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1
CaMinade, Anne Marie, Fayez El Khatib, Max Koenig, and Jean Marie Aubry. "Ozonides de phosphite source d'oxygène singulet: rendement, mécanisme." Canadian Journal of Chemistry 63, no. 11 (November 1, 1985): 3203–9. http://dx.doi.org/10.1139/v85-530.
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The ozonides of several phosphites in solution in dichloromethane have been reacted with some scavengers of singlet oxygen (1O2) like rubrene (2), tetraphenylcyclopentadienone (4), and 9,10-diphenylanthracene (6). These ozonides react on the scavengers (−47 °C < t <30 °C) upon their decomposition. The Foote curves obtained by varying the respective concentrations of ozonides and of scavengers lead to parameters similar to those obtained upon the photooxidation of the scavengers by 1O2. Results confirm that these ozonides can lead to the formation of 1O2. The absolute yield of 1O2 is 100% (ρ = 1). These results also confirm the high efficiency of the rubrene toward 1O2 (γ = 1) and the lower efficiency of the tetraphenylcyclopentadienone (γ = 0.46). However, the low value (γ = 0.3) for the efficiency of the 9,10-diphenylanthracene (4) is unexpected.
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Al-Mumen, Haider, Fubo Rao, Wen Li, and Lixin Dong. "Singular Sheet Etching of Graphene with Oxygen Plasma." Nano-Micro Letters 6, no. 2 (March 20, 2014): 116–24. http://dx.doi.org/10.1007/bf03353775.
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Alkahtani, Badr S., Obaid J. Algahtani, Ravi Shanker Dubey, and Pranay Goswami. "Solution of fractional oxygen diffusion problem having without singular kernel." Journal of Nonlinear Sciences and Applications 10, no. 1 (January 29, 2017): 299–307. http://dx.doi.org/10.22436/jnsa.010.01.28.
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Barlow, Clyde H., Katherine A. Kelly, and Jeffrey J. Kelly. "Simultaneous Determination of Hemoglobin and Myoglobin Oxygen Binding Curves by Spectral Curve Fitting." Applied Spectroscopy 46, no. 5 (May 1992): 758–63. http://dx.doi.org/10.1366/0003702924124763.
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A completely optical method is described for the simultaneous determination of hemoglobin and myoglobin oxygen saturation. Solution oxygen concentrations were computed from measurements of phosphorescence decay of a soluble palladium porphyrin using the Stern-Volmer quenching relationship. Visible absorption spectra were recorded of hemoglobin/myoglobin mixtures progressively deoxygenated by bacterial aerobic metabolism. Separate hemoglobin and myoglobin oxygenation curves were resolved from the spectra of solutions containing both proteins by curve fitting, with the use of singular value decomposition of the spectra vs. oxygen concentration matrix. The method yielded a P50 of 1.2 Torr for horse heart myoglobin at 24 ± 1°C, while the P50 for sheep hemoglobin was 23 Torr at the same temperature. These values, obtained from mixtures, compare favorably with literature values determined for hemoglobin and myoglobin separately.
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Gupta, Santosh K., B. Modak, Debarati Das, P. Modak, A. K. Yadav, and K. Sudarshan. "Multiphoton light emission in barium stannate perovskites driven by oxygen vacancies, Eu3+ and La3+: accessing the role of defects and local structures." Physical Chemistry Chemical Physics 23, no. 32 (2021): 17479–92. http://dx.doi.org/10.1039/d1cp02349g.
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The work probes the multicolor emission in BaSnO3 perovskite, singular orange emission in BaSnO3:Eu3+ and quantum yield suppression in BaSnO3:Eu3+, La3+ using XRD, photoluminescence, positron annihilation measurements and DFT calculations.
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Poulet, Patrick, Renée Chabrier, and Thérèse Schunck. "Calorimetrie photoacoustique des réactions de photosensibilisation induites par l'oxygène singulet The photoacoustic calorimetry of photosensitized reactions induced by singlet oxygen." Journal of Optics 28, no. 6 (December 1997): 252–59. http://dx.doi.org/10.1088/0150-536x/28/6/004.
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Sekerci, Yadigar, and Ramazan Ozarslan. "Respiration Effect on Plankton–Oxygen Dynamics in view of non-singular time fractional derivatives." Physica A: Statistical Mechanics and its Applications 553 (September 2020): 123942. http://dx.doi.org/10.1016/j.physa.2019.123942.
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Zuev, Vladimir V., Svetlana L. Bondarenko, and Irina G. Ustinova. "Additive singular spectral model of a dendrochronological signal." Bulletin of the Tomsk Polytechnic University Geo Assets Engineering 334, no. 12 (December 27, 2023): 56–64. http://dx.doi.org/10.18799/24131830/2023/12/4282.
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Relevance. Allocation of structural components in a dendrochronological signal of annual rings of coniferous trees expands the possibilities of the bioindication method and allows obtaining information about changes in environmental conditions in the past for extended territories. Aim. Creation of an additive singular spectral model based on the frequency trigonometric components of the dendrochronological signal; reconstruction of changes in the total ozone content in the atmosphere in the past, affecting the level of ultraviolet radiation in the B range radiation. Objects. Time series of total ozone content in the atmosphere (data from 1932), width and density of annual rings (data from 1686–2004) on the example of the territory near the observatory in Arosa, Switzerland, time series of stable oxygen isotopes δ18Oc, France. Methods. Time series analysis (decomposition of a time series, identification of model parameters, prediction of a time series), statistical analysis (F-criterion, χ2 – Pearson criterion), experimental measurements of the percentage components of the wood of annual rings, correlation analysis, spectral singular analysis. Results. Decomposition of the dendrochronological signal of individual chronologies into trigonometric components in the Caterpillar program. Correlation analysis of the sensitivity of trees to atmospheric effects. Reconstruction of the ozone level in the stratosphere using the first trigonometric component of the dendrochronological signal. In cellulose, the first low-frequency component of the signal and the structural component of wood, a reliable response of trees to long-period fluctuations in the total ozone content is recorded. This allows assessment of the impact of the stress factor on conditions of exploitation of forest resources. The use of data on the width of the annual rings allows you to expand the territorial boundaries of the method.
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Zhang, Feng, Jilin Fan, Fei Qiu, Bing Xie, Xianghui Li, and Hui Zhang. "An enhanced accuracy method to determine oil saturation by carbon/oxygen logging in tight reservoirs." GEOPHYSICS 87, no. 2 (February 1, 2022): D21—D31. http://dx.doi.org/10.1190/geo2021-0309.1.
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The low porosity and permeability characteristics of tight oil reservoirs have brought challenges to monitoring oil saturation recently. Although carbon/oxygen logging is effective for oil saturation evaluation, the statistical fluctuations of the measured energy spectrum in tight reservoirs make it impossible to distinguish the different signals between oil and water. Thus, noise adjusted singular-value decomposition (NASVD) is applied to denoise the raw energy spectrum and evaluate the oil saturation quantitatively. The energy spectrum matrix, which is composed of the energy spectrum of the measurement point and its adjacent depth points, is decomposed and reconstructed to remove noninformative signals and improve the signal-to-noise ratio of the raw energy spectrum. The parameter K evaluates the smoothness of the logging curves, reflecting the influence of the number of energy spectra and singular values on NASVD. Meanwhile, the NASVD, Savitzky-Golay filtering, and depth averaging methods are compared for calculating the accuracy of C/O, Si/Ca, and oil saturation with the Monte Carlo method, indicating that the NASVD is better than the other two methods for eliminating the statistical fluctuations of the raw energy spectrum. A simulation example indicates that the NASVD can control the calculation errors of tight reservoir oil saturation to within 15%, which significantly improves the accuracy of the estimated oil saturation. An oil field example indicates that the oil saturation interpretation result for tight reservoirs is in good agreement with the oil saturation from open-hole log analysis, signifying that the NASVD energy spectrum denoising method can provide a quantitative estimate of oil saturation in tight oil reservoirs.
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Roul, Pradip, and Ujwal Warbhe. "A New Homotopy Perturbation Scheme for Solving Singular Boundary Value Problems Arising in Various Physical Models." Zeitschrift für Naturforschung A 72, no. 8 (August 28, 2017): 733–43. http://dx.doi.org/10.1515/zna-2017-0141.
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AbstractThe classical homotopy perturbation method proposed by J. H. He, Comput. Methods Appl. Mech. Eng. 178, 257 (1999) is useful for obtaining the approximate solutions for a wide class of nonlinear problems in terms of series with easily calculable components. However, in some cases, it has been found that this method results in slowly convergent series. To overcome the shortcoming, we present a new reliable algorithm called the domain decomposition homotopy perturbation method (DDHPM) to solve a class of singular two-point boundary value problems with Neumann and Robin-type boundary conditions arising in various physical models. Five numerical examples are presented to demonstrate the accuracy and applicability of our method, including thermal explosion, oxygen-diffusion in a spherical cell and heat conduction through a solid with heat generation. A comparison is made between the proposed technique and other existing seminumerical or numerical techniques. Numerical results reveal that only two or three iterations lead to high accuracy of the solution and this newly improved technique introduces a powerful improvement for solving nonlinear singular boundary value problems (SBVPs).
