Academic literature on the topic 'Stroke volume variability'
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Journal articles on the topic "Stroke volume variability"
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Liu, Hongjian, Tomoyuki Yambe, Hiroshi Sasada, Shunsuke Nanka, Akira Tanaka, Ryoichi Nagatomi, and Shin-ichi Nitta. "Comparison of heart rate variability and stroke volume variability." Autonomic Neuroscience 116, no. 1-2 (November 2004): 69–75. http://dx.doi.org/10.1016/j.autneu.2004.09.003.
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Mailloux, Patrick, and William McGee. "STROKE VOLUME VARIABILITY, SVO2 AND INTRAVASCULAR VOLUME DURING CVVHD." Critical Care Medicine 34 (December 2006): A174. http://dx.doi.org/10.1097/00003246-200612002-00602.
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Cote, Anita T., Shannon SD Bredin, Aaron A. Phillips, and Darren ER Warburton. "Predictors of orthostatic intolerance in healthy young women." Clinical & Investigative Medicine 35, no. 2 (April 1, 2012): 65. http://dx.doi.org/10.25011/cim.v35i2.16290.
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Purpose: Orthostatic intolerance is more prevalent in women. The purpose of this investigation was to evaluate the physiological responses of orthostatic tolerant and intolerant females to progressive lower body negative pressure (LBNP) and to identify predictors of orthostatic tolerance. Methods: Following baseline measurements, eleven healthy, moderately active women (mean age 24 ± 3 yr) underwent an orthostatic challenge involving four 12-minute stages of progressive LBNP at -15, -30, -45 and -60 mmHg. Traditional haemodynamic characteristics, as well as baroreceptor sensitivity, were analyzed across all stages. Results: Five women became presyncopal during the test and were classified as low tolerant (LT) while the remaining six were classified as high tolerant (HT). LBNP by group (tolerance) interactions were significantly different for stroke volume (P=0.008) and the rate of decline (slope) of stroke volume (P=0.03). During the early stages of LBNP, the LT group displayed a higher stroke volume than the HT group (76.4 ± 8.6 vs. 60.0 ± 13.3 mL/beat; P=0.02) yet by the final stage, stroke volumes were similar (22.5 ± 11.9 vs. 22.7 ± 4.5 mL/beat, P = 0.99). Baroreceptor sensitivity, heart rate variability and blood pressure variability were not significantly different between the groups. Conclusions: The results of this investigation suggest that orthostatic intolerance in women can be identified during the initial stages of an LBNP challenge, as evidenced by a more rapid decline in stroke volume.
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Robertson, Donald U., Lynda Federoff, and Keith E. Eisensmith. "Cardiac Response During Trumpet Playing." Medical Problems of Performing Artists 25, no. 1 (March 1, 2010): 16–21. http://dx.doi.org/10.21091/mppa.2010.1004.
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Heart rate, heart rate variability, stroke volume, and cardiac output were measured while six college students and six professionals played trumpet. One-minute rest periods were followed by 1 minute of playing exercises designed to assess the effects of pitch and articulation. Heart rate and heart rate variability increased during playing, but stroke volume decreased. Changes in heart rate between resting and playing were greater for students, although beat-to-beat variability was larger for professionals in the upper register. These results suggest that expertise is characterized by greater physiological efficiency.
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Steendijk, P., E. T. Van der Velde, and J. Baan. "Left ventricular stroke volume by single and dual excitation of conductance catheter in dogs." American Journal of Physiology-Heart and Circulatory Physiology 264, no. 6 (June 1, 1993): H2198—H2207. http://dx.doi.org/10.1152/ajpheart.1993.264.6.h2198.
