No / This paper is part of a research theme to develop methods that enhance risk assessment studies by the use of 'automated' failure analysis. The paper presents an approach to mechanical failure analysis and introduces a mechanical failure analysis module that can be used in a virtual reality (VR) environment. The module is used to analyse and predict failures in mechanical assemblies; it considers stress related failures within components, as well as failures due to component interactions. Mechanical failures are divided into two categories in this paper: material failures and interference failures. The former occur in components and the latter happen at the interface between components. Individual component failures can be analysed readily; a contribution of the mechanical failure analysis module is to predict interference failures. A mechanical failure analysis system that analyses and visualizes mechanical failures in a virtual environment has been developed. Two case studies demonstrate how the system carries out failure analysis and visualization as design parameters are changed.

ITC/USA 2008 Conference Proceedings / The Forty-Fourth Annual International Telemetering Conference and Technical Exhibition / October 27-30, 2008 / Town and Country Resort & Convention Center, San Diego, California / Unique vehicle designs encourage the use of the builder to complete its own failure analysis. Current failure analysis practices use telemetry and diagnostic technology developed over the past 100 years to identify root-cause. When telemetry isn't available speculation is used to create a list of prioritized, potential causes. Prognostic technology consists of generic algorithms that identify equipment that has failed and is going to fail while the equipment is still at the factory allowing the equipment to be repaired or replaced while it is still on the ground for any spacecraft, satellite, launch vehicle and missile.

ITC/USA 2007 Conference Proceedings / The Forty-Third Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2007 / Riviera Hotel & Convention Center, Las Vegas, Nevada / Telemetry Prognostics is Failure Prediction using telemetry for launch vehicle and satellite space flight equipment to stop launch failures, launch pad delays, satellite infant mortalities and satellite on orbit failures. This technology characterizes telemetry behaviors that are latent, transient, and go undetected by the most experienced engineering personnel and software diagnostic tools during integration and test, launch operations and on orbit activities stopping launch pad delays, launch failures, infant mortalities and on orbit failures. Telemetry prognostics yield a technology with state-of-the-art innovative techniques for determining critical on-board equipment remaining useful life taking into account system states, attitude reorientations, equipment usage patterns, failure modes and piece part failure characteristics to increase the reliability, usability, serviceability, availability and safety of our nation’s space systems.

Heart failure (HF) is a clinical syndrome associated with high morbidity and mortality with a large economic burden, and is the leading cause of hospitalizations among Medicare beneficiaries in the United States. Healthcare reform has focused on strategies to reduce HF readmissions, including outpatient HF clinics. Purpose: The purpose of this DNP Project was to answer the following question: In adult patients diagnosed with HF, how does enrollment in the HF clinic, compared to non-enrollment affect hospital admission and readmission rates? Methods: A retrospective analysis of 767 unique patients and their 1,014 respective admissions and readmissions was conducted. Continuous and categorical data was analyzed and presented as a mean (M), standard deviation (SD), absolute number (N) and percentage (%). A Pearson Chi Square test was used for categorical variables and Analysis of Variance was used for age and ejection fraction (EF). Results: Study sample demographics (N=767); age (M=79.72, SD=7.48); gender (57.6 % male) and EF (M=0.43, SD=0.16) were evaluated. The No HF clinic (No HFC) and HF clinic (HFC) enrollment groups (N=573) were compared for age (M=79.49, SD=7.65) (M=80.39, SD=6.94), male gender (54.6%, 66.5%) and EF (M= 0.44, SD=0.17) (M=0.42, SD=0.15), respectively. Each sample patient had at least one admission for HF during 2015; of which 573 (46.2%) were in the No HFC group and 194 (8.4%) were in the HFC group (p<0.001). There was no difference in all-cause readmissions between the No HFC group [n=95(14.5%)] and the HFC group [n=37(16.2%)] (p=0.534) and no difference in HF-related readmissions between the No HFC group [n=72(11.0%)] and the HFC group [n=23(10.0%)] (p=0.700). Conclusions: This DNP project demonstrated a significant difference in HF admission rates in favor of the HFC group. While no differences were found in all-cause or HF-related readmission rates in No HFC and HFC groups, the rates are less than the national average. Unintended findings were that datasets can be very poorly constructed and populated, resulting in large amounts of unusable data. Recommendations are for more rigor in the organization of datasets to assure accurate comparisons between admission and readmission rates based on enrollment in HF clinics.

