Effects of Boron Purity, Mg Stoichiometry and Carbon Substitution on Properties of Polycrystalline MgB2_{2}

By synthesizing MgB$_{2}$ using boron of different nominal purity we found values of the residual resistivity ratio ($RRR = R(300 K) / R(42 K)$) from 4 to 20, which covers almost all values found in literature. To obtain high values of $RRR$, high purity reagents are necessary. With the isotopically pure boron we obtained the highest $RRR \sim$ 20 for the stoichiometric compound. We also investigated Mg$_{x}$$^{11}$B$_{2}$ samples with 0.8 $< x <$ 1.2. For the range Mg$_{0.8}$$^{11}$B$_{2}$ up to Mg$_{1.2}$$^{11}$B$_{2}$ we found average values of $RRR$ between 14 and 24. For smaller variations in stoichiometry ($x=1\pm 0.1$) $RRR = 18 \pm 3$. All of our data point to the conclusion that high $RRR$ ($\sim 20$) and low $\rho_{0}$ ($\leq 0.4 \mu \Omega cm$) are intrinsic material properties associated with high purity MgB$_{2}$. In addition we have performed initial work on optimizing the formation of carbon doped MgB$_{2}$ via the use of B$_{4}$C. Nearly single phase material can be formed by reaction of nominal Mg(B$_{0.8}$C$_{0.2}$)$_{2}$ for 24 hours at $1200^{\circ}C$. The $T_{c}$ for this composition is between $21.9 K$ and $22.7 K$ (depending on criterion).Comment: accepted to Physica C, special MgB2 issu

Draft genome sequence of Agrobacterium deltaense strain CNPSo 3391, isolated from a soybean nodule in Mozambique

Open Access Article; Published online: 7 March 2019Agrobacterium deltaense strain CNPSo 3391 was isolated from a soybean nodule in Mozambique. Its genome size was estimated at 4,926,588 bp. This isolate carries several coding sequences for stress tolerance, but no identifiable nodulation or virulence genes. Possible ecological roles of bacteria isolated from legume nodules and closely related to Agrobacterium are discussed

Effects of stoichiometry, purity, etching and distilling on resistance of MgB2 pellets and wire segments

We present a study of the effects of non-stoichiometry, boron purity, wire diameter and post-synthesis treatment (etching and Mg distilling) on the temperature dependent resistance and resistivity of sintered MgB2 pellets and wire segments. Whereas the residual resistivity ratio (RRR) varies between RRR \~ 4 to RRR > 20 for different boron purity, it is only moderately affected by non-stoichiometry (from 20% Mg deficiency to 20% Mg excess) and is apparently independent of wire diameter and presence of Mg metal traces on the wire surface. The obtained set of data indicates that RRR values in excess of 20 and residual resistivities as low as rho{0} ~ 0.4 mu Ohm cm are intrinsic material properties of high purity MgB2

Association Between Oxygenation And Ventilation Index With The Time On Mechanical Ventilation In Pediatric Intensive Care Patients [relação Entre índice De Oxigenação E Ventilação Com O Tempo Em Ventilação Mecânica De Pacientes Em Terapia Intensiva Pediátrica]

