Resistance to Coking Determination by Temperature Programmed Reaction of n-Butane with Steam

Resistance to coking is one of the most important characteristics of nickel catalysts used for steam reforming of hydrocarbons, CO₂ reforming or methanation of carbon oxides. Microbalance reactors have for a long time played an important role in catalyst deactivation studies, providing coking and coke gasification rates. However, conventional thermogravimetric microbalances have a number of limitations. The aim of this paper is to compare initial temperatures of coking of Ni and Ni-Mo catalysts (with different resistance to coking) obtained in the temperature-programmed reaction of _n-butane with steam with the results of coking rates obtained by the traditional thermogravimetric method. The investigations showed great agreement of the results.     

Spherulite nucleation in polypropylene blends with low density polyethylene

Primary nucleation of spherulites in blends of isotactic polypropylene (iPP) with low density polyethylene (LDPE) was investigated by means of differential scanning calorimetry and optical microscopy. The number of iPP spherulites in the blend decreases with increasing LDPE concentration to a much greater extent than follows from the decreasing amount of iPP. The shapes of spherulite size distributions indicate that athermal (heterogeneous) primary nucleation is inhibited. The density of primary nucleation in the blends decreases strongly with increasing mixing time. The same effect was observed in the blends with the nucleating agent which was added to iPP or LDPE. These experiments demonstrate that heterogenoeus nuclei migrate across interphase boundaries from the iPP melt to the LDPE melt during the mixing process. It is suggested that the interfacial energy difference between the nuclei and the molten components of the blend is responsible for the migration of nuclei.     

PdCl2(P(OPh)3)2 Catalyzed Coupling and Carbonylative Coupling of Phenylacetylenes with Aryl Iodides in Organic Solvents and in Ionic Liquids

Efficient cross-coupling and carbonylative coupling of terminal alkynes with aryl iodides catalyzed by PdCl₂(P(OPh)₃)₂ in the presence of NEt₃ in toluene and in ionic liquids is described. In imidazolium ionic liquids, [bmim]PF₆ or [mokt]PF₆ (bmim = 1-butyl-3-methyl imidazolium cation, mokt = 1-methyl-3-octyl imidazolium cation) catalyst was recycled and used in four concecutive catalytic cycles with high activity. In the absence of aryl iodide the same catalytic system catalyzed head-to-tail dimerization of phenylacetylene to the 1,3-diphenyl enyne, trans-PhC ≡ C–C(Ph)=CH₂, with a yield of 85%.     

Synthesis of oligocarbonate diols from ethylene carbonate and aliphatic diols catalyzed by alkali metal salts

The influence of alkali metal salt catalysts and reaction conditions on the oxyethylene units formation in the synthesis of oligocarbonate diols from five-membered cyclic carbonates and aliphatic diols is presented. The reaction mechanism, involving the alkoxide group formation from cyclic carbonate and alkali metal salts has been proposed and discussed. The oligomeric products were analyzed by means of MALDI-TOF mass spectrometry and NMR spectroscopy.     

Preparation of modified active carbon from brown coal by ammoxidation

The technology of obtaining active carbon enriched in nitrogen from brown coal is described. The effect of ammoxidation by a mixture of ammonia and air at the ratio 1:3 at 300 and 350 °C, at each stage of the active carbon production has been tested. The amount of nitrogen introduced into the active carbon has been proved to depend on the stage at which ammoxidation was performed. Carbonisation and activation with steam of the samples enriched in nitrogen have been found to lead to a significant decrease in its content and to cause an increase in the stability of the nitrogen groups. The ammoxidation of the active carbon has decreased their surface area, while the ammoxidation and high temperature of activation favour the formation of surface oxide groups of basic character.     

