Nanocompuestos bio-basados de polimirceno/nanocristales de celulosa obtenidos por polimerización “in situ”

Se reporta la preparación de nanocompuestos elastoméricos 100 % bio-basados a partir de la polimerización de β-mirceno usando como carga nanocristales de celulosa, mediante un proceso “in situ”, es decir, llevar a cabo la polimerización en presencia de las nanocargas. La polimerización fue vía coordinación en solución usando un sistema catalítico base neodimio, NdV3/DIBAH/ Me2SiCl2 en relación molar 1/20/1 y variando la concentración de nanocristales de celulosa de 0.5, 1.5, 3 y 5 % en peso, los cuales fueron probados con y sin modificación superficial por plasma utilizando β-mirceno como modificante. Dicha modificación se demostró caracterizando los materiales mediante FTIR, XRD y TGA. Los nanocompuestos elastoméricos obtenidos se caracterizaron mediante GPC para la obtención de los pesos moleculares, así como por NMR para calcular el porcentaje de estructuras 1,4 (cis + trans) vs 3,4. A medida que se incrementó el porcentaje de la carga en las polimerizaciones se produjeron matrices poliméricas con mayores pesos moleculares y amplias distribuciones, pero el alto contenido de la microestructura cis-1,4 no se vio comprometido. La temperatura de transición vítrea tampoco fue significativamente modificada por las nanocargas, pero sí se observó un incremento en los módulos G’ y G’’ por la presencia de éstas. DOI: https://doi.org/10.54167/tch.v17i4.133

Ciencia Odontológica 2.0

Libro que muestra avances de la Investigación Odontológica en MéxicoEs para los integrantes de la Red de Investigación en Estomatología (RIE) una enorme alegría presentar el segundo de una serie de 6 libros sobre casos clínicos, revisiones de la literatura e investigaciones. La RIE está integrada por cuerpos académicos de la UAEH, UAEM, UAC y UdeG

Complete and versatile post‐synthetic modification on iron‐triazole spin crossover complexes: a relevant material elaboration method

International audienceIn this paper we study the post‐synthetic modification (PSM) reaction on solid spin crossover (SCO) [Fe(NH 2 trz) 3 ]X 2 (X = NO 3 , OTs, Cl, SO 4 , BF 4 ) complexes with different substrates. The wide access to a diversity of functionalized complexes with imine, amide and carbamide groups from the same amino parent compound demonstrates the synthetic approach value of this method. The as‐obtained post‐synthetic complexes were studied by IR, solid NMR, elemental analyses and powder X‐ray diffraction, and compared to the corresponding compounds obtained by direct synthesis (DS) routes. Moreover, after digestion of the complexes obtained by PSM reactions, the free ligands were characterized by NMR in solution, which allowed us to indirectly confirm the formation of complexes we wished to synthesize. The study reveals in numerous cases that a complete post synthetic modification is possible despite the structural cohesion that is established between the 1D coordination chains within these materials. Spin crossover properties of some complexes obtained by both methods are also reported and compared

State of the Art of Boron and Tin Complexes in Second- and Third-Order Nonlinear Optics ^§

Boron and tin complexes have been a versatile and very interesting scaffold for the design of nonlinear optical (NLO) chromophores. In this paper we present a wide range of reports since the 1990s to date, which include second-order (e.g., second harmonic generation) and third-order (e.g., two-photon absorption) NLO properties. After a short introduction on the origin of the NLO response in molecules, the different features associated with the introduction of these inorganic motifs in the organic-based NLO materials are discussed: Their effect on the accepting/donating capabilities of the substituents, on the efficiency of the π-conjugated linkage, and on the topology of the chromophores which can be tuned from the first generation of “push-pull„ chromophores to more sophisticated two- or three-dimensional architectures

Photoactuation of micromechanical devices by photochromic molecules

International audienceSpiropyran doped P(VDF-TrFE) nanocomposite films were spray-coated onto silicon micro-cantilevers. We show that switching the molecules from the closed- to the open-ring form by UV light gives rise to a downward bending of the cantilever as well as to a decrease of its resonance frequency. This photoactuation is reversible by means of heating and simultaneous visible light irradiation. From the flexural bending and resonance data, we extracted the actuation strain (0.13 ± 0.03%), stress (4 ± 1 MPa) and elastic energy density (2.3 ± 1 mJ cm−3) associated with the photoisomerization of spiropyran molecules in the composite films

Microbioma Rizosférico de Bacterias en Maíz Criollo de Grano: Impacto Sobre el Rendimiento Bajo Transición Agroecológica

