scholarly journals Lack of Production of Electron-Shuttling Compounds or Solubilization of Fe(III) during Reduction of Insoluble Fe(III) Oxide by Geobacter metallireducens

2000 ◽  
Vol 66 (5) ◽  
pp. 2248-2251 ◽  
Author(s):  
Kelly P. Nevin ◽  
Derek R. Lovley
Keyword(s):  
Oxide Reduction ◽  
Semipermeable Membranes ◽  
Geobacter Metallireducens ◽  
Electron Shuttling ◽  
Common Technique ◽  
Experimental Approaches ◽  
The Common

ABSTRACT Studies with the dissimilatory Fe(III)-reducing microorganismGeobacter metallireducens demonstrated that the common technique of separating Fe(III)-reducing microorganisms and Fe(III) oxides with semipermeable membranes in order to determine whether the Fe(III) reducers release electron-shuttling compounds and/or Fe(III) chelators is invalid. This raised doubts about the mechanisms for Fe(III) oxide reduction by this organism. However, several experimental approaches indicated that G. metallireducens does not release electron-shuttling compounds and does not significantly solubilize Fe(III) during Fe(III) oxide reduction. These results suggest that G. metallireducens directly reduces insoluble Fe(III) oxide.

scholarly journals Mechanisms for Accessing Insoluble Fe(III) Oxide during Dissimilatory Fe(III) Reduction by Geothrix fermentans

2002 ◽  
Vol 68 (5) ◽  
pp. 2294-2299 ◽  
Author(s):  
Kelly P. Nevin ◽  
Derek R. Lovley
Keyword(s):  
Defined Medium ◽  
Alginate Beads ◽  
Water Soluble ◽  
Oxide Reduction ◽  
Geobacter Metallireducens ◽  
Electron Shuttling ◽  
Electron Shuttles ◽  
Culture Filtrates ◽  
Subsurface Environments ◽  
Geothrix Fermentans

ABSTRACT Mechanisms for Fe(III) oxide reduction were investigated in Geothrix fermentans, a dissimilatory Fe(III)-reducing microorganism found within the Fe(III) reduction zone of subsurface environments. Culture filtrates of G. fermentans stimulated the reduction of poorly crystalline Fe(III) oxide by washed cell suspensions, suggesting that G. fermentans released one or more extracellular compounds that promoted Fe(III) oxide reduction. In order to determine if G. fermentans released electron-shuttling compounds, poorly crystalline Fe(III) oxide was incorporated into microporous alginate beads, which prevented contact between G. fermentans and the Fe(III) oxide. G. fermentans reduced the Fe(III) within the beads, suggesting that one of the compounds that G. fermentans releases is an electron-shuttling compound that can transfer electrons from the cell to Fe(III) oxide that is not in contact with the organism. Analysis of culture filtrates by thin-layer chromatography suggested that the electron shuttle has characteristics similar to those of a water-soluble quinone. Analysis of filtrates by ion chromatography demonstrated that there was as much as 250 μM dissolved Fe(III) in cultures of G. fermentans growing with Fe(III) oxide as the electron acceptor, suggesting that G. fermentans released one or more compounds capable of chelating and solubilizing Fe(III). Solubilizing Fe(III) is another strategy for alleviating the need for contact between cells and Fe(III) oxide for Fe(III) reduction. This is the first demonstration of a microorganism that, in defined medium without added electron shuttles or chelators, can reduce Fe(III) derived from Fe(III) oxide without directly contacting the Fe(III) oxide. These results are in marked contrast to those with Geobacter metallireducens, which does not produce electron shuttles or Fe(III) chelators. These results demonstrate that phylogenetically distinct Fe(III)-reducing microorganisms may use significantly different strategies for Fe(III) reduction. Thus, it is important to know which Fe(III)-reducing microorganisms predominate in a given environment in order to understand the mechanisms for Fe(III) reduction in the environment of interest.

scholarly journals Microbially Mediated Biodegradation of Hexahydro-1,3,5-Trinitro-1,3,5- Triazine by Extracellular Electron Shuttling Compounds

2006 ◽  
Vol 72 (9) ◽  
pp. 5933-5941 ◽  
Author(s):  
Man Jae Kwon ◽  
Kevin T. Finneran
Keyword(s):  
Humic Substances ◽  
Electron Donor ◽  
Cell Suspensions ◽  
Electron Shuttle ◽  
Geobacter Metallireducens ◽  
Electron Shuttling ◽  
Resting Cell ◽  
Molar Basis ◽  
Novel Approach

