A comparison of charge transport behavior in functionalized and non-functionalized poly 3,4-(ethylenedioxythiophene) films

Poly 3,4-(ethylenedioxythiophene) (PEDOT) films electropolymerized from an aqueous micellar solution containing sodium dioctyl sulfosuccinate and the monomer were functionalized with 1-fluoro-2-nitro-4-azidobenzene (FNAB) molecules by a photochemical nitrene insertion reaction. The variation in redox activity and the changes in the charge transfer and diffusion (through bulk) behavior of the functionalized and the non-functionalized PEDOT films have been followed by electrochemical impedance spectroscopy and cyclic voltammetry. While the functionalized film allows a reversible insertion and extraction of guest cations and anions, the non-functionalized film is capable of exchanging only anions. The higher level of oxidation attained in the functionalized film is also reflected in the longer diffusion length (l_D) observed for the ions in this film. In both films the barrier to charge transfer is resistive rather than capacitive. Both charge transfer and diffusion resistance (R_CT and R_D) are lower for the functionalized film, a consequence of a higher surface roughness and a more nodular morphology and therefore higher optical contrast and faster color-bleach kinetics are achieved in this film. For the functionalized and the non-functionalized films, both R_CT and R_D are greatly enhanced during reduction than for oxidation. In particular, in the low frequency regime, the hindered diffusion-controlled extraction of anions from the bulk of the film is also evident from the larger R_D as compared to R_CT and the difference in their magnitudes is more pronounced for the functionalized film thus confirming that functionalization is a useful method for controlling the redox response of conducting polymer films.     

Comparative studies on physico-chemical characterization of yeast cells entrapped with alginate and hybrid beads

Natural polymers used as carrier materials in immobilization technology have the advantage of being non-toxic, biocompatible and biodegradable. In the present investigation, immobilization of yeast cells using different polymers has been carried out and the properties such as morphological, hardening, thermal stability and characterization of functional groups of alginate and hybrid beads (alginate–carrageenan and alginate–xanthan gum) have been studied by different techniques such as scanning electron microscope, texture analyzer, differential scanning calorimetry, and Fourier transfer infrared spectroscopy. The swelling behavior in terms of pH variation as well as flow properties of alginate and hybrid beads has also been examined. The hybrid beads prepared from alginate and carrageenan were found to be the best in terms of strength, cell holding capacity, pH and thermal stability. The reusability of beads was also studied in terms of enzyme activity of the entrapped yeast cells. The beads prepared by alginate–carrageenan were found to be more stable than alginate and alginate–xanthan beads. The yeast cells entrapped in alginate–carrageenan beads showed no significant decrease in enzyme activity up to seven batches. Thus, alginate–carrageenan beads can be used as a polymeric carrier/support to develop a stable and long-term immobilized cell system, which indicates its high potential for commercial applications in food and pharmaceutical sector.     

Differential Modulation of S1PR(1–5) and Specific Activities of SphK and nSMase in Pulmonary and Cerebral Tissues of Rats Exposed to Hypobaric Hypoxia

Recent preclinical and clinical studies have unfolded the potential of pharmacological modulation of activities of sphingosine‐1‐phosphate (S1P) receptors and S1P metabolizing enzymes for the development of therapeutic interventions against a variety of pathologies. An understanding of differential and temporal effects of hypoxia exposure on the key components of S1P signalling would certainly aid in designing improved drug development strategies in this direction. In view of this, the aim of the present study was to assess the effect of progressive hypobaric hypoxia exposure on expression of S1P receptors (S1PR_1–5) and specific activities of S1P synthesizing enzymes—neutral sphingomyelinase (nSMase) and sphingosine kinase (Sphk) in pulmonary and cerebral tissues of rats exposed to simulated altitude of 21,000 feet in an animal decompression chamber. Along with this, development of cerebral and pulmonary edema and markers of inflammation were studied at 12, 24, and 48 h to validate our study model of hypobaric hypoxia‐induced stress. The protein expression of S1PR_1–5 and activities of Sphk and nSMase enzymes were observed to be dramatically affected by simulated hypobaric hypoxia exposure, concurrent with deterioration of pathology, with 12 h of exposure appearing to be the most critical of the various time points studied.     

Environmentally sustainable composite resistors with low temperature coefficient of resistance

Temperature coefficient of resistance (TCR) of thick film resistors are based on fired conducting grains and glass composites. Many analog sensor and control circuits require low (<100 ppm/°C) TCR value. To prepare resistors with low TCR value, knowledge of processing conditions and conduction mechanism parameters are of particular importance because TCR is finalised during firing and cannot be trimmed in the latter stage to a target value as resistors can be. This paper reports the preparation and properties such as microstructural and electrical in particular to sheet resistance, TCR (hot and cold) of eco-friendly composite resistor paste compositions. Our resistor compositions showed the sheet resistance in the range of 1.18–1.38 KΩ/□ and the hot and cold TCR of the compositions reduced substantially from 360 to 100 ppm/°C and 175 to 60 ppm/°C with the addition of TCR modifier.     

Noise considerations for a tunnel diode integrated rectangular patch antenna

The tunnel diode integrated rectangular patch antenna is investigated, with emphasis mainly on noise considerations. Noise power is calculated and is found to increase very slightly with frequency for both GaAs and Ge tunnel diode loaded patches. Noise figure and noise temperature also increase with frequency for GaAs and Ge tunnel diode loaded patches. Loading the patch with the tunnel diode increases the effective noise figure and effective noise temperature of the patch, degrading the performance of the communication system significantly.     