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The conductance method employs a multielectrode catheter to measure intracavitary electric conductance from which left ventricular volume is estimated. A dual-excitation method introduced by us uses a more homogeneous electric field and thereby should enable more accurate volume estimation. In six anesthetized open-chest dogs we compared stroke volume obtained from electromagnetic flow probes with the conventional single-excitation method and with the new dual-excitation conductance method. Caval occlusion and left atrial hemorrhage were used to obtain a wide range of stroke volumes. The slope of the relation between stroke volume calculated from the flow probes and from the conductance catheter increased significantly (P < 0.001) from 0.635 with single excitation to 0.835 with dual excitation, but the interanimal variability was not reduced. The linearity of the relation was substantially improved.
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Dunn, Lauren E., Adam B. Schweber, Daniel K. Manson, Andrea Lendaris, Charlotte Herber, Randolph S. Marshall, and Ronald M. Lazar. "Variability in Motor and Language Recovery during the Acute Stroke Period." Cerebrovascular Diseases Extra 6, no. 1 (March 22, 2016): 12–21. http://dx.doi.org/10.1159/000444149.
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Background: Most stroke recovery occurs by 90 days after onset, with proportional recovery models showing an achievement of about 70% of the maximal remaining recovery. Little is known about recovery during the acute stroke period. Moreover, data are described for groups, not for individuals. In this observational cohort study, we describe for the first time the daily changes of acute stroke patients with motor and/or language deficits over the first week after stroke onset. Methods: Patients were enrolled within 24-72 h after stroke onset with upper extremity hemiparesis, aphasia, or both, and were tested daily until day 7 or discharge with the upper-extremity Fugl-Meyer Assessment of Motor Recovery after Stroke, the Boston Naming Test, and the comprehension domain from the Western Aphasia Battery. Discharge scores, and absolute and proportional changes were examined using t-tests for pairwise comparisons and linear regression to determine relative contributions of initial impairment, lesion volume, and age to recovery over this period. Results: Thirty-four patients were enrolled: 19 had motor deficits alone, 8 had aphasia alone, and 7 had motor and language deficits. In a group analysis, statistically significant changes in absolute scores were found in the motor (p < 0.001) and comprehension (p < 0.001) domains but not in naming. Day-by-day recovery curves for individual patients displayed wide variation with comparable initial impairment. Proportional recovery calculations revealed that, on average, patients achieved less than 1/3 of their potential recovery by the time of discharge. Multivariate regression showed that the amount of variance accounted for by initial severity, age, and lesion volume in this early time period was not significant for motor or language domains. Conclusions: Over the first week after stroke onset, recovery of upper extremity hemiparesis and aphasia were not predictable on the basis of initial impairment, lesion volume, or age. In addition, patients only achieved about 1/3 of their remaining possible recovery based on the anticipated 70% proportion found at 90 days. These findings suggest that the complex interaction between poststroke structural repair, regeneration, and functional reorganization during the first week after stroke has yet to be elucidated.
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Smeshnoi, I. A., I. N. Pasechnik, E. I. Skobelev, D. A. Timashkov, М. A. Onegin, Yu V. Nikiforov, and S. I. Kontarev. "Infusion Therapy Optimization in Selective Abdominal Surgery." General Reanimatology 14, no. 5 (October 28, 2018): 4–15. http://dx.doi.org/10.15360/1813-9779-2018-5-4-15.
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Purpose. Evaluation of the influence of intra-operative targeted infusion therapy managed by the monitoring of stroke volume variability on post-operative results of major surgeries of gastrointestinal organs.Materials and Methods. The prospective study included 80 patients subjected to selective operative interventions of abdominal organs involving entero-enteroanastomosis. In the experimental group (n=39), the infusion therapy was conducted according to the developed targeted therapy protocol, of which the key parameter was stroke volume variability. In the control group (n=41), infusion therapy was conducted based on routine hemodynamic monitoring (average arterial pressure, heart rate, blood loss level with regard to intra-operative situation). In both groups, operative intervention was carried out in identical conditions (combined anesthesia, identical drugs to induce and maintain anesthesia); the only differences included infusion therapy.Results. In the experimental group versus the control group the intra-operative infusion volume was smaller, the number of patients with complications and the total number of complications were reliably lower, and the gastrointestinal tract functional recovery occurred earlier. Conclusion. A targeted infusion therapy based on a stroke volume variability monitoring as the key parameter allows optimizing the infusion load and facilitates reduction of the number of patients with complications and earlier recovery of gastrointestinal tract functions after major operative abdominal interventions.