Objective: To correlate the oxygenation index (OI) and the ventilation index (VI) with the time of invasive mechanical ventilation (IMV) in pediatric patients. Methods: This prospective and observational study enrolled patients from 28 days to 14 years of age, admitted in the Pediatric Intensive Care Unit of a university hospital. The values of age, weight, pH, partial pressure of oxygen (PaO 2), partial pressure of carbon dioxide (PaCO 2), OI and VI were measured from day one to the day five and they were correlated with the time on IMV. The total time on mechanical ventilation was divided into: &lt;7 days and ≥7 days. Results: 28 patients were studied. The time spent on IMV showed a significant negative correlation with the pH on the fourth day and with the PaO 2 on the fifth day. The time on IMV showed a positive correlation with the OI on the third and fourth days and with the VI on the third, fourth and fifth days. There were significant differences in the age and pH on the fourth and fifth days and in the VI from the second to fifth days between the group that remained less than seven days and those that remained seven days or more on IMV. Conclusions: VI, OI, pH and PaO 2 measured during the first five days of IMV were associated with prolonged IMV, reflecting the severity of the initial ventilatory disturb.293348351Farias, J.A., Frutos, F., Esteban, A., Flores, J.C., Retta, A., Baltodano, A., What is the daily practice of mechanical ventilation in pediatric intensive care units? A multicenter study (2004) Intensive Care Med, 30, pp. 918-925Torres, A., Gatell, J.M., Aznar, E., El-Ebiary, M., de la, B.P.J., Gonzalez, J., Re-intubation increases the risk of nosocomial pneumonia in patients needing mechanical ventilation (1995) Am J Respir Crit Care Med, 152, pp. 137-141Almeida-Júnior, A.A., da Silva, M.T., Almeida, C.C., Jacomo, A.D., Nery, B.M., Ribeiro, J.D., Association between ventilation index and time on mechanical ventilation in infants with acute viral bronchiolits (2005) J Pediatr (Rio J), 81, pp. 466-470Khan, N., Brown, A.R., Venkataraman, S.T., Predictors of extubation success and failure in mechanically ventilated infants and children (1996) Crit Care Med, 24, pp. 1568-1579Paret, G., Ziv, T., Barzilai, A., Ben-Abraham, R., Vardi, A., Manisterski, Y., Ventilation index and outcome in children with acute respiratory distress syndrome (1998) Pediatr Pulmonol, 26, pp. 125-128Peters, M.J., Tasker, R.C., Kiff, K.M., Yates, R., Hatch, D.J., Acute hypoxemic respiratory failure in children: Case mix and the utility of respiratory severity indices (1998) Intensive Care Med, 24, pp. 699-705Trachsel, D., McCrindle, B.W., Nakagawa, S., Bohn, D., Oxygenation index predicts outcome in children with acute hypoxemic respiratory failure (2005) Am J Respir Crit Care Med, 172, pp. 206-211Venkataraman, S.T., Khan, N., Brown, A., Validation of predictors of extubation success and failure in mechanically ventilated infants and children (2000) Crit Care Med, 28, pp. 2991-2996Aggarwal, R., Downe, L., Use of high frequency ventilation as a rescue measure in premature babies with severe respiratory failure (2000) Indian Pediatr, 37, pp. 522-526Goldman, A.P., Tasker, R.C., Hosiasson, S., Henrichsen, T., Macrae, D.J., Early response to inhaled nitric oxide and its relationship to outcome in children with severe hypoxemic respiratory failure (1997) Chest, 112, pp. 752-758Relvas, M.S., Silver, P.C., Sagy, M., Prone positioning of pediatric patients with ARDS results in improvement in oxygenation if maintained > 12 h daily (2003) Chest, 124, pp. 269-274Wessel, D.L., Adatia, I., van Marter, L.J., Thompson, J.E., Kane, J.W., Stark, A.R., Improved oxygenation in a randomized trial of inhaled nitric oxide for persistent pulmonary hypertension of the newborn (1997) Pediatrics, 100, pp. E7Yapicioǧlu, H., Yildizdaş, D., Bayram, I., Sertdemir, Y., Yilmaz, H.L., The use of surfactant in children with acute respiratory distress syndrome: Efficacy in terms of oxygenation, ventilation and mortality (2003) Pulm Pharmacol Ther, 16, pp. 327-33

Demands of physical activities and efforts in elite basketbal

There is a great importance in describing the demands of physical exertion of the players in official games for we can organize better periodization training. The aim of this study is to propose a new form of demand physical exertion rating of basketball players and analyze the five existing positions in the game. The classification was divided into five classes and their subclass, as follows: a displacement class with its subclasses: forward pair back side, stopped and defensive position, the class of power contact with its subclass one against one, box out, pick and faults, the class of jump, upper-body movements and dribble. We analyzed two teams in a game quarter of the New Basketball Brazil, the players were divided by the positions / functions operating in the basketball game. Found difference between the frequencies, medium time and total time in the displacement class and power contact between positions thus we conclude that it is necessary to detail the demands of physical exertion and analyze five separate positions indicating the need individualized training

Demandas de las actividades físicas y los esfuerzos en el baloncesto de elite

Existe una gran importancia en la descripción de las exigencias de esfuerzo físico de los jugadores en los juegos oficiales podemos organizar mejor la formación periodización. El objetivo de este estudio es proponer una nueva forma de demanda de calificación esfuerzo físico de los jugadores de baloncesto y analizar las cinco posiciones existentes en el juego. La clasificación se divide en cinco clases y sus subclases, como sigue: una clase de desplazamiento horizontal con su lado trasero hacia adelante par subclase, se detuvo y posición defensiva, la clase de intercambio contacto de potencia con sus subclases uno contra uno, rebote de protección, las cerraduras y las fallas, la clase de los desplazamientos verticales, el movimiento de los miembros superiores e regate. Se analizaron dos equipos en una sala de juegos Nuevo Baloncesto Brasil, los jugadores se dividieron por las posiciones / funciones que operan en el juego de baloncesto. diferencia encontrada entre la frecuencia, el tiempo medio y el tiempo total en el desplazamiento horizontal y clases de contacto de potencia de cambio entre las posiciones tanto, llegamos a la conclusión de que es necesario detallar las exigencias de esfuerzo físico y analizar cinco posiciones independientes, indicando la necesidad formación individualizada.There is a great importance in describing the demands of physical exertion of the players in official games for we can organize better periodization training. The aim of this study is to propose a new form of demand physical exertion rating of basketball players and analyze the five existing positions in the game. The classification was divided into five classes and their subclass, as follows: a displacement class with its subclasses: forward pair back side, stopped and defensive position, the class of power contact with its subclass one against one, box out, pick and faults, the class of jump, upper-body movements and dribble. We analyzed two teams in a game quarter of the New Basketball Brazil, the players were divided by the positions / functions operating in the basketball game. Found difference between the frequencies, medium time and total time in the displacement class and power contact between positions thus we conclude that it is necessary to detail the demands of physical exertion and analyze five separate positions indicating the need individualized training.Existe uma grande importância em descrever as demandas de esforço físico dos jogadores em jogos oficias para podemos organizar uma melhor periodização de treinamento. O objetivo deste estudo é propor uma nova forma de classificação da demanda de esforço físico de jogadores de basquetebol e analisar nas cinco posições existente no jogo. A classificação foi dividida em cinco classes e com as suas subclasses, sendo elas: a classe de deslocamento horizontais com as suas subclasses: para frente, par trás, lateral, parado e posição defensiva, a classe de troca de contato de força com as suas subclasses de um contra um, proteção de rebote, bloqueios e faltas, a classe de deslocamentos verticais, movimentação de membros superiores e drible. Analisamos dois times em um quarto de jogo do Novo Basquete Brasil, os jogadores foram divididos pelas posições/funções que atuam no jogo de basquete. Encontramos diferença entre a frequência, tempo médio e tempo total nas classes de deslocamento horizontais e troca de contato de força entre as posições, deste modo, podemos concluir que é necessário detalhar as demandas de esforço físico e analisar as cinco posições separadas, indicando a necessidade de treinamento individualizado.peerReviewe