Echocardiography has an prominent role in the era of CRT by virtue of its non-invasive nature with high feasibility and reproducibility. The clinical applications include not only quantification of the change in systolic function, hemodynamics, LV volume, or mitral regurgitation, but also assessment of systolic dyssynchrony. A number of new echocardiographic techniques were employed in this study, such as tissue Doppler imaging (TDI) and its post-processing modalities including strain, strain rate and displacement mappings, tissue synchronization imaging (TSI), as well as three-dimentional (3D) echocardiography. / For heart failure patients with wide QRS complexes who received CRT, LV volumes, cardiac function and synchronicity were shown to change acutely between CRT-on and CRT-off modes by both 2D and 3D echocardiography methods. Furthermore, the usefulness of 3D echocardiography and its accuracy in assessing volumetric changes / Systolic dyssynchrony, which illustrates discoordinated contraction of the heart, is relatively common in heart failure patients, in particular those with prolonged QRS complexes. It is caused by electromechanical delay in some regions of the failing heart and will result in further reduction of cardiac function. Cardiac resynchronization therapy (CRT) is a rapidly evolving pacing modality for advanced heart failure, characterized by implantation of the left ventricular (LV) lead through coronary sinus to the free wall region. It is recommended to patients who have refractory heart failure despite optimal medical treatment, LV dilatation with ejection fraction lower than 35%, and prolonged QRS duration on surface ECG. / The main findings were as followed: The Ts-SD was 17.0+/-7.8ms in normal control, 33.8+/-16.9ms in narrow QRS group and 42.0+/-16.5ms in wide QRS group, respectively. The prevalence of systolic dyssynchrony in heart failure population was 43% in the narrow QRS group, and 64% in the wide QRS group, when a Ts-SD of > 32.6 ms (+2 SD of normal controls) was used to define significant dyssynchrony. QRS duration does not have a linear relationship with systolic dyssynchrony. / TSI was useful to predict a reverse remodeling and gain in ejection fraction after CRT. Qualitative identification of the latest peak systolic contraction at the lateral wall was a quick and specific guide to predict a favorable reverse remodeling response while quantitative computation of "Asynchrony Index" from 12 LV segments in ejection phase was beneficial in the absence of lateral wall delay. In conclusion, the improvement of cardiac function and LV reverse remodeling after CRT is more obvious in heart failure patients with wide QRS complex and echocardiographic evidence of significant systolic dyssynchrony. Reverse remodeling is not only an objective measure of favorable responses, but also a prognosticator of disease outcomes. "Asynchrony Index" is a strong predictor of LV reverse remodeling response after CRT. Assessment of systolic dyssynchrony by various echocardiographic tools is promising, however, further studies are needed to compare the predictive values of different parameters objectively and prospectively. / We performed echocardiography with TDI in 200 subjects, including 67 patients with heart failure and narrow QRS complexes (&le; 120ms), 45 patients with heart failure and wide QRS complexes (>120ms), and 88 normal controls, which served as a polit study. Severity and prevalence of systolic dyssynchrony were assessed by the maximal difference in time to peak myocardial systolic velocity (Ts-dif-12) and the standard deviation (Ts-SD) of the 12 LV segments. / We recruited a group of seventy patients with chronic heart failure who fulfilled the established criteria and received CRT. Serial echocardiographic assessment with clinical evaluation was performed at baseline, predischarge, 1-month, 3-month, 6-month and long-term follow up. The objective was to demonstrate the improvement of cardiac function and dyssynchrony after CRT by echocardiographic parameters, in particular the reduction of LV end-systolic volume (LVESV) which is also known as reverse remodeling, and its relationship with the improvement in clinical status and prognosis. We also attempted to identify dyssynchrony parameters which are useful in predicting LV reverse remodeling after CRT. / Zhang Qing. / "October 2006." / Adviser: Yu Cheuk-Man. / Source: Dissertation Abstracts International, Volume: 68-09, Section: B, page: 5852. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract in English and Chinese. / School code: 1307.

