Bulges

We model the evolution of the galactic bulge and of the bulges of a selected sample of external spiral galaxies, via the multiphase multizone evolution model. We address a few questions concerning the role of the bulges within galactic evolution schemes and the properties of bulge stellar populations. We provide solutions to the problems of chemical abundances and spectral indices, the two main observational constraints to bulge structure.Comment: 15 pages, 10 figures, to be published in MNRA

Physiological flow in a model of arterial stenosis

No abstract available

Weathering of the Ethiopian volcanic province: a new weathering index to characterize and compare soils

© Walter de Gruyter Berlin/Boston 2015.Soil formation occurs through numerous physical and chemical weathering processes acting to alter the parent rock on the Earths surface. Samples of surface soils were collected over a range of elevations (2000-3600 m) from profiles directly overlying basaltic to more felsic parent rocks, over a region in NW Ethiopia. The soils were investigated to determine their chemical composition and X-ray diffraction was used to identify and quantify individual mineral phases. The data set was analyzed using non-parametric statistics (Spearmans Rank and Mann-Whitney U tests) to compare the soils forming over the two parent rocks. Principal component analysis (PCA) was used to identify the mineral alteration assemblage and formation during pedogenesis. The extent of alteration was quantified using several chemical weathering indices (Chemical Index of Alteration = CIA; Chemical Index of Weathering = CIW), including an index calculated by multivariate analyses of the soil chemical composition data (weathering W index). Further to this we devised and tested a new weathering index (Wmin) using multivariate analysis of the soil mineralogy, to estimate the extent of weathering and physico-chemical proprieties of the parent rock from which the soil formed. The soils present a fair to advanced stage of alteration, with abundant iron (Fe) oxides (up to 40 wt%) and phyllosilicates (up to 57 wt%), including kaolinite-smectite (K-S) mixed-layer phases. The K-S was composed of either 30-50% kaolinite or 94-98% kaolinite layers. Discrete kaolinite was also present. The bimodal K-S mineralogical composition is likely due to two precursor phases: feldspar for the kaolinite-rich K-S and volcanic glass for the smectite-rich K-S. K-S with intermediate composition (50-94% kaolinite) was rare, due to its instability. Statistical analysis showed significant differences between the chemical compositions of the soils developed on the two different parent volcanic compositions. The soils overlying the more felsic parent rocks were less altered than those overlying the flood basalt. When comparing the weathering indices calculated in this study, we conclude that while the CIA and CIW may be more readily determined, the W and Wmin indices can elucidate information on the composition of the original rock from which they formed. The W index is more sensitive to certain variables when compared with the newly derived mineralogical Wmin index; however the Wmin index takes into account mineral phases within the sample, which provides a more detailed interpretation of weathering rates than chemistry alone. In addition the Wmin index correlated with meteorological variables, such as elevation (and consequently temperature and precipitation), known to influence the degree of pedogenesis. The Wmin index can be used to enhance our understanding of the processes that occur during weathering processes to supplement information gained from traditional chemical weathering indices

Utilización de fijadores externos circulares en el tratamiento de la pseudoartrosis infectada de tibia secuela de aplastamiento de miembros

Se revisan 7 casos de pseudoartrosis infectada de tibia, secuela de aplastamiento de miembros, tratadas inicialmente en el momento de la fractura con desbridamiento y fijador externo monolateral. Todos los casos eran iniciamente fracturas abiertas grado III de Gustilo. El tratamiento de la pseudoartrosis se realizó mediante desbridamiento, estabilización con fijador externo circular, cobertura de partes blandas e injerto óseo. La unión ósea se consiguió en todos los casos con una buena recuperación funcional. Se discuten las ventajas del fijador externo circular en estos casos.Seven patients with infected tibial pseuarthrosis due to crush injuries of the lower extremity and treated by using circular cxternal fixators were reviewed. All cases had tibial open fractures, Gustillo's type III. Treatment consisted of debridement, stabilization with a circular device, bone graft and coverage of soft tissues. Bone union «as achieved in all cases with a satisfactory functional recovery. The advantages of external fixators for this type of lesion are addressed

Characterization of the Covalently Bound Anionic Flavin Radical in Monoamine Oxidase A by Electron Paramagnetic Resonance

It was recently suggested that partially reduced monoamine oxidase (MAO) A contains an equilibrium mixture of an anionic flavin radical and a tyrosyl radical (Rigby, S. E.; et al. J. Biol. Chem. 2005, 280, 4627-4632). These observations formed the basis for a revised radical mechanism for MAO. In contrast, an earlier study of MAO B only found evidence for an anionic flavin radical (DeRose, V. J.; et al. Biochemistry 1996, 35, 11085-11091). To resolve the discrepancy, we have performed continuous-wave electron paramagnetic resonance at 94 GHz (W-band) on the radical form of MAO A. A comparison with D-amino acid oxidase (DAAO) demonstrates that both enzymes only contain anionic flavin radicals. Pulsed electron-nuclear double resonance spectra of the two enzymes recorded at 9 GHz (X-band) reveal distinct hyperfine coupling patterns for the two flavins. Density functional theory calculations show that these differences can be understood in terms of the difference at C8 of the isoalloxazine ring. DAAO contains a noncovalently bound flavin whereas MAO A contains a flavin covalently bound to a cysteinyl residue at C8. The similar electronic structures and hydrophobic environments of MAO and DAAO, and the similar structural motifs of their substrates suggest that a direct hydride transfer catalytic mechanism established for DAAO (Umhau, S.; et al. Proc. Natl. Acad. Sci. U.S.A. 2000, 97, 12463-12468) should be considered for MAO

