Universal Magnetic-Field-Driven Metal-Insulator-Metal Transformations in Graphite and Bismuth

Applied magnetic field induces metal - insulator and re-entrant insulator-metal transitions in both graphite and rhombohedral bismuth. The corresponding transition boundaries plotted on the magnetic field - temperature (B - T) plane nearly coincide for these semimetals and can be best described by power laws T ~ (B - B_c)^k, where B_c is a critical field at T = 0 and k = 0.45 +/- 0.05. We show that insulator-metal-insulator (I-M-I) transformations take place in the Landau level quantization regime and illustrate how the IMT in quasi-3D graphite transforms into a cascade of I-M-I transitions, related to the quantum Hall effect in quasi-2D graphite samples. We discuss the possible coupling of superconducting and excitonic correlations with the observed phenomena, as well as the signatures of quantum phase transitions associated with the M-I and I-M transformations.Comment: 23 pages including 14 figure

Physiological and biochemical responses of Eucalyptus seedlings to hypoxia

International audienceAbstractKey messageHypoxia promoted distinct changes in the levels of hormones, amino acids and organic acids in the roots and shoots of a seedling from 2Eucalyptusclones. These results indicate that modulation of hormone production, as well as specific chemical constituents associated with primary metabolism, contributes to the regulation of growth ofEucalyptusseedlings under hypoxic conditions.ContextAlthough floods in areas under Eucalyptus cultivation in Brazil negatively affect plant growth, chemical markers and/or indicators of hypoxia contributes to the regulation.sAimsThis study aimed to evaluate the hormonal and metabolic alterations induced by hypoxia on seedling growth.MethodsSeedlings of Eucalyptus urograndis clones VCC 975 and 1004 were grown in liquid solution and submitted to bubbling with air or with nitrogen. Levels of indol-3-acetic acid (IAA), abscisic acid (ABA), ethylene, 1-aminocyclopropane-1-carboxylic acid (ACC), primary metabolite profile and photosynthetic parameters were evaluated after fourteen days.ResultsHypoxia did not affect shoot dry mass of the seedlings. However, it decreased stomatal conductance and photosynthetic CO2 assimilation rate, and increased levels of ABA in the shoot. Hypoxia greatly reduced the dry mass and volume of roots, concomitantly with higher ACC and ethylene production. Moreover, hypoxia promoted distinct changes in IAA levels, and in amino acid and organic acid metabolism in roots and shoots.ConclusionThe biosynthesis of ABA, ethylene and IAA and its quantity in root tissues indicates the regulation of metabolism in response to hypoxia in Eucalyptus clones

Mangal communities of the "Salgado Paraense": Ecological heterogeneity along the Bragança peninsula assessed through soil and leaf analyses

Mangroves in the Bragança peninsula occur in a variety of environmental settings differing in tidal influence and fresh water run-off. The construction of a paved road running through the middle of the peninsula modified the transversal flow of water. Five sites were sampled along this road: I. Coastal site near the village of Ajuruteua, II. Tidal creeks flowing into the lower Caeté river, III. Central lagoons, IV. Avicennia basin forest, and V. Upper Caeté estuary near the village of Acarajó. All but site III, harbored the three common mangroves species Rhizophora mangle, Laguncularia racemosa and Avicennia germinans. Monospecific communities of shrub-like Avicennia germinans stands characterized site III. Soils were highly organic therefore bulk density was inversely correlated to the concentrations of C and N. Sites I and V had the lowest salinity values. The highest salinity was measured ii the Avicennia dominated sites III and IV. Nitrogen showed similar values in all sites, but S was clearly more abundant in sites II and V. Leaf dimensions varied significantly between sites. Considering leaf area expansion as indicator ofstress and δ 13C values as indicator of water use efficiency, site V was more favorable for Rhizophora and Laguncularia while site IV was so for Avicennia. Leaf shape measured as the length/width ratio was more variable in Avicennia and least variable in Rhizophora. Leaf nutrients were not correlated with soil nutrient content. Sodium and Mg were more concentrated in Avicennia leaves while Fe was more concentrated in Laguncularia and Mn in Rhizophora leaves. Avicennia showed the highest N and the lowest Ca concentrations as expected for being a glycinbetaine accumulator and an oxalate-former. δ 15N values indicate that N source for mangroves is essentially the mineralization of organic matter

