In total, approximately 400 million people worldwide suffer from urinary bladder cancer (Nat Biotechnol 17 (1999) 149). When radical cysectomy is required as treatment, a replacement material is ...clearly necessitated. For this purpose, three-dimensional poly(lactic-co-glycolic acid) (PLGA) scaffolds were constructed using solvent casting and salt leaching processes. These scaffolds were manipulated to possess nano-dimensional surface features by soaking in sodium hydroxide at select concentrations and for various periods of time. Human bladder smooth muscle cells were then seeded onto these nano-dimensional scaffolds; adhesion and longer-term cell growth experiments were performed for either 4h, or 1, 3, and 5 days, respectively. Additionally, collagen and elastin production was quantified following each experiment. In all cases, control cells were placed in an incubator and subjected to normal atmospheric pressure, while experimental cells were placed in a pressure chamber and subjected to a sustained pressure of 10cm H2O. Results of this study provided evidence that porous, nano-dimensional polymeric scaffolds enhanced cell adhesion and growth, while also promoting increased elastin and collagen production. Moreover, in general, exposure to pressure did not alter cellular adhesion, growth, or extracellular matrix protein production, which suggests that the scaffolds and their resident cells will fair well in the complex mechanical environment of the bladder wall. In combination, these results provide evidence that the nano-dimensional PLGA scaffolds created in this research are promising as the next generation of bladder wall replacement materials.
•Development of W-fibre enhanced W-composites incorporating extrinsic toughening mechanisms.•Production of a large sample (more than 2000 long fibres) for mechanical and thermal testing.•Even in a ...fully embrittled state, toughening mechanisms are still effective.•Emissions of volatile W-oxides can be suppressed by alloying W with elements forming stable oxides.•WCr10Ti2 has been successfully tested under accidental conditions and high heat fluxes.
Tungsten is the major candidate material for the armour of plasma facing components in future fusion devices. To overcome the intrinsic brittleness of tungsten, which strongly limits its operational window, a W-fibre enhanced W-composite material (Wf/W) has been developed incorporating extrinsic toughening mechanisms. Small Wf/W samples show a large increase in toughness. Recently, a large sample (50mm×50mm×3mm) with more than 2000 long fibres has been successfully produced allowing further mechanical and thermal testing. It could be shown that even in a fully embrittled state, toughening mechanisms as crack bridging by intact fibres, as well as the energy dissipation by fibre-matrix interface debonding and crack deflection are still effective. A potential problem with the use of pure W in a fusion reactor is the formation of radioactive and highly volatile WO3 compounds and their potential release under accidental conditions. It has been shown that the oxidation of W can be strongly suppressed by alloying with elements forming stable oxides. WCr10Ti2 alloy has been produced on a technical scale and has been successfully tested in the high heat flux test facility GLADIS. Recently, W-Cr-Y alloys have been produced on a lab-scale. They seem to have even improved properties compared to the previously investigated W alloys.
All the recent DEMO design studies for helium cooled divertors utilize tungsten materials and alloys, mainly due to their high temperature strength, good thermal conductivity, low erosion, and ...comparably low activation under neutron irradiation. The long-term objective of the EFDA fusion materials programme is to develop structural as well as armor materials in combination with the necessary production and fabrication technologies for future divertor concepts. The programmatic roadmap is structured into four engineering research lines which comprise fabrication process development, structural material development, armor material optimization, and irradiation performance testing, which are complemented by a fundamental research programme on “Materials Science and Modeling”. This paper presents the current research status of the EFDA experimental and testing investigations, and gives a detailed overview of the latest results on fabrication, joining, high heat flux testing, plasticity, modeling, and validation experiments.
► The crack resistance as a function of crack extension was investigated for tungsten. ► The fracture type is mainly dependent on the crack propagation direction. ► R-curve behavior was found for ...intergranularly and transgranularly fractured samples. ► Crack initiation and pre-crack location influence the R-curve behavior.
Recrystallized and deformed tungsten were investigated regarding their crack resistance as a function of crack extension. The compact tension specimens were manufactured with different crack plane orientations with respect to the axis of a rod. All recrystallized samples fractured predominantly intergranularly, whereas the deformed samples fractured transgranularly in certain crack propagation directions. Both showed an increase in the fracture resistance with crack extension, i.e. they exhibit R-curve behavior. It was determined in this study that the consolidation of the various fracture planes and crack bridging cause this R-curve behavior in tungsten.
