MOCVD-Fabricated TiO2 Thin Films: Influence of Growth Conditions on Fibroblast Cells Culture

TiO2 thin films with various morphologies were grown on Ti substrates by the LP-MOCVD technique (Low Pressure Chemical Vapour Deposition from Metal-Organic precursor), with titanium tetra-iso-propoxide as a precursor. All the films were prepared in the same conditions except the deposition time. They were characterized by X-ray diffraction, scanning electron microscopy, optical 15 interferometry, water contact angle measurements. MOCVD-fabricated TiO2 thin films are known to be adapted to cell culture for implant requirements. Human gingival fibroblasts were cultured on the various TiO2 deposits. Differences in cell viability (MTT tests) and cell spreading (qualitative assessment) were observed and related to film roughness, wettability and allotropic composition

Effects of Stone Size on the Comminution Process and Efficiency in Shock Wave Lithotripsy

The effects of stone size on the process and comminution efficiency in shock wave lithotripsy (SWL) are investigated by experiments, numerical simulations, and scale analysis. Cylindrical BegoStone phantoms with approximately equal height and diameter of either 4-, or 7- or 10-mm, in a total aggregated mass of about 1.5 g, were treated in an electromagnetic shock wave lithotripter field. The resultant stone comminution (SC) was found to correlate closely with the average peak pressure, P+(avg), incident on the stones. The P+(avg) threshold to initiate stone fragmentation in water increased from 7.9 to 8.8 to 12.7 MPa, respectively, when the stone size decreased from 10 to 7 to 4 mm. Similar changes in the P+(avg) threshold were observed for the 7- and 10-mm stones treated in 1,3-butanediol where cavitation is suppressed, suggesting that the observed size dependency is due to changes in stress distribution within different size stones. Moreover, the slope of the correlation curve between SC and ln(P‒+(avg)) in water increased with decreasing stone size, while the opposite trend was observed in 1,3-butanediol. The progression of stone comminution in SWL showed a size-dependency with the 7- and 10-mm stones fragmented into progressively smaller pieces while a significant portion (> 30%) of the 4-mm stones were stalemated within the size range of 2.8 ~ 4 mm even after 1,000 shocks. Analytical scaling considerations suggest size-dependent fragmentation behaviour, a hypothesis further supported by numerical model calculations that exhibit changing patterns of constructive and destructive wave interference, and thus variations in the maximum tensile stress or stress integral produced in cylindrical and spherical stone of different sizes

A consistent hierarchy of generalized kinetic equation approximations to the chemical master equation applied to surface catalysis

We develop a hierarchy of approximations to the master equation for systems that exhibit translational invariance and finite-range spatial correlation. Each approximation within the hierarchy is a set of ordinary differential equations that considers spatial correlations of varying lattice distance; the assumption is that the full system will have finite spatial correlations and thus the behavior of the models within the hierarchy will approach that of the full system. We provide evidence of this convergence in the context of one- and two-dimensional numerical examples. Lower levels within the hierarchy that consider shorter spatial correlations, are shown to be up to three orders of magnitude faster than traditional kinetic Monte Carlo methods (KMC) for one-dimensional systems, while predicting similar system dynamics and steady states as KMC methods. We then test the hierarchy on a two-dimensional model for the oxidation of CO on RuO2(110), showing that low-order truncations of the hierarchy efficiently capture the essential system dynamics. By considering sequences of models in the hierarchy that account for longer spatial correlations, successive model predictions may be used to establish empirical approximation of error estimates. The hierarchy may be thought of as a class of generalized phenomenological kinetic models since each element of the hierarchy approximates the master equation and the lowest level in the hierarchy is identical to a simple existing phenomenological kinetic models

A Laboratory Investigation of Supersonic Clumpy Flows: Experimental Design and Theoretical Analysis

