Explore the vast range of titles available.

Trata-se da condição limite da Educação em Dewey, no quadro contemporâneo da crise da Democracia. Traz como questões de fundo: a importância da Democracia para a formação do cidadão e o desafio que se coloca em torno da experiência da crise da Democracia. Tem como circunscrição temática as obras do autor que, embora especulativas e de caráter teórico, oferecem pensar a condição limite do princípio básico da experiência – pressuposto à proposta de uma educação democrática – naquilo que concerne ao eixo de articulação das diferentes instâncias que têm como referência a Democracia e a sua participação na formação do cidadão. Assim, tem-se por objeto da discussão de fundo a crise atual da Democracia – a abordagem do critério democrático pressuposto à formação educacional do cidadão – situada no quadro experiencial da compreensão da educação, como uma necessidade da vida social e do ideal democrático subentendido. This is the limit condition of Education in Dewey, in the contemporary context of the crisis of Democracy. It brings as fundamental questions: the importance of Democracy for the formation of citizens and the challenge that arises around the experience of the crisis of Democracy. Its thematic circumscription is the author's works which, although speculative and theoretical in nature, offer reflection on the limiting condition of the basic principle of experience - presupposed to the proposal of a democratic education - in what concerns the axis of articulation of the different instances that have as reference Democracy and its participation in the formation of citizens. Thus, the object of the underlying discussion is the current crisis of Democracy – the approach of the democratic criteria presupposed to the educational training of citizens – situated in the experiential framework of understanding education, as a necessity of social life and the implied democratic ideal. Se trata de la condición límite de la Educación em Dewey, en el cuadro contemporáneo de la crisis de la Democracia. Trae como puntos de fondo: la importancia de la Democracia para la formación del ciudadano y el desafío se coloca alrededor de la experiencia de la crisis de la Democracia. Tiene como circunscripción temática las obras del autor, que a pesar de especulativas y de carácter teórico, ofrecen pensar la condición límite del principio básico de la experiencia, presupuesto a la propuesta de una educación democrática, en aquello que concierne al eje de articulación de las diferentes instancias, que tienen como referencia la Democracia y su participación en la formación del ciudadano. De esa forma, se tiene por objeto de discusión de fondo de la crisis actual de la Democracia, el abordaje del criterio democrático presupuesto a la formación educacional del ciudadano, situado en el cuadro experiencial de la comprensión de la educación, como una necesidad de la vida social y del ideal democrático sobreentendido.

Thalidomide possesses two optical isomers which have been reported to exhibit different pharmacological and toxicological activities. However, the precise mechanism by which the two isomers exert their different activities remains poorly understood. Here, we present structural and biochemical studies of ( S )- and ( R )-enantiomers bound to the primary target of thalidomide, cereblon (CRBN). Our biochemical studies employed deuterium-substituted thalidomides to suppress optical isomer conversion, and established that the ( S )-enantiomer exhibited ~10-fold stronger binding to CRBN and inhibition of self-ubiquitylation compared to the ( R )-enantiomer. The crystal structures of the thalidomide-binding domain of CRBN bound to each enantiomer show that both enantiomers bind the tri-Trp pocket, although the bound form of the ( S )-enantiomer exhibited a more relaxed glutarimide ring conformation. The ( S )-enantiomer induced greater teratogenic effects on fins of zebrafish compared to the ( R )-enantiomer. This study has established a mechanism by which thalidomide exerts its effects in a stereospecific manner at the atomic level.

Skeletal forms in vertebrates have been regarded as good models of morphological diversification. Fish fins show great diversity in form, with their supporting skeletal structure being classified into soft rays and spiny rays. In fish evolution, spiny-ray morphologies are known to be sometimes extremely modified; however, it remains unknown how the developmental mechanisms of spiny rays have contributed to their morphological diversification. By using the rainbowfish Melanotaenia praecox for examination of the extracellular matrix (ECM) and cell dynamics of spiny-ray development, we demonstrate that spiny-ray development is independent of the actinotrichia (needle-shaped collagen polymers at the tip of fins), which are known as an important ECM in soft-ray morphogenesis. Furthermore, we found that in the thorny spiny ray of the filefish Stephanolepis cirrhifer , the lateral protrusions are associated with BMP-positive osteoblast condensation, as in the spiny-ray tips in M. praecox and S. cirrhifer . Taken together, our findings reveal that osteoblast distribution and signaling-molecule intensity would contribute to spiny-ray modification. In comparison to soft ray development, the independence from actinotrichia in spiny rays would facilitate growth direction change, leading to their morphological diversification. This suggests that variation in cell distribution and ECM usage may be important contributors to morphological diversification, not only in Acanthomorpha, but also in other animal taxa. Fish fins are a good model for studying the evolutionary basis for morphological diversity. Here, they show that variation in cell distribution, signaling intensity, and ECM assembly all contribute to spiny ray diversification in Acanthomorpha fins.

