Poly(vinyl alcohol) (PVA) networks of different cross-linking densities were prepared by reaction with hexamethylene diisocyanate in solution and casting. The dynamic-mechanical properties of PVA films have been investigated in the temperature range of −150 to +150 °C. Two relaxations processes labeled α and β in order of decreasing temperature were observed. The α-relaxation shifts to lower temperature and the average molecular weight between cross-links decreases with increasing cross-linking density. Isothermal sorption from vapor and liquid water allowed determination of the Flory-Huggins interaction parameter between water and the polymer chain segments, which decreased with the water activity in the hydrogel and increased with the cross-linking density as a consequence of the hydrophobic character of the cross-linking agent. The water diffusion coefficients, D, in the networks obtained by means of dynamic sorption experiments increased with increasing water activity. This behavior is interpreted in terms of plasticization of the polymer by water molecules. 相似文献
This paper reports on the structure, mechanical, and photocatalytic properties of titanium dioxide (TiO2) and tungsten oxide (WO3) films on a brass substrate. TiO2 and WO3 films have been successfully deposited on brass by a simple sol‐gel dip‐coating method and it has been shown that, while both films possess photocatalytic properties, WO3 films were superior to TiO2. Higher surface area and rod‐like morphology of WO3 films might have contributed to their higher photocatalytic activity. Nanoindentation results have shown that both films attach well to the substrate and possess good mechanical properties. 相似文献
Genistein has been reported to stimulate luminal HCO3− secretion. We hypothesized that genistein mediates this effect via SLC26A6 and SLC4A4 (NBCe1) transporters. Our study aimed to: investigate changes in uterine fluid pH, Na+ and HCO3− concentration and expression of uterine SLC26A6 and NBCe1 under genistein effect. Ovariectomized adult female rats received 25, 50 and 100 mg/kg/day genistein for a week with and without ICI 182780. A day after the last injection, in vivo uterine perfusion was performed to collect uterine fluid for Na+, HCO3− and pH determination. The animals were then sacrificed and uteri were removed for mRNA and protein expression analyses. SLC26A6 and NBCe1-A and NBCe1-B distribution were visualized by immunohistochemistry (IHC). Genistein at 50 and 100 mg/kg/day stimulates uterine fluid pH, Na+ and HCO3− concentration increase. Genistein at 100 mg/kg/day up-regulates the expression of SLC26A6 and SLC4A4 mRNA, which were reduced following concomitant ICI 182780 administration. In parallel, SLC26A6 and NBCe1-B protein expression were also increased following high dose genistein treatment and were localized mainly at the apical membrane of the luminal epithelia. SLC26A6 and NBCe1-B up-regulation by genistein could be responsible for the observed increase in the uterine fluid pH, Na+ and HCO3− concentration under this condition. 相似文献
The indigenous materials such as tea waste were exploited as antimicrobial adsorbent for removing heavy metal ions. It was well known that tea waste was characterized with biodegradability and environmental-friendly product. Grafting copolymerization of acrylic acid onto tea waste was carried out using gamma radiation. The effects of solvent, dose and feeding concentration of acrylic acid have been investigated to achieve the optimum conditions. Grating (%) ranged from 30 to 70 for DMSO and H2O, respectively. The grafted tea waste was characterized by Fourier transform infrared (FTIR) spectroscopy, swelling study, scanning electron microscopy (SEM) and energy dispersive spectrometry X-rays (EDS). The grafted samples were used in waste water treatment to remove heavy metal ions (Cr3+, Pb2+ and Hg2+). The highest adsorption capacity was 35 and 200 mg/g of Hg+2 ions for ungrafted and grafted samples, respectively. The results showed that the selectivity among these metal ions is different onto tea waste-graft-polyacrylic acid. The grafted tea waste samples, which complexed with Cr3+, Pb2+ and Hg2+ ions, were found to have antimicrobial features. Therefore, they could be used as adsorbent in removing heavy metal ions with antimicrobial features as well.
Silicon - One of the basic principles of a successful laparoscopic procedure is a clear operating area. The endoscopic lens should be able to visualize the internal organs as clearly as possible.... 相似文献
Recently a new, large family of two‐dimensional (2D) early transition metal carbides and carbonitrides, called MXenes, was discovered. MXenes are produced by selective etching of the A element from the MAX phases, which are metallically conductive, layered solids connected by strong metallic, ionic, and covalent bonds, such as Ti2AlC, Ti3AlC2, and Ta4AlC3. MXenes combine the metallic conductivity of transition metal carbides with the hydrophilic nature of their hydroxyl or oxygen terminated surfaces. In essence, they behave as “conductive clays”. This article reviews progress—both experimental and theoretical—on their synthesis, structure, properties, intercalation, delamination, and potential applications. MXenes are expected to be good candidates for a host of applications. They have already shown promising performance in electrochemical energy storage systems. A detailed outlook for future research on MXenes is also presented. 相似文献
Chitin and chitosan are natural polymers with a huge potential in numerous fields, namely, biomedical, biological, and many industrial applications such as waste water treatment due to the fact that they can absorb and chelate many metal cations. Electrospinning is a growing field of research to produce submicron fibers with promising applications in biomedical fields like tissue engineering scaffolds and wound healing capabilities. Both chitin and chitosan polymers were found to be hard to electrospun, however, many researchers manage to produce nano-fibers using special solvents; for example, 90% acetic acid was found to reduce the surface tension making electrospinning feasible. Mixtures of organic acids were also experimented to produce homogenous and uniform fibers. Bigger attention was given to electrospinning of their soluble derivatives such as dibutyryl and carboxymethyl chitin. More derivatives of chitosan were investigated to produce nano-fibers such as hexanoyl, polyethyleneglycol, carboxymethyl, and a series of quaternized chitosan derivatives. The obtained nano-fibers were found to have much better qualities than normal chitosan fibers. Several polymer blends of chitin/chitosan with many commercial polymers were found to be amenable for electrospinning producing uniform beads free fibers. The review surveys the various approaches for successful electrospinning of chitin, chitosan, their derivatives, and blends with several other polymers. 相似文献
Chromosomal abnormalities are commonly associated with cancer, and their importance in the pathogenesis of the disease has been well recognized. Also recognized in recent years is the possibility that, together with chromosomal abnormalities, DNA ploidy of breast cancer aspirate cells, measured by image cytometric techniques, may correlate with prognosis of the disease. Here, we have examined the use of an artificial neural network to predict: 1) subclinical metastatic disease in the regional lymph nodes and 2) histological assessment, through the analysis of data obtained by image cytometric techniques of fine needle aspirates of breast tumors. The cellular features considered were: 1) DNA ploidy measured in terms of nuclear DNA content as well as by cell cycle distribution; 2) size of the S-phase fraction; and 3) nuclear pleomorphism. A further objective of the study was to analyze individual markers in terms of impact significance on predicting outcome in both cases. DNA ploidy, indicated by cell cycle distribution, was found markedly to influence the prediction of nodal spread of breast cancer, and nuclear pleomorphism to a lesser degree. Furthermore, a comparison between histological assessment and artificial neural network prediction shows a closer correlation between the neural approach and the development of further metastases as indicated in subsequent follow-up, than does histological assessment 相似文献