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Sample records for predict extubation failure

  1. Review article: Extubation of the difficult airway and extubation failure.

    PubMed

    Cavallone, Laura F; Vannucci, Andrea

    2013-02-01

    Respiratory complications after tracheal extubation are associated with significant morbidity and mortality, suggesting that process improvements in this clinical area are needed. The decreased rate of respiratory adverse events occurring during tracheal intubation since the implementation of guidelines for difficult airway management supports the value of education and guidelines in advancing clinical practice. Accurate use of terms in defining concepts and describing distinct clinical conditions is paramount to facilitating understanding and fostering education in the treatment of tracheal extubation-related complications. As an example, understanding the distinction between extubation failure and weaning failure allows one to appreciate the need for pre-extubation tests that focus on assessing airway patency in addition to evaluating the ability to breathe spontaneously. Tracheal reintubation after planned extubation is a relatively rare event in the postoperative period of elective surgeries, with reported rates of reintubation in the operating room and postanesthesia care unit between 0.1% and 0.45%, but is a fairly common event in critically ill patients (0.4%-25%). Conditions such as obesity, obstructive sleep apnea, major head/neck and upper airway surgery, and obstetric and cervical spine procedures carry significantly increased risks of extubation failure and are frequently associated with difficult airway management. Extubation failure follows loss of upper airway patency. Edema, soft tissue collapse, and laryngospasm are among the most frequent mechanisms of upper airway obstruction. Planning for tracheal extubation is a critical component of a successful airway management strategy, particularly when dealing with situations at increased risk for extubation failure and in patients with difficult airways. Adequate planning requires identification of patients who have or may develop a difficult airway, recognition of situations at increased risk of

  2. Predictors of Extubation Failure in Neurocritical Patients Identified by a Systematic Review and Meta-Analysis

    PubMed Central

    Huang, Kaibin; Lin, Zhenzhou; Qiao, Weiguang; Pan, Suyue

    2014-01-01

    Background Prediction of extubation failure, particularly in neurocritical patients, is unique and controversial. We conducted a systematic review and meta-analysis to identify the risk factors for extubation failure in these patients. Methods A literature search of databases (MEDLINE, EMBASE, the Cochrane Library, and Web of Science) was performed up to August of 2013 to identify trials that evaluated extubation failure predictors. Included trials were either prospective or retrospective cohort studies. Results Nine studies involving 928 participants were included. The systematic review and meta-analysis revealed that the following were predictive for extubation failure: pneumonia, atelectasis, mechanical ventilation of >24 h, a low Glasgow Coma Scale score (7–9T) (OR = 4.96, 95% CI = 1.61–15.26, P = 0.005), the inability to follow commands (OR = 2.07, 95% CI = 1.15–3.71, P = 0.02), especially the command to close the eyes, thick secretion, and no intact gag reflex. Meanwhile, the following were not predictive for extubation failure: sex, secretion volume, coughing upon suctioning, and the inability to follow one command among showing two fingers, wiggling the toes, or coughing on command. Additionally, some traditional weaning parameters were shown to poorly predict extubation failure in neurocritical patients. Conclusions Besides pneumonia, atelectasis, and the duration of mechanical ventilation, other factors that should be taken into consideration in the prediction of extubation failure when neurocritical patients are weaned from tracheal intubation include neurologic abilities (Glasgow Coma Scale score and following commands), the secretion texture, and the presence of a gag reflex. PMID:25486091

  3. Perioperative Predictors of Extubation Failure and the Effect on Clinical Outcome After Infratentorial Craniotomy

    PubMed Central

    Cai, Ye-Hua; Wang, Hai-Tang; Zhou, Jian-Xin

    2016-01-01

    Background The purpose of the study was to analyze the risk factors for failed extubation in subjects submitted to infratentorial craniotomy. Material/Methods Patients aged over 18 years who received infratentorial craniotomy for brain tumor resection were consecutively included in this study. Perioperative variables were collected and analyzed. Univariate analyses and multiple logistic regression were used to derive factors related to failed extubation. Patients had follow-up care until either out of hospital or death. Results Throughout the course of the study, 2118 patients were eligible and 94 (4.4%) suffered from extubation failure at some point during their hospital stay. Five factors were recognized as independent risk factors for postoperative failed extubation: craniotomy history, preoperative lower cranial nerve dysfunction, tumor size, tumor position, and maximum change in blood pressure (BP) during the operation. Failed extubation was related to a higher incidence rate of pneumonia, mortality, unfavorable Glasgow Outcome Scale score, longer stay in the neuro-intensive care unit (ICU) and hospitalization, and higher hospitalization costs compared with successful extubation. Conclusions History of craniotomy, preoperative lower cranial nerve dysfunction, tumor size, tumor position, and maximum change in BP during the operation were independent risk factors related to postoperative failed extubation in patients submitted to infratentorial craniotomy. Extubation failure raises the incidences of postoperative pneumonia, mortality, and higher hospitalization costs, and prolongs neuro-ICU and postoperative length of stay. PMID:27404044

  4. Perioperative Predictors of Extubation Failure and the Effect on Clinical Outcome After Infratentorial Craniotomy.

    PubMed

    Cai, Ye-Hua; Wang, Hai-Tang; Zhou, Jian-Xin

    2016-01-01

    BACKGROUND The purpose of the study was to analyze the risk factors for failed extubation in subjects submitted to infratentorial craniotomy. MATERIAL AND METHODS Patients aged over 18 years who received infratentorial craniotomy for brain tumor resection were consecutively included in this study. Perioperative variables were collected and analyzed. Univariate analyses and multiple logistic regression were used to derive factors related to failed extubation. Patients had follow-up care until either out of hospital or death. RESULTS Throughout the course of the study, 2118 patients were eligible and 94 (4.4%) suffered from extubation failure at some point during their hospital stay. Five factors were recognized as independent risk factors for postoperative failed extubation: craniotomy history, preoperative lower cranial nerve dysfunction, tumor size, tumor position, and maximum change in blood pressure (BP) during the operation. Failed extubation was related to a higher incidence rate of pneumonia, mortality, unfavorable Glasgow Outcome Scale score, longer stay in the neuro-intensive care unit (ICU) and hospitalization, and higher hospitalization costs compared with successful extubation. CONCLUSIONS History of craniotomy, preoperative lower cranial nerve dysfunction, tumor size, tumor position, and maximum change in BP during the operation were independent risk factors related to postoperative failed extubation in patients submitted to infratentorial craniotomy. Extubation failure raises the incidences of postoperative pneumonia, mortality, and higher hospitalization costs, and prolongs neuro-ICU and postoperative length of stay. PMID:27404044

  5. Extubation outcome after a successful spontaneous breathing trial: A multicenter validation of a 3-factor prediction model

    PubMed Central

    LIU, YANG; MU, YU; LI, GUO-QIANG; YU, XIN; LI, PEI-JUN; SHEN, ZHI-QI; WANG, HAO-XUN; WEI, LU-QING

    2015-01-01

    The aim of the present study was to validate, and if necessary update, a predictive model previously developed using a classification and regression tree (CART) algorithm for predicting successful extubation (ES) using a new cohort. This prospective cohort study enrolled adults admitted to 10 intensive care units, who had successfully passed a spontaneous breathing trial (SBT) and were considered ready for extubation. After extubation, the patients were followed up for 48 h. The primary outcome measure was ES, defined as the ability to maintain spontaneous unassisted breathing for >48 h after extubation. The 3-factor CART model was applied to patients in this cohort. The predicted probability of ES for each patient in this validation cohort was calculated based on the original CART model using the Laplace correction method. The performance was assessed by discrimination and calibration. A decision curve analysis was used assess the clinical net benefit (NB). Extubation failure (EF) occurred in 90/530 patients (17%). Among the 90 patients, 72 (13.6%) were reintubated, while 18 patients remained on rescue noninvasive ventilation within 48 h after extubation. The original CART model showed high discrimination but only moderate calibration with predicted probabilities that were systematically lower than expected. The original CART model was updated, and the updated model preserved excellent discrimination (area under the receiver operating characteristic curve, 0.91; 95% confidence interval, 0.87 to 0.93), but exhibited near-perfect calibration (calibration slope, 1; intercept, 0). Between threshold probabilities of 50 and 80%, the NB of using this updated model is significantly improved compared with the current strategy. The updated CART model may be used to estimate the predicted probability of ES after a successful SBT for individual patients. Applying this model appears to produce a substantial clinical consequence with regard to potential reduction in unexpected

  6. Can Machine Learning Methods Predict Extubation Outcome in Premature Infants as well as Clinicians?

    PubMed Central

    Mueller, Martina; Almeida, Jonas S.; Stanislaus, Romesh; Wagner, Carol L.

    2014-01-01

    Rationale Though treatment of the prematurely born infant breathing with assistance of a mechanical ventilator has much advanced in the past decades, predicting extubation outcome at a given point in time remains challenging. Numerous studies have been conducted to identify predictors for extubation outcome; however, the rate of infants failing extubation attempts has not declined. Objective To develop a decision-support tool for the prediction of extubation outcome in premature infants using a set of machine learning algorithms Methods A dataset assembled from 486 premature infants on mechanical ventilation was used to develop predictive models using machine learning algorithms such as artificial neural networks (ANN), support vector machine (SVM), naïve Bayesian classifier (NBC), boosted decision trees (BDT), and multivariable logistic regression (MLR). Performance of all models was evaluated using area under the curve (AUC). Results For some of the models (ANN, MLR and NBC) results were satisfactory (AUC: 0.63–0.76); however, two algorithms (SVM and BDT) showed poor performance with AUCs of ~0.5. Conclusion Clinician's predictions still outperform machine learning due to the complexity of the data and contextual information that may not be captured in clinical data used as input for the development of the machine learning algorithms. Inclusion of preprocessing steps in future studies may improve the performance of prediction models. PMID:25419493

  7. Efficacy and predictors of success of noninvasive ventilation for prevention of extubation failure in critically ill children with heart disease.

    PubMed

    Gupta, Punkaj; Kuperstock, Jacob E; Hashmi, Sana; Arnolde, Vickie; Gossett, Jeffrey M; Prodhan, Parthak; Venkataraman, Shekhar; Roth, Stephen J

    2013-04-01

    The study aimed primarily to evaluate the efficacy of noninvasive ventilation (NIV) and to identify possible predictors for success of NIV therapy in preventing extubation failure in critically ill children with heart disease. The secondary objectives of this study were to assess the efficacy of prophylactic NIV therapy initiated immediately after tracheal extubation and to determine the characteristics, outcomes, and complications associated with NIV therapy in pediatric cardiac patients. A retrospective review examined the medical records of all children between the ages 1 day and 18 years who sustained acute respiratory failure (ARF) that required NIV in the cardiovascular intensive care unit (CVICU) at Lucile Packard Children's Hospital between January 2008 and June 2010. Patients were assigned to a prophylactic group if NIV was started directly after extubation and to a nonprophylactic group if NIV was started after signs and symptoms of ARF developed. Patients were designated as responders if they received NIV and did not require reintubation during their CVICU stay and nonresponders if they failed NIV and reintubation was performed. The data collected included demographic data, preexisting conditions, pre-event characteristics, event characteristics, and outcome data. The outcome data evaluated included success or failure of NIV, duration of NIV, CVICU length of stay (LOS), hospital LOS, and hospital mortality. The two complications of NIV assessed in the study included nasal bridge or forehead skin necrosis and pneumothorax. The 221 eligible events during the study period involved 172 responders (77.8 %) and 49 nonresponders (22.2 %). A total of 201 events experienced by the study cohort received continuous positive airway pressure (CPAP), with 156 responders (78 %), whereas 20 events received bilevel positive airway pressure (BiPAP), with 16 responders (80 %). In the study, 58 events (26.3 %) were assigned to the prophylactic group and 163 events (73

  8. Clinical efficacy of high-flow nasal cannula compared to noninvasive ventilation in patients with post-extubation respiratory failure

    PubMed Central

    Yoo, Jung-Wan; Synn, Ara; Huh, Jin Won; Hong, Sang-Bum; Koh, Younsuck; Lim, Chae-Man

    2016-01-01

    Background/Aims: Post-extubation respiratory failure (PERF) is associated with poor clinica l outcomes. High-f low nasa l cannula (HF NC) ox ygen therapy has been used in patients with respiratory failure, but the clinical benefit in patients with PERF remains unclear. The aim of this study was to evaluate the clinical efficacy of HFNC compared to noninvasive ventilation (NIV) in patients with PERF. Methods: A historic retrospective cohort analysis was performed in 28 beds in the medical Intensive Care Unit (ICU) at a single medical center in South Korea. In total, 73 patients with PERF were enrolled: 39 patients who underwent NIV from April 2007 to March 2009 and 34 patients who received HFNC from April 2009 to May 2011. Results: The rate of avoidance of reintubation was not different between the HFNC group (79.4%) and NIV group (66.7%, p = 0.22). All patients with HFNC tolerated the device, whereas five of those with NIV did not tolerate treatment (p = 0.057). The mean duration of ICU stay was significantly shorter in the HFNC group than in the NIV group (13.4 days vs. 20.6 days, p = 0.015). There was no difference in ICU or in-hospital mortality rate. Conclusions: HFNC is likely to be as effective as, and better tolerated than, NIV for treatment of PERF. PMID:26767861

  9. Predictive Factors for Efficacy and Safety of Prophylactic Theophylline for Extubation in Infants with Apnea of Prematurity

    PubMed Central

    Orita, Yuji; Mitarai, Fumi; Ishitsuka, Yoichi; Irikura, Mitsuru; Shimodozono, Yoshihiro; Douchi, Tsutomu; Takeda, Yasuo; Irie, Tetsumi

    2016-01-01

    Purpose This study aimed to evaluate predictive factors involved in efficacy and safety in Japanese infants who received theophylline therapy to prevent apnea of prematurity (AOP) after weaning from mechanical ventilation. Methods We retrospectively reviewed the medical records of infants who were administered intravenous aminophylline (theophylline ethylenediamine) for AOP at the neonatal intensive care unit, Kagoshima University Hospital, Japan, between January 2009 and June 2013. Results A total of 100 infants were evaluated as two separate groups in terms of efficacy and safety of theophylline. Sixty-seven (67.0%) infants had effective theophylline therapy. Multivariate logistic regression analysis showed that gestational age at birth was significant, with an odds ratio of 0.59 (p < 0.001). Receiver operating characteristic analysis showed that the cut-off value was 31.1 weeks old for predicting the efficacy of theophylline (specificity, 66.7%; sensitivity, 86.6%; p < 0.001; area under the curve, 0.750; 95% confidence interval, 0.45–0.74). Adverse reactions were identified in 21 (21.0%) infants. Multivariate logistic regression analysis showed that the number of days of theophylline administration from birth was associated with an increased risk of adverse reactions after theophylline administration (p = 0.01). Conclusions Physicians need to be aware of the possibility that theophylline fails to produce therapeutic effects for extubation in infants aged less than 31.1 weeks old, and adverse reactions can easily develop when theophylline is administered soon after birth. PMID:27388444

  10. Detecting failure of climate predictions

    USGS Publications Warehouse

    Runge, Michael C.; Stroeve, Julienne C.; Barrett, Andrew P.; McDonald-Madden, Eve

    2016-01-01

    The practical consequences of climate change challenge society to formulate responses that are more suited to achieving long-term objectives, even if those responses have to be made in the face of uncertainty1, 2. Such a decision-analytic focus uses the products of climate science as probabilistic predictions about the effects of management policies3. Here we present methods to detect when climate predictions are failing to capture the system dynamics. For a single model, we measure goodness of fit based on the empirical distribution function, and define failure when the distribution of observed values significantly diverges from the modelled distribution. For a set of models, the same statistic can be used to provide relative weights for the individual models, and we define failure when there is no linear weighting of the ensemble models that produces a satisfactory match to the observations. Early detection of failure of a set of predictions is important for improving model predictions and the decisions based on them. We show that these methods would have detected a range shift in northern pintail 20 years before it was actually discovered, and are increasingly giving more weight to those climate models that forecast a September ice-free Arctic by 2055.

  11. Predicting Electronic Failure from Smoke

    SciTech Connect

    Tanaka, T.J.

    1999-01-15

    Smoke can cause electronic equipment to fail through increased leakage currents and shorts. Sandia National Laboratories is studying the increased leakage currents caused by smoke with varying characteristics. The objective is to develop models to predict the failure of electronic equipment exposed to smoke. This requires the collection of data on the conductivity of smoke and knowledge of critical electrical systems that control high-consequence operations. We have found that conductivity is a function of the type of fuel, how it is burned, and smoke density. Video recordings of highly biased dc circuits exposed in a test chamber show that during a fire, smoke is attracted to high voltages and can build fragile carbon bridges that conduct leakage currents. The movement of air breaks the bridges, so the conductivity decreases after the fire is extinguished and the test chamber is vented. During the fire, however, electronic equipment may not operate correctly, leading to problems for critical operations dependent on electronic control. The potential for electronic failure is highly dependent on the type of electrical circuit, and Sandia National Laboratories plans to include electrical circuit modeling in the failure models.

  12. [Factors influencing early extubation after open heart surgery].

    PubMed

    Varró, M; Gombocz, K; Wrana, G

    2001-06-10

    The authors have performed a retrospective study in order to review the occurrence and the influencing factors of early extubation among their patients. Those patients who had any severe complication in the immediate postoperative period (pericardial tamponade, low cardiac output syndrome, re-operation due to excessive bleeding, postperfusion lung syndrome, pulmonary edema) preventing early extubation, have been excluded from the study. In the remaining 690 patients early extubation within 8 hours and within 4 hours could be carried out in 525 (76.1%) and 164 cases (23.8%) respectively. Late (beyond 12 hours) extubation occurred in 68 cases (9.9%). Anaesthesia was governed by two different methods. Midazolam and alfentanyl (group 1) were used in 137 cases (19.9%) whilst 553 patients (80.1%) received propofol and alfentanyl (group 2). In group 1 and 2 early extubation was possible in 50.4 and 82.5% respectively (p < 0.0001). In further investigations 27 pre- and intraoperative variables of each patient have been studied and analysed. For statistical analysis authors used the SPSS software including T-test, Mann-Whitney-test, chi-square test and multivariate logistical regression analysis. On the basis of multivariate regression analysis factors influencing early extubation were as follows: age (B = 0.0775; p < 0.001), sex (B = 1.2900; p < 0.001), method of anaesthesia (B = 1.9753; p < 0.001), duration of anaesthesia (B = 0.0053; p < 0.001), re-do operation (B = 1.0482; p = 0.0469) and preoperative congestive heart failure (B = 0.9008; p = 0.0125). Pulmonary diseases known from patient history have not had a deep impact on early extubation. On the basis of our study early extubation has not resulted in an increased number of either the postoperative complications or the occurrence of perioperative myocardial infarction. PMID:11433920

  13. Strain limit criteria to predict failure

    SciTech Connect

    Flanders, H.E.

    1995-12-31

    In recent years extensive effort has been expended to qualify existing structures for conditions that are beyond the original design basis. Determination of the component failure load is useful for this type of evaluation. This paper presents criteria based upon strain limits to predict the load at failure. The failure modes addressed are excessive plastic deformations, localized plastic strains, and structural instability. The effects of analytical method sophistication, as built configurations, material properties degradation, and stress state are addressed by the criteria.

  14. Failure mode analysis to predict product reliability.

    NASA Technical Reports Server (NTRS)

    Zemanick, P. P.

    1972-01-01

    The failure mode analysis (FMA) is described as a design tool to predict and improve product reliability. The objectives of the failure mode analysis are presented as they influence component design, configuration selection, the product test program, the quality assurance plan, and engineering analysis priorities. The detailed mechanics of performing a failure mode analysis are discussed, including one suggested format. Some practical difficulties of implementation are indicated, drawn from experience with preparing FMAs on the nuclear rocket engine program.

  15. Uncertainties in container failure time predictions

    SciTech Connect

    Williford, R.E.

    1990-01-01

    Stochastic variations in the local chemical environment of a geologic waste repository can cause corresponding variations in container corrosion rates and failure times, and thus in radionuclide release rates. This paper addresses how well the future variations in repository chemistries must be known in order to predict container failure times that are bounded by a finite time period within the repository lifetime. Preliminary results indicate that a 5000 year scatter in predicted container failure times requires that repository chemistries be known to within {plus minus}10% over the repository lifetime. These are small uncertainties compared to current estimates. 9 refs., 3 figs.

  16. Myocardial ischaemia during tracheal intubation and extubation.

    PubMed

    Edwards, N D; Alford, A M; Dobson, P M; Peacock, J E; Reilly, C S

    1994-10-01

    The incidence of myocardial ischaemia during tracheal intubation and extubation was compared using ambulatory ECG monitoring in 60 patients undergoing a variety of different surgical operations. Seven patients had myocardial ischaemia after tracheal intubation and seven patients during tracheal extubation. The patients who developed myocardial ischaemia during tracheal extubation had significantly greater rate-pressure products immediately before tracheal extubation (P < 0.05) and 1 min after tracheal extubation (P < 0.01) compared with those patients who did not develop myocardial ischaemia during extubation. PMID:7999498

  17. Prediction of Cascading Failures in Spatial Networks

    PubMed Central

    Shunkun, Yang; Dan, Lu

    2016-01-01

    Cascading overload failures are widely found in large-scale parallel systems and remain a major threat to system reliability; therefore, they are of great concern to maintainers and managers of different systems. Accurate cascading failure prediction can provide useful information to help control networks. However, for a large, gradually growing network with increasing complexity, it is often impractical to explore the behavior of a single node from the perspective of failure propagation. Fortunately, overload failures that propagate through a network exhibit certain spatial-temporal correlations, which allows the study of a group of nodes that share common spatial and temporal characteristics. Therefore, in this study, we seek to predict the failure rates of nodes in a given group using machine-learning methods. We simulated overload failure propagations in a weighted lattice network that start with a center attack and predicted the failure percentages of different groups of nodes that are separated by a given distance. The experimental results of a feedforward neural network (FNN), a recurrent neural network (RNN) and support vector regression (SVR) all show that these different models can accurately predict the similar behavior of nodes in a given group during cascading overload propagation. PMID:27093054

  18. Role of Hematocrit Concentration on Successful Extubation in Critically Ill Patients in the Intensive Care Units

    PubMed Central

    Beigmohammadi, Mohammad Taghi; Hussain Khan, Zahid; Samadi, Shahram; Mahmoodpoor, Ata; Fotouhi, Akbar; Rahimiforoushani, Abbas; Asadi Gharabaghi, Mehrnaz

    2016-01-01

    Background: Hematocrit (Hct) is an important parameter for optimal oxygenation during discontinuation from ventilator, but there is no consensus about its concentration and effectiveness on successful extubation. Objectives: The current study aimed to determine the role of Hct concentration on extubation failure in critically ill patients. Patients and Methods: The current prospective cohort study investigated the effect of age, gender and Hct level on successful extubation of 163 mechanically ventilated patients in Imam Khomeini hospital intensive care units (ICUs), Tehran, Iran. Following successful weaning process, the patients were classified into two groups on the basis of Hct level; 62 with an Hct level of 21% - 27% and the other 101 patients with Hct levels above 27%. The data were analyzed by chi-square test and multiple logistic regressions. A probability value of less than 0.05 was considered significant. Results: There was no significant association between the level of Hct concentration and extubation failure (8.9% vs. 9.2%, P = 0.507). Gender and age were significantly associated with extubation failure (OR = 9.1, P = 0.034, OR = 12.5, P = 0.014, respectively). Although the differences between, before and after extubation of PaO2 and P/F ratio, were of significant values between the two different groups of Hct (P = 0.001, P = 0.004 respectively), they had no effect on the failure of extubation (P= 0.259, P = 0.403, respectively). Conclusions: Although some studies showed association between anemia and extubation failure, the current study could not confirm it. The study showed that males, regardless of the Hct level, had a better extubation success rate than those of females. PMID:27110535

  19. Videos in clinical medicine. Endotracheal extubation.

    PubMed

    Ortega, Rafael; Connor, Christopher; Rodriguez, Gerardo; Spencer, Caresse

    2014-01-16

    Endotracheal extubation should be performed without causing trauma, while maintaining adequate oxygenation and ventilation. The equipment needed to provide suction, ventilation, and reintubation should be readily available. If extubation is judged to be unsafe, the procedure should be postponed and the patient reevaluated. Most complications related to extubation are preventable. Before performing extubation, the clinician must carefully prepare the medical resources needed to address reasonably foreseeable complications. A failed extubation can lead to a precipitous deterioration in the patient's condition, and attempts to improvise solutions under these challenging circumstances are rarely satisfactory. PMID:24428490

  20. Multifactorial Risk Index for Predicting Postoperative Respiratory Failure in Men After Major Noncardiac Surgery

    PubMed Central

    Arozullah, Ahsan M.; Daley, Jennifer; Henderson, William G.; Khuri, Shukri F.

    2000-01-01

    Objective To develop and validate a preoperative risk index for predicting postoperative respiratory failure (PRF). Summary Background Data Respiratory failure is an important postoperative complication. Method Based on a prospective cohort study, cases from 44 Veterans Affairs Medical Centers (n = 81,719) were used to develop the models. Cases from 132 Veterans Affairs Medical Centers (n = 99,390) were used as a validation sample. PRF was defined as mechanical ventilation for more than 48 hours after surgery or reintubation and mechanical ventilation after postoperative extubation. Ventilator-dependent, comatose, do not resuscitate, and female patients were excluded. Results PRF developed in 2,746 patients (3.4%). The respiratory failure risk index was developed from a simplified logistic regression model and included abdominal aortic aneurysm repair, thoracic surgery, neurosurgery, upper abdominal surgery, peripheral vascular surgery, neck surgery, emergency surgery, albumin level less than 30 g/L, blood urea nitrogen level more than 30 mg/dL, dependent functional status, chronic obstructive pulmonary disease, and age. Conclusions The respiratory failure risk index is a validated model for identifying patients at risk for developing PRF and may be useful for guiding perioperative respiratory care. PMID:10903604

  1. Factors Predicting Meniscal Allograft Transplantation Failure

    PubMed Central

    Parkinson, Ben; Smith, Nicholas; Asplin, Laura; Thompson, Peter; Spalding, Tim

    2016-01-01

    Background: Meniscal allograft transplantation (MAT) is performed to improve symptoms and function in patients with a meniscal-deficient compartment of the knee. Numerous studies have shown a consistent improvement in patient-reported outcomes, but high failure rates have been reported by some studies. The typical patients undergoing MAT often have multiple other pathologies that require treatment at the time of surgery. The factors that predict failure of a meniscal allograft within this complex patient group are not clearly defined. Purpose: To determine predictors of MAT failure in a large series to refine the indications for surgery and better inform future patients. Study Design: Cohort study; Level of evidence, 3. Methods: All patients undergoing MAT at a single institution between May 2005 and May 2014 with a minimum of 1-year follow-up were prospectively evaluated and included in this study. Failure was defined as removal of the allograft, revision transplantation, or conversion to a joint replacement. Patients were grouped according to the articular cartilage status at the time of the index surgery: group 1, intact or partial-thickness chondral loss; group 2, full-thickness chondral loss 1 condyle; and group 3, full-thickness chondral loss both condyles. The Cox proportional hazards model was used to determine significant predictors of failure, independently of other factors. Kaplan-Meier survival curves were produced for overall survival and significant predictors of failure in the Cox proportional hazards model. Results: There were 125 consecutive MATs performed, with 1 patient lost to follow-up. The median follow-up was 3 years (range, 1-10 years). The 5-year graft survival for the entire cohort was 82% (group 1, 97%; group 2, 82%; group 3, 62%). The probability of failure in group 1 was 85% lower (95% CI, 13%-97%) than in group 3 at any time. The probability of failure with lateral allografts was 76% lower (95% CI, 16%-89%) than medial allografts at

  2. PET(CO2) measurement and feature extraction of capnogram signals for extubation outcomes from mechanical ventilation.

    PubMed

    Rasera, Carmen C; Gewehr, Pedro M; Domingues, Adriana Maria T

    2015-02-01

    Capnography is a continuous and noninvasive method for carbon dioxide (CO2) measurement, and it has become the standard of care for basic respiratory monitoring for intubated patients in the intensive care unit. In addition, it has been used to adjust ventilatory parameters during mechanical ventilation (MV). However, a substantial debate remains as to whether capnography is useful during the process of weaning and extubation from MV during the postoperative period. Thus, the main objective of this study was to present a new use for time-based capnography data by measuring the end-tidal CO2 pressure ([Formula: see text]), partial pressure of arterial CO2 ([Formula: see text]) and feature extraction of capnogram signals before extubation from MV to evaluate the capnography as a predictor of outcome extubation in infants after cardiac surgery. Altogether, 82 measurements were analysed, 71.9% patients were successfully extubated, and 28.1% met the criteria for extubation failure within 48 h. The ROC-AUC analysis for quantitative measure of the capnogram showed significant differences (p < 0.001) for: expiratory time (0.873), slope of phase III (0.866), slope ratio (0.923) and ascending angle (0.897). In addition, the analysis of [Formula: see text] (0.895) and [Formula: see text] (0.924) obtained 30 min before extubation showed significant differences between groups. The [Formula: see text] mean value for success and failure extubation group was 39.04 mmHg and 46.27 mmHg, respectively. It was also observed that high CO2 values in patients who had returned MV was 82.8  ±  21 mmHg at the time of extubation failure. Thus, [Formula: see text] measurements and analysis of features extracted from a capnogram can differentiate extubation outcomes in infant patients under MV, thereby reducing the physiologic instability caused by failure in this process. PMID:25582400

  3. 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.

  4. Predicting Failure Progression and Failure Loads in Composite Open-Hole Tension Coupons

    NASA Technical Reports Server (NTRS)

    Arunkumar, Satyanarayana; Przekop, Adam

    2010-01-01

    Failure types and failure loads in carbon-epoxy [45n/90n/-45n/0n]ms laminate coupons with central circular holes subjected to tensile load are simulated using progressive failure analysis (PFA) methodology. The progressive failure methodology is implemented using VUMAT subroutine within the ABAQUS(TradeMark)/Explicit nonlinear finite element code. The degradation model adopted in the present PFA methodology uses an instantaneous complete stress reduction (COSTR) approach to simulate damage at a material point when failure occurs. In-plane modeling parameters such as element size and shape are held constant in the finite element models, irrespective of laminate thickness and hole size, to predict failure loads and failure progression. Comparison to published test data indicates that this methodology accurately simulates brittle, pull-out and delamination failure types. The sensitivity of the failure progression and the failure load to analytical loading rates and solvers precision is demonstrated.

  5. Failure strength prediction for adhesively bonded single lap joints

    NASA Astrophysics Data System (ADS)

    Rahman, Niat Mahmud

    For adhesively bonded joint, failure strength depends on many factors such as material properties (both adhesive and adherend), specimen geometries, test environments, surface preparation procedures, etc. Failure occurs inside constitutive materials or along joint interfaces. Based on location, adhesively bonded failure mode can be classified as adhesive failure mode, cohesive failure mode and adherend failure mode. Failure mode directly affects the failure strength of joint. For last eight decades, researchers have developed analytical, empirical or semi-empirical methods capable of predicting failure strength for adhesively bonded joints generating either cohesive failure or adherend failure. Applicability of most of the methods is limited to particular cases. In this research, different failure modes for single lap joints (SLJs) were generated experimentally using epoxy based paste adhesive. Based on experimental data and analytical study, simplified failure prediction methods were developed for each failure mode. For adhesive failure mode, it is observed that peel stress distributions concur along interface near crack initiation points. All SLJs for this test endured consistent surface treatments. Geometric parameters of the joints were varied to study their effect on failure strength. Peel stress distributions were calculated using finite analysis (FEA). Based on peel stress distribution near crack initiation point, a failure model is proposed. Numerous analytical, empirical and semi-empirical models are available for predicting failure strengths of SLJs generating cohesive failures. However, most of the methods in the literature failed to capture failure behavior of SLJs having thickness of adhesive layer as variable. Cohesive failure mode was generated experimentally using aluminum as adherend and epoxy adhesive considering thickness of adhesive layers as variable within SLJs. Comparative study was performed among various methods. It was observed that

  6. Predicting Computer System Failures Using Support Vector Machines

    SciTech Connect

    Fulp, Errin W.; Fink, Glenn A.; Haack, Jereme N.

    2008-12-07

    Mitigating the impact of computer failure is possible if accurate failure predictions are provided. Resources, applications, and services can be scheduled around predicted failure and limit the impact. Such strategies are especially important for multi-computer systems, such as compute clusters, that experience a higher rate failure due to the large number of components. However providing accurate predictions with sufficient lead time remains a challenging problem. This paper describes a new spectrum-kernel Support Vector Machine (SVM) approach to predict failure events based on system log files. These files contain messages that represent a change of system state. While a single message in the file may not be sufficient for predicting failure, a sequence or pattern of messages may be. The approach described in this paper will use a sliding window (sub-sequence) of messages to predict the likelihood of failure. The frequency representation of the message sub-sequences observed are then used as input to the SVM that associates the messages to a class of failed or non-failed system. Experimental results using actual system log files from a Linux-based compute cluster indicate the proposed SVM approach can predict hard disk failure with an accuracy of 76% one day in advance.

  7. Ultra fast-track extubation in heart transplant surgery patients

    PubMed Central

    Kianfar, Amir Abbas; Ahmadi, Zargham Hossein; Mirhossein, Seyed Mohsen; Jamaati, Hamidreza; Kashani, Babak Sharif; Mohajerani, Seyed Amir; Firoozi, Ehsan; Salehi, Farshid; Radmand, Golnar; Hashemian, Seyed Mohammadreza

    2015-01-01

    Background: Heart transplant surgeries using cardiopulmonary bypass (CPB) typically requires mechanical ventilation in intensive care units (ICU) in post-operation period. Ultra fast-track extubation (UFE) have been described in patients undergoing various cardiac surgeries. Aim: To determine the possibility of ultra-fast-track extubation instead of late extubation in post heart transplant patients. Materials and Methods: Patients randomly assigned into two groups; Ultra fast-track extubation (UFE) group was defined by extubation inside operating room right after surgery. Late extubation group was defined by patients who were not extubated in operating room and transferred to post operation cardiac care unit (CCU) to extubate. Results: The mean cardiopulmonary bypass time was 136.8 ± 25.7 minutes in ultra-fast extubation and 145.3 ± 29.8 minutes in late extubation patients (P > 0.05). Mechanical ventilation duration (days) was 0 days in ultra-fast and 2.31 ± 1.8 days in late extubation. Length of ICU stay was significantly higher in late extubation group (4.2 ± 1.2 days) than the UFE group (1.72 ± 1.5 days) (P = 0.02). In survival analysis there was no significant difference between ultra-fast and late extubation groups (Log-rank test, P = 0.9). Conclusions: Patients undergoing cardiac transplant could be managed with “ultra-fast-track extubation”, without increased morbidity and mortality. PMID:26157651

  8. Stress chemiluminescence: predictive applications to polymer failure

    SciTech Connect

    Richardson, J.H.; Monaco, S.B.; Breshears, J.D.; Johnson, D.C.; Lanning, S.M.; Morgan, R.J.

    1981-10-01

    A computer-controlled stress chemiluminescence instrument has been designed and assembled. A LSI-11 microprocessor is used to ramp the stepping motor which applies the stress to the polymer sample. The computer also acquires data from the load cell and the photon counter, and outputs the essential data to either a printer or floppy disk for storage and subsequent manipulation. The stress chemiluminescence technique has been previously reported by Levy and Fanter: the significant result of this work is the correlation of an enhanced chemiluminescence signal in a low stress environment with the subsequent premature mechanical failure of the polymer sample. Currently only epoxy and nylon samples have been examined; not all epoxy polymers appear to have this correlation between mechanical failure and stress chemiluminescence signal (of course, previous work by Levy and Fanter indicated that not all polymers exhibit a correlation between stress and chemiluminescence). The technique will be extended to fibers, composites, and polymers subjected to accelerated aging.

  9. Predictability of steel containment response near failure

    SciTech Connect

    Costello, J.F.; Ludwigsen, J.S.; Luk, V.K.; Hessheimer, M.F.

    2000-01-06

    The Nuclear Power Engineering Corporation of Japan and the US Nuclear Regulatory Commission Office of Nuclear Regulatory Research, are co-sponsoring and jointly funding a Cooperative Containment Research Program at Sandia National Laboratories, Albuquerque, New Mexico, USA. As a part of this program, a steel containment vessel model and contact structure assembly was tested to failure with over pressurization at Sandia on December 11--12, 1996. The steel containment vessel model was a mixed-scale model (1:10 in geometry and 1:4 in shell thickness) of a steel containment for an improved Mark-II Boiling Water Reactor plant in Japan. The contact structure, which is a thick, bell-shaped steel shell separated at a nominally uniform distance from the model, provides a simplified representation of features of the concrete reactor shield building in the actual plant. The objective of the internal pressurization test was to provide measurement data of the structural response of the model up to its failure in order to validate analytical modeling, to find its pressure capacity, and to observe the failure model and mechanisms.

  10. Reflex cough PEF as a predictor of successful extubation in neurological patients*

    PubMed Central

    Kutchak, Fernanda Machado; Debesaitys, Andressa Maciel; Rieder, Marcelo de Mello; Meneguzzi, Carla; Skueresky, Amanda Soares; Alberto, Luiz; Bianchin, Marino Muxfeldt

    2015-01-01

    Abstract Objective: To evaluate the use of reflex cough PEF as a predictor of successful extubation in neurological patients who were candidates for weaning from mechanical ventilation. Methods: This was a cross-sectional study of 135 patients receiving mechanical ventilation for more than 24 h in the ICU of Cristo Redentor Hospital, in the city of Porto Alegre, Brazil. Reflex cough PEF, the rapid shallow breathing index, MIP, and MEP were measured, as were ventilatory, hemodynamic, and clinical parameters. Results: The mean age of the patients was 47.8 ± 17 years. The extubation failure rate was 33.3%. A reflex cough PEF of < 80 L/min showed a relative risk of 3.6 (95% CI: 2.0-6.7), and the final Glasgow Coma Scale score showed a relative risk of 0.64 (95% CI: 0.51-0.83). For every 1-point increase in a Glasgow Coma Scale score of 8, there was a 36% reduction in the risk of extubation failure. Conclusions: Reflex cough PEF and the Glasgow Coma Scale score are independent predictors of extubation failure in neurological patients admitted to the ICU. PMID:26398756

  11. Predicting viscoelastic response and delayed failures in general laminated composites

    NASA Technical Reports Server (NTRS)

    Dillard, D. A.; Morris, D. H.; Brinson, H. F.

