Quantifying uncertainty in structural responses of polymer sandwich composites: a comparative analysis of neural networks

The manufacturing and fabrication of complex polymer sandwich composite plates involve various processes and parameters, and the lack of control over them causes uncertain system parameters. It is essential to consider randomness in varying parameters to analyse polymer sandwich composite plates. The present study portrays uncertainty quantification in structural responses (such as natural frequencies) of polymer sandwich composite plates using the surrogate model. The comparative study of artificial neural network (ANN) and polynomial neural network (PNN) for uncertain structural responses of the sandwich plate is presented. The proposed ANN as well as PNN algorithm is found to be convergent with intensive Monte Carlo simulation (MCS) for uncertain vibration responses. The predictability of PNN is observed to be more efficient than that of ANN. Typical material properties, skew angle, fibre orientation angle, number of laminate and core thickness are randomly varied to quantify the uncertainties. The use of both the surrogate models (PNN and ANN) results in a significant saving of computational time and cost compared to that of full-scale intensive finite element-based MCS approach.</p

Assays to Measure the Activity of Influenza Virus Polymerase.

Influenza viruses use an RNA-dependent RNA polymerase (RdRp) to transcribe and replicate their segmented negative-stranded RNA genomes. The influenza A virus RdRp consists of a heterotrimeric complex of the proteins PB1, PB2, and PA. The RdRp is associated with the incoming influenza A viral RNA (vRNA) genome bound by the viral nucleoprotein (NP), in complexes called viral ribonucleoproteins, vRNPs. During the viral replication cycle, the RdRp snatches capped primers from nascent host mRNAs to carry out primary viral transcription. Viral mRNA translation produces new copies of the RdRp subunits and NP, which are required to stabilize and encapsidate complementary copies of the genome (cRNAs), forming cRNPs. These cRNPs then use the cRNAs to make new vRNAs, which are encapsidated into new vRNPs. Secondary transcription by new vRNPs results in further viral mRNAs and an increase of the viral protein load in the cell. The activities of the RdRp (mRNA, cRNA, and vRNA synthesis) in the influenza virus replication cycle can be measured on several levels, ranging from assessment of the accumulation of RNA products in virus-infected cells, through in situ reconstitution of the RdRp from cloned cDNAs, to in vitro biochemical assays that allow the dissection of individual functions of the RdRp enzyme. Here we describe these assays and point out the advantages and drawbacks of each