Transport of chloramphenicol into sensitive strains of Escherichia coli and Pseudomonas aeruginosa

The uptake of chloramphenicol by susceptible strains of Escherichia coli and Pseudomonas aeruginosa was measured as the depletion of 14C-chloramphenicol from the supernatant of centrifuged cultures. Chloramphenicol did not bind to non-growing cells or isolated cell envelopes. Chloramphenicol was recovered from cells in an unchanged form and was intracellularly concentrated several times above external concentrations. The net accumulation of the drug was reduced by an inhibitor of electron transport, by an oxidative phosphorylation uncoupler, by an inhibitor of high energy phosphate synthesis, and by lowering the temperature to + 15°C. The initial uptake of drug was saturated at 1.98 mM chloramphenicol in the medium. A 100-fold excess of each of the unlabelled isomers: L-threo, D-threo, and L-erythro chloramphenicol in cultures of either strain effectively reduced the uptake of 14C-chloramphenicol. These results indicate that chloramphenicol enters Gram-negative bacteria by means of an energy-dependent proces

ABC Diffusion in the Age of Digital Economy: the UK Experience

Since the beginning of the 21st century, there has been a call for further research to trace the effects of the speedy changes in business environment on management accounting practices. This study assesses the impact of different information technologies on ABC adoption and implementation. It uses a cross-sectional survey of financial directors and controllers in the UK firms. Postal and electronic questionnaires have been used in order to collect the empirical data. The findings revealed that the rate of ABC adoption has shown a number of changes between 1999 and 2005. The proportions of ABC users and those currently assessing it have dramatically fallen. The percentage of firms rejecting ABC has slightly fallen as well. However, there has been a considerable increase in the number of firms that abandoned ABC implementation and those firms that gave no consideration for its implementation. These results indicate a decrease in the popularity of ABC. ERP systems seem to have a slightly low significant impact on the initial decision of ABC adoption in those firms that do not have any consideration for ABC and firms that have an ERP system before ABC adoption. Furthermore, the results indicate that firms use different information technologies in the ABC assessment and implementation. For ABC assessment, general software applications are the most preferable software packages while a mix of different ABC software packages is the most popular in the case of ABC implementation. Finally, the findings of this study provide an indication on the nature of the possible effect of general IT-related problems on ABC implementation

Assessment of Multi-Story Building Seismic Design Factors with Structural Irregularity

Many high-rise buildings are practically irregular as a result of the architectural and service requirements in the design process, errors and modification during the construction phase, and changes of the building use throughout its service life. Structural irregularities could increase the uncertainties related to the ability of the building to meet the design objectives. This study is thus devoted to assess the safety margins and calibrate the seismic design response factors of modern high-rise buildings with different vertical irregularity features. A brief survey of the most common vertical irregularities inn reinforced concrete multi-story buildings is conducted to select reference structures. Five 50-story high-rise buildings are then selected and fully designed using international building codes to represent well-designed tall buildings with principal vertical irregularity types. Fiber-based simulation models are developed to assess the seismic response of the five benchmark buildings under the effect of forty earthquake records representing far-field and near-field seismic scenarios. The comprehensive results obtained from inelastic pushover and incremental dynamic analyses are employed to provide insights into the local and global seismic response of the reference structures. The probabilistic vulnerability assessment of the five high-rise buildings is conducted at different limit states using fragility relationships. The study concluded that the seismic performance of well-designed regular and vertically irregular high-rise buildings is satisfactory under the design earthquake. Under severe earthquakes, the seismic response of tall buildings with extreme soft story and geometry irregularity is not inferior to that of the regular counterpart at different seismic performance levels. Despite the over strength factor adopted in the design of buildings with discontinuities in the lateral-force-resisting system and extreme weak story, the observed negative impacts of these irregularity categories on increasing the vulnerability of high-rise buildings are substantial. This confirms the pressing need for mitigation strategies to reduce the expected seismic losses of the latter classes of building. The calibration of seismic design response factors of the reference high-rise buildings also confirms that, although the code coefficients are adequately conservative, they can be revised to arrive at a more efficient and cost-effective design of regular and irregular high-rise building