612 research outputs found
Distance Measures for Reduced Ordering Based Vector Filters
Reduced ordering based vector filters have proved successful in removing
long-tailed noise from color images while preserving edges and fine image
details. These filters commonly utilize variants of the Minkowski distance to
order the color vectors with the aim of distinguishing between noisy and
noise-free vectors. In this paper, we review various alternative distance
measures and evaluate their performance on a large and diverse set of images
using several effectiveness and efficiency criteria. The results demonstrate
that there are in fact strong alternatives to the popular Minkowski metrics
Mutations of penicillin acylase residue B71 extend substrate specificity by decreasing steric constraints for substrate binding
Two mutant forms of penicillin acylase from Escherichia coli strains, selected using directed evolution for the ability to use glutaryl-L-leucine for growth [Forney, Wong and Ferber (1989) Appl. Environ. Microbiol. 55, 2550-2555], are changed within one codon, replacing the B-chain residue Phe(B71) with either Cys or Leu. Increases of up to a factor of ten in k(cat)/K-m values for substrates possessing a phenylacetyl leaving group are consistent with a decrease in K-s. Values of k(cat/)K(m) for glutaryl-L-leucine are increased at least 100-fold. A decrease in k(cat)/K-m for the CySB71 mutant with increased pH is consistent with binding of the uncharged glutaryl group. The mutant proteins are more resistant to urea denaturation monitored by protein fluorescence, to inactivation in the presence of substrate either in the presence of urea or at high pH, and to heat inactivation. The crystal structure of the Leu(B71) mutant protein, solved to 2 X resolution, shows a flip of the side chain of Phe(B256) into the periphery of the catalytic centre, associated with loss of the pi-stacking interactions between Phe(B256) and Phe(B71). Molecular modelling demonstrates that glutaryl-L-leucine may bind with the uncharged glutaryl group in the S-1 subsite of either the wild-type or the Leu(B71) mutant but with greater potential freedom of rotation of the substrate leucine moiety in the complex with the mutant protein. This implies a smaller decrease in the conformational entropy of the substrate on binding to the mutant proteins and consequently greater catalytic activity
Introducing migratory flows in life table construction
The purpose of life tables is to describe the mortality behav
iour of particular groups. The
construction of general life tables is based on death statis
tics and census figures of resident
populations under the hypothesis of closed demographic sys
tem. Among other assumptions, this
hypothesis implicitly assumes that entries (immigrants) a
nd exits (emigrants) of the population
are usually not significant (being almost of the same magnitu
de for each age compensating each
other). This paper theoretically extends the classical sol
ution to open demographic systems and
studies the impact of this hypothesis in constructing a life
table. In particular, using the data of
residential variations made available to the public by the S
panish National Statistical Office (INE,
Instituto Nacional de Estad
́
ıstica) to approximate migratory flows, we introduce in the p
rocess of
constructing a life table these flows and compare, before and
after graduation, the crude mortality
rates and the adjusted death probabilities obtained when mi
gratory flows are, and are not, taken
into accountPeer Reviewe
Oxidative Stress and Antioxidant Defenses Induced by Physical Exercise
This chapter intends to present the physiological and biochemical mechanisms by which exercise induces the appearance of oxidative stress, as well as the characteristics of the physical exercise that involve the appearance of oxidative stress in the human organism
Algorithms for identification and categorization
The main features of a family of efficient algorithms for recognition and
classification of complex patterns are briefly reviewed. They are inspired in
the observation that fast synaptic noise is essential for some of the
processing of information in the brain.Comment: 6 pages, 5 figure
Introducing migratory flows in life table construction
The purpose of life tables is to describe the mortality behaviour of particular groups. The construction of general life tables is based on death statistics and census figures of resident populations under the hypothesis of closed demographic system. Among other assumptions, this hypothesis implicitly assumes that entries (immigrants) and exits (emigrants) of the population are usually not significant (being almost of the same magnitude for each age compensating each other). This paper theoretically extends the classical solution to open demographic systems and studies the impact of this hypothesis in constructing a life table. In particular, using the data of residential variations made available to the public by the Spanish National Statistical Office (INE, Instituto Nacional de Estadística) to approximate migratory flows, we introduce in the process of constructing a life table these flows and compare, before and after graduation, the crude mortality rates and the adjusted death probabilities obtained when migratory flows are, and are not, taken into account
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