Chunky graphite in spheroidal graphite iron: review of recent results and definition of an predicting index

International audienceGraphite degeneracy in heavy-section spheroidal graphite cast irons is mostly associated with the formation of chunky graphite which consists of large eutectic cells with interconnected graphite strings. At low level, appearance of chunky graphite is limited to its non-aesthetic effect on machined surfaces, while at higher level it is detrimental for mechanical properties of the components. Chunky graphite is often related to high silicon levels and too high cerium additions during the spheroidization treatment. The appearance of this defect may be limited by controlled additions of antimony that is thought to tight the excess of cerium, but other impurities and low level elements may have to be considered during melt preparation. This contribution proposes a review of recent results and approaches on chunky graphite appearance, primarily but not exclusively in the case of heavy-section cast irons. Based on this literature review and series of experimental data, a predictive index for evaluating the risk of chunky graphite appearance is proposed. Lines for further research work aimed at a better understanding of graphite degeneracy are finally suggested. Introduction The need for melt control before casting of spheroidal graphite cast irons have led for long to look for graphite degeneracy as resulting from melt chemistry. Thielemann developed a trace element evaluation number S b for assessing the ability of the charge to give well-formed nodules [1]

Presencia de las ciencias básicas en el Examen Nacional de Aspirantes a Residencias Médicas (ENARM)

ResumenIntroducciónEl informe Flexner enfatiza la importancia de las ciencias básicas en el currículum médico.ObjetivoDeterminar la presencia e importancia que se otorga a las ciencias básicas en el ENARM.MétodosEs un estudio observacional, retrospectivo y transversal. Se revisaron los contenidos académicos de los programas de las ciencias básicas incluidas en el Plan de Estudios 2010 de la Facultad de Medicina de la Universidad Nacional Autónoma de México (UNAM) y se clasificaron los 1 200 reactivos de conocimientos médicos, que conformaron los ENARM 2005 y 2006. Para el análisis de los resultados se utilizó la prueba de ji cuadrada (X2).ResultadosSe encontró que 288 (24%) de los 1 200 reactivos exploraron conocimientos de las ciencias básicas. Asimismo, que este porcentaje es inferior al que corresponde a los créditos que se otorgan a las ciencias básicas en el Plan de Estudios de medicina (31%). También se encontró que representación de las ciencias fisiológicas (13.5%) es relativamente mayor que las morfológicas (10.5%), siendo la asignatura de Farmacología la de mayor representación (8%); en el otro extremo se encuentran las asignaturas de Biología Celular y Tisular (1.3%) y de inmunología (1.2%).ConclusiónLa presencia de las ciencias básicas en los ENARM confirma la importancia que se otorga a las ciencias básicas en la educación médica y en el ejercicio de la buena medicina. Se sugiere mantener y, de ser posible, aumentar su presencia en todas las evaluaciones en medicina.AbstractIntroductionThe Flexner report emphasized the importance of the basic sciences in the medical curriculum.ObjectiveTo determine the presence and importance given to basic sciences in the ENARM. Methods: We performed an observational, retrospective, transversal study. We reviewed the academic content of the programs included in the basic sciences curriculum of the Faculty of Medicine of the UNAM and classified the 1 200 medical knowledge questions that shaped the 2005 and 2006 ENARM. For the analysis of the results was used for chi square test X2.ResultsWe found that 288 (24%) of the 1 200 questions analyzed explored basic science knowledge and that this percentage is below that corresponding to the academic credits granted to the basic sciences in the medical curriculum (31%). Also, that the physiological sciences are more represented (13.5%) than the morphological disciplines (10.5%), being Pharmacology (8%) the subject with more representation; at the other extreme were Histology (1.3%) and Immunology (1.2%).ConclusionThe presence of basic science in ENARM confirms the importance given to bio-medical knowledge in medical education and practice of good medicine. It is suggested to maintain and, if possible, increase its presence in all assessments in medicine

LA ESTIMULACIÓN VISUAL DE LOS NIÑOS CON ESTRABISMO Y AMBLIOPÍA DESDE EL CONTEXTO FAMILIAR (Original)

