damage initiation and propagation throughout the entire load history were examined via real-time holographic interferometry and photomicrography of the hole surface. Multilayered composite flat plates made of T300/BP907 and IM7/8551-7 were tested. It is shown that the failure is initiated as a localized instability in the 0-deg plies at the hole surface approximately at right angles to the loading direction. A series of events is described which culminates in the complete loss of flexural stiffness of each of the delaminated portions, leading to catastrophic failure of the plate.

An improved approach for flight readiness certification: Methodology for failure risk assessment and application examples. Volume 3: Structure and listing of programs

NASA Technical Reports Server (NTRS)

Moore, N. R.; Ebbeler, D. H.; Newlin, L. E.; Sutharshana, S.; Creager, M.

1992-01-01

An improved methodology for quantitatively evaluating failure risk of spaceflight systems to assess flight readiness and identify risk control measures is presented. This methodology, called Probabilistic Failure Assessment (PFA), combines operating experience from tests and flights with engineering analysis to estimate failure risk. The PFA methodology is of particular value when information on which to base an assessment of failure risk, including test experience and knowledge of parameters used in engineering analyses of failure phenomena, is expensive or difficult to acquire. The PFA methodology is a prescribed statistical structure in which engineering analysis models that characterize failure phenomena are used conjointly with uncertainties about analysis parameters and/or modeling accuracy to estimate failure probability distributions for specific failure modes. These distributions can then be modified, by means of statistical procedures of the PFA methodology, to reflect any test or flight experience. Conventional engineering analysis models currently employed for design of failure prediction are used in this methodology. The PFA methodology is described and examples of its application are presented. Conventional approaches to failure risk evaluation for spaceflight systems are discussed, and the rationale for the approach taken in the PFA methodology is presented. The statistical methods, engineering models, and computer software used in fatigue failure mode applications are thoroughly documented.

Sex Differences in Learned Helplessness: IV. An Experimental and Naturalistic Study of Failure Generalization and Its Mediators.

ERIC Educational Resources Information Center

And Others; Dweck, Carol S.

1980-01-01

Two experiments were conducted to examine the role of sex differences in learned helplessness in the generalization of failure experience. Subjects in experiment 1 were fifth graders and subjects in experiment 2 were fourth, fifth, and sixth graders. (MP)

On Deviations between Observed and Theoretically Estimated Values on Additivity-Law Failures

NASA Astrophysics Data System (ADS)

Nayatani, Yoshinobu; Sobagaki, Hiroaki

The authors have reported in the previous studies that the average observed results are about a half of the corresponding predictions on the experiments with large additivity-law failures. One of the reasons of the deviations is studied and clarified by using the original observed data on additivity-law failures in the Nakano experiment. The conclusion from the observations and their analyses clarified that it was essentially difficult to have a good agreement between the average observed results and the corresponding theoretical predictions in the experiments with large additivity-law failures. This is caused by a kind of unavoidable psychological pressure existing in subjects participated in the experiments. We should be satisfied with the agreement in trend between them.

The impact of initial antibiotic treatment failure: Real-world insights in healthcare-associated or nosocomial pneumonia.

PubMed

Ryan, Kellie; Karve, Sudeep; Peeters, Pascale; Baelen, Elisa; Potter, Danielle; Rojas-Farreras, Sonia; Pascual, Esther; Rodríguez-Baño, Jesús

2018-05-06

To assess real-world treatment patterns and clinical outcomes associated with initial antibiotic therapy (IAT, antibiotics received ≤ 48 h post-initiation of antibiotic therapy), including level of IAT failure, and potential risk factors for IAT failure in healthcare-associated infections. Data were obtained from medical records of adult patients hospitalized with healthcare-associated pneumonia (HCAP) and nosocomial pneumonia (NP), including ventilator-associated pneumonia, from 1 July 2013 to 30 June 2014 in Brazil, France, Italy, Russia and Spain during the retrospective, observational study, RECOMMEND (NCT02364284; D4280R00005). Potential risk factors for IAT failure were explored using logistic regression analyses. Mean (standard deviation) age and Deyo-Charlson Comorbidity Score were 66.0 (16.2) years and 2.4 (2.4), respectively (N = 451). Most patients (62.5%) received monotherapy. Mean (standard deviation) duration of IAT was 8.8 (7.2) days. Multidrug-resistant (MDR) pathogens were identified in 52.4% of patients with ≥ 1 pathogen isolated (154/294). IAT failure was recorded in 72.5% of patients and was significantly associated with isolation of a MDR pathogen and country using multivariate analyses. Real-world data demonstrate the burden of HCAP/NP, with high rates of IAT failure. The association of IAT failure with MDR pathogens highlights the urgent need to understand and account for local prevalence of MDR pathogens when selecting IAT for the management of HCAP/NP. Copyright © 2018. Published by Elsevier Ltd.

Antimicrobial treatment failures in patients with community-acquired pneumonia: causes and prognostic implications.

PubMed

Arancibia, F; Ewig, S; Martinez, J A; Ruiz, M; Bauer, T; Marcos, M A; Mensa, J; Torres, A

2000-07-01

The aim of the study was to determine the causes and prognostic implications of antimicrobial treatment failures in patients with nonresponding and progressive life-threatening, community-acquired pneumonia. Forty-nine patients hospitalized with a presumptive diagnosis of community-acquired pneumonia during a 16-mo period, failure to respond to antimicrobial treatment, and documented repeated microbial investigation >/= 72 h after initiation of in-hospital antimicrobial treatment were recorded. A definite etiology of treatment failure could be established in 32 of 49 (65%) patients, and nine additional patients (18%) had a probable etiology. Treatment failures were mainly infectious in origin and included primary, persistent, and nosocomial infections (n = 10 [19%], 13 [24%], and 11 [20%] of causes, respectively). Definite but not probable persistent infections were mostly due to microbial resistance to the administered initial empiric antimicrobial treatment. Nosocomial infections were particularly frequent in patients with progressive pneumonia. Definite persistent infections and nosocomial infections had the highest associated mortality rates (75 and 88%, respectively). Nosocomial pneumonia was the only cause of treatment failure independently associated with death in multivariate analysis (RR, 16.7; 95% CI, 1.4 to 194.9; p = 0.03). We conclude that the detection of microbial resistance and the diagnosis of nosocomial pneumonia are the two major challenges in hospitalized patients with community-acquired pneumonia who do not respond to initial antimicrobial treatment. In order to establish these potentially life-threatening etiologies, a regular microbial reinvestigation seems mandatory for all patients presenting with antimicrobial treatment failures.

[INTESTINAL FAILURE IN PEDIATRIC PATIENTS: EXPERIENCE AND MANAGEMENT BY A MULTIDISCIPLINARY GROUP].

PubMed

Giraldo Villa, Adriana; Martínez Volkmar, María Isabel; Valencia Quintero, Andrés Felipe; Montoya Delgado, Diana Catalina; Henao Roldan, Catherine; Ruiz Navas, Patricia; García Loboguerrero, Fanny; Contreras Ramírez, Mónica María

2015-12-01

institutions with multidisciplinary teams have shown improvements in patient outcomes with intestinal failure. Multidisciplinary approach allows an integral management and effective communication between families and care teams. describe the multidisciplinary management and outcome in pediatric patients with intestinal failure. retrospective study in patients 18 years old or less, with intestinal failure and Total Parenteral Nutrition (TPN) required. Simple frequencies and percentages were used for qualitative variables, and central tendency and dispersion measures were used for quantitative variables. 33 patients with a median follow up of 281 days were evaluated. The median duration of the TPN was 68 days and the mean of catheter-related infections was 2.26 per patient. In 31 patients oral or enteral nutrition was provided, starting in 61.3% of cases through tube and continuous infusion. As concomitant treatment 72.7% of children received ursodeoxycholic acid, 67.7%, cholestyramine 57.6% loperamide, 48.5% antibiotics and 36.4% probiotic. The families of 24 patients were evaluated by social work professionals. Intestinal autonomy was achieved in 69.7% of cases, 72.7% of them showed an improvement in the score z of weight and showed an end albumin significantly higher than the initial (p value: 0.012). the management of patients with intestinal failure is a challenge for health institutions and require care based on a standardized protocol and a multidisciplinary group. Copyright AULA MEDICA EDICIONES 2014. Published by AULA MEDICA. All rights reserved.

Translating and testing the ENABLE: CHF-PC concurrent palliative care model for older adults with heart failure and their family caregivers.

PubMed

Dionne-Odom, J Nicholas; Kono, Alan; Frost, Jennifer; Jackson, Lisa; Ellis, Daphne; Ahmed, Ali; Azuero, Andres; Bakitas, Marie

2014-09-01

Heart failure (HF) and palliative care (PC) organizations recommend early PC to improve the quality of life of patients living with HF. We conducted a two-phase formative evaluation study to translate a cancer-focused concurrent PC intervention into one that would be appropriate for rural-dwelling adults with New York Heart Association Class III-IV HF and their primary caregivers. Phase I: We tailored the intervention for an HF population via literature review, expert consultation, and clinician (N=15) small group interviews. Phase II: We enrolled 11 patient/caregiver dyads to assess intervention feasibility and satisfaction. We assessed participants' experiences and satisfaction after session/week three and session/week six via digitally recorded interviews. Clinician and participant interviews were transcribed and content analyzed. Outcome measures were evaluated for completion rates and effect sizes. Phase I: Clinicians described barriers to initiating PC in HF, triggers for initiating PC, and suggestions for intervention improvement. Phase II: Participants were able to complete the majority of study sessions, measures, and interviews. Satisfaction interviews revealed the content to be relevant and comprehensive in addressing HF patient and caregiver primary concerns; however, participants unanimously suggested making the intervention available earlier in the illness trajectory. Efficacy measures demonstrated small to medium effect sizes. We tailored and demonstrated feasibility of providing an early, concurrent palliative care intervention to patients with advanced HF and their caregivers. Based on this experience we are now conducting an efficacy trial in a racially diverse sample.

Examining Productive Failure, Productive Success, Unproductive Failure, and Unproductive Success in Learning

ERIC Educational Resources Information Center

Kapur, Manu

2016-01-01

Learning and performance are not always commensurable. Conditions that maximize performance in the initial learning may not maximize learning in the longer term. I exploit this incommensurability to theoretically and empirically interrogate four possibilities for design: productive success, productive failure, unproductive success, and…

Rates and determinants of early initiation of breastfeeding and exclusive breast feeding at 42 days postnatal in six low and middle-income countries: A prospective cohort study

PubMed Central

2015-01-01

Background Early initiation of breastfeeding after birth and exclusive breastfeeding through six months of age confers many health benefits for infants; both are crucial high impact, low-cost interventions. However, determining accurate global rates of these crucial activities has been challenging. We use population-based data to describe: (1) rates of early initiation of breastfeeding (defined as within 1 hour of birth) and of exclusive breastfeeding at 42 days post-partum; and (2) factors associated with failure to initiate early breastfeeding and exclusive breastfeeding at 42 days post-partum. Methods Prospectively collected data from women and their live-born infants enrolled in the Global Network’s Maternal and Newborn Health Registry between January 1, 2010-December 31, 2013 included women-infant dyads in 106 geographic areas (clusters) at 7 research sites in 6 countries (Kenya, Zambia, India [2 sites], Pakistan, Argentina and Guatemala). Rates and risk factors for failure to initiate early breastfeeding were investigated for the entire cohort and rates and risk factors for failure to maintain exclusive breastfeeding was assessed in a sub-sample studied at 42 days post-partum. Result A total of 255,495 live-born women-infant dyads were included in the study. Rates and determinants for the exclusive breastfeeding sub-study at 42 days post-partum were assessed from among a sub-sample of 105,563 subjects. Although there was heterogeneity by site, and early initiation of breastfeeding after delivery was high, the Pakistan site had the lowest rates of early initiation of breastfeeding. The Pakistan site also had the highest rate of lack of exclusive breastfeeding at 42 days post-partum. Across all regions, factors associated with failure to initiate early breastfeeding included nulliparity, caesarean section, low birth weight, resuscitation with bag and mask, and failure to place baby on the mother’s chest after delivery. Factors associated with failure to achieve exclusive breastfeeding at 42 days varied across the sites. The only factor significant in all sites was multiple gestation. Conclusions In this large, prospective, population-based, observational study, rates of both early initiation of breastfeeding and exclusive breastfeeding at 42 days post-partum were high, except in Pakistan. Factors associated with these key breastfeeding indicators should assist with more effective strategies to scale-up these crucial public health interventions. Trial registration Registration at the Clinicaltrials.gov website (ID# NCT01073475). PMID:26063291

Rates and determinants of early initiation of breastfeeding and exclusive breast feeding at 42 days postnatal in six low and middle-income countries: A prospective cohort study.

PubMed

Patel, Archana; Bucher, Sherri; Pusdekar, Yamini; Esamai, Fabian; Krebs, Nancy F; Goudar, Shivaprasad S; Chomba, Elwyn; Garces, Ana; Pasha, Omrana; Saleem, Sarah; Kodkany, Bhalachandra S; Liechty, Edward A; Kodkany, Bhala; Derman, Richard J; Carlo, Waldemar A; Hambidge, K; Goldenberg, Robert L; Althabe, Fernando; Berrueta, Mabel; Moore, Janet L; McClure, Elizabeth M; Koso-Thomas, Marion; Hibberd, Patricia L

2015-01-01

Early initiation of breastfeeding after birth and exclusive breastfeeding through six months of age confers many health benefits for infants; both are crucial high impact, low-cost interventions. However, determining accurate global rates of these crucial activities has been challenging. We use population-based data to describe: (1) rates of early initiation of breastfeeding (defined as within 1 hour of birth) and of exclusive breastfeeding at 42 days post-partum; and (2) factors associated with failure to initiate early breastfeeding and exclusive breastfeeding at 42 days post-partum. Prospectively collected data from women and their live-born infants enrolled in the Global Network's Maternal and Newborn Health Registry between January 1, 2010-December 31, 2013 included women-infant dyads in 106 geographic areas (clusters) at 7 research sites in 6 countries (Kenya, Zambia, India [2 sites], Pakistan, Argentina and Guatemala). Rates and risk factors for failure to initiate early breastfeeding were investigated for the entire cohort and rates and risk factors for failure to maintain exclusive breastfeeding was assessed in a sub-sample studied at 42 days post-partum. A total of 255,495 live-born women-infant dyads were included in the study. Rates and determinants for the exclusive breastfeeding sub-study at 42 days post-partum were assessed from among a sub-sample of 105,563 subjects. Although there was heterogeneity by site, and early initiation of breastfeeding after delivery was high, the Pakistan site had the lowest rates of early initiation of breastfeeding. The Pakistan site also had the highest rate of lack of exclusive breastfeeding at 42 days post-partum. Across all regions, factors associated with failure to initiate early breastfeeding included nulliparity, caesarean section, low birth weight, resuscitation with bag and mask, and failure to place baby on the mother's chest after delivery. Factors associated with failure to achieve exclusive breastfeeding at 42 days varied across the sites. The only factor significant in all sites was multiple gestation. In this large, prospective, population-based, observational study, rates of both early initiation of breastfeeding and exclusive breastfeeding at 42 days post-partum were high, except in Pakistan. Factors associated with these key breastfeeding indicators should assist with more effective strategies to scale-up these crucial public health interventions. Registration at the Clinicaltrials.gov website (ID# NCT01073475).

High Technology Systems with Low Technology Failures: Some Experiences with Rockets on Software Quality and Integration

NASA Technical Reports Server (NTRS)

Craig, Larry G.

2010-01-01

This slide presentation reviews three failures of software and how the failures contributed to or caused the failure of a launch or payload insertion into orbit. In order to avoid these systematic failures in the future, failure mitigation strategies are suggested for use.

Multiple Fatigue Failure Behaviors and Long-Life Prediction Approach of Carburized Cr-Ni Steel with Variable Stress Ratio

PubMed Central

Deng, Hailong; Li, Wei; Zhao, Hongqiao; Sakai, Tatsuo

2017-01-01

Axial loading tests with stress ratios R of −1, 0 and 0.3 were performed to examine the fatigue failure behavior of a carburized Cr-Ni steel in the long-life regime from 104 to 108 cycles. Results show that this steel represents continuously descending S-N characteristics with interior inclusion-induced failure under R = −1, whereas it shows duplex S-N characteristics with surface defect-induced failure and interior inclusion-induced failure under R = 0 and 0.3. The increasing tension eliminates the effect of compressive residual stress and promotes crack initiation from the surface or interior defects in the carburized layer. The FGA (fine granular area) formation greatly depends on the number of loading cycles, but can be inhibited by decreasing the compressive stress. Based on the evaluation of the stress intensity factor at the crack tip, the surface and interior failures in the short life regime can be characterized by the crack growth process, while the interior failure with the FGA in the long life regime can be characterized by the crack initiation process. In view of the good agreement between predicted and experimental results, the proposed approach can be well utilized to predict fatigue lives associated with interior inclusion-FGA-fisheye induced failure, interior inclusion-fisheye induced failure, and surface defect induced failure. PMID:28906454

Test and Analysis Correlation for a Y-Joint Specimen for a Composite Cryotank

NASA Technical Reports Server (NTRS)

Mason, Brian H.; Sleight, David W.; Grenoble, Ray

2015-01-01

The Composite Cryotank Technology Demonstration (CCTD) project under NASA's Game Changing Development Program (GCDP) developed space technologies using advanced composite materials. Under CCTD, NASA funded the Boeing Company to design and test a number of element-level joint specimens as a precursor to a 2.4-m diameter composite cryotank. Preliminary analyses indicated that the y-joint in the cryotank had low margins of safety; hence the y-joint was considered to be a critical design region. The y-joint design includes a softening strip wedge to reduce localized shear stresses at the skirt/dome interface. In this paper, NASA-developed analytical models will be correlated with the experimental results of a series of positive-peel y-joint specimens from Boeing tests. Initial analytical models over-predicted the experimental strain gage readings in the far-field region by approximately 10%. The over-prediction was attributed to uncertainty in the elastic properties of the laminate and a mismatch between the thermal expansion of the strain gages and the laminate. The elastic properties of the analytical model were adjusted to account for the strain gage differences. The experimental strain gages also indicated a large non-linear effect in the softening strip region that was not predicted by the analytical model. This non-linear effect was attributed to delamination initiating in the softening strip region at below 20% of the failure load for the specimen. Because the specimen was contained in a thermally insulated box during cryogenic testing to failure, delamination initiation and progression was not visualized during the test. Several possible failure initiation locations were investigated, and a most likely failure scenario was determined that correlated well with the experimental data. The most likely failure scenario corresponded to damage initiating in the softening strip and delamination extending to the grips at final failure.

30 CFR 722.13 - Failure to abate.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 3 2010-07-01 2010-07-01 false Failure to abate. 722.13 Section 722.13 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR INITIAL PROGRAM REGULATIONS ENFORCEMENT PROCEDURES § 722.13 Failure to abate. An authorized representative of the Secretary...

30 CFR 722.13 - Failure to abate.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 30 Mineral Resources 3 2013-07-01 2013-07-01 false Failure to abate. 722.13 Section 722.13 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR INITIAL PROGRAM REGULATIONS ENFORCEMENT PROCEDURES § 722.13 Failure to abate. An authorized representative of the Secretary...

30 CFR 722.13 - Failure to abate.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 30 Mineral Resources 3 2014-07-01 2014-07-01 false Failure to abate. 722.13 Section 722.13 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR INITIAL PROGRAM REGULATIONS ENFORCEMENT PROCEDURES § 722.13 Failure to abate. An authorized representative of the Secretary...

30 CFR 722.13 - Failure to abate.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 30 Mineral Resources 3 2011-07-01 2011-07-01 false Failure to abate. 722.13 Section 722.13 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR INITIAL PROGRAM REGULATIONS ENFORCEMENT PROCEDURES § 722.13 Failure to abate. An authorized representative of the Secretary...

30 CFR 722.13 - Failure to abate.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 30 Mineral Resources 3 2012-07-01 2012-07-01 false Failure to abate. 722.13 Section 722.13 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR INITIAL PROGRAM REGULATIONS ENFORCEMENT PROCEDURES § 722.13 Failure to abate. An authorized representative of the Secretary...

Constitutively Active Acetylcholine-Dependent Potassium Current Increases Atrial Defibrillation Threshold by Favoring Post-Shock Re-Initiation

PubMed Central

Bingen, Brian O.; Askar, Saïd F. A.; Neshati, Zeinab; Feola, Iolanda; Panfilov, Alexander V.; de Vries, Antoine A. F.; Pijnappels, Daniël A.

2015-01-01

Electrical cardioversion (ECV), a mainstay in atrial fibrillation (AF) treatment, is unsuccessful in up to 10–20% of patients. An important aspect of the remodeling process caused by AF is the constitutive activition of the atrium-specific acetylcholine-dependent potassium current (IK,ACh → IK,ACh-c), which is associated with ECV failure. This study investigated the role of IK,ACh-c in ECV failure and setting the atrial defibrillation threshold (aDFT) in optically mapped neonatal rat cardiomyocyte monolayers. AF was induced by burst pacing followed by application of biphasic shocks of 25–100 V to determine aDFT. Blocking IK,ACh-c by tertiapin significantly decreased DFT, which correlated with a significant increase in wavelength during reentry. Genetic knockdown experiments, using lentiviral vectors encoding a Kcnj5-specific shRNA to modulate IK,ACh-c, yielded similar results. Mechanistically, failed ECV was attributed to incomplete phase singularity (PS) removal or reemergence of PSs (i.e. re-initiation) through unidirectional propagation of shock-induced action potentials. Re-initiation occurred at significantly higher voltages than incomplete PS-removal and was inhibited by IK,ACh-c blockade. Whole-heart mapping confirmed our findings showing a 60% increase in ECV success rate after IK,ACh-c blockade. This study provides new mechanistic insight into failing ECV of AF and identifies IK,ACh-c as possible atrium-specific target to increase ECV effectiveness, while decreasing its harmfulness. PMID:26487066

The influence of temperature on brittle creep in sandstones

NASA Astrophysics Data System (ADS)

Heap, M. J.; Baud, P.; Meredith, P. G.; Vinciguerra, S.

2009-04-01

The characterization of time-dependent brittle rock deformation is fundamental to understanding the long-term evolution and dynamics of the Earth's upper crust. The presence of water promotes time-dependent deformation through environment-dependent stress corrosion cracking that allows rocks to deform at stresses far below their short-term failure stress. Here we report results from an experimental study of the influence of an elevated temperature on time-dependent brittle creep in water-saturated samples of Darley Dale (initial porosity of 13%), Bentheim (23%) and Crab Orchard (4%) sandstones. We present results from both conventional creep experiments (or ‘static fatigue' tests) and stress-stepping creep experiments performed under 20°C and 75°C and an effective confining pressure of 30 MPa (50 MPa confining pressure and a 20 MPa pore fluid pressure). The evolution of crack damage was monitored throughout each experiment by measuring the three proxies for damage (1) axial strain (2) pore volume change and (3) the output of AE energy. Conventional creep experiments have demonstrated that, for any given applied differential stress, the time-to-failure is dramatically reduced and the creep strain rate is significantly increased by application of an elevated temperature. Stress-stepping creep experiments have allowed us to investigate the influence of temperature in detail. Results from these experiments show that the creep strain rate for Darley Dale and Bentheim sandstones increases by approximately 3 orders of magnitude, and for Crab Orchard sandstone increases by approximately 2 orders of magnitude, as temperature is increased from 20°C to 75°C at a fixed effective differential stress. We discuss these results in the context of the different mineralogical and microstructural properties of the three rock types and the micro-mechanical and chemical processes operating on them.

Salvage Stereotactic Body Radiotherapy (SBRT) Following In-Field Failure of Initial SBRT for Spinal Metastases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thibault, Isabelle; Campbell, Mikki; Tseng, Chia-Lin

2015-10-01

Purpose: We report our experience in salvaging spinal metastases initially irradiated with stereotactic body radiation therapy (SBRT), who subsequently progressed with imaging-confirmed local tumor progression, and were re-irradiated with a salvage second SBRT course to the same level. Methods and Materials: From a prospective database, 56 metastatic spinal segments in 40 patients were identified as having been irradiated with a salvage second SBRT course to the same level. In addition, 24 of 56 (42.9%) segments had initially been irradiated with conventional external beam radiation therapy before the first course of SBRT. Local control (LC) was defined as no progression onmore » magnetic resonance imaging at the treated segment, and calculated according to the competing risk model. Overall survival (OS) was evaluated for each patient treated by use of the Kaplan-Meier method. Results: The median salvage second SBRT total dose and number of fractions was 30 Gy in 4 fractions (range, 20-35 Gy in 2-5 fractions), and for the first course of SBRT was 24 Gy in 2 fractions (range, 20-35 Gy in 1-5 fractions). The median follow-up time after salvage second SBRT was 6.8 months (range, 0.9-39 months), the median OS was 10.0 months, and the 1-year OS rate was 48%. A longer time interval between the first and second SBRT courses predicted for better OS (P=.02). The crude LC was 77% (43/56), the 1-year LC rate was 81%, and the median time to local failure was 3.0 months (range, 2.7-16.7 months). Of the 13 local failures, 85% (11/13) and 46% (6/13) showed progression within the epidural space and paraspinal soft tissues, respectively. Absence of baseline paraspinal disease predicted for better LC (P<.01). No radiation-induced vertebral compression fractures or cases of myelopathy were observed. Conclusion: A second course of spine SBRT, most often with 30 Gy in 4 fractions, for spinal metastases that failed initial SBRT is a feasible and efficacious salvage treatment option.« less

Leishmania Antigenuria to Predict Initial Treatment Failure and Relapse in Visceral Leishmaniasis/HIV Coinfected Patients: An Exploratory Study Nested Within a Clinical Trial in Ethiopia.

PubMed

van Griensven, Johan; Mengesha, Bewketu; Mekonnen, Tigist; Fikre, Helina; Takele, Yegnasew; Adem, Emebet; Mohammed, Rezika; Ritmeijer, Koert; Vogt, Florian; Adriaensen, Wim; Diro, Ermias

2018-01-01

Background: Biomarkers predicting the risk of VL treatment failure and relapse in VL/HIV coinfected patients are needed. Nested within a two-site clinical trial in Ethiopia (2011-2015), we conducted an exploratory study to assess whether (1) levels of Leishmania antigenuria measured at VL diagnosis were associated with initial treatment failure and (2) levels of Leishmania antigenuria at the end of treatment (parasitologically-confirmed cure) were associated with subsequent relapse. Methods: Leishmania antigenuria at VL diagnosis and cure was determined using KAtex urine antigen test and graded as negative (0), weak/moderate (grade 1+/2+) or strongly-positive (3+). Logistic regression and Kaplan-Meier methods were used to assess the association between antigenuria and (1) initial treatment failure, and (2) relapse over the 12 months after cure, respectively. Results: The analysis to predict initial treatment failure included sixty-three coinfected adults [median age: 30 years interquartile range (IQR) 27-35], median CD4 count: 56 cells/μL (IQR 38-113). KAtex results at VL diagnosis were negative in 11 (17%), weak/moderate in 17 (27%) and strongly-positive in 35 (36%). Twenty (32%) patients had parasitologically-confirmed treatment failure, with a risk of failure of 9% (1/11) with KAtex-negative results, 0% (0/17) for KAtex 1+/2+ and 54% (19/35) for KAtex 3+ results. Compared to KAtex-negative patients, KAtex 3+ patients were at increased risk of treatment failure [odds ratio 11.9 (95% CI 1.4-103.0); P : 0.025]. Forty-four patients were included in the analysis to predict relapse [median age: 31 years (IQR 28-35), median CD4 count: 116 cells/μL (IQR 95-181)]. When achieving VL cure, KAtex results were negative in 19 (43%), weak/moderate (1+/2+) in 10 (23%), and strongly positive (3+) in 15 patients (34%). Over the subsequent 12 months, eight out of 44 patients (18%) relapsed. The predicted 1-year relapse risk was 6% for KAtex-negative results, 14% for KAtex 1+/2+ and 42% for KAtex 3+ results [hazard ratio of 2.2 (95% CI 0.1-34.9) for KAtex 1+/2+ and 9.8 (95% CI 1.8-82.1) for KAtex 3+, compared to KAtex negative patients; P : 0.03]. Conclusion: A simple field-deployable Leishmania urine antigen test can be used for risk stratification of initial treatment failure and VL relapse in HIV-patients. A dipstick-format would facilitate field implementation.

Decision-making Processes among Prostate Cancer Survivors with Rising PSA Levels: Results from a Qualitative Analysis.

PubMed

Shen, Megan Johnson; Nelson, Christian J; Peters, Ellen; Slovin, Susan F; Hall, Simon J; Hall, Matt; Herrera, Phapichaya Chaoprang; Leventhal, Elaine A; Leventhal, Howard; Diefenbach, Michael A

2015-05-01

Prostate cancer survivors with a rising prostate-specific antigen (PSA) level have few treatment options, experience a heightened state of uncertainty about their disease trajectory that might include the possibility of cancer metastasis and death, and often experience elevated levels of distress as they have to deal with a disease they thought they had conquered. Guided by self-regulation theory, the present study examined the cognitive and affective processes involved in shared decision making between physicians and patients who experience a rising PSA after definitive treatment for prostate cancer. In-depth interviews were conducted with 34 prostate cancer survivors who had been diagnosed with a rising PSA (i.e., biochemical failure) within the past 12 months. Survivors were asked about their experiences and affective responses after being diagnosed with a rising PSA and while weighing potential treatment options. In addition, patients were asked about their decision-making process for the initial prostate cancer treatment. Compared with the initial diagnosis, survivors with a rising PSA reported increased negative affect following their diagnosis, concern about the treatability of their disease, increased planning and health behavior change, heightened levels of worry preceding doctor appointments (especially prior to the discussion of PSA testing results), and a strong reliance on physicians' treatment recommendations. Prostate cancer survivors' decision-making processes for the treatment of a rising PSA are markedly different from those of the initial diagnosis of prostate cancer. Because patients experience heightened distress and rely more heavily on their physicians' recommendations with a rising PSA, interactions with the health care provider provide an excellent opportunity to address and assist patients with managing the uncertainty and distress inherent with rising PSA levels. © The Author(s) 2014.

A Weibull distribution accrual failure detector for cloud computing.

PubMed

Liu, Jiaxi; Wu, Zhibo; Wu, Jin; Dong, Jian; Zhao, Yao; Wen, Dongxin

2017-01-01

Failure detectors are used to build high availability distributed systems as the fundamental component. To meet the requirement of a complicated large-scale distributed system, accrual failure detectors that can adapt to multiple applications have been studied extensively. However, several implementations of accrual failure detectors do not adapt well to the cloud service environment. To solve this problem, a new accrual failure detector based on Weibull Distribution, called the Weibull Distribution Failure Detector, has been proposed specifically for cloud computing. It can adapt to the dynamic and unexpected network conditions in cloud computing. The performance of the Weibull Distribution Failure Detector is evaluated and compared based on public classical experiment data and cloud computing experiment data. The results show that the Weibull Distribution Failure Detector has better performance in terms of speed and accuracy in unstable scenarios, especially in cloud computing.

Experimental study on deformation field evolution in rock sample with en echelon faults using digital speckle correlation method

NASA Astrophysics Data System (ADS)

Ma, S.; Ma, J.; Liu, L.; Liu, P.

2007-12-01

Digital speckle correlation method (DSCM) is one kind of photomechanical deformation measurement method. DSCM could obtain continuous deformation field contactlessly by just capturing speckle images from specimen surface. Therefore, it is suitable to observe high spatial resolution deformation field in tectonophysical experiment. However, in the general DSCM experiment, the inspected surface of specimen needs to be painted to bear speckle grains in order to obtain the high quality speckle image. This also affects the realization of other measurement techniques. In this study, an improved DSCM system is developed and utilized to measure deformation field of rock specimen without surface painting. The granodiorite with high contrast nature grains is chosen to manufacture the specimen, and a specially designed DSCM algorithm is developed to analyze this kind of nature speckle images. Verification and calibration experiments show that the system could inspect a continuous (about 15Hz) high resolution displacement field (with resolution of 5μm) and strain field (with resolution of 50μɛ), dispensing with any preparation on rock specimen. Therefore, it could be conveniently utilized to study the failure of rock structure. Samples with compressive en echelon faults and extensional en echelon faults are studied on a two-direction servo-control test machine. The failure process of the samples is discussed based on the DSCM results. Experiment results show that: 1) The contours of displacement field could clearly indicate the activities of faults and new cracks. The displacement gradient adjacent to active faults and cracks is much greater than other areas. 2) Before failure of the samples, the mean strain of the jog area is largest for the compressive en echelon fault, while that is smallest for the extensional en echelon fault. This consists with the understanding that the jog area of compressive fault subjects to compression and that of extensional fault subjects to tension. 3) For the extensional en echelon sample, the dislocation across fault on load-driving end is greater than that cross fault on fixed end. Within the same fault, the dislocation across branch far from the jog area is greater than that across branch near the jog area. This indicates the restriction effect of jog area on the activity of fault. Moreover, the average dislocation across faults is much greater than that across the cracks. 4) For the compressive en echelon fault, the wing cracks initialized firstly and propagate outwards the jog area. Subsequently, a wedge strain concentration area is initialized and developed in the jog area because of the interaction of the two faults. Finally, the jog area failed when one crack propagates rapidly and connects the two ends of faults. The DSCM system used in this study could clearly show the deformation and failure process of the en echelon fault sample. The experiment using DSCM could be performed dispensing with any preparation on specimen and not affecting other inspection. Therefore, DSCM is expected to be a suitable tool for experimental study of fault samples in laboratory.

