Cytotoxic Potential of a-Azepano- and 3-Amino-3,4-SeCo-Triterpenoids

Semi-synthetic triterpenoids, holding an amino substituted seven-membered A-ring (azepano-ring), which could be synthesized from triterpenic oximes through a Beckmann type rearrangement followed by a reduction of lactame fragment, are considered to be novel promising agents exhibiting anti-microbial, alpha-glucosidase, and butyrylcholinesterase inhibitory activities. In this study, in an attempt to develop new antitumor candidates, a series of A-ring azepano- and 3-amino-3,4-seco-derivatives of betulin, oleanolic, ursolic, and glycyrrhetinic acids were evaluated for their cytotoxic activity against five human cancer cell lines and non-malignant mouse fibroblasts by means of a colorimetric sulforhodamine assay. Azepanoallobetulinic acid amide derivative 11 was the most cytotoxic compound of this series but showed little selectivity between the different human tumor cell lines. Flow cytometry experiments showed compound 11 to act mainly by apoptosis (44.3%) and late apoptosis (21.4%). The compounds were further screened at the National Cancer Institute towards a panel of 60 cancer cell lines. It was found that compounds 3, 4, 7, 8, 9, 11, 15, 16, 19, and 20 showed growth inhibitory (GI₅₀) against the most sensitive cell lines at submicromolar concentrations (0.20–0.94 μM), and their cytotoxic activity (LC₅₀) was also high (1–6 μM). Derivatives 3, 8, 11, 15, and 16 demonstrated a certain selectivity profile at GI₅₀ level from 5.16 to 9.56 towards K-562, CCRF-CEM, HL-60(TB), and RPMI-8226 (Leukemia), HT29 (Colon cancer), and OVCAR-4 (Ovarian cancer) cell lines. Selectivity indexes of azepanoerythrodiol 3 at TGI level ranged from 5.93 (CNS cancer cell lines SF-539, SNB-19 and SNB-75) to 14.89 for HCT-116 (colon cancer) with SI 9.56 at GI₅₀ level for the leukemia cell line K-562. The present study highlighted the importance of A-azepano-ring in the triterpenic core for the development of novel antitumor agents, and a future aim to increase the selectivity profile will thus lie in the area of modifications of azepano-triterpenic acids at their carboxyl group.     

梯度铝蜂窝夹芯板的力学行为

梯度分层铝合金蜂窝板是一种有效的吸能结构,本工作在梯度铝蜂窝结构的基础上根据梯度率的概念,通过改变蜂窝芯层的胞壁长度,设计了4种质量相同、梯度率不同的铝蜂窝夹芯结构。通过准静态压缩实验,并结合非线性有限元模拟准静态及冲击态下梯度铝蜂窝夹芯结构的变形情况及其力学性能,分析对比了相同质量下梯度铝蜂窝夹芯结构在准静态下的变形模式以及冲击载荷下分层均质蜂窝结构和不同梯度率的分层梯度蜂窝结构的动态响应和能量吸收特性。结果表明:在准静态压缩过程中,铝蜂窝梯度夹芯板的变形具有明显的局部化特征,蜂窝芯的变形为低密度优先变形直至密实,层级之间的密实化应变差随芯层密度的增大而逐渐减小;在高速冲击下,梯度蜂窝板并非严格按照准静态过程中逐级变形直至密实,而是在锤头冲击惯性及芯层密度的相互作用下整体发生的线弹性变形、弹性屈曲、塑性坍塌及密实化;另外,在本工作所设计的梯度率中,当梯度率为γ₁=0.0276时,梯度蜂窝夹芯板的吸能性达到最好,相较于同等质量下的均质蜂窝夹芯板,能量吸收提高了10.63%。     

镁合金网格壁板压弯成形数值模拟及实验研究

为探索镁合金整体壁板压弯成形的可行性,以及镁合金壁板压弯成形过程中金属的流动规律,对AZ31镁合金网格壁板压弯成形进行了数值模拟和实验研究。建立了有限元数值模拟的几何模型,采用有限元计算软件对AZ31镁合金网格壁板压弯成形过程进行了数值模拟研究,分析了镁合金网格壁板压弯成形中的温度场、应变场、应力场、破坏系数等的分布规律。确定了合适的AZ31镁合金壁板压弯成形工艺参数,并对镁合金网格壁板压弯成形进行了实验研究,获得了合格的镁合金网格壁板弯曲件,并分析了镁合金网格壁板成形件尺寸精度,模拟结果与实验结果相吻合,最大相对误差为16.7%。     

长周期扰动应力下盘区柱内巷道锚杆支护动态响应规律

长周期扰动应力下盘区柱内巷道稳定及盘区柱整体稳定是大规模开采的关注重点。采用数值模拟方法,构建了大规模、多中段、长周期强烈开采扰动下的数值模型,建立了锚杆支护的拉伸破断、剪切破断数值力学模型,研究了不同水平、不同阶段回采过程中盘区柱内巷道锚杆支护的受力特性和盘区柱围岩的应力和塑性区发展特征。研究结果表明:不同开采阶段不同开采水平的锚杆轴力和巷道顶板变形响应明显,锚杆剪力由于变形监测部位的限制响应程度甚微,盘区柱内巷道稳定性好。盘区柱内巷道围岩偏应力场与塑性区动态演化仅在前两个中段开采时反应强烈,大规模开采结束时盘区柱仍然能够保持正常稳定。分析方法及分析结果能够对盘区柱内巷道稳定及盘区柱整体稳定做出提前预判,为盘区柱的正常使用提供安全保障。     

