Evolution of instabilities in filament buckling processes

In this work we study the dynamical buckling process of a thin filament immersed in a highly viscous medium. We perform an experimental study to track the shape evolution of the filament during a constant velocity compression. Numerical simulations reproduce the dynamical features observed from the experimental data and allow quantifying the filament's load. We observe that both the filament's load and the wave number evolve in a stepwise manner. In order to achieve a physical insight of the process, we apply a theoretical model to describe the buckling of a filament in a viscous medium. We solve a hydrodynamic equation in terms of normal modes for clamped-clamped boundary conditions and constant applied load. We find a good agreement between experimental data and simulations, suggesting that the proposed mechanistic model captures the essential features underlying the dynamical buckling process.Fil: Monastra, Alejandro Gabriel. Universidad Nacional de General Sarmiento. Instituto de Ciencias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Carusela, María Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de General Sarmiento. Instituto de Ciencias; ArgentinaFil: Van Der Velde, Guido Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: D'angelo, María Verónica. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería; ArgentinaFil: Bruno, Luciana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentin

CONCEPÇÕES DE GESTÃO ESCOLAR DEMOCRÁTICA: ESTUDO FENOMENOGRÁFICO COM DIRETORES DE ESCOLAS PÚBLICAS

Given the scarcity of empirical studies on democratic school management in Brazil, the objective of this research is to analyze, in the light of phenomenography, the different conceptions of democratic school management and their implications for the management practices of public school principals. Data production took place through in-depth individual interviews with 19 principals of municipal elementary schools. Data were analyzed using a phenomenographic protocol established in the literature. Three different conceptions of democratic school management were identified: (1) as role fulfillment; (2) as input for decision making; (3) as meeting the needs of the community. The main contribution of this research is to show how these conceptions induce school principals to different democratic management practices. Another contribution is to offer an alternative interpretation to the role of street-level bureaucrats and other actors who modify a public policy when implementing it. The findings also show that the promotion of participation, through dialogue, fosters organizational authorship. Finally, phenomenography is presented as a promising research method for the field of school management.Dada la escasez de estudios empíricos sobre gestión escolar democrática en el país, el objetivo de esta investigación es analizar, a la luz de la fenomenografía, las diferentes concepciones de gestión escolar democrática y sus implicaciones para las prácticas de gestión de los directores de escuelas públicas. La producción de datos se realizó a través de entrevistas individuales en profundidad con 19 directores de escuelas primarias municipales. Los datos fueron analizados utilizando un protocolo fenomenográfico establecido en la literatura. Se identificaron tres concepciones diferentes de gestión escolar democrática: (1) como cumplimiento de roles; (2) como insumo para la toma de decisiones; (3) como satisfacción de las necesidades de la comunidad. La principal contribución de esta investigación es mostrar cómo estas concepciones inducen a los directores de escuela a diferentes prácticas de gestión democrática. Otro aporte es ofrecer una interpretación alternativa al rol de los burócratas de calle y otros actores que modifican una política pública al momento de implementarla. Los hallazgos también muestran que la promoción de la participación, a través del diálogo, fomenta la autoría organizacional. Finalmente, la fenomenografía se presenta como un método de investigación promisorio para el campo de la gestión escolar.Diante da escassez de estudos empíricos sobre gestão escolar democrática no país, o objetivo dessa pesquisa é analisar, à luz da fenomenografia, as diferentes concepções de gestão escolar democrática e suas implicações nas práticas de gestão dos diretores de escolas públicas. A produção de dados se deu por meio de entrevistas individuais em profundidade com 19 diretores de escolas municipais de ensino fundamental. Os dados foram analisados a partir de protocolo fenomenográfico consagrado na literatura. Foram identificadas três diferentes concepções de gestão escolar democrática: (1) como cumprimento de papéis; (2) como insumo para a tomada de decisão; (3) como atendimento das necessidades da comunidade. A principal contribuição desta pesquisa é mostrar como essas concepções induzem os diretores escolares a diferentes práticas de gestão democrática. Outra contribuição é oferecer uma interpretação alternativa à atuação dos burocratas de nível de rua e outros atores que modificam uma política pública ao implementá-la. Os achados também mostram que a promoção da participação, por meio do diálogo, fomenta a autoria organizacional. Finalmente, apresenta-se a fenomenografia como método de investigação promissor para o campo da gestão escolar

