Structural diversity of sphingomyelin microdomains

In cells plasma membrane, sphingomyelin (SM) plays a key role in the formation of a category of lipid microdomains enriched in cholesterol (Chl) often referred to as rafts. Atomic force microscopy (AFM) was used to analyze the mesoscopic topography of enriched SM microdomains in supported bilayers made of SM/dioleoylphosphatidylcholine (SM/DOPC) and SM/palmitoyl-oleoyl-phosphatidylcholine (SM/POPC) equimolar mixtures, in buffer, at room temperature. Gel–fluid phase separation occurs in both SM/DOPC and SM/POPC bilayers. The gel phase SM-enriched microdomains adopt a variety of size, shape and mesoscopic structure, from homogeneous flat domains of a few hundreds of nanometer in diameter to domains of several micrometers made of closely packed globular structures. Gel–gel phase separation in SM domains is also observed which gives rise to different structures for the diunsaturated and the mixed-saturated PC species. These differences could also extend to the interactions with Chl. This suggests that studies on rafts formation commonly performed using SM/DOPC mixture as a model should also include the physiologically more relevant POPC species.     

Ar assisted carbidization of TiO2 (1 1 0) supported Mo nanoparticles by decomposition of C2H4

Ar⁺ assisted carbidization of Mo nanoparticles supported on TiO₂ (1 1 0) is studied by scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). In order to activate the diffusion of carbon into the bulk of Mo nanoparticles we applied Ar ions (1 keV) during the exposure of C₂H₄. XPS exhibited that the decomposition of C₂H₄ at 850 K accompanied by ion bombardment results in an almost complete carbidization of nanocrystalline Mo while this treatment performed without ion bombardment results only in the carbidization of the particle surface. The modification of the crystallinity of the Mo-carbide particles was deduced from STM measurements.     

The LookingGlass distributed shared workspace

This paper describes a shared workspace system known as the LookingGlass. The system allows pairs of geographically distributed designers to work together in real-time via a computer-based shared drawing surface, a video link and an audio link. The system integrates many of the features found in previous shared drawing surface systems and additionally provides eye-to-eye contact between the users; awareness of onea's partner's direction of gaze in relation to oneself and the worksurface; and the ability to communicate using gestures in relation to the worksurface.These features are achieved in the LookingGlass system using a technique referred to as video-overlay which combines a full screen video image of a remote partner with a full screen shared drawing surface. Various configurations of video-overlay have been explored and the results of these studies are presented. The results of trials into the suitability of the LookingGlass for various types of design work are also presented and described.     

Removal of refractory S-containing compounds from liquid fuels on novel bifunctional CoMo/HMS catalysts modified with Ti

This study shows that titanium incorporation into hexagonal mesoporous silica (HMS) material has a positive effect on the activity of supported CoMo catalysts in the hydrodesulfurization (HDS) of dibenzothiophene (DBT) and 4-ethyl,6-methyl-dibenzothiophene (4E6MDBT). All catalysts showed the highest activity in the HDS of DBT than in the HDS of 4E6MDBT. The low reactivity observed in the HDS of 4E6MDBT is caused by the steric hindrance of the two alkyl groups at positions 4 and 6. The HDS of DBT over Ti-free catalyst proceeds exclusively via the direct desulfurization (DDS) route whereas over Ti-containing catalysts proceed via DDS (main route) and hydrogenation (HYD) pathway. The catalyst with a Si/Ti = 40 (molar ratio) was the most active in the HDS of DBT. A further increase in the Ti-content led to a decrease in Brønsted acidity and the S_BET specific area of the catalysts, which implies a decrease in the bifunctional character of the catalysts. Raman spectroscopy demonstrated that Ti-incorporation into HMS material leads to a decrease in the degree of polymerization of Mo species, and this implies a better dispersion of MoS₂, in good agreement with the XPS measurements. Regarding the HDS-resistant 4E6MDBT, the HDS reaction over the Ti-free catalyst was found to proceed exclusively via the dealkylation (DA) route. After Ti-incorporation into HMS material, additional acid-catalyzed isomerization occurs. With respect to industrial sample, the catalyst with Si/Ti = 40 showed lower intrinsic activity as well as greater selectivity toward isomerization route products.     

