We investigate evaporative lithography as a route for patterning colloidal films. Films are dried beneath a mask that induces periodic variations between regions of free and hindered evaporation. Direct imaging reveal...
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We investigate evaporative lithography as a route for patterning colloidal films. Films are dried beneath a mask that induces periodic variations between regions of free and hindered evaporation. Direct imaging reveals that particles segregate laterally within the film, as fluid and entrained particles migrate towards regions of higher evaporative flux. The films exhibit remarkable pattern formation that can be regulated by tuning the initial suspension composition, separation distance between the mask and underlying film, and mask geometry.
In cartilage tissue engineering, as a cell source, adult stem cells are very attractive for clinical applications. Recent studies suggest that human adipose tissue-derived stromal cells (ASCs) have multilineage potent...
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In cartilage tissue engineering, as a cell source, adult stem cells are very attractive for clinical applications. Recent studies suggest that human adipose tissue-derived stromal cells (ASCs) have multilineage potential similar to bone marrow-derived stromal cells (BMSCs). ASCs are obtained from adipose tissue easily isolated by suction-assisted lipectomy in various body parts. Also, as one of major factors of cartilage tissue engineering, scaffolds have an important role in cartilage formation. Poly(L-lactide-co-Ε-carprolactone) scaffolds have physiological activity, biodegradability, high cell affinity, and mechano-activity. The object of this study is cartilaginous tissue formation using highly elastic PLCL scaffolds and ASCs in vitro and in vivo. Poly(L-lactide-co-Ε-carprolactone) copolymers were synthesized from lactide and Ε-carprolactone in the presence of stannous octoate as catalyst. The scaffolds with 85% porosity and 300-500μm pore size were fabricated by gel-pressing method. ASCs were seeded on scaffolds and cultured for 21days in vitro. Cell/polymer constructs were characterized by reverse transcriptase-polymerase chain reaction for confirming differentiation to chondrocytes onto PLCL scaffolds. Also, for examining cartilaginous tissue formation in vivo, ASCs seeded scaffolds which were induced chondrogenesis for 2 weeks were implanted in nude mice subcutaneously for up to 8weeks. Histological studies showed that implants partially developed cartilaginous tissue within lacunae. And there was an accumulation of sulfated glycoaminoglycans. Immunohistochemical analysis revealed that implants were positively stained for specific extracellular matrix. These results indicate that ASCs and PLCL scaffols could be used to cartilage tissue engineering.
Thin‐film EXAFS samples have been fabricated using semiconductor‐processing and wet‐chemical etching techniques to eliminate artifacts associated with transmission and fluorescence measurements. Examples include cr...
Thin‐film EXAFS samples have been fabricated using semiconductor‐processing and wet‐chemical etching techniques to eliminate artifacts associated with transmission and fluorescence measurements. Examples include crystalline GexSi1−x alloys, amorphous GaAs and Cu and Au nanocrystals in SiO2. In general, thin films of several microns thickness were first formed on bulk substrates then EXAFS samples were fabricated by separating the thin film and substrate. For transmission measurements, thin films were stacked together to yield the optimum absorption while sample inhomogeneity, non‐uniformity and non‐continuity were readily eliminated. For fluorescence measurements, scattering/diffraction from the substrate was eliminated and stacking the thin films together increased the areal concentration of the absorber. The use of such techniques to fabricate EXAFS samples yielded a significant increase in accessible photo‐electron wave number range and hence more accurate structural parameter determinations.
The introduction of inorganic nanomaterials as additives into polymer matrix systems has resulted in polymer nanostructured materials exhibiting multi-functional, high performance polymer characteristics beyond what t...
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ISBN:
(纸本)1934551007
The introduction of inorganic nanomaterials as additives into polymer matrix systems has resulted in polymer nanostructured materials exhibiting multi-functional, high performance polymer characteristics beyond what traditional polymer composites possess. Multi-functional features attributable to polymer nanocomposites consist of improved thermal resistance, flame resistance, moisture resistance, decreased permeability, charge dissipation, and chemical resistance. Through control/alteration of the additive at the nanoscale level, one is able to maximize property enhancement of selected polymer systems to meet or exceed the requirements of current military, aerospace, and commercial applications. In this study, Lonza Corporation's PT-15 cyanate ester, a low viscosity, high performance resin system was mixed with Carbon Nanotechnologies' buckytubes to create a new type of cyanate ester-buckytubes nanocomposite. The IKA high shear mixer was used to uniformly disperse the nanoparticles in the resin matrix. Several processing parameters such as mixing speed and mixing duration were examined to produce optimal dispersion of nanoparticles into the resin matrix. Polymer nanocomposites morphological microstructures are characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) to determine whether nanoparticles are distributed uniformly within the polymer matrix. Thermogravimetric analysis (TGA) was used to study the thermal stability of these nanocomposites. Differential scanning calorimeter (DSC) was used to determine the Tg of the polymer nanocomposites. Further processing-structure- property relationships of these novel polymer nanocomposites will be discussed.
