Development and validation of a glass-silicon microdroplet-based system to measure sulfite concentrations in beverages

Sulfite is often added to beverages as an antioxidant and antimicrobial agent. In fermented beverages, sulfite is also naturally produced by yeast cells. However, sulfite causes adverse health effects in asthmatic patients and accurate measurement of the sulfite concentration is therefore very important. Current sulfite analysis methods are time- and reagent-consuming and often require costly equipment. Here, we present a system allowing sensitive, ultralow-volume sulfite measurements based on a reusable glass-silicon microdroplet platform on which microdroplet generation, addition of enzymes through chemical-induced emulsion destabilization and pillar-induced droplet merging, emulsion restabilization, droplet incubation, and fluorescence measurements are integrated. In a first step, we developed and verified a fluorescence-based enzymatic assay for sulfite by measuring its analytical performance (LOD, LOQ, the dynamic working range, and the influence of salts, colorant, and sugars) and comparing fluorescent microplate readouts of fermentation samples with standard colorimetric measurements using the 5,5′-dithiobis-(2-nitrobenzoic acid) assay of the standard Gallery Plus Beermaster analysis platform. Next, samples were analyzed on the microdroplet platform, which also showed good correlation with the standard colorimetric analysis. Although the presented platform does not allow stable reinjection of droplets due to the presence of a tight array of micropillars at the fluidics entrances to prevent channel clogging by dust, removing the pillars, and integrating miniaturized pumps and optics in a future design would allow to use this platform for high-throughput, automated, and portable screening of microbes, plant, or mammalian cells.

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Simultaneous quantification of levofloxacin,pefloxacin, ciprofloxacin and moxifloxacin in microvolumes of human plasma using high‐performance liquid chromatography with ultraviolet detection

Levofloxacin, pefloxacin, ciprofloxacin and moxifloxacin are four fluoroquinolones used in the treatment of serious bacterial infections. The antibacterial activity of fluoroquinolones is concentration dependent. Therefore, therapeutic drug monitoring in daily clinical practice is warranted to ensure the therapy's efficacy and prevent bacterial resistance. The purpose of the present study was to develop a method using high‐pressure liquid chromatography with an ultraviolet detector for simultaneous quantification of these four fluoroquinolones in human plasma. A 50 μL aliquot of plasma was precipitated by 200 μL of methanol using gatifloxacin as internal standard. The chromatographic separation was performed on a Kinetex XB‐C₁₈ column using a mobile phase composed of a mixture of orthophosphoric acid 0.4% (v/v), acetonitrile and methanol at a flow rate of 1.2 mL/min. Dual UV wavelength mode was used, with levofloxacin and moxifloxacin monitored at 293 nm, and pefloxacin and ciprofloxacin monitored at 280 nm. The calibration was linear over the ranges of 0.125–25 mg/L for levofloxacin, 0.1–20mg/L for moxifloxacin and 0.05‐10 mg/L for both pefloxacin and ciprofloxacin. Inter‐ and intra‐day trueness and precision were <13% for all the compounds under study. The proposed method was simple, reliable, cost‐effective and suitable for therapeutic drug monitoring or pharmacokinetics studies.     

A priori bounds and multiplicity for fully nonlinear equations with quadratic growth in the gradient

We consider fully nonlinear uniformly elliptic equations with quadratic growth in the gradient, such as

$?F(x,u,Du,D^{2}u)=\lambda c(x)u+〈M(x)Du,Du〉+h(x)$

in a bounded domain with a Dirichlet boundary condition; here $\lambda \in \mathbb{R}$, $c,h\in L^p(\mathrm{\Omega })$, $p>n\ge 1$, $c?0$ and the matrix M satisfies $0<{\mu }_{1}I\le M\le {\mu }_{2}I$. Recently this problem was studied in the “coercive” case $\lambda c\le 0$, where uniqueness of solutions can be expected; and it was conjectured that the solution set is more complex for noncoercive equations. This conjecture was verified in 2015 by Arcoya, de Coster, Jeanjean and Tanaka for equations in divergence form, by exploiting the integral formulation of the problem. Here we show that similar phenomena occur for general, even fully nonlinear, equations in nondivergence form. We use different techniques based on the maximum principle.We develop a new method to obtain the crucial uniform a priori bounds, which permit to us to use degree theory. This method is based on basic regularity estimates such as half-Harnack inequalities, and on a Vázquez type strong maximum principle for our kind of equations.     