Like any muscle, cardiac contraction is evoked by action potentials. In the healthy heart, atrial and ventricular activation occur through impulse conduction via the rapid conduction system. Normal cardiac function requires a highly synchronized series of mechanical events occurring in the atria and the ventricles. This synchronization is achieved by rapid conduction of action potentials through the electrical conduction system, which leads to coordinated mechanical activation and deactivation of the myocardium — a process known as electromechanical coupling. As a result of this coordinated electromechanical coupling, the left ventricle functions efficiently as a pump. On the contrary, asynchronous electrical activation leads to asynchronous contraction. The presence of a bundle branch block or other intraventricular conduction delay can worsen heart failure due to systolic dysfunction by causing ventricular dyssynchrony, thereby inducing regional loading disparities and reducing the efficiency of contraction. Consistent with the idea that ventricular dyssynchrony exacerbates left ventricular dysfunction is the observation that a variety of hemodynamic benefits follow the correction of dyssynchrony with cardiac resynchronization therapy (CRT) using biventricular pacing. With decades of research on electromechanical coupling in the heart, it is now recognized that (1) cardiac dyssynchrony worsens ventricular efficiency and contributes to the progression of systolic heart failure; (2) cardiac dyssynchrony can be accurately assessed by echocardiography; (3) cardiac dyssynchrony independently predicts worse prognosis in patients with systolic heart failure; and (4) CRT has established as an effective treatment for systolic heart failure, leading to improved symptomatic status and better survival. / Concerning the subject of cardiac dyssynchrony there are still a lot of unanswered questions which are important to complete understanding of disease mechanisms of heart failure and hence to develop better treatment strategies. First, patients with heart failure but with a preserved ejection fraction (HFPEF) constitutes about half of the heart failure occurrence. Yet, it is not completely understood whether cardiac dyssynchrony, as a potential pathogenic mechanism and therapeutic target, is present in these patients. Second, the heart and circulation is a dynamic system. Nevertheless, scarce data exists on how cardiac dyssynchrony alters in response to exercise and other hemodynamic stressors in patients with heart failure. The potential clinical significance of dynamic dyssynchrony is unknown. Furthermore, identification of precipitating factors of acute hemodynamic decompensation in heart failure is important to prevent recurrent acute exacerbation and hospitalization. Cardiac dyssynchrony has been suspected to be an insidious, potentially correctable trigger of acute decompensated heart failure (ADHF), but scientific evidence is limited. Last but not least, about 30% of the CRT recipients did not respond to the treatment. It was proposed that inadequate optimization of atrioventricular (AV) synchronization is the most common contributory factor, hence the routine practice of AV optimization after CRT implantation. But again, electromechanical coupling is a dynamic process. It is uncertain, however, whether AV optimization should be performed at rest or during exercise to achieve optimal hemodynamic and clinical benefit. / In Part I of this thesis, I will review the literature on heart failure, cardiac dyssynchrony, and exercise impact on the cardiovascular system. In Chapter 1, the definition, clinical classification, and epidemiology of heart failure, as well as the biomechanical model for heart failure progression will be discussed. In Chapter 2, the literature on the normal and pathological electromechanical coupling mechanism, the clinical implication of dyssynchrony in heart failure, and the effect of CRT will be reviewed. In Chapter 3, I will discuss the current understanding of the physiologic effect of exercise, heart rate and stress on cardiac function and synchronicity. In Part II, the hypotheses (Chapter 4) and general objectives (Chapter 5) of the studies included in this thesis will be specified. In Part III, I will describe in detail the general methodology used inthese studies including the study population involved (Chapter 6), the echocardiographic techniques (Chapter 7), and the exercise/pharmacological stress protocols (Chapter 8) used in these studies. / Part IV will be a thorough and logical reporting of the background, methods, findings, discussion, and conclusion