El maíz es un cereal de importancia en términos de nutrición humana y animal a nivel mundial. En el presente estudio se comparó el microbioma bacteriano de la rizosfera del suelo entre tres razas criollas de maíz (Zea mays L.), forrajero (C1), doble propósito (C2) y grano (C3); asimismo se determinó su impacto sobre el rendimiento. Se trabajó en parcelas ubicadas en el Campo Experimental El Retiro de la Universidad Autónoma Agraria Antonio Narro (UAAAN). El muestreo de suelo se efectuó el 13 de junio del 2021, 51 días después de la siembra. El DNA se extrajo a partir de tres muestras de cada tipo de raza de maíz. Se amplificó la región V3-V4 del gen 16S rRNA y se realizó secuenciación masiva de siguiente generación con Illumina; el análisis bioinformático se desarrolló en QIIME utilizando la referencia taxonómica bacteriana EzBioCloud. El phylum Proteobacteria, la clase Phycisphaerae, los órdenes Shingomonadales, Micrococcales y Phycisphaerales, las familias Moroxellaceae, Micrococcaceae, Chitinophagaceae, Shingobacteriaceae y Enterobacteriaceae, así como los géneros Acinetobacter, Shingobacterium y Cryseobacterium, fueron los taxa bacterianos que difirieron en abundancia relativa entre las tres razas (P 0.10 en el análisis SIMPER). Dentro de los taxa mencionados se detectaron bacterias promotoras de crecimiento vegetal (BPCV) como Acinetobacter y Sphingobacterium. Se concluye que, de las razas analizadas, la C2 mostró los mejores rendimientos de peso del grano (15.56 Mg ha-1) y peso seco en forraje (10.61 Mg ha-1), la cual representa una buena opción para preservar la semilla y realizar investigaciones posteriores bajo diferentes condiciones

Bimetallic Ruthenium Nitrosyl Complexes with Enhanced Two‐Photon Absorption Properties for Nitric Oxide Delivery

International audienceOne monometallic and three bimetallic ruthenium nitrosyl (RuNO) complexes are presented and fully characterized in reference to a parent monometallic complex of formula [FTRu(bpy)(NO)]3+, where FT is a fluorenyl-substituted terpyridine ligand, and bpy the 2,2’-bipyridine. These new complexes are built with the new ligands FFT, TFT, TFFT, and TF-CC-TF (where an alkyne C≡C group is inserted between two fluorenes). The crystal structures of the bis-RuNO2 and bis-RuNO complexes built from the TFT ligand are presented. The evolution of the spectroscopic features (intensities and energies) along the series, at one-photon absorption (OPA) correlates well with the TD-DFT computations. A spectacular effect is observed at two-photon absorption (TPA) with a large enhancement of the molecular cross-section (σTPA), in the bimetallic species. In the best case, σTPA is equal to 1523±98 GM at 700 nm, in the therapeutic window of transparency of biological tissues. All compounds are capable of releasing NO⋅ under irradiation, which leads to promising applications in TPA-based drug delivery

Neotropical ornithology: Reckoning with historical assumptions, removing systemic barriers, and reimagining the future

A major barrier to advancing ornithology is the systemic exclusion of professionals from the Global South. A recent special feature, Advances in Neotropical Ornithology, and a shortfalls analysis therein, unintentionally followed a long-standing pattern of highlighting individuals, knowledge, and views from the Global North, while largely omitting the perspectives of people based within the Neotropics. Here, we review current strengths and opportunities in the practice of Neotropical ornithology. Further, we discuss problems with assessing the state of Neotropical ornithology through a northern lens, including discovery narratives, incomplete (and biased) understanding of history and advances, and the promotion of agendas that, while currently popular in the north, may not fit the needs and realities of Neotropical research. We argue that future advances in Neotropical ornithology will critically depend on identifying and addressing the systemic barriers that hold back ornithologists who live and work in the Neotropics: unreliable and limited funding, exclusion from international research leadership, restricted dissemination of knowledge (e.g., through language hegemony and citation bias), and logistical barriers. Moving forward, we must examine and acknowledge the colonial roots of our discipline, and explicitly promote anti-colonial agendas for research, training, and conservation. We invite our colleagues within and beyond the Neotropics to join us in creating new models of governance that establish research priorities with vigorous participation of ornithologists and communities within the Neotropical region. To include a diversity of perspectives, we must systemically address discrimination and bias rooted in the socioeconomic class system, anti-Blackness, anti-Brownness, anti-Indigeneity, misogyny, homophobia, tokenism, and ableism. Instead of seeking individual excellence and rewarding top-down leadership, institutions in the North and South can promote collective leadership. In adopting these approaches, we, ornithologists, will join a community of researchers across academia building new paradigms that can reconcile our relationships and transform science. Spanish and Portuguese translations are available in the Supplementary Material.• Research conducted by ornithologists living and working in Latin America and the Caribbean has been historically and systemically excluded from global scientific paradigms, ultimately holding back ornithology as a discipline.• To avoid replicating systems of exclusion in ornithology, authors, editors, reviewers, journals, scientific societies, and research institutions need to interrupt long-held assumptions, improve research practices, and change policies around funding and publication.• To advance Neotropical ornithology and conserve birds across the Americas, institutions should invest directly in basic field biology research, reward collective leadership, and strengthen funding and professional development opportunities for people affected by current research policies.Peer reviewe