Ce-exchange capacity of zeolite L in different cationic forms: a structural investigation

Cerium exchange by microporous materials, such as zeolites, has important applications in different fields, for example, rare earth element recovery from waste or catalytic processes. This work investigated the Ce-exchange capacity of zeolite L in three different cationic forms (the as-synthesized K form and Naand NH4-exchanged ones) from a highly concentrated solution. Chemical analyses and structural investigations allowed determination of the mechanisms involved in the exchanges and give new insights into the interactions occurring between the cations and the zeolite framework. Different cation sites are involved: (i) K present in the original LTL in the cancrinite cage (site KB) cannot be exchanged; (ii) the cations in KD (in the 12-membered ring channel) are always exchanged; while (iii) site KC (in the eight-membered ring channel) is involved only when K+ is substituted by NH4+, thus promoting a higher exchange rate for NH4+ -> K+ than for Na+ -> K+. In the Ce-exchanged samples, a new site occupied by Ce appears in the centre of the main channel, accompanied by an increase in the number of and a rearrangement of H2O molecules. In terms of Ce exchange, the three cationic forms behave similarly, from both the chemical and structural point of view (exchanged Ce ranges from 38 to 42% of the pristine cation amount). Beyond the intrinsic structural properties of the zeolite L framework, the Ce exchange seems thus also governed by the water coordination sphere of the cation. Complete Ce recovery from zeolite pores was achieved

Cost-effective Paper-based Diagnostic Using Split Proteins to Detect Yeast Infections

The common yeast infection, vulvovaginal candidiasis, affects three out of four women throughout their lifetime and can be spread to their child in the form of oral candidiasis (thrush). This disease is caused by the fungal pathogen Candida albicans, which is also a major cause of systemic candidiasis, a rarer but deadly disease with up to a 49% lethality rate. Current widely-used diagnostic methods include cell cultures, pH tests, and antibody detection, to assist effective treatment. Despite availability of various diagnostic methods, there is no inexpensive, rapid, and accurate way to detect C. albicans infection. This project aims to develop a paper-based diagnostic test for C. albicans that is, cost-effective, quick, and precise. The test detects the specific biomarkers farnesol and tyrosol produced by C. albicans by binding them to the split proteins pqsR and tyrosinase, respectively. Upon binding, a split horseradish peroxidase catalyzes and produces an amplified colorimetric signal by oxidizing the substrate tetramethylbenzidine (TMB) turning the paper blue. This test will produce a colorimetric output for a simple-to-understand diagnosis without any infrastructure. We predict that this device can give a response in under 2 minutes while costing around an estimated 10 cents per device This test may provide a way for an easy and cheap way to diagnose candidiasis worldwide, reducing the abuse of antifungals and provide an accurate way to treat vulvovaginal candidiasis and systemic candidiasis

Cost-effective Paper-based Diagnostic Using Split Proteins to Detect Yeast Infections

The common yeast infection, vulvovaginal candidiasis, affects three out of four women throughout their lifetime and can be spread to their child in the form of oral candidiasis (thrush). This disease is caused by the fungal pathogen Candida albicans, which is also a major cause of systemic candidiasis, a rarer but deadly disease with up to a 49% lethality rate. Current widely-used diagnostic methods include cell cultures, pH tests, and antibody detection, to assist effective treatment. Despite availability of various diagnostic methods, there is no inexpensive, rapid, and accurate way to detect C. albicans infection. This project aims to develop a paper-based diagnostic test for C. albicans that is, cost-effective, quick, and precise. The test detects the specific biomarkers farnesol and tyrosol produced by C. albicans by binding them to the split proteins pqsR and tyrosinase, respectively. Upon binding, a split horseradish peroxidase catalyzes and produces an amplified colorimetric signal by oxidizing the substrate tetramethylbenzidine (TMB) turning the paper blue. This test will produce a colorimetric output for a simple-to-understand diagnosis without any infrastructure. We predict that this device can give a response in under 2 minutes while costing around an estimated 10 cents per device This test may provide a way for an easy and cheap way to diagnose candidiasis worldwide, reducing the abuse of antifungals and provide an accurate way to treat vulvovaginal candidiasis and systemic candidiasis

Thermal expansion and rattling behavior of Gd-filled Co_(4)Sb_(12) skutterudite determined by high-resolution synchrotron x-ray diffraction

In this work, Gd-filled skutterudite Gd_(x)Co_(4)Sb_(12) was prepared using one step method under high pressure in a piston-cylinder-based press at 3.5 GPa and moderate temperature of 800 degrees C. A detailed structural characterization was performed using synchrotron X-ray diffraction (SXRD), revealing a filling fraction of x = 0.033(2) and an average bond length of 3.3499(3) angstrom. The lattice thermal expansion accessed via temperature-dependent SXRD led to a precise determination of a Debye temperature of 322(3) K, from the fitting of the unit-cell volume expansion using the second order Gruneisen approximation. This parameter, when evaluated through the mean square displacements of Co and Sb, displayed a value of 265(2) K, meaning that the application of the harmonic Debye theory underestimates the Debye temperature in skutterudites. Regarding the Gd atom, its intrinsic disorder value was similar to 5x and similar to 25x higher than those of the Co and Sb, respectively, denoting that Gd has a strong rattling behavior with an Einstein temperature of theta(E) = 67(2) K. As a result, an ultra-low thermal conductivity of 0.89 W/m center dot K at 773 K was obtained, leading to a thermoelectric efficiency zT of 0.5 at 673 K

The “Historical Materials BAG”: A New Facilitated Access to Synchrotron X-ray Diffraction Analyses for Cultural Heritage Materials at the European Synchrotron Radiation Facility

The European Synchrotron Radiation Facility (ESRF) has recently commissioned the new Extremely Brilliant Source (EBS). The gain in brightness as well as the continuous development of beamline instruments boosts the beamline performances, in particular in terms of accelerated data acquisition. This has motivated the development of new access modes as an alternative to standard proposals for access to beamtime, in particular via the “block allocation group” (BAG) mode. Here, we present the recently implemented “historical materials BAG”: a community proposal giving to 10 European institutes the opportunity for guaranteed beamtime at two X-ray powder diffraction (XRPD) beamlines—ID13, for 2D high lateral resolution XRPD mapping, and ID22 for high angular resolution XRPD bulk analyses—with a particular focus on applications to cultural heritage. The capabilities offered by these instruments, the specific hardware and software developments to facilitate and speed-up data acquisition and data processing are detailed, and the first results from this new access are illustrated with recent applications to pigments, paintings, ceramics and wood

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

High Amino Acid Lattice Loading at Nonambient Conditions Causes Changes in Structure and Expansion Coefficient of Calcite

Biogenic crystals produced by organisms have been known for several decades to exhibit intracrystalline organic macromolecules. Here, using a reductionist approach, we tackle the question of whether the incorporation of single amino acids is driven by kinetics or by thermodynamics. We show that when calcite is grown in the presence of amino acids under nonambient conditions, extremely high loading levels of up to 6.12 mol % of aspartic acid (Asp) are achieved. This incorporation leads to marked changes in the host calcite crystal's structure and expansion coefficient. The latter is as much as twice as high as that of pure calcite. This is the first example showing that an organic molecule incorporated into an inorganic host can strongly affect the expansion coefficient. Most importantly, we show that the incorporation of amino acids in calcite is controlled by their thermodynamic solubility in calcite rather than kinetically and that hybrid amino acid-calcite crystals can indeed be considered a solid solution