252,617 research outputs found
Conférence de M. Su-Min Ri
No full textRi Su-Min. Conférence de M. Su-Min Ri. In: École pratique des hautes études, Section des sciences religieuses. Annuaire. Tome 98, 1989-1990. 1989. pp. 340-342
Catalytic properties and mechanism studies of the PepQ prolidase from Escherichia coli
No full textThe PepQ prolidase from Escherichia coli catalyzes the hydrolysis of dipeptide substrates with proline residues at the C-terminus. The PepQ gene has been cloned, overexpressed and the enzyme purified to homogeneity. The kcat and kcat/Km values for the hydrolysis of Met-Pro are 109 s-1 and 8.4 x 105 M-1 s-1, respectively. The enzyme also catalyzes the stereoselective hydrolysis of organophosphate triesters and organophosphonate diesters. A series of 16 organophosphate triesters with a p-nitrophenyl leaving group was assessed as substrates for this enzyme. The SP-enantiomer of methyl phenyl p-nitrophenyl phosphate was hydrolyzed with a kcat of 36 min-1 and a kcat/Km of 710 M-1 s-1. The corresponding RP-enantiomer was more slowly hydrolyzed with a kcat of 0.4 min-1 and a kcat/Km of 11 M-1 s-1. The PepQ prolidase can be utilized for the kinetic resolution of racemic phosphate esters. The PepQ prolidase was shown to hydrolyze the p-nitrophenyl analogs of the nerve agents GB (sarin), GD (soman), GF, and VX. The pH-rate profiles for the wild-type E. coli prolidase using proline dipeptides as substrates were obtained. The roles of H346, H228, and E384 in the enzyme catalytic mechanism were also investigated by obtaining the pH-rate profiles for the mutants H346N, H228N, and E384Q. In an effort to clarify the mechanistic role of the interaction of the ������-amino group of Xaa-Pro with metal at the enzyme active site, comparisons of the hydrolytic activity for Ala-Pro and 1-(1-oxopropyl)-L-proline, in which a hydrogen replaces the ������-amino group of Ala-Pro, were performed
Author Correction: Human fingerprint in global weather
No full textIn the version of this News & Views originally published, the ref. 5 author surnames Meihnausen, Fisher and Szekely were spelled incorrectly; they should have been spelled Meinshausen, Fischer and Székely, respectively. This has now been corrected. © 2020, Springer Nature Limited.11Nsciessciscopu
Energy Crop Supply in France: A Min-Max Regret Approach
No full textThis paper attempts to estimate energy crop supply using an LP model comprising hundreds of representative farms of the arable cropping sector in France. In order to enhance the predictive ability of such a model and to provide an analytical tool useful to policy makers, interval linear programming (ILP) is used to formalise bounded rationality conditions. In the presence of uncertainty related to yields and prices it is assumed that the farmer minimises the distance from optimality once uncertainty resolves introducing an alternative criterion to the classic profit maximisation rationale. Model validation based on observed activity levels suggests that about 40% of the farms adopt the min-max regret criterion. Then energy crop supply curves, generated by the min-max regret model, are proved to be upward sloped alike classic LP supply curves.interval linear programming, min-max regret, energy crops, France, Crop Production/Industries, Resource /Energy Economics and Policy, C61, D81, Q18,
The practice of access pricing : telecommunications in the United Kingdom
No full textTelecommunications was the first network utility to be privatized in the United Kingdom. Drawing on 15 years'experience and discussion in the field, the author shows the economic principles of regulation in general and access pricing in particular that have been implemented. British Telecommunications (BT), formed as a public enterprise in 1980-81, was privatized in 1984. Since then the approaches to regulation have changed in three broad periods: the duoply, the transition to competition, and the recently introduced normalization phase. Dealing with each period, the author focuses on how the actual implementation of access charges are determined, at the same time providing background needed on regulatory intervention generally. Rather than follow the model of competition for a common infrastructure, Oftel [the Office of Telecommunications, the regulatory agency]has encouraged competition between alternative networks, which benefits customers but involves duplication of fixed costs. As a result of Oftel's approach, customers have seen their bills reduced 50 percent in real terms since privatization. It is difficult to know how much to attribute this remarkable result to technological progress (BT halved its workforce in the same period), to regulatory intervention (Oftel set string caps until 1997), or to competition (there are hundreds of players in the market). The author contends more weight should probably be given to the first two. Entrants have not achieved big market shares, if one considers the asymmetric regulation that has been in place for more than a decade. Indirectly, at least, competition benefited consumers by applying discipline to BT's behavior. Oftel's approach was interventionist until 1997, when it began trying to normalize the industry, as authority overseeing competition. The odds on complete deregulation are slight, and some controls on industry will remain. In the longer term, Oftel should especially monitor anticompetitive practices and collusive behavior among the bigger players (BT, CWC, and cellulator operators), The United Kingdom's interconnection experience demonstrates the complexity of the problem and its relationship to other topics, such as tariff rebalancing, access deficit, and universal service. Although a bit ad hoc, the recent incentive regulation, with a network cap based on proper accounting procedures and engineering models, may represent the best practice available today in the telecommunications industry, says the author.Public Sector Economics&Finance,Decentralization,Knowledge Economy,Economic Theory&Research,Payment Systems&Infrastructure,Public Sector Economics&Finance,Education for the Knowledge Economy,Knowledge Economy,Economic Theory&Research,ICT Policy and Strategies
