Knowledge of the leftventricular (LV) pressure-volume relation, along withparameters derived from this relation, have led to newpossibilities for the characterisation of cardiac pumpfunction, in both experimental studies and clinicalsettings. The pressure-volume diagram is apowerful tool for visualising LV performance, but in order tobe clinically useful it is necessary to make plots continuouslyand on-line. The conductance catheter technique offers thispossibility. The conductance catheter system has experiencedgrowing interest among cardiologists, physiologists, surgeons,and anaesthesiologists around the world as a powerful newresearch tool, but the invasiveness of this technique has beena limiting factor for most clinical applications. The catheterneeds to be thinner and softer in order to make this techniquemore suitable for human use. This thesis reports of a newthin and soft conductance catheter for continuously and on-linemeasurements of LV pressure and volume. One way to reduce both cathetersize and stiffness is to decrease the number of electrodes onthe catheter. Theoretical calculations shown in this thesisproves that it is possible to obtain the same performance witha single segment catheter as with a five-segment catheter. Thethin catheter has been tested and compared to a commercialfive-segment conductance catheter in animal studies. We conclude that the thin singlesegment conductance catheter can measure left ventricularvolume and pessure. The regression coefficient between the twomethods is good independent of loading condition and duringbaseline conditions the catheters produce very similar volumecurves. During preload reduction the estimated volume reductionis different in the two systems. Our thin catheter does notdisturb the heart's normal electrophysiology, neither by thecatheter current nor by any mechanical stimuli. The resultsdemonstrates that our thin, soft, single segment conductancecatheter has performance characteristics which warrant furtherdevelopment, with the goal to make the method available forhuman use. / NR 20140805

No description available.

The Left Atrial Appendage, once thought to be "a relatively insignificant portion of cardiac anatomy," has currently been realized to possess "important pathological associations [1a]" particularly in its role in promoting serious, frequent thromboembolic events common in individuals suffering from Atrial Fibrillation. Prior approaches to mitigating these events have either required invasive procedures, proved less than fully effective, or presented with problematic sequelae of their own. This work will present a new procedure that addresses both the prevention of the thromboembolic events and the correction of the shortcomings of the major prior methods utilized. A compliant hydrogel that can conform to the geometry of the appendage is proposed as a more effective method of occluding the chamber. This material would be transported to the LAA in liquid form via a multi-lumen catheter, and then solidify within the chamber to form a solid plug. Previous research has identified a candidate hydrogel, comprised of PEG-tetra-thiol and Dextran vinyl sulfone as a candidate hydrogel for this application. Experimental work has investigated fluid properties of the material, as well as degradation and swelling properties of the material. Results from this experimentation were used for fluid transport analysis, and for evaluation of anchoring force of the hydrogel within the chamber. Finally, subfunctions of the occlusion procedure were modeled and tested. During the actual procedure, a catheter balloon will isolate the appendage from the rest of the heart. A model was developed to study interactions between the appendage and this balloon. Additionally, due to fast solidification time, hydrogel components in the surgical procedure will be mixed in a mixing chamber at the tip of the catheter. Potential mixing chamber designs were modeled, and a ternary diffusion model was developed to better understand hydrogel mixing. Prototypes for both these subfunctions were built and tested as well. Additional analysis looked at the overall occlusion procedure, and how various subfunctions interacted with each other. / text

ABSTRACT There is substantial evidence to suggest that independent of conventional BP, LV mass (LVM) is higher in African-Americans than in European-Americans a difference that may translate into a higher prevalence of cardiovascular diseases. In the present thesis I assessed whether LVM is similarly elevated in groups of African descent living in Africa, and subsequently whether 24-hour, day or night BP or indices of arterial stiffness could explain the variability in LVM beyond conventional BP in this population group. As there is considerable controversy as to whether 24-hour BP measurements are better predictors of the regression of LVH than conventional BP and whether antihypertensive agents that target the renin-angiotensin system (RAS) regress LV hypertrophy (LVH) independent of BP in groups of African descent, in the present thesis I therefore also assessed these questions. In 141 healthy adult participants obtained from a random sample of nuclear families (n=399) of African ancestry living in Soweto, I determined that LVM adjusted for body surface area to the first power was an appropriate allometric signal to account for growth effects on LVM. The allometric signals established in other populations considerably over-adjusted for LVM in the group that I studied with marked negative relations noted. After adjusting for body surface area I noted upper thresholds of LVM index (LVMI) of 134 g/m2 for men and 112 g/m2 for women. As compared to thresholds described for other population samples these thresholds were noted to be modestly higher. In 187 women from randomly recruited nuclear families of African ancestry, after appropriate adjustments, conventional BP was as closely associated with LVMI as 24- hour BP, and daytime BP was as closely associated with LVMI as night-time BP in women. However, in 110 men from randomly recruited nuclear families of African ancestry, after appropriate adjustments, only night-time BP was associated with LVMI, an effect that was independent of conventional BP (r=0.21, p<0.05). Indices of nocturnal decreases in BP were not associated with LVMI in either gender group. Furthermore, in randomly recruited nuclear families of African ancestry, after appropriate adjustments, including systolic BP or pulse pressure, pulse wave velocity (an index of arterial stiffness assessed using applanation tonometry) was independently associated with LVMI in women (n=204, r=0.25, p<0.0005), but not in men (n=123, r=-0.07). In 173 hypertensive patients of African descent of whom 64 were previously untreated and 109 were previously treated, I assessed whether ambulatory BP is a better predictor of on-treatment decreases in LVMI over a 4 month treatment period. In the previously untreated patients, the regression in LVMI correlated to a similar degree (p<0.09) with decreases in conventional (r=0.34; p<0.005) and 24-hour (r=0.26; p<0.04) systolic BP. In this same study sample followed prospectively for 25 months, accounting for effects on ambulatory BP at each time point, the use of the angiotensin-converting enzyme inhibitor, enalapril, was not associated with LVMI, whereas, on-treatment conventional systolic BP (p=0.01) and night-time systolic BP (p=0.01) were associated with LVMI. In a further study conducted in 87 patients of African ancestry with hypertension and LVH, I showed that changes in systolic ambulatory BP (daytime, r=0.46, p=0.006) were predictive of changes in LVMI after 2 months of treatment with an angiotensin II receptor blocker (candesartan), ACE-I (ramipril) and the diuretic agent, hydrochlorothiazide. Moreover, in a final study I showed that in hypertensive patients of African ancestry, initiating therapy with the diuretic, indapamide SR and then adding the ACE-I, perindopril 4 mg (n=42), was equally as effective as amlodipine (calcium channel blocker) (n=44) therapy at reducing ambulatory BP and LVMI. Thus, in conclusion, groups of African descent living in Africa have only marginally higher thresholds for LVM than other population groups. Moreover, in this population group, nocturnal BP has a conventional BP-independent effect on LVMI in men, but not in women, whereas arterial stiffness has a conventional BP-independent effect on LVMI in women, but not in men. Further, in this population, reductions in LVM produced by antihypertensive therapy appear to be equally as closely related to conventional as ambulatory BP and in contrast to findings in groups of European ancestry, where RAS blockers produce unique benefits on LVM beyond conventional BP reductions, in groups of African ancestry in Africa, RAS blockers produce no BPindependent reductions in LVM. Moreover, in this population, decreases in LVM in patients with LVH produced by RAS blockers are related to ambulatory BP changes and despite the ineffectiveness of RAS blockers on BP when used as monotherapy in this population, RAS blockers together with diuretics are equally as effective in decreasing BP and LVM as compared to a class of antihypertensive agents with established efficacy (calcium channel blockers). Hence when compelling indications for RAS blockade exist, RAS blocker-diuretic combinations are effective therapy in patients of African descent living in Africa.