Improving the Estimates of International Space Station (ISS) Induced K-Factor Failure Rates for On-Orbit Replacement Unit (ORU) Supportability Analyses

NASA Technical Reports Server (NTRS)

Anderson, Leif F.; Harrington, Sean P.; Omeke, Ojei, II; Schwaab, Douglas G.

2009-01-01

This is a case study on revised estimates of induced failure for International Space Station (ISS) on-orbit replacement units (ORUs). We devise a heuristic to leverage operational experience data by aggregating ORU, associated function (vehicle sub -system), and vehicle effective' k-factors using actual failure experience. With this input, we determine a significant failure threshold and minimize the difference between the actual and predicted failure rates. We conclude with a discussion on both qualitative and quantitative improvements the heuristic methods and potential benefits to ISS supportability engineering analysis.

Normotensive cardiomyopathy and malignant hypertension in phaeochromocytoma

PubMed Central

Shapiro, L. M.; Trethowan, N.; Singh, S. P.

1982-01-01

A patient with two different presentations of phaeochromocytoma is described. She initially presented with normal blood pressure and heart failure following a prolonged feverish prodrome. A provisional diagnosis of myocarditis or early congestive cardiomyopathy was made and she improved with digoxin and diuretics. Eighteen months later, after a period of normotension free from heart failure, she developed malignant hypertension with recurrence of heart failure. A phaeochromocytoma was surgically removed, with return to normal of blood pressure and cardiac status. It would seem that the initial presentation of the phaeochromocytoma was a catecholamine-induced myocarditis without hypertension and this resolved with the subsequent development of malignant hypertension. The possible mechanisms responsible for this are discussed and it is concluded that phaeochromocytoma should be considered in patients who have heart failure and persistent features of myocarditis. PMID:7100023

SURFplus Model Calibration for PBX 9502

DOE Office of Scientific and Technical Information (OSTI.GOV)

Menikoff, Ralph

2017-12-06

The SURFplus reactive burn model is calibrated for the TATB based explosive PBX 9502 at three initial temperatures; hot (75 C), ambient (23 C) and cold (-55 C). The CJ state depends on the initial temperature due to the variation in the initial density and initial specific energy of the PBX reactants. For the reactants, a porosity model for full density TATB is used. This allows the initial PBX density to be set to its measured value even though the coeffcient of thermal expansion for the TATB and the PBX differ. The PBX products EOS is taken as independent ofmore » the initial PBX state. The initial temperature also affects the sensitivity to shock initiation. The model rate parameters are calibrated to Pop plot data, the failure diameter, the limiting detonation speed just above the failure diameters, and curvature effect data for small curvature.« less

Failure propagation in multi-cell lithium ion batteries

DOE PAGES

Lamb, Joshua; Orendorff, Christopher J.; Steele, Leigh Anna M.; ...

2014-10-22

Traditionally, safety and impact of failure concerns of lithium ion batteries have dealt with the field failure of single cells. However, large and complex battery systems require the consideration of how a single cell failure will impact the system as a whole. Initial failure that leads to the thermal runaway of other cells within the system creates a much more serious condition than the failure of a single cell. This work examines the behavior of small modules of cylindrical and stacked pouch cells after thermal runaway is induced in a single cell through nail penetration trigger [1] within the module.more » Cylindrical cells are observed to be less prone to propagate, if failure propagates at all, owing to the limited contact between neighboring cells. However, the electrical connectivity is found to be impactful as the 10S1P cylindrical cell module did not show failure propagation through the module, while the 1S10P module had an energetic thermal runaway consuming the module minutes after the initiation failure trigger. Modules built using pouch cells conversely showed the impact of strong heat transfer between cells. In this case, a large surface area of the cells was in direct contact with its neighbors, allowing failure to propagate through the entire battery within 60-80 seconds for all configurations (parallel or series) tested. This work demonstrates the increased severity possible when a point failure impacts the surrounding battery system.« less

Time-lapsed investigation of three-dimensional failure and damage accumulation in trabecular bone using synchrotron light.

PubMed

Thurner, P J; Wyss, P; Voide, R; Stauber, M; Stampanoni, M; Sennhauser, U; Müller, R

2006-08-01

Synchrotron radiation micro-computed tomography (SRmicroCT) is a very useful technique when it comes to three-dimensional (3D) imaging of complex internal and external geometries. Being a fully non-destructive technique, SRmicroCT can be combined with other experiments in situ for functional imaging. We are especially interested in the combination of SRmicroCT with mechanical testing in order to gain new insights in the failure mechanism of trabecular bone. This interest is motivated by the immense costs in health care due to patients suffering from osteoporosis, a systemic skeletal disease resulting in decreased bone stability and increased fracture risk. To better investigate the different failure mechanisms on the microlevel, we have developed a novel in situ mechanical compression device, capable of exerting both static and dynamic displacements on experimental samples. The device was calibrated for mechanical testing using solid aluminum and bovine trabecular bone samples. To study different failure mechanisms in trabecular bone, we compared a fatigued and a non-fatigued bovine bone sample with respect to failure initiation and propagation. The fatigued sample failed in a burst-like fashion in contrast to the non-fatigued sample, which exhibited a distinct localized failure band. Moreover, microscopic cracks - microcracks and microfractures - were uncovered in a 3D fashion illustrating the failure process in great detail. The majority of these cracks were connected to a bone surface. The data also showed that the classification of microcracks and -fractures from 2D section can sometimes be ambiguous, which is also true for the distinction of diffuse and distinct microdamage. Detailed investigation of the failure mechanism in these samples illustrated that trabecular bone often fails in delamination, providing a mechanism for energy dissipation while conserving trabecular bone architecture. In the future, this will allow an even better understanding of bone mechanics related to its hierarchical structural organization.

People's Financial Choice Depends on their Previous Task Success or Failure.

PubMed

Sekścińska, Katarzyna

2015-01-01

Existing knowledge about the impact of the experience prior to financial choices has been limited almost exclusively to single risky choices. Moreover, the results obtained in these studies have not been entirely consistent. For example, some studies suggested that the experience of success makes people more willing to take a risk, while other studies led to the opposite conclusions. The results of the two experimental studies presented in this paper provide evidence for the hypothesis that the experience of success or failure influences people's financial choices, but the effect of the success or failure depends on the type of task (financial and non-financial) preceding a financial decision. The experience of success in financial tasks increased participants' tendency to invest and make risky investment choices, while it also made them less prone to save. On the other hand, the experience of failure heightened the amount of money that participants decided to save, and lowered their tendency to invest and make risky investment choices. However, the effects of the experience of success or failure in non-financial tasks were exactly the opposite. The presented studies indicated the role of the specific circumstances in which the individual gains the experience as a possible way to explain the discrepancies in the results of studies on the relationship between the experience prior to financial choice with a tendency to take risks.

People’s Financial Choice Depends on their Previous Task Success or Failure

PubMed Central

Sekścińska, Katarzyna

2015-01-01

Existing knowledge about the impact of the experience prior to financial choices has been limited almost exclusively to single risky choices. Moreover, the results obtained in these studies have not been entirely consistent. For example, some studies suggested that the experience of success makes people more willing to take a risk, while other studies led to the opposite conclusions. The results of the two experimental studies presented in this paper provide evidence for the hypothesis that the experience of success or failure influences people’s financial choices, but the effect of the success or failure depends on the type of task (financial and non-financial) preceding a financial decision. The experience of success in financial tasks increased participants’ tendency to invest and make risky investment choices, while it also made them less prone to save. On the other hand, the experience of failure heightened the amount of money that participants decided to save, and lowered their tendency to invest and make risky investment choices. However, the effects of the experience of success or failure in non-financial tasks were exactly the opposite. The presented studies indicated the role of the specific circumstances in which the individual gains the experience as a possible way to explain the discrepancies in the results of studies on the relationship between the experience prior to financial choice with a tendency to take risks. PMID:26635654

The initial effectiveness of liposomal amphotericin B (AmBisome) and miltefosine combination for treatment of visceral leishmaniasis in HIV co-infected patients in Ethiopia: A retrospective cohort study.

PubMed

Abongomera, Charles; Diro, Ermias; de Lima Pereira, Alan; Buyze, Jozefien; Stille, Kolja; Ahmed, Fareed; van Griensven, Johan; Ritmeijer, Koert

2018-05-01

North-west Ethiopia faces the highest burden world-wide of visceral leishmaniasis (VL) and HIV co-infection. VL-HIV co-infected patients have higher (initial) parasitological failure and relapse rates than HIV-negative VL patients. Whereas secondary prophylaxis reduces the relapse rate, parasitological failure rates remain high with the available antileishmanial drugs, especially when administered as monotherapy. We aimed to determine the initial effectiveness (parasitologically-confirmed cure) of a combination of liposomal amphotericin B (AmBisome) and miltefosine for treatment of VL in HIV co-infected patients. We conducted a retrospective cohort study at a Médecins Sans Frontières-supported health center in north-west Ethiopia. We included VL-HIV co-infected adults, treated for VL between January 2011 and August 2014, with AmBisome infusion (30 mg/kg total dose) and miltefosine orally for 28 days (100 mg/day). Proportions of initial treatment outcome categories were calculated. Predictors of initial parasitological failure and of death were determined using multivariable logistic regression. Of the 173 patients included, 170 (98.3%) were male and the median age was 32 years. The proportion of patients with primary VL (48.0%) and relapse VL (52.0%) were similar. The majority had advanced HIV disease (n = 111; 73.5%) and were on antiretroviral therapy prior to VL diagnosis (n = 106; 64.2%). Initial cure rate was 83.8% (95% confidence interval [CI], 77.6-88.6); death rate 12.7% (95% CI, 8.5-18.5) and parasitological failure rate 3.5% (95% CI, 1.6-7.4). Tuberculosis co-infection at VL diagnosis was predictive of parasitological failure (adjusted odds ratio (aOR), 8.14; p = 0.02). Predictors of death were age >40 years (aOR, 5.10; p = 0.009), hemoglobin ≤6.5 g/dL (aOR, 5.20; p = 0.002) and primary VL (aOR, 8.33; p = 0.001). Initial parasitological failure rates were very low with AmBisome and miltefosine combination therapy. This regimen seems a suitable treatment option. Knowledge of predictors of poor outcome may facilitate better management. These findings remain to be confirmed in clinical trials.

Effect of Discontinuities and Uncertainties on the Response and Failure of Composite Structures

NASA Technical Reports Server (NTRS)

Noor, Ahmed K.; Perry, Ferman W.; Poteat, Marcia M. (Technical Monitor)

2000-01-01

The overall goal of this research was to assess the effect of discontinuities and uncertainties on the nonlinear response and failure of composite structures subjected to combined mechanical and thermal loads. The four key elements of the study were: (1) development of simple and efficient procedures for the accurate determination of transverse shear and transverse normal stresses in structural sandwiches as well as in unstiffened and stiffened composite panels and shells; (2) study the effects of transverse stresses on the response, damage initiation and propagation in composite and sandwich structures; (3) use of hierarchical sensitivity coefficients to identify the major parameters that affect the response and damage in each of the different levels in the hierarchy (micro-mechanical, layer, panel, subcomponent and component levels); and (4) application of fuzzy set techniques to identify the range and variation of possible responses. The computational models developed were used in conjunction with experiments, to understand the physical phenomena associated with the nonlinear response and failure of composite and sandwich structures. A toolkit was developed for use in conjunction with deterministic analysis programs to help the designer in assessing the effect of uncertainties in the different computational model parameters on the variability of the response quantities.

Psychosocial presentation of revisional LAGB patients: a qualitative study.

PubMed

Janse Van Vuuren, M; Strodl, E; White, K M; Lockie, P

2015-10-01

This qualitative study offers insight into the experiences, expectations, perceptions and beliefs that may lead to laparoscopic adjustable gastric band patients' failure to achieve expected weight loss and seek revisional bariatric surgery. The 23 participants from two sites were interviewed and data were analysed from a grounded theory methodology in order to build a causal model. Analysis of participants' reports identified 'unrealistic expectations of the LAGB' as the core category. Additionally, the restriction of the band had a negative impact on participants' social interactions, leading to feelings of deprivation and, thus, to a desire for reward from food choices and consequently an increase of consumption of high-calorie-dense foods. These foods were chosen because of their specific texture or ability to provide reward. The resulting increase in weight or failure to achieve excess weight loss, led to feelings of shame and loneliness and emotional eating resulting in increased the consumption of rewarding foods. Thus, identifying unrealistic expectations of laparoscopic adjustable gastric band (LAGB) and emotional eating behaviours are important in those who are present initially for primary bariatric and revisional bariatric surgery, as they may contribute specifically to these patients' weight regain and consequent failure to achieve excess weight loss. © 2015 World Obesity.

Porting Inition and Failure to Linked Cheetah

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vitello, P; Souers, P C

2007-07-18

Linked CHEETAH is a thermo-chemical code coupled to a 2-D hydrocode. Initially, a quadratic-pressure dependent kinetic rate was used, which worked well in modeling prompt detonation of explosives of large size, but does not work on other aspects of explosive behavior. The variable-pressure Tarantula reactive flow rate model was developed with JWL++ in order to also describe failure and initiation, and we have moved this model into Linked CHEETAH. The model works by turning on only above a pressure threshold, where a slow turn-on creates initiation. At a higher pressure, the rate suddenly leaps to a large value over amore » small pressure range. A slowly failing cylinder will see a rapidly declining rate, which pushes it quickly into failure. At a high pressure, the detonation rate is constant. A sequential validation procedure is used, which includes metal-confined cylinders, rate-sticks, corner-turning, initiation and threshold, gap tests and air gaps. The size (diameter) effect is central to the calibration.« less

Fracture Surface Analysis of Clinically Failed Fixed Partial Dentures

PubMed Central

Taskonak, B.; Mecholsky, J.J.; Anusavice, K.J.

2008-01-01

Ceramic systems have limited long-term fracture resistance, especially when they are used in posterior areas or for fixed partial dentures. The objective of this study was to determine the site of crack initiation and the causes of fracture of clinically failed ceramic fixed partial dentures. Six Empress 2® lithia-disilicate (Li2O·2SiO2)-based veneered bridges and 7 experimental lithia-disilicate-based non-veneered ceramic bridges were retrieved and analyzed. Fractography and fracture mechanics methods were used to estimate the stresses at failure in 6 bridges (50%) whose fracture initiated from the occlusal surface of the connectors. Fracture of 1 non-veneered bridge (8%) initiated within the gingival surface of the connector. Three veneered bridges fractured within the veneer layers. Failure stresses of the all-core fixed partial dentures ranged from 107 to 161 MPa. Failure stresses of the veneered fixed partial dentures ranged from 19 to 68 MPa. We conclude that fracture initiation sites are controlled primarily by contact damage. PMID:16498078

The initiation, propagation, and effect of matrix microcracks in cross-ply and related laminates

NASA Technical Reports Server (NTRS)

Nairn, John A.; Hu, Shoufeng; Liu, Siulie; Bark, Jong

1991-01-01

Recently, a variational mechanics approach was used to determine the thermoelastic stress state in cracked laminates. Described here is a generalization of the variational mechanics techniques to handle other cross-ply laminates, related laminates, and to account for delaminations emanating from microcrack tips. Microcracking experiments on Hercules 3501-6/AS4 carbon fiber/epoxy laminates show a staggered cracking pattern. These results can be explained by the variational mechanics analysis. The analysis of delaminations emanating from microcrack tips has resulted in predictions about the structural and material variables controlling competition between microcracking and delamination failure modes.

Full-scale physical model of landslide triggering

NASA Astrophysics Data System (ADS)

Lora, M.; Camporese, M.; Salandin, P.

2013-12-01

Landslide triggering induced by high-intensity rainfall infiltration in hillslopes is a complex phenomenon that involves hydrological processes operating at different spatio-temporal scales. Empirical methods give rough information about landslide-prone areas, without investigating the theoretical framework needed to achieve an in-depth understanding of the involved physical processes. In this study, we tackle this issue through physical experiments developed in an artificial hillslope realized in the Department of Civil, Environmental and Architectural Engineering of the University of Padua. The structure consists of a reinforced concrete box containing a soil prism with the following maximum dimensions: 3.5 m high, 6 m long, and 2 m wide. In order to analyze and examine the triggered failure state, the experiments are carried out with intensive monitoring of pore water pressure and moisture content response. Subsurface monitoring instruments are installed at several locations and depths to measure downward infiltration and/or a rising groundwater table. We measure the unsaturated soil water pressure as well as positive pore pressures preceding failure in each experiments with six tensiometers. The volumetric water content is determined through six Time Domain Reflectometry probes. Two pressure transducers are located in observation wells to determine the position of the water table in time. Two stream gauges are positioned at the toeslope, for measuring both runoff and subsurface outflow. All data are collected and recorded by an acquisition data system from Campbell Scientific. The artificial hillslope is characterized by well-known and controlled conditions, which are designed to reproduce an ideal set-up susceptible to heavy rainfall landslide. The hydrologic forcing is generated by a rainfall simulator realized with nozzles from Sprying System and. specifically designed to produce a spatially uniform rainfall of intensity ranging from 50 to 150 mm/h. The aim of our experiments is to reproduce the instability trigger that occurs in saturated or partially unsaturated conditions depending on the specific characteristics of the soil and its initial conditions; the retention curve of fine sand and the initial porosity are taken into account to highlight the hydrological condition of the surface layer during the trigger occurrence. Through our experimental setup we can investigate the succession of phases and their magnitude that cause the landslide trigger, in order to understand the instability mechanism that heavy rainfall can induce in fine sandy hillslopes. Particular attention is given on the role of water pressure head, not only with respect to the violation of Coulomb failure within a sloping soil, but also with respect to the subsequent deformation that involves the upper hillslope layers. In particular, we report here on the characterization of the sandy terrain used in the experiments and the preliminary results, together with a first discussion of the observed data.

Numerical research on the lateral global buckling characteristics of a high temperature and pressure pipeline with two initial imperfections

PubMed Central

Liu, Wenbin; Liu, Aimin

2018-01-01

With the exploitation of offshore oil and gas gradually moving to deep water, higher temperature differences and pressure differences are applied to the pipeline system, making the global buckling of the pipeline more serious. For unburied deep-water pipelines, the lateral buckling is the major buckling form. The initial imperfections widely exist in the pipeline system due to manufacture defects or the influence of uneven seabed, and the distribution and geometry features of initial imperfections are random. They can be divided into two kinds based on shape: single-arch imperfections and double-arch imperfections. This paper analyzed the global buckling process of a pipeline with 2 initial imperfections by using a numerical simulation method and revealed how the ratio of the initial imperfection’s space length to the imperfection’s wavelength and the combination of imperfections affects the buckling process. The results show that a pipeline with 2 initial imperfections may suffer the superposition of global buckling. The growth ratios of buckling displacement, axial force and bending moment in the superposition zone are several times larger than no buckling superposition pipeline. The ratio of the initial imperfection’s space length to the imperfection’s wavelength decides whether a pipeline suffers buckling superposition. The potential failure point of pipeline exhibiting buckling superposition is as same as the no buckling superposition pipeline, but the failure risk of pipeline exhibiting buckling superposition is much higher. The shape and direction of two nearby imperfections also affects the failure risk of pipeline exhibiting global buckling superposition. The failure risk of pipeline with two double-arch imperfections is higher than pipeline with two single-arch imperfections. PMID:29554123

U.S. Food safety and Inspection Service testing for Salmonella in selected raw meat and poultry products in the United States, 1998 through 2003: an establishment-level analysis.

PubMed

Eblen, Denise R; Barlow, Kristina E; Naugle, Alecia Larew

2006-11-01

The U.S. Food Safety and Inspection Service (FSIS) pathogen reduction-hazard analysis critical control point systems final rule, published in 1996, established Salmonella performance standards for broiler chicken, cow and bull, market hog, and steer and heifer carcasses and for ground beef, chicken, and turkey meat. In 1998, the FSIS began testing to verify that establishments are meeting performance standards. Samples are collected in sets in which the number of samples is defined but varies according to product class. A sample set fails when the number of positive Salmonella samples exceeds the maximum number of positive samples allowed under the performance standard. Salmonella sample sets collected at 1,584 establishments from 1998 through 2003 were examined to identify factors associated with failure of one or more sets. Overall, 1,282 (80.9%) of establishments never had failed sets. In establishments that did experience set failure(s), generally the failed sets were collected early in the establishment testing history, with the exception of broiler establishments where failure(s) occurred both early and late in the course of testing. Small establishments were more likely to have experienced a set failure than were large or very small establishments, and broiler establishments were more likely to have failed than were ground beef, market hog, or steer-heifer establishments. Agency response to failed Salmonella sample sets in the form of in-depth verification reviews and related establishment-initiated corrective actions have likely contributed to declines in the number of establishments that failed sets. A focus on food safety measures in small establishments and broiler processing establishments should further reduce the number of sample sets that fail to meet the Salmonella performance standard.

New early warning system for gravity-driven ruptures based on codetection of acoustic signal

NASA Astrophysics Data System (ADS)

Faillettaz, J.

2016-12-01

Gravity-driven rupture phenomena in natural media - e.g. landslide, rockfalls, snow or ice avalanches - represent an important class of natural hazards in mountainous regions. To protect the population against such events, a timely evacuation often constitutes the only effective way to secure the potentially endangered area. However, reliable prediction of imminence of such failure events remains challenging due to the nonlinear and complex nature of geological material failure hampered by inherent heterogeneity, unknown initial mechanical state, and complex load application (rainfall, temperature, etc.). Here, a simple method for real-time early warning that considers both the heterogeneity of natural media and characteristics of acoustic emissions attenuation is proposed. This new method capitalizes on codetection of elastic waves emanating from microcracks by multiple and spatially separated sensors. Event-codetection is considered as surrogate for large event size with more frequent codetected events (i.e., detected concurrently on more than one sensor) marking imminence of catastrophic failure. Simple numerical model based on a Fiber Bundle Model considering signal attenuation and hypothetical arrays of sensors confirms the early warning potential of codetection principles. Results suggest that although statistical properties of attenuated signal amplitude could lead to misleading results, monitoring the emergence of large events announcing impeding failure is possible even with attenuated signals depending on sensor network geometry and detection threshold. Preliminary application of the proposed method to acoustic emissions during failure of snow samples has confirmed the potential use of codetection as indicator for imminent failure at lab scale. The applicability of such simple and cheap early warning system is now investigated at a larger scale (hillslope). First results of such a pilot field experiment are presented and analysed.

Outcome and Management of Refractory Respiratory Failure With Timely Extracorporeal Membrane OxygenationSingle-Center Experience With Legionella Pneumonia.

PubMed

Roncon-Albuquerque, Roberto; Vilares-Morgado, Rodrigo; van der Heijden, Gert-Jan; Ferreira-Coimbra, João; Mergulhão, Paulo; Paiva, José Artur

2017-01-01

To analyze the management and outcome of patients with refractory respiratory failure complicating severe Legionella pneumonia rescued with extracorporeal membrane oxygenation (ECMO) in our Center. Observational study of patients with refractory respiratory failure treated with ECMO in Hospital S.João (Porto, Portugal), between November 2009 and September 2016. A total of 112 patients rescued with ECMO, of which 14 had Legionella pneumonia. Patients with Legionella pneumonia were slightly older than patients with acute respiratory failure of other etiologies (51 [48-56] vs 45 [35-54]), but with no significant differences in acute respiratory failure severity between groups: Pao 2 /Fio 2 ratio 67 (60-75) versus 69 (55-85) and Respiratory Extracorporeal Membrane Oxygenation Survival Prediction score 4 (1-5) versus 2 (-1-4), respectively. Legionella pneumonia was associated with earlier ECMO initiation (days of invasive mechanical ventilation [IMV] before ECMO: 2.0 [1.0-4.0] vs 5.0 [2.0-9.5]). After IMV adjustment to "lung rest" settings, this group presented higher respiratory system (RS) static compliance (28.7 [18.8-37.4] vs 16.0 [10.0-20.8] mL/cmH 2 O) but required higher ECMO support (blood flow 5.0 [4.3-5.4] vs 4.2 [3.6-4.8]). Patients with Legionella pneumonia had shorter IMV (16 [14-23] vs 27 [20-42] days) and lower incidence of intensive care unit nosocomial infections (35.7% vs 64.3%), with a trend to higher hospital survival (85.7% vs 62.2%; P = .13). In Legionella pneumonia complicated by refractory respiratory failure, ECMO support allowed patient stabilization under lung protective ventilation and high survival rates. Timely ECMO referral should be considered for Legionella pneumonia failing conventional treatment.

How and why of orthodontic bond failures: An in vivo study

PubMed Central

Vijayakumar, R. K.; Jagadeep, Raju; Ahamed, Fayyaz; Kanna, Aprose; Suresh, K.

2014-01-01

Introduction: The bonding of orthodontic brackets and their failure rates by both direct and in-direct procedures are well-documented in orthodontic literature. Over the years different adhesive materials and various indirect bonding transfer procedures have been compared and evaluated for bond failure rates. The aim of our study is to highlight the use of a simple, inexpensive and ease of manipulation of a single thermo-plastic transfer tray and the use the of a single light cure adhesive to evaluate the bond failure rates in clinical situations. Materials and Methods: A total of 30 patients were randomly divided into two groups (Group A and Group B). A split-mouth study design was used, for, both the groups so that they were distributed equally with-out bias. After initial prophylaxis, both the procedures were done as per manufactures instructions. All patients were initially motivated and reviewed for bond failures rates for 6 months. Results: Bond failure rates were assessed for over-all direct and indirect procedures, anterior and posterior arches, and for individual tooth. Z-test was used for statistically analyzing, the normal distribution of the sample in a spilt mouth study. The results of the two groups were compared and P value was calculated using Z-proportion test to assess the significance of the bond failure. Conclusion: Over-all bond failure was more for direct bonding. Anterior bracket failure was more in-direct bonding than indirect procedure, which showed more posterior bracket failures. In individual tooth bond failure, mandibular incisor, and premolar brackets showed more failure, followed by maxillary premolars and canines. PMID:25210392

Reliability Programs for Nonelectronic Designs. Volume 2

DTIC Science & Technology

1983-04-01

afforded. Differ- ences between critical and minor failures must be defined in the RFP so that the test need not be stopped for minor failures. However...not be afforded. Specialized test plans must be developed for nonelectronic equipment. First, differences between critical and minor failures must be...determined prior to initiating the test program so that the test need not be stopped for minor failures. Second, although the test must be interrupted

Deformation and failure of single- and multi-phase silicate liquids: seismic precursors and mechanical work

NASA Astrophysics Data System (ADS)

Vasseur, Jeremie; Lavallée, Yan; Hess, Kai-Uwe; Wassermann, Joachim; Dingwell, Donald B.

2013-04-01

Along with many others, volcanic unrest is regarded as a catastrophic material failure phenomenon and is often preceded by diverse precursory signals. Although a volcanic system intrinsically behave in a non-linear and stochastic way, these precursors display systematic evolutionary trends to upcoming eruptions. Seismic signals in particular are in general dramatically increasing prior to an eruption and have been extensively reported to show accelerating rates through time, as well as in the laboratory before failure of rock samples. At the lab-scale, acoustic emissions (AE) are high frequency transient stress waves used to track fracture initiation and propagation inside a rock sample. Synthesized glass samples featuring a range of porosities (0 - 30%) and natural rock samples from volcán de Colima, Mexico, have been failed under high temperature uniaxial compression experiments at constant stresses and strain rates. Using the monitored AEs and the generated mechanical work during deformation, we investigated the evolutionary trends of energy patterns associated to different degrees of heterogeneity. We observed that the failure of dense, poorly porous glasses is achieved by exceeding elevated strength and thus requires a significant accumulation of strain, meaning only pervasive small-scale cracking is occurring. More porous glasses as well as volcanic samples need much lower applied stress and deformation to fail, as fractures are nucleating, propagating and coalescing into localized large-scale cracks, taking the advantage of the existence of numerous defects (voids for glasses, voids and crystals for volcanic rocks). These observations demonstrate that the mechanical work generated through cracking is efficiently distributed inside denser and more homogeneous samples, as underlined by the overall lower AE energy released during experiments. In contrast, the quicker and larger AE energy released during the loading of heterogeneous samples shows that the mechanical work tends to concentrate in specific weak regions facilitating dynamical failure of the material through dissipation of the accumulated strain energy. Applying a statistical Global Linearization Method (GLM) in multi-phase silicate liquids samples leads to a maximum likelihood power-law fit of the accelerating rates of released AEs. The calculated α exponent of the famous empirical Failure Forecast Method (FFM) tends to decrease from 2 towards 1 with increasing porosity, suggesting a shift towards an idealized exponential-like acceleration. Single-phase silicate liquids behave more elastically during deformation without much cracking and suddenly releasing their accumulated strain energy at failure, implying less clear trends in monitored AEs. In a predictive prospective, these results support the fact that failure forecasting power is enhanced by the presence of heterogeneities inside a material.

Discussions on attitude determination and control system for micro/nano/pico-satellites considering survivability based on Hodoyoshi-3 and 4 experiences

NASA Astrophysics Data System (ADS)

Nakasuka, Shinichi; Miyata, Kikuko; Tsuruda, Yoshihiro; Aoyanagi, Yoshihide; Matsumoto, Takeshi

2018-04-01

The recent advancement of micro/nano/pico-satellites technologies encourages many universities to develop three axis stabilized satellites. As three axis stabilization is high level technology requiring the proper functioning of various sensors, actuators and control software, many early satellites failed in their initial operation phase because of shortage of solar power generation or inability to realize the initial step of missions because of unexpected attitude control system performance. These results come from failure to design the satellite attitude determination and control system (ADCS) appropriately and not considering "satellite survivability." ADCS should be designed such that even if some sensors or actuators cannot work as expected, the satellite can survive and carry out some of its missions, even if not full. This paper discusses how to realize ADCS while taking satellite survivability into account, based on our experiences of design and in-orbit operations of Hodoyoshi-3 and 4 satellites launched in 2014, which suffered from various component anomalies but could complete their missions.

"I never thought that it would happen … " Experiences of HIV seroconverters among HIV-discordant partnerships in a prospective HIV prevention study in Kenya.

PubMed

Ngure, Kenneth; Vusha, Sophie; Mugo, Nelly; Emmanuel-Fabula, Mira; Ngutu, Mariah; Celum, Connie; Baeten, Jared M; Heffron, Renee

2016-12-01

In spite of access to behavioral and biomedical HIV prevention strategies, HIV transmission occurs. For HIV-serodiscordant couples, prevention programs can be tailored to address individual and couples' needs to preserve their relationship while minimizing HIV risk. Programs for serodiscordant couples may benefit from learning from experiences of couples who transmit HIV. We conducted 20 individual in-depth interviews with 10 initially HIV-serodiscordant couples who transmitted HIV during prospective follow-up at a peri-urban research site in Thika, Kenya. Data were analyzed inductively to identify situations that led to prevention failure and coping mechanisms. Inconsistent condom use driven by low HIV risk perception and alcohol use often preceded seroconversion while persistent blame frequently hindered couples' communication soon after seroconversion. In this emerging era of antiretroviral-based HIV prevention, couples' counseling can capitalize on opportunities to foster a supportive environment to discuss initiation and adherence to time-limited pre-exposure prophylaxis and lifelong antiretroviral therapy, in addition to strategies to reduce alcohol use, diffuse blame, and use condoms.

Great expectations and hard times: developing community indicators in a healthy communities initiative in Canada.

PubMed

Smith, Neale; Littlejohns, Lori Baugh; Hawe, Penelope; Sutherland, Lisa

2008-06-01

This paper reports on expectations for and community members' experience in the development of community indicators in a healthy communities initiative (HCI) in Alberta, Canada. The HCI process involved community visioning, the creation of action plans to further the vision by addressing key health priorities and/or community capacity building activities and the development of indicators to monitor and report on progress towards goals. Nineteen semi-structured interviews were conducted with community participants to discuss definitions of success in the HCI and participant experience in developing indicators. Three themes emerged: the formal indicators lacked relevance to community members; the community did not own the HCI indicators and participants instead drew upon measures of success which were largely experiential in nature. The study provides a critically reflective, candid account of on-the-ground work with communities. The findings reveal limitations in the process of developing community indicators in this HCI, which we attribute in part to skills and discontinuities on the staffing side of the health authority and in part to failure to recognize and fully appreciate 'different ways of knowing' between communities and agencies.

Nuclear and ionic charge distribution experiment on ISEE-1 and ISEE-3

NASA Technical Reports Server (NTRS)

Gloeckler, G.; Ipavich, F. M.; Galvin, A. B.

1987-01-01

The experimental work carried out under this contract is a continuation of that originally performed under Contracts NAS5-20062 and NAS5-26739. The data analyzed are from the Max-Planck Institut/Univ. of Maryland experiment on ISEE-1 and ISEE-3. Each spacecraft experiment consists of a nearly identical set of three sensors (designated the ULECA, ULEWAT, and ULEZEQ sensors) designed to measure the energy spectra and composition of suprathermal and energetic ions over a broad energy range (less than 3 keV/e to more than 20 MeV/nucleon). Since the launch of ISEE's 2 and 3, the MPI/Univ. of Maryland experiments have generally performed as expected except for a partial failure of the ULEWAT sensor on ISEE-1 in August 1978. A number of scientific studies have either been completed, initiated or are at various stages of completion. A brief summary of Primary Results is given, followed by a more detailed summary of the major accomplishments at the Univ. of Maryland.

Dynamic fracture behavior of single and contacting Poly(methyl methacrylate) particles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parab, Niranjan D.; Guo, Zherui; Hudspeth, Matthew C.

