Silica gel modified carbon paste electrode for electrochemical detection of insulin

A silica gel-modified carbon paste electrode (Si-CPE) was fabricated and used for selective and sensitive determination of insulin. The experimental results suggested that insulin effectively accumulated on surface of the modified electrode resulting in a marked enhancement of its oxidation current response. Therefore, the modified electrode was used as an electrochemical sensor for the differential pulse adsorptive stripping voltammetric and hydrodynamic amperometric determination of insulin. The influence of various experimental parameters on the voltammetric response of insulin was investigated. Using hydrodynamic amperometry, under optimum conditions, calibration plot for insulin was linear in the range of 90–1400 pM. The sensitivity and detection limit of the proposed amperometric method were found to be 107.3 pA/pM (1511.3 pA/pM cm²) and 36 pM, respectively. The electrode has the remarkable advantages of simple preparation using inexpensive material, high reproducibility, good chemical and mechanical stabilities, and easy surface renewal owing to bulk modification. The high selectivity of the modified electrode towards oxidation of insulin in the presence of sulfur containing amino acids including cystine, cysteine, and glutathione is a key advantage of the proposed electrode.     

Omniphobic surfaces: state-of-the-art and future perspectives

Limited oleophobicity of the Lotus-inspired superhydrophobic surfaces accompanied by low stability and self-healing inability, have led to the evolution of synthetic omniphobic surfaces that repels a variety of liquids. This review summarized recently developed concepts for preparation of such surfaces, based on engineering the surface properties. Future challenges and perspectives for this growing field of research have also been addresses.     

Microstructural,optical, and electrical characteristics of Ni/C doped BST thin films

In the present work the effect of simultaneous doping of carbon and nickel on the microstructural, optical, and electrical properties of barium strontium titanate (BST) is investigated. Thin films of BST were prepared by the sol-gel method in six different compositions ((Ba_0.6Sr_0.4)(Ni_xC_yTi_1-x-y)O₃): x?=?y?=?0.00 (BST), x?=?0.04?y?=?0.00 (BST4N), x?=?0.04?y?=?0.01 (BST4N-1C), x?=?0.04?y?=?0.02 (BST4N-2C), x?=?0.04?y?=?0.03 (BST4N-3C), and x?=?y?=?0.04 (BST4N-4C). Structural features and chemical bonds of the films were studied by TGA/DSC, XRD, FT-IR, and FE-SEM. The electrical and optical properties of the films were analysed by impedance spectroscopy and UV–VIS spectroscopy. The results show that addition of Ni and C leads to Ti⁴⁺-Ni²⁺ and Ti⁴⁺-C⁴⁺ replacements, respectively. These replacements lead to a gradual increase in the band gap energy; from 3.15?eV for BST to 3.44, 3.5, 3.66, 3.73 and 3.76?eV for BST4N, BST4N-1C, BST4N-2C, BST4N-3C, and BST4N-4C, respectively. In contrast, the dielectric loss decreases significantly from 0.055 for BST to 0.031, 0.033, 0.03, 0.022 and 0.01 for BST4N, BST4N-1C, BST4N-2C, BST4N-3C, and BST4N-4C, respectively. At the same time, the quality factor Q_f (1/ tanδ) increases substantially from 15 for BST to 32, 30, 33, 44 and 87 for BST4N, BST4N-1C, BST4N-2C, BST4N-3C, and BST4N-4C, respectively. In contrast, the frequency dependence of the capacity decreases in comparison to un-doped BST. Among all films, the BST4N-4C had the highest figure of merit (FOM), least dielectric loss, and very low frequency-dependence, making it the best candidate for tuneable device applications.     

