Accelerated aging effect in physical and thermo-mechanical properties of maize starch biocomposites reinforced with agave salmiana fibers from different leaf ages

In this study, lignocellulosic fibers from Agave salmiana –an important socio-economical species endemic to Mexico– were used to reinforce thermoplastic maize starch (TPS). Fibers from young raw leaves (YRL) and old roasted leaves (ORL) were obtained according to the traditional methods used by small producers. The formulations of biocomposites were obtained varying the content of both types of fiber and processed by extrusion and injection molding. Morphological, structural, mechanical, thermal, and thermomechanical properties of biocomposites were evaluated. To use the hydrophilicity of these materials as an advantage in unexplored applications, biocomposites behavior under degradative tests such as accelerated aging and salt water immersion was evaluated. The processes of heating the old leaves partially removed the lignin and hemicellulose layer from the fibers, which led to a better interaction fiber-matrix, as confirmed by FESEM, ATR FTIR, and TGA. Biocomposites with 30 wt% of YRL fiber reported the highest values of tensile strength and Young’s modulus when compared to ORL biocomposites and with TPS. Accelerated aging exposure affected mainly the thermomechanical properties of TPS and confirmed the reinforcing effect of the fibers due to the thermal and mechanical stability they provided to the matrix, especially when 20 wt% of fiber was added. This was also observed when biocomposites were immersed in salt water solution. Using Agave salmiana fiber obtained from different leaf ages by traditional methods in the production of biocomposites promotes the complete harnessing of this species and represents a possibility to small producers in Mexico to introduce circular economy in their communities.A. Reyes-Samilpa acknowledges the scholarship 553944 from CONACYT; the mobility grant from CCA-IPN; the grants 251504 and 264110 from CONACYT, and 20195514 from SIP-IPN. We thank Dr. Edith Ariza from SEMAT Lab UMINHO and Dr. Ángel R. Hernández and M. C. Gerardo Fonseca from CFATA-UNAM for technical support in characterization tests; the Manuscript Writing Training Team (CEMAI in Spanish) of CONACyT for their help with reviews and constructive criticism, and Prof. Robert Leavitt and Maria del Sagrario Velasco García for also providing language help

Analysis of substrate specificity of cytochrome P450 monooxygenases involved in trichothecene toxin biosynthesis

[EN]Trichothecenes are a structurally diverse family of toxic secondary metabolites produced by certain species of multiple fungal genera. All trichothecene analogs share a core 12,13-epoxytrichothec-9-ene (EPT) structure but differ in presence, absence and types of substituents attached to various positions of EPT. Formation of some of the structural diversity begins early in the biosynthetic pathway such that some producing species have few trichothecene biosynthetic intermediates in common. Cytochrome P450 monooxygenases (P450s) play critical roles in formation of trichothecene structural diversity. Within some species, relaxed substrate specificities of P450s allow individual orthologs of the enzymes to modify multiple trichothecene biosynthetic intermediates. It is not clear, however, whether the relaxed specificity extends to biosynthetic intermediates that are not produced by the species in which the orthologs originate. To address this knowledge gap, we used a mutant complementation-heterologous expression analysis to assess whether orthologs of three trichothecene biosynthetic P450s (TRI11, TRI13 and TRI22) from Fusarium sporotrichioides, Trichoderma arundinaceum, and Paramyrothecium roridum can modify trichothecene biosynthetic intermediates that they do not encounter in the organism in which they originated. The results indicate that TRI13 and TRI22 could not modify the intermediates that they do not normally encounter, whereas TRI11 could modify an intermediate that it does not normally encounter. These findings indicate that substrate promiscuity varies among trichothecene biosynthetic P450s. One structural feature that likely impacts the ability of the P450s to use biosynthetic intermediates as substrates is the presence and absence of an oxygen atom attached to carbon atom 3 of EPT.SIOpen Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature.Publicación en abierto financiada por el Consorcio de Bibliotecas Universitarias de Castilla y León (BUCLE), con cargo al Programa Operativo 2014ES16RFOP009 FEDER 2014-2020 DE CASTILLA Y LEÓN, Actuación:20007-CL - Apoyo Consorcio BUCL

Contaminación bacteriana de Productos Cárnicos Ovinos Comercializados en la Meseta Central de México

