scholarly journals Photoelectrochemical Stability under Anodic and Cathodic Conditions of Meso-Tetra-(4-Sulfonatophenyl)-Porphyrinato Cobalt (II) Immobilized in Polypyrrole Thin Films

Polymers ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 657
Author(s):  
Jhon Puerres ◽  
Mauro Díaz ◽  
John Hurtado ◽  
Pablo Ortiz ◽  
María T. Cortés
Keyword(s):  
Raman Spectroscopy ◽  
Oxygen Reduction ◽  
Low Cost ◽  
The Other ◽  
Anodic Process ◽  
Polypyrrole Films ◽  
The Earth ◽  
Vis Spectroscopy ◽  
Cobalt Porphyrins

Cobalt porphyrins have emerged as promising catalysts for electrochemical and photoelectrochemical applications because of their good performance, low cost and the abundance of cobalt in the earth. Herein, a negatively charged porphyrin meso-tetra-(4-sulfonatophenyl)-porphin (TPPS) was immobilized in polypyrrole (PPy) during the electro-polymerization, and then it was metallized with cobalt to obtain meso-tetra-(4-sulfonatophenyl)-porphyrinato cobalt (II) (CoTPPS) as a dopant in PPy. The coatings were evaluated as photoelectrodes towards thiosulfate oxidation and oxygen reduction. For comparison purposes, the photoelectrochemical behavior of ClO4−-doped polypyrrole films was also evaluated. Characterizations by chronoamperometry, UV-Vis spectroscopy and Raman spectroscopy showed that polypyrrole is stable under anodic and cathodic conditions, but CoTPPS and TPPS immobilized in PPy are degraded during the anodic process. Thus, decreases in photocurrent of up to 87% and 97% for CoTPPS-doped PPy and TPPS-doped PPy were observed after a 30-min chronoamperometry test. On the other hand, good stability of CoTPPS and TPPS immobilized in PPy was observed during photoelectrochemical oxygen reduction, which was reflected in almost constant photocurrents obtained by chronoamperometry. These findings are relevant to understanding the role of CoTPPS as a catalyst or pre-catalyst in photoelectrochemical applications such as water splitting. In addition, these results could pave the way for further research to include CoTPPS-doped PPy in the design of novel photocathodes.

Membrane Potentials in Amoeba Proteus

1966 ◽  
Vol 45 (2) ◽  
pp. 251-267
Author(s):  
M. S. BINGLEY
Keyword(s):  
Plasma Membrane ◽  
Membrane Potential ◽  
Morphological Changes ◽  
Amoeba Proteus ◽  
Membrane Potentials ◽  
The Other ◽  
The Earth ◽  
Electrode Resistance ◽  
Alternating Voltage

1. Amoebae can be penetrated by microelectrodes at either end. One records voltage and the other supplies alternating current. 2. Step-like increases in alternating voltage superimposed on potentials recorded by the voltage electrode when in either the pseudopod or rear region demonstrate that low potentials recorded from a pseudopod and high ones from the rear region exist across a discrete impedance barrier. The only structure so far shown to fulfil this function is the plasma membrane. 3. A resistance inserted in the earth path monitors current flowing through the system and confirms observations made when recording with single electrodes that there is a reduction of electrode resistance when the cell is entered. 4. Pronounced depolarization in the rear region is shown when the current-carrying electrode penetrates the pseudopod, but not vice versa. 5. Morphological changes associated with membrane potential reversal are illustrated. 6. Consideration is given to the role of step-like potential changes in movement.

Thermal evolution of MnxOy nanofibres as catalysts for the oxygen reduction reaction

2017 ◽  
Vol 19 (42) ◽  
pp. 28781-28787 ◽  
Author(s):  
L. Delmondo ◽  
J. A. Muñoz-Tabares ◽  
A. Sacco ◽  
N. Garino ◽  
G. Massaglia ◽  
...  
Keyword(s):  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Crystalline Phase ◽  
Manganese Oxides ◽  
Thermal Evolution ◽  
Low Cost ◽  
Reduction Reaction ◽  
Electrospinning Technique ◽  
Catalytic Behaviour

The present study shows how, starting from green and low-cost precursors, nanostructured manganese oxides with good catalytic efficiencies for the oxygen reduction reaction can be fabricated through the electrospinning technique. The role of the crystalline phase and morphological features, on the electro-catalytic behaviour, is discussed.