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Harismah, Kun, Mahmoud Mirzaei, and Reza Moradi. "DFT Studies of Single Lithium Adsorption on Coronene." Zeitschrift für Naturforschung A 73, no. 8 (August 28, 2018): 685–91. http://dx.doi.org/10.1515/zna-2017-0458.
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AbstractDensity functional theory (DFT) calculations were performed to study the adsorption of neutral and cationic forms of single lithium (Li) on representative original and each of oxygen/sulfur-terminated coronene monolayer surfaces. First, the monolayers of coronene structures were prepared. Next, Li/Li+ adsorptions were investigated on the surfaces of the already optimised coronene models. The results indicate that the singular coronene models can be considered as appropriate surfaces for Li/Li+ adsorption, with stronger Li+ adsorption. Localisations of LI/Li+ species were carefully examined at the central carbon zone of the monolayer surface; however, only one model showed discrepancy by getting localised at the monolayer edge. Energy levels and distribution patters for the molecular orbitals indicate the effects of atomic terminations and Li/Li+ adsorptions, in which the singular and Li+-adsorbed models reveal identical results. Atomic-scale nuclear quadrupole resonance (NQR) properties were also evaluated, with the results indicating that the atomic properties can determine the major electronic properties for applying the coronene structure for specific applications.
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Uhl, Werner, Mohammad R. Halvagar, Henrik R. Bock, Beate Jasper-Peter, and Marcus Layh. "New Organogallium Peroxides." Zeitschrift für Naturforschung B 64, no. 11-12 (December 1, 2009): 1369–74. http://dx.doi.org/10.1515/znb-2009-11-1217.
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Treatment of (Me3C)2Ga-CH(SiMe3)2 (1) with oxygen gave the oxidation of both quaternary carbon atoms of the tert-butyl groups, while the bis(trimethylsilyl)methyl substituent was not affected. One tert-butyl group was transferred to an alkoxide which in the dimeric formula unit of the product 2 occupies the bridging position between both gallium atoms. The second one afforded a terminally arranged tert-butylperoxo ligand by the insertion of a complete oxygen molecule into the respective Ga-C bond. Another organogallium peroxide (5) was obtained by the reaction of Li(OEt2)[H3GaCH(SiMe3)2] (3) with H-O-O-CMe2OMe (4). Two hydrido ligands of the trihydridogallanate were replaced by peroxo groups, while the third Ga-H bond gave a hydroxide (Ga-OH) by insertion of a single oxygen atom. The product, Li[Ga(OH)(OOCMe2OMe)2R] [5, R=CH(SiMe3)2], forms a singular dimeric formula unit with a complicated oligocyclic structure in which all peroxo groups are in bridging positions between lithium and gallium atoms
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Zabolotsky, S. V., G. A. Novikov, and N. L. Gusakova. "Globin proteins in evolution vertebrata." Тенденции развития науки и образования 96, no. 7 (2023): 116–20. http://dx.doi.org/10.18411/trnio-04-2023-370.
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Globins are heme-containing proteins involved in the binding and transport of oxygen, though they also have other functions. These proteins are present in a wide variety of organisms. Formed at an early stage in the development of life on Earth, this group of proteins has made a significant contribution to the development of various groups of organisms. These proteins originated from a singular predecessor that gave rise to three different evolutionary branches of proteins. In this article we give a brief overview of how this group diversified in Vertebrata as well as their evolutionary significance.
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Lorca, Sebastián, Javier Torres, José L. Serrano, José Pérez, José Abad, Florencio Santos, and Antonio J. Fernández Romero. "Bifunctional P-Containing RuO2 Catalysts Prepared from Surplus Ru Co-Ordination Complexes and Applied to Zn/Air Batteries." Nanomaterials 13, no. 1 (December 26, 2022): 115. http://dx.doi.org/10.3390/nano13010115.
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An innovative synthetic route that involves the thermal treatment of selected Ru co−ordination complexes was used to prepare RuO2-based materials with catalytic activity for oxygen reduction (ORR) and oxygen evolution (OER) reactions. Extensive characterization confirmed the presence of Ru metal and RuP3O9 in the materials, with an improved electrocatalytic performance obtained from calcinated [(RuCl2(PPh3)3]. A mechanistic approach for the obtention of such singular blends and for the synergetic contribution of these three species to electrocatalysis is suggested. Catalysts added to carbon−based electrodes were also tested in all−solid and flooded alkaline Zn/air batteries. The former displayed a specific discharge capacity of 10.5 A h g−1 at 250 mA g−1 and a power density of 4.4 kW kg−1 cm−2. Besides, more than 800 discharge/charge cycles were reached in the flooded alkaline Zn/air battery
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Mouridsen, Kim, Mikkel Bo Hansen, Leif Østergaard, and Sune Nørhøj Jespersen. "Reliable Estimation of Capillary Transit Time Distributions Using DSC-MRI." Journal of Cerebral Blood Flow & Metabolism 34, no. 9 (June 18, 2014): 1511–21. http://dx.doi.org/10.1038/jcbfm.2014.111.
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The regional availability of oxygen in brain tissue is traditionally inferred from the magnitude of cerebral blood flow ( CBF) and the concentration of oxygen in arterial blood. Measurements of CBF are therefore widely used in the localization of neuronal response to stimulation and in the evaluation of patients suspected of acute ischemic stroke or flow-limiting carotid stenosis. It was recently demonstrated that capillary transit time heterogeneity ( CTH) limits maximum oxygen extraction fraction ( OEFmax) that can be achieved for a given CBF. Here we present a statistical approach for determining CTH, mean transit time ( MTT), and CBF using dynamic susceptibility contrast magnetic resonance imaging (DSC-MRI). Using numerical simulations, we demonstrate that CTH, MTT, and OEFmax can be estimated with low bias and variance across a wide range of microvascular flow patterns, even at modest signal-to-noise ratios. Mean transit time estimated by singular value decomposition (SVD) deconvolution, however, is confounded by CTH. The proposed technique readily identifies malperfused tissue in acute stroke patients and appears to highlight information not detected by the standard SVD technique. We speculate that this technique permits the non-invasive detection of tissue with impaired oxygen delivery in neurologic disorders such as acute ischemic stroke and Alzheimer's disease during routine diagnostic imaging.
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Mahalingam, Malini, S. Feba, Viveka Veeramani, Rachit Mehta, and Indira Jayakumar. "Unveiling the therapeutic marvel: HHHFNC oxygen therapy in paediatric HSCT patients - A tale of singular excellence." Pediatric Hematology Oncology Journal 8, no. 4 (2023): S92. http://dx.doi.org/10.1016/j.phoj.2023.10.245.
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Pavoni, Eleonora, Elaheh Mohebbi, Pierluigi Stipa, Davide Mencarelli, Luca Pierantoni, and Emiliano Laudadio. "The Role of Zr on Monoclinic and Orthorhombic HfxZryO2 Systems: A First-Principles Study." Materials 15, no. 12 (June 13, 2022): 4175. http://dx.doi.org/10.3390/ma15124175.
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HfO2 shows different polymorphs, including monoclinic and orthorhombic ones, that exhibit singular properties. Moreover, the character of HfO2 is also influenced by the Zr atoms as a doping agent. Here, an extensive study of the monoclinic P21/c and the orthorhombic Pca21 polymorphs of HfO2, Hf0.75Zr0.25O2, and Hf0.5Zr0.5O2 is reported. For all six systems, density functional theory (DFT) methods based on generalized gradient approximations (GGAs) were first used; then the GGA + U method was settled and calibrated to describe the electrical and optical properties of polymorphs and the responses to the oxygen vacancies. Zr had different effects in relation to the polymorph; moreover, the amount of Zr led to important differences in the optical properties of the Pca21 polymorph. Finally, oxygen vacancies were investigated, showing an important modulation of the properties of HfxZryO2 nanostructures. The combined GGA and GGA + U methods adopted in this work generate a reasonable prediction of the physicochemical properties of o- and m-HfxZryO2, identifying the effects of doping phenomena.
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CE, Fernandes. "Histopathology: an Ancient Technique for a New Insight in the Ecotoxicology." International Journal of Zoology and Animal Biology 7, no. 6 (2024): 1–2. https://doi.org/10.23880/izab-16000630.
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The biotic integrity of an ecological system is often reflected in the health of the organisms that inhabit it. In aquatic ecosystems, fish and amphibians, particularly those species at the top of the food chain, are representative bioindicators of the system’s overall health. In general, aquatic organisms in their natural environments are typically exposed to numerous stressors, includaing adverse or fluctuating temperatures, poor water quality and sediment loads, low dissolved oxygen concentrations, limited food availability, and other episodic variables. In addition, anthropogenic stressors such as contaminant loads (e.g., agrochemical compounds) can add to the insults already experienced by these organisms in many aquatic systems. In this context, the histopathology is a singular tool in ecotoxicological studies.
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Ji, Yun-qing, Min Jiang, Xiao-xuan Deng, Chun-yang Liu, Fu-xiang Huang, and Xin-hua Wang. "Study on the utilization of supersaturation degree in Al deoxidation to improve cleanliness and control of Al2O3 inclusions in ultra-low carbon steel." Metallurgical Research & Technology 118, no. 3 (2021): 308. http://dx.doi.org/10.1051/metal/2021007.
