Rajender Parsad

Controlled release formulations of metribuzin: Release kinetics in water and soil

Controlled release (CR) formulations of metribuzin in Polyvinyl chloride [(PVC) (emulsion)], carboxy methyl cellulose (CMC), and carboxy methyl cellulose-kaolinite composite (CMC-KAO), are reported. Kinetics of its release in water and soil was studied in comparison with the commercial formulation (75 DF). Metribuzin from the commercial formulation became non-detectable after 35 days whereas it attained maxima between 35–49 days and became non-detectable after 63 days in the developed products. Amongst the CR formulations, the release in both water and soil was the fastest in CMC and slowest in PVC. The CMC-KAO composite reduced the rate of release as compared to CMC alone. The diffusion exponent (n value) of metribuzin in water and soil ranged from 0.515 to 0.745 and 0.662 to 1.296, respectively in the various formulations. The release was diffusion controlled with half release time (t1/2) from different controlled release matrices of 12.98 to 47.63 days in water and 16.90 to 51.79 days in soil. It was 3.25 and 4.66 days, respectively in the commercial formulation. The period of optimum availability of metribuzin in water and soil from controlled released formulations ranged from 15.09 to 31.68 and 17.99 to 34.72 days as against 5.03 and 8.80 days in the commercial formulation.

Two-Level Supersaturated Designs: A Review

Supersaturated Designs (SSDs) are fractional factorial designs in which the run size is not enough to estimate the main effects of all the factors in the experiment. Two-level SSDs have been studied extensively in the literature. The thrust of research has been on obtaining lower bounds to the value of E(s2), a measure of departure from orthogonality, and constructing designs that attain these lower bounds. The focus of this paper is to review the literature on two-level SSDs.

IPPS Sampling Plans Excluding Adjacent Units

The concept of inclusion probability proportional to size sampling plans excluding adjacent units separated by at most a distance of m (≥ 1) units {IPPSEA plans} is introduced. IPPSEA plans ensure that the first-order inclusion probabilities of units are proportional to size measures of the units, while the second-order inclusion probabilities are zero for pairs of adjacent units separated by a distance of m units or less. IPPSEA plans have been obtained by making use of binary, proper, and unequireplicated block designs and linear programing approach. The performance of IPPSEA plans using Horvitz–Thompson estimator of population total has been compared with existing sampling plans such as simple random sampling without replacement (SRSWOR), balanced sampling plans excluding adjacent units {BSA (m) plans}, probability proportional to size with replacement, Hartley and Raos plan (1962), Rao et al.s strategy (1962), and Sampfords IPPS plan (1967) using a real life population. Unbiased estimation of Horvitz–Thompson estimator of population total is not possible in these types of plans because some of the second-order inclusion probabilities are zero. To resolve this problem, one approximate variance estimation technique has been suggested.

A-Efficient block designs for comparing two disjoint sets of treatments

This article studies an experimental setting in which it is desired to compare v1 test treatments with v2 sun control treatments via bk experimental units arranged in b blocks of size k each. Under this setting some sufficient conditions are obtained to establish the A-optimality of designs for making test treatments -control treatments comparisons. Some general methods of construction of variance balanced designs for making test treatments-control treatments comparisons are given. The A-efficiencies of the designs constructed is investigated. A table of some designs for two control treatments alongwith their A-efficiencies is prepared.

Pesticidal seed coats based on azadirachtin‐A: release kinetics, storage life and performance

