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Sample records for monocrotaline n-oxide mno

  1. Methods to obtain radiolabelled monocrotaline

    Energy Technology Data Exchange (ETDEWEB)

    Lame, M.W.; Morin, D.; Wilson, D.W.; Segall, H.J. [University of California, Davis, CA (United States)

    1996-12-01

    Crotalaria spectabilis, a plant found in many areas of the world is associated with the pyrrolizidine alkaloid monocrotaline. Monocrotaline when injected subcutaneously in Sprague Dawley rats has been utilized for years to create a condition known to mimic pulmonary hypertension in humans. We attempted to determine the optimum conditions for the biosynthesis of radiolabelled monocrotaline. Our work describes the plant growth conditions and the time periods associated with the production of radiolabelled monocrotaline. In addition, the incorporation of {sup 14}CO{sub 2} or [2,3-{sup 3}H]-putrescine dihydrochloride and the specific activity plus the amount(s) of recovered radiolabelled monocrotaline are discussed. We conclude that the most efficient and cost effective method for the biosynthesis of radiolabelled monocrotaline is still the utilization of {sup 14}CO{sub 2}. (author).

  2. Compound list: monocrotaline [Open TG-GATEs

    Lifescience Database Archive (English)

    Full Text Available monocrotaline MCT 00058 ftp://ftp.biosciencedbc.jp/archive/open-tggates/LATEST/Human/in_vitro/monocrotaline....Human.in_vitro.Liver.zip ftp://ftp.biosciencedbc.jp/archive/open-tggates/LATEST/Rat/in_vitro/monocrotaline..._vivo/Liver/Single/monocrotaline.Rat.in_vivo.Liver.Single.zip ftp://ftp.bioscienc...edbc.jp/archive/open-tggates/LATEST/Rat/in_vivo/Liver/Repeat/monocrotaline.Rat.in_vivo.Liver.Repeat.zip ftp:...//ftp.biosciencedbc.jp/archive/open-tggates/LATEST/Rat/in_vivo/Kidney/Single/monocrotaline.Rat.in_vivo.Kidne

  3. Pyrrolizidine alkaloid-derived DNA adducts are common toxicological biomarkers of pyrrolizidine alkaloid N-oxides.

    Science.gov (United States)

    He, Xiaobo; Xia, Qingsu; Woodling, Kellie; Lin, Ge; Fu, Peter P

    2017-10-01

    There are 660 pyrrolizidine alkaloids (PAs) and PA N-oxides present in the plants, with approximately half being possible carcinogens. We previously reported that a set of four PA-derived DNA adducts is formed in the liver of rats administered a series of hepatocarcinogenic PAs and a PA N-oxide. Based on our findings, we hypothesized that this set of DNA adducts is a common biological biomarker of PA-induced liver tumor formation. In this study, we determined that rat liver microsomal metabolism of five hepatocarcinogenic PAs (lasiocarpine, retrorsine, riddelliine, monocrotaline, and heliotrine) and their corresponding PA N-oxides produced the same set of DNA adducts. Among these compounds, lasiocarpine N-oxide, retrorsine N-oxide, monocrotaline N-oxide, and heliotrine N-oxide are for first time shown to be able to produce these DNA adducts. These results further support the role of these DNA adducts as potential common biomarkers of PA-induced liver tumor initiation. Copyright © 2017. Published by Elsevier B.V.

  4. Therapeutic oral sesame oil is ineffectual against monocrotaline-induced sinusoidal obstruction syndrome in rats.

    Science.gov (United States)

    Periasamy, Srinivasan; Chien, Se-Ping; Liu, Ming-Yie

    2013-01-01

    The chemotherapeutic drug oxaliplatin causes sinusoidal obstruction syndrome (SOS), which is analogous to that of monocrotaline-induced SOS. Sesame oil is a nutrient-rich antioxidant in alternative medicine. It contains phenol, sesamin, sesamol, and sesamolin, all of which contribute to its antioxidant property. The authors investigated the therapeutic effect of oral sesame oil against monocrotaline-induced SOS in rats. Male Sprague-Dawley rats were gavaged with monocrotaline (90 mg/kg) to induce SOS. Control rats were treated with saline only at 0 and 24 hours. Sesame oil (0.5, 1, 2, or 4 mL/kg, orally) was given 24 hours after monocrotaline in rats. Blood samples were collected at 24 and 48 hours after monocrotaline was given to assess the level of aspartate aminotransferase (AST) and alanine aminotransferase (ALT). Histopathology was also assessed 48 hours after monocrotaline was given. AST and ALT were significantly higher in monocrotaline-treated rats than in control rats. Oral sesame oil did not decrease AST and ALT in monocrotaline-treated rats. In addition, liver pathology revealed that oral sesame oil had no therapeutic effect against SOS. Oral sesame oil is therapeutically ineffectual against monocrotaline-induced SOS.

  5. Downhill exercise training in monocrotaline-injected rats: Effects on echocardiographic and haemodynamic variables and survival.

    Science.gov (United States)

    Enache, Irina; Favret, Fabrice; Doutreleau, Stéphane; Goette Di Marco, Paola; Charles, Anne-Laure; Geny, Bernard; Charloux, Anne

    2017-02-01

    Eccentric exercise training has been shown to improve muscle force strength without excessive cardiovascular stress. Such an exercise modality deserves to be tested in pulmonary arterial hypertension. We aimed to assess the effects of an eccentric training modality on cardiac function and survival in an experimental monocrotaline-induced model of pulmonary arterial hypertension with right ventricular dysfunction. Forty rats were randomly assigned to one of four groups: 40mg/kg monocrotaline-injected sedentary rats; 40mg/kg monocrotaline-injected eccentric-trained rats; sedentary control rats; or eccentric-trained control rats. Eccentric exercise training consisted of downhill running on a treadmill with a -15° slope for 30minutes, 5 days a week for 4 weeks. Training tolerance was assessed by echocardiography, right ventricle catheterization and the rats' maximal eccentric speed. Survival in monocrotaline-injected eccentric-trained rats was not different from that in monocrotaline-injected sedentary rats. Monocrotaline-injected eccentric-trained rats tolerated this training modality well, and haemodynamic status did not deteriorate further compared with monocrotaline-injected sedentary rats. The eccentric maximal speed decline was less pronounced in trained compared with sedentary pulmonary arterial hypertension rats. Eccentric exercise training had no detrimental effects on right heart pressure, cardiac function and survival in rats with stable monocrotaline-induced pulmonary hypertension. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

  6. Lodenafil treatment in the monocrotaline model of pulmonary hypertension in rats

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    Igor Bastos Polonio

    2014-08-01

    Full Text Available We assessed the effects of lodenafil on hemodynamics and inflammation in the rat model of monocrotaline-induced pulmonary hypertension (PH. Thirty male Sprague-Dawley rats were randomly divided into three groups: control; monocrotaline (experimental model; and lodenafil (experimental model followed by lodenafil treatment, p.o., 5 mg/kg daily for 28 days Mean pulmonary artery pressure (mPAP was obtained by right heart catheterization. We investigated right ventricular hypertrophy (RVH and IL-1 levels in lung fragments. The number of cases of RVH was significantly higher in the monocrotaline group than in the lodenafil and control groups, as were mPAP and IL-1 levels. We conclude that lodenafil can prevent monocrotaline-induced PH, RVH, and inflammation.

  7. Therapeutic efficacy of TBC3711 in monocrotaline-induced pulmonary hypertension

    OpenAIRE

    Brandes Ralf P; Janssen Wiebke; Cornitescu Teodora; Sydykov Akylbek; Dahal Bhola K; Luitel Himal; Kojonazarov Baktybek; Kosanovic Djuro; Davie Neil; Ghofrani Hossein A; Weissmann Norbert; Grimminger Friedrich; Seeger Werner; Schermuly Ralph T

    2011-01-01

    Abstract Background Endothelin-1 signalling plays an important role in pathogenesis of pulmonary hypertension. Although different endothelin-A receptor antagonists are developed, a novel therapeutic option to cure the disease is still needed. This study aims to investigate the therapeutic efficacy of the selective endothelin-A receptor antagonist TBC3711 in monocrotaline-induced pulmonary hypertension in rats. Methods Monocrotaline-injected male Sprague-Dawley rats were randomized and treated...

  8. Modulation of monocrotaline-induced cor pulmonale by grape juice.

    Science.gov (United States)

    Ludke, Ana R L; Mosele, Francisca; Caron-Lienert, Rafaela; Ribeiro, Maria Flávia; Partata, Wânia; Llesuy, Susana; Araujo, Alex Sander; Singal, Pawan; Belló-Klein, Adriane

    2010-01-01

    The study was designed to test whether the ingestion grape juice (GJ) could modulate monocrotaline (MCT)-induced Cor pulmonale resulting from antioxidant properties. Three-week-old male Wistar rats received GJ (10 mL/kg/day) by gavage for 6 weeks. A single injection of MCT (60 mg/kg body weight intraperitoneally) was administered at the end of the third week. Animals were divided in four groups: control, MCT, GJ, and GJ + MCT. MCT promoted a significant increase in right ventricle (36%) and lung (70%) weight to body weight ratio. There was an increase in the right systolic (38%) as well as in the end diastolic (70%) ventricular pressures. MCT caused a significant decrease in lung endothelial nitric oxide synthase (20%) but increase in lipid peroxidation (13%) and catalase (43%). MCT-induced decrease in the endothelial nitric oxide synthase and increase in the right ventricular end diastolic pressure were prevented by GJ, whereas right systolic ventricular pressure and lung weight to body weight ratio were corrected only partially. MCT-induced increase in heart and right ventricle to body weight ratios was not changed by GJ. GJ blunted MCT-induced increase in lipid peroxidation but had no effect on the changes in catalase and superoxide dismutase activities. GJ appears to offer some protection against MCT-induced Cor pulmonale and right ventricle function changes.

  9. Pathophysiology of infantile pulmonary arterial hypertension induced by monocrotaline.

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    Dias-Neto, Marina; Luísa-Neves, Ana; Pinho, Sónia; Gonçalves, Nádia; Mendes, Maria; Eloy, Catarina; Lopes, José M; Gonçalves, Daniel; Ferreira-Pinto, Manuel; Leite-Moreira, Adelino F; Henriques-Coelho, Tiago

    2015-06-01

    Pediatric pulmonary arterial hypertension (PAH) presents certain specific features. In this specific age group, experimental models to study the pathophysiology of PAH are lacking. To characterize hemodynamic, morphometric, and histological progression as well as the expression of neurohumoral factors and regulators of cardiac transcription in an infantile model of PAH induced by monocrotaline (MCT), eight-day-old Wistar rats were randomly injected with MCT (30 mg/kg, sc, n = 95) or equal volume of saline solution (n = 92). Animals were instrumented for biventricular hemodynamic recording 7, 14, and 21 days after MCT, whereas samples were collected at 1, 3, 7, 14, and 21 days after MCT. Different time point postinjections were defined for further analysis. Hearts and lungs were collected for morphometric characterization, assessment of right- and left-ventricle (RV and LV) cardiomyocyte diameter and collagen type-I and type-III ratio, RV collagen volume fraction, and pulmonary vessels wall thickness. mRNA quantification was undertaken for brain natriuretic peptide (BNP), endothelin-1 (ET-1), and for cardiac transcription regulators (HOP and Islet1). Animals treated with MCT at the 8th day of life presented RV hypertrophy since day 14 after MCT injection. There were no differences on the RV collagen volume fraction or collagen type-I and type-III ratio. Pulmonary vascular remodelling and PAH were present on day 21, which were accompanied by an increased expression of BNP, ET-1, HOP, and Islet1. The infantile model of MCT-induced PAH can be useful for the study of its pathophysiology and to test new therapeutic targets in pediatric age group.

  10. Effects of pravastatin on pulmonary arteries and aorta reactivity in monocrotalin-induced pulmonary hypertension

    Institute of Scientific and Technical Information of China (English)

    PGUERARD; 0BARTHEZ; FGOIRAND; LROCHETTE; MBARDOU; MDUMAS

    2004-01-01

    AIM: Vascular injury caused by monocrotalin (MC) can affect endothelial regulation and induces pulmonary hypertension and heart failure. We showed previously that pravastatin prevented the development of MC-induced pulmonary hypertension by improving pulmonary arteries (PA) endothelium dependent vasodilation. The aims of this study were to compare the protective

  11. Experimental and theoretical studies on the characterization of monocrotaline by infrared and Raman spectroscopies

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    Oliveira, Ramon Prata; Demuner, Antonio Jacinto; Alvarenga, Elson Santiago; Parma, Monica Cropo; Barbosa, Luiz Claudio Almeida; de Moura Guimarães, Luciano; Aguiar, Alex Ramos

    2017-05-01

    The use of plants in folk medicine has a long and ancient history in the treatment of various diseases. Currently, a large proportion of commercial drugs are based on natural products or are synthetic compounds inspired on such natural substances. Therefore, in this communication to aid that research, structural and spectroscopic analysis of the natural pyrrolizidine alkaloid called monocrotaline was carried out. Pyrrolizidine alkaloids that are commonly found in the Boraginaceae and Asteraceae families are among the great diversity of secondary metabolites which are produced by plants to act as a defense mechanism against herbivores and microbes. In the present study, the natural product, monocrotaline, an alkaloid isolated from the leaves of Crotalaria paulina, with potential application in medicine, was characterized by infrared (IR) and Raman spectroscopy with the support of Density Functional Theory (DFT) calculations. IR and Raman spectra of monocrotaline were recorded at room temperature ranging from 4000 to 400 cm-1. DFT calculations with the hybrid functional B3LYP and the basis set 6-31 + G(d,p) were performed with the purpose of obtaining information on the structural and vibrational properties of this structure. A perfect fit between the experimentally measured frequencies of the IR and Raman spectra and the calculated values were observed, and we have performed the complete identification of monocrotaline by these techniques.

  12. Cellular fibronectin and von Willebrand factor concentrations in plasma of rats treated with monocrotaline pyrrole

    NARCIS (Netherlands)

    Schultze, A.E.; Emeis, J.J.; Roth, R.A.

    1996-01-01

    The monocrotaline pyrrole (MCTP)-treated rat is a useful model for the study of certain chronic pulmonary vascular diseases. A single, i.v. administration of a low dose of MCTP causes pneumotoxicity, pulmonary vascular remodeling, sustained increases in pulmonary arterial pressure, and right ventric

  13. Reliable experimental model of hepatic veno-occlusive disease caused by monocrotaline

    Institute of Scientific and Technical Information of China (English)

    Miao-Yan Chen; Jian-Ting Cai; Qin Du; Liang-Jing Wang; Jia-Min Chen; Li-Ming Shao

    2008-01-01

    BACKGROUND:Hepatic veno-occlusive disease (HVOD) is a severe complication of chemotherapy before hematopoietic stem cell transplantation and dietary ingestion of pyrrolizidine alkaloids. Many experimental models were established to study its mechanisms or therapy, but few are ideal. This work aimed at evaluating a rat model of HVOD induced by monocrotaline to help advance research into this disease. METHODS:Thirty-two male rats were randomly classiifed into 5 groups, and PBS or monocrotaline was administered (100 mg/kg or 160 mg/kg). They were sacriifced on day 7 (groups A, B and D) or day 10 (groups C and E). Blood samples were collected to determine liver enzyme concentrations. The weight of the liver and body and the amount of ascites were measured. Histopathological changes of liver tissue on light microscopy were assessed by a modiifed Deleve scoring system. The positivity of proliferating cell nuclear antigen (PCNA) was estimated. RESULTS:The rats that were treated with 160 mg/kg monocrotaline presented with severe clinical symptoms (including two deaths) and the histopathological picture of HVOD. On the other hand, the rats that were fed with 100 mg/kg monocrotaline had milder and reversible manifestations. Comparison of the rats sacriifced on day 10 with those sacriifced on day 7 showed that the positivity of PCNA increased, especially that of hepatocytes. CONCLUSIONS:Monocrotaline induces acute, dose-dependent HVOD in rats. The model is potentially reversible with a low dose, but reliable and irreversible with a higher dose. The modiifed scoring system seems to be more accurate than the traditional one in relfecting the histopathology of HVOD. The enhancement of PCNA positivity may be associated with hepatic tissue undergoing recovery.

  14. All-TRANS RETINOIC ACID INTERFERES DEVELOPMENT OF PULMONARY HYPERTENSION INDUCED BY MONOCROTALINE IN RATS

    Institute of Scientific and Technical Information of China (English)

    秦玉明; 周爱卿; 贲晓明; 沈捷; 梁瑛; 李奋

    2001-01-01

    Objective To determine whether all-trans retinoic acid (atRA) affects the metabolism of collagen in main pulmonary artery and exerts an inhibitory effect in rats with pulmonary hypertension induced by monocrotaline . Methods All rats (n=72) were divided into 3 groups as control, model, and atRA . In model and atRA groups, rats (n=48) were assigned at random to be given a single subcutaneous injection of monocrotaline (60mgg/kg) and administrated with either atRA (30rng·kg-1·d-1) for atRA group or saline through oral-gastro intubation for model group. In control group, rats (n=24) received a single subcutaneous injection of an equal volume of 0. 9% saline. On day 7, 14,21 and 28 after monocrotaline or saline injection, cardiovascular catheters were inserted into the pulmonary artery of rats in each group to examine their mean pulmonary artery pressure, in addition with their hydroxyproline content determined by chromometry. Results In comparison with the control rats, the mean pulmonary artery pressure of rats in model group increased significantly on day 21 and up to the peak on day 28 (P<0.01), while their hydroxyproline contents decreased significantly on day 14 ( P < 0.05) and increased significantly on day 21 and 28. The atRA group when compared with the model group show reduction in the content of hydroxyproline and the mean pulmonary artery pressure ( P < 0.01 ). Conclusion The atRA inhibits the accumulation of collagen in main pulmonary artery and interferes the development of pulmonary hypertension which might elicit favorable geometric remodeling of rat pulmonary hypertension induced by monocrotaline.

  15. Arrhythmogenic substrate in hearts of rats with monocrotaline-induced pulmonary hypertension and right ventricular hypertrophy

    OpenAIRE

    Benoist, David; Stones, Rachel; Drinkhill, Mark; Bernus, Olivier; White, Ed

    2011-01-01

    Mechanisms associated with right ventricular (RV) hypertension and arrhythmias are less understood than those in the left ventricle (LV). The aim of our study was to investigate whether and by what mechanisms a proarrhythmic substrate exists in a rat model of RV hypertension and hypertrophy. Rats were injected with monocrotaline (MCT; 60 mg/kg) to induce pulmonary artery hypertension or with saline (CON). Myocardial levels of mRNA for genes expressing ion channels were measured by real-time R...

  16. Therapeutic efficacy of TBC3711 in monocrotaline-induced pulmonary hypertension

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    Brandes Ralf P

    2011-06-01

    Full Text Available Abstract Background Endothelin-1 signalling plays an important role in pathogenesis of pulmonary hypertension. Although different endothelin-A receptor antagonists are developed, a novel therapeutic option to cure the disease is still needed. This study aims to investigate the therapeutic efficacy of the selective endothelin-A receptor antagonist TBC3711 in monocrotaline-induced pulmonary hypertension in rats. Methods Monocrotaline-injected male Sprague-Dawley rats were randomized and treated orally from day 21 to 35 either with TBC3711 (Dose: 30 mg/kg body weight/day or placebo. Echocardiographic measurements of different hemodynamic and right-heart hypertrophy parameters were performed. After day 35, rats were sacrificed for invasive hemodynamic and right-heart hypertrophy measurements. Additionally, histologic assessment of pulmonary vascular and right-heart remodelling was performed. Results The novel endothelin-A receptor antagonist TBC3711 significantly attenuated monocrotaline-induced pulmonary hypertension, as evident from improved hemodynamics and right-heart hypertrophy in comparison with placebo group. In addition, muscularization and medial wall thickness of distal pulmonary vessels were ameliorated. The histologic evaluation of the right ventricle showed a significant reduction in fibrosis and cardiomyocyte size, suggesting an improvement in right-heart remodelling. Conclusion The results of this study suggest that the selective endothelin-A receptor antagonist TBC3711 demonstrates therapeutic benefit in rats with established pulmonary hypertension, thus representing a useful therapeutic approach for treatment of pulmonary hypertension.

  17. Characterization of hepatic DNA damage induced in rats by the pyrrolizidine alkaloid monocrotaline

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    Petry, T.W.; Bowden, G.T.; Huxtable, R.J.; Sipes, I.G.

    1984-04-01

    Hepatic DNA damage induced by the pyrrolizidine alkaloid monocrotaline was evaluated following i.p. administration to adult male Sprague-Dawley rats. Animals were treated with various doses ranging upward from 5 mg/kg, and hepatic nuclei were isolated 4 hr later. Hepatic nuclei were used as the DNA source in all experiments. DNA damage was characterized by the alkaline elution technique. A mixture of DNA-DNA interstrand cross-links and DNA-protein cross-links was induced. Following an injection of monocrotaline, 30 mg/kg i.p., DNA-DNA interstrand cross-linking reached a maximum within 12 hr or less and thereafter decreased over a protracted period of time. By 96 hr postadministration, the calculated cross-linking factor was no longer statistically different from zero. No evidence for the induction of DNA single-strand breaks was observed, although the presence of small numbers of DNA single-strand breaks could have been masked by the overwhelming predominance of DNA cross-links. These DNA cross-links may be related to the hepatocarcinogenic, hepatotoxic, and/or antimitotic effects of monocrotaline.

  18. The beneficial effect of suramin on monocrotaline-induced pulmonary hypertension in rats.

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    Mohamed Izikki

    Full Text Available BACKGROUND: Pulmonary hypertension (PH is a progressive disorder characterized by an increase in pulmonary artery pressure and structural changes in the pulmonary vasculature. Several observations indicate that growth factors play a key role in PH by modulating pulmonary artery smooth muscle cell (PA-SMC function. In rats, established monocrotaline-induced PH (MCT-PH can be reversed by blocking platelet-derived growth factor receptors (PDGF-R, epidermal growth factor receptors (EGF-R, or fibroblast growth factor receptors (FGF-R. All these receptors belong to the receptor tyrosine kinase (RTK family. METHODS AND RESULTS: We evaluated whether RTK blockade by the nonspecific growth factor inhibitor, suramin, reversed advanced MCT-PH in rats via its effects on growth-factor signaling pathways. We found that suramin inhibited RTK and ERK1/2 phosphorylation in cultured human PA-SMCs. Suramin inhibited PA-SMC proliferation induced by serum, PDGF, FGF2, or EGF in vitro and ex vivo. Treatment with suramin from day 1 to day 21 after monocrotaline injection attenuated PH development, as shown by lower values for pulmonary artery pressure, right ventricular hypertrophy, and distal vessel muscularization on day 21 compared to control rats. Treatment with suramin from day 21 to day 42 after monocrotaline injection reversed established PH, thereby normalizing the pulmonary artery pressure values and vessel structure. Suramin treatment suppressed PA-SMC proliferation and attenuated both the inflammatory response and the deposition of collagen. CONCLUSIONS: RTK blockade by suramin can prevent MCT-PH and reverse established MCT-PH in rats. This study suggests that an anti-RTK strategy that targets multiple RTKs could be useful in the treatment of pulmonary hypertension.

  19. The Beneficial Effect of Suramin on Monocrotaline-Induced Pulmonary Hypertension in Rats

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    Izikki, Mohamed; Mercier, Olaf; Lecerf, Florence; Lubert Guin, Lauriane; Hoang, Eric; Dorfmüller, Peter; Perros, Frédéric; Humbert, Marc; Simonneau, Gerald; Dartevelle, Philippe; Fadel, Elie; Eddahibi, Saadia

    2013-01-01

    Background Pulmonary hypertension (PH) is a progressive disorder characterized by an increase in pulmonary artery pressure and structural changes in the pulmonary vasculature. Several observations indicate that growth factors play a key role in PH by modulating pulmonary artery smooth muscle cell (PA-SMC) function. In rats, established monocrotaline-induced PH (MCT-PH) can be reversed by blocking platelet-derived growth factor receptors (PDGF-R), epidermal growth factor receptors (EGF-R), or fibroblast growth factor receptors (FGF-R). All these receptors belong to the receptor tyrosine kinase (RTK) family. Methods and Results We evaluated whether RTK blockade by the nonspecific growth factor inhibitor, suramin, reversed advanced MCT-PH in rats via its effects on growth-factor signaling pathways. We found that suramin inhibited RTK and ERK1/2 phosphorylation in cultured human PA-SMCs. Suramin inhibited PA-SMC proliferation induced by serum, PDGF, FGF2, or EGF in vitro and ex vivo. Treatment with suramin from day 1 to day 21 after monocrotaline injection attenuated PH development, as shown by lower values for pulmonary artery pressure, right ventricular hypertrophy, and distal vessel muscularization on day 21 compared to control rats. Treatment with suramin from day 21 to day 42 after monocrotaline injection reversed established PH, thereby normalizing the pulmonary artery pressure values and vessel structure. Suramin treatment suppressed PA-SMC proliferation and attenuated both the inflammatory response and the deposition of collagen. Conclusions RTK blockade by suramin can prevent MCT-PH and reverse established MCT-PH in rats. This study suggests that an anti-RTK strategy that targets multiple RTKs could be useful in the treatment of pulmonary hypertension. PMID:24143201

  20. A metabonomic evaluation of the monocrotaline-induced sinusoidal obstruction syndrome (SOS) in rats

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    Conotte, R.; Colet, J.-M., E-mail: jean-marie.colet@umons.ac.be

    2014-04-15

    The main curative treatment of colorectal cancer remains the surgery. However, when metastases are suspected, surgery is followed by a preventive chemotherapy using oxaliplatin which, unfortunately, may cause liver sinusoidal obstruction syndrome (SOS). Such hepatic damage is barely detected during or after chemotherapy due to a lack of effective diagnostic procedures, but liver biopsy. The primary objective of the present study was to identify potential early diagnosis biomarkers of SOS using a metabonomic approach. SOS was induced in rats by monocrotaline, a prototypical toxic substance. {sup 1}H NMR spectroscopy analysis of urine samples collected from rats treated with monocrotaline showed significant metabolic changes as compared to controls. During a first phase, cellular protective mechanisms such as an increased synthesis of GSH (reduced taurine) and the recruitment of cell osmolytes in the liver (betaine) were seen. In the second phase, the disturbance of the urea cycle (increased ornithine and urea reduction) leading to the depletion of NO, the alteration in the GSH synthesis (increased creatine and GSH precursors (glutamate, dimethylglycine and sarcosine)), and the liver necrosis (decrease taurine and increase creatine) all indicate the development of SOS. - Highlights: • Urine metabonomic profiles of SOS have been identified. • Urine osmoprotectants and anti-oxidants indicated an initial liver protection. • Liver necrosis was demonstrated by increased urine levels of taurine and creatine. • NO depletion was suggested by changes in ornithine and urea.

  1. Development and validation of a rapid multiplex ELISA for pyrrolizidine alkaloids and their N-oxides in honey and feed.

    Science.gov (United States)

    Oplatowska, Michalina; Elliott, Christopher T; Huet, Anne-Catherine; McCarthy, Mark; Mulder, Patrick P J; von Holst, Christoph; Delahaut, Philippe; Van Egmond, Hans P; Campbell, Katrina

    2014-01-01

    Pyrrolizidine alkaloids (PAs) are a group of plant secondary metabolites with carcinogenic and hepatotoxic properties. When PA-producing plants contaminate crops, toxins can be transferred through the food chain and cause illness in humans and animals, most notably hepatic veno-occlusive disease. Honey has been identified as a direct risk of human exposure. The European Food Safety Authority has recently identified four groups of PAs that are of particular importance for food and feed: senecionine-type, lycopsamine-type, heliotrine-type and monocrotaline-type. Liquid or gas chromatography methods are currently used to detect PAs but there are no rapid screening assays available commercially. Therefore, the aim of this study was to develop a rapid multiplex ELISA test for the representatives of three groups of alkaloids (senecionine, lycopsamine and heliotrine types) that would be used as a risk-management tool for the screening of these toxic compounds in food and feed. The method was validated for honey and feed matrices and was demonstrated to have a detection capability less than 25 μg/kg for jacobine, lycopsamine, heliotrine and senecionine. The zinc reduction step introduced to the extraction procedure allows for the additional detection of the presence of N-oxides of PAs. This first multiplex immunoassay for PA detection with N-oxide reduction can be used for the simultaneous screening of 21 samples for >12 PA analytes. Honey samples (n = 146) from various origins were analysed for PA determination. Six samples were determined to contain measurable PAs >25 μg/kg by ELISA which correlated to >10 μg/kg by LC-MS/MS.

  2. Rosuvastatin, Sildenafil and Their Combination in Monocrotaline-Induced Pulmonary Hypertension in Rat

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    Jasińska-Stroschein Magdalena

    2014-09-01

    Full Text Available There is considerable interest in the pleiotropic effects of statins and their potential role in the treatment of pulmonary hypertension. Previous experimental findings indicate that a combination of lipophilic statins with phosphodiesterase type-5 inhibitor, sildenafil, can offer preventive effects on rat monocrotaline-induced pulmonary hypertension. The present study is aimed to assess whether therapeutic regimen provides any benefits. Seven days after pulmonary hypertension induction, hydrophilic rosuvastatin and sildenafil were given for 14 days to male Wistar outbred rats. Right ventricular pressure, right ventricle mass and three biomarkers were evaluated after 21 days: brain natriuretic peptide, high-density lipoprotein cholesterol and vascular endothelial growth factor. The present study demonstrates that administration of hydrophilic statin with sildenafil results in reduction of pulmonary vascular remodeling and right ventricular pressure. The results of biochemical measurements may suggest that statins play a positive role in right ventricle function or the process of angiogenesis in pulmonary hypertension development.

  3. The protective effects of cerium oxide nanoparticles against hepatic oxidative damage induced by monocrotaline

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    Kamal A Amin

    2011-01-01

    Full Text Available Kamal A Amin1, Mohamed S Hassan2, El-Said T Awad3, Khalid S Hashem11Department of Biochemistry, 2Department of Internal Medicine, Faculty of Veterinary Medicine, Beni-Suef University, Beni-Suef, Egypt; 3Department of Biochemistry, Faculty of Veterinary Medicine, Cairo University, Cairo, EgyptObjective: The objective of the present study was to determine the ability of cerium oxide (CeO2 nanoparticles to protect against monocrotaline (MCT-induced hepatotoxicity in a rat model.Method: Twenty male Sprague Dawley rats were arbitrarily assigned to four groups: control (received saline, CeO2 (given 0.0001 nmol/kg intraperitoneally [IP], MCT (given 10 mg/kg body weight IP as a single dose, and MCT + CeO2 (received CeO2 both before and after MCT. Electron microscopic imaging of the rat livers was carried out, and hepatic total glutathione (GSH, glutathione reductase (GR, glutathione peroxidase (GPX, glutathione S-transferase (GST, superoxide dismutase (SOD, and catalase (CAT enzymatic activities were quantified.Results: Results showed a significant MCT-induced decrease in total hepatic GSH, GPX, GR, and GST normalized to control values with concurrent CeO2 administration. In addition, MCT produced significant increases in hepatic CAT and SOD activities, which also ameliorated with CeO2.Conclusions: These results indicate that CeO2 acts as a putative novel and effective hepatoprotective agent against MCT-induced hepatotoxicity.Keywords: monocrotaline, ceruim oxide nanoparticle, hepatotoxicity, oxidative stress

  4. Role of oxidative stress, inflammation, nitric oxide and transforming growth factor-beta in the protective effect of diosgenin in monocrotaline-induced pulmonary hypertension in rats.

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    Ahmed, Lamiaa A; Obaid, Al Arqam Z; Zaki, Hala F; Agha, Azza M

    2014-10-05

    Pulmonary hypertension is a progressive disease of various origins that is associated with right ventricular dysfunction. In the present study, the protective effect of diosgenin was investigated in monocrotaline-induced pulmonary hypertension in rats. Pulmonary hypertension was induced by a single subcutaneous injection of monocrotaline (60 mg/kg). Diosgenin (100 mg/kg) was given by oral administration once daily for 3 weeks. At the end of the experiment, mean arterial blood pressure, electrocardiography and echocardiography were recorded. Rats were then sacrificed and serum was separated for determination of total nitrate/nitrite level. Right ventricles and lungs were isolated for estimation of oxidative stress markers, tumor necrosis factor-alpha, total nitrate/nitrite and transforming growth factor-beta contents. Myeloperoxidase and caspase-3 activities in addition to endothelial and inducible nitric oxide synthase protein expression were also determined. Moreover, histological analysis of pulmonary arteries and cardiomyocyte cross-sectional area was performed. Diosgenin treatment provided a significant improvement toward preserving hemodynamic changes and alleviating oxidative stress, inflammatory and apoptotic markers induced by monocrotaline in rats. Furthermore, diosgenin therapy prevented monocrotaline-induced changes in nitric oxide production, endothelial and inducible nitric oxide synthase protein expression as well as histological analysis. These findings support the beneficial effect of diosgenin in pulmonary hypertension induced by monocrotaline in rats. Copyright © 2014 Elsevier B.V. All rights reserved.

  5. Na Deposition on MnO(100)

    Science.gov (United States)

    Feng, Xu; Cox, David F.

    2016-03-01

    Na deposition on the MnO(100) surface was investigated by temperature programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS) and low energy electron diffraction (LEED). Na TPD and XPS results indicate that adsorbed Na interacts strongly with the MnO substrate to form an irreversibly-adsorbed, oxidic Na compound on the surface for coverages up to 1 monolayer (ML). This strongly-bound Na diffuses into the MnO subsurface and bulk at elevated temperatures above 500 K. For Na coverages above 1 ML, metallic Na is present and desorbs from the surface below 500 K. The deposition of Na on MnO(100) follows a Stranski-Krastanov (SK) growth mode, with the formation of metallic Na islands following completion of the first Na monolayer. After Na deposition, the surface exhibits a diffuse (1 × 1) LEED pattern, suggesting the formation of disordered Na overlayers. After heating to 1000 K, the surface presents a (2 × 2) LEED pattern indicating that a surface reconstruction is induced by the diffusion of Na into the near surface region. CO2 can be used as a probe molecule in TPD to distinguish between metallic Na islands and oxidic Na in the first ML, and to indicate when Na that is still observable by XPS goes subsurface.

  6. Metabolic Changes Precede the Development of Pulmonary Hypertension in the Monocrotaline Exposed Rat Lung.

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    Olga Rafikova

    Full Text Available There is increasing interest in the potential for metabolic profiling to evaluate the progression of pulmonary hypertension (PH. However, a detailed analysis of the metabolic changes in lungs at the early stage of PH, characterized by increased pulmonary artery pressure but prior to the development of right ventricle hypertrophy and failure, is lacking in a preclinical animal model of PH. Thus, we undertook a study using rats 14 days after exposure to monocrotaline (MCT, to determine whether we could identify early stage metabolic changes prior to the manifestation of developed PH. We observed changes in multiple pathways associated with the development of PH, including activated glycolysis, increased markers of proliferation, disruptions in carnitine homeostasis, increased inflammatory and fibrosis biomarkers, and a reduction in glutathione biosynthesis. Further, our global metabolic profile data compare favorably with prior work carried out in humans with PH. We conclude that despite the MCT-model not recapitulating all the structural changes associated with humans with advanced PH, including endothelial cell proliferation and the formation of plexiform lesions, it is very similar at a metabolic level. Thus, we suggest that despite its limitations it can still serve as a useful preclinical model for the study of PH.

  7. Vitamin E and selenium treatment of monocrotaline induced hepatotoxicity in rats.

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    Cuce, G; Canbaz, H T; Sozen, M E; Yerlikaya, F H; Kalkan, S

    2017-01-01

    Monocrotaline (MCT) is a hepatotoxic pyrrolizidine alkaloid that is derived from plants; exposure may occur by consumption of contaminated grains, herbal teas and medicines. MCT can cause liver damage. We investigated the antioxidant effects of selenium (Se) and vitamin E against the toxic effects of MCT. Female Wistar albino rats were divided into four groups: a control group, an MCT group, an MCT + Se group, and an MCT + vitamin E group. Liver tissues were harvested, fixed, processed to paraffin and sections were cut. Anti-von Willebrand factor (vWF) immunohistochemistry, terminal deoxynucleotidyl transferase dUTP nick end-labeling (TUNEL), and hematoxylin and eosin staining were performed. Serum and liver tissue glutathione (GSH), catalase (CAT), and glutathione peroxidase (GPx) levels were measured. Histopathological and TUNEL data showed significantly increased liver damage in the MCT group compared to controls. Histopathological and TUNEL staining indicated significant improvements in the MCT + vitamin E and MCT + Se groups compared to the MCT group. MCT significantly reduced the serum GSH level and GPx activity, and liver GPx activity. Biochemical data indicated a significant improvement in serum GSH level in the MCT + vitamin E group compared to the MCT group. We suggest that vitamin E and Se afford limited protection against MCT hepatotoxicity.

  8. Thymosin Beta 4 protects mice from monocrotaline-induced pulmonary hypertension and right ventricular hypertrophy.

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    Chuanyu Wei

    Full Text Available Pulmonary hypertension (PH is a progressive vascular disease of pulmonary arteries that impedes ejection of blood by the right ventricle. As a result there is an increase in pulmonary vascular resistance and pulmonary arterial pressure causing right ventricular hypertrophy (RVH and RV failure. The pathology of PAH involves vascular cell remodeling including pulmonary arterial endothelial cell (PAEC dysfunction and pulmonary arterial smooth muscle cell (PASMC proliferation. Current therapies are limited to reverse the vascular remodeling. Investigating a key molecule is required for development of new therapeutic intervention. Thymosin beta-4 (Tβ4 is a ubiquitous G-actin sequestering protein with diverse biological function and promotes wound healing and modulates inflammatory responses. However, it remains unknown whether Tβ4 has any protective role in PH. The purpose of this study is to evaluate the whether Tβ4 can be used as a vascular-protective agent. In monocrotaline (MCT-induced PH mouse model, we showed that mice treated with Tβ4 significantly attenuated the systolic pressure and RVH, compared to the MCT treated mice. Our data revealed for the first time that Tβ4 selectively targets Notch3-Col 3A-CTGF gene axis in preventing MCT-induced PH and RVH. Our study may provide pre-clinical evidence for Tβ4 and may consider as vasculo-protective agent for the treatment of PH induced RVH.

  9. Arterial morphology responds differently to Captopril then N-acetylcysteine in a monocrotaline rat model of pulmonary hypertension

    Science.gov (United States)

    Molthen, Robert; Wu, Qingping; Baumgardt, Shelley; Kohlhepp, Laura; Shingrani, Rahul; Krenz, Gary

    2010-03-01

    Pulmonary hypertension (PH) is an incurable condition inevitably resulting in death because of increased right heart workload and eventual failure. PH causes pulmonary vascular remodeling, including muscularization of the arteries, and a reduction in the typically large vascular compliance of the pulmonary circulation. We used a rat model of monocrotaline (MCT) induced PH to evaluated and compared Captopril (an angiotensin converting enzyme inhibitor with antioxidant capacity) and N-acetylcysteine (NAC, a mucolytic with a large antioxidant capacity) as possible treatments. Twenty-eight days after MCT injection, the rats were sacrificed and heart, blood, and lungs were studied to measure indices such as right ventricular hypertrophy (RVH), hematocrit, pulmonary vascular resistance (PVR), vessel morphology and biomechanics. We implemented microfocal X-ray computed tomography to image the pulmonary arterial tree at intravascular pressures of 30, 21, 12, and 6 mmHg and then used automated vessel detection and measurement algorithms to perform morphological analysis and estimate the distensibility of the arterial tree. The vessel detection and measurement algorithms quickly and effectively mapped and measured the vascular trees at each intravascular pressure. Monocrotaline treatment, and the ensuing PH, resulted in a significantly decreased arterial distensibility, increased PVR, and tended to decrease the length of the main pulmonary trunk. In rats with PH induced by monocrotaline, Captopril treatment significantly increased arterial distensibility and decrease PVR. NAC treatment did not result in an improvement, it did not significantly increase distensibility and resulted in further increase in PVR. Interestingly, NAC tended to increase peripheral vascular density. The results suggest that arterial distensibility may be more important than distal collateral pathways in maintaining PVR at normally low values.

  10. Farnesoid-X-receptor expression in monocrotaline-induced pulmonary arterial hypertension and right heart failure

    Energy Technology Data Exchange (ETDEWEB)

    Ye, Lusi [Department of Rheumatology, Xiangya Hospital, Central South University, 87 Xiangya Road, Changsha, Hunan 410008 (China); Department of Rheumatology, The First Affiliated Hospital, Wenzhou Medical University, Wenzhou, Zhejiang 325015 (China); Jiang, Ying [Department of Rheumatology, Xiangya Hospital, Central South University, 87 Xiangya Road, Changsha, Hunan 410008 (China); Zuo, Xiaoxia, E-mail: susanzuo@hotmail.com [Department of Rheumatology, Xiangya Hospital, Central South University, 87 Xiangya Road, Changsha, Hunan 410008 (China)

    2015-11-06

    Objective: The farnesoid-X-receptor (FXR) is a metabolic nuclear receptor superfamily member that is highly expressed in enterohepatic tissue and is also expressed in the cardiovascular system. Multiple nuclear receptors, including FXR, play a pivotal role in cardiovascular disease (CVD). Pulmonary arterial hypertension (PAH) is an untreatable cardiovascular system disease that leads to right heart failure (RHF). However, the potential physiological/pathological roles of FXR in PAH and RHF are unknown. We therefore compared FXR expression in the cardiovascular system in PAH, RHF and a control. Methods and results: Hemodynamic parameters and morphology were assessed in blank solution-exposed control, monocrotaline (MCT)-exposed PAH (4 weeks) and RHF (7 weeks) Sprague–Dawley rats. Real-time reverse transcription polymerase chain reaction (real-time RT-PCR), Western blot (WB), immunohistochemistry (IHC) analysis and immunofluorescence (IF) analysis were performed to assess FXR levels in the lung and heart tissues of MCT-induced PAH and RHF rats. In normal rats, low FXR levels were detected in the heart, and nearly no FXR was expressed in rat lungs. However, FXR expression was significantly elevated in PAH and RHF rat lungs but reduced in PAH and RHF rat right ventricular (RV) tissues. FXR expression was reduced only in RHF rat left ventricular (LV) tissues. Conclusions: The differential expression of FXR in MCT-induced PAH lungs and heart tissues in parallel with PAH pathophysiological processes suggests that FXR contributes to PAH. - Highlights: • FXR was expressed in rat lung and heart tissues. • FXR expression increased sharply in the lung tissues of PAH and RHF rats. • FXR expression was reduced in PAH and RHF rat RV tissue. • FXR expression was unaltered in PAH LV but reduced in RHF rat LV tissue. • FXR expression was prominent in the neovascularization region.

  11. Pioglitazone alleviates cardiac and vascular remodelling and improves survival in monocrotaline induced pulmonary arterial hypertension.

    Science.gov (United States)

    Behringer, Arnica; Trappiel, Manuela; Berghausen, Eva Maria; Ten Freyhaus, Henrik; Wellnhofer, Ernst; Odenthal, Margarete; Blaschke, Florian; Er, Fikret; Gassanov, Natig; Rosenkranz, Stephan; Baldus, Stephan; Kappert, Kai; Caglayan, Evren

    2016-04-01

    Pulmonary arterial hypertension (PAH) is a fatal disease with limited therapeutic options. Pathophysiological changes comprise obliterative vascular remodelling of small pulmonary arteries, elevated mean pulmonary arterial systolic pressure (PASP) due to elevated resistance of pulmonary vasculature, adverse right ventricular remodelling, and heart failure. Recent findings also indicate a role of increased inflammation and insulin resistance underlying the development of PAH. We hypothesized that treatment of this condition with the peroxisome proliferator-activated receptor-γ (PPARγ) activator pioglitazone, known to regulate the expression of different genes addressing insulin resistance, inflammatory changes, and vascular remodelling, could be a beneficial approach. PAH was induced in adult rats by a single subcutaneous injection of monocrotaline (MCT). Pioglitazone was administered for 2 weeks starting 3 weeks after MCT-injection. At day 35, hemodynamics, organ weights, and -indices were measured. We performed morphological and molecular characterization of the pulmonary vasculature, including analysis of the degree of muscularization, proliferation rates, and medial wall thickness of the small pulmonary arteries. Furthermore, markers of cardiac injury, collagen content, and cardiomyocyte size were analyzed. Survival rates were monitored throughout the experimental period. Pioglitazone treatment improved survival, reduced PASP, muscularization of small pulmonary arteries, and medial wall thickness. Further, MCT-induced right ventricular hypertrophy and fibrosis were attenuated. This was accompanied with reduced cardiac expression of brain natriuretic peptide, as well as decreased cardiomyocyte size. Finally, pulmonary macrophage content and osteopontin gene expression were attenuated. Based on the beneficial impact of pioglitazone, activation of PPARγ might be a promising treatment option in PAH.

  12. Characterization and screening of pyrrolizidine alkaloids and N-oxides from botanicals and dietary supplements using UHPLC-high resolution mass spectrometry.

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    Avula, Bharathi; Sagi, Satyanarayanaraju; Wang, Yan-Hong; Zweigenbaum, Jerry; Wang, Mei; Khan, Ikhlas A

    2015-07-01

    The UHPLC-QToF-MS analysis of pyrrolizidine alkaloids (PAs) from various parts of 37 botanicals and 7 products was performed. A separation by LC was achieved using a reversed-phase column and a gradient of water/acetonitrile each containing formic acid as the mobile phase. MS-MS detection was used because of its high selectivity, and ability to provide structural information. Free base and N-oxides were observed by this method. PAs were analyzed and detected in plants from three different families, viz., Asteraceae, Boraginaceae and Fabaceae. The Asteraceae family was found to contain senecionine and lycopsamine type PAs. The Boraginaceae family contained lycopsamine and heliotrine type PAs and the Fabaceae family contained senecionine and monocrotaline type PAs. These PAs may serve as important markers for the detection of these plant materials in food and dietary supplements. PAs were identified in 44 samples by comparing their retention times, accurate mass and mass fragmentation patterns with those of 25 reference standards.

  13. New Conjugated Benzothiazole-N-oxides: Synthesis and Biological Activity

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    Pavlína Foltínová

    2009-12-01

    Full Text Available Eleven new 2-styrylbenzothiazole-N-oxides have been prepared by aldol – type condensation reactions between 2-methylbenzothiazole–N-oxide and para-substituted benzaldehydes. Compounds with cyclic amino substituents showed typical push-pull molecule properties. Four compounds were tested against various bacterial strains as well as the protozoan Euglena gracilis as model microorganisms. Unlike previously prepared analogous benzothiazolium salts, only weak activity was recorded.

  14. Superoxide dismutase/catalase mimetic EUK-134 prevents diaphragm muscle weakness in monocrotalin-induced pulmonary hypertension

    Science.gov (United States)

    Tatebayashi, Daisuke; Lee, Jaesik; Westerblad, Håkan; Lanner, Johanna T.

    2017-01-01

    Patients with pulmonary hypertension (PH) suffer from inspiratory insufficiency, which has been associated with intrinsic contractile dysfunction in diaphragm muscle. Here, we examined the role of redox stress in PH-induced diaphragm weakness by using the novel antioxidant, EUK-134. Male Wistar rats were randomly divided into control (CNT), CNT + EUK-134 (CNT + EUK), monocrotaline-induced PH (PH), and PH + EUK groups. PH was induced by a single intraperitoneal injection of monocrotaline (60 mg/kg body weight). EUK-134 (3 mg/kg body weight/day), a cell permeable mimetic of superoxide dismutase (SOD) and catalase, was daily intraperitoneally administered starting one day after induction of PH. After four weeks, diaphragm muscles were excised for mechanical and biochemical analyses. There was a decrease in specific tetanic force in diaphragm bundles from the PH group, which was accompanied by increases in: protein expression of NADPH oxidase 2/gp91phox, SOD2, and catalase; 3-nitrotyrosine content and aggregation of actin; glutathione oxidation. Treatment with EUK-134 prevented the force decrease and the actin modifications in PH diaphragm bundles. These data show that redox stress plays a pivotal role in PH-induced diaphragm weakness. Thus, antioxidant treatment can be a promising strategy for PH patients with inspiratory failure. PMID:28152009

  15. Inhalable delivery of AAV-based MRP4/ABCC4 silencing RNA prevents monocrotaline-induced pulmonary hypertension

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    Caroline Claude

    2015-01-01

    Full Text Available The ATP-binding cassette transporter MRP4 (encoded by ABCC4 regulates membrane cyclic nucleotides concentrations in arterial cells including smooth muscle cells. MRP4/ABCC4 deficient mice display a reduction in smooth muscle cells proliferation and a prevention of pulmonary hypertension in response to hypoxia. We aimed to study gene transfer of a MRP4/ABCC4 silencing RNA via intratracheal delivery of aerosolized adeno-associated virus 1 (AAV1.shMRP4 or AAV1.control in a monocrotaline-induced model of pulmonary hypertension in rats. Gene transfer was performed at the time of monocrotaline administration and the effect on the development of pulmonary vascular remodeling was assessed 35 days later. AAV1.shMRP4 dose-dependently reduced right ventricular systolic pressure and hypertrophy with a significant reduction with the higher doses (i.e., >1011 DRP/animal as compared to AAV1.control. The higher dose of AAV1.shMRP4 was also associated with a significant reduction in distal pulmonary arteries remodeling. AAV1.shMRP4 was finally associated with a reduction in the expression of ANF, a marker of cardiac hypertrophy. Collectively, these results support a therapeutic potential for downregulation of MRP4 for the treatment of pulmonary artery hypertension.

  16. Local and systemic renin-angiotensin system participates in cardiopulmonary-renal interactions in monocrotaline-induced pulmonary hypertension in the rat.

    Science.gov (United States)

    Malikova, Eva; Galkova, Kristina; Vavrinec, Peter; Vavrincova-Yaghi, Diana; Kmecova, Zuzana; Krenek, Peter; Klimas, Jan

    2016-07-01

    Renin-angiotensin system (RAS) is one of the pathophysiological mechanisms in heart failure. Recently, involvement of the kidney in the disease progression has been proposed in patients with pulmonary arterial hypertension (PAH). We hypothesized that local and systemic RAS could be the central regulators of cardiopulmonary-renal interactions in experimental monocrotaline-induced pulmonary hypertension (PH) in rats. Male 12-week-old Wistar rats were injected subcutaneously with monocrotaline (60 mg/kg). The experiment was terminated 4 weeks after monocrotaline administration. Using RT-PCR, we measured the expression of RAS-related genes in right and left ventricles, lungs and kidneys, together with indicators of renal dysfunction and damage. We observed a significantly elevated expression of angiotensin-converting enzyme (ACE) in both left and right ventricles and kidneys (P < 0.05), but a significantly decreased ACE in the lungs (P < 0.05). Kidneys showed a significant 2.5-fold increase in renin mRNA (P < 0.05) along with erythropoietin, TGFβ1, COX-2, NOS-1 and nephrin. Expression of erythropoietin correlated inversely with hemoglobin oxygen saturation and positively with renin expression. In conclusion, monocrotaline-induced PH exhibited similar alterations of ACE expression in the left and right ventricles, and in the kidney, in contrast to the lungs. Increased renal renin was likely a consequence of renal hypoxia/hypoperfusion, as was increased renal erythropoietin expression. Alterations in RAS in the monocrotaline model are probably a result of hypoxic state, and while they could serve as a compensatory mechanism at a late stage of the disease, they could be viewed also as an indicator of multiorgan failure in PAH.

  17. Synthesis of nanosize MnO2 and its performence

    Institute of Scientific and Technical Information of China (English)

    顾大明; 魏杰

    2003-01-01

    Sol sol-gel method and solid phase redox reaction were respectively applied in preparation of Nanos-ize MnO2 powders. The experiments showed that only Mn2O3 could be obtained from ignition of Mn( Ⅱ ) in themuffle furnace in air, and Mn2O3 had to be disproportionated in acids to gain MnO2. The analysis of XRD andTEM technique revealed that the diameters of nanosize MnO2 obtained by sol-gel method was 35 ~45 nm andthe x in MnOx was 1.9; the particle size of MnO2 produced from solid phase redox reaction was 10 ~ 20 nm andthe x in MnOx equaled 1.94. The test results have proved that the discharge property of alkaline-manganese bat-tery could be improved by nanosize MnO2.

  18. Nicorandil attenuates monocrotaline-induced vascular endothelial damage and pulmonary arterial hypertension.

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    Makoto Sahara

    Full Text Available BACKGROUND: An antianginal K(ATP channel opener nicorandil has various beneficial effects on cardiovascular systems; however, its effects on pulmonary vasculature under pulmonary arterial hypertension (PAH have not yet been elucidated. Therefore, we attempted to determine whether nicorandil can attenuate monocrotaline (MCT-induced PAH in rats. MATERIALS AND METHODS: Sprague-Dawley rats injected intraperitoneally with 60 mg/kg MCT were randomized to receive either vehicle; nicorandil (5.0 mg·kg(-1·day(-1 alone; or nicorandil as well as either a K(ATP channel blocker glibenclamide or a nitric oxide synthase (NOS inhibitor N(ω-nitro-L-arginine methyl ester (L-NAME, from immediately or 21 days after MCT injection. Four or five weeks later, right ventricular systolic pressure (RVSP was measured, and lung tissue was harvested. Also, we evaluated the nicorandil-induced anti-apoptotic effects and activation status of several molecules in cell survival signaling pathway in vitro using human umbilical vein endothelial cells (HUVECs. RESULTS: Four weeks after MCT injection, RVSP was significantly increased in the vehicle-treated group (51.0±4.7 mm Hg, whereas it was attenuated by nicorandil treatment (33.2±3.9 mm Hg; P<0.01. Nicorandil protected pulmonary endothelium from the MCT-induced thromboemboli formation and induction of apoptosis, accompanied with both upregulation of endothelial NOS (eNOS expression and downregulation of cleaved caspase-3 expression. Late treatment with nicorandil for the established PAH was also effective in suppressing the additional progression of PAH. These beneficial effects of nicorandil were blocked similarly by glibenclamide and l-NAME. Next, HUVECs were incubated in serum-free medium and then exhibited apoptotic morphology, while these changes were significantly attenuated by nicorandil administration. Nicorandil activated the phosphatidylinositol 3-kinase (PI3K/Akt and extracellular signal-regulated kinase (ERK

  19. CPU 86017, p-chlorobenzyltetrahydroberberine chloride, attenuates monocrotaline-induced pulmonary hypertension by suppressing endothelin pathway.

    Science.gov (United States)

    Zhang, Tian-tai; Cui, Bing; Dai, De-zai; Su, Wei

    2005-11-01

    To elucidate the involvement of the endothelin (ET) pathway in the pathogenesis of monocrotaline (MCT)-induced pulmonary arterial hypertension (PAH) and the therapeutic effect of CPU 86017 (p-chlorobenzyltetrahydroberberine chloride) in rats. Rats were injected with a single dose (60 mg/kg, sc) of MCT and given CPU 86017 (20, 40, and 80 mg/kg-1/d-1, po) or saline for 28 d. The hemodynamics, mRNA expression, and vascular activity were evaluated. Right ventricular systolic pressure and central venous pressures were elevated markedly in the PAH model and decreased by CPU 86017. In the PAH group, the endothelin-1 (ET-1) in serum and lungs was dramatically increased by 54% (79.9 pg/mL, PCPU 86017 decreased the content of ET-1 to the normal level in lung tissue, but was less effective in serum. The level of NO was significantly increased in CPU 86017 at 80 and 40 mg/kg-1/d-1 groups in tissue, whereas the difference in serum was not significant. A significant reduction in MDA production and an increase in the SOD activity in the serum and lungs was observed in all three CPU 86017 groups. CPU 86017 80 mg/kg-1/d-1 po increased the activity of cNOS by 33% (PCPU 86017 groups, and preproET-1 mRNA abundance was also reduced notably in CPU 86017 80 mg/kg-1/d-1 group vs the PAH group. The KCl-induced vasoconstrictions in the calcium-free medium decreased markedly in PAH group but recovered partially after CPU 86017 intervention. The constrictions in the presence of Ca(2+) was not improved by CPU 86017. The phenylephrine-induced vasoconstrictions in the calcium-free medium decreased markedly in PAH group but not recovered after CPU 86017 intervention. The constrictions in the presence of Ca(2+) completely returned to the normal after CPU 86017 intervention. CPU 86017 suppressed MCT-induced PAH mainly through an indirect suppression of the ET-1 system, which was involved in the pathogenesis of the disease.

  20. MnO2-modified hierarchical graphene fiber electrochemical supercapacitor

    Science.gov (United States)

    Chen, Qing; Meng, Yuning; Hu, Chuangang; Zhao, Yang; Shao, Huibo; Chen, Nan; Qu, Liangti

    2014-02-01

    A novel hybrid fiber that MnO2 modified graphene sheets on graphene fiber has been fabricated by direct deposition of MnO2 onto graphene network surrounding graphene fiber (MnO2/G/GF). In this hierarchical structure, the graphene fiber with a sheath of 3D graphene network is coated with MnO2 nanoflowers. The 3D graphene on graphene fibers (G/GF) serves as highly conductive backbones with high surface area for deposition of nanostructured MnO2, which provide the high accessibility of electrolytic ions for shorten diffusion paths. An all-solid-state flexible supercapacitor based on a MnO2/G/GF hybrid fiber structure has been developed on the basis of the intrinsic mechanical flexibility of GF and the unique hierarchical structure. By combination of electric double layer capacitance of graphene network with the pseudocapacitance of MnO2 nanostructures, the all-solid-state fiber supercapacitor shows the much enhanced electrochemical capacitive behaviors with robust tolerance to mechanical deformation, promising for being woven into a textile for wearable electronics.

  1. [A sharp increase in the density of pulmonary and pericardial mast cells under monocrotaline-induced pulmonary hypertension in rats].

    Science.gov (United States)

    Erokhina, I L; Okovityĭ, S V; Kazachenko, A A; Kulikov, A N; Emel'ianova, O I; Bystrova, O A

    2011-01-01

    Multifunctional granular mast cells (MCs) are involved in various pathological processes. The response of MC populations of myocardium, pericardium and lung to pulmonary hypertension (PH) has been studies 8 weeks after injection of monocrotaline. Five intact and five experimental rats were used. The density of MCs of different maturity was estimated on paraffin sections stained with Alcian blue and Safranin. Expressiveness of PH was estimated by functional parameters with the help of echocardiograms and by morphological markers. The MC density in myocardium of the intact and experimental rats was relatively low: 2 to 4 cells/mm2. MC density in the pericardium of intact rats was 14 times higher than in myocardium and increased 3 times for PH. The mature Safranin-positive cells predominated (70-80%) in myocardium and pericardium of intact and experimental rats. The MC density in the lungs of intact rats was about 30 cells/mm2; 98% of these cells were immature Alcian-positive cells. The mean density of MCs in the lungs of rats with PH increased 5.6 times. The mature Safranin-positive cells appeared in the lungs of rats with severe pathology. The greatest number of MCs in lungs was in the rats with the most pronounced disorders of myocardium function and marked histological damages (injuries) of myocardium and lungs. The finding show active response of MC population to monocrotaline-induced PH that stimulates migration of immature MCs into pericardium and lungs from the outside. Our data indicate the important role of MCs in the pathogenesis of PH.

  2. Early treatment with fumagillin, an inhibitor of methionine aminopeptidase-2, prevents Pulmonary Hypertension in monocrotaline-injured rats.

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    Daniel J Kass

    Full Text Available Pulmonary Hypertension (PH is a pathophysiologic condition characterized by hypoxemia and right ventricular strain. Proliferation of fibroblasts, smooth muscle cells, and endothelial cells is central to the pathology of PH in animal models and in humans. Methionine aminopeptidase-2 (MetAP2 regulates proliferation in a variety of cell types including endothelial cells, smooth muscle cells, and fibroblasts. MetAP2 is inhibited irreversibly by the angiogenesis inhibitor fumagillin. We have previously found that inhibition of MetAP2 with fumagillin in bleomycin-injured mice decreased pulmonary fibrosis by selectively decreasing the proliferation of lung myofibroblasts. In this study, we investigated the role of fumagillin as a potential therapy in experimental PH. In vivo, treatment of rats with fumagillin early after monocrotaline injury prevented PH and right ventricular remodeling by decreasing the thickness of the medial layer of the pulmonary arteries. Treatment with fumagillin beginning two weeks after monocrotaline injury did not prevent PH but was associated with decreased right ventricular mass and decreased cardiomyocyte hypertrophy, suggesting a direct effect of fumagillin on right ventricular remodeling. Incubation of rat pulmonary artery smooth muscle cells (RPASMC with fumagillin and MetAP2-targeting siRNA inhibited proliferation of RPASMC in vitro. Platelet-derived growth factor, a growth factor that is important in the pathogenesis of PH and stimulates proliferation of fibroblasts and smooth muscle cells, strongly increased expression of MetP2. By immunohistochemistry, we found that MetAP2 was expressed in the lesions of human pulmonary arterial hypertension. We propose that fumagillin may be an effective adjunctive therapy for treating PH in patients.

  3. Vascular endothelial-cadherin downregulation as a feature of endothelial transdifferentiation in monocrotaline-induced pulmonary hypertension.

    Science.gov (United States)

    Nikitopoulou, Ioanna; Orfanos, Stylianos E; Kotanidou, Anastasia; Maltabe, Violetta; Manitsopoulos, Nikolaos; Karras, Panagiotis; Kouklis, Panos; Armaganidis, Apostolos; Maniatis, Nikolaos A

    2016-08-01

    Increased pulmonary vascular resistance in pulmonary hypertension (PH) is caused by vasoconstriction and obstruction of small pulmonary arteries by proliferating vascular cells. In analogy to cancer, subsets of proliferating cells may be derived from endothelial cells transitioning into a mesenchymal phenotype. To understand phenotypic shifts transpiring within endothelial cells in PH, we injected rats with alkaloid monocrotaline to induce PH and measured lung tissue levels of endothelial-specific protein and critical differentiation marker vascular endothelial (VE)-cadherin. VE-cadherin expression by immonoblotting declined significantly 24 h and 15 days postinjection to rebound to baseline at 30 days. There was a concomitant increase in transcriptional repressors Snail and Slug, along with a reduction in VE-cadherin mRNA. Mesenchymal markers α-smooth muscle actin and vimentin were upregulated by immunohistochemistry and immunoblotting, and α-smooth muscle actin was colocalized with endothelial marker platelet endothelial cell adhesion molecule-1 by confocal microscopy. Apoptosis was limited in this model, especially in the 24-h time point. In addition, monocrotaline resulted in activation of protein kinase B/Akt, endothelial nitric oxide synthase (eNOS), nuclear factor (NF)-κB, and increased lung tissue nitrotyrosine staining. To understand the etiological relationship between nitrosative stress and VE-cadherin suppression, we incubated cultured rat lung endothelial cells with endothelin-1, a vasoconstrictor and pro-proliferative agent in pulmonary arterial hypertension. This resulted in activation of eNOS, NF-κB, and Akt, in addition to induction of Snail, downregulation of VE-cadherin, and synthesis of vimentin. These effects were blocked by eNOS inhibitor N(ω)-nitro-l-arginine methyl ester. We propose that transcriptional repression of VE-cadherin by nitrosative stress is involved in endothelial-mesenchymal transdifferentiation in experimental PH.