Tissue vascularization entails the formation of a blood vessel plexus, which remodels into arteries and veins. Here we show, by using time-lapse imaging of zebrafish fin regeneration and genetic lineage tracing of endothelial cells in the mouse retina, that vein-derived endothelial tip cells contribute to emerging arteries. Our movies uncover that arterial-fated tip cells change migration direction and migrate backwards within the expanding vascular plexus. This behaviour critically depends on chemokine receptor cxcr4a function. We show that the relevant Cxcr4a ligand Cxcl12a selectively accumulates in newly forming bone tissue even when ubiquitously overexpressed, pointing towards a tissue-intrinsic mode of chemokine gradient formation. Furthermore, we find that cxcr4a mutant cells can contribute to developing arteries when in association with wild-type cells, suggesting collective migration of endothelial cells. Together, our findings reveal specific cell migratory behaviours in the developing blood vessel plexus and uncover a conserved mode of artery formation. Sprouting of new blood vessels depends on the migration of endothelial tip cells into surrounding tissue. Here the authors reveal the existence of a distinct migratory signalling circuit that guides endothelial cells from developing veins to the leading tip position in developing arteries.

The zebrafish hoxa13a, hoxa13b , and hoxd13a genes have been shown to be essential for proper pectoral fin patterning. Combined mutations in these genes cause an elaboration of the pectoral fin endoskeleton, and a size reduction of the rays. In this study, we further examine the impact of partial deletions in these genes on the fin exoskeleton. Using morphological and micro-CT scan analyses, we found that rays of all fins of triple hox13 mutants are strongly affected, except for the caudal fin that is much less perturbed. Rays are shorter and thicker than wildtype rays, and present a loss of joints, bifurcations, and actinotrichia. Altogether, they lose many of the typical soft ray features and resemble more to the spiny rays of acanthomorphs. In these species, actinotrichia are present in spiny rays but organized differently than in soft rays, and spiny rays develop in the absence of hoxa13a/b expression. Gene expression analysis of triple hox13 mutant zebrafish larvae shows an expansion of the alx4a expression domain relative to the size of the dorsal and anal fin primordia and a reduction in grem1b expression that are reminiscent of the differences observed in acanthomorph spiny versus soft rays. Using various combinations of genotypes, hoxa13a and hoxa13b were found to be more important for normal soft ray formation than hoxd13a. In conclusion, our results demonstrate the importance of the hox13 paralogs for proper soft ray development and suggest a lack of hox13 expression could be important for their transformation into spiny rays.

Rapid phase change heat storage has significant application value in high-power density thermal management systems. This paper presents a comparative numerical simulation study of the rapid heat storage and release dynamics of two types of finned plate heat exchangers with different fin shapes. The study reveals that, under the same fin thickness and volume fraction, the contact surface area of triangular fins is 1.6 times that of rectangular fins, but the heat storage rate of triangular fin heat exchangers is 2 times that of rectangular fin heat exchangers. Due to the small characteristic scale and high material viscosity of the heat exchanger, the natural convection velocity of the liquid phase during the heat storage process is low, and its influence on enhancing the heat storage rate is weak.

