4D Imaging and Diffraction Dynamics of Single-Particle Phase Transition in Heterogeneous Ensembles

In this Letter, we introduce conical-scanning dark-field imaging in four-dimensional (4D) ultrafast electron microscopy to visualize single-particle dynamics of a polycrystalline ensemble undergoing phase transitions. Specifically, the ultrafast metal–insulator phase transition of vanadium dioxide is induced using laser excitation and followed by taking electron-pulsed, time-resolved images and diffraction patterns. The single-particle selectivity is achieved by identifying the origin of all constituent Bragg spots on Debye–Scherrer rings from the ensemble. Orientation mapping and dynamic scattering simulation of the electron diffraction patterns in the monoclinic and tetragonal phase during the transition confirm the observed behavior of Bragg spots change with time. We found that the threshold temperature for phase recovery increases with increasing particle sizes and we quantified the observation through a theoretical model developed for single-particle phase transitions. The reported methodology of conical scanning, orientation mapping in 4D imaging promises to be powerful for heterogeneous ensemble, as it enables imaging and diffraction at a given time with a full archive of structural information for each particle, for example, size, morphology, and orientation while minimizing radiation damage to the specimen

Investigating Instructor Talk in Novel Contexts: Widespread Use, Unexpected Categories, and an Emergent Sampling Strategy.

Instructor Talk-noncontent language used by instructors in classrooms-is a recently defined and promising variable for better understanding classroom dynamics. Having previously characterized the Instructor Talk framework within the context of a single course, we present here our results surrounding the applicability of the Instructor Talk framework to noncontent language used by instructors in novel course contexts. We analyzed Instructor Talk in eight additional biology courses in their entirety and in 61 biology courses using an emergent sampling strategy. We observed widespread use of Instructor Talk with variation in the amount and category type used. The vast majority of Instructor Talk could be characterized using the originally published Instructor Talk framework, suggesting the robustness of this framework. Additionally, a new form of Instructor Talk-Negatively Phrased Instructor Talk, language that may discourage students or distract from the learning process-was detected in these novel course contexts. Finally, the emergent sampling strategy described here may allow investigation of Instructor Talk in even larger numbers of courses across institutions and disciplines. Given its widespread use, potential influence on students in learning environments, and ability to be sampled, Instructor Talk may be a key variable to consider in future research on teaching and learning in higher education

GATA2 Mediates Thyrotropin-Releasing Hormone-Induced Transcriptional Activation of the Thyrotropin β Gene

Thyrotropin-releasing hormone (TRH) activates not only the secretion of thyrotropin (TSH) but also the transcription of TSHβ and α-glycoprotein (αGSU) subunit genes. TSHβ expression is maintained by two transcription factors, Pit1 and GATA2, and is negatively regulated by thyroid hormone (T3). Our prior studies suggest that the main activator of the TSHβ gene is GATA2, not Pit1 or unliganded T3 receptor (TR). In previous studies on the mechanism of TRH-induced activation of the TSHβ gene, the involvements of Pit1 and TR have been investigated, but the role of GATA2 has not been clarified. Using kidney-derived CV1 cells and pituitary-derived GH3 and TαT1 cells, we demonstrate here that TRH signaling enhances GATA2-dependent activation of the TSHβ promoter and that TRH-induced activity is abolished by amino acid substitution in the GATA2-Zn finger domain or mutation of GATA-responsive element in the TSHβ gene. In CV1 cells transfected with TRH receptor expression plasmid, GATA2-dependent transactivation of αGSU and endothelin-1 promoters was enhanced by TRH. In the gel shift assay, TRH signal potentiated the DNA-binding capacity of GATA2. While inhibition by T3 is dominant over TRH-induced activation, unliganded TR or the putative negative T3-responsive element are not required for TRH-induced stimulation. Studies using GH3 cells showed that TRH-induced activity of the TSHβ promoter depends on protein kinase C but not the mitogen-activated protein kinase, suggesting that the signaling pathway is different from that in the prolactin gene. These results indicate that GATA2 is the principal mediator of the TRH signaling pathway in TSHβ expression

A influência da estrutura de propriedade e controle sobre o valor de mercado corporativo no Brasil

O modelo brasileiro de governança corporativa é caracterizado pela elevada concentração na estrutura societária que, em geral, culmina na sobreposição da propriedade e da administração das companhias. Segundo a literatura, o acúmulo de ações pelo(s) controlador(es) pode impactar o desempenho corporativo devido ao efeito-alinhamento (ou incentivo) e ao efeito-entrincheiramento. A princípio, a presença de grandes acionistas estaria associada a benefícios para a organização, uma vez que poderia aumentar a eficácia do monitoramento da gestão. Todavia, patamares muito elevados de concentração acionária podem permitir que os controladores dominem o processo decisório da corporação, o que poderia resultar na expropriação da riqueza dos acionistas minoritários. A relevância da estrutura societária como mecanismo interno dos sistemas de governança corporativa motivou a realização do presente estudo. Este artigo teve como objetivo testar se a concentração de propriedade e controle influencia o valor de mercado corporativo. Para tanto, foi utilizado um painel não balanceado para o período de 2001 a 2010, composto por 237 empresas brasileiras não financeiras de capital aberto, que somou 1.199 observações. Foram empregados modelos dinâmicos de regressão, estimados pelo Método dos Momentos Generalizado Sistêmico (MMG-Sis), para mitigar possíveis fontes de endogeneidade como a omissão de variáveis, o efeito-feedback e a simultaneidade. Constatou-se a existência de relação quadrática entre concentração no direito sobre o fluxo de caixa do acionista controlador e o valor de mercado das firmas. Ademais, os resultados indicam que o valor de mercado corrigido das ações do maior acionista captou o efeito-incentivo, enquanto a concentração no direito de voto capturou o efeito-entrincheiramento