Polycrystalline Ni nanotubes under compression: a molecular dynamics study

Mechanical properties of nanomaterials, such as nanowires and nanotubes, are an important feature for the design of novel electromechanical nano-architectures. Since grain boundary structures and surface modifications can be used as a route to modify nanostructured materials, it is of interest to understand how they affect material strength and plasticity. We report large-scale atomistic simulations to determine the mechanical response of nickel nanowires and nanotubes subject to uniaxial compression. Our results suggest that the incorporation of nanocrystalline structure allows completely flexible deformation, in sharp contrast with single crystals. While crystalline structures at high compression are dominated by dislocation pinning and the multiplication of highly localized shear regions, in nanocrystalline systems the dislocation distribution is significantly more homogeneous. Therefore, for large compressions (large strains) coiling instead of bulging is the dominant deformation mode. Additionally, it is observed that nanotubes with only 70% of the nanowire mass but of the same diameter, exhibit similar mechanical behavior up to 0.3 strain. Our results are useful for the design of new flexible and light-weight metamaterials, when highly deformable struts are required.Fil: Rojas Nunez, J.. Universidad de Santiago de Chile; ChileFil: Baltazar, S. E.. Universidad de Santiago de Chile; ChileFil: Gonzalez, R. I.. Universidad Mayor; ChileFil: Bringa, Eduardo Marcial. Universidad Mayor; Chile. Universidad de Mendoza. Facultad de Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Allende, S.. Universidad de Santiago de Chile; ChileFil: Kiwi, M.. Universidad de Santiago de Chile; ChileFil: Valencia, F. J.. Universidad de Santiago de Chile; Chile. Universidad Mayor; Chil

Transiciones, conflictos y democracia : estudios de coyuntura

México ha vivido un largo proceso de transición que ha desencadenado dinamismos económicos, culturales y políticos. En la actual coyuntura, estos dinamismos muestran toda su complejidad, su inevitable articulación y la tensión entre las fuerzas que intentan sostener un viejo modelo de gobernar y decidir el rumbo del país, y aquellas que buscan abrirse a un espectro mucho más amplio y diversificado de actores. En ellos se conjuntan las aspiraciones más legítimas de los mexicanos por avanzar en el reconocimiento y respeto de la pluralidad étnica, de género y entre generaciones, y por impulsar una dinámica en la que —en medio de los procesos de mundialización— los distintos grupos e intereses de los mexicanos puedan ser incluidos. La transición mexicana tiende a centrarse en la dimensión política. La intensidad que cobran los procesos políticos y el énfasis que importantes analistas ponen en dichos procesos, contribuyen a que esta asociación vaya cobrandoíuerza. En este sentido, es necesario advertir que en las transiciones la tendencia privatizadora, la reducción del gasto social, así como la necesidad de pactos sociales que sean respetados, la participación creciente de la sociedad civil, etc. son factores importantes que, en medio de contradicciones, van generando nuevos esquemas de relación entre gobierno y sociedad.ITESO, A.C

Alcoholism and Strongyloides stercoralis: Daily Ethanol Ingestion Has a Positive Correlation with the Frequency of Strongyloides Larvae in the Stools

It has been reported that Strongyloides stercoralis infection is more prevalent in chronic alcoholic patients than in non alcoholics living in the same country. In a retrospective study on the prevalence of S. stercoralis infection in a large sample of alcoholic patients, we demonstrate that this prevalence is significantly higher than in non-alcoholic patients admitted at the same hospital. Moreover, the frequency of the parasite was in close relationship with the daily amount of ingested ethanol, even in the absence of liver cirrhosis, reinforcing the idea that chronic alcoholism is associated with increased susceptibility to Strongyloides infection. Beside the bad hygiene profile of alcoholic patients, which explains high risk for acquisition of the parasite, the high prevalence of S. stercoralis in alcoholics may be in relationship with other effects of ethanol on the intestinal motility, steroid metabolism and immune system, which could enhance the chance of autoinfection and the survival and fecundity of females in duodenum. In this way, the number of larvae in the stools is higher in alcoholic patients, increasing the chance of a positive result in a stool examination by sedimentation method

Photography-based taxonomy is inadequate, unnecessary, and potentially harmful for biological sciences

The question whether taxonomic descriptions naming new animal species without type specimen(s) deposited in collections should be accepted for publication by scientific journals and allowed by the Code has already been discussed in Zootaxa (Dubois & Nemésio 2007; Donegan 2008, 2009; Nemésio 2009a–b; Dubois 2009; Gentile & Snell 2009; Minelli 2009; Cianferoni & Bartolozzi 2016; Amorim et al. 2016). This question was again raised in a letter supported by 35 signatories published in the journal Nature (Pape et al. 2016) on 15 September 2016. On 25 September 2016, the following rebuttal (strictly limited to 300 words as per the editorial rules of Nature) was submitted to Nature, which on 18 October 2016 refused to publish it. As we think this problem is a very important one for zoological taxonomy, this text is published here exactly as submitted to Nature, followed by the list of the 493 taxonomists and collection-based researchers who signed it in the short time span from 20 September to 6 October 2016

