Exchange-spring behavior in bimagnetic CoFe2O4/CoFe2 nanocomposite

In this work we report a study of the magnetic behavior of ferrimagnetic oxide CoFe2O4 and ferrimagnetic oxide/ferromagnetic metal CoFe2O4/CoFe2 nanocomposites. The latter compound is a good system to study hard ferrimagnet/soft ferromagnet exchange coupling. Two steps were used to synthesize the bimagnetic CoFe2O4/CoFe2 nanocomposites: (i) first preparation of CoFe2O4 nanoparticles using the a simple hydrothermal method and (ii) second reduction reaction of cobalt ferrite nanoparticles using activated charcoal in inert atmosphere and high temperature. The phase structures, particle sizes, morphology, and magnetic properties of CoFe2O4 nanoparticles have been investigated by X-Ray diffraction (XRD), Mossbauer spectroscopy (MS), transmission electron microscopy (TEM), and vibrating sample magnetometer (VSM) with applied field up to 3.0 kOe at room temperature and 50K. The mean diameter of CoFe2O4 particles is about 16 nm. Mossbauer spectra reveal two sites for Fe3+. One site is related to Fe in an octahedral coordination and the other one to the Fe3+ in a tetrahedral coordination, as expected for a spinel crystal structure of CoFe2O4. TEM measurements of nanocomposite show the formation of a thin shell of CoFe2 on the cobalt ferrite and indicate that the nanoparticles increase to about 100 nm. The magnetization of nanocomposite showed hysteresis loop that is characteristic of the exchange spring systems. A maximum energy product (BH)max of 1.22 MGOe was achieved at room temperature for CoFe2O4/CoFe2 nanocomposites, which is about 115% higher than the value obtained for CoFe2O4 precursor. The exchange-spring interaction and the enhancement of product (BH)max in nanocomposite CoFe2O4/CoFe2 have been discussed.Comment: 9 pages, 10 figure

Genomic priming of the antisecretory response to estrogen in rat distal colon throughout the estrous cycle.

The secretion of Cl(-) across distal colonic crypt cells provides the driving force for the movement of fluid into the luminal space. 17beta-Estradiol (E2) produces a rapid and sustained reduction in secretion in females, which is dependent on the novel protein kinase C delta (PKC delta) isozyme and PKA isoform I targeting of KCNQ1 channels. This sexual dimorphism in the E2 response is associated with a higher expression level of PKC delta in female compared with the male tissue. The present study revealed the antisecretory response is regulated throughout the female reproductive (estrous) cycle and is primed by genomic regulation of the kinases. E2 (1-10 nm) decreased cAMP-dependent secretion in colonic epithelia during the estrus, metestrus, and diestrus stages. A weak inhibition of secretion was demonstrated in the proestrus stage. The expression levels of PKC delta and PKA fluctuated throughout the estrous cycle and correlated with the potency of the antisecretory effect of E2. The expression of PKC delta and PKA were up-regulated by estrogen at a transcriptional level via a PKC delta-MAPK-cAMP response element-binding protein-regulated pathway indicating a genomic priming of the antisecretory response. PK Cdelta was activated by the membrane-impermeant E2-BSA, and this response was inhibited by the estrogen receptor antagonist ICI 182,780. The 66-kDa estrogen receptor-alpha isoform was present at the plasma membrane of female colonic crypt cells with a lower abundance found in male colonic crypts. The study demonstrates estrogen regulation of intestinal secretion both at a rapid and transcriptional level, demonstrating an interdependent relationship between both nongenomic and genomic hormone responses

Berberine Reduces cAMP-Induced Chloride Secretion in T84 Human Colonic Carcinoma Cells through Inhibition of Basolateral KCNQ1 Channels