scholarly journals The Role of Zinc(II) Ion in Fluorescence Tuning of Tridentate Pincers: A Review

Molecules ◽  
2020 ◽  
Vol 25 (21) ◽  
pp. 4984 ◽  
Author(s):  
Rosita Diana ◽  
Barbara Panunzi
Keyword(s):  
Low Cost ◽  
The Other ◽  
Donor Atom ◽  
Structural And Optical Properties ◽  
Tridentate Ligands ◽  
Emission Pattern ◽  
Excellent Candidate ◽  
Sulfur Donor

Tridentate ligands are simple low-cost pincers, easy to synthetize, and able to guarantee stability to the derived complexes. On the other hand, due to its unique mix of structural and optical properties, zinc(II) ion is an excellent candidate to modulate the emission pattern as desired. The present work is an overview of selected articles about zinc(II) complexes showing a tuned fluorescence response with respect to their tridentate ligands. A classification of the tridentate pincers was carried out according to the binding donor atom groups, specifically nitrogen, oxygen, and sulfur donor atoms, and depending on the structure obtained upon coordination. Fluorescence properties of the ligands and the related complexes were compared and discussed both in solution and in the solid state, keeping an eye on possible applications.

Stabilization and detection of nitroxyl by iron and cobalt porphyrins in solution and on surfaces

2010 ◽  
Vol 14 (12) ◽  
pp. 1012-1018 ◽  
Author(s):  
Fabio Doctorovich ◽  
Damian Bikiel ◽  
Juan Pellegrino ◽  
Sebastián A. Suárez ◽  
Marcelo A. Martí
Keyword(s):  
Heme Proteins ◽  
Chemical Reduction ◽  
Gold Surface ◽  
The Other ◽  
Biologically Relevant ◽  
Other Hand ◽  
Anion Complex ◽  
Cobalt Porphyrins ◽  
The One

Nitroxyl (HNO/NO-) is a small short-lived molecule that has been suggested to be produced by nitric oxide (NO) synthases under certain conditions. As for NO , biologically relevant targets of HNO are mainly heme-proteins and therefore, it has been difficult to discriminate the physio-pathological role of each molecule conclusively. Therefore, accurate discrimination between them is still an unresolved matter. On the other hand, there is only scarce information about nitroxyl-metalloporphyrin complexes. Hence, there is growing interest in obtaining and characterizing stable heme model nitroxyl complexes. In this review we show how HNO and NO can be discriminated electrochemically by a Co porphyrin attached to a gold surface, and how nitroxyl can be stabilized by coordination to an electron-poor Fe porphyrin. The Co porphyrin with four anchors, cobalt(II)-5,10,15,20-tetrakis[3-(p-acetylthio-propoxy)phenyl]porphyrin [Co(P)] was covalently attached to gold electrodes, and its reactions with NO and HNO donors were studied electrochemically. By fixing the potential to values that oxidize CoIII(P)NO- , HNO can be selectively detected by amperometric techniques. On the other hand, the one-electron chemical reduction of FeII(TFPPBr8)NO (TFPPBr8 = 2 ,3,7,8,12,13,17,18-octa-β-bromo-5,10,15,20-[tetrakis-(pentafluorophenyl)]porphyrin) with cobaltocene yields the significantly stable {FeNO}8 nitroxyl anion complex, [Co(C5H5)2]+[Fe(TFPPBr8)NO]- , which was isolated and characterized by several spectroscopies and DFT calculations. This species is intermediate between FeIINO- and FeINO , which is contrasted with the predominant FeIINO- character of known non-heme {FeNO}8 complexes.

scholarly journals Synthesis of Polyaniline in Seawater

Polymers ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 375 ◽  
Author(s):  
Takuya Yonehara ◽  
Kyoka Komaba ◽  
Hiromasa Goto
Keyword(s):  
Electrical Conductivity ◽  
Electron Spin Resonance ◽  
Conducting Polymer ◽  
Daily Life ◽  
Low Cost ◽  
Pure Water ◽  
Charge Carriers ◽  
The Earth ◽  
Spin Resonance