ABSTRACT The potential for humic substances to stimulate the reduction of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) was investigated. This study describes a novel approach for the remediation of RDX-contaminated environments using microbially mediated electron shuttling. Incubations without cells demonstrated that reduced AQDS transfers electrons directly to RDX, which was reduced without significant accumulation of the nitroso intermediates. Three times as much reduced AQDS (molar basis) was needed to completely reduce RDX. The rate and extent of RDX reduction differed greatly among electron shuttle/acceptor amendments for resting cell suspensions of Geobacter metallireducens and G. sulfurreducens with acetate as the sole electron donor. AQDS and purified humic substances stimulated the fastest rate of RDX reduction. The nitroso metabolites did not significantly accumulate in the presence of AQDS or humic substances. RDX reduction in the presence of poorly crystalline Fe(III) was relatively slow and metabolites transiently accumulated. However, adding humic substances or AQDS to Fe(III)-containing incubations increased the reduction rates. Cells of G. metallireducens alone reduced RDX; however, the rate of RDX reduction was slow relative to AQDS-amended incubations. These data suggest that extracellular electron shuttle-mediated RDX transformation is not organism specific but rather is catalyzed by multiple Fe(III)- and humic-reducing species. Electron shuttle-mediated RDX reduction may eventually become a rapid and effective cleanup strategy in both Fe(III)-rich and Fe(III)-poor environments.

A SFMEA Method Based on Modeling and Simulation by Rhapsody

2013 ◽  
Vol 470 ◽  
pp. 304-309
Author(s):  
Yu Mei Wu ◽  
Lei Sun ◽  
Li Jin Wu
Keyword(s):  
Modeling And Simulation ◽  
Failure Modes ◽  
Object Oriented ◽  
Safety Analysis ◽  
Software Failure ◽  
Common Technique ◽  
The Common

Software Failure Modes and Effects Analysis (SFMEA) technology is the most common technique in reliability and safety analysis. The common software FMEA methods are summarized and for object-oriented software, combined with the Rhapsodys characteristic of modeling and simulation, we proposed the SFMEA method based on modeling and simulation by Rhapsody and gave the process of implementation, the acquisition methods of failure modes and the SFMEA example.

scholarly journals Outer Cell Surface Components Essential for Fe(III) Oxide Reduction by Geobacter metallireducens

2012 ◽  
Vol 79 (3) ◽  
pp. 901-907 ◽  
Author(s):  
Jessica A. Smith ◽  
Derek R. Lovley ◽  
Pier-Luc Tremblay
Keyword(s):  
Outer Surface ◽  
Surface Protein ◽  
Transcript Abundance ◽  
Geobacter Sulfurreducens ◽  
Extracellular Electron Transfer ◽  
Outer Cell ◽  
Gene Transcript ◽  
Oxide Reduction ◽  
Geobacter Metallireducens ◽  
Content Type

ABSTRACTGeobacterspecies are important Fe(III) reducers in a diversity of soils and sediments. Mechanisms for Fe(III) oxide reduction have been studied in detail inGeobacter sulfurreducens, but a number of the most thoroughly studied outer surface components ofG. sulfurreducens, particularlyc-type cytochromes, are not well conserved amongGeobacterspecies. In order to identify cellular components potentially important for Fe(III) oxide reduction inGeobacter metallireducens, gene transcript abundance was compared in cells grown on Fe(III) oxide or soluble Fe(III) citrate with whole-genome microarrays. Outer-surface cytochromes were also identified. Deletion of genes forc-type cytochromes that had higher transcript abundance during growth on Fe(III) oxides and/or were detected in the outer-surface protein fraction identified sixc-type cytochrome genes, that when deleted removed the capacity for Fe(III) oxide reduction. Several of thec-type cytochromes which were essential for Fe(III) oxide reduction inG. metallireducenshave homologs inG. sulfurreducensthat are not important for Fe(III) oxide reduction. Other genes essential for Fe(III) oxide reduction included a gene predicted to encode an NHL (Ncl-1–HT2A–Lin-41) repeat-containing protein and a gene potentially involved in pili glycosylation. Genes associated with flagellum-based motility, chemotaxis, and pili had higher transcript abundance during growth on Fe(III) oxide, consistent with the previously proposed importance of these components in Fe(III) oxide reduction. These results demonstrate that there are similarities in extracellular electron transfer betweenG. metallireducensandG. sulfurreducensbut the outer-surfacec-type cytochromes involved in Fe(III) oxide reduction are different.

