Quasiperiodic Patterns in Boundary-Modulated Excitable Waves

We investigate the impact of the domain shape on wave propagation in excitable media. Channelled domains with sinusoidal boundaries are considered. Trains of fronts generated periodically at an extreme of the channel are found to adopt a quasiperiodic spatial configuration stroboscopically frozen in time. The phenomenon is studied in a model for the photo-sensitive Belousov-Zabotinsky reaction, but we give a theoretical derivation of the spatial return maps prescribing the height and position of the successive fronts that is valid for arbitrary excitable reaction-diffusion systems.Comment: 4 pages (figures included

The Complex Ginzburg-Landau Equation in the Presence of Walls and Corners

We investigate the influence of walls and corners (with Dirichlet and Neumann boundary conditions) in the evolution of twodimensional autooscillating fields described by the complex Ginzburg-Landau equation. Analytical solutions are found, and arguments provided, to show that Dirichlet walls introduce strong selection mechanisms for the wave pattern. Corners between walls provide additional synchronization mechanisms and associated selection criteria. The numerical results fit well with the theoretical predictions in the parameter range studied.Comment: 10 pages, 9 figures; for related work visit http://www.nbi.dk/~martine

The role of the surface acidic/basic centers and redox sites on TiO2 in the photocatalytic CO2 reduction

The development of sustainable processes for CO reduction to fuels and chemicals is one of the most important challenges to provide clean energy solutions. The use of sunlight as renewable energy source is an interesting alternative to power the electron transfer required for artificial photosynthesis. Even if redox sites are mainly responsible for this process, other reactive acidic/basic centers also contribute to the overall reaction pathway. However, a full understanding of the CO photoreduction mechanism is still a scientific challenge. In fact, the lack of agreement on standardized comparison criteria leads to a wide distribution of reported productions, even using the same catalyst, which hinders a reliable interpretation. An additional difficulty is ascertaining the origin of carbon-containing products and effect of surface carbon residues, as well as the reaction intermediates and products under real dynamic conditions. To determine the elusive reaction mechanism, we report an interconnected strategy combining in-situ spectroscopies, theoretical studies and catalytic experiments. These studies show that CO photoreduction productions are influenced by the presence of carbon deposits (i.e. organic molecules, carbonates and bicarbonates) over the TiO surface. Most importantly, the acid/base character of the surface and the reaction medium play a key role in the selectivity and deactivation pathways. This TiO deactivation is mainly initiated by the formation of carbonates and peroxo- species, while activity can be partially recovered by a mild acid washing treatment. We anticipate that these findings and methodology enlighten the main shadows still covering the CO reduction mechanism, and, most importantly, provide essential clues for the design of emergent materials and reactions for photo(electro)catalytic energy conversion

Sample dilution and bacterial community composition influence empirical leucine-to-carbon conversion factors in surface waters of the world's oceans

Research articleThe transformation of leucine incorporation into prokaryotic carbon production rates requires the use of either theoretical or empirically determined conversion factors. Empirical leucine-to-carbon conversion factors (eCFs) vary widely across environments, and little is known about their potential controlling factors. We conducted 10 surface seawater manipulation experiments across the world’s oceans, where the growth of the natural prokaryotic assemblages was promoted by filtration (i.e. removal of grazers; F treatment) or filtration combined with dilution (i.e. relieving also resource competition; FD treatment). The impact of sunlight exposure was also evaluated in the FD treatments, and we did not find a significant effect on the eCFs. The eCFs varied from 0.09 to 1.47 kg C mol Leu-1 and were significantly lower in the filtered and diluted (FD) than in the filtered (F) treatments. Also, changes in bacterial community composition during the incubations, as assessed by Automated Ribosomal Intergenic Spacer Analysis (ARISA), were stronger in the FD than in the F treatments, as compared to unmanipulated controls. Thus, we discourage the common procedure of diluting samples (in addition to filtration) for eCFs determination. The eCFs in the filtered treatment were negatively correlated with the initial chlorophyll a concentration, picocyanobacterial abundance (mostly Prochlorococcus) and the percentage of heterotrophic prokaryotes with high nucleic acid content (%HNA). The latter two variables explained 80% of the eCFs variability in the F treatment, supporting the view that both Prochlorococcus and HNA prokaryotes incorporate leucine in substantial amounts although resulting into relatively low carbon production rates in the oligotrophic ocean.En prensa3,829