Impurity effects on the nucleation and growth of primary Al sub(3)(Sc,Zr) phase have been investigated in high purity Al alloys and commercial purity Al alloys, respectively. In the case of high ...purity Al alloys, primary Al sub(3)(Sc,Zr) phases were found to be pushed to grain boundaries ahead of the solidification front. Such type of primary Al sub(3)(Sc,Zr) phase did not contribute to the heterogeneous nucleation, and thereby the grain refinement of Al alloys. In the case of commercial purity Al alloys, the presence of Fe, Si, Cu, Mg, Ti, and other impurities significantly enhanced the heterogeneous nucleation of primary Al sub(3)(Sc,Zr) phase. Most primary Al sub(3)(Sc,Zr) phases were found to be located within the alpha -Al matrix, and kept an identical orientation relationship with the alpha -Al matrix. Furthermore, the presence of the impurities also changed the growth mode on the primary Al sub(3)(Sc,Zr) phase. In the case of commercial purity Al alloys, a peritectic to eutectic reaction was induced due to the presence of the impurities. A layered growth was observed leading to a narrow particle size distribution. In contrast, in the case of high purity Al alloys, a featureless structure was observed. This investigation demonstrates that impurities and their concentrations are important factors affecting the nucleation and growth of primary Al sub(3)(Sc,Zr) phases, and thereby for the successful grain refinement in Al-based alloys.
Impurity effects on the nucleation and growth of primary Al.sub.3(Sc, Zr) phase have been investigated in high purity Al alloys and commercial purity Al alloys, respectively. In the case of high ...purity Al alloys, primary Al.sub.3(Sc, Zr) phases were found to be pushed to grain boundaries ahead of the solidification front. Such type of primary Al.sub.3(Sc, Zr) phase did not contribute to the heterogeneous nucleation, and thereby the grain refinement of Al alloys. In the case of commercial purity Al alloys, the presence of Fe, Si, Cu, Mg, Ti, and other impurities significantly enhanced the heterogeneous nucleation of primary Al.sub.3(Sc, Zr) phase. Most primary Al.sub.3(Sc,Zr) phases were found to be located within the α-Al matrix, and kept an identical orientation relationship with the a-Al matrix. Furthermore, the presence of the impurities also changed the growth mode on the primary Al.sub.3(Sc, Zr) phase. In the case of commercial purity Al alloys, a peritectic to eutectic reaction was induced due to the presence of the impurities. A layered growth was observed leading to a narrow particle size distribution. In contrast, in the case of high purity Al alloys, a featureless structure was observed. This investigation demonstrates that impurities and their concentrations are important factors affecting the nucleation and growth of primary Al.sub.3(Sc, Zr) phases, and thereby for the successful grain refinement in Al-based alloys.
Neuropeptide FF (NPFF) and prolactin-releasing peptide (PrRP) are two members of the RFamide peptide family. In this study we investigated whether these RFamide peptides, which have common structural ...features in their C-terminal RFamide motif and share several physiologically important functions, could exert their effects through the same set of receptors. The affinity and functional activity of several related RFamide peptides were determined at the human neuropeptide FF receptor subtype 2 (hNPFF2) and the human prolactin-releasing peptide (hPrRP) receptors. The full-length human prolactin releasing peptide 31 (hPrRP31) had significantly higher efficacy compared with NPFF and its stable analog, (1DMe)Y8Fa, at the hNPFF2 receptor. In contrast, NPFF and (1DMe)Y8Fa were not efficacious at the hPrRP receptor. Our study indicated a generally relatively low level of discrimination for RFamide peptides at the NPFF receptor, whereas the hPrRP receptor clearly preferred PrRP or very closely related peptides. The seemingly promiscuous binding of the RFamide peptides to the NPFF receptor was further confirmed by receptor autoradiography. PrRP may thus signal through the NPFF receptors in vivo.
