Measurement of transverse vibrations/visualization of mode shapes in square plate by using digital speckle pattern interferometry and wavelet transform

New filtering scheme is investigated and implemented on digital speckle pattern interferometric fringes to enhance the signal-to-noise ratio (SNR) in the speckle interferograms. To establish the potential of new filtering scheme the experiment was conducted on the vibrating cantilever beam. Experimental results revealed that the new filtering scheme is more powerful than other known filtering schemes (Kumar et al. Opt Laser Eng 2004;41:81–93. Kumar et al. Opt Laser Technol 2001;33:567–571. Shakher et al. Opt Eng 2002;41:176–180. Shakher et al. Proceedings ICICS, Singapore, 9–12 September 1997, p. 953–956. Bowler et al. Proceedings of IEE second international conference on image processing, London, 1986, p. 24–26. Lim. Opt Eng 1981;20:670–678. Devila et al. J Mod Opt 1995;42:1795–1804; Kaufmann et al. Opt Eng 1996;35:9–14). The new scheme reduced the speckle noise and improved SNR in speckle interferograms. Further, the new investigated filtering scheme is implemented to study the mode shapes of square plates under two different boundary conditions. In the first condition all the edges of the square plate were fixed while in the second condition two adjacent edges were fixed and the remaining two edges were free. From the experimental results it is clear that the mode shapes are more distinctly visible with the implementation of the new filtering scheme as compared to other known schemes. Under both the boundary conditions the recorded resonance frequencies were compared with the calculated values of resonance frequencies based on classical theory. The results obtained form DSPI show good agreement with classical theory.     

A DFT+U study of the catalytic activity of lanthanum nickelate

A density functional theory + Hubbard U (DFT+U) method is implemented to investigate the catalytic activity of lanthanum nickelate (LaNiO₃) for oxygen reduction reaction. Comparison of the surface energies of different LaNiO₃ surfaces shows that {001} surface has the lowest surface energy and hence maximum stability. Two possible terminations of the {001} surface namely LaO and NiO₂ are considered to carry out all our DFT calculations. Calculation of bond lengths of the atoms near the surface and adsorption energies for the reaction intermediates revealed that LaO terminated {001} surface is unstable for the process of OOH adsorption and hence not preferred for the oxygen reduction reaction. However, NiO₂ terminated {001} surface shows excellent catalytic activity for adsorption of all the reaction intermediates and hence is a favourable surface for reactions to occur. Superiority of the NiO₂ terminated {001} surface as catalyst over the LaO terminated one, is also confirmed from the total and partial density of states of the surfaces in presence of the adsorbates, which also shows that the desorption rate of the reaction intermediates is low in case of LaO terminated {001} surface compared to the NiO₂ terminated one.     

Hydrogen atom abstraction from Piperazine by hydroxyl radical: a theoretical investigation

Dual level of quantum mechanical calculations have been carried out for hydrogen abstraction from Piperazine [HN(CH₂CH₂)₂NH] initiated by OH radical. Geometry optimisation and frequency calculations of all species involved in the titled reaction have been performed at M06-2X/6-31+G(d,p) level of theory. For the accuracy in the thermochemistry and kinetics data, single-point energy calculations have been further carried out at coupled cluster CCSD(T) method along with 6-311G(d,p) basis set. An energy profile diagram for the reaction has been plotted along with pre-reactive and post-reactive complexes at entrance and exit channels. Intrinsic reaction coordinates (IRCs) calculations have been performed for identification of real transition states that connect it via reactant to product. Our result shows that the H-atom abstraction takes place from the C–H position of Piperazine. The rate constant is calculated using canonical transition state theory (CTST) is found to be 2.86 × 10^?10 cm³ molecule^?1 s^?1 which is in good agreement with the reported experimental rate constant (2.38 ± 0.28) × 10^?10 cm³ molecule^?1 s^?1 at 298 K. We have also reported rate constant for the temperature range 300–500 K. Using group-balance isodesmic reaction, the standard enthalpies of formation for Piperazine and product radicals generated by hydrogen abstraction are reported. The branching ratios for both reaction channel (i.e. H-abstraction from –CH₂ and –NH position of Piperazine) are found to be 93% and 7%, respectively. The calculated atmospheric life time of Piperazine is found to be 0.97 hour.     

