No abstract

There is growing interest in the concept of ''mechanism'' across many areas of the social sciences. In the field of program and policy evaluation, a number of scholars have also emphasized the importance of causal mechanisms for explaining how and why programs work. However, there appears to be some ambiguity about the meaning and uses of mechanism-based thinking in both the social science and evaluation literature. In this article we attempt to clarify what is meant by mechanisms in the context of program evaluation by identifying three main characteristics of mechanisms and outlining a possible typology of mechanisms. A number of theoretical and practical implications for evaluators are also discussed, along with some precautions to consider when investigating mechanisms that might plausibly account for program outcomes.

Nowadays,statesspendmoreattention,time,andmoneyonperformancemeasurement and evaluation in the public sector than ever before (Organization for Economic Cooperation and Development [OECD], 1996; Pollitt & Bouckaert, 2000, p. 87; Power, 1997). Results-based management is the talk of the day at all levels of the public sector: local, regional, national, and even supra national. Schools and universities, local governments, and other administrative agencies, also developmental aid organizations (nongovernmental organizations and international nongovernmental organizations) and organizations such as the World Bank, are all involved in producing data and information on performance results and-if possible-impact. Power (1994, 1997, 2000) even refers to the "audit explosion" or the "audit society." Believers in New Public Management (NPM) attribute a high priority to measuring output and outcomes and aim to base their new policies and management activities on this type of information-ideally meant to make policy implementation more efficient and effective. However, evaluation studies show that many attempts to introduce results-based management are still unsuccessful (see, for example, Leeuw & Van Gils, 1999, for a review of Dutch studies). Nevertheless, the need for measuring output, outcomes, and evaluation activities remains an important element in statements by politicians and administrators focused on improving government's performance. Below, we will argue that this increase of output measurement in the public sector can lead to several unintended consequences that may not only invalidate conclusions on public sector performance but can also negatively influence that performance. We will show that a number of characteristics of the public sector can be counterproductive to developing and using performance indicators, illustrated by different examples. Finally, we will conclude with some suggestions on how to deal with the problem of performance assessment in the public sector. We believe this question is important

Nowadays,statesspendmoreattention,time,andmoneyonperformancemeasurement and evaluation in the public sector than ever before (Organization for Economic Cooperation and Development [OECD], 1996; Pollitt & Bouckaert, 2000, p. 87; Power, 1997). Results-based management is the talk of the day at all levels of the public sector: local, regional, national, and even supra national. Schools and universities, local governments, and other administrative agencies, also developmental aid organizations (nongovernmental organizations and international nongovernmental organizations) and organizations such as the World Bank, are all involved in producing data and information on performance results and-if possible-impact. Power (1994, 1997, 2000) even refers to the "audit explosion" or the "audit society." Believers in New Public Management (NPM) attribute a high priority to measuring output and outcomes and aim to base their new policies and management activities on this type of information-ideally meant to make policy implementation more efficient and effective. However, evaluation studies show that many attempts to introduce results-based management are still unsuccessful (see, for example, Leeuw & Van Gils, 1999, for a review of Dutch studies). Nevertheless, the need for measuring output, outcomes, and evaluation activities remains an important element in statements by politicians and administrators focused on improving government's performance. Below, we will argue that this increase of output measurement in the public sector can lead to several unintended consequences that may not only invalidate conclusions on public sector performance but can also negatively influence that performance. We will show that a number of characteristics of the public sector can be counterproductive to developing and using performance indicators, illustrated by different examples. Finally, we will conclude with some suggestions on how to deal with the problem of performance assessment in the public sector. We believe this question is important

