Restrictions of Minimum Spanner Problems

At-spanner of a graphGis a spanning subgraphHsuch that the distance between any two vertices inHis at mostttimes their distance inG. Spanners arise in the context of approximating the original graph with a sparse subgraph (Peleg, D., and Schäffer, A. A. (1989),J. Graph. Theory13(1), 99–116). The MINIMUMt-SPANNER problem seeks to find at-spanner with the minimum number of edges for the given graph. In this paper, we completely settle the complexity status of this problem for various values oft, on chordal graphs, split graphs, bipartite graphs and convex bipartite graphs. Our results settle an open question raised by L. Cai (1994,Discrete Appl. Math.48, 187–194) and also greatly simplify some of the proofs presented by Cai and by L. Cai and M. Keil (1994,Networks24, 233–249). We also give a factor 2 approximation algorithm for the MINIMUM 2-SPANNER problem on interval graphs. Finally, we provide approximation algorithms for the bandwidth minimization problem on convex bipartite graphs and split graphs using the notion of tree spanners.     

Space-Variant Approaches to Recovery of Depth from Defocused Images

The recovery of depth from defocused images involves calculating the depth of various points in a scene by modeling the effect that the focal parameters of the camera have on images acquired with a small depth of field. In the approach to depth from defocus (DFD), previous methods assume the depth to be constant over fairly large local regions and estimate the depth through inverse filtering by considering the system to be shift-invariant over those local regions. But a subimage when analyzed in isolation introduces errors in the estimate of the depth. In this paper, we propose two new approaches for estimating the depth from defocused images. The first approach proposed here models the DFD system as a block shift-variant one and incorporates the interaction of blur among neighboring subimages in an attempt to improve the estimate of the depth. The second approach looks at the depth from defocus problem in the space-frequency representation framework. In particular, the complex spectrogram and the Wigner distribution are shown to be likely candidates for recovering the depth from defocused images. The performances of the proposed methods are tested on both synthetic and real images. The proposed methods yield good results and the quality of the estimates obtained using these methods is compared with the existing method.     

A Comparative Evaluation of Air-Jet Sieve for Particle Size Analysis of Pharmaceutical Powders

The performance of the air-jet sieve (AJS), for the particle size analysis of pharmaceutical powder, was evaluated and compared with the conventional sieve shaker (ESS). Two grades of acetaminophen (APAP) were used as test pharmaceutical powders. The particle size analysis by the AJS was simple, reproducible, efficient and accurate. The problematic powder, possessing excessive electrostatic charges and ranging in mean diameter from 17 nm to 800 nm (beyond the scope of ESS) could be evaluated accurately by AJS. The analysis time required by AJS was relatively less than that required by ESS. The accuracy of the determination by AJS was not affected by the sample size. Both the speed of rotation (vibrations and/or shaking) and the total time of sifting affected the results of the determination by ESS. The particle size value of APAP-special determined by ESS and AJS were 680.0 ± 0.14 nm and 40.0 ± 0.32 respectively, whereas the value assigned by the manufacturer was below 74 nm (-200 mesh). The precision of either method for particle size analysis of powder possessing excessive electrostatic charge was improved by the use of carbon black as an anti-static agent.     

Optimization of prestressed concrete solid and voided slabs

A methodology is presented for the minimum cost optimization of prestressed concrete solid and voided slabs. Apart from the rationale imparted to the design process, the method is shown to yield considerable savings in prestressing steel and therefore savings in energy. Computer programs developed for the implementation of the methodology have facilitated the speedy running of the procedure a myriad of times over a wide range of design parameters such as span, live load, material and erection cost ratios, concrete and strand strengths, prestress effectiveness etc. Qualitative and quantitative conclusions regarding the behavioural characteristics of the parameters and the manner of their interplay in the optimal picture are advanced.     

Starch urea formaldehyde matrix encapsulation of solid agrochemicals. II. Release mechanism and release modeling

Based on experimental observation, a mechanism is proposed to describe the release of carbofuran from a starch-UF matrix. A simple mathematical model is developed to describe the diffusion-controlled release of a solid insecticide from a porous starch-UF matrix undergoing both volume and surface erosions. The model is tested with the release data collected for different matrices and with different pH values of the environmental liquid. The comparison between the model predictions and data is found to be reasonably good. The model describes the release process at different pH values by accounting for the influence of pH on the erosion rates.     

In search of novel water soluble forskolin analogues for positive inotropic activity

Using the novel lead from hydroxy acetyl substituted forskolin analogues, such as 7 beta-hydroxyacetyl-7 beta-deacetyl forskolin or 6 beta-hydroxyacetyl forskolin, a number of water soluble omega-amino acyl derivatives were synthesized. Two such compounds 6 and 18 showed better in vitro activity but failed to show in vivo activity.