ANALYSIS OF RELIABILITY AND CONDUCTION MECHANISMS IN EMBEDDED PLANAR CAPACITORS

An embedded planar capacitor is a thin laminate embedded in a multilayered printed wiring board (PWB) that functions both as a power-ground plane and as a parallel plate capacitor. The capacitor laminate consists of a dielectric material (epoxy-BaTiO3 composite dielectric is widely used) sandwiched between two Cu layers. These capacitors have gained importance with an increase in the operating frequency and a decrease in the supply voltage in electronic circuits since it can lead to PWB miniaturization. Further, the use of embedded planar capacitor leads to better electrical performance of the PWB. Although embedded planar capacitors have various advantages there are some issues such as lack of reliability information and a high leakage current in the epoxy-BaTiO3 composite dielectric. This dissertation aims in investigating these issues that needs to be investigated for wide scale commercialization of these capacitors. The reliability of embedded planar capacitors is critical since these capacitors are not reworkable and its failure can lead to PWB failure. In this work the reliability of an embedded planar capacitor (with epoxy-BaTiO3 composite dielectric) is investigated under environmental stress conditions in the presence of an applied bias. Temperature-humidity-bias (THB) tests and highly accelerated life test (HALT) was performed at multiple stress levels to investigate the reliability under these conditions. The failure modes and mechanisms during THB and HALT are investigated. Further, during HALT the life time is also modeled using the Prokopowicz model and regression of the in-situ capacitor data. The loading of BaTiO3 in the epoxy-BaTiO3 composite dielectric should be as high as possible (until the theoretical maximum packing density is achieved) to maximize the effective dielectric constant of the composite. But as the loading of BaTiO3 in the composite dielectric increases, the undesirable leakage current also increases. The mechanism of current conduction in this composite dielectric is investigated in this work. The effect of various factors such as BaTiO3 loading, BaTiO3 particle diameter, temperature, and voltage on the resulting leakage current has been modeled. Measurements of leakage current were performed on embedded capacitors with varying BaTiO3 loading and varying particle diameters over a range of temperature and voltage. The consistence of the leakage current data with standard conduction models is compared to investigate the conduction mechanism

Systems Biology of Immunomodulation for Post-Stroke Neuroplasticity: Multimodal Implications of Pharmacotherapy and Neurorehabilitation.

AIMS: Recent studies indicate that anti-inflammatory drugs, act as a double-edged sword, not only exacerbating secondary brain injury but also contributing to neurological recovery after stroke. Our aim is to explore whether there is a beneficial role for neuroprotection and functional recovery using anti-inflammatory drug along with neurorehabilitation therapy using transcranial direct current stimulation (tDCS) and repetitive transcranial magnetic stimulation (rTMS), so as to improve functional recovery after ischemic stroke. METHODS: We develop a computational systems biology approach from preclinical data, using ordinary differential equations, to study the behavior of both phenotypes of microglia, such as M1 type (pro-inflammatory) vis-à-vis M2 type (anti-inflammatory) under anti-inflammatory drug action (minocycline). We explore whether pharmacological treatment along with cerebral stimulation using tDCS and rTMS is beneficial or not. We utilize the systems pathway analysis of minocycline in nuclear factor kappa beta (NF-κB) signaling and neurorehabilitation therapy using tDCS and rTMS that act through brain-derived neurotrophic factor (BDNF) and tropomyosin-related kinase B (TrkB) signaling pathways. RESULTS: We demarcate the role of neuroinflammation and immunomodulation in post-stroke recovery, under minocycline activated-microglia and neuroprotection together with improved neurogenesis, synaptogenesis, and functional recovery under the action of rTMS or tDCS. We elucidate the feasibility of utilizing rTMS/tDCS to increase neuroprotection across the reperfusion stage during minocycline administration. We delineate that the signaling pathways of minocycline by modulation of inflammatory genes in NF-κB and proteins activated by tDCS and rTMS through BDNF, TrkB, and calmodulin kinase (CaMK) signaling. Utilizing systems biology approach, we show that the activation pathways for pharmacotherapy (minocycline) and neurorehabilitation (rTMS applied to ipsilesional cortex and tDCS) results into increased neuronal and synaptic activity that commonly occur through activation of N-methyl-d-aspartate receptors. We construe that considerable additive neuroprotection effect would be obtained and delayed reperfusion injury can be remedied, if one uses multimodal intervention of minocycline together with tDCS and rTMS. CONCLUSION: Additive beneficial effect is, thus, noticed for pharmacotherapy along with neurorehabilitation therapy, by maneuvering the dynamics of immunomodulation using anti-inflammatory drug and cerebral stimulation for augmenting the functional recovery after stroke, which may engender clinical applicability for enhancing plasticity, rehabilitation, and neurorestoration

Microwave-assisted green synthesis and antimicrobial activity of silver nanoparticles derived from a supercritical carbon dioxide extract of the fresh aerial parts of Phyllanthus niruri L

