12-run Plackett-Burman Design Research Articles

A novel experimental design for boar sperm cryopreservation.

Cryopreservation of sperm is a routine technology in many livestock species, but not in swine. Frozen sperm must result in acceptable conception rates and produce 11 to 12 piglets/litter to be competitive with traditional cooled semen. The development of an extender that results in high post-thaw sperm quality and acceptable litter size requires the identification of factors that markedly affect post-thaw semen quality. The present study aims to first identify factors in boar sperm cryopreservation that significantly affect post-thaw sperm quality using an efficient, cost-effective, and relatively rapid approach. The Plackett-Burman experimental design is ideal for the screening of factors at their extreme, greatly reducing the amount of time and resources needed for a follow-up, full factorial design. Using commercial semen, a 9-factor, 12-run Plackett-Burman design was used on 10 boars split between 12 treatments. Through this method, glycerol concentration, cooling rate, antioxidant supplementation with GameteGuard (Membrane Protective Technologies, Inc. Fort Collins, CO), and straw size were identified as highly influential factors that affect post-thaw sperm quality. Extender type, starting osmolality, sodium dodecyl sulfate addition, and stepwise addition of glycerol were also influential for some but not all post-thaw sperm parameters (P < 0.05). Equilibration time in the straws before freezing was determined to have no impact on post-thaw sperm quality parameters. Using the Plackett-Burman design, it can be concluded that four of the nine factors warrant detailed investigation in full factorial experiments in the development of boar sperm cryopreservation extenders.

Improved production of melanin from Aspergillus fumigatus AFGRD105 by optimization of media factors.

Melanins are indolic polymers produced by many genera included among plants, animals and microorganisms and targeted mainly for their wide range of applications in cosmetics, agriculture and medicine. An approach to analyse the cumulative effect of parameters for enhanced melanin production was carried out using response surface methodology. In this present study, optimization of media and process parameters for melanin production from Aspergillus fumigatus AFGRD105 (GenBank: JX041523; NFCCI accession number: 3826) was carried out by an initial univariate approach followed by statistical response surface methodology. The univariate approach was used to standardise the parameters that can be used for the 12-run Plackett–Burman design that is used for screening for critical parameters. Further optimization of parameters was analysed using Box–Behnken design. The optimum conditions observed were temperature, moisture and sodium dihydrogen phosphate concentration. The yield of every run of both designs were confirmed to be melanin by laboratory tests of analysis in the presence of acids, base and water. This is the first report confirming an increase in melanin production A. fumigatus AFGRD105 without the addition of costly additives.

Factor screening in nonregular two-level designs based on projection-based variable selection

In this paper, we focus on the problem of factor screening in nonregular two-level designs through gradually reducing the number of possible sets of active factors. We are particularly concerned with situations when three or four factors are active. Our proposed method works through examining fits of projection models, where variable selection techniques are used to reduce the number of terms. To examine the reliability of the methods in combination with such techniques, a panel of models consisting of three or four active factors with data generated from the 12-run and the 20-run Plackett–Burman (PB) design is used. The dependence of the procedure on the amount of noise, the number of active factors and the number of experimental factors is also investigated. For designs with few runs such as the 12-run PB design, variable selection should be done with care and default procedures in computer software may not be reliable to which we suggest improvements. A real example is included to show how we propose factor screening can be done in practice.

Graphical Aids for the Analysis of Two-Level Nonregular Designs

The complex alias pattern between main effects and two-factor interactions for two-level nonregular designs has been considered a problem when analyzing these designs. If only a few two-factor interactions are active, however, the pattern induced into the estimated main effects contrasts from the active interactions may be very structured. This is, in particular, true for the 12-run and the 20-run Plackett–Burman (PB) designs, probably the two most important designs for physical experimentation. This article presents a graphical method for the analysis of nonregular two-level designs. The method consists of two steps. The first step is called contrast plots interpretation and is directed toward revealing the cause for the pattern observed in contrast plots. The second step is called alias reduction and aims at simplifying the interpretation of the contrast plots by reducing the aliasing caused by effects that, with a high degree of certainty, may be considered active. The method is tested on the 12-run PB design both with simulated and real data and on the 20-run PB design for one particular case with real data. Supplementary materials (MINITAB codes for performing calculations and plots) are available online.

