Modelling the distribution of stamp paper thickness via finite normal mixtures: The 1872 Hidalgo stamp issue of Mexico revisited

Izenman and Sommer (1988) used a non-parametric Kernel density estimation technique to fit a seven-component model to the paper thickness of the 1872 Hidalgo stamp issue of Mexico. They observed an apparent conflict when fitting a normal mixture model with three components with unequal variances. This conflict is examined further by investigating the most appropriate number of components when fitting a normal mixture of components with equal variances.

Structural and electron self-exchange rate variations in isomeric (hexaamine)cobalt(III/II) complexes

The syntheses and characterisation of the new macrocyclic hexaamine trans-(5(S),7(S),12(R),14(R)-tetramethyl)-1,4,8,11-tetraazacyclotetradecane-6,13-diamine (L-6) and its Co-III complex are reported. The X-ray crystal structural analyses of [CoL6]Cl-2(ClO4) [monoclinic, space group C2/c, a = 16.468(3) Angstrom, b = 9.7156(7) Angstrom, c = 15.070(3) Angstrom, beta = 119.431(8)degrees, Z = 4] and the closely related cis-diamino-substituted macrocyclic complex [CoL2](ClO4)(3) . 2H(2)O (L-2 = cis-6,13-dimethyl-1,4,8,11-tetraazacyclotetradecane-6,13-diamine) [orthorhombic, space group Pna2(1), a = 16.8220(8) Angstrom, b = 10.416(2) Angstrom, c = 14.219(3) Angstrom, Z = 4] reveal significant variations in the observed Co-N bond lengths and coordination geometries, which may be attributed to the trans or cis disposition of the pendent primary amines. The Co-III/II self-exchange electron transfer rate constants for these and other closely related hexaamines have been determined, and variations of some 2 orders of magnitude are found between pairs of trans and cis isomeric Co-III complexes.

Relationship between induced sputum cytology and inflammatory status with lung structural and functional abnormalities in asbestosis

Background Asbestosis is associated with lung cellular and immunological abnormalities. Induced sputum cytology and local and systemic markers of inflammation may be helpful to characterize disease status and progression in these patients. Methods Thirty-nine ex-workers with asbestosis on high-resolution CT (HRCT) and 21 non-exposed controls were evaluated. Sputum cytology and IL-8 in serum and sputum were related to lung function impairment. Results Subjects with asbestosis had reduced sputum cellularity but higher macrophagel neutrophil ratio and % macrophage as compared with controls. Sputum and serum IL-8 were also higher in patients with asbestosis (P < 0.05). In addition, evidence of lung architectural distorption on HRCT was associated with increased levels of serum IL-8. Interestingly, absolute macrophage number was negatively correlated with total lung capacity (r = -0.40; P = 0.04) and serum IL-8 to lung diffiusing capacity (r = -0.45; P = 0.01). Conclusions Occupationally exposed subjects with asbestosis on HRCT have cytologic abnormalities in induced sputum and increased local and systemic pro-inflammatory status which are correlated to functional impairment.

The structure of a novel insecticidal neurotoxin, omega-atracotoxin-HV1, from the venom of an Australian funnel web spider

A family of potent insecticidal toxins has recently been isolated from the venom of Australian funnel web spiders. Among these is the 37-residue peptide omega-atracotoxin-HV1 (omega-ACTX-HV1) from Hadronyche versuta. We have chemically synthesized and folded omega-ACTX-HV1, shown that it is neurotoxic, ascertained its disulphide bonding pattern, and determined its three-dimensional solution structure using NMR spectroscopy. The structure consists of a solvent-accessible beta-hairpin protruding from a disulphide-bonded globular core comprising four beta-turns. The three intramolecular disulphide bonds form a cystine knot motif similar to that seen in several other neurotoxic peptides. Despite limited sequence identity, omega-ACTX-HV1 displays significant structural homology with the omega-agatoxins and omega-conotoxins, both of which are vertebrate calcium channel antagonists; however, in contrast with these toxins, we show that omega-ACTX-HV1 inhibits insect, but not mammalian, voltage-gated calcium channel currents.

