32 CFR 634.36 - Detection, apprehension, and testing of intoxicated drivers.

Code of Federal Regulations, 2012 CFR

2012-07-01

... unusual or abnormal driving behavior. Drivers showing such behavior will be stopped immediately. The cause of the unusual driving behavior will be determined, and proper enforcement action will be taken. (b...

Genetic and biochemical investigations of the role of MamP in redox control of iron biomineralization in Magnetospirillum magneticum.

PubMed

Jones, Stephanie R; Wilson, Tiffany D; Brown, Margaret E; Rahn-Lee, Lilah; Yu, Yi; Fredriksen, Laura L; Ozyamak, Ertan; Komeili, Arash; Chang, Michelle C Y

2015-03-31

Magnetotactic bacteria have evolved complex subcellular machinery to construct linear chains of magnetite nanocrystals that allow the host cell to sense direction. Each mixed-valent iron nanoparticle is mineralized from soluble iron within a membrane-encapsulated vesicle termed the magnetosome, which serves as a specialized compartment that regulates the iron, redox, and pH environment of the growing mineral. To dissect the biological components that control this process, we have carried out a genetic and biochemical study of proteins proposed to function in iron mineralization. In this study, we show that the redox sites of c-type cytochromes of the Magnetospirillum magneticum AMB-1 magnetosome island, MamP and MamT, are essential to their physiological function and that ablation of one or both heme motifs leads to loss of function, suggesting that their ability to carry out redox chemistry in vivo is important. We also develop a method to heterologously express fully heme-loaded MamP from AMB-1 for in vitro biochemical studies, which show that its Fe(III)-Fe(II) redox couple is set at an unusual potential (-89 ± 11 mV) compared with other related cytochromes involved in iron reduction or oxidation. Despite its low reduction potential, it remains competent to oxidize Fe(II) to Fe(III) and mineralize iron to produce mixed-valent iron oxides. Finally, in vitro mineralization experiments suggest that Mms mineral-templating peptides from AMB-1 can modulate the iron redox chemistry of MamP.

Murburn Concept: A Molecular Explanation for Hormetic and Idiosyncratic Dose Responses.

PubMed

Parashar, Abhinav; Gideon, Daniel Andrew; Manoj, Kelath Murali

2018-01-01

Recently, electron transfers and catalyses in a bevy of redox reactions mediated by hemeproteins were explained by murburn concept. The term "murburn" is abstracted from " mur ed burn ing " or " m ild u n r estricted burn ing " and connotes a novel " m olecule- u nbound ion- r adical " interaction paradigm. Quite unlike the genetic regulations and protein-level affinity-based controls that govern order and specificity/selectivity in conventional treatments, murburn concept is based on stochastic/thermodynamic regulatory principles. The novel insight necessitates a "reactivity outside the active-site" perspective, because select redox enzymatic activity is obligatorily mediated via diffusible radical/species. Herein, reactions employing key hemeproteins (as exemplified by CYP2E1) establish direct experimental connection between "additive-influenced redox catalysis" and "unusual dose responses" in reductionist and physiological milieu. Thus, direct and conclusive molecular-level experimental evidence is presented, supporting the mechanistic relevance of murburn concept in "maverick" concentration-based effects brought about by additives. Therefore, murburn concept could potentially explain several physiological hormetic and idiosyncratic dose responses.

The chemical behavior of acidified chromium (3) solutions. B.S. Thesis

NASA Technical Reports Server (NTRS)

Terman, D. K.

1981-01-01

A unique energy-storage system has been developed at NASA's Lewis Research Center called REDOX. This NASA-REDOX system is an electrochemical storage device that utilized the oxidation and reduction of two fully soluble redox couples for charging and discharging. The redox couples now being investigated are acidified chloride solutions of chromium (Cr(+2)/Cr(+3)) and iron (Fe(+2)/Fe(+3)).

In Vivo Test for Chemical Induction of Micronucleated Polychromatic Erythrocytes in Mouse Bone Marrow Cells. Test Article: Dimethylamine-2-2ethyl azide (DMAZ)

DTIC Science & Technology

2008-06-25

Hunched Back Unusual Body Secretions - Nasal Discharge - Lacrimation - Salivation - Bloody Stool - Dianhea Abnormal Behavior - Convulsions...WetGroin - Hunched Back Unusual Body Secretions - Nasal Discharge - Lacrimation - Salivation - Bloody Stool - Diarrhea Abnormal Behavior...Ataxia - Piloerection - WetGrain - Hunched Back Unusual Body Secretions - Nasal Discharge - Lacrimation - Salivation - Bloody Stool

Structural and Mechanistic Insights into Unusual Thiol Disulfide Oxidoreductase

PubMed Central

Garcin, Edwige B.; Bornet, Olivier; Elantak, Latifa; Vita, Nicolas; Pieulle, Laetitia; Guerlesquin, Françoise; Sebban-Kreuzer, Corinne

2012-01-01

Cytoplasmic desulfothioredoxin (Dtrx) from the anaerobe Desulfovibrio vulgaris Hildenborough has been identified as a new member of the thiol disulfide oxidoreductase family. The active site of Dtrx contains a particular consensus sequence, CPHC, never seen in the cytoplasmic thioredoxins and generally found in periplasmic oxidases. Unlike canonical thioredoxins (Trx), Dtrx does not present any disulfide reductase activity, but it presents instead an unusual disulfide isomerase activity. We have used NMR spectroscopy to gain insights into the structure and the catalytic mechanism of this unusual Dtrx. The redox potential of Dtrx (−181 mV) is significantly less reducing than that of canonical Trx. A pH dependence study allowed the determination of the pKa of all protonable residues, including the cysteine and histidine residues. Thus, the pKa values for the thiol group of Cys31 and Cys34 are 4.8 and 11.3, respectively. The His33 pKa value, experimentally determined for the first time, differs notably as a function of the redox states, 7.2 for the reduced state and 4.6 for the oxidized state. These data suggest an important role for His33 in the molecular mechanism of Dtrx catalysis that is confirmed by the properties of mutant DtrxH33G protein. The NMR structure of Dtrx shows a different charge repartition compared with canonical Trx. The results presented are likely indicative of the involvement of this protein in the catalysis of substrates specific of the anaerobe cytoplasm of DvH. The study of Dtrx is an important step toward revealing the molecular details of the thiol-disulfide oxidoreductase catalytic mechanism. PMID:22128175

The H-bond network surrounding the pyranopterins modulates redox cooperativity in the molybdenum-bisPGD cofactor in arsenite oxidase.

PubMed

Duval, Simon; Santini, Joanne M; Lemaire, David; Chaspoul, Florence; Russell, Michael J; Grimaldi, Stephane; Nitschke, Wolfgang; Schoepp-Cothenet, Barbara

2016-09-01

While the molybdenum cofactor in the majority of bisPGD enzymes goes through two consecutive 1-electron redox transitions, previous protein-film voltammetric results indicated the possibility of cooperative (n=2) redox behavior in the bioenergetic enzyme arsenite oxidase (Aio). Combining equilibrium redox titrations, optical and EPR spectroscopies on concentrated samples obtained via heterologous expression, we unambiguously confirm this claim and quantify Aio's redox cooperativity. The stability constant, Ks, of the Mo(V) semi-reduced intermediate is found to be lower than 10(-3). Site-directed mutagenesis of residues in the vicinity of the Mo-cofactor demonstrates that the degree of redox cooperativity is sensitive to H-bonding interactions between the pyranopterin moieties and amino acid residues. Remarkably, in particular replacing the Gln-726 residue by Gly results in stabilization of (low-temperature) EPR-observable Mo(V) with KS=4. As evidenced by comparison of room temperature optical and low temperature EPR titrations, the degree of stabilization is temperature-dependent. This highlights the importance of room-temperature redox characterizations for correctly interpreting catalytic properties in this group of enzymes. Geochemical and phylogenetic data strongly indicate that molybdenum played an essential biocatalytic roles in early life. Molybdenum's redox versatility and in particular the ability to show cooperative (n=2) redox behavior provide a rationale for its paramount catalytic importance throughout the evolutionary history of life. Implications of the H-bonding network modulating Molybdenum's redox properties on details of a putative inorganic metabolism at life's origin are discussed. Copyright © 2016. Published by Elsevier B.V.

Unusual social behavior in HPC-1/syntaxin1A knockout mice is caused by disruption of the oxytocinergic neural system.

PubMed

Fujiwara, Tomonori; Sanada, Masumi; Kofuji, Takefumi; Akagawa, Kimio

2016-07-01

HPC-1/syntaxin1A (STX1A), a neuronal soluble N-ethylmaleimide-sensitive fusion attachment protein receptor, contributes to neural function in the CNS by regulating transmitter release. Recent studies reported that STX1A is associated with human neuropsychological disorders, such as autism spectrum disorder and attention deficit hyperactivity disorder. Previously, we showed that STX1A null mutant mice (STX1A KO) exhibit neuropsychological abnormalities, such as fear memory deficits, attenuation of latent inhibition, and unusual social behavior. These observations suggested that STX1A may be involved in the neuropsychological basis of these abnormalities. Here, to study the neural basis of social behavior, we analyzed the profile of unusual social behavior in STX1A KO with a social novelty preference test, which is a useful method for quantification of social behavior. Interestingly, the unusual social behavior in STX1A KO was partially rescued by intracerebroventricular administration of oxytocin (OXT). In vivo microdialysis studies revealed that the extracellular OXT concentration in the CNS of STX1A KO was significantly lower compared with wild-type mice. Furthermore, dopamine-induced OXT release was reduced in STX1A KO. These results suggested that STX1A plays an important role in social behavior through regulation of the OXTergic neural system. Dopamine (DA) release is reduced in CNS of syntaxin1A null mutant mice (STX1A KO). Unusual social behavior was observed in STX1A KO. We found that oxytocin (OXT) release, which was stimulated by DA, was reduced and was rescued the unusual social behavior in STX1A KO was rescued by OXT. These results indicated that STX1A plays an important role in promoting social behavior through regulation of DA-induced OXT release in amygdala. © 2016 International Society for Neurochemistry.

Energy Taxis Is the Dominant Behavior in Azospirillum brasilense

PubMed Central

Alexandre, Gladys; Greer, Suzanne E.; Zhulin, Igor B.

2000-01-01

Energy taxis encompasses aerotaxis, phototaxis, redox taxis, taxis to alternative electron acceptors, and chemotaxis to oxidizable substrates. The signal for this type of behavior is originated within the electron transport system. Energy taxis was demonstrated, as a part of an overall behavior, in several microbial species, but it did not appear as the dominant determinant in any of them. In this study, we show that most behavioral responses proceed through this mechanism in the alpha-proteobacterium Azospirillum brasilense. First, chemotaxis to most chemoeffectors typical of the azospirilla habitat was found to be metabolism dependent and required a functional electron transport system. Second, other energy-related responses, such as aerotaxis, redox taxis, and taxis to alternative electron acceptors, were found in A. brasilense. Finally, a mutant lacking a cytochrome c oxidase of the cbb3 type was affected in chemotaxis, redox taxis, and aerotaxis. Altogether, the results indicate that behavioral responses to most stimuli in A. brasilense are triggered by changes in the electron transport system. PMID:11029423

Formation of heterobimetallic zirconium/cobalt diimido complexes via a four-electron transformation.

PubMed

Wu, Bing; Hernández Sánchez, Raúl; Bezpalko, Mark W; Foxman, Bruce M; Thomas, Christine M

2014-10-06

The reactivity of the reduced heterobimetallic complex Zr((i)PrNP(i)Pr2)3CoN2 (1) toward aryl azides was examined, revealing a four-electron redox transformation to afford unusual heterobimetallic zirconium/cobalt diimido complexes. In the case of p-tolyl azide, the diamagnetic C3-symmetric bis(terminal imido) complex 3 is formed, but mesityl azide instead leads to asymmetric complex 4 featuring a bridging imido fragment.

Origin and tunability of unusually large surface capacitance in doped cerium oxide studied by ambient-pressure X-ray photoelectron spectroscopy

DOE PAGES

Gopal, Chirranjeevi Balaji; Gabaly, Farid El; McDaniel, Anthony H.; ...

2016-03-31

Here, the volumetric redox (chemical) capacitance of the surface of CeO 2–δ films is quantified in situ to be 100-fold larger than the bulk values under catalytically relevant conditions. Sm addition slightly lowers the surface oxygen nonstoichiometry, but effects a 10-fold enhancement in surface chemical capacitance by mitigating defect interactions, highlighting the importance of differential nonstoichiometry for catalysis.

Lysosomal ROS formation.

PubMed

Nohl, Hans; Gille, Lars

2005-01-01

Ubiquinone is inhomogenously distributed in subcellular biomembranes. Apart from mitochondria, where ubiquinone has bioenergetic and pathophysiological functions, unusually high levels of ubiquinone have also been reported in Golgi vesicles and lysosomes. In lysosomes, the interior differs from other organelles in its low pH value which is important to ensure optimal activity of hydrolytic enzymes. Since redox-cycling of ubiquinone is associated with the acceptance and release of protons, we assumed that ubiquinone is part of a redox chain contributing to unilateral proton distribution. A similar function of ubiquinone was earlier suggested by Crane to operate in Golgi vesicles. Support for the involvement of ubiquinone in a presumed couple of redox carriers came from our observation that almost 70% of total lysosomal ubiquinone was in the divalently reduced state. Further reduction was seen in the presence of external NADH. Analysis of the components involved in the transfer of reducing equivalents from cytosolic NADH to ubiquinone revealed the existence of an FAD-containing NADH dehydrogenase. The latter was found to reduce ubiquinone by means of a b-type cytochrome. Proton translocation into the interior was linked to the activity of the novel lysosomal redox chain. Oxygen was found to be the terminal electron acceptor, thereby also regulating acidification of the lysosomal matrix. In contrast to mitochondrial respiration, oxygen was only trivalently reduced giving rise to the release of HO radicals. The role of this novel proton-pumping redox chain and the significance of the associated ROS formation has to be elucidated.

Screening of redox couples and electrode materials

NASA Technical Reports Server (NTRS)

Giner, J.; Swette, L.; Cahill, K.

1976-01-01

Electrochemical parameters of selected redox couples that might be potentially promising for application in bulk energy storage systems were investigated. This was carried out in two phases: a broad investigation of the basic characteristics and behavior of various redox couples, followed by a more limited investigation of their electrochemical performance in a redox flow reactor configuration. In the first phase of the program, eight redox couples were evaluated under a variety of conditions in terms of their exchange current densities as measured by the rotating disk electrode procedure. The second phase of the program involved the testing of four couples in a redox reactor under flow conditions with a varity of electrode materials and structures.

Redox reaction characteristics of riboflavin: a fluorescence spectroelectrochemical analysis and density functional theory calculation.

PubMed

Chen, Wei; Chen, Jie-Jie; Lu, Rui; Qian, Chen; Li, Wen-Wei; Yu, Han-Qing

2014-08-01

Riboflavin (RF), the primary redox active component of flavin, is involved in many redox processes in biogeochemical systems. Despite of its wide distribution and important roles in environmental remediation, its redox behaviors and reaction mechanisms in hydrophobic sites remain unclear yet. In this study, spectroelectrochemical analysis and density functional theory (DFT) calculation were integrated to explore the redox behaviors of RF in dimethyl sulfoxide (DMSO), which was used to create a hydrophobic environment. Specifically, cyclic voltafluorometry (CVF) and derivative cyclic voltafluorometry (DCVF) were employed to track the RF concentration changing profiles. It was found that the reduction contained a series of proton-coupled electron transfers dependent of potential driving force. In addition to the electron transfer-chemical reaction-electron transfer process, a disproportionation (DISP1) process was also identified to be involved in the reduction. The redox potential and free energy of each step obtained from the DFT calculations further confirmed the mechanisms proposed based on the experimental results. The combination of experimental and theoretical approaches yields a deep insight into the characteristics of RF in environmental remediation and better understanding about the proton-coupled electron transfer mechanisms. Copyright © 2014 Elsevier B.V. All rights reserved.

Nickel containing CO dehydrogenases and hydrogenases.

PubMed

Ragsdale, S W

2000-01-01

The two redox catalysts described here can generate very low potential electrons in one direction and perform chemically difficult reductions in the other. The chemical transformations occur at unusual metal clusters. Spectroscopic, crystallographic, and kinetic analyses are converging on answers to how the metals in these clusters are arranged and how they are involved in the chemical and redox steps. The first structure of CO dehydrogenase, which will appear in the next year, will help define a firm chemical basis for future mechanistic studies. In the immediate future, we hope to learn whether the hydride intermediate in hydrogenase or the carbonyl intermediate in CO dehydrogenase bind to the Ni or Fe subsites in these heterometallic clusters. Or perhaps could they be bridged to two metals? Inter- and intramolecular wires have been proposed that connect the catalytic redox machine to proximal redox centers leading eventually to the ultimate redox partners. Elucidating the pathways of electron flow is a priority for the future. There is evidence for molecular channels delivering substrates to the active sites of these enzymes. In the next few years, these channels will be better defined. The products of CO2 and proton reduction are passed to the active sites of other enzymes and, in the case of H2, even passed from one organism to another. In the future, the mechanism of gas transfer will be uncovered. General principles of how these redox reactions are catalyzed are becoming lucid as the reactions are modeled theoretically and experimentally. Proton and CO2 reduction and the generation of C-C bonds from simple precursors are important reactions in industry. H2 could be the clean fuel of the future. Hopefully, the knowledge gained from studies of hydrogenase, CO dehydrogenase, and acetyl-CoA synthase can be used to improve life on earth.

Selenoprotein K form an intermolecular diselenide bond with unusually high redox potential

PubMed Central

Liu, Jun; Zhang, Zhengqi; Rozovsky, Sharon

2014-01-01

Selenoprotein K (SelK) is a membrane protein involved in antioxidant defense, calcium regulation and the ER-associated protein degradation pathway. We found that SelK exhibits a peroxidase activity with a rate that is low but within the range of other peroxidases. Notably, SelK reduced hydrophobic substrates, such as phospholipid hydroperoxides, which damage membranes. Thus, SelK might be involved in membrane repair or related pathways. SelK was also found to contain a diselenide bond — the first intramolecular bond of that kind reported for a selenoprotein. The redox potential of SelK was −257 mV, significantly higher than that of diselenide bonds in small molecules or proteins. Consequently, SelK can be reduced by thioredoxin reductase. These finding are essential for understanding SelK activity and function. PMID:25117454

Unusual Internal Electron Transfer in Conjugated Radical Polymers.

PubMed

Li, Fei; Gore, Danielle N; Wang, Shaoyang; Lutkenhaus, Jodie L

2017-08-07

Nitroxide-containing organic radical polymers (ORPs) have captured attention for their high power and fast redox kinetics. Yet a major challenge is the polymer's aliphatic backbone, resulting in a low electronic conductivity. Recent attempts that replace the aliphatic backbone with a conjugated one have not met with success. The reason for this is not understood until now. We examine a family of polythiophenes bearing nitroxide radical groups, showing that while both species are electrochemically active, there exists an internal electron transfer mechanism that interferes with stabilization of the polymer's fully oxidized form. This finding directs the future design of conjugated radical polymers in energy storage and electronics, where careful attention to the redox potential of the backbone relative to the organic radical species is needed. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Structure and Function of the Unusual Tungsten Enzymes Acetylene Hydratase and Class II Benzoyl-Coenzyme A Reductase.

PubMed

Boll, Matthias; Einsle, Oliver; Ermler, Ulrich; Kroneck, Peter M H; Ullmann, G Matthias

2016-01-01

In biology, tungsten (W) is exclusively found in microbial enzymes bound to a bis-pyranopterin cofactor (bis-WPT). Previously known W enzymes catalyze redox oxo/hydroxyl transfer reactions by directly coordinating their substrates or products to the metal. They comprise the W-containing formate/formylmethanofuran dehydrogenases belonging to the dimethyl sulfoxide reductase (DMSOR) family and the aldehyde:ferredoxin oxidoreductase (AOR) families, which form a separate enzyme family within the Mo/W enzymes. In the last decade, initial insights into the structure and function of two unprecedented W enzymes were obtained: the acetaldehyde forming acetylene hydratase (ACH) belongs to the DMSOR and the class II benzoyl-coenzyme A (CoA) reductase (BCR) to the AOR family. The latter catalyzes the reductive dearomatization of benzoyl-CoA to a cyclic diene. Both are key enzymes in the degradation of acetylene (ACH) or aromatic compounds (BCR) in strictly anaerobic bacteria. They are unusual in either catalyzing a nonredox reaction (ACH) or a redox reaction without coordinating the substrate or product to the metal (BCR). In organic chemical synthesis, analogous reactions require totally nonphysiological conditions depending on Hg2+ (acetylene hydration) or alkali metals (benzene ring reduction). The structural insights obtained pave the way for biological or biomimetic approaches to basic reactions in organic chemistry. © 2016 S. Karger AG, Basel.

Organoelement chemistry: promising growth areas and challenges

NASA Astrophysics Data System (ADS)

Abakumov, G. A.; Piskunov, A. V.; Cherkasov, V. K.; Fedushkin, I. L.; Ananikov, V. P.; Eremin, D. B.; Gordeev, E. G.; Beletskaya, I. P.; Averin, A. D.; Bochkarev, M. N.; Trifonov, A. A.; Dzhemilev, U. M.; D'yakonov, V. A.; Egorov, M. P.; Vereshchagin, A. N.; Syroeshkin, M. A.; Jouikov, V. V.; Muzafarov, A. M.; Anisimov, A. A.; Arzumanyan, A. V.; Kononevich, Yu N.; Temnikov, M. N.; Sinyashin, O. G.; Budnikova, Yu H.; Burilov, A. R.; Karasik, A. A.; Mironov, V. F.; Storozhenko, P. A.; Shcherbakova, G. I.; Trofimov, B. A.; Amosova, S. V.; Gusarova, N. K.; Potapov, V. A.; Shur, V. B.; Burlakov, V. V.; Bogdanov, V. S.; Andreev, M. V.

2018-05-01

The chemistry of organoelement compounds is now one of the most rapidly developing fields of research, regarding both fundamental science and solution of applied problems. This review covers a variety of classes of organoelement compounds, ranging from molecules with highly labile carbon–element bonds to compounds with stable bonds that form the basis of novel structural materials and demonstrates their role in scientific research and industrial production. The use of Grignard reagents in modern organic synthesis and application of catalytic cyclomagnesiation and cycloalumination reactions for the preparation of difficult-to-access metallacycles are considered. The electron transfer processes in redox-active derivatives of Group 14 elements and the role of radical ions in these processes are discussed. Considerable attention is paid to organometallic compounds, first of all, as catalysts; the dynamic nature of catalysis with these compounds is noted. Unusual strained metallacycles of high thermal stability, zirconacyclocumulenes, which also exhibit catalytic activity, are described. Complexes with redox-active ligands that substantially affect the reactivity of the metal centre and directly participate in reactions with various substrates as well as organometallic compounds of lanthanides are considered. Modern environmentally benign methods for the synthesis of organosilicon compounds and production of unique materials based on them are discussed. Particular Sections are devoted to organophosphorus compounds, including those exhibiting therapeutic properties and possessing unusual optical characteristics, and organic chalcogen compounds, which find use as ligands and biologically active molecules. The bibliography includes 1045 references.

The Role of Ru Redox in pH-Dependent Oxygen Evolution on Rutile Ruthenium Dioxide Surfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stoerzinger, Kelsey A.; Rao, Reshma R.; Wang, Xiao Renshaw

Rutile RuO 2 is known to exhibit high catalytic activity for the oxygen evolution reaction (OER) and large pseudocapacitance associated with redox of surface Ru, however the mechanistic link between these properties and the role of pH is yet to be understood. Here we report that the OER activities of the (101), (001) and (111) RuO 2 surfaces were found to increase while the potential of a pseudocapacitive feature just prior to OER shifted to lower potentials (“super-Nernstian” shift) with increasing pH on the reversible hydrogen electrode (RHE) scale. This behavior is in contrast to the (100) and (110) surfacesmore » that have pH-independent Ru redox and OER activity. The link in catalytic and pseudocapacitive behavior illustrates the importance of this redox feature in generating active sites, building new mechanistic understanding of the OER.« less

Rheological Characterization of Unusual DWPF Slurry Samples (U)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koopman, D. C.

2005-09-01

A study was undertaken to identify and clarify examples of unusual rheological behavior in Defense Waste Processing Facility (DWPF) simulant slurry samples. Identification was accomplished by reviewing sludge, Sludge Receipt and Adjustment Tank (SRAT) product, and Slurry Mix Evaporator (SME) product simulant rheological results from the prior year. Clarification of unusual rheological behavior was achieved by developing and implementing new measurement techniques. Development of these new methods is covered in a separate report, WSRC-TR-2004-00334. This report includes a review of recent literature on unusual rheological behavior, followed by a summary of the rheological measurement results obtained on a set ofmore » unusual simulant samples. Shifts in rheological behavior of slurries as the wt. % total solids changed have been observed in numerous systems. The main finding of the experimental work was that the various unusual DWPF simulant slurry samples exhibit some degree of time dependent behavior. When a given shear rate is applied to a sample, the apparent viscosity of the slurry changes with time rather than remaining constant. These unusual simulant samples are more rheologically complex than Newtonian liquids or more simple slurries, neither of which shows significant time dependence. The study concludes that the unusual rheological behavior that has been observed is being caused by time dependent rheological properties in the slurries being measured. Most of the changes are due to the effect of time under shear, but SB3 SME products were also changing properties while stored in sample bottles. The most likely source of this shear-related time dependence for sludge is in the simulant preparation. More than a single source of time dependence was inferred for the simulant SME product slurries based on the range of phenomena observed. Rheological property changes were observed on the time-scale of a single measurement (minutes) as well as on a time scale of hours to weeks. The unusual shape of the slurry flow curves was not an artifact of the rheometric measurement. Adjusting the user-specified parameters in the rheometer measurement jobs can alter the shape of the flow curve of these time dependent samples, but this was not causing the unusual behavior. Variations in the measurement parameters caused the time dependence of a given slurry to manifest at different rates. The premise of the controlled shear rate flow curve measurement is that the dynamic response of the sample to a change in shear rate is nearly instantaneous. When this is the case, the data can be fitted to a time independent rheological equation, such as the Bingham plastic model. In those cases where this does not happen, interpretation of the data is difficult. Fitting time dependent data to time independent rheological equations, such as the Bingham plastic model, is also not appropriate.« less

Analysis of Braking Behavior of Train Drivers to Detect Unusual Driving

NASA Astrophysics Data System (ADS)

Marumo, Yoshitaka; Tsunashima, Hitoshi; Kojima, Takashi; Hasegawa, Yasushi

The safety devices for train systems are activated in emergency situations when a risk becomes obvious, and the emergency brake is applied. If such systems are faulty, the drivers' operating errors may cause immediate accidents. So it is necessary to evaluate potential risks by detecting improper driving behavior before overt risks appear. This study analyzes the driving behavior of train drivers using a train-driving simulator. We focus on braking behavior when approaching a station. Two methods for detecting unusual braking operation are examined by giving drivers mental calculation problems as a mental workload. The first is a method monitoring the driver's brake handle operation, and the second is a method measuring vehicle deceleration. These methods make it possible to detect unusual driving.

WORKSHOP ON MONITORING OXIDATION-REDUCTION PROCESSES FOR GROUND-WATER RESTORATION

EPA Science Inventory

Redox conditions are among the most important parameters for controlling contaminant transport and fate in ground-water systems. Oxidation-reduction (redox) reactions mediate the chemical behavior of both inorganic and organic chemical constituents by affecting solubility, rea...

Reversible anionic redox chemistry in high-capacity layered-oxide electrodes.

PubMed

Sathiya, M; Rousse, G; Ramesha, K; Laisa, C P; Vezin, H; Sougrati, M T; Doublet, M-L; Foix, D; Gonbeau, D; Walker, W; Prakash, A S; Ben Hassine, M; Dupont, L; Tarascon, J-M

2013-09-01

Li-ion batteries have contributed to the commercial success of portable electronics and may soon dominate the electric transportation market provided that major scientific advances including new materials and concepts are developed. Classical positive electrodes for Li-ion technology operate mainly through an insertion-deinsertion redox process involving cationic species. However, this mechanism is insufficient to account for the high capacities exhibited by the new generation of Li-rich (Li(1+x)Ni(y)Co(z)Mn(1-x-y-z)O₂) layered oxides that present unusual Li reactivity. In an attempt to overcome both the inherent composition and the structural complexity of this class of oxides, we have designed structurally related Li₂Ru(1-y)Sn(y)O₃ materials that have a single redox cation and exhibit sustainable reversible capacities as high as 230 mA h g(-1). Moreover, they present good cycling behaviour with no signs of voltage decay and a small irreversible capacity. We also unambiguously show, on the basis of an arsenal of characterization techniques, that the reactivity of these high-capacity materials towards Li entails cumulative cationic (M(n+)→M((n+1)+)) and anionic (O(2-)→O₂(2-)) reversible redox processes, owing to the d-sp hybridization associated with a reductive coupling mechanism. Because Li₂MO₃ is a large family of compounds, this study opens the door to the exploration of a vast number of high-capacity materials.

Biogeochemical Stability of Contaminants in the Subsurface Following In Situ Treatment

EPA Science Inventory

In recent years, innovative treatment technologies have emerged to meet groundwater cleanup goals. In many cases these methods take advantage of the redox behavior of contaminant species. For example, remedial technologies that strategically manipulate subsurface redox conditio...

Characterizing Sexual Behavior in Frontotemporal Dementia.

PubMed

Ahmed, Rebekah M; Kaizik, Cassandra; Irish, Muireann; Mioshi, Eneida; Dermody, Nadene; Kiernan, Matthew C; Piguet, Olivier; Hodges, John R

2015-01-01

Frontotemporal dementia (FTD) is characterized by a number of prominent behavioral changes. While FTD has been associated with the presence of aberrant or unusual sexual behaviors in a proportion of patients, few studies have formally investigated changes in sexual function in this disease. We aimed to systematically quantify changes in sexual behavior, including current symptoms and changes from prior diagnoses, in behavioral-variant (bvFTD) and semantic dementia (SD), compared to Alzheimer's disease (AD). Carers of 49 dementia patients (21 bvFTD, 11 SD, 17 AD) were interviewed using the Sexual Behavior and Intimacy Questionnaire (SIQ), a survey designed to assess changes in sexual function across multiple domains including initiating, level of affection, and aberrant or unusual sexual behavior. BvFTD patients show prominent hyposexual behavior including decreased affection, initiation, and response to advances by partners, and decreased frequency of sexual relations, compared to AD and to SD patients. The greatest changes in sexual behavior compared to pre-diagnoses were found in the bvFTD group with a 90-100% decrease in initiation, response, and frequency of sexual relations. Notably, aberrant or unusual sexual behavior was reported in a minority of bvFTD and SD patients and occurred in patients who also showed hyposexual behavior toward their partner. Overall loss of affection, reduced initiation of sexual activity, and responsiveness is an overwhelming feature of bvFTD. In contrast, aberrant or unusual sexual behavior is observed in the minority of bvFTD patients. The underlying pathophysiology of these changes likely reflects structural and functional changes in frontoinsular and limbic regions including the hypothalamus.

Strategic redox relay enables a scalable synthesis of ouabagenin, a bioactive cardenolide.

PubMed

Renata, Hans; Zhou, Qianghui; Baran, Phil S

2013-01-04

Here, we report on a scalable route to the polyhydroxylated steroid ouabagenin with an unusual take on the age-old practice of steroid semisynthesis. The incorporation of both redox and stereochemical relays during the design of this synthesis resulted in efficient access to more than 500 milligrams of a key precursor toward ouabagenin-and ultimately ouabagenin itself-and the discovery of innovative methods for carbon-hydrogen (C-H) and carbon-carbon activation and carbon-oxygen bond homolysis. Given the medicinal relevance of the cardenolides in the treatment of congestive heart failure, a variety of ouabagenin analogs could potentially be generated from the key intermediate as a means of addressing the narrow therapeutic index of these molecules. This synthesis also showcases an approach to bypass the historically challenging problem of selective C-H oxidation of saturated carbon centers in a controlled fashion.

S-adenosyl methionine prevents ASD like behaviors triggered by early postnatal valproic acid exposure in very young mice.

PubMed

Ornoy, Asher; Weinstein-Fudim, Liza; Tfilin, Matanel; Ergaz, Zivanit; Yanai, Joseph; Szyf, Moshe; Turgeman, Gadi

2018-01-16

A common animal model of ASD is the one induced by valproic acid (VPA), inducing epigenetic changes and oxidative stress. We studied the possible preventive effect of the methyl donor for epigenetic enzymatic reactions, S-adenosine methionine (SAM), on ASD like behavioral changes and on redox potential in the brain and liver in this model. ICR albino mice were injected on postnatal day 4 with one dose of 300 mg/kg of VPA, with normal saline (controls) or with VPA and SAM that was given orally for 3 days at the dose of 30 mg/kg body weight. From day 50, we carried out neurobehavioral tests and assessment of the antioxidant status of the prefrontal cerebral cortex, liver assessing SOD and CAT activity, lipid peroxidation and the expression of antioxidant genes. Mice injected with VPA exhibited neurobehavioral deficits typical of ASD that were more prominent in males. Changes in the activity of SOD and CAT increased lipid peroxidation and changes in the expression of antioxidant genes were observed in the prefrontal cortex of VPA treated mice, more prominent in females, while ASD like behavior was more prominent in males. There were no changes in the redox potential of the liver. The co-administration of VPA and SAM alleviated most ASD like neurobehavioral symptoms and normalized the redox potential in the prefrontal cortex. Early postnatal VPA administration induces ASD like behavior that is more severe in males, while the redox status changes are more severe in females; SAM corrects both. VPA-induced ASD seems to result from epigenetic changes, while the redox status changes may be secondary. Copyright © 2018. Published by Elsevier Inc.

Redox-active porous coordination polymer based on trinuclear pivalate: Temperature-dependent crystal rearrangement and redox-behavior

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lytvynenko, Anton S.; Kiskin, Mikhail A., E-mail: mkiskin@igic.ras.ru; Dorofeeva, Victoria N.

2015-03-15

Linking of trinuclear pivalate Fe{sub 2}NiO(Piv){sub 6} (Piv=O{sub 2}CC(CH{sub 3}){sub 3}) by 2,6-bis(4-pyridyl)-4-(1-naphthyl)pyridine (L) resulted in formation of 1D-porous coordination polymer Fe{sub 2}NiO(Piv){sub 6}(L)·Solv, which was characterized in two forms: DMSO solvate Fe{sub 2}NiO(Piv){sub 6}(L)(DMSO)·2.5DMSO (1) or water solvate Fe{sub 2}NiO(Piv){sub 6}(L)(H{sub 2}O) (2). X-ray structure of 1 was determined. Crystal lattice of 1 at 160 K contained open channels, filled by captured solvent, while temperature growth to 296 K led to the crystal lattice rearrangement and formation of closed voids. Redox-behavior of 2 was studied by cyclic voltammetry for a solid compound, deposited on glassy-carbon electrode. Redox-activity of Lmore » preserved upon incorporation in the coordination polymer. The presence of pores in desolvated sample Fe{sub 2}NiO(Piv){sub 6}(L) was confirmed by the measurements of N{sub 2} and H{sub 2} adsorption at 77 K. Potential barriers of the different molecules diffusion through pores were estimated by the means of molecular mechanics. - Graphical abstract: Redox-behavior of 1D-porous coordination polymer Fe{sub 2}NiO(Piv){sub 6}(L)(H{sub 2}O) was studied by cyclic voltammetry in thin film, deposited on glassy-carbon electrode. Redox-activity of L preserved upon incorporation in the coordination polymer. Potential barriers of different molecules diffusion through pores were estimated by the means of molecular mechanics. - Highlights: • Porous 1D coordination polymer was synthesized. • Temperature growth led to pores closing due to crystal lattice rearrangement. • Redox-activity of ligand preserved upon incorporation into coordination polymer. • Redox-properties of solid coordination polymer were studied in thin film. • Diffusion barriers were evaluated by molecular mechanics.« less

Glutathione and redox signaling in substance abuse.

PubMed

Uys, Joachim D; Mulholland, Patrick J; Townsend, Danyelle M

2014-07-01

Throughout the last couple decades, the cause and consequences of substance abuse has expanded to identify the underlying neurobiological signaling mechanisms associated with addictive behavior. Chronic use of drugs, such as cocaine, methamphetamine and alcohol leads to the formation of oxidative or nitrosative stress (ROS/RNS) and changes in glutathione and redox homeostasis. Of importance, redox-sensitive post-translational modifications on cysteine residues, such as S-glutathionylation and S-nitrosylation could impact on the structure and function of addiction related signaling proteins. In this commentary, we evaluate the role of glutathione and redox signaling in cocaine-, methamphetamine- and alcohol addiction and conclude by discussing the possibility of targeting redox pathways for the therapeutic intervention of these substance abuse disorders. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

Redox-Active vs Redox-Innocent: A Comparison of Uranium Complexes Containing Diamine Ligands.

PubMed

Pattenaude, Scott A; Mullane, Kimberly C; Schelter, Eric J; Ferrier, Maryline G; Stein, Benjamin W; Bone, Sharon E; Lezama Pacheco, Juan S; Kozimor, Stosh A; Fanwick, Phillip E; Zeller, Matthias; Bart, Suzanne C

2018-05-11

Uranium complexes ( Mes DAE) 2 U(THF) (1-DAE) and Cp 2 U( Mes DAE) (2-DAE) ( Mes DAE = [ArN-CH 2 CH 2 -NAr]; Ar = 2,4,6-trimethylphenyl (Mes)), bearing redox-innocent diamide ligands, have been synthesized and characterized for a full comparison with previously published, redox-active diimine complexes, ( Mes DAB Me ) 2 U(THF) (1-DAB) and Cp 2 U( Mes DAB Me ) (2-DAB) ( Mes DAB Me = [ArN═C(Me)C(Me)═NAr]; Ar = Mes). These redox-innocent analogues maintain an analogous steric environment to their redox-active ligand counterparts to facilitate a study aimed at determining the differing electronic behavior around the uranium center. Structural analysis by X-ray crystallography showed 1-DAE and 2-DAE have a structural environment very similar to 1-DAB and 2-DAB, respectively. The main difference occurs with coordination of the ene-backbone to the uranium center in the latter species. Electronic absorption spectroscopy reveals these new DAE complexes are nearly identical to each other. X-ray absorption spectroscopy suggests all four species contain +4 uranium ions. The data also indicates that there is an electronic difference between the bis(diamide)-THF uranium complexes as opposed to those that only contain one diamide and two cyclopentadienyl rings. Finally, magnetic measurements reveal that all complexes display temperature-dependent behavior consistent with uranium(IV) ions that do not include ligand radicals. Overall, this study determines that there is no significant bonding difference between the redox-innocent and redox-active ligand frameworks on uranium. Furthermore, there are no data to suggest covalent bonding character using the latter ligand framework on uranium, despite what is known for transition metals.

PDILT, a divergent testis-specific protein disulfide isomerase with a non-classical SXXC motif that engages in disulfide-dependent interactions in the endoplasmic reticulum.

PubMed

van Lith, Marcel; Hartigan, Nichola; Hatch, Jennifer; Benham, Adam M

2005-01-14

Protein disulfide isomerase (PDI) is the archetypal enzyme involved in the formation and reshuffling of disulfide bonds in the endoplasmic reticulum (ER). PDI achieves its redox function through two highly conserved thioredoxin domains, and PDI can also operate as an ER chaperone. The substrate specificities and the exact functions of most other PDI family proteins remain important unsolved questions in biology. Here, we characterize a new and striking member of the PDI family, which we have named protein disulfide isomerase-like protein of the testis (PDILT). PDILT is the first eukaryotic SXXC protein to be characterized in the ER. Our experiments have unveiled a novel, glycosylated PDI-like protein whose tissue-specific expression and unusual motifs have implications for the evolution, catalytic function, and substrate selection of thioredoxin family proteins. We show that PDILT is an ER resident glycoprotein that liaises with partner proteins in disulfide-dependent complexes within the testis. PDILT interacts with the oxidoreductase Ero1alpha, demonstrating that the N-terminal cysteine of the CXXC sequence is not required for binding of PDI family proteins to ER oxidoreductases. The expression of PDILT, in addition to PDI in the testis, suggests that PDILT performs a specialized chaperone function in testicular cells. PDILT is an unusual PDI relative that highlights the adaptability of chaperone and redox function in enzymes of the endoplasmic reticulum.

Almahata Sitta MS-MU-011 and MS-MU-012: Formation Conditions of Two Unusual Rocks From the Ureilite Parent Body

NASA Technical Reports Server (NTRS)

Mikouchi, T.; Takenouchi, A.; Zolensky, M. E.; Hoffmann, V. H.

2018-01-01

Almahata Sitta meteorites are unique polymict breccia, comprising of many different meteorite groups as individual fragments dominated by ureilite lithologies and are considered to be recovered fragments of the asteroid 2008TC3. Recently, two unusual Almahata Sitta samples (MS-MU-011 and MS-MU-012) have been reported that show close petrogenetic relationships to ureilites. MS-MU-011 is a trachyandesite mainly composed of feldspar (plagioclase and anorthoclase) and pyroxene (pigeonite and augite) having ureilitic oxygen isotopic ratios. MS-MU-012 is the first ureilite example (unbrecciated) containing primary plagioclase crystals. The findings of these two rock types are important to better understand formation conditions of ureilites and the evolution of their parent body(s). In this abstract we discuss formation conditions of these ureilite-related rocks using redox state estimate by Fe valence states of plagioclase and olivine cooling rate calculations.

Electronic structure of the unique [4Fe-3S] cluster in O2-tolerant hydrogenases characterized by 57Fe Mössbauer and EPR spectroscopy

PubMed Central

Pandelia, Maria-Eirini; Bykov, Dmytro; Izsak, Robert; Infossi, Pascale; Giudici-Orticoni, Marie-Thérèse; Bill, Eckhard; Neese, Frank; Lubitz, Wolfgang

2013-01-01

Iron–sulfur clusters are ubiquitous electron transfer cofactors in hydrogenases. Their types and redox properties are important for H2 catalysis, but, recently, their role in a protection mechanism against oxidative inactivation has also been recognized for a [4Fe-3S] cluster in O2-tolerant group 1 [NiFe] hydrogenases. This cluster, which is uniquely coordinated by six cysteines, is situated in the proximity of the catalytic [NiFe] site and exhibits unusual redox versatility. The [4Fe-3S] cluster in hydrogenase (Hase) I from Aquifex aeolicus performs two redox transitions within a very small potential range, forming a superoxidized state above +200 mV vs. standard hydrogen electrode (SHE). Crystallographic data has revealed that this state is stabilized by the coordination of one of the iron atoms to a backbone nitrogen. Thus, the proximal [4Fe-3S] cluster undergoes redox-dependent changes to serve multiple purposes beyond classical electron transfer. In this paper, we present field-dependent 57Fe-Mössbauer and EPR data for Hase I, which, in conjunction with spectroscopically calibrated density functional theory (DFT) calculations, reveal the distribution of Fe valences and spin-coupling schemes for the iron–sulfur clusters. The data demonstrate that the electronic structure of the [4Fe-3S] core in its three oxidation states closely resembles that of corresponding conventional [4Fe-4S] cubanes, albeit with distinct differences for some individual iron sites. The medial and distal iron–sulfur clusters have similar electronic properties as the corresponding cofactors in standard hydrogenases, although their redox potentials are higher. PMID:23267108

Resolving the Iron Phthalocyanine Redox Transitions for ORR Catalysis in Aqueous Media

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alsudairi, Amell; Li, Jingkun; Ramaswamy, Nagappan

Metal macrocycles are among the most important catalytic systems in electrocatalysis and biocatalysis owing to their rich redox chemistry. Precise understanding of the redox behavior of metal macrocycles in operando is essential for fundamental studies and practical applications of this catalytic system. Here we present electrochemical data for the representative iron phthalocyanine (FePc) in both aqueous and nonaqueous media coupled with in situ Raman and X-ray absorption analyses to challenge the traditional notion of the redox transition of FePc at the low potential end in aqueous media by showing that it arises from the redox transition of the ring. Ourmore » data unequivocally demonstrate that the electron is shuttled to the Pc ring via the Fe(II)/Fe(I) redox center. The Fe(II)/Fe(I) redox transition of FePc in aqueous media is indiscernible by normal spectroscopic methods owing to the lack of a suitable axial ligand to stabilize the Fe(I) state.« less

Modulation of Chlamydomonas reinhardtii flagellar motility by redox poise

PubMed Central

Wakabayashi, Ken-ichi; King, Stephen M.

2006-01-01

Redox-based regulatory systems are essential for many cellular activities. Chlamydomonas reinhardtii exhibits alterations in motile behavior in response to different light conditions (photokinesis). We hypothesized that photokinesis is signaled by variations in cytoplasmic redox poise resulting from changes in chloroplast activity. We found that this effect requires photosystem I, which generates reduced NADPH. We also observed that photokinetic changes in beat frequency and duration of the photophobic response could be obtained by altering oxidative/reductive stress. Analysis of reactivated cell models revealed that this redox poise effect is mediated through the outer dynein arms (ODAs). Although the global redox state of the thioredoxin-related ODA light chains LC3 and LC5 and the redox-sensitive Ca2+-binding subunit of the docking complex DC3 did not change upon light/dark transitions, we did observe significant alterations in their interactions with other flagellar components via mixed disulfides. These data indicate that redox poise directly affects ODAs and suggest that it may act in the control of flagellar motility. PMID:16754958

Redox condition in molten salts and solute behavior: A first-principles molecular dynamics study

NASA Astrophysics Data System (ADS)

Nam, Hyo On; Morgan, Dane

2015-10-01

Molten salts technology is of significant interest for nuclear, solar, and other energy systems. In this work, first-principles molecular dynamics (FPMD) was used to model the solute behavior in eutectic LiCl-KCl and FLiBe (Li2BeF4) melts at 773 K and 973 K, respectively. The thermo-kinetic properties for solute systems such as the redox potential, solute diffusion coefficients and structural information surrounding the solute were predicted from FPMD modeling and the calculated properties are generally in agreement with the experiments. In particular, we formulate an approach to model redox energetics vs. chlorine (or fluorine) potential from first-principles approaches. This study develops approaches for, and demonstrates the capabilities of, FPMD to model solute properties in molten salts.

Reversible anionic redox chemistry in high-capacity layered-oxide electrodes

NASA Astrophysics Data System (ADS)

Sathiya, M.; Rousse, G.; Ramesha, K.; Laisa, C. P.; Vezin, H.; Sougrati, M. T.; Doublet, M.-L.; Foix, D.; Gonbeau, D.; Walker, W.; Prakash, A. S.; Ben Hassine, M.; Dupont, L.; Tarascon, J.-M.

2013-09-01

Li-ion batteries have contributed to the commercial success of portable electronics and may soon dominate the electric transportation market provided that major scientific advances including new materials and concepts are developed. Classical positive electrodes for Li-ion technology operate mainly through an insertion-deinsertion redox process involving cationic species. However, this mechanism is insufficient to account for the high capacities exhibited by the new generation of Li-rich (Li1+xNiyCozMn(1-x-y-z)O2) layered oxides that present unusual Li reactivity. In an attempt to overcome both the inherent composition and the structural complexity of this class of oxides, we have designed structurally related Li2Ru1-ySnyO3 materials that have a single redox cation and exhibit sustainable reversible capacities as high as 230 mA h g-1. Moreover, they present good cycling behaviour with no signs of voltage decay and a small irreversible capacity. We also unambiguously show, on the basis of an arsenal of characterization techniques, that the reactivity of these high-capacity materials towards Li entails cumulative cationic (Mn+→M(n+1)+) and anionic (O2-→O22-) reversible redox processes, owing to the d-sp hybridization associated with a reductive coupling mechanism. Because Li2MO3 is a large family of compounds, this study opens the door to the exploration of a vast number of high-capacity materials.

Electrochemical behaviour of naked sub-nanometre sized copper clusters and effect of CO 2

DOE PAGES

Passalacqua, Rosalba; Parathoner, Siglinda; Centi, Gabriele; ...

2016-08-04

The study of the electrochemical behavior (in the presence of N 2 or CO 2) of size-controlled naked Cu 5 and Cu 20 nanoclusters, prepared using a combination of gas-phase cluster ion sources, mass spectrometry, and soft-landing techniques, evidences some relevant results regarding the redox behavior of these sub-nanometre sized copper particles and the effect of CO 2 on them. Cu 20 nanoclusters show anodic redox processes occurring at much lower potential with respect to Cu 5 nanoclusters, which behave relatively similar to much larger Cu particles. However, Cu 5 nanoclusters coordinate effectively CO 2 (hydrogen carbonate) in solution, differentmore » from Cu 20 nanoclusters and larger Cu particles. This effect, rather than the redox behavior, is apparently connected to the ability of Cu 5 nanoclusters to reduce CO 2 under cathodic conditions at low overpotential. In conclusion, although preliminary, these results provide rather exciting indications on the possibility of realizing low overpotential electrocatalytic conversion of CO 2.« less

Electrochemical behaviour of naked sub-nanometre sized copper clusters and effect of CO 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Passalacqua, Rosalba; Parathoner, Siglinda; Centi, Gabriele

The study of the electrochemical behavior (in the presence of N 2 or CO 2) of size-controlled naked Cu 5 and Cu 20 nanoclusters, prepared using a combination of gas-phase cluster ion sources, mass spectrometry, and soft-landing techniques, evidences some relevant results regarding the redox behavior of these sub-nanometre sized copper particles and the effect of CO 2 on them. Cu 20 nanoclusters show anodic redox processes occurring at much lower potential with respect to Cu 5 nanoclusters, which behave relatively similar to much larger Cu particles. However, Cu 5 nanoclusters coordinate effectively CO 2 (hydrogen carbonate) in solution, differentmore » from Cu 20 nanoclusters and larger Cu particles. This effect, rather than the redox behavior, is apparently connected to the ability of Cu 5 nanoclusters to reduce CO 2 under cathodic conditions at low overpotential. In conclusion, although preliminary, these results provide rather exciting indications on the possibility of realizing low overpotential electrocatalytic conversion of CO 2.« less

Suppression of single-wall carbon nanotube redox reaction by adsorbed proteins

NASA Astrophysics Data System (ADS)

Nakayama, Tomohito; Tanaka, Takeshi; Shiraki, Kentaro; Hase, Muneaki; Hirano, Atsushi

2018-07-01

Single-wall carbon nanotubes (SWCNTs) are widely used in biological applications. In biological systems, proteins readily adsorb to SWCNTs. However, little is known about the effects of proteins on the physicochemical properties of SWCNTs, such as their redox reaction. In this study, we measured the absorption and Raman spectra of SWCNTs dispersed in the presence of proteins such as bovine serum albumin to observe the redox reaction of the protein-adsorbed SWCNTs. The adsorbed proteins suppressed the redox reaction by forming thick and dense layers around the SWCNTs. Our findings are useful for understanding the behaviors of SWCNTs in biological systems.

Effects of Hypoxia on Animal Burrow Constraction and Consequent Effects on Sediment Redox Profiles (SETAC08)

EPA Science Inventory

We investigated the effects of mild hypoxia on the burrowing behavior of three marine species (the hard clam Mercenaria mercenaria, the polychaete worm Nereis virens, and the amphipod Leptocheirus plumulosus) and consequent effects on sediment redox profiles. Animals were introdu...

The Varied Variability of PKS 0736+017

NASA Astrophysics Data System (ADS)

Clements, S. D.; Cubides, L. A.; Greiwe, C. L.; Habermas, K. S.; Jenks, A. K.; Long, A. M.; Patel, J. A.; Torres, Y. V.

2003-05-01

The flat spectrum radio quasar PKS 0736+017 has been an exciting observing target, exhibiting diverse optical variability behaviors and even sharing its field one evening with a minor planet. The behavior of PKS 0736+017 has included persistently faint and quiescent periods, episodes of quasi-periodic microvariability, dramatic flaring events, and periods of unusual oscillations. These assorted behaviors are examined, with particular emphasis on the quasi-periodic variations and unusual oscillations that accompanied a dramatic flare.

Cocaine-Induced Adaptations in Cellular Redox Balance Contributes to Enduring Behavioral Plasticity

PubMed Central

Uys, Joachim D; Knackstedt, Lori; Hurt, Phelipe; Tew, Kenneth D; Manevich, Yefim; Hutchens, Steven; Townsend, Danyelle M; Kalivas, Peter W

2011-01-01

Impaired glutamate homeostasis in the nucleus accumbens has been linked to cocaine relapse in animal models, and results in part from cocaine-induced downregulation of the cystine–glutamate exchanger. In addition to regulating extracellular glutamate, the uptake of cystine by the exchanger is a rate-limiting step in the synthesis of glutathione (GSH). GSH is critical for balancing cellular redox in response to oxidative stress. Cocaine administration induces oxidative stress, and we first determined if downregulated cystine–glutamate exchange alters redox homeostasis in rats withdrawn from daily cocaine injections and then challenged with acute cocaine. Among the daily cocaine-induced changes in redox homeostasis were an increase in protein S-glutathionylation and a decrease in expression of GSH-S-transferase pi (GSTpi). To mimic reduced GSTpi, a genetic mouse model of GSTpi deletion or pharmacological inhibition of GSTpi by administering ketoprofen during daily cocaine administration was used. The capacity of cocaine to induce conditioned place preference or locomotor sensitization was augmented, indicating that reducing GSTpi may contribute to cocaine-induced behavioral neuroplasticity. Conversely, an acute cocaine challenge after withdrawal from daily cocaine elicited a marked increase in accumbens GSTpi, and the expression of behavioral sensitization to a cocaine challenge injection was inhibited by ketoprofen pretreatment; supporting a protective effect by the acute cocaine-induced rise in GSTpi. Together, these data indicate that cocaine-induced oxidative stress induces changes in GSTpi that contribute to cocaine-induced behavioral plasticity. PMID:21796101

Unusual ferromagnetic critical behavior owing to short-range antiferromagnetic correlations in antiperovskite Cu1-xNMn3+x (0.1 ≤ x ≤ 0.4)

PubMed Central

Lin, Jianchao; Tong, Peng; Cui, Dapeng; Yang, Cheng; Yang, Jie; Lin, Shuai; Wang, Bosen; Tong, Wei; Zhang, Lei; Zou, Youming; Sun, Yuping

2015-01-01

For ferromagnets, varying from simple metals to strongly correlated oxides,the critical behaviors near the Curie temperature (TC) can be grouped into several universal classes. In this paper, we report an unusual critical behavior in manganese nitrides Cu1-xNMn3+x (0.1 ≤ x ≤ 0.4). Although the critical behavior below TC can be well described by mean field (MF) theory, robust critical fluctuations beyond the expectations of any universal classes are observed above TC in x = 0.1. The critical fluctuations become weaker when x increases, and the MF-like critical behavior is finally restored at x = 0.4. In addition, the paramagnetic susceptibility of all the samples deviates from the Curie-Weiss (CW) law just above TC. This deviation is gradually smeared as x increases. The short-range antiferromagnetic ordering above TC revealed by our electron spin resonance measurement explains both the unusual critical behavior and the breakdown of the CW law. PMID:25604754

Transport of gadolinium- and arsenic-based pharmaceuticals in saturated soil under various redox conditions.

PubMed

Menahem, Adi; Dror, Ishai; Berkowitz, Brian

2016-02-01

The release of pharmaceuticals and personal care products (PPCPs) to the soil-water environment necessitates understanding of PPCP transport behavior under conditions that account for dynamic flow and varying redox states. This study investigates the transport of two organometallic PPCPs, Gd-DTPA and roxarsone (arsenic compound) and their metal salts (Gd(NO3)3, AsNaO2); Gd-DTPA is used widely as a contrasting agent for MRI, while roxarsone is applied extensively as a food additive in the broiler poultry industry. Here, we present column experiments using sand and Mediterranean red sandy clay soil, performed under several redox conditions. The metal salts were almost completely immobile. In contrast, transport of Gd-DTPA and roxarsone was affected by the soil type. Roxarsone was also affected by the different redox conditions, showing delayed breakthrough curves as the redox potential became more negative due to biological activity (chemically-strong reducing conditions did not affect the transport). Mechanisms that include adsorptive retardation for aerobic and nitrate-reducing conditions, and non-adsorptive retardation for iron-reducing, sulfate-reducing and biologically-strong reducing conditions, are suggested to explain the roxarsone behavior. Gd-DTPA is found to be a stable complex, with potential for high mobility in groundwater systems, whereas roxarsone transport through groundwater systems is affected by redox environments, demonstrating high mobility under aerobic and nitrate-reducing conditions and delayed transport under iron-reducing, sulfate-reducing and biologically-strong reducing conditions. Copyright © 2015 Elsevier Ltd. All rights reserved.

Requirements for optimization of electrodes and electrolyte for the iron/chromium Redox flow cell

NASA Technical Reports Server (NTRS)

Jalan, V.; Stark, H.; Giner, J.

1981-01-01

Improved catalyzation techniques that included a pretreatment of carbon substrate and provided normalized carbon surface for uniform gold deposition were developed. This permits efficient use of different batches of carbon felt materials which initially vary significantly in their physical and surface chemical properties, as well as their electrochemical behavior. Further modification of gold impregnation technique gave the best performing electrodes. In addition to the linear sweep voltammetry, cyclic voltammetry was used to determine the effects of different activation procedures on the Cr(3)/Cr(2) Redox and H2 evolution reactions. The roles of carbon, gold and lead in the overall Redox cycle are identified. The behavior of the electrodes at both normal battery operating potentials and more extreme potentials is discussed preparing efficient and stable electrodes for the energy storage battery is implicated.

INFLUENCE OF PH AND REDOX CONDITIONS ON COPPER LEACHING

EPA Science Inventory

Leaching behavior of metals from a mineral processing waste at varying pH and redox conditions was studies. Effect of combinations of pH and Eh on leaching of copper is described. Leaching of copper was found to be dependent on both pH and Eh. Higher concentrations of Cu were ...

Low potential manganese ions as efficient electron donors in native anoxygenic bacteria.

PubMed

Deshmukh, Sasmit S; Protheroe, Charles; Ivanescu, Matei-Alexandru; Lag, Sarah; Kálmán, László

2018-04-01

Systematic control over molecular driving forces is essential for understanding the natural electron transfer processes as well as for improving the efficiency of the artificial mimics of energy converting enzymes. Oxygen producing photosynthesis uniquely employs manganese ions as rapid electron donors. Introducing this attribute to anoxygenic photosynthesis may identify evolutionary intermediates and provide insights to the energetics of biological water oxidation. This work presents effective environmental methods that substantially and simultaneously tune the redox potentials of manganese ions and the cofactors of a photosynthetic enzyme from native anoxygenic bacteria without the necessity of genetic modification or synthesis. A spontaneous coordination with bis-tris propane lowered the redox potential of the manganese (II) to manganese (III) transition to an unusually low value (~400 mV) at pH 9.4 and allowed its binding to the bacterial reaction center. Binding to a novel buried binding site elevated the redox potential of the primary electron donor, a dimer of bacteriochlorophylls, by up to 92 mV also at pH 9.4 and facilitated the electron transfer that is able to compete with the wasteful charge recombination. These events impaired the function of the natural electron donor and made BTP-coordinated manganese a viable model for an evolutionary alternative. Copyright © 2018 Elsevier B.V. All rights reserved.

Impact of copper ligand mutations on a cupredoxin with a green copper center.

PubMed

Roger, Magali; Sciara, Giuliano; Biaso, Frédéric; Lojou, Elisabeth; Wang, Xie; Bauzan, Marielle; Giudici-Orticoni, Marie-Thérèse; Vila, Alejandro J; Ilbert, Marianne

2017-05-01

Mononuclear cupredoxins contain a type 1 copper center with a trigonal or tetragonal geometry usually maintained by four ligands, a cystein, two histidines and a methionine. The recent discovery of new members of this family with unusual properties demonstrates, however, the versatility of this class of proteins. Changes in their ligand set lead to drastic variation in their metal site geometry and in the resulting spectroscopic and redox features. In our work, we report the identification of the copper ligands in the recently discovered cupredoxin AcoP. We show that even though AcoP possesses a classical copper ligand set, it has a highly perturbed copper center. In depth studies of mutant's properties suggest a high degree of constraint existing in the copper center of the wild type protein and even the addition of exogenous ligands does not lead to the reconstitution of the initial copper center. Not only the chemical nature of the axial ligand but also constraints brought by its covalent binding to the protein backbone might be critical to maintain a green copper site with high redox potential. This work illustrates the importance of experimentally dissecting the molecular diversity of cupredoxins to determine the molecular determinants responsible for their copper center geometry and redox potential. Copyright © 2017 Elsevier B.V. All rights reserved.

The self-assembly of redox active peptides: Synthesis and electrochemical capacitive behavior.

PubMed

Piccoli, Julia P; Santos, Adriano; Santos-Filho, Norival A; Lorenzón, Esteban N; Cilli, Eduardo M; Bueno, Paulo R

2016-05-01

The present work reports on the synthesis of a redox-tagged peptide with self-assembling capability aiming applications in electrochemically active capacitive surfaces (associated with the presence of the redox centers) generally useful in electroanalytical applications. Peptide containing ferrocene (fc) molecular (redox) group (Ac-Cys-Ile-Ile-Lys(fc)-Ile-Ile-COOH) was thus synthesized by solid phase peptide synthesis (SPPS). To obtain the electrochemically active capacitive interface, the side chain of the cysteine was covalently bound to the gold electrode (sulfur group) and the side chain of Lys was used to attach the ferrocene in the peptide chain. After obtaining the purified redox-tagged peptide, the self-assembly and redox capability was characterized by cyclic voltammetry (CV) and electrochemical impedance-based capacitance spectroscopy techniques. The obtained results confirmed that the redox-tagged peptide was successfully attached by forming an electroactive self-assembled monolayer onto gold electrode. The design of redox active self-assembly ferrocene-tagged peptide is predictably useful in the development of biosensor devices precisely to detect, in a label-free platform, those biomarkers of clinical relevance. © 2016 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 106: 357-367, 2016. © 2016 Wiley Periodicals, Inc.

Model creation of moving redox reaction boundary in agarose gel electrophoresis by traditional potassium permanganate method.

PubMed

Xie, Hai-Yang; Liu, Qian; Li, Jia-Hao; Fan, Liu-Yin; Cao, Cheng-Xi

2013-02-21

A novel moving redox reaction boundary (MRRB) model was developed for studying electrophoretic behaviors of analytes involving redox reaction on the principle of moving reaction boundary (MRB). Traditional potassium permanganate method was used to create the boundary model in agarose gel electrophoresis because of the rapid reaction rate associated with MnO(4)(-) ions and Fe(2+) ions. MRB velocity equation was proposed to describe the general functional relationship between velocity of moving redox reaction boundary (V(MRRB)) and concentration of reactant, and can be extrapolated to similar MRB techniques. Parameters affecting the redox reaction boundary were investigated in detail. Under the selected conditions, good linear relationship between boundary movement distance and time were obtained. The potential application of MRRB in electromigration redox reaction titration was performed in two different concentration levels. The precision of the V(MRRB) was studied and the relative standard deviations were below 8.1%, illustrating the good repeatability achieved in this experiment. The proposed MRRB model enriches the MRB theory and also provides a feasible realization of manual control of redox reaction process in electrophoretic analysis.

Redox-responsive theranostic nanoplatforms based on inorganic nanomaterials.

PubMed

Han, Lu; Zhang, Xiao-Yong; Wang, Yu-Long; Li, Xi; Yang, Xiao-Hong; Huang, Min; Hu, Kun; Li, Lu-Hai; Wei, Yen

2017-08-10

Spurred on by advances in materials chemistry and nanotechnology, scientists have developed many novel nanopreparations for cancer diagnosis and therapy. To treat complex malignant tumors effectively, multifunctional nanomedicines with targeting ability, imaging properties and controlled drug release behavior should be designed and exploited. The therapeutic efficiency of loaded drugs can be dramatically improved using redox-responsive nanoplatforms which can sense the differences in the redox status of tumor tissues and healthy ones. Redox-sensitive nanocarriers can be constructed from both organic and inorganic nanomaterials; however, at present, drug delivery nanovectors progressively lean towards inorganic nanomaterials because of their facile synthesis/modification and their unique physicochemical properties. In this review, we focus specifically on the preparation and application of redox-sensitive nanosystems based on mesoporous silica nanoparticles (MSNs), carbon nanomaterials, magnetic nanoparticles, gold nanomaterials and other inorganic nanomaterials. We discuss relevant examples of redox-sensitive nanosystems in each category. Finally, we discuss current challenges and future strategies from the aspect of material design and practical application. Copyright © 2017 Elsevier B.V. All rights reserved.

Direct mapping of local redox current density on a monolith electrode by laser scanning.

PubMed

Lee, Seung-Woo; Lopez, Jeffrey; Saraf, Ravi F

2013-09-15

An optical method of mapping local redox reaction over a monolith electrode using simple laser scanning is described. As the optical signal is linearly proportional to the maximum redox current that is measured concomitantly by voltammetry, the optical signal quantitatively maps the local redox current density distribution. The method is demonstrated on two types of reactions: (1) a reversible reaction where the redox moieties are ionic, and (2) an irreversible reaction on two different types of enzymes immobilized on the electrode where the reaction moieties are nonionic. To demonstrate the scanning capability, the local redox behavior on a "V-shaped" electrode is studied where the local length scale and, hence, the local current density, is nonuniform. The ability to measure the current density distribution by this method will pave the way for multianalyte analysis on a monolith electrode using a standard three-electrode configuration. The method is called Scanning Electrometer for Electrical Double-layer (SEED). Copyright © 2013 Elsevier B.V. All rights reserved.

Rab7-a novel redox target that modulates inflammatory pain processing.

PubMed

Kallenborn-Gerhardt, Wiebke; Möser, Christine V; Lorenz, Jana E; Steger, Mirco; Heidler, Juliana; Scheving, Reynir; Petersen, Jonas; Kennel, Lea; Flauaus, Cathrin; Lu, Ruirui; Edinger, Aimee L; Tegeder, Irmgard; Geisslinger, Gerd; Heide, Heinrich; Wittig, Ilka; Schmidtko, Achim

2017-07-01

Chronic pain is accompanied by production of reactive oxygen species (ROS) in various cells that are important for nociceptive processing. Recent data indicate that ROS can trigger specific redox-dependent signaling processes, but the molecular targets of ROS signaling in the nociceptive system remain largely elusive. Here, we performed a proteome screen for pain-dependent redox regulation using an OxICAT approach, thereby identifying the small GTPase Rab7 as a redox-modified target during inflammatory pain in mice. Prevention of Rab7 oxidation by replacement of the redox-sensing thiols modulates its GTPase activity. Immunofluorescence studies revealed Rab7 expression to be enriched in central terminals of sensory neurons. Knockout mice lacking Rab7 in sensory neurons showed normal responses to noxious thermal and mechanical stimuli; however, their pain behavior during inflammatory pain and in response to ROS donors was reduced. The data suggest that redox-dependent changes in Rab7 activity modulate inflammatory pain sensitivity.

Increased Prevalence of Unusual Sensory Behaviors in Infants at Risk For, and Teens With, Autism Spectrum Disorder

ERIC Educational Resources Information Center

Van Etten, Hannah M.; Kaur, Maninderjit; Srinivasan, Sudha M.; Cohen, Shereen J.; Bhat, Anjana; Dobkins, Karen R.

2017-01-01

The current study investigated the prevalence and pattern of unusual sensory behaviors (USBs) in teens with Autism Spectrum Disorder (ASD) and infants (3-36 months) at risk for ASD. From two different sites (UCSD and UConn), caregivers of infants at high (n = 32) and low risk (n = 33) for ASD, and teenagers with (n = 12) and without ASD (n = 11),…

A Statistical Procedure for Testing Unusually Frequent Exactly Matching Responses and Nearly Matching Responses. Research Report. ETS RR-17-23

ERIC Educational Resources Information Center

Haberman, Shelby J.; Lee, Yi-Hsuan

2017-01-01

In investigations of unusual testing behavior, a common question is whether a specific pattern of responses occurs unusually often within a group of examinees. In many current tests, modern communication techniques can permit quite large numbers of examinees to share keys, or common response patterns, to the entire test. To address this issue,…

Selective synthesis and redox sequence of a heterobimetallic nickel/copper complex of the noninnocent Siamese-twin porphyrin.

PubMed

Blusch, Lina K; Mitevski, Oliver; Martin-Diaconescu, Vlad; Pröpper, Kevin; DeBeer, Serena; Dechert, Sebastian; Meyer, Franc

2014-08-04

The Siamese-twin porphyrin (1H4) is a redox noninnocent pyrazole-expanded porphyrin with two equivalent dibasic {N4} binding sites. It is now shown that its selective monometalation can be achieved to give the nickel(II) complex 1H2Ni with the second {N4} site devoid of a metal ion. This intermediate is then cleanly converted to 1Ni2 and to the first heterobimetallic Siamese-twin porphyrin 1CuNi. Structural characterization of 1H2Ni shows that it has the same helical structure previously seen for 1Cu2, 1Ni2, and free base 1H6(2+). Titration experiments suggest that the metal-devoid pocket of 1H2Ni can accommodate two additional protons, giving [1H4Ni](2+). Both bimetallic complexes 1Ni2 and 1CuNi feature rich redox chemistry, similar to the recently reported 1Cu2, including two chemically reversible oxidations at moderate potentials between -0.3 and +0.5 V (vs Cp2Fe/Cp2Fe(+)). The locus of these oxidations, in singly oxidized [1Ni2](+) and [1CuNi](+) as well as twice oxidized [1CuNi](2+), has been experimentally derived from comparison of the electrochemical properties of the complete series of complexes 1Cu2, 1Ni2, and 1CuNi, and from electron paramagnetic resonance (EPR) spectroscopy and X-ray absorption spectroscopy (XAS) (Ni and Cu K edges). All redox events are largely ligand-based, and in heterobimetallic 1CuNi, the first oxidation takes place within its Cu-subunit, while the second oxidation then occurs in its Ni-subunit. Adding pyridine to solutions of [1Ni2](+) and [1CuNi](2+) cleanly converts them to metal-oxidized redox isomers with axial EPR spectra typical for Ni(III) having significant dz(2)(1) character, reflecting close similarity with nickel complexes of common porphyrins. The possibility of selectively synthesizing heterobimetallic complexes 1MNi from a symmetric binucleating ligand scaffold, with the unusual situation of three distinct contiguous redox sites (M, Ni, and the porphyrin-like ligand), further expands the Siamese-twin porphyrin's potential to serve as an adjustable platform for multielectron redox processes in chemical catalysis and in electronic applications.

Unraveling the charge transfer/electron transport in mesoporous semiconductive TiO2 films by voltabsorptometry.

PubMed

Renault, Christophe; Nicole, Lionel; Sanchez, Clément; Costentin, Cyrille; Balland, Véronique; Limoges, Benoît

2015-04-28

In this work, we demonstrate that chronoabsorptometry and more specifically cyclic voltabsorptometry are particularly well suited techniques for acquiring a comprehensive understanding of the dynamics of electron transfer/charge transport within a transparent mesoporous semiconductive metal oxide film loaded with a redox-active dye. This is illustrated with the quantitative analysis of the spectroelectrochemical responses of two distinct heme-based redox probes adsorbed in highly-ordered mesoporous TiO2 thin films (prepared from evaporation-induced self-assembly, EISA). On the basis of a finite linear diffusion-reaction model as well as the establishment of the analytical expressions governing the limiting cases, it was possible to quantitatively analyse, predict and interpret the unusual voltabsorptometric responses of the adsorbed redox species as a function of the potential applied to the semiconductive film (i.e., as a function of the transition from an insulating to a conductive state or vice versa). In particular, we were able to accurately determine the interfacial charge transfer rates between the adsorbed redox species and the porous semiconductor. Another important and unexpected finding, inferred from the voltabsorptograms, is an interfacial electron transfer process predominantly governed by the extended conduction band states of the EISA TiO2 film and not by the localized traps in the bandgap. This is a significant result that contrasts those previously observed for dye-sensitized solar cells formed of randomly sintered TiO2 nanoparticles, a behaviour that was ascribed to a particularly low density of localized surface states in EISA TiO2. The present methodology also provides a unique and straightforward access to an activation-driving force relationship according to the Marcus theory, thus opening new opportunities not only to investigate the driving-force effects on electron recombination dynamics in dye-sensitized solar cells but also to study the electron transfer/transport mechanisms in heterogeneous photoelectrocatalytic systems combining nanostructured semiconductor electrodes and heterogeneous redox-active catalysts.

Anticancer activity of metal complexes: involvement of redox processes.

PubMed

Jungwirth, Ute; Kowol, Christian R; Keppler, Bernhard K; Hartinger, Christian G; Berger, Walter; Heffeter, Petra

2011-08-15

Cells require tight regulation of the intracellular redox balance and consequently of reactive oxygen species for proper redox signaling and maintenance of metal (e.g., of iron and copper) homeostasis. In several diseases, including cancer, this balance is disturbed. Therefore, anticancer drugs targeting the redox systems, for example, glutathione and thioredoxin, have entered focus of interest. Anticancer metal complexes (platinum, gold, arsenic, ruthenium, rhodium, copper, vanadium, cobalt, manganese, gadolinium, and molybdenum) have been shown to strongly interact with or even disturb cellular redox homeostasis. In this context, especially the hypothesis of "activation by reduction" as well as the "hard and soft acids and bases" theory with respect to coordination of metal ions to cellular ligands represent important concepts to understand the molecular modes of action of anticancer metal drugs. The aim of this review is to highlight specific interactions of metal-based anticancer drugs with the cellular redox homeostasis and to explain this behavior by considering chemical properties of the respective anticancer metal complexes currently either in (pre)clinical development or in daily clinical routine in oncology.

