Principles of gamma ray densitometry

The use of gamma rays provides an important non-destructive method for determining the density of PM and other powder-based components. Its use within press shops can reduce tool setup times and improve press utilization. In this first article in a two-part series, Georg Schlieper of Gammatec details the principles of the test method, and addresses issues such as safety and accuracy.     

Review of Teaching children with learning and behavior problems.

Reviews the book, Teaching children with learning and behavior problems by Donald D. Hammill, Nettie R. Bartel, and Gary Owen Bunch (1984). This book was published in 1975 and re-edited in 1978 and 1982 as a practical reference book for classroom teachers. The 1984 "Canadian Edition" by Hammill, Bartel, and Bunch essentially consists of the 1982 text with an introductory chapter by Bunch and with additions and deletions aimed at providing a Canadian orientation. The authors seem deliberately to have kept the book's Canadian features separate from the basic text. Not only are there two prefaces and two introductory chapters: all textual additions are referenced in a separate bibliography and separate subject and author indexes. This referencing system is especially irritating because it is not always possible to guess from context whether a citation will appear in the "standard" or the Canadian listing. Finally, a useful list is given of Canadian sources for tests and materials. The overall effect of this format is to emphasize the book's discontinuities and to remind the reader that the preexisting text has not undergone a major revision or re-integration. This text begins with a general statement on special education needs and continues with chapters on reading, spelling, handwriting, composition, mathematics, language, behaviour problems, and perceptual-motor training. The traditional subject-area chapters are its strongest feature and include excellent scope-and-sequence charts, useful information on identification, and practical remedial suggestions. this ill-assorted book offers a stimulating Canadian-focused introduction to a worthwhile but rather time-worn text that does not cover Canadian issues in any meaningful way. A better book might have resulted from an updating for the international market rather than from this attempt at Canadianization. Our need for material that addresses the specifically Canadian aspects of special education is as great as ever. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A lethal mutant of the catabolite gene activator protein CAP of Escherichia coli

The dimeric catabolite gene activator protein (CAP) of Escherichia coli uses its recognition helix to bind with each subunit the DNA sequence motif 5' G-7T-6G-5A-4 3'. It makes a direct amino acid-base contact with E181 and cytosine in position-5' on the reverse strand. While testing mutants of CAP in position 181 for specificity changes, we found that CAP E181Q is lethal in high amounts for the E. coli strains we used for cloning. We cloned this CAP mutant successfully in cya- strains, where CAP is inactive. Examination of the in vitro binding activities of CAP E181Q, and of in vivo activity when present in low, non-lethal amounts, revealed loss of specificity but not of binding capacity for its DNA targets. It binds well to CAP consensus with G or T in position-5, better to CAP consensus with A, C in position-5, quite well to lambda consensus operator with G in position-7 and rather weakly to lambda consensus.