Dehydrogenation of Light Alkanes Over Rhenium Catalysts on Conventional and Mesoporous MFI Supports

Recently, Re/HZSM-5 (Si/Al = 15) was shown to be an efficient catalyst for ethane dehydrogenation and aromatization at 823 K and atmospheric pressure. In this reaction, the major initial products were benzene, toluene and xylene (BTX), but increasing amounts of ethene were produced with time on stream due to deactivation of the catalyst. We show that by use of rhenium impregnated MFI supports with very few or no acidic sites (Si/Al > 500), highly selective ethane dehydrogenation catalysts are obtained with ethene selectivities of 98%. By use of mesoporous MFI supports (Si/Al >500) the lifetime of the catalyst appears to be slightly improved compared to conventional MFI crystals. The beneficial effect of a mesoporous MFI support is convincingly demonstrated in propane dehydrogenation, where both conversion and selectivities on the mesoporous MFI (Si/Al > 500) impregnated with Re are significantly higher than on Re supported on a comparable conventional MFI support.     

In formation: Support for flexibility, mobility, collaboration, and coherence

This paper describes support for flexibility, mobility and collaboration in engaging with, and making sense of, information. Our focus lies on the transitions people make between different, dynamic configurations of digital and physical materials, technologies, people and spaces. The technologies we describe have been developed in partnership with landscape architects over the past two years. We show that appliances and people can come together in a way that creates scope for such transitions, collaboration, and the emergence of new ways of working.     

Synthesis of supervisory controllers for hybrid systems based onapproximating automata

The paper concerns the synthesis of supervisory controllers for a class of continuous-time hybrid systems with discrete-valued input signals that select differential inclusions for continuous-valued state trajectories and event-valued output signals generated by threshold crossings in the continuous state space, the supervisor is allowed to switch the input signal value when threshold events are observed. The objective is to synthesize a nonblocking supervisor such that the set of possible sequences of control and threshold event pairs for the closed-loop system lies between given upper and lower bounds in the sense of set containment. We show how this problem can be converted into a supervisor synthesis problem for a standard controlled discrete-event system (DES). A finite representation may not exist for the exact DES model of the hybrid system, however. To circumvent this difficulty, we present an algorithm for constructing finite-state Muller automata that accept outer approximations to the exact controlled threshold-event language, and we demonstrate that supervisors that solve the synthesis problem for the approximating automata achieve the control specifications when applied to the original hybrid system     

Two Subgroups within the GH43_36 α-l-Arabinofuranosidase Subfamily Hydrolyze Arabinosyl from Either Mono-or Disubstituted Xylosyl Units in Wheat Arabinoxylan

Fungal arabinofuranosidases (ABFs) catalyze the hydrolysis of arabinosyl substituents (Ara) and are key in the interplay with other glycosyl hydrolases to saccharify arabinoxylans (AXs). Most characterized ABFs belong to GH51 and GH62 and are known to hydrolyze the linkage of α-(1→2)-Ara and α-(1→3)-Ara in monosubstituted xylosyl residues (Xyl) (ABF-m2,3). Nevertheless, in AX a substantial number of Xyls have two Aras (i.e., disubstituted), which are unaffected by ABFs from GH51 and GH62. To date, only two fungal enzymes have been identified (in GH43_36) that specifically release the α-(1→3)-Ara from disubstituted Xyls (ABF-d3). In our research, phylogenetic analysis of available GH43_36 sequences revealed two major clades (GH43_36a and GH43_36b) with an expected substrate specificity difference. The characterized fungal ABF-d3 enzymes aligned with GH43_36a, including the GH43_36 from Humicola insolens (HiABF43_36a). Hereto, the first fungal GH43_36b (from Talaromyces pinophilus) was cloned, purified, and characterized (TpABF43_36b). Surprisingly, TpABF43_36b was found to be active as ABF-m2,3, albeit with a relatively low rate compared to other ABFs tested, and showed minor xylanase activity. Novel specificities were also discovered for the HiABF43_36a, as it also released α-(1→2)-Ara from a disubstitution on the non-reducing end of an arabinoxylooligosaccharide (AXOS), and it was active to a lesser extent as an ABF-m2,3 towards AXOS when the Ara was on the second xylosyl from the non-reducing end. In essence, this work adds new insights into the biorefinery of agricultural residues.     

