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Potential Shift (potential + shift)
Selected AbstractsElectrochemical Behavior and Detection of Dopamine and Ascorbic Acid at an Iron(II)tetrasulfophthalocyanine Modified Carbon Paste MicroelectrodeELECTROANALYSIS, Issue 10 2003Joshua Oni Abstract In this article the electrocatalytic behavior of an iron(II)tetrasulfophthalocyanine modified carbon paste microelectrode for the oxidation of dopamine (DA) and ascorbic acid (AA) is described. Although the oxidation potential of ascorbic acid is shifted by over 100,mV to more positive potentials, no peak separation could be obtained. This can be explained by the immediate homogeneous reduction of the oxidation product of dopamine by ascorbic acid in solution. However, this reaction induces a shift of the half-wave potential as a function of ratio of concentration of dopamine to ascorbic acid (cDA/cAA). Therefore it was possible to determine the cAA and cDA from this potential shift and the experimental peak current. Detection limits of 4.5±0.2×10,7 and 7.5±0.5×10,7,mol,L,1 were obtained respectively for dopamine and ascorbic acid for cDA/cAA>0.01. [source] Hydrogen peroxide-induced oxidative stress responses in Desulfovibrio vulgaris HildenboroughENVIRONMENTAL MICROBIOLOGY, Issue 10 2010Aifen Zhou Summary To understand how sulphate-reducing bacteria respond to oxidative stresses, the responses of Desulfovibrio vulgaris Hildenborough to H2O2 -induced stresses were investigated with transcriptomic, proteomic and genetic approaches. H2O2 and induced chemical species (e.g. polysulfide, ROS) and redox potential shift increased the expressions of the genes involved in detoxification, thioredoxin-dependent reduction system, protein and DNA repair, and decreased those involved in sulfate reduction, lactate oxidation and protein synthesis. A gene coexpression network analysis revealed complicated network interactions among differentially expressed genes, and suggested possible importance of several hypothetical genes in H2O2 stress. Also, most of the genes in PerR and Fur regulons were highly induced, and the abundance of a Fur regulon protein increased. Mutant analysis suggested that PerR and Fur are functionally overlapped in response to stresses induced by H2O2 and reaction products, and the upregulation of thioredoxin-dependent reduction genes was independent of PerR or Fur. It appears that induction of those stress response genes could contribute to the increased resistance of deletion mutants to H2O2 -induced stresses. In addition, a conceptual cellular model of D. vulgaris responses to H2O2 stress was constructed to illustrate that this bacterium may employ a complicated molecular mechanism to defend against the H2O2 -induced stresses. [source] Changes in direct current (DC) potentials and infra-slow EEG oscillations at the onset of the luteinizing hormone (LH) pulseEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2000Lisa Marshall Abstract An essential function of the neuroendocrine system lies in the coordination of hypothalamo-pituitary secretory activity with neocortical neuronal activity. Cortical direct current (DC) potential shifts and EEG were monitored in conjunction with the circulating concentration of luteinizing hormone (LH) in humans while asleep to assess a hypothalamic,neocortical interaction. The onset of an LH pulse was accompanied (i) at frontocortical locations by a transient positive DC potential shift of ,,3 min duration and peak amplitude 50 ,V; (ii) at frontal and central locations by an increase in power of infra-slow EEG oscillations for periodicities between 64 and 320 s. Results uniquely demonstrate a coupling of hypothalamo-pituitary activity with regulation of neocortical excitability. [source] Boundary element simulation of DC stray currents in oil industry due to cathodic protection interferenceEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 5 2007I. A. Metwally Abstract This paper presents a 3D theoretical simulation and analysis of DC stray current corrosion (SCC) in oil fields that could contribute to oil leak and finally oil deferment of electric submersible pump (ESP) systems. Application of the boundary element analysis system (BEASY) allowed cathodic protection (CP) interference to be assessed in terms of the normal current density, which is directly proportional to the corrosion rate, rather than using the qualitative approach of measuring the potential shift of the soil. Different real structures consisting of pipelines and/or well casings with different arrangements and interference conditions are simulated. The results reveal that the application of impressed current cathodic protection (ICCP) systems creates DC SCC on other nearby unprotected structures. This is