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Effects of supersaturation degree (S) in Al deoxidation on cleanliness and alumina inclusions in steel were studied. If enough Al was added to steel, higher initial dissolve oxygen before Al deoxidation resulted in higher steel cleanliness. In the experiments, with the rise of [mass% O] from 102 ppm to 340 ppm and 931 ppm, logS in steel melts were increased from 4.8, to 7.0 and 8.8, respectively. As a result, total oxygen (T.O) was decreased to 25 ppm, 22 ppm and 21 ppm, respectively. Based on the results, important influence of supersaturation degree on the formation of Al2O3 was revealed. At lower S, Al2O3 would be singular and smaller particles ≤ 5 µm that was difficult to be removed. However, Al2O3 would exist as large clusters in steel at higher S, which can be efficiently removed. By utilizing the findings in laboratory, RH refining of ultra-low-carbon steel was optimized. Steel cleanness and control of inclusions were improved. As a result, surface defects in cold rolling sheets caused by Al2O3 inclusions were effectively minimized.
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Weber, Roy E., Angela Fago, Hans Malte, Jay F. Storz, and Thomas A. Gorr. "Lack of conventional oxygen-linked proton and anion binding sites does not impair allosteric regulation of oxygen binding in dwarf caiman hemoglobin." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 305, no. 3 (August 1, 2013): R300—R312. http://dx.doi.org/10.1152/ajpregu.00014.2013.
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In contrast to other vertebrate hemoglobins (Hbs) whose high intrinsic O2 affinities are reduced by red cell allosteric effectors (mainly protons, CO2, organic phosphates, and chloride ions), crocodilian Hbs exhibit low sensitivity to organic phosphates and high sensitivity to bicarbonate (HCO3−), which is believed to augment Hb-O2 unloading during diving and postprandial alkaline tides when blood HCO3− levels and metabolic rates increase. Examination of α- and β-globin amino acid sequences of dwarf caiman ( Paleosuchus palpebrosus) revealed a unique combination of substitutions at key effector binding sites compared with other vertebrate and crocodilian Hbs: β82Lys→Gln, β143His→Val, and β146His→Tyr. These substitutions delete positive charges and, along with other distinctive changes in residue charge and polarity, may be expected to disrupt allosteric regulation of Hb-O2 affinity. Strikingly, however, P. palpebrosus Hb shows a strong Bohr effect, and marked deoxygenation-linked binding of organic phosphates (ATP and DPG) and CO2 as carbamate (contrasting with HCO3− binding in other crocodilians). Unlike other Hbs, it polymerizes to large complexes in the oxygenated state. The highly unusual properties of P. palpebrosus Hb align with a high content of His residues (potential sites for oxygenation-linked proton binding) and distinctive surface Cys residues that may form intermolecular disulfide bridges upon polymerization. On the basis of its singular properties, P. palpebrosus Hb provides a unique opportunity for studies on structure-function coupling and the evolution of compensatory mechanisms for maintaining tissue O2 delivery in Hbs that lack conventional effector-binding residues.
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Liu, Gang, Hai Qiang Shi, Qing Wei Ping, Jian Zhang, Na Li, and Mei Hong Niu. "Flocculation Process of PEO for Lignin Removal from Pre-Hydrolysis Liquor of Mixed Hardwood." Advanced Materials Research 726-731 (August 2013): 1859–62. http://dx.doi.org/10.4028/www.scientific.net/amr.726-731.1859.
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To isolate lignin of PHL, PEO with various molecular weights (MW) s were added to PHL under different process conditions, and the turbidity and size of complexes formed in the PHL, as well as the lignin, hemicelluloses (sugar) and chemical oxygen demand (COD) of PHL were assessed after PEO treatments. Alternatively, poly aluminum chloride (PAC) (200 mg/l) and PEO (8 MDa MW) (200 mg/l) were employed in a dual polymer system to extract the lignin of PHL. In this work, the maximum removals of 46% lignin, 18.8% sugars, and 32% COD were obtained under the conditions of 400 mg/g PEO (with a MW of 8 MDa) at pH 2 and room temperature in a singular PEO polymer system.
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Lin, Weili, Hongyu An, Azim Celik, and Yueh Lee. "Quantitative Measurements of Cerebral Metabolic Rate of Oxygen (CMRO2) Using MRI." Stroke 32, suppl_1 (January 2001): 340. http://dx.doi.org/10.1161/str.32.suppl_1.340.
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P10 Recently, we have demonstrated that a quantitative estimate of cerebral blood oxygen saturation can be obtained in vivo via blood oxygen level dependent contrast. With a ROI analysis, a mean cerebral blood oxygen saturation (CBOS) of 58.4% ± 1.8% was obtained from 8 normal healthy volunteers. When converting the MR measured CBOS to the oxygen extraction fraction (OEF) via the Hill equation as well as the oxygen dissociation curve, an MR-OEF of 42.6% was obtained, in excellent agreement with the known OEF under normal physiological conditions via PET. While it is known that the level of OEF is a strong indicator of the functional status of brain tissue, OEF by itself does not uniquely indicate brain ischemia or brain viability. Therefore, CMRO2, which includes both CBF and OEF, has been utilized to better characterize the balance between oxygen supply and demand in brain tissue. In order to obtain a quantitative estimate of MR-CMRO2, a measure of both OEF and CBF is required. In total, 5 normal healthy volunteers were studied. A 2D multiecho gradient/spin echo sequence was employed to acquire images, which were subsequently post-processed to obtain an estimate of MR-OEF. In addition, a dynamic imaging approach was utilized to acquire images before, during and after the injection of a paramagnetic contrast agent and post-processed via the singular value decomposition so that a quantitative estimate of CBF can be obtained. Finally, pixe-by-pixel MR-CMRO2 maps were calculated as the product of MR-OEF and MR-CBF. Four ROIs: one located in the cortical and one in the subcortical regions of each hemisphere, were defined to obtain measurements of MR-CMRO2 in all volunteers. A mean MR-CMRO2 of 27.7±6.2 ml/100gm/min and 10.5±3.2 ml/100gm/min was obtained for the cortical and subcortical regions, respectively. Notice the MR-CMRO2 differs from the conventionally measured CMRO2 via PET. No normalization with respect to the arterial oxygen content of each volunteer was made for the MR-CMRO2. With the non-invasive nature of MRI and the ability to provide quantitative estimates of cerebral oxygen metabolism in vivo, MR-CMRO2 should open a new avenue for the investigation of cerebrovascular disease.
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Cherian, P. J., M. Vos, R. M. Swarte, J. H. Blok, G. H. Visser, P. Govaert, S. Huffel, and W. Deburchgraeve. "Time Varying Neonatal Seizure Localization." Methods of Information in Medicine 49, no. 05 (2010): 473–78. http://dx.doi.org/10.3414/me09-02-0041.
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Summary Background: A common cause for damage to the neonatal brain is a shortage in the oxygen supply to the brain or asphyxia. Neonatal seizures are the most frequent manifestation of neonatal neurologic disorders. Multichannel EEG recordings allow topographic localization of seizure foci. Objectives: We want to objectively determine the spatial distribution of the seizure on the scalp, the location in time and order the dominant sources in the brain based on their strength. Methods: In this paper we combine a method based on higher order CP-decomposition with subsequent singular value decomposition (SVD). Results: We illustrate the abilities of the method on simulated as well as on real neonatal seizure EEG. Conclusions: The proposed method provides reliable time and spatial information about the seizure, gives a clear overview of what is going on in the EEG and allows easy interpretation.
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Castillo-Villanueva, Adriana, Horacio Reyes-Vivas, and Jesús Oria-Hernández. "Comparison of cysteine content in whole proteomes across the three domains of life." PLOS ONE 18, no. 11 (November 13, 2023): e0294268. http://dx.doi.org/10.1371/journal.pone.0294268.
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An empirical observation suggests that Giardia lamblia proteins have larger cysteine content than their counterparts in other organisms. As this parasite lacks conventional antioxidant stress systems, it is generally accepted that high cysteine content helps G. lamblia cope with oxygen toxicity, a strategy apparently shared by other organisms. Here, we question whether the high cysteine content in some organisms is genuine or just a simple assumption based on singular observations. To this end, we analyzed the cysteine content in 78 proteomes of organisms spanning the three domains of life. The results indicate that the cysteine content in eukaryota is approximately double that in archaea and bacteria, with G. lamblia among the highest. Atypical cysteine contents were found in a few organisms correlating with specific environmental conditions, supporting the evolutionary amino acid-level selection of amino acid composition.
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Petersen, B., K. Gernaey, and P. A. Vanrolleghem. "Practical identifiability of model parameters by combined respirometric-titrimetric measurements." Water Science and Technology 43, no. 7 (April 1, 2001): 347–55. http://dx.doi.org/10.2166/wst.2001.0444.