Purpose: To synthesize and evaluate the antimicrobial activity of silver nanoparticles (AgNPs) derived from a supercritical carbon dioxide extract of the fresh aerial parts of Phyllanthus niruri. Methods: The synthesis of AgNPs of a P. niruri extract was carried out in a microwave oven. The extraction was carried out using a supercritical fluid extractor. The AgNPs were characterized by the Ultraviolet-visible (UV-vis) spectral analysis, Dynamic Light Scattering (DLS) zetasizer analysis, Transmission electron microscopy (TEM), X-ray diffraction (XRD) analysis and Fourier transform infrared (FT-IR) spectroscopy. The antimicrobial assays of AgNPs were carried out against different bacterial and fungal strains. Results: Results of various analytical techniques confirmed the synthesis of AgNPs of a P. niruri extract. The UV–vis spectroscopy showed an intense silver surface plasmon resonance band at 415 NM. The AgNPs had a mean size of 110 nm in the Zetasizer analysis. TEM images illustrated spherical AgNPs having a mean particle size of 110 nm. The X-ray diffractograms showed peaks at 38.17°, 44.28°, and 64.52°. The average crystallite size of Ag-NPs was found to be 110 nm. FT-IR spectra confirmed the stability of the AgNPs. The AgNPs demonstrated good antimicrobial effects against several tested pathogenic microbes. Conclusion: An efficiently synthesized AgNPs of P. niruri (SC-CO2) extract has been prepared by a simple, eco-friendly, cost-effective, rapid green chemistry methodology. The AgNPs of P. niruri extract possesses significant antimicrobial properties against the tested bacterial and fungal strains. Keywords: Nanoparticles, Phyllanthus niruri, Supercritical fluid extraction, Microwave, Antimicrobial activit

Study of intraocular pressure among individuals working on computer screens for long hours: Effect of exposure to computer screens on IOP

In today’s world computers are ubiquitous and found in different forms which can effect intraocular pressure (IOP). Present study was undertaken to find out effect of day-to-day exposure to computer screen on IOP in normal individuals. 70 individuals (who met the screening conditions and devoid of obvious ocular pathology and systemic diseases) had their IOP’s checked before and 4 hour after computer session on same day, all working in general day shift, involving reading English printed material. The results showed significant (p<0.005) increase with IOP values before exposure being 17.89±3.25 and 16.99±2.84 and after exposure being 19.67±3.4 and 18.70±2.4 in left and right eye respectively. Increase in IOP was noted in 70% and 67% individuals in left and right eye. Differences in IOP of right and left eye may be due to dominance of eye or direction of script from left to right

Turbulence model selection for low Reynolds number flows

One of the major flow phenomena associated with low Reynolds number flow is the formation of separation bubbles on an airfoil’s surface. NACA4415 airfoil is commonly used in wind turbines and UAV applications. The stall characteristics are gradual compared to thin airfoils. The primary criterion set for this work is the capture of laminar separation bubble. Flow is simulated for a Reynolds number of 120,000. The numerical analysis carried out shows the advantages and disadvantages of a few turbulence models. The turbulence models tested were: one equation Spallart Allmars (S-A), two equation SST K-ω, three equation Intermittency (γ) SST, k-kl-ω and finally, the four equation transition γ-Reθ SST. However, the variation in flow physics differs between these turbulence models. Procedure to establish the accuracy of the simulation, in accord with previous experimental results, has been discussed in detail

Flapping membrane wing: a prediction towards inter-domain flight

The purpose of this research is to gain initial knowledge and to predict the sustainability of an all-weather Micro-Aerial-Vehicle (MAV). The observed parameters are: the maximum coefficient of lift, CL and the changes in CL after impact, the fluctuation of CL upon entering simulated rain environment, and length of stability recovery in terms of time and flapping cycle, t and t/T, at flapping frequencies of 8, 16, and 24 Hz, at t/T = 3/8 and 7/8. At 24 Hz, the increase in peak CL value after impact of entering rain environment is 0.59. The average fluctuations in CL occurred when entering the rain environment are 410.263. The stability recovery time recorded is 0.006 seconds. Small birds (especially hummingbirds) have a very high flapping frequency that enables them to efficiently withstand external disturbances caused by nature and to instantly adapt to new environments

Exploring Rapid Photocatalytic Degradation of Organic Pollutants with Porous CuO Nanosheets: Synthesis, Dye Removal, and Kinetic Studies at Room Temperature

In this work, we report the facile, environmentally friendly, room-temperature (RT) synthesis of porous CuO nanosheets and their application as a photocatalyst to degrade an organic pollutant/food dye using NaBH4 as the reducing agent in an aqueous medium. Ultrahigh-resolution field effect scanning electron microscopy images of CuO displayed a broken nanosheet-like (a length of ∼160 nm, a width of ∼65 nm) morphology, and the lattice strain was estimated to be ∼1.24 × 10-3 using the Williamson-Hall analysis of X-ray diffraction plots. Owing to the strong quantum size confinement effect, CuO nanosheets resulted in an optical energy band gap of ∼1.92 eV, measured using Tauc plots of the ultraviolet-visible (UV-vis) spectrum, resulting in excellent photocatalytic efficiency. The RT synthesized CuO catalyst showed a high Brunauer-Emmet-Teller surface area of 30.88 ± 0.2313 m2/g (a correlation coefficient of 0.99972) with an average Barrett-Joyner-Halenda pore size of ∼20.385 nm. The obtained porous CuO nanosheets exhibited a high crystallinity of 73.5% with a crystallite size of ∼12 nm and was applied as an efficient photocatalyst for degradation of the organic pollutant/food dye, Allura Red AC (AR) dye, as monitored by UV-vis spectrophotometric analysis and evidenced by a color change from red to colorless. From UV-vis spectra, CuO nanosheets exhibited an efficient and ultrafast photocatalytic degradation efficiency of ∼96.99% for the AR dye in an aqueous medium within 6 min at RT. According to the Langmuir-Hinshelwood model, photodegradation reaction kinetics followed a pseudo-first-order reaction with a rate constant of k = 0.524 min-1 and a half-life (t1/2) of 2.5 min for AR dye degradation in the aqueous medium. The CuO nanosheets showed an outstanding recycling ability for AR degradation and would be highly favorable and an efficient catalyst due to the synergistic effect of high adsorption capability and photodegradation of the food dye. © 2021 The Authors. Published by American Chemical Society1