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Trotman-Lucas, Melissa, and Claire L. Gibson. "A review of experimental models of focal cerebral ischemia focusing on the middle cerebral artery occlusion model." F1000Research 10 (March 26, 2021): 242. http://dx.doi.org/10.12688/f1000research.51752.1.
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Cerebral ischemic stroke is a leading cause of death and disability, but current pharmacological therapies are limited in their utility and effectiveness. In vitro and in vivo models of ischemic stroke have been developed which allow us to further elucidate the pathophysiological mechanisms of injury and investigate potential drug targets. In vitro models permit mechanistic investigation of the biochemical and molecular mechanisms of injury but are reductionist and do not mimic the complexity of clinical stroke. In vivo models of ischemic stroke directly replicate the reduction in blood flow and the resulting impact on nervous tissue. The most frequently used in vivo model of ischemic stroke is the intraluminal suture middle cerebral artery occlusion (iMCAO) model, which has been fundamental in revealing various aspects of stroke pathology. However, the iMCAO model produces lesion volumes with large standard deviations even though rigid surgical and data collection protocols are followed. There is a need to refine the MCAO model to reduce variability in the standard outcome measure of lesion volume. The typical approach to produce vessel occlusion is to induce an obstruction at the origin of the middle cerebral artery and reperfusion is reliant on the Circle of Willis (CoW). However, in rodents the CoW is anatomically highly variable which could account for variations in lesion volume. Thus, we developed a refined approach whereby reliance on the CoW for reperfusion was removed. This approach improved reperfusion to the ischemic hemisphere, reduced variability in lesion volume by 30%, and reduced group sizes required to determine an effective treatment response by almost 40%. This refinement involves a methodological adaptation of the original surgical approach which we have shared with the scientific community via publication of a visualised methods article and providing hands-on training to other experimental stroke researchers.
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Trotman-Lucas, Melissa, and Claire L. Gibson. "A review of experimental models of focal cerebral ischemia focusing on the middle cerebral artery occlusion model." F1000Research 10 (June 11, 2021): 242. http://dx.doi.org/10.12688/f1000research.51752.2.
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Cerebral ischemic stroke is a leading cause of death and disability, but current pharmacological therapies are limited in their utility and effectiveness. In vitro and in vivo models of ischemic stroke have been developed which allow us to further elucidate the pathophysiological mechanisms of injury and investigate potential drug targets. In vitro models permit mechanistic investigation of the biochemical and molecular mechanisms of injury but are reductionist and do not mimic the complexity of clinical stroke. In vivo models of ischemic stroke directly replicate the reduction in blood flow and the resulting impact on nervous tissue. The most frequently used in vivo model of ischemic stroke is the intraluminal suture middle cerebral artery occlusion (iMCAO) model, which has been fundamental in revealing various aspects of stroke pathology. However, the iMCAO model produces lesion volumes with large standard deviations even though rigid surgical and data collection protocols are followed. There is a need to refine the MCAO model to reduce variability in the standard outcome measure of lesion volume. The typical approach to produce vessel occlusion is to induce an obstruction at the origin of the middle cerebral artery and reperfusion is reliant on the Circle of Willis (CoW). However, in rodents the CoW is anatomically highly variable which could account for variations in lesion volume. Thus, we developed a refined approach whereby reliance on the CoW for reperfusion was removed. This approach improved reperfusion to the ischemic hemisphere, reduced variability in lesion volume by 30%, and reduced group sizes required to determine an effective treatment response by almost 40%. This refinement involves a methodological adaptation of the original surgical approach which we have shared with the scientific community via publication of a visualised methods article and providing hands-on training to other experimental stroke researchers.
