Persistent fluctuations in the distribution of galaxies from the Two degree Field Galaxy Redshift Survey

We apply the scale-length method to several three dimensional samples of the Two degree Field Galaxy Redshift Survey. This method allows us to map in a quantitative and powerful way large scale structures in the distribution of galaxies controlling systematic effects. By determining the probability density function of conditional fluctuations we show that large scale structures are quite typical and correspond to large fluctuations in the galaxy density field. We do not find a convergence to homogeneity up to the samples sizes, i.e. ~ 75 Mpc/h. We then measure, at scales r <~ 40 Mpc/h, a well defined and statistically stable power-law behavior of the average number of galaxies in spheres, with fractal dimension D=2.2 +- 0.2. We point out that standard models of structure formation are unable to explain the existence of the large fluctuations in the galaxy density field detected in these samples. This conclusion is reached in two ways: by considering the scale, determined by the linear perturbation analysis of a self-gravitating fluid, below which large fluctuations are expected in standard models and through the determination of statistical properties of mock galaxy catalogs generated from cosmological N-body simulations of the Millenium consortitum.Comment: 6 pages, 3 figures, Europhysics Letters in the press, higher resolution figures available from http://pil.phys.uniroma1.it/~sylos

Fast Image-Based Model of Mitral Valve Closure for Surgical Planning

Surgical repair of the mitral valve results in better outcomes than valve replacement, yet diseased valves are often replaced due to the technical difficulty of the repair process. A surgical planning system based on patient-specific medical images that allows surgeons to simulate and compare potential repair strategies could greatly improve surgical outcomes. The system must simulate valve closure quickly and handle the complex boundary conditions imposed by the chords that tether the valve leaflets. We have developed a process for generating a triangulated mesh of the valve surface from volumetric image data of the opened valve. The closed position of the mesh is then computed using a mass-spring model of dynamics. In the mass-spring model, triangle sides are treated as linear springs supporting only tension. Chords are also treated as linear springs, and self-collisions are detected and handled inelastically. The equations of motion are solved using implicit numerical integration. The simulated closed state is compared with an image of the same valve taken in the closed state to assess accuracy of the model. The model exhibits rapid valve closure and is able to predict the closed state of the valve with reasonable accuracy.Engineering and Applied Science

A novel cardioport for beating-heart, image-guided intracardiac surgery

Objective Intracardiac beating-heart procedures require the introduction and exchange of complex instruments and devices. To prevent potential complications such as air embolism and bleeding, a universal cardioport was designed and tested. Methods The design consists of a port body and a series of interchangeable sleeves. The port uses a fluid purging system to remove air from the instrument before insertion into the heart, and a valve system minimizes blood loss during instrument changes. Results The cardioport was tested ex vivo and in vivo in pigs (n = 5). Beating-heart procedures, such as septal defect closure and mitral valve repair, were modeled. Ex vivo trials (n = 150) were performed, and no air emboli were introduced using the port. In comparison, air emboli were detected in 40% to 85% of the cases without the use of the port-based purging system. Port operation revealed excellent ergonomics and minimal blood loss. Conclusions A novel cardioport system designed to prevent air entry and blood loss from transcardiac instrument introduction was shown to be an enabling platform for intracardiac beating-heart surgery. The port system improves safety and facilitates further development of complex instruments and devices for transcardiac beating-heart surgery.Center for Integration of Medicine and Innovative Technology (Award 07-026)National Institutes of Health (U.S.) (National Heart, Lung, and Blood Institute Award 5R01HL073647)Massachusetts Technology Transfer Cente

Cleft closure and undersizing annuloplasty improve mitral repair in atrioventricular canal defects