of each of the clinical studies of this thesis. Chapter 9, 10 and 11 will focus on patients with preserved ejection fraction and Chapter 12 and 13 will attempt to fill the gap of knowledge of cardiac dyssynchrony in patients with systolic heart failure. / In the study discussed in Chapter 9, the prevalence of left ventricular mechanical dyssynchrony in coronary artery disease with preserved ejection fraction was evaluated. Ninety-four consecutive patients with chronic coronary artery disease and preserved ejection fraction (≥50%) were evaluated using echocardiography with tissue Doppler imaging and compared to 217 patients with depressed ejection fraction and (<50%) and 117 healthy subjects. Left ventricular systolic and diastolic dyssynchrony were determined by measuring the standard deviations of peak systolic (Ts-SD) and early diastolic myocardial (Te-SD) velocities, respectively, using a six-basal/six-mid-segmental model. In patients with coronary artery disease and preserved ejection fraction, both Ts-SD (32.2±17.3 compared with 17.7±8.6 ms; p<0.05) and Te-SD (26.2±13.6 compared with 20.3±8.1 ms; p<0.05) were significantly prolonged when compared with controls, although they were less prolonged than patients with coronary artery disease and depressed ejection fraction (Ts-SD, 37.8±16.5 ms; and Te-SD, 36.0±23.9 ms; both p<0.005). Patients with preserved ejection fraction who had no prior myocardial infarction had Ts-SD (32.9±17.5 ms) and Te-SD (28.6±14.8 ms) prolonged to a similar extent (p=NS) to those with prior myocardial infarction (Ts-SD, 28.4±16.8 ms; and Te-SD, 25.5±15.0 ms). Patients with class III/IV angina or multi-vessel disease were associated with more severe mechanical dyssynchrony (P<0.05). Furthermore, the majority of patients with mechanical dyssynchrony had narrow QRS complexes in those with preserved ejection fraction. This is in contrast with patients with depressed ejection fraction in whom systolic and diastolic dyssynchrony were more commonly associated with wide QRS complexes. / In Chapter 10, focus will be shifted to patients with acute coronary syndrome complicated by acute HFPEF. One hundred two patients presenting with acute coronary syndrome (ejection fraction ≥50%) and 104 healthy controls were studied using tissue Doppler imaging: group 1 (n=55) had HFPEF on presentation and group 2 (n=47) had no clinical HFPEF. Te-SD was found to be greater in group 1 (33±13 ms) than group 2 (21±9 ms) (p<0.001), and diastolic mechanical dyssynchrony was evident in 35% of patients in group 1 but in only 9% in group 2 (p<0.001). Worsening of the diastolic dysfunction grade was associated with a parallel increase in Te-SD (grades 0, 1, 2, and 3: 16±3 ms, 21±5 ms, 28±9 ms, and 41±17 ms, respectively; p<0.001). Te-SD correlated negatively with mean early diastolic basal myocardial velocity (Em) (r=-0.56, p<0.001) and positively with peak mitral inflow velocity of the early rapid-filling wave/Em (r=0.69, p<0.001). Multivariate analysis identified peak mitral inflow velocity of the early rapid-filling wave/Em as the only variable independently associated with HFPEF [odd sratio (OR)=1.48, p=0.001]. When peak mitral inflow velocity of the early rapid-filling wave/Em was excluded from the model, Te-SD (OR=1.13, p<0.001) and mean Em (odds ratio=0.37, p<0.001) became independently associated with HFPEF. / In Chapter 11, I will evaluate the impact of hemodynamic stress on left ventricular dyssynchrony and the relationship and predictive value of dynamic changes of left ventricular dyssynchrony on hypertensive HFPEF. In this study, a total of 131 subjects including 47 hypertensive HFPEF patients, 34 hypertensive patients with left ventricular hypertrophy without HFPEF, and 50 normal controls were studied by dobutamine stress echocardiography with tissue Doppler imaging. In normal controls, systolic and diastolic dyssynchrony did not develop during stress. The prevalence of resting systolic (36.2% vs. 38.2%, p=0.85) and diastolic (34.0% vs. 29.4%, p=0.66) dyssynchrony was similar in patients with HFPEF and left ventricular hypertrophy. During stress, the prevalence of systolic and diastolic dyssynchrony increased dramatically to 85.1% and 87.2%, respectively, in patients with HFPEF, but only 52.9% and 58.8% in patients with left ventricular hypertrophy (p<0.005). In HFPEF group, stress-induced increase in mean systolic basal myocardial velocity (Sm) was significantly blunted (2.8±2.0 vs. 4.2±2.4 cm/s, p=0.004), and the increase was abolished for mean Em (-0.3±2.5 vs. 2.4±3.4 cm/s, p<0.001). On multivariate analysis, stress-induced changes in mean Em (OR=0.69, p=0.004) and