Probing radiation resistance in simulated metallic core–shell nanoparticles

We present molecular dynamics (MD) simulations of radiation damage in Fe nanoparticles (NP) and bimetallic FeCu core–shell nanoparticles (CSNP). The CSNP includes a perfect body-centered cubic (bcc) Fe core coated with a face-centered cubic (fcc) Cu shell. Irradiation with Fe Primary Knock-on Atoms (PKA) with energies between 1 and 7 keV leads to point defects, without clustering beyond divacancies and very few slightly larger vacancy clusters, and without interstitial clusters, unlike what happens in bulk at the same PKA energies. The Fe-Cu interface and shell can act as a defect sink, absorbing radiation-induced damage and, therefore, the final number of defects in the Fe core is significantly lower than in the Fe NP. In addition, the Cu shell substantially diminishes the number of sputtered Fe atoms, acting as a barrier for recoil ejection. Structurally, the Cu shell responds to the stress generated by the collision cascade by creating and destroying stacking faults across the shell width, which could also accommodate further irradiation defects. We compare our MD results to Monte Carlo Binary Collision Approximation (BCA) simulations using the SRIM code, for the irradiation of an amorphous 3-layer thin film with a thickness equal to the CSNP diameter. BCA does not include defect recombination, so the number of Frenkel pairs is significantly higher than in MD, as expected. Sputtering yield (Y) is underestimated by BCA, which is also expected since the simulation is for a thin film at normal incidence. We also compare MD defect production to bulk predictions of the analytic Athermal Recombination Corrected Displacements Per Atom (arc-dpa) model. The number of vacancies in the Fe core is only slightly lower than arc-dpa predictions, but the number of interstitials is reduced by about one order of magnitude compared to vacancies, at 5 keV. According to the radiation resistance found for FeCu CSNP in our simulations, this class of nanomaterial could be suitable for developing new radiation-resistant coatings, nanostructured components, and shields for use in extreme environments, for instance, in nuclear energy and astrophysical applications.Fil: Tramontina Videla, Diego Ramiro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; Argentina. Universidad de Mendoza; ArgentinaFil: Deluigi, Orlando Raul. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; Argentina. Universidad de Mendoza; ArgentinaFil: Pinzón, R.. Universidad Tecnologica de Panamá.; Panamá. Sistema Nacional de Investigación; Panamá. Centro de Estudios Multidisciplinarios de Ingeniería Ciencias y Tecnología; PanamáFil: Rojas Nunez, J.. Universidad de Santiago de Chile; Chile. Center for the Development of Nanoscience and Nanotechnology; ChileFil: Valencia, F. J.. Center For Development Of Nanoscience And Technology; Chile. Universidad Católica de Maule; ChileFil: Pasianot, Roberto Cesar. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia de Área de Energía Nuclear. Gerencia Materiales; Argentina. Universidad Nacional de San Martín. Instituto Sabato; ArgentinaFil: Baltazar, S. E.. Universidad de Santiago de Chile; Chile. Center For Development Of Nanoscience And Technology; ChileFil: Gonzalez, R. I.. Center For Development Of Nanoscience And Nanotechnology; Chile. Universidad Mayor; ChileFil: Bringa, Eduardo Marcial. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; Argentina. Universidad de Mendoza; Argentina. Universidad Mayor; Chil

Hidatidose do esterno e musculatura peitoral Sternal and pectoral musculature hydatidosis

A hidatidose é uma infecção ciclozoonótica causada pela tênia Echinococcus granulosus, cuja forma larvária acomete acidentalmente o homem, formando cistos hidáticos, preferencialmente nos pulmões e no fígado. A hidatidose óssea é um evento raro, caracterizado por crescimento lento e com poucos sintomas. Relata-se o caso de um homem de 36 anos com história de nódulos na parte anterior do tórax havia nove anos. Os exames de diagnóstico por imagem evidenciaram massas expansivas, loculadas e de conteúdo espesso nos músculos peitorais e lesão lítica no esterno. O diagnóstico de hidatidose foi feito na exploração cirúrgica. Recebeu alta sob tratamento com albendazol 2.400mg/dia por 28 dias.<br>Hydatidosis is a cyclezoonotic infection caused by taenia Echinococcus granulosus, whose larval form accidentally affects men by forming hydatic cysts preferably in the lungs and liver. Osseous hydatidosis is a rare event characterized by slow growth and few symptoms. It is reported on a 36-year-old man who had presented nodes in the anterior thorax for nine years. Imaging diagnostic examinations revealed thick, loculated, expansive masses in the pectoral muscles and sternal lytic lesions. The diagnosis of hydatidosis was established by exploratory surgery. The patient showed good clinical-surgical evolution and was discharged receiving albendazole, 2,400 mg/day, for 28 days