Effect of the addition of alkali metals on the metallic phase of Pt/Al2O3 catalysts

The effect of the addition of alkali metals to Pt/Al₂O₃ catalysts for dehydrogenation of paraffins was studied. Results can be interpreted in terms of different effects. Thus, the addition of alkali metals produces a poisoning of the acid sites of the alumina support and a modification of the characteristics of the metallic phase. The latter effect involves not only an increase of the Pt particles size, but also an electronic modification of the metallic phase. These two effects are more marked with alkali metals with higher ionic radius, such as K.     

Langmuir and Langmuir-Blodgett Films of Polyfluorenes and Their Use in Polymer Light-Emitting Diodes

The Langmuir and Langmuir-Blodgett (LB) film properties of two polyfluorene derivatives, namely poly(2,7-9,9′-dihexylfluorene-dyil) (PDHF) and poly(9,9 dihexylfluorene-dyil-vynilene-alt-1,4-phenylene-vyninele) (PDHF-PV), are reported. Surface pressure (П-A) and surface potential (ΔV-A) isotherms indicated that PDHF-PV forms true monolayers at the air/water interface, but PDHF does not. LB films could be transferred onto various types of substrate for both PDHF and PDHF-PV. Only the LB films from PDHF-PV could withstand deposition of a layer of evaporated metal to form a light-emitting diode (PLED), which had typical rectifying characteristics and emitted blue light. It is inferred that the ability of the polymer to form true monomolecular layers at the air/water interface seems to be associated with the viability of the LB films in PLEDs.     

The effect of tin on dezincification of archaeological copper alloys

Archaeological objects are a unique source of information for long-term corrosion studies. The present work concerns a hoard of Roman imperial coins, contained in a vase, excavated in the neighbourhoods of Rome. Aim of the research is to explain different conservation conditions by correlating visually perceivable parameters, such as corrosion morphology and extent with compositional information obtained by non-destructive investigations. The best preserved coins were found to have high zinc, low lead and small amounts of tin consistently with what occurs in modern brasses; it was observed that the latter prevents selective corrosion of zinc, otherwise causing heavy surface deterioration.     

Quantitative Determination of Acetaminophen in Pharmaceutical Formulations Using Differential Scanning Calorimetry. Comparison with Spectrophotometric Method

In this paper our previous researches dealing with compatibility, thermoanalytical characterization, the kinetics of thermal degradation of acetaminophen, either pure or contained in some commercial pharmaceutical formulations, have found applications outlets. In a previous investigation the possible interactions between acetaminophen and four excipients contained in the commercial pharmaceutical formulations were tested. As a continuation of this research in the present study an analytical method based on differential scanning calorimetry (DSC) was applied to determine the acetaminophen content of four commercial pharmaceutical formulations. For a fifth drug it was shown that the method is not applicable owing to observed incompatibility with one of the excipients. Finally, the analytical results obtained were compared with those derived from two UV spectrophotometric methods (one, i.e., “direct method,” recommended by the Pharmacopeia and the other based on the first-order derivative UV spectra).     

Green Cloud Meta-Scheduling

This article aims to evaluate the flexibility of GreenMACC (Metascheduling Green Architecture to Provide Quality of Service in Cloud Computing). The GreenMACC has a module called LRAM (Local Resource Allocation Manager) to automate the execution of all scheduling policies implemented in the architecture. This module enables the Meta-scheduler automatically adjust for each type of service requested by the user of a private cloud. Due to this function, can be ensure the most appropriate behavior to the principles of GreenIT while worrying about the quality of service. In this paper is shown the importance of the LRAM on GreenMACC. This article is also shown how to include a new policy in GreenMACC in a way that identifies the LRAM and automatically use. Through the performance evaluation of the new policy included it could be concluded that the GreenMACC is a flexible, reliable architecture and the LRAM module enables the automation of choosing the best scheduling mechanism in a private cloud.     