scholarly journals Pulsed Radiofrequency for Metastatic Pain Treatment

2008 ◽  
Vol 6;11 (12;6) ◽  
pp. 863-875
Author(s):  
Joseph F. Jasper
Keyword(s):  
Pain Treatment ◽  
X Rays ◽  
Zygapophyseal Joint ◽  
Physical Medicine ◽  
Nerve Branch ◽  
New Device ◽  
Phantom Model ◽  
Bony Landmarks ◽  
Common Technique ◽  
The Common

Background: Radiofrequency neurolysis is a common technique used in the treatment of chronic pain, particularly facet (zygapophyseal joint) arthralgia. A needle-like cannula is insulated except for the exposed active tip, which is positioned as parallel and adjacent as possible to the targeted nerve branch. Via an inserted probe connected to a radiofrequency generator, energy flowing from the tip of the cannula creates a heat lesion in the 80 – 85 degree Celsius range mostly about the length of the exposed active tip and in proportion to the diameter of the probe. The common active tip lengths used for neurolysis are 5mm or 10mm. The cannulae are FDA approved. The manufacturer advises physicians not to bend or otherwise modify a cannula prior to use. The cannulae are available straight or bent, sharp and blunt. The technique is guided under C-arm fluoroscopy. X-rays passing through the patient demonstrate in 2 dimensions the projected relative radio-opaque bony landmarks and the metallic cannula. Most currently available cannulae are uniform in their radio-opacity from tip to hub. The physician must make an educated guess as to the portion of the cannula that will be making the lesion in relationship to the bony landmark. Objective: A new radiofrequency cannula with a radio-opaque marker (ROC) delineates the proximal end of the active tip. The cannula was used in a phantom model. Images were reproduced with explanation of the potential advantage of the new device. Result: The marker on the new cannula was visible and did help delineate the active tip as well as its orientation. It was also helpful in making sequential lesions at the same nerve using a “tip to tail” repositioning technique. Conclusion: The ROC did represent an improvement over standard cannulae to optimize visualization of cannula and thus lesion placement using a phantom model. The applications described were only for conventional or “hot” RF. Key words: Anesthesiology, neurology, neurosurgery, physical medicine and rehabilitation, radiology, radiofrequency, neurolysis, rhizotomy

scholarly journals A modified delay-time method for statics estimation with the virtual refraction

Geophysics ◽  
2012 ◽  
Vol 77 (6) ◽  
pp. A29-A33 ◽  
Author(s):  
T. Dylan Mikesell ◽  
Kasper van Wijk ◽  
Elmer Ruigrok ◽  
Andrew Lamb ◽  
Thomas E. Blum
Keyword(s):  
Wave Equation ◽  
Delay Time ◽  
Source Term ◽  
Seismic Interferometry ◽  
Receiver Side ◽  
Near Surface ◽  
Arrival Times ◽  
Delay Times ◽  
Common Technique ◽  
The Common

Topography and near-surface heterogeneities lead to traveltime perturbations in surface land-seismic experiments. Usually, these perturbations are estimated and removed prior to further processing of the data. A common technique to estimate these perturbations is the delay-time method. We have developed the “modified delay-time method,” wherein we isolate the arrival times of the virtual refraction and estimate receiver-side delay times. The virtual refraction is a spurious arrival found in wavefields estimated by seismic interferometry. The new method removes the source term from the delay-time equation, is more robust in the presence of noise, and extends the lateral aperture compared to the conventional delay-time method. We tested this in an elastic 2D numerical example, where we estimated the receiver delay-times above a horizontal refractor. Taking advantage of reciprocity of the wave equation and rearranging the common shot gathers into common receiver gathers, isolated source delay times could also be obtained.

