Impact of the sintering parameters on the grain size, crystal phases, translucency, biaxial flexural strength, and fracture load of zirconia materials

Objectives: To investigate the influence of the zirconia and sintering parameters on the optical and mechanical properties. Methods: Three zirconia materials (3/4Y-TZP, 4Y-TZP, 3Y-TZP) were high-speed (HSS), speed (SS) or conventionally (CS) sintered. Disc-shaped specimens nested in 4 vertical layers of the blank were examined for grain size (GS), crystal phases (c/t’/t/m-phase), translucency (T), and biaxial flexural strength. Fracture load (FL) of threeunit fixed dental prostheses was determined initially and after thermomechanical aging. Fracture types were classified, and data statistically analyzed. Results: 4Y-TZP showed a higher amount of c + t’-phase and lower amount of t-phase, and higher optical and lower mechanical properties than 3Y-TZP. In all materials, T declined from Layer 1 to 4. 3/4Y-TZP showed the highest FL, followed by 3Y-TZP, while 4Y-TZP showed the lowest. In 4Y-TZP, the sintering parameters exercised a direct impact on GS and T, while mechanical properties were largely unaffected. The sintering parameters showed a varying influence on 3Y-TZP. Thermomechanical aging resulted in comparable or higher FL. Conclusion: 3/4Y-TZP presenting the highest FL underscores the principle of using strength-gradient multi-layer blanks to profit from high optical properties in the incisal area, while ensuring high mechanical properties in the lower areas subject to tensile forces. With all groups exceeding maximum bite forces, the examined three-unit FDPs showed promising long-term mechanical properties

Sodium‐Doped Tin Sulfide Single Crystal: A Nontoxic Earth‐Abundant Material with High Thermoelectric Performance

Lead‐free tin sulfide (SnS), with an analogous structure to SnSe, has attracted increasing attention because of its theoretically predicted high thermoelectric performance. In practice, however, polycrystalline SnS performs rather poorly as a result of its low power factor. In this work, bulk sodium (Na)‐doped SnS single crystals are synthesized using a modified Bridgman method and a detailed transport evaluation is conducted. The highest zT value of ≈1.1 is reached at 870 K in a 2 at% Na‐doped SnS single crystal along the b‐axis direction, in which high power factors (2.0 mW m−1 K−2 at room temperature) are realized. These high power factors are attributed to the high mobility associated with the single crystalline nature of the samples as well as to the enhanced carrier concentration achieved through Na doping. An effective single parabolic band model coupled with first‐principles calculations is used to provide theoretical insight into the electronic transport properties. This work demonstrates that SnS‐based single crystals composed of earth‐abundant, low‐cost, and nontoxic chemical elements can exhibit high thermoelectric performance and thus hold potential for application in the area of waste heat recovery.Large size Sn1−xNaxS single crystals were firstly obtained using a modified Bridgman method. The multiple band feature along with the single crystalline nature favors a large power factor, leading to the highest dimensionless figure of merit (zT) of ~1.1 at 870 K for 2 at% Na‐doped SnS single crystal along the b‐axis, which is one of the best results for thermoelectric sulfides to date.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/145294/1/aenm201800087_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/145294/2/aenm201800087-sup-0001-S1.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/145294/3/aenm201800087.pd

Diagnóstico Situacional de Adolescencia y Juventud

El presente diagnóstico situacional de adolescencia y juventud elaborado por las estudiantes de la Licenciatura en Trabajo Social que realizan su servicio social, en apoyo a la Asociación Mangle, busca dar a conocer la situación actual de la multidimensionalidad de las y los adolescentes, así como de las y los jóvenes de las comunidades que pertenecen al radio de acción con el cual trabaja la Asociación Mangle, para que se puedan brindar nuevas oportunidades y fortalecer las capacidades de las y los adolescentes y jóvenes. Para recopilar la información que se presenta en el diagnóstico situacional de adolescencia y juventud fue necesaria la utilización del instrumento de llenado de encuestas en el cual se tomó como muestra a treinta y nueve jóvenes y 11 adolescentes de nueve comunidades; la población encuestada proporcionó datos de su realidad social, económica, educativa, ambiental y socio cultural, que permitieron identificar algunos aspectos que impiden el desarrollo personal de ellas y ellos, así como su desarrollo dentro de las comunidades. Otro instrumento utilizado fueron las entrevistas para integrantes de ADESCOS y de Asociación Mangle, las cuales dieron lugar a que se ampliara la información obtenida de las encuestas en cuanto al contexto socio ambiental, educativo y de salud. Posteriormente a la recopilación de información se analizaron los datos obtenidos y se hizo una sistematización de toda la información. El diagnostico situacional presenta como primer momento la caracterización general del contexto que hace referencia al marco geográfico, marco histórico, marco socioambiental y marco demográfico. Como segundo momento se analizan los datos del estado situacional de las y los jóvenes encuestados que viven dentro del territorio que se está conociendo y lo cual representa lo social, la economía, la educación y la salud dentro de la población joven y adolescente de las diferentes comunidades. Posteriormente del análisis de datos se establece una priorización de problemas que se están presentando dentro de la población, para lo cual se formulan estrategias de acción, con el fin de que puedan ser tomadas en cuenta para contribuir al desarrollo integral de las y los adolescentes y jóvenes. Finalmente se muestran la prognosis, recomendaciones, referencias bibliográficas y los anexos utilizados para realizar el diagnostico situacional