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Roeth, Nathan A., Timothy R. Ball, William C. Culp, W. Todd Bohannon, Marvin D. Atkins, and William E. Johnston. "Effect of Increasing Heart Rate and Tidal Volume on Stroke Volume Variability in Vascular Surgery Patients." Journal of Cardiothoracic and Vascular Anesthesia 28, no. 6 (December 2014): 1516–20. http://dx.doi.org/10.1053/j.jvca.2014.05.014.
Full textDissertations / Theses on the topic "Stroke volume variability"
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Alomari, Abdul-Hakeem Hussein Electrical Engineering & Telecommunications Faculty of Engineering UNSW. "Spectral analysis of arterial blood prssure and stroke volume variability: the role of Calcium channel blockers and sensitizers." Publisher:University of New South Wales. Electrical Engineering & Telecommunications, 2008. http://handle.unsw.edu.au/1959.4/43923.
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In this thesis, we included results from two studies. The first one considered the effects of the blood volume changes, during blood donation, on the heart rate variability (HRV) measured, non-invasively, form electrocardiographic (ECG) and photoplethysmographic (PPG) signals. Our results showed that, during blood donation, there were no significant changes in the pulsatile area of PPG signal, while heart rate increased. No significant changes were noticed in HRV extracted from both signals. Error analysis between the HRV extracted from ECG and peak interval variability (PIV) suggested that the error during blood donation was increased which means that the use of PIV extracted from PPG signal, used as a replacement diagnostic tool in clinical applications, needs further investigations and should be carefully studied in non-stationary cardiovascular situations such as blood donation. The imbalance between the two branches of the autonomic nervous system, sympathetic and parasympathetic, vagal, may result in a harmful activation of myocardial tissues which cause arrhythmias and sudden cardiac death. Although the study of the sympathovagal balance have been attracting many researchers, further studies are needed to elucidate the effects of many kinds of drugs on the autonomic modulation of the cardiac muscle, specifically, the cells of sinoatrial (SA) node. The aim of the second part of this thesis was to assess the effects of calcium channel blocker (Verapamil), calcium channel sensitizer (Levosimendan), calcium chloride (CaCl2), the combinations of verapamil/ CaCl2, levosimendan/ CaCl2, and noradrenaline infusion on beat-to-beat cardiovascular variability represented, in this research, by systolic blood pressure variability (SBPV), and stroke volume variability (SVV) signals. We used Fat Fourier Transform (FFT) to evaluate the power spectral density of the fluctuations in both signals to evaluate the effects of short-term treatments with those drugs on the sympathovagal balance in normal rats. Then, we compared the spectra obtained from SBPV and SVV to decide which of these fluctuations along with corresponding spectrum was more able to provide a clear feedback about the autonomic nervous system. Our data suggests that there were a significant correlations between low- (LF), mid- (MF), and high-frequency (HF) spectra obtained from SBPV and SVV except between the HF spectra estimated from after the infusion of levosimendan where a poor correlation (r = 0.530, p = 0.281) was noticed. This that both HF components obtained provide different information regarding the autonomic nervous system modulation of the SA node cells, while the results obtained from the rest of experiments showed that both signals provide same information about the modulation of sympathetic and parasympathetic tone due to all stages of different drugs infusion studied in this thesis. Besides that, we found that both spectra may be used to track the fluctuations in the cardiac output as a result of the drugs infusion.
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Fernandes, Vargas Pedro Miguel. "Acute cardiovascular responses to slow and deep breathing." Thesis, Brunel University, 2017. http://bura.brunel.ac.uk/handle/2438/16415.