Carbon doping of superconducting magnesium diboride

We present details of synthesis optimization and physical properties of nearly single phase carbon doped MgB2 with a nominal stoichiometry of Mg(B{0.8}C{0.2})2 synthesized from magnesium and boron carbide (B4C) as starting materials. The superconducting transition temperature is ~ 22 K (~ 17 K lower than in pure MgB2). The temperature dependence of the upper critical field is steeper than in pure MgB2 with Hc2(10K) ~ 9 T. Temperature dependent specific heat data taken in different applied magnetic fields suggest that the two-gap nature of superconductivity is still preserved for carbon doped MgB2 even with such a heavily suppressed transition temperature. In addition, the anisotropy ratio of the upper critical field for T/Tc ~ 2/3 is gamma ~ 2. This value is distinct from 1 (isotropic) and also distinct from 6 (the value found for pure MgB2).Comment: 11 pages, 13 figures, submitted to Physica

Electrical resistivity and tunneling anomalies in CeCuAs2

The compound CeCuAs2 is found to exhibit negative temperature (T) coefficient of electrical resistivity (rho) under ambient pressure conditions in the entire T-range of investigation (45 mK to 300 K), even in the presence of high magnetic fields. Preliminary tunneling spectroscopic measurements indicate the existence of a psuedo-gap at least at low temperatures, thereby implying that this compound could be classified as a Kondo semi-conductor, though rho(T) interestingly is not found to be of an activated type.Comment: To appear in the proceedings of SCES200

Collaborative dynamic decision making: a case study from B2B supplier selection

The problem of supplier selection can be easily modeled as a multiple-criteria decision making (MCDM) problem: businesses express their preferences with respect to suppliers, which can then be ranked and selected. This approach has two major pitfalls: first, it does not consider a dynamic scenario, in which suppliers and their ratings are constantly changing; second, it only addressed the problem from the point of view of a single business, and cannot be easily applied when considering more than one business. To overcome these problems, we introduce a method for supplier selection that builds upon the dynamic MCDM framework of Campanella and Ribeiro [1] and, by means of a linear programming model, can be used in the case of multiple collaborating businesses plan- ning their next batch of orders together.Fundação para a Ciência e a Tecnologia, Portugal, under contract CONT DOUT/49/UNINOVA/0/5902/1/200

Magnetic Properties Of Gdt2zn20 (t=fe, Co) Investigated By X-ray Diffraction And Spectroscopy

We investigate the magnetic and electronic properties of the GdT2Zn20 (T=Fe and Co) compounds using x-ray resonant magnetic scattering (XRMS), x-ray absorption near-edge structure (XANES), and x-ray magnetic circular dichroism (XMCD). The XRMS measurements reveal that GdCo2Zn20 has a commensurate antiferromagnetic spin structure with a magnetic propagation vector τ - =(12,12,12) below the Néel temperature (TN∼5.7 K). Only the Gd ions carry a magnetic moment forming an antiferromagnetic structure with magnetic representation Γ6. For the ferromagnetic GdFe2Zn20 compound, an extensive investigation was performed at low temperature and under magnetic field using XANES and XMCD. A strong XMCD signal of about 12.5% and 9.7% is observed below the Curie temperature (TC∼85K) at the Gd L2 and L3 edges, respectively. In addition, a small magnetic signal of about 0.06% of the jump is recorded at the Zn K edge, suggesting that the Zn 4p states are spin polarized by the Gd 5d extended orbitals. © 2016 American Physical Society.93