On the plastic deformation behaviour of nickel-based superalloys: low cycle fatigue and stress orientation effects

This dissertation expands upon the current knowledge of plastic deformation in nickel-based superalloys, with a focus on dislocation mechanisms and the effect of microstructure. The two main topics treated are the evolution of the dislocation structure during low cycle fatigue and the effect of loading orientation on the propagation of stacking faults. A series of experimental and modelling techniques are employed throughout the thesis. Low cycle fatigue is investigated with the motivation of understanding how slip bands form and develop prior to crack initiation. Electron microscopy techniques are used in alloy RR1000 to characterise these dislocation structures at different length scales in interrupted tests at room temperature and 700°C. The true slip line spacings and shear step lengths at the precipitate interfaces are measured for the first time ever with a new methodology, allowing for quantitative comparisons. Non-coplanar stacking faults are observed to be the main obstacles against which dislocations in a slip band pile up and accumulate in the form of mutipoles. The combination of these techniques provides a unique mechanistic and quantitative insight into the slip band and precipitate morphology evolution. The characteristic response of these alloys, i.e. cyclic hardening followed by cyclic softening, is linked with the underlying evolution of the microstructure. A study on alloy 718Plus with different ageing heat treatments looks particularly at the influence from precipitate size and volume fraction. Microstructural characterisation is used as an input to a new physics-based mesoscale model that accounts for the prolonged precipitate shearing observed. Local accumulation of precipitate shearing near surface cracks is identified and regarded as an additional factor for fatigue failure. Alternatively, the effect of loading orientation on the plastic deformation behaviour is investigated here in a more theoretical way. This variable is often oversimplified due to the complexity of some mechanisms, in particular those driven by dislocation reactions or splitting into Shockley partials. A novel orientation analysis framework is introduced as an alternative to simultaneously scrutinise the behaviour of multiple slip systems in a graphical and intuitive way. Due to the generality of this approach, this is developed for fcc crystals. Its application in the analysis of two simplistic twin nucleation models is performed to exemplify the use of the orientation maps generated. This framework opens the door to the study of many more deformation mechanisms in a new and more in-depth manner. The orientation analysis framework is then expanded to the specific case of stacking faults in nickel-based superalloys, accounting for the presence of glide obstacles. The regions where stacking fault propagation is promoted are developed analytically and validated with simulations from the literature for different precipitate morphologies and distributions. This theory is then extended to include thermally assisted superlattice stacking faults and microtwinning in a comprehensive way. Mechanistic maps that simultaneously consider stress, orientation and microstructure are developed for low and intermediate temperatures. The results found are in full agreement with data from the literature

Attitude, knowledge and perception of the altruistic donation of blood in a city in Northeastern Mexico

Objectives: To identify the causes due to which potential blood donors do not make voluntary donations: lack of knowledge, attitude, and the perception of blood donations as unwholesome. Materials and methods: We conducted a transversal, observational, descriptive, prospective, and a survey-based study of 435 subjects in Monterrey, Mexico in November of 2011. Results: 135 (31%) subjects were already donors, of which only 16 (3.6%) did it altruistically. Of the total amount of subjects, 161 (37%) were associated with some benefits from donating blood, 154 (35%) identified some kind of damage, the most mentioned was transmission of diseases with 77 (50%) mentions. The most common cause of refusal toward donation was ‘‘saving blood for a relative in need’’ with 137 (33%) mentions. Of the subjects surveyed, 55% (n = 240) refer having very few thoughts for donating blood voluntarily. Also, 360 (86%) subjects will donate without expecting something in return. Finally, 348 (80%) subjects do not remember seeing or hearing any kind of promotional information about altruistic blood donation. Conclusions: A great deal of people will donate blood altruistically without receiving any reward for doing so. 80% of the subjects do not remember seeing or hearing any kind of advertisement for blood donation which is proof of lack of adequate publicity. The analysis of perception of damages or benefits from blood donation will help in the development of more focused blood donation campaigns

Ratio of hemocomponents in massive transfusion and mortality of trauma patients in a university hospital

