Summary: Two different types of biodegradable polyester composites, PLLA fiber‐reinforced PCL and PCL/PLLA blend films were prepared at PCL/PLLA ratio of 88/12 (w/w), together with pure PCL and PLLA films. Their enzymatic degradation was investigated by the use of Rhizopus arrhizus lipase and proteinase K as degradation enzymes for PCL and PLLA chains, respectively. In the FRP film, the presence of PLLA fibers accelerated the lipase‐catalyzed enzymatic degradation of PCL matrix compared with that in the pure PCL film, whereas in the blend film, the presence of PLLA chains dissolved in the continuous PCL‐rich domain retarded the lipase‐catalyzed enzymatic degradation of PCL chains. In contrast, in the FRP film, the proteinase K‐catalyzed enzymatic degradation of PLLA fibers was disturbed compared with that of the pure PLLA film, whereas in the blend film, the proteinase K‐catalyzed enzymatic degradation rate of particulate PLLA‐rich domains was higher than that of pure PLLA film. The reasons for aforementioned enhanced and disturbed enzymatic degradation are discussed.
Normalized PCL weight loss of pure PCL, FRP, and blend films as a function of Rhizopus arrhizus lipase‐catalyzed enzymatic degradation time. 相似文献
Human estrogens prescribed for hormone replacement therapy (HRT) are known to be potent carcinogens. To find safer estrogens, several chlorinated estrogens were synthesized and their carcinogenic potential were determined. A pellet containing either 2-chloro-17β-estradiol (2-ClE2) or 4-chloro-17β-estradiol (4-ClE2) was implanted subcutaneously for 52 weeks into August Copenhagen Irish (ACI) rats, a preferred animal model for human breast cancer. 17β-Estradiol (E2) frequently induced mammary tumors while both 2-ClE2 and 4-ClE2 did not. Their 17α-ethinyl forms, thought to be orally active estrogens, were also synthesized. Neither 2-chloro-17α-ethinylestradiol (2-ClEE2) nor 4-chloro-17α-ethinylestradiol (4-ClEE2) induced tumors. The less carcinogenic effects were supported by histological examination of mammary glands of ACI rats treated with the chlorinated estrogens. A chlorine atom positioned at the 2- or 4-position of E2 may prevent the metabolic activation, resulting in reducing the carcinogenicity. 2-ClE2 and 4-ClE2 administered subcutaneously and 2-ClEE2 and 4-ClEE2 given orally to ovariectomized rats all showed uterotrophic potency, albeit slightly weaker than that of E2. Our results indicate that less carcinogenic chlorinated estrogens retaining estrogenic potential could be safer alternatives to the carcinogenic estrogens now in use for HRT. 相似文献
The crystallization behavior of the stereoblock copolymer of substituted and non-substituted poly(lactide)s, i.e., poly(d-2-hydroxybutyrate) and poly(l-lactide) chains having the opposite configurations [P(D-2HB)-b-PLLA] and the reference block copolymer of poly(d-2-hydroxybutyrate) and poly(d-lactide) chains with the identical configurations [P(D-2HB)-b-PDLA] was investigated. At the crystallizable temperature range of 60-160 °C, the crystallized P(D-2HB)-b-PLLA contained solely the hetero-stereocomplex crystallites as a crystalline species, without formation of poly(d-2-hydroxybutyrate) or poly(l-lactide) homo-crystallites, in contrast with their polymer blends. On the other hand, at the crystallizable temperature range of 60-140 °C, the crystallized P(D-2HB)-b-PDLA had only PDLA homo-crystallites as crystalline species, reflecting no co-crystallites formation between poly(d-2-hydroxybutyrate) and poly(d-lactide) chains having the same configurations. The equilibrium melting temperature of hetero-stereocomplex crystallites in P(D-2HB)-b-PLLA was 189.0 °C, which was higher than 171.3 °C of PDLA homo-crystallites in P(D-2HB)-b-PDLA. Although the final crystallinity of P(D-2HB)-b-PLLA was higher than those of P(D-2HB)-b-PDLA, the spherulite growth rate of P(D-2HB)-b-PLLA was lower.The regime analysis indicated unusual nucleation mechanism of P(D-2HB)-b-PLLA. 相似文献
The surface adsorption effect of CO on the hydrogen permeability of a 12.5 micron-thick Pd77Ag23 membrane has been evaluated quantitatively under experimental conditions close to the operating conditions of the highly-efficient membrane reformer (MRF) system developed by Tokyo Gas. The permeability of the membrane was measured in the conditions of CO concentration between 1 and 5 vol.% at a temperature and pressure of up to 500 °C and 0.6 MPa, respectively. High feed flow rates and a microchannel module configuration were applied in the flux measurements to ensure that the results are obtained with limited influence of concentration polarization adjacent to the membrane surface and hydrogen depletion along the microchannel length. While the CO inhibition effect was close to negligible at 500 °C, it was significant at lower temperatures. At a feed pressure of 0.2 MPa, the CO inhibition effect was only 0.2% at a CO concentration of 1 vol.% and the effect was 3.6% at a CO concentration of 5 vol.% at 500 °C. The CO inhibition effect were 3.4% for 1 vol.% CO and 14.1% for 5 vol.% CO at 400 °C. Measurements were also carried out at a high feed pressure of 0.6 MPa to evaluate the pressure dependence of the CO inhibition effect. The CO inhibition effect decreased to 0.7% at a CO feed concentration of 5 vol.% at 500 °C. Lower CO inhibition effect were also observed at 450 and 400 °C compared to the data obtained with the feed pressure of 0.2 MPa, while the inhibition levels were almost the same at 350 °C. Though the CO inhibition effect is larger at a lower feed pressure of 0.2 MPa, the effect was only 0.2% at 1 vol.% CO at 500 °C, which is close to the operating conditions of the MRF system. This study quantitatively revealed that the CO inhibition effect on hydrogen flux is extremely small when the membrane is operated at temperatures equal to or higher than 500 °C, even for state-of-the-art thin membranes. The performance of the Tokyo Gas MRF seems thus mainly limited by concentration polarization effects. 相似文献
