Reactions to extreme events: moving threshold model

In spite of precautions to avoid the harmful effects of extreme events, we experience recurrently phenomena that overcome the preventive barriers. These barriers usually increase drastically right after the occurrence of such extreme events, but steadily decay in their absence. In this paper we consider a simple model that mimics the evolution of the protection barriers to study the efficiency of the system's reaction to extreme events and how it changes our perception of the sequence of extreme events itself. We obtain that the usual method of fighting extreme events introduces a periodicity in their occurrence and is generally less efficient than the use of a constant barrier. On the other hand, it shows a good adaptation to the presence of slow non-stationarities.Comment: 14 pages and 7 figure

Controlled electron-beam synthesis of transparent hydrogels for drug delivery applications

In this study, we highlight hydrogels prepared by electron-beam polymerization. In general, the electron-beam-polymerized hydrogels showed improved mechanical and optical transmittances compared to the conventional UV-cured hydrogels. They were more elastic and had a higher crosslinking density. Additionally, they were transparent over a broader wavelength range. The dependence of the mechanical and optical properties of the hydrogels on the number of single differential and total irradiation doses was analyzed in detail. The hydrogels were prepared for usage as a drug delivery material with methylene blue as a drug model. In the first set of experiments, methylene blue was loaded reversibly after the hydrogel synthesis. Electron-beam-polymerized hydrogels incorporated twice as much methylene blue compared to the UV-polymerized gels. Furthermore, the release of the model drug was found to depend on the crosslinking degree of the hydrogels. In addition, electron-beam polymerization enabled the irreversible binding of the drug molecules if they were mixed with monomers before polymerization

ARL Digital Scholarship Institute

This poster reflects on the Association of Research Libraries’ (ARL) upcoming inaugural week-long Digital Scholarship Institute for library professionals. Held in June 2017 at Boston College, the Institute introduced librarians and staff who are not currently involved in digital scholarship to the methodologies and considerations of such work. This multi-institutional initiative will provide an opportunity for broader transformation in the academic library ecosystem at the level necessary to create a strong community of practice around digital scholarship wor

Evaluation of a luminometric cell counting system in context of antimicrobial photodynamic inactivation

Antimicrobial resistance belongs to the most demanding medical challenges, and antimicrobial photodynamic inactivation (aPDI) is considered a promising alternative to classical antibiotics. However, the pharmacologic characterization of novel compounds suitable for aPDI is a tedious and time-consuming task that usually requires preparation of bacterial cultures and counting of bacterial colonies. In this study, we established and utilized a luminescence-based microbial cell viability assay to analyze the aPDI effects of two porphyrin-based photosensitizers (TMPyP and THPTS) on several bacterial strains with antimicrobial resistance. We demonstrate that after adaptation of the protocol and initial calibration to every specific bacterial strain and photosensitizer, the luminometric method can be used to reliably quantify aPDI effects in most of the analyzed bacterial strains. The interference of photosensitizers with the luminometric readout and the bioluminescence of some bacterial strains were identified as possible confounders. Using this method, we could confirm the susceptibility of several bacterial strains to photodynamic treatment, including extensively drug-resistant pathogens (XDR). In contrast to the conventional culture-based determination of bacterial density, the luminometric assay allowed for a much more time-effective analysis of various treatment conditions. We recommend this luminometric method for high-throughput tasks requiring measurements of bacterial viability in the context of photodynamic treatment approaches

Photosensitizer-loaded hydrogels for photodynamic inactivation of multirestistant bacteria in wounds

Photodynamic treatment is a promising tool for the therapy of multidrug-resistant bacteria. In this study, we highlight photosensitizer-loaded hydrogels as an application system for infected wounds. The poly(ethylene glycol) diacrylate-based and electron beam-polymerized hydrogels were mechanically stable and transparent. They were loaded with two photoactive, porphyrin-based drugs – tetrakis(1 methylpyridinium-4-yl)porphyrin p-toluenesulfonate (TMPyP) and tetrahydroporphyrin – p toluenesulfonate (THPTS). The hydrogels released a sufficient amount of the photosensitizers (up to 300 μmol l(−1)), relevant for efficiency. The antimicrobial effectivity of loaded hydrogels was investigated in a tissue-like system as well as in a liquid system against a multiresistant Escherichia coli. In both systems, light induced eradication was possible. In contrast, hydrogels alone showed only minor antimicrobial activity. Furthermore, the loaded hydrogels were successfully tested against seven multidrug-resistant bacterial strains, namely Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumonia, Acinetobacter baumannii, Pseudomonas aeruginosa, Escherichia coli and Achromobacter xylosoxidans. The eradication of these pathogens, except A. xylosoxidans, was successfully demonstrated. In general, TMPyP-loaded hydrogels were more effective than THPTS-loaded ones. Nevertheless, both photosensitizers displayed effectivity against all investigated bacteria strains. Taken together, our data demonstrate that photosensitizer-loaded hydrogels are a promising new tool to improve the treatment of wounds infected with problematic bacterial pathogens

Meeting Report: The 2nd Annual Argonne Soils Workshop, Argonne National Laboratory, Chicago Illinois, USA, October 6-8, 2010

This report summarizes the proceedings of the 2nd Annual Argonne Soils Workshop held at Argonne National Laboratory October 6–8, 2010. The workshop assembled a diverse group of soil ecologists, microbiologists, molecular biologists, and computational scientists to discuss the challenges and opportunities related to implementation of metagenomics approaches in soil microbial ecology. The overarching theme of the workshop was “designing ecologically meaningful soil metagenomics research”, which encouraged presentations on both ecological and computational topics. The workshop fostered valuable cross-discipline communication and delivered the message that soil metagenomics research must be based on an iterative process between biological inquiry and bioinformatics tools

The meta-substituted isomer of TMPyP enables more effective photodynamic bacterial inactivation than para-TMPyP in vitro

Porphyrinoid-based photodynamic inactivation (PDI) provides a promising approach to treating multidrug-resistant infections. However, available agents for PDI still have optimization potential with regard to effectiveness, toxicology, chemical stability, and solubility. The currently available photosensitizer TMPyP is provided with a para substitution pattern (para-TMPyP) of the pyridinium groups and has been demonstrated to be effective for PDI of multidrug-resistant bacteria. To further improve its properties, we synthetized a structural variant of TMPyP with an isomeric substitution pattern in a meta configuration (meta-TMPyP), confirmed the correct structure by crystallographic analysis and performed a characterization with NMR-, UV/Vis-, and IR spectroscopy, photostability, and singlet oxygen generation assay. Meta-TMPyP had a hypochromic shift in absorbance (4 nm) with a 55% higher extinction coefficient and slightly improved photostability (+6.9%) compared to para-TMPyP. Despite these superior molecular properties, singlet oxygen generation was increased by only 5.4%. In contrast, PDI, based on meta-TMPyP, reduced the density of extended spectrum β-lactamase-producing and fluoroquinolone-resistant Escherichia coli by several orders of magnitude, whereby a sterilizing effect was observed after 48 min of illumination, while para-TMPyP was less effective (p < 0.01). These findings demonstrate that structural modification with meta substitution increases antibacterial properties of TMPyP in PDI