Anticancer Activity of Metal Complexes: Involvement of Redox Processes

PubMed Central

Jungwirth, Ute; Kowol, Christian R.; Keppler, Bernhard K.; Hartinger, Christian G.; Berger, Walter; Heffeter, Petra

2012-01-01

Cells require tight regulation of the intracellular redox balance and consequently of reactive oxygen species for proper redox signaling and maintenance of metal (e.g., of iron and copper) homeostasis. In several diseases, including cancer, this balance is disturbed. Therefore, anticancer drugs targeting the redox systems, for example, glutathione and thioredoxin, have entered focus of interest. Anticancer metal complexes (platinum, gold, arsenic, ruthenium, rhodium, copper, vanadium, cobalt, manganese, gadolinium, and molybdenum) have been shown to strongly interact with or even disturb cellular redox homeostasis. In this context, especially the hypothesis of “activation by reduction” as well as the “hard and soft acids and bases” theory with respect to coordination of metal ions to cellular ligands represent important concepts to understand the molecular modes of action of anticancer metal drugs. The aim of this review is to highlight specific interactions of metal-based anticancer drugs with the cellular redox homeostasis and to explain this behavior by considering chemical properties of the respective anticancer metal complexes currently either in (pre)clinical development or in daily clinical routine in oncology. PMID:21275772

Redox reactions with empirical potentials: atomistic battery discharge simulations.

PubMed

Dapp, Wolf B; Müser, Martin H

2013-08-14

Batteries are pivotal components in overcoming some of today's greatest technological challenges. Yet to date there is no self-consistent atomistic description of a complete battery. We take first steps toward modeling of a battery as a whole microscopically. Our focus lies on phenomena occurring at the electrode-electrolyte interface which are not easily studied with other methods. We use the redox split-charge equilibration (redoxSQE) method that assigns a discrete ionization state to each atom. Along with exchanging partial charges across bonds, atoms can swap integer charges. With redoxSQE we study the discharge behavior of a nano-battery, and demonstrate that this reproduces the generic properties of a macroscopic battery qualitatively. Examples are the dependence of the battery's capacity on temperature and discharge rate, as well as performance degradation upon recharge.

Spectroscopic insights into the oxygen-tolerant membrane-associated [NiFe] hydrogenase of Ralstonia eutropha H16.

PubMed

Saggu, Miguel; Zebger, Ingo; Ludwig, Marcus; Lenz, Oliver; Friedrich, Bärbel; Hildebrandt, Peter; Lendzian, Friedhelm

2009-06-12

This study provides the first spectroscopic characterization of the membrane-bound oxygen-tolerant [NiFe] hydrogenase (MBH) from Ralstonia eutropha H16 in its natural environment, the cytoplasmic membrane. The H2-converting MBH is composed of a large subunit, harboring the [NiFe] active site, and a small subunit, capable in coordinating one [3Fe4S] and two [4Fe4S] clusters. The hydrogenase dimer is electronically connected to a membrane-integral cytochrome b. EPR and Fourier transform infrared spectroscopy revealed a strong similarity of the MBH active site with known [NiFe] centers from strictly anaerobic hydrogenases. Most redox states characteristic for anaerobic [NiFe] hydrogenases were identified except for one remarkable difference. The formation of the oxygen-inhibited Niu-A state was never observed. Furthermore, EPR data showed the presence of an additional paramagnetic center at high redox potential (+290 mV), which couples magnetically to the [3Fe4S] center and indicates a structural and/or redox modification at or near the proximal [4Fe4S] cluster. Additionally, significant differences regarding the magnetic coupling between the Nia-C state and [4Fe4S] clusters were observed in the reduced form of the MBH. The spectroscopic properties are discussed with regard to the unusual oxygen tolerance of this hydrogenase and in comparison with those of the solubilized, dimeric form of the MBH.

The endogenous adrenodoxin reductase-like flavoprotein arh1 supports heterologous cytochrome P450-dependent substrate conversions in Schizosaccharomyces pombe.

PubMed

Ewen, Kerstin M; Schiffler, Burkhard; Uhlmann-Schiffler, Heike; Bernhardt, Rita; Hannemann, Frank

2008-05-01

Mitochondrial cytochromes P450 are essential for biosynthesis of steroid hormones, vitamin D and bile acids. In mammals, the electrons needed for these reactions are provided via adrenodoxin and adrenodoxin reductase (AdR). Recently, Schizosaccharomyces pombe was introduced as a new host for the functional expression of human mitochondrial steroid hydroxylases without the coexpression of their natural redox partners. This fact qualifies S. pombe for the biotechnological production of steroids and for application as inhibitor test organism of heterologously expressed cytochromes P450. In this paper, we present evidence that the S. pombe ferredoxin reductase, arh1, and ferredoxin, etp1fd provide mammalian class I cytochromes P450 with reduction equivalents. The recombinant reductase showed an unusual weak binding of flavin adenine dinucleotide (FAD), which was mastered by modifying the FAD-binding region by site-directed mutagenesis yielding a stable holoprotein. The modified reductase arh1_A18G displayed spectroscopic characteristics similar to AdR and was shown to be capable of accepting electrons with no evident preference for NADH or NADPH, respectively. Arh1_A18G can substitute for AdR by interacting not only with its natural redox partner etp1fd but also with the mammalian homolog adrenodoxin. Cytochrome P450-dependent substrate conversion with all combinations of the mammalian and yeast redox proteins was evaluated in a reconstituted system.

Evaluation and optimization of mass transport of redox species in silicon microwire-array photoelectrodes

PubMed Central

Xiang, Chengxiang; Meng, Andrew C.; Lewis, Nathan S.

2012-01-01

Physical integration of a Ag electrical contact internally into a metal/substrate/microstructured Si wire array/oxide/Ag/electrolyte photoelectrochemical solar cell has produced structures that display relatively low ohmic resistance losses, as well as highly efficient mass transport of redox species in the absence of forced convection. Even with front-side illumination, such wire-array based photoelectrochemical solar cells do not require a transparent conducting oxide top contact. In contact with a test electrolyte that contained 50 mM/5.0 mM of the cobaltocenium+/0 redox species in CH3CN–1.0 M LiClO4, when the counterelectrode was placed in the solution and separated from the photoelectrode, mass transport restrictions of redox species in the internal volume of the Si wire array photoelectrode produced low fill factors and limited the obtainable current densities to 17.6 mA cm-2 even under high illumination. In contrast, when the physically integrated internal Ag film served as the counter electrode, the redox couple species were regenerated inside the internal volume of the photoelectrode, especially in regions where depletion of the redox species due to mass transport limitations would have otherwise occurred. This behavior allowed the integrated assembly to operate as a two-terminal, stand-alone, photoelectrochemical solar cell. The current density vs. voltage behavior of the integrated photoelectrochemical solar cell produced short-circuit current densities in excess of 80 mA cm-2 at high light intensities, and resulted in relatively low losses due to concentration overpotentials at 1 Sun illumination. The integrated wire array-based device architecture also provides design guidance for tandem photoelectrochemical cells for solar-driven water splitting. PMID:22904185

Swiss roll nanomembranes with controlled proton diffusion as redox micro-supercapacitors.

PubMed

Ji, Hengxing; Mei, Yongfeng; Schmidt, Oliver G

2010-06-14

We demonstrate a redox Swiss roll micro-supercapacitor by rolling up a multilayered nanomembrane with an electrochemical active layer at either the outer or inner surface for different proton diffusion behaviors. The Swiss roll micro-supercapacitor could achieve high performance (e.g. capacity and life time) in a microscale power source and is helpful for studying charge transfer at the electrolyte/electrode interface.

Actively targeted delivery of anticancer drug to tumor cells by redox-responsive star-shaped micelles.

PubMed

Shi, Chunli; Guo, Xing; Qu, Qianqian; Tang, Zhaomin; Wang, Yi; Zhou, Shaobing

2014-10-01

In cancer therapy nanocargos based on star-shaped polymer exhibit unique features such as better stability, smaller size distribution and higher drug capacity in comparison to linear polymeric micelles. In this study, we developed a multifunctional star-shaped micellar system by combination of active targeting ability and redox-responsive behavior. The star-shaped micelles with good stability were self-assembled from four-arm poly(ε-caprolactone)-poly(ethylene glycol) copolymer. The redox-responsive behaviors of these micelles triggered by glutathione were evaluated from the changes of micellar size, morphology and molecular weight. In vitro drug release profiles exhibited that in a stimulated normal physiological environment, the redox-responsive star-shaped micelles could maintain good stability, whereas in a reducing and acid environment similar with that of tumor cells, the encapsulated agent was promptly released. In vitro cellular uptake and subcellular localization of these micelles were further studied with confocal laser scanning microscopy and flow cytometry against the human cervical cancer cell line HeLa. In vivo and ex vivo DOX fluorescence imaging displayed that these FA-functionalized star-shaped micelles possessed much better specificity to target solid tumor. Both the qualitative and quantitative results of the antitumor effect in 4T1 tumor-bearing BALB/c mice demonstrated that these redox-responsive star-shaped micelles have a high therapeutic efficiency to artificial solid tumor. Therefore, the multifunctional star-shaped micelles are a potential platform for targeted anticancer drug delivery. Copyright © 2014 Elsevier Ltd. All rights reserved.

Redox regulation of protein tyrosine phosphatase 1B (PTP1B): Importance of steric and electronic effects on the unusual cyclization of the sulfenic acid intermediate to a sulfenyl amide

NASA Astrophysics Data System (ADS)

Sarma, Bani Kanta

2013-09-01

The redox regulation of protein tyrosine phosphatase 1B (PTP1B) via the unusual transformation of its sulfenic acid (PTP1B-SOH) to a cyclic sulfenyl amide intermediate is studied by using small molecule chemical models. These studies suggest that the sulfenic acids derived from the H2O2-mediated reactions o-amido thiophenols do not efficiently cyclize to sulfenyl amides and the sulfenic acids produced in situ can be trapped by using methyl iodide. Theoretical calculations suggest that the most stable conformer of such sulfenic acids are stabilized by nO → σ*S-OH orbital interactions, which force the -OH group to adopt a position trans to the S⋯O interaction, leading to an almost linear arrangement of the O⋯S-O moiety and this may be the reason for the slow cyclization of such sulfenic acids to their corresponding sulfenyl amides. On the other hand, additional substituents at the 6-position of o-amido phenylsulfenic acids that can induce steric environment and alter the electronic properties around the sulfenic acid moiety by S⋯N or S⋯O nonbonded interactions destabilize the sulfenic acids by inducing strain in the molecule. This may lead to efficient the cyclization of such sulfenic acids. This model study suggests that the amino acid residues in the close proximity of the sulfenic acid moiety in PTP1B may play an important role in the cyclization of PTP1B-SOH to produce the corresponding sulfenyl amide.

The mechanism of formation, structure and physiological relevance of covalent hemoglobin attachment to the erythrocyte membrane.

PubMed

Welbourn, Elizabeth M; Wilson, Michael T; Yusof, Ashril; Metodiev, Metodi V; Cooper, Chris E

2017-02-01

Covalent hemoglobin binding to membranes leads to band 3 (AE1) clustering and the removal of erythrocytes from the circulation; it is also implicated in blood storage lesions. Damaged hemoglobin, with the heme being in a redox and oxygen-binding inactive hemichrome form, has been implicated as the binding species. However, previous studies used strong non-physiological oxidants. In vivo hemoglobin is constantly being oxidised to methemoglobin (ferric), with around 1% of hemoglobin being in this form at any one time. In this study we tested the ability of the natural oxidised form of hemoglobin (methemoglobin) in the presence or absence of the physiological oxidant hydrogen peroxide to initiate membrane binding. The higher the oxidation state of hemoglobin (from Fe(III) to Fe(V)) the more binding was observed, with approximately 50% of this binding requiring reactive sulphydryl groups. The hemoglobin bound was in a high molecular weight complex containing spectrin, ankyrin and band 4.2, which are common to one of the cytoskeletal nodes. Unusually, we showed that hemoglobin bound in this way was redox active and capable of ligand binding. It can initiate lipid peroxidation showing the potential to cause cell damage. In vivo oxidative stress studies using extreme endurance exercise challenges showed an increase in hemoglobin membrane binding, especially in older cells with lower levels of antioxidant enzymes. These are then targeted for destruction. We propose a model where mild oxidative stress initiates the binding of redox active hemoglobin to the membrane. The maximum lifetime of the erythrocyte is thus governed by the redox activity of the cell; from the moment of its release into the circulation the timer is set. Copyright © 2016. Published by Elsevier Inc.

Multiple Redox Modes in the Reversible Lithiation of High-Capacity, Peierls-Distorted Vanadium Sulfide

DOE PAGES

Britto, Sylvia; Leskes, Michal; Hua, Xiao; ...

2015-06-08

Vanadium sulfide VS 4 in the patronite mineral structure, is a linear chain compound comprising vanadium atoms coordinated by disulfide anions [S 2] 2–. 51V NMR shows that the material, despite having V formally in the d 1 configuration, is diamagnetic, suggesting potential dimerization through metal-metal bonding associated with a Peierls distortion of the linear chains. This is supported by density functional calculations, and is also consistent with the observed alternation in V-V distances of 2.8 Å and 3.2 Å along the chains. Partial lithiation results in reduction of the disulfide ions to sulfide S 2–, including via an internalmore » redox process whereby an electron from V 4+ is transferred to [S 2] 2– resulting in oxidation of V 4+ to V 5+ and reduction of the [S 2] 2– to S 2- to form Li 3VS 4 containing tetrahedral [VS 4] 3– anions. On further lithiation this is followed by reduction of the V 5+ in Li 3VS 4 to form Li 3+xVS 4 (x=0.5-1), a mixed valent V 4+/V 5+ compound. Eventually reduction to Li 2S plus elemental V occurs. Despite the complex redox processes involving both the cation and the anion occurring in this material, the system is found to be partially reversible between 0 and 3 V. In conclusion, the unusual redox processes in this system are elucidated using a suite of short range characterization tools including 51V Nuclear Magnetic Resonance spectroscopy (NMR), S Kedge X-ray Absorption Near Edge Spectroscopy (XANES) and Pair Distribution Function (PDF) Analysis of X-ray data.« less

Atypical profiles and modulations of heme-enzymes catalyzed outcomes by low amounts of diverse additives suggest diffusible radicals' obligatory involvement in such redox reactions.

PubMed

Manoj, Kelath Murali; Parashar, Abhinav; Venkatachalam, Avanthika; Goyal, Sahil; Satyalipsu; Singh, Preeti Gunjan; Gade, Sudeep K; Periyasami, Kalaiselvi; Jacob, Reeba Susan; Sardar, Debosmita; Singh, Shanikant; Kumar, Rajan; Gideon, Daniel A

2016-06-01

Peroxidations mediated by heme-enzymes have been traditionally studied under a single-site (heme distal pocket), non-sequential (ping-pong), two-substrates binding scheme of Michaelis-Menten paradigm. We had reported unusual modulations of peroxidase and P450 reaction outcomes and explained it invoking diffusible reactive species [Manoj, 2006; Manoj et al., 2010; Andrew et al., 2011, Parashar et al., 2014 & Venkatachalam et al., 2016]. A systematic investigation of specific product formation rates was undertaken to probe the hypothesis that involvement of diffusible reactive species could explain undefined substrate specificities and maverick modulations (sponsored by additives) of heme-enzymes. When the rate of specific product formation was studied as a function of reactants' concentration or environmental conditions, we noted marked deviations from normal profiles. We report that heme-enzyme mediated peroxidations of various substrates are inhibited (or activated) by sub-equivalent concentrations of diverse redox-active additives and this is owing to multiple redox equilibriums in the milieu. At low enzyme and peroxide concentrations, the enzyme is seen to recycle via a one-electron (oxidase) cycle, which does not require the substrate to access the heme centre. Schemes are provided that explain the complex mechanistic cycle, kinetics & stoichiometry. It is not obligatory for an inhibitor or substrate to interact with the heme centre for influencing overall catalysis. Roles of diffusible reactive species explain catalytic outcomes at low enzyme and reactant concentrations. The current work highlights the scope/importance of redox enzyme reactions that could occur "out of the active site" in biological or in situ systems. Copyright © 2016 Elsevier B.V. and Société française de biochimie et biologie Moléculaire (SFBBM). All rights reserved.

Reduction of CO2 using a Rhenium Bipyridine Complex Containing Ancillary BODIPY Redox Reservoirs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Teesdale, Justin; Pistner, Allen; Yapp, Glenn P. A.

2014-01-01

The reduction of carbon dioxide to chemical fuels such as carbon monoxide is an important challenge in the field of renewable energy conversion. Given the thermodynamic stability of carbon dioxide, it is difficult to efficiently activate this substrate in a selective fashion and the development of new electrocatalysts for CO2 reduction is of prime importance. To this end, we have prepared and studied a new fac-ReI(CO)3 complex supported by a bipyridine ligand containing ancillary BODIPY moieties ([Re(BB2)(CO)3Cl]). Voltammetry experiments revealed that this system displays a rich redox chemistry under N2, as [Re(BB2)(CO)3Cl] can be reduced by up to four electronsmore » at modest potentials. These redox events have been characterized as the ReI/0 couple, and three ligand based reductions two of which are localized on the BODIPY units. The ability of the BB2 ligand to serve as a noninnocent redox reservoir is manifest in an enhanced electrocatalysis with CO2 as compared to an unsubstituted Re-bipyridine complex lacking BODIPY units ([Re(bpy)(CO)3Cl]). The second order rate constant for reduction of CO2 by [Re(BB2)(CO)3Cl] was measured to be k = 3400 M 1s 1 at an applied potential of 2.0 V versus SCE, which is roughly three times greater than the corresponding unsubstituted Re-bipyridine homologue. Photophysical and photochemical studies were also carried out to determine if [Re(BB2)(CO)3Cl] was a competent platform for CO2 reduction using visible light. These experiments showed that this complex supports unusual excited state dynamics that are not typically observed for fac- ReI(CO)3 complexes.« less

TEMPO/viologen electrochemical heterojunction for diffusion-controlled redox mediation: a highly rectifying bilayer-sandwiched device based on cross-reaction at the interface between dissimilar redox polymers.

PubMed

Tokue, Hiroshi; Oyaizu, Kenichi; Sukegawa, Takashi; Nishide, Hiroyuki

2014-03-26

A couple of totally reversible redox-active molecules, which are different in redox potentials, 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) and viologen (V(2+)), were employed to give rise to a rectified redox conduction effect. Single-layer and bilayer devices were fabricated using polymers containing these sites as pendant groups per repeating unit. The devices were obtained by sandwiching the redox polymer layer(s) with indium tin oxide (ITO)/glass and Pt foil electrodes. Electrochemical measurements of the single-layer device composed of polynorbornene-bearing TEMPO (PTNB) exhibited a diffusion-limited current-voltage response based on the TEMPO(+)/TEMPO exchange reaction, which was almost equivalent to a redox gradient through the PTNB layer depending upon the thickness. The bilayer device gave rise to the current rectification because of the thermodynamically favored cross-reaction between TEMPO(+) and V(+) at the polymer/polymer interface. A current-voltage response obtained for the bilayer device demonstrated a two-step diffusion-limited current behavior as a result of the concurrent V(2+)/V(+) and V(+)/V(0) exchange reactions according to the voltage and suggested that the charge transport process through the device was most likely to be rate-determined by a redox gradient in the polymer layer. Current collection experiments revealed a charge transport balance throughout the device, as a result of the electrochemical stability and robustness of the polymers in both redox states.

The effects of lipoic acid on redox status in brain regions and systemic circulation in streptozotocin-induced sporadic Alzheimer's disease model.

PubMed

Erdoğan, Mehmet Evren; Aydın, Seval; Yanar, Karolin; Mengi, Murat; Kansu, Ahmet Doğukan; Cebe, Tamer; Belce, Ahmet; Çelikten, Mert; Çakatay, Ufuk

2017-08-01

While the deterioration of insulin-glucose metabolism (IGM), impaired redox homeostasis (IRH), β-amyloid accumulation was reported in Sporadic Alzheimer's Disease (SAD) model, aforementioned factors related to lipoic acid administration and anthropometric indexes (AIs) are not yet studied with integrative approach. β-amyloid accumulation, redox homeostasis biomarkers and AIs are investigated in SAD model. Streptozotocin-induced inhibition of insulin-signaling cascade but not GLUT-2 and GLUT-3 transporters takes a role in β-amyloid accumulation. Inhibition types are related to IRH in cortex, hippocampus and systemic circulation. Lipoic acid (LA) shows both antioxidant and prooxidant effect according to the anatomical location. LA administration also leads to improved AIs during GLUT-2 inhibition and cortical redox status in GLUT-3 inhibited group. Optimal LA action could be possible if its redox behavior is balanced to antioxidant effect. Diagnostic usage of systemic IRH parameters as biomarkers and their possible correlations with deteriorated IGM should be investigated. Graphical abstract ᅟ.

Vanadium Electrolyte Studies for the Vanadium Redox Battery-A Review.

PubMed

Skyllas-Kazacos, Maria; Cao, Liuyue; Kazacos, Michael; Kausar, Nadeem; Mousa, Asem

2016-07-07

The electrolyte is one of the most important components of the vanadium redox flow battery and its properties will affect cell performance and behavior in addition to the overall battery cost. Vanadium exists in several oxidation states with significantly different half-cell potentials that can produce practical cell voltages. It is thus possible to use the same element in both half-cells and thereby eliminate problems of cross-contamination inherent in all other flow battery chemistries. Electrolyte properties vary with supporting electrolyte composition, state-of-charge, and temperature and this will impact on the characteristics, behavior, and performance of the vanadium battery in practical applications. This Review provides a broad overview of the physical properties and characteristics of the vanadium battery electrolyte under different conditions, together with a description of some of the processing methods that have been developed to produce vanadium electrolytes for vanadium redox flow battery applications. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Redox properties of samarium, europium and ytterbium in molten eutectic mixture of sodium, potassium and cesium chlorides

NASA Astrophysics Data System (ADS)

Golovanova, O. A.; Tropin, O. A.; Volkovich, V. A.

2017-09-01

The redox behavior of samarium, europium and ytterbium ions was investigated in the ternary 6NaCl-9KCl- 5CsCl eutectic based melts between 823 and 1073 K employing cyclic voltammetry on a tungsten working electrode. Ln(II)/Ln(III) (Ln=Sm, Eu, Yb) reduction-oxidation is reversible and controlled by diffusion of the electroactive species at the potential scan rates up to 0.1 V/s. Formal standard redox potentials E*Ln(II)/Ln(III) were determined, and the thermodynamic and transport properties of the corresponding Ln(III) and Ln(II) ions were estimated.

Unusual behavior in the parental care of a house wren (Troglodytes aedon): Post fledging use of an old nest during cold nights

USGS Publications Warehouse

Scholer, Micah N.

2015-01-01

I report on the unusual behavior of an adult House Wren (Troglodytes aedon) leading recently fledged young back to the nest for two consecutive nights. The ambient temperature reached below 0°C during both nights. Despite disadvantages associated with remaining in the nest, this observation suggests that adult birds may assess trade-offs between perceived risks versus the benefits of engaging in other activities, in this case roosting communally for thermoregulation.

Redox-active antibiotics control gene expression and community behavior in divergent bacteria.

PubMed

Dietrich, Lars E P; Teal, Tracy K; Price-Whelan, Alexa; Newman, Dianne K

2008-08-29

It is thought that bacteria excrete redox-active pigments as antibiotics to inhibit competitors. In Pseudomonas aeruginosa, the endogenous antibiotic pyocyanin activates SoxR, a transcription factor conserved in Proteo- and Actinobacteria. In Escherichia coli, SoxR regulates the superoxide stress response. Bioinformatic analysis coupled with gene expression studies in P. aeruginosa and Streptomyces coelicolor revealed that the majority of SoxR regulons in bacteria lack the genes required for stress responses, despite the fact that many of these organisms still produce redox-active small molecules, which indicates that redox-active pigments play a role independent of oxidative stress. These compounds had profound effects on the structural organization of colony biofilms in both P. aeruginosa and S. coelicolor, which shows that "secondary metabolites" play important conserved roles in gene expression and development.

Analysis of minerals containing dissolved traces of the fluid phase components water and carbon dioxide

NASA Technical Reports Server (NTRS)

Freund, Friedemann

1991-01-01

Substantial progress has been made towards a better understanding of the dissolution of common gas/fluid phase components, notably H2O and CO2, in minerals. It has been shown that the dissolution mechanisms are significantly more complex than currently believed. By judiciously combining various solid state analytical techniques, convincing evidence was obtained that traces of dissolved gas/fluid phase components undergo, at least in part, a redox conversion by which they split into reduced H2 and and reduced C on one hand and oxidized oxygen, O(-), on the other. Analysis for 2 and C as well as for any organic molecules which may form during the process of co-segregation are still impeded by the omnipresent danger of extraneous contamination. However, the presence of O(-), an unusual oxidized form of oxygen, has been proven beyond a reasonable doubt. The presence of O(-) testifies to the fact that a redox reaction must have taken place in the solid state involving the dissolved traces of gas/fluid phase components. Detailed information on the techniques used and the results obtained are given.

Dual overcharge protection and solid electrolyte interphase-improving action in Li-ion cells containing a bis-annulated dialkoxyarene electrolyte additive

NASA Astrophysics Data System (ADS)

Zhang, Jingjing; Shkrob, Ilya A.; Assary, Rajeev S.; Zhang, Shuo; Hu, Bin; Liao, Chen; Zhang, Zhengcheng; Zhang, Lu

2018-02-01

1,4-Dialkoxybenzene additives are commonly used as redox active shuttles in lithium-ion batteries in order to prevent runaway oxidation of electrolyte when overcharge conditions set in. During this action the shuttle molecule goes through a futile cycle, becoming oxidized at the cathode and reduced at the anode. Minimizing parasitic reactions in all states of charge is paramount for sustained protective action. Here we demonstrate that recently developed bis-annulated 9,10-bis(2-methoxyethoxy)-1,2,3,4,5,6,7,8-octahydro-1,4:5,8-dimethano-anthracene shuttle molecule (that yields exceptionally stable radical cations) survives over 120 cycles of overcharge abuse with 100% overcharge ratio at C/5 rate. Equally remarkably, in the presence of this additive the cell impedance becomes significantly lower compared to the control cells without the additive; this decrease is observed during the formation, normal cycling, and even under overcharge conditions. This unusual dual action has not been observed in other redox shuttle systems, and it presents considerable practical interest.

Optoelectronic tuning of organoborylazadipyrromethenes via effective electronegativity at the metalloid center.

PubMed

Berhe, Seare A; Rodriguez, Marco T; Park, Eunsol; Nesterov, Vladimir N; Pan, Hongjun; Youngblood, W Justin

2014-03-03

Organoborylazadipyrromethenes were synthesized from free base and fluoroborylazadipyrromethenes and characterized with regard to their structural and electronic properties. B-N bond lengths, along with photophysical and redox behavior, appear dependent on the effective electronegativity at the boron atom as tuned by its substituents, with stronger electronegativity correlating to a shorter B-N bond length, red-shifted absorbance, enhanced fluorescence lifetime and yield, and positively shifted redox potentials.

3D-printed conductive static mixers enable all-vanadium redox flow battery using slurry electrodes

NASA Astrophysics Data System (ADS)

Percin, Korcan; Rommerskirchen, Alexandra; Sengpiel, Robert; Gendel, Youri; Wessling, Matthias

2018-03-01

State-of-the-art all-vanadium redox flow batteries employ porous carbonaceous materials as electrodes. The battery cells possess non-scalable fixed electrodes inserted into a cell stack. In contrast, a conductive particle network dispersed in the electrolyte, known as slurry electrode, may be beneficial for a scalable redox flow battery. In this work, slurry electrodes are successfully introduced to an all-vanadium redox flow battery. Activated carbon and graphite powder particles are dispersed up to 20 wt% in the vanadium electrolyte and charge-discharge behavior is inspected via polarization studies. Graphite powder slurry is superior over activated carbon with a polarization behavior closer to the standard graphite felt electrodes. 3D-printed conductive static mixers introduced to the slurry channel improve the charge transfer via intensified slurry mixing and increased surface area. Consequently, a significant increase in the coulombic efficiency up to 95% and energy efficiency up to 65% is obtained. Our results show that slurry electrodes supported by conductive static mixers can be competitive to state-of-the-art electrodes yielding an additional degree of freedom in battery design. Research into carbon properties (particle size, internal surface area, pore size distribution) tailored to the electrolyte system and optimization of the mixer geometry may yield even better battery properties.

Synthesis and CV Studies of Dithiol-terminated Metal Terpyridine Complexes

NASA Technical Reports Server (NTRS)

Asano, Sylvia; Fan, Wendy; Ng, Hou-Tee; Han, Jie; Meyyappan, M.

2003-01-01

Transition metal coordination complexes possess unique electronic structures that should be a good model for studying electronic transport behavior at a molecular level. The discrete, multiple redox states, low redox potential and the superb ability to establish contact with other molecular and electronic components by coordination chemistry have made this a subject of investigation for their possible application as active electronic components in molecular devices. We present the synthesis and electrochemical characterization of 4'-thioacetylphenyl-2'2:6',2"-terpyridine iron(II) complex and compare it with a model bis-terpyridine iron(II) complex by cyclic voltammetry. With the use of different working electrodes, the behavior of these complexes show different electron transfer rates.

Hourly and daily variation of sediment redox potential in tidal wetland sediments

USGS Publications Warehouse

Catallo, W. James

1999-01-01

Variation of electrochemical oxidation-reduction (redox) potential was examined in surface salt march sediments under conditions of flooding and tidal simulation in mesocosms and field sites. Time series were generated of redox potential measured in sediment profiles at 2-10 cm depth using combination Pt-Ag/AgCl (ORP) electrodes. Redox potential data were acquired at rapid rates (1-55 samples/h) over extended periods (3-104 days) along with similar times series of temperature (water, air, soil) and pH. It was found that redox potential vaired as a result of water level changes and was unrelated to diurnal changes in temperature or pH, the latter of which changed by 370 mV redox potential decrease in under 48 hours). Attenuatoin of microbial activity by [gamma] y-radiation and toxic chemicals elimintated this response. In tidal salt marsh mesocosms where the sediment-plant assemblages were exposed to a simulated diurnal tide, redox potenial oscillations of 40-300 mV amplitude were recoded that has the same periodicity as the flood-drain cycle. Periodic redoc potential time series were observed repeatedly in sediments receiving tidal pulsing but not in those sediments exposed to static hydrological conditions. Data collected over 12 days from a coastal marsh site experiencing diurnal tides showed similar fluctuations in redox potential. Data from the experimentents indicated that (a) redox potential can be a dynamic, nonlinear variable in coastal and estuarine wetland sediments over hourly and daily scales, and the designs of biogeochemical experiments should reflect this, (b) redox potential can change rapidly and signigicantly in coastal wetland sediments in response of flooding and draining, (c) microbial community processes are primarily determinants of the time course of redox potential in wetland sediments, and elimination of inhibition of microbial activity (e.g. by pollutants) can significantly alter that behavior, and (d) fast redox potential dynamics appear to be characteristic of sediments that experience changes in hydrology. The rapid redox potential changes observed in these systems indicated dynamic metabolic and biogeochemical conditions in the field, and confirmed that hourly and daily redox potential variations should be resolved in studies of sediment functioning.

Theoretical estimation of equilibrium sulfur isotope fractionations among aqueous sulfite species: Implications for isotope models of microbial sulfate reduction

NASA Astrophysics Data System (ADS)

Eldridge, D. L.; Farquhar, J.; Guo, W.

2015-12-01

Sulfite (sensu lato), an intermediate in a variety sulfur redox processes, plays a particularly important role in microbial sulfate reduction. It exists intracellularly as multiple species between sets of enzymatic reactions that transform sulfate to sulfide, with the exact speciation depending on pH, T, and ionic strength. However, the complex speciation of sulfite is ignored in current isotope partitioning models of microbial sulfate reduction and simplified solely to the pyramidal SO32- (sulfite sensu stricto), due to a lack of appropriate constraints. We theoretically estimated the equilibrium sulfur isotope fractionations (33S/32S, 34S/32S, 36S/32S) among all documented sulfite species in aqueous solution, including sulfite (SO32-), bisulfite isomers and dimers ((HS)O3-, (HO)SO2-, S2O52-), and SO2(aq), through first principles quantum mechanical calculations. The calculations were performed at B3LYP/6-31+G(d,p) level using cluster models with 30-40 water molecules surrounding the solute. Our calculated equilibrium fractionation factors compare well to the available experimental constraints and suggest that the minor and often-ignored tetrahedral (HS)O3- isomer of bisulfite strongly influences isotope partitioning behavior in the sulfite system under most environmentally relevant conditions, particularly fractionation magnitudes and unusual temperature dependence. For example, we predict that sulfur isotope fractionation between sulfite and bulk bisulfite in solution should have an apparent inverse temperature dependence due to the influence of (HS)O3- and its increased stability at higher temperatures. Our findings highlight the need to appropriately account for speciation/isomerization of sulfur species in sulfur isotope studies. We will also present similar calculation results of other aqueous sulfur compounds (e.g., H2S/HS-, SO42-, S2O32-, S3O62-, and poorly documented SO22- species), and discuss the implication of our results for microbial sulfate reduction models and other sulfur-redox processes in nature.

Impact of Backbone Tether Length and Structure on the Electrochemical Performance of Viologen Redox Active Polymers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burgess, Mark; Chénard, Etienne; Hernández-Burgos, Kenneth

The design of chemically stable and electrochemically reversible redox active polymers (RAPs) is of great interest for energy storage technologies. Particularly, RAPs are new players for flow batteries relying on a size-exclusion based mechanism of electrolyte separation, but few studies have provided detailed molecular understanding of redox polymers in solution. Here, we use a systematic molecular design approach to investigate the impact of linker and redox-pendant electronic interactions on the performance of viologen RAPs. We used scanning electrochemical microscopy, cyclic voltammetry, bulk electrolysis, temperature-dependent absorbance, and spectroelectrochemistry to study the redox properties, charge transfer kinetics, and self-exchange of electrons throughmore » redox active dimers and their equivalent polymers. Stark contrast was observed between the electrochemical properties of viologen dimers and their corresponding polymers. Electron self-exchange kinetics in redox active dimers that only differ by their tether length and rigidity influences their charge transfer properties. Predictions from the Marcus Hush theory were consistent with observations in redox active dimers, but they failed to fully capture the behavior of macromolecular systems. For example, polymer bound viologen pendants, if too close in proximity, do not retain chemical reversibility. In contrast to polymer films, small modifications to the backbone structure decisively impact the bulk electrolysis of polymer solutions. This first comprehensive study highlights the careful balance between electronic interactions and backbone rigidity required to design RAPs with superior electrochemical performance.« less

Ropinirole

MedlinePlus

... people who took medications such as ropinirole developed gambling problems or other intense urges or behaviors that ... even if you do not realize that your gambling or any other intense urges or unusual behaviors ...

Amantadine

MedlinePlus

... medications used to treat Parkinson's disease, have developed gambling problems or had other intense urges or behaviors ... even if you do not realize that your gambling or any other intense urges or unusual behaviors ...

Safinamide

MedlinePlus

... people who took medications such as safinamide developed gambling problems or other intense urges or behaviors that ... even if you do not realize that your gambling or any other intense urges or unusual behaviors ...

Unusual Thermoelectric Behavior Indicating a Hopping to Bandlike Transport Transition in Pentacene

NASA Astrophysics Data System (ADS)

Germs, W. Chr.; Guo, K.; Janssen, R. A. J.; Kemerink, M.

2012-07-01

An unusual increase in the Seebeck coefficient with increasing charge carrier density is observed in pentacene thin film transistors. This behavior is interpreted as being due to a transition from hopping transport in static localized states to bandlike transport, occurring at temperatures below ˜250K. Such a transition can be expected for organic materials in which both static energetic disorder and dynamic positional disorder are important. While clearly visible in the temperature and density dependent Seebeck coefficient, the transition hardly shows up in the charge carrier mobility.

Injectable dual redox responsive diselenide-containing poly(ethylene glycol) hydrogel.

PubMed

Gong, Chu; Shan, Meng; Li, Bingqiang; Wu, Guolin

2017-09-01

An injectable dual redox responsive diselenide-containing poly(ethylene glycol) (PEG) hydrogel was successfully developed by combining the conceptions of injectable hydrogels and dual redox responsive diselenides. In the first step, four-armed PEG was modified with N-hydroxysuccinimide (NHS)-activated esters and thereafter, crosslinked by selenocystamine crosslinkers to form injectable hydrogels via the rapid reaction between NHS-activated esters and amino groups. The cross-sectional morphology, mechanical properties, and crosslinking modes of hydrogels were well characterized via scanning electron microscope (SEM), rheological measurements, and Fourier transform infrared spectra, respectively. In addition, the oxidation- and reduction-responsive degradation behaviors of hydrogels were observed and analyzed. The model drug, rhodamine B, was encapsulated in the hydrogel. The drug-loaded hydrogel exhibited a dual redox responsive release profile, which was consistent with the degradation experiments. The results of all experiments indicated that the formulated injectable dual redox responsive diselenide-containing PEG hydrogel can have potential applications in various biomedical fields such as drug delivery and stimuli-responsive drug release. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2451-2460, 2017. © 2017 Wiley Periodicals, Inc.

Effect of Iron Redox Equilibrium on the Foaming Behavior of MgO-Saturated Slags

NASA Astrophysics Data System (ADS)

Park, Youngjoo; Min, Dong Joon

2018-04-01

In this study, the foaming index of CaO-SiO2-FetO and CaO-SiO2-FetO-Al2O3 slags saturated with MgO was measured to understand the relationship between their foaming behavior and physical properties. The foaming index of MgO-saturated slags increases with the FetO content due to the redox equilibrium of FetO. Experimental results indicated that MgO-saturated slag has relatively high ferric ion concentration, and the foaming index increases due to the effect of ferric ion. Therefore, the foaming behavior of MgO-saturated slag is more reasonably explained by considering the effect of ferric ion on the estimation of slag properties such as viscosity, surface tension, and density. Specifically, the estimation of slag viscosity was additionally verified by NBO/T, and this is experimentally obtained through Raman spectroscopy.

Protein sequences and redox titrations indicate that the electron acceptors in reaction centers from heliobacteria are similar to Photosystem I

NASA Technical Reports Server (NTRS)

Trost, J. T.; Brune, D. C.; Blankenship, R. E.

1992-01-01

Photosynthetic reaction centers isolated from Heliobacillus mobilis exhibit a single major protein on SDS-PAGE of 47 000 Mr. Attempts to sequence the reaction center polypeptide indicated that the N-terminus is blocked. After enzymatic and chemical cleavage, four peptide fragments were sequenced from the Heliobacillus mobilis apoprotein. Only one of these sequences showed significant specific similarity to any of the protein and deduced protein sequences in the GenBank data base. This fragment is identical with 56% of the residues, including both cysteines, found in highly conserved region that is proposed to bind iron-sulfur center Fx in the Photosystem I reaction center peptide that is the psaB gene product. The similarity to the psaA gene product in this region is 48%. Redox titrations of laser-flash-induced photobleaching with millisecond decay kinetics on isolated reaction centers from Heliobacterium gestii indicate a midpoint potential of -414 mV with n = 2 titration behavior. In membranes, the behavior is intermediate between n = 1 and n = 2, and the apparent midpoint potential is -444 mV. This is compared to the behavior in Photosystem I, where the intermediate electron acceptor A1, thought to be a phylloquinone molecule, has been proposed to undergo a double reduction at low redox potentials in the presence of viologen redox mediators. These results strongly suggest that the acceptor side electron transfer system in reaction centers from heliobacteria is indeed analogous to that found in Photosystem I. The sequence similarities indicate that the divergence of the heliobacteria from the Photosystem I line occurred before the gene duplication and subsequent divergence that lead to the heterodimeric protein core of the Photosystem I reaction center.

Molecular interaction studies revealed the bifunctional behavior of triheme cytochrome PpcA from Geobacter sulfurreducens toward the redox active analog of humic substances

DOE PAGES

Dantas, Joana M.; Kokhan, Oleksandr; Pokkuluri, P. Raj; ...

2015-06-09

Humic substances (HS) constitute a significant fraction of natural organic matter in terrestrial and aquatic environments and can act as terminal electron acceptors in anaerobic microbial respiration. Geobacter sulfurreducens has a remarkable respiratory versatility and can utilize the HS analog anthraquinone-2,6-disulfonate (AQDS) as a terminal electron acceptor or its reduced form (AH 2QDS) as an electron donor. Previous studies set the triheme cytochrome PpcA as a key component for HS respiration in G. sulfurreducens, but the process is far from fully understood. In this work, NMR chemical shift perturbation measurements were used to map the interaction region between PpcA andmore » AH 2QDS, and to measure their binding affinity. The results showed that the AH 2QDS binds reversibly to the more solvent exposed edge of PpcA heme IV. The NMR and visible spectroscopies coupled to redox measurements were used to determine the thermodynamic parameters of the PpcA:quinol complex. The higher reduction potential of heme IV (- 127 mV) compared to that of AH 2QDS (- 184 mV) explains why the electron transfer is more favorable in the case of reduction of the cytochrome by the quinol. The clear evidence obtained for the formation of an electron transfer complex between AH 2QDS and PpcA, combined with the fact that the protein also formed a redox complex with AQDS, revealed for the first time the bifunctional behavior of PpcA toward an analog of the HS. In conclusion, such behavior might confer selective advantage to G. sulfurreducens, which can utilize the HS in any redox state available in the environment for its metabolic needs.« less

Reversible conversion of valence-tautomeric copper metal-organic frameworks dependent single-crystal-to-single-crystal oxidation/reduction: a redox-switchable catalyst for C-H bonds activation reaction.

PubMed

Huang, Chao; Wu, Jie; Song, Chuanjun; Ding, Ran; Qiao, Yan; Hou, Hongwei; Chang, Junbiao; Fan, Yaoting

2015-06-28

Upon single-crystal-to-single-crystal (SCSC) oxidation/reduction, reversible structural transformations take place between the anionic porous zeolite-like Cu(I) framework and a topologically equivalent neutral Cu(I)Cu(II) mixed-valent framework. The unique conversion behavior of the Cu(I) framework endowed it as a redox-switchable catalyst for the direct arylation of heterocycle C-H bonds.

Prolonged intensive dominance behavior between gray wolves, Canis lupus

USGS Publications Warehouse

Mech, L. David; Cluff, H. Dean

2010-01-01

Dominance is one of the most pervasive and important behaviors among wolves in a pack, yet its significance in free-ranging packs has been little studied. Insights into a behavior can often be gained by examining unusual examples of it. In the High Arctic near Eureka, Nunavut, Canada, we videotaped and described an unusually prolonged and intensive behavioral bout between an adult male Gray Wolf (Canis lupus) and a male member of his pack, thought to be a maturing son. With tail raised, the adult approached a male pack mate about 50 m from us and pinned and straddled this packmate repeatedly over 6.5 minutes, longer than we had ever seen in over 50 years of studying wolves. We interpreted this behavior as an extreme example of an adult wolf harassing a maturing offspring, perhaps in prelude to the offspring?s dispersal.

In vivo relationship between monoamine oxidase type B and alcohol dehydrogenase: effects of ethanol and phenylethylamine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aliyu, S.U.; Upahi, L.

The role of acute ethanol and phenylethylamine on the brain and platelet monoamine oxidase activities, hepatic cytosolic alcohol dehydrogenase, redox state and motor behavior were studied in male rats. Ethanol on its own decreased the redox couple ratio, as well as, alcohol dehydrogenase activity in the liver while at the same time it increased brain and platelet monoamine oxidase activity due to lower Km with no change in Vmax. The elevation in both brain and platelet MAO activity was associated with ethanol-induced hypomotility in the rats. Co-administration of phenylethylamine and ethanol to the animals, caused antagonism of the ethanol-induced effectsmore » described above. The effects of phenylethylamine alone, on the above mentioned biochemical and behavioral indices, are more complex. Phenylethylamine on its own, like ethanol, caused reduction of the cytosolic redox, ratio and elevation of monoamine oxidase activity in the brain and platelets. However, in contrast to ethanol, this monoamine produced hypermotility and activation of the hepatic cytosolic alcohol dehydrogenase activity in the animals.« less

Versatile Organic Chemistry on Vanadium-Based Multi-Electron Reservoirs.

PubMed

Nachtigall, Olaf; Spandl, Johann

2018-02-21

We report the synthesis, post-functionalization, and redox behavior of two organically functionalized aggregates, [V 6 O 7 (OMe) 9 {(OCH 2 ) 3 C-CH 2 N 3 }] and [V 6 O 7 (OMe) 9 {(OCH 2 ) 3 C-NH 2 }]. All twelve μ 2 -oxo groups on the edges of the Lindqvist-type {V 6 O 19 } core were replaced by alkoxo ligands. The absence of a negative charge and the closed organic shell make these neutral mixed-valence compounds very stable towards hydrolysis and well soluble in almost all common organic solvents. These are important advantages over classical POMs. By post-functionalization through copper(I)-catalyzed Huisgen cycloaddition or imine formation, various organic moieties could be introduced. Even a well-soluble trimer composed of three hexanuclear vanadium units connected through an aromatic triimino core was synthesized and studied. The diverse redox behavior, the versatile reactivity, the good stability, and the excellent solubility make our vanadium compounds highly interesting for applications as building blocks in macromolecular chemistry as well as redox labels in biochemistry. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electrochemical analysis in a liposome suspension using lapachol as a hydrophobic electro active species.

PubMed

Okumura, Noriko; Wakamatsu, Shiori; Uno, Bunji

2014-01-01

This study demonstrated that the electro-chemical analysis of hydrophobic quinones can be performed in liposome suspension systems. We prepared and analyzed liposome suspensions containing lapachol, which is a quinone-based anti-tumor activity compound. In this suspension system, a simple one redox couple of lapachol is observed. These results are quite different from those obtained in organic solvents. In addition, the pH dependence of redox behaviors of lapachol could be observed in multilamellar vesicle (MLV) suspension system. This MLV suspension system method may approximate the electrochemical behavior of hydrophobic compounds in aqueous conditions. A benefit of this liposome suspension system for electrochemical analysis is that it enables to observe water-insoluble compounds without using organic solvents.

Transient behavior of redox flow battery connected to circuit based on global phase structure

NASA Astrophysics Data System (ADS)

Mannari, Toko; Hikihara, Takashi

A Redox Flow Battery (RFB) is one of the promising energy storage systems in power grid. An RFB has many advantages such as a quick response, a large capacity, and a scalability. Due to these advantages, an RFB can operate in mixed time scale. Actually, it has been demonstrated that an RFB can be used for load leveling, compensating sag, and smoothing the output of the renewable sources. An analysis on transient behaviors of an RFB is a key issue for these applications. An RFB is governed by electrical, chemical, and fluid dynamics. The hybrid structure makes the analysis difficult. To analyze transient behaviors of an RFB, the exact model is necessary. In this paper, we focus on a change in a concentration of ions in the electrolyte, and simulate the change with a model which is mainly based on chemical kinetics. The simulation results introduces transient behaviors of an RFB in a response to a load variation. There are found three kinds of typical transient behaviors including oscillations. As results, it is clarified that the complex transient behaviors, due to slow and fast dynamics in the system, arise by the quick response to load.

Critical rate of electrolyte circulation for preventing zinc dendrite formation in a zinc-bromine redox flow battery

NASA Astrophysics Data System (ADS)

Yang, Hyeon Sun; Park, Jong Ho; Ra, Ho Won; Jin, Chang-Soo; Yang, Jung Hoon

2016-09-01

In a zinc-bromine redox flow battery, a nonaqueous and dense polybromide phase formed because of bromide oxidation in the positive electrolyte during charging. This formation led to complicated two-phase flow on the electrode surface. The polybromide and aqueous phases led to different kinetics of the Br/Br- redox reaction; poor mixing of the two phases caused uneven redox kinetics on the electrode surface. As the Br/Br- redox reaction was coupled with the zinc deposition reaction, the uneven redox reaction on the positive electrode was accompanied by nonuniform zinc deposition and zinc dendrite formation, which degraded battery stability. A single-flow cell was operated at varying electrolyte circulation rates and current densities. Zinc dendrite formation was observed after cell disassembly following charge-discharge testing. In addition, the flow behavior in the positive compartment was observed by using a transparent version of the cell. At low rate of electrolyte circulation, the polybromide phase clearly separated from the aqueous phase and accumulated at the bottom of the flow frame. In the corresponding area on the negative electrode, a large amount of zinc dendrites was observed after charge-discharge testing. Therefore, a minimum circulation rate should be considered to avoid poor mixing of the positive electrolyte.

10 CFR 712.17 - Instructional requirements.

Code of Federal Regulations, 2010 CFR

2010-01-01

... responding to behavioral change and aberrant or unusual behavior that may result in a risk to national... supervisors and managers responsible for HRP positions with the knowledge described in paragraph (b)(1) of...

Unusual Electrical Transport Driven by the Competition between Antiferromagnetism and Ferromagnetism in Antiperovskite Mn3Zn1−xCoxN

PubMed Central

Chu, Lihua; Wang, Cong; Guo, Yanjiao; Liu, Zhuohai

2018-01-01

The magnetic, electrical transport and thermal expansion properties of Mn3Zn1−xCoxN (x = 0.2, 0.4, 0.5, 0.7, 0.9) have been systematically investigated. Co-doping in Mn3ZnN complicates the magnetic interactions, leading to a competition between antiferromagnetism and ferromagnetism. Abrupt resistivity jump phenomenon and negative thermal expansion behavior, both associated with the complex magnetic transition, are revealed in all studied cases. Furthermore, semiconductor-like transport behavior is found in sample x = 0.7, distinct from the metallic behavior in other samples. Below 50 K, resistivity minimum is observed in samples x = 0.4, 0.7, and 0.9, mainly caused by e-e scattering mechanism. We finally discussed the strong correlation among unusual electrical transport, negative thermal expansion and magnetic transition in Mn3Zn1−xCoxN, which allows us to conclude that the observed unusual electrical transport properties are attributed to the shift of the Fermi energy surface entailed by the abrupt lattice contraction. PMID:29439522

Study of uranium oxidation states in geological material.

PubMed

Pidchenko, I; Salminen-Paatero, S; Rothe, J; Suksi, J

2013-10-01

A wet chemical method to determine uranium (U) oxidation states in geological material has been developed and tested. The problem faced in oxidation state determinations with wet chemical methods is that U redox state may change when extracted from the sample material, thereby leading to erroneous results. In order to quantify and monitor U redox behavior during the acidic extraction in the procedure, an analysis of added isotopic redox tracers, (236)U(VI) and (232)U(IV), and of variations in natural uranium isotope ratio ((234)U/(238)U) of indigenous U(IV) and U(VI) fractions was performed. Two sample materials with varying redox activity, U bearing rock and U-rich clayey lignite sediment, were used for the tests. The Fe(II)/Fe(III) redox-pair of the mineral phases was postulated as a potentially disturbing redox agent. The impact of Fe(III) on U was studied by reducing Fe(III) with ascorbic acid, which was added to the extraction solution. We observed that ascorbic acid protected most of the U from oxidation. The measured (234)U/(238)U ratio in U(IV) and U(VI) fractions in the sediment samples provided a unique tool to quantify U oxidation caused by Fe(III). Annealing (sample heating) to temperatures above 500 °C was supposed to heal ionizing radiation induced defects in the material that can disturb U redox state during extraction. Good agreement between two independent methods was obtained for DL-1a material: an average 38% of U(IV) determined by redox tracer corrected wet chemistry and 45% for XANES. Copyright © 2013 Elsevier Ltd. All rights reserved.

Thioredoxin Selectivity for Thiol-based Redox Regulation of Target Proteins in Chloroplasts*

PubMed Central

Yoshida, Keisuke; Hara, Satoshi; Hisabori, Toru

2015-01-01

Redox regulation based on the thioredoxin (Trx) system is believed to ensure light-responsive control of various functions in chloroplasts. Five Trx subtypes have been reported to reside in chloroplasts, but their functional diversity in the redox regulation of Trx target proteins remains poorly clarified. To directly address this issue, we studied the Trx-dependent redox shifts of several chloroplast thiol-modulated enzymes in vitro and in vivo. In vitro assays using a series of Arabidopsis recombinant proteins provided new insights into Trx selectivity for the redox regulation as well as the underpinning for previous suggestions. Most notably, by combining the discrimination of thiol status with mass spectrometry and activity measurement, we identified an uncharacterized aspect of the reductive activation of NADP-malate dehydrogenase; two redox-active Cys pairs harbored in this enzyme were reduced via distinct utilization of Trxs even within a single polypeptide. In our in vitro assays, Trx-f was effective in reducing all thiol-modulated enzymes analyzed here. We then investigated the in vivo physiological relevance of these in vitro findings, using Arabidopsis wild-type and Trx-f-deficient plants. Photoreduction of fructose-1,6-bisphosphatase was partially impaired in Trx-f-deficient plants, but the global impact of Trx-f deficiency on the redox behaviors of thiol-modulated enzymes was not as striking as expected from the in vitro data. Our results provide support for the in vivo functionality of the Trx system and also highlight the complexity and plasticity of the chloroplast redox network. PMID:25878252

Colloidal chirality in wormlike micellar systems exclusively originated from achiral species: Role of secondary assembly and stimulus responsivity.

PubMed

Zhao, Wenrong; Hao, Jingcheng

2016-09-15

Colloidal chirality in wormlike micellar systems exclusively originated from achiral species and discussion of the role of secondary assembly of fiber-like aggregates in chirality generation were presented in this paper. Herein, formation of colloidal wormlike micelles for the first time incorporated chirality and redox-responsiveness into one design via noncovalent interaction. A dual-stimuli-responsive gel of wormlike micelles which were designed by employing a dual-responsive cationic surfactant (FTMA) and a strong gelator (AzoNa4) and regulated by redox reaction and host-guest inclusion is presented. Both the redox and host-guest interaction play an important role in regulating the viscosity and supramolecular chirality of gels of the wormlike micelles. The supramolecular chirality and viscosity of the wormlike micelle gels were switched reversibly by exerting chemical redox onto the ferrocenyl groups. For the amphiphile FTMA containing redox-active ferrocenyl group, reversible control of the oxidation state of ferrocenyl groups leads to the charge and hydrophobicity changes of FTMA, therefore change its self-assembly behavior. Of equal interest, β-CD successfully detached the wormlike micelles via the recognition-inclusion behavior with FTMA and invalidate the H-bond and hydrophobic interaction between FTMA and AzoH4. This designed system provides a new strategy to tune the supramolecular chirality of colloidal aggregates and explore the specific packing mode detail within the micelles or the secondary assembly of the inter-micelles. We anticipate this dual-responsive H-bond-directed chiral gel switch could propose a new strategy when researchers designing new, multi-responsive functional gel materials. Copyright © 2016 Elsevier Inc. All rights reserved.

Another Demo of the Unusual Thermal Properties of Rubber

ERIC Educational Resources Information Center

Liff, Mark I.

2010-01-01

The unusual thermal behavior of rubbers, though discovered a long time ago, can still be mind-boggling for students and teachers who encounter this class of polymeric systems. Unlike other solids, stretched elastic polymers shrink upon heating. This is a manifestation of the Gough-Joule (G-J) effect. Joule in the 1850s studied the thermal behavior…

Harnessing out-of-plane deformation to design 3D architected lattice metamaterials with tunable Poisson's ratio.

PubMed

Li, Tiantian; Hu, Xiaoyi; Chen, Yanyu; Wang, Lifeng

2017-08-21

Auxetic materials exhibiting a negative Poisson's ratio are of great research interest due to their unusual mechanical responses and a wide range of potential deployment. Efforts have been devoted to exploring novel 2D and 3D auxetic structures through rational design, optimization, and taking inspiration from nature. Here we report a 3D architected lattice system showing a negative Poisson's ratio over a wide range of applied uniaxial stretch. 3D printing, experimental tests, numerical simulation, and analytical modeling are implemented to quantify the evolution of the Poisson's ratio and reveal the underlying mechanisms responsible for this unusual behavior. We further show that the auxetic behavior can be controlled by tailoring the geometric features of the ligaments. The findings reported here provide a new routine to design architected metamaterial systems exhibiting unusual properties and having a wide range of potential applications.

Transistor-like behavior of single metalloprotein junctions.

PubMed

Artés, Juan M; Díez-Pérez, Ismael; Gorostiza, Pau

2012-06-13

Single protein junctions consisting of azurin bridged between a gold substrate and the probe of an electrochemical tunneling microscope (ECSTM) have been obtained by two independent methods that allowed statistical analysis over a large number of measured junctions. Conductance measurements yield (7.3 ± 1.5) × 10(-6)G(0) in agreement with reported estimates using other techniques. Redox gating of the protein with an on/off ratio of 20 was demonstrated and constitutes a proof-of-principle of a single redox protein field-effect transistor.

Biohydrogen Production by the Thermophilic Bacterium Caldicellulosiruptor saccharolyticus: Current Status and Perspectives

PubMed Central

Bielen, Abraham A. M.; Verhaart, Marcel R. A.; van der Oost, John; Kengen, Servé W. M.

2013-01-01

Caldicellulosiruptor saccharolyticus is one of the most thermophilic cellulolytic organisms known to date. This Gram-positive anaerobic bacterium ferments a broad spectrum of mono-, di- and polysaccharides to mainly acetate, CO2 and hydrogen. With hydrogen yields approaching the theoretical limit for dark fermentation of 4 mol hydrogen per mol hexose, this organism has proven itself to be an excellent candidate for biological hydrogen production. This review provides an overview of the research on C. saccharolyticus with respect to the hydrolytic capability, sugar metabolism, hydrogen formation, mechanisms involved in hydrogen inhibition, and the regulation of the redox and carbon metabolism. Analysis of currently available fermentation data reveal decreased hydrogen yields under non-ideal cultivation conditions, which are mainly associated with the accumulation of hydrogen in the liquid phase. Thermodynamic considerations concerning the reactions involved in hydrogen formation are discussed with respect to the dissolved hydrogen concentration. Novel cultivation data demonstrate the sensitivity of C. saccharolyticus to increased hydrogen levels regarding substrate load and nitrogen limitation. In addition, special attention is given to the rhamnose metabolism, which represents an unusual type of redox balancing. Finally, several approaches are suggested to improve biohydrogen production by C. saccharolyticus. PMID:25371332

Critical transport issues for improving the performance of aqueous redox flow batteries

NASA Astrophysics Data System (ADS)

Zhou, X. L.; Zhao, T. S.; An, L.; Zeng, Y. K.; Wei, L.

2017-01-01

As the fraction of electricity generated from intermittent renewable sources (such as solar and wind) grows, developing reliable energy storage technologies to store electrical energy in large scale is of increasing importance. Redox flow batteries are now enjoying a renaissance and regarded as a leading technology in providing a well-balanced solution for current daunting challenges. In this article, state-of-the-art studies of the complex multicomponent transport phenomena in aqueous redox flow batteries, with a special emphasis on all-vanadium redox flow batteries, are reviewed and summarized. Rather than elaborating on the details of previous experimental and numerical investigations, this article highlights: i) the key transport issues in each battery's component that need to be tackled so that the rate capability and cycling stability of flow batteries can be significantly improved, ii) the basic mechanisms that control the active species/ion/electron transport behaviors in each battery's component, and iii) the key experimental and numerical findings regarding the correlations between the multicomponent transport processes and battery performance.

Factors That Affect Oxygen Activation and Coupling of the Two Redox Cycles in the Aromatization Reaction Catalyzed by NikD, an Unusual Amino Acid Oxidase

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kommoju, Phaneeswara-Rao; Bruckner, Robert C.; Ferreira, Patricia

2009-10-21

NikD is a flavoprotein oxidase that catalyzes the oxidation of piperideine-2-carboxylate (P2C) to picolinate in a remarkable aromatization reaction comprising two redox cycles and at least one isomerization step. Tyr258 forms part of an 'aromatic cage' that surrounds the ring in picolinate and its precursors. Mutation of Tyr258 to Phe does not perturb the structure of nikD but does affect the coupling of the two redox cycles and causes a 10-fold decrease in turnover rate. Tyr258Phe catalyzes a quantitative two-electron oxidation of P2C, but only 60% of the resulting dihydropicolinate intermediate undergoes a second redox cycle to produce picolinate. Themore » mutation does not affect product yield with an alternate substrate (3,4-dehydro-l-proline) that is aromatized in a single two-electron oxidation step. Wild-type and mutant enzymes exhibit identical rate constants for oxidation of P2C to dihydropicolinate and isomerization of a reduced enzyme-dihydropicolinate complex. The observed rates are 200- and 10-fold faster, respectively, than the mutant turnover rate. Release of picolinate from Tyr258Phe is 100-fold faster than turnover. The presence of a bound substrate or product is a key factor in oxygen activation by wild-type nikD, as judged by the 10-75-fold faster rates observed for complexes of the reduced enzyme with picolinate, benzoate, or 1-cyclohexenoate, a 1-deaza-P2C analogue. The reduced Tyr258Phe-1-cyclohexenoate complex is 25-fold less reactive with oxygen than the wild-type complex. We postulate that mutation of Tyr258 causes subtle changes in active site dynamics that promote release of the reactive dihydropicolinate intermediate and disrupt the efficient synchronization of oxygen activation observed with wild-type nikD.« less

Real-time monitoring of capacity loss for vanadium redox flow battery

NASA Astrophysics Data System (ADS)

Wei, Zhongbao; Bhattarai, Arjun; Zou, Changfu; Meng, Shujuan; Lim, Tuti Mariana; Skyllas-Kazacos, Maria

2018-06-01

The long-term operation of the vanadium redox flow battery is accompanied by ion diffusion across the separator and side reactions, which can lead to electrolyte imbalance and capacity loss. The accurate online monitoring of capacity loss is therefore valuable for the reliable and efficient operation of vanadium redox flow battery system. In this paper, a model-based online monitoring method is proposed to detect capacity loss in the vanadium redox flow battery in real time. A first-order equivalent circuit model is built to capture the dynamics of the vanadium redox flow battery. The model parameters are online identified from the onboard measureable signals with the recursive least squares, in seeking to keep a high modeling accuracy and robustness under a wide range of working scenarios. Based on the online adapted model, an observer is designed with the extended Kalman Filter to keep tracking both the capacity and state of charge of the battery in real time. Experiments are conducted on a lab-scale battery system. Results suggest that the online adapted model is able to simulate the battery behavior with high accuracy. The capacity loss as well as the state of charge can be estimated accurately in a real-time manner.

Water Oxidation Catalysis via Size-Selected Iridium Clusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Halder, Avik; Liu, Cong; LIU, ZHUN

The detailed mechanism and efficacy of four electron electrochemical water oxidation depend critically upon the detailed atomic structure of each catalytic site, which are numerous and diverse in most metal oxides anodes. In order to limit the diversity of sites, arrays of discrete iridium clusters with identical metal atom number (Ir-2, Ir-4, or Ir-8) were deposited in submonolayer coverage on conductive oxide supports, and the electrochemical properties and activity of each was evaluated. Exceptional electroactivity for the oxygen evolving reaction (OER) was observed for all cluster samples in acidic electrolyte. Reproducible cluster-size-dependent trends in redox behavior were also resolved. First-principlesmore » computational models of the individual discrete-size clusters allow correlation of catalytic-site structure and multiplicity with redox behavior.« less

Diagnostic Utility of Wireless Video-Electroencephalography in Unsedated Dogs.

PubMed

James, F M K; Cortez, M A; Monteith, G; Jokinen, T S; Sanders, S; Wielaender, F; Fischer, A; Lohi, H

2017-09-01

Poor agreement between observers on whether an unusual event is a seizure drives the need for a specific diagnostic tool provided by video-electroencephalography (video-EEG) in human pediatric epileptology. That successful classification of events would be positively associated with increasing EEG recording length and higher event frequency reported before video-EEG evaluation; that a novel wireless video-EEG technique would clarify whether unusual behavioral events were seizures in unsedated dogs. Eighty-one client-owned dogs of various breeds undergoing investigation of unusual behavioral events at 4 institutions. Retrospective case series: evaluation of wireless video-EEG recordings in unsedated dogs performed at 4 institutions. Electroencephalography achieved/excluded diagnosis of epilepsy in 58 dogs (72%); 25 dogs confirmed with epileptic seizures based on ictal/interictal epileptiform discharges, and 33 dogs with no EEG abnormalities associated with their target events. As reported frequency of the target events decreased (annually, monthly, weekly, daily, hourly, minutes, seconds), EEG was less likely to achieve diagnosis (P < 0.001). Every increase in event frequency increased the odds of achieving diagnosis by 2.315 (95% confidence interval: 1.36-4.34). EEG recording length (mean = 3.69 hours, range: 0.17-22.5) was not associated (P = 0.2) with the likelihood of achieving a diagnosis. Wireless video-EEG in unsedated dogs had a high success for diagnosis of unusual behavioral events. This technique offered a reliable clinical tool to investigate the epileptic origin of behavioral events in dogs. Copyright © 2017 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals, Inc. on behalf of the American College of Veterinary Internal Medicine.

The Fumarate Reductase of Bacteroides thetaiotaomicron, unlike That of Escherichia coli, Is Configured so that It Does Not Generate Reactive Oxygen Species

PubMed Central

Lu, Zheng

2017-01-01

ABSTRACT The impact of oxidative stress upon organismal fitness is most apparent in the phenomenon of obligate anaerobiosis. The root cause may be multifaceted, but the intracellular generation of reactive oxygen species (ROS) likely plays a key role. ROS are formed when redox enzymes accidentally transfer electrons to oxygen rather than to their physiological substrates. In this study, we confirm that the predominant intestinal anaerobe Bacteroides thetaiotaomicron generates intracellular ROS at a very high rate when it is aerated. Fumarate reductase (Frd) is a prominent enzyme in the anaerobic metabolism of many bacteria, including B. thetaiotaomicron, and prior studies of Escherichia coli Frd showed that the enzyme is unusually prone to ROS generation. Surprisingly, in this study biochemical analysis demonstrated that the B. thetaiotaomicron Frd does not react with oxygen at all: neither superoxide nor hydrogen peroxide is formed. Subunit-swapping experiments indicated that this difference does not derive from the flavoprotein subunit at which ROS normally arise. Experiments with the related enzyme succinate dehydrogenase discouraged the hypothesis that heme moieties are responsible. Thus, resistance to oxidation may reflect a shift of electron density away from the flavin moiety toward the iron-sulfur clusters. This study shows that the autoxidizability of a redox enzyme can be suppressed by subtle modifications that do not compromise its physiological function. One implication is that selective pressures might enhance the oxygen tolerance of an organism by manipulating the electronic properties of its redox enzymes so they do not generate ROS. PMID:28049145

Redox-active triazatruxene-based conjugated microporous polymers for high-performance supercapacitors† †Electronic supplementary information (ESI) available: Synthetic procedures and characterization data for all new compounds; general experimental method; thermogravimetry curves; PXRD patterns; SEM and TEM images; XPS spectra. See DOI: 10.1039/c6sc05532j Click here for additional data file.

PubMed Central

Li, Xiang-Chun; Zhang, Yizhou; Wang, Chun-Yu; Wan, Yi

2017-01-01

Conjugated polymers (CPs) have been intensively explored for various optoelectronic applications in the last few decades. Nevertheless, CP based electrochemical energy storage devices such as supercapacitors remain largely unexplored. This is mainly owing to the low specific capacitance, poor structural/electrochemical stability, and low energy density of most existing CPs. In this contribution, a novel set of redox-active conjugated microporous polymers, TAT-CMP-1 and TAT-CMP-2, based on nitrogen-rich and highly conductive triazatruxene building blocks, were successfully designed and synthesized to explore their potential application as efficient and stable electrode materials for supercapacitors. Despite a moderate surface area of 88 m2 g–1 for TAT-CMP-1 and 106 m2 g–1 for TAT-CMP-2, exceptional specific capacitances of 141 F g–1 and 183 F g–1 were achieved at a current density of 1 A g–1. The resulting polymers exhibited unusually high areal specific capacitance (>160 μF cm–2), which is attributed to the pseudocapacitance resulting from redox-active structures with high nitrogen content. More importantly, the TAT-CMP-2 electrode exhibits excellent cycling stability: only 5% capacitance fading is observed after 10 000 cycles at a high current density of 10 A g–1, enabling the possible use of these materials as electrodes in electrochemical devices. PMID:28451362

A new approach to design safe CNTs with an understanding of redox potential.

PubMed

Tsuruoka, Shuji; Cassee, Flemming R; Castranova, Vincent

2013-09-02

Carbon nanotubes (CNTs) are being increasingly industrialized and applied for various products. As of today, although several toxicological evaluations of CNTs have been conducted, designing safer CNTs is not practiced because reaction kinetics of CNTs with bioactive species is not fully understood. The authors propose a kinetic mechanism to establish designing safe CNTs as a new goal. According to a literature search on the behavior of CNTs and the effects of impurities, it is found that chemical reactions on CNT surface are attributed to redox reactions involving metal impurities and carbon structures at the CNT surface. A new goal is proposed to design safer CNTs using the redox potential hypothesis. The value of this hypothesis must be practically investigated and proven through the further experiments.

Timing Behavior of the Magnetically Active Rotation-Powered Pulsar in the Supernova Remnant Kesteven 75

NASA Technical Reports Server (NTRS)

Livingstone, Margaret A.; Gavriil, Fotis P.; Kaspi, Victoria M.

2009-01-01

We report a large spin-up glitch in PSR J1846-0258 which coincided with the onset of magnetar-like behavior on 2006 May 31. We show that the pulsar experienced an unusually large glitch recovery, with a recovery fraction of Q = 5.9+/-0.3, resulting in a net decrease of the pulse frequency. Such a glitch recovery has never before been observed in a rotation-powered pulsar, however, similar but smaller glitch over-recovery has been recently reported in the magnetar AXP 4U 0142+61 and may have occurred in the SGR 1900+14. We discuss the implications of the unusual timing behavior in PSR J1846-0258 on its status as the first identified magnetically active rotation-powered pulsar.

Entropy production and energy dissipation in symmetric redox supercapacitors

NASA Astrophysics Data System (ADS)

Palma-Aramburu, N.; Santamaría-Holek, I.

2017-08-01

In this work we propose a theoretical model that accounts for the main features of the loading-unloading process of a symmetric redox MnO2-based supercapacitor dominated by fast electrochemical reactions at the electrodes. The model is formulated on the basis of nonequilibrium thermodynamics from which we are able to deduce generalized expressions for the electrochemical affinity, the load-voltage and the current-voltage equations that constitute generalizations of the current-overpotential and Butler-Volmer equations, and that are used to describe experimental voltagram data with good agreement. These equations allowed us to derive the behavior of the energy dissipated per cycle showing that it has a nonmonotonic behavior and that in the operation regime it follows a power-law behavior as a function of the frequency. The existence of a maximum for the energy dissipated as a function of the frequency suggests the that the corresponding optimal operation frequency should be similar in value to ωmax.

Antimalarial NADPH-Consuming Redox-Cyclers As Superior Glucose-6-Phosphate Dehydrogenase Deficiency Copycats.

PubMed

Bielitza, Max; Belorgey, Didier; Ehrhardt, Katharina; Johann, Laure; Lanfranchi, Don Antoine; Gallo, Valentina; Schwarzer, Evelin; Mohring, Franziska; Jortzik, Esther; Williams, David L; Becker, Katja; Arese, Paolo; Elhabiri, Mourad; Davioud-Charvet, Elisabeth

2015-05-20

Early phagocytosis of glucose-6-phosphate dehydrogenase (G6PD)-deficient erythrocytes parasitized by Plasmodium falciparum were shown to protect G6PD-deficient populations from severe malaria. Here, we investigated the mechanism of a novel antimalarial series, namely 3-[substituted-benzyl]-menadiones, to understand whether these NADPH-consuming redox-cyclers, which induce oxidative stress, mimic the natural protection of G6PD deficiency. We demonstrated that the key benzoylmenadione metabolite of the lead compound acts as an efficient redox-cycler in NADPH-dependent methaemoglobin reduction, leading to the continuous formation of reactive oxygen species, ferrylhaemoglobin, and subsequent haemichrome precipitation. Structure-activity relationships evidenced that both drug metabolites and haemoglobin catabolites contribute to potentiate drug effects and inhibit parasite development. Disruption of redox homeostasis by the lead benzylmenadione was specifically induced in Plasmodium falciparum parasitized erythrocytes and not in non-infected cells, and was visualized via changes in the glutathione redox potential of living parasite cytosols. Furthermore, the redox-cycler shows additive and synergistic effects in combination with compounds affecting the NADPH flux in vivo. The lead benzylmenadione 1c is the first example of a novel redox-active agent that mimics the behavior of a falciparum parasite developing inside a G6PD-deficient red blood cell (RBC) giving rise to malaria protection, and it exerts specific additive effects that are inhibitory to parasite development, without harm for non-infected G6PD-sufficient or -deficient RBCs. This strategy offers an innovative perspective for the development of future antimalarial drugs for G6PD-sufficient and -deficient populations.

