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Myocardial injury in critically ill patients with co-existing cardiovascular diseaseDocherty, Annemarie Beth January 2018 (has links)
Approximately 30% of people admitted to ICU in the UK have co-existing cardiovascular disease (CVD), and this may rise as life-expectancy increases. Patients with CVD have impaired compensatory mechanisms to enable maximum oxygen delivery to the tissues in the event of critical illness, which itself increases global oxygen demand, further stressing the heart. This is exacerbated by tachycardia and hypotension, which may relatively reduce blood flow to the coronary arteries, and catecholamines which increase myocardial oxygen demand. The myocardium extracts 75% of the oxygen supplied by the coronary arteries at rest, and atheroma-related flow limitation further compromises myocardial oxygen delivery. However, the diagnosis of acute coronary syndrome in critical illness is not straightforward, due to patient inability to communicate symptoms, non-specific ECG changes, and poorly understood cardiac biomarker troponin elevation. My overall hypothesis is that patients with CVD benefit from increased oxygen delivery to the myocardium during critical illness. A focus is the importance of anaemia. The aims of the studies presented in this thesis are (i) to systematically review the literature regarding blood transfusion thresholds specifically in patients with CVD; (ii) to explore the association between Troponin I (TnI) within 24 hours of ICU admission and hospital mortality (iii) to describe and quantify the dynamics of TnI in patients with CVD during the first ten days after ICU admission; and (iv) to define myocardial infarction in the context of critical illness. I have performed a systematic review and meta-analysis of randomised controlled trials comparing a restrictive with liberal transfusion threshold and that included patients with CVD. In total, 11 trials enrolling patients with CVD (n=3033) were included for meta-analysis (restrictive n=1514, liberal=1519). The pooled risk ratio for the association between a restrictive transfusion threshold and 30 day mortality was 1.15 (95% CI 0.88 to 1.50, p=0.50, I2=14%). The risk of acute coronary syndrome in patients managed with restrictive compared with liberal transfusion was increased (nine trials, risk ratio 1.78, 95% CI 1.18 to 2.70, p=0.0, I2=0%). In contrast to broader literature supporting restrictive thresholds, our systematic review shows that a restrictive transfusion threshold of less than 80g/l may not be safe in patients with co-existing CVD, and highlights the variability in diagnostic definitions of ACS and the potential for ascertainment bias in transfusion trials. I undertook a retrospective cohort study in two independently collected cohorts of general ICU patients who had TnI measured within 24 hours of ICU admission. Importantly, the majority of TnI samples were collected routinely rather than for clinical indications. We used the Abbott ARCHITECT Stat assay (limit of detection 0.01mcg/l. We performed multivariable regression, adjusting for components of the APACHE II model. We derived the risk prediction score from the multivariable model with TnI. TnI was associated with all cause hospital mortality (OR per doubling TnI 1.16, 95% CI 1.13 to 1.20, p < 0.001) which persisted after adjustment for APACHE II model components (OR TnI 1.05, 95% CI 1.01 to 1.09, p=0.003). TnI correlated highly with the Acute Physiological Score component of APACHE II (r=0.39), suggesting that TnI release may be largely explained by acute physiological stress. Addition of TnI to the APACHE II model did not improve the performance of the risk prediction model and we would not advocate the adoption of a routine single troponin sample at admission. I designed, set up, and recruited 279 patients to a prospective cohort study TROPonin I in Cardiovascular patients in CriticAL care (TROPICCAL, UKCRN 19253) in 11 UK centres. The aims were to (i) determine the incidence of Myocardial Injury and Infarction, defined by the Third Universal Definition of Myocardial Infarction; (ii) explore factors associated with Injury and Infarction from multivariable analyses; and (iii) explore the relationship between Injury/Infarction and outcome in unadjusted and adjusted analyses. We recorded baseline characteristics, and took daily hs-TnI for ten days after ICU admission, severity of illness measures and ECGs for 5 days. There was a wide range of peak TnI (med 114ng/l (min 3, Q1 27, Q3 412, max 58820ng/l)) and a high prevalence of myocardial injury on systematic screening: 71% of patients had peak TnI greater than the sex-specific