Healing Pattern Analysis for Dental Implants Using the Mechano-Regulatory Tissue Differentiation Model

(1) Background: Our aim is to reveal the influence of the geometry designs on biophysical stimuli and healing patterns. The design guidelines for dental implants can then be provided. (2) Methods: A two-dimensional axisymmetric finite element model was developed based on mechano-regulatory algorithm. The history of tissue differentiation around eight selected implants can be predicted. The performance of the implants was evaluated by bone area (BA), bone-implant contact (BIC); (3) Results: The predicted healing patterns have very good agreement with the experimental observation. Many features observed in literature, such as soft tissues covering on the bone-implant interface; crestal bone loss; the location of bone resorption bumps, were reproduced by the model and explained by analyzing the solid and fluid biophysical stimuli and (4) Conclusions: The results suggested the suitable depth, the steeper slope of the upper flanks, and flat roots of healing chambers can improve the bone ingrowth and osseointegration. The mechanism related to solid and fluid biophysical stimuli were revealed. In addition, the model developed here is efficient, accurate and ready to extend to any geometry of dental implants. It has potential to be used as a clinical application for instant prediction/evaluation of the performance of dental implants.     

The effects of silver nitrate on the structure and properties of polyurethanes containing pyridyl units

In this study, 2,6-pyridinedimethanol was used as a chain extender to synthesize a new polyurethane, PDM-PU. Further, various amounts of silver nitrate were incorporated to produce PDM-PU/AgNO₃ complexes. FT-IR and UV–Vis analyses confirm the formation of complex in the PDM-PU/AgNO₃. DSC and DMA results show that the glass transition temperature (T _g), dynamic T _g and storage modulus at 25 °C of the PDM-PU/AgNO₃ complexes increase with increasing AgNO₃ content. This is due to the formation of complex structure that can restrict the segmental motion of polymer chains. The TGA and stress–strain test results show that the thermal decomposition temperature, tensile strength and elongation at break increase with the AgNO₃ content initially. Then, they decrease inversely. This indicates that the formation of complex structure raises these properties when the AgNO₃ content is below certain value. But as more coordinate bonds were formed, the specimens become brittle. In addition, the crosslink effect caused by coordinate bonds inhibits the dissolution of polymer chains and thereby reduces the swelling degree of the complexes in solvent. Furthermore, AgNO₃ imparts antibacterial activity against S. aureus and K. pneumoniae to the complexes     

Flow pattern maps and transition criteria for flow boiling of binary mixtures in a diverging microchannel

This paper presents a visualization study of flow boiling of binary mixtures (methanol–water and ethanol–water mixtures) in a diverging microchannel. The flow pattern and transition criteria are studied in terms of effects of mass flux, heat flux, and molar fraction of the more volatile component (i.e., methanol or ethanol). Four boiling regimes are identified: bubbly-elongated slug flow, annular flow, liquid film breakup, and dryout. Further, generalized flow pattern maps are constructed using coordinates of nondimensional parameter space (boiling number, Weber number, and Marangoni number), wherein relatively distinct boundaries between the flow patterns are identified. Criteria for transitions between flow patterns are proposed in the form of nondimensional groups and are successfully used to predict the experimental results. More than 92% of the data are correctly located within transition boundaries. The criterion for the onset of nucleate boiling—the boundary between single-phase flow and bubbly-elongated slug flow—is also determined for both methanol–water and ethanol–water mixtures on the basis of the same set of nondimensional parameters.     

How to manipulate the electrospinning jet with controlled properties to obtain uniform fibers with the smallest diameter?—a brief discussion of solution electrospinning process

Solutions of five different polymers, namely, polystyrene (PS), polyacrylonitrile (PAN), polyhydroxybutrate (PHB), poly(D-L-lactic acid) (PLA), and Nylon6, were used to investigate their rheological properties on the electrospinnability. In order to effectively reduce the diameter of electrospun fibers, polymers with higher molecular weights (MW) were needed to develop entangled solutions at much lower concentrations and with viscosities as low as that of a pure solvent. A minimum polymer concentration 1.0–2.0 times larger than the entanglement concentration was required to prepare the bead-free fibers. Using this strategy, uniform PS fibers with the lowest ever diameter of ∼15 nm were successfully obtained using an MW of 3 × 10⁷ g/mol at a concentration of 0.1 vol.%. For a given electrospinning solution, processing variables of low flow-rate (Q) and high voltage (V) were desirable in obtaining fibers with small diameters. However, Q and V were correlated by a power law relation: V∼Q ^a, wherein the exponent a had a value of 0.1–0.4, which was relevant with the solution types. Based on the finite element analysis (FEA), a significant measure of electric field (E) occurred around the needle tip used in the experiment, and its magnitude decayed with increasing distance from the needle end (z): E∼z ⁻ⁿ. The exponent n was 1.0–2.0, depending on the needle–plate geometry, i.e., needle length, needle diameter (D _o ), plate diameter, and tip-to-plate distance (H). According to FEA results, H exhibited negligible effects on the electric field in the region of interest, i.e., z/D _o ∼1 to 10. Due to the presence of high measures of E at the needle end, approaches to render a shorter and thinner straight jet issuing from the Taylor cone to yield thinner fibers were sought because a more significant jet stretching in the “jet whipping region” can take place. A feasible route to predict the as-spun fiber diameter produced by the manipulation of the electrified jet is provided by experimentally measuring the jet diameter and numerically calculating the electric field for the jet whipping process.     