Thickness-dependent electrical and optical properties of Ge8Sb2Te11 thin films

The amorphous Ge₈Sb₂Te₁₁thin films with varying thickness are thermally deposited on well-cleaned glass substrate from its polycrystalline bulk. Absence of any sharp peak confirms the amorphous nature of deposited films. Thickness-dependent electrical and optical properties including dc-activation energy, sheet resistivity, optical band gap, band tailing parameter, etc. of Ge₈Sb₂Te₁₁thin films have been studied. The optical parameters have been calculated from transmission, reflection and absorbance data in the spectral range of 200–1100 nm. It has been found that optical band gap and band tailing parameter decreases with the increase in Ge₈Sb₂Te₁₁thin films thickness. The dc-activation energy and sheet resistivity decreases while the crystallization temperature of the amorphous Ge₈Sb₂Te₁₁ films increases with the increase in thickness of the films. The decrease of the sheet resistivity has been substantiated quantitatively using the classical size-effect theory. These results have been explained on the basis of rearrangements of defects and disorders in the amorphous chalcogenide system.     

Ag implantation-induced modification of Ni–Ti shape memory alloy thin films

Nanocrystalline thin films of Ni–Ti shape memory alloy are deposited on an Si substrate by the DC-magnetron co-sputtering technique and 120?keV Ag ions are implanted at different fluences. The thickness and composition of the pristine films are determined by Rutherford Backscattering Spectrometry (RBS). X-Ray diffraction (XRD), atomic force microscopy (AFM) and four-point probe resistivity methods have been used to study the structural, morphological and electrical transport properties. XRD analysis has revealed the existence of martensitic and austenite phases in the pristine film and also evidenced the structural changes in Ag-implanted Ni–Ti films at different fluences. AFM studies have revealed that surface roughness and grain size of Ni–Ti films have decreased with an increase in ion fluence. The modifications in the mechanical behaviour of implanted Ni–Ti films w.r.t pristine film is determined by using a Nano-indentation tester at room temperature. Higher hardness and the ratio of higher hardness (H) to elastic modulus (E_r) are observed for the film implanted at an optimized fluence of 9?×?10¹⁵ ions/cm². This improvement in mechanical behaviour could be understood in terms of grain refinement and dislocation induced by the Ag ion implantation in the Ni–Ti thin films.     

Numerical study of reacting flow characteristics of a 2D twin cavity trapped vortex combustor

In the present work, reacting flow characteristics of a 2D trapped vortex combustor (TVC) have been investigated numerically. Turbulent flow prevailing in the combustor is modelled using the two equation shear stress transport (SST) k-ω model and the turbulence–chemistry interactions are modelled using the eddy dissipation concept (EDC) model. Validation study reveals that the data generated by numerical model for reacting flow cases matches reasonably well with the experimental data. Simulation results indicate that for a particular operating condition, the flow structure within the cavity for reacting flow cases is significantly different from non-reacting flow cases. Besides this, under reacting flow condition, the vortex core location shifts with variation in operating condition. This study also reveals significant differences in the velocity gradient at the shear layer between reacting and non-reacting flow conditions. Furthermore, the turbulent kinetic energy at the cavity zone increases for the reacting flow condition, which is attributed to the volume expansion associated with the combustion processes. Also, temperature contours at locations downstream of the trailing edge indicate that both cavity flames are merged together for higher primary air velocity cases, and this is essential for efficient performance of TVC.     

Co-delivery of doxorubicin and AS1411 aptamer by poly(ethylene glycol)-poly(<Emphasis Type="Italic">β</Emphasis>-amino esters) polymeric micelles for targeted cancer therapy

Recently, targeted drug delivery systems (TDDS) have offered a great potential and benefits towards the anti-tumor drug delivery. In this work, we designed the TDDS using a biocompatible poly(ethylene glycol)-poly(β-amino esters) amphiphilic block copolymer (PEG-PAEs) synthesized by Michael addition polymerization for combinatorial therapy. Further, the chemotherapeutic agents’ doxorubicin (DOX) and AS1411 DNA aptamer (Apt) are encapsulated in the PEG-PAEs NPs (PDANs) for co-delivery therapeutics. PDANs have shown the monodisperse spherical shape, smooth surface with a net positive charge (average diameter—183.1 ± 27.2 nm, zeta potential—31.2 ± 6.3 mV), and good colloidal stability (critical micelle concentration of PEG-PAEs is about 6.3 μg/mL). The pH-sensitive PAEs endowed PDANs both pH-triggered drug release characteristics and enhanced endo/lysosomal escape ability, thus improving the localization and cytotoxicity of DOX. AS1411 Apt conjugated PDANs precisely targeted nucleolin and their uptake correlates to a significant activity enhancement only in tumor cells (MCF-7) but not in normal cells (MCF-10A). Thus, PDANs can be a very promising targeted drug delivery platform for effective breast cancer therapy.

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Graphical abstract Scheme 1 Schematic illustration of the preparation and cellular uptake of targeted co-delivery system