Double-crowned valved stents for off-pump mitral valve replacement

Objective: An animal model has been designed to assess the feasibility of off-pump mitral valve replacement using valved stents. Methods: Glutaraldehyde-preserved homograft was sutured inside a prosthetic tube (Dacron). Then, two self-expandable nitinol Z-stents were sutured on the external surface of the prosthesis in such a way to create two self-expanding crowns for fixation. In adult pigs and under general anesthesia, the left atrium was exposed through a left thoracotomy and atrio-ventricular roadmapping was performed with intravascular ultrasound (IVUS) and fluoroscopy. The double-crowned valved stents were loaded into a delivery sheath. The sheath was then introduced into the left atrium and the valved stents was deployed in mitral position in such a way that the part in between the two stents was at the level of the mitral annulus. Intracardiac Unltrasound (ICUS) was used to assess the valve function. Hemodynamic parameters were gathered as well. Animal survived for no more than 3h after the valve deployment and gross anatomy examination of the left heart was carried out. Results: The mean height of the valved stents was 29.4±0.2mm, with an internal diameter of 20.4±1.0mm, and an external diameter of 25.5±0.8mm. The procedure was successfully carried out in eight animals. In vivo evaluation showed a native mitral annulus diameter of 24.9±0.6mm, and a mean mitral valve area of 421.4±17.5mm2. ICUS showed a mild mitral regurgitation in three out of eight animals. Mean pressure gradient across the valved stents was 2.6±3.1mmHg. Mean pressure gradient across the left ventricular outflow tract (LVOT) was 6.6±5.2mmHg. The mean survival time was 97.5±56.3min (survival time range was 40-180min). One animal died due to the occlusion of the LVOT because of valved stents displacement. Postmortem evaluation confirmed correct positioning of the valved stent in the mitral position in seven out of eight animals. No atrial or ventricular lesions due to the valved stents were found. Conclusions: Off-pump implantation of a self-expandable valved stent in the mitral position is technically feasible. Further studies will assess if this procedure is also feasible in human

Effects of an irregular bedtime schedule on sleep quality, daytime sleepiness, and fatigue among university students in Taiwan

<p>Abstract</p> <p>Background</p> <p>An irregular bedtime schedule is a prevalent problem in young adults, and could be a factor detrimentally affecting sleep quality. The goal of the present study was to explore the association between an irregular bedtime schedule and sleep quality, daytime sleepiness, and fatigue among undergraduate students in Taiwan.</p> <p>Methods</p> <p>A total of 160 students underwent a semi-structured interview and completed a survey comprising 4 parts: Pittsburgh Sleep Quality Index (PSQI), Epworth Sleepiness Scale (ESS), Fatigue Severity Scale (FSS), and a rating of irregular bedtime frequency. Participants were grouped into 3 groups in terms of irregular bedtime frequency: low, intermediate, or high according to their 2-week sleep log. To screen for psychological disorders or distress that may have affected responses on the sleep assessment measures, the Chinese health questionnaire-12 (CHQ-12) was also administered.</p> <p>Results</p> <p>We found an increase in bedtime schedule irregularity to be significantly associated with a decrease in average sleep time per day (Spearman r = -0.22, p = 0.05). Multivariate regression analysis revealed that irregular bedtime frequency and average sleep time per day were correlated with PSQI scores, but not with ESS or FSS scores. A significant positive correlation between irregular bedtime frequency and PSQI scores was evident in the intermediate (partial r = 0.18, p = 0.02) and high (partial r = 0.15, p = 0.05) frequency groups as compared to low frequency group.</p> <p>Conclusion</p> <p>The results of our study suggest a high prevalence of both an irregular bedtime schedule and insufficient sleep among university students in Taiwan. Students with an irregular bedtime schedule may experience poor sleep quality. We suggest further research that explores the mechanisms involved in an irregular bedtime schedule and the effectiveness of interventions for improving this condition.</p