mean Sm (OR=0.56, p=0.004), and diastolic (OR=4.6, p=0.005) and systolic dyssynchrony during stress (OR=4.3, p=0.038) were independent determinants for occurrence of HFPEF. / In Chapter 12, the role of dyssynchrony in patients with systolic heart failure presentating with acute decompensation (ADHF) will be studied. In this study, it was hypothesized that acute left ventricular systolic dyssynchrony might be a hidden triggering mechanism for ADHF. Echocardiography with tissue Doppler imaging was performed in 145 subjects with systolic heart failure (ejection fraction <50%), including 84 consecutive patients presented with ADHF requiring hospitalization, comparing them to 61 chronic stable heart failure patients who had no heart failure exacerbation or hospitalization in the past 6 months. The ADHF group was observed to have higher heart rate on admission than patients with stable heart failure (82±15 vs 68±13 bpm, P<0.001), greater left ventricular wall thicknesses and mass (all P<0.05), and mitral regurgitation was more common (71% vs 46%, P<0.0001; ERO=0.12±0.11 vs 0.02±0.04 cm2, P<0.0001), but the overall severity of mitral regurgitation was mild or moderate. Despite no difference in ejection fraction, the ADHF group had significantly lower mean Sm (2.7±0.9 cm/s vs 3.0±0.9 cm/s, P=0.04). The Ts-SD was significantly prolonged in the ADHF group compared to patients with stable heart failure (44.7±16.6 vs 33.4±17.7 ms, P=0.0001). Significant left ventricular systolic dyssynchrony was evident in 75% (63 of 84) of patients of the ADHF group, compared to only 44% (27 of 61) of patients with chronic stable heart failure (P=0.0002). / In Chapter 13, I will focus on the role of dynamic AV dyssynchrony during exercise in patients with systolic heart failure who receive CRT. AV delay in CRT recipients are typically optimised at rest. However, there are limited data on the impact of exercise-induced changes in heart rate on the optimal AV delay and left ventricular function. In this study, AV delays were serially programmed in 41 CRT patients with intrinsic sinus rhythm at rest and during two stages of supine bicycle exercise with heart rates at 20 bpm (stage I) and 40 bpm (stage II) above baseline. The optimal AV delay during exercise was determined by the iterative method to maximise cardiac output using Doppler echocardiography. Results were compared to physiological change in PR intervals in 56 normal controls during treadmill exercise. The optimal AV delay was progressively shortened (p<0.05) with escalating exercise level (baseline: 123±26 ms vs. stage I: 102±24 ms vs stage II: 70±22 ms, p<0.05). AV delay optimisation led to a significantly higher cardiac output than without optimisation did during stage I (6.2±1.2 l/min vs. 5.2±1.2 l/min, p<0.001) and stage II (6.8±1.6 l/min vs. 5.9±1.3 l/min, p<0.001) exercise. A linear inverse relationship existed between optimal AV delays and heart rates in CRT patients (AV delay=241-1.61 x heart rate, R²=0.639, p<0.001) and healthy controls (R²=0.646, p<0.001), but the slope of regression was significantly steeper in CRT patients (p<0.001). / In conclusion, the works included in this thesis provide new evidence that left ventricular mechanical dyssynchrony is common in patients with coronary artery disease and preserved ejection fraction, even in patients without prior myocardial infarction or evidence of eletromechanical delay. In particular, left ventricular diastolic mechanical dyssynchrony may impair diastolic function and contribute to the pathophysiology of HFPEF during acute coronary syndrome. Moreover, dynamic dyssynchrony and impaired myocardial longitudinal function reserve during stress may contribute importantly to the pathophysiology of hypertensive HFPEF. In patients with heart failure and reduced ejection fraction, a high prevalence of left ventricular systolic dyssynchrony during acute decompensation suggests that acute or dynamic left ventricular systolic dyssynchrony may be an important precipitating factor and a potential therapeutic target. Progressive shortening of hemodynamically optimal AV delay with increasing heart rate during exercise suggests that dyssynchrony is dynamic and there may be a need for programming of rate-adaptive AV delay in CRT recipients to optimise clinical response. I believe this work will provide new understanding of the prevalence, mechanism, and clinical significance of cardiac dyssynchrony in heart failure. / Lee, Pui Wai. / Thesis (M.D.))--Chinese University of Hong Kong, 2015. / Includes bibliographical references (leaves 138-174). / Title from PDF title page (viewed on 24, October, 2016).