The importance of the ligation of the inferior thyroid artery in parathyroid function after subtotal thyroidectomy

We prospectively studied the effects of the ligation of the inferior thyroid artery (ITA) on postoperative hypoparathyroidism in 48 patients who underwent functional subtotal thyroidectomy. Patients were randomized into two groups: A, with bilateral ligation of the ITA and B, without ligation of the ITA. Parathyroid function was checked preoperatively and after surgery by clinical examination and measurement of total calcium, intact PTH, urinary calcium, and AMPc. RESULTS: A significant incidence of postoperative hypocalcemia occurred: 17% in group A and 13% in B on the 4th postoperative day. Six months later, the incidence was 5% in Group A and 0% in Group B. These differences were not statistically significant between the two groups, and neither were any of the other clinical and laboratory observations. CONCLUSION: The ligation of the ITA was not an important causal factor for the occurrence of postoperative hypocalcemia after subtotal thyroidectomy.Com o objetivo de observar os efeitos da ligadura da artéria tireoidiana inferior (ITA) no hipoparatireoidismo, 48 pacientes submetidos à tireoidectomia subtotal funcional foram estudados de forma prospectiva. Dois grupos foram randomizados, A: com a ligadura troncular bilateral da ITA e B: sem a ligadura troncular da ITA. A função paratireoidiana foi verificada no período pré-operatório e após a cirurgia através de exame clínico e dosagens de cálcio total, PTH, cálcio urinário e cAMP. Os resultados demostraram incidência importante e significativa de hipocalcemia pós-operatória, de 17% no grupo A e 13% no grupo B no 4º PO. Seis meses após, a incidência foi de 5% no grupo A e 0% no grupo B. Estas diferenças não foram estatisticamente significativas entre os dois grupos, nem nenhum dos outros dados clínicos ou laboratoriais estudados. Concluímos que a ligadura da ITA não é um fator causal importante de hipocalcemia pós-operatória após tireoidectomia subtotal

Oxidation of cyclohexanol and cyclohexene with triazenido complexes of chromium immobilized in biosorption FAU supports

This work presents the recovery of biosorption supports as an alternative source of benign production of heterogeneous catalysts for oxidation reactions in mild conditions. Cr-containing FAU zeolite, in sodium form (NaY) and in proton form (HY), was recovered from biosorption studies and reused as support for the preparation of heterogeneous catalysts by the flexible ligand method, using 1,3-diphenyltriazene derivatives. Results showed that the ligand play an important role in the coordination of Cr inside the zeolite. The catalysts showed good activity for the oxidation of cyclohexanol, reaching a maximum of 63.5% conversion. Cr leaching was evaluated and it was found that the Cr-FAU supports lost some of the Cr into the reaction medium, whereas immobilization of Cr-complexes reduced the referred leaching. For the cyclohexene oxidation, a maximum 72.9% conversion was achieved with a HY zeolite-based catalyst.H. Figueiredo and B. Silva are thankful to the "FCT - Fundacao para a Ciencia e Tecnologia" for their respective research grants. IKB thanks FO' for the contract under the program Ciencia 2007. This work was partially funded by the Centre of Biological Engineering and the Centre of Chemistry (University of Minho, Portugal) through FCT strategic projects PEst-OE/EQB/LA0023/ 2013 and PEst-C/QUI/UI0686/2011 (nF-COMP-01-0124-FEDER022716), the Project "BioEnv - Biotechnology and Bioengineering for a sustainable world", REF. NORTE-07-0124-FEDER-000048, co-funded by the Programa Operacional Regional do Norte (ON.2 - 0 Novo Norte), QREN and FEDER, and by the Spanish Ministry of Science and Innovation (CTQ2008-04261/PPQ)

Possible Fractional Quantum Hall Effect in Graphite

Measurements of basal plane longitudinal rho_b(B) and Hall rho_H(B) resistivities were performed on highly oriented pyrolytic graphite (HOPG) samples in pulsed magnetic field up to B = 50 T applied perpendicular to graphene planes, and temperatures 1.5 K 30 T and for all studied samples, we observed a sign change in rho_H(B) from electron- to hole-like. For our best quality sample, the measurements revealed the enhancement in rho_b(B) for B > 34 T (T = 1.8 K), presumably associated with the field-driven charge density wave or Wigner crystallization transition. Besides, well defined plateaus in rho_H(B) were detected in the ultra-quantum limit revealing the signatures of fractional quantum Hall effect in graphite.Comment: 15 pages, including 4 figure