整体壁板离散填料滚弯成形有限元模拟

具有一定曲率外形的铝合金整体壁板属于典型的多筋零部件,传统弯曲成形工艺成形困难,容易产生多种缺陷。提出了离散填料辅助滚弯成形整体2A12T4铝合金壁板滚弯工艺,并通过实验与整体填料滚变成形进行了对比,同时采用有限元模拟技术,探究了离散填料辅助整体壁板滚弯成形中的影响因素。研究结果表明:填料数量、上下垫板厚度等因素对成形性能影响较大,填料在3~6块时成形稳定,可以有效地避免筋条屈曲与失稳;随垫板厚度增加,壁板表面圆弧更加光滑、连续,但是回弹性增强;上下垫板分别在10~20 mm厚度时,综合性能较好。通过离散填料辅助滚弯技术可以成形出质量较高的整体壁板。     

Characterization of an acrylic polymer under hygrothermal aging as an optically clear adhesive for touch screen panels

Optically clear adhesives (OCAs) are key components of touch screen panels (TSPs). It is important that OCAs do not affect the transparent electrodes in TSPs because OCAs are contacted to the transparent electrodes. Therefore, N-vinyl caprolactam (NVC) was incorporated in the composition of an acrylic pressure sensitive adhesive (PSA) with excluding an acidic component to maintain the cohesion for OCA preparation. With increasing amounts of NVC, the tack and peel strength of UV-cured PSA increased, but high amounts of NVC led to decreased peel strength. The UV-cured PSA films were placed in a high temperature and humidity chamber for 8 weeks to investigate the durability and corrosion property under hygrothermal conditions. In this study, the corrosion test method using copper foil was suggested as a simple and economical method and was used to evaluate the effect of NVC on the corrosion property of PSA. This method helped identify suitable OCAs that do not have corrosive property. PSA films containing more than 20 wt% of NVC promoted the corrosion of copper foil under hygrothermal aging conditions. The caprolactam ring was opened by moisture, and the PSA structure morphed into a polar structure during the aging process. This change caused a glass transition shift, an increase in the storage modulus at the rubbery plateau, and an increase in peel strength. The surface free energy of the PSA films also increased due to the increase in the polar property. However, high amounts of NVC caused a decrease in the peel strength after 8 weeks of aging because of increased molecular interactions.     

一种新型高杆灯灯盘挂接装置模型的设计与实验研究

高杆灯是由钢制柱型灯杆和大功率组合式灯架构成的新型照明装置。文中对高杆灯顶部灯盘的挂接进行研究,设计了一套挂接和脱卸方便,电极对接可靠的灯盘挂接装置模型,以指导实际产品的设计制作。通过改变挂接方式与挂接装置结构,借助SolidWorks软件进行三维模型结构设计,加工装配得到挂接装置实物模型。整套机构模型利用单片机控制,引导灯盘挂接顺利完成。     

车门内饰板优化分析及模具设计

利用CAE分析软件Moldex3D先找出整个设计是否存在缺陷,为了增加优化效率,采用田口实验设计法规划控制因子与配置。L9(34)直交表来求得成型条件的最佳化参数组别,观察结果并找出最佳成型条件,以降低成型后所发生的体积收缩率以及翘曲位移量。由S/N因子反应表可看出对于Z轴变形量在塑料温度209℃、保压时间11.025 s、冷却时间17.85 s时较优良。Z轴的翘曲从1.64 mm降低到1.04 mm,整体改善了36.5%,最终根据优化结果进行了模具设计。     

Green touch for hydrogen production via alkaline electrolysis: The semi-flexible PV panels mounted wind turbine design,production and performance analysis

The novel solar-wind integrated system has been firstly used for hydrogen production in literature with validating theoretical, simulated and experimental studies. This integrated system consists of two main parts; solar-assisted wind turbine and alkaline electrolysis cell.In the first part of this system, the semi-flexible PV panels are smoothly integrated on the vertical axis wind turbine blade. This is a unique design in literature, unlike the hybrid systems that include wind turbines and solar PV panels in published literature. The production and testing of the hybrid integrated system in a single structure were performed both in laboratory conditions and also the system was set up the roof of ATU (Adana Alparslan Turkes Science and Technology University) in Adana. The second part includes hydrogen production via alkaline electrolysis system. The cathodes consist of nickel-coated copper (Cu/Ni) and nickel-vanadium binary coated copper (Cu/NiV), that was produced via electrodeposition technique by self-supporting. The performance of electrodes was compared in 1 M KOH solution via I–V behavior, electrochemical impedance spectroscopy, and long term cathodic polarization analysis. Results showed that polarization resistance was decreased almost 4 times by NiV when comparing the Ni. The surface inhomogeneity values were 0.91 and 0.81 for Cu/Ni and Cu/NiV respectively. The hydrogen gas evolved at the cathodes was also measured and higher volumes were detected for NiV binary coating.     

Investigation of seasonal variations of Beijing pavement condition data using unevenly spaced dynamic panel data model

Beijing municipal highway administration started to collect pavement condition data on its major expressways since 2006. It is advised in the Chinese practice standard that data collection shall be conducted on annual basis. However, pavement data are usually collected at different seasons of the year, which may cause significant seasonal variations in the observed condition. Moreover, for some reasons, data are missing for some of the pavement sections at certain years, which could bring up difficulties in performance model estimation and inference. These concerns have been simply neglected in past practice. This study proposed an unevenly spaced dynamic panel data model to investigate the seasonal patterns of a performance indicator called Ride Quality Index (RQI). A quasi-differencing approach was adopted for the estimation. Data collected from the 5th Ring Road of Beijing were used in the case study. It was found that RQI data collected during the fall season are expected to be lower than that collected during the spring or summer seasons. Findings from this research would be helpful to pavement engineers in using unevenly spaced pavement condition data for future condition estimation.