    1982-01-01

    Although graphite fibers behave in an essentially elastic manner, the polymeric matrix of graphite/epoxy composites is a viscoelastic material which exhibits creep and delayed failures. The creep process is quite slow at room temperature, but may be accelerated by higher temperatures, moisture absorption, and other factors. Techniques are being studied to predict long-term behavior of general laminates based on short-term observations of the unidirectional material at elevated temperatures. A preliminary numerical procedure based on lamination theory is developed for predicting creep and delayed failures in laminated composites. A modification of the Findley nonlinear power law is used to model the constitutive behavior of a lamina. An adaptation of the Tsai-Hill failure criterion is used to predict the time-dependent strength of a lamina. Predicted creep and delayed failure results are compared with typical experimental data.

  12. Prediction of Technological Failures in Nuclear Power Plant Operation

    SciTech Connect

    Salnykov, A. A.

    2015-01-15

    A method for predicting operating technological failures in nuclear power plants which makes it possible to reduce the unloading of the generator unit during the onset and development of an anomalous engineering state of the equipment by detecting a change in state earlier and taking suitable measures. With the circulating water supply loop of a nuclear power plant as an example, scenarios and algorithms for predicting technological failures in the operation of equipment long before their actual occurrence are discussed.

  13. Computational Methods for Failure Analysis and Life Prediction

    NASA Technical Reports Server (NTRS)

    Noor, Ahmed K. (Compiler); Harris, Charles E. (Compiler); Housner, Jerrold M. (Compiler); Hopkins, Dale A. (Compiler)

    1993-01-01

    This conference publication contains the presentations and discussions from the joint UVA/NASA Workshop on Computational Methods for Failure Analysis and Life Prediction held at NASA Langley Research Center 14-15 Oct. 1992. The presentations focused on damage failure and life predictions of polymer-matrix composite structures. They covered some of the research activities at NASA Langley, NASA Lewis, Southwest Research Institute, industry, and universities. Both airframes and propulsion systems were considered.

  14. Two-parameter Failure Model Improves Time-independent and Time-dependent Failure Predictions

    SciTech Connect

    Huddleston, R L

    2004-01-27

    A new analytical model for predicting failure under a generalized, triaxial stress state was developed by the author and initially reported in 1984. The model was validated for predicting failure under elevated-temperature creep-rupture conditions. Biaxial data for three alloy steels, Types 304 and 316 stainless steels and Inconel 600, demonstrated two to three orders of magnitude reduction in the scatter of predicted versus observed creep-rupture times as compared to the classical failure models of Mises, Tresca, and Rankine. In 1990, the new model was incorporated into American Society of Mechanical Engineers (ASME) Code Case N47-29 for design of components operating under creep-rupture conditions. The current report provides additional validation of the model for predicting failure under time-independent conditions and also outlines a methodology for predicting failure under cyclic, time-dependent, creep-fatigue conditions. The later extension of the methodology may have the potential to improve failure predictions there as well. These results are relevant to most design applications, but they have special relevance to high-performance design applications such as components for high-pressure equipment, nuclear reactors, and jet engines.

  15. Review on failure prediction techniques of composite single lap joint

    NASA Astrophysics Data System (ADS)

    Ab Ghani A., F.; Rivai, Ahmad

    2016-03-01

    Adhesive bonding is the most appropriate joining method in construction of composite structures. The use of reliable design and prediction technique will produce better performance of bonded joints. Several papers from recent papers and journals have been reviewed and synthesized to understand the current state of the art in this area. It is done by studying the most relevant analytical solutions for composite adherends with start of reviewing the most fundamental ones involving beam/plate theory. It is then extended to review single lap joint non linearity and failure prediction and finally on the failure prediction on composite single lap joint. The review also encompasses the finite element modelling part as tool to predict the elastic response of composite single lap joint and failure prediction numerically.

  16. A multiple regression equation for prediction of posthepatectomy liver failure.

    PubMed Central

    Yamanaka, N; Okamoto, E; Kuwata, K; Tanaka, N

    1984-01-01

    This article reports a multiple regression equation for prediction of posthepatectomy liver failure. In phase I, using the correlations between 17 preoperative parameters (Xi) and the postoperative course scored (Y) of the past 36 hepatectomized patients, we proposed the following multiple regression equation: Y = -110 + 0.942 X resection rate (%) + 1.36 X ICG retention rate (%) + 1.17 X patient's age + 5.94 X ICG maximal removal rate (mg/kg/min). With the equation, the calculated Y value (prediction score) of these patients revealed that prediction scores of the eight nonsurvivors with liver failure were more than 50 points while those of the 28 survivors were 50 points or less. In phase II, the relationships between early prognosis and a precalculated prediction score were prospectively found the same as that seen in phase I. These findings indicate that our formula is a useful prognostic index for prediction of posthepatectomy liver failure. PMID:6486915

  17. Predicting Modes and Displacements of Seismic Rock Slope Failures

    NASA Astrophysics Data System (ADS)

    Gibson, M. D.; Wartman, J.; Keefer, D. K.; Maclaughlin, M.; Arnold, L.; Applegate, K. N.; Smith, S.; Adams, S.

    2013-12-01

    Seismically induced rock slope failures have resulted in billions of dollars of economic damage and enormous loss of life throughout the world. Accurate prediction of the triggering and run out of these failures is elusive for a variety of reasons, including knowledge of the physical modes of failure. Our research explores the potential failure modes of an idealized rigid rock block and expands the modes typically considered to include not only sliding but also toppling (pure forward rotation) and slumping (combined backward rotation and translation). The yield acceleration (or minimum inertial acceleration to cause block movement) for slumping, similar to toppling, is found to be lower than for pure translational sliding. These yield accelerations indicate the initial modes of rock block failure; however, they do not always predict the ultimate failure mode. To predict the final failure modes, the results of discrete element numerical analyses were compared to pseudo static yield acceleration to develop a seismic failure mode decision-making chart based on block geometry and interface friction. With regard to seismic displacement predictions, current simplified models predicting ultimate displacement of a mass under seismic conditions are limited to purely translating, sliding blocks (i.e. Newmark's sliding block method). Our modeling introduces additional simplified analyses to predict ultimate displacement in toppling and slumping modes as well. Important findings from these new methods are that the magnitude of seismically-induced displacement is dependent on the size of the block (or failure mass) and that as the yield acceleration decreases the seismically induced displacements increase. We plan to map these tools into analyses that evaluate rock slope systems with complex geology and geotechnical characteristics. It is envisioned that the decision chart, which predicts the initial and ultimate modes of failure based on block geometry and interface friction

  18. Prediction failure of a wolf landscape model

    USGS Publications Warehouse

    Mech, L.D.

    2006-01-01

    I compared 101 wolf (Canis lupus) pack territories formed in Wisconsin during 1993-2004 to the logistic regression predictive model of Mladenoff et al. (1995, 1997, 1999). Of these, 60% were located in putative habitat suitabilities 50% remained unoccupied by known packs after 24 years of recolonization. This model was a poor predictor of wolf re-colonizing locations in Wisconsin, apparently because it failed to consider the adaptability of wolves. Such models should be used cautiously in wolf-management or restoration plans.

  19. Electrical impedance tomography to evaluate air distribution prior to extubation in very-low-birth-weight infants: a feasibility study

    PubMed Central

    de Souza Rossi, Felipe; Yagui, Ana Cristina Zanon; Haddad, Luciana Branco; Deutsch, Alice D'Agostini; Rebello, Celso Moura

    2013-01-01

    OBJECTIVES: Nasal continuous positive airway pressure is used as a standard of care after extubation in very-low-birth-weight infants. A pressure of 5 cmH2O is usually applied regardless of individual differences in lung compliance. Current methods for evaluation of lung compliance and air distribution in the lungs are thus imprecise for preterm infants. This study used electrical impedance tomography to determine the feasibility of evaluating the positive end-expiratory pressure level associated with a more homogeneous air distribution within the lungs before extubation. METHODS: Ventilation homogeneity was defined by electrical impedance tomography as the ratio of ventilation between dependent and non-dependent lung areas. The best ventilation homogeneity was achieved when this ratio was equal to 1. Just before extubation, decremental expiratory pressure levels were applied (8, 7, 6 and 5 cmH20; 3 minutes each step), and the pressure that determined the best ventilation homogeneity was defined as the best positive end-expiratory pressure. RESULTS: The best positive end-expiratory pressure value was 6.3±1.1 cmH20, and the mean continuous positive airway pressure applied after extubation was 5.2±0.4 cmH20 (p = 0.002). The extubation failure rate was 21.4%. X-Ray and blood gases after extubation were also checked. CONCLUSION: This study demonstrates that electrical impedance tomography can be safely and successfully used in patients ready for extubation to suggest the best ventilation homogeneity, which is influenced by the level of expiratory pressure applied. In this feasibility study, the best lung compliance was found with pressure levels higher than the continuous positive airway pressure levels that are usually applied for routine extubation. PMID:23644854

  20. Failure prediction for cross-rolled beryllium sheet material

    SciTech Connect

    Roschke, P.; Mascorro, E.

    1996-04-01

    A failure model for cross-rolled beryllium SR-200 sheets is developed for material loaded in a complex state of stress. Coefficients of the Tsai-Wu criterion are determined from a series of special laboratory experiments. Tests include circular plates loaded by a concentric ring, as well as in-plane compression and off-axis plate specimens. Complex states of stress lead to brittle failure of the anisotropic material. Failure surfaces obtained from the criterion form a family of ellipses when plotted in standard Cartesian coordinates. The criterion is incorporated into a general purpose finite element analysis code. Numerical simulation incrementally applies loads to a structural component that i being designed and checks each nodal point in the model for exceedance of the failure criterion. To demonstrate applicability of the predictive capability of the criterion, a 2.54-mm thick beryllium plate is placed under clamped edge conditions and loaded to failure by a central transverse point load. A numerical model of the structure predicts the failure load to within 3%.

  1. Predicted and actual high voltage failure - A case history

    NASA Astrophysics Data System (ADS)

    Fowler, P. H.; Brent, D. A.; Sidio, G. J.

    In the process of re-developing a high voltage transformer for space use, excellent correlation was found between predicted mechanical failure, predicted partial discharge signature, and real behavior of the parts. Some useful design and inspection criteria for potted high voltage parts were developed on a consistent basis. It was found that partial discharge testing as normally implemented will not necessarily discern all life limiting defects. Three lines of investigation were followed: material properties and stress analysis, prediction of partial discharge signature as a function of defect size, and computer field stress analysis to predict which defects are capable of discharge.

  2. Composite failure prediction of π-joint structures under bending

    NASA Astrophysics Data System (ADS)

    Huang, Hong-mei; Yuan, Shen-fang

    2012-03-01

    In this article, the composite -joint is investigated under bending loads. The "L" preform is the critical component regarding composite -joint failure. The study is presented in the failure detection of a carbon fiber composite -joint structure under bending loads using fiber Bragg grating (FBG) sensor. Firstly, based on the general finite element method (FEM) software, the 3-D finite element (FE) model of composite -joint is established, and the failure process and every lamina failure load of composite -joint are investigated by maximum stress criteria. Then, strain distributions along the length of FBG are extracted, and the reflection spectra of FBG are calculated according to the strain distribution. Finally, to verify the numerical results, a test scheme is performed and the experimental spectra of FBG are recorded. The experimental results indicate that the failure sequence and the corresponding critical loads of failure are consistent with the numerical predictions, and the computational error of failure load is less than 6.4%. Furthermore, it also verifies the feasibility of the damage detection system.

  3. Respiratory and hemodynamic outcomes following exchange extubation with laryngeal mask airway as compared to traditional awake extubation

    PubMed Central

    Suppiah, Ramanathan Kannan; Rajan, Sunil; Paul, Jerry; Kumar, Lakshmi

    2016-01-01

    Background: Traditional awake extubation leads to respiratory complications and hemodynamic response which are detrimental in neurosurgery, ENT surgery and patients with comorbidities. Aims: The primary objective was to compare the respiratory complications and hemodynamic stress response between traditional awake extubation of a endotracheal tube (ETT) and that following exchange extubation of ETT by using a laryngeal mask airway (LMA). Settings and Design: This prospective randomized study was conducted in a Tertiary Care Centre in 60 American Society of Anesthesiologists I and II patients coming for general surgery. Materials and Methods: Patients were randomized by permuted blocks into traditional awake extubation group and exchange extubation group. At the end of surgery in traditional group, awake extubation of ETT was done. In exchange group, 0.3 mg/kg propofol was administered, and the ETT was exchanged for a LMA. Awake extubation of LMA was then performed. Respiratory complications such as bucking, coughing, desaturation and the need for airway maneuvers and hemodynamic response were noted in both groups. Analysis Tools: Chi-square test, independent sample t- and paired t-tests were used as applicable. Results: Incidence of respiratory complication was 93.3% in traditional extubation while it was only 36.7% in exchange extubation group (P < 0.001). Hemodynamic response measured immediately at extubation in terms of heart rate, systolic blood pressure (BP), diastolic BP, mean arterial pressure, and rate pressure product were all significantly lesser in exchange group when compared to traditional extubation. Conclusion: Exchange extubation with LMA decreases respiratory complications and hemodynamic stress response when compared to traditional awake extubation. PMID:27212749

  4. Bispectral index monitoring to facilitate early extubation following cardiovascular surgery.

    PubMed

    Anderson, Jennifer; Henry, Linda; Hunt, Sharon; Ad, Niv

    2010-01-01

    Frequently, intensive care nurses assume responsibility for extubating patients after undergoing cardiac surgery. Bispectral index (BIS) monitoring assesses level of mental arousal and awareness when sedated. This study was to determine if the BIS might facilitate earlier extubation of patients following cardiac surgery. A study was conducted comparing 25 stable patients returning to the intensive care unit with a BIS with 25 patients managed without the BIS (N = 50). Data collected included age, sex, surgery, pH, CO2, and temperature on arrival/extubation, total intravenous propofol and pain medication, and BIS scores. Student t tests determined that there were no differences between groups for age, amount of propofol and pain medication received, or time to extubation (P > .05). Regression analysis determined that total propofol, total hydromorphone, and age were significant predictors of time to extubation. In this study, the BIS monitor did not facilitate earlier extubation in the stable patient after cardiac surgery. PMID:20404622

  5. Application of Weibull Criterion to failure prediction in compsites

    SciTech Connect

    Cain, W. D.; Knight, Jr., C. E.

    1981-04-20

    Fiber-reinforced composite materials are being widely used in engineered structures. This report examines how the general form of the Weibull Criterion, including the evaluation of the parameters and the scaling of the parameter values, can be used for the prediction of component failure.

  6. Model-Biased, Data-Driven Adaptive Failure Prediction

    NASA Technical Reports Server (NTRS)

    Leen, Todd K.

    2004-01-01

    This final report, which contains a research summary and a viewgraph presentation, addresses clustering and data simulation techniques for failure prediction. The researchers applied their techniques to both helicopter gearbox anomaly detection and segmentation of Earth Observing System (EOS) satellite imagery.

  7. Anticipating the future: Automatic prediction failures in schizophrenia

    PubMed Central

    Ford, Judith M.; Mathalon, Daniel H.

    2011-01-01

    People with schizophrenia often misperceive sensations and misinterpret experiences, perhaps contributing to psychotic symptoms. These misperceptions and misinterpretations might result from an inability to make valid predictions about expected sensations and experiences. Healthy normal people take advantage of neural mechanisms that allow them to make predictions unconsciously, facilitating processing of expected sensations and distinguishing the expected from the unexpected. In this paper, we focus on two types of automatic, unconscious mechanisms that allow us to predict our perceptions. The first involves predictions made via innate mechanisms basic to all species in the animal kingdom—the efference copy and corollary discharge mechanisms. They accompany our voluntary movements and allow us to suppress sensations resulting from our actions. We study this during talking, and show that auditory cortical response to the speech sounds during talking is reduced compared to when they are played back. This suppression is reduced in schizophrenia, suggesting a failure to predict the sensations resulting from talking. The second mechanism involves implicitly learning what to expect from the current context of events. We study this by observing the brain's response to an unexpected repetition of an event, when a change would have been predicted. That patients have a reduced response suggests they failed to predict that it was time for a change. Both types of predictions should happen automatically and effortlessly, allowing for economic processing of expected events and orientation to unexpected ones. These prediction failures characterize the diagnosis of schizophrenia rather than reflecting specific symptoms. PMID:21959054

  8. 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

  9. Failure prediction of thin beryllium sheets used in spacecraft structures

    NASA Technical Reports Server (NTRS)

    Roschke, Paul N.; Papados, Photios; Mascorro, Edward

    1991-01-01

    In an attempt to predict failure for cross-rolled beryllium sheet structures, high order macroscopic failure criteria are used. These require the knowledge of in-plane uniaxial and shear strengths. Test results are included for in-plane biaxial tension, uniaxial compression for two different material orientations, and shear. All beryllium specimens have the same chemical composition. In addition, all experimental work was performed in a controlled laboratory environment. Numerical simulation complements these tests. A brief bibliography supplements references listed in a previous report.

  10. Empirical sediment transport function predicting seepage erosion undercutting for cohesive bank failure prediction

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Seepage erosion is an important factor in hillslope instability and failure. However, predicting erosion by subsurface flow or seepage and incorporating its effects into stability models remains a challenge. Limitations exist with all existing seepage erosion sediment transport functions, including ...

  11. Comparison of Two Levels of Pressure Support Ventilation on Success of Extubation in Preterm Neonates: A Randomized Clinical Trial

    PubMed Central

    Farhadi, Roya; Lotfi, Hamid Reza; Alipour, Abbas; Nakhshab, Maryam; Ghaffari, Vajiheh; Hashemi, Seyyed Abbas

    2016-01-01

    Background: Pressure Support Ventilation (PSV) is one of the modes of mechanical ventilation that can be used alone as a weaning strategy in neonates. However, studies on the appropriate pressure level for this mode in neonates are limited. Objectives: Because the use of adequate pressure support in this mode, keeping the appropriate neonate’s tidal volume, and preventing the respiratory complications, this study was aimed to compare extubation failure in the two levels of pressure support ventilation of 10 and 14 cmH2O when removing the neonates from the ventilator. Materials & Methods: In this randomized clinical trial 50 premature infants of 27-37 weeks with respiratory distress syndrome (RDS) were under mechanical ventilation for at least 48 hours, were randomly assigned to two groups. One group was extubated in PSV mode with pressure of 14 cmH2O and the other with 10 cmH2O. Extubation failure rate and complications such as pneumothorax, death and respiratory parameters were compared in the two groups. Results: Twenty five neonates in each group were assessed. Weaning time, extubation failure rate, and mean airway pressure was lesser in PSV of 10 cmH20 group than Level of 14 cmH2O and those differences were statistically significant (P<0.05). Difference between work of breathing, ventilation time, pneumothorax and mortality rate between two groups were not statistically significant (P>0.05). Conclusion: The results of our study show that extubation of the neonates using 10 CmH2O in PSV mode increases the success rate of extubation. Although when Volume- assured PSV can be used, it is more logical to use it for guaranteeing tidal volume, but using the appropriate level of pressure support when the PSV mode is used alone is inevitable and further studies are necessary to demonstrate the level of pressure in this mode. PMID:26383214

  12. Product component genealogy modeling and field-failure prediction

    DOE PAGESBeta

    King, Caleb; Hong, Yili; Meeker, William Q.

    2016-04-13

    Many industrial products consist of multiple components that are necessary for system operation. There is an abundance of literature on modeling the lifetime of such components through competing risks models. During the life-cycle of a product, it is common for there to be incremental design changes to improve reliability, to reduce costs, or due to changes in availability of certain part numbers. These changes can affect product reliability but are often ignored in system lifetime modeling. By incorporating this information about changes in part numbers over time (information that is readily available in most production databases), better accuracy can bemore » achieved in predicting time to failure, thus yielding more accurate field-failure predictions. This paper presents methods for estimating parameters and predictions for this generational model and a comparison with existing methods through the use of simulation. Our results indicate that the generational model has important practical advantages and outperforms the existing methods in predicting field failures.« less

  13. Progressive Failure And Life Prediction of Ceramic and Textile Composites

    NASA Technical Reports Server (NTRS)

    Xue, David Y.; Shi, Yucheng; Katikala, Madhu; Johnston, William M., Jr.; Card, Michael F.

    1998-01-01

    An engineering approach to predict the fatigue life and progressive failure of multilayered composite and textile laminates is presented. Analytical models which account for matrix cracking, statistical fiber failures and nonlinear stress-strain behavior have been developed for both composites and textiles. The analysis method is based on a combined micromechanics, fracture mechanics and failure statistics analysis. Experimentally derived empirical coefficients are used to account for the interface of fiber and matrix, fiber strength, and fiber-matrix stiffness reductions. Similar approaches were applied to textiles using Repeating Unit Cells. In composite fatigue analysis, Walker's equation is applied for matrix fatigue cracking and Heywood's formulation is used for fiber strength fatigue degradation. The analysis has been compared with experiment with good agreement. Comparisons were made with Graphite-Epoxy, C/SiC and Nicalon/CAS composite materials. For textile materials, comparisons were made with triaxial braided and plain weave materials under biaxial or uniaxial tension. Fatigue predictions were compared with test data obtained from plain weave C/SiC materials tested at AS&M. Computer codes were developed to perform the analysis. Composite Progressive Failure Analysis for Laminates is contained in the code CPFail. Micromechanics Analysis for Textile Composites is contained in the code MicroTex. Both codes were adapted to run as subroutines for the finite element code ABAQUS and CPFail-ABAQUS and MicroTex-ABAQUS. Graphic user interface (GUI) was developed to connect CPFail and MicroTex with ABAQUS.

  14. On predicting and modeling material failure under impact loading

    SciTech Connect

    Lewis, M.W.

    1998-09-01

    A method for predicting and modeling material failure in solids subjected to impact loading is outlined. The method uses classical void growth models of Gurson and Tvergaard in a material point method (MPM). Because of material softening, material stability is lost. At this point, the character of the governing partial differential equations changes, and localization occurs. This localization results in mesh dependence for many problems of interest. For many problems, predicting the occurrence of material failure and its extent is necessary. To enable this modeling, it is proposed that a discontinuity be introduced into the displacement field. By including a dissipation-based force-displacement relationship, the mesh dependence of energy dissipation can be avoided. Additionally, the material point method provides a means of allowing large deformations without mesh distortion or introduction of error through remapping.

  15. Relational Neural Evolution Approach to Bank Failure Prediction

    NASA Astrophysics Data System (ADS)

    Abudu, Bolanle; Markose, Sheri

    2007-12-01

    Relational neural networks as a concept offers a unique opportunity for improving classification accuracy by exploiting relational structure in data. The premise is that a relational classification technique, which uses information implicit in relationships, should classify more accurately than techniques that only examine objects in isolation. In this paper, we study the use of relational neural networks for predicting bank failure. Alongside classical financial ratios normally used as predictor variables, we introduced new relational variables for the network. The relational neural network structure, specified as a combination of feed forward and recurrent neural networks, is determined by bank data through neuro-evolution. We discuss empirical results comparing performance of the relational approach to standard propositional methods used for bank failure prediction.

  16. Relational Neural Evolution Approach to Bank Failure Prediction

    SciTech Connect

    Abudu, Bolanle; Markose, Sheri

    2007-12-26

    Relational neural networks as a concept offers a unique opportunity for improving classification accuracy by exploiting relational structure in data. The premise is that a relational classification technique, which uses information implicit in relationships, should classify more accurately than techniques that only examine objects in isolation. In this paper, we study the use of relational neural networks for predicting bank failure. Alongside classical financial ratios normally used as predictor variables, we introduced new relational variables for the network. The relational neural network structure, specified as a combination of feed forward and recurrent neural networks, is determined by bank data through neuro-evolution. We discuss empirical results comparing performance of the relational approach to standard propositional methods used for bank failure prediction.

  17. Failure Prediction in Fine Blanking Process with Stress Limit Model

    NASA Astrophysics Data System (ADS)

    Tong, Longchang; Manopulo, Niko; Hora, Pavel

    2010-06-01

    Extremely small blanking clearance and nearly sharp edges of blanking tool are the characteristics of fine blanking that produces near net shape parts. The extreme forming conditions make the failure prediction for fine blanking more difficult than for ordinary forming processes. Stress Limit Criterion (SLC) is adopted in this work to perform the failure prediction of 3D fine blanking process. In comparison with the stress triaxiality diagram, SLC is not sensitively affected by complex nonlinear deformation paths and can perform the task as well. However, the parameters that support the model have to be obtained with combination of dedicatedly designed experiments and numerical simulation. The FEM simulation must also be able to provide stable and reliable results.

  18. What is the optimal rate of failed extubation?

    PubMed Central

    2012-01-01

    Failed extubation (FE), defined as reintubation 48 or 72 hours after planned extubation, occurs in a significant percentage of patients and is associated with a substantial burden of morbidity and mortality. This commentary reviews the literature describing FE rates and the clinical consequences of FE and proposes an 'optimal' rate of FE as well as avenues for future research. PMID:22356725

  19. Prediction of long-term failure in Kevlar 49 composites

    SciTech Connect

    Gerstle, F.P. Jr.

    1982-01-01

    Creep rupture data in Kevlar 49 epoxy usually exhibit considerable scatter: the coefficient of variation (CV) about the mean failure time at a given stress exceeds 100%. Quasi-static strength data, in contrast, shows little scatter: <4% CV for pressure vessels and <10% for impregnated strands. In this paper analysis of existing creep rupture data on Kevlar epoxy vessels at four storage pressures has produced an interesting and useful result. It was found that a significant portion of the scatter in failure times for pressure vessels is due to spool-to-spool variation in the eight spools of Kevlar fibers used to wind the vessels. The order rank of mean times to failure was consistent over a pressure range from 3400 to 4300 psi, 68 to 86% of short term burst. Also, the coefficient of variation about the mean failure time for each spool was less than that for the total sample. The statistical inference that the sample is nonhomogeneous was supported by a nonparametric check using the Kruskal-Wallis test, and by a parametric analysis of variance. The order rank found in long-term tests did not unequivocally agree with static strength ranks; several spool sets were distinctly high or low. The implication is that, while static strengths are not valid predictors of long-term behavior, short term creep rupture tests at high stress definitely are. The material difference which causes the spool-to-spool variations has not yet been identified for all eight spools. However, it appears that Kevlar behavior at lower pressures may be predicted through the use of curves fitted to the data for each spool. A power law relating failure time to pressure, t = t/sub 0/(p/p/sub 0/)/sup m/, was found to fit the data reasonably well. The implication is that, both in composite vessel design and in creep rupture experiments, the pressure (or stress) level be carefully controlled.

  20. Brittle failure prediction of ceramics using a multiscale approach

    SciTech Connect

    Berdin, C.; Cailletaud, G.; Jeulin, D.

    1996-11-01

    Brittle failure is classically modeled by the Weibull distribution, based on a phenomenological approach. The procedure fails if the distribution of the failure-initiating defects varies within material batches and may lead to a wrong conclusion about the predictive power of the model. The purpose of this paper is to highlight this problem, which can occur with brittle materials such as ceramics. This study, based on the results of tensile and bending tests made on silicon nitride specimens, consists of three steps: (i) micrographic and fractographic studies are performed to determine the defect-size density in each type of specimen and the mechanical behavior of the defects, (ii) the classical modeling with a Weibull distribution is shown to fail to predict the results, and (iii) a new approach for the identification of a fracture model is developed, based on step (i). The fracture prediction is computed from the actual defect-size distribution in each material batch, so that the procedure can be adapted to changes in the defect-size distribution caused by the manufacturing process.

  1. Recipient Criteria Predictive of Graft Failure in Kidney Transplantation.

    PubMed

    Molmenti, Ernesto P; Alex, Asha; Rosen, Lisa; Alexander, Mohini; Nicastro, Jeffrey; Yang, Jingyan; Siskind, Eric; Alex, Leesha; Sameyah, Emil; Bhaskaran, Madhu; Ali, Nicole; Basu, Amit; Sachdeva, Mala; Agorastos, Stergiani; Rajendran, Prejith; Krishnan, Prathik; Ramadas, Poornima; Amodu, Leo; Cagliani, Joaquin; Rehman, Sameer; Kressel, Adam; Sethna, Christine B; Sotiropoulos, Georgios C; Radtke, Arnold; Sgourakis, George; Schwarz, Richard; Fishbane, Steven; Bellucci, Alessandro; Coppa, Gene; Rilo, Horacio; Molmenti, Christine L

    2016-03-01

    Several classifications systems have been developed to predict outcomes of kidney transplantation based on donor variables. This study aims to identify kidney transplant recipient variables that would predict graft outcome irrespective of donor characteristics. All U.S. kidney transplant recipients between October 25,1999 and January 1, 2007 were reviewed. Cox proportional hazards regression was used to model time until graft failure. Death-censored and nondeath-censored graft survival models were generated for recipients of live and deceased donor organs. Recipient age, gender, body mass index (BMI), presence of cardiac risk factors, peripheral vascular disease, pulmonary disease, diabetes, cerebrovascular disease, history of malignancy, hepatitis B core antibody, hepatitis C infection, dialysis status, panel-reactive antibodies (PRA), geographic region, educational level, and prior kidney transplant were evaluated in all kidney transplant recipients. Among the 88,284 adult transplant recipients the following groups had increased risk of graft failure: younger and older recipients, increasing PRA (hazard ratio [HR],1.03-1.06], increasing BMI (HR, 1.04-1.62), previous kidney transplant (HR, 1.17-1.26), dialysis at the time of transplantation (HR, 1.39-1.51), hepatitis C infection (HR, 1.41-1.63), and educational level (HR, 1.05-1.42). Predictive criteria based on recipient characteristics could guide organ allocation, risk stratification, and patient expectations in planning kidney transplantation. PMID:26900309

  2. Wavelet-based signal analysis for heart failure hospitalization prediction.

    PubMed

    Iakovidis, Dimitris K; Douska, Dimitra; Barba, Evaggelia; Koulaouzidis, George

    2016-01-01

    Heart failure (HF) is commonly a chronic condition associated with frequent hospital admissions. Early knowledge about a possible deterioration of this condition would enable early treatment for the prevention of adverse events and related hospital admissions. In this paper we present a computational method for predictive information extraction from daily physiological signals, which can be obtained by a telemonitoring system with wearable sensors. It is based on wavelet analysis of temporal signal patterns. Experiments with data from patients enrolled in a telemonitoring protocol show that the proposed method is capable of predicting HF hospitalization events one day before they happen, even in the case of low compliance to the protocol. These results indicate a promising perspective towards a monitoring system that would provide improved life quality for HF patients. PMID:27225548

  3. A multichannel model-based methodology for extubation readiness decision of patients on weaning trials.

    PubMed

    Casaseca-de-la-Higuera, Pablo; Simmross-Wattenberg, Federico; Martín-Fernández, Marcos; Alberola-López, Carlos

    2009-07-01

    Discontinuation of mechanical ventilation is a challenging task that involves a number of subtle clinical issues. The gradual removal of the respiratory support (referred to as weaning) should be performed as soon as autonomous respiration can be sustained. However, the prediction rate of successful extubation is still below 25% based on previous studies. Construction of an automatic system that provides information on extubation readiness is thus desirable. Recent works have demonstrated that the breathing pattern variability is a useful extubation readiness indicator, with improving performance when multiple respiratory signals are jointly processed. However, the existing methods for predictor extraction present several drawbacks when length-limited time series are to be processed in heterogeneous groups of patients. In this paper, we propose a model-based methodology for automatic readiness prediction. It is intended to deal with multichannel, nonstationary, short records of the breathing pattern. Results on experimental data yield an 87.27% of successful readiness prediction, which is in line with the best figures reported in the literature. A comparative analysis shows that our methodology overcomes the shortcomings of so far proposed methods when applied to length-limited records on heterogeneous groups of patients. PMID:19362908

  4. Rational temporal predictions can underlie apparent failures to delay gratification

    PubMed Central

    McGuire, Joseph T.; Kable, Joseph W.

    2013-01-01

    An important category of seemingly maladaptive decisions involves failure to postpone gratification. A person pursuing a desirable long-run outcome may abandon it in favor of a short-run alternative that has been available all along. Here we present a theoretical framework in which this seemingly irrational behavior emerges from stable preferences and veridical judgments. Our account recognizes that decision makers generally face uncertainty regarding the time at which future outcomes will materialize. When timing is uncertain, the value of persistence depends crucially on the nature of a decision-maker’s prior temporal beliefs. Certain forms of temporal beliefs imply that a delay’s predicted remaining length increases as a function of time already waited. In this type of situation, the rational, utility-maximizing strategy is to persist for a limited amount of time and then give up. We show empirically that people’s explicit predictions of remaining delay lengths indeed increase as a function of elapsed time in several relevant domains, implying that temporal judgments offer a rational basis for limiting persistence. We then develop our framework into a simple working model and show how it accounts for individual differences in a laboratory task (the well-known “marshmallow test”). We conclude that delay-of-gratification failure, generally viewed as a manifestation of limited self-control capacity, can instead arise as an adaptive response to the perceived statistics of one’s environment. PMID:23458085

  5. Rational temporal predictions can underlie apparent failures to delay gratification.

    PubMed

    McGuire, Joseph T; Kable, Joseph W

    2013-04-01

    An important category of seemingly maladaptive decisions involves failure to postpone gratification. A person pursuing a desirable long-run outcome may abandon it in favor of a short-run alternative that has been available all along. Here we present a theoretical framework in which this seemingly irrational behavior emerges from stable preferences and veridical judgments. Our account recognizes that decision makers generally face uncertainty regarding the time at which future outcomes will materialize. When timing is uncertain, the value of persistence depends crucially on the nature of a decision maker's prior temporal beliefs. Certain forms of temporal beliefs imply that a delay's predicted remaining length increases as a function of time already waited. In this type of situation, the rational, utility-maximizing strategy is to persist for a limited amount of time and then give up. We show empirically that people's explicit predictions of remaining delay lengths indeed increase as a function of elapsed time in several relevant domains, implying that temporal judgments offer a rational basis for limiting persistence. We then develop our framework into a simple working model and show how it accounts for individual differences in a laboratory task (the well-known "marshmallow test"). We conclude that delay-of-gratification failure, generally viewed as a manifestation of limited self-control capacity, can instead arise as an adaptive response to the perceived statistics of one's environment. PMID:23458085

  6. A numerical procedure for predicting creep and delayed failures in laminated composites

    NASA Technical Reports Server (NTRS)

    Dillard, D. A.; Brinson, H. F.

    1983-01-01

    A numerical procedure is described for predicting the viscoelastic response of general laminates. A nonlinear compliance model is used to predict the creep response of the individual laminae. A biaxial delayed failure model predicts ply failure. The numerical procedure, based on lamination theory, increases by increments through time to predict creep compliance and delayed failures in laminates. Numerical stability problems and experimental verification are discussed. Although the program has been quite successful in predicting creep of general laminates, the assumptions associated with lamination theory have resulted in erroneous bounds on the predicted material response. Delayed failure predictions have been conservative. Several improvements are suggested to increase the accuracy of the procedure.

  7. The effect of coughing at extubation on oxygenation in the post-anaesthesia care unit.

    PubMed

    Lumb, A B; Bradshaw, K; Gamlin, F M C; Heard, J

    2015-04-01

    We prospectively studied 84 patients to investigate whether there is a relationship between coughing during emergence and tracheal extubation, and impaired oxygenation in the post-anaesthesia care unit. Our primary outcome measure was a change in the alveolar-arterial oxygen partial pressure gradient ((A-a)DO2 ) between time A (during general anaesthesia) and time B (1 h after extubation). Patients demonstrated a worsening of oxygenation with mean (SD) (A-a)DO2 increasing from 7.5 (5.2) kPa at time A to 13.9 (4.2) kPa at time B (p < 0.01). An overall linear regression model was not predictive for the observed change (adjusted R(2) = 0.01, p = 0.31) and nor were any of the individual predictors studied, including subjective cough score (p = 0.33), number of coughs (p = 0.95) and duration of coughing (p = 0.39). Despite the abnormal cough that occurs while tracheally intubated, we have been unable to demonstrate that coughing at extubation is associated with impaired oxygenation in the immediate postoperative period. PMID:25376328

  8. Predictive modelling of fatigue failure in concentrated lubricated contacts.

    PubMed

    Evans, H P; Snidle, R W; Sharif, K J; Bryant, M J

    2012-01-01

    Reducing frictional losses in response to the energy agenda will require use of less viscous lubricants causing hydrodynamically-lubricated bearings to operate with thinner films leading to "mixed lubrication" conditions in which a degree of direct interaction occurs between surfaces protected only by boundary tribofilms. The paper considers the consequences of thinner films and mixed lubrication for concentrated contacts such as those occurring between the teeth of power transmission gears and in rolling element bearings. Surface fatigue in gears remains a serious problem in demanding applications, and its solution will become more pressing with the tendency towards thinner oils. The particular form of failure examined here is micropitting, which is identified as a fatigue phenomenon occurring at the scale of the surface roughness asperities. It has emerged recently as a systemic difficulty in the operation of large scale wind turbines where it occurs in both power transmission gears and their support bearings. Predictive physical modelling of these contacts requires a transient mixed lubrication analysis for conditions in which the predicted lubricant film thickness is of the same order or significantly less than the height of surface roughness features. Numerical solvers have therefore been developed which are able to deal with situations in which transient solid contacts occur between surface asperity features under realistic engineering conditions. Results of the analysis, which reveal the detailed time-varying behaviour of pressure and film clearance, have been used to predict fatigue and damage accumulation at the scale of surface asperity features with the aim of improving understanding of the micropitting phenomenon. The possible consequences on fatigue of residual stress fields resulting from plastic deformation of surface asperities is also considered. PMID:23285624

  9. Flood Water Level Mapping and Prediction Due to Dam Failures

    NASA Astrophysics Data System (ADS)

    Musa, S.; Adnan, M. S.; Ahmad, N. A.; Ayob, S.

    2016-07-01

    Sembrong dam has undergone overflow failure. Flooding has been reported to hit the town, covering an area of up to Parit Raja, located in the district of Batu Pahat. This study aims to identify the areas that will be affected by flood in the event of a dam failure in Sembrong Dam, Kluang, Johor at a maximum level. To grasp the extent, the flood inundation maps have been generated by using the InfoWorks ICM and GIS software. By using these maps, information such as the depth and extent of floods can be identified the main ares flooded. The flood map was created starting with the collection of relevant data such as measuring the depth of the river and a maximum flow rate for Sembrong Dam. The data were obtained from the Drainage and Irrigation Department Malaysia and the Department of Survey and Mapping and HLA Associates Sdn. Bhd. Then, the data were analyzed according to the established Info Works ICM method. The results found that the flooded area were listed at Sri Lalang, Parit Sagil, Parit Sonto, Sri Paya, Parit Raja, Parit Sempadan, Talang Bunut, Asam Bubok, Tanjung Sembrong, Sungai Rambut and Parit Haji Talib. Flood depth obtained for the related area started from 0.5 m up to 1.2 m. As a conclusion, the flood emanating from this study include the area around the town of Ayer Hitam up to Parit Raja approximately of more than 20 km distance. This may give bad implication to residents around these areas. In future studies, other rivers such as Sungai Batu Pahat should be considered for this study to predict and reduce the yearly flood victims for this area.