Fracture behaviors of single, two, and multiple contacting spherical Poly (methyl methacrylate) (PMMA) particles were recorded using high speed synchrotron X-ray phase contrast imaging. A miniaturized Kolsky bar setup was used to apply dynamic compressive loading on the PMMA particles. In both single and two particle experiments, cracking initiated near the center of the particles and propagated towards the contacts. The crack bifurcated near the contact points for single particle experiments, thus forming conical fragments. The crack bifurcation and subsequent conical fragment formation was observed only at the particle-particle contact for two particle experiments. The particles were observed to fracturemore » in hemispherical fragments normal to the contact plane in the multiparticle experiments. The observed failure mechanisms strongly suggest that the maximum tensile stress near the center of the particle is the critical parameter governing fracture of the particles. Moreover, the compressive stress under the contact areas led to the bifurcation and subsequent conical fragment formation.« less

Dynamic fracture behavior of single and contacting Poly(methyl methacrylate) particles

DOE PAGES

Parab, Niranjan D.; Guo, Zherui; Hudspeth, Matthew C.; ...

2017-09-19

Fracture behaviors of single, two, and multiple contacting spherical Poly (methyl methacrylate) (PMMA) particles were recorded using high speed synchrotron X-ray phase contrast imaging. A miniaturized Kolsky bar setup was used to apply dynamic compressive loading on the PMMA particles. In both single and two particle experiments, cracking initiated near the center of the particles and propagated towards the contacts. The crack bifurcated near the contact points for single particle experiments, thus forming conical fragments. The crack bifurcation and subsequent conical fragment formation was observed only at the particle-particle contact for two particle experiments. The particles were observed to fracturemore » in hemispherical fragments normal to the contact plane in the multiparticle experiments. The observed failure mechanisms strongly suggest that the maximum tensile stress near the center of the particle is the critical parameter governing fracture of the particles. Moreover, the compressive stress under the contact areas led to the bifurcation and subsequent conical fragment formation.« less

76 FR 81015 - Notice of Public Webinar on Implementation of Distribution Integrity Management Programs

Federal Register 2010, 2011, 2012, 2013, 2014

2011-12-27

... discussion of analyses of the initial submissions of data concerning mechanical fitting failures in... information. The DIMP rule also required distribution pipeline operators to report failures of mechanical... mechanical fitting failure reporting will be preliminary at this time. They will be based on a limited set of...

Effects of soil-engineering properties on the failure mode of shallow landslides

USGS Publications Warehouse

McKenna, Jonathan Peter; Santi, Paul Michael; Amblard, Xavier; Negri, Jacquelyn

2012-01-01

Some landslides mobilize into flows, while others slide and deposit material immediately down slope. An index based on initial dry density and fine-grained content of soil predicted failure mode of 96 landslide initiation sites in Oregon and Colorado with 79% accuracy. These material properties can be used to identify potential sources for debris flows and for slides. Field data suggest that loose soils can evolve from dense soils that dilate upon shearing. The method presented herein to predict failure mode is most applicable for shallow (depth 8), with few to moderate fines (fine-grained content <18%), and with liquid limits <40.

Failure Mechanisms of Brittle Rocks under Uniaxial Compression

NASA Astrophysics Data System (ADS)

Liu, Taoying; Cao, Ping

2017-09-01

The behaviour of a rock mass is determined not only by the properties of the rock matrix, but mostly by the presence and properties of discontinuities or fractures within the mass. The compression test on rock-like specimens with two prefabricated transfixion fissures, made by pulling out the embedded metal inserts in the pre-cured period was carried out on the servo control uniaxial loading tester. The influence of the geometry of pre-existing cracks on the cracking processes was analysed with reference to the experimental observation of crack initiation and propagation from pre-existing flaws. Based on the rock fracture mechanics and the stress-strain curves, the evolution failure mechanism of the fissure body was also analyzed on the basis of exploring the law of the compression-shear crack initiation, wing crack growth and rock bridge connection. Meanwhile, damage fracture mechanical models of a compression-shear rock mass are established when the rock bridge axial transfixion failure, tension-shear combined failure, or wing crack shear connection failure occurs on the specimen under axial compression. This research was of significance in studying the failure mechanism of fractured rock mass.

Management of failure after surgery for gastro-esophageal reflux disease.

PubMed

Gronnier, C; Degrandi, O; Collet, D

2018-04-01

Surgical treatment of gastro-esophageal reflux disease (ST-GERD) is well-codified and offers an alternative to long-term medical treatment with a better efficacy for short and long-term outcomes. However, failure of ST-GERD is observed in 2-20% of patients; management is challenging and not standardized. The aim of this study is to analyze the causes of failure and to provide a treatment algorithm. The clinical aspects of ST-GERD failure are variable including persistent reflux, dysphagia or permanent discomfort leading to an important degradation of the quality of life. A morphological and functional pre-therapeutic evaluation is necessary to: (i) determine whether the symptoms are due to recurrence of reflux or to an error in initial indication and (ii) to understand the cause of the failure. The most frequent causes of failure of ST-GERD include errors in the initial indication, which often only need medical treatment, and surgical technical errors, for which surgical redo surgery can be difficult. Multidisciplinary management is necessary in order to offer the best-adapted treatment. Copyright © 2018. Published by Elsevier Masson SAS.

The deformation and failure response of closed-cell PMDI foams subjected to dynamic impact loading

DOE PAGES

Koohbor, Behrad; Mallon, Silas; Kidane, Addis; ...

2015-04-07

The present work aims to investigate the bulk deformation and failure response of closed-cell Polymeric Methylene Diphenyl Diisocyanate (PMDI) foams subjected to dynamic impact loading. First, foam specimens of different initial densities are examined and characterized in quasi-static loading conditions, where the deformation behavior of the samples is quantified in terms of the compressive elastic modulus and effective plastic Poisson's ratio. Then, the deformation response of the foam specimens subjected to direct impact loading is examined by taking into account the effects of material compressibility and inertia stresses developed during deformation, using high speed imaging in conjunction with 3D digitalmore » image correlation. The stress-strain response and the energy absorption as a function of strain rate and initial density are presented and the bulk failure mechanisms are discussed. As a result, it is observed that the initial density of the foam and the applied strain rates have a substantial influence on the strength, bulk failure mechanism and the energy dissipation characteristics of the foam specimens.« less

Cervical lung herniation complicating a case of acute asphyxial asthma in a child.

PubMed

Martchek, Melissa A; Padilla, Benjamin E; Zonfrillo, Mark R; Friedlaender, Eron Y

2015-04-01

The abrupt onset of respiratory failure secondary to asthma, known as acute asphyxial asthma (AAA) in adults, is uncommonly reported in children. Here, we report a case of a child with the acute onset of respiratory failure consistent with AAA complicated by the finding of a neck mass during resuscitation. This 11-year-old boy with a history of asthma initially presented in respiratory failure with altered mental status after the complaint of difficulty in breathing minutes before collapsing at home. Initially, his respiratory failure was thought to be secondary to status asthmaticus, and treatment was initiated accordingly. However, a neck mass noted during the resuscitation was cause for concern, and other etiologies for his respiratory failure were considered, including an airway obstructing neck mass. After pediatric surgery and anesthesia consultation for intubation and possible tracheostomy placement, general anesthesia was induced in the operating room with an inhaled anesthetic, with prompt resolution of the bronchspasm and decompression of the neck mass. Review of the imaging and clinical course ultimately yielded a diagnosis of cervical lung herniation as the etiology of his neck mass. We report this case of AAA and cervical lung herniation and a review of the literature of these 2 uncommon phenomena in children.

A Weibull distribution accrual failure detector for cloud computing

PubMed Central

Wu, Zhibo; Wu, Jin; Zhao, Yao; Wen, Dongxin

2017-01-01

Failure detectors are used to build high availability distributed systems as the fundamental component. To meet the requirement of a complicated large-scale distributed system, accrual failure detectors that can adapt to multiple applications have been studied extensively. However, several implementations of accrual failure detectors do not adapt well to the cloud service environment. To solve this problem, a new accrual failure detector based on Weibull Distribution, called the Weibull Distribution Failure Detector, has been proposed specifically for cloud computing. It can adapt to the dynamic and unexpected network conditions in cloud computing. The performance of the Weibull Distribution Failure Detector is evaluated and compared based on public classical experiment data and cloud computing experiment data. The results show that the Weibull Distribution Failure Detector has better performance in terms of speed and accuracy in unstable scenarios, especially in cloud computing. PMID:28278229

Self-Healing Nanotextured Vascular-like Materials: Mode I Crack Propagation.

PubMed

Lee, Min Wook; Sett, Soumyadip; An, Seongpil; Yoon, Sam S; Yarin, Alexander L

2017-08-16

Here, we investigate crack propagation initiated from an initial notch in a self-healing material. The crack propagation in the core-shell nanofiber mats formed by coelectrospinning and the composites reinforced by them is in focus. All samples are observed from the crack initiation until complete failure. Due to the short-time experiments done on purpose, the resin and cure released from the cores of the core-shell nanofibers could not achieve a complete curing and stop crack growth, especially given the fact that no heating was used. The aim is to elucidate their effect on the rate of crack propagation. The crack propagation speed in polyacrylonitrile (PAN)-resin-cure nanofiber mats (with PAN being the polymer in the shell) was remarkably lower than that in the corresponding monolithic PAN nanofiber mat, down to 10%. The nanofiber mats were also encased in polydimethylsiloxane (PDMS) matrix to form composites. The crack shape and propagation in the composite samples were studied experimentally and analyzed theoretically, and the theoretical results revealed agreement with the experimental data.

A study to define an in-flight dynamics measurement and data applications program for space shuttle payloads

NASA Technical Reports Server (NTRS)

Rader, W. P.; Barrett, S.; Payne, K. R.

1975-01-01

Data measurement and interpretation techniques were defined for application to the first few space shuttle flights, so that the dynamic environment could be sufficiently well established to be used to reduce the cost of future payloads through more efficient design and environmental test techniques. It was concluded that: (1) initial payloads must be given comprehensive instrumentation coverage to obtain detailed definition of acoustics, vibration, and interface loads, (2) analytical models of selected initial payloads must be developed and verified by modal surveys and flight measurements, (3) acoustic tests should be performed on initial payloads to establish realistic test criteria for components and experiments in order to minimize unrealistic failures and retest requirements, (4) permanent data banks should be set up to establish statistical confidence in the data to be used, (5) a more unified design/test specification philosophy is needed, (6) additional work is needed to establish a practical testing technique for simulation of vehicle transients.

Damage Progression in Buckle-Resistant Notched Composite Plates Loaded in Uniaxial Compression

NASA Technical Reports Server (NTRS)

McGowan, David M.; Davila, Carlos G.; Ambur, Damodar R.

2001-01-01

Results of an experimental and analytical evaluation of damage progression in three stitched composite plates containing an angled central notch and subjected to compression loading are presented. Parametric studies were conducted systematically to identify the relative effects of the material strength parameters on damage initiation and growth. Comparisons with experiments were conducted to determine the appropriate in situ values of strengths for progressive failure analysis. These parametric studies indicated that the in situ value of the fiber buckling strength is the most important parameter in the prediction of damage initiation and growth in these notched composite plates. Analyses of the damage progression in the notched, compression-loaded plates were conducted using in situ material strengths. Comparisons of results obtained from these analyses with experimental results for displacements and axial strains show good agreement.

Key results from irradiation and post-irradiation examination of AGR-1 UCO TRISO fuel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Demkowicz, Paul A.; Hunn, John D.; Petti, David A.

The AGR-1 irradiation experiment was performed as the first test of tristructural isotropic (TRISO) fuel in the US Advanced Gas Reactor Fuel Development and Qualification Program. The experiment consisted of 72 right cylinder fuel compacts containing approximately 3 × 105 coated fuel particles with uranium oxide/uranium carbide (UCO) fuel kernels. The fuel was irradiated in the Advanced Test Reactor for a total of 620 effective full power days. Fuel burnup ranged from 11.3 to 19.6% fissions per initial metal atom and time-average, volume-average irradiation temperatures of the individual compacts ranged from 955 to 1136 °C. This paper focuses on keymore » results from the irradiation and post-irradiation examination, which revealed a robust fuel with excellent performance characteristics under the conditions tested and have significantly improved the understanding of UCO coated particle fuel irradiation behavior. The fuel exhibited zero TRISO coating failures (failure of all three dense coating layers) during irradiation and post-irradiation safety testing at temperatures up to 1700 °C. Advanced PIE methods have allowed particles with SiC coating failure that were discovered to be present in a very-low population to be isolated and meticulously examined, which has elucidated the specific causes of SiC failure in these specimens. The level of fission product release from the fuel during irradiation and post-irradiation safety testing has been studied in detail. Results indicated very low release of krypton and cesium through intact SiC and modest release of europium and strontium, while also confirming the potential for significant silver release through the coatings depending on irradiation conditions. Focused study of fission products within the coating layers of irradiated particles down to nanometer length scales has provided new insights into fission product transport through the coating layers and the role various fission products may have on coating integrity. The broader implications of these results and the application of lessons learned from AGR-1 to fuel fabrication and post-irradiation examination for subsequent fuel irradiation experiments as part of the US fuel program are also discussed.« less

Key results from irradiation and post-irradiation examination of AGR-1 UCO TRISO fuel

DOE PAGES

Demkowicz, Paul A.; Hunn, John D.; Petti, David A.; ...

2017-09-10

The AGR-1 irradiation experiment was performed as the first test of tristructural isotropic (TRISO) fuel in the US Advanced Gas Reactor Fuel Development and Qualification Program. The experiment consisted of 72 right cylinder fuel compacts containing approximately 3 × 105 coated fuel particles with uranium oxide/uranium carbide (UCO) fuel kernels. The fuel was irradiated in the Advanced Test Reactor for a total of 620 effective full power days. Fuel burnup ranged from 11.3 to 19.6% fissions per initial metal atom and time-average, volume-average irradiation temperatures of the individual compacts ranged from 955 to 1136 °C. This paper focuses on keymore » results from the irradiation and post-irradiation examination, which revealed a robust fuel with excellent performance characteristics under the conditions tested and have significantly improved the understanding of UCO coated particle fuel irradiation behavior. The fuel exhibited zero TRISO coating failures (failure of all three dense coating layers) during irradiation and post-irradiation safety testing at temperatures up to 1700 °C. Advanced PIE methods have allowed particles with SiC coating failure that were discovered to be present in a very-low population to be isolated and meticulously examined, which has elucidated the specific causes of SiC failure in these specimens. The level of fission product release from the fuel during irradiation and post-irradiation safety testing has been studied in detail. Results indicated very low release of krypton and cesium through intact SiC and modest release of europium and strontium, while also confirming the potential for significant silver release through the coatings depending on irradiation conditions. Focused study of fission products within the coating layers of irradiated particles down to nanometer length scales has provided new insights into fission product transport through the coating layers and the role various fission products may have on coating integrity. The broader implications of these results and the application of lessons learned from AGR-1 to fuel fabrication and post-irradiation examination for subsequent fuel irradiation experiments as part of the US fuel program are also discussed.« less

Long-term outcomes after primary failures of artificial urinary sphincter implantation.

PubMed

Wang, Rou; McGuire, Edward J; He, Chang; Faerber, Gary J; Latini, Jerilyn M

2012-04-01

To assess our institutional outcomes after primary artificial urinary sphincter (AUS) failures. From 1985 to 2010, a total of 149 patients underwent 318 primary and additional AUS procedures. We classified additional procedures as revisions, replacements, or explantations. At a median of 52 months (range, 6-250 months), 53% of patients had required at least 1 additional procedure beyond their initial implantation. These included 106 (63%) revisions, 42 (24.9%) explantations, and 21 (12.4%) replacements. The most common revision was reservoir upsizing (37/106). Reasons for first revision included recurrent incontinence (56.7%), mechanical malfunction (22%), and infection or erosion (18.6%). Explantations were performed primarily for infection and erosion (64.3%). Median time to first revision was 20.1 months (range, 0.1-173 months) after implantation, with a median of 9.5 months (range, 1-102 months) between revisions. Explantation occurred at a median of 22 months (range, 1-221 months) after implant, and subsequent replacement at a median of 33.6 months (range, 2-138 months). At 5 years, 28/83 (33.7%) patients had undergone no additional procedures. Patients with previous radiation were more likely to experience infection (P = .03; OR 3.99; 95% CI 1.03-15.42). Patients with previous myocardial infarction were more likely to experience erosion (P = .04; OR 2.29; 95% CI 1.05-5.02), and obese patients were more likely to experience mechanical malfunction (P = .04; OR 2.62; 95% CI 1.07-6.4). More than half of patients with an AUS will require additional procedures, most likely revision. Radiation, previous myocardial infarction, and obesity are linked to complications. Median time to first revision or explantation is slightly less than 2 years, indicating that long-term follow-up is required after initial implantation. Copyright © 2012 Elsevier Inc. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rimner, Andreas, E-mail: rimnera@mskcc.org; Spratt, Daniel E.; Zauderer, Marjorie G.

Purpose: We previously reported our technique for delivering intensity modulated radiation therapy (IMRT) to the entire pleura while attempting to spare the lung in patients with malignant pleural mesothelioma (MPM). Herein, we report a detailed pattern-of-failure analysis in patients with MPM who were unresectable or underwent pleurectomy/decortication (P/D), uniformly treated with hemithoracic pleural IMRT. Methods and Materials: Sixty-seven patients with MPM were treated with definitive or adjuvant hemithoracic pleural IMRT between November 2004 and May 2013. Pretreatment imaging, treatment plans, and posttreatment imaging were retrospectively reviewed to determine failure location(s). Failures were categorized as in-field (within the 90% isodose line),more » marginal (<90% and ≥50% isodose lines), out-of-field (outside the 50% isodose line), or distant. Results: The median follow-up was 24 months from diagnosis and the median time to in-field local failure from the end of RT was 10 months. Forty-three in-field local failures (64%) were found with a 1- and 2-year actuarial failure rate of 56% and 74%, respectively. For patients who underwent P/D versus those who received a partial pleurectomy or were deemed unresectable, the median time to in-field local failure was 14 months versus 6 months, respectively, with 1- and 2-year actuarial in-field local failure rates of 43% and 60% versus 66% and 83%, respectively (P=.03). There were 13 marginal failures (19%). Five of the marginal failures (38%) were located within the costomediastinal recess. Marginal failures decreased with increasing institutional experience (P=.04). Twenty-five patients (37%) had out-of-field failures. Distant failures occurred in 32 patients (48%). Conclusions: After hemithoracic pleural IMRT, local failure remains the dominant form of failure pattern. Patients treated with adjuvant hemithoracic pleural IMRT after P/D experience a significantly longer time to local and distant failure than patients treated with definitive pleural IMRT. Increasing experience and improvement in target delineation minimize the incidence of avoidable marginal failures.« less

Implementation of a Tabulated Failure Model Into a Generalized Composite Material Model Suitable for Use in Impact Problems

NASA Technical Reports Server (NTRS)

Goldberg, Robert K.; Carney, Kelly S.; Dubois, Paul; Hoffarth, Canio; Khaled, Bilal; Shyamsunder, Loukham; Rajan, Subramaniam; Blankenhorn, Gunther

2017-01-01

The need for accurate material models to simulate the deformation, damage and failure of polymer matrix composites under impact conditions is becoming critical as these materials are gaining increased use in the aerospace and automotive communities. The aerospace community has identified several key capabilities which are currently lacking in the available material models in commercial transient dynamic finite element codes. To attempt to improve the predictive capability of composite impact simulations, a next generation material model is being developed for incorporation within the commercial transient dynamic finite element code LS-DYNA. The material model, which incorporates plasticity, damage and failure, utilizes experimentally based tabulated input to define the evolution of plasticity and damage and the initiation of failure as opposed to specifying discrete input parameters such as modulus and strength. The plasticity portion of the orthotropic, three-dimensional, macroscopic composite constitutive model is based on an extension of the Tsai-Wu composite failure model into a generalized yield function with a non-associative flow rule. For the damage model, a strain equivalent formulation is used to allow for the uncoupling of the deformation and damage analyses. For the failure model, a tabulated approach is utilized in which a stress or strain based invariant is defined as a function of the location of the current stress state in stress space to define the initiation of failure. Failure surfaces can be defined with any arbitrary shape, unlike traditional failure models where the mathematical functions used to define the failure surface impose a specific shape on the failure surface. In the current paper, the complete development of the failure model is described and the generation of a tabulated failure surface for a representative composite material is discussed.

Examining the causes of memory strength variability: Recollection, attention failure, or encoding variability?

PubMed Central

Koen, Joshua D.; Aly, Mariam; Wang, Wei-Chun; Yonelinas, Andrew P.

2013-01-01

A prominent finding in recognition memory is that studied items are associated with more variability in memory strength than new items. Here, we test three competing theories for why this occurs - the encoding variability, attention failure, and recollection accounts. Distinguishing amongst these theories is critical because each provides a fundamentally different account of the processes underlying recognition memory. The encoding variability and attention failure accounts propose that old item variance will be unaffected by retrieval manipulations because the processes producing this effect are ascribed to encoding. The recollection account predicts that both encoding and retrieval manipulations that preferentially affect recollection will affect memory variability. These contrasting predictions were tested by examining the effect of response speeding (Experiment 1), dividing attention at retrieval (Experiment 2), context reinstatement (Experiment 3), and increased test delay (Experiment 4) on recognition performance. The results of all four experiments confirmed the predictions of the recollection account, and were inconsistent with the encoding variability account. The evidence supporting the attention failure account was mixed, with two of the four experiments confirming the account and two disconfirming the account. These results indicate that encoding variability and attention failure are insufficient accounts of memory variance, and provide support for the recollection account. Several alternative theoretical accounts of the results are also considered. PMID:23834057

The effect of box preparation on the strength of glass fiber-reinforced composite inlay-retained fixed partial dentures.

PubMed

Ozcan, Mutlu; Breuklander, Marijn H; Vallittu, Pekka K

2005-04-01

Nonstandardized box dimensions for inlay-retained fixed partial dentures (FPDs) may result in uneven distribution of the forces on the connector region of such restorations. The objective of this in vitro study was to evaluate the effect of box dimensions on the initial and final failure strength of inlay-retained fiber-reinforced composite (FRC) FPDs. Twenty-one inlay-retained FPDs were prepared using FRC (everStick) frameworks with unidirectional fiber reinforcement between mandibular first premolars and first molars. Boxes were prepared using conventional inlay burs (Cerinlay), and small and large ultrasonic tips (SONICSYS approx). Box dimensions were measured after preparation with a digital micrometer. All restorations were subjected to thermal cycling (6000 cycles, 5 degrees C-55 degrees C). Fracture testing was performed in a universal testing machine (1 mm/min). Acoustic emission signals were monitored during loading of the specimens. Initial and final fracture strength values (2-way ANOVA, Bonferroni post hoc tests, alpha =.05) and failure types (Fisher exact test) were statistically compared for each group. Significant differences (P =.0146 and P =.0086) were observed between the groups in the dimensions of the boxes prepared using conventional burs buccolingually (2.8-3.0 mm in molars, 3.1-4.3 mm in premolars) and the small size (2.5-2.9, 2.9-3.8 mm) or large size (2.6-3.8, 3.2-4.9 mm) ultrasonic tips for the premolars and the molars, respectively. No significant differences were found at the initial and final failures between the conventionally prepared group (842 +/- 267 N, 1161 +/- 428 N) and those prepared with either small (1088 +/- 381 N, 1320 +/- 380 N) or large ultrasonic tips (1070 +/- 280 N, 1557 +/- 321 N), respectively. The failure analysis demonstrated no significant difference in failure types but predominant delamination of the veneering resin (85%) in all experimental groups. According to acoustic emission tests, a higher energy level was required for final failure of the FRC FPDs with boxes finished using small ultrasonic tips. Standardized box dimensions showed no significant effect on fracture strength at either initial or final failure of the fiber-reinforced FPDs. The FRC FPDs with boxes refined with small ultrasonic burs required a greater energy level before failure. The type of failure observed after the fracture tests was primarily delamination of the veneering resin.

[Biochemical failure after curative treatment for localized prostate cancer].

PubMed

Zouhair, Abderrahim; Jichlinski, Patrice; Mirimanoff, René-Olivier

2005-12-07

Biochemical failure after curative treatment for localized prostate cancer is frequent. The diagnosis of biochemical failure is clear when PSA levels rise after radical prostatectomy, but may be more difficult after external beam radiation therapy. The main difficulty once biochemical failure is diagnosed is to distinguish between local and distant failure, given the low sensitivity of standard work-up exams. Metabolic imaging techniques currently under evaluation may in the future help us to localize the site of failures. There are several therapeutic options depending on the initial curative treatment, each with morbidity risks that should be considered in multidisciplinary decision-making.

Simulating Initial and Progressive Failure of Open-Hole Composite Laminates under Tension

NASA Astrophysics Data System (ADS)

Guo, Zhangxin; Zhu, Hao; Li, Yongcun; Han, Xiaoping; Wang, Zhihua

2016-12-01

A finite element (FE) model is developed for the progressive failure analysis of fiber reinforced polymer laminates. The failure criterion for fiber and matrix failure is implemented in the FE code Abaqus using user-defined material subroutine UMAT. The gradual degradation of the material properties is controlled by the individual fracture energies of fiber and matrix. The failure and damage in composite laminates containing a central hole subjected to uniaxial tension are simulated. The numerical results show that the damage model can be used to accurately predicte the progressive failure behaviour both qualitatively and quantitatively.

Emotional reactivity and awareness of task performance in Alzheimer's disease.

PubMed

Mograbi, Daniel C; Brown, Richard G; Salas, Christian; Morris, Robin G

2012-07-01

Lack of awareness about performance in tasks is a common feature of Alzheimer's disease. Nevertheless, clinical anecdotes have suggested that patients may show emotional or behavioural responses to the experience of failure despite reporting limited awareness, an aspect which has been little explored experimentally. The current study investigated emotional reactions to success or failure in tasks despite unawareness of performance in Alzheimer's disease. For this purpose, novel computerised tasks which expose participants to systematic success or failure were used in a group of Alzheimer's disease patients (n=23) and age-matched controls (n=21). Two experiments, the first with reaction time tasks and the second with memory tasks, were carried out, and in each experiment two parallel tasks were used, one in a success condition and one in a failure condition. Awareness of performance was measured comparing participant estimations of performance with actual performance. Emotional reactivity was assessed with a self-report questionnaire and rating of filmed facial expressions. In both experiments the results indicated that, relative to controls, Alzheimer's disease patients exhibited impaired awareness of performance, but comparable differential reactivity to failure relative to success tasks, both in terms of self-report and facial expressions. This suggests that affective valence of failure experience is processed despite unawareness of task performance, which might indicate implicit processing of information in neural pathways bypassing awareness. Copyright © 2012 Elsevier Ltd. All rights reserved.

Failure Mode Identification Through Clustering Analysis

NASA Technical Reports Server (NTRS)

Arunajadai, Srikesh G.; Stone, Robert B.; Tumer, Irem Y.; Clancy, Daniel (Technical Monitor)

2002-01-01

Research has shown that nearly 80% of the costs and problems are created in product development and that cost and quality are essentially designed into products in the conceptual stage. Currently, failure identification procedures (such as FMEA (Failure Modes and Effects Analysis), FMECA (Failure Modes, Effects and Criticality Analysis) and FTA (Fault Tree Analysis)) and design of experiments are being used for quality control and for the detection of potential failure modes during the detail design stage or post-product launch. Though all of these methods have their own advantages, they do not give information as to what are the predominant failures that a designer should focus on while designing a product. This work uses a functional approach to identify failure modes, which hypothesizes that similarities exist between different failure modes based on the functionality of the product/component. In this paper, a statistical clustering procedure is proposed to retrieve information on the set of predominant failures that a function experiences. The various stages of the methodology are illustrated using a hypothetical design example.

Investigating compression failure mechanisms in composite laminates with a transparent fiberglass-epoxy birefringent materials

NASA Technical Reports Server (NTRS)

Shuart, M. J.; Williams, J. G.

1984-01-01

The response and failure of a + or - 45s class laminate was studied by transparent fiberglass epoxy composite birefringent material. The birefringency property allows the laminate stress distribution to be observed during the test and also after the test if permanent residual stresses occur. The location of initial laminate failure and of the subsequent failure propagation are observed through its transparency characteristics. Experimental results are presented.

Independent Orbiter Assessment (IOA): Analysis of the Orbiter Experiment (OEX) subsystem

NASA Technical Reports Server (NTRS)

Compton, J. M.

1987-01-01

The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA approach features a top-down analysis of the hardware to determine failure modes, criticality, and potential critical items. To preserve independence, this analysis was accomplished without reliance upon the results contained within the NASA FMEA/CIL documentation. This report documents the independent analysis results corresponding to the Orbiter Experiments hardware. Each level of hardware was evaluated and analyzed for possible failure modes and effects. Criticality was assigned based upon the severity of the effect for each failure mode. The Orbiter Experiments (OEX) Program consists of a multiple set of experiments for the purpose of gathering environmental and aerodynamic data to develop more accurate ground models for Shuttle performance and to facilitate the design of future spacecraft. This assessment only addresses currently manifested experiments and their support systems. Specifically this list consists of: Shuttle Entry Air Data System (SEADS); Shuttle Upper Atmosphere Mass Spectrometer (SUMS); Forward Fuselage Support System for OEX (FFSSO); Shuttle Infrared Laced Temperature Sensor (SILTS); Aerodynamic Coefficient Identification Package (ACIP); and Support System for OEX (SSO). There are only two potential critical items for the OEX, since the experiments only gather data for analysis post mission and are totally independent systems except for power. Failure of any experiment component usually only causes a loss of experiment data and in no way jeopardizes the crew or mission.

A new test apparatus for studying the failure process during loading experiments of snow

NASA Astrophysics Data System (ADS)

Capelli, Achille; Reiweger, Ingrid; Schweizer, Jürg

2016-04-01

We developed a new apparatus for fully load-controlled snow failure experiments. The deformation and applied load are measured with two displacement and two force sensors, respectively. The loading experiments are recorded with a high speed camera, and the local strain is derived by a particle image velocimetry (PIV) algorithm. To monitor the progressive failure process within the snow sample, our apparatus includes six piezoelectric transducers that record the acoustic emissions in the ultrasonic range. The six sensors allow localizing the sources of the acoustic emissions, i.e. where the failure process starts and how it develops with time towards catastrophic failure. The quadratic snow samples have a side length of 50 cm and a height of 10 to 20 cm. With an area of 0.25 m2 they are clearly larger than samples used in previous experiments. The size of the samples, which is comparable to the critical size for the onset of crack propagation leading to dry-snow slab avalanche release, allows studying the failure nucleation process and its relation to the spatial distribution of the recorded acoustic emissions. Furthermore the occurrence of features in the acoustic emissions typical for imminent failure of the samples can be analysed. We present preliminary results of the acoustic emissions recorded during tests with homogeneous as well as layered snow samples, including a weak layer, for varying loading rates and loading angles.

Biventricular hypertrophy and heart failure as initial presentation of Cushing's disease

PubMed Central

Hey, Thomas Morris; Dahl, Jordi Sanchez; Brix, Thomas Heiberg; Søndergaard, Eva Vad

2013-01-01

We present a unique case of a 32-year-old woman with severe biventricular hypertrophy and acute heart failure with reduced left ventricular ejection fraction of 25–30% due to Cushing's disease. The patient was admitted to a specialised cardiac unit and treated with conventional therapy against heart failure. The department of endocrinology was consulted because of clinical suspicion of Cushing's syndrome. Initial biochemistry indicated the presence of adrenocorticotropic hormone (ACTH) dependent Cushing's syndrome and a dexamethasone suppression test confirmed the diagnosis. A cerebral MRI scan revealed a pituitary adenoma and a sinus petrosus inferior catheterisation confirmed increased production of ACTH from the pituitary. The patient was referred to the neurosurgical department and the adenoma was successfully removed by transsphenoidalic catheterisation and ablation. Five months following the initial hospitalisation the patient was nearly in full recovery with respect to her cardiac function and biochemically there were no signs of Cushing's syndrome. PMID:24186856

The Effects of Hot Corrosion Pits on the Fatigue Resistance of a Disk Superalloy

NASA Technical Reports Server (NTRS)

Gabb, Timothy P.; Telesman, Jack; Hazel, Brian; Mourer, David P.

2009-01-01

The effects of hot corrosion pits on low cycle fatigue life and failure modes of the disk superalloy ME3 were investigated. Low cycle fatigue specimens were subjected to hot corrosion exposures producing pits, then tested at low and high temperatures. Fatigue lives and failure initiation points were compared to those of specimens without corrosion pits. Several tests were interrupted to estimate the fraction of fatigue life that fatigue cracks initiated at pits. Corrosion pits significantly reduced fatigue life by 60 to 98 percent. Fatigue cracks initiated at a very small fraction of life for high temperature tests, but initiated at higher fractions in tests at low temperature. Critical pit sizes required to promote fatigue cracking were estimated, based on measurements of pits initiating cracks on fracture surfaces.