Berberine is a plant alkaloid with multiple pharmacological actions, including antidiarrhoeal activity and has been shown to inhibit Cl− secretion in distal colon. The aims of this study were to determine the molecular signaling mechanisms of action of berberine on Cl− secretion and the ion transporter targets. Monolayers of T84 human colonic carcinoma cells grown in permeable supports were placed in Ussing chambers and short-circuit current measured in response to secretagogues and berberine. Whole-cell current recordings were performed in T84 cells using the patch-clamp technique. Berberine decreased forskolin-induced short-circuit current in a concentration-dependent manner (IC50 80 ± 8 μM). In apically permeabilized monolayers and whole-cell current recordings, berberine inhibited a cAMP-dependent and chromanol 293B-sensitive basolateral membrane K+ current by 88%, suggesting inhibition of KCNQ1 K+ channels. Berberine did not affect either apical Cl− conductance or basolateral Na+–K+-ATPase activity. Berberine stimulated p38 MAPK, PKCα and PKA, but had no effect on p42/p44 MAPK and PKCδ. However, berberine pre-treatment prevented stimulation of p42/p44 MAPK by epidermal growth factor. The inhibitory effect of berberine on Cl− secretion was partially blocked by HBDDE (∼65%), an inhibitor of PKCα and to a smaller extent by inhibition of p38 MAPK with SB202190 (∼15%). Berberine treatment induced an increase in association between PKCα and PKA with KCNQ1 and produced phosphorylation of the channel. We conclude that berberine exerts its inhibitory effect on colonic Cl− secretion through inhibition of basolateral KCNQ1 channels responsible for K+ recycling via a PKCα-dependent pathway

Sexual Dimorphism and Estrogen Regulation of KCNE3 Expression Modulates the Functional Properties of KCNQ1 K+ Channels

The KCNQ1 potassium channel associates with various KCNE ancillary subunits that drastically affect channel gating and pharmacology. Co-assembly with KCNE3 produces a current with nearly instantaneous activation, some time-dependent activation at very positive potentials, a linear current voltage relationship and a 10-fold higher sensitivity to chromanol 293B. KCNQ1:KCNE3 channels are expressed in colonic crypts and mediate basolateral K+ recycling required for Cl- secretion. We have previously reported the female-specific anti-secretory effects of estrogen via KCNQ1:KCNE3 channel inhibition in colonic crypts. This study was designed to determine whether gender and estrogen regulate the expression and function of KCNQ1 and KCNE3 in rat distal colon. Colonic crypts were isolated from Sprague-Dawley rats and used for whole-cell patch-clamp and to extract total RNA and protein. Sheets of epithelium were used for short-circuit current recordings. KCNE1 and KCNE3 mRNA and protein abundance was significantly higher in male than female crypts. No expression of KCNE2 was found and no difference was observed in KCNQ1 expression between male and female (at estrous) colonic crypts. Male crypts showed a 2.2-fold higher level of association of KCNQ1 and KCNE3 compared to female cells. In female colonic crypts, KCNQ1 and KCNE3 protein expression fluctuated throughout the estrous cycle and 17-estradiol (E2 10 nM) produced a rapid (\u3c15\u3emin) dissociation of KCNQ1 and KCNE3 in female crypts only. Whole-cell K+ currents showed a linear current-voltage relationship in male crypts, while K+ currents in colonic crypts isolated from females displayed voltage-dependent outward rectification. Currents in isolated male crypts and epithelial sheets were 10-fold more sensitive to specific KCNQ1 inhibitors, such as chromanol 293B and HMR-1556, than in female. The effect of E2 on K+ currents mediated by KCNQ1 with or without different -subunits was assayed from current-voltage relations elicited in CHO cells transfected with KCNQ1 and KCNE3 or KCNE1 cDNA. E2 (100 nM) reduced the currents mediated by the KCNQ1:KCNE3 potassium channel and had no effect on currents via KCNQ1:KCNE1 or KCNQ1 alone. Currents mediated by the complex formed by KCNQ1 and the mutant KCNE3-S82A β-subunit showed rapid run-down and insensitivity to E2. Together, these data suggest that estrogen regulates the expression of the KCNE1 and KCNE3 and with it the gating and pharmacological properties of the K+ conductance required for Cl- secretion. The decreased association of the KCNQ1:KCNE3 channel complex promoted by estrogen exposure underlies the molecular mechanism for the sexual dimorphism and estrous cycle dependence of the anti-secretory actions of estrogen in the intestine

Factores que determinan la adopci?n de la facturaci?n electr?nica v?a SMS por las MYPES de Lima