  10. Self‐Rated Health Predicts Healthcare Utilization in Heart Failure

    PubMed Central

    Chamberlain, Alanna M.; Manemann, Sheila M.; Dunlay, Shannon M.; Spertus, John A.; Moser, Debra K.; Berardi, Cecilia; Kane, Robert L.; Weston, Susan A.; Redfield, Margaret M.; Roger, Véronique L.

    2014-01-01

    Background Heart failure (HF) patients experience impaired functional status, diminished quality of life, high utilization of healthcare resources, and poor survival. Yet, the identification of patient‐centered factors that influence prognosis is lacking. Methods and Results We determined the association of 2 measures of self‐rated health with healthcare utilization and skilled nursing facility (SNF) admission in a community cohort of 417 HF patients prospectively enrolled between October 2007 and December 2010 from Olmsted County, MN. Patients completed a 12‐item Short Form Health Survey (SF‐12). Low self‐reported physical functioning was defined as a score ≤25 on the SF‐12 physical component. The first question of the SF‐12 was used as a measure of self‐rated general health. After 2 years, 1033 hospitalizations, 1407 emergency department (ED) visits, and 19,780 outpatient office visits were observed; 87 patients were admitted to a SNF. After adjustment for confounding factors, an increased risk of hospitalizations (1.52 [1.17 to 1.99]) and ED visits (1.48 [1.04 to 2.11]) was observed for those with low versus moderate‐high self‐reported physical functioning. Patients with poor and fair self‐rated general health also experienced an increased risk of hospitalizations (poor: 1.73 [1.29 to 2.32]; fair: 1.46 [1.14 to 1.87]) and ED visits (poor: 1.73 [1.16 to 2.56]; fair: 1.48 [1.13 to 1.93]) compared with good‐excellent self‐rated general health. No association between self‐reported physical functioning or self‐rated general health with outpatient visits and SNF admission was observed. Conclusion In community HF patients, self‐reported measures of physical functioning predict hospitalizations and ED visits, indicating that these patient‐reported measures may be useful in risk stratification and management in HF. PMID:24870937

  11. Predicting failure: acoustic emission of berlinite under compression.

    PubMed

    Nataf, Guillaume F; Castillo-Villa, Pedro O; Sellappan, Pathikumar; Kriven, Waltraud M; Vives, Eduard; Planes, Antoni; Salje, Ekhard K H

    2014-07-01

    Acoustic emission has been measured and statistical characteristics analyzed during the stress-induced collapse of porous berlinite, AlPO4, containing up to 50 vol% porosity. Stress collapse occurs in a series of individual events (avalanches), and each avalanche leads to a jerk in sample compression with corresponding acoustic emission (AE) signals. The distribution of AE avalanche energies can be approximately described by a power law p(E)dE = E(-ε)dE (ε ~ 1.8) over a large stress interval. We observed several collapse mechanisms whereby less porous minerals show the superposition of independent jerks, which were not related to the major collapse at the failure stress. In highly porous berlinite (40% and 50%) an increase of energy emission occurred near the failure point. In contrast, the less porous samples did not show such an increase in energy emission. Instead, in the near vicinity of the main failure point they showed a reduction in the energy exponent to ~ 1.4, which is consistent with the value reported for compressed porous systems displaying critical behavior. This suggests that a critical avalanche regime with a lack of precursor events occurs. In this case, all preceding large events were 'false alarms' and unrelated to the main failure event. Our results identify a method to use pico-seismicity detection of foreshocks to warn of mine collapse before the main failure (the collapse) occurs, which can be applied to highly porous materials only. PMID:24919038

  12. Gender Bias in Predictions of Boys' Academic Failure

    ERIC Educational Resources Information Center

    Van Duzer, Eric

    2006-01-01

    A study was conducted to examine the gendered expectations of academic failure among 52 students preparing to enter a teacher-credentialing program at a California state university. As part of a technology class, student pairs completed a database and mail-merge assignment in which they named three imaginary students and identified one of the…

  13. Rational Temporal Predictions Can Underlie Apparent Failures to Delay Gratification

    ERIC Educational Resources Information Center

    McGuire, Joseph T.; Kable, Joseph W.

    2013-01-01

    An important category of seemingly maladaptive decisions involves failure to postpone gratification. A person pursuing a desirable long-run outcome may abandon it in favor of a short-run alternative that has been available all along. Here we present a theoretical framework in which this seemingly irrational behavior emerges from stable preferences…

  14. Experiences of patients with abnormal extubation of PICC tubes: a qualitative study

    PubMed Central

    Gao, Wei; Luan, Xiao-Rong; Sun, Yuan-Yuan; Zhang, Ming; Li, Kan; Li, Qiu-Huan; Zhang, Hong; Liu, De-Shan

    2015-01-01

    Objective: To explore the experiences of patients with abnormal extubation of PICC tubes. Methods: Using phenomenological research methods, 15 cases of patients with abnormal extubation of PICC tubes were enrolled in semi-structured interviews. Data were analyzed by Nancy’s phenomenological procedure. Results: After abnormal extubation, patients exhibited conflicting complicated mood which combined negative experience and positive experience. Negative experience was mainly for complaint, helpless, worry and fear. Positive experience was mainly for relief and peace of mind. Conclusions: Patients with abnormal extubation often possessed negative experience. So nursing staff should be suggested to communicate with patients before extubation in order to reduce the dispute between nurses and patients. At the same time, we should summarize and analyze the reasons and factors for abnormal extubation, and take targeted intervention measures in clinical to ensure the safety and effectiveness of PICC extubation. PMID:26770567

  15. Effect of various approximations on predicted progressive failure in plain weave composites

    NASA Technical Reports Server (NTRS)

    Whitcomb, John; Srirengan, Kanthikannan

    1995-01-01

    Three-dimensional finite element analysis was used to simulate progressive failure of a plain weave composite subjected to in-plane extension. The loading was parallel to one of the tow directions. The effects of various characteristics of the finite element model on predicted behavior were examined. The predicted behavior was found to be sensitive to quadrature order, mesh refinement, and the material degradation model. Also the sensitivity of the predictions to the tow waviness was studied. The predicted strength decreased considerably with increased waviness. More numerical studies and comparisons with experimental data are needed to establish reliable guidelines for accurate progressive failure prediction.

  16. Predicting Time Series Outputs and Time-to-Failure for an Aircraft Controller Using Bayesian Modeling

    NASA Technical Reports Server (NTRS)

    He, Yuning

    2015-01-01

    Safety of unmanned aerial systems (UAS) is paramount, but the large number of dynamically changing controller parameters makes it hard to determine if the system is currently stable, and the time before loss of control if not. We propose a hierarchical statistical model using Treed Gaussian Processes to predict (i) whether a flight will be stable (success) or become unstable (failure), (ii) the time-to-failure if unstable, and (iii) time series outputs for flight variables. We first classify the current flight input into success or failure types, and then use separate models for each class to predict the time-to-failure and time series outputs. As different inputs may cause failures at different times, we have to model variable length output curves. We use a basis representation for curves and learn the mappings from input to basis coefficients. We demonstrate the effectiveness of our prediction methods on a NASA neuro-adaptive flight control system.

  17. Patient Characteristics Predicting Readmission Among Individuals Hospitalized for Heart Failure

    PubMed Central

    O'Connor, Melissa; Murtaugh, Christopher M.; Shah, Shivani; Barrón-Vaya, Yolanda; Bowles, Kathryn H.; Peng, Timothy R.; Zhu, Carolyn W.; Feldman, Penny H.

    2015-01-01

    Heart failure is difficult to manage and increasingly common with many individuals experiencing frequent hospitalizations. Little is known about patient factors consistently associated with hospital readmission. A literature review was conducted to identify heart failure patient characteristics, measured before discharge, that contribute to variation in hospital readmission rates. Database searches yielded 950 potential articles, of which 34 studies met inclusion criteria. Patient characteristics generally have a very modest effect on all-cause or heart failure–related readmission within 7 to 180 days of index hospital discharge. A range of cardiac diseases and other comorbidities only minimally increase readmission rates. No single patient characteristic stands out as a key contributor across multiple studies underscoring the challenge of developing successful interventions to reduce readmissions. Interventions may need to be general in design with the specific intervention depending on each patient's unique clinical profile. PMID:26180045

  18. Method of Testing and Predicting Failures of Electronic Mechanical Systems

    NASA Technical Reports Server (NTRS)

    Iverson, David L.; Patterson-Hine, Frances A.

    1996-01-01

    A method employing a knowledge base of human expertise comprising a reliability model analysis implemented for diagnostic routines is disclosed. The reliability analysis comprises digraph models that determine target events created by hardware failures human actions, and other factors affecting the system operation. The reliability analysis contains a wealth of human expertise information that is used to build automatic diagnostic routines and which provides a knowledge base that can be used to solve other artificial intelligence problems.

  19. Real-time forecasting and predictability of catastrophic failure events: from rock failure to volcanoes and earthquakes

    NASA Astrophysics Data System (ADS)

    Main, I. G.; Bell, A. F.; Naylor, M.; Atkinson, M.; Filguera, R.; Meredith, P. G.; Brantut, N.

    2012-12-01

    Accurate prediction of catastrophic brittle failure in rocks and in the Earth presents a significant challenge on theoretical and practical grounds. The governing equations are not known precisely, but are known to produce highly non-linear behavior similar to those of near-critical dynamical systems, with a large and irreducible stochastic component due to material heterogeneity. In a laboratory setting mechanical, hydraulic and rock physical properties are known to change in systematic ways prior to catastrophic failure, often with significant non-Gaussian fluctuations about the mean signal at a given time, for example in the rate of remotely-sensed acoustic emissions. The effectiveness of such signals in real-time forecasting has never been tested before in a controlled laboratory setting, and previous work has often been qualitative in nature, and subject to retrospective selection bias, though it has often been invoked as a basis in forecasting natural hazard events such as volcanoes and earthquakes. Here we describe a collaborative experiment in real-time data assimilation to explore the limits of predictability of rock failure in a best-case scenario. Data are streamed from a remote rock deformation laboratory to a user-friendly portal, where several proposed physical/stochastic models can be analysed in parallel in real time, using a variety of statistical fitting techniques, including least squares regression, maximum likelihood fitting, Markov-chain Monte-Carlo and Bayesian analysis. The results are posted and regularly updated on the web site prior to catastrophic failure, to ensure a true and and verifiable prospective test of forecasting power. Preliminary tests on synthetic data with known non-Gaussian statistics shows how forecasting power is likely to evolve in the live experiments. In general the predicted failure time does converge on the real failure time, illustrating the bias associated with the 'benefit of hindsight' in retrospective analyses

  20. Multiscale Model Predicts Tissue-Level Failure From Collagen Fiber-Level Damage

    PubMed Central

    Hadi, Mohammad F.; Sander, Edward A.; Barocas, Victor H.

    2013-01-01

    Excessive tissue-level forces communicated to the microstructure and extracellular matrix of soft tissues can lead to damage and failure through poorly understood physical processes that are multiscale in nature. In this work, we propose a multiscale mechanical model for the failure of collagenous soft tissues that incorporates spatial heterogeneity in the microstructure and links the failure of discrete collagen fibers to the material response of the tissue. The model, which is based on experimental failure data derived from different collagen gel geometries, was able to predict the mechanical response and failure of type I collagen gels, and it demonstrated that a fiber-based rule (at the micrometer scale) for discrete failure can strongly shape the macroscale failure response of the gel (at the millimeter scale). The model may be a useful tool in predicting the macroscale failure conditions for soft tissues and engineered tissue analogs. In addition, the multiscale model provides a framework for the study of failure in complex fiber-based mechanical systems in general. PMID:22938372

  1. Peridynamics for failure and residual strength prediction of fiber-reinforced composites

    NASA Astrophysics Data System (ADS)

    Colavito, Kyle

    Peridynamics is a reformulation of classical continuum mechanics that utilizes integral equations in place of partial differential equations to remove the difficulty in handling discontinuities, such as cracks or interfaces, within a body. Damage is included within the constitutive model; initiation and propagation can occur without resorting to special crack growth criteria necessary in other commonly utilized approaches. Predicting damage and residual strengths of composite materials involves capturing complex, distinct and progressive failure modes. The peridynamic laminate theory correctly predicts the load redistribution in general laminate layups in the presence of complex failure modes through the use of multiple interaction types. This study presents two approaches to obtain the critical peridynamic failure parameters necessary to capture the residual strength of a composite structure. The validity of both approaches is first demonstrated by considering the residual strength of isotropic materials. The peridynamic theory is used to predict the crack growth and final failure load in both a diagonally loaded square plate with a center crack, as well as a four-point shear specimen subjected to asymmetric loading. This study also establishes the validity of each approach by considering composite laminate specimens in which each failure mode is isolated. Finally, the failure loads and final failure modes are predicted in a laminate with various hole diameters subjected to tensile and compressive loads.

  2. Young Children's Predictions of Illness: Failure To Recognize Probabilistic Causation.

    ERIC Educational Resources Information Center

    Kalish, Charles W.

    1998-01-01

    Three experiments examined whether preschoolers viewed outcomes of familiar causes of illness as definite or probabilistic. Findings indicated that children judged that a common cause would affect all group members the same, and believed they could definitely predict illness outcomes in a single case, contrasting with adults' variable and…

  3. A New Method for Extubation: Comparison between Conventional and New Methods

    PubMed Central

    Yousefshahi, Fardin; Barkhordari, Khosro; Movafegh, Ali; Tavakoli, Vida; Paknejad, Omalbanin; Bina, Payvand; Yousefshahi, Hadi; Sheikh Fathollahi, Mahmood

    2012-01-01

    Background: Extubation is associated with the risk of complications such as accumulated secretion above the endotracheal tube cuff, eventual atelectasia following a reduction in pulmonary volumes because of a lack of physiological positive end expiratory pressure, and intra-tracheal suction. In order to reduce these complications, and, based on basic physiological principles, a new practical extubation method is presented in this article. Methods: The study was designed as a six-month prospective cross-sectional clinical trial. Two hundred fifty-seven patients undergoing coronary artery bypass grafting (CABG) were divided into two groups based on their scheduled surgery time. The first group underwent the conventional extubation method, while the other group was extubated according to a new described method. Arterial blood gas (ABG) analysis results before and after extubation were compared between the two groups to find the effect of the extubation method on the ABG parameters and the oxygenation profile. Results: In all time intervals, the partial pressure of oxygen in arterial blood / fraction of inspired oxygen (PaO2/FiO2) ratio in the new method group patients was improved compared to that in the conventional method; some differences, like PaO2/FiO2 four hours after extubation, were statistically significant, however (p value=0.0063). Conclusion: The new extubation method improved some respiratory parameters and thus attenuated oxygenation complications and amplified oxygenation after extubation. PMID:23304181

  4. Role of dexmedetomidine in early extubation of the intensive care unit patients

    PubMed Central

    Gupta, Shikha; Singh, Dupinder; Sood, Dinesh; Kathuria, Suneet

    2015-01-01

    Background and Aims: Patients on ventilatory support in intensive care unit (ICU) require sedation and analgesia to facilitate mechanical ventilation and endotracheal tube tolerance. The selection of the agent should be such that it does not interfere with the early extubation of the patients. We compared the efficacy of dexmedetomidine with midazolam to facilitate extubation of patients from mechanical ventilation in terms of the sedative properties, cardiovascular responses, ventilation, and extubation characteristics and safety profile. Materials and Methods: A total of 40 adult, mechanically ventilated patients of either sex, aged 18-60 years, meeting the standard criteria for weaning, randomized into 2 groups of 20 patients each, received intravenous infusion of dexmedetomidine (0.2-0.7 mcg/kg/h) or midazolam (0.04-0.2 mg/kg/h) as needed for Ramsay sedation scale 2-4. Extubation following standard extubation protocol was done. Time for extubation and vital parameters were regularly recorded. Results: The time to extubation in the dexmedetomidine group was significantly lower than in the midazolam group. Heart rate and blood pressure was significantly lower in dexmedetomidine group than the midazolam group at most of the times. Conclusions: Dexmedetomidine has clinically relevant benefits compared with midazolam in facilitating extubation due to its shorter time to extubation, more hemodynamic stability, easy arousability, and lack of respiratory depression. PMID:25788780

  5. Predicting the Failure Behavior of Textile Composite Laminates by Using a Multi-Scale Correlating Approach

    NASA Astrophysics Data System (ADS)

    Deng, Yan; Chen, Xiuhua; Wang, Hai

    2015-12-01

    This paper investigates the elastic and failure behavior of textile composite laminates by using an analytical multi-scale correlating approach. The analyses are performed under the four scale levels, i.e. the laminate scale, representative unit cell (RUC) scale, tow architecture scale and fiber/matrix scale levels. The correlation between different scales is derived based on the continuum mechanics and homogenization method from which the stress and strain fields in multiple scales can be obtained concurrently. Effective modulus and ultimate failure strengths of different textile composite (plain weave, twill weave and satin weave) laminates are predicted solely from the corresponding constituent properties, braid geometrical parameters and lay-up. The damage and failure mechanisms at the constituent level are also determined by the micromechanical failure criteria. All the predicted results compare favorably with available experimental data. Parametric studies are also performed to examine the effect of various mechanical and geometrical parameters on the resulting mechanical properties.

  6. A new method for failure prediction of SR-200 beryllium sheet structures

    NASA Technical Reports Server (NTRS)

    Papados, P. P.; Roschke, P. N.

    1994-01-01

    Contemporary applications of failure criteria frequently incorporate two-dimensional or simplified three-dimensional methodologies for prediction of stresses. Motivation behind the development of a new multi-dimensional failure criterion is due mainly to the lack of a sufficiently accurate mathematical tool that accounts for the behavior of brittle material with anisotropic properties. Such a criterion should be able to provide a reliable maximum load estimate so that design of the structure is not penalized in terms of excessive weight requirements. The failure criterion developed is represented by a fracture surface in a six-dimensional stress space. The criterion is applied for failure prediction of SR-200 beryllium sheet structures, a non-homogeneous orthotropic material used widely in space applications. Two experiments are used to verify the criterion.

  7. Prediction of acute renal failure following soft-tissue injury using the venous bicarbonate concentration.

    PubMed

    Muckart, D J; Moodley, M; Naidu, A G; Reddy, A D; Meineke, K R

    1992-12-01

    Sixty-four patients with soft-tissue injuries were studied prospectively to determine whether an initial venous bicarbonate concentration (VBC) of less than 17 mmol/L would predict the development of myoglobin-induced acute renal failure. The VBC was > 17 mmol/L in 59 patients, seven of whom had myoglobinuria. All recovered without renal complications. The remaining five patients all had VBC < 17 mmol/L and four had myoglobinuria. Acute renal failure developed in four patients (p < 0.001). The VBC on hospital arrival was the most accurate predictor of these patients' risk for the development of acute renal failure following soft-tissue injury. PMID:1474620

  8. Methodology to predict the number of forced outages due to creep failure

    SciTech Connect

    Palermo, J.V. Jr.

    1996-12-31

    All alloy metals at a temperature above 950 degrees Fahrenheit experience creep damage. Creep failures in boiler tubes usually begin after 25 to 40 years of operation. Since creep damage is irreversible, the only remedy is to replace the tube sections. By predicting the number of failures per year, the utility can make the best economic decision concerning tube replacement. This paper describes a methodology to calculate the number of forced outages per yea due to creep failures. This methodology is particularly useful to utilities that have boilers that have at least 25 years of operation.

  9. Endothelial Cell Density to Predict Endothelial Graft Failure After Penetrating Keratoplasty

    PubMed Central

    Lass, Jonathan H.; Sugar, Alan; Benetz, Beth Ann; Beck, Roy W.; Dontchev, Mariya; Gal, Robin L.; Kollman, Craig; Gross, Robert; Heck, Ellen; Holland, Edward J.; Mannis, Mark J.; Raber, Irving; Stark, Walter; Stulting, R. Doyle

    2010-01-01

    Objective To determine whether preoperative and/or postoperative central endothelial cell density (ECD) and its rate of decline postoperatively are predictive of graft failure caused by endothelial decompensation following penetrating keratoplasty to treat a moderate-risk condition, principally, Fuchs dystrophy or pseudophakic corneal edema. Methods In a subset of Cornea Donor Study participants, a central reading center determined preoperative and postoperative ECD from available specular images for 17 grafts that failed because of endothelial decompensation and 483 grafts that did not fail. Results Preoperative ECD was not predictive of graft failure caused by endothelial decompensation (P = .91). However, the 6-month ECD was predictive of subsequent failure (P < .001). Among those that had not failed within the first 6 months, the 5-year cumulative incidence (±95% confidence interval) of failure was 13% (±12%) for the 33 participants with a 6-month ECD of less than 1700 cells/mm2 vs 2%(±3%) for the 137 participants with a 6-monthECDof 2500 cells/mm2 or higher. After 5 years’ follow-up, 40 of 277 participants (14%) with a clear graft had an ECD below 500 cells/mm2. Conclusions Preoperative ECD is unrelated to graft failure from endothelial decompensation, whereas there is a strong correlation of ECD at 6 months with graft failure from endothelial decompensation. A graft can remain clear after 5 years even when the ECD is below 500 cells/mm2. PMID:20065219

  10. Automated failure mode effects and criticality analyses for reliability prediction of multibody mechanical systems

    NASA Astrophysics Data System (ADS)

    Chiang, Alex Chih-Chien

    Reliability is important to ensure both serviceability and safety of a mechanical system. A method for simulation-based Failure Mode Effects and Criticality Analysis (FMECA) for reliability prediction of mechanical systems is presented. This approach integrates recursive formulation for dynamic analysis, failure criteria for failure determination, graphics techniques for collision detection, and new techniques for modifying dynamics model during the simulation. The automated FMECA method developed consists of three libraries and a graphics collision detection technique. First, a library of mechanical failure modes is created using cause-effect relationships for mechanical failure modes. Second, a library of component failure criteria is constructed by collecting different material test data. Third, a library of simulation algorithms and supporting techniques is built by developing simulation technologies to perform FMECA for mechanical failure modes. In addition, the automated FMECA method uses the developed graphics software VDS for collision detection. Finally, this approach is used to investigate the consequences of four failure modes of a vehicle system. The difficulty in formulating mathematical expressions for a damaged mechanical system is resolved by manipulating the number of cut joint constraints and generalized coordinates to implicitly update the original system topology. Formulations for virtual joints are derived, as well as other new techniques to permit multiple failures during a dynamic simulation. A near-minimum set of generalized coordinates is thus retained throughout the dynamic simulation. Four general-purpose dynamics codes are implemented and effects of four mechanical failure modes of a mechanical system are investigated; suspension failure, joint degradation and breakage, joint stiction, and component yielding and breakage. Failure histories as well as Mean Time Between Failure (MTBF) and Mean Time To Failure (MTTF) are obtained. The

  11. Impact and Challenges of a Policy Change to Early Track Extubation in the Operating Room for Fontan.

    PubMed

    Kawaguchi, Atsushi; Liu, Qi; Coquet, Sean; Yasui, Yutaka; Cave, Dominic

    2016-08-01

    hemodynamic instability in the pre-policy-change era (6/39, 15.4 %) and excessive bleeding or respiratory etiologies in the post-policy-change era (10/88, 11.4 %). Significant reduction of PICU length of stay was achieved without any evidence of worsening of patient outcomes. RCA suggests watchful observations with respect to bleeding and respiratory etiologies are the key to prevent failure of extubation in the current practice. PMID:27160099

  12. An investigation of gear mesh failure prediction techniques. M.S. Thesis - Cleveland State Univ.

    NASA Technical Reports Server (NTRS)

    Zakrajsek, James J.

    1989-01-01

    A study was performed in which several gear failure prediction methods were investigated and applied to experimental data from a gear fatigue test apparatus. The primary objective was to provide a baseline understanding of the prediction methods and to evaluate their diagnostic capabilities. The methods investigated use the signal average in both the time and frequency domain to detect gear failure. Data from eleven gear fatigue tests were recorded at periodic time intervals as the gears were run from initiation to failure. Four major failure modes, consisting of heavy wear, tooth breakage, single pits, and distributed pitting were observed among the failed gears. Results show that the prediction methods were able to detect only those gear failures which involved heavy wear or distributed pitting. None of the methods could predict fatigue cracks, which resulted in tooth breakage, or single pits. It is suspected that the fatigue cracks were not detected because of limitations in data acquisition rather than in methodology. Additionally, the frequency response between the gear shaft and the transducer was found to significantly affect the vibration signal. The specific frequencies affected were filtered out of the signal average prior to application of the methods.

  13. Feasibility of using adaptive logic networks to predict compressor unit failure

    SciTech Connect

    Armstrong, W.W.; Chungying Chu; Thomas, M.M.

    1995-12-31

    In this feasibility study, an adaptive logic network (ALN) was trained to predict failures of turbine-driven compressor units using a large database of measurements. No expert knowledge about compressor systems was involved. The predictions used only the statistical properties of the measurements and the indications of failure types. A fuzzy set was used to model measurements typical of normal operation. It was constrained by a requirement imposed during ALN training, that it should have a shape similar to a Gaussian density, more precisely, that its logarithm should be convex-up. Initial results obtained using this approach to knowledge discovery in the database were encouraging.

  14. [Accidental extubation in a pediatric intensive care unit].

    PubMed

    Piva, J P; Amantéa, S; Luchese, S; Giugno, K; Maia, T R; Einloft, L

    1995-01-01

    It is an on-going practice in the pediatric ICUs to obtain and to maintain a working artificial airway. Nevertheless this procedure bears not infrequent risks of accidental extubation (AE) which ranges in several services from 0.9 to 3.3 for each 100 days of intubation. The risk factors that are involved in AE are related to: sedation level, age-group, intubation path, and others. The purpose of the authors in this article was to observe the incidence of AE in their service and to compare the relative risk in the rate of AE among orotracheal and nasotracheal intubation population. A prospective study was taken during six months, in which every patients with artificial airway admitted at the PICU of the Santo Antonio Hospital in Porto Alegre (Brazil) was included except those with tracheostomy. The total number of cases were 673 patients-day with artificial airway, with an average of 3.7 patients with tracheal tube per day. In the period there were 18 AE, with a rate of 2.7 AE/ 100 days. The incidence rate of AE in the orotracheal group was 3.1% and 1.6% in the nasotracheal group with no statistically significant difference (p=0.6). The authors concluded that the pathway of intubation in their study does not carry any additional risk in the incidence of accidental extubation. PMID:14689021

  15. Multiple immune deviations predictive for IVF failure as possible markers for IVIG therapy.

    PubMed

    Chernyshov, Viktor P; Dons'koi, Boris V; Sudoma, Iryna O; Goncharova, Yana O

    2016-08-01

    Recently we have shown that immune deviations (ID) may predict IVF failure. Benefit from IVIG therapy was observed in 115 women with repeated IVF failure according to proposed multiple ID that appeared unfavorable for implantation and live birth. Group of 123 women with repeated IVF failure without IVIG therapy was compared with former group. Immune phenotype and NK activity of peripheral blood lymphocytes were studied by flow cytometry. Potentially predictive for IVF failure ID included elevated expression of CD56, CD158a in T lymphocytes, decreased levels of CD4T lymphocytes, up-regulated expression of HLA DR in CD8+ T cells and NK cells, elevated number of NK cells and increased NK cytotoxicity, increased or decreased expression of CD158a and CD8 in NK cells. Three or more ID may predict implantation failure to a greater degree than one or two ID. In women receiving IVIG in subgroups with 0-1 and 2 ID, there was no increase in implantation rate (IR) and live birth rate (LBR) after IVIG in comparison with patients with the same number of ID but without IVIG correction. After IVIG therapy decreased IR and LBR were restored in women with three or more immune deviations. Multiple immune deviations indicate IVF patients who may benefit from IVIG therapy. IVIG seems to convert "unfavorable" immune phenotype to "favorable" one. PMID:27233364

  16. Predicting age of ovarian failure after radiation to a field that includes the ovaries

    SciTech Connect

    Wallace, W. Hamish B. . E-mail: Hamish.Wallace@ed.ac.uk; Thomson, Angela B.; Saran, Frank; Kelsey, Tom W.

    2005-07-01

    Purpose: To predict the age at which ovarian failure is likely to develop after radiation to a field that includes the ovary in women treated for cancer. Methods and Materials: Modern computed tomography radiotherapy planning allows determination of the effective dose of radiation received by the ovaries. Together with our recent assessment of the radiosensitivity of the human oocyte, the effective surviving fraction of primordial oocytes can be determined and the age of ovarian failure, with 95% confidence limits, predicted for any given dose of radiotherapy. Results: The effective sterilizing dose (ESD: dose of fractionated radiotherapy [Gy] at which premature ovarian failure occurs immediately after treatment in 97.5% of patients) decreases with increasing age at treatment. ESD at birth is 20.3 Gy; at 10 years 18.4 Gy, at 20 years 16.5 Gy, and at 30 years 14.3 Gy. We have calculated 95% confidence limits for age at premature ovarian failure for estimated radiation doses to the ovary from 1 Gy to the ESD from birth to 50 years. Conclusions: We report the first model to reliably predict the age of ovarian failure after treatment with a known dose of radiotherapy. Clinical application of this model will enable physicians to counsel women on their reproductive potential following successful treatment.

  17. Predicting Outcomes of Hospitalization for Heart Failure Using Logistic Regression and Knowledge Discovery Methods

    PubMed Central

    Phillips, Kirk T.; Street, W. Nick

    2005-01-01

    The purpose of this study is to determine the best prediction of heart failure outcomes, resulting from two methods -- standard epidemiologic analysis with logistic regression and knowledge discovery with supervised learning/data mining. Heart failure was chosen for this study as it exhibits higher prevalence and cost of treatment than most other hospitalized diseases. The prevalence of heart failure has exceeded 4 million cases in the U.S.. Findings of this study should be useful for the design of quality improvement initiatives, as particular aspects of patient comorbidity and treatment are found to be associated with mortality. This is also a proof of concept study, considering the feasibility of emerging health informatics methods of data mining in conjunction with or in lieu of traditional logistic regression methods of prediction. Findings may also support the design of decision support systems and quality improvement programming for other diseases. PMID:16779367

  18. Prediction of Composite Pressure Vessel Failure Location using Fiber Bragg Grating Sensors

    NASA Technical Reports Server (NTRS)

    Kreger, Steven T.; Taylor, F. Tad; Ortyl, Nicholas E.; Grant, Joseph

    2006-01-01

    Ten composite pressure vessels were instrumented with fiber Bragg grating sensors in order to assess the strain levels of the vessel under various loading conditions. This paper and presentation will discuss the testing methodology, the test results, compare the testing results to the analytical model, and present a possible methodology for predicting the failure location and strain level of composite pressure vessels.

  19. Prediction of Brittle Failure for TBM Tunnels in Anisotropic Rock: A Case Study from Northern Norway

    NASA Astrophysics Data System (ADS)

    Dammyr, Øyvind

    2016-06-01

    Prediction of spalling and rock burst is especially important for hard rock TBM tunneling, because failure can have larger impact than in a drill and blast tunnel and ultimately threaten excavation feasibility. The majority of research on brittle failure has focused on rock types with isotropic behavior. This paper gives a review of existing theory and its application before a 3.5-m-diameter TBM tunnel in foliated granitic gneiss is used as a case to study brittle failure characteristics of anisotropic rock. Important aspects that should be considered in order to predict brittle failure in anisotropic rock are highlighted. Foliation is responsible for considerable strength anisotropy and is believed to influence the preferred side of v-shaped notch development in the investigated tunnel. Prediction methods such as the semi- empirical criterion, the Hoek- Brown brittle parameters, and the non-linear damage initiation and spalling limit method give reliable results; but only as long as the angle between compression axis and foliation in uniaxial compressive tests is relevant, dependent on the relation between tunnel trend/plunge, strike/dip of foliation, and tunnel boundary stresses. It is further demonstrated that local in situ stress variations, for example, due to the presence of discontinuities, can have profound impact on failure predictions. Other carefully documented case studies into the brittle failure nature of rock, in particular anisotropic rock, are encouraged in order to expand the existing and relatively small database. This will be valuable for future TBM planning and construction stages in highly stressed brittle anisotropic rock.

  20. Noninvasive Failure Load Prediction of Vertebrae with Simulated Lytic Defects and Biomaterial Augmentation.

    PubMed

    Giambini, Hugo; Fang, Zhong; Zeng, Heng; Camp, Jon J; Yaszemski, Michael J; Lu, Lichun

    2016-08-01

    The spine is the most common site for secondary bone metastases, and clinical management for fractures is based on size and geometry of the defect. About 75% of the bone needs to be damaged before lesions are detectable, so clinical tools should measure changes in both geometry and material properties. We have developed an automated, user-friendly, Spine Cancer Assessment (SCA) image-based analysis method that builds on a platform designed for clinical practice providing failure characteristics of vertebrae. The objectives of this study were to (1) validate SCA predictions with experimental failure load outcomes; (2) evaluate the planning capabilities for prophylactic vertebroplasty procedures; and (3) investigate the effect of computed tomography (CT) protocols on predicted failure loads. Twenty-one vertebrae were randomly divided into two groups: (1) simulated defect without treatment (negative control) [n = 9] and (2) with treatment [n = 12]. Defects were created and a polymeric biomaterial was injected into the vertebrae in the treated-defect group. Spines were scanned, reconstructed with two algorithms, and analyzed for fracture loads. To virtually plan for prophylactic intervention, vertebrae with empty lesions were simulated to be augmented with either poly(methyl methacrylate) (PMMA) or a novel bone replacement copolymer, poly(propylene fumarate-co-caprolactone) [P(PF-co-CL)]. Axial rigidities were calculated from the CT images. Failure loads, determined from the cross section with the lowest axial rigidity, were compared with experimental values. Predicted loads correlated well with experimental outcomes (R(2) = 0.73, p < 0.0001). Predictions from negative control specimens highly correlated with measured values (R(2) = 0.90, p < 0.0001). Although a similar correlation was obtained using both algorithms, the smooth reconstruction (B30) tended to underestimate predicted failure loads by ∼50% compared with the ∼10% underestimate

  1. Identifying the necessary and sufficient number of risk factors for predicting academic failure.

    PubMed

    Lucio, Robert; Hunt, Elizabeth; Bornovalova, Marina

    2012-03-01

    Identifying the point at which individuals become at risk for academic failure (grade point average [GPA] < 2.0) involves an understanding of which and how many factors contribute to poor outcomes. School-related factors appear to be among the many factors that significantly impact academic success or failure. This study focused on 12 school-related factors. Using a thorough 5-step process, we identified which unique risk factors place one at risk for academic failure. Academic engagement, academic expectations, academic self-efficacy, homework completion, school relevance, school safety, teacher relationships (positive relationship), grade retention, school mobility, and school misbehaviors (negative relationship) were uniquely related to GPA even after controlling for all relevant covariates. Next, a receiver operating characteristic curve was used to determine a cutoff point for determining how many risk factors predict academic failure (GPA < 2.0). Results yielded a cutoff point of 2 risk factors for predicting academic failure, which provides a way for early identification of individuals who are at risk. Further implications of these findings are discussed. PMID:22182300

  2. Modeling Stress Strain Relationships and Predicting Failure Probabilities For Graphite Core Components

    SciTech Connect

    Duffy, Stephen

    2013-09-09

    This project will implement inelastic constitutive models that will yield the requisite stress-strain information necessary for graphite component design. Accurate knowledge of stress states (both elastic and inelastic) is required to assess how close a nuclear core component is to failure. Strain states are needed to assess deformations in order to ascertain serviceability issues relating to failure, e.g., whether too much shrinkage has taken place for the core to function properly. Failure probabilities, as opposed to safety factors, are required in order to capture the bariability in failure strength in tensile regimes. The current stress state is used to predict the probability of failure. Stochastic failure models will be developed that can accommodate possible material anisotropy. This work will also model material damage (i.e., degradation of mechanical properties) due to radiation exposure. The team will design tools for components fabricated from nuclear graphite. These tools must readily interact with finite element software--in particular, COMSOL, the software algorithm currently being utilized by the Idaho National Laboratory. For the eleastic response of graphite, the team will adopt anisotropic stress-strain relationships available in COMSO. Data from the literature will be utilized to characterize the appropriate elastic material constants.

  3. Finite-Element Damage Analysis for Failure Prediction of Warm Hydroforming Tubular Magnesium Alloy Sheets

    NASA Astrophysics Data System (ADS)

    Chan, L. C.

    2015-02-01

    Bursting has been recognized by many researchers as a common failure mode in the tube hydroforming (THF) process. Therefore, the prediction of the bursting that occurs during the THF process has received much attention in the manufacturing industry and research institutions. Effective prediction of failure can reduce significantly the number of practical trials required to obtain the desired products. However, the prediction of such bursting for magnesium-based (Mg-based) alloy can be a rather difficult issue due to the nonlinear nature of the model used to describe the deformation process at elevated temperatures. This article proposes the failure prediction of Mg-based alloy during the THF process at elevated temperatures by using the Marciniak and Kuczynski (M-K) model. In the study, numerical simulation was performed by the finite-element (FE) analysis commercial software ABAQUS, with the material model assumed to be elastic-plastic. The constitutive model of Mg-based alloy (AZ31B) tube at different elevated temperatures, for instance at 493 K, 523 K, and 553 K, was represented by the Fields-Backofen constitutive equation, with material parameters collected from relevant literature. Accordingly, THF experiments were conducted by a self-developed thermal hydroforming attachment coping with an existing hydraulic power press to validate the prediction of the numerical results. The geometrical parameters for the specimen tubes used in the experiment were Ø22 × 150 mm, and 1.5 mm wall thickness. The numerical and the experimental results were demonstrated to have good agreement. The results of the simulation and the THF experiments imply that the model proposed in this study can provide a reliable prediction of the failure analysis of the Mg-based alloy tube during the THF process.