diagnostic threshold ('Injury'), and 24% had peak TnI greater than the sex-specific diagnostic threshold and dynamic changes on ECG consistent with ischaemia ('Infarction'). TnI consistently showed a rise-and-fall pattern consistent with an acute myocardial 'hit' rather than persisting injury, which peaked early during ICU stay. Importantly, only 12 (4.4%) patients were diagnosed with MI by the clinicians looking after the patients. Independent predictors of peak TnI in the preceding 24 hours were SOFA score, dynamic ECG ischaemia, lactate, haemoglobin, and age. The lack of association with CRP (representing systemic inflammation), with stronger association with lactate (representing inadequate perfusion/oxygen supply), Hb and ECG ischaemia support the conjecture that injury results in part from an acute ischaemic hit in this population. Patients with Infarction had similar baseline demographics to patients with Injury, but had higher peak TnI concentrations, and higher hospital and six month mortality (Figure 2). This supports the importance of including systematic assessment of dynamic ECG changes in the myocardial injury 'construct' in ICU. My work has shown an increased risk of ACS in patients with CVD randomised to restrictive transfusion thresholds. TnI elevation is prevalent in general ICU patients, and is independently associated with hospital mortality. A systematic approach to the detection of myocardial injury in critically ill patients with co-existing CVD who are unable to communicate symptoms, can identify a high risk population who have poorer survival than patients with no injury. Markers of ischaemia are more associated with TnI rise than markers of inflammation, supporting the hypothesis that myocardial injury in this population is at least in part due to oxygen supply-demand imbalance 'myocardial infarction'. From this work, I would recommend (i) a more liberal transfusion threshold of at least 80g/l in patients with coexisting CVD; (ii) systematic use of sequential ECGs in ICU to screen for myocardial injury in 'at risk' patients; and (iii) manipulation of physiological parameters such as anaemia, hypotension and tachycardia should be considered for patients with dynamic ECG changes plus troponin increase consistent with Infarction. Future research should include 'precision medicine' trials in the substantial cohort of ICU patients with co-existing CVD to explore whether interventions that increase myocardial oxygen supply and/or treat infarction alter outcomes.
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Americko-čínské hospodářské vztahy na počátku 21. století a jejich význam pro světovou ekonomiku. / Sino-american economic relations at the begining of the 21st century and their impact on the world economy.Hanák, Jiří January 2010 (has links)
The thesis deals with sino-american economic cooperation with the emphasis on the period after 2000 and the current situation. The objective was to evaluate these relations and to analyse selected problems associated with the international trade. The thesis is dividend into six chapters. First two deal with general description of both economies and short summary of up to date relations. The third chapter concentrates on the structure of mutual trade and investment, with the emphasis on the concentration of foreign exchange in present China and its role in the U.S. federal debt. The fourth chapter targets three selected problems -- mutual cooperation within the WTO and the existing trade barriers, current Chinese exchange rate policy and the problem of unemployment and open economy. The fifth chapter targets the international trade theory, especially sustainability of long term deficit in the current account, problem of foreign debt and international investment position. The last chapter is handling with the impact of USA and China on the imbalance in the world economy and changes associated with the rise of China as the second-largest world economy.
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Force Production Symmetry During Static, Isometric, and Dynamic TasksBailey, Christopher A 01 August 2014 (has links)
The purpose of this dissertation was to examine the existence of force production and strength symmetry while concentrating on its role with performance. Specifically, in this dissertation I sought to determine if differences in symmetry exist between male and female athletes as well as between athletes of different strength levels. Various symmetry assessments were used and the amount of carryover between tests was also evaluated. Furthermore, the relationship between asymmetry magnitude and various aspects of jump performance was also assessed.
