1,099 research outputs found
RLE Plots: Visualising Unwanted Variation in High Dimensional Data
Unwanted variation can be highly problematic and so its detection is often
crucial. Relative log expression (RLE) plots are a powerful tool for
visualising such variation in high dimensional data. We provide a detailed
examination of these plots, with the aid of examples and simulation, explaining
what they are and what they can reveal. RLE plots are particularly useful for
assessing whether a procedure aimed at removing unwanted variation, i.e. a
normalisation procedure, has been successful. These plots, while originally
devised for gene expression data from microarrays, can also be used to reveal
unwanted variation in many other kinds of high dimensional data, where such
variation can be problematic.Comment: 9 pages, 3 figure
Study of properties of high field superconductors, ac field induced flux jumps Technical summary report, 21 Jun. 1965 - 26 Apr. 1966
Magnetization experiments in superimposed dc and audiofrequency ac magnetic fields on cold worked NbTi alloy samples - ac field induced flux jump
Study of properties of high-field superconductors at elevated temperatures Final technical report, 27 Apr. - 26 Aug. 1966
Properties of high field superconductors at high temperatures - magnetization experiments on niobium and niobium compound
Computational Analysis of Self-Expanding and Balloon-Expandable Transcatheter Heart Valves
Bicuspid aortic valve (BAV) patients are usually excluded from transcatheter aortic valve implantation (TAVI) as this valve anatomy likely leads to oval expansion. This study presents a numerical study of TAVI using both self-expanding and balloon expandable transcatheter heart valve (THV) in bicuspid patients with severe stenosis. The simulation framework included a patient-specific anatomy of the aortic root, calcifications and BAV leaflets extracted from medical imaging analysis as well as a realistic crimping and deployment of the THV. Tissue stress analysis highlighted local maxima in the contact area between the inner aortic lumen and the THV stent frame. Flow analysis based on the smoothed particle hydrodynamics (SPH) technique displayed the area at risk of paravalvular leakage (PVL). These findings provide insights on the TAVI in BAV and thus represents a further step towards the use of in-silico for the virtual planning of TAVI, aiming at improving not only the efficacy of the implantation but also the exploration of borderline anatomy as the case of TAVI in BAVs
Molecular Conformation of Pyridinic Aromatic Esters. II. Electronic Absorption Spectra and Dipole Moments by Semiempirical Methods
The semiempirical MIM method was applied to calculate the
UV spectra of nine pyridine-aromatic-ester derivatives (having the
general formula R1-COO-R2) assuming a planar geometry. Benzene,
pyridine and formic acid were adopted as component systems.
The dipole moments of the same compounds were evaluated at the
MIM and INDO levels and the equilibrium percentage of the conformers
was deduced from experimental and theoretical values.
Comparable results were generally obtained. On the whole the
results are satisfactory but not sufficient to affirm with certainty
if the molecular skeleton is or is not planar
Structural Simulation of Transcatheter Heart Valve in Transcatheter Heart Valve
The durability of transcatheter heart valves (TAV) remains the main disadvantage of transcatheter heart valve implantation (TAVI) for treating aortic valve stenosis. In this study, we assessed the structural mechanics of TAV-in-TAVI using patient-specific modeling. A parametric analysis highlighted that the outcome of TAV-in-TAV depends on the implanted device position and the planned device to be implanted. Contact pressure evinced the impact of different implantation depth and device size on the TAV-in-TAV. This study may bring new insight in the biomechanical performance of TAV to evaluate options for future interventions when the current TAVs experience device failure
Molecular Conformation of Aza-substituted Benzanilides by Electronic Absorption Spectra and Dipole Moments
The electronic absorption spectra of thirteen pyridine aromatic
amides of general formula R1-CO-NH- R2 (Ri, R2 = pyridil or
phenyl) were obtained in methanol and dioxane solution.
The band assignment is briefly discussed.
The dipole moments were measured in dioxane at 25 ± 0.1 °c
and compared with values calculated by both the S. H. M. 0. method
and vectorial model. The comparison suggests the most probable
conformation of derivatives which have the nitrogen either in the
ortho or meta position in one or both rings of the molecule
Parametric analysis of transcatheter aortic valve replacement in transcatheter aortic valve replacement: evaluation of coronary flow obstruction
Transcatheter aortic valve replacement (TAVR) is increasingly being considered for use in younger patients having longer life expectancy than those who were initially treated. The TAVR-in-TAVR procedure represents an appealing strategy to treat failed transcatheter heart valves (THV) likely occurring in young patients. However, the permanent displacement of first THV can potentially compromise the coronary access and ultimately inhibit the blood flow circulation. The objective of this study was to use finite-element analysis (FEA) to quantify coronary flow in a patient who underwent TAVR-in-TAVR. A parametric investigation was carried out to determine the impact of both the implantation depth and device size on coronary flow for several deployment configurations. The FEAs consisted of first delivering the SAPIEN 3 Ultra THV and then positioning the Evolut PRO device. Findings indicates that high implantation depth and device undersize of the second THV could significantly reduce coronary flow to 20% of its estimated level before TAVR. Additionally, a positive correlation was observed between coronary flow and the valve-to-coronary distance (R = 0.86 and p = 0.032 for the left coronary artery, and R = 0.93 and p = 0.014 for the right coronary artery). This study demonstrated that computational modeling can provide valuable insights to improve the pre-procedural planning of TAVR-in-TAVR
Biomechanical performance of the Bicaval Transcatheter System for the treatment of severe tricuspid regurgitation
Introduction: Tricuspid regurgitation (TR) is a relatively common valvular disease, which can result from structural abnormalities of any anatomic part of the tricuspid valve. Severe TR is linked to congestive heart failure and hemodynamic impairment, resulting in high mortality when repaired by elective surgery. This study was undertaken to quantify the structural and hemodynamic performance of the novel Transcatheter Bicaval Valves System (TricValve) percutaneously implanted in the superior vena cava (SVC) and inferior vena cava (IVC) of two patients with severe TR and venous congestion. Methods: After developing the SVC and IVC device models, the contact pressure exerted on the vena cava wall was obtained by computational analysis. Both smoothed-particle hydrodynamics (SPH) and computational fluid dynamics were carried out to quantify caval reflux in the right atrium and the pressure field of pre- and post-TricValve scenarios, respectively. Results: Analysis of contact pressure highlighted the main anchoring area of the SVC device occurring near the SVC device belly, while the IVC device exerted pronounced forces in the device’s proximal and distal parts. SPH-related flow velocities revealed the absence of caval reflux, and a decrease in time-averaged pressure was observed near the SVC and IVC after TricValve implantation. Discussion: Findings demonstrated the potential of computational tools for enhancing our understanding of the biomechanical performance of structural tricuspid valve interventions and improving the way we design next-generation transcatheter therapies to treat the tricuspid valve with heterotopic caval valve implantation
TAVI nel trattamento della stenosi aortica degenerativa: stato dell’arte e prospettive
Degenerative aortic stenosis is the most common form of heart valve disease in developed countries and predominantly affects the elderly. Aortic valve replacement (AVR) has been the gold standard, but recently, transcatheter aortic valve implantation has emerged as an effective therapeutic alternative to conventional AVR for high-risk patients. This review analyzed the literature about AVR, with the objective of evaluating the outcomes of transcatheter aortic valve implantation in patients who are not eligible for surgery showing an improvement in quality of life and middle-term outcomes. The crucial point is the lack of studies with long-term follow-up that could give therapeutic importance to percutaneous valve replacemen
- …