Minimum cost linear trend-free 12-run fractional factorial designs

Time trend resistant fractional factorial experiments have often been based on regular fractionated designs where several algorithms exist for sequencing their runs in minimum number of factor-level changes (i.e. minimum cost) such that main effects and/or two-factor interactions are orthogonal to and free from aliasing with the time trend, which may be present in the sequentially generated responses. On the other hand, only one algorithm exists for sequencing runs of the more economical non-regular fractional factorial experiments, namely Angelopoulos et al. [1]. This research studies sequential factorial experimentation under non-regular fractionated designs and constructs a catalog of 8 minimum cost linear trend-free 12-run designs (of resolution III) in 4 up to 11 two-level factors by applying the interactions-main effects assignment technique of Cheng and Jacroux [3] on the standard 12-run Plackett–Burman design, where factor-level changes between runs are minimal and where main effects are orthogonal to the linear time trend. These eight 12-run designs are non-orthogonal but are more economical than the linear trend-free designs of Angelopoulos et al. [1], where they can accommodate larger number of two-level factors in smaller number of experimental runs. These non-regular designs are also more economical than many regular trend-free designs. The following will be provided for each proposed systematic design:(1) The run order in minimum number of factor-level changes.(2) The total number of factor-level changes between the 12 runs (i.e. the cost).(3) The closed-form least-squares contrast estimates for all main effects as well as their closed-form variance–covariance structure.In addition, combined designs of each of these 8 designs that can be generated by either complete or partial foldover allow for the estimation of two-factor interactions involving one of the factors (i.e. the most influential).

Optimization of cross-linked high amylose starch microspheres containing 5-fluorouracil

The objective of the present investigation was the preparation of microspheres consisting of high amylose starch cross-linked in situ by means of sodium trimetaphosphate. 5-fluorouracil was chosen as a model drug. Since this preparation entailed several process and formulation variables, a preliminary screening design was applied to identify the most important factors and thereby simplify the system under study. This was performed with regard to the spherical shape and the capacity of drug encapsulation of the obtainable microparticles. An eight-factor 12-run Plackett-Burman design enabled the factor number to be reduced so that a three-factor face-centered central composite design could subsequently be applied in order to optimize the formulation by response surface methodology. The factors involved in the optimization process were the concentrations of the following components: 5-fluorouracil, starch and cross-linker. The responses evaluated were the morphology of the microspheres (a qualitative response) and the drug encapsulation efficiency. An optimal formulation yielded microparticles that were spherical in shape, with a volume diameter of 25.5±0.6pm and a narrow particle size distribution. Particle yield ranged from 85 to 98%, the encapsulation efficiency reached about 30% and the drug loading was in the range of 0.8-1.5%. Due to polymer swelling properties, 5-fluorouracil was released in vitro in a sustained manner by an anomalous release mechanism. Microparticles also showed good mucoadhesion properties that would make them suitable for peroral drug administration.

Choosing columns from the 12-run Plackett–Burman design

There are two non-isomorphic choices of 5 columns and of 6 columns from the 12-run Plackett–Burman design which are essentially identical in terms of E( s 2) and extended word length pattern. Surprisingly, in each case one choice is superior to the other for exploring models with main effects and a small number of 2-factor interactions. For 6 columns the difference between choices is substantial.

Using the Folded-Over 12-Run Plackett—Burman Design to Consider Interactions

This article demonstrates that the folded-over 12-run Plackett–Burman design is useful for considering up to 12 factors in 24 runs, even if one anticipates that some two-factor interactions may be significant. The properties of this design are investigated, and a sequential procedure for analyzing the data from such a design is proposed. The performance of the procedure is investigated through the analysis of real and constructed examples and through a small simulation study. Applications to other folded-over Plackett–Burman designs are also briefly discussed.

Miscellanea. Some hidden projection properties of orthogonal arrays with strength three

SUMMARY It is shown that a two-level orthogonal array with strength three whose run size is not a multiple of 16 has the hidden projection property that in its projection on to any five factors, all the main effects and two-factor interactions are estimable if the higher-order interactions are negligible. The result applies to the fold-over of any strength-two orthogonal array whose run size is not a multiple of 8. This extends Diamond's (1995) result on the fold-over of the 12-run Plackett-Burman design. Some connections with search designs are also presented.

A study of polyethylene-gr-2-tert-butyl amino methacrylate-supported TiCl4 catalyst for ethylene polymerization

The use of a polyethylene-based copolymer with dual functional groups (polyethylene-gr-2-tert-butyl amino ethyl methacrylate) as the support for TiCl4 catalyst in ethylene polymerization was studied. Different methods for treating the support were examined and treatment with BuMgCl was found to be the most effective. With the BuMgCl-modified support, a 12-run Plackett-Burman design was used to screen 11 factors in catalyst preparation. Statistical analysis of the results from this design identified significant factors with the amount of BuMgCl singled out to be the most important one for the four response variables of interest, Mg loading, Ti loading, catalyst activity per gram catalyst, and catalyst activity per gram Ti. © 1996 John Wiley & Sons, Inc.