Application of diffusion dialysis for reduction of acidity of real pregnant leach solutions containing Ni and Co ions

ABSTRACT

Diffusion dialysis (DD) was proposed as a pretreatment step to reduce the acidity of real sulfate/chloride pregnant leach solutions containing cobalt(II) and nickel(II). Optimum DD conditions that enable reduction of acidity in the feed while maintaining a high rejection level of metal ions present in PLS were proposed, e.g. for 0.06 dm³/min flow of both aqueous phases H⁺ concentration in the dialysate reached 3.8 and 2.99 M for PLS1 and PLS2, respectively. Acid diffusion coefficients varied from 0.32 ?10 ^?6 to 3.15?10^?6 m/s and decreased with increasing phase flow rates. Moreover, dialysate neutralization was beneficial for the H⁺ reduction in the feed.     

Comparison of selected algorithms for scheduling workflow applications with dynamically changing service availability

This paper compares the quality and execution times of several algorithms for scheduling service based workflow applications with changeable service availability and parameters. A workflow is defined as an acyclic directed graph with nodes corresponding to tasks and edges to dependencies between tasks. For each task, one out of several available services needs to be chosen and scheduled to minimize the workflow execution time and keep the cost of service within the budget. During the execution ofa workflow, some services may become unavailable, new ones may appear, and costs and execution times may change with a certain probability. Rescheduling is needed to obtain a better schedule. A solution is proposed on how integer linear pro- gramming can be used to solve this problem to obtain optimal solutions for smaller problems or suboptimal solutions for larger ones. It is compared side-by-side with GAIN, divide-and-conquer, and genetic algorithms for various probabilities of service unavailability or change in service parameters. The algorithms are implemented and subsequently tested in a real BeesyCluster environment.     

Bioelectrorheological model of the cell. 4. Analysis of the extensil deformation of cellular membrane in alternating electric field

Analysis of the angular distribution of extensil mechanical stress, sigma e, generated in cytoplasmic membranes by an external oscillating electric field, is presented. Theoretical considerations show that sigma e is directly proportional to the local relative increase in membrane area and/or to the local relative decrease in its thickness. The magnitude of this stress depends on the position of the analyzed point of the membrane in relation to field direction. The maximal value, sigma eo, is reached at the cell "poles." The magnitude of sigma eo depends on electric and geometric parameters (in particular on field frequency) of the system studied. The foregoing analysis can be applied to quantitatively describe the destabilizing effects of the electric field on the cellular membrane, leading to its poration, fusion, and destruction.     

Psychological Determinants of Using Facebook: A Research Review

In recent years, Facebook has become the most popular of social networking sites (SNSs). Due to its increasing popularity and rising number of its users, the phenomenon of Facebook has aroused academic interest as well. There has been a growing number of studies on this subject. The aim of this article is to present the main trends in Facebook research and to provide an overview of major empirical findings. Among the most intensively explored topics in Facebook research, studies that concentrate on personality and individual differences among users, the role of self-efficacy, and motivation for using that specific SNS were identified. There is also a growing trend in empirical studies that focuses on testing advanced theoretical models of Facebook usage determinants. Technology acceptance model, presented in this article, is one of the most often used among them. This kind of approach may serve as a suggestion for a methodological conceptualization in the future confirmatory research on Facebook.     

SpaDeS: Detecting spammers at the source network

Despite the large variety and wide adoption of different techniques to detect and filter unsolicited messages (spams), the total amount of such messages over the Internet remains very large. Some reports point out that around 80% of all emails are spams. As a consequence, significant amounts of network resources are still wasted as filtering strategies are usually performed only at the email destination server. Moreover, a considerable part of these unsolicited messages is sent by users who are unaware of their spamming activity and may thus inadvertently be classified as spammers. In this case, these oblivious users act as spambots, i.e., members of a spamming botnet. This paper proposes a new method for detecting spammers at the source network, whether they are individual malicious users or oblivious members of a spamming botnet. Our method, called SpaDeS, is based on a supervised classification technique and relies only on network-level metrics, thus not requiring inspection of message content. We evaluate SpaDeS using real datasets collected from a Brazilian broadband ISP. Our results show that our method is quite effective, correctly classifying the vast majority (87%) of the spammers while misclassifying only around 2% of the legitimate users.