Diffusion of water in zeolites

The self-diffusion coefficient D of water occluded in samples of near-faujasite has been determined by pulsed field-gradient spin-echo nuclear magnetic resonance. The value of D in square centimeters per second x 10(5) at 30 degrees C is 1.34, 1.65, and 1.88 in the following zeolites, respectively: Na X, Ca X, and Ca Y (X and Y being an indication of ratio of silicon to aluminum in the zeolites). By comparison, the value of D in pure water at 30 degrees C is 2.5 x 10(-5) cm(2)/sec. Arrhenius activation energies for D are 6.9, 6.8, and 5.6 kilocalories per mole, respectively, for the three faujasites and 5.0 kcal/mole for pure water. Thus, there appears to be little difference in diffusion behavior between free water and water occluded in faujasite.     

Simulating the adsorption of alkanes in zeolites

The configurational-bias Monte Carlo technique is applied to simulate the adsorption of long chain alkanes in zeolites. This simulation technique is several orders of magnitude more efficient than conventional methods that can be used to simulate the adsorption of long chain alkanes. The calculated heats of adsorption are found to be in excellent agreement with experimental data. The results show a surprising chain length dependence of the heats of adsorption. This dependence has a simple molecular explanation in terms of preferential siting of the long chain alkanes.     

Effect of zeolites on adaptation processes in cows

The possibility of using Khotynets natural zeolites for preventing the development of oxidative stress and correcting disorders in the antioxidant system of cows when treating diseases of the reproductive system and under unfavorable housing and feeding conditions during the winter stabling period is shown.     

Alkalinity and formation of zeolites in saline alkaline lakes

The solubility of rhyolitic glass increases with increasing alkalinity, whereas the ratio of silicon to aluminum decreases with increasing alkalinity. The strong correlation observed between alkalinity and zeolite mineralogy in saline, alkaline lakes is thought to be a function of this relationship between pH and the Si/Al ratio. It is suggested that this function is a result of the reaction between silicic glass and alkaline solution whereby (i) a gel forms, whose Si/Al ratio is controlled by the Si/Al ratio of the solution, and (ii) a zeolite forms from the gel, whose Si/Al ratio is, in turn, controlled by the composition of the gel.     

Organic-inorganic hybrid zeolites containing organic frameworks

Organic-inorganic hybrid zeolite materials containing an organic framework have been synthesized by partially superseding a lattice oxygen atom by a methylene group. The use of methylene-bridged organosilane as a silicon source gives zeolite materials containing an organic group as lattice (ZOL), with several zeolitic phases such as the MFI and the LTA structures. Through various characterization methods, the presence of methylene frameworks (Si-CH2-Si) that replace siloxane bonds (Si-O-Si) has been verified, although the Si-C bonds are partly cleaved to give rise to terminal methyl groups. The shape-selective lipophilicity of a ZOL material indicates that it is not a physical mixture of conventional zeolite and amorphous organic-containing material but contains a genuine organic-inorganic hybrid zeolite.     

天然沸石饲喂艾维因肉鸡试验

将750只两周龄艾维因肉仔鸡随机分为3组,每组250只。1组作为对照,2组添加1％沸石,3组添加3％沸石,饲养期42天。结果表明,各组间增重、饲料消耗差异不显著,但添加沸石使增重略有提高,肌肉中蛋白质及Fe,Zn,Cu,Mn等的含量有所增加,消化道内容物氨的浓度明显降低。因此,日粮中添加一定量的沸石可以节约饲料,降低生产成本,而且可以增进鸡群健康,改善肌肉品质。     

Synthetic zeolites: growth of larger single crystals

Synthetic zeolites 4A, P, and X were grown in acrylic gel to a size suitable for study of single crystals by x-ray diffraction.     

Desulfurization of transportation fuels with zeolites under ambient conditions

Deep desulfurization of transportation fuels (gasoline, diesel, and jet fuels) is being mandated by U.S. and foreign governments and is also needed for future fuel cell applications. However, it is extremely difficult and costly to achieve with current technology, which requires catalytic reactors operated at high pressure and temperature. We show that Cu+ and Ag+ zeolite Y can adsorb sulfur compounds from commercial fuels selectively and with high sulfur capacities (by pi complexation) at ambient temperature and pressure. Thus, the sulfur content was reduced from 430 to <0.2 parts per million by weight in a commercial diesel at a sorbent capacity of 34 cubic centimeters of clean diesel produced per gram of sorbent. This sulfur selectivity and capacity are orders of magnitude higher than those obtained by previously known sorbents.     