an inherent potential problem with the application of such systems which dominates with decreasing soil conductivity, and/or increasing the anode current density and its proximity to the protected structures. On the contrary, SCC can be reduced by using multi-groundbed anodes. Copyright © 2006 John Wiley & Sons, Ltd. [source] Ethanol and Acetaldehyde Adsorption on a Carbon-Supported Pt Catalyst: A Comparative DEMS StudyFUEL CELLS, Issue 1-2 2004H. Wang Abstract The adsorption of ethanol and acetaldehyde on carbon Vulcan supported Pt fuel cell catalyst and the electrochemical desorption of the adsorption products were studied, using electrochemical measurements and differential electrochemical mass spectrosmetry (DEMS), under continuous flow conditions. Faradaic current adsorption transients at different constant adsorption potentials, which also include CO adsorption for comparison, show pronounced effects of the adsorption potential and the nature of the reactant molecule. Acetaldehyde adsorption is much faster than ethanol adsorption at all potentials. Pronounced Had induced blocking effects for ethanol adsorption are observed at very cathodic adsorption potentials, < 0.16,V, while for acetaldehyde adsorption this effect is much less significant. Comparison of the adsorption charge for CO adsorption with the H-upd charge allows differentiation between H-displacement and double-layer charging effects. Continuous bulk oxidation is observed for both reactants at potentials > 0.31,V; for acetaldehyde adsorption, increasing bulk reduction is found at low potentials. Based on the electron yield per CO2 molecule formed and on the similarity with the CO stripping characteristics the dominant stable adsorbate is CO, coadsorbed with smaller amounts of (partly oxidized) hydrocarbon decomposition fragments, which are also oxidized at higher potentials (> 0.85,V) and which can be reductively desorbed as methane or, to a very small extent, as ethane. The presence of small amounts of adsorbed C2 species and the oxidative dissociation of these species in the main CO oxidation potential range is clearly demonstrated by increased methane desorption after a potential shift to 0.85,V. The data demonstrate that the Pt/Vulcan catalyst is very reactive for C-C bond breaking upon adsorption of these reactants. [source] In situ Raman spectra of an NAD+ -modified silver electrode at various potentialsJOURNAL OF RAMAN SPECTROSCOPY, Issue 3 2004Haifeng Yang Abstract At various potentials, the in situ confocal Raman technique was employed to detect SERS signals from a silver electrode surface modified with NAD+ through a self-assembled monolayer (SAM) method. The SERS bands of the NAD+ molecule are much more sensitive to changes in the applied potential compared with experimental results reported previously. It is demonstrated in detail that the NAD+ molecules undergo reorientation at or desorption from the silver electrode surface with a potential shift from ,0.5 to 0.0 V vs a saturated calomel electrode based on a charge-transfer mechanism for explanation of the SERS signals. The effect of buffer electrolytes on the results of the SERS experiment was also investigated. Copyright © 2004 John Wiley & Sons, Ltd. [source] Chronic cerebrospinal venous insufficiency and multiple sclerosisANNALS OF NEUROLOGY, Issue 3 2010Omar Khan MD A chronic state of impaired venous drainage from the central nervous system, termed chronic cerebrospinal venous insufficiency (CCSVI), is claimed to be a pathologic phenomenon exclusively seen in multiple sclerosis (MS). This has invigorated the causal debate of MS and generated immense interest in the patient and scientific communities. A potential shift in the treatment paradigm of MS involving endovascular balloon angioplasty or venous stent placement has been proposed as well as conducted in small patient series. In some cases, it may have resulted in serious injury. In this Point of View, we discuss the recent investigations that led to the description of CCSVI as well as the conceptual and technical shortcomings that challenge the potential relationship of this phenomenon to MS. The need for conducting carefully designed and rigorously controlled studies to investigate CCVSI has been recognized by the scientific bodies engaged in MS research. Several scientific endeavors examining the presence of CCSVI in MS are being undertaken. At present, invasive and potentially dangerous endovascular procedures as therapy for patients with MS should be discouraged until such studies have been completed, analyzed, and debated in the scientific arena. ANN NEUROL 2010;67:286,290 [source] Influence of the Protonic State of an Imidazole-Containing Ligand on the Electrochemical and Photophysical Properties of a