A Rapidly Responsive Sensor for Wireless Detection of Early and Mature Microbial Biofilms

Biofilm-associated infections, which are able to resist antibiotics, pose a significant challenge in clinical treatments. Such infections have been linked to various medical conditions, including chronic wounds and implant-associated infections, making them a major public-health concern. Early-detection of biofilm formation offers significant advantages in mitigating adverse effects caused by biofilms. In this work, we aim to explore the feasibility of employing a novel wireless sensor for tracking both early-stage and matured-biofilms formed by the medically relevant bacteria Staphylococcus aureus and Pseudomonas aeruginosa. The sensor utilizes electrochemical reduction of an AgCl layer bridging two silver legs made by inkjet-printing, forming a part of near-field-communication tag antenna. The antenna is interfaced with a carbon cloth designed to promote the growth of microorganisms, thereby serving as an electron source for reduction of the resistive AgCl into a highly-conductive Ag bridge. The AgCl−Ag transformation significantly alters the impedance of the antenna, facilitating wireless identification of an endpoint caused by microbial growth. To the best of our knowledge, this study for the first time presents the evidence showcasing that electrons released through the actions of bacteria can be harnessed to convert AgCl to Ag, thus enabling the wireless, battery-less, and chip-less early-detection of biofilm formation.     

Analysis of DNA methylation markers for tissue identification in individuals with different clinical phenotypes

Deoxyribonucleic acid (DNA) methylation patterns can be used to identify the type of tissue or body fluid found at a crime scene. However, tissue-related methylation levels have not been analyzed in individuals with different illnesses and medical conditions in forensic-specific studies. The primary goal of this study was to investigate if certain clinical phenotypes can alter the methylation levels of CpG sites in genes involved in tissue typing. Four studies with focus on DNA methylation analysis on individuals with different clinical conditions were selected from the Gene Expression Omnibus database. Then, a list of 137 CpG sites was compiled for further investigation. Statistical tests were performed to compare the beta-values results obtained for the control groups and the individuals affected by medical conditions. For each study, CpG sites that presented significant statistical differences between patients and control group were identified and it was possible to notice that DNA methylation levels can be affected in sites with potential forensic use. Although the observed DNA methylation variation (less than 10% difference) in this study would likely not cause any issues in body fluid identification, the results are important to show that this type of analysis should be taken into consideration when investigating and further validating body fluid markers. The CpG sites identified in this study should be further investigated by future studies on body fluids identification, and due to the significant difference in methylation levels in samples from affected individuals, caution must be taken before including these sites in tissue identification investigations.     

Halogen Interactions in Halogenated Oxindoles: Crystallographic and Computational Investigations of Intermolecular Interactions

X-ray structural determinations and computational studies were used to investigate halogen interactions in two halogenated oxindoles. Comparative analyses of the interaction energy and the interaction properties were carried out for Br···Br, C-H···Br, C-H···O and N-H···O interactions. Employing Møller–Plesset second-order perturbation theory (MP2) and density functional theory (DFT), the basis set superposition error (BSSE) corrected interaction energy (E_int(BSSE)) was determined using a supramolecular approach. The E_int(BSSE) results were compared with interaction energies obtained by Quantum Theory of Atoms in Molecules (QTAIM)-based methods. Reduced Density Gradient (RDG), QTAIM and Natural bond orbital (NBO) calculations provided insight into possible pathways for the intermolecular interactions examined. Comparative analysis employing the electron density at the bond critical points (BCP) and molecular electrostatic potential (MEP) showed that the interaction energies and the relative orientations of the monomers in the dimers may in part be understood in light of charge redistribution in these two compounds.     

Dihydrofolate Reductase Inhibitors: The Pharmacophore as a Guide for Co-Crystal Screening

In this work, co-crystal screening was carried out for two important dihydrofolate reductase (DHFR) inhibitors, trimethoprim (TMP) and pyrimethamine (PMA), and for 2,4-diaminopyrimidine (DAP), which is the pharmacophore of these active pharmaceutical ingredients (API). The isomeric pyridinecarboxamides and two xanthines, theophylline (THEO) and caffeine (CAF), were used as co-formers in the same experimental conditions, in order to evaluate the potential for the pharmacophore to be used as a guide in the screening process. In silico co-crystal screening was carried out using BIOVIA COSMOquick and experimental screening was performed by mechanochemistry and supported by (solid + liquid) binary phase diagrams, infrared spectroscopy (FTIR) and X-ray powder diffraction (XRPD). The in silico prediction of low propensities for DAP, TMP and PMA to co-crystallize with pyridinecarboxamides was confirmed: a successful outcome was only observed for DAP + nicotinamide. Successful synthesis of multicomponent solid forms was achieved for all three target molecules with theophylline, with DAP co-crystals revealing a greater variety of stoichiometries. The crystalline structures of a (1:2) TMP:THEO co-crystal and of a (1:2:1) DAP:THEO:ethyl acetate solvate were solved. This work demonstrated the possible use of the pharmacophore of DHFR inhibitors as a guide for co-crystal screening, recognizing some similar trends in the outcome of association in the solid state and in the molecular aggregation in the co-crystals, characterized by the same supramolecular synthons.     