The special school has the responsibility of introducing methods, procedures and alternating for the family manners, that potency the stimulation of the visual perception of the children with strabismus and amblyopic from the family environment. The article has like objective offer a model of family orientation for the stimulation of the visual perception to the children with strabismus and amblyopic, hit constitute the fundamental contribution. This construct offers an answer concrete the contradiction dialectical between the general character and the interactive and integrationist in the family orientation; she favor the stimulations of the visual perception of the children with strabismus and amblyopic, in order to contribute to the solution of the scientific problem: Inadequacies in the process of manners of the families of the children with strabismus and amblyopic, that they limit the stimulations of the visual perception of these children. The population and the pattern is represented by 35 families and 35 children with strabismus and amblyopic that meet in the grades of first to third of the school Ernesto Guevara of the Serna, of the Bayamo municipality, Granma, by being families of the children that present limitations in the stimulations of the visual perception, that receive attention pedagogical and ophthalmological in the special school and that she it should have continuity from the home. La escuela especial tiene la responsabilidad de introducir métodos, procedimientos y alternativas para la educación familiar, que potencien la estimulación de la percepción visual de los niños con estrabismo y ambliopía desde el ámbito familiar. El artículo tiene como objetivo ofrecer un modelo de orientación familiar para la estimulación de la percepción visual a los niños con estrabismo y ambliopía, el que constituye el aporte fundamental. Este constructo ofrece una respuesta concreta a la contradicción dialéctica entre el carácter general y el interactivo e integracionista en la orientación familiar; favorece la estimulación de la percepción visual de los niños con estrabismo y ambliopía, para contribuir a la solución del problema científico: insuficiencias en el proceso de educación de las familias de los niños con estrabismo y ambliopía, que limitan la estimulación de la percepción visual de estos niños. La población y la muestra están representadas 35 familias y sus 35  niños respectivos con estrabismo y ambliopía que se encuentran en los grados de primero a tercero de la escuela Ernesto Guevara de la Serna, del municipio Bayamo, Granma, por ser familias de los niños que presentan limitaciones en la estimulación de la percepción visual, que reciben atención pedagógica y oftalmológica en la escuela especial y que debe tener continuidad desde el hogar.&nbsp

Influence of the Laser Deposited 316L Single Layers on Corrosion in Physiological Media

[EN] A multilayer laser-deposited lining of AISI 316L stainless steel makes a regular structural steel surface corrosion resistant in physiological media. Despite the application of single-layer stainless-steel linings being economically beneficial and allowing thinner surface modifications, dilution effects that modify the pitting resistance of the coating must be accounted for. In order to study the feasibility of employing single-layer coatings instead of multilayer coatings for corrosion protection in physiological media, a polarization testing back-to-back comparison was performed between laser-deposited AISI 316L monolayers on 42CrMo4 quenched and tempered steel and cold-rolled AISI 316L sheet in Dulbecco’s Phosphate Buffer Solution at 36 °C. A higher dispersion in pitting resistance, ranging from 800 mV to 1200 mV, was found on the coated samples, whereas the cold-rolled material was more stable in the 1200 mV range. The resulting differences in corrosion rates and pitting potentials open the discussion on whether the chemical composition deviations on AISI 316L dilution layers are acceptable in terms of surface functionality in medical device

Dibenzo[1,2,5]thiadiazepines are non-competitive GABAA receptor antagonists

"A new process for obtaining dibenzo[c,f][1,2,5]thiadiazepines (DBTDs) and their effects on GABAA receptors of guinea pig myenteric neurons are described. Synthesis of DBTD derivatives began with two commercial aromatic compounds. An azide group was obtained after two sequential reactions, and the central ring was closed via a nitrene to obtain the tricyclic sulfonamides (DBTDs). Whole-cell recordings showed that DBTDs application did not affect the holding current but inhibited the currents induced by GABA (IGABA), which are mediated by GABAA receptors. These DBTDs effects reached their maximum 3 min after application and were: (i) reversible, (ii) concentration-dependent (with a rank order of potency of 2c = 2d > 2b), (iii) mediated by a non-competitive antagonism, and (iv) only observed when applied extracellularly. Picrotoxin (which binds in the channel mouth) and DBTDs effects were not modified when both substances were simultaneous applied. Our results indicate that DBTD acted on the extracellular domain of GABAA channels but independent of the picrotoxin, benzodiazepine, and GABA binding sites. DBTDs used here could be the initial model for synthesizing new GABAA receptor inhibitors with a potential to be used as antidotes for positive modulators of these receptors or to induce experimental epilepsy.

Technical and economic optimum in feedlot cattle

The beef cattle producers in the southern zone of the State of Mexico generally do not carry out adequate market planning of their finished steers. In addition, they lack technical and administrative management in their productive units, focused on the use of efficient input, which has prevented them from maximizing their monetary profits. The present investigation was made to estimate the technical (TOL) and economic optimum levels (EOL) of feedlot beef cattle, using two cubic production functions with decreasing marginal yields. One hundred steers of Bos Taurus x Bos indicus were used, with Live Weight at the start of fattening of 290 ± 15 kg, age 21 to 24 months, fattened in feedlots during 93 days consuming a totally mixed diet (Crude protein: 133.33, FDN: 237.44, FDA 114.33 g/kg DM and 2.62 Mcal/kg of DM of metabolizable energy) To estimate both functions (TOL and EOL), weight gain was considered as independent variable. For the first production function, feed intake was taken as independent variable and in the second function, time defined in days. For the first production function the TOL was 475.04 and the EOL was 473.94 kg Live Weight; with a daily feed intake of 12.58 and 12.36 kg/day. For the second production function the TOL was 475.01 and the EOL was 460.21kg of Live Weight, with a period of 93.29 and 77.21 days. The optimal point of sale and the maximum gain is obtained with the second production function, when the animals reach a Live Weight of 460.21 kg during a feeding period of 77.21 days

Effects of high silicon contents on graphite morphology and room temperature mechanical properties of as-cast ferritic ductile cast irons. Part I – Microstructure