  4. Therapeutic efficacy of valproic acid in a combined monocrotaline and chronic hypoxia rat model of severe pulmonary hypertension.

    Directory of Open Access Journals (Sweden)

    Beidi Lan

    Full Text Available Pulmonary hypertension (PH is a serious disease with poor prognosis. Reports show that cells in remodeled pulmonary arteries of PH patients have similar characteristics to cancer cells, such as exuberant inflammation, increased proliferation, and decreased apoptosis. An ideal strategy for developing PH therapies is to directly target pulmonary vascular remodeling. High levels of histone deacetylase (HDAC expression and activity are found in certain cancers, and research has shown the potential of HDAC inhibitors in repressing tumor growth via anti-inflammatory and anti-proliferative effects. To date, little is known about the effectiveness of HDAC inhibitors against pulmonary vascular remodeling in severe PH.To investigate whether class I HDAC inhibitors suppress or reverse the development of severe PH in rats.Male Sprague-Dawley rats were injected with a single, subcutaneous dose of monocrotaline (60 mg/kg, and were exposed to chronic hypoxia to induce severe PH. Valproic acid, a class I HDAC inhibitor, was administered to rats daily via gastric gavage (300 mg/kg in a PH prevention study (during the first 3 weeks or a PH reversal study (from 3 to 5 weeks. At the end of experiment, hemodynamic indices were measured, ventricular hypertrophy indices were calculated and vascular remodeling phenotypes were analyzed.After 3 weeks exposure to a combined stimulation of monocrotaline and chronic hypoxia, rats exhibited a reduced body weight, elevated right ventricular systolic pressure, an increased Fulton index, right ventricle weight ratio, medial wall thickness and muscularized peripheral pulmonary arteries. These parameters for PH evaluation were exacerbated from 3 to 5 weeks. Daily administration of valproic acid therapy prevented and partially reversed the development of severe PH in rats, and decreased inflammation and proliferation in remodeled pulmonary arteries.These data show that class I HDAC inhibitors may be effective for treating severe

  5. Heterocyclic N-Oxides – An Emerging Class of Therapeutic Agents

    OpenAIRE

    Mfuh, Adelphe M.; Larionov, Oleg V.

    2015-01-01

    Heterocyclic N-oxides have emerged as potent compounds with anticancer, antibacterial, antihypertensive, antiparasitic, anti-HIV, anti-inflammatory, herbicidal, neuroprotective, and procognitive activities. The N-oxide motif has been successfully employed in a number of recent drug development projects. This review surveys the emergence of this scaffold in the mainstream medicinal chemistry with a focus on the discovery of the heterocyclic N-oxide drugs, N-oxide-specific mechanisms of action,...

  6. Reducing dissolution of MnO2 nanofibers by doping with ferric ion

    Directory of Open Access Journals (Sweden)

    Huimin Chen et al

    2007-01-01

    Full Text Available MnO2 nanofiber was found to possess high adsorption capacities for heavy metal ions such as, arsenic and lead, in water due to its high specific surface area (SSA and high surface activity. However, a significant amount of manganese was found to leach from MnO2 nanofibers. Reducing MnO2 dissolution is very important for improving its applications in drinking water treatment. In this study, MnO2 nanofiber was doped with Fe3+ to reduce its dissolution in water. Dissolution tests were conducted on un-doped and Fe-doped MnO2 nanofibers. The results revealed that doping with Fe3+ significantly reduced MnO2 dissolution. SSA and defects of MnO2 materials were analyzed by BET and XRD methods. The effects of Fe3+ on MnO2 dissolution were discussed and the optimal dopant amount was identified.

  7. Magnetic phase transition in confined MnO nanoparticles studied by polarized neutron scattering

    OpenAIRE

    Feygenson, M.; Schweika, W.; Ioffe, A.; Vakhrushev, S. B.; Brückel, T.

    2010-01-01

    We have investigated the magnetic ordering and the phase transition in MnO nanoparticles confined in a porous glass using polarized neutron scattering. These MnO nanoparticles are best described as extended wormlike structures with a mean diameter of 70 angstrom. We observe an apparent continuous magnetic phase transition in MnO nanoparticles, in contrast to the well-known discontinuous phase transition in bulk MnO. By polarization analysis, separating the magnetic scattering, it is found tha...

  8. Genotoxicity and morphological changes induced by the alkaloid monocrotaline, extracted from Crotalaria retusa, in a model of glial cells.

    Science.gov (United States)

    Silva-Neto, J P; Barreto, R A; Pitanga, B P S; Souza, C S; Silva, V D; Silva, A R; Velozo, E S; Cunha, S D; Batatinha, M J M; Tardy, M; Ribeiro, C S O; Costa, M F D; El-Bachá, R S; Costa, S L

    2010-01-01

    Plants of Crotalaria genus (Leguminosae) present large amounts of the pyrrolizidine alkaloid monocrotaline (MCT) and cause intoxication to animals and humans. Therefore, we investigated the MCT-induced cytotoxicity, morphological changes, and oxidative and genotoxic damages to glial cells, using the human glioblastoma cell line GL-15 as a model. The comet test showed that 24h exposure to 1-500microM MCT and 500microM dehydromonocrotaline (DHMC) caused significant increases in cell DNA damage index, which reached 42-64% and 53%, respectively. Cells exposed to 100-500microM MCT also featured a contracted cytoplasm presenting thin cellular processes and vimentin destabilisation. Conversely, exposure of GL-15 cells to low concentrations of MCT (1-10microM) clearly induced megalocytosis. Moreover, MCT also induced down regulation of MAPs, especially at the lower concentrations adopted (1-10microM). Apoptosis was also evidenced in cells treated with 100-500microM MCT, and a later cytotoxicity was only observed after 6 days of exposure to 500microM MCT. The data obtained provide support for heterogenic and multipotential effects of MCT on GL-15 cells, either interfering on cell growth and cytoskeletal protein expression, or inducing DNA damage and apoptosis and suggest that the response of glial cells to this alkaloid might be related to the neurological signs observed after Crotalaria intoxication.

  9. 1H NMR-Based Analysis of Serum Metabolites in Monocrotaline-Induced Pulmonary Arterial Hypertensive Rats

    Directory of Open Access Journals (Sweden)

    Taijie Lin

    2016-01-01

    Full Text Available Aims. To study the changes of the metabolic profile during the pathogenesis in monocrotaline (MCT induced pulmonary arterial hypertension (PAH. Methods. Forty male Sprague-Dawley (SD rats were randomly divided into 5 groups (n=8, each. PAH rats were induced by a single dose intraperitoneal injection of 60 mg/kg MCT, while 8 rats given intraperitoneal injection of 1 ml normal saline and scarified in the same day (W0 served as control. Mean pulmonary arterial pressure (mPAP was measured through catherization. The degree of right ventricular hypertrophy and pulmonary hyperplasia were determined at the end of first to fourth weeks; nuclear magnetic resonance (NMR spectra of sera were then acquired for the analysis of metabolites. Principal component analysis (PCA and orthogonal partial least-squares discriminant analysis (OPLS-DA were used to discriminate different metabolic profiles. Results. The prominent changes of metabolic profiles were seen during these four weeks. Twenty specific metabolites were identified, which were mainly involved in lipid metabolism, glycolysis, energy metabolism, ketogenesis, and methionine metabolism. Profiles of correlation between these metabolites in each stage changed markedly, especially in the fourth week. Highly activated methionine and betaine metabolism pathways were selected by the pathway enrichment analysis. Conclusions. Metabolic dysfunction is involved in the development and progression of PAH.

  10. Tetraaquabis[3-(2-pyridylsulfanylpropionato N-oxide]nickel(II

    Directory of Open Access Journals (Sweden)

    B. Ravindran Durai Nayagam

    2009-04-01

    Full Text Available In the centrosymmetric title compound, [Ni(C8H8NO3S2(H2O4], the NiII ion, which lies on an inversion centre, is six coordinated by four water molecules and two propionate O atoms from two 2-pyridylsulfanylpropionate N-oxide ligands, forming a slightly distorted octahedral geometry. An intramolecular O—H...O hydrogen bond stabilizes the molecular conformation. The crystal packing is consolidated by intermolecular O—H...O and C—H...O hydrogen bonding.

  11. Aqueous ultracapacitors using amorphous MnO2 and reduced graphene oxide

    Science.gov (United States)

    Mery, Adrien; Ghamouss, Fouad; Autret, Cécile; Farhat, Douaa; Tran-Van, François

    2016-02-01

    Herein, synthesis and characterization of amorphous MnO2 and application in asymmetric aqueous ultracapacitors are reported. Different amorphous manganese oxide (MnO2) materials were synthesized from the reduction of KMnO4 in different media such as ethanol (EtOH) or dimethylformamide (DMF). The electrochemical behavior of amorphous MnO2, labeled MnO2-Et and MnO2-DMF, were studied by using cyclic voltammetry, impedance spectroscopy, and galvanostatic cycling in aqueous electrolyte. XRD, BET, TEM, and SEM characterizations highlighted the amorphous nature and the nanostructuration of these MnO2 materials. BET measurement established that these amorphous MnO2 are mesoporous. In addition, MnO2-Et exhibits a larger specific surface area (168 m2 g-1), a narrower pore diameters distribution with lower diameters compared to MnO2-DMF. These results are in agreement with the electrochemical results. Indeed, MnO2-Et shows a higher specific capacitance and lower impedance in aqueous K2SO4 electrolyte. Furthermore, aqueous asymmetric ultracapacitors were assembled and studied using amorphous MnO2 as positive electrode and reduced graphene oxide (rGO) as negative electrode. These asymmetric systems exhibit an electrochemical stability for more than 20,000 galvanostatic cycles at current density of 1 A g-1 with an operating voltage of 2 V.

  12. Versatility of MnO2 for lithium battery applications

    CSIR Research Space (South Africa)

    Thackeray, MM

    1993-03-15

    Full Text Available that exist in the manganese dioxide family, the battery industry has used gamma-MnO2 exclusively as the positive electrode in these cells. With the advent of rechargeable lithium battery technology, research efforts have demonstrated that other MnO2...

  13. Pulmonary oxidative stress is increased in cyclooxygenase-2 knockdown mice with mild pulmonary hypertension induced by monocrotaline.

    Directory of Open Access Journals (Sweden)

    Francesca Seta

    Full Text Available The aim of this study was to examine the role of cyclooxygenase-2 (COX-2 and downstream signaling of prostanoids in the pathogenesis of pulmonary hypertension (PH using mice with genetically manipulated COX-2 expression. COX-2 knockdown (KD mice, characterized by 80-90% suppression of COX-2, and wild-type (WT control mice were treated weekly with monocrotaline (MCT over 10 weeks. Mice were examined for cardiac hypertrophy/function and right ventricular pressure. Lung histopathological analysis was performed and various assays were carried out to examine oxidative stress, as well as gene, protein, cytokine and prostanoid expression. We found that MCT increased right ventricular systolic and pulmonary arterial pressures in comparison to saline-treated mice, with no evidence of cardiac remodeling. Gene expression of endothelin receptor A and thromboxane synthesis, regulators of vasoconstriction, were increased in MCT-treated lungs. Bronchoalveolar lavage fluid and lung sections demonstrated mild inflammation and perivascular edema but activation of inflammatory cells was not predominant under the experimental conditions. Heme oxygenase-1 (HO-1 expression and indicators of oxidative stress in lungs were significantly increased, especially in COX-2 KD MCT-treated mice. Gene expression of NOX-4, but not NOX-2, two NADPH oxidase subunits crucial for superoxide generation, was induced by ∼4-fold in both groups of mice by MCT. Vasodilatory and anti-aggregatory prostacyclin was reduced by ∼85% only in MCT-treated COX-2 KD mice. This study suggests that increased oxidative stress-derived endothelial dysfunction, vasoconstriction and mild inflammation, exacerbated by the lack of COX-2, contribute to the pathogenesis of early stages of PH when mild hemodynamic changes are evident and not yet accompanied by vascular and cardiac remodeling.

  14. Endostatin is protective against monocrotaline-induced right heart disease through the inhibition of T-type Ca(2+) channel.

    Science.gov (United States)

    Imoto, Keisuke; Kumatani, Sayaka; Okada, Muneyoshi; Yamawaki, Hideyuki

    2016-07-01

    Endostatin (ES), a C-terminal fragment of collagen XVIIIα1, has a potent anti-angiogenic effect. ES prevents tumor proliferation through inhibiting T-type Ca(2+) channel. T-type Ca(2+) channel is re-expressed during heart diseases including monocrotaline (MCT)-induced right heart failure. The present study aimed to clarify the effects of ES on T-type Ca(2+) channel and pathogenesis of MCT-induced right ventricular disease. MCT or saline was injected intraperitoneally to rats. After cardiomyocytes were isolated from right ventricles (RVs), T-type Ca(2+) channel current (I CaT) was measured by a patch-clamp method. After ES small interfering RNA (siRNA) or control siRNA (20 μg) was administrated for 1 week via the right jugular vein 1 week after MCT injection, echocardiography and histological analysis were done. I CaT was significantly increased in RV from MCT-injected rats, and ES significantly inhibited it. The survival rate of ES siRNA-administrated MCT rats (MCT ES si group) was decreased. In echocardiography, although ES siRNA did not affect pulmonary arterial pressure, RV systolic function was impaired in MCT ES si group compared with control siRNA-administrated MCT rats (MCT cont si group). In the histological analysis of RV, ES expression was increased in MCT cont si group, and ES siRNA inhibited it. Furthermore, although MCT cont si group showed only cardiomyocyte hypertrophy, MCT ES si group showed notable enlargement of intercellular spaces. The present study for the first time revealed that ES inhibits T-type Ca(2+) channel activity in RV from MCT-injected rats. ES gene knockdown deteriorates MCT-induced right heart disease. ES is thus cardioprotective possibly through inhibiting T-type Ca(2+) channel activity.

  15. Effects of captopril on cardiovascular reflexes and respiratory mechanisms in rats submitted to monocrotaline-induced pulmonary arterial hypertension.

    Science.gov (United States)

    Wittmer, Verônica Lourenço; Waichert, Élio Junior; Gava, Pablo Lúcio; Pereira, Fausto Edmundo Lima; Guimarães, Marco Cesar Cunegundes; de Figueiredo, Suely Gomes; Mauad, Hélder

    2015-02-01

    Pulmonary Arterial Hypertension (PAH) is a disease associated with increased arteriolar resistance in the lungs. Due to hypoxemia, some physiological mechanisms can be posteriorly affected, including respiratory and cardiovascular reflexes, but this has not yet been fully investigated. This study aimed to evaluate how these mechanisms were affected by monocrotaline (MCT)-induced PAH and the possible therapeutic role of angiotensin converting enzyme inhibitor (ACEi), captopril, in reversing this remodeling process. Groups of Wistar rats received MCT injections (60 mg kg(-1)). Three weeks later, they received captopril (CPT, 100 mg kg(-1)) in their drinking water (MCT + CPT) or water alone (MCT) for 2 weeks. As control, saline-treated animals received captopril in their drinking water (CPT) or water alone (CON), also for 2 weeks. Results showed that PAH was fully induced in the MCT group, evidenced by a high pulmonary index. Gasometrical and respiratory analyses showed hypoxemia and compensatory hyperventilation. CPT treatment brought these parameters to similar values to those observed in the CON group. We observed that autonomic dysfunction in the MCT group was suppressed by CPT. Finally, cardiovascular reflexes analysis showed increased chemoreflex responses in the MCT group, while baroreflex sensibility was decreased. Surprisingly, CPT normalized these reflex responses to values similar to the CON group. The present study demonstrates that MCT-induced PAH induces compensatory respiratory responses, dysautonomia, and baroreflex dysfunction and increases chemoreflex responses. The data also indicate that CPT was effective in reversing these cardio-respiratory disorders, suggesting that ACEi could be a potential therapeutic target for PAH. Copyright © 2014 Elsevier Ltd. All rights reserved.

  16. H2S inhibits pulmonary arterial endothelial cell inflammation in rats with monocrotaline-induced pulmonary hypertension.

    Science.gov (United States)

    Feng, Shasha; Chen, Siyao; Yu, Wen; Zhang, Da; Zhang, Chunyu; Tang, Chaoshu; Du, Junbao; Jin, Hongfang

    2017-03-01

    This study aimed to determine whether hydrogen sulfide (H2S) inhibits pulmonary arterial endothelial inflammation in rats with monocrotaline (MCT)-induced pulmonary hypertension and its possible mechanisms. Twenty-four male Wistar rats were divided randomly into control, MCT, and MCT+H2S treatment groups. Human pulmonary arterial endothelial cells (HPAEC) were cultured and divided into four groups: control, MCT, MCT+H2S, and H2S. Pulmonary artery pressure was determined using a right cardiac catheterization procedure 3 weeks after MCT administration. Pulmonary vascular morphological changes and inflammatory infiltration were measured. Endogenous H2S levels, cystathionine-γ-lyase (CSE) expression, and inflammatory cytokines were determined both in vivo and in vitro. In addition, phosphorylation of NF-κB p65 and IκBα was detected by western blotting, and NF-κB p65 nuclear translocation, as well as its DNA-binding activity, was determined. Pulmonary hypertension and vascular remolding developed 3 wks after MCT administration, with elevated lung tissue inflammatory infiltration and cytokine level associated with activation of the NF-κB pathway, both in vivo and in vitro. However, the endogenous H2S/CSE pathway was downregulated in MCT rats. By contrast, an H2S donor markedly reduced pulmonary artery pressure, pulmonary vascular structural remolding, and increased lung inflammatory infiltration and cytokine levels of MCT-treated rats. Meanwhile, H2S reversed the activation of the NF-κB pathway successfully. The downregulated pulmonary arterial endothelial H2S/CSE pathway is involved in the pulmonary inflammatory response in MCT-treated pulmonary hypertensive rats. H2S attenuated endothelial inflammation by inhibiting the NF-κB pathway.

  17. Redetermination of 2-methyl-4-nitropyridine N-oxide

    Directory of Open Access Journals (Sweden)

    Max Peukert

    2014-04-01

    Full Text Available An improved crystal structure of the title compound, C6H6N2O3, is reported. The structure, previously solved [Li et al. (1987. Jiegou Huaxue (Chin. J. Struct. Chem., 6, 20–24] in the orthorhombic space group Pca21 and refined to R = 0.067, has been solved in the orthorhombic space group Pbcm with data of enhanced quality, giving an improved structure (R = 0.0485. The molecule adopts a planar conformation with all atoms lying on a mirror plane. The crystal structure is composed of molecular sheets extending parallel to the ab plane and connected via C—H...O contacts involving ring H atoms and O atoms of the N-oxide and nitro groups, while van der Waals forces consolidate the stacking of the layers.

  18. The Composite Effect of Nanometer MnO2 Mixed with the Electrolytic MnO2

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The nanometer MnO2 has outstanding electrochemical performance theoretically, but it is not suitable for actual utilization, which may result in capacity decrease and resource waste. In this study we have utilized the characterizations of the nanometer material, synthesized a type of nanometer α-MnO2 through KMnO4 and KNO3 with hydrothermal method, and mixed the products into micron electrolytic manganese dioxide (EMD) to enhance the electrochemical performance of the electrode.The cyclic voltammogram and galvanostatical discharge measurements of the samples were investigated. It is found that the 50% nanometer MnO2 mixed electrode has the best electrochemical performance. The electrochemical performance improvement mechanism of the sample nanometer MnO2 mixed into micron EMD was discussed. With the existence of electrolyte, the nanometer MnO2 particles filled into the interspaces of the micron EMD particles, the mass and charge transfer conditions of the electrode reaction were improved, and the electrode polarization was diminished.

  19. Influence of deuteration and fluorination on the supramolecular architecture of pyridine N-oxide crystals.

    Science.gov (United States)

    Shishkin, Oleg V; Shishkina, Svitlana V; Maleev, Andrey V; Zubatyuk, Roman I; Vasylyeva, Vera; Merz, Klaus

    2013-03-18

    To understand how deuterium and fluorine substituents influence the supramolecular architecture of pyridine N-oxide crystals, the crystal structure of 3-fluoropyridine N-oxide (PNO-3F) was determined and the crystal packing motives of non-deuterated pyridine-N-oxide (PNO), partial-deuterated pyridine-N-oxide (PNO-D) and PNO-3F were analyzed based on ab initio quantum-chemical calculations of the intermolecular interaction energy, using the MP2/6-311G(d,p) method. The appearance of the weak-directing substituents deuterium and fluorine leads to significant changes in the crystal organization of the isotropic packing of PNO molecules.

  20. Synthesis of Quinoxaline 1,4-di-N-Oxide Analogues and Crystal Structure of 2-Carbomethoxy-3-hydroxyquinoxaline-di-N-oxide

    Directory of Open Access Journals (Sweden)

    Minmin Zhang

    2011-08-01

    Full Text Available A series of quinoxaline 1,4-di-N-oxide analogues were prepared from benzofurazan N-oxide derivatives and β-diketone ester compounds by the improved Beirut reaction. The structures of the target products were characterized by NMR, MS, IR and elemental analysis measurements, and that of 2-carbomethoxy-3-hydroxyquinoxaline- di-N-oxide was further confirmed by single-crystal X-ray diffraction. Its crystal structure belongs to the monoclinic system, space group C2/c with a = 14.4320 (12 Å, b = 10.7514 (9 Å, c = 13.2728 (11 Å, V = 1958.5 (3 Å 3, Z = 8. The X-ray crystallographic analysis reveals that quinoxaline 1,4-di-N-oxide displays acyloin-endiol tautomerism.

  1. Fluorescent glutathione probe based on MnO2-phenol formaldehyde resin nanocomposite.

    Science.gov (United States)

    Wang, Xudong; Wang, Dan; Guo, Yali; Yang, Chengduan; Liu, Xiaoyu; Iqbal, Anam; Liu, Weisheng; Qin, Wenwu; Yan, Dan; Guo, Huichen

    2016-03-15

    MnO2-phenol formaldehyde resin (MnO2-PFR) nanocomposite is successfully prepared by a simple chemical reduction process. The resultant MnO2-PFR nanocomposite is well characterized. The absorption band of non-fluorescent MnO2 nanosheets overlaps well with the fluorescence emission of PFR nanoparticles. The green fluorescence of PFR in this nanocomposite can be effectively quenched by fluorescence resonance energy transfer from PFR to MnO2. In the presence of glutathione (GSH), the fluorescence of PFR could be recovered due to MnO2 was reduced to Mn(2+) by GSH. The nanocomposite can be use for detecting glutathione in blood serum.

  2. Synthesis, optical properties and growth mechanism of MnO nano structures

    Science.gov (United States)

    Pandey, B. K.; Shahi, A. K.; Gopal, R.

    2013-10-01

    Manganese oxide (MnO) colloidal nanoparticles have been successfully synthesized by pulse laser ablation in double distilled water. Nd: YAG laser with focused output operating at different pulse energies (20, 30, 40, 50 mJ/pulse) was used for ablation. Synthesized MnO nano crystal phase and structure were confirmed by X-ray diffraction and SAED pattern. Optical properties of as synthesized MnO nano colloidal solution were studied by UV-vis absorption spectroscopy. Optical particle size and band gap of as synthesized MnO colloidal nanoparticles were calculated. Particle shape and size were determined by TEM/SEM image. It is observed that MnO nano colloidal particles assembled to make different structures after aging in the liquid media. Aspect ratio has been calculated from SEM picture. MnO nanoparticles show weak antiferromagnetic behavior at room temperature as measured by VSM. A typical mechanism has been proposed for the formation of different nanostructures.

  3. Synthesis, optical properties and growth mechanism of MnO nano structures

    Energy Technology Data Exchange (ETDEWEB)

    Pandey, B.K., E-mail: bishnu.pandey750@gmail.com; Shahi, A.K.; Gopal, R., E-mail: profrgopal@gmail.com

    2013-10-15

    Manganese oxide (MnO) colloidal nanoparticles have been successfully synthesized by pulse laser ablation in double distilled water. Nd: YAG laser with focused output operating at different pulse energies (20, 30, 40, 50 mJ/pulse) was used for ablation. Synthesized MnO nano crystal phase and structure were confirmed by X-ray diffraction and SAED pattern. Optical properties of as synthesized MnO nano colloidal solution were studied by UV–vis absorption spectroscopy. Optical particle size and band gap of as synthesized MnO colloidal nanoparticles were calculated. Particle shape and size were determined by TEM/SEM image. It is observed that MnO nano colloidal particles assembled to make different structures after aging in the liquid media. Aspect ratio has been calculated from SEM picture. MnO nanoparticles show weak antiferromagnetic behavior at room temperature as measured by VSM. A typical mechanism has been proposed for the formation of different nanostructures.

  4. Interruption of CD40 Pathway Improves Efficacy of Transplanted Endothelial Progenitor Cells in Monocrotaline Induced Pulmonary Arterial Hypertension

    Directory of Open Access Journals (Sweden)

    YanYun Pan

    2015-05-01

    Full Text Available Background/Aims: Transplantation of endothelial progenitor cells (EPCs plays a therapeutic role in pulmonary arterial hypertension (PAH. Meanwhile, recruitment of progenitors has potential inflammatory effects and exaggerates vascular injury. CD40 pathway is identified as a major player in vascular inflammatory events. In this study, we investigated the role of CD40 pathway in regulating early outgrowth EPC functions, and searched for improvements in PAH cell therapy. Methods: EPCs were isolated from rat bone marrow and cultured for 7 days. After treatment with soluble CD40 ligand (sCD40L for 24 hours, EPC migration, adhesion, proliferation, paracrine and vasculogenesis functions were tested. Rat PAH model was founded by subcutaneous injection of monocrotaline (MCT. Control EPCs or lentivirus vectors (Lv-shRNA-CD40 EPCs were infused via tail vein at day 7, 14, and 21 after MCT injection. Therapeutic effects were evaluated at day 28. Results: sCD40L dose-dependently impaired EPC migration, adhesion, proliferation, and vasculogenesis functions. However, paracrine effects of soluble intercellular adhesion molecule-1, vascular endothelial growth factor and interleukin-6 were dose-dependently improved by sCD40L. Control EPC-derived conditioned medium protected endothelial cell in vitro vasculogenesis, while sCD40L-pretreated ones showed detrimental effects. After MCT injection, sCD40L levels in rat serum increased gradually. Other than in vitro results, benefits of both two EPC treatments were obvious, even taken at day 21. Benefits of control EPCs wore off over time, but those of Lv-shRNA-CD40 EPCs were more effective and enduring, as characterized by both ameliorated rat hemodynamic and reversed vascular remodeling. Furthermore, Lv-shRNA-CD40 EPCs integrated into endothelium better, rather than into adventitia and media. Conclusion: sCD40L impaired protective effects of EPCs. Traditional EPC treatments were limited in PAH, while interruption of CD

  5. Direct 2-acetoxylation of quinoline N-oxides via copper catalyzed C-H bond activation.

    Science.gov (United States)

    Chen, Xuan; Zhu, Chongwei; Cui, Xiuling; Wu, Yangjie

    2013-08-07

    An efficient and direct 2-acetoxylation of quinoline N-oxides via copper(I) catalyzed C-H bond activation has been developed. This transformation was achieved using TBHP as an oxidant in the cross-dehydrogenative coupling (CDC) reaction of quinoline N-oxides with aldehydes, and provided a practical pathway to 2-acyloxyl quinolines.

  6. Epoxidation reaction of perfluoroalkenes with tert-amine N-oxide

    Institute of Scientific and Technical Information of China (English)

    Xing Wei Cai; Min Sha; Biao Jiang; Ren Ming Pan

    2012-01-01

    Straight-chain aliphatic tert-amine N-oxides were found to be useful oxidizing agent for epoxidation of tri-and tetra-substituted perfluoroalkenes under mild conditions in high yields.The process for epoxidation by employing tri-n-butylamine N-oxide gave the best result in the reagent survey.

  7. Simplified Synthesis of Isotopically Labeled 5,5-Dimethyl-pyrroline N-Oxide

    Directory of Open Access Journals (Sweden)

    Ronald P. Mason

    2011-10-01

    Full Text Available 5,5-Dimethylpyrroline N-oxide (15N and 5,5-di(trideuteromethylpyrroline N-oxide were synthesized from the respective isotopically labeled 2-nitropropane analogs obtained from the reaction of sodium nitrate with 2-halopropanes. This facile, straightforward process allows synthesizing isotopically labeled DMPO analogs in a 4-step reaction without special equipment.

  8. The Magnetic Structure of Paramagnetic MnO

    OpenAIRE

    Paddison, Joseph A. M.; Gutmann, Matthias J.; Stewart, J. Ross; Tucker, Matthew G.; Dove, Martin T.; Keen, David A.; Goodwin, Andrew L.

    2016-01-01

    Using a combination of single-crystal neutron scattering and reverse Monte Carlo refinements, we study the magnetic structure of paramagnetic MnO at a temperature (160\\,K) substantially below the Curie-Weiss temperature $|\\theta|\\sim550$\\,K. The microscopic picture we develop reveals a locally-ordered domain structure that persists over distances many times larger than the correlation length implied by direct analysis of the spin correlation function. Moreover, the directional dependence of p...

  9. Charge-discharge process of MnO2 supercapacitor

    Institute of Scientific and Technical Information of China (English)

    LIU Kai-yu; ZHANG Ying; ZHANG Wei; ZHENG He; SU Geng

    2007-01-01

    Mechanochemical synthesis of α-MnO2 was carried out with KMnO4 and Mn(CH3COO)2 in 1-1 mole ratio. The electrochemical performance of MnO2 electrode was investigated by cyclic voltammograms and alternating current impedance. The charge-discharge process of MnO2 supercapacitor in 6 mol/L KOH was studied within 1.2 V at 200 mA/g, suggesting that it displays double-layer capacibility in low potential scope and pseudo-capacitance properties in high potential scope. It is found that Mn3O4, an electrochemical inert, mainly forms in the initial 40 charge-discharge cycles. During cycling, the pseudo-capacitance properties disappear and the discharge curves are close to ideal ones, indicating double-layer capability. The maximum capacitance of MnO2 electrode is as high as 416 F/g, and retains 240 F/g after 200 cycles. The equivalent series resistance increases from 17 to 41 Ω.

  10. Core-Shell MnO2-SiO2 Nanorods for Catalyzing the Removal of Dyes from Water

    OpenAIRE

    Wei Gong; Xianling Meng; Xiaohong Tang; Peijun Ji

    2017-01-01

    This work presented a novel core-shell MnO2@m-SiO2 for catalyzing the removal of dyes from wastewater. MnO2 nanorods were sequentially coated with polydopamine (PDA) and polyethyleneimine (PEI) forming MnO2@PDA-PEI. By taking advantage of the positively charged amine groups, MnO2@PDA-PEI was further silicificated, forming MnO2@PDA-PEI-SiO2. After calcination, the composite MnO2@m-SiO2 was finally obtained. MnO2 nanorod is the core and mesoporous SiO2 (m-SiO2) is the shell. MnO2@m-SiO2 has bee...

  11. Downregulation of Kv4.2 and Kv4.3 channel gene expression in right ventricular hypertrophy induced by monocrotaline in rat

    Institute of Scientific and Technical Information of China (English)

    Tian-tai ZHANG; Bing CUI; De-zai DAI

    2004-01-01

    AIM: To investigate the differences in gene expression of transient outward potassium ion channel between the free wall of right ventricle, free wall of left ventricle, and the septum in monocrotaline (MCT)-induced right ventricular hypertrophy of rat. METHODS: Twenty rats were randomly divided into two groups: a single injection of monocrotaline (MCT) 60 mg/kg (model) or saline (control). Four weeks later, hemodynamic parameters were measured and the gene expression of Ito channels were detected by semi-quantitative RT-PCR. RESUITS: After 28 d, the right ventricular systolic pressure and central venous pressure were remarkably elevated by 128 % and 533 % in the MCT-treated group, accompanied by an overt right ventricle (RV) remodeling. The difference of mRNA expression of Kv1.4 was not significant in free wall of RV, left ventricle (LV), and septum in MCT group compared with control group. In contrast, mRNA of Ky4.2 and Ky4.3 in the free wall of RV in MCT-induced rat was dramatically decreased by 45.2 % and 51.1% vs control, however, in free wall of LV and septum, no difference was found. In addition, mRNA expression level of Ky4.2 in control rat was significantly lower in septum than that in free wall of RV and LV. CONCLUSION: Expression of Kv1.4. Ky4.2, and Kv4.3 differs between regions in normal rat hearts. The down-regulation of Ky4 family gene expression of Ito contributed to the pathophysiological changes in ventricular hypertrophy and pulmonary hypertension induced by MCT.

  12. One-pot synthesis of hierarchical MnO2-modified diatomites for electrochemical capacitor electrodes

    Science.gov (United States)

    Zhang, Yu Xin; Huang, Ming; Li, Fei; Wang, Xue Li; Wen, Zhong Quan

    2014-01-01

    The hierarchical and porous MnO2-modified diatomite structures are prepared for the first time by a one-pot hydrothermal method. The morphology and structure of MnO2-modified diatomite hierarchical structures are examined by focus ion beam scanning electron microscopy (FIB/SEM) and X-ray diffraction spectroscopy (XRD). The results show that Birnessite-type MnO2 nanosheets are observed to grow vertically on the purified diatomite, thus building hierarchical architecture. Furthermore, the electrochemical properties of the MnO2-modified diatomite electrodes are elucidated by cyclic voltammograms, galvanostatic charge/discharge tests and electrochemical impedance spectroscopy in 1 M Na2SO4 electrolyte. The electrochemical results demonstrate that the MnO2-modified diatomite electrode exhibits highly reversible features and good rate abilities, respectively. Significantly, it exhibits the specific capacitance of 202.6 F g-1 for the MnO2-modified diatomite and 297.8 F g-1 for the MnO2 nanostructures after etching the diatomite. The capacitance retention of 95.92% over 5000 cycles further indicates the suitability of the low-cost MnO2-modified diatomite structure as a potential electrode material for supercapacitors.

  13. Magnetic phase transition in confined MnO nanoparticles studied by polarized neutron scattering

    Science.gov (United States)

    Feygenson, Mikhail; Schweika, Werner; Ioffe, Alexander; Vakhrushev, Sergey B.; Brückel, Thomas

    2010-02-01

    We have investigated the magnetic ordering and the phase transition in MnO nanoparticles confined in a porous glass using polarized neutron scattering. These MnO nanoparticles are best described as extended wormlike structures with a mean diameter of 70Å . We observe an apparent continuous magnetic phase transition in MnO nanoparticles, in contrast to the well-known discontinuous phase transition in bulk MnO. By polarization analysis, separating the magnetic scattering, it is found that within the individual MnO nanoparticles about 60% of atoms remain disordered in the low-temperature limit, presumably due to interactions between nanoparticles and glass walls. The continuous character of the phase transition and the unusual temperature dependence suggests a surface-induced disorder phenomenon.

  14. In situ study of hydrothermal MnO2 formation

    DEFF Research Database (Denmark)

    Birgisson, Steinar; Shen, Yanbin; Iversen, Bo Brummerstedt

    time using Rietveld refinements [2]. TS data gives information about all the material in the solution; from complexes to amorphous particles to crystalline particles. Properties such as bond lengths, scale factors and particle sizes as a function of reaction time can be extracted via real space...... in supercapacitors and positive electrode material in lithium batteries (both primary and secondary) [4, 5]. In this study we investigate the hydrothermal formation of different phases of MnO2 in situ using the experimental setup described above. Alpha-, beta- and delta-MnO2 are synthesized from different aqueous...

  15. Highly Regioselective Halogenation of Pyridine N-Oxide: Practical Access to 2-Halo-Substituted Pyridines.

    Science.gov (United States)

    Chen, Ying; Huang, Jinkun; Hwang, Tsang-Lin; Chen, Maosheng J; Tedrow, Jason S; Farrell, Robert P; Bio, Matthew M; Cui, Sheng

    2015-06-19

    A highly efficient and regioselective halogenation reaction of unsymmetrical pyridine N-oxide under mild conditions is described. The methodology provides a practical access to various 2-halo-substituted pyridines, which are pharmaceutically important intermediates.

  16. Vibrational studies of benzene, pyridine, pyridine-N-oxide and their cations.

    Science.gov (United States)

    Kumar, M; Srivastava, Mayuri; Yadav, R A

    2013-07-01

    IR and Raman spectra of pyridine and pyridine-N-oxide have been recorded and analyzed. The optimized molecular geometries, APT charges and vibrational characteristics for benzene, pyridine, pyridine-N-oxide and their cations have been computed using DFT method. Due to attachment of O atom at N site or removal of electron all the modes are affected in magnitudes. However, significant changes are noticed in their IR intensities, Raman activities and depolarization ratios of the Raman bands in going from pyridine to its N-oxide or in going from neutrals to their cations. It is interesting to note that in going from benzene to benzene cation charge redistribution takes place to reduce the symmetry from D6h to D2h. The calculated frequencies have been correlated with the experimental frequencies for the pyridine and pyridine-N-oxide molecules.

  17. Core-Shell MnO2-SiO2 Nanorods for Catalyzing the Removal of Dyes from Water

    Directory of Open Access Journals (Sweden)

    Wei Gong

    2017-01-01

    Full Text Available This work presented a novel core-shell MnO2@m-SiO2 for catalyzing the removal of dyes from wastewater. MnO2 nanorods were sequentially coated with polydopamine (PDA and polyethyleneimine (PEI forming MnO2@PDA-PEI. By taking advantage of the positively charged amine groups, MnO2@PDA-PEI was further silicificated, forming MnO2@PDA-PEI-SiO2. After calcination, the composite MnO2@m-SiO2 was finally obtained. MnO2 nanorod is the core and mesoporous SiO2 (m-SiO2 is the shell. MnO2@m-SiO2 has been used to degrade a model dye Rhodamine B (RhB. The shell m-SiO2 functioned to adsorb/enrich and transfer RhB, and the core MnO2 nanorods oxidized RhB. Thus, MnO2@m-SiO2 combines multiple functions together. Experimental results demonstrated that MnO2@m-SiO2 exhibited a much higher efficiency for degradation of RhB than MnO2. The RhB decoloration and degradation efficiencies were 98.7% and 84.9%, respectively. Consecutive use of MnO2@m-SiO2 has demonstrated that MnO2@m-SiO2 can be used to catalyze multiple cycles of RhB degradation. After six cycles of reuse of MnO2@m-SiO2, the RhB decoloration and degradation efficiencies were 98.2% and 71.1%, respectively.

  18. Halonium ion mediated synthesis of 2-halomethylene-3-oxoketoxime derivatives from isoxazoline N-oxides.

    Science.gov (United States)

    Raihan, Mustafa J; Rajawinslin, R R; Kavala, Veerababurao; Kuo, Chun-Wei; Kuo, Ting-Shen; He, Chiu-Hui; Huang, Hsiu-Ni; Yao, Ching-Fa

    2013-09-06

    A protocol for the N-bromosuccinimide (NBS)- and trichloroisocyanuric acid (TCCA)-mediated synthesis of novel 2-halomethylene-3-oxoketoximes via one-pot halogenation/oxidation of isoxazoline N-oxide derivatives is described here. The keto functionality of 3-ketoximes was selectively reduced by lithiumaluminum hydride to synthesize an unprecedented type of Baylis-Hillman oxime, which underwent N-O coupling to produce new isoxazoline N-oxide derivative.

  19. Comparison of the biological behaviour of morphine and its N-oxides in rats

    Energy Technology Data Exchange (ETDEWEB)

    Gurkan, E.; Demirel, B.; Ozker, K. (Cekmece Nuclear Research and Training Center, Istanbul (Turkey))

    1982-04-01

    /sup 14/C labelled morphine and morphine N-oxide solutions are injected into rats for the in vivo detection and comparison of morphine N-oxides, the natural presence of which in Papaver somniferum L. was proved by us in an earlier work /1/ and morphine itself and the distributions of these two substances in the kidneys, liver, blood and urine of the injected animals are investigated, in various time intervals.

  20. Low Temperature Synthesis of MnO2/Graphene Nanocomposites for Supercapacitors

    Directory of Open Access Journals (Sweden)

    Hao Huang

    2015-01-01

    Full Text Available MnO2/graphene nanocomposites were synthesized through a simple route in a water-reflux condenser system. The as-prepared composites were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman microscope, and Brunauer-Emmett-Teller surface area analysis. Capacitive properties of the synthesized composite electrodes were investigated via cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectrometry in a 0.5 M Na2SO4 electrolyte. Results show that this method can control the morphology and structure of MnO2 loaded onto the graphene sheets. Because excessive MnO2 enwrapping graphene would affect the overall conductivity, the composite prepared by lower temperature has better characteristics of supercapacitor. 60-MnO2/graphene composite (48 wt% MnO2 displays the specific capacitance as high as 350 F/g at 1000 mA/g, which is higher than that of 100-MnO2/graphene (302 F/g, and it is almost two times higher than that of MnO2 (163 F/g. Furthermore, the composite exhibits excellent long cycle life along with ~93% specific capacitance retained after 5000 cycle tests.

  1. Morphological and electrochemical cycling effects in MnO2 nanostructures by 3D electron tomography

    KAUST Repository

    Chen, Wei

    2014-02-12

    In this study, MnO2 nanostructures with well-controlled morphology and crystal phase are successfully prepared by chemical synthesis, and characterized by three-dimensional electron tomography for use as supercapacitor electrode materials. The growth process of the various MnO 2 nanostructures is revealed in detail, and correlated to their electrochemical performance as supercapacitor materials. The specific capacitance of MnO2 electrodes is found to be strongly correlated with the inner morphology and crystal phase of the MnO2 nanostructures. Furthermore, it is demonstrated that the increased capacity with electrochemical cycling of the materials is due to the formation of defective regions embedded in the MnO2 nanostructures; these regions form during electrochemical cycling of the electrodes, resulting in increased porosity, surface area, and consequently, increased electrochemical capacity. The preparation, characterization and supercapacitor application of MnO 2 nanostructures by 3D electron tomography are studied. The electrochemical performance of MnO2 is correlated to its surface area, determined by the morphological effect, as well as the cycling effect, determined by the formation of defective regions on the nanostructures during electrochemical cycling tests. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Structure of Electrochemically Lithiated Li0.33MnO2

    Institute of Scientific and Technical Information of China (English)

    CHEN Hong; WEI Ying-jin; WANG Chun-zhong; CHEN Gang

    2011-01-01

    Li0.33MnO2 cathode material was synthesized by solid state reaction which showed a monoclinic structure.In situ synchrotron diffraction showed a reversible structural transition of Li0.33MnO2 during Li+ insertion/extraction.However,it is difficult to determine the crystal structure of lithiated Li0.33+xMnO2 based on their poorly resolved diffraction patterns.This difficulty was successfully resolved by X-ray absorption spectroscopy(XAS) and Raman scattering which are sensitive to the short-range ordering of material lattice.Extended X-ray absorption fine structure shows the co-existence of corner- and edge-shared[MnO6]in Li0.33MnO2,whereas only edge-shared[MnO6]in lithiated Li0.96MnO2.Significantly,the differences between the Raman spectra of Li0.33MnO2 and Li0.96MnO2 indicate the phase transition of the material with Li+ intercalation.This work shows that Li0.33MnO2 transforms to monoclinic LiMnO2 with Li+ intercalation.This phase transformation was suggested to evolve from the migration of Mn ions.

  3. As(III) oxidation by MnO2 during groundwater treatment.

    Science.gov (United States)

    Gude, J C J; Rietveld, L C; van Halem, D

    2017-03-15

    The top layer of natural rapid sand filtration was found to effectively oxidise arsenite (As(III)) in groundwater treatment. However, the oxidation pathway has not yet been identified. The aim of this study was to investigate whether naturally formed manganese oxide (MnO2), present on filter grains, could abiotically be responsible for As(III) oxidation in the top of a rapid sand filter. For this purpose As(III) oxidation with two MnO2 containing powders was investigated in aerobic water containing manganese(II) (Mn(II)), iron(II) (Fe(II)) and/or iron(III) (Fe(III)). The first MnO2 powder was a very pure - commercially available - natural MnO2 powder. The second originated from a filter sand coating, produced over 22 years in a rapid filter during aeration and filtration. Jar test experiments showed that both powders oxidised As(III). However, when applying the MnO2 in aerated, raw groundwater, As(III) removal was not enhanced compared to aeration alone. It was found that the presence of Fe(II)) and Mn(II) inhibited As(III) oxidation, as Fe(II) and Mn(II) adsorption and oxidation were preferred over As(III) on the MnO2 surface (at pH 7). Therefore it is concluded that just because MnO2 is present in a filter bed, it does not necessarily mean that MnO2 will be available to oxidise As(III). However, unlike Fe(II), the addition of Fe(III) did not hinder As(III) oxidation on the MnO2 surface; resulting in subsequent effective As(V) removal by the flocculating hydrous ferric oxides. Copyright © 2016 Elsevier Ltd. All rights reserved.

  4. Structural and electronic properties of polar MnO ultrathin film grown on Ag(111)

    Science.gov (United States)

    Kundu, Asish K.; Menon, Krishnakumar S. R.

    2016-05-01

    Surface electronic structure of ultrathin polar MnO film was studied by Low-energy Electron Diffraction (LEED) and Photoemission Spectroscopic (PES) techniques. Epitaxial monolayer to facet formation with increasing film thickness has been observed by LEED. Our LEED result shows p(2x2) surface reconstruction along with facet formation, stabilize the polar MnO(111) surface. The core levels and the valence band electronic structure of MnO films have been studied as a function of film thickness using X-ray and ultraviolet photoelectron spectroscopy techniques.

  5. Fibrotic Effects of Arecoline N-Oxide in Oral Potentially Malignant Disorders.

    Science.gov (United States)

    Kuo, Tzer-Min; Luo, Shun-Yuan; Chiang, Shang-Lun; Yeh, Kun-Tu; Hsu, Hui-Ting; Wu, Cheng-Tien; Lu, Chi-Yu; Tsai, Ming-Hsui; Chang, Jan-Gowth; Ko, Ying-Chin

    2015-06-24

    The metabolites of environmental chemicals play key roles in carcinogenesis. Areca nut is strongly associated with the development of oral potentially malignant disorders (OPMD) or cancer. The main alkaloid in the areca nut is arecoline, which is highly cytotoxic and genotoxic. Arecoline N-oxide, a metabolite of areca nut alkaloids, which has been identified in animal urine, has been shown to induce mutagenicity in bacteria. In this study, it was found that its protein adduct could be detected in oral keratinocytes treated with areca nut extract. Increased collagen expression and severity of squamous hyperplasia were observed in arecoline N-oxide treated mice. In cultured oral fibroblasts, arecoline N-oxide showed stronger effects on the increase of fibrotic related genes including TGF-beta1, S100A4, MMP-9, IL-6, and fibronectin and a decrease of E-cadherin as compared with arecoline. Finally, arecoline N-oxide stimulation effectively increased the DNA damage marker, gamma-H2A.X, both in vitro and in vivo. Taken together, these results indicate that arecoline N-oxide shows a high potential for the induction of OPMD.

  6. New quinoxaline 1,4-di-N-oxides. Part 1: Hypoxia-selective cytotoxins and anticancer agents derived from quinoxaline 1,4-di-N-oxides.

    Science.gov (United States)

    Amin, Kamelia M; Ismail, Magda M F; Noaman, Eman; Soliman, Dalia H; Ammar, Yousry A

    2006-10-15

    Hypoxic cells which are common feature of solid tumors are resistant to both anticancer drugs and radiation therapy. Thus, the identification of drugs with the selective toxicity toward hypoxic cells is an important target in anticancer chemotherapy. Tirapazamine has been shown to be an efficient and selective cytotoxin after bioreductive activation in hypoxic cells which is thought to be due to the presence of the 1,4-di-N-oxide. A new series of quinoxaline 1,4-di-N-oxides and fused quinoxaline di-N-oxides were synthesized and evaluated for hypoxic-cytotoxic activity on EAC cell line. Compound 10a was the most potent cytotoxin IC(50) 0.9 microg/mL, potency 75 microg/mL, and was approximately 15 times more selective cytotoxin (HCR>111) than 3-aminoquinoxaline-2-carbonitrile which has been used as a standard (HCR>7.5). Compounds 4 and 3a,b were more selective than the standard. In addition, antitumor activity against Hepg2 (liver) and U251 (brain) human cell lines was evaluated, compounds 9c and 8a were the most active against Hepg2 with IC(50) values 1.9 and 2.9 microg/mL, respectively, however, all the tested compounds were nontoxic against U251 cell line.

  7. Efficient Reduction of Antibacterial Activity and Cytotoxicity of Fluoroquinolones by Fungal-Mediated N-Oxidation.

    Science.gov (United States)

    Rusch, Marina; Spielmeyer, Astrid; Meißner, Jessica; Kietzmann, Manfred; Zorn, Holger; Hamscher, Gerd

    2017-04-19

    Extensive usage of fluoroquinolone antibiotics in livestock results in their occurrence in manure and subsequently in the environment. Fluoroquinolone residues may promote bacterial resistance and are toxic to plants and aquatic organisms. Moreover, fluoroquinolones may enter the food chain through plant uptake, if manure is applied as fertilizer. Thus, the presence of fluoroquinolones in the environment may pose a threat to human and ecological health. In this study, the biotransformation of enrofloxacin, marbofloxacin, and difloxacin by the fungus X. longipes (Xylaria) was investigated. The main metabolites were unequivocally identified as the respective N-oxides by mass spectrometry and nuclear magnetic resonance spectroscopy. Fungal-mediated N-oxidation of fluoroquinolones led to a 77-90% reduction of the initial antibacterial activity. In contrast to their respective parent compounds, N-oxides showed low cytotoxic potential and had a reduced impact on cell proliferation. Thus, biotransformation by X. longipes may represent an effective method for inactivating fluoroquinolones.

  8. Fluorescence Quenching Study of Zinc Bisporphyrins by Fulleropyrrolidines and Their N-Oxides

    Institute of Scientific and Technical Information of China (English)

    XU Hua; YANG Yi; ZHU Yi-Zhou; ZHENG Jian-Yu

    2006-01-01

    Novel phenylene-bridged zinc bisporphyrins (1-4), fulleropyrrolidines (C60-m, C60-h) and their N-oxides C6o-mo, C60-ho) were synthesized. The fluorescence quenching processes of bisporphyrins in toluene solution by fulleropyrrolidines and their N-oxides were investigated by steady-state fluorescence spectra. The fluorescence quenching constants proved that the fluorescence quenching ability was decreased as reduction of thepyrrolidinefunctionalgroups of fullerene surface: C60-h>C60-m>C60, and the fluorescence quenching ability was increased about 1.3-7.4 times by utilizing fulleropyrrolidine N-oxides (C60-mo, C60-ho) compared to fulleropyrrolidine compounds (C60-m, C60-h). The results revealed photoinduced electron transfer (PET) efficiencybetweenbisporphyrinandfullerenederivativescould be tunable by change of functional groups on fullerene surface.

  9. Pentaerythritol Tetranitrate In Vivo Treatment Improves Oxidative Stress and Vascular Dysfunction by Suppression of Endothelin-1 Signaling in Monocrotaline-Induced Pulmonary Hypertension

    Science.gov (United States)

    Steven, Sebastian; Oelze, Matthias; Brandt, Moritz; Ullmann, Elisabeth; Kröller-Schön, Swenja; Heeren, Tjebo; Tran, Lan P.; Daub, Steffen; Dib, Mobin; Stalleicken, Dirk; Wenzel, Philip; Münzel, Thomas

    2017-01-01

    Objective. Oxidative stress and endothelial dysfunction contribute to pulmonary arterial hypertension (PAH). The role of the nitrovasodilator pentaerythritol tetranitrate (PETN) on endothelial function and oxidative stress in PAH has not yet been defined. Methods and Results. PAH was induced by monocrotaline (MCT, i.v.) in Wistar rats. Low (30 mg/kg; MCT30), middle (40 mg/kg; MCT40), or high (60 mg/kg; MCT60) dose of MCT for 14, 28, and 42 d was used. MCT induced endothelial dysfunction, pulmonary vascular wall thickening, and fibrosis, as well as protein tyrosine nitration. Pulmonary arterial pressure and heart/body and lung/body weight ratio were increased in MCT40 rats (28 d) and reduced by oral PETN (10 mg/kg, 24 d) therapy. Oxidative stress in the vascular wall, in the heart, and in whole blood as well as vascular endothelin-1 signaling was increased in MCT40-treated rats and normalized by PETN therapy, likely by upregulation of heme oxygenase-1 (HO-1). PETN therapy improved endothelium-dependent relaxation in pulmonary arteries and inhibited endothelin-1-induced oxidative burst in whole blood and the expression of adhesion molecule (ICAM-1) in endothelial cells. Conclusion. MCT-induced PAH impairs endothelial function (aorta and pulmonary arteries) and increases oxidative stress whereas PETN markedly attenuates these adverse effects. Thus, PETN therapy improves pulmonary hypertension beyond its known cardiac preload reducing ability.

  10. Pentaerythritol Tetranitrate In Vivo Treatment Improves Oxidative Stress and Vascular Dysfunction by Suppression of Endothelin-1 Signaling in Monocrotaline-Induced Pulmonary Hypertension

    Directory of Open Access Journals (Sweden)

    Sebastian Steven

    2017-01-01

    Full Text Available Objective. Oxidative stress and endothelial dysfunction contribute to pulmonary arterial hypertension (PAH. The role of the nitrovasodilator pentaerythritol tetranitrate (PETN on endothelial function and oxidative stress in PAH has not yet been defined. Methods and Results. PAH was induced by monocrotaline (MCT, i.v. in Wistar rats. Low (30 mg/kg; MCT30, middle (40 mg/kg; MCT40, or high (60 mg/kg; MCT60 dose of MCT for 14, 28, and 42 d was used. MCT induced endothelial dysfunction, pulmonary vascular wall thickening, and fibrosis, as well as protein tyrosine nitration. Pulmonary arterial pressure and heart/body and lung/body weight ratio were increased in MCT40 rats (28 d and reduced by oral PETN (10 mg/kg, 24 d therapy. Oxidative stress in the vascular wall, in the heart, and in whole blood as well as vascular endothelin-1 signaling was increased in MCT40-treated rats and normalized by PETN therapy, likely by upregulation of heme oxygenase-1 (HO-1. PETN therapy improved endothelium-dependent relaxation in pulmonary arteries and inhibited endothelin-1-induced oxidative burst in whole blood and the expression of adhesion molecule (ICAM-1 in endothelial cells. Conclusion. MCT-induced PAH impairs endothelial function (aorta and pulmonary arteries and increases oxidative stress whereas PETN markedly attenuates these adverse effects. Thus, PETN therapy improves pulmonary hypertension beyond its known cardiac preload reducing ability.

  11. Role of secretory phospholipase A(2) in rhythmic contraction of pulmonary arteries of rats with monocrotaline-induced pulmonary arterial hypertension.

    Science.gov (United States)

    Tanabe, Yoshiyuki; Saito-Tanji, Maki; Morikawa, Yuki; Kamataki, Akihisa; Sawai, Takashi; Nakayama, Koichi

    2012-01-01

    Excessive stretching of the vascular wall in accordance with pulmonary arterial hypertension (PAH) induces a variety of pathogenic cellular events in the pulmonary arteries. We previously reported that indoxam, a selective inhibitor for secretory phospholipase A(2) (sPLA(2)), blocked the stretch-induced contraction of rabbit pulmonary arteries by inhibition of untransformed prostaglandin H(2) (PGH(2)) production. The present study was undertaken to investigate involvement of sPLA(2) and untransformed PGH(2) in the enhanced contractility of pulmonary arteries of experimental PAH in rats. Among all the known isoforms of sPLA(2), sPLA(2)-X transcript was most significantly augmented in the pulmonary arteries of rats with monocrotaline-induced pulmonary hypertension (MCT-PHR). The pulmonary arteries of MCT-PHR frequently showed two types of spontaneous contraction in response to stretch; 27% showed rhythmic contraction, which was sensitive to indoxam and SC-560 (selective COX-1 inhibitor), but less sensitive to NS-398 (selective COX-2 inhibitor); and 47% showed sustained incremental tension (tonic contraction), which was insensitive to indoxam and SC-560, but sensitive to NS-398 and was attenuated to 45% of the control. Only the rhythmically contracting pulmonary arteries of MCT-PHR produced a substantial amount of untransformed PGH(2), which was abolished by indoxam. These results suggest that sPLA(2)-mediated PGH(2) synthesis plays an important role in the rhythmic contraction of pulmonary arteries of MCT-PHR.

  12. Pentaerythritol Tetranitrate In Vivo Treatment Improves Oxidative Stress and Vascular Dysfunction by Suppression of Endothelin-1 Signaling in Monocrotaline-Induced Pulmonary Hypertension.

    Science.gov (United States)

    Steven, Sebastian; Oelze, Matthias; Brandt, Moritz; Ullmann, Elisabeth; Kröller-Schön, Swenja; Heeren, Tjebo; Tran, Lan P; Daub, Steffen; Dib, Mobin; Stalleicken, Dirk; Wenzel, Philip; Münzel, Thomas; Daiber, Andreas

    2017-01-01

    Objective. Oxidative stress and endothelial dysfunction contribute to pulmonary arterial hypertension (PAH). The role of the nitrovasodilator pentaerythritol tetranitrate (PETN) on endothelial function and oxidative stress in PAH has not yet been defined. Methods and Results. PAH was induced by monocrotaline (MCT, i.v.) in Wistar rats. Low (30 mg/kg; MCT30), middle (40 mg/kg; MCT40), or high (60 mg/kg; MCT60) dose of MCT for 14, 28, and 42 d was used. MCT induced endothelial dysfunction, pulmonary vascular wall thickening, and fibrosis, as well as protein tyrosine nitration. Pulmonary arterial pressure and heart/body and lung/body weight ratio were increased in MCT40 rats (28 d) and reduced by oral PETN (10 mg/kg, 24 d) therapy. Oxidative stress in the vascular wall, in the heart, and in whole blood as well as vascular endothelin-1 signaling was increased in MCT40-treated rats and normalized by PETN therapy, likely by upregulation of heme oxygenase-1 (HO-1). PETN therapy improved endothelium-dependent relaxation in pulmonary arteries and inhibited endothelin-1-induced oxidative burst in whole blood and the expression of adhesion molecule (ICAM-1) in endothelial cells. Conclusion. MCT-induced PAH impairs endothelial function (aorta and pulmonary arteries) and increases oxidative stress whereas PETN markedly attenuates these adverse effects. Thus, PETN therapy improves pulmonary hypertension beyond its known cardiac preload reducing ability.

  13. PRX-08066, a novel 5-hydroxytryptamine receptor 2B antagonist, reduces monocrotaline-induced pulmonary arterial hypertension and right ventricular hypertrophy in rats.

    Science.gov (United States)

    Porvasnik, Stacy L; Germain, Sean; Embury, Jennifer; Gannon, Kimberley S; Jacques, Vincent; Murray, Justin; Byrne, Barry J; Shacham, Sharon; Al-Mousily, Faris

    2010-08-01

    Pulmonary arterial hypertension (PAH) is a life-threatening disease that results in right ventricular failure. 5-((4-(6-Chlorothieno[2,3-d]pyrimidin-4-ylamino)piperidin-1-yl)methyl)-2-fluorobenzonitrile monofumarate (PRX-08066) is a selective 5-hydroxytryptamine receptor 2B (5-HT2BR) antagonist that causes selective vasodilation of pulmonary arteries. In the current study, the effects of PRX-08066 were assessed by using the monocrotaline (MCT)-induced PAH rat model. Male rats received 40 mg/kg MCT or phosphate-buffered saline and were treated orally twice a day with vehicle or 50 or 100 mg/kg PRX-08066 for 5 weeks. Pulmonary and cardiac functions were evaluated by hemodynamics, heart weight, magnetic resonance imaging (MRI), pulmonary artery (PA) morphology, and histology. Cardiac MRI demonstrated that PRX-08066 (100 mg/kg) significantly (P PRX-08066 significantly reduced peak PA pressure at 50 and 100 mg/kg (P PRX-08066 therapy also significantly reduced right ventricle (RV)/body weight and RV/left ventricle + septum (P PRX-08066 (P PRX-08066 significantly attenuated the elevation in PA pressure and RV hypertrophy and maintained cardiac function. Pulmonary vascular remodeling was also diminished compared with MCT control rats. PRX-08066 prevents the severity of PAH in the MCT rat model.

  14. MnO2 Based Nanostructures for Supercapacitor Energy Storage Applications

    KAUST Repository

    Chen, Wei

    2013-11-01

    Nanostructured materials provide new and exciting approaches to the development of supercapacitor electrodes for high-performance electrochemical energy storage applications. One of the biggest challenges in materials science and engineering, however, is to prepare the nanomaterials with desirable characteristics and to engineer the structures in proper ways. This dissertation presents the successful preparation and application of very promising materials in the area of supercapacitor energy storage, including manganese dioxide and its composites, polyaniline and activated carbons. Attention has been paid to understanding their growth process and performance in supercapacitor devices. The morphological and electrochemical cycling effects, which contribute to the understanding of the energy storage mechanism of MnO2 based supercapacitors is thoroughly investigated. In addition, MnO2 based binary (MnO2-carbon nanocoils, MnO2-graphene) and ternary (MnO2-carbon nanotube-graphene) nanocomposites, as well as two novel electrodes (MnO2-carbon nanotube-textile and MnO2-carbon nanotube-sponge) have been studied as supercapacitor electrode materials, showing much improved electrochemical storage performance with good energy and power densities. Furthermore, a general chemical route was introduced to synthesize different conducting polymers and activated carbons by taking the MnO2 nanostructures as reactive templates. The electrochemical behaviors of the polyaniline and activated nanocarbon supercapacitors demonstrate the morphology-dependent enhancement of capacitance. Excellent energy and power densities were obtained from the template-derived polyaniline and activated carbon based supercapacitors, indicating the success of our proposed chemical route toward the preparation of high performance supercapacitor materials. The work discussed in this dissertation conclusively showed the significance of the preparation of desirable nanomaterials and the design of effective

  15. Synthesis of MnO2 Microfiber with Secondary Nanostructure by Cotton Template

    Directory of Open Access Journals (Sweden)

    Huan-qin Wang

    2010-01-01

    Full Text Available Hierarchical MnO2 microfibers were prepared by using cotton as the template and KMnO4 as the precursor via an ultrasonic assistance route. The results of scanning electron microscope characterization showed that the concentration of KMnO4 had a significant effect on the morphology of MnO2 microfiber. At low concentration of KMnO4, the microfiber was composed of MnO2 nanorods with single crystal structure. With increasing the concentration of KMnO4, the secondary nanostructure of MnO2 microfibers had a transformation from nanorod to nanoparticle. The results of N2 adsorption-desorption analysis indicated that MnO2 microfibers had BET surface area of about 25 m2/g. This synthesis provides a new way to control the secondary nanostructure of MnO2 microfiber by adjusting the concentration of precursor. Furthermore, the mechanism for the replication was proposed and discussed.

