Progressive NO2 Sensors with Rapid Alarm and Persistent Memory-Type Responses for Wide-Range Sensing Using Antimony Triselenide Nanoflakes

Antimony triselenide (Sb₂Se₃) nanoflake-based nitrogen dioxide (NO₂) sensors exhibit a progressive bifunctional gas-sensing performance, with a rapid alarm for hazardous highly concentrated gases, and an advanced memory-type function for low-concentration (<1 ppm) monitoring repeated under potentially fatal exposure. Rectangular and cuboid shaped Sb₂Se₃ nanoflakes, comprising van der Waals planes with large surface areas and covalent bond planes with small areas, can rapidly detect a wide range of NO₂ gas concentrations from 0.1 to 100 ppm. These Sb₂Se₃ nanoflakes are found to be suitable for physisorption-based gas sensing owing to their anisotropic quasi-2D crystal structure with extremely enlarged van der Waals planes, where they are humidity-insensitive and consequently exhibit an extremely stable baseline current. The Sb₂Se₃ nanoflake sensor exhibits a room-temperature/low-voltage operation, which is noticeable owing to its low energy consumption and rapid response even under a NO₂ gas flow of only 1 ppm. As a result, the Sb₂Se₃ nanoflake sensor is suitable for the development of a rapid alarm system. Furthermore, the persistent gas-sensing conductivity of the sensor with a slow decaying current can enable the development of a progressive memory-type sensor that retains the previous signal under irregular gas injection at low concentrations.     

Benchmarks of simple, generic, shaped plates for validation oflow-frequency electromagnetic computational codes

The validation of low-frequency measurements and electromagnetic (EM) scattering computations for several simple, generic shapes, such as an equilateral-triangular plate, an equilateral-triangular plate with a concentric equilateral-triangular hole, and diamond- and hexagonal-shaped plates, is discussed. The plates were constructed from a thin aluminium sheet with a thickness of 0.08 cm. EM scattering by the planar plates was measured in the experimental test range (ETR) facility of NASA Langley Research Center. The dimensions of the plates were selected such that, over the frequency range of interest, the dimensions were in the range of λ₀ to 3λ₀. In addition, the triangular plate with a triangular hole was selected to study internal-hole resonances     

The effect of biphasic waveform tilt in transvenous atrial defibrillation

Atrial defibrillation can be accomplished using low energy shocks and transvenous catheters. The biphasic waveform tilt required to achieve optimal atrial defibrillation thresholds (ADFTs) is, however, not known. The effect of single capacitor biphasic waveform tilt modification on ADFT was assessed in 20 patients. Following AF induction the defibrillation pulses were delivered between the catheters positioned in the coronary sinus and the right atrium. The single capacitor biphasic waveform shocks, delivered over the same pathways, consisted of 65% tilt (65/65 biphasic waveform) to produce an overall tilt of 88%, or 50% tilt (50/50 biphasic waveform) to produce an overall tilt of 75%. Although 65/65 biphasic waveform delivers more energy, the shorter duration 50/50 biphasic waveform reduced stored energy ADFT 21%, from 1.34 +/- 0.82 J with 65/65 biphasic to 1.06 +/- 0.81 J. These differences were not statistically significant. Nine patients had lower ADFT with 50/50 biphasic waveform while five patients had lower ADFT with 65/65 biphasic waveform. Equivalent reduction in ADFT was seen in the remaining six patients. The ADFT was 0.83 +/- 0.65 J when both tilts were considered. In conclusion, biphasic waveform tilt modification may affect the ADFT in an individual patient. The optimal biphasic waveform for ADFT is not known.     

Fast RCS computation over a frequency band using method of momentsin conjunction with asymptotic waveform evaluation technique

The method of moments (MoM) in conjunction with the asymptotic waveform evaluation (AWE) technique is applied to obtain the radar cross section (RCS) of an arbitrarily shaped three-dimensional (3-D) perfect electric conductor (PEC) body over a frequency band. The electric field integral equation (EFIE) is solved using the MoM to obtain the equivalent surface current on the PEC body. In the AWE technique, the equivalent surface current is expanded in a Taylor's series around a frequency in the desired frequency band. The Taylor series coefficients are then matched via the Pade approximation to a rational function. Using the rational function, the surface current is obtained at any frequency within the frequency range, which is in turn used to calculate the RCS of the 3-D PEC body. A rational function approximation is also obtained using the model-based parameter estimation (MBPE) method and compared with the Pade approximation. Numerical results for a square plate, a cube, and a sphere are presented over a frequency bandwidth. Good agreement between the AWE and the exact solution over the bandwidth is observed     