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An earlier study on theoretical identifiability of parameters for a two-step nitrification model showed that a unique estimation of the yield YA1 is possible with combined respirometric-titrimetric data, contrary to the case where only one type of measurement is available. Here, the practical identifiability of model parameters was investigated via evaluation of the output sensitivity functions and the corresponding Fisher Information Matrix (FIM). It appeared that the FIM was not sufficiently powerful to predict the practical identifiability of this case with combined measurements as parameters could indeed be identified despite the fact that the FIM became singular. The accuracy of parameter estimates based on respirometric and titrimetric data and combination thereof was also investigated. Estimation on titrimetric data (Hp) was very accurate and a fast convergence of the objective function towards a minimum was obtained. The latter also holds for estimation on oxygen uptake rate data (rO), however with a lower accuracy. Parameter estimation based on oxygen concentration data (SO) was more complex but resulted in a higher accuracy. Thus, when the highest accuracy is needed it is recommended to estimate parameters initially on Hp and/or rO data, and to subsequently use these parameters as initial values for final, and more accurate estimation on SO data.
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Hoteit, I., G. Triantafyllou, G. Petihakis, and J. I. Allen. "A singular evolutive extended Kalman filter to assimilate real in situ data in a 1-D marine ecosystem model." Annales Geophysicae 21, no. 1 (January 31, 2003): 389–97. http://dx.doi.org/10.5194/angeo-21-389-2003.
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Abstract. A singular evolutive extended Kalman (SEEK) filter is used to assimilate real in situ data in a water column marine ecosystem model. The biogeochemistry of the ecosystem is described by the European Regional Sea Ecosystem Model (ERSEM), while the physical forcing is described by the Princeton Ocean Model (POM). In the SEEK filter, the error statistics are parameterized by means of a suitable basis of empirical orthogonal functions (EOFs). The purpose of this contribution is to track the possibility of using data assimilation techniques for state estimation in marine ecosystem models. In the experiments, real oxygen and nitrate data are used and the results evaluated against independent chlorophyll data. These data were collected from an offshore station at three different depths for the needs of the MFSPP project. The assimilation results show a continuous decrease in the estimation error and a clear improvement in the model behavior. Key words. Oceanography: general (ocean prediction; numerical modelling) – Oceanography: biological and chemical (ecosystems and ecology)
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Onifade, Oluwakemisola, Norazanita Shamsuddin, Jason Lee Zse Jin, Daphne Teck Ching Lai, and Stefan Herwig Gödeke. "Assessment of Pollution Status in Brunei River Using Water Quality Indices, Brunei Darussalam." Water 16, no. 17 (August 29, 2024): 2439. http://dx.doi.org/10.3390/w16172439.
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The Water Quality Index (WQI) is a tool designed to provide a singular figure representing the overall water quality status of a water body. This study applies Malaysia WQI, National Sanitation Foundation WQI (NSFWQI) and statistical analysis to investigate the impact of diverse pollution sources on the Brunei River’s water quality, a critical aquatic ecosystem affected by the rapid escalation of urbanization, industrial activities, and agricultural runoff. Principal component analysis (PCA), expert judgement, and correlation analysis were used to propose parameters for developing Brunei River’s WQI. Eight monitoring stations were selected to analyze 16 water quality parameters (pH, water temperature (T), dissolved oxygen (DO), oxidation-reduction potential (ORP), chemical oxygen demand (COD), the five-day biochemical oxygen demand (BOD5), salinity, electrical conductivity (EC), total dissolved solids (TDS), turbidity, total suspended solids (TSS), ammoniacal-nitrogen (NH3-N), fecal coliform (FC), total coliform (TC), phosphate and nitrate (NO3−) in this study. The results showed that NSFWQI classified the Brunei River as moderately polluted, while Malaysia (WQI) status was classified as slightly polluted except for Station Q around the quarry area. Statistical analysis revealed that the primary pollution sources are anthropogenic activities such as quarrying, domestic waste, and agricultural and urban runoff. Other specific areas of concern with low WQI and significant pollution levels are situated at Kampong Ayer Stations (N and J) due to proximal anthropogenic activities. The proposed water quality parameters for developing Brunei River’s WQI are pH, DO, EC, FC, NO3−, BOD5, T, TSS, turbidity and phosphate. This study addresses the current pollution status of the Brunei River and sets a precedent for future research emphasizing collaborative data-driven strategies for water quality management.
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Alessio, S., G. Vivaldo, C. Taricco, and M. Ghil. "Natural variability and anthropogenic effects in a Central Mediterranean core." Climate of the Past 8, no. 2 (April 20, 2012): 831–39. http://dx.doi.org/10.5194/cp-8-831-2012.
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Abstract. We evaluate the contribution of natural variability to the modern decrease in foraminiferal δ18O by relying on a 2200-yr-long, high-resolution record of oxygen isotopic ratio from a Central Mediterranean sediment core. Pre-industrial values are used to train and test two sets of algorithms that are able to forecast the natural variability in δ18O over the last 150 yr. These algorithms are based on autoregressive models and neural networks, respectively; they are applied separately to each of the δ18O series' significant variability components, rather than to the complete series. The separate components are extracted by singular-spectrum analysis and have narrow-band spectral content, which reduces the forecast error. By comparing the sum of the predicted low-frequency components to its actual values during the Industrial Era, we deduce that the natural contribution to these components of the modern δ18O variation decreased gradually, until it reached roughly 40%, as early as the end of the 1970s.
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Alessio, S., G. Vivaldo, C. Taricco, and M. Ghil. "Natural variability and anthropogenic effects in a Central Mediterranean core." Climate of the Past Discussions 7, no. 5 (October 27, 2011): 3699–718. http://dx.doi.org/10.5194/cpd-7-3699-2011.
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Abstract. We evaluate the contribution of natural variability to the modern decrease in foraminiferal δ18O by relying on a 2200-years-long, high-resolution record of oxygen isotopic ratio from a Central Mediterranean sediment core. Pre-industrial values are used to train and test two sets of algorithms that are able to forecast the natural variability in δ18O over the last 150 yr. These algorithms are based on autoregressive models and neural networks, respectively; they are applied separately to each of the δ18O series' significant variability components, rather than to the complete series. The separate components are extracted by singular-spectrum analysis and have narrow-band spectral content, which reduces the forecast error. By comparing the sum of the predicted components to the actual values during the Industrial Era, we deduce that the natural contribution to the modern δ18O variation decreased gradually, until it reached roughly 40% as early as the end of the 1970s.
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Saito, Gustavo Pereira, Ana Carolina Lanfredi Matsumoto, Renata Pires Assis, Iguatemy Lourenço Brunetti, Marco Aurélio Cebim, and Marian Rosaly Davolos. "Zn(ferulate)-LSH Systems as Multifunctional Filters." Molecules 26, no. 8 (April 17, 2021): 2349. http://dx.doi.org/10.3390/molecules26082349.
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Excessive UV solar radiation exposure causes human health risks; therefore, the study of multifunctional filters is important to skin UV protective ability and also to other beneficial activities to the human organism, such as reduction of reactive oxygen species (ROS) responsible for cellular damages. Potential multifunctional filters were obtained by intercalating of ferulate anions into layered simple metal hydroxides (LSH) through anion exchange and precipitation at constant pH methods. Ultrasound treatment was used in order to investigate the structural changes in LSH-ferulate materials. Structural and spectroscopic analyses show the formation of layered materials composed by a mixture of LSH intercalated with ferulate anions, where carboxylate groups of ferulate species interact with LSH layers. UV-VIS absorption spectra and in vitro SPF measurements indicate that LSH-ferulate systems have UV shielding capacity, mainly UVB protection. The results of reactive species assays show the ability of layered compounds in capture DPPH•, ABTS•+, ROO•, and HOCl/OCl− reactive species. LSH-ferulate materials exhibit antioxidant activity and singular optical properties that enable their use as multifunctional filters.
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Dong, Jin, Taowen Ye, Yanli Dong, Jie Hui, and Xiaorong Wang. "Ursolic acid attenuates oligospermia in busulfan-induced mice by promoting motor proteins." PeerJ 12 (July 5, 2024): e17691. http://dx.doi.org/10.7717/peerj.17691.
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Background Oligospermia is one of the most common reasons for male infertility which is troubling numerous couples of child-bearing age. This investigation scrutinizes the implications and mechanistic underpinnings of ursolic acid’s effect on busulfan-induced oligospermia in mouse models. Methods A singular intraperitoneal injection of busulfan at a dosage of 30 mg/kg induced oligospermia. Two weeks subsequent to this induction, mice were subjected to various dosages of ursolic acid (10, 30, and 50 mg/kg body weight, respectively) on a daily basis for four consecutive weeks. Following this treatment period, a meticulous analysis of epididymal sperm parameters, encompassing concentration and motility, was conducted using a computer-assisted sperm analysis system. The histopathology of the mice testes was performed utilizing hematoxylin and eosin staining, and the cytoskeleton regeneration of the testicular tissues was analyzed via immunofluorescent staining. Serum hormone levels, including testosterone, luteinizing hormone, and follicle-stimulating hormone, as well as reactive oxygen species levels (inclusive of reactive oxygen species and malondialdehyde), were gauged employing specific enzyme-linked immunosorbent assay kits. Differentially expressed genes of testicular mRNA between the oligospermia-induced group and the various ursolic acid treatment groups were identified through RNA sequencing analysis. Results The results revealed that a dosage of 50 mg/kg ursolic acid treatment could increase the concentration of epididymal sperm in oligospermia mice, promote the recovery of testicular morphology, regulate hormone levels and ameliorate oxidative damage. The mechanism research results indicated that ursolic acid increased the expression level of genes related to motor proteins in oligospermia mice.