Facility Update: APS Operations and New Beamlines

Twenty years is a long time, but it seems to me as if it were yesterday when the three of us—Michel Belakhovsky, Christian Riekel and I—first scientists of the Experiments Division (except the directors) at the not yet created European Synchrotron Radiation Facility, living in a temporary and not very solid building, made the last corrections to the text of the famous “Red Book,” the ESRF Foundation Phase Report published in February 1987. The floor was shaking in our office when Ruprecht Haensel, the first Director General, walked along the corridor…. We had convened workshops of experts in the various fields to define the first set of beamlines to be built at the ESRF. The program was quite complete, comprising inelastic scattering, imaging (topography), microfocusing, small angle scattering, nuclear resonance, high energy, etc. Costs were particularly difficult to estimate, but finally we were not so far from the real figures.     

A statistical model of horizontal auditory localization performance data

Horizontal localization experiments are used to evaluate the listener's ability to locate the position of a sound source, and determine how signal characteristics affect this ability. These experiments generate circular, bimodal, and repeated data that are challenging to statistically analyze. A two-part mixture of wrapped Cauchys is proposed for these data, with the effects of signal type and position on localization bias, precision, and front-back confusion modeled using regression. The model is illustrated using mid- (1.0-2.0 kHz) and high- (3.0-6.0 kHz) frequency narrow band noises localization collected among ten normal hearing listeners.     

Novel proresolving aspirin-triggered DHA pathway

Endogenous mechanisms in the resolution of acute inflammation are of interest because excessive inflammation underlies many pathologic abnormalities. We report an aspirin-triggered DHA metabolome that biosynthesizes a potent product in inflammatory exudates and human leukocytes, namely aspirin-triggered Neuroprotectin D1/Protectin D1 [AT-(NPD1/PD1)]. The complete stereochemistry of AT-(NPD1/PD1) proved to be 10R,17R-dihydroxydocosa-4Z,7Z,11E,13E,15Z,19Z-hexaenoic acid. The chirality of hydroxyl groups and geometry of the conjugated triene system essential for bioactivity were established by matching biological materials with stereochemically pure isomers prepared by organic synthesis. AT-(NPD1/PD1) reduced neutrophil (PMN) recruitment in murine peritonitis in a dose-dependent fashion whereby neither a Δ(15)-trans-isomer nor DHA was effective. With human cells, AT-(NPD1/PD1) decreased transendothelial PMN migration as well as enhanced efferocytosis of apoptotic human PMN by macrophages. These results indicate that AT-(NPD1/PD1) is a potent anti-inflammatory proresolving molecule.     

Solvatomorphism in (E)‐2‐(2,6‐dichloro‐4‐hydroxybenzylidene)hydrazinecarboximidamide

The structures of orthorhombic (E)‐4‐(2‐{[amino(iminio)methyl]amino}vinyl)‐3,5‐dichlorophenolate dihydrate, C₈H₈Cl₂N₄O·2H₂O, (I), triclinic (E)‐4‐(2‐{[amino(iminio)methyl]amino}vinyl)‐3,5‐dichlorophenolate methanol disolvate, C₈H₈Cl₂N₄O·2CH₄O, (II), and orthorhombic (E)‐amino[(2,6‐dichloro‐4‐hydroxystyryl)amino]methaniminium acetate, C₈H₉Cl₂N₄O⁺·C₂H₃O₂⁻, (III), all crystallize with one formula unit in the asymmetric unit, with the molecule in an E configuration and the phenol H atom transferred to the guanidine N atom. Although the molecules of the title compounds form extended chains via hydrogen bonding in all three forms, owing to the presence of different solvent molecules, those chains are connected differently in the individual forms. In (II), the molecules are all coplanar, while in (I) and (III), adjacent molecules are tilted relative to one another to varying degrees. Also, because of the variation in hydrogen‐bond‐formation ability of the solvents, the hydrogen‐bonding arrangements vary in the three forms.     

Tris-[2.21]- and tris-[2.2.2]-σ-homobenzenes

Tris-[2.2.1]- and tris-[2.2.2]-σ-homobenzenes are synthesised by reaction of 1,1′-bicyclobutenyl with appropriate dienophiles and hydrogenation of the adducts.     

Meeting Report: Fifth International Conference on Synchrotron Radiation in Materials Science

More than 250 scientists from 22 countries gathered in Chicago, Illinois, from July 30 to August 2, 2006, to participate in the Fifth International Conference on Synchrotron Radiation in Materials Science (SRMS-5). The SRMS conference is held every two years, bringing together leading-edge researchers in the materials sciences making use of synchrotron radiation. The conference, which was organized and hosted this year by Argonne National Laboratory and the Advanced Photon Source, provided an overview of the latest research developments in a broad range of areas, such as polymers and biomaterials, magnetic and superconducting materials, glasses and ceramics, engineering materials, materials under extreme conditions, complex oxides, innovative instrumentation, membranes, and thin films. The aim of SRMS-5 was to highlight recent breakthroughs in materials science using synchrotron radiation and to open doors to future innovation and discovery.