BACKGROUND Infestation of seeds by pests during storage leads to deterioration in quality. Seed coating is an effective option to overcome the menace. Unlike synthetic fungicidal seed coats, little is known of those based on botanicals. This study aims at developing azadirachtin-A-based pesticidal seed coats to maintain seed quality during storage. RESULTS Polymer- and clay-based coats containing azadirachtin-A were prepared and evaluated for quality maintenance of soybean seed during storage. Gum acacia, gum tragacanth, rosin, ethyl cellulose, hydroxyethyl cellulose, polyethyl methacrylate, methyl cellulose, polyethylene glycol, polyvinyl chloride, polyvinyl acetate, polyvinyl pyrrolidone and Agrimer VA 6 polymers and the clay bentonite were used as carriers. The time for 50% release (t(1/2)) of azadirachtin-A into water from the seeds coated with the different coats ranged from 8.02 to 21.36 h. The half-life (T(1/2)) of azadirachtin-A in the coats on seed ranged from 4.37 to 11.22 months, as compared with 3.45 months in azadirachtin-A WP, showing an increase by a factor of nearly 1.3-3.3 over the latter. The coats apparently acted as a barrier to moisture to reduce azadirachtin-A degradation and prevented proliferation of storage fungi. Polyethyl methacrylate, polyvinyl acetate and polyvinyl pyrrolidone were significantly superior to the other polymers. Azadirachtin-A showed a significant positive correlation with seed germination and vigour, and negative correlation with moisture content. CONCLUSION Effective polymeric carriers for seed coats based on azadirachtin-A are reported. These checked seed deterioration during storage by acting as a barrier to moisture and reduced the degradation of azadirachtin-A.

Weighted a-efficiency of block designs for making treatment-control and treatment-treatment comparisons

Abstract The problem of comparing v test treatments and a control in b blocks of size k each is considered. Two different sets of contrasts, test treatment–control and test treatment–test treatment contrasts, are considered. Conditions under which a design is weighted A-optimal for estimating these two sets of contrasts with unequal precision are derived. A general method of construction of BTIB designs is given and their weighted A-efficiencies are worked out. A catalogue of weighted A-efficient BTIB designs is also given.

Structurally Incomplete Row–Column Designs

Abstract This article studies the optimality and construction aspects of structurally incomplete row–column designs in which the number of non-empty nodes in rows and/or columns are unequal. Universal optimality of structurally incomplete row-column designs with unequal row and/or column sizes has been investigated. General methods of construction of universally optimal designs are obtained using pairwise balanced block designs and block designs with nested rows and columns. One method of construction gives SIRC design with equal row and equal column sizes. A method of construction of structurally incomplete row–column designs for comparing test treatments with control treatment(s) is also given.

Weighted A-optimal block designs for comparing test treatments with controls with unequal precision

The problem of comparing w test treatments with u controls in b blocks of size k(⩽w) each is considered. Conditions under which a design is weighted A-optimal for estimating test treatments vs. controls contrasts with unequal precision are derived, the weights being given according to the relative importance of the controls. A new class of designs called generalised balanced treatment incomplete block (GBTIB) designs has been introduced. A general method of construction of GBTIB designs for two controls is given. Catalogues of weighted A-optimal designs for two controls and weighted A-efficient GBTIB designs are given. A method of construction of GBTIB designs using resolvable balanced incomplete block designs has also been given and illustrated through an example.

Computer Aided Construction of Efficient Multi-level Supersaturated Designs

Motivated by the computer search algorithms for constructing two-level supersaturated designs by Heavlin and Finnegan (1993), Li and Wu (1997), Nguyen (1996), Lejeune (2003) and Gupta, Parsad, Kole and Bhar (2008), this paper develops an algorithm to generate multi-level supersaturated designs. Popular E(fNOD) and E(χ2) criterion have been used as a measure of non-orthogonality for the designs generated. The algorithm also ensures that no two columns in the designs generated are fully aliased. A catalogue of 120 optimal supersaturated designs for different number of factors m, design runs n, with 5 ≤ n ≤ 16 runs, and different number of factor levels q, with 3 ≤ q ≤ 6, has been prepared. All the designs generated are fNOD-optimal; some designs are χ2-optimal too.

Efficient Incomplete Block Designs Through Linear Integer Programming

SYNOPTIC ABSTRACT The purpose of this paper is to present a linear integer programming approach to construct efficient binary incomplete block designs for any given number of treatments v, number of blocks b, with common block-size k, and with a nearly balanced concurrence matrix. The proposed approach is illustrated by constructing an efficient incomplete block design. A-efficient and D-efficient incomplete block designs have been constructed and catalogued using the proposed algorithm for a restricted range of parameters 3 ⩽ v ⩽ 20, b ⩾ v, and 2 ⩽ k ⩽ min(10, v − 1), with vb⩽1, 000. An R package is developed to implement the proposed approach.