Dynamic Morse decompositions for semigroups of homeomorphisms and control systems

In this paper, we introduce the concept of dynamic Morse decomposition for an action of a semigroup of homeomorphisms. Conley has shown in [5, Sec. 7] that the concepts of Morse decomposition and dynamic Morse decompositions are equivalent for flows in metric spaces. Here, we show that a Morse decomposition for an action of a semigroup of homeomorphisms of a compact topological space is a dynamic Morse decomposition. We also define Morse decompositions and dynamic Morse decompositions for control systems on manifolds. Under certain condition, we show that the concept of dynamic Morse decomposition for control system is equivalent to the concept of Morse decomposition.

The unequal influences of the left and right vagi on the control of the heart and pulmonary artery in the rattlesnake, Crotalus durissus

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Vagal control of heart rate and cardiac shunts in reptiles: Relation to metabolic state

The vagus is clearly of primary importance in the regulation of reptilian cardiorespiratory systems. Vagal control of pulmonary blood flow and cardiac shunts provides reptiles with an additional means of regulating arterial oxygen levels that is not present in endothermic vertebrates (birds and mammals). Within a given species, there exists a clear correlation between withdrawal of vagal tone on the cardiovascular system and elevated metabolic rate. Undisturbed and resting reptiles are normally characterised by high vagal tone, low pulmonary blood flow and large right-left (R-L) cardiac shunts. The low oxygen levels that result from the large R-L shunt may serve to regulate metabolism. However, when metabolism is increased by temperature, exercise or digestion, the R-L cardiac shunt is reduced, which serves to increase oxygen delivery. This response is partially elicit ed by reduction of vagal tone. Interspecies comparisons reveal a similar pattern. Thus, species that are able to sustain the highest metabolic rates possess the highest degree of anatomical ventricular separation and, therefore, less cardiac shunting. It is interesting to note that when cardiac shunts occur in mammals, due for example to developmental defects, they are associated with reduced maximal metabolic rates and impaired exercise tolerance. It appears, therefore, that full separation of ventricular blood flows was a prerequisite for the evolution of high aerobic metabolic rates and exercise stamina in mammals and birds.

Central control of cardiorespiratory interactions in fish

Fish control the relative flow rates of water and blood over the gills in order to optimise respiratory gas exchange. As both flows are markedly pulsatile, close beat-to-beat relationships can be predicted. Cardiorespiratory interactions in fish are controlled primarily by activity in the parasympathetic nervous system that has its origin in cardiac vagal. preganglionic neurons. Recordings of efferent activity in the cardiac vagus include units firing in respiration-related bursts. Bursts of electrical stimuli delivered peripherally to the cardiac vagus or centrally to respiratory branches of cranial, nerves can recruit the heart over a range of frequencies. So, phasic, efferent activity in cardiac vagi, that in the intact fish are respiration-related, can cause heart rate to be modulated by the respiratory rhythm. In elasmobranch fishes this phasic activity seems to arise primarily from central feed-forward interactions with respiratory motor neurones that have overlapping distributions with cardiac neurons in the brainstem. In teleost fish, they arise from increased levels of efferent vagal activity arising from reflex stimulation of chemoreceptors and mechanoreceptors in the orobranchial, cavity. However, these differences are largely a matter of emphasis as both groups show elements of feed-forward and feed-back control of cardiorespiratory interactions. (C) 2008 Elsevier GmbH. All rights reserved.

Development of a DC-DC converter for DC bus voltage control of series connected device

The purpose of this work is to study voltage control and energy balance of a split DC bus topology within a power electronics equipment connected to the AC mains, such as UPS systems, wind power generators, active filters and FACTS devices. A typical configuration in such equipment has two mains connected converters sharing a common DC bus, one series connected and the other parallel connected. The DC bus is usually composed by a battery or a capacitor bank. In the proposed topology, the DC bus is divided in two sides, interconnected with a buck-boost converter, which controls power flow and DC voltage on both sides. © 2009 IEEE.

The use of molecular spectra simulation for diagnostics of reactive flows

The C 2 * radical is used as a system probe tool to the reactive flow diagnostic, and it was chosen due to its large occurrence in plasma and combustion in aeronautics and aerospace applications. The rotational temperatures of C 2 * species were determined by the comparison between experimental and theoretical data. The simulation code was developed by the authors, using C++ language and the object oriented paradigm, and it includes a set of new tools that increase the efficacy of the C 2 * probe to determine the rotational temperature of the system. A brute force approach for the determination of spectral parameters was adopted in this version of the computer code. The statistical parameter c 2 was used as an objective criterion to determine the better match of experimental and synthesized spectra. The results showed that the program works even with low-quality experimental data, typically collected from in situ airborne compact apparatus. The technique was applied to flames of a Bunsen burner, and the rotational temperature of ca. 2100 K was calculated.