Assessing intensification options of common bean cultivation to improve food security on smallholder farms in the northern highlands of Tanzania

A Thesis Submitted in Fulfilment of the Requirements for the Degree of Doctor of Philosophy in Life Sciences of the Nelson Mandela African Institution of Science and TechnologyComplementarities of common bean (Phaseolus vulgaris L.) with non-legume food crops and their significances to the agricultural systems are underexploited. Based on the description of this study, eight options were assessed for the sustainable intensification of common bean cultivation (through manipulations of intercropping and rotation) against the monocultures of maize (Zea mays L.), and the improved and local varieties of common bean in the northern highlands of Tanzania. The factors assessed were the cropping seasons/years (S) (2015 to 2017), agro-ecological zones (A) above sea level (lower 843 m, middle 1051 m, upper 1743 m), cropping systems (C) (sole, intercrop, rotation), and bean varieties (V) (improved Lyamungu 90 and local Mkanamna) and their interactions. Results indicated that S, A, C, and S×A, S×C, S×A×C were significant and bean grain yields increased in intercrops ranging from 1.5 to 2.9 t ha-1 with land equivalent ratio (LER) of 1.58. Intercropping over five cropping seasons indicated that with S×V grain yields increased from 0.2 to 3.5 t ha-1 in bean and from 2.3 to 2.6 t ha-1 in maize with LERs of 1.48 and 1.55. In rotations, higher bean grain yields were attributed to S (3.3 t ha-1 ), C (3.4 t ha-1 ), and V (2.7 t ha-1 ) and for maize were in C (2.9 t ha-1 ) and S (2.6 t ha-1 ). In conclusion, out of eight assessed options, this study found two main useful options for improving food security on smallholder farms in the northern highlands of Tanzania. The options were continuous cultivation of the improved and/or local varieties of common bean in intercrops with the maize throughout two rainy seasons of the year (long and short). Another option was cultivation of the improved and/or local varieties of common bean intercropped with maize in the long rainy season and rotating of these intercrops with the maize cultivated in the short rainy seasons. Importantly, the improved bean variety Lyamungu 90 was heavier in weight, using the same number of seeds, than the local bean variety Mkanamna, which provided additional factors to be considered to improve income where weight is the acceptable standard in the market

Flexural strength, fracture toughness, and translucency of cubic/tetragonal zirconia materials

STATEMENT OF PROBLEM The development of zirconia materials with optimized properties has been rapid, and studies comparing the mechanical and optical properties of recently introduced zirconia with lithium disilicate materials are limited. PURPOSE The purpose of this in vitro study was to compare the mechanical and optical properties of cubic/tetragonal zirconia materials with those of a lithium disilicate ceramic. MATERIAL AND METHODS Specimens were fabricated from 6 different noncolored zirconia materials: Ceramill Zolid FX (CZ), CopraSmile (CS), DD cubeX$^{2}$ (DD), NOVAZIR MaxT (NZ), priti multidisc ZrO₂ (PD), and StarCeram Z-Smile (SC), and 1 lithium disilicate ceramic as a control, IPS e.max Press LT A2 (CG). Four-point flexural strength (N=105/n=15) and fracture toughness using the single-edge V-notched beam (N=105/n=15) were examined according to International Organization for Standardization standard 6872:2015. Translucency (N=70/n=10) was evaluated with an ultraviolet spectrophotometer. Grain size (N=6/n=1) of zirconia was investigated by using scanning electron microscopy. Data were analyzed using the Kolmogorov-Smirnov test, multivariate analysis, 1-way analysis of variance, followed by the post hoc Scheffé test and Kruskal-Wallis and Mann-Whitney U tests, and Weibull analysis, using the maximum likelihood estimation method at 95% confidence level (α=.05). RESULTS Zirconia materials showed higher mechanical and lower optical properties than CG (P<.001). No differences were observed among the zirconia materials with respect to flexural strength (P=.259) or fracture toughness (P=.408). CG and CS showed significantly higher Weibull modulus than SC and PD. The lowest translucency values were measured for NZ and SC, followed by CS, DD, and PD (P<.001). CZ showed the highest translucency values (P<.001). The lowest grain sizes were found for NZ, DD, and SC; the largest were shown for CS (P<.001). CONCLUSIONS Cubic/tetragonal zirconia showed better mechanical properties than lithium disilicate ceramic. However, the optical properties and the reliability of zirconia are lower than those of lithium disilicate ceramic