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Slow and deep breathing (SDB) has long been regarded as a nonpharmacological method for dealing with several physiological and emotional imbalances, and widely used for relaxation purposes. There is, however, limited understanding of the putative mechanisms by which SDB acutely impacts the cardiovascular and autonomic systems to elicit chronic adaptations. The present thesis explored how the manipulation of breathing pattern and intrathoracic pressure during SDB could further the understanding of the regulatory mechanisms that underpin the acute cardiovascular response to SDB. This thesis makes an original contribution to the existing knowledge by reporting a previously undescribed inversion of normal within-breath (inspiration vs. expiration) left ventricular stroke volume (LVSV) pattern for breathing frequencies < 8 breaths∙min-1. This finding might reflect the influence of a lag between enhanced right atrial filling and right ventricular stroke volume during inspiration, and its expression in left ventricular stroke volume; this lag results from the time required for blood to transit the pulmonary circulation. Furthermore, blood pressure variability (BPV) was reduced significantly at the lowest breathing frequencies, likely due to the involvement of baroreflex mediated responses. The pattern of responses was consistent with the buffering of respiratory-driven fluctuations in left ventricular cardiac output (Q̇) and arterial blood pressure (ABP) by within breath fluctuations in heart rate (fc), i.e., respiratory sinus arrhythmia (RSA) (Chapter 4). Chapter 5 demonstrated that magnifying negative intrathoracic pressure with inspiratory loading during SDB increased inspiratory pressure-driven fluctuations in LVSV and fc, and enhanced Q̇, independently of changes in VT and fR. The data support an important contribution to the amplification of RSA, during SDB, of previously underappreciated reflex, and/or 'myogenic', cardiac response mechanisms. The findings in Chapter 6 confirmed that inspiratory loading during SDB amplified the effects observed with un-loaded SDB (reported in chapter 5). In contrast, expiratory loading increased ABP and attenuated RSA, LVSV and Q̇ during SDB. A lower RSA for higher ABP, supports the presence of a formerly underappreciated contribution of sinoatrial node stretch to RSA, and throws into question the clinical benefits of expiratory resisted SDB, particularly in hypertensive populations. In conclusion, the findings of the present thesis provide novel information regarding the mechanisms contributing to acute cardiovascular response to SDB. These new insights may contribute to the development of more effective SDB interventions, geared towards maximising the perturbation to the cardiovascular control systems.
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Ciatti, Stephen A. "Spark ignition effects on two-stroke cyclic variability." 1997. http://catalog.hathitrust.org/api/volumes/oclc/37516631.html.
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Thesis (M.S.)--University of Wisconsin--Madison, 1997.Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 95-98).
Book chapters on the topic "Stroke volume variability"
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Schekotov, V. V., M. A. Zubarev, O. R. Parandey, and A. A. Dumler. "Beat – to - beat variability of stroke volume output velocity measured by an impedance cardiographic method." In IFMBE Proceedings, 579–81. Berlin, Heidelberg: Springer Berlin Heidelberg, 2007. http://dx.doi.org/10.1007/978-3-540-73841-1_149.
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Smith, Raymond C. "Introductory Overview." In Climate Variability and Ecosystem Response in Long-Term Ecological Research Sites. Oxford University Press, 2003. http://dx.doi.org/10.1093/oso/9780195150599.003.0014.
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The El Niño–Southern Oscillation (ENSO) is a coupled ocean–atmosphere phenomena that has a worldwide impact on climate. An aperiodic phenomena that reoccurs every 2 to 7 years, the ENSO is second only to seasonal variability in driving worldwide weather patterns. As Greenland notes in chapter 6, the term “quasi-quintennial” is chosen to recognize that climatic events other than ENSO-related events might occur at this timescale, although it is widely recognized that ENSO contributes the lion’s share of the higher frequency variability in paleorecords of the past several thousand years. In this section, we consider variability with cycles of 2 to 7 years and the resulting ecological response. Although we emphasize the ENSO timescale in this section, there is growing evidence that this phenomena is neither spatially nor temporally stable over longer time periods. Indeed, Allan (2000) suggests the ENSO climatic variability must be viewed within the context of climate fluctuations at decadal to interdecadal timescales, which often modulate the higher frequency ENSO variability. As a consequence, results in this and the next section often display overlapping patterns of variability, and their separation is not sharply defined. An important theme in this section is the worldwide influence of ENSO-related climate variability. Greenland (chapter 6) provides an LTER network overview with an analysis of ENSO-related variability of temperature and precipitation records for many LTER sites from the Arctic to the Antarctic. He discusses the general nature of ENSO and its climatic effects, summarizes previous climate-related work in the LTER network, and provides a cross-site analysis of the correlations between the Southern Oscillation Index (SOI) and temperature and precipitation at LTER sites. His results are consistent with the expected patterns of the geography of ENSO effects on the climate. Greenland’s cross-site analysis provides the basis for studying climate variability and ecosystem response within the context of the series of framework questions that form an underlying theme for this volume. Brazel and Ellis (chapter 7) provide an excellent analysis of climate-related parameters within the context of ENSO indices. Reporting on the Central Arizona and Phoenix (CAP) LTER urban-rural ecosystem, these authors provide a comprehensive analysis linking water-related parameters to climate forcing, as indicated by these indexes. Their studies show a strong connection between ENSO and winter moisture in Arizona, perhaps making it possible to forecast impending conditions.