Aproximación a la prevención del uso de sustancias psicoactivas a partir de los Conocimientos, actitudes y prácticas de consumidores activos

Objective To determine the knowledge, attitudes, and practices related to the consumption of psychoactive substances, alcohol, and tobacco in young consumers in the municipality of San Gil to generate strategies for the prevention of consumption. Methodology The research carried out was a cross-sectional study in which collected data through a validated and commonly used survey, consisting of 43 questions and divided into three parts, the first of knowledge, the second of attitudes and the third of practices, which was applied to young people between 18-27 years of age. age of the different neighborhoods of San Gil. Results The survey was answered by 140 volunteers, with a majority participation of women, indicating that the greatest consumption occurs in substances such as alcohol and tobacco. Discussion There has been evidence of an early onset of both cigarette and alcohol consumption and by the influence of a family member, so it is believed that the main prevention strategies should be aimed at education in the family. Conclusions The consumption of psychoactive substances has become a big problem nowadays since their naturalization has made us lose sight of the complications that they can have at the level of physical and mental health, therefore, the educational-preventive approach is urgent to alleviate this difficult health situation.Objetivo Determinar los Conocimientos, actitudes y prácticas relacionados con el consumo de sustancias psicoactivas, alcohol y tabaco en jóvenes consumidores del municipio de San Gil para generar estrategias de prevención del consumo. Metodología La investigación realizada fue un estudio de corte transversal en el que se recolectaron datos a través de una encuesta validada y de uso corriente, constituida por 43 preguntas y divida en tres partes, la primera de conocimientos, la segunda de actitudes y la tercera de prácticas, que fue aplicada a jóvenes entres los 18-27 años de edad de los diferentes barrios de San Gil. Resultados La encuesta fue respondida por 140 voluntarios, con una participación mayoritaria de mujeres, indicando que el mayor consumo se da en sustancias como el alcohol y el tabaco. Discusión Se ha evidenciado un inicio de consumo temprano tanto de cigarrillo como de alcohol y por influencia de algún familiar, con lo que, se cree que las principales estrategias de prevención deberían ir encaminadas a la educación en la familia. Conclusiones El consumo de las Sustancias psicoactivas se ha convertido en un gran problema actualmente ya que su naturalización ha hecho que se pierda de vista las complicaciones que pueden tener a nivel de salud física y mental, por lo tanto, el enfoque educativo- preventivo se hace urgente para paliar esta difícil situación de salud

Medios de comunicación y derecho a la información en Jalisco, 2015

El octavo informe Q ITESO: Análisis Crítico de Medios revisa el funcionamiento del sistema de comunicación política durante el proceso electoral de 2015, así como diversos aspectos relevantes de unas elecciones que culminaron con un cambio radical en el panorama político en Jalisco. En el universo de los medios de comunicación, se analizan los cambios experimentados por estos en el marco de la coyuntura electoral local, la equidad y profundidad en la cobertura por parte de los periódicos y la difusión que hicieron de las encuestas, así como el discurso e impacto de la propaganda difundida a través de la televisión y la Internet, a lo que se suma los debates registrados en redes sociales como Twitter, y la percepción sobre las campañas por parte de la audiencia tapatía. El examen político se enfoca en la campaña realizada por los candidatos independientes, el planteamiento socioeconómico de los contendientes por la capital del estado y el impacto electoral de un personaje incómodo como el papá del gobernador, para culminar este informe con una reflexión general y un balance de quiénes perdieron y quiénes ganaron al término de las elecciones de 2015.ITESO, A.C

Do migrant remittances promote human capital formation? Evidence from 89 developing countries

The few published empirical studies on the effect of migrant remittances on educational attainments are roughly based on cross-sectional microdata from household surveys. This paper applies the generalised method of moments (GMM) estimator on aggregate level data from 1970 to 2010 in five-year intervals to examine the impact of migrant remittances on human capital formation in 89 developing countries. The estimation results show that, on average, an increase in migrant remittance inflows by 1% is associated with a 2% rise in years of schooling at both the secondary and tertiary levels. This suggests that migrant remittances have the potential to relax liquidity constraints and generate spillover effects that facilitate more schooling opportunities in remittance-receiving countries