Effect of Sulfur or Nitrogen Poisoning on the Activity and Selectivity of Y-Zeolite-Supported Pt–Pd Catalysts in the Hydrogenation of Tetralin

The partial oxidation of methane (POM) to synthesis gas over SiO₂-supported Rh and Ru catalysts was studied by in situ microprobe Raman and in situ time-resolved FTIR (TR-FTIR) spectroscopies. The results of in situ microprobe Raman spectroscopic characterization indicated that no Raman band of Rh₂O₃ was detected at 500°C over the Rh/SiO₂ catalyst under a flow of a CH₄/O₂/Ar (2/1/45, molar ratio) mixture, while the Raman bands of RuO₂ can even be detected at 600°C over the Ru/SiO₂ catalyst under the same atmosphere. The experiments of in situ TR-FTIR spectroscopic characterizations on the reactions of CH₄ over O₂ pre-treated Rh/SiO₂ and Ru/SiO₂ catalysts indicated that the products of CH₄ oxidation over Rh/SiO₂ and Ru/SiO₂ greatly depend on the concentration of O²– species over the catalysts. On the catalysts with high concentration of O²–, CH₄ will be completely oxidized to CO₂. However, if the concentration of O²– species over the catalysts is low enough, CH₄ can be selectively converted to CO without the formation of CO₂. The parallel experiments using in situ TR-FTIR spectroscopy to monitor the reaction of the CH₄/O₂/Ar (2/1/45, molar ratio) mixture over Rh/SiO₂ and Ru/SiO₂ catalysts show that the mechanisms of synthesis gas formation over the two catalysts are quite different. On the Rh/SiO₂ catalyst, synthesis gas is mainly formed by the direct oxidation of CH₄, while on the Ru/SiO₂ catalyst, the dominant pathway of synthesis gas formation is via the sequence of total oxidation of CH₄ followed by reforming of unconverted CH₄ with CO₂ and H₂O. The significant difference in the mechanisms of partial oxidation of CH₄ to synthesis gas over Rh/SiO₂ and Ru/SiO₂ catalysts can be well related to the difference in the concentration of O²– species over the catalysts under the reaction conditions mainly due to the difference in oxygen affinity of the two metals.     

Composite coatings based on linear and branched block copolymers for hydroxyapatite deposition in simulated body-fluid

ABSTRACT

In this work, the fabrication of composite coatings based on block copolymers and silicates deposited on stainless-steel plates through electrophoretic deposition technique was studied. Linear poly(?-caprolactone), and poly(dimethylsiloxane-block-ε-caprolactone) copolymers were obtained through ROP polymerization, whereas branched poly(hydroxyethyl methacrylate-co-(hydroxyethylmethacrylate-graft-ε-caprolactone)-block-ε-caprolactone) copolymers were synthesized by a one-pot technique by combining ROP and RAFT synthesis. SEM micrographs revealed homogenous and dense structures over the metallic substrate and the absence of micro-cracks. Thermal characterization revealed residual percentages of solids between 63% and 72% wt/wt. Finally, an in-vitro assessment confirmed the presence of a hydroxyapatite layer over coatings after immersion in a simulated body-fluid solution by XRD analyses.     

Unifying classes and processes

Previously, we presented Circus, an integration of Z, CSP, and Morgan’s refinement calculus, with a semantics based on the unifying theories of programming. Circus provides a basis for development of state-rich concurrent systems; it has a formal semantics, a refinement theory, and a development strategy. The design of Circus is our solution to combining data and behavioural specifications. Here, we further explore this issue in the context of object-oriented features. Concretely, we present an object-oriented extension of Circus called OhCircus. We present its syntax, describe its semantics, explain the formalisation of method calls, and discuss our approach to refinement.     

Employing the algebraic Riccati equation for a parametrization of the solutions of the finite-horizon LQ problem: the discrete-time case

In this paper, a new methodology is developed for the closed-form solution of a generalized version of the finite-horizon linear-quadratic regulator problem for LTI discrete-time systems. The problem considered herein encompasses the classical version of the LQ problem with assigned initial state and weighted terminal state, as well as the so-called fixed-end point version, in which both the initial and the terminal states are sharply assigned. The present approach is based on a parametrization of all the solutions of the extended symplectic system. In this way, closed-form expressions for the optimal state trajectory and control law may be determined in terms of the boundary conditions. By taking advantage of standard software routines for the solution of the algebraic Riccati and Stein equations, our results lead to a simple and computationally attractive approach for the solution of the considered optimal control problem without the need of iterating the Riccati difference equation.     