  16. Effect of Butanol and Propylene Glycol in Amorphous MnO2 Nanoparticles

    Directory of Open Access Journals (Sweden)

    Johnson HENRY

    2014-05-01

    Full Text Available Amorphous MnO2 are synthesized using KMnO4, butanol, and propylene glycol in an aqueous solution by using the precipitation method, under ambient conditions. The structure, molecular vibrations, surface morphological and optical properties of MnO2 powders are studied using XRD, FTIR, SEM and UV-vis spectroscopy. From the XRD patterns, it is clear that both butanol and propylene glycol assisted MnO2 particles are amorphous in nature. While the strong peak is noticed at 1384 cm-1 in the FTIR spectra, which is due to the characteristic peak of MnO2. SEM photographs show spherical shapes of MnO2 particles, and the average size of a particle is about 200 nm for butanol assisted samples and is around 500 nm for propylene glycol assisted samples. Butanol assisted MnO2 particles exhibit higher optical absorption in the visible region than propylene glycol. However, the estimated optical band gap of both the samples is found around 2.33 eV.doi:10.14456/WJST.2014.22

  17. Nitrogen inversion barriers affect the N-oxidation of tertiary alkylamines by cytochromes P450

    DEFF Research Database (Denmark)

    Rydberg, Patrik; Jørgensen, Martin S.; Jacobsen, T.A.

    2013-01-01

    Calculations: Cytochrome P450 enzymes facilitate a number of chemically different reactions. For example, amines can be either N-dealkylated or N-oxidized, but it is complex to rationalize which of these competing reactions occurs. It is shown that the barrier for inversion of the alkylamine...

  18. Copper(II)-catalyzed electrophilic amination of quinoline N-oxides with O-benzoyl hydroxylamines.

    Science.gov (United States)

    Li, Gang; Jia, Chunqi; Sun, Kai; Lv, Yunhe; Zhao, Feng; Zhou, Kexiao; Wu, Hankui

    2015-03-21

    Copper acetate-catalyzed C-H bond functionalization amination of quinoline N-oxides was achieved using O-benzoyl hydroxylamine as an electrophilic amination reagent, thereby affording the desired products in moderate to excellent yields. Electrophilic amination can also be performed in good yield on a gram scale.

  19. A sensitive trimethylamine-N-oxide aldolase assay in two steps without deproteinisation

    DEFF Research Database (Denmark)

    Nielsen, Michael Krogsgaard; Havemeister, W.; Rehbein, H.;

    2000-01-01

    A two-step assay for trimethylamine-N-oxide aldolase (the target enzyme) is described in which the second step, the indicator reaction, is of the enzymatic end-point type. This indicator reaction is carried out at a slightly alkaline pH, outside the target enzyme's active pH range. An effective i...

  20. The synthesis of a pyridine-N-oxide isophthalamide rotaxane utilizing supplementary amide hydrogen bond interactions.

    Science.gov (United States)

    Evans, Nicholas H; Gell, Charles E; Peach, Michael J G

    2016-08-16

    The synthesis of a pyridine-N-oxide containing rotaxane, not requiring an additional ionic template, has been achieved in 32% yield. Successful rotaxane formation is dependent upon the structure of the isophthalamide macrocycle used, an observation which has been rationalised by a combination of NMR spectroscopy, X-ray crystallography and computational modelling.

  1. Arecoline N-oxide: its mutagenicity and possible role as ultimate carcinogen in areca oral carcinogenesis.

    Science.gov (United States)

    Lin, Kuo-Hui; Lin, Ching-Yuan; Liu, Chin-Chih; Chou, Ming-Young; Lin, Jen-Kun

    2011-04-13

    The areca nut is the most widely consumed psychoactive substance in Taiwan, India, and Southeast Asia. It is considered to be an environmental risk factor for the development of oral submucous fibrosis and cancer. Arecoline, the major alkaloid of areca nut, has been known to cause cytotoxicity and genotoxicity in various systems. However, the active compound accounting for arecoline-induced damage in normal human oral cells is still uncharacterized. The present study was undertaken to identify the active metabolite of arecoline that might induce damage in human oral tissues and cause mutagenicity in Salmonella typhimurium tester strains TA 100 and TA 98. It is interesting to find that the major metabolite of arecoline, arecoline N-oxide, is moderately mutagenic to these Salmonella tester strains. This mutagenicity was potently inhibited by sulfhydryl compounds, namely, glutathione, N-acetylcysteine, and cysteine, whereas methionine is inactive in this inhibition. The mutagenicity of arecoline N-oxide was strongly inhibited by the N-oxide reducing agent titanium trichloride. The possible role of arecoline N-oxide in the induction of oral carcinogenesis by areca nut chewing is discussed.

  2. The Two-Dimensional MnO2/Graphene Interface: Half-metallicity and Quantum Anomalous Hall State

    KAUST Repository

    Gan, Liyong

    2015-10-07

    We explore the electronic properties of the MnO2/graphene interface by first-principles calculations, showing that MnO2 becomes half-metallic. MnO2 in the MnO2/graphene/MnO2 system provides time-reversal and inversion symmetry breaking. Spin splitting by proximity occurs at the Dirac points and a topologically nontrivial band gap is opened, enabling a quantum anomalous Hall state. The half-metallicity, spin splitting, and size of the band gap depend on the interfacial interaction, which can be tuned by strain engineering.

  3. Modeling anti-Trypanosoma cruzi activity of N-oxide containing heterocycles.

    Science.gov (United States)

    Boiani, Mariana; Cerecetto, Hugo; Gonzalez, Mercedes; Gasteiger, Johann

    2008-01-01

    In the present study a systematic approach was used to model the anti-T. cruzi activity of a series of N-oxide containing heterocycles belonging to four chemical families with a wide structural diversity. The proposed mode of action implies the reduction of the N-oxide moiety; however, the biochemical mechanism underlying the anti-T. cruzi activity is still unkown. For structural representation two types of descriptors were analyzed: quantum chemical (AM1) global descriptors and properties coded by radial distribution function (RDF). Both types of descriptors point to the relevance of electronic properties. The local-RDF (LRDF) identified an electrophilic center at 4.1-4.9 A from the oxygen atom of the N-oxide moiety, although other properties are required to explain the biological activity. While the mode of action of N-oxide containing heterocycles is still unknown, the results obtained here strengthen the importance of the electrophilic character of the molecule and the possible participation of the heterocycle in a reduction process. The ability of these descriptors to distinguish among activity classes was assessed using Kohonen neural networks, and the best clustering descriptors were later used for model building. Different learning algorithms were used for model development, and stratified 10-fold cross-validation was used to evaluate the performance of each classifier. The best results were obtained using k-nearest neighbors (k-NN) and decision tree (J48) methods combined with global descriptors. Since tree-based methods are easily translated into classification rules, the J48 model is a useful tool in the de novo construction of new N-oxide containing heterocycle lead structures.

  4. N-demethylation and N-oxidation of imipramine in rat thoracic aortic endothelial cells.

    Science.gov (United States)

    Ueda, Yukari; Yaginuma, Toshihiko; Sakurai, Eiko; Sakurai, Eiichi

    2014-06-01

    The aim of this study was to examine whether cultured rat thoracic aortic endothelial cells (TAECs) have the ability to metabolize the tertiary amine, imipramine. In rat TAECs, imipramine was biotransformed into N-demethylate and N-oxide by cytochrome P450 (CYP) and flavin-containing monooxygenase (FMO), respectively. The intrinsic clearance (V max/K m) for the N-oxide formation was approximately five times as high as that for the N-demethylate formation, indicating that oxidation by CYP was much higher than that by FMO. Moreover, we suggest that CYP2C11 and CYP3A2 are key players in the metabolism to N-demethylate in rat TAECs using the respective anti-rat CYP antibodies (anti-CYP2C11 and anti-CYP3A2). The presence of CYP2C11 and CYP3A2 proteins was also confirmed in cultured rat TAECs using a polyclonal anti-CYP antibody and immunofluorescence microscopy. In contrast, the formation rate of N-oxide at pH 8.4 was higher than that at pH 7.4. Inhibition of N-oxide formation by methimazole was found to be the best model of competitive inhibition yielding an apparent K i value of 0.80 μmol/L, demonstrating that N-oxidation was catalyzed by FMO in rat TAECs. These results suggest that rat TAEC enzymes can convert substrates of exogenous origin such as imipramine, indicating that TAECs have an important function for metabolic products, besides hepatic cells.

  5. N-oxide 1,2,4,5-tetrazine-based high-performance energetic materials.

    Science.gov (United States)

    Wei, Hao; Gao, Haixiang; Shreeve, Jean'ne M

    2014-12-15

    One route to high density and high performance energetic materials based on 1,2,4,5-tetrazine is the introduction of 2,4-di-N-oxide functionalities. Based on several examples and through theoretical analysis, the strategy of regioselective introduction of these moieties into 1,2,4,5-tetrazines has been developed. Using this methodology, various new tetrazine structures containing the N-oxide functionality were synthesized and fully characterized using IR, NMR, and mass spectroscopy, elemental analysis, and single-crystal X-ray analysis. Hydrogen peroxide (50 %) was used very effectively in lieu of the usual 90 % peroxide in this system to generate N-oxide tetrazine compounds successfully. Comparison of the experimental densities of N-oxide 1,2,4,5-tetrazine compounds with their 1,2,4,5-tetrazine precursors shows that introducing the N-oxide functionality is a highly effective and feasible method to enhance the density of these materials. The heats of formation for all compounds were calculated with Gaussian 03 (revision D.01) and these values were combined with measured densities to calculate detonation pressures (P) and velocities (νD ) of these energetic materials (Explo 5.0 v. 6.01). The new oxygen-containing tetrazines exhibit high density, good thermal stability, acceptable oxygen balance, positive heat of formation, and excellent detonation properties, which, in some cases, are superior to those of 1,3,5-tritnitrotoluene (TNT), 1,3,5-trinitrotriazacyclohexane (RDX), and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Complexation facilitated reduction of aromatic N-oxides by aqueous Fe(II)-tiron complex: reaction kinetics and mechanisms.

    Science.gov (United States)

    Chen, Yiling; Zhang, Huichun

    2013-10-01

    Rapid reduction of carbadox (CDX), olaquindox and several other aromatic N-oxides were investigated in aqueous solution containing Fe(II) and tiron. Consistent with previous work, the 1:2 Fe(II)-tiron complex, FeL2(6-), is the dominant reactive species as its concentration linearly correlates with the observed rate constant kobs under various conditions. The N-oxides without any side chains were much less reactive, suggesting direct reduction of the N-oxides is slow. UV-vis spectra suggest FeL2(6-) likely forms 5- or 7-membered rings with CDX and olaquindox through the N and O atoms on the side chain. The formed inner-sphere complexes significantly facilitated electron transfer from FeL2(6-) to the N-oxides. Reduction products of the N-oxides were identified by HPLC/QToF-MS to be the deoxygenated analogs. QSAR analysis indicated neither the first electron transfer nor N-O bond cleavage is the rate-limiting step. Calculations of the atomic spin densities of the anionic N-oxides confirmed the extensive delocalization between the aromatic ring and the side chain, suggesting complex formation can significantly affect the reduction kinetics. Our results suggest the complexation facilitated N-oxide reduction by Fe(II)-tiron involves a free radical mechanism, and the subsequent deoxygenation might also benefit from the weak complexation of Fe(II) with the N-oxide O atom.

  7. Integrative analysis of hepatic microRNA and mRNA to identify potential biological pathways associated with monocrotaline-induced liver injury in mice.

    Science.gov (United States)

    Huang, Zhenlin; Chen, Minwei; Zhang, Jiaqi; Sheng, Yuchen; Ji, Lili

    2017-10-15

    Pyrrolizidine alkaloids (PAs) are a type of natural hepatotoxic compounds. Monocrotaline (MCT), belongs to PAs, is a main compound distributed in medicinal herb Crotalaria ferruginea Grah. ex Benth. This study aims to identify the potential biological signaling pathway associated with MCT-induced liver injury by analyzing the integrative altered hepatic microRNA (miRNA) and mRNA expression profile. C57BL/6 mice were orally given with MCT (270, 330mg/kg). Serum alanine/aspartate aminotransferase (ALT/AST) activity, total bilirubin (TBil) amount and liver histological evaluation showed the liver injury induced by MCT. Results of miRNA chip analysis showed that the hepatic expression of 15 miRNAs (whose signal intensity>200) was significantly altered in MCT-treated mice, and among them total 11 miRNAs passed further validation by using Real-time PCR assay. Results of mRNA chip analysis demonstrated that the hepatic expression of 569 genes was up-regulated and of other 417 genes was down-regulated in MCT-treated mice. There are total 426 predicted target genes of those above altered 11 miRNAs, and among them total 10 genes were also altered in mice treated with both MCT (270mg/kg) and MCT (330mg/kg) from the results of mRNA chip. Among these above 10 genes, total 8 genes passed further validation by using Real-time PCR assay. Only 1 biological signaling pathway was annotated by using those above 8 genes, which is phagosome. In conclusion, this study demonstrated the integrative altered expression profile of liver miRNA and mRNA, and identified that innate immunity may be critically involved in MCT-induced liver injury in mice. Copyright © 2017 Elsevier Inc. All rights reserved.

  8. Telmisartan attenuates monocrotaline-induced pulmonary artery endothelial dysfunction through a PPAR gamma-dependent PI3K/Akt/eNOS pathway.

    Science.gov (United States)

    Li, He; Lu, Wei; Cai, Wei-Wei; Wang, Pei-Jian; Zhang, Ning; Yu, Chang-Ping; Wang, Dong-Liang; Liu, Bai-Cheng; Sun, Wei

    2014-06-01

    Pulmonary artery endothelial dysfunction has been demonstrated in pulmonary arterial hypertension (PAH). Telmisartan has beneficial effects in endothelial function in PAH patients; however, the underlying mechanisms for these effects remain unknown. In this study, we observed the effects of telmisartan on monocrotaline (MCT)-induced Sprague Dawley (SD) rat model of PAH. After a single-dose injection of MCT (60 mg/kg), oral administration of telmisartan (10 mg/kg/d) was started from day 1 to day 28 or with saline as MCT control. The vasorelaxation and remodelling of pulmonary arteries; the expression of peroxisome proliferator-activated receptor γ (PPARγ), Akt, eNOS; levels of phosphorylation of Akt (p-Akt) and phosphorylation of eNOS (p-eNOS) were analysed in isolated rat pulmonary arteries and cultured human pulmonary artery endothelial cells (HPAECs). Compared to MCT control group, telmisartan treatment ameliorated pulmonary artery endothelial dysfunction and remodelling, prevented the elevation of right ventricular systolic pressure (RVSP) induced by MCT. Immunoblotting results indicated lower levels of PPARγ, p-Akt and p-eNOS in pulmonary arteries treated with MCT alone and levels were significantly restored by co-treatment with telmisartan. In isolated pulmonary arteries, the impaired endothelium-dependent vasorelaxation of pulmonary arteries was improved following incubation with telmisartan for 12 h, whereas this effect was blocked by the inhibition of either PPARγ or phosphoinositide 3-kinase (PI3K) signals transduction. In cultured HPAECs, treatment with telmisartan increased PPARγ expression and promoted the phosphorylation of Akt and eNOS, thereby increasing the production of NO. These effects were abolished by the inhibition of PPARγ or PI3K. Telmisartan protected against endothelial dysfunction in MCT-induced PAH through a PPARγ-dependent PI3K/Akt/eNOS pathway. Thus, telmisartan may be a promising therapeutic strategy for patients with a high

  9. Inhalation of the BK(Ca-opener NS1619 attenuates right ventricular pressure and improves oxygenation in the rat monocrotaline model of pulmonary hypertension.

    Directory of Open Access Journals (Sweden)

    Marc Revermann

    Full Text Available BACKGROUND: Right heart failure is a fatal consequence of chronic pulmonary hypertension (PH. The development of PH is characterized by increased proliferation of vascular cells, in particular pulmonary artery smooth muscle cells (PASMCs and pulmonary artery endothelial cells. In the course of PH, an escalated right ventricular (RV afterload occurs, which leads to increased perioperative morbidity and mortality. BK(Ca channels are ubiquitously expressed in vascular smooth muscle cells and their opening induces cell membrane hyperpolarization followed by vasodilation. Moreover, BK activation induces anti-proliferative effects in a multitude of cell types. On this basis, we hypothesized that treatment with the nebulized BK channel opener NS1619 might be a therapy option for pulmonary hypertension and tested this in rats. METHODS: (1 Rats received monocrotaline injection for PH induction. Twenty-four days later, rats were anesthetized and NS1619 or the solvent was administered by inhalation. Systemic hemodynamic parameters, RV hemodynamic parameters, and blood gas analyses were measured before as well as 30 and 120 minutes after inhalation. (2 Rat PASMCs were stimulated with PDGF-BB in the presence and absence of NS1619. AKT, ERK1 and ERK2 activation were investigated by western blot analyses, and relative cell number was determined 48 hours after stimulation. RESULTS: Inhalation of a 12 µM and 100 µM NS1619 solution significantly reduced RV pressure without affecting systemic arterial pressure. Blood gas analyses demonstrated significantly reduced carbon dioxide and improved oxygenation in NS1619-treated animals pointing towards a considerable pulmonary shunt-reducing effect. In PASMC's, NS1619 (100 µM significantly attenuated PASMC proliferation by a pathway independent of AKT and ERK1/2 activation. CONCLUSION: NS1619 inhalation reduces RV pressure and improves oxygen supply and its application inhibits PASMC proliferation in vitro. Hence, BK

  10. Influence of electron beam irradiation on the structural, electrical and thermal properties of Gd0.5Sr0.5MnO3 and Dy0.5Sr0.5MnO3 manganites

    Science.gov (United States)

    Nagaraja, B. S.; Rao, Ashok; Babu, P. D.; Sanjeev, Ganesh; Okram, G. S.

    2016-01-01

    We present systematic studies on the effect of electron beam irradiation on structural, electrical and thermal properties of Gd0.5Sr0.5MnO3 and Dy0.5Sr0.5MnO3 manganites. The XRD patterns and Rietveld analysis show that the samples remain single phased even after they undergo electron beam irradiation. Both the series of the samples Gd0.5Sr0.5MnO3 and Dy0.5Sr0.5MnO3 show insulating trends in their temperature dependent electrical resistivity, ρ(T) behavior. The resistivity data for both the series of samples (pristine as well as irradiated) indicate that the small polaron hopping model is valid in high temperature region; on contrary, variable range hopping model governs the low temperature regime. Magnetic studies demonstrate that the Neel temperatures of pristine and irradiated samples of Gd0.5Sr0.5MnO3 and Dy0.5Sr0.5MnO3 do not change appreciably when they are subjected to irradiation. Thermo-electrical power is observed to increase with irradiation in Gd0.5Sr0.5MnO3 samples, whereas for Dy0.5Sr0.5MnO3 samples a decrease in thermo-electric power is seen when the samples are irradiated.

  11. Growth and characterization of ultrathin epitaxial MnO film on Ag(001)

    Science.gov (United States)

    Kundu, Asish K.; Menon, Krishnakumar S. R.

    2016-07-01

    We present here a comprehensive growth procedure to obtain a well-ordered MnO(001) ultrathin film on Ag(001) substrate. Depending upon the oxygen partial pressure during the growth, different phases of manganese oxide have been detected by Low Energy Electron Diffraction (LEED) and X-ray Photoelectron Spectroscopic (XPS) studies. A modified growth scheme has been adopted to get well-ordered and stoichiometric MnO(001) ultrathin film. The detailed growth mechanism of epitaxial MnO film on Ag(001) has been studied step by step, using LEED and XPS techniques. Observation of sharp (1 × 1) LEED pattern with a low inelastic background, corresponds to a long-range atomic order with low defect densities indicating the high structural quality of the film. The Mn 2p and Mn 3s core-level spectra confirm the oxidation state as well as the stoichiometry of the grown MnO films. Apart from the growth optimization, the evolution of strain relaxation of the MnO(001) film with film thickness has been explored.

  12. Spontaneous Synthesis and Electrochemical Characterization of Nanostructured MnO2 on Nitrogen-Incorporated Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Ying-Chu Chen

    2012-01-01

    Full Text Available This paper investigated the layered manganese dioxide with hydrate (MnO2⋅xH2O deposits onto nitrogen-containing carbon nanotube (CNxNTs as a hierarchical electrode for an energy-storage device. The dense and entangled CNxNTs were directly grown by microwave plasma-enhanced chemical vapor deposition (MPECVD on a carbon cloth (CC, and subsequently used as a current collector. By controlling the pH value of KMnO4 precursor solution, and incorporating nitrogen into CNTs as a reducing agent, the MnO2 thin layer was uniformly fabricated on the CNxNTs at room temperature by using a spontaneous reduction method. The role of incorporation nitrogen is not only capable of creating active sites on the CNT surface, but can also donate electrons to reduce MnO4- to MnO2 spontaneously. From the measurements of cyclic voltammograms and galvanostatic charge/discharge, MnO2/CNxNTs/CC composite electrodes illustrated excellent specific capacitance of 589.1 Fg-1. The key factor for high performance could be attributed to the thin-layered MnO2 nanostructure, which resulted in the full utilization of MnO2 deposits. Hence, the hierarchically porous MnO2/CNxNTs/CC electrodes exhibited excellent capacitive behavior for electrochemical capacitor application.

  13. Comparative study on nanostructured MnO2/carbon composites synthesized by spontaneous reduction for supercapacitor application

    KAUST Repository

    Lin, Yen-Po

    2011-10-01

    MnO2 has been deposited onto two types of carbon (C) substrates, including a non-porous multi-wall carbon nano-tube (CNT) and a porous carbon black (CB) powder, by a solution reduction process where MnO4 - was reduced at 80 °C by the C substrate so as to give nano-crystalline MnO2 directly at the C surface. The nature of the C substrate has profound effects on polymorphicity, microstructure and electrochemical properties, in terms of supercapacitor application, of the resulting oxide. Deposition on CNT produces meso/macro-porous layer containing predominantly spinel MnO2 strongly bonded to the CNTs and having a larger surface area, while that on CB results in birnessite granules with a lower surface area. In addition to having a higher specific capacitance (309 F g-1), the MnO2/CNT electrode exhibits superior power performance (221 F g-1 at 500 mV s-1 or ca. 20 Wh kg -1at 88 kW kg-1) to MnO2/CB due to reduced electronic and ion-diffusion resistances. Furthermore, the MnO2/CNT electrode also exhibits slower self-discharging rate and greater cycling stability. The results indicate that the MnO2 spinel/CNT holds promise for supercapacitor applications. © 2011 Elsevier B.V. All rights reserved.

  14. Effect of MnO2 morphology on the catalytic oxidation of toluene over Ag/MnO2 catalysts

    Science.gov (United States)

    Li, Jiamin; Qu, Zhenping; Qin, Yuan; Wang, Hui

    2016-11-01

    The Ag/MnO2 catalysts with different morphologies (wire-like, rod-like and tube-like) are used as toluene oxidation catalysts in an attempt to investigate how the structures of support affect the interaction of Ag and MnO2, and thus the toluene catalytic activity. Analysis by TEM, H2-TPR and XPS measurements reveals that the structures of MnO2 influence the particle size and dispersion of silver particles and the combination of silver particles with MnO2. Meanwhile, the addition of Ag regulates the performance of MnO2. The small particle size and hemispherically shaped Ag particles are easily to form and homogeneously dispersed on the surface of wire-like MnO2. And this specific form of Ag shows the strongest interaction with MnO2, which promotes the low-temperature reducibility of support and generated more lattice oxygen in metal oxides. The Ag/MnO2 nanowires sample exhibits the highest reactivity for toluene oxidation with a complete conversion at 220 °C. Therefore, the excellent catalytic performance of Ag/MnO2 nanowires catalyst for toluene oxidation is clearly connected with the interaction between the Ag and MnO2, which is determined by the morphology of MnO2 support.

  15. Fabrication of Alternate Stacking MnO2/MoS2 Layered Nanohybrid by a Sonochemistry Technology

    Institute of Scientific and Technical Information of China (English)

    SU Zhi-Kui; CUI Yan-Hua; TANG Xiu-Hua; ZHOU Qing; LIU Zong-Huai

    2008-01-01

    Layered manganese oxide was delaminated in a tetramethylammonium hydroxide by sonicating treatment for hated MnO2 colloid by ultrasonic treatment, and alternate stacking MnO2/MoS2 nanohybrid with a novel layered structure was fabricated by using a sonochemistry technology. A new hybridization method between two kinds of inorganic nanosheets with the same charge character was developed.

  16. Novel quinoxaline 1,4-di-N-oxide derivatives as new potential antichagasic agents.

    Science.gov (United States)

    Torres, Enrique; Moreno-Viguri, Elsa; Galiano, Silvia; Devarapally, Goutham; Crawford, Philip W; Azqueta, Amaia; Arbillaga, Leire; Varela, Javier; Birriel, Estefanía; Di Maio, Rossanna; Cerecetto, Hugo; González, Mercedes; Aldana, Ignacio; Monge, Antonio; Pérez-Silanes, Silvia

    2013-08-01

    As a continuation of our research and with the aim of obtaining new agents against Chagas disease, an extremely neglected disease which threatens 100 million people, eighteen new quinoxaline 1,4-di-N-oxide derivatives have been synthesized following the Beirut reaction. The synthesis of the new derivatives was optimized through the use of a new and more efficient microwave-assisted organic synthetic method. The new derivatives showed excellent in vitro biological activity against Trypanosoma cruzi. Compound 17, which was substituted with fluoro groups at the 6- and 7-positions of the quinoxaline ring, was the most active and selective in the cytotoxicity assay. The electrochemical study showed that the most active compounds, which were substituted by electron-withdrawing groups, possessed a greater ease of reduction of the N-oxide groups.

  17. Geissoschizine methyl ether N-oxide, a new alkaloid with antiacetylcholinesterase activity from Uncaria rhynchophylla.

    Science.gov (United States)

    Jiang, Wei-Wei; Su, Jia; Wu, Xing-De; He, Juan; Peng, Li-Yan; Cheng, Xiao; Zhao, Qin-Shi

    2015-01-01

    Geissoschizine methyl ether N-oxide, a new oxindole alkaloid, along with 14 known alkaloids, was isolated from the aerial part of Uncaria rhynchophylla. Their structures were identified by comprehensive spectral methods, including 2D NMR experiments, and confirmed by comparing with the literature data. In vitro acetylcholinesterase (AChE) inhibitory activity assay showed that the new compound exhibited anti-AChE activity with IC₅₀ value of 23.4 μM.

  18. Quinoxaline 1,4-di-N-Oxides: Biological Activities and Mechanisms of Actions

    OpenAIRE

    Cheng, Guyue; Sa, Wei; Cao, Chen; Guo, Liangliang; Hao, Haihong; Liu, Zhenli; Wang, Xu; Yuan, Zonghui

    2016-01-01

    Quinoxaline 1,4-di-N-oxides (QdNOs) have manifold biological properties, including antimicrobial, antitumoral, antitrypanosomal and antiinflammatory/antioxidant activities. These diverse activities endow them broad applications and prospects in human and veterinary medicines. As QdNOs arouse widespread interest, the evaluation of their medicinal chemistry is still in progress. In the meantime, adverse effects have been reported in some of the QdNO derivatives. For example, genotoxicity and ba...

  19. SYNTHESIS OF CONDUCTIVE POLYANILINE VIA OXIDATION BY MnO2

    Institute of Scientific and Technical Information of China (English)

    Yu Sheng; Jian-ding Chen; De-qin Zhu; Christian Carrot; Jacques Guillet

    2004-01-01

    A unique process of chemical oxidation polymerization of aniline using manganese dioxide (MnO2) as the oxidizing agent in an aqueous medium is described. The reaction between aniline and MnO2 follows a mechanism by which the organic monomer is oxidized while the metal oxide undergoes reductive dissolution. The effects of the amount of oxidizing agent and aniline, pH and temperature of the reactive system, type of acid on the yield and conductivity of polyaniline are discussed. The resulting polyaniline was characterized by IR and UV-Vis spectrometry. Polyaniline with a conductivity of 12.5 S/cm was obtained using 0.033 mol of aniline oxidized by 0.023 mol MnO2 in the presence of 100 mL of 2.7 mol/L HCl at 25℃ for 4 h.

  20. Electrochemical oxidation of methanol on Pt nanoparticles composited MnO 2 nanowire arrayed electrode

    Science.gov (United States)

    Zhao, Guang-Yu; Li, Hu-Lin

    2008-03-01

    By use of the membrane-template synthesis route, MnO 2 nanowire arrayed electrodes are successfully synthesized by means of the anodic deposition technique. The Pt nanoparticles composited MnO 2 nanowire arrayed electrodes (PME) are obtained through depositing Pt on MnO 2 nanowire arrayed electrode by cathode deposition technique. For comparison of electrochemical performance, Pt nanowire arrayed electrodes which have the same amount of Pt with PME are also prepared. The electro-oxidation of methanol on PME and Pt nanowire arrayed electrodes is investigated at room temperature by cyclic voltammetry, which show that about 110 mV decreased overpotential and 2.1-fold enhanced votammetric current are achieved on PME. The chronoamperometry result demonstrates that the resistance to carbon monoxide for PME is improved.

  1. Orthogonal 4,10 and 6,12 substitution of dibenzo[def,mno]chrysene polycyclic aromatic small molecules

    KAUST Repository

    Koldemir, Unsal

    2017-07-14

    A series of new polycyclic aromatic hydrocarbon compounds based on (4,10-disubstituted-dibenzo[def,mno]chrysene-6,12-dione) and 4,10 di-substituted 6,12-bis(triisopropylsilylethynyl)dibenzo[def,mno]chrysene are reported with tunable electronic properties through varied molecular architecture. Starting with an inexpensive commercially available textile dye known as Vat Orange #3, (4,10-dibromo-dibenzo[def,mno] chrysene-6,12-dione) we extended the conjugation at the 4- and 10-positions by the attachment of both electron rich and deficient hexylvinylphthalimide, thiophene, hexylthiophene, triphenylamine, and hexylbithiophene aromatic groups, and studied the resultant optoelectronic properties. By applying various synthetic metal-catalyzed reactions, soluble dibenzo[def,mno]chrysene and dibenzo[def,mno]chrysene-6,12-dione derivatives were achieved with optical edge band gaps between 2.30 eV and 1.65 eV.

  2. Enhancement of supercapacitance property of electrochemically deposited MnO2 thin films grown in acidic medium

    Science.gov (United States)

    Jana, S. K.; Rao, V. P.; Banerjee, S.

    2014-02-01

    In this communication we present supercapacitance property of MnO2 thin-films which are fabricated on stainless steel (SS) substrate by electro-deposition method carried out in different pH of the electrolyte. A significant improvement of the device performance of acid mediated grown (AMG) MnO2 over normal MnO2 (grown in neutral medium) has been achieved. We have also investigated role of interfacial structure on the internal resistance of the device material. AMG MnO2 film exhibits superior device performance with specific capacitance of 652 F/g which is 2 times better than that obtained in normal MnO2 and also energy density of 90.69 Wh/kg.

  3. Facile Synthesis of Novel Nanostructured MnO2Thin Films and Their Application in Supercapacitors

    Directory of Open Access Journals (Sweden)

    Xia H

    2009-01-01

    Full Text Available Abstract Nanostructured α-MnO2thin films with different morphologies are grown on the platinum substrates by a facile solution method without any assistance of template or surfactant. Microstructural characterization reveals that morphology evolution from dandelion-like spheres to nanoflakes of the as-grown MnO2is controlled by synthesis temperature. The capacitive behavior of the MnO2thin films with different morphologies are studied by cyclic voltammetry. The α-MnO2thin films composed of dandelion-like spheres exhibit high specific capacitance, good rate capability, and excellent long-term cycling stability.

  4. Size-driven magnetic transitions in monodisperse MnO nanocrystals

    OpenAIRE

    Lee, Yi-Cheng; Pakhomov, Alexandre B.; Krishnan, Kannan M.

    2010-01-01

    We report the observation of weak ferromagnetism up to TC≈250 K and a spin-glass-like behavior at temperatures below TSG≈30 K in nanoscale MnO particles. TSG is considerably lower and TC is much higher than the Néel temperature (TN=122 K) of bulk MnO. While the dominant low temperature behavior (below 30 K) may be attributed to the effects studied in this system before, such as uncompensated surface spins in antiferromagnetic particles, no manganese oxides have been observed with the Curie te...

  5. The effect of fluxing agent MnO2 on alumina silicate porcelain insulator properties

    Science.gov (United States)

    Dudi, Dharmender; Shekhawat, M. S.; Singh, G. P.

    2016-05-01

    Higher strength electrical porcelain is a requirement for industry. This will be achieved by a specific composition of raw materials, which is consisted of clays and feldspars. High mechanical resistance, low porosity and water absorption are among their important properties. By decreasing the silica and increasing the alumina provides a higher mechanical strength in porcelain but on the other hand increases the body's baking temperature. Therefore adding MnO2 in different percentage is a suitable and practical solution to improve strength without increasing sinter temperature. Results have shown that addition of 1% MnO2 in body enhances mechanical strength of the body.

  6. Effects of surface modification on electrochemical performance of MnO2

    Institute of Scientific and Technical Information of China (English)

    LIU Li-qing; WANG Jjan-ming; FAN Yu-kai; WANG Guo-guang; ZHANG Jian-qing

    2005-01-01

    The MnO2 samples coated with Ca(OH)2 were prepared by a liquid-phase surface treatment method.The physical properties of the samples were examined by SEM, EDAX and chemical analysis, and their electrochemical performances were investigated by means of galvanostatic charge-discharge, cyclic voltammetry and electrochemical impedance spectroscopy (EIS). The SEM results show that the samples coated with Ca(OH)2 display a porous surface structure. The electrochemical experiments indicate that the surface modification decreases the polarization of MnO2 electrodes and improves their discharge potentials and discharge capacities.

  7. Substitutions of Fluorine Atoms and Phenoxy Groups in the Synthesis of Quinoxaline 1,4-di-N-oxide Derivatives

    Directory of Open Access Journals (Sweden)

    Antonio Monge

    2008-01-01

    Full Text Available The unexpected substitution of fluorine atoms and phenoxy groups attached toquinoxaline or benzofuroxan rings is described. The synthesis of 2-benzyl- and 2-phenoxy-3-methylquinoxaline 1,4-di-N-oxide derivatives was based on the classical Beirut reaction.The tendency of fluorine atoms linked to quinoxaline or benzofuroxan rings to be replacedby a methoxy group when dissolved in an ammonia saturated solution of methanol wasclearly demonstrated. In addition, 2-phenoxyquinoxaline 1,4-di-N-oxide derivativesbecame 2-aminoquinoxaline 1,4-di-N-oxide derivatives in the presence of gaseousammonia.

  8. Electrocatalysis of Oxygen Evolution Reaction on Ti/SnO2+ RuO2+ MnO2/MnO2 Electrode in Sulfuric Acid Solution

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The Ti-Supported MnO2 electrode was modified by introducing SnO2 +RuO2 +MnO2 as an intermediate layer into the Ti/MnO2 interface. The anodic polarization curves were measured at various temperatures ranging from 30 to 80 ℃ and the activation energy for the oxygen evolution reaction was evaluated. The experimental activation energy increased linearly with increasing the overpotential. The activation energy at the equilibrium potential was linearly correlated with the difference between the crystal field stabilization energies of Mn4+ at initial state and Mn4+ at transition state. The electrocatalysis characteristics of the anode were discussed by means of themechanism of the substitution reaction of the ligand(SN 1 and SN2) and molecular orbital theory.The results show that the anode has better electrocatalystic characteristics.

  9. Design and Preparation of MnO2/CeO2-MnO2 Double-Shelled Binary Oxide Hollow Spheres and Their Application in CO Oxidation.

    Science.gov (United States)

    Zhang, Jian; Cao, Yidan; Wang, Chang-An; Ran, Rui

    2016-04-06

    Herein, we designed an extremely facile method to prepare well-defined MnO2@CeO2-MnO2 ball-in-ball binary oxide hollow spheres by employing carbon spheres (CSs) as sacrificial templates. The synthesis process involves a novel self-assembled approach to prepare core-shell CSs@CeO2 precursor, which would directly react with KMnO4 aqueous solution to form yolk-shell CSs@MnO2/CeO2-MnO2 precursor in the following step. Well-dispersed Ce-Mn binary oxide with double-shelled hollow sphere structure could be achieved after annealing the precursor in air. The evolution process and formation mechanism of this novel structure were thoroughly studied in this paper. Especially the as-prepared double-shell MnO2/CeO2-MnO2 hollow spheres exhibited enhanced catalytic activity for CO oxidation compared with the pure MnO2 hollow spheres and pure CeO2 hollow spheres. We believe the high surface area, hierarchical porous structures, and strong synergistic interaction between CeO2 and MnO2 contribute to the excellent catalytic activity. Most importantly, this method could be extended to prepare other transition metal oxides. As an example, triple-shelled Co-Mn composite hollow spheres assembled by ultrathin nanoplates were successfully prepared.

  10. Synthesis of meta-substituted [(18)F]3-fluoro-4-aminopyridine via direct radiofluorination of pyridine N-oxides.

    Science.gov (United States)

    Brugarolas, P; Freifelder, R; Cheng, S-H; DeJesus, O

    2016-06-04

    Due to their electron-rich aromatic structure, nucleophilic (radio)fluorination of pyridines is challenging, especially at the meta position. In this paper, we describe the first example of direct fluorination of a pyridine N-oxide to produce a meta fluorinated pyridine. Specifically, fluorination of 3-bromo-4-nitropyridine N-oxide produced in several minutes 3-fluoro-4-nitropyridine N-oxide in moderate yield at room temperature. This intermediate compound was later converted to 3-fluoro-4-aminopyridine easily by catalytic hydrogenation. Furthermore, this approach was successfully applied for labeling with fluorine-18. The use of pyridine N-oxides for the preparation of fluoropyridines is unprecedented in the chemical literature and has the potential to offer a new way for the synthesis of these important structures in pharmaceuticals and radiopharmaceuticals.

  11. Solubilization of silica: Synthesis, characterization and study of penta-coordinated pyridine N-oxide silicon complexes

    Indian Academy of Sciences (India)

    Subramania Ranganathan; Ch Chandrashekhar Rao; Suvarchala Devi Vudayagiri; Y B R D Rajesh; B Jagadeesh

    2004-03-01

    In an effort to design agents that could solubilize silica in water, under ambient conditions and pH, as takes place in nature, novel zwitterionic, penta-oxo-coordinated silicon compounds with siliconate cores have been prepared from 4-substituted pyridine N-oxides (H, OMe, morpholino, NO2) as donor ligands, their structures established by 1H, 13C and MS, and the coordination number of silicon, by 29Si NMR. The formation of complexes from pyridine N-oxides is noteworthy since they arise from interaction with a weakly nucleophilic oxygen centre. The ability of the pyridine N-oxides to enhance the solubilization of silica in water has been experimentally demonstrated. Possible rationalization of this observation on the basis of O→Si coordination via the oxygen atom of pyridine N-oxide is suggested.

  12. An improved understanding of the reaction of bis(bromomethyl)quinoxaline 1-N-oxides with amines using substituent effects.

    Science.gov (United States)

    Evans, Kathryn M; Slawin, Alexandra M Z; Lebl, Tomas; Philp, Douglas; Westwood, Nicholas J

    2007-04-27

    The reaction of bis(bromomethyl)quinoxaline N-oxides with amines is interesting from a reaction mechanism perspective and due to the reported biological activity of compounds in this general class. The complex mechanism of this reaction (particularly in the case of primary amines) is complicated further when C6 or C7 substituted mono-N-oxides are considered. In this study, the synthesis and subsequent characterization of a series of 2,3-bis(bromomethyl)quinoxaline 1-N-oxides is reported. Experimental and computational evidence is used to show that the observed product ratios from the reaction with diethylamine reflect the influence of both the C6/C7 substituent and the N-oxide functional group on the initial nucleophilic substitution reaction.

  13. Synthesis of 2-substituted pyridines via a regiospecific alkylation, alkynylation, and arylation of pyridine N-oxides.

    Science.gov (United States)

    Andersson, Hans; Almqvist, Fredrik; Olsson, Roger

    2007-03-29

    [structure: see text]. Sequential addition of Grignard reagents to pyridine N-oxides in THF at room temperature followed by treatment with acetic anhydride at 120 degrees C afforded 2-substituted pyridines in good to high yields. Furthermore, by exchanging acetic anhydride for DMF in the second step, 2-substituted pyridine N-oxides were obtained, as intermediates suitable for addition of a second Grignard reagent for the synthesis of 2,6-disubstituted pyridines.

  14. 锂离子电池正极材料Li2MnO3的研究进展%Review on Li2MnO3 as Cathode of Li-ion Battery

    Institute of Scientific and Technical Information of China (English)

    刘昌位; 郭玉忠; 邵威; 王剑华

    2014-01-01

    Li2MnO3在稳定富锂锰正极材料结构及贡献容量等方面扮演着重要角色.综述了Li2MnO3的晶体结构和充放电机理方面的最新研究进展,尤其关注堆垛层错等晶体缺陷对电化学活性的作用,以及愈来愈受到重视的高活性Li2MnO3材料的制备.

  15. Effect of MnO content on the interfacial property of mold flux and steel

    Science.gov (United States)

    Wang, Wanlin; Li, Jingwen; Zhou, Lejun; Yang, Jian

    2016-07-01

    The interfacial property between liquid mold flux and steel has significant impact on the quality of casting slab, and this property is mainly determined by the chemical composition of mold flux and the reaction between the flux and steel. The effect of MnO content on the contact angle and interfacial tension between liquid mold flux and ultra-low carbon steel was investigated by sessile drop method in this article, and the results suggested that both the contact angle and interfacial tension decreased with the increase of MnO content in the mold flux. The increase of Si and Mn and the reduction of Al and Ti in the interaction layer were caused by the chemical reactions occurred in the vicinity of interface between mold flux and steel substrate. Besides, the thickness of the interaction layer increased from 4 μm to 7 μm, then to 9 μm, 11 μm and 15 μm when the MnO content was added from 1 wt% to 3 wt%, then to 5 wt%, 7 wt%, and 9 wt% due to the fact that MnO can simplify the polymerized structure of the melt and improve the penetrability of molten mold flux to make the interfacial reaction easier.

  16. Functional characterization of the Escherichia coli K-12 yiaMNO transport protein genes

    NARCIS (Netherlands)

    Plantinga, TH; van der Does, C; Badia, J; Aguilar, J; Konings, WN; Driessen, AJM; Plantinga, Titia H.

    2004-01-01

    The yiaMNO genes of Escherichia coli K-12 encode a binding protein-dependent secondary, or tri-partite ATP-independent periplasmic (TRAP), transporter. Since only a few members of this family have been functionally characterized to date, we aimed to identify the substrate for this transporter. Cells

  17. Low Temperature Synthesis of MnO2/Graphene Nanocomposites for Supercapacitors

    OpenAIRE

    Hao Huang; Guangren Sun; Jie Hu; Tifeng Jiao

    2015-01-01

    MnO2/graphene nanocomposites were synthesized through a simple route in a water-reflux condenser system. The as-prepared composites were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman microscope, and Brunauer-Emmett-Teller surface area analysis. Capacitive properties of the synthesized composite electrodes were investigated via cyclic voltammetry, galvanostatic charge/d...

  18. Photocatalytic oxidation of aromatic amines using MnO2@g-C3N4

    Data.gov (United States)

    U.S. Environmental Protection Agency — An efficient and direct oxidation of aromatic amines to aromatic azo-compounds has been achieved using a MnO2@g-C3N4 catalyst under visible light as a source of...

  19. Generating MnO2 nanoparticles using simulated amorphization and recrystallization

    CSIR Research Space (South Africa)

    Sayle, TXT

    2005-09-21

    Full Text Available . The resulting MnO2 nanoparticle is about 8 nm in diameter, conforms to the pyrolusite structure (isostructural with rutile TiO2, comprising 1 x 1 octahedra) is heavily twinned and comprises a wealth of isolated and clustered point defects such as cation...

  20. High-performance asymmetric supercapacitor based on graphene hydrogel and nanostructured MnO2.

    Science.gov (United States)

    Gao, Hongcai; Xiao, Fei; Ching, Chi Bun; Duan, Hongwei

    2012-05-01

    We have successfully fabricated an asymmetric supercapacitor with high energy and power densities using graphene hydrogel (GH) with 3D interconnected pores as the negative electrode and vertically aligned MnO(2) nanoplates on nickel foam (MnO(2)-NF) as the positive electrode in a neutral aqueous Na(2)SO(4) electrolyte. Because of the desirable porous structure, high specific capacitance and rate capability of GH and MnO(2)-NF, complementary potential window of the two electrodes, and the elimination of polymer binders and conducting additives, the asymmetric supercapacitor can be cycled reversibly in a wide potential window of 0-2.0 V and exhibits an energy density of 23.2 Wh kg(-1) with a power density of 1.0 kW kg(-1). Energy density of the asymmetric supercapacitor is significantly improved in comparison with those of symmetric supercapacitors based on GH (5.5 Wh kg(-1)) and MnO(2)-NF (6.7 Wh kg(-1)). Even at a high power density of 10.0 kW kg(-1), the asymmetric supercapacitor can deliver a high energy density of 14.9 Wh kg(-1). The asymmetric supercapacitor also presents stable cycling performance with 83.4% capacitance retention after 5000 cycles.

  1. Reduction Kinetics of MnO from High-Carbon Ferromanganese Slags by Carbonaceous Materials in Ar and CO Atmospheres

    Science.gov (United States)

    Safarian, J.; Tranell, G.; Kolbeinsen, L.; Tangstad, M.; Gaal, S.; Kaczorowski, J.

    2008-10-01

    The kinetics of MnO reduction from synthetic and industrial high-carbon ferromanganese slags were investigated using a sessile drop technique at 1600 °C. The effects of the reductant type, ambient atmosphere, and slag composition on the MnO reduction were illuminated. Six different types of carbonaceous reductants were used as substrates for small slag droplets, which were reacted in a CO or Ar atmosphere, with the reaction studied in situ. The cross sections of the reacted slag-carbon samples were subsequently studied by electron-probe microanalysis (EPMA), to find the extent of the MnO reduction as a function of the reaction time. It was found that the rate of the MnO reduction is affected by both the type of reductant and the ambient atmosphere. It was observed that the MnO reduction rate from synthetic slag by cokes produced from single coals is lower than that from industrial cokes. Reduction rates obtained when charcoal was used as the reductant were higher than when coke was used, while the CO atmosphere yielded a faster initial MnO reduction than did the Ar atmosphere. It was found that the faster reduction rates in the CO atmosphere are related to the MnO reduction by CO gas. A newly developed kinetic method was applied, to calculate the rate constants for the MnO reduction by carbon and CO that considered the reaction interfaces. It was indicated that the rate of the MnO reduction by CO is less than that by carbon; however, the contribution of these reductants to slag reduction is very dependent on their contact with the slag.

  2. Effect of MnO2 on properties of NiFe2O4 spinel based inert anode

    Institute of Scientific and Technical Information of China (English)

    XI; Jin-hui; YAO; Guang-chun; LIU; Yi-han; ZHANG; Xiao-ming

    2005-01-01

    In order to improve the properties of NiFe2O4 spinel based inert anode, some additive MnO2 were added to raw materials. NiFe2O4 spinel with MnO2 was made by solid-phase reaction at 1200℃for 6 h. XRD were carried out and the effects of MnO2 on density, conductivity and corrosion resistance were measured. XRD shows when MnO2 was added no new phases exist and MnO2 and NiFe2O4 formed solid solution; Mn4+ replaced parts of Fe3+ and the sample still had the structure of NiFe2O4 spinel. The crystal lattice of NiFe2 O4 spinel became aberrated when MnO2 was added, which can promote sintering, and improve density. Because Mn4+ replaces parts of Fe3+ and produces conduction electron, which can improve conductivity.The corrosion resistance of the samples was enhanced. When MnO2 is 1.0%, the sample's corrosion rate is 1/5 of that of the sample without MnO2. The reason is that Al2 O3 in the melt reacts with Mn4+ in the sample to produce MnAl2O4. MnAl2 O4 forms a dense protecting coat, which can prevent melt from eroding further.Because the key problem with inert anodes is anode corrosion, so we consider the optimal amount of MnO2 is 1.0%.

  3. Mononuclear copper(II) nitrato complexes with methyl-substituted 4-nitropyridine N-oxide. Physicochemical and cytotoxic characteristics.

    Science.gov (United States)

    Puszko, Aniela; Krojcer, Anna; Pełczynska, Marzena; Wietrzyk, Joanna; Cieślak-Golonka, Maria; Jezierska, Julia; Adach, Anna; Kubiak, Maria

    2010-02-01

    Three new complexes, products of the interaction of Cu(NO(3))(2) and methyl-substituted 4-nitropyridine N-oxides were synthesized and characterized by elemental analysis, magnetic, spectroscopic (IR, FIR and EPR), thermal and X-ray methods. The complexes (magnetic moments 1.70-1.81 BM at 300K) of general formula [Cu(H(2)O)(NO(3))(2)L(2)], L=2-methyl-4-nitropyridine N-oxide and [Cu(NO(3))(2) L'(2)], where L'=2,6-dimethyl- and 2,3,6-trimethyl-4-nitropyridine N-oxide were obtained. The compounds were unstable upon dissolution. The X-ray single crystal structure of Cu(II) complex with 2,6-dimethyl-4-nitropyridine N-oxide was determined and analysed. The compounds and free ligands were tested in vitro on the cytotoxic activity against MCF-7 and SW-707 human cancer cell lines. The complexes with 4-nitropyridine N-oxide (a reference) and 2-methyl-4-nitropyridine N-oxide show a significant anti-proliferative activity against studied cell lines. A reciprocal relationship between the activity and the number of methyl groups was observed. Both ligands and complexes are cytotoxic active but to the different cell lines.

  4. The effects of solvents and structure on the electronic absorption spectra of the isomeric pyridine carboxylic acid N-oxides

    Directory of Open Access Journals (Sweden)

    Drmanić Saša Ž.

    2013-01-01

    Full Text Available The ultraviolet absorption spectra of the carboxyl group of three isomeric pyridine carboxylic acids N-oxides (picolinic acid N-oxide, nicotinic acid N-oxide and isonicotinic acid N-oxide were determined in fourteen solvents in the wavelength range from 200 to 400 nm. The position of the absorption maxima (λmax of the examined acids showed that the ultraviolet absorption maximum wavelengths of picolinic acid N-oxide are the shortest, and those of isonicotinic acid N-oxide acid are the longest. In order to analyze the solvent effect on the obtained absorption spectra, the ultraviolet absorption frequencies of the electronic transitions in the carboxylic group of the examined acids were correlated using a total solvatochromic equation of the form max = v0 + sπ + aα+ bβ, where υmax is the absorption frequency (1/λmax, p is a measure of the solvent polarity, β represents the scale of solvent hydrogen bond acceptor basicities and α represent the scale of solvent hydrogen bond donor acidities. The correlation of the spectroscopic data was carried out by means of multiple linear regression analysis. The solvent effects on the ultraviolet absorption maximums of the examined acids were discussed.

  5. Effects of Trimethylamine-N -oxide on the Conformation of Peptides and its Implications for Proteins

    Science.gov (United States)

    Su, Zhaoqian; Mahmoudinobar, Farbod; Dias, Cristiano L.

    2017-09-01

    To provide insights into the stabilizing mechanisms of trimethylamine-N -oxide (TMAO) on protein structures, we perform all-atom molecular dynamics simulations of peptides and the Trp-cage miniprotein. The effects of TMAO on the backbone and charged residues of peptides are found to stabilize compact conformations, whereas effects of TMAO on nonpolar residues lead to peptide swelling. This suggests competing mechanisms of TMAO on proteins, which accounts for hydrophobic swelling, backbone collapse, and stabilization of charge-charge interactions. These mechanisms are observed in Trp cage.

  6. A New 3D Coordination Polymer of Bismuth with Nicotinic Acid N-Oxide

    Directory of Open Access Journals (Sweden)

    Farzin Marandi

    2013-01-01

    Full Text Available The new three-dimensional coordination polymer {[Bi(NNO2(NO3]·1.5H2O}n (1, NNO− = nicotinate N-oxide was synthesized and characterized by elemental analysis, IR and 1H-NMR spectroscopy, as well as single-crystal X-ray diffraction analysis. 1 crystallizes in the monoclinic space group C2/c. The crystal structure consists of a rectangular-shaped grid constructed with NNO linkers. Cavities of a diameter of 7.9–8.3 Å2 are filled with disordered water molecules. The thermal stability of the compound was evaluated by thermogravimetric analysis.

  7. New complexes of heteroaromatic N-oxides with europium, uranyl and zinc ions

    Institute of Scientific and Technical Information of China (English)

    Zbigniew Hnatejko

    2012-01-01

    New solid complexes of europium,uranyl and zinc ions with N-oxides of 4-chloro-2,6-dimethylpyridine,quinoline and 4-methoxyquinaldinic acid in presence different anions were obtained and characterized by elemental and TG analyses,IR and luminescence spectra.The compounds are crystalline,hydrated or anhydrous salts with colours typical of metal ions.Thermal studies showed that in hydrated salts lattice or coordination water molecules are present.A role of different anions in the formation of various types of the complexes is presented.

  8. Diaqua-bis(2-pyridylphospho-nato N-oxide-κO,O)cobalt(II).

    Science.gov (United States)

    Ma, Yun-Sheng; Lu, Tian-Xian

    2008-11-13

    In the title complex, [Co(C(5)H(5)NO(4)P)(2)(H(2)O)(2)], the Co(II) ion, which lies on a crystallographic inversion center, is coordin-ated by four O atoms from two bidentate 2-phospho-nato-pyridine N-oxide ligands and two O atoms from two water ligands in a slightly distorted octa-hedral environment. Mol-ecules are inter-linked by three O-H⋯O hydrogen bonds and one weak C-H⋯O inter-action, forming a three-dimensional supra-molecular structure.

  9. Toward an Active and Stable Catalyst for Oxygen Evolution in Acidic Media: Ti-Stabilized MnO2

    DEFF Research Database (Denmark)

    Frydendal, Rasmus; Paoli, Elisa Antares; Chorkendorff, Ib;

    2015-01-01

    Catalysts are required for the oxygen evolution reaction, which are abundant, active, and stable in acid. MnO2 is a promising candidate material for this purpose. However, it dissolves at high overpotentials. Using first-principles calculations, a strategy to mitigate this problem by decorating...... undercoordinated surface sites of MnO2 with a stable oxide is developed here. TiO2 stands out as the most promising of the different oxides in the simulations. This prediction is experimentally verified by testing sputter-deposited thin films of MnO2 and Ti-MnO2. A combination of electrochemical measurements...

  10. Hydrothermal synthesis, structure and photocatalytic property of nano-TiO2-MnO2

    Institute of Scientific and Technical Information of China (English)

    DING; Shiwen(丁士文); WANG; Liyong(王利勇); ZHANG; Shaoyan(张绍岩); ZHOU; Qiuxiang(周秋香); DING; Yu(丁宇); LIU; Shujuan(刘淑娟); LIU; Yanchao(刘燕朝); KANG; Quanying(康全影)

    2003-01-01

    TiCl4 and MnSO4·H2O as raw materials are hydrolyzed stiochiometrically, following the intermediate of oxide hydrating reacts at 150℃, 0.5 Mpa in high-pressure reactor, after filtering, washing and drying, nanometric TiO2-MnO2 (Ti1-xMnxO2) is prepared. The effects of the reaction temperature and time on nanometric TiO2-MnO2 are also discussed. XRD shows that the product is TiO2-MnO2 with amorphous phase. After being sintered at above 780℃, it transfers into Ti1-xMnxO2 with a rutile structure. TEM shows that TiO2-MnO2 is the spherical particle. And the average diameter of the particles is 20 nm. The optical absorbance was determined by UV-265 spectrophotometer after dispersing the sample in the mixture of water and glycerol with the ratio of 1︰1 equably. It is found that the nano-material possesses the advantages of both nano-TiO2 and nano-MnO2, and it has strong absorption in the UV and visible region. Photodegradation of dyes in an aqueous solution is investigated using nanometricTiO2-MnO2 as a photocatalyst. The results show that after 60 min illumination, the decolorization rate of the acidic red B and acidic black 234 dye can be as high as 100%.

  11. Non-ferromagnetic Insulating Interface Region in La0.14Pr0.56Sr0.3MnO3/SrTiO3 and La0.7Ca0.3MnO3/Gd0.7Ca0.3MnO3 Multilayers

    Institute of Scientific and Technical Information of China (English)

    王昕; 刘大猛; 连贵君; 熊光成

    2004-01-01

    La0.14Pr0.56Sr0.3MnO3/SrTiO3 and La0.7Ca0.3MnO3/Gd0.7Ca0.3MnO3 multilayers have been fabricated by using pulsed laser deposition. The insulator-metal transition temperatures of the multilayers decrease with the decreasing thickness of the ferromagnetic layers. It is confirmed from the experiment and analysis that a nonferromagnetic insulating region exists near the interface, which could not be attributed to the roughness of the growth surfaces and disorder of the ferromagnetic layers.

  12. Activities of MnO in CaO-SiO2-Al2O3-MnO (FetO(<3 pct) slags saturated with liquid iron

    Science.gov (United States)

    Ohta, Hiroki; Suito, Hideaki

    1995-04-01

    Activity coefficients of MnO and Fe,0 in CaO-SiO2-Al2O3-MnO(FetO were found to be constant in the studied concentration range of MnO and FetO. The former increased with an increase in the CaO content, while the latter increased with an increase in the SiO2 content.

  13. Effect of A-site cation substitution on magnetic transition temperature of (LaCa) MnO3

    Institute of Scientific and Technical Information of China (English)

    李可斌; 王守国; 程荣胜; 李西军; 侯登录; 聂向富; 张裕恒

    1999-01-01

    The ferromagnetic transition temperatures have been measured on two bathes of perovskite manganese oxides such as (La1-xRx)2/3Ca1/3MnO3(R=Ce, Pr, Nd, etc.) and La2/3(Ca1-yCd)y)1/3MnO3. It is found that the (La1-xRx)2/3Ca1/3MnO3 samples have obviously different Curie temperature TC although their (the average A-site cation radius) are almost identical, and the TC in the system of (La1-xRx)2/3Ca1/3MnO3 compounds increases with increasing y although decreases slightly. It is suggested that the Curie temperature should be influenced by the average local A-site magnetic moment in the ferromagnetic perovskite manganite system.

  14. Positive magnetoresistance of La0.7Sr0.3MnO3/C composites

    Science.gov (United States)

    Kabirov, Yu. V.; Gavrilyachenko, V. G.; Bogatin, A. S.

    2016-07-01

    The perovskite manganite La0.7Sr0.3MnO3 compound is used as a component in ceramic (1-x)(La0.7Sr0.3MnO3)-xC composites at x = 0.15-0.85. It is found that every studied specimen is characterized by the linear dependence of the positive magnetoresistance (PMR) on the magnetic field strength at room temperature. The 0.6(La0.7Sr0.3MnO3)-0.4C composite has the largest magnetoresistance value (15%) at room temperature and intensity of magnetic field H=15kOe. A possible mechanism for the PMR of (1-x)(La0.7Sr0.3MnO3)-xC composites is discussed.

  15. Shear strain in Nd0.5Ca0.5MnO3 at high pressures.

    Science.gov (United States)

    Arulraj, Anthony; Dinnebier, Robert E; Carlson, Stefan; Hanfland, Michael; van Smaalen, Sander

    2005-04-29

    High-pressure x-ray powder diffraction has been measured on the half doped rare earth manganite Nd0.5Ca0.5MnO3 up to a pressure of 15 GPa. We report the presence of a quantifiable amount of shear distortion of the MnO6 octahedra in Nd0.5Ca0.5MnO3 at high pressures. The lattice strain of Nd0.5Ca0.5MnO3 is minimal at a crossover pressure of p* approximately 7 GPa, with the same lattice strain above and below this pressure achieved by shear and Jahn-Teller-type distortions, respectively. The increase in shear strain with increasing pressure provides a mechanism for the insulating behavior of manganites at high pressures that has not been considered before.

  16. Study of coexisting phases in Bi doped La0.67Sr0.33MnO3

    KAUST Repository

    Kambhala, Nagaiah

    2015-12-28

    We report the remarkable phase separation behaviour in La0.67Sr0.33MnO3 doped with Bi3+ ion at La site. The temperature dependent resistivity and magnetization of La0.67−xBixSr0.33MnO3 (x>0) show the presence of phase separation of ferromagnetic metallic and charge ordered antiferromagnetic insulating phases. Markedly, the field dependant magnetization studies of La0.67−xBixSr0.33MnO3 (x=0.3) show the metamagnetic nature of ferromagnetic metallic state implying the competition of coexisting ferromagnetic metallic and charge ordered antiferromagnetic phases. The electron spin resonance and exchange bias studies of La0.67−xBixSr0.33MnO3 (x=0.4 and 0.5) substantiate the coexistence of ferromagnetic clusters in antiferromagnetic matrix.

  17. Polarized Raman scattering in single crystals of Nd0.7Sr0.3MnO3

    Indian Academy of Sciences (India)

    M Pattabiraman; G Rangarajan; Kwang-Yong Choi; P Lemmens; G Guentherodt; G Balakrishnan; D McK Paul; M R Less

    2002-05-01

    We report polarized Raman scattering in single crystals of Nd0.7Sr0.3MnO3. The temperature dependence of the MnO6 octahedral bending and stretching modes observed in the XX spectra points to the existence of local lattice distortions, possibly polarons. The XY spectra have been analyzed using a collision-dominated model, which allows the extraction of the carrier scattering rate.