Dislocation multiplication inside contact holes

Ion implantation into contact holes has been widely used to dope the specific contact area and to reduce the contact resistance. In this study, mask edge defects were observed at the edge area of small contact holes with high aspect ratio, which resulted in multiplied dislocations penetrating into Si substrate for more than 0.3 μm after back-end processings. Those dislocations were identified to be Schockley partial dislocations and stair rod dislocations lying on 4 sets of inclined {111}Si planes.     

Compatible and crystallization properties of poly(lactic acid)/poly(butylene adipate‐co‐terephthalate) blends

Differential scanning calorimetry (DSC), wide angle X‐ray diffraction (WAXD) and dynamic mechanical analysis (DMA) properties of poly(lactic acid)/ poly(butylene adipate‐co‐terephthalate) (PLA/PBAT) specimens suggest that only small amounts of poor PLA and/or PBAT crystals are present in their corresponding melt crystallized specimens. In fact, the percentage crystallinity, peak melting temperature and onset re‐crystallization temperature values of PLA/PBAT specimens reduce gradually as their PBAT contents increase. However, the glass transition temperatures of PLA molecules found by DSC and DMA analysis reduce to the minimum value as the PBAT contents of PLA_xPBAT_y specimens reach 2.5 wt %. Further morphological and DMA analysis of PLA/PBAT specimens reveal that PBAT molecules are miscible with PLA molecules at PBAT contents equal to or less than 2.5 wt %, since no distinguished phase‐separated PBAT droplets and tan δ transitions were found on fracture surfaces and tan δ curves of PLA/PBAT specimens, respectively. In contrast to PLA, the PBAT specimen exhibits highly deformable properties. After blending proper amounts of PBAT in PLA, the inherent brittle deformation behavior of PLA was successfully improved. Possible reasons accounting for these interesting crystallization, compatible and tensile properties of PLA/PBAT specimens are proposed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Portrait Vision Fusion for Augmented Reality

Kinect(+openCV); Dynamic portrait segmentation; Skeletal tracking; Edge transparent processing; Video interactive     

The Parallel Image Processing Environment (PIPE): automated parallelization of satellite data analyses

A Beowulf‐type cluster can: (1) mitigate many issues associated with the analysis of large, complex remotely sensed data sets; (2) shorten the response time of operational agencies to crisis‐management situations; and (3) expedite the reanalysis of large archives of satellite data. Whereas most Beowulf‐type designs support modeling applications, the Parallel Image Processing Environment (PIPE) addresses the unique requirements of remote sensing applications. PIPE has four hierarchical layers: hardware, operating system, middleware and applications. Rocks, a middleware sublayer, manages the cluster. DIAL‐developed interprocess communication and control daemons form the second middleware sublayer. They encapsulate user‐defined applications and thereby support automated, user‐transparent parallelization of satellite data analyses, implemented in the applications layer using generalized constructs. The daemons also monitor resource (computational and I/O) utilization on a node/thread basis, a feature not supported by other generally available monitoring utilities. The application support libraries are fully extensible, facilitate the reuse of modular and commonly used software functions in new applications and thereby reduce both the cost and time to implement new applications. Two applications (signal analysis, image classification) show PIPE's versatility and performance characteristics. PIPE is intrinsically scalable, reliable and can be incrementally implemented. A comparison with other embarrassingly parallel systems is also provided. Copyright © 2006 John Wiley & Sons, Ltd.     

A packing algorithm for three-dimensional convex particles

Simulation of granular particles is an important tool in many fields. However, simulation of particles of complex shapes remains largely out of reach even in two-dimension. One of the major hurdles is the difficulty in representing particles in an efficient, flexible, and accurate manner. By representing particles as convex polyhedrons which are themselves the intersection of a set of half spaces, we develop a method that allows one to efficiently carry out key operations, including particle–particle and particle–container wall overlapping detection, precise identification of the overlapping region, particle shifting, particle rotation, and others. The simulation of packing 1,000 particles into a container takes only a few minutes with this approach. We further demonstrate the potential of this approach with a simulation that re-generates the “Brazil nut” phenomenon by mixing and shaking particles of two different sizes.