One-pot foam-gelcasting/nitridation synthesis of high porosity nano-whiskers based 3D Si3N4 porous ceramics

Nano-whiskers based 3D Si₃N₄ porous ceramics (3D-NWSNPC) with high-porosity (about 91–93 %), low density (0.17–0.25 g/cm³), low thermal conductivity, and a certain degree of recoverability under cyclic compressive loading and reasonably strengths were prepared at 1423–1523 K via a one-pot foam-gelcasting/nitridation route using inexpensive commercial Si powders as starting materials and hexadecyl trimethyl ammonium bromide as foaming agent. After nitridation at 1523 K, the sample with an original solid loading of 12.5 wt% exhibited the highest compressive strength of 1.9 MPa, even though its density was lowered to 0.25 g/cm³. The sample nitrided at 1473 K had a relative density of 7.3 %. Its compressive and specific strength were respectively 1.1 MPa and 5.5 MPa·cm³ g^?1, and its thermal conductivity was as low as 0.074 W/(m K) (measured at 323 K). These outstanding properties would make the as-prepared 3D-NWSNPC a promising candidate for applications in catalysis, filtration, thermal insulation and many other important areas.     

Effects of Basic Chemical Surface Treatment on PBO and PBO Fiber Reinforced Epoxy Composites

The effects of chemical surface treatment on PBO fiber and its composite materials were investigated using a basic sodium hydroxide solution. We evaluated several important treatment parameters quantitatively, including treatment concentration, treatment temperature and treatment time. Both as-spun (AS) and high-modulus (HM) PBO fibers were studied. The results showed that PBO fibers exhibited minimum or negligible reduction in their tensile strengths after the proposed treatment processes. The fibers’ contact angles with several liquid media were greatly reduced and the surface free energy could be increased to 58 mJ/m² or by 17%. The interfacial shear strength between PBO fiber and the epoxy matrix was improved to 38 MPa or by 11% with the same treatment process. The composite’s failure mode also shifted from fiber/matrix interface adhesive failure to partly cohesive failure.     

Meso-scale strain mapping in UD woven composites

Unidirectional (UD) woven laminates have complex tow geometry due to unbalanced weave architecture. Warp tows are held together by fine weft. Unit cell models for textile composites found in the literature are based on balanced weaves with identical warp and weft specifications. In this paper, unit cell geometry of unbalanced UD weaves has been considered. Unbalanced laminates have complex tow geometry with in-plane tow waviness and a significant overlap between adjacent tows. Main objective of this work is to measure full-field strain distribution at meso-scale or unit cell level and compare the results with FE analysis. Raman spectroscopy is a powerful technique for in situ strain measurement. A UD woven composite laminate with Kevlar fibres is used in this study, as Kevlar fibres exhibit clear Raman band shifts under strain. Influence of in-plane tow waviness on local strain gradients has been demonstrated.     

The chemical and biological characteristics of coke-oven wastewater by ozonation

A bench-scale bubble column reactor was used to investigate the biological and chemical characteristics of coke-oven wastewater after ozonation treatment through the examination of selected parameters. Color and thiocyanate could be removed almost entirely; however, organic matter and cyanide could not, due to the inadequate oxidation ability of ozone to remove ozonated byproducts under given experimental conditions. The removal of cyanide and total organic carbon were pH-dependent and were found to be efficient under neutral to alkaline conditions. The removal rate for thiocyanate was about five times that of cyanide. The ozone consumption ratio approached to about 1 at the early stage of ozonation (time <20 min), indicating that easily degraded matter was present, and mostly ozone was used to oxidize the pollutants. As ozonation progressed, the consumption ratio decreased to 0.2, and TOC removal (eta(TOC)) increased to 30%, indicating that easily degraded pollutants were degraded almost entirely. The effect of ozonation on the subsequent biological treatment unit (i.e., activated sludge process) was determined by observing the ratio of 5-day biological oxygen demand to chemical oxygen demand (BOD(5)/COD) and the specific oxygen utilization rate (SOUR). The results indicated that the contribution of ozonation to inhibition reduction was very significant but limited to the enhancement of biodegradation. The operation for ozonation of coke-oven wastewater was feasible under neutral condition and short ozone contact time in order to achieve better performance and cost savings.     

An integration method combining Rough Set Theory with formal concept analysis for personal investment portfolios

The classical Rough Set Theory (RST) always generates too many rules, making it difficult for decision makers to choose a suitable rule. In this study, we use two processes (pre process and post process) to select suitable rules and to explore the relationship among attributes. In pre process, we propose a pruning process to select suitable rules by setting up a threshold on the support object of decision rules, to thereby solve the problem of too many rules. The post process used the formal concept analysis from these suitable rules to explore the attribute relationship and the most important factors affecting decision making for choosing behaviours of personal investment portfolios. In this study, we explored the main concepts (characteristics) for the conservative portfolio: the stable job, less than 4 working years, and the gender is male; the moderate portfolio: high school education, the monthly salary between NT$30,001 (US$1000) and NT$80,000 (US$2667), the gender is male; and the aggressive portfolio: the monthly salary between NT$30,001 (US$1000) and NT$80,000 (US$2667), less than 4 working years, and a stable job. The study result successfully explored the most important factors affecting the personal investment portfolios and the suitable rules that can help decision makers.     

