Microstructural optimization of a zeolite membrane for organic vapor separation

A seeded growth method for the fabrication of high-permeance, high-separation-factor zeolite (siliceous ZSM-5, [Si96O192]-MFI) membranes is reported. The method consists of growing the crystals of an oriented seed layer to a well-intergrown film by avoiding events that lead to a loss of preferred orientation, such as twin overgrowths and random nucleation. Organic polycations are used as zeolite crystal shape modifiers to enhance relative growth rates along the desirable out-of-plane direction. The polycrystalline films are thin (approximately 1 micrometer) with single grains extending along the film thickness and with large in-plane grain size (approximately 1 micrometer). The preferred orientation is such that straight channels with an open diameter of approximately 5.5 angstroms run down the membrane thickness. Comparison with previously reported membranes shows that these microstructurally optimized films have superior performance for the separation of organic mixtures with components that have small differences in size and shape, such as xylene isomers.     

一种纯化苏云金杆菌Cry1Ac蛋白的方法

Cry蛋白的纯化技术在很大程度上制约了其结构与功能的研究.为此,提出了一种以等电点沉淀方法纯化苏云金杆菌Cry1Ac的原毒素,用分子筛层析纯化其活性毒素的方法.结果表明:Cry1Ac的原毒素在pH值5.05条件下沉淀纯化效果好;以纯化的原毒素激活进行分子筛层析,收集其最大峰便可获得较高浓度的活性毒素;该方法不仅纯化效果...     

Synthesis of self-pillared zeolite nanosheets by repetitive branching

Hierarchical zeolites are a class of microporous catalysts and adsorbents that also contain mesopores, which allow for fast transport of bulky molecules and thereby enable improved performance in petrochemical and biomass processing. We used repetitive branching during one-step hydrothermal crystal growth to synthesize a new hierarchical zeolite made of orthogonally connected microporous nanosheets. The nanosheets are 2 nanometers thick and contain a network of 0.5-nanometer micropores. The house-of-cards arrangement of the nanosheets creates a permanent network of 2- to 7-nanometer mesopores, which, along with the high external surface area and reduced micropore diffusion length, account for higher reaction rates for bulky molecules relative to those of other mesoporous and conventional MFI zeolites.     

Growth of uniformly oriented silica MFI and BEA zeolite films on substrates

Applications of zeolite films benefit from alignment of the integrated channels, but methods for film growth have nearly always introduced orientational randomization in the direction normal to the substrate. We now report facile methods to grow silicalite-1 films and pure silica beta zeolite films on substrates with straight or sinusoidal channels positioned uniformly upright at a thickness of up to 8 micrometers. Precise gel compositions and processing temperatures are critical to promote secondary growth on pre-formed oriented crystal monolayers while suppressing self-crystallization in the bulk medium. Preliminary results highlight the potential of these uniformly oriented films in the nonlinear optical response and separation of xylene isomers.     

Intra- and intermolecular band dispersion in an organic crystal

The high crystallinity of many inorganic materials allows their band structures to be determined through angle-resolved photoemission spectroscopy (ARPES). Similar studies of conjugated organic molecules of interest in optoelectronics are often hampered by difficulties in growing well-ordered and well-oriented crystals or films. We have grown crystalline films of uniaxially oriented sexiphenyl molecules and obtained ARPES data. Supported by density-functional calculations, we show that, in the direction parallel to the principal molecular axis, a quasi-one-dimensional band structure of a system of well-defined finite size develops out of individual molecular orbitals. In contrast, perpendicular to the molecules, the band structure reflects the periodicity of the molecular crystal, and continuous bands with a large dispersion were observed.     

分离CH4/CO2吸附剂优选及其工艺参数研究

选用5A分子筛、13X分子筛和硅胶作为吸附剂,采用变压吸附法进行脱除沼气中CO2试验,考察不同的吸附压力条件下CH4/CO2分离的效果,并对三种吸附剂的吸附性能进行分析和比较.结果表明,5A分子筛在0.7 Mpa下脱除CO2效果最好,获得CH4含量最大为90%~92%.5A分子筛在流量22.1 L·min-1的穿透时间约为200 s,获得CH4浓度最大,平均纯度为83.5%;脱附时间为560 s,再生效果较好     