Min-Max Dom-Saturation Number of a Tree
No full textIn this paper we present a dynamic programming algorithm for determining the min-max domsaturation number of a tree
[M(OOCC6H4PO3H)(H2O)] (M(II) = Mn, Co, Ni): layered metal phosphonates showing variable magnetic behavior
No full textThree novel isomorphous transition metal phosphonate compounds with formula [M(OOCC6H4PO3H)(H2O)] [M(II) = Mn(1), Co(2), Ni(3)] were prepared through hydrothermal reaction of 2-carboxyphenylphosphonic acid and metal salts. Within the structure, the {M2O2} dimers made up of edge-sharing{MO6} octahedra are connected by carboxylate and/orphosphonate groups, leading to a 2-D layer. The phenyl groups fill in the inter-layer spaces. Magnetic measurements reveal that dominant antiferromagnetic interactions are observed in compounds 1 and 2, while for compound 3, the dominant ferromagnetic interaction leads to a spontaneous ferromagnetic long range ordering below T-c = 4.0 K
General fuzzy min-max neural network for clustering and classification
No full textThis paper describes a general fuzzy min-max (GFMM) neural network which is a generalization and extension of the fuzzy min-max clustering and classification algorithms of Simpson (1992, 1993). The GFMM method combines supervised and unsupervised learning in a single training algorithm. The fusion of clustering and classification resulted in an algorithm that can be used as pure clustering, pure classification, or hybrid clustering classification. It exhibits a property of finding decision boundaries between classes while clustering patterns that cannot be said to belong to any of existing classes. Similarly to the original algorithms, the hyperbox fuzzy sets are used as a representation of clusters and classes. Learning is usually completed in a few passes and consists of placing and adjusting the hyperboxes in the pattern space; this is an expansion-contraction process. The classification results can be crisp or fuzzy. New data can be included without the need for retraining. While retaining all the interesting features of the original algorithms, a number of modifications to their definition have been made in order to accommodate fuzzy input patterns in the form of lower and upper bounds, combine the supervised and unsupervised learning, and improve the effectiveness of operations. A detailed account of the GFMM neural network, its comparison with the Simpson's fuzzy min-max neural networks, a set of examples, and an application to the leakage detection and identification in water distribution systems are given
An extension of min/max flow framework
No full textIn this paper, the min/max flow scheme for image restoration is revised. The novelty consists of the fol-
24 lowing three parts. The first is to analyze the reason of the speckle generation and then to modify the
25 original scheme. The second is to point out that the continued application of this scheme cannot result
26 in an adaptive stopping of the curvature flow. This is followed by modifications of the original scheme
27 through the introduction of the Gradient Vector Flow (GVF) field and the zero-crossing detector, so as
28 to control the smoothing effect. Our experimental results with image restoration show that the proposed
29 schemes can reach a steady state solution while preserving the essential structures of objects. The third is
30 to extend the min/max flow scheme to deal with the boundary leaking problem, which is indeed an
31 intrinsic shortcoming of the familiar geodesic active contour model. The min/max flow framework pro-
32 vides us with an effective way to approximate the optimal solution. From an implementation point of
33 view, this extended scheme makes the speed function simpler and more flexible. The experimental
34 results of segmentation and region tracking show that the boundary leaking problem can be effectively
35 suppressed
Min Eng
No full textCanopy air curtains on roof bolting machines have been proven to protect miners from respirable dust, preventing their overexposure to dust. Another desired application for canopy air curtains is in the compartments of shuttle cars. The challenges faced in developing the design of canopy air curtains for shuttle cars include mine ventilation rates in tandem with the shuttle car tram speeds. The resulting cab airspeeds may exceed 182 m/min (600 fpm), as found in the present study conducted in a central Appalachian underground coal mine by U.S. National Institute for Occupational Safety and Health (NIOSH) researchers. Prior research and laboratory testing had indicated that successfully protecting a miner in high air velocities is difficult, because the clean air from the canopy air curtain is unable to penetrate through the high-velocity mine air. In this study, the dust concentrations to which a shuttle car operator was exposed were measured, and air velocities experienced by the operator were measured as well using a recording vane anemometer. The results indicate that the highest exposure to respirable dust, 2.22 mg/m|, occurred when the shuttle car was loading at the continuous miner, where the average airspeed was 48 m/min (157 fpm). While tramming, the operator was exposed to 0.77 mg/m| of respirable dust with an average airspeed of 62 m/min (203 fpm). This study indicates that a canopy air curtain system can be designed to greatly reduce an operator's exposure to respirable dust by providing clean air to the operator, as the majority of the operator's dust exposure occurs in air velocities slower than 61 m/min (200 fpm).CC999999/Intramural CDC HHS/United States2018-12-18T00:00:00Z30573922PMC6298443vault:3126
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