Abstract Limbs exhibit adaptive differentiation along their dorsal-ventral (DV) axis, determined by the dorsal expression of the LIM homeobox gene Lmx1b. The paired appendages (ie the pectoral and pelvic fins from which limbs evolved) arose in an early jawless ancestor via co-option of a midline-fin genetic program including modules for anterior–posterior (AP) and proximal–distal (PD) patterning. Unlike the AP and PD axes, median fins lack an unambiguous DV axis, leaving the origin of this DV pattern in paired appendages unresolved. Here, we describe Lmx1b expression in the posterior midline fins of cichlids, sturgeons, catsharks, and lampreys, revealing an ancestral role for this gene predating the origin of paired appendages. In median fins, Lmx1b activation depends on shh from the ZPA, whereas in paired fins it relies on ectodermal wnt signaling, indicating the evolution of novel regulatory inputs for dorsal patterning. We observe that ephA4b, a putative Lmx1b target, is co-expressed with Lmx1b in dorsal pectoral and posterior midline fins and downregulated alongside Lmx1b, suggesting a role in both fin types related to axon guidance. We propose that novel regulation drove the repurposing of Lmx1b from posterior to dorsal fin determinant, with co-option of conserved downstream targets. Altogether, our findings demonstrate that the DV axis of paired appendages represents an evolutionary innovation arising from the integration of ancestral midline fin and flank determinants with novel regulatory inputs. Graphical Abstract Graphical Abstract

Despite their evolutionary, developmental and functional importance, the origin of vertebrate paired appendages remains uncertain. In mice, a single enhancer termed ZRS is solely responsible for Shh expression in limbs. Here, zebrafish and mouse transgenic assays trace the functional equivalence of ZRS across the gnathostome phylogeny. CRISPR/Cas9-mediated deletion of the medaka ( Oryzias latipes ) ZRS and enhancer assays identify the existence of ZRS shadow enhancers in both teleost and human genomes. Deletion of both ZRS and shadow ZRS abolishes shh expression and completely truncates pectoral fin formation. Strikingly, deletion of ZRS results in an almost complete ablation of the dorsal fin. This finding indicates that a ZRS- Shh regulatory module is shared by paired and median fins and that paired fins likely emerged by the co-option of developmental programs established in the median fins of stem gnathostomes. Shh function was later reinforced in pectoral fin development with the recruitment of shadow enhancers, conferring additional robustness. The authors study the cis-regulatory evolution of the Shh locus in vertebrates. Using genomic editing and chromatin profiling, they conclude that paired fins emerged through the co-option of developmental programs for the median fins of gnathostomes.

Background Zebrafish can faithfully regenerate injured fins through the formation of a blastema, a mass of proliferative cells that can grow and develop into the lost body part. After amputation, various cell types contribute to blastema formation, where each cell type retains fate restriction and exclusively contributes to regeneration of its own lineage. Epigenetic changes that are associated with lineage restriction during regeneration remain underexplored. Results We produce epigenome maps, including DNA methylation and chromatin accessibility, as well as transcriptomes, of osteoblasts and other cells in uninjured and regenerating fins. This effort reveals regeneration as a process of highly dynamic and orchestrated transcriptomic and chromatin accessibility changes, coupled with stably maintained lineage-specific DNA methylation. The epigenetic signatures also reveal many novel regeneration-specific enhancers, which are experimentally validated. Regulatory networks important for regeneration are constructed through integrative analysis of the epigenome map, and a knockout of a predicted upstream regulator disrupts normal regeneration, validating our prediction. Conclusion Our study shows that lineage-specific DNA methylation signatures are stably maintained during regeneration, and regeneration enhancers are preset as hypomethylated before injury. In contrast, chromatin accessibility is dynamically changed during regeneration. Many enhancers driving regeneration gene expression as well as upstream regulators of regeneration are identified and validated through integrative epigenome analysis.

In this study, a special charge structure is designed to form an explosively formed projectile (EFP) with fins for stable flight. By using LS-DYNA for numerical simulation, the influence of charge structure parameters on the EFP characteristics of the tail fins was analyzed. The results show that the irregular charge structure can reliably form an EFP with fins, and the number of EFP tail fins can be controlled by changing the number of sides n of the regular polygon at the top section of the charge. Changing the shape parameters n and Dn of the top section of the charge will greatly affect the shape of the tail fins, while the charge height H has a significant impact on the length to diameter ratio of EFP, the appropriate range of H values should be between 0.5 Dc and 0.8 Dc . The research results can provide reference for the design ideas of tail wing EFP.