The history of the development of the piano works for left-hand has spanned for more than one hundred and fifty years, and the piano concertos for left-hand, which made special historical significance in the concerts, were mostly written for one-arm pianist Paul Wittgenstein. The purpose of the thesis is the study of the stylistic features of one-movement piano concertos for one-hand, including Concerto pour la main gauche by Ravel, Parergon and Panathenaenzug by Richard Struass, and Diversions by Britten. The discussions contain the structure, form, orchestration, and performing technique. The contents of the thesis includes four chapters, in addition to the introduction. The first chapter discusses the general historical background for the creation of left-hand playing, and the development of the creation of the piano works for left hand. The second chapter is basic literature research for the piano concertos for left hand, and introduces the creative background to four piano concertos for left hand. The third chapter emphasizes the detailed analysis of the piano concertos for left hand of the selected works of Ravel, Richard Strauss and Britten. In the four left-hand piano concertos, Concerto pour la main gauche and the Parergon are designed in multi-sectional stracyure, the Panathenaenzug is planted for a symphonic studies in Passacaglia form and the Diversions is in a form of thematic variations in which each variation is characteristic in different title. In addition, composers frequently make use of the different instrumental colors of orchestra to replenish the lacks of rich acoustics of the piano playing, including accompaniment, support of harmony, momentum and dynamic of sounding expression. Richard Struass¡¦s Panathenaenzug employs the glockenspiel and celesta to enrich the sounding expression. The difficulties of left-hand piano techniques are variable; Ravel use the different and difficult piano skills in his two candenzas, Richard Struass¡¦s Panathenaenzug is also collected left-hand piano techniques in it, and Britten¡¦s Diversions is in different point of view that the composer employs the whole register of eighty-eight keys to makes this piano concerto sounding rich.

Not available / text

Highway safety evaluation has traditionally been performed using crash data. However crash data based safety analysis has limitations in terms of timeliness and efficiency. Previous studies show that the use of surrogate safety data allows for earlier evaluation of safety in comparison to the significantly longer time horizon required for collecting crash data. However, the predictive capability of surrogate measures is an area of ongoing research. Previous studies have often resulted in inconsistent findings in the relationship between surrogates and crashes, one of the primary reasons being inconsistent definitions of a conflict. This study evaluated the effectiveness of certain surrogate measures (Acceleration-Deceleration profile, intersection entering speed of through vehicles, and Post Encroachment Time (PET)) in assessing the safety of opposing left-turn interactions at 4-legged signalized intersections by collection of time resolved video from eighteen selected intersections throughout Georgia. Overall, this research demonstrated that surrogate measures can be effective in safety evaluation, specifically demonstrating the use of PET as a surrogate for crashes between left-turning vehicles and opposing through vehicles. The analysis of data found that the selected surrogate threshold is critical to the effectiveness of any surrogate measure. For example, the required PET threshold was found to be as low as 1 second to identify high crash intersections, significantly lower than the commonly reported 3 second threshold. Non-parametric rank analysis methods and generalized linear modeling techniques were used to model PET with other intersection and traffic characteristics to demonstrate the degree to which these surrogates can be used to identify potential high-crash intersections without resorting to a crash history. Finally, the effectiveness of PET and its assistance to decision makers is also been demonstrated through an example that helped find errors in reported crash data.

Thesis (B.A. Hons.))--University of Adelaide, Dept. of Psychology, 1978.

Thesis (Ph. D.)--Johns Hopkins University, 1910. / Vita. Bibliography: p. 7-8.

Published also as Thesis (Ph. D.)--Johns Hopkins University. / Bibliography: p. 121.