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General Environmental Science and Education

Article, Applied Microbiology and Biotechnology, Microbiology, Biotechnology, Redox, Nanotechnology, Biofilm, Microbial fuel cell, Electrochromism, Chemical engineering, Electron acceptor, chemistry.chemical_classification, chemistry, Materials science, Conductive polymer, Biofouling, PEDOT:PSS, lcsh:Microbial ecology, lcsh:QR100-130, and biochemical phenomena, metabolism, and nutrition

Biofouling is a major problem caused by bacteria colonizing abiotic surfaces, such as medical devices. Biofilms are formed as the bacterial metabolism adapts to an attached growth state. We studied whether bacterial metabolism, hence biofilm formation, can be modulated in electrochemically active surfaces using the conducting conjugated polymer poly(3,4-ethylenedioxythiophene) (PEDOT). We fabricated composites of PEDOT doped with either heparin, dodecyl benzene sulfonate or chloride, and identified the fabrication parameters so that the electrochemical redox state is the main distinct factor influencing biofilm growth. PEDOT surfaces fitted into a custom-designed culturing device allowed for redox switching in Salmonella cultures, leading to oxidized or reduced electrodes. Similarly large biofilm growth was found on the oxidized anodes and on conventional polyester. In contrast, biofilm was significantly decreased (52–58%) on the reduced cathodes. Quantification of electrochromism in unswitched conducting polymer surfaces revealed a bacteria-driven electrochemical reduction of PEDOT. As a result, unswitched PEDOT acquired an analogous electrochemical state to the externally reduced cathode, explaining the similarly decreased biofilm growth on reduced cathodes and unswitched surfaces. Collectively, our findings reveal two opposing effects affecting biofilm formation. While the oxidized PEDOT anode constitutes a renewable electron sink that promotes biofilm growth, reduction of PEDOT by a power source or by bacteria largely suppresses biofilm formation. Modulating bacterial metabolism using the redox state of electroactive surfaces constitutes an unexplored method with applications spanning from antifouling coatings and microbial fuel cells to the study of the role of bacterial respiration during infection.
Biofilm control: An electrifying effect Biofilm formation on surfaces can be inhibited or promoted by controlling the availability of electrons and electron-acceptors. This offers a novel way to protect medical devices and machinery from biofilm fouling. It could also assist studies of bacterial metabolism during the formation of biofilms. Agneta Richter-Dahlfors and colleagues at the Swedish Medical Nanoscience Center at Karolinska Institutet investigated the effect with cultured Salmonella bacteria. They used electrodes composed of an electrically conducting polymer to maintain the surfaces exposed to bacteria in an electron-rich or electron-deficient state. The research highlights the crucial role of electron transfer in biofilm formation. The rate of biofilm production can be tuned and studied by varying the electron-donating or electron-accepting property of a surface. Healthcare devices, food processing and industrial machinery are potential areas for application of the anti-biofilm effect.

Electrical and Electronic Engineering, Materials science, Near and far field, Radome, law.invention, law, Phase (waves), Surface integral, Surface (mathematics), Wavelength, Integral equation, Dielectric, Optics, business.industry, and business

Radome diagnostics are acquired in the design process, the delivery control, and in performance verification of repaired and newly developed radomes. A measured near or far field may indicate deviations, e.g., increased side-lobe levels, but the origins of the flaws are not revealed. In this paper, radome diagnostics is performed by visualizing the equivalent surface currents on the 3-D radome body, illuminated from the inside. Three different far-field measurement series at 10 GHz are employed. The measured far field is related to the equivalent surface currents on the radome surface by using a surface integral representation. In addition, a surface integral equation is employed to ensure that the sources are located inside the radome. Phase shifts, insertion phase delays (IPD), caused by patches of dielectric tape attached to the radome surface, are localized. Specifically, patches of various edge sizes (0.5-2.0 free-space wavelengths), and with the smallest thickness corresponding to a phase shift of a couple of degrees are imaged.

Electrical and Electronic Engineering, Condensed Matter Physics, Electronic, Optical and Magnetic Materials, Group delay and phase delay, Radome, law.invention, law, Linear system, Axial symmetry, Optics, business.industry, business, Integral equation, Singular value decomposition, Antenna (radio), Mathematics, Observable, and Mathematical analysis

In this paper an inverse source problem is investigated. The measurement set-up is a re∞ector antenna covered by a radome. Equivalent currents are reconstructed on a surface shaped as the radome in order to diagnose the radome's interaction with the radiated fleld. To tackle this inverse source problem an analysis of a full-wave integral representation, with the equivalent currents as unknowns, is used. The extinction theorem and its associated integral equation ensure that the reconstructed currents represent sources within the radome. The axially symmetric experimental set-up reduces the computational complexity of the problem. The resulting linear system is inverted by using a singular value decomposition. We visualize how the presence of the radome alters the components of the equivalent currents. The method enables us to determine the phase shift of the fleld due to the transmission of the radome, i.e., the IPD (insertion phase delay). Also, disturbances due to defects, not observable in the measured near fleld, are localized in the equivalent currents.

