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

Expansivity of arsenopyrite (FeAsS) determined by in situ synchrotron X-ray diffraction experiment at high temperature and ambient pressure

The high-temperature cell parameters of arsenopyrite (FeAsS) have been determined from 300 to 673 K through in situ angle-dispersive X-ray diffraction experiments with synchrotron radiation at Beijing Synchrotron Radiation Facility (BSRF). No phase change has been observed up to the maximum temperature in this study. Thermal expansion coefficients of arsenopyrite were determined from the measured cell volumes with equations of the form alpha= alpha(0) + alpha T-1+alpha(2)/T(2)for the first time. The value of volume expansion coefficient is 3.1(2) x 10(-5) K-1. Furthermore, we confirm that the linear expansivities along a, b and c directions of arsenopyrite are almost isotropic [alpha(a) = 1.2(3) x 10(-5), alpha(b) = 0.8(3) x 10(-5), and alpha(c), = 0.8(2) x 10(-5) K-1] within their uncertainties. Furthermore, the effects of anionic substitution on the determination of expansivity between arsenopyrite and pyrite were discussed

The high-pressure elastic properties of celestine and the high-pressure behavior of barite-type sulphates

The structural stability and elastic properties of celestine have been investigated at room temperature and pressure up to 15GPa, by using in situ angle-dispersive X-ray diffraction and a diamond anvil cell. No phase change is observed within the range of pressure in this study. Analysis of room temperature P-V data to a third-order Birch-Murnaghan (BM) Eos yields: the zero-pressure volume V-0 = 306.0(6) angstrom(3), isothermal bulk modulus K-0 = 62(5) GPa and its pressure derivative K'(0) = 11(1). If K'(0) is fixed at 4, then the isothermal bulk modulus is K-0 = 98(2) GPa. In addition, the axial compressiblity moduli of the three unit cell axes of celestine are obtained as K-a0 = 102(2) GPa, K-b0 = 92(2) GPa and K-c0 = 98(2) GPa, indicating the anisotropy of axial compressibility, with the a axis the most incompressible and the b axis the most compressible. Furthermore, the elastic properties of barite-type sulfates are discussed by combining the results in this study with previous studies on barite-group minerals

Phase transition and thermoelastic behavior of cadmium sulfide at high pressure and high temperature

The phase transition and thermal equation of state of cadmium sulfide (CdS) were studied at high pressure and temperature conditions up to 21.9 GPa and 650 K, by using in situ synchrotron angle-dispersive X-ray diffraction and an externally-heated diamond anvil cell (DAC). A pressure-induced phase transition from wurtzite structure (WZ) to rocksalt structure (RS) was observed at about 2.6 GPa, which was agreed with previous studies (2.0-3.5 GPa). In addition, fitting of the experimental data by means of the third-order Brich-Murnaghan equation of state (III-BM EoS) gives the bulk modulus K-0 = 81.6 (13) GPa, its pressure derivative K'(0) = 3.68 (13), and the volumetric thermal expansion coefficient alpha(0) = 2.97 (25) x 10(-5) K-1 for RS phase of CdS. Simultaneously, the thermal expansion coefficient (alpha(0) = 1.51 x 10(-5) K-1), and its axial thermal expansivities (8.30 x 10(-6) K-1 and 5.96 x 10(-6) K-1) along a-axis and c-axis for WZ phase of CdS at ambient conditions were obtained, respectively. Moreover, it was found that the phase transition pressure from WZ (or ZB) type to RS type of cadmium chalcogenides (CdS, CdSe and CdTe) is quite similar by comparing their phase transition pressures. Furthermore, the elastic properties of metal sulfides (ZnS, CdS, HgS, PbS) with the same crystal structure but different metal cations were also discussed, and found that the bulk moduli for the RS phase of metal sulfides (ZnS, CdS, HgS, PbS) have a negative correlation with the cation radius, but a positive correlation with the electronegativity. (c) 2018 Elsevier B.V. All rights reserved

Crystal-Chemical Properties of Synthetic Almandine-Pyrope Solid Solution by X-Ray Single-Crystal Diffraction and Raman Spectroscopy

Crystal-chemical properties of synthetic Almandine-Pyrope (Alm-Pyr) solid solutions were investigated by X-ray single-crystal diffraction and Raman spectroscopy. Garnet solid solution with different compositions were synthesized from powder at 4.0 GPa and annealed at 1200 °C for 48 h by a multi-anvil pressure apparatus. Garnet crystals with different sizes (about 60–1000 μm) were obtained from synthesis. The results of X-ray single-crystal diffraction show that the unit cell constants decrease with increasing Pyr contents in the synthetic Alm-Pyr crystals due to the smaller ionic radius of Mg2+ in eightfold coordination than that of Fe2+. The data exhibit obviously positive deviations from ideal mixing volumes across the Alm-Pyr join which may be caused by the distortion of the SiO4 tetrahedron. Moreover, the significant decrease in the average M-O bond length and volume of the [MgO8]/[FeO8] dodecahedron with increasing Pyr contents are the most important factors to the decrease in the Alm-Pyr crystal unit cell constant and volume. On the other hand, selected bond distances (average <M-O>, <Al-O>, and <D-O> distances) have a linear correlation with the unit-cell parameter, but the <Si-O> distance has nonlinear correlation. With increasing the unit-cell parameter, the average <M-O> distance increases significantly, followed by the average <D-O> and <Al-O> distances. While the <Si-O> distance changes negligibly further confirming the conclusion that the significant decrease of the average M-O bond length of the [MgO8]/[FeO8] dodecahedron with increasing Pyr contents are the most important factors to the decrease in the Alm-Pyr crystal unit cell volume. In the Raman spectra collected for the Alm-Pyr solid solutions, Raman vibration mode assignments indicate that the Raman vibrational spectra change along the Alm-Pyr binary solution. The mode frequencies of Si-O stretching, Si-O bending, and the rotation of the SiO4-tetrahedron (R(SiO4)) decrease linearly, while the translational modes of the SiO4-tetrahedron (T(SiO4)) increase with increasing Alm contents

Topaz, a Potential Volatile-Carrier in Cold Subduction Zone: Constraint from Synchrotron X-ray Diffraction and Raman Spectroscopy at High Temperature and High Pressure

The equation of state and stability of topaz at high-pressure/high-temperature conditions have been investigated by in situ synchrotron X-ray diffraction (XRD) and Raman spectroscopy in this study. No phase transition occurs on topaz over the experimental pressure–temperature (P-T) range. The pressure–volume data were fitted by the third-order Birch–Murnaghan equation of state (EoS) with the zero-pressure unit–cell volume V0 = 343.86 (9) Å3, the zero-pressure bulk modulus K0 = 172 (3) GPa, and its pressure derivative K’0 = 1.3 (4), while the obtained K0 = 155 (2) GPa when fixed K’0 = 4. In the pressure range of 0–24.4 GPa, the vibration modes of in-plane bending OH-groups for topaz show non-linear changes with the increase in pressure, while the other vibration modes show linear changes. Moreover, the temperature–volume data were fitted by Fei’s thermal equation with the thermal expansion coefficient α300 = 1.9 (1) × 10−5 K−1 at 300 K. Finally, the P-T stability of topaz was studied by a synchrotron-based single-crystal XRD at simultaneously high P-T conditions up to ~10.9 GPa and 700 K, which shows that topaz may maintain a metastable state at depths above 370 km in the upper mantle along the coldest subducting slab geotherm. Thus, topaz may be a potential volatile-carrier in the cold subduction zone. It can carry hydrogen and fluorine elements into the deep upper mantle and further affect the geochemical behavior of the upper mantle