Power flow optimization for grid connected inverter using evolutionary algorithm and additional control loop

In this work it is proposed to validate an evolutionary tuning algorithm in plants composed by a grid connected inverter. The optimization aims the tuning of the slopes of P-Ω and Q-V curves so that the system is stable, damped and minimum settling time. Simulation and experimental results are presented to prove the feasibility of the proposed approach. However, experimental results demonstrate a compromising effect of grid frequency oscillations in the active power transferring. In addition, it was proposed an additional loop to compensate this effect ensuring a constant active power flow. © 2011 IEEE.

Robust control applied to power flow control in single-phase inverter with LCL filter, using droop control and D-stability

This paper proposes a new methodology to control the power flow between a distributed generator (DG) and the electrical power distribution grid. It is used the droop voltage control to manage the active and reactive power. Through this control a sinusoidal voltage reference is generated to be tracked by voltage loop and this loop generates the current reference for the current loop. The proposed control introduces feed-forward states improving the control performance in order to obtain high quality for the current injected to the grid. The controllers were obtained through the linear matrix inequalities (LMI) using the D-stability analysis to allocate the closed-loop controller poles. Therefore, the results show quick transient response with low oscillations. Thus, this paper presents the proposed control technique, the main simulation results and a prototype with 1000VA was developed in the laboratory in order to demonstrate the feasibility of the proposed control. © 2012 IEEE.

Trade and investment flows between the Caribbean and the rest of the hemisphere in the context of the FTAA

Includes bibliography

Capital flows to Latin America: recent developments

The external environment has deteriorated sharply as a result of the spiraling financial turmoil, and has led to a weakening in commodity prices and fears of a worldwide recession. Latin America and the Caribbean's fastest expansion in 40 years may be threatened as the global credit crunch makes financing scarce and squeezes demand for the region's commodities. This time around the region is better positioned to weather the crisis than in the past, given improvements in macroeconomic and financial policies as well as a reduced net dependency on external capital inflows. However, Latin American markets are feeling the effects of the crisis through a slowdown in capital inflows, large declines in stock price indexes, significant currency adjustments and an increase in debt spreads. Volatility has soared, with the closely watched Chicago Board Options Exchange Volatility Index moving to an all-time high of 70.33 on October 17, indicating that fear (rather than greed) has been ruling the markets.After reaching record lows in May 2007, emerging markets bond spreads are now above pre-Asian crisis levels. The JPMorgan EMBI+ Latin American composite widened by 146 basis points in the third quarter, with spreads reaching 448 basis points at the end of September. Spreads have widened sharply in recent weeks as foreign investors cut back regional exposure for the safety of U.S. Treasuries. The ongoing lack of liquidity and subsequent liquidation of assets is leading to a collapse in asset prices and a sharp widening in spreads. Daily spreads in October have risen to levels not seen since December 2002, making it much more difficult for governments that need financing to get it. Risk premiums for Latin corporates and sovereigns have risen substantially, but have remained well below U.S. junk (high-yield) bonds. Latin corporates are facing a steep rise in foreign exchange borrowing costs (although less than firms in other emerging markets), which raises concerns that refinancing risks will climb.So far, emerging markets vulnerabilities have been more focused on corporates, as sovereigns have improved public debt dynamics and countries' financing needs are under control. Market performance has been driven by the rapid deterioration of emerging markets bank and corporate market, as well as ongoing losses in emerging markets equities. From January to September 2008, the Morgan Stanley Capital International (MSCI) Latin American Index lost almost 28%, while the Emerging Markets Index lost 37% and the G-7 Index lost 24%. While in 2007 the Latin America component gained 47%, almost nine times as much as the MSCI-G7 index for developed markets, since mid-September 2008 stocks in Latin America have been doing worse than stocks in developed countries, as concerns about access to credit and the adverse impact of sharp falls in commodity prices and in local currencies contribute to increased risk aversion and to outflows of capital. Many governments in the region have used revenue from the commodity boom to pay down debt and build reserves. Now, facing a global financial crisis and the threat of recession in developed countries, the biggest question for Latin America is how long and deep this cyclical downturn will be, and how much it is going to reduce commodity prices. Prices for commodities such as soy, gold, copper and oil, which helped fund the region's boom, have fallen 28% since their July 2 high, according to the RJ/CRB Commodity Price Index. According to Morgan Stanley (in a September 29 report), should prices return to their 10-year average, Latin America's balanced budgets would quickly revert to a deficit of 4.1% of GDP. As risk aversion increases, investors are rapidly pulling out massive amounts of money, creating problems for local markets and banks. There is an ongoing shortage of dollars (as investors liquidate assets in Latin American markets), and as currencies depreciate, inflation concerns increase despite the global slowdown. In Brazil and Mexico, central banks deployed billions of dollars of reserves to stem steep currency declines, as companies in these countries, believing their local currencies would continue to strengthen against the U.S. dollar, took debts in dollars. Some companies also made bets using currency derivatives that have led to losses in the billions of dollars. Dramatic currency swings have caused heavy losses for many companies, from Mexico's cement giant Cemex SAB to the Brazilian conglomerate Grupo Votorantim. Mexico's third-largest retailer, Controladora Comercial Mexicana, declared bankruptcy recently after reporting huge losses related to exchange rate bets. As concerns about corporate exposure to dollar-denominated derivatives increases, yields on bonds issued by many of Brazil's and Mexico's leading companies have started to rise, sharply raising the cost of issuing new debt. Latin American external debt issuance came to a halt in the third quarter of 2008, totaling only US$ 690 million. The cost of obtaining loans for capital expenditures, M&A and debt refinancing is also rising substantially for Latin American corporates amid contagion from the U.S. financial crisis. According to bankers, a protracted trend of shortening tenors and widening spreads has intensified in the past few weeks, indicating that bank lending is quickly following the way of bonds and equity. Finally, money transfers from Latin American migrants are expected to decline for the first time this decade, as a result of economic downturns in the U.S. and Spain, inflation and a weaker dollar. The Mexican Central Bank announced that money transfers from Mexicans living in the U.S. dropped a record 12.2% in August. In 2008, migrants from the region will send some 1.7% less in remittances year-on-year when adjusted for inflation, according to the IADB, compounding the adverse effects of the deepening financial turmoil.