Lot Streaming Flow Shop with a Heterogeneous Machine

Abstract

It is possible to obtain greater productivity of a production system by overlapping the operations required to process a manufacturing order. This methodology, known as lot streaming, requires dividing the production order (lot) into smaller sublots. In this article, we study production systems that include machines that operate in batch mode (processing a group of units at the same time) and single processing machines (processing one unit at a time) arranged in a flow shop configuration, that is all jobs must go through the same production stages in the same order. The obtained results show that addressing the problem with consistent sublots (a common sublot size used for the whole process) is inefficient. On the other hand, addressing the problem considering the sizing of sublots for each machine (variable sublots) greatly improves the quality of the solution but is computationally intensive (limiting the size of the problem that can be solved). Therefore, a decomposition procedure is proposed on the decision of sublots sizing. This procedure greatly improves the solution obtained using consistent sublots and does so with lower computational requirements than the variable sublots approach.     

Refinement of Actions in Circus,

This paper presents refinement laws to support the development of actions in Circus, a combination of Z and CSP adequate to specify the data structures and behavioural aspects of concurrent systems. In this language, systems are characterised as a set of processes; each process is a unit that encapsulates state and reactive behaviour defhed by actions. Previously, we have addressed the issue of refining processes. Here, we are concerned with the actions that compose the behaviour of such processes, and that may involve both Z and CSP constructs. We present a number of useful laws, and a case study that illustrates their application.     

Aqueous ferrofluids based on manganese and cobalt ferrites

Synthesis of two new aqueous ferrofluids is performed chemically according to Massart's procedure. Manganese and cobalt ferrite magnetic particles are precipitated and treated in order to obtain colloidal sols by creating a charge density on their surface. Such ionic ferrofluids can be prepared in an acidic (after a treatment by ferric nitrate) or in an alkaline medium at a concentration as high as 17moll^–1, i.e. a volumic fraction of 0.26. This result makes these new compounds of great interest.     

Phytosterols and tocopherols content of pulps and nuts of Brazilian fruits

Fruits and nuts from the North and Northeast regions of Brazil were collected to determine their phytosterol and tocopherol content. The species studied were Cotia nut (Aptandra spruceana M.), Brazil nut (Bertholletia excelsa H.B.K.), Mucajá (Couma rigida M.), Red Açaí (Euterpe oleracea M.), Inajá (Maximiliana maripa D.), Jenipapo (Genipa Americana L.), Buriti (Mauritia flexuosa L.) and Uxi (Endopleura uchi C.). Phytosterols were analyzed by GC–FID using β-cholestanol as an internal standard, while tocopherols were determined by RP-HPLC-DAD. The pulps of Mucajá (26–236 mg 100 g^–1), Inajá (119–285 mg 100 g^–1) and Jenipapo (216 mg 100 g^–1) showed the highest total phytosterol contents. Considering α-tocopherol equivalents, the pulps of Buriti (346.72 μg g^–1) and Uxi (200.92 μg g^–1) contained the highest vitamin E activity. Therefore, the results indicate that these fruits and nuts have great potential to be cultivated and marketed as alternative dietary sources for these bioactive compounds.     

Structured Methods of New Product Development and Creativity Management: A Teaching Experience

Using structured methods for managing business innovation can be an effective way to improve the ideation process. Teaching structured methods is a potent way to enhance the innovative capabilities of companies and to develop creative products for the marketplace. In this paper, structured models of innovation and product development are reviewed and an approach to them is presented, based on several MSc student projects. The implications for managers, such as the need to train employees in structured methods, and the implications for those who teach innovation management are discussed in detail.     

Use of mass spectrometry to characterize proteolysis in cheese

A rapid method for characterizing proteolysis in different cheese varieties was developed using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-ToF-MS). pH 4.6-soluble extracts of different cheese varieties were sub-fractionated using ethanol and 70% ethanol-soluble extracts were analyzed using MALDI-ToF-MS. Sample analysis time was ∼3 min compared to ∼100 min for reversed-phase HPLC; moreover, the method yielded accurate molecular masses of peptides originating as a result of proteolysis. Small peptides (<3500 m/z) were monitored and data for relative intensities of peptides were analyzed using multidimensional scaling (MDS) to demonstrate the similarity between profiles obtained from different cheese varieties. The similarities between the profiles of MALDI-ToF mass spectra were demonstrated in a two-dimensional space by performing MDS on the similarity matrix. Use of MALDI-ToF-MS is thus a fast and effective method for monitoring small peptides produced in cheese as a result of proteolysis.