Geothrix fermentans Secretes Two Different Redox-Active Compounds To Utilize Electron Acceptors across a Wide Range of Redox Potentials

PubMed Central

Mehta-Kolte, Misha G.

2012-01-01

The current understanding of dissimilatory metal reduction is based primarily on isolates from the proteobacterial genera Geobacter and Shewanella. However, environments undergoing active Fe(III) reduction often harbor less-well-studied phyla that are equally abundant. In this work, electrochemical techniques were used to analyze respiratory electron transfer by the only known Fe(III)-reducing representative of the Acidobacteria, Geothrix fermentans. In contrast to previously characterized metal-reducing bacteria, which typically reach maximal rates of respiration at electron acceptor potentials of 0 V versus standard hydrogen electrode (SHE), G. fermentans required potentials as high as 0.55 V to respire at its maximum rate. In addition, G. fermentans secreted two different soluble redox-active electron shuttles with separate redox potentials (−0.2 V and 0.3 V). The compound with the lower midpoint potential, responsible for 20 to 30% of electron transfer activity, was riboflavin. The behavior of the higher-potential compound was consistent with hydrophilic UV-fluorescent molecules previously found in G. fermentans supernatants. Both electron shuttles were also produced when cultures were grown with Fe(III), but not when fumarate was the electron acceptor. This study reveals that Geothrix is able to take advantage of higher-redox-potential environments, demonstrates that secretion of flavin-based shuttles is not confined to Shewanella, and points to the existence of high-potential-redox-active compounds involved in extracellular electron transfer. Based on differences between the respiratory strategies of Geothrix and Geobacter, these two groups of bacteria could exist in distinctive environmental niches defined by redox potential. PMID:22843516

Nanoporous polysulfone membranes via a degradable block copolymer precursor for redox flow batteries

DOE PAGES

Gindt, Brandon P.; Abebe, Daniel G.; Tang, Zhijiang J.; ...

2016-02-16

In this study, nanoporous polysulfone (PSU) membranes were fabricated via post-hydrolysis of polylactide (PLA) from PLA–PSU–PLA triblock copolymer membranes. The PSU scaffold was thermally crosslinked before sacrificing PLA blocks. The resulting nanopore surface was chemically modified with sulfonic acid moieties. The membranes were analyzed and evaluated as separators for vanadium redox flow batteries. Nanoporous PSU membranes prepared by this new method and further chemically modified to a slight degree exhibited unique behavior with respect to their ionic conductivity when exposed to solutions of increasing acid concentration.

An Electrochemical Study on the Copolymer Formed from Piperazine and Aniline Monomers.

PubMed

Dkhili, Samiha; López-Bernabeu, Sara; Kedir, Chahineze Nawel; Huerta, Francisco; Montilla, Francisco; Besbes-Hentati, Salma; Morallon, Emilia

2018-06-14

A study on the electrochemical oxidation of piperazine and its electrochemical copolymerization with aniline in acidic medium is presented. It was found that the homopolymerization of piperazine cannot be achieved under electrochemical conditions. A combination of electrochemistry, in situ Fourier transform infrared (FTIR), and ex situ X-ray photoelectron spectroscopy (XPS) spectroscopies was used to characterize both the chemical structure and the redox behavior of an electrochemically synthesized piperazine⁻aniline copolymer. The electrochemical sensing properties of the deposited material were also tested against ascorbic acid and dopamine as redox probes.

The Young Offender.

ERIC Educational Resources Information Center

MacLeod, Hinson

1979-01-01

Looks at delinquency from the viewpoint of a training school chaplain and outlines factors believed to contribute to the development of delinquent behavior. Signs of maladjustment include overactivity, acute anxiety and fear, depression, psychosomatic disorders, unusual behavior, negative attitudes toward others and themselves, and resistance to…

The logic of kinetic regulation in the thioredoxin system

PubMed Central

2011-01-01

Background The thioredoxin system consisting of NADP(H), thioredoxin reductase and thioredoxin provides reducing equivalents to a large and diverse array of cellular processes. Despite a great deal of information on the kinetics of individual thioredoxin-dependent reactions, the kinetic regulation of this system as an integrated whole is not known. We address this by using kinetic modeling to identify and describe kinetic behavioral motifs found within the system. Results Analysis of a realistic computational model of the Escherichia coli thioredoxin system revealed several modes of kinetic regulation in the system. In keeping with published findings, the model showed that thioredoxin-dependent reactions were adaptable (i.e. changes to the thioredoxin system affected the kinetic profiles of these reactions). Further and in contrast to other systems-level descriptions, analysis of the model showed that apparently unrelated thioredoxin oxidation reactions can affect each other via their combined effects on the thioredoxin redox cycle. However, the scale of these effects depended on the kinetics of the individual thioredoxin oxidation reactions with some reactions more sensitive to changes in the thioredoxin cycle and others, such as the Tpx-dependent reduction of hydrogen peroxide, less sensitive to these changes. The coupling of the thioredoxin and Tpx redox cycles also allowed for ultrasensitive changes in the thioredoxin concentration in response to changes in the thioredoxin reductase concentration. We were able to describe the kinetic mechanisms underlying these behaviors precisely with analytical solutions and core models. Conclusions Using kinetic modeling we have revealed the logic that underlies the functional organization and kinetic behavior of the thioredoxin system. The thioredoxin redox cycle and associated reactions allows for a system that is adaptable, interconnected and able to display differential sensitivities to changes in this redox cycle. This work provides a theoretical, systems-biological basis for an experimental analysis of the thioredoxin system and its associated reactions. PMID:21266044

Reversible redox and clusterization of silver in glasses by X-ray irradiation and heat treatment: Mechanism of photochromic behavior of halogen-free silver-doped glass

NASA Astrophysics Data System (ADS)

Isaji, Tomoya; Wakasugi, Takashi; Fukumi, Kohei; Kadono, Kohei

2012-01-01

We investigated photochromic behavior, i.e. X-ray irradiation and post-heat-treatment-induced reversible redox and clusterization reactions of silver, in soda-lime silicate (74SiO2·16Na2O·8CaO·2Al2O3) and aluminosilicate ((75 - x)SiO2·25Na2O·xAl2O3 (x = 5-25)) glasses. Generation and annihilation of silver nanoparticles were observed for soda-lime silicate and x = 5 aluminosilicate glasses doped with 0.05 wt.% or less of Ag while no nanoparticles were formed for x = 15-25 aluminosilicate glasses even doped with 0.5 wt.% of Ag. These results were analyzed from the viewpoints of the reaction kinetics and network structures of the glasses.

Multiply Intercalator-Substituted Cu(II) Cyclen Complexes as DNA Condensers and DNA/RNA Synthesis Inhibitors.

PubMed

Hormann, Jan; Malina, Jaroslav; Lemke, Oliver; Hülsey, Max J; Wedepohl, Stefanie; Potthoff, Jan; Schmidt, Claudia; Ott, Ingo; Keller, Bettina G; Brabec, Viktor; Kulak, Nora

2018-05-07

Many drugs that are applied in anticancer therapy such as the anthracycline doxorubicin contain DNA-intercalating 9,10-anthraquinone (AQ) moieties. When Cu(II) cyclen complexes were functionalized with up to three (2-anthraquinonyl)methyl substituents, they efficiently inhibited DNA and RNA synthesis resulting in high cytotoxicity (selective for cancer cells) accompanied by DNA condensation/aggregation phenomena. Molecular modeling suggests an unusual bisintercalation mode with only one base pair between the two AQ moieties and the metal complex as a linker. A regioisomer, in which the AQ moieties point in directions unfavorable for such an interaction, had a much weaker biological activity. The ligands alone and corresponding Zn(II) complexes (used as redox inert control compounds) also exhibited lower activity.

Apatite/Melt Partitioning Experiments Reveal Redox Sensitivity to Cr, V, Mn, Ni, Eu, W, Th, and U

NASA Technical Reports Server (NTRS)

Righter, K.; Yang, S.; Humayun, M.

2016-01-01

Apatite is a common mineral in terrestrial, planetary, and asteroidal materials. It is commonly used for geochronology (U-Pb), sensing volatiles (H, F, Cl, S), and can concentrate rare earth elements (REE) during magmatic fractionation and in general. Some recent studies have shown that some kinds of phosphate may fractionate Hf and W and that Mn may be redox sensitive. Experimental studies have focused on REE and other lithophile elements and at simplified or not specified oxygen fugacities. There is a dearth of partitioning data for chalcophile, siderophile and other elements between apatite and melt. Here we carry out several experiments at variable fO2 to study the partitioning of a broad range of trace elements. We compare to existing data and then focus on several elements that exhibit redox dependent partitioning behavior.

S-Glutathionylation and Redox Protein Signaling in Drug Addiction

PubMed Central

Womersley, Jacqueline S.; Uys, Joachim D.

2016-01-01

Drug addiction is a chronic relapsing disorder that comes at a high cost to individuals and society. Therefore understanding the mechanisms by which drugs exert their effects is of prime importance. Drugs of abuse increase the production of reactive oxygen and nitrogen species resulting in oxidative stress. This change in redox homeostasis increases the conjugation of glutathione to protein cysteine residues; a process called S-glutathionylation. Although traditionally regarded as a protective mechanism against irreversible protein oxidation, accumulated evidence suggests a more nuanced role for S-glutathionylation, namely as a mediator in redox-sensitive protein signaling. The reversible modification of protein thiols leading to alteration in function under different physiologic/pathologic conditions provides a mechanism whereby change in redox status can be translated into a functional response. As such, S-glutathionylation represents an understudied means of post-translational protein modification that may be important in the mechanisms underlying drug addiction. This review will discuss the evidence for S-glutathionylation as a redox-sensing mechanism and how this may be involved in the response to drug-induced oxidative stress. The function of S-glutathionylated proteins involved in neurotransmission, dendritic spine structure, and drug-induced behavioral outputs will be reviewed with specific reference to alcohol, cocaine, and heroin. PMID:26809999

Hypoxia and Redox Signaling on Extracellular Matrix Remodeling: From Mechanisms to Pathological Implications.

PubMed

Labrousse-Arias, David; Martínez-Ruiz, Antonio; Calzada, María J

2017-10-20

The extracellular matrix (ECM) is an essential modulator of cell behavior that influences tissue organization. It has a strong relevance in homeostasis and translational implications for human disease. In addition to ECM structural proteins, matricellular proteins are important regulators of the ECM that are involved in a myriad of different pathologies. Recent Advances: Biochemical studies, animal models, and study of human diseases have contributed to the knowledge of molecular mechanisms involved in remodeling of the ECM, both in homeostasis and disease. Some of them might help in the development of new therapeutic strategies. This review aims to review what is known about some of the most studied matricellular proteins and their regulation by hypoxia and redox signaling, as well as the pathological implications of such regulation. Matricellular proteins have complex regulatory functions and are modulated by hypoxia and redox signaling through diverse mechanisms, in some cases with controversial effects that can be cell or tissue specific and context dependent. Therefore, a better understanding of these regulatory processes would be of great benefit and will open new avenues of considerable therapeutic potential. Characterizing the specific molecular mechanisms that modulate matricellular proteins in pathological processes that involve hypoxia and redox signaling warrants additional consideration to harness the potential therapeutic value of these regulatory proteins. Antioxid. Redox Signal. 27, 802-822.

S-Glutathionylation and Redox Protein Signaling in Drug Addiction.

PubMed

Womersley, Jacqueline S; Uys, Joachim D

2016-01-01

Drug addiction is a chronic relapsing disorder that comes at a high cost to individuals and society. Therefore understanding the mechanisms by which drugs exert their effects is of prime importance. Drugs of abuse increase the production of reactive oxygen and nitrogen species resulting in oxidative stress. This change in redox homeostasis increases the conjugation of glutathione to protein cysteine residues; a process called S-glutathionylation. Although traditionally regarded as a protective mechanism against irreversible protein oxidation, accumulated evidence suggests a more nuanced role for S-glutathionylation, namely as a mediator in redox-sensitive protein signaling. The reversible modification of protein thiols leading to alteration in function under different physiologic/pathologic conditions provides a mechanism whereby change in redox status can be translated into a functional response. As such, S-glutathionylation represents an understudied means of post-translational protein modification that may be important in the mechanisms underlying drug addiction. This review will discuss the evidence for S-glutathionylation as a redox-sensing mechanism and how this may be involved in the response to drug-induced oxidative stress. The function of S-glutathionylated proteins involved in neurotransmission, dendritic spine structure, and drug-induced behavioral outputs will be reviewed with specific reference to alcohol, cocaine, and heroin. Copyright © 2016. Published by Elsevier Inc.

Insights into the redox components of dissolved organic matters during stabilization process.

PubMed

Yuan, Ying; Xi, Bei-Dou; He, Xiao-Song; Ma, Yan; Zhang, Hui; Li, Dan; Zhao, Xin-Yu

2018-05-01

The changes of dissolved organic matter (DOM) components during stabilization process play significant effects on its redox properties but are little reported. Composting is a stabilization process of DOM, during which both the components and electron transfer capacities (ETCs) of DOM change. The redox components within compost-derived DOM during the stabilization process are investigated in this study. The results show that compost-derived DOM contained protein-like, fulvic-like, and humic-like components. The protein-like component decreases during composting, whereas the fulvic- and humic-like components increase during the process. The electron-donating capacity (EDC), electron-accepting capacity (EAC), and ETC of compost-derived DOM all increase during composting but their correlations with the components presented significant difference. The humic-like components were the main functional component responsible for both EDC and ETC, whereas the protein- and fluvic-like components show negative effects with the EAC, EDC, and ETC, suggesting that the components within DOM have specific redox properties during the stabilization process. These findings are very meaningful for better understanding the geochemical behaviors of DOM in the environment.

Characterization of a BODIPY Dye as an Active Species for Redox Flow Batteries.

PubMed

Kosswattaarachchi, Anjula M; Friedman, Alan E; Cook, Timothy R

2016-12-08

An all-organic redox flow battery (RFB) employing a fluorescent boron-dipyrromethene (BODIPY) dye (PM567) was investigated. In a RFB, the stability of the electrolyte in all charged states is critically linked to coulombic efficiency. To evaluate stability, bulk electrolysis and cyclic voltammetry (CV) experiments were performed. Oxidized and reduced, PM567 does not remain intact; however, the products of bulk electrolysis evolve over time to show stable redox behavior, making the dye a precursor for the active species of an RFB. A theoretical cell potential of 2.32 V was predicted from CV experiments with a working discharge voltage of approximately 1.6 V in a static test cell. Mass spectrometry was used to identify the products of bulk electrolysis. Related experiments were carried out using ferrocene and cobaltocenium hexafluorophosphate as redox-stable benchmarks to further explain the stability results. The coulombic efficiency of a model cell using PM567 as a precursor for charge carriers stabilized around 73 %. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

The phenomenon of claimed memories of previous lives: possible interpretations and importance.

PubMed

Stevenson, I

2000-04-01

Several disorders or abnormalities observed in medicine and psychology are not explicable (or not fully explicable) by genetics and environmental influences, either alone or together. These include phobias and philias observed in early infancy, unusual play in childhood, homosexuality, gender identity disorder, a child's idea of having parents other than its own, differences in temperament manifested soon after birth, unusual birthmarks and their correspondence with wounds on a deceased person, unusual birth defects, and differences (physical and behavioral) between monozygotic twins. The hypothesis of previous lives can contribute to the further understanding of these phenomena. Copyright 2000 Harcourt Publishers Ltd.

Epigenetic oxidative redox shift (EORS) theory of aging unifies the free radical and insulin signaling theories.

PubMed

Brewer, Gregory J

2010-03-01

Harman's free radical theory of aging posits that oxidized macromolecules accumulate with age to decrease function and shorten life-span. However, nutritional and genetic interventions to boost anti-oxidants have generally failed to increase life-span. Furthermore, the free radical theory fails to explain why exercise causes higher levels of oxyradical damage, but generally promotes healthy aging. The separate anti-aging paradigms of genetic or caloric reductions in the insulin signaling pathway is thought to slow the rate of living to reduce metabolism, but recent evidence from Westbrook and Bartke suggests metabolism actually increases in long-lived mice. To unify these disparate theories and data, here, we propose the epigenetic oxidative redox shift (EORS) theory of aging. According to EORS, sedentary behavior associated with age triggers an oxidized redox shift and impaired mitochondrial function. In order to maintain resting energy levels, aerobic glycolysis is upregulated by redox-sensitive transcription factors. As emphasized by DeGrey, the need to supply NAD(+) for glucose oxidation and maintain redox balance with impaired mitochondrial NADH oxidoreductase requires the upregulation of other oxidoreductases. In contrast to the 2% inefficiency of mitochondrial reduction of oxygen to the oxyradical, these other oxidoreductases enable glycolytic energy production with a deleterious 100% efficiency in generating oxyradicals. To avoid this catastrophic cycle, lactate dehydrogenase is upregulated at the expense of lactic acid acidosis. This metabolic shift is epigenetically enforced, as is insulin resistance to reduce mitochondrial turnover. The low mitochondrial capacity for efficient production of energy reinforces a downward spiral of more sedentary behavior leading to accelerated aging, increased organ failure with stress, impaired immune and vascular functions and brain aging. Several steps in the pathway are amenable to reversal for exit from the vicious cycle of EORS. Examples from our work in the aging rodent brain as well as other aging models are provided. Copyright 2010 Elsevier Inc. All rights reserved.

Intracellular redox status controls membrane localization of pro- and anti-migratory signaling molecules.

PubMed

Hempel, Nadine; Melendez, J Andres

2014-01-01

Shifts in intracellular Reactive Oxygen Species (ROS) have been shown to contribute to carcinogenesis and to tumor progression. In addition to DNA and cell damage by surges in ROS, sub-lethal increases in ROS are implicated in regulating cellular signaling that enhances pro-metastatic behavior. We previously showed that subtle increases in endogenous H2O2 regulate migratory and invasive behavior of metastatic bladder cancer cells through phosphatase inhibition and consequential phosphorylation of p130cas, an adapter of the FAK signaling pathway. We further showed that enhanced redox status contributed to enhanced localization of p130cas to the membrane of metastatic cells. Here we show that this signaling complex can similarly be induced in a redox-engineered cell culture model that enables regulation of intracellular steady state H2O2 level by enforced expression of superoxide dismutase 2 (Sod2) and catalase. Expression of Sod2 leads to enhanced p130cas phosphorylation in HT-1080 fibrosarcoma and UM-UC-6 bladder cancer cells. These changes are mediated by H2O2, as co-expression of Catalase abrogates p130cas phosphorylation and its interaction with the adapter protein Crk. Importantly, we establish that the redox environment influence the localization of the tumor suppressor and phosphatase PTEN, in both redox-engineered and metastatic bladder cancer cells that display endogenous increases in H2O2. Importantly, PTEN oxidation leads to its dissociation from the plasma membrane. This indicates that oxidation of PTEN not only influences its activity, but also regulates its cellular localization, effectively removing it from its primary site of lipid phosphatase activity. These data introduce hitherto unappreciated paradigms whereby ROS can reciprocally regulate the cellular localization of pro- and anti-migratory signaling molecules, p130cas and PTEN, respectively. These data further confirm that altering antioxidant status and the intracellular ROS environment can have profound effects on pro-metastatic signaling pathways.

Diamond and moissanite in ophiolitic mantle rocks and podiform chromitites: A deep carbon source?

NASA Astrophysics Data System (ADS)

Yang, J.; Xu, X.; Wiedenbeck, M.; Trumbull, R. B.; Robinson, P. T.

2010-12-01

Diamonds are known from a variety of occurreces, mainly from mantle-derived kimberlites, meteorite impact craters, and continental deep subduction and collision zones. Recently, an unusual mineral group was discovered in the Luobusa ophiolitic chromitites from the Yarlung Zangbu suture, Tibet, which probably originated from a depth of over 300 km in the mantle. Minerals of deep origin include coesite apparently pseudomorphing stishovite, and diamond as individual grains or inclusions in OsIr alloy. To determine if such UHP and unusual minerals occur elsewhere, we collected about 1.5 t of chromitite from two orebodies in an ultramafic body in the Polar Urals. Thus far, more than 60 different mineral species have been separated from these ores. The most exciting discovery is the common occurrence of diamond, a typical UHP mineral in the Luobusa chromitites. These minerals are very similar in composition and structure to those reported from the Luobusa chromitites. So far diamond and/or moissanite have been discovered from many different ophiolitic ultramafic rocks, including in-situ grains in polished chromitite fragments. These discoveries demonstrate that the Luobusa ophiolite is not a unique diamond-bearing massif. Secondary ion mass spectrometric (SIMS) analysis shows that the ophiolite-hosted diamond has a distinctive 13C-depleted isotopic composition (δ13C from -18 to -28‰, n=70), compatible to the ophiolite-hosted moissanite (δ13C from -18 to -35‰, n=36), both are much lighter than the main carbon reservoir in the upper mantle (δ13C near -5‰). The compiled data from moissanite from kimberlites and other mantle settings share the characteristic of strongly 13C-depleted isotopic composition. This suggests that diamond and moissanite originates from a separate carbon reservoir in the mantle or that its formation involved strong isotopic fractionation. Subduction of biogenic carbonaceous material could potentially satisfy both the unusual isotopic and redox constraints on diamond and moissanite formation, but this material would need to stay chemically isolated from the upper mantle until it reached the high-T stability field of diamond and moissanite. The origin of diamond and moissanite in the mantle is still unsolved, but all evidence from the upper mantle indicates that they cannot have formed there, except under special and local redox conditions. We suggest, alternatively, that diamond and moissanite may have formed in the lower mantle, where the existence of 13C-depleted carbon is strongly suspected.

Modeling Temporal Behavior in Large Networks: A Dynamic Mixed-Membership Model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rossi, R; Gallagher, B; Neville, J

Given a large time-evolving network, how can we model and characterize the temporal behaviors of individual nodes (and network states)? How can we model the behavioral transition patterns of nodes? We propose a temporal behavior model that captures the 'roles' of nodes in the graph and how they evolve over time. The proposed dynamic behavioral mixed-membership model (DBMM) is scalable, fully automatic (no user-defined parameters), non-parametric/data-driven (no specific functional form or parameterization), interpretable (identifies explainable patterns), and flexible (applicable to dynamic and streaming networks). Moreover, the interpretable behavioral roles are generalizable, computationally efficient, and natively supports attributes. We applied ourmore » model for (a) identifying patterns and trends of nodes and network states based on the temporal behavior, (b) predicting future structural changes, and (c) detecting unusual temporal behavior transitions. We use eight large real-world datasets from different time-evolving settings (dynamic and streaming). In particular, we model the evolving mixed-memberships and the corresponding behavioral transitions of Twitter, Facebook, IP-Traces, Email (University), Internet AS, Enron, Reality, and IMDB. The experiments demonstrate the scalability, flexibility, and effectiveness of our model for identifying interesting patterns, detecting unusual structural transitions, and predicting the future structural changes of the network and individual nodes.« less

Disturbed mouse circadian rhythm before the Kobe EQ in 1995

NASA Astrophysics Data System (ADS)

Yokoi, Sayoko

2013-04-01

Legends of macro-anomalies before large earthquakes have been passed down for generations in Asia. Most of the statements on earthquake precursors are considered unreliable afterthoughts by traditional scientists. However, disturbed biological rhythms in mice were observed before the Kobe EQ in 1995 (Yokoi et al, 2003). The records of unusual mouse behavior before the earthquake were obtained to study biological clock at Institute for Protein Research, Osaka University. It is clarified that the disturbance was very rare phenomena statistically. Similar phenomenon was observed before the Wenchuan earthquake in 2008, too (Li et al, 2009). In the presentation, I will discuss the phenomena as one example of preseismic unusual animal behaviors.

Unusual raptor nests around the world

USGS Publications Warehouse

Ellis, D.H.; Craig, T.; Craig, E.; Postupalsky, S.; LaRue, C.T.; Nelson, R.W.; Anderson, D.W.; Henny, C.J.; Watson, J.; Millsap, B.A.; Dawson, J.W.; Cole, K.L.; Martin, E.M.; Margalida, A.; Kung, P.

2009-01-01

From surveys in many countries, we report raptors using unusual nesting materials (e.g., paper money, rags, metal, antlers, and large bones) and unusual nesting situations. For example, we documented nests of Steppe Eagles Aquila nipalensis and Upland Buzzards Buteo hemilasius on the ground beside well-traveled roads, Saker Falcon Falco cherrug eyries in attics and a cistern, and Osprey Pandion haliaetus nests on the masts of boats and on a suspended automobile. Other records include a Golden Eagle A. chrysaetos nest 7.0 m in height, believed to be the tallest nest ever described, and, for the same species, we report nesting in rudimentary nests. Some nest sites are within a few meters of known predators or competitors. These unusual observations may be important in revealing the plasticity of a species' behavioral repertoire. ?? 2009 The Raptor Research Foundation, Inc.

L-Ascorbic acid metabolism during fruit development in an ascorbate-rich fruit crop chestnut rose (Rosa roxburghii Tratt).

PubMed

Huang, Ming; Xu, Qiang; Deng, Xiu-Xin

2014-09-01

Chestnut rose (Rosa roxburghii Tratt) is a fruit crop that contains unusually high levels of l-ascorbic acid (AsA; ∼1300 mg 100g(-1) FW). To explore the mechanisms underlying AsA metabolism, we investigated the distribution and abundance of AsA during fruit development. We also analyzed gene expression patterns, enzyme activities, and content of metabolites related to AsA biosynthesis and recycling. AsA first accumulated during late fruit development and continued to accumulate during ripening, with the highest accumulation rate near fruit maturity. The redox state of AsA in fruit was also enhanced during late fruit development, while leaf and other tissues had much lower levels of AsA and the redox state of AsA was lower. In mature fruit, AsA was mainly distributed in the cytoplasm of the mesocarp. Correlation analysis suggested that the gene expression patterns, enzyme activities, and related metabolite concentrations involved in the l-galactose pathway showed relatively high correlations with the accumulation rate of AsA. The gene expression pattern and activity of dehydroascorbate reductase (DHAR, EC 1.8.5.1) correlated strongly with AsA concentration, possibly indicating the crucial role of DHAR in the accumulation of high levels of AsA in chestnut rose fruit. Over expression of DHAR in Arabidopsis significantly increased the reduced AsA content and redox state. This was more effective than over expression of the l-galactose pathway gene GDP-d-mannose-3,5-epimerase (EC 5.1.3.18). These findings will enhance understanding of the molecular mechanisms regulating accumulation of AsA in chestnut rose. Copyright © 2014 Elsevier GmbH. All rights reserved.

Identification and characterization of a selenoprotein family containing a diselenide bond in a redox motif

PubMed Central

Shchedrina, Valentina A.; Novoselov, Sergey V.; Malinouski, Mikalai Yu.; Gladyshev, Vadim N.

2007-01-01

Selenocysteine (Sec, U) insertion into proteins is directed by translational recoding of specific UGA codons located upstream of a stem-loop structure known as Sec insertion sequence (SECIS) element. Selenoproteins with known functions are oxidoreductases containing a single redox-active Sec in their active sites. In this work, we identified a family of selenoproteins, designated SelL, containing two Sec separated by two other residues to form a UxxU motif. SelL proteins show an unusual occurrence, being present in diverse aquatic organisms, including fish, invertebrates, and marine bacteria. Both eukaryotic and bacterial SelL genes use single SECIS elements for insertion of two Sec. In eukaryotes, the SECIS is located in the 3′ UTR, whereas the bacterial SelL SECIS is within a coding region and positioned at a distance that supports the insertion of either of the two Sec or both of these residues. SelL proteins possess a thioredoxin-like fold wherein the UxxU motif corresponds to the catalytic CxxC motif in thioredoxins, suggesting a redox function of SelL proteins. Distantly related SelL-like proteins were also identified in a variety of organisms that had either one or both Sec replaced with Cys. Danio rerio SelL, transiently expressed in mammalian cells, incorporated two Sec and localized to the cytosol. In these cells, it occurred in an oxidized form and was not reducible by DTT. In a bacterial expression system, we directly demonstrated the formation of a diselenide bond between the two Sec, establishing it as the first diselenide bond found in a natural protein. PMID:17715293

Structural and functional roles of a conserved proline residue in the alpha2 helix of Escherichia coli thioredoxin.

PubMed

de Lamotte-Guéry, F; Pruvost, C; Minard, P; Delsuc, M A; Miginiac-Maslow, M; Schmitter, J M; Stein, M; Decottignies, P

1997-12-01

Proline 40 in Escherichia coli thioredoxin is located close to the redox active site (Cys32-Cys35) within the alpha2 helix. The conservation of this residue among most of the thioredoxins suggests that it could play an important role in the structure and/or function of this protein. We have substituted Pro40 for Ala by using site-directed mutagenesis and expressed the mutant P40A in E.coli. The effects of the mutation on the biophysical and biological properties of thioredoxin have been analyzed and compared with molecular dynamics simulations. Modeling predicted that the replacement of Pro40 by Ala induced a displacement of the active site which exposes Trp31 to the solvent and opens a cleft located between helices alpha2 and alpha3. The solvation free energy (SFE) calculation also indicated that P40A became more hydrophobic as W31 became more accessible. These predictions were totally in agreement with the experimental results. The mutant P40A exhibited chromatographic behavior and fluorescence properties very different from those of the wild-type (WT) protein, in relationship with the displacement of W31. The determination of the free energy of unfolding of P40A showed that the mutant was globally destabilized by 2.9 kcal/mol. However, the effect of the mutation on the transition curve was highly unusual as the midpoint of the unfolding transition increased, indicating that some local structures were actually stabilized by the mutation. Despite these structural modifications, neither the ability of the protein to reduce a chloroplastic enzyme nor its reactivity with the bacterial reductase decreased. The only functional difference was the higher stability of P40A in light activation of NADP-malate dehydrogenase under air, which suggests that the mutant was less rapidly re-oxidized than WT. Therefore, it can be concluded that Pro40 is not essential for maintaining the redox function of thioredoxin but rather is required for the stability of the protein.

Response of the Pre-Oriented Goal-Directed Attention to Usual and Unusual Distractors: A Preliminary Study

PubMed Central

Baghdadi, Golnaz; Towhidkhah, Farzad; Rostami, Reza; Raza, Mohsen

2017-01-01

Introduction: In this study, we investigated the distraction power of the unusual and usual images on the attention of 20 healthy primary school children. Methods: Our study was different from previous ones in that the participants were asked to fix the initial position of their attention on a predefined location after being presented with unusual images as distractors. The goals were presented in locations, which were far from the attraction basin of distractors. We expected that the pre-orienting of the attention to the position of targets would reduce the attractive effect of unusual images compared to the usual ones. The percentage of correct responses and the reaction time were measured as behavioral indicators of attention performance. Results: Results showed that using the goal-directed attention, subjects ignored both kinds of distractors nearly the same way. Conclusion: With regard to previous reports about more attraction towards the unusual images, it is suggested that the dynamics of the visual attention system be sensitive to the initial condition. That is, changing the initial position of the attention can lead to the decrement of the unusual images effects. However, several other possibilities such as a probable delay in processing unusual features could explain this observation, too. PMID:28540000

Simulation of electron-proton coupling with a Monte Carlo method: application to cytochrome c3 using continuum electrostatics.

PubMed Central

Baptista, A M; Martel, P J; Soares, C M

1999-01-01

A new method is presented for simulating the simultaneous binding equilibrium of electrons and protons on protein molecules, which makes it possible to study the full equilibrium thermodynamics of redox and protonation processes, including electron-proton coupling. The simulations using this method reflect directly the pH and electrostatic potential of the environment, thus providing a much closer and realistic connection with experimental parameters than do usual methods. By ignoring the full binding equilibrium, calculations usually overlook the twofold effect that binding fluctuations have on the behavior of redox proteins: first, they affect the energy of the system by creating partially occupied sites; second, they affect its entropy by introducing an additional empty/occupied site disorder (here named occupational entropy). The proposed method is applied to cytochrome c3 of Desulfovibrio vulgaris Hildenborough to study its redox properties and electron-proton coupling (redox-Bohr effect), using a continuum electrostatic method based on the linear Poisson-Boltzmann equation. Unlike previous studies using other methods, the full reduction order of the four hemes at physiological pH is successfully predicted. The sites more strongly involved in the redox-Bohr effect are identified by analysis of their titration curves/surfaces and the shifts of their midpoint redox potentials and pKa values. Site-site couplings are analyzed using statistical correlations, a method much more realistic than the usual analysis based on direct interactions. The site found to be more strongly involved in the redox-Bohr effect is propionate D of heme I, in agreement with previous studies; other likely candidates are His67, the N-terminus, and propionate D of heme IV. Even though the present study is limited to equilibrium conditions, the possible role of binding fluctuations in the concerted transfer of protons and electrons under nonequilibrium conditions is also discussed. The occupational entropy contributions to midpoint redox potentials and pKa values are computed and shown to be significant. PMID:10354425

Ligand-hole localization in oxides with unusual valence Fe

PubMed Central

Chen, Wei-Tin; Saito, Takashi; Hayashi, Naoaki; Takano, Mikio; Shimakawa, Yuichi

2012-01-01

Unusual high-valence states of iron are stabilized in a few oxides. A-site-ordered perovskite-structure oxides contain such iron cations and exhibit distinct electronic behaviors at low temperatures, e.g. charge disproportionation (4Fe4+ → 2Fe3+ + 2Fe5+) in CaCu3Fe4O12 and intersite charge transfer (3Cu2+ + 4Fe3.75+ → 3Cu3+ + 4Fe3+) in LaCu3Fe4O12. Here we report the synthesis of solid solutions of CaCu3Fe4O12 and LaCu3Fe4O12 and explain how the instabilities of their unusual valence states of iron are relieved. Although these behaviors look completely different from each other in simple ionic models, they can both be explained by the localization of ligand holes, which are produced by the strong hybridization of iron d and oxygen p orbitals in oxides. The localization behavior in the charge disproportionation of CaCu3Fe4O12 is regarded as charge ordering of the ligand holes, and that in the intersite charge transfer of LaCu3Fe4O12 is regarded as a Mott transition of the ligand holes. PMID:22690318

Childhood and Current Autistic Features in Adolescents with Schizotypal Personality Disorder

PubMed Central

Esterberg, Michelle L.; Trotman, Hanan D.; Brasfield, Joy L.; Compton, Michael T.; Walker, Elaine F.

2008-01-01

The diagnostic boundaries between autistic- and schizophrenia-spectrum disorders have varied over the years, and some overlap in diagnostic criteria persists. The present study examined childhood and current signs of autistic disorder (AD) in adolescents with schizotypal personality disorder (SPD) or other personality disorders, as well as healthy controls. A structured interview was administered to rate participants’ current symptoms. Participants’ guardians were interviewed with the Autism Diagnostic Inventory-Revised (ADI-R), a clinical assessment of childhood and current autistic signs. Compared to both the other personality-disordered and healthy groups, adolescents with SPD were rated as having significantly more impairment on childhood and current social functioning, and having more unusual interests and behaviors. For the entire sample, impaired childhood social functioning and unusual interests and behaviors were associated with higher negative symptom scores. Current impairments in social functioning, unusual interests and behaviors, and communication were also linked with greater negative symptoms. However, neither childhood nor current autistic features significantly predicted later conversion to an Axis I psychotic disorder over the course of three years of follow-up. The findings indicate that past and current autistic signs are more common in adolescents with SPD, but neither current nor childhood autistic features are linked with conversion to psychosis. PMID:18554872

Cyclic Voltammetry Experiment.

ERIC Educational Resources Information Center

Van Benschoten, James J.; And Others

1983-01-01

Describes a three-part experiment designed to introduce cyclic voltammetry to graduate/undergraduate students. Part 1 demonstrates formal reduction potential, redox electron transfer, diffusion coefficient, and electrochemical reversibility. Part 2 investigates electrochemical behavior of acetaminophen. Part 3 examines such experimental variables…

Synthesis of 2-Azulenyltetrathiafulvalenes by Palladium-Catalyzed Direct Arylation of 2-Chloroazulenes with Tetrathiafulvalene and Their Optical and Electrochemical Properties.

PubMed

Shoji, Taku; Araki, Takanori; Sugiyama, Shuhei; Ohta, Akira; Sekiguchi, Ryuta; Ito, Shunji; Okujima, Tetsuo; Toyota, Kozo

2017-02-03

Tetrathiafulvalene (TTF) derivatives with 2-azulenyl substituents 5-11 were prepared by the palladium-catalyzed direct arylation reaction of 2-chloroazulenes with TTF in good yield. Photophysical properties of these compounds were investigated by UV-vis spectroscopy and theoretical calculations. Redox behavior of the novel azulene-substituted TTFs was examined by using cyclic voltammetry and differential pulse voltammetry, which revealed their multistep electrochemical oxidation and/or reduction properties. Moreover, these TTF derivatives showed significant spectral change in the visible region under the redox conditions.

Trace elements in coal ash

USGS Publications Warehouse

Deonarine, Amrika; Kolker, Allan; Doughten, Michael W.

2015-01-01

In this fact sheet, the form, distribution, and behavior of trace elements of environmental interest in samples of coal fly ash were investigated in response to concerns about element mobility in the event of an ash spill. The study includes laboratory-based leaching experiments to examine the behavior of trace elements, such as arsenic (As) and chromium (Cr), in response to key environmental factors including redox conditions (degree of oxygenation), which are known to vary with depth within coal ash impoundments and in natural ecosystems. The experiments show that As dissolves from samples of coal fly ash into simulated freshwater under both oxic (highly oxygenated) and anoxic (poorly oxygenated) conditions, whereas dissolved Cr concentrations are very redox dependent. This U.S. Geological Survey research helps define the distribution of elements such as As in coal ash and shows that element mobility can vary considerably under different conditions expected in the environment.

Faradic redox active material of Cu7S4 nanowires with a high conductance for flexible solid state supercapacitors

NASA Astrophysics Data System (ADS)

Javed, Muhammad Sufyan; Dai, Shuge; Wang, Mingjun; Xi, Yi; Lang, Qiang; Guo, Donglin; Hu, Chenguo

2015-08-01

The exploration of high Faradic redox active materials with the advantages of low cost and low toxicity has been attracting great attention for producing high energy storage supercapacitors. Here, the high Faradic redox active material of Cu7S4-NWs coated on a carbon fiber fabric (CFF) is directly used as a binder-free electrode for a high performance flexible solid state supercapacitor. The Cu7S4-NW-CFF supercapacitor exhibits excellent electrochemical performance such as a high specific capacitance of 400 F g-1 at the scan rate of 10 mV s-1 and a high energy density of 35 Wh kg-1 at a power density of 200 W kg-1, with the advantages of a light weight, high flexibility and long term cycling stability by retaining 95% after 5000 charge-discharge cycles at a constant current of 10 mA. The high Faradic redox activity and high conductance behavior of the Cu7S4-NWs result in a high pseudocapacitive performance with a relatively high specific energy and specific power. Such a new type of pseudocapacitive material of Cu7S4-NWs with its low cost is very promising for actual application in supercapacitors.The exploration of high Faradic redox active materials with the advantages of low cost and low toxicity has been attracting great attention for producing high energy storage supercapacitors. Here, the high Faradic redox active material of Cu7S4-NWs coated on a carbon fiber fabric (CFF) is directly used as a binder-free electrode for a high performance flexible solid state supercapacitor. The Cu7S4-NW-CFF supercapacitor exhibits excellent electrochemical performance such as a high specific capacitance of 400 F g-1 at the scan rate of 10 mV s-1 and a high energy density of 35 Wh kg-1 at a power density of 200 W kg-1, with the advantages of a light weight, high flexibility and long term cycling stability by retaining 95% after 5000 charge-discharge cycles at a constant current of 10 mA. The high Faradic redox activity and high conductance behavior of the Cu7S4-NWs result in a high pseudocapacitive performance with a relatively high specific energy and specific power. Such a new type of pseudocapacitive material of Cu7S4-NWs with its low cost is very promising for actual application in supercapacitors. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr03363b

Ingestion Reiterada de Cuerpos Extranos. Forma Inusual de Presentacion del Sindrome de Munchausen por Poderes (Reiterated Ingestion of Foreign Bodies. Unusual Form of Presentation of Munchausen Syndrome by Proxy).

ERIC Educational Resources Information Center

Terreros, I. Gomez de; And Others

1996-01-01

An unusual case of Munchausen syndrome by proxy is reported. A mother with a psychiatric record of behavior disorders and family dysfunction perpetrated the ingestion of foreign bodies (for example, earrings, a screw, sewing needles) on a 10-month-old infant with a history of prematurity, repeated visits to emergency rooms, and nonjustified…

Electron nematic fluid in a strained S r3R u2O7 film

NASA Astrophysics Data System (ADS)

Marshall, Patrick B.; Ahadi, Kaveh; Kim, Honggyu; Stemmer, Susanne

2018-04-01

S r3R u2O7 belongs to the family of layered strontium ruthenates and exhibits a range of unusual emergent properties, such as electron nematic behavior and metamagnetism. Here, we show that epitaxial film strain significantly modifies these phenomena. In particular, we observe enhanced magnetic interactions and an electron nematic phase that extends to much higher temperatures and over a larger magnetic-field range than in bulk single crystals. Furthermore, the films show an unusual anisotropic non-Fermi-liquid behavior that is controlled by the direction of the applied magnetic field. At high magnetic fields, the metamagnetic transition to a ferromagnetic phase recovers isotropic Fermi-liquid behavior. The results support the interpretation that these phenomena are linked to the special features of the Fermi surface, which can be tuned by both film strain and an applied magnetic field.

Older Adults and Mental Health

MedlinePlus

... Join A Study News & Events News & Events Home Science News Meetings and Events Multimedia Social Media Press Resources Newsletters NIMH News Feeds About ... or behaviors that interfere with work, family, or social life Unusual thinking or behaviors that ... 2016 • Science Update An individualized program of follow-up treatment ...

Changes in Illness-Related Behavior and Dysphoria Accompanying Behavioral Treatment of Recurrent Headache.

ERIC Educational Resources Information Center

Rains, Jeanetta C.; Lohr, Jeffrey M.

Psychophysiologic research indicates that muscle-contraction headache often is not characterized by excessive or unusual muscular activity, and muscular changes seldom accompany headache improvement resulting from treatment. Multidimensional models have been proposed, which emphasize the interdependence of physiological and psychological systems…

Understanding Williams Syndrome: Behavioral Patterns and Interventions.

ERIC Educational Resources Information Center

Semel, Eleanor; Rosner, Sue R.

This guide to Williams syndrome (WS), a congenital disorder characterized by developmental/cognitive limitations but relatively high verbal and social skills, explains the strengths, difficulties and variations found among individuals with the condition and offers guidelines for intervention in the unusual properties of the WS behavioral profile.…

10 CFR 712.17 - Instructional requirements.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 10 Energy 4 2011-01-01 2011-01-01 false Instructional requirements. 712.17 Section 712.17 Energy DEPARTMENT OF ENERGY HUMAN RELIABILITY PROGRAM Establishment of and Procedures for the Human Reliability... responding to behavioral change and aberrant or unusual behavior that may result in a risk to national...

10 CFR 712.17 - Instructional requirements.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 10 Energy 4 2012-01-01 2012-01-01 false Instructional requirements. 712.17 Section 712.17 Energy DEPARTMENT OF ENERGY HUMAN RELIABILITY PROGRAM Establishment of and Procedures for the Human Reliability... responding to behavioral change and aberrant or unusual behavior that may result in a risk to national...

10 CFR 712.17 - Instructional requirements.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 10 Energy 4 2013-01-01 2013-01-01 false Instructional requirements. 712.17 Section 712.17 Energy DEPARTMENT OF ENERGY HUMAN RELIABILITY PROGRAM Establishment of and Procedures for the Human Reliability... responding to behavioral change and aberrant or unusual behavior that may result in a risk to national...

10 CFR 712.17 - Instructional requirements.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 10 Energy 4 2014-01-01 2014-01-01 false Instructional requirements. 712.17 Section 712.17 Energy DEPARTMENT OF ENERGY HUMAN RELIABILITY PROGRAM Establishment of and Procedures for the Human Reliability... responding to behavioral change and aberrant or unusual behavior that may result in a risk to national...

Possible Electromagnetic Effects on Abnormal Animal Behavior Before an Earthquake

PubMed Central

Hayakawa, Masashi

2013-01-01

Simple Summary Possible electromagnetic effects on abnormal animal behavior before earthquakes. Abstract The former statistical properties summarized by Rikitake (1998) on unusual animal behavior before an earthquake (EQ) have first been presented by using two parameters (epicentral distance (D) of an anomaly and its precursor (or lead) time (T)). Three plots are utilized to characterize the unusual animal behavior; (i) EQ magnitude (M) versus D, (ii) log T versus M, and (iii) occurrence histogram of log T. These plots are compared with the corresponding plots for different seismo-electromagnetic effects (radio emissions in different frequency ranges, seismo-atmospheric and -ionospheric perturbations) extensively obtained during the last 15–20 years. From the results of comparisons in terms of three plots, it is likely that lower frequency (ULF (ultra-low-frequency, f ≤ 1 Hz) and ELF (extremely-low-frequency, f ≤ a few hundreds Hz)) electromagnetic emissions exhibit a very similar temporal evolution with that of abnormal animal behavior. It is also suggested that a quantity of field intensity multiplied by the persistent time (or duration) of noise would play the primary role in abnormal animal behavior before an EQ. PMID:26487307

Enhanced performance of ultracapacitors using redox additive-based electrolytes

NASA Astrophysics Data System (ADS)

Jain, Dharmendra; Kanungo, Jitendra; Tripathi, S. K.

2018-05-01

Different concentrations of potassium iodide (KI) as redox additive had been added to 1 M sulfuric acid (H2SO4) electrolyte with an aim of enhancing the capacitance and energy density of ultracapacitors via redox reactions at the interfaces of electrode-electrolyte. Ultracapacitors were fabricated using chemically treated activated carbon as electrode with H2SO4 and H2SO4-KI as an electrolyte. The electrochemical performances of fabricated supercapacitors were investigated by impedance spectroscopy, cyclic voltammetry and charge-discharge techniques. The maximum capacitance ` C' was observed with redox additives-based electrolyte system comprising 1 M H2SO4-0.3 M KI (1072 F g- 1), which is very much higher than conventional 1 M H2SO4 (61.3 F g- 1) aqueous electrolyte-based ultracapacitors. It corresponds to an energy density of 20.49 Wh kg- 1 at 2.1 A g- 1 for redox additive-based electrolyte, which is six times higher as compared to that of pristine electrolyte (1 M H2SO4) having energy density of only 3.36 Wh kg- 1. The temperature dependence behavior of fabricated cell was also analyzed, which shows increasing pattern in its capacitance values in a temperature range of 5-70 °C. Under cyclic stability test, redox electrolyte-based system shows almost 100% capacitance retention up to 5000 cycles and even more. For comparison, ultracapacitors based on polymer gel electrolyte polyvinyl alcohol (PVA) (10 wt%)—{H2SO4 (1 M)-KI (0.3 M)} (90 wt%) have been fabricated and characterized with the same electrode materials.

Arsenic behavior in river sediments under redox gradient: a review.

PubMed

Gorny, Josselin; Billon, Gabriel; Lesven, Ludovic; Dumoulin, David; Madé, Benoît; Noiriel, Catherine

2015-02-01

The fate of arsenic - a redox sensitive metalloid - in surface sediments is closely linked to early diagenetic processes. The review presents the main redox mechanisms and final products of As that have been evidenced over the last years. Oxidation of organic matter and concomitant reduction of oxidants by bacterial activity result in redox transformations of As species. The evolution of the sediment reactivity will also induce secondary abiotic reactions like complexation/de-complexation, sorption, precipitation/dissolution and biotic reactions that could, for instance, lead to the detoxification of some As species. Overall, abiotic redox reactions that govern the speciation of As mostly involve manganese (hydr)-oxides and reduced sulfur species produced by the sulfate-reducing bacteria. Bacterial activity is also responsible for the inter-conversion between As(V) and As(III), as well as for the production of methylated arsenic species. In surficial sediments, sorption processes also control the fate of inorganic As(V), through the formation of inner sphere complexes with iron (hydr)-oxides, that are biologically reduced in buried sediment. Arsenic species can also be bound to organic matter, either directly to functional groups or indirectly through metal complexes. Finally, even if the role of reduced sulfur species in the cycling of arsenic in sediments has been evidenced, some of the transformations remain hypothetical and deserve further investigation. Copyright © 2014 Elsevier B.V. All rights reserved.

Ultramicroelectrode voltammetry and scanning electrochemical microscopy in room-temperature ionic liquid electrolytes.

PubMed

Walsh, Darren A; Lovelock, Kevin R J; Licence, Peter

2010-11-01

The high viscosity and unusual properties of room temperature ionic liquids (RTILs) present a number of challenges when performing steady-state voltammetry and scanning electrochemical microscopy in RTILs. These include difficulties in recording steady-state currents at ultramicroelectrode surfaces due to low diffusion coefficients of redox species and problems associated with unequal diffusion coefficients of oxidised and reduced species in RTILs. In this tutorial review, we highlight the recent progress in the use of RTILs as electrolytes for ultramicroelectrode voltammetry and SECM. We describe the basic principles of ultramicroelectrode voltammetry and SECM and, using examples from the recent literature, we discuss the conditions that must be met to perform steady-state voltammetry and SECM measurements in RTILs. Finally, we briefly discuss the electrochemical insights that can be obtained from such measurements.

Assessment and Management of Unusual Auditory Behavior in Infants and Toddlers.

ERIC Educational Resources Information Center

Kile, Jack E.; And Others

1994-01-01

This article describes assessment and management strategies for infants and toddlers with normal hearing or fluctuating conductive hearing loss, who are identified as having central auditory impairment and/or judged to have abnormal auditory behavior. Management strategies include audiologic, medical, and speech and language management. Three case…

Influence of Sulfur Metalation on the Accessibility of the Ni(II/I) Couple in [N,N'-Bis(2-mercaptoethyl)-1,5-diazacyclooctanato]nickel(II): Insight into the Redox Properties of [NiFe]-Hydrogenase.

PubMed

Musie, Ghezai; Farmer, Patrick J.; Tuntulani, Thawatchai; Reibenspies, Joseph H.; Darensbourg, Marcetta Y.

1996-04-10

A redox model study of [NiFe] hydrogenase has examined a series of five polymetallics based on the metalation of the dithiolate complex [1,5-bis(mercaptoethyl)-1,5-diazacyclooctane]Ni(II), Ni-1. Crystal structures of three polymetallics of the series have been reported earlier: [(Ni-1)(2)()Ni]Cl(2)(), [(Ni-1)(2)()FeCl(2)()](2)(), and [(Ni-1)(3)()(ZnCl)(2)()]Cl(2)(). Two are described here: [(Ni-1)(2)()Pd]Cl(2)().2H(2)()Ocrystallizes in the monoclinic system, space group P2(1)/c with cell constants a = 12.212(4) Å, b = 7.642(2) Å, c = 16.625(3) Å, beta = 107.69(2) degrees, V = 1443.230(0) Å(3), Z = 2, R = 0.051, and R(w) = 0.056. [(Ni-1)(2)()CoCl]PF(6)() crystallizes in the triclinic system, space group P&onemacr;, with cell constants a = 8.14(2) Å, b = 13.85(2) Å, c = 15.67(2) Å, alpha = 113.59(10) degrees, beta = 101.84(14) degrees, gamma = 94.0(2) degrees, V = 1561.620(0)Å(3), Z = 2, R = 0.072, and R(w) = 0.077. In all Ni-1 serves as a bidentate metallothiolate ligand with a "hinge" angle in the range 105-118 degrees and Ni-M distances of 2.7- 3.7 Å. The most accessible redox event is shown by EPR and electrochemistry to reside in the N(2)S(2)Ni unit and is the Ni(II/I) couple. Charge neutralization of the thiolate sulfurs by metalation can (dependent on the interacting metal) stabilize the Ni(I) state as efficiently as methylation forming a thioether. The implication of these results for the heterometallic active site of [NiFe]-hydrogenase as structured from Desulfovibrio gigas (Volbeda, A., et al. Nature, 1995, 373, 580), the generality of the Ni(&mgr;-SR)(2)M hinge structure, and a possible explanation for the unusual redox potentials are discussed.

Unpacking paleoenvironmental change across OAE2 using paired d34S records of pyrite and organic matter

NASA Astrophysics Data System (ADS)

Raven, M. R.; Gomes, M.; Fike, D. A.

2017-12-01

Pyrite sulfur isotopes have proven to be a powerful tool for reconstructing major changes in global redox state and the emergence of microbial metabolisms. Still, pyrite can be a challenging archive, as its formation depends on the availability of reactive iron species and can occur over multiple generations of sedimentary processes. Accordingly, pyrite δ34S records commonly have large point-to-point variability reflecting local processes. By pairing pyrite δ34S records with those of coexisting organic matter (OM), including both kerogens and extractable bitumens, we can begin to parse the various potential causes of this variability and gain greater insights into changes in the sedimentary paleoenvironment. Here, we present the first collection of records of OM δ34S for the Cretaceous, focusing on sections spanning Ocean Anoxic Event 2 (OAE2, 94 Mya), a period of globally widespread marine anoxia and carbon cycle disruption. In carbonates and shales from OAE2 in Pont d'Issole, France, pyrite and OM δ34S values vary in parallel throughout most of the section, consistent with their shared sulfide source. There are also distinct exceptions: In one interval, an excursion in pyrite δ34S is entirely absent from the organic sulfur record but associated with unusual organic sulfur redox speciation (by XAS), potentially reflecting later exposure to oxic porewaters. Across the core interval of shale deposition during OAE2, the offset between pyrite and OM δ34S values declines smoothly from +17.4 to -7.9‰, which we interpret in terms of changes in the speciation of detrital iron minerals that may have regional implications. We then compare these results with data for other well-characterized OAE2 sections, including Cismon (Italy), Tarfaya (Morocco), and the Demerara Rise (offshore Brazil), which represent environments with a variety of apparent redox states. These paired pyrite - OM δ34S profiles yield new information about how the local and global forcings associated with OAE2 impacted environmental redox states, which in turn drove major changes in microbial energy cycling and sulfur and carbon burial fluxes during this critical period of Earth history.

Urologic sequelae of childhood genitourinary trauma and abuse in men: principles of recognition with fifteen case illustrations.

PubMed

McCarty, T; Roberts, L W; Hendrickson, K

1996-05-01

Providing urologic care to men who have been traumatized during childhood may be especially challenging because of the extent, severity, and unusual character of their urogenital problems. Recognition of past trauma entails attentiveness to patients' background and behaviors. As illustrated through these 15 cases, patients who present with too many past surgeries, too many unremitting urologic complaints, too little sexual function and too few genital parts, sexual impulses that are too strong, sexualized conduct in clinical settings, and self-destructive behaviors surrounding sexuality may have experienced trauma in the past. While empirical studies are necessary to demonstrate the ultimate utility of these categories, appreciation of these clinical indications improves the urologic care provided to traumatized men in four ways: by elucidating unusual and unusually recalcitrant urologic complaints, thereby clarifying clinical decisions; by allowing for appropriate use of psychiatric consultation; by promoting a better understanding of the sequelae of trauma in men; and by alleviating the discomfort naturally felt by urologists and their staff when caring for these difficult, multiproblem patients.

Neuronal Nitric Oxide Synthase and NADPH Oxidase Interact to Affect Cognitive, Affective, and Social Behaviors in Mice

PubMed Central

Walton, James C.; Selvakumar, Balakrishnan; Weil, Zachary M.; Snyder, Solomon H.; Nelson, Randy J.

2013-01-01

Both nitric oxide (NO) and reactive oxygen species (ROS) generated by nNOS and NADPH oxidase (NOX), respectively, in the brain have been implicated in an array of behaviors ranging from learning and memory to social interactions. Although recent work has elucidated how these separate redox pathways regulate neural function and behavior, the interaction of these two pathways in the regulation of neural function and behavior remains unspecified. Toward this end, the p47phox subunit of NOX, and nNOS were deleted to generate double knockout mice that were used to characterize the behavioral outcomes of concurrent impairment of the NO and ROS pathways in the brain. Mice were tested in a battery of behavioral tasks to evaluate learning and memory, as well as social, affective, and cognitive behaviors. p47phox deletion did not affect depressive-like behavior, whereas nNOS deletion abolished it. Both p47phox and nNOS deletion singly reduced anxiety-like behavior, increased general locomotor activity, impaired spatial learning and memory, and impaired preference for social novelty. Deletion of both genes concurrently had synergistic effects to elevate locomotor activity, impair spatial learning and memory, and disrupt prepulse inhibition of acoustic startle. Although preference for social novelty was impaired in single knockouts, double knockout mice displayed elevated levels of preference for social novelty above that of wild type littermates. These data demonstrate that, depending upon modality, deletion of p47phox and nNOS genes have dissimilar, similar, or additive effects. The current findings provide evidence that the NOX and nNOS redox signaling cascades interact in the brain to affect both cognitive function and social behavior. PMID:23948215

The Reactive Sulfur Species Concept: 15 Years On.

PubMed

Giles, Gregory I; Nasim, Muhammad Jawad; Ali, Wesam; Jacob, Claus

2017-05-23

Fifteen years ago, in 2001, the concept of "Reactive Sulfur Species" or RSS was advocated as a working hypothesis. Since then various organic as well as inorganic RSS have attracted considerable interest and stimulated many new and often unexpected avenues in research and product development. During this time, it has become apparent that molecules with sulfur-containing functional groups are not just the passive "victims" of oxidative stress or simple conveyors of signals in cells, but can also be stressors in their own right, with pivotal roles in cellular function and homeostasis. Many "exotic" sulfur-based compounds, often of natural origin, have entered the fray in the context of nutrition, ageing, chemoprevention and therapy. In parallel, the field of inorganic RSS has come to the forefront of research, with short-lived yet metabolically important intermediates, such as various sulfur-nitrogen species and polysulfides (S x 2- ), playing important roles. Between 2003 and 2005 several breath-taking discoveries emerged characterising unusual sulfur redox states in biology, and since then the truly unique role of sulfur-dependent redox systems has become apparent. Following these discoveries, over the last decade a "hunt" and, more recently, mining for such modifications has begun-and still continues-often in conjunction with new, innovative and complex labelling and analytical methods to capture the (entire) sulfur "redoxome". A key distinction for RSS is that, unlike oxygen or nitrogen, sulfur not only forms a plethora of specific reactive species, but sulfur also targets itself, as sulfur containing molecules, i.e., peptides, proteins and enzymes, preferentially react with RSS. Not surprisingly, today this sulfur-centred redox signalling and control inside the living cell is a burning issue, which has moved on from the predominantly thiol/disulfide biochemistry of the past to a complex labyrinth of interacting signalling and control pathways which involve various sulfur oxidation states, sulfur species and reactions. RSS are omnipresent and, in some instances, are even considered as the true bearers of redox control, perhaps being more important than the Reactive Oxygen Species (ROS) or Reactive Nitrogen Species (RNS) which for decades have dominated the redox field. In other(s) words, in 2017, sulfur redox is "on the rise", and the idea of RSS resonates throughout the Life Sciences. Still, the RSS story isn't over yet. Many RSS are at the heart of "mistaken identities" which urgently require clarification and may even provide the foundations for further scientific revolutions in the years to come. In light of these developments, it is therefore the perfect time to revisit the original hypotheses, to select highlights in the field and to question and eventually update our concept of "Reactive Sulfur Species".

The Reactive Sulfur Species Concept: 15 Years On

PubMed Central

Giles, Gregory I.; Nasim, Muhammad Jawad; Ali, Wesam; Jacob, Claus

2017-01-01

Fifteen years ago, in 2001, the concept of “Reactive Sulfur Species” or RSS was advocated as a working hypothesis. Since then various organic as well as inorganic RSS have attracted considerable interest and stimulated many new and often unexpected avenues in research and product development. During this time, it has become apparent that molecules with sulfur-containing functional groups are not just the passive “victims” of oxidative stress or simple conveyors of signals in cells, but can also be stressors in their own right, with pivotal roles in cellular function and homeostasis. Many “exotic” sulfur-based compounds, often of natural origin, have entered the fray in the context of nutrition, ageing, chemoprevention and therapy. In parallel, the field of inorganic RSS has come to the forefront of research, with short-lived yet metabolically important intermediates, such as various sulfur-nitrogen species and polysulfides (Sx2−), playing important roles. Between 2003 and 2005 several breath-taking discoveries emerged characterising unusual sulfur redox states in biology, and since then the truly unique role of sulfur-dependent redox systems has become apparent. Following these discoveries, over the last decade a “hunt” and, more recently, mining for such modifications has begun—and still continues—often in conjunction with new, innovative and complex labelling and analytical methods to capture the (entire) sulfur “redoxome”. A key distinction for RSS is that, unlike oxygen or nitrogen, sulfur not only forms a plethora of specific reactive species, but sulfur also targets itself, as sulfur containing molecules, i.e., peptides, proteins and enzymes, preferentially react with RSS. Not surprisingly, today this sulfur-centred redox signalling and control inside the living cell is a burning issue, which has moved on from the predominantly thiol/disulfide biochemistry of the past to a complex labyrinth of interacting signalling and control pathways which involve various sulfur oxidation states, sulfur species and reactions. RSS are omnipresent and, in some instances, are even considered as the true bearers of redox control, perhaps being more important than the Reactive Oxygen Species (ROS) or Reactive Nitrogen Species (RNS) which for decades have dominated the redox field. In other(s) words, in 2017, sulfur redox is “on the rise”, and the idea of RSS resonates throughout the Life Sciences. Still, the RSS story isn’t over yet. Many RSS are at the heart of “mistaken identities” which urgently require clarification and may even provide the foundations for further scientific revolutions in the years to come. In light of these developments, it is therefore the perfect time to revisit the original hypotheses, to select highlights in the field and to question and eventually update our concept of “Reactive Sulfur Species”. PMID:28545257

40 CFR 797.1400 - Fish acute toxicity test.

Code of Federal Regulations, 2013 CFR

2013-07-01

... appearance or physiology such as discoloration, excessive mucous production, hyperventilation, opaque eyes... showing signs of stress, such as discoloration, hemorrhaging, disorientation or other unusual behavior...

40 CFR 797.1400 - Fish acute toxicity test.

Code of Federal Regulations, 2014 CFR

2014-07-01

... appearance or physiology such as discoloration, excessive mucous production, hyperventilation, opaque eyes... showing signs of stress, such as discoloration, hemorrhaging, disorientation or other unusual behavior...

40 CFR 797.1400 - Fish acute toxicity test.

Code of Federal Regulations, 2012 CFR

2012-07-01

... appearance or physiology such as discoloration, excessive mucous production, hyperventilation, opaque eyes... showing signs of stress, such as discoloration, hemorrhaging, disorientation or other unusual behavior...

Effect of thiamine hydrochloride on the redox reactions of iron at pyrite surface. [Fourth quarterly techical progress report, September 1990--November 1990

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pesic, B.; Oliver, D.J.

1990-12-31

The present investigation is a part of our studies on the electro chemical aspects of pyrite bioleaching involving Thiobacillus ferrooxidans. Previously (1,2) we have examined the effect of T. ferrooxidans and their metabolic products on the redox reactions of Fe{sup 2+}/Fe{sup 3+} couple at the pyrite surface. Results obtained suggest that beyond 1. 5 days during their growth in a batch fermenter, the bacteria and their metabolic products completely cover the pyrite surface and shut down all electron transfer across the electrode-solution interface. In addition, it has been observed that the bacteria serve as the nucleation site for jarosite formation,more » which is found detrimental to bioleaching. In the present work we have focussed on the effect of the presence of vitamins on the redox chemistry of iron. Our examination of the effect of the presence of thiamine hydrochloride in the redox behavior of Fe{sup 2+}/Fe{sup 3+} at the pyrite surface has revealed that thiamine hydrochloride does not undergo chemical interaction with ferrous or ferric iron. However, it may adsorb onto the pyrite surface causing polarization of the pyrite electrode.« less

Effect of thiamine hydrochloride on the redox reactions of iron at pyrite surface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pesic, B.; Oliver, D.J.

1990-01-01

The present investigation is a part of our studies on the electro chemical aspects of pyrite bioleaching involving Thiobacillus ferrooxidans. Previously (1,2) we have examined the effect of T. ferrooxidans and their metabolic products on the redox reactions of Fe[sup 2+]/Fe[sup 3+] couple at the pyrite surface. Results obtained suggest that beyond 1. 5 days during their growth in a batch fermenter, the bacteria and their metabolic products completely cover the pyrite surface and shut down all electron transfer across the electrode-solution interface. In addition, it has been observed that the bacteria serve as the nucleation site for jarosite formation,more » which is found detrimental to bioleaching. In the present work we have focussed on the effect of the presence of vitamins on the redox chemistry of iron. Our examination of the effect of the presence of thiamine hydrochloride in the redox behavior of Fe[sup 2+]/Fe[sup 3+] at the pyrite surface has revealed that thiamine hydrochloride does not undergo chemical interaction with ferrous or ferric iron. However, it may adsorb onto the pyrite surface causing polarization of the pyrite electrode.« less

Reduced Mu Power in Response to Unusual Actions Is Context-Dependent in 1-Year-Olds

PubMed Central

Langeloh, Miriam; Buttelmann, David; Matthes, Daniel; Grassmann, Susanne; Pauen, Sabina; Hoehl, Stefanie

2018-01-01

During social interactions infants predict and evaluate other people’s actions. Previous behavioral research found that infants’ imitation of others’ actions depends on these evaluations and is context-dependent: 1-year-olds predominantly imitated an unusual action (turning on a lamp with one’s forehead) when the model’s hands were free compared to when the model’s hands were occupied or restrained. In the present study, we adapted this behavioral paradigm to a neurophysiological study measuring infants’ brain activity while observing usual and unusual actions via electroencephalography. In particular, we measured differences in mu power (6 – 8 Hz) associated with motor activation. In a between-subjects design, 12- to 14-month-old infants watched videos of adult models demonstrating that their hands were either free or restrained. Subsequent test frames showed the models turning on a lamp or a soundbox by using their head or their hand. Results in the hands-free condition revealed that 12- to 14-month-olds displayed a reduction of mu power in frontal regions in response to unusual and thus unexpected actions (head touch) compared to usual and expected actions (hand touch). This may be explained by increased motor activation required for updating prior action predictions in response to unusual actions though alternative explanations in terms of general attention or cognitive control processes may also be considered. In the hands-restrained condition, responses in mu frequency band did not differ between action outcomes. This implies that unusual head-touch actions compared to hand-touch actions do not necessarily evoke a reduction of mu power. Thus, we conclude that reduction of mu frequency power is context-dependent during infants’ action perception. Our results are interpreted in terms of motor system activity measured via changes in mu frequency band as being one important neural mechanism involved in action prediction and evaluation from early on. PMID:29441034

Redox-Controlled Olefin (Co)Polymerization Catalyzed by Ferrocene-Bridged Phosphine-Sulfonate Palladium Complexes.

PubMed

Chen, Min; Yang, Bangpei; Chen, Changle

2015-12-14

The facile and reversible interconversion between neutral and oxidized forms of palladium complexes containing ferrocene-bridged phosphine sulfonate ligands was demonstrated. The activity of these palladium complexes could be controlled using redox reagents during ethylene homopolymerization, ethylene/methyl acrylate copolymerization, and norbornene oligomerization. Specifically in norbornene oligomerization, the neutral complexes were not active at all whereas the oxidized counterparts showed appreciable activity. In situ switching between the neutral and oxidized forms resulted in an interesting "off" and "on" behavior in norbornene oligomerization. This work provides a new strategy to control the olefin polymerization process. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Cave speleothems as repositories of microbial biosignatures

NASA Astrophysics Data System (ADS)

Miller, Ana Z.; Jurado, Valme; Pereira, Manuel F. C.; Fernández, Octavio; Calaforra, José M.; Dionísio, Amélia; Saiz-Jimenez, Cesareo

2015-04-01

The need to better understand the biodiversity, origins of life on Earth and on other planets, and the wide applications of the microbe-mineral interactions have led to a rapid expansion of interest in subsurface environments. Recently reported results indicated signs of an early wet Mars and rather recent volcanic activity which suggest that Mars's subsurface can house organic molecules or traces of microbial life, making the search for microbial life on Earth's subsurface even more compelling. Caves on Earth are windows into the subsurface that harbor a wide variety of mineral-utilizing microorganisms, which may contribute to the formation of biominerals and unusual microstructures recognized as biosignatures. These environments contain a wide variety of redox interfaces and stable physicochemical conditions, which enhance secondary mineral precipitation and microbial growth under limited organic nutrient inputs. Enigmatic microorganisms and unusual mineral features have been found associated with secondary mineral deposits or speleothems in limestone caves and lava tubes. In this study, Field Emission Scanning Electron Microscopy (FESEM) and Energy Dispersive X-ray spectroscopy (EDS) analyses were conducted on cave speleothem samples to assess microbe-mineral interactions, evaluate biogenicity, as well as to describe unusual mineral formations and microbial features. Microbial mats, extracellular polymeric substances, tubular empty sheaths, mineralized cells, filamentous fabrics, as well as "cell-sized" etch pits or microborings produced by bacterial cells were observed on minerals. These features evidence microbe-mineral interactions and may represent mineralogical signatures of life. We can thus consider that caves on Earth are plausible repositories of terrestrial biosignatures where we can look for microbial signatures. Acknowledgments: AZM acknowledges the support from the Marie Curie Intra-European Fellowship within the 7th European Community Framework Programme (PIEF-GA-2012-328689- DECAVE). The authors acknowledge the Spanish Ministry of Economy and Competitiveness (project CGL2013-41674-P) for financial support.

Clonazepam

MedlinePlus

... to your doctor, even if you experience side effects such as unusual changes in behavior or mood, ... constant movement) that may occur as a side effect of treatment with antipsychotic medications (medications for mental ...

Brivaracetam

MedlinePlus

... the medication works for you, and the side effects you experience. Be sure to tell your doctor ... to your doctor, even if you experience side effects such as unusual changes in behavior or mood. ...

Aripiprazole

MedlinePlus

... a mental illness that causes disturbed or unusual thinking, loss of interest in life, and strong or ... people who took medications such as aripiprazole developed gambling problems or other intense urges or behaviors that ...

Unusual reaction paths of SN2 nucleophile substitution reactions CH4 + H- → CH4 + H- and CH4 + F- → CH3F + H-: Quantum chemical calculations

NASA Astrophysics Data System (ADS)

Minyaev, Ruslan M.; Quapp, Wolfgang; Schmidt, Benjamin; Getmanskii, Ilya V.; Koval, Vitaliy V.

2013-11-01

Quantum chemical (CCSD(full)/6-311++G(3df,3pd), CCSD(T)(full)/6-311++G(3df,3pd)) and density function theory (B3LYP/6-311++G(3df,3pd)) calculations were performed for the SN2 nucleophile substitution reactions CH4 + H- → CH4 + H- and CH4 + F- → CH3F + H-. The calculated gradient reaction pathways for both reactions have an unusual behavior. An unusual stationary point of index 2 lies on the gradient reaction path. Using Newton trajectories for the reaction path, we can detect VRI point at which the reaction path branches.

Characteristics of challenging behaviours in adults with autistic disorder, PDD-NOS, and intellectual disability.

PubMed

Matson, Johnny L; Rivet, Tessa T

2008-12-01

Challenging behaviours are frequently a problem for people with autism spectrum disorders (ASD) and intellectual disability (ID). A better understanding of which individuals display which behaviours, at what rates, and the relationship of these behaviours to comorbid psychopathology would have important implications. A group of 161 adults with ASD (autistic disorder or Pervasive Developmental Disorder--Not Otherwise Specified [PDD-NOS]) and 159 matched controls with ID only residing in two large residential facilities in Southeastern United States, were studied using the Autism Spectrum Disorders--Behavior Problems for Adults (ASD-BPA). In all four categories of challenging behaviour measured by the ASD-BPA (Aggression/Destruction, Stereotypy, Self-Injurious Behavior, and Disruptive Behavior), frequency of challenging behaviours increased with severity of autistic symptoms. The greatest group differences were found for Stereotypy (repeated/unusual vocalisations/body movements and unusual object play), Self-Injurious Behavior (harming self and mouthing/swallowing objects), Aggression/Destruction (banging on objects), and Disruptive Behavior (elopement). Challenging behaviours in people with ASD and ID are barriers to effective education, training, and social development, and often persist throughout adulthood. Thus, programs designed to remediate such behaviours should continue across the life-span of these individuals.

Observation of a pretransitional effect near a virtual smectic-A--smectic-C* transition.

PubMed

Shibahara, S; Takanishi, Y; Yamamoto, J; Ogasawara, T; Ishikawa, K; Yokoyama, H; Takezoe, H

2001-06-01

Unusual softening of the layer compression modulus B has been observed near the phase boundary where the smectic-C* phase vanishes in a naphtalene-based liquid crystal mixture. From the systematic study of x-ray and layer compression measurements, this unusual effect is attributed to the pretransitional softening near a virtual smectic-A-smectic-C* phase transition in the smectic-A phase, which no longer appears on the thermoequilibrium phase diagram. This phenomenon is similar but not equivalent to supercritical behavior.