La Superintendencia Nacional de Administraci?n Tributaria (SUNAT), es la encargada, entre otras funciones, de recaudar impuestos de diferente origen en nuestro pa?s. En la actualidad esta se puede realizar de manera f?sica y/o electr?nica; siendo esta ultima la que brinda mejores capacidades sobre todo por temas de automatizaci?n; cre?ndose un ecosistema, en el que empresas como proveedores de servicios electr?nicos (PSE) brindan servicios de emisi?n electr?nica. La SUNAT prev? a largo plazo que la facturaci?n electr?nica reemplace a la facturaci?n f?sica el 100% de los casos; sin embargo, la realidad de nuestro pa?s hace notoria diversas dificultades para este cometido, principalmente por la conectividad a internet. Ante ello se plantea una soluci?n que no requiera conexi?n a internet, simplemente red telef?nica, como es una arquitectura basada en emisi?n por SMS, cubri?ndose as? un mayor territorio. Creemos que las empresas m?s grandes tendr?an alguna dificultad para usar este sistema ya que emiten muchas facturas en periodos cortos y una soluci?n de SMS al menos en una soluci?n b?sica ser?a poco usable. Adem?s de ello, estas tienen la capacidad de obtener servicios de una PSE por su fuerte financiero

Estrogen inhibits chloride secretion caused by cholera and Escherichia coli enterotoxins in female rat distal colon.

Excessive Cl(-) secretion is the driving force for secretory diarrhea. 17β-Estradiol has been shown to inhibit Cl(-) secretion in rat distal colon through a nongenomic pathway. We examined whether 17β-estradiol inhibits Cl(-) secretion in an animal model of secretory diarrhea and the downstream effectors involved. The effect of 17β-estradiol on cholera toxin and heat-stable enterotoxin induced Cl(-) secretion in rat colonic mucosal sheets was studied by current-voltage clamping. Selective permeabilization of apical or basolateral membranes with amphotericin B or nystatin was used to isolate basolateral K(+) channel and apical Cl(-) channel activity, respectively. 17β-Estradiol dose-dependently inhibited secretory responses to both toxins with IC(50) values of approximately 1nM. This effect was female-gender specific, with no inhibition observed in male tissues. 17β-Estradiol responses were insensitive to the pure anti-estrogen ICI 182,720. 17β-Estradiol exerted its effects downstream of enterotoxin-induced production of second messengers (cAMP and cGMP) but was dependent on PKCδ activation. In nystatin-permeabilized tissues, apical Cl(-) currents were unaffected by 17β-estradiol treatment while basolateral K(+) current was profoundly inhibited by the hormone. This current was sensitive to the specific KCNQ1 channel inhibitors chromanol 293B and HMR-1556. In conclusion, 17β-estradiol inhibits enterotoxin-induced Cl(-) secretion via a PKCδ-dependent mechanism involving inhibition of basolateral KCNQ1 channels. These data elucidate mechanisms of 17β-estradiol inhibition of Cl(-) secretion induced by enterotoxins in intestinal epithelia, which may be relevant for the treatment of diarrheal diseases.</p

Influ?ncia das tens?es induzidas por realces em lavra por subn?veis nas condi??es de estabilidade de galerias de desenvolvimento em minas subterr?neas.

This work aims to investigate the influence of induced stresses by sublevel stopes in development excavations, which are excavated to access these stopes. Parametric studies changing the position of development openings in relation to stopes were performed in order to evaluate the stability conditions of these openings. Numerical modeling using finite element method was applied to the simulations. An elastic behavior of the rock mass was assumed to allow the simulation of a lot of different opening locations. The results have showed distinct scenarios. Some cases of global collapse were found as well as some situations where the integrity of the openings could be kept. Therefore, the most favorable situations were chosen to perform a plastic analysis in order to have a better knowledge of opening stability conditions. The geometry of the excavations from Caraiba Mining Company, which extracts copper from an underground mine in Brazil, was used in these analyses to illustrate a real situation where many failure problems in these development openings were observed.Este trabalho tem por objetivo analisar a influ?ncia das tens?es induzidas por realces em lavra por subn?vel nas galerias de desenvolvimento, que s?o escavadas para acesso a esses realces. Foram feitos estudos param?tricos variando a posi??o das galerias em rela??o aos realces para avaliar as condi??es de estabilidade dessas galerias, utilizando modelagem num?rica atrav?s do m?todo dos elementos finitos. Um comportamento el?stico para o maci?o rochoso foi assumido para permitir a simula??o de v?rias posi??es para as galerias de acesso. Os resultados mostraram cen?rios distintos. Alguns casos de colapso global das galerias, bem como situa??es onde a integridade dessas aberturas pode ser mantida. Como consequ?ncia, nas situa??es mais favor?veis foram feitas an?lises pl?sticas de modo a obter um melhor conhecimento acerca das condi??es de estabilidade dessas galerias. A geometria das escava??es da Mina Cara?ba, que extrai cobre em mina subterr?nea no Brasil, foi utilizada para ilustrar uma situa??o real, onde muitos problemas de ruptura nas galerias de acesso aos realces foram observados