干热河谷不同树龄攀枝花苏铁丛枝菌根真菌多样性研究

攀枝花苏铁是我国特有的古老残遗树种,为适应干热河谷气候,攀枝花苏铁与丛枝菌根真菌（arbuscular mycorrhizal fungi,AMF）建立特殊的共生体系。选用不同树龄的攀枝花苏铁为研究对象,采集攀枝花苏铁根系及根际土壤样品,采用醋酸墨水染色法观察根系的AMF定殖情况并计算定殖率;同时采用湿筛沉淀法对AMF孢子进行分离,通过形态学特征及分子生物学鉴定相结合的方法研究攀枝花苏铁AMF的种类、多样性及与树龄的关系。结果表明,14年生、8年生和3年生攀枝花苏铁根系AMF定殖率分别为36.13%、28.54%、21.10%;根际土壤AMF孢子密度分别为16.02、14.13、13.3个·g^-1,形态学鉴定到6属22种,分别为球囊霉属（Glomus）、无梗囊霉属（Acaulospora）、近明球囊霉属（Claroideoglomus）、斗管囊霉属（Funneliforms）、盾巨孢囊霉属（Scutellospora）和硬囊霉属（Sclerocystis）,球囊霉属和无梗囊霉属为优势属,相对多度分别为56.91%和28.23%。分子生物学鉴定到3属6种,分别为近明球囊霉（C.claroideum）、明球囊霉（G.clarum）、缩球囊霉（G.constrictum）、无梗囊霉属（A.srobiculata）、黑球囊霉（G.melanosporum）和地表球囊霉（G.versiforme）。统计分析表明,AMF定殖率与AMF孢子密度之间的相关性是0.873 9,呈显著的正相关关系。该研究为攀枝花苏铁的保育提供了理论依据。     

松香催化裂解及裂解产物组成

以活性白土、磷钨酸等为催化剂进行了松香催化裂解试验,并以活性白土为催化剂进行松香裂解反应条件及裂解产物组成的研究。结果表明：活性白土和磷钨酸的催化性能较强,反应2 h后可使松香酸值分别降至1.20 mg·g^－1和2.07 mg·g^－1;活性白土催化裂解松香的工艺条件为温度220 ～ 240 ℃、催化剂用量5.0% ～ 10.0%、反应时间1.0 h;在此反应条件下得到的裂解产物经气相色谱/质谱（GC/MS）分析表明是各种芳香类化合物的混合物,主要由萘、吲哚、吡啶和菲类等物质组成;松香裂解反应除了松香脱羧反应外,同时伴随着大量碳—碳键和碳—氢键的断裂和重排。图1表5参9     

Vertical aluminophosphate molecular sieve crystals grown at inorganic-organic interfaces

Tubular aluminophosphate molecular sieve crystals were grown at an organic interface with their channels (7 angstroms in cross section) vertical to the substrate. To induce surface nucleation and oriented growth of AIPO(4)-5 crystals, organophosphonate layers cross-linked with Zr(IV) were assembled on a gold substrate and the modified substrate was immersed in a hydrothermal bath containing reagents for the synthesis of the molecular sieve. Reflection-absorption infrared studies demonstrated the stability of the phosphonate layers under these conditions. Drastic changes in the morphology of the surface-grown crystals from spherical agglomerates to vertical needles to thin tilted needles could be achieved by adjusting the water content of the synthesis bath. Nitrogen sorption in these structures on a piezoelectric device confirmed the presence of zeolitic microporosity.     

Unimpeded permeation of water through helium-leak-tight graphene-based membranes

Permeation through nanometer pores is important in the design of materials for filtration and separation techniques and because of unusual fundamental behavior arising at the molecular scale. We found that submicrometer-thick membranes made from graphene oxide can be completely impermeable to liquids, vapors, and gases, including helium, but these membranes allow unimpeded permeation of water (H(2)O permeates through the membranes at least 10(10) times faster than He). We attribute these seemingly incompatible observations to a low-friction flow of a monolayer of water through two-dimensional capillaries formed by closely spaced graphene sheets. Diffusion of other molecules is blocked by reversible narrowing of the capillaries in low humidity and/or by their clogging with water.     

甘薯块根发育早期木质部内单位面积筛管束数与收获期淀粉含量的相关性

本文主要研究甘薯块根发育早期。即插植后40天的膨大块根中木质部内单位面积的筛管束数与收获期的淀粉含量有明显的相关性,可以作为甘薯高淀粉育种的早期鉴定的指标。     

Fabrication and properties of free-standing c60 membranes

Van der Waals forces that bind C(60) molecular solids are found to be sufficiently strong to allow the reproducible fabrication of free-standing C(60) membranes on (100) silicon wafers. Membranes, 2000 to 6000 angstroms thick, were fabricated by a modified silicon micro-machining process and were found to be smooth, flat, and mechanically robust. An important aspect of the silicon-compatible fabrication procedure is the demonstration that C(60) films can be uniformly and nondestructively thinned in a CF(4) plasma. Young's modulus and fracture strength measurements were made on membranes with areas larger than 6 millimeters by 6 millimeters. It may be possible to use C(60), membranes for physical property measurements and applications.     

Two molecular transitions influence cardiac sodium channel gating

Sodium channels from diverse excitable membranes are very similar in their structure, yet surprisingly heterogeneous in their behavior. The processes that govern the opening and closing of sodium channels have appeared difficult to describe in terms of a single, unifying molecular scheme. Now cardiac sodium channels have been analyzed by high-resolution single-channel recordings over a broad range of potentials. Channels exhibited both complex and simple gating patterns at different voltages. Such behavioral diversity can be explained by the balance between two molecular transitions whereby channels can exit the open state.     