Biodiesel production from jatropha seeds: Solvent extraction and in situ transesterification in a single step

The objective of this study was to investigate solvent extraction and in situ transesterification in a single step to allow direct production of biodiesel from jatropha seeds. Experiments were conducted using milled jatropha seeds, and n-hexane as extracting solvent. The influence of methanol to seed ratio (2:1–6:1), amount of alkali (KOH) catalyst (0.05–0.1 mol/L in methanol), stirring speed (700–900 rpm), temperature (40–60 °C) and reaction time (3–5 h) was examined to define optimum biodiesel yield and biodiesel quality after water washing and drying. When stirring speed, temperature and reaction time were fixed at 700 rpm, 60 °C and 4 h respectively, highest biodiesel yield (80% with a fatty acid methyl ester purity of 99.9%) and optimum biodiesel quality were obtained with a methanol to seed ratio of 6:1 and 0.075 mol/L KOH in methanol. Subsequently, the influence of stirring speed, temperature and reaction time on biodiesel yield and biodiesel quality was studied, by applying the randomized factorial experimental design with ANOVA (F-test at p = 0.05), and using the optimum values previously found for methanol to seed ratio and KOH catalyst level. Most experimental runs conducted at 50 °C resulted to high biodiesel yields, while stirring speed and reaction time did not give significantly effect. The highest biodiesel yield (87% with a fatty acid methyl ester purity of 99.7%) was obtained with a methanol to seed ratio of 6:1, KOH catalyst of 0.075 mol/L in methanol, a stirring speed of 800 rpm, a temperature of 50 °C, and a reaction time of 5 h. The effects of stirring speed, temperature and reaction time on biodiesel quality were not significant. Most of the biodiesel quality obtained in this study conformed to the Indonesian Biodiesel Standard

Double-crowned valved stents for off-pump mitral valve replacement

OBJECTIVE: An animal model has been designed to assess the feasibility of off-pump mitral valve replacement using valved stents. METHODS: Glutaraldehyde-preserved homograft was sutured inside a prosthetic tube (Dacron). Then, two self-expandable nitinol Z-stents were sutured on the external surface of the prosthesis in such a way to create two self-expanding crowns for fixation. In adult pigs and under general anesthesia, the left atrium was exposed through a left thoracotomy and atrio-ventricular roadmapping was performed with intravascular ultrasound (IVUS) and fluoroscopy. The double-crowned valved stents were loaded into a delivery sheath. The sheath was then introduced into the left atrium and the valved stents was deployed in mitral position in such a way that the part in between the two stents was at the level of the mitral annulus. Intracardiac Unltrasound (ICUS) was used to assess the valve function. Hemodynamic parameters were gathered as well. Animal survived for no more than 3h after the valve deployment and gross anatomy examination of the left heart was carried out. RESULTS: The mean height of the valved stents was 29.4+/-0.2 mm, with an internal diameter of 20.4+/-1.0mm, and an external diameter of 25.5+/-0.8 mm. The procedure was successfully carried out in eight animals. In vivo evaluation showed a native mitral annulus diameter of 24.9+/-0.6 mm, and a mean mitral valve area of 421.4+/-17.5 mm2. ICUS showed a mild mitral regurgitation in three out of eight animals. Mean pressure gradient across the valved stents was 2.6+/-3.1 mmHg. Mean pressure gradient across the left ventricular outflow tract (LVOT) was 6.6+/-5.2 mmHg. The mean survival time was 97.5+/-56.3 min (survival time range was 40-180 min). One animal died due to the occlusion of the LVOT because of valved stents displacement. Postmortem evaluation confirmed correct positioning of the valved stent in the mitral position in seven out of eight animals. No atrial or ventricular lesions due to the valved stents were found. CONCLUSIONS: Off-pump implantation of a self-expandable valved stent in the mitral position is technically feasible. Further studies will assess if this procedure is also feasible in humans