Modulating D-amino acid oxidase substrate specificity: production of an enzyme for analytical determination of all D-amino acids by directed evolution

Recent research on the flavoenzyme D-amino acid oxidase from Rhodotorula gracilis (RgDAAO) has revealed new, intriguing properties of this catalyst and offers novel biotechnological applications. Among them, the reaction of RgDAAO has been exploited in the analytical determination of the D-amino acid content in biological samples. However, because the enzyme does not oxidize acidic D-amino acids, it cannot be used to detect the total amount of D-amino acids. We now present the results obtained using a random mutagenesis approach to produce RgDAAO mutants with a broader substrate specificity. The libraries of RgDAAO mutants were generated by error-prone PCR, expressed in BL21(DE3)pLysS Escherichia coli cells and screened for their ability to oxidize different substrates by means of an activity assay. Five random mutants that have a 'modified' substrate specificity, more useful for the analytical determination of the entire content of D-amino acids than wild-type RgDAAO, have been isolated. With the only exception of Y223 and G199, none of the effective amino acid substitutions lie in segments predicted to interact directly with the bound substrate. The substitutions appear to cluster on the protein surface: it would not have been possible to predict that these substitutions would enhance DAAO activity. We can only conclude that these substitutions synergistically generate small structural changes that affect the dynamics and/or stability of the protein in a way that enhances substrate binding or subsequently catalytic turnover

Engineering the substrate specificity of D-amino-acid oxidase

The high resolution crystal structure of D-amino-acid oxidase (DAAO) from the yeast Rhodotorula gracilis provided us with the tool to engineer the substrate specificity of this flavo-oxidase. DAAO catalyzes the oxidative deamination of D-amino acids, with the exception of D-aspartate and D-glutamate (which are oxidized by D-aspartate oxidase, DASPO). Following sequence homology, molecular modeling, and simulated annealing docking analyses, the active site residue Met-213 was mutated to arginine. The mutant enzyme showed properties close to those of DASPO (e.g. the oxidation of D-aspartate and the binding of l-tartrate), and it was still active on D-alanine. The presence of an additional guanidinium group in the active site of the DAAO mutant allowed the binding (and thus the oxidation) of D-aspartate, but it was also responsible for a lower catalytic activity on D-alanine. Similar results were also obtained when two additional arginines were simultaneously introduced in the active site of DAAO (M213R/Y238R mutant, yielding an architecture of the active site more similar to that obtained for the DASPO model), but the double mutant showed very low stability in solution. The decrease in maximal activity observed with these DAAO mutants could be due to alterations in the precise orbital alignment required for efficient catalysis, although even the change in the redox properties (more evident in the DAAO-benzoate complex) could play a role. The rational design approach was successful in producing an enzymatic activity with a new, broader substrate specificity, and this approach could also be used to develop DAAO variants suitable for use in biotechnological applications

Cosmological Tests of f(R,G,T)f(R,G,\mathcal{T}) Dark Energy Model in FRW Universe

This research article presents a new cosmological model formulated within the $f(R,G,\mathcal{T})$ framework, focusing on the observational signatures and parameter constraints of the model. The Markov Chain Monte Carlo (MCMC) technique is employed to effectively explore the parameter space using data from 36 Cosmic Chronometers and 1701 Pantheon Plus data points. A comparative analysis is conducted between the proposed $f(R,G,\mathcal{T})$ model and the widely accepted $\Lambda$CDM model, considering various cosmological parameters, such as Deceleration, Snap, and Jerk. By evaluating these parameters, valuable insights into the dynamics and evolution of the universe within the context of the new model are obtained. Diagnostic tests including Statefinder and Om Diagnostic are performed to further investigate the behavior and consistency of the $f(R,G,\mathcal{T})$ model. These tests provide deeper insights into the properties of the model and its compatibility with observational data. The model is subjected to statistical analysis using Information Criteria to rigorously assess its goodness of fit to the data. This analysis helps determine the level of agreement between the $f(R,G,\mathcal{T})$ model and the observational data, establishing the viability and reliability of the proposed cosmological framework. The results highlight the potential of the $f(R,G,\mathcal{T})$ framework in understanding the fundamental aspects of the universe's evolution and dynamics. The comparative analysis with the $\Lambda$CDM model, along with the comprehensive diagnostic tests performed, demonstrates the efficacy and validity of the $f(R,G,\mathcal{T})$ model in explaining observed cosmological phenomena. These findings contribute to the ongoing pursuit of accurate and comprehensive models that provide a deeper understanding of the nature of our universe.Comment: 19 pages, 10 figures; accepted for publication in EPJ