Robustness of supervisors for discrete-event systems

Supervisory control in the context of ω-languages is considered. The nominal supervisor design problem is to find a non-blocking supervisor for a nominal plant such that the closed-loop infinite behavior equals a specified closed-loop behavior. The robustness of solutions to the nominal problem is defined with respect to variations in the plant. It is shown there exists a supervisor solving the nominal problem which maximizes the set of plants for which the closed-loop languages for all other plants in the set satisfy lower and upper bounds in the sense of language containment. Computational issues are discussed and the theoretical results are illustrated with an example     

Effects of ginseng treatment on neutrophil chemiluminescence and immunoglobulin G subclasses in a rat model of chronic Pseudomonas aeruginosa pneumonia

OBJECTIVE: To examine the effect of different concentrations of calcium on the contractile responses of isolated strips of rabbit bladder detrusor to various forms of stimulation after 2 h incubation in the presence of substrate and oxygen depletion (in vitro ischaemia), followed by 1 h of recovery. The resultant contractile responses were correlated with the level of lipid peroxidation as determined by malonedialdehyde (MDA) concentration. MATERIALS AND METHODS: Isolated strips of rabbit bladder detrusor smooth muscle were incubated in Tyrode's solution containing different concentrations of calcium (0-5.4 mmol/L). The effect of 2 h of incubation in oxygen- and substrate-free medium (in vitro ischaemia), followed by a 1-h incubation in the presence of oxygen and substrate, on the contractile responses to field stimulation, carbachol and KCl were determined. The effects of repetitive stimulation (15 s of stimulation at 32 Hz applied every 5 min during the 2-h experimental period) were also assessed. RESULTS: The contractile responses to all stimuli increased as the extracellular calcium concentration was increased from 0.6 to 5.4 mmol/L. A 2 h exposure to in vitro ischaemia, followed by a return to normal solution, resulted in a diminished response to all stimuli. This contractile dysfunction was least in the presence of calcium chelator (EGTA) and greatest in the presence of 5.4 mmol/L calcium. Repetitive stimulation during in vitro ischaemia also exacerbated the contractile dysfunction. Lipid peroxidation increased during in vitro ischaemia in proportion to the calcium concentration and was enhanced by repetitive stimulation during this period. Regardless of the incubation conditions, the reduction in the contractile response was significantly greater for field-stimulated tissues than for those stimulated with carbachol or KCl. CONCLUSIONS: These results show that the magnitude of contractile dysfunction induced by incubation in the presence of substrate and oxygen depletion is reduced in the presence of low calcium concentrations, increased in the presence of high calcium levels and increased in the presence of repetitive stimulation. In addition, the level of lipid peroxidation after the recovery period was proportional to the magnitude of contractile dysfunction present.     

On Petri net models of infinite state supervisors

A class of supervisory control problems that require infinite state supervisors is considered, and Petri nets with inhibitor arcs (PNs) are introduced to model the supervisors. This PN-based approach to supervisory control is compared to automata-based approaches. The primary advantage of a PN-based supervisory controller is that it provides a finite representation of an infinite state supervisor. For verification, implementation, and testing reasons, a finite PN-based representation of an infinite state supervisor is preferred over an automata-based supervisor. It is shown that this modeling advantage is accompanied by a decision disadvantage, in that in general the controllability of a language that can be generated by the closed-loop system is undecidable     

Life stage specific impact of dimethoate on the predatory mite Hypoaspis aculeifer canestrini (Gamasida: Laelapidae)

Toxicants may affect juveniles more than adults because of physiological and behavioral aspects. When developing toxicity tests, this issue is often not addressed, and the most sensitive end point may be ignored. The topic was raised by a European working group aiming to develop a standard toxicity test with the predatory mite, Hypoaspis (Geolaelaps) aculeifer Canestrini, as this species was included in the EU Guidance documentfortesting of pesticides. To assess whether the juvenile life stages are the most susceptible, we examined the acute toxicity of dimethoate on larvae, protonymphs, deutonymphs, males, and females of H. aculeifer. The mites were exposed to 0, 2, 4, and 6 mg dimethoate kg(-1) for 7 days in an OECD artificial soil (5% organic matter). Total juvenile biomass, reproduction, mortality, and population growth rate (pgr) lambda were assessed at the end of the test. A comparison of mortality ranked the sensitivity of the life stages: Larvae (LC50 = 3.8 mg kg(-1)) > protonymphs (LC50 = 5.3 mg kg(-1)) > males (LC50 = 5.6 mg kg(-1)) > deutonymphs (LC50 = 7.1 mg kg(-1)) > females (LC50 = 7.6 mg kg(-1)). Effects on reproduction and pgr were significant at 2 mg dimethoate kg(-1), with population decline starting at this concentration. Thus, a test system with H. aculeifer including reproduction as end point is a rational approach, as reproduction will encompass juvenile mortality, at least with respect to dimethoate. Moreover, we suggest that pgr should be included in chronic standard tests because of high ecological relevance and the feasibility of applying it.