  4. Venovenous extracorporeal membrane oxygenation in adult respiratory failure: Scores for mortality prediction.

    PubMed

    Hsin, Chun-Hsien; Wu, Meng-Yu; Huang, Chung-Chi; Kao, Kuo-Chin; Lin, Pyng-Jing

    2016-06-01

    Despite a potentially effective therapy for adult respiratory failure, a general agreement on venovenous extracorporeal membrane oxygenation (VV-ECMO) has not been reached among institutions due to its invasiveness and high resource usage. To establish consensus on the timing of intervention, large ECMO organizations have published the respiratory extracorporeal membrane oxygenation survival prediction (RESP) score and the ECMOnet score, which allow users to predict hospital mortality for candidates with their pre-ECMO presentations. This study was aimed to test the predictive powers of these published scores in a medium-sized cohort enrolling adults treated with VV-ECMO for acute respiratory failure, and develop an institutional prediction model under the framework of the 3 scores if a superior predictive power could be achieved. This retrospective study included 107 adults who received VV-ECMO for severe acute respiratory failure (a PaO2/FiO2 ratio <70 mm Hg) in a tertiary referral center from 2007 to 2015. Essential demographic and clinical data were collected to calculate the RESP score, the ECMOnet score, and the sequential organ failure assessment (SOFA) score before VV-ECMO. The predictive power of hospital mortality of each score was presented as the area under receiver-operating characteristic curve (AUROC). The multivariate logistic regression was used to develop an institutional prediction model. The surviving to discharge rate was 55% (n = 59). All of the 3 published scores had a real but poor predictive power of hospital mortality in this study. The AUROCs of RESP score, ECMOnet score, and SOFA score were 0.662 (P = 0.004), 0.616 (P = 0.04), and 0.667 (P = 0.003), respectively. An institutional prediction model was established from these score parameters and presented as follows: hospital mortality (Y) = -3.173 + 0.208 × (pre-ECMO SOFA score) + 0.148 × (pre-ECMO mechanical ventilation day) + 1.021

  5. Prediction of failure envelopes of composite tubes subjected to biaxial loadings

    NASA Astrophysics Data System (ADS)

    Gargiulo, C.; Marchetti, M.; Rizzo, A.

    1996-09-01

    Practical cylindrical structures including pressure vessels, pipes, drive shafts and rochet motors are usually subjected to complex loads involving biaxial or triaxial stress systems. In particular, filamentary composite vessels are used in applications of Space Shuttle tankage, as well as for the storage of fluids in various commercial applications. The object of this work is to provide numerical and experiment data on the strength of filament wound carbon fibre reinforced epoxy resin thin tubes under biaxial loading conditions. Internal or external pressure and axial loads are applied simultaneously to produce a variety of biaxial stress conditions. The effects of the winding angle of the fibre reinforcements on the failure loads of the pipes have been examined. Finite elements and thin shell analysis have been applied to the problem using different failure criteria in order to predict the specimen's failure for a comparison with experimental results.

  6. Predicting Renal Failure Progression in Chronic Kidney Disease Using Integrated Intelligent Fuzzy Expert System

    PubMed Central

    Norouzi, Jamshid; Mirbagheri, Seyed Ahmad; Mazdeh, Mitra Mahdavi; Hosseini, Seyed Ahmad

    2016-01-01

    Background. Chronic kidney disease (CKD) is a covert disease. Accurate prediction of CKD progression over time is necessary for reducing its costs and mortality rates. The present study proposes an adaptive neurofuzzy inference system (ANFIS) for predicting the renal failure timeframe of CKD based on real clinical data. Methods. This study used 10-year clinical records of newly diagnosed CKD patients. The threshold value of 15 cc/kg/min/1.73 m2 of glomerular filtration rate (GFR) was used as the marker of renal failure. A Takagi-Sugeno type ANFIS model was used to predict GFR values. Variables of age, sex, weight, underlying diseases, diastolic blood pressure, creatinine, calcium, phosphorus, uric acid, and GFR were initially selected for the predicting model. Results. Weight, diastolic blood pressure, diabetes mellitus as underlying disease, and current GFR(t) showed significant correlation with GFRs and were selected as the inputs of model. The comparisons of the predicted values with the real data showed that the ANFIS model could accurately estimate GFR variations in all sequential periods (Normalized Mean Absolute Error lower than 5%). Conclusions. Despite the high uncertainties of human body and dynamic nature of CKD progression, our model can accurately predict the GFR variations at long future periods. PMID:27022406

  7. A relation to predict the failure of materials and potential application to volcanic eruptions and landslides

    PubMed Central

    Hao, Shengwang; Liu, Chao; Lu, Chunsheng; Elsworth, Derek

    2016-01-01

    A theoretical explanation of a time-to-failure relation is presented, with this relationship then used to describe the failure of materials. This provides the potential to predict timing (tf − t) immediately before failure by extrapolating the trajectory as it asymptotes to zero with no need to fit unknown exponents as previously proposed in critical power law behaviors. This generalized relation is verified by comparison with approaches to criticality for volcanic eruptions and creep failure. A new relation based on changes with stress is proposed as an alternative expression of Voight’s relation, which is widely used to describe the accelerating precursory signals before material failure and broadly applied to volcanic eruptions, landslides and other phenomena. The new generalized relation reduces to Voight’s relation if stress is limited to increase at a constant rate with time. This implies that the time-derivatives in Voight’s analysis may be a subset of a more general expression connecting stress derivatives, and thus provides a potential method for forecasting these events. PMID:27306851

  8. A relation to predict the failure of materials and potential application to volcanic eruptions and landslides

    NASA Astrophysics Data System (ADS)

    Hao, Shengwang; Liu, Chao; Lu, Chunsheng; Elsworth, Derek

    2016-06-01

    A theoretical explanation of a time-to-failure relation is presented, with this relationship then used to describe the failure of materials. This provides the potential to predict timing (tf ‑ t) immediately before failure by extrapolating the trajectory as it asymptotes to zero with no need to fit unknown exponents as previously proposed in critical power law behaviors. This generalized relation is verified by comparison with approaches to criticality for volcanic eruptions and creep failure. A new relation based on changes with stress is proposed as an alternative expression of Voight’s relation, which is widely used to describe the accelerating precursory signals before material failure and broadly applied to volcanic eruptions, landslides and other phenomena. The new generalized relation reduces to Voight’s relation if stress is limited to increase at a constant rate with time. This implies that the time-derivatives in Voight’s analysis may be a subset of a more general expression connecting stress derivatives, and thus provides a potential method for forecasting these events.

  9. A relation to predict the failure of materials and potential application to volcanic eruptions and landslides.

    PubMed

    Hao, Shengwang; Liu, Chao; Lu, Chunsheng; Elsworth, Derek

    2016-01-01

    A theoretical explanation of a time-to-failure relation is presented, with this relationship then used to describe the failure of materials. This provides the potential to predict timing (tf - t) immediately before failure by extrapolating the trajectory as it asymptotes to zero with no need to fit unknown exponents as previously proposed in critical power law behaviors. This generalized relation is verified by comparison with approaches to criticality for volcanic eruptions and creep failure. A new relation based on changes with stress is proposed as an alternative expression of Voight's relation, which is widely used to describe the accelerating precursory signals before material failure and broadly applied to volcanic eruptions, landslides and other phenomena. The new generalized relation reduces to Voight's relation if stress is limited to increase at a constant rate with time. This implies that the time-derivatives in Voight's analysis may be a subset of a more general expression connecting stress derivatives, and thus provides a potential method for forecasting these events. PMID:27306851

  10. A simple nonlocal damage model for predicting failure of notched laminates

    NASA Technical Reports Server (NTRS)

    Kennedy, T. C.; Nahan, M. F.

    1995-01-01

    The ability to predict failure loads in notched composite laminates is a requirement in a variety of structural design circumstances. A complicating factor is the development of a zone of damaged material around the notch tip. The objective of this study was to develop a computational technique that simulates progressive damage growth around a notch in a manner that allows the prediction of failure over a wide range of notch sizes. This was accomplished through the use of a relatively simple, nonlocal damage model that incorporates strain-softening. This model was implemented in a two-dimensional finite element program. Calculations were performed for two different laminates with various notch sizes under tensile loading, and the calculations were found to correlate well with experimental results.

  11. Failure of Tube Models to Predict the Linear Rheology of Star/Linear Blends

    NASA Astrophysics Data System (ADS)

    Hall, Ryan; Desai, Priyanka; Kang, Beomgoo; Katzarova, Maria; Huang, Qifan; Lee, Sanghoon; Chang, Taihyun; Venerus, David; Mays, Jimmy; Schieber, Jay; Larson, Ronald

    We compare predictions of two of the most advanced versions of the tube model, namely the Hierarchical model by Wang et al. (J. Rheol. 54:223, 2010) and the BOB (branch-on-branch) model by Das et al. (J. Rheol. 50:207-234, 2006), against linear viscoelastic data on blends of monodisperse star and monodisperse linear polybutadiene polymers. The star was carefully synthesized/characterized by temperature gradient interaction chromatography, and rheological data in the high frequency region were obtained through time-temperature superposition. We found massive failures of both the Hierarchical and BOB models to predict the terminal relaxation behavior of the star/linear blends, despite their success in predicting the rheology of the pure star and pure linear. This failure occurred regardless of the choices made concerning constraint release, such as assuming arm retraction in fat or skinny tubes, or allowing for disentanglement relaxation to cut off the constraint release Rouse process at long times. The failures call into question whether constraint release can be described as a combination of constraint release Rouse processes and dynamic tube dilation within a canonical tube model of entanglement interactions.

  12. Prediction of failure in notched carbon-fibre-reinforced-polymer laminates under multi-axial loading.

    PubMed

    Tan, J L Y; Deshpande, V S; Fleck, N A

    2016-07-13

    A damage-based finite-element model is used to predict the fracture behaviour of centre-notched quasi-isotropic carbon-fibre-reinforced-polymer laminates under multi-axial loading. Damage within each ply is associated with fibre tension, fibre compression, matrix tension and matrix compression. Inter-ply delamination is modelled by cohesive interfaces using a traction-separation law. Failure envelopes for a notch and a circular hole are predicted for in-plane multi-axial loading and are in good agreement with the observed failure envelopes from a parallel experimental study. The ply-by-ply (and inter-ply) damage evolution and the critical mechanisms of ultimate failure also agree with the observed damage evolution. It is demonstrated that accurate predictions of notched compressive strength are obtained upon employing the band broadening stress for microbuckling, highlighting the importance of this damage mode in compression. This article is part of the themed issue 'Multiscale modelling of the structural integrity of composite materials'. PMID:27242302

  13. Hybrid neural intelligent system to predict business failure in small-to-medium-size enterprises.

    PubMed

    Borrajo, M Lourdes; Baruque, Bruno; Corchado, Emilio; Bajo, Javier; Corchado, Juan M

    2011-08-01

    During the last years there has been a growing need of developing innovative tools that can help small to medium sized enterprises to predict business failure as well as financial crisis. In this study we present a novel hybrid intelligent system aimed at monitoring the modus operandi of the companies and predicting possible failures. This system is implemented by means of a neural-based multi-agent system that models the different actors of the companies as agents. The core of the multi-agent system is a type of agent that incorporates a case-based reasoning system and automates the business control process and failure prediction. The stages of the case-based reasoning system are implemented by means of web services: the retrieval stage uses an innovative weighted voting summarization of self-organizing maps ensembles-based method and the reuse stage is implemented by means of a radial basis function neural network. An initial prototype was developed and the results obtained related to small and medium enterprises in a real scenario are presented. PMID:21809475

  14. Tension Strength, Failure Prediction and Damage Mechanisms in 2D Triaxial Braided Composites with Notch

    NASA Technical Reports Server (NTRS)

    Norman, Timothy L.; Anglin, Colin

    1995-01-01

    The unnotched and notched (open hole) tensile strength and failure mechanisms of two-dimensional (2D) triaxial braided composites were examined. The effect of notch size and notch position were investigated. Damage initiation and propagation in notched and unnotched coupons were also examined. Theory developed to predict the normal stress distribution near an open hole and failure for tape laminated composites was evaluated for its applicability to 2D triaxial braided textile composite materials. Four different fiber architectures were considered; braid angle, yarn and braider size, percentage of longitudinal yarns and braider angle varied. Tape laminates equivalent to textile composites were also constructed for comparison. Unnotched tape equivalents were stronger than braided textiles but exhibited greater notch sensitivity. Notched textiles and tape equivalents have roughly the same strength at large notch sizes. Two common damage mechanisms were found: braider yarn cracking and near notch longitudinal yarn splitting. Cracking was found to initiate in braider yarns in unnotched and notched coupons, and propagate in the direction of the braider yarns until failure. Damage initiation stress decreased with increasing braid angle. No significant differences in prediction of near notch strain between textile and tape equivalents could be detected for small braid angle, but the correlations were weak for textiles with large braid angle. Notch strength could not be predicted using existing anisotropic theory for braided textiles due to their insensitivity to notch.

  15. A Predictive Safety Management System Software Package Based on the Continuous Hazard Tracking and Failure Prediction Methodology

    NASA Technical Reports Server (NTRS)

    Quintana, Rolando

    2003-01-01

    The goal of this research was to integrate a previously validated and reliable safety model, called Continuous Hazard Tracking and Failure Prediction Methodology (CHTFPM), into a software application. This led to the development of a safety management information system (PSMIS). This means that the theory or principles of the CHTFPM were incorporated in a software package; hence, the PSMIS is referred to as CHTFPM management information system (CHTFPM MIS). The purpose of the PSMIS is to reduce the time and manpower required to perform predictive studies as well as to facilitate the handling of enormous quantities of information in this type of studies. The CHTFPM theory encompasses the philosophy of looking at the concept of safety engineering from a new perspective: from a proactive, than a reactive, viewpoint. That is, corrective measures are taken before a problem instead of after it happened. That is why the CHTFPM is a predictive safety because it foresees or anticipates accidents, system failures and unacceptable risks; therefore, corrective action can be taken in order to prevent all these unwanted issues. Consequently, safety and reliability of systems or processes can be further improved by taking proactive and timely corrective actions.

  16. A numerical stress based approach for predicting failure in NBG-18 nuclear graphite components with verification problems

    NASA Astrophysics Data System (ADS)

    Hindley, Michael P.; Mitchell, Mark N.; Erasmus, Christiaan; McMurtry, Ross; Becker, Thorsten H.; Blaine, Deborah C.; Groenwold, Albert A.

    2013-05-01

    This paper presents a methodology that can be used for calculating the probability of failure of graphite core components in a nuclear core design, such as that of the Pebble Bed Modular Reactor. The proposed methodology is shown to calculate the failure of multiple geometries using the parameters obtained from tensile specimen test data. Experimental testing of various geometries is undertaken to verify the results. The analysis of the experimental results and a discussion on the accuracy of the failure prediction methodology are presented. The analysis is done at 50% probability of failure as well as lower probabilities of failure.

  17. Intravenous Lignocaine to Blunt Extubation Responses: A Double-Edged Sword.

    PubMed

    Haldar, Rudrashish; Dubey, Madhulika; Rastogi, Amit; Singh, Prabhat K

    2016-01-01

    Extubation after general anesthetic procedures is often accompanied by transient undesirable responses such as hypertension, tachycardia, coughing, bucking, and raised intracranial and intraocular pressures. In neurosurgical procedures, they need to be stringently controlled to prevent the rise in cerebral blood flow, increase in intracranial pressure, and intracranial bleeding. Intravenous (IV) lignocaine (1-1.5 mg/kg) administration is one such method to blunt extubation responses. We describe a case where IV lignocaine was administered within the recommended doses to inhibit the extubation response, but the same resulted in generalized convulsions because of the clinical and physiological status of the patient at that point of time. Intravenous lignocaine administered to obtund extubation responses can itself manifest in toxic reactions depending on the preexisting clinical and physiological state of the patients. Thus, extreme caution and vigilance is to be maintained whenever IV local anesthetics are used for such purposes. PMID:25807045

  18. Development of A Tabulated Thermo-Viscoplastic Material Model with Regularized Failure for Dynamic Ductile Failure Prediction of Structures under Impact Loading

    NASA Astrophysics Data System (ADS)

    Buyuk, Murat

    It is important to understand the dynamic failure behavior of structures subjected to impact loading in order to improve the survivability. Materials under impact are utterly affected by large deformations, high strain-rates, temperature softening and varying stress-states, which finally may lead to failure. It is shown that the impact characteristics are prone to change with several independent factors such as; impact speed, material thickness, and shape and orientation of the impacting object. Validated numerical simulations of impact tests reveal that the failure on ductile metals occur at certain locations of the failure locus that is constructed on a space as a function of all three stress invariants, which indicates that the failure depends profoundly on the state-of-stress. It is shown that existing material models are not always successful enough to cover the whole range of the failure locus and predict the failure. Therefore, it is a common practice to use different sets of material model parameters tuned or calibrated to cover a specific region of the failure loci in an ad hoc manner for practical reasons to match particular test results. Even in that case, specially tuned material properties are not capable of predicting these limited cases if differences in the mesh size and pattern need to be considered. In this dissertation a new, generic, thermo-elastic/viscoplastic material model with regularized failure is introduced. The new material model is implemented into a non-linear, explicit dynamics finite element code, LS-DYNA. A von Mises type isotropic, isochoric plasticity is utilized, where isotropic hardening, strain-rate hardening and temperature softening is considered. The model takes adiabatic heating and softening into account due to the plastic work. The constitutive relation is coupled with a new regularized accumulated failure law that is specifically developed to cover a large extent of the failure locus as a function of state

  19. Predicting Ductility and Failure Modes of TRIP Steels under Different Loading Conditions

    SciTech Connect

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

    2010-06-12

    We study the ultimate ductility and failure modes of a TRIP (TRansformation-Induced Plasticity) 800 steel under different loading conditions with an advanced micromechanics-based finite element analysis. The representative volume element (RVE) for the TRIP800 under examination is developed based on an actual microstructure obtained from scanning electron microscopy (SEM). The evolution of retained austenite during deformation process and the mechanical properties of the constituent phases of the TRIP800 steel are obtained from the synchrotron-based in-situ high-energy X-ray diffraction (HEXRD) experiments and a self-consistent (SC) model. The ductile failure of the TRIP800 under different loading conditions is predicted in the form of plastic strain localization without any prescribed failure criteria for the individual phases. Comparisons of the computational results with experimental measurements suggest that the microstructure-based finite element analysis can well capture the overall macroscopic behavior of the TRIP800 steel under different loading conditions. The methodology described in this study may be extended for studying the ultimate ductile failure mechanisms of TRIP steels as well as the effects of the various processing parameters on the macroscopic behaviors of TRIP steels.

  20. The Effect of Delamination on Damage Path and Failure Load Prediction for Notched Composite Laminates

    NASA Technical Reports Server (NTRS)

    Satyanarayana, Arunkumar; Bogert, Philip B.; Chunchu, Prasad B.

    2007-01-01

    The influence of delamination on the progressing damage path and initial failure load in composite laminates is investigated. Results are presented from a numerical and an experimental study of center-notched tensile-loaded coupons. The numerical study includes two approaches. The first approach considers only intralaminar (fiber breakage and matrix cracking) damage modes in calculating the progression of the damage path. In the second approach, the model is extended to consider the effect of interlaminar (delamination) damage modes in addition to the intralaminar damage modes. The intralaminar damage is modeled using progressive damage analysis (PDA) methodology implemented with the VUMAT subroutine in the ABAQUS finite element code. The interlaminar damage mode has been simulated using cohesive elements in ABAQUS. In the experimental study, 2-3 specimens each of two different stacking sequences of center-notched laminates are tensile loaded. The numerical results from the two different modeling approaches are compared with each other and the experimentally observed results for both laminate types. The comparisons reveal that the second modeling approach, where the delamination damage mode is included together with the intralaminar damage modes, better simulates the experimentally observed damage modes and damage paths, which were characterized by splitting failures perpendicular to the notch tips in one or more layers. Additionally, the inclusion of the delamination mode resulted in a better prediction of the loads at which the failure took place, which were higher than those predicted by the first modeling approach which did not include delaminations.

  1. Methods for predicting peak discharge of floods caused by failure of natural and constructed earthen dams

    USGS Publications Warehouse

    Walder, J.S.; O'Connor, J. E.

    1997-01-01

    Floods from failures of natural and constructed dams constitute a widespread hazard to people and property. Expeditious means of assessing flood hazards are necessary, particularly in the case of natural dams, which may form suddenly and unexpectedly. We revise statistical relations (derived from data for past constructed and natural dam failures) between peak discharge (Q(p)) and water volume released (V(0)) or drop in lake level (d) but assert that such relations, even when cast into a dimensionless form, are of limited utility because they fail to portray the effect of breach-formation rate. We then analyze a simple, physically based model of dam-breach formation to show that the hydrograph at the breach depends primarily on a dimensionless parameter ?? = kV0/g1/2d7/2, where k is the mean erosion rate of the breach and g is acceleration due to gravity. The functional relationship between Q(p) and ?? takes asymptotically distinct forms depending on whether ?? << 1 (relatively slow breach formation or small lake volume) or ?? >> 1 (relatively fast breach formation or large lake volume). Theoretical predictions agree well with data from dam failures for which k, and thus ??, can be estimated. The theory thus provides a rapid means of predicting the plausible range of values of peak discharge at the breach in an earthen dam as long as the impounded water volume and the water depth at the dam face can be estimated.

  2. Prediction of early lethal SEGR failures of VDMOSFETs for commercial space systems

    SciTech Connect

    Titus, J.L.; Wheatley, C.F.; Wheatley, T.H.

    1999-12-01

    Quantitative risk assessments are presented for two radiation-hardened MOSFETs (Harris FSL11A0 and FRL11A0) using an extracted expression, integral flux curves representing different conditions, and experimentally-determined signature curves taken at different ion impact angles. The effectiveness of certain parameters including the selected orbit, spacecraft shielding thickness, drain and gate biases, device hardness, and time of exposure are discussed. Failures are studied using normalized Monte Carlo simulations validated by statistical methods. These validated Monte Carlo simulations are then used to extract and present an extracted expression. The concept of a lethal ion rate is discussed. Single event gate rupture (SEGR) failure thresholds at different ion impact angles are measured and reported on the Harris FSL11A0 and FRL11A0 (radiation-hardened vertical MOSFETs having similar layouts but with different SEGR sensitivities). Integral flux curves are presented for various orbits and conditions. Predictions of very early failures are performed using the extracted expression, the integral flux curves, and the new signature curves. Based upon these predictions, the influence of selected parameters are evaluated.

  3. A general model for predicting coolant activity behaviour for fuel-failure monitoring analysis

    NASA Astrophysics Data System (ADS)

    El-Jaby, A.; Lewis, B. J.; Thompson, W. T.; Iglesias, F.; Ip, M.

    2010-04-01

    A mathematical treatment has been developed to predict the release of volatile fission products from operating defective nuclear fuel elements. The fission product activity in both the fuel-to-sheath gap and primary heat transport system as a function of time can be predicted during all reactor operating conditions, including: startup, steady-state, shutdown, and bundle-shifting manoeuvres. In addition, an improved ability to predict the coolant activity of the 135Xe isotope in commercial reactors is discussed. A method is also proposed to estimate both the burnup and the amount of tramp uranium deposits in-core. The model has been validated against in-reactor experiments conducted with defective fuel elements containing natural and artificial failures at the Chalk River Laboratories. Lastly, the model has been benchmarked against a defective fuel occurrence in a commercial reactor.

  4. An endometrial gene expression signature accurately predicts recurrent implantation failure after IVF

    PubMed Central

    Koot, Yvonne E. M.; van Hooff, Sander R.; Boomsma, Carolien M.; van Leenen, Dik; Groot Koerkamp, Marian J. A.; Goddijn, Mariëtte; Eijkemans, Marinus J. C.; Fauser, Bart C. J. M.; Holstege, Frank C. P.; Macklon, Nick S.

    2016-01-01

    The primary limiting factor for effective IVF treatment is successful embryo implantation. Recurrent implantation failure (RIF) is a condition whereby couples fail to achieve pregnancy despite consecutive embryo transfers. Here we describe the collection of gene expression profiles from mid-luteal phase endometrial biopsies (n = 115) from women experiencing RIF and healthy controls. Using a signature discovery set (n = 81) we identify a signature containing 303 genes predictive of RIF. Independent validation in 34 samples shows that the gene signature predicts RIF with 100% positive predictive value (PPV). The strength of the RIF associated expression signature also stratifies RIF patients into distinct groups with different subsequent implantation success rates. Exploration of the expression changes suggests that RIF is primarily associated with reduced cellular proliferation. The gene signature will be of value in counselling and guiding further treatment of women who fail to conceive upon IVF and suggests new avenues for developing intervention. PMID:26797113

  5. NASA Langley developments in response calculations needed for failure and life prediction

    NASA Astrophysics Data System (ADS)

    Housner, Jerrold M.

    1993-10-01

    NASA Langley developments in response calculations needed for failure and life predictions are discussed. Topics covered include: structural failure analysis in concurrent engineering; accuracy of independent regional modeling demonstrated on classical example; functional interface method accurately joins incompatible finite element models; interface method for insertion of local detail modeling extended to curve pressurized fuselage window panel; interface concept for joining structural regions; motivation for coupled 2D-3D analysis; compression panel with discontinuous stiffener coupled 2D-3D model and axial surface strains at the middle of the hat stiffener; use of adaptive refinement with multiple methods; adaptive mesh refinement; and studies on quantity effect of bow-type initial imperfections on reliability of stiffened panels.

  6. NASA Langley developments in response calculations needed for failure and life prediction

    NASA Technical Reports Server (NTRS)

    Housner, Jerrold M.

    1993-01-01

    NASA Langley developments in response calculations needed for failure and life predictions are discussed. Topics covered include: structural failure analysis in concurrent engineering; accuracy of independent regional modeling demonstrated on classical example; functional interface method accurately joins incompatible finite element models; interface method for insertion of local detail modeling extended to curve pressurized fuselage window panel; interface concept for joining structural regions; motivation for coupled 2D-3D analysis; compression panel with discontinuous stiffener coupled 2D-3D model and axial surface strains at the middle of the hat stiffener; use of adaptive refinement with multiple methods; adaptive mesh refinement; and studies on quantity effect of bow-type initial imperfections on reliability of stiffened panels.

  7. 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.

  8. Risk Analysis of the Space Shuttle: Pre-Challenger Bayeisan Prediction of Failure

    SciTech Connect

    Dana L. Kelly

    2008-02-01

    Dalal et al performed a statistical analysis of field and nozzle O-ring data collected prior to the ill-fated launch of the Challenger in January 1986. The purpose of their analysis was to show how statistical analysis could be used to provide information to decisionmakers prior to the launch, information that could have been expected to lead to a decision to abort the launch due to the low temperatures (~30o F.) present at the launch pad on the morning of the scheduled launch. Dalal et al. performed a frequentist analysis of the O-ring data, and found that a logistic regression model provided a relatively good fit to the past data. In the second portion of their paper, Dalal et al. propagated parameter uncertainties through the fitted logistic regression model in order to estimate the probability of shuttle failure due to O-ring failure at the estimated launch temperature of ~30o F. Because their analysis was frequentist in nature, probability distributions representing epistemic uncertainty in the input parameters were not available, and the authors had to resort to an approximate approach based on bootstrap confidence intervals. In this paper, we will re-evaluate the analyses of Dalal et al. from a Bayesian perspective. Markov chain Monte Carlo (MCMC) sampling will be used to sample from the joint posterior distribution of the model parameters, and to sample from the posterior predictive distributions at the estimated launch temperature, a temperature that had not been observed in prior launches of the space shuttle. Uncertainties, which are represented by probability distributions in the Bayesian approach, are propagated through the model to obtain a probability distribution for O-ring failure, and subsequently for shuttle failure as a result of O-ring failure. No approximations are required in the Bayesian approach and the resulting distributions can be input to a decision analysis to obtain expected utility for the decision to launch.

  9. Predicting heart failure decompensation using cardiac implantable electronic devices: a review of practices and challenges.

    PubMed

    Hawkins, Nathaniel M; Virani, Sean A; Sperrin, Matthew; Buchan, Iain E; McMurray, John J V; Krahn, Andrew D

    2016-08-01

    Cardiac implantable electronic devices include remote monitoring tools intended to guide heart failure management. The monitoring focus has been on averting hospitalizations by predicting worsening heart failure. However, although device measurements including intrathoracic impedance correlate with risk of decompensation, they individually predict hospitalizations with limited accuracy. Current 'crisis detection' methods involve repeatedly screening for impending decompensation, and do not adhere to the principles of diagnostic testing. Complex substrate, limited test performance, low outcome incidence, and long test to outcome times inevitably generate low positive and high negative predictive values. When combined with spectrum bias, the generalizability, incremental value, and cost-effectiveness of device algorithms are questionable. To avoid these pitfalls, remote monitoring may need to shift from crisis detection to health maintenance, keeping the patient within an ideal physiological range through continuous 'closed loop' interaction and dynamic therapy adjustment. Test performance must also improve, possibly through combination with physiological sensors in different dimensions, static baseline characteristics, and biomarkers. Complex modelling may tailor monitoring to individual phenotypes, and thus realize a personalized medicine approach. Future randomized controlled trials should carefully consider these issues, and ensure that the interventions tested are generalizable to clinical practice. PMID:26663507

  10. Failure prediction method for hydro forming simulation of thick walled tubes

    NASA Astrophysics Data System (ADS)

    Kolleck, Ralf; Auer, Peter; Auer, Gerfried

    2011-05-01

    The industrial production of thick walled hydro formed steel parts is a process difficult to control. In particular the prevention of cracks in the production of these parts is very important. It is of utmost importance to have a virtual tool to predict forming results. Standard methods for the simulation of hydro formed parts base upon processes using a shell element formulation and implement a forming limit curve (FLC) for crack prediction. But the forming limit curve is limited to the case of linear strain paths. The initial FLC is no longer valid in the case of nonlinear strain paths. Because of the geometric specifications of the investigated parts—thick walls, compact dimensions, high strains—and the known limitations of the forming limit curve—which don't accord to the hydro forming process— these standard simulation methods are not applicable for the present investigations. A new approach to simulate thick walled hydro formed parts is the use of a volume element formulation in combination with a more complex failure criterion, which gives information about the risk of ductile normal fracture and ductile shear fractures with nonlinear strain paths. The onset of necking must be predicted directly by the volume elements. The aim of this work is to implement the failure criteria in a hydroforming simulation and to compare the results of the simulation with real cracked test parts. The commercial FEM code PamStamp 2G is used as a solver and a comprehensive fracture model is applied. This fracture model distinguishes between two mechanisms responsible for ductile fracture. One is the void growth and coalescence (ductile normal fracture) and the other one is the shear failure model (ductile shear fracture).

  11. A standardized model for predicting flap failure using indocyanine green dye

    NASA Astrophysics Data System (ADS)

    Zimmermann, Terence M.; Moore, Lindsay S.; Warram, Jason M.; Greene, Benjamin J.; Nakhmani, Arie; Korb, Melissa L.; Rosenthal, Eben L.

    2016-03-01

    Techniques that provide a non-invasive method for evaluation of intraoperative skin flap perfusion are currently available but underutilized. We hypothesize that intraoperative vascular imaging can be used to reliably assess skin flap perfusion and elucidate areas of future necrosis by means of a standardized critical perfusion threshold. Five animal groups (negative controls, n=4; positive controls, n=5; chemotherapy group, n=5; radiation group, n=5; chemoradiation group, n=5) underwent pre-flap treatments two weeks prior to undergoing random pattern dorsal fasciocutaneous flaps with a length to width ratio of 2:1 (3 x 1.5 cm). Flap perfusion was assessed via laser-assisted indocyanine green dye angiography and compared to standard clinical assessment for predictive accuracy of flap necrosis. For estimating flap-failure, clinical prediction achieved a sensitivity of 79.3% and a specificity of 90.5%. When average flap perfusion was more than three standard deviations below the average flap perfusion for the negative control group at the time of the flap procedure (144.3+/-17.05 absolute perfusion units), laser-assisted indocyanine green dye angiography achieved a sensitivity of 81.1% and a specificity of 97.3%. When absolute perfusion units were seven standard deviations below the average flap perfusion for the negative control group, specificity of necrosis prediction was 100%. Quantitative absolute perfusion units can improve specificity for intraoperative prediction of viable tissue. Using this strategy, a positive predictive threshold of flap failure can be standardized for clinical use.

  12. Progressive failure methodologies for predicting residual strength and life of laminated composites

    NASA Technical Reports Server (NTRS)

    Harris, Charles E.; Allen, David H.; Obrien, T. Kevin

    1991-01-01

    Two progressive failure methodologies currently under development by the Mechanics of Materials Branch at NASA Langley Research Center are discussed. The damage tolerance/fail safety methodology developed by O'Brien is an engineering approach to ensuring adequate durability and damage tolerance by treating only delamination onset and the subsequent delamination accumulation through the laminate thickness. The continuum damage model developed by Allen and Harris employs continuum damage laws to predict laminate strength and life. The philosophy, mechanics framework, and current implementation status of each methodology are presented.

  13. Congestive heart failure and converting enzyme inhibition: failure of current prognostic criteria for predicting subsequent renal insufficiency.

    PubMed Central

    Odum, J.; Carson, P.; Russell, G.

    1991-01-01

    Angiotensin-1-converting enzyme inhibitors have an effective and established role in the treatment of patients with congestive heart failure. However, a small number of such patients will subsequently develop renal insufficiency. These patients may be identified prior to, or shortly after, commencement of therapy by recognized criteria. This report describes 4 patients with congestive heart failure who developed severe renal insufficiency secondary to either enalapril or captopril therapy in the absence of any currently recognized predisposing factors. One patient died. PMID:2068028

  14. Predictions of High Strain Rate Failure Modes in Layered Aluminum Composites

    NASA Astrophysics Data System (ADS)

    Khanikar, Prasenjit; Zikry, M. A.

    2014-01-01

    A dislocation density-based crystalline plasticity formulation, specialized finite-element techniques, and rational crystallographic orientation relations were used to predict and characterize the failure modes associated with the high strain rate behavior of aluminum layered composites. Two alloy layers, a high strength alloy, aluminum 2195, and an aluminum alloy 2139, with high toughness, were modeled with representative microstructures that included precipitates, dispersed particles, and different grain boundary distributions. Different layer arrangements were investigated for high strain rate applications and the optimal arrangement was with the high toughness 2139 layer on the bottom, which provided extensive shear strain localization, and the high strength 2195 layer on the top for high strength resistance The layer thickness of the bottom high toughness layer also affected the bending behavior of the roll-bonded interface and the potential delamination of the layers. Shear strain localization, dynamic cracking, and delamination are the mutually competing failure mechanisms for the layered metallic composite, and control of these failure modes can be used to optimize behavior for high strain rate applications.

  15. Human Factors Predicting Failure and Success in Hospital Information System Implementations in Sub-Saharan Africa.

    PubMed

    Verbeke, Frank; Karara, Gustave; Nyssen, Marc

    2015-01-01

    From 2007 through 2014, the authors participated in the implementation of open source hospital information systems (HIS) in 19 hospitals in Rwanda, Burundi, DR Congo, Congo-Brazzaville, Gabon, and Mali. Most of these implementations were successful, but some failed. At the end of a seven-year implementation effort, a number of risk factors, facilitators, and pragmatic approaches related to the deployment of HIS in Sub-Saharan health facilities have been identified. Many of the problems encountered during the HIS implementation process were not related to technical issues but human, cultural, and environmental factors. This study retrospectively evaluates the predictive value of 14 project failure factors and 15 success factors in HIS implementation in the Sub-Saharan region. Nine of the failure factors were strongly correlated with project failure, three were moderately correlated, and one weakly correlated. Regression analysis also confirms that eight factors were strongly correlated with project success, four moderately correlated, and two weakly correlated. The study results may help estimate the expedience of future HIS projects. PMID:26262097

  16. Predicting the Probability of Failure of Cementitious Sewer Pipes Using Stochastic Finite Element Method.

    PubMed

    Alani, Amir M; Faramarzi, Asaad

    2015-06-01

    In this paper, a stochastic finite element method (SFEM) is employed to investigate the probability of failure of cementitious buried sewer pipes subjected to combined effect of corrosion and stresses. A non-linear time-dependant model is used to determine the extent of concrete corrosion. Using the SFEM, the effects of different random variables, including loads, pipe material, and corrosion on the remaining safe life of the cementitious sewer pipes are explored. A numerical example is presented to demonstrate the merit of the proposed SFEM in evaluating the effects of the contributing parameters upon the probability of failure of cementitious sewer pipes. The developed SFEM offers many advantages over traditional probabilistic techniques since it does not use any empirical equations in order to determine failure of pipes. The results of the SFEM can help the concerning industry (e.g., water companies) to better plan their resources by providing accurate prediction for the remaining safe life of cementitious sewer pipes. PMID:26068092

  17. Predicting the Probability of Failure of Cementitious Sewer Pipes Using Stochastic Finite Element Method

    PubMed Central

    Alani, Amir M.; Faramarzi, Asaad

    2015-01-01

    In this paper, a stochastic finite element method (SFEM) is employed to investigate the probability of failure of cementitious buried sewer pipes subjected to combined effect of corrosion and stresses. A non-linear time-dependant model is used to determine the extent of concrete corrosion. Using the SFEM, the effects of different random variables, including loads, pipe material, and corrosion on the remaining safe life of the cementitious sewer pipes are explored. A numerical example is presented to demonstrate the merit of the proposed SFEM in evaluating the effects of the contributing parameters upon the probability of failure of cementitious sewer pipes. The developed SFEM offers many advantages over traditional probabilistic techniques since it does not use any empirical equations in order to determine failure of pipes. The results of the SFEM can help the concerning industry (e.g., water companies) to better plan their resources by providing accurate prediction for the remaining safe life of cementitious sewer pipes. PMID:26068092

  18. Potential Impact of a Free Online HIV Treatment Response Prediction System for Reducing Virological Failures and Drug Costs after Antiretroviral Therapy Failure in a Resource-Limited Setting

    PubMed Central

    Revell, Andrew D.; Wang, Dechao; Pozniak, Anton; Montaner, Julio S.; Lane, H. Clifford; Larder, Brendan A.