  18. Effects of Subcutaneous Injection MnO2 Micro- and Nanoparticles on Blood Glucose Level and Lipid Profile in Rat

    Directory of Open Access Journals (Sweden)

    Zahra Mousavi

    2016-11-01

    Full Text Available Background: The use of nanotechnology has led to rapid growth in various areas. Thus, health and safety issues of nanoparticles (NPs should be promptly addressed. Manganese oxide (MnO2 nanoparticles (NPs are typically used for biomedical and industrial applications. However, characterizing the potential human health effects of MnO2 NPs is required before fully exploiting these materials. The aim of this study was to investigate the toxicity of MnO2 micro- and nanoparticles on blood glucose level and lipid profile in male Wistar rats. Methods: A total of 105 rats were divided into one control and two experimental groups. Each experimental group received a single subcutaneous injection of MnO2 micro- and nanoparticles (100 µg/kg, respectively, every two weeks for 14 weeks. Their blood glucose, cholesterol, triglycerides, LDL, and HDL levels were then measured. The data presented as mean±SEM and compared with the repeated measures using the Prism statistical software (version 6.0. Results: Biochemical assessment in plasma samples showed that MnO2 micro- and nanoparticles injection significantly (P<0.01 increased the plasma glucose and cholesterol levels in all and few weeks, respectively. MnO2 nanoparticles significantly (P<0.01 decreased the HDL level in weeks 6, 12, and 14, but MnO2 microparticles decreased the HDL level only in week 12. In both MnO2 micro- and nanoparticles groups, LDL alterations were near to the control group, except for week 10. However, the same treatment had no effect on triglycerides concentrations compared to the control group. Conclusion: Our results show that exposure to nanosized particles at subchronic doses caused adverse changes in animal biochemical profiles, especially in glucose level. It seems that the high oxidative power of these particles is the main reason for these disturbances.

  19. Quantum chemical studies on three novel 1,2,4-triazole N-oxides as potential insensitive high explosives.

    Science.gov (United States)

    Wu, Qiong; Zhu, Weihua; Xiao, Heming

    2014-09-01

    Three novel explosives were designed by introducing N-oxides into 1,2,4-triazole: 1-amino-3,5-dinitro-1,2,4-triazole-2 N-oxide (ADT2NO), 1-amino-2,5-dinitro-1,2,4-triazole-3 N-oxide (ADT3NO), and 1-amino-3,5-dinitro-1,2,4-triazole-4 N-oxide (ADT4NO). Their detonation performance and sensitivity were estimated by using density functional theory and compared with some famous explosives like 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) and 1-methyl-2,4,6-trinitrobenzene (TNT). All three designed molecules are more powerful than HMX and less sensitive than TNT, indicating that ADT2NO, ADT3NO, and ADT4NO have high detonation performance as HMX and low sensitivity as TNT, making them being very valuable and may be considered as the potential candidates of insensitive high explosives. Properly introducing N-oxides into the energetic triazole derivatives can generate some superior energetic compounds with both high explosive performance and reduced sensitivity.

  20. A Study of Acid-Base Equilibria in Acetonitrile Systems of 2-Halo(Cl,Br,I-4-nitropicoline(3,5,6 N-oxides

    Directory of Open Access Journals (Sweden)

    Lech Chmurzynski

    1999-03-01

    Full Text Available An attempt has been made to determine potentiometrically (1 acid dissociation constants of cations obtained by protonation of nine trisubstituted pyridine N-oxides, namely 2-halo(Cl, Br and I-4-nitropicoline N-oxides with the methyl group at positions 3, 5, and 6, as well as (2 the cationic homoconjugation constants of these cationic acids with conjugated N-oxides in acetonitrile. On the basis of the substitution effect, variations of the acid dissociation constants of the trisubstituted pyridine N-oxide cations are discussed. The determined pKa values of the protonated 2-halo-4-nitropicoline N-oxides are compared with the previously determined equilibrium constants of the cationic acids conjugated with the mono- and disubstituted pyridine N-oxides in acetonitrile. Further, based on the pKa values of the protonated 2-halo-4-nitropicoline N-oxides in acetonitrile, supplemented with correlations between pKa’s of the protonated mono- and disubstituted pyridine N-oxides in acetonitrile and water, the pKa's of the acids conjugated with the trisubstituted N-oxides studied in aqueous solutions have been estimated. Moreover, it has been concluded that the cationic homoconjugation constants cannot be determined by potentiometric titration in acetonitrile solutions of the 2-halo-4-nitropicoline N-oxide systems.

  1. Thermoelectric properties of Ca0.8Dy0.2MnO3 synthesized by solution combustion process

    Directory of Open Access Journals (Sweden)

    Park Kyeongsoon

    2011-01-01

    Full Text Available Abstract High-quality Ca0.8Dy0.2MnO3 nano-powders were synthesized by the solution combustion process. The size of the synthesized Ca0.8Dy0.2MnO3 powders was approximately 23 nm. The green pellets were sintered at 1150-1300°C at a step size of 50°C. Sintered Ca0.8Dy0.2MnO3 bodies crystallized in the perovskite structure with an orthorhombic symmetry. The sintering temperature did not affect the Seebeck coefficient, but significantly affected the electrical conductivity. The electrical conductivity of Ca0.8Dy0.2MnO3 increased with increasing temperature, indicating a semiconducting behavior. The absolute value of the Seebeck coefficient gradually increased with an increase in temperature. The highest power factor (3.7 × 10-5 Wm-1 K-2 at 800°C was obtained for Ca0.8Dy0.2MnO3 sintered at 1,250°C. In this study, we investigated the microstructure and thermoelectric properties of Ca0.8Dy0.2MnO3, depending on sintering temperature.

  2. Synthesis of flake-like MnO2/CNT composite nanotubes and their applications in electrochemical capacitors.

    Science.gov (United States)

    Bi, Rong-Rong; Yin, Ya-Xia; Guo, Yu-Guo; Wan, Li-Jun

    2011-03-01

    MnO2/CNT composite nanotubes with nanometer-sized flake-like MnO2 on carbon nanotubes' surfaces have been synthesized through an easy and efficient solution-based method. Similarly, Mn3O4/CNT composite nanotubes have also been synthesized by using the same method but different heat treatment process. The structures and compositions of the two types of composite nanotubes are characterized by using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and nitrogen adsorption-desorption isotherms. Electrochemical measurements indicate that the MnO2/CNT composites nanotubes exhibit significantly enhanced supercapacitance performance compared with the Mn3O4/CNT composite nanotubes, the as-synthesized MnO2 nanoparticles and commercial MnO2. The possibilities of the enhanced properties are illustrated on the basis of analysis of XRD and X-ray photoelectron spectroscopy measurements. Our results presented here can give clear evidence of the superiority of nanocrystalline MnO2 to nanocrystalline Mn3O4 toward the applications as electrode materials in electrochemical capacitors.

  3. Wire-type MnO2/Multilayer graphene/Ni electrode for high-performance supercapacitors

    Science.gov (United States)

    Hu, Minglei; Liu, Yuhao; Zhang, Min; Wei, Helin; Gao, Yihua

    2016-12-01

    Commercially available wearable energy storage devices need a wire-type electrode with high strength, conductivity and electrochemical performance, as well as stable structure under deformation. Herein, we report a novel wire-type electrode of hierarchically structure MnO2 on Ni wire with multilayer graphene (MGr) as a buffer layer to enhance the electrical conductivity of the MnO2 and interface contact between the MnO2 and Ni wire. Thus, the wire-type MnO2/MGr/Ni electrode has a stable and high quality interface. The wire-type supercapacitor (WSC) based on wire-type MnO2/MGr/Ni electrode exhibits good electrochemical performance, high rate capability, extraordinary flexibility, and superior cycle lifetime. Length (area, volumetric) specific capacitance of the WSC reaches 6.9 mF cm-1 (73.2 mF cm-2, 9.8 F cm-3). Maximum length (volumetric) energy density of the WSC based on MnO2/MGr/Ni reaches 0.62 μWh cm-1 (0.88 mWh cm-3). Furthermore, the WSC has a short time constant (0.5-400 ms) and exhibits minimal change in capacitance under different bending shapes.

  4. Symmetrical MnO2-carbon nanotube-textile nanostructures for wearable pseudocapacitors with high mass loading

    KAUST Repository

    Hu, Liangbing

    2011-11-22

    While MnO2 is a promising material for pseudocapacitor applications due to its high specific capacity and low cost, MnO2 electrodes suffer from their low electrical and ionic conductivities. In this article, we report a structure where MnO2 nanoflowers were conformally electrodeposited onto carbon nanotube (CNT)-enabled conductive textile fibers. Such nanostructures effectively decrease the ion diffusion and charge transport resistance in the electrode. For a given areal mass loading, the thickness of MnO2 on conductive textile fibers is much smaller than that on a flat metal substrate. Such a porous structure also allows a large mass loading, up to 8.3 mg/cm2, which leads to a high areal capacitance of 2.8 F/cm2 at a scan rate of 0.05 mV/s. Full cells were demonstrated, where the MnO2-CNT-textile was used as a positive electrode, reduced MnO2-CNT-textile as a negative electrode, and 0.5 M Na2SO4 in water as the electrolyte. The resulting pseudocapacitor shows promising results as a low-cost energy storage solution and an attractive wearable power. © 2011 American Chemical Society.

  5. Quinoxaline 1,4-di-N-oxide and the potential for treating tuberculosis.

    Science.gov (United States)

    Vicente, Esther; Villar, Raquel; Pérez-Silanes, Silvia; Aldana, Ignacio; Goldman, Robert C; Mong, Antonio

    2011-04-01

    New drugs active against drug-resistant tuberculosis are urgently needed to extend the range of TB treatment options to cover drug resistant infections. Quinoxaline derivatives show very interesting biological properties (antibacterial, antiviral, anticancer, antifungal, antihelmintic, insecticidal) and evaluation of their medicinal chemistry is still in progress. In this review we report the properties and the recent developments of quinoxaline 1,4-di-N-oxide derivatives as potential anti-tuberculosis agents. Specific agents are reviewed that have excellent antitubercular drug properties, are active on drug resistant strains and non-replicating mycobacteria. The properties of select analogs that have in vivo activity in the low dose aerosol infection model in mice will be reviewed.

  6. Radical Chemistry and Cytotoxicity of Bioreductive 3-Substituted Quinoxaline Di-N-Oxides.

    Science.gov (United States)

    Anderson, Robert F; Yadav, Pooja; Shinde, Sujata S; Hong, Cho R; Pullen, Susan M; Reynisson, Jóhannes; Wilson, William R; Hay, Michael P

    2016-08-15

    The radical chemistry and cytotoxicity of a series of quinoxaline di-N-oxide (QDO) compounds has been investigated to explore the mechanism of action of this class of bioreductive drugs. A series of water-soluble 3-trifluoromethyl (4-10), 3-phenyl (11-19), and 3-methyl (20-21) substituted QDO compounds were designed to span a range of electron affinities consistent with bioreduction. The stoichiometry of loss of QDOs by steady-state radiolysis of anaerobic aqueous formate buffer indicated that one-electron reduction of QDOs generates radicals able to initiate chain reactions by oxidation of formate. The 3-trifluoromethyl analogues exhibited long chain reactions consistent with the release of the HO(•), as identified in EPR spin trapping experiments. Several carbon-centered radical intermediates, produced by anaerobic incubation of the QDO compounds with N-terminal truncated cytochrome P450 reductase (POR), were characterized using N-tert-butyl-α-phenylnitrone (PBN) and 5-(diethoxyphosphoryl)-5-methyl-1-pyrroline-N-oxide (DEPMPO) spin traps and were observed by EPR. Experimental data were well simulated for the production of strongly oxidizing radicals, capable of H atom abstraction from methyl groups. The kinetics of formation and decay of the radicals produced following one-electron reduction of the parent compounds, both in oxic and anoxic solutions, were determined using pulse radiolysis. Back oxidation of the initially formed radical anions by molecular oxygen did not compete effectively with the breakdown of the radical anions to form oxidizing radicals. The QDO compounds displayed low hypoxic selectivity when tested against oxic and hypoxic cancer cell lines in vitro. The results from this study form a kinetic description and explanation of the low hypoxia-selective cytotoxicity of QDOs against cancer cells compared to the related benzotriazine 1,4-dioxide (BTO) class of compounds.

  7. Transverse ultrasonic anomaly in La1/3Sr2/3MnO3

    CERN Document Server

    Hui, Kong

    2014-01-01

    The charge ordering (CO) transition in polycrystalline La1/3Sr2/3MnO3 has been studied by measuring the resistivity, magnetization and transverse ultrasonic velocity. At about 235K, a conspicuous increase in resistivity was observed, while the magnetization shows a cusp structure, corresponding to an antiferromagnetic charge ordering transition. Around this transition temperature, dramatic anomaly in transverse sound velocity was observed. The simultaneous occurrence of electron, magnon and phonon anomalous features implies strong spin-phonon coupling and electron-phonon in La1/3Sr2/3MnO3. The analysis suggests that the spin-phonon interaction is due to single-ion magnetostriction, and electron-phonon coupling originates from the Jahn-Teller effect of Mn3+.

  8. Carbon-based air electrodes carrying MnO 2 in zinc-air batteries

    Science.gov (United States)

    Wei, Zidong; Huang, Wenzhang; Zhang, Shengtao; Tan, Jun

    Catalysts prepared from the carbon black impregnated with manganous nitrate solution and then heated at temperature from 270°C to 450°C were investigated. It was found that the impregnated catalysts heated at temperature of 340°C exhibited the best catalytic activity for oxygen reduction in alkaline electrolyte. It was also found that the XRD spectra of pyrolytic MnO 2 from manganous nitrate over 340°C were different from those below 340°C. The enhanced catalysis of air electrodes was ascribed to the formation of MnO 2 crystal with d-value of 2.72 Å as the impregnated-catalysts was heated at temperature of 340°C. The other factors in preparation of air electrodes were also discussed.

  9. Microstructural and electromagnetic properties of MnO2 coated nickel particles with submicron size

    Institute of Scientific and Technical Information of China (English)

    Tang Bao-Lin; He Jun; Ji Tian-Hao; Wang Xin-Lin

    2009-01-01

    Nickel particles with submicron size are prepared by using the solvothermal method. These spheres are then coated with a layer of MnO2 using the soft chemical method. The microstructure is characterized by x-ray diffraction,transmission electron microscopy, and scanning electron microscopy. Energy x-ray dispersive spectrometry and high-resolution images show that the granular composites have a classical core/shell structure with an MnO2 superficial layer, no more than 10 nm in thickness. The hysteresis measurements indicate that these submicron-size Ni composite powders have small remanence and moderate coercivity. The electromagnetic properties of the powders measured by a vector network analyzer in a frequency range of 2-18 GHz are also reported in detail.

  10. Microwave properties of La0.8Ag0.2MnO3 nanoparticles

    Science.gov (United States)

    Rostamnejadi, Ali

    2016-11-01

    In this research, single-phase nanoparticles of La0.8Ag0.2MnO3 with mean particle size of 15 nm have been synthesized by sol-gel method. The microwave properties of La0.8Ag0.2MnO3/paraffin nanocomposite are studied by measuring the complex permittivity and permeability in the frequency range of 1-18 GHz. The composite shows both reflection and absorption electromagnetic shielding effectiveness with maximum total value of 36 dB, which is suitable for defense and microwave radiation shielding applications at high temperatures. The electromagnetic absorption properties are described in terms of dielectric relaxation processes.

  11. Comparative studies on the cumene hydroperoxide- and NADPH-supported N-oxidation of 4-chloroaniline by cytochrome P-450.

    Science.gov (United States)

    Hlavica, P; Golly, I; Mietaschk, J

    1983-06-15

    The present study confirms that cytochrome P-450 can act as a catalyst in the cumene hydroperoxide-supported N-oxidation of 4-chloroaniline. Analogous to the NADPH/O2-driven N-oxidation process, product dissociation is likely to limit the overall rate of cytochrome P-450 cycling also in the peroxidatic pathway. The oxy complexes involved in either metabolic route differ with respect to stability, spectral properties and need for thiolate-mediated resonance stabilization. With the organic hydroperoxide, the metabolic profile is shifted from the preponderant production of N-(4-chlorophenyl)hydroxylamine to the formation of 1-chloro-4-nitrobenzene. This finding suggests that the peroxide-sustained N-oxidation mechanism differs in several ways from that functional in the NADPH/O2-dependent oxenoid reaction. Thus one-electron oxidation, triggered by homolytic cleavage of the oxygen donor, is proposed as the mechanism of peroxidatic transformation of 4-chloroaniline.

  12. Topotactic Solid-State Metal Hydride Reductions of Sr2MnO4.

    Science.gov (United States)

    Hernden, Bradley C; Lussier, Joey A; Bieringer, Mario

    2015-05-04

    We report novel details regarding the reactivity and mechanism of the solid-state topotactic reduction of Sr2MnO4 using a series of solid-state metal hydrides. Comprehensive details describing the active reducing species are reported and comments on the reductive mechanism are provided, where it is shown that more than one electron is being donated by H(-). Commonly used solid-state hydrides LiH, NaH, and CaH2, were characterized in terms of reducing power. In addition the unexplored solid-state hydrides MgH2, SrH2, and BaH2 are evaluated as potential solid-state reductants and characterized in terms of their reductive reactivities. These 6 group I and II metal hydrides show the following trend in terms of reactivity: MgH2 metal electronegativity and bond strengths. NaH and the novel use of SrH2 allowed for targeted synthesis of reduced Sr2MnO(4-x) (0 ≤ x ≤ 0.37) phases. The enhanced control during synthesis demonstrated by this soft chemistry approach has allowed for a more comprehensive and systematic evaluation of Sr2MnO(4-x) phases than previously reported phases prepared by high temperature methods. Sr2MnO3.63(1) has for the first time been shown to be monoclinic by powder X-ray diffraction and the oxidative monoclinic to tetragonal transition occurs at 450 °C.

  13. Nanoflaky MnO2/functionalized carbon nanotubes for supercapacitors: an in situ X-ray absorption spectroscopic investigation.

    Science.gov (United States)

    Chang, Han-Wei; Lu, Ying-Rui; Chen, Jeng-Lung; Chen, Chi-Liang; Lee, Jyh-Fu; Chen, Jin-Ming; Tsai, Yu-Chen; Chang, Chien-Min; Yeh, Ping-Hung; Chou, Wu-Ching; Liou, Ya-Hsuan; Dong, Chung-Li

    2015-02-07

    The surfaces of acid- and amine-functionalized carbon nanotubes (C-CNT and N-CNT) were decorated with MnO2 nanoflakes as supercapacitors by a spontaneous redox reaction. C-CNT was found to have a lower edge plane structure and fewer defect sites than N-CNT. MnO2/C-CNT with a highly developed surface area exhibited favorable electrochemical performance. To determine the atomic/electronic structures of the MnO2/functionalized CNTs (MnO2/C-CNT and MnO/N-CNT) during the charge/discharge process, in situ X-ray absorption spectroscopy (XAS) measurements were made at the Mn K-edge. Both C-CNT and N-CNT are highly conductive. The effect of the scan rate on the capacitance behavior was also examined, revealing that the π* state of CNT and the size of the tunnels in pseudo-capacitor materials (which facilitate conduction and the transport of electrolyte ions) are critical for the capacitive performance, and their role depends on the scan rate. In the slow charge/discharge process, MnO2/N-CNT has a more symmetrical rectangular cyclic voltammetry (CV) curve. In the fast charge/discharge process, MnO2/C-CNT with a highly developed surface provides fast electronic and ionic channels that support a reversible faradaic redox reaction between MnO2 nanoflakes and the electrolyte, significantly enhancing its capacitive performance over that of MnO2/N-CNT. The MnO2/C-CNT architecture has great potential for supercapacitor applications. The information that was obtained herein helps to elucidate CNT surface modification and the design of the MnO2/functionalized CNT interface with a view for the further development of supercapacitors. This work, and especially the combination of CV with in situ XAS measurements, will be of value to readers with an interest in nanomaterial, nanotechnology and their applications in energy storage.

  14. Photochemical activation of ruthenium(II)-pyridylamine complexes having a pyridine-N-oxide pendant toward oxygenation of organic substrates.

    Science.gov (United States)

    Kojima, Takahiko; Nakayama, Kazuya; Sakaguchi, Miyuki; Ogura, Takashi; Ohkubo, Kei; Fukuzumi, Shunichi

    2011-11-09

    Ruthenium(II)-acetonitrile complexes having η(3)-tris(2-pyridylmethyl)amine (TPA) with an uncoordinated pyridine ring and diimine such as 2,2'-bipyridine (bpy) and 2,2'-bipyrimidine (bpm), [Ru(II)(η(3)-TPA)(diimine)(CH(3)CN)](2+), reacted with m-chloroperbenzoic acid to afford corresponding Ru(II)-acetonitrile complexes having an uncoordinated pyridine-N-oxide arm, [Ru(II)(η(3)-TPA-O)(diimine)(CH(3)CN)](2+), with retention of the coordination environment. Photoirradiation of the acetonitrile complexes having diimine and the η(3)-TPA with the uncoordinated pyridine-N-oxide arm afforded a mixture of [Ru(II)(TPA)(diimine)](2+), intermediate-spin (S = 1) Ru(IV)-oxo complex with uncoordinated pyridine arm, and intermediate-spin Ru(IV)-oxo complex with uncoordinated pyridine-N-oxide arm. A Ru(II) complex bearing an oxygen-bound pyridine-N-oxide as a ligand and bpm as a diimine ligand was also obtained, and its crystal structure was determined by X-ray crystallography. Femtosecond laser flash photolysis of the isolated O-coordinated Ru(II)-pyridine-N-oxide complex has been investigated to reveal the photodynamics. The Ru(IV)-oxo complex with an uncoordinated pyridine moiety was alternatively prepared by reaction of the corresponding acetonitrile complex with 2,6-dichloropyridine-N-oxide (Cl(2)py-O) to identify the Ru(IV)-oxo species. The formation of Ru(IV)-oxo complexes was concluded to proceed via intermolecular oxygen atom transfer from the uncoordinated pyridine-N-oxide to a Ru(II) center on the basis of the results of the reaction with Cl(2)py-O and the concentration dependence of the consumption of the starting Ru(II) complexes having the uncoordinated pyridine-N-oxide moiety. Oxygenation reactions of organic substrates by [Ru(II)(η(3)-TPA-O)(diimine)(CH(3)CN)](2+) were examined under irradiation (at 420 ± 5 nm) and showed selective allylic oxygenation of cyclohexene to give cyclohexen-1-ol and cyclohexen-1-one and cumene oxygenation to afford cumyl alcohol

  15. Building new discrete supramolecular assemblies through the interaction of iso-tellurazole N-oxides with Lewis acids and bases.

    Science.gov (United States)

    Ho, Peter C; Jenkins, Hilary A; Britten, James F; Vargas-Baca, Ignacio

    2017-07-21

    The supramolecular macrocycles spontaneously assembled by iso-tellurazole N-oxides are stable towards Lewis bases as strong as N-heterocyclic carbenes (NHC) but readily react with Lewis acids such as BR3 (R = Ph, F). The electron acceptor ability of the tellurium atom is greatly enhanced in the resulting O-bonded adducts, which consequently enables binding to a variety of Lewis bases that includes acetonitrile, 4-dimethylaminopyridine, 4,4'-bipyridine, triphenyl phosphine, a N-heterocyclic carbene and a second molecule of iso-tellurazole N-oxide.

  16. Magnetostructural phase transitions in NiO and MnO: Neutron diffraction data

    Science.gov (United States)

    Balagurov, A. M.; Bobrikov, I. A.; Sumnikov, S. V.; Yushankhai, V. Yu.; Mironova-Ulmane, N.

    2016-07-01

    Structural and magnetic phase transitions in NiO and MnO antiferromagnets have been studied by high-precision neutron diffraction. The experiments have been performed on a high-resolution Fourier diffractometer (pulsed reactor IBR-2), which has the record resolution for the interplanar distance and a high intensity in the region of large interplanar distances; as a result, the characteristics of both transitions have been determined simultaneously. It has been shown that the structural and magnetic transitions in MnO occur synchronously and their temperatures coincide within the experimental errors: T str ≈ T mag ≈ (119 ± 1) K. The measurements for NiO have been performed with powders with different average sizes of crystallites (~1500 nm and ~138 nm). It has been found that the transition temperatures differ by ~50 K: T str = (471 ± 3) K, T mag = (523 ± 2) K. It has been argued that a unified mechanism of the "unsplit" magnetic and structural phase transition at a temperature of T mag is implemented in MnO and NiO. Deviation from this scenario in the behavior of NiO is explained by the quantitative difference—a weak coupling between the magnetic and secondary structural order parameters.

  17. Magneto-reactance based detection of MnO nanoparticle-embedded Lewis lung carcinoma cells

    Science.gov (United States)

    Devkota, J.; Howell, M.; Mukherjee, P.; Srikanth, H.; Mohapatra, S.; Phan, M. H.

    2015-05-01

    We demonstrate the capacity of detecting magnetically weak manganese oxide (MnO) nanoparticles and the Lewis lung carcinoma (LLC) cancer cells that have taken up these nanoparticles using a novel biosensor based on the magneto-reactance (MX) effect of a soft ferromagnetic amorphous ribbon with a microhole-patterned surface. While the magnetic moment of the MnO nanoparticles is relatively small, and a magneto-impedance based sensor fails to detect them in solution (0.05 mg/ml manganese oxide lipid micellar nanoparticles) and inside cells at low concentrations (8.25 × 104 cells/ml), the detection of these nanoparticles and the LLC cells containing them is achieved with the MX-based sensor, which, respectively, reaches the detection sensitivity of ˜3.6% and 2.8% as compared to the blank cells. Since the MnO nanoparticles are a promising contrast agent for magnetic resonance imaging (MRI) of lung cells, the MX-based biosensing technique can be developed as a pre-detection method for MRI of lung cancer cells.

  18. Synthesis and Electrochemical Properties of Semicrystalline Gyroidal Mesoporous MnO2

    Institute of Scientific and Technical Information of China (English)

    ZHOU, Qin; LI, Xiang; LI, Yan-Guang; TIAN, Bo-Zhi; ZHAO, Dong-Yuan; JIANG, Zhi-Yu

    2006-01-01

    Mesoporous silica KIT-6 has novel three-dimensional gyroidal channel structure, space group of Ia-3d, and ordered tunable pores up to 10 nm. In this paper, such mesostructured silica was employed as hard template to prepare semicrystalline gyroidal mesoporous MnO2. The structure was investigated by XRD, TEM and HRTEM, and found to be of high quality Ia-3d symmetry, in good accordance with the template structure. The material has a BET surface of 118 m2·g-1 and pore volume of 0.35 cm3·g-1 after eliminating template. Mesoporous MnO2 has shown good electrochemical property as supercapacitor material in 1 mol·L-1 Na2SO4 and 1 mol·L-1 LiClO4 solutions, but interesting pseudocapacitance behavior was observed in the case of 6 mol·L-1 KOH. It was found that mesoporous MnO2 performed stable reversible electrochemical behavior with capacitance of 220 F·g-1 in a potential range of -0.1-0.55 V vs. Hg/HgO in alkaline solution, demonstrating that it is a promising novel electrode material for the fabrication of electrochemical capacitors.

  19. Prevention of PVDF ultrafiltration membrane fouling by coating MnO2 nanoparticles with ozonation

    Science.gov (United States)

    Yu, Wenzheng; Brown, Matthew; Graham, Nigel. J. D.

    2016-07-01

    Pre-treatment is normally required to reduce or control the fouling of ultrafiltration (UF) membranes in drinking water treatment process. Current pre-treatment methods, such as coagulation, are only partially effective to prevent long-term fouling. Since biological activities are a major contributor to accumulated fouling, the application of an oxidation/disinfection step can be an effective complement to coagulation. In this study, a novel pre-treatment method has been evaluated at laboratory scale consisting of the addition of low dose ozone into the UF membrane tank after coagulation and the use of a hollow-fibre membrane coated with/without MnO2 nanoparticles over a test period of 70 days. The results showed that there was minimal fouling of the MnO2 coated membrane (0.5 kPa for 70 days), while the uncoated membrane experienced both reversible and irreversible fouling. The difference was attributed to the greatly reduced presence of bacteria and organic matter because of the catalytic decomposition of ozone to hydroxyl radicals and increase of the hydrophilicity of the membrane surface. In particular, the MnO2 coated membrane had a much thinner cake layer, with significantly less polysaccharides and proteins, and much less accumulated organic matter within the membrane pores.

  20. Electrochemical characterizati on of MnO2 as electrocatalytic energy material for fuel cell electrode

    Institute of Scientific and Technical Information of China (English)

    Subir Paul; Asmita Ghosh

    2015-01-01

    Development of inexpensive non Pt based high electrocatalytic energy materials is the need of the hour for fuel cell electrode to produce clean alternative green energy from synthesized bio alcohol using biomass.MnO2 , electro synthesized at different current density is found to be well performed electrocatalytic material, comparable to Pt, with higher current density, very low overvoltage for the electrochemical oxidation of methanol.From EIS study, the polarization resistance of the coate d MnO2 is found to be much low and electrical double layer capacitance is high, the effect increases with increase in current density of electro deposition.XRD, EDX and AAS analysis confirm the MnO2 depositio n.Them orphology of SEM im agese xhibits an enhanced 3D effective sub strat e area, for elect ro oxidation oft he fuel.A few nano structured grains of the deposite d MnO2 is also observed at higher current density.The fact supports that a high energet ic ine xpensive electroc atalytic material has beenf ound for fu el cell electrodet o synthesis renewable energy from methanol fuel.

  1. MnO2/CeO2 for catalytic ultrasonic degradation of methyl orange.

    Science.gov (United States)

    Zhao, He; Zhang, Guangming; Zhang, Quanling

    2014-05-01

    Catalytic ultrasonic degradation of aqueous methyl orange was studied in this paper. Heterogeneous catalyst MnO2/CeO2 was prepared by impregnation of manganese oxide on cerium oxide. Morphology and specific surface area of MnO2/CeO2 catalyst were characterized and its composition was determined. Results showed big differences between fresh and used catalyst. The removal efficiency of methyl orange by MnO2/CeO2 catalytic ultrasonic process was investigated. Results showed that ultrasonic process could remove 3.5% of methyl orange while catalytic ultrasonic process could remove 85% of methyl orange in 10 min. The effects of free radical scavengers were studied to determine the role of hydroxyl free radical in catalytic ultrasonic process. Results showed that methyl orange degradation efficiency declined after adding free radical scavengers, illustrating that hydroxyl free radical played an important role in degrading methyl orange. Theoretic analysis showed that the resonance size of cavitation bubbles was comparable with the size of catalyst particles. Thus, catalyst particles might act as cavitation nucleus and enhance ultrasonic cavitation effects. Measurement of H2O2 concentration in catalytic ultrasonic process confirmed this hypothesis. Effects of pre-adsorption on catalytic ultrasonic process were examined. Pre-adsorption significantly improved methyl orange removal. The potential explanation was that methyl orange molecules adsorbed on catalysts could enter cavitation bubbles and undergo stronger cavitation.

  2. Magneto-transport properties of La0.7Ca0.3MnO3/SrTiO3/La0.7Ce0.3MnO3 tunnel junction

    Indian Academy of Sciences (India)

    P Raychaudhuri; C Mitra; K Dorr; K H Muller; G Kobernik; R Pinto

    2002-05-01

    Hole-doped rare-earth manganite La0.7Ca0.3MnO3 and the electron-doped manganite La0.7Ce0.3MnO3 both show a metal–insulator transition around 250 K associated with a ferromagnetic transition and colossal magnetoresistance. In an earlier publication we have reported the rectifying characteristic of La0.7Ca0.3MnO3/SrTiO3/La0.7Ce0.3MnO3 tunnel junction at room temperature, showing that it is possible to fabricate a diode out of the polaronic insulator regime of doped manganites. Here we report the magneto-transport properties of such a tunnel junction above and below the metal–insulator transition. We show, from the large positive magnetoresistance of the tunnel junction at low temperature, that La0.7Ce0.3MnO3 could be a minority spin carrier ferromagnet. The implication of this observation is discussed.

  3. Effects of Propiverine and Its Metabolite Propiverine-N-Oxide on Bladder Contraction and Salivation in Mini Pigs

    NARCIS (Netherlands)

    Scheepe, J. R.; Braun, P. M.; Jnemann, K. P.; Alken, P.

    2008-01-01

    Purpose: The objective of this study was to evaluate the influence of propiverine-HCl (P4) and propiverine-N-oxide (P4NO), one of the major metabolites of P4, on bladder contraction in a standardized in vivo model. Additionally, salivary flow measurements enabled the evaluation of hyposalivation, on

  4. Comparative study of MnO2 nanoparticle synthesis by marine bacterium Saccharophagus degradans and yeast Saccharomyces cerevisiae.

    Science.gov (United States)

    Salunke, Bipinchandra K; Sawant, Shailesh S; Lee, Sang-Ill; Kim, Beom Soo

    2015-07-01

    Microorganisms are one of the most attractive and simple sources for the synthesis of different types of metal nanoparticles. The synthesis of manganese dioxide nanoparticles (MnO2 NPs) by microorganisms from reducing potassium permanganate was investigated for the first time in the present study. The microbial supernatants of the bacterium Saccharophagus degradans ATCC 43961 (Sde 2-40) and of the yeast Saccharomyces cerevisiae showed positive reactions to the synthesis of MnO2 NPs by displaying a change of color in the permanganate solution from purple to yellow. KMnO4-specific peaks also disappeared and MnO2-specific peaks emerged at an absorption maximum of 365 nm in UV-visible spectrophotometry. The washed Sde 2-40 cells did not show any ability to synthesize MnO2 NPs. The medium and medium constituents of Sde 2-40 showed similar positive reactions as supernatants, which indicate the role of the Sde 2-40 medium constituents in the synthesis of MnO2 NPs. This suggests that microorganisms without nanoparticle synthesis ability can be misreported for their abilities to synthesize nanoparticles. S. cerevisiae washed cells showed an ability to synthesize MnO2 NPs. The strategies of keeping yeast cells in tea bags and dialysis membranes showed positive tests for the synthesis of MnO2 NPs. A Fourier transform-infrared spectroscopy study suggested roles for the proteins, alcoholic compounds, and cell walls of S. cerevisiae cells in the synthesis of MnO2 NPs. Electron-dispersive X-ray spectroscopy analyses confirmed the presence of Mn and O in the sample. X-ray photoelectron spectroscopy revealed characteristic binding energies for MnO2 NPs. Transmission electron microscopy micrographs revealed the presence of uniformly dispersed hexagonal- and spherical-shaped particles with an average size of 34.4 nm. The synthesis approach using yeast is possible by a simple reaction at low temperature without any need for catalysts, templates, or expensive and precise equipment

  5. Effect of MgO and MnO on Phosphorus Utilization in P-Bearing Steelmaking Slag

    Science.gov (United States)

    Lin, Lu; Bao, Yan-Ping; Wang, Min; Li, Xiang

    2016-04-01

    In order to recycle the phosphorus in P-bearing converter slag and make it used as slag phosphate fertilizer, the effect of MgO and MnO in P-bearing steelmaking slag on phosphorus existence form, P2O5 solubility and magnetic separation behavior were researched systematically. The results show that the phosphorus in slag is mainly in the form of n2CaO · SiO2-3CaO · P2O5 (for short nC2S-C3P) solid solution in the P-rich phase for CaO-SiO2-FetO-P2O5-X (X stands for MgO and MnO, respectively). And the increasing of MgO and MnO content has no influence on precipitation of nC2S-C3P solid solution in slag, MnO and MgO mainly enter into RO phase and base phase to form MnFe2O4 and MgFe2O4, which has little effect on the P2O5 content of P-rich phase, so which has little effect on the degree of phosphorus enrichment and phosphorus occurrence form of the P-bearing slag. And adding MgO and MnO into CaO-SiO2-P2O5-Fe2O3 slag system can break the complex net structure formed by Si-O on certain degree, and also hinder the precipitation of β-Ca3(PO4)2 crystal with low citric acid solubility during the melting-cooling process. Therefore, adding appropriate MgO and MnO content into slag can improve the slag P2O5 solubility, but the effect of different amounts of MgO and MnO on the P2O5 solubility has little difference. Meanwhile, adding MgO and MnO into slag can improve the metallization of slag and magnetism of iron-rich phase, make the magnetic substances content increase and separation of phosphorus and iron incomplete, so it is adverse to phosphorus resources recovery from P-bearing slag by magnetic separation method. In order to recycle the phosphorus in P-bearing converter slag, the MgO and MnO content in the P-bearing slag should be controlled in the steelmaking process.

  6. Protective effect of Silymarin on rats with monocrotaline induced pulmonary hypertension%水飞蓟素对野百合碱诱发肺动脉高压大鼠肺血管重构的保护作用

    Institute of Scientific and Technical Information of China (English)

    杨勇; 吕进泉; 赵文生

    2012-01-01

    目的 探讨水飞蓟素对野百合碱(MCT)诱发肺动脉高压大鼠模型肺血管重构的保护作用及机制.方法 24只雄性SD大鼠随机分为正常对照组(C组)、MCT诱发肺动脉高压模型组(M组)、水飞蓟素治疗组(S组),每组8只.28 d后,右心导管法测量各组右心室收缩压(RVSP),称量法计算右心室肥大指数(RVHI),HE染色和α-平滑肌肌动蛋白(α-SMA)免疫组织化学染色观察肺血管重构,TUNEL法检测肺动脉平滑肌细胞凋亡,RT-PCR法行肺组织Fas mRNA半定量检测.结果 与M组比较,S组RVSP、RVHI、α-SMA表达均降低(P<0.01),肺动脉平滑肌细胞凋亡稍升高,肺组织Fas mRNA表达升高(P<0.05).结论 水飞蓟素对野百合碱诱发肺动脉高压大鼠肺血管重构具有保护作用.%Objective To investigate the protective effects of silymarin on rats with monocrotaline induced pulmonary hypertension and explore its therapeutic mechanism. Methods 24 male SD rats were randomly divided into 3 groups,the control group(n = 8) , the pulmonary hypertension model group(n = 8) and the silmymarin treatment group(n = 8). Right ventricular systolic pressure (RVSP) were detected by right heart catheter after twenty-eight days. Right ventricular hypertrophy index(RVHI) was calculated as the right ventricle to the left ventricular plus septum weight. With HK staining,immunohistochemical analysis of crsmooth muscle actin(crSMA) to observe pulmonary artery structural changes. The pulmonary artery smooth muscle cells apoptosis were detected by TUNEL. The expression of Fas mRNA in the pulmonary tissue was detected by RT-PCR. Results Compared with the model group,silymarin treatment group decreased RVSP,RVHI and α-SMA,increased apoptosis of pulmonary artery smooth muscle cells and Fas mRNA. Conclusion Silymarin could protect rats with monocrotaline induced pulmonary hypertension.

  7. Hierarchical MnO2 nanowire/graphene hybrid fibers with excellent electrochemical performance for flexible solid-state supercapacitors

    Science.gov (United States)

    Ma, Wujun; Chen, Shaohua; Yang, Shengyuan; Chen, Wenping; Cheng, Yanhua; Guo, Yiwei; Peng, Shengjie; Ramakrishna, Seeram; Zhu, Meifang

    2016-02-01

    Towards rapid development of lightweight, flexible, and even wearable electronics, a highly efficient energy-storage device is required for their energy supply management. Graphene fiber-based supercapacitor is considered as one of the promising candidates because of the remarkable mechanical and electrical properties of graphene fibers. However, supercapacitors based on bare graphene fibers generally suffer a low capacitance, which certainly restricts their potentially wide applications. In this work, hierarchically structured MnO2 nanowire/graphene hybrid fibers are fabricated through a simple, scalable wet-spinning method. The hybrid fibers form mesoporous structure with large specific surface area of 139.9 m2 g-1. The mass loading of MnO2 can be as high as 40 wt%. Due to the synergistic effect between MnO2 nanowires and graphene, the main pseudocapacitance of MnO2 and the electric double-layer capacitance of graphene are improved simultaneously. In view of the practical demonstration, a highly flexible solid-state supercapacitor is fabricated by twisting of two MnO2/graphene fibers coated by polyvinyl alcohol/H3PO4 electrolyte. The supercapacitor exhibits a high volumetric capacitance (66.1 F cm-3, normalized by the total volume of two fiber electrodes), excellent cycling stability (96% capacitance retention over 10,000 cycles), high energy and power density (5.8 mWh cm-3 and 0.51 W cm-3, respectively).

  8. Influence of Synthesis Condition onIn-situ Grown of MnO2 on Activated Carbon Fiber Cloth

    Institute of Scientific and Technical Information of China (English)

    YAN Qinglong; ZHANG Shilei; CHU Ruixia; WANG Jieqiang; LIU Huakun

    2015-01-01

    The in-situ grown of nanostructured MnO2 on activated carbon fiber cloth (ACFC) was obtained with a potas-sium permanganate solution in the absence of oxidant, reductant or binder additionvia a typical microwave hydrother-mal synthesis procedure. The carbon fiber cloth serves as a sacrificial reductant and a substrate material to guarantee MnO2 deposition. The results show that the synthesis condition has a great influence on the morphology and structure of MnO2 grown on ACFC.Highly ordered grass-blade-likeδ-MnO2/ACFC hybrid nanocomposites were synthesized at 70℃ for 60 min. The grass-blade-likeδ-MnO2 are 500 nm in length and 10 nm in depth, and they are well-proportioned grown on the surface of ACFC. The combination of ACFC and MnO2is rather tight, thus improving the toughness of MnO2. This free-standing, flexible hybrid structure material could be used as a favorable candidate of flexible superca-pacitor electrode materials.

  9. Influence of Synthesis Condition on In-situ Grown of MnO2 on Activated Carbon Fiber Cloth

    Institute of Scientific and Technical Information of China (English)

    YAN; Qinglong; ZHANG; Shilei; CHU; Ruixia; WANG; Jieqiang; LIU; Huakun

    2015-01-01

    The in-situ grown of nanostructured MnO2 on activated carbon fiber cloth(ACFC) was obtained with a potassium permanganate solution in the absence of oxidant, reductant or binder addition via a typical microwave hydrothermal synthesis procedure. The carbon fiber cloth serves as a sacrificial reductant and a substrate material to guarantee MnO2 deposition. The results show that the synthesis condition has a great influence on the morphology and structure of MnO2 grown on ACFC.Highly ordered grass-blade-like δ-MnO2/ACFC hybrid nanocomposites were synthesized at 70℃ for 60 min. The grass-blade-like δ-MnO2 are 500 nm in length and 10 nm in depth, and they are well-proportioned grown on the surface of ACFC. The combination of ACFC and MnO2 is rather tight, thus improving the toughness of MnO2. This free-standing, flexible hybrid structure material could be used as a favorable candidate of flexible supercapacitor electrode materials.

  10. MnO2-induced synthesis of fluorescent polydopamine nanoparticles for reduced glutathione sensing in human whole blood.

    Science.gov (United States)

    Kong, Xiang-Juan; Wu, Shuang; Chen, Ting-Ting; Yu, Ru-Qin; Chu, Xia

    2016-08-25

    Polydopamine (PDA) nanoparticles, as a kind of popular polymer material, have attracted a great deal of attention from various areas including materials science, biomedicine, energy, environmental science and so on owing to their striking physicochemical properties. Herein, we reported for the first time the synthesis of intrinsic fluorescent PDA nanoparticles using MnO2 as an oxidant. In the presence of MnO2, dopamine was quickly oxidized into its quinone derivative, and autopolymerized into fluorescent PDA nanoparticles. Using fluorescent PDA nanoparticles as a fluorescence signal indicator, we further established a cost-effective sensor for rapid, sensitive and selective sensing of reduced glutathione (GSH) based on the redox reaction between MnO2 and GSH, and the key role of MnO2 in the formation of fluorescent PDA nanoparticles. GSH has the capability of reducing MnO2 into Mn(2+), which inhibited the formation of the fluorescent PDA nanoparticles. Thus, the concentration of GSH was directly related to the decreased fluorescence signal intensity of the PDA nanoparticles. The sensor showed good sensing performance for GSH detection with high sensitivity and desirable selectivity over other potential interfering species. Additionally, the sensor exhibited excellent practical applications for GSH detection in human whole blood samples, which presents potential applications in biological detection and clinical diagnosis.

  11. Nanoflaky MnO2/functionalized carbon nanotubes for supercapacitors: an in situ X-ray absorption spectroscopic investigation

    Science.gov (United States)

    Chang, Han-Wei; Lu, Ying-Rui; Chen, Jeng-Lung; Chen, Chi-Liang; Lee, Jyh-Fu; Chen, Jin-Ming; Tsai, Yu-Chen; Chang, Chien-Min; Yeh, Ping-Hung; Chou, Wu-Ching; Liou, Ya-Hsuan; Dong, Chung-Li

    2015-01-01

    The surfaces of acid- and amine-functionalized carbon nanotubes (C-CNT and N-CNT) were decorated with MnO2 nanoflakes as supercapacitors by a spontaneous redox reaction. C-CNT was found to have a lower edge plane structure and fewer defect sites than N-CNT. MnO2/C-CNT with a highly developed surface area exhibited favorable electrochemical performance. To determine the atomic/electronic structures of the MnO2/functionalized CNTs (MnO2/C-CNT and MnO/N-CNT) during the charge/discharge process, in situ X-ray absorption spectroscopy (XAS) measurements were made at the Mn K-edge. Both C-CNT and N-CNT are highly conductive. The effect of the scan rate on the capacitance behavior was also examined, revealing that the π* state of CNT and the size of the tunnels in pseudo-capacitor materials (which facilitate conduction and the transport of electrolyte ions) are critical for the capacitive performance, and their role depends on the scan rate. In the slow charge/discharge process, MnO2/N-CNT has a more symmetrical rectangular cyclic voltammetry (CV) curve. In the fast charge/discharge process, MnO2/C-CNT with a highly developed surface provides fast electronic and ionic channels that support a reversible faradaic redox reaction between MnO2 nanoflakes and the electrolyte, significantly enhancing its capacitive performance over that of MnO2/N-CNT. The MnO2/C-CNT architecture has great potential for supercapacitor applications. The information that was obtained herein helps to elucidate CNT surface modification and the design of the MnO2/functionalized CNT interface with a view for the further development of supercapacitors. This work, and especially the combination of CV with in situ XAS measurements, will be of value to readers with an interest in nanomaterial, nanotechnology and their applications in energy storage.The surfaces of acid- and amine-functionalized carbon nanotubes (C-CNT and N-CNT) were decorated with MnO2 nanoflakes as supercapacitors by a spontaneous redox

  12. MnO2/CeO2 for catalytic ultrasonic decolorization of methyl orange: Process parameters and mechanisms.

    Science.gov (United States)

    Zhao, He; Zhang, Guangming; Chong, Shan; Zhang, Nan; Liu, Yucai

    2015-11-01

    MnO2/CeO2 catalyst was prepared and characterized by means of Brunauer-Emmet-Teller (BET) method, X-ray diffraction (XRD) and scanning electron microscope (SEM). The characterization showed that MnO2/CeO2 had big specific surface area and MnO2 was dispersed homogeneously on the surface of CeO2. Excellent degradation efficiency of methyl orange was achieved by MnO2/CeO2 catalytic ultrasonic process. Operating parameters were studied and optimized. The optimal conditions were 10 min of ultrasonic irradiation, 1.0 g/L of catalyst dose, 2.6 of pH value and 1.3 W/ml of ultrasonic density. Under the optimal conditions, nearly 90% of methyl orange was removed. The mechanism of methyl orange degradation was further studied. The decolorization mechanism in the ultrasound-MnO2/CeO2 system was quite different with that in the ultrasound-MnO2 system. Effects of manganese and cerium in catalytic ultrasonic process were clarified. Manganese ions in solution contributed to generating hydroxyl free radical. MnO2/CeO2 catalyst strengthened the oxidation ability of ultrasound and realized complete decolorization of methyl orange.

  13. Electrochemical characterization of nano V, Ti doped MnO2 in primary lithium manganese dioxide batteries with high rate

    Science.gov (United States)

    Sun, Yang; Wang, Shengping; Dai, Yu; Lei, Xinrong

    2016-10-01

    The nano-sized γ-MnO2 precursor is synthesized using a room temperature, liquid-phase reaction route with the assistance of ultrasonic waves. The MnO2 precursor as an electrode material in lithium manganese dioxide primary batteries displays a low capacity of 140mAhg-1 (45.5% for the theoretical capacity of MnO2) at 20mAg-1. Therefore, the doped MnO2 with cationic V or/and Ti are prepared at high temperature. After the heat treatment, the γ phase precursor powder gradually converts into the β-MnO2 and exhibits a higher specific surface area with a larger pore volume and pore size, providing significantly more electrochemically active sites for the redox reaction. The doped MnO2 matrix has advantage of the ideal lattice parameters and the higher conductivity, resulting in an enhancement of the Li+ diffusion kinetics in the tunnel structure. Especially for co-doped MnO2 with V and Ti, the modified material shows an outstanding electrochemical capacity of 190mAhg-1 (61.7% for the theoretical capacity) at 20mAg-1 and 169mAhg-1 for a higher power output of 100mAg-1.

  14. Membranes of MnO Beading in Carbon Nanofibers as Flexible Anodes for High-Performance Lithium-Ion Batteries

    Science.gov (United States)

    Zhao, Xin; Du, Yuxuan; Jin, Lei; Yang, Yang; Wu, Shuilin; Li, Weihan; Yu, Yan; Zhu, Yanwu; Zhang, Qinghua

    2015-01-01

    Freestanding yet flexible membranes of MnO/carbon nanofibers are successfully fabricated through incorporating MnO2 nanowires into polymer solution by a facile electrospinning technique. During the stabilization and carbonization processes of the as-spun membranes, MnO2 nanowires are transformed to MnO nanoparticles coincided with a conversion of the polymer from an amorphous state to a graphitic structure of carbon nanofibers. The hybrids consist of isolated MnO nanoparticles beading in the porous carbon and demonstrate superior performance when being used as a binder-free anode for lithium-ion batteries. With an optimized amount of MnO (34.6 wt%), the anode exhibits a reversible capacity of as high as 987.3 mAh g−1 after 150 discharge/charge cycles at 0.1 A g−1, a good rate capability (406.1 mAh g−1 at 3  A g−1) and an excellent cycling performance (655 mAh g−1 over 280 cycles at 0.5 A g−1). Furthermore, the hybrid anode maintains a good electrochemical performance at bending state as a flexible electrode. PMID:26374601

  15. Facile preparation of three-dimensional multilayer porous MnO2/reduced graphene oxide composite and its supercapacitive performance

    Science.gov (United States)

    Li, Yiju; Wang, Guiling; Ye, Ke; Cheng, Kui; Pan, Yue; Yan, Peng; Yin, Jinling; Cao, Dianxue

    2014-12-01

    Three-dimensional (3D) multilayer porous MnO2/reduced graphene oxide composites are coated on a nickel foam substrate (denoted as MnO2/R-GO@Ni-foam) by a facile and scalable spray method following by low temperature annealing. The composite electrodes are characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy and Fourier transform infrared spectroscopy. The content of MnO2 in the MnO2/R-GO@Ni-foam composites is determined by thermal gravimetric analysis. The supercapacitive performance of the composite electroides is investigated by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. The results show that the MnO2/R-GO@Ni-foam composite displays a high specific capacitance of 267 F g-1 at 0.25 A g-1 and excellent capacitance retention of 89.5% after 1000 cycles. This study provides a facile way for the preparation of composite electrodes for high-performance supercapacitor.

  16. Systematic coordination chemistry and cytotoxicity of copper(II) complexes with methyl substituted 4-nitropyridine N-oxides.

    Science.gov (United States)

    Puszko, Aniela; Brzuszkiewicz, Anna; Jezierska, Julia; Adach, Anna; Wietrzyk, Joanna; Filip, Beata; Pełczynska, Marzena; Cieslak-Golonka, Maria

    2011-08-01

    Three new nitrato copper(II) complexes of dimethyl substituted 4-nitropyridine N-oxide were synthesized and characterized by elemental analysis, magnetic, spectroscopic, thermal and X-ray methods, respectively. They were isolated as trans isomers, mononuclear (μ=1.70-1.88 BM), five (1-2) and four (3) coordinate species of general formula [Cu(NO3)2(H2O)L2] where L=2,3-dimethyl-, 2,5-dimethyl-4-nitropyridine N-oxide and [Cu (NO3)2L2], L=3,5-dimethyl-4-nitropyridine N-oxide, respectively. The X-ray crystal structure of (1) (L=2,3-dimethyl-4-nitropyridine N-oxide) was determined. The organic ligands, the complexes and copper hexaqua ion as a reference were tested in vitro on the cytotoxic activity against human cancer cell lines: MCF-7 (breast), SW-707 (colon) and P-388 (murine leukemia). The complexes are relatively strong cytotoxic agents towards P-388 cell line. Comparative analysis was performed for all known copper(II) complexes containing methyl derivatives of the 4-nitropyridine N-oxide on the basis of their composition, structure and cytotoxic activities. To obtain the typical structure for these species (i.e., 4-coordinate mononuclear of the type trans-[Cu(inorganic anion)2L2]), two methyl groups must be situated on both sides of nitrogen atom(s) (i.e., NO and NO2) in the ligand. The biological activity was found to be strongly dependent upon the number of the methyl groups and the type of cell line. The best cytotoxic results were found for the complexes without substituents or with one methyl group. Generally, for all cell lines, the complexation increased cytotoxicity when compared with the free ligands.

  17. Experimental and Computational Evidence for the Reduction Mechanisms of Aromatic N-oxides by Aqueous Fe(II)-Tiron Complex.

    Science.gov (United States)

    Chen, Yiling; Dong, Hao; Zhang, Huichun

    2016-01-05

    A combined experimental-theoretical approach was taken to elucidate the reduction mechanisms of five representative aromatic N-oxides (ANOs) by Fe(II)-tiron complex and to identify the rate-limiting step. Based on the possible types of complexes formed with the reductant, three groups of ANOs were studied: type I refers to those forming 5-membered ring complexes through the N and O atoms on the side chain; type II refers to those forming 6-membered ring complexes through the N-oxide O atom and the O atom on the side chain; and type III refers to complexation through the N-oxide O atom only. Density functional theory calculations suggested that the elementary reactions, including protonation, N-O bond cleavage, and the second electron transfer processes, are barrierless, indicating that the first electron transfer is rate-limiting. Consistent with the theoretical results, the experimental solvent isotope effect, KIEH, for the reduction of quinoline N-oxide (a type III ANO) was obtained to be 1.072 ± 0.025, suggesting protonation was not involved in the rate-limiting step. The measured nitrogen kinetic isotope effect, KIEN, for the reduction of pyridine N-oxide (a type III ANO) (1.022 ± 0.006) is in good agreement with the calculated KIEN for its first electron transfer (1.011-1.028), confirming that the first electron transfer is rate-limiting. Electrochemical cell experiments demonstrated that the electron transfer process can be facilitated significantly by type I complexation with FeL2(6-) (1:2 Fe(II)-tiron complex), to some extent by type II complexation with free Fe(II), but not by weak type III complexation.

  18. Quinoxaline 1, 4-di-N-oxides: Biological activities and mechanisms of actions

    Directory of Open Access Journals (Sweden)

    Guyue eCheng

    2016-03-01

    Full Text Available Quinoxaline 1, 4-di-N-oxides (QdNOs have manifold biological properties, including antimicrobial, antitumoral, antitrypanosomal and antiinflammatory/antioxidant activities. These diverse activities endow them broad applications and prospects in human and veterinary medicines. As QdNOs arouse widespread interest, the evaluation of their medicinal chemistry is still in progress. In the meantime, adverse effects have been reported in some of the QdNO derivatives. For example, genotoxicity and bacterial resistance have been found in QdNO antibacterial growth promoters, conferring urgent need for discovery of new QdNO drugs. However, the modes of actions of QdNOs are not fully understood, hindering the development and innovation of these promising compounds. Here, QdNOs are categorized based on the activities and usages, among which the antimicrobial activities are consist of antibacterial, antimycobacterial and anticandida activities, and the antiprotozoal activities include antitrypanosomal, antimalarial, antitrichomonas and antiamoebic activities. The structure-activity relationship and the mode of actions of each type of activity of QdNOs are summarized, and the toxicity and the underlying mechanisms are also discussed, providing insight for the future research and development of these fascinating compounds.

  19. Trimethylamine N-Oxide: The Good, the Bad and the Unknown

    Directory of Open Access Journals (Sweden)

    Manuel T. Velasquez

    2016-11-01

    Full Text Available Trimethylamine N-oxide (TMAO is a small colorless amine oxide generated from choline, betaine, and carnitine by gut microbial metabolism. It accumulates in the tissue of marine animals in high concentrations and protects against the protein-destabilizing effects of urea. Plasma level of TMAO is determined by a number of factors including diet, gut microbial flora and liver flavin monooxygenase activity. In humans, a positive correlation between elevated plasma levels of TMAO and an increased risk for major adverse cardiovascular events and death is reported. The atherogenic effect of TMAO is attributed to alterations in cholesterol and bile acid metabolism, activation of inflammatory pathways and promotion foam cell formation. TMAO levels increase with decreasing levels of kidney function and is associated with mortality in patients with chronic kidney disease. A number of therapeutic strategies are being explored to reduce TMAO levels, including use of oral broad spectrum antibiotics, promoting the growth of bacteria that utilize TMAO as substrate and the development of target-specific molecules with varying level of success. Despite the accumulating evidence, it is questioned whether TMAO is the mediator of a bystander in the disease process. Thus, it is important to undertake studies examining the cellular signaling in physiology and pathological states in order to establish the role of TMAO in health and disease in humans.

  20. Purification and characterization of trimethylamine-N-oxide demethylase from jumbo squid (Dosidicus gigas).

    Science.gov (United States)

    Fu, Xue-Yan; Xue, Chang-Hu; Miao, Ben-Chun; Liang, Jun-Ni; Li, Zhao-Jie; Cui, Feng-Xia

    2006-02-08

    Trimethylamine-N-oxide demethylase (TMAOase) was purified from Jumbo squid (Dosidicus gigas) and characterized in detail herein. The TMAOase was extracted from squid with 20 mM Tris-acetate buffer (pH 7.0) containing 1.0 M NaCl, followed by acid treatment and heat treatment. Then it was purified by deithylaminoethyl-cellulose and Sephacryl S-300 chromatography, subsequently resulting in an 839-fold purification. The molecular mass of the TMAOase was defined to be 17.5 kDa. The optimum pH of the purified TMAOase was 7.0, and its optimum temperature was confirmed to be 55 degrees C. The TMAOase was stable to heat treatment up to 50 degrees C and stable at pH 7.0-9.0. Reducing agents such as DTT, Na2SO3, and NADH were effective at activating TMAOase, and ethylenediaminetetraacetic acid, as well as Mg2+ and Ca2+, could also enhance the activity of TMAOase remarkably, whereas the TMAOase could be significantly inhibited by tea polyphenol, phytic acid and acetic acid. In addition, the TMAOase converted TMAO to dimethylamine and formaldehyde stoichiometrically with a K(m) of 26.2 mM.

  1. Further investigations into the genotoxicity of quinoxaline-di-N-oxides and their primary metabolites.

    Science.gov (United States)

    Liu, Qianying; Zhang, Jianwu; Luo, Xun; Ihsan, Awais; Liu, Xianglian; Dai, Menghong; Cheng, Guyue; Hao, Haihong; Wang, Xu; Yuan, Zonghui

    2016-07-01

    Quinoxaline-di-N-oxides (QdNOs) are potential antibacterial agents with a wide range of biological properties. Quinocetone (QCT), carbadox (CBX), olaquindox (OLA), mequindox (MEQ) and cyadox (CYA) are classical QdNOs. Though the genotoxicity of parent drugs has been evaluated, the genotoxicity of their primary N → O reduced metabolites remains unclear. In the present study, a battery of four different short-term tests, mouse lymphoma assay (MLA), Ames test, chromosomal aberration assay in vitro and bone marrow erythrocyte micronucleus assay in vivo was carried out to investigate the genotoxicity of the six primary N → O reduced metabolites. Additionally, the genotoxicity of five parent drugs was evaluated by the MLA. Strong genotoxicity of N1-MEQ, B-MEQ and B-CBX was found in three of the assays but not in the Ames assay, and the rank order was N1-MEQ>B-MEQ>B-CBX that is consistent with prototype QdNOs. Negative results for the five QdNOs were noted in the MLA. We present for the first time a comparison of the genotoxicity of primary N → O reduced metabolites, and evaluate the ability of five QdNOs to cause mutations in the MLA. The present study demonstrates that metabolites are involved in genetic toxicity mediated by QdNOs, and improve the prudent use of QdNOs for public health.

  2. Quinoxaline 1,4-di-N-Oxides: Biological Activities and Mechanisms of Actions.

    Science.gov (United States)

    Cheng, Guyue; Sa, Wei; Cao, Chen; Guo, Liangliang; Hao, Haihong; Liu, Zhenli; Wang, Xu; Yuan, Zonghui

    2016-01-01

    Quinoxaline 1,4-di-N-oxides (QdNOs) have manifold biological properties, including antimicrobial, antitumoral, antitrypanosomal and antiinflammatory/antioxidant activities. These diverse activities endow them broad applications and prospects in human and veterinary medicines. As QdNOs arouse widespread interest, the evaluation of their medicinal chemistry is still in progress. In the meantime, adverse effects have been reported in some of the QdNO derivatives. For example, genotoxicity and bacterial resistance have been found in QdNO antibacterial growth promoters, conferring urgent need for discovery of new QdNO drugs. However, the modes of actions of QdNOs are not fully understood, hindering the development and innovation of these promising compounds. Here, QdNOs are categorized based on the activities and usages, among which the antimicrobial activities are consist of antibacterial, antimycobacterial and anticandida activities, and the antiprotozoal activities include antitrypanosomal, antimalarial, antitrichomonas, and antiamoebic activities. The structure-activity relationship and the mode of actions of each type of activity of QdNOs are summarized, and the toxicity and the underlying mechanisms are also discussed, providing insight for the future research and development of these fascinating compounds.