PATOGENICIDAD Y VIRULENCIA DE CEPAS DE BACILLUS THURINGIENSIS NATIVAS DEL ESTADO DE MORELOS SOBRE DIATRAEA MAGNIFACTELLA (LEPIDOPTERA: CRAMBIDAE)

Sugarcane is one of the most important industrial crops in Mexico, several insects feed on it, causing important economic losses. At the state of Morelos two species are found; Diatraea magnifactella and Eoreuma loftini. To control these borers chemical insecticides are used, today there are not any bioinsecticide based on entomopathogenic bacteria. It has already been reported in the literature against other borer species the use of entomopathogenic bacteria, so in this work was proposed to isolate Bacillus thuringiensis (Bt) from cadavers of D. magnifactella to evaluate the pathogenicity and virulence of bacterial isolates on neonate larva. It was possible the establishment a colony of D. magnifactella at laboratory, ensuring the health of the larvae used in bioassays. We obtained a total of 118 bacterial isolates, presumably from B. thuringiensis. Which were grouped into three groups, depending on thier protein profile. Six of the 118 strains caused more than 50% of mortality in neonate larvae of D. magnifactella. The LC50 of isolates been defined, the best was the B148 by 254.01 ng/cm2 of food. The LC50 the commercial strain HD1 was 417.61 ng/cm2, used as appositive control. The five remaining isolates showed LC50 greater than that of the positive control.La caña de azúcar representa uno de los cultivos industriales más importantes en México, diversos insectos se alimentan de ésta, provocando pérdidas económicas considerables. Para el estado de Morelos se reporta la presencia de los barrenadores Diatraea magnifactella y Eoreuma loftini. Para su control se han usado insecticidas químicos, a la fecha no existen bioinsecticidas a base de bacterias entomopatógenas. Existen reportes de evaluaciones in vitro y en campo contra otras especies de barrenadores, por lo que en el presente trabajo se aislaron cepas de Bacillus thuringiensis (Bt) a partir de cadáveres de D. magnifactella. Se evaluó la patogenicidad y virulencia de las cepas bacterianas sobre larvas neonatas del barrenador para lo cual se estableció un pie de cría de D. magnifactella en laboratorio, garantizando así la sanidad de las larvas usadas en los bioensayos. Se obtuvo un total de 118 cepas de B. thuringiensis. Los cuales se agruparon en tres categorías, dependiendo del peso molecular de las proteínas mayoritarias (perfil proteico) producidas por la bacteria. De los bioensayos de patogenicidad realizados, seis de las 118 cepas evaluadas fueron las que ocasionaron una mortalidad mayor al 50% en las larvas neonatas de D. magnifactella. Se determinó la Concentración Letal 50 de éstas seis cepas, la que presentó mejores resultados fue la cepa B148 con CL50 de 254.01 ng/cm2 de dieta, menor a la de la cepa comercial HD1 417.61 ng/cm2, evaluada como testigo positivo. Las cinco cepas restantes presentaron CL50 superiores a la de la cepa testigo

Scaling properties of protein family phylogenies

One of the classical questions in evolutionary biology is how evolutionary processes are coupled at the gene and species level. With this motivation, we compare the topological properties (mainly the depth scaling, as a characterization of balance) of a large set of protein phylogenies with a set of species phylogenies. The comparative analysis shows that both sets of phylogenies share remarkably similar scaling behavior, suggesting the universality of branching rules and of the evolutionary processes that drive biological diversification from gene to species level. In order to explain such generality, we propose a simple model which allows us to estimate the proportion of evolvability/robustness needed to approximate the scaling behavior observed in the phylogenies, highlighting the relevance of the robustness of a biological system (species or protein) in the scaling properties of the phylogenetic trees. Thus, the rules that govern the incapability of a biological system to diversify are equally relevant both at the gene and at the species level.Comment: Replaced with final published versio

Chitosan–Starch–Keratin composites: Improving thermo-mechanical and degradation properties through chemical modification