On the non-disabled perceptions of four common mobility devices in Norway: A comparative study based on semantic differentials

acceptedVersio

Radiation reaction for multipole moments

We propose a Poincare-invariant description for the effective dynamics of systems of charged particles by means of intrinsic multipole moments. To achieve this goal we study the effective dynamics of such systems within two frameworks -- the particle itself and hydrodynamical one. We give a relativistic-invariant definition for the intrinsic multipole moments both pointlike and extended relativistic objects. Within the hydrodynamical framework we suggest a covariant action functional for a perfect fluid with pressure. In the case of a relativistic charged dust we prove the equivalence of the particle approach to the hydrodynamical one to the problem of radiation reaction for multipoles. As the particular example of a general procedure we obtain the effective model for a neutral system of charged particles with dipole moment.Comment: 12 pages, 1 figure, RevTeX 4; references updated, minor textual correction

Determinants of persistence in hypertensive patients treated with irbesartan: results of a postmarketing survey

BACKGROUND: Persistence is a key factor for long-term blood pressure control, which is of high prognostic importance for patients at increased cardiovascular risk. Here we present the results of a post-marketing survey including 4769 hypertensive patients treated with irbesartan in 886 general practices in Switzerland. The goal of this survey was to evaluate the tolerance and the blood pressure lowering effect of irbesartan as well as the factors affecting persistence in a large unselected population. METHODS: Prospective observational survey conducted in general practices in all regions of Switzerland. Previously untreated and uncontrolled pre-treated patients were started with a daily dose of 150 mg irbesartan and followed up to 6 months. RESULTS: After an observation time slightly exceeding 4 months, the average reduction in systolic and diastolic blood pressure was 20 (95% confidence interval (CI) -19.6 to -20.7 mmHg) and 12 mmHg (95% CI -11.4 to -12.1 mmHg), respectively. At this time, 26% of patients had a blood pressure < 140/90 mmHg and 60% had a diastolic blood pressure < 90 mmHg. The drug was well tolerated with an incidence of adverse events (dizziness, headaches,...) of 8.0%. In this survey more than 80% of patients were still on irbesartan at 4 month. The most important factors predictive of persistence were the tolerability profile and the ability to achieve a blood pressure target ≤ 140/90 mmHg before visit 2. Patients who switched from a fixed combination treatment tended to discontinue irbesartan more often whereas those who abandoned the previous treatment because of cough (a class side effect of ACE-Inhibitors) were more persistent with irbesartan. CONCLUSION: The results of this survey confirm that irbesartan is effective, well tolerated and well accepted by patients, as indicated by the good persistence. This post-marketing survey also emphasizes the importance of the tolerability profile and of achieving an early control of blood pressure as positive predictors of persistence

Fingertip force control during bimanual object lifting in hemiplegic cerebral palsy

In the present study we examined unimanual and bimanual fingertip force control during grasping in children with hemiplegic cerebral palsy (CP). Participants lifted, transported and released an object with one hand or both hands together in order to examine the effect on fingertip force control for each hand separately and to determine whether any benefit exists for the affected hand when it performed the task concurrently with the less-affected hand. Seven children with hemiplegic CP performed the task while their movement and fingertip force control were measured. In the bimanual conditions, the weight of the instrumented objects was equal or unequal. The durations of the all temporal phases for the less-affected hand were prolonged during bimanual control compared to unimanual control. We observed close synchrony of both hands when the task was performed with both hands, despite large differences in duration between both hands when they performed separately. There was a marginal benefit for two of the five force related variables for the affected hand (grip force at onset of load force, and peak grip force) when it transported the object simultaneously with the less-affected hand. Collectively, these results corroborate earlier findings of reaching studies that showed slowing down of the less-affected hand when it moved together with the affected hand. A new finding that extends these studies is that bimanual tasks may have the potential to facilitate force control of the affected hand. The implications of these findings for recent rehabilitative therapies in children with CP that make use of bimanual training are discussed