The results showed that female athletes were more asymmetrical than their male counterparts for most assessments. Interestingly, weaker athletes regardless of gender were more asymmetrical than stronger athletes for all assessments. Symmetry characteristics appeared to carryover between all tests and conditions with the exception of the bilateral strength assessment. When separated by strength level, good carryover of explosive strength symmetry characteristics was noted. A trend of negative relationships was noted between jump performance and kinetic asymmetry, measured during jumps and weight distribution. Isometric mid-thigh pull force production asymmetry did not relate to jump performance as it had previously. Kinetic asymmetry was shown to influence the direction of center of mass displacement (COMd). Specifically, asymmetrical rate of force development showed the most ability to differentiate between values of COMd in the mediolateral direction.
The finding that female athletes are more likely to produce force asymmetrically may indicate that they are more susceptible to the performance detriments that accompany force production asymmetry. This may also indicate that female athletes are more susceptible to injury if force asymmetry is an injury predictor. However, differences in asymmetry magnitude between the sexes may be due to differences in strength level between the sexes in the current study, as weaker athletes were shown to be more asymmetrical than their stronger counterparts. Thus, it may be inadequate strength level that is a risk factor to performance detriments and possible injury. It also appears that force production asymmetry can both alter and hinder optimal jump performance. In order to optimize performance and possibly reduce injury risk, it is recommended that weaker athletes focus on bilateral strengthening exercises.
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Applying the Wrapper Approach for Auto Discovery of Under-Sampling and Over-Sampling Percentages on Skewed DatasetsJoshi, Ajay D 03 November 2004 (has links)
Machine learning applications are plagued by the imbalance observed among the class sizes in many real world datasets. A dataset is said to be skewed or imbalanced when its classes are very unequally represented. A naïve classifier learned from these skewed datasets is always biased towards the majority classes which constitute a major percentage of the samples in the dataset. As a result the accuracy on the minority classes is hampered. In many real world applications like network intrusion detection, cancer detection from mammography images, etc. the events of interest are very rare and the cost of not detecting these events is very high. Hence it very important to improve accuracies on the minority classes. It has been proposed previously that under-sampling of the majority classes can reduce the bias of the learned classifier and over-sampling of the minority classes - especially SMOTE (Synthetic Minority Over-sampling TEchnique) can boost the classifier accuracy on minority classes. But the question of how much under-sampling and over-sampling to be done for a particular induction learning algorithm and dataset remains. We present a wrapper approach for searching for the under-sampling and over-sampling (i.e. SMOTE) percentages for a particular learning algorithm for a given skewed dataset. We compare the results obtained by the classifiers built on wrapper selected under sampled and SMOTEd datasets with the ones obtained by classifiers built on the original datasets to show a statistically significant improvement in accuracies over minority classes. This proves the efficacy of the wrapper approach in searching for the under-sampling and over-sampling percentages. Further, it provides an automated method to select the number of synthetic examples to be created.
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Information Imbalance in the Age of TechnologyOsthoff-Magalhaes, Isabela 01 January 2013 (has links)
This study investigates the phenomenon of asymmetric interpersonal relationships—dyads in which one individual has greater knowledge of personal information about the other. Relationships usually benefit from self-disclosure when it is done in a reciprocal, personal manner; acquiring information through such means as Facebook can disrupt the process, offset information balance and negatively affect interrelationship factors. This study investigates the effect of information asymmetry on such factors as interpersonal attraction, subjective power, and social interaction anxiety. Participants were given Facebook profiles with varying amounts of information (high, low, or none) prior to interacting with a confederate. I predicted that participants in the high information condition would experience the greatest social interaction anxiety and the least interpersonal attraction. Increased anxiety would mediate a reduction in interpersonal attraction. Participants with no prior information were expected to exhibit opposite tendencies compared to the high information condition. A secondary effect on subjective power was also explored. Results did not reach statistical significance but were in the directions as hypothesized. Findings indicate that imbalance of interpersonal information has the potential to negatively impact relationship factors.
