Characterization and kinetic modeling of secondary phases in squeeze cast Al alloy A380 by DSC thermal analysis

Thermal analyses on squeeze cast aluminum alloy A380(SC A380) solidified under 90MPa were carried out to study the microstructure development of the alloy, in which a differential scanning calorimeter(DSC) was employed. During the DSC runs, heating and cooling rates of 1, 3, 10, and 20 °C·min^(-1) were applied to investigate the heating and cooling effects on dissolution of secondary eutectic phases and microstructure evolution. Various reactions corresponding to troughs and peaks of the DSC curves were identified as corresponding to phase transformations taking place during dissolution or precipitation suggested by the principles of thermodynamics and kinetics. The comparison of the identified characteristic temperatures in the measured heating and cooling curves are generally in good agreement with the computed equilibrium temperatures. The microstructure analyses by scanning electron microscopy(SEM) with energy dispersive X-ray spectroscopy(EDS) indicate that the distribution and morphology of secondary phases present in the microstructure of the annealed sample are similar to the as-cast A380, i.e., strip β(Si), buck bone like or dot distributed θ(Al_2Cu), β(Al_5Fe Si) and Al_(15)(FeMn)_3Si_2. Two kinetic methods are employed to calculate the activation energies of the three common troughs and three common peaks in DSC curves of SC A380. The activation energies of the identified reaction θ_(CuAl_2) = α(Al)+β(Si) is 188.7 and 187.1 k J?mol^(-1) when the activation energies of reaction α(Al)+β(Si)→θCu Al_2 is^(-1)22.7 and^(-1)21.8 k J?mol^(-1), by the Kissinger and Starink methods, respectively.

An Effective Platform for SARS-CoV-2 Prevention by Combining Neutralization and RNAi Technology

At present,the coronavirus disease 2019(COVID-19)pandemic is a global health crisis.Scientists all over the globe are urgently looking forward to an effective solution to prevent the spread of the epidemic and avoid more casualties at an early date.In this study,we establish an effective platform for the prevention of SARS-CoV-2 by combining the neutralization strategy and RNAi technology.To protect normal cells from infection,the customized cells are constructed to stably express viral antigenic receptor ACE2 on the cell membrane.These modified cells are used as bait for inducing the viral entry.The transcription and replication activities of viral genome are intercepted subsequently by the intracellular sh RNAs,which are complementary to the viral gene fragments.A pseudotyped virus reconstructed from the HIV lentivirus is utilized as a virus model,by which we validate the feasibility and effectiveness of our strategy in vitro.Our work establishes an initial model and lays the foundation for future prevention and treatment of various RNA viruses.