Welding sequence optimisation in the automotive industry: A review

2019 ◽  
Vol 233 (17) ◽  
pp. 5945-5952
Author(s):  
Varshan Beik ◽  
Hormoz Marzbani ◽  
Reza Jazar
Keyword(s):  
Automotive Industry ◽  
Spot Welding ◽  
Fast Rate ◽  
Welding Process ◽  
Future Research ◽  
Automotive Body ◽  
Welding Sequence ◽  
Common Technique ◽  
The Common

Spot welding is the most common technique used to join sheet metals in the automotive industry due to the fast rate of production. Optimising the welding process including the sequence, number and location of the welds would significantly improve the quality of the final product and production cost. This paper presents an overview on the available methods to plan and optimise various aspects of the welding process including welding sequence, weld quantity and location. Firstly, the welding concept in the automotive industry is briefly reviewed. Secondly, the welding process optimisation with emphasis on the welding sequence is discussed. The common gaps and challenges are identified and, lastly, future research to plan and optimise the welding sequence in the automotive body is outlined.

scholarly journals Aluminium Metal Matrix Composition with Reinforcement Particles of Tungsten Carbide and Graphite

2020 ◽  
Vol 8 (4S5) ◽  
pp. 184-188
Keyword(s):  
Tungsten Carbide ◽  
Metal Matrix ◽  
Casting Process ◽  
Stir Casting ◽  
Matrix Composition ◽  
Common Technique ◽  
The Common ◽  
Strength And Stiffness ◽  
Aluminium Metal ◽  
Reinforced Materials

Aluminium Metal Matrix composition were used in application of the aerospace and automobiles because of its strength and stiffness. Although tribological characteristics of the materials like wear resistance is low. Many research has been carried out in the particle reinforcement with the Aluminium Metal Matrix. In this paper, the several reinforced particles with the aluminium matrix were reviewed. The reinforced materials like Tungsten carbide, graphite or hybrid reinforced materials were analyzed. The stir casting process is the common technique to fabricate these materials. The reinforcement of graphite particles in aluminium materials were shows the considerable mechanical properties.

scholarly journals Better Use Case Diagrams by Using Work System Snapshots

2016 ◽  
Vol 9 (2) ◽  
pp. 1-22 ◽  
Author(s):  
Narasimha Bolloju ◽  
Steven Alter
Keyword(s):  
Information System ◽  
Use Cases ◽  
Control Group ◽  
Use Case ◽  
Test Scenario ◽  
Work System ◽  
System Method ◽  
Common Technique ◽  
The Common ◽  
Student Subjects

Research to date shows significant variability in the success of applying the common technique of use case diagramming for identifying information system scope in terms of use cases performed by actors interacting with an information system or performed automatically by the information system. The current research tests a) the benefits of using a work system snapshot, a basic analytical tool from the work system method, before producing use case diagrams, and b) the additional benefits of enhancing use case diagramming constructs to distinguish between automated activities, activities supported by the information system, and relevant manual activities. Teams of student subjects in an experiment produced substantially better use case diagrams - containing far more use cases and qualitatively better use cases than did the teams in control group - when provided with a work system snapshot that summarized a test scenario in terms of work system concepts.

scholarly journals Microparticle Size and Quantities Effect on the Mechanical Features of End of Life Tires in Thermoplastic Composites

Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5561
Author(s):  
Marc Marín-Genescà ◽  
Jordi García-Amorós ◽  
Ramon Mujal-Rosas ◽  
Lluís Massagués Vidal ◽  
Xavier Colom Fajula
Keyword(s):  
Mechanical Properties ◽  
End Of Life ◽  
Environmental Problem ◽  
Thermoplastic Composites ◽  
Ground Tire Rubber ◽  
Microparticle Size ◽  
Polymer Properties ◽  
Mechanical Methods ◽  
Common Technique ◽  
The Common

Currently, the huge use of tires generates large quantities of waste material which represents a severe environmental problem. The common technique used for processing waste tires is crushing using mechanical methods and separating tire components like fibers, metals, and rubber from the used tire. The aim of this research is the recycling of this rubber from crushed tires, called ground tire rubber (GTR). With this aim, the manuscript analyses key mechanical properties of the thermoplastic composites produced by blending of crushed and micronized small particles of waste rubber tires with several industrial thermoplastic polymers. These types of composites are defined based on the total amount GTR in percent by weight, in the composite, and also, the particle sizes used in each case, so these aforementioned two variables (microparticle size and amounts) along with seven common industrial polymers define a series of composites for which the mechanical properties were tested, studied, analyzed and finally presented. Finally, the results obtained show that this proposed recycling method could be a way to enhance some specific polymer properties and could contribute to reducing the total of end of life used tire stocks environmental problem.

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