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Damping Subsynchronous Resonance Using Static Synchronous Series Compensators and Static Synchronous CompensatorsRai, Dipendra 04 September 2008
Electricity systems are very complex systems and are composed of numerous transmission lines, generators and loads. The generating stations are generally far away from load centres and that may cause transmission line congestion and overloading. Series capacitive compensation is the most economical way to increase transmission capacity and improve transient stability of transmission grids. However, one of the impeding factors for the widespread use of series capacitive compensation is the potential risk of Subsynchronous Resonance (SSR). Subsynchronous Resonance is a phenomenon in which electrical power is exchanged with the generator shaft system in an increasing manner which may result in damage to the turbine generator shaft system. Therefore, mitigating SSR continues to be a subject of research and development aiming at developing effective SSR countermeasures.<p>This research work presents new methods of alleviating the SSR problem using a Static Synchronous Series Compensator (SSSC) and a Static Synchronous Compensator (STATCOM). These methods are based on using the SSSC and STATCOM to inject unbalanced series quadrature voltages and unbalanced shunt reactive currents in transmission line just after clearing faults. When the subsynchronous oscillations drive unsymmetrical phase currents, the developed electromagnetic torque will be lower than the condition when the three-phase currents are symmetrical. The unsymmetrical currents result in a lower coupling strength between the mechanical and the electrical system at asynchronous oscillations. Therefore, the energy exchange between the electrical and the mechanical systems at subsynchronous oscillations will be suppressed, thus, avoiding the build-up of torsional stresses on the generator shaft systems under subsynchronous resonance condition. The validity of proposed methods are demonstrated by time simulation results using the electromagnetic transient program EMTP-RV.
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Production Control MechanismsComparison using Multi-ObjectiveSimulation OptimizationZia, Muhammad Irfan January 2009 (has links)
The choice of an efficient and effective production control mechanism (PCM)along with the appropriate buffer allocation pattern is very important for anyproduction engineer/decision maker when designing a production line in order toattain the required system performance. This project work aims to give an insightwith different PCMs, different buffer allocation patterns and arrangement ofworkers of different capability to help the production engineers/decision makersto select the right mechanism and pattern. This study has been performed withmulti-objective simulation optimisation (MOSO) tool. The result from manyexperiments have shown that the ascending buffer allocation pattern stands outas the prominent choice when the goal was to attain maximum throughput (TP)and simultaneously keeping minimum cycle time (CT) and work in process (WIP).The PCMs and workers imbalance patterns performance is different in differentregions of the Pareto-optimal CT-TP data plots obtained from MOSO so theirselection is depending on the interest of the desired level of throughput togetherwith the limit of cycle time.
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Damping Subsynchronous Resonance Using Static Synchronous Series Compensators and Static Synchronous CompensatorsRai, Dipendra 04 September 2008 (has links)
Electricity systems are very complex systems and are composed of numerous transmission lines, generators and loads. The generating stations are generally far away from load centres and that may cause transmission line congestion and overloading. Series capacitive compensation is the most economical way to increase transmission capacity and improve transient stability of transmission grids. However, one of the impeding factors for the widespread use of series capacitive compensation is the potential risk of Subsynchronous Resonance (SSR). Subsynchronous Resonance is a phenomenon in which electrical power is exchanged with the generator shaft system in an increasing manner which may result in damage to the turbine generator shaft system. Therefore, mitigating SSR continues to be a subject of research and development aiming at developing effective SSR countermeasures.<p>This research work presents new methods of alleviating the SSR problem using a Static Synchronous Series Compensator (SSSC) and a Static Synchronous Compensator (STATCOM). These methods are based on using the SSSC and STATCOM to inject unbalanced series quadrature voltages and unbalanced shunt reactive currents in transmission line just after clearing faults. When the subsynchronous oscillations drive unsymmetrical phase currents, the developed electromagnetic torque will be lower than the condition when the three-phase currents are symmetrical. The unsymmetrical currents result in a lower coupling strength between the mechanical and the electrical system at asynchronous oscillations. Therefore, the energy exchange between the electrical and the mechanical systems at subsynchronous oscillations will be suppressed, thus, avoiding the build-up of torsional stresses on the generator shaft systems under subsynchronous resonance condition. The validity of proposed methods are demonstrated by time simulation results using the electromagnetic transient program EMTP-RV.