Being vs. Appearing Socially Uninterested: Challenging Assumptions about Social Motivation in Autism.

PubMed

Jaswal, Vikram K; Akhtar, Nameera

2018-06-19

Progress in psychological science can be limited by a number of factors, not least of which are the starting assumptions of scientists themselves. We believe that some influential accounts of autism rest on a questionable assumption that many of its behavioral characteristics indicate a lack of social interest-an assumption that is flatly contradicted by the testimony of many autistic people themselves. In this paper, we challenge this assumption by describing alternative explanations for four such behaviors: (a) low levels of eye contact, (b) infrequent pointing, (c) motor stereotypies, and (d) echolalia. The assumption that autistic people's unusual behaviors indicate diminished social motivation has had profound and often negative effects on the ways they are studied and treated. We argue that understanding and supporting autistic individuals will require interrogating this assumption, taking autistic testimony seriously, considering alternative explanations for unusual behaviors, and investigating unconventional-even idiosyncratic-ways that autistic individuals may express their social interest. These steps are crucial, we believe, for creating a more accurate, humane, and useful science of autism.

Unusual Stiffening and Elastic Response of Polyisobutylene Nanometric Thin Films

NASA Astrophysics Data System (ADS)

Yoon, Heedong; Wigham, Caleb; McKenna, Gregory

The TTU bubble inflation technique was used to study the elastic response and unusual stiffening behavior of nanometirc polyisobutylene (PIB) films. Mechanical properties and surface tension of PIB films were measured through the strain-stress response for film thicknesses ranging from 13 nm to 126 nm. The tests were performed at room temperature, far above the glass transition temperature of PIB. It is found that the stiffening increases with decreasing film thickness, while the surface tension is independent of the film thickness. Similar to the prior bubble inflation measurements in polymeric thin films, the thickness dependence of the stiffening followed a power law behavior in this case of Ds h1.5. These results are consistent with the Ngai et al proposition that rubbery stiffening is related to the separation of the α relaxation and Rouse modes. In addition, we compare stiffening index (S) with fragility (m) based on our prior observation that the S follows a linear behavior with dynamic m. Unlike other polymeric materials seen in prior bubble inflation measurements, the S of PIB does not follow the linear behavior with m.

Functionalized carbon nanotube based hybrid electrochemical capacitors using neutral bromide redox-active electrolyte for enhancing energy density

NASA Astrophysics Data System (ADS)

Tang, Xiaohui; Lui, Yu Hui; Chen, Bolin; Hu, Shan

2017-06-01

A hybrid electrochemical capacitor (EC) with enhanced energy density is realized by integrating functionalized carbon nanotube (FCNT) electrodes with redox-active electrolyte that has a neutral pH value (1 M Na2SO4 and 0.5 M KBr mixed aqueous solution). The negative electrode shows an electric double layer capacitor-type behavior. On the positive electrode, highly reversible Br-/Br3- redox reactions take place, presenting a battery-type behavior, which contributes to increase the capacitance of the hybrid cell. The voltage window of the whole cell is extended up to 1.5 V because of the high over-potentials of oxygen and hydrogen evolution reactions in the neutral electrolyte. Compared with raw CNT, the FCNT has better wettability in the aqueous electrolyte and contributes to increase the electric double layer capacitance of the cell. As a result, the maximum energy density of 28.3 Wh kg-1 is obtained from the hybrid EC at 0.5 A g-1 without sacrificing its power density, which is around 4 times larger than that of the electrical double layer capacitor constructed by FCNT electrodes and 1 M Na2SO4 electrolyte. Moreover, the discharge capacity retained 86.3% of its initial performance after 10000 cycles of galvanostatic charge and discharge test (10 A/g), suggesting its long life cycle even at high current loading.

Metabolic changes and DNA hypomethylation in cerebellum are associated with behavioral alterations in mice exposed to trichloroethylene postnatally

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blossom, Sarah J., E-mail: blossomsarah@uams.edu; Cooney, Craig A.; Melnyk, Stepan B.

2013-06-15

Previous studies demonstrated that low-level postnatal and early life exposure to the environmental contaminant, trichloroethylene (TCE), in the drinking water of MRL +/+ mice altered glutathione redox homeostasis and increased biomarkers of oxidative stress indicating a more oxidized state. Plasma metabolites along the interrelated transmethylation pathway were also altered indicating impaired methylation capacity. Here we extend these findings to further characterize the impact of TCE exposure in mice exposed to water only or two doses of TCE in the drinking water (0, 2, and 28 mg/kg/day) postnatally from birth until 6 weeks of age on redox homeostasis and biomarkers ofmore » oxidative stress in the cerebellum. In addition, pathway intermediates involved in methyl metabolism and global DNA methylation patterns were examined in cerebellar tissue. Because the cerebellum is functionally important for coordinating motor activity, including exploratory and social approach behaviors, these parameters were evaluated in the present study. Mice exposed to 28 mg/kg/day TCE exhibited increased locomotor activity over time as compared with control mice. In the novel object exploration test, these mice were more likely to enter the zone with the novel object as compared to control mice. Similar results were obtained in a second test when an unfamiliar mouse was introduced into the testing arena. The results show for the first time that postnatal exposure to TCE causes key metabolic changes in the cerebellum that may contribute to global DNA methylation deficits and behavioral alterations in TCE-exposed mice. - Highlights: • We exposed male mice to low-level trichloroethylene from postnatal days 1 through 42. • This exposure altered redox potential and increased oxidative stress in cerebellum. • This exposure altered metabolites important in cellular methylation in cerebellum. • This exposure promoted DNA hypomethylation in cerebellum. • This exposure enhanced locomotor activity and exploratory behavior.« less

Redox-sensitive self-assembled nanoparticles based on alpha-tocopherol succinate-modified heparin for intracellular delivery of paclitaxel.

PubMed

Yang, Xiaoye; Cai, Xiaoqing; Yu, Aihua; Xi, Yanwei; Zhai, Guangxi

2017-06-15

To remedy the problems riddled in cancer chemotherapy, such as poor solubility, low selectivity, and insufficient intra-cellular release of drugs, novel heparin-based redox-sensitive polymeric nanoparticles were developed. The amphiphilic polymer, heparin-alpha-tocopherol succinate (Hep-cys-TOS) was synthesized by grafting hydrophobic TOS to heparin using cystamine as the redox-sensitive linker, which could self-assemble into nanoparticles in phosphate buffer saline (PBS) with low critical aggregation concentration (CAC) values ranging from 0.026 to 0.093mg/mL. Paclitaxel (PTX)-loaded Hep-cys-TOS nanoparticles were prepared via a dialysis method, exhibiting a high drug-loading efficiency of 18.99%. Physicochemical properties of the optimized formulation were characterized by dynamic light scattering (DLS), transmission electron microscope (TEM) and differential scanning calorimetry (DSC). Subsequently, the redox-sensitivity of Hep-cys-TOS nanoparticles was confirmed by the changes in size distribution, morphology and appearance after dithiothreitol (DTT) treatment. Besides, the in vitro release of PTX from Hep-cys-TOS nanoparticles also exhibited a redox-triggered profile. Also, the uptake behavior and pathways of coumarin 6-loaded Hep-cys-TOS nanoparticles were investigated, suggesting the nanoparticles could be taken into MCF-7 cells in energy-dependent, caveolae-mediated and cholesterol-dependent endocytosis manners. Later, MTT assays of different PTX-free and PTX-loaded formulations revealed the desirable safety of PTX-free nanoparticles and the enhanced anti-cancer activity of PTX-loaded Hep-cys-TOS nanoparticles (IC 50 =0.79μg/mL). Apoptosis study indicated the redox-sensitive formulation could induce more apoptosis of MCF-7 cells than insensitive one (55.2% vs. 41.7%), showing the importance of intracellular burst release of PTX. Subsequently, the hemolytic toxicity confirmed the safety of the nanoparticles for intravenous administration. The results indicated the developed redox-sensitive nanoparticles were promising as intracellular drug delivery vehicles for cancer treatment. Copyright © 2017 Elsevier Inc. All rights reserved.

Tracking Catalyst Redox States and Reaction Dynamics in Ni-Fe Oxyhydroxide Oxygen Evolution Reaction Electrocatalysts: The Role of Catalyst Support and Electrolyte pH.

PubMed

Görlin, Mikaela; Ferreira de Araújo, Jorge; Schmies, Henrike; Bernsmeier, Denis; Dresp, Sören; Gliech, Manuel; Jusys, Zenonas; Chernev, Petko; Kraehnert, Ralph; Dau, Holger; Strasser, Peter

2017-02-08

Ni-Fe oxyhydroxides are the most active known electrocatalysts for the oxygen evolution reaction (OER) in alkaline electrolytes and are therefore of great scientific and technological importance in the context of electrochemical energy conversion. Here we uncover, investigate, and discuss previously unaddressed effects of conductive supports and the electrolyte pH on the Ni-Fe(OOH) catalyst redox behavior and catalytic OER activity, combining in situ UV-vis spectro-electrochemistry, operando electrochemical mass spectrometry (DEMS), and in situ cryo X-ray absorption spectroscopy (XAS). Supports and pH > 13 strongly enhanced the precatalytic voltammetric charge of the Ni-Fe oxyhydroxide redox peak couple, shifted them more cathodically, and caused a 2-3-fold increase in the catalytic OER activity. Analysis of DEMS-based faradaic oxygen efficiency and electrochemical UV-vis traces consistently confirmed our voltammetric observations, evidencing both a more cathodic O 2 release and a more cathodic onset of Ni oxidation at higher pH. Using UV-vis, which can monitor the amount of oxidized Ni +3/+4 in situ, confirmed an earlier onset of the redox process at high electrolyte pH and further provided evidence of a smaller fraction of Ni +3/+4 in mixed Ni-Fe centers, confirming the unresolved paradox of a reduced metal redox activity with increasing Fe content. A nonmonotonic super-Nernstian pH dependence of the redox peaks with increasing Fe content-displaying Pourbaix slopes as steep as -120 mV/pH-suggested a two proton-one electron transfer. We explain and discuss the experimental pH effects using refined coupled (PCET) and decoupled proton transfer-electron transfer (PT/ET) schemes involving negatively charged oxygenate ligands generated at Fe centers. Together, we offer new insight into the catalytic reaction dynamics and associated catalyst redox chemistry of the most important class of alkaline OER catalysts.

Redox activity distinguishes solid-state electron transport from solution-based electron transfer in a natural and artificial protein: cytochrome C and hemin-doped human serum albumin.

PubMed

Amdursky, Nadav; Ferber, Doron; Pecht, Israel; Sheves, Mordechai; Cahen, David

2013-10-28

Integrating proteins in molecular electronic devices requires control over their solid-state electronic transport behavior. Unlike "traditional" electron transfer (ET) measurements of proteins that involve liquid environments and a redox cycle, no redox cofactor is needed for solid-state electron transport (ETp) across the protein. Here we show the fundamental difference between these two approaches by macroscopic area measurements, which allow measuring ETp temperature dependence down to cryogenic temperatures, via cytochrome C (Cyt C), an ET protein with a heme (Fe-porphyrin) prosthetic group as a redox centre. We compare the ETp to electrochemical ET measurements, and do so also for the protein without the Fe (with metal-free porphyrin) and without porphyrin. As removing the porphyrin irreversibly alters the protein's conformation, we repeat these measurements with human serum albumin (HSA), 'doped' (by non-covalent binding) with a single hemin equivalent, i.e., these natural and artificial proteins share a common prosthetic group. ETp via Cyt C and HSA-hemin are very similar in terms of current magnitude and temperature dependence, which suggests similar ETp mechanisms via these two systems, thermally activated hopping (with ~0.1 eV activation energy) >190 K and tunneling by superexchange <190 K. Also, ET rates to and from the Fe redox centres (Fe(2+) <=> Fe(3+) + e(-)), measured by electrochemistry of HSA-hemin are only 4 times lower than those for Cyt C. However, while removing the Fe redox centre from the porphyrin ring markedly affects the ET rate, it hardly changes the ETp currents through these proteins, while removing the macrocycle (from HSA, which retains its conformation) significantly reduces ETp efficiency. These results show that solid-state ETp across proteins does not require the presence of a redox cofactor, and that while for ET the Fe ion is the main electron mediator, for ETp the porphyrin ring has this function.

Changes in redox properties of humic acids upon sorption to alumina

NASA Astrophysics Data System (ADS)

Subdiaga, Edisson; Orsetti, Silvia; Jindal, Sharmishta; Haderlein, Stefan B.

2016-04-01

1. Introduction A prominent role of Natural Organic Matter (NOM) in biogeochemical processes is its ability to act as an electron shuttle, accelerating rates between a bulk electron donor and an acceptor. The underlying processes are reversible redox reactions of quinone moieties.1 This shuttling effect has been studied in two major areas: transformation of redox active pollutants and microbial respiration.2-3 Previous studies primarily compared effects in the presence or absence of NOM without addressing the redox properties of NOM nor its speciation. The interaction between humic acids (HA) and minerals might change properties and reactivity of organic matter. Specifically, we investigate whether changes in the redox properties of a HA occur upon sorption to redox inactive minerals. Since fractionation and conformational rearrangements of NOM moieties upon sorption are likely to happen, the redox properties of the NOM fractions upon sorption might differ as well. 2. Materials and methods Elliot Soil Humic Acid (ESHA), Pahokee Peat Humic Acid (PPHA) and Suwannee River Humic Acid (SRHA) were used as received from IHSS. Aluminum oxide (Al2O3) was suspended in 0.1M KCl. Sorption was studied at pH 7.0 in duplicate batch experiments for several HA/Al2O3 ratios. For the suspension (mineral + sorbed HA, plus dissolved HA), the filtrate (0.45μm) and the HA stock solution, the electron donating and accepting capacities (EDC and EAC) were determined following established procedures.4 3. Results All studied HA-Al2O3 systems showed similar behavior with regard to changes in redox properties. There was a significant increase in the EDC of the whole suspension compared to the stock solutions and the non-sorbed HA in the filtrate (up to 300% for PPHA). This effect was more pronounced with increasing amounts of sorbed HA in the suspension. Although ESHA had the highest sorption capacity on Al2O3 (~ 6 times higher than PPHA & SRHA), it showed the smallest changes in redox properties upon sorption. Considering the total electron exchange capacities, significant changes were found mainly at higher amounts of sorbed PPHA and SRHA. 4. Conclusions Overall, our results suggest a change in the redox properties of sorbed HA but not for the dissolved fraction. The sorbed fraction showed a higher redox capacity than the stock samples. Given the absence of redox transfer between the HA and the redox inert aluminum oxide, such changes might be due to conformational changes in the humic substances. 5. References [1] Scott D., Mcknight, D., Blunt-Harris, E., Kolesar, S., Lovley, A. Environ. Sci. Technol. 1998, 32, 2984-2989. [2] Dunnivant, F. Schwarzenbach, R., Macalady, D. Environ. Sci. Technol. 1992, 26(11), 2133-2141. [3] Jiang, J. & Kappler, A. Environ. Sci. Technol. 2008, 42(10), 3562-3569. [4] Aeschbacher, M., Sander M., Schwarzenbach, R. Environ. Sci. Technol. 2010, 44(1), 87-93.

U3Si2 behavior in H2O environments: Part II, pressurized water with controlled redox chemistry

NASA Astrophysics Data System (ADS)

Nelson, A. T.; Migdisov, A.; Wood, E. Sooby; Grote, C. J.

2018-03-01

Recent interest in U3Si2 as an advanced light water reactor fuel has driven assessment of numerous properties, but characterization of its response to H2O environments is sparse in available literature. The behavior of U3Si2 in H2O containing atmospheres is investigated and presented in a two-part series of articles. This work examines the behavior of U3Si2 following exposure to pressurized H2O at temperatures from 300 to 350 °C. Testing was performed using two autoclave configurations and multiple redox conditions. Use of solid state buffers to attain a controlled water chemistry is also presented as a means to test actinide-bearing systems. Buffers were used to vary the hydrogen concentration between 1 and 30 parts per million H2. Testing included UN, U3Si5, and UO2. Both UN and U3Si5 were found to rapidly pulverize in less than 50 h at 300 °C. Uranium dioxide was included as a control for the autoclave system, and was found to be minimally impacted by exposure to pressurized water at the conditions tested for extended time periods. Testing of U3Si2 at 300 °C found reasonable stability through 30 days in 1-5 ppm H2. However, pulverization was observed following 35 days. The redox condition of testing strongly affected pulverization. Characterization of the resulting microstructures suggests that the mechanism responsible for pulverization under more strongly reducing conditions differs from that previously identified. Hydride formation is hypothesized to drive this transition. Testing performed at 350 °C resulted in rapid pulverization of U3Si2 in under 50 h.

U 3Si 2 behavior in H 2O environments: Part II, pressurized water with controlled redox chemistry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nelson, Andrew Thomas; Migdisov, Artaches; Wood, Elizabeth Sooby

Recent interest in U 3Si 2 as an advanced light water reactor fuel has driven assessment of numerous properties, but characterization of its response to H 2O environments is sparse in available literature. The behavior of U 3Si 2 in H 2O containing atmospheres is investigated and presented in a two-part series of articles. This work examines the behavior of U 3Si 2 following exposure to pressurized H 2O at temperatures from 300 to 350 °C. Testing was performed using two autoclave configurations and multiple redox conditions. Use of solid state buffers to attain a controlled water chemistry is alsomore » presented as a means to test actinide-bearing systems. Buffers were used to vary the hydrogen concentration between 1 and 30 parts per million H 2. Testing included UN, U 3Si 5, and UO 2. Both UN and U 3Si 5 were found to rapidly pulverize in less than 5 h at 300 °C. Uranium dioxide was included as a control for the autoclave system, and was found to be minimally impacted by exposure to pressurized water at the conditions tested for extended time periods. Testing of U 3Si 2 at 300 °C found reasonable stability through 30 days in 1–5 ppm H 2. However, pulverization was observed following 35 days. The redox condition of testing strongly affected pulverization. Characterization of the resulting microstructures suggests that the mechanism responsible for pulverization under more strongly reducing conditions differs from that previously identified. Hydride formation is hypothesized to drive this transition. In conclusion, testing performed at 350 °C resulted in rapid pulverization of U 3Si 2 in under 50 h.« less

U 3Si 2 behavior in H 2O environments: Part II, pressurized water with controlled redox chemistry

DOE PAGES

Nelson, Andrew Thomas; Migdisov, Artaches; Wood, Elizabeth Sooby; ...

2017-12-16

Recent interest in U 3Si 2 as an advanced light water reactor fuel has driven assessment of numerous properties, but characterization of its response to H 2O environments is sparse in available literature. The behavior of U 3Si 2 in H 2O containing atmospheres is investigated and presented in a two-part series of articles. This work examines the behavior of U 3Si 2 following exposure to pressurized H 2O at temperatures from 300 to 350 °C. Testing was performed using two autoclave configurations and multiple redox conditions. Use of solid state buffers to attain a controlled water chemistry is alsomore » presented as a means to test actinide-bearing systems. Buffers were used to vary the hydrogen concentration between 1 and 30 parts per million H 2. Testing included UN, U 3Si 5, and UO 2. Both UN and U 3Si 5 were found to rapidly pulverize in less than 5 h at 300 °C. Uranium dioxide was included as a control for the autoclave system, and was found to be minimally impacted by exposure to pressurized water at the conditions tested for extended time periods. Testing of U 3Si 2 at 300 °C found reasonable stability through 30 days in 1–5 ppm H 2. However, pulverization was observed following 35 days. The redox condition of testing strongly affected pulverization. Characterization of the resulting microstructures suggests that the mechanism responsible for pulverization under more strongly reducing conditions differs from that previously identified. Hydride formation is hypothesized to drive this transition. In conclusion, testing performed at 350 °C resulted in rapid pulverization of U 3Si 2 in under 50 h.« less

Phenytoin

MedlinePlus

... talking to your doctor, even if you experience side effects such as unusual changes in behavior or mood. ... acid (Depakene); methadone (Dolophine, Methadose); methotrexate (Otrexup, Rasuvo); methylphenidate (Daytrana, Concerta, Metadate, Ritalin); mexiletine; nifedipine (Adalat, Afeditab), ...

Aripiprazole Injection

MedlinePlus

... a mental illness that causes disturbed or unusual thinking, loss of interest in life, and strong or ... aripiprazole injection and aripiprazole extended-release injection developed gambling problems or other intense urges or behaviors that ...

Random walk on a leash: a simple single-molecule diffusion model for surface-tethered redox molecules with flexible linkers.

PubMed

Huang, Kuan-Chun; White, Ryan J

2013-08-28

We develop a random walk model to simulate the Brownian motion and the electrochemical response of a single molecule confined to an electrode surface via a flexible molecular tether. We use our simple model, which requires no prior knowledge of the physics of the molecular tether, to predict and better understand the voltammetric response of surface-confined redox molecules when motion of the redox molecule becomes important. The single molecule is confined to a hemispherical volume with a maximum radius determined by the flexible molecular tether (5-20 nm) and is allowed to undergo true three-dimensional diffusion. Distance- and potential-dependent electron transfer probabilities are evaluated throughout the simulations to generate cyclic voltammograms of the model system. We find that at sufficiently slow cyclic voltammetric scan rates the electrochemical reaction behaves like an adsorbed redox molecule with no mass transfer limitation; thus, the peak current is proportional to the scan rate. Conversely, at faster scan rates the diffusional motion of the molecule limits the simulated peak current, which exhibits a linear dependence on the square root of the scan rate. The switch between these two limiting regimes occurs when the diffusion layer thickness, (2Dt)(1/2), is ~10 times the tether length. Finally, we find that our model predicts the voltammetric behavior of a redox-active methylene blue tethered to an electrode surface via short flexible single-stranded, polythymine DNAs, allowing the estimation of diffusion coefficients for the end-tethered molecule.

Engineering Folate-Targeting Diselenide-containing Triblock Copolymer as a Redox-Responsive Shell-sheddable Micelle for Antitumor Therapy In Vivo.

PubMed

Behroozi, Farnaz; Abdkhodaie, Mohammad-Jafar; Sadeghi Abandansari, Hamid; Satarian, Leila; Molazem, Mohammad; Al-Jamal, Khuloud T; Baharvand, Hossein

2018-06-18

The oxidation-reduction (redox)-responsive micelle system is based on a diselenide-containing triblock copolymer, poly(ε-caprolactone)-bis(diselenide-methoxy poly(ethylene glycol)/poly(ethylene glycol)-folate) [PCL-(SeSe-mPEG/PEG-FA) 2 ]. This has helped in the development of tumor-targeted delivery for hydrophobic anticancer drugs. The diselenide bond, as a redox-sensitive linkage, was designed in such a manner that it is located at the hydrophilic-hydrophobic hinge to allow complete collapse of the micelle and thus efficient drug release in redox environments. The amphiphilic block copolymers self-assembled into micelles at concentrations higher than the critical micelle concentration (CMC) in an aqueous environment. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) analyses showed that the micelles were spherical with an average diameter of 120 nm. The insoluble anticancer drug paclitaxel (PTX) was loaded into micelles, and its triggered release behavior under different redox conditions was verified. Folate-targeting micelles showed an enhanced uptake in 4T1 breast cancer cells and in vitro cytotoxicity by flow cytometry and (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) (MTS) assay, respectively. Delayed tumor growth was confirmed in the subcutaneously implanted 4T1 breast cancer in mice after intraperitoneal injection. The proposed redox-responsive copolymer offers a new type of biomaterial for drug delivery into cancer cells in vivo. On-demand drug actuation is highly desired. Redox-responsive polymeric DDSs have been shown to be able to respond and release their cargo in a selective manner when encountering a significant change in the potential difference, such as that present between cancerous and healthy tissues. This study offers an added advantage to the field of redox-responsive polymers by reporting a new type of shell-sheddable micelle based on an amphiphilic triblock co-polymer, containing diselenide as a redox-sensitive linkage. The linkage was smartly located at the hydrophilic-hydrophilic bridge in the co-polymer offering complete collapse of the micelle when exposed to the right trigger. The system was able to delay tumor growth and reduce toxicity in a breast cancer tumor model following intraperitoneal injection in mice. Copyright © 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Pyrene Molecular Orbital Shuffle-Controlling Excited State and Redox Properties by Changing the Nature of the Frontier Orbitals.

PubMed

Merz, Julia; Fink, Julian; Friedrich, Alexandra; Krummenacher, Ivo; Al Mamari, Hamad H; Lorenzen, Sabine; Haehnel, Martin; Eichhorn, Antonius; Moos, Michael; Holzapfel, Marco; Braunschweig, Holger; Lambert, Christoph; Steffen, Andreas; Ji, Lei; Marder, Todd B

2017-09-21

We show that by judicious choice of substituents at the 2- and 7-positions of pyrene, the frontier orbital order of pyrene can be modified, giving enhanced control over the nature and properties of the photoexcited states and the redox potentials. Specifically, we introduced a julolidine-like moiety and Bmes 2 (mes=2,4,6-Me 3 C 6 H 2 ) as very strong donor (D) and acceptor (A), respectively, giving 2,7-D-π-D- and unsymmetric 2,7-D-π-A-pyrene derivatives, in which the donor destabilizes the HOMO-1 and the acceptor stabilizes the LUMO+1 of the pyrene core. Consequently, for 2,7-substituted pyrene derivatives, unusual properties are obtained. For example, very large bathochromic shifts were observed for all of our compounds, and unprecedented green light emission occurs for the D/D system. In addition, very high radiative rate constants in solution and in the solid state were recorded for the D-π-D- and D-π-A-substituted compounds. All compounds show reversible one-electron oxidations, and Jul 2 Pyr exhibits a second oxidation, with the largest potential splitting (ΔE=440 mV) thus far reported for 2,7-substituted pyrenes. Spectroelectrochemical measurements confirm an unexpectedly strong coupling between the 2,7-substituents in our pyrene derivatives. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

TCDD decreases ATP levels and increases reactive oxygen production through changes in mitochondrial F F{sub 1}-ATP synthase and ubiquinone

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shertzer, Howard G.; Genter, Mary Beth; Shen, Dongxiao

2006-12-15

Mitochondria generate ATP and participate in signal transduction and cellular pathology and/or cell death. TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) decreases hepatic ATP levels and generates mitochondrial oxidative DNA damage, which is exacerbated by increasing mitochondrial glutathione redox state and by inner membrane hyperpolarization. This study identifies mitochondrial targets of TCDD that initiate and sustain reactive oxygen production and decreased ATP levels. One week after treating mice with TCDD, liver ubiquinone (Q) levels were significantly decreased, while rates of succinoxidase and Q-cytochrome c oxidoreductase activities were increased. However, the expected increase in Q reduction state following TCDD treatment did not occur; instead, Q wasmore » more oxidized. These results could be explained by an ATP synthase defect, a premise supported by the unusual finding that TCDD lowers ATP/O ratios without concomitant changes in respiratory control ratios. Such results suggest either a futile cycle in ATP synthesis, or hydrolysis of newly synthesized ATP prior to release. The TCDD-mediated decrease in Q, concomitant with an increase in respiration, increases complex 3 redox cycling. This acts in concert with glutathione to increase membrane potential and reactive oxygen production. The proposed defect in ATP synthase explains both the greater respiratory rates and the lower tissue ATP levels.« less

Anaerobic electron acceptor chemotaxis in Shewanella putrefaciens

NASA Technical Reports Server (NTRS)

Nealson, K. H.; Moser, D. P.; Saffarini, D. A.

1995-01-01

Shewanella putrefaciens MR-1 can grow either aerobically or anaerobically at the expense of many different electron acceptors and is often found in abundance at redox interfaces in nature. Such redox interfaces are often characterized by very strong gradients of electron acceptors resulting from rapid microbial metabolism. The coincidence of S. putrefaciens abundance with environmental gradients prompted an examination of the ability of MR-1 to sense and respond to electron acceptor gradients in the laboratory. In these experiments, taxis to the majority of the electron acceptors that S. putrefaciens utilizes for anaerobic growth was seen. All anaerobic electron acceptor taxis was eliminated by the presence of oxygen, nitrate, nitrite, elemental sulfur, or dimethyl sulfoxide, even though taxis to the latter was very weak and nitrate and nitrite respiration was normal in the presence of dimethyl sulfoxide. Studies with respiratory mutants of MR-1 revealed that several electron acceptors that could not be used for anaerobic growth nevertheless elicited normal anaerobic taxis. Mutant M56, which was unable to respire nitrite, showed normal taxis to nitrite, as well as the inhibition of taxis to other electron acceptors by nitrite. These results indicate that electron acceptor taxis in S. putrefaciens does not conform to the paradigm established for Escherichia coli and several other bacteria. Carbon chemo-taxis was also unusual in this organism: of all carbon compounds tested, the only positive response observed was to formate under anaerobic conditions.

Electron and Oxygen Atom Transfer Chemistry of Co(II) in a Proton Responsive, Redox Active Ligand Environment.

PubMed

Cook, Brian J; Pink, Maren; Pal, Kuntal; Caulton, Kenneth G

2018-05-21

The bis-pyrazolato pyridine complex LCo(PEt 3 ) 2 serves as a masked form of three-coordinate Co II and shows diverse reactivity in its reaction with several potential outer sphere oxidants and oxygen atom transfer reagents. N-Methylmorpholine N-oxide (NMO) oxidizes coordinated PEt 3 from LCo(PEt 3 ) 2 , but the final cobalt product is still divalent cobalt, in LCo(NMO) 2 . The thermodynamics of a variety of oxygen atom transfer reagents, including NMO, are calculated by density functional theory, to rank their oxidizing power. Oxidation of LCo(PEt 3 ) 2 with AgOTf in the presence of LiCl as a trapping nucleophile forms the unusual aggregate [LCo(PEt 3 ) 2 Cl(LiOTf) 2 ] 2 held together by Li + binding to very nucleophilic chloride on Co(III) and triflate binding to those Li + . In contrast, Cp 2 Fe + effects oxidation to trivalent cobalt, to form (HL)Co(PEt 3 ) 2 Cl + ; proton and the chloride originate from solvent in a rare example of CH 2 Cl 2 dehydrochlorination. An unexpected noncomplementary redox reaction is reported involving attack by 2e reductant PEt 3 nucleophile on carbon of the 1e oxidant radical Cp 2 Fe + , forming a P-C bond and H + ; this reaction competes in the reaction of LCo(PEt 3 ) 2 with Cp 2 Fe + .

Regulated methionine oxidation by monooxygenases

PubMed Central

Manta, Bruno; Gladyshev, Vadim N.

2017-01-01

Protein function can be regulated via post-translational modifications by numerous enzymatic and non-enzymatic mechanisms, including oxidation of cysteine and methionine residues. Redox-dependent regulatory mechanisms have been identified for nearly every cellular process, but the major paradigm has been that cellular components are oxidized (damaged) by reactive oxygen species (ROS) in a relatively unspecific way, and then reduced (repaired) by designated reductases. While this scheme may work with cysteine, it cannot be ascribed to other residues, such as methionine, whose reaction with ROS is too slow to be biologically relevant. However, methionine is clearly oxidized in vivo and enzymes for its stereoselective reduction are present in all three domains of life. Here, we revisit the chemistry and biology of methionine oxidation, with emphasis on its generation by enzymes from the monooxygenase family. Particular attention is placed on MICALs, a recently discovered family of proteins that harbor an unusual flavin-monooxygenase domain with an NADPH-dependent methionine sulfoxidase activity. Based on the structural and kinetic information we provide a rational framework to explain MICAL mechanism, inhibition, and regulation. Methionine residues that are targeted by MICALs are reduced back by methionine sulfoxide reductases, suggesting that reversible methionine oxidation may be a general mechanism analogous to the regulation by phosphorylation by kinases/phosphatases. The identification of new enzymes that catalyze the oxidation of methionine will open a new area of research at the forefront of redox signaling. PMID:28229915

Redox effects on the microbial degradation of refractory organic matter in marine sediments

NASA Astrophysics Data System (ADS)

Reimers, Clare E.; Alleau, Yvan; Bauer, James E.; Delaney, Jennifer; Girguis, Peter R.; Schrader, Paul S.; Stecher, Hilmar A.

2013-11-01

Microbially mediated reduction-oxidation (redox) reactions are often invoked as being the mechanisms by which redox state influences the degradation of sedimentary organic matter (OM) in the marine environment. To evaluate the effects of elevated, oscillating and reduced redox potentials on the fate of primarily aged, mineral-adsorbed OM contained in continental shelf sediments, we used microbial fuel cells to control redox state within and around marine sediments, without amending the sediments with reducing or oxidizing substances. We subsequently followed electron fluxes in the redox elevated and redox oscillating treatments, and related sediment chemical, isotopic and bacterial community changes to redox conditions over a 748-day experimental period. The electron fluxes of the elevated and oscillating redox cells were consistent with models of organic carbon (OC) oxidation with time-dependent first-order rate constants declining from 0.023 to 0.005 y-1, in agreement with rate constants derived from typical OC profiles and down core ages of offshore sediments, or from sulfate reduction rate measurements in similar sediments. Moreover, although cumulative electron fluxes were higher in the continuously elevated redox treatment, incremental rates of electron harvesting in the two treatments converged over the 2 year experiment. These similar rates were reflected in chemical indicators of OM metabolism such as dissolved OC and ammonia, and particulate OC concentrations, which were not significantly different among all treatments and controls over the experimental time-scale. In contrast, products of carbonate and opal dissolution and metal mobilization showed greater enrichments in sediments with elevated and oscillating redox states. Microbial community composition in anode biofilms and surrounding sediments was assessed via high-throughput 16S rRNA gene sequencing, and these analyses revealed that the elevated and oscillatory redox treatments led to the enrichment of Deltaproteobacteria on the sediment-hosted anodes over time. Many Deltaproteobacteria are capable of using electrodes as terminal electron acceptors to completely oxidize organic substrates. Notably, Deltaproteobacteria were not measurably enriched in the sediments adjacent to anodes, suggesting that - in these experiments - electron-shuttling bacterial networks did not radiate out away from the electrodes, affecting millimeters or centimeters of sediment. Rather, microbial phylotypes allied to the Clostridia appeared to dominate in the sediment amongst all treatments, and likely played essential roles in converting complex dissolved and particulate sources of OM to simple fermentation products. Thus, we advance that the rate at which fermentation products are generated and migrate to oxidation fronts is what limits the remineralization of OM in many subsurface sediments removed from molecular oxygen. This is a diagenetic scenario that is consistent with the discharging behavior of redox oscillating sediment MFCs. It is also compatible with hypotheses that molecular O2 - and not just the resulting elevated redox potential - may be required to effectively catalyze the degradation of refractory OM. Such decomposition reactions have been suggested to depend on substrate interactions with highly reactive oxygen-containing radicals and/or with specialized extracellular enzymes produced by aerobic prokaryotic or eukaryotic cells.

Redox behavior of uranium at the nanoporous aluminum oxide-water interface: implications for uranium remediation.

PubMed

Jung, Hun Bok; Boyanov, Maxim I; Konishi, Hiromi; Sun, Yubing; Mishra, Bhoopesh; Kemner, Kenneth M; Roden, Eric E; Xu, Huifang

2012-07-03

Sorption-desorption experiments show that the majority (ca. 80-90%) of U(VI) presorbed to mesoporous and nanoporous alumina could not be released by extended (2 week) extraction with 50 mM NaHCO(3) in contrast with non-nanoporous α alumina. The extent of reduction of U(VI) presorbed to aluminum oxides was semiquantitatively estimated by comparing the percentages of uranium desorbed by anoxic sodium bicarbonate between AH(2)DS-reacted and unreacted control samples. X-ray absorption spectroscopy confirmed that U(VI) presorbed to non-nanoporous alumina was rapidly and completely reduced to nanoparticulate uraninite by AH(2)DS, whereas reduction of U(VI) presorbed to nanoporous alumina was slow and incomplete (<5% reduction after 1 week). The observed nanopore size-dependent redox behavior of U has important implications in developing efficient remediation techniques for the subsurface uranium contamination because the efficiency of in situ bioremediation depends on how effectively and rapidly U(VI) bound to sediment or soil can be converted to an immobile phase.

Synthesis, properties, and redox behavior of 1,1,4,4-tetracyano-2-ferrocenyl-1,3-butadienes connected by aryl, biaryl, and teraryl spacers.

PubMed

Shoji, Taku; Maruyama, Akifumi; Yaku, Chisa; Kamata, Natsumi; Ito, Shunji; Okujima, Tetsuo; Toyota, Kozo

2015-01-02

Aryl-substituted 1,1,4,4-tetracyano-1,3-butadienes (FcTCBDs) and bis(1,1,4,4-tetracyanobutadiene)s (bis-FcTCBDs), possessing a ferrocenyl group on each terminal, were prepared by the reaction of a variety of alkynes with tetracyanoethylene (TCNE) in a [2+2] cycloaddition reaction, followed by retro-electrocyclization of the initially formed [2+2] cycloadducts (i.e., cyclobutene derivatives). The characteristic intramolecular charge transfer (ICT) between the donor (ferrocene) and acceptor (TCBD) moieties were investigated by using UV/Vis spectroscopy. The redox behaviors of FcTCBDs and bis-FcTCBDs were examined by cyclic voltammetry (CV) and differential pulse voltammetry (DPV), which revealed their properties of multi-electron transfer depending on the number of ferrocene and TCBD moieties. Moreover, significant color changes were observed by visible spectroscopy under the electrochemical reduction conditions. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Intracellular antioxidants dissolve man-made antioxidant nanoparticles: using redox vulnerability of nanoceria to develop a responsive drug delivery system.

PubMed

Muhammad, Faheem; Wang, Aifei; Qi, Wenxiu; Zhang, Shixing; Zhu, Guangshan

2014-01-01

Regeneratable antioxidant property of nanoceria has widely been explored to minimize the deleterious influences of reactive oxygen species. Limited information is, however, available regarding the biological interactions and subsequent fate of nanoceria in body fluids. This study demonstrates a surprising dissolution of stable and ultrasmall (4 nm) cerium oxide nanoparticles (CeO2 NPs) in response to biologically prevalent antioxidant molecules (glutathione, vitamin C). Such a redox sensitive behavior of CeO2 NPs is subsequently exploited to design a redox responsive drug delivery system for transporting anticancer drug (camptothecin). Upon exposing the CeO2 capped and drug loaded nanoconstruct to vitamin c or glutathione, dissolution-accompanied aggregation of CeO2 nanolids unleashes the drug molecules from porous silica to achieve a significant anticancer activity. Besides stimuli responsive drug delivery, immobilization of nanoceria onto the surface of mesoporous silica also facilitates us to gain a basic insight into the biotransformation of CeO2 in physiological mediums.

Self-Assembly Assisted Fabrication of Dextran-Based Nanohydrogels with Reduction-Cleavable Junctions for Applications as Efficient Drug Delivery Systems

PubMed Central

Wang, Hao; Dai, Tingting; Zhou, Shuyan; Huang, Xiaoxiao; Li, Songying; Sun, Kang; Zhou, Guangdong; Dou, Hongjing

2017-01-01

In order to overcome the key challenge in improving both fabrication efficiency and their drug delivery capability of anti-cancer drug delivery systems (ACDDS), here polyacrylic acid (PAA) grafted dextran (Dex) nanohydrogels (NGs) with covalent crosslinked structure bearing redox sensitive disulfide crosslinking junctions (Dex-SS-PAA) were synthesized efficiently through a one-step self-assembly assisted methodology (SAA). The Dex-SS-PAA were subsequently conjugated with doxorubicin through an acid-labile hydrazone bond (Dex-SS-PAA-DOX). The in vitro drug release behavior, anti-cancer effects in vivo, and biosafety of the as-prepared acid- and redox-dual responsive biodegradable NGs were systematically investigated. The results revealed that the Dex-SS-PAA-DOX exhibited pH- and redox-controlled drug release, greatly reduced the toxicity of free DOX, while exhibiting a strong ability to inhibit the growth of MDA-MB-231 tumors. Our study demonstrated that the Dex-SS-PAA-DOX NGs are very promising candidates as ACDDS for anti-cancer therapeutics. PMID:28071743

Comparison of electrokinetic soil remediation methods using one fixed anode and approaching anodes.

PubMed

Shen, Zhemin; Chen, Xuejun; Jia, Jinping; Qu, Liya; Wang, Wenhua

2007-11-01

During the cation exchange membrane (CEM) enhanced electrokinetic (EK) soil remediation, the nearer to the anode, the higher are the H+ concentrations and the redox potentials. As both low pH and high redox potential are helpful to speed-up Cd electro-migration, soils near the anode can be quickly remedied. Usually EK process is operated with one fixed anode (FA). A novel CEM enhanced EK method with approaching anodes (AAs) is proposed to accelerate electro-migration effect. Several mesh Ti/Ru anodes were inserted as AAs in the treated soil. They were switched in turn from the anode towards the cathode. Thus high H+ ions concentrations and high redox potentials quickly migrate to the cathode. Consequently, soil remediation is accelerated and nearly 44% of energy and 40% of time can be saved. The mechanism of Cd electro-migration behavior in soils during CEM enhanced EK is described as the elution in an electrokinetically driven chromatogram.

Self-Assembly Assisted Fabrication of Dextran-Based Nanohydrogels with Reduction-Cleavable Junctions for Applications as Efficient Drug Delivery Systems

NASA Astrophysics Data System (ADS)

Wang, Hao; Dai, Tingting; Zhou, Shuyan; Huang, Xiaoxiao; Li, Songying; Sun, Kang; Zhou, Guangdong; Dou, Hongjing

2017-01-01

In order to overcome the key challenge in improving both fabrication efficiency and their drug delivery capability of anti-cancer drug delivery systems (ACDDS), here polyacrylic acid (PAA) grafted dextran (Dex) nanohydrogels (NGs) with covalent crosslinked structure bearing redox sensitive disulfide crosslinking junctions (Dex-SS-PAA) were synthesized efficiently through a one-step self-assembly assisted methodology (SAA). The Dex-SS-PAA were subsequently conjugated with doxorubicin through an acid-labile hydrazone bond (Dex-SS-PAA-DOX). The in vitro drug release behavior, anti-cancer effects in vivo, and biosafety of the as-prepared acid- and redox-dual responsive biodegradable NGs were systematically investigated. The results revealed that the Dex-SS-PAA-DOX exhibited pH- and redox-controlled drug release, greatly reduced the toxicity of free DOX, while exhibiting a strong ability to inhibit the growth of MDA-MB-231 tumors. Our study demonstrated that the Dex-SS-PAA-DOX NGs are very promising candidates as ACDDS for anti-cancer therapeutics.

Unusual Sleep Experiences, Dissociation, and Schizotypy: Evidence for a Common Domain

PubMed Central

Koffel, Erin; Watson, David

2009-01-01

This paper reviews studies that have examined associations between unusual sleep experiences (including nightmares, vivid dreaming, narcolepsy symptoms, and complex nighttime behaviors) and dissociation and schizotypy. Using correlational studies and structural analyses, evidence is provided that unusual sleep experiences, dissociation, and schizotypy belong to a common domain. It is demonstrated that unusual sleep experiences show specificity to dissociation and schizotypy compared to other daytime symptoms (e.g., anxiety, depression, substance use) and other sleep disturbances (e.g., insomnia, lassitude/fatigue). The paper also outlines the methodological limitations of the existing evidence and makes suggestions for future research. Finally, three models for the overlap of daytime and nighttime symptoms are reviewed, including biological abnormalities, trauma, and personality traits. Although further research is needed, it is suggested that daytime and nighttime symptoms result from problems with sleep-wake state boundaries, which may be precipitated by stress or trauma. In addition, association between daytime and nighttime symptoms can be attributed to the higher order personality trait of Oddity. PMID:19581031

Vibrational spectroscopy reveals the initial steps of biological hydrogen evolution.

PubMed

Katz, S; Noth, J; Horch, M; Shafaat, H S; Happe, T; Hildebrandt, P; Zebger, I

2016-11-01

[FeFe] hydrogenases are biocatalytic model systems for the exploitation and investigation of catalytic hydrogen evolution. Here, we used vibrational spectroscopic techniques to characterize, in detail, redox transformations of the [FeFe] and [4Fe4S] sub-sites of the catalytic centre (H-cluster) in a monomeric [FeFe] hydrogenase. Through the application of low-temperature resonance Raman spectroscopy, we discovered a novel metastable intermediate that is characterized by an oxidized [Fe I Fe II ] centre and a reduced [4Fe4S] 1+ cluster. Based on this unusual configuration, this species is assigned to the first, deprotonated H-cluster intermediate of the [FeFe] hydrogenase catalytic cycle. Providing insights into the sequence of initial reaction steps, the identification of this species represents a key finding towards the mechanistic understanding of biological hydrogen evolution.

Conversion of Methane into Methanol and Ethanol over Nickel Oxide on Ceria-Zirconia Catalysts in a Single Reactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Okolie, Chukwuemeka; Belhseine, Yasmeen F.; Lyu, Yimeng

Direct conversion of methane into alcohols is a promising technology for converting stranded methane reserves into liquids that can be transported in pipelines and upgraded to value-added chemicals. We demonstrate that a catalyst consisting of small nickel oxide clusters supported on ceria-zirconia (NiO/CZ) can selectively oxidize methane to methanol and ethanol in a single, steady-state process at 723 K using O2 as an abundantly available oxidant. The presence of steam is required to obtain alcohols rather than CO2 as the product of catalytic combustion. The unusual activity of this catalyst is attributed to the synergy between the small Lewis acidicmore » NiO clusters and the redox-active CZ support, which also stabilizes the small NiO clusters.« less

Conversion of Methane to Methanol and Ethanol over Nickel Oxide on Ceria-Zirconia Catalysts in a Single Reactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Okolie, Chukwuemeka; Belhseine, Yasmeen F.; Lyu, Yimeng

Here, the conversion of methane into alcohols under moderate reaction conditions is a promising technology for converting stranded methane reserves into liquids that can be transported in pipelines and upgraded to value-added chemicals. We demonstrate that a catalyst consisting of small nickel oxide clusters supported on ceria-zirconia (NiO/CZ) can convert methane to methanol and ethanol in a single, steady-state process at 723 K using O 2 as an abundantly available oxidant. The presence of steam is required to obtain alcohols rather than CO 2 as the product of catalytic combustion. The unusual activity of this catalyst is attributed to themore » synergy between the small Lewis acidic NiO clusters and the redox-active CZ support, which also stabilizes the small NiO clusters.« less

Conversion of Methane to Methanol and Ethanol over Nickel Oxide on Ceria-Zirconia Catalysts in a Single Reactor

DOE PAGES

Okolie, Chukwuemeka; Belhseine, Yasmeen F.; Lyu, Yimeng; ...

2017-08-08

Here, the conversion of methane into alcohols under moderate reaction conditions is a promising technology for converting stranded methane reserves into liquids that can be transported in pipelines and upgraded to value-added chemicals. We demonstrate that a catalyst consisting of small nickel oxide clusters supported on ceria-zirconia (NiO/CZ) can convert methane to methanol and ethanol in a single, steady-state process at 723 K using O 2 as an abundantly available oxidant. The presence of steam is required to obtain alcohols rather than CO 2 as the product of catalytic combustion. The unusual activity of this catalyst is attributed to themore » synergy between the small Lewis acidic NiO clusters and the redox-active CZ support, which also stabilizes the small NiO clusters.« less

Discussion on the structure stability and the luminescence switch under irradiation of a Ce-doped elpasolite compound.

PubMed

Cornu, Lucile; Gaudon, Manuel; Veber, Philippe; Villesuzanne, Antoine; Pechev, Stanilas; Garcia, Alain; Jubera, Véronique

2015-03-23

Ce-doped Rb2 KInF6 elpasolite has the potential for tunable luminescence due to an unusual reversible redox process between the cerium and indium cations. Coupled with a deep understanding of the luminescence properties, XRD analysis and DFT calculations are used to locate the doping elements in the host lattice. The origin explanation of the charge-transfer mechanism that causes a decrease or increase in the blue-green cerium emission in opposition to the red indium emission is discussed regarding the crystallographic structure, the connection of the metallic cations and their equilibrium valence. Still detectable after nineteen years, the optical contrast created under irradiation makes this material a good candidate as photosensor for data storage. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Toddlers and Sexual Behavior

MedlinePlus

... children their body parts). Children are curious about naked bodies. They may be interested in watching their ... because it feels good. Children are curious about naked bodies. It is not unusual for toddlers to ...

The Psychometric Properties of a New Measure of Sensory Behaviors in Autistic Children

ERIC Educational Resources Information Center

Neil, Louise; Green, Dido; Pellicano, Elizabeth

2017-01-01

Unusual reactions to sensory input became part of the diagnostic criteria for autism spectrum disorder in the DSM-5. Measures accurately assessing these symptoms are important for clinical decisions. This study examined the reliability and validity of the Sensory Behavior Questionnaire, a parent-report scale designed to assess frequency and impact…

Graph Learning for Anomaly Detection using Psychological Context GLAD-PC

DTIC Science & Technology

2015-08-03

comparison study of user behavior on Facebook and Gmail, ArXiv: 1305.6082, (11 2013): 0. doi: 10.1016/j.chb.2013.06.043 TOTAL: 1 Received Paper...Fournelle, Steve Gaffigan, Oliver Brdiczka, Jianqiang Shen, Juan Liu, Kendra E. Moore. Characterizing user behavior and information propagation on a...media data; and c) detecting unusual and anomalous behavior from on-line activities. (5) Summary of the most important results With regard to

The unusual chemical bonding and thermoelectric properties of a new type Zintl phase compounds Ba3Al2As4

NASA Astrophysics Data System (ADS)

Yang, Gui; Zhang, Guangbiao; Wang, Chao; Wang, Yuanxu

2016-07-01

Ba3Al2As4 exhibits an unusual anisotropic electrical conductivity, that is, the electrical conductivity along the chain is smaller than those along other two directions. The results is conflict with previous conclusion for Ca5M2Pn6. Earlier studies on Ca5M2Pn6 showed that a higher electrical conductivity could be obtained along the chain. The band decomposed charge density is used to explain such unusual behavior. Our calculations indicate the existence of a conductive pathway near the Fermi level is responsible for the electrons transport. Further, the Ba-As bonding of Ba3Al2As4 has some degree covalency which is novel for the Zintl compounds.

Understanding the nanoscale redox-behavior of iron-anodes for rechargeable iron-air batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weinrich, Henning; Come, Jérémy; Tempel, Hermann

Iron-air cells provide a promising and resource-efficient alternative battery concept with superior area specific power density characteristics compared to state-of-the-art Li-air batteries and potentially superior energy density characteristics compared to present Li-ion batteries. Understanding charge-transfer reactions at the anode-electrolyte interface is the key to develop high-performance cells. By employing in-situ electrochemical atomic force microscopy (in-situ EC-AFM), in-depth insight into the electrochemically induced surface reaction processes on iron in concentrated alkaline electrolyte is obtained. The results highlight the formation and growth of the redox-layer on iron over the course of several oxidation/reduction cycles. By this means, a direct correlation between topographymore » changes and the corresponding electrochemical reactions at the nanoscale could unambiguously be established. Here in this paper, the twofold character of the nanoparticulate redox-layer in terms of its passivating character and its contribution to the electrochemical reactions is elucidated. Furthermore, the evolution of single nanoparticles on the iron electrode surface is evaluated in unprecedented and artifact-free detail. Based on the dedicated topography analysis, a detailed structural model for the evolution of the redox-layer which is likewise elementary for corrosion science and battery research is derived.« less

Redox transformation and reductive immobilization of Cr(VI) in the Columbia River hyporheic zone sediments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Fen; Liu, Yuanyuan; Zachara, John

An experimental and modeling study was conducted to investigate the redox transformation and reductive immobilization of groundwater contaminant Cr in hyporheic zone (HZ) sediments from U.S. Department of Energy’s Hanford site, where groundwater Cr(VI) is migrating and discharging to the nearby Columbia River. Experimental results revealed that Cr(VI) can be reduced to immobile reduced Cr by the HZ sediments in the presence/absence of O2. Anaerobic pre-incubation of the sediments increased the effective rate of Cr reduction that was correlated with the increase in HCl-extractable Fe(II) content in the sediments. The reduced Cr was stable in exposure to O2 under field-relevantmore » pH (~7.5) and Mn-containing (~0.02% w/w) conditions. The Cr(VI) reduction rate showed a multi-rate behavior, apparently reflecting the presence of reductants with different reactivity in the sediments. The results from this study indicated that the HZ sediments can reductively immobilize Cr and the sediment redox capacity can be recharged through microbial activities. The results implied that HZ can play a role as a natural permeable redox barrier for removing groundwater Cr before it discharges into a river system.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Twu, Nancy; Metzger, Michael; Balasubramanian, Mahalingam

Here, the lithium-excess Li xNi 2-4x/3Sb x/3O 2 (LNSO) materials were previously shown to demonstrate higher capacities and improved cyclability with increasing lithium content. While the performance trend is promising, observed capacities are much lower than theoretical capacities, pointing to a need for further understanding of active redox processes in these materials. In this work, we study the electrochemical behavior of the LNSO materials as a function of lithium content and at slow and fast rates. Surprisingly, Li 1.15Ni 0.47Sb 0.38O 2 (LNSO-15) exhibits higher discharge capacities at faster rates and traverses distinct voltage curves at slow and fast rates.more » To understand these two peculiarities, we characterize the redox activity of nickel, antimony, and oxygen at different rates. While experiments confirm some nickel redox activity and oxygen loss, these two mechanisms cannot account for all observed capacity. We propose that the balance of the observed capacity may be due reversible oxygen redox and that the rate-dependent voltage curve features may derive from irreversible nickel migration occurring on slow charge. As future high energy density cathodes are likely to contain both lithium excess and high nickel content, both of these findings have important implications for the development of novel high capacity cathode materials.« less

Redox transformation and reductive immobilization of Cr(VI) in the Columbia River hyporheic zone sediments

NASA Astrophysics Data System (ADS)

Xu, Fen; Liu, Yuanyuan; Zachara, John; Bowden, Mark; Kennedy, David; Plymale, Andrew E.; Liu, Chongxuan

2017-12-01

An experimental and modeling study was conducted to investigate the redox transformation and reductive immobilization of groundwater contaminant Cr in hyporheic zone (HZ) sediments from U.S. DOE's Hanford Site, where groundwater Cr(VI) is migrating and discharging to the nearby Columbia River. Experimental results revealed that Cr(VI) can be reduced and immobilized by the HZ sediments in the presence/absence of O2. Anaerobic pre-incubation of the sediments increased the effective rate of Cr reduction that was correlated with the increase in HCl-extractable Fe(II) content in the sediments. The reduced Cr was stable when exposed to O2 under field-relevant pH (7.5) with and without dissolved Mn(II), which might be oxidized to form Mn(III/IV) oxides that may oxidize reduced Cr. The Cr(VI) reduction rate showed a multi-rate behavior, apparently reflecting the presence of reductants with different reactivity in the sediments. The results from this study indicated that the HZ sediments can reductively immobilize Cr and the sediment redox capacity can be recharged through microbial activities. The results implied that HZ can play a role as a natural permeable redox barrier for removing groundwater Cr before it discharges into a river system.

An aqueous all-organic redox-flow battery employing a (2,2,6,6-tetramethylpiperidin-1-yl)oxyl-containing polymer as catholyte and dimethyl viologen dichloride as anolyte

NASA Astrophysics Data System (ADS)

Hagemann, Tino; Winsberg, Jan; Grube, Mandy; Nischang, Ivo; Janoschka, Tobias; Martin, Norbert; Hager, Martin D.; Schubert, Ulrich S.

2018-02-01

Herein we present a new redox-flow battery (RFB) that employs a (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) containing copolymer (P1) as catholyte and the viologen derivative N,N‧-dimethyl-4,4‧-bipyridinium dichloride (MV) as anolyte in an aqueous sodium chloride solution. This is the first time that a combination of an organic polymer and a low-molar-mass organic redox-active material is presented. The electrochemical behavior of the utilized charge-storage materials were investigated by cyclic voltammetry (CV) and feature reversible redox-reactions at E½ = 0.7 V (TEMPO/TEMPO+) and E½ = -0.6 V vs. AgCl/Ag (MV++/MV+•), which lead to a promising cell voltage of 1.3 V in the subsequent battery application. Studies were performed to determine the most suitable anion-exchange membrane (AEM), the ideal conducting salt concentration and the optimal flow rate. The resulting battery reveals a stable charge/discharge performance over 100 consecutive cycles with coulombic efficiencies of up to 95%, a high energy efficiency of 85% and an overall energy density of the electrolyte system of 3.8 W h L-1.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Su, Liang; Ferrandon, Magali; Barton, John L.

The identification and development of conductive electrolytes with high concentrations of redox active species is key to realizing energy-dense nonaqueous flow batteries. Herein, we explore the use of ether solvents (1,3-dioxolane (DOL), 1,2-dimethoxyethane (DME), diethylene glycol dimethyl ether (DEGDME), and tetraethylene glycol dimethyl ether (TEGDME)) as the basis for redox electrolytes containing a lithium ion supporting salt (LiBF4 or LiTFSI) and 2,5-di-tert-butyl-1,4-bis(2-methoxyethoxy)benzene (DBBB) as an active material. An automated high-throughput platform is employed to screen various electrolyte compositions by measuring solution conductivity and solute solubility as a function of solvent and salt type, component concentration, and temperature. Subsequently, the electrochemicalmore » and transport properties of select redox electrolytes are characterized by cyclic voltammetry using glassy carbon disk electrodes and by linear sweep voltammetry using carbon fiber ultramicroelectrodes. In general, improvements in electrolyte conductivity and solute solubility are observed with ether-based formulations as compared to previously reported propylene carbonate (PC)-based formulations. In particular, the addition of DOL to a DME-based electrolyte increases the conductivity and decreases the temperature for solubilization at high LiTFSI and DBBB concentrations. The redox behavior of DBBB remains consistent across the range of concentrations tested while the diffusion coefficient scales with changes in solution viscosity.« less

A metal-organic tetrahedron as a redox vehicle to encapsulate organic dyes for photocatalytic proton reduction.

PubMed

Jing, Xu; He, Cheng; Yang, Yang; Duan, Chunying

2015-03-25

The design of artificial systems that mimic highly evolved and finely tuned natural photosynthetic systems is a subject of intensive research. We report herein a new approach to constructing supramolecular systems for the photocatalytic generation of hydrogen from water by encapsulating an organic dye molecule into the pocket of a redox-active metal-organic polyhedron. The assembled neutral Co4L4 tetrahedron consists of four ligands and four cobalt ions that connect together in alternating fashion. The cobalt ions are coordinated by three thiosemicarbazone NS chelators and exhibit a redox potential suitable for electrochemical proton reduction. The close proximity between the redox site and the photosensitizer encapsulated in the pocket enables photoinduced electron transfer from the excited state of the photosensitizer to the cobalt-based catalytic sites via a powerful pseudo-intramolecular pathway. The modified supramolecular system exhibits TON values comparable to the highest values reported for related cobalt/fluorescein systems. Control experiments based on a smaller tetrahedral analogue of the vehicle with a filled pocket and a mononuclear compound resembling the cobalt corner of the tetrahedron suggest an enzymatic dynamics behavior. The new, well-elucidated reaction pathways and the increased molarity of the reaction within the confined space render these supramolecular systems superior to other relevant systems.

Carbon nanosheets-based supercapacitors: Design of dual redox additives of 1, 4-dihydroxyanthraquinone and hydroquinone for improved performance

NASA Astrophysics Data System (ADS)

Xu, Dong; Sun, Xiao Na; Hu, Wei; Chen, Xiang Ying

2017-07-01

Using thiocarbanilide and Mg(OH)2 powders as carbon precursor and template, respectively, novel 2D carbon nanosheets with large area have been produced. Next, based on the cooperative effect, 1, 4-dihydroxyanthraquinone (DQ) and hydroquinone (HQ) regarded as efficient dual redox additives have been incorporated into the electrode carbon material and H2SO4 electrolyte, respectively, to largely elevate the capacitive performance of supercapacitors. More importantly, the cooperative effect results from the redox processes of DQ and HQ consecutively occurring in the electrode carbon material and aqueous H2SO4 electrolyte, respectively. Besides, the molar ratio of DQ and HQ exerts a crucial role in the determination of the electrochemical behaviors and eventually the optimum condition is the mass ratio of 1:1 concerning the DQ and porous carbon within solid electrode while retaining the HQ concentration as 20 mmol L-1 in 1 mol L-1 H2SO4 electrolyte. As a result, the maximum specific capacitance is achieved of 239 F g-1 at 3 A g-1, and furthermore the maximum energy density up to 21.1 Wh kg-1 is almost 3.5 times larger than that of the one without introducing any redox additive.

Does assisted driving behavior lead to safety-critical encounters with unequipped vehicles' drivers?

PubMed

Preuk, Katharina; Stemmler, Eric; Schießl, Caroline; Jipp, Meike

2016-10-01

With Intelligent Transport Systems (e.g., traffic light assistance systems) assisted drivers are able to show driving behavior in anticipation of upcoming traffic situations. In the years to come, the penetration rate of such systems will be low. Therefore, the majority of vehicles will not be equipped with these systems. Unequipped vehicles' drivers may not expect the driving behavior of assisted drivers. However, drivers' predictions and expectations can play a significant role in their reaction times. Thus, safety issues could arise when unequipped vehicles' drivers encounter driving behavior of assisted drivers. This is why we tested how unequipped vehicles' drivers (N=60) interpreted and reacted to the driving behavior of an assisted driver. We used a multi-driver simulator with three drivers. The three drivers were driving in a line. The lead driver in the line was a confederate who was followed by two unequipped vehicles' drivers. We varied the equipment of the confederate with an Intelligent Transport System: The confederate was equipped either with or without a traffic light assistance system. The traffic light assistance system provided a start-up maneuver before a light turned green. Therefore, the assisted confederate seemed to show unusual deceleration behavior by coming to a halt at an unusual distance from the stop line at the red traffic light. The unusual distance was varied as we tested a moderate (4m distance from the stop line) and an extreme (10m distance from the stop line) parameterization of the system. Our results showed that the extreme parametrization resulted in shorter minimal time-to-collision of the unequipped vehicles' drivers. One rear-end crash was observed. These results provided initial evidence that safety issues can arise when unequipped vehicles' drivers encounter assisted driving behavior. We recommend that future research identifies counteractions to prevent these safety issues. Moreover, we recommend that system developers discuss the best parameterizations of their systems to ensure benefits but also the safety in encounters with unequipped vehicles' drivers. Copyright © 2016 Elsevier Ltd. All rights reserved.

Reprint Characteristics of Non-Silver Films.

ERIC Educational Resources Information Center

Microform Review, 1990

1990-01-01

Describes reprint characteristics of diazo and vesicular films. Use with microform reader-printers and autogeneration of copies are discussed, and methods of dealing with the unusual reprint behavior of these films are outlined. (MES)

Nuclear Forensics and Radiochemistry: Chemistry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rundberg, Robert S.

The chemical behavior of radioactive elements can differ from conventional wisdom because the number of atoms can be unusually small. Kinetic effects and unusual oxidation states are phenomena that make radiochemistry different from conventional analytic chemistry. The procedures developed at Los Alamos are designed to minimize these effects and provide reproducible results over a wide range of sample types. The analysis of nuclear debris has the additional complication of chemical fractionation and the incorporation of environmental contaminants. These are dealt with through the use of three component isotope ratios and the use of appropriate end members.

Review of the genus Hemistola Warren, 1893 in Taiwan with notes on an unusual conifer-feeding larva and descriptions of three new species (Lepidoptera, Geometridae, Geometrinae).

PubMed

Chang, Wei-Chun; Wu, Shipher

2013-11-29

The genus Hemistola Warren, 1893 in Taiwan is reviewed. Seven species are confirmed, with descriptions of three new species provided: H. piceacola sp. nov., H. fui sp. nov. and H. taiwanensis sp. nov. The immature stages and unusual conifer-feeding behavior of H. piceacola on Taiwan spruce (Picea morrisonicola) are reported. The distribution of H. tenuilinea (Alphéraky, 1897) is discussed and this species is omitted from the Taiwanese fauna.

Antipsychotic polypharmacy prescribing patterns and costs in the Florida adult and child Medicaid populations.

PubMed

Becker, Edmund R; Constantine, Robert J; McPherson, Marie A; Jones, Mary Elizabeth

2013-01-01

The rapid growth in the use of antipsychotic medications and their related costs have resulted in states developing programs to measure, monitor, and insure their beneficial relevance to public program populations. One such program developed in the state of Florida has adopted an evidence-based approach to identify prescribers with unusual psychotherapeutic prescription patterns and track their utilization and costs among Florida Medicaid patients. This study reports on the prescriber prescription and cost patterns for adults and children using three measures of unusual antipsychotic prescribing patterns: (1) two antipsychotics for 60 days (2AP60), (2) three antipsychotics for 60 days (3AP60), and (2) two antipsychotics for 90 or more days (2AP90). We find that over the four-year study period there were substantial increases in several aspects of the Florida Medicaid behavioral drug program. Overall, for adults and children, patient participation increased by 29 percent, the number of prescriptions grew by 30 percent, and the number of prescribers that wrote at least one prescription grew 48.5 percent, while Medicaid costs for behavioral drugs increased by 32 percent. But the results are highly skewed. We find that a relatively small number of prescribers account for a disproportionately large share of prescriptions and costs of the unusual antipsychotic prescriptions. In general, the top 350 Medicaid prescribers accounted for more than 70 percent of the unusual antipsychotic prescriptions, and we find that this disparity in unusual prescribing patterns appears to be substantially more pronounced in adults than in children prescribers. For just the top 13 adult and children prescribers, their practice patterns accounted for 11 percent to 21 percent of the unusual prescribing activity and, overall, these 13 top prescribers accounted for 13 percent of the total spent on antipsychotics by the Florida Medicaid program and 9.3 percent of the total expenditure by the state for all drugs. Our findings suggest that a strategy to monitor and ensure patient safety and prescribing patterns that targets a relatively small number of Medicaid providers could have a substantial benefit and prove to be cost effective.

Macroscopic experimental and modeling evaluation of selenite and selenate adsorption mechanisms on gibbsite

USDA-ARS?s Scientific Manuscript database

Selenite Se(IV) and selenate Se(VI) selenium adsorption behavior was investigated on gibbsite as a function of solution pH and solution ionic strength. Adsorption of both Se redox states decreased with increasing solution pH. Electrophoretic mobility measurements showed downward shifts in point of...

Low-temperature behavior of the quark-meson model

NASA Astrophysics Data System (ADS)

Tripolt, Ralf-Arno; Schaefer, Bernd-Jochen; von Smekal, Lorenz; Wambach, Jochen

2018-02-01

We revisit the phase diagram of strong-interaction matter for the two-flavor quark-meson model using the functional renormalization group. In contrast to standard mean-field calculations, an unusual phase structure is encountered at low temperatures and large quark chemical potentials. In particular, we identify a regime where the pressure decreases with increasing temperature and discuss possible reasons for this unphysical behavior.

Redox Reactions of the Iron-Sulfur Cluster in a Ribosomal RNA Methyltransferase, RumA

PubMed Central

Agarwalla, Sanjay; Stroud, Robert M.; Gaffney, Betty J.

2005-01-01

An unprecedented [4Fe-4S] iron-sulfur cluster was found in RumA, the enzyme that methylates U1939 in Escherichia coli 23 S ribosomal RNA (Agarwalla, S., Kealey, J. T., Santi, D. V., and Stroud, R. M. (2002) J. Biol. Chem. 277, 8835–8840; Lee, T. T., Agarwalla, S., and Stroud, R. M. (2004) Structure 12, 397–407). Methyltransferase reactions do not involve a redox step. To understand the structural and functional roles of the cluster in RumA, we have characterized redox reactions of the iron-sulfur cluster. As isolated aerobically, RumA exhibits a visible absorbance maximum at 390 nm and is EPR silent. It cannot be reduced by anaerobic additions of dithionite. Photoreduction by deazariboflavin/EDTA gives EPR spectra, the quantity (56% of S = 1/2 species) and details (gav ~ 1.96–1.93) of which indicate a [4Fe-4S]1+ cluster in the reduced RumA. Oxidation of RumA by ferricyanide leads to loss of the 390-nm band and appearance of lower intensity bands at 444 and 520 nm. EPR spectra of ferricyanide-oxidized RumA show a fraction (<8%) of the FeS cluster trapped in the [3Fe-4S]1+ form (gav ~ 2.011) together with unusual radical-like spectrum (g′ values 2.015, 2.00, and 1.95). RumA also reacts with nitric oxide to give EPR spectra characteristic of the protein-bound iron dinitrosyl species. Oxidation of the cluster leads to its decomposition and that could be a mechanism for regulating the activity of RumA under conditions of oxidative stress in the cell. Sequence data base searches revealed that RumA homologs are widespread in various kingdoms of life and contain a conserved and unique iron-sulfur cluster binding motif, CX5CGGC. PMID:15181002

Relationship Between Unusual High-Temperature Fatigue Crack Growth Threshold Behavior in Superalloys and Sudden Failure Mode Transitions

NASA Technical Reports Server (NTRS)

Telesman, J.; Smith, T. M.; Gabb, T. P.; Ring, A. J.

2017-01-01

An investigation of high temperature cyclic fatigue crack growth (FCG) threshold behavior of two advanced nickel disk alloys was conducted. The focus of the study was the unusual crossover effect in the near-threshold region of these type of alloys where conditions which produce higher crack growth rates in the Paris regime, produce higher resistance to crack growth in the near threshold regime. It was shown that this crossover effect is associated with a sudden change in the fatigue failure mode from a predominant transgranular mode in the Paris regime to fully intergranular mode in the threshold fatigue crack growth region. This type of a sudden change in the fracture mechanisms has not been previously reported and is surprising considering that intergranular failure is typically associated with faster crack growth rates and not the slow FCG rates of the near-threshold regime. By characterizing this behavior as a function of test temperature, environment and cyclic frequency, it was determined that both the crossover effect and the onset of intergranular failure are caused by environmentally driven mechanisms which have not as yet been fully identified. A plausible explanation for the observed behavior is proposed.

Intramantle Inking: A Stress Behavior in Octopus bimaculoides (Mollusca: Cephalopoda)

PubMed Central

Toll, Ronald B

2011-01-01

Several Pacific 2-spot octopuses (Octopus bimaculoides) shipped from California and held in a recirculating seawater system at Illinois College exhibited an unusual postshipping stress behavior not previously documented in the literature. Ink, normally ejected into the surrounding seawater, was uncharacteristically retained in the mantle cavity. We describe the resulting behaviors, discuss successful resuscitation efforts, and briefly consider the possible role(s) that ink may have played in the death of one octopus. PMID:22330791

Needs Assessment for Behavioral Health Workforce: a State-Level Analysis.

PubMed

Nayar, Preethy; Apenteng, Bettye; Nguyen, Anh T; Shaw-Sutherland, Kelly; Ojha, Diptee; Deras, Marlene

2017-07-01

This study describes trends in the supply and the need for behavioral health professionals in Nebraska. A state-level health workforce database was used to estimate the behavioral health workforce supply and need. Compared with national estimates, Nebraska has a lower proportion of all categories of behavioral health professionals. The majority of Nebraska counties have unusually high needs for mental health professionals, with rural areas experiencing a decline in the supply of psychiatrists over the last decade. Availability of robust state-level health workforce data can assist in crafting effective policy for successful systems change, particularly for behavioral health.

Tunnel structured manganese oxide nanowires as redox active electrodes for hybrid capacitive deionization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Byles, Bryan W.; Cullen, David A.; More, Karren Leslie

We report that hybrid capacitive deionization (HCDI), which combines a capacitive carbon electrode and a redox active electrode in a single device, has emerged as a promising method for water desalination, enabling higher ion removal capacity than devices containing two carbon electrodes. However, to date, the desalination performance of few redox active materials has been reported. For the first time, we present the electrochemical behavior of manganese oxide nanowires with four different tunnel crystal structures as faradaic electrodes in HCDI cells. Two of these phases are square tunnel structured manganese oxides, α-MnO 2 and todorokite-MnO 2. The other two phasesmore » have novel structures that cross-sectional scanning transmission electron microscopy analysis revealed to have ordered and disordered combinations of structural tunnels with different dimensions. The ion removal performance of the nanowires was evaluated not only in NaCl solution, which is traditionally used in laboratory experiments, but also in KCl and MgCl 2 solutions, providing better understanding of the behavior of these materials for desalination of brackish water that contains multiple cation species. High ion removal capacities (as large as 27.8 mg g -1, 44.4 mg g -1, and 43.1 mg g -1 in NaCl, KCl, and MgCl 2 solutions, respectively) and high ion removal rates (as large as 0.112 mg g -1 s -1, 0.165 mg g -1 s -1, and 0.164 mg g -1 s -1 in NaCl, KCl, and MgCl 2 solutions, respectively) were achieved. By comparing ion removal capacity to structural tunnel size, it was found that smaller tunnels do not favor the removal of cations with larger hydrated radii, and more efficient removal of larger hydrated cations can be achieved by utilizing manganese oxides with larger structural tunnels. Extended HCDI cycling and ex situ X-ray diffraction analysis revealed the excellent stability of the manganese oxide electrodes in repeated ion removal/ion release cycles, and compositional analysis of the electrodes indicated that ion removal is achieved through both surface redox reactions and intercalation of ions into the structural tunnels. In conclusion, this work contributes to the understanding of the behavior of faradaic materials in electrochemical water desalination and elucidates the relationship between the electrode material crystal structure and the ion removal capacity/ion removal rate in various salt solutions.« less

Tunnel structured manganese oxide nanowires as redox active electrodes for hybrid capacitive deionization

DOE PAGES

Byles, Bryan W.; Cullen, David A.; More, Karren Leslie; ...

