Low environmental impact bleaching sequences for attaining high brightness level with eucalyptus SPP pulp

The alternatives used for minimizing the usage of chlorine dioxide in bleaching sequences included a hot acid hydrolysis (Ahot) stage, the use of hot chlorine dioxide (Dhot) and ozone stages at medium consistency and high consistency (Zmc and Zhc), in addition to stages with atmospheric hydrogen peroxide (P) and pressurized hydrogen peroxide (PO). The results were interpreted based on the cost of the chemical products, bleaching process yields and on minimizing the environmental impact of the bleaching process. In spite of some process restrictions, high ISO brightness levels were kept around 90 % brightness. Additionally, the inclusion of stages like acid hydrolysis, pressurized peroxide and ozone in the bleaching sequences provided an increase in operating flexibility, aimed at reducing environmental impact (ECF Light). The Dhot(EOP)D(PO) sequence presented lower operating cost for ISO brightness above 92 %. However, this kind of sequence was not allowed for closing the wastewater circuit, even partially. For ISO brightness level around 91%, the AhotZhcDP sequence presented a lower operating cost than the others

A note on the degree sequences of graphs with restrictions

Degree sequences of some types of graphs will be studied and characterizedin this paper.

Divergent evolution and purifying selection of the flaA gene sequences in Aeromonas

BACKGROUND: The bacterial flagellum is the most important organelle of motility in bacteria and plays a key role in many bacterial lifestyles, including virulence. The flagellum also provides a paradigm of how hierarchical gene regulation, intricate protein-protein interactions and controlled protein secretion can result in the assembly of a complex multi-protein structure tightly orchestrated in time and space. As if to stress its importance, plants and animals produce receptors specifically dedicated to the recognition of flagella. Aside from motility, the flagellum also moonlights as an adhesion and has been adapted by humans as a tool for peptide display. Flagellar sequence variation constitutes a marker with widespread potential uses for studies of population genetics and phylogeny of bacterial species. RESULTS: We sequenced the complete flagellin gene (flaA) in 18 different species and subspecies of Aeromonas. Sequences ranged in size from 870 (A. allosaccharophila) to 921 nucleotides (A. popoffii). The multiple alignment displayed 924 sites, 66 of which presented alignment gaps. The phylogenetic tree revealed the existence of two groups of species exhibiting different FlaA flagellins (FlaA1 and FlaA2). Maximum likelihood models of codon substitution were used to analyze flaA sequences. Likelihood ratio tests suggested a low variation in selective pressure among lineages, with an omega ratio of less than 1 indicating the presence of purifying selection in almost all cases. Only one site under potential diversifying selection was identified (isoleucine in position 179). However, 17 amino acid positions were inferred as sites that are likely to be under positive selection using the branch-site model. Ancestral reconstruction revealed that these 17 amino acids were among the amino acid changes detected in the ancestral sequence. CONCLUSION: The models applied to our set of sequences allowed us to determine the possible evolutionary pathway followed by the flaA gene in Aeromonas, suggesting that this gene have probably been evolving independently in the two groups of Aeromonas species since the divergence of a distant common ancestor after one or several episodes of positive selection. REVIEWERS: This article was reviewed by Alexey Kondrashov, John Logsdon and Olivier Tenaillon (nominated by Laurence D Hurst).

Visualitzador de molècules d'ADN per laboratori virtual

Com a continuació del treball de final de carrera “Desenvolupament d’un laboratori virtual per a les pràctiques de Biologia Molecular” de Jordi Romero, s’ha realitzat una eina complementaria per a la visualització de molècules integrada en el propi laboratori virtual. Es tracta d’una eina per a la visualització gràfica de gens, ORF, marques i seqüències de restricció de molècules reals o fictícies. El fet de poder treballar amb molècules fictícies és la gran avantatge respecte a les solucions com GENBANK que només permet treballar amb molècules pròpies. Treballar amb molècules fictícies fa que sigui una solució ideal per a l’ensenyament, ja que dóna la possibilitat als professors de realitzar exercicis o demostracions amb molècules reals o dissenyades expressament per a l’exercici a demostrar. A més, permet mostrar de forma visual les diferents parts simultàniament o per separat, de manera que ofereix una primera aproximació interpretació dels resultats. Per altra banda, permet marcar gens, crear marques, localitzar seqüències de restricció i generar els ORF de la molècula que nosaltres creem o modificar una ja existent. Per l’implementació, s’ha continuat amb l’idea de separar la part de codi i la part de disseny en les aplicacions Flash. Per fer-ho, s’ha utilitzat la plataforma de codi lliure Ariware ARPv2.02 que proposa un marc de desenvolupament d’aplicacions Flash orientades a objectes amb el codi (classes ActionScript 2.0) separats del movieclip. Per al processament de dades s’ha fet servir Perl per ser altament utilitzat en Bioinformàtica i per velocitat de càlcul. Les dades generades es guarden en una Base de Dades en MYSQL (de lliure distribució), de la que s’extreuen les dades per generar fitxers XML, fent servir tant PHP com la plataforma AMFPHP com a enllaç entre Flash i la resta de parts.