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Khan, Hares, Alo Laas, Rafael Marcé, and Biel Obrador. "Major Effects of Alkalinity on the Relationship Between Metabolism and Dissolved Inorganic Carbon Dynamics in Lakes." Ecosystems 23, no. 8 (February 5, 2020): 1566–80. http://dx.doi.org/10.1007/s10021-020-00488-6.
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AbstractSeveral findings suggest that CO2 emissions in lakes are not always directly linked to changes in metabolism but can be associated with interactions with the dissolved inorganic carbon equilibrium. Alkalinity has been described as a determining factor in regulating the relative contributions of biological and inorganic processes to carbon dynamics in lakes. Here we analyzed the relationship between metabolic changes in dissolved oxygen (DO) and dissolved inorganic carbon (DIC) at different timescales in eight lakes covering a wide range in alkalinity. We used high-frequency data from automatic monitoring stations to explore the sensitivity of DIC to metabolic changes inferred from oxygen. To overcome the problem of noisy data, commonly found in high-frequency measurements datasets, we used Singular Spectrum Analysis to enhance the diel signal-to-noise ratio. Our results suggest that in most of the studied lakes, a large part of the measured variability in DO and DIC reflects non-metabolic processes. Furthermore, at low alkalinity, DIC dynamics appear to be mostly driven by aquatic metabolism, but this relationship weakens with increasing alkalinity. The observed deviations from the metabolic 1:1 stoichiometry between DO and DIC were strongly correlated with the deviations expected to occur from calcite precipitation, with a stronger correlation when accounting also for the benthic contribution of calcite precipitation. This highlights the role of calcite precipitation as an important driver of CO2 supersaturation in lakes with alkalinity above 1 meq L−1, which represents 57% of the global area of lakes and reservoirs around the world.
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Lin, Weili, Jin-Moo Lee, Katie D. Vo, Hongyu An, Azim Celik, Yueh Lee, and Chung Y. Hsu. "Clinical Utility of CMRO2 Obtained with MRI in Determining Ischemic Brain Tissue at Risk." Stroke 32, suppl_1 (January 2001): 341–42. http://dx.doi.org/10.1161/str.32.suppl_1.341-d.
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P16 It has been suggested that the relationship between oxygen delivery and oxygen demand defines brain tissue at risk during cerebral ischemia. We have recently demonstrated that a quantitative estimate of cerebral blood oxygen saturation (and thereby oxygen extraction fraction, OEF) can be obtained using MRI in vivo. When combined with MR estimated cerebral blood flow (CBF), a quantitative measure of MR-CMRO2 can be calculated. In this study, we sought to explore the potential clinical utility of MR-CMRO2 in determining brain tissue at risk during cerebral ischemia. Seven patients with acute ischemic strokes were imaged at 4.5±.9 hrs (tp1) and 6 of the patients were imaged 3–5 days after stroke onset (tp2) with diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI). In addition, a 2D multiecho gradient/spin echo sequence was employed to acquire images which were subsequently used to estimate MR-OEF. Singular value decomposition was used to obtain a quantitative estimate of CBF to calculate MR-CMRO2 (= MR-OEF x MR-CBF). At tp1, 5/7 patients showed a DWI-PWI mismatch (PWI>DWI) while 2/7 patients exhibited match. At tp2, only 1 patient showed PWI<DWI, and the remaining patients had matched defects. In addition, 4/6 patients had DWI lesion volumes similar to tp1 abnormal PWI volumes, while 2/6 had smaller lesion volumes at tp2. Regional measurements of MR-CMRO2 were obtained in the regions where PWI and DWI abnormalities coincided (“core”), regions where PWI were abnormal (“core+penumbra”), and the corresponding regions on the contralateral hemisphere. In patients who demonstrated mismatched PWI-DWI defects at tp1, CMRO2 in the “core” regions was 35.3±3.4% of the contralateral region. In contrast, CMRO2 in the “core+penumbra” was 48.9±5.4% of the contralateral region, which was significantly different from “core” CMRO2 (p<0.003). Furthermore, the two patients with matched DWI-PWI at tp1 had CMRO2 values 16.6±14.1% of the contralateral regions. Analysis of tp2 images revealed that all “core” regions became infarcted. These results suggest that brain regions with CMRO2 above 35.3% of the contralateral hemisphere may represent salvageable tissue.
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Diekman, Casey O., Peter J. Thomas, and Christopher G. Wilson. "Eupnea, tachypnea, and autoresuscitation in a closed-loop respiratory control model." Journal of Neurophysiology 118, no. 4 (October 1, 2017): 2194–215. http://dx.doi.org/10.1152/jn.00170.2017.
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How sensory information influences the dynamics of rhythm generation varies across systems, and general principles for understanding this aspect of motor control are lacking. Determining the origin of respiratory rhythm generation is challenging because the mechanisms in a central circuit considered in isolation may be different from those in the intact organism. We analyze a closed-loop respiratory control model incorporating a central pattern generator (CPG), the Butera-Rinzel-Smith (BRS) model, together with lung mechanics, oxygen handling, and chemosensory components. We show that 1) embedding the BRS model neuron in a control loop creates a bistable system; 2) although closed-loop and open-loop (isolated) CPG systems both support eupnea-like bursting activity, they do so via distinct mechanisms; 3) chemosensory feedback in the closed loop improves robustness to variable metabolic demand; 4) the BRS model conductances provide an autoresuscitation mechanism for recovery from transient interruption of chemosensory feedback; and 5) the in vitro brain stem CPG slice responds to hypoxia with transient bursting that is qualitatively similar to in silico autoresuscitation. Bistability of bursting and tonic spiking in the closed-loop system corresponds to coexistence of eupnea-like breathing, with normal minute ventilation and blood oxygen level and a tachypnea-like state, with pathologically reduced minute ventilation and critically low blood oxygen. Disruption of the normal breathing rhythm, through either imposition of hypoxia or interruption of chemosensory feedback, can push the system from the eupneic state into the tachypneic state. We use geometric singular perturbation theory to analyze the system dynamics at the boundary separating eupnea-like and tachypnea-like outcomes. NEW & NOTEWORTHY A common challenge facing rhythmic biological processes is the adaptive regulation of central pattern generator (CPG) activity in response to sensory feedback. We apply dynamical systems tools to understand several properties of a closed-loop respiratory control model, including the coexistence of normal and pathological breathing, robustness to changes in metabolic demand, spontaneous autoresuscitation in response to hypoxia, and the distinct mechanisms that underlie rhythmogenesis in the intact control circuit vs. the isolated, open-loop CPG.
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Luo, Juhua, Ruiliang Pu, Ronghua Ma, Xiaolong Wang, Xijun Lai, Zhigang Mao, Li Zhang, Zhaoliang Peng, and Zhe Sun. "Mapping Long-Term Spatiotemporal Dynamics of Pen Aquaculture in a Shallow Lake: Less Aquaculture Coming along Better Water Quality." Remote Sensing 12, no. 11 (June 9, 2020): 1866. http://dx.doi.org/10.3390/rs12111866.
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Pen aquaculture is the main form of aquaculture in some shallow lakes in eastern China. It is valuable to map the spatiotemporal changes of pen aquaculture in eutrophic lakes to assess its effect on water quality, thereby helping the relevant decision-making agencies to manage the water quality (WQ) of lakes. In this study, an automatic approach for extracting the pen aquaculture area was developed based on Landsat data. The approach integrates five algorithms, including grey transformation, discrete wavelet transform, fast Fourier transform, singular value decomposition and k-nearest neighbor classification. It was successfully applied in the automatic mapping of the pen aquaculture areas in Lake Yangcheng from 1990 to 2016. The overall accuracies were greater than 92%. The result indicted that the practice of pen aquaculture experienced five stages, with the general area increasing in the beginning and decreasing by the end of the last stage. Meanwhile, the changes of nine WQ parameters observed from 2000 to 2016, such as ammonia (NH3-N), pH, total nitrogen (TN), total phosphorus (TP), chlorophyll a, biochemical oxygen demand (BOD), chemiluminescence detection of permanganate index (CODMn), Secchi disk depth (SDD) and dissolved oxygen (DO), were analyzed in the lake sectors of Lake Yangcheng, and then their relationships were explored with the percentage of pen aquaculture area. The result suggested that the percentage of pen aquaculture area exhibits significantly positive correlations with NH3-N, TN, TP, chlorophyll a, BOD and CODMn, but significantly negative correlations with SDD and DO. The experimental results may offer an important implication for managing similar shallow lakes with pen aquaculture expansion and water pollution problems.