2017-12-18

We report that hybrid capacitive deionization (HCDI), which combines a capacitive carbon electrode and a redox active electrode in a single device, has emerged as a promising method for water desalination, enabling higher ion removal capacity than devices containing two carbon electrodes. However, to date, the desalination performance of few redox active materials has been reported. For the first time, we present the electrochemical behavior of manganese oxide nanowires with four different tunnel crystal structures as faradaic electrodes in HCDI cells. Two of these phases are square tunnel structured manganese oxides, α-MnO 2 and todorokite-MnO 2. The other two phasesmore » have novel structures that cross-sectional scanning transmission electron microscopy analysis revealed to have ordered and disordered combinations of structural tunnels with different dimensions. The ion removal performance of the nanowires was evaluated not only in NaCl solution, which is traditionally used in laboratory experiments, but also in KCl and MgCl 2 solutions, providing better understanding of the behavior of these materials for desalination of brackish water that contains multiple cation species. High ion removal capacities (as large as 27.8 mg g -1, 44.4 mg g -1, and 43.1 mg g -1 in NaCl, KCl, and MgCl 2 solutions, respectively) and high ion removal rates (as large as 0.112 mg g -1 s -1, 0.165 mg g -1 s -1, and 0.164 mg g -1 s -1 in NaCl, KCl, and MgCl 2 solutions, respectively) were achieved. By comparing ion removal capacity to structural tunnel size, it was found that smaller tunnels do not favor the removal of cations with larger hydrated radii, and more efficient removal of larger hydrated cations can be achieved by utilizing manganese oxides with larger structural tunnels. Extended HCDI cycling and ex situ X-ray diffraction analysis revealed the excellent stability of the manganese oxide electrodes in repeated ion removal/ion release cycles, and compositional analysis of the electrodes indicated that ion removal is achieved through both surface redox reactions and intercalation of ions into the structural tunnels. In conclusion, this work contributes to the understanding of the behavior of faradaic materials in electrochemical water desalination and elucidates the relationship between the electrode material crystal structure and the ion removal capacity/ion removal rate in various salt solutions.« less

Redox-mediated dissolution of paramagnetic nanolids to achieve a smart theranostic system

NASA Astrophysics Data System (ADS)

Wang, Aifei; Guo, Mingyi; Wang, Nan; Zhao, Jianyun; Qi, Wenxiu; Muhammad, Faheem; Chen, Liang; Guo, Yingjie; Nguyen, Nam-Trung; Zhu, Guangshan

2014-04-01

Manganese oxide (Mn3O4) nanoparticles have recently emerged as a promising T1 contrast agent. In this study, for the first time, we demonstrated an interaction of Mn3O4 with a biological system, and found redox sensitive behavior of these paramagnetic nanoparticles in intracellular reducing environment. Inspired by these findings, we for the first time used this interaction for some therapeutic advantages and designed a versatile mesoporous silica based nanotheranostic system to realize redox-activated enhanced magnetic resonance imaging and responsive anticancer drug delivery. Contrary to previous reports, we firstly prepared high quality amine terminated hydrophilic Mn3O4 nanolids, without using multistep ligand exchange strategies. The resulting water stable and small-sized Mn3O4 nanolids were subsequently used as nanolids to cap drug loaded nanochannels of a porous carrier. Exposure to highly prevalent intracellular reducing environment resulted in the steady-state dissolution of these nanolids and attained an intelligent drug release. Furthermore, the redox receptive dissolution of paramagnetic Mn3O4 nanolids into Mn2+ in turn increases the T1 signal to twofold, providing an added opportunity to even track the feedback of therapy. This study, in addition to simultaneously realizing drug delivery and imaging, also provides a new insight into the fate and interaction of manganese oxide nanoparticles with components of biological systems.Manganese oxide (Mn3O4) nanoparticles have recently emerged as a promising T1 contrast agent. In this study, for the first time, we demonstrated an interaction of Mn3O4 with a biological system, and found redox sensitive behavior of these paramagnetic nanoparticles in intracellular reducing environment. Inspired by these findings, we for the first time used this interaction for some therapeutic advantages and designed a versatile mesoporous silica based nanotheranostic system to realize redox-activated enhanced magnetic resonance imaging and responsive anticancer drug delivery. Contrary to previous reports, we firstly prepared high quality amine terminated hydrophilic Mn3O4 nanolids, without using multistep ligand exchange strategies. The resulting water stable and small-sized Mn3O4 nanolids were subsequently used as nanolids to cap drug loaded nanochannels of a porous carrier. Exposure to highly prevalent intracellular reducing environment resulted in the steady-state dissolution of these nanolids and attained an intelligent drug release. Furthermore, the redox receptive dissolution of paramagnetic Mn3O4 nanolids into Mn2+ in turn increases the T1 signal to twofold, providing an added opportunity to even track the feedback of therapy. This study, in addition to simultaneously realizing drug delivery and imaging, also provides a new insight into the fate and interaction of manganese oxide nanoparticles with components of biological systems. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr05687b

Unusual masturbatory practice as an etiological factor in the diagnosis and treatment of sexual dysfunction in young men.

PubMed

Bronner, Gila; Ben-Zion, Itzhak Z

2014-07-01

Masturbation is a common sexual activity among people of all ages throughout life. It has been traditionally prohibited and judged as immoral and sinful by several religions. Although it is no longer perceived as a negative behavior, masturbation is often omitted in the diagnostic inquiry of patients with sexual problems. The aims of this study are to increase the awareness of clinicians to the importance of including questions regarding masturbatory habits in the process of sexual history taking, to analyze cases of male sexual dysfunction (SD) associated with unusual masturbatory practices, and to propose a practical tool for clinicians to diagnose and manage such problems. A clinical study of four cases that include a range of unusual masturbatory practices by young males who applied for sex therapy is described. An intervention plan involving specific questions in case history taking was devised. It was based on detailed understanding of each patient's masturbatory practice and its manifestation in his SD. Effects of identifying and altering masturbatory practices on sexual function. The four men described unusual and awkward masturbatory practices, each of which was associated with different kinds of SD. The unlearning of the masturbatory practices contributed notably to improvement of their sexual function. The four cases in this study indicate that the detailed questioning of masturbatory habits is crucial for a thorough assessment and adequate treatment of sexual problems in men. We propose specific questions on masturbatory behavior as well as a diagnostic and therapeutic flowchart for physicians and sex therapists to address those problems. © 2014 International Society for Sexual Medicine.

Transient cocaine-associated behavioral symptoms rated with a new instrument, the scale for assessment of positive symptoms for cocaine-induced psychosis (SAPS-CIP).

PubMed

Tang, Yi-lang; Kranzler, Henry R; Gelernter, Joel; Farrer, Lindsay A; Pearson, Deborah; Cubells, Joseph F

2009-01-01

Chronic use of cocaine is associated with a variety of behavioral symptoms. The current report describes the assessment of cocaine-related behavioral symptoms (CRB) using the Scale for Assessment of Positive Symptoms of Cocaine-Induced Psychosis (SAPS-CIP). The CRB section, one of the three domains in the SAPS-CIP, consists of sub-domains, including Aggressive/Agitated Behavior, Repetitive/Stereotyped Behavior, and Unusual Social or Sexual Behavior. Severity scores are assigned according to operational criteria, and range from 0 (not present) to 5 (severe). We interviewed 261 unrelated cocaine-abusing adults using the SAPS-CIP, and 243 of them met criteria for inclusion in the study. The proportion of subjects endorsing different classes of CRBs varied across categories, with 109 of 243 (44.9%) subjects reporting aggressive and agitated behaviors, 180 subjects (74.1%) repetitive/stereotyped behaviors, and 192 (79.0%) unusual social/sexual behaviors. A substantial minority of the subjects (10.3-25.1%) reported that they experienced marked-to-severe behavioral symptoms associated with cocaine use. The proportions of subjects endorsing CRB did not differ by ethnic/racial group or by sex. Correlations among the different domains of CRB were strong, but behaviors rated in the CRB section were less well correlated with psychotic symptoms, which were rated in the hallucination and delusion sections of the instrument. A variety of CRBs are common in cocaine-dependent subjects, and many of these are highly intercorrelated. CRBs also correlate with hallucinations and delusions induced by cocaine, but to a lesser degree. Our findings suggest that there may be some common vulnerability factors that contribute to both cocaine-induced psychosis and CRBs.

Arctic Ozone Depletion from UARS MLS Measurements

NASA Technical Reports Server (NTRS)

Manney, G. L.

1995-01-01

Microwave Limb Sounder (MLS) measurements of ozone during four Arctic winters are compared. The evolution of ozone in the lower stratosphere is related to temperature, chlorine monoxide (also measured by MLS), and the evolution of the polar vortex. Lagrangian transport calculations using winds from the United Kingdom Meteorological Office's Stratosphere-Troposphere Data Assimilation system are used to estimate to what extent the evolution of lower stratospheric ozone is controlled by dynamics. Observations, along with calculations of the expected dynamical behavior, show evidence for chemical ozone depletion throughout most of the Arctic lower stratospheric vortex during the 1992-93 middle and late winter, and during all of the 1994-95 winter that was observed by MLS. Both of these winters were unusually cold and had unusually cold and had unusually strong Arctic polar vortices compared to meteorological data over the past 17 years.

Redox Active Polymers as Soluble Nanomaterials for Energy Storage.

PubMed

Burgess, Mark; Moore, Jeffrey S; Rodríguez-López, Joaquín

2016-11-15

It is an exciting time for exploring the synergism between the chemical and dimensional properties of redox nanomaterials for addressing the manifold performance demands faced by energy storage technologies. The call for widespread adoption of alternative energy sources requires the combination of emerging chemical concepts with redesigned battery formats. Our groups are interested in the development and implementation of a new strategy for nonaqueous flow batteries (NRFBs) for grid energy storage. Our motivation is to solve major challenges in NRFBs, such as the lack of membranes that simultaneously allow fast ion transport while minimizing redox active species crossover between anolyte (negative electrolyte) and catholyte (positive electrolyte) compartments. This pervasive crossover leads to deleterious capacity fade and materials underutilization. In this Account, we highlight redox active polymers (RAPs) and related polymer colloids as soluble nanoscopic energy storing units that enable the simple but powerful size-exclusion concept for NRFBs. Crossover of the redox component is suppressed by matching high molecular weight RAPs with simple and inexpensive nanoporous commercial separators. In contrast to the vast literature on the redox chemistry of electrode-confined polymer films, studies on the electrochemistry of solubilized RAPs are incipient. This is due in part to challenges in finding suitable solvents that enable systematic studies on high polymers. Here, viologen-, ferrocene- and nitrostyrene-based polymers in various formats exhibit properties that make amenable their electrochemical exploration as solution-phase redox couples. A main finding is that RAP solutions store energy efficiently and reversibly while offering chemical modularity and size versatility. Beyond the practicality toward their use in NRFBs, the fundamental electrochemistry exhibited by RAPs is fascinating, showing clear distinctions in behavior from that of small molecules. Whereas RAPs conveniently translate the redox properties of small molecules into a nanostructure, they give rise to charge transfer mechanisms and electrolyte interactions that elicit distinct electrochemical responses. To understand how the electrochemical characteristics of RAPs depend on molecular features, including redox moiety, macromolecular size, and backbone structure, a range of techniques has been employed by our groups, including voltammetry at macro- and microelectrodes, rotating disk electrode voltammetry, bulk electrolysis, and scanning electrochemical microscopy. RAPs rely on three-dimensional charge transfer within their inner bulk, which is an efficient process and allows quantitative electrolysis of particles of up to ∼800 nm in radius. Interestingly, we find that interactions between neighboring pendants create unique opportunities for fine-tuning their electrochemical reactivity. Furthermore, RAP interrogation toward the single particle limit promises to shed light on fundamental charge storage mechanisms.

An embodied view of octopus neurobiology.

PubMed

Hochner, Binyamin

2012-10-23

Octopuses have a unique flexible body and unusual morphology, but nevertheless they are undoubtedly a great evolutionary success. They compete successfully with vertebrates in their ecological niche using a rich behavioral repertoire more typical of an intelligent predator which includes extremely effective defensive behavior--fast escape swimming and an astonishing ability to adapt their shape and color to their environment. The most obvious characteristic feature of an octopus is its eight long and flexible arms, but these pose a great challenge for achieving the level of motor and sensory information processing necessary for their behaviors. First, coordinating motion is a formidable task because of the infinite degrees of freedom that have to be controlled; and second, it is hard to use body coordinates in this flexible animal to represent sensory information in a central control system. Here I will review experimental results suggesting that these difficulties, arising from the animal's morphology, have imposed the evolution of unique brain/body/behavior relationships best explained as intelligent behavior which emerges from the octopus's embodied organization. The term 'intelligent embodiment' comes from robotics and refers to an approach to designing autonomous robots in which the behavior emerges from the dynamic physical and sensory interactions of the agent's materials, morphology and environment. Consideration of the unusual neurobiology of the octopus in the light of its unique morphology suggests that similar embodied principles are instrumental for understanding the emergence of intelligent behavior in all biological systems. Copyright © 2012 Elsevier Ltd. All rights reserved.

Novel metal-filled polyimide electrodes

NASA Technical Reports Server (NTRS)

Furtsch, T. A.; Finklea, H. O.; Taylor, L. T.

1984-01-01

Palladium-coated polyimide films are evaluated as electrochemical electrodes. The film electrodes exhibit essentially identical behavior compared to bulk palladium electrodes. In aqueous 0.5M H2SO4, current peaks due to oxide formation, oxide stripping, hydrogen adsorption, and H2 oxidation are observed. The ferri/ferrocyanide redox couple is grossly irreversible in the same electrolyte. Reversible electrochemical behavior is obtained for Fe(EDTA)(1-/2-) in 1M KCl/H2O, and for ferrocene/ferricenium in 0.1M TEAP/dimethylacetamide.

Fast and stable redox reactions of MnO2/CNT hybrid electrodes for dynamically stretchable pseudocapacitors

NASA Astrophysics Data System (ADS)

Gu, Taoli; Wei, Bingqing

2015-07-01

Pseudocapacitors, which are energy storage devices that take advantage of redox reactions to store electricity, have a different charge storage mechanism compared to lithium-ion batteries (LIBs) and electric double-layer capacitors (EDLCs), and they could realize further gains if they were used as stretchable power sources. The realization of dynamically stretchable pseudocapacitors and understanding of the underlying fundamentals of their mechanical-electrochemical relationship have become indispensable. We report herein the electrochemical performance of dynamically stretchable pseudocapacitors using buckled MnO2/CNT hybrid electrodes. The extremely small relaxation time constant of less than 0.15 s indicates a fast redox reaction at the MnO2/CNT hybrid electrodes, securing a stable electrochemical performance for the dynamically stretchable pseudocapacitors. This finding and the fundamental understanding gained from the pseudo-capacitive behavior coupled with mechanical deformation under a dynamic stretching mode would provide guidance to further improve their overall performance including a higher power density than LIBs, a higher energy density than EDLCs, and a long-life cycling stability. Most importantly, these results will potentially accelerate the applications of stretchable pseudocapacitors for flexible and biomedical electronics.Pseudocapacitors, which are energy storage devices that take advantage of redox reactions to store electricity, have a different charge storage mechanism compared to lithium-ion batteries (LIBs) and electric double-layer capacitors (EDLCs), and they could realize further gains if they were used as stretchable power sources. The realization of dynamically stretchable pseudocapacitors and understanding of the underlying fundamentals of their mechanical-electrochemical relationship have become indispensable. We report herein the electrochemical performance of dynamically stretchable pseudocapacitors using buckled MnO2/CNT hybrid electrodes. The extremely small relaxation time constant of less than 0.15 s indicates a fast redox reaction at the MnO2/CNT hybrid electrodes, securing a stable electrochemical performance for the dynamically stretchable pseudocapacitors. This finding and the fundamental understanding gained from the pseudo-capacitive behavior coupled with mechanical deformation under a dynamic stretching mode would provide guidance to further improve their overall performance including a higher power density than LIBs, a higher energy density than EDLCs, and a long-life cycling stability. Most importantly, these results will potentially accelerate the applications of stretchable pseudocapacitors for flexible and biomedical electronics. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr02310f

Emerging regulatory paradigms in glutathione metabolism

PubMed Central

Liu, Yilin; Hyde, Annastasia S.; Simpson, Melanie A.; Barycki, Joseph J.

2015-01-01

One of the hallmarks of cancer is the ability to generate and withstand unusual levels of oxidative stress. In part, this property of tumor cells is conferred by elevation of the cellular redox buffer glutathione. Though enzymes of the glutathione synthesis and salvage pathways have been characterized for several decades, we still lack a comprehensive understanding of their independent and coordinate regulatory mechanisms. Recent studies have further revealed that overall central metabolic pathways are frequently altered in various tumor types, resulting in significant increases in biosynthetic capacity, and feeding into glutathione synthesis. In this review, we will discuss the enzymes and pathways affecting glutathione flux in cancer, and summarize current models for regulating cellular glutathione through both de novo synthesis and efficient salvage. In addition, we examine the integration of glutathione metabolism with other altered fates of intermediary metabolites, and highlight remaining questions about molecular details of the accepted regulatory modes. PMID:24974179

Enzymatic Reductive Dehalogenation Controls the Biosynthesis of Marine Bacterial Pyrroles.

PubMed

El Gamal, Abrahim; Agarwal, Vinayak; Rahman, Imran; Moore, Bradley S

2016-10-12

Enzymes capable of performing dehalogenating reactions have attracted tremendous contemporary attention due to their potential application in the bioremediation of anthropogenic polyhalogenated persistent organic pollutants. Nature, in particular the marine environment, is also a prolific source of polyhalogenated organic natural products. The study of the biosynthesis of these natural products has furnished a diverse array of halogenation biocatalysts, but thus far no examples of dehalogenating enzymes have been reported from a secondary metabolic pathway. Here we show that the penultimate step in the biosynthesis of the highly brominated marine bacterial product pentabromopseudilin is catalyzed by an unusual debrominase Bmp8 that utilizes a redox thiol mechanism to remove the C-2 bromine atom of 2,3,4,5-tetrabromopyrrole to facilitate oxidative coupling to 2,4-dibromophenol. To the best of our knowledge, Bmp8 is first example of a dehalogenating enzyme from the established genetic and biochemical context of a natural product biosynthetic pathway.

Mössbauer spectroscopy of the chloroplast-targeted DnaJ-like proteins CDJ3 and CDJ4

NASA Astrophysics Data System (ADS)

Auerbach, H.; Kalienkova, V.; Schroda, M.; Schünemann, V.

2017-11-01

The heat shock protein 70 (HSP70) in the chloroplast of Chlamydomonas reinhardtii, termed HSP70B, interacts with chloroplast-targeted DnaJ-like proteins (CDJs). In this work we focus on two CDJ co-chaperones (CDJ3 and CDJ4) of HSP70B which contain a redox-active Fe-S cluster (Dorn et al. Biochem. J. 427, 205 [2010]). We have performed Mössbauer spectroscopy on 57Fe enriched CDJ3 an) CDJ4. Our results indicate that both proteins have unusual [4Fe4S] 2+ clusters showing structural inhomogeneity of the two [Fe 2.5+-Fe 2.5+] pairs. The spectra have been analyzed by means of two components with δ-values characteristic for Fe 2.5+ centers, but the differences in Δ E Q indicate variations in their tetrahedral coordination spheres.

Polarization curve measurements combined with potential probe sensing for determining current density distribution in vanadium redox-flow batteries

NASA Astrophysics Data System (ADS)

Becker, Maik; Bredemeyer, Niels; Tenhumberg, Nils; Turek, Thomas

2016-03-01

Potential probes are applied to vanadium redox-flow batteries for determination of effective felt resistance and current density distribution. During the measurement of polarization curves in 100 cm2 cells with different carbon felt compression rates, alternating potential steps at cell voltages between 0.6 V and 2.0 V are applied. Polarization curves are recorded at different flow rates and states of charge of the battery. Increasing compression rates lead to lower effective felt resistances and a more uniform resistance distribution. Low flow rates at high or low state of charge result in non-linear current density distribution with high gradients, while high flow rates give rise to a nearly linear behavior.

High Field Remagnetization of Hematite Concretions from Utah, USA and Czech Republic

NASA Astrophysics Data System (ADS)

Adachi, T.; Kletetschka, G.; Chan, M.; Mikula, V.; Adamovic, J.; Pruner, P.; Schnabl, P.; Wasilewski, P.

2007-03-01

Terrestrial hematite concretions of the Navajo Sandstone have been discussed as analogues to the blueberries on Mars. Magnetic investigation of terrestrial concretions showed unusual behavior of antiferromagnetic hematite-goethite composition that may mem

EXPLOITATION AND OPTIMIZATION OF RESERVOIR PERFORMANCE IN HUNTON FORMATION, OKLAHOMA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mohan Kelkar

2002-03-31

The West Carney Field in Lincoln County, Oklahoma is one of few newly discovered oil fields in Oklahoma. Although profitable, the field exhibits several unusual characteristics. These include decreasing water-oil ratios, decreasing gas-oil ratios, decreasing bottomhole pressures during shut-ins in some wells, and transient behavior for water production in many wells. This report explains the unusual characteristics of West Carney Field based on detailed geological and engineering analyses. We propose a geological history that explains the presence of mobile water and oil in the reservoir. The combination of matrix and fractures in the reservoir explains the reservoir's flow behavior. Wemore » confirm our hypothesis by matching observed performance with a simulated model and develop procedures for correlating core data to log data so that the analysis can be extended to other, similar fields where the core coverage may be limited.« less

Increased Prevalence of Unusual Sensory Behaviors in Infants at Risk for, and Teens with, Autism Spectrum Disorder.

PubMed

Van Etten, Hannah M; Kaur, Maninderjit; Srinivasan, Sudha M; Cohen, Shereen J; Bhat, Anjana; Dobkins, Karen R

2017-11-01

The current study investigated the prevalence and pattern of unusual sensory behaviors (USBs) in teens with Autism Spectrum Disorder (ASD) and infants (3-36 months) at risk for ASD. From two different sites (UCSD and UConn), caregivers of infants at high (n = 32) and low risk (n = 33) for ASD, and teenagers with (n = 12) and without ASD (n = 11), completed age-appropriate Sensory Profile questionnaires (Infant/Toddler Sensory Profile; Dunn 2002; Adolescent/Adult Sensory Profile; Brown and Dunn 2002). The results show that high-risk infants and teenagers with ASD exhibit higher-than-typical prevalence of USBs. Results of our distribution analyses investigating the direction of sensory atypicalities (greater-than-typical vs. less-than-typical) revealed a fair degree of consistency amongst teens, however, USB patterns were more varied in high-risk infants.

Unusual Crystallization Behavior Close to the Glass Transition

NASA Astrophysics Data System (ADS)

Desgranges, Caroline; Delhommelle, Jerome

2018-03-01

Using molecular simulations, we shed light on the mechanism underlying crystal nucleation in metal alloys and unravel the interplay between crystal nucleation and glass transition, as the conditions of crystallization lie close to this transition. While decreasing the temperature of crystallization usually results in a lower free energy barrier, we find an unexpected reversal of behavior for glass-forming alloys as the temperature of crystallization approaches the glass transition. For this purpose, we simulate the crystallization process in two glass-forming Copper alloys, Ag6 Cu4 , which has a positive heat of mixing, and CuZr, characterized by a large negative heat of mixing. Our results allow us to identify this unusual behavior as directly correlated with a nonmonotonic temperature dependence for the formation energy of connected icosahedral structures, which are incompatible with crystalline order and impede the development of the crystal nucleus, leading to an unexpectedly larger free energy barrier at low temperature. This, in turn, promotes the formation of a predominantly closed-packed critical nucleus, with fewer defects, thereby suggesting a new way to control the structure of the crystal nucleus, which is of key importance in catalysis.

Redox levels in aqueous solution: Effect of van der Waals interactions and hybrid functionals.

PubMed

Ambrosio, Francesco; Miceli, Giacomo; Pasquarello, Alfredo

2015-12-28

We investigate redox levels in aqueous solution using a combination of ab initio molecular dynamics (MD) simulations and thermodynamic integration methods. The molecular dynamics are performed with both the semilocal Perdew-Burke-Ernzerhof functional and a nonlocal functional (rVV10) accounting for van der Waals (vdW) interactions. The band edges are determined through three different schemes, namely, from the energy of the highest occupied and of the lowest unoccupied Kohn-Sham states, from total-energy differences, and from a linear extrapolation of the density of states. It is shown that the latter does not depend on the system size while the former two are subject to significant finite-size effects. For the redox levels, we provide a formulation in analogy to the definition of charge transition levels for defects in crystalline materials. We consider the H(+)/H2 level defining the standard hydrogen electrode, the OH(-)/OH(∗) level corresponding to the oxidation of the hydroxyl ion, and the H2O/OH(∗) level for the dehydrogenation of water. In spite of the large structural modifications induced in liquid water, vdW interactions do not lead to any significant structural effect on the calculated band gap and band edges. The effect on the redox levels is also small since the solvation properties of ionic species are little affected by vdW interactions. Since the electronic properties are not significantly affected by the underlying structural properties, it is justified to perform hybrid functional calculations on the configurations of our MD simulations. The redox levels calculated as a function of the fraction α of Fock exchange are found to remain constant, reproducing a general behavior previously observed for charge transition levels of defects. Comparison with experimental values shows very good agreement. At variance, the band edges and the band gap evolve linearly with α. For α ≃ 0.40, we achieve a band gap, band-edge positions, and redox levels in overall good agreement with experiment.

A redox-stratified ocean 3.2 billion years ago

NASA Astrophysics Data System (ADS)

Satkoski, Aaron M.; Beukes, Nicolas J.; Li, Weiqiang; Beard, Brian L.; Johnson, Clark M.

2015-11-01

Before the Great Oxidation Event (GOE) 2.4-2.2 billion years ago it has been traditionally thought that oceanic water columns were uniformly anoxic due to a lack of oxygen-producing microorganisms. Recently, however, it has been proposed that transient oxygenation of shallow seawater occurred between 2.8 and 3.0 billion years ago. Here, we present a novel combination of stable Fe and radiogenic U-Th-Pb isotope data that demonstrate significant oxygen contents in the shallow oceans at 3.2 Ga, based on analysis of the Manzimnyama Banded Iron Formation (BIF), Fig Tree Group, South Africa. This unit is exceptional in that proximal, shallow-water and distal, deep-water facies are preserved. When compared to the distal, deep-water facies, the proximal samples show elevated U concentrations and moderately positive δ56Fe values, indicating vertical stratification in dissolved oxygen contents. Confirmation of oxidizing conditions using U abundances is robustly constrained using samples that have been closed to U and Pb mobility using U-Th-Pb geochronology. Although redox-sensitive elements have been commonly used in ancient rocks to infer redox conditions, post-depositional element mobility has been rarely tested, and U-Th-Pb geochronology can constrain open- or closed-system behavior. The U abundances and δ56Fe values of the Manzimnyama BIF suggest the proximal, shallow-water samples record precipitation under stronger oxidizing conditions compared to the distal deeper-water facies, which in turn indicates the existence of a discrete redox boundary between deep and shallow ocean waters at this time; this work, therefore, documents the oldest known preserved marine redox gradient in the rock record. The relative enrichment of O2 in the upper water column is likely due to the existence of oxygen-producing microorganisms such as cyanobacteria. These results provide a new approach for identifying free oxygen in Earth's ancient oceans, including confirming the age of redox proxies, and indicate that cyanobacteria evolved prior to 3.2 Ga.

Redox levels in aqueous solution: Effect of van der Waals interactions and hybrid functionals

NASA Astrophysics Data System (ADS)

Ambrosio, Francesco; Miceli, Giacomo; Pasquarello, Alfredo

2015-12-01

We investigate redox levels in aqueous solution using a combination of ab initio molecular dynamics (MD) simulations and thermodynamic integration methods. The molecular dynamics are performed with both the semilocal Perdew-Burke-Ernzerhof functional and a nonlocal functional (rVV10) accounting for van der Waals (vdW) interactions. The band edges are determined through three different schemes, namely, from the energy of the highest occupied and of the lowest unoccupied Kohn-Sham states, from total-energy differences, and from a linear extrapolation of the density of states. It is shown that the latter does not depend on the system size while the former two are subject to significant finite-size effects. For the redox levels, we provide a formulation in analogy to the definition of charge transition levels for defects in crystalline materials. We consider the H+/H2 level defining the standard hydrogen electrode, the OH-/OH∗ level corresponding to the oxidation of the hydroxyl ion, and the H2O/OH∗ level for the dehydrogenation of water. In spite of the large structural modifications induced in liquid water, vdW interactions do not lead to any significant structural effect on the calculated band gap and band edges. The effect on the redox levels is also small since the solvation properties of ionic species are little affected by vdW interactions. Since the electronic properties are not significantly affected by the underlying structural properties, it is justified to perform hybrid functional calculations on the configurations of our MD simulations. The redox levels calculated as a function of the fraction α of Fock exchange are found to remain constant, reproducing a general behavior previously observed for charge transition levels of defects. Comparison with experimental values shows very good agreement. At variance, the band edges and the band gap evolve linearly with α. For α ≃ 0.40, we achieve a band gap, band-edge positions, and redox levels in overall good agreement with experiment.

Critical behavior in the system cyclopentanone + water + secondary butyl alcohol

NASA Astrophysics Data System (ADS)

Krishna, U. Santhi; Unni, P. K. Madhavan

2018-05-01

We report detailed measurements of coexistence surface in the ternary system cylcopentanone + water + secondary butyl alcohol. The coexistence surface is seen to have an unusual tunnel like feature and is a potential system in which special critical points such as the Quadruple Critical Point (QCP) could be studied. Analysis of coexistence curves indicates that the system shows 3D-Ising like critical behavior.

Disorders of Behavioral and Emotional Regulation in the First Years of Life: Early Risks and Intervention in the Developing Parent-Infant Relationship

ERIC Educational Resources Information Center

Papousek, Mechthild, Ed.; Schieche, Michael, Ed.; Wurmser, Harald, Ed.

2007-01-01

For every five healthy babies and infants, there is at least one who brings unusual stresses for its parents with behaviors such as inconsolable crying, sleep disorders, refusal to eat, chronic moodiness, incessant demands for attention, fearful clinging, or tantrums. Available for the first time in English, this influential German collection…

Base Rates of Social Skills Acquisition/Performance Deficits, Strengths, and Problem Behaviors: An Analysis of the Social Skills Improvement System-Rating Scales

ERIC Educational Resources Information Center

Gresham, Frank M.; Elliott, Stephen N.; Kettler, Ryan J.

2010-01-01

Base rate information is important in clinical assessment because one cannot know how unusual or typical a phenomenon is without first knowing its base rate in the population. This study empirically determined the base rates of social skills acquisition and performance deficits, social skills strengths, and problem behaviors using a nationally…

Cavitation in flowing superfluid helium

NASA Technical Reports Server (NTRS)

Daney, D. E.

1988-01-01

Flowing superfluid helium cavitates much more readily than normal liquid helium, and there is a marked difference in the cavitation behavior of the two fluids as the lambda point is traversed. Examples of cavitation in a turbine meter and centrifugal pump are given, together with measurements of the cavitation strength of flowing superfluid helium. The unusual cavitation behavior of superfluid helium is attributed to its immense thermal conductivity .

Redox-mediated dissolution of paramagnetic nanolids to achieve a smart theranostic system.

PubMed

Wang, Aifei; Guo, Mingyi; Wang, Nan; Zhao, Jianyun; Qi, Wenxiu; Muhammad, Faheem; Chen, Liang; Guo, Yingjie; Nguyen, Nam-Trung; Zhu, Guangshan

2014-05-21

Manganese oxide (Mn3O4) nanoparticles have recently emerged as a promising T1 contrast agent. In this study, for the first time, we demonstrated an interaction of Mn3O4 with a biological system, and found redox sensitive behavior of these paramagnetic nanoparticles in intracellular reducing environment. Inspired by these findings, we for the first time used this interaction for some therapeutic advantages and designed a versatile mesoporous silica based nanotheranostic system to realize redox-activated enhanced magnetic resonance imaging and responsive anticancer drug delivery. Contrary to previous reports, we firstly prepared high quality amine terminated hydrophilic Mn3O4 nanolids, without using multistep ligand exchange strategies. The resulting water stable and small-sized Mn3O4 nanolids were subsequently used as nanolids to cap drug loaded nanochannels of a porous carrier. Exposure to highly prevalent intracellular reducing environment resulted in the steady-state dissolution of these nanolids and attained an intelligent drug release. Furthermore, the redox receptive dissolution of paramagnetic Mn3O4 nanolids into Mn(2+) in turn increases the T1 signal to twofold, providing an added opportunity to even track the feedback of therapy. This study, in addition to simultaneously realizing drug delivery and imaging, also provides a new insight into the fate and interaction of manganese oxide nanoparticles with components of biological systems.

Redox-responsive microbeads containing thiolated pectin-doxorubicin conjugate inhibit tumor growth and metastasis: An in vitro and in vivo study.

PubMed

Cheewatanakornkool, Kamonrak; Niratisai, Sathit; Dass, Crispin R; Sriamornsak, Pornsak

2018-07-10

The objective of this study was to investigate the in vitro cytotoxicity and in vivo anticancer efficacy of redox-responsive microbeads containing thiolated pectin-doxorubicin (DOX) conjugate. Oral microbeads were coated with an enteric polymer to protect the drug from release in the upper gastrointestinal (GI) tract and allow redox-triggered drug release in the colon. Morphology, particle size, drug content, and in vitro drug release behavior of the microbeads were characterized; in vitro cytotoxicity was tested on mouse colon carcinoma, human colorectal adenocarcinoma, and human bone osteosarcoma cell lines. In vivo anticancer efficacy of coated microbeads was examined in BALB/c mice with murine colon carcinoma. These coated microbeads significantly inhibited the growth of all cell lines. The in vivo study confirmed delivery of DOX to the colorectal tumor site, redox-responsiveness, and anticancer efficacy of coated microbeads. Coated microbeads also effectively inhibited primary tumor growth and suppressed tumor metastases without gross toxicity to the non-target tissue. No noticeable damage was found in mouse GI tissues, indicating lack of DOX toxicity. These novel coated microbeads containing thiolated pectin-DOX conjugate may be a promising vehicle for targeted clinical delivery of DOX to the colorectal cancer site by oral administration. Crown Copyright © 2018. Published by Elsevier B.V. All rights reserved.

Impedance spectroscopy study of a catechol-modified activated carbon electrode as active material in electrochemical capacitor

NASA Astrophysics Data System (ADS)

Cougnon, C.; Lebègue, E.; Pognon, G.

2015-01-01

Modified activated carbon (Norit S-50) electrodes with electrochemical double layer (EDL) capacitance and redox capacitance contributions to the electric charge storage were tested in 1 M H2SO4 to quantify the benefit and the limitation of the surface redox reactions on the electrochemical performances of the resulting pseudo-capacitive materials. The electrochemical performances of an electrochemically anodized carbon electrode and a catechol-modified carbon electrode, which make use both EDL capacitance of the porous structure of the carbon and redox capacitance, were compared to the performances obtained for the pristine carbon. Nitrogen gas adsorption measurements have been used for studying the impact of the grafting on the BET surface area, pore size distribution, pore volume and average pore diameter. The electrochemical behavior of carbon materials was studied by cyclic voltammetry and electrochemical impedance spectroscopy (EIS). The EIS data were discussed by using a complex capacitance model that allows defining the characteristic time constant, the global capacitance and the frequency at which the maximum charge stored is reached. The EIS measurements were achieved at different dc potential values where a redox activity occurs and the evolution of the capacitance and the capacitive relaxation time with the electrode potential are presented. Realistic galvanostatic charge/discharge measurements performed at different current rates corroborate the results obtained by impedance.

Antioxidants and Autism: Teachers' Perceptions of Behavioral Changes.

PubMed

Sadek, Amy; Berk, Lee S; Mainess, Karen; Daher, Noha S

2018-06-05

BACKGROUND- Children with Autism Spectrum Disorder (ASD) demonstrate a physiological imbalance between free radicals, resultant from oxidative stress, and antioxidants. Oxidative stress is linked to the pathogenesis of this neurocognitive disorder. The aim of this pilot feasibility study was to examine the effect of consumption of high concentration antioxidant cacao on behavior of children with ASD. METHODS- This was a 4-week pre-test post-test experimental pilot study of high antioxidant cacao and children with ASD. Participants consumed 8 squares (or 16 grams) per day of the dark chocolate which had a concentration of 70% cacao and 30% organic cane sugar (total antioxidant concentration was 8,320). The two main behavioral measures were the Aberrant Behavior Checklist- 2nd Edition and the Autism Spectrum Rating Scale which were completed by the child's teacher at baseline and end of week four. RESULTS- Sixteen participants were recruited for this study. Follow up data was available on 12 participants (9 males, 3 females, mean age of 10.9 ±3.9 years). Significant improvements on the Autism Spectrum Rating Scale were noted in Social/Communication (p=0.03, η2=0.79), Unusual Behaviors (p=0.02, η2=0.70), and Self-Regulation (p=0.04, η2=0.59). No significant changes were noted on any of the Aberrant Behavior Checklist-2 subscales (p>.05). CONCLUSION- Results from this study support the potential therapeutic benefit of antioxidants in improving social communication, unusual behaviors, and self-regulation behaviors of children with ASD. Further robust randomized controlled trials are now necessary to elaborate the validity of these findings.

Macroscopic experimental and modeling evaluation of selenite and selenate adsorption mechanisms on gibbsite

USDA-ARS?s Scientific Manuscript database

Selenite Se(IV) and selenate Se(VI) adsorption behavior was investigated on gibbsite as a function of solution pH and solution ionic strength. Adsorption of both Se redox states decreased with increasing solution pH. Electrophoretic mobility measurements showed downward shifts in point of zero cha...

BEHAVIOR OF ARSENIC AND OTHER REDOX-SENSITIVE ELEMENTS IN CROWLEY LAKE, CA: A RESERVOIR IN THE LOS ANGELES AQUEDUCT SYSTEM. (R826202)

EPA Science Inventory

Elevated arsenic concentrations in Crowley Lake derive from upstream geothermal inputs. We examined the water column of Crowley Lake under stratified and unstratified conditions, seeking evidence for algal uptake and transformation of arsenic and its deposition to and release fro...

Experimental Observation of Redox-Induced Fe-N Switching Behavior as a Determinant Role for Oxygen Reduction Activity.

PubMed

Jia, Qingying; Ramaswamy, Nagappan; Hafiz, Hasnain; Tylus, Urszula; Strickland, Kara; Wu, Gang; Barbiellini, Bernardo; Bansil, Arun; Holby, Edward F; Zelenay, Piotr; Mukerjee, Sanjeev

2015-12-22

The commercialization of electrochemical energy conversion and storage devices relies largely upon the development of highly active catalysts based on abundant and inexpensive materials. Despite recent achievements in this respect, further progress is hindered by the poor understanding of the nature of active sites and reaction mechanisms. Herein, by characterizing representative iron-based catalysts under reactive conditions, we identify three Fe-N4-like catalytic centers with distinctly different Fe-N switching behaviors (Fe moving toward or away from the N4-plane) during the oxygen reduction reaction (ORR), and show that their ORR activities are essentially governed by the dynamic structure associated with the Fe(2+/3+) redox transition, rather than the static structure of the bare sites. Our findings reveal the structural origin of the enhanced catalytic activity of pyrolyzed Fe-based catalysts compared to nonpyrolyzed Fe-macrocycle compounds. More generally, the fundamental insights into the dynamic nature of transition-metal compounds during electron-transfer reactions will potentially guide rational design of these materials for broad applications.

Acid azo dye remediation in anoxic-aerobic-anoxic microenvironment under periodic discontinuous batch operation: bio-electro kinetics and microbial inventory.

PubMed

Venkata Mohan, S; Suresh Babu, P; Naresh, K; Velvizhi, G; Madamwar, Datta

2012-09-01

Functional behavior of anoxic-aerobic-anoxic microenvironment on azo dye (C.I. Acid black 10B) degradation was evaluated in a periodic discontinuous batch mode operation for 26 cycles. Dye removal efficiency and azo-reductase activity (30.50 ± 1 U) increased with each feeding event until 13th cycle and further stabilized. Dehydrogenase activity also increased gradually and stabilized (2.0 ± 0.2 μg/ml) indicating the stable proton shuttling between metabolic intermediates providing higher number of reducing equivalents towards dye degradation. Voltammetric profiles showed drop in redox catalytic currents during stabilized phase also supports the consumption of reducing equivalents towards dye removal. Change in Tafel slopes, polarization resistance and other bioprocess parameters correlated well with the observed dye removal and biocatalyst behavior. Microbial community analysis documented the involvement of specific organism pertaining to aerobic and facultative functions with heterotrophic and autotrophic metabolism. Integrating anoxic microenvironment with aerobic operation might have facilitated effective dye mineralization due to the possibility of combining redox functions. Copyright © 2012 Elsevier Ltd. All rights reserved.

Superior pseudocapacitive behavior of confined lignin nanocrystals for renewable energy-storage materials.

PubMed

Kim, Sung-Kon; Kim, Yun Ki; Lee, Hyunjoo; Lee, Sang Bok; Park, Ho Seok

2014-04-01

Strong demand for high-performance energy-storage devices has currently motivated the development of emerging capacitive materials that can resolve their critical challenge (i.e., low energy density) and that are renewable and inexpensive energy-storage materials from both environmental and economic viewpoints. Herein, the pseudocapacitive behavior of lignin nanocrystals confined on reduced graphene oxides (RGOs) used for renewable energy-storage materials is demonstrated. The excellent capacitive characteristics of the renewable hybrid electrodes were achieved by synergizing the fast and reversible redox charge transfer of surface-confined quinone and the interplay with electron-conducting RGOs. Accordingly, pseudocapacitors with remarkable rate and cyclic performances (~96 % retention after 3000 cycles) showed a maximum capacitance of 432 F g(-1), which was close to the theoretical capacitance of 482 F g(-1) and sixfold higher than that of RGO (93 F g(-1)). The chemical strategy delineated herein paves the way to develop advanced renewable electrodes for energy-storage applications and understand the redox chemistry of electroactive biomaterials. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A preliminary study on the potency of nanofluids as the electro-active materials for nanoelectrofuel flow batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kristiawan, B., E-mail: budi-k@uns.ac.id; Wijayanta, A. T., E-mail: agungtw@uns.ac.id; Juwana, W. E., E-mail: wibawa.ej@gmail.com

2016-03-29

This study presents a characterization of nanofluids as electroactive materials with dispersing metal oxide nanoparticles into aqueous polyelectrolytes of 20 wt.%, in particular, their electrochemical activites. The fundamental characterizations including X-ray diffraction, transmission electron microscopy, and Fourier ttransform iinfrared measurement were performed to ensure metal oxide component used in this work. Alumina (Al{sub 2}O{sub 3}) and copper oxide (CuO) nanoparticles of 0.5 vol.% in volume fraction were dispersed into Poly(diallyldimethylammonium chloride) solution (PDADMAC) and Poly(sodium 4-styrenesulfonate) (PSS), respectively. Alumina and copper oxide nanoparticles were dispersed into ionic solution with volume fraction of 0.5 vol.% by using two-step method. The generalmore » cyclic voltammetry measurement was used to analyze electrochemical behavior within three-electrode cell setup. The results show that PSS-based nanofluids demonstrate redox process. However, unclearly redox phenomenon was depicted PDADMAC-based nanofluids. Dispersing nanoparticles could shift pure ionic solution’s cyclic profile. It is clear that a significant impact on electrochemical behavior can be provided because of the existence metal oxide nanoparticles into polyelectrolyte solution.« less

Effect of metronidazole supplemented with hydroquinone on the adhesion of Lactobacillus acidophilus in ovine vaginal cells.

PubMed

Coletti Zabala, Tamara L; Zerbatto, María E; Perotti, Elda B R; Smacchia, Ana M; Ombrella, Adriana; Pidello, Alejandro R

This work demonstrates that the addition of metronidazole together with a ubiquitous quinone compound reduces adherence of Lactobacillus acidophilus to ovine vaginal cells. Spectrophotometric and voltammetric studies have shown that neoformed compounds were observed in these systems; there were also changes in their electroactive composition, and the oxidant status had a significantly higher value compared to the control (p<0.05). Based on reduction potential (E; mV), the distribution of electroactive compound concentrations suggests that the compounds with low reduction potential induce this behavior, which would indicate that the addition of metronidazole with a ubiquitous quinone compound to the vaginal system might increase the reductive capacity of these systems. This work shows that the study of behavior and fluctuations of the redox compounds that compose the vaginal environment, in terms of concentration and species of redox molecules, must be hierarchized in order to better understand the early stages of colonization by microorganisms. Copyright © 2016 Asociación Argentina de Microbiología. Publicado por Elsevier España, S.L.U. All rights reserved.

Scaling Behavior in Mitochondrial Redox Fluctuations

PubMed Central

Ramanujan, V. Krishnan; Biener, Gabriel; Herman, Brian A.

2006-01-01

Scale-invariant long-range correlations have been reported in fluctuations of time-series signals originating from diverse processes such as heart beat dynamics, earthquakes, and stock market data. The common denominator of these apparently different processes is a highly nonlinear dynamics with competing forces and distinct feedback species. We report for the first time an experimental evidence for scaling behavior in NAD(P)H signal fluctuations in isolated mitochondria and intact cells isolated from the liver of a young (5-month-old) mouse. Time-series data were collected by two-photon imaging of mitochondrial NAD(P)H fluorescence and signal fluctuations were quantitatively analyzed for statistical correlations by detrended fluctuation analysis and spectral power analysis. Redox [NAD(P)H / NAD(P)+] fluctuations in isolated mitochondria and intact liver cells were found to display nonrandom, long-range correlations. These correlations are interpreted as arising due to the regulatory dynamics operative in Krebs' cycle enzyme network and electron transport chain in the mitochondria. This finding may provide a novel basis for understanding similar regulatory networks that govern the nonequilibrium properties of living cells. PMID:16565066

Autoregulation of von Willebrand factor function by a disulfide bond switch

PubMed Central

Butera, Diego; Passam, Freda; Ju, Lining; Cook, Kristina M.; Woon, Heng; Aponte-Santamaría, Camilo; Gardiner, Elizabeth; Davis, Amanda K.; Murphy, Deirdre A.; Bronowska, Agnieszka; Luken, Brenda M.; Baldauf, Carsten; Jackson, Shaun; Andrews, Robert; Gräter, Frauke; Hogg, Philip J.

2018-01-01

Force-dependent binding of platelet glycoprotein Ib (GPIb) receptors to plasma von Willebrand factor (VWF) plays a key role in hemostasis and thrombosis. Previous studies have suggested that VWF activation requires force-induced exposure of the GPIb binding site in the A1 domain that is autoinhibited by the neighboring A2 domain. However, the biochemical basis of this “mechanopresentation” remains elusive. From a combination of protein chemical, biophysical, and functional studies, we find that the autoinhibition is controlled by the redox state of an unusual disulfide bond near the carboxyl terminus of the A2 domain that links adjacent cysteine residues to form an eight-membered ring. Only when the bond is cleaved does the A2 domain bind to the A1 domain and block platelet GPIb binding. Molecular dynamics simulations indicate that cleavage of the disulfide bond modifies the structure and molecular stresses of the A2 domain in a long-range allosteric manner, which provides a structural explanation for redox control of the autoinhibition. Significantly, the A2 disulfide bond is cleaved in ~75% of VWF subunits in healthy human donor plasma but in just ~25% of plasma VWF subunits from heart failure patients who have received extracorporeal membrane oxygenation support. This suggests that the majority of plasma VWF binding sites for platelet GPIb are autoinhibited in healthy donors but are mostly available in heart failure patients. These findings demonstrate that a disulfide bond switch regulates mechanopresentation of VWF. PMID:29507883

Autoregulation of von Willebrand factor function by a disulfide bond switch.

PubMed

Butera, Diego; Passam, Freda; Ju, Lining; Cook, Kristina M; Woon, Heng; Aponte-Santamaría, Camilo; Gardiner, Elizabeth; Davis, Amanda K; Murphy, Deirdre A; Bronowska, Agnieszka; Luken, Brenda M; Baldauf, Carsten; Jackson, Shaun; Andrews, Robert; Gräter, Frauke; Hogg, Philip J

2018-02-01

Force-dependent binding of platelet glycoprotein Ib (GPIb) receptors to plasma von Willebrand factor (VWF) plays a key role in hemostasis and thrombosis. Previous studies have suggested that VWF activation requires force-induced exposure of the GPIb binding site in the A1 domain that is autoinhibited by the neighboring A2 domain. However, the biochemical basis of this "mechanopresentation" remains elusive. From a combination of protein chemical, biophysical, and functional studies, we find that the autoinhibition is controlled by the redox state of an unusual disulfide bond near the carboxyl terminus of the A2 domain that links adjacent cysteine residues to form an eight-membered ring. Only when the bond is cleaved does the A2 domain bind to the A1 domain and block platelet GPIb binding. Molecular dynamics simulations indicate that cleavage of the disulfide bond modifies the structure and molecular stresses of the A2 domain in a long-range allosteric manner, which provides a structural explanation for redox control of the autoinhibition. Significantly, the A2 disulfide bond is cleaved in ~75% of VWF subunits in healthy human donor plasma but in just ~25% of plasma VWF subunits from heart failure patients who have received extracorporeal membrane oxygenation support. This suggests that the majority of plasma VWF binding sites for platelet GPIb are autoinhibited in healthy donors but are mostly available in heart failure patients. These findings demonstrate that a disulfide bond switch regulates mechanopresentation of VWF.

Vertical stratification of subsurface microbial community composition across geological formations at the Hanford Site.

PubMed

Lin, Xueju; Kennedy, David; Fredrickson, Jim; Bjornstad, Bruce; Konopka, Allan

2012-02-01

Microbial diversity in subsurface sediments at the Hanford Site 300 Area near Richland, Washington state (USA) was investigated by analysing 21 samples recovered from depths of 9-52 m. Approximately 8000 near full-length 16S rRNA gene sequences were analysed across geological strata that include a natural redox transition zone. These strata included the oxic coarse-grained Hanford formation, fine-grained oxic and anoxic Ringold Formation sediments, and the weathered basalt group. We detected 1233 and 120 unique bacterial and archaeal OTUs (operational taxonomic units at the 97% identity level) respectively. Microbial community structure and richness varied substantially across the different geological strata. Bacterial OTU richness (Chao1 estimator) was highest (> 700) in the upper Hanford formation, and declined to about 120 at the bottom of the Hanford formation. Just above the Ringold oxic-anoxic interface, richness was about 325 and declined to less than 50 in the deeper reduced zones. The deeper Ringold strata were characterized by a preponderance (c. 90%) of Proteobacteria. The bacterial community in the oxic sediments contained not only members of nine well-recognized phyla but also an unusually high proportion of three candidate divisions (GAL15, NC10 and SPAM). Additionally, 13 novel phylogenetic orders were identified within the Deltaproteobacteria, a clade rich in microbes that carry out redox transformations of metals that are important contaminants on the Hanford Site. © 2011 Society for Applied Microbiology and Blackwell Publishing Ltd.

Deficient expression of aldehyde dehydrogenase 1A1 is consistent with increased sensitivity of Gorlin syndrome patients to radiation carcinogenesis

DOE PAGES

Wright, Aaron T.; Magnaldo, Thierry; Sontag, Ryan L.; ...

2013-11-27

Human phenotypes that are highly susceptible to radiation carcinogenesis have been identified. Sensitive phenotypes often display robust regulation of molecular features that modify biological response, which can facilitate identification of relevant pathways/networks. Here we interrogate primary dermal fibroblasts isolated from Gorlin syndrome patients (GDFs), who display a pronounced tumorigenic response to radiation, in comparison to normal human dermal fibroblasts (NHDFs). Our approach exploits newly developed thiol-reactive probes with a flexible click chemistry functional group to define changes in protein thiol profiles in live cell studies, which minimizes artifacts associated with cell lysis. We observe qualitative differences in protein thiol profilesmore » by SDS-PAGE analysis when detection by iodoacetamide vs maleimide probe chemistries are compared, and pretreatment of cells with hydrogen peroxide eliminates detection of the majority of SDS-PAGE bands. Redox probes revealed deficient expression of an apparent 55 kDa protein thiol in GDFs from independent donors, compared with NHDFs. Proteomics tentatively identified this protein as aldehyde dehydrogenase 1A1 (ALDH1A1), a key enzyme regulating retinoic acid synthesis, and this deficiency was confirmed by Western blot. Redox probes revealed additional protein thiol differences between GDFs and NHDFs, including radiation responsive annexin family members. Our results indicate a multifactorial basis for the unusual sensitivity of Gorlin syndrome to radiation carcinogenesis, and the pathways identified have plausible implications for radiation health effects.« less

Deficient expression of aldehyde dehydrogenase 1A1 is consistent with increased sensitivity of Gorlin syndrome patients to radiation carcinogenesis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wright, Aaron T.; Magnaldo, Thierry; Sontag, Ryan L.

Human phenotypes that are highly susceptible to radiation carcinogenesis have been identified. Sensitive phenotypes often display robust regulation of molecular features that modify biological response, which can facilitate identification of relevant pathways/networks. Here we interrogate primary dermal fibroblasts isolated from Gorlin syndrome patients (GDFs), who display a pronounced tumorigenic response to radiation, in comparison to normal human dermal fibroblasts (NHDFs). Our approach exploits newly developed thiol-reactive probes with a flexible click chemistry functional group to define changes in protein thiol profiles in live cell studies, which minimizes artifacts associated with cell lysis. We observe qualitative differences in protein thiol profilesmore » by SDS-PAGE analysis when detection by iodoacetamide vs maleimide probe chemistries are compared, and pretreatment of cells with hydrogen peroxide eliminates detection of the majority of SDS-PAGE bands. Redox probes revealed deficient expression of an apparent 55 kDa protein thiol in GDFs from independent donors, compared with NHDFs. Proteomics tentatively identified this protein as aldehyde dehydrogenase 1A1 (ALDH1A1), a key enzyme regulating retinoic acid synthesis, and this deficiency was confirmed by Western blot. Redox probes revealed additional protein thiol differences between GDFs and NHDFs, including radiation responsive annexin family members. Our results indicate a multifactorial basis for the unusual sensitivity of Gorlin syndrome to radiation carcinogenesis, and the pathways identified have plausible implications for radiation health effects.« less

Unusual negative magnetoresistance in Bi2Se3-ySy topological insulator under perpendicular magnetic field

NASA Astrophysics Data System (ADS)

Singh, Rahul; Gangwar, Vinod K.; Daga, D. D.; Singh, Abhishek; Ghosh, A. K.; Kumar, Manoranjan; Lakhani, A.; Singh, Rajeev; Chatterjee, Sandip

2018-03-01

The magneto-transport properties of Bi2Se3-ySy were investigated. Magnetoresistance (MR) decreases with an increase in the S content, and finally, for 7% (i.e., y = 0.21) S doping, the magnetoresistance becomes negative. This negative MR is unusual as it is observed when a magnetic field is applied in the perpendicular direction to the plane of the sample. The magneto-transport behavior shows the Shubnikov-de Haas (SdH) oscillation, indicating the coexistence of surface and bulk states. The negative MR has been attributed to the non-trivial bulk conduction.

Numerical Study of a Long-Lived, Isolated Wake Vortex in Ground Effect

NASA Technical Reports Server (NTRS)

Proctor, Fred H.

2014-01-01

This paper examines a case observed during the 1990 Idaho Falls Test program, in which a wake vortex having an unusually long lifetime was observed while in ground effect. A numerical simulation is performed with a Large Eddy Simulation model to understand the response of the environment in affecting this event. In the simulation, it was found that one of the vortices decayed quickly, with the remaining vortex persisting beyond the time-bound of typical vortex lifetimes. This unusual behavior was found to be related to the first and second vertical derivatives of the ambient crosswind.

Stability Behavior and Thermodynamic States of Iron and Manganese in Sandy Soil Aquifer, Manukan Island, Malaysia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Chin Yik, E-mail: cy_lin_ars@hotmail.com; Abdullah, Mohd. Harun; Musta, Baba

2011-03-15

A total of 20 soil samples were collected from 10 boreholes constructed in the low lying area, which included ancillary samples taken from the high elevation area. Redox processes were investigated in the soil as well as groundwater in the shallow groundwater aquifer of Manukan Island, Sabah, Malaysia. Groundwater samples (n = 10) from each boreholes were also collected in the low lying area to understand the concentrations and behaviors of Fe and Mn in the dissolved state. This study strives to obtain a general understanding of the stability behaviors on Fe and Mn at the upper unsaturated and themore » lower-saturated soil horizons in the low lying area of Manukan Island as these elements usually play a major role in the redox chemistry of the shallow groundwater. Thermodynamic calculations using PHREEQC showed that the groundwater samples in the study area are oversaturated with respect to goethite, hematite, Fe(OH){sub 3} and undersaturated with respect to manganite and pyrochroite. Low concentrations of Fe and Mn in the groundwater might be probably due to the lack of minerals of iron and manganese oxides, which exist in the sandy aquifer. In fact, high organic matters that present in the unsaturated horizon are believed to be responsible for the high Mn content in the soil. It was observed that the soil samples collected from high elevation area (BK) comprises considerable amount of Fe in both unsaturated (6675.87 mg/kg) and saturated horizons (31440.49 mg/kg) compared to the low Fe content in the low lying area. Based on the stability diagram, the groundwater composition lies within the stability field for Mn{sup 2+} and Fe{sup 2+} under suboxic condition and very close to the FeS/Fe{sup 2+} stability boundary. This study also shows that both pH and Eh values comprise a strong negative value thus suggesting that the redox potential is inversely dependent on the changes of pH.« less

Test-beds for molecular electronics: metal-molecules-metal junctions based on Hg electrodes.

PubMed

Simeone, Felice Carlo; Rampi, Maria Anita

2010-01-01

Junctions based on mesoscopic Hg electrodes are used to characterize the electrical properties of the organic molecules organized in self-assembled monolayers (SAMs). The junctions M-SAM//SAM-Hg are formed by one electrode based on metals (M) such as Hg, Ag, Au, covered by a SAM, and by a second electrode always formed by a Hg drop carrying also a SAM. The electrodes, brought together by using a micromanipulator, sandwich SAMs of different nature at the contact area (approximately = 0.7 microm2). The high versatility of the system allows a series of both electrical and electrochemical junctions to be assembled and characterized: (i) The compliant nature of the Hg electrodes allows incorporation into the junction and measurement of the electrical behavior of a large number of molecular systems and correlation of their electronic structure to the electrical behavior; (ii) by functionalizing both electrodes with SAMs exposing different functional groups, X and Y, it is possible to compare the rate of electron transfer through different X...Y molecular interactions; (iii) when the junction incorporates one of the electrode formed by a semitransparent film of Au, it allows electrical measurements under irradiation of the sandwiched SAMs. In this case the junction behaves as a photoswitch; iv) incorporation of redox centres with low lying, easily reachable energy levels, provides electron stations as indicated by the hopping mechanism dominating the current flow; (v) electrochemical junctions incorporating redox centres by both covalent and electrostatic interactions permit control of the potential of the electrodes with respect to that of the redox state by means of an external reference electrode. Both these junctions show an electrical behavior similar to that of conventional diodes, even though the mechanism generating the current flow is different. These systems, demonstrating high mechanical stability and reproducibility, easy assembly, and a wide variety of produced results, are convenient test-beds for molecular electronics and represent a useful complement to physics-based experimental methods.

Redox-signals and macrophage biology (for the upcoming issue of molecular aspects of medicine on signaling by reactive oxygen species).

PubMed

Weigert, Andreas; von Knethen, Andreas; Fuhrmann, Dominik; Dehne, Nathalie; Brüne, Bernhard

2018-01-11

Macrophages are known for their versatile role in biology. They sense and clear structures that contain exogenous or endogenous pathogen-associated molecular patterns. This process is tightly linked to the production of a mixture of potentially harmful oxidants and cytokines. Their inherent destructive behavior is directed against foreign material or structures of 'altered self', which explains the role of macrophages during innate immune reactions and inflammation. However, there is also another side of macrophages when they turn into a tissue regenerative, pro-resolving, and healing phenotype. Phenotype changes of macrophages are termed macrophage polarization, representing a continuum between classical and alternative activation. Macrophages as the dominating producers of superoxide/hydrogen peroxide and nitric oxide are not only prone to oxidative modifications but also to more subtle signaling properties of redox-active molecules conveying redox regulation. We review basic concepts of the enzymatic nitric oxide and superoxide production within macrophages, refer to their unique chemical reactions and outline biological consequences not only for macrophage biology but also for their communication with cells in the microenvironment. These considerations link hypoxia to the NO system, addressing feedforward as well as feedback circuits. Moreover, we summarize the role of redox-signaling affecting epigenetics and reflect the central role of mitochondrial-derived oxygen species in inflammation. To better understand the diverse functions of macrophages during initiation as well as resolution of inflammation and to decode their versatile roles during innate and adaptive immunity with the entire spectrum of cell protective towards cell destructive activities we need to appreciate the signaling properties of redox-active species. Herein we discuss macrophage responses in terms of nitric oxide and superoxide formation with the modulating impact of hypoxia. Copyright © 2018. Published by Elsevier Ltd.

Postnatal exposure to trichloroethylene alters glutathione redox homeostasis, methylation potential, and neurotrophin expression in the mouse hippocampus

PubMed Central

Blossom, Sarah J.; Melnyk, Stepan; Cooney, Craig A.; Gilbert, Kathleen M.; James, S. Jill

2012-01-01

Previous studies have shown that continuous exposure throughout gestation until the juvenile period to environmentally-relevant doses of trichloroethylene (TCE) in the drinking water of MRL+/+ mice promoted adverse behavior associated with glutathione depletion in the cerebellum indicating increased sensitivity to oxidative stress. The purpose of this study was to extend our findings and further characterize the impact of TCE exposure on redox homeostasis and biomarkers of oxidative stress in the hippocampus, a brain region prone to oxidative stress. Instead of a continuous exposure, the mice were exposed to water only or two environmentally relevant doses of TCE in the drinking water postnatally from birth until 6 weeks of age. Biomarkers of plasma metabolites in the transsulfuration pathway and the transmethylation pathway of the methionine cycle were also examined. Gene expression of neurotrophins was examined to investigate a possible relationship between oxidative stress, redox imbalance and neurotrophic factor expression with TCE exposure. Our results show that hippocampi isolated from male mice exposed to TCE showed altered glutathione redox homeostasis indicating a more oxidized state. Also observed was a significant, dose dependent increase in glutathione precursors. Plasma from the TCE treated mice showed alterations in metabolites in the transsulfuration and transmethylation pathways indicating redox imbalance and altered methylation capacity. 3-Nitrotyrosine, a biomarker of protein oxidative stress, was also significantly higher in plasma and hippocampus of TCE-exposed mice compared to controls. In contrast, expression of key neurotrophic factors in the hippocampus (BDNF, NGF, and NT-3) was significantly reduced compared to controls. Our results demonstrate that low-level postnatal and early life TCE exposure modulates neurotrophin gene expression in the mouse hippocampus and may provide a mechanism for TCE-mediated neurotoxicity. PMID:22421312

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hu, Q; Zavarin, M; Rose, T P

Laboratory batch sorption experiments were used to investigate variations in the retardation behavior of redox-sensitive radionuclides. Water-rock compositions used during these experiments were designed to simulate subsurface conditions at the Nevada Test Site (NTS), where a suite of radionuclides were deposited as a result of underground nuclear testing. Experimental redox conditions were controlled by varying the oxygen content inside an enclosed glove box and by adding reductants into the testing solutions. Under atmospheric (oxidizing) conditions, the radionuclide distribution coefficients varied with the mineralogical composition of the sorbent and the water chemistry. Under reducing conditions, distribution coefficients showed marked increases formore » {sup 99}Tc and {sup 237}Np in devitrified tuff, but much smaller variations in alluvium, carbonate rock, and zeolitic tuff. This effect was particularly important for {sup 99}Tc, which tends to be mobile under oxidizing conditions. Unlike other redox-sensitive radionuclides, iodine sorption may decrease under reducing conditions when I{sup -} is the predominant species. Overall, sorption of U to alluvium, devitrified tuff, and zeolitic tuff under atmospheric conditions was less than in the glove-box tests. However, the mildly reducing conditions achieved here were not likely to result in substantial U(VI) reduction to U(IV). Sorption of Pu was not affected by the decreasing redox conditions achieved in this study, as the predominant sorbed Pu species in all conditions was expected to be the low-solubility and strongly sorbing Pu(OH){sub 4}. Depending on the aquifer lithology, the occurrence of reducing conditions along a groundwater flowpath could potentially contribute to the retardation of redox-sensitive radionuclides {sup 99}Tc and {sup 237}Np, which are commonly identified as long-term dose contributors in the risk assessment in various nuclear facilities.« less

Comparative study of the oxidation behavior of sulfur-containing amino acids and glutathione by electrochemistry-mass spectrometry in the presence and absence of cisplatin.

PubMed

Zabel, Robert; Weber, Günther

2016-02-01

Small sulfur-containing compounds are involved in several important biochemical processes, including-but not limited to-redox regulation and drug conjugation/detoxification. While methods for stable redox pairs of such compounds (thiols/disulfides) are available, analytical data on more labile and short-lived redox intermediates are scarce, due to highly challenging analytical requirements. In this study, we employ the direct combination of reagentless electrochemical oxidation and mass spectrometric (EC-MS) identification for monitoring oxidation reactions of cysteine, N-acetylcysteine, methionine, and glutathione under simulated physiological conditions (pH 7.4, 37 °C). For the first time, all theoretically expected redox intermediates-with only one exception-are detected simultaneously and in situ, including sulfenic, sulfinic, and sulfonic acids, disulfides, thiosulfinates, thiosulfonates, and sulfoxides. By monitoring the time/potential-dependent interconversion of sulfur species, mechanistic oxidation routes are confirmed and new reactions detected, e.g., sulfenamide formation due to reaction with ammonia from the buffer. Furthermore, our results demonstrate a highly significant impact of cisplatin on the redox reactivity of sulfur species. Namely, the amount of thiol oxidation to sulfonic acid via sulfenic and sulfinic acid intermediates is diminished for glutathione in the presence of cisplatin in favor of the disulfide formation, while for N-acetylcysteine the contrary applies. N-acetylcysteine is the only ligand which displays enhanced oxidation currents upon cisplatin addition, accompanied by increased levels of thiosulfinate and thiosulfonate species. This is traced back to thiol reactivity and highlights the important role of sulfenic acid intermediates, which may function as a switch between different oxidation routes.

Mechanical Behavior of AZ31B Mg Alloy Sheets under Monotonic and Cyclic Loadings at Room and Moderately Elevated Temperatures

PubMed Central

Nguyen, Ngoc-Trung; Seo, Oh Suk; Lee, Chung An; Lee, Myoung-Gyu; Kim, Ji-hoon; Kim, Heon Young

2014-01-01

Large-strain monotonic and cyclic loading tests of AZ31B magnesium alloy sheets were performed with a newly developed testing system, at different temperatures, ranging from room temperature to 250 °C. Behaviors showing significant twinning during initial in-plane compression and untwinning in subsequent tension at and slightly above room temperature were recorded. Strong yielding asymmetry and nonlinear hardening behavior were also revealed. Considerable Bauschinger effects, transient behavior, and variable permanent softening responses were observed near room temperature, but these were reduced and almost disappeared as the temperature increased. Different stress–strain responses were inherent to the activation of twinning at lower temperatures and non-basal slip systems at elevated temperatures. A critical temperature was identified to account for the transition between the twinning-dominant and slip-dominant deformation mechanisms. Accordingly, below the transition point, stress–strain curves of cyclic loading tests exhibited concave-up shapes for compression or compression following tension, and an unusual S-shape for tension following compression. This unusual shape disappeared when the temperature was above the transition point. Shrinkage of the elastic range and variation in Young’s modulus due to plastic strain deformation during stress reversals were also observed. The texture-induced anisotropy of both the elastic and plastic behaviors was characterized experimentally. PMID:28788514

Attitude-behavior congruity, mindfulness, and self-focused attention: A behavior-analytic reconstruction

PubMed Central

Street, Warren R.

1994-01-01

Social psychologists have responded to research reporting low agreement between attitude measures and related behavior with attempts to explain the incongruities and enhance agreement. This article examines attitude-behavior incongruity from a behavior-analytic point of view. Traditional and behavior-analytic views of attitudes and behaviors are compared. In the behavior-analytic view, answering an attitude scale should be considered as behavior displayed by a person under rather unusual social conditions, not as a reflection of an enduring personal disposition. Reasons why questionnaire-answering behavior will not resemble behavior in other functionally different social conditions are reviewed. Special attention is extended to two representative lines of attitude-behavior research: mindfulness and self-focused attention. Discriminative stimuli in both areas of study have produced more predictable agreement between questionnaire-answering behavior and behavior in other settings. PMID:22478180

Assessment of attenuation processes in a chlorinated ethene plume by use of stream bed Passive Flux Meters, streambed Point Velocity Probes and contaminant mass balances

NASA Astrophysics Data System (ADS)

Rønde, V.; McKnight, U. S.; Annable, M. D.; Devlin, J. F.; Cremeans, M.; Sonne, A. T.; Bjerg, P. L.

2017-12-01

Chlorinated ethenes (CE) are abundant groundwater contaminants and pose risk to both groundwater and surface water bodies, as plumes can migrate through aquifers to streams. After release to the environment, CE may undergo attenuation. The hyporheic zone is believed to enhance CE attenuation, however studies contradicting this have also been reported. Since dilution commonly reduces contaminant concentrations in streams to below quantification limits, use of mass balances along the pathway from groundwater to stream is unusual. Our study is conducted at the low-land Grindsted stream, Denmark, which is impacted by a contaminant plume. CE have been observed in the stream water; hence our study site provides an unusual opportunity to study attenuation processes in a CE plume as it migrates through the groundwater at the stream bank, through the stream bed and further to the point of fully mixed conditions in the stream. The study undertook the determination of redox conditions and CE distribution from bank to stream; streambed contaminant flux estimation using streambed Passive Flux Meters (sPFM); and quantification of streambed water fluxes using temperature profiling and streambed Point Velocity Probes (SBPVP). The advantage of the sPFM is that it directly measures the contaminant flux without the need for water samples, while the advantage of the SBPVP is its ability to measure the vertical seepage velocity without the need for additional geological parameters. Finally, a mass balance assessment along the plume pathway was conducted to account for any losses or accumulations. The results show consistencies in spatial patterns between redox conditions and extent of dechlorination; between contaminant fluxes from sPFM and concentrations from water samples; and between seepage velocities from SBPVP and temperature-based water fluxes. Mass balances and parent-metabolite compound ratios indicate limited degradation between the bank and the point of fully mixed stream water. Since the plume at the bank mainly consists of cis-DCE and vinyl chloride, this implies high and persistent stream water concentrations of these compounds. Finally, this study demonstrates the usefulness and complementary nature of sPFM and SBPVP measurements for assessing the attenuation processes through mass balance calculations.

Paleomagnetism and Mineralogy of Unusual Silicate Glasses and Baked Soils on the Surface of the Atacama Desert of Northern Chile: A Major Airburst Impact ~12ka ago?.

NASA Astrophysics Data System (ADS)

Roperch, P. J.; Blanco, N.; Valenzuela, M.; Gattacceca, J.; Devouard, B.; Lorand, J. P.; Tomlinson, A. J.; Arriagada, C.; Rochette, P.

2015-12-01

Unusual silicate glasses were found in northern Chile in one of the driest place on earth, the Atacama Desert. The scoria-type melted rocks are littered on the ground at several localities distributed along a longitudinal band of about 50km. The silicate glasses have a stable natural remanent magnetization carried by fine-grained magnetite and acquired during cooling. At one locality, fine-grained overbank sediments were heated to form a 10 to 20 cm-thick layer of brick-type samples. Magnetic experiments on oriented samples demonstrate that the baked clays record a thermoremanent magnetization acquired in situ above 600°C down to more than 10cm depth and cooled under a normal polarity geomagnetic field with a paleointensity of 40μT. In some samples of the silicate glass, large grains of iron sulphides (troilite) are found in the glass matrix with numerous droplets of native iron, iron sulphides and iron phosphides indicating high temperature and strong redox conditions during melting. The paleomagnetic record of the baked clays and the unusual mineralogy of the silicate glasses indicate a formation mainly by in situ high temperature radiation. Paleomagnetic experiments and chemical analyses indicate that the silicate glasses are not fulgurite type rocks due to lightning events, nor volcanic glasses or even metallurgical slags related to mining activity. The existence of a well-developped baked clay layer indicates that the silicate glasses are not impact-related ejectas. The field, paleomagnetic and mineralogical observations support evidence for a thermal event likely related to a major airburst. The youngest calibrated 14C age on a charcoal sample closely associated with the glass indicates that the thermal event occurred around 12 to 13 ka BP. The good conservation of the surface effects of this thermal event in the Atacama Desert could provide a good opportunity to further estimate the threats posed by large asteroid airbursts.