Cardiac pacing has been the only effective treatment in the management of patients with symptomatic bradycardia caused by sinus node dysfunction or atrioventricular block for decades. Conventional dual-chamber pacing is performed by implanting two leads in right atrial (RA) appendage and right ventricular (RV) apex separately. RV apex is the most commonly applied pacing site because it can be easily reached and allows a chronically stable position and stimulation thresholds. However, large randomized clinical trials have suggested that right ventricular apical (RVA) pacing may cause abnormal ventricular contraction and reduce pump function and lead to myocardial hypertrophy, in particular in patients with impaired left ventricular (LV) function. Recent studies have also reported a reduced LV systolic function in patients with pacing indications and preserved ejection fraction. The deleterious effects of RVA pacing on LV function may be related to the abnormal electrical and mechanical activation pattern or ventricular dyssynchrony. During RVA pacing, conduction of the electrical wave front propagates slowly through ventricular myocardium rather than through the His-Purkinje conduction system, comparable to left bundle branch block (LBBB). In addition , RVA pacing alters ventricular synchrony and loading conditions which may result in diastolic heart failure with abnormal LV relaxation, high filling pressure and low cardiac output state. Furthermore, it is possible that left atrial (LA) remodeling and reduction of atrial function may occur during RVA pacing . However, it is not been carefully studied. / Echocardiography is a convenient, non-invasive and established tool to assess cardiac function in clinical practice. Conventional two-dimensional echocardiography is useful to assess cardiac chamber size, volume and function. With the development of real time three-dimensional echocardiography (RT3DE) and color tissue Doppler imaging (TDI), echocardiography provides further valuable information and more accurate measurements which include myocardial velocity and parameters of dyssynchrony. In the present study, the main echocardiographic parameters including the maximal left atrial volume (LAVmax), pre-atrial contraction volume (LAVpre) and the minimal left atria l volume (LAVmin) were assessed by two-dimensional echocardiography. Peak systolic (Sm-la), peak early diastolic (Em-la), peak late diastolic (Am-la) velocities of left atrium (LA) and atrial conduction time (from onset of P wave on electrocardiogram to onset of atrial velocity) were measured by TDI. / In a cross-sectional study, ninety-eight patients who had been implanted with RVA-based dual-chamber pacemakers were enrolled. Four patients with pacing dependent were excluded. Eventually 94 patients were included in the final analysis. Echocardiography was performed (iE33, Philips) during intrinsic ventricular conduction (V-sense) and RVA pacing (V-pace) modes with 15 minutes between switching modes. We aimed to investigate if RVA pacing has any acute effects on atrial remodeling and function in patients with preserved ejection fraction (LV ejection fraction> 45%). The result showed that during V-pace, LA volumes increased significantly when compared with V-sense (LAVmax: 52.0 +/- 18.8 vs. 55.2 +/- 21.1 ml, p = 0.005; LAVpre: 39.8 +/- 16.4 vs. 41.3 +/- 16.6 ml, p = 0.014; LAVmin: 27.4 +/- 14.0 vs. 29.1 +/- 15.1 ml, p = 0.001) . TDI parameters showed significant reduction in Sm-la (3.0 +/- 1.1 vs. 2.7 +/- 0.9 cm/s, p &lt; 0.01), Em-la (2.7 +/- 1.1 vs. 2.4 +/- 1.0 cm/s, p = 0.001). However, there was no change in Am-la. / In a prospective study, patients with symptomatic bradycardia, preserved ejection fraction, and received RVA pacing were recruited. Echocardiography was performed at both baseline and one year follow up through a standard protocol by experienced echocardiographers. LA volumes and velocities as well as intra- and interatrial dyssynchrony were measured offline with the use of dedicated software. The objectives of this study were to investigate: (1) if RVA pacing has any deleterious effects on LA remodeling and function during long-term follow up; (2) if RA appendage pacing has separate effects on atrial pump function, intra- and interatrial dyssynchrony; (3) if atrial dysfunction and dyssynchrony can predict atrial high rate episodes (AHREs) burden in the first year of RVA pacing. The main findings of this study were: (a) at one year follow up, LA volumes and indexes were increased with reduction in passive emptying fraction and total emptying fraction. Atrial velocities showed significant reduction when compared with baseline; (b) in multivariate regression analysis, the ratio of transmitral early diastolic filling velocity to mitral annular early diastolic velocity (E/e') > 15 at one year and reduction of LV ejection fraction &ge; 5% were independent predictors of reduction of Am-la > 30%; (c) high percent of RA appendage pacing prolonged atrial conduction and induced intra- and interatrial dyssynchrony. (d) Am-la &lt; 5.3 cm/s can predict AHREs burden which had a sensitivity of 71% and specificity of 75%. / In conclusion, our studies suggest even short-term RVA pacing induces LA dilatation and impaired passive atrial function, though it did not have direct effect on active atrial contractility. However, chronic RVA pacing results in LA remodeling and reduces atrial function with decreased contractility. This was more likely to occur in those with impaired LV ejection fraction and evidence of diastolic dysfunction. Atrial dysfunction and interatrial dyssynchrony can predict AHREs burden after chronic RVA pacing. Therefore, measures that may minimize such adverse effect of pacing on atrial function need to considered for patients receiving RVA pacing, such as the use of new pacing modalities. / Xie, Junmin. / "December 2010"--Abstract. / Adviser: Yu Cheuk Man. / Source: Dissertation Abstracts International, Volume: 73-04, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 142-161). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