We present a design for high energy density laboratory experiments studying the interaction of hypersonic shocks with a large number of inhomogeneities. These ``clumpy'' flows are relevant to a wide variety of astrophysical environments including the evolution of molecular clouds, outflows from young stars, Planetary Nebulae and Active Galactic Nuclei. The experiment consists of a strong shock (driven by a pulsed power machine or a high intensity laser) impinging on a region of randomly placed plastic rods. We discuss the goals of the specific design and how they are met by specific choices of target components. An adaptive mesh refinement hydrodynamic code is used to analyze the design and establish a predictive baseline for the experiments. The simulations confirm the effectiveness of the design in terms of articulating the differences between shocks propagating through smooth and clumpy environments. In particular, we find significant differences between the shock propagation speeds in a clumpy medium compared to a smooth one with the same average density. The simulation results are of general interest for foams in both inertial confinement fusion and laboratory astrophysics studies. Our results highlight the danger of using average properties of inhomogeneous astrophysical environments when comparing timescales for critical processes such as shock crossing and gravitational collapse times.Comment: 7 pages, 6 figures. Submitted to the Astrophysical Journal. For additional information, including simulation animations and the pdf and ps files of the paper with embedded high-quality images, see http://pas.rochester.edu/~wm

Localized compliance measurement of the airway wall using anatomic optical coherence elastography

We describe an elastographic method to circumferentially-resolve airway wall compliance using endoscopic, anatomic optical coherence tomography (aOCT) combined with an intraluminal pressure catheter. The method was first demonstrated on notched silicone phantoms of known elastic modulus under respiratory ventilation, where localized compliance measurements were validated against those predicted by finite element modeling. Then, ex vivo porcine tracheas were scanned, and the pattern of compliance was found to be consistent with histological identification of the locations of (stiff) cartilage and (soft) muscle. This quantitative method may aid in diagnosis and monitoring of collapsible airway wall tissues in obstructive respiratory disorders

Designing Plasmon-Enhanced Thermochromic Films Using a Vanadium Dioxide Nanoparticle Elastomeric Composite

Vanadium dioxide (VO2) is a common material for use in thermochromic windows due to a semiconductor-to-metal transition (SMT) that is coupled with a change in infrared opacity. Commercialization of VO2-based thermochromic technology is hampered by relatively expensive synthesis and film fabrication techniques as well as overall low performance as a window material. Here, simulations that indicate the plasmon resonance of VO2 nanoparticles in a composite film, which can be tuned to achieve record performance values, are reported. These simulations are experimentally verified by fabricating a VO2 nanoparticle composite in an elastomeric matrix using low-temperature and atmospheric processing conditions. The optical properties of the films are analyzed, yielding visible transmittance and infrared modulation values within the range of top-performing thermochromic windows. In addition, an improvement in performance is observed upon stretching the films, an effect that can be attributed to a local refractive index modulation. The results highlight the potential use of elastomeric composites as a low-cost route to higher-performance smart windows

Improving the lens design and performance of a contemporary electromagnetic shock wave lithotripter.

The efficiency of shock wave lithotripsy (SWL), a noninvasive first-line therapy for millions of nephrolithiasis patients, has not improved substantially in the past two decades, especially in regard to stone clearance. Here, we report a new acoustic lens design for a contemporary electromagnetic (EM) shock wave lithotripter, based on recently acquired knowledge of the key lithotripter field characteristics that correlate with efficient and safe SWL. The new lens design addresses concomitantly three fundamental drawbacks in EM lithotripters, namely, narrow focal width, nonidealized pulse profile, and significant misalignment in acoustic focus and cavitation activities with the target stone at high output settings. Key design features and performance of the new lens were evaluated using model calculations and experimental measurements against the original lens under comparable acoustic pulse energy (E+) of 40 mJ. The -6-dB focal width of the new lens was enhanced from 7.4 to 11 mm at this energy level, and peak pressure (41 MPa) and maximum cavitation activity were both realigned to be within 5 mm of the lithotripter focus. Stone comminution produced by the new lens was either statistically improved or similar to that of the original lens under various in vitro test conditions and was significantly improved in vivo in a swine model (89% vs. 54%, P = 0.01), and tissue injury was minimal using a clinical treatment protocol. The general principle and associated techniques described in this work can be applied to design improvement of all EM lithotripters

Sensing Inhalation Injury-Associated Changes in Airway Wall Compliance by Anatomic Optical Coherence Elastography

Quantitative methods for assessing the severity of inhalation (burn) injury are needed to aid in treatment decisions. We hypothesize that it is possible to assess the severity of injuries on the basis of differences in the compliance of the airway wall. Here, we demonstrate the use of a custom-built, endoscopic, anatomic optical coherence elastography (aOCE) system to measure airway wall compliance. The method was first validated using airway phantoms, then performed on ex vivo porcine tracheas under varying degrees of inhalation (steam) injury. A negative correlation between aOCE-derived compliance and severity of steam injuries is found, and spatially-resolved compliance maps reveal regional heterogeneity in airway properties