Structural analysis of three His32 mutants of DsbA: Support for an electrostatic role of His32 in DsbA stability

DsbA, a 21-kDa protein from Escherichia coli, is a potent oxidizing disulfide catalyst required for disulfide bond formation in secreted proteins. The active site of DsbA is similar to that of mammalian protein disulfide isomerases, and includes a reversible disulfide bond formed from cysteines separated by two residues (Cys3O-Pro31-His32-Cys33). Unlike most protein disulfides, the active-site disulfide of DsbA is highly reactive and the oxidized form of DsbA is much less stable than the reduced form at physiological pH. His32, one of the two residues between the active-site cysteines, is critical to the oxidizing power of DsbA and to the relative instability of the protein in the oxidized form. Mutation of this single residue to tyrosine, serine, or leucine results in a significant increase in stability (of similar to 5-7 kcal/mol) of the oxidized His32 variants relative to the oxidized wild-type protein. Despite the dramatic changes in stability, the structures of all three oxidized DsbA His32 Variants are very similar to the wild-type oxidized structure, including conservation of solvent atoms near the active-site residue, Cys3O. These results show that the His32 residue does not exert a conformational effect on the structure of DsbA. The destabilizing effect of His32 on oxidized DsbA is therefore most likely electrostatic in nature.

Virtual plants - integrating architectural and physiological models

Recent advances in computer technology have made it possible to create virtual plants by simulating the details of structural development of individual plants. Software has been developed that processes plant models expressed in a special purpose mini-language based on the Lindenmayer system formalism. These models can be extended from their architectural basis to capture plant physiology by integrating them with crop models, which estimate biomass production as a consequence of environmental inputs. Through this process, virtual plants will gain the ability to react to broad environmental conditions, while crop models will gain a visualisation component. This integration requires the resolution of the fundamentally different time scales underlying the approaches. Architectural models are usually based on physiological time; each time step encompasses the same amount of development in the plant, without regard to the passage of real time. In contrast, physiological models are based in real time; the amount of development in a time step is dependent on environmental conditions during the period. This paper provides a background on the plant modelling language, then describes how widely-used concepts of thermal time can be implemented to resolve these time scale differences. The process is illustrated using a case study. (C) 1997 Elsevier Science Ltd.

Structural characterisation of galactoglucomannan secreted by suspension-cultured cells of Nicotiana plumbaginifolia

Galactoglucomannan (GGM) from cultures of Nicotiana plumbaginifolia has Man:Glc:Gal:Ara:Xyl in 1.0:1.1:1.0:0.1:0.04 ratio. Linkage analysis contained 4- and 4,6-Manp, 4-Glcp, terminal Galp and 2-Galp, small amounts and terminal Arap and terminal Xylp, and similar to 0.03 mol acetyl per mol of glucosyl residue. Treatment with alpha- and beta-D-galactosidases showed that the majority of the side-chains were either single Galp-alpha-(1 --> residues or the disaccharide Galp-beta-(1 --> 2)-Galp-alpha-(1 --> linked to O-6 of the 4-Manp residues of the glucomannan backbone. Analysis of the oligosaccharides generated by endo-(1 --> 4)-beta-mannanase digestion confirmed that the GGM comprises a backbone of predominantly alternating --> 4)-D-Manp-beta-(1 --> and --> Lt)-D-Glcp-beta-(1 --> branched at O-6 of 65% of the 4-Manp residues. The major oligosaccharide identified was D-Glcp-beta-(1 --> 4)-[D-Galp-beta-(1 --> 2)-D-Galp-alpha-(1 --> 6)]-D-Manp-beta-(1 --> 4)-D-Glcp-beta-(I --> 4)-[D-Galp-alpha-(1 --> 6)]-D-Manp-beta-(1 --> (27%), and most of the other oligosaccharides produced in significant quantities were based on this structure. (C) 1997 Elsevier Science Ltd.

Proton transport model in the ionosphere .1. Multistream approach of the transport equations

The suprathermal particles, electrons and protons, coming from the magnetosphere and precipitating into the high-latitude atmosphere are an energy source of the Earth's ionosphere. They interact with ambient thermal gas through inelastic and elastic collisions. The physical quantities perturbed by these precipitations, such as the heating rate, the electron production rate, or the emission intensities, can be provided in solving the kinetic stationary Boltzmann equation. This equation yields particle fluxes as a function of altitude, energy, and pitch angle. While this equation has been solved through different ways for the electron transport and fully tested, the proton transport is more complicated. Because of charge-changing reactions, the latter is a set of two-coupled transport equations that must be solved: one for protons and the other for H atoms. We present here a new approach that solves the multistream proton/hydrogen transport equations encompassing the collision angular redistributions and the magnetic mirroring effect. In order to validate our model we discuss the energy conservation and we compare with another model under the same inputs and with rocket observations. The influence of the angular redistributions is discussed in a forthcoming paper.

