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921.
We investigate an initial value problem which is closely related to the Williams-Bjerknes tumour model for a cancer which spreads through an epithelial basal layer modeled onI ⊂ Z 2. The solution of this problem is a familyp = (p i(t)), where eachp i(t)could be considered as an approximation to the probability that the cell situated ati is cancerous at timet. We prove that this problem has a unique solution, it is defined on [0, +∞[, and, for some relevant situations, limt→∞ P i(t) = 1 for alli ∈ I. Moreover, we study the expected number of cancerous cells at timet.  相似文献   
922.
This paper reports how pyrite films were prepared by thermal sulfurization of magnetron sputtered iron films and characterized by x-ray absorption near edge structure spectra and x-ray photoelectron spectroscopy on a 4B9B beam line at the Beijing Synchrotron Radiation Facility. The band gap of the pyrite agrees well with the optical band gap obtained by a spectrophotometer. The octahedral symmetry of pyrite leads to the splitting of the d orbit into t_{\rm 2g} and e_{\rm g} levels. The high spin and low spin states were analysed through the difference of electron exchange interaction and the orbital crystal field. Only when the crystal field splitting is higher than 1.5 eV, the two weak peaks above the white lines can appear, and this was approved by experiments in the present work.  相似文献   
923.
This paper studies boron contamination at the interface between the p and i layers of μ c-Si:H solar cells deposited in a single-chamber PECVD system. The boron depth profile in the i layer was measured by Secondary Ion Mass Spectroscopy. It is found that the mixed-phase μ c-Si:H materials with 40% crystalline volume fraction is easy to be affected by the residual boron in the reactor. The experimental results showed that a 500-nm thick μ c-Si:H covering layer or a 30-seconds of hydrogen plasma treatment can effectively reduce the boron contamination at the p/i interface. However, from viewpoint of cost reduction, the hydrogen plasma treatment is desirable for solar cell manufacture because the substrate is not moved during the hydrogen plasma treatment.  相似文献   
924.
A new diamine monomer containing benzimidazole‐5‐sulfonic acid has been synthesised. It has been reacted, alone or mixed with diaminodiphenyl ether, with naphthalenic dianhydride to attain polynaphthalimides in which the sulfonic acid functionality is borne by pendant benzimidazole groups. The presence of sulfonic and benzimidazole groups greatly affected the physical properties of the polyimides as the novel polymers were found to be soluble in polar organic solvents and exhibited a lower thermal resistance than their non‐sulfonated counterparts. The polymer films exhibited good mechanical properties with tensile strength in the range 100–120 MPa and with moduli in the range 2.2–3.1 GPa. Sulfonic and benzimidazole groups significantly enhanced the hydrophilicity of the copolyimides, which showed water uptake up to 39%.

  相似文献   

925.
Resveratrol, a natural plant phytoalexin, is produced in response to fungal infection or− UV irradiation. It exists as an isomeric pair with cis- and trans-conformation. Whereas multiple physiological effects of the trans-form, including a pronounced anti-tumoral activity, are nowadays elucidated, much less knowledge exists concerning the cis-isomer. In our work, we analyzed the antiproliferative and cytotoxic properties of cis-resveratrol in four different human tumor entities in direct comparison to trans-resveratrol. We used human cell lines as tumor models for hepatocellular carcinoma (HCC; HepG2, Hep3B), colon carcinoma (HCT-116, HCT-116/p53(−/−)), pancreatic carcinoma (Capan-2, MiaPaCa-2), and renal cell carcinoma (A498, SN12C). Increased cytotoxicity in all investigated tumor cells was observed for the trans-isomer. To verify possible effects of the tumor suppressor p53 on resveratrol-induced cell death, we used wild type and p53-deleted or -mutated cell lines for every tested tumor entity. Applying viability and cytotoxicity assays, we demonstrated a differential, dose-dependent sensitivity towards cis- or trans-resveratrol among the respective tumor types.  相似文献   
926.
聚乳酸的层层自组装修饰及其内皮细胞相容性研究   总被引:4,自引:0,他引:4  
通过胺解反应在生物降解聚(L-乳酸)表面引入带有正电荷的自由氨基,并通过静电吸引层层(Layer-by-layer,LBL)自组装技术将具有良好生物相容性的硫酸软骨素(CS)和细胞外基质成分型胶原组装到该PLLA材料表面.通过反应性荧光探针标记、紫外-可见吸收光谱以及荧光能量转移等测试技术跟踪并表征了自组装过程的进行.组装层的厚度开始随组装层数的增加而线性增加,而后增加变缓.内皮细胞的体外培养证明,表面组装CS和胶原(以胶原为最外层)以后,细胞的增殖率和细胞活性显著提高,材料的细胞相容性得到明显改善.细胞体现了充分铺展的多角形内皮细胞形貌,而且局部已融合形成了一单层内皮细胞层.  相似文献   
927.
直接甲醇燃料电池用磺化聚醚醚酮膜初探   总被引:1,自引:0,他引:1  
应用电化学方法研究了SPEEK膜的甲醇渗透性能.SPEEK膜具有比Nafion115膜低的甲醇渗透.以其作质子交换膜电解质组装的直接甲醇燃料电池(DMFCs)开路电压高于Nafion115膜组装的DMFC开路电压,但电池的放电性能尚待改进.本研究可为SPEEK应用于直接甲醇燃料电池提供一定的依据.  相似文献   
928.
Summary: The electrochemical behaviour of four types of (phenylene ethynylene)‐alt‐(phenylene vinylene) hybrid polymers, 1 , 2 , 3 , and 4 have been investigated with respect to the influence of the grafted alkoxy side chains. In the case of the fully substituted polymers 2 , 3 , and 4 , the strong insulating nature of longer linear octadecyl or bulky branched 2‐ethylhexyl side chains lowers the HOMO levels of the polymers thereby increasing the discrepancy, ΔEg, between the electrochemical, Eequation/tex2gif-stack-1.gif, and the optical, Eequation/tex2gif-stack-2.gif, bandgap energies. Thus it is not possible to establish a direct correlation between the open circuit voltage, VOC, of bulk heterojunction solar cell devices of the configuration glass substrate/ITO/PEDOT:PSS/polymer 3 :PCBM(1:3, w/w)/LiF/Al and the HOMO energy levels of polymer 3 solely, as postulated in the literature. The photovoltaic (PV) parameters greatly depend on the grafted side chains.

