THE DESIGN AND ANALYSIS OF EXPERIMENTS. By Oscar Kempthorne. New York, John Wiley and Sons, Inc., 1952. 631 pp. $8.50. This book by a teacher of statistics (as well as a consultant for \"experimenters\") is a comprehensive study of the philosophical background for the statistical design of experiment. It is necessary to have some facility with algebraic notation and manipulation to be able to use the volume intelligently. The problems are presented from the theoretical point of view, without such practical examples as would be helpful for those not acquainted with mathematics. The mathematical justification for the techniques is given. As a somewhat advanced treatment of the design and analysis of experiments, this volume will be interesting and helpful for many who approach statistics theoretically as well as practically. With emphasis on the \"why,\" and with description given broadly, the author relates the subject matter to the general theory of statistics and to the general problem of experimental inference. MARGARET J. ROBERTSON

The Design and Analysis of Experiments

Pretreatments to enhance the digestibility of lignocellulosic biomass

Principles and potential of the anaerobic digestion of waste-activated sludge

Our perspective on microbial diversity has improved enormously over the past few decades. In large part this has been due to molecular phylogenetic studies that objectively relate organisms. Phylogenetic trees based on gene sequences are maps with which to articulate the elusive concept of

https://espace.library.uq.edu.au/view/UQ:262656/UQ262656_OA.pdf

Impact of Culture-Independent Studies on the Emerging Phylogenetic View of Bacterial Diversity

https://espace.library.uq.edu.au/view/UQ:262654/UQ262654_OA.pdf

Impact of culture-independent studies on the emerging phylogenetic view of bacterial diversity (vol 180, pg 4765, 1998)

Tetrachloroethene is a prominent groundwater pollutant that can be reductively dechlorinated by mixed anaerobic microbial populations to the nontoxic product ethene. Strain 195, a coccoid bacterium that dechlorinates tetrachloroethene to ethene, was isolated and characterized. Growth of strain 195 with H2 and tetrachloroethene as the electron donor and acceptor pair required extracts from mixed microbial cultures. Growth of strain 195 was resistant to ampicillin and vancomycin; its cell wall did not react with a peptidoglycan-specific lectin and its ultrastructure resembled S-layers of Archaea. Analysis of the 16S ribosomal DNA sequence of strain 195 indicated that it is a eubacterium without close affiliation to any known groups.

https://science.sciencemag.org/content/sci/276/5318/1568.full.pdf

Isolation of a Bacterium That Reductively Dechlorinates Tetrachloroethene to Ethene

A modification to the EPICS procedure for measuring Henry's constants is proposed, wherein the original assumption of equal solute mass additions to bottle pairs has been eliminated via a gravimetric accounting, resulting in increased precision. The modified procedure was applied to 13 volatile C/sub 1/ and C/sub 2/ chlorinated hydrocarbons at temperatures from 10 to 35/sup 0/C, representing a range in dimensionless Henry's constant (H/sub c/) of from 0.05 to 1.8. The mean coefficient of variation (CV) in Henry's constant was 3-4%; however, by employment of greater differentials in liquid volumes within bottle pairs, CV may be reduced to an estimated 2.5-3.5%. Precision deteriorates markedly at very low Henry's constants (i.e., H/sub c/ < 0.1). Dilute aqueous mixtures of volatile solutes (with methanol also present) were employed in these measurements of Henry's constant. Comparison with previous results from single-solute assays supports the use of mixtures - at least within the range explored here. The effects of ionic strength on apparent Henry's constants were evaluated for six of the compounds, with KCl concentrations up to 1.0 M. The practical impact of ionic strength appears to be minimal. Salting-out coefficients (k) ranged from 0.107 to 0.213 L mol/sup -1/ at 20/sup 0/C.more » 8 references, 5 figures, 3 tables.« less

Measurement of Henry's law constants for C1 and C2 chlorinated hydrocarbons

A biological process for remediation of groundwater contaminated with tetrachloroethylene (PCE) and trichloroethylene (TCE) can only be applied if the transformation products are environmentally acceptable. Studies with enrichment cultures of PCE- and TCE-degrading microorganisms provide evidence that, under methanogenic conditions, mixed cultures are able to completely dechlorinate PCE and TCE to ethylene, a product which is environmentally acceptable. Radiotracer studies with [14C]PCE indicated that [14C]ethylene was the terminal product; significant conversion to 14CO2 or 14CH4 was not observed. The rate-limiting step in the pathway appeared to be conversion of vinyl chloride to ethylene. To sustain reductive dechlorination of PCE and TCE, it was necessary to supply an electron donor; methanol was the most effective, although hydrogen, formate, acetate, and glucose also served. Studies with the inhibitor 2-bromoethanesulfonate suggested that methanogens played a key role in the observed biotransformations of PCE and TCE.

