Magnetic resonance imaging-based computational modelling of blood flow and nanomedicine deposition in patients with peripheral arterial disease

Peripheral arterial disease (PAD) is generally attributed to the progressive vascular accumulation of lipoproteins and circulating monocytes in the vessel walls leading to the formation of atherosclerotic plaques. This is known to be regulated by the local vascular geometry, haemodynamics and biophysical conditions. Here, an isogeometric analysis framework is proposed to analyse the blood flow and vascular deposition of circulating nanoparticles (NPs) into the superficial femoral artery (SFA) of a PAD patient. The local geometry of the blood vessel and the haemodynamic conditions are derived from magnetic resonance imaging (MRI), performed at baseline and at 24 months post intervention. A dramatic improvement in blood flow dynamics is observed post intervention. A 500% increase in peak flow rate is measured in vivo as a consequence of luminal enlargement. Furthermore, blood flow simulations reveal a 32% drop in the mean oscillatory shear index, indicating reduced disturbed flow post intervention. The same patient information (vascular geometry and blood flow) is used to predict in silico in a simulation of the vascular deposition of systemically injected nanomedicines. NPs, targeted to inflammatory vascular molecules including VCAM-1, E-selectin and ICAM-1, are predicted to preferentially accumulate near the stenosis in the baseline configuration, with VCAM-1 providing the highest accumulation (approx. 1.33 and 1.50 times higher concentration than that of ICAM-1 and E-selectin, respectively). Such selective deposition of NPs within the stenosis could be effectively used for the detection and treatment of plaques forming in the SFA. The presented MRI-based computational protocol can be used to analyse data from clinical trials to explore possible correlations between haemodynamics and disease progression in PAD patients, and potentially predict disease occurrence as well as the outcome of an intervention.     

A Comparison of Different Nitinol Material Data Sources for Finite Element Analysis

Nitinol (NiTi) is widely used for minimal invasive vascular implants due to its superelastic material behavior. Today computerized finite element analysis (FEA) modeling is a standard tool for the development of medical devices and an essential part of the product design and device approval process (X. Gong and A.R. Pelton, ABAQUS Analysis on Nitinol Medical Applications, Proceedings of ABAQUS User??s Conference, New Port, Rhode Island, 2001, p 1; N. Rebelo and M. Perry, Finite Element Analysis for the Design of Nitinol Medical Devices, Min. Invas. Ther. Allied Technol., 2000, 9(2), p 75). Quality of simulation depends on a multitude of parameters such as the mathematical material model and FE model generation (meshing). As such, a superior material data input is crucial in order to calculate the correct stress and strain conditions. In this study, we used different sources for material data input for our FE simulations. We compared simulated output versus the experimental results using a stent-like structure after various heat treatments. We used NiTi literature data, tensile data from raw as-supplied NiTi tubes as well as tensile and compression data from microtest samples which underwent stent-like processing for our FEA modeling. A FEA model of the diamond shape (DS) was constructed to quantify and visualize the force and motion response after applying different loading conditions similar to physiologic stress and strain. Force-deflection response of the virtual model was compared against the differently processed DS specimen. All results were put into a matrix in order to evaluate the quality of the different inputs for the FEA. The goal of this study was to demonstrate the importance of selecting and applying the correct material parameter inputs and to further show the importance of not just using given parameter, but also calibrating the values to get accurate results of FE simulations.     

Pulsed Laser Deposition of Photoresponsive Two‐Dimensional GaSe Nanosheet Networks

Synthesis of functional metal chalcogenide (GaSe) nanosheet networks by stoichiometric transfer of laser‐vaporized material from bulk GaSe targets is presented. Uniform coverage of interconnected, crystalline, and photoresponsive GaSe nanosheets in both in‐plane and out‐of‐plane orientations are achieved under different ablation conditions. The propagation of the laser‐vaporized material is characterized by in situ ICCD‐imaging. High (1 Torr) Ar background gas pressure is found to be crucial for the stoichiometric growth of GaSe nanosheet networks. Individual 1–3 layer GaSe triangular nanosheets of ≈200 nm domain size are formed within 30 laser pulses, coalescing to form nanosheet networks in as few as 100 laser pulses. The thickness of the deposited networks increases linearly with pulse number, adding layers in a two‐dimensional (2D) growth mode. GaSe nanosheet networks show p‐type semiconducting characteristics with mobilities reaching as high as 0.1 cm²V^?1s^?1. Spectrally‐resolved photoresponsivities and external quantum efficiencies range from 0.4 AW^?1 and 100% at 700 nm, to 1.4 AW^?1 and 600% at 240 nm, respectively. Pulsed laser deposition under these conditions appears to provide a versatile and rapid approach to stoichiometrically transfer and deposit functional networks of 2D nanosheets with digital thickness control and uniformity for a variety of applications.     

Effects of dietary supplementation of vitamins D(3) and E on quality characteristics of pigs and longissimus muscle antioxidative capacity

The effects of addition of vitamin D₃ and vitamin E to pig diets on blood plasma calcium concentration, meat quality (longissimus muscle) and antioxidative capacity were investigated. Two treatments consisted of supplementation with vitamin D₃ (500,000 IU/d) for 5 days separately (group D) and a combination of vitamin E (500 mg α-tocopheryl acetate/kg diet) for 30 days and vitamin D₃ (500,000 IU/d) for 5 days (group D + E) to growing-finishing pigs before slaughter. Pigs fed with vitamin D₃ had higher (P < 0.01) plasma calcium concentration compared with control pigs. Dietary supplementation of vitamin E significantly (P < 0.05) increased the concentration of α-tocopherol in meat (longissimus muscle). Vitamin D₃ supplementation resulted in higher (P = 0.07) a^∗ values of loin chops at 5 days of storage. Vitamin D₃ and vitamin E supplementation did not affect other meat quality characteristics or tenderness (quantified by Warner–Bratzler shear force). Antioxidative capacity (measured as MDA production after incubation of longissimus muscle homogenates with Fe²⁺/ascorbate) was improved by vitamin E and partly by vitamin D₃ supplementation.     

Monoclinic Zirconia Bodies by Thermoplastic Ceramic Extrusion

Two ultrafine, undoped ZrO₂ powders with median primary particle sizes of 9 and 25 nm were used to prepare ceramic suspensions for thermoplastic extrusion. The organic vehicle consisted of an industrial-grade poly(ethylene- co -vinyl acetate) (EVA) or polyethylene (PE-HD) and decanoic acid as a dispersing agent. The powder volume loadings achieved were 44% and 52% by volume for the two powders, respectively. The amount of dispersant needed was calculated from a new model based on available chemisorption sites on the powder surface. Mixing and extrusion were conducted using a conventional modular plastic processing unit. Green bodies were dewaxed up to 450°C in an inert atmosphere and sintered to full density in air at 1060° and 1100°C, respectively. Analysis of the ceramic phase content and the microstructure of the bodies is presented.     

Die Rolle des Experiments in der Verfahrensentwicklung

Experiments in process development . Design data for the improvement of existing plants or for the development of new chemical processes are determined by experiments in laboratories or pilot plants. These frequently expensive testruns should lower the scaling-up risk for industrial plant and should ensure its long-term functioning and its economy. The various methods of scaling-up and the influence of errors are discussed. Some examples will show how an exact planning of the experiments can minimize the costs of development and product.