Highly robust ion gels, termed double‐network (DN) ion gels, composed of inorganic/organic interpenetrating networks and a large amount of ionic liquids (ILs), are fabricated. The DN ion gels with an 80 wt% IL content show extraordinarily high mechanical strength: more than 28 MPa of compressive fracture stress. In the DN ion gel preparation, a brittle inorganic network of physically bonded silica nanoparticles and a ductile organic network of polydimethylacrylamide (PDMAAm) are formed in the IL. Because of the different reaction mechanisms of the inorganic/organic networks, the DN ion gels can be formed by an easy and free‐shapeable one‐pot synthesis. They can be prepared in a controllable manner by manipulating the formation order of the inorganic and organic networks via not only multistep but also single‐step processes. When silica particles form a network prior to the PDMAAm network formation, DN ion gels can be prepared. The brittle silica particle network in the DN ion gel, serving as sacrificial bonds, easily ruptures under loading to dissipate energy, while the ductile PDMAAm network maintains the shape of the material by the rubber elasticity. Given the reversible physical bonding between the silica particles, the DN ion gels exhibit a significant degree of self‐recovery by annealing. 相似文献
Primary biliary cholangitis (PBC) has a wide variation in clinical presentation and course. There is no significant correlation between these symptoms and the disease stage, although patients with more advanced stages generally have more symptoms. It is important to develop biomarkers in order to identify patients with an increased risk of complications and end-stage liver disease. This study investigated surrogate markers for risk estimation of PBC-related complications, including a study population of 77 patients with PBC who underwent liver biopsy and were measured for serum levels of macrophage activation markers, soluble CD163 (sCD163), soluble mannose receptor (sMR), and zonulin. Patients with PBC were divided into symptomatic (Group S, n = 20) and asymptomatic (Group A, n = 57) groups. The correlations of histological stages based on both Scheuer and Nakanuma classifications with the three serum markers were investigated. The Nakanuma classification involves grading for liver fibrosis and bile duct loss. The three biomarkers were assessed for their diagnostic ability to identify patients with PBC having high risk of developing complications. The predictive factors of these complications were examined as well. Group S had significantly higher serum sMR (p = 0.011) and sCD163 (p = 0.048) levels versus Group A. A composite index of sMR and sCD163 measurements had significantly better prediction performance than sCD163 alone (p = 0.012), although not when compared to sMR alone (p = 0.129). Serum sMR was an independent factor for developing complications on both univariate (Odds ratio (OR) = 30.20, 95% confidence interval (95% CI): 3.410–267.0, p = 0.00220), and multivariate (OR = 33.70, 95% CI: 3.6600–311.0, p = 0.0019) analyses. Patients with PBC having sMR of ≥56.6 had a higher incidence of clinical complications versus those with a sMR of <56.6. Serum sMR predicts the development of complications in patients with PBC. sMR plus sCD163 showed better predictive power than either marker alone, although the addition of sCD163 did not improve the predictive power of sMR. Future prospective studies are required in order to validate the findings of the present study. 相似文献
We first applied the Twomey iteration method to the low-angle laser light scattering (LALLS) method. The Twomey method is known by the simple iteration algorithm for Fredholm integral equation. However, the algorithm is not applied to the LALLS result itself because the kernel function pattern is not stable. We solved the unstable kernel issue by modifying the Twomey algorithm to fit the LALLS data in this study. The performance of inversion was studied by computer simulation and experimental results from detectors containing 24 elements from angle 0.0005 to 2.5 rad. The computer simulation was carried out for particles of mean sizes from 0.1 to 1000 μm with mono-dispersion and log-normal distributions. A conventional algorithm is also carried out to compare the performance of the Twomey method. The noise effect of the inverse problem was tested by computer simulation. Experimental results were measured with standard polystyrene latex from 0.081 to 1007 μm. All the tests were performed under conditions in which the light from a linearly polarized laser at 633 nm was scattered by a diluted aqueous suspension. The modified Twomey (MT) method and conventional method show good reproduction results for particles with log-normal distributions. However, narrow distribution particles indicate that the MT method shows excellent reproduction results when compared with the conventional method. 相似文献
This paper deals with the assignment problem of cells to switches in a personal communication service network. Three types of costs in a PCS network are considered in detail: the cost of handoffs, the cost of cabling, and the cost of switching. The optimal assignment problem is formulated as an integer-programming problem. A heuristic algorithm is proposed to obtain an assignment of cells in a PCS network. The proposed algorithm is compared with an existing heuristic cell assignment algorithm. By numerical examination, it is shown that the switching cost has a large effect on the solution of the cell assignment problem. The proposed algorithm obtains much better cell assignment in which the load of each switch is balanced and the total cost of a PCS network is much lower than what is obtained by the existing algorithm that does not take account of the switching cost. If the switching cost is taken into account, it has also been shown that our proposed algorithm achieves substantially the same results as the existing algorithm while requiring much less computation time. 相似文献