Anatase-rutile transformation in Fe/TiO2, Th/TiO2 and Cu/TiO2 catalysts and its possible role in metal-support interaction

Based onin-situ Mössbauer and X-ray diffraction studies, it is shown that in the Fe/TiO₂ catalyst, the anatase-rutile transformation of the TiO₂ support is facilitated by the Fe²⁺ ions formed during the reduction. The transformation occurs at lower temperatures in Th/TiO₂ and Cu/TiO₂ compared to pure TiO₂. In general, the transformation of anatase to rutile seems to occur at or below the temperature (770 K) at which strong-metal-support-interaction manifests itself.Contribution No. 718 from the Solid State and Structural Chemistry Unit.     

ns级脉冲磁场传感器的研制

变电站内存在具有ns级上升沿且幅值较高、频带较宽的快速瞬态电磁脉冲,以辐射和传导的方式干扰保护与控制等二次设备。为了评估变电站内电磁干扰及防护措施对干扰抑制效果的问题,基于法拉第电磁感应定律,研制了一套可用于测量高幅值、宽频带磁脉冲的ns级脉冲磁场传感器,并分析了其基本原理、幅频特性、灵敏度、方波磁场的幅值响应和测量干扰,阐述了其设计原则及应注意的问题。通过模拟电磁脉冲对其标定与测试,结果表明,此传感器的灵敏度为703.42V/T,频带为400kHz～100MHz,满足变电站内瞬态脉冲磁场测量的要求。     

Performance and characterization of supported metal catalysts for complete oxidation of formaldehyde at low temperatures

Activities of a series of metals (Pt, Pd, Rh, Cu, Mn) supported on TiO₂ were investigated for the catalytic oxidation of formaldehyde. Among them, Pt/TiO₂ was found to be the most promising catalyst. Nitrogen adsorption, hydrogen chemisorption, X-ray diffraction (XRD), transmission electron microscopy (TEM) and temperature programmed reduction (TPR) by H₂ were used to characterize the platinum catalysts. Using Ce_0.8Zr_0.2O₂, Ce_0.2Zr_0.8O₂, SiO₂ as supports instead of TiO₂, the activity sequence of 0.6 wt.% platinum with respect to the supports is TiO₂ > SiO₂ > Ce_0.8Zr_0.2O₂ > Ce_0.2Zr_0.8O₂, and this appears to be correlated with the dispersion of platinum on supports rather than the specific surface areas of the catalysts. Platinum loading on TiO₂ has a great effect on the catalytic activity, and 0.6 wt.% Pt/TiO₂ catalyst was observed to be the most active, which could be attributed to the well-dispersed platinum surface phase. The reduction temperature greatly affects the particle size and, consequently, the catalytic activity. The smaller particle size of platinum, due to its high dispersion on support, has a positive effect on catalytic performance. Increasing formaldehyde concentration and space velocity exhibits an inhibiting effect on the catalytic activity.     

New synthesis technique of supported ZSM-5 using organo-alumino-silicic gels

This contribution deals with the synthesis of a silicon-rich ZSM-5 obtained from an amorphous organo-alumino-silicic gel. The gel was formed by reacting a mechanical mixture of RHA (rice hull ash), silica’s source, and of natural clinoptilolite, source of alumina, with glycerol during 2 h at 200 °C. After a maturation period of one day at 60 °C, the reaction product was hydrolyzed by a tetra-propyl-ammonium (TPA) solution and then aged for two days at 135 °C in a stainless steel autoclave. After washing and drying, the X-ray pattern showed a well crystallized ZSM-5. The textural analysis of the slowly calcined solid at 500 °C for 4 h, and the SEM micrographies evidence that the zeolite was supported on mesoporous silica. The proportion of both components depends on the tunable hydrolysis conditions.     

对硝基苯胺水相加氢合成对苯二胺

以对硝基苯胺为原料,水为溶剂,考察了水相中负载型镍催化剂催化对硝基苯胺加氢还原的反应性能,并开展了中试实验。考察了反应温度、压力、保温时间、对硝基苯胺浓度、废水套用等因素对催化加氢反应性能的影响。实验结果表明,产品对苯二胺质量分数较高,催化剂和水可循环使用。得到较佳的工艺条件为:温度110℃,保温时间1 h,压力2.0 MPa,搅拌转速800 r/min,起始催化剂用量10%(以对硝基苯胺的质量为基准,下同),催化剂损耗0.2%(以起始添加催化剂的质量为基准)。在该工艺条件下,对苯二胺产率达99.5%以上。废水套用后排放废水量很少,且对催化剂催化活性、产品质量等没有影响。     

基于电流内环的一种逆变器控制策略研究

比较了几种电流内环控制的方法,提出了基于电感电流反馈的SPWM电流控制型双环控制策略。针对输出电压对电流环的交叉反馈作用,通过采用电容电压解耦方法,削弱了电容电压对内环的影响;针对负载电流扰动对电压外环的影响,采用负载电流前馈补偿方法,很大程度上增加了系统对负载电流扰动的抑制能力;针对电压外环的PI调节器存在的相位滞后,提出了基准电容电流前馈补偿方法,理论上达到输出电压与基准正弦给定的零相差。通过仿真和实验,证实了本控制方案的可行性和优越性。