Water Content and Thermoplastic Polyurethane Effects on Thrombosis Clotting

One of the main factors that can increase the chance of heart disease is unwanted blood clotting, or thrombosis. In addition, implantable biomaterials and/or medical devices are likely to trigger a series of adverse reactions that can lead to unwanted blood clotting. Herein, we study a thromboresistant polymeric material, specifically thermoplastic polyurethanes (TPUs), on their physical properties and anticoagulation performance. Their hydrophobic nature and superior mechanical properties make them an ideal candidate for coating materials on implantable medical devices, such as vascular stents. Our results show that hydrophobic TPUs absorbed minimal to negligible water content and provided excellent thromboresistant properties against human plasma.Cockrell School of Engineerin

Prevention Strategies of Traumatic Brain Injury in Football Players

In this project, we study the effects of the impact angle during a helmet-to-helmet collision on stress distribution and deacceleration values of the brain tissue in efforts to reduce brain injuries for football players. The overall goal is to provide sufficient information to improve the design of helmet technology. In addition, our study will be able to inform the athletes to avoid a helmet-to-helmet collision, such that, they can be trained to shift their heads in the horizontal direction to create a “glancing blow” effect. It is suggested that by avoiding a helmet-to-helmet collision, both rotational acceleration and stress can be reduced leading to a lower probability of receiving concussions and subsequent brain injuries [1].Cockrell School of Engineerin

Fabrication and Characterization of Electrospun Drug-eluting Nanofibers from Polycaprolactone/Chitosan Blends

Electrospinning has emerged as a widely accepted technique with ability to produce nanofibers that can be employed in many biomedical applications. In particular, drug-eluting nanofibers have become very popular in controlled release of small molecule drugs. In this study, nanofibers from blends of polylactocaprone (PCL) and chitosan (CHI) were electrospun with the ability to load a model drug, acetylsalicylic acid (ASA), at 10 wt%. PCL/CHI fibers exhibited smooth surface morphology at polymer compositions ranging from 100/0 to 40/60 with or without the incorporation of ASA. Mechanical properties suggested a brittle failure mechanism for fibers loaded with drug. In vitro drug release study displayed a controlled release profile of ASA up to 48 h. Our study aims to explore the drug-polymer interactions and their effects on fiber structure, mechanical properties and drug release profile.Cockrell School of Engineerin

Analysis of Service-Retrieved TBC-Coated Industrial Gas Turbine Components

Thermal barrier coatings (TBCs) have been widely used in gas turbine applications such as aerospace and power generation. TBC systems serve numerous purposes – the bond coat acts as a sacrificial layer for oxidation and the ceramic top coat works together with internal cooling systems to protect the superalloys from extreme temperature environments. With the rising demand for better fuel efficiency, the hot gas temperature within modern gas turbine engines has exceeded the working temperature of most advanced superalloys. The state-of-the-art TBCs have raised the high temperature capabilities of modern superalloys to a new level and have become an absolute necessity in modern gas turbine applications. While most research focus on the improvements of TBCs, the present study examines the environmental attacks which could lead to failures of TBCs. To be more exact, sand and dust particles often enter the mainstream hot gas flow path of gas turbines due to the powerful suction of its compressors, and internally generated particles, such as wear debris of the components, also could enter the mainstream hot gas flow path of the gas turbine. Once these particles (external and internal) pass through the combustion stage of the gas turbine engine, some of these particles become molten and adhere onto the surface of TBC-coated turbine components. These sand particles and debris gradually build-up in thickness and cause discoloration on the TBC surface. In some cases, the accumulated deposits could reduce the lifetime of TBCs. In other cases where particles carried by the mainstream hot gas flow path remain in solid state after passing through the hot combustion stage, such solid particles are very likely to impact the TBC coated turbine components, mainly the nozzle guide vanes and turbine blades right after the combustion chamber, damaging the TBCs. Since the gas stream inside the gas turbine engine travels at a high velocity, even micron size particles could build-up high kinetic energies. Upon striking the TBCs, these particles wear down the thickness of the TBCs, reducing its thermal insulation capability. Ex-service roll one (R1) turbine nozzle guide vanes and second stage turbine blades were retrieved from a land-based gas turbine for power generation and an aero-engine for transportation respectively, and the three nozzle guide vanes received were contaminated with surface deposits of various colours, while the turbine blades suffered from erosion and foreign object damage. These turbine components were analyzed using laboratory techniques, primarily by scanning electron microscopy with energy dispersive X-ray analysis and X-ray diffraction. In addition, heat treatment tests are also conducted to study the effect of these environmental attacks on the performance and lifetime of TBCs to determine the response of the deposit to prolonged thermal exposure

Decoherence Patterns of Topological Qubits from Majorana Modes

We investigate the decoherence patterns of topological qubits in contact with the environment by a novel way of deriving the open system dynamics other than the Feynman-Vernon. Each topological qubit is made of two Majorana modes of a 1D Kitaev's chain. These two Majorana modes interact with the environment in an incoherent way which yields peculiar decoherence patterns of the topological qubit. More specifically, we consider the open system dynamics of the topological qubits which are weakly coupled to the fermionic/bosonic Ohmic-like environments. We find atypical patterns of quantum decoherence. In contrast to the cases of non-topological qubits for which they always decohere completely in all Ohmic-like environments, the topological qubits decohere completely in the Ohmic and sub-Ohmic environments but not in the super-Ohmic ones. Moreover, we find that the fermion parities of the topological qubits though cannot prevent the qubit states from decoherence in the sub-Ohmic environments, can prevent from thermalization turning into Gibbs state. We also study the cases in which each Majorana mode can couple to different Ohmic-like environments and the time dependence of concurrence for two topological qubits.Comment: 20 pages, 10 figures; v2 ref updated to match NJP versio

Coexistence of the Electron Cooper Pair and Antiferromagnetic Short-Range Correlation in Copper Oxide Materials

Within the fermion-spin theory, the physical properties of the electron pairing state in the copper oxide materials are discussed. According to the common form of the electron Cooper pair, it is shown that there is a coexistence of the electron Cooper pair and magnetic short-range correlation, and hence the antiferromagnetic short-range correlation can persist into the superconducting state. Moreover, the mean-field results indicate that the electron pairing state originating from the pure magnetic interaction in the two-dimensional t-J model is the local state, and then does not reveal the true superconducting ground-state.Comment: 6 pages, Revtex, Four figures are adde

Quantum Decoherence with Holography

Quantum decoherence is the loss of a system's purity due to its interaction with the surrounding environment. Via the AdS/CFT correspondence, we study how a system decoheres when its environment is a strongly-coupled theory. In the Feynman-Vernon formalism, we compute the influence functional holographically by relating it to the generating function of Schwinger-Keldysh propagators and thereby obtain the dynamics of the system's density matrix. We present two exactly solvable examples: (1) a straight string in a BTZ black hole and (2) a scalar probe in AdS$_5$. We prepare an initial state that mimics Schr\"odinger's cat and identify different stages of its decoherence process using the time-scaling behaviors of R\'enyi entropy. We also relate decoherence to local quantum quenches, and by comparing the time evolution behaviors of the Wigner function and R\'enyi entropy we demonstrate that the relaxation of local quantum excitations leads to the collapse of its wave-function.Comment: 55 pages, 13 figures; v2 47 pages & 13 figs, minor revision to match published versio