Simulation Experiment and Acoustic Emission Study on Coal and Gas Outburst

NASA Astrophysics Data System (ADS)

Li, Hui; Feng, Zengchao; Zhao, Dong; Duan, Dong

2017-08-01

A coal and gas outburst is an extreme hazard in underground mining. The present paper conducts a laboratory simulation of a coal and gas outburst combined with acoustic emission analysis. The experiment uses a three-dimensional stress loading system and a PCI-2 acoustic emission monitoring system. Furthermore, the development of a coal and gas outburst is numerically studied. The results demonstrate that the deformation and failure of a coal sample containing methane under three-dimensional stress involves four stages: initial compression, elastic deformation, plastic deformation and failure. The development of internal microscale fractures within a coal sample containing methane is reflected by the distribution of acoustic emission events. We observed that the deformation and failure zone for a coal sample under three-dimensional stress has an ellipsoid shape. Primary acoustic emission events are generated at the weak structural surface that compresses with ease due to the external ellipsoid-shaped stress. The number of events gradually increases until an outburst occurs. A mathematical model of the internal gas pressure and bulk stress is established through an analysis of the internal gas pressure and bulk stress of a coal sample, and it is useful for reproducing experimental results. The occurrence of a coal and gas outburst depends not only on the in situ stress, gas pressure and physical and mechanical characteristics of the coal mass but also on the free weak surface of the outburst outlet of the coal mass. It is more difficult for an outburst to occur from a stronger free surface.

Illinois Prekindergarten Program for Children At Risk of Academic Failure. FY 93 Summary Report.

ERIC Educational Resources Information Center

Illinois State Board of Education, Springfield, Dept. of Planning, Research and Evaluation.

The Illinois Prekindergarten Program for Children at Risk of Academic Failure was a grant program for public school districts to enhance growth and development of children ages 3 to 5 who are at risk of academic failure. The program has experienced significant growth since its initial implementation, and the number of participating projects…

Triaxial testing of Lopez Fault gouge at 150 MPa mean effective stress

USGS Publications Warehouse

Scott, D.R.; Lockner, D.A.; Byerlee, J.D.; Sammis, C.G.

1994-01-01

Triaxial compression experiments were performed on samples of natural granular fault gouge from the Lopez Fault in Southern California. This material consists primarily of quartz and has a self-similar grain size distribution thought to result from natural cataclasis. The experiments were performed at a constant mean effective stress of 150 MPa, to expose the volumetric strains associated with shear failure. The failure strength is parameterized by the coefficient of internal friction ??, based on the Mohr-Coulomb failure criterion. Samples of remoulded Lopez gouge have internal friction ??=0.6??0.02. In experiments where the ends of the sample are constrained to remain axially aligned, suppressing strain localisation, the sample compacts before failure and dilates persistently after failure. In experiments where one end of the sample is free to move laterally, the strain localises to a single oblique fault at around the point of failure; some dilation occurs but does not persist. A comparison of these experiments suggests that dilation is confined to the region of shear localisation in a sample. Overconsolidated samples have slightly larger failure strengths than normally consolidated samples, and smaller axial strains are required to cause failure. A large amount of dilation occurs after failure in heavily overconsolidated samples, suggesting that dilation is occurring throughout the sample. Undisturbed samples of Lopez gouge, cored from the outcrop, have internal friction in the range ??=0.4-0.6; the upper end of this range corresponds to the value established for remoulded Lopez gouge. Some kind of natural heterogeneity within the undisturbed samples is probably responsible for their low, variable strength. In samples of simulated gouge, with a more uniform grain size, active cataclasis during axial loading leads to large amounts of compaction. Larger axial strains are required to cause failure in simulated gouge, but the failure strength is similar to that of natural Lopez gouge. Use of the Mohr-Coulomb failure criterion to interpret the results from this study, and other recent studies on intact rock and granular gouge, leads to values of ?? that depend on the loading configuration and the intact or granular state of the sample. Conceptual models are advanced to account for these descrepancies. The consequences for strain-weakening of natural faults are also discussed. ?? 1994 Birkha??user Verlag.

Eclogite-facies metamorphic reactions under stress and faulting in granulites from the Bergen Arcs, Norway: an experimental investigation

NASA Astrophysics Data System (ADS)

Incel, Sarah; Hilairet, Nadège; Labrousse, Loïc; Andersen, Torgeir B.; Wang, Yanbin; Schubnel, Alexandre

2017-04-01

Field observations from the Bergen Arcs, Norway, demonstrate a network of pseudotachylites quenched under eclogite-facies conditions in mafic granulites. In these nominally anhydrous high-pressure high-temperature (HP/HT) rocks the formation of pseudotachylites, believed to represent fossilized earthquakes, cannot be explained by processes akin to dehydration embrittlement. On the contrary, the transition to eclogite is expected to involve hydration of the initial rock. To experimentally investigate the underlying mechanisms leading to brittle failure in HP/HT rocks, we performed deformation experiments on natural granulite samples from the Bergen Arcs. The experiments were conducted under eclogite-facies conditions (2-3 GPa, 990-1220 K) to trigger the breakdown of plagioclase - the main constituent of granulite. For these experiments, both a D-DIA and a Griggs apparatus were used. The D-DIA press is mounted on a synchrotron beamline, enabling us to monitor strain, stress, and phase changes in-situ while contemporaneously recording acoustic emissions. The Griggs experiments were performed on a new device installed at ENS Paris, in which only stress-strain were recorded, and post-mortem microstructures investigated. The initial material consisted of a fine grain size granulite powder (< 38 µm) composed of mainly plagioclase and minor amount of pyroxene. Hydrous phases are phlogopite and epidote group minerals that make up less than 1 vol. % of the total bulk rock powder plus the adhesion water on grain surfaces. Mechanical data together with XRD observations and the record of acoustic emissions demonstrate a correlation between stress drops, the growth of plagioclase breakdown products and the onset of acoustic emissions during deformation of our specimen within the eclogitic field. Microstructural analysis show remarkable similarities with that of the natural ecoligitic pseudotachylites of the Bergen arcs. The plagioclase decomposition products form narrow conjugated shear bands, along which dissected and displaced crystals are found in the samples. The lack of microstructural evidence for macroscopic brittle failure in our microstructures could be due to plastic overprinting of early brittle structures. Nevertheless, our preliminary experimental results show a strong correlation between strain localization, dynamic fracture propagation (rapid enough to produce AEs) and the eclogitization of granulite.

Porting Initiation and Failure into Linked CHEETAH

NASA Astrophysics Data System (ADS)

Souers, Clark; Vitello, Peter

2007-06-01

Linked CHEETAH is a thermo-chemical code coupled to a 2-D hydrocode. Initially, a quadratic-pressure dependent kinetic rate was used, which worked well in modeling prompt detonation of explosives of large size, but does not work on other aspects of explosive behavior. The variable-pressure Tarantula reactive flow rate model was developed with JWL++ in order to also describe failure and initiation, and we have moved this model into Linked CHEETAH. The model works by turning on only above a pressure threshold, where a slow turn-on creates initiation. At a higher pressure, the rate suddenly leaps to a large value over a small pressure range. A slowly failing cylinder will see a rapidly declining rate, which pushes it quickly into failure. At a high pressure, the detonation rate is constant. A sequential validation procedure is used, which includes metal-confined cylinders, rate-sticks, corner-turning, initiation and threshold, gap tests and air gaps. The size (diameter) effect is central to the calibration. This work was performed under the auspices of the U.S. Department of Energy by the University of California Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.

Optimizing the robustness of electrical power systems against cascading failures.

PubMed

Zhang, Yingrui; Yağan, Osman

2016-06-21

Electrical power systems are one of the most important infrastructures that support our society. However, their vulnerabilities have raised great concern recently due to several large-scale blackouts around the world. In this paper, we investigate the robustness of power systems against cascading failures initiated by a random attack. This is done under a simple yet useful model based on global and equal redistribution of load upon failures. We provide a comprehensive understanding of system robustness under this model by (i) deriving an expression for the final system size as a function of the size of initial attacks; (ii) deriving the critical attack size after which system breaks down completely; (iii) showing that complete system breakdown takes place through a first-order (i.e., discontinuous) transition in terms of the attack size; and (iv) establishing the optimal load-capacity distribution that maximizes robustness. In particular, we show that robustness is maximized when the difference between the capacity and initial load is the same for all lines; i.e., when all lines have the same redundant space regardless of their initial load. This is in contrast with the intuitive and commonly used setting where capacity of a line is a fixed factor of its initial load.

Managing heart failure in the long-term care setting: nurses' experiences in Ontario, Canada.

PubMed

Strachan, Patricia H; Kaasalainen, Sharon; Horton, Amy; Jarman, Hellen; D'Elia, Teresa; Van Der Horst, Mary-Lou; Newhouse, Ian; Kelley, Mary Lou; McAiney, Carrie; McKelvie, Robert; Heckman, George A

2014-01-01

Implementation of heart failure guidelines in long-term care (LTC) settings is challenging. Understanding the conditions of nursing practice can improve management, reduce suffering, and prevent hospital admission of LTC residents living with heart failure. The aim of the study was to understand the experiences of LTC nurses managing care for residents with heart failure. This was a descriptive qualitative study nested in Phase 2 of a three-phase mixed methods project designed to investigate barriers and solutions to implementing the Canadian Cardiovascular Society heart failure guidelines into LTC homes. Five focus groups totaling 33 nurses working in LTC settings in Ontario, Canada, were audiorecorded, then transcribed verbatim, and entered into NVivo9. A complex adaptive systems framework informed this analysis. Thematic content analysis was conducted by the research team. Triangulation, rigorous discussion, and a search for negative cases were conducted. Data were collected between May and July 2010. Nurses characterized their experiences managing heart failure in relation to many influences on their capacity for decision-making in LTC settings: (a) a reactive versus proactive approach to chronic illness; (b) ability to interpret heart failure signs, symptoms, and acuity; (c) compromised information flow; (d) access to resources; and (e) moral distress. Heart failure guideline implementation reflects multiple dynamic influences. Leadership that addresses these factors is required to optimize the conditions of heart failure care and related nursing practice.

A Summary of Taxonomies of Digital System Failure Modes Provided by the DigRel Task Group

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chu T. L.; Yue M.; Postma, W.

2012-06-25

Recently, the CSNI directed WGRisk to set up a task group called DIGREL to initiate a new task on developing a taxonomy of failure modes of digital components for the purposes of PSA. It is an important step towards standardized digital I&C reliability assessment techniques for PSA. The objective of this paper is to provide a comparison of the failure mode taxonomies provided by the participants. The failure modes are classified in terms of their levels of detail. Software and hardware failure modes are discussed separately.

Progressive Failure Analysis Methodology for Laminated Composite Structures

NASA Technical Reports Server (NTRS)

Sleight, David W.

1999-01-01

A progressive failure analysis method has been developed for predicting the failure of laminated composite structures under geometrically nonlinear deformations. The progressive failure analysis uses C(exp 1) shell elements based on classical lamination theory to calculate the in-plane stresses. Several failure criteria, including the maximum strain criterion, Hashin's criterion, and Christensen's criterion, are used to predict the failure mechanisms and several options are available to degrade the material properties after failures. The progressive failure analysis method is implemented in the COMET finite element analysis code and can predict the damage and response of laminated composite structures from initial loading to final failure. The different failure criteria and material degradation methods are compared and assessed by performing analyses of several laminated composite structures. Results from the progressive failure method indicate good correlation with the existing test data except in structural applications where interlaminar stresses are important which may cause failure mechanisms such as debonding or delaminations.

The impact of patient-perceived restricted access to anti-TNF therapy for rheumatoid arthritis: a qualitative study

PubMed Central

Sanderson, Tessa; Calnan, Michael; Morris, Marianne; Richards, Pam; Hewlett, Sarah

2010-01-01

Objective To explore rheumatoid arthritis patients’ experience of access to anti-TNF therapy in the UK, and of switching therapies after an initial failure. Methods Patients were asked about their experience of accessing, receiving and discontinuing anti-TNF therapy in face-to-face informal interviews, within the context of the larger study about treatment outcomes. 17 individuals with a diagnosis of rheumatoid arthritis and experience of receiving anti-TNF therapy were interviewed in one hospital trust in England. Results Different emotions (Theme 1) surrounded the process of accessing anti-TNF therapy: hope, desperation, apprehension, anxiety, and frustration. Experience of receiving anti-TNF therapy (Theme 2) included not only positive transformation, but also fear of failure and discontinuation. The subsequent value that patients placed on anti-TNF therapy (Theme 3) included having a right to receive therapy and being lucky. These three themes were underpinned by the core category of ‘willing to try anything’. Those switching therapies reported increased caution over the possibility of recurring side effects, but some suggestion of benefit. There was a perception that access to anti-TNF therapy was restricted by cost, rather than being recommended for those in clinical need. Conclusions Anti-TNF therapies may have a sudden and dramatic impact on RA patients’ lives that contrasts with other available medications. However, the stress of the patient’s journey through the need to “qualify” for anti-TNF therapy, and the fear of failing or discontinuation of therapy should not be underestimated by clinicians. PMID:19127529

Understanding the gendered patterns of substance use initiation among adolescents living in rural, central Mexico

PubMed Central

Ayers, Stephanie; Marsiglia, Flavio; Hoffman, Steven; Urbaeva, Zhyldyz

2012-01-01

Background Little is known about the age of initiation and gender differences in substance use among adolescents in rural, central Mexico. Methods The cross-sectional data were collected from students enrolled in the Videobachillerato (VIBA) (video high school) program in Guanajuato, Mexico. Questionnaires asked students about the age at which they had used alcohol, cigarettes, or marijuana for the first time. Kaplan-Meier Survival Functions were used to estimate if males and females were significantly different in their cumulative probabilities of initiating substances over time. Results On average, alcohol is initiated at 14.7 years of age, cigarettes at 15.1 years of age, and marijuana at 16.5 years of age. Over time, males had a significantly higher probability of initiating alcohol (Kaplan-Meier Failure Curve: Χ2=26.35, p<0.001), cigarettes (Kaplan-Meier Failure Curve: Χ2=41.90, p<0.001), and marijuana (Kaplan-Meier Failure Curve: Χ2=38.01, p<0.001) compared to females. Conclusions These results highlight the gendered patterns of substance use initiation among adolescents in rural, central Mexico and underscore the need for gendered substance use prevention interventions with these adolescents. By putting forth efforts to understand substance use initiation patterns of adolescents living in rural, central Mexico, culturally specific and efficacious prevention efforts can be tailor-made to create lasting differences. PMID:22421555

Dynamic Failure and Fragmentation of a Hot-Pressed Boron Carbide

NASA Astrophysics Data System (ADS)

Sano, Tomoko; Vargas-Gonzalez, Lionel; LaSalvia, Jerry; Hogan, James David

2017-12-01

This study investigates the failure and fragmentation of a hot-pressed boron carbide during high rate impact experiments. Four impact experiments are performed using a composite-backed target configuration at similar velocities, where two of the impact experiments resulted in complete target penetration and two resulted in partial penetration. This paper seeks to evaluate and understand the dynamic behavior of the ceramic that led to either the complete or partial penetration cases, focusing on: (1) surface and internal failure features of fragments using optical, scanning electron, and transmission electron microscopy, and (2) fragment size analysis using state-of-the-art particle-sizing technology that informs about the consequences of failure. Detailed characterization of the mechanical properties and the microstructure is also performed. Results indicate that transgranular fracture was the primary mode of failure in this boron carbide material, and no stress-induced amorphization features were observed. Analysis of the fragment sizes for the partial and completely penetrated experiments revealed a possible correlation between larger fragment sizes and impact performance. The results will add insight into designing improved advanced ceramics for impact protection applications.

Experimental Study on Reaction Characteristics of PTFE/Ti/W Energetic Materials under Explosive Loading

PubMed Central

Li, Yan; Jiang, Chunlan; Wang, Zaicheng; Luo, Puguang

2016-01-01

Metal/fluoropolymer composites represent a new category of energetic structural materials that release energy through exothermic chemical reactions initiated under shock loading conditions. This paper describes an experiment designed to study the reaction characteristics of energetic materials with low porosity under explosive loading. Three PTFE (polytetrafluoroethylene)/Ti/W mixtures with different W contents are processed through pressing and sintering. An inert PTFE/W mixture without reactive Ti particles is also prepared to serve as a reference. Shock-induced chemical reactions are recorded by high-speed video through a narrow observation window. Related shock parameters are calculated based on experimental data, and differences in energy release are discussed. The results show that the reaction propagation of PTFE/Ti/W energetic materials with low porosity under explosive loading is not self-sustained. As propagation distance increases, the energy release gradually decreases. In addition, reaction failure distance in PTFE/Ti/W composites is inversely proportional to the W content. Porosity increased the failure distance due to higher shock temperature. PMID:28774056

Computational simulation of the creep-rupture process in filamentary composite materials

NASA Technical Reports Server (NTRS)

Slattery, Kerry T.; Hackett, Robert M.

1991-01-01

A computational simulation of the internal damage accumulation which causes the creep-rupture phenomenon in filamentary composite materials is developed. The creep-rupture process involves complex interactions between several damage mechanisms. A statistically-based computational simulation using a time-differencing approach is employed to model these progressive interactions. The finite element method is used to calculate the internal stresses. The fibers are modeled as a series of bar elements which are connected transversely by matrix elements. Flaws are distributed randomly throughout the elements in the model. Load is applied, and the properties of the individual elements are updated at the end of each time step as a function of the stress history. The simulation is continued until failure occurs. Several cases, with different initial flaw dispersions, are run to establish a statistical distribution of the time-to-failure. The calculations are performed on a supercomputer. The simulation results compare favorably with the results of creep-rupture experiments conducted at the Lawrence Livermore National Laboratory.

Seminoma at Roswell Park, 1970 to 1979. An analysis of treatment failures.

PubMed

Huben, R P; Williams, P D; Pontes, J E; Panahon, A M; Murphy, G P

1984-04-01

A retrospective study of all cases of seminoma treated at Roswell Park Memorial Institute from 1970 through 1979 was conducted. Fifty-six evaluable patients treated initially with radiation therapy were seen during this period, and the overall survival rate at an average follow-up period of 52 months was 82%. The survival rate in patients with bulky abdominal or supradiaphragmatic metastases was only 33% (4 of 12 patients). Treatment failures were analyzed to determine their apparent causes and the implication of such failures to the future management of seminoma. The use of combination chemotherapy as the initial treatment modality in advanced seminoma is discussed in light of these results.

Failure prediction in ceramic composites using acoustic emission and digital image correlation

NASA Astrophysics Data System (ADS)

Whitlow, Travis; Jones, Eric; Przybyla, Craig

2016-02-01

The objective of the work performed here was to develop a methodology for linking in-situ detection of localized matrix cracking to the final failure location in continuous fiber reinforced CMCs. First, the initiation and growth of matrix cracking are measured and triangulated via acoustic emission (AE) detection. High amplitude events at relatively low static loads can be associated with initiation of large matrix cracks. When there is a localization of high amplitude events, a measurable effect on the strain field can be observed. Full field surface strain measurements were obtained using digital image correlation (DIC). An analysis using the combination of the AE and DIC data was able to predict the final failure location.

Flexure fatigue testing of 90 deg graphite/epoxy composites

NASA Technical Reports Server (NTRS)

Peck, Ann Nancy W.

1995-01-01

A great deal of research has been performed characterizing the in-plane fiber-dominated properties, under both static and fatigue loading, of advanced composite materials. To the author's knowledge, no study has been performed to date investigating fatigue characteristics in the transverse direction. This information is important in the design of bonded composite airframe structure where repeated, cyclic out-of-plane bending may occur. Recent tests characterizing skin/stringer debond failures in reinforced composite panels where the dominant loading in the skin is flexure along the edge of the frame indicate failure initiated either in the skin or else the flange, near the flange tip. When failure initiated in the skin, transverse matrix cracks formed in the surface skin ply closest to the flange and either initiated delaminations or created matrix cracks in the next lower ply, which in turn initiated delaminations. When failure initiated in the flanges, transverse cracks formed in the flange angle ply closest to the skin and initiated delamination. In no configuration did failure propagate through the adhesive bond layer. For the examined skin/flange configurations, the maximum transverse tension stress at failure correlates very well with the transverse tension strength of the composites. Transverse tension strength (static) data of graphite epoxy composites have been shown to vary with the volume of material stressed. As the volume of material stressed increased, the strength decreased. A volumetric scaling law based on Weibull statistics can be used to predict the transverse strength measurements. The volume dependence reflects the presence of inherent flaws in the microstructure of the lamina. A similar approach may be taken to determine a volume scale effect on the transverse tension fatigue behavior of graphite/epoxy composites. The objective of this work is to generate transverse tension strength and fatigue S-N characteristics for composite materials using 3-point flexure tests of 90 deg graphite/epoxy specimens. Investigations will include the volume scale effect as well as frequency and span-to-thickness ratio effects. Prior to the start of the experimental study, an analytical study using finite element modeling will be performed to investigate the span-to-thickness effect. The ratio of transverse flexure stress to shear stress will be monitored and its values predicted by the FEM analysis compared with the value obtained using a 'strength of materials' based approach.

Two-IMU FDI performance of the sequential probability ratio test during shuttle entry

NASA Technical Reports Server (NTRS)

Rich, T. M.

1976-01-01

Performance data for the sequential probability ratio test (SPRT) during shuttle entry are presented. Current modeling constants and failure thresholds are included for the full mission 3B from entry through landing trajectory. Minimum 100 percent detection/isolation failure levels and a discussion of the effects of failure direction are presented. Finally, a limited comparison of failures introduced at trajectory initiation shows that the SPRT algorithm performs slightly worse than the data tracking test.

Experimental study on the stability and failure of individual step-pool

NASA Astrophysics Data System (ADS)

Zhang, Chendi; Xu, Mengzhen; Hassan, Marwan A.; Chartrand, Shawn M.; Wang, Zhaoyin

2018-06-01

Step-pools are one of the most common bedforms in mountain streams, the stability and failure of which play a significant role for riverbed stability and fluvial processes. Given this importance, flume experiments were performed with a manually constructed step-pool model. The experiments were carried out with a constant flow rate to study features of step-pool stability as well as failure mechanisms. The results demonstrate that motion of the keystone grain (KS) caused 90% of the total failure events. The pool reached its maximum depth and either exhibited relative stability for a period before step failure, which was called the stable phase, or the pool collapsed before its full development. The critical scour depth for the pool increased linearly with discharge until the trend was interrupted by step failure. Variability of the stable phase duration ranged by one order of magnitude, whereas variability of pool scour depth was constrained within 50%. Step adjustment was detected in almost all of the runs with step-pool failure and was one or two orders smaller than the diameter of the step stones. Two discharge regimes for step-pool failure were revealed: one regime captures threshold conditions and frames possible step-pool failure, whereas the second regime captures step-pool failure conditions and is the discharge of an exceptional event. In the transitional stage between the two discharge regimes, pool and step adjustment magnitude displayed relatively large variabilities, which resulted in feedbacks that extended the duration of step-pool stability. Step adjustment, which was a type of structural deformation, increased significantly before step failure. As a result, we consider step deformation as the direct explanation to step-pool failure rather than pool scour, which displayed relative stability during step deformations in our experiments.

The dynamic failure behavior of tungsten heavy alloys subjected to transverse loads

NASA Astrophysics Data System (ADS)

Tarcza, Kenneth Robert

Tungsten heavy alloys (WHA), a category of particulate composites used in defense applications as kinetic energy penetrators, have been studied for many years. Even so, their dynamic failure behavior is not fully understood and cannot be predicted by numerical models presently in use. In this experimental investigation, a comprehensive understanding of the high-rate transverse-loading fracture behavior of WHA has been developed. Dynamic fracture events spanning a range of strain rates and loading conditions were created via mechanical testing and used to determine the influence of surface condition and microstructure on damage initiation, accumulation, and sample failure under different loading conditions. Using standard scanning electron microscopy metallographic and fractographic techniques, sample surface condition is shown to be extremely influential to the manner in which WHA fails, causing a fundamental change from externally to internally nucleated failures as surface condition is improved. Surface condition is characterized using electron microscopy and surface profilometry. Fracture surface analysis is conducted using electron microscopy, and linear elastic fracture mechanics is used to understand the influence of surface condition, specifically initial flaw size, on sample failure behavior. Loading conditions leading to failure are deduced from numerical modeling and experimental observation. The results highlight parameters and considerations critical to the understanding of dynamic WHA fracture and the development of dynamic WHA failure models.

Failure analysis of thick composite cylinders under external pressure

NASA Technical Reports Server (NTRS)

Caiazzo, A.; Rosen, B. W.

1992-01-01

Failure of thick section composites due to local compression strength and overall structural instability is treated. Effects of material nonlinearity, imperfect fiber architecture, and structural imperfections upon anticipated failure stresses are determined. Comparisons with experimental data for a series of test cylinders are described. Predicting the failure strength of composite structures requires consideration of stability and material strength modes of failure using linear and nonlinear analysis techniques. Material strength prediction requires the accurate definition of the local multiaxial stress state in the material. An elasticity solution for the linear static analysis of thick anisotropic cylinders and rings is used herein to predict the axisymmetric stress state in the cylinders. Asymmetric nonlinear behavior due to initial cylinder out of roundness and the effects of end closure structure are treated using finite element methods. It is assumed that local fiber or ply waviness is an important factor in the initiation of material failure. An analytical model for the prediction of compression failure of fiber composites, which includes the effects of fiber misalignments, matrix inelasticity, and multiaxial applied stresses is used for material strength calculations. Analytical results are compared to experimental data for a series of glass and carbon fiber reinforced epoxy cylinders subjected to external pressure. Recommendations for pretest characterization and other experimental issues are presented. Implications for material and structural design are discussed.

Graft failure after allogeneic hematopoietic stem cell transplantation.

PubMed

Ozdemir, Zehra Narli; Civriz Bozdağ, Sinem

2018-04-18

Graft failure is a serious complication of allogeneic hematopoietic stem cell transplantation (allo-HSCT) defined as either lack of initial engraftment of donor cells (primary graft failure) or loss of donor cells after initial engraftment (secondary graft failure). Successful transplantation depends on the formation of engrafment, in which donor cells are integrated into the recipient's cell population. In this paper, we distinguish two different entities, graft failure (GF) and poor graft function (PGF), and review the current comprehensions of the interactions between the immune and hematopoietic compartments in these conditions. Factors associated with graft failure include histocompatibility locus antigen (HLA)-mismatched grafts, underlying disease, type of conditioning regimen and stem cell source employed, low stem cell dose, ex vivo T-cell depletion, major ABO incompatibility, female donor grafts for male recipients, disease status at transplantation. Although several approaches have been developed which aimed to prevent graft rejection, establish successful engraftment and treat graft failure, GF remains a major obstacle to the success of allo-HSCT. Allogeneic hematopoietic stem cell transplantation (allo-HSCT) still remains to be the curative treatment option for various non-malignant and malignant hematopoietic diseases. The outcome of allo-HSCT primarily depends on the engraftment of the graft. Graft failure (GF), is a life-threatening complication which needs the preferential therapeutic manipulation. In this paper, we focused on the definitions of graft failure / poor graft function and also we reviewed the current understanding of the pathophysiology, risk factors and treatment approaches for these entities. Copyright © 2018. Published by Elsevier Ltd.

Optimal maintenance policy incorporating system level and unit level for mechanical systems

NASA Astrophysics Data System (ADS)

Duan, Chaoqun; Deng, Chao; Wang, Bingran

2018-04-01

The study works on a multi-level maintenance policy combining system level and unit level under soft and hard failure modes. The system experiences system-level preventive maintenance (SLPM) when the conditional reliability of entire system exceeds SLPM threshold, and also undergoes a two-level maintenance for each single unit, which is initiated when a single unit exceeds its preventive maintenance (PM) threshold, and the other is performed simultaneously the moment when any unit is going for maintenance. The units experience both periodic inspections and aperiodic inspections provided by failures of hard-type units. To model the practical situations, two types of economic dependence have been taken into account, which are set-up cost dependence and maintenance expertise dependence due to the same technology and tool/equipment can be utilised. The optimisation problem is formulated and solved in a semi-Markov decision process framework. The objective is to find the optimal system-level threshold and unit-level thresholds by minimising the long-run expected average cost per unit time. A formula for the mean residual life is derived for the proposed multi-level maintenance policy. The method is illustrated by a real case study of feed subsystem from a boring machine, and a comparison with other policies demonstrates the effectiveness of our approach.

Arteriovenous fistula maturation in patients with permanent access created prior to or after hemodialysis initiation.

PubMed

Duque, Juan C; Martinez, Laisel; Tabbara, Marwan; Dvorquez, Denise; Mehandru, Sushil K; Asif, Arif; Vazquez-Padron, Roberto I; Salman, Loay H

2017-05-15

Multiple factors and comorbidities have been implicated in the ability of arteriovenous fistulas (AVF) to mature, including vessel anatomy, advanced age, and the presence of coronary artery disease or peripheral vascular disease. However, little is known about the role of uremia on AVF primary failure. In this study, we attempt to evaluate the effect of uremia on AVF maturation by comparing AVF outcomes between pre-dialysis chronic kidney disease (CKD) stage five patients and those who had their AVF created after hemodialysis (HD) initiation. We included 612 patients who underwent AVF creation between 2003 and 2015 at the University of Miami Hospital and Jackson Memorial Hospital. Effects of uremia on primary failure were evaluated using univariate statistical comparisons and multivariate logistic regression analyses. Primary failure occurred in 28.1% and 26.3% of patients with an AVF created prior to or after HD initiation, respectively (p = 0.73). The time of HD initiation was not associated with AVF maturation in multivariate logistic regression analysis (p = 0.57). In addition, pre-operative blood urea nitrogen (p = 0.78), estimated glomerular filtration rate (p = 0.66), and serum creatinine levels (p = 0.14) were not associated with AVF primary failure in pre-dialysis patients. Our results show that clearance of uremia with regular HD treatments prior to AVF creation does not improve the frequency of vascular access maturation.

Characterization of failure processes in tungsten copper composites under fatigue loading conditions

NASA Technical Reports Server (NTRS)

Kim, Yong-Suk; Verrilli, Michael J.; Gabb, Timothy P.

1989-01-01

A fractographic and metallographic investigation was performed on specimens of a tungsten fiber reinforced copper matrix composite (9 vol percent), which had experienced fatigue failures at elevated temperatures. Major failure modes and possible failure mechanisms, with an emphasis placed on characterizing fatigue damage accumulation, were determined. Metallography of specimens fatigued under isothermal cyclic loading suggested that fatigue damage initiates in the matrix. Cracks nucleated within the copper matrix at grain boundaries, and they propagated through cavity coalescence. The growing cracks subsequently interacted with the reinforcing tungsten fibers, producing a localized ductile fiber failure. Examinations of interrupted tests before final failure confirmed the suggested fatigue damage processes.

Hodgkin's lymphoma coexisting with liver failure secondary to acute on chronic hepatitis B.

PubMed

Palta, Renee; McClune, Amy; Esrason, Karl

2013-04-16

Acute on chronic liver failure (ACLF) is rarely the initial manifestation of a malignant process or precipitated by the initiation of anti-viral treatment with a nucleoside or nucleotide agent. We report an unusual case of ACLF temporally associated with initiation of Entecavir for treatment of chronic hepatitis B. Early Hodgkin's lymphoma (HL) was unmasked with initiation of the anti-viral treatment which may have exacerbated ACLF. To the best of our knowledge, this has not been described in the literature. In reviewing our patients clinical course and liver autopsy, he developed a severe acute exacerbation of his chronic hepatitis B virus coinciding with the institution of antiviral therapy and the underlying HL perhaps modulating the overall degree of hepatic injury.

Examining the causes of memory strength variability: recollection, attention failure, or encoding variability?

PubMed

Koen, Joshua D; Aly, Mariam; Wang, Wei-Chun; Yonelinas, Andrew P

2013-11-01

A prominent finding in recognition memory is that studied items are associated with more variability in memory strength than new items. Here, we test 3 competing theories for why this occurs-the encoding variability, attention failure, and recollection accounts. Distinguishing among these theories is critical because each provides a fundamentally different account of the processes underlying recognition memory. The encoding variability and attention failure accounts propose that old item variance will be unaffected by retrieval manipulations because the processes producing this effect are ascribed to encoding. The recollection account predicts that both encoding and retrieval manipulations that preferentially affect recollection will affect memory variability. These contrasting predictions were tested by examining the effect of response speeding (Experiment 1), dividing attention at retrieval (Experiment 2), context reinstatement (Experiment 3), and increased test delay (Experiment 4) on recognition performance. The results of all 4 experiments confirm the predictions of the recollection account and are inconsistent with the encoding variability account. The evidence supporting the attention failure account is mixed, with 2 of the 4 experiments confirming the account and 2 disconfirming the account. These results indicate that encoding variability and attention failure are insufficient accounts of memory variance and provide support for the recollection account. Several alternative theoretical accounts of the results are also considered. PsycINFO Database Record (c) 2013 APA, all rights reserved.

An accelerating precursor to predict "time-to-failure" in creep and volcanic eruptions

NASA Astrophysics Data System (ADS)

Hao, Shengwang; Yang, Hang; Elsworth, Derek

2017-09-01

Real-time prediction by monitoring of the evolution of response variables is a central goal in predicting rock failure. A linear relation Ω˙Ω¨-1 = C(tf - t) has been developed to describe the time to failure, where Ω represents a response quantity, C is a constant and tf represents the failure time. Observations from laboratory creep failure experiments and precursors to volcanic eruptions are used to test the validity of the approach. Both cumulative and simple moving window techniques are developed to perform predictions and to illustrate the effects of data selection on the results. Laboratory creep failure experiments on granites show that the linear relation works well during the final approach to failure. For blind prediction, the simple moving window technique is preferred because it always uses the most recent data and excludes effects of early data deviating significantly from the predicted trend. When the predicted results show only small fluctuations, failure is imminent.

Survey of HEPA filter experience

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carbaugh, E.H.