Controlling the assembly of hydrophobized gold nanoparticles at the air-water interface by varying the interfacial tension

Controlled assembly is the key to harness the nanoscale properties of nanoparticles in most technological applications and it has been an important challenge as it leads to the manipulation of interparticle properties. The present work depicts the control of the assembly of nanoparticles in the monolayers by evaporation kinetics and particle interactions at the air-liquid interface. In the presence of attractive particle-particle and particle-monolayers interactions, nanoparticles self assemble into a superlattice structure upon drying from a colloidal suspension on to the preformed lipid monolayers. This self-assembly mechanism produces monolayers with long-range ordering. However, rapid dewetting and high rate of evaporation can significantly undermine the extent of ordering. Using gold nanoparticles as vehicles for experimentation and by changing the monolayers and solvent, we here demonstrate that the extent of ordering of nanoparticles can be controlled.     

Synthesis of Ag-Au bimetallic film at liquid-liquid interface and its application in vapor sensing

We demonstrate a novel process for preparing densely packed film of silver nanoparticles at the liquid-liquid interface followed by a transmetallation reaction with gold ion to yield a film of bimetallic nanoparticles. Films of assembled silver as well as Ag-Au bimetallic were characterized by UV-vis-spectroscopy, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) analysis. I-V measurement shows linear behavior for both the films with ca. five orders of magnitude drop in resistance for the Ag-Au bimetallic film. Temperature dependent I-V measurement revealed a semiconductor to metal transition after transmetallation reaction. The films where checked for their potential application in chemical vapor sensing to ammonia vapors.     

Characterization of transition metal oxide ceramic material for continuous thermocouple and its use as NTC fire wire sensor

The ceramic powder prepared from the mixture of Mn₃O₄ and La₂O₃ have been characterized for NTC behavior and the same have been used as CT²C (continuous thermocouple) sensor in the form of a thin metal cable to detect over-heating. These materials have mega ohm resistance at room temperature and showed exponential drop in resistance with the rise in temperature over a temperature range of 100–400 °C. It has been observed that as the concentration of La₂O₃ increases from 0 to 10% the NTC behavior drops from (400–260 °C) ±10%. The material was pressed into pellets and sintered at 700 °C for 3 h resulting in good bonding strength. Electrical characterization of the material was done by measuring the resistance over a temperature range of 100–400 °C. The material showed reproducible NTC characteristics over the temperature range 400, 370, 340, 280, and 260 °C with decreasing thermistor constant values (B = 9588, 9210, 8500, 5170, 3330 K⁻¹) and activation energy (ΔE = 826, 794, 733, 445, 287 meV), respectively. The decrease in activation energy of the ceramic powder with increase in La₂O₃ concentration makes it possible to fabricate thermal sensors which can be used in different temperature ranges. The microstructure was studied using SEM and evidence of a sintered body with grain size around 1 μm was observed in the material. XRD analysis indicated the single-phase tetragonal structure of the ceramic material. The process of using this ceramic material for fabrication of 10 ft continuous fire wire sensor has been explained.     

Robust design and optimization procedure for piled-raft foundation to support tall wind turbine in clay and sand

A geotechnical design and optimization procedure for piled-raft foundations to support tall wind turbines in clayey and sandy soil are presented in this paper. From the conventional geotechnical design, it was found that the differential settlement controlled the final design and was considered as the response of concern in the optimization procedure. A parametric study was subsequently conducted to examine the effect of the soil shear strength parameters and wind speed (random variables) on the design parameters (number and length of piles and radius of raft). Finally, a robust design optimization procedure was conducted using a Genetic Algorithm coupled with a Monte Carlo simulation considering the total cost of the foundation and the standard deviation of differential settlement as the objectives. This procedure resulted in a set of acceptable designs forming a Pareto front which can be readily used to select the best design for given performance requirements and cost limitations.     

Effect of Cooking on Isoflavones,Phenolic Acids,and Antioxidant Activity in Sprouts of Prosoy Soybean (Glycine max)

Soy sprouts possess health benefits and is required to be cooked before consumption. The effects of cooking on the phenolic components and antioxidant properties of soy sprouts with different germination days were investigated. A food‐grade cultivar Prosoy with a high protein content was germinated for 1, 2, 3, 5, and 7 d and cooked till palatable for 20, 20, 5, 5, and 7 min, respectively. Total phenolic content (TPC), total flavonoids content (TFC), condensed tannins content (CTC), individual phenolic acids, isoflavones, DPPH, ferric‐reducing antioxidant power (FRAP), and oxygen radical absorbance capacity (ORAC) of raw and cooked sprouts were measured. Cooking caused significant losses in phenolic content and antioxidant activities, and maximum loss was on day 3 > 5 > 7, including TPC (32%, 23%, and 15%), TFC (50%, 44%, and 20%), CTC (73%, 47%, and 12%), DPPH (31%, 15%, and 5%), FRAP (34%, 25%, and 1%), and ORAC (34%, 22%, 32%), respectively. Cooking caused significant losses in most individual phenolic acid, benzoic group, cinnamic group, total phenolic composition, individual isoflavones, and total isoflavones. The losses of phenolic acids such as gallic, protocatechuic, hydroxybenzoic, syringic, chlorogenic, or sinapic acids during cooking were not compensated by the increases in trihydroxybenzoic, vanillic or coumaric acids on certain days of germination. Cooking caused minimal changes in phenolic acid composition of day 1 and 2 sprouts compared to 3, 5, and 7 d sprouts.