Modeling of nonlinear extensional and shear rheology of low-viscosity polymer melts

The hierarchical multi-mode molecular stress function (HMMSF) model developed by Narimissa and Wagner [Rheol. Acta 54, 779–791 (2015), and J. Rheol. 60, 625–636 (2016)] for linear and long-chain branched (LCB) polymer melts were used to analyze the set of transient elongational and shear viscosity data of two LCB low-density polyethylenes (1840H and 2426 k), and a linear poly-(ethylene-co-α-butene), PEB A-780090 as reported by [Li et al. J. Rheol. 64, 177 (2020)], who had developed a new horizontal extensional rheometer to extend the lower limits of elongational viscosity measurements of polymer melts. Comparison between model predictions and elongational stress growth data reveals excellent agreement within the experimental window, and good consistency with shear stress growth data, based exclusively on the linear-viscoelastic relaxation spectrum and only two nonlinear model parameters, the dilution modulus G_D for extensional flows, and in addition a constraint release parameter for shear flow.     

Study of graphene device electronic properties with horizontal and vertical double vacancy defects

Abstract

Graphene device electronic properties with double vacancy (DV) defects for two cases, along the direction and perpendicular to the current pathways graphene device, were investigated by using the first principles calculations in combination with density functional theory. The bond lengths, density of states, transmission probability, and current-voltage curves are computed. For relaxed pristine graphene the bond length is around 1.43?Å. However, the bond lengths near the defects for relaxed graphene for DV case are modified to 1.40-1.49?Å. It is also observed that I???V graph is nonlinear based on the current-voltage curve of graphene device which contain DV defects. Furthermore, it has been shown that having the DV defects lead to reduce the current relative to the case of perfect graphene device. Moreover, we noted that when the voltage is increased from zero to one volt new peaks are created near Fermi level in the transmission spectrum graphs. In addition, we noted that the current for the vertical DV defect is smaller than the pristine and horizontal DV device because the number of blocked electrons current pathways in vertical DV defect is larger than the two other cases, namely the pristine and horizontal DV defect cases The obtained results can be useful for the construction of new nanoelectronic devices and may have practical applications.     

A novel zero dead zone PFD and efficient CP for PLL applications

This paper presents a high dynamic range programmable gain amplifier (PGA) with linear-in-dB and digital to analog converter (DAC) gain control using a BiCMOS process. The proposed PGA is composed of a folded Gilbert variable gain amplifier cell, a DC offset cancellation circuitry, two inductorless fixed gain amplifiers with bandwidth extension, a symmetrical exponential voltage generator, a novel buffer amplifier with active inductive peaking for testing purposes and a 10 bit R-2R DAC. The linear-in-dB and DAC gain control scheme facilitate the analog baseband gain tuning accuracy and stability, which also provides an efficient way for digital baseband automatic gain control. The PGA chip is fabricated using 0.13 μm SiGe BiCMOS technology. With a power consumption of 80 mA@1.2 V supply voltage, the fabricated circuit exhibits a tunable gain range of ? 30–27 dB (DAC linear gain step guaranteed), a 3 dB bandwidth of around 3.5 GHz and a gain resolution of better than 0.07 dB.     

UV‐Light‐Driven Oxygen Pumping in a High‐Temperature Solid Oxide Photoelectrochemical Cell

A solid‐state photoelectrochemical cell is operated between 400 and 500 °C under 365 nm UV light. The cell consists of a photovoltaic part, based on a La_0.8Sr_0.2CrO₃/SrTiO₃ junction, and an electrochemical part including a zirconia solid electrolyte with a shared (La,Sr)FeO₃ electrode. The photovoltaic cell part leads to open circuit voltages up to 920 mV at 400 °C. Upon UV light, this driving force is used in the electrochemical part of the cell to pump oxygen from low to high partial pressures, i.e., to convert radiation energy to chemical energy. This demonstrates the feasibility of high‐temperature photoelectrochemical cells for solar energy storage. The detailed characterization of the different resistance contributions in the system by DC and AC methods reveals the parts of the cell to be optimized for finally achieving high‐temperature photoelectrochemical water splitting.     

An Evolutionary Game-Theoretic Approach for Base Station Allocation in Wireless Femtocell Networks

Wireless Personal Communications - A set of moving nodes communicating with each other without any infrastructure is considered a mobile ad hoc network (MANET). Stability is a big problem with this...