The lysozyme test shows an improved in the degradability rate, the weight loss of the films at 21 days is reduced from 73 % for chitosan-starch matrix up to 16 % for the composites with 5wt% of quill; but all films show a biodegradable character depending on keratin type and chemical modification. The outstanding properties related to the addition of treated keratin materials show that these natural composites are a remarkable alternative to potentiat-ing chitosan–starch films with sustainable featuresChitosan–starch polymers are reinforced with different keratin materials obtained from chicken feather. Keratin materials are treated with sodium hydroxide; the modified surfaces are rougher in comparison with untreated surfaces, observed by Scanning Electron Microscopy. The results obtained by Differential Scanning Calorimetry show an increase in the endothermic peak related to water evaporation of the films from 92 °C (matrix) up to 102–114 °C (reinforced composites). Glass transition temperature increases from 126 °C in the polymer matrix up to 170–200 °C for the composites. Additionally, the storage modulus in the composites is enhanced up to 1614 % for the composites with modified ground quill, 2522 % for composites with modified long fiber and 3206 % for the composites with modified short fiber. The lysozyme test shows an improved in the degradability rate, the weight loss of the films at 21 days is reduced from 73 % for chitosan-starch matrix up to 16 % for the composites with 5wt% of quill; but all films show a biodegradable character depending on keratin type and chemical modification. The outstanding properties related to the addition of treated keratin materials show that these natural composites are a remarkable alternative to potentiat-ing chitosan–starch films with sustainable featuresUniversidad Autónoma del Estado de México Tecnológico Nacional de México, Instituto Tecnológico de Querétaro Universidad Nacional Autónoma de México Tecnológico Nacional de México, Instituto Tecnológico de Celaya Universidad Autónoma de Cd. Juáre

Characterising the KMP-11 and HSP-70 recombinant antigens' humoral immune response profile in chagasic patients

11 pages, 6 figures.-- The pre-publication history for this paper can be accessed here: http://www.biomedcentral.com/1471-2334/9/186/pre pubBackground: Antigen specificity and IgG subclass could be significant in the natural history of Chagas' disease. The relationship between the different stages of human Chagas' disease and the profiles of total IgG and its subclasses were thus analysed here; they were directed against a crude T. cruzi extract and three recombinant antigens: the T. cruzi kinetoplastid membrane protein-11 (rKMP-11), an internal fragment of the T. cruzi HSP-70 protein192-433, and the entire Trypanosoma rangeli HSP-70 protein. Methods: Seventeen Brazilian acute chagasic patients, 50 Colombian chronic chagasic patients (21 indeterminate and 29 cardiopathic patients) and 30 healthy individuals were included. Total IgG and its subtypes directed against the above-mentioned recombinant antigens were determined by ELISA tests. Results: The T. cruzi KMP-11 and T. rangeli HSP-70 recombinant proteins were able to distinguish both acute from chronic chagasic patients and infected people from healthy individuals. Specific antibodies to T. cruzi crude antigen in acute patients came from IgG3 and IgG4 subclasses whereas IgG1 and IgG3 were the prevalent isotypes in indeterminate and chronic chagasic patients. By contrast, the specific prominent antibodies in all disease stages against T. cruzi KMP-11 and T. rangeli HSP-70 recombinant antigens were the IgG1 subclass.This work was supported by Colciencias Research project No. 1203-333- 18692. IDF was supported by Colciencias and the Universidad Javeriana's Young Researcher 2008 Programme (Bogotá, Colombia). MCT and MCL were supported by P06-CTS-02242 Grant from PAI (Junta de Andalucia) and RICET-RD06/0021-0014, Spain. MS received financial support from the Brazilian agency - CNPq.Peer reviewe

Radiaciones ionizantes y su impacto Primer Simposio Internacional sobre Medioambiente (ISE 2017)

Son ya varias las décadas en las que en América Latina se ha trabajado arduamente sobre las radiaciones ionizantes; tanto en las ionizantes directas, tales como las partículas beta positivas y negativas, las partículas alfa, los protones, los mesones cargados, los muones y los iones pesados, así como también en las ionizantes indirectas (las producidas por partículas sin cargas), como las generadas por fotones con energías superiores a los 10 keV y los neutrones. Por otro lado, las radiaciones no ionizantes también han sido objeto de detallados estudios, y muy especialmente las provenientes del Sol, como el factor natural más influyente sobre la Tierra. En esta obra se presentan algunos de los avances en los que han participado reconocidos científicos latinoamericanos, como el Dr. Héctor Vega Carrillo, Dr. Daniel Palacios, Dra. Patrizia Pereyra, Dra. Sheila Serrano, y el Dr. Manuel Ernesto Delgado, entre otros. Esta obra puede ser de interés para profesionales del área de la protección radiológica, la ingeniería ambiental, física de la atmósfera y áreas afines, así como para estudiantes