    2013-01-01

    Objective. Antiretroviral drug selection in resource-limited settings is often dictated by strict protocols as part of a public health strategy. The objective of this retrospective study was to examine if the HIV-TRePS online treatment prediction tool could help reduce treatment failure and drug costs in such settings. Methods. The HIV-TRePS computational models were used to predict the probability of response to therapy for 206 cases of treatment change following failure in India. The models were used to identify alternative locally available 3-drug regimens, which were predicted to be effective. The costs of these regimens were compared to those actually used in the clinic. Results. The models predicted the responses to treatment of the cases with an accuracy of 0.64. The models identified alternative drug regimens that were predicted to result in improved virological response and lower costs than those used in the clinic in 85% of the cases. The average annual cost saving was $364 USD per year (41%). Conclusions. Computational models that do not require a genotype can predict and potentially avoid treatment failure and may reduce therapy costs. The use of such a system to guide therapeutic decision-making could confer health economic benefits in resource-limited settings. PMID:24175292

  19. Prediction of Heart Failure Decompensation Events by Trend Analysis of Telemonitoring Data.

    PubMed

    Henriques, J; Carvalho, P; Paredes, S; Rocha, T; Habetha, J; Antunes, M; Morais, J

    2015-09-01

    This paper aims to assess the predictive value of physiological data daily collected in a telemonitoring study in the early detection of heart failure (HF) decompensation events. The main hypothesis is that physiological time series with similar progression (trends) may have prognostic value in future clinical states (decompensation or normal condition). The strategy is composed of two main steps: a trend similarity analysis and a predictive procedure. The similarity scheme combines the Haar wavelet decomposition, in which signals are represented as linear combinations of a set of orthogonal bases, with the Karhunen-Loève transform, that allows the selection of the reduced set of bases that capture the fundamental behavior of the time series. The prediction process assumes that future evolution of current condition can be inferred from the progression of past physiological time series. Therefore, founded on the trend similarity measure, a set of time series presenting a progression similar to the current condition is identified in the historical dataset, which is then employed, through a nearest neighbor approach, in the current prediction. The strategy is evaluated using physiological data resulting from the myHeart telemonitoring study, namely blood pressure, respiration rate, heart rate, and body weight collected from 41 patients (15 decompensation events and 26 normal conditions). The obtained results suggest, in general, that the physiological data have predictive value, and in particular, that the proposed scheme is particularly appropriate to address the early detection of HF decompensation. PMID:25248206

  20. Failure Mode Classification for Life Prediction Modeling of Solid-State Lighting

    SciTech Connect

    Sakalaukus, Peter Joseph

    2015-08-01

    light power” of the SSL luminaire. The use of the Arrhenius equation necessitates two different temperature conditions, 25°C and 45°C are suggested by TM28, to determine the SSL lamp specific activation energy. One principal issue with TM28 is the lack of additional stresses or parameters needed to characterize non-temperature dependent failure mechanisms. Another principal issue with TM28 is the assumption that lumen maintenance or lumen depreciation gives an adequate comparison between SSL luminaires. Additionally, TM28 has no process for the determination of acceleration factors or lifetime estimations. Currently, a literature gap exists for established accelerated test methods for SSL devices to assess quality, reliability and durability before being introduced into the marketplace. Furthermore, there is a need for Physics-of-Failure based approaches to understand the processes and mechanisms that induce failure for the assessment of SSL reliability in order to develop generalized acceleration factors that better represent SSL product lifetime. This and the deficiencies in TM28 validate the need behind the development of acceleration techniques to quantify SSL reliability under a variety of environmental conditions. The ability to assess damage accrual and investigate reliability of SSL components and systems is essential to understanding the life time of the SSL device itself. The methodologies developed in this work increases the understanding of SSL devices iv through the investigation of component and device reliability under a variety of accelerated test conditions. The approaches for suitable lifetime predictions through the development of novel generalized acceleration factors, as well as a prognostics and health management framework, will greatly reduce the time and effort needed to produce SSL acceleration factors for the development of lifetime predictions.

  1. Slope Failure Prediction and Early Warning Awareness Education for Reducing Landslides Casualty in Malaysia

    NASA Astrophysics Data System (ADS)

    Koay, S. P.; Tay, L. T.; Fukuoka, H.; Koyama, T.; Sakai, N.; Jamaludin, S. B.; Lateh, H.

    2015-12-01

    Northeast monsoon causes heavy rain in east coast of Peninsular Malaysia from November to March, every year. During this monsoon period, besides the happening of flood along east coast, landslides also causes millions of Malaysian Ringgit economical losses. Hence, it is essential to study the prediction of slope failure to prevent the casualty of landslides happening. In our study, we introduce prediction method of the accumulated rainfall affecting the stability of the slope. If the curve, in the graph, which is presented by rainfall intensity versus accumulated rainfall, crosses over the critical line, the condition of the slope is considered in high risk where the data are calculated and sent from rain gauge in the site via internet. If the possibility of slope failure is going high, the alert message will be sent out to the authorities for decision making on road block or setting the warning light at the road side. Besides road block and warning light, we propose to disseminate short message, to pre-registered mobile phone user, to notify the public for easing the traffic jam and avoiding unnecessary public panic. Prediction is not enough to prevent the casualty. Early warning awareness of the public is very important to reduce the casualty of landslides happening. IT technology does not only play a main role in disseminating information, early warning awareness education, by using IT technology, should be conducted, in schools, to give early warning awareness on natural hazard since childhood. Knowing the pass history on landslides occurrence will gain experience on the landslides happening. Landslides historical events with coordinate information are stored in database. The public can browse these historical events via internet. By referring to such historical landslides events, the public may know where did landslides happen before and the possibility of slope failure occurrence again is considered high. Simulation of rainfall induced slope failure mechanism

  2. Multi-Marker Strategy in Heart Failure: Combination of ST2 and CRP Predicts Poor Outcome.

    PubMed

    Dupuy, Anne Marie; Curinier, Corentin; Kuster, Nils; Huet, Fabien; Leclercq, Florence; Davy, Jean Marc; Cristol, Jean Paul; Roubille, François

    2016-01-01

    Natriuretic peptides (BNP and NT-proBNP) are recognized as gold-standard predictive markers in Heart Failure (HF). However, currently ST2 (member of the interleukin 1 receptor family) has emerged as marker of inflammation, fibrosis and cardiac stress. We evaluated ST2 and CRP as prognostic markers in 178 patients with chronic heart failure in comparison with other classical markers such as clinical established parameters but also biological markers: NT-proBNP, hs-cTnT alone or in combination. In multivariate analysis, subsequent addition of ST2 led to age, CRP and ST2 as the only remaining predictors of all-cause mortality (HR 1.03, HR 1.61 and HR 2.75, respectively) as well as of cardiovascular mortality (HR 1.00, HR 2.27 and HR 3.78, respectively). The combined increase of ST2 and CRP was significant for predicting worsened outcomes leading to identify a high risk subgroup that individual assessment of either marker. The same analysis was performed with ST2 in combination with Barcelona score. Overall, our findings extend previous data demonstrating that ST2 in combination with CRP as a valuable tool for identifying patients at risk of death. PMID:27311068

  3. Failure Predictions of Out-of-Autoclave Sandwich Joints with Delaminations Under Flexure Loads

    NASA Technical Reports Server (NTRS)

    Nordendale, Nikolas; Goyal, Vinay; Lundgren, Eric; Patel, Dhruv; Farrokh, Babak; Jones, Justin; Fischetti, Grace; Segal, Kenneth

    2015-01-01

    An analysis and a test program was conducted to investigate the damage tolerance of composite sandwich joints. The joints contained a single circular delamination between the face-sheet and the doubler. The coupons were fabricated through out-of-autoclave (OOA) processes, a technology NASA is investigating for joining large composite sections. The four-point bend flexure test was used to induce compression loading into the side of the joint where the delamination was placed. The compression side was chosen since it tends to be one of the most critical loads in launch vehicles. Autoclave cure was used to manufacture the composite sandwich sections, while the doubler was co-bonded onto the sandwich face-sheet using an OOA process after sandwich panels were cured. A building block approach was adopted to characterize the mechanical properties of the joint material, including the fracture toughness between the doubler and face-sheet. Twelve four-point-bend samples were tested, six in the sandwich core ribbon orientation and six in sandwich core cross-ribbon direction. Analysis predicted failure initiation and propagation at the pre-delaminated location, consistent with experimental observations. Fracture analyses methods predicted failure loads in close agreement with tests. This investigation demonstrated a strength reduction of 10 percent due to a flaw of significant size compared to the width of the sample. Therefore, concerns of bonding an OOA material to an in-autoclave material was mitigated for the geometries, materials, and load configurations considered.

  4. Failure Predictions of Out-of-Autoclave Sandwich Joints with Delaminations under Flexure Loads

    NASA Technical Reports Server (NTRS)

    Nordendale, Nikolas; Goyal, Vinay; Lundgren, Eric; Patel, Dhruv; Farrokh, Babak; Jones, Justin; Fischetti, Grace; Segal, Kenneth

    2015-01-01

    An analysis and a test program was conducted to investigate the damage tolerance of composite sandwich joints. The joints contained a single circular delamination between the face-sheet and the doubler. The coupons were fabricated through out-of-autoclave (OOA) processes, a technology NASA is investigating for joining large composite sections. The four-point bend flexure test was used to induce compression loading into the side of the joint where the delamination was placed. The compression side was chosen since it tends to be one of the most critical loads in launch vehicles. Autoclave cure was used to manufacture the composite sandwich sections, while the doubler was co-bonded onto the sandwich face-sheet using an OOA process after sandwich panels were cured. A building block approach was adopted to characterize the mechanical properties of the joint material, including the fracture toughness between the doubler and facesheet. Twelve four-point-bend samples were tested, six in the sandwich core ribbon orientation and six in sandwich core cross-ribbon direction. Analysis predicted failure initiation and propagation at the pre-delaminated location, consistent with experimental observations. A building block approach using fracture analyses methods predicted failure loads in close agreement with tests. This investigation demonstrated a small strength reduction due to a flaw of significant size compared to the width of the sample. Therefore, concerns of bonding an OOA material to an in-autoclave material was mitigated for the geometries, materials, and load configurations considered.

  5. Application of a neural network as a potential aid in predicting NTF pump failure

    NASA Technical Reports Server (NTRS)

    Rogers, James L.; Hill, Jeffrey S.; Lamarsh, William J., II; Bradley, David E.

    1993-01-01

    The National Transonic Facility has three centrifugal multi-stage pumps to supply liquid nitrogen to the wind tunnel. Pump reliability is critical to facility operation and test capability. A highly desirable goal is to be able to detect a pump rotating component problem as early as possible during normal operation and avoid serious damage to other pump components. If a problem is detected before serious damage occurs, the repair cost and downtime could be reduced significantly. A neural network-based tool was developed for monitoring pump performance and aiding in predicting pump failure. Once trained, neural networks can rapidly process many combinations of input values other than those used for training to approximate previously unknown output values. This neural network was applied to establish relationships among the critical frequencies and aid in predicting failures. Training pairs were developed from frequency scans from typical tunnel operations. After training, various combinations of critical pump frequencies were propagated through the neural network. The approximated output was used to create a contour plot depicting the relationships of the input frequencies to the output pump frequency.

  6. Diagnostic prediction of renal failure from blood serum analysis by FTIR spectrometry and chemometrics

    NASA Astrophysics Data System (ADS)

    Khanmohammadi, Mohammdreza; Ghasemi, Keyvan; Garmarudi, Amir Bagheri; Ramin, Mehdi

    2015-02-01

    A new diagnostic approach based on Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectrometry and classification algorithm has been introduced which provides a rapid, reliable, and easy way to perform blood test for the diagnosis of renal failure. Blood serum samples from 35 renal failure patients and 40 healthy persons were analyzed by ATR-FTIR spectrometry. The resulting data was processed by Quadratic Discriminant Analysis (QDA) and QDA combined with simple filtered method. Spectroscopic studies were performed in 900-2000 cm-1 spectral region with 3.85 cm-1 data space. Results showed 93.33% and 100% of accuracy for QDA and filter-QDA models, respectively. In the first step, 30 samples were applied to construct the model. In order to modify the capability of QDA in prediction of test samples, filter-based feature selection methods were applied. It was found that the filtered spectra coupled with QDA could correctly predict the test samples in most of the cases.

  7. Failure Predictions of Out-of-Autoclave Sandwich Joints with Delaminations Under Flexure Loads

    NASA Technical Reports Server (NTRS)

    Nordendale, Nikolas A.; Goyal, Vinay K.; Lundgren, Eric C.; Patel, Dhruv N.; Farrokh, Babak; Jones, Justin; Fischetti, Grace; Segal, Kenneth N.

    2015-01-01

    An analysis and a test program was conducted to investigate the damage tolerance of composite sandwich joints. The joints contained a single circular delamination between the face-sheet and the doubler. The coupons were fabricated through out-of-autoclave (OOA) processes, a technology NASA is investigating for joining large composite sections. The four-point bend flexure test was used to induce compression loading into the side of the joint where the delamination was placed. The compression side was chosen since it tends to be one of the most critical loads in launch vehicles. Autoclave cure was used to manufacture the composite sandwich sections, while the doubler was co-bonded onto the sandwich face-sheet using an OOA process after sandwich panels were cured. A building block approach was adopted to characterize the mechanical properties of the joint material, including the fracture toughness between the doubler and face-sheet. Twelve four-point-bend samples were tested, six in the sandwich core ribbon orientation and six in sandwich core cross-ribbon direction. Analysis predicted failure initiation and propagation at the pre-delaminated location, consistent with experimental observations. A building block approach using fracture analyses methods predicted failure loads in close agreement with tests. This investigation demonstrated a small strength reduction due to a flaw of significant size compared to the width of the sample. Therefore, concerns of bonding an OOA material to an in-autoclave material was mitigated for the geometries, materials, and load configurations considered.

  8. Failure mechanisms and lifetime prediction methodology for polybutylene pipe in water distribution system

    NASA Astrophysics Data System (ADS)

    Niu, Xiqun

    Polybutylene (PB) is a semicrystalline thermoplastics. It has been widely used in potable water distribution piping system. However, field practice shows that failure occurs much earlier than the expected service lifetime. What are the causes and how to appropriately evaluate its lifetime motivate this study. In this thesis, three parts of work have been done. First is the understanding of PB, which includes material thermo and mechanical characterization, aging phenomena and notch sensitivity. The second part analyzes the applicability of the existing lifetime testing method for PB. It is shown that PB is an anomaly in terms of the temperature-lifetime relation because of the fracture mechanism transition across the testing temperature range. The third part is the development of the methodology of lifetime prediction for PB pipe. The fracture process of PB pipe consists of three stages, i.e., crack initiation, slow crack growth (SCG) and crack instability. The practical lifetime of PB pipe is primarily determined by the duration of the first two stages. The mechanism of crack initiation and the quantitative estimation of the time to crack initiation are studied by employing environment stress cracking technique. A fatigue slow crack growth testing method has been developed and applied in the study of SCG. By using Paris-Erdogan equation, a model is constructed to evaluate the time for SCG. As a result, the total lifetime is determined. Through this work, the failure mechanisms of PB pipe has been analyzed and the lifetime prediction methodology has been developed.

  9. Post-Exercise Heart Rate Recovery Independently Predicts Mortality Risk in Patients with Chronic Heart Failure

    PubMed Central

    Tang, Yi-Da; Dewland, Thomas A.; Wencker, Detlef; Katz, Stuart D.

    2009-01-01

    Background Post-exercise heart rate recovery (HRR) is an index of parasympathetic function associated with clinical outcomes in populations with and without documented coronary heart disease. Decreased parasympathetic activity is thought to be associated with disease progression in chronic heart failure (HF), but an independent association between post-exercise HRR and clinical outcomes among such patients has not been established. Methods and Results We measured HRR (calculated as the difference between heart rate at peak exercise and after 1 minute of recovery) in 202 HF subjects and recorded 17 mortality and 15 urgent transplantation outcome events over 624 days of follow-up. Reduced post-exercise HRR was independently associated with increased event risk after adjusting for other exercise-derived variables (peak oxygen uptake and VE/VCO2 slope), for the Heart Failure Survival Score (adjusted HR 1.09 for one beat/min reduction, 95% CI 1.05-1.13, p<0.0001) and the Seattle Heart Failure Model score (adjusted HR 1.08 for one beat/min reduction, 95% CI 1.05-1.12, p<0.0001). Subjects in the lowest risk tertile based on post-exercise HRR (≥30 beats/min) had low risk of events irrespective of the risk predicted by the survival scores. In a subgroup of 15 subjects, reduced post-exercise HRR was associated with increased serum markers of inflammation (interleukin-6 r=0.58, p=0.024, high sensitivity C-reactive protein r=0.66, p=0.007). Conclusions Post-exercise HRR predicts mortality risk in patients with HF and provides prognostic information independent of previously described survival models. Pathophysiologic links between autonomic function and inflammation may be mediators of this association. PMID:19944361

  10. Postoperative Prostate-Specific Antigen Velocity Independently Predicts for Failure of Salvage Radiotherapy After Prostatectomy

    SciTech Connect

    King, Christopher R. Presti, Joseph C.; Brooks, James D.; Gill, Harcharan; Spiotto, Michael T.

    2008-04-01

    Purpose: Identification of patients most likely to benefit from salvage radiotherapy (RT) using postoperative (postop) prostate-specific antigen (PSA) kinetics. Methods and Materials: From 1984 to 2004, 81 patients who fit the following criteria formed the study population: undetectable PSA after radical prostatectomy (RP); pathologically negative nodes; biochemical relapse defined as a persistently detectable PSA; salvage RT; and two or more postop PSAs available before salvage RT. Salvage RT included the whole pelvic nodes in 55 patients and 4 months of total androgen suppression in 56 patients. The median follow-up was >5 years. All relapses were defined as a persistently detectable PSA. Kaplan-Meier and Cox proportional hazards multivariable analysis were performed for all clinical, pathological, and treatment factors predicting for biochemical relapse-free survival (bRFS). Results: There were 37 biochemical relapses observed after salvage RT. The 5-year bRFS after salvage RT for patients with postop prostate-specific antigen velocity {<=}1 vs. >1 ng/ml/yr was 59% vs. 29%, p = 0.002. In multivariate analysis, only postop PSAV (p = 0.0036), pre-RT PSA level {<=}1 (p = 0.037) and interval-to-relapse >10 months (p = 0.012) remained significant, whereas pelvic RT, hormone therapy, and RT dose showed a trend (p = {approx}0.06). PSAV, but not prostate-specific antigen doubling time, predicted successful salvage RT, suggesting an association of zero-order kinetics with locally recurrent disease. Conclusions: Postoperative PSA velocity independently predicts for the failure of salvage RT and can be considered in addition to high-risk features when selecting patients in need of systemic therapy following biochemical failure after RP. For well-selected patients, salvage RT can achieve high cure rates.

  11. Neuroendocrine prediction of left ventricular function and heart failure after acute myocardial infarction

    PubMed Central

    Richards, A; Nicholls, M; Yandle, T; Ikram, H; Espiner, E; Turner, J; Buttimore, R; Lainchbury, J; Elliott, J; Frampton, C; Crozier, I; Smyth, D

    1999-01-01

    Objective—To determine the relations of plasma levels of brain natriuretic peptide (BNP), atrial natriuretic factor (ANF), N-terminal ANF (N-ANF), cyclic guanosine monophosphate (cGMP; the cardiac peptide second messenger), and plasma catecholamines to left ventricular function and to prognosis in patients admitted with acute myocardial infarction.
Design—Plasma hormones and ventricular function (radionuclide ventriculography) were measured 1-4 days after myocardial infarction in 220 patients admitted to a single coronary care unit. Radionuclide scanning was repeated 3-5 months after infarction. Clinical events were recorded over a mean period of 14 months.
Results—Both early and late left ventricular ejection fraction (LVEF) were most closely related to plasma BNP (r = −0.60, n = 220, p < 0.001; and r = −0.53, n = 192, p < 0.001, respectively), followed by ANF, N-ANF, cGMP, and the plasma catecholamines. Early plasma BNP concentrations less than twofold the upper limit of normal (20 pmol/l) had 100% negative predictive value for LVEF < 40% at 3-5 months after infarction. In multivariate analysis incorporating all the neurohormonal factors, only BNP remained independently predictive of LVEF < 40% (p < 0.005). Survival analysis by median levels of candidate predictors identified BNP as the most powerful discriminator for death (p < 0.0001). No early deaths (within 4 months) occurred in patients with plasma BNP concentrations below the group median (27 pmol/l), and over follow up only three of 26 deaths occurred in this subgroup. Of all episodes of left ventricular failure, 85% occurred in patients with plasma BNP above the median (p < 0.001). In multivariate analyses, BNP alone gave additional predictive information beyond sex, age, clinical history, LVEF, and plasma noradrenaline for both subsequent onset of LVF and death.
Conclusions—Plasma BNP measured within 1-4 days of acute myocardial infarction is a powerful

  12. Predictions and Experimental Microstructural Characterization of High Strain Rate Failure Modes in Layered Aluminum Composites

    NASA Astrophysics Data System (ADS)

    Khanikar, Prasenjit

    Different aluminum alloys can be combined, as composites, for tailored dynamic applications. Most investigations pertaining to metallic alloy layered composites, however, have been based on quasi-static approaches. The dynamic failure of layered metallic composites, therefore, needs to be characterized in terms of strength, toughness, and fracture response. A dislocation-density based crystalline plasticity formulation, finite-element techniques, rational crystallographic orientation relations and a new fracture methodology were used to predict the failure modes associated with the high strain rate behavior of aluminum layered composites. Two alloy layers, a high strength alloy, aluminum 2195, and an aluminum alloy 2139, with high toughness, were modeled with representative microstructures that included precipitates, dispersed particles, and different grain boundary (GB) distributions. The new fracture methodology, based on an overlap method and phantom nodes, is used with a fracture criteria specialized for fracture on different cleavage planes. One of the objectives of this investigation, therefore, was to determine the optimal arrangements of the 2139 and 2195 aluminum alloys for a metallic layered composite that would combine strength, toughness and fracture resistance for high strain-rate applications. Different layer arrangements were investigated for high strain-rate applications, and the optimal arrangement was with the high toughness 2139 layer on the bottom, which provided extensive shear strain localization, and the high strength 2195 layer on the top for high strength resistance. The layer thickness of the bottom high toughness layer also affected the bending behavior of the roll-boned interface and the potential delamination of the layers. Shear strain localization, dynamic cracking and delamination were the mutually competing failure mechanisms for the layered metallic composite, and control of these failure modes can be optimized for high strain

  13. The second Sandia Fracture Challenge. Predictions of ductile failure under quasi-static and moderate-rate dynamic loading

    DOE PAGESBeta

    Boyce, B. L.; Kramer, S. L. B.; Bosiljevac, T. R.; Corona, E.; Moore, J. A.; Elkhodary, K.; Simha, C. H. M.; Williams, B. W.; Cerrone, A. R.; Nonn, A.; et al

    2016-03-14

    Ductile failure of structural metals is relevant to a wide range of engineering scenarios. Computational methods are employed to anticipate the critical conditions of failure, yet they sometimes provide inaccurate and misleading predictions. Challenge scenarios, such as the one presented in the current work, provide an opportunity to assess the blind, quantitative predictive ability of simulation methods against a previously unseen failure problem. Instead of evaluating the predictions of a single simulation approach, the Sandia Fracture Challenge relied on numerous volunteer teams with expertise in computational mechanics to apply a broad range of computational methods, numerical algorithms, and constitutive modelsmore » to the challenge. This exercise is intended to evaluate the state of health of technologies available for failure prediction. In the first Sandia Fracture Challenge, a wide range of issues were raised in ductile failure modeling, including a lack of consistency in failure models, the importance of shear calibration data, and difficulties in quantifying the uncertainty of prediction [see Boyce et al. (Int J Fract 186:5–68, 2014) for details of these observations]. This second Sandia Fracture Challenge investigated the ductile rupture of a Ti–6Al–4V sheet under both quasi-static and modest-rate dynamic loading (failure in ~ 0.1 s). Like the previous challenge, the sheet had an unusual arrangement of notches and holes that added geometric complexity and fostered a competition between tensile- and shear-dominated failure modes. The teams were asked to predict the fracture path and quantitative far-field failure metrics such as the peak force and displacement to cause crack initiation. Fourteen teams contributed blind predictions, and the experimental outcomes were quantified in three independent test labs. In addition, shortcomings were revealed in this second challenge such as inconsistency in the application of appropriate boundary

  14. Pro: early extubation in the operating room following cardiac surgery in adults.

    PubMed

    Singh, Karen E; Baum, Victor C

    2012-12-01

    There is growing evidence that the general current approach in many centers of continued mechanical ventilation following cardiac surgery has evolved through historical experience rather than having a strong physiological basis in current practice. There is evidence going back several decades supporting very early (in the operating room [OR]) extubation in pediatric cardiac anesthesia. The authors provide evidence from numerous sources showing that extubation in the OR or shortly after arrival in the ICU is safe and cost-effective and is not prevented by the type of cardiac surgery or the use of cardiopulmonary bypass. They query if the paradigm should not be reversed and very early extubation be the routine unless contraindicated. Like any anesthetic technique, appropriate patient selection is called for, but this technique is widely appropriate. PMID:22798230

  15. Model for end-stage liver disease predicts right ventricular failure in patients with left ventricular assist devices.

    PubMed

    Yost, Gardner L; Coyle, Laura; Bhat, Geetha; Tatooles, Antone J

    2016-03-01

    High rates of right ventricular failure continue to affect postoperative outcomes in patients implanted with left ventricular assist devices (LVADs). Development of right ventricular failure and implantation with right ventricular assist devices is known to be associated with significantly increased mortality. The model for end-stage liver disease (MELD) score is an effective means of evaluating liver dysfunction. We investigated the prognostic utility of postoperative MELD on post-LVAD implantation outcomes. MELD scores, demographic data, and outcomes including length of stay, survival, and postoperative right ventricular failure were collected for 256 patients implanted with continuous flow LVADs. Regression and Kaplan-Meier analyses were used to investigate the relationship between MELD and all outcomes. Increased MELD score was found to be an independent predictor of both right heart failure and necessity for RVAD implantation (OR 1.097, CI 1.040-1.158, p = 0.001; OR 1.121, CI 1.015, p = 0.024, respectively). Patients with RV failure and who underwent RVAD implantation had reduced postoperative survival compared to patients with RV dysfunction (no RV failure = 651.4 ± 609.8 days, RV failure = 392.6 ± 444.8 days, RVAD = 89.3 ± 72.8 days; p < 0.001). In conclusion, MELD can be used to reliably predict postoperative right heart failure and the necessity for RVAD implantation. Those patients with RV failure and RVADs experience significantly increased postoperative mortality compared to those without RV dysfunction. PMID:26187243

  16. Predictive Values of Red Blood Cell Distribution Width in Assessing Severity of Chronic Heart Failure.

    PubMed

    Liu, Sen; Wang, Ping; Shen, Ping-Ping; Zhou, Jian-Hua

    2016-01-01

    BACKGROUND This retrospective study was performed to evaluate the value of baseline red blood cell distribution width (RDW) for predicting the severity of chronic heart failure (CHF) compared with N-terminal prohormone brain natriuretic peptide (NT-ProBNP) and other hematological and biochemical parameters. MATERIAL AND METHODS Hematological and biochemical parameters were obtained from 179 patients with New York Heart Association (NYHA) CHF class I (n=44), II (n=39), III (n=41), and IV (n=55). Receiver operator characteristic (ROC) curves were used for assessing predictive values. RESULTS RDW increased significantly in class III and IV compared with class I (14.3±2.3% and 14.3±1.7% vs. 12.9±0.8%, P<0.01). Areas under ROCs (AUCs) of RDW and NT-ProBNP for class IV HF were 0.817 and 0.840, respectively. RDW was markedly elevated in the mortality group compared with the survival group (13.7±1.7 vs. 15.8±1.8, P<0.01). The predictive value of RDW was lower than that of NT-ProBNP but was comparable to white blood cell (WBC), neutrophil (NEU), lymphocyte (L), and neutrophil/lymphocyte ratio (N/L) for mortality during hospitalization, with AUCs of 0.837, 0.939, 0.858, 0.891, 0.885, and 0.885, respectively. RDW and NT-proBNP showed low predictive values for repeated admission (≥3). RDW was an independent risk factor for mortality (OR=2.531, 95% CI: 1.371-4.671). CONCLUSIONS RDW increased significantly in class III and IV patients and in the mortality group. The predictive value of RDW is comparable to NT-proBNP for class IV and lower than that of NT-proBNP for mortality. Elevated RDW is an independent risk factor for mortality. PMID:27324271

  17. The EST Model for Predicting Progressive Damage and Failure of Open Hole Bending Specimens

    NASA Technical Reports Server (NTRS)

    Joseph, Ashith P. K.; Waas, Anthony M.; Pineda, Evan J.

    2016-01-01

    Progressive damage and failure in open hole composite laminate coupons subjected to flexural loading is modeled using Enhanced Schapery Theory (EST). Previous studies have demonstrated that EST can accurately predict the strength of open hole coupons under remote tensile and compressive loading states. This homogenized modeling approach uses single composite shell elements to represent the entire laminate in the thickness direction and significantly reduces computational cost. Therefore, when delaminations are not of concern or are active in the post-peak regime, the version of EST presented here is a good engineering tool for predicting deformation response. Standard coupon level tests provides all the input data needed for the model and they are interpreted in conjunction with finite element (FE) based simulations. Open hole bending test results of three different IM7/8552 carbon fiber composite layups agree well with EST predictions. The model is able to accurately capture the curvature change and deformation localization in the specimen at and during the post catastrophic load drop event.

  18. Predicting success or failure of brace treatment for adolescents with idiopathic scoliosis.

    PubMed

    Chalmers, Eric; Westover, Lindsey; Jacob, Johith; Donauer, Andreas; Zhao, Vicky H; Parent, Eric C; Moreau, Marc J; Mahood, James K; Hedden, Douglas M; Lou, Edmond H M

    2015-10-01

    Adolescent idiopathic scoliosis (AIS) is a three-dimensional spinal deformity. Brace treatment is a common non-surgical treatment, intended to prevent progression (worsening) of the condition during adolescence. Estimating a braced patient's risk of progression is an essential part of planning treatment, so method for predicting this risk would be a useful decision support tool for practitioners. This work attempts to discover whether failure of brace treatment (progression) can be predicted at the start of treatment. Records were obtained for 62 AIS patients who had completed brace treatment. Subjects were labeled as "progressive" if their condition had progressed despite brace treatment and "non-progressive" otherwise. Wrapper-based feature selection selected two useful predictor variables from a list of 14 clinical measurements taken from the records. A logistic regression model was trained to classify patients as "progressive" or "non-progressive" using these two variables. The logistic regression model's simplicity and interpretability should facilitate its clinical acceptance. The model was tested on data from an additional 28 patients and found to be 75 % accurate. This accuracy is sufficient to make the predictions clinically useful. It can be used online: http://www.ece.ualberta.ca/~dchalmer/SimpleBracePredictor.html . PMID:26002592

  19. Perineural invasion on prostate needle biopsy does not predict biochemical failure following brachytherapy for prostate cancer

    SciTech Connect

    Weight, Christopher J.; Ciezki, Jay P.; Reddy, Chandana A.; Zhou Ming; Klein, Eric A.

    2006-06-01

    Purpose: To determine if the presence of perineural invasion (PNI) predicts biochemical recurrence in patients who underwent low-dose-rate brachytherapy for the treatment of localized prostate cancer. Methods and Materials: A retrospective case control matching study was performed. The records of 651 patients treated with brachytherapy between 1996 and 2003 were reviewed. Sixty-three of these patients developed biochemical failure. These sixty-three patients were then matched in a one-to-one ratio to patients without biochemical failure, controlling for biopsy Gleason score, clinical stage, initial prostate-specific antigen, age, and the use of androgen deprivation. The pathology of the entire cohort was then reviewed for evidence of perineural invasion on initial prostate biopsy specimens. The biochemical relapse free survival rates for these two groups were compared. Results: Cases and controls were well matched, and there were no significant differences between the two groups in age, Gleason grade, clinical stage, initial prostate-specific antigen, and the use of androgen deprivation. PNI was found in 19 (17%) patients. There was no significant difference in the rates of PNI between cases and controls, 19.6% and 14.3% respectively (p 0.45). PNI did not correlate with biochemical relapse free survival (p 0.40). Conclusion: Perineural invasion is not a significant predictor of biochemical recurrence in patients undergoing brachytherapy for prostate cancer.

  20. A state-based approach to trend recognition and failure prediction for the Space Station Freedom

    NASA Technical Reports Server (NTRS)

    Nelson, Kyle S.; Hadden, George D.

    1992-01-01

    A state-based reasoning approach to trend recognition and failure prediction for the Altitude Determination, and Control System (ADCS) of the Space Station Freedom (SSF) is described. The problem domain is characterized by features (e.g., trends and impending failures) that develop over a variety of time spans, anywhere from several minutes to several years. Our state-based reasoning approach, coupled with intelligent data screening, allows features to be tracked as they develop in a time-dependent manner. That is, each state machine has the ability to encode a time frame for the feature it detects. As features are detected, they are recorded and can be used as input to other state machines, creating a hierarchical feature recognition scheme. Furthermore, each machine can operate independently of the others, allowing simultaneous tracking of features. State-based reasoning was implemented in the trend recognition and the prognostic modules of a prototype Space Station Freedom Maintenance and Diagnostic System (SSFMDS) developed at Honeywell's Systems and Research Center.

  1. Predicting mortality in patients with acute heart failure: Role of risk scores

    PubMed Central

    Passantino, Andrea; Monitillo, Francesco; Iacoviello, Massimo; Scrutinio, Domenico

    2015-01-01

    Acute heart failure is a leading cause of hospitalization and death, and it is an increasing burden on health care systems. The correct risk stratification of patients could improve clinical outcome and resources allocation, avoiding the overtreatment of low-risk subjects or the early, inappropriate discharge of high-risk patients. Many clinical scores have been derived and validated for in-hospital and post-discharge survival; predictive models include demographic, clinical, hemodynamic and laboratory variables. Data sets are derived from public registries, clinical trials, and retrospective data. Most models show a good capacity to discriminate patients who reach major clinical end-points, with C-indices generally higher than 0.70, but their applicability in real-world populations has been seldom evaluated. No study has evaluated if the use of risk score-based stratification might improve patient outcome. Some variables (age, blood pressure, sodium concentration, renal function) recur in most scores and should always be considered when evaluating the risk of an individual patient hospitalized for acute heart failure. Future studies will evaluate the emerging role of plasma biomarkers. PMID:26730296

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

    SciTech Connect

    Fok, Alex

    2013-10-30

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

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

    NASA Technical Reports Server (NTRS)

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

    2008-01-01

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

  4. Predicting treatment failure in severe sepsis and septic shock: looking for the Holy Grail

    PubMed Central

    2013-01-01

    Procalcitonin has been proposed as a specific biomarker of bacterial infections and has been related to the severity of sepsis. The prognostic ability of the initial concentrations of procalcitonin in sepsis is controversial. Some studies find higher initial concentrations in non-survivors but others find no differences. Prognostic assessment based on follow-up of procalcitonin levels may be better than evaluation of the initial levels of procalcitonin. The persistence of elevated procalcitonin levels is indicative of poor prognosis and is associated with mortality. Procalcitonin kinetics could be a tool for assessing the evolution of severe sepsis and sepsis shock. Procalcitonin should find its place as a biomarker for predicting treatment failure of severe sepsis and septic shock. PMID:24004571

  5. Prediction of reliability on thermoelectric module through accelerated life test and Physics-of-failure

    NASA Astrophysics Data System (ADS)

    Choi, Hyoung-Seuk; Seo, Won-Seon; Choi, Duck-Kyun

    2011-09-01

    Thermoelectric cooling module (TEM) which is electric device has a mechanical stress because of temperature gradient in itself. It means that structure of TEM is vulnerable in an aspect of reliability but research on reliability of TEM was not performed a lot. Recently, the more the utilization of thermoelectric cooling devices grows, the more the needs for life prediction and improvement are increasing. In this paper, we investigated life distribution, shape parameter of the TEM through accelerated life test (ALT). And we discussed about how to enhance life of TEM through the Physics-of-failure. Experimental results of ALT showed that the thermoelectric cooling module follows the Weibull distribution, shape parameter of which is 3.6. The acceleration model is coffin Coffin-Manson and material constant is 1.8.

  6. Improved measurement of soil moisture using an ultrasonic waveguide to predict rainfall-induced slope failure

    NASA Astrophysics Data System (ADS)

    Tanaka, Katsuhiko; Hiraoka, Nobutaka; Nakano, Shunya; Kameda, Takuma; Fujimoto, Masamitsu; Fukagawa, Ryoichi

    2015-10-01

    Field monitoring of soil moisture and groundwater level is important to predict shallow slope failure stemming from heavy rainfall. We previously proposed a monitoring technique using ultrasonic waveguides in which soil moisture and groundwater levels are monitored on the basis of the intensity and propagation time of ultrasonic waves reflected from the underground soil surface, respectively. In field monitoring, the reflective intensity depends on the depth of monitoring points and the inhomogeneity of grains, so it has been difficult to examine the reflective intensity change quantitatively. In the present work, we propose improvements that will allow us to measure the intensity change quantitatively. Specifically, we utilize an ultrasonic waveguide of a constant length by using casing pipes with different lengths depending on the monitoring depth and cover the surface of coarse-grained soil with a homogeneous fine soil to obtain repeatable data for wetting and drying cycles. The positive effects of these improvements were confirmed by a field monitoring test.

  7. A co-training-based approach for prediction of remaining useful life utilizing both failure and suspension data

    NASA Astrophysics Data System (ADS)

    Hu, Chao; Youn, Byeng D.; Kim, Taejin; Wang, Pingfeng

    2015-10-01

    Traditional data-driven prognostics often requires some amount of failure data for the offline training in order to achieve good accuracy for the online prediction. Failure data refer to condition monitoring data collected from the very beginning of an engineered system's lifetime till the occurrence of its failure. However, in many engineered systems, failure data are fairly expensive and time-consuming to obtain while suspension data are readily available. Suspension data refer to condition monitoring data acquired from the very beginning of an engineered system's lifetime till planned inspection or maintenance when the system is taken out of service. In such cases, it becomes essentially critical to utilize suspension data which may carry rich information regarding the degradation trend and help achieve more accurate remaining useful life (RUL) prediction. To this end, this paper proposes a co-training-based data-driven prognostic approach, denoted by COPROG, which uses two data-driven algorithms with each predicting RULs of suspension units for the other. After a suspension unit is chosen and its RUL is predicted by an individual algorithm, it becomes a virtual failure unit that is added to the training data set of the other individual algorithm. Results obtained from two case studies suggest that COPROG gives more accurate RUL prediction, as compared to any individual algorithm with no use of suspension data, and that COPROG can effectively exploit suspension data to improve the prognostic accuracy.

  8. Failure behavior of internally pressurized flawed and unflawed steam generator tubing at high temperatures -- Experiments and comparison with model predictions

    SciTech Connect

    Majumdar, S.; Shack, W.J.; Diercks, D.R.; Mruk, K.; Franklin, J.; Knoblich, L.

    1998-03-01

    This report summarizes experimental work performed at Argonne National Laboratory on the failure of internally pressurized steam generator tubing at high temperatures ({le} 700 C). A model was developed for predicting failure of flawed and unflawed steam generator tubes under internal pressure and temperature histories postulated to occur during severe accidents. The model was validated by failure tests on specimens with part-through-wall axial and circumferential flaws of various lengths and depths, conducted under various constant and ramped internal pressure and temperature conditions. The failure temperatures predicted by the model for two temperature and pressure histories, calculated for severe accidents initiated by a station blackout, agree very well with tests performed on both flawed and unflawed specimens.

