Formulation and characterisation of nanosuspensions of BCS class II and IV drugs by combinative method

Drug nanocrystals are known to increase the solubility of Biopharmaceutics Classification System (BCS) class II and IV drugs. SmartCrystals are the second generation nanocrystals with particle size of less than 100 nm and increased the stability and solubility of drug and drug product. The combinative methods adopted for the preparation of SmartCrystals are reported to shorten the processing time to reduce the particle size of the drug. This study was carried out with the aim to prepare nanosuspensions of aprepitant and ibuprofen using two pretreatment methods, precipitation and ball milling in a combination of high-pressure homogenisation (HPH). Ball milling and precipitation resulted in nanosuspensions having a particle size less than 1 µ, which were subjected to high HPH. HPH further led to a reduction in the particle size. However, the precipitation method failed to reduce the size of ibuprofen particles to 1 µ.     

Tropospheric ozone variability over the Indian coastline and adjacent land and sea

A tropospheric ozone variability study is carried out to investigate the spatial and temporal distribution over the coastline of the Indian peninsula and adjacent land and sea using NASA Langley Tropospheric Ozone Residual data set for the period 1979–2005. A strong seasonal cycle has been observed with large variation (～ 55%) over the upper eastern coast, followed by the upper and lower western coast, compared to the lower eastern coast (～ 33%). A negative gradient in ozone concentration is observed along eastern and western coasts during summer (slope ～ –0.78 and –0.65) and a positive gradient (slope ～ 0.16 and 0.21) during winter. The same is observed over the adjacent land and sea along the coastline with slight variation. This change in gradient can be attributed to the anthropogenic emission of precursor gases that reinforce localized photochemical production of ozone. In addition, topography, transport, seasonality of emission of precursor gases and the solar insolation cycle play a vital role.     

Optimal coverage of an infrastructure network using sensors with distance-decaying sensing quality

Motivated by recent applications of wireless sensor networks in monitoring infrastructure networks, we address the problem of optimal coverage of infrastructure networks using sensors whose sensing performance decays with distance. We show that this problem can be formulated as a continuous p-median problem on networks. The literature has addressed the discrete p-median problem   on networks and in continuum domains, and the continuous p$p$-median problem in continuum domains extensively. However, in-depth analysis of the continuous p$p$-median problem on networks has been lacking. With the sensing performance model that decays with distance, each sensor covers a region equivalent to its Voronoi partition on the network in terms of the shortest path distance metric. Using Voronoi partitions, we define a directional partial derivative of the coverage metric with respect to a sensor’s location. We then propose a gradient descent algorithm to obtain a locally optimal solution with guaranteed convergence. The quality of an optimal solution depends on the choice of the initial configuration of sensors. We obtain an initial configuration using two approaches: by solving the discrete p$p$-median problem on a lumped   network and by random sampling. We consider two methods of random sampling: uniform sampling and D²$D^2$-sampling. The first approach with the initial solution of the discrete p$p$-median problem leads to the best coverage performance for large networks, but at the cost of high running time. We also observe that the gradient descent on the initial solution with the D²$D^2$-sampling method yields a solution that is within at most 7% of the previous solution and with much shorter running time.     

Transparent hashing in the encrypted domain for privacy preserving image retrieval

Search through a database of encrypted images against a crumpled and encrypted query will remain privacy preserving only if comparisons between selective features derived from these images is executed in the encrypted domain itself. To facilitate this, the encryption process must remain transparent to specific image statistics computed in the spatial or transform domain. Consequently, the perceptual hash formed by quantizing the image statistics remains the same before and after the encryption process. In this paper, we propose a transparent privacy preserving hashing scheme tailored to preserve the DCT-AC coefficient distributions, despite a constrained inter-block shuffling operation. These DCT distributions can be mapped onto a generalized Gaussian model characterized by shape and scale parameters, which can be quantized and Gray-coded into a binary hash matrix. The encryption scheme has been shown to be perceptually secure and does not impair the search reliability and accuracy of the hashing procedure. Experimental results have been provided to verify the robustness of the hash to content-preserving transformations, while demonstrating adequate sensitivity to discriminate between different images.     

