A practical method to fabricate gold substrates for surface-enhanced Raman spectroscopy

We describe a practical method of fabricating surface-enhanced Raman spectroscopy (SERS) substrates based on dip-coating poly-l-lysine derivatized microscope slides in a gold colloidal suspension. The use of only commercially available starting materials in this preparation is particularly advantageous, aimed at both reducing time and the inconsistency associated with surface modification of substrates. The success of colloid deposition has been demonstrated by scanning electron microscopy (SEM) and the corresponding SERS response (giving performance comparable to the corresponding traditional colloidal SERS substrates). Reproducibility was evaluated by conducting replicate measurements across six different locations on the substrate and assessing the extent of the variability (standard deviation values of spectral parameters: peak width and height), in response to either Rhodamine 6G or Isoniazid. Of particular interest is the observation of how some peaks in a given spectrum are more susceptible to data variability than others. For example, in a Rhodamine 6G SERS spectrum, spectral parameters of the peak at 775 cm(-1) were shown to have a relative standard deviation (RSD) % of <10%, while the peak at 1573 cm(-1) has a RSD of >/=10%. This observation is best explained by taking into account spectral variations that arise from the effect of a chemisorption process and the local nature of chemical enhancement mechanisms, which affects the enhancement of some spectral peaks but not others (analogous to resonant Raman phenomenon).     

Morphological and mechanical properties of PP/ABS blends compatibilized with PP‐g‐acrylic acid

Polypropylene (PP) and acrylonitrile–butadiene–styrene (ABS) blends were prepared by a melt extrusion process. PP‐g‐acrylic acid was used as a compatibilizer. Blends with various compositions of PP, compatibilizer, and ABS were prepared and studied for morphological and mechanical properties. PP‐rich ternary blends showed good morphological and mechanical properties. The use of 5 wt % PP‐g‐acrylic acid as a compatibilizer resulted in a fine and homogeneous dispersion of the ABS phase in the PP phase. The experimental data of the tensile modulus showed good agreement in PP‐rich compositions with that generated from Kerner's model with perfect adhesion. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1731–1741, 2001     

Thermal Behaviour of Amylose-g-Poly (Styrene) Graft Copolymer

The graft copolymer amylose-g-poly (styrene) was prepared by Fe²⁺-H₂O₂ initiation method. Thermal analyses of grafted samples having different styrene content have been carried out in nitrogen atmosphere. Thermal stability of amylose has been found to increase when it is grafted. Chatterjee and Freeman-Anderson methods have been applied to TG-data (Thermogravimetric Data). TG showed that degradation occurred through two distinct steps. DTA (Differential Thermal Analysis) of all samples having different degrees of grafting indicated that graft copolymers decompose before melting. From the DSC (Differential Scanning Calorimeter) study it is revealed that TG of graft copolymers is independent of the degree of grafting.     

Grafting of 2-HEMA on IPP and in situ chlorinated PP through solution polymerization

Grafting of 2-hydroxyethyl methacrylate (2-HEMA) on isotactic polypropylene (IPP) and in situ chlorinated polypropylene (CPP) by free radical process was carried out at 110°C using toluene as solvent. Various conditions for grafting were optimized. The maximum percent of grafting of 2-HEMA achieved on IPP was 3.6%, whereas that on in situ CPP was 8.7%. The products were characterized by Fourier transform infrared spectroscopy and thermal and contact angle measurements. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 69: 2107–2113, 1998     

Oral bioavailability enhancement of raloxifene by developing microemulsion using D-optimal mixture design: optimization and in-vivo pharmacokinetic study

