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Can titanium oxide nanotubes facilitate intracellular delivery by laser-assisted photoporation?
No full textIn the present study, a newly developed nanosecond pulse laser-assisted photoporation using titanium-oxide nanotubes (TNT) for highly efficient intracellular delivery has been established. The proof of concept for the possibilities of intracellular delivery after irradiation of nanosecond pulse laser on TNT has been validated. TNT on titanium sheets using the electrochemical anodization technique at different voltage and time has been developed. The extensive X-ray photoelectron spectroscopy (XPS) study confirms the presence of different titanium oxide species such as TiO2, TixOy (TiO/Ti2O3/Ti3O5) having different concentrations in TNT formed by different anodization voltage and time along with a minor quantity of Ti metal (Ti0). Formation of sub-oxides results in oxygen defects in TNT. It has also been evidenced from XPS that the anodization voltage and time can change the concentration of oxygen defects on the nanotubes. Due to the formation of oxygen defects, nanotubes have the quasi-metallic and metallic properties. These properties of the nanotubes may facilitate the intracellular delivery by various mechanisms after irradiation of nanosecond pulse laser. Using this technique, we successfully have delivered Propidium iodide (PI) and dextran into HeLa cells (HeLa- human cervical cancer cells) with high transfection efficiency and cell viability on nanotubes formed at 15 V/2 h
Multiscale instabilities of Magnus-Robins effect for compressible flow past rotating cylinder
No full textIn the present research, the instability suffered by flow past a rotating cylinder with very high rotation rates is studied. Special emphasis is given on exploring the effects of compressibility by solving two-dimensional Navier–Stokes equations. The first account of this instability has been provided in “T. K. Sengupta, K. Gupta, and M. T. Nair, “Lift generation and limiting mechanism via unsteady flow development for Magnus-Robins effect,” Proceedings of the 8th Asian Congress of Fluid Mechanics, Shenzhen, China (1999).” Subsequently, there have been other efforts on the same with different numerical models based on incompressible and compressible flow formulation. Apart from the efforts reported by the present group, other reported results did not identify this as a phenomenon of flow instability. The perceived temporal variations of lift and drag by both the incompressible and compressible flow formulation have been correlated with each other, without highlighting the role of compressibility in triggering the flow instability. Here, we report the sensitive dependence of the temporal instability on the accuracy of the simulation for the growth of the disturbance field during the transient monotonic variations of lift and drag. Of specific interest is the role of compressibility in promoting the disturbance growth and limiting the maximum lift that is generated. The compressibility effects have been incorporated by considering lower Mach numbers for the oncoming uniform flow, so that nowhere in the flow field there is the formation of a supersonic pocket
Influence of Ti3AlC2 Ceramic Particles in AZ91 Alloy: Produced by Melt Infiltration Method
No full textThe processing approach and conditions to fabricate AZ91–Ti3AlC2 composites through melt infiltration (MI) were optimized. Ti3AlC2 reinforcement was varied from ~ 30 to ~ 50 vol.%. In the processing approach, AZ91 alloy cubes were spread in Ti3AlC2 powder packing and heated to 600–750 °C at an applied pressure of 0.2–7 MPa, resulting in AZ91–Ti3AlC2 composite. The effect of starting particle size of Ti3AlC2 powder applied pressure, temperature and time to obtain 95% relative density composites was studied. Further, it was demonstrated that the processing parameters differ with the varying Ti3AlC2 vol.%. The effect of reinforcement particle size on distribution within the AZ91 matrix was established. The processing approach is a single step, wherein the preform fabrication process is not required, as reported in the literature. Microhardness, compressive strength and flexural strength of AZ91–50Ti3AlC2 composite were 307 ± 14 HV0.5, 592 ± 13 MPa and 560 ± 9 MPa, respectively
Synthesis, structure, CO oxidation, and H2 production activities of CaCu3−xMnxTi4−xMnxO12 (x = 0, 0.5, and 1.0).