Magnesium castings are experiencing increased use in the transportation industry because of their high strength to weight ratio, high stiffness, and excellent castability. The casting characteristics allow complicated...
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The locally wall thinned phenomenon of pipes is simulated as metal loss due to erosion/corrosion. Therefore, fracture behaviors of pipes with local wall thinning are very important for the integrity of nuclear power p...
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The locally wall thinned phenomenon of pipes is simulated as metal loss due to erosion/corrosion. Therefore, fracture behaviors of pipes with local wall thinning are very important for the integrity of nuclear power plant. In this study, monotonic bending tests without internal pressure are conducted on 1.91-inch diameter Schedule 80 STS370 full-scale carbon steel pipe specimens. We investigated fracture strengths and failure modes of locally wall thinned pipes that welded and unwelded by four point bending test. From test results, we could be divided three types of failure modes.
Substantial R&D activities are presently under way toward the development of advanced pulsed-laser-based production tools and processes that can enable sophisticated yet effective crystallization of Si films for m...
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We report an observation of low-temperature, athermal, ion-induced decay of infrared-active bond-center hydrogen (BCH) in silicon. Specifically, the infrared intensity of BCH is found to decay monotonically as a funct...
We report an observation of low-temperature, athermal, ion-induced decay of infrared-active bond-center hydrogen (BCH) in silicon. Specifically, the infrared intensity of BCH is found to decay monotonically as a function of ion dose with a decay constant determined by the electronic energy deposited by each ion. Our data indicate that ion-induced decay of BCH results in a different final configuration when compared to the thermal decay process. These findings provide insight into the structure and stability of hydrogen related defects in silicon, and thus have implications for the reliability of state-of-the-art semiconductor devices, radiation damage, and ion-beam characterization studies of hydrogen containing solids.
The pressure dependence of the magnetic transitions in the giant magnetocaloric materials Gd5(SixGe1−x)4 (x=0.125,0.5) has been investigated using x-ray magnetic circular dichroism (XMCD) measurements in a diamond anv...
The pressure dependence of the magnetic transitions in the giant magnetocaloric materials Gd5(SixGe1−x)4 (x=0.125,0.5) has been investigated using x-ray magnetic circular dichroism (XMCD) measurements in a diamond anvil cell (DAC). We found that the most notable features of the x−T phase diagram are also present in the P−T phase diagram. These include a nearly linear increase in Curie temperature, Tc, with increasing both x and P up to 275K, and a discontinuity accompanied by a change in slope, dTc∕d(x,P), at this temperature. However, the results indicate that a similar volume change results in ∼3 times larger increase in Tc with Si doping than with pressure. Si doping, hence, does more to stabilize ferromagnetic interactions than simply uniformly reducing the unit cell volume.
Mechano-active scaffolds were fabricated from very elastic poly(lactide-co-carprolactone) by a gel-pressing method. The scaffolds were seeded with bone marrow stromal cells and the continuous compressive deformation w...
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Mechano-active scaffolds were fabricated from very elastic poly(lactide-co-carprolactone) by a gel-pressing method. The scaffolds were seeded with bone marrow stromal cells and the continuous compressive deformation was applied to cell-polymer constructs in the chondrogenic media. Then, they were implanted in nude mice subcutaneously to evaluate for the effect of dynamic compression for regeneration of cartilage. From the biochemical analyses, chondrogenic differentiation was sustained and enhanced significantly and chondral extracellular matrix was increased through mechanical stimulation. Histological analyses showed that implants stimulated mechanically formed mature and well-developed cartilaginous tissue, as evidenced by bone marrow derived chondrocytes within lacunae. Consequently, the periodic application of dynamic compression can encourage bone marrow stromal cells to differentiation to chondrogenic lineage and to maintain their phenotypes.
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