Following ion diffusion in solution

An x-ray projection microscope equipped with a charge-coupled device camera allows direct observation of zinc (Zn(2+)) ions diffusing in aqueous hydrochloric acid solution during the corrosion of zinc foil and pellets. Time series of microradiographic images with a lateral resolution on the order of 10 micrometers allow observation of the time and spatial evolution of the colorless Zn(2+) ions in solution without any previous treatment. The concentration distribution of the ions can be quantified from these images. This technique should find applications in the biology, chemistry, and electrochemistry of aqueous solutions, allowing direct observation of the behavior and concentration fluctuations of medium or heavy ions moving in a weakly absorbing medium.     

Cation diffusion in plagioclase feldspar

Steep compositional gradients in igneous plagioclase feldspar from slowly cooled intrusive bodies imply a maximum value of the intracrystalline diffusion coefficient for NaSi [unknown] CaAl exchange, D(max) approximately 10(-20) centimeters squared per second for temperatures in the range 1250 degrees to 1000 degrees C. Millimeter-sized grains cannot be homogenized in all geologic time; hence reactive equilibrium crystallization of plagioclase from the melt does not occur in dry systems.     

Farmer innovation diffusion via network building: a case of winter greenhouse diffusion in China

Farmer innovation diffusion (FID) in the developing world is not simply the adoption of an innovation made by farmers, but a process of communication and cooperation between farmers, governments, and other stakeholders. While increasing attention has been paid to farmer innovation, little is known about how farmers’ innovations are successfully diffused. To fill this gap, this paper aims to address the following questions: What conditions are necessary for farmers to participate in FID? How is a collaborative network built up between farmers and stakeholders for this purpose? And what roles can government play? The above questions are addressed through analysis of the diffusion of winter greenhouse technology in China. A framework for analyzing a FID system is developed, and the conclusion is drawn that building mutual trust and collaborative networks is crucial for the success of FID. Furthermore, this network building can be broken down into various levels with different scales, speeds and consequences for FID: informal networks among farmers themselves, farmer-led networks, and government-facilitated networks. The success of government intervention depends upon building and enhancing the collaborative networks in which farmer leadership is crucial.     

Chemical potential of water from measurements of optic axial angle of zeolites

Values of the uncorrected optic axial angle (2H(alpha)) of a crystal of the calcium zeolite stellerite (CaAl(2)Si(7)O(l8) . 7H(2)0) immersed in calcium chloride solutions of known activity of water (a(w)) are directly proportional to log a(w). A general relationship between the chemical potential of water in the crystal and the optic axial angle is obeyed.     

Single-file diffusion of colloids in one-dimensional channels

Single-file diffusion, prevalent in many processes, refers to the restricted motion of interacting particles in narrow micropores with the mutual passage excluded. A single-filing system was developed by confining colloidal spheres in one-dimensional circular channels of micrometer scale. Optical video microscopy study shows evidence that the particle self-diffusion is non-Fickian for long periods of time. In particular, the distribution of particle displacement is a Gaussian function.     

Myoglobin diffusion in bovine heart muscle

The rotational mobility of myoglobin in situ was determined by proton nuclear magnetic resonance line width measurements of a characteristic myoglobin resonance observed in bovine heart muscle spectra. The protein diffuses intracellularly at nearly half the rate observed in dilute solution. This high mobility allows the oxygenated form of myoglobin to contribute significantly to the overall diffusive flux of oxygen in respiring heart muscle.     

Protonic diffusion in high-pressure ice VII

Near ambient pressures, molecular diffusion dominates protonic diffusion in ice. Theoretical studies have predicted that protonic diffusion will dominate at high pressures in ice. We measured the protonic diffusion coefficient for the highest temperature molecular phase of ice VII at 400 kelvin over its entire stable pressure region. The values ranged from 10(-17) to 10(-15) square meters per second at pressures of 10 to 63 gigapascals. The diffusion coefficients extrapolated to high temperatures close to the ice VII melting curve were less by a factor of 10(2) to 10(3) than a superionic criterion of approximately 10(-8) square meters per second, at which protons would diffuse freely.     