El estudio se realizó para evaluar la contaminación microbiológica de las canales de ovino comercializadas en el Altiplano Central Mexicano, durante el período Primavera - Verano 2012. Se recolectaron muestras en tres expendios mayoristas de las canales de ovino antes de la refrigeración, las manos de los trabajadores, y los cuchillos, utilizando la técnica de hisopo húmedo. Las muestras se analizaron para Cuenta Total de Aerobios Viables (TAVC), Cuenta Coliformes Totales (CCT) y Cuenta Coliformes Fecales (FCC), los conteos se determinaron por el método de recuento estándar en placa. Las medias de TAVC de las canales de ovino, las manos del personal, y los cuchillos fueron de 0,99 ± 0,81, 0,78 ± 0,53y 1,84 ± 0,28 log10UFC / mL, respectivamente; no se encontraron diferencias estadísticamente significativas (P <0,05). La media de TCC para las canales fue de 0,74 ± 0,56 log10 UFC / mL y 0,36 ± 0,48 log10UFC/mL para cuchillos, no se encontraron diferencias estadísticamente significativas (P <0,05). No se detectaron FCC en las canales de ovino, el personal y los cuchillos. Los resultados indicaron buenas condiciones higiénicas y de manipulación durante los canales de comercialización

Finite axisymmetric charged dust disks in conformastatic spacetimes

An infinite family of axisymmetric charged dust disks of finite extension is presented. The disks are obtained by solving the vacuum Einstein-Maxwell equations for conformastatic spacetimes, which are characterized by only one metric function. In order to obtain the solutions, it is assumed that the metric function and the electric potential are functionally related and that the metric function is functionally dependent of another auxiliary function, which is taken as a solution of Laplace equation. The solutions for the auxiliary function are then taken as given by the infinite family of generalized Kalnajs disks recently obtained by Gonz\'alez and Reina (MNRAS 371, 1873, 2006), which is expressed in terms of the oblate spheroidal coordinates and represents a well behaved family of finite axisymmetric flat galaxy models. The so obtained relativistic thin disks have then a charge density that is equal, except maybe by a sign, to their mass density, in such a way that the electric and gravitational forces are in exact balance. The energy density of the disks is everywhere positive and well behaved, vanishing at the edge. Accordingly, as the disks are made of dust, their energy-momentum tensor it agrees with all the energy conditions.Comment: Submitted to PR

Identification of polyketide synthase genes required for aspinolide biosynthesis in Trichoderma arundinaceum

https://link.springer.com/article/10.1007/s00253-022-12182-9[EN] The fungus Trichoderma arundinaceum exhibits biological control activity against crop diseases caused by other fungi. Two mechanisms that likely contribute to this activity are upregulation of plant defenses and production of two types of antifungal secondary metabolites: the sesquiterpenoid harzianum A (HA) and the polyketide-derived aspinolides. The goal of the current study was to identify aspinolide biosynthetic genes as part of an effort to understand how these metabolites contribute to the biological control activity of T. arundinaceum. Comparative genomics identified two polyketide synthase genes (asp1 and asp2) that occur in T. arundinaceum and Aspergillus ochraceus, which also produces aspinolides. Gene deletion and biochemical analyses in T. arundinaceum indicated that both genes are required for aspinolide production: asp2 for formation of a 10-member lactone ring and asp1 for formation of a butenoyl subsituent at position 8 of the lactone ring. Gene expression and comparative genomics analyses indicated that asp1 and asp2 are located within a gene cluster that occurs in both T. arundinaceum and A. ochraceus. A survey of genome sequences representing 35 phylogenetically diverse Trichoderma species revealed that intact homologs of the cluster occurred in only two other species, which also produced aspinolides. An asp2 mutant inhibited fungal growth more than the wild type, but an asp1 mutant did not, and the greater inhibition by the asp2 mutant coincided with increased HA production. These findings indicate that asp1 and asp2 are aspinolide biosynthetic genes and that loss of either aspinolide or HA production in T. arundinaceum can be accompanied by increased production of the other metabolite(s).SIPublicación en abierto financiada por el Consorcio de Bibliotecas Universitarias de Castilla y León (BUCLE), con cargo al Programa Operativo 2014ES16RFOP009 FEDER 2014-2020 DE CASTILLA Y LEÓN, Actuación:20007-CL - Apoyo Consorcio BUCL

Acute Respiratory Diseases and Carboxyhemoglobin Status in School Children of Quito, Ecuador

Outdoor carbon monoxide comes mainly from vehicular emissions, and high concentrations occur in areas with heavy traffic congestion. CO binds to hemoglobin, forming carboxyhemoglobin (COHb), and reduces oxygen delivery. We investigated the link between the adverse effects of CO on the respiratory system using COHb as a marker for chronic CO exposure. We examined the relationship between acute respiratory infections (ARIs) and COHb concentrations in school-age children living in urban and suburban areas of Quito, Ecuador. We selected three schools located in areas with different traffic intensities and enrolled 960 children. To adjust for potential confounders we conducted a detailed survey. In a random subsample of 295 children, we determined that average COHb concentrations were significantly higher in children attending schools in areas with high and moderate traffic, compared with the low-traffic area. The percentage of children with COHb concentrations above the safe level of 2.5% were 1, 43, and 92% in low-, moderate-, and high-traffic areas, respectively. Children with COHb above the safe level are 3.25 [95% confidence interval (CI), 1.65–6.38] times more likely to have ARI than children with COHb < 2.5%. Furthermore, with each percent increase in COHb above the safety level, children are 1.15 (95% CI, 1.03–1.28) times more likely to have an additional case of ARI. Our findings provide strong evidence of the relation between CO exposure and susceptibility to respiratory infections

