Design, Fabrication, and Characterization of a Shape Memory Polymer Embolic Device

Shape memory polymers (SMPs) are a unique class of smart materials that can remember two shapes, and can be remotely actuated to achieve a predefined shape by application of thermal energy. Porous scaffold of SMP foams enable high volume change up to 70 times. Use of these SMP foams in a minimally invasive treatment of cerebral aneurysms is of significant interest in the biomedical community. In the application of treating aneurysms, a spheroid SMP foam is envisioned to be compressed to a rod-like cylindrical secondary shape. The device in this secondary shape can then be delivered through a catheter to the aneurysm site and, once in the aneurysm, can be actuated to recover the primary shape to fill the aneurysmal protuberance. Blood is expected to infiltrate and clot within the porous internal structure of the expanded SMP foam, ultimately leading to complete isolation of the aneurysm from the parent artery through tissue healing. This study reports the functional characterization of SMP foam with respect to the design and the fabrication of the prototype embolic device for treatment of cerebral aneurysms. The pressure exerted by the expanding SMP foam on the aneurysms wall during the occlusion is estimated. Frictional loads between SMP foam and a catheter pathway are investigated. This is a critical factor in the feasibility of transcatheter delivery of a SMP foam device. Porcine in vitro and in vivo aneurysm models are used to test and validate the deployment process of the proposed device. Important aspects are studied and discussed, such as deliverability through a catheter, recovery of the primary shape by thermal actuation, and fluoroscopic visualization of the device during the delivery. Finally, the performance of SMP embolic device, which is the endovascular delivery and the occlusion of porcine aneurysms, are compared to performance of Guglielmi Detachable Coil that is considered as the standard treatment. 90 and 180 days follow-up studies present promising healing responses of the SMP treated aneurysm. This study forms an important step towards the realization of these devices in clinical practice

Geometric characterization of anomalous Landau levels of isolated flat bands

According to the Onsager's semiclassical quantization rule, the Landau levels of a band are bounded by its upper and lower band edges at zero magnetic field. However, there are two notable systems where the Landau level spectra violate this expectation, including topological bands and flat bands with singular band crossings, whose wave functions possess some singularities. Here, we introduce a distinct class of flat band systems where anomalous Landau level spreading (LLS) appears outside the zero-field energy bounds, although the relevant wave function is nonsingular. The anomalous LLS of isolated flat bands are governed by the cross-gap Berry connection that measures the wave-function geometry of multi bands. We also find that symmetry puts strong constraints on the LLS of flat bands. Our work demonstrates that an isolated flat band is an ideal system for studying the fundamental role of wave-function geometry in describing magnetic responses of solids.Comment: 10+8 pages, 5+3 figure

Expression of Functional Recombinant Mussel Adhesive Protein Mgfp-5 in Escherichia coli

Mussel adhesive proteins have been suggested as a basis for environmentally friendly adhesives for use in aqueous conditions and in medicine. However, attempts to produce functional and economical recombinant mussel adhesive proteins (mainly foot protein type 1) in several systems have failed. Here, the cDNA coding for Mytilus galloprovincialis foot protein type 5 (Mgfp-5) was isolated for the first time. Using this cDNA, we produced a recombinant Mgfp-5 fused with a hexahistidine affinity ligand, which was expressed in a soluble form in Escherichia coli and was highly purified using affinity chromatography. The adhesive properties of purified recombinant Mgfp-5 were compared with the commercial extracted mussel adhesive Cell-Tak by investigating adhesion force using atomic force microscopy, material surface coating, and quartz crystal microbalance. Even though further macroscale assays are needed, these microscale assays showed that recombinant Mgfp-5 has significant adhesive ability and may be useful as a bioadhesive in medical or underwater environments.X119196sciescopu

Financial Hurdles for Human Capital Accumulation: Revisiting the Galor-Zeira Model

Against the background of inconclusive evidence about the inequality–growth relation, this paper suggests that the level of inequality increases via the human capital channel with credit market imperfections and that this increasing inequality negatively affects economic growth. We expand the model presented by Galor and Zeira (1993) to represent the fact that the economy benefits from endogenous technological progress and that the government provides financial aid to reduce the financial hurdles for human capital accumulation. The presented empirical results, using Korean data from 1998 to 2008, imply that education plays a significant role in the divergence of household wealth over time and that the government’s financial aid package in the form of the new student loans program positively influences equality and short-run economic growth by promoting the number of skilled workers

Financial Hurdles for Human Capital Accumulation: Revisiting the Galor-Zeira Model

Against the background of inconclusive evidence about the inequality–growth relation, this paper suggests that the level of inequality increases via the human capital channel with credit market imperfections and that this increasing inequality negatively affects economic growth. We expand the model presented by Galor and Zeira (1993) to represent the fact that the economy benefits from endogenous technological progress and that the government provides financial aid to reduce the financial hurdles for human capital accumulation. The presented empirical results, using Korean data from 1998 to 2008, imply that education plays a significant role in the divergence of household wealth over time and that the government’s financial aid package in the form of the new student loans program positively influences equality and short-run economic growth by promoting the number of skilled workers

Wave-function geometry of band crossing points in two-dimensions

Geometry of the wave function is a central pillar of modern solid state physics. In this work, we unveil the wave-function geometry of two-dimensional semimetals with band crossing points (BCPs). We show that the Berry phase of BCPs are governed by the quantum metric describing the infinitesimal distance between quantum states. For generic linear BCPs, we show that the corresponding Berry phase is determined either by an angular integral of the quantum metric, or equivalently, by the maximum quantum distance of Bloch states. This naturally explains the origin of the $\pi$-Berry phase of a linear BCP. In the case of quadratic BCPs, the Berry phase can take an arbitrary value between 0 and $2\pi$. We find simple relations between the Berry phase, maximum quantum distance, and the quantum metric in two cases: (i) when one of the two crossing bands is flat; (ii) when the system has rotation and/or time-reversal symmetries. To demonstrate the implication of the continuum model analysis in lattice systems, we study tight-binding Hamiltonians describing quadratic BCPs. We show that, when the Berry curvature is absent, a quadratic BCP with an arbitrary Berry phase always accompanies another quadratic BCP so that the total Berry phase of the periodic system becomes zero. This work demonstrates that the quantum metric plays a critical role in understanding the geometric properties of topological semimetals.Comment: 7+9 pages, 4+1 figures, published versio