  3. Plasma trimethylamine-N-oxide following supplementation with vitamin D or D plus B vitamins.

    Science.gov (United States)

    Obeid, Rima; Awwad, Hussain M; Kirsch, Susanne H; Waldura, Christiane; Herrmann, Wolfgang; Graeber, Stefan; Geisel, Juergen

    2017-02-01

    We compared the effect of supplementation with vitamin D + B or vitamin D on plasma trimethylamine N-oxide (TMAO) and choline metabolites. This is a randomized single-blinded nonplacebo-controlled study. Twenty-seven participants received 1200 IU vitamin D3 and 800 mg calcium, and 25 participants received additionally 0.5 mg folic acid, 50 mg B6, and 0.5 mg B12 for 1 year. Plasma homocysteine (Hcy), TMAO, and choline metabolites were measured at baseline and 12 months later. TMAO declined in the vitamin D arm by 0.5 versus 2.8 μmol/L in the D + B arm (p = 0.005). Hcy decreased and betaine increased in the D + B compared to the D arm. Within-subject levels of plasma choline and dimethylglycine and urine betaine increased in both arms and changes did not differ between the arms. TMAO reduction was predicted by higher baseline TMAO and lowering Hcy in stepwise regression analysis. The test-retest variations of TMAO were greater in the D + B arm compared to vitamin D arm. B vitamins plus vitamin D lowered plasma fasting TMAO compared to vitamin D. Vitamin D caused alterations in choline metabolism, which may reflect the metabolic flexibility of C1-metabolism. The molecular mechanisms and health implications of these changes are currently unknown. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Synthesis and Structure,of bis( μ-2-aminopyridine N-oxide)-bis[dichlorocopper(Ⅱ)

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The complex [Cu2(apo)4Cl4]·2H2O (apo=2-aminopyridine N-oxide) was obtained. A single- crystal X-ray study shows that the complex is a binuclear compound (Cu2C20H28C14NsO6). The coordination geometry about each copper atom is best described as a distorted square pyramid. The compound [Cu2(apo)4Cl4]·2H2O belongs to the triclinic system with space group P1, lattice constants: a = 7.8550(7), b = 8.5378(7), c = 12.082(1) A, α = 72.807(1),β = 77.641(1),γ = 70.800(1)° , V=724.85(11) A3, Z=1, Mr=745.38, Dc=1.708 g/cm3, μ =1.886mm-1, F(000) =378, R=0.0359, wR2=0.0884 for 2220 reflections with I >2σ(I). The distances between Cu(Ⅱ) and O atoms are in the range from 1.934(2) to 2.042(2)A. The distance between two copper atoms Cu-Cu(A) is 3.2978(8) A. The distances of Cu-Cl(1) and Cu-Cl(2) are 2.2322(9), 2.5095(10) A, respectively. There is no evident hydrogen bond between N and Cl.

  5. Effects of the osmolyte TMAO (Trimethylamine-N-oxide) on aqueous hydrophobic contact-pair interactions.

    Science.gov (United States)

    Macdonald, Ryan D; Khajehpour, Mazdak

    2013-12-31

    Osmolytes are small, soluble organic molecules produced by living organisms for maintaining cell volume. These molecules have also been shown to have significant effects on the stability of proteins. Perhaps one of the most studied osmolytes is Trimethylamine-N-oxide (TMAO). Thermodynamic studies of the effects of TMAO on proteins have shown that this molecule is a strong stabilizer of the protein folded state, thus being able to counteract the effects of protein denaturants such as urea and guanidine hydrochloride. Most studies of TMAO effects on bio-molecular stability have until now been focused on how the osmolyte reduces the solubility of polypeptide backbones, while the effects of TMAO on hydrophobic interactions are still not well understood. In fact, there are few experimental data measuring the effect of TMAO on hydrophobic interactions. This work studies phenyl and alkyl contact pairs as model hydrophobic contact pairs. The formation of these contact pairs is monitored using fluorescence, i.e., through the quenching of phenol fluorescence by carboxylate ions; and a methodology is developed to isolate hydrophobic contributions from other interactions. The data demonstrate that the addition of TMAO to the aqueous solvent destabilizes hydrophobic contact pairs formed between alkyl and phenyl moieties. In other words, TMAO acts as a "denaturant" for hydrophobic interactions.

  6. Synthesis of free-standing MnO2/reduced graphene oxide membranes and electrochemical investigation of their performances as anode materials for half and full lithium-ion batteries

    Science.gov (United States)

    Zhao, Xiaojun; Wang, Gang; Wang, Hui

    2016-10-01

    MnO2 nanotubes/reduced graphene oxide (MnO2/RGO) membranes with different MnO2 contents are successfully synthesized by a facile two-step method including vacuum filtration and subsequent thermal reduction route. The MnO2 nanotubes obtained are 38 nm in diameter and homogeneously imbedded in RGO sheets as spacers. The synthesized MnO2/RGO membranes exhibit excellent mechanical flexibilities and free-standing properties. Using the membranes directly as anode materials for lithium batteries (LIBs), the membranes for half LIBs show superb cycling stabilities and rate performances. Importantly, the electrochemical performances of MnO2/RGO membranes show a strong dependence on the MnO2 nanotube contents in the hybrids. In addition, our results show that the hybrid membranes with 49.0 wt% MnO2 nanotube in half LIBs achieve a high reversible capacity of 1006.7 mAh g-1 after 100 cycles at a current density of 0.1 A g-1, which is higher lithium storage capacity than that of reported MnO2-carbon electrodes. Furthermore, the synthesized full cell (MnO2/RGO//LiCoO2) system also exhibit excellent electrochemical performances, which can be attributed to the unique microstructures of MnO2 and GRO, coupled with the strong synergistic interaction between MnO2 nanotubes and GRO sheets.

  7. Microstructural Characteristics of La0.7Ca0.3MnO3 Films and Multilayers

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    La0.7Ca0.3MnO3 (LCMO) films and La0.7Ca0.3MnO3/Gd0.7Ca0.3MnO3 (LCMO/GCMO) multilayers have been prepared by pulsed laser deposition. The microstructures of both systems were investigated by transmission electron microscopy (TEM). The main structure of the films and the multilayers was monoclinic with a unit cell of size 2ap × √-2ap × √-2ap, where ap is the lattice constant of single perovskite crystal. The LCMO films were composed of three-dimension multitwinning domains, while the LCMO/GCMO multilayers showed two-domain structure. In LCMO/GCMO multilayers, LCMO layers were coherent with GCMO layers and the interfaces between LCMO and GCMO layers were free from mismatch dislocation, which resulted in highly strained multilayerd structures.

  8. MnO2/PVP/MWCNT hybrid nano composites as electrode materials for high performance supercapacitor

    Science.gov (United States)

    Jaggi, Neena; Sharma, Deepa; Sharma, Priya

    2016-10-01

    In this work, we developed supercapacitors with electrodes of manganese oxide (MnO2) and its nanocomposites with multiwalled carbon nanotubes (MWCNT) and polyvinylpyrrolidone (PVP) and studied the effect of the electrode material on various performance parameters of the supercapacitor. Cyclic voltammetry (CV) curves, galvanostatic charge/discharge measurement curves, XRD (x-ray diffraction), I-V characteristics and electrochemical impedance spectroscopy were employed for the characterization and analysis. CV curves were used to verify the supercapacitor behavior and the specific capacitance of the capacitors composed of the nanocomposite electrodes was calculated. I-V characteristics of MnO2 and MnO2/PVP/MWCNT were plotted and compared and conductivity measurements were also performed. Dielectric properties and equivalent series resistance were investigated using electrochemical impedance spectroscopy.

  9. Sonochemical preparation of stable porous MnO2 and its application as an efficient electrocatalyst for oxygen reduction reaction.

    Science.gov (United States)

    Zuo, Ling-Xia; Jiang, Li-Ping; Abdel-Halim, E S; Zhu, Jun-Jie

    2017-03-01

    Porous MnO2 as a non-noble metal oxygen reduction reaction (ORR) electrocatalyst was prepared by a simple sonochemical route. The as-prepared porous MnO2 exhibited higher electrocatalytic activity, superior stability and better methanol tolerance than commercial Pt/C catalyst in alkaline media. Furthermore, the ORR proceeded via a nearly four-electron pathway. Cyclic voltammetry (CV) and rotating-disk electrode (RDE) measurements verified that the ORR enhancement was attributed to the porous structure and good dispersity, which facilitated sufficient transport of ions, electrons, O2 and other reactants in the process of ORR. The results indicated that a facile and feasible sonochemical route could be used to prepare highly active porous MnO2 electrocatalyst for ORR, which might be promising for direct methanol fuel cells.

  10. MnO nanoparticles as the cause of ferromagnetism in bulk dilute Mn-doped ZnO

    Science.gov (United States)

    Lançon, Diane; Nilsen, Gøran J.; Wildes, Andrew R.; Nemkovski, Kirill; Huang, Ping; Fejes, Dóra; Rønnow, Henrik M.; Magrez, Arnaud

    2016-12-01

    We show that the observed ferromagnetic behavior of ZnO lightly doped with Mn coincides with the presence of MnO nanoparticles, whereas cluster-free Mn doped ZnO behaves paramagnetically. This conclusion is reached by a study of the structural and magnetic properties of powdered samples of (Mnx,Zn1-x)O with x ≤ 0.033 using polarized neutron scattering. Two types of samples were synthesized via, respectively, a solid state method and the decomposition of hydrozincite. Further characterization has been performed using standard X-ray diffraction and magnetization measurements. The results show evidence for the formation of MnO nanoparticles in the highest doped samples for both synthesis methods, with a ferromagnetic behavior attributed to uncompensated Mn2+ in the MnO nanoparticles. The lower Mn-doped samples showed no evidence for structural segregation or magnetic correlations and showed only a paramagnetic behaviour.

  11. Analysis of Swainsonine and Swainsonine N-Oxide as Trimethylsilyl Derivatives by Liquid Chromatography-Mass Spectrometry and Their Relative Occurrence in Plants Toxic to Livestock.

    Science.gov (United States)

    Gardner, Dale R; Cook, Daniel

    2016-08-10

    There are limited data concerning the occurrence of swainsonine N-oxide in plants known to contain swainsonine and its relative impact on toxicity of the plant material. A liquid chromatography-mass spectrometry method based on a solvent partitioning extraction procedure followed by trimethylsilylation and analysis using reversed phase high-pressure liquid chromatography-mass spectrometry was developed for the analysis of swainsonine and its N-oxide. The concentrations of each were measured in several swainsonine-containing taxa as well as two endophytic isolates that produce swainsonine. In vegetative samples the relative percent of N-oxide to free base ranged from 0.9 to 18%. In seed samples the N-oxide to free base ratio ranged from 0 to 10%. The measured concentrations of swainsonine N-oxide relative to swainsonine only slightly increases the actual toxicity of the various plant samples in a combined assay of both compounds.

  12. Recovery of MnO2 from a spent alkaline battery leach solution via ozone treatment

    Science.gov (United States)

    Cruz-Díaz, Martín R.; Arauz-Torres, Yennifer; Caballero, Francisco; Lapidus, Gretchen T.; González, Ignacio

    2015-01-01

    This work investigates the reaction rate of Mn(II) to generate solid manganese dioxide (MnO2) as a function of the gaseous ozone mass flow rate (27.5-77 g h-1). The experimental studies were carried out in a semi-continuous reactor, using a synthetic solution (300 mL of 1 M H2SO4 with 6000 ppm of Mn(II) added as MnSO4) that simulated the composition of an acid leaching solution from spent alkaline battery material (SBM). It was observed that at 1.3-1.45 V/SHE and pH < 1.0 a selective formation of MnO2 powder was obtained; at values greater than 1.45 V/SHE, permanganate ion (MnO41-) was formed. On the other hand, a linear relation was perceived between the volumetric mass transfer coefficient (kLa) and the ozone mass flow rate (19.3-77 g h-1 in 600 mL of the 1 M H2SO4 solution). The rate constant (k) was determined in the presence and absence of nonporous plastic spheres (D = 3 mm). In both cases the rate of Mn(II) conversion increased proportionally with the ozone mass flow rate, although the conversions obtained with non-porous plastic spheres (x = 82%) were always higher than those without non-porous plastic spheres (x = 72%). A pseudo-homogenous mass transfer model adequately approximated the experimental data.

  13. Magnetocaloric effect in sandwich structures of La1- x K x MnO3 manganites

    Science.gov (United States)

    Gamzatov, A. G.; Aliev, A. M.; Kamilov, I. K.; Kaul', A. R.

    2016-07-01

    This paper reports on the results of the investigation into the magnetocaloric properties of sandwich structures of La1- x K x MnO3 manganites with x = 0.11 (LKM11), 0.13 (LKM13), and 0.15 (LKM15) in magnetic fields of up to 18 kOe. The results of the analysis of the field and temperature dependences of the magnetocaloric effect in the structures LKM11 + LKM13 and LKM13 + LKM15 have demonstrated that the use of sandwich structures increases the efficiency of magnetic cooling in a magnetic field of 18 kOe by 45%.

  14. Kinetics of Reduction of MnO in Molten Slag with Carbon Undersaturated Liquid Iron

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The reduction of MnO in molten slag with carbon undersaturated iron was studied. It was found that the process is affected by the carbon content of molten metal and the temperature. The higher the carbon content and the temperature, the faster both the reduction and the emerging of the hump on curve of ωFeO, the larger the difference betwe en ωFeO, max and ωFeO, e. The phenomena were explained with three-step reaction model.

  15. Development of MnO2 cathode inks for flexographically printed rechargeable zinc-based battery

    Science.gov (United States)

    Wang, Zuoqian; Winslow, Rich; Madan, Deepa; Wright, Paul K.; Evans, James W.; Keif, Malcolm; Rong, Xiaoying

    2014-12-01

    A novel roll-to-roll flexographic printing process for rechargeable zinc-based battery manufacturing was presented in this paper. Based on the fundamental operating mechanism of flexography, key criteria for developing functional flexographic printing inks were established, including composite ink rheology (steady-state viscosity and yield stress), ink wettability as well as ink dispersing qualities. A variety of MnO2 cathode inks were developed and analyzed comprehensively based on these criteria. A novel type of aqueous cathode ink based on PSBR polymeric binder showed excellent flexographic printability as well as promising electrochemical performance.

  16. Effect of dodecylbenzenesulfonate on the electrochemical performance of the MnO2%十二烷基苯磺酸钠对 MnO 2电化学性能影响的研究∗

    Institute of Scientific and Technical Information of China (English)

    陈娜丽; 翁立娟; 冯辉霞; 谭琳; 杨树荣; 王冰

    2015-01-01

    In this paper,manganese oxide (MnO 2 )nanostructures were synthesized by fluid co-precipitation method with surfactant sodium dodecylbenzenesulfonate (SDBS).The effect of SDBS on the structure,mor-phology and electrochemical performance of the as prepared MnO 2 was studied.The structure and morphology of the products were characterized by Fourier transform infrared spectrum (FT-IR),X-ray diffraction (XRD) and scanning electron microscopy (SEM).The electrochemical properties of the as prepared MnO 2 were investi-gated by cyclic voltammetry (CV),galvanostatic charge-discharge (CD)test and electrochemical impedance spectroscopy (EIS)in 1 mol/L Na2 SO 4 aqueous electrolyte.The results showed that SDBS had no significant in-fluence on the crystal structure of the as prepared MnO 2 ,but made the size of the as prepared MnO 2 smaller. As the concentration of SDBS increased,the specific capacitance of the as-obtained MnO 2 first increased and then decreased,and 0.023 mol/L was found to be the optimum impact concentration of SDBS.The MnO 2 syn-thesized under optimum concentration delived a high specific capacitance of 1 93 F/g at the current density of 1 A/g,compared to the 156 F/g of the MnO 2 synthesized without surfactant.%在表面活性剂十二烷基苯磺酸钠(SDBS)存在下,采用液相共沉淀法制备了二氧化锰(MnO 2)电极材料,研究了 SDBS 对其结构、形貌和电化学性能的影响.利用傅利叶变换红外光谱(FT-IR)、X 射线衍射(XRD)、扫描电镜(SEM)对所制备 MnO 2结构和形貌进行了表征.在1 mol/L Na2 SO 4溶液中,通过循环伏安法(CV)、恒电流充放电(CD)和交流阻抗法(EIS)测试了电极材料的电化学性能.结果表明,SDBS 对MnO 2的晶型无明显影响,但使其粒径尺寸减小,形貌发生变化.MnO 2的比电容随 SDBS 浓度的增加先增大后减小,SDBS 浓度为0.023 mol/L 时制得的 MnO 2比电容可达193 F/g(电流密度为1 A/g),而不加 SD-BS 时制得的 MnO 2比电容为156 F/g.

  17. Short-term high-fat diet increases postprandial trimethylamine-N-oxide in humans.

    Science.gov (United States)

    Boutagy, Nabil E; Neilson, Andrew P; Osterberg, Kristin L; Smithson, Andrew T; Englund, Tessa R; Davy, Brenda M; Hulver, Matthew W; Davy, Kevin P

    2015-10-01

    The gut microbiota plays an obligatory role in the metabolism of nutrients containing trimethylamine moieties, such as L-carnitine and choline, leading to the production of the proatherogenic trimethylamine-N-oxide (TMAO). We hypothesized that a short-term, high-fat diet would increase fasting and postprandial plasma concentrations of TMAO in response to a high-fat meal challenge. Following a 2-week eucaloric control diet, 10 nonobese men (18-30 years) consumed a eucaloric, high-fat diet (55% fat) for 5 days. Plasma TMAO was measured after a 12-hour fast and each hour after for 4 hours following a high-fat meal (63% fat) at baseline and after the high-fat diet using ultraperformance liquid chromatography/ tandem mass spectrometry. Fasting plasma TMAO did not increase significantly following the high-fat diet (1.83 ± 0.21 vs 1.6 ± 0.24 μmol/L). However, plasma TMAO was higher at hour 1 (2.15 ± 0.28 vs 1.7 ± 0.30 μmol/L), hour 2 (2.3 ± 0.29 vs 1.8 ± 0.32 μmol/L), hour 3 (2.4 ± 0.34 vs 1.58 ± 0.19 μmol/L), and hour 4 (2.51 ± 0.33 vs 1.5 ± 0.12 μmol/L) (all P fasting plasma TMAO concentrations but appears to increase postprandial TMAO concentrations in healthy, nonobese, young men. Future studies are needed to determine the mechanisms responsible for these observations.

  18. Effect of trimethylamine-N-oxide on pressure-induced dissolution of hydrophobic solute.

    Science.gov (United States)

    Sarma, Rahul; Paul, Sandip

    2012-09-21

    Molecular dynamics simulations are performed to study the effects of increasing trimethylamine-N-oxide (TMAO) concentration on the pressure-induced dissolution of hydrophobic solutes immersed in water. Such systems are of interest mainly because pressure increases the dissolution of hydrophobic protein interior causing protein denaturation and TMAO acts to offset the protein denaturing effect of high hydrostatic pressures. In view of this, in this study, methane molecules are considered as model hydrophobic molecules and simulations are performed for four independent TMAO solutions each at four different pressures ranging from 2 to 8 kbar. From potentials of mean force calculations, it is found that application of pressure reduces the free energy difference between contact minimum (CM) and solvent-separated (SSM) minimum of hydrophobic solute, suggesting dissolution at high pressures. TMAO, on the other hand, increases the relative stability of CM state of methane molecules relative to its SSM state. High packing efficiency of water molecules around the hydrophobic solute at high pressure is observed. Also observed are TMAO-induced enhancement of water structure and direct hydrogen-bonding interaction between TMAO and water and the correlated dehydration of hydrophobic solute. From hydrogen bond properties and dynamics calculations, it is observed that pressure increases average number of water-water hydrogen bonds while reduces their life-times. In contrast, TMAO reduces water-water hydrogen bonding but enhances their life-times. These results suggest that TMAO can reduce water penetration into the protein interior by enhancing water structure and also forming hydrogen bonds with water and hence counteracts protein unfolding.

  19. Toxic effects of strychnine and strychnine N-oxide on zebrafish embryos.

    Science.gov (United States)

    Li, Yu; Qi, Xu; Yang, Yu-Wei; Pan, Yang; Bian, Hui-Min

    2014-10-01

    The application of strychnine (S) is limited due to its toxicity; strychnine N-oxide (SNO) is a derivative of strychnine. The aim was to employ zebrafish embryos to investigate and compare the developmental toxicity induced by S and SNO. The toxicity of S and SNO was examined through the hatching rate and survival rate. Morphological changes of the zebrafish were observed with a dissecting microscope. Apoptosis was detected through acridine orange (AO) staining and flow cytometry. Apoptotic genes were measured by RT-PCR. Embryo malformation was observed in the embryos exposed to S at 200 μmol·L(-1). When SNO concentration was increased to 1 mmol·L(-1), scoliolosis, and pericardial edema could be seen in some embryos. Results from fluorescence microscopy and flow cytometry analysis showed that S at 200 μmol·L(-1) induced apoptosis, whereas the apoptotic rate in the SNO-treated group (200 μmol·L(-1)) was much lower than that in the S group. RT-PCR analysis showed that p53 mRNA expression and the ratio of Bax/Bcl-2 in the S group were significantly altered compared with the control group (*P < 0.05). Moreover, Bax mRNA expression in both S and SNO group were significantly different from that in the control group (**P < 0.01). These results lead to the conclusion that SNO has significantly lower toxicity than S in zebrafish embryos. Copyright © 2014 China Pharmaceutical University. Published by Elsevier B.V. All rights reserved.

  20. Activation of cholera toxin production by anaerobic respiration of trimethylamine N-oxide in Vibrio cholerae.

    Science.gov (United States)

    Lee, Kang-Mu; Park, Yongjin; Bari, Wasimul; Yoon, Mi Young; Go, Junhyeok; Kim, Sang Cheol; Lee, Hyung-Il; Yoon, Sang Sun

    2012-11-16

    Vibrio cholerae is a gram-negative bacterium that causes cholera. Although the pathogenesis caused by this deadly pathogen takes place in the intestine, commonly thought to be anaerobic, anaerobiosis-induced virulence regulations are not fully elucidated. Anerobic growth of the V. cholerae strain, N16961, was promoted when trimethylamine N-oxide (TMAO) was used as an alternative electron acceptor. Strikingly, cholera toxin (CT) production was markedly induced during anaerobic TMAO respiration. N16961 mutants unable to metabolize TMAO were incapable of producing CT, suggesting a mechanistic link between anaerobic TMAO respiration and CT production. TMAO reductase is transported to the periplasm via the twin arginine transport (TAT) system. A similar defect in both anaerobic TMAO respiration and CT production was also observed in a N16961 TAT mutant. In contrast, the abilities to grow on TMAO and to produce CT were not affected in a mutant of the general secretion pathway. This suggests that V. cholerae may utilize the TAT system to secrete CT during TMAO respiration. During anaerobic growth with TMAO, N16961 cells exhibit green fluorescence when stained with 2',7'-dichlorofluorescein diacetate, a specific dye for reactive oxygen species (ROS). Furthermore, CT production was decreased in the presence of an ROS scavenger suggesting a positive role of ROS in regulating CT production. When TMAO was co-administered to infant mice infected with N16961, the mice exhibited more severe pathogenic symptoms. Together, our results reveal a novel anaerobic growth condition that stimulates V. cholerae to produce its major virulence factor.

  1. Characterization of in vitro metabolites of methylenedioxypyrovalerone (MDPV): An N-oxide metabolite formation mediated by flavin monooxygenase.

    Science.gov (United States)

    Kim, In Sook; Rehman, Shaheed Ur; Choi, Min Sun; Jang, Moonhee; Yang, Wonkyung; Kim, Eunmi; Yoo, Hye Hyun

    2016-11-30

    Methylenedioxypyrovalerone (MDPV) has emerged in recent years as a recreational substance with psychostimulant properties. In this study, in vitro metabolites of MDPV were characterized based on liquid chromatography/quadrupole-time-of-flight mass spectrometry (LC/QTOF MS). MDPV was incubated with human liver microsomes, human recombinant cDNA-expressed cytochrome P450 enzymes and flavin monooxygenase (FMO). MDPV was metabolized to yield eight metabolites (M1-M8) with major metabolic reactions such as demethylenation and oxidation. Among them, M6 was assigned as an N-oxide metabolite. FMO was found to be a principal enzyme responsible for the formation of M6; FMO1 and FMO3 were the main enzymes involved in N-oxidation of MDPV. Copyright © 2016 Elsevier B.V. All rights reserved.

  2. In Silico Studies of Quinoxaline-2-Carboxamide 1,4-di-N-Oxide Derivatives as Antimycobacterial Agents

    Directory of Open Access Journals (Sweden)

    Awwad A. Radwan

    2014-02-01

    Full Text Available Molecular modelling studies were performed on some previously reported novel quinoxaline-2-carboxamide 1,4-di-N-oxide derivatives (series 1–9. Using the LigandScout program, a pharmacophore model was developed to further optimize the antimycobacterial activity of this series of compounds. Using the Dock6 program, docking studies were performed in order to investigate the mode of binding of these compounds. The molecular modeling study allowed us to confirm the preferential binding mode of these quinoxaline-2-carboxamide 1,4-di-N-oxide derivatives inside the active site. The obtained binding mode was as same as that of the novobiocin X-ray structure.

  3. Synthesis of Diethyl Pyridin-2-ylphosphonates and Quinolin-2-ylphosphonates by Deoxygenative Phosphorylation of the Corresponding N-Oxides

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Sangjin; Kim, Hyunsoo; Yang, Haewon; Yoo, Byungwoo; Yoon, Cheol Min [Korea Univ., Seoul (Korea, Republic of)

    2014-07-15

    The reaction of pyridine N-oxide and quinoline N-oxide activated by ethyl chloroformate with triethyl phosphites at rt gave the corresponding diethyl pyridin-2-ylphosphonate and diethyl quinolin-2-ylphosphonate regio-selectively in good to excellent yield through oxygenative phosphorylation. The reaction condition is mild and efficient compared to the reported methods. All chemicals including commercially available pyridine N-oxides were purchased from specialized suppliers with analytical purity and used without further purification. Non commercially available pyridine N-oxide for the reaction were prepared by known method. IR spectra of products were recorded on a Perkin-Elmer FT-IR 240-c spectrometer using KBr disks. {sup 1}H NMR (300 MHz) and {sup 13}C NMR (75 MHz) spectra were recorded on a Bruker 300 spectrometer in CDCl{sub 3}. High-resolution ESI-MS spectra were obtained on an IT-TOF (Shimadzu, Japan) at Korea Basic Science Institute (KBSI). Column chromatography was performed using Merck silica gel (230-400 mesh). Some known products have physical, spectroscopic, and analytic data identical to those (shown as a CAS registry number) given in the literature. Dialkyl pyridin-2-ylphosphonates widely used as corrosion inhibitors, dispersing and emulsifying agents, antistatics and lubricant additives in various technological fields are known as potent insecticides, fungicides and herbicides. Pyridin-2-ylphosphonates have also been reported to have a promising cytokinin activity, anti-proliferating and antiplatelet activating factor (anti-PAF) activities, and to be used as a chelate ligand to prepare various metal-organic frameworks, such as polymeric material with Zn, Cd and Ag showing luminescence properties, iron complex as a catalyst and copper complex with weak ferromagnetism. Because biological properties of dialkyl pyridin-2-ylphosphonates and physical properties of their complexes depend both on the phosphorus-containing ligand, simple and efficient

  4. Copper-catalyzed direct amination of quinoline N-oxides via C-H bond activation under mild conditions.

    Science.gov (United States)

    Zhu, Chongwei; Yi, Meiling; Wei, Donghui; Chen, Xuan; Wu, Yangjie; Cui, Xiuling

    2014-04-04

    A highly efficient and concise one-pot strategy for the direct amination of quinoline N-oxides via copper-catalyzed dehydrogenative C-N coupling has been developed. The desired products were obtained in good to excellent yields for 22 examples starting from the parent aliphatic amines. This methodology provides a practical pathway to 2-aminoquinolines and features a simple system, high efficiency, environmental friendliness, low reaction temperature, and ligand, additives, base, and external oxidant free conditions.

  5. Unimolecular decomposition of tetrazine-N-oxide based high nitrogen content energetic materials from excited electronic states

    Science.gov (United States)

    Bhattacharya, A.; Guo, Y. Q.; Bernstein, E. R.

    2009-11-01

    Unimolecular excited electronic state decomposition of novel high nitrogen content energetic molecules, such as 3,3'-azobis(6-amino-1,2,4,5-tetrazine)-mixed N-oxides (DAATO3.5), 3-amino-6-chloro-1,2,4,5-tetrazine-2,4-dioxide (ACTO), and 3,6-diamino-1,2,4,5-tetrazine-1,4-dioxde (DATO), is investigated. Although these molecules are based on N-oxides of a tetrazine aromatic heterocyclic ring, their decomposition behavior distinctly differs from that of bare tetrazine, in which N2 and HCN are produced as decomposition products through a concerted dissociation mechanism. NO is observed to be an initial decomposition product from all tetrazine-N-oxide based molecules from their low lying excited electronic states. The NO product from DAATO3.5 and ACTO is rotationally cold (20 K) and vibrationally hot (1200 K), while the NO product from DATO is rotationally hot (50 K) and vibrationally cold [only the (0-0) vibronic transition of NO is observed]. DAATO3.5 and ACTO primarily differ from DATO with regard to molecular structure, by the relative position of oxygen atom attachment to the tetrazine ring. Therefore, the relative position of oxygen in tetrazine-N-oxides is proposed to play an important role in their energetic behavior. N2O is ruled out as an intermediate precursor of the NO product observed from all three molecules. Theoretical calculations at CASMP2/CASSCF level of theory predict a ring contraction mechanism for generation of the initial NO product from these molecules. The ring contraction occurs through an (S1/S0)CI conical intersection.

  6. Mechanism of porcine liver xanthine oxidoreductase mediated N-oxide reduction of cyadox as revealed by docking and mutagenesis studies.

    Directory of Open Access Journals (Sweden)

    Chigang Chen

    Full Text Available Xanthine oxidoreductase (XOR is a cytoplasmic molybdenum-containing oxidoreductase, catalyzing both endogenous purines and exogenous compounds. It is suggested that XOR in porcine hepatocytes catalyzes the N-oxide reduction of quinoxaline 1,4-di-N-oxides (QdNOs. To elucidate the molecular mechanism underlying this metabolism, the cDNA of porcine XOR was cloned and heterologously expressed in Spodoptera frugiperda insect cells. The bovine XOR, showing sequence identity of 91% to porcine XOR, was employed as template for homology modeling. By docking cyadox, a representative compound of QdNOs, into porcine XOR model, eight amino acid residues, Gly47, Asn352, Ser360, Arg427, Asp430, Asp431, Ser1227 and Lys1230, were located at distances of less than 4Å to cyadox. Site-directed mutagenesis was performed to analyze their catalytic functions. Compared with wild type porcine XOR, G47A, S360P, D431A, S1227A, and K1230A displayed altered kinetic parameters in cyadox reduction, similarly to that in xanthine oxidation, indicating these mutations influenced electron-donating process of xanthine before subsequent electron transfer to cyadox to fulfill the N-oxide reduction. Differently, R427E and D430H, both located in the 424-434 loop, exhibited a much lower K(m and a decreased V(max respectively in cyadox reduction. Arg427 may be related to the substrate binding of porcine XOR to cyadox, and Asp430 is suggested to be involved in the transfer of electron to cyadox. This study initially reveals the possible catalytic mechanism of porcine XOR in cyadox metabolism, providing with novel insights into the structure-function relationship of XOR in the reduction of exogenous di-N-oxides.

  7. A successive ionic layer adsorption and reaction (SILAR) method to fabricate a layer-by-layer (LbL) MnO2-reduced graphene oxide assembly for supercapacitor application

    Science.gov (United States)

    Jana, Milan; Saha, Sanjit; Samanta, Pranab; Murmu, Naresh Chandra; Kim, Nam Hoon; Kuila, Tapas; Lee, Joong Hee

    2017-02-01

    A facile, cost effective and additive-free successive ionic layer adsorption and reaction (SILAR) technique is demonstrated to develop layer-by-layer (LbL) assembly of reduced graphene oxide (RGO) and MnO2 (MnO2-RGOSILAR) on a stainless steel current collector, for designing light-weight and small size supercapacitor electrode. The transmission electron microscopy and field emission scanning electron microscopy images shows uniform distribution of RGO and MnO2 in the MnO2-RGOSILAR. The LbL (MnO2-RGOSILAR) demonstrates improved physical and electrochemical properties over the hydrothermally prepared MnO2-RGO (MnO2-RGOHydro). The electrochemical environment of MnO2-RGOSILAR is explained by constant phase element in the high frequency region, and a Warburg element in the low frequency region in the Z-View fitted Nyquist plot. The equivalent circuit of the MnO2-RGOHydro, displays the co-existence of EDL and constant phase element, indicating inhomogeneous distribution of MnO2 and RGO by the hydrothermal technique. An asymmetric supercapacitor device is designed with MnO2-RGOSILAR as positive electrode, and thermally reduced GO (TRGO) as negative electrode. The designed cell exhibits high energy density of ∼88 Wh kg-1, elevated power density of ∼23,200 W kg-1, and ∼79% retention in capacitance after 10,000 charge-discharge cycles.

  8. Direct electrochemistry and electrocatalysis of horseradish peroxidase in MnO2 nanosheet film

    Institute of Scientific and Technical Information of China (English)

    XIAO Han; WU JinLing; CHEN Xu YANG; WenSheng

    2008-01-01

    A novel material MnO2 nanosheet has been used as the support matrix for the immobilization of horseradish peroxidase (HRP), HRP entrapped in MnO2 nanosheet film exhibits facile direct electron transfer with the electron transfer rate constant of 6.86 s-1, The HRP/MnO2 nanosheet film gives a re-versible redox couple with the apparent formal peak potential (E0) of -0,315 V (vs. Ag/AgCl) in pH 6.5 phosphate buffer solution (PBS). The formal potential E0 of HRP shifts linearly with pH with a slope of -53.75 mV.pH-1, denoting that an electron transfer accompanies single-proton transportation. The immobilized HRP shows an electrocatalytic activity to the reduction of H2O2. The response time of the biosensor for H2O2 is less than 3 s, and the detection limit is 0.21μmol· L-1 based on signal/noise=3.

  9. La substituted Sr 2MnO 4 as a possible cathode material in SOFC

    Science.gov (United States)

    Liping, Sun; Lihua, Huo; Hui, Zhao; Qiang, Li; Pijolat, Christophe

    Sr 2- xLa xMnO 4+ δ (x = 0.4, 0.5, 0.6) oxides were studied as the cathode material for solid oxide fuel cells (SOFC). The reactivity tests indicated that no reaction occurred between Sr 2- xLa xMnO 4+ δ and CGO at annealing temperature of 1000 °C, and the electrode formed good contact with the electrolyte after being sintered at 1000 °C for 4 h. The total electrical conductivity, which has strong effect on the electrode properties, was determined in a temperature range from 100 to 800 °C. The maximum value of 5.7 S cm -1 was found for the x = 0.6 phase at 800 °C in air. The cathode polarization and AC impedance results showed that Sr 1.4La 0.6MnO 4+ δ exhibited the lowest cathode overpotential. The area specific resistance (ASR) was 0.39 Ω cm 2 at 800 °C in air. The charge transfer process is the rate-limiting step for oxygen reduction reaction on Sr 1.4La 0.6MnO 4+ δ electrode.

  10. Nanostructured MnO2 catalyst in E. crassipes (water hyacinth for indigo carmine degradation

    Directory of Open Access Journals (Sweden)

    Tatiana Cuervo Blanco

    2016-11-01

    Full Text Available The use of water hyacinth’s dried matter (Eichhornia crasippes as a support matrix for nano-MnO2 and its application for the removal of indigo carmine (IC was studied. Different pretreatment processes were tested and results indicated that an acid-alkali pretreatment is an efficient method to binding nanoparticles (NPs to cellulosic matrix. In adittion, the MnO2 NPs were synthesized by sonochemical reduction of MnO4- using different methods (ultrasonic horn system, ultrasonic bath and reaction with ethanol, where the influence of the precursor concentration was observed. The synthesized material was further characterized by ATR-IR, AAS, XRD, SEM, nitrogen isotherms adsorption, EDS, and pHpzc. The IC removal capacity of the nanostructured material, the chemical nature of the degradation products and the effect of various parameters (temperature, pH, initial IC concentration, among others were explored in water samples. After this process, the material, obtained by the ultrasonic bath method, was able to remove 97.6% of IC color in five min, without losing dye degradability efficiency for several consecutive cycles. Through this approach, environmental dangerous effluents from many commercial activities such as textile industry can be efficiently removed with low cost, using synthesize process biodegradable nanocomposite materials.

  11. Phonon, magnon and electron contributions to low temperature specific heat in metallic state of La0.85Sr0.15MnO3 and Er0.8Y0.2MnO3 manganites

    Indian Academy of Sciences (India)

    Dinesh Varshney; Irfan Mansuri; E Khan

    2013-12-01

    The reported specific heat \\ () data of the perovskite manganites, La0.85Sr0.15MnO3 and Er0.8Y0.2MnO3, is theoretically investigated in the temperature domain 3 ≤ ≤ 50 K. Calculations of \\ () have been made within the three-component scheme: one is the fermion and the others are boson (phonon and magnon) contributions.Lattice specific heat is well estimated fromthe Debye temperature for La0.85Sr0.15MnO3 and Er0.8Y0.2MnO3 manganites. Fermion component as the electronic specific heat coefficient is deduced using the band structure calculations. Later on, following double-exchange mechanism the role of magnon is assessed towards specific heat and found that at much low temperature, specific heat shows almost T3/2 dependence on the temperature. The present investigation allows us to believe that electron correlations are essential to enhance the density of states over simple Fermi-liquid approximation in the metallic phase of both the manganite systems. The present numerical analysis of specific heat shows similar results as those revealed from experiments.

  12. Decreasing urea∶trimethylamine N-oxide ratios with depth in chondrichthyes: a physiological depth limit?

    Science.gov (United States)

    Laxson, Carrie J; Condon, Nicole E; Drazen, Jeffrey C; Yancey, Paul H

    2011-01-01

    In marine osmoconformers, cells use organic osmolytes to maintain osmotic balance with seawater. High levels of urea are utilized in chondrichthyans (sharks, rays, skates, and chimaeras) for this purpose. Because of urea's perturbing nature, cells also accumulate counteracting methylamines, such as trimethylamine N-oxide (TMAO), at about a 2∶1 urea∶methylamine ratio, the most thermodynamically favorable mixture for protein stabilization, in shallow species. However, previous work on deep-sea teleosts (15 species) and chondrichthyans (three species) found an increase in muscle TMAO content and a decrease in urea content in chondrichthyans with depth. We hypothesized that TMAO counteracts protein destabilization resulting from hydrostatic pressure, as is demonstrated in vitro. Chondrichthyans are almost absent below 3,000 m, and we hypothesized that a limitation in urea excretion and/or TMAO retention might play a role. To test this, we measured the content of major organic osmolytes in white muscle of 13 chondrichthyan species caught with along-contour trawls at depths of 50-3,000 m; the deepest species caught was from 2,165 m. Urea and TMAO contents changed significantly with depth, with urea∶TMAO declining from 2.96 in the shallowest (50-90 m) groups to 0.67 in the deepest (1,911-2,165 m) groups. Urea content was 291-371 mmol/kg in the shallowest group and 170-189 mmol/kg in the deepest group, declining linearly with depth and showing no plateau. TMAO content was 85-168 mmol/kg in the shallowest group and 250-289 mmol/kg in the deepest groups. With data from a previous study for a skate at 2,850 m included, a second-order polynomial fit suggested a plateau at the greatest depths. When data for skates (Rajidae) were analyzed separately, a sigmoidal fit was suggested. Thus, the deepest chondrichthyans may be unable to accumulate sufficient TMAO to counteract pressure; however, deeper-living specimens are needed to fully test this hypothesis.

  13. Injectable silica-permanganate gel as a slow-release MnO4(-) source for groundwater remediation: rheological properties and release dynamics.

    Science.gov (United States)

    Yang, S; Oostrom, M; Truex, M J; Li, G; Zhong, L

    2016-02-01

    Injectable slow-release permanganate gels (ISRPGs), formed by mixing aqueous KMnO4 solution with fumed silica powders, may have potential applications in remediating chlorinated solvent plumes in groundwater. A series of batch, column, and two-dimensional (2-D) flow cell experiments has been completed to characterize the ISRPG and study the release of permanganate (MnO4(-)) under a variety of conditions. The experiments have provided information on ISRPG rheology, MnO4(-) release dynamics and distribution in porous media, and trichloroethene (TCE) destruction by the ISRPG-released oxidant. The gel possesses shear thinning characteristics, resulting in a relatively low viscosity during mixing, and facilitating subsurface injection and distribution. Batch tests clearly showed that MnO4(-) diffused out from the ISRPG into water. During this process, the gel did not dissolve or disperse into water, but rather maintained its initial shape. Column experiments demonstrated that MnO4(-) release from the ISRPG lasted considerably longer than that from an aqueous solution. In addition, due to the longer release duration, TCE destruction by ISRPG-released MnO4(-) was considerably more effective than that when MnO4(-) was delivered using aqueous solution injection. In the 2-D flow cell experiments, it was demonstrated that ISRPGs released a long-lasting, low-concentration MnO4(-) plume potentially sufficient for sustainable remediation in aquifers.

  14. Anti-Mycobacterium tuberculosis agents derived from quinoxaline-2-carbonitrile and quinoxaline-2-carbonitrile 1,4-di-N-oxide.

    Science.gov (United States)

    Ortega, Miguel Angel; Sainz, Yolanda; Montoya, María Elena; Jaso, Andrés; Zarranz, Belén; Aldana, Ignacio; Monge, Antonio

    2002-01-01

    In this paper new quinoxaline derivatives with different substituents in positions 3, 6, 7 and 8 are reported. Their biological activities against Mycobacterium tuberculosis have been assessed and most of the 1,4-di-N-oxide derivatives have been shown to strongly inhibit the bacteria growth in the first in vitro screening. One of these N-oxides (4) is a promising candidate due to its good Selectivity Index (7.95). On the other hand, those compounds without N-oxide moieties showed no or very low activity (growth inhibition: 17% and 39%).

  15. Evaluation of In Vitro Cytochrome P450 Inhibition and In Vitro Fate of Structurally Diverse N-Oxide Metabolites: Case Studies with Clozapine, Levofloxacin, Roflumilast, Voriconazole and Zopiclone.

    Science.gov (United States)

    Giri, Poonam; Naidu, Sneha; Patel, Nirmal; Patel, Harilal; Srinivas, Nuggehally R

    2017-08-01

    The role of metabolite(s) to elicit potential clinical drug-drug interaction (DDI) via cytochrome P450 enzymes (CYP) is gaining momentum. In this context, the role of N-oxides for in vitro CYP inhibition has not been evaluated. The objectives of this study were: (a) to examine in vitro CYP inhibition of N-oxides of clozapine, levofloxacin, roflumilast, voriconazole and zopiclone in a tiered approach and (b) evaluate in vitro fate of aforementioned N-oxides examined in recombinant CYPs, human microsomes and hepatocytes. CYP enzymes evaluated in the work included: CYP1A2, 2B6, 2C9, 2C19, 2D6 and 3A4 using standard procedures for incubation with appropriate probe substrates. The initial cutoff for CYP inhibition was ≥50% using 2 and 10 µM concentrations of various N-oxide metabolites (Tier 1). IC50 values were constructed for the CYP pathway(s) that showed ≥50% inhibition (Tier 2). In addition, co-incubation of N-oxides with parent was performed to evaluate potentiation of CYP inhibition (Tier 3). N-oxides of clozapine (CYP2B6/2C19) and voriconazole (CYP2C9/3A4) showed CYP inhibition ≥50%. Clozapine-N-oxide inhibited CYP2B6 and CYP2C19 pathways with IC50 of 8.3 and 8.7 µM, respectively. Voriconazole-N-oxide inhibited CYP2B6 and CYP2C19 pathways with IC50 of 10.5 and 11.2 µM, respectively. Co-incubation of clozapine-N-oxide with clozapine potentiated CYP2B6/2C19 pathways; however, incubation of voriconazole-N-oxide with voriconazole did not appear to potentiate the CYP pathways because parent caused an inhibition of almost 80%. None of the N-oxides appeared to further undergo biotransformation as judged by the in vitro metabolic fate experiments (stage 2). Clinical DDI potential of specific CYP enzymes needs to be considered arising due to circulatory concentrations of certain N-oxides depending on the dose size and/or frequency of dosing of the respective parent drugs.

  16. Role of MnO in manganese–borate binary glass systems: a study on structure and thermal properties

    Indian Academy of Sciences (India)

    TOMASZ LEWANDOWSKI; MARCIN ŁAPINSKI; MICHALINA WALAS; MARTA PRZE´SNIAK-WELENC; LESZEK WICIKOWSKI

    2017-09-01

    Structural and thermal properties of $x$MnO−($100−x$)B$_2$O$_3$ (where $x = 40, 50$ and 60 mol%) glass samples have been investigated with the employment of various techniques. Fourier transform infrared spectroscopy results revealed the influence of MnO on glass matrix. Decrease of B–O bond-related band intensities has been observed. MnO addition was found to introduce broken [BO$_2$O$^−$]$_n$ chains. Differential scanning calorimetry (DSC) measurements presented decreasing $T_g$ that indicates depolymerization of glass matrix in the considered compositional range. Moreover, thermal stability (TS) parameter has been evaluated using the DSC technique. It slightly decreased with MnO content. X-ray photoelectron spectroscopy results provided the evidence for Mn$^{2+}$ and Mn$^{3+}$ presence. Multiplet splitting, close to that of MnO, has been observed. It has been concluded that most of the manganese ions existed in the divalent state. Photoluminescence study revealed that manganese ions are tetragonally co-ordinated in a glassy matrix.

  17. Single-layer MnO2 nanosheets for sensitive and selective detection of glutathione by a colorimetric method

    Science.gov (United States)

    Di, Weihua; Zhang, Xiang; Qin, Weiping

    2017-04-01

    The rapid, sensitive and selective detection of glutathione (GSH) is of great importance in the biological systems. In this work, a template-free and one-step method was used to synthesize the single-layer MnO2 nanosheets via a redox reaction. The resulting product was characterized by XRD, TEM, FTIR, XPS and UV-vis absorption. The addition of GSH results in the change of solution color depth owing to the occurrence of a redox reaction between MnO2 and GSH, enabling colorimetric detection of GSH. At a pH of 3.6, the proposed sensor gives a linear calibration over a GSH concentration range of 10-100 μM, with a rapid response of less than 2 min and a low detection limit of 0.5 μM. The relative standard deviation for seven repeated determinations of GSH is lower than 5.6%. Furthermore, the chemical response of the synthesized MnO2 nanosheets toward GSH is selective. Owing to the advantages with good water solubility, rapid response, high sensitivity, good biocompatibility and operation simplicity, this two-dimensional MnO2-based sensing material might be potential for detecting GSH in biological applications.

  18. Carnation-like MnO2 modified activated carbon air cathode improve power generation in microbial fuel cells

    Science.gov (United States)

    Zhang, Peng; Li, Kexun; Liu, Xianhua

    2014-10-01

    Highly active and low-cost electrocatalysts are of great importance for large-scale commercial applications of microbial fuel cells (MFCs). In this work, we prepared an activated carbon (AC) air cathode containing electrodeposited γ-MnO2 using a potentiostatic method. The results indicated that carnation-like MnO2 crystals were bound to the surface of the AC air cathode after a deposition time of 10 min, which greatly improved the performance of the cathode. BET analysis results demonstrated that the electrodeposition of MnO2 decreased the micropore surface area of the cathode but increased the mesopore surface area. When compared with a bare AC air cathode, the electrodeposited MnO2 cathode exhibited higher catalytic activity for oxygen reduction reaction. The maximum power density of the MFC equipped with the electrodeposited MnO2 AC air cathode was 1554 mW m-2, which is 1.5 times higher than the control cathode.

  19. MnO2-Carbon nanotube composite for high-areal-density supercapacitors with high rate performance

    Science.gov (United States)

    Wang, Ke; Gao, Shan; Du, Zhaolong; Yuan, Anbao; Lu, Wei; Chen, Liwei

    2016-02-01

    Practical supercapacitor devices require high areal capacitance and areal power density, and thus demand high utilization of active material and good rate performance under high areal mass loading. However, ion transport in high-mass-loading electrodes can be a challenge, which leads to deteriorate specific capacitance and rate performance. In this paper, a well-dispersed porous MnO2-carbon nanotube (CNT) composite was prepared for use as a supercapacitor electrode material. The small MnO2 nanoparticles and porous CNT network facilitated fast electron/ion transfer kinetics in the electrode. With a mass loading as high as 6.4 mg cm-2 on the electrode, the MnO2-CNT composite exhibited an excellent areal capacitance of 1.0 F cm-2 at 0.2 A g-1 (1.28 mA cm-2), with a retention of 77% even at a high current density of 20 A g-1 (128 mA cm-2). The electrode exhibited a high power density of 45.2 kW kg-1 (0.29 W cm-2) while maintaining a reasonable energy density of 16.7 Wh kg-1 (106 μWh cm-2). No apparent fading was observed even after 3000 charge/discharge cycles at 1 A g-1. This porous and evenly distributed MnO2-CNT composite has great potential for practical applications in supercapacitors.

  20. Critical thickness and orbital ordering in ultrathin La0.7Sr0.3MnO3 films

    NARCIS (Netherlands)

    Huijben, M.; Martin, L.W.; Chu, Y.-H.; Holcomb, M.B.; Yu, P.; Rijnders, G.; Blank, D.H.A.; Ramesh, R.

    2008-01-01

    Detailed analysis of transport, magnetism, and x-ray absorption spectroscopy measurements on ultrathin La0.7Sr0.3MnO3 films with thicknesses from 3 to 70 unit cells resulted in the identification of a lower critical thickness for a nonmetallic nonferromagnetic layer at the interface with the SrTiO3

  1. Exchange biasing of single-domain Ni nanoparticles spontaneously grown in an antiferromagnetic MnO matrix

    Energy Technology Data Exchange (ETDEWEB)

    Shoemaker, Daniel P; Grossman, Madeleine; Seshadri, Ram [Materials Department, Materials Research Laboratory, University of California, Santa Barbara, CA 93106 (United States); Department of Chemistry and Biochemistry, Materials Research Laboratory, University of California, Santa Barbara, CA 93106 (United States)], E-mail: dshoe@mrl.ucsb.edu

    2008-05-14

    Exchange biased composites of ferromagnetic single-domain Ni nanoparticles embedded within and on the surface of large grains of MnO have been prepared by the reduction of Ni{sub x}Mn{sub 3-x}O{sub 4} monoliths in flowing 5% H{sub 2}/N{sub 2}. The Ni precipitates are 20-30 nm in extent, and the majority are completely encased within MnO. The manner in which the Ni nanoparticles are spontaneously formed-starting from a single homogeneous phase-ensures a high degree of dispersion of the Ni and large Ni/MnO interface/volume ratios. The interfaces between ferromagnetic Ni and antiferromagnetic MnO result in magnetic exchange bias below the Neel temperature of MnO. A threefold change in exchange bias fields (from 40 to 120 Oe at 5 K) is observed, depending on the starting Ni content x in the precursor Ni{sub x}Mn{sub 3-x}O{sub 4}, with smaller x values-fewer or smaller Ni nanoparticles-resulting in larger exchange fields. The exchange bias leads to significant hardening of the magnetization, with coercive fields scaling nearly linearly with the exchange field. The strategies outlined here suggest new and simple routes for creating highly interfacial, functional biphasic composites of nanoparticles embedded within or supported on an oxide matrix.

  2. MnO2 prepared by hydrothermal method and electrochemical performance as anode for lithium-ion battery.

    Science.gov (United States)

    Feng, Lili; Xuan, Zhewen; Zhao, Hongbo; Bai, Yang; Guo, Junming; Su, Chang-Wei; Chen, Xiaokai

    2014-01-01

    Two α-MnO2 crystals with caddice-clew-like and urchin-like morphologies are prepared by the hydrothermal method, and their structure and electrochemical performance are characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), galvanostatic cell cycling, cyclic voltammetry, and electrochemical impedance spectroscopy (EIS). The morphology of the MnO2 prepared under acidic condition is urchin-like, while the one prepared under neutral condition is caddice-clew-like. The identical crystalline phase of MnO2 crystals is essential to evaluate the relationship between electrochemical performances and morphologies for lithium-ion battery application. In this study, urchin-like α-MnO2 crystals with compact structure have better electrochemical performance due to the higher specific capacity and lower impedance. We find that the relationship between electrochemical performance and morphology is different when MnO2 material used as electrochemical supercapacitor or as anode of lithium-ion battery. For lithium-ion battery application, urchin-like MnO2 material has better electrochemical performance.

  3. MnO2 prepared by hydrothermal method and electrochemical performance as anode for lithium-ion battery

    Science.gov (United States)

    2014-01-01

    Two α-MnO2 crystals with caddice-clew-like and urchin-like morphologies are prepared by the hydrothermal method, and their structure and electrochemical performance are characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), galvanostatic cell cycling, cyclic voltammetry, and electrochemical impedance spectroscopy (EIS). The morphology of the MnO2 prepared under acidic condition is urchin-like, while the one prepared under neutral condition is caddice-clew-like. The identical crystalline phase of MnO2 crystals is essential to evaluate the relationship between electrochemical performances and morphologies for lithium-ion battery application. In this study, urchin-like α-MnO2 crystals with compact structure have better electrochemical performance due to the higher specific capacity and lower impedance. We find that the relationship between electrochemical performance and morphology is different when MnO2 material used as electrochemical supercapacitor or as anode of lithium-ion battery. For lithium-ion battery application, urchin-like MnO2 material has better electrochemical performance. PMID:24982603

  4. Biocompatible and pH Sensitive PLGA Encapsulated MnO Nanocrystals for Molecular and Cellular MRI

    Science.gov (United States)

    Bennewitz, Margaret F.; Lobo, Tricia L.; Nkansah, Michael K.; Ulas, Gözde; Brudvig, Gary W.; Shapiro, Erik M.

    2011-01-01

    Inorganic manganese based particles are becoming attractive for molecular and cellular imaging, due to their ability to provide bright contrast on MRI, as opposed to the dark contrast generated from iron based particles. Using a single emulsion technique, we have successfully fabricated pH sensitive, poly(lactic-co-glycolic acid) (PLGA) encapsulated manganese oxide (MnO) nanocrystals. Two classes of particles were fabricated at ~ 140 nm and 1.7 μm, and incorporated 15 to 20 nm MnO nanocrystals with high encapsulation efficiencies. Intact particles at physiological pH cause little contrast in MRI, but following endocytosis into low pH compartments within the cells, the particles erode, and MnO dissolves to release Mn2+. This causes the cells to appear bright on MR images. The magnitude of the change in MRI properties is as high as 35-fold, making it the most dynamic ‘smart’ MRI contrast agent yet reported. Possible applications of these MnO particles include slow release Mn2+, tumor targeting, and confirmation of cell uptake. PMID:21495676

  5. Biocompatible and pH-sensitive PLGA encapsulated MnO nanocrystals for molecular and cellular MRI.

    Science.gov (United States)

    Bennewitz, Margaret F; Lobo, Tricia L; Nkansah, Michael K; Ulas, Gözde; Brudvig, Gary W; Shapiro, Erik M

    2011-05-24

    Inorganic manganese-based particles are becoming attractive for molecular and cellular imaging, due to their ability to provide bright contrast on MRI, as opposed to the dark contrast generated from iron-based particles. Using a single emulsion technique, we have successfully fabricated pH-sensitive poly(lactic-co-glycolic acid) (PLGA)-encapsulated manganese oxide (MnO) nanocrystals. Two classes of particles were fabricated at ∼140 nm and 1.7 μm and incorporated 15 to 20 nm MnO nanocrystals with high encapsulation efficiencies. Intact particles at physiological pH cause little contrast in MRI, but following endocytosis into low pH compartments within the cells, the particles erode and MnO dissolves to release Mn(2+). This causes the cells to appear bright on MR images. The magnitude of the change in MRI properties is as high as 35-fold, making it the most dynamic "smart" MRI contrast agent yet reported. Possible applications of these MnO particles include slow release Mn(2+), tumor targeting, and confirmation of cell uptake.

  6. An aqueous rechargeable battery based on zinc anode and Na(0.95)MnO2.

    Science.gov (United States)

    Zhang, Baihe; Liu, Yu; Wu, Xiongwei; Yang, Yaqiong; Chang, Zheng; Wen, Zubiao; Wu, Yuping

    2014-02-07

    An aqueous rechargeable battery system is assembled by using metallic zinc and Na(0.95)MnO2 as the negative and positive electrodes, respectively. It is cheap and environmentally friendly, and its energy density is 78 Wh kg(-1). Its cycling performance is very good with only 8% capacity loss after 1000 cycles at 4 C between 1 and 2 V.

  7. Visual colorimetric sensor array for discrimination of antioxidants in serum using MnO2 nanosheets triggered multicolor chromogenic system.

    Science.gov (United States)

    Huang, Wei; Deng, Yuequan; He, Yi

    2017-05-15

    Here we report a unique visual colorimetric sensor array for discrimination of antioxidants in serum based on MnO2 nanosheets-3,3',5,5'-tetramethylbenzidine (TMB) multicolor chromogenic system. The absorbance values of the system at 370, 450, and 650nm provide three cross-reactive sensing elements. The presence of antioxidant will inhibit the reaction between TMB and MnO2 nanosheets due to the presence of the competitive reaction of MnO2 nanosheets and antioxidants. Different antioxidants containing uric acid, glutathione, ascorbic acid, cysteine, and melatonin have distinct reducing ability, producing a differential inhibition of MnO2 nanosheets-TMB system, and therefore generating distinct colorimetric response patterns at 370, 450, and 650nm. The obtained patterns for each antioxidant at a concentration of 20μM were successfully discriminated using principal component analysis both in buffer and when spiked into fetal bovine serum (FBS). The identification accuracy of 45 unknown samples was found to be 100%. Remarkably, this sensor assay can visually discriminate antioxidants in diluted FBS with the naked eye. Copyright © 2016 Elsevier B.V. All rights reserved.

  8. Preparation of PPy-Coated MnO2 Hybrid Micromaterials and Their Improved Cyclic Performance as Anode for Lithium-Ion Batteries

    Science.gov (United States)

    Feng, Lili; Zhang, Yinyin; Wang, Rui; Zhang, Yanli; Bai, Wei; Ji, Siping; Xuan, Zhewen; Yang, Jianhua; Zheng, Ziguang; Guan, Hongjin

    2017-09-01

    MnO2@PPy core-shell micromaterials are prepared by chemical polymerization of pyrrole on the MnO2 surface. The polypyrrole (PPy) is formed as a homogeneous organic shell on the MnO2 surface. The thickness of PPy shell can be adjusted by the usage of pyrrole. The analysis of SEM, FT-IR, X-ray photoelectron spectroscopy (XPS), thermo-gravimetric analysis (TGA), and XRD are used to confirm the formation of PPy shell. Galvanostatic cell cycling and electrochemical impedance spectroscopy (EIS) are used to evaluate the electrochemical performance as anode for lithium-ion batteries. The results show that after formation of MnO2@PPy core-shell micromaterials, the cyclic performance as anode for lithium-ion batteries is improved. Fifty microliters of PPy-coated caddice-clew-like MnO2 has the best cyclic performances as has 620 mAh g-1 discharge specific capacities after 300 cycles. As a comparison, the discharge specific capacity of bare MnO2 materials falls to below 200 mAh g-1 after 10 cycles. The improved lithium-storage cyclic stability of the MnO2@PPy samples attributes to the core-shell hybrid structure which can buffer the structural expansion and contraction of MnO2 caused by the repeated embedding and disengagement of Li ions and can prevent the pulverization of MnO2. This experiment provides an effective way to mitigate the problem of capacity fading of the transition metal oxide materials as anode materials for (lithium-ion batteries) LIBs.

  9. Correlation between Electroresistance and Magnetoresistance in Slight Oxygen-Deficient Nd0.67Sr0.33MnO3-δ Polycrystalline Ceramics

    Institute of Scientific and Technical Information of China (English)

    YANG Chang-Ping; DENG Heng; CHEN Shun-Sheng; WANG Hao; WEN Zhen-Chao; HAN Xiu-Feng; K. B(a)rnera

    2008-01-01

    A colossal electroresistance effect is found in Nd0.67Sr0.33MnO3-δ polycrystalline ceramics with a very slight oxygen deficiency δ = 0.05. The electroresistance behaviour of Nd0.67Sr0.33MnO3-δ(δ = 0.05) displays the striking similarity to its counterpart magnetoresistance. It reveals that the boundary effect plays an important role in electroresistance and the same physical origin is likely responsible for both magnetoresistance and electroresistance effects in Nd0.67Sr0.33MnO3-δ polycrystals.

  10. Spin-Dependent Electroresistance Behaviour of Nd0.67Sr0.33MnO3-δ(0≤δ≤0.20)

    Institute of Scientific and Technical Information of China (English)

    Zhou Zhihui; Yang Changping; Deng Heng; Yang Fujun

    2007-01-01

    Oxygen deficient Nd0.67Sr0.33MnO3-δ ceramic samples were prepared using conventional ceramic technology. A colossal electroresistance (CER) effect was found in Nd0.67Sr0.33MnO3-δ series. The electrical transport is magnetically coupled and spin-dependent over grain or phase boundaries. Electrical-field-induced changes of the spin array orientations inside of and between the magnetic domains by grain or phase boundaries have to be concluded for the strong electroresistive effect in Nd0.67Sr0.33MnO3-δ series.

  11. MnO2-protected silver nanoparticles: New electromagnetic nanoresonators for Raman analysis of surfaces in basis environment

    Science.gov (United States)

    Abdulrahman, Heman Burhanalden; Kołątaj, Karol; Lenczewski, Paweł; Krajczewski, Jan; Kudelski, Andrzej

    2016-12-01

    The first example of the synthesis of Ag nanoparticles protected by a few nanometers thick layer of MnO2 (Ag@MnO2) has been reported. Synthesized Ag@MnO2 nanoparticles effectively locally enhance the electric field of the incident visible radiation, which allows, for example, for a large enhancement of the efficiency of Raman scattering for species located in the close proximity to such nanostructures. It means that Ag@MnO2 nanoparticles may be used as nanoresonators for shell-isolated nanoparticle-enhanced Raman scattering (SHINERS) measurements. The obtained Ag@MnO2 nanoparticles are almost two orders of magnitude more efficient in enhancing Raman signal than previously used for SHINERS measurements in the alkali environment Au@MnO2 nanostructures. Moreover, in comparison to Ag@SiO2 nanoparticles, which are standard silver nanoresonators for SHINERS experiments, Ag@MnO2 nanoparticles are significantly more stable in the basic conditions. Deposition of the MnO2 layer (by the reduction of KMnO4 with by K2C2O4 in an alkaline condition) on hollow silver nanoparticles (h-Ag) has been also analyzed. Hollow silver shells are significantly less stable than the solid Ag nanostructures and are practically entirely destroyed during the process of the MnO2 deposition. However, in this condition, the majority of h-Ag nanoparticles form agglomerates containing about 101 h-Ag items which are connected by MnO2, and after dissolution of the silver auxiliary templates very regular MnO2 sponge nanostructures with the diameter of 150-300 nm are formed.