The Newell Test Should Commit to Diagnosing Dysfunctions

NASA Technical Reports Server (NTRS)

Clancey, William J.

2003-01-01

"Conceptual coordination" analysis bridges connectionism and symbolic approaches by posting a "process memory" by which categories are physically coordinated (as neural networks) in time. Focusing on dysfunctions and odd behaviors like slips reveals the function of consciousness, especially taken-for-granted constructive processes, different from conventional programming constructs. Newell strongly endorsed identifying architectural limits; the heuristic of "diagnose unusual behaviors" will provide targets of opportunity that greatly strengthens the Newell Test.

Usual and Unusual Care: Existing Practice Control Groups In Randomized Controlled Trials of Behavioral Interventions

PubMed Central

Freedland, Kenneth E.; Mohr, David C.; Davidson, Karina W.; Schwartz, Joseph E.

2011-01-01

Objective To examine the use of existing practice control groups in randomized controlled trials of behavioral interventions, and the role of extrinsic healthcare services in the design and conduct of behavioral trials. Method Selective qualitative review. Results Extrinsic healthcare services, also known as nonstudy care, have important but under-recognized effects on the design and conduct of behavioral trials. Usual care, treatment as usual, standard of care, and other existing practice control groups pose a variety of methodological and ethical challenges, but they play a vital role in behavioral intervention research. Conclusion This review highlights the need for a scientific consensus statement on control groups in behavioral trials. PMID:21536837

Usual and unusual care: existing practice control groups in randomized controlled trials of behavioral interventions.

PubMed

Freedland, Kenneth E; Mohr, David C; Davidson, Karina W; Schwartz, Joseph E

2011-05-01

To evaluate the use of existing practice control groups in randomized controlled trials of behavioral interventions and the role of extrinsic health care services in the design and conduct of behavioral trials. Selective qualitative review. Extrinsic health care services, also known as nonstudy care, have important but under-recognized effects on the design and conduct of behavioral trials. Usual care, treatment-as-usual, standard of care, and other existing practice control groups pose a variety of methodological and ethical challenges, but they play a vital role in behavioral intervention research. This review highlights the need for a scientific consensus statement on control groups in behavioral trials.

Nitroxide amide-BODIPY probe behavior in fibroblasts analyzed by advanced fluorescence microscopy.

PubMed

Liras, M; Simoncelli, S; Rivas-Aravena, A; García, O; Scaiano, J C; Alarcon, E I; Aspée, A

2016-04-26

A novel synthesized nitroxide amide-BODIPY prefluorescent probe was used to study cellular redox balance that modulates nitroxide/hydroxylamine ratio in cultured human fibroblasts. FLIM quantitatively differentiated between nitroxide states of the cytoplasm-localized probe imaged by TIRF, monitoring nitroxide depletion by hydrogen peroxide; eluding incorrect interpretation if only fluorescence intensity is considered.

Electron-Deficient Near-Infrared Pt(II) and Pd(II) Benzoporphyrins with Dual Phosphorescence and Unusually Efficient Thermally Activated Delayed Fluorescence: First Demonstration of Simultaneous Oxygen and Temperature Sensing with a Single Emitter.

PubMed

Zach, Peter W; Freunberger, Stefan A; Klimant, Ingo; Borisov, Sergey M

2017-11-01

We report a family of Pt and Pd benzoporphyrin dyes with versatile photophysical properties and easy access from cheap and abundant chemicals. Attaching 4 or 8 alkylsulfone groups onto a meso-tetraphenyltetrabenzoporphyrin (TPTBP) macrocylcle renders the dyes highly soluble in organic solvents, photostable, and electron-deficient with the redox potential raised up to 0.65 V versus the parent porphyrin. The new dyes intensively absorb in the blue (Soret band, 440-480 nm) and in the red (Q-band, 620-650 nm) parts of the electromagnetic spectrum and show bright phosphorescence at room-temperature in the NIR with quantum yields up to 30% in solution. The small singlet-triplet energy gap yields unusually efficient thermally activated delayed fluorescence (TADF) at elevated temperatures in solution and in polymeric matrices with quantum yields as high as 27% at 120 °C, which is remarkable for benzoporphyrins. Apart from oxygen sensing, these properties enable unprecedented simultaneous, self-referenced oxygen and temperature sensing with a single indicator dye: whereas oxygen can be determined either via the decay time of phosphorescence or TADF, the temperature is accessed via the ratio of the two emissions. Moreover, the dyes are efficient sensitizers for triplet-triplet annihilation (TTA)-based upconversion making possible longer sensitization wavelength than the conventional benzoporphyrin complexes. The Pt-octa-sulfone dye also features interesting semireversible transformation in basic media, which generates new NIR absorbing species.

Stepwise Elastic Behavior in a Model Elastomer

NASA Astrophysics Data System (ADS)

Bhawe, Dhananjay M.; Cohen, Claude; Escobedo, Fernando A.

2004-12-01

MonteCarlo simulations of an entanglement-free cross-linked polymer network of semiflexible chains reveal a peculiar stepwise elastic response. For increasing stress, step jumps in strain are observed that do not correlate with changes in the number of aligned chains. We show that this unusual behavior stems from the ability of the system to form multiple ordered chain domains that exclude the cross-linking species. This novel elastomer shows a toughening behavior similar to that observed in biological structural materials, such as muscle proteins and abalone shell adhesive.

Zolpidem-induced amnesia and somnambulism: rare occurrences?

PubMed

Tsai, Jui-Hsiu; Yang, Pinchen; Chen, Cheng-Chung; Chung, Weilum; Tang, Tze-Chun; Wang, Shing-Yaw; Liu, Jong-Kang

2009-01-01

Zolpidem, a non-benzodiazepine hypnotic of the imidazopyridine class, is very effective in treating insomnia with previous claims of little adverse effects. However, zolpidem-induced somnambulism and amnesic sleep-related behavioral problems were begun to be reported in literature but no systemic investigation has been undertaken in non-Western cultures. In our current retrospective survey, 5.1% (13 out of 255) of Taiwanese patients reported change in sleep-related behavior as adverse effects. This serves as a reminder for clinicians to inquire regarding any unusual behavior of parasomniac activities when prescribing zolpidem.

Video cameras on wild birds.

PubMed

Rutz, Christian; Bluff, Lucas A; Weir, Alex A S; Kacelnik, Alex

2007-11-02

New Caledonian crows (Corvus moneduloides) are renowned for using tools for extractive foraging, but the ecological context of this unusual behavior is largely unknown. We developed miniaturized, animal-borne video cameras to record the undisturbed behavior and foraging ecology of wild, free-ranging crows. Our video recordings enabled an estimate of the species' natural foraging efficiency and revealed that tool use, and choice of tool materials, are more diverse than previously thought. Video tracking has potential for studying the behavior and ecology of many other bird species that are shy or live in inaccessible habitats.

Mitochondrial capacity, oxidative damage and hypoxia gene expression are associated with age-related division of labor in honey bee (Apis mellifera L.) workers.

PubMed

Cervoni, Mário S; Cardoso-Júnior, Carlos A M; Craveiro, Giovana; Souza, Anderson de O; Alberici, Luciane C; Hartfelder, Klaus

2017-11-01

During adult life, honey bee workers undergo a succession of behavioral states. Nurse bees perform tasks inside the nest, and when they are about 2-3 weeks old they initiate foraging. This switch is associated with alterations in diet, and with the levels of juvenile hormone and vitellogenin circulating in hemolymph. It is not clear whether this behavioral maturation involves major changes at the cellular level, such as mitochondrial activity and the redox environment in the head, thorax and abdomen. Using high-resolution respirometry, biochemical assays and RT-qPCR, we evaluated the association of these parameters with this behavioral change. We found that tissues from the head and abdomen of nurses have a higher oxidative phosphorylation capacity than those of foragers, while for the thorax we found the opposite situation. As higher mitochondrial activity tends to generate more H 2 O 2 , and H 2 O 2 is known to stabilize HIF-1α, this would be expected to stimulate hypoxia signaling. The positive correlation that we observed between mitochondrial activity and hif-1α gene expression in abdomen and head tissue of nurses would be in line with this hypothesis. Higher expression of antioxidant enzyme genes was observed in foragers, which could explain their low levels of protein carbonylation. No alterations were seen in nitric oxide (NO) levels, suggesting that NO signaling is unlikely to be involved in behavioral maturation. We conclude that the behavioral change seen in honey bee workers is reflected in differential mitochondrial activities and redox parameters, and we consider that this can provide insights into the underlying aging process. © 2017. Published by The Company of Biologists Ltd.

High-temperature thermochemical energy storage based on redox reactions using Co-Fe and Mn-Fe mixed metal oxides

NASA Astrophysics Data System (ADS)

André, Laurie; Abanades, Stéphane; Cassayre, Laurent

2017-09-01

Metal oxides are potential materials for thermochemical heat storage via reversible endothermal/exothermal redox reactions, and among them, cobalt oxide and manganese oxide are attracting attention. The synthesis of mixed oxides is considered as a way to answer the drawbacks of pure metal oxides, such as slow reaction kinetics, loss-in-capacity over cycles or sintering issues, and the materials potential for thermochemical heat storage application needs to be assessed. This work proposes a study combining thermodynamic calculations and experimental measurements by simultaneous thermogravimetric analysis and calorimetry, in order to identify the impact of iron oxide addition to Co and Mn-based oxides. Fe addition decreased the redox activity and energy storage capacity of Co3O4/CoO, whereas the reaction rate, reversibility and cycling stability of Mn2O3/Mn3O4 was significantly enhanced with added Fe amounts above 15 mol%, and the energy storage capacity was slightly improved. The formation of a reactive cubic spinel explained the improved re-oxidation yield of Mn-based oxides that could be cycled between bixbyite and cubic spinel phases, whereas a low reactive tetragonal spinel phase showing poor re-oxidation was formed below 15 mol% Fe. Thermodynamic equilibrium calculations predict accurately the behavior of both systems. The possibility to identify other suitable mixed oxides becomes conceivable, by enabling the selection of transition metal additives for tuning the redox properties of mixed metal oxides destined for thermochemical energy storage applications.

Understanding the Origins of Higher Capacities at Faster Rates in Lithium-Excess Li xNi 2–4x/3Sb x/3O 2

DOE PAGES

Twu, Nancy; Metzger, Michael; Balasubramanian, Mahalingam; ...

2017-02-08

Here, the lithium-excess Li xNi 2-4x/3Sb x/3O 2 (LNSO) materials were previously shown to demonstrate higher capacities and improved cyclability with increasing lithium content. While the performance trend is promising, observed capacities are much lower than theoretical capacities, pointing to a need for further understanding of active redox processes in these materials. In this work, we study the electrochemical behavior of the LNSO materials as a function of lithium content and at slow and fast rates. Surprisingly, Li 1.15Ni 0.47Sb 0.38O 2 (LNSO-15) exhibits higher discharge capacities at faster rates and traverses distinct voltage curves at slow and fast rates.more » To understand these two peculiarities, we characterize the redox activity of nickel, antimony, and oxygen at different rates. While experiments confirm some nickel redox activity and oxygen loss, these two mechanisms cannot account for all observed capacity. We propose that the balance of the observed capacity may be due reversible oxygen redox and that the rate-dependent voltage curve features may derive from irreversible nickel migration occurring on slow charge. As future high energy density cathodes are likely to contain both lithium excess and high nickel content, both of these findings have important implications for the development of novel high capacity cathode materials.« less

A pH and redox dual stimuli-responsive poly(amino acid) derivative for controlled drug release.

PubMed

Gong, Chu; Shan, Meng; Li, Bingqiang; Wu, Guolin

2016-10-01

A pH and redox dual stimuli-responsive poly(aspartic acid) derivative for controlled drug release was successfully developed through progressive ring-opening reactions of polysuccinimide (PSI). Polyethylene glycol (PEG) chains were grafted onto the polyaspartamide backbone via redox-responsive disulfide linkages, providing a sheddable shell for the polymeric micelles in a reductive environment. Phenyl groups were introduced into the polyaspartamide backbone via the aminolysis reaction of PSI to serve as the hydrophobic segment of micelles. The polyaspartamide scaffold was also functionalized with N-(3-aminopropyl)-imidazole to obtain the pH-responsiveness manifesting as a swelling of the core of micelles at a low pH. The polymeric micelles with a core-shell nanostructure forming in neutral media exhibited both pH and redox responsive characteristics. Doxorubicin (DOX) as a model drug was encapsulated into the core of micelles through both hydrophobic and π-π interactions between aromatic rings and the DOX-loaded polymeric micelles exhibited accelerated drug release behaviors in an acidic and reductive environment due to the swelling of hydrophobic cores and the shedding of PEG shells. Furthermore, the cytocompability of the polymer and the cytotoxicity of DOX-loaded micelles towards Hela cells under corresponding conditions were evaluated, and the endocytosis of DOX-loaded polymeric micelles and the intracellular drug release from micelles were observed. All obtained data indicated that the micelle was a promising candidate for controlled drug release. Copyright © 2016 Elsevier B.V. All rights reserved.

Monitoring Chemical and Biological Electron Transfer Reactions with a Fluorogenic Vitamin K Analogue Probe.

PubMed

Belzile, Mei-Ni; Godin, Robert; Durantini, Andrés M; Cosa, Gonzalo

2016-12-21

We report herein the design, synthesis, and characterization of a two-segment fluorogenic analogue of vitamin K, B-VK Q , prepared by coupling vitamin K 3 , also known as menadione (a quinone redox center), to a boron-dipyrromethene (BODIPY) fluorophore (a lipophilic reporter segment). Oxidation-reduction reactions, spectroelectrochemical studies, and enzymatic assays conducted in the presence of DT-diaphorase illustrate that the new probe shows reversible redox behavior on par with that of vitamin K, provides a high-sensitivity fluorescence signal, and is compatible with biological conditions, opening the door to monitor remotely (i.e., via imaging) redox processes in real time. In its oxidized form, B-VK Q is non-emissive, while upon reduction to the hydroquinone form, B-VK QH 2 , BODIPY fluorescence is restored, with emission quantum yield values of ca. 0.54 in toluene. Density functional theory studies validate a photoinduced electron transfer intramolecular switching mechanism, active in the non-emissive quinone form and deactivated upon reduction to the emissive dihydroquinone form. Our results highlight the potential of B-VK Q as a fluorogenic probe to study electron transfer and transport in model systems and biological structures with optimal sensitivity and desirable chemical specificity. Use of such a probe may enable a better understanding of the role that vitamin K plays in biological redox reactions ubiquitous in key cellular processes, and help elucidate the mechanism and pathological significance of these reactions in biological systems.

Interaction and Correlation Effects in Quasi Two-dimensional Materials

NASA Astrophysics Data System (ADS)

Louie, Steven G.

2015-03-01

Experimental and theoretical studies of atomically thin quasi two-dimensional materials (typically related to some parent van der Waals layered crystals) and their nanostructures have revealed that these systems can exhibit highly unusual behaviors. In this talk, we discuss some theoretical studies of the electronic, transport and optical properties of such systems. We present results on graphene and graphene nanostructures as well as other quasi-2D systems such as monolayer and few-layer transition metal dichalcogenides (e.g., MoS2, MoSe2, WS2, and WSe2) and metal monochalcogenides (such as GaSe and FeSe). Owing to their reduced dimensionality, these systems present opportunities for unusual manifestation of concepts and phenomena that may not be so prominent or have not been seen in bulk materials. Symmetry and many-body interaction effects often play a critical role in shaping qualitatively and quantitatively their properties. Several quantum phenomena are discussed, including novel and dominant exciton effects, tunable magnetism, electron supercollimation by disorder, unusual plasmon behaviors, and possible enhanced superconductivity in some of these systems. We investigate their physical origins and compare theoretical predictions with experimental data. This work was supported by DOE under Contract No. DE-AC02-05CH11231 and by NSF under Grant No. DMR10-1006184. I would like to acknowledge collaborations with members of the Louie group and the experimental groups of Crommie, Heinz, Wang, and Zhang.

An unusual metallic behavior in a Ag4SSe single crystal

NASA Astrophysics Data System (ADS)

Matteppanavar, Shidaling; Bui, Nguyen Hai An; van Smaalen, Sander; Thamizhavel, A.; Ramakrishnan, S.

2018-04-01

We report the magnetic susceptibility, resistivity and heat capacity measurements on high quality single crystalline tetra silver sulphoselenide (Ag4SSe). The magnetic susceptibility and resistivity measurements show anomalies around 260 K. The large diamagnetic drop with hysteresis at the transition implies a first order transition. Such a diamagnetic drop cannot be ascribed to the formation of charge density wave (CDW) since the temperature dependence of the resistivity shows no upturn at this transition. Infact the resistivity is decreasing with decreasing temperature, indicating a metallic behavior. However, unlike normal metals, the resistivity is almost temperature independent in the temperature range from 4-180 K. Usually, when one observes a diamagnetic transition, it is assumed to be due to a drop in the density of states at the Fermi level which leads to the decrease in the Pauli paramagnetic susceptibility. Such a decrease in the density of states often results in an increase in resistivity unless mobility of the charge carriers changes significantly. Hence, we believe that in Ag4SSe, the structural transition causes an unusual Fermi surface reconstruction which in turn leads to a strange metallic behavior at low temperatures.

Particle size effect on strength, failure, and shock behavior in polytetrafluoroethylene-Al-W granular composite materials

NASA Astrophysics Data System (ADS)

Herbold, E. B.; Nesterenko, V. F.; Benson, D. J.; Cai, J.; Vecchio, K. S.; Jiang, F.; Addiss, J. W.; Walley, S. M.; Proud, W. G.

2008-11-01

The variation of metallic particle size and sample porosity significantly alters the dynamic mechanical properties of high density granular composite materials processed using a cold isostatically pressed mixture of polytetrafluoroethylene (PTFE), aluminum (Al), and tungsten (W) powders. Quasistatic and dynamic experiments are performed with identical constituent mass fractions with variations in the size of the W particles and pressing conditions. The relatively weak polymer matrix allows the strength and fracture modes of this material to be governed by the granular type behavior of agglomerated metal particles. A higher ultimate compressive strength was observed in relatively high porosity samples with small W particles compared to those with coarse W particles in all experiments. Mesoscale granular force chains of the metallic particles explain this unusual phenomenon as observed in hydrocode simulations of a drop-weight test. Macrocracks forming below the critical failure strain for the matrix and unusual behavior due to a competition between densification and fracture in dynamic tests of porous samples were also observed. Numerical modeling of shock loading of this granular composite material demonstrated that the internal energy, specifically thermal energy, of the soft PTFE matrix can be tailored by the W particle size distribution.

Thermodynamic properties of an emerging chemical disinfectant, peracetic acid.

PubMed

Zhang, Chiqian; Brown, Pamela J B; Hu, Zhiqiang

2018-04-15

Peracetic acid (PAA or CH 3 COOOH) is an emerging disinfectant with a low potential to form carcinogenic disinfection by-products (DBPs). Basic thermodynamic properties of PAA are, however, absent or inconsistently reported in the literature. This review aimed to summarize important thermodynamic properties of PAA, including standard Gibbs energy of formation and oxidation-reduction (redox) potential. The standard Gibbs energies of formation of CH 3 COOOH (aq) , CH 3 COOOH (g) , CH 3 COOOH (l) , and CH 3 COOO (aq) - are -299.41kJ·mol -1 , -283.02kJ·mol -1 , -276.10kJ·mol -1 , and -252.60kJ·mol -1 , respectively. The standard redox potentials of PAA are 1.748V and 1.005V vs. standard hydrogen electrode (SHE) at pH 0 and pH 14, respectively. Under biochemical standard state conditions (pH 7, 25°C, 101,325Pa), PAA has a redox potential of 1.385V vs. SHE, higher than many disinfectants. Finally, the environmental implications of the thermodynamic properties of PAA were systematically discussed. Those properties can be used to predict the physicochemical and biological behavior of aquatic systems exposed to PAA. Copyright © 2017 Elsevier B.V. All rights reserved.

Ultrasensitive thrombin detection based on direct electrochemistry of highly loaded hemoglobin spheres-encapsulated platinum nanoparticles as labels and electrocatalysts.

PubMed

Wu, Yongmei; Xu, Wenju; Bai, Lijuan; Yuan, Yali; Yi, Huayu; Chai, Yaqin; Yuan, Ruo

2013-12-15

For the first time, a sandwich-type electrochemical method was proposed for ultrasensitive thrombin (TB) detection based on direct electrochemistry of highly loaded hemoglobin spheres-encapsulated platinum nanoparticles (PtNPs@Hb) as labels and electrocatalysts. The prepared PtNPs@Hb not only exhibited good biocompatibility, excellent electrocatalytic activity, but also presented redox activity of Hb. Thus, it was employed for the fabrication of aptasensor without any extraneous redox mediators, leading to a simple preparation process for the aptasensor. The high loading of Hb spheres as redox mediators could enhance the electrochemical signal. Importantly, the synergetic electrocatalytic behavior of Hb and PtNPs toward H2O2 reduction greatly amplified the electrochemical signal, resulting in the high sensitivity of aptasensor. Consequently, under optimal conditions, the designed aptasensor exhibited a lower detection limit of 0.05 pM and wide dynamic linear range from 0.15 pM to 40 nM for TB detection. Additionally, the proposed mediator-free and signal-amplified electrochemical aptasensor showed great potential in portable and cost-effective TB sensing devices. Copyright © 2013 Elsevier B.V. All rights reserved.

Fast and stable redox reactions of MnO₂/CNT hybrid electrodes for dynamically stretchable pseudocapacitors.

PubMed

Gu, Taoli; Wei, Bingqing

2015-07-21

Pseudocapacitors, which are energy storage devices that take advantage of redox reactions to store electricity, have a different charge storage mechanism compared to lithium-ion batteries (LIBs) and electric double-layer capacitors (EDLCs), and they could realize further gains if they were used as stretchable power sources. The realization of dynamically stretchable pseudocapacitors and understanding of the underlying fundamentals of their mechanical-electrochemical relationship have become indispensable. We report herein the electrochemical performance of dynamically stretchable pseudocapacitors using buckled MnO2/CNT hybrid electrodes. The extremely small relaxation time constant of less than 0.15 s indicates a fast redox reaction at the MnO2/CNT hybrid electrodes, securing a stable electrochemical performance for the dynamically stretchable pseudocapacitors. This finding and the fundamental understanding gained from the pseudo-capacitive behavior coupled with mechanical deformation under a dynamic stretching mode would provide guidance to further improve their overall performance including a higher power density than LIBs, a higher energy density than EDLCs, and a long-life cycling stability. Most importantly, these results will potentially accelerate the applications of stretchable pseudocapacitors for flexible and biomedical electronics.

Redox transformations and transport of cesium and iodine (-1, 0, +5) in oxidizing and reducing zones of a sand and gravel aquifer

USGS Publications Warehouse

Fox, P.M.; Kent, D.B.; Davis, J.A.

2010-01-01

Tracer tests were performed in distinct biogeochemical zones of a sand and gravel aquifer in Cape Cod, MA, to study the redox chemistry (I) and transport (Cs, I) of cesium and iodine in a field setting. Injection of iodide (I -) into an oxic zone of the aquifer resulted in oxidation of I - to molecular iodine (I2) and iodate (IO3-) over transport distances of several meters. Oxidation is attributed to Mn-oxides present in the sediment. Transport of injected IO 3- and Cs+ was retarded in the mildly acidic oxic zone, with retardation factors of 1.6-1.8 for IO3- and 2.3-4.4for Cs. Cs retardation was likely due to cation exchange reactions. Injection of IO3- into a Fe-reducing zone of the aquifer resulted in rapid and complete reduction to I- within 3 m of transport. The nonconservative behavior of Cs and I observed during the tracer tests underscores the necessity of taking the redox chemistry of I as well as sorption properties of I species and Cs into account when predicting transport of radionuclides (e.g., 129I and 137Cs) in the environment.

[Development and application of electroanalytical methods in biomedical fields].

PubMed

Kusu, Fumiyo

2015-01-01

To summarize our electroanalytical research in the biomedical field over the past 43 years, this review describes studies on specular reflection measurement, redox potential determination, amperometric acid sensing, HPLC with electrochemical detection, and potential oscillation across a liquid membrane. The specular reflection method was used for clarifying the adsorption of neurotransmitters and their related drugs onto a gold electrode and the interaction between dental alloys and compound iodine glycerin. A voltammetric screening test using a redox potential for the antioxidative effect of flavonoids was proposed. Amperometric acid sensing based on the measurement of the reduction prepeak current of 2-methyl-1,4-naphthoquinone (VK3) or 3,5-di-tert-buty1-1,2-benzoquinone (DBBQ) was applied to determine acid values of fats and oils, titrable acidity of coffee, and enzyme activity of lipase, free fatty acids (FFAs) in serum, short-chain fatty acids in feces, etc. The electrode reactions of phenothiazines, catechins, and cholesterol were applied to biomedical analysis using HPLC with electrochemical detection. A three-channel electrochemical detection system was utilized for the sensitive determination of redox compounds in Chinese herbal medicines. The behavior of barbituric acid derivatives was examined based on potential oscillation measurements.

Redox behavior and biological properties of ferrocene bearing porphyrins.

PubMed

Lippert, Rainer; Shubina, Tatyana E; Vojnovic, Sandra; Pavic, Aleksandar; Veselinovic, Jovana; Nikodinovic-Runic, Jasmina; Stankovic, Nada; Ivanović-Burmazović, Ivana

2017-06-01

In order to improve antimicrobial effects of previously studied meso-tetrakis(4-ferrocenylphenyl)porphyrin 1, we have modified its structure by replacing two trans-positioned ferrocenylphenyl moieties with methoxy methylene substituted tert-butylphenyl moieties. Newly synthesized 5 4 ,15 4 -bis-(ferrocenyl)-10 4 ,20 4 -bis-(tert-butyl)-10 2 ,10 6 ,20 2 ,20 6 -tetrakis-(methoxy-methylene)-5,10,15,20-tetraphenylporphyrin 4 was chemically characterized in detail (by NMR, UV/Vis, IR, MALDI-TOF and ESI MS spectrometry, cyclic voltammetry, prediction of the relative lipophilicity as well as computational methods) and its biological effects were studied in terms of its antibacterial and antifungal activity (both with and without photoactivation), cytotoxicity, hemolysis and DNA cleavage. New ferrocene bearing porphyrin 4 has demonstrated a broader antimicrobial spectrum and modified effects on eukaryotic cells compared to 1. This was discussed in terms of its i) increased lipophilicity, while exhibiting lower toxicity, and ii) the redox potential of a two-electron process that is shifted to lower values, in comparison to ferrocene, thus, entering the physiologically available range and being activated towards redox interactions with biomolecules. Copyright © 2017 Elsevier Inc. All rights reserved.

10 CFR 712.13 - Supervisory review.

Code of Federal Regulations, 2012 CFR

2012-01-01

... HRP management official. Types of behavior and conditions that would indicate a concern include, but...) Irresponsibility in performing assigned duties; (10) Inability to deal with stress, or the appearance of being under unusual stress; (11) Failure to comply with work directives, hostility or aggression toward fellow...

10 CFR 712.13 - Supervisory review.

Code of Federal Regulations, 2011 CFR

2011-01-01

... HRP management official. Types of behavior and conditions that would indicate a concern include, but...) Irresponsibility in performing assigned duties; (10) Inability to deal with stress, or the appearance of being under unusual stress; (11) Failure to comply with work directives, hostility or aggression toward fellow...

10 CFR 712.13 - Supervisory review.

Code of Federal Regulations, 2013 CFR

2013-01-01

... HRP management official. Types of behavior and conditions that would indicate a concern include, but...) Irresponsibility in performing assigned duties; (10) Inability to deal with stress, or the appearance of being under unusual stress; (11) Failure to comply with work directives, hostility or aggression toward fellow...

10 CFR 712.13 - Supervisory review.

Code of Federal Regulations, 2014 CFR

2014-01-01

... HRP management official. Types of behavior and conditions that would indicate a concern include, but...) Irresponsibility in performing assigned duties; (10) Inability to deal with stress, or the appearance of being under unusual stress; (11) Failure to comply with work directives, hostility or aggression toward fellow...

Eating Disorders among College Women.

ERIC Educational Resources Information Center

Basow, Susan A.; Schneck, Renae

In the past 10 years, eating disorders among adolescent females have become of increasing concern. To assess the prevalence of eating disorders, unusual eating-related behaviors and attitudes, and psychological states among college women, 677 women, from three private northeastern United States colleges, completed a questionnaire assessing…

Technology-Enhanced Discovery

ERIC Educational Resources Information Center

Harrow, Chris; Chin, Lillian

2014-01-01

Exploration, innovation, proof: For students, teachers, and others who are curious, keeping an open mind and being ready to investigate unusual or unexpected properties will always lead to learning something new. Technology can further this process, allowing various behaviors to be analyzed that were previously memorized or poorly understood. This…

Coherence parameter measurements for neon and hydrogen

NASA Astrophysics Data System (ADS)

Wright, Robert; Hargreaves, Leigh; Khakoo, Murtadha; Zatsarinny, Oleg; Bartschat, Klaus; Stauffer, Al

2015-09-01

We present recent coherence parameter measurements for excitation of neon and hydrogen by 50 eV electrons. The measurements were made using a crossed electron/gas beam spectrometer, featuring a hemispherically selected electron energy analyzer for detecting scattered electrons and double-reflection VUV polarization analyzer to register fluorescence photons. Time-coincidence counting methods on the electron and photon signals were employed to determine Stokes Parameters at each scattering angle, with data measured at angles between 20 - 115 degrees. The data are compared with calculated results using the B-Spline R-Matrix (BSR) and Relativistic Distorted Wave (RDW) approaches. Measurements were made of both the linear (Plin and γ) and circular (Lperp) parameters for the lowest lying excited states in these two targets. We particularly focus on results in the Lperp parameter, which shows unusual behavior in these particular targets, including strong sign changes implying reversal of the angular momentum transfer. In the case of neon, the unusual behavior is well captured by the BSR, but not by other models.

Tuning the Growth Pattern in 2D Confinement Regime of Sm2O3 and the Emerging Room Temperature Unusual Superparamagnetism

PubMed Central

Guria, Amit K.; Dey, Koushik; Sarkar, Suresh; Patra, Biplab K.; Giri, Saurav; Pradhan, Narayan

2014-01-01

Programming the reaction chemistry for superseding the formation of Sm2O3 in a competitive process of formation and dissolution, the crystal growth patterns are varied and two different nanostructures of Sm2O3 in 2D confinement regime are designed. Among these, the regular and self-assembled square platelets nanostructures exhibit paramagnetic behavior analogous to the bulk Sm2O3. But, the other one, 2D flower like shaped nanostructure, formed by irregular crystal growth, shows superparamagnetism at room temperature which is unusual for bulk paramagnet. It has been noted that the variation in the crystal growth pattern is due to the difference in the binding ability of two organic ligands, oleylamine and oleic acid, used for the synthesis and the magnetic behavior of the nanostructures is related to the defects incorporated during the crystal growth. Herein, we inspect the formation chemistry and plausible origin of contrasting magnetism of these nanostructures of Sm2O3. PMID:25269458

The use of marine reserves in evaluating the dive fishery for the warty sea cucumber, Parastichopus parvimensis in California, U.S.A

USGS Publications Warehouse

Schroeder, S.C.; Reed, D.C.; Kushner, D.J.; Estes, J.A.; Ono, D.S.

2001-01-01

In this paper we describe an instance of unusual, agonistic behavior in a flock of migrant Short-billed Dowitchers (Limnodromus griseus) . We compare this behavior to that of other flocks feeding at the same time at other locations in the same estuary and then present evidence suggesting that this behavior resulted from the patchy distribution of the probable foraging resource of this flock, eggs of the horseshoe crab (Limulus polyphemus). We propose that an extremely patchy resource has increased the agonistic behavior within the flock by increasing the variation in foraging success among individuals.

Mechanistic Insights into Ring Cleavage and Contraction of Benzene over a Titanium Hydride Cluster.

PubMed

Kang, Xiaohui; Luo, Gen; Luo, Lun; Hu, Shaowei; Luo, Yi; Hou, Zhaomin

2016-09-14

Carbon-carbon bond cleavage of benzene by transition metals is of great fundamental interest and practical importance, as this transformation is involved in the production of fuels and other important chemicals in the industrial hydrocracking of naphtha on solid catalysts. Although this transformation is thought to rely on cooperation of multiple metal sites, molecular-level information on the reaction mechanism has remained scarce to date. Here, we report the DFT studies of the ring cleavage and contraction of benzene by a molecular trinuclear titanium hydride cluster. Our studies suggest that the reaction is initiated by benzene coordination, followed by H2 release, C6H6 hydrometalation, repeated C-C and C-H bond cleavage and formation to give a MeC5H4 unit, and insertion of a Ti atom into the MeC5H4 unit with release of H2 to give a metallacycle product. The C-C bond cleavage and ring contraction of toluene can also occur in a similar fashion, though some details are different due to the presence of the methyl substituent. Obviously, the facile release of H2 from the metal hydride cluster to provide electrons and to alter the charge population at the metal centers, in combination with the flexible metal-hydride connections and dynamic redox behavior of the trimetallic framework, has enabled this unusual transformation to occur. This work has not only provided unprecedented insights into the activation and transformation of benzene over a multimetallic framework but it may also offer help in the design of new molecular catalysts for the activation and transformation of inactive aromatics.

Disentangling prenatal and inherited influences in humans with an experimental design.

PubMed

Rice, Frances; Harold, Gordon T; Boivin, Jacky; Hay, Dale F; van den Bree, Marianne; Thapar, Anita

2009-02-17

Exposure to adversity in utero at a sensitive period of development can bring about physiological, structural, and metabolic changes in the fetus that affect later development and behavior. However, the link between prenatal environment and offspring outcomes could also arise and confound because of the relation between maternal and offspring genomes. As human studies cannot randomly assign offspring to prenatal conditions, it is difficult to test whether in utero events have true causal effects on offspring outcomes. We used an unusual approach to overcome this difficulty whereby pregnant mothers are either biologically unrelated or related to their child as a result of in vitro fertilization (IVF). In this sample, prenatal smoking reduces offspring birth weight in both unrelated and related offspring, consistent with effects arising through prenatal mechanisms independent of the relation between the maternal and offspring genomes. In contrast, the association between prenatal smoking and offspring antisocial behavior depended on inherited factors because association was only present in related mothers and offspring. The results demonstrate that this unusual prenatal cross-fostering design is feasible and informative for disentangling inherited and prenatal effects on human health and behavior. Disentangling these different effects is invaluable for pinpointing markers of prenatal adversity that have a causal effect on offspring outcomes. The origins of behavior and many common complex disorders may begin in early life, therefore this experimental design could pave the way for identifying prenatal factors that affect behavior in future generations.

Redox levels in aqueous solution: Effect of van der Waals interactions and hybrid functionals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ambrosio, Francesco, E-mail: Francesco.Ambrosio@epfl.ch; Miceli, Giacomo; Pasquarello, Alfredo

2015-12-28

We investigate redox levels in aqueous solution using a combination of ab initio molecular dynamics (MD) simulations and thermodynamic integration methods. The molecular dynamics are performed with both the semilocal Perdew-Burke-Ernzerhof functional and a nonlocal functional (rVV10) accounting for van der Waals (vdW) interactions. The band edges are determined through three different schemes, namely, from the energy of the highest occupied and of the lowest unoccupied Kohn-Sham states, from total-energy differences, and from a linear extrapolation of the density of states. It is shown that the latter does not depend on the system size while the former two are subjectmore » to significant finite-size effects. For the redox levels, we provide a formulation in analogy to the definition of charge transition levels for defects in crystalline materials. We consider the H{sup +}/H{sub 2} level defining the standard hydrogen electrode, the OH{sup −}/OH{sup ∗} level corresponding to the oxidation of the hydroxyl ion, and the H{sub 2}O/OH{sup ∗} level for the dehydrogenation of water. In spite of the large structural modifications induced in liquid water, vdW interactions do not lead to any significant structural effect on the calculated band gap and band edges. The effect on the redox levels is also small since the solvation properties of ionic species are little affected by vdW interactions. Since the electronic properties are not significantly affected by the underlying structural properties, it is justified to perform hybrid functional calculations on the configurations of our MD simulations. The redox levels calculated as a function of the fraction α of Fock exchange are found to remain constant, reproducing a general behavior previously observed for charge transition levels of defects. Comparison with experimental values shows very good agreement. At variance, the band edges and the band gap evolve linearly with α. For α ≃ 0.40, we achieve a band gap, band-edge positions, and redox levels in overall good agreement with experiment.« less

Thorium/U systematics of Precambrian deep-sea pelagic balck shales: implications for redox state of the early atmosphere

NASA Astrophysics Data System (ADS)

Jia, Y.; McCulloch, M.; Charlotte, A.

2003-12-01

To address the question of the redox state of the Precambrian atmosphere-hydrosphere system via sediments requires measurement of redox sensitive trace elements, and inter-element ratios, in deep water black shales with a chemical sedimentary "hydrogenic" component. This approach is endorsed by recent progress in research of redox-sensitive trace metals records in late Proterozoic and Phanerozoic sedimentary rocks, which has provided important clues to how the redox state of depositional environments has changed over time. Many conventional studies, in contrast, have been on first cycle volcanogenic turbidites with a minimal hydrogenic input (Taylor and McLennan, 1995). Accordingly, we have analyzed the redox-sensitive, trace element compositions of the 2.1 Ga black shales in Birimian Blet, West Africa, and the 2.7 Ga Archean counterparts in Timmins, Canada, Tati Belt, Botswana, and Kanowna District, Western Australia. These pyrite-bearing black shales, which were originally argillaceous sediments containing organic matter and low in thermal maturity, were primarily deposited in the deep-sea pelagic environments. Th/U ratios are lower in the Proterozoic shales (0.38-0.82, average 0.67), and Archean shales (0.47-3.65, average 2.43) relative to "conventional" Archean upper crust (3.8), PAAS (4.7), or average upper continental crust (3.8). Calculated U concentrations from hydrogenic component are between 0.90 and 2.45 in the Proterozoic shales, and range from 0.06 to 0.96 for the Archean black shales. Given the conservative behavior of Th in the sedimentary cycle, variably low Th/U ratios in these Precambrian black shales signify that U6+, soluble in oxidized surface waters, was reduced to insoluble U4+ in reducing bottom waters, as in the contemporary Black Sea. The results are consistent with a locally to globally oxidized atmosphere-shallow hydrosphere pre-2.0 Ga. Taylor, S.R., and McLennan, S.C., 1995. The geochemical evolution of the continental crust: Reviews of Geophysics, v. 33. p. 241-265.

Redox-dependent spatially resolved electrochemistry at graphene and graphite step edges.

PubMed

Güell, Aleix G; Cuharuc, Anatolii S; Kim, Yang-Rae; Zhang, Guohui; Tan, Sze-yin; Ebejer, Neil; Unwin, Patrick R

2015-04-28

The electrochemical (EC) behavior of mechanically exfoliated graphene and highly oriented pyrolytic graphite (HOPG) is studied at high spatial resolution in aqueous solutions using Ru(NH3)6(3+/2+) as a redox probe whose standard potential sits close to the intrinsic Fermi level of graphene and graphite. When scanning electrochemical cell microscopy (SECCM) data are coupled with that from complementary techniques (AFM, micro-Raman) applied to the same sample area, different time-dependent EC activity between the basal planes and step edges is revealed. In contrast, other redox couples (ferrocene derivatives) whose potential is further removed from the intrinsic Fermi level of graphene and graphite show uniform and high activity (close to diffusion-control). Macroscopic voltammetric measurements in different environments reveal that the time-dependent behavior after HOPG cleavage, peculiar to Ru(NH3)6(3+/2+), is not associated particularly with any surface contaminants but is reasonably attributed to the spontaneous delamination of the HOPG with time to create partially coupled graphene layers, further supported by conductive AFM measurements. This process has a major impact on the density of states of graphene and graphite edges, particularly at the intrinsic Fermi level to which Ru(NH3)6(3+/2+) is most sensitive. Through the use of an improved voltammetric mode of SECCM, we produce movies of potential-resolved and spatially resolved HOPG activity, revealing how enhanced activity at step edges is a subtle effect for Ru(NH3)6(3+/2+). These latter studies allow us to propose a microscopic model to interpret the EC response of graphene (basal plane and edges) and aged HOPG considering the nontrivial electronic band structure.

Layer-by-layer grown scalable redox-active ruthenium-based molecular multilayer thin films for electrochemical applications and beyond.

PubMed

Kaliginedi, Veerabhadrarao; Ozawa, Hiroaki; Kuzume, Akiyoshi; Maharajan, Sivarajakumar; Pobelov, Ilya V; Kwon, Nam Hee; Mohos, Miklos; Broekmann, Peter; Fromm, Katharina M; Haga, Masa-aki; Wandlowski, Thomas

2015-11-14

Here we report the first study on the electrochemical energy storage application of a surface-immobilized ruthenium complex multilayer thin film with anion storage capability. We employed a novel dinuclear ruthenium complex with tetrapodal anchoring groups to build well-ordered redox-active multilayer coatings on an indium tin oxide (ITO) surface using a layer-by-layer self-assembly process. Cyclic voltammetry (CV), UV-Visible (UV-Vis) and Raman spectroscopy showed a linear increase of peak current, absorbance and Raman intensities, respectively with the number of layers. These results indicate the formation of well-ordered multilayers of the ruthenium complex on ITO, which is further supported by the X-ray photoelectron spectroscopy analysis. The thickness of the layers can be controlled with nanometer precision. In particular, the thickest layer studied (65 molecular layers and approx. 120 nm thick) demonstrated fast electrochemical oxidation/reduction, indicating a very low attenuation of the charge transfer within the multilayer. In situ-UV-Vis and resonance Raman spectroscopy results demonstrated the reversible electrochromic/redox behavior of the ruthenium complex multilayered films on ITO with respect to the electrode potential, which is an ideal prerequisite for e.g. smart electrochemical energy storage applications. Galvanostatic charge-discharge experiments demonstrated a pseudocapacitor behavior of the multilayer film with a good specific capacitance of 92.2 F g(-1) at a current density of 10 μA cm(-2) and an excellent cycling stability. As demonstrated in our prototypical experiments, the fine control of physicochemical properties at nanometer scale, relatively good stability of layers under ambient conditions makes the multilayer coatings of this type an excellent material for e.g. electrochemical energy storage, as interlayers in inverted bulk heterojunction solar cell applications and as functional components in molecular electronics applications.

Light-driven enzymatic catalysis of DNA repair: a review of recent biophysical studies on photolyase.

PubMed

Weber, Stefan

2005-02-25

More than 50 years ago, initial experiments on enzymatic photorepair of ultraviolet (UV)-damaged DNA were reported [Proc. Natl. Acad. Sci. U. S. A. 35 (1949) 73]. Soon after this discovery, it was recognized that one enzyme, photolyase, is able to repair UV-induced DNA lesions by effectively reversing their formation using blue light. The enzymatic process named DNA photoreactivation depends on a non-covalently bound cofactor, flavin adenine dinucleotide (FAD). Flavins are ubiquitous redox-active catalysts in one- and two-electron transfer reactions of numerous biological processes. However, in the case of photolyase, not only the ground-state redox properties of the FAD cofactor are exploited but also, and perhaps more importantly, its excited-state properties. In the catalytically active, fully reduced redox form, the FAD absorbs in the blue and near-UV ranges of visible light. Although there is no direct experimental evidence, it appears generally accepted that starting from the excited singlet state, the chromophore initiates a reductive cleavage of the two major DNA photodamages, cyclobutane pyrimidine dimers and (6-4) photoproducts, by short-distance electron transfer to the DNA lesion. Back electron transfer from the repaired DNA segment is believed to eventually restore the initial redox states of the cofactor and the DNA nucleobases, resulting in an overall reaction with net-zero exchanged electrons. Thus, the entire process represents a true catalytic cycle. Many biochemical and biophysical studies have been carried out to unravel the fundamentals of this unique mode of action. The work has culminated in the elucidation of the three-dimensional structure of the enzyme in 1995 that revealed remarkable details, such as the FAD-cofactor arrangement in an unusual U-shaped configuration. With the crystal structure of the enzyme at hand, research on photolyases did not come to an end but, for good reason, intensified: the geometrical structure of the enzyme alone is not sufficient to fully understand the enzyme's action on UV-damaged DNA. Much effort has therefore been invested to learn more about, for example, the geometry of the enzyme-substrate complex, and the mechanism and pathways of intra-enzyme and enzyme <-->DNA electron transfer. Many of the key results from biochemical and molecular biology characterizations of the enzyme or the enzyme-substrate complex have been summarized in a number of reviews. Complementary to these articles, this review focuses on recent biophysical studies of photoreactivation comprising work performed from the early 1990s until the present.

The Fumarate Reductase of Bacteroides thetaiotaomicron, unlike That of Escherichia coli, Is Configured so that It Does Not Generate Reactive Oxygen Species.

PubMed

Lu, Zheng; Imlay, James A

2017-01-03

The impact of oxidative stress upon organismal fitness is most apparent in the phenomenon of obligate anaerobiosis. The root cause may be multifaceted, but the intracellular generation of reactive oxygen species (ROS) likely plays a key role. ROS are formed when redox enzymes accidentally transfer electrons to oxygen rather than to their physiological substrates. In this study, we confirm that the predominant intestinal anaerobe Bacteroides thetaiotaomicron generates intracellular ROS at a very high rate when it is aerated. Fumarate reductase (Frd) is a prominent enzyme in the anaerobic metabolism of many bacteria, including B. thetaiotaomicron, and prior studies of Escherichia coli Frd showed that the enzyme is unusually prone to ROS generation. Surprisingly, in this study biochemical analysis demonstrated that the B. thetaiotaomicron Frd does not react with oxygen at all: neither superoxide nor hydrogen peroxide is formed. Subunit-swapping experiments indicated that this difference does not derive from the flavoprotein subunit at which ROS normally arise. Experiments with the related enzyme succinate dehydrogenase discouraged the hypothesis that heme moieties are responsible. Thus, resistance to oxidation may reflect a shift of electron density away from the flavin moiety toward the iron-sulfur clusters. This study shows that the autoxidizability of a redox enzyme can be suppressed by subtle modifications that do not compromise its physiological function. One implication is that selective pressures might enhance the oxygen tolerance of an organism by manipulating the electronic properties of its redox enzymes so they do not generate ROS. Whether in sediments or pathogenic biofilms, the structures of microbial communities are configured around the sensitivities of their members to oxygen. Oxygen triggers the intracellular formation of reactive oxygen species (ROS), and the sensitivity of a microbe to oxygen likely depends upon the rates at which ROS are formed inside it. This study supports that idea, as an obligate anaerobe was confirmed to generate ROS very rapidly upon aeration. However, the suspected source of the ROS was disproven, as the fumarate reductase of the anaerobe did not display the high oxidation rate of its E. coli homologue. Evidently, adjustments in its electronic structure can suppress the tendency of an enzyme to generate ROS. Importantly, this outcome suggests that evolutionary pressure may succeed in modifying redox enzymes and thereby diminishing the stress that an organism experiences in oxic environments. The actual source of ROS in the anaerobe remains to be discovered. Copyright © 2017 Lu and Imlay.

Environmental Redox Potential and Redox Capacity Concepts Using a Simple Polarographic Experiment

NASA Astrophysics Data System (ADS)

Pidello, Alejandro

2003-01-01

The redox status of a system may be analyzed in terms of the redox potential (redox intensity component) and the size of the pool of electrons able to be transferred (redox capacity component). In single chemical systems, both terms are thermodynamically related by means of the Nernst equation, the classical redox equilibrium equation. Consequently, either the redox potential measurement or the redox capacity may be used without distinction to define the redox characteristics of these systems. However, in natural environments, which are a complex mixture of compounds undergoing redox reactions in several stages of nonequilibrium, it is difficult to establish the relationships linking redox potential and redox capacity. In this situation, as suggested by various authors, the complementary use of intensity and capacity measurements improves the characterization of the redox status of these systems. The aim of this laboratory experiment is to enable undergraduate students of applied biology (agronomy, veterinary or environmental sciences) to distinguish clearly between redox potential and redox capacity concepts through concrete results obtained in complex natural system such as soil, and to discuss the ecological significance of both concepts.

A Series of F-Element Chelators; Diaza Crown Ethers Functionalized with Catecholate Binding Substituents

DOE PAGES

Stein, Benjamin W.; Cary, Samantha K.; Berg, John M.; ...

2017-12-06

Here, we report on the preparation of azacrown ethers functionalized with catechol groups. The synthetic approach was (1st) novel in that it made use of the Mannich reaction and (2nd) valuable in that it provided an improved synthesis (in terms of practical deployment) of the known N,N'-bis(2,3-dihydroxybenzyl)-4,13-diaza-18-crown-6, H 4ChaCha. Moreover, it demonstrated potential application of the synthetic method for accommodating a wide range of catecholate functionalities by using the synthetic strategy to prepare N,N'-bis(2,3-dihydroxy-5-tert-butylbenzyl)-4,13-diaza-18-crown-6 (H 4 tBu 2ChaCha) for the first time. These H 4ChaCha and H 4 tBu2ChaCha macrocycles offer exciting opportunity to expand redox chemistry for the f-elements.more » As “proof-of-principle,” we isolated the unusual tetrameric cluster [La 2( tBuChaCha) 2] 2 from reactions between H 4 tBu 2ChaCha and La[N(SiMe 3) 2] 3. Characterization of [La 2( tBuChaCha) 2] 2 by elemental analysis, single crystal X-ray diffraction, IR, and UV–vis–NIR spectroscopy suggested that the complex represented a rare example of an f-element semiquinone. It further demonstrated that the combination of La 3+ and H 4 tBu 2ChaCha provided access to one-electron oxidation chemistry within redox potential windows that were amenable to mild reaction conditions.« less

Changing the ligation of the distal [4Fe4S] cluster in NiFe hydrogenase impairs inter- and intramolecular electron transfers.

PubMed

Dementin, Sébastien; Belle, Valérie; Bertrand, Patrick; Guigliarelli, Bruno; Adryanczyk-Perrier, Géraldine; De Lacey, Antonio L; Fernandez, Victor M; Rousset, Marc; Léger, Christophe

2006-04-19

In NiFe hydrogenases, electrons are transferred from the active site to the redox partner via a chain of three Iron-Sulfur clusters, and the surface-exposed [4Fe4S] cluster has an unusual His(Cys)3 ligation. When this Histidine (H184 in Desulfovibrio fructosovorans) is changed into a cysteine or a glycine, a distal cubane is still assembled but the oxidative activity of the mutants is only 1.5 and 3% of that of the WT, respectively. We compared the activities of the WT and engineered enzymes for H2 oxidation, H+ reduction and H/D exchange, under various conditions: (i) either with the enzyme directly adsorbed onto an electrode or using soluble redox partners, and (ii) in the presence of exogenous ligands whose binding to the exposed Fe of H184G was expected to modulate the properties of the distal cluster. Protein film voltammetry proved particularly useful to unravel the effects of the mutations on inter and intramolecular electron transfer (ET). We demonstrate that changing the coordination of the distal cluster has no effect on cluster assembly, protein stability, active-site chemistry and proton transfer; however, it slows down the first-order rates of ET to and from the cluster. All-sulfur coordination is actually detrimental to ET, and intramolecular (uphill) ET is rate determining in the glycine variant. This demonstrates that although [4Fe4S] clusters are robust chemical constructs, the direct protein ligands play an essential role in imparting their ability to transfer electrons.

Surface multiheme c-type cytochromes from Thermincola potens and implications for respiratory metal reduction by Gram-positive bacteria

PubMed Central

Carlson, Hans K.; Iavarone, Anthony T.; Gorur, Amita; Yeo, Boon Siang; Tran, Rosalie; Melnyk, Ryan A.; Mathies, Richard A.; Auer, Manfred; Coates, John D.

2012-01-01

Almost nothing is known about the mechanisms of dissimilatory metal reduction by Gram-positive bacteria, although they may be the dominant species in some environments. Thermincola potens strain JR was isolated from the anode of a microbial fuel cell inoculated with anaerobic digester sludge and operated at 55 °C. Preliminary characterization revealed that T. potens coupled acetate oxidation to the reduction of hydrous ferric oxides (HFO) or anthraquinone-2,6-disulfonate (AQDS), an analog of the redox active components of humic substances. The genome of T. potens was recently sequenced, and the abundance of multiheme c-type cytochromes (MHCs) is unusual for a Gram-positive bacterium. We present evidence from trypsin-shaving LC-MS/MS experiments and surface-enhanced Raman spectroscopy (SERS) that indicates the expression of a number of MHCs during T. potens growth on either HFO or AQDS, and that several MHCs are localized to the cell wall or cell surface. Furthermore, one of the MHCs can be extracted from cells with low pH or denaturants, suggesting a loose association with the cell wall or cell surface. Electron microscopy does not reveal an S-layer, and the precipitation of silver metal on the cell surface is inhibited by cyanide, supporting the involvement of surface-localized redox-active heme proteins in dissimilatory metal reduction. These results provide unique direct evidence for cell wall-associated cytochromes and support MHC involvement in conducting electrons across the cell envelope of a Gram-positive bacterium. PMID:22307634

A Series of F-Element Chelators; Diaza Crown Ethers Functionalized with Catecholate Binding Substituents

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stein, Benjamin W.; Cary, Samantha K.; Berg, John M.

Here, we report on the preparation of azacrown ethers functionalized with catechol groups. The synthetic approach was (1st) novel in that it made use of the Mannich reaction and (2nd) valuable in that it provided an improved synthesis (in terms of practical deployment) of the known N,N'-bis(2,3-dihydroxybenzyl)-4,13-diaza-18-crown-6, H 4ChaCha. Moreover, it demonstrated potential application of the synthetic method for accommodating a wide range of catecholate functionalities by using the synthetic strategy to prepare N,N'-bis(2,3-dihydroxy-5-tert-butylbenzyl)-4,13-diaza-18-crown-6 (H 4 tBu 2ChaCha) for the first time. These H 4ChaCha and H 4 tBu2ChaCha macrocycles offer exciting opportunity to expand redox chemistry for the f-elements.more » As “proof-of-principle,” we isolated the unusual tetrameric cluster [La 2( tBuChaCha) 2] 2 from reactions between H 4 tBu 2ChaCha and La[N(SiMe 3) 2] 3. Characterization of [La 2( tBuChaCha) 2] 2 by elemental analysis, single crystal X-ray diffraction, IR, and UV–vis–NIR spectroscopy suggested that the complex represented a rare example of an f-element semiquinone. It further demonstrated that the combination of La 3+ and H 4 tBu 2ChaCha provided access to one-electron oxidation chemistry within redox potential windows that were amenable to mild reaction conditions.« less

High voltage AC/AC electrochemical capacitor operating at low temperature in salt aqueous electrolyte

NASA Astrophysics Data System (ADS)

Abbas, Qamar; Béguin, François

2016-06-01

We demonstrate that an activated carbon (AC)-based electrochemical capacitor implementing aqueous lithium sulfate electrolyte in 7:3 vol:vol water/methanol mixture can operate down to -40 °C with good electrochemical performance. Three-electrode cell investigations show that the faradaic contributions related with hydrogen chemisorption in the negative AC electrode are thermodynamically unfavored at -40 °C, enabling the system to work as a typical electrical double-layer (EDL) capacitor. After prolonged floating of the AC/AC capacitor at 1.6 V and -40°C, the capacitance, equivalent series resistance and efficiency remain constant, demonstrating the absence of ageing related with side redox reactions at this temperature. Interestingly, when temperature is increased back to 24 °C, the redox behavior due to hydrogen storage reappears and the system behaves as a freshly prepared one.

Electronic transport properties of a quinone-based molecular switch

NASA Astrophysics Data System (ADS)

Zheng, Ya-Peng; Bian, Bao-An; Yuan, Pei-Pei

2016-09-01

In this paper, we carried out first-principles calculations based on density functional theory and non-equilibrium Green's function to investigate the electronic transport properties of a quinone-based molecule sandwiched between two Au electrodes. The molecular switch can be reversibly switched between the reduced hydroquinone (HQ) and oxidized quinone (Q) states via redox reactions. The switching behavior of two forms is analyzed through their I- V curves, transmission spectra and molecular projected self-consistent Hamiltonian at zero bias. Then we discuss the transmission spectra of the HQ and Q forms at different bias, and explain the oscillation of current according to the transmission eigenstates of LUMO energy level for Q form. The results suggest that this kind of a quinone-based molecule is usable as one of the good candidates for redox-controlled molecular switches.

76 FR 21073 - Notice of Intent To Seek Approval To Continue an Information Collection

Federal Register 2010, 2011, 2012, 2013, 2014

2011-04-14

... Excellence in Science, Mathematics and Engineering Mentoring (PAESMEM) program. In 2003, to comply with E... would ``receive recommendations made by any other nationally representative scientific or engineering..., biological, mathematical, engineering or social and behavioral sciences. 2. Achievements of an unusually...

Music Therapy for the Visually Impaired.

ERIC Educational Resources Information Center

Steele, Anita Louise; Crawford, Celeste

1982-01-01

The development and implementation of a music therapy program to achieve behavioral change in visually impaired children and adolescents are described. Goals targeted by the music therapist at the Cleveland Society for the Blind include altering unusual body movements, poor posture, and other mannerisms often associated with blindness. (SEW)

76 FR 12761 - Notice of Intent To Seek Approval To Continue an Information Collection

Federal Register 2010, 2011, 2012, 2013, 2014

2011-03-08

... social and behavioral sciences. 2. Achievements of an unusually significant nature in relation to the... NATIONAL SCIENCE FOUNDATION Notice of Intent To Seek Approval To Continue an Information Collection AGENCY: National Science Foundation. ACTION: Notice and Request for Comments. SUMMARY: The...

Aggregation and foraging behavior of imported cabbageworm (Lepidoptera: pieridae) adults on blue vervain flowers

USDA-ARS?s Scientific Manuscript database

The imported cabbageworm [Pieris rapae (L.) (Lepidoptera: Pieridae)], also known as the cabbage white butterfly, is an important specialized pest on cruciferous plants (Brassicales: Brassicaceae) worldwide. an unusual aggregation of the cabbage white butterflies was observed on a patch of flowering...

Who Can You Trust? Protecting Your Organization from Internal Fraud.

ERIC Educational Resources Information Center

Lukaszewski, Thomas E.

1997-01-01

Discusses how to protect a child care organization from employee fraud. Differentiates employee and management fraud and examines reasons fraud is committed. Suggests procedures for protecting an organization from fraud, including establishing an effective internal control system, paying attention to unusual employee behavior, reviewing expense…

Enantioseparation of angiotensin II receptor type 1 blockers: evaluation of 6-substituted carbamoyl benzimidazoles on immobilized polysaccharide-based chiral stationary phases. Unusual temperature behavior.

PubMed

Su, Ran; Hou, Zhun; Sang, Lihong; Zhou, Zhi-Ming; Fang, Hao; Yang, Xinying

2017-09-15

Enantioseparation of thirteen 6-substituted carbamoyl benzimidazoles by high-performance liquid chromatography (HPLC) was investigated using two immobilized polysaccharide-based chiral stationary phases (CSPs), Chiralpak IC and Chiralpak IA, in normal-phase mode. Most of the examined compounds were completely resolved. The effects of a polar alcohol modifier, analyte structure, and column temperature on the chiral recognition were investigated. Furthermore, the structure-retention relationship was evaluated, and thermodynamic parameters were calculated from plots of ln k' or ln α versus 1/T. The thermodynamic parameters indicated that the separations were enthalpy-driven. Moreover, nonlinear van't Hoff plots were obtained on Chiralpak IA. However, two unusual phenomena were observed: (1) an unusual increase in retention with increasing temperature with linear van't Hoff plots on Chiralpak IC and (2) an extremely high T iso value (i.e., several thousand degrees centigrade). Copyright © 2017 Elsevier B.V. All rights reserved.

Innovation in Aerodynamic Design Features of Soviet Missiles

NASA Technical Reports Server (NTRS)

Spearman, M. Leroy

2006-01-01

Wind tunnel investigations of some tactical and strategic missile systems developed by the former Soviet Union have been included in the basic missile research programs of the NACA/NASA. Studies of the Soviet missiles sometimes revealed innovative design features that resulted in unusual or unexpected aerodynamic characteristics. In some cases these characteristics have been such that the measured performance of the missile exceeds what might have been predicted. In other cases some unusual design features have been found that would alleviate what might otherwise have been a serious aerodynamic problem. In some designs, what has appeared to be a lack of refinement has proven to be a matter of expediency. It is a purpose of this paper to describe some examples of unusual design features of some Soviet missiles and to illustrate the effectiveness of the design features on the aerodynamic behavior of the missile. The paper draws on the experience of the author who for over 60 years was involved in the aerodynamic wind tunnel testing of aircraft and missiles with the NACA/NASA.

Unusual magnetoelectric memory and polarization reversal in the kagome staircase compound N i3V2O8

NASA Astrophysics Data System (ADS)

Liu, Y. J.; Wang, J. F.; He, Z. Z.; Lu, C. L.; Xia, Z. C.; Ouyang, Z. W.; Liu, C. B.; Chen, R.; Matsuo, A.; Kohama, Y.; Kindo, K.; Tokunaga, M.

2018-05-01

We study the electric polarization of the kagome staircase N i3V2O8 in magnetic fields up to 30 T and report a magnetoelectric memory effect controlled by bias electric fields. The explored ferroelectric phase in 19 -24 T is electrically controlled, whereas the ferroelectric phase in 2 -11 T exhibits unusual memory effects. We determine a characteristic critical magnetic field H3=11 T , below which strong memory exists and the polarization is frozen even in opposite bias fields. But when magnetic fields exceed H3, the frozen polarization is released and polarization reversal appears by tuning bias electric fields. We ascribe these phenomena to the pinning-depinning mechanism: nucleation and the accompanying pinning of chiral domain walls cooperatively induce the frozen behavior; the polarization reversal results from the depinning through the ferroelectrtic-to-paraelectric phase transition in high magnetic fields. Our experimental results reveal that the first-order phase transition plays an important role in these unusual memory effects.

Successful lithium treatment of transvestism associated with manic-depression.

PubMed

Ward, N G

1975-09-01

A case of transvestism in a 24-year-old manic-depressive man is described. The behavior had been maintained for 2 years and disappeared soon after lithium treatment was begun. It has not returned during the first year on lithium. Dynamic and behavioral explanations for this unusual therapeutic response are considered. The dynamic explanation involves the assumption that the transvestism was perpetuated by mood-dependent motives that were eliminated by lithium. The behavioral explanation involves the assumption that the manic state itself became an intermittent reinforcer for the transvestism, and the lithium, by eliminating the mania, created a relatively permanent extinction period.

Translational animal models of autism and neurodevelopmental disorders.

PubMed

Crawley, Jacqueline N

2012-09-01

Autism is a neurodevelopmental disorder whose diagnosis is based on three behavioral criteria: unusual reciprocal social interactions, deficits in communication, and stereotyped repetitive behaviors with restricted interests. A large number of de novo single gene mutations and chromosomal deletions are associated with autism spectrum disorders. Based on the strong genetic evidence, mice with targeted mutations in homologous genes have been generated as translational research tools. Mouse models of autism have revealed behavioral and biological outcomes of mutations in risk genes. The field is now poised to employ the most robust phenotypes in the most replicable mouse models for preclinical screening of novel therapeutics.

Unusual behavior by Bison, Bison bison, toward Elk, Cervus elaphus, and wolves, Canis lupus

USGS Publications Warehouse

Mech, L.D.; McIntyre, R.T.; Smith, D.W.

2004-01-01

Incidents are described of Bison (Bison bison) in Yellowstone National Park mauling and possibly killing a young Elk (Cervus elaphus) calf, chasing wolves (Canis lupus) off Elk they had just killed or were killing, and keeping the wolves away for extended periods. During one of the latter cases, the Bison knocked a wolf-wounded Elk down. Bison were also seen approaching wolves that were resting and sleeping, rousting them, following them to new resting places and repeating this behavior. These behaviors might represent some type of generalized hyper-defensiveness that functions as an anti-predator strategy.

Unusual behavior by bison, Bison bison, toward elk, Cervus elaphus, and wolves, Canis lupus

USGS Publications Warehouse

Mech, L.D.; McIntyre, R.T.; Smith, D.W.

2004-01-01

Incidents are described of bison (Bison bison) in Yellowstone National Park mauling and possibly killing a young elk (Cervus elaphus) calf, chasing wolves (Canis lupus) off elk they had just killed or were killing, and keeping the wolves away for extended periods. During one of the latter cases, the bison knocked a wolf-wounded elk down. Bison were also seen approaching wolves that were resting and sleeping, rousting them, following them to new resting places and repeating this behavior. These behaviors might represent some type of generalized hyper-defensiveness that functions as an anti-predator strategy.

Structure, reactivity and electronic properties of Mn doped Ni13 clusters

NASA Astrophysics Data System (ADS)

Banerjee, Radhashyam; Datta, Soumendu; Mookerjee, Abhijit

2013-06-01

In this work we have studied the structural and magnetic properties of Ni13 cluster mono- and bi-doped with Mn atoms. We have noted their tendency of being reactive toward the H2 molecule. We have found unusually enhanced stability in the mono-doped cluster (i.e. of the Ni12Mn) and the diminished stability of the corresponding chemisorbed cluster, Ni12MnH2. Our analysis of the stability and HOMO-LUMO gap explains this unusual behavior. Interestingly, we have also seen the quenching in the net magnetic moment upon H2 absorption in the doped NiMnm alloy clusters. This has been reported earlier for smaller Nin clusters [1].

Vibrational spectroscopy reveals the initial steps of biological hydrogen evolution† †Electronic supplementary information (ESI) available: Complementary resonance Raman and infrared spectroscopic data. See DOI: 10.1039/c6sc01098a Click here for additional data file.

PubMed Central

Katz, S.; Noth, J.; Shafaat, H. S.; Happe, T.; Hildebrandt, P.

2016-01-01

[FeFe] hydrogenases are biocatalytic model systems for the exploitation and investigation of catalytic hydrogen evolution. Here, we used vibrational spectroscopic techniques to characterize, in detail, redox transformations of the [FeFe] and [4Fe4S] sub-sites of the catalytic centre (H-cluster) in a monomeric [FeFe] hydrogenase. Through the application of low-temperature resonance Raman spectroscopy, we discovered a novel metastable intermediate that is characterized by an oxidized [FeIFeII] centre and a reduced [4Fe4S]1+ cluster. Based on this unusual configuration, this species is assigned to the first, deprotonated H-cluster intermediate of the [FeFe] hydrogenase catalytic cycle. Providing insights into the sequence of initial reaction steps, the identification of this species represents a key finding towards the mechanistic understanding of biological hydrogen evolution. PMID:28451119

Unusual Iron Redox Systematics of Martian Magmas

NASA Technical Reports Server (NTRS)

Danielson, L.; Righter, K.; Pando, K.; Morris, R. V.; Graff, T.; Agresti, D.; Martin, A.; Sutton, S.; Newville, M.; Lanzirotti, A.

2012-01-01

Martian magmas are known to be FeO-rich and the dominant FeO-bearing mineral at many sites visited by the Mars Exploration rovers (MER) is magnetite. Morris et al. proposed that the magnetite appears to be igneous in origin, rather than of secondary origin. However, magnetite is not typically found in experimental studies of martian magmatic rocks. Magnetite stability in terrestrial magmas is well understood, as are the stabilities of FeO and Fe2O3 in terrestrial magmas. In order to better understand the variation of FeO and Fe2O3, and the stability of magnetite (and other FeO-bearing phases) in martian magmas, we have undertaken an experimental study with two emphases. First, we determine the FeO and Fe2O3 contents of super- and sub-liquidus glasses from a shergottite bulk composition at 1 bar to 4 GPa, and variable fO2. Second, we document the stability of magnetite with temperature and fO2 in a shergottite bulk composition.

An orphan cbb3-type cytochrome oxidase subunit supports Pseudomonas aeruginosa biofilm growth and virulence

PubMed Central

Jo, Jeanyoung; Cortez, Krista L; Cornell, William Cole; Price-Whelan, Alexa

2017-01-01

Hypoxia is a common challenge faced by bacteria during associations with hosts due in part to the formation of densely packed communities (biofilms). cbb3-type cytochrome c oxidases, which catalyze the terminal step in respiration and have a high affinity for oxygen, have been linked to bacterial pathogenesis. The pseudomonads are unusual in that they often contain multiple full and partial (i.e. ‘orphan’) operons for cbb3-type oxidases and oxidase subunits. Here, we describe a unique role for the orphan catalytic subunit CcoN4 in colony biofilm development and respiration in the opportunistic pathogen Pseudomonas aeruginosa PA14. We also show that CcoN4 contributes to the reduction of phenazines, antibiotics that support redox balancing for cells in biofilms, and to virulence in a Caenorhabditis elegans model of infection. These results highlight the relevance of the colony biofilm model to pathogenicity and underscore the potential of cbb3-type oxidases as therapeutic targets. PMID:29160206

The Involvement of Hydrogen-producing and ATP-dependent NADPH-consuming Pathways in Setting the Redox Poise in the Chloroplast of Chlamydomonas reinhardtii in Anoxia

PubMed Central

Clowez, Sophie; Godaux, Damien; Cardol, Pierre; Wollman, Francis-André; Rappaport, Fabrice

2015-01-01

Photosynthetic microalgae are exposed to changing environmental conditions. In particular, microbes found in ponds or soils often face hypoxia or even anoxia, and this severely impacts their physiology. Chlamydomonas reinhardtii is one among such photosynthetic microorganisms recognized for its unusual wealth of fermentative pathways and the extensive remodeling of its metabolism upon the switch to anaerobic conditions. As regards the photosynthetic electron transfer, this remodeling encompasses a strong limitation of the electron flow downstream of photosystem I. Here, we further characterize the origin of this limitation. We show that it stems from the strong reducing pressure that builds up upon the onset of anoxia, and this pressure can be relieved either by the light-induced synthesis of ATP, which promotes the consumption of reducing equivalents, or by the progressive activation of the hydrogenase pathway, which provides an electron transfer pathway alternative to the CO2 fixation cycle. PMID:25691575

Unusual kinetics of poly(ethylene glycol) oxidation with cerium(IV) ions in sulfuric acid medium and implications for copolymer synthesis.

PubMed

Szymański, Jan K; Temprano-Coleto, Fernando; Pérez-Mercader, Juan

2015-03-14

The cerium(IV)-alcohol couple in an acidic medium is an example of a redox system capable of initiating free radical polymerization. When the alcohol has a polymeric nature, the outcome of such a process is a block copolymer, a member of a class of compounds possessing many useful properties. The most common polymer with a terminal -OH group is poly(ethylene glycol) (PEG); however, the detailed mechanism of its reaction with cerium(IV) remains underexplored. In this paper, we report our findings for this reaction based on spectrophotometric measurements and kinetic modeling. We find that both the reaction order and the net rate constant for the oxidation process depend strongly on the nature of the acidic medium used. In order to account for the experimental observations, we postulate that protonation of PEG decreases its affinity for some of the cerium(IV)-sulfate complexes formed in the system.

Information processing through a bio-based redox capacitor: signatures for redox-cycling.

PubMed

Liu, Yi; Kim, Eunkyoung; White, Ian M; Bentley, William E; Payne, Gregory F

2014-08-01

Redox-cycling compounds can significantly impact biological systems and can be responsible for activities that range from pathogen virulence and contaminant toxicities, to therapeutic drug mechanisms. Current methods to identify redox-cycling activities rely on the generation of reactive oxygen species (ROS), and employ enzymatic or chemical methods to detect ROS. Here, we couple the speed and sensitivity of electrochemistry with the molecular-electronic properties of a bio-based redox-capacitor to generate signatures of redox-cycling. The redox capacitor film is electrochemically-fabricated at the electrode surface and is composed of a polysaccharide hydrogel with grafted catechol moieties. This capacitor film is redox-active but non-conducting and can engage diffusible compounds in either oxidative or reductive redox-cycling. Using standard electrochemical mediators ferrocene dimethanol (Fc) and Ru(NH3)6Cl3 (Ru(3+)) as model redox-cyclers, we observed signal amplifications and rectifications that serve as signatures of redox-cycling. Three bio-relevant compounds were then probed for these signatures: (i) ascorbate, a redox-active compound that does not redox-cycle; (ii) pyocyanin, a virulence factor well-known for its reductive redox-cycling; and (iii) acetaminophen, an analgesic that oxidatively redox-cycles but also undergoes conjugation reactions. These studies demonstrate that the redox-capacitor can enlist the capabilities of electrochemistry to generate rapid and sensitive signatures of biologically-relevant chemical activities (i.e., redox-cycling). Published by Elsevier B.V.

Sugar beet factory lime affects the mobilization of Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn under dynamic redox conditions in a contaminated floodplain soil.

