Cetyltrimethylammonium bromide-modified spherical and cube-like gold nanoparticles as extrinsic Raman labels in surface-enhanced Raman spectroscopy based heterogeneous immunoassays

This paper reports on the characterization and preliminary comparison of gold nanoparticles of differing surface modification and shape when used as extrinsic Raman labels (ERLs) in high-sensitivity heterogeneous immunoassays based on surface enhanced Raman scattering (SERS). ERLs are gold nanoparticles coated with an adlayer of an intrinsically strong Raman scatterer, followed by a coating of a molecular recognition element (e.g., antibody). Three types of ERLs, all with a nominal size of approximately 30 nm, were fabricated by using spherical citrate-capped gold nanoparticles (sp-cit-Au NPs), spherical CTAB-capped gold nanoparticles (sp-CTAB-Au NPs), or cube-like CTAB-capped gold nanoparticles (cu-CTAB-Au NPs) as cores. The performance of these particles was assessed via a sandwich immunoassay for human IgG in phosphate buffered saline. The ERLs fabricated with sp-CTAB-Au NPs as cores proved to be more than 50 times more sensitive than those with sp-cit-Au NPs as cores; the same comparison showed that the ERLs with cu-CTAB-Au NPs as cores were close to 200 times more sensitive. Coupled with small differences in levels of nonspecific adsorption, these sensitivities translated to a limit of detection (LOD) of 94, 2.3, and 0.28 ng/mL, respectively, for the detection of human IgG in the case of sp-cit-Au NPs, sp-CTAB-Au NPs, and cu-CTAB-Au NPs. The LOD of the cu-CTAB-Au NPs is therefore approximately 340 times below that for the sp-cit-Au NPs. Potential applications of these labels to bioassays are briefly discussed.     

Efficient compressed sensing based object detection system for video surveillance application in WMSN

Limited memory, energy and bandwidth are the major constraints in wireless visual sensor network (WVSN). Video surveillance applications in WVSN attracts a lot of attention in recent years which requires high detection accuracy and increased network lifetime that can be achieved by reducing the energy consumption in the sensor nodes. Compressed sensing (CS) based background subtraction plays a significant role in video surveillance application for detecting the presence of anomaly with reduced complexity and energy. This paper presents a system based on CS for single and multi object detection that can detect the presence of an anomaly with higher detection accuracy and minimum energy. A novel and efficient mean measurement differencing approach with adaptive threshold strategy is proposed for detection of the objects with less number of measurements, thereby reducing transmission energy. The performance of the system is evaluated in terms of detection accuracy, transmission energy and network lifetime. Furthermore, the proposed approach is compared with the conventional background subtraction approach. The simulation results show that the proposed approach yields better detection accuracy with 90% reduction in samples compared to conventional approach.     

Characterization of acidic groups in oxycelluloses IV. Effect of accelerated aging on yellowing as well as carboxyl groups and lactones in pulp

Bleached bamboo pulp as well as two oxypulps were subjected to accelerated aging by heating as well as steaming, and the yellowing or color reversion was studied. The yellowing is increased by the presence of free carboxyl and the reducing groups in oxycelluloses. The again treatments were found to cause an increase in free carboxyl groups accompanied by a reduction in copper number. A differentiation between free carboxyl and various lactone groups in oxidized and also aged samples was carried out based on the variation in their reaction rates with KI/KIO₃ solution, and the characteristic acidic group spectrum showed that on steam again the fastreacting lactones are lost.     