  12. 1,4-Di-N-oxide quinoxaline-2-carboxamide: Cyclic voltammetry and relationship between electrochemical behavior, structure and anti-tuberculosis activity

    OpenAIRE

    Moreno-Viguri, E. (Elsa); Perez-Silanes, S. (Silvia); Gouravaram, S. (S.); Macharam, A. (Abinav); Ancizu, S. (Saioa); Torres, E; Aldana, I.; Monge, A; Crawford, P.W. (Philip W.)

    2011-01-01

    To gain insight into the mechanism of action, the redox properties of 37 quinoxaline-2-carboxamide 1,4-di-N-oxides with varying degrees of anti-tuberculosis activity were studied in dimethylformamide (DMF) using cyclic voltammetry and first derivative cyclic voltammetry. For all compounds studied, electrochemical reduction in DMF is consistent with the reduction of the N-oxide functionality to form a radical anion. The influence of molecular structure on reduction potential is addressed and i...

  13. Simultaneous determination of trimethylamine and trimethylamine N-oxide in mouse plasma samples by hydrophilic interaction liquid chromatography coupled to tandem mass spectrometry.

    Science.gov (United States)

    Mi, Si; Zhao, Yuan-Yuan; Jacobs, René L; Curtis, Jonathan M

    2017-02-01

    A method was developed that applies hydrophilic interaction liquid chromatography with tandem mass spectrometry in the multiple reaction monitoring mode to separate and accurately quantify trimethylamine and trimethylamine N-oxide in a single chromatographic run. This was achieved by converting trimethylamine to ethyl betaine, which is less volatile and hence results in greatly improved quantitation. Ethyl betaine also gives a similar response to trimethylamine N-oxide using positive-ion electrospray ionization mass spectrometry. It is readily separated from trimethylamine N-oxide by hydrophilic liquid chromatography in a 5 min run and with improved peak shape compared to underivatized trimethylamine. Validation of the method yielded a limit of detection (S/N ≥ 3) of 0.5 ng/mL for trimethylamine and 0.25 ng/mL for trimethylamine N-oxide. Method accuracies of 91.4-105.3% with precisions of 0.4-5.5% were obtained for standard mixtures over the range of 2.5-500 ng/mL. Recoveries measured for the extraction of trimethylamine and trimethylamine N-oxide spikes into mouse plasma were both >90%. The method, which simultaneously measures trimethylamine and trimethylamine N-oxide, was successfully applied to mouse plasma samples and could be adapted for use with other biological fluids.

  14. Polyhedral C2@Agn cages distorted by ancillary pyridine N-oxide ligands in silver-acetylenediide complexes.

    Science.gov (United States)

    Zhao, Xiao-Li; Zhang, Lin-Ping; Mak, Thomas C W

    2006-07-01

    Reactions of the pyridine N-oxide ligands L, L2 and L3 with the silver acetylenediide-containing system under hydrothermal conditions gave rise to four silver-acetylenediide complexes bearing interesting C2@Agn motifs: (Ag2C2)2(AgCF3CO2)8(L1)3.5 (1), (Ag2C2)2(AgCF3CO2)8(L2)2 (2), (Ag2C2)(AgCF3CO2)4(L3) (3) and [(Ag7(C2)(CF3SO3)3(L3)2(H2O)2] x 2CF3SO3 (4) (L = nicotinic acid N-oxide, L(1) = pyridine N-oxide, L2 = 1,2-bis(4-pyridyl)ethane N,N'-dioxide, L3 = 1,3-bis(4-pyridyl)propane N,N'-dioxide), which exhibit new distorted polyhedral C2@Agn cage motifs. Complex 1 has a pair of acetylenediide dianions encapsulated in a Ag(14) aggregate composed of three polyhedral parts, whereas 2 contains an irregular (C2)2@Ag13 double cage. In 3, the basic building unit is a centrosymmetric (C2)2@Ag12 double cage with each component single cage taking the shape of a highly distorted triangulated dodecahedron with one missing vertex. As to complex 4, the core is a C2@Ag7 single cage in the form of a slightly distorted monocapped trigonal prism with four cleaved edges that include all three vertical sides. Furthermore, in the silver-rich environment, the pyO-type ligands are induced to exhibit unprecedented coordination modes, such as the mu(5)-O,O,O,O',O' ligation mode of L2 in 2 and the mu4-O,O,O',O' mode of L3 in 3 and 4.

  15. New complexes of cobalt(II) ions with pyridinecarboxylic acid N-oxides and 4,4‧-byp

    Science.gov (United States)

    Hnatejko, Zbigniew; Dutkiewicz, Grzegorz; Kubicki, Maciej; Lis, Stefan

    2013-02-01

    This paper reports a study concerning the isolation and characterization of mixed ligand complexes of the Co(II) ions with pyridinecarboxylic acids N-oxides (picolinic (PNO), nicotinic (NNO) and isonicotinic (INO)), [Co(PNO)2(4,4'-byp)]·6H2O 1, [Co(NNO)(4,4'-byp)NO3]·8H2O 2 and [Co(INO)(4,4'-byp)NO3]·7H2O 3; (4,4'-byp = 4,4'-bipyridine). The complexes 2 and 3 were prepared by the hydrothermal synthesis. The structures of the complexes were elucidated on the basis of elemental analysis, thermal decomposition, IR and mass spectroscopy. IR spectra show that N-oxides act as bidentate ligands, in which both the N-oxide and the carboxylate groups are involved in coordination. In 2 and 3 the Co(II) ion exists in the same coordination environment. For 1, the X-ray crystal structure has been determined and it turned out that it contains the coordination polymers, created by the chains of Co ions joined by 4,4'-byp ligands. The Co(II) ion occupies the center of symmetry in the space group C2/c. This ion is coordinated by two nitrogen atoms (from two 4,4'-byp ligands) and four oxygen atoms from two PNO anions. The extensive network of hydrogen bonds involving six different water molecules connects the one-dimensional polymers into three-dimensional crystal structure.

  16. Two nitro derivatives of azabenzo[a]pyrene N-oxide: Electronic properties and their relation to mutagenic activity

    Energy Technology Data Exchange (ETDEWEB)

    Ostojić, Bojana D., E-mail: bostojic@chem.bg.ac.rs; Đorđević, Dragana S.

    2015-03-21

    Highlights: • Molecular properties of nitro isomers of azabenzo[a]pyrene N-oxide are investigated. • Stability, ionization potential, electron affinity, and polarizability are determined. • High quality DFT methods are employed. • Nitroreduction, oxidation, and polarizability are not crucial for mutagenicity. • Dipole moment and electronic charge distribution are important for characterization. - Abstract: The equilibrium geometries, relative energies, IR and Raman spectra, vertical ionization potentials (IP), vertical electron affinities (EA), dipole moments (μ), electronic dipole polarizabilities (α), and molecular electrostatic potentials (MEP) of two species that show very high mutagenicity, 1-nitro-6-azabenzo[a]pyrene N-oxide (1-N-6-ABPO) and 3-nitro-6-azabenzo[a]pyrene N-oxide (3-N-6-ABPO), are investigated by means of Density Functional Theory (DFT) using B3LYP functional with different basis sets. The 3-N-6-ABPO isomer was estimated to be much more mutagenic in Salmonella typhimurium tester strain TA98 (396 000 revertants/nmol) than 1-N-6-ABPO (36 100 revertants/nmol) (Fukuhara et al., 1992). The results show that for both isomers the structural, energetic, and vibrational properties are similar. The orientation of the nitro group with respect to the plane of the aromatic system as well as the nitroreduction and oxidation reaction and polarizability seem not be important for the determination of different mutagenic behavior of these isomers. However, the dipole moment of 3-N-6-ABPO is about 3 times that of 1-N-6-ABPO. The larger dipole moment and the different electronic charge distribution of 3-N-6-ABPO compared to 1-N-6-ABPO imply stronger electrostatic and inductive molecular interactions so that the active site of the enzyme involved in the mutagenic activation can more effectively bind 3-N-6-ABPO compared to 1-N-6-ABPO.

  17. Floating zone growth of α-Na0.90MnO2 single crystals

    Science.gov (United States)

    Dally, Rebecca; Clément, Raphaële J.; Chisnell, Robin; Taylor, Stephanie; Butala, Megan; Doan-Nguyen, Vicky; Balasubramanian, Mahalingam; Lynn, Jeffrey W.; Grey, Clare P.; Wilson, Stephen D.

    2017-02-01

    Single crystal growth of α-NaxMnO2 (x=0.90) is reported via the floating zone technique. The conditions required for stable growth and intergrowth-free crystals are described along with the results of trials under alternate growth atmospheres. Chemical and structural characterizations of the resulting α-Na0.90MnO2 crystals are performed using ICP-AES NMR, XANES, XPS, and neutron diffraction measurements. As a layered transition metal oxide with large ionic mobility and strong correlation effects, α-NaxMnO2 is of interest to many communities, and the implications of large volume, high purity, single crystal growth are discussed.

  18. Interpretation of the pre-edge X-ray absorption fine structures in MnO

    Institute of Scientific and Technical Information of China (English)

    LI Shu-Jun; HU Rong; HU Tian-Dou; XIE Ya-Ning; ZHANG Jing; TAO Ye; WU Zi-Yu

    2003-01-01

    The weak pre-edge features in the Mn K-edge X-ray absorption near-edge structure (XANES) spectrumof manganese monoxide (MnO) were investigated by comparing experimental data with dipolar and quadrupolarcross-section calculations in the framework of multiple-scattering theory. We assign the first pre-edge feature to a di-rect quadrupolar transition from Is core state to 3d molecular orbitals of the central atom, e.g., the lowest in energy,due to the more effective attraction of the core hole. The second peak in this region arises unambiguously from thehybridization between p-orbitals of the central atom with higher-shell metal octahedral orbitals.

  19. Nonohmic behavior of SnO2.MnO2-based ceramics

    Directory of Open Access Journals (Sweden)

    Marcelo O. Orlandi

    2003-06-01

    Full Text Available The present paper describes the nonohmic behavior of the SnO2.MnO-based system and analyzes the influence of the sintering time and the Nb2O5 concentration on this system's electrical properties. A nonlinear coefficient of ~7 was obtained for a 0.2 mol%-doped Nb2O5 composition, which is comparable to other values reported in the literature for the ternary SnO2-based systems. A recent barrier formation model proposed in the literature to explain the nonlinear electrical behavior of SnO2-based systems is used to clarify the role of the MnO constituent in the formation of the barrier, taking into account the influence of segregated atoms, precipitated phase and oxygen species in the grain boundary region.

  20. Polydopamine and MnO2 core-shell composites for high-performance supercapacitors

    Science.gov (United States)

    Hou, Ding; Tao, Haisheng; Zhu, Xuezhen; Li, Maoguo

    2017-10-01

    Polydopamine and MnO2 core-shell composites (PDA@MnO2) for high-performance supercapacitors had been successfully synthesized by a facile and fast method. The morphology, crystalline phase and chemical composition of PDA@MnO2 composites are characterized using SEM, TEM, XRD, EDS and XPS. The performance of PDA@MnO2 composites are further investigated by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy in 1 M Na2SO4 electrolyte. The PDA@MnO2 core-shell nanostructure composites exhibit a high capacitance of 193 F g-1 at the current density of 1A g-1 and retained over 81.2% of its initial capacitance after 2500 cycles of charge-discharge at 2 A g-1. The results manifest that the PDA@MnO2 composites can be potentially applied in supercapacitors.

  1. Phonon spectra of La0.5Ca0.5MnO3

    Institute of Scientific and Technical Information of China (English)

    Cao Xian-Sheng; Chen Chang-Le

    2009-01-01

    This paper presents a microscopic theory to explain different Raman modes of La0.5Ca0.5MnO3 based on the electronic Hamiltonian of the Kondo lattice model, which adds phonon interaction to the hybridization between the conduction electrons of the system and the l-electrons. The spectral density is calculated by the Green function technique of Zubarev at zero wave vector and in the low temperature limit. It finds that there are three Raman-active modes and the spectral densities of these modes are substantially influenced by model parameters such as the position of Mevel (εJT), the effective electron-phonon coupling strength (g) and the hybridization parameter (v). Finally, the intensity changes of those peaks are investigated.

  2. MnO2-Based Electrochemical Supercapacitors on Flexible Carbon Substrates

    Science.gov (United States)

    Tadjer, Marko J.; Mastro, Michael A.; Rojo, José M.; Mojena, Alberto Boscá; Calle, Fernando; Kub, Francis J.; Eddy, Charles R.

    2014-04-01

    Manganese dioxide films were grown on large area flexible carbon aerogel substrates. Characterization by x-ray diffraction confirmed α-MnO2 growth. Three types of films were compared as a function of hexamethylenetetramine (HMTA) concentration during growth. The highest concentration of HM TA produced MnO2 flower-like films, as observed by scanning electron microscopy, whose thickness and surface coverage lead to both a higher specific capacitance and higher series resistance. Specific capacitance was measured to be 64 F/g using a galvanostatic setup, compared to the 47 F/g-specific capacitance of the carbon aerogel substrate. Such supercapacitor devices can be fabricated on large area sheets of carbon aerogel to achieve high total capacitance.

  3. Nanostructured MnO2-Based Cathodes for Li-Ion/Polymer Cells

    Science.gov (United States)

    Skandan, Ganesh; Singhal, Amit

    2005-01-01

    Nanostructured MnO2-based cathodes for Li-ion/polymer electrochemical cells have been investigated in a continuing effort to develop safe, high-energy-density, reliable, low-toxicity, rechargeable batteries for a variety of applications in NASA programs and in mass-produced commercial electronic equipment. Whereas the energy densities of state-of-the-art lithium-ion/polymer batteries range from 150 to 175 W h/kg, the goal of this effort is to increase the typical energy density to about 250 W h/kg. It is also expected that an incidental benefit of this effort will be increases in power densities because the distances over which Li ions must diffuse through nanostructured cathode materials are smaller than those through solid bulk cathode materials.

  4. Synthesis and Antiplasmodial Activity of 3-Furyl and 3-Thienylquinoxaline-2-carbonitrile 1,4-Di-N-oxide Derivatives

    Directory of Open Access Journals (Sweden)

    Antonio Monge

    2008-01-01

    Full Text Available The aim of this study was to identify new compounds active againstPlasmodium falciparum based on our previous research carried out on 3-phenylquinoxaline-2-carbonitrile 1,4-di-N-oxide derivatives. Twelve compounds weresynthesized and evaluated for antimalarial activity. Eight of them showed an IC50 less than 1 μMagainst the 3D7 strain. Derivative 1 demonstrated high potency (IC50= 0.63 μM and goodselectivity (SI=10.35, thereby becoming a new lead-compound.

  5. Unexpected Reduction of Ethyl 3-Phenylquinoxaline-2- carboxylate 1,4-Di-N-oxide Derivatives by Amines

    Directory of Open Access Journals (Sweden)

    Antonio Monge

    2008-01-01

    Full Text Available The unexpected tendency of amines and functionalized hydrazines to reduceethyl 3-phenylquinoxaline-2-carboxylate 1,4-di-N-oxide (1 to afford a quinoxaline 1c andmono-oxide quinoxalines 1a and 1b is described. The experimental conditions werestandardized to the use of two equivalents of amine in ethanol under reflux for two hours,with the aim of studying the distinct reductive profiles of the amines and thechemoselectivity of the process. With the exception of hydrazine hydrate, which reducedcompound 1 to a 3-phenyl-2-quinoxalinecarbohydrazide derivative, the amines only actedas reducing agents.

  6. Quinoxaline N-oxide containing potent angiotensin II receptor antagonists: synthesis, biological properties, and structure-activity relationships.

    Science.gov (United States)

    Kim, K S; Qian, L; Bird, J E; Dickinson, K E; Moreland, S; Schaeffer, T R; Waldron, T L; Delaney, C L; Weller, H N; Miller, A V

    1993-08-01

    A series of novel quinoxaline heterocycle containing angiotensin II receptor antagonist analogs were prepared. This heterocycle was coupled to the biphenyl moiety via an oxygen atom linker instead of a carbon atom. Many of these analogs exhibit very potent activity and long duration of effect. Interestingly, the N-oxide quinoxaline analog was more potent than the nonoxidized quinoxaline as in the comparison of compounds 5 vs 30. In order to improve oral activity, the carboxylic acid function of these compounds was converted to the double ester. This change did result in an improvement in oral activity as represented by compound 44.

  7. Brief Report: Intestinal Microbiota-Produced Trimethylamine-N-Oxide and Its Association With Coronary Stenosis and HIV Serostatus.

    Science.gov (United States)

    Miller, P Elliott; Haberlen, Sabina A; Brown, Todd T; Margolick, Joseph B; DiDonato, Joseph A; Hazen, Stanley L; Witt, Mallory D; Kingsley, Lawrence A; Palella, Frank J; Budoff, Matthew; Jacobson, Lisa P; Post, Wendy S; Sears, Cynthia L

    2016-05-01

    Recent evidence has shown a complex relationship between the gut microbiota, dietary nutrients, and cardiovascular disease (CVD). Trimethylamine-N-oxide (TMAO) production, initiated by the microbiota, has been associated with CVD events. We sought to test if this association exists in HIV-infected persons. After adjusting for aspirin use and CVD risk factors, HIV-infected men were more likely to have coronary stenosis in the second and third TMAO quartiles compared with the first quartile, but did not differ significantly in the fourth quartile. We found an inverted U-shaped association between TMAO levels and the presence of coronary artery stenosis among HIV-infected men.

  8. Molecular and component volumes of N,N-dimethyl-N-alkylamine N-oxides in DOPC bilayers

    DEFF Research Database (Denmark)

    Belicka, Michal; Klacsova, Maria; Karlovska, Janka

    2014-01-01

    The volumetric properties of fluid bilayers formed of dioleoylphosphatidylcholine (DOPC) with incorporated N ,N -dimethyl-N -alkylamine N -oxides (Cn NO, n = 6, 10–18 is the even number of carbons in alkyl chain) were studied by vibrating tube densitometry in the temperature interval from 20 °C...... to 50 °C. It was found that the DOPC and Cn NO mixed ideally in the investigated composition range and hence the molecular volumes of DOPC (V DOPC) and incorporated Cn NO (V CnNO) were constant and additive within error limits. From the temperature dependencies of the molecular volumes of DOPC and Cn...

  9. Pyridine N-Oxide vs Pyridine Substrates for Rh(III)-Catalyzed Oxidative C-H Bond Functionalization.

    Science.gov (United States)

    Neufeldt, Sharon R; Jiménez-Osés, Gonzalo; Huckins, John R; Thiel, Oliver R; Houk, K N

    2015-08-12

    The origin of the high reactivity and site selectivity of pyridine N-oxide substrates in O-pivaloyl hydroxamic acid-directed Rh(III)-catalyzed (4+2) annulation reactions with alkynes was investigated computationally. The reactions of the analogous pyridine derivatives were previously reported to be slower and to display poor site selectivity for functionalization of the C(2)-H vs the C(4)-H bonds of the pyridine ring. The N-oxide substrates are found to be more reactive overall because the directing group interacts more strongly with Rh. For N-oxide substrates, alkyne insertion is rate-limiting and selectivity-determining in the reaction with a dialkyl alkyne, but C-H activation can be selectivity-determining with other coupling partners such as terminal alkynes. The rates of reaction with a dialkyl alkyne at the two sites of a pyridine substrate are limited by two different steps: C-H activation is limiting for C(2)-functionalization, while alkyne insertion is limiting for C(4)-functionalization. Consistent with the observed poor site selectivity in the reaction of a pyridine substrate, the overall energy barriers for functionalization of the two positions are nearly identical. High C(2)-selectivity in the C-H activation step of the reaction of the N-oxide is due to a cooperative effect of the C-H Brønsted acidity, the strength of the forming C-Rh bond, and intramolecular electrostatic interactions between the [Rh]Cp* and the heteroaryl moieties. On the other hand, some of these forces are in opposition in the case of the pyridine substrate, and C(4)-H activation is moderately favored overall. The alkyne insertion step is favored at C(2) over C(4) for both substrates, and this preference is largely influenced by electrostatic interactions between the alkyne and the heteroarene. Experimental results that support these calculations, including kinetic isotope effect studies, H/D exchange studies, and results using a substituted pyridine, are also described.

  10. Chlorido(dimethyl sulfoxide(pyridine-2-thiolato N-oxide-κ2S,Oplatinum(II

    Directory of Open Access Journals (Sweden)

    Dieter Schollmeyer

    2008-07-01

    Full Text Available The asymmetric unit of the title compound, [Pt(C5H4NOSCl(C2H6OS], contains two independent complex molecules having similar geometries. Each PtII atom is four-coordinated in a distorted square-planar geometry by S and O atoms of one pyridine N-oxide ligand, the S atom of one dimethyl sulfoxide molecule and one terminal Cl− ion. The molecules are linked into a three-dimensional framework by C—H...O and C—H...Cl hydrogen bonds.

  11. Recovery of Mn as MnO2 from spent batteries leaching solutions

    Directory of Open Access Journals (Sweden)

    Manciulea A. L.

    2013-04-01

    Full Text Available The recycling of spent batteries and recovery of metals from them is of great scientific and economic interest, on account of recycling requirement of these wastes and recovery of valuable materials (De Michellis et al., 2007. Usage of recycled materials is diminishing the energy consumption and pollution. It is important that the recycling process to be environmentally friendly, practical and cost-effective. Tests for the process of manganese removal from spent battery leaching solutions, with ammonium peroxodisulfate, prior to recovery of zinc by electrolysis are presented. The experiments were carried out according to a 23 full factorial design as a function of ammonium peroxodisulfate concentration, temperature and pH. Because the excessive manganese in the spent batteries leach solutions can cause problems in the process of Zn recovery by electrolysis the main focus of this study is the manganese removal without altering the concentration of zinc in solutions. Data from XRF and AAS during the reaction at different time are presented. Manganese is obtained with high extraction degree as MnO2, which is economic and commercial important with applications in battery industry, water treatment plants, steel industry and chemicals (Pagnanelli et al., 2007. The analysis of variance (ANOVA was carried out on the extraction yields of Zn after 30min, 1h, 2h and 3h of reaction. The preliminary results denoted that by chemical oxidation with ammonium peroxodisulfate is a suitable method for manganese removal as MnO2 prior zinc recovery by electrolysis, from spent batteries solutions and it could be used in a plant for recycling batteries.

  12. A new concept for high-cycle-life LEO: Rechargeable MnO2-hydrogen

    Science.gov (United States)

    Appleby, A. John; Dhar, Y. J.; Murphy, O. J.; Srinivasan, Supramaniam

    1989-01-01

    The nickel-hydrogen secondary battery system is now the one of choice for use in GEO satellites. It offers superior energy density to that of nickel-cadmium, with a lifetime that is at least comparable in terms of both cycle life and overall operating life. While the number of deep cycles required for GEO use is small, LEO satellites with long lifetimes (5 to 10 years) will require secondary battery systems allowing 30,000 to 60,000 useful cycles which are characterized by an approximately 2C charge rate and C average discharge rate. Recent work has shown that birnessite MnO2 doped with bismuth oxide can be cycled at very high rates (6C) over a very large number of cycles (thousands) at depths-of-discharge in the 85 to 90 percent range, based on two electrons, which discharge at the same potential in a flat plateau. The potential is about 0.7 V vs. hydrogen, with a cut-off at 0.6 V. At first sight, this low voltage would seem to be a disadvantage, since the theoretical energy density will be low. However, it permits the use of lightweight materials that are immune from corrosion at the positive. The high utilization and low equivalent weight of the active material, together with the use of teflon-bonded graphite for current collection, result in very light positives, especially when these are compared with those in a derated nickel-hydrogen system. In addition, the weight of the pressure vessel falls somewhat, since the dead volume is lower. Calculations show that a total system will have 2.5 times the Ah capacity of a derated nickel-hydrogen LEO battery, so that the energy density, based on 1.2 V for nickel-hydrogen and 0.7 V for MnO2-hydrogen, will be 45 percent higher for comparable cycling performance.

  13. Synthesis, characterization and a thermal (TG-DSC study of gadolinium and lutetium methanesulfonate coordination compounds with pyridine-N-oxide and 2-, 3- and 4-picoline-N-oxides

    Directory of Open Access Journals (Sweden)

    MARIADE F. V. DEMOURA

    2005-09-01

    Full Text Available The synthesis, characterization and a thermal (TG and DSC study of the coordination compounds Gd(MS3·(py-NO2, Gd(MS3·(2-picNO2, Gd(MS3·(3-picNO2, Gd(MS3·(4-picNO2, Lu(MS3·(py-NO2·2H2O, Lu(MS3·(2-picNO1.5·H2O, Lu(MS3·(3-picNO and Lu(MS3·(4-picNO2 are reported (MS = methanesulfonate, py-NO = pyridine-N-oxide, 2-picNO, 3-picNo and 4-picNO are 2-, 3- and 4-picoline-N-oxides, respectively. The observed thermal stability trend is: 2-picNO < py-NO < 4-picNO < 3-picNO for Gd and 2-picNO < 4-picNO < 3-picNO < py-NO for Lu. It was shown that the release of ligand molecules (endothermic is followed by the thermal degradation of the ligands (exothermic.

  14. Determination of strychnine, brucine, strychnine N-oxide, and brucine N-oxide in plasma samples after the oral administration of processed semen strychni extract by high-performance liquid chromatography with ultrasound-assisted mixed cloud point extraction.

    Science.gov (United States)

    Guo, Jun; Meng, Hua; Li, Huang Huang; Wang, Qiao Feng

    2016-07-01

    A sensitive and efficient mixed cloud point extraction combined with high-performance liquid chromatography was developed for the simultaneous separation and determination of four alkaloids (strychnine, strychnine N-oxide, brucine, and brucine N-oxide) in plasma after the oral administration of processed semen strychni extract. Tergitol TMN-6 and cetyl-trimethyl ammonium bromide were chosen as the mixed surfactants, and ultrasound was employed to enhance the extraction efficiency. Some important parameters affecting the mixed cloud point extraction efficiency, such as the content of Tergitol TMN-6 and cetyl-trimethyl ammonium bromide, pH, salt effect, extraction temperature, and ultrasound time were studied and optimized. Under optimum conditions, the linear range of four alkaloids was from 1.0 to 1000 ng/mL. All correlation coefficients of the calibration curves were higher than 0.9993. The intraday and interday precision were below 8.65% and the limits of detection for the four alkaloids were less than 1.0 ng/mL (S/N = 3).

  15. Synthesis, characterization and a thermal (TG-DSC) study of gadolinium and lutetium methanesulfonate coordination compounds with pyridine-N-oxide and 2-, 3- and 4-picoline-N-oxides

    OpenAIRE

    MARIADE F. V. DEMOURA; MATOS, JIVALDO do R.; ROBSON F. DE FARIAS

    2005-01-01

    The synthesis, characterization and a thermal (TG and DSC) study of the coordination compounds Gd(MS)3·(py-NO)2, Gd(MS)3·(2-picNO)2, Gd(MS)3·(3-picNO)2, Gd(MS)3·(4-picNO)2, Lu(MS)3·(py-NO)2·2H2O, Lu(MS)3·(2-picNO)1.5·H2O, Lu(MS)3·(3-picNO) and Lu(MS)3·(4-picNO)2 are reported (MS = methanesulfonate, py-NO = pyridine-N-oxide, 2-picNO, 3-picNo and 4-picNO are 2-, 3- and 4-picoline-N-oxides, respectively). The observed thermal stability trend is: 2-picNO < py-NO < 4-picNO < 3-picNO for Gd and 2-p...

  16. Synthesis and characterization of reduced graphene oxide decorated with CeO2-doped MnO2 nanorods for supercapacitor applications.

    Science.gov (United States)

    Ojha, Gunendra Prasad; Pant, Bishweshwar; Park, Soo-Jin; Park, Mira; Kim, Hak-Yong

    2017-05-15

    A novel and efficient CeO2-doped MnO2 nanorods decorated reduced graphene oxide (CeO2-MnO2/RGO) nanocomposite was successfully synthesized via hydrothermal method. The growth of the CeO2 doped MnO2 nanorods over GO sheets and reduction of GO were simultaneously carried out under hydrothermal treatment. The morphology and structure of as-synthesized nanocomposite were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman spectroscopy, which revealed the formation of CeO2-MnO2 decorated RGO nanocomposites. The electrochemical performance of as-prepared CeO2-MnO2/RGO nanocomposites as an active electrode material for supercapacitor was evaluated by cyclic voltammetry, charge-discharge, and electrochemical impedance spectroscopy (EIS) methods in 2M alkaline medium. The obtained results revealed that as-synthesized CeO2-MnO2/RGO nanocomposite exhibited higher specific capacitance (648F/g) as compared to other formulations (MnO2/RGO nanocomposites: 315.13 F/g and MnO2 nanorods: 228.5 F/g) at the scan rate of 5mV/s. After 1000 cycles, it retained ∼90.4%, exhibiting a good stability. The high surface area, enhanced electrical conductivity, and good stability possess by the nanocomposite make this material a promising candidate to be applied as a supercapacitor electrode.

  17. 3D hierarchical MnO2 nanorod/welded Ag-nanowire-network composites for high-performance supercapacitor electrodes.

    Science.gov (United States)

    Qiao, Zhensong; Yang, Xiaopeng; Yang, Shuhua; Zhang, Liqiang; Cao, Bingqiang

    2016-06-28

    3D MnO2 nanorod/welded Ag-nanowire-network supercapacitor electrodes were prepared. Welding treatment of the Ag nanowire-network leads to low resistance and long lifetime. Galvanostatic charge/discharge (GCD) induces an ever-lasting morphology changing from flower-like to honeycomb-like for MnO2, which manifests as increasing specific capacitance to 663.4 F g(-1) after 7000 GCD cycles.

  18. Graphene oxide electrocatalyst on MnO2 air cathode as an efficient electron pump for enhanced oxygen reduction in alkaline solution

    Science.gov (United States)

    Basirun, Wan Jeffrey; Sookhakian, Mehran; Baradaran, Saeid; Endut, Zulkarnain; Mahmoudian, Mohammad Reza; Ebadi, Mehdi; Yousefi, Ramin; Ghadimi, Hanieh; Ahmed, Sohail

    2015-03-01

    Graphene oxide (GO) was deposited on the surface of a MnO2 air cathode by thermal evaporation at 50°C from a GO colloidal suspension. Fourier transformed infrared spectroscopy and field emission scanning electron microscopy confirmed the presence of GO on the MnO2 air cathode (GO-MnO2). Voltammetry and chrono-amperometry showed increased currents for the oxygen reduction reaction (ORR) in 6 M KOH solution for GO-MnO2 compared to the MnO2 cathode. The GO-MnO2 was used as an air cathode in an alkaline tin-air cell and produced a maximum power density of 13 mW cm-2, in contrast to MnO2, which produced a maximum power density of 9.2 mW cm-2. The electrochemical impedance spectroscopy results suggest that the chemical step for the ORR is the rate determining step, as proposed earlier by different researchers. It is suggested that the presence of GO and electrochemically reduced graphene oxide (ERGO) on the MnO2 surface are responsible for the increased rate of this step, whereby GO and ERGO accelerate the process of electron donation to the MnO2 and to adsorbed oxygen atoms.

  19. Co3O4 nanoparticle-modified MnO2 nanotube bifunctional oxygen cathode catalysts for rechargeable zinc-air batteries

    Science.gov (United States)

    Du, Guojun; Liu, Xiaogang; Zong, Yun; Hor, T. S. Andy; Yu, Aishui; Liu, Zhaolin

    2013-05-01

    We report the preparation of MnO2 nanotubes functionalized with Co3O4 nanoparticles and their use as bifunctional air cathode catalysts for oxygen reduction reaction and oxygen evolution reaction in rechargeable zinc-air batteries. These hybrid MnO2/Co3O4 nanomaterials exhibit enhanced catalytic reactivity toward oxygen evolution reaction under alkaline conditions compared with that in the presence of MnO2 nanotubes or Co3O4 nanoparticles alone.We report the preparation of MnO2 nanotubes functionalized with Co3O4 nanoparticles and their use as bifunctional air cathode catalysts for oxygen reduction reaction and oxygen evolution reaction in rechargeable zinc-air batteries. These hybrid MnO2/Co3O4 nanomaterials exhibit enhanced catalytic reactivity toward oxygen evolution reaction under alkaline conditions compared with that in the presence of MnO2 nanotubes or Co3O4 nanoparticles alone. Electronic supplementary information (ESI) available: Zinc-air cell device, XPS survey scan and power density of the cell. See DOI: 10.1039/c3nr00300k

  20. MnO2 nanorods/3D-rGO composite as high performance anode materials for Li-ion batteries

    Science.gov (United States)

    Liu, Hongdong; Hu, Zhongli; Su, Yongyao; Ruan, Haibo; Hu, Rong; Zhang, Lei

    2017-01-01

    MnO2 nanorods/three-dimensional reduced graphene oxide (3D-rGO) composite has been synthesized by a simple in situ hydrothermal methord. The X-ray diffraction (XRD) pattern of the as-prepared composite reveals tetragonal structure of α-MnO2. Raman spectroscopic and X-ray photoelectron spectroscopy (XPS) of the samples confirm the coexistence of MnO2 and graphene. The Brunauer-Emmett-Teller (BET) analysis shows the large surface area of the composite. The electron microscopy images of the as-synthesized products reveals the MnO2 nanorods are homogeneously grown on 3D-rGO matrix. Electrochemical characterization exhibits the MnO2 nanorods/3D-rGO composite with large reversible capacity (595 mA h g-1 over 60 cycles at 100 mA g-1), high coulombic efficiency (above 99%), excellent rate capability and good cyclic stability. The superior electrochemical performance can be attributed to the turf-like nanostructure of composite, high capacity of MnO2 and superior electrical conductivity of 3D-rGO. It suggests that MnO2 nanorods/3D-rGO composite will be a promising anode material for Li-ion batteries.

  1. Asymmetric Magnetization Reversal Probed by Recoil Loop Measurements in an Exchange QBiased La0.67Sr0.33MnO3/La0.33Ca0.67MnO3 Bilayer Film

    Institute of Scientific and Technical Information of China (English)

    WANG Zhi-Hong; H.-U.HABERMEIER; G.CRISTIANI; SUN Ji-Rong; SHEN Bao-Gen

    2008-01-01

    We exploit the recoil loop measurements to study the asymmetric magnetization reversal in an exchange-biased La0.37Sr0.33MnO3/La0.33 Ca0 67MnO3 bilayer film.It is found that the recoil curve encloses a marked area only in the second quadrant of the hysteresis loop,and the recoil susceptibility in the descending branch of the major loop is evidently higher than that in the ascending branch.The study indicates that the exchange anisotropy of a unidirectional nature and an orientation deviated from the easy axis of the ferromagnetic layer plays a crucial role in creating the reversal asymmetry.

  2. Two nitro derivatives of azabenzo[a]pyrene N-oxide: electronic properties and their relation to mutagenic activity.

    Science.gov (United States)

    Ostojić, Bojana D; Đorđević, Dragana S

    2015-03-21

    The equilibrium geometries, relative energies, IR and Raman spectra, vertical ionization potentials (IP), vertical electron affinities (EA), dipole moments (μ), electronic dipole polarizabilities (α), and molecular electrostatic potentials (MEP) of two species that show very high mutagenicity, 1-nitro-6-azabenzo[a]pyrene N-oxide (1-N-6-ABPO) and 3-nitro-6-azabenzo[a]pyrene N-oxide (3-N-6-ABPO), are investigated by means of Density Functional Theory (DFT) using B3LYP functional with different basis sets. The 3-N-6-ABPO isomer was estimated to be much more mutagenic in Salmonella typhimurium tester strain TA98 (396,000 revertants/nmol) than 1-N-6-ABPO (36100 revertants/nmol) (Fukuhara et al., 1992). The results show that for both isomers the structural, energetic, and vibrational properties are similar. The orientation of the nitro group with respect to the plane of the aromatic system as well as the nitroreduction and oxidation reaction and polarizability seem not be important for the determination of different mutagenic behavior of these isomers. However, the dipole moment of 3-N-6-ABPO is about 3 times that of 1-N-6-ABPO. The larger dipole moment and the different electronic charge distribution of 3-N-6-ABPO compared to 1-N-6-ABPO imply stronger electrostatic and inductive molecular interactions so that the active site of the enzyme involved in the mutagenic activation can more effectively bind 3-N-6-ABPO compared to 1-N-6-ABPO.

  3. Discovery of syn-/anti-cocaine-N-oxide diastereomers in unwashed postmortem hair via LC-MS-MS.

    Science.gov (United States)

    Marsh, Christine M; Crawley, Lindsey R; Himes, Sarah K; Aranda, Roman; Miller, Mark L

    2014-01-01

    The discovery of two cocaine-N-oxide (CNO) diastereomers, syn- and anti-CNO, is reported for the first time. Prior to this study, only one structural form of CNO was known to exist and has not been analyzed in hair before. CNO is a metabolite of cocaine (COC) and may be considered as an additional biomarker of COC use, along with other known COC metabolites. The analysis of COC in hair for forensic applications is under scrutiny due to the possibility of external contamination. A qualitative liquid chromatography-tandem mass spectrometry method was developed, validated and applied to unwashed postmortem hair samples from drug users. The limit of detection in hair was 8 pg/mg (using 10 mg of unwashed hair) for each CNO diastereomer. The presence of both syn- and anti-forms of CNO was verified in vivo using hair samples collected from known COC-using individuals. Due to the low levels of CNO, it will not always be detectable in COC user hair. In the hair samples analyzed, syn-CNO was detected in more samples than anti-CNO. The stereoselective N-oxidation of COC which favors syn-CNO could have a diagnostic value for COC ingestion determination in hair analysis.

  4. Strain dependent magnetocaloric effect in La0.67Sr0.33MnO3 thin-films

    Directory of Open Access Journals (Sweden)

    V. Suresh Kumar

    2013-05-01

    Full Text Available The strain dependent magnetocaloric properties of La0.67Sr0.33MnO3 thin films deposited on three different substrates (001 LaAlO3 (LAO, (001 SrTiO3 (STO, and (001 La0.3Sr0.7Al0.65Ta0.35O9 (LSAT have been investigated under low magnetic fields and around magnetic phase transition temperatures. Compared to bulk samples, we observe a remarkable decrease in the ferromagnetic transition temperature that is close to room temperature, closely matched isothermal magnetic entropy change and relative cooling power values in tensile strained La0.67Sr0.33MnO3 films. The epitaxial strain plays a significant role in tuning the peak position of isothermal magnetic entropy change towards room temperature with improved cooling capacity.

  5. Selective Growth and Structural Analysis of Regular MnO Nanooctapods Bearing Multiple High-Index Surface Facets.

    Science.gov (United States)

    Shin, Dongwoo; Kim, Mijong; Song, Hyunjoon

    2015-08-01

    Although numerous morphologies of MnO nanostructures have been reported, an exact structural analysis and mechanistic study has been lacking. In the present study, the formation of regular MnO octapods was demonstrated in a simple procedure, comprising the thermal decomposition of manganese oleate. Because of their structural uniformity, an ideal three-dimensional model was successfully constructed. The eight arms protruded from the cubic center with tip angles of 38° and surface facets of {311} and {533} with rounded edges. The concentrations of oleate and chloride ions were the determining factors for the octapod formation. Selective coordination of the oleate ions to the {100} faces led to edge growth along the direction, which was then limited by the chloride ions bound to the high-index surface facets. These structural and mechanistic analyses should be helpful for understanding the complex nanostructures and for tuning their structure-related properties.

  6. Oxygen nonstoichiometry and defect equilibrium in Ca1- x Pr x MnO3-δ manganites

    Science.gov (United States)

    Leonidov, I. A.; Konstantinova, E. I.; Markov, A. A.; Merkulov, O. V.; Patrakeev, M. V.; Kozhevnikov, V. L.

    2016-08-01

    The content of oxygen in Ca1- x Pr x MnO3-δ ( x = 0.1) material with perovskite-like structure is determined at 750-950°C and oxygen partial pressures in the gas phase from 3 × 10-6 to 0.55 atm. The regions of existence of orthorhombic, tetragonal, and cubic structural modifications are determined. The equilibrium constants, enthalpies, and entropies of reactions of the formation of defects are determined, allowing us to describe the experimental δ ({p_{{O_2}}}, T) dependences accurately and calculate the concentrations of manganese ions. It is shown that a change in Ca0.9Pr0.1MnO3-δ structure has a considerable effect on the thermodynamic functions of reactions of the formation of defects.

  7. Fabrication and microstructure of nanostructured Mg-3Ni-2MnO_2 by ball milling in hydrogen atmosphere

    Institute of Scientific and Technical Information of China (English)

    FANG Wen-bin; FANG Wa; SUN Hong-fei; YU Zhen-xing

    2009-01-01

    Nanostructured Mg-3Ni-2MnO_2 was synthesized by ball milling elemental powders of Mg, Ni and MnO_2 in hydrogen atmosphere. The microstructures of the powder prepared at different milling time were analyzed by X-ray diffractometry(XRD), scanning electron microscopy(SEM) and high resolution electron microscopy(HREM). The milling time is the most key parameter impacting on the grain size and the microstructure of material. With prolonging the milling time, particle size becomes smaller and smaller. But after the ball milling time reaches about 20 h, reduction of grain size becomes slowly. When the milling time is more than 50 h, nanocrystailine fully forms. When the milling time is more than 80 h, there are more amorphous phases in materials. The average particle diameter of material is about 1 μm and the grain size is 10-30 nm.

  8. Ultrasensitive Glutathione Detection Based on Lucigenin Cathodic Electrochemiluminescence in the Presence of MnO2 Nanosheets.

    Science.gov (United States)

    Gao, Wenyue; Liu, Zhongyuan; Qi, Liming; Lai, Jianping; Kitte, Shimeles Addisu; Xu, Guobao

    2016-08-02

    Glutathione (GSH) is a crucial antioxidant produced endogenously and plays key roles in biological systems. It is vitally important to design simple, selective, and sensitive methods to sense GSH and monitor changes of GSH concentration. In this work, the cathodic electrochemiluminescence (ECL) of lucigenin in the presence of MnO2 nanosheets at a glassy carbon electrode was utilized for GSH detection. GSH can reduce MnO2 nanosheets into Mn(2+) which can obviously inhibit the ECL of lucigenin. The ECL inhibition efficiencies increase linearly with the concentrations of glutathione in the range of 10 to 2000 nM. The detection limit for GSH measurement is 3.7 nM. This proposed method is highly sensitive, selective, simple, fast, and cost-effective. Moreover, this approach can detect GSH in human serum samples with excellent recoveries, which indicates its promising application under physiological conditions.

  9. Modelling multi-MNO business for MVNOs in their evolution to LTE, VoLTE & advanced policy

    OpenAIRE

    COPELAND, Rebecca; Crespi, Noel

    2011-01-01

    International audience; The MVNO (Mobile Virtual Network Operator) business in Europe is maturing, with growing pressure on margins. To cope, MVNOs seek independence and flexibility which they can gain by advanced 4G access agnostic technology. This evolution is supported by three overlapping MVNO models: 4G "Full MVNO", Multi-MNO and "Always Best Connected", which are all enhanced by advanced Policy functions. The paper assesses these models against top ten MVNO success factors and argues th...

  10. Raman study of the antiferromagnetic phase transitions in hexagonal Y MnO3 and LuMnO3

    Science.gov (United States)

    Vermette, J.; Jandl, S.; Mukhin, A. A.; Ivanov, V. Yu; Balbashov, A.; Gospodinov, M. M.; Pinsard-Gaudart, L.

    2010-09-01

    The A1, E1 and E2 Raman active modes in hexagonal Y MnO3 and LuMnO3 single crystals are studied as a function of temperature and compared with previous measurements. In addition to anharmonicity, some phonon frequencies show below TN anomalous temperature dependences that reflect the atomic displacements while some other phonon frequencies are more sensitive to the spin-phonon coupling.

  11. Laser-induced Voltage in La0.85Sr0.015MnO3/Fe Heterostructure

    Institute of Scientific and Technical Information of China (English)

    Kexin JIN; Changle CHEN; Shenggui ZHAO; Yongcang WANG; Zhoumo SONG; Xiao YUAN

    2006-01-01

    The La0.85Sr0.015MnO3/Fe heterostructure deposited on Si (100) substrate was prepared by the magnetron sputtering. The laser-induced voltage in the sample and the difference in the voltage signals between the current-in-plane geometry and current-perpendicular-to-plane geometry at 77 K were investigated.This difference can be attributed to the different transport mechanisms.

  12. Large Magnetic Entropy Effect in La2/3Ca1/3MnO3

    Institute of Scientific and Technical Information of China (English)

    彭振生

    2004-01-01

    The magnetocaloric effect in the colossal magnetoresistance material La2/3Ca1/3MnO3 was studied.From the measurements of temperature dependence of magnetization in various magnetic fields,the large magnetic entropy change associated with the ferromagnetic-paramagnetic transition was discovered.This result suggests that perovskite manganites are suitable candidates as working substance in magnetic refrigeration technology.

  13. Theoretical studies on the photoelectron and absorption spectra of MnO4(-) and TcO4(-).

    Science.gov (United States)

    Su, Jing; Xu, Wen-Hua; Xu, Chao-Fei; Schwarz, W H E; Li, Jun

    2013-09-03

    The tetraoxo pertechnetate anion (TcO4(-)) is of great interest for nuclear waste management and radiopharmceuticals. To elucidate its electronic structure and to compare with that of its lighter congener MnO4(-), the photoelectron and electronic absorption spectra of MnO4(-) and TcO4(-) are investigated with density functional theory (DFT) and ab initio wave function theory (WFT). The vertical electron detachment energies (VDEs) of MnO4(-) obtained with the CR-EOM-CCSD(T) method are in good agreement with the lowest two experimental VDEs; the differences are less than 0.1 eV, representing a significant improvement over the IP-EOM-CCSD(T) result in the literature. Combining our CCSD(T) and CR-EOM-CCSD(T) results, the first five VDEs of TcO4(-) are estimated between 5 and 10 eV with an estimated accuracy of about ±0.2 eV. The vertical excitation energies are determined by using TD-DFT, CR-EOM-CCSD(T), and RAS-PT2 methods. The excitation energies and the assignments of the spectra are analyzed and partly improved. They are compared with reported SAC-CI results and available experimental data. Both dynamic and nondynamic electron correlations are important in the ground and excited states of MnO4(-) and TcO4(-). Nondynamical correlations are particularly relevant in TcO4(-) for reliable prediction of excitation energies. In TcO4(-) one Rydberg state interlaces but does not mix with the valence excited states, and it disappears in the condensed phase.

  14. Electrochemical behavior of nanostructured MnO2/C (Vulcan® composite in aqueous electrolyte LiNO3

    Directory of Open Access Journals (Sweden)

    Vujković Milica

    2011-01-01

    Full Text Available The electrolytic solutions of contemporary Li-ion batteries are made exclusively with the organic solvents since anodic materials of these batteries have potentials with greater negativity than the potential of the water reduction, thus the organic electrolytes can withstand the voltages of 3-5 V that are characteristic for these batteries. Ever since it was discovered that some materials can electrochemically intercalate and deintercalate Li+ ions in aqueous solutions, numerous studies have been conducted with the aim of extending operational time of the aqueous Li-ion batteries. Manganese oxide has been studied as the electrode material in rechargeable lithium-ion batteries with organic electrolytes. In this paper its electrochemical behavior as an anode material in aqueous electrolyte solutions was examined. MnO2 as a component of nanodispersed MnO2/C (Vulcan® composite was successfully synthesized hydrothermally. Electrochemical properties of this material were investigated in aqueous saturated LiNO3 solution by both cyclic voltammetry and galvanostatic charging/discharging (LiMn2O4 as cathode material techniques. The obtained composite shows a relatively good initial discharge capacity of 96.5 mAh/g which, after 50th charging/discharging cycles, drops to the value of 57mAh/g. MnO2/C (Vulcan® composite, in combination with LiMn2O4 as a cathode material, shows better discharge capacity compared to other anodic materials used in aqueous Li-ion batteries according to certain studies that have been conducted. Its good reversibility and cyclability, and the fact that hydrothermal method is simple and effective, makes MnO2/C(Vulcan® composite a promising anodic material for aqueous Li-ion batteries.

  15. Resistance switching mechanism of La0.8Sr0.2MnO3-δ thin films

    Science.gov (United States)

    Luo, X. D.; Gao, R. L.; Fu, C. L.; Cai, W.; Chen, G.; Deng, X. L.; Zhang, H. R.; Sun, J. R.

    2016-02-01

    Effects of oxygen vacancies on the electrical transport properties of oxygen stoichiometric La0.8Sr0.2MnO3 and oxygen-deficient La0.8Sr0.2MnO3-δ films have been investigated. The result presents that the oxygen-deficient films annealed in vacuum show obvious increase of resistance and lattice parameter. With the sweeping voltage or temperature increasing, the resistance exhibits obvious bipolar switching effect, no forming process was needed. Oxygen deficiency in the annealed film leads to the formation of a structural disorder in the Mn-O-Mn conduction channel due to the accumulation of oxygen vacancies under high external electric field or temperatures and hence is believed to be responsible for the bipolar resistance switching effect and the enhanced resistivity compared with oxygen stoichiometric La0.8Sr0.2MnO3 film. These results may be important for practical applications in photoelectric or storage devices and point to a useful direction for other oxidizing materials.

  16. Polarity Switchable Photovoltages in Miscut La0.67Ca0.33MnO3 Films

    Directory of Open Access Journals (Sweden)

    J. Wang

    2012-01-01

    Full Text Available We report the transient laser-induced anomalous photovoltaic effect in the La0.67Ca0.33MnO3 film grown on miscut LaSrAlO4 (001 substrate under 248 nm pulsed laser irradiation at ambient temperature without any applied bias. A photovoltaic pulse signal was observed when the La0.67Ca0.33MnO3 film was irradiated directly, and the signal polarity was reversed when the sample was irradiated through the LaSrAlO4 substrate, while the signal recorded between the two electrodes on the surface of LaSrAlO4 was not reversed when the sample was irradiated through La0.67Ca0.33MnO3 film rather than at the surface of LaSrAlO4. The switchable signal polarity provides a potential application of miscut manganite films as optical components. A possible mechanism is introduced to explain the experiment results.

  17. Dimensionality dependent magnetic and magnetocaloric response of La0.6Ca0.4MnO3 manganite.

    Science.gov (United States)

    Anwar, M S; Ahmed, Faheem; Koo, Bon Heun

    2014-11-01

    We report the sol-gel synthesis and impact of reduced dimensionality on the magnetocaloric properties of La0.6Ca0.4MnO3 manganite. The synthesized powders were characterized by using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and magnetization measurements. The XRD results indicated that the La0.6Ca0.4MnO3 nanoparticles have single phase nature with orthorhombic structure. FE-SEM results suggested that the nanoparticles are agglomerated and crystallite size increases with the annealing temperature. Magnetization measurements show that the La0.6Ca0.4MnO3 nanoparticles exhibit transition temperature (T(c)) below room temperature. The transition temperature was found to increase with the increasing the crystallite size. Maximum in magnetic entropy change, (ΔS(M))(max) shows interesting behaviour and was found to vary with the particle size. At magnetic field of 1 T, the value of (ΔS(M))(max) - 0.13 J/kg K was observed at 213 K for the sample annealed at 600 degrees C. Also, the increment in the value of (ΔS(M))(max) was observed at higher annealing temperature. This study shows that the magnetic entropy of pervoskite manganite can be tuned by tuning the crystallite size of the manganites.

  18. Electrochemical characterization of MnO2 as the cathode material for a high voltage hybrid capacitor

    Institute of Scientific and Technical Information of China (English)

    Jian-ling Li; Fei Gao; Yan Jing; Rui-ying Miao; Ke-zhong Wu; Xin-dong Wang

    2009-01-01

    Manganese dioxide (MnO_2) was prepared using the ultrasonic method. Its electrochemical performance was evaluated as the cathode material for a high voltage hybrid capacitor. And the specific capacitance of the MnO_2 electrode reached 240 F-g-1. The new hybrid capacitor was constructed, combining Al/Al_2O_3 as the anode and MnO_2 as the cathode with electrolyte for the aluminum electrolytic capacitor to solve the problem of low working voltage of a supercapacitor unit. The results showed that the hybrid ca-pacitor had a high energy density and the ability of quick charging and discharging according to the electrochemical performance test. The capacitance was 84.4 μF, and the volume and mass energy densities were greatly improved compared to those of the traditional aluminum electrolytic capacitor of 47 μF. The analysis of electrochemical impedance spectroscopy (EIS) showed that the hybrid ca-pacitor had good impedance characteristics.

  19. Porous graphitic carbon microtubes derived from willow catkins as a substrate of MnO2 for supercapacitors

    Science.gov (United States)

    Zhang, Xiaohua; Zhang, Kang; Li, Hengxiang; Cao, Qing; Jin, Li'e.; Li, Ping

    2017-03-01

    Biomass is receiving considerable attention because of its significant advantages as a sustainable and renewable material. Willow catkins, which have a single-walled microtubular structure are used as both a template and a precursor for synthesizing porous graphitic carbon microtubes (PGCMT) induced by the simultaneous activation-graphitization of K4Fe(CN)6. In addition to providing low-resistant pathways and short ion diffusion channels, as-obtained PGCMT with tubular structure also serves as an ideal platform for anchoring MnO2. The PGCMT/MnO2 composite electrode obtained by MnO2 electrodeposition expressed excellent electrochemical performance, including a significantly enhanced specific capacitance (550.8 F g-1 for the mass of MnO2 at a current density of 2 A g-1), a high capacitance retention of 61.8% even at a high current density of 50 A g-1, and an excellent cycling stability of 89.6% capability retention after 5000 cycles. These findings offer a simple and environmentally friendly strategy for preparing advanced energy materials by utilizing the unique structure of biomass waste from nature.

  20. EFFECT OF MnO2 ADDITIVE ON PERFORMANCES OF NiFe2O4 SPINEL BASED INERT ANODE

    Institute of Scientific and Technical Information of China (English)

    W.L. Jiao; L. Zhang; G. C. Yao

    2005-01-01

    The NiFe2O4 inert anode is synthesized by high-temperature solid-state reaction method using NiO and Fe2O3 as main raw materials and adding MnO2 powder as additive. Archimedes method using water immersion technique is used to measure the sintering performances of samples. The static thermal corrosion rates of samples are measured by weight loss. SEM is employed for the observation of material microstructure, and phase structure of the sample surface after corrosion is determined by XRD. The experimental results indicate that a suitable MnO2additive content is 2%, while the sintering performance is the best, and the static thermal corrosion rate is the lowest. Because of MnO2 dopant enriching at crystal boundary, the corrosion reaction of molten salt to crystal grain creates Mn2AlO4 phase, which is denser than NiFe2O4phase, and prevents the cryolite molten salt to penetrate into the inert anode, thus reducing the corrosion.

  1. Development and Long-Term Stability of a Novel Microbial Fuel Cell BOD Sensor with MnO2 Catalyst

    Science.gov (United States)

    Kharkwal, Shailesh; Tan, Yi Chao; Lu, Min; Ng, How Yong

    2017-01-01

    A novel microbial fuel cell (MFC)-based biosensor was designed for continuous monitoring of biochemical oxygen demand (BOD) in real wastewater. To lower the material cost, manganese dioxide (MnO2) was tested as an innovative cathode catalyst for oxygen reduction in a single chamber air-cathode MFC, and two different crystalline structures obtained during synthesis of MnO2 (namely β- and γ-MnO2) were compared. The BOD sensor was studied in a comprehensive way, using both sodium acetate solution and real domestic wastewater (DWW). The optimal performance of the sensor was obtained with a β-MnO2 catalyst, with R2 values of 0.99 and 0.98 using sodium acetate solution and DWW, respectively. The BOD values predicted by the β-MnO2 biosensor for DWW were in agreement with the BOD5 values, determined according to standard methods, with slight variations in the range from 3% to 12%. Finally, the long-term stability of the BOD biosensor was evaluated over 1.5 years. To the best of our knowledge, this is the first report of an MFC BOD sensor using an MnO2 catalyst at the cathode; the feasibility of using a low-cost catalyst in an MFC for online measurement of BOD in real wastewater broadens the scope of applications for such devices. PMID:28134838

  2. The Influence of Carbonaceous Matrices and Electrocatalytic MnO2 Nanopowders on Lithium-Air Battery Performances

    Directory of Open Access Journals (Sweden)

    Alessandro Minguzzi

    2016-01-01

    Full Text Available Here, we report new gas diffusion electrodes (GDEs prepared by mixing two different pore size carbonaceous matrices and pure and silver-doped manganese dioxide nanopowders, used as electrode supports and electrocatalytic materials, respectively. MnO2 nanoparticles are finely characterized in terms of structural (X-ray powder diffraction (XRPD, energy dispersive X-ray (EDX, morphological (SEM, high-angle annular dark field (HAADF-scanning transmission electron microscopy (STEM/TEM, surface (Brunauer Emmet Teller (BET-Barrett Joyner Halenda (BJH method and electrochemical properties. Two mesoporous carbons, showing diverse surface areas and pore volume distributions, have been employed. The GDE performances are evaluated by chronopotentiometric measurements to highlight the effects induced by the adopted materials. The best combination, hollow core mesoporous shell carbon (HCMSC with 1.0% Ag-doped hydrothermal MnO2 (M_hydro_1.0%Ag allows reaching very high specific capacity close to  1400 mAh·g−1. Considerably high charge retention through cycles is also observed, due to the presence of silver as a dopant for the electrocatalytic MnO2 nanoparticles.

  3. Preparation of MnO2and calcium silicate hydrate from electrolytic manganese residue and evaluation of adsorption properties

    Institute of Scientific and Technical Information of China (English)

    李昌新; 钟宏; 王帅; 薛建荣; 武芳芳; 张振宇

    2015-01-01

    Electrolytic manganese residue (EMR), a high volume byproduct resulting from the electrolytic manganese industry, was used as a cheap and abundant chemical source for preparing MnO2 and EMR-made calcium silicate hydrate (EMR-CSH). The MnO2 is successfully synthesized from the metal cations extracted from EMR, which can effectively recycle the manganese in the EMR. By the combination of XRD, SEM and EDX analysis, the as-prepared MnO2 is found to exhibit a single-phase with the purity of 90.3%. Furthermore, EMR-CSH is synthesized from EMR via hydrothermal method. Based on the detailed analyses using XRD, FT-IR, FE-SEM, EDX and BET surface area measurement, the product synthesized under the optimum conditions (pH 12.0 and 100 °C) is identified to be a calcium silicate hydrate with a specific surface area of 205 m2/g incorporating the slag-derived metals (Al and Mg) in its structure. The as-synthesized material shows good adsorption properties for removal of Mn2+ and phosphate ions diluted in water, making it a promising candidate for efficient bulk wastewater treatment. This conversion process, which enables us to fabricate two different kinds of valuable materials from EMR at low cost and through convenient preparation steps, is surely beneficial from the viewpoint of the chemical and economical use of EMR.

  4. Hierarchical structured MnO2@SiO2 nanofibrous membranes with superb flexibility and enhanced catalytic performance.

    Science.gov (United States)

    Wang, Xueqin; Dou, Lvye; Yang, Liu; Yu, Jianyong; Ding, Bin

    2017-02-15

    Constructing nanostructured catalyst-embedded ceramic fibrous membranes would facilitate the remediation or preliminary treatment of dyeing wastewater, however, most of such membranes are brittle with low deformation resistance, thus, restricting their widely applications. Herein, the flexible and hierarchical nanostructured MnO2-immobilized SiO2 nanofibrous membranes (MnO2@SiO2 NFM) were fabricated by combining the electrospinning technique with hydrothermal method. The morphologies of membranes could be regulated from nanowires and nanoflower to mace-like structure via varying concentration of reactants. The resultant MnO2@SiO2 NFM could cooperate with hydrogen peroxide to form a Fenton-like reagent for the degradation of methylene blue (MB). The resultant membrane exhibited prominent catalytic performance towards MB, including high degradation degree of 95% within 40min, fast degradation rate of 0.0865min(-1), and excellent reusability in 5 cycles. Moreover, the membranes could be used in a wide pH range of 0 to 14 and the degradation degree reached 76% during dynamic filtration process with a flux of 490,000Lm(-2)h(-1). The successful fabricating of such membrane with extraordinary catalytic performance would provide a platform for preparing high-performance catalysts for remediation of dyeing wastewater. Copyright © 2016 Elsevier B.V. All rights reserved.

  5. Ultrathin MnO2 nanoflakes deposited on carbon nanotube networks for symmetrical supercapacitors with enhanced performance

    Science.gov (United States)

    Sun, Peng; Yi, Huan; Peng, Tianquan; Jing, Yuting; Wang, Ruijing; Wang, Huanwen; Wang, Xuefeng

    2017-02-01

    Manganese dioxide is a promising electrode material for electrochemical supercapacitors, but its poor electronic conductivity (10-5∼10-6 S cm-1) limits the fast charge/discharge rate for practical applications. In the present work, we use the chemical vapor deposition (CVD) method to grow highly conductive carbon nanotube (CNT) networks on flexible Ni mesh, on which MnO2 nanoflake layers are deposited by a simple solution method, forming a hierarchical core-shell structure. Under the optimized mass loading, the as-fabricated MnO2 nanoflake@CNTs/Ni mesh electrode exhibits a high specific capacitance of 1072 F g-1 at 1 A g-1 in three-electrode configuration. Due to advantageous features of these core-shell electrodes (e.g., high conductivity, direct current path, structure stability), the as-assembled symmetric supercapacitor (SSC) based on MnO2@CNTs/Ni mesh has a wide working voltage (2.0 V) in 1 M Na2SO4 aqueous electrolyte. Finally an impressive energy density of 94.4 Wh kg-1 at 1000 W kg-1 and a high power density of 30.2 kW kg-1 at 33.6 Wh kg-1 have been achieved for the as-assembled SSC, which exhibits a great potential as a low-cost, high energy density and attractive wearable energy storage device.