New body fat prediction equations for severely obese patients

Background & aims: Severe obesity imposes physical limitations to body composition assessment. Our aim was to compare body fat (BF) estimations of severely obese patients obtained by bioelectrical impedance (BIA) and air displacement plethysmography (ADP) for development of new equations for BF prediction. Methods: Severely obese subjects (83 female/36 mate, mean age = 41.6 +/- 11.6 years) had BF estimated by BIA and ADP. The agreement of the data was evaluated using Bland-Altman`s graphic and concordance correlation coefficient (CCC). A multivariate regression analysis was performed to develop and validate new predictive equations. Results: BF estimations from BIA (64.8 +/- 15 kg) and ADP (65.6 +/- 16.4 kg) did not differ (p > 0.05, with good accuracy, precision, and CCC), but the Bland- Altman graphic showed a wide Limit of agreement (- 10.4; 8.8). The standard BIA equation overestimated BF in women (-1.3 kg) and underestimated BF in men (5.6 kg; p < 0.05). Two BF new predictive equations were generated after BIA measurement, which predicted BF with higher accuracy, precision, CCC, and limits of agreement than the standard BIA equation. Conclusions: Standard BIA equations were inadequate for estimating BF in severely obese patients. Equations developed especially for this population provide more accurate BF assessment. (C) 2008 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.

Folding processes and solitary waves in structural geology

Evolution of localized folding patterns in layered elastic and visco-elastic materials is reviewed in the context of compressed geological systems. The thin strut or plate embedded in a visco-elastic medium is used as an archetypal example to describe localized buckles which, in contrast to those from earlier formulations, appear in the absence of triggering imperfections. Structural and material effects are surveyed and important nonlinear characteristics are identified. A brief review of possible methods of analysis is conducted.

The structure of versutoxin (delta-atracotoxin-Hv1) provides insights into the binding of site 3 neurotoxins to the voltage-gated sodium channel

Background: Versutoxin (delta-ACTX-Hv1) is the major component of the venom of the Australian Blue Mountains funnel web spider, Hadronyche versuta. delta-ACTX-Hv1 produces potentially fatal neurotoxic symptoms in primates by slowing the inactivation of voltage-gated sodium channels; delta-ACTX-Hv1 is therefore a useful tool for studying sodium channel function. We have determined the three-dimensional structure of delta ACTX-Hv1 as the first step towards understanding the molecular basis of its interaction with these channels. Results: The solution structure of delta-ACTX-Hv1, determined using NMR spectroscopy, comprises a core beta region containing a triple-stranded antiparallel beta sheet, a thumb-like extension protruding from the beta region and a C-terminal 3(10) helix that is appended to the beta domain by virtue of a disulphide bond. The beta region contains a cystine knot motif similar to that seen in other neurotoxic polypeptides. The structure shows homology with mu-agatoxin-l, a spider toxin that also modifies the inactivation kinetics of vertebrate voltage-gated sodium channels. More surprisingly, delta-ACTX-Hv1 shows both sequence and structural homology with gurmarin, a plant polypeptide. This similarity leads us to suggest that the sweet-taste suppression elicited by gurmarin may result from an interaction with one of the downstream ion channels involved in sweet-taste transduction. Conclusions: delta-ACTX-Hv1 shows no structural homology with either sea anemone or alpha-scorpion toxins, both of which also modify the inactivation kinetics of voltage-gated sodium channels by interacting with channel recognition site 3. However, we have shown that delta-ACTX-Hv1 contains charged residues that are topologically related to those implicated in the binding of sea anemone and alpha-scorpion toxins to mammalian voltage-gated sodium channels, suggesting similarities in their mode of interaction with these channels.

Modelling congenital transmission of Chagas` disease

The successful elimination of vectorial and transfusional transmission of Chagas` disease from some countries is a result of the reduction of domestic density of the primary vector Triatoma infestans, of almost 100% of coverage in blood serological selection and to the fact that the basic reproductive number of Chagas` disease is very close to one (1.25). Therefore, congenital transmission is currently the only way of acquiring Chagas` Disease in such regions. In this paper we propose a model of congenital transmission of Chagas` disease. Its aim is to provide an estimation of the time period it will take to eliminate this form of transmission in regions where vetorial transmission was reduced to close to zero, like in Brazil. (C) 2009 Elsevier Ireland Ltd. All rights reserved.