The objective of this work was to utilize a potential of microemulsion for the improvement in oral bioavailability of raloxifene hydrochloride, a BCS class-II drug with 2% bioavailability. Drug-loaded microemulsion was prepared by water titration method using Capmul MCM C8, Tween 20, and Polyethylene glycol 400 as oil, surfactant, and co-surfactant respectively. The pseudo-ternary phase diagram was constructed between oil and surfactants mixture to obtain appropriate components and their concentration ranges that result in large existence area of microemulsion. D-optimal mixture design was utilized as a statistical tool for optimization of microemulsion considering oil, S_mix, and water as independent variables with percentage transmittance and globule size as dependent variables. The optimized formulation showed 100?±?0.1% transmittance and 17.85?±?2.78?nm globule size which was identically equal with the predicted values of dependent variables given by the design expert software. The optimized microemulsion showed pronounced enhancement in release rate compared to plain drug suspension following diffusion controlled release mechanism by the Higuchi model. The formulation showed zeta potential of value ?5.88?±?1.14?mV that imparts good stability to drug loaded microemulsion dispersion. Surface morphology study with transmission electron microscope showed discrete spherical nano sized globules with smooth surface. In-vivo pharmacokinetic study of optimized microemulsion formulation in Wistar rats showed 4.29-fold enhancements in bioavailability. Stability study showed adequate results for various parameters checked up to six months. These results reveal the potential of microemulsion for significant improvement in oral bioavailability of poorly soluble raloxifene hydrochloride.     

Measurement of the D alpha spectrum produced by fast ions in DIII-D

Fast ions are produced by neutral beam injection and ion cyclotron heating in toroidal magnetic fusion devices. As deuterium fast ions orbit around the device and pass through a neutral beam, some deuterons neutralize and emit D(alpha) light. For a favorable viewing geometry, the emission is Doppler shifted away from other bright interfering signals. In the 2005 campaign, we built a two channel charge-coupled device based diagnostic to measure the fast-ion velocity distribution and spatial profile under a wide variety of operating conditions. Fast-ion data are acquired with a time resolution of approximately 1 ms, spatial resolution of approximately 5 cm, and energy resolution of approximately 10 keV. Background subtraction and fitting techniques eliminate various contaminants in the spectrum. Neutral particle and neutron diagnostics corroborate the D(alpha) measurement. Examples of fast-ion slowing down and pitch angle scattering in quiescent plasma and fast-ion acceleration by high harmonic ion cyclotron heating are presented.     

A low-cost and efficient cloud monitoring camera system design for imaging satellites

Design and development of a cloud monitoring camera (CMC) as a secondary camera for imaging/remote-sensing satellites is proposed here. It is well known that presence of clouds alters the earth-atmospheree energy budget by scattering and absorbing the shortwave radiation and absorbing and re-emitting the infrared radiation. Detection of clouds at precise positions, prior to the initiation of the imaging session of the primary (super resolution) camera can aid in saving power as well as memory storage of the satellite. Key feature of the proposed system is the implementation of an onboard cloud detection system in the visible band. The proposed system is miniature in size and cost-effective when compared to the existing integrated visible and infrared band detection system. It primarily consists of lens assembly, detector head assembly, field programmable gate array (FPGA)-based camera electronics system with supporting proximity electronics. Cloud detection algorithm for the visible band images is derived and simulated with the help of Laboratory Virtual Instrument Engineering Workbench software. The verification and hardware realization of the algorithm is achieved by implementing it on a FPGA-based system. Overall simulated and measured efficiency of more than 94% was achieved. The volume of the system is 85 mm × 85 mm × 25 mm and weighs approximately 2 kg, making it suitable for satellite mounting.     

Studies On The Crosslinking Of Poly (Vinyl Alcohol)

This paper is concerned with the cross-linking of poly(vinyl alcohol) (PVA) using maleic acid as the cross-linker. The curative (maleic acid) dose and the curing temperature and time were varied between 2.5 and 60% (w/w), 120 and 160 °C and 30 and 120 min, respectively. From a thorough swelling study in both hot and cold water (percentage swelling, gel content, swelling ratio, etc-) the optimum curative dose and curing conditions have been evaluated. The molecular weight between the cross-links exhibited a sharp fall up to a maleic acid dose of 20% (w/w). A comparative evaluation of maleic acid cross-linked and heat-treated PVA films has been done. Better heat stability for maleic acid cross-linked PVA was observed from thermogravimetric analysis. A shift in glass transition temperature was observed for both heat-treated and maleic acid treated PVA compared with the virgin one. IR spectroscopic study indicated the presence of an ester linkage and an olefinic double bond in maleic acid treated and heat-treated PVA films, respectively. Maleic acid cross-linked PVA is quite stable in different polar and nonpolar solvents. A definite structural pattern has been observed in maleic acid cross-linked PVA films through scanning electron microscopy.