Extra-large-pore zeolites with two-dimensional channels formed by 14 and 12 rings

Stable zeolites that have larger pore apertures and a three-dimensional pore topology are of interest because they could be used to adsorb larger molecules, particularly for application in oil refining. Several large-pore zeolitic materials with channels formed by openings of more than 12 rings are known, but all of them have a one-dimensional channel system that limits their use in catalysis. We report the synthesis and some characterizations of IM-12, a thermally stable germanium-containing zeolite that contains the first two-dimensional channel system with extra-large pores formed by 14- and 12-ring channels.     

Innovation in industry and the diffusion of technology

The varied definitions used in the sources that have been discussed make any aggregate analysis difficult. A simple three-stage analysis of flows to, from, and within the firm was used to facilitate comparisons. Even so, each of the generalizations is drawn from relatively small and unrepresentative samples. Case studies may continue to be a source of ideas and hypotheses for further research, but do not appear to offer a means for deeper understanding of the innovation process. The retrospective nature of nearly all of the sources discussed probably means that the process has been viewed as much more rational and well-ordered than it is in fact. This failing is partially overcome in firsthand accounts such as those of Suites and Bueche (63) and Frey and Goldman (64). Each of these accounts involves a successful innovation according to technical or commercial criteria, or both. However, many of the characteristics of innovations that have failed commercially (10) appear to be similar to those of successful cases. The few longitudinal studies, and studies comparing more and less successful cases, do support the main conclusions drawn above (10, 32, 38). More serious problems are raised by the distinctly nonrepresentative nature of the samples used. There are few cases (17, 33, 65) in which the contributions of more than one organization, or details of interactions over a significant period of time, are discussed. There is a wide variation in the importance of the innovations included, ranging from those affecting the economy as a whole to cases involving production in a single firm, albeit with significant commercial results (66). In addition to questions of comparability and sampling, a central problem for further research on innovation will be to devise an operational model to account for interfirm and interindustry differences. Polar definitions used in past studies, "high technology" and "mature industry," for example, are insufficient. One possibility is to use the strategy for growth or competition evident in a firm or an industry, such as sales maximization (automotive), cost minimization (transportation, communications), performance maximization (aircraft, chemicals), or control of materials resources (mining, petroleum), as a basis for drawing distinctions (67). For example, in an industry that seeks to maximize sales, one would expect innovations that would be highly visible to consumers to be developed rapidly (68). In a cost-minimizing situation, production, as opposed to product technology, would be a major source of uncertainty, while the reverse might be the case in a performance-maximizing situation. Greater uncertainty arising from technical sources would imply greater sophistication in effective firms' product planning approaches, while a more stable technology would imply greater sophistication in market research and market-oriented strategies for innovation, and so forth. Much more work is needed along these lines if outcomes of interventions in the innovative process are to be predicted with any accuracy. Some implications for providing incentives and reducing barriers do seem clear from the work to date. Effective directions for federal action lie in strategies such as creating new markets through purchases or procurement policies; aggregating or focusing markets through regulation and other means; providing for market entry by contracts to smaller firms, venture capital, stronger patent protection, and so on; and providing for mobility and informal contacts within the technical community. Technology "push" strategies (such as tax incentives) to increase most research spending, prizes for new technology, and documentation and information retrieval systems would probably be less important in stimulating innovation. Definitive answers will require the most difficult kind of research-experiments in the field. Since the interventions required are difficult and expensive in most cases, they will not be under the researcher's control. Nor will the effect of policy changes be visible over a short period. Thus it seems imperative to take advantage of interventions that occur fortuitously to construct "quasi-experiments" (69) with as great a degree of control over other factors as possible. For example, have recent changes in policy regarding federally held patents increased the commercial use of these patents? Have changes in the capital gains laws retarded the development and growth of "spin-off" enterprises? Has the identification of technology gaps (3) and competitive opportunities stimulated innovation? The effects of such actions on technical innovation could be carefully observed with a modest but sustained research effort, which promises to yield valuable information beyond that available from largely historical sources.