Observing many researchers using the same data and hypothesis reveals a hidden universe of uncertainty

This study explores how researchers' analytical choices affect the reliability of scientific findings. Most discussions of reliability problems in science focus on systematic biases. We broaden the lens to emphasize the idiosyncrasy of conscious and unconscious decisions that researchers make during data analysis. We coordinated 161 researchers in 73 research teams and observed their research decisions as they used the same data to independently test the same prominent social science hypothesis: that greater immigration reduces support for social policies among the public. In this typical case of social science research, research teams reported both widely diverging numerical findings and substantive conclusions despite identical start conditions. Researchers' expertise, prior beliefs, and expectations barely predict the wide variation in research outcomes. More than 95% of the total variance in numerical results remains unexplained even after qualitative coding of all identifiable decisions in each team's workflow. This reveals a universe of uncertainty that remains hidden when considering a single study in isolation. The idiosyncratic nature of how researchers' results and conclusions varied is a previously underappreciated explanation for why many scientific hypotheses remain contested. These results call for greater epistemic humility and clarity in reporting scientific findings.

Factors affecting client response to HIV outreach efforts

PURPOSE

This article describes 12 HIV Outreach Demonstration Projects funded by the Center for Substance Abuse Treatment in 1995, and the clients these projects served. The article also summarizes the findings of multivariate statistical analyses aimed at identifying important project and client characteristics that influenced project success in achieving two key outcomes: persuading at-risk clients to obtain HIV tests, and facilitating entry by substance-abusing clients into structured substance abuse treatment (SAT).

METHODS

Hierarchical linear modeling (HLM) analysis was used to conduct the analyses.

RESULTS

The findings support the hypothesis that HIV Outreach, as an integrated approach to addressing the multiple problems clients have due to substance abuse and related problems, can be an effective model for reaching clients who have not been reached through traditional means.

IMPLICATIONS

By implementing a complement of comprehensive HIV Outreach interventions, many of the HIV Outreach projects were successful in addressing the various needs of their clients. However, as detailed in this article, some services and service delivery procedures, were more effective than others in achieving project objectives.

MioC is an FMN-binding protein that is essential for Escherichia coli biotin synthase activity in vitro

Biotin synthase is required for the conversion of dethiobiotin to biotin and requires a number of accessory proteins and small molecule cofactors for activity in vitro. We have previously identified two of these proteins as flavodoxin and ferredoxin (flavodoxin) NADP(+) reductase. We now report the identification of MioC as a third essential protein, together with its cloning, purification, and characterization. Purified MioC has a UV-visible spectrum characteristic of a flavoprotein and contains flavin mononucleotide. The presence of flavin mononucleotide and the primary sequence similarity to flavodoxin suggest that MioC may function as an electron transport protein. The role of MioC in the biotin synthase reaction is discussed, and the structure and function of MioC is compared with that of flavodoxin.

Murein chemistry of cell division in Escherichia coli

The length distribution of the glycan strands of murein has been analysed with a novel method in filamentous and spherical cells of Escherichia coli, as well as during septum formation and cell separation. A shift to the longer glycan strands was observed in the murein of furazlocillin-induced filaments. In contrast, shorter glycan strands were increased in the murein of mecillinam-induced spherical cells. During septum formation in a chain-forming envA mutant that is defective in the splitting process of the septum, a shift to the shorter glycan strands was detected that was not seen in wild type E. coli cells. It is concluded that septum-specific murein structures of rather short glycan strands are released during splitting of the septum. This intermediate material remains present in the septum of the envA mutant. The splitting process of the septum was investigated by analysing the murein during penicillin-induced bacteriolysis, which is known to take place by strictly localized murein degradation in the equatorial zone of the cell. No changes in the length distribution of the glycan strands could be detected during penicillin-induced lysis, with the exception of an increase in disaccharides, the shortest glycan strands possible. This is explained by the action of exo-muramidases progressively digesting glycan strands, leaving disaccharide units covalently linked to the remaining murein at the sites of murein cross-linkage. It is proposed that this "zipper-like" mechanism represents the normal cutting process of the septum during cell separation.

Isolation and separation of the glycan strands from murein of Escherichia coli by reversed-phase high-performance liquid chromatography

The length distribution of the glycan strands in the murein (peptidoglycan) sacculus of Escherichia coli has been analyzed after solubilization of the murein by complete digestion with human serum amidase. The glycan strands released were separated according to length by reversed-phase HPLC on wide-pore Nucleosil 300 C18 material at 50 degrees C, employing a convex gradient from 5 to 11% acetonitrile. The length of the fractionated glycan strands, which carry a nonreducing 1,6-anhydromuramic acid as a natural end group, was calculated from the ratio of total to nonreducing terminal muramic acid residues. This was possible after complete hydrolysis of the isolated glycan strands by muramidase followed by separation of the released nonreducing and reducing di- and tetrasaccharides by reversed-phase HPLC on Hypersil C18. The method established allows the separation of the glycan strands of murein, a poly-GlcNAc(beta 1-4)MurNAc-polysaccharide, up to a degree of polymerization of approximately 60. The predominant lengths of the glycan strands were 5 to 10 GlcNAc(beta 1-4)MurNAc disaccharide units.