Establecimiento y producción de materia seca de gramíneas promisorias en el departamento de Jutiapa, Guatemala

Con el objetivo de seleccionar gramíneas de pastoreo de comportamiento superior bajo las condiciones de bosque húmedo subtropical templado del departamento de Jutiapa, se evaluaron 4 accesiones, seleccionadas en evaluaciones previas, en un diseño e bosques al azar con cuatro repeticiones y arreglo de tratamientos en parcela dividida, correspondiendo la parcela a la accesión y la subparcela a la frecuencia de corte (3, 5, 7 y 9 semanas). Las variables de respuesta fueron medidas en períodos de máxima y mínima precipitación en 1988 y 1989. La cobertura promedio fue de 82.9 ± 8.15 y 72.5 ± 8.34 % para máxima y mínima precipitación, respectivamente. Se encontró efecto significativo (P ≤ 0.01) del año, época de corte, accesión, frecuencia de corte e interacciones entre estos factores sobre la producción de materia seca. El rendimiento promedio de máxima precipitación fue 4.3 t / ha, resultado B. dictyoneura, CIAT 6133 con 6.63 t / ha, superior al esto de materiales (P ≤ 0.05). En mínima precipitación, recuencias de corte de 7 y 9 semanas fueron iguales y superiores a 3 y 5, con 4.92 t / ha (P ≤ 0.05). B. decumbens CIAT 606, P. decumbens CIA T 606, P. maximun CIA T 673, P. maximun (local) P. purpureum cv. Mott, mostraron un ataque moderado de lagas. Con relación a enfermedades P. maximun (local) y C. nlemfuensis EAP 138 mostraron daño moderado

Exploring the surface-enhanced Raman scattering (SERS) activity of gold nanostructures embedded around nanogaps at wafer scale: Simulations and experiments

A unique way of converting free space light into a local electromagnetic field in small spaces is via metallic nanostructuring. In this work fabrication, experimental characterization and simulation of surface-enhanced Raman scattering (SERS) active specimens based on Au nanostructures are discussed. We used displacement Talbot lithography (DTL) to fabricate silicon nano-wedge substrates with Au nanostructures embedded around their apices. After the ion beam etching process, a nanogap is introduced between two Au nanostructures templated over nano-wedges, yielding specimens with SERS characteristics. The Au nanostructures and the nanogaps have symmetric and asymmetric configurations with respect to the wedges. With this nanofabrication method, various wafer-scale specimens were fabricated with highly controllable nanogaps with a size in the order of 6 nm for symmetric gaps and 8 nm for asymmetric gaps. SERS characteristics of these specimens were analyzed experimentally by calculating their analytical enhancement factor (AEF). According to finite-difference time-domain (FDTD) simulations, the Raman enhancement arises at the narrow gap due to plasmonic resonances, yielding a maximum AEF of 6.9 × 106. The results highlight the SERS activity of the nanostructures and ultimately comply with reliable substrates for practical applications

Health-care guidelines and policies during the COVID-19 pandemic in Mexico: a case of health-inequalities

Background Heterogeneous government responses have been reported in reaction to COVID-19. The aim of this study is to generate an exploratory review of healthcare policies published during COVID-19 by health-care institutions in Mexico. Analyzing policies within different health sub-systems becomes imperative in the Mexican case due to the longstanding fragmentation of the health-care system and health inequalities. Data and Methods Policies purposely included in the analysis were published by four public health institutions (IMSS, ISSSTE, SSA and PEMEX) during the COVID-19 epidemic in Mexico (from February 29th to June 15th, 2020) on official institutional websites. Researchers reviewed each document and classified them into seven policy categories set by the Rapid Research Evaluation and Appraisal Lab (RREAL): public health response, health-care delivery, human resources, health-system infrastructure and supplies, clinical response, health-care management, and epidemiological surveillance. Results Policy types varied by health institution. The largest number of policies were aimed at public health responses followed by health-care delivery and human resources. Policies were mainly published during the community transmission phase. Conclusions The pandemic exposed underlying health-care system inequalities and a reactive rather than prepared response to the outbreak. Additionally, this study outlines potential policy gaps and delays in the response that could be avoided in the future