Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

A DSP-based Readout and Online Processing System for a new Focal-plane Polarimeter at AGOR

A Focal-Plane Polarimeter (FPP) for the large acceptance Big-Bite Spectrometer (BBS) at AGOR using a novel readout architecture has been commissioned at the KVI Groningen. The instrument is optimized for medium-energy polarized proton scattering near or at 0 degrees. For the handling of the high counting rates at extreme forward angles and for the suppression of small-angle scattering in the graphite analyzer, a high-performance data processing DSP system connecting to the LeCroy FERA and PCOS ECL bus architecture has been made operational and tested successfully. Details of the system and the functions of the various electronic components are described. (C) 1999 Elsevier Science B.V. All rights reserved.</p

A DSP-based readout and online processing system for a new focal-plane polarimeter at AGOR.

A Focal-Plane Polarimeter (FPP) for the large acceptance Big-Bite Spectrometer (BBS) at AGOR using a novel readout architecture has been commissioned at the KVI Groningen. The instrument is optimized for medium-energy polarized proton scattering near or at 0 degrees. For the handling of the high counting rates at extreme forward angles and for the suppression of small-angle scattering in the graphite analyzer, a high-performance data processing DSP system connecting to the LeCroy FERA and PCOS ECL bus architecture has been made operational and tested successfully. Details of the system and the functions of the various electronic components are described. (C) 1999 Elsevier Science B.V. All rights reserved

Measurement and microscopic analysis of the B (p,p) reaction at Ep=150MeV.II Depolarization in elastic scattering from odd-A nuclei

The polarization-transfer coefficient Dnn&#039; in the elastic scattering of 150-MeV protons from 11B has been measured in the angular range 5º&lt;theta c.m.&lt;31º. Significant deviations of Dnn&#039; from unity are observed starting around a center-of-mass scattering angle of 23º. The observed angular variation of Dnn&#039; is analyzed using phenomenological and microscopically generated optical-model potentials to describe the monopole attributes of elastic scattering and to generate the distorted waves used in a distorted-wave approximation evaluation of nonzero multipole contributions to the elastic scattering process. The same approach is used to analyze datasets of Dnn&#039; in elastic scattering from 13C and off 15N, which are available in the literature. The agreement of the fully microscopic analysis with the data is comparable or, in the case of 11B, slightly better than what is achieved with conventional phenomenological optical-model calculations

Performance of an ASD-8 based wire chamber readout system.

For the medium-energy proton polarimeter mounted at the focal-plane of the Big-Bite Spectrometer at Kernfysisch Versneller Instituut Groningen, a new wire-chamber readout has been developed. The charge-sensitive preamplifier is based on the ASD-8 B chip which has an input impedance of 115 Omega. This low impedance and the short integration time of 6 ns at a usable sensitivity of 5 fC allow high readout rates and low gas amplifications. This front-end circuit is mounted on all four multi-wire proportional chambers and on two vertical-drift chambers with 3872 wires in total. Measurements have been made using sources and intermediate energy protons. Special attention was given to determine the time-over-threshold properties of the circuit, The time-over-threshold capabilities of the readout system extend future applications to particle discrimination, or, in connection with other detector types, to energy-resolving readout, The operational performance of the readout system is presented