伏毛铁棒锤根系异常次生生长及生物碱组化定位

[目的]明确宁夏六盘山伏毛铁棒锤根系结构、生长方式及生物碱在组织中的分布。[方法]采用石蜡切片及生物碱定位技术。[结果]伏毛铁棒锤根系由主根、侧根和不定根（块根）组成。根系初生结构正常,次生结构异常。主根的形成层和额外形成层产生了异常次生结构中的＂U＂形次生维管束和三生维管束,且主根的筛管群是由初生韧皮部和形成层分化的小筛管群组成。而块根的次生木质部呈＂U＂形,次生韧皮薄壁细胞占据了块根的绝大部分,且块根的筛管群主要由次生韧皮薄壁细胞分化形成。[结论]主根和块根的形成层组成及活动方式的不同导致了二者异常次生结构的不同。生物碱在主根中主要积累于内侧皮层和束间薄壁细胞,在块根中主要在次生韧皮薄壁细胞和髓中。     

伏毛铁棒锤根系异常次生生长及生物碱组化定位

[目的]明确宁夏六盘山伏毛铁棒锤根系结构、生长方式及生物碱在组织中的分布。[方法]采用石蜡切片及生物碱定位技术。[结果]伏毛铁棒锤根系由主根、侧根和不定根（块根）组成。根系初生结构正常,次生结构异常。主根的形成层和额外形成层分别产生了异常次生结构中的＂U＂形次生维管束和三生维管束,且主根的筛管群是由初生韧皮部和形成层分化的小筛管群组成;块根的次生木质部呈＂U＂形,次生韧皮薄壁细胞占据了块根的绝大部分,且块根的筛管群主要由次生韧皮薄壁细胞分化形成。[结论]主根和块根的形成层组成及活动方式的不同导致了二者异常次生结构的不同。生物碱在主根中主要积累于内侧皮层和束间薄壁细胞,在块根中主要在次生韧皮薄壁细胞和髓中。     

SAPO-5分子筛的合成技术及应用

讨论了影响SAPO-5分子筛合成的重要因素,对SAPO-5分子筛以及掺杂金属离子的SAPO-5分子筛催化剂在催化领域的应用进行了归纳,以期对影响SAPO-5分子筛合成的因素和掺杂金属离子的SAPO-5分子筛催化剂的性能有比较全面的认识。还对SAPO-5分子筛在择形催化、材料制备、吸附和分离、载体等领域的应用前景进行了展望。     

4种分离机械对规模化猪场污水处理效果研究

用4种分离机械对规模化猪场污水前处理降污效果进行试验,结果表明,板框压滤机易被猪场污水粗杂物堵塞,运行不稳定。离心机,斜板筛挤压机和振动筛挤压机都有显著降污效果;其中振动筛挤压机更适合规模化猪场使用,处理能力达15m3/h,对TS、CODcr和BOD5去除率分别达62.6%、61.2%和57.5%。分离出的粪渣含水率为53.2%;对万头猪场应用振动筛挤压机前处理,设备及工程相关投资约5.3万元,收集的粪渣出售收入,扣除运行成本,年可增收利税4.9万元,投资回报率达92.5%,1年多可收回投资,经济效益显著。     

Methane to ethylene with 85 percent yield in a gas recycle electrocatalytic reactor-separator

Methane was oxidatively coupled to ethylene with an ethylene yield up to 85 percent and a total C(2) hydrocarbon yield up to 88 percent in a gas recycle high-temperature (800 degrees C) electrocatalytic or catalytic reactor where the recycled gas passes continuously through a molecular sieve trap in the recycle loop. Oxygen is supplied either electrocatalytically by means of the solid electrolyte support of the silver-based catalyst or in the gas phase. The C(2) products are obtained by subsequent heating of the molecular sieve trap. The selectivity to ethylene is up to 88 percent for methane conversion up to 97 percent.     

Curving and frustrating flatland

Two polymer chains that occupy equal volumes when covalently linked together at one end self-assemble into an alternating lamellar morphology that has a characteristic period dictated by the molecular weight. When such copolymers are confined within alumina membranes that have cylindrical pores with diameters comparable to the repeat period, the interaction of the blocks with the confining walls and the imposed curvature induces a morphological transformation to relieve the constraints. Here, we show a lamella-to-toroid transition, captured through the dissolution of the surrounding membrane.     

FG-rich repeats of nuclear pore proteins form a three-dimensional meshwork with hydrogel-like properties

Nuclear pore complexes permit rapid passage of cargoes bound to nuclear transport receptors, but otherwise suppress nucleocytoplasmic fluxes of inert macromolecules >/=30 kilodaltons. To explain this selectivity, a sieve structure of the permeability barrier has been proposed that is created through reversible cross-linking between Phe and Gly (FG)-rich nucleoporin repeats. According to this model, nuclear transport receptors overcome the size limit of the sieve and catalyze their own nuclear pore-passage by a competitive disruption of adjacent inter-repeat contacts, which transiently opens adjoining meshes. Here, we found that phenylalanine-mediated inter-repeat interactions indeed cross-link FG-repeat domains into elastic and reversible hydrogels. Furthermore, we obtained evidence that such hydrogel formation is required for viability in yeast.