To date, polyaniline (PANI) has been synthesized in pure water. Aside from this, the application of PANI as a conducting polymer could be extended if it can be effectively synthesized in seawater, which constitutes 70% of the surface of the Earth. The production of functional plastics using natural resources without any additional purification would improve industrial production and enhance the comfort associated with our daily life. However, no examples of the effective application of seawater to PANI synthesis have been reported. Herein, PANI with an electrical conductivity of ~10−2 S/cm was synthesized in seawater as the reaction solvent. The electron spin resonance measurements confirmed the role of the polarons of PANI as charge carriers. In addition, a PANI/silk composite was prepared in seawater to produce a conducting cloth for further applications. The performance of the PANI prepared in seawater as the solvent was comparable to that of the PANI prepared in pure water. Thus, the proposed method allowed for the production of the conducting polymer via a convenient and low-cost method. This is the first study to report the usage of seawater as an abundant natural resource for synthesizing conducting polymers, promoting their wide application.

scholarly journals Felix Andries Vening Meinesz, 1887-1966

1967 ◽  
Vol 13 ◽  
pp. 294-308 ◽  
Keyword(s):  
The Netherlands ◽  
International Association ◽  
The Other ◽  
International Meeting ◽  
Mountainous Regions ◽  
The Earth ◽  
Gravity Measurements ◽  
Vening Meinesz ◽  
Technological University

Felix Andries Vening Meinesz was born at Scheveningen on 30 July 1887. He was one of the four children of Sjoerd Anne Vening Meinesz by his marriage to the Honourable Miss C. A. C. den Tex. His father was mayor of the towns of Rotterdam (1880-1890) and Amsterdam (1891-1901). Vening Meinesz attended primary and secondary schools at Amsterdam and in 1905 enrolled as a student at the Technological University of Delft, where he graduated in civil engineering in 1910. Vening Meinesz was at once offered employment by The Netherlands Geodetic Committee and was requested to take charge of the gravity measurements in the Netherlands. His appointment followed on 1 October 1910. Shortly before his death he recalled the accidental character of this decision which so much influenced his career. The significance of Vening Meinesz’s task with The Netherlands Geodetic Committee will be better understood if one keeps track of the discussions during the meetings of the International Association of Geodesy held between 1885 and 1910. As argued by Helmert, the role of the direction and the intensity of gravity in determining the shape of the earth was being stressed more and more. Helmert himself frequently reported on the pendulum observations contributed by different countries. However, he considered it desirable to determine the earth’s shape not only by means of arc measurements on the continents, but also by means of gravity measurements in the ocean areas. He had already noticed the relation between the intensity of gravity and the local constitution of the earth’s crust; on the other hand he suggested that the geologists should be careful not to draw premature conclusions. Thus according to The Netherlands Geodetic Committee in a report of 1889 concerning an international meeting in Paris: ‘Communications on the investigation of the intensity and the direction of gravity were very important. These could be used as an example of what could be performed in the Netherlands in this respect. For, although because of the minor differences in elevation and the uniformity of the landscape in this country, probably the results to be expected will not be as important as those obtained in more mountainous regions, observations of this kind are desirable in addition to the work accomplished in Germany and France.’

scholarly journals Figures and Mirrors in Demetrios Triklinios's 'Selenography'

2021 ◽  
pp. 54-73
Author(s):  
Divna Manolova
Keyword(s):  
Fourteenth Century ◽  
Visual Cognition ◽  
The Other ◽  
Lunar Theory ◽  
The Sun ◽  
The Moon ◽  
The Earth ◽  
Mediterranean World ◽  
The One

This article is about the interplay between diagrammatic representation, the mediation of mirrors, and visual cognition. It centres on Demetrios Triklinios (fl. ca. 1308–25/30) and his treatise on lunar theory. The latter includes, first, a discussion of the lunar phases and of the Moon's position in relation to the Sun, and second, a narrative and a pictorial description of the lunar surface. Demetrios Triklinios's Selenography is little-known (though edited in 1967 by Wasserstein) and not available in translation into a modern scholarly language. Therefore, one of the main goals of the present article is to introduce its context and contents and to lay down the foundations for their detailed study at a later stage. When discussing the Selenography, I refer to a bricolage consisting of the two earliest versions of the work preserved in Bayerische Staatsbibliothek, graecus 482, ff. 92r–95v (third quarter of the fourteenth century) and Paris, Bibliothèque nationale de France, graecus 2381, ff. 78r–79v (last quarter of the fourteenth century). I survey the available evidence concerning the role of Demetrios Triklinios (the author), John Astrapas (?) (the grapheus or scribe-painter), and Neophytos Prodromenos and Anonymus (the scribes-editors) in the production of the two manuscript copies. Next, I discuss the diagrams included in the Selenography and their functioning in relation to Triklinios's theory concerning the Moon as a mirror reflecting the geography of the Earth, on the one hand, and to the mirror experiment described by Triklinios, on the other. Finally, I demonstrate how, even though the Selenography is a work on lunar astronomy, it can also be read as a discussion focusing on the Mediterranean world and aiming at elevating its centrality and importance on a cosmic scale.