  6. Use of mesoporous MnO2 as a support for immobilization of lipase from Candida rugosa

    Directory of Open Access Journals (Sweden)

    Babaei Mahsa

    2014-01-01

    Full Text Available In this study, immobilization of lipase from Candida rugosa on mesoporous manganese dioxide by adsorption method was carried out and the effect of three immobilization variables including temperature, process time and enzyme/support ratio on immobilization efficiency were studied. The characteristics of synthesized MnO2 and lipase-bound MnO2 were investigated by scanning electron microscopy (SEM, transmission electron microscopy (TEM and Fourier Transform Infrared Spectroscopy (FT-IR methods. The porous property of the support particles was also studied by X-ray diffraction (XRD and Brunauer, Emmett, and Teller (BET measurements. Thermal stability of immobilized lipase was determined to be better than that of free enzyme. Also the operational stability of lipase-bound MnO2 was studied and showed an almost strong attachment of enzyme to support. The Michaelis-Menten kinetic parameters (Km and Vmax were also determined for both free and immobilized lipases. It was observed that there is an increase of the Km value (672.96 mg/ml and a decrease of the Vmax value (130.99 U/mg for the immobilized enzyme comparing with the corresponding values of the free lipase.

  7. Preparation and thermoelectric properties of M0.05Ca0.95MnO3%M0.05Ca0.95MnO3的制备及其热电性能

    Institute of Scientific and Technical Information of China (English)

    许洁; 魏长平; 贾坤

    2011-01-01

    采用溶胶-凝胶法,以硝酸盐为原料,在常压空气气氛中于1 000℃烧结8 h制备出CaMnO3和M0.05Ca0.95MnO3(M=Sr2+,Sm3+)块体材料。利用X线衍射、扫描电子显微镜等研究材料的物相和微观形貌,考察Sr2+和Sm3+M+掺杂对CaMnO3的高温热电性能参数Seebeck系数、电阻率和功率因子的影响。研究结果表明:制备的样品具有单一的物相,结构致密;金属离子Sr2+和Sm3+掺杂可以有效地改善其热电性能;当Sm3+的掺杂量为0.05时可获得最佳的热电性能,600℃时功率因子为23×10-5W·m-1·K-2。%CaMnO3 and M0.05Ca0.95MnO3 (M=Sr2+, Sm3+) samples were synthesized by sol-gel method and sintered in air at 1 000 "C for 8 h with nitrates as starting materials. The phase composition and microstructure were studied by XRD and SEM. Thermoelectric properties such as the Seebeck coefficient, electrical resistivity and power factor of M0.05Ca0.95MnO3 samples were studied. The results show that theM0.05Ca0.95MnO3 samples have single phase and condensed microstructure. The samples substituted by metal ions(Sr2+, Sm3+) enhance the electrical transmission performance effectively, and the highest power factor is 23×10-5 W·m-1·K-2 at 600 ℃ for the sample of Sm0.05Ca0.95MnO3.

  8. Preparation, structure, magnetic properties and special magnetoresistance effect of La0.67Sr0.33MnO3 + δ/Pr0.7Ca0.3MnO3 + δ/La0.67Sr0.33MnO3 + δ trilayered thin films

    Institute of Scientific and Technical Information of China (English)

    熊曹水; 皮雳; 汤业庆; 朱弘; 宗登刚; 张骏峰; 邓云飞; 朱警生; 张裕恒

    1999-01-01

    The La0.67Sr0.33MnO3+δ/Pr0.7Ca0.3MnO3+δ/La0.67Sr0.33MnO3+δ(LPL) trilayered films on (100) LaAlO3 substrates are prepared by using direct current (DC) magnetron sputtering method. The results obtained by means of X-ray powder diffractometer show that all films are the high quality epitaxial films. The results gained by SQUID magnetometer indicate that there is a magnetic coupling in the LPL trilayered films. The resistivities of LSMO, PCMO and LPL films are measured using standard four-probe method and analyzed logρ-1/T curve. From the results it is concluded that the middle-layered PCMO which is ferromagnetic may play a role of intra-magnetic field, which weakens the paramagnetism of LSMO film, lowers ρmax and enlarges Tp which is the transition temperature from metal to insulator, just as the applied magnetic field does. And the middle-layered PCMO may induce the change of the density of states in the LSMO’s gap. The two reasons above make the resistivity and Tp of

  9. Porous honeycomb structures formed from interconnected MnO2 sheets on CNT-coated substrates for flexible all-solid-state supercapacitors

    Science.gov (United States)

    Ko, Wen-Yin; Chen, You-Feng; Lu, Ke-Ming; Lin, Kuan-Jiuh

    2016-01-01

    The use of lightweight and easily-fabricated MnO2/carbon nanotube (CNT)-based flexible networks as binder-free electrodes and a polyvinyl alcohol/H2SO4 electrolyte for the formation of stretchable solid-state supercapacitors was examined. The active electrodes were fabricated from 3D honeycomb porous MnO2 assembled from cross-walled and interconnected sheet-architectural MnO2 on CNT-based plastic substrates (denoted as honeycomb MnO2/CNT textiles).These substrates were fabricated through a simple two-step procedure involving the coating of multi-walled carbon nanotubes (MWCNTs) onto commercial textiles by a dipping-drying process and subsequent electrodeposition of the interconnected MnO2 sheets onto the MWCNT-coated textile. With such unique MnO2 architectures integrated onto CNT flexible films, good performance was achieved with a specific capacitance of 324 F/g at 0.5 A/g. A maximum energy density of 7.2 Wh/kg and a power density as high as 3.3 kW/kg were exhibited by the honeycomb MnO2/CNT network device, which is comparable to the performance of other carbon-based and metal oxide/carbon-based solid-state supercapacitor devices. Specifically, the long-term cycling stability of this material is excellent, with almost no loss of its initial capacitance and good Coulombic efficiency of 82% after 5000 cycles. These impressive results identify these materials as a promising candidate for use in environmentally friendly, low-cost, and high-performance flexible energy-storage devices.

  10. Improvement of enzymatic hydrolysis and ethanol production from corn stalk by alkali and N-methylmorpholine-N-oxide pretreatments.

    Science.gov (United States)

    Cai, Ling-Yan; Ma, Yu-Long; Ma, Xiao-Xia; Lv, Jun-Min

    2016-07-01

    A combinative technology of alkali and N-methylmorpholine-N-oxide (NMMO) was used to pretreat corn stalk (CS) for improving the efficiencies of subsequent enzymatic hydrolysis and ethanol fermentation. The results showed that this strategy could not only remove hemicellulose and lignin but also decrease the crystallinity of cellulose. About 98.0% of enzymatic hydrolysis yield was obtained from the pretreated CS as compared with 46.9% from the untreated sample. The yield for corresponding ethanol yield was 64.6% while untreated CS was only 18.8%. Besides, xylose yield obtained from the untreated CS was only 11.1%, while this value was 93.8% for alkali with NMMO pretreated sample. These results suggest that a combination of alkali with 50% (wt/wt) NMMO solution may be a promising alternative for pretreatment of lignocellulose, which can increase the productions of subsequent enzymatic hydrolysis and ethanol fermentation.

  11. Simultaneous targeted analysis of trimethylamine-N-oxide, choline, betaine, and carnitine by high performance liquid chromatography tandem mass spectrometry.

    Science.gov (United States)

    Liu, Jia; Zhao, Mingming; Zhou, Juntuo; Liu, Changjie; Zheng, Lemin; Yin, Yuxin

    2016-11-01

    Trimethylamine-N-oxide (TMAO) is a metabolite generated from choline, betaine and carnitine in a gut microbiota-dependent way. This molecule is associated with development of atherosclerosis and cardiovascular events. A sensitive liquid chromatographic electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) has been developed and validated for the simultaneous determination of TMAO related molecules including TMAO, betaine, choline, and carnitine in mouse plasma. Analytes are extracted after protein precipitation by methanol and subjected to LC-ESI-MS/MS without preliminary derivatization. Separation of analytes was achieved on an amide column with acetonitrile-water as the mobile phase. This method has been fully validated in this study in terms of selectivity, linearity, sensitivity, precision, accuracy, and carryover effect, and the stability of the analyte under various conditions has been confirmed. This developed method has successfully been applied to plasma samples of our mouse model.

  12. Synthesis and antimycobacterial activity of new quinoxaline-2-carboxamide 1,4-di-N-oxide derivatives.

    Science.gov (United States)

    Zarranz, Belén; Jaso, Andrés; Aldana, Ignacio; Monge, Antonio

    2003-05-15

    As a continuation of our research and with the aim of obtaining new antituberculosis agents which can improve the current chemotherapeutic antituberculosis treatments, new series of quinoxaline-2-carboxamide 1,4-di-N-oxide derivatives were synthesized and evaluated for in vitro antituberculosis activity against Mycobacterium tuberculosis strain H(37)Rv, using the radiometric BACTEC 460-TB methodology. Active compounds were also screened by serial dilution to assess toxicity to a VERO cell line. The results indicate that some compounds exhibited a good antituberculosis activity and the arylcarboxamide analogues 3, 8, and 9 were the most active compounds (EC(90)/MIC1). Also, the cytotoxic effects indicate that these compounds have a good Selectivity Index (SI).

  13. Evaluation of indium-111-2-mercaptopyridine-N-oxide for labeling leukocytes in plasma: a kit preparation

    Energy Technology Data Exchange (ETDEWEB)

    Thakur, M.L.; McKenney, S.L.; Park, C.H.

    1985-05-01

    Pure neutrophils, lymphocytes, and mixed leukocytes have been labeled in vitro with /sup 111/In chelated to a nontoxic, water soluble agent 2-mercaptopyridine-N-oxide (Merc). Cells were labeled in isotonic salt-balanced medium with preformed (/sup 111/In)Merc, or in 0.5 ml autologous plasma by incubation with dry Merc first and then with /sup 111/In. The latter method facilitated a kit procedure that required 2 ..mu..g dry Merc when acid citrate dextrose was used as anticoagulant or 20..mu..g when heparin was used. Labeling efficiency was dependent on cell concentration and pH. Labeled cells accumulated avidly in experimental abscesses. In dogs, the liver uptake of labeled cells was only 18.8% compared to that of 48.5% when cells were labeled with (/sup 111/In) oxine.

  14. Antiinflammatory and neurological activity of pyrithione and related sulfur-containing pyridine N-oxides from Persian shallot (Allium stipitatum)

    DEFF Research Database (Denmark)

    Krejčová, Petra; Kučerová, Petra; Stafford, Gary Ivan

    2014-01-01

    antiinflammatory effects which are comparable with those of common pharmaceuticals (IC50 of 7.8 and 15.4µM for COX-1 and COX-2, respectively). On the other hand, neurological activities of the compounds were rather modest. Some compounds moderately inhibited AChE (IC50 of 104-1041µM) and MAO-A (IC50 of 98-241µ......ETHNOPHARMACOLOGICAL RELEVANCE: Persian shallot (Allium stipitatum) is a bulbous plant native to Turkey, Iran and Central Asia. It is frequently used in folk medicine for the treatment of a variety of disorders, including inflammation and stress. Antiinflammatory and neurological activities...... of pyrithione and four related sulfur-containing pyridine N-oxides which are prominent constituents of Allium stipitatum were tested. METHODS: The antiinflammatory activity was tested by the ability of the compounds to inhibit cyclooxygenase (COX-1 and COX-2), whereas the neurological activities were evaluated...

  15. Comparative acute systemic toxicity of several quinoxaline 1,4-di-N-oxides in Wistar rats.

    Science.gov (United States)

    Azqueta, Amaya; Gil, Ana Gloria; García-Rodríguez, Alba; García-Jalón, Jose Antonio; Cia, Felipe; Zarranz, Belén; Monge, Antonio; de Cerain, Adela López

    2007-01-01

    The acute toxicity of six quinoxaline 1,4-di-N-oxides has been evaluated in an attempt to determine: a) the feasibility of testing systemic toxicity of these compounds in a very preliminary phase without an adequate formulation for in vivo administration, b) the LD50 range and the toxic target organ of these compounds in order to have an approximation of the structure-activity relationship. Quinoxaline 1,4-di-N-oxides have shown a great variety of biological activities with potential therapeutic application in cancer, malaria, etc. Problems of toxicity hinder the progression of these compounds to clinical phases. The compounds dissolved in DMSO at their solubility limit were administered i.v. to female Wistar rats (8 weeks, 160 g), using an infusion pump (300 microL; 20 microl/min). Animals were observed for a period of 14 days. This dose of the vehicle (1.7 ml/kg) was well tolerated by the animals. The LD50 could not be determined, but a marked hypoactivity was induced by the treatment. The same compounds were also injected intraperitoneally, suspended in 0.01% Tween 80/0.09 % saline, and the animals that did not die were observed for a period of 14 days. The LD50 could be estimated to be in a range between 30 and 120 mg/kg, except for one of the compounds. A decrease in the evolution of body weight and hypoactivity were the principal symptoms induced by the treatment. In both assays, histopathologic study of heart, liver, kidney, lung, spleen and ovaries indicated that the target organs may be heart and spleen. In conclusion, the i.v. route is not adequate for estimating the LD50 of these compounds due to solubility problems; by i.p. route, the LD50 interval is between 30 and 120 mg/kg. The data did not permit the deduction of any specific structure-activity relationship.

  16. Effect of Water Content in N-Methylmorpholine N-Oxide/Cellulose Solutions on Thermodynamics, Structure, and Hydrogen Bonding.

    Science.gov (United States)

    Rabideau, Brooks D; Ismail, Ahmed E

    2015-12-03

    Native crystalline cellulose is notoriously difficult to dissolve due to its dense hydrogen bond network between chains and weaker hydrophobic forces between cellulose sheets. N-Methylmorpholine N-oxide (NMMO), the solvent behind the Lyocell process, is one of the most successful commercial solvents for the nonderivatized dissolution of cellulose. In this process, water plays a very important role. Its presence at low concentrations allows NMMO to dissolve substantial amounts of cellulose, while at much higher concentrations it precipitates the crystalline fibers. Using all-atom molecular dynamics, we study the thermodynamic and structural properties of ternary solutions of cellulose, NMMO, and water. Using the two-phase thermodynamic method to calculate solvent entropy, we estimate the free energy of dissolution of cellulose as a function of the water concentration and find a transition of spontaneity that is in excellent agreement with experiment. In pure water, we find that cellulose dissolution is nonspontaneous, a result that is due entirely to strong decreases in water entropy. Although the combined effect of enthalpy on dissolution in water is negligible, we observe a net loss of hydrogen bonds, resulting in a change in hydrogen bond energy that opposes dissolution. At lower water concentrations, cellulose dissolution is spontaneous and largely driven by decreases in enthalpy, with solvent entropy playing only a very minor role. When searching for the root causes of this enthalpy decrease, a complex picture emerges in which not one but many different factors contribute to NMMO's good solvent behavior. The reduction in enthalpy is led by the formation of strong hydrogen bonds between cellulose and NMMO's N-oxide, intensified through van der Waals interactions between NMMO's nonpolar body and the nonpolar surfaces of cellulose and unhindered by water at low concentrations due to the formation of efficient hydrogen bonds between water and cellulose.

  17. Immunomodulation by different types of N-oxides in the hemocytes of the marine bivalve Mytilus galloprovincialis.

    Directory of Open Access Journals (Sweden)

    Caterina Ciacci

    Full Text Available The potential toxicity of engineered nanoparticles (NPs for humans and the environment represents an emerging issue. Since the aquatic environment represents the ultimate sink for NP deposition, the development of suitable assays is needed to evaluate the potential impact of NPs on aquatic biota. The immune system is a sensitive target for NPs, and conservation of innate immunity represents an useful basis for studying common biological responses to NPs. Suspension-feeding invertebrates, such as bivalves, are particularly at risk to NP exposure, since they have extremely developed systems for uptake of nano and microscale particles integral to intracellular digestion and cellular immunity. Evaluation of the effects of NPs on functional parameters of bivalve immunocytes, the hemocytes, may help understanding the major toxic mechanisms and modes of actions that could be relevant for different NP types in aquatic organisms.In this work, a battery of assays was applied to the hemocytes of the marine bivalve Mytilus galloprovincialis to compare the in vitro effects of different n-oxides (n-TiO(2, n-SiO(2, n-ZnO, n-CeO(2 chosen on the basis of their commercial and environmental relevance. Physico-chemical characterization of both primary particles and NP suspensions in artificial sea water-ASW was performed. Hemocyte lysosomal and mitochondrial parameters, oxyradical and nitric oxide production, phagocytic activity, as well as NP uptake, were evaluated. The results show that different n-oxides rapidly elicited differential responses hemocytes in relation to their chemical properties, concentration, behavior in sea water, and interactions with subcellular compartments. These represent the most extensive data so far available on the effects of NPs in the cells of aquatic organisms. The results indicate that Mytilus hemocytes can be utilized as a suitable model for screening the potential effects of NPs in the cells of aquatic invertebrates, and may

  18. BSA-templated MnO2 nanoparticles as both peroxidase and oxidase mimics.

    Science.gov (United States)

    Liu, Xing; Wang, Qi; Zhao, Huihui; Zhang, Lichun; Su, Yingying; Lv, Yi

    2012-10-01

    Inorganic nanomaterials that mimic enzymes are fascinating as they potentially have improved properties relative to native enzymes, such as greater resistance to extremes of pH and temperature and lower sensitivity to proteases. Although many artificial enzymes have been investigated, searching for highly-efficient and stable catalysts is still of great interest. In this paper, we first demonstrated that bovine serum albumin (BSA)-stabilized MnO(2) nanoparticles (NPs) exhibited highly peroxidase-, oxidase-, and catalase-like activities. The activities of the BSA-MnO(2) NPs were evaluated using the typical horseradish peroxidase (HRP) substrates o-phenylenediamine (OPD) and 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of either hydrogen peroxide or dissolved oxygen. These small-sized BSA-MnO(2) NPs with good dispersion, solubility and biocompatibility exhibited typical Michaelis-Menten kinetics and high affinity for H(2)O(2), OPD and TMB, indicating that BSA-MnO(2) NPs can be used as satisfactory enzyme mimics. Based on these findings, BSA-MnO(2) NPs were used as colorimetric immunoassay tags for the detection of goat anti-human IgG in place of HRP. The colorimetric immunoassay using BSA-MnO(2) NPs has the advantages of being fast, robust, inexpensive, easily prepared and with no HRP and H(2)O(2) being needed. These water-soluble BSA-MnO(2) NPs may have promising potential applications in biotechnology, bioassays, and biomedicine.

  19. Direct chemical synthesis of MnO2 nanowhiskers on MXene surfaces for supercapacitor applications

    KAUST Repository

    Rakhi, Raghavan Baby

    2016-07-05

    Transition metal carbides (MXenes) are an emerging class of two dimensional (2D) materials with promising electrochemical energy storage performance. Herein, for the first time, by direct chemical synthesis, nanocrystalline ε-MnO2 whiskers were formed on MXene nanosheet surfaces (ε-MnO2/Ti2CTx and ε-MnO2/Ti3C2Tx) to make nanocomposite electrodes for aqueous pseudocapacitors. The ε-MnO2 nanowhiskers increase the surface area of the composite electrode and enhance the specific capacitance by nearly three orders of magnitude compared to pure MXene based symmetric supercapacitors. Combined with enhanced pseudocapacitance, the fabricated ε-MnO2/MXene supercapacitors exhibited excellent cycling stability with ~88% of the initial specific capacitance retained after 10000 cycles which is much higher than pure ε-MnO2 based supercapacitors (~74%). The proposed electrode structure capitalizes on the high specific capacitance of MnO2 and the ability of MXenes to improve conductivity and cycling stability.

  20. Novel Nanostructured MnO2 Prepared by Pulse Electrodeposition: Characterization and Electrokinetics

    Institute of Scientific and Technical Information of China (English)

    H.Adelkhani; M. Ghaemi; S.M. Jafari

    2008-01-01

    Pulse current technique was applied for the preparation of novel electroactive manganese dioxide and possible influences of different electrokinetic phenomena on material characteristics were discussed.The characteriza-tions of pulse deposited sample (pcMD) were carried out by different techniques: Fourier transform infrared spectroscopy (FTIR),scanning electron microscopy (SEM),X-ray diffraction (XRD),Brunauer-Emmett-Teller (BET) method,Raman spectroscopy,and atomic force microscopy (AFM).SEM image revealed that pulse current could improve the current distribution.This was confirmed by AFM images showing a decrease in surface roughness of pcMDs in comparison to amorphous samples,which were deposited by direct current (dcMD).Higher distortion of MnO6 octahedral environment of dcMD was detected by FTIR and Raman spectroscopy.Cyclic voltammetric (CV) measurements showed a generally higher energy level drained from the second electron discharge of pcMD.This is mainly attributed to a higher surface area and a lower diffusion pass of electrons and protons arisen via a rather unique nanostructural arrangement of pcMD grains.Results indicate a higher surface area available for the non homogenous second electron discharge of pcMD grains.

  1. Synthesis of quinoxaline 1,4-di-n-oxide derivatives on solid support using room temperature and microwave-assisted solvent-free procedures

    Energy Technology Data Exchange (ETDEWEB)

    Gomez-Caro, Lilia C.; Sanchez-Sanchez, Mario; Bocanegra-Garcia, Virgilio; Rivera, Gildardo [Universidad Autonoma de Tamaulipas, Reynosa (Mexico). Dept. de Farmacia y Quimica Medicinal; Monge, Antonio [Universidad de Navarra, Pamplona (Spain). Centro de Investigacion en Farmacobiologia Aplicada. Unidad de Investigacion y Desarrollo de Medicamentos

    2011-07-01

    We describe the synthesis of 12 new ethyl and methyl quinoxaline-7-carboxylate 1,4-di-N-oxide derivatives on solid supports with room temperature and microwave-assisted solvent-free procedures. Results show that solid supports have good catalytic activity in the formation of quinoxaline 1,4-di-N-oxide derivatives. We found that florisil and montmorillonite KSF and K10 could be used as new, easily available, inexpensive alternatives of catalysts. Additionally, room temperature and microwave-irradiation solvent-free synthesis was more efficient than a conventional procedure (Beirut reaction), reducing reaction time and increasing yield. (author)

  2. Synthesis of new 2-acetyl and 2-benzoyl quinoxaline 1,4-di-N-oxide derivatives as anti-Mycobacterium tuberculosis agents.

    Science.gov (United States)

    Jaso, Andrés; Zarranz, Belén; Aldana, Ignacio; Monge, Antonio

    2003-09-01

    A series of 2-acetyl and 2-benzoyl-6(7)-substituted quinoxaline 1,4-di-N-oxide derivatives were synthesized and evaluated for in vitro antituberculosis activity. The results show that 2-acetyl-3-methylquinoxaline 1,4-di-N-oxide derivatives with chlorine, methyl or methoxy group in position 7 of the benzene moiety (compounds 2, 4 and 6, respectively) and unsubstituted (3) have good antitubercular activity, exhibiting EC(90)/MIC values between 0.80 and 4.29. In conclusion, the potency, selectivity and low cytotoxicity of these compounds make them valid leads for synthesizing new compounds that possess better activity.

  3. A one pot synthesis and evaluation of 13-oxo-quino[3,4-b]carbazol-N-oxides as antimicrobial agents.

    Science.gov (United States)

    Danish, Isravel Antony; Prasad, Karnam Jayarampillai Rajendra

    2003-12-01

    1-Oxo-1,2,3,4-tetrahydrocarbazoles (1a-e) upon mixed aldol condensation with o-nitrobenzaldehyde (2) yielded 13-oxo-quino[3,4-b]carbazol-N-oxides (3a-e). All the prepared compounds were characterized by elemental and spectral analysis. A plausible mechanism for the formation of the final products is proposed. The title compounds proved to have great potentialities as antibacterial and antifungal agents due to the presence of the N-oxide group. Particularly, the chloro substituted derivative, 3d, showed excellent antimicrobial activity.

  4. Design, synthesis and study of quinoxaline-2- carboxamide 1,4-DI-N-Oxide derivatives as anti-tuberculosis agents

    OpenAIRE

    Moreno-Viguri, E. (Elsa); Monge, A; Perez-Silanes, S. (Silvia)

    2013-01-01

    The experimental work presented in this memory is based on the hypothesis that quinoxalines di-N-oxide, considered to be the core of the structure, which present a carboxamide moiety on position two and aliphatic linker between this group and an aromatic system, can be proposed as potent anti-tuberculosis agents. The main purpose of this project is the synthesis of new quinoxaline di-N-oxide derivatives as anti-tuberculosis agents. The strategy consists of the design and synthesis of several ...

  5. Hydrothermal Preparation of Li2MnO3/graphene as Cathode Materials for the Improved Electrochemical Properties%石墨烯改性Li2MnO3的热制备及其电化学性能的研究

    Institute of Scientific and Technical Information of China (English)

    刘洋; 赵蒙晰; 江学范; 尹凡; 杨刚

    2016-01-01

    Because of the increasing global demand for clean energy, one of the specific requirements is elec⁃trode material for lithium-ion batteries with high capacity, low cost and friendly environment. Li2MnO3 has met the requirement of the novel electrode materials of lithium-ion batteries. This paper reports a hydrothermal meth⁃od to synthesize Li2MnO3/graphene as cathode materials for lithium-ion battery. Due to the high conductivity of graphite oxide and graphene, the electrochemical performance of Li2MnO3 is improved. Compared with the initial discharge capacity 88.8 mAh/g of Li2MnO3, LMO/GO and LMO/RGO deliver the initial capacities of 141.2 mAh/g and 159.8 mAh/g, respectively.%采用MnSO4和KMnO4制备前驱体MnOOH,将MnOOH、LiOH、(NH4)2S2O8与氧化石墨烯复合,用传统水热法制备Li2MnO3/氧化石墨及Li2MnO3/石墨烯的复合材料。氧化石墨、石墨烯的存在对Li2MnO3的晶体形貌和结构具有明显的影响。氧化石墨和石墨烯具有优良的导电性,显著提高了Li2MnO3材料的导电性和电化学性能。

  6. Identification of a c-Type Cytochrome Specific for Manganese Dioxide (MnO2) Reduction in Anaeromyxobacter dehalogenans Strain 2CP-C

    Science.gov (United States)

    Pfiffner, S. M.; Nissen, S.; Liu, X.; Chourey, K.; Vishnivetskaya, T. A.; Hettich, R.; Loeffler, F.

    2014-12-01

    Anaeromyxobacter dehalogenans is a metabolically versatile Deltaproteobacterium and conserves energy from the reduction of various electron acceptors, including insoluble MnO2 and ferric oxides/oxyhydroxides (FeOOH). The goal of this study was to identify c-type cytochromes involved in electron transfer to MnO2. The characterization of deletion mutants has revealed a number of c-type cytochromes involved in electron transfer to solid metal oxides in Shewanella spp. and Geobacter spp; however, a genetic system for Anaeromyxobacter is not available. The A. dehalogenans str. 2CP-C genome encodes 68 putative c-type cytochromes, which all lack functional assignments. To identify c-type cytochromes involved in electron transfer to solid MnO2, protein expression profiles of A. dehalogenans str. 2CP-C cells grown with acetate as electron donor and MnO2, ferric citrate, FeOOH, nitrate or fumarate as electron acceptors were compared. Whole cell proteomes were analyzed after trypsin proteolysis using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Distinct c-type cytochrome expression patterns were observed with cells grown with different electron acceptors. A. dehalogenans str. 2CP-C grown with MnO2 expressed 25 out of the 68 c-type cytochromes encoded on the genome. The c-type cytochrome Adeh_1278 was only expressed in strain 2CP-C grown with MnO2. Reverse transcription PCR confirmed that the Adeh_1278 gene was transcribed in MnO2-grown cells but not in cells grown with other terminal electron acceptors. The expression of the Adeh_1278 gene correlated with Mn(IV) reduction activity. Adeh_1278 has three heme binding motifs and is predicted to be located in the periplasm. The identification of Adeh_1278 as a protein uniquely expressed when MnO2 serves as electron acceptor suggests its utility as a biomarker for MnO2 reduction. This example demonstrates the value of the LC-MS/MS approach for identifying specific proteins of interest and making functional assignments

  7. Arsenic removal from groundwater by MnO2-modified natural clinoptilolite zeolite: effects of pH and initial feed concentration.

    Science.gov (United States)

    Camacho, Lucy M; Parra, Ramona R; Deng, Shuguang

    2011-05-15

    Adsorption of arsenic (As(5+)) on natural and MnO(2)-modified clinoptilolite-Ca zeolite adsorbents was investigated to explore the feasibility of removing arsenic from groundwater using natural zeolite adsorbents. The natural and MnO(2)-modified clinoptilolite-Ca zeolite adsorbents were characterized with nitrogen adsorption at 77K for pore textural properties, scanning electron microscopy with energy dispersive X-ray spectroscopy and X-ray fluorescence for morphology, elemental composition and distribution. Batch adsorption equilibrium experiments were conducted to study the effects of pH and initial feed concentration on arsenic removal efficiency. It was found that the amphoteric properties and arsenic removal efficiency of the natural clinoptilolite-Ca zeolite were significantly improved after modification with MnO(2). The MnO(2)-modified zeolite could effectively remove arsenic from water at a wide pH range, and the arsenic removal efficiency that is basically independent of the pH of feed solutions varies slightly with the initial arsenic concentration in the feed solutions. The removal efficiency obtained on the modified zeolite was doubled as compared to that obtained on the unmodified zeolite. The MnO(2)-modified clinoptilolite-Ca zeolite appears to be a promising adsorbent for removing trace arsenic amounts from water.

  8. Magnetic, electric and electron magnetic resonance properties of orthorhombic self-doped La sub 1 sub - sub x MnO sub 3 single crystals

    CERN Document Server

    Markovich, V; Shames, A I; Puzniak, R; Rozenberg, E; Yuzhelevski, Y; Mogilyansky, D; Wisniewski, A; Mukovskii, Y M; Gorodetsky, G

    2003-01-01

    The effect of lanthanum deficiency on structural, magnetic, transport, and electron magnetic resonance (EMR) properties has been studied in a series of La sub 1 sub - sub x MnO sub 3 (x = 0.01, 0.05, 0.11, 0.13) single crystals. The x-ray diffraction study results for the crystals were found to be compatible with a single phase of orthorhombic symmetry. The magnetization curves exhibit weak ferromagnetism for all samples below 138 K. It was found that both the spontaneous magnetization and the coercive field increase linearly with x. The pressure coefficient dT sub N /dP decreases linearly with self-doping, from a value of 0.68 K kbar sup - sup 1 for La sub 0 sub . sub 9 sub 9 MnO sub 3 to 0.33 K kbar sup - sup 1 for La sub 0 sub . sub 8 sub 7 MnO sub 3. The resistivity of low-doped La sub 0 sub . sub 9 sub 9 MnO sub 3 crystal is of semiconducting character, while that of La sub 0 sub . sub 8 sub 7 MnO sub 3 depends weakly on temperature between 180 and 210 K. It was found that the magnetic and transport prop...

  9. Influence of MnO2 on the photocatalytic activity of P-25 TiO2 in the degradation of methyl orange

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Influences of α-MnO2, β-MnO2, and δ-MnO2 on the photocatalytic activity of Degussa P-25 TiO2 have been investigated through the photocatalytic degradation of methyl orange. The TiO2 photocatalyst, before and after being contaminated by MnO2, was characterized by UV-visible diffuse reflectance spectroscopy (UV-vis DRS), photoluminescence (PL), and X-ray photoelectron spectroscopy (XPS). The results showed that photocatalytic activity of TiO2 could be inhibited significantly or completely deactivated due to the presence of even a small amount of MnO2 particles. It was found that the poisoning effect varied with the crystal phases of MnO2 and the effect was in the order δ-MnO2 >α-MnO2 >β-MnO2. The poisoning effect was attributed to the formation of heterojunctions between MnO2 and TiO2 particles. The heterojunctions changed the chemical state of Ti4+ and O2 sites in the crystalline phase of TiO2. MnO2 in contact with TiO2 particles also broadens the band-gap of TiO2, which decreases UV absorption of TiO2. It can also create some deep impurity energy levels serving as photoelec-tron-photohole recombination center, which accelerates the electron-hole recombination.

  10. Hierarchical core/shell structure of MnO2@polyaniline composites grown on carbon fiber paper for application in pseudocapacitors.

    Science.gov (United States)

    Yang, MinHo; Hong, Seok Bok; Choi, Bong Gill

    2015-11-28

    Hierarchical core/shell structured arrays of MnO2@polyaniline (PANI) nanosheets are successfully deposited on the surface of carbon fiber paper (CFP) by a two-step method of a redox reaction-assisted deposition of MnO2 and post electrodeposition of PANI. The CFP is used as a three-dimensional (3D) current collector to ensure 3D transport of ions and electrons with a large surface area. In addition, the electrodeposition technique enables conformal and thin coating of a layer of PANI across the entire MnO2 nanosheet. The MnO2@PANI on the CFP shows a unique architecture for efficient ion diffusion pathways in hierarchical porous structures and rapid electron transfer through PANI coated layers. The MnO2@PANI/CFP can be applied as a binder- and carbon-free electrode for supercapacitors. Evaluation of the electrochemical performance revealed that the as-prepared electrodes have a high value of specific capacitance (437 F g(-1) at 1 A g(-1)), high rate capability (62.4% retention at 15 A g(-1)), and good cycle life (∼100% at sequential current densities of 1 and 5 A g(-1) over 3000 cycles).

  11. Suppressing the Coffee-Ring Effect in Semitransparent MnO2 Film for a High-Performance Solar-Powered Energy Storage Window.

    Science.gov (United States)

    Jin, Huanyu; Qian, Jiasheng; Zhou, Limin; Yuan, Jikang; Huang, Haitao; Wang, Yu; Tang, Wing Man; Chan, Helen Lai Wa

    2016-04-13

    We introduce a simple and effective method to deposit a highly uniform and semitransparent MnO2 film without coffee-ring effect (CRE) by adding ethanol into MnO2 ink for transparent capacitive energy storage devices. By carefully controlling the amount of ethanol added in the MnO2 droplet, we could significantly reduce the CRE and thus improve the film uniformity. The electrochemical properties of supercapacitor (SC) devices using semitransparent MnO2 film electrodes with or without CRE were measured and compared. The SC device without CRE shows a superior capacitance, high rate capability, and lower contact resistance. The CRE-free device could achieve a considerable volumetric capacitance of 112.2 F cm(-3), resulting in a high volumetric energy density and power density of 10 mWh cm(-3) and 8.6 W cm(-3), respectively. For practical consideration, both flexible SC and large-area rigid SC devices were fabricated to demonstrate their potential for flexible transparent electronic application and capacitive energy-storage window application. Moreover, a solar-powered energy storage window which consists of a commercial solar cell and our studied semitransparent MnO2-film-based SCs was assembled. These SCs could be charged by the solar cell and light up a light emitting diode (LED), demonstrating their potential for self-powered systems and energy-efficient buildings.

  12. A high performance flexible all solid state supercapacitor based on the MnO2 sphere coated macro/mesoporous Ni/C electrode and ionic conducting electrolyte.

    Science.gov (United States)

    Zhi, Jian; Reiser, Oliver; Wang, Youfu; Hu, Aiguo

    2016-06-09

    A high contact resistance between the active materials and the current collector, a low ionic conductivity of the gel electrolyte, and an impenetrable electrode structure are the three major barriers which greatly limit the capacitance of MnO2 in solid state supercapacitors. As a potential solution to these problems, in this work we report a novel electrode for solid state supercapacitors, based on a ternary system composed of hierarchical MnO2 spheres as the active material, macroporous Ni foam as gel penetrable skeletons and an ordered mesoporous carbon (OMC) membrane as the charge-transport accelerating layer. By employing butyl-3-methylimidazolium chloride (BMIMCl) modified gels as the ionic conducting electrolyte, the utilization efficiency of MnO2 on the specific capacitance was enhanced up to 88% of the theoretical value, delivering a volumetric capacitance of 81 F cm(-3), which is the highest value among MnO2 based solid state supercapacitors. Moreover, such a flexible device exhibits exceptional volumetric energy and power density (6.6 Wh L(-1) and 549 W L(-1), based on the whole device volume) combined with a small capacity loss of 8.5% after 6000 cycles under twisting. These encouraging findings unambiguously overcome the energy bottleneck of MnO2 in solid state supercapacitors, and open up a new application of macro/mesoporous materials in flexible devices.

  13. Reverse micellar synthesis and properties of nanocrystalline GMR materials (LaMnO3, La0.67Sr0.33MnO3 and La0.67Ca0.33MnO3): Ramifications of size considerations

    Indian Academy of Sciences (India)

    Tokeer Ahmad; Kandalam V Ramanujachary; Samuel E Lofland; Ashok K Ganguli

    2006-11-01

    Nanoparticles of complex manganites (viz. LaMnO3, La0.67Sr0.33MnO3 and La0.67Ca0.33MnO3) have been synthesized using the reverse micellar route. These manganites are prepared at 800°C and the monophasic nature of all the oxides has been established by powder X-ray diffraction studies. TEM studies show an average grain size of 68, 80 and 50 nm for LaMnO3, La0.67Sr0.33MnO3 and La0.67Ca0.33MnO3 respectively. Ferromagnetic ordering is observed at around 250 K for LaMnO3, 350 K for La0.67Sr0.33MnO3 and 200 K for La0.67Ca0.33MnO3. These Curie temperatures correspond well with those reported for bulk materials with similar composition.

  14. Magnetotransport properties of La2/3Ca1/3MnO3/ YBa2Cu4O8/La2/3Ca1/3MnO3 sandwiches

    Institute of Scientific and Technical Information of China (English)

    Zhao Kun; Feng Jia-Feng; Huang Yan-Hong; Wong Hong-Kuen

    2005-01-01

    La2/3Ca1/3MnO3 (LCMO)/YBa2Cu4O8 (YBCO)/LCMO sandwiches are prepared by the facing-target sputtering technique. The superconducting transition temperature as a function of spacer layer thickness is described by the magnetic proximity effect in the superconductor/ferromagnet structure. The metal-semiconductor transition temperature exhibits a nonmonotonic behaviour which is strongly dependent upon the YBCO layer thickness, and is also shown from the measurement of resistance and magnetoresistance. These results imply that the magnetic spin interaction between the two LCMO layers may occur through the normal-conductive YBCO layer.

  15. Anisotropic Magnetoresistance of Perovskite La2/3 Ca1/3MnO3/YBa2Cu4O8/La2/3Ca1/3MnO3 Trilayer Films

    Institute of Scientific and Technical Information of China (English)

    Wu Cheng; Zhang Li; Zhao Kun

    2005-01-01

    The anisotropic magnetoresistance (MR) of La2/3Ca1/3MnO3 (LCMO)/YBa2Cu4O8 (YBCO) /LCMO sandwiches on (001) SrTiO3 were investigated. Single layer LCMO and sandwiches show in-plane anisotropy of MR. MR strongly depends on the magnetic field direction. A nearly sinusoidal dependence on the angle between the applied magnetic field and the film plane or transport current was observed. A positive MR was present with lower fields applied not only out-of-plane but also in-plane.

  16. Rh(III)- and Zn(II)-Catalyzed Synthesis of Quinazoline N-Oxides via C-H Amidation-Cyclization of Oximes.

    Science.gov (United States)

    Wang, Qiang; Wang, Fen; Yang, Xifa; Zhou, Xukai; Li, Xingwei

    2016-12-02

    Quinazoline N-oxides have been prepared from simple ketoximes and 1,4,2-dioxazol-5-ones via Rh(III)-catalyzed C-H activation-amidation of the ketoximes and subsequent Zn(II)-catalyzed cyclization. The substrate scope and functional group compatibility were examined. The reaction features relay catalysis by Rh(III) and Zn(II).

  17. Detection of high levels of pyrrolizidine-N-oxides in the endangered plant cryptantha crassipes (Terlingua creek cat's-eye)using HPLC-ESI-MS

    Science.gov (United States)

    Chemical investigation of nine species of Cryptantha identified at least two chemotypes within the genus. It was determined that under especially harsh and dry growing conditions of the Chihuahuah desert of Texas, the N-oxides of two major pyrrolizidine alkaloids, lycopsamine and intermedine, foun...

  18. Synthesis, Characterization and Activity of Rare Earth Complexes with Schiff Base From 2,6-Diformylpyridine N-Oxide and 4-Amino-antipyrine

    Institute of Scientific and Technical Information of China (English)

    于青; 唐瑜; 谭民裕

    2002-01-01

    Six new rare earth complexes with Schiff base from 2,6-diformylpyridine N-oxide and 4-amino-antipyrine were synthesized. These complexes with general formula REL(NO3)3 (RE=La, Pr, Eu, Tb, Er, Y) were characterized by elemental analysis, IR, UV, molar conductance measurements and antimicrobial activity.

  19. Simultaneous determination of ammonia, dimethylamine, trimethylamine and trimethylamine-N-oxide in fish extracts by capillary electrophoresis with indirect UV-detection

    DEFF Research Database (Denmark)

    Timm Heinrich, Maike; Jørgensen, Bo

    2002-01-01

    A capillary electrophoretic method with indirect UV detection is described for simultaneous determination of ammonia, dimethylamine (DMA), trimethylamine (TMA) and trimethylamine-N- oxide (TMAO) in aqueous extracts of fish, A buffer consisting of 4 mM formic acid, 5 mM copper(II)sulfate and 3 m...

  20. Analysis of swainsonine and swainsonine N-oxide as trimethylsilyl derivatives by Liquid Chromatography-Mass Spectrometry and their relative occurrence in plants toxic to livestock

    Science.gov (United States)

    A liquid chromatography-mass spectrometry method was developed for the analysis of the indolizidine alkaloid swainsonine and its N-oxide. The method is based on a one step solvent partitioning extraction procedure followed by trimethylsilylation of the dried extract and subsequent detection and qua...

  1. The effect of 1,2-dimethoxyethane on the storage and performance of lithium cells with MnO 2 and (CF) n cathodes

    Science.gov (United States)

    Fr açkowiak, E.; Kuksenko, S.

    The characteristics of lithium cells with MnO 2 and (CF) n cathodes were investigated for two different electrolyte compositions, i.e., LiClO 4/PC+DME and LiClO 4/PC. For such lithium cells, the greater loss of long-term storage capacity was found in the case of cells using mixed PC+DME electrolyte. The oxidation process of DME by the cathode elements during the storage period is assumed to be the cause of the capacity loss. In the case of cells using MnO 2 as a cathode, the polymerisation process of the oxidation products of DME on the cathode surface can be also considered. After storage at 45°C, the smaller loss of capacity was found for the cells using MnO 2 as a cathode. The different behaviour of these two kinds of cells during a pulse discharge was also confirmed.

  2. SÍNTESE DO ESPINÉLIO Al 2 MnO4 VIA REDUÇÃO COM H2

    Directory of Open Access Journals (Sweden)

    Rogério Navarro Correia de Siqueira

    2014-06-01

    Full Text Available Nanostructured oxides with interesting magnetic properties, such as the spinel Al2 MnO4 , can be synthesized through thermal decomposition of nitrate solution followed by thermal treatment under a reducing atmosphere. The present work can be understood as a study of the synthesis of Al2 MnO4 samples based on the H2 reduction of Al and Mn oxide mixtures, including a discussion of the effect of some important process variables over the kinetic behavior of the system, such as temperature and thermal treatment time. For the temperature range considered (1,073 K to 1,173 K both the total reduction of manganese oxides to MnO, as well as the formation of spinel structures could be verified. At the beginning of the formation process, the spinel shows considerable cationic disorder (non-stoichiometric structure. The structure then evolves to the equilibrium stoichiometric form for higher process temperature and time.

  3. Analyses of monocrotaline-induced rabbit model of chronic pulmonary hypertension%以野百合碱建立兔慢性肺动脉高压模型的效果分析

    Institute of Scientific and Technical Information of China (English)

    孙丹丹; 段云友; 陈洪茂; 王跃民; 梁宁南; 王宇; 熊华强

    2011-01-01

    目的:探讨野百合碱(MCT)腹腔注射建立新西兰兔慢性肺动脉高压(CPH)模型的可行性.方法:将84只新西兰兔随机分为两组,即对照组(24只)和模型组(60只).在相同的饲料和饲养条件下,模型组腹腔注射MCT溶液60mg/kg,对照组注射相同剂量的乙醇与生理盐水混合液,28 d后进行右心导管压力测定肺动脉的压力.结果:右心导管各心腔压力的测定值显示,模型组肺的动脉收缩压、舒张压,右室收缩压、舒张压及右房收缩压、舒张压与对照组比较均呈升高的趋势,但仅右房舒张压的差异具有统计学意义(P<0.01);模型组的平均肺动脉收缩压未达到30mmHg,说明模型的制备不理想.病理检测的结果显示,与对照组比较,模型组兔肺小动脉血管的管壁增厚,平滑肌组织增殖明显.结论:MCT注射可致兔肺动脉血管平滑肌层增厚,造成血流动力学改变,但所致肺动脉压力升高的结果并不稳定,仍需进一步研究.%AIM: To explore the feasibility of a rabbit model with chronic monocrotaline (MCT)-induced pulmonary hypertension. METHODS; Eighty-four New Zealand rabbits were randomly divided into two groups: control group of 24 rabbits and MCT group of 60 rabbits. The rats in both groups were given the same diet and were raised under the same conditions. Chronic pulmonary hypertension in the MCT group was developed by injection of MCT solution into the abdominal cavity, whereas only the same dosage of the mixed pure ethanol and physiologic saline was injected into the abdominal cavity in the control group. The pulmonary artery systolic pressure was detected by pressure-guided microcatheter into the pulmonary artery 28 days after injection. RESULTS; The results of the right heart catheterization showed that, except for the right atrial diastolic pressure, the pressures of the heart chambers in the MCT group were not significantly different from those in the control group. The average pulmonary

  4. Fabrication and evaluation of tumor-targeted positive MRI contrast agent based on ultrasmall MnO nanoparticles.

    Science.gov (United States)

    Huang, Haitao; Yue, Tao; Xu, Ke; Golzarian, Jafar; Yu, Jiahui; Huang, Jin

    2015-07-01

    Gd(III) chelate is currently used as positive magnetic resonance imaging (MRI) contrast agent in clinical diagnosis, but generally induces the risk of nephrogenic systemic fibrosis (NSF) due to the dissociated Gd(3+) from Gd(III) chelates. To develop a novel positive MRI contrast agent with low toxicity and high sensitivity, ultrasmall MnO nanoparticles were PEGylated via catechol-Mn chelation and conjugated with cRGD as active targeting function to tumor. Particularly, the MnO nanoparticles with a size of ca. 5nm were modified by α,β-poly(aspartic acid)-based graft polymer containing PEG and DOPA moieties and, meanwhile, conjugated with cRGD to produce the contrast agent with a size of ca. 100nm and a longitudinal relaxivity (r1) of 10.2mM(-1)S(-1). Such nanoscaled contrast agent integrated passive- and active-targeting function to tumor, and its efficient accumulation behavior in tumor was verified by in vivo distribution study. At the same time, the PEG moiety played a role of hydrophilic coating to improve the biocompatibility and stability under storing and physiological conditions, and especially might guarantee enough circulation time in blood. Moreover, in vivo MRI revealed a good and long-term effect of enhancing MRI signal for as-fabricated contrast agent while cell viability assay proved its acceptable cytotoxicity for MRI application. On the whole, the as-fabricated PEGylated and cRGD-functionalized contrast agent based on ultrasmall MnO nanoparticles showed a great potential to the T1-weighted MRI diagnosis of tumor.

  5. Predicting heavy metals' adsorption edges and adsorption isotherms on MnO2 with the parameters determined from Langmuir kinetics.

    Science.gov (United States)

    Hu, Qinghai; Xiao, Zhongjin; Xiong, Xinmei; Zhou, Gongming; Guan, Xiaohong

    2015-01-01

    Although surface complexation models have been widely used to describe the adsorption of heavy metals, few studies have verified the feasibility of modeling the adsorption kinetics, edge, and isotherm data with one pH-independent parameter. A close inspection of the derivation process of Langmuir isotherm revealed that the equilibrium constant derived from the Langmuir kinetic model, KS-kinetic, is theoretically equivalent to the adsorption constant in Langmuir isotherm, KS-Langmuir. The modified Langmuir kinetic model (MLK model) and modified Langmuir isotherm model (MLI model) incorporating pH factor were developed. The MLK model was employed to simulate the adsorption kinetics of Cu(II), Co(II), Cd(II), Zn(II) and Ni(II) on MnO2 at pH3.2 or 3.3 to get the values of KS-kinetic. The adsorption edges of heavy metals could be modeled with the modified metal partitioning model (MMP model), and the values of KS-Langmuir were obtained. The values of KS-kinetic and KS-Langmuir are very close to each other, validating that the constants obtained by these two methods are basically the same. The MMP model with KS-kinetic constants could predict the adsorption edges of heavy metals on MnO2 very well at different adsorbent/adsorbate concentrations. Moreover, the adsorption isotherms of heavy metals on MnO2 at various pH levels could be predicted reasonably well by the MLI model with the KS-kinetic constants.

  6. Predicting heavy metals' adsorption edges and adsorption isotherms on MnO2 with the parameters determined from Langmuir kinetics

    Institute of Scientific and Technical Information of China (English)

    Qinghai Hu; Zhongjin Xiao; Xinmei Xiong; Gongming Zhou; Xiaohong Guan

    2015-01-01

    Although surface complexation models have been widely used to describe the adsorption of heavy metals,few studies have verified the feasibility of modeling the adsorption kinetics,edge,and isotherm data with one pH-independent parameter.A close inspection of the derivation process of Langrnuir isotherm revealed that the equilibrium constant derived from the Langmuir kinetic model,Ks-kinetic,is theoretically equivalent to the adsorption constant in Langrnuir isotherm,Ks-Langmuir.The modified Langmuir kinetic model (MLK model) and modified Langmuir isotherm model (MLI model) incorporating pH factor were developed.The MLK model was employed to simulate the adsorption kinetics of Cu(Ⅱ),Co(Ⅱ),Cd(Ⅱ),Zn(Ⅱ) and Ni(Ⅱ) on MnO2 at pH 3.2 or 3.3 to get the values of Ks-kinetic.The adsorption edges of heavy metals could be modeled with the modified metal partitioning model (MMP model),and the values of Ks-Langrnuir were obtained.The values of Ks-kinetic and Ks-Langrnuir are very close to each other,validating that the constants obtained by these two methods are basically the same.The MMP model with Ks-kinetic constants could predict the adsorption edges of heavy metals on MnO2 very well at different adsorbent/adsorbate concentrations.Moreover,the adsorption isotherms of heavy metals on MnO2 at various pH levels could be predicted reasonably well by the MLI model with the Ks-kinetic constants.

  7. A Facile Method for in Situ Preparation of the MnO2/LaMnO3 Catalyst for the Removal of Toluene.

    Science.gov (United States)

    Si, Wenzhe; Wang, Yu; Zhao, Shen; Hu, Fangyun; Li, Junhua

    2016-04-19

    MOx/ABO3 is a promising catalyst for the high-efficiency removal of volatile organic compounds. However, this catalyst is limited on practical applications due to its complex synthesis procedure and high cost. In this work, the MnO2/LaMnO3 catalyst was prepared in situ using a facile one-step method for the first time, in which partial La cations were selectively removed from three dimensionally chain-like ordered macroporous (3DOM) LaMnO3 material. After selective removal, the obtained MnO2/LaMnO3 sample expressed an excellent catalytic performance on toluene oxidation. Toluene could be completely oxidized into CO2 and H2O at 290 °C over the MnO2/LaMnO3 catalyst with a toluene/oxygen molar ratio of 1/100 and a space velocity of 120 000 mL/(g h). In addition, the apparent activation energy value of MnO2/LaMnO3 was 57 kJ/mol, which was lower than those of other metal oxides catalysts. According to O2-TPD and XPS results, it is concluded that the high catalytic performance of MnO2/LaMnO3 was mainly associated with the large amount of oxygen species and the excellent lattice oxygen mobility. MnO2/LaMnO3 is a promising catalyst for the practical removal of volatile organic compounds due to its high efficiency, good stability, low cost, and convenient preparation.

  8. Kinetics and Mechanism of the Simultaneous Carbothermic Reduction of FeO and MnO from High-Carbon Ferromanganese Slag

    Science.gov (United States)

    Safarian, Jafar; Kolbeinsen, Leiv; Tangstad, Merete; Tranell, Gabriella

    2009-12-01

    The carbothermic reduction of 38.7 pct MnO-12.1 pct CaO-5.4 pct MgO-9.3 pct Al2O3-24.1 pct SiO2-10.4 pct FeO slag in Ar at 1600 °C was studied using the sessile drop wettability technique. Pure graphite, coke, and charcoal were used as the carbon material substrates. The reduction rates were evaluated by sampling at different reduction times and by analyzing the chemical compositions of the reduced slag and the produced metal. The carbothermic FeO reduction from slag is initially fast followed by a much slower reduction rate. However, the rate of the MnO reduction is slow in the fast FeO reduction stage, and it starts to increase significantly during the slow FeO reduction stage. The kinetics of FeO and MnO reduction are affected by the type of carbonaceous materials. Moreover, the rate of the carbon dissolution/transfer into the produced metal phase and the amount of the transferred manganese to the metal phase depend on the type of carbon. Based on the experimental observations and the thermodynamic calculations, a mechanism for MnO reduction was proposed. According to this mechanism, MnO is mainly reduced through a metallothermic reduction by Fe and the rate of MnO reduction is controlled by the rate of the consumption of FeO from the slag, which takes place simultaneously. In contrast, the rate of FeO reduction in the fast initial reduction stage is controlled by the rate of the carbon dissolution/transfer into the metal phase. However, at the second slow FeO reduction stage, it is reduced mainly by the solid carbon.

  9. A detailed study of the hysteresis in La0.67Ca0.33MnO3

    Science.gov (United States)

    Bez, Henrique N.; Nielsen, Kaspar K.; Smith, Anders; Bahl, Christian R. H.

    2016-10-01

    We report a thorough study of the thermal hysteretic behaviour of a single phase sample of the magnetocaloric material La0.67Ca0.33MnO3. Previous reports in the literature have variously found hysteretic and non-hysteretic behaviour. We show the importance of measuring under carefully defined heating and cooling procedures. Careful analysis of the specific heat, measured at five different temperature ramp rates, and the magnetic entropy change indicates that there is no observable hysteresis, even though the behaviour of both quantities is consistent with a first-order phase transition. We discuss the reasons for this and for the differing results previously found.

  10. Phase Separation and Magnetoresistance in Nd0.52Sr0.48MnO3

    Institute of Scientific and Technical Information of China (English)

    李志青; 姜恩永; 刘晖; 李养贤; 于奡; 刘新典; 吴萍; 白海力

    2003-01-01

    Polycrystalline Nd0.52Sr0.48MnO3 ceramic is prepared by a Pechini process. Its electron spin resonance spectra,magnetic and transport properties have been investigated experimentally. At temperature above 270K, the compound is paramagnetic insulator, while in temperature between 160K and 270K, the compound is separated into a paramagnetic insulator and a ferromagnetic metal coexisting state. Below 160 K, the ferromagnetic phase coexists with an antiferromagnetic state, but the ferromagnetic phase remains to be dominant. This makes the compound exhibiting a metallic character even at temperature far below TN.

  11. Substrate-induced strain effects on Pr_{0.6}Ca_{0.4}MnO_{3} films

    OpenAIRE

    2003-01-01

    We report the characterization of the crystal structure, low-temperature charge and orbital ordering, transport, and magnetization of Pr_{0.6}Ca_{0.4}MnO_{3} films grown on LaAlO_{3}, NdGaO_{3}, and SrTiO_{3} substrates, which provide compressive (LaAlO_{3}) and tensile (NdGaO_{3} and SrTiO_{3}) strain. The films are observed to exhibit different crystallographic symmetries than the bulk material, and the low-temperature ordering is found to be more robust under compressive-- as opposed to te...

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

    Science.gov (United States)

    Gu, Taoli; Wei, Bingqing

    2015-07-01

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

  13. Interlinked multiphase Fe-doped MnO2 nanostructures: a novel design for enhanced pseudocapacitive performance

    Science.gov (United States)

    Wang, Ziya; Wang, Fengping; Li, Yan; Hu, Jianlin; Lu, Yanzhen; Xu, Mei

    2016-03-01

    Structure designing and morphology control can lead to high performance pseudocapacitive materials for supercapacitors. In this work, we have designed interlinked multiphase Fe-doped MnO2 nanostructures (α-MnO2/R-MnO2/ε-MnO2) to enhance the electrochemical properties by a facile method. These hierarchical hollow microspheres assembled by interconnected nanoflakes, and with plenty of porous nanorods radiating from the spherical shells were hydrothermally obtained. The supercapacitor electrode prepared from the unique construction exhibits outstanding specific capacitance of 267.0 F g-1 even under a high mass loading (~5 mg cm-2). Obviously improved performances compared to pure MnO2 are also demonstrated with a good rate capability, high energy density (1.30 mW h cm-3) and excellent cycling stability of 100% capacitance retention after 2000 cycles at 2 A g-1. The synergistic effects of alternative crystal structures, appropriate crystallinity and optimal morphology are identified to be responsible for the observations. This rational multiphase composite strategy provides a promising idea for materials scientists to design and prepare scalable electrode materials for energy storage devices.Structure designing and morphology control can lead to high performance pseudocapacitive materials for supercapacitors. In this work, we have designed interlinked multiphase Fe-doped MnO2 nanostructures (α-MnO2/R-MnO2/ε-MnO2) to enhance the electrochemical properties by a facile method. These hierarchical hollow microspheres assembled by interconnected nanoflakes, and with plenty of porous nanorods radiating from the spherical shells were hydrothermally obtained. The supercapacitor electrode prepared from the unique construction exhibits outstanding specific capacitance of 267.0 F g-1 even under a high mass loading (~5 mg cm-2). Obviously improved performances compared to pure MnO2 are also demonstrated with a good rate capability, high energy density (1.30 mW h cm-3) and

  14. Spin-Polarized Intergrain Tunneling in La2/3Sr1/3MnO3

    Science.gov (United States)

    Hwang, H. Y.; Cheong, S.-W.; Ong, N. P.; Batlogg, B.

    1996-09-01

    The magnetoresistance (MR) and the field dependent magnetization have been systematically examined in the low temperature ferromagnetic metallic state of single crystal and polycrystalline La2/3Sr1/3MnO3. We find that the intrinsic negative MR in single crystal is due to the suppression of spin fluctuations, and magnetic domain boundaries do not dominate the scattering process. In contrast, we demonstrate that the MR in the polycrystalline samples exhibits two distinct regions: large MR at low fields dominated by spin-polarized tunneling between grains and high field MR which is remarkably temperature independent from 5 to 280 K.

  15. Reversal transient laser-induced voltages in La2/3Ca1/3MnO3 films

    Institute of Scientific and Technical Information of China (English)

    Zhao Kun; He Meng; Lü Hui-Bin

    2007-01-01

    This paper reports that the transient laser-induced voltages have been observed in La2/3Ca1/3MnO3 thin films on MgO (001) in the absence of an applied current.A peak voltage of~0.15V Was detected in response to 0.015 J pulse of 308 nm laser.It is demonstrated that the signal polarity is reversed when the films are irradiated through the substrate rather than at the air/film interface.Off-diagonal thermoelectricity may support the inversion of the signal when the irradiation direction is reversed.

  16. Interfacial magnetic coupling in ultrathin all-manganite La0.7Sr0.3MnO3-TbMnO3 superlattices

    KAUST Repository

    Tian, Y. F.

    2014-04-14

    We report the growth and magnetic properties of all-manganite superlattices composed of ultrathin double-exchange ferromagnetic La0.7Sr0.3MnO3 and noncollinear multiferroic TbMnO3 layers. Spontaneous magnetization and hysteresis loops are observed in such superlattices with individual La0.7Sr0.3MnO3 layers as thin as two unit cells, which are accompanied by pronounced exchange bias and enhanced coercivity. Our results indicate substantial interfacial magnetic coupling between spin sublattices in such superlattices, providing a powerful approach towards tailoring the properties of artificial magnetic heterostructures.

  17. Magnetocaloric Effect in Colossal Magnetoresistance Material (La0.6Dy0.1)Sr0.3MnO3

    Institute of Scientific and Technical Information of China (English)

    Cai Zhirang; Xu Sujun; Liu Ning; Sun Yong; Tong Wei; Zhang Yuheng

    2005-01-01

    The magnetocaloric effect in the A-site doping colossal magnetoresistance material (La0.6Dy0.1)Sr0.3MnO3 was studied. From the measurement and calculation of isothermal magnetization (M-H) curves under various temperatures, a large magnetocaloric effect with ferromagnetic-paramagnetic transition, additional magnetism exchange action introduces additional magnetic entropy change was discovered. This result suggests that (La0.6Dy0.1)Sr0.3MnO3 is a suitable candidate as working substance at room temperature in magnetic refrigeration technology.

  18. Effective capture and release of circulating tumor cells using core-shell Fe3O4@MnO2 nanoparticles

    Science.gov (United States)

    Xiao, Liang; He, Zhao-Bo; Cai, Bo; Rao, Lang; Cheng, Long; Liu, Wei; Guo, Shi-Shang; Zhao, Xing-Zhong

    2017-01-01

    Circulating tumor cells (CTCs) have been believed to hold significant insights for cancer diagnosis and therapy. Here, we developed a simple and effective method to capture and release viable CTCs using core-shell Fe3O4@MnO2 nanoparticles. Fe3O4@MnO2 nanoparticles bioconjugated with anti-EpCAM antibody have characteristics of specific recognition, magnetic-driven cell isolation and oxalic acid-assisted cell release. The capture and release efficiency of target cancer cells were ∼83% and ∼55%, respectively. And ∼70% of released cells kept good viability, which could facilitate the subsequent cellular analysis.

  19. Magnetic vortex evolution in self-assembled La0.7Sr0.3MnO3 nanoislands under in-plane magnetic field

    Directory of Open Access Journals (Sweden)

    J. Zabaleta

    2014-07-01

    Full Text Available The magnetic vortex formation at room temperature and its evolution under in-plane magnetic field is studied in chemically grown self-assembled La0.7Sr0.3MnO3 nanoislands of less than 200 nm in width. We use variable field magnetic force microscopy and numerical simulations to confirm that the vortex state is ubiquitous in these square-base pyramid shape epitaxial La0.7Sr0.3MnO3 nanostructures, and that it requires in-plane magnetic fields below 40 kA/m to be annihilated.