We are in the midst of a fundamental shift in the economics of information--a shift that will precipitate changes in the structure of entire industries and in the ways companies compete. This shift ...is made possible by the widespread adoption of Internet technologies, but it is less about technology than about the fact that a new behavior is reaching critical mass. Millions of people are communicating at home and at work in an explosion of connectivity that threatens to undermine the established value chains for businesses in many sectors of the economy. What will happen, for instance, to dominant retailers such as Toys "R" Us and Home Depot when a search through the Internet gives consumers more choice than any store? What will be the point of cultivating a long-standing supplier relationship with General Electric when it posts its purchasing requirements on an Internet bulletin board and entertains bids from anybody inclined to respond? The authors present a conceptual framework for approaching such questions--for understanding the relationship of information to the physical components of the value chain and how the Internet's ability to separate the two will lead to the reconfiguration of the value proposition in many industries. In any business where the physical value chain has been compromised for the sake of delivering information, there will be an opportunity to create a separate information business and a need to streamline the physical one. Executives must mentally deconstruct their businesses to see the real value of what they have. If they don't, the authors warn, someone else will.
Three-dimensional electron backscatter diffraction, focused ion beam, transmission electron microscopy and energy filtered transmission electron microscopy were employed to investigate the structural ...information of primary Al{sub 3}(Sc,Zr) phase, i.e. size, shape, element distribution and orientation relationship with the α-Al matrix. It was found that (i) most primary Al{sub 3}(Sc,Zr) phases have a cubic three-dimensional morphology, with a size of about 6–10 μm, (ii) most primary Al{sub 3}(Sc,Zr) phases are located within the α-Al matrix, and exhibit a cube to cube orientation relationship with the α-Al matrix, and (iii) a layer by layer growth was observed within primary Al{sub 3}(Sc,Zr) phases. Al, Cu, Si and Fe are enriched in the α-Al matrix between the layers of cellular eutectic Al{sub 3}(Sc,Zr) phase, while Sc, Ti and Zr are enriched in small Al{sub 3}(Sc,Zr) phases. A peritectic reaction and subsequent eutectic reaction between Al{sub 3}Sc and Al was proposed to interpret the observed layer by layer growth. This paper demonstrates that the presence of impurities (Fe, Si, Cu, Ti) in the diffusion field surrounding the growing Al{sub 3}(Sc,Zr) particle enhances the heterogeneous nucleation of Al{sub 3}(Sc,Zr) phases. - Highlights: • Most fine cubic primary Al{sub 3}(Sc,Zr) phases were observed within the α-Al matrix. • A layer by layer growth within primary Al{sub 3}(Sc,Zr) phase was observed. • A peritectic and subsequent eutectic reaction between Al{sub 3}Sc and Al was proposed. • Impurities in diffusion fields enhance heterogeneous nucleation of Al{sub 3}(Sc,Zr)
Although intraperitoneal administration of sodium carboxymethylcellulose (SCMC) prevents the formation of adhesions following laparotomy in rats, it remains unknown whether SCMC treatment prevents ...the recurrence of preformed peritoneal adhesions following surgical lysis. Additionally, the optimal amount of SCMC required for adhesion prevention, as well as the effects of SCMC upon the healing of bowel anastomoses, has yet to he determined. To study this, 114 male rats underwent laparotomy and adhesion induction via peeling of the cecal serosa with a gauze sponge. Two weeks later, all animals again underwent laparotomy, the adhesions were graded, and surgical lysis of adhesions was performed. Following this, 3 to 12 ml of either normal saline or 1% SCMC solution was instilled into the peritoneal cavity prior to closure. A segment of small bowel was transected and reanastomosed prior to administration of SCMC or saline in another group of 70 rats. After an additional 2 weeks, the animals were sacrificed, the adhesions graded, and all the abdominal contents removed for fixation. The results show that treatment with high volume (i.e., 12 ml) intraperitoneal SCMC prevents reformation of adhesions following surgical lysis. This effect is demonstrated by a proportionate and significant decrease in the incidence of intraabdominal adhesions associated with administration of increasing amounts of SCMC (
P < 0.05). While high volume SCMC did prevent adhesion of peritoneal structures to newly formed small bowel anastomoses, SCMC did not impair anastomotic healing.
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