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Goodin, Douglas G. "Introductory Overview." In Climate Variability and Ecosystem Response in Long-Term Ecological Research Sites. Oxford University Press, 2003. http://dx.doi.org/10.1093/oso/9780195150599.003.0022.
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Timescale is the organizing framework of this volume. In various sections, we consider the effects of climate variability on ecosystems at timescales ranging from weeks or months to centuries. In part III, we turn our attention to interdecadal-scale events. The timescales we consider are not absolutely defined, but for our purposes we define the interdecadal scale to encompass effects occurring with recurring cycles generally ranging from 10 to 50 years. A recurring theme in many of the chapters in this section is the effect on ecosystem response of teleconnection patterns associated with recognized quasi-periodic atmospheric circulation modes. These circulation modes include the well-known El Niño– Southern Oscillation (ENSO) phenomenon, which is generally thought to recur at shorter, interdecadal timescales but also includes some longer-term periodicities. Several other climate variability modes, including the Pacific North American index (PNA), North Atlantic Oscillation (NAO), Pacific Decadal Oscillation (PDO), and North Pacific index (NP) also show strong interdecadal scale signatures and figure prominently in the chapters of part III. McHugh and Goodin begin the section by examining the climate record at several North American LTER sites for evidence of interdecadal-scale fluctuation. They note that interdecadal-scale contributions to climate variability can best be described in terms of two types of variation: (1) discontinuities in mean value, and (2) the presence of trends in the data. Evaluation of interdecadal periodicities in LTER data is complicated by the relatively short time series of observations available. McHugh and Goodin approach the problem mainly through the use of power spectrum analysis, a widely used tool for evaluating the periodicity in a time series of data. Principal components analysis is used to decompose the time series of growing-season climate data for each of the LTER sites into their principal modes of variability. These modes are then subjected to power spectrum analysis to evaluate the proportions of the variance in the data occurring at various timescales. McHugh and Goodin’s results suggest that significant effects on precipitation and temperature at interdecadal timescales are uncommon in these data, although significant periodicities at both shorter and longer frequencies do emerge from the data (a finding of relevance to other sections of this volume).
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David, Greenland, and Douglas G. Goodin. "Climate Variability and Ecosystem Response—Synthesis." In Climate Variability and Ecosystem Response in Long-Term Ecological Research Sites. Oxford University Press, 2003. http://dx.doi.org/10.1093/oso/9780195150599.003.0039.