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West, Hannah, Fiona Roberts, Paul Sweeney, Simon Walker-Samuel, Joseph Leedale, Helen Colley, Craig Murdoch, Rebecca J. Shipley, and Steven Webb. "A mathematical investigation into the uptake kinetics of nanoparticles in vitro." PLOS ONE 16, no. 7 (July 22, 2021): e0254208. http://dx.doi.org/10.1371/journal.pone.0254208.
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Nanoparticles have the potential to increase the efficacy of anticancer drugs whilst reducing off-target side effects. However, there remain uncertainties regarding the cellular uptake kinetics of nanoparticles which could have implications for nanoparticle design and delivery. Polymersomes are nanoparticle candidates for cancer therapy which encapsulate chemotherapy drugs. Here we develop a mathematical model to simulate the uptake of polymersomes via endocytosis, a process by which polymersomes bind to the cell surface before becoming internalised by the cell where they then break down, releasing their contents which could include chemotherapy drugs. We focus on two in vitro configurations relevant to the testing and development of cancer therapies: a well-mixed culture model and a tumour spheroid setup. Our mathematical model of the well-mixed culture model comprises a set of coupled ordinary differential equations for the unbound and bound polymersomes and associated binding dynamics. Using a singular perturbation analysis we identify an optimal number of ligands on the polymersome surface which maximises internalised polymersomes and thus intracellular chemotherapy drug concentration. In our mathematical model of the spheroid, a multiphase system of partial differential equations is developed to describe the spatial and temporal distribution of bound and unbound polymersomes via advection and diffusion, alongside oxygen, tumour growth, cell proliferation and viability. Consistent with experimental observations, the model predicts the evolution of oxygen gradients leading to a necrotic core. We investigate the impact of two different internalisation functions on spheroid growth, a constant and a bond dependent function. It was found that the constant function yields faster uptake and therefore chemotherapy delivery. We also show how various parameters, such as spheroid permeability, lead to travelling wave or steady-state solutions.
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Li, Y. J., Q. Chen, M. I. Guzman, C. K. Chan, and S. T. Martin. "Second-generation products of β-caryophyllene ozonolysis are the dominant contributors to particle mass concentration." Atmospheric Chemistry and Physics Discussions 10, no. 7 (July 22, 2010): 17699–726. http://dx.doi.org/10.5194/acpd-10-17699-2010.
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Abstract. The production of secondary organic aerosol (SOA) by the dark ozonolysis of gas-phase β-caryophyllene was studied. The experiments were conducted in a continuous-flow environmental chamber for organic particle mass concentrations of 0.5 to 30 μg m−3 and with ozone in excess, thereby allowing the study of second-generation particle-phase products under atmospherically relevant conditions. The particle-phase products were characterized by an ultra-performance liquid chromatograph equipped with an electrospray ionization time-of-flight mass spectrometer (UPLC-ESI-ToF-MS). Fragmentation mass spectra were used for the structural elucidation of each product, and the structures were confirmed as consistent with the accurate m/z values of the parent ions. In total, fifteen products were identified, three of which are reported for the first time in this study. The structures showed that 9 out of 15 particle-phase products were second generation, including all three of the new products. The relative abundance of the second-generation products was approximately 90% by mass among the 15 observed products. The O:C and H:C elemental ratios of the 15 products ranged from 0.13 to 0.50 and from 1.43 to 1.60, respectively. Fourteen of the products contained 3 to 5 oxygen atoms. A singular product, which was one of the three newly identified ones, had 7 oxygen atoms, including 1 carboxylic group, 2 carbonyl groups, and 3 hydroxyl groups. It was identified as 2,3-dihydroxy-4-[2-(4-hydroxy-3-oxobutyl)-3,3-dimethylcyclobutyl]-4-oxobutanoic acid (C14H22O7). The estimated saturation vapor pressure of this product is sufficiently low (3.3×10−13 Pa) that it can contribute to new particle formation in the atmosphere.
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Li, Y. J., Q. Chen, M. I. Guzman, C. K. Chan, and S. T. Martin. "Second-generation products contribute substantially to the particle-phase organic material produced by β-caryophyllene ozonolysis." Atmospheric Chemistry and Physics 11, no. 1 (January 6, 2011): 121–32. http://dx.doi.org/10.5194/acp-11-121-2011.
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Abstract. The production of secondary organic aerosol (SOA) by the dark ozonolysis of gas-phase β-caryophyllene was studied. The experiments were conducted in a continuous-flow environmental chamber for organic particle mass concentrations of 0.5 to 30 μg m−3 and with ozone in excess, thereby allowing the study of second-generation particle-phase products under atmospherically relevant conditions. The particle-phase products were characterized by an ultra-performance liquid chromatograph equipped with an electrospray ionization time-of-flight mass spectrometer (UPLC-ESI-ToF-MS). Fragmentation mass spectra were used for the structural elucidation of each product, and the structures were confirmed as consistent with the accurate m/z values of the parent ions. In total, fifteen products were identified. Of these, three are reported for the first time. The structures showed that 9 out of 15 particle-phase products were second generation, including all three of the new products. The relative abundance of the second-generation products was approximately 90% by mass among the 15 observed products. The O:C and H:C elemental ratios of the 15 products ranged from 0.13 to 0.50 and from 1.43 to 1.60, respectively. Fourteen of the products contained 3 to 5 oxygen atoms. A singular product, which was one of the three newly identified ones, had 7 oxygen atoms, including 1 carboxylic group, 2 carbonyl groups, and 3 hydroxyl groups. It was identified as 2, 3-dihydroxy-4-[2-(4-hydroxy-3-oxobutyl)-3, 3-dimethylcyclobutyl]-4-oxobutanoic acid (C14H22O7). The estimated saturation vapor pressure of this product is 3.3×10−13 Pa, making this product a candidate contributor to new particle formation in the atmosphere.
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Reusch, Rosetta N. "Low molecular weight complexed poly(3-hydroxybutyrate): a dynamic and versatile molecule in vivo." Canadian Journal of Microbiology 41, no. 13 (December 15, 1995): 50–54. http://dx.doi.org/10.1139/m95-167.
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It is increasingly clear that poly(3-hydroxybutyrate) (PHB) is not just an inert storage polymer, confined to certain bacteria, but a ubiquitous, interactive, solvating biopolymer involved in important physiological functions. Low molecular weight PHB, complexed to other macromolecules (c-PHB), is widely distributed in biological cells, being found in representative organisms of nearly all phyla. Complexation modifies the physical and chemical properties of c-PHB, allowing it to pervade aqueous as well as hydrophobic regions of the cell, and as a result c-PHB can be found in cytoplasm and intracellular fluids as well as in membranes and lipoproteins. The lipidic homopolymer associates with other macromolecules primarily via its ester carbonyl oxygens, which can act as hydrogen-bond acceptors or as ligands for coordinate bonds to cations. The spacing of the electron-donating groups along the flexible backbone allows for multiple bonding interactions, and forms the basis for the ability of c-PHB to bind to proteins, or to form ion-conducting complexes with salts. The singular ability of c-PHB to dissolve salts and facilitate their transfer across hydrophobic barriers defines a potential physiological niche for c-PHB in cell metabolism.Key words: polyhydroxybutyrate, polyphosphate, polymer electrolyte, ion transport.
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Bass, L., A. J. Bracken, K. Holmåker, and B. R. F. Jefferies. "Integro-differential equations for the self-organisation of liver zones by competitive exclusion of cell-types." Journal of the Australian Mathematical Society. Series B. Applied Mathematics 29, no. 2 (October 1987): 156–94. http://dx.doi.org/10.1017/s0334270000005701.
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AbstractA model is developed for the seif-organisation of zones of enzymatic activity along a liver capillary (hepatic sinusoid) lined with cells of two types, which contain different enzymes and compete for sites on the wall of the sinusoid. An effectively non-local interaction between the cells arises from local consumption of oxygen from blood flowing throug1 the sinusoid, which gives rise to gradients of oxygen concentration in turn influencing rates of division and of death of the two cell-types. The process is modelled by a pair of coupled non-linear integro-differential equations for the cell-densities as functions of time and position along the sinusoid. Existence of a unique, bounded, non-negative solution of the equations is proved, for prescribed initial values. The equations admit infinitely many stationary solutions, but it is shown that all except one are unstable, for any given set of the model parameters. The remaining solution is shown to be asymptotically stable against a large class of perturbations. For certain ranges of the model parameters, the asymptotically stable stationaxy solution has a zonal structure, with cells of one type located entirely upstream of cells of the other type, and with jump discontinuities in the cell densities at a certain distance along the sinusoid. Such sinusoidal zones can account for zones of enzymatic activity observed in the intact liver. Exceptional cases are found for singular choices of model parameters, such that stationary cell-densities cannot be asymptotically stable individually, but together form an asymptotically stable set. Certain mathematical questions are left open, notably the behaviour of large deviations from stationary solutions, and the global stability of such solutions. Possible generalisations of the model are described.
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Silakari, Pragati, Aditi Yadav, Aneesha Arora, Anushka Arora, Gulsheen, Paranjeet Kaur, and Sanjeev Kumar Sahu. "Investigating Holistic Natural Strategies for The Management of Huntington's Disease." BIO Web of Conferences 86 (2024): 01041. http://dx.doi.org/10.1051/bioconf/20248601041.