1982-07-01

A survey of high efficiency particulate air (HEPA) filter applications and experience at Department of Energy (DOE) sites was conducted to provide an overview of the reasons and magnitude of HEPA filter changeouts and failures. Results indicated that approximately 58% of the filters surveyed were changed out in the three year study period, and some 18% of all filters were changed out more than once. Most changeouts (63%) were due to the existence of a high pressure drop across the filter, indicative of filter plugging. Other reasons for changeout included leak-test failure (15%), preventive maintenance service life limit (13%), suspectedmore » damage (5%) and radiation buildup (4%). Filter failures occurred with approximately 12% of all installed filters. Of these failures, most (64%) occurred for unknown or unreported reasons. Handling or installation damage accounted for an additional 19% of reported failures. Media ruptures, filter-frame failures and seal failures each accounted for approximately 5 to 6% of the reported failures.« less

49 CFR Appendix A to Part 232 - Schedule of Civil Penalties 1

Code of Federal Regulations, 2013 CFR

2013-10-01

...) Failure to meet general design requirements 2,500 5,000 (d) Failure to have proper percentage of operative brakes from Class I brake test 5,000 7,500 (e) Operating with less than 85 percent operative brakes 5,000...) Failure to adopt and comply with periodic assessment plan 7,500 11,000 232.205Class I brake test—initial...

49 CFR Appendix A to Part 232 - Schedule of Civil Penalties 1

Code of Federal Regulations, 2012 CFR

2012-10-01

...) Failure to meet general design requirements 2,500 5,000 (d) Failure to have proper percentage of operative brakes from Class I brake test 5,000 7,500 (e) Operating with less than 85 percent operative brakes 5,000...) Failure to adopt and comply with periodic assessment plan 7,500 11,000 232.205Class I brake test—initial...

49 CFR Appendix A to Part 232 - Schedule of Civil Penalties 1

Code of Federal Regulations, 2010 CFR

2010-10-01

...) Failure to meet general design requirements 2,500 5,000 (d) Failure to have proper percentage of operative brakes from Class I brake test 5,000 7,500 (e) Operating with less than 85 percent operative brakes 5,000...) Failure to adopt and comply with periodic assessment plan 7,500 11,000 232.205Class I brake test—initial...

49 CFR Appendix A to Part 232 - Schedule of Civil Penalties 1

Code of Federal Regulations, 2014 CFR

2014-10-01

...) Failure to meet general design requirements 2,500 5,000 (d) Failure to have proper percentage of operative brakes from Class I brake test 5,000 7,500 (e) Operating with less than 85 percent operative brakes 5,000...) Failure to adopt and comply with periodic assessment plan 7,500 11,000 232.205Class I brake test—initial...

Numerical Analysis of Solids at Failure

DTIC Science & Technology

2011-08-20

failure analyses include the formulation of invariant finite elements for thin Kirchhoff rods, and preliminary initial studies of growth in...analysis of the failure of other structural/mechanical systems, including the finite element modeling of thin Kirchhoff rods and the constitutive...algorithm based on the connectivity graph of the underlying finite element mesh. In this setting, the discontinuities are defined by fronts propagating

Isothermal fatigue mechanisms in Ti-based metal matrix composites

NASA Technical Reports Server (NTRS)

Majumdar, Bhaskar S.; Newaz, Golam M.

1993-01-01

Stress-controlled isothermal fatigue experiments were performed at room temperature (RT) and 548 C (in argon) on (0)8 SCS6/Ti 15-3 metal matrix composites (MMC's) with 15 and 41 volume percent SCS6 (SiC) fibers. The primary objectives were to evaluate the mechanical responses, and to obtain a clear understanding of the damage mechanisms leading to failure of the MMC's. The mechanical data indicated that strain ranges attained fairly constant values in the stress-controlled experiments at both RT and 538 C, and remained so for more than 85 percent of life. The fatigue data for MMC's with different volume fraction fibers showed that MMC life was controlled by the imposed strain range rather than the stress range. At RT, and at low and intermediate strain ranges, the dominant fatigue mechanism was matrix fatigue, and this was confirmed metallurgically from fractographic evidence as well as from observations of channel type dislocation structures in the matrix of fatigued MMC specimens. Reaction-zone cracks acted as important crack initiating sites at RT, with their role being to facilitate slip band formation and consequent matrix crack initiation through classical fatigue mechanisms. MMC life agreed with matrix life at the lower strain ranges, but was smaller than matrix life at higher strain ranges. Unlike the case of monotonic deformation, debonding damage was another major damage mechanism during fatigue at RT, and it increased for higher strain ranges. At high strain ranges at RT, fractography and metallography showed an absence of matrix cracks, but long lengths of debonds in the outer layers of the SCS6 fibers. Such debonding and consequent rubbing during fatigue is believed to have caused fiber damage and their failure at high strain ranges. Thus, whereas life was matrix dominated at low and intermediate strain ranges, it was fiber dominated at high strain ranges. At 538 C, the mean stain constantly increased (ratchetting) with the number of cycles. At high strain ranges, such ratchetting led to overload failure of the fibers, and debonding of the type at RT was very small. At intermediate strain ranges, fractography showed large areas of matrix cracks. However, in spite of this matrix dominated mechanism, the MMC life at elevated temperatures was significantly less than the matrix fatigue life at all strain ranges. The reason for this difference is still unclear, although metallographic and fractographic evidences suggest that internal crack initiation sites at Mo-ribbons and reaction-zone cracks may have played a critical role, with the former tending to dominate.

NINTH INTERIM STATUS REPORT: MODEL 9975 PCV O-RING FIXTURE LONG-TERM LEAK PERFORMANCE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Daugherty, W.

2014-08-06

A series of experiments to monitor the aging performance of Viton® GLT O-rings used in the Model 9975 package has been ongoing since 2004 at the Savannah River National Laboratory. One approach has been to periodically evaluate the leak performance of O-rings being aged in mock-up 9975 Primary Containment Vessels (PCVs) at elevated temperatures. Other methods such as compression-stress relaxation (CSR) tests and field surveillance are also on-going to evaluate O-ring behavior. Seventy tests using PCV mock-ups were assembled and heated to temperatures ranging from 200 to 450 ºF. They were leak-tested initially and have been tested periodically to determinemore » if they continue to meet the leak-tightness criterion defined in ANSI standard N14.5-97. Due to material substitution, fourteen additional tests were initiated in 2008 with GLT-S O-rings heated to temperatures ranging from 200 to 400 ºF. High temperature aging continues for 23 GLT O-ring fixtures at 200 – 270 ºF. Room temperature leak test failures have been experienced in all of the GLT O-ring fixtures aging at 350 ºF and higher temperatures, and in 8 fixtures aging at 300 ºF. The earliest 300 °F GLT O-ring fixture failure was observed at 34 months. The remaining GLT O-ring fixtures aging at 300 ºF have been retired from testing following more than 5 years at temperature without failure. No failures have yet been observed in GLT O-ring fixtures aging at 200 ºF for 72 - 96 months, which bounds O-ring temperatures anticipated during storage in K-Area Complex (KAC). Based on expectations that the 200 ºF fixtures will remain leak-tight for a significant period yet to come, 2 additional fixtures began aging in 2011 at 270 ºF, with hopes that they may reach a failure condition before the 200 ºF fixtures, thus providing additional time to failure data. High temperature aging continues for 6 GLT-S O-ring fixtures at 200 – 300 ºF. Room temperature leak test failures have been experienced in all 8 of the GLT-S O-ring fixtures aging at 350 and 400 ºF. No failures have yet been observed in GLT-S O-ring fixtures aging at 200 - 300 ºF for 54 - 57 months. No additional O-ring failures have been observed since the last interim report was issued. Aging and periodic leak testing will continue for the remaining PCV fixtures. Additional irradiation of several fixtures is recommended to maintain a balance between thermal and radiation exposures similar to that experienced in storage, and to show the degree of consistency of radiation response between GLT and GLT-S O-rings.« less

Interprofessional Education Among Student Health Professionals Using Human Patient Simulation

PubMed Central

Chmil, Joyce V.

2014-01-01

Objective. To describe the planning, implementation, and outcomes of an interprofessional education clinical laboratory facilitated through human patient simulation. Design. An interprofessional education clinical laboratory was developed with a patient-care scenario of acute exacerbation of heart failure that incorporated the use of a high-fidelity patient simulator. Pharmacy and nursing students assumed clinical roles in this realistic scenario and collaborated to diagnose and treat the patient. Assessment. Student attitudes toward and readiness to participate in interprofessional education improved following participation in the laboratory. Students reported that the greatest benefit of the experience was in their communication skills. Conclusion. Students’ ability to participate in interprofessional education experiences and their attitudes toward them improved following participation in this curricular initiative. Further evaluation of the impact of interprofessional education on student learning outcomes and changes in practice is warranted. PMID:24954934

Refurbishment of the cryogenic coolers for the Skylab earth resources experiment package

NASA Technical Reports Server (NTRS)

Smithson, J. C.; Luksa, N. C.

1975-01-01

Skylab Earth Resources Experiment Package (EREP) experiments, S191 and S192, required a cold temperature reference for operation of a spectrometer. This cold temperature reference was provided by a subminiature Stirling cycle cooler. However, the failure of the cooler to pass the qualification test made it necessary for additional cooler development, refurbishment, and qualification. A description of the failures and the cause of these failures for each of the coolers is presented. The solutions to the various failure modes are discussed along with problems which arose during the refurbishment program. The rationale and results of various tests are presented. The successful completion of the cryogenic cooler refurbishment program resulted in four of these coolers being flown on Skylab. The system operation during the flight is presented.

Childhood Cigarette and Alcohol Use: Negative Links with Adjustment

PubMed Central

Staff, Jeremy; Maggs, Jennifer; Cundiff, Kelsey; Evans-Polce, Rebecca J.

2016-01-01

Children who initiate cigarette or alcohol use early—during childhood or early adolescence—experience a heightened risk of nicotine and alcohol dependence in later life as well as school failure, crime, injury, and mortality. Using prospective intergenerational data from the Millennium Cohort Study (MCS), we investigate the association between early substance use initiation (cigarettes or alcohol) and age 11 school engagement, academic achievement, and wellbeing. The ongoing MCS tracks the development of a nationally representative sample of children in the United Kingdom (born 2000–2002) from infancy through adolescence. At age 11, MCS children (n=13,221) indicated whether they had ever used cigarettes or alcohol; at age 7 and 11 they reported on school engagement and wellbeing and completed investigator-assessed tests of academic achievement. Using propensity score methods, children who had initiated cigarette or alcohol use by age 11 were matched to abstaining children with similar risks (or propensities) of early substance use, based on numerous early life risk and protective factors assessed from infancy to age 7. We then examined whether early initiators differed from non-initiators in age 11 adjustment and achievement. Results show that substance use by age 11 was uncommon (3% cigarettes; 13% alcohol). After matching for propensity for early initiation, school engagement and wellbeing were significantly lower among initiators compared to non-initiators. Academic achievement was not consistently related to early initiation. We conclude that initiation of smoking and drinking in childhood is associated with poorer adjustment. PMID:27347653

Piezoelectrically Initiated Pyrotechnic Igniter

NASA Technical Reports Server (NTRS)

Quince, Asia; Dutton, Maureen; Hicks, Robert; Burnham, Karen

2013-01-01

This innovation consists of a pyrotechnic initiator and piezoelectric initiation system. The device will be capable of being initiated mechanically; resisting initiation by EMF, RF, and EMI (electromagnetic field, radio frequency, and electromagnetic interference, respectively); and initiating in water environments and space environments. Current devices of this nature are initiated by the mechanical action of a firing pin against a primer. Primers historically are prone to failure. These failures are commonly known as misfires or hang-fires. In many cases, the primer shows the dent where the firing pin struck the primer, but the primer failed to fire. In devices such as "T" handles, which are commonly used to initiate the blowout of canopies, loss of function of the device may result in loss of crew. In devices such as flares or smoke generators, failure can result in failure to spot a downed pilot. The piezoelectrically initiated ignition system consists of a pyrotechnic device that plugs into a mechanical system (activator), which on activation, generates a high-voltage spark. The activator, when released, will strike a stack of electrically linked piezo crystals, generating a high-voltage, low-amperage current that is then conducted to the pyro-initiator. Within the initiator, an electrode releases a spark that passes through a pyrotechnic first-fire mixture, causing it to combust. The combustion of the first-fire initiates a primary pyrotechnic or explosive powder. If used in a "T" handle, the primary would ramp the speed of burn up to the speed of sound, generating a shock wave that would cause a high explosive to go "high order." In a flare or smoke generator, the secondary would produce the heat necessary to ignite the pyrotechnic mixture. The piezo activator subsystem is redundant in that a second stack of crystals would be struck at the same time with the same activation force, doubling the probability of a first strike spark generation. If the first activation fails to ignite, the device is capable of multiple attempts. Another unique aspect is in the design of the pyrotechnic device. There is an electrode that aids the generation of a directed spark and the use of a conductive matrix to support the first-fire material so that the spark will penetrate to the second electrode.

On a Stochastic Failure Model under Random Shocks

NASA Astrophysics Data System (ADS)

Cha, Ji Hwan

2013-02-01

In most conventional settings, the events caused by an external shock are initiated at the moments of its occurrence. In this paper, we study a new classes of shock model, where each shock from a nonhomogeneous Poisson processes can trigger a failure of a system not immediately, as in classical extreme shock models, but with delay of some random time. We derive the corresponding survival and failure rate functions. Furthermore, we study the limiting behaviour of the failure rate function where it is applicable.

Preliminary Failure Modes and Effects Analysis of the US DCLL Test Blanket Module

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee C. Cadwallader

2010-06-01

This report presents the results of a preliminary failure modes and effects analysis (FMEA) of a small tritium-breeding test blanket module design for the International Thermonuclear Experimental Reactor. The FMEA was quantified with “generic” component failure rate data, and the failure events are binned into postulated initiating event families and frequency categories for safety assessment. An appendix to this report contains repair time data to support an occupational radiation exposure assessment for test blanket module maintenance.

Preliminary Failure Modes and Effects Analysis of the US DCLL Test Blanket Module

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee C. Cadwallader

2007-08-01

This report presents the results of a preliminary failure modes and effects analysis (FMEA) of a small tritium-breeding test blanket module design for the International Thermonuclear Experimental Reactor. The FMEA was quantified with “generic” component failure rate data, and the failure events are binned into postulated initiating event families and frequency categories for safety assessment. An appendix to this report contains repair time data to support an occupational radiation exposure assessment for test blanket module maintenance.

Myxoedema in a patient with achondroplasia in rural area of Guatemala.

PubMed

Juarez, Michel; Rohloff, Peter

2017-03-09

A 43-year-old indigenous Guatemalan woman with achondroplasia presented to our clinic with chronic fatigue and generalised oedema. She had limited contact with the formal healthcare system. However, 1 year prior, she had sought medical evaluation from a private physician. Her symptoms had been attributed to a combination of heart failure and physical disability due to the musculoskeletal complications of her achondroplasia. She was lost to follow-up due to inability to pay for further testing or treatment. On initial laboratory evaluation in our clinic, she was found to have a thyrotropin level greater than assay. With initiation of oral levothyroxine supplementation, her dyspnoea and oedema completely resolved. The case illustrates how indigenous patients in rural Guatemala experience many barriers to accessing high-quality medical care. As a result, presentations of common illnesses are often very advanced and definitive diagnoses and treatments are frequently delayed. 2017 BMJ Publishing Group Ltd.

Characterization and modeling of tensile behavior of ceramic woven fabric composites

NASA Technical Reports Server (NTRS)

Kuo, Wen-Shyong; Chen, Wennei Y.; Parvizi-Majidi, Azar; Chou, Tsu-Wei

1991-01-01

This paper examines the tensile behavior of SiC/SiC fabric composites. In the characterization effort, the stress-strain relation and damage evolution are studied with a series of loading and unloading tensile test experiments. The stress-strain relation is linear in response to the initial loading and becomes nonlinear when loading exceeds the proportional limit. Transverse cracking has been observed to be a dominant damage mode governing the nonlinear deformation. The damage is initiated at the inter-tow pores where fiber yarns cross over each other. In the modeling work, the analysis is based upon a fiber bundle model, in which fiber undulation in the warp and fill directions and gaps among fiber yarns have been taken into account. Two limiting cases of fabric stacking arrangements are studied. Closed form solutions are obtained for the composite stiffness and Poisson's ratio. Transverse cracking in the composite is discussed by applying a constant failure strain criterion.

Treatment of neuro-ophthalmic sarcoidosis.

PubMed

Frohman, Larry P

2015-03-01

Because of the rarity of neuro-ophthalmic sarcoidosis, there are no therapeutic guidelines based on evidence-based medicine for this disorder. Review of literature combined with personal experience. Corticosteroids are the preferred initial therapy for neuro-ophthalmic sarcoidosis. If patients cannot tolerate the requisite dose of corticosteroid needed to control their disease, or if corticosteroids fail to adequately control the disease process, the choices of a second agent are based on the consideration of rapidity of clinical response and the safety profile. Although methotrexate and mycophenolate mofetil are the medications that are often selected after corticosteroid failure, more rapidly acting agents that have been used are infliximab and intravenous cyclophosphamide.

EXPERIMENTAL STUDIES OF TRANSIENT EFFECTS IN FAST REACTOR FUELS. SERIES I. UO$sub 2$ IRRADIATIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Field, J.H.

1962-11-15

An experimental program to evaluate the performance of FCR and EFCR fuel during transient operation is outlined, and the initial series of tests are described in some detail. Test results from five experiments in the TREAT reactor, using 1-in. OD SS-clad UO/sub 2/ fuel specimens, are compared with regard to fuel temperatures, mechanical integrity, and post-irradiation appearance. Incipient fuel pin failure limits for transients are identified with maximum fuel temperatures in the range of 7000 deg F. Multiple transient damage to the cladding is likely for transients above the melting point of the fuel. (auth)

Medical students' personal experience of high-stakes failure: case studies using interpretative phenomenological analysis.

PubMed

Patel, R S; Tarrant, C; Bonas, S; Shaw, R L

2015-05-12

Failing a high-stakes assessment at medical school is a major event for those who go through the experience. Students who fail at medical school may be more likely to struggle in professional practice, therefore helping individuals overcome problems and respond appropriately is important. There is little understanding about what factors influence how individuals experience failure or make sense of the failing experience in remediation. The aim of this study was to investigate the complexity surrounding the failure experience from the student's perspective using interpretative phenomenological analysis (IPA). The accounts of three medical students who had failed final re-sit exams, were subjected to in-depth analysis using IPA methodology. IPA was used to analyse each transcript case-by-case allowing the researcher to make sense of the participant's subjective world. The analysis process allowed the complexity surrounding the failure to be highlighted, alongside a narrative describing how students made sense of the experience. The circumstances surrounding students as they approached assessment and experienced failure at finals were a complex interaction between academic problems, personal problems (specifically finance and relationships), strained relationships with friends, family or faculty, and various mental health problems. Each student experienced multi-dimensional issues, each with their own individual combination of problems, but experienced remediation as a one-dimensional intervention with focus only on improving performance in written exams. What these students needed to be included was help with clinical skills, plus social and emotional support. Fear of termination of the their course was a barrier to open communication with staff. These students' experience of failure was complex. The experience of remediation is influenced by the way in which students make sense of failing. Generic remediation programmes may fail to meet the needs of students for whom personal, social and mental health issues are a part of the picture.

Fault Injection Techniques and Tools

NASA Technical Reports Server (NTRS)

Hsueh, Mei-Chen; Tsai, Timothy K.; Iyer, Ravishankar K.

1997-01-01

Dependability evaluation involves the study of failures and errors. The destructive nature of a crash and long error latency make it difficult to identify the causes of failures in the operational environment. It is particularly hard to recreate a failure scenario for a large, complex system. To identify and understand potential failures, we use an experiment-based approach for studying the dependability of a system. Such an approach is applied not only during the conception and design phases, but also during the prototype and operational phases. To take an experiment-based approach, we must first understand a system's architecture, structure, and behavior. Specifically, we need to know its tolerance for faults and failures, including its built-in detection and recovery mechanisms, and we need specific instruments and tools to inject faults, create failures or errors, and monitor their effects.

Lived experiences of women who developed uterine rupture following severe obstructed labor in Mulago hospital, Uganda

PubMed Central

2014-01-01

Background Maternal mortality is a major public health challenge in Uganda. Whereas uterine rupture remains a major cause of maternal morbidity and mortality, there is limited research into what happens to women who survive such severe obstetric complications. Understanding their experiences might delineate strategies to support survivors. Methods This qualitative study used a phenomenological approach to explore lived experiences of women who developed uterine rupture following obstructed labor. In-depth interviews initially conducted during their hospitalization were repeated 3–6 months after the childbirth event to explore their health and meanings they attached to the traumatic events and their outcomes. Data were analyzed using thematic analysis. Results The resultant themes included barriers to access healthcare, multiple “losses” and enduring physical, psychosocial and economic consequences. Many women who develop uterine rupture fail to access critical care needed due to failure to recognise danger signs of obstructed labor, late decision making for accessing care, geographical barriers to health facilities, late or failure to diagnose obstructed labor at health facilities, and failure to promptly perform caesarean section. Secondly, the sequel of uterine rupture includes several losses (loss of lives, loss of fertility, loss of body image, poor quality of life and disrupted marital relationships). Thirdly, uterine rupture has grim economic consequences for the survivors (with financial loss and loss of income during and after the calamitous events). Conclusion Uterine rupture is associated with poor quality of care due to factors that operate at personal, household, family, community and society levels, and results in dire physical, psychosocial and financial consequences for survivors. There is need to improve access to and provision of emergency obstetric care in order to prevent uterine rupture consequent to obstructed labor. There is also critical need to provide counselling and support to survivors to enable them cope with physical, social, psychological and economic consequences. PMID:24758354

Early Caffeine Prophylaxis and Risk of Failure of Initial Continuous Positive Airway Pressure in Very Low Birth Weight Infants.

PubMed

Patel, Ravi M; Zimmerman, Kanecia; Carlton, David P; Clark, Reese; Benjamin, Daniel K; Smith, P Brian

2017-11-01

To test the hypothesis that early caffeine treatment on the day of birth, compared with later treatment in very low birth weight (VLBW, <1500 g) infants receiving continuous positive airway pressure (CPAP) therapy, is associated with a decreased risk of CPAP failure in the first week of life. Multicenter, observational cohort study in 366 US neonatal intensive care units. We evaluated inborn, VLBW infants discharged from 2000 to 2014, who received only CPAP therapy without surfactant treatment on day of life (DOL) 0, had a 5-minute Apgar ≥3, and received caffeine in the first week of life. We used multivariable conditional logistic regression to compare the risk of CPAP failure, defined as invasive mechanical ventilation or surfactant therapy on DOL 1-6, by timing of caffeine treatment as either early (initiation on DOL 0) or routine (initiation on DOL 1-6). We identified 11 133 infants; 4528 (41%) received early caffeine and 6605 (59%) received routine caffeine. Median gestational age was lower in the early caffeine group, 29 weeks (25th, 75th percentiles; 28, 30) vs the routine caffeine group, 30 weeks (29, 31); P < 0.001. The incidence of CPAP failure on DOL 1-6 was similar between the early and routine caffeine groups: 22% vs 21%; adjusted OR = 1.05 (95% CI: 0.93, 1.18). Early caffeine treatment on the day of birth was not associated with a decreased risk of CPAP failure in the first week of life for VLBW infants initially treated with CPAP. Copyright © 2017 Elsevier Inc. All rights reserved.

Potential Unintended Consequences of a Conservative Management Strategy for Patent Ductus Arteriosus.

PubMed

Elhoff, Justin J; Ebeling, Myla; Hulsey, Thomas C; Atz, Andrew M

2016-01-01

A recent review supports a strategy of deferring treatment of patent ductus arteriosus (PDA) in the preterm neonate until at least the second week after birth. In light of previous suggestion that later initiation of treatment may be less efficacious for closing PDAs it is reasonable to question if delayed treatment may be less effective. We conducted a single center retrospective review of a neonatal intensive care unit database of infants ≤37 weeks gestation with the diagnosis of PDA and treated with indomethacin from 1999 to 2007. We determined gestational age (GA), timing of indomethacin initiation, and status of the PDA at hospital discharge. Treatment failure was defined as neonates requiring further intervention to close their PDA or those who died without echo-proven PDA closure. Of the 341 infants meeting the study criteria, 77 (23%) had defined treatment failure. The failure group had a younger median GA of 25 weeks (interquartile range [IQR], 24-26) vs. 28 weeks (IQR, 26-30) for the successful group (P < .0001). The failure group had a median treatment initiation on day of life (DOL) 4 (IQR, 1-8) compared with DOL 3 (IQR, 1-6) for those in the successful group (P = .15). Taken as a whole, infants treated after DOL 5 were significantly more likely to have treatment failure (30.1% vs. 19.3% for those treated DOL 1-5, P = .03). Our study confirms that younger GA at birth is correlated with increased likelihood of failed PDA closure. We also show a trend indicating that later initiation of treatment may decrease the chances of successfully closing a PDA. Future examination of PDA management should consider the potential unintended consequences that may accompany a delayed treatment strategy. © 2015 Wiley Periodicals, Inc.

Vascular Physiology according to Clinical Scenario in Patients with Acute Heart Failure: Evaluation using the Cardio-Ankle Vascular Index.

PubMed

Goto, Toshihiko; Wakami, Kazuaki; Mori, Kento; Kikuchi, Shohei; Fukuta, Hidekatsu; Ohte, Nobuyuki

2016-09-01

Increased aortic stiffness may be an important cause of acute heart failure (AHF). Clinical scenario (CS), which classifies the pathophysiology of AHF based on the initial systolic blood pressure (sBP), was proposed to provide the most appropriate therapy for AHF patients. In CS, elevated aortic stiffness, vascular failure, has been considered as a feature of patients categorized as CS1 (sBP > 140 mmHg at initial presentation). However, whether elevated aortic stiffness, vascular failure, is present in such patients has not been fully elucidated. Therefore, we assessed aortic stiffness in AHF patients using the cardio-ankle vascular index (CAVI), which is considered to be independent of instantaneous blood pressure. Sixty-four consecutive AHF patients (mean age, 70.6 ± 12.8 years; 39 men) were classified with CS, based on their initial sBP: CS1: sBP > 140 mmHg (n = 29); CS2: sBP 100-140 mmHg (n = 22); and CS3: sBP < 100 mmHg (n = 13). There were significant group differences in CAVI (CS1 vs. CS2 vs. CS3: 9.7 ± 1.4 vs. 8.4 ± 1.7 vs. 8.3 ± 1.7, p = 0.006, analysis of variance). CAVI was significantly higher in CS1 than in CS2 (p = 0.02) and CS3 (p = 0.04). CAVI did not significantly correlate with sBP at the time of measurement of CAVI (r = 0.24 and p = 0.06). Aortic stiffness assessed using blood pressure-independent methodology apparently increased in CS1 AHF patients. We conclude that vascular failure is a feature of CS1 AHF initiation.

Relative risk of home hemodialysis attrition in patients using a telehealth platform.

PubMed

Weinhandl, Eric D; Collins, Allan J

2017-12-06

Home hemodialysis (HHD) facilitates increased treatment frequency, which may improve patient outcomes. However, attrition due to technique failure limits the clinical effectiveness of the modality. Nx2me Connected Health is a telehealth platform that enables ongoing assessment of HHD patients using NxStage equipment, and that may reduce patient burden. We aimed to assess whether use of Nx2me was associated with risk of HHD attrition. We compared risks of all-cause attrition, dialysis cessation (i.e., death or transplant), and technique failure in Nx2me users and matched control patients, using a retrospective cohort study. We also compared the likelihood of HHD training graduation in patients who initiated use of Nx2me during training with the likelihood in matched control patients. Matching factors included date of HHD initiation, NxStage treatment duration at initiation of follow-up, and prescribed treatment frequency. We used stratified Fine-Gray and Cox regression to compare risks, with adjustment for demographic factors and vascular access modality, and stratification by matched cluster. We identified 606 Nx2me users; 49.5% initiated use of Nx2me in <3 months after initiation of HHD with NxStage equipment. Adjusted hazard ratios (AHRs) of all-cause attrition, dialysis cessation, and technique failure were 0.80 (95% confidence interval, 0.68-0.95), 1.10 (0.86-1.41), and 0.71 (0.57-0.87), respectively, for Nx2me users vs. matched controls. AHRs were similar in patients who initiated use of Nx2me in <3 months after initiation of HHD. The AHR of HHD training graduation was 1.61 (1.10-2.36) in patients who initiated use of Nx2me within 2 weeks of training initiation vs. matched controls. Use of Nx2me was associated with lower risk of all-cause attrition, lower risk of technique failure, and higher likelihood of HHD training graduation. Further studies are needed to identify the mechanisms by which use of a telehealth platform may improve clinical outcomes and reduce patient burden. © 2017 The Authors Hemodialysis International published by Wiley Periodicals, Inc. on behalf of International Society for Hemodialysis.

A model for predicting high-temperature fatigue failure of a W/Cu composite

NASA Technical Reports Server (NTRS)

Verrilli, M. J.; Kim, Y.-S.; Gabb, T. P.

1991-01-01

The material studied, a tungsten-fiber-reinforced, copper-matrix composite, is a candidate material for rocket nozzle liner applications. It was shown that at high temperatures, fatigue cracks initiate and propagate inside the copper matrix through a process of initiation, growth, and coalescence of grain boundary cavities. The ductile tungsten fibers neck and rupture locally after the surrounding matrix fails, and complete failure of the composite then ensues. A simple fatigue life prediction model is presented for the tungsten/copper composite system.

Initial Experience With the New Ahmed Glaucoma Valve Model M4: Short-term Results.

PubMed

Cvintal, Victor; Moster, Marlene R; Shyu, Andrew P; McDermott, Katie; Ekici, Feyzahan; Pro, Michael J; Waisbourd, Michael

2016-05-01

To evaluate the clinical outcomes of the new Ahmed glaucoma valve (AGV) model M4. The device consists of a porous polyethylene shell designed for improved tissue integration and reduced encapsulation of the plate for better intraocular pressure (IOP) control. Medical records of patients with an AGV M4 implantation between December 1, 2012 and December 31, 2013 were reviewed. The main outcome measure was surgical failure, defined as either (1) IOP<5 mm Hg or >21 mm Hg and/or <20% reduction of IOP at last follow-up visit, (2) a reoperation for glaucoma, and/or (3) loss of light perception. Seventy-five eyes of 73 patients were included. Postoperative IOP at all follow-up visits significantly decreased from a baseline IOP of 31.2 mm Hg (P<0.01). However, IOP increased significantly at 3 months (20.4 mm Hg), 6 months (19.3 mm Hg), and 12 months (20.3 mm Hg) compared with 1 month (13.8 mm Hg) postoperatively (P<0.05). At 6 months and 1 year, the cumulative probability of failure was 32% and 72%, respectively. The AGV M4 effectively reduced IOP in the first postoperative month, but IOP steadily increased thereafter. Consequently, failure rates were high after 1 year of follow-up.

Sediment gravity flows triggered by remotely generated earthquake waves

NASA Astrophysics Data System (ADS)

Johnson, H. Paul; Gomberg, Joan S.; Hautala, Susan L.; Salmi, Marie S.

2017-06-01

Recent great earthquakes and tsunamis around the world have heightened awareness of the inevitability of similar events occurring within the Cascadia Subduction Zone of the Pacific Northwest. We analyzed seafloor temperature, pressure, and seismic signals, and video stills of sediment-enveloped instruments recorded during the 2011-2015 Cascadia Initiative experiment, and seafloor morphology. Our results led us to suggest that thick accretionary prism sediments amplified and extended seismic wave durations from the 11 April 2012 Mw8.6 Indian Ocean earthquake, located more than 13,500 km away. These waves triggered a sequence of small slope failures on the Cascadia margin that led to sediment gravity flows culminating in turbidity currents. Previous studies have related the triggering of sediment-laden gravity flows and turbidite deposition to local earthquakes, but this is the first study in which the originating seismic event is extremely distant (> 10,000 km). The possibility of remotely triggered slope failures that generate sediment-laden gravity flows should be considered in inferences of recurrence intervals of past great Cascadia earthquakes from turbidite sequences. Future similar studies may provide new understanding of submarine slope failures and turbidity currents and the hazards they pose to seafloor infrastructure and tsunami generation in regions both with and without local earthquakes.

Sediment gravity flows triggered by remotely generated earthquake waves

USGS Publications Warehouse

Johnson, H. Paul; Gomberg, Joan S.; Hautala, Susan; Salmi, Marie

2017-01-01

Recent great earthquakes and tsunamis around the world have heightened awareness of the inevitability of similar events occurring within the Cascadia Subduction Zone of the Pacific Northwest. We analyzed seafloor temperature, pressure, and seismic signals, and video stills of sediment-enveloped instruments recorded during the 2011–2015 Cascadia Initiative experiment, and seafloor morphology. Our results led us to suggest that thick accretionary prism sediments amplified and extended seismic wave durations from the 11 April 2012 Mw8.6 Indian Ocean earthquake, located more than 13,500 km away. These waves triggered a sequence of small slope failures on the Cascadia margin that led to sediment gravity flows culminating in turbidity currents. Previous studies have related the triggering of sediment-laden gravity flows and turbidite deposition to local earthquakes, but this is the first study in which the originating seismic event is extremely distant (> 10,000 km). The possibility of remotely triggered slope failures that generate sediment-laden gravity flows should be considered in inferences of recurrence intervals of past great Cascadia earthquakes from turbidite sequences. Future similar studies may provide new understanding of submarine slope failures and turbidity currents and the hazards they pose to seafloor infrastructure and tsunami generation in regions both with and without local earthquakes.

How to manage unresponsiveness to misoprostol in failed second trimester pregnancy termination.