  9. Predicting outcomes among patients with atrial fibrillation and heart failure receiving anticoagulation with warfarin.

    PubMed

    Kim, Eun-Jeong; Ozonoff, Al; Hylek, Elaine M; Berlowitz, Dan R; Ash, Aelene S; Miller, Donald R; Zhao, Shibei; Reisman, Joel I; Jasuja, Guneet K; Rose, Adam J

    2015-07-01

    Among patients receiving oral anticoagulation for atrial fibrillation (AF), heart failure (HF) is associated with poor anticoagulation control. However, it is not known which patients with heart failure are at greatest risk of adverse outcomes. We evaluated 62,156 Veterans Health Administration (VA) patients receiving warfarin for AF between 10/1/06-9/30/08 using merged VA-Medicare dataset. We predicted time in therapeutic range (TTR) and rates of adverse events by categorising patients into those with 0, 1, 2, or 3+ of five putative markers of HF severity such as aspartate aminotransferase (AST)> 80 U/l, alkaline phosphatase> 150 U/l, serum sodium< 130 mEq/l, any receipt of metolazone, and any inpatient admission for HF exacerbation. These risk categories predicted TTR: patients without HF (referent) had a mean TTR of 65.0 %, while HF patients with 0, 1, 2, 3 or more markers had mean TTRs of 62.2 %, 57.2 %, 53.5 %, and 50.7 %, respectively (p< 0.001). These categories also discriminated for major haemorrhage well; compared to patients without HF, HF patients with increasing severity had hazard ratios of 1.84, 3.06, 3.52 and 5.14 respectively (p< 0.001). However, although patients with HF had an elevated hazard for bleeding compared to those without HF, these categories did not effectively discriminate risk of ischaemic stroke across HF. In conclusion, we developed a HF severity model using easily available clinical characteristics that performed well to risk-stratify patients with HF who are receiving anticoagulation for AF with regard to major haemorrhage. PMID:25948532

  10. High-Sensitivity C-Reactive Protein Predicts Mortality and Technique Failure in Peritoneal Dialysis Patients

    PubMed Central

    Liu, Shou-Hsuan; Li, Yi-Jung; Wu, Hsin-Hsu; Lee, Cheng-Chia; Lin, Chan-Yu; Weng, Cheng-Hao; Chen, Yung-Chang; Chang, Ming-Yang; Hsu, Hsiang-Hao; Fang, Ji-Tseng; Hung, Cheng-Chieh; Yang, Chih-Wei; Tian, Ya-Chung

    2014-01-01

    Introduction An elevated level of serum C-reactive protein (CRP) is widely considered an indicator of an underlying inflammatory disease and a long-term prognostic predictor for dialysis patients. This cross-sectional cohort study was designed to assess the correlation between the level of high-sensitivity CRP (HS-CRP) and the outcome of peritoneal dialysis (PD) patients. Methods A total of 402 patients were stratified into 3 tertiles (lower, middle, upper) according to serum HS-CRP level and and followed up from October 2009 to September 2011. During follow-up, cardiovascular events, infection episodes, technique failure, and mortality rate were recorded. Results During the 24-month follow-up, 119 of 402 patients (29.6%) dropped out from PD, including 28 patients (7.0%) who died, 81 patients (20.1%) who switched to hemodialysis, and 10 patients (2.5%) who underwent kidney transplantation. The results of Kaplan–Meier analysis and log-rank test demonstrated a significant difference in the cumulative patient survival rate across the 3 tertiles (the lowest rate in upper tertile). On multivariate Cox regression analysis, only higher HS-CRP level, older age, the presence of diabetes mellitus (DM), lower serum albumin level, and the occurrence of cardiovascular events during follow-up were identified as independent predictors of mortality. Every 1 mg/L increase in HS-CRP level was independently predictive of a 1.4% increase in mortality. Multivariate Cox regression analysis also showed that higher HS-CRP level, the presence of DM, lower hemoglobin level, lower serum albumin level, higher dialysate/plasma creatinine ratio, and the occurrence of infective episodes and cardiovascular events during follow-up were independent predictors of technique failure. Conclusions The present study shows the importance of HS-CRP in the prediction of 2-year mortality and technique survival in PD patients independent of age, diabetes, hypoalbuminemia, and the occurrence of

  11. Incremental and independent value of cardiopulmonary exercise test measures and the Seattle Heart Failure Model for prediction of risk in patients with heart failure

    PubMed Central

    Dardas, Todd; Li, Yanhong; Reed, Shelby D.; O’Connor, Christopher M.; Whellan, David J.; Ellis, Stephen J.; Schulman, Kevin A.; Kraus, William E.; Forman, Daniel E.; Levy, Wayne C.

    2016-01-01

    Background Multivariable risk scores and exercise measures are well-validated risk prediction methods. Combining information from a functional evaluation and a risk model may improve accuracy of risk predictions. We analyzed whether adding exercise measures to the Seattle Heart Failure Model (SHFM) improves risk prediction accuracy in systolic heart failure. Methods and Results We used a sample of patients from the Heart Failure and A Controlled Trial Investigating Outcomes of Exercise TraiNing (HF-ACTION) study to examine the addition of peak VO2, VE/VCO2 slope, 6-minute walk distance (6MWD) or exercise duration (CPXDUR) to the SHFM. Multivariable Cox proportional hazards models were used to test the association between the combined endpoint (death, LVAD or cardiac transplantation) and the addition of exercise variables to the SHFM. 2152 patients were included in the sample. The SHFM and all exercise measures were associated with events (all p-values<0.0001) in proportional hazards models. There was statistically significant improvement in risk estimation when exercise measures were added to the SHFM. However, the improvement in c-index for addition of peak VO2 (+0.01), VE/VCO2 (+0.02), 6MWD (−0.001) and CPXDUR (+0.001) to the SHFM was small or slightly worse than the SHFM alone. Changes in risk assignment with the addition of exercise variables were minimal for patients above or below a15% 1-year mortality. Conclusions Exercise performance measures and the SHFM are independently useful for predicting risk in systolic heart failure. Adding CPET measures and 6MWD to the SHFM offers only minimal improvement in risk reassignment at clinically meaningful cutpoints. PMID:25940075

  12. Could "safe practice" be compromising safe practice? Should anesthetists have to deflate the cuff of the endotracheal tube before extubation?

    PubMed

    Priebe, Hans-Joachim

    2016-02-01

    Deflation of the cuff of the endotracheal tube (ETT) before tracheal extubation is considered mandatory and safe practice. However, there are potential shortcomings associated with this practice (e.g., aspiration around the uncuffed ETT, loss of positive airway pressure, difficulty in generating an effective cough at the time of extubation). By contrast, keeping the cuff inflated during extubation will minimize the risk of tracheal aspiration around the ETT, and it will reliably allow maintenance of positive airway pressure until extubation, effective lung recruitment before extubation, and generation of an effective cough during extubation. All of these factors might reduce the overall risk of immediate postextubation and postoperative respiratory and pulmonary complications. Mandatory monitoring of cuff pressure ensures a remaining rather small, highly compressible cuff volume around the ETT which is unlikely to carry per se the risk of producing laryngeal trauma. In my view, as the overall advantages of not deflating the cuff before extubation outweigh the disadvantages, anesthetists should not have to deflate the cuff of the ETT before extubation. Ultimately, only a randomized controlled trial will be able to assess the effect of such practice on patient outcome. PMID:26126979

  13. Strength Evaluation and Failure Prediction of Short Carbon Fiber Reinforced Nylon Spur Gears by Finite Element Modeling

    NASA Astrophysics Data System (ADS)

    Hu, Zhong; Hossan, Mohammad Robiul

    2013-06-01

    In this paper, short carbon fiber reinforced nylon spur gear pairs, and steel and unreinforced nylon spur gear pairs have been selected for study and comparison. A 3D finite element model was developed to simulate the multi-axial stress-strain behaviors of the gear tooth. Failure prediction has been conducted based on the different failure criteria, including Tsai-Wu criterion. The tooth roots, where has stress concentration and the potential for failure, have been carefully investigated. The modeling results show that the short carbon fiber reinforced nylon gear fabricated by properly controlled injection molding processes can provide higher strength and better performance.

  14. The failure analysis and lifetime prediction for the solder joint of the magnetic head

    NASA Astrophysics Data System (ADS)

    Xiao, Xianghui; Peng, Minfang; Cardoso, Jaime S.; Tang, Rongjun; Zhou, YingLiang

    2015-02-01

    Micro-solder joint (MSJ) lifetime prediction methodology and failure analysis (FA) are to assess reliability by fatigue model with a series of theoretical calculations, numerical simulation and experimental method. Due to shortened time of solder joints on high-temperature, high-frequency sampling error that is not allowed in productions may exist in various models, including round-off error. Combining intermetallic compound (IMC) growth theory and the FA technology for the magnetic head in actual production, this thesis puts forward a new growth model to predict life expectancy for solder joint of the magnetic head. And the impact of IMC, generating from interface reaction between slider (magnetic head, usually be called slider) and bonding pad, on mechanical performance during aging process is analyzed in it. By further researching on FA of solder ball bonding, thesis chooses AuSn4 growth model that affects least to solder joint mechanical property to indicate that the IMC methodology is suitable to forecast the solder lifetime. And the diffusion constant under work condition 60 °C is 0.015354; the solder lifetime t is 14.46 years.

  15. Long-term Failure Prediction based on an ARP Model of Global Risk Network

    NASA Astrophysics Data System (ADS)

    Lin, Xin; Moussawi, Alaa; Szymanski, Boleslaw; Korniss, Gyorgy

    Risks that threaten modern societies form an intricately interconnected network. Hence, it is important to understand how risk materializations in distinct domains influence each other. In the paper, we study the global risks network defined by World Economic Forum experts in the form of Stochastic Block Model. We model risks as Alternating Renewal Processes with variable intensities driven by hidden values of exogenous and endogenous failure probabilities. Based on the expert assessments and historical status of each risk, we use Maximum Likelihood Evaluation to find the optimal model parameters and demonstrate that the model considering network effects significantly outperforms the others. In the talk, we discuss how the model can be used to provide quantitative means for measuring interdependencies and materialization of risks in the network. We also present recent results of long-term predictions in the form of predicated distributions of materializations over various time periods. Finally we show how the simulation of ARP's enables us to probe limits of the predictability of the system parameters from historical data and ability to recover hidden variable. Supported in part by DTRA, ARL NS-CTA.

  16. Life Prediction and Classification of Failure Modes in Solid State Luminaires Using Bayesian Probabilistic Models

    SciTech Connect

    Lall, Pradeep; Wei, Junchao; Sakalaukus, Peter

    2014-05-27

    A new method has been developed for assessment of the onset of degradation in solid state luminaires to classify failure mechanisms by using metrics beyond lumen degradation that are currently used for identification of failure. Luminous Flux output, Correlated Color Temperature Data on Philips LED Lamps has been gathered under 85°C/85%RH till lamp failure. The acquired data has been used in conjunction with Bayesian Probabilistic Models to identify luminaires with onset of degradation much prior to failure through identification of decision boundaries between lamps with accrued damage and lamps beyond the failure threshold in the feature space. In addition luminaires with different failure modes have been classified separately from healthy pristine luminaires. It is expected that, the new test technique will allow the development of failure distributions without testing till L70 life for the manifestation of failure.

  17. A Comprehensive Method for Predicting Fatal Liver Failure of Patients With Liver Cancer Resection

    PubMed Central

    Li, Jiangfa; Lei, Biao; Nie, Xingju; Lin, Linku; Tahir, Syed Abdul; Shi, Wuxiang; Jin, Junfei; He, Songqing

    2015-01-01

    Abstract There are many methods to assess liver function, but none of them has been verified as fully effective. The purpose of this study is to establish a comprehensive method evaluating perioperative liver reserve function (LRF) in patients with primary liver cancer (PLC). In this study, 310 PLC patients who underwent liver resection were included. The cohort was divided into a training set (n = 235) and a validation set (n = 75). The factors affecting postoperative liver dysfunction (POLD) during preoperative, intraoperative, and postoperative periods were confirmed by logistic regression analysis. The equation for calculating the preoperative liver functional evaluation index (PLFEI) was established; the cutoff value of PLFEI determined through analysis by receiver-operating characteristic curve was used to predict postoperative liver function. The data showed that body mass index, international normalized ratio, indocyanine green (ICG) retention rate at 15 minutes (ICGR15), ICG elimination rate, standard remnant liver volume (SRLV), operative bleeding volume (OBV), blood transfusion volume, and operative time were statistically different (all P < 0.05) between 2 groups of patients with and without POLD. The relationship among PLFEI, ICGR15, OBV, and SRLV is expressed as an equation of “PLFEI = 0.181 × ICGR15 + 0.001 × OBV − 0.008 × SRLV.” The cutoff value of PLFEI to predict POLD was −2.16 whose sensitivity and specificity were 90.3% and 73.5%, respectively. However, when predicting fatal liver failure (FLF), the cutoff value of PLFEI was switched to −1.97 whose sensitivity and specificity were 100% and 68.8%, respectively. PLFEI will be a more comprehensive, sensitive, and accurate index assessing perioperative LRF in liver cancer patients who receive liver resection. And keeping PLFEI <−1.97 is a safety margin for preventing FLF in PLC patients who underwent liver resection. PMID:25929924

  18. Serum microRNA expression patterns that predict early treatment failure in prostate cancer patients

    PubMed Central

    Singh, Prashant K.; Preus, Leah; Hu, Qiang; Yan, Li; Long, Mark D.; Morrison, Carl D.; Nesline, Mary; Johnson, Candace S.; Koochekpour, Shahriar; Kohli, Manish; Liu, Song; Trump, Donald L.

    2014-01-01

    We aimed to identify microRNA (miRNA) expression patterns in the serum of prostate cancer (CaP) patients that predict the risk of early treatment failure following radical prostatectomy (RP). Microarray and Q-RT-PCR analyses identified 43 miRNAs as differentiating disease stages within 14 prostate cell lines and reflectedpublically available patient data. 34 of these miRNA were detectable in the serum of CaP patients. Association with time to biochemical progression was examined in a cohort of CaP patients following RP. A greater than two-fold increase in hazard of biochemical progression associated with altered expression of miR-103, miR-125b and miR-222 (p <.0008) in the serum of CaP patients. Prediction models based on penalized regression analyses showed that the levels of the miRNAs and PSA together were better at detecting false positives than models without miRNAs, for similar level of sensitivity. Analyses of publically available data revealed significant and reciprocal relationships between changes in CpG methylation and miRNA expression patterns suggesting a role for CpG methylation to regulate miRNA. Exploratory validation supported roles for miR-222 and miR-125b to predict progression risk in CaP. The current study established that expression patterns of serum-detectable miRNAs taken at the time of RP are prognostic for men who are at risk of experiencing subsequent early biochemical progression. These non-invasive approaches could be used to augment treatment decisions. PMID:24583788

  19. Systemic Inflammatory Response and Serum Lipopolysaccharide Levels Predict Multiple Organ Failure and Death in Alcoholic Hepatitis

    PubMed Central

    Michelena, Javier; Altamirano, José; Abraldes, Juan G.; Affò, Silvia; Morales-Ibanez, Oriol; Sancho-Bru, Pau; Dominguez, Marlene; García-Pagán, Juan Carlos; Fernández, Javier; Arroyo, Vicente; Ginès, Pere; Louvet, Alexandre; Mathurin, Philippe; Mehal, Wajahat Z.; Caballería, Juan; Bataller, Ramón

    2015-01-01

    Alcoholic hepatitis (AH) frequently progresses to multiple organ failure (MOF) and death. However, the driving factors are largely unknown. At admission, patients with AH often show criteria of systemic inflammatory response syndrome (SIRS) even in the absence of an infection. We hypothesize that the presence of SIRS may predispose to MOF and death. To test this hypothesis, we studied a cohort including 162 patients with biopsy-proven AH. The presence of SIRS and infections was assessed in all patients, and multivariate analyses identified variables independently associated with MOF and 90-day mortality. At admission, 32 (19.8%) patients were diagnosed with a bacterial infection, while 75 (46.3%) fulfilled SIRS criteria; 58 patients (35.8%) developed MOF during hospitalization. Short-term mortality was significantly higher among patients who developed MOF (62.1% versus 3.8%, P <0.001). The presence of SIRS was a major predictor of MOF (odds ratio = 2.69, P=0.025) and strongly correlated with mortality. Importantly, the course of patients with SIRS with and without infection was similar in terms of MOF development and short-term mortality. Finally, we sought to identify serum markers that differentiate SIRS with and without infection. We studied serum levels of high-sensitivity C-reactive protein, procalcitonin, and lipopolysaccharide at admission. All of them predicted mortality. Procalcitonin, but not high-sensitivity C-reactive protein, serum levels identified those patients with SIRS and infection. Lipopolysaccharide serum levels predicted MOF and the response to prednisolone. Conclusion In the presence or absence of infections, SIRS is a major determinant of MOF and mortality in AH, and the mechanisms involved in the development of SIRS should be investigated; procalcitonin serum levels can help to identify patients with infection, and lipopolysaccharide levels may help to predict mortality and the response to steroids. PMID:25761863

  20. Reduced Cognitive Function Predicts Functional Decline in Patients with Heart Failure over 12 months

    PubMed Central

    Alosco, Michael L.; Spitznagel, Mary Beth; Cohen, Ronald; Sweet, Lawrence H.; Colbert, Lisa H.; Josephson, Richard; Hughes, Joel; Rosneck, Jim; Gunstad, John

    2016-01-01

    Background Impaired activities of daily living (ADL) are common in heart failure (HF) patients and contribute to the elevated mortality and hospitalization rates in this population. Cognitive impairment is also prevalent in HF, though its ability to predict functional decline over time is unknown. Aims This study examined the longitudinal pattern of activities of daily living in HF persons and whether reduced baseline cognitive status predicts functional decline in this population. Methods 110 persons with HF completed the Lawton-Brody Activities of Daily Living Scale and were administered the Modified Mini-Mental Status Examination (3MS) at baseline and a 12-month follow-up. Three composite scores were derived from the Lawton-Brody, including total, instrumental, and basic ADLs. Results HF patients reported high rates of baseline impairments in instrumental ADLs, including shopping, food preparation, housekeeping duties, laundry, among others. Repeated measures analyses showed significant declines in total and instrumental ADLs from baseline to the 12-month follow-up in HF (p < .05). Hierarchical regression analyses showed that poorer baseline performance on the 3MS predicted worse total ADL performance at 12-months (β = .15, p = .049), including greater dependence in shopping, driving, feeding, and physical ambulation (p < .05 for all). Conclusion The current results show that HF patients report significant functional decline over a 12-month period and brief cognitive tests can identify those patients at highest risk for decline. If replicated, such findings encourage the use of cognitive screening measures to identify HF patients most likely to require assistance with ADL tasks. PMID:23754840

  1. Prediction factors for failure to seek treatment following traumatic dental injuries to primary teeth.

    PubMed

    Firmino, Ramon Targino; Siqueira, Maria Betânia Lins Dantas; Vieira-Andrade, Raquel Gonçalves; Gomes, Genara Brum; Martins, Carolina Castro; Paiva, Saul Martins; Granville-Garcia, Ana Flávia

    2014-01-01

    The objective of this study was to evaluate prediction factors for failure to seek treatment following a traumatic dental injury (TDI) to primary teeth among preschool children in the city of Campina Grande, Brazil. A cross-sectional study was carried out involving 277 children 3 to 5 years of age, with TDI, enrolled in public and private preschools. Parents filled out a form addressing demographic data and whether or not they had sought treatment. Clinical examinations were performed by three dentists who had undergone a calibration exercise (Kappa: 0.85 to 0.90) for the evaluation of TDI. Bivariate and multivariate Poisson regression models were constructed (α=5%). Enamel fracture was the most prevalent type of TDI (48.7%) and the upper central incisors were the most affected teeth (88.4%). The frequency of seeking dental treatment was low (9.7%). The following variables were associated with failure to seek treatment following TDI: a household income greater than one minimum wage (PR=1.170; 95%CI 1.018-1.341), parents/caregivers' perception of a child's oral health as poor (PR=1.100; 95%CI 1.026-1.176), and the non-perception of TDI by parents/caregivers (PR=1.250; 95%CI 1.142-1.360). In the present study, the frequency of seeking treatment following TDI was low, and parents/caregivers with a higher income, a poor perception of their child's oral health and a lack of awareness regarding the trauma were more likely to fail to seek treatment following TDI to primary teeth. PMID:24918361

  2. Predictive Values of Red Blood Cell Distribution Width in Assessing Severity of Chronic Heart Failure

    PubMed Central

    Liu, Sen; Wang, Ping; Shen, Ping-Ping; Zhou, Jian-Hua

    2016-01-01

    Background This retrospective study was performed to evaluate the value of baseline red blood cell distribution width (RDW) for predicting the severity of chronic heart failure (CHF) compared with N-terminal prohormone brain natriuretic peptide (NT-ProBNP) and other hematological and biochemical parameters. Material/Methods Hematological and biochemical parameters were obtained from 179 patients with New York Heart Association (NYHA) CHF class I (n=44), II (n=39), III (n=41), and IV (n=55). Receiver operator characteristic (ROC) curves were used for assessing predictive values. Results RDW increased significantly in class III and IV compared with class I (14.3±2.3% and 14.3±1.7% vs. 12.9±0.8%, P<0.01). Areas under ROCs (AUCs) of RDW and NT-ProBNP for class IV HF were 0.817 and 0.840, respectively. RDW was markedly elevated in the mortality group compared with the survival group (13.7±1.7 vs. 15.8±1.8, P<0.01). The predictive value of RDW was lower than that of NT-ProBNP but was comparable to white blood cell (WBC), neutrophil (NEU), lymphocyte (L), and neutrophil/lymphocyte ratio (N/L) for mortality during hospitalization, with AUCs of 0.837, 0.939, 0.858, 0.891, 0.885, and 0.885, respectively. RDW and NT-proBNP showed low predictive values for repeated admission (≥3). RDW was an independent risk factor for mortality (OR=2.531, 95% CI: 1.371–4.671). Conclusions RDW increased significantly in class III and IV patients and in the mortality group. The predictive value of RDW is comparable to NT-proBNP for class IV and lower than that of NT-proBNP for mortality. Elevated RDW is an independent risk factor for mortality. PMID:27324271

  3. Inappropriate fixation of an endotracheal tube causing cuff malfunction resulting in difficult extubation.

    PubMed

    Nag, Deb Sanjay; Samaddar, Devi Prasad

    2016-01-01

    We discuss a case of difficult extubation, due to inadequate deflation of the tracheal tube cuff, despite collapse of the pilot balloon, on its aspiration. This was caused by inadvertent kinking of the pilot balloon tubing due to inappropriate tape fixation of the endotracheal tube. PMID:27591469

  4. A Statistical Approach to Predict the Failure Enthalpy and Reliability of Irradiated PWR Fuel Rods During Reactivity-Initiated Accidents

    SciTech Connect

    Nam, Cheol; Jeong, Yong-Hwan; Jung, Youn-Ho

    2001-11-15

    During the last decade, the failure behavior of high-burnup fuel rods under a reactivity-initiated accident (RIA) condition has been a serious concern since fuel rod failures at low enthalpy have been observed. This has resulted in the reassessment of existing licensing criteria and failure-mode study. To address the issue, a statistics-based methodology is suggested to predict failure probability of irradiated fuel rods under an RIA. Based on RIA simulation results in the literature, a failure enthalpy correlation for an irradiated fuel rod is constructed as a function of oxide thickness, fuel burnup, and pulse width. Using the failure enthalpy correlation, a new concept of ''equivalent enthalpy'' is introduced to reflect the effects of the three primary factors as well as peak fuel enthalpy into a single damage parameter. Moreover, the failure distribution function with equivalent enthalpy is derived, applying a two-parameter Weibull statistical model. Finally, the sensitivity analysis is carried out to estimate the effects of burnup, corrosion, peak fuel enthalpy, pulse width, and cladding materials used.

  5. Implicit and Explicit Attitudes Predict Smoking Cessation: Moderating Effects of Experienced Failure to Control Smoking and Plans to Quit

    PubMed Central

    Chassin, Laurie; Presson, Clark C.; Sherman, Steven J.; Seo, Dong-Chul; Macy, Jon

    2010-01-01

    The current study tested implicit and explicit attitudes as prospective predictors of smoking cessation in a Midwestern community sample of smokers. Results showed that the effects of attitudes significantly varied with levels of experienced failure to control smoking and plans to quit. Explicit attitudes significantly predicted later cessation among those with low (but not high or average) levels of experienced failure to control smoking. Conversely, however, implicit attitudes significantly predicted later cessation among those with high levels of experienced failure to control smoking, but only if they had a plan to quit. Because smoking cessation involves both controlled and automatic processes, interventions may need to consider attitude change interventions that focus on both implicit and explicit attitudes. PMID:21198227

  6. A model for predicting coolant activity behaviour for fuel-failure monitoring analysis

    NASA Astrophysics Data System (ADS)

    El-Jaby, Ali

    A CANDU fuel element becomes defective when the Zircaloy-4 sheath is breached, allowing high pressure heavy water (D2O) coolant to enter the fuel-to-sheath gap, thereby creating a direct path for fission products (mainly volatile species of iodine and noble gases) and fuel debris to escape into the primary heat transport system (PHTS). In addition, the entry of D 2O coolant into the fuel-to-sheath gap may cause the UO2 fuel to oxidize, which in turn can augment the rate of fission product release into the PHTS. The release of fission products and fuel debris into the PHTS will elevate circuit contamination levels, consequently increasing radiation exposure to station personnel during maintenance tasks. Moreover, the continued operation of a defective fuel element may diminish its thermal performance due to fuel oxidation effects. It is therefore desirable to discharge defective fuel as soon as possible. Hence, a better understanding of defective fuel behaviour is required in order to develop an improved methodology for fuel-failure monitoring and PHTS coolant activity prediction. A mathematical model has been developed to predict the release of volatile fission products from operating defective nuclear fuel elements. The fission product activity in both the fuel-to-sheath gap and PHTS coolant as a function of time can be predicted during all reactor operations including steady-state operation as well as reactor shutdown, startup, and bundle-shifting manoeuvres. In addition, an improved ability to predict the PHTS coolant activity of the 135Xe isotope in commercial reactors is discussed. Moreover, a method to approximate both the burnup and the amount of the tramp uranium deposits in-core, as well as the tramp uranium fission rate is proposed. The model has been implemented as the STAR (Steady-state and Transient Activity Release) stand-alone code written in the C++ programming language using a custom developed finite-difference variable-mesh (FDVM) numerical

  7. Serum biomarkers may help predict successful misoprostol management of early pregnancy failure.

    PubMed

    Schreiber, Courtney A; Ratcliffe, Sarah J; Quinley, Kelly E; Miller, Carrie; Sammel, Mary D

    2015-06-01

    In order to simplify management of early pregnancy loss, our goal was to elucidate predictors of successful medical management of miscarriage with a single dose of misoprostol. In this secondary analysis of data from a multicenter randomized controlled trial, candidate biomarkers were compared between 49 women with missed abortion who succeeded in passing their pregnancy with a single dose of misoprostol and 46 women who did not pass their pregnancy with a misoprostol single dose. We computed the precision of trophoblastic protein and hormone concentrations to discriminate between women who succeed or fail single dose misoprostol management. We also included demographic factors in our analyses. We found overlap in the concentrations of the individual markers between women who succeeded and failed single-dose misoprostol. However, hCG levels ≥ 4000 mIU/mL and ADAM-12 levels ≥ 2500 pg/mL were independently associated with complete uterine expulsion after one dose of misoprostol in our population. A multivariable logistic model for success included non-Hispanic ethnicity and parity <2 in addition to hCG ≥ 4000 mIU/mL and ADAM-12 ≥ 2500 pg/mL and had an area under the receiver operating characteristic (ROC) of 0.81 (95% confidence interval: 72-90%). Categorizing women with a predicted probability of ≥ 0.65 resulted in a sensitivity of 75.0%, specificity 77.1% and positive predictive value of 81.8%. While preliminary, our data suggest that serum biomarkers, especially when combined with demographic characteristics, may be helpful in guiding patient decision-making regarding the management of early pregnancy failure (EPF). Further study is warranted. PMID:26051455

  8. Serum Uric Acid Predicts Declining of Circulating Proangiogenic Mononuclear Progenitor Cells in Chronic Heart Failure Patients

    PubMed Central

    Berezin, Alexander E.; Kremzer, Alexander A.; Samura, Tatyana A.; Berezina, Tatyana A.; Martovitskaya, Yulia V.

    2014-01-01

    Introduction: Serum uric acid (SUA) is considered a marker for natural progression of chronic heart failure (CHF) mediated cardiovascular remodelling. CHF associates with declining of circulating mononuclear progenitor cells (MPCs). The objective of this study was to evaluate the interrelationship between SUA concentrations and proangiogenic MPCs in ischemic CHF patients. Methods: The study population was structured retrospectively after determining the coronary artery disease (CAD) by contrast-enhanced spiral computed tomography angiography in 126 subjects with symptomatic ischemic mild-to-severe CHF and 128 CAD subjects without CHF. Baseline biomarkers were measured in all patients. Cox proportional multivariate hazard ratio was calculated for predictors of MPCs declining in both CHF and non-CHF patient population predictors of MPCs declining in CHF subjects were examined in stepwise logistic regression. C-statistics, integrated discrimination indices (IDI) and net-reclassification improvement were utilized for prediction performance analyses. Results: Cox proportional adjusted hazard ratio analyses for CD14+CD309+ and CD14+CD309+Tie2+ MPCs by SUA has shown that the higher quartiles (Q3 and Q4) of SUA compared to the lower quartiles (Q1 and Q2) are associated with increased risks of depletion of both CD14+CD309+ and CD14+CD309+Tie2+ MPCs. The addition of Q4 SUA to the ABC model improved the relative IDI by 13.8% for depletion of CD14+CD309+ MPCs and by 14.5% for depletion of CD14+CD309+Tie2+ MPCs. Conclusion: Circulating levels of proangiogenic MPCs are declined progressively depending on the levels of SUA in the HF subjects with CHF. We suggest that even mild elevations of SUA might be used to predict of relative depletion of proangiogenic MPCs among chronic HF patients. PMID:25320662

  9. Pitfalls and Precautions When Using Predicted Failure Data for Quantitative Analysis of Safety Risk for Human Rated Launch Vehicles

    NASA Technical Reports Server (NTRS)

    Hatfield, Glen S.; Hark, Frank; Stott, James

    2016-01-01

    Launch vehicle reliability analysis is largely dependent upon using predicted failure rates from data sources such as MIL-HDBK-217F. Reliability prediction methodologies based on component data do not take into account risks attributable to manufacturing, assembly, and process controls. These sources often dominate component level reliability or risk of failure probability. While consequences of failure is often understood in assessing risk, using predicted values in a risk model to estimate the probability of occurrence will likely underestimate the risk. Managers and decision makers often use the probability of occurrence in determining whether to accept the risk or require a design modification. Due to the absence of system level test and operational data inherent in aerospace applications, the actual risk threshold for acceptance may not be appropriately characterized for decision making purposes. This paper will establish a method and approach to identify the pitfalls and precautions of accepting risk based solely upon predicted failure data. This approach will provide a set of guidelines that may be useful to arrive at a more realistic quantification of risk prior to acceptance by a program.

  10. TBCs for Gas Turbines under Thermomechanical Loadings: Failure Behaviour and Life Prediction

    NASA Astrophysics Data System (ADS)

    Beck, T.; Trunova, O.; Herzog, R.; Singheiser, L.

    2012-10-01

    The present contribution gives an overview about recent research on a thermal barrier coating (TBC) system consisted of (i) an intermetallic MCrAlY-alloy Bondcoat (BC) applied by vacuum plasma spraying (VPS) and (ii) an Yttria Stabilised Zirconia (YSZ) top coat air plasma sprayed (APS) at Forschungszentrum Juelich, Institute of Energy and Climate Research (IEK-1). The influence of high temperature dwell time, maximum and minimum temperature on crack growth kinetics during thermal cycling of such plasma sprayed TBCs is investigated using infrared pulse thermography (IT), acoustic emission (AE) analysis and scanning electron microscopy. Thermocyclic life in terms of accumulated time at maximum temperature decreases with increasing high temperature dwell time and increases with increasing minimum temperature. AE analysis proves that crack growth mainly occurs during cooling at temperatures below the ductile-to-brittle transition temperature of the BC. Superimposed mechanical load cycles accelerate delamination crack growth and, in case of sufficiently high mechanical loadings, result in premature fatigue failure of the substrate. A life prediction model based on TGO growth kinetics and a fracture mechanics approach has been developed which accounts for the influence of maximum and minimum temperature as well as of high temperature dwell time with good accuracy in an extremely wide parameter range.

  11. Predicting time-to-failure in rock extrapolated from secondary creep

    NASA Astrophysics Data System (ADS)

    Hao, Sheng-Wang; Zhang, Bao-Ju; Tian, Ji-Feng; Elsworth, Derek

    2014-03-01

    Stress relaxation experiments are reported that culminate in energetic failure in rocks analogous to the loading cycle and subsequent localization or reactivation on brittle faults embedded in an elastic medium. Universally, rapid primary deformation arrests and transitions into a long secondary deformation phase that ultimately accelerates to catastrophic rupture. Primary deformation (u) conforms to Andrade's law as du/dt ~ (tc - t0)θ with a standard exponent of 2/3. In the long, and readily observable, secondary phase, the samples both deform and analogously shed load near linearly in time. This stress relaxation rate exhibits a robust power law dependency with time-to-rupture and exhibits the same 2/3 power law exponent observed in the primary phase. Similarly, the brittle strain energy released in the tertiary collapse scales with a normalized secondary stress relaxation rate. Together, these observations suggest a way to predict both the timing of rupture and its energetics from the observed stress (or strain) rate during the secondary relaxation stage.

  12. Early warning and clinical outcome prediction of acute-on-chronic hepatitis B liver failure

    PubMed Central

    Chen, En-Qiang; Zeng, Fan; Zhou, Ling-Yun; Tang, Hong

    2015-01-01

    Hepatitis B virus (HBV) associated acute-on-chronic liver failure (ACLF) is an increasingly recognized fatal liver disease encompassing a severe acute exacerbation of liver function in patients with chronic hepatitis B (CHB). Despite the introduction of an artificial liver support system and antiviral therapy, the short-term prognosis of HBV-ACLF is still extremely poor unless emergency liver transplantation is performed. In such a situation, stopping or slowing the progression of CHB to ACLF at an early stage is the most effective way of reducing the morbidity and mortality of HBV-ACLF. It is well-known that the occurrence and progression of HBV-ACLF is associated with many factors, and the outcomes of HBV-ACLF patients can be significantly improved if timely and appropriate interventions are provided. In this review, we highlight recent developments in early warning and clinical outcome prediction in patients with HBV-ACLF and provide an outlook for future research in this field. PMID:26576085

  13. Failure location prediction by finite element analysis for an additive manufactured mandible implant.

    PubMed

    Huo, Jinxing; Dérand, Per; Rännar, Lars-Erik; Hirsch, Jan-Michaél; Gamstedt, E Kristofer

    2015-09-01

    In order to reconstruct a patient with a bone defect in the mandible, a porous scaffold attached to a plate, both in a titanium alloy, was designed and manufactured using additive manufacturing. Regrettably, the implant fractured in vivo several months after surgery. The aim of this study was to investigate the failure of the implant and show a way of predicting the mechanical properties of the implant before surgery. All computed tomography data of the patient were preprocessed to remove metallic artefacts with metal deletion technique before mandible geometry reconstruction. The three-dimensional geometry of the patient's mandible was also reconstructed, and the implant was fixed to the bone model with screws in Mimics medical imaging software. A finite element model was established from the assembly of the mandible and the implant to study stresses developed during mastication. The stress distribution in the load-bearing plate was computed, and the location of main stress concentration in the plate was determined. Comparison between the fracture region and the location of the stress concentration shows that finite element analysis could serve as a tool for optimizing the design of mandible implants. PMID:26227805

  14. Prediction of the Chemoreflex Gain by Common Clinical Variables in Heart Failure

    PubMed Central

    Mirizzi, Gianluca; Giannoni, Alberto; Ripoli, Andrea; Iudice, Giovanni; Bramanti, Francesca; Emdin, Michele; Passino, Claudio

    2016-01-01

    Background Peripheral and central chemoreflex sensitivity, assessed by the hypoxic or hypercapnic ventilatory response (HVR and HCVR, respectively), is enhanced in heart failure (HF) patients, is involved in the pathophysiology of the disease, and is under investigation as a potential therapeutic target. Chemoreflex sensitivity assessment is however demanding and, therefore, not easily applicable in the clinical setting. We aimed at evaluating whether common clinical variables, broadly obtained by routine clinical and instrumental evaluation, could predict increased HVR and HCVR. Methods and results 191 patients with systolic HF (left ventricular ejection fraction—LVEF—<50%) underwent chemoreflex assessment by rebreathing technique to assess HVR and HCVR. All patients underwent clinical and neurohormonal evaluation, comprising: echocardiogram, cardiopulmonary exercise test (CPET), daytime cardiorespiratory monitoring for breathing pattern evaluation. Regarding HVR, multivariate penalized logistic regression, Bayesian Model Averaging (BMA) logistic regression and random forest analysis identified, as predictors, the presence of periodic breathing and increased slope of the relation between ventilation and carbon dioxide production (VE/VCO2) during exercise. Again, the above-mentioned statistical tools identified as HCVR predictors plasma levels of N-terminal fragment of proBNP and VE/VCO2 slope. Conclusions In HF patients, the simple assessment of breathing pattern, alongside with ventilatory efficiency during exercise and natriuretic peptides levels identifies a subset of patients presenting with increased chemoreflex sensitivity to either hypoxia or hypercapnia. PMID:27099934

  15. GenSo-EWS: a novel neural-fuzzy based early warning system for predicting bank failures.

    PubMed

    Tung, W L; Quek, C; Cheng, P

    2004-05-01

    Bank failure prediction is an important issue for the regulators of the banking industries. The collapse and failure of a bank could trigger an adverse financial repercussion and generate negative impacts such as a massive bail out cost for the failing bank and loss of confidence from the investors and depositors. Very often, bank failures are due to financial distress. Hence, it is desirable to have an early warning system (EWS) that identifies potential bank failure or high-risk banks through the traits of financial distress. Various traditional statistical models have been employed to study bank failures [J Finance 1 (1975) 21; J Banking Finance 1 (1977) 249; J Banking Finance 10 (1986) 511; J Banking Finance 19 (1995) 1073]. However, these models do not have the capability to identify the characteristics of financial distress and thus function as black boxes. This paper proposes the use of a new neural fuzzy system [Foundations of neuro-fuzzy systems, 1997], namely the Generic Self-organising Fuzzy Neural Network (GenSoFNN) [IEEE Trans Neural Networks 13 (2002c) 1075] based on the compositional rule of inference (CRI) [Commun ACM 37 (1975) 77], as an alternative to predict banking failure. The CRI based GenSoFNN neural fuzzy network, henceforth denoted as GenSoFNN-CRI(S), functions as an EWS and is able to identify the inherent traits of financial distress based on financial covariates (features) derived from publicly available financial statements. The interaction between the selected features is captured in the form of highly intuitive IF-THEN fuzzy rules. Such easily comprehensible rules provide insights into the possible characteristics of financial distress and form the knowledge base for a highly desired EWS that aids bank regulation. The performance of the GenSoFNN-CRI(S) network is subsequently benchmarked against that of the Cox's proportional hazards model [J Banking Finance 10 (1986) 511; J Banking Finance 19 (1995) 1073], the multi

  16. A methodology for probabilistic prediction of structural failures of launch vehicle propulsion systems

    NASA Technical Reports Server (NTRS)

    Moore, N.; Ebbeler, D.; Creager, M.