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At the outset we identified the theme of this book as how ecosystems respond to climate variability. We have examined this theme at a variety of LTER sites and at a variety of timescales. The subject matter of the book was also to be focused on a series of framework questions. We noted that the theme of climate variability and ecosystem response is inherently deterministic and implicitly carries with it the notion of climate cause and ecosystem result. The analyses in this volume demonstrated that this is a valid and fruitful working assumption. However, the idea of a simple single climate cause and effect might be true in some cases, but it is obviously simplistic. More realistically, the effects of climate variability cascade through ecosystems. In almost all cases there is the probability of many secondary and associated effects accompanying the primary effects. As an example, the possible results of potential warming in the Pacific Northwest forests include changes in global carbon dioxide input, nutrient cycling between the plants and the soil, and feedback links between the plant and soil organisms (Perry and Borchers 1990). In general there seem to be at least three broad classes of interaction between climate and ecosystems. First, the ecosystem simply responds to individual climate events or episodes that exceed some threshold for response. Second, ecosystems may buffer climate variability. In this sense they are filtering the effect of the climate event or episode. The same component in an ecosystem can sometimes act as a buffer and sometimes not, according to the nature of the climate event. Thus a riparian environment might provide soil moisture that acts as a buffer to a drought, but the whole environment might be destroyed by a large flood event. Third, we hypothesize that the ecosystem may move into resonance with the climate variability with positive and negative feedbacks that produce a strong ecosystem response. The relationship between fire and the Southern Oscillation indicates that the South west United States (Swetnam and Betancourt 1990) may provide an example of such resonance. Other examples of resonance, discussed subsequently, may exist in the forests of Interior Alaska and Puerto Rico. If there is indeed an ecosystem response to climate variability, the response tends to occur in cascades.
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Hinkel, Kenneth M., and Andrew W. Ellis. "Cryosphere." In Geography in America at the Dawn of the 21st Century. Oxford University Press, 2004. http://dx.doi.org/10.1093/oso/9780198233923.003.0013.
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The cryosphere refers to the Earth’s frozen realm. As such, it includes the 10 percent of the terrestrial surface covered by ice sheets and glaciers, an additional 14 percent characterized by permafrost and/or periglacial processes, and those regions affected by ephemeral and permanent snow cover and sea ice. Although glaciers and permafrost are confined to high latitudes or altitudes, areas seasonally affected by snow cover and sea ice occupy a large portion of Earth’s surface area and have strong spatiotemporal characteristics. Considerable scientific attention has focused on the cryosphere in the past decade. Results from 2 ×CO2 General Circulation Models (GCMs) consistently predict enhanced warming at high latitudes, especially over land (Fitzharris 1996). Since a large volume of ground and surface ice is currently within several degrees of its melting temperature, the cryospheric system is particularly vulnerable to the effects of regional warming. The Third Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) states that there is strong evidence of Arctic air temperature warming over land by as much as 5 °C during the past century (Anisimov et al. 2001). Further, sea-ice extent and thickness has recently decreased, permafrost has generally warmed, spring snow extent over Eurasia has been reduced, and there has been a general warming trend in the Antarctic (e.g. Serreze et al. 2000). Most climate models project a sustained warming and increase in precipitation in these regions over the twenty-first century. Projected impacts include melting of ice sheets and glaciers with consequent increase in sea level, possible collapse of the Antarctic ice shelves, substantial loss of Arctic Ocean sea ice, and thawing of permafrost terrain. Such rapid responses would likely have a substantial impact on marine and terrestrial biota, with attendant disruption of indigenous human communities and infrastructure. Further, such changes can trigger positive feedback effects that influence global climate. For example, melting of organic-rich permafrost and widespread decomposition of peatlands might enhance CO2 and CH4 efflux to the atmosphere. Cryospheric researchers are therefore involved in monitoring and documenting changes in an effort to separate the natural variability from that induced or enhanced by human activity.
Conference papers on the topic "Stroke volume variability"
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Elstad, Maja, and Lars Walloe. "Heart rate variability and stroke volume variability to detect central hypovolemia in spontaneously breathing, young, healthy volunteers." In 2014 8th Conference of the European Study Group on Cardiovascular Oscillations (ESGCO). IEEE, 2014. http://dx.doi.org/10.1109/esgco.2014.6847545.