Age-related central regulation of orexin and NPY in the short-lived African killifish Nothobranchius furzeri

Orexin A (OXA) and neuropeptide Y (NPY) are two hypothalamic neuropeptides involved in the regulation of feeding behavior and food intake in all vertebrates. Accumulating evidences document that they undergo age-related modifications, with consequences on metabolism, sleep/wake disorders and progression of neurodegenerations. The present study addressed the age related changes in expression and distribution of orexin A (its precursor is also known as hypocretin\u2014HCRT) and NPY, and their regulation by food intake in the short-lived vertebrate model Nothobranchius furzeri. Our experiments, conducted on male specimens, show that: (a) HCRT and OXA and NPY mRNA and protein are localized in neurons of diencephalon and optic tectum, as well as in numerous fibers projecting through the entire neuroaxis, and are colocalized in specific nuclei; (b) in course of aging, HCRT and NPY expressing neurons are localized also in telencephalon and rhombencephalon; (c) HCRT expressing neurons increased slightly in the diencephalic area of old animals and in fasted animals, whereas NPY increased sharply; (d) central HCRT levels are not regulated neither in course of aging nor by food intake; and (e) central NPY levels are augmented in course of aging, and regulated by food intake only in young. These findings represent a great novelty in the study of central orexinergic and NPY-ergic systems in vertebrates', demonstrating an uncommon and unprecedented described regulation of these two orexigenic neuropeptides

Expression and distribution of leptin and its receptors in the digestive tract of DIO (diet-induced obese) zebrafish.

The expression and localization of leptin (A and B) and its receptor family in control and diet-induced obese (DIO) adult male zebrafish gut, after 5-weeks overfeeding, administering Artemia nauplii, as fat-rich food, were investigated. Recently, the obese adult zebrafish was considered an experimental model with pathophysiological pathways similar to mammalian obesity. Currently, there are no reports about leptin in fish obesity, or in a state of altered energy balance. By qRT-PCR, leptin A and leptin B expression levels were significantly higher in DIO zebrafish gut than in the control group (CTRL), and the lowest levels of leptin receptor mRNA appeared in DIO zebrafish gut. The presence of leptin and its receptor proteins in the intestinal tract was detected by western blot analysis in both control and DIO zebrafish. By single immunohistochemical staining, leptin and leptin receptor immunoreactive endocrine cells were identified in the intestinal tract either in DIO or control zebrafish. Moreover, leptin immunopositive enteric nervous system elements were observed in both groups. By double immunohistochemical staining, leptin and its receptor were colocalized especially in DIO zebrafish. Thus, our study represents a starting point in the investigation of a possible involvement of leptin in control of energy homeostasis in control and DIO zebrafish

Orexins and receptor OX2R in the gastroenteric apparatus of two teleostean species: Dicentrarchus labrax and Carassius auratus

Orexin A and B peptides and the receptor OX2R were studied in sea bass and goldfish gastroenteric tract by immunoblotting combined with densitometric analysis using NIH Image J software and immunohistochemical techniques. These teleost species present a different gut organization and diverse feeding habits. Immunoblotting experiments showed one band of 16 kDa corresponding to prepro-orexin, and one band of 38 kDa corresponding to the OX2R receptor. Immunohistochemical localization of OXA and OXB was observed in the enteric nervous system throughout the gastroenteric tract of both species. OXA and OXB immunoreactive cells were found in the gastric and intestinal regions of sea bass, and were mainly found in the basal region of folds in intestinal bulb, and in the midgut and hindgut of goldfish. The distribution of OX2R was mainly detected in the mucosa of the gastroenteric tract of sea bass and goldfish. This distribution suggests an endocrine action of OXA and OXB in the gastrointestinal tract as well as involvement in the peripheral control of food intake and digestive processes in both species. This study might also serve to determine the productive factors in breeding and as a baseline for future experimental studies on the regulation of the gastroenteric functions in non-mammalian vertebrates

Nutrition in preschool children and later risk of obesity: a systematic review and meta analysis