A complex network approach to text summarization

Automatic summarization of texts is now crucial for several information retrieval tasks owing to the huge amount of information available in digital media, which has increased the demand for simple, language-independent extractive summarization strategies. In this paper, we employ concepts and metrics of complex networks to select sentences for an extractive summary. The graph or network representing one piece of text consists of nodes corresponding to sentences, while edges connect sentences that share common meaningful nouns. Because various metrics could be used, we developed a set of 14 summarizers, generically referred to as CN-Summ, employing network concepts such as node degree, length of shortest paths, d-rings and k-cores. An additional summarizer was created which selects the highest ranked sentences in the 14 systems, as in a voting system. When applied to a corpus of Brazilian Portuguese texts, some CN-Summ versions performed better than summarizers that do not employ deep linguistic knowledge, with results comparable to state-of-the-art summarizers based on expensive linguistic resources. The use of complex networks to represent texts appears therefore as suitable for automatic summarization, consistent with the belief that the metrics of such networks may capture important text features.     

Kinetic study of the selective catalytic hydrogenation of 1,3-butadiene in a mixture of n-butenes

The selective hydrogenation in liquid phase of 1,3-butadiene in the presence of n-butenes, over a commercial Pd/Al₂O₃ catalyst of the egg-shell type was studied.Experiments were carried out in a batch reactor at 44 °C. Initial concentration were in the range of 1%–2% of 1,3-butadiene, up to 10% of 1-butene, trans-2-butene and cis-2-butene. Partial hydrogen pressures ($p_{{\text{H}}_2}$) were between 1 and 8 atm.Two kinetic models were proposed to fit the experimental data. Both models give an adequate representation of the experimental data.     

Alkaline extraction conditions determine gelling properties of corn bran arabinoxylans

Alkali treatment is used for extraction of arabinoxylans (AXs) from cereal brans. Our objective was to determine the effect of alkali treatment conditions on oxidative gelling of corn bran AXs. AXs extracted through mild alkali treatment formed strong gels through ferulic acid (FA) crosslinking by the action of laccase. Increasing harshness of alkali treatment caused a decrease in average FA content of AXs and elasticity of gels. However, gelling capacity of the AX samples was not predicted well by average FA content. We hypothesize that this is due to the presence of AX molecules with different FA contents within a sample. AX molecules rich in FA would form crosslinks and participate in the network, while those with low FA contents would not. The proportion of participating molecules would be the factor deciding the gelling capacity of the sample. This concept of participating molecules was tested by establishing the presence of crosslinks in non-gelling samples through HPSEC and rheological measurements pertaining to the Cox–Merz rule. The study provides an approach to design of gels with different strengths, textures and colonic fermentation properties.     

An optimization algorithm for estimation of microbial survival parameters during thermal processing

Isothermal microbial survival curves are usually described by either linear or nonlinear time-dependent models, from which non-isothermal survival curves can be generated if the parameters describing the survival kinetics of the microbial population are known. In order to estimate these parameters, an algorithm based on the steepest decent optimization method was developed. The algorithm searches the values of the survival parameters which minimize the sum of the squared differences between the experimental data and the calculated values provided by the model. The difference of the proposed algorithm with a typical optimization technique is that each data point used is not necessarily coming from the same thermal treatment; instead, data from different non-isothermal processes can be used. The developed algorithm was tested by using published non-isothermal survival data of Salmonella. The data showed that the survival curves can be described by the Weibull model, an already accepted and frequently used nonlinear model. Salmonella's survival parameters were estimated from the end points and all data points, respectively, of three non-isothermal survival curves. The results obtained showed that the number of survival data points must be sufficiently large to obtain true or statistically sound values of the survival parameters. A suitable way to achieve this is to implement the algorithm using all data points of multiple non-isothermal survival curves or a large number of end points of non-isothermal treatments. Mathematically, the developed algorithm should be applicable to any microbial survival kinetics accurately describing the inactivation of the microorganisms because no specific survival kinetics has to be pre-assumed to run the algorithm.