scholarly journals Role of Radial Artery Varians on Transradial Procedure

2015 ◽  
pp. 40-9
Author(s):  
Loretta C. Wangko ◽  
Bambang Budiono ◽  
Reggy L. Lefrandt
Keyword(s):  
Aortic Arch ◽  
Radial Artery ◽  
Low Cost ◽  
Coronary Intervention ◽  
The Other ◽  
Transradial Approach

Nowadays, transradial approach has become the most chosen procedure by the intervention cardiologists, either in diagnostic or coronary intervention. Possibilities of vascular variants of the radial artery and along the vascular axis until the aortic arch are not a reasonable challenge for not using this transradial approach. Complications due to the transradial approach are very rare and mostly are easier to be managed than due to the other approaches. Besides that, eary ambulation, comfortability and satisfaction of the patients, and a relative low cost lead it to be the most preferable one. Data and publication of variants along the axis of the radial artery to the aortic arch are very supporting to the procedure success. A thorough understanding and consideration about the variants can diminish the failure of this transradial approach or the crossover to another approach.

Note on Selection of Coordinate Systems for Geodynamics

1975 ◽  
Vol 26 ◽  
pp. 395-407
Author(s):  
S. Henriksen
Keyword(s):  
Sea Level ◽  
The Other ◽  
Coordinate Systems ◽  
Mean Sea Level ◽  
The Earth ◽  
The One ◽  
Static Systems ◽  
Selection Of

The first question to be answered, in seeking coordinate systems for geodynamics, is: what is geodynamics? The answer is, of course, that geodynamics is that part of geophysics which is concerned with movements of the Earth, as opposed to geostatics which is the physics of the stationary Earth. But as far as we know, there is no stationary Earth – epur sic monere. So geodynamics is actually coextensive with geophysics, and coordinate systems suitable for the one should be suitable for the other. At the present time, there are not many coordinate systems, if any, that can be identified with a static Earth. Certainly the only coordinate of aeronomic (atmospheric) interest is the height, and this is usually either as geodynamic height or as pressure. In oceanology, the most important coordinate is depth, and this, like heights in the atmosphere, is expressed as metric depth from mean sea level, as geodynamic depth, or as pressure. Only for the earth do we find “static” systems in use, ana even here there is real question as to whether the systems are dynamic or static. So it would seem that our answer to the question, of what kind, of coordinate systems are we seeking, must be that we are looking for the same systems as are used in geophysics, and these systems are dynamic in nature already – that is, their definition involvestime.

Plasma Levels of Protein S, Protein C, and Factor X: Effects of Sex, Hormonal State and Age

1995 ◽  
Vol 74 (05) ◽  
pp. 1271-1275 ◽  
Author(s):  
C M A Henkens ◽  
V J J Bom ◽  
W van der Schaaf ◽  
P M Pelsma ◽  
C Th Smit Sibinga ◽  
...  
Keyword(s):  
Regression Analysis ◽  
Postmenopausal Women ◽  
Protein C ◽  
Blood Donors ◽  
Premenopausal Women ◽  
Protein S ◽  
The Other ◽  
Factor X ◽  
Normal Ranges

SummaryWe measured total and free protein S (PS), protein C (PC) and factor X (FX) in 393 healthy blood donors to assess differences in relation to sex, hormonal state and age. All measured proteins were lower in women as compared to men, as were levels in premenopausal women as compared to postmenopausal women. Multiple regression analysis showed that both age and subgroup (men, pre- and postmenopausal women) were of significance for the levels of total and free PS and PC, the subgroup effect being caused by the differences between the premenopausal women and the other groups. This indicates a role of sex-hormones, most likely estrogens, in the regulation of levels of pro- and anticoagulant factors under physiologic conditions. These differences should be taken into account in daily clinical practice and may necessitate different normal ranges for men, pre- and postmenopausal women.

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