    1990-01-01

    A quantitative methodology for estimating the probability of occurrence of critical structural failure modes of launch vehicle propulsion systems during mission operation is presented. In this approach, engineering analysis models that characterize specific failure modes based on the physics and mechanics of the failure phenomenon are used in a prescribed probabalistic structure in which quantified uncertainty in the information used in the analysis and quantified uncertainty of the engineering analysis models themselves are both considered in estimating failure risk. The methodology is applicable to high cycle fatigue, low cycle fatigue, flaw propagation stress rupture, and other failure modes of launch vehicle propulsion systems and other space-flight systems. The probabalistic failure assessment presented provides the capability of performing quantitative analyses to rank options to improve reliability, thereby enabling limited financial resources of development and improvement programs to be more effectively allocated.

  17. Lamivudine Concentration in Hair and Prediction of Virologic Failure and Drug Resistance among HIV Patients Receiving Free ART in China

    PubMed Central

    Wang, Zhe; Wu, Jianjun; Zhang, Jiafeng; Ruan, Yuhua; Hsi, Jenny; Liao, Lingjie; Shao, Yiming; Xing, Hui

    2016-01-01

    Background The assessment of adherence to antiretroviral therapy (ART) is important in order to predict treatment outcomes. Lamivudine (3TC) is one of the most widely used NRTIs in China, but its concentrations in hair and association with virologic failure and drug resistance have not been studied. Methods We conducted a cross-sectional survey to investigate 3TC concentrations in hair as a predictor of virologic failure and drug resistance among HIV patients receiving free ART. We also compared the capacity of hair 3TC concentrations with self-reported adherence in predicting virologic responses. Hair 3TC concentrations were detected through the LC-MS/MS system. Results In patients without HIV drug resistance (HIVDR), with a threshold hair 3TC concentration of 260 ng/g, the sensitivity and specificity in predicting virologic suppression were 76.9% and 89.9%, respectively. Some factors, including CD4+ cell counts, initial treatment regimens with 3TC, and current regimens with second-line drugs, influenced the association between hair 3TC concentrations and virologic suppression. In patients who experienced virologic failure with HIVDR, with a threshold of 180 ng/g, the sensitivity and specificity were 70.0% and 74.4%, respectively. Hair 3TC concentrations had higher sensitivity and specificity in predicting virologic failure and drug resistance than self-reported adherence. Conclusions The hair 3TC concentration was a stronger indicator than self-reported adherence in predicting virologic failure and drug resistance in HIV patients receiving free ART. PMID:27119346

  18. Predictive value of arterial ammonia for complications and outcome in acute liver failure

    PubMed Central

    Bhatia, V; Singh, R; Acharya, S K

    2006-01-01

    Background and aim In acute liver failure (ALF), the brain is exposed to high levels of ammonia. Human studies defining the clinical significance of ammonia in ALF are lacking. This prospective study evaluated the relationship of arterial ammonia levels at admission to complications and survival among patients with ALF. Methods Eighty consecutive ALF patients admitted from March 2001 to December 2003 were followed up until death or complete recovery. All had arterial ammonia estimation at admission (enzymatic method). Logistic regression analysis was performed to identify independent predictors of mortality. Results Forty two (52.5%) patients died. Non‐survivors had significantly higher median ammonia levels than survivors (174.7 v 105.0 μmol/l; p<0.001). An arterial ammonia level of ⩾ 124 μmol/l was found to predict mortality with 78.6% sensitivity and 76.3% specificity, and had 77.5% diagnostic accuracy. Patients with higher ammonia levels also developed more complications, including deeper encephalopathy (p = 0.055), cerebral oedema (p = 0.020), need for ventilation (p<0.001), and seizures (p = 0.006). Logistic regression analysis showed that pH, presence of cerebral oedema, and arterial ammonia at admission were independent predictors of mortality (odds ratios 6.6, 12.6, and 10.9, respectively). Incorporating these variables, a score predicting mortality risk at admission was derived: 2.53 + 2.91 ammonia + 2.41 oedema + 1.40 pH, where ammonia is scored as 0 (if <124 μmol/l) or 1 (if ⩾124 μmol/l); oedema is scored as 0 (absent) or 1(present); and pH is scored as 1 (if ⩽7.40) or 0 (if >7.40). Levels of partial pressure of ammonia were equally correlated with outcome. Conclusion Arterial ammonia at presentation is predictive of outcome and can be used for risk stratification. Ammonia lowering therapies in patients with ALF should be evaluated. PMID:16024550

  19. Genomic Prostate Cancer Classifier Predicts Biochemical Failure and Metastases in Patients After Postoperative Radiation Therapy

    SciTech Connect

    Den, Robert B.; Feng, Felix Y.; Showalter, Timothy N.; Mishra, Mark V.; Trabulsi, Edouard J.; Lallas, Costas D.; Gomella, Leonard G.; Kelly, W. Kevin; Birbe, Ruth C.; McCue, Peter A.; Ghadessi, Mercedeh; Yousefi, Kasra; Davicioni, Elai; Knudsen, Karen E.; Dicker, Adam P.

    2014-08-01

    Purpose: To test the hypothesis that a genomic classifier (GC) would predict biochemical failure (BF) and distant metastasis (DM) in men receiving radiation therapy (RT) after radical prostatectomy (RP). Methods and Materials: Among patients who underwent post-RP RT, 139 were identified for pT3 or positive margin, who did not receive neoadjuvant hormones and had paraffin-embedded specimens. Ribonucleic acid was extracted from the highest Gleason grade focus and applied to a high-density-oligonucleotide microarray. Receiver operating characteristic, calibration, cumulative incidence, and Cox regression analyses were performed to assess GC performance for predicting BF and DM after post-RP RT in comparison with clinical nomograms. Results: The area under the receiver operating characteristic curve of the Stephenson model was 0.70 for both BF and DM, with addition of GC significantly improving area under the receiver operating characteristic curve to 0.78 and 0.80, respectively. Stratified by GC risk groups, 8-year cumulative incidence was 21%, 48%, and 81% for BF (P<.0001) and for DM was 0, 12%, and 17% (P=.032) for low, intermediate, and high GC, respectively. In multivariable analysis, patients with high GC had a hazard ratio of 8.1 and 14.3 for BF and DM. In patients with intermediate or high GC, those irradiated with undetectable prostate-specific antigen (PSA ≤0.2 ng/mL) had median BF survival of >8 years, compared with <4 years for patients with detectable PSA (>0.2 ng/mL) before initiation of RT. At 8 years, the DM cumulative incidence for patients with high GC and RT with undetectable PSA was 3%, compared with 23% with detectable PSA (P=.03). No outcome differences were observed for low GC between the treatment groups. Conclusion: The GC predicted BF and metastasis after post-RP irradiation. Patients with lower GC risk may benefit from delayed RT, as opposed to those with higher GC; however, this needs prospective validation. Genomic-based models

  20. Positive Predictive Value of the WHO Clinical and Immunologic Criteria to Predict Viral Load Failure among Adults on First, or Second-Line Antiretroviral Therapy in Kenya

    PubMed Central

    Muttai, Hellen; Ng’ang’a, Lucy; Ackers, Marta; Kim, Andrea; Miruka, Fredrick; Erick, Opiyo; Okonji, Julie; Ayuaya, Tolbert; Schwarcz, Sandra

    2016-01-01

    Routine HIV viral load (VL) monitoring is the standard of care for persons receiving antiretroviral therapy (ART) in developed countries. Although the World Health Organization recommends annual VL monitoring of patients on ART, recognizing difficulties in conducting routine VL testing, the WHO continues to recommend targeted VL testing to confirm treatment failure for persons who meet selected immunologic and clinical criteria. Studies have measured positive predictive value (PPV), negative predictive value, sensitivity and specificity of these criteria among patients receiving first-line ART but not specifically among those on second-line or subsequent regimens. Between 2008 and 2011, adult ART patients in Nyanza, Kenya who met national clinical or immunologic criteria for treatment failure received targeted VL testing. We calculated PPV and 95% confidence intervals (CI) of these criteria to detect virologic treatment failure among patients receiving a) first-line ART, b) second/subsequent ART, and c) any regimen. Of 12,134 patient specimens tested, 2,874 (23.7%) were virologically confirmed as treatment failures. The PPV for 2,834 first-line ART patients who met either the clinical or immunologic criteria for treatment failure was 34.4% (95% CI 33.2–35.7), 33.1% (95% CI 24.7–42.3) for the 40 patients on second-line/subsequent regimens, and 33.4% (95% CI 33.1–35.6) for any ART. PPV, regardless of criteria, for first-line ART patients was lowest among patients over 44 years old and highest for patients aged 15 to 34 years. PPV of immunological and clinical criteria for correctly identifying treatment failure was similarly low for adult patients receiving either first-line or second-line/subsequent ART regimens. Our data confirm the inadequacy of clinical and immunologic criteria to correctly identify treatment failure and support the implementation of routine VL testing. PMID:27383834

  1. Better Adherence to Treatment Recommendations in Heart Failure Predicts Improved Cognitive Function at a One Year Follow Up

    PubMed Central

    Alosco, Michael L.; Spitznagel, Mary Beth; Cohen, Ronald; Sweet, Lawrence H.; Josephson, Richard; Hughes, Joel; Rosneck, Jim; Gunstad, John

    2016-01-01

    Introduction Treatment non-adherence is common in heart failure and associated with poor health outcomes in this population. Recent cross-sectional work in heart failure and past work in other medical populations suggests cognitive function is a key determinant of patient’s ability to adhere to treatment recommendations. However, it is also possible that treatment adherence is an important modifier and predictor of cognitive function, though no study has examined this possibility and we sought to do so in a sample of heart failure patients. Methods 115 patients with heart failure self-reported adherence to treatment recommendations. The Modified Mini Mental State Examination (3MS), Trail Making Test parts A and B, and the California Verbal Learning Test-II (CVLT-II) assessed cognitive function. These procedures were performed at baseline and a 12-month follow-up. Results Global cognition and memory abilities improved over the 12-month period. Regression analyses controlling for baseline and medical and demographic factors showed better baseline treatment adherence predicted improved 12-month performances on the 3MS and CVLT-II. Adherence to medication and diet regimens and smoking abstinence emerged as the most important contributors. Conclusions Better treatment adherence predicted improved cognition one-year later in HF. Prospective studies that utilize objective assessments of treatment adherence are needed to confirm our findings and examine whether improved treatment adherence preserves cognitive function in heart failure. PMID:25352233

  2. Serum Procalcitonin and Peripheral Venous Lactate for Predicting Dengue Shock and/or Organ Failure: A Prospective Observational Study

    PubMed Central

    Thanachartwet, Vipa; Desakorn, Varunee; Sahassananda, Duangjai; Jittmittraphap, Akanitt; Oer-areemitr, Nittha; Osothsomboon, Sathaporn; Surabotsophon, Manoon; Wattanathum, Anan

    2016-01-01

    Background Currently, there are no biomarkers that can predict the incidence of dengue shock and/or organ failure, although the early identification of risk factors is important in determining appropriate management to reduce mortality. Therefore, we sought to determine the factors associated with dengue shock and/or organ failure and to evaluate the prognostic value of serum procalcitonin (PCT) and peripheral venous lactate (PVL) levels as biomarkers of dengue shock and/or organ failure. Methodology/Principal Findings A prospective observational study was conducted among adults hospitalized for confirmed viral dengue infection at the Hospital for Tropical Diseases in Bangkok, Thailand between October 2013 and July 2015. Data, including baseline characteristics, clinical parameters, laboratory findings, serum PCT and PVL levels, management, and outcomes, were recorded on pre-defined case report forms. Of 160 patients with dengue, 128 (80.0%) patients had dengue without shock or organ failure, whereas 32 (20.0%) patients developed dengue with shock and/or organ failure. Using a stepwise multivariate logistic regression analysis, PCT ≥0.7 ng/mL (odds ratio [OR]: 4.80; 95% confidence interval [CI]: 1.60–14.45; p = 0.005) and PVL ≥2.5 mmol/L (OR: 27.99, 95% CI: 8.47–92.53; p <0.001) were independently associated with dengue shock and/or organ failure. A combination of PCT ≥0.7 ng/mL and PVL ≥2.5 mmol/L provided good prognostic value for predicting dengue shock and/or organ failure, with an area under the receiver operating characteristics curve of 0.83 (95% CI: 0.74–0.92), a sensitivity of 81.2% (95% CI: 63.6–92.8%), and a specificity of 84.4% (95% CI: 76.9–90.2%). Dengue shock patients with non-clearance of PCT and PVL expired during hospitalization. Conclusions/Significance PCT ≥0.7 ng/mL and PVL ≥2.5 mmol/L were independently associated with dengue shock and/or organ failure. The combination of PCT and PVL levels could be used as prognostic

  3. Failure prediction of thin beryllium sheets used in spacecraft structures. Semiannual Status Report, 1 Jul. - 31 Dec. 1990

    SciTech Connect

    Roschke, P.N.; Papados, P.; Mascorro, E.

    1991-01-01

    In an attempt to predict failure for cross-rolled beryllium sheet structures, high order macroscopic failure criteria are used. These require the knowledge of in-plane uniaxial and shear strengths. Test results are included for in-plane biaxial tension, uniaxial compression for two different material orientations, and shear. All beryllium specimens have the same chemical composition. In addition, all experimental work was performed in a controlled laboratory environment. Numerical simulation complements these tests. A brief bibliography supplements references listed in a previous report.

  4. Predicting In-Hospital Treatment Failure (≤ 7 days) in Patients with COPD Exacerbation Using Antibiotics and Systemic Steroids.

    PubMed

    Crisafulli, Ernesto; Torres, Antoni; Huerta, Arturo; Guerrero, Mónica; Gabarrús, Albert; Gimeno, Alexandra; Martinez, Raquel; Soler, Néstor; Fernández, Laia; Wedzicha, Jadwiga A; Menéndez, Rosario

    2016-01-01

    Although pharmacological treatment of COPD exacerbation (COPDE) includes antibiotics and systemic steroids, a proportion of patients show worsening of symptoms during hospitalization that characterize treatment failure. The aim of our study was to determine in-hospital predictors of treatment failure (≤ 7 days). Prospective data on 110 hospitalized COPDE patients, all treated with antibiotics and systemic steroids, were collected; on the seventh day of hospitalization, patients were divided into treatment failure (n = 16) or success (n = 94). Measures of inflammatory serum biomarkers were recorded at admission and at day 3; data on clinical, laboratory, microbiological, and severity, as well data on mortality and readmission, were also recorded. Patients with treatment failure had a worse lung function, with higher serum levels of C-reactive protein (CRP), procalcitonin (PCT), tumour necrosis factor-alpha (TNF-α), interleukin (IL) 8, and IL-10 at admission, and CRP and IL-8 at day 3. Longer length of hospital stay and duration of antibiotic therapy, higher total doses of steroids and prevalence of deaths and readmitted were found in the treatment failure group. In the multivariate analysis, +1 mg/dL of CRP at admission (OR, 1.07; 95% CI, 1.01 to 1.13) and use of penicillins or cephalosporins (OR, 5.63; 95% CI, 1.26 to 25.07) were independent variables increasing risk of treatment failure, whereas cough at admission (OR, 0.20; 95% CI, 0.05 to 0.75) reduces risk of failure. In hospitalized COPDE patients CRP at admission and use of specific class of antibiotics predict in-hospital treatment failure, while presence of cough has a protective role. PMID:26451913

  5. Predicting treatment failure in patients with community acquired pneumonia: a case-control study

    PubMed Central

    2014-01-01

    Introduction Treatment failure in community-acquired-pneumonia (CAP) patients is associated with a high mortality rate, and therefore are a matter of great concern in clinical management. Those patients have increased mortality and are a target population for randomized clinical trials. Methods A case–control study was performed in patients with CAP (non-failure cases vs. failure cases, discriminating by late and early failure). CRP, PCT, interleukin 1, 6, 8 and 10 and TNF were determined at days 1 and 3 of hospitalization. Results A total of 253 patients were included in this study where 83 patients presented treatment failure. Of these, 40 (48.2%) had early failure. A discriminative effect was found for a higher CURB-65 score among late failure patients (p = 0.004). A significant increase on day 1 of hospitalization in CRP (p < 0.001), PCT (p = 0.004), IL-6 (p < 0.001) and IL-8 (p = 0.02), and a decrease in IL-1 (p = 0.06) in patients with failure was observed compared with patients without failure. On day 3, only the increase in CRP (p < 0.001), PCT (p = 0.007) and IL-6 (p < 0.001) remained significant. Independent predictors for early failure were higher IL-6 levels on day 1 (OR = 1.78, IC = 1.2-2.6) and pleural effusion (OR = 2.25, IC = 1.0-5.3), and for late failure, higher PCT levels on day 3 (OR = 1.60, IC = 1.0-2.5), CURB-65 score ≥ 3 (OR = 1.43, IC = 1.0-2.0), and multilobar involvement (OR = 4.50, IC = 2.1-9.9). Conclusions There was a good correlation of IL-6 levels and CAP failure and IL-6 & PCT with late CAP failure. Pleural effusion and multilobar involvement were simple clinical predictors of early and late failure, respectively. Trial registration IRB Register: http://2009/5451. PMID:24996572

  6. Utility of Socioeconomic Status in Predicting 30-Day Outcomes After Heart Failure Hospitalization

    PubMed Central

    Eapen, Zubin J.; McCoy, Lisa A.; Fonarow, Gregg C.; Yancy, Clyde W.; Miranda, Marie Lynn; Peterson, Eric D.; Califf, Robert M.; Hernandez, Adrian F.

    2015-01-01

    Background An individual's socioeconomic status (SES) is associated with health outcomes and mortality, yet it is unknown whether accounting for SES can improve risk-adjustment models for 30-day outcomes among Centers for Medicare & Medicaid Services (CMS) beneficiaries hospitalized with heart failure (HF). Methods and Results We linked clinical data on hospitalized HF patients in the Get With The Guidelines®-HF™ database (01/2005–12/2011) with CMS claims and county-level SES data from the 2012 Area Health Resources Files. We compared the discriminatory capabilities of multivariable models that adjusted for SES, patient, and/or hospital characteristics to determine whether county-level SES data improved prediction or changed hospital rankings for 30-day all-cause mortality and rehospitalization. After adjusting for patient and hospital characteristics, median household income (per $5,000 increase) was inversely associated with odds of 30-day mortality (OR 0.97, 95% CI 0.95–1.00, p=0.032), and the percentage of persons with at least a high school diploma (per 5 unit increase) was associated with lower odds of 30-day rehospitalization (OR 0.95, 95% CI 0.91–0.99).After adjustment for county-level SES data, relative to whites, Hispanic ethnicity (OR 0.70, 95% CI 0.58, 0.83) and black race (OR 0.57, 95% CI: 0.50–0.65) remained significantly associated with lower 30-day mortality, but had similar 30-day rehospitalization. County-level SES did not improve risk adjustment or change hospital rankings for 30-day mortality or rehospitalization. Conclusions County-level SES data are modestly associated with 30-day outcomes for CMS beneficiaries hospitalized with HF, but do not improve risk adjustment models based on patient characteristics alone. PMID:25747700

  7. Time shift in slope failure prediction between unimodal and bimodal modeling approaches

    NASA Astrophysics Data System (ADS)

    Ciervo, Fabio; Casini, Francesca; Nicolina Papa, Maria; Medina, Vicente

    2016-04-01

    within the Bishop stress theory framework (Ciervo et al., 2015). The proposed work tends to emphasize how a more accurate slope stability analysis that accounts dual-structure could be useful to reach a more accurate definition of the stability conditions. The effects in practical analysis may be significant. The highlighted discrepancies between the different approaches in describing the timing processes and strength contribution due to capillary forces may entail no negligible differences in slope stability predictions, especially in those cases where the possibility of a failure in unsaturated terrains is contemplated.

  8. The utility of biomarker risk prediction score in patients with chronic heart failure

    PubMed Central

    Berezin, Alexander E; Kremzer, Alexander A; Martovitskaya, Yulia V; Samura, Tatyana A; Berezina, Tatyana A; Zulli, Anthony; Klimas, Jan; Kruzliak, Peter

    2015-01-01

    Chronic heart failure (CHF) remains a leading cause of cardiovascular death worldwide. Current risk models allow better prognosis, however further tools for assessing risk are needed. Thus, this study was aimed to evaluate whether biomarker risk prediction score is powerful tool for risk assessment of three-year fatal and non-fatal cardiovascular events in CHF patients. Methods: A prospective study on the incidence of fatal and non-fatal cardiovascular events, as well as the frequency of occurrence of death from any cause in a cohort of 388 patients with CHF during 3 years of observation was performed. Circulating levels of NT-pro brain natriuretic peptide (NT-pro-BNP), galectin-3, high-sensitivity C-reactive protein (hs-CRP), osteoprotegerin and its soluble receptor sRANKL, osteopontin, osteonectin, adiponectin, endothelial apoptotic microparticles (EMPs) and mononuclear progenitor cells (MPCs) were measured at baseline. Results: Median follow-up of patients included in the study was 2.76 years. There were 285 cardiovascular events determined, including 43 deaths and 242 readmissions. Independent predictors of clinical outcomes in patients with CHF were NT-pro-BNP, galectin-3, hs-CRP, osteoprotegerin, CD31+/annexin V+ EMPs and EMPs/CD14+CD309+ MPCs ratio. Index of cardiovascular risk was calculated by mathematical summation of all ranks of independent predictors, which occurred in the patients included in the study. The findings showed that the average value of the index of cardiovascular risk in patients with CHF was 3.17 points (95% CI = 1.65-5.10 points). Kaplan-Meier analysis showed that patients with CHF and the magnitude of the risk of less than 4 units have an advantage in survival when compared with patients for whom obtained higher values of ranks cardiovascular risk score. Conclusion: Biomarker risk score for cumulative cardiovascular events, constructed by measurement of circulating NT-pro-BNP, galectin-3, hs-CRP, osteoprotegerin, CD31+/annexin V+ EMPs

  9. Patency of Femoral Tunneled Hemodialysis Catheters and Factors Predictive of Patency Failure

    SciTech Connect

    Burton, Kirsteen R.; Guo, Lancia L. Q.; Tan, Kong T.; Simons, Martin E.; Sniderman, Kenneth W.; Kachura, John R.; Beecroft, John R.; Rajan, Dheeraj K.

    2012-12-15

    Purpose: To determine the patency rates of and factors associated with increased risk of patency failure in patients with femoral vein tunneled hemodialysis catheters. Methods: All femoral tunneled catheter insertions from 1996 to 2006 were reviewed, during which time 123 catheters were inserted. Of these, 66 were exchanges. Patients with femoral catheter failure versus those with femoral catheter patency were compared. Confounding factors, such as demographic and procedural factors, were incorporated and assessed using univariate and multivariable Cox proportional hazards regression analyses. Results: Mean catheter primary patency failure time was 96.3 days (SE 17.9 days). Primary patency at 30, 60, 90, and 180 days was 53.8%, 45.4%, 32.1%, and 27.1% respectively. Crude rates of risk of catheter failure did not suggest a benefit for patients receiving catheters introduced from one side versus the other, but more cephalad location of catheter tip was associated with improved patency. Multivariate analysis showed that patients whose catheters were on the left side (p = 0.009), were of increasing age at the time of insertion (p = 0.002) and that those who had diabetes (p = 0.001) were at significantly greater risk of catheter failure. The catheter infection rate was 1.4/1000 catheter days. Conclusion: Patients who were of a more advanced age and had diabetes were at greater risk of femoral catheter failure, whereas those who received femoral catheters from the right side were less at risk of catheter failure.

  10. Pitfalls and Precautions When Using Predicted Failure Data for Quantitative Analysis of Safety Risk for Human Rated Launch Vehicles

    NASA Technical Reports Server (NTRS)

    Hatfield, Glen S.; Hark, Frank; Stott, James

    2016-01-01

    Launch vehicle reliability analysis is largely dependent upon using predicted failure rates from data sources such as MIL-HDBK-217F. Reliability prediction methodologies based on component data do not take into account system integration risks such as those attributable to manufacturing and assembly. These sources often dominate component level risk. While consequence of failure is often understood, using predicted values in a risk model to estimate the probability of occurrence may underestimate the actual risk. Managers and decision makers use the probability of occurrence to influence the determination whether to accept the risk or require a design modification. The actual risk threshold for acceptance may not be fully understood due to the absence of system level test data or operational data. This paper will establish a method and approach to identify the pitfalls and precautions of accepting risk based solely upon predicted failure data. This approach will provide a set of guidelines that may be useful to arrive at a more realistic quantification of risk prior to acceptance by a program.

  11. Predicting the Velocity and Azimuth of Fragments Generated by the Range Destruction or Random Failure of Rocket Casings and Tankage

    SciTech Connect

    Eck, Marshall B.; Mukunda, Meera

    1988-10-01

    The details of a predictive analytical modeling process as well as the development of normalized relations for momentum partition as a function of SRM burn time and initial geometry are discussed in this paper. Methods for applying similar modeling techniques to liquid-tankage-over-pressure failures are also discussed. These methods have been calibrated against observed SRM ascent failures and on-orbit tankage failures. Casing-quadrant sized fragments with velocities exceeding 100 m/s resulted from Titan 34D-SRM range destruct actions at 10 sec mission elapsed time (MET). Casing-quadrant sized fragments with velocities of approximately 200 m/s resulted from STS-SRM range destruct actions at 110 sec MET. Similar sized fragments for Ariane third stage and Delta second stage tankage were predicted to have maximum velocities of 260 m/s and 480 m/s respectively. Good agreement was found between the predictions and observations for five specific events and it was concluded that the methods developed have good potential for use in predicting the fragmentation process of a number of generically similar casing and tankage systems. There are three copies in the file, one of these is loose.

  12. Attenuation of circulatory and airway responses to endotracheal extubation in craniotomies for intracerebral space occupying lesions: Dexmedetomidine versus lignocaine

    PubMed Central

    Kothari, Dilip; Tandon, Neelima; Singh, Meena; Kumar, Arun

    2014-01-01

    Objectives: The objective of the study is to compare the effect of dexmedetomidine versus lignocaine in attenuation of circulatory and airway responses during endotracheal extubation in craniotomies for intracerebral space occupying lesions (ICSOL). Materials and Methods: A total of 50 patients of American Society of Anesthesiologists Grade I and II of either sex, aged 18-50 years undergoing craniotomies for non-vascular ICSOL under general anesthesia were divided into two groups according to drug received. Group D (n = 25) received dexmedetomidine (0.5 mcg/kg) whereas group L (n = 25) received lignocaine (1.5 mg/kg). Both the drugs were given 5 min before the extubation over a period of 60 s. Values for heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), were recorded just before (A0) and 1, 3, 5 (A1, A3, A5) min after the study drug administration, at extubation (E) and 1, 3, 5, 10, 15 min after extubation (E1, E3, E5, E10 and E15). Respiratory rate, oxygen saturation and airway responses like coughing, breath-holding, laryngospasm/bronchospasm were recorded only at extubation (E) and 1, 3, 5, 10, 15 min after extubation (E1, E3, E5, E10, E15). Quality of extubation was recorded with four point scale. After extubation all these patients were also observed for sedation by Ramsey sedation score. Results: Both groups showed a statistically significant increase (D < L) in HR, SBP and DBP during (E) and immediately after extubation (E1) (P < 0.05). Dexmedetomidine (72%) produced a higher degree of sedation (Grade 3) as compare with lignocaine (0%) and with no incidence of coughing or breath holding (P < 0.05). Conclusion: Single dose of dexmedetomidine (0.5 mcg/kg) given 5 min before extubation produced significant attenuation of circulatory and airway responses produced during extubation as compared to Lignocaine (1.5 mg/kg) in ICSOL. PMID:25886109

  13. Accuracy of finite element analyses of CT scans in predictions of vertebral failure patterns under axial compression and anterior flexion.

    PubMed

    Jackman, Timothy M; DelMonaco, Alex M; Morgan, Elise F

    2016-01-25

    Finite element (FE) models built from quantitative computed tomography (QCT) scans can provide patient-specific estimates of bone strength and fracture risk in the spine. While prior studies demonstrate accurate QCT-based FE predictions of vertebral stiffness and strength, the accuracy of the predicted failure patterns, i.e., the locations where failure occurs within the vertebra and the way in which the vertebra deforms as failure progresses, is less clear. This study used digital volume correlation (DVC) analyses of time-lapse micro-computed tomography (μCT) images acquired during mechanical testing (compression and anterior flexion) of thoracic spine segments (T7-T9, n=28) to measure displacements occurring throughout the T8 vertebral body at the ultimate point. These displacements were compared to those simulated by QCT-based FE analyses of T8. We hypothesized that the FE predictions would be more accurate when the boundary conditions are based on measurements of pressure distributions within intervertebral discs of similar level of disc degeneration vs. boundary conditions representing rigid platens. The FE simulations captured some of the general, qualitative features of the failure patterns; however, displacement errors ranged 12-279%. Contrary to our hypothesis, no differences in displacement errors were found when using boundary conditions representing measurements of disc pressure vs. rigid platens. The smallest displacement errors were obtained using boundary conditions that were measured directly by DVC at the T8 endplates. These findings indicate that further work is needed to develop methods of identifying physiological loading conditions for the vertebral body, for the purpose of achieving robust, patient-specific FE analyses of failure mechanisms. PMID:26792288

  14. Comparison of tracheal extubation in patients deeply anesthetized with desflurane or isoflurane.

    PubMed

    Smith, I; Taylor, E; White, P F

    1994-10-01

    A randomized, single-blind study design was used to compare desflurane with isoflurane in 31 adults undergoing intraocular surgery to determine whether the lower blood:gas partition coefficient of desflurane would result in a more rapid emergence after endotracheal extubation of deeply anesthetized patients. A standardized general anesthetic technique was used, consisting of sufentanil, 0.25 microgram/kg, and propofol, 1.5 mg/kg, followed by either isoflurane (n = 15) or desflurane (n = 16) in an air/oxygen mixture. After the operation and reversal of residual neuromuscular block, spontaneous ventilation was reestablished and the patients' tracheas were extubated at equianesthetic concentrations of desflurane and isoflurane (i.e., approximately 1.4 times the minimum alveolar anesthetic concentration [MAC]). Spontaneous movements occurred 5.7 (+/- 2.4) and 8.7 min (+/- 3.1; P = 0.005) after extubation in the desflurane and isoflurane groups, respectively. Eye opening and orientation also occurred significantly earlier after desflurane compared to isoflurane. Patients receiving desflurane (versus isoflurane) were also able to be transferred from the operating room significantly earlier (10.4 +/- 3.7 vs 14.5 +/- 4.3 min, P = 0.01). Use of desflurane (versus isoflurane) was not associated with an increased incidence of coughing or airway irritation during the emergence period. However, use of desflurane did not significantly reduce the duration of the postanesthesia care unit (PACU) stay or alter later recovery events compared to isoflurane. In conclusion, the more rapid emergence would favor the use of desflurane when tracheal extubation during deep anesthesia is required. PMID:7943769

  15. Factors associated with extubation time in coronary artery bypass grafting patients

    PubMed Central

    Rezaianzadeh, Abbas; Maghsoudi, Behzad; Tabatabaee, Hamidreza; Keshavarzi, Sareh; Bagheri, Zahra; Sajedianfard, Javad; Gerami, Hamid

    2015-01-01

    Background and Objectives. Cardiovascular diseases are the leading cause of death worldwide, with coronary artery disease being the most common. With increasing numbers of patients, Coronary Artery Bypass Grafting (CABG) has become the most common operation in the world. Respiratory disorder is one of the most prevalent complications of CABG. Thus, weaning off the mechanical ventilation and extubation are of great clinical importance for these patients. Some post-operative problems also relate to the tracheal tube and mechanical ventilation. Therefore, an increase in this leads to an increase in the number of complications, length of hospital stay, and treatment costs. Since a large number of factors affect the post-operative period, the present study aims to identify the predictors of extubation time in CABG patients using casualty network analysis. Method. This longitudinal study was conducted on 800 over 18 year old patients who had undergone CABG surgery in three treatment centers affiliated to Shiraz University of Medical Sciences. The patients’ information, including pre-operative, peri-operative, and post-operative variables, was retrospectively extracted from their medical records. Then, the data was comprehensively analyzed through path analysis using MPLUS-7.1 software. Results. The mean of extubation time was 10.27 + 4.39 h. Moreover, extubation time was significantly affected by packed cells during the Cardiopulmonary Bypass (CPB), packed cells after CPB, inotrope use on arrival at ICU, mean arterial pressure 1st ICU, packed cells 1st ICU, platelets 1st ICU, Blood Urea Nitrogen 1st ICU, and hematocrit 1st ICU. Conclusion. Considering all of the factors under investigation, some peri-operative and post-operative factors had significant effects. Therefore, considering the post-operative factors is important for designing a treatment plan and evaluating patients’ prognosis. PMID:26644972

  16. Health literacy and global cognitive function predict e-mail but not internet use in heart failure patients.

    PubMed

    Schprechman, Jared P; Gathright, Emily C; Goldstein, Carly M; Guerini, Kate A; Dolansky, Mary A; Redle, Joseph; Hughes, Joel W

    2013-01-01

    Background. The internet offers a potential for improving patient knowledge, and e-mail may be used in patient communication with providers. However, barriers to internet and e-mail use, such as low health literacy and cognitive impairment, may prevent patients from using technological resources. Purpose. We investigated whether health literacy, heart failure knowledge, and cognitive function were related to internet and e-mail use in older adults with heart failure (HF). Methods. Older adults (N = 119) with heart failure (69.84 ± 9.09 years) completed measures of health literacy, heart failure knowledge, cognitive functioning, and internet use in a cross-sectional study. Results. Internet and e-mail use were reported in 78.2% and 71.4% of this sample of patients with HF, respectively. Controlling for age and education, logistic regression analyses indicated that higher health literacy predicted e-mail (P < .05) but not internet use. Global cognitive function predicted e-mail (P < .05) but not internet use. Only 45% used the Internet to obtain information on HF and internet use was not associated with greater HF knowledge. Conclusions. The majority of HF patients use the internet and e-mail, but poor health literacy and cognitive impairment may prevent some patients from accessing these resources. Future studies that examine specific internet and email interventions to increase HF knowledge are needed. PMID:24282634

  17. Health Literacy and Global Cognitive Function Predict E-Mail but Not Internet Use in Heart Failure Patients

    PubMed Central

    Schprechman, Jared P.; Gathright, Emily C.; Goldstein, Carly M.; Guerini, Kate A.; Dolansky, Mary A.; Redle, Joseph; Hughes, Joel W.

    2013-01-01

    Background. The internet offers a potential for improving patient knowledge, and e-mail may be used in patient communication with providers. However, barriers to internet and e-mail use, such as low health literacy and cognitive impairment, may prevent patients from using technological resources. Purpose. We investigated whether health literacy, heart failure knowledge, and cognitive function were related to internet and e-mail use in older adults with heart failure (HF). Methods. Older adults (N = 119) with heart failure (69.84 ± 9.09 years) completed measures of health literacy, heart failure knowledge, cognitive functioning, and internet use in a cross-sectional study. Results. Internet and e-mail use were reported in 78.2% and 71.4% of this sample of patients with HF, respectively. Controlling for age and education, logistic regression analyses indicated that higher health literacy predicted e-mail (P < .05) but not internet use. Global cognitive function predicted e-mail (P < .05) but not internet use. Only 45% used the Internet to obtain information on HF and internet use was not associated with greater HF knowledge. Conclusions. The majority of HF patients use the internet and e-mail, but poor health literacy and cognitive impairment may prevent some patients from accessing these resources. Future studies that examine specific internet and email interventions to increase HF knowledge are needed. PMID:24282634

  18. Deformation, Failure, and Fatigue Life of SiC/Ti-15-3 Laminates Accurately Predicted by MAC/GMC

    NASA Technical Reports Server (NTRS)

    Bednarcyk, Brett A.; Arnold, Steven M.

    2002-01-01

    NASA Glenn Research Center's Micromechanics Analysis Code with Generalized Method of Cells (MAC/GMC) (ref.1) has been extended to enable fully coupled macro-micro deformation, failure, and fatigue life predictions for advanced metal matrix, ceramic matrix, and polymer matrix composites. Because of the multiaxial nature of the code's underlying micromechanics model, GMC--which allows the incorporation of complex local inelastic constitutive models--MAC/GMC finds its most important application in metal matrix composites, like the SiC/Ti-15-3 composite examined here. Furthermore, since GMC predicts the microscale fields within each constituent of the composite material, submodels for local effects such as fiber breakage, interfacial debonding, and matrix fatigue damage can and have been built into MAC/GMC. The present application of MAC/GMC highlights the combination of these features, which has enabled the accurate modeling of the deformation, failure, and life of titanium matrix composites.

  19. Exercise End-Tidal CO2 Predicts Central Sleep Apnea in Patients With Heart Failure

    PubMed Central

    Cundrle, Ivan; Somers, Virend K.; Johnson, Bruce D.; Scott, Christopher G.