/pdf/biological-reductive-dechlorination-of-tetrachloroethylene-3cdz2gyfeo.pdf

Biological reductive dechlorination of tetrachloroethylene and trichloroethylene to ethylene under methanogenic conditions.

Previous studies indicated that dechlorinators can utilize H2 at lower concentrations than can methanogens. This suggests a strategy for selective enhancement of dechlorinationmanaging H2 delivery so as to impart a competitive advantage to dechlorinators. Four H2 donorsbutyric and propionic acids, which can only be fermented when the H2 partial pressure is lower than 10-3.5 or 10-4.4 atm, respectively, and ethanol and lactic acid, which are readily fermented at H2 partial pressures 2−3 orders of magnitude higherwere administered to anaerobic mixed cultures. Comparison of the resulting enrichment cultures during time-intensive, short-term tests showed significant differences in patterns of donor degradation, H2 production and use, and distribution of reduction equivalents between dechlorination and competing methanogenesis. Amendment with butyric and propionic acids resulted in less methanogenesis than did amendment with ethanol or lactic acid, which generated much higher H2 levels. Ethanol did not support...

Comparison of Butyric Acid, Ethanol, Lactic Acid, and Propionic Acid as Hydrogen Donors for the Reductive Dechlorination of Tetrachloroethene

Tetrachloroethene, also known as perchloroethylene (PCE), is a common groundwater contaminant throughout the United States. The incomplete reductive dechlorination of PCE--resulting in accumulations of trichloroethene, dichloroethene isomers, and/or vinyl chloride--has been observed by many investigators in a wide variety of methanogenic environments. Previous mixed-culture studies have demonstrated that complete dechlorination to ethene is possible, although the final dechlorination step from vinyl chloride to ethene is rate limiting, with significant levels of vinyl chloride typically persisting. In this study, anaerobic methanol-PCE enrichment cultures which proved capable of dechlorinating high concentrations PCE to ethene were developed. Added concentrations of PCE as high as 550 microM (91-mg/liter nominal concentration; approximately 55-mg/liter actual aqueous concentration) were routinely dechlorinated to 80% ethene and 20% vinyl chloride within 2 days at 35 degrees C. The methanol level used was approximately twice that needed for complete dechlorination of PCE to ethene. The observed transformations occurred in the absence of methanogenesis, which was apparently inhibited by the high concentrations of PCE. When incubation was allowed to proceed for as long as 4 days, virtually complete conversion of PCE to ethene resulted, with less than 1% persisting as vinyl chloride. An electron balance demonstrated that methanol consumption was completely accounted for by dechlorination (31%) and acetate production (69%). The high volumetric rates of PCE dechlorination (up to 275 mumol/liter/day) and the relatively large fraction (ca. one-third) of the supplied electron donor used for dechlorination suggest that reductive dechlorination could be exploited for bioremediation of PCE-contaminated sites.

https://aem.asm.org/content/aem/57/8/2287.full.pdf

James M. Gossett

Papers

Isolation of a Bacterium That Reductively Dechlorinates Tetrachloroethene to Ethene

Measurement of Henry's law constants for C1 and C2 chlorinated hydrocarbons

Biological reductive dechlorination of tetrachloroethylene and trichloroethylene to ethylene under methanogenic conditions.

Comparison of Butyric Acid, Ethanol, Lactic Acid, and Propionic Acid as Hydrogen Donors for the Reductive Dechlorination of Tetrachloroethene

Reductive dechlorination of high concentrations of tetrachloroethene to ethene by an anaerobic enrichment culture in the absence of methanogenesis.