No full textSynthesis of nanocrystalline pristine and Mn-doped calcium copper titanate quadruple perovskites, CaCu3−xMnxTi4−xMnxO12 (x = 0, 0.5, and 1.0) by modified citrate solution combustion method has been reported. Powder X-ray diffraction patterns attest the phase purity of the perovskite materials. Average particle sizes of all the materials obtained from the Scherrer's formula are in the range of 55–70 nm. The specific surface areas for all the perovskites obtained from BET isotherms are found to be low as expected for the condensed oxide systems and fall in the range of 13–17 m2 g−1. Transmission electron microscopy studies show a reduction in particle size of CaCu3Ti4O12 with increase in Mn doping. Ca and Ti are present in +2 and +4 oxidation states in all the materials as demonstrated by X-ray photoelectron spectroscopy analyses. Cu2+ gets reduced in CaCu3Ti4O12 with higher Mn content. Mn is observed to be present only in +3 oxidation state. All the materials have been examined to be active in CO oxidation as well as H2 production from methanol steam reforming. CaCu3Ti4O12 with ~14 at.% Mn is found to show best catalytic activities among these materials. A comprehensive analysis of the catalytic activities of these perovskites toward CO oxidation and H2 production from MSR reveal the cooperative activity of copper-manganese in the doped perovskites and it is more effective at lower manganese content
An experimental study on impact behavior of quasi-isotropic CFRP laminates
No full textThis work was carried out to bring out the differences in drop weight low velocity impact behavior of two quasi-isotropic (QI) laminates. These laminates were made of AS4/914 carbon fiber reinforced plastic (CFRP). The layup sequence chosen was [0/45/-45/90]2S and [0//90/45/-45]2S. Two types of impactors were employed for the impact tests. One is a hemispherical-end and the other is of a conical-end. Coupon level specimens were supported on all four sides during the impact test. The impact energy was calculated for the laminates and the difference, as a comparison, in each case is presented. It has been observed that the layup sequence has a significant effect on the impact resistance of the laminates under hemispherical impactor. In the case of conical impactor, both the laminates were perforated while absorbing similar energy levels
Nanoindentation based fracture studies of ITO coating.
No full textNano-scale load (P) dependency of fracture toughness (K1C) of indium tin oxide (ITO) coating on silicon (Si) substrate is evaluated by nanoindentation based direct and energy methods. A Berkovich triangular diamond nanoindenter is used with nine different P values e.g., 10, 15, 20, 30, 40, 50, 100, 150 and 200 mN. Extensive utilization of both optical microscopy (OM) and field emission scanning electron microscopy (FESEM) techniques reveal that up to P ≤ 40 mN only the sharp radial cracks form from three corners of the nanoindent. However, for P > 40 mN, multiple cracks occur over and above the radial cracks. Finally, at P: 150–200 mN coating gets chipped off from the substrate. The K1C values of the ITO coating are calculated on the basis of both the conventional radial crack length measurement based method and the strain energy release based method. The K1C values are strongly sensitive to variations in P. Further, the strain energy method results in higher magnitudes of the K1C values
Correlation Between Physiological and Performance-Based Metrics to Estimate Pilots' Cognitive Workload
No full textThis paper discusses the utilization of pilots’ physiological indications such as electroencephalographic (EEG) signals, ocular parameters, and pilot performance-based quantitative metrics to estimate cognitive workload. The study aims to derive a non-invasive technique to estimate pilot’s cognitive workload and study their correlation with standard physiological parameters. Initially, we conducted a set of user trials using well-established psychometric tests for evaluating the effectiveness of pupil and gaze-based ocular metrics for estimating cognitive workload at different levels of task
difficulty and lighting conditions. Later, we conducted user trials with the NALSim flight simulator using a business class Learjet aircraft model. We analyzed participants’ ocular parameters, power levels of different EEG frequency bands, and flight parameters for estimating variations in cognitive workload. Results indicate that introduction of
