Microstructure and wear behaviour of high alloyed hot-work tool steels 1.2343 and 1.2367 under thermo-mechanical loading

Tools and their maintenance costs in hot forging processes account for a considerable proportion of the total components' costs. Forging tools undergo extreme heating and subsequent cooling during the forging process and between the forging cycles, respectively. This cyclic heating and cooling of the tool surfaces leads to local changes in the tool microstructure which result in hardening or softening of the material in different regions of the tool and consequently influence the tool strength. Temperature in the tool areas experiencing high thermo-mechanical loadings can exceed the austenitic temperature. Hence, a strong cooling, for example by spraying or lubrication, can lead to formation of a martensitic layer in the boundary zone of the tool. Due to its higher hardness, martensitic layer has greater resistance to wear as compared to the basic or tempered materials. In the scope of this paper, the austenitisation behaviours of two high alloyed hot-work tool steels, 1.2343 and 1.2367, have been characterized by means of dilatometer tests to obtain time-temperature-austenitisation (TTA) diagrams for specimen under thermo-mechanical loads. Moreover, continuous-cooling-transformation (CCT) diagrams were recorded. Metallographic investigations were carried out to gather a detailed understanding of the microstructure behaviour and its resulting hardness. With the results of this works, it is aimed to gather a detailed and accurate insight into the arising hardening and softening effects. This would eventually lead to an optimisation of the numerical modelling for tool wear prediction

The proteolytic digestive activity and growth during ontogeny of Parachromis dovii larvae (Pisces: Cichlidae) using two feeding protocols

Se evaluó la actividad proteolítica digestiva y el crecimiento de larvas de Parachromis dovii durante la ontogenia en un sistema de recirculación utilizando dos estrategias de alimentación durante un período de 28 días. Las larvas se criaron utilizando dos protocolos de alimentación (tres réplicas cada uno): (A) Nauplios de Artemia (en saciedad), alimentados con alimentación exógena [8 días después de la eclosión (DAH)] hasta los 15 DAH seguido de sustitución de nauplios por pienso formulado (20% día -1) hasta los 20 DAH y luego pienso formulado hasta los 28 DAH; (B) pienso formulado (100% de peso corporal al día) desde la alimentación exógena hasta los 28 días. Se midieron los niveles de proteasas digestivas ácidas (tipo pepsina) y alcalinas, así como el crecimiento y la supervivencia de las larvas a lo largo del período de alimentación. La supervivencia fue alta y similar entre tratamientos: 98,9 ± 0,0 para Artemia, 97,3 ± 0,0% para pienso formulado. La tasa de crecimiento específico para la longitud y el peso fue mayor en las larvas alimentadas con nauplios de Artemia que en las larvas criadas con alimento formulado: 3.4 ± 0.1 versus 1.8 ± 0.1% día-1 para la longitud corporal (P = 0.009) y 12.2 ± 0.1 versus 6.5 ± 0,3% día-1 para el peso corporal (P = 0,002). La actividad proteolítica ácida y alcalina se detectó, en ambos tratamientos, desde el inicio del experimento, a las 8 DAD. La actividad enzimática total (U larva-1) para las proteasas ácidas y alcalinas fue mayor en las larvas criadas con Artemia después de 12 DAD, mientras que la actividad enzimática específica fue similar para ambos tipos de enzimas en los dos tratamientos. Los resultados sugieren que las larvas de P. dovii eran capaces de digerir dietas formuladas desde el comienzo de la alimentación exógena y que podían criarse con piensos formulados. Sin embargo, el pienso formulado utilizado debe mejorarse nutricionalmente debido al escaso crecimiento obtenido en esta investigación.The proteolytic digestive activity and growth of Parachromis dovii larvae during the ontogeny were evaluated in a recirculation system using two feeding strategies during a 28-day period. Larvae were reared using two feeding protocols (three replicates each): (A) Artemia nauplii (at satiation), fed from exogenous feeding [8 days after hatching (DAH)] until 15 DAH followed by nauplii substitution by formulated feed (20 % day-1) until 20 DAH and then formulated feed until 28 DAH; (B) formulated feed (100 % BW daily) from exogenous feeding until 28 DAH. Levels of acid (pepsin type) and alkaline digestive proteases as well as growth and survival of larvae were measured along the feeding period. Survival was high and similar between treatments: 98.9 ± 0.0 for Artemia, 97.3 ± 0.0 % for formulated feed. The specific growth rate for length and weight was higher in larvae fed with Artemia nauplii than in larvae reared with formulated feed: 3.4 ± 0.1 versus 1.8 ± 0.1 % day-1 for body length (P = 0.009) and 12.2 ± 0.1 versus 6.5 ± 0.3 % day-1 for body weight (P = 0.002). The acid and alkaline proteolytic activity was detected, in both treatments, from the beginning of the experiment, at 8 DAH. The total enzymatic activity (U larva-1) for acid and alkaline proteases was higher in larvae reared with Artemia after 12 DAH, whereas the specific enzymatic activity was similar for both enzyme types in the two treatments. The results suggest that P. dovii larvae were capable to digest formulated diets from the beginning of exogenous feeding and that they could be reared with formulated feeds. However, the formulated feed used should be nutritionally improved because of the poor growth obtained in this research.Universidad Nacional, Costa RicaEscuela de Ciencias Biológica

Caregiver-Mediated Intervention for Low-Resourced Preschoolers With Autism: An RCT

OBJECTIVES: To compare 2 short-term, community caregiver training interventions for preschool-aged children with Autism Spectrum Disorder who had low resources. Low resource was defined by the US Department of Housing and Urban Development low-income index or 1 “indicator,” (eg, Medicaid eligibility). Child outcomes focused on joint engagement, joint attention, and play. METHODS: Participants included 112 families of a child who had Autism Spectrum Disorder who met criteria for being low-resourced and who were randomly assigned to 1 of 2 3-month interventions, group caregiver education or individualized caregiver-mediated intervention (CMM). Children were assessed for social communication skills pre- and post-treatment, and followed up at 3 months. RESULTS: All children improved in joint engagement and initiating joint attention, with significantly greater improvement by the CMM group. Outcomes on play skills were mixed, with improvement of symbolic play for the CMM group and no change in functional play skills. Joint engagement maintained over time for the CMM group, and initiating joint attention maintained for both groups over time. CONCLUSIONS: This study is among the first randomized trials comparing 2 active interventions with a large sample of low-resourced families. Results suggest improvements in core autism deficits of joint engagement, joint attention, and symbolic play with relatively brief, caregiver-mediated interventions, but additional support is necessary to maintain and generalize these gains over time

The road to Ithaca: a mentee’s and mentor’s journey

In this article a teacher/researcher and an academic mentor explore the potency, possibilities and tensions of the mentoring relationship from personal perspectives. The concept of mentoring as described in this article uses the model of mentor/mentee relationship as portrayed in Homer's epic narrative the Odyssey. In the examination of the experience of the mentoring process, as it was interpreted and implemented by Genie Gabel-Dunk and Anna Craft, significant elements emerge as tools for professional development: Being a Teacher to a Teacher; Being a Role Model; Being a Counsellor; Being a Facilitator; Being a Supportive Protector; and Being a Guide. The concept of mentorship is critical to quality education in that it fosters the creativity, professional development and growth of individuals and is a facilitator in the passing on of skills and professional standards. The authors believe that if as educators we value individuality, then we must work diligently to preserve the concept and practice of mentorship within the current context of the economic rationalisation of teaching resources