PubMed

Pongsatha, Saipin; Tongsong, Theera

2013-01-01

To present the experience of management of second trimester pregnancy termination by misoprostol after failure to abort within 48 h of its use. A retrospective, cohort descriptive study was carried out in the Department of Obstetrics and Gynecology, Faculty of Medicine, Chiang Mai University Thailand between 1998 and 2010. All women at 14-28 weeks of gestation who failed to abort using misoprostol within 48 h were included. Management of failed pregnancy termination among these women is described here. Of a total of 680 women undergoing termination of pregnancy, 68 (10%) failed to abort. Mean maternal age was 28.71 years and mean gestational age was 19.91 weeks. Further management after failure included additional administration of misoprostol only (19.1%), modified condom balloon technique only (17.7%), modified condom balloon technique plus other methods (16.1%), while 47.1% needed only oxytocin as necessary. The mean interval between initiation of termination and delivery was 96.97 h.   Failure of pregnancy termination using misoprostol can be successfully managed by introducing additional misoprostol, modified condom balloon technique and oxytocin infusion. These methods should be considered before proceeding to hysterotomy. © 2012 The Authors. Journal of Obstetrics and Gynaecology Research © 2012 Japan Society of Obstetrics and Gynecology.

Hypervelocity impact testing of the Space Station utility distribution system carrier

NASA Technical Reports Server (NTRS)

Lazaroff, Scott

1993-01-01

A two-phase, joint JSC and McDonnell Douglas Aerospace-Huntington Beach hypervelocity impact (HVI) test program was initiated to develop an improved understanding of how meteoroid and orbital debris (M/OD) impacts affect the Space Station Freedom (SSF) avionic and fluid lines routed in the Utility Distribution System (UDS) carrier. This report documents the first phase of the test program which covers nonpowered avionic line segment and pressurized fluid line segment HVI testing. From these tests, a better estimation of avionic line failures is approximately 15 failures per year and could very well drop to around 1 or 2 avionic line failures per year (depending upon the results of the second phase testing of the powered avionic line at White Sands). For the fluid lines, the initial McDonnell Douglas analysis calculated 1 to 2 line failures over a 30 year period. The data obtained from these tests indicate the number of predicted fluid line failures increased slightly to as many as 3 in the first 10 years and up to 15 for the entire 30 year life of SSF.

Deep flaws in weldments of aluminum and titanium

NASA Technical Reports Server (NTRS)

Masters, J. N.; Engstrom, W. L.; Bixler, W. D.

1974-01-01

Surface flawed specimens of 2219-T87 and 6Al-4V STA titanium weldments were tested to determine static failure modes, failure strength, and fatigue flaw growth characteristics. Thicknesses selected for this study were purposely set at values where, for most test conditions, abrupt instability of the flaw at fracture would not be expected. Static tests for the aluminum weldments were performed at room, LN2 and LH2 temperatures. Titanium static tests for tests were performed at room and LH2 temperatures. Results of the static tests were used to plot curves relating initial flaw size to leakage- or failure-stresses (i.e. "failure" locus curves). Cyclic tests, for both materials, were then performed at room temperature, using initial flaws only slightly below the previously established failure locus for typical proof stress levels. Cyclic testing was performed on pairs of specimens, one with and one without a simulated proof test cycle. Comparisons were made then to determine the value and effect of proof testing as affected by the various variables of proof and operating stress, flaw shape, material thickness, and alloy.

Outcome of Early Initiation of Peritoneal Dialysis in Patients with End-Stage Renal Failure

PubMed Central

Oh, Kook-Hwan; Hwang, Young-Hwan; Cho, Jung-Hwa; Kim, Mira; Ju, Kyung Don; Joo, Kwon Wook; Kim, Dong Ki; Kim, Yon Su; Ahn, Curie

2012-01-01

Recent studies reported that early initiation of hemodialysis may increase mortality. However, studies that assessed the influence of early initiation of peritoneal dialysis (PD) yielded controversial results. In the present study, we evaluated the prognosis of early initiation of PD on the various outcomes of end stage renal failure patients by using propensity-score matching methods. Incident PD patients (n = 491) who started PD at SNU Hospital were enrolled. The patients were divided into 'early starters (n = 244)' and 'late starters (n = 247)' on the basis of the estimated glomerular filtration rate (eGFR) at the start of dialysis. The calculated propensity-score was used for one-to-one matching. After propensity-score-based matching (n = 136, for each group), no significant differences were observed in terms of all-cause mortality (P = 0.17), technique failure (P = 0.62), cardiovascular event (P = 0.96) and composite event (P = 0.86) between the early and late starters. Stratification analysis in the propensity-score quartiles (n = 491) exhibited no trend toward better or poorer survival in terms of all-cause mortality. In conclusion, early commencement of PD does not reduce the mortality risk and other outcomes. Although the recent guidelines suggest that initiation of dialysis at higher eGFR, physicians should not determine the time to initiate PD therapy simply rely on the eGFR alone. PMID:22323864

630A MARITIME NUCLEAR STEAM GENERATOR. Progress Report No. 1

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

1962-07-31

Work on the 630A Maritime Nuclear Steam Generator Scoping Study is summarized. The objective of the program is to establish a specific 630A configuration and to develop specifications for components and test equipment. During the period, work was initiated in critical experiment design and fabrication, additional fuel and materials investigations, boiler-test design and fabrication; blower studies; design of component tests; nuclear, thermodynamic, mechanical and safety analysis, and test facility and equipment studies. Design of the critical experiment mockup and test equipment was completed and fabrication of the parts is approximately 50% complete. A rough draft of the critical experiment hazardsmore » report was completed. A fuel test in the ORR completed 876.5 hr of testing out of a planned 2200-hr test without indication of failure. The burnup was equivalent to about 6000 hr of 630A operation. Damage to the capsule during refueling of the ORR caused termination of the test. The design of an MTR fuel-burnup test was completed and fabrication of the sample initiated. Ni-Cr fuel sheet and cladding stock are being tested for creep and oxidation properties at temperatures up to 1750 deg F and have accumulated times up to 5000 hr; no failures have occurred. These tests are continuing. Specimens of Ni-Cr were fabricated and will be tested to determine the effect of neutron irradiation. Cycle operating conditions with 120O deg F reactor-discharge-air temperature were studied and found to be acceptable for the proposed maritime application. Increases in cycle efficiency above 30.2% appear to be possible and practical. Studies during the period indicate that an acceptable power distribution can be maintained through the life of the reactor and the maximum hot spot temperature and maximum burnup location would not coincide. Specifications for the fuel loading of the critical experiment are being prepared. Study of the pressure vessel resulted in selection of 304 SS. Containment studies indfcated the practicality of designing the shield tank outer shell as part of the containment vessel. A blower scoping study subcontract was completed. The study verified the feasibility of the main and afterblower concept. Alternate shaft-seal designs were proposed. The design of a performance test for the two seal types has been initiated. The design of the boiler test from which control characteristics will be determined was completed and fabrication started. The decision was made that the Low Power Test Facility (LPTF) will be the site used for the critical experiment. A preliminary study of the power test facility requirements were completed. The study indicated that locating the facility adjacent to the LPTF would be operationally and economically feasible. (auth)« less

Experimental Investigation on the Basic Law of Directional Hydraulic Fracturing Controlled by Dense Linear Multi-Hole Drilling

NASA Astrophysics Data System (ADS)

Zhao, Xinglong; Huang, Bingxiang; Wang, Zhen

2018-06-01

Directional rupture is a significant and routine problem for ground control in mines. Directional hydraulic fracturing controlled by dense linear multi-hole drilling was proposed. The physical model experiment, performed by the large-scale true triaxial hydraulic fracturing experimental system, aims to investigate the basic law of directional hydraulic fracturing controlled by dense linear multi-hole drilling, the impact of three different pumping modes on the initiation and propagation of hydraulic fractures among boreholes are particular investigated. The experimental results indicated that there are mutual impacts among different boreholes during crack propagation, which leads to a trend of fracture connection. Furthermore, during propagation, the fractures not only exhibit an overall bias toward the direction in which the boreholes are scattered but also partially offset against the borehole axes and intersect. The directional fracturing effect of equivalent pumping rate in each borehole is better than the other two pumping modes. In practical applications, because of rock mass heterogeneity, there may be differences in terms of filtration rate and effective input volume in different boreholes; thus, water pressure increase and rupture are not simultaneous in different boreholes. Additionally, if the crack initiation directions of different boreholes at different times are not consistent with each other, more lamellar failure planes will occur, and the mutual influences of these lamellar failure planes cause fractures to extend and intersect.

Older kidneys donor transplantation: five years' experience without biopsy and using clinical laboratory and macroscopic anatomy evaluation.

PubMed

Santangelo, M; Zuccaro, M; De Rosa, P; Tammaro, V; Grassia, S; Federico, S; Ciotola, A L; Spinosa, G; Renda, A

2007-01-01

The exponential increase in organ demand is not associated with a similar increase of available kidneys. This emergency led to expanded criteria to consider a kidney transplantable. The aim of this retrospective study was to explain our use of older donor kidneys without biopsy. Between 2000 and 2005, 58 older kidneys were harvested: 27 were transplanted in our center; 13 were discarded; and 18 were transplanted in other centers. We considered 3 factors to define kidney quality: macroscopic anatomy, multiple factors linked to the donor, and clinical-laboratory data. After transplantation, we observed the patients for at least 1 year and up to 6 years. At 1 year, 24/27 (89%) patients had a functional kidney, 2 patients showed an initial renal failure and 1 patient lost the kidney. At maximum follow-up, 19 patients (70%) had functional kidneys, 4 with initial renal failure. These results compared with the kidneys harvested using Standard Donor Kidney Criteria are acceptable. Obviously we need long-term follow-up to increase, the amount of data and obtain a definitive outcome. Biopsy is the gold standard for the definition of an older kidney's quality. When a biopsy is not feasible, the study of the macroscopic anatomy the kidney's donor and of some donor's parameters represent an acceptable biopsy alternative, being able to rescue some organs that would be otherwise lost.

Confident failures: Lapses of working memory reveal a metacognitive blind spot.

PubMed

Adam, Kirsten C S; Vogel, Edward K

2017-07-01

Working memory performance fluctuates dramatically from trial to trial. On many trials, performance is no better than chance. Here, we assessed participants' awareness of working memory failures. We used a whole-report visual working memory task to quantify both trial-by-trial performance and trial-by-trial subjective ratings of inattention to the task. In Experiment 1 (N = 41), participants were probed for task-unrelated thoughts immediately following 20% of trials. In Experiment 2 (N = 30), participants gave a rating of their attentional state following 25% of trials. Finally, in Experiments 3a (N = 44) and 3b (N = 34), participants reported confidence of every response using a simple mouse-click judgment. Attention-state ratings and off-task thoughts predicted the number of items correctly identified on each trial, replicating previous findings that subjective measures of attention state predict working memory performance. However, participants correctly identified failures on only around 28% of failure trials. Across experiments, participants' metacognitive judgments reliably predicted variation in working memory performance but consistently and severely underestimated the extent of failures. Further, individual differences in metacognitive accuracy correlated with overall working memory performance, suggesting that metacognitive monitoring may be key to working memory success.

75 FR 34156 - United States

Federal Register 2010, 2011, 2012, 2013, 2014

2010-06-16

... the package's failure. A failure of the package could expose the medical device to microbes, bacteria... research and development efforts, including, but not limited to, designs and experiments and the results of successful and unsuccessful designs and experiments; and (b) With respect to any intangible assets that are...

A small-scale experiment using microwave interferometry to investigate detonation and shock-to-detonation transition in pressed TATB

NASA Astrophysics Data System (ADS)

Renslow, Peter John

A small-scale characterization test utilizing microwave interferometry was developed to dynamically measure detonation and run to detonation distance in explosives. The technique was demonstrated by conducting two experimental series on the well-characterized explosive triaminotrinitrobenzene (TATB). In the first experiment series, the detonation velocity was observed at varying porosity. The velocity during TATB detonation matched well with predictions made using CHEETAH and an empirical relation from the Los Alamos National Laboratory (LANL). The microwave interferometer also captured unsteady propagation of the reaction when a low density charge was near the failure diameter. In the second experiment series, Pop-plots were produced using data obtained from shock initiation of the TATB through a polymethyl methacrylate (PMMA) attenuator. The results compared well to wedge test data from LANL despite the microwave interferometer test being of substantially smaller scale. The results showed the test method is attractive for rapid characterization of new and improvised explosive materials.

Large-displacement structural durability analyses of simple bend specimen emulating rocket nozzle liners

NASA Technical Reports Server (NTRS)

Arya, Vinod K.; Halford, Gary R.

1994-01-01

Large-displacement elastic and elastic-plastic, finite-element stress-strain analyses of an oxygen-tree high-conductivity (OFHC) copper plate specimen were performed using an updated Lagrangian formulation. The plate specimen is intended for low-cost experiments that emulate the most important thermomechanical loading and failure modes of a more complex rocket nozzle. The plate, which is loaded in bending at 593 C, contains a centrally located and internally pressurized channel. The cyclic crack initiation lives were estimated using the results from the analyses and isothermal strain-controlled low-cycle fatigue data for OFHC copper. A comparison of the predicted and experimental cyclic lives showed that an elastic analysis predicts a longer cyclic life than that observed in experiments by a factor greater than 4. The results from elastic-plastic analysis for the plate bend specimen, however, predicted a cyclic life in close agreement with experiment, thus justifying the need for the more rigorous stress-strain analysis.

Sterilization failures in Singapore: an examination of ligation techniques and failure rates.

PubMed

Cheng, M C; Wong, Y M; Rochat, R W; Ratnam, S S

1977-04-01

The University Department of Obstetrics and Gynecology, Kandang Kerbau Hospital in Singapore, initiated a study in early 1974 of failure rates for various methods of sterilization and the factors responsible for the failures. During the period January 1974 to March 1976, 51 cases of first pregnancy following ligation were discovered. Cumulative failure rates at 24 months were 0.34 per 100 women for abdominal sterilization, 1.67 for culdoscopic, 3.12 for vaginal, and 4.49 for laparoscopic procedures. Findings for 35 patients who underwent religation showed that recanalization and the establishment of a fistulous opening caused the majority of failures. Clearly, more effective methods of tubal occlusion in sterilization are needed.

Practical Implementation of Failure Mode and Effects Analysis for Safety and Efficiency in Stereotactic Radiosurgery

DOE Office of Scientific and Technical Information (OSTI.GOV)

Younge, Kelly Cooper, E-mail: kyounge@med.umich.edu; Wang, Yizhen; Thompson, John

2015-04-01

Purpose: To improve the safety and efficiency of a new stereotactic radiosurgery program with the application of failure mode and effects analysis (FMEA) performed by a multidisciplinary team of health care professionals. Methods and Materials: Representatives included physicists, therapists, dosimetrists, oncologists, and administrators. A detailed process tree was created from an initial high-level process tree to facilitate the identification of possible failure modes. Group members were asked to determine failure modes that they considered to be the highest risk before scoring failure modes. Risk priority numbers (RPNs) were determined by each group member individually and then averaged. Results: A totalmore » of 99 failure modes were identified. The 5 failure modes with an RPN above 150 were further analyzed to attempt to reduce these RPNs. Only 1 of the initial items that the group presumed to be high-risk (magnetic resonance imaging laterality reversed) was ranked in these top 5 items. New process controls were put in place to reduce the severity, occurrence, and detectability scores for all of the top 5 failure modes. Conclusions: FMEA is a valuable team activity that can assist in the creation or restructuring of a quality assurance program with the aim of improved safety, quality, and efficiency. Performing the FMEA helped group members to see how they fit into the bigger picture of the program, and it served to reduce biases and preconceived notions about which elements of the program were the riskiest.« less

Timing of Radiation Therapy and Chemotherapy After Breast-Conserving Surgery for Node-Positive Breast Cancer: Long-Term Results From International Breast Cancer Study Group Trials VI and VII

DOE Office of Scientific and Technical Information (OSTI.GOV)

Karlsson, Per, E-mail: per.karlsson@oncology.gu.se; Cole, Bernard F.; Price, Karen N.

Purpose: To update the previous report from 2 randomized clinical trials, now with a median follow-up of 16 years, to analyze the effect of radiation therapy timing on local failure and disease-free survival. Patients and Methods: From July 1986 to April 1993, International Breast Cancer Study Group trial VI randomly assigned 1475 pre-/perimenopausal women with node-positive breast cancer to receive 3 or 6 cycles of initial chemotherapy (CT). International Breast Cancer Study Group trial VII randomly assigned 1212 postmenopausal women with node-positive breast cancer to receive tamoxifen for 5 years, or tamoxifen for 5 years with 3 early cycles of initial CT. Formore » patients who received breast-conserving surgery (BCS), radiation therapy (RT) was delayed until initial CT was completed; 4 or 7 months after BCS for trial VI and 2 or 4 months for trial VII. We compared RT timing groups among 433 patients on trial VI and 285 patients on trial VII who received BCS plus RT. Endpoints were local failure, regional/distant failure, and disease-free survival (DFS). Results: Among pre-/perimenopausal patients there were no significant differences in disease-related outcomes. The 15-year DFS was 48.2% in the group allocated 3 months initial CT and 44.9% in the group allocated 6 months initial CT (hazard ratio [HR] 1.12; 95% confidence interval [CI] 0.87-1.45). Among postmenopausal patients, the 15-year DFS was 46.1% in the no-initial-CT group and 43.3% in the group allocated 3 months initial CT (HR 1.11; 95% CI 0.82-1.51). Corresponding HRs for local failures were 0.94 (95% CI 0.61-1.46) in trial VI and 1.51 (95% CI 0.77-2.97) in trial VII. For regional/distant failures, the respective HRs were 1.15 (95% CI 0.80-1.63) and 1.08 (95% CI 0.69-1.68). Conclusions: This study confirms that, after more than 15 years of follow-up, it is reasonable to delay radiation therapy until after the completion of standard CT.« less

Hodgkin’s lymphoma coexisting with liver failure secondary to acute on chronic hepatitis B

PubMed Central

Palta, Renee; McClune, Amy; Esrason, Karl

2013-01-01

Acute on chronic liver failure (ACLF) is rarely the initial manifestation of a malignant process or precipitated by the initiation of anti-viral treatment with a nucleoside or nucleotide agent. We report an unusual case of ACLF temporally associated with initiation of Entecavir for treatment of chronic hepatitis B. Early Hodgkin’s lymphoma (HL) was unmasked with initiation of the anti-viral treatment which may have exacerbated ACLF. To the best of our knowledge, this has not been described in the literature. In reviewing our patients clinical course and liver autopsy, he developed a severe acute exacerbation of his chronic hepatitis B virus coinciding with the institution of antiviral therapy and the underlying HL perhaps modulating the overall degree of hepatic injury. PMID:24303460

The Role of Fine Sediment Content on Soil Consolidation and Debris Flows Development after Earthquake

NASA Astrophysics Data System (ADS)

Lyu, L.; Xu, M., III; Wang, Z.

2017-12-01

Fine sediment has been identified as an important factor determining the critical runoff that initiates debris flows because its contribution to shear strength through consolidation. Especially, owing to the 2008 Wenchuan earthquake in China enormous of loose sediment with different fractions of fine particles was eroded and supplied as materials for debris flows. The loose materials are gradually consolidated along with time, and therefore stronger rainfall is required to overcome the shear strength and to initiate debris flows. In this study, flume experiments were performed to explore soil consolidation and shear strength on mass failure and debris flow initiation under the conditions that different fractions of fine sediment were contained in the materials. Under the low content of fine sediment conditions (mass percentages: 0-10%), the debris flows formed with large pores and low shear strength and thus fine particles were too few to fill up the pores among the coarse particles. The consolidation rate was mostly influenced by the content of the fine particles. Consolidation of fine particles caused an increase of the shear strength and decrease of the rainfall infiltration, and therefore, debris flow initiation required stronger rainfall as the consolidation of the fine particles developed.

Failure detection and recovery in the assembly/contingency subsystem

NASA Technical Reports Server (NTRS)

Gantenbein, Rex E.

1993-01-01

The Assembly/Contingency Subsystem (ACS) is the primary communications link on board the Space Station. Any failure in a component of this system or in the external devices through which it communicates with ground-based systems will isolate the Station. The ACS software design includes a failure management capability (ACFM) that provides protocols for failure detection, isolation, and recovery (FDIR). The the ACFM design requirements as outlined in the current ACS software requirements specification document are reviewed. The activities carried out in this review include: (1) an informal, but thorough, end-to-end failure mode and effects analysis of the proposed software architecture for the ACFM; and (2) a prototype of the ACFM software, implemented as a C program under the UNIX operating system. The purpose of this review is to evaluate the FDIR protocols specified in the ACS design and the specifications themselves in light of their use in implementing the ACFM. The basis of failure detection in the ACFM is the loss of signal between the ground and the Station, which (under the appropriate circumstances) will initiate recovery to restore communications. This recovery involves the reconfiguration of the ACS to either a backup set of components or to a degraded communications mode. The initiation of recovery depends largely on the criticality of the failure mode, which is defined by tables in the ACFM and can be modified to provide a measure of flexibility in recovery procedures.

14 French pigtail catheters placed by surgeons to drain blood on trauma patients: is 14-Fr too small?

PubMed

Kulvatunyou, Narong; Joseph, Bellal; Friese, Randall S; Green, Donald; Gries, Lynn; O'Keeffe, Terence; Tang, Andy L; Wynne, Julie L; Rhee, Peter

2012-12-01

Small 14F pigtail catheters (PCs) have been shown to drain air quite well in patients with traumatic pneumothorax (PTX). But their effectiveness in draining blood in patients with traumatic hemothorax (HTX) or hemopneumothorax (HPTX) is unknown. We hypothesized that 14F PCs can drain blood as well as large-bore 32F to 40F chest tubes. We herein report our early case series experience with PCs in the management of traumatic HTX and HPTX. We prospectively collected data on all bedside-inserted PCs in patients with traumatic HTX or HPTX during a 30-month period (July 2009 through December 2011) at our Level I trauma center. We then compared our PC prospective data with our trauma registry-derived retrospective chest tube data (January 2008 through December 2010) at our center. Our primary outcome of interest was the initial drainage output. Our secondary outcomes were tube duration, insertion-related complications, and failure rate. For our statistical analysis, we used the unpaired Student's t-test, χ test, and Wilcoxon rank-sum test; we defined significance by a value of p < 0.05. A total of 36 patients received PCs, and 191 received chest tubes. Our PC group had a higher rate of blunt mechanism injuries than our chest tube group did (83 vs. 62%; p = 0.01). The mean initial output was similar between our PC group (560 ± 81 mL) and our chest tube group (426 ± 37 mL) (p = 0.13). In the PC group, the tube was inserted later (median, Day 1; interquartile range, Days 0-3) than the tube inserted in our chest tube group (median, Day 0; interquartile range, Days 0-0) (p < 0.001). Tube duration, rate of insertion-related complications, and failure rate were all similar. In our early experience, 14F PCs seemed to drain blood as well as large-bore chest tubes based on initial drainage output and other outcomes studied. In this early phase, we were being selective in inserting PCs in only stable blunt trauma patients, and PCs were inserted at a later day from the time of the initial evaluation. In the future, we will need a larger sample size and possibly a well-designed prospective study. Therapeutic study, level V.

The Slip Behavior of Serpentinite and its Significance in Controlling the Mode of Fault Failure

NASA Astrophysics Data System (ADS)

Scuderi, M.; Carpenter, B. M.; Marone, C.; Saffer, D. M.

2013-12-01

Recent observations of deep tremor and low-frequency earthquakes (LFE) have raised fundamental questions about the physics and processes responsible for such slip behaviors. Current hypotheses propose that these events represent shear failure on a critically stressed fault, possibly in the presence of near-lithostatic pore fluid pressure. The presence of serpentinite at characteristic P-T conditions where most deep tremor and LFE are located is suggested by slow seismic velocities, high Poisson`s ratios, and studies of exhumed fault systems. Despite the inferred presence of serpentinite and its role in the generation of tremors and LFE, little is known about its physical and mechanical properties under conditions of extremely low effective stress. Here, we report on experiments designed to investigate the frictional behavior of intact serpentinite recovered from New Idria, California. These serpentinites were emplaced as diapirs associated with Cretaceous subduction predating the formation of the SAF. They currently outcrop along the SAF, and are believed to represent protolith for material present at depth along the fault zone. In this context, they serve as important natural analogs for serpentinites associated with both subduction megathrusts and the SAF. We cut samples parallel to the original foliation from intact blocks, and sheared them in a single direct shear configuration (SDS) using a true triaxial deformation apparatus. To simulate shear between oceanic and continental wall rocks, we sheared intact wafers of serpentine against intact Westerly granite. To simulate internal deformation within the serpentine body, we sheared two intact blocks of serpentinite against each other. Additional experiments were performed on pulverized serpentinite gouge in a double direct shear configuration and under similar boundary conditions for comparison. Effective normal stress (σ'n = σ n - Pp) was kept constant throughout our experiments at values of 2 MPa (with Pp = 1.5 MPa). Shear stress was applied via a constant load point displacement rate, and velocity was increased stepwise from 0.1 to 300 μm/s, after which a series of slide-hold-slide (SHS), were performed to characterize frictional constitutive properties. Our initial results show that powders are stronger (μ ~ 0.65) than the intact wafers (0.2 <μ< 0.3). When serpentinite is sheared against Westerly granite, we observe stick-slip failure events during the initial stage of shearing at constant velocity. Our experimental materials exhibit overall velocity strengthening behavior, for both powders and intact wafers, with values of the frictional parameter, b, becoming more negative as velocity increases for the serpentinite against Westerly granite case. During SHS tests, friction increases log-linearly with time for pulverized gouge. However, for intact wafers we observe zero to negative frictional healing. Our findings suggest that when intact wafers of serpentinite gouge are sheared against simulated wall rock, it can behave unstably and has the potentiality to generate tremors and LFE. Conversely, failure through aseismic creep is suggested when serpentinite fault gouge is present.

Bone Marrow Failure Secondary to Cytokinesis Failure

DTIC Science & Technology

2015-12-01

SUPPLEMENTARY NOTES 14. ABSTRACT Fanconi anemia (FA) is a human genetic disease characterized by a progressive bone marrow failure and heightened...Fanconi anemia (FA) is the most commonly inherited bone marrow failure syndrome. FA patients develop bone marrow failure during the first decade of...experiments proposed in specific aims 1- 3 (Tasks 1-3). Task 1: To determine whether HSCs from Fanconi anemia mouse models have increased cytokinesis

Experience reveals ways to minimize failures in rod-pumped wells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patterson, J.C.; Bucaram, S.M.; Curfew, J.V.

From the experience gained over the past 25 years, ARCO Oil and Gas Co. has developed recommendations to reduce equipment failure in sucker-rod pumping installations. These recommendations include equipment selection and design, operating procedures, and chemical treatment. Equipment failure and its attendant costs are extremely important in today's petroleum industry. Because rod pumping is the predominant means of artificial lift, minimizing equipment failure in rod pumped wells can have a significant impact on profitability. This compilation of recommendations comes from field locations throughout the US and other countries. The goal is to address and solve problems on a well-by-well basis.

Spatio-temporal propagation of cascading overload failures in spatially embedded networks

NASA Astrophysics Data System (ADS)

Zhao, Jichang; Li, Daqing; Sanhedrai, Hillel; Cohen, Reuven; Havlin, Shlomo

2016-01-01

Different from the direct contact in epidemics spread, overload failures propagate through hidden functional dependencies. Many studies focused on the critical conditions and catastrophic consequences of cascading failures. However, to understand the network vulnerability and mitigate the cascading overload failures, the knowledge of how the failures propagate in time and space is essential but still missing. Here we study the spatio-temporal propagation behaviour of cascading overload failures analytically and numerically on spatially embedded networks. The cascading overload failures are found to spread radially from the centre of the initial failure with an approximately constant velocity. The propagation velocity decreases with increasing tolerance, and can be well predicted by our theoretical framework with one single correction for all the tolerance values. This propagation velocity is found similar in various model networks and real network structures. Our findings may help to predict the dynamics of cascading overload failures in realistic systems.

Spatio-temporal propagation of cascading overload failures in spatially embedded networks

PubMed Central

Zhao, Jichang; Li, Daqing; Sanhedrai, Hillel; Cohen, Reuven; Havlin, Shlomo

2016-01-01

Different from the direct contact in epidemics spread, overload failures propagate through hidden functional dependencies. Many studies focused on the critical conditions and catastrophic consequences of cascading failures. However, to understand the network vulnerability and mitigate the cascading overload failures, the knowledge of how the failures propagate in time and space is essential but still missing. Here we study the spatio-temporal propagation behaviour of cascading overload failures analytically and numerically on spatially embedded networks. The cascading overload failures are found to spread radially from the centre of the initial failure with an approximately constant velocity. The propagation velocity decreases with increasing tolerance, and can be well predicted by our theoretical framework with one single correction for all the tolerance values. This propagation velocity is found similar in various model networks and real network structures. Our findings may help to predict the dynamics of cascading overload failures in realistic systems. PMID:26754065

Failure Mode Analysis of V-Shaped Pyrotechnically Actuated Valves

NASA Technical Reports Server (NTRS)

Sachdev, Jai S.; Hosangadi, A.; Chenoweth, James D.; Saulsberry, Regor L.; McDougle, Stephen H.

2012-01-01

Current V-shaped stainless steel pyrovalve initiators have rectified many of the deficiencies of the heritage Y-shaped aluminum design. However, a credible failure mode still exists for dual simultaneous initiator (NSI) firings in which low temperatures were detected at the booster cap and less consistent ignition was observed than when a single initiator was fired. In order to asses this issue, a numerical framework has been developed for predicting the flow through pyrotechnically actuated valves. This framework includes a fully coupled solution of the gas-phase equation with a non-equilibrium dispersed phase for solid particles as well as the capability to model conjugate gradient heat transfer to the booster cap. Through a hierarchy of increasingly complex simulations, a hypothesis for the failure mode of the nearly simultaneous dual NSI firings has been proven. The simulations indicate that the failure mode for simultaneous dual NSI firings may be caused by flow interactions between the flame channels. The shock waves from each initiator interact in the booster cavity resulting in a high pressure that prevents the gas and particulate velocity from rising in the booster cap region. This impedes the bulk of the particulate phase from impacting the booster cap and reduces the heat transfer to the booster cap since the particles do not impact it. Heat transfer calculations to the solid metal indicate that gas-phase convective heat transfer may not be adequate by itself and that energy transfer from the particulate phase may be crucial for the booster cap burn through.

Multimaterial lamination as a means of retarding penetration and spallation failures in plates

NASA Technical Reports Server (NTRS)

Dibattista, J. D.; Humes, D. H.

1972-01-01

Experimental data are presented which show that hypervelocity impact spallation and penetration failures of a single solid aluminum plate and of a solid aluminum plate spaced a distance behind a Whipple meteor bumper may be retarded by replacing the solid aluminum plate with a laminated plate. Four sets of experiments were conducted. The first set of experiments was conducted with projectile mass and velocity held constant and with polycarbonate cylinders impacted into single plates of different construction. The second set of experiments was done with single plates of various construction and aluminum spherical projectiles of similar mass but different velocities. These two experiments showed that a laminated plate of aluminum and polycarbonate or aluminum and methyl methacrylate could prevent spallation and penetration failures with a lower areal density than either an all-aluminum laminated plate or a solid aluminum plate. The aluminum laminated plate was in turn superior to the solid aluminum plate in resisting spallation and penetration failures. In addition, through an example of 6061-T6 aluminum and methyl methacrylate, it is shown that a laminated structure ballistically superior to its parent materials may be built. The last two sets of experiments were conducted using bumper-protected main walls of solid aluminum and of laminated aluminum and polycarbonate. Again, under hypervelocity impact conditions, the laminated main walls were superior to the solid aluminum main walls in retarding spallation and penetration failures.

Presenting hydrothorax predicts failure of needle aspiration in primary spontaneous pneumothorax.

PubMed

Wu, Kwok Kei; Lui, Chun Tat; Ho, Chik Leung; Tsui, Kwok Leung; Fung, Hin Tat

2016-06-01

The objective was to evaluate if existence of hydrothorax in initial chest radiograph predicts treatment outcome in patients with primary spontaneous pneumothorax who received needle thoracostomy. This is a retrospective cohort study carried out from January 2011 to August 2014 in 1 public hospital in Hong Kong. All consecutive adult patients aged 18years or above who attended the emergency department with the diagnosis of primary spontaneous pneumothorax with needle aspiration performed as primary treatment were included. Age, smoking status, size of pneumothorax, previous history of pneumothorax, aspirated gas volume and presence of hydropneumothorax in initial radiograph were included in the analysis. The outcome was success or failure of the needle aspiration. Logistic regression was used to identify the predicting factors of failure of needle aspiration. There were a total of 127 patients included. Seventy-three patients (57.5%) were successfully treated with no recurrence upon discharge. Among 54 failure cases, 13 patients (10.2%) failed immediately after procedure as evident by chest radiograph and required second treatment. Forty-one patients (32.3%) failed upon subsequent chest radiographs. Multivariate logistic regression showed factors independently associated with the failure of needle aspiration, which included hydropneumothorax in the initial radiograph (odds ratio [OR]=4.47 [1.56i12.83], P=.005), previous history of pneumothorax (OR=3.92 [1.57-9.79], P=.003), and large size of pneumothorax defined as apex-to-cupola distance ≥5cm (OR=2.75 [1.21-6.26], P=.016). Hydropneumothorax, previous history of pneumothorax, and large size were independent predictors of failure of needle aspiration in treatment of primary spontaneous pneumothorax. Copyright © 2016 Elsevier Inc. All rights reserved.