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Jena, Bhagya, Girija Rath, Vikas Chouhan, Nidhi Gupta, Siddharth Chavali, and Arvind Chaturvedi. "A0012 Pleth Variability Index versus Stroke Volume Variation as Predictors of Fluid Responsiveness in Prone Position." In 20th Annual Conference of Indian Society of Neuroanaesthesiology and Critical Care (ISNACC). Thieme Medical and Scientific Publishers Private Ltd., 2019. http://dx.doi.org/10.1055/s-0039-1684119.
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"THE POWER SPECTRA RESPONSE OF STROKE VOLUME AND ARTERIAL BLOOD PRESSURE VARIABILITY SIGNALS TO AUTONOMIC NERVOUS SYSTEM MODULATION OF THE HEART." In International Conference on Bio-inspired Systems and Signal Processing. SciTePress - Science and and Technology Publications, 2009. http://dx.doi.org/10.5220/0001775804110415.
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Rosa, Isamar, Henning Roedel, Michael D. Lepech, and David J. Loftus. "Creation of Statistically Equivalent Periodic Unit Cells for Protein-Bound Soils." In ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-52029.
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In 2010, NASA was directed to develop technologies to reduce the cost and risk of space exploration and send humans beyond the International Space Station. A central challenge to long-duration space missions is a lack of available construction materials in situ. This work focuses on a novel class of composites that can be produced extraterrestrially in situ by desiccating a mixture of soil, water, and protein binder to create a strong, versatile material. To date, experimental tests of mechanical properties have shown significant variability among samples. This paper focuses on the creation of Statistically Equivalent Periodic Unit Cells (SEPUC) to stochastically model protein-bound composites for the purpose of creating FE models that provide insights into experimental results. Model inputs include the soil granulometry and volume fractions of the phases. Ellipsoidal particles are placed, and protein coatings and bridges are created, using a Level Set based Random Sequential Addition algorithm. Each image is assigned a statistical descriptor and a simple genetic algorithm is used to optimize for a statistical descriptor close to that of experimental specimens. The framework is validated by comparing experimental images of protein-bound soils obtained by micro-CT scanning with those obtained through the SEPUC framework.
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Nocivelli, Lorenzo, Anqi Zhang, Brandon A. Sforzo, Aniket Tekawade, Alexander K. Voice, Meng Tang, Christopher F. Powell, Sibendu Som, Yuanjiang Pei, and Robert S. Levy. "Comparison Between a Center-Mounted and a Side-Mounted Injector for Gasoline Applications: A Computational Study." In ASME 2020 Internal Combustion Engine Division Fall Technical Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/icef2020-2991.
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Abstract The differences between a center-mounted and a side-mounted injector for gasoline direct injection (GDI) applications are analyzed through computational fluid dynamics (CFD). The Engine Combustion Network’s (ECN) axisymmetric 8-hole Spray G injector is compared to a 6-hole injector designed to be side-mounted in an engine. Nozzle-flow simulations are carried out with the commercial CFD software CONVERGE, injecting Euro 5 certification gasoline into a constant volume chamber. Low-load operating conditions are targeted, setting the injection pressure at 50 bar and the ambient pressure to be representative of very early pilot injections. The phase change is handled with the Homogeneous Relaxation Model (HRM), which is assessed and adapted to gasoline flash-boiling conditions. The simulation domains are generated leveraging real injector internal geometries obtained by micron-resolution X-ray tomographic measurements, which introduce manufacturing tolerances and surface roughness in the computational study. Steady needle lift conditions are analyzed. The near-field fuel density distributions and plume morphologies are evaluated, validated and compared to X-ray radiography measurements. A computational best practice is defined and single plume characteristics and variability trends are highlighted as functions of the geometry of the orifices. The plume-plume interaction dynamics are identified and assessed, underlining differences from center- to side-mounted injectors at strong flashing conditions. The obtained numerical framework allows the identification of near-nozzle injection characteristics such as single plume direction, cone angle, spray initial velocity and spatial fuel density distribution. The presented results represent a unique dataset for the initialization of more-affordable Lagrangian spray models, which differentiate the behavior of side-mounted and center-mounted injectors.