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The use of low GWP refrigerants has been extended around of world due to new environmental policies in the last decade. In this sense, commercial refrigerants that are replacing R134a have a principal characteristic of a low global warming potential (GWP). This paper presents an experimental study of energy performance on a commercial freezer using R1234yf as a replacement to R134a considering three thermal load conditions: without thermal load, medium load thermal load, and full thermal load. Results showed that the use of R1234yf promotes a reduction in the internal temperature on the freezer which is 2.3% lowest cold R134a, while the steady thermal time gets with R134a is lower than R1234yf in 11.1%, 11.7%, and 4.4% respectively for each thermal load level. El uso de refrigerantes bajo GWP se ha extendido cada vez más a nivel mundial debido a las nuevas políticas ambientales que han surgido en la última década. En este contexto, los refrigerantes comerciales que están desplazando al actual R134a, son aquellos que presentan bajo potencial de calentamiento global (GWP) en comparación con el mencionado anteriormente. En este trabajo se presenta el estudio experimental del desempeño energético de un congelador comercial utilizando el refrigerante R1234yf como sustituto al R134a a tres condiciones de carga térmica: sin carga, media carga y carga completa. Los resultados muestran que, con el uso del R1234yf, la temperatura en el interior del congelador es 2.3% más fría que con el R134a, mientras que el tiempo de estabilización térmica de alcanzado con el R134a es menor al alcanzado por el R1234yf en un 11.1%, 11.7% y 4.4% para cada nivel de carga térmica, respectivamente. O uso de refrigerantes de baixo PAG foi estendido ao redor do mundo devido a novas políticas ambientais na última década. Nesse sentido, os refrigerantes comerciais que estão substituindo o R134a têm como principal característica o baixo potencial de aquecimento global (GWP). Este trabalho apresenta um estudo experimental de desempenho energético em um freezer comercial usando R1234yf em substituição ao R134a considerando três condições de carga térmica: sem carga térmica, carga térmica média e carga térmica total. Os resultados mostraram que o uso de R1234yf promove uma redução na temperatura interna do freezer, que é 2,3% mais baixa fria R134a, enquanto o tempo térmico constante com R134a é inferior a R1234yf em 11,1%, 11,7% e 4,4% respectivamente para cada nível de carga térmica.

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Biología Molecular. Fecha de lectura: 16-07-2014, One of the central pathways that enhances cell survival, division and migration, and is frequently deregulated in cancer is that of PI3K/PTEN (phosphoinositide 3- -kinase/phosphatase and tensin homolog). Although four genes encode PI3K p110 catalytic subunits and there are seven regulatory subunits, only the p110α and p110β isoforms and the p85 regulatory subunits are expressed ubiquitously in body tissues. When cells are activated to enter the cell cycle, the PI3K catalyze formation of the phosphatidylinositol (PI)(3,4,5)P3, a second messenger that triggers a number of important signaling cascades; PTEN subsequently reduces PI(3,4,5)P3 to basal levels. Activation of p110α precedes that of p110β at several points in the cell cycle, during G0/G1 and G1/S transitions and at mitosis entry; nonetheless, it is not known whether p110α and p110β activation are linked. In addition, PI3K activation precedes that of PTEN, but its ability to regulate PTEN activation has not been studied. We explored the potential connections between p110α, p110β and PTEN activation, and found that serum stimulation of cells promotes p110α and p110β association, which demonstrates oligomerization of PI3K catalytic subunits within the cells. Moreover, p110α regulates optimal p110β activation by direct association of the two isoforms. p85 dimerization through N-terminal SH3-BcR domains is necessary for p110α/p110β complex formation. PTEN is also incorporated into the p110α/p110β complex, and its activation depends on its association to this oligomer. Our results show that PI3K and PTEN activities regulate one other within a multimolecular complex that controls cell PI(3,4,5)P3 levels.