Sulfated zirconia catalysts: Are Brønsted acid sites the source of the activity?

The thermal decomposition products of pyridinium sulfate differ from those of pyridinium sulfate supported on zirconia which in turn differs from that of pyridine adsorbed on a sulfated zirconia. Unsupported pyridinium sulfate decomposes to produce pyridine and sulfuric acid, and these subsequently react to produce oxides of carbon and sulfur. Zirconia that is sulfated and then exposed to pyridine does not release detectable amount of pyridine during heating in an inert gas; rather the pyridine undergoes oxidation reduction reactions simultaneously to release CO₂ and sulfur compounds. Pyridinium sulfate supported on zirconia decomposes upon heating to release pyridine and sulfuric acid, which reacts with the zirconia. The desorption of pyridine in one case and only CO₂/SO_x in the other case suggests that sulfated zirconia does not contain Brønsted acidity that can form pyridinium sulfate.     

Current practice in software quality and the impact of certification schemes

The paper presents the findings of a survey that investigated the level of quality management practice within some 150 UK companies from a sample of 500. It provides a snapshot of practice at the time of the survey, and assesses the impact of government quality initiatives particularly, the TickIT scheme at that time. The survey methodology is described, together with the results and conclusions. The sample has been graded by size of company, which the authors consider to have a significant effect upon the adoption of quality practices. The survey highlights the need to encourage small companies to adopt quality practices and to assist them with the short-term costs incurred.     

Efficient random subcloning of DNA sheared in a recirculating point-sink flow system

Based on a high-performance liquid chromatographic pump, we have built a device that allows recirculation of DNA through a 63-microm orifice with ensuing fractionation to a minimum fragment size of approximately 300 base pairs. Residence time of the DNA fragments in the converging flow created by a sudden contraction was found to be sufficiently long to allow extension of the DNA molecules into a highly extended conformation and, hence, breakage to occur at midpoint. In most instances, 30 passages sufficed to obtain a narrow size distribution, with >90% of the fragments lying within a 2-fold size distribution. The shear rate required to achieve breakage was found to be inversely proportional to the 1.0 power of the molecular weight. Compared with a restriction digest, up to 40% of all fragments could be cloned directly, with only marginal improvements in cloning efficiency having been observed upon prior end repair with Klenow, T4 polymerase or T4 polynucleotide kinase. Sequencing revealed a fairly random distribution of the fragments.     

Comments on “Editorial: fuzzy models-what are they andwhy?”

In the editorial by J.C. Bezdek (ibid., p.1), an example is presented to demonstrate differences between fuzzy membership and probability. The authors argue that probability can be used in a way much more closely analogous to this use of fuzzy membership, weakening the argument for the latter     

Long-term follow-up of a randomized post-induction therapy trial in acute myelogenous leukemia (a Southeastern Cancer Study Group trial)

A phase III clinical trial was designed to determine if more intensive induction and consolidation therapy for acute myeloblastic leukemia increases the remission rate and prolongs survival. A minor objective was to determine if the use of non-cross resistant drugs was more effective than the same drugs used for induction. Patients with untreated leukemia between the ages of 15 and 50 were given daunorubicin 45 mg/m2 for the first 3 days of a 10-day continuous infusion of cytosine arabinoside, initially at a dose of 2000 mg/m2 but reduced to 100 mg/m2 because of toxicity. Those under 36 achieving a complete remission and with an histocompatible donor were assigned to a transplant arm. The rest were randomized to receive one of three consolidation arms: A, cytosine arabinoside, 200 mg/m2 daily for 7 days and daunorubicin 45 mg/m2 daily for 3 days for three courses; B, one course as in Arm A followed by amsacrine, 120 mg/m2 daily for 5 days followed by a 5-day continuous infusion of azacytidine, 150 mg/m2/day; C, thioguanine and cytosine arabinoside, 100 mg/m2 every 12 h and daunorubicin 10 mg/m2 daily for 5 days for three courses followed by four maintenance courses of cytosine arabinoside, 100 mg/m2 daily for 5 days and daunorubicin, 45 mg/m2 for 2 days every 13 weeks. From 1981 to 1986, 398 eligible patients were enrolled and 219 achieved a complete remission. The initial induction dose of cytosine arabinoside was reduced after five of 29 patients exhibited fatal gastrointestinal toxicity. Only 11 patients were assigned to the transplant arm. There were no significant differences in the consolidation arms. The 5 year disease-free survivals were 38, 31 and 27% in arms A, B, and C respectively. Intensive consolidation therapy with the same or different drugs used in induction was as effective as lower dose consolidation followed by maintenance therapy.     

The use of stokeslets to describe the arbitrary translation of a disk near a plane wall

A previously presented method is extended to describe the fully three-dimensional Stokes flow generated by the translation in any direction of an arbitrarily oriented disk in fluid bounded by a plane wall. The velocity field is represented solely in terms of stokeslet distributions on the disk, modified to take account of the bounding wall according to the century-old idea of Lorentz. Sets of integral equations of the second kind, not all disjoint, are obtained for the Abel transforms in each Fourier mode of the density functions. However, only a few modes need be considered in determining the flow field to order D ^-3, where D is the distance of the disk axis from the wall. Less detail is required to evaluate the drag force and torque experienced by the disk.     

A multi-agent decision support system for stock trading

A distributed problem solving system can be characterized as a group of individual cooperating agents running to solve common problems. As dynamic application domains continue to grow in scale and complexity, it becomes more difficult to control the purposeful behavior of agents, especially when unexpected events may occur. This article presents an information and knowledge exchange framework to support distributed problem solving. From the application viewpoint the article concentrates on the stock trading domain; however, many presented solutions can be extended to other dynamic domains. It addresses two important issues: how individual agents should be interconnected so that their resources are efficiently used and their goals accomplished effectively; and how information and knowledge transfer should take place among the agents to allow them to respond successfully to user requests and unexpected external situations. The article introduces an architecture, the MASST system architecture, which supports dynamic information and knowledge exchange among the cooperating agents. The architecture uses a dynamic blackboard as an interagent communication paradigm to facilitate factual data, business rule, and command exchange between cooperating MASST agents. The critical components of the MASST architecture have been implemented and tested in the stock trading domain, and have proven to be a viable solution for distributed problem solving based on cooperating agents     

Energy use in controlled temperature marine aquaculture

Temperature control offers benefits in land‐based marine aquaculture: stock growth rates may be enhanced by heating in winter; mortality rates in summer may be reduced by cooling. However, if the plant is not well designed, temperature control may create very large energy demands. This paper describes the application of temperature control in abalone aquaculture in New Zealand, with a focus on energy considerations in plant design. An abalone farm using a semi‐closed water conditioning system is used as a case study for which an energy model, based on a heat pump system, is developed. The model is used to determine the impact of plant design and tank conditions on the economics of the operation. Copyright © 2002 John Wiley & Sons, Ltd.