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Huntington's disease (HD), a multifaceted neurological disorder, presents a complex clinical scenario. An autosomal dominant neurodegenerative ailment called Huntington's disease is brought on by increase in number of CAG (Cytosine-Adenine-Guanine) repeats, which causes the creation of a mutant Huntingtin protein (mHTT) resulting in neuronal death and mental disabilities in human beings. End signs and symptoms can include significant weight loss, difficulty swallowing or breathing, recurrent aspiration pneumonia, declined health and uncontrolled pain. The excessive production of ROS (Reactive Oxygen Species) in nervous tissues is considered a significant risk factor in most of the neurological diseases including HD. Transcriptional regulation, immunological system, and mitochondrial function are all disrupted by mHTT. Although natural products have shown promise in ameliorating symptoms, it is important to note that no singular "phytoconstituent" has been definitively linked to its therapeutic intervention. Nevertheless, certain naturally occurring compounds have exhibited promising outcomes in preclinical investigations. This article focuses on a few phytoconstituents that are known to have a variety of neuroprotective effects through a wide range of biological activities. By stimulating the Nrf2 (Nuclear factor erythroid 2-related factor) pathway and suppressing NF-κB (Nuclear Factor Kappa-light-chain-enhancer of activated B cells), astaxanthin, berberine, and sulfarophane increase the antioxidant and anti-inflammatory activity, resulting in neuroprotection. Curcumin leads to metal chelating effect and decline in reactive oxygen species which are certainly one among the vital processes to impede and manage the disorders causing neurodegeneration including HD. This affects the upregulation of HSPs (Heat Shock Proteins) which helps in HD management. Naringin reduces level of oxidative stress and inflammation by free radical scavenging, NF-κB stimulates cell survival and prevents apoptosis by upregulating anti-apoptotic genes expression and downregulating proapoptotic genes.
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Hasnita, Hasnita, Hariyanti Hariyanti, and Asmiyenti Djaliasrin Djalil. "A Review: Photodynamic Therapy on Wound Healing." PHARMACY: Jurnal Farmasi Indonesia (Pharmaceutical Journal of Indonesia) 21, no. 2 (January 7, 2025): 124. https://doi.org/10.30595/pharmacy.v21i2.24377.
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Background: Wound infection poses a significant challenge in wound healing, so overcoming microbial infections and accelerating wounds can be done using PDT (Photodynamic Therapy). PDT is a non-invasive therapeutic method, light-based therapeutic method that can treat several pathological conditions such as wound healing, antimicrobial, antibiotic resistance bacteria, cancer, and skin repair. Objective: The review article aims to evaluate the effectiveness of PDT in accelerating wound healing. Methods: All articles in this review were taken from the Pubmed and Google Scholar internet databases from 2019 to 2024. Results: Twelve photosensitizers were explored for wound healing using PDT. Some were used in singular form, while others were used in combination. PDT promotes wound healing by killing bacterial cells and stimulating fibroblast proliferation, producing collagen and elastin. The mechanism for faster wound healing was detected by increasing the epithelialization process, decreasing angiogenesis, reducing the number of fibroblast cells, and raising collagen density. Conclusion: Based on research, PDT uses a specific photosensitizer that is activated by light to produce Reactive Oxygen Species (ROS) so that in wound healing, PDT stimulates the wound healing process by improving the quality of tissue formed, fast wound closure, reducing the risk of complications, increasing blood circulation, reduces inflammation and promotes the proliferation of cells involved in tissue regeneration.
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Fitamo, Temesgen, Olli Dahl, Emma Master, and Torsten Meyer. "Biochemical methane potential of kraft bleaching effluent and codigestion with other in-mill streams." February 2016 15, no. 2 (March 1, 2016): 80–88. http://dx.doi.org/10.32964/tj15.2.80.
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A biochemical methane potential assay was conducted to investigate the anaerobic digestibility of bleaching effluent from hardwood kraft pulping and the potential of codigestion with other effluents from an integrated pulp and paper mill. Four in-mill streams were tested individually and in combination: total bleaching effluent, alkaline bleaching effluent, kraft evaporator condensate, and chemithermomechanical pulping effluent. The total bleaching effluent, consisting of the chlorine dioxide bleaching and alkaline bleaching effluents, exhibited the highest potential for organic matter degradation and methane generation. Chemical oxygen demand (COD) removal ranged from 57%–76%, and methane generation was 220–280 mL/g COD contained in the wastewater, depending on the degree of dilution. When codigestion was tested, the composite consisting of total bleaching effluent, chemithermomechanical pulping effluent, and kraft condensate was most efficient in terms of COD removal (51%) and methane generation (200 mL/g COD contained in the wastewater). The total bleaching effluent is the largest contributor to the overall amount of wastewater at this mill; it contains relatively low concentrations of anaerobic inhibitors such as adsorbable organic halogens (36 mg/L), total sulfur (170 mg/L), and resin and fatty acids (3.2 mg/L). Therefore, the total bleaching effluent from hardwood kraft pulping may be considered for full-scale anaerobic wastewater treatment, either as a singular stream or as part of a composite stream including other in-mill effluents.
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Qiu, Zhijuan, Subhajit Mukherjee, Jonathan Schouten, Nandini Acharya, Leigh Maher, Juan Salazar, Jorge Cervantes, Sridhar Mani, and Kamal Khanna. "Pregnane X receptor regulates the innate inflammatory response against intracellular bacterial infection (P4209)." Journal of Immunology 190, no. 1_Supplement (May 1, 2013): 130.4. http://dx.doi.org/10.4049/jimmunol.190.supp.130.4.
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Abstract Pregnane X receptor (PXR) is a member of the nuclear receptor family and is primarily expressed in stromal cells of liver and intestine. It’s well established that PXR regulates the metabolism of xenobiotics. Here we demonstrate that PXR signaling specifically in hematopoietic cells is also essential for regulating innate antimicrobial immune responses. Compared to wild type mice, Pxr-/- animals exhibited significantly higher inflammatory response to intracellular bacteria Listeria Monocytogenes (LM) infection. However, strikingly, despite the more robust innate immune response, Pxr-/- mice were unable to control LM infection. Our data demonstrated that the inflammatory monocyte response was significantly reduced in Pxr-/- mice, and these monocytes produced elevated amounts of TNF-α and reactive oxygen species that are known to induce cell death. We propose that the dysregulated inflammatory response in Pxr-/- monocytes results in their increased cell death and thus elevated bacterial burden. Surprisingly, increased activation of the TLR pathway in Pxr-/- mice was the singular determinant of the susceptibility since Pxr-/-Tlr4-/- mice were efficient in clearing LM. In conclusion, our study for the first time defines a novel role of PXR as a critical negative regulator of the innate immune response. Our results also illustrate the need for exquisite fine tuning and balance of the innate inflammatory pathways to ensure the clearance of an intracellular pathogen.
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Moore, Courtney, Weijue Gao, and Pedram Fatehi. "Cationic Lignin Polymers as Flocculant for Municipal Wastewater." Polymers 13, no. 22 (November 9, 2021): 3871. http://dx.doi.org/10.3390/polym13223871.
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The radical polymerization of acid-washed and unwashed softwood kraft lignin with [2-(methacryloyloxy) ethyl] trimethylammonium chloride (METAC) was attempted to investigate the production of lignin-based flocculants for simulated wastewater. The incorporation of METAC onto lignin resulted in a cationic charge density (2.3–3.3 meq/g), increased water solubility (89–96% in neutral pH), and increased molecular weight (70,000–210,000 g/mol) of lignin. The lignin–METAC polymers generated from acid-washed lignin had higher molecular weights than those generated from unwashed lignin. The lignin–METAC polymers showed lower resistance to thermal decomposition than unmodified lignin due to the inclusion of PolyMETAC. The unmodified acid-washed lignin samples did not significantly affect the COD of the wastewater, while the unmodified unwashed lignin samples contributed to the COD, implying that unmodified lignin was not suitable for wastewater treatment. The flocculation of wastewater with lignin–METAC led to the chemical oxygen demand (COD) reduction of 17–23% and total organic carbon (TOC) drop of 51–60%. The lignin–METAC polymer with the highest molecular weight (produced from acid-washed lignin) reached the highest COD removal, while lignin–METAC polymer with the highest charge density (produced from unwashed lignin) reached the highest TOC removal. Focused beam reflectance measurement (FBRM) studies revealed that the lignin–METAC polymer produced from acid-washed lignin with a high molecular weight generated larger and more flocs in wastewater than the lignin–METAC polymer produced from unwashed lignin. The comparison of theoretical and experimental dosages required for neutralizing the charges of wastewater demonstrated that charge neutralization was the main flocculation mechanism, although a bridging mechanism was also involved for component removals from wastewater. The use of 1 mg/L of alum along with 65 mg/L lignin–METAC in a dual coagulation–flocculation system led to higher average phosphorous (42%) and COD (44%) removals than the singular flocculation system only using 65 mg/L of lignin–METAC (with phosphorous removals of 3.4% and COD removals of 18.7%). However, lignin–METAC flocculant slightly increased the ammonia–nitrogen content in both singular flocculation and dual coagulation–flocculation systems due to the residual ammonia content of lignin–METAC. The coagulation–flocculation system determined that the use of lignin–METAC (65 mg/L) could reduce the alum dosage significantly while maintaining a similar organic content reduction of 44% for wastewater.