Studying a series of near eutectic spheroidal graphite cast irons with various amounts of silicon up to 9.12wt% confirmed that: 1. silicon stabilizes ferrite to such an extent that ferrite is the Fe-rich phase appearing during solidification at the highest silicon contents; 2. silicon triggers graphite degeneracy such as chunky graphite. As well-known, cerium and magnesium do also increase the risk of chunky graphite formation while antimony counteracts cerium. Based on the metallographic observations of the present work, an index is proposed to evaluate the risk of chunky graphite appearance from the silicon, magnesium, cerium and antimony contents. Above a critical value of this index, the risk for chunky graphite formation increases steadily. Using data from previous studies, it is further demonstrated that the critical value decreases with increase in casting modulus as expected. The evolution of mechanical properties of the prepared cast irons will be presented in a second part of this study

Machine learning-based routing and wavelength assignment in software-defined optical networks

Recently, machine learning (ML) has attracted the attention of both researchers and practitioners to address several issues in the optical networking field. This trend has been mainly driven by the huge amount of available data (i.e., signal quality indicators, network alarms, etc.) and to the large number of optimization parameters which feature current optical networks (such as, modulation format, lightpath routes, transport wavelength, etc.). In this paper, we leverage the techniques from the ML discipline to efficiently accomplish the routing and wavelength assignment (RWA) for an input traffic matrix in an optical WDM network. Numerical results show that near-optimal RWA can be obtained with our approach, while reducing computational time up to 93% in comparison to a traditional optimization approach based on integer linear programming. Moreover, to further demonstrate the effectiveness of our approach, we deployed the ML classifier into an ONOS-based software defined optical network laboratory testbed, where we evaluate the performance of the overall RWA process in terms of computational time.The authors would like to acknowl-edge the support of the project TEXEO (TEC2016-80339-R), funded by Spanish MINECO and the EU-H2020 Metrohaul project (grant no. 761727)

Effects of high silicon contents on graphite morphology and room temperature mechanical properties of as-cast ferritic ductile cast irons. Part II – Mechanical properties

In this second part of the investigation, room temperature mechanical properties and hardness evolution of cast irons with silicon contents ranging from 2.29 wt% to 9.12 wt% have been studied and related to structural results from the first part. Increasing silicon content increases ultimate tensile strength and yield stress until a maximum value of 719 MPa at around 5.0−5.2 wt% silicon for the former and 628 MPa at 5.2−5.4 wt% silicon for the latter. Brinell hardness remains increasing with silicon content with a maximum value of 396 at 9.12 wt% silicon. Elongation at rupture shows an opposite evolution and gradually decreases to zero at 5.3 wt% silicon. This evolution is related to chemical ordering of the ferritic matrix (embrittlement effect). Chunky graphite shows apparently no significant effect on the ultimate tensile strength and yield strength in cast irons with silicon contents higher than 4.0 wt%. However, it has a negative effect on elongation. This result contrasts with the negative effect of chunky graphite on mechanical properties of ductile irons reported in the literature for alloys with silicon contents lower than 3 wt%. It is suggested that this difference is due to the matrix strengthening effect of high silicon contents which overtakes the detrimental effect of chunky graphite. This study suggests that cast irons with silicon content as high as 5.0 wt% could be considered for industrial applications when high resistance and some ductility are requested

Detección del promotor 35S mediante PCR tiempo-real: indicador de transgenicidad en alimentos y Gossypium sp.

Introducción. Los cultivos genéticamente modificados (CGM) son de particular interés, debido al impacto en la economía global. Por lo tanto, como preocupación general, muchos países han establecido regulaciones con respecto a estos organismos. En Costa Rica, el cultivo de OGM se realiza desde 1991; sin embargo, existe un faltante de estudios que monitoreen la ejecución y el cumplimiento de las regulaciones de bioseguridad. Objetivo. El objetivo del presente estudio fue identificar la presencia o ausencia de transgenicidad en alimentos procesados para consumo humano y animal, así como en semillas provenientes de algodón. Materiales y métodos. Se utilizó la técnica de PCR tiempo real dirigida a la secuencia promotora 35S, derivada del virus del mosaico de la coliflor (CaMV, siglas en inglés), como marcador para detectar presencia de transgenes en alimentos procesados para consumo humano y animal y en semillas de algodón, silvestre o cultivado, recolectadas en áreas aledañas a una finca de algodón GM en mayo de 2017. Resultados. En las muestras analizadas hubo una alta incidencia de fragmentos de 82 pb, correspondientes a la secuencia promotora 35S, que estuvo ausente solo en cultivos de maíz orgánico y sus derivados (tortillas y harina de maíz). Los resultados sugieren la presencia de trazas de OGM en el mercado alimentario costarricense; adicionalmente, revela la urgencia de implementar un adecuado etiquetado para trazabilidad alimentaria. Se identificó, además, la presencia de algodón transgénico en las cercanías de una finca de algodón GM, lo que sugiere la pertinencia de vigilancia en aspectos de bioseguridad y manipulación genética de cultivos. Conclusiones. La presencia de trazas de OGM en alimentos procesados muestra la importancia de continuar este monitoreo para proveer elementos de discusión en cuanto a trazabilidad alimentaria y potencial flujo de transgenes en material vegetal silvestre