Objectives and study: Nutrition in infants and preschool children has been suggested to influence the risk of later obesity. However, the evidence for this association is conflicting and few studies have investigated this prospectively or considered the role of energy and specific macronutrients. Here we report a systematic review and meta-analyis of studies that tested the hypothesis that nutrition in the preschool period, between the ages of 6 months and 3 years, is associated with later obesity risk. Methods: MEDLINE, EMBASE and CENTRAL databases were searched from January 1988 to June 2015 for studies reporting nutritional intake in infants and preschool children aged 6-36 months and later measures of obesity. Bibliographies of included studies were hand searched and authors and other experts consulted to identify omissions. We included all studies that investigated dietary energy and/or macronutrient intake during 6-36 months in relation to later measures of obesity. Methodological quality was assessed using the Downs and Black checklist designed specifically to appraise both randomised and non-randomised studies. The checklist was adapted to include aspects of particular relevance to studies investigating nutritional exposures. Two reviewers independently scored studies against the 28 item checklist which included questions on study reporting, external validity, internal validity (bias and confounding), and statistical power. A statistician independently scored questions relating to statistical methods and their decision was final. Data from studies amenable to meta-analysis were analysed using STATA (StataCrop 12, Texas). For continuous outcomes, results were expressed as standardised mean difference (SMD) between the high and low protein intake groups. For dichotomous outcomes, results for each study were expressed as relative risk (RR). Both dichotomous and continuous outcomes were presented with 95% confidence intervals (CI). Between-study heterogeneity was assessed by the Q and I2 statistics. Results: 24 eligible articles (comprising 16 primary studies) were included in a narrative synthesis, and 13 studies in a random-effects meta-analysis. A higher protein intake was associated with later risk of obesity in 15 studies. In 13 studies included in the meta-analysis protein in the preschool period was associated with higher BMI z-score later in childhood (pooled effect size: 0.28 z-scores, 95% CI 0.20 to 0.35)(Figure 1). There was no significant hererogeneity between studies (I2 0.0%, p = 0.932). Associations of energy, fat and carbohydrate were inconclusive. Conclusion: Our findings suggest that nutrition and particularly high protein intake in infants and preschool children is important for risk of later obesity. Although further experimental data are required to establish causality, these findings suggest that optimising the protein intake of these children could be important for their long term health

Hypertonic Stress Induces VEGF Production in Human Colon Cancer Cell Line Caco-2: Inhibitory Role of Autocrine PGE2

Vascular Endothelial Growth Factor (VEGF) is a major regulator of angiogenesis. VEGF expression is up regulated in response to micro-environmental cues related to poor blood supply such as hypoxia. However, regulation of VEGF expression in cancer cells is not limited to the stress response due to increased volume of the tumor mass. Lipid mediators in particular arachidonic acid-derived prostaglandin (PG)E2 are regulators of VEGF expression and angiogenesis in colon cancer. In addition, increased osmolarity that is generated during colonic water absorption and feces consolidation seems to activate colon cancer cells and promote PGE2 generation. Such physiological stimulation may provide signaling for cancer promotion. Here we investigated the effect of exposure to a hypertonic medium, to emulate colonic environment, on VEGF production by colon cancer cells. The role of concomitant PGE2 generation and MAPK activation was addressed by specific pharmacological inhibition. Human colon cancer cell line Caco-2 exposed to a hypertonic environment responded with marked VEGF and PGE2 production. VEGF production was inhibited by selective inhibitors of ERK 1/2 and p38 MAPK pathways. To address the regulatory role of PGE2 on VEGF production, Caco-2 cells were treated with cPLA2 (ATK) and COX-2 (NS-398) inhibitors, that completely block PGE2 generation. The Caco-2 cells were also treated with a non selective PGE2 receptor antagonist. Each treatment significantly increased the hypertonic stress-induced VEGF production. Moreover, addition of PGE2 or selective EP2 receptor agonist to activated Caco-2 cells inhibited VEGF production. The autocrine inhibitory role for PGE2 appears to be selective to hypertonic environment since VEGF production induced by exposure to CoCl2 was decreased by inhibition of concomitant PGE2 generation. Our results indicated that hypertonicity stimulates VEGF production in colon cancer cell lines. Also PGE2 plays an inhibitory role on VEGF production by Caco-2 cells exposed to hyperosmotic stress through EP2 activation

Terapia Immunosoppressiva nella sindrome nefrosica

Atti del Convegno "Le basi razionali dell'uso dei diuretici in medicina interna" (Padova, 8-9 giugno), 142-150, 200