Background: Nowadays, there are very few studies about massive transfusion in our country. This situation generates the necessity to the elevation of possible new strategies to diminish mortality and its adverse effects. Material and methods: All massive transfusions were evaluated in a retrospective way from October 2010 to October 2012. All diagnosis groups were recorded and the patients were divided into three groups depending on the ratio between packed red blood cells (PRBC) and fresh frozen plasma (FFP) units (ratios ≤2, >2, and without FFP). Their mortality and/or survival were evaluated 30 days after as well as all the factors associated with the event. Results: A total of 69 patients were included (37 trauma patients, 28 gunshot wounds and 4 with lacerated wounds); the groups (ratios ≤2, >2, and no plasma at all) were distributed as follows: 30, 30 and 9 patients each, with an overall mortality rate of 60.8% within 30 days. A lower survival rate (12%) in the no plasma group (P=.015) was found and systolic blood pressure during transfusion had a mean of 67.7 mmHg (P=.012) in this group. Fresh frozen plasma units were 136 and 249 for >2 and ≤2 ratios respectively (P<.01); 85.5% of all patients developed metabolic acidosis during the transfusion, and the number of days in the hospital after the event had a mean of 24.5 days in all patients. Conclusions: High rates of massive transfusion mortality are still being reported in our ield. The use of transfusion strategies contribute to elevate the survival rate in patients with massive transfusion treatmen

Trombosis venosa cerebral secundaria a estado protrombótico transitorio del embarazo y puerperio. Un reporte de caso

La trombosis venosa cerebral es una causa frecuente de evento vascular cerebral en la paciente embarazada o en etapa de puerperio debido al estado protrombótico transitorio generado por los diferentes cambios fisiológicos suscitados durante estas dos etapas. En México, cerca del 50% de los casos se encuentran durante embarazo o puerperio. El diagnóstico se puede realizar y confirmar con imagen por resonancia magnética o con estudios invasivos como la angiografía cerebral. La instauración de un régimen de tratamiento involucra la anticoagulación por un periodo de hasta seis meses y, por lo general, se tiene una buena respuesta y evolución favorable. Se presenta el caso de una paciente en puerperio inmediato que debuta con evento vascular cerebral asociado a trombosis venosa cerebral, quien al descartar otras etiologías relacionadas, se determinó ser secundario al estado procoagulante transitorio del embarazo y puerperio. Cursó con evolución favorable durante su hospitalización con anticoagulación con heparina de bajo peso molecular y egresa con anticoagulación vía oral sin secuelas neurológicas residuales durante su seguimiento por 6 meses. Se resalta la importancia de identificar factores de riesgo que predispongan al desarrollo de patología vascular cerebral durante la atención de la mujer gestante y en periodo posparto, que si bien de baja frecuencia, debe ser siempre una entidad clínica a considerar para no retrasar el diagnóstico y otorgar tratamiento oportuno de forma temprana para evitar el riesgo de secuelas neurológicas residuales y/o mortalidad materna. Palabras clave: trombosis venosa cerebral, embarazo, puerperio, medicina interna, neurología, ginecología y obstetricia

Is ultra-violet radiation the main force shaping molecular evolution of varicella-zoster virus?

<p>Abstract</p> <p>Background</p> <p>Varicella (chickenpox) exhibits a characteristic epidemiological pattern which is associated with climate. In general, primary infections in tropical regions are comparatively less frequent among children than in temperate regions. This peculiarity regarding varicella-zoster virus (VZV) infection among certain age groups in tropical regions results in increased susceptibility during adulthood in these regions. Moreover, this disease shows a cyclic behavior in which the number of cases increases significantly during winter and spring. This observation further supports the participation of environmental factors in global epidemiology of chickenpox. However, the underlying mechanisms responsible for this distinctive disease behavior are not understood completely. In a recent publication, Philip S. Rice has put forward an interesting hypothesis suggesting that ultra-violet (UV) radiation is the major environmental factor driving the molecular evolution of VZV.</p> <p>Discussion</p> <p>While we welcomed the attempt to explain the mechanisms controlling VZV transmission and distribution, we argue that Rice's hypothesis takes lightly the circulation of the so called "temperate VZV genotypes" in tropical regions and, to certain degree, overlooks the predominance of such lineages in certain non-temperate areas. Here, we further discuss and present new information about the overwhelming dominance of temperate VZV genotypes in Mexico regardless of geographical location and climate.</p> <p>Summary</p> <p>UV radiation does not satisfactorily explain the distribution of VZV genotypes in different tropical and temperate regions of Mexico. Additionally, the cyclic behavior of varicella does not shown significant differences between regions with different climates in the country. More studies should be conducted to identify the factors directly involved in viral spreading. A better understanding of the modes of transmissions exploited by VZV and their effect on viral fitness is likely to facilitate the implementation of preventive measures for disease control.</p