Conservative force fields in non-Gaussian statistics

In this Letter, we determine the κ-distribution function for a gas in the presence of an external field of force described by a potential U(r). In the case of a dilute gas, we show that the κ-power law distribution including the potential energy factor term can rigorously be deduced in the framework of kinetic theory with basis on the Vlasov equation. Such a result is significant as a preliminary to the discussion on the role of long range interactions in the Kaniadakis thermostatistics and the underlying kinetic theory.     

Multivariate analysis applied to particle‐induced X‐ray emission mapping

The use of particle‐induced X‐ray emission (PIXE) for elemental speciation and quantification has gained new attention thanks to mapping capabilities. Microprobes are able to raster a proton beam and produce elemental maps on the micrometre scale. Moreover, recent developments of in‐air PIXE instrumentation have enabled the acquisition of large area elemental maps. However, the amount of data produced is very large, and the data processing is not trivial. In this paper, we propose the use of multivariate analysis to process data of PIXE mapping. First, we apply the non‐negative matrix factorization (NMF), which is a nonsupervised machine‐learning algorithm, to decompose the data into a smaller number of components; then, we use the k‐means algorithm to divide the pixels into categories regarding similarities in the NMF results; finally, we sum the spectra of all pixels in the same category so that the results can be analyzed by standard procedures for PIXE quantification. This last step is important to enable the quantification of the elements found in each component by correctly accounting for matrix self‐absorptions. With the procedure described in this paper, not just, we reduced the number of variables, facilitating the reasoning process on the data by employing the multivariate analysis, but we also increased the counting statistics by summing similar pixels leading to better results concerning the quantification of trace elements. We also propose methods for both, the automatic determination of the optimal number of components to describe the dataset, and for the combined analysis of multiple detectors.     

Combination of hollow‐fiber‐supported liquid membrane and dispersive liquid–liquid microextraction as a fast and sensitive technique for the extraction of pesticides from grape juice followed by high‐performance liquid chromatography

The simultaneous use of a hollow‐fiber‐supported liquid membrane and dispersive liquid–liquid microextraction for the determination of pesticides directly in grape juice was investigated. The detection and quantification were performed by liquid chromatography with diode array detection. The optimum extraction condition was reached by filling the pores of the membrane wall with dodecanol and using hexane/acetone as extraction/dispersion solvents. Salt addition had a highly negative effect on the extraction efficiency and the optimum extraction time was 60 min. The volume of hexane/acetone mixture and the sample pH did not affect the signal at the levels studied. Therefore, an intermediate amount of these solvents (250 μL; 1:7.5 v/v) and pH 6 were selected. The optimum desorption condition was obtained with acetonitrile and 10 min of desorption time. The linear working range varied from 58 to 500 μg/L (parathion‐methyl), 62–500 μg/L (difenoconazole) and 107–500 μg/L (chlorpyrifos), with correlation coefficients ranging from 0.9980–0.9942. The limits of detection and quantification found were, respectively, 17 and 58 μg/L for parathion‐methyl, 19 and 62 μg/L for difenoconazole and 32 and 107 μg/L for chlorpyrifos. The relative standard deviation ranged between 3.5 and 11.2%.     

Nonuniform dichotomic behavior: Lipschitz invariant manifolds for ODEs

We obtain global and local theorems on the existence of invariant manifolds for perturbations of nonautonomous linear differential equations assuming a very general form of dichotomic behavior for the linear equation. Besides some new situations that are far from the hyperbolic setting, our results include, and sometimes improve, some known stable manifold theorems.     

The analyticity of a generalized Ruelle’s operator

In this work we propose a generalization of the concept of Ruelle’s operator for one dimensional lattices used in thermodynamic formalism and ergodic optimization, which we call generalized Ruelle’s operator. Our operator generalizes both the Ruelle operator proposed in [2] and the Perron Frobenius operator defined in [7]. We suppose the alphabet is given by a compact metric space, and consider a general a-priori measure to define the operator. We also consider the case where the set of symbols that can follow a given symbol of the alphabet depends on such symbol, which is an extension of the original concept of transition matrices from the theory of subshifts of finite type. We prove the analyticity of the Ruelle’s operator and present some examples.     

A note on nonstable monomorphisms¶of vector bundles

In this paper we consider the question of the existence of a nonstable vector bundle monomorphism u:α→β over a closed, connected and smooth manifold M, when dimension of α= 3, dimension of β= dimension of M=n≡ 0(4). The singularity method provides the full obstruction to this problem and under some homological hypothesis we can compute it in terms of well known invariants. Received: 31 May 1999