secondary task increases pilot’s cognitive workload significantly. The beta frequency band of EEG, nearest neighborhood index specifying distribution of gaze fixation, L1 Norm of power spectral density of pupil diameter, and the duty cycle metric indicated variations in cognitive workload
High-resolution climate change projection of northeast monsoon rainfall over peninsular India
No full textIn this study, projected changes in mean northeast monsoon (NEM) rainfall and associated extreme rainfall and temperature events, over peninsular India (PI) and its six subdivisions, are quantified. High-resolution dynamically downscaled simulations of the Weather Research and Forecasting (WRF) regional climate model driven by the boundary conditions from the Community Climate System Model version 4 (CCSM4) model (WRF-CCSM4) are compared with statistically downscaled simulations of NASA Earth Exchange Global Daily Downscaled Projections (NEX-GDDP). Over PI, these downscaled simulations show low bias in mean NEM rainfall (≤ − 0.44 mm·day−1) and high pattern correlation coefficient (≥0.75), giving confidence in their future projections. Under future warming over PI, both downscaled simulations project future significant enhancement in NEM rainfall with WRF-CCSM4 projecting 1.98 mm·day−1 (83.78% change with respect to the present-day mean) whereas the multimodel ensemble (MME) of eight NEX-GDDP models project 0.67 ± 0.58 mm·day−1 (19.78%) by the midddle of the century and 1.42 ± 0.97 mm·day−1 (42.76%) by the end of the century. Analysis of extreme rainfall events shows that WRF-CCSM4 projects future enhancement (reduction) in extreme rainfall (R95p) days over 91.4% (8.6%) of grid-points over PI. In future, coastal areas of Karnataka and Andhra Pradesh will likely experience increased extreme rainfall occurrence by more than 25 days and 15–20 days respectively. Projected future enhancement in the mean and extreme NEM rainfall is attributed to the increased precipitable water under a warming climate. Future projection of extreme temperature indices shows an increase in minimum and maximum temperatures over PI during the NEM season. Over PI, future winter nights and days are found to be warmer than those in the present day and the temperature change in future winter nights is found to be larger than that in winter days. This climate change information would help decision-makers in evaluating existing policies and devising revised policies to reduce risk due to climate change
A non-iterative design for aileron to rudder interconnect gain
No full textAileron to Rudder Interconnect (ARI) gain is implemented on most fighter aircraft, primarily to reduce the side slip produced due to adverse yaw from pilot lateral control stick input and to improve the turn rate response. A systematic and non-iterative design procedure for ARI gain is proposed herein based on the evaluation of a transfer function magnitude at the aircraft roll mode frequency. The simplicity of the proposed method makes it useful for real-time flight control law reconfiguration in situations where the aileron control authority is diminished due to damage. This is demonstrated by a simulation example considering an aileron surface damage scenario
Effect of Reynolds Number on Typical Civil Transport Aircraft
No full textReynolds Averaged Navier–Stokes (RANS) simulations have been performed over a civil transport aircraft at Mach number 0.17. The present work aims to understand the effect of various Reynolds number on the aerodynamic performance of aircraft since the Reynolds number is considered as a most important parameter in fluid dynamics. The current study also helps to identify the various hot spots for higher drag so that the design team can focus on these specific areas to minimise the total drag. The present CFD solver uses a Roe scheme for convective flux discretisation and Spallart-Allmaras turbulence model for eddy viscosity computations. Calculations showed that with an increase in Reynolds number, the maximum lift coefficient increases and minimum drag coefficient decreases. The paper also highlights the sectional Cp plots and pressure contours along with the velocity streamlines at different span-wise stations of an aircraft wing. The strength of vortex over a midboard flap gradually decreases with the increase in Reynolds number. The drag of various aircraft components is also shown in the form of Pie chart so that the major drag contributing parts can be identified