Small businesses play a vital role in the modern economy. They represent the main catalyst for economic development. However, small businesses fail at a high rate, especially small independent restaurants. Around 25% of small independent restaurants fail within the first year of operation, and around 60% do not survive for more than 3 years. The purpose of this multiple case study was to explore what strategies small independent full-service restaurant owners in the Al Rehab District, Cairo, Egypt implemented to sustain operations for more than 5 years. The restaurant viability model provided the conceptual framework for this study. The population of this study comprised of 14 owners of small independent full-service restaurant with less than 50 employees in the Al Rehab District, Cairo, Egypt, who sustained their businesses operations for more than 5 years. The data sources included semistructured interviews, restaurant review websites, and social media platforms. Based on methodological triangulation of the data sources, open coding, analyzing the data using qualitative data analysis software, and member checking, 5 themes emerged: restaurant infrastructure strategies, marketing strategies, operations strategies, management strategies, and emotive strategies. The potential implications for positive social change include increasing the success rate of small independent restaurant owners, which in return will create wealth for the owners, generate employment opportunities, increase the government tax revenues, and contribute to the growth of the Egyptian economy.

This dissertation explored ways that college students reflectively described the social influences related to their learning failures. This exploration was conducted using semi-structured interviews and Stake's multiple case analysis method. The findings from the interviews were used to develop a framework that describes the key social influence attributes of the learning failure experiences. The key attributes of the framework include: (a) roles, (b) context, and (c) phases. Each key attribute is discussed in detail. The framework serves as the means for exploring several related strands of research related to learning failure in a cohesive way, potentially enriching our understanding of these experiences. This improved understanding may lead to improved intervention designs and advisement strategies that could improve learning outcomes for students.

This thesis deals with the reliability and life-time ofelectronic components and ways to determine these factors.Plastic encapsulated and open test circuits were assessed atdifferent humidity and temperature conditions. From the resultsan acceleration factor could be derived using the Arrheniusrelation. This factor is used to determine failure rates atdifferent drift conditions under accelerated test conditions. Aformula for the factor containing both relative humidity andtemperature could be established and was found to hold also formeasurements published by others. Electrostatic discharge (ESD) transients were studiedexperimentally and by simulation with good agreement. A verysensitive method to detect latent failures of two kinds wasintroduced by nonlinearity measurements utilizing the thirdharmonic of a test signal. The ESD-susceptibility dependence ondesign and technology is shown and can be used to improvebuilt-in reliability. Influences in the performance of semiconductor devices fromdefects like fixed charges and ions were interpreted for thefirst time by simulation using a 2D- finite element componentprogram. Significant results gave an application to a MOSFETdevice showing parameter derating, especially the change of thethreshold value. A short description of later development insimulation methods with new, more powerful tools improvingcomponent performance and reliability is given. Charged thin films of Teflon, so calledelectrets, are used as microphone membranes. Theelectret voltage is a suitable reliability factor. Fromexperimental results a mathematical relation including thetemperature was established for the rate of decay of theelectret voltage with time. A method to charge the electretswith radioactive sources is outlined and described in apatent. Finally an attempt was done to analyze the reliability ofthin film circuits by mathematical methods. Bell LabsintroducedRC-feedback filters realized in tantalum thin filmtechnology. The phase shift of the filter is about π or180°. A mathematical apparatus was developed to calculatethe change in frequency and attenuation from small componentvariations in resistors and capacitors. First and higher ordercorrections were derived, using expansion by the Taylor seriesfor the higher order. <b>Keywords:</b>reliability, failure mechanism, accelerationtests, ESD, latent failure, plastic encapsulation, electret,thin film