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Kang, Yan, Jinling Song, Zhuo Lin, Liming Huang, Xiaoang Zhai, and Haipeng Feng. "Water Quality Prediction Based on SSA-MIC-SMBO-ESN." Computational Intelligence and Neuroscience 2022 (August 3, 2022): 1–11. http://dx.doi.org/10.1155/2022/1264385.
Full textAbstract:
Water pollution threatens the safety of human production and life. To quickly respond to water pollution, it is important for water management staff to predict water quality changes in advance. Drawing on the temporality of water quality data, the leaky integrator echo state network (ESN) was introduced to construct the water quality prediction models for dissolved oxygen (DO), permanganate index (CODMn), and total phosphorus (TP), respectively. First, the missing values were filled by the linear trend method of adjacent points, and the outliers were detected and corrected by the Z-score method and the linear trend method. Second, the singular spectrum analysis (SSA) was performed to denoise the original monitoring data, such that the predicted data catch up with the real data, and the model accuracy is not affected by the hidden noise in the data. Third, the correlation between water quality indices was measured by the maximum information coefficient (MIC), and the strongly correlated indices were imported to the prediction model. Finally, according to these strong correlation indicators, the water quality prediction models based on multiple features were constructed, respectively, using the offline and online learning algorithms of the ESN. The hyperparameters of the models were optimized through the sequential model-based optimization (SMBO). Experimental results show that the proposed water quality prediction models, namely, SSA-MIC-SMBO-Offline ESN and SSA-MIC-SMBO-Online ESN, predicted DO, CODMn, and TP accurately, providing suitable tools for practical applications.
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Viégas, Ricardo Almeida, and Joaquim Albenísio Gomes Silveira. "Activation of nitrate reductase of cashew leaf by exogenous nitrite." Brazilian Journal of Plant Physiology 14, no. 1 (January 2002): 39–44. http://dx.doi.org/10.1590/s1677-04202002000100005.
Full textAbstract:
Nitrate reductase (NR) plays a central role in plant primary metabolism and exhibits complex regulation mechanisms for its catalytic activity. There is controversy in the literature concerning the possible direct effect of NO2- on the stimulation and/or activation of NR activity. The influence of NO2- was studied on the NR activity in the leaves of 30-day-old cashew (Anacardium occidentale L.) seedlings. Addition of NO2- to the reaction mixture containing leaf enzymatic extract resulted in a remarkable increase in NR activity. A trace amount (5 mumol.L-1) of NO2- was required to achieve full NR activity. The in vitro NR-activity showed a steady time-dependent increase when incubated in the presence of only NO3- + NO2-. In contrast, in vitro NR activity was practically absent in a NO2- -free reaction medium, even in the presence of a saturating NO3- concentration. No oxidation of NO2- to NO3- was detected during the experiment. Although NO2- clearly activated the in vitro NR activity, it had no effect on the in vivo leaf-NR activity determined under absence of oxygen. NADH at concentrations greater than 0.5 mmol.L-1 decreased the rates of in vitro NR activity. These results indicated, at least partially, a strong cashew leaf NO2- dependency of NR activation and/or activity. Finally, based on these results, it is suggested that this singular NR activity model induced by exogenous NO2- in cashew leaf extracts is caused by changes in the NR activation state by NO2- itself.
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Attanzio, Alessandro, Antonella D’Anneo, Francesco Pappalardo, Francesco Paolo Bonina, Maria Antonia Livrea, Mario Allegra, and Luisa Tesoriere. "Phenolic Composition of Hydrophilic Extract of Manna from Sicilian Fraxinus angustifolia Vahl and its Reducing, Antioxidant and Anti-Inflammatory Activity in Vitro." Antioxidants 8, no. 10 (October 18, 2019): 494. http://dx.doi.org/10.3390/antiox8100494.
Full textAbstract:
Manna, a very singular vegetable product derived from the spontaneous solidification of the sap of some Fraxinus species, has long been known for its mild laxative and emollient properties. In this work, a hydro-alcoholic extract of manna (HME) from Sicilian Fraxinus angustifolia Vahl was investigated using HPLC-DAD to find phenol components and using chemical and biological in vitro assays to determine its reducing, antioxidant and anti-inflammatory capacity. We identified elenolic acid, tyrosol, hydroxytyrosol, catechin, fraxetin, verbascoside, gallic acid, procyanidin-B1, and luteolin 3,7 glucoside, in order of abundance. Measurements of total antioxidant activity by Folin-Ciocalteu reaction and ferric reducing ability (FRAP), as well as of scavenger activity towards ABTS•+, DPPH•, and perferryl-myoglobin radicals, showed that the phytocomplex effectively reduced oxidants with different standard potentials. When compared with vitamin E, HME also behaved as an efficient chain-breaking antioxidant against lipoperoxyl radicals from methyl linoleate. In cellular models for oxidative stress, HME counteracted membrane lipid oxidation of human erythrocytes stimulated by tert-butyl hydroperoxide and prevented the generation of reactive oxygen species, as well as the GSH decay in IL-1β–activated intestinal normal-like cells. Moreover, in this in vitro intestinal bowel disease model, HME reduced the release of the pro-inflammatory cytokines IL-6 and IL-8. These findings may suggest that manna acts as an antioxidant and anti-inflammatory natural product in humans, beyond its well-known effects against constipation.
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Park, Moon Gyu, Hau Wang, Rachid Amine, Rajeev S. Assary, Khalil Amine, and Larry A. Curtiss. "Lithium Superoxide in Li-O2 Batteries: Performance and Mechanisms." ECS Meeting Abstracts MA2024-01, no. 3 (August 9, 2024): 634. http://dx.doi.org/10.1149/ma2024-013634mtgabs.
Full textAbstract:
Lithium superoxide (LiO2) is generally regarded as an intermediate formed during the Li-O2 battery discharge and transformed into lithium peroxide (Li2O2). Indeed, its chemical/electrochemical stability is low, making it recognized as a temporary discharge product in Li-O2 battery chemistry. However, in 2016, utilizing an iridium (Ir)-based electrocatalyst, Curtiss and Amine et al. found that LiO2 can be epitaxially grown on the surface of Ir catalyst and can be stable under cycling conditions.1 In the study, a templating mechanism was suggested, where a good lattice matching of LiIr3 surfaces (formed on the Ir catalyst) with that of LiO2 facilitates LiO2 formation as a singular discharge product. Following studies showed some superior electrochemical properties of LiO2 in comparison to Li2O2, including lower charge overpotentials. Meanwhile, some other transition metal compounds have recently exhibited LiO2 formation, where the formation mechanism suggested may not be a templating method. In this case, there could be strong adsorption of LiO2 in specific structures, resulting in suppressed Li2O2 generation. Herein, we will present experimental and computational results on some new catalysts for LiO2 formation and discuss possible underlying mechanisms. Acnowledgement This work was primarily supported by the US Department of Energy under contract DE-AC02-06CH11357 from the Vehicle Technologies Office, Department of Energy, Office of Energy Efficiency and Renewable Energy. Reference 1 Curtiss. L. and Amine. K. et al. A lithium–oxygen battery based on lithium superoxide. Nature 2016, 529, 377-382
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Rogers, M. S., G. D. Jones, G. Antonini, M. T. Wilson, and M. Brunori. "Electron transfer from Phanerochaete chrysosporium cellobiose oxidase to equine cytochrome c and Pseudomonas aeruginosa cytochrome c-551." Biochemical Journal 298, no. 2 (March 1, 1994): 329–34. http://dx.doi.org/10.1042/bj2980329.
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The electron-transfer reactions of cellobiose oxidase (CBO) have been investigated by conventional and by rapid-scan stopped-flow spectroscopy at pH 6.0. Analysis of the absorbance/time/wavelength matrix by Singular Value Decomposition (SVD) confirms earlier studies showing that cellobiose rapidly reduces the flavin group (7.7 s-1; cellobiose, 100 microM) which in turn slowly (0.2 s-1) reduces the cytochrome b moiety. In the presence of CBO, cellobiose reduces cytochromes c in a reaction that does not depend on oxygen or superoxide. The rate limit for this process is independent of the source of the cytochromes c and is identical with the rate of cytochrome b reduction. Rapid-mixing experiments show that cytochrome b may donate electrons very rapidly to either mammalian cytochrome c or bacterial cytochrome c-551. The reactions were second-order (kc = 1.75 x 10(7) M-1 x s-1; kc-551 = 4.3 x 10(6) M-1 x s-1; pH 6.0, 21 degrees C and I0.064) and strongly ionic-strength (I)-dependent: kc decreasing with I and kc-551 increasing with I. These results suggest the electron-transfer site near cytochrome b bears a significant negative charge. Equilibrium gel chromatography confirms that CBO oxidase and positively charged mammalian cytochrome c make stable complexes. These results are discussed in terms of a model suggesting an electron-transfer role for cytochrome b in vivo, possibly connected with radical-mediated cellulose breakdown.