The influence of charge density and steric factor of aminated chloromethyl polystyrene homologs in bilirubin adsorption

Bilirubin, a bile pigment, was studied for its extent of adsorption on substituted aminechloromethyl polystyrene by UV spectrophotometry. By performing simple displacement reactions on chloromethyl polystyrene with secondary and tertiary amines, the amount of charge density and steric factor on substituted nitrogen atom have been varied. Adsorption isotherms of bilirubin at 0°C by different amine–chloromethyl polystyrene homologs suggest the existence of electrostatic interaction of polymeric resin with bilirubin moiety. Results of adsorption of bilirubin to polymeric resin have shown that the extent of adsorption of bilirubin depends on the unit charge, and on the structure of the substituted amine–chloromethyl polystyrene. The effects of porosity of resin on bilirubin adsorption have also been discussed.     

Kinetics of hydroformylation of 1-decene using homogeneous HRh(CO)(PPh3)3 catalyst: a molecular level approach

The kinetics of hydroformylation of 1-decene using homogenous HRh(CO)(PPh₃)₃ catalyst has been reported in the temperature range of 50–70 °C. The effect of catalyst,P _{H 2},P _CO, and 1-decene concentration on the rate of hydroformylation has been studied. Based on the analysis of initial rate data, a rate equation has been proposed and kinetic parameters evaluated. The activation energy was found to be 11.76 kcal/mol. A molecular level approach to kinetic modelling has also been illustrated. The rate equation derived assuming oxidative addition of H₂ as a rate determining step, has been found to represent the data satisfactorily. The rate parameters for the mechanistic model have been evaluated for the data at 60 °C.NCL Communication No. 5735.     

A new characteristic of liquid-liquid systems—inversion holdup of intensely agitated dispersions

As the holdup of dispersed phase in an agitated liquid-liquid dispersion is increased at fixed agitation, a point is reached (called inversion holdup) when the dispersion inverts—the dispersed phase becomes continuous and vice versa. In this work, we present experimental data which suggest that the inversion holdup for sufficiently intense turbulence is independent of all the operational parameters associated with a stirred tank, e.g., stirrer speed, vessel volume, impeller size, and impeller type; it depends only on the properties of the liquid-liquid system. The inversion holdup was verified to remain unchanged even for inversion in turbulent flow field in the annular space between two coaxial cylinders. A hypothesis involving drops in near contact with each other at high holdups is used to explain the experimental data. The new finding may also provide a qualitative basis for selecting a liquid-liquid system with desired extent of mixing in the dispersed phase for carrying out transport and reactions in multiphase systems.     

Polypropylene/Clay nanocomposites: Effect of compatibilizer on the thermal,crystallization and dynamic mechanical behavior

Polypropylene (PP)/clay nanocomposites are prepared using different grades of PP, compatibilizers, and organically modified clays. The melt intercalation of the PP is carried out in presence of a compatibilizer. The nanocomposites are characterized using various techniques for the structure and properties. X‐ray diffraction results indicate well‐defined structures. Thermogravimetric analysis indicates improved thermal stability of PP/clay nanocomposites. Isothermal crystallization studies carried out using differential scanning calorimeter illustrate enhanced crystallization of PP in all the nanocomposites. Optical microscopic study demonstrates that the nanocomposites can be crystallized at higher temperatures, exhibiting well‐defined birefringent structures. The dynamic mechanical analysis reveals higher storage moduli over a temperature range of ?40⁰C to 120⁰C for nanocomposites, and the extent of increase in the storage modulus is dependent on the type of compatibilizer used.     

Thermal behavior of cast polyurethane elastomers

Thermal properties like glass transition temperature (T_g), initial decomposition temperature (idt), integral procedural decomposition temperature (ipdt), and temperature at various % weight loss of a number of polyurethane systems are reported in this paper. Glass transition temperature was determined on TMA, and other thermal properties were determined by thermogravimetry. The experiments were designed to understand various factors such as length of chain extender moiety, flexibility of chain extender units by substitution of ether link in the diol chain, nature of bonds (unsaturation) in the extender unit, and nature of diisocyanates.