Extended Daily Dialysis in Acute Kidney Injury Patients: Metabolic and Fluid Control and Risk Factors for Death

Intermittent hemodialysis (IHD) and continuous renal replacement therapies (CRRT) are used as Acute Kidney Injury (AKI) therapy and have certain advantages and disadvantages. Extended daily dialysis (EDD) has emerged as an alternative to CRRT in the management of hemodynamically unstable AKI patients, mainly in developed countries.Objectives: We hypothesized that EDD is a safe option for AKI treatment and aimed to describe metabolic and fluid control of AKI patients undergoing EDD and identify complications and risk factors associated with death.Study Selection: This is an observational and retrospective study describing introduction of EDD at our institution. A total of 231 hemodynamically unstable AKI patients (noradrenalin dose between 0.3 and 1.0 ucg/kg/min) were assigned to 1367 EDD session. EDD consisted of 6-8 h of HD 6 days a week, with blood flow of 200 ml/min, dialysate flows of 300 ml/min.Data Synthesis: Mean age was 60.6 +/- 15.8 years, 97.4% of patients were in the intensive care unit, and sepsis was the main etiology of AKI (76.2). BUN and creatinine levels stabilized after four sessions at around 38 and 2.4 mg/dl, respectively. Fluid balance decreased progressively and stabilized around zero after five sessions. Weekly delivered Kt/V was 5.94 +/- 0.7. Hypotension and filter clotting occurred in 47.5 and 12.4% of treatment session, respectively. Regarding AKI outcome, 22.5% of patients presented renal function recovery, 5.6% of patients remained on dialysis after 30 days, and 71.9% of patients died. Age and focus abdominal sepsis were identified as risk factors for death. Urine output and negative fluid balance were identified as protective factors.Conclusions: EDD is effective for AKI patients, allowing adequate metabolic and fluid control. Age, focus abdominal sepsis, and lower urine output as well as positive fluid balance after two EDD sessions were associated significantly with death.

Aerobic exercise training delays cardiac dysfunction and improves autonomic control of circulation in diabetic rats undergoing myocardial infarction

Background: Exercise training (ET) has been used as a nonpharmacological strategy for treatment of diabetes and myocardial infarction (MI) separately. We evaluated the effects ET on functional and molecular left ventricular (LV) parameters as well as on autonomic function and mortality in diabetics after MI. Methods and Results: Male Wistar rats were divided into control (C), sedentary-diabetic infarcted (SDI), and trained-diabetic infarcted (TDI) groups. MI was induced after 15 days of streptozotocin-diabetes induction. Seven days after MI, the trained group underwent ET protocol (90 days, 50-70% maximal oxygen consumption-VO(2)max). LV function was evaluated noninvasively and invasively; baroreflex sensitivity, pulse interval variability, cardiac output, tissue blood flows, VEGF mRNA and protein, HIF1-alpha mRNA, and Ca2+ handling proteins were measured. MI area was reduced in TDI (21 +/- 4%) compared with SDI (38 +/- 4%). ET induced improvement in cardiac function, hemodynamics, and tissue blood flows. These changes were probable consequences of a better expression of Ca2+ handling proteins, increased VEGF mRNA and protein expression as well as improvement in autonomic function, that resulted in reduction of mortality in TDI (33%) compared with SDI (68%) animals. Conclusions: ET reduced cardiac and peripheral dysfunction and preserved autonomic control in diabetic infarcted rats. Consequently, these changes resulted in improved VO(2)max and survival after MI. (J Cardiac Fail 2012; 18:734-744)

