Katznelson-Tzafriri type theorems for individual solutions of evolution equations

In this paper we present an extension of the Katznelson-Tzafriri Theorem to the asymptotic behavior of individual solutions of evolution equations . The obtained results do not require the uniform continuity of solutions as well as the well-posedness of the equations. The method of study is based on a recently developed approach to the spectral theory of functions that is direct and free of -semigroups.

     

p,p′-芳炔桥连的四联萘拓扑环芳分子的设计与合成

基于联萘衍生物手性构型高度稳定的特点, 以光学活性的(R)-2,2'-二乙炔基-1,1'-联萘为模板, 设计了3个有趣的拓扑环芳分子——含有4个手性联萘单元的(R,R,R,R)-2a～2c, 并探讨了它们的合成. 合成路线涉及三甲基硅(Me₃Si-)保护基的控制导入, 对位取代的芳基连接桥的链接, 保护基的脱去以及分子间偶合成环4个步骤. 用比旋光度([α]_D), MS, IR, UV-Vis, ¹H和¹³C NMR以及元素分析表征了这些化合物.     

Laser desorption/ionization mass spectrometry fingerprinting of complex hydrocarbon mixtures: application to crude oils using data mining techniques

Crude oil fingerprints were obtained from four crude oils by laser desorption/ionization mass spectrometry (LDI-MS) using a silver nitrate cationization reagent. Replicate analyses produced spectral data with a large number of features for each sample (>11,000 m/z values) which were statistically analyzed to extract useful information for their differentiation. Individual characteristic features from the data set were identified by a false discovery rate based feature selection procedure based on the analysis of variance models. The selected features were, in turn, evaluated using classification models. A substantially reduced set of 23 features was obtained through this procedure. One oil sample containing a high ratio of saturated/aromatic hydrocarbon content was easily distinguished from the others using this reduced set. The other three samples were more difficult to distinguish by LDI-MS using a silver cationization reagent; however, a minimal number of significant features were still identified for this purpose. Focus is placed on presenting this multivariate statistical method as a rapid and simple analytical procedure for classifying and distinguishing complex mixtures.     

Growth of narrowly dispersed porphyrin nanowires and their hierarchical assembly into macroscopic columns

The self-assembly of amphiphilic (porphyrin)Sn 1 in an aqueous Pluronic F127 media results in the formation of narrowly dispersed nanowires. Variation of aqueous Pluronic concentrations allows for a systematic variation of porphyrin nanowire lengths while keeping their widths constant. These nanowires can be further assembled into secondary macroscopic columns.     

Chemical constituents from the leaves of Manglietia phuthoensis and their effects on osteoblastic MC3T3-E1 cells

Two new phenyl glycosides, mangliesides A and B (1, 2), a new ionol glycoside, manglieside C (3), two new lignan glycosides, mangliesides D and E (4, 5), were isolated from the leaves of Manglietia phuthoensis, along with two known lignans, 3-methoxymagnolol (6) and obovatol (7). Their structures were established by means of 1D and 2D NMR, electrospray ionization (ESI)-MS and HR-ESI-MS experiments. Among them, compounds 2 and 5 significantly (p<0.05) increased the growth and differentiation of osteoblastic MC3T3-E1 cells in vitro.     

离子液体中钴的电沉积行为

在含有氯化钴的室温离子液体氯化1-甲基-3-乙基咪唑(EMIC)和乙二醇(EG)体系中研究了金属钴的电沉积. 循环伏安法测试表明, 在EMIC-CoCl2熔盐中, 乙二醇的加入促进了EMIC的解离, 从而使氧化还原电流增大, 在EMIC-CoCl2-EG体系中钴的电沉积是受扩散控制的非可逆电极过程, 在该电解液体系中, Co(II)在Pt电极上的传递系数α为0.30, 扩散系数D0为4.16×10^-6 cm·s^-1; 计时电流法研究表明, 钴在铂电极上的电结晶过程符合三维连续成核的生长机理; 场发射扫描电子显微镜(FE-SEM)观察镀层的微观形貌显示, 金属钴的结晶细小. XRD分析证实, 镀层为纯钴, 沉积的钴是晶态和微晶态的混合物, 并且晶粒尺寸为纳米级.     