Comparación de la castración quirúrgica al nacimiento versus inmunocastración sobre el comportamiento conductual y parámetros sanguíneos (testosterona y cortisol) en machos Holstein en engorda

The behavioural response and blood parameters were compared in immunocastrated and surgically castrated bovine males. In total, 720 Holstein males, 7-8 months old and approximately 240 kg body weight were used. One group was immunocastrated by vaccination with Bopriva (commercial anti-GnRH vaccine) on days 1, 21, 101 and 181 days of the fattening and the other group was surgically castrated at birth. Blood samples were taken on vaccination days for testosterone determination and on days 181 and during slaughtering to analyse blood cortisol. Sexual behaviour (mounts and flehmen signs) and aggressive (threats and head butting) and social behaviour (sniffing, grooming, lowered head, and vocalization) were evaluated, finding no significant differences between treatments. Testosterone concentration in both treatments was below 1 ng/ml in all samples. Cortisol levels on day 181 of fattening were lower (p&lt;0.05) with respect to the day of slaughtering in both treatments. Slaughter weight (242 days fattening) was 595.0 kg in immunocastrated males and 620.74 kg in surgically castrated males.Se comparó el comportamiento conductual y parámetros sanguíneos en toros inmunocastrados y quirúrgicamente castrados. Se utilizaron 720 machos Holstein de 7-8 meses de edad y peso aproximado de 240 kg. Un grupo fue inmunocastrado mediante vacunación con Bopriva (vacuna comercial anti-GnRH) los días 1, 21, 101 y 181 días de engorda y el otro grupo fue castrado quirúrgicamente al nacimiento. Se tomaron muestras de sangre los días de las vacunaciones para la determinación de testosterona y los días 181 y durante el desangrado en el sacrificio para analizar cortisol sanguíneo. Se evaluó el comportamiento sexual (montas y signos de flehmen), agresivo (amenazas y topetazos) y social (olfateos, acicalamiento, cabeza baja y vocalizaciones) no encontrándose diferencias significativas entre tratamientos. La concentración de testosterona en ambos tratamientos fue por debajo de 1 ng/ml en todos los muestreos. Los niveles de cortisol en el día 181 de engorda fueron más bajos (p&lt;0.05) con respecto al día de sacrificio en ambos tratamientos. El peso al sacrificio (242 días de engorda) fue de 595.0 kg en machos inmunocastrados y 620.74 kg en castrados quirúrgicamente

Comparación de la castración quirúrgica al nacimiento versus inmunocastration sobre las características de la canal y carne en machos Holstein

El objetivo fue comparar el efecto de la castración quirúrgica al nacimiento vs immunocastración, sobre las características de la canal y carne en machos Holstein en engorda; se utilizaron 720 machos Holstein aproximadamente de 7 a 8 meses de edad con peso inicial de 240.82 kg. Se formaron 2 tratamientos con 4 corrales de 90 animales en cada uno: toros castrados quirúrgicamente que fueron castrados 24 h después del nacimiento y toros inmunocastrados vacunados con Bopriva aplicando cuatro dosis, al día 1, 21, 101 y 181 de engorda. Se tomaron pesos individuales en cada vacunación. Los animales se sacrificaron a los 242 días de engorda. A partir de la segunda vacunación se observaron diferencias (P0.05) entre tratamientos mientras que los valores de b*, C* y H* fueron más altos (P<0.05) en los animales inmunocastrados. Para fines de producción, el sacrificar los machos Holstein al nacimiento, se obtienen animales más pesados y con mejores características en la canal; sin embargo es importante evaluar el impacto del bienestar animal por la castración al nacimiento

