Synthesis and Characterization of Microparticles for Templating Porous Shape Memory Polymer Scaffolds

Shape memory polymers (SMPs) are proposed for use in a variety of medical devices, such as neural and peripheral embolism coils for aneurysm occlusion. These “smart” materials have unique advantages over shape memory alloys, such as light weight, large shape recovery of up to 400% plastic strain, nontoxicity, nonmutagenicity, ease of processing. and low cost. Processing SMPs into porous forms increases their potential for use in a number of applications due to unique properties, such as increased thermal and electrical insulation, large volume changes on recovery from compressive strain, and low density. Current SMP foams utilize a gas blowing technique to create the pores. This method results in inhomogeneous pore sizes and may result in shearing of the foams. By templating the SMP foam matrix with microparticles of controlled diameters, we hypothesize that we will be able to finely tune pore sizes within a set range and ensure pore interconnectivity. Here, we fabricated alginate microparticles using a co-flow emulsion technique. The microparticles were sieved to a size range of 75 – 125 μm before utilizing them to template poly(dimethyl siloxane) (PDMS) matrices. The resulting polymer matrices were characterized in terms of pore size and morphology. We found that utilizing the microparticles to template the matrices resulted in an interconnected pore matrix with homogeneous pores, which we hypothesize will allow for controlled expansion of the matrix. These results found using PDMS matrix will lay the groundwork for future generation of SMP foams with controlled porosity, reduced risk of shearing, and enhanced material properties for a variety of medical applications

Synthesis and Characterization of Microparticles for Templating Porous Shape Memory Polymer Scaffolds

Shape memory polymers (SMPs) are proposed for use in a variety of medical devices, such as neural and peripheral embolism coils for aneurysm occlusion. These “smart” materials have unique advantages over shape memory alloys, such as light weight, large shape recovery of up to 400% plastic strain, nontoxicity, nonmutagenicity, ease of processing. and low cost. Processing SMPs into porous forms increases their potential for use in a number of applications due to unique properties, such as increased thermal and electrical insulation, large volume changes on recovery from compressive strain, and low density. Current SMP foams utilize a gas blowing technique to create the pores. This method results in inhomogeneous pore sizes and may result in shearing of the foams. By templating the SMP foam matrix with microparticles of controlled diameters, we hypothesize that we will be able to finely tune pore sizes within a set range and ensure pore interconnectivity. Here, we fabricated alginate microparticles using a co-flow emulsion technique. The microparticles were sieved to a size range of 75 – 125 μm before utilizing them to template poly(dimethyl siloxane) (PDMS) matrices. The resulting polymer matrices were characterized in terms of pore size and morphology. We found that utilizing the microparticles to template the matrices resulted in an interconnected pore matrix with homogeneous pores, which we hypothesize will allow for controlled expansion of the matrix. These results found using PDMS matrix will lay the groundwork for future generation of SMP foams with controlled porosity, reduced risk of shearing, and enhanced material properties for a variety of medical applications

Universal relaxational dynamics of gapped one dimensional models in the quantum sine-Gordon universality class

A semiclassical approach to the low-temperature real time dynamics of generic one-dimensional, gapped models in the sine-Gordon model universality class is developed. Asymptotically exact universal results for correlation functions are obtained in the temperature regime T << Delta, where Delta is the energy gap.Comment: 4 pages, 1 figur

Cyclic mutually unbiased bases, Fibonacci polynomials and Wiedemann's conjecture

We relate the construction of a complete set of cyclic mutually unbiased bases, i. e., mutually unbiased bases generated by a single unitary operator, in power-of-two dimensions to the problem of finding a symmetric matrix over F_2 with an irreducible characteristic polynomial that has a given Fibonacci index. For dimensions of the form 2^(2^k) we present a solution that shows an analogy to an open conjecture of Wiedemann in finite field theory. Finally, we discuss the equivalence of mutually unbiased bases.Comment: 11 pages, added chapter on equivalenc

Symmetric extendibility for qudits and tolerable error rates in quantum cryptography

Symmetric extendibility of quantum states has recently drawn attention in the context of quantum cryptography to judge whether quantum states shared between two distant parties can be purified by means of one-way error correction protocols. In this letter we study the symmetric extendibility in a specific class of two-qudit states, i. e. states composed of two d-level systems, in order to find upper bounds on tolerable error rates for a wide class of qudit-based quantum cryptographic protocols using two-way error correction. In important cases these bounds coincide with previously known lower bounds, thereby proving sharpness of these bounds in arbitrary finite-dimensional systems.Comment: 4 pages, no figure

Primary ovarian ectopic pregnancy: early diagnosis is the key

Ectopic pregnancy means implantation of the embryo outside the uterine cavity. It may occur in the fallopian tubes, ovaries or the cervix. Primary ovarian ectopic is a very rare condition. In such cases preservation of ovary is extremely important, particularly in patients with infertility. We report a case of primary ovarian ectopic which was managed conservatively in a patient of primary infertility. Preservation of ovary is extremely important, particularly in patients with infertility

Sildenafil citrate to improve colour doppler indices in patient with pre-eclampsia: a path less taken

Presented a case of high-risk pregnancy of an elderly primigravida who had abnormal colour doppler indices. Addition of sildenafil citrate lead to improvement of colour doppler indices and growth parameters, thus prolonging the period of gestation by 6 weeks. This led to decreased neonatal ICU stay and reduction in neonatal morbidity

Symmetry breaking perturbations and strange attractors

The asymmetrically forced, damped Duffing oscillator is introduced as a prototype model for analyzing the homoclinic tangle of symmetric dissipative systems with \textit{symmetry breaking} disturbances. Even a slight fixed asymmetry in the perturbation may cause a substantial change in the asymptotic behavior of the system, e.g. transitions from two sided to one sided strange attractors as the other parameters are varied. Moreover, slight asymmetries may cause substantial asymmetries in the relative size of the basins of attraction of the unforced nearly symmetric attracting regions. These changes seems to be associated with homoclinic bifurcations. Numerical evidence indicates that \textit{strange attractors} appear near curves corresponding to specific secondary homoclinic bifurcations. These curves are found using analytical perturbational tools

Stickiness in Hamiltonian systems: from sharply divided to hierarchical phase space

We investigate the dynamics of chaotic trajectories in simple yet physically important Hamiltonian systems with non-hierarchical borders between regular and chaotic regions with positive measures. We show that the stickiness to the border of the regular regions in systems with such a sharply divided phase space occurs through one-parameter families of marginally unstable periodic orbits and is characterized by an exponent \gamma= 2 for the asymptotic power-law decay of the distribution of recurrence times. Generic perturbations lead to systems with hierarchical phase space, where the stickiness is apparently enhanced due to the presence of infinitely many regular islands and Cantori. In this case, we show that the distribution of recurrence times can be composed of a sum of exponentials or a sum of power-laws, depending on the relative contribution of the primary and secondary structures of the hierarchy. Numerical verification of our main results are provided for area-preserving maps, mushroom billiards, and the newly defined magnetic mushroom billiards.Comment: To appear in Phys. Rev. E. A PDF version with higher resolution figures is available at http://www.pks.mpg.de/~edugal