ObjectiveReoperation rates to correct left atrioventricular valve regurgitation after primary repair of atrioventricular canal defects remain relatively high. The causes of valvular regurgitation are likely multifactorial, and simple cleft closure is often insufficient to prevent recurrence.MethodsTo elucidate the mechanisms leading to regurgitation, we conducted hemodynamic studies using isolated native mitral valves. Anatomy of these valves was altered to mimic atrioventricular canal type valves and studied under pediatric hemodynamic conditions. The impact of subvalvular geometry, cleft closure, annular dilatation, and annular undersizing on regurgitation were investigated.ResultsPapillary muscle position did not have a significant effect on regurgitation. Cleft closure had a significant impact on valvular competence, with reduction in regurgitation volume with increased cleft closure. Regurgitation volume decreased from 12.5 ± 2.4 mL/beat for an open cleft to 4.9 ± 1.9 mL/beat for a partially closed cleft and to 1.4 ± 1.6 mL/beat when the cleft was completely closed. Annular dilatation had a significant impact on regurgitation even after cleft closure. A 40% increase in annular size increased regurgitation by 59% for a partially closed cleft and by 84% for a fully closed cleft. Reducing the annular size by 20% from the physiologic level decreased the regurgitation volume by 12% for a fully open cleft and by 58% for the partially closed cleft case.ConclusionsAnnular dilatation after primary repair has a potentially significant role in the recurrence of atrioventricular valve regurgitation. Reducing the annular size and restricting dilatation as an adjunct to cleft closure is a promising surgical approach in such valve anatomies

Importance of Preserved Tricuspid Valve Function for Effective Soft Robotic Augmentation of the Right Ventricle in Cases of Elevated Pulmonary Artery Pressure

Purpose: In clinical practice, many patients with right heart failure (RHF) have elevated pulmonary artery pressures and increased afterload on the right ventricle (RV). In this study, we evaluated the feasibility of RV augmentation using a soft robotic right ventricular assist device (SRVAD), in cases of increased RV afterload. Methods: In nine Yorkshire swine of 65-80 kg, a pulmonary artery band was placed to cause RHF and maintained in place to simulate an ongoing elevated afterload on the RV. The SRVAD was actuated in synchrony with the ventricle to augment native RV output for up to one hour. Hemodynamic parameters during SRVAD actuation were compared to baseline and RHF levels. Results: Median RV cardiac index (CI) was 1.43 (IQR, 1.37-1.80) L/min/m(2) and 1.26 (IQR 1.05-1.57) L/min/m(2) at first and second baseline. Upon PA banding RV CI fell to a median of 0.79 (IQR 0.63-1.04) L/min/m(2). Device actuation improved RV CI to a median of 0.87 (IQR 0.78-1.01), 0.85 (IQR 0.64-1.59) and 1.11 (IQR 0.67-1.48) L/min/m(2) at 5 min (p = 0.114), 30 min (p = 0.013) and 60 (p = 0.033) minutes respectively. Statistical GEE analysis showed that lower grade of tricuspid regurgitation at time of RHF (p = 0.046), a lower diastolic pressure at RHF (p = 0.019) and lower mean arterial pressure at RHF (p = 0.024) were significantly associated with higher SRVAD effectiveness. Conclusions: Short-term augmentation of RV function using SRVAD is feasible even in cases of elevated RV afterload. Moderate or severe tricuspid regurgitation were associated with reduced device effectiveness

DISCIPLINE MASTERING LEVEL AND COMPETENCY MASTERING LEVEL: POSSIBILITY TO INTEGRATE THE ESTIMATIONS

The articleproposes anapproach which enables an integration of two estimations - the assessment of discipline mastering level and the assessment of competency mastering level. Disciplinary examinations, tests, and other control measures need to be fully focused on the identification of student’s level of competence formation. This allows the estimations obtained by students in disciplinary control events to translate in assessing the competence level. The article is an example of a communication matrix between competencies and disciplines, estimations of their mastering level applying to Bachelor programmeof Mechanical Engineering. An important characteristic of the proposed method is the ability to quantify the level of competence. There is a possibility of establishing and monitoring the planned competence level. The technique is universal and is essentially independent of competence content