Electrical and Electronic Engineering, Signal Processing, Microwave imaging, Inverse scattering problem, Mathematical optimization, Fisher information, symbols.namesake, symbols, Inverse problem, Antenna (radio), Near and far field, Multipole expansion, Algorithm, Cramér–Rao bound, and Mathematics

Although imaging and inverse scattering problems have been thoroughly studied during the last century, there is only a partial understanding of these complex problems. Most of the efforts have been placed on the development of efficient inversion algorithms and mathematical uniqueness results. In comparison, there are very few results and a limited knowledge about the information content in the inversion data. In this paper, we provide a mathematical framework for sensitivity analysis of antenna near-field imaging problems, based on the multipole expansion of the electromagnetic field and the Fisher information to quantify the quality of data. By exploiting this framework, a fundamental relation for accuracy and resolution is formulated based on the Crameacuter-Rao bound (CRB). The sensitivity analysis is illustrated using a relevant example with cylindrical measurement data

Cell Biology, Molecular Biology, Biochemistry, Microbiology, Biology, Proinflammatory cytokine, Coagulation, Fibrin, biology.protein, Immune system, Bacteria, biology.organism_classification, Escherichia coli, medicine.disease_cause, medicine, Fibrinogen, medicine.drug, and Kinin

The inflammatory response to bacterial infection is the result of a complex interplay between bacterial products and host effector systems, such as the immune and complement systems. Here we show that Escherichia coli bacteria expressing fibrous surface proteins, known as curli, assemble and activate factors of the human coagulation cascade at their surface. As a result of this interaction, fibrinogen is converted to fibrin and fibrinogen-derived peptides, termed fibrinopeptides, are generated. The molecular mechanisms behind the bacteria-induced formation of fibrinopeptides were investigated and shown to be triggered by the activation of the contact system, also known as the kallikrein/kinin system or the intrinsic pathway of coagulation. Samples containing fibrinopeptides generated by the interaction between bacteria and plasma were injected into animals and the inflammatory response was monitored. We found that this treatment provoked an infiltration of white blood cells, and the induction of the proinflammatory cytokine MCP-1 at the inflamed site. Our results therefore demonstrate that activation of the coagulation system at the bacterial surface contributes to the pathophysiology of bacterial infectious diseases.

Endocrinology, Receptor, Insulin receptor substrate, Insulin receptor, biology.protein, biology, Glucagon, Islet, geography.geographical_feature_category, geography, Gastrin-releasing peptide, Internal medicine, medicine.medical_specialty, medicine, Insulin, medicine.medical_treatment, Insulin resistance, medicine.disease, hormones, hormone substitutes, and hormone antagonists, and endocrine system

Gastrin-releasing peptide (GRP) is an islet neuropeptide that stimulates insulin secretion. To explore whether islet GRP contributes to neurally mediated insulin secretion, we studied GRP receptor (GRPR)-deleted mice. By using RT-PCR we showed that GRPR mRNA is expressed in islets of wild-type mice, but is lost in GRPR-deleted mice. Functional studies revealed that GRP potentiates glucose-stimulated insulin secretion in wild-type animals, but not in GRPR-deleted mice. This shows that GRPR is the receptor subtype mediating GRP-induced insulin secretion and that GRPR-deleted mice are tools for studying the physiological role of islet GRP. We found that GRPR-deleted mice display 1) augmentation of the insulin response to glucose by a mechanism inhibited by ganglionic blockade; 2) increased insulin responsiveness also to the cholinergic agonist carbachol, but not to arginine; 3) impaired insulin and glucagon responses to autonomic nerve activation by 2-deoxyglucose; 4) normal islet adaptation to high fat-induced insulin resistance and fasting; and 5) normal islet cytoarchitecture, as revealed by immunocytochemistry of insulin and glucagon. In conclusion, 1) GRPR is the receptor subtype mediating the islet effects of GRP; 2) GRP contributes to insulin secretion induced by activation of the autonomic nerves; and 3) deletion of GRPR is compensated by increased cholinergic sensitivity.

Nuclear Energy and Engineering, General Materials Science, Nuclear and High Energy Physics, Ab initio, Phase diagram, Solid solution, Chemistry, Electronic structure, Rhenium, chemistry.chemical_element, Condensed matter physics, Crystal structure, Lattice (order), Tungsten, Condensed Matter::Materials Science, and Condensed Matter::Other

Tungsten has been suggested as a material in applications where it is irradiated by neutrons and undergoes transmutation to rhenium. Pure W has the bcc lattice structure. According to the equilibrium phase diagram about 30 at.% Re can go into a bcc W–Re solid solution. However, ab initio electronic structure calculations show that the bcc lattice becomes dynamically unstable at high Re concentrations. Through a detailed calculation of the phonon spectrum, we find that bcc W1−cRec does not become dynamically unstable until c≳0.7, i.e., well above the equilibrium solubility limit of Re in bcc W. Concentration fluctuations of Re in irradiated W will therefore not lead to any significant number of regions where the bcc lattice collapses due to a dynamical instability.