Analysis of interfacial micromechanics of model composites using synchrotron microfocus X-ray diffraction

The deformation micromechanics of single-fibre embedded model composites of poly(p-phenylene benzobisoxazole) (PBO) and poly(p-phenylene terephthalamide) (PPTA) fibres, embedded in an epoxy resin have been examined using synchrotron microfocus X-ray diffraction. Single fibres (in air) were deformed and the c-spacing monitored to establish a calibration of crystal strain against applied stress. Subsequently, the variation in crystal strain along fibres, embedded in the resin matrix was mapped using synchrotron microfocus X-ray diffraction. Raman spectroscopy was then used to map molecular deformation on the same samples (recorded as shifts in the Raman band wavenumber) in order to provide a complementary stress data. A shear-lag analysis was conducted on the axial fibre stress data in order to calculate interfacial shear stress and identify different stress-transfer modes at fibre/resin interfaces. The results establish that the axial fibre stress distributions measured by synchrotron microfocus X-ray diffraction correlate well with those obtained using Raman spectroscopy. The interfacial shear stress data derived from the stress-transfer profiles also show a good degree of correlation.     

Sulfated glycans stimulate endocytosis of the cellular isoform of the prion protein, PrPC, in cultured cells

There is currently no effective therapy for human prion diseases. However, several polyanionic glycans, including pentosan sulfate and dextran sulfate, prolong the incubation time of scrapie in rodents, and inhibit the production of the scrapie isoform of the prion protein (PrPSc), the major component of infectious prions, in cultured neuroblastoma cells. We report here that pentosan sulfate and related compounds rapidly and dramatically reduce the amount of PrPC, the non-infectious precursor of PrPSc, present on the cell surface. This effect results primarily from the ability of these agents to stimulate endocytosis of PrPC, thereby causing a redistribution of the protein from the plasma membrane to the cell interior. Pentosan sulfate also causes a change in the ultrastructural localization of PrPC, such that a portion of the protein molecules are shifted into late endosomes and/or lysosomes. In addition, we demonstrate, using PrP-containing bacterial fusion proteins, that cultured cells express saturable and specific surface binding sites for PrP, many of which are glycosaminoglycan molecules. Our results raise the possibility that sulfated glycans inhibit prion production by altering the cellular localization of PrPC precursor, and they indicate that endogenous proteoglycans are likely to play an important role in the cellular metabolism of both PrPC and PrPSc.     

The effects of selected parameters on the nitric oxide removal by biofilter

A bench-scale biofilter was used to demonstrate the treatability of off-gas containing nitric oxide (NO) by examining selected operational parameters. After 6 days of operation, the biofilter reached to a steady state and NO reduction was significant, reducing from 200 ppm to 95 and 40 ppm after 6 and 40 days of continuous operation. The oxygen concentrations in the inlet would affect NO removal performance significantly; as oxygen content decreasing from 6% to 0%, the NO removal efficiency increased from 55% to 99%, indicating that oxygen inhibited the progress of denitrification. NO removal was inversely proportional to inlet NO concentration, removal efficiency decreased from 88% to 40 % as NO concentration increasing from 60 to 500 ppm. Column height would significant effect on the NO removal efficiency, under column height=6.5m and O(2)=6% conditions, 90% of removal efficiency was achievable. The effect of glucose added into biofilter would significantly enhance the NO removal efficiencies for both anaerobic and aerobic conditions of which 99% and 55%, respectively.     

Depletion of intracellular polyamines relieves inward rectification of potassium channels

Two different approaches were used to examine the in vivo role of polyamines in causing inward rectification of potassium channels. In two-microelectrode voltage-clamp experiments, 24-hr incubation of Xenopus oocytes injected with 50 nl of difluoromethylornithine (5 mM) and methylglyoxal bis(guanylhydrazone) (1 mM) caused an approximate doubling of expressed Kir2.1 currents and relieved rectification by causing an approximately +10-mV shift of the voltage at which currents are half-maximally inhibited. Second, a putrescine auxotrophic, ornithine decarboxylase-deficient Chinese hamster ovary (O-CHO) cell line was stably transfected with the cDNA encoding Kir2.3. Withdrawal of putrescine from the medium led to rapid (1-day) loss of the instantaneous phase of Kir2.3 channel activation, consistent with a decline of intracellular putrescine levels. Four days after putrescine withdrawal, macroscopic conductance, assessed using an 86Rb+ flux assay, was approximately doubled, and this corresponded to a +30-mV shift of V1/2 of rectification. With increasing time after putrescine withdrawal, there was an increase in the slowest phase of current activation, corresponding to an increase in the spermine-to-spermidine ratio over time. These results provide direct evidence for a role of each polyamine in induction of rectification, and they further demonstrate that in vivo modulation of rectification is possible by manipulation of polyamine levels using genetic and pharmacological approaches.     

Reliability of multistacked tantalum-based structure as the barrier film in ultralarge-scale integrated metallization

Diffusion barrier properties of Ta films with and without plasma treatments have been investigated in the study. The nitrogen-incorporated Ta films were prepared by NH₃ plasma treatment or reactive sputtering. Barrier properties were evaluated by sheet resistance, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy and reverse-biased junction leakage current. An amorphous-like TaN_x layer was formed on Ta barrier film after plasma treatments. The thickness of the amorphous TaN_x layer is about 3 nm and NH₃ plasma-treated Ta films (TaN_x/Ta) possess lower resistivity and smaller grain sizes. The Cu/TaN_x/Ta(10 nm)/Si remained stable after annealing at 750 °C for 1 h. NH₃ plasma-treated Ta films (TaN_x/Ta) possess better thermal stability than Ta and TaN films. It is attributed to the formation of a new amorphous layer on the surface of Ta film after the plasma treatments. For thermal stability of Cu/Ta(-N)/n⁺-p diodes, Cu/Ta/n⁺-p and Cu/TaN/n⁺-p junction diodes resulted in large reverse-bias junction leakage current after annealing at 500 and 525 °C, respectively. On the other hand, TaN_x/Ta diffusion barriers will improve the integrity of Cu/Ta(-N)/n⁺-p junction diodes to 650 °C.