Proposta didáctica para favorecer o desenvolvimento sócio-emocional e a transição para o ensino superior dos estudantes do ensino secundário

El presente trabajo consiste en describir una propuesta didáctica para el desarrollo socioemocional de estudiantes de enseñanza secundaria, a partir de habilidades de autoconocimiento, autorregulación y toma de decisiones postsecundarias. Esto, en el marco de necesidades de atención psicoeducativa y de aumento de expectativas de estudiantes, observadas durante el contexto de pandemia en establecimientos acompañados por el programa PACE de la Universidad de Playa Ancha, Valparaíso, Chile. Aquí, se exponen las potencialidades de una secuencia didáctica implementada por el área de exploración vocacional del programa durante el 2021, que considera la generación de espacios seguros para favorecer el diálogo y potenciar la motivación por la continuidad de estudios en estudiantes de 4° año medio, posibilitando, asimismo, su atención socioemocional. Tal secuencia se divide en 3 etapas, una de diagnóstico y reconocimiento de la situación emocional de los(as) estudiantes; una de implementación de sesiones sincrónicas a partir de una metodología de tipo activa participativa construida en relación con insumos de la etapa diagnóstica y su vinculación con los ejes de autoconocimiento, autorregulación; vocación y propósitos frente al ingreso a la educación superior. La última etapa, propone una evaluación del proceso implementado a partir de la satisfacción de las comunidades educativas acompañadasO presente trabalho consiste em descrever uma proposta didática para o desenvolvimento sócio-emocional dos estudantes do ensino secundário, baseada no auto-conhecimento, auto-regulação e capacidade de decisão pós-secundária. Isto se dá, no contexto das necessidades de atenção psico-educacional e do aumento das expectativas dos estudantes, observado durante o contexto pandémico em estabelecimentos acompanhados pelo programa PACE da Universidad de Playa Ancha, Valparaíso, Chile. Aqui é apresentado o potencial de uma sequência didática implementada pela área de exploração profissional do programa durante 2021, que considera a geração de espaços seguros para promover o diálogo e aumentar a motivação para a continuação dos estudos nos estudantes do 4º ano do ensino secundário, permitindo também a sua atenção sócio-emocional. Esta sequência está dividida em 3 fases, uma de diagnóstico e reconhecimento da situação emocional dos estudantes; uma de implementação de sessões síncronas baseadas numa metodologia participativa ativa construída em relação às entradas da fase de diagnóstico e a em relação com os eixos de auto-conhecimento, auto-regulação, vocação e propósitos em quanto ao ingresso no ensino superior. A última fase propõe uma avaliação do processo implementado com base na satisfação das comunidades educativas acompanhadasUniversidad de Playa Ancha. ChileUniversidad de Playa Ancha. ChileUniversidad de Playa Ancha. Chil

Rapid responses to steroid hormones: from frog skin to human colon. A homage to Hans Ussing

AbstractFifty years ago, Hans Ussing described the mechanism by which ions are actively transported across frog skin. Since then, an enormous amount of effort has been invested in determining the cellular and molecular specifics of the transport mechanisms and their regulatory pathways. Ion transport in high-resistance epithelia is regulated by a variety of hormonal and non-hormonal factors. In vertebrates, steroid hormones such as mineralocorticoids, glucocorticoids and estrogens are major regulators of ion and water transport and hence are central to the control of extracellular fluid volume and blood pressure. Steroid hormones act through nuclear receptors to control the transcriptional activity of specific target genes, such as ion channels, ion transporters and ion pumps. These effects are observed after a latency of several hours and can last for days leading to cellular differentiation that allows a higher transport activity. This pathway is the so-called genomic phase. However, in the past 10 years, it has become apparent that steroid hormones can regulate electrolyte and water transport in tight epithelia independently of the transcription of these ion channels and transporters by regulating ion transporter activity in a non-genomic fashion via modulation of various signal transduction pathways. The molecular mechanisms underlying the steroid hormone-induced activation of signal transduction pathways such as protein kinase C (PKC), protein kinase A (PKA), intracellular calcium, intracellular pH and mitogen-activated protein kinases (MAPKs) and how non-genomic activation of these pathways influences epithelial ion transport will be discussed in this review