A 500, 400 and 300 MHz proton NMR study of the reaction product of cis-Pt(NH3)2Cl2 or cis-[Pt(NH3)2 (H2O)2] (NO3)2 with the deoxydinucleotide d(GpG): cis-[Pt(NH3)2 d(GpG)] was carried out. Complete assignment of the proton resonances by decoupling experiments and computer simulation of the high field part of the spectrum yield proton-proton and proton-phosphorus coupling constants of high precision. Analysis of these coupling constants reveal a 100% N (C3'-endo) conformation for the deoxyribose ring at the 5'-terminal part of the chelated d(GpG) moiety. In contrast, the 3'-terminal -pG part of the molecule displays the normal behaviour for deoxyriboses: the sugar ring prefers to adopt an S (C2'-endo) conformation (about 70%). Extrapolating from this model compound, it is suggested that Pt chelation by a -dGpdG- sequence of DNA would require a S to N conformational change of one deoxyribose moiety as the main conformational alteration and lead to a kink in one strand of the double-helical structure of DNA.

SynopsisThe relationship between published vicinal proton-proton coupling constants and the pseudorotation properties of the pyrrolidine ring in L-proline, 4-hydroxy-~-proline, 4-fluoro-L-proline, and several linear and cyclic model proline peptides is investigated. Compared to earlier studies, several important improvements are incorporated (1) a new empirical generalization of the classical Karplus equation is utilized, which allows a valid correction for the effects of electronegativity and orientation of substituents on 35HH; (2) an empirical correlation between proton-proton torsion angles and the pseudorotational parameters P and T, is derived; and (3) the best fit of the conformational parameters to the experimental coupling constants is obtained by means of a computerized iterative least-squares procedure. Two pseudorotation ranges were considered, classified as type N ( x 2 positive sign) and type S (XZ negative sign). The conformational equilibrium is fully described in terms of four geometrical parameters (PN, TN, Ps, 7s) and the equilibrium constant K . The present results indicate that, in general, the geometrical properties found in x-ray studies of proline and hydroxyproline residues are well preserved in solution. Several novel features are encountered, however. It is demonstrated that the proline ring occurs in a practically 1:l conformational equilibrium between well-defined N-and S-type forms. Introduction of an amide group at the C-terminal end has no observable effect on this equilibrium, but the formation of a peptide bond a t the imino nitrogen site results in a pronounced, but not exclusive, preference for an S-type form which is roughly 1.1 kcal/mol more stable than its N-type counterpart. The hydroxyproline ring system in neutral or acidic medium displays a pure N-type state, but N-acetylation results in the appearance of a minor (S-type) conformation. Cyclic proline dipeptides similarly exist in a biased conformational equilibrium. The major form (77-88%) corresponds to the N-type conformer observed in the solid state; the minor S-form has not been observed before. In contrast, cyclic hydroxyproline dipeptides display complete conformational purity. Ranges of endocyclic torsion angles deduced for the various classes of pyrrolidine derivatives in solution are presented. Each torsion appears confined to a surprisingly narrow range, comprising about 4'-8" in most cases. In all, the proline ring is far less "floppy" than hitherto assumed.

No abstract

The relationship between vicinal N M R proton-proton coupling constants and the pseudorotational properties of the sugar ring in nucleosides and nucleotides is reinvestigated. Compared with our earlier study several important improvements are introduced: first, a new empirical generalization of the classical Karplus equation is utilized, which allows an accurate correction for the effects of electronegativity and orientation of substituents on 3J(EIH); second, empirical correlations between the parameters governing the conformation of p-D-furanosides (taken from an analysis of 178 crystal stmctores) were used to define proton-proton torsion angles as a fnnctiou of the pseudorotation parameters P and a,,,; and, third an iterative least-squares computer program was devised to obtain the best fit of the conformational parameters to the experimental coupling constants. N M R data for the sugar ring in the following compounds were taken from the literature and analysed: 3',5'-cy&c nudeotides, a base-stacked nionucleotide, 2'-~ydroarabinonucleosides, or-~-2',2-0-cyclouridine, 2'-and 3'-aminosubstituted ribonucleosides, 2'-and 3'-deoxyribonucleosides. The present results confirm that the conformational properties found in the solid state are, on the whole, preserved in solution.