Variations in Health Insurance Policies Regarding Biologic Therapy Use in Inflammatory Bowel Disease.

PubMed

Yadav, Abhijeet; Foromera, Joshua; Feuerstein, Ilana; Falchuk, Kenneth R; Feuerstein, Joseph D

2017-06-01

The American Gastroenterological Association (AGA) has developed guidelines for the management of ulcerative colitis and Crohn's disease (CD) recommending anti-TNF therapy in moderate-severe disease. However, which drug is used is often dictated by insurance company policies. We sought to determine the insurance policy requirements prior to approval of biologic therapies. Using the National Association of Insurance Commissioners report of the top 125 insurance companies by market share in 2014, we reviewed the first 50 that had online policies regarding anti-TNF and vedolizumab available. Policies were reviewed for criteria needed for approval of anti-TNF or vedolizumab therapy, and for compliance with the current AGA clinical pathway recommendations. Ninety-eight percent of policies are inconsistent with the AGA ulcerative colitis pathway and require step-wise drug failure before approval of an anti-TNF. Only 11% of the policies allowed starting vedolizumab without initial failures of an anti-TNF agent, and 21% required the failure of two or more anti-TNF agents. Ninety percent of the policies are inconsistent with AGA CD pathway and require step-wise drug failure before approval of an anti-TNF. Seventy-four percent allowed for initiating infliximab specifically for fistulizing CD. Twenty-eight percent required failing of at least two or more drugs before starting anti-TNF. Only 8% policies allowed starting vedolizumab without initial failures of an anti-TNF agent, and 28% required the failure of two anti-TNF agents. The majority of the policies reviewed fail to adhere to the current AGA pathway recommendations for ulcerative colitis and CD. Further interventions are needed to better align policies with optimal evidence-based drug therapy.

Risk Predictors and Causes of Technique Failure Within the First Year of Peritoneal Dialysis: An Australia and New Zealand Dialysis and Transplant Registry (ANZDATA) Study.

PubMed

See, Emily J; Johnson, David W; Hawley, Carmel M; Pascoe, Elaine M; Badve, Sunil V; Boudville, Neil; Clayton, Philip A; Sud, Kamal; Polkinghorne, Kevan R; Borlace, Monique; Cho, Yeoungjee

2017-12-22

Concern regarding technique failure is a major barrier to increased uptake of peritoneal dialysis (PD), and the first year of therapy is a particularly vulnerable time. A cohort study using competing-risk regression analyses to identify the key risk factors and risk periods for early transfer to hemodialysis therapy or death in incident PD patients. All adult patients who initiated PD therapy in Australia and New Zealand in 2000 through 2014. Patient demographics and comorbid conditions, duration of prior renal replacement therapy, timing of referral, PD modality, dialysis era, and center size. Technique failure within the first year, defined as transfer to hemodialysis therapy for more than 30 days or death. Of 16,748 patients included in the study, 4,389 developed early technique failure. Factors associated with increased risk included age older than 70 years, diabetes or vascular disease, prior renal replacement therapy, late referral to a nephrology service, or management in a smaller center. Asian or other race and use of continuous ambulatory PD were associated with reduced risk, as was initiation of PD therapy in 2010 through 2014. Although the risk for technique failure due to death or infection was constant during the first year, mechanical and other causes accounted for a greater number of cases within the initial 9 months of treatment. Potential for residual confounding due to limited data for residual kidney function, dialysis prescription, and socioeconomic factors. Several modifiable and nonmodifiable factors are associated with early technique failure in PD. Targeted interventions should be considered in high-risk patients to avoid the consequences of an unplanned transfer to hemodialysis therapy or death. Crown Copyright © 2017. Published by Elsevier Inc. All rights reserved.

Characterization of the Edge Crack Torsion (ECT) Test for Mode III Fracture Toughness Measurement of Laminated Composites

NASA Technical Reports Server (NTRS)

Ratcliffe, James G.

2004-01-01

The edge crack torsion (ECT) test is designed to initiate mode III delamination growth in composite laminates. The test has undergone several design changes during its development. The objective of this paper was to determine the suitability of the current ECT test design a mode III fracture test. To this end, ECT tests were conducted on specimens manufactured from IM7/8552 and S2/8552 tape laminates. Three-dimensional finite element analyses were performed. The analysis results were used to calculate the distribution of mode I, mode II, and mode III strain energy release rate along the delamination front. The results indicated that mode IIIdominated delamination growth would be initiated from the specimen center. However, in specimens of both material types, the measured values of GIIIc exhibited significant dependence on delamination length. Load-displacement response of the specimens exhibited significant deviation from linearity before specimen failure. X-radiographs of a sample of specimens revealed that damage was initiated in the specimens prior to failure. Further inspection of the failure surfaces is required to identify the damage and determine that mode III delamination is initiated in the specimens.

Risk of Unsuccessful Noninvasive Ventilation for Acute Respiratory Failure in Heterogeneous Neuromuscular Diseases: A Retrospective Study.

PubMed

Kataoka, Hiroshi; Nanaura, Hitoki; Kinugawa, Kaoru; Uchihara, Yuto; Ohara, Hiroya; Eura, Nobuyuki; Syobatake, Ryogo; Sawa, Nobuhiro; Takao, Kiriyama; Sugie, Kazuma; Ueno, Satoshi

2017-02-20

If invasive ventilation can be avoided by performing noninvasive mechanical ventilation (NIV) in patients with acute respiratory failure (ARF), the disease can be effectively managed. It is important to clarify the characteristics of patients with neuromuscular diseases in whom initial NIV is likely to be unsuccessful. We studied 27 patients in stable neuromuscular condition who initially received NIV to manage fatal ARF to identify differences in factors immediately before the onset of ARF among patients who receive continuous NIV support, patients who are switched from NIV to invasive ventilation, and patients in whom NIV is discontinued. Endpoints were evaluated 24 and 72 hours after the initiation of NIV. After 24 hours, all but 1 patient with amyotrophic lateral sclerosis (ALS) received continuous NIV support. 72 hours later, 5 patients were switched from NIV to invasive ventilation, and 5 patients continued to receive NIV support. 72 hours after the initiation of NIV, the proportion of patients with a diagnosis of ALS differed significantly among the three groups (P=0.039). NIV may be attempted to manage acute fatal respiratory failure associated with neuromuscular diseases, but clinicians should carefully manage the clinical course in patients with ALS.

The respiratory system.

PubMed

Zifko, U; Chen, R

1996-10-01

Neurological disorders frequently contribute to respiratory failure in critically ill patients. They may be the primary reason for the initiation of mechanical ventilation, or may develop later as a secondary complication. Disorders of the central nervous system leading to respiratory failure include metabolic encephalopathies, acute stroke, lesions of the motor cortex and brain-stem respiratory centres, and their descending pathways. Guillan-Barré syndrome, critical illness polyneuropathy and acute quadriplegic myopathy are the more common neuromuscular causes of respiratory failure. Clinical observations and pulmonary function tests are important in monitoring respiratory function. Respiratory electrophysiological studies are useful in the investigation and monitoring of respiratory failure. Transcortical and cervical magnetic stimulation can assess the central respiratory drive, and may be useful in determining the prognosis in ventilated patients, with cervical cord dysfunction. It is also helpful in the assessment of failure to wean, which is often caused by a combination of central and peripheral nervous system disorders. Phrenic nerve conduction studies and needle electromyography of the diaphragm and chest wall muscles are useful to characterize neuropathies and myopathies affecting the diaphragm. Repetitive phrenic nerve stimulation can assess neuromuscular transmission defects. It is important to identify patients at risk of respiratory failure. They should be carefully monitored and mechanical ventilation should be initiated before the development of severe hypoxaemia.

Initial use of echinocandins does not negatively influence outcome in Candida parapsilosis bloodstream infection: a propensity score analysis.

PubMed

Fernández-Ruiz, Mario; Aguado, José María; Almirante, Benito; Lora-Pablos, David; Padilla, Belén; Puig-Asensio, Mireia; Montejo, Miguel; García-Rodríguez, Julio; Pemán, Javier; Ruiz Pérez de Pipaón, Maite; Cuenca-Estrella, Manuel

2014-05-01

Concerns have arisen regarding the optimal antifungal regimen for Candida parapsilosis bloodstream infection (BSI) in view of its reduced susceptibility to echinocandins. The Prospective Population Study on Candidemia in Spain (CANDIPOP) is a prospective multicenter, population-based surveillance program on Candida BSI conducted through a 12-month period in 29 Spanish hospitals. Clinical isolates were identified by DNA sequencing, and antifungal susceptibility testing was performed by the European Committee on Antimicrobial Susceptibility Testing methodology. Predictors for clinical failure (all-cause mortality between days 3 to 30, or persistent candidemia for ≥72 hours after initiation of therapy) in episodes of C. parapsilosis species complex BSI were assessed by logistic regression analysis. We further analyzed the impact of echinocandin-based regimen as the initial antifungal therapy (within the first 72 hours) by using a propensity score approach. Among 752 episodes of Candida BSI identified, 200 (26.6%) were due to C. parapsilosis species complex. We finally analyzed 194 episodes occurring in 190 patients. Clinical failure occurred in 58 of 177 (32.8%) of evaluable episodes. Orotracheal intubation (adjusted odds ratio [AOR], 2.81; P = .018) and septic shock (AOR, 2.91; P = .081) emerged as risk factors for clinical failure, whereas early central venous catheter removal was protective (AOR, 0.43; P = .040). Neither univariate nor multivariate analysis revealed that the initial use of an echinocandin-based regimen had any impact on the risk of clinical failure. Incorporation of the propensity score into the model did not change this finding. The initial use of an echinocandin-based regimen does not seem to negatively influence outcome in C. parapsilosis BSI.

Vasopressor use after initial damage control laparotomy increases risk for anastomotic disruption in the management of destructive colon injuries.

PubMed

Fischer, Peter E; Nunn, Andrew M; Wormer, Blair A; Christmas, A Britton; Gibeault, Lindsay A; Green, John M; Sing, Ronald F

2013-12-01

Management of destructive colon injuries during damage control (DC) laparotomy is debated. The authors reviewed a single institution's experience with destructive colon injuries to identify risk factors for anastomotic failure after colon reconstruction. The authors identified all trauma patients sustaining destructive colon injuries between 2002 and 2011 from their medical center's trauma registry. Anastomotic leak was defined as suture or staple line disruption or enteral fistula formation. Of 171 identified patients, 68 had DC procedures, 41 (60%) had subsequent anastomoses performed during the same hospitalization, and 27 (40%) were diverted. The colon anastomotic leak rate in patients who underwent DC laparotomy was higher than in patients who were reconstructed at the primary operation in a non-DC setting (17% vs 6%, P = .09). The use of vasopressors after the initial DC operation more than quadrupled the leak rate to 50% (P = .02). Colonic anastomotic disruptions yield deadly consequences, and diversion rather than anastomosis should be used in patients who require vasopressor support after the initial DC procedure. Copyright © 2013 Elsevier Inc. All rights reserved.

Analysis of Discrete-Source Damage Progression in a Tensile Stiffened Composite Panel

NASA Technical Reports Server (NTRS)

Wang, John T.; Lotts, Christine G.; Sleight, David W.

1999-01-01

This paper demonstrates the progressive failure analysis capability in NASA Langley s COMET-AR finite element analysis code on a large-scale built-up composite structure. A large-scale five stringer composite panel with a 7-in. long discrete source damage was analyzed from initial loading to final failure including the geometric and material nonlinearities. Predictions using different mesh sizes, different saw cut modeling approaches, and different failure criteria were performed and assessed. All failure predictions have a reasonably good correlation with the test result.

Ductile Crack Initiation Criterion with Mismatched Weld Joints Under Dynamic Loading Conditions.

PubMed

An, Gyubaek; Jeong, Se-Min; Park, Jeongung

2018-03-01

Brittle failure of high toughness steel structures tends to occur after ductile crack initiation/propagation. Damages to steel structures were reported in the Hanshin Great Earthquake. Several brittle failures were observed in beam-to-column connection zones with geometrical discontinuity. It is widely known that triaxial stresses accelerate the ductile fracture of steels. The study examined the effects of geometrical heterogeneity and strength mismatches (both of which elevate plastic constraints due to heterogeneous plastic straining) and loading rate on critical conditions initiating ductile fracture. This involved applying the two-parameter criterion (involving equivalent plastic strain and stress triaxiality) to estimate ductile cracking for strength mismatched specimens under static and dynamic tensile loading conditions. Ductile crack initiation testing was conducted under static and dynamic loading conditions using circumferentially notched specimens (Charpy type) with/without strength mismatches. The results indicated that the condition for ductile crack initiation using the two parameter criterion was a transferable criterion to evaluate ductile crack initiation independent of the existence of strength mismatches and loading rates.

Effect of Antenatal Expression of Breast Milk at Term in Reducing Breast Feeding Failures.

PubMed

Singh, G; Chouhan, R; Sidhu, K

2009-04-01

Though breast feeding is natural, during the first 2-3 days, when enough breast milk is not available with mother, she may introduce bottle feeding erroneously for improving nutrition to her baby. We studied the effect of antenatal expression of breast milk at term in reducing breast feeding failure as compared to conventional method of initiation of breast feeding. A prospective study was carried out in 180 booked cases at term. Daily expression of breast milk at least once a day after 37 weeks of pregnancy was introduced in randomly selected 90 pregnant ladies. Prior examination was done to exclude any inverted or cracked nipples and appropriate treatment instituted. The study group who expressed breast milk daily after 37 weeks did not find it difficult to initiate breast feeding after vaginal or cesarean delivery. Sufficient milk started flowing within half an hour of initiation of breast feeding in most 85 (94.4%) subjects of study group as compared to 63 (70%) patients of control group, which was statistically significant. There was no increase in any delivery complication. There were two partial breast feeding failures in control group but none in study group. Daily antenatal breast milk expression after 37 completed weeks of pregnancy significantly reduced the time for establishing full breast feeding and reduced breast feeding failures.

Risk factors for shunt malfunction in pediatric hydrocephalus: a multicenter prospective cohort study.

PubMed

Riva-Cambrin, Jay; Kestle, John R W; Holubkov, Richard; Butler, Jerry; Kulkarni, Abhaya V; Drake, James; Whitehead, William E; Wellons, John C; Shannon, Chevis N; Tamber, Mandeep S; Limbrick, David D; Rozzelle, Curtis; Browd, Samuel R; Simon, Tamara D

2016-04-01

OBJECT The rate of CSF shunt failure remains unacceptably high. The Hydrocephalus Clinical Research Network (HCRN) conducted a comprehensive prospective observational study of hydrocephalus management, the aim of which was to isolate specific risk factors for shunt failure. METHODS The study followed all first-time shunt insertions in children younger than 19 years at 6 HCRN centers. The HCRN Investigator Committee selected, a priori, 21 variables to be examined, including clinical, radiographic, and shunt design variables. Shunt failure was defined as shunt revision, subsequent endoscopic third ventriculostomy, or shunt infection. Important a priori-defined risk factors as well as those significant in univariate analyses were then tested for independence using multivariate Cox proportional hazard modeling. RESULTS A total of 1036 children underwent initial CSF shunt placement between April 2008 and December 2011. Of these, 344 patients experienced shunt failure, including 265 malfunctions and 79 infections. The mean and median length of follow-up for the entire cohort was 400 days and 264 days, respectively. The Cox model found that age younger than 6 months at first shunt placement (HR 1.6 [95% CI 1.1-2.1]), a cardiac comorbidity (HR 1.4 [95% CI 1.0-2.1]), and endoscopic placement (HR 1.9 [95% CI 1.2-2.9]) were independently associated with reduced shunt survival. The following had no independent associations with shunt survival: etiology, payer, center, valve design, valve programmability, the use of ultrasound or stereotactic guidance, and surgeon experience and volume. CONCLUSIONS This is the largest prospective study reported on children with CSF shunts for hydrocephalus. It confirms that a young age and the use of the endoscope are risk factors for first shunt failure and that valve type has no impact. A new risk factor-an existing cardiac comorbidity-was also associated with shunt failure.

External events analysis for the Savannah River Site K reactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brandyberry, M.D.; Wingo, H.E.

1990-01-01

The probabilistic external events analysis performed for the Savannah River Site K-reactor PRA considered many different events which are generally perceived to be external'' to the reactor and its systems, such as fires, floods, seismic events, and transportation accidents (as well as many others). Events which have been shown to be significant contributors to risk include seismic events, tornados, a crane failure scenario, fires and dam failures. The total contribution to the core melt frequency from external initiators has been found to be 2.2 {times} 10{sup {minus}4} per year, from which seismic events are the major contributor (1.2 {times} 10{supmore » {minus}4} per year). Fire initiated events contribute 1.4 {times} 10{sup {minus}7} per year, tornados 5.8 {times} 10{sup {minus}7} per year, dam failures 1.5 {times} 10{sup {minus}6} per year and the crane failure scenario less than 10{sup {minus}4} per year to the core melt frequency. 8 refs., 3 figs., 5 tabs.« less

Effects of Stress Ratio and Microstructure on Fatigue Failure Behavior of Polycrystalline Nickel Superalloy

NASA Astrophysics Data System (ADS)

Zhang, H.; Guan, Z. W.; Wang, Q. Y.; Liu, Y. J.; Li, J. K.

2018-05-01

The effects of microstructure and stress ratio on high cycle fatigue of nickel superalloy Nimonic 80A were investigated. The stress ratios of 0.1, 0.5 and 0.8 were chosen to perform fatigue tests in a frequency of 110 Hz. Cleavage failure was observed, and three competing failure crack initiation modes were discovered by a scanning electron microscope, which were classified as surface without facets, surface with facets and subsurface with facets. With increasing the stress ratio from 0.1 to 0.8, the occurrence probability of surface and subsurface with facets also increased and reached the maximum value at R = 0.5, meanwhile the probability of surface initiation without facets decreased. The effect of microstructure on the fatigue fracture behavior at different stress ratios was also observed and discussed. Based on the Goodman diagram, it was concluded that the fatigue strength of 50% probability of failure at R = 0.1, 0.5 and 0.8 is lower than the modified Goodman line.

Fulminate Hepatic Failure as an Initial Presentation of Non-Hodgkin Lymphoma: A Case Report

PubMed Central

Ahmadi, Bizhan; Shafieipour, Sara; Akhavan Rezayat, Kambiz

2014-01-01

Viral hepatitis and toxins comprise most common causes of fulminate hepatic failure that are often diagnosed with standard laboratory tests. Herein we discuss a rare, difficult to diagnosis etiology of acute liver failure (ALF). A 62-year-old man presented with a two-week history of fever and fatigue. At four days before admission he became lethargic. His past medical and drug histories were unremarkable. Physical examination revealed generalized jaundice, fever and loss of consciousness. Laboratory tests showed elevated liver transaminases with direct hyper-bilirubinemia. Abdominal ultrasonography and CT scan showed hepatosplenomegaly and para-aortic abdominal lymphadenopathy. A further work-up included liver biopsy. The histopathology and imunohistochemistry was compatible with diffuse large B-cell lymphoma. He underwent high dose glucocorticoid therapy but his condition deteriorated rapidly and he died eight days after admission. ALF as an initial manifestation of malignant hepatic infiltration is extremely rare yet should be considered in all patients with unknown hepatic failure that are highly suspicious for malignant neoplasm. PMID:24872870

Experiences of Patients Living With Heart Failure: A Descriptive Qualitative Study.

PubMed

Seah, Alvin Chuen Wei; Tan, Khoon Kiat; Huang Gan, Juvena Chew; Wang, Wenru

2016-07-01

The purpose of this study was to explore the experiences, needs, and coping strategies of patients living with heart failure in Singapore. A descriptive qualitative design was used. A purposive sample of 15 informants was recruited from two cardiology wards of a tertiary public hospital in Singapore. Individual face-to-face interviews were conducted with a semistructured interview guideline that was developed based on a review of the literature and a pilot study. Content analysis was adopted to analyze the data, and four main categories were identified: perceived causes, manifestations, and prognosis; enduring emotions; managing the condition; and needs from health care professionals. The informants were overwhelmed with the experience of living with heart failure due to the disruptive and uncertain nature of the condition. This study offers health care professionals practical and useful suggestions when providing holistic care for patients with heart failure. © The Author(s) 2015.

Performance deficits following failure: learned helplessness or self-esteem protection?

PubMed

Witkowski, T; Stiensmeier-Pelster, J

1998-03-01

We report two laboratory experiments which compare two competing explanations of performance deficits following failure: one based on Seligman's learned helplessness theory (LHT), and the other, on self-esteem protection theory (SEPT). In both studies, participants (Study 1: N = 40 pupils from secondary schools in Walbrzych, Poland; Study 2: N = 45 students from the University of Bielefeld, Germany) were confronted with either success or failure in a first phase of the experiment. Then, in the second phase of the experiment the participants had to work on a set of mathematical problems (Study 1) or a set of tasks taken from Raven's Progressive Matrices (Study 2) either privately or in public. In both studies failure in the first phase causes performance deficits in the second phase only if the participants had to solve the test tasks in public. These results were interpreted in line with SEPT and as incompatible with LHT.

Retrieval Failure Contributes to Gist-Based False Recognition

PubMed Central

Guerin, Scott A.; Robbins, Clifford A.; Gilmore, Adrian W.; Schacter, Daniel L.

2011-01-01

People often falsely recognize items that are similar to previously encountered items. This robust memory error is referred to as gist-based false recognition. A widely held view is that this error occurs because the details fade rapidly from our memory. Contrary to this view, an initial experiment revealed that, following the same encoding conditions that produce high rates of gist-based false recognition, participants overwhelmingly chose the correct target rather than its related foil when given the option to do so. A second experiment showed that this result is due to increased access to stored details provided by reinstatement of the originally encoded photograph, rather than to increased attention to the details. Collectively, these results suggest that details needed for accurate recognition are, to a large extent, still stored in memory and that a critical factor determining whether false recognition will occur is whether these details can be accessed during retrieval. PMID:22125357

Breastfeeding and employment: an assessment of employer attitudes.

PubMed

Libbus, M Kay; Bullock, Linda F C

2002-08-01

Both research and anecdotal reports suggest that maternal employment is associated with failure to initiate breastfeeding and early breastfeeding attrition. The objective of this study was to describe the experience with and attitudes toward breastfeeding of a sample of employers in a small Midwestern city in the United States. Based on an analysis of 85 mail-out questionnaires, we found that less than half of the employers had personal experience with breastfeeding. A large percentage of the sample, however, indicated that they would be willing to facilitate women who wished to breastfeed or express milk in the workplace. However, these employers also stated that they saw little value to their business of supporting breastfeeding in the work environment. Thus, enhancement of breastfeeding opportunity in the work environment may come as a result of public and employer education but, more likely, will require some type of directive from official sources.

Estimation of metal strength at very high rates using free-surface Richtmyer–Meshkov Instabilities

DOE PAGES

Prime, Michael Bruce; Buttler, William Tillman; Buechler, Miles Allen; ...

2017-03-08

Recently, Richtmyer–Meshkov Instabilities (RMI) have been proposed for studying the average strength at strain rates up to at least 10 7/s. RMI experiments involve shocking a metal interface that has initial sinusoidal perturbations. The perturbations invert and grow subsequent to shock and may arrest because of strength effects. In this work we present new RMI experiments and data on a copper target that had five regions with different perturbation amplitudes on the free surface opposite the shock. We estimate the high-rate, low-pressure copper strength by comparing experimental data with Lagrangian numerical simulations. From a detailed computational study we find thatmore » mesh convergence must be carefully addressed to accurately compare with experiments, and numerical viscosity has a strong influence on convergence. We also find that modeling the as-built perturbation geometry rather than the nominal makes a significant difference. Because of the confounding effect of tensile damage on total spike growth, which has previously been used as the metric for estimating strength, we instead use a new strength metric: the peak velocity during spike growth. Furthermore, this new metric also allows us to analyze a broader set of experimental results that are sensitive to strength because some larger initial perturbations grow unstably to failure and so do not have a finite total spike growth.« less

Estimation of metal strength at very high rates using free-surface Richtmyer–Meshkov Instabilities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prime, Michael Bruce; Buttler, William Tillman; Buechler, Miles Allen

Recently, Richtmyer–Meshkov Instabilities (RMI) have been proposed for studying the average strength at strain rates up to at least 10 7/s. RMI experiments involve shocking a metal interface that has initial sinusoidal perturbations. The perturbations invert and grow subsequent to shock and may arrest because of strength effects. In this work we present new RMI experiments and data on a copper target that had five regions with different perturbation amplitudes on the free surface opposite the shock. We estimate the high-rate, low-pressure copper strength by comparing experimental data with Lagrangian numerical simulations. From a detailed computational study we find thatmore » mesh convergence must be carefully addressed to accurately compare with experiments, and numerical viscosity has a strong influence on convergence. We also find that modeling the as-built perturbation geometry rather than the nominal makes a significant difference. Because of the confounding effect of tensile damage on total spike growth, which has previously been used as the metric for estimating strength, we instead use a new strength metric: the peak velocity during spike growth. Furthermore, this new metric also allows us to analyze a broader set of experimental results that are sensitive to strength because some larger initial perturbations grow unstably to failure and so do not have a finite total spike growth.« less

Free-Swinging Failure Tolerance for Robotic Manipulators

NASA Technical Reports Server (NTRS)

English, James

1997-01-01

Under this GSRP fellowship, software-based failure-tolerance techniques were developed for robotic manipulators. The focus was on failures characterized by the loss of actuator torque at a joint, called free-swinging failures. The research results spanned many aspects of the free-swinging failure-tolerance problem, from preparing for an expected failure to discovery of postfailure capabilities to establishing efficient methods to realize those capabilities. Developed algorithms were verified using computer-based dynamic simulations, and these were further verified using hardware experiments at Johnson Space Center.

Resilience to emotional distress in response to failure, error or mistakes: A systematic review.

PubMed

Johnson, Judith; Panagioti, Maria; Bass, Jennifer; Ramsey, Lauren; Harrison, Reema

2017-03-01

Perceptions of failure have been implicated in a range of psychological disorders, and even a single experience of failure can heighten anxiety and depression. However, not all individuals experience significant emotional distress following failure, indicating the presence of resilience. The current systematic review synthesised studies investigating resilience factors to emotional distress resulting from the experience of failure. For the definition of resilience we used the Bi-Dimensional Framework for resilience research (BDF) which suggests that resilience factors are those which buffer the impact of risk factors, and outlines criteria a variable should meet in order to be considered as conferring resilience. Studies were identified through electronic searches of PsycINFO, MEDLINE, EMBASE and Web of Knowledge. Forty-six relevant studies reported in 38 papers met the inclusion criteria. These provided evidence of the presence of factors which confer resilience to emotional distress in response to failure. The strongest support was found for the factors of higher self-esteem, more positive attributional style, and lower socially-prescribed perfectionism. Weaker evidence was found for the factors of lower trait reappraisal, lower self-oriented perfectionism and higher emotional intelligence. The majority of studies used experimental or longitudinal designs. These results identify specific factors which should be targeted by resilience-building interventions. Resilience; failure; stress; self-esteem; attributional style; perfectionism. Copyright © 2016 Elsevier Ltd. All rights reserved.

Transfer Failure and Proactive Interference in Short-Term Memory

ERIC Educational Resources Information Center

Ellis, John A.

1977-01-01

Two experiments tested the hypothesis that proactive interference over a series of Brown-Peterson trials results from a combination of the subject's failure to transfer information to a permanent memory state and failure to retrieve information from permanent memory. (Editor)

Design/Analysis of Metal/Composite Bonded Joints for Survivability at Cryogenic Temperatures

NASA Technical Reports Server (NTRS)

Bartoszyk, Andrew E.

2004-01-01

A major design and analysis challenge for the JWST ISM structure is the metal/composite bonded joints that will be required to survive down to an operational ultra-low temperature of 30K (-405 F). The initial and current baseline design for the plug-type joint consists of a titanium thin walled fitting (1-3mm thick) bonded to the interior surface of an M555/954-6 composite truss square tube with an axially stiff biased lay-up. Metallic fittings are required at various nodes of the truss structure to accommodate instrument and lift-point bolted interfaces. Analytical experience and design work done on metal/composite bonded joints at temperatures below liquid nitrogen are limited and important analysis tools, material properties, and failure criteria for composites at cryogenic temperatures are virtually nonexistent. Increasing the challenge is the difficulty in testing for these required tools and parameters at 30K. A preliminary finite element analysis shows that failure due to CTE mismatch between the biased composite and titanium or aluminum is likely. Failure is less likely with Invar, however an initial mass estimate of Invar fittings demonstrates that Invar is not an automatic alternative. In order to gain confidence in analyzing and designing the ISM joints, a comprehensive joint development testing program has been planned and is currently running. The test program is designed for the correlation of the analysis methodology, including tuning finite element model parameters, and developing a composite failure criterion for the effect of multi-axial composite stresses on the strength of a bonded joint at 30K. The testing program will also consider stress mitigation using compliant composite layers and potential strength degradation due to multiple thermal cycles. Not only will the finite element analysis be correlated to the test data, but the FEA will be used to guide the design of the test. The first phase of the test program has been completed and the preliminary analysis has been revisited based on the test data In this work, we present an overview of the test plan, results today, and resulting design improvements.

Cognitive Performance Is Highly Sensitive to Prior Experience in Mice with a Learning and Memory Deficit: Failure Leads to More Failure

ERIC Educational Resources Information Center

Hebda-Bauer, Elaine K.; Watson, Stanley J.; Akil, Huda

2005-01-01

The impact of a previously successful or unsuccessful experience on the subsequent acquisition of a related task is not well understood. The nature of past experience may have even greater impact in individuals with learning deficits, as their cognitive processes can be easily disrupted. Mice with a targeted disruption of the [alpha] and [delta]…

Vibrational fatigue failures in short cantilevered piping with socket-welding fittings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, J.K.

1996-12-01

Approximately 80% of the vibrational fatigue failures in nuclear power plants have been caused by high cycle vibrational fatigue. Many of these failures have occurred in short, small bore (2 in. nominal diameter and smaller), unbraced, cantilevered piping with socket-welding fittings. The fatigue failures initiated in the socket welds. These failures have been unexpected, and have caused costly, unscheduled outages in some cases. In order to reduce the number of vibrational fatigue failures in these short cantilevered pipes, an acceleration based vibrational fatigue screening criteria was developed under Electric Power Research Institute (EPRI) sponsorship. In this paper, the acceleration basedmore » criteria will be compared to the results obtained from detailed dynamic modeling of a short, cantilevered pipe.« less

Renal Denervation for Chronic Heart Failure: Background and Pathophysiological Rationale.

PubMed

Böhm, Michael; Ewen, Sebastian; Mahfoud, Felix

2017-01-01

The activation of the sympathetic nervous system is associated with cardiovascular hospitalizations and death in heart failure. Renal denervation has been shown to effectively reduce sympathetic overdrive in certain patients with uncontrolled hypertension. Pilot trials investigating renal denervation as a potential treatment approach for heart failure were initiated. Heart failure comorbidities like obstructive sleep apnea, metabolic syndrome and arrhythmias could also be targets for renal denervation, because these occurrences are also mediated by the activation of the sympathetic nervous system. Therefore, renal denervation in heart failure is worthy of further investigation, although its effectiveness still has to be proven. Herein, we describe the pathophysiological rationale and the effect of renal denervation on surrogates of the heart failure syndrome.

Renal Denervation for Chronic Heart Failure: Background and Pathophysiological Rationale

PubMed Central

Ewen, Sebastian; Mahfoud, Felix

2017-01-01

The activation of the sympathetic nervous system is associated with cardiovascular hospitalizations and death in heart failure. Renal denervation has been shown to effectively reduce sympathetic overdrive in certain patients with uncontrolled hypertension. Pilot trials investigating renal denervation as a potential treatment approach for heart failure were initiated. Heart failure comorbidities like obstructive sleep apnea, metabolic syndrome and arrhythmias could also be targets for renal denervation, because these occurrences are also mediated by the activation of the sympathetic nervous system. Therefore, renal denervation in heart failure is worthy of further investigation, although its effectiveness still has to be proven. Herein, we describe the pathophysiological rationale and the effect of renal denervation on surrogates of the heart failure syndrome. PMID:28154583

Progressive Damage Analyses of Skin/Stringer Debonding

NASA Technical Reports Server (NTRS)

Daville, Carlos G.; Camanho, Pedro P.; deMoura, Marcelo F.

2004-01-01

The debonding of skin/stringer constructions is analyzed using a step-by-step simulation of material degradation based on strain softening decohesion elements and a ply degradation procedure. Decohesion elements with mixed-mode capability are placed at the interface between the skin and the flange to simulate the initiation and propagation of the delamination. In addition, the initiation and accumulation of fiber failure and matrix damage is modeled using Hashin-type failure criteria and their corresponding material degradation schedules. The debonding predictions using simplified three-dimensional models correlate well with test results.

Small sample estimation of the reliability function for technical products

NASA Astrophysics Data System (ADS)

Lyamets, L. L.; Yakimenko, I. V.; Kanishchev, O. A.; Bliznyuk, O. A.

2017-12-01

It is demonstrated that, in the absence of big statistic samples obtained as a result of testing complex technical products for failure, statistic estimation of the reliability function of initial elements can be made by the moments method. A formal description of the moments method is given and its advantages in the analysis of small censored samples are discussed. A modified algorithm is proposed for the implementation of the moments method with the use of only the moments at which the failures of initial elements occur.

Initial load-to-failure and failure analysis in single- and double-row repair techniques for rotator cuff repair.