Ruthenium(II),Polypyridine-Type ComplexCHEMISTRY - A EUROPEAN JOURNAL, Issue 29 2007Annamaria Quaranta Dr. Abstract The synthesis and characterisation of [Ru(bpy)2(PhenImHPh)]2+ where PhenImHPh represents the 2-(3,5-di- tert -butylphenyl)imidazo[4,5- f][1,10]phenanthroline ligand are described. The compounds issued from the three different protonic states of the imidazole ring [Ru(bpy)2(PhenImPh)]+ (I), [Ru(bpy)2(PhenImHPh)]2+ (II) and [Ru(bpy)2(PhenImH2Ph)]3+ (III) were isolated and spectroscopically characterised. The X-ray structures of [Ru(bpy)2(PhenImPh)](PF6),H2O,6,MeOH, [Ru(bpy)2(PhenImHPh)](NO3)2,H2O,3,MeOH and [Ru(bpy)2(PhenImH2Ph)](PF6)3, 5,H2O are reported. Electrochemical data obtained on these complexes indicate almost no potential shift for the RuIII/II redox couple. Therefore a Coulombic effect between the imidazole ring and the metal centre can be ruled out. The monooxidised forms of I and II have been characterised by EPR spectroscopy and are reminiscent of the presence of a radical species. The emission properties of the parent compound [Ru(bpy)2(PhenImHPh)]2+ were studied as a function of pH and both the lifetimes and intensities decreased upon deprotonation. Photophysical properties, investigated in the absence and presence of an electron acceptor (methylviologen), were distinctly different for the three compounds. Transient absorption features indicate that unique excited states are involved. Theoretical data obtained from DFT calculations in water on the three protonic forms are presented and discussed in the light of the experimental results. [source] DC electrical stimulation of the pretectal thalamus and its effects on the feeding behavior of the toad (Bufo bufo)DEVELOPMENTAL NEUROBIOLOGY, Issue 7 2007James McConville Abstract The feeding motivation of the common European common toad (Bufo bufo) can be quantified by the feeding sequence of arousal-orientation-approach-fixate-snap. Previous work has found that the optic tectum is an important structure responsible for the mediation of feeding behaviors, and combined electrical and visual stimulation of the optic tectum was found to increase the animals feeding behaviors. However, the pretectal thalamus has an inhibitory influence upon the optic tectum and its lesion results in disinhibited feeding behaviors. This suggests that feeding behavior of anurans is also subject to influence from the pretectal thalamus. Previous studies involving the application of DC stimulation to brain tissue has generated slow potential shifts and these shifts have been implicated in the modulation of the neural mechanisms associated with behavior. The current study investigated the application of DC stimulation to the diencephalon surface dorsal to the lateral posterodorsal pretectal thalamic nucleus in Bufo bufo, in order to assess effects on feeding motivation. The application of DC stimulation increased the incidence of avoidance behaviors to a visual prey stimulus while reducing the prey catching behavior component of approach, suggesting that the DC current applied to the pretectum increased the inhibition upon the feeding elements of the optic tectum. This can be explained by the generation of slow potential shifts. © 2007 Wiley Periodicals, Inc. Develop Neurobiol, 2007. [source] Effect of cortical spreading depression on synaptic transmission of rat hippocampal tissuesEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 5 2006Brigitta Wernsmann Abstract Cortical spreading depression (CSD) is believed to be a putative neuronal mechanism underlying migraine aura and subsequent pain. In vitro and ex vivo/in vitro brain slice techniques were used to investigate CSD effects on the field excitatory postsynaptic potentials (fEPSP) and tetanus-induced long-term potentiation (LTP) in combined rat hippocampus,cortex slices. Induction of CSD in combined hippocampus,cortex slices in which DC negative deflections did not propagate from neocortex to hippocampus significantly augmented fEPSP amplitude and LTP in the hippocampus. Propagation of CSD to the hippocampus resulted in a transient suppression followed by reinstatement of fEPSP with amplitude of pre-CSD levels. LTP was inhibited when DC potential shifts were recorded in the hippocampus. Furthermore, CSD was induced in anaesthetized rats and, thereafter, hippocampal tissues were examined in vitro. LTP was significantly enhanced in hippocampal slices obtained from ipsilateral site to the hemisphere in which CSD was evoked. The results indicate the disturbances of hippocampal synaptic transmission triggered by propagation of CSD. This perturbation of hippocampal synaptic transmission induced by CSD may relate to some symptoms occurring during migraine attacks, such as amnesia and hyperactivity. [source] Changes in direct