Linear IV curves of solar cell devices from polymers 3a – d , measured in the dark and under 100 mW · cm−2 solar simulator illumination.  相似文献   

929.
Irinotecan and Topotecan are two Camptothecin derivatives (CPTs) whose resistance is associated with the high expression of breast cancer resistance protein (BCRP) and P-glycoprotein (P-gp). To reverse this resistance, two novel CPTs, FL77-28 (7-(3-Fluoro-4-methylphenyl)-10,11-methylenedioxy-20(S)-CPT) and FL77-29 (7-(4-Fluoro-3-methylphenyl)-10,11-methylenedioxy-20(S)-CPT), were synthesized by our group. In this study, the anti-tumor activities of FL77-28, FL77-29, and their parent, FL118 (10,11-methylenedioxy-20(S)-CPT), were evaluated and the results showed that FL77-28 and FL77-29 had stronger anti-tumor activities than FL118. The transport and uptake of FL118, FL77-28, and FL77-29 were investigated in Caco-2 cells for the preliminary prediction of intestinal absorption. The apparent permeability coefficient from apical to basolateral (Papp AP-BL) values of FL77-28 and FL77-29 were (2.32 ± 0.04) × 10−6 cm/s and (2.48 ± 0.18) × 10−6 cm/s, respectively, suggesting that the compounds had moderate absorption. Since the transport property of FL77-28 was passive diffusion and the efflux ratio (ER) was less than 2, two chemical inhibitors were added to further confirm the involvement of efflux proteins. The results showed that FL77-28 was not a substrate of P-gp or BCRP, but FL77-29 was mediated by P-gp. In conclusion, FL77-28 might be a promising candidate to overcome drug resistance induced by multiple efflux proteins.  相似文献   
930.
As a global health problem, liver fibrosis still does not have approved treatment. It was proved that N-(3,4,5-trichlorophenyl)-2(3-nitrobenzenesulfonamide) benzamide (IMB16-4) has anti-hepatic fibrosis activity. However, IMB16-4 displays poor water solubility and poor bioavailability. We are devoted to developing biodegraded liposome-coated polymeric nanoparticles (LNPs) as IMB16-4 delivery systems for improving aqueous solubility, cellular uptake, and anti-fibrotic effects. The physical states of IMB16-4−LNPs were analyzed using a transmission electron microscope (TEM), high-performance liquid chromatography (HPLC), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and differential scanning calorimeter (DSC). The results show that IMB16-4−LNPs increased the drug loading compared to liposomes and enhanced cellular uptake behavior compared with IMB16-4−NPs. In addition, IMB16-4−LNPs could repress the expression of hepatic fibrogenesis-associated proteins, indicating that IMB16-4−LNPs exhibited evident anti-fibrotic effects.  相似文献   
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