Three-dimensional Structure of L-2-Haloacid Dehalogenase from Xanthobacter autotrophicus GJ10 Complexed with the Substrate-analogue Formate

The L-2-haloacid dehalogenase from the 1,2-dichloroethane degrading bacterium Xanthobacter autotrophicus GJ10 catalyzes the hydrolytic dehalogenation of small L-2-haloalkanoic acids to yield the corresponding D-2-hydroxyalkanoic acids. Its crystal structure was solved by the method of multiple isomorphous replacement with incorporation of anomalous scattering information and solvent flattening, and was refined at 1.95-Å resolution to an R factor of 21.3%. The three-dimensional structure is similar to that of the homologous L-2-haloacid dehalogenase from Pseudomonas sp. YL (1), but the X. autotrophicus enzyme has an extra dimerization domain, an active site cavity that is completely shielded from the solvent, and a different orientation of several catalytically important amino acid residues. Moreover, under the conditions used, a formate ion is bound in the active site. The position of this substrate-analogue provides valuable information on the reaction mechanism and explains the limited substrate specificity of the Xanthobacter L-2-haloacid dehalogenase.

Imaging Molecular Structure through Femtosecond Photoelectron Diffraction on Aligned and Oriented Gas-Phase Molecules

This paper gives an account of our progress towards performing femtosecond time-resolved photoelectron diffraction on gas-phase molecules in a pump-probe setup combining optical lasers and an X-ray Free-Electron Laser. We present results of two experiments aimed at measuring photoelectron angular distributions of laser-aligned 1-ethynyl-4-fluorobenzene (C8H5F) and dissociating, laseraligned 1,4-dibromobenzene (C6H4Br2) molecules and discuss them in the larger context of photoelectron diffraction on gas-phase molecules. We also show how the strong nanosecond laser pulse used for adiabatically laser-aligning the molecules influences the measured electron and ion spectra and angular distributions, and discuss how this may affect the outcome of future time-resolved photoelectron diffraction experiments.Comment: 24 pages, 10 figures, Faraday Discussions 17

Confidentiality and public protection: ethical dilemmas in qualitative research with adult male sex offenders

This paper considers the ethical tensions present when engaging in in-depth interviews with convicted sex offenders. Many of the issues described below are similar to those found in other sensitive areas of research. However, confidentiality and public protection are matters that require detailed consideration when the desire to know more about men who have committed serious and harmful offences is set against the possibility of a researcher not disclosing previously unknown sensitive information that relates to the risk of someone being harmed.</p

Ultraintense X-Ray Induced Ionization, Dissociation, and Frustrated Absorption in Molecular Nitrogen

Sequential multiple photoionization of the prototypical molecule N_2 is studied with femtosecond time resolution using the Linac Coherent Light Source (LCLS). A detailed picture of intense x-ray induced ionization and dissociation dynamics is revealed, including a molecular mechanism of frustrated absorption that suppresses the formation of high charge states at short pulse durations. The inverse scaling of the average target charge state with x-ray peak brightness has possible implications for single-pulse imaging applications

A comparison of new occupational progressive lens versus the Varilux for occupational use

Seventeen presbyopic subjects with a need of an occupational lens for intermediate distance tasks were selected from the Pacific University faculty and staff for fitting with the Varilux progressive addition lens (PAL) and an experimental PAL manufactured by Essilor Corporation. Subjects wore each set of lenses for a period of three weeks and responded to a questionnaire assessing adaptability, visual comfort, visual acuity, and effectiveness at intermediate tasks. Subjects were then given both sets of lenses for one week. When finished they were asked to make a choice of which lenses they preferred for occupational and recreational tasks. The results indicate that the experimental lens is not significantly better than the Varilux for occupational or recreational use

Testing for knowledge: Application of machine learning techniques for prediction of flashover in a 1/5 scale ISO 13784‐1 enclosure

A machine learning algorithm was applied to predict the onset of flashover in archival experiments in a 1/5 scale ISO 13784‐1 enclosure constructed with sandwich panels. The experiments were performed to assess whether a small‐scale model could provide a better full‐scale correlation than the single burning item test. To predict the binary output, a regularized logistic regression model was chosen as ML environment, for which lasso‐regression significantly reduced the amount of variance at a negligible increase in bias. With the regularized model, it was possible to discern the predictive variables and determine the decision boundary. In addition, a methodology was put forward on how to use the to update the learning algorithm iteratively. As a result, it was shown how a learning algorithm can be used to facilitate ongoing experimentation. At first as a crude guideline, and in later stages, as an accurate prediction algorithm. It is foreseen that, by iteratively updating the algorithm, by compiling existing and new experiments in databases, and by applying fire safety knowledge, the final learned algorithm will be able to make accurate predictions for unseen samples and test conditions