current (DC) potentials and infra-slow EEG oscillations at the onset of the luteinizing hormone (LH) pulseEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2000Lisa Marshall Abstract An essential function of the neuroendocrine system lies in the coordination of hypothalamo-pituitary secretory activity with neocortical neuronal activity. Cortical direct current (DC) potential shifts and EEG were monitored in conjunction with the circulating concentration of luteinizing hormone (LH) in humans while asleep to assess a hypothalamic,neocortical interaction. The onset of an LH pulse was accompanied (i) at frontocortical locations by a transient positive DC potential shift of ,,3 min duration and peak amplitude 50 ,V; (ii) at frontal and central locations by an increase in power of infra-slow EEG oscillations for periodicities between 64 and 320 s. Results uniquely demonstrate a coupling of hypothalamo-pituitary activity with regulation of neocortical excitability. [source] Development Section, April 2008GEOGRAPHY COMPASS (ELECTRONIC), Issue 3 2008Cheryl McEwan EDITORIAL It is a great privilege to serve as Editor for the Development section of Geography Compass. The journal is an exciting new venture in electronic publishing that aims to publish state-of-the-art peer-reviewed surveys of key contemporary issues in geographical scholarship. As the first Editor of this section, it is my responsibility to establish the key aims and innovations for this section of the journal. These include: publishing reviews of scholarship on topics of contemporary relevance that are accessible and useful to researchers, teachers, students and practitioners; developing the range of topics covered across the spectrum of development geography; helping to set agendas in development geography by identifying gaps in existing empirical and conceptual research; commissioning articles from both established and graduate/early career researchers who are working at the frontiers of development geography; and communicating the distinctiveness of Geography Compass. Part of this distinctiveness is in publishing articles that are both of scholarly excellence and accessible to a wide audience. The first volume of Geography Compass was published in 2007, covering a wide range of topics (e.g. migration, children, technology, grassroots women's organizations, civil society, biodiversity, tourism, inequality, agrarian change, participatory development, disability, spirituality) in a number of specific geographical areas (e.g. Africa/southern Africa, Caribbean, China, Peru). Forthcoming in 2008/2009 are articles on the Gambia, Latin America, the Philippines, Southeast Asia, Bangladesh and South Africa, focusing on topics such as food security, comparative post-socialism, foreign aid and fair trade. Building on these diverse and excellent articles, I plan to communicate the distinctiveness of Development in a number of ways. First, I encourage an ecumenical approach to the notion of ,development geography' and welcome contributions from scholars across a range of social science disciplines whose work would be useful to a geography audience. This is important, not least because both development and geography, in disciplinary terms, are largely European inventions. Many scholars in Latin America, Africa and Asia, for example, do not refer to themselves as either development specialists or geographers but are producing important research in areas of direct relevance to students and researchers of ,development geography'. As the first editions illustrate, I also seek to publish articles that reflect ,development' in its broadest sense, encompassing economic, (geo)political, social, cultural and environmental issues. 2008 will be an interesting year for development, with a number of important issues and events shaping discourse and policy. These include: the Beijing Olympics and increasing focus on China's role in international development; political change in a number of African countries (Kenya, Zimbabwe, South Africa); the US presidential elections and potential shifts in policy on climate change, trade and security; the impacts of the Bali roadmap on climate change in the current economic context; the increasing number of impoverished people in Asia (notably China and India), sub-Saharan Africa and Latin America (notably Brazil) that even the World Bank has acknowledged; the implications of the increasing role of philanthropic foundations (e.g. the Gates Foundation and those emerging in India and Russia) in international development. I hope to see some of these issues covered in this journal. Second, I am keen to break down the association between ,development' and parts of the world variously categorized as ,Third World', ,Global South' or ,Developing