PubMed

Shaheen, Sabry M; Rinklebe, Jörg

2017-01-15

The impact of sugar beet factory lime (SBFL) on the release dynamics and mobilization of toxic metals (TMs) under dynamic redox conditions in floodplain soils has not been studied up to date. Therefore, the aim of this study was to verify the scientific hypothesis that SBFL is able to immobilize Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, and Zn under different redox potentials (E H ) in a contaminated floodplain soil. For this purpose, the non-treated contaminated soil (CS) and the same soil treated with SBFL (CS+SBFL) were flooded in the laboratory using a highly sophisticated automated biogeochemical microcosm apparatus. The experiment was conducted stepwise from reducing (-13 mV) to oxidizing (+519 mV) soil conditions. Soil pH decreased under oxic conditions in CS (from 6.9 to 4.0) and in CS+SBFL (from 7.5 to 4.4). The mobilization of Cu, Cr, Pb, and Fe were lower in CS+SBFL than in CS under both reducing/neutral and oxic/acidic conditions. Those results demonstrate that SBFL is able to decrease concentrations of these elements under a wide range of redox and pH conditions. The mobilization of Cd, Co, Mn, Mo, Ni, and Zn were higher in CS+SBFL than in CS under reducing/neutral conditions; however, these concentrations showed an opposite behavior under oxic/acidic conditions and were lower in CS+SBFL than in CS. We conclude that SBFL immobilized Cu, Cr, Pb, and Fe under dynamic redox conditions and immobilized Cd, Co, Mn, Mo, Ni, and Zn under oxic acidic conditions; however, the latter elements were mobilized under reducing neutral conditions in the studied soil. Therefore, the addition of SBFL to acid floodplain soils contaminated with TMs might be an important alternative for ameliorating these soils with view to a sustainable management of these soils. Copyright © 2016 Elsevier Ltd. All rights reserved.

Fish scales in sediments from off Callao, central Peru

NASA Astrophysics Data System (ADS)

Díaz-Ochoa, J. A.; Lange, C. B.; Pantoja, S.; De Lange, G. J.; Gutiérrez, D.; Muñoz, P.; Salamanca, M.

2009-07-01

We study fish scales as a proxy of fish abundance and preservation biases together with phosphorus from fish remains (P fish) in a sediment core retrieved off Callao, Peru (12°1'S, 77°42'W; water depth=179 m; core length=52 cm). We interpret our results as a function of changing redox conditions based on ratios of redox-sensitive trace elements (Cu/Al, Mo/Al, Ni/Al, Zn/Al, V/Al), terrigenous indicators (Fe in clays, Ti, Al), and biogenic proxies (CaCO 3, biogenic opal, total nitrogen, organic carbon, barite Ba). The core covers roughly 700 years of deposition, based on 210Pb activities extrapolated downcore and 14C dating at selected intervals. Our fish-scale record is dominated by anchovy ( Engraulis ringens) scales followed by hake ( Merluccius gayii) scales. The core presented an abrupt lithological change at 17 cm (corresponding to the early 19th century). Above that depth, it was laminated and was more organic-rich (10-15% organic carbon) than below, where the core was partly laminated and less organic-rich (<10%). The lithological shift coincides with abrupt changes in dry bulk density and in the contents of terrigenous and redox-sensitive trace elements, biogenic proxies, and fish scales. The remarkable increase in redox-sensitive trace elements in the upper 17 cm of the core suggests more reducing conditions when compared with deeper and older horizons, and is interpreted as an intensification of the oxygen minimum zone off Peru beginning in the early 19th century. Higher fish-scale contents and higher P fish/P total ratios were also observed within the upper 17 cm of the core. The behavior of biogenic proxies and redox-sensitive trace elements was similar; more reduced conditions corresponded to higher contents of CaCO 3, C org, total nitrogen and fish scales, suggesting that these proxies might convey an important preservation signal.

"Sticky electrons" transport and interfacial transfer of electrons in the dye-sensitized solar cell.

PubMed

Peter, Laurence

2009-11-17

Dye-sensitized solar cells (DSCs, also known as Gratzel cells) mimic the photosynthetic process by using a sensitizer dye to harvest light energy to generate electrical power. Several functional features of these photochemical devices are unusual, and DSC research offers a rewarding arena in which to test new ideas, new materials, and new methodologies. Indeed, one of the most attractive chemical features of the DSC is that the basic concept can be used to construct a range of devices, replacing individual components with alternative materials. Despite two decades of increasing research activity, however, many aspects of the behavior of electrons in the DSC remain puzzling. In this Account, we highlight current understanding of the processes involved in the functioning of the DSC, with particular emphasis on what happens to the electrons in the mesoporous film following the injection step. The collection of photoinjected electrons appears to involve a random walk process in which electrons move through the network of interconnected titanium dioxide nanoparticles while undergoing frequent trapping and detrapping. During their passage to the cell contact, electrons may be lost by transfer to tri-iodide species in the redox electrolyte that permeates the mesoporous film. Competition between electron collection and back electron transfer determines the performance of a DSC: ideally, all injected electrons should be collected without loss. This Account then goes on to survey recent experimental and theoretical progress in the field, placing particular emphasis on issues that need to be resolved before we can gain a clear picture of how the DSC works. Several important questions about the behavior of "sticky" electrons, those that undergo multiple trapping and detrapping, in the DSC remain unanswered. The most fundamental of these concerns is the nature of the electron traps that appear to dominate the time-dependent photocurrent and photovoltage response of DSCs. The origin of the nonideality factor in the relationship between the intensity and the DSC photovoltage is also unclear, as is the discrepancy in electron diffusion length values determined by steady-state and non-steady-state methods. With these unanswered questions, DSC research is likely to remain an active and fruitful area for some years to come.

SORPTION AND DESORPTION BY IDEAL TWO-COMPARTMENT SYSTEMS: UNUSUAL BEHAVIOR AND DATA INTERPRETATION PROBLEMS

EPA Science Inventory

This paper presents an evaluation of the results of fitting curves to isotherm and kinetic data for idealized two-compartment systems of soil or sediment. Data were produced by numerically solving sets of Freundlich isotherm and first-order kinetics equations for mixtures of up ...

Broad Ligament Perivascular Epithelioid Cell Tumor (PEComa) of Uncertain Malignant Potential.

PubMed

Mathew, Mary; Nayal, Bhavna; Rao, Lakshmi; Nagel, Bhawna

2016-01-01

PEComas are uncommon mesenchymal tumors often involving the pelvic organs. They have an unpredictable behavior. Accurate diagnosis and long-term follow-up is therefore essential in these patients. We report this case of PEComa of uncertain malignant potential in an unusual location with excellent prognosis.

The Unusual Suspects: Myths and Misconceptions Associated with PECS

ERIC Educational Resources Information Center

Bondy, Andy

2012-01-01

The Picture Exchange Communication System (PECS) is an alternative/augmentative communication protocol designed to help children and adults with autism and related disabilities to engage in functional communication. The protocol was developed over a number of years and was based on Skinner's analysis of verbal behavior. Publications about the…

A Short Stay, a Long-Lasting Lesson.

ERIC Educational Resources Information Center

Benham, Dianne C.

1991-01-01

Presents an integrated schoolwide program in which students learn about pet care and the behaviors of 14 unusual animals. Each participating teacher sets up one animal center describing the animal and the animal's habitat. Centers change at the end of each month. Discusses costs and learning benefits of the program. (MDH)

Unveiling Surface Redox Charge Storage of Interacting Two-Dimensional Hetero-Nanosheets in Hierarchical Architectures

DOE PAGES

Mahmood, Qasim; Bak, Seong-Min; Kim, Min G.; ...

2015-03-03

Two-dimensional (2D) heteronanosheets are currently the focus of intense study due to the unique properties that emerge from the interplay between two low-dimensional nanomaterials with different properties. However, the properties and new phenomena based on the two 2D heteronanosheets interacting in a 3D hierarchical architecture have yet to be explored. Here, we unveil the surface redox charge storage mechanism of surface-exposed WS2 nanosheets assembled in a 3D hierarchical heterostructure using in situ synchrotron X-ray absorption and Raman spectroscopic methods. The surface dominating redox charge storage of WS2 is manifested in a highly reversible and ultrafast capacitive fashion due to themore » interaction of heteronanosheets and the 3D connectivity of the hierarchical structure. In contrast, compositionally identical 2D WS2 structures fail to provide a fast and high capacitance with different modes of lattice vibration. The distinctive surface capacitive behavior of 3D hierarchically structured heteronanosheets is associated with rapid proton accommodation into the in-plane W–S lattice (with the softening of the E2g bands), the reversible redox transition of the surface-exposed intralayers residing in the electrochemically active 1T phase of WS2 (with the reversible change in the interatomic distance and peak intensity of W–W bonds), and the change in the oxidation state during the proton insertion/deinsertion process. This proposed mechanism agrees with the dramatic improvement in the capacitive performance of the two heteronanosheets coupled in the hierarchical structure.« less

How Reducing was the Late Devonian Ocean? The Role of Extensive Expansion of Anoxia in Marine Biogeochemical Cycles of Redox Sensitive Metals.

NASA Astrophysics Data System (ADS)

Sahoo, S. K.; Jin, H.

2017-12-01

The evolution of Earth's biogeochemical cycles is intimately linked to the oxygenation of the oceans and atmosphere. The Late Devonian is no exception as its characterized with mass extinction and severe euxinia. Here we use concentrations of Molybdenum (Mo), Vanadium (V), Uranium (U) and Chromium (Cr) in organic rich black shales from the Lower Bakken Formation of the Williston Basin, to explore the relationship between extensive anoxia vs. euxinia and it's relation with massive release of oxygen in the ocean atmosphere system. XRF data from 4 core across the basin shows that modern ocean style Mo, U and Cr enrichments are observed throughout the Lower Bakken Formation, yet V is not enriched until later part of the formation. Given the coupling between redox-sensitive-trace element cycles and ocean redox, various models for Late Devonian ocean chemistry imply different effects on the biogeochemical cycling of major and trace nutrients. Here, we examine the differing redox behavior of molybdenum and vanadium under an extreme anoxia and relatively low extent of euxinia. The model suggests that Late Devonian was perhaps extensively anoxic- 40-50% compared to modern seafloor area, and a very little euxinia. Mo enrichments extend up to 500 p.p.m. throughout the section, representative of a modern reducing ocean. However, coeval low V enrichments only support towards anoxia, where anoxia is a source of V, and a sink for Mo. Our model suggests that the oceanic V reservoir is extremely sensitive to perturbations in the extent of anoxic condition, particularly during post glacial times.

Biotransformation of trace organic chemicals during groundwater recharge: How useful are first-order rate constants?

PubMed

Regnery, J; Wing, A D; Alidina, M; Drewes, J E

2015-08-01

This study developed relationships between the attenuation of emerging trace organic chemicals (TOrC) during managed aquifer recharge (MAR) as a function of retention time, system characteristics, and operating conditions using controlled laboratory-scale soil column experiments simulating MAR. The results revealed that MAR performance in terms of TOrC attenuation is primarily determined by key environmental parameters (i.e., redox, primary substrate). Soil columns with suboxic and anoxic conditions performed poorly (i.e., less than 30% attenuation of moderately degradable TOrC) in comparison to oxic conditions (on average between 70-100% attenuation for the same compounds) within a residence time of three days. Given this dependency on redox conditions, it was investigated if key parameter-dependent rate constants are more suitable for contaminant transport modeling to properly capture the dynamic TOrC attenuation under field-scale conditions. Laboratory-derived first-order removal kinetics were determined for 19 TOrC under three different redox conditions and rate constants were applied to MAR field data. Our findings suggest that simplified first-order rate constants will most likely not provide any meaningful results if the target compounds exhibit redox dependent biotransformation behavior or if the intention is to exactly capture the decline in concentration over time and distance at field-scale MAR. However, if the intention is to calculate the percent removal after an extended time period and subsurface travel distance, simplified first-order rate constants seem to be sufficient to provide a first estimate on TOrC attenuation during MAR. Copyright © 2015 Elsevier B.V. All rights reserved.

Hydroxyl radical generation in electro-Fenton process with a gas-diffusion electrode: Linkages with electro-chemical generation of hydrogen peroxide and iron redox cycle.

PubMed

Yatagai, Tomonori; Ohkawa, Yoshiko; Kubo, Daichi; Kawase, Yoshinori

2017-01-02

The hydroxyl radical generation in an electro-Fenton process with a gas-diffusion electrode which is strongly linked with electro-chemical generation of hydrogen peroxide and iron redox cycle was studied. The OH radical generation subsequent to electro-chemical generations of H 2 O 2 was examined under the constant potential in the range of Fe 2+ dosage from 0 to 1.0 mM. The amount of generated OH radical initially increased and gradually decreased after the maximum was reached. The initial rate of OH radical generation increased for the Fe 2+ dosage <0.25 mM and at higher Fe 2+ dosages remained constant. At higher Fe 2+ dosages the precipitation of Fe might inhibit the enhancement of OH radical generation. The experiments for decolorization and total organic carbon (TOC) removal of azo-dye Orange II by the electro-Fenton process were conducted and the quick decolorization and slow TOC removal of Orange II were found. To quantify the linkages of OH radical generation with dynamic behaviors of electro-chemically generated H 2 O 2 and iron redox cycle and to investigate effects of OH radical generation on the decolorization and TOC removal of Orange II, novel reaction kinetic models were developed. The proposed models could satisfactory clarify the linkages of OH radical generation with electro-chemically generated H 2 O 2 and iron redox cycle and simulate the decolorization and TOC removal of Orange II by the electro-Fenton process.

Mechanisms of neptunium redox reactions in nitric acid solutions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chatterjee, Sayandev; Bryan, Samuel A.; Casella, Amanda J.

First transuranium element neptunium (Np) exhibits complicated behavior in acidic solutions because it can adopt wide range of oxidation states typically from +3 to +6 and coordinate large variety of ligands. In particular, accurate determination of Np redox potentials in nitric acid solutions is challenging due to overlapping chemical and electrochemical reactions leading to significant experimental uncertainties. Furthermore, over past decades spectrophotometry has been extensively applied to identify and characterize Np solution species in different oxidation states. However, relevant spectral database of Np in nitric acid solutions that can serve for the reference purposes has yet to be established duemore » to the experimental difficulty to isolate and stabilize Np species in pure oxidation states without compromising solution optical properties. This work demonstrates that combination of voltammetry and controlled-potential in situ thin-layer spectropotentiometry overcomes these challenges so that Np species in pure +3, +4, +5, or +6 oxidation states were electrochemically generated in the systematically varied 0.1 – 5 M nitric acid solutions, and corresponding vis-NIR spectral signatures were obtained. In situ optical monitoring of the interconversion between adjacent Np oxidation states resulted in elucidation of the mechanisms of the involved redox reactions, in-depth understanding of the relative stability of the Np oxidation states, and allowed benchmarking of the redox potentials of the NpO22+/NpO2+, NpO2+/Np4+ and Np4+/Np3+ couples. Notably, the NpO2+/Np4+ couple was distinguished from the proximal Np4+/Np3+ process overcoming previous concerns and challenges encountered in accurate determination of the respective potentials.« less

Trace elements at the intersection of marine biological and geochemical evolution

USGS Publications Warehouse

Robbins, Leslie J.; Lalonde, Stefan V.; Planavsky, Noah J.; Partin, Camille A.; Reinhard, Christopher T.; Kendall, Brian; Scott, Clinton T.; Hardisty, Dalton S.; Gill, Benjamin C.; Alessi, Daniel S.; Dupont, Christopher L.; Saito, Mak A.; Crowe, Sean A.; Poulton, Simon W.; Bekker, Andrey; Lyons, Timothy W.; Konhauser, Kurt O.

2016-01-01

Life requires a wide variety of bioessential trace elements to act as structural components and reactive centers in metalloenzymes. These requirements differ between organisms and have evolved over geological time, likely guided in some part by environmental conditions. Until recently, most of what was understood regarding trace element concentrations in the Precambrian oceans was inferred by extrapolation, geochemical modeling, and/or genomic studies. However, in the past decade, the increasing availability of trace element and isotopic data for sedimentary rocks of all ages has yielded new, and potentially more direct, insights into secular changes in seawater composition – and ultimately the evolution of the marine biosphere. Compiled records of many bioessential trace elements (including Ni, Mo, P, Zn, Co, Cr, Se, and I) provide new insight into how trace element abundance in Earth's ancient oceans may have been linked to biological evolution. Several of these trace elements display redox-sensitive behavior, while others are redox-sensitive but not bioessential (e.g., Cr, U). Their temporal trends in sedimentary archives provide useful constraints on changes in atmosphere-ocean redox conditions that are linked to biological evolution, for example, the activity of oxygen-producing, photosynthetic cyanobacteria. In this review, we summarize available Precambrian trace element proxy data, and discuss how temporal trends in the seawater concentrations of specific trace elements may be linked to the evolution of both simple and complex life. We also examine several biologically relevant and/or redox-sensitive trace elements that have yet to be fully examined in the sedimentary rock record (e.g., Cu, Cd, W) and suggest several directions for future studies.

Amplified and in situ detection of redox-active metabolite using a biobased redox capacitor.

PubMed

Kim, Eunkyoung; Gordonov, Tanya; Bentley, William E; Payne, Gregory F

2013-02-19

Redox cycling provides a mechanism to amplify electrochemical signals for analyte detection. Previous studies have shown that diverse mediators/shuttles can engage in redox-cycling reactions with a biobased redox capacitor that is fabricated by grafting redox-active catechols onto a chitosan film. Here, we report that redox cycling with this catechol-chitosan redox capacitor can amplify electrochemical signals for detecting a redox-active bacterial metabolite. Specifically, we studied the redox-active bacterial metabolite pyocyanin that is reported to be a virulence factor and signaling molecule for the opportunistic pathogen P. aeruginosa. We demonstrate that redox cycling can amplify outputs from various electrochemical methods (cyclic voltammetry, chronocoulometry, and differential pulse voltammetry) and can lower the detection limit of pyocyanin to 50 nM. Further, the compatibility of this biobased redox capacitor allows the in situ monitoring of the production of redox-active metabolites (e.g., pyocyanin) during the course of P. aeruginosa cultivation. We anticipate that the amplified output of redox-active virulence factors should permit an earlier detection of life-threatening infections by the opportunistic pathogen P. aeruginosa while the "bio-compatibility" of this measurement approach should facilitate in situ study of the spatiotemporal dynamics of bacterial redox signaling.

Redox Abnormalities as a Vulnerability Phenotype for Autism and Related Alterations in CNS Development

DTIC Science & Technology

2011-10-01

ming during pre- and post-natal neurodevelopment . Previously, we reported that many children with autism have abnormal plasma levels of metabolites...dysregulation in autism . 1. Introduction Autism is a behaviorally defined neurodevelopmental disor- der that usually presents in early childhood and is charac...Phenotype for Autism and Related Alterations in CNS Development PRINCIPAL INVESTIGATOR: Sandra Jill James, Ph.D

Novel insights into redox system and the mechanism of redox regulation.

PubMed

Wang, Xin; Hai, Chunxu

2016-07-01

In view of the critical role of redox system in numerous physiological and pathophysiological processes, it is important to clearly understand the family members and regulatory mechanism of redox system. In this work, we will systematically review the current data detailing the reactive oxygen species (ROS), enzymatic and non-enzymatic antioxidants and redox sensitive transcription factors and we give a brief description of redox-mediated epigenetic and post-translational regulation. We propose that the redox system functions as a "Redox Chain", consisting of "ROS-generating Enzyme Chain", "Combined Antioxidant Chain" and "Transcription Factor Chain". We suggest that an individualized assessment of the redox status in the body should be conducted for the redox intervention of a patient. The strategy of intervention is to maintain redox homeostasis via either facilitation of ROS signaling or enhancement of antioxidant defense. These findings provide valuable new insights into redox system and open up new paths for the control of redox-related disorders.

Polyoxometalate active charge-transfer material for mediated redox flow battery

DOEpatents

Anderson, Travis Mark; Hudak, Nicholas; Staiger, Chad; Pratt, Harry

2017-01-17

Redox flow batteries including a half-cell electrode chamber coupled to a current collecting electrode are disclosed herein. In a general embodiment, a separator is coupled to the half-cell electrode chamber. The half-cell electrode chamber comprises a first redox-active mediator and a second redox-active mediator. The first redox-active mediator and the second redox-active mediator are circulated through the half-cell electrode chamber into an external container. The container includes an active charge-transfer material. The active charge-transfer material has a redox potential between a redox potential of the first redox-active mediator and a redox potential of the second redox-active mediator. The active charge-transfer material is a polyoxometalate or derivative thereof. The redox flow battery may be particularly useful in energy storage solutions for renewable energy sources and for providing sustained power to an electrical grid.

The Structure-Dependent Electric Release and Enhanced Oxidation of Drug in Graphene Oxide-Based Nanocarrier Loaded with Anticancer Herbal Drug Berberine.

PubMed

Yu, Danni; Ruan, Pan; Meng, Ziyuan; Zhou, Jianping

2015-08-01

The aim of the current investigation is to explore graphene oxide (GO) special electric and electrochemical properties in modulating and tuning drug delivery in tumor special environment of electrophysiology. The electric-sensitive drug release and redox behavior of GO-bearing berberine (Ber) was studied. Drug release in cell potential was applied in a designed electrode system: tumor environment was simulated at pH 6.2 with 0.1 V pulse voltage, whereas the normal was at pH 7.4 with 0.2 V. Quite different from the pH-depended profile, the electricity-triggered behavior indicated a high correlation with the carriers' structure: GO-based nanocomposite showed a burst release on its special "skin effect," whereas the PEGylated ones released slowly owing to the electroviscous effect of polymer. Cyclic voltammetry was used to investigate the redox behaviors of colloid PEGylated GO toward absorbed Ber in pH 5.8 and 7.2 solutions. After drug loading, the oxidation of Ber was enhanced in a neutral environment, whereas the enhancement of PEG-GO was in an acidic one, which means a possible increased susceptibility of their biotransformation in vivo. The studies designed in this work may help to establish a kind of carrier system for the sensitive delivery and metabolic regulation of drugs according to the different electrophysiological environment in tumor therapy. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association.

Subcellular Redox Targeting: Bridging in Vitro and in Vivo Chemical Biology.

PubMed

Long, Marcus J C; Poganik, Jesse R; Ghosh, Souradyuti; Aye, Yimon

2017-03-17

Networks of redox sensor proteins within discrete microdomains regulate the flow of redox signaling. Yet, the inherent reactivity of redox signals complicates the study of specific redox events and pathways by traditional methods. Herein, we review designer chemistries capable of measuring flux and/or mimicking subcellular redox signaling at the cellular and organismal level. Such efforts have begun to decipher the logic underlying organelle-, site-, and target-specific redox signaling in vitro and in vivo. These data highlight chemical biology as a perfect gateway to interrogate how nature choreographs subcellular redox chemistry to drive precision redox biology.

Predictive Framework and Experimental Tests of the Kinetic Isotope Effect at Redox-Active Interfaces

NASA Astrophysics Data System (ADS)

Kavner, A.; John, S.; Black, J. R.

2013-12-01

Electrochemical reactions provide a compelling framework to study kinetic isotope effects because redox-related processes are important for a wide variety of geological and environmental processes. In the laboratory, electrochemical reaction rates can be electronically controlled and measured in the laboratory using a potentiostat. This enables variation of redox reactions rates independent of changes in chemistry and, and the resulting isotope compositions of reactants and products can be separated and analyzed. In the past years, a series of experimental studies have demonstrated a large, light, and tunable kinetic isotope effect during electrodeposition of metal Fe, Zn, Li, Cu, and Mo from a variety of solutions (e.g. Black et al., 2009, 2010, 2011). A theoretical framework based on Marcus kinetic theory predicts a voltage-dependent kinetic isotope effect (Kavner et al., 2005, 2008), however while this framework was able to predict the tunable nature of the effect, it was not able to simultaneously predict absolute reaction rates and relative isotope rates. Here we present a more complete development of a statistical mechanical framework for simple interfacial redox reactions, which includes isotopic behavior. The framework is able to predict a kinetic isotope effect as a function of temperature and reaction rate, starting with three input parameters: a single reorganization energy which describes the overall kinetics of the electron transfer reaction, and the equilibrium reduced partition function ratios for heavy and light isotopes in the product and reactant phases. We show the framework, elucidate some of the predictions, and show direct comparisons against isotope fractionation data obtained during laboratory and natural environment redox processes. A. Kavner, A. Shahar, F. Bonet, J. Simon and E. Young (2005) Geochim. Cosmochim. Acta, 69(12), 2971-2979. A. Kavner, S. G. John, S. Sass, and E. A. Boyle (2008), Geochim. Cosmochim. Acta, vol 72, pp. 1731-1741. J. R. Black, Umeda, G., Dunn, B., McDonough, W. F. and A. Kavner. (2009), J. Amer. Chem. Soc., vol. 131, No.29 2009 pp. 9904-9905 DOI: 10.1021/ja903926x. J. R. Black, S. John, E.D. Young, and A. Kavner, (2010), Geochim. Cosmochim. Acta, vol 74 (18) pp. 5187-5201. J. R. Black, J. Crawford, S. John, and A. Kavner, (2011) Redox-driven stable isotope fractionation, in Aquatic Redox Chemistry ACS Symposium Series, Vol. 1071. Tratnyek, P.G., T. J. Grundl, and S. B. Haderlein, eds. Chapter 16, pp 345-359

The Redox Code

PubMed Central

Jones, Dean P.

2015-01-01

Abstract Significance: The redox code is a set of principles that defines the positioning of the nicotinamide adenine dinucleotide (NAD, NADP) and thiol/disulfide and other redox systems as well as the thiol redox proteome in space and time in biological systems. The code is richly elaborated in an oxygen-dependent life, where activation/deactivation cycles involving O2 and H2O2 contribute to spatiotemporal organization for differentiation, development, and adaptation to the environment. Disruption of this organizational structure during oxidative stress represents a fundamental mechanism in system failure and disease. Recent Advances: Methodology in assessing components of the redox code under physiological conditions has progressed, permitting insight into spatiotemporal organization and allowing for identification of redox partners in redox proteomics and redox metabolomics. Critical Issues: Complexity of redox networks and redox regulation is being revealed step by step, yet much still needs to be learned. Future Directions: Detailed knowledge of the molecular patterns generated from the principles of the redox code under defined physiological or pathological conditions in cells and organs will contribute to understanding the redox component in health and disease. Ultimately, there will be a scientific basis to a modern redox medicine. Antioxid. Redox Signal. 23, 734–746. PMID:25891126

[Asperger Syndrome and/or Clinical High Risk of Psychosis? A Differential Diagnostic Challenge].

PubMed

Schmidt, Stefanie J; Behar, Ayla; Schultze-Lutter, Frauke

2018-03-01

Asperger Syndrome and/or Clinical High Risk of Psychosis? A Differential Diagnostic Challenge This case-study deals with the often difficult differential diagnosis of Asperger syndrome and a clinical high risk state of psychosis, in particular as indicated by attenuated psychotic symptoms, as well as with its therapeutic implications. The presented case is a 10-year old girl, who has not been diagnosed with an autism spectrum disorder before being referred to a specialized center for early detection of psychosis due to possible hallucinatory experiences and delusional ideas. We demonstrate how to perform a context-sensitive differential diagnosis to distinguish between specific interests as well as related behaviors and unusual thought content as well as perceptive abnormalities, between paranoid ideas and biased interpretations of the behaviors of others typical for autism, and between disorganized symptoms and autistic unusual communication and social behavior. The resulting dual diagnoses in our case-study formed the basis for a complex differential indication, which considered both the increased stress vulnerability associated with an increased risk for the development of psychosis as well as the rigid thinking style associated with autism. Our case-report shows that such a precise differential indication can lead to stabilization over the long-term, even in patients with dual diagnoses.

Emoticon-Based Ambivalent Expression: A Hidden Indicator for Unusual Behaviors in Weibo.

PubMed

Hu, Yue; Zhao, Jichang; Wu, Junjie

2016-01-01

Recent decades have witnessed online social media being a big-data window for testifying conventional social theories quantitatively and exploring much detailed human behavioral patterns. In this paper, by tracing the emoticon use in Weibo, a group of hidden "ambivalent users" are disclosed for frequently posting ambivalent tweets containing both positive and negative emotions. Further investigation reveals that this ambivalent expression could be a novel indicator of many unusual social behaviors. For instance, ambivalent users with the female as the majority like to make a sound in midnights and at weekends. They mention their close friends frequently in ambivalent tweets, which attract more replies and serve as a more private communication way. Ambivalent users also respond differently to public affairs from others and demonstrate more interests in entertainment and sports events. Moreover, the sentiment shift in ambivalent tweets is more evident than usual and exhibits a clear "negative to positive" pattern. The above observations, though being promiscuous seemingly, actually point to the self-regulation of negative mood in Weibo, which could find its basis from the traditional emotion management theories in sociology but makes an important extension to the online environment in this study. Finally, as an interesting corollary, ambivalent users are found connected with compulsive buyers and turn out to be perfect targets for online marketing.

Redox Species of Redox Flow Batteries: A Review.

PubMed

Pan, Feng; Wang, Qing

2015-11-18

Due to the capricious nature of renewable energy resources, such as wind and solar, large-scale energy storage devices are increasingly required to make the best use of the renewable power. The redox flow battery is considered suitable for large-scale applications due to its modular design, good scalability and flexible operation. The biggest challenge of the redox flow battery is the low energy density. The redox active species is the most important component in redox flow batteries, and the redox potential and solubility of redox species dictate the system energy density. This review is focused on the recent development of redox species. Different categories of redox species, including simple inorganic ions, metal complexes, metal-free organic compounds, polysulfide/sulfur and lithium storage active materials, are reviewed. The future development of redox species towards higher energy density is also suggested.

Rapidly reversible redox transformation in nanophase manganese oxides at room temperature triggered by changes in hydration

PubMed Central

Birkner, Nancy; Navrotsky, Alexandra

2014-01-01

Chemisorption of water onto anhydrous nanophase manganese oxide surfaces promotes rapidly reversible redox phase changes as confirmed by calorimetry, X-ray diffraction, and titration for manganese average oxidation state. Surface reduction of bixbyite (Mn2O3) to hausmannite (Mn3O4) occurs in nanoparticles under conditions where no such reactions are seen or expected on grounds of bulk thermodynamics in coarse-grained materials. Additionally, transformation does not occur on nanosurfaces passivated by at least 2% coverage of what is likely an amorphous manganese oxide layer. The transformation is due to thermodynamic control arising from differences in surface energies of the two phases (Mn2O3 and Mn3O4) under wet and dry conditions. Such reversible and rapid transformation near room temperature may affect the behavior of manganese oxides in technological applications and in geologic and environmental settings. PMID:24733903

High Electromagnetic Field Enhancement of TiO2 Nanotube Electrodes.

PubMed

Öner, Ibrahim Halil; Querebillo, Christine Joy; David, Christin; Gernert, Ulrich; Walter, Carsten; Driess, Matthias; Leimkühler, Silke; Ly, Khoa Hoang; Weidinger, Inez M

2018-06-11

We present the fabrication of TiO 2 nanotube electrodes with high biocompatibility and extraordinary spectroscopic properties. Intense surface-enhanced resonance Raman signals of the heme unit of the redox enzyme Cytochrome b 5 were observed upon covalent immobilization of the protein matrix on the TiO 2 surface, revealing overall preserved structural integrity and redox behavior. The enhancement factor could be rationally controlled by varying the electrode annealing temperature, reaching a record maximum value of over 70 at 475 °C. For the first time, such high values are reported for non-directly surface-interacting probes, for which the involvement of charge-transfer processes in signal amplification can be excluded. The origin of the surface enhancement is exclusively attributed to enhanced localized electric fields resulting from the specific optical properties of the nanotubular geometry of the electrode. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rapidly reversible redox transformation in nanophase manganese oxides at room temperature triggered by changes in hydration.

PubMed

Birkner, Nancy; Navrotsky, Alexandra

2014-04-29

Chemisorption of water onto anhydrous nanophase manganese oxide surfaces promotes rapidly reversible redox phase changes as confirmed by calorimetry, X-ray diffraction, and titration for manganese average oxidation state. Surface reduction of bixbyite (Mn2O3) to hausmannite (Mn3O4) occurs in nanoparticles under conditions where no such reactions are seen or expected on grounds of bulk thermodynamics in coarse-grained materials. Additionally, transformation does not occur on nanosurfaces passivated by at least 2% coverage of what is likely an amorphous manganese oxide layer. The transformation is due to thermodynamic control arising from differences in surface energies of the two phases (Mn2O3 and Mn3O4) under wet and dry conditions. Such reversible and rapid transformation near room temperature may affect the behavior of manganese oxides in technological applications and in geologic and environmental settings.

Chemical and electrochemical behavior of the Cr(3)/Cr(2) half cell in the NASA Redox Energy Storage System

NASA Technical Reports Server (NTRS)

Johnson, D. A.; Reid, M. A.

1982-01-01

The Cr(III) complexes in the NASA Redox Energy Storage System were isolated and identified as Cr(H2O)6(+3) and Cr(H2O)5Cl(+2) by ion exchange chromatography and visible spectrophotometry. The cell reactions during charge-discharge cycles were followed by means of visible spectrophotometry. The spectral bands were resolved into component peaks and concentrations calculated using Beer's Law. During the charge mode Cr(H2O)5Cl(+2) is reduced to Cr(H2O)5Cl(+) and during the discharge mode Cr(H2O)5Cl(+) is oxidized back to Cr(H2O)5Cl(+2). Both electrode reactions occur via a chloride-bridge inner-sphere reaction pathway. Hysteresis effects can be explained by the slow attainment of equilibrium between Cr(H2O)6(+3) and Cr(H2O)5Cl(+2).

Coordination behavior of ligand based on NNS and NNO donors with ruthenium(III) complexes and their catalytic and DNA interaction studies

NASA Astrophysics Data System (ADS)

Manikandan, R.; Viswnathamurthi, P.

2012-11-01

Reactions of 2-acetylpyridine-thiosemicarbazone HL1, 2-acetylpyridine-4-methyl-thiosemicarbazone HL2, 2-acetylpyridine-4-phenyl-thiosemicarbazone HL3 and 2-acetylpyridine-semicarbazone HL4 with ruthenium(III) precursor complexes were studied and the products were characterized by analytical and spectral (FT-IR, electronic, EPR and EI-MS) methods. The ligands coordinated with the ruthenium(III) ion via pyridine nitrogen, azomethine nitrogen and thiolate sulfur/enolate oxygen. An octahedral geometry has been proposed for all the complexes based on the studies. All the complexes are redox active and display an irreversible and quasireversible metal centered redox processes. Further, the catalytic activity of the new complexes has been investigated for the transfer hydrogenation of ketones in the presence of isopropanol/KOH and the Kumada-Corriu coupling of aryl halides with aryl Grignard reagents. The DNA cleavage efficiency of new complexes has also been tested.

Ferrocenyl-substituted dinuclear Cu(II) complex: Synthesis, spectroscopy, electrochemistry, DFT calculations and catecholase activity

NASA Astrophysics Data System (ADS)

Emirik, Mustafa; Karaoğlu, Kaan; Serbest, Kerim; Menteşe, Emre; Yilmaz, Ismail

2016-02-01

A new ferrocenyl-substituted heterocyclic hydrazide ligand and its Cu(II) complex were prepared. The DFT calculations were performed to determine the electronic and molecular structures of the title compounds. The electronic spectra were calculated by using time-dependent DFT method, and the transitions were correlated with the molecular orbitals of the compounds. The bands assignments of IR spectra were achieved in the light of the theoretical vibrational spectral data and total energy distribution values calculated at DFT/B3LYP/6-311++G(d,p) level. The redox behaviors of the ferrocene derivatives were investigated by cyclic voltammetry. The compounds show reversible redox couple assignable to Fc+/Fc couple. The copper(II) complex behaves as an effective catalyst towards oxidation of 3,5-di-tert-butylcatechol to its corresponding quinone derivative in DMF saturated with O2. The reaction follows Michaelis-Menten enzymatic reaction kinetics with turnover numbers 2.32 × 103.

Ultrasensitive ROS-Responsive Coassemblies of Tellurium-Containing Molecules and Phospholipids.

PubMed

Wang, Lu; Fan, Fuqiang; Cao, Wei; Xu, Huaping

2015-07-29

Reactive oxygen species (ROS) play crucial roles in cell signaling and redox homeostasis and are strongly related to metabolic activities. The increase of the ROS concentration in organisms can result in several diseases, such as cardiovascular diseases and cancer. The concentration of ROS in biologically relevant conditions is typically as low as around tens of micromolars to 100 μM H2O2, which makes it necessary to develop ultrasensitive ROS-responsive systems. A general approach is reported here to fabricate an ultrasensitive ROS-responsive system via coassembly between tellurium-containing molecules and phospholipids, combining the ROS-responsiveness of tellurium and the biocompatibility of phospholipids. By using dynamic light scattering, transmission electron microscopy, scanning electron microscopy, and NMR spectra, coassembly behaviors and the responsiveness of the coassemblies have been investigated. These coassemblies can respond to 100 μM H2O2, which is a biologically relevant ROS concentration, and demonstrate reversible redox properties.

Design and Evaluation of a Boron Dipyrrin Electrophore for Redox Flow Batteries.

PubMed

Heiland, Niklas; Cidarér, Clemens; Rohr, Camilla; Piescheck, Mathias; Ahrens, Johannes; Bröring, Martin; Schröder, Uwe

2017-08-29

A boron dipyrrin (BODIPY) dye was designed as a molecular single-component electrophore for redox flow batteries. All positions of the BODIPY core were assessed on the basis of literature data, in particular cyclic voltammetry and density functional calculations, and a minimum required substitution pattern was designed to provide solubility, aggregation, radical cation and anion stabilities, a large potential window, and synthetic accessibility. In-depth electrochemical and physical studies of this electrophore revealed suitable cathodic behavior and stability of the radical anion but rapid anodic decomposition of the radical cation. The three products that formed under the conditions of controlled oxidative electrolysis were isolated, and their structures were determined by spectroscopy and comparison with a synthetic model compound. From these structures, a benzylic radical reactivity, initiated by one-electron oxidation, was concluded to play the major role in this unexpected decomposition. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Inflammatory and redox reactions in colorectal carcinogenesis.

PubMed

Guina, Tina; Biasi, Fiorella; Calfapietra, Simone; Nano, Mario; Poli, Giuseppe

2015-03-01

It has been established that there is a relationship between chronic inflammation and cancer development. The constant colonic inflammation typical of inflammatory bowel diseases is now considered a risk factor for colorectal carcinoma (CRC) development. The inflammatory network of signaling molecules is also required during the late phases of carcinogenesis, to enable cancer cells to survive and to metastasize. Oxidative reactions are an integral part of the inflammatory response, and are generally associated with CRC development. However, when the malignant phenotype is acquired, increased oxidative status induces antioxidant defenses in cancer cells, favoring their aggressiveness. This contradictory behavior of cancer cells toward redox status is of great significance for potential anticancer therapies. This paper summarizes the essential background information relating to the molecules involved in regulating oxidative stress and inflammation during carcinogenesis. Understanding more of their function in CRC stages might provide the foundation for future developments in CRC treatment. © 2015 New York Academy of Sciences.

Geomicrobiological redox cycling of the transuranic element neptunium.

PubMed

Law, Gareth T W; Geissler, Andrea; Lloyd, Jonathan R; Livens, Francis R; Boothman, Christopher; Begg, James D C; Denecke, Melissa A; Rothe, Jörg; Dardenne, Kathy; Burke, Ian T; Charnock, John M; Morris, Katherine

2010-12-01

Microbial processes can affect the environmental behavior of redox sensitive radionuclides, and understanding these reactions is essential for the safe management of radioactive wastes. Neptunium, an alpha-emitting transuranic element, is of particular importance because of its long half-life, high radiotoxicity, and relatively high solubility as Np(V)O(2)(+) under oxic conditions. Here, we describe experiments to explore the biogeochemistry of Np where Np(V) was added to oxic sediment microcosms with indigenous microorganisms and anaerobically incubated. Enhanced Np removal to sediments occurred during microbially mediated metal reduction, and X-ray absorption spectroscopy showed this was due to reduction to poorly soluble Np(IV) on solids. In subsequent reoxidation experiments, sediment-associated Np(IV) was somewhat resistant to oxidative remobilization. These results demonstrate the influence of microbial processes on Np solubility and highlight the critical importance of radionuclide biogeochemistry in nuclear legacy management.

The Redox Code.

PubMed

Jones, Dean P; Sies, Helmut

2015-09-20

The redox code is a set of principles that defines the positioning of the nicotinamide adenine dinucleotide (NAD, NADP) and thiol/disulfide and other redox systems as well as the thiol redox proteome in space and time in biological systems. The code is richly elaborated in an oxygen-dependent life, where activation/deactivation cycles involving O₂ and H₂O₂ contribute to spatiotemporal organization for differentiation, development, and adaptation to the environment. Disruption of this organizational structure during oxidative stress represents a fundamental mechanism in system failure and disease. Methodology in assessing components of the redox code under physiological conditions has progressed, permitting insight into spatiotemporal organization and allowing for identification of redox partners in redox proteomics and redox metabolomics. Complexity of redox networks and redox regulation is being revealed step by step, yet much still needs to be learned. Detailed knowledge of the molecular patterns generated from the principles of the redox code under defined physiological or pathological conditions in cells and organs will contribute to understanding the redox component in health and disease. Ultimately, there will be a scientific basis to a modern redox medicine.

Direct structural evidence of protein redox regulation obtained by in-cell NMR.

PubMed

Mercatelli, Eleonora; Barbieri, Letizia; Luchinat, Enrico; Banci, Lucia

2016-02-01

The redox properties of cellular environments are critical to many functional processes, and are strictly controlled in all living organisms. The glutathione-glutathione disulfide (GSH-GSSG) couple is the most abundant intracellular redox couple. A GSH redox potential can be calculated for each cellular compartment, which reflects the redox properties of that environment. This redox potential is often used to predict the redox state of a disulfide-containing protein, based on thermodynamic considerations. However, thiol-disulfide exchange reactions are often catalyzed by specific partners, and the distribution of the redox states of a protein may not correspond to the thermodynamic equilibrium with the GSH pool. Ideally, the protein redox state should be measured directly, bypassing the need to extrapolate from the GSH. Here, by in-cell NMR, we directly observe the redox state of three human proteins, Cox17, Mia40 and SOD1, in the cytoplasm of human and bacterial cells. We compare the observed distributions of redox states with those predicted by the GSH redox potential, and our results partially agree with the predictions. Discrepancies likely arise from the fact that the redox state of SOD1 is controlled by a specific partner, its copper chaperone (CCS), in a pathway which is not linked to the GSH redox potential. In principle, in-cell NMR allows determining whether redox proteins are at the equilibrium with GSH, or they are kinetically regulated. Such approach does not need assumptions on the redox potential of the environment, and provides a way to characterize each redox-regulating pathway separately. Copyright © 2015 Elsevier B.V. All rights reserved.

Organic Redox Species in Aqueous Flow Batteries: Redox Potentials, Chemical Stability and Solubility

PubMed Central

Wedege, Kristina; Dražević, Emil; Konya, Denes; Bentien, Anders

2016-01-01

Organic molecules are currently investigated as redox species for aqueous low-cost redox flow batteries (RFBs). The envisioned features of using organic redox species are low cost and increased flexibility with respect to tailoring redox potential and solubility from molecular engineering of side groups on the organic redox-active species. In this paper 33, mainly quinone-based, compounds are studied experimentially in terms of pH dependent redox potential, solubility and stability, combined with single cell battery RFB tests on selected redox pairs. Data shows that both the solubility and redox potential are determined by the position of the side groups and only to a small extent by the number of side groups. Additionally, the chemical stability and possible degradation mechanisms leading to capacity loss over time are discussed. The main challenge for the development of all-organic RFBs is to identify a redox pair for the positive side with sufficiently high stability and redox potential that enables battery cell potentials above 1 V. PMID:27966605

Organic Redox Species in Aqueous Flow Batteries: Redox Potentials, Chemical Stability and Solubility

NASA Astrophysics Data System (ADS)

Wedege, Kristina; Dražević, Emil; Konya, Denes; Bentien, Anders

2016-12-01

Organic molecules are currently investigated as redox species for aqueous low-cost redox flow batteries (RFBs). The envisioned features of using organic redox species are low cost and increased flexibility with respect to tailoring redox potential and solubility from molecular engineering of side groups on the organic redox-active species. In this paper 33, mainly quinone-based, compounds are studied experimentially in terms of pH dependent redox potential, solubility and stability, combined with single cell battery RFB tests on selected redox pairs. Data shows that both the solubility and redox potential are determined by the position of the side groups and only to a small extent by the number of side groups. Additionally, the chemical stability and possible degradation mechanisms leading to capacity loss over time are discussed. The main challenge for the development of all-organic RFBs is to identify a redox pair for the positive side with sufficiently high stability and redox potential that enables battery cell potentials above 1 V.

Organic Redox Species in Aqueous Flow Batteries: Redox Potentials, Chemical Stability and Solubility.

PubMed

Wedege, Kristina; Dražević, Emil; Konya, Denes; Bentien, Anders

2016-12-14

Organic molecules are currently investigated as redox species for aqueous low-cost redox flow batteries (RFBs). The envisioned features of using organic redox species are low cost and increased flexibility with respect to tailoring redox potential and solubility from molecular engineering of side groups on the organic redox-active species. In this paper 33, mainly quinone-based, compounds are studied experimentially in terms of pH dependent redox potential, solubility and stability, combined with single cell battery RFB tests on selected redox pairs. Data shows that both the solubility and redox potential are determined by the position of the side groups and only to a small extent by the number of side groups. Additionally, the chemical stability and possible degradation mechanisms leading to capacity loss over time are discussed. The main challenge for the development of all-organic RFBs is to identify a redox pair for the positive side with sufficiently high stability and redox potential that enables battery cell potentials above 1 V.

Extended dynamic model for ion diffusion in all-vanadium redox flow battery including the effects of temperature and bulk electrolyte transfer

NASA Astrophysics Data System (ADS)

Badrinarayanan, Rajagopalan; Zhao, Jiyun; Tseng, K. J.; Skyllas-Kazacos, Maria

2014-12-01

As with all redox flow batteries, the Vanadium Redox flow Battery (VRB) can suffer from capacity loss as the vanadium ions diffuse at different rates leading to a build-up on one half-cell and dilution on the other. In this paper an extended dynamic model of the vanadium ion transfer is developed including the effect of temperature and bulk electrolyte transfer. The model is used to simulate capacity decay for a range of different ion exchange membranes that are being used in the VRB. The simulations show that Selemion CMV and Nafion 115 membranes have similar behavior where the impact of temperature on capacity loss is highest within the first 100 cycles. The results for Selemion AMV membrane however are seen to be very different where the capacity loss at different temperatures observed to increase linearly with increasing charging/discharging cycles. The model is made more comprehensive by including the effect of bulk electrolyte transfer. A volume change of 19% is observed in each half-cell for Nafion 115 membrane based on the simulation parameters. The effect of this change in volume directly affects concentration, and the characteristics are analyzed for each vanadium species as well as the overall concentration in the half-cells.

Reduction Dynamics of Doped Ceria, Nickel Oxide, and Cermet Composites Probed Using In Situ Raman Spectroscopy

PubMed Central

Shearing, Paul R.; Brightman, Edward; Brett, Dan J. L.; Brandon, Nigel P.; Cohen, Lesley F.

2016-01-01

The redox properties of gadolinium doped ceria (CGO) and nickel oxide (NiO) composite cermets underpin the operation of solid oxide electrochemical cells. Although these systems have been widely studied, a full comprehension of the reaction dynamics at the interface of these materials is lacking. Here, in situ Raman spectroscopic monitoring of the redox cycle is used to investigate the interplay between the dynamic and competing processes of hydrogen spillover and water dissociation on the doped ceria surface. In order to elucidate these mechanisms, the redox process in pure CGO and NiO is studied when exposed to wet and dry hydrogen and is compared to the cermet behavior. In dry hydrogen, CGO reduces relatively rapidly via a series of intermediate phases, while NiO reduces via a single‐step process. In wet reducing atmospheres, however, the oxidation state of pure CGO is initially stabilized due to the dissociation of water by reduced Ce(III) and subsequent incorporation of oxygen into the structure. In the reduction process involving the composite cermet, the close proximity of the NiO improves the efficiency and speed of the composite reduction process. Although NiO is already incorporated into working cells, these observations suggest direct routes to further improve cell performance. PMID:27595058

Reduction Dynamics of Doped Ceria, Nickel Oxide, and Cermet Composites Probed Using In Situ Raman Spectroscopy.

PubMed

Maher, Robert C; Shearing, Paul R; Brightman, Edward; Brett, Dan J L; Brandon, Nigel P; Cohen, Lesley F

2016-01-01

The redox properties of gadolinium doped ceria (CGO) and nickel oxide (NiO) composite cermets underpin the operation of solid oxide electrochemical cells. Although these systems have been widely studied, a full comprehension of the reaction dynamics at the interface of these materials is lacking. Here, in situ Raman spectroscopic monitoring of the redox cycle is used to investigate the interplay between the dynamic and competing processes of hydrogen spillover and water dissociation on the doped ceria surface. In order to elucidate these mechanisms, the redox process in pure CGO and NiO is studied when exposed to wet and dry hydrogen and is compared to the cermet behavior. In dry hydrogen, CGO reduces relatively rapidly via a series of intermediate phases, while NiO reduces via a single-step process. In wet reducing atmospheres, however, the oxidation state of pure CGO is initially stabilized due to the dissociation of water by reduced Ce(III) and subsequent incorporation of oxygen into the structure. In the reduction process involving the composite cermet, the close proximity of the NiO improves the efficiency and speed of the composite reduction process. Although NiO is already incorporated into working cells, these observations suggest direct routes to further improve cell performance.

Circadian clock proteins regulate neuronal redox homeostasis and neurodegeneration

PubMed Central

Musiek, Erik S.; Lim, Miranda M.; Yang, Guangrui; Bauer, Adam Q.; Qi, Laura; Lee, Yool; Roh, Jee Hoon; Ortiz-Gonzalez, Xilma; Dearborn, Joshua T.; Culver, Joseph P.; Herzog, Erik D.; Hogenesch, John B.; Wozniak, David F.; Dikranian, Krikor; Giasson, Benoit I.; Weaver, David R.; Holtzman, David M.; FitzGerald, Garret A.

2013-01-01

Brain aging is associated with diminished circadian clock output and decreased expression of the core clock proteins, which regulate many aspects of cellular biochemistry and metabolism. The genes encoding clock proteins are expressed throughout the brain, though it is unknown whether these proteins modulate brain homeostasis. We observed that deletion of circadian clock transcriptional activators aryl hydrocarbon receptor nuclear translocator–like (Bmal1) alone, or circadian locomotor output cycles kaput (Clock) in combination with neuronal PAS domain protein 2 (Npas2), induced severe age-dependent astrogliosis in the cortex and hippocampus. Mice lacking the clock gene repressors period circadian clock 1 (Per1) and period circadian clock 2 (Per2) had no observed astrogliosis. Bmal1 deletion caused the degeneration of synaptic terminals and impaired cortical functional connectivity, as well as neuronal oxidative damage and impaired expression of several redox defense genes. Targeted deletion of Bmal1 in neurons and glia caused similar neuropathology, despite the retention of intact circadian behavioral and sleep-wake rhythms. Reduction of Bmal1 expression promoted neuronal death in primary cultures and in mice treated with a chemical inducer of oxidative injury and striatal neurodegeneration. Our findings indicate that BMAL1 in a complex with CLOCK or NPAS2 regulates cerebral redox homeostasis and connects impaired clock gene function to neurodegeneration. PMID:24270424

Facile electrocatalytic redox of hemoglobin by flower-like gold nanoparticles on boron-doped diamond surface.

PubMed

Li, Mingfang; Zhao, Guohua; Geng, Rong; Hu, Huikang

2008-11-01

The flower-like gold nanoparticles together with spherical and convex polyhedron gold nanoparticles were fabricated on boron-doped diamond (BDD) surface by one-step and simple electrochemical method through easily controlling the applied potential and the concentration of HAuCl(4). The recorded X-ray diffraction (XRD) patterns confirmed that these three shapes of gold nanoparticles were dominated by different crystal facets. The cyclic voltammetric results indicated that the morphology of gold nanoparticles plays big role in their electrochemical behaviors. The direct electrochemistry of hemoglobin (Hb) was realized on all the three different shapes of nanogold-attached BDD surface without the aid of any electron mediator. In pH 4.5 acetate buffer solutions (ABS), Hb showed a pair of well defined and quasi-reversible redox peaks. However, the results obtained demonstrated that the redox peak potential, the average surface concentration of electroactive heme, and the electron transfer rates of Hb are greatly dependent upon the surface morphology of gold nanoparticles. The electron transfer rate constant of hemoglobin over flower-like nanogold/BDD electrode was more than two times higher than that over spherical and convex polyhedron nanogold. The observed differences may be ascribed to the difference in gold particle characteristics including surface roughness, exposed surface area, and crystal structure.

An iron-iron hydrogenase mimic with appended electron reservoir for efficient proton reduction in aqueous media

PubMed Central

Becker, René; Amirjalayer, Saeed; Li, Ping; Woutersen, Sander; Reek, Joost N. H.

2016-01-01

The transition from a fossil-based economy to a hydrogen-based economy requires cheap and abundant, yet stable and efficient, hydrogen production catalysts. Nature shows the potential of iron-based catalysts such as the iron-iron hydrogenase (H2ase) enzyme, which catalyzes hydrogen evolution at rates similar to platinum with low overpotential. However, existing synthetic H2ase mimics generally suffer from low efficiency and oxygen sensitivity and generally operate in organic solvents. We report on a synthetic H2ase mimic that contains a redox-active phosphole ligand as an electron reservoir, a feature that is also crucial for the working of the natural enzyme. Using a combination of (spectro)electrochemistry and time-resolved infrared spectroscopy, we elucidate the unique redox behavior of the catalyst. We find that the electron reservoir actively partakes in the reduction of protons and that its electron-rich redox states are stabilized through ligand protonation. In dilute sulfuric acid, the catalyst has a turnover frequency of 7.0 × 104 s−1 at an overpotential of 0.66 V. This catalyst is tolerant to the presence of oxygen, thereby paving the way for a new generation of synthetic H2ase mimics that combine the benefits of the enzyme with synthetic versatility and improved stability. PMID:26844297

Mössbauer spectroscopic studies on the iron forms of deep-sea sediments

NASA Astrophysics Data System (ADS)

Drodt, M.; Trautwein, A. X.; König, I.; Suess, E.; Koch, C. Bender

Mössbauer spectroscopy was applied to characterize the valence states Fe(II) and Fe(III) in sedimentary minerals from a core of the Peru Basin. The procedure in unraveling this information includes temperature-dependent measurements from 275 K to very low temperature (300 mK) in zero-field and also at 4.2 K in an applied field (up to 6.2 T) and by mathematical procedures (least-squares fits and spectral simulations) in order to resolve individual spectral components. The depth distribution of the amount of Fe(II) is about 11% of the total Fe to a depth of 19 cm with a subsequent steep increase (within 3 cm) to about 37%, after which it remains constant to the lower end of the sediment core (at about 40 cm). The steep increase of the amount of Fe(II) defines a redox boundary which coincides with the position where the tan/green color transition of the sediment occurs. The isomer shifts and quadrupole splittings of Fe(II) and Fe(III) in the sediment are consistent with hexacoordination by oxygen or hydroxide ligands as in oxide and silicate minerals. Goethite and traces of hematite are observed only above the redox boundary, with a linear gradient extending from about 20% of the total Fe close to the sediment surface to about zero at the redox boundary. The superparamagnetic relaxation behavior allows to estimate the order of magnitude for the size of the largest goethite and hematite particles within the particle-site distribution, e.g. 170 Å and 50 Å, respectively. The composition of the sediment spectra recorded at 300 mK in zero-field, apart from the contributions due to goethite and hematite, resembles that of the sheet silicates smectite, illite and chlorite, which have been identified as major constituents of the sediment in the <2 μm fraction by X-ray diffraction. The specific ``ferromagnetic'' type of magnetic ordering in the sediment, as detected at 4.2 K in an applied field, also resembles that observed in sheet silicates and indicates that both Fe(II) and Fe(III) are involved in magnetic ordering. This ``ferromagnetic'' behavior is probably due to the double-exchange mechanism known from other mixed-valence Fe(II)-Fe(III) systems. A significant part of the clay-mineral iron is redox sensitive. It is proposed that the color change of the sediment at the redox boundary from tan to green is related to the increase of Fe(II)-Fe(III) pairs in the layer silicates, because of the intervalence electron transfer bands which are caused by such pairs.

Fostering Academic Creativity in Gifted Students. ERIC Digest #E484.

ERIC Educational Resources Information Center

Torrance, E. Paul; Goff, Kathy

This digest describes academic creativity and offers suggestions for its development in gifted students. Creative learning and learning by authority are contrasted and examples of each are given. The naturally creative behavior of young children is noted. Among suggestions offered to teachers are: respect the unusual questions of children; show…

Taking Charge: A Handbook for Parents Whose Children Have Emotional Handicaps.

ERIC Educational Resources Information Center

Kelker, Katharin A.

The manual is designed to provide information and support to parents of emotionally disturbed children. The first chapter, "Feelings Come First," deals with such topics as identifying unusual behavior, impact on parents and other family members, coming to terms with feelings, and advice from other parents. Chapter 2, "Finding Some Help," defines…

Multidisciplinary Developmental Evaluation Improves Early Diagnosis of Infantile Autism.

ERIC Educational Resources Information Center

Siegel, B.; And Others

A life-course perspective of the diagnostic histories of 75 autistic individuals (ages 4-25) was obtained through the use of parent surveys and a review of their charts. The study was made to understand better how children who presented with uneven or unusual behavioral development are identified as developmentally multihandicapped. Areas examined…

The Effect of Microgravity on the Growth of Silica Nanostructures

NASA Technical Reports Server (NTRS)

Smith, D. D.; Sibille, L.; Cronise, R.; Oldenburg, S. J.; Wolfe, D.; Halas, N. J.

2001-01-01

The process of the formation of structures from coagulating ensembles is fundamentally important since the collective behavior of the constituents often results in dramatically improved or unusual mechanical, thermal, chemical, and optical properties. In this study we examine the effect of microgravity on the formation of silica structures, specifically particles and gels.

Unusual behavior of quiet-time zonal and vertical plasma drift velocities over Jicamarca during the recent extended solar minimum of 2008

NASA Astrophysics Data System (ADS)

Santos, Ângela M.; Abdu, Mangalathayil A.; Souza, Jonas R.; Batista, Inez S.; Sobral, José H. A.

2017-11-01

The influence of the recent deep and prolonged solar minimum on the daytime zonal and vertical plasma drift velocities during quiet time is investigated in this work. Analyzing the data obtained from incoherent scatter radar from Jicamarca (11.95° S, 76.87° W) we observe an anomalous behavior of the zonal plasma drift during June 2008 characterized by lower than usual daytime westward drift and its early afternoon reversal to eastward. As a case study the zonal drift observed on 24 June 2008 is modeled using a realistic low-latitude ionosphere simulated by the Sheffield University Plasmasphere-Ionosphere Model-INPE (SUPIM-INPE). The results show that an anomalously low zonal wind was mainly responsible for the observed anomalous behavior in the zonal drift. A comparative study of the vertical plasma drifts obtained from magnetometer data for some periods of maximum (2000-2002) and minimum solar activity (1998, 2008, 2010) phases reveal a considerable decrease on the E-region conductivity and the dynamo electric field during 2008. However, we believe that the contribution of these characteristics to the unusual behavior of the zonal plasma drift is significantly smaller than that arising from the anomalously low zonal wind. The SUPIM-INPE result of the critical frequency of the F layer (foF2) over Jicamarca suggested a lower radiation flux than that predicted by solar irradiance model (SOLAR2000) for June 2008.

Redox chemistry and natural organic matter (NOM): Geochemists' dream, analytical chemists' nightmare

USGS Publications Warehouse

Macalady, Donald L.; Walton-Day, Katherine

2011-01-01

Natural organic matter (NOM) is an inherently complex mixture of polyfunctional organic molecules. Because of their universality and chemical reversibility, oxidation/reductions (redox) reactions of NOM have an especially interesting and important role in geochemistry. Variabilities in NOM composition and chemistry make studies of its redox chemistry particularly challenging, and details of NOM-mediated redox reactions are only partially understood. This is in large part due to the analytical difficulties associated with NOM characterization and the wide range of reagents and experimental systems used to study NOM redox reactions. This chapter provides a summary of the ongoing efforts to provide a coherent comprehension of aqueous redox chemistry involving NOM and of techniques for chemical characterization of NOM. It also describes some attempts to confirm the roles of different structural moieties in redox reactions. In addition, we discuss some of the operational parameters used to describe NOM redox capacities and redox states, and describe nomenclature of NOM redox chemistry. Several relatively facile experimental methods applicable to predictions of the NOM redox activity and redox states of NOM samples are discussed, with special attention to the proposed use of fluorescence spectroscopy to predict relevant redox characteristics of NOM samples.

Redox-Directed Cancer Therapeutics: Molecular Mechanisms and Opportunities

PubMed Central

2009-01-01

Abstract Redox dysregulation originating from metabolic alterations and dependence on mitogenic and survival signaling through reactive oxygen species represents a specific vulnerability of malignant cells that can be selectively targeted by redox chemotherapeutics. This review will present an update on drug discovery, target identification, and mechanisms of action of experimental redox chemotherapeutics with a focus on pro- and antioxidant redox modulators now in advanced phases of preclinal and clinical development. Recent research indicates that numerous oncogenes and tumor suppressor genes exert their functions in part through redox mechanisms amenable to pharmacological intervention by redox chemotherapeutics. The pleiotropic action of many redox chemotherapeutics that involves simultaneous modulation of multiple redox sensitive targets can overcome cancer cell drug resistance originating from redundancy of oncogenic signaling and rapid mutation. Moreover, some redox chemotherapeutics may function according to the concept of synthetic lethality (i.e., drug cytotoxicity is confined to cancer cells that display loss of function mutations in tumor suppressor genes or upregulation of oncogene expression). The impressive number of ongoing clinical trials that examine therapeutic performance of novel redox drugs in cancer patients demonstrates that redox chemotherapy has made the crucial transition from bench to bedside. Antioxid. Redox Signal. 11, 3013–3069. PMID:19496700

AN UNUSUAL PATTERN OF GENE FLOW BETWEEN THE TWO SOCIAL FORMS OF THE FIRE ANT SOLENOPSIS INVICTA.

PubMed

Ross, Kenneth G; Shoemaker, D DeWayne

1993-10-01

Uncertainty over the role of shifts in social behavior in the process of speciation in social insects has stimulated interest in determining the extent of gene flow between conspecific populations differing in colony social organization. Allele and genotype frequencies at 12 neutral polymorphic protein markers, as well as the numbers of alleles at the sex-determining locus (loci), are shown here to be consistent with significant ongoing gene flow between two geographically adjacent populations of Solenopsis invicta that differ in colony queen number. Data from a thirteenth protein marker that is under strong differential selection in the two social forms confirm that such gene flow occurs. Data from this selected locus, combined with knowledge of the reproductive biology of the two social forms, further suggest that interform gene flow is largely unidirectional and mediated through males only. This unusual pattern of gene flow results from the influence of the unique social enviroments of the two forms on the behavior of workers and on the reproductive physiology of sexuals. © 1993 The Society for the Study of Evolution.

Diblock copolymers of polystyrene- b-poly(1,3-cyclohexadiene) exhibiting unique three-phase microdomain morphologies

DOE PAGES

Misichronis, Konstantinos; Chen, Jihua; Kahk, Jong K.; ...

2016-03-29

Here, the synthesis and molecular characterization of a series of conformationally asymmetric polystyrene-block-poly(1,3-cyclohexadiene) (PS- b-PCHD) diblock copolymers (PCHD: ~90% 1,4 and ~10% 1,2), by sequential anionic copolymerization high vacuum techniques, is reported. A wide range of volume fractions (0.27 ≤ Φ PS ≤ 0.91) was studied by transmission electron microscopy and small-angle X-ray scattering in order to explore in detail the microphase separation behavior of these flexible/semiflexible diblock copolymers. Unusual morphologies, consisting of PCHD core(PCHD-1,4)–shell(PCHD-1,2) cylinders in PS matrix and three-phase (PS, PCHD-1,4, PCHD-1,2) four-layer lamellae, were observed suggesting that the chain stiffness of the PCHD block and the strongmore » dependence of the interaction parameter χ on the PCHD microstructures are important factors for the formation of this unusual microphase separation behavior in PS- b-PCHD diblock copolymers. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 1564–1572« less

Materials Genomics Screens for Adaptive Ion Transport Behavior by Redox-Switchable Microporous Polymer Membranes in Lithium-Sulfur Batteries.

PubMed

Ward, Ashleigh L; Doris, Sean E; Li, Longjun; Hughes, Mark A; Qu, Xiaohui; Persson, Kristin A; Helms, Brett A

2017-05-24

Selective ion transport across membranes is critical to the performance of many electrochemical energy storage devices. While design strategies enabling ion-selective transport are well-established, enhancements in membrane selectivity are made at the expense of ionic conductivity. To design membranes with both high selectivity and high ionic conductivity, there are cues to follow from biological systems, where regulated transport of ions across membranes is achieved by transmembrane proteins. The transport functions of these proteins are sensitive to their environment: physical or chemical perturbations to that environment are met with an adaptive response. Here we advance an analogous strategy for achieving adaptive ion transport in microporous polymer membranes. Along the polymer backbone are placed redox-active switches that are activated in situ, at a prescribed electrochemical potential, by the device's active materials when they enter the membrane's pore. This transformation has little influence on the membrane's ionic conductivity; however, the active-material blocking ability of the membrane is enhanced. We show that when used in lithium-sulfur batteries, these membranes offer markedly improved capacity, efficiency, and cycle-life by sequestering polysulfides in the cathode. The origins and implications of this behavior are explored in detail and point to new opportunities for responsive membranes in battery technology development.

Characterizing redox conditions and monitoring attenuation of selected pharmaceuticals during artificial recharge through a reactive layer.

PubMed

Valhondo, Cristina; Carrera, Jesús; Ayora, Carlos; Tubau, Isabel; Martinez-Landa, Lurdes; Nödler, Karsten; Licha, Tobias

2015-04-15

A permeable reactive layer was installed at the floor of an infiltration basin. The reactive layer comprised 1) vegetable compost to provide a sorption surface for neutral organic compounds and to release easily degradable organic matter, thus generating a sequence of redox states, and 2) minor amounts of clay and iron oxide to increase sorption of cationic and anionic species, respectively. Field application of this design was successful in generating denitrification, and manganese-, and iron-reducing conditions beneath the basin. This, together with the increase in types of sorption sites, may explain the improved removal of three of the four selected pharmaceuticals compared with their behavior prior to installation of the layer. After installation of the reactive layer, atenolol concentrations were below the detection limits in the vadose zone. Moreover, concentrations of gemfibrozil and cetirizine were reduced to 20% and 40% of their initial concentrations, respectively, after 200 h of residence time. In contrast, prior to installation of the reactive layer, the concentrations of these three pharmaceuticals in both the vadose zone and the aquifer were more than 60% of the initial concentration. Carbamazepine exhibited recalcitrant behavior both prior to and after the reactive barrier installation. Copyright © 2015 Elsevier B.V. All rights reserved.

Materials Genomics Screens for Adaptive Ion Transport Behavior by Redox-Switchable Microporous Polymer Membranes in Lithium–Sulfur Batteries

PubMed Central

2017-01-01

Selective ion transport across membranes is critical to the performance of many electrochemical energy storage devices. While design strategies enabling ion-selective transport are well-established, enhancements in membrane selectivity are made at the expense of ionic conductivity. To design membranes with both high selectivity and high ionic conductivity, there are cues to follow from biological systems, where regulated transport of ions across membranes is achieved by transmembrane proteins. The transport functions of these proteins are sensitive to their environment: physical or chemical perturbations to that environment are met with an adaptive response. Here we advance an analogous strategy for achieving adaptive ion transport in microporous polymer membranes. Along the polymer backbone are placed redox-active switches that are activated in situ, at a prescribed electrochemical potential, by the device’s active materials when they enter the membrane’s pore. This transformation has little influence on the membrane’s ionic conductivity; however, the active-material blocking ability of the membrane is enhanced. We show that when used in lithium–sulfur batteries, these membranes offer markedly improved capacity, efficiency, and cycle-life by sequestering polysulfides in the cathode. The origins and implications of this behavior are explored in detail and point to new opportunities for responsive membranes in battery technology development. PMID:28573201

Concurrent ionic migration and electronic effects at the memristive TiO x /La1/3Ca2/3MnO3-x interface

NASA Astrophysics Data System (ADS)

Román Acevedo, W.; Ferreyra, C.; Sánchez, M. J.; Acha, C.; Gay, R.; Rubi, D.

2018-03-01

The development of reliable redox-based resistive random-access memory devices requires understanding and disentangling concurrent effects present at memristive interfaces. We report on the fabrication and electrical characterization of TiO x /La1/3Ca2/3MnO3-x microstructured interfaces and on the modeling of their memristive behavior. We show that a careful tuning of the applied external electrical stimuli allows controlling the redox process between both layers, obtaining multilevel non-volatile resistance states. We simulate the oxygen vacancies dynamics at the interface between both oxides, and successfully reproduce the experimental electrical behavior after the inclusion of an electronic effect, related to the presence of an n-p diode at the interface. The formation of the diode is due to the n- and p-character of TiO x and La1/3Ca2/3MnO3-x , respectively. Our analysis indicates that oxygen vacancies migration between both layers is triggered after the diode is polarized either in forward mode or in reverse mode above breakdown. Electrical measurements at different temperatures suggest that the diode can be characterized as Zener-type. The advantages of our junctions for their implementation in RRAM devices are finally discussed.

Dissection of the Voltage Losses of an Acidic Quinone Redox Flow Battery

DOE PAGES

Chen, Qing; Gerhardt, Michael R.; Aziz, Michael J.

2017-03-28

We measure the polarization characteristics of a quinone-bromide redox flow battery with interdigitated flow fields, using electrochemical impedance spectroscopy and voltammetry of a full cell and of a half cell against a reference electrode. We find linear polarization behavior at 50% state of charge all the way to the short-circuit current density of 2.5 A/cm 2. We uniquely identify the polarization area-specific resistance (ASR) of each electrode, the membrane ASR to ionic current, and the electronic contact ASR. We use voltage probes to deduce the electronic current density through each sheet of carbon paper in the quinone-bearing electrode. By alsomore » interpreting the results using the Newman 1-D porous electrode model, we deduce the volumetric exchange current density of the porous electrode. We uniquely evaluate the power dissipation and identify a correspondence to the contributions to the electrode ASR from the faradaic, electronic, and ionic transport processes. We find that, within the electrode, more power is dissipated in the faradaic process than in the electronic and ionic conduction processes combined, despite the observed linear polarization behavior. We examine the sensitivity of the ASR to the values of the model parameters. The greatest performance improvement is anticipated from increasing the volumetric exchange current density.« less

Hydrothermal synthesis of mesoporous rod-like nanocrystalline vanadium oxide hydrate V{sub 3}O{sub 7}·H{sub 2}O from hydroquinone and V{sub 2}O{sub 5}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mjejri, I.; Etteyeb, N.; Sediri, F., E-mail: faouzi.sediri@ipeit.rnu.tn

2013-09-01

Graphical abstract: - Highlights: • Rod-like nanocrystalline V{sub 3}O{sub 7}·H{sub 2}O has heen synthesized hydrothermally. • Molar ratio is key factor for structure and morphology. • Electrochemical properties were also studied. • CV has revealed reversible redox behavior with charge–discharge cycling. - Abstract: Rod-like nanocrystalline V{sub 3}O{sub 7}·H{sub 2}O has been synthesized hydrothermally via a simple and elegant route. Techniques X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, thermal analysis (TG-DTA), X-ray photoelectron spectroscopy (XPS), UV–vis spectroscopy and nitrogen adsorption/desorption isotherms have been used to characterize the structure, morphology and composition of the materials.more » The as-prepared V{sub 3}O{sub 7}·H{sub 2}O nanorods are up to several of micrometers in length, about 130 nm in width and about 70 nm in thickness in average, respectively. Cyclic voltammetric characterization of thin films of V{sub 3}O{sub 7}·H{sub 2}O nanorods has revealed reversible redox behavior with charge–discharge cycling corresponding to the reversible lithium intercalation/deintercalation.« less

Imaging Mitochondrial Redox Potential and Its Possible Link to Tumor Metastatic Potential

PubMed Central

Li, Lin Z.

2012-01-01

Cellular redox states can regulate cell metabolism, growth, differentiation, motility, apoptosis, signaling pathways, and gene expressions etc. Growing body of literature suggest importance of redox status for cancer progression. While most studies on redox state were done on cells and tissue lysates, it is important to understand the role of redox state in tissue in vivo/ex vivo and image its heterogeneity. Redox scanning is a clinically-translatable method for imaging tissue mitochondrial redox potential with a submillimeter resolution. Redox scanning data in mouse models of human cancers demonstrate a correlation between mitochondrial redox state and tumor metastatic potential. I will discuss the significance of this correlation and possible directions for future research. PMID:22895837

Translational animal models of autism and neurodevelopmental disorders

PubMed Central

Crawley, Jacqueline N.