Analysis of patient flows for orthopedic procedures using small area analysis in Switzerland

BACKGROUND: In general cantons regulate and control the Swiss health service system; patient flows within and between cantons are thereby partially disregarded. This paper develops an alternative spatial model, based upon the construction of orthopedic hospital service areas (HSAOs), and introduces indices for the analysis of patient streams in order to identify areas, irrespective of canton, with diverse characteristics, importance, needs, or demands. METHODS: HSAOs were constructed using orthopedic discharge data. Patient streams between the HSAOs were analysed by calculating three indices: the localization index (% local residents discharged locally), the netindex (the ratio of discharges of nonlocal incoming residents to outgoing local residents), and the market share index (% of local resident discharges of all discharges in local hospitals). RESULTS: The 85 orthopedic HSAOs show a median localization index of 60.8%, a market share index of 75.1%, and 30% of HSAOs have a positive netindex. Insurance class of bed, admission type, and patient age are partially but significantly associated with those indicators. A trend to more centrally provided health services can be observed not only in large urban HSAOs such as Geneva, Bern, Basel, and Zurich, but also in HSAOs in mountain sport areas such as Sion, Davos, or St.Moritz. Furthermore, elderly and emergency patients are more frequently treated locally than younger people or those having elective procedures. CONCLUSION: The division of Switzerland into HSAOs provides an alternative spatial model for analysing and describing patient streams for health service utilization. Because this small area model allows more in-depth analysis of patient streams both within and between cantons, it may improve support and planning of resource allocation of in-patient care in the Swiss healthcare system.

Computational study of internal and external condensing flows and experimental synthesis to investigate their attainability and stability in ground-based and space-based environments

This doctoral thesis presents the computational work and synthesis with experiments for internal (tube and channel geometries) as well as external (flow of a pure vapor over a horizontal plate) condensing flows. The computational work obtains accurate numerical simulations of the full two dimensional governing equations for steady and unsteady condensing flows in gravity/0g environments. This doctoral work investigates flow features, flow regimes, attainability issues, stability issues, and responses to boundary fluctuations for condensing flows in different flow situations. This research finds new features of unsteady solutions of condensing flows; reveals interesting differences in gravity and shear driven situations; and discovers novel boundary condition sensitivities of shear driven internal condensing flows. Synthesis of computational and experimental results presented here for gravity driven in-tube flows lays framework for the future two-phase component analysis in any thermal system. It is shown for both gravity and shear driven internal condensing flows that steady governing equations have unique solutions for given inlet pressure, given inlet vapor mass flow rate, and fixed cooling method for condensing surface. But unsteady equations of shear driven internal condensing flows can yield different “quasi-steady” solutions based on different specifications of exit pressure (equivalently exit mass flow rate) concurrent to the inlet pressure specification. This thesis presents a novel categorization of internal condensing flows based on their sensitivity to concurrently applied boundary (inlet and exit) conditions. The computational investigations of an external shear driven flow of vapor condensing over a horizontal plate show limits of applicability of the analytical solution. Simulations for this external condensing flow discuss its stability issues and throw light on flow regime transitions because of ever-present bottom wall vibrations. It is identified that laminar to turbulent transition for these flows can get affected by ever present bottom wall vibrations. Detailed investigations of dynamic stability analysis of this shear driven external condensing flow result in the introduction of a new variable, which characterizes the ratio of strength of the underlying stabilizing attractor to that of destabilizing vibrations. Besides development of CFD tools and computational algorithms, direct application of research done for this thesis is in effective prediction and design of two-phase components in thermal systems used in different applications. Some of the important internal condensing flow results about sensitivities to boundary fluctuations are also expected to be applicable to flow boiling phenomenon. Novel flow sensitivities discovered through this research, if employed effectively after system level analysis, will result in the development of better control strategies in ground and space based two-phase thermal systems.

Length of the annular regime for condensing flows inside a horizontal channel - the experimental determination of its values and its trends

The experiments observe and measure the length of the annular regime in fully condensing quasi-steady (steady-in-the-mean) flows of pure FC-72 vapor in a horizontal condenser (rectangular cross-section of 2 mm height, 15 mm width, and 1 m length). The sides and top of the duct are made of clear plastic that allows flow visualization. The experimental system in which this condenser is used is able to control and achieve different quasi-steady mass flow rates, inlet pressures, and wall cooling conditions (by adjustment of the temperature and flow rate of the cooling water flowing underneath the condensing-plate). The reported correlations and measurements for the annular length are also vital information for determining the length of the annular regime and proposing extended correlation (covering many vapors and a larger parameter set than the experimentally reported version here) by ongoing independent modeling and computational simulation approach.