World' by publishing articles that cut across North and South, East and West. The intellectual and disciplinary practices within (Western) geography that separate those researching issues in the South and post-socialist contexts from those researching similar issues in advanced capitalist economies are, it seems, no longer sustainable or sensible. Moreover, while studies of transnational and ethical trade, neoliberalism, household economies and ,commodity chains', for example, incorporate a multitude of case studies from across the world, these tend to be understood through conceptual lenses that almost always have their theoretical antecedents in Western theorization. The notion of ,learning from' debates, policy and practice in other parts of the world is still relatively alien within the discipline. There are thus issues in how we research and teach ethically and responsibly in and about different parts of the world, and in which this journal might make a contribution. Third, and related, part of my responsibility is to ensure that Compass reflects the breadth of debate about ,development' by publishing articles written by a truly international range of scholars. This has proved to be a challenge to date, in part reflecting the newness of the journal and the difficulties posed by English language publication. However, an immediate aim is to publish the work and ideas of scholars based outside of Anglophone contexts, in the Global South and in post-socialist contexts, and to use international referees who are able to provide valuable commentaries on the articles. A longer-term aim is to also further internationalize the Editorial Board. Currently, one-third of the Editorial Board is non-UK and I plan to increase this to at least 50% in future. Fourth, I plan to ensure that the Development section takes full advantage of electronic publication and the opportunities this offers. Thus, while I am keen to retain a word limit in the interest of publishing accessible articles, the lack of constraint regarding page space enables authors to include a wide range of illustrative and other material that is impossible in print journals. I plan to encourage authors to make greater use of visual materials (maps, photographs/photo-essays, video, sound recordings, model simulations and datasets) alongside text as well as more innovative forms of presentation where this might be appropriate. Finally, in the coming year, I intend to work more closely with other Compass section Editors to realize the potential for fostering debate that cuts across subdisciplinary and even disciplinary boundaries. The journal publishes across the full spectrum of the discipline and there is thus scope for publishing articles and/or special issues on development-related topics that might best be approached through dialogue between the natural and social sciences. Such topics might include resources (e.g. water, oil, bio-fuels), hazard and risk (from environmental issues to human and state security), and sustainability and quality of life (planned for 2008). Part of the distinctiveness of Compass is that electronic-only publication ensures that articles are published in relatively quick time , in some cases less than 3 months from initial submission to publication. It thus provides an important outlet for researchers working in fast-changing contexts and for those, such as graduate and early-career researchers, who might require swift publication for career purposes. Of course, as Editor I am reliant on referees both engaging with Manuscript Central and providing reports on articles in a relatively short space of time to fully expedite the process. My experience so far has been generally very positive and I would like to thank the referees for working within the spirit of the journal. Editing a journal is, of course, a collaborative and shared endeavour. The Development Editorial Board has been central to the successful launch of Development by working so generously to highlight topics and potential authors and to review articles; I would like to take this opportunity to thank Tony Bebbington, Reg Cline-Cole, Sara Kindon, Claire Mercer, Giles Mohan, Warwick Murray, Richa Nagar, Rob Potter, Saraswati Raju, Jonathan Rigg, Jenny Robinson and Alison Stenning. The Editors-in-Chief , Mike Bradshaw and Basil Gomez , have provided invaluable advice while adding humour (and colour) to the editorial process. Colleagues at Wiley-Blackwell have provided superb support, in particular, Helen Ashton who is constantly on hand to provide advice and assistance. I look forward to working closely with these people again in the coming year, as well as with the authors and readers who are vital to ensuring that Geography Compass fulfils its remit. [source] | |||||||||||||