2012-01-01

Autism is a neurodevelopmental disorder whose diagnosis is based on three behavioral criteria: unusual reciprocal social interactions, deficits in communication, and stereotyped repetitive behaviors with restricted interests. A large number of de novo single gene mutations and chromosomal deletions are associated with autism spectrum disorders. Based on the strong genetic evidence, mice with targeted mutations in homologous genes have been generated as translational research tools. Mouse models of autism have revealed behavioral and biological outcomes of mutations in risk genes. The field is now poised to employ the most robust phenotypes in the most replicable mouse models for preclinical screening of novel therapeutics. PMID:23226954

Late Neandertals and the intentional removal of feathers as evidenced from bird bone taphonomy at Fumane Cave 44 ky B.P., Italy.

PubMed

Peresani, Marco; Fiore, Ivana; Gala, Monica; Romandini, Matteo; Tagliacozzo, Antonio

2011-03-08

A large and varied avifaunal bone assemblage from the final Mousterian levels of Grotta di Fumane, northern Italy, reveals unusual human modifications on species that are not clearly relatable to feeding or utilitarian uses (i.e., lammergeier, Eurasian black vulture, golden eagle, red-footed falcon, common wood pigeon, and Alpine chough). Cut, peeling, and scrape marks, as well as diagnostic fractures and a breakthrough, are observed exclusively on wings, indicating the intentional removal of large feathers by Neandertals. The species involved, the anatomical elements affected, and the unusual type and location of the human modifications indicate an activity linked to the symbolic sphere and the behavioral modernity of this European autochthonous population.

Anomalous glassy dynamics in simple models of dense biological tissue

NASA Astrophysics Data System (ADS)

Sussman, Daniel M.; Paoluzzi, M.; Marchetti, M. Cristina; Manning, M. Lisa

2018-02-01

In order to understand the mechanisms for glassy dynamics in biological tissues and shed light on those in non-biological materials, we study the low-temperature disordered phase of 2D vertex-like models. Recently it has been noted that vertex models have quite unusual behavior in the zero-temperature limit, with rigidity transitions that are controlled by residual stresses and therefore exhibit very different scaling and phenomenology compared to particulate systems. Here we investigate the finite-temperature phase of two-dimensional Voronoi and Vertex models, and show that they have highly unusual, sub-Arrhenius scaling of dynamics with temperature. We connect the anomalous glassy dynamics to features of the potential energy landscape associated with zero-temperature inherent states.

Unusually large Stokes shift for a near-infrared emitting DNA-stabilized silver nanocluster

NASA Astrophysics Data System (ADS)

Ammitzbøll Bogh, Sidsel; Carro-Temboury, Miguel R.; Cerretani, Cecilia; Swasey, Steven M.; Copp, Stacy M.; Gwinn, Elisabeth G.; Vosch, Tom

2018-04-01

In this paper we present a new near-IR emitting silver nanocluster (NIR-DNA-AgNC) with an unusually large Stokes shift between absorption and emission maximum (211 nm or 5600 cm-1). We studied the effect of viscosity and temperature on the steady state and time-resolved emission. The time-resolved results on NIR-DNA-AgNC show that the relaxation dynamics slow down significantly with increasing viscosity of the solvent. In high viscosity solution, the spectral relaxation stretches well into the nanosecond scale. As a result of this slow spectral relaxation in high viscosity solutions, a multi-exponential fluorescence decay time behavior is observed, in contrast to the more mono-exponential decay in low viscosity solution.

Rapid Speech Transmission Index predictions and auralizations of unusual instructional spaces at MIT's new Stata Center

NASA Astrophysics Data System (ADS)

Conant, David A.

2005-04-01

The Stata Center for Computer, Information and Intelligence Sciences, recently opened at the Massachusetts Institute of Technology, includes a variety of oddly-shaped seminar rooms in addition to lecture spaces of somewhat more conventional form. The architects design approach prohibited following conventional, well understood room-acoustical behavior yet MIT and the design team were keenly interested in ensuring that these spaces functioned exceptionally well, acoustically. CATT-Acoustic room modeling was employed to assess RASTI through multiple design iterations for all these spaces. Presented here are computational and descriptive results achieved for these rooms which are highly-regarded by faculty. They all sound peculiarly good, given their unusual form. In addition, binaural auralizations for selected spaces are provided.

Tuning of superconductivity by Ni substitution into noncentrosymmetric ThC o1 -xN ixC2

NASA Astrophysics Data System (ADS)

Grant, T. W.; Cigarroa, O. V.; Rosa, P. F. S.; Machado, A. J. S.; Fisk, Z.

2017-07-01

The recently discovered noncentrosymmetric superconductor ThCoC2 was observed to show unusual superconducting behavior with a critical temperature of Tc=2.65 K . Here we investigate the effect of nickel substitution on the superconducting state in ThC o1 -xN ixC2 . Magnetization, resistivity, and heat capacity measurements demonstrate Ni substitution has a dramatic effect with critical temperature increased up to Tc=12.1 K for x =0.4 Ni concentration, which is a rather high transition temperature for a noncentrosymmetric superconductor. In addition, the unusual superconducting characteristics observed in pure ThCoC2 appear to be suppressed or tuned with Ni substitution towards a more conventional fully gapped superconductor.

Imaging dynamic redox processes with genetically encoded probes.

PubMed

Ezeriņa, Daria; Morgan, Bruce; Dick, Tobias P

2014-08-01

Redox signalling plays an important role in many aspects of physiology, including that of the cardiovascular system. Perturbed redox regulation has been associated with numerous pathological conditions; nevertheless, the causal relationships between redox changes and pathology often remain unclear. Redox signalling involves the production of specific redox species at specific times in specific locations. However, until recently, the study of these processes has been impeded by a lack of appropriate tools and methodologies that afford the necessary redox species specificity and spatiotemporal resolution. Recently developed genetically encoded fluorescent redox probes now allow dynamic real-time measurements, of defined redox species, with subcellular compartment resolution, in intact living cells. Here we discuss the available genetically encoded redox probes in terms of their sensitivity and specificity and highlight where uncertainties or controversies currently exist. Furthermore, we outline major goals for future probe development and describe how progress in imaging methodologies will improve our ability to employ genetically encoded redox probes in a wide range of situations. This article is part of a special issue entitled "Redox Signalling in the Cardiovascular System." Copyright © 2014 Elsevier Ltd. All rights reserved.

Impact on the Fe redox cycling of organic ligands released by Synechococcus PCC 7002, under different iron fertilization scenarios. Modeling approach

NASA Astrophysics Data System (ADS)

Samperio-Ramos, Guillermo; González-Dávila, Melchor; Santana-Casiano, J. Magdalena

2018-06-01

The kinetics of Fe redox transformations are of crucial importance in determining the bioavailability of iron, due to inorganic Fe(II) and Fe weakly organic complexes being the most easily assimilated species by phytoplankton. The role played by the natural organic ligands excreted by the cyanobacteria Synecococcus PCC 7002 on the iron redox chemistry was studied at different stages of growth, considering changes in the organic exudation of the cyanobacteria, associated with growth under two different scenarios of iron availability. The oxidation/reduction processes of iron were studied at nanomolar levels and under different physicochemical conditions of pH (7.2- 8.2), temperature (5- 35 °C) and salinity (10- 37). The presence of natural organic exudates of Synechococcus affected the redox behavior of iron. A pH-dependent and photo-induced Fe(III) reduction process was detected in the presence of exudates produced under Fe-Low conditions. Photolytic reactions also modified the reactivity of those exudates with respect to Fe(II), increasing its lifetime in seawater. Without light mediated processes, organic ligands excreted under iron deficient conditions intensified the Fe(II) oxidation at pH < 7.5. The organic exudates released under High-Fe conditions retarded the Fe(II) oxidation rate, as a function of DOC produced. The changes in the apparent oxidation rate were fitted to polynomial functions for both of the Fe-scenarios considered. A kinetic modeling approach to describe the speciation and the contribution of individual Fe(II) species to the overall oxidation rate was applied, considering the experimental data and delimiting the equilibrium and redox constants between iron and the major ligands present in solution. Two organic type ligands for the exudates of Synechococcus PCC 7002, with different iron-chelation properties were included in the model. The Fe(II) speciation was radically affected when organic ligands were considered. The individual contributions to the overall Fe(II) oxidation rate demonstrated that these organic ligands played a key role in the oxidation process, although their contributions were dependent on the prescribed iron conditions. The study, therefore, suggests that the variability in the composition and nature of organic exudates released, due to iron availability conditions, might determine the redox behaviour of iron in seawater.

Dissecting Redox Biology Using Fluorescent Protein Sensors.

PubMed

Schwarzländer, Markus; Dick, Tobias P; Meyer, Andreas J; Morgan, Bruce

2016-05-01

Fluorescent protein sensors have revitalized the field of redox biology by revolutionizing the study of redox processes in living cells and organisms. Within one decade, a set of fundamental new insights has been gained, driven by the rapid technical development of in vivo redox sensing. Redox-sensitive yellow and green fluorescent protein variants (rxYFP and roGFPs) have been the central players. Although widely used as an established standard tool, important questions remain surrounding their meaningful use in vivo. We review the growing range of thiol redox sensor variants and their application in different cells, tissues, and organisms. We highlight five key findings where in vivo sensing has been instrumental in changing our understanding of redox biology, critically assess the interpretation of in vivo redox data, and discuss technical and biological limitations of current redox sensors and sensing approaches. We explore how novel sensor variants may further add to the current momentum toward a novel mechanistic and integrated understanding of redox biology in vivo. Antioxid. Redox Signal. 24, 680-712.

Hyperthermophile Protein Behavior: Partially-Structured Conformations of Pyrococcus furiosus Rubredoxin Monomers Generated through Forced Cold-Denaturation and Refolding

PubMed Central

Ahmed, Shubbir; Guptasarma, Purnananda

2014-01-01

Some years ago, we showed that thermo-chemically denatured, partially-unfolded forms of Pyrococcus furiosus triosephosphateisomerase (PfuTIM) display cold-denaturation upon cooling, and heat-renaturation upon reheating, in proportion with the extent of initial partial unfolding achieved. This was the first time that cold-denaturation was demonstrated for a hyperthermophile protein, following unlocking of surface salt bridges. Here, we describe the behavior of another hyperthermophile protein, the small, monomeric, 53 residues-long rubredoxin from Pyrococcus furiosus (PfRd), which is one of the most thermostable proteins known to man. Like PfuTIM, PfRd too displays cold-denaturation after initial thermo-chemical perturbation, however, with two differences: (i) PfRd requires considerably higher temperatures as well as higher concentrations of guanidium hydrochloride (Gdm.HCl) than PfuTIM; (ii) PfRd's cold-denaturation behavior during cooling after thermo-chemical perturbation is incompletely reversible, unlike PfuTIM's, which was clearly reversible (from each different conformation generated). Differential cold-denaturation treatments allow PfRd to access multiple partially-unfolded states, each of which is clearly highly kinetically-stable. We refer to these as ‘Trishanku’ unfolding intermediates (or TUIs). Fascinatingly, refolding of TUIs through removal of Gdm.HCl generates multiple partially-refolded, monomeric, kinetically-trapped, non-native ‘Trishanku’ refolding intermediates (or TRIs), which differ from each other and from native PfRd and TUIs, in structural content and susceptibility to proteolysis. We find that the occurrence of cold denaturation and observations of TUI and TRI states is contingent on the oxidation status of iron, with redox agents managing to modulate the molecule's behavior upon gaining access to PfRd's iron atom. Mass spectrometric examination provides no evidence of the formation of disulfide bonds, but other experiments suggest that the oxidation status of iron (and its extent of burial) together determine whether or not PfRd shows cold denaturation, and also whether redox agents are able to modulate its behavior. PMID:24603413

Lithium-ion batteries with intrinsic pulse overcharge protection

DOEpatents

Chen, Zonghai; Amine, Khalil

2013-02-05

The present invention relates in general to the field of lithium rechargeable batteries, and more particularly relates to the positive electrode design of lithium-ion batteries with improved high-rate pulse overcharge protection. Thus the present invention provides electrochemical devices containing a cathode comprising at least one primary positive material and at least one secondary positive material; an anode; and a non-aqueous electrolyte comprising a redox shuttle additive; wherein the redox potential of the redox shuttle additive is greater than the redox potential of the primary positive material; the redox potential of the redox shuttle additive is lower than the redox potential of the secondary positive material; and the redox shuttle additive is stable at least up to the redox potential of the secondary positive material.

Response of dorsomedial prefrontal cortex predicts altruistic behavior

PubMed Central

Waytz, Adam; Zaki, Jamil; Mitchell, Jason P.

2012-01-01

Human beings have an unusual proclivity for altruistic behavior, and recent commentators have suggested that these prosocial tendencies arise from our unique capacity to understand the minds of others (i.e., to mentalize). The current studies test this hypothesis by examining the relation between altruistic behavior and the reflexive engagement of a neural system reliably associated with mentalizing. Results indicated that activity in the dorsomedial prefrontal cortex (dorsal MPFC)—a region consistently involved in understanding others’ mental states—predicts both monetary donations to others and time spent helping others. These findings address long-standing questions about the proximate source of human altruism by suggesting that prosocial behavior results, in part, from our broader tendency for social-cognitive thought. PMID:22649243

Spectroelectrochemistry of EuCl 3 in Four Molten Salt Eutectics; 3 LiCl−NaCl, 3 LiCl−2 KCl, LiCl−RbCl, and 3 LiCl−2 CsCl; at 873 K

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schroll, Cynthia A.; Chatterjee, Sayandev; Levitskaia, Tatiana

Key electrochemical properties affecting pyroprocessing of nuclear fuel were examined in four eutectic melts using using Eu3+/2+ as a representative probe. We report the electrochemical and spectroelectrochemical behavior of EuCl3 in four molten salt eutectics (3 LiCl – NaCl, 3 LiCl – 2 KCl, LiCl – RbCl and 3 LiCl – 2 CsCl) at 873 K. Cyclic voltammetry was used to determine the redox potential for Eu3+/2+ and the applied potentials for spectroelectrochemistry. Single step chronoabsorptometry and thin-layer spectroelectrochemistry were used to obtain the number of electrons transferred, redox potentials and diffusion coefficients for Eu3+ in each eutectic melt. Themore » redox potentials determined by thin-layer spectroelectrochemistry were extremely close to those obtained using cyclic voltammetry. The redox potential for Eu3+/2+ was most positive in the 3 LiCl - NaCl melt, showed a negative shift in the 3 LiCl - 2 KCl melt, and was the most negative in the LiCl - RbCl and 3 LiCl - 2 CsCl eutectics. The diffusion coefficient for Eu3+ followed this same trend; it was the largest in the 3 LiCl - NaCl melt and the smallest in the LiCl - RbCl and 3 LiCl - 2 CsCl melts. The basic one-electron reversible electron transfer for Eu3+/2+ was not changed by melt composition.« less

Distribution of dissolved manganese in the Peruvian Upwelling and Oxygen Minimum Zone

NASA Astrophysics Data System (ADS)

Vedamati, Jagruti; Chan, Catherine; Moffett, James W.

2015-05-01

The geochemistry of manganese (Mn) in seawater is dominated by its redox chemistry, as Mn(II) is soluble and Mn(IV) forms insoluble oxides, and redox transformations are mediated by a variety of processes in the oceans. Dissolved Mn (DMn) accumulates under reducing conditions and is depleted under oxidizing conditions. Thus the Peruvian upwelling region, characterized by highly reducing conditions over a broad continental shelf and a major oxygen minimum zone extending far offshore, is potentially a large source of Mn to the eastern Tropical South Pacific. In this study, DMn was determined on cruises in October 2005 and February 2010 in the Peruvian Upwelling and Oxygen Minimum Zone, to evaluate the relationship between Mn, oxygen and nitrogen cycle processes. DMn concentrations were determined using simple dilution and matrix-matched external standardization inductively coupled mass spectrometry. Surprisingly, DMn was depleted under the most reducing conditions along the Peruvian shelf. Concentrations of dissolved Mn in surface waters increased offshore, indicating that advection of Mn offshore from the Peruvian shelf is a minor source. Subsurface Mn maxima were observed within the oxycline rather than within the oxygen minimum zone (OMZ), indicating they arise from remineralization of organic matter rather than reduction of Mn oxides. The distribution of DMn appears to be dominated by non-redox processes and inputs from the atmosphere and from other regions associated with specific water masses. Lower than expected DMn concentrations on the shelf probably reflect limited fluvial inputs from the continent and efficient offshore transport. This behavior is in stark contrast to Fe, reported in a companion study which is very high on the shelf and undergoes dynamic redox cycling.

An Inner Membrane Cytochrome Required Only for Reduction of High Redox Potential Extracellular Electron Acceptors

PubMed Central

Levar, Caleb E.; Chan, Chi Ho; Mehta-Kolte, Misha G.

2014-01-01

ABSTRACT Dissimilatory metal-reducing bacteria, such as Geobacter sulfurreducens, transfer electrons beyond their outer membranes to Fe(III) and Mn(IV) oxides, heavy metals, and electrodes in electrochemical devices. In the environment, metal acceptors exist in multiple chelated and insoluble forms that span a range of redox potentials and offer different amounts of available energy. Despite this, metal-reducing bacteria have not been shown to alter their electron transfer strategies to take advantage of these energy differences. Disruption of imcH, encoding an inner membrane c-type cytochrome, eliminated the ability of G. sulfurreducens to reduce Fe(III) citrate, Fe(III)-EDTA, and insoluble Mn(IV) oxides, electron acceptors with potentials greater than 0.1 V versus the standard hydrogen electrode (SHE), but the imcH mutant retained the ability to reduce Fe(III) oxides with potentials of ≤−0.1 V versus SHE. The imcH mutant failed to grow on electrodes poised at +0.24 V versus SHE, but switching electrodes to −0.1 V versus SHE triggered exponential growth. At potentials of ≤−0.1 V versus SHE, both the wild type and the imcH mutant doubled 60% slower than at higher potentials. Electrodes poised even 100 mV higher (0.0 V versus SHE) could not trigger imcH mutant growth. These results demonstrate that G. sulfurreducens possesses multiple respiratory pathways, that some of these pathways are in operation only after exposure to low redox potentials, and that electron flow can be coupled to generation of different amounts of energy for growth. The redox potentials that trigger these behaviors mirror those of metal acceptors common in subsurface environments where Geobacter is found. PMID:25425235

An inner membrane cytochrome required only for reduction of high redox potential extracellular electron acceptors

DOE PAGES

Levar, Caleb E.; Chan, Chi Ho; Mehta-Kolte, Misha G.; ...

2014-10-28

Dissimilatory metal-reducing bacteria, such as Geobacter sulfurreducens, transfer electrons beyond their outer membranes to Fe(III) and Mn(IV) oxides, heavy metals, and electrodes in electrochemical devices. In the environment, metal acceptors exist in multiple chelated and insoluble forms that span a range of redox potentials and offer different amounts of available energy. Despite this, metal-reducing bacteria have not been shown to alter their electron transfer strategies to take advantage of these energy differences. Disruption of imcH, encoding an inner membrane c-type cytochrome, eliminated the ability of G. sulfurreducens to reduce Fe(III) citrate, Fe(III)-EDTA, and insoluble Mn(IV) oxides, electron acceptors with potentialsmore » greater than 0.1 V versus the standard hydrogen electrode (SHE), but the imcH mutant retained the ability to reduce Fe(III) oxides with potentials of ≤–0.1 V versus SHE. The imcH mutant failed to grow on electrodes poised at +0.24 V versus SHE, but switching electrodes to –0.1 V versus SHE triggered exponential growth. At potentials of ≤–0.1 V versus SHE, both the wild type and the imcH mutant doubled 60% slower than at higher potentials. Electrodes poised even 100 mV higher (0.0 V versus SHE) could not trigger imcH mutant growth. These results demonstrate that G. sulfurreducens possesses multiple respiratory pathways, that some of these pathways are in operation only after exposure to low redox potentials, and that electron flow can be coupled to generation of different amounts of energy for growth. Redox potentials that trigger these behaviors mirror those of metal acceptors common in subsurface environments where Geobacter is found.« less

Redox Indicator Mice Stably Expressing Genetically Encoded Neuronal roGFP: Versatile Tools to Decipher Subcellular Redox Dynamics in Neuropathophysiology.

PubMed

Wagener, Kerstin C; Kolbrink, Benedikt; Dietrich, Katharina; Kizina, Kathrin M; Terwitte, Lukas S; Kempkes, Belinda; Bao, Guobin; Müller, Michael

2016-07-01

Reactive oxygen species (ROS) and downstream redox alterations not only mediate physiological signaling but also neuropathology. For long, ROS/redox imaging was hampered by a lack of reliable probes. Genetically encoded redox sensors overcame this gap and revolutionized (sub)cellular redox imaging. Yet, the successful delivery of sensor-coding DNA, which demands transfection/transduction of cultured preparations or stereotaxic microinjections of each subject, remains challenging. By generating transgenic mice, we aimed to overcome limiting cultured preparations, circumvent surgical interventions, and to extend effectively redox imaging to complex and adult preparations. Our redox indicator mice widely express Thy1-driven roGFP1 (reduction-oxidation-sensitive green fluorescent protein 1) in neuronal cytosol or mitochondria. Negative phenotypic effects of roGFP1 were excluded and its proper targeting and functionality confirmed. Redox mapping by ratiometric wide-field imaging reveals most oxidizing conditions in CA3 neurons. Furthermore, mitochondria are more oxidized than cytosol. Cytosolic and mitochondrial roGFP1s reliably report cell endogenous redox dynamics upon metabolic challenge or stimulation. Fluorescence lifetime imaging yields stable, but marginal, response ranges. We therefore developed automated excitation ratiometric 2-photon imaging. It offers superior sensitivity, spatial resolution, and response dynamics. Redox indicator mice enable quantitative analyses of subcellular redox dynamics in a multitude of preparations and at all postnatal stages. This will uncover cell- and compartment-specific cerebral redox signals and their defined alterations during development, maturation, and aging. Cross-breeding with other disease models will reveal molecular details on compartmental redox homeostasis in neuropathology. Combined with ratiometric 2-photon imaging, this will foster our mechanistic understanding of cellular redox signals in their full complexity. Antioxid. Redox Signal. 25, 41-58.

Mitochondrial pharmacology: electron transport chain bypass as strategies to treat mitochondrial dysfunction.

PubMed

Atamna, Hani; Mackey, Jeanette; Dhahbi, Joseph M

2012-01-01

Mitochondrial dysfunction (primary or secondary) is detrimental to intermediary metabolism. Therapeutic strategies to treat/prevent mitochondrial dysfunction could be valuable for managing metabolic and age-related disorders. Here, we review strategies proposed to treat mitochondrial impairment. We then concentrate on redox-active agents, with mild-redox potential, who shuttle electrons among specific cytosolic or mitochondrial redox-centers. We propose that specific redox agents with mild redox potential (-0.1 V; 0.1 V) improve mitochondrial function because they can readily donate or accept electrons in biological systems, thus they enhance metabolic activity and prevent reactive oxygen species (ROS) production. These agents are likely to lack toxic effects because they lack the risk of inhibiting electron transfer in redox centers. This is different from redox agents with strong negative (-0.4 V; -0.2 V) or positive (0.2 V; 0.4 V) redox potentials who alter the redox status of redox-centers (i.e., become permanently reduced or oxidized). This view has been demonstrated by testing the effect of several redox active agents on cellular senescence. Methylene blue (MB, redox potential ≅10 mV) appears to readily cycle between the oxidized and reduced forms using specific mitochondrial and cytosolic redox centers. MB is most effective in delaying cell senescence and enhancing mitochondrial function in vivo and in vitro. Mild-redox agents can alter the biochemical activity of specific mitochondrial components, which then in response alters the expression of nuclear and mitochondrial genes. We present the concept of mitochondrial electron-carrier bypass as a potential result of mild-redox agents, a method to prevent ROS production, improve mitochondrial function, and delay cellular aging. Thus, mild-redox agents may prevent/delay mitochondria-driven disorders. Copyright © 2012 International Union of Biochemistry and Molecular Biology, Inc.

Redox Indicator Mice Stably Expressing Genetically Encoded Neuronal roGFP: Versatile Tools to Decipher Subcellular Redox Dynamics in Neuropathophysiology

PubMed Central

Wagener, Kerstin C.; Kolbrink, Benedikt; Dietrich, Katharina; Kizina, Kathrin M.; Terwitte, Lukas S.; Kempkes, Belinda; Bao, Guobin

2016-01-01

Abstract Aims: Reactive oxygen species (ROS) and downstream redox alterations not only mediate physiological signaling but also neuropathology. For long, ROS/redox imaging was hampered by a lack of reliable probes. Genetically encoded redox sensors overcame this gap and revolutionized (sub)cellular redox imaging. Yet, the successful delivery of sensor-coding DNA, which demands transfection/transduction of cultured preparations or stereotaxic microinjections of each subject, remains challenging. By generating transgenic mice, we aimed to overcome limiting cultured preparations, circumvent surgical interventions, and to extend effectively redox imaging to complex and adult preparations. Results: Our redox indicator mice widely express Thy1-driven roGFP1 (reduction–oxidation-sensitive green fluorescent protein 1) in neuronal cytosol or mitochondria. Negative phenotypic effects of roGFP1 were excluded and its proper targeting and functionality confirmed. Redox mapping by ratiometric wide-field imaging reveals most oxidizing conditions in CA3 neurons. Furthermore, mitochondria are more oxidized than cytosol. Cytosolic and mitochondrial roGFP1s reliably report cell endogenous redox dynamics upon metabolic challenge or stimulation. Fluorescence lifetime imaging yields stable, but marginal, response ranges. We therefore developed automated excitation ratiometric 2-photon imaging. It offers superior sensitivity, spatial resolution, and response dynamics. Innovation and Conclusion: Redox indicator mice enable quantitative analyses of subcellular redox dynamics in a multitude of preparations and at all postnatal stages. This will uncover cell- and compartment-specific cerebral redox signals and their defined alterations during development, maturation, and aging. Cross-breeding with other disease models will reveal molecular details on compartmental redox homeostasis in neuropathology. Combined with ratiometric 2-photon imaging, this will foster our mechanistic understanding of cellular redox signals in their full complexity. Antioxid. Redox Signal. 25, 41–58. PMID:27059697

Origin of Unusual Dependencies of LUMO Levels on Conjugation Length in Quinoidal Fused Oligosiloles

NASA Astrophysics Data System (ADS)

Misawa, Nana; Fujii, Mikiya; Shintani, Ryo; Tsuda, Tomohiro; Nozaki, Kyoko; Yamashita, Koichi

Quinoidal fused oligosiloles, a new family of silicon-bridged π-conjugated compounds, have been synthesized and their physical properties showed a unique trend in their LUMO levels, which become higher with longer π-conjugation. Although this trend was reproduced by the DFT calculations, its origin remained to be discussed. In this work we performed quantum chemical calculations and discovered that the unusual LUMO trend is attributable to the π-frameworks. We elucidated its origin by orbital correlation diagrams based on classical Hückel calculations, essentially. However, LUMO trends cannot fully be explained only by Hückel calculations because of the lack of the consideration of geometries. In the case of quinoidal fused oligosiloles, judging from DFT calculation results, the presence of silole fused structure play an important role in fixing the bond angles of the linear polyenes as an interior angle of siloles, leading to the unusual LUMO behavior. The qualitative but essential understanding of these LUMO trend would provide new insight into molecular design of π-conjugated compounds for tuning their LUMO levels.

A pediatric intramedullary spinal cord tumor with unusual solid-cystic and papillary features: a case report.

PubMed

Iwasaki, Takeshi; Kato, Masako; Horie, Yasushi; Kato, Shinsuke; Akatsuka, Keiichi; Watanabe, Takashi; Kuwamoto, Satoshi; Murakami, Ichiro; Hayashi, Kazuhiko

2011-12-01

Spinal cord tumors are rare in children. We report a novel case of pediatric intramedullary spinal cord tumor with unusual solid-cystic and papillary features. Clinically, the patient presented at the age of 3 years with motor deficit and urinary incontinence, and MRI demonstrated multilocular cystic lesions in the thoracic spine. Histologically the tumor consisted of solid, sheet-like components and branching papillary structures, and immunohistochemistry demonstrated positive reactivity for epithelial membrane antigen, cytokeratins (7, AE1/3, CAM5.2), E-cadherin and transthyretin, and negativity for GFAP, S-100 protein, synaptophysin and neurofilament. These histological and immunohistochemical findings appeared to be unique, and were not compatible with the features of classical ependymoma or choroid plexus papilloma. The clinical behavior, characterized by relatively rapid tumor regrowth after surgical resection and a relatively high MIB-1 labeling index, suggest that this tumor might have had moderate malignant potential. This pediatric case appears to be particularly informative with regard to the tumor biology or tumorigenesis of intramedullary spinal cord tumor with unusual solid-cystic and papillary features. © 2011 Japanese Society of Neuropathology.

Phase coherent transport in hybrid superconductor-topological insulator devices

NASA Astrophysics Data System (ADS)

Finck, Aaron

2015-03-01

Heterostructures of superconductors and topological insulators are predicted to host unusual zero energy bound states known as Majorana fermions, which can robustly store and process quantum information. Here, I will discuss our studies of such heterostructures through phase-coherent transport, which can act as a unique probe of Majorana fermions. We have extensively explored topological insulator Josephson junctions through SQUID and single-junction diffraction patterns, whose unusual behavior give evidence for low-energy Andreev bound states. In topological insulator devices with closely spaced normal and superconducting leads, we observe prominent Fabry-Perot oscillations, signifying gate-tunable, quasi-ballistic transport that can elegantly interact with Andreev reflection. Superconducting disks deposited on the surface of a topological insulator generate Aharonov-Bohm-like oscillations, giving evidence for unusual states lying near the interface between the superconductor and topological insulator surface. Our results point the way towards sophisticated interferometers that can detect and read out the state of Majorana fermions in topological systems. This work was done in collaboration with Cihan Kurter, Yew San Hor, and Dale Van Harlingen. We acknowledge funding from Microsoft Project Q.

Monitoring thioredoxin redox with a genetically encoded red fluorescent biosensor.

PubMed

Fan, Yichong; Makar, Merna; Wang, Michael X; Ai, Hui-Wang

2017-09-01

Thioredoxin (Trx) is one of the two major thiol antioxidants, playing essential roles in redox homeostasis and signaling. Despite its importance, there is a lack of methods for monitoring Trx redox dynamics in live cells, hindering a better understanding of physiological and pathological roles of the Trx redox system. In this work, we developed the first genetically encoded fluorescent biosensor for Trx redox by engineering a redox relay between the active-site cysteines of human Trx1 and rxRFP1, a redox-sensitive red fluorescent protein. We used the resultant biosensor-TrxRFP1-to selectively monitor perturbations of Trx redox in various mammalian cell lines. We subcellularly localized TrxRFP1 to image compartmentalized Trx redox changes. We further combined TrxRFP1 with a green fluorescent Grx1-roGFP2 biosensor to simultaneously monitor Trx and glutathione redox dynamics in live cells in response to chemical and physiologically relevant stimuli.

Method for characterization of the redox condition of cementitious materials

DOEpatents

Almond, Philip M.; Langton, Christine A.; Stefanko, David B.

2015-12-22

Disclosed are methods for determining the redox condition of cementitious materials. The methods are leaching methods that utilize an in situ redox indicator that is present in the cementitious materials as formed. The in situ redox indicator leaches from cementitious material and, when the leaching process is carried out under anaerobic conditions can be utilized to determine the redox condition of the material. The in situ redox indicator can exhibit distinct characteristics in the leachate depending upon the redox condition of the indicator.

Charge transfer mediator based systems for electrocatalytic oxygen reduction

DOEpatents

Stahl, Shannon S.; Gerken, James B.; Anson, Colin W.

2017-11-07

Disclosed are systems for the electrocatalytic reduction of oxygen, having redox mediator/redox catalyst pairs and an electrolyte solution in contact with an electrode. The redox mediator is included in the electrolyte solution, and the redox catalyst may be included in the electrolyte solution, or alternatively, may be in contact with the electrolyte solution. In one form a cobalt redox catalyst is used with a quinone redox mediator. In another form a nitrogen oxide redox catalyst is used with a nitroxyl type redox mediator. The systems can be used in electrochemical cells wherein neither the anode nor the cathode comprise an expensive metal such as platinum.

Charge transfer mediator based systems for electrocatalytic oxygen reduction

DOEpatents

Stahl, Shannon S.; Gerken, James B.; Anson, Colin W.

2017-07-18

Disclosed are systems for the electrocatalytic reduction of oxygen, having redox mediator/redox catalyst pairs and an electrolyte solution in contact with an electrode. The redox mediator is included in the electrolyte solution, and the redox catalyst may be included in the electrolyte solution, or alternatively, may be in contact with the electrolyte solution. In one form a cobalt redox catalyst is used with a quinone redox mediator. In another form a nitrogen oxide redox catalyst is used with a nitroxyl type redox mediator. The systems can be used in electrochemical cells wherein neither the anode nor the cathode comprise an expensive metal such as platinum.

Redox-capacitor to connect electrochemistry to redox-biology.

PubMed

Kim, Eunkyoung; Leverage, W Taylor; Liu, Yi; White, Ian M; Bentley, William E; Payne, Gregory F

2014-01-07

It is well-established that redox-reactions are integral to biology for energy harvesting (oxidative phosphorylation), immune defense (oxidative burst) and drug metabolism (phase I reactions), yet there is emerging evidence that redox may play broader roles in biology (e.g., redox signaling). A critical challenge is the need for tools that can probe biologically-relevant redox interactions simply, rapidly and without the need for a comprehensive suite of analytical methods. We propose that electrochemistry may provide such a tool. In this tutorial review, we describe recent studies with a redox-capacitor film that can serve as a bio-electrode interface that can accept, store and donate electrons from mediators commonly used in electrochemistry and also in biology. Specifically, we (i) describe the fabrication of this redox-capacitor from catechols and the polysaccharide chitosan, (ii) discuss the mechanistic basis for electron exchange, (iii) illustrate the properties of this redox-capacitor and its capabilities for promoting redox-communication between biology and electrodes, and (iv) suggest the potential for enlisting signal processing strategies to "extract" redox information. We believe these initial studies indicate broad possibilities for enlisting electrochemistry and signal processing to acquire "systems level" redox information from biology.

Redox sensing: Orthogonal control in cell cycle and apoptosis signaling

PubMed Central

Jones, Dean P.

2010-01-01

Living systems have three major types of cell signaling systems that are dependent upon high-energy chemicals, redox environment and transmembranal ion gating mechanisms. Development of integrated systems biology descriptions of cell signaling require conceptual models incorporating all three. Recent advances in redox biology show that thiol/disulfide redox systems are regulated under dynamic, non-equilibrium conditions, progressively oxidized with the life cycle of cells and distinct in terms of redox potentials among subcellular compartments. The present article uses these observations as a basis to distinguish “redox-sensing” mechanisms, which are more global biologic redox control mechanisms, from “redox signaling”, which involves conveyance of discrete activating or inactivating signals. Both redox sensing and redox signaling use sulfur switches, especially cysteine (Cys) residues in proteins which are sensitive to reversible oxidation, nitrosylation, glutathionylation, acylation, sulfhydration or metal binding. Unlike specific signaling mechanisms, the redox-sensing mechanisms provide means to globally affect the rates and activities of the high-energy, ion gating and redox-signaling systems by controlling sensitivity, distribution, macromolecular interactions and mobility of signaling proteins. Effects mediated through Cys residues not directly involved in signaling means redox-sensing control can be orthogonal to the signaling mechanisms. This provides a capability to integrate signals according to cell cycle and physiologic state without fundamentally altering the signaling mechanisms. Recent findings that thiol/disulfide pools in humans are oxidized with age, environmental exposures and disease risk suggest that redox-sensing thiols could provide a central mechanistic link in disease development and progression. PMID:20964735

Unusual superconducting behavior in HfV2Ga4

NASA Astrophysics Data System (ADS)

Santos, F. B.; Correa, L. E.; de Lima, B. S.; Cigarroa, O. V.; da Luz, M. S.; Grant, T.; Fisk, Z.; Machado, A. J. S.

2018-04-01

Bulk superconductivity in HfV2Ga4 with critical temperature close to 4.1 K was determined via magnetic susceptibility, electrical resistivity and specific heat measurements. Both the upper and lower critical field dependence with reduced temperature (T /Tc) exhibit non-conventional behavior. The electronic component of specific heat shows a double-jump, the first close to Tc and the other close to 0.75Tc. We speculate about the nature of the douple jump observed in specific heat considering two plausable scenarios: bulk inhomogeneities and the existence of a second gap.

HCH, endosulfan, and fluvalinate residue behavior in pigeonpea (Cajanus cajan L. Millsp)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mukherjee, I.; Gopal, M.; Yaduraju, N.T.

Pigeonpea (Cajanus cajan L. Millsp) is one of the major pulse crop of India. The loss of pigeonpea crop due to pod and foliage pests is significant, the major pests being pod fly, hairy caterpillar, aphids, white fly, plume moth borer, leaf caterpillar and jassids. It is imperative to save every grain by chemical control methods but these toxicants should not leave unusually high residues on the edible parts. In this paper the authors report the residue behavior of three different insecticides namely, hexachlorocyclohexane, endosulfan and fluvalinate on this crop.

Critical behavior in graphene with Coulomb interactions.

PubMed

Wang, Jianhui; Fertig, H A; Murthy, Ganpathy

2010-05-07

We demonstrate that, in the presence of Coulomb interactions, electrons in graphene behave like a critical system, supporting power law correlations with interaction-dependent exponents. An asymptotic analysis shows that the origin of this behavior lies in particle-hole scattering, for which the Coulomb interaction induces anomalously close approaches. With increasing interaction strength the relevant power law changes from real to complex, leading to an unusual instability characterized by a complex-valued susceptibility in the thermodynamic limit. Measurable quantities, as well as the connection to classical two-dimensional systems, are discussed.

Complex structural behavior of oligopurine-oligopyrimidine sequence cloned within the supercoiled plasmid.

PubMed Central

Parniewski, P; Galazka, G; Wilk, A; Klysik, J

1989-01-01

Synthetic sequence GATCC(AG)7ATCG(AT)4CG(AG)7 was cloned into plasmid and its structural behavior under the influence of supercoiling was analysed by chemical modification at variety of experimental conditions. It was found that this sequence adopts at least two different non-B conformations depending on -delta and pH values. Moreover, 12 nucleotide long non-pur.pyr spacer region separating two identical (AG)7 blocks does not provide a significant energy barrier protecting against unusual structures formation. Images PMID:2644622

Sickness behaviors in response to unusual external events in healthy cats and cats with feline interstitial cystitis

PubMed Central

Stella, Judi L.; Lord, Linda K.; Buffington, C. A. Tony

2013-01-01

Objective To compare sickness behaviors (SB) in response to unusual external events (UEE) in healthy cats with those of cats with feline interstitial cystitis (FIC). Design Prospective observational study. Animals 12 healthy cats and 20 donated cats with FIC. Procedures Cats were housed in a vivarium. Sickness behaviors referable to the gastrointestinal and urinary tracts, the skin, and behavior problems were recorded by a single observer for 77 weeks. Instances of UEE (eg, changes in caretakers, vivarium routine, and lack of interaction with the investigator) were identified during 11 of the 77 weeks. No instances of UEE were identified during the remaining 66 weeks, which were considered control weeks. Results An increase in age and exposure to UEE, but not disease status, significantly increased total number of SB when results were controlled for other factors. Evaluation of individual SB revealed a protective effect of food intake for healthy males. An increase in age conferred a small increase in relative risk (RR) for upper gastrointestinal tract signs (RR, 1.2) and avoidance behavior (1.7). Exposure to UEE significantly increased the RR for decreases in food intake (RR, 9.3) and for no eliminations in 24 hours (6.4). Exposure to UEE significantly increased the RR for defecation (RR, 9.8) and urination (1.6) outside the litter box. Conclusions and Clinical Relevance SB, including some of the most commonly observed abnormalities in client-owned cats, were observed after exposure to UEE in both groups. Because healthy cats and cats with FIC were comparably affected by UEE, clinicians should consider the possibility of exposure to UEE in cats evaluated for these signs. PMID:21194324

Redox Regulation of Mitochondrial Function

PubMed Central

Handy, Diane E.

2012-01-01

Abstract Redox-dependent processes influence most cellular functions, such as differentiation, proliferation, and apoptosis. Mitochondria are at the center of these processes, as mitochondria both generate reactive oxygen species (ROS) that drive redox-sensitive events and respond to ROS-mediated changes in the cellular redox state. In this review, we examine the regulation of cellular ROS, their modes of production and removal, and the redox-sensitive targets that are modified by their flux. In particular, we focus on the actions of redox-sensitive targets that alter mitochondrial function and the role of these redox modifications on metabolism, mitochondrial biogenesis, receptor-mediated signaling, and apoptotic pathways. We also consider the role of mitochondria in modulating these pathways, and discuss how redox-dependent events may contribute to pathobiology by altering mitochondrial function. Antioxid. Redox Signal. 16, 1323–1367. PMID:22146081

Species-Specific Standard Redox Potential of Thiol-Disulfide Systems: A Key Parameter to Develop Agents against Oxidative Stress

NASA Astrophysics Data System (ADS)

Mirzahosseini, Arash; Noszál, Béla

2016-11-01

Microscopic standard redox potential, a new physico-chemical parameter was introduced and determined to quantify thiol-disulfide equilibria of biological significance. The highly composite, codependent acid-base and redox equilibria of thiols could so far be converted into pH-dependent, apparent redox potentials (E’°) only. Since the formation of stable metal-thiolate complexes precludes the direct thiol-disulfide redox potential measurements by usual electrochemical techniques, an indirect method had to be elaborated. In this work, the species-specific, pH-independent standard redox potentials of glutathione were determined primarily by comparing it to 1-methylnicotinamide, the simplest NAD+ analogue. Secondarily, the species-specific standard redox potentials of the two-electron redox transitions of cysteamine, cysteine, homocysteine, penicillamine, and ovothiol were determined using their microscopic redox equilibrium constants with glutathione. The 30 different, microscopic standard redox potential values show close correlation with the respective thiolate basicities and provide sound means for the development of potent agents against oxidative stress.

Redox active polymers and colloidal particles for flow batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gavvalapalli, Nagarjuna; Moore, Jeffrey S.; Rodriguez-Lopez, Joaquin

The invention provides a redox flow battery comprising a microporous or nanoporous size-exclusion membrane, wherein one cell of the battery contains a redox-active polymer dissolved in the non-aqueous solvent or a redox-active colloidal particle dispersed in the non-aqueous solvent. The redox flow battery provides enhanced ionic conductivity across the electrolyte separator and reduced redox-active species crossover, thereby improving the performance and enabling widespread utilization. Redox active poly(vinylbenzyl ethylviologen) (RAPs) and redox active colloidal particles (RACs) were prepared and were found to be highly effective redox species. Controlled potential bulk electrolysis indicates that 94-99% of the nominal charge on different RAPsmore » is accessible and the electrolysis products are stable upon cycling. The high concentration attainable (>2.0 M) for RAPs in common non-aqueous battery solvents, their electrochemical and chemical reversibility, and their hindered transport across porous separators make them attractive materials for non-aqueous redox flow batteries based on size-selectivity.« less

[Redox Molecular Imaging Using ReMI].

PubMed

Hyodo, Fuminori; Ito, Shinji; Utsumi, Hideo

2015-01-01

Tissue redox status is one of the most important parameters to maintain homeostasis in the living body. Numerous redox reactions are involved in metabolic processes, such as energy production in the mitochondrial electron transfer system. A variety of intracellular molecules such as reactive oxygen species, glutathione, thioredoxins, NADPH, flavins, and ascorbic acid may contribute to the overall redox status in tissues. Breakdown of redox balance may lead to oxidative stress and can induce many pathological conditions such as cancer, neurological disorders, and aging. Therefore imaging of tissue redox status and monitoring antioxidant levels in living organisms can be useful in the diagnosis of disease states and assessment of treatment response. In vivo redox molecular imaging technology such as electron spin resonance imaging (ESRI), magnetic resonance imaging (MRI), and dynamic nuclear polarization (DNP)-MRI (redox molecular imaging; ReMI) is emerging as a viable redox status imaging modality. This review focuses on the application of magnetic resonance technologies using MRI or DNP-MRI and redox-sensitive contrast agents.

Clinically Evaluated Cancer Drugs Inhibiting Redox Signaling.

PubMed

Kirkpatrick, D Lynn; Powis, Garth

2017-02-20

There are a number of redox-active anticancer agents currently in development based on the premise that altered redox homeostasis is necessary for cancer cell's survival. Recent Advances: This review focuses on the relatively few agents that target cellular redox homeostasis to have entered clinical trial as anticancer drugs. The success rate of redox anticancer drugs has been disappointing compared to other classes of anticancer agents. This is due, in part, to our incomplete understanding of the functions of the redox targets in normal and cancer tissues, leading to off-target toxicities and low therapeutic indexes of the drugs. The field also lags behind in the use biomarkers and other means to select patients who are most likely to respond to redox-targeted therapy. If we wish to derive clinical benefit from agents that attack redox targets, then the future will require a more sophisticated understanding of the role of redox targets in cancer and the increased application of personalized medicine principles for their use. Antioxid. Redox Signal. 26, 262-273.

Implications of Marcus-Hush theory for steady-state heterogeneous electron transfer at an inlaid disk electrode.

PubMed

Feldberg, Stephen W

2010-06-15

For an outer-sphere heterogeneous electron transfer, Ox + e = Red, between an electrode and a redox couple, the Butler-Volmer formalism predicts that the operative heterogeneous rate constant, k(red) (cm s(-1)) for reduction (or k(ox) for oxidation) increases without limit as an exponential function of -alpha (E - E(0)) for reduction (or (1 - alpha)(E - E(0)) for oxidation), where E is the applied electrode potential, alpha (~1/2) is the transfer coefficient and E(0) is the formal potential. The Marcus-Hush formalism, as exposited by Chidsey (Chidsey, C. E. D. Science 1991, 215, 919), predicts that the value of k(red) or k(ox) limits at sufficiently large values of -(E - E(0)) or (E - E(0)). The steady-state currents at an inlaid disk electrode obtained for a redox species in solution were computed using both formalisms with the Oldham-Zoski approximation (Oldham, K. B.; Zoski, C. G. J. Electroanal. Chem. 1988, 256, 11). Significant differences are noted for the two formalisms. When k(0)r(0)/D is sufficiently small (k(0) is the standard rate constant, r(0) is the radius of the disk electrode, and D is the diffusion coefficient of the redox species), the Marcus-Hush formalism effects a limiting current that can be significantly smaller than the mass transport limited current. This is easily explained in terms of the limiting values of k(red) and k(ox) predicted by the Marcus-Hush formalism. The experimental conditions that must be met to effect significant differences in behavior are discussed; experimental conditions that effect virtually identical behavior are also discussed. As a caveat for experimentalists, applications of the Butler-Volmer formalism to systems that are more properly described using the Marcus-Hush formalism are shown to yield incorrect values of k(0) and meaningless values of alpha, which serves only as a fitting parameter.

Ferrocene bound poly(vinyl chloride) as ion to electron transducer in electrochemical ion sensors.

PubMed

Pawlak, Marcin; Grygolowicz-Pawlak, Ewa; Bakker, Eric

2010-08-15

We report here on the synthesis of poly(vinyl chloride) (PVC) covalently modified with ferrocene groups (FcPVC) and the electrochemical behavior of the resulting polymeric membranes in view of designing all solid state voltammetric ion sensors. The Huisgen cycloaddition ("click chemistry") was found to be a simple and efficient method for ferrocene attachment. A degree of PVC modification with ferrocene groups between 1.9 and 6.1 mol % was achieved. The chemical modification of the PVC backbone does not significantly affect the ion-selective properties (selectivity, mobility, and solvent casting ability) of potentiometric sensing membranes applying this polymer. Importantly, the presence of such ferrocene groups may eliminate the need for an additional redox-active layer between the membrane and the inner electric contact in all solid state sensor designs. Electrochemical doping of this system was studied in a symmetrical sandwich configuration: glassy carbon electrode |FcPVC| glassy carbon electrode. Prior electrochemical doping from aqueous solution, resulting in a partial oxidation of the ferrocene groups, was confirmed to be necessary for the sandwich configuration to pass current effectively. The results suggest that only approximately 2.3 mol % of the ferrocene groups are electrochemically accessible, likely due to surface confined electrochemical behavior in the polymer. Indeed, cyclic voltammetry of aqueous hexacyanoferrate (III) remains featureless at cathodic potentials (down to -0.5 V). This indicates that the modified membrane is not responsive to redox-active species in the sample solution, making it possible to apply this polymer as a traditional, single membrane. Yet, the redox capacity of the electrode modified with this type of membrane was more than 520 microC considering a 20 mm(2) active electrode area, which appears to be sufficient for numerous practical ion voltammetric applications. The electrode was observed to operate reproducibly, with 1% standard deviation, when applying pulsed amperometric techniques.

Redox subpopulations and the risk of cancer progression: a new method for characterizing redox heterogeneity

NASA Astrophysics Data System (ADS)

Xu, He N.; Li, Lin Z.

2016-02-01

It has been shown that a malignant tumor is akin to a complex organ comprising of various cell populations including tumor cells that are genetically, metabolically and functionally different. Our redox imaging data have demonstrated intra-tumor redox heterogeneity in all mouse xenografts derived from human melanomas, breast, prostate, and colon cancers. Based on the signals of NADH and oxidized flavoproteins (Fp, including flavin adenine dinucleotide (FAD)) and their ratio, i.e., the redox ratio, which is an indicator of mitochondrial metabolic status, we have discovered several distinct redox subpopulations in xenografts of breast tumors potentially recapitulating functional/metabolic heterogeneity within the tumor. Furthermore, xenografts of breast tumors with higher metastatic potential tend to have a redox subpopulation whose redox ratio is significantly different from that of tumors with lower metastatic potential and usually have a bi-modal distribution of the redox ratio. The redox subpopulations from human breast cancer samples can also be very complex with multiple subpopulations as determined by fitting the redox ratio histograms with multi- Gaussian functions. In this report, we present a new method for identifying the redox subpopulations within individual breast tumor xenografts and human breast tissues, which may be used to differentiate between breast cancer and normal tissue and among breast cancer with different risks of progression.

Redox Biology in Neurological Function, Dysfunction, and Aging.

PubMed

Franco, Rodrigo; Vargas, Marcelo R

2018-04-23

Reduction oxidation (redox) reactions are central to life and when altered, they can promote disease progression. In the brain, redox homeostasis is recognized to be involved in all aspects of central nervous system (CNS) development, function, aging, and disease. Recent studies have uncovered the diverse nature by which redox reactions and homeostasis contribute to brain physiology, and when dysregulated to pathological consequences. Redox reactions go beyond what is commonly described as oxidative stress and involve redox mechanisms linked to signaling and metabolism. In contrast to the nonspecific nature of oxidative damage, redox signaling involves specific oxidation/reduction reactions that regulate a myriad of neurological processes such as neurotransmission, homeostasis, and degeneration. This Forum is focused on the role of redox metabolism and signaling in the brain. Six review articles from leading scientists in the field that appraise the role of redox metabolism and signaling in different aspects of brain biology including neurodevelopment, neurotransmission, aging, neuroinflammation, neurodegeneration, and neurotoxicity are included. An original research article exemplifying these concepts uncovers a novel link between oxidative modifications, redox signaling, and neurodegeneration. This Forum highlights the recent advances in the field and we hope it encourages future research aimed to understand the mechanisms by which redox metabolism and signaling regulate CNS physiology and pathophysiology. Antioxid. Redox Signal. 00, 000-000.

Sex steroids and human behavior: prenatal androgen exposure and sex-typical play behavior in children.

PubMed

Hines, Melissa

2003-12-01

Gonadal hormones, particularly androgens, direct certain aspects of brain development and exert permanent influences on sex-typical behavior in nonhuman mammals. Androgens also influence human behavioral development, with the most convincing evidence coming from studies of sex-typical play. Girls exposed to unusually high levels of androgens prenatally, because they have the genetic disorder, congenital adrenal hyperplasia (CAH), show increased preferences for toys and activities usually preferred by boys, and for male playmates, and decreased preferences for toys and activities usually preferred by girls. Normal variability in androgen prenatally also has been related to subsequent sex-typed play behavior in girls, and nonhuman primates have been observed to show sex-typed preferences for human toys. These findings suggest that androgen during early development influences childhood play behavior in humans at least in part by altering brain development.

Breast Cancer Redox Heterogeneity Detectable with Chemical Exchange Satruation Transfer (CEST) MRI

PubMed Central

Cai, Kejia; Xu, He N.; Singh, Anup; Moon, Lily; Haris, Mohammad; Reddy, Ravinder; Li, Lin

2014-01-01

Purpose Tissue redox state is an important mediator of various biological processes in health and diseases such as cancer. Previously, we discovered that the mitochondrial redox state of ex vivo tissues detected by redox scanning (an optical imaging method) revealed interesting tumor redox state heterogeneity that could differentiate tumor aggressiveness. Because the noninvasive chemical exchange saturation transfer (CEST) MRI can probe the proton transfer and generate contrasts from endogenous metabolites, we aim to investigate if the in vivo CEST contrast is sensitive to proton transfer of the redox reactions so as to reveal the tissue redox states in breast cancer animal models. Procedures CEST MRI has been employed to characterize tumor metabolic heterogeneity and correlated with the redox states measured by the redox scanning in two human breast cancer mouse xenograft models, MDA-MB-231 and MCF-7. The possible biological mechanism on the correlation between the two imaging modalities was further investigated by phantom studies where the reductants and the oxidants of the representative redox reactions were measured. Results The CEST contrast is found linearly correlated with NADH concentration and the NADH redox ratio with high statistical significance, where NADH is the reduced form of nicotinamide adenine dinucleotide. The phantom studies showed that the reductants of the redox reactions have more CEST contrast than the corresponding oxidants, indicating that higher CEST effect corresponds to the more reduced redox state. Conclusions This preliminary study suggests that CEST MRI, once calibrated, might provide a novel noninvasive imaging surrogate for the tissue redox state and a possible diagnostic biomarker for breast cancer in the clinic. PMID:24811957

Breast cancer redox heterogeneity detectable with chemical exchange saturation transfer (CEST) MRI.

PubMed

Cai, Kejia; Xu, He N; Singh, Anup; Moon, Lily; Haris, Mohammad; Reddy, Ravinder; Li, Lin Z

2014-10-01

Tissue redox state is an important mediator of various biological processes in health and diseases such as cancer. Previously, we discovered that the mitochondrial redox state of ex vivo tissues detected by redox scanning (an optical imaging method) revealed interesting tumor redox state heterogeneity that could differentiate tumor aggressiveness. Because the noninvasive chemical exchange saturation transfer (CEST) MRI can probe the proton transfer and generate contrasts from endogenous metabolites, we aim to investigate if the in vivo CEST contrast is sensitive to proton transfer of the redox reactions so as to reveal the tissue redox states in breast cancer animal models. CEST MRI has been employed to characterize tumor metabolic heterogeneity and correlated with the redox states measured by the redox scanning in two human breast cancer mouse xenograft models, MDA-MB-231 and MCF-7. The possible biological mechanism on the correlation between the two imaging modalities was further investigated by phantom studies where the reductants and the oxidants of the representative redox reactions were measured. The CEST contrast is found linearly correlated with NADH concentration and the NADH redox ratio with high statistical significance, where NADH is the reduced form of nicotinamide adenine dinucleotide. The phantom studies showed that the reductants of the redox reactions have more CEST contrast than the corresponding oxidants, indicating that higher CEST effect corresponds to the more reduced redox state. This preliminary study suggests that CEST MRI, once calibrated, might provide a novel noninvasive imaging surrogate for the tissue redox state and a possible diagnostic biomarker for breast cancer in the clinic.

Emoticon-Based Ambivalent Expression: A Hidden Indicator for Unusual Behaviors in Weibo

PubMed Central

Hu, Yue; Zhao, Jichang; Wu, Junjie

2016-01-01

Recent decades have witnessed online social media being a big-data window for testifying conventional social theories quantitatively and exploring much detailed human behavioral patterns. In this paper, by tracing the emoticon use in Weibo, a group of hidden “ambivalent users” are disclosed for frequently posting ambivalent tweets containing both positive and negative emotions. Further investigation reveals that this ambivalent expression could be a novel indicator of many unusual social behaviors. For instance, ambivalent users with the female as the majority like to make a sound in midnights and at weekends. They mention their close friends frequently in ambivalent tweets, which attract more replies and serve as a more private communication way. Ambivalent users also respond differently to public affairs from others and demonstrate more interests in entertainment and sports events. Moreover, the sentiment shift in ambivalent tweets is more evident than usual and exhibits a clear “negative to positive” pattern. The above observations, though being promiscuous seemingly, actually point to the self-regulation of negative mood in Weibo, which could find its basis from the traditional emotion management theories in sociology but makes an important extension to the online environment in this study. Finally, as an interesting corollary, ambivalent users are found connected with compulsive buyers and turn out to be perfect targets for online marketing. PMID:26800119

Development of redox-sensitive red fluorescent proteins for imaging redox dynamics in cellular compartments.

PubMed

Fan, Yichong; Ai, Hui-wang

2016-04-01

We recently reported a redox-sensitive red fluorescent protein, rxRFP1, which is one of the first genetically encoded red-fluorescent probes for general redox states in living cells. As individual cellular compartments have different basal redox potentials, we hereby describe a group of rxRFP1 mutants, showing different midpoint redox potentials for detection of redox dynamics in various subcellular domains, such as mitochondria, the cell nucleus, and endoplasmic reticulum (ER). When these redox probes were expressed and subcellularly localized in human embryonic kidney (HEK) 293 T cells, they responded to membrane-permeable oxidants and reductants. In addition, a mitochondrially localized rxRFP1 mutant, Mito-rxRFP1.1, was used to detect mitochondrial oxidative stress induced by doxorubicin-a widely used cancer chemotherapy drug. Our work has expanded the fluorescent protein toolkit with new research tools for studying compartmentalized redox dynamics and oxidative stress under various pathophysiological conditions.

Sepiapterin Reductase Mediates Chemical Redox Cycling in Lung Epithelial Cells*

PubMed Central

Yang, Shaojun; Jan, Yi-Hua; Gray, Joshua P.; Mishin, Vladimir; Heck, Diane E.; Laskin, Debra L.; Laskin, Jeffrey D.

2013-01-01

In the lung, chemical redox cycling generates highly toxic reactive oxygen species that can cause alveolar inflammation and damage to the epithelium, as well as fibrosis. In this study, we identified a cytosolic NADPH-dependent redox cycling activity in mouse lung epithelial cells as sepiapterin reductase (SPR), an enzyme important for the biosynthesis of tetrahydrobiopterin. Human SPR was cloned and characterized. In addition to reducing sepiapterin, SPR mediated chemical redox cycling of bipyridinium herbicides and various quinones; this activity was greatest for 1,2-naphthoquinone followed by 9,10-phenanthrenequinone, 1,4-naphthoquinone, menadione, and 2,3-dimethyl-1,4-naphthoquinone. Whereas redox cycling chemicals inhibited sepiapterin reduction, sepiapterin had no effect on redox cycling. Additionally, inhibitors such as dicoumarol, N-acetylserotonin, and indomethacin blocked sepiapterin reduction, with no effect on redox cycling. Non-redox cycling quinones, including benzoquinone and phenylquinone, were competitive inhibitors of sepiapterin reduction but noncompetitive redox cycling inhibitors. Site-directed mutagenesis of the SPR C-terminal substrate-binding site (D257H) completely inhibited sepiapterin reduction but had minimal effects on redox cycling. These data indicate that SPR-mediated reduction of sepiapterin and redox cycling occur by distinct mechanisms. The identification of SPR as a key enzyme mediating chemical redox cycling suggests that it may be important in generating cytotoxic reactive oxygen species in the lung. This activity, together with inhibition of sepiapterin reduction by redox-active chemicals and consequent deficiencies in tetrahydrobiopterin, may contribute to tissue injury. PMID:23640889

Unusual early-onset Huntingtons disease.

PubMed

Vargas, Antonio P; Carod-Artal, Francisco J; Bomfim, Denise; Vázquez-Cabrera, Carolina; Dantas-Barbosa, Carmela

2003-06-01

Huntington's disease is an autosomal dominant progressive neurodegenerative disorder characterized by involuntary movements, cognitive decline, and behavioral disorders leading to functional disability. In contrast to patients with adult onset, in which chorea is the major motor abnormality, children often present with spasticity, rigidity, and significant intellectual decline associated with a more rapidly progressive course. An unusual early-onset Huntington's disease case of an 11-year-old boy with severe hypokinetic/rigid syndrome appearing at the age of 2.5 years is presented. Clinical diagnosis was confirmed by polymerase chain reaction study of the expanded IT-15 allele with a compatible size of 102 cytosine-adenosine-guanosine repeats L-Dopa mildly ameliorated rigidity, bradykinesia, and dystonia. We conclude that Huntington's disease should be included in the differential diagnoses of regressive syndromes of early childhood.

Late Neandertals and the intentional removal of feathers as evidenced from bird bone taphonomy at Fumane Cave 44 ky B.P., Italy

PubMed Central

Peresani, Marco; Fiore, Ivana; Gala, Monica; Romandini, Matteo; Tagliacozzo, Antonio

2011-01-01

A large and varied avifaunal bone assemblage from the final Mousterian levels of Grotta di Fumane, northern Italy, reveals unusual human modifications on species that are not clearly relatable to feeding or utilitarian uses (i.e., lammergeier, Eurasian black vulture, golden eagle, red-footed falcon, common wood pigeon, and Alpine chough). Cut, peeling, and scrape marks, as well as diagnostic fractures and a breakthrough, are observed exclusively on wings, indicating the intentional removal of large feathers by Neandertals. The species involved, the anatomical elements affected, and the unusual type and location of the human modifications indicate an activity linked to the symbolic sphere and the behavioral modernity of this European autochthonous population. PMID:21368129

Kinetic mechanism and quaternary structure of Aminobacter aminovorans NADH:flavin oxidoreductase: an unusual flavin reductase with bound flavin.

PubMed

Russell, Thomas R; Demeler, Borries; Tu, Shiao-Chun

2004-02-17

The homodimeric NADH:flavin oxidoreductase from Aminobacter aminovorans is an NADH-specific flavin reductase herein designated FRD(Aa). FRD(Aa) was characterized with respect to purification yields, thermal stability, isoelectric point, molar absorption coefficient, and effects of phosphate buffer strength and pH on activity. Evidence from this work favors the classification of FRD(Aa) as a flavin cofactor-utilizing class I flavin reductase. The isolated native FRD(Aa) contained about 0.5 bound riboflavin-5'-phosphate (FMN) per enzyme monomer, but one bound flavin cofactor per monomer was obtainable in the presence of excess FMN or riboflavin. In addition, FRD(Aa) holoenzyme also utilized FMN, riboflavin, or FAD as a substrate. Steady-state kinetic results of substrate titrations, dead-end inhibition by AMP and lumichrome, and product inhibition by NAD(+) indicated an ordered sequential mechanism with NADH as the first binding substrate and reduced FMN as the first leaving product. This is contrary to the ping-pong mechanism shown by other class I flavin reductases. The FMN bound to the native FRD(Aa) can be fully reduced by NADH and subsequently reoxidized by oxygen. No NADH binding was detected using 90 microM FRD(Aa) apoenzyme and 300 microM NADH. All results favor the interpretation that the bound FMN was a cofactor rather than a substrate. It is highly unusual that a flavin reductase using a sequential mechanism would require a flavin cofactor to facilitate redox exchange between NADH and a flavin substrate. FRD(Aa) exhibited a monomer-dimer equilibrium with a K(d) of 2.7 microM. Similarities and differences between FRD(Aa) and certain flavin reductases are discussed.

Spectroscopic Characterization of a Green Copper Site in a Single-Domain Cupredoxin

PubMed Central

Roger, Magali; Biaso, Frédéric; Castelle, Cindy J.; Bauzan, Marielle; Chaspoul, Florence; Lojou, Elisabeth; Sciara, Giuliano; Caffarri, Stefano; Giudici-Orticoni, Marie-Thérèse; Ilbert, Marianne

2014-01-01

Cupredoxins are widespread copper-binding proteins, mainly involved in electron transfer pathways. They display a typical rigid greek key motif consisting of an eight stranded β-sandwich. A fascinating feature of cupredoxins is the natural diversity of their copper center geometry. These geometry variations give rise to drastic changes in their color, such as blue, green, red or purple. Based on several spectroscopic and structural analyses, a connection between the geometry of their copper-binding site and their color has been proposed. However, little is known about the relationship between such diversity of copper center geometry in cupredoxins and possible implications for function. This has been difficult to assess, as only a few naturally occurring green and red copper sites have been described so far. We report herein the spectrocopic characterization of a novel kind of single domain cupredoxin of green color, involved in a respiratory pathway of the acidophilic organism Acidithiobacillus ferrooxidans. Biochemical and spectroscopic characterization coupled to bioinformatics analysis reveal the existence of some unusual features for this novel member of the green cupredoxin sub-family. This protein has the highest redox potential reported to date for a green-type cupredoxin. It has a constrained green copper site insensitive to pH or temperature variations. It is a green-type cupredoxin found for the first time in a respiratory pathway. These unique properties might be explained by a region of unknown function never found in other cupredoxins, and by an unusual length of the loop between the second and the fourth copper ligands. These discoveries will impact our knowledge on non-engineered green copper sites, whose involvement in respiratory chains seems more widespread than initially thought. PMID:24932914

A common variant in combination with a nonsense mutation in a member of the thioredoxin family causes primary ciliary dyskinesia

PubMed Central

Duriez, Bénédicte; Duquesnoy, Philippe; Escudier, Estelle; Bridoux, Anne-Marie; Escalier, Denise; Rayet, Isabelle; Marcos, Elisabeth; Vojtek, Anne-Marie; Bercher, Jean-François; Amselem, Serge

2007-01-01

Thioredoxins belong to a large family of enzymatic proteins that function as general protein disulfide reductases, therefore participating in several cellular processes via redox-mediated reactions. So far, none of the 18 members of this family has been involved in human pathology. Here we identified TXNDC3, which encodes a thioredoxin–nucleoside diphosphate kinase, as a gene implicated in primary ciliary dyskinesia (PCD), a genetic condition characterized by chronic respiratory tract infections, left–right asymmetry randomization, and male infertility. We show that the disease, which segregates as a recessive trait, results from the unusual combination of the following two transallelic defects: a nonsense mutation and a common intronic variant found in 1% of control chromosomes. This variant affects the ratio of two physiological TXNDC3 transcripts: the full-length isoform and a novel isoform, TXNDC3d7, carrying an in-frame deletion of exon 7. In vivo and in vitro expression data unveiled the physiological importance of TXNDC3d7 (whose expression was reduced in the patient) and the corresponding protein that was shown to bind microtubules. PCD is known to result from defects of the axoneme, an organelle common to respiratory cilia, embryonic nodal cilia, and sperm flagella, containing dynein arms, with, to date, the implication of genes encoding dynein proteins. Our findings, which identify a another class of molecules involved in PCD, disclose the key role of TXNDC3 in ciliary function; they also point to an unusual mechanism underlying a Mendelian disorder, which is an SNP-induced modification of the ratio of two physiological isoforms generated by alternative splicing. PMID:17360648

Essential Role of an Unusually Long-lived Tyrosyl Radical in the Response to Red Light of the Animal-like Cryptochrome aCRY*

PubMed Central

Oldemeyer, Sabine; Franz, Sophie; Wenzel, Sandra; Essen, Lars-Oliver; Mittag, Maria

2016-01-01

Cryptochromes constitute a group of flavin-binding blue light receptors in bacteria, fungi, plants, and insects. Recently, the response of cryptochromes to light was extended to nearly the entire visible spectral region on the basis of the activity of the animal-like cryptochrome aCRY in the green alga Chlamydomonas reinhardtii. This finding was explained by the absorption of red light by the flavin neutral radical as the dark state of the receptor, which then forms the anionic fully reduced state. In this study, time-resolved UV-visible spectroscopy on the full-length aCRY revealed an unusually long-lived tyrosyl radical with a lifetime of 2.6 s, which is present already 1 μs after red light illumination of the flavin radical. Mutational studies disclosed the tyrosine 373 close to the surface to form the long-lived radical and to be essential for photoreduction. This residue is conserved exclusively in the sequences of other putative aCRY proteins distinguishing them from conventional (6–4) photolyases. Size exclusion chromatography showed the full-length aCRY to be a dimer in the dark at 0.5 mm injected concentration with the C-terminal extension as the dimerization site. Upon illumination, partial oligomerization was observed via disulfide bridge formation at cysteine 482 in close proximity to tyrosine 373. The lack of any light response in the C-terminal extension as evidenced by FTIR spectroscopy differentiates aCRY from plant and Drosophila cryptochromes. These findings imply that aCRY might have evolved a different signaling mechanism via a light-triggered redox cascade culminating in photooxidation of a yet unknown substrate or binding partner. PMID:27189948

Spectroscopic characterization of a green copper site in a single-domain cupredoxin.

PubMed

Roger, Magali; Biaso, Frédéric; Castelle, Cindy J; Bauzan, Marielle; Chaspoul, Florence; Lojou, Elisabeth; Sciara, Giuliano; Caffarri, Stefano; Giudici-Orticoni, Marie-Thérèse; Ilbert, Marianne

2014-01-01

Cupredoxins are widespread copper-binding proteins, mainly involved in electron transfer pathways. They display a typical rigid greek key motif consisting of an eight stranded β-sandwich. A fascinating feature of cupredoxins is the natural diversity of their copper center geometry. These geometry variations give rise to drastic changes in their color, such as blue, green, red or purple. Based on several spectroscopic and structural analyses, a connection between the geometry of their copper-binding site and their color has been proposed. However, little is known about the relationship between such diversity of copper center geometry in cupredoxins and possible implications for function. This has been difficult to assess, as only a few naturally occurring green and red copper sites have been described so far. We report herein the spectrocopic characterization of a novel kind of single domain cupredoxin of green color, involved in a respiratory pathway of the acidophilic organism Acidithiobacillus ferrooxidans. Biochemical and spectroscopic characterization coupled to bioinformatics analysis reveal the existence of some unusual features for this novel member of the green cupredoxin sub-family. This protein has the highest redox potential reported to date for a green-type cupredoxin. It has a constrained green copper site insensitive to pH or temperature variations. It is a green-type cupredoxin found for the first time in a respiratory pathway. These unique properties might be explained by a region of unknown function never found in other cupredoxins, and by an unusual length of the loop between the second and the fourth copper ligands. These discoveries will impact our knowledge on non-engineered green copper sites, whose involvement in respiratory chains seems more widespread than initially thought.

Model studies of the Cu(B) site of cytochrome c oxidase utilizing a Zn(II) complex containing an imidazole-phenol cross-linked ligand.

PubMed

Pesavento, Russell P; Pratt, Derek A; Jeffers, Jerry; van der Donk, Wilfred A

2006-07-21

Cytochrome c oxidase, the enzyme complex responsible for the four-electron reduction of O2 to H2O, contains an unusual histidine-tyrosine cross-link in its bimetallic heme a3-CuB active site. We have synthesised an unhindered, tripodal chelating ligand, BPAIP, containing the unusual ortho-imidazole-phenol linkage, which mimics the coordination environment of the CuB center. The ligand was used to investigate the physicochemical (pKa, oxidation potential) and coordination properties of the imidazole-phenol linkage when bound to a dication. Zn(II) coordination lowers the pKa of the phenol by 0.6 log units, and increases the potential of the phenolate/phenoxyl radical couple by approximately 50 mV. These results are consistent with inductive withdrawal of electron density from the phenolic ring. Spectroscopic data and theoretical calculations (DFT) were used to establish that the cationic complex [Zn(BPAIP)Br]+ has an axially distorted trigonal bipyramidal structure, with three coordinating nitrogen ligands (two pyridine and one imidazole) occupying the equatorial plane and the bromide and the tertiary amine nitrogen of the tripod in the axial positions. Interestingly, the Zn-Namine bonding interaction is weak or absent in [Zn(BPAIP)Br]+ and the complex gains stability in basic solutions, as indicated by 1H NMR spectroscopy. These observations are supported by theoretical calculations (DFT), which suggest that the electron-donating capacity of the equatorial imidazole ligand can be varied by modulation of the protonation and/or redox state of the cross-linked phenol. Deprotonation of the phenol makes the equatorial imidazole a stronger sigma-donor, resulting in an increased Zn-Nimd interaction and thereby leading to distortion of the axial ligand axis toward a more tetrahedral geometry.

Hanging out at the airport: Unusual upside-down perching behavior by Eurasian Jackdaws (Corvus monedula) in a human-dominated environment

USGS Publications Warehouse

Katzner, Todd E.

2016-01-01

Animals occupying human-dominated environments show the capacity for behavioral flexibility. Corvids are among the most intelligent synanthropic bird species. During a layover at Schipol Airport in Amsterdam, Netherlands, I photographically documented Eurasian Jackdaws (Corvus monedula) perching upside down from a building cornice. In contrast to other reports of hanging birds, these jackdaws did not forage or play while upside down and appeared to use the perching spot to observe their surroundings. Although Corvids and Psittacines are known to hang upside down, especially in captive situations, such behaviors are rarely documented in the wild, and never before in association with human-built structures.