Analysis of the wetting behaviour of pigments and the effectiveness of surfactants

A new test method is introduced to analyse the wetting behaviour of pigments and the effectiveness of surfactants. The method involves the study of torque vs time curves obtained during the wetting of pigments by surfactant solutions. These curves provide valuable information regarding the wetting behaviour of pigments and the ability of the surfactant to wet the pigment. To study the wetting behaviour, two pigments which varied widely in their surface character are studied with the same surfactant, while, to study the effectiveness of the surfactant, different surfactants with differing polarity are studied using the same pigment. The results are found to be consistent with the theoretical expectations.     

Liquefaction of coal using supercritical fluid mixtures

Powhatan No. 5 and Bruceton coals were liquefied for 15–60 min at 653 K and 30 MPa in supercritical aqueous mixtures containing 10–20 wt% tetrahydroquinoline (THQ), quinoline or tetralin. The THQ-water mixtures produced the highest conversion to tetrahydrofuran (THF) soluble products (up to 74%). Tetralin-water, quinoline-water and pure water solvents gave increasingly lower yields of THF solubles. Addition of hydrogen to the quinoline-water solvent mixture increased yields slightly, but not to the level obtained using the THQ-water mixture.The yields of THF solubles in all instances depended upon the concentration of solvent in the mixture, with the 10 wt% THQ and 10 wt% tetralin (in water) giving higher yields than either 0 or 20 wt% concentrations. The nitrogen-containing solvents were chemically bonded to the THF-soluble product, as observed by g.p.c.     

Comparative Evaluation of Four Dissolution Apparatus

Four dissolution methods, the rotating basket, the rotating paddle, the rotating basket with paddle and the stationary basket-rotating paddle, were evaluated using capsules and non-disintegrating pellets of salicylic acid. The agitation intensity produced by the rotating basket method was very low and differed significantly throughout the vessel. However, it did not differ significantly at different positions in the stationary basket-rotating paddle method. This method offered considerable advantages and hence appears to be a suitable alternative to the existing compendial methods which have limitations for evaluation of dosage forms which tend to float on the dissolution medium.     

Metal oxide nanoparticles for advanced energy applications

Hot-wire chemical vapor deposition (HWCVD) has been employed as an economically scalable method for the deposition of crystalline molybdenum oxide nanoparticles at high density. Under optimal synthesis conditions, only crystalline nanostructures with a smallest dimension of ~ 3-50 nm are observed with extensive transmission electron microscopy analyses. The incorporation of crystalline molybdenum oxide nanoparticles into battery electrodes has led to profound advancements in state-of-the-art negative electrodes (anodes) in lithium-ion batteries. The nanoparticle materials exhibit a high rate capability as anticipated for the reduced solid-state Li-ion diffusion length.     

Study of Formulation Variables on Properties of Drug-Gellan Beads by Factorial Design

ABSTRACT

The aim of the present study was to obtain cross-linked calcium-gellan beads containing diclofenac sodium as model drug, using full 3³ factorial design. Drug quantity, pH of cross-linking solution, and speed of agitation were selected as variables for factorial design. The resultant beads were evaluated by scanning electron microscopy (SEM), percent yield, entrapment efficiency, micromeritic properties, swelling and drug release studies. The drug-loaded beads were spherical with size range of 0.85–1.8 mm. Percent yield and entrapment efficiency of various batches were in the range of 86.48–98.28% w/w and 72.52–92.74% w/w, respectively. Calcium-gellan beads containing diclofenac sodium showed pH-dependent swelling and drug release properties. Swelling and drug release were significantly higher in pH 7.4 phosphate buffer than 0.1N HCl. The swelling ratio for beads was up to 22 and 3 for phosphate buffer and 0.1N HCl, respectively. Cumulative diclofenac sodium release from calcium-gellan beads was 12–35% in 0.1N HCl within 2 h, whereas complete drug release was observed within 3–4 h in pH 7.4 phosphate buffer.