TiO2-B纳米管负载过渡金属氧化物的电化学嵌锂性能

采用碱性条件下的水热法合成了质子钛酸盐纳米管,在此基础上采用化学沉淀方法制备了负载过渡金属(Co,Ni和Cu)氢氧化物的纳米管材料,然后在300 ℃氩气氛下烧结后得到负载过渡金属(Co,Ni和Cu)氧化物TiO₂-B纳米管。采用XRD和TEM等对其结构与形态进行了表征,采用恒电流充放电、循环伏安以及交流阻抗测试研究了其电化学嵌/脱锂性能。结果表明,TiO₂-B纳米管通过负载过渡金属(Co,Ni和Cu)氧化物纳米颗粒之后,改善了TiO₂-B纳米管的高倍率放电性能和循环稳定性。其中,负载NiO和CuO的TiO₂-B纳米管的高倍率放电性能和循环稳定性较为突出。研究还表明,负载过渡金属氧化物纳米颗粒后,有助于保持TiO₂-B纳米管在动态反应条件下的拟电容反应控制特征,并不同程度地减小了TiO₂-B纳米管的表面电荷转移电阻,这是TiO₂-B纳米管的电化学性能改善的主要原因。     

Effects of Charged Surfactants on Interfacial Water Structure and Macroscopic Properties of the Air-Water Interface

Surfactants are used to control the macroscopic properties of the air-water interface. However, the link between the surfactant molecular structure and the macroscopic properties remains unclear. Using sum-frequency generation spectroscopy and molecular dynamics simulations, two ionic surfactants (dodecyl trimethylammonium bromide, DTAB, and sodium dodecyl sulphate, SDS) with the same carbon chain lengths and charge magnitude (but different signs) of head groups interact and reorient interfacial water molecules differently. DTAB forms a thicker but sparser interfacial layer than SDS. It is due to the deep penetration into the adsorption zone of Br⁻ counterions compared to smaller Na⁺ ones, and also due to the flip-flop orientation of water molecules. SDS alters two distinctive interfacial water layers into a layer where H⁺ points to the air, forming strong hydrogen bonding with the sulphate headgroup. In contrast, only weaker dipole-dipole interactions with the DTAB headgroup are formed as they reorient water molecules with H⁺ point down to the aqueous phase. Hence, with more molecules adsorbed at the interface, SDS builds up a higher interfacial pressure than DTAB, producing lower surface tension and higher foam stability at a similar bulk concentration. Our findings offer improved knowledge for understanding various processes in the industry and nature.     

Characterization and Optimization of Injectable In Situ Crosslinked Chitosan-Genipin Hydrogels

In recent years, there has been an increased interest in injectable, in situ crosslinking hydrogels due to their minimally invasive application and ability to conform to their environment. Current in situ crosslinking chitosan hydrogels are either mechanically robust with poor biocompatibility and limited biodegradation due to toxic crosslinking agents or the hydrogels are mechanically weak and undergo biodegradation too rapidly due to insufficient crosslinking. Herein, the authors developed and characterized a thermally-driven, injectable chitosan-genipin hydrogel capable of in situ crosslinking at 37 °C that is mechanically robust, biodegradable, and maintain high biocompatibility. The natural crosslinker genipin is utilized as a thermally-driven, non-toxic crosslinking agent. The chitosan-genipin hydrogel's crosslinking kinetics, injectability, viscoelasticity, swelling and pH response, and biocompatibility against human keratinocyte cells are characterized. The developed chitosan-genipin hydrogels are successfully crosslinked at 37 °C, demonstrating temperature sensitivity. The hydrogels maintained a high percentage of swelling over several weeks before degrading in biologically relevant environments, demonstrating mechanical stability while remaining biodegradable. Long-term cell viability studies demonstrated that chitosan-genipin hydrogels have excellent biocompatibility over 7 days, including during the hydrogel crosslinking phase. Overall, these findings support the development of an injectable, in situ crosslinking chitosan-genipin hydrogel for minimally invasive biomedical applications.