    2015-01-01

    BACKGROUND: Increased CO2 chemosensitivity and augmented exercise ventilation are characteristic of patients with heart failure (HF) with central sleep apnea (CSA). The aim of this study was to test the hypothesis that decreased end-tidal CO2 by cardiopulmonary exercise testing predicts CSA in patients with HF. METHODS: Consecutive ambulatory patients with New York Heart Association II to III HF were prospectively evaluated by CO2 chemosensitivity by rebreathe, cardiopulmonary exercise testing, and polysomnography (PSG). Subjects were classified as having either CSA (n = 20) or no sleep apnea (n = 13) by PSG; a central apnea-hypopnea index (AHI) ≥ 5 was used to define CSA. Subgroups were compared by t test or Mann-Whitney test and data summarized as mean ± SD. P < .05 was considered significant. RESULTS: At rest, subjects with CSA had higher central CO2 chemosensitivity (Δminute ventilation [V.e]/Δpartial pressure of end-tidal CO2 [Petco2], 2.3 ± 1.0 L/min/mm Hg vs 1.6 ± 0.4 L/min/mm Hg, P = .02) and V.e (15 ± 7 L/min vs 10 ± 3 L/min, P = .02) and lower Petco2 (31 ± 4 mm Hg vs 35 ± 4 mm Hg, P < .01) than control subjects. At peak exercise, the ventilatory equivalents per expired CO2 (V.e/V.co2) was higher (43 ± 9 vs 33 ± 6, P < .01) and Petco2 lower (29 ± 6 mm Hg vs 36 ± 5 mm Hg, P < .01) in subjects with CSA. In addition, CO2 chemosensitivity, peak exercise V.e/V.co2, and Petco2 were independently correlated with CSA severity as quantified by the AHI (P < .05). Peak exercise Petco2 was most strongly associated with CSA (OR, 1.29; 95% CI, 1.08-1.54; P = .01; area under the curve, 0.88). CONCLUSIONS: In patients with HF and CSA, ventilatory drive is increased while awake at rest and during exercise and associated with heightened CO2 chemosensitivity and decreased arterial CO2 set point. PMID:25742609

  20. A longitudinal linear model of patient characteristics to predict failure to attend an inner-city chronic pain clinic

    PubMed Central

    Shaparin, N; White, RS; Andreae, MH; Hall, CB; Kaufman, AG

    2014-01-01

    Patients often fail to attend appointments in chronic pain clinics for unknown reasons. We hypothesized that certain patient characteristics predict failure to attend scheduled appointments pointing to systematic barriers to access chronic pain services for certain underserved populations. We collected retrospective data from a longitudinal observational cohort of patients at an academic pain clinic in Newark, New Jersey. To examine the effect of demographic factors on appointment status, we fit a marginal logistic regression using generalized estimating equations with exchangeable correlation. 1394 patients with 3488 total encounters between January 1, 2006 and December 31, 2009 were included. Spanish spoken as a primary language (alternatively Hispanic or other race) and living between five and ten miles from the clinic were associated with reduced odds of arriving for an appointment; making an appointment for a particular complaint such as cancer pain or back pain, an interventional pain procedure scheduled in connection with the appointment, unemployed status, and continuity of care (as measured by office visit number) were associated with increased odds of arriving. Spanish spoken as primary language and distance to the pain clinic predicted failure to attend a scheduled appointment in our cohort. If these constitute systematic barriers to access, they may be amendable to targeted interventions. Perspective We identified certain patient characteristics, specifically Spanish spoken as primary language and geographic distance from the clinic, that predict failure to attend an inner-city chronic pain clinic. These identified barriers to access chronic pain services may be modifiable by simple cost effective interventions. PMID:24747766

  1. A comparative study of early and late extubation following transoral odontoidectomy and posterior fixation

    PubMed Central

    Marda, Manish; Pandia, Mihir Prakash; Rath, Girija Prasad; Kale, Shashank Sharad; Dash, Harihara

    2016-01-01

    Background and Aims: Elective ventilation is the usual practice after transoral odontoidectomy (TOO) and posterior fixation. This practice of elective ventilation is not based on any evidence. The primary objective of our study was to find out the difference in oxygenation and ventilation in patients extubated early compared to those extubated late after TOO and posterior fixation. The secondary objectives were to compare the length of Intensive Care Unit (ICU)/hospital stay and pulmonary complications between the two groups. Material and Methods: After TOO and posterior fixation, patients were either extubated in the operating room (Group E) or extubated next day (Group D). The oxygenation (PaO2:FiO2 ratio) and ventilation (PaCO2) of the two groups before surgery, at 30 min and at 6/12/24 and 48 h after extubation were compared. Complications, durations of ICU and hospital stay were noted. Results: The base-line PaO2:FiO2 and PaCO2 was comparable between the groups. No significant change in the PaO2:FiO2 was noted in the postoperative period in either group as compared to the preoperative values. Except for at 12 h after surgery, there was no significant difference between the two groups at various time intervals. No significant change in the PaCO2 level was seen during the study period in either group. PaCO2 measured at 30 min after surgery was more in Group E (37.5 ± 3.2 mmHg in Group E vs. 34.6 ± 2.9 mmHg in Group D), otherwise there was no significant difference between the two groups at various time intervals. One patient in Group E (7.1%) and two patients in Group D (13%) developed postoperative respiratory complication, but the difference was not statistically significant. The mean ICU stay (Group D = 42 ± 25 h vs. Group E = 25.1 ± 16.9 h) and mean hospital stay (Group D = 9.9 ± 4 days vs. Group E = 7.6 ± 2.2 days) were longer in Group D patients. Conclusion: Ventilation and oxygenation in the postoperative period in patients undergoing TOO and

  2. Low-frequency nevirapine resistance at multiple sites may predict treatment failure in infants on nevirapine-based treatment

    PubMed Central

    Lehman, Dara A.; Wanalwa, Dalton C.; McCoy, Connor O.; Matsen, Frederick A.; Langat, Agnes; Chohan, Bhavna H.; Benki-Nugent, Sarah; Custers-Allen, Rebecca; Bushman, Frederic D.; John-Stewart, Grace C.; Overbaugh, Julie

    2012-01-01

    Background Resistance commonly arises in infants exposed to single-dose nevirapine (sdNVP) for prevention of mother to child transmission (PMTCT). While K103N and Y181C are common following sdNVP, multiple other mutations also confer NVP-resistance. It remains unclear whether specific NVP-resistance mutations or combinations of mutations predict virologic failure in infants when present at low frequencies prior to NVP-based treatment. Methods Twenty sdNVP-exposed infants who were subsequently treated with NVP-based highly active antiretroviral therapy (HAART) were examined. Pre-treatment plasma samples were tested for the presence of NVP-resistance mutations by allele-specific PCR (ASPCR) for K103N and Y181C and ultra-deep pyrosequencing (UDPS) for all primary NVP mutations. Viral levels were determined every 3 months for up to 24months on NVP-HAART. Cox proportional hazard models were used to determine correlates of viral failure. Results The NVP resistance mutations K103N or Y181C were detected in pre-treatment plasma samples in 6 infants by ASPCR. NVP resistance at these or other sites was detectable by UDPS in 10 out of 20 infants tested. Virologic failure occurred in 50% of infants with any NVP resistance mutations detected, while only 20% of infants without resistance experienced viral failure, but the difference was not significant (p=0.19). An increase in the number of NVP resistance mutations detectable by UDPS in an infant was significantly associated with an increased risk of virologic failure (HR=1.79 (95%CI: 1.07, 2.99), p=0.027). Conclusions Low frequencies of multiple NVP resistance mutations, in addition to K103N and Y181C, present in infants before NVP-based treatment may predict treatment outcome. PMID:22395670

  3. Predictive factors for renal failure and a control and treatment algorithm

    PubMed Central

    Cerqueira, Denise de Paula; Tavares, José Roberto; Machado, Regimar Carla

    2014-01-01

    Objectives to evaluate the renal function of patients in an intensive care unit, to identify the predisposing factors for the development of renal failure, and to develop an algorithm to help in the control of the disease. Method exploratory, descriptive, prospective study with a quantitative approach. Results a total of 30 patients (75.0%) were diagnosed with kidney failure and the main factors associated with this disease were: advanced age, systemic arterial hypertension, diabetes mellitus, lung diseases, and antibiotic use. Of these, 23 patients (76.6%) showed a reduction in creatinine clearance in the first 24 hours of hospitalization. Conclusion a decline in renal function was observed in a significant number of subjects, therefore, an algorithm was developed with the aim of helping in the control of renal failure in a practical and functional way. PMID:26107827

  4. Is there a way to predict failure after direct vision internal urethrotomy for single and short bulbar urethral strictures?

    PubMed Central

    Harraz, Ahmed M.; El-Assmy, Ahmed; Mahmoud, Osama; Elbakry, Amr A.; Tharwat, Mohamed; Omar, Helmy; Farg, Hashim; Laymon, Mahmoud; Mosbah, Ahmed

    2015-01-01

    Objective To identify patient and stricture characteristics predicting failure after direct vision internal urethrotomy (DVIU) for single and short (<2 cm) bulbar urethral strictures. Patients and methods We retrospectively analysed the records of adult patients who underwent DVIU between January 2002 and 2013. The patients’ demographics and stricture characteristics were analysed. The primary outcome was procedure failure, defined as the need for regular self-dilatation (RSD), redo DVIU or substitution urethroplasty. Predictors of failure were analysed. Results In all, 430 adult patients with a mean (SD) age of 50 (15) years were included. The main causes of stricture were idiopathic followed by iatrogenic in 51.6% and 26.3% of patients, respectively. Most patients presented with obstructive lower urinary tract symptoms (68.9%) and strictures were proximal bulbar, i.e. just close to the external urethral sphincter, in 35.3%. The median (range) follow-up duration was 29 (3–132) months. In all, 250 (58.1%) patients did not require any further instrumentation, while RSD was maintained in 116 (27%) patients, including 28 (6.5%) who required a redo DVIU or urethroplasty. In 64 (6.5%) patients, a redo DVIU or urethroplasty was performed. On multivariate analysis, older age at presentation [odds ratio (OR) 1.017; P = 0.03], obesity (OR 1.664; P = 0.015), and idiopathic strictures (OR 3.107; P = 0.035) were independent predictors of failure after DVIU. Conclusion The failure rate after DVIU accounted for 41.8% of our present cohort with older age at presentation, obesity, and idiopathic strictures independent predictors of failure after DVIU. This information is important in counselling patients before surgery. PMID:26609447

  5. A Novel MiRNA-Based Predictive Model for Biochemical Failure Following Post-Prostatectomy Salvage Radiation Therapy

    PubMed Central

    Stegmaier, Petra; Drendel, Vanessa; Mo, Xiaokui; Ling, Stella; Fabian, Denise; Manring, Isabel; Jilg, Cordula A.; Schultze-Seemann, Wolfgang; McNulty, Maureen; Zynger, Debra L.; Martin, Douglas; White, Julia; Werner, Martin; Grosu, Anca L.; Chakravarti, Arnab

    2015-01-01

    Purpose To develop a microRNA (miRNA)-based predictive model for prostate cancer patients of 1) time to biochemical recurrence after radical prostatectomy and 2) biochemical recurrence after salvage radiation therapy following documented biochemical disease progression post-radical prostatectomy. Methods Forty three patients who had undergone salvage radiation therapy following biochemical failure after radical prostatectomy with greater than 4 years of follow-up data were identified. Formalin-fixed, paraffin-embedded tissue blocks were collected for all patients and total RNA was isolated from 1mm cores enriched for tumor (>70%). Eight hundred miRNAs were analyzed simultaneously using the nCounter human miRNA v2 assay (NanoString Technologies; Seattle, WA). Univariate and multivariate Cox proportion hazards regression models as well as receiver operating characteristics were used to identify statistically significant miRNAs that were predictive of biochemical recurrence. Results Eighty eight miRNAs were identified to be significantly (p<0.05) associated with biochemical failure post-prostatectomy by multivariate analysis and clustered into two groups that correlated with early (≤ 36 months) versus late recurrence (>36 months). Nine miRNAs were identified to be significantly (p<0.05) associated by multivariate analysis with biochemical failure after salvage radiation therapy. A new predictive model for biochemical recurrence after salvage radiation therapy was developed; this model consisted of miR-4516 and miR-601 together with, Gleason score, and lymph node status. The area under the ROC curve (AUC) was improved to 0.83 compared to that of 0.66 for Gleason score and lymph node status alone. Conclusion miRNA signatures can distinguish patients who fail soon after radical prostatectomy versus late failures, giving insight into which patients may need adjuvant therapy. Notably, two novel miRNAs (miR-4516 and miR-601) were identified that significantly improve

  6. On the development of life prediction methodologies for the failure of human teeth

    SciTech Connect

    Nalla, R.K.; Imbeni, V.; Kinney, J.H.; Marshall, S.J.; Ritchie, R.O.

    2002-09-18

    Human dentin is known to be susceptible to failure under cyclic loading. Surprisingly, there are few reports that quantify the effect of such loading, considering the fact that a typical tooth experiences a million or so loading cycles annually. In the present study, a systematic investigation is described of the effects of prolonged cyclic loading on human dentin in a simulated physiological environment. In vitro stress-life (S/N) data are discussed in the context of possible mechanisms of fatigue damage and failure.

  7. Microstructure-Based Constitutive Modeling of TRIP Steel: Prediction of Ductility and Failure Modes under Different Loading Conditions

    SciTech Connect

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

    2009-05-01

    In this study, an advanced micromechanics-based finite element model is developed based on the actual microstructure of a TRIP (TRansformation-Induced Plasticity) 800 steel to model complex deformation behavior of TRIP steels, including its ductile failure behaviors. The evolution of volume fraction of retained austenite during loading and the mechanical properties of the constituent phases of the TRIP 800 steel are obtained from the synchrotron-based in-situ high-energy X-ray diffraction (HEXRD) experiments and a self-consistent (SC) model. The ductile failure of the TRIP 800 under different loading conditions is predicted in the form of plastic strain localization without any prescribed failure criteria for the individual phases. The computational results suggest that the response of the microstructure-based representative volume element (RVE) well represents the overall macroscopic behavior of the deformed TRIP 800 steel under different loading and boundary conditions. The methodology described in this study may be extended for studying the ultimate ductile failure mechanisms of TRIP steels as well as the effects of the various processing parameters on the macroscopic behaviors of TRIP steels.

  8. Seismic energy data analysis of Merapi volcano to test the eruption time prediction using materials failure forecast method (FFM)

    NASA Astrophysics Data System (ADS)

    Anggraeni, Novia Antika

    2015-04-01

    The test of eruption time prediction is an effort to prepare volcanic disaster mitigation, especially in the volcano's inhabited slope area, such as Merapi Volcano. The test can be conducted by observing the increase of volcanic activity, such as seismicity degree, deformation and SO2 gas emission. One of methods that can be used to predict the time of eruption is Materials Failure Forecast Method (FFM). Materials Failure Forecast Method (FFM) is a predictive method to determine the time of volcanic eruption which was introduced by Voight (1988). This method requires an increase in the rate of change, or acceleration of the observed volcanic activity parameters. The parameter used in this study is the seismic energy value of Merapi Volcano from 1990 - 2012. The data was plotted in form of graphs of seismic energy rate inverse versus time with FFM graphical technique approach uses simple linear regression. The data quality control used to increase the time precision employs the data correlation coefficient value of the seismic energy rate inverse versus time. From the results of graph analysis, the precision of prediction time toward the real time of eruption vary between -2.86 up to 5.49 days.

  9. Seismic energy data analysis of Merapi volcano to test the eruption time prediction using materials failure forecast method (FFM)

    SciTech Connect

    Anggraeni, Novia Antika

    2015-04-24

    The test of eruption time prediction is an effort to prepare volcanic disaster mitigation, especially in the volcano’s inhabited slope area, such as Merapi Volcano. The test can be conducted by observing the increase of volcanic activity, such as seismicity degree, deformation and SO2 gas emission. One of methods that can be used to predict the time of eruption is Materials Failure Forecast Method (FFM). Materials Failure Forecast Method (FFM) is a predictive method to determine the time of volcanic eruption which was introduced by Voight (1988). This method requires an increase in the rate of change, or acceleration of the observed volcanic activity parameters. The parameter used in this study is the seismic energy value of Merapi Volcano from 1990 – 2012. The data was plotted in form of graphs of seismic energy rate inverse versus time with FFM graphical technique approach uses simple linear regression. The data quality control used to increase the time precision employs the data correlation coefficient value of the seismic energy rate inverse versus time. From the results of graph analysis, the precision of prediction time toward the real time of eruption vary between −2.86 up to 5.49 days.

  10. An Evolutionary Algorithm for Feature Subset Selection in Hard Disk Drive Failure Prediction

    ERIC Educational Resources Information Center

    Bhasin, Harpreet

    2011-01-01

    Hard disk drives are used in everyday life to store critical data. Although they are reliable, failure of a hard disk drive can be catastrophic, especially in applications like medicine, banking, air traffic control systems, missile guidance systems, computer numerical controlled machines, and more. The use of Self-Monitoring, Analysis and…

  11. Early Treatment Outcome in Failure to Thrive: Predictions from a Transactional Model.

    ERIC Educational Resources Information Center

    Drotar, Dennis

    Children diagnosed with environmentally based failure to thrive early during their first year of life were seen at 12 and 18 months for assessment of psychological development (cognition, language, symbolic play, and behavior during testing). Based on a transactional model of outcome, factors reflecting biological vulnerability (wasting and…

  12. Predictive failure analysis: planning for the worst so that it never happens!

    PubMed

    Hipple, Jack

    2008-01-01

    This article reviews an alternative approach to failure analysis involving a deliberate saboteurial approach rather than a checklist approach to disaster and emergency preparedness. This process is in the form of an algorithm that is easily applied to any planning situation. PMID:18091086

  13. Predicting Student Nurse Academic Failures: An Analysis of Four Baccalaureate Classes.

    ERIC Educational Resources Information Center

    Wold, Jean E.; Worth, Charles

    A study was done of pre-admission or early performance predictors of persistence versus academic failure among baccalaureate program nursing students. As part of a larger longitudinal research project, 155 students from four successive classes of students admitted to the program were studied, using multiple predictor and criterion variables. The…

  14. Predicting Success, Preventing Failure: An Investigation of the California High School Exit Exam

    ERIC Educational Resources Information Center

    Zau, Andrew C.; Betts, Julian R.

    2008-01-01

    Many educators, parents, and policymakers continue to call for reforms to the California High School Exit Exam (CAHSEE), citing concern about the 10 percent of California students who do not graduate because of their failure to pass the test. By law, current funding for tutoring those at risk of failing the CAHSEE is targeted at those in grade 12…

  15. Predicting the velocity and azimuth of fragments generated by the range destruction or random failure of rocket casings and tankage

    NASA Technical Reports Server (NTRS)

    Eck, Marshall; Mukunda, Meera

    1988-01-01

    A calculational method is described which provides a powerful tool for predicting solid rocket motor (SRM) casing and liquid rocket tankage fragmentation response. The approach properly partitions the available impulse to each major system-mass component. It uses the Pisces code developed by Physics International to couple the forces generated by an Eulerian-modeled gas flow field to a Lagrangian-modeled fuel and casing system. The details of the predictive analytical modeling process and the development of normalized relations for momentum partition as a function of SRM burn time and initial geometry are discussed. Methods for applying similar modeling techniques to liquid-tankage-overpressure failures are also discussed. Good agreement between predictions and observations are obtained for five specific events.

  16. A data-driven feature extraction framework for predicting the severity of condition of congestive heart failure patients.

    PubMed

    Sideris, Costas; Alshurafa, Nabil; Pourhomayoun, Mohammad; Shahmohammadi, Farhad; Samy, Lauren; Sarrafzadeh, Majid

    2015-08-01

    In this paper, we propose a novel methodology for utilizing disease diagnostic information to predict severity of condition for Congestive Heart Failure (CHF) patients. Our methodology relies on a novel, clustering-based, feature extraction framework using disease diagnostic information. To reduce the dimensionality we identify disease clusters using cooccurence frequencies. We then utilize these clusters as features to predict patient severity of condition. We build our clustering and feature extraction algorithm using the 2012 National Inpatient Sample (NIS), Healthcare Cost and Utilization Project (HCUP) which contains 7 million discharge records and ICD-9-CM codes. The proposed framework is tested on Ronald Reagan UCLA Medical Center Electronic Health Records (EHR) from 3041 patients. We compare our cluster-based feature set with another that incorporates the Charlson comorbidity score as a feature and demonstrate an accuracy improvement of up to 14% in the predictability of the severity of condition. PMID:26736808

  17. Risk Prediction Models of Locoregional Failure After Radical Cystectomy for Urothelial Carcinoma: External Validation in a Cohort of Korean Patients

    SciTech Connect

    Ku, Ja Hyeon; Kim, Myong; Jeong, Chang Wook; Kwak, Cheol; Kim, Hyeon Hoe

    2014-08-01

    Purpose: To evaluate the predictive accuracy and general applicability of the locoregional failure model in a different cohort of patients treated with radical cystectomy. Methods and Materials: A total of 398 patients were included in the analysis. Death and isolated distant metastasis were considered competing events, and patients without any events were censored at the time of last follow-up. The model included the 3 variables pT classification, the number of lymph nodes identified, and margin status, as follows: low risk (≤pT2), intermediate risk (≥pT3 with ≥10 nodes removed and negative margins), and high risk (≥pT3 with <10 nodes removed or positive margins). Results: The bootstrap-corrected concordance index of the model 5 years after radical cystectomy was 66.2%. When the risk stratification was applied to the validation cohort, the 5-year locoregional failure estimates were 8.3%, 21.2%, and 46.3% for the low-risk, intermediate-risk, and high-risk groups, respectively. The risk of locoregional failure differed significantly between the low-risk and intermediate-risk groups (subhazard ratio [SHR], 2.63; 95% confidence interval [CI], 1.35-5.11; P<.001) and between the low-risk and high-risk groups (SHR, 4.28; 95% CI, 2.17-8.45; P<.001). Although decision curves were appropriately affected by the incidence of the competing risk, decisions about the value of the models are not likely to be affected because the model remains of value over a wide range of threshold probabilities. Conclusions: The model is not completely accurate, but it demonstrates a modest level of discrimination, adequate calibration, and meaningful net benefit gain for prediction of locoregional failure after radical cystectomy.

  18. Predicting the velocity and azimuth of fragments generated by the range destruction or random failure of rocket casings and tankage

    NASA Astrophysics Data System (ADS)

    Eck, M.; Mukunda, M.

    The proliferation of space vehicle launch sites and the projected utilization of these facilities portends an increase in the number of on-pad, ascent, and on-orbit solid-rocket motor (SRM) casings and liquid-rocket tanks which will randomly fail or will fail from range destruct actions. Beyond the obvious safety implications, these failures may have serious resource implications for mission system and facility planners. SRM-casing failures and liquid-rocket tankage failures result in the generation of large, high velocity fragments which may be serious threats to the safety of launch support personnel if proper bunkers and exclusion areas are not provided. In addition, these fragments may be indirect threats to the general public's safety if they encounter hazardous spacecraft payloads which have not been designed to withstand shrapnel of this caliber. They may also become threats to other spacecraft if, by failing on-orbit, they add to the ever increasing space-junk collision cross-section. Most prior attempts to assess the velocity of fragments from failed SRM casings have simply assigned the available chamber impulse to available casing and fuel mass and solved the resulting momentum balance for velocity. This method may predict a fragment velocity which is high or low by a factor of two depending on the ratio of fuel to casing mass extant at the time of failure. Recognizing the limitations of existing methods, the authors devised an analytical approach which properly partitions the available impulse to each major system-mass component. This approach uses the Physics International developed PISCES code to couple the forces generated by an Eulerian modeled gas flow field to a Lagrangian modeled fuel and casing system. The details of a predictive analytical modeling process as well as the development of normalized relations for momentum partition as a function of SRM burn time and initial geometry are discussed in this paper. Methods for applying similar modeling

  19. Texture feature analysis for prediction of postoperative liver failure prior to surgery

    NASA Astrophysics Data System (ADS)

    Simpson, Amber L.; Do, Richard K.; Parada, E. Patricia; Miga, Michael I.; Jarnagin, William R.

    2014-03-01

    Texture analysis of preoperative CT images of the liver is undertaken in this study. Standard texture features were extracted from portal-venous phase contrast-enhanced CT scans of 36 patients prior to major hepatic resection and correlated to postoperative liver failure. Differences between patients with and without postoperative liver failure were statistically significant for contrast (measure of local variation), correlation (linear dependency of gray levels on neighboring pixels), cluster prominence (asymmetry), and normalized inverse difference moment (local homogeneity). Though texture features have been used to diagnose and characterize lesions, to our knowledge, parenchymal statistical variation has not been quantified and studied. We demonstrate that texture analysis is a valuable tool for quantifying liver function prior to surgery, which may help to identify and change the preoperative management of patients at higher risk for overall morbidity.

  20. A novel prediction methodology for detecting failures and instabilities in directional wireless networks

    NASA Astrophysics Data System (ADS)

    Coleman, David M.; Milner, Stuart D.; Davis, Christopher C.

    2012-10-01

    Even though advances in wireless technology have yielded lower power consumption, higher data rates, and numerous other improvements, the ability to develop a proactive strategy towards handling degradations and failures in directional wireless networks has evaded the research community. In this paper, we introduce a methodology using an analogy to molecular systems in which a directional wireless network utilizing free space optical (FSO) or RF links is modeled as a molecule whose links can grow/retract similarly to bonds. A normal mode analysis (NMA) is performed to identify link instabilities (degradations and failures) and an N-dimensional potential energy surface (PES) is derived with respect to network and environmental parameters to aide in the detection of when a new topology is available ahead of the topology computation stage. Together, the NMA and PES form a basis for a proactive network methodology aimed at improving performance in directional wireless networks.

  1. Comparative Study on Failure Prediction in Warm Forming Processes of Mg Alloy Sheet by the FEM and Ductile Fracture Criteria

    NASA Astrophysics Data System (ADS)

    Kim, Sang-Woo; Lee, Young-Seon

    2014-04-01

    An important concern in metal forming is whether the desired deformation can be accomplished without any failure of the material, even at elevated temperatures. This paper describes the utilization of ductile fracture criteria in conjunction with the finite element (FE) method for predicting the onset of fracture in warm metal working processes of magnesium alloy sheets. The uniaxial tensile tests of AZ31 alloy sheets with a thickness of 3 mm and FE simulations were performed to calculate the critical damage values for three kinds of ductile fracture criteria. The critical damage values for each criterion were expressed as the function of strain rate at various temperatures. In order to find out the best criterion for failure prediction, Erichsen cupping tests under isothermal conditions were carried out at various temperatures and punch velocities. Based on the plastic deformation histories obtained from FE analysis of the Erichsen cupping tests and the critical damage value curves, the initiation time and location of fracture were predicted under bi-axial tensile conditions. As a result, Cockcroft-Latham's criterion showed good agreement with the experiments.

  2. Ply level failure prediction of carbon fibre reinforced laminated composite panels subjected to low velocity drop-weight impact using adaptive meshing techniques

    NASA Astrophysics Data System (ADS)

    Farooq, Umar; Myler, Peter

    2014-09-01

    This work is concerned with physical testing and numerical simulations of flat and round nose drop-weight impact of carbon fibre-reinforced laminate composite panels to predict ply level failure. Majority of the existing studies on impact of composites by spherical nose impactors are experimental, computational models are simplified, and based on classical laminated plate theories where contributions of through-thickness stresses are neglected. Present work considers flat nose impact and contributions from through-thickness stresses and is mainly simulation based. A computational model was developed in ABAQUS™ software using adaptive meshing techniques. Simulation produced (2D model) stresses were numerically integrated using MATALB™ code to predict through-thickness (3D) stresses. Through-the-thickness stresses were then utilised in advanced failure criteria coded in MATLAB™ software to predict ply level failures. Simulation produced results demonstrate that the computational model can efficiently and effectively predict ply-by-ply failure status of relatively thick laminates.

  3. Crisis Management of Accidental Extubation in a Prone-Positioned Patient with Klippel-Feil Syndrome.

    PubMed

    Spond, Matthew; Burns, Tyler; Rosenbaum, Thea; Lienhart, Kristen

    2016-06-15

    We present the case of an accidental extubation in a prone-positioned patient with a challenging airway because of Klippel-Feil syndrome and previous cervical spine fusions. The surgical procedure was well underway when this occurred, which added substantially to the difficulties produced by this event. We herein highlight the corrective steps we took in our case. We also recommend the need for a comprehensive preoperative briefing with all operating room personnel together with an action plan for how to prevent this particular scenario. PMID:27301052

  4. Serum sodium based modification of the MELD does not improve prediction of outcome in acute liver failure

    PubMed Central

    2013-01-01

    Background Acute liver failure (ALF) is a devastating clinical syndrome with a high mortality rate. The MELD score has been implied as a prognostic tool in ALF. Hyponatremia is associated with lethal outcome in ALF. Inclusion of serum sodium (Na) into the MELD score was found to improve its predictive value in cirrhotic patients. Therefore the aim of this study was to determine whether inclusion of serum Na improves the predictive value of MELD in ALF compared to established criteria. Methods In a prospective single center study (11/2006–12/2010), we recruited 108 consecutive ALF patients (64% females / 36% males), who met the criteria defined by the “Acute Liver Failure Study Group Germany”. Upon admission, clinical and laboratory data were collected, King’s College Criteria (KCC), Model of End Stage Liver Disease score (MELD), and serum sodium based modifications like the MELD-Na score and the United Kingdom Model of End Stage Liver Disease score (UKELD) were calculated and area under the receiver operating characteristic curve analyses were performed regarding the prediction of spontaneous recovery (SR) or non-spontaneous recovery (NSR; death or transplantation). Results Serum bilirubin was of no prognostic value in ALF, and Na also failed to predict NSR in ALF. The classical MELD score was superior to sodium-based modifications and KCC. Conclusions We validated the prognostic value of MELD-Na and UKELD in ALF. Classic MELD score calculations performed superior to KCC in the prediction of NSR. Serum Na and Na-based modifications of MELD did not further improve its prognostic value. PMID:23551795

  5. A Novel Risk Stratification to Predict Local-Regional Failures in Urothelial Carcinoma of the Bladder After Radical Cystectomy

    SciTech Connect

    Baumann, Brian C.; Guzzo, Thomas J.; He Jiwei; Keefe, Stephen M.; Tucker, Kai; Bekelman, Justin E.; Hwang, Wei-Ting; Vaughn, David J.; Malkowicz, S. Bruce; Christodouleas, John P.

    2013-01-01

    Purpose: Local-regional failures (LF) following radical cystectomy (RC) plus pelvic lymph node dissection (PLND) with or without chemotherapy for invasive urothelial bladder carcinoma are more common than previously reported. Adjuvant radiation therapy (RT) could reduce LF but currently has no defined role because of previously reported morbidity. Modern techniques with improved normal tissue sparing have rekindled interest in RT. We assessed the risk of LF and determined those factors that predict recurrence to facilitate patient selection for future adjuvant RT trials. Methods and Materials: From 1990-2008, 442 patients with urothelial bladder carcinoma at University of Pennsylvania were prospectively followed after RC plus PLND with or without chemotherapy with routine pelvic computed tomography (CT) or magnetic resonance imaging (MRI). One hundred thirty (29%) patients received chemotherapy. LF was any pelvic failure detected before or within 3 months of distant failure. Competing risk analyses identified factors predicting increased LF risk. Results: On univariate analysis, pathologic stage {>=}pT3, <10 nodes removed, positive margins, positive nodes, hydronephrosis, lymphovascular invasion, and mixed histology significantly predicted LF; node density was marginally predictive, but use of chemotherapy, number of positive nodes, type of surgical diversion, age, gender, race, smoking history, and body mass index were not. On multivariate analysis, only stage {>=}pT3 and <10 nodes removed were significant independent LF predictors with hazard ratios of 3.17 and 2.37, respectively (P<.01). Analysis identified 3 patient subgroups with significantly different LF risks: low-risk ({<=}pT2), intermediate-risk ({>=}pT3 and {>=}10 nodes removed), and high-risk ({>=}pT3 and <10 nodes) with 5-year LF rates of 8%, 23%, and 42%, respectively (P<.01). Conclusions: This series using routine CT and MRI surveillance to detect LF confirms that such failures are relatively common

  6. Prediction of ppm level electrical failure by using physical variation analysis

    NASA Astrophysics Data System (ADS)

    Hou, Hsin-Ming; Kung, Ji-Fu; Hsu, Y.-B.; Yamazaki, Y.; Maruyama, Kotaro; Toyoshima, Yuya; Chen, Chu-en

    2016-03-01

    their spatial correlation distance. For local variations (LV) there is no correlation, whereas for global variations (GV) the correlation distance is very large [7]-[9]. This is the first time to certificate the validation of spatial distribution from the affordable bias contour big data fundamental infrastructures. And then apply statistical techniques to dig out the variation sources. The GV come from systematic issue, which could be compensated by adaptive LT condition or OPC correction. But LV comes from random issue, which being considered as intrinsic problem such as structure, material, tool capability… etc. In this paper studying, we can find out the advanced technology node SRAM contact CD local variation (LV) dominates in total variation, about 70%. It often plays significant in-line real time catching WP-DPMO role of the product yield loss, especially for wafer edge is the worst loss within wafer distribution and causes serious reliability concern. The major root cause of variations comes from the PR material induced burr defect (LV), the second one comes from GV enhanced wafer edge short opportunity, which being attributed to three factors, first one factor is wafer edge CD deliberated enlargement for yield improvement as shown in Fig. 10. Second factor is overlaps/AA shifts due to tool capability dealing with incoming wafer's war page issue and optical periphery layout dependent working pitch issue as shown in Fig. 9 (1)., the last factor comes from wafer edge burr enhanced by wafer edge larger Photo Resistance (PR) spin centrifugal force. After implementing KPIs such as GV related AA/CD indexes as shown in Fig. 9 (1) and 10, respectively, and LV related burr index as shown in Fig. 11., we can construct the parts per million (PPM) level short probability model via multi-variables regression, canonical correlation analysis and logistic transformation. The model provides prediction of PPM level electrical failure by using in-line real time physical

  7. Predicting the occurrence of mixed mode failure associated with hydraulic fracturing, part 2 water saturated tests

    SciTech Connect

    Bauer, Stephen J.; Broome, Scott Thomas; Choens, Charles; Barrow, Perry Carl

    2015-09-14

    Seven water-saturated triaxial extension experiments were conducted on four sedimentary rocks. This experimental condition was hypothesized more representative of that existing for downhole hydrofracture and thus it may improve our understanding of the phenomena. In all tests the pore pressure was 10 MPa and confirming pressure was adjusted to achieve tensile and transitional failure mode conditions. Using previous work in this LDRD for comparison, the law of effective stress is demonstrated in extension using this sample geometry. In three of the four lithologies, no apparent chemo-mechanical effect of water is apparent, and in the fourth lithology test results indicate some chemo-mechanical effect of water.

  8. A Comparison of Logistic Regression Model and Artificial Neural Networks in Predicting of Student’s Academic Failure

    PubMed Central

    Teshnizi, Saeed Hosseini; Ayatollahi, Sayyed Mohhamad Taghi

    2015-01-01

    Background and objective: Artificial Neural Networks (ANNs) have recently been applied in situations where an analysis based on the logistic regression (LR) is a standard statistical approach; direct comparisons of the results, however, are seldom attempted. In this study, we compared both logistic regression models and feed-forward neural networks on the academic failure data set. Methods: The data for this study included 18 questions about study situation of 275 undergraduate students selected randomly from among nursing and midwifery and paramedic schools of Hormozgan University of Medical Sciences in 2013. Logistic regression with forward method and feed forward Artificial Neural Network with 15 neurons in hidden layer were fitted to the dataset. The accuracy of the models in predicting academic failure was compared by using ROC (Receiver Operating Characteristic) and classification accuracy. Results: Among nine ANNs, the ANN with 15 neurons in hidden layer was a better ANN compared with LR. The Area Under Receiver Operating Characteristics (AUROC) of the LR model and ANN with 15 neurons in hidden layers, were estimated as 0.55 and 0.89, respectively and ANN was significantly greater than the LR. The LR and ANN models respectively classified 77.5% and 84.3% of the students correctly. Conclusion: Based on this dataset, it seems the classification of the students in two groups with and without academic failure by using ANN with 15 neurons in the hidden layer is better than the LR model. PMID:26635438

  9. Early detection of heart failure with varying prediction windows by structured and unstructured data in electronic health records.

    PubMed

    Wang, Yajuan; Ng, Kenney; Byrd, Roy J; Hu, Jianying; Ebadollahi, Shahram; Daar, Zahra; deFilippi, Christopher; Steinhubl, Steven R; Stewart, Walter F

    2015-08-01

    Heart failure (HF) prevalence is increasing and is among the most costly diseases to society. Early detection of HF would provide the means to test lifestyle and pharmacologic interventions that may slow disease progression and improve patient outcomes. This study used structured and unstructured data from electronic health records (EHR) to predict onset of HF with a particular focus on how prediction accuracy varied in relation to time before diagnosis. EHR data were extracted from a single health care system and used to identify incident HF among primary care patients who received care between 2001 and 2010. A total of 1,684 incident HF cases were identified and 13,525 controls were selected from the same primary care practices. Models were compared by varying the beginning of the prediction window from 60 to 720 days before HF diagnosis. As the prediction window decreased, the performance [AUC (95% CIs)] of the predictive HF models increased from 65% (63%-66%) to 74% (73%-75%) for the unstructured, from 73% (72%-75%) to 81% (80%-83%) for the structured, and from 76% (74%-77%) to 83% (77%-85%) for the combined data. PMID:26736807

  10. What Predicts Children's Fixed and Growth Intelligence Mind-Sets? Not Their Parents' Views of Intelligence but Their Parents' Views of Failure.

    PubMed

    Haimovitz, Kyla; Dweck, Carol S

    2016-06-01

    Children's intelligence mind-sets (i.e., their beliefs about whether intelligence is fixed or malleable) robustly influence their motivation and learning. Yet, surprisingly, research has not linked parents' intelligence mind-sets to their children's. We tested the hypothesis that a different belief of parents-their failure mind-sets-may be more visible to children and therefore more prominent in shaping their beliefs. In Study 1, we found that parents can view failure as debilitating or enhancing, and that these failure mind-sets predict parenting practices and, in turn, children's intelligence mind-sets. Study 2 probed more deeply into how parents display failure mind-sets. In Study 3a, we found that children can indeed accurately perceive their parents' failure mind-sets but not their parents' intelligence mind-sets. Study 3b showed that children's perceptions of their parents' failure mind-sets also predicted their own intelligence mind-sets. Finally, Study 4 showed a causal effect of parents' failure mind-sets on their responses to their children's hypothetical failure. Overall, parents who see failure as debilitating focus on their children's performance and ability rather than on their children's learning, and their children, in turn, tend to believe that intelligence is fixed rather than malleable. PMID:27113733