PubMed

Baums, M H; Buchhorn, G H; Gilbert, F; Spahn, G; Schultz, W; Klinger, H-M

2010-09-01

This experimental study aimed to compare the load-to-failure rate and stiffness of single- versus double-row suture techniques for repairing rotator cuff lesions using two different suture materials. Additionally, the mode of failure of each repair was evaluated. In 32 sheep shoulders, a standardized tear of the infraspinatus tendon was created. Then, n = 8 specimen were randomized to four repair methods: (1) Double-row Anchor Ethibond coupled with polyester sutures, USP No. 2; (2) Double-Row Anchor HiFi with polyblend polyethylene sutures, USP No. 2; (3) Single-Row Anchor Ethibond coupled with braided polyester sutures, USP No. 2; and (4) Single-Row Anchor HiFi with braided polyblend polyethylene sutures, USP No. 2. Arthroscopic Mason-Allen stitches were placed (single-row) and combined with medial horizontal mattress stitches (double-row). All specimens were loaded to failure at a constant displacement rate on a material testing machine. Group 4 showed lowest load-to-failure result with 155.7 +/- 31.1 N compared to group 1 (293.4 +/- 16.1 N) and group 2 (397.7 +/- 7.4 N) (P < 0.001). Stiffness was highest in group 2 (162 +/- 7.3 N/mm) and lowest in group 4 (84.4 +/- 19.9 mm) (P < 0.001). In group 4, the main cause of failure was due to the suture cutting through the tendon (n = 6), a failure case observed in only n = 1 specimen in group 2 (P < 0.001). A double-row technique combined with arthroscopic Mason-Allen/horizontal mattress stitches provides high initial failure strength and may minimize the risk of the polyethylene sutures cutting through the tendon in rotator cuff repair when a single load force is used.

Simulation Assisted Risk Assessment Applied to Launch Vehicle Conceptual Design

NASA Technical Reports Server (NTRS)

Mathias, Donovan L.; Go, Susie; Gee, Ken; Lawrence, Scott

2008-01-01

A simulation-based risk assessment approach is presented and is applied to the analysis of abort during the ascent phase of a space exploration mission. The approach utilizes groupings of launch vehicle failures, referred to as failure bins, which are mapped to corresponding failure environments. Physical models are used to characterize the failure environments in terms of the risk due to blast overpressure, resulting debris field, and the thermal radiation due to a fireball. The resulting risk to the crew is dynamically modeled by combining the likelihood of each failure, the severity of the failure environments as a function of initiator and time of the failure, the robustness of the crew module, and the warning time available due to early detection. The approach is shown to support the launch vehicle design process by characterizing the risk drivers and identifying regions where failure detection would significantly reduce the risk to the crew.

Dissociative detachment and memory impairment: reversible amnesia or encoding failure?

PubMed

Allen, J G; Console, D A; Lewis, L

1999-01-01

The authors propose that clinicians endeavor to differentiate between reversible and irreversible memory failures in patients with dissociative symptoms who report "memory gaps" and "lost time." The classic dissociative disorders, such as dissociative amnesia and dissociative identity disorder, entail reversible memory failures associated with encoding experience in altered states. The authors propose another realm of memory failures associated with severe dissociative detachment that may preclude the level of encoding of ongoing experience needed to support durable autobiographical memories. They describe how dissociative detachment may be intertwined with neurobiological factors that impair memory, and they spell out the significance of distinguishing reversible and irreversible memory impairment for diagnosis, patient education, psychotherapy, and research.

Community Capacity Building: Starting with People Not Projects.

ERIC Educational Resources Information Center

Simpson, Lyn; Wood, Leanne; Daws, Leonie

2003-01-01

A remote Australian town's initiative to develop an Internet cafe was based on a foundation of community empowerment and capacity building. The project's failure illustrates factors that inhibit community control: overstretched local resources, failure to understand impact on existing social infrastructure and social networks, and lack of…

[Acute renal failure: a rare presentation of Addison's disease].

PubMed

Salhi, Houda

2016-01-01

Addison's disease is a rare condition. Its onset of symptoms most often is nonspecific contributing to a diagnostic and therapeutic delay. Acute renal failure can be the first manifestation of this disease. We report the case of a patient with Addison's disease who was initially treated for acute renal failure due to multiple myeloma and whose diagnosis was adjusted thereafter. Patient's condition dramatically improved after treatment with intravenous rehydration; injectable hydrocortisone.

Probability of failure prediction for step-stress fatigue under sine or random stress

NASA Technical Reports Server (NTRS)

Lambert, R. G.

1979-01-01

A previously proposed cumulative fatigue damage law is extended to predict the probability of failure or fatigue life for structural materials with S-N fatigue curves represented as a scatterband of failure points. The proposed law applies to structures subjected to sinusoidal or random stresses and includes the effect of initial crack (i.e., flaw) sizes. The corrected cycle ratio damage function is shown to have physical significance.

Association between Platelet Counts before and during Pharmacological Therapy for Patent Ductus Arteriosus and Treatment Failure in Preterm Infants.

PubMed

Sallmon, Hannes; Weber, Sven C; Dirks, Juliane; Schiffer, Tamara; Klippstein, Tamara; Stein, Anja; Felderhoff-Müser, Ursula; Metze, Boris; Hansmann, Georg; Bührer, Christoph; Cremer, Malte; Koehne, Petra

2018-01-01

The role of platelets for mediating closure of the ductus arteriosus in human preterm infants is controversial. Especially, the effect of low platelet counts on pharmacological treatment failure is still unclear. In this retrospective study of 471 preterm infants [<1,500 g birth weight (BW)], who were treated for a patent ductus arteriosus (PDA) with indomethacin or ibuprofen, we investigated whether platelet counts before or during pharmacological treatment had an impact on the successful closure of a hemodynamically significant PDA. The effects of other factors, such as sepsis, preeclampsia, gestational age, BW, and gender, were also evaluated. Platelet counts before initiation of pharmacological PDA treatment did not differ between infants with later treatment success or failure. However, we found significant associations between low platelet counts during pharmacological PDA therapy and treatment failure ( p  < 0.05). Receiver operating characteristic (ROC) curve analysis showed that platelet counts after the first, and before and after the second cyclooxygenase inhibitor (COXI) cycle were significantly associated with treatment failure (area under the curve of >0.6). However, ROC curve analysis did not reveal a specific platelet cutoff-value that could predict PDA treatment failure. Multivariate logistic regression analysis showed that lower platelet counts, a lower BW, and preeclampsia were independently associated with COXI treatment failure. We provide further evidence for an association between low platelet counts during pharmacological therapy for symptomatic PDA and treatment failure, while platelet counts before initiation of therapy did not affect treatment outcome.

Incidence and Outcome of CPAP Failure in Preterm Infants.

PubMed

Dargaville, Peter A; Gerber, Angela; Johansson, Stefan; De Paoli, Antonio G; Kamlin, C Omar F; Orsini, Francesca; Davis, Peter G

2016-07-01

Data from clinical trials support the use of continuous positive airway pressure (CPAP) for initial respiratory management in preterm infants, but there is concern regarding the potential failure of CPAP support. We aimed to examine the incidence and explore the outcomes of CPAP failure in Australian and New Zealand Neonatal Network data from 2007 to 2013. Data from inborn preterm infants managed on CPAP from the outset were analyzed in 2 gestational age ranges (25-28 and 29-32 completed weeks). Outcomes after CPAP failure (need for intubation <72 hours) were compared with those succeeding on CPAP using adjusted odds ratios (AORs). Within the cohort of 19 103 infants, 11 684 were initially managed on CPAP. Failure of CPAP occurred in 863 (43%) of 1989 infants commencing on CPAP at 25-28 weeks' gestation and 2061 (21%) of 9695 at 29-32 weeks. CPAP failure was associated with a substantially higher rate of pneumothorax, and a heightened risk of death, bronchopulmonary dysplasia (BPD) and other morbidities compared with those managed successfully on CPAP. The incidence of death or BPD was also increased: (25-28 weeks: 39% vs 20%, AOR 2.30, 99% confidence interval 1.71-3.10; 29-32 weeks: 12% vs 3.1%, AOR 3.62 [2.76-4.74]). The CPAP failure group had longer durations of respiratory support and hospitalization. CPAP failure in preterm infants is associated with increased risk of mortality and major morbidities, including BPD. Strategies to promote successful CPAP application should be pursued vigorously. Copyright © 2016 by the American Academy of Pediatrics.

Graft survival of diabetic versus nondiabetic donor tissue after initial keratoplasty.

PubMed

Vislisel, Jesse M; Liaboe, Chase A; Wagoner, Michael D; Goins, Kenneth M; Sutphin, John E; Schmidt, Gregory A; Zimmerman, M Bridget; Greiner, Mark A

2015-04-01

To compare corneal graft survival using tissue from diabetic and nondiabetic donors in patients undergoing initial Descemet stripping automated endothelial keratoplasty (DSAEK) or penetrating keratoplasty (PKP). A retrospective chart review of pseudophakic eyes that underwent DSAEK or PKP was performed. The primary outcome measure was graft failure. Cox proportional hazard regression and Kaplan-Meier survival analyses were used to compare diabetic versus nondiabetic donor tissue for all keratoplasty cases. A total of 183 eyes (136 DSAEK, 47 PKP) were included in the statistical analysis. Among 24 procedures performed using diabetic donor tissue, there were 4 cases (16.7%) of graft failure (3 DSAEK, 1 PKP), and among 159 procedures performed using nondiabetic donor tissue, there were 18 cases (11.3%) of graft failure (12 DSAEK, 6 PKP). Cox proportional hazard ratio of graft failure for all cases comparing diabetic with nondiabetic donor tissue was 1.69, but this difference was not statistically significant (95% confidence interval, 0.56-5.06; P = 0.348). There were no significant differences in Kaplan-Meier curves comparing diabetic with nondiabetic donor tissue for all cases (P = 0.380). Statistical analysis of graft failure by donor diabetes status within each procedure type was not possible because of the small number of graft failure events involving diabetic tissue. We found similar rates of graft failure in all keratoplasty cases when comparing tissue from diabetic and nondiabetic donors, but further investigation is needed to determine whether diabetic donor tissue results in different graft failure rates after DSAEK compared with PKP.

Scanning electron microscope fractography in failure analysis of steels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wouters, R.; Froyen, L.

1996-04-01

For many failure cases, macroscopic examination of the fracture surface permits discrimination of fatigue fractures from overload fractures. For clarifying fatigue fractures, the practical significance of microfractography is limited to an investigation of the crack initiation areas. Scanning electron microscopy is successfully used in tracing local material abnormalities that act as fatigue crack initiators. The task for the scanning electron microscope, however, is much more substantial in failure analysis of overload fractures, especially for steels. By revealing specific fractographic characteristics, complemented by information about the material and the loading conditions, scanning electron microscopy provides a strong indication of the probablemore » cause of failure. A complete dimple fracture is indicative of acceptable bulk material properties; overloading, by subdimensioning or excessive external loading, has to be verified. The presence of cleavage fracture makes the material properties questionable if external conditions causing embrittlement are absent. Intergranular brittle fracture requires verification of grain-boundary weakening conditions--a sensitized structure, whether or not combined with a local stress state or a specific environment. The role of scanning electron microscopy in failure analysis is illustrated by case histories of the aforementioned fracture types.« less

Development, characterization, and modeling of ballistic impact on composite laminates under compressive pre-stress

NASA Astrophysics Data System (ADS)

Kerr-Anderson, Eric

Structural composite laminates were ballistically impacted while under in-plane compressive pre-stress. Residual properties, damage characterization, and energy absorption were compared to determine synergistic effects of in-plane compressive pre-stress and impact velocity. A fixture was developed to apply in-plane compressive loads up to 30 tons to structural composites during an impact event using a single-stage light-gas gun. Observed failure modes included typical conical delamination, the development of an impact initiated shear crack (IISC), and the shear failure of a pre-stressed composite due to impact. It was observed that the compressive failure threshold quadratically decreased in relation to the impact velocity up to velocities that caused partial penetration. For all laminates impacted at velocities causing partial or full penetration up to 350 ms-1, the failure threshold was consistent and used as an experimental normalization. Samples impacted below 65% of the failure threshold witnessed no significant change in damage morphology or residual properties when compared to typical conical delamination. Samples impacted above 65% of the failure threshold witnessed additional damage in the form of a shear crack extending perpendicular to the applied load from the point of impact. The presence of an IISC reduced the residual properties and even caused failure upon impact at extreme combinations. Four failure envelopes have been established as: transient failure, steady state failure, impact initiated shear crack, and conical damage. Boundaries and empirically based equations for residual compressive strength have been developed for each envelope with relation to two E-glass/vinyl ester laminate systems. Many aspects of pre-stressed impact have been individually examined, but there have been no comprehensive examinations of pre-stressed impact. This research has resulted in the exploration and characterization of compressively pre-stressed damage for impact velocities resulting in reflection, partial penetration, and penetration at pre-stress levels resulting in conical damage, shear cracking, and failure.

Investigation of Thermal High Cycle and Low Cycle Fatigue Mechanisms of Thick Thermal Barrier Coatings

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Miller, Robert A.

1998-01-01

Thick thermal barrier coating systems in a diesel engine experience severe thermal low cycle fatigue (LCF) and high cycle fatigue (HCF) during engine operation. In this paper, the mechanisms of fatigue crack initiation and propagation in a ZrO2-8wt.% Y2O3 thermal barrier coating, under simulated engine thermal LCF and HCF conditions, are investigated using a high power CO2 laser. Experiments showed that the combined LCF/HCF tests induced more severe coating surface cracking, microspallation and accelerated crack growth, as compared to the pure LCF test. Lateral crack branching and the ceramic/bond coat interface delaminations were also facilitated by HCF thermal loads, even in the absence of severe interfacial oxidation. Fatigue damages at crack wake surfaces, due to such phenomena as asperity/debris contact induced cracking and splat pull-out bending during cycling, were observed especially for the combined LCF/HCF tests. It is found that the failure associated with LCF is closely related to coating sintering and creep at high temperatures, which induce tensile stresses in the coating after cooling. The failure associated with HCF process, however, is mainly associated with a surface wedging mechanism. The interaction between the LCF, HCF and ceramic coating creep, and the relative importance of LCF and HCF in crack propagation are also discussed based on the experimental evidence.

Results from sudden loss of vacuum on scaled superconducting radio frequency cryomodule experiment

NASA Astrophysics Data System (ADS)

Dalesandro, Andrew A.; Dhuley, Ram C.; Theilacker, Jay C.; Van Sciver, Steven W.

2014-01-01

Superconducting radio frequency (SRF) cavities for particle accelerators are at risk of failure due to sudden loss of vacuum (SLV) adjacent to liquid helium (LHe) spaces. To better understand this failure mode and its associated risks an experiment is designed to test the longitudinal effects of SLV within the beam tube of a scaled SRF cryomodule that has considerable length relative to beam tube cross section. The scaled cryomodule consists of six individual SRF cavities each roughly 350 mm long, initially cooled to 2 K by a superfluid helium bath and a beam tube pumped to vacuum. A fast-acting solenoid valve is used to simulate SLV on the beam tube, from which point it takes over 3 s for the beam tube pressure to equalize with atmosphere, and 30 s for the helium space to reach the relief pressure of 4 bara. A SLV longitudinal effect in the beam tube is evident in both pressure and temperature data, but interestingly the temperatures responds more quickly to SLV than do the pressures. It takes 500 ms (roughly 100 ms per cavity) for the far end of the 2 m long beam tube to respond to a pressure increase compared to 300 ms for temperature (approximately 50 ms per cavity). The paper expands upon these and other results to better understand the longitudinal effect for SRF cryomodules due to SLV.

Eight years' experience with an IVF surrogate gestational pregnancy programme.

PubMed

Raziel, Arieh; Schachter, Morey; Strassburger, Deborah; Komarovsky, Dafna; Ron-El, Raphael; Friedler, Shevach

2005-08-01

The aim of this study was to retrospectively audit eight years' experience of an IVF surrogate gestational programme and to compare the outcome of surrogacy due to absence of the uterus with surrogacy indicated for repeated IVF failure and recurrent abortions. A total of 60 cycles of IVF surrogate pregnancy were initiated in 19 treated couples. Absence of the uterus was the indication for surrogacy in 10 cases: Rokitansky syndrome (eight cases) and post-hysterectomy (two cases) designated as group A. The indications in the remaining nine patients (group B) were: IVF implantation failure (three cases), habitual abortions (four cases) and deteriorating maternal diseases (two cases). IVF performance and subsequent pregnancy outcome of groups A and B were compared. There was no difference in ovarian stimulation parameters and in IVF performance between the groups A and B. The overall pregnancy rate per transfer was 10/60 (17%). The pregnancy rates per patient and per transfer were 7/10 (70%) and 7/35 (20%) in group A compared with 3/9 (33%) and 3/25 (12%) in group B. A median number of three treatment cycles were needed to achieve pregnancy. In conclusion, the existence or absence of the uterus in the commissioning mothers is irrelevant for their IVF performance and conception rates. In patients who conceived after more than three IVF cycles, an additional 'oocyte factor' might be present.

SEVENTH INTERIM STATUS REPORT: MODEL 9975 PCV O-RING FIXTURE LONG-TERM LEAK PERFORMANCE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Daugherty, W.

2012-08-30

A series of experiments to monitor the aging performance of Viton® GLT O-rings used in the Model 9975 package has been ongoing since 2004 at the Savannah River National Laboratory. Seventy tests using mock-ups of 9975 Primary Containment Vessels (PCVs) were assembled and heated to temperatures ranging from 200 to 450 ºF. They were leak-tested initially and have been tested periodically to determine if they meet the criterion of leak-tightness defined in ANSI standard N14.5-97. Fourteen additional tests were initiated in 2008 with GLT-S O-rings heated to temperatures ranging from 200 to 400 ºF. High temperature aging continues for 23more » GLT O-ring fixtures at 200 – 270 ºF. Room temperature leak test failures have been experienced in all of the GLT O-ring fixtures aging at 350 ºF and higher temperatures, and in 8 fixtures aging at 300 ºF. The remaining GLT O-ring fixtures aging at 300 ºF have been retired from testing following more than 5 years at temperature without failure. No failures have yet been observed in GLT O-ring fixtures aging at 200 ºF for 54-72 months, which is still bounding to O-ring temperatures during storage in K-Area Complex (KAC). Based on expectations that the fixtures aging at 200 ºF will remain leak-tight for a significant period yet to come, 2 additional fixtures began aging in 2011 at an intermediate temperature of 270 ºF, with hopes that they may reach a failure condition before the 200 ºF fixtures. High temperature aging continues for 6 GLT-S O-ring fixtures at 200 – 300 ºF. Room temperature leak test failures have been experienced in all 8 of the GLT-S O-ring fixtures aging at 350 and 400 ºF. No failures have yet been observed in GLT-S O-ring fixtures aging at 200 - 300 ºF for 30 - 36 months. For O-ring fixtures that have failed the room temperature leak test and been disassembled, the O-rings displayed a compression set ranging from 51 – 96%. This is greater than seen to date for any packages inspected during KAC field surveillance (24% average). For GLT O-rings, separate service life estimates have been made based on the O-ring fixture leak test data and based on compression stress relaxation (CSR) data. These two predictive models show reasonable agreement at higher temperatures (350 – 400 ºF). However, at 300 ºF, the room temperature leak test failures to date experienced longer aging times than predicted by the CSRbased model. This suggests that extrapolations of the CSR model predictions to temperatures below 300 ºF will provide a conservative prediction of service life relative to the leak rate criterion. Leak test failure data at lower temperatures are needed to verify this apparent trend. Insufficient failure data exist currently to perform a similar comparison for GLT-S O-rings. Aging and periodic leak testing will continue for the remaining PCV O-ring fixtures.« less

Design and implementation of the protective cap/biobarrier experiment at the Idaho National Engineering Laboratory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Limbach, W.E.; Ratzlaff, T.D.; Anderson, J.E.

1994-12-31

The Protective Cap/Biobarrier Experiment (PCBE), initiated in 1993 at the Idaho National Engineering Laboratory (INEL), is a strip-split plot experiment with three replications designed to rigorously test a 2.0-m loessal soil cap against a cap recommended by the US Environmental Protection Agency and two caps with biological intrusion barriers. Past research at INEL indicates that it should be possible to exclude water from buried wastes using natural materials and natural processes in arid environments rather than expensive materials (geotextiles) and highly engineered caps. The PCBE will also test the effects of two vegetal covers and three irrigation levels on capmore » performance. Drainage pans, located at the bottom of each plot, will monitor cap failure. Soil water profiles will be monitored biweekly by neutron probe and continuously by time domain reflectometry. The performance of each cap design will be monitored under a variety of conditions through 1998. From 1994 to 1996, the authors will assess plant establishment, rooting depths, patterns of moisture extraction and their interactions among caps, vegetal covers, and irrigation levels. In 1996, they will introduce ants and burrowing mammals to test the structural integrity of each cap design. In 1998, the authors will apply sufficient water to determine the failure limit for each cap design. The PCBE should provide reliable knowledge of the performances of the four cap designs under a variety of conditions and aid in making hazardous-waste management decisions at INEL and at disposal sites in similar environments.« less

Editor's Choice-The role of the emergency department in the management of acute heart failure: An international perspective on education and research.

PubMed

Pang, Peter S; Collins, Sean P; Miró, Òscar; Bueno, Hector; Diercks, Deborah B; Di Somma, Salvatore; Gray, Alasdair; Harjola, Veli-Pekka; Hollander, Judd E; Lambrinou, Ekaterini; Levy, Phillip D; Papa, AnnMarie; Möckel, Martin

2017-08-01

Emergency departments are a major entry point for the initial management of acute heart failure (AHF) patients throughout the world. The initial diagnosis, management and disposition - the decision to admit or discharge - of AHF patients in the emergency department has significant downstream implications. Misdiagnosis, under or overtreatment, or inappropriate admission may place patients at increased risk for adverse events, and add costs to the healthcare system. Despite the critical importance of initial management, data are sparse regarding the impact of early AHF treatment delivered in the emergency department compared to inpatient or chronic heart failure management. Unfortunately, outcomes remain poor, with nearly a third of patients dying or re-hospitalised within 3 months post-discharge. In the absence of robust research evidence, consensus is an important source of guidance for AHF care. Thus, we convened an international group of practising emergency physicians, cardiologists and advanced practice nurses with the following goals to improve outcomes for AHF patients who present to the emergency department or other acute care setting through: (a) a better understanding of the pathophysiology, presentation and management of the initial phase of AHF care; (b) improving initial management by addressing knowledge gaps between best practices and current practice through education and research; and (c) to establish a framework for future emergency department-based international education and research.

Success and Failure in Adult Education: The Immigrant Experience 1914-1924.

ERIC Educational Resources Information Center

Seller, Maxine S.

The educational experience of adult immigrants to the United States between 1914-24 is discussed. Attempts of educators and Americanization agencies to reach adult immigrants are described and reasons for the failure of these attempts are given, including inadequate funding, narrowness in subject matter and methods, and insensitivity to ethnic…

Construction of Academic Success and Failure in School Memories

ERIC Educational Resources Information Center

Kaya, Gamze Inan

2018-01-01

The idea of "Apprenticeship of Observation", proposing that pre-service teachers' early academic experiences might have effects on their professional development, has been a concern in teacher education in the last forty years. Early success or failure experiences of pre-service teachers in school may have a role in their professional…

Glovebox and Experiment Safety

NASA Astrophysics Data System (ADS)

Maas, Gerard

2005-12-01

Human spaceflight hardware and operations must comply with NSTS 1700.7. This paper discusses how a glovebox can help.A short layout is given on the process according NSTS/ISS 13830, explaining the responsibility of the payload organization, the approval authority of the PSRP and the defined review phases (0 till III).Amongst others, the following requirement has to be met:"200.1 Design to Tolerate Failures. Failure tolerance is the basic safety requirement that shall be used to control most payload hazards. The payload must tolerate a minimum number of credible failures and/or operator errors determined by the hazard level. This criterion applies when the loss of a function or the inadvertent occurrence of a function results in a hazardous event.200.1a Critical Hazards. Critical hazards shall be controlled such that no single failure or operator error can result in damage to STS/ISS equipment, a nondisabling personnel injury, or the use of unscheduled safing procedures that affect operations of the Orbiter/ISS or another payload.200.1b Catastrophic Hazards. Catastrophic hazards shall be controlled such that no combination of two failures or operator errors can result in the potential for a disabling or fatal personnel injury or loss of the Orbiter/ISS, ground facilities or STS/ISS equipment."For experiments in material science, biological science and life science that require real time operator manipulation, the above requirement may be hard or impossible to meet. Especially if the experiment contains substances that are considered hazardous when released into the habitable environment. In this case operation of the experiment in a glovebox can help to comply.A glovebox provides containment of the experiment and at the same time allows manipulation and visibility to the experiment.The containment inside the glovebox provides failure tolerance because the glovebox uses a negative pressure inside the working volume (WV). The level of failure tolerance is dependent of: the identified failure case and the hazardous substance being released (chemical, biological or different).The principle of the glovebox operation is explained, including: mechanical enclosure, air circulation, air filtration and operational modes.Limitations of the glovebox are presented: inability of an experiment fire to be detected by the ASDA, containment only with respect to specified substances, etc. There are requirements induced by the glovebox that the experiment must comply with: Compatibility with the glovebox filter system, thermal limitations, safe without glovebox services, parameter monitoring when a fire hazard is credible, sufficient containment when entering the glovebox and after the experiment, etc.Experiments that are using a glovebox to be operated in shall assess this integrated set-up and the associated operations for compliance to the safety requirements. During this assessment the PSRP shall determine if the provided failure tolerance is sufficient.The gloveboxes that Bradford Engineering (co-) built for human space flight are: USML-1 and 2, MGBX (STS and MIR), MSG, PGBX, LSG-WVA, BGB and PGB. Some of the evolutions are pointed out (experiment services added without compromising safety levels). The major differences of the gloveboxes are presented. For the gloveboxes that are in operation at this time (MSG) or in the near future (BGB, LSG- WVA and PGB) the specific applications are presented.

The ethical issues in uranium mining research in the Navajo Nation.

PubMed

Panikkar, Bindu; Brugge, Doug

2007-01-01

We explore the experience of Navajo communities living under the shadow of nuclear age fallout who were subjects of five decades of research. In this historical analysis of public health (epidemiological) research conducted in the Navajo lands since the inception of uranium mining from the 1950s untill the end of the 20th century, we analyze the successes and failures in the research initiatives conducted on Navajo lands, the ethical breaches, and the harms and benefits that this research has brought about to the community. We discuss how scientific and moral uncertainty, lack of full stakeholder participation and community wide outreach and education can impact ethical decisions made in research.

STUDIES OF FAST REACTOR FUEL ELEMENT BEHAVIOR UNDER TRANSIENT HEATING TO FAILURE. I. INITIAL EXPERIMENTS ON METALLIC SAMPLES IN THE ABSENCE OF COOLANT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dickerman, C. E.; Sowa, E. S.; Okrent, D.

1961-08-01

Meltdown tests on single metallic unirradiated fuel elements in TREAT are described. The fuel elements (EBRII Mark I fuel pins, EBR-II fuel pins with retractory Nb or Ta cladding, and Fermi-I fuel pins) are tested in an inert atmosphere, with no coolant. The fuel elements are exposed to reactor power bursts of 200 msec to 25 sec duration, under conditions simulating fast reactor operations. For these tests, the type of power burst, the integrated power, the fuel enrichment, the maximum cladding temperature, and the effects of the test on the fuel element are recorded. ( T.F.H.)

Comparison of Crack Initiation, Propagation and Coalescence Behavior of Concrete and Rock Materials

NASA Astrophysics Data System (ADS)

Zengin, Enes; Abiddin Erguler, Zeynal

2017-04-01

There are many previously studies carried out to identify crack initiation, propagation and coalescence behavior of different type of rocks. Most of these studies aimed to understand and predict the probable instabilities on different engineering structures such as mining galleries or tunnels. For this purpose, in these studies relatively smaller natural rock and synthetic rock-like models were prepared and then the required laboratory tests were performed to obtain their strength parameters. By using results provided from these models, researchers predicted the rock mass behavior under different conditions. However, in the most of these studies, rock materials and models were considered as contains none or very few discontinuities and structural flaws. It is well known that rock masses naturally are extremely complex with respect to their discontinuities conditions and thus it is sometimes very difficult to understand and model their physical and mechanical behavior. In addition, some vuggy rock materials such as basalts and limestones also contain voids and gaps having various geometric properties. Providing that the failure behavior of these type of rocks controlled by the crack initiation, propagation and coalescence formed from their natural voids and gaps, the effect of these voids and gaps over failure behavior of rocks should be investigated. Intact rocks are generally preferred due to relatively easy side of their homogeneous characteristics in numerical modelling phases. However, it is very hard to extract intact samples from vuggy rocks because of their complex pore sizes and distributions. In this study, the feasibility of concrete samples to model and mimic the failure behavior vuggy rocks was investigated. For this purpose, concrete samples were prepared at a mixture of %65 cement dust and %35 water and their physical and mechanical properties were determined by laboratory experiments. The obtained physical and mechanical properties were used to constitute numerical models, and then uniaxial compressive strength (UCS) tests were performed on these models by using a commercial software called as Particle Flow Code (PFC2D). When the crack behavior of concrete samples obtained from both laboratory tests and numerical models are compared with the results of previous studies, a significant similarity was found. As a result, due to the observed similarity crack behavior between concretes and rocks, it can be concluded that intact concrete samples can be used for modelling purposes to understand the effect of voids and gaps on failure characteristics of vuggy rocks.

Revealing catastrophic failure of leaf networks under stress

PubMed Central

Brodribb, Timothy J.; Bienaimé, Diane; Marmottant, Philippe

2016-01-01

The intricate patterns of veins that adorn the leaves of land plants are among the most important networks in biology. Water flows in these leaf irrigation networks under tension and is vulnerable to embolism-forming cavitations, which cut off water supply, ultimately causing leaf death. Understanding the ways in which plants structure their vein supply network to protect against embolism-induced failure has enormous ecological and evolutionary implications, but until now there has been no way of observing dynamic failure in natural leaf networks. Here we use a new optical method that allows the initiation and spread of embolism bubbles in the leaf network to be visualized. Examining embolism-induced failure of architecturally diverse leaf networks, we found that conservative rules described the progression of hydraulic failure within veins. The most fundamental rule was that within an individual venation network, susceptibility to embolism always increased proportionally with the size of veins, and initial nucleation always occurred in the largest vein. Beyond this general framework, considerable diversity in the pattern of network failure was found between species, related to differences in vein network topology. The highest-risk network was found in a fern species, where single events caused massive disruption to leaf water supply, whereas safer networks in angiosperm leaves contained veins with composite properties, allowing a staged failure of water supply. These results reveal how the size structure of leaf venation is a critical determinant of the spread of embolism damage to leaves during drought. PMID:27071104

Modeling of damage driven fracture failure of fiber post-restored teeth.

PubMed

Xu, Binting; Wang, Yining; Li, Qing

2015-09-01

Mechanical failure of biomaterials, which can be initiated by either violent force, or progressive stress fatigue, is a serious issue. Great efforts have been made to improve the mechanical performances of dental restorations. Virtual simulation is a promising approach for biomechanical investigations, which presents significant advantages in improving efficiency than traditional in vivo/in vitro studies. Over the past few decades, a number of virtual studies have been conducted to investigate the biomechanical issues concerning dental biomaterials, but only with limited incorporation of brittle failure phenomena. Motivated by the contradictory findings between several finite element analyses and common clinical observations on the fracture resistance of post-restored teeth, this study aimed to provide an approach using numerical simulations for investigating the fracture failure process through a non-linear fracture mechanics model. The ability of this approach to predict fracture initiation and propagation in a complex biomechanical status based on the intrinsic material properties was investigated. Results of the virtual simulations matched the findings of experimental tests, in terms of the ultimate fracture failure strengths and predictive areas under risk of clinical failure. This study revealed that the failure of dental post-restored restorations is a typical damage-driven continuum-to-discrete process. This approach is anticipated to have ramifications not only for modeling fracture events, but also for the design and optimization of the mechanical properties of biomaterials for specific clinically determined requirements. Copyright © 2015 Elsevier Ltd. All rights reserved.

Revealing catastrophic failure of leaf networks under stress.

PubMed

Brodribb, Timothy J; Bienaimé, Diane; Marmottant, Philippe

2016-04-26

The intricate patterns of veins that adorn the leaves of land plants are among the most important networks in biology. Water flows in these leaf irrigation networks under tension and is vulnerable to embolism-forming cavitations, which cut off water supply, ultimately causing leaf death. Understanding the ways in which plants structure their vein supply network to protect against embolism-induced failure has enormous ecological and evolutionary implications, but until now there has been no way of observing dynamic failure in natural leaf networks. Here we use a new optical method that allows the initiation and spread of embolism bubbles in the leaf network to be visualized. Examining embolism-induced failure of architecturally diverse leaf networks, we found that conservative rules described the progression of hydraulic failure within veins. The most fundamental rule was that within an individual venation network, susceptibility to embolism always increased proportionally with the size of veins, and initial nucleation always occurred in the largest vein. Beyond this general framework, considerable diversity in the pattern of network failure was found between species, related to differences in vein network topology. The highest-risk network was found in a fern species, where single events caused massive disruption to leaf water supply, whereas safer networks in angiosperm leaves contained veins with composite properties, allowing a staged failure of water supply. These results reveal how the size structure of leaf venation is a critical determinant of the spread of embolism damage to leaves during drought.