Contra un diseño dependiente : un modelo para la autodeterminación nacional

254 páginasEl presente trabajo se publicó por primera vez en 1977. Fue el esfuerzo de un grupo de profesores fundadores de la División de Ciencias y Artes para el Diseño, de la Universidad Autónoma Metropolitana y se instituyó en ese momento como el fundamento operativo para una teoría unificada del diseño. Su antecedente, fue el postulado innovador que propuso a las diferentes disciplinas del diseño a reunirse en un conjunto interdisciplinario unificado donde la integración de los diferentes cuerpos teóricos posibilitaron al diseño a constituir un sistema de conocimientos coherentes con su campo de acción y su objeto de estudio. El resultado del trabajo fue una propuesta metodológica, un "Modelo General del Proceso de Diseño". Se tuvo entonces el cuidado de considerar que constituirse en su marco general y ser por ello un sistema flexible en su desarrollo y desenvolvimiento

Familial hypercholesterolaemia in children and adolescents from 48 countries: a cross-sectional study

Background: Approximately 450 000 children are born with familial hypercholesterolaemia worldwide every year, yet only 2·1% of adults with familial hypercholesterolaemia were diagnosed before age 18 years via current diagnostic approaches, which are derived from observations in adults. We aimed to characterise children and adolescents with heterozygous familial hypercholesterolaemia (HeFH) and understand current approaches to the identification and management of familial hypercholesterolaemia to inform future public health strategies. Methods: For this cross-sectional study, we assessed children and adolescents younger than 18 years with a clinical or genetic diagnosis of HeFH at the time of entry into the Familial Hypercholesterolaemia Studies Collaboration (FHSC) registry between Oct 1, 2015, and Jan 31, 2021. Data in the registry were collected from 55 regional or national registries in 48 countries. Diagnoses relying on self-reported history of familial hypercholesterolaemia and suspected secondary hypercholesterolaemia were excluded from the registry; people with untreated LDL cholesterol (LDL-C) of at least 13·0 mmol/L were excluded from this study. Data were assessed overall and by WHO region, World Bank country income status, age, diagnostic criteria, and index-case status. The main outcome of this study was to assess current identification and management of children and adolescents with familial hypercholesterolaemia. Findings: Of 63 093 individuals in the FHSC registry, 11 848 (18·8%) were children or adolescents younger than 18 years with HeFH and were included in this study; 5756 (50·2%) of 11 476 included individuals were female and 5720 (49·8%) were male. Sex data were missing for 372 (3·1%) of 11 848 individuals. Median age at registry entry was 9·6 years (IQR 5·8-13·2). 10 099 (89·9%) of 11 235 included individuals had a final genetically confirmed diagnosis of familial hypercholesterolaemia and 1136 (10·1%) had a clinical diagnosis. Genetically confirmed diagnosis data or clinical diagnosis data were missing for 613 (5·2%) of 11 848 individuals. Genetic diagnosis was more common in children and adolescents from high-income countries (9427 [92·4%] of 10 202) than in children and adolescents from non-high-income countries (199 [48·0%] of 415). 3414 (31·6%) of 10 804 children or adolescents were index cases. Familial-hypercholesterolaemia-related physical signs, cardiovascular risk factors, and cardiovascular disease were uncommon, but were more common in non-high-income countries. 7557 (72·4%) of 10 428 included children or adolescents were not taking lipid-lowering medication (LLM) and had a median LDL-C of 5·00 mmol/L (IQR 4·05-6·08). Compared with genetic diagnosis, the use of unadapted clinical criteria intended for use in adults and reliant on more extreme phenotypes could result in 50-75% of children and adolescents with familial hypercholesterolaemia not being identified. Interpretation: Clinical characteristics observed in adults with familial hypercholesterolaemia are uncommon in children and adolescents with familial hypercholesterolaemia, hence detection in this age group relies on measurement of LDL-C and genetic confirmation. Where genetic testing is unavailable, increased availability and use of LDL-C measurements in the first few years of life could help reduce the current gap between prevalence and detection, enabling increased use of combination LLM to reach recommended LDL-C targets early in life