Abstract The dynamics of rising bubbles in a liquid sodium pool plays a significant role in the estimation of the radiological source term during anticipated transients and normal operation of a fast reactor. Sodium is chemically reactive with air and water. Therefore, carrying out experiments using sodium on a reactor scale level requires extra precautions. We report an in-house experimental technique to depict the bubble dynamics along with numerical support to establish similarity behavior between water and liquid sodium, to reduce the number of experiments in sodium systems for in-depth knowledge of bubble dynamics in the case of the fast breeder reactor. In the present work, 3-D bubble dynamics is studied in the OpenFOAM platform and the validated numerical model is used to study bubble dynamics in sodium to establish similitude between the water and sodium systems. The bubble aspect ratio of 0.9 cm diameter bubbles in the sodium system is found to be in close agreement with that of 0.5 cm bubbles in the water system. Experimental and numerical findings suggest similarity of the aspect ratio between water and scaled-up sodium systems. The similarity criteria established between water and sodium are found to be very useful in conducting water-based experiments to study bubble dynamics in sodium systems.

Aim: Polyamidoamine (PAMAM) dendrimers inherent properties have made it the nanocarrier of choice in the current era of innovation. Dendrimer based products are growing and mushrooming like anything in the current time. Although it suffer from hemolytic toxicity which could be reduced by protecting free amino group. Methods: In the present work alternate acetylated method for PAMAM dendrimers was discussed. 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide Linker was used for acetylation. The acetylated conjugate was evaluated for color reaction, Ultraviolet-visible spectroscopy, Fourier Transform infrared spectroscopy, Differential scanning calorimetric, Nuclear magnetic resonance spectra studies. Results: The PAMAM dendrimers were synthesized using divergent approach and further acetylated. Change in λmax values from 282.0 to 282.5 nm was observed for acetylated dendrimers. Characteristic peak of N-H stretch of primary amine at 3284.16 cm-1 was disappeared due to conversion of primary amine to secondary amine. A new peak of -(CO)-NH stretch was obtained at 1640.28 cm-1 (medium) which shows attachment of acetic acid surface group. The changes in Endothermic peak from 120.56 to 110.40ºC were observed which shows the PAMAM dendrimers surface modifications The peak of -NH2 at 2.99 ppm was replaced by (-NHCOCH3) at 2.42 ppm further supports the proof of acetylation. Conclusions: The spectral data clearly revealed that this approach for acetylation gives considerable amount of acetylation in less time duration with elimination of organic solvent. This method could be employed for regular acetylation of amine terminated nanocarriers. EDC linker mediated capping of amine groups opened a new avenue for acetylation of amine terminated protein/peptides.

Objetivos: Las propiedades inherentes de la poliamidoamina (PAMAM) la han convertido en el nanotransportador de elección en la era actual de la innovación. A pesar de que sufren de toxicidad hemolítica que podría ser reducido mediante la protección del grupo amino libre. En el presente trabajo se discutió el método alternativo de acetilación para los dendrímeros PAMAM. Material y Métodos: El enlazador 1-Etill-3-(3-dimetilaminopropil) carbodiimida (EDC) se utilizó para la acetilación. El conjugado acetilado se evaluó mediante la reacción de color, mediante espectroscopia Ultravioleta visible, espectroscopia infrarroja con transformado de Fourrier, Calorimetría Diferencial de barrido y los estudios de los espectros de Resonancia magnetica nuclear. Resultados: Los dendrímeros PAMAM se sintetizaron utilizando el método divergente y más acetilado. Cambio en los valores λmax 282,0 a 282,5 nm se observó para dendrímeros acetilados. El pico característico del NH de amina primaria a 3284,16 cm-1, desapareció debido a la conversión de amina primaria a amina secundaria. Un nuevo pico de - (CO) -NH se obtuvo a 1640,28 cm-1 (medianas), que muestra la unión de grupo de superficie de ácido acético. Se observaron los cambios en el pico endotérmico de 120,56 a 110.40 ºC que muestra las modificaciones superficiales de dendrímeros PAMAM. El pico de -NH2 en 2,99 ppm fue sustituido por (-NHCOCH3) a 2,42 ppm apoya aun más la prueba de acetilación. Conclusión: Los datos espectrales revelaron claramente que este enfoque para la acetilación da considerable cantidad de acetilación en menos tiempo de duración con la eliminación de disolvente orgánico. Este método podría ser empleado para regular la acetilación de las aminas terminales de nanovehículos. El enlazador EDC de grupos amino abre una nueva vía para la acetilación de amina terminales de proteínas / péptidos.