Investigation of polymer dynamics in chitosan-maghemite nanocomposites: a potential green superparamagnetic material

Magnetic composites with superparamagnetic properties have attracted great scientific interest recently. In this article we have investigated chitosan-maghemite (γ-Fe₂O₃) nanocomposite. We have analyzed the effect of temperature and the concentration of maghemite nanoparticles upon the relaxation behaviour of the nanocomposite using Broad band dielectric spectroscopy (BDS). Additionally, various characterization techniques such as X-ray diffraction (XRD), Fourier transform infra red spectra (FTIR), Scanning electron microscopy (SEM), Transmission electron spectroscopy (TEM), Thermo gravimetric Analysis (TGA), Vibrating Sample Magnetometer (VSM), Atomic Force Microscopy (AFM) and Raman spectroscopy have been used for our investigation. Our investigation shows that maghemite nanoparticles interact with chitosan leading to morphological changes in the films and results in modifications in the dielectric and electrical characteristics of the nanocomposite. New relaxations have been identified and their modifications due to maghemite nanoparticles have been investigated. The nanocomposites exhibit superparamagnetic behaviour. This research will benefit research in battery technology and super capacitors.     

Optimized 2.4 GHz voltage controlled oscillator with a high-Q MWCNT network-based pulse-shaped inductor

This paper focuses on the use of a high-Q Multi-Wall Carbon Nano-Tube (MWCNT)-based pulse-shaped inductor in the implementation of an LC differential voltage-controlled oscillator (LCVCO). The topology integrates a micro-scaled capacitor and a MWCNT network-based inductor together with the CMOS circuits. The CMOS circuits were designed to enhance the quality factor and to control the oscillation amplitude. The high quality factor of the inductor improves the overall quality factor and phase noise of the oscillator. The measurement results show that the LCVCO operates at 2.3982 GHz and achieves a phase noise of ?133.3 dBc/Hz at 1 MHz away from the carrier frequency. The VCO produces frequency tuning from 2.07 GHz to 2.77 GHz (29.16%) with an ultra low power consumption of 1.7 mW from a 0.6 V supply voltage. The output power level of the VCO is ?10 dBm, with an improved quality factor of 49.     

Phenolic composition,antioxidant and antimicrobial activities of free and bound phenolic extracts of Moringa oleifera seed flour

Phenolic compounds, antioxidant and antibacterial activities of defatted Moringa oleifera seed flour (DMF) were investigated. The total phenolic and flavonoid contents were measured using colorimetric methods. Free phenolic acid and flavonoid profiles were analyzed by high performance liquid chromatography, while antioxidant capacities were evaluated using scavenging assays of 1,1-diphenyl-2-picrylhydrazyl radical (DPPH), ferric reducing antioxidant power and total antioxidant capacity. The results showed that extractability of phenolic compounds was significantly higher (p < 0.05) in bound phenolic extract (4173.00 ± 32.22 mg gallic acid equivalents (GAE)/100 g) than in free phenolic extract (780.00 ± 14.2 mg GAE/100 g) and it showed higher antioxidant and antimicrobial activities. The IC₅₀ value for DPPH radical scavenging activity was 0.9 ± 0.05 and 14.9 ± 0.07 mg/mL for bound phenolic and free phenolic extracts, respectively. Bound phenolic extract was more effective (minimum inhibitory concentration (MIC), 0.06–0.157%) than free phenolic extract (MIC, 0.117–0.191%) against tested bacteria. Ten phenolic compounds (gallic acid, p-coumaric acid, ferulic acid, caffeic acid, protocatechuic acid, cinnamic acid, catechin, epicatechin, vanillin and quercetin) were identified and quantified in both extracts. These natural plant phenolics from Moringa seeds could be a good source of antioxidants and antibacterials for food and pharmaceutical industries.     

Metal nanowire grating patterns

Metal nanowire patterning in the form of grating structures has been carried out using a wide range of lithography techniques, and many hybrid methods derived from them. The challenge is to achieve sub-100 nm linewidths with controllable spacing and thickness over large areas of substrates with high throughput. In particular, the patterns with linewidth and spacing of a few tens of nm offer properties of great interest in optoelectronics and plasmonics. Crossbar grating structures--two gratings patterned perpendicular to each other--will play an important role as ultra-high density electrode grids in memristive devices for non-volatile memory.