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A Study on Management Strategy of Seafarer Officers for Vessel ¡V Taking the S Company as ExampleYeh, Jiin-Shin 30 July 2011 (has links)
Officers played an important role on the vessel, including instrument operations, navigational safety, and cargo handling. Therefore, all the shipping companies desired to recruit outstanding people to fit the business strategies and enhance organizational performance. In 2005, according to BIMCO (Baltic International Maritime Council) / ISF (International Shipping Federation), there is the imbalance of the demand and supply. Shipping industry acts as an important role for Taiwan¡¦s economic development in past decades. An effective shipping development policy must contain those projects of officers¡¦ training, employment, and welfare scheme. All these measures have to be adopted through legislative efforts which will rely on the efforts of government and private sectors. In view of Taiwan¡¦s officers¡¦ policy has faced some challenges and needs to be reviewed in order to provide solutions to the difficulties. In this way, this study focuses on those officers of S company by qualitative interview, knowing the imbalance of the demand and supply and provides strategies recommendations.
The results showed that small and medium carriers operate this industry with limited funds and lacking of complete structure. In this situation, those officers¡¦ welfare need to be enforced. The Government should develop complete and effective policies. In this way, we can build up a promising marine industry. In this case, we can find out that the company in the whole welfare system is worse than other companies. The policy-related issues including the flag of convenience problem, national mechanism for the overall training system, and the imbalance of demand and supply¡Ketc. We expect that the industry, government, academia provides an effective and sustainable policies to enhance and develop the shipping business.
Keywords: Shipping development policy, officer¡¦s policy, imbalance of officer¡¦s supply and demand
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Compensation For Gain/Phase Imbalance And DC Offset At Quadrature Modulator And Demodulator With Adaptive Inverse QRD-RLS AlgorithmHuang, Chun-Ying 08 July 2002 (has links)
There has been much effort in new design for transceiver used in mobile communications. The general approach is to combine RF functions with DSP to allow linear modulation techniques and permit flexibility of modulation format and receiver processing. In practice, with the quadrature modulation technique there is always some imbalance between the I- and Q channels of modulator and demodulator. This is mainly due to finite tolerances of capacitor and resistor values used to implement the analog components. The unavoidable imbalance between the I- and Q channels is known to degrade the performance of quadrature communication system.
The main concern of this thesis is to propose a new blind scheme and with fast convergence algorithm, such as the inverse QRD-RLS algorithm, to deal with the problem described above for compensation in the transmitter and receiver. First, for the transmitter, the so-called adaptive estimation and compensation with power measurement implemented by the inverse QRD-RLS algorithm is employed. While in the receiver, a new blind adaptive filtering approach of the nonlinear parameters estimation and compensation, along with the power measurement in the receiver, is devised to adaptively compensate for the gain/phase imbalance and DC offsets in a quadrature demodulator. Where the conventional inverse QRD-RLS algorithm is employed for estimating the parameters of compensator, without using any reference signal transmitted from the transmitter. To document the merits of the proposed scheme, computer simulation for the coherent 16-PSK-communication system is carried out. With our proposed method a great improvement for eliminating the effects of the imbalance and offset over the existing techniques has verified. It has rapidly convergence rate and the smaller mean square error in steady state.
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