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S W Singer

Publications and source records attributed to S W Singer.

5 recordsLinked to original sources
PubMed2001

Hydrogen transfer to carbonyls and imines from a hydroxycyclopentadienyl ruthenium hydride: evidence for concerted hydride and proton transfer.

Reaction of ([2,5-Ph(2)-3,4-Tol(2)(eta(5)-C(4)CO)](2)H)Ru(2)(CO)(4)(mu-H) (6) with H(2) formed [2,5-Ph(2)-3,4-Tol(2)(eta(5)-C(4)COH)Ru(CO)(2)H] (8), the active species in catalytic carbonyl reductions developed by Shvo. Kinetic studies of the reduction of PhCHO by 8 in THF at -10 degrees C showed second-order kinetics with Delta H(double dagger) = 12.0 kcal mol(-1) and Delta S(double dagger) = -28 eu. The rate of reduction was not accelerated by CF(3)CO(2)H, and was not inhibited by CO. Selective deuteration of the RuH and OH positions in 8 gave individual kinetic isotope effects k(RuH)/k(RuD) = 1.5 +/- 0.2 and k(OH)/k(OD) = 2.2 +/- 0.1 for PhCHO reduction at 0 degrees C. Simultaneous deuteration of both positions in 8 gave a combined kinetic isotope effect of k(OHRuH)/k(ODRuD) = 3.6 +/- 0.3. [2,5-Ph(2)-3,4-Tol(2)(eta(5)-C(4)COSiEt(3))Ru(CO)(2)H] (12) and NEt(4)(+)[2,5-Ph(2)-3,4-Tol(2)(eta(4)-C(4)CO)Ru(CO)(2)H](-) (13) were unreactive toward PhCHO under conditions where facile PhCHO reduction by 8 occurred. PhCOMe was reduced by 8 30 times slower than PhCHO; MeN=CHPh was reduced by 8 26 times faster than PhCHO. Cyclohexene was reduced to cyclohexane by 8 at 80 degrees C only in the presence of H(2.) Concerted transfer of a proton from OH and hydride from Ru of 8 to carbonyls and imines is proposed.

Aldehydes↗
PubMed1995

Format-independent data collection forms.

Good form design is generally acknowledged to be a key element of clinical trials and follow-up studies. Although some data are collected directly from automated equipment, most measurements, examination findings, and interview responses require at least one manual transcription, either onto paper forms or directly into a computer. Regardless of the transcription method adopted, there is broad agreement that the quality of study data depends strongly on the format and layout of the data collection instruments. The task of form design and production is complicated by two facts: first, a series of different forms is needed even when the period of follow-up is short; and second, form design is an ongoing process that starts before the first person is enrolled and continues over the course of the trial. This paper (1) presents a concept (format independence) aimed at simplifying the design and revision of data collection forms; (2) explains how a feature (styles) present in most word processing software can be used to implement the concept; (3) discusses the advantages and disadvantages of a format-independent approach as compared to more traditional form development tools; and (4) describes the environment that prompted this approach to form development.

Clinical Trials as Topic↗
PubMed1986

Design, development, and implementation of a data processing system for multiple controlled trials and epidemiologic studies.

We were given the opportunity to design and implement a general data processing system to accommodate several different epidemiologic studies to be conducted by a new research group. A survey of 15 operating data centers was conducted in preparation for undertaking the design and development of our system. The results of the survey indicated that data processing activities can be classified, both conceptually and operationally, into three modules: data recording and data entry, data management, and data analysis, and that the data management functions were those amenable to generalization. Based on our survey and the varying needs of our studies, we selected a "mixed" hardware environment, using both a computer center mainframe and microcomputers. We created the systems using commercially available software, including a mainframe database manager and mainframe statistics packages, microcomputer data entry software, and a communications package to link the two environments. Our strategy was to buy software, when possible, rather than to build custom programs, and to let software tools govern hardware needs. Hardware independence, price, and functional capability directed our software choices, while hardware selection was constrained most importantly by available software, then by budget, by available computing resources, and finally by the marketplace. The system has been used successfully in three studies differing in design, size, data collection locale, and rate of data accrual.

Data Collection↗