  20. MOF-derived ultrafine MnO nanocrystals embedded in a porous carbon matrix as high-performance anodes for lithium-ion batteries

    Science.gov (United States)

    Zheng, Fangcai; Xia, Guoliang; Yang, Yang; Chen, Qianwang

    2015-05-01

    Although MnO has been demonstrated to be a promising anode material for lithium-ion batteries (LIBs) in terms of its high theoretical capacity (755 mA h g-1), comparatively low voltage hysteresis (storage applications.Although MnO has been demonstrated to be a promising anode material for lithium-ion batteries (LIBs) in terms of its high theoretical capacity (755 mA h g-1), comparatively low voltage hysteresis (storage applications. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr00528k

  1. Systematic and Molecular Basis of the Antibacterial Action of Quinoxaline 1,4-Di-N-Oxides against Escherichia coli.

    Directory of Open Access Journals (Sweden)

    Guyue Cheng

    Full Text Available Quinoxaline 1,4-di-N-oxides (QdNOs are widely known as potent antibacterial agents, but their antibacterial mechanisms are incompletely understood. In this study, the transcriptomic and proteomic profiles of Escherichia coli exposed to QdNOs were integratively investigated, and the results demonstrated that QdNOs mainly induced an SOS response and oxidative stress. Moreover, genes and proteins involved in the bacterial metabolism, cellular structure maintenance, resistance and virulence were also found to be changed, conferring bacterial survival strategies. Biochemical assays showed that reactive oxygen species were induced in the QdNO-treated bacteria and that free radical scavengers attenuated the antibacterial action of QdNOs and DNA damage, suggesting an oxidative-DNA-damage action of QdNOs. The QdNO radical intermediates, likely carbon-centered and aryl-type radicals, as identified by electron paramagnetic resonance, were the major radicals induced by QdNOs, and xanthine oxidase was one of the QdNO-activating enzymes. This study provides new insights into the action of QdNOs in a systematic manner and increases the current knowledge of bacterial physiology under antibiotic stresses, which may be of great value in the development of new antibiotic-potentiating strategies.

  2. Synthesis and Crystal Structure of Tri-(2-mercaptopyridine N-oxide)bis(dimethyl sulfoxide) Dysprosium(Ⅲ)

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A range of rare earth metal complexes of 2-mercaptopyridine N-oxide (Hmpo) have been synthesized, and studied by elemental analysis and IR spectroscopic technique. Crystal structure of Dy(mpo)3(DMSO)2 (DMSO = dimethyl sulfoxide) has been determined. The complex crystallizes in the triclinic system, space group Pī with lattice parameters: a = 9.602(3), b = 9.803(3), c = 15.498(5)A, α= 89.51(1), β= 85.73(1), γ= 62.99(1)°, Dc = 1.787 g/cm3, C19H24N3O5S5Dy, Mr = 697.21, Z = 2, F(000) = 690, μ = 3.321mm-1, the final R = 0.0237 and wR = 0.0587 for 4116 reflections with I>σ2(I). The coordination number of dysprosium Ⅲ is eight, and its coordination geometry is a somewhat distorted square antiprism with O(3), O(4), O(5), S(3) and O(1), O(2), S(1), S(2) at the tetragonal bases (dihedral angle between their mean planes is 2.9(1)0). Around the Dy atom, three five-membered ring planes (Dy, O, N, C, S) make the dihedral angles of 74.42, 11.31 and 83.72, respectively.

  3. Furoxans (1,2,5-Oxadiazole-N-Oxides) as Novel NO Mimetic Neuroprotective and Procognitive Agents

    Energy Technology Data Exchange (ETDEWEB)

    Schiefer, Isaac T.; VandeVrede, Lawren; Fa; , Mauro; Arancio, Ottavio; Thatcher, Gregory R.J. (Columbia); (UIC)

    2012-08-31

    Furoxans (1,2,5-oxadiazole-N-oxides) are thiol-bioactivated NO-mimetics that have not hitherto been studied in the CNS. Incorporation of varied substituents adjacent to the furoxan ring system led to modulation of reactivity toward bioactivation, studied by HPLC-MS/MS analysis of reaction products. Attenuated reactivity unmasked the cytoprotective actions of NO in contrast to the cytotoxic actions of higher NO fluxes reported previously for furoxans. Neuroprotection was observed in primary neuronal cell cultures following oxygen glucose deprivation (OGD). Neuroprotective activity was observed to correlate with thiol-dependent bioactivation to produce NO{sub 2}{sup -}, but not with depletion of free thiol itself. Neuroprotection was abrogated upon cotreatment with a sGC inhibitor, ODQ, thus supporting activation of the NO/sGC/CREB signaling cascade by furoxans. Long-term potentiation (LTP), essential for learning and memory, has been shown to be potentiated by NO signaling, therefore, a peptidomimetic furoxan was tested in hippocampal slices treated with oligomeric amyloid-{beta} peptide (A{beta}) and was shown to restore synaptic function. The novel observation of furoxan activity of potential therapeutic use in the CNS warrants further studies.

  4. Synthesis and Crystal Structure of 3-Nitrophthalic Acid·3-methyl-4-nitropyridine N-Oxide Adducts

    Institute of Scientific and Technical Information of China (English)

    WANG Yi; FENG Wei; XUE Lin; ZHENG Ji-Min

    2006-01-01

    The title compound, a 1:1 molecular adduct of 3-nitrophthalic acid and 3-methyl-4-nitropyridine N-oxide (PPOM), has been synthesized and characterized by X-ray single-crystal structure analysis. It crystallizes in triclinic, space group P-1 with a = 7.6076(15), b = 7.8180(16), c= 14.546(3) (A), α= 93.90(3), β = 97.21(3), γ= 114.43(3)°, C14H11N3O9, Mr = 365.26,Z=2,V=774.6(3) (A)3, Dc = 1.566 g/m3, u(MoKα) = 0.134 mm-1, F(000) = 376, R = 0.0538 and Wr = 0.1460 for 885 observed reflections (I>2σ(I)). The protons of the carbonylic acids in the molecule are not transferred and the O-H…O and C-H…O hydrogen bonds form zigzag chains in the molecule.

  5. Blood Trimethylamine-N-Oxide Originates from Microbiota Mediated Breakdown of Phosphatidylcholine and Absorption from Small Intestine

    Science.gov (United States)

    Stremmel, Wolfgang; Schmidt, Kathrin V.; Schuhmann, Vera; Kratzer, Frank; Garbade, Sven F.; Langhans, Claus-Dieter; Fricker, Gert; Okun, Jürgen G.

    2017-01-01

    Elevated serum trimethylamine-N-oxide (TMAO) was previously reported to be associated with an elevated risk for cardiovascular events. TMAO originates from the microbiota-dependent breakdown of food-derived phosphatidylcholine (PC) to trimethylamine (TMA), which is oxidized by hepatic flavin-containing monooxygenases to TMAO. Our aim was to investigate the predominant site of absorption of the bacterial PC-breakdown product TMA. A healthy human proband was exposed to 6.9 g native phosphatidylcholine, either without concomitant treatment or during application with the topical antibiotic rifaximin, or exposed only to 6.9 g of a delayed-release PC formulation. Plasma and urine concentrations of TMA and TMAO were determined by electrospray ionization tandem mass spectrometry (plasma) and gas chromatography-mass spectrometry (urine). Native PC administration without concomitant treatment resulted in peak plasma TMAO levels of 43 ± 8 μM at 12 h post-ingestion, which was reduced by concomitant rifaximin treatment to 22 ± 8 μM (p intestine and large bowel. Our results showed that the microbiota in the small intestine generated the PC breakdown product TMA. The resulting TMAO, as a cardiovascular risk factor, was suppressed by topical-acting antibiotics or when PC was presented in an intestinally delayed release preparation. PMID:28129384

  6. Polyanionic pH-responsive polystyrene-b-poly(4-vinyl pyridine-N-oxide) isoporous membranes

    KAUST Repository

    Shevate, Rahul

    2015-12-01

    Recently isoporous block copolymer (BCP) membranes obtained by non-solvent induced phase separation gained a lot of attention due to their highly ordered surface layer, high flux and superior separation properties. These polystyrene-b-poly-4-vinylpyridine (PS-b-P4VP) based membranes showed a strong flux dependence of pH; pores closed at low pH and opened at high pH. The pH-response could now be reversed by a simple post modification; pores are now opening at low pH and closing at high pH. The original membrane was transformed into a polyanionic pH responsive membrane in a one step chemical modification without affecting the isoporous surface morphology. A polystyrene-b-poly-4-vinylpyridine-N-oxide (PS-b-P4VPN-oxide) membrane is obtained by selective oxidation of the PS-b-P4VP membrane. The in situ generated peracid obtained by reacting acetic acid and hydrogen peroxide is employed for oxidation. Surprisingly not only the asymmetric membrane structure with the isoporous skin was retained, but also the mechanical and chemical membrane stability was improved significantly. The modified membranes are insoluble in solvents like DMF, NMP and DMSO. Two kinds of PS-b-P4VP based isoporous membranes are available now with reverse flux response to pH. This opens the door to new interesting charge based fractionations.

  7. Volume Exclusion and H-Bonding Dominate the Thermodynamics and Solvation of Trimethylamine-N-oxide in Aqueous Urea

    Science.gov (United States)

    2012-01-01

    Trimethylamine-N-oxide (TMAO) and urea represent the extremes among the naturally occurring organic osmolytes in terms of their ability to stabilize/destabilize proteins. Their mixtures are found in nature and have generated interest in terms of both their physiological role and their potential use as additives in various applications (crystallography, drug formulation, etc.). Here we report experimental density and activity coefficient data for aqueous mixtures of TMAO with urea. From these data we derive the thermodynamics and solvation properties of the osmolytes, using Kirkwood–Buff theory. Strong hydrogen-bonding at the TMAO oxygen, combined with volume exclusion, accounts for the thermodynamics and solvation of TMAO in aqueous urea. As a result, TMAO behaves in a manner that is surprisingly similar to that of hard-spheres. There are two mandatory solvation sites. In plain water, these sites are occupied with water molecules, which are seamlessly replaced by urea, in proportion to its volume fraction. We discuss how this result gives an explanation both for the exceptionally strong exclusion of TMAO from peptide groups and for the experimentally observed synergy between urea and TMAO. PMID:22280147

  8. Fish oil ameliorates trimethylamine N-oxide-exacerbated glucose intolerance in high-fat diet-fed mice.

    Science.gov (United States)

    Gao, Xiang; Xu, Jie; Jiang, Chengzi; Zhang, Yi; Xue, Yong; Li, Zhaojie; Wang, Jingfeng; Xue, Changhu; Wang, Yuming

    2015-04-01

    Trimethylamine N-oxide (TMAO), a component commonly present in seafood, has been found to have a harmful impact on glucose tolerance in high-fat diet (HFD)-fed mice. However, seafood also contains fish oil (FO), which has been shown to have beneficial effects on metabolism. Here, we investigated the effect of FO on TMAO-induced impaired glucose tolerance in HFD-fed mice. Male C57BL/6 mice were randomly assigned to the high fat (HF), TMAO, and fish oil groups. The HF group was fed a diet containing 25% fat, the TMAO group was fed the HFD plus 0.2% TMAO, and the FO group was fed the HFD plus 0.2% TMAO and 2% fish oil for 12 weeks. After 10 weeks of feeding, oral glucose tolerance tests were performed. Dietary FO improved the fasting glucose level, the fasting insulin level, HOMA-IR value, QUICKI score and ameliorated TMAO-induced exacerbated impaired glucose tolerance in HFD-fed mice. These effects were associated with the expression of genes related to the insulin signalling pathway, glycogen synthesis, gluconeogenesis, and glucose transport in peripheral tissues. Dietary fish oil also decreased TMAO-aggravated adipose tissue inflammation. Our results suggested that dietary FO ameliorated TMAO-induced impaired glucose tolerance, insulin signal transduction in peripheral tissue, and adipose tissue inflammation in HFD-fed mice.

  9. Fabrication of water-dispersible single-walled carbon nanotube powder using N-methylmorpholine N-oxide.

    Science.gov (United States)

    Choi, Hyejun; Woo, Jong Seok; Han, Joong Tark; Park, Soo-Young

    2017-09-13

    Dispersion of nanocarbon materials in liquid media is one of prerequisites for practical applications via solution processing such as spraying, printing, spinning, etc. Here we report that water-dispersible single-walled carbon nanotubes (SWCNTs) were prepared through successive treatments with chlorosulfuric acid (CSA)/H2O2 and N-methylmorpholine N-oxide (NMO) monohydrate. The powder of the CSA/H2O2- and NMO-treated SWCNTs (N-SWCNTs) could be readily redispersed in water in concentrations as high as 1 g L-1 without requiring a dispersant. The mechanism responsible for the high dispersity of the N-SWCNT powder in polar solvents, including water, was elucidated based on the high polarity of the NMO molecule. In order to highlight the wide applicability of the N-SWCNTs, they were used successfully to prepare conducting thin films by spray-coating plastic substrates with an aqueous hybrid solution containing the N-SWCNTs and Ag nanowires (NWs). In addition, a flexible, large-area thin-film heater was prepared based on the N-SWCNT/AgNW hybrid film with a transmittance of 93% and sheet resistance of 30 Ω sq-1. © 2017 IOP Publishing Ltd.

  10. Synthesis of Pr0.70Sr0.30MnO3δ and Nd0.70Sr0.30MnO3δ powders by solution-combustion technique

    Directory of Open Access Journals (Sweden)

    Reinaldo Azevedo Vargas

    2011-01-01

    Full Text Available Powders of Pr0.70Sr0.30MnO3δ (PSM and Nd0.70Sr0.30MnO3δ (NSM compositions are being investigated as alternative cathode materials for Intermediate Temperature Solid Oxide Fuel Cells. The compositions were synthesized by a solution-combustion method using metal nitrates and urea as fuel. Combustion synthesis is a highly suitable synthesis route for achieving fine and homogeneous powders at low temperatures. Single phase pseudo-perovskite was obtained by X-ray diffraction after heat treatment of PSM and NSM powders at 900 ºC. The synthesized and milling powders had an average particle size between 0.27 to 0.07 μm. Chemical analyses of the powders calcined was performed by X-ray fluorescence and morphological analysis by scanning electron microscopy. The results were compared with literature values, indicating characteristics adjusted for preparation of ceramic suspensions.

  11. La0.7Sr0.3MnO3-PZT双层膜中的磁电耦合%Magnetoelectric Coupling in Bilayers of La0.7Sr0.3MnO3-PZT

    Institute of Scientific and Technical Information of China (English)

    杨全民; 张宁

    2006-01-01

    讨论了La0.7Sr0.3MnO3-Pb(Zr,Ti)O3双层膜的磁电(ME)效应.La0.7Sr0.3MnO3粉料由溶胶-凝胶法制成,经1300 K热压并在1573 K高温下烧结而成.在该双层膜中测量到了很强的磁电相互作用.相较于厚膜型(tape casting)复合样品,该双层膜显示出更为优良的ME耦合.反映其ME耦合效应强弱的电压系数αE是在一定的磁场、温度和频率下测得的.横向耦合要比纵向耦合更为强烈,并在225 K时ME电压系数达到峰值.分析表明由磁场和频率变化导致的ME系数变化的实验值与理论值符合的很好.

  12. Electrochemical characterizations on MnO2 supercapacitors with potassium polyacrylate and potassium polyacrylate-co-polyacrylamide gel polymer electrolytes

    KAUST Repository

    Lee, Kuang-Tsin

    2009-11-01

    MnO2·nH2O supercapacitors with potassium polyacrylate (PAAK) and potassium polyacrylate-co-polyacrylamide (PAAK-co-PAAM) gel polymer electrolytes (GPEs) having the weight compositions of polymer:KCl:H2O = 9%:6.7%:84.3% have been characterized for their electrochemical performance. Compared with the liquid electrolyte (LE) counterpart, the GPE cells exhibit remarkable (∼50-130%) enhancement in specific capacitance of the oxide electrode, and the extent of the enhancement increases with increasing amount of the carboxylate groups in the polymers as well as with increasing oxide/electrolyte interfacial area. In situ X-ray absorption near-edge structure (XANES) analysis indicates that the oxide electrodes of the GPE cells possess higher Mn-ion valences and are subjected to greater extent of valence variation than that of the LE cell upon charging/discharging over the same potential range. Copolymerization of PAAK with PAAM greatly improves the cycling stability of the MnO2·nH2O electrode, and the improvement is attributable to the alkaline nature of the amino groups. Both GPEs exhibit ionic conductivities greater than 1.0 × 10-1 S cm-1 and are promising for high-rate applications. © 2009 Elsevier Ltd. All rights reserved.

  13. Magnetic properties of rare-earth-doped La0.7Sr0.3MnO3

    Science.gov (United States)

    Veverka, Pavel; Kaman, Ondřej; Knížek, Karel; Novák, Pavel; Maryško, Miroslav; Jirák, Zdeněk

    2017-01-01

    Rare-earth-doped ferromagnetic manganites La0.63RE0.07Sr0.30MnO3 (RE  =  Gd, Tb, Dy, and Ho) are synthesized in the form of sintered ceramics and nanocrystalline phases with the mean size of crystallites  ≈30 nm. The electronic states of the dopants are investigated by SQUID magnetometry and theoretically interpreted based on the calculations of the crystal field splitting of rare-earth energy levels. The samples show the orthorhombic perovskite structure of Ibmm symmetry, with a complete FM order of Mn spins in bulk and reduced order in nanoparticles. Non-zero moments are also detected at the perovskite A sites, which can be attributed to magnetic polarization of the rare-earth dopants. The measurements in external field up to 70 kOe show a standard Curie-type contribution of the spin-only moments of Gd3+ ions, whereas Kramers ions Dy3+ and non-Kramers ions Ho3+ contribute by Ising moments due to their doublet ground states. The behaviour of non-Kramers ions Tb3+ is anomalous, pointing to singlet ground state with giant Van Vleck paramagnetism. The Tb3+ doping leads also to a notably increased coercivity compared to other La0.63RE0.07Sr0.30MnO3 systems.

  14. Application of biomass-derived flexible carbon cloth coated with MnO2 nanosheets in supercapacitors

    Science.gov (United States)

    He, Shuijian; Chen, Wei

    2015-10-01

    Successful application of inexpensive energy storage devices lies in the exploitation of fabrication approaches that are based on cost-efficient materials and that can be easily scaled up. Here, inexpensive textile weaved by natural flax fiber is selected as raw material in preparing flexible and binder-free electrode material for supercapacitors. Although carbon fiber cloth obtained from the direct carbonization of flax textile exhibits a low specific capacitance of 0.78 F g-1, carbon fiber cloth electrode shows a very short relaxation time of 39.1 m s and good stability with almost 100% capacitance retaining after 104 cycles at 5 A g-1. To extend the application of the resulting carbon cloth in supercapacitor field, a layer of MnO2 nanosheets is deposited on the surface of carbon fiber via in situ redox reaction between carbon and KMnO4. The specific capacitance of MnO2 reaches 683.73 F g-1 at 2 A g-1 and still retains 269.04 F g-1 at 300 A g-1, indicating the excellent rate capacitance performance of the carbon cloth/MnO2 hybrids. The present study shows that carbon cloth derived from flax textile can provide a low-cost material platform for the facile, cost-efficient and large scale fabrication of binder-free electrode materials for energy storage devices.

  15. Effect of P2O5 and MnO2 on crystallization of magnetic glass ceramics

    Directory of Open Access Journals (Sweden)

    Salwa A.M. Abdel-Hameed

    2014-09-01

    Full Text Available This work pointed out the effect of adding P2O5 and/or MnO2 on the crystallization behavior of magnetic glass ceramic in the system Fe2O3·ZnO·CaO·SiO2·B2O3. The differential thermal analysis of the quenched samples revealed decrease in the thermal effects by adding P2O5 and/or MnO2 to the base sample. The X-ray diffraction patterns show the development of nanometric magnetite crystals in a glassy matrix. Heat treatment at 800 °C for 2 h, under reducing atmosphere, caused an increase in the amount of the crystallized magnetite with the appearance of minor hematite and Ca2SiO4. The transmission electron microscope revealed a crystallite size in the range 10–30 nm. Magnetic hysteresis cycles were analyzed with a maximum applied field of 25 kOe at room temperature. The prepared magnetic glass ceramics are expected to be useful for localized treatment of cancer.

  16. Redetermination of the distorted perovskite Nd0.53Sr0.47MnO3

    Directory of Open Access Journals (Sweden)

    Ryoko Makita

    2008-11-01

    Full Text Available Neodymium strontium manganese oxide with ideal composition Nd0.5Sr0.5MnO3 was reported to have two different structure models. In one model, the x coordinate of an O atom is at x > 1/2, while in the other model the x-coordinate of this atom is at x < 1/2. Difference-density maps around this O atom obtained from the current redetermination clearly show that the structure with the O atom at x < 1/2 result in a more satisfactory model than that with x > 1/2. The title compound with a refined composition of Nd0.53 (5Sr0.47 (5MnO3 is a distorted perovskite-type structure with site symmetries 2mm for the statistically occupied (Nd, Sr site and for the above-mentioned O atom, .2/m. for the Mn atom and ..2 for a second O-atom site. In contrast to previous studies, the displacement factors for all atoms were refined anisotropically.

  17. Verification of Anderson Superexchange in MnO via Magnetic Pair Distribution Function Analysis and ab initio Theory

    Science.gov (United States)

    Frandsen, Benjamin A.; Brunelli, Michela; Page, Katharine; Uemura, Yasutomo J.; Staunton, Julie B.; Billinge, Simon J. L.

    2016-05-01

    We present a temperature-dependent atomic and magnetic pair distribution function (PDF) analysis of neutron total scattering measurements of antiferromagnetic MnO, an archetypal strongly correlated transition-metal oxide. The known antiferromagnetic ground-state structure fits the low-temperature data closely with refined parameters that agree with conventional techniques, confirming the reliability of the newly developed magnetic PDF method. The measurements performed in the paramagnetic phase reveal significant short-range magnetic correlations on a ˜1 nm length scale that differ substantially from the low-temperature long-range spin arrangement. Ab initio calculations using a self-interaction-corrected local spin density approximation of density functional theory predict magnetic interactions dominated by Anderson superexchange and reproduce the measured short-range magnetic correlations to a high degree of accuracy. Further calculations simulating an additional contribution from a direct exchange interaction show much worse agreement with the data. The Anderson superexchange model for MnO is thus verified by experimentation and confirmed by ab initio theory.

  18. Reactivity of Nanostructured MnO_2 in Alkaline Medium Studied with a Microcavity Electrode: Effect of Oxidizing Agent

    Institute of Scientific and Technical Information of China (English)

    L.Benhaddad; L.Makhloufi; B.Messaoudi1; K.Rahmouni; H.Takenouti

    2011-01-01

    The synthesis of MnO2 powders by hydrothermal method with different oxidizing agents has been successfully achieved. The characterizations by scanning electron microscopy, energy-dispersive X-ray analyses, transmission electron microscopy, and X-ray diffraction techniques confirm the synthesis of nanostructured γ-MnO2 powders. The electrochemical reactivity of these powders in 1 mol/l KOH is investigated by cyclic voltammetry and electrochemical impedance spectroscopy (EIS) by using microcavity electrode. The results reveal that the MnO2 synthesized with Na2S2O8 shows the highest electrochemical reactivity in the test medium. This is due both to its large expanded surface area and its crystallographic variety γ-MnO2 formed in the matrix of ramsdellite, which is largely used as cathodic material for primary batteries. However, the presence of pyrolusite in the structure of γ-MnO2 synthesized with (NH4)2S2O8 decreases its electrochemical reactivity due to its narrow 1×1 size tunnel, which hinders the protons insertion.

  19. Electrodeposition of amorphous MnO x films on Fe–Ni substrates from aqueous sulfate solution

    Science.gov (United States)

    Pires, Manoel J. M.; Fernandes, Lucas S.

    2017-09-01

    Manganese oxides have a number of promising applications from new magnetic phases to high electrical capacitance systems. A common way of producing these materials is by electrochemical deposition using, for instance, baths with manganous acetate or chloride. As an alternative to acetate or chloride, we have used a solution with MnSO4 for the deposition of MnO x films on a magnetic alloy. Fe–Ni sheets with composition around the Invar point were used as substrates showing the practicability of this kind of growth of the Fe–Ni/MnO x system. The films were characterized by cyclic voltammetry, chronoamperometry, x-ray diffraction, optical and scanning electron microscopies. The obtained films are predominantly amorphous oxides with compositions tending to MnO2, and the most homogeneous samples were deposited from a solution with MnSO4 and H3BO3. Solutions with Na2SO4 and (NH4)2SO4 were also tested, but the resulting films were rather heterogeneous and presented poor adhesion to the Fe–Ni substrates. Direct deposition at constant electric potential as well as deposition by cycling the applied potential were analyzed, and the films prepared by both methods are very similar each other respect to morphology, composition and structure.

  20. Effect of P2O5 and MnO2 on crystallization of magnetic glass ceramics.

    Science.gov (United States)

    Abdel-Hameed, Salwa A M; Marzouk, Mohamed A; Farag, Mohamed M

    2014-09-01

    This work pointed out the effect of adding P2O5 and/or MnO2 on the crystallization behavior of magnetic glass ceramic in the system Fe2O3·ZnO·CaO·SiO2·B2O3. The differential thermal analysis of the quenched samples revealed decrease in the thermal effects by adding P2O5 and/or MnO2 to the base sample. The X-ray diffraction patterns show the development of nanometric magnetite crystals in a glassy matrix. Heat treatment at 800 °C for 2 h, under reducing atmosphere, caused an increase in the amount of the crystallized magnetite with the appearance of minor hematite and Ca2SiO4. The transmission electron microscope revealed a crystallite size in the range 10-30 nm. Magnetic hysteresis cycles were analyzed with a maximum applied field of 25 kOe at room temperature. The prepared magnetic glass ceramics are expected to be useful for localized treatment of cancer.

  1. Synthesis of vertical MnO2 wire arrays on hemp-derived carbon for efficient and robust green catalysts

    Science.gov (United States)

    Yang, MinHo; Kim, Dong Seok; Sim, Jae-Wook; Jeong, Jae-Min; Kim, Do Hyun; Choi, Jae Hyung; Kim, Jinsoo; Kim, Seung-Soo; Choi, Bong Gill

    2017-06-01

    Three-dimensional (3D) carbon materials derived from waste biomass have been attracted increasing attention in catalysis and materials science because of their great potential of catalyst supports with respect to multi-functionality, unique structures, high surface area, and low cost. Here, we present a facile and efficient way for preparing 3D heterogeneous catalysts based on vertical MnO2 wires deposited on hemp-derived 3D porous carbon. The 3D porous carbon materials are fabricated by carbonization and activation processes using hemp (Cannabis Sttiva L.). These 3D porous carbon materials are employed as catalyst supports for direct deposition of vertical MnO2 wires using a one-step hydrothermal method. The XRD and XPS results reveal the crystalline structure of α-MnO2 wires. The resultant composites are further employed as a catalyst for glycolysis of poly(ethylene terephthalate) (PET) with high conversion yield of 98%, which is expected to be expressly profitable for plastics recycling industry.

  2. The Photovoltaic Properties of BiFeO3Lao.7Sro.3MnO3 Heterostructures

    Institute of Scientific and Technical Information of China (English)

    LUO Bing-Cheng; CHEN Chang-Le; FAN Fei; JIN Ke-Xin

    2012-01-01

    An epitaxial BiFeO3/La0.7Sr0.3MnO3 (BFO/LSMO) multiferroic heterostructure is grown on an LaAlO3 (001) substrate by laser molecular beam epitaxy,and its photovoltaic properties are investigated.It is found that the photocurrent is significantly increased under illumination,and the short-circuit photocurrent has a linear relationship with the laser intensity.Furthermore,when the ferroelectric polarization of the BFO layer is switched,the short-circuit photocurrent and open-circuit voltage can be switched.These results are discussed by considering the contributions from the ferroelectric polarization and the electrode/film interface.%An epitaxial BifeO3/La0.7Sr0.3Mno3 (BFO/LSMO) multiferroic heterostructure is grown on an LaAIO3. Substrate by laser molecular beam epitaxy, and its photovoltaic properties are investigated. It is found that the photocurrent is significantly increased under illumination, and the short-circuit photocurrent has a linear relationship with the laser intensity. Furthermore, when the ferroelectric polarization of the BFO layer is switched, the short-circuit photocurrent and open-circuit voltage can be switched. These results are discussed by considering the contributions from the ferroelectric polarization and the electrode/rim interface.

  3. Probing the Degradation Mechanism of Li2MnO3 Cathode for Li-Ion Batteries

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Pengfei; Xiao, Liang; Zheng, Jianming; Zhou, Yungang; He, Yang; Zu, Xiaotao; Mao, Scott X.; Xiao, Jie; Gao, Fei; Zhang, Jiguang; Wang, Chong M.

    2015-02-10

    Capacity and voltage fading of Li2MnO3 is a major challenge for the application of this category of material, which is believed to be associated with the structural and chemical evolution of the materials. This paper reports the detailed structural and chemical evolutions of Li2MnO3 cathode captured by using aberration corrected scanning/transmission electron microscope (S/TEM) after certain numbers of charge-discharge cycling of the batteries. It is found that structural degradation occurs from the very first cycle and is spatially initiated from the surface of the particle and propagates towards the inner bulk as cyclic number increase, featuring the formation of the surface phase transformation layer and gradual thickening of this layer. The structure degradation is found to follow a sequential phase transformation: monoclinic C2/m → tetragonal I41 → cubic spinel, which is consistently supported by the decreasing lattice formation energy based on DFT calculations. For the first time, high spatial resolution quantitative chemical analysis reveals that 20% oxygen in the surface phase transformation layer is removed and such newly developed surface layer is a Li-depleted layer with reduced Mn cations. This work demonstrates a direct correlation between structural degradation and cell’s electrochemical degradation, which enhances our understanding of Li-Mn-rich (LMR) cathode materials.

  4. Magnetic Coupling in La0.67Ca0.33MnO3/La0.67Sr0.33CoO3/La0.67Ca0.33 MnO3 Trilayer Films

    Institute of Scientific and Technical Information of China (English)

    赵昆; 李昊; 黄康权

    2004-01-01

    The perovskite La0.67Ca0.33MnO3/La0.67Sr0.33CoO3/La0.67Ca0.33MnO3 trilayers were fabricated by a facing-target sputtering technique and their magnetotransport properties were investigated. The magnetoresistance is dependent on spacer thickness and dramatically decreases when La0.67Sr0.33CoO3 layer is thick enough because of its short-circuiting effect. Different from La0.67Ca0.33MnO3 single layer, trilayer films with thin La0.67Sr0.33CoO3 spacer have the enhanced metal-semiconductor transition temperature (TMS) of La0.67Ca0.33MnO3 layers. The magnetic coercivity HC shows a nonmonotonic behavior with changing the spacer layer thickness at 230 K. The waist-like hysteresis indicates that there is an indirect exchange coupling between the top and bottom La0.67Ca0.33MnO3 layers across the spacer La0.67Sr0.33CoO3 layer.

  5. Determination of trimethylamine, trimethylamine N-oxide, and taurine in human plasma and urine by UHPLC-MS/MS technique.

    Science.gov (United States)

    Awwad, Hussain Mohamad; Geisel, Juergen; Obeid, Rima

    2016-12-01

    Trimethylamine-N-oxide (TMAO) is produced in the liver from trimethylamine (TMA) and is an important cellular osmolyte and potential atherogenic factor. Taurine is involved in cholesterol metabolism and also serves as a cellular osmolyte. Given their significant biological functions, the development of reliable measurement techniques is crucial to further study their role in health and disease METHODS: A new ultrahigh performance liquid chromatography-tandem mass spectrometry method was developed and validated for the simultaneous determination of TMA, TMAO, and taurine in plasma and urine. The method consisted of a deproteinization step using methanol/acetonitrile (15:85) that contained 0.2% formic acid and isotope-labeled internal standards. Samples were separated by centrifugation and injected into the UHPLC system. Quantification was conducted using a triple-quadrupole mass spectrometer detector with electrospray ionization interface in positive mode. The limits of detection ranged from 0.08 to 0.12μmol/L. The calibration curves were linear (r≥0.999) over the range examined (0.15-400μmol/L) for all compounds. The inter- and intra-day coefficients of variations were≤14.5% for TMA and ≤8% for TMAO and taurine. TMAO and taurine were found to be stable in EDTA plasma for at least 14 months at -70°C. Mean recoveries ranged from 95% to 109% and the relative matrix effects were≤4.0%. The method was applied to study physiological and pre-analytical factors in plasma and urine samples. The new UHPLC-MS/MS method has good accuracy, precision, and recovery. The assay combines simple sample processing with a short run time, making it well suited for high-throughput routine clinical or research purposes. Copyright © 2016 Elsevier B.V. All rights reserved.

  6. The effect of aqueous solutions of trimethylamine-N-oxide on pressure induced modifications of hydrophobic interactions.

    Science.gov (United States)

    Sarma, Rahul; Paul, Sandip

    2012-09-07

    To understand the mechanism of protein protection by the osmolyte trimethylamine-N-oxide (TMAO) at high pressure, using molecular dynamics (MD) simulations, solvation of hydrophobic group is probed in aqueous solutions of TMAO over a wide range of pressures relevant to protein denaturation. The hydrophobic solute considered in this study is neopentane which is a considerably large molecule. The concentrations of TMAO range from 0 to 4 M and for each TMAO concentration, simulations are performed at five different pressures ranging from 1 atm to 8000 atm. Potentials of mean force are calculated and the relative stability of solvent-separated state over the associated state of hydrophobic solute are estimated. Results suggest that high pressure reduces association of hydrophobic solutes. From computations of site-site radial distribution function followed by analysis of coordination number, it is found that water molecules are tightly packed around the nonpolar particle at high pressure and the hydration number increases with increasing pressure. On the other hand, neopentane interacts preferentially with TMAO over water and although hydration of neopentane reduces in presence of this osmolyte, TMAO does not show any tendency to prevent the pressure-induced dispersion of neopentane moieties. It is also observed that TMAO molecules prefer a side-on orientation near the neopentane surface, allowing its oxygen atom to form favorable hydrogen bonds with water while maintaining some hydrophobic contacts with neopentane. Analysis of hydrogen-bond properties and solvation characteristics of TMAO reveals that TMAO can form hydrogen bonds with water and it reduces the identical nearest neighbor water molecules caused by high hydrostatic pressures. Moreover, TMAO enhances life-time of water-water hydrogen bonds and makes these hydrogen bonds more attractive. Implication of these results for counteracting effect of TMAO against protein denaturation at high pressures are

  7. Mechanisms of antibacterial action of Quinoxaline 1,4-di-N-oxides against Clostridium perfringens and Brachyspira hyodysenteriae

    Directory of Open Access Journals (Sweden)

    Fanfan Xu

    2016-12-01

    Full Text Available Quinoxaline 1,4-di-N-oxides (QdNOs are a class of bioreductive compounds, however their antibacterial mechanisms are still unclarified. The aim of this study was to assess the ability of two representative QdNO drugs, cyadox (CYA and olaquindox (OLA, to produce reactive oxide species (ROS in Gram-positive anaerobe Clostridium perfringens CVCC1125 and Gram-negative anaerobe Brachyspira hyodysenteriae B204. In addition, the effects of QdNOs on the integrity of bacterial cell walls and membranes as well as the morphological alterations and DNA oxidative damage in C. perfringens and B. hyodysenteriae were analyzed. It was demonstrated that under anaerobic conditions, QdNOs were metabolized into the reduced products which did not show any antibacterial activity. A significant dose-related increase of intracellular ROS level and intracellular hydroxyl radicals were evident in bacteria exposed to QdNOs. The result of biochemical assay showed that the cell walls and membranes of the bacteria treated with QdNOs were damaged. After exposure to 1/2MIC to 4MIC of CYA and OLA, C. perfringens and B. hyodysenteriae became elongated and filamentous. Morphological observation with scanning and transmission electron microscopes revealed rupture, loss of cytoplasmic material and cell lysis in QdNO-treated bacteria, indicating serious damage of cells. There was an increase of 8-OHdG in the two strains treated by QdNOs, but it was lower in Gram-positive than in Gram-negative bacteria. Agarose gel electrophoresis showed the degradation of chromosomal DNA in both of the two anaerobes treated by QdNOs. The results suggest that QdNOs may kill C. perfringens and B. hyodysenteriae via the generation of ROS and hydroxyl radicals from the bacterial metabolism of QdNOs, which cause oxidative damage in bacteria under anaerobic conditions.

  8. Mechanisms of Antibacterial Action of Quinoxaline 1,4-di-N-oxides against Clostridium perfringens and Brachyspira hyodysenteriae.

    Science.gov (United States)

    Xu, Fanfan; Cheng, Guyue; Hao, Haihong; Wang, Yulian; Wang, Xu; Chen, Dongmei; Peng, Dapeng; Liu, Zhenli; Yuan, Zonghui; Dai, Menghong

    2016-01-01

    Quinoxaline 1,4-di-N-oxides (QdNOs) are a class of bioreductive compounds, however, their antibacterial mechanisms are still unclarified. The aim of this study was to assess the ability of two representative QdNO drugs, cyadox (CYA) and olaquindox (OLA), to produce reactive oxide species (ROS) in Gram-positive anaerobe Clostridium perfringens CVCC1125 and Gram-negative anaerobe Brachyspira hyodysenteriae B204. In addition, the effects of QdNOs on the integrity of bacterial cell walls and membranes as well as the morphological alterations and DNA oxidative damage in C. perfringens and B. hyodysenteriae were analyzed. It was demonstrated that under anaerobic conditions, QdNOs were metabolized into the reduced products which did not show any antibacterial activity. A significant dose-related increase of intracellular ROS level and intracellular hydroxyl radicals were evident in bacteria exposed to QdNOs. The result of biochemical assay showed that the cell walls and membranes of the bacteria treated with QdNOs were damaged. After exposure to 1/2MIC to 4MIC of CYA and OLA, C. perfringens and B. hyodysenteriae became elongated and filamentous. Morphological observation with scanning and transmission electron microscopes revealed rupture, loss of cytoplasmic material and cell lysis in QdNO-treated bacteria, indicating serious damage of cells. There was an increase of 8-OHdG in the two strains treated by QdNOs, but it was lower in C. perfringens CVCC1125 than in B. hyodysenteriae B204. Agarose gel electrophoresis showed the degradation of chromosomal DNA in both of the two anaerobes treated by QdNOs. The results suggest that QdNOs may kill C. perfringens and B. hyodysenteriae via the generation of ROS and hydroxyl radicals from the bacterial metabolism of QdNOs, which cause oxidative damage in bacteria under anaerobic conditions.

  9. Cholera toxin production during anaerobic trimethylamine N-oxide respiration is mediated by stringent response in Vibrio cholerae.

    Science.gov (United States)

    Oh, Young Taek; Park, Yongjin; Yoon, Mi Young; Bari, Wasimul; Go, Junhyeok; Min, Kyung Bae; Raskin, David M; Lee, Kang-Mu; Yoon, Sang Sun

    2014-05-09

    As a facultative anaerobe, Vibrio cholerae can grow by anaerobic respiration. Production of cholera toxin (CT), a major virulence factor of V. cholerae, is highly promoted during anaerobic growth using trimethylamine N-oxide (TMAO) as an alternative electron acceptor. Here, we investigated the molecular mechanisms of TMAO-stimulated CT production and uncovered the crucial involvement of stringent response in this process. V. cholerae 7th pandemic strain N16961 produced a significantly elevated level of ppGpp, the bacterial stringent response alarmone, during anaerobic TMAO respiration. Bacterial viability was impaired, and DNA replication was also affected under the same growth condition, further suggesting that stringent response is induced. A ΔrelA ΔspoT ppGpp overproducer strain produced an enhanced level of CT, whereas anaerobic growth via TMAO respiration was severely inhibited. In contrast, a ppGpp-null strain (ΔrelA ΔspoT ΔrelV) grew substantially better, but produced no CT, suggesting that CT production and bacterial growth are inversely regulated in response to ppGpp accumulation. Bacterial capability to produce CT was completely lost when the dksA gene, which encodes a protein that works cooperatively with ppGpp, was deleted. In the ΔdksA mutant, stringent response growth inhibition was alleviated, further supporting the inverse regulation of CT production and anaerobic growth. In vivo virulence of ΔrelA ΔspoT ΔrelV or ΔdksA mutants was significantly attenuated. The ΔrelA ΔspoT mutant maintained virulence when infected with exogenous TMAO despite its defective growth. Together, our results reveal that stringent response is activated under TMAO-stimulated anaerobic growth, and it regulates CT production in a growth-dependent manner in V. cholerae.

  10. Advanced chronic kidney disease populations have elevated trimethylamine N-oxide levels associated with increased cardiovascular events.

    Science.gov (United States)

    Kim, Richard B; Morse, Bridget L; Djurdjev, Ognjenka; Tang, Mila; Muirhead, Norman; Barrett, Brendan; Holmes, Daniel T; Madore, Francois; Clase, Catherine M; Rigatto, Claudio; Levin, Adeera

    2016-05-01

    Cardiovascular disease is more common in patients with chronic kidney disease (CKD), and traditional risk factors do not adequately predict those at risk for cardiovascular (CV) events. Recent evidence suggests elevated trimethylamine N-oxide (TMAO), created by gut microflora from dietary L-carnitine and choline, is associated with CV events. We investigated the relationship of TMAO levels in patients with stages 3b and 4 CKD to ischemic CV events using the CanPREDDICT cohort, a Canada-wide observational study with prospective 3-year follow-up of adjudicated CV events. Baseline samples were obtained for 2529 CKD patients. TMAO, choline, and L-carnitine levels were measured using tandem mass spectrometry. Baseline median TMAO level was high for the whole cohort (20.41 μM; interquartile range [IQR]: 12.82-32.70 μM). TMAO was independently associated with CV events (hazard ratio 1.23; 95% confidence interval: 1.06-1.42 / 1 SD lnTMAO) after adjusting for all potential CV risk factors. Those in the highest TMAO quartile had significantly higher risk of CV events (adjusted hazard ratio 1.59; 95% confidence interval: 1.04-2.43; P = 0.0351) in the analysis of recurring ischemic events. Among those with stage 3b CKD (hazard ratio 1.45; 95% confidence interval: 1.12-1.87 / 1 SD lnTMAO), independent of kidney function, TMAO levels identified those at highest risk for events. Our results suggest that TMAO may represent a new potentially modifiable CV risk factor for CKD patients. Further studies are needed to determine sources of variability and if lowering of TMAO reduces CV risk in CKD.

  11. Impact of interfacial coupling of oxygen octahedra on ferromagnetic order in La0.7Sr0.3MnO3/SrTiO3 heterostructures

    Science.gov (United States)

    Li, Xiaoyan; Lindfors-Vrejoiu, Ionela; Ziese, Michael; Gloter, Alexandre; van Aken, Peter A.

    2017-01-01

    La0.7Sr0.3MnO3, a half-metallic ferromagnet with full spin polarization, is generally used as a standard spin injector in heterostructures. However, the magnetism of La0.7Sr0.3MnO3 is strongly modified near interfaces, which was addressed as “dead-layer” phenomenon whose origin is still controversial. Here, both magnetic and structural properties of La0.7Sr0.3MnO3/SrTiO3 heterostructures were investigated, with emphasis on the quantitative analysis of oxygen octahedral rotation (OOR) across interfaces using annular-bright-field imaging. OOR was found to be significantly altered near interface for both La0.7Sr0.3MnO3 and SrTiO3, as linked to the magnetism deterioration. Especially in La0.7Sr0.3MnO3/SrTiO3 superlattices, the almost complete suppression of OOR in 4 unit-cell-thick La0.7Sr0.3MnO3 results in a canted ferromagnetism. Detailed comparisons between strain and OOR relaxation and especially the observation of an unexpected La0.7Sr0.3MnO3 lattice c expansion near interfaces, prove the relevance of OOR for the magnetic properties. These results indicate the capability of tuning the magnetism by engineering OOR at the atomic scale.

  12. Impact of interfacial coupling of oxygen octahedra on ferromagnetic order in La0.7Sr0.3MnO3/SrTiO3 heterostructures

    Science.gov (United States)

    Li, Xiaoyan; Lindfors-Vrejoiu, Ionela; Ziese, Michael; Gloter, Alexandre; van Aken, Peter A.

    2017-01-01

    La0.7Sr0.3MnO3, a half-metallic ferromagnet with full spin polarization, is generally used as a standard spin injector in heterostructures. However, the magnetism of La0.7Sr0.3MnO3 is strongly modified near interfaces, which was addressed as “dead-layer” phenomenon whose origin is still controversial. Here, both magnetic and structural properties of La0.7Sr0.3MnO3/SrTiO3 heterostructures were investigated, with emphasis on the quantitative analysis of oxygen octahedral rotation (OOR) across interfaces using annular-bright-field imaging. OOR was found to be significantly altered near interface for both La0.7Sr0.3MnO3 and SrTiO3, as linked to the magnetism deterioration. Especially in La0.7Sr0.3MnO3/SrTiO3 superlattices, the almost complete suppression of OOR in 4 unit-cell-thick La0.7Sr0.3MnO3 results in a canted ferromagnetism. Detailed comparisons between strain and OOR relaxation and especially the observation of an unexpected La0.7Sr0.3MnO3 lattice c expansion near interfaces, prove the relevance of OOR for the magnetic properties. These results indicate the capability of tuning the magnetism by engineering OOR at the atomic scale. PMID:28074836

  13. Direct and indirect measurement of the magnetocaloric effect in a La0.6Ca0.4MnO3 ceramic perovskite

    DEFF Research Database (Denmark)

    Dinesen, A.R.; Linderoth, Søren; Mørup, Steen

    2002-01-01

    The adiabatic temperature change DeltaT(ad) due to a change of the external magnetic field (the magnetocaloric effect) for a perovskite-type La0.6Ca0.4MnO3 sample has been measured directly and indirectly (from the entropy change) and the results are compared. From the indirect method, involving...

  14. Enhanced room temperature magnetoresistance in maganites La0.60Sr0.25-yNa0.15Δy MnO 31

    Institute of Scientific and Technical Information of China (English)

    TANG Guide; ZHAO Fuwei; LI Zhuangzhi; HOU Denglu; ZHAO Xu; LI Zhiqing

    2006-01-01

    Bulk polycrystalline samples of La0.60Sr0.4MnO3 and La0.60Sr0.25-yNa0.15ΔyMnO3 with 0.00≤ y ≤0.15 ("Δ" representing cation vacancy) were successfully synthesized using the sol-gel method. The structural, magnetic, and electrical properties of the polycrystallineof the samples were investigated. The results of X-ray powder diffraction patterns show that these compounds crystallize in a distorted rhombohedral structure with the space group R(3)C . The measurement shows that, with vacancy content y increasing, the unit cell volume V of samples increases, furthermore, the Curie temperature TC decreases. The temperature dependence of resistivity shows that all samples undergo a metal-semiconductor transition accompanying a ferromagnetic to paramagnetic transition with the increase of temperature. Under an applied filed of 1.8 T, a maximum room temperature magnetoresistance ( MR ) of 20% is obtained at 293 K for the compound La0.60Sr0.1Na0.15Δ0.15MnO3. The MR peak value of La0.60Sr0.1Na0.15Δ0.15MnO3 increases2 times more than that of La0.60Sr0.40MnO3 ( MRP=6.4%, TMR =373 K), and the MR peak is shifted from 373 K to room temperature.

  15. High-rate performance electrospun Na0.44MnO2 nanofibers as cathode material for sodium-ion batteries

    Science.gov (United States)

    Fu, Bi; Zhou, Xuan; Wang, Yaping

    2016-04-01

    Sodium-ion batteries (SIBs) are considered as one of the most promising candidates to replace lithium-ion batteries (LIBs), because of their similar electrochemical properties, and geographical limitations of lithium. However, searching for the appropriate cathode materials for SIBs that can accommodate structure change during the insertion and extraction of sodium ions is facing great challenges due to the relatively larger size of sodium ion. Na0.44MnO2 has recently attracted significant attention because its crystal structure exhibits two types of large channels formed by MnO6 octahedra and MnO5 square pyramids, which facilitate the transportation of sodium ions. However, suffering from the slow kinetics and structural degradation, its rate performance is still not satisfied. Here, we report the fabrication of two types of Na0.44MnO2 hierarchical structures by optimized electrospinning and controlled subsequent annealing process. One is nanofiber (NF) which demonstrates a superior rate performance with reversible specific capacity of 69.5 mAh g-1 at 10 C, attributed to its one-dimensional (1D) ultralong and continuous fibrous network structure; the other is nanorod (NR) which exhibits an excellent cyclic performance with reversible specific capacity of 120 mAh g-1 after 140 cycles, due to its large S-shaped tunnel structure with a single crystalline structure.

  16. Ultrasound-assisted MnO2 catalyzed homolysis of peracetic acid for phenol degradation: The assessment of process chemistry and kinetics

    NARCIS (Netherlands)

    Rokhina, E.V.; Makarova, K.; Lathinen, M.; Golovina, E.A.; As, van H.; Virkutyte, J.

    2013-01-01

    The combination of peracetic acid (PAA) and heterogeneous catalyst (MnO2) was used for the degradation of phenol in an aqueous solution in the presence of ultrasound irradiation (US). As a relevant source of free radicals (e.g. OH), peracetic acid was comprehensively studied by means of electron spi

  17. Electronic transport in ferroelectric-ferromagnetic composites La5/8(Ba,Ca)3/8MnO3:LuMnO3

    Science.gov (United States)

    Mandal, P.; Choudhury, P.; Ghosh, B.

    2006-09-01

    An almost complete immiscibility between metallic ferromagnet La5/8Ba3/8MnO3 or La5/8Ca3/8MnO3 and insulating ferroelectric LuMnO3 has been established from structural, magnetic, and transport studies. Both (x) La5/8Ba3/8MnO3:(1-x)LuMnO3 and (x) La5/8Ca3/8MnO3:(1-x)LuMnO3 show a metal-insulator transition below a critical volume fraction xvc of the metallic component. Over the entire range of x>xvc , electronic conduction follows a classical percolation model. The conductivity scaling exponent t is the same as that of the universal value (=2) for the three-dimensional (3D) system; xvc is also close to the theoretical prediction for the 3D continuum model. For xLuMnO3 . The temperature dependence of both resistivity and thermopower for 0≤x

  18. Multiangular Rod-Shaped Na0.44MnO2 as Cathode Materials with High Rate and Long Life for Sodium-Ion Batteries.

    Science.gov (United States)

    Liu, Qiannan; Hu, Zhe; Chen, Mingzhe; Gu, Qinfen; Dou, Yuhai; Sun, Ziqi; Chou, Shulei; Dou, Shi Xue

    2017-02-01

    The tunnel-structured Na0.44MnO2 is considered as a promising cathode material for sodium-ion batteries because of its unique three-dimensional crystal structure. Multiangular rod-shaped Na0.44MnO2 have been first synthesized via a reverse microemulsion method and investigated as high-rate and long-life cathode materials for Na-ion batteries. The microstructure and composition of prepared Na0.44MnO2 is highly related to the sintering temperature. This structure with suitable size increases the contact area between the material and the electrolyte and guarantees fast sodium-ion diffusion. The rods prepared at 850 °C maintain specific capacity of 72.8 mA h g(-1) and capacity retention of 99.6% after 2000 cycles at a high current density of 1000 mA g(-1). The as-designed multiangular Na0.44MnO2 provides new insight into the development of tunnel-type electrode materials and their application in rechargeable sodium-ion batteries.

  19. Hierarchical NiCo2O4@MnO2 core-shell heterostructured nanowire arrays on Ni foam as high-performance supercapacitor electrodes.

    Science.gov (United States)

    Yu, Le; Zhang, Genqiang; Yuan, Changzhou; Lou, Xiong Wen David

    2013-01-07

    An advanced integrated electrode for high-performance supercapacitors has been designed by growing hierarchical NiCo(2)O(4)@MnO(2) core-shell heterostructured nanowire arrays on nickel foam. Such unique array nanoarchitectures exhibit remarkable electrochemical performance with high capacitance and desirable cycle life at high rates.

  20. Folic acid-conjugated MnO nanoparticles as a T1 contrast agent for magnetic resonance imaging of tiny brain gliomas.

    Science.gov (United States)

    Chen, Ning; Shao, Chen; Qu, Yanming; Li, Shuai; Gu, Wei; Zheng, Tingting; Ye, Ling; Yu, Chunjiang

    2014-11-26

    Detection of brain gliomas at the earliest stage is of great importance to improve outcomes, but it remains a most challenging task. In this study, oleic acid capped manganese oxide (MnO) nanoparticles (NPs) were prepared by the thermal decomposition of manganese oleate precursors and then transformed to water-dispersible MnO NPs by replacing oleic acid with N-(trimethoxysilylpropyl) ethylene diamine triacetic acid (TETT) silane. The covalently bonded TETT silane offers MnO NPs colloidal stability and abundant carboxylic functional groups allowing the further conjugation of the glioma-specific moiety, folic acid (FA). Moreover, the thin layer of TETT silane ensures a short distance between external Mn ion and water proton, which endows the FA-conjugated, TETT modified MnO (MnO-TETT-FA) NPs a longitudinal relaxivity as high as 4.83 mM(-1) s(-1). Accordingly, the in vivo magnetic resonance (MR) images demonstrated that MnO-TETT-FA NPs could efficiently enhance the MRI contrast for tiny brain gliomas. More importantly, due to the specificity of FA, MnO-TETT-FA NPs led to a clearer margin of the tiny glioma. This together with the good biocompatibility discloses the great potential of MnO-TETT-FA NPs as effective MRI contrast agents for the early diagnosis of brain gliomas.

  1. Evolution of three-dimensional correlations during the photoinduced melting of antiferromagnetic order in La0.5Sr1.5MnO4

    NARCIS (Netherlands)

    Tobey, R. I.; Wall, S.; Foerst, M.; Bromberger, H.; Khanna, V.; Turner, J. J.; Schlotter, W.; Trigo, M.; Krupin, O.; Lee, W. S.; Chuang, Y. -D.; Moore, R.; Cavalieri, A. L.; Wilkins, S. B.; Zheng, H.; Mitchell, J. F.; Dhesi, S. S.; Cavalleri, A.; Hill, J.P.

    2012-01-01

    Using time-resolved resonant soft x-ray diffraction, we measure the evolution of the full three-dimensional scattering volume of the antiferromagnetic superlattice reflection in the single-layer manganite La0.5Sr1.5MnO4 on femtosecond time scales following photoexcitation. We find that the in-plane

  2. Magnetic anisotropy and magnetization reversal of La 0.67 Sr 0.33 MnO 3 thin films on SrTiO 3 (110)

    NARCIS (Netherlands)

    Boschker, Hans; Kautz, Jaap; Houwman, Evert P.; Koster, Gertjan; Blank, Dave H.A.; Rijnders, Guus

    2010-01-01

    The magnetic behavior of La 0.67 Sr 0.33 MnO 3 (LSMO) filmsgrown on SrTiO 3 (110) substrates was studied. In-plane uniaxial magnetic anisotropy with the easy axis aligned with the [001] lattice direction was observed, together with an out-of-plane component. This is explained by the crystal stru

  3. CURRENT-DEPENDENT POSITIVE MAGNETORESISTANCE IN Ga-DOPED a0.5Ca0.5MnO3

    Institute of Scientific and Technical Information of China (English)

    CHEN XIN; WANG ZHI-HONG; LI RUN-WEI; SHEN BAO-GEN; ZHAO HONG-WU; ZHAN WEN-SHAN; CHEN JIN-SONG; ZHANG XI-XIANG

    2001-01-01

    The magnetic and transport properties of the Ga-doped charge-ordering state Lao.5Cao.5MnO3 have been studied.A current-dependent large positive magnetoresistance (1080%) at 5 K was observed. These observations are interpreted in terms of the spin-dependent tunnelling process between ferromagnetic clusters embedded in an antiferromagnetic matrix.

  4. Simple explanation for the reentrant magnetic phase transition in Pr0.5Sr0.41Ca0.09MnO3 perovskite

    Indian Academy of Sciences (India)

    B T Cong; P N A Huy; N H Long; D D Long

    2003-01-01

    The reentrant magnetic phase transition in Pr0.5Sr0.41Ca0.09MnO3 perovskite is explained using the Ising spin model on the square lattice with mixed ferromagnetic and antiferromagnetic exchange interactions. It is shown using numerical calculations that this effect is strongly affected by the external magnetic field and lattice disorder.

  5. Self-construction of magnetic hollow La0.7Sr0.3MnO3 microspheres with complex units.

    Science.gov (United States)

    Chu, Xuefeng; Huang, Keke; Han, Mei; Feng, Shouhua

    2013-04-15

    Perovskite structure La0.7Sr0.3MnO3 magnetic hollow microspheres with complex units were prepared via the hydrothermal route without hard and soft templates. The formation of hollow microspheres follows the self-construction mechanism involving oriented attachment, dissolution, and recrystallization processes. It exhibits a ferromagnetic behavior at room temperature.

  6. Temperature-dependent and anisotropic optical response of layered Pr0.5Ca1.5MnO4 probed by spectroscopic ellipsometry

    NARCIS (Netherlands)

    Majidi, M. A.; Thoeng, E.; Gogoi, P. K.; Wendt, F.; Wang, S. H.; Santoso, I.; Asmara, T. C.; Handayani, I. P.; van Loosdrecht, P. H. M.; Nugroho, A. A.; Ruebhausen, M.; Rusydi, A.; Rübhausen, M.

    2013-01-01

    We study the temperature dependence as well as anisotropy of optical conductivity (sigma(1)) in the pseudocubic single crystal Pr0.5Ca1.5MnO4 using spectrocopic ellipsometry. Three transition temperatures are observed and can be linked to charge-orbital (T-CO/OO similar to 320 K), two-dimensional-an

  7. Methylresorcinarene: a reaction vessel to control the coordination geometry of copper(II) in pyridine N-oxide copper(II) complexes.

    Science.gov (United States)

    Beyeh, Ngong Kodiah; Puttreddy, Rakesh

    2015-06-07

    Pyridine and 2-picolinic acid N-oxides form 2 : 2 and 2 : 1 ligand : metal (L : M) discrete L2M2 and polymeric complexes with CuCl2 and Cu(NO3)2, respectively, with copper(ii) salts. The N-oxides also form 1 : 1 host-guest complexes with methylresorcinarene. In combination, the three components form a unique 2 : 2 : 1 host-ligand-metal complex. The methylresorcinarene acts as a reaction vessel/protecting group to control the coordination of copper(ii) from cis-see-saw to trans-square planar, and from octahedral to square planar coordination geometry. These processes were studied in solution and in the solid state via(1)H NMR spectroscopy and single crystal X-ray diffraction.

  8. A Car-Parrinello and path integral molecular dynamics study of the intramolecular lithium bond in the lithium 2-pyridyl-N-oxide acetate

    Science.gov (United States)

    Durlak, Piotr; Latajka, Zdzisław; Berski, Sławomir

    2009-07-01

    Lithium bonding in lithium 2-pyridyl-N-oxide acetate has been investigated using classic Car-Parrinello molecular dynamics (CPMD) and the path integral approach [path integrals molecular dynamics (PIMD)]. The simulations have been performed in 300 K. Structures, energies, and lithium trajectories have been determined. The CPMD results show that the lithium atom is generally equidistant between heavy atoms in the (O⋯Li⋯O) bridge. Applying quantum effects through the PIMD leads to similar conclusion. The theoretical lithium 2-pyridyl-N-oxide acetate infrared spectrum has also been determined using the CPMD calculations. This shows very good agreement with available experimental results and reproduces well the broad low-frequency band observed experimentally. In order to gain deeper understanding of the nature of the lithium bonding topological analysis of the electron localization function has been applied.

  9. Simultaneous determination of dimethylamine, trimethylamine and trimethylamine-n-oxide in aquatic products extracts by ion chromatography with non-suppressed conductivity detection.

    Science.gov (United States)

    Li, Feng; Liu, Hong-ying; Xue, Chang-hu; Xin, Xue-qian; Xu, Jie; Chang, Yao-guang; Xue, Yong; Yin, Li-ang

    2009-07-31

    An ion chromatography method with non-suppressed conductivity detection was developed for the simultaneous determination of dimethylamine (DMA), trimethylamine (TMA) and trimethylamine-n-oxide (TMAO) in aquatic products. They were separated by means of cation-exchange chromatography using a 3.0 mmol/L methanesulfonic acid solution as eluent and an IonPac CS17 column (250 mm x 4 mm i.d.) as the separation column. Detection limits of dimethylamine, trimethylamine and trimethylamine-n-oxide were 0.06, 0.08 and 0.10 mg/L, respectively. The relative standard deviations (RSDs) of peak area were less than 3.53%. The recoveries were between 93.7% and 104.1%. Unlike traditional methods, this validated method is inexpensive and stable.

  10. Synthesis, 3D-QSAR analysis and biological evaluation of quinoxaline 1,4-di-N-oxide derivatives as antituberculosis agents.

    Science.gov (United States)

    Pan, Yuanhu; Li, Panpan; Xie, Shuyu; Tao, Yanfei; Chen, Dongmei; Dai, Menghong; Hao, Haihong; Huang, Lingli; Wang, Yulian; Wang, Liye; Liu, Zhenli; Yuan, Zonghui

    2016-08-15

    A series of quinoxaline 1,4-di-N-oxide derivatives variously substituted at C-2 position were synthesized and evaluated for in vitro antimycobacterial activity. Seventeen compounds exhibited potential activity (MIC ⩽6.25μg/mL) against Mycobacterium tuberculosis (H37Rv), in particular the compounds 3d and 3j having an MIC value of 0.39μg/mL. None of the compounds exhibited cytotoxicity when using an MTT assay in VERO cells. To further investigate the structure-activity relationship, CoMFA (q(2)=0.507, r(2)=0.923) and CoMSIA (q(2)=0.665, r(2)=0.977) models were performed on the basis of antimycobacterial activity data. The 3D-QSAR study of these compounds can provide useful information for further rational design of novel quinoxaline 1,4-di-N-oxides for treatment of tuberculosis.

  11. Studies on Log Po/w of Quinoxaline di-N-Oxides: A Comparison of RP-HPLC Experimental and Predictive Approaches

    Directory of Open Access Journals (Sweden)

    James A. Platts

    2011-09-01

    Full Text Available As reported in our previous papers, a series of quinoxaline-2-carboxamide 1,4-di-N-oxide derivatives were synthesized and studied as anti-tuberculosis agents. Here, the capability of the shake-flask method was studied and the retention time (expressed as log K of 20 compounds were determined by RP-HPLC analysis. We found that the prediction of log P by the RP-HPLC analysis can result in a high accuracy and can replace the shake-flask method avoiding the experimental problems presented by quinoxaline di-N-oxides. The studied compounds were subjected to the ALOGPS module with the aim of comparing experimental log Po/w values and predicted data. Moreover, a preliminary in silico screening of the QSAR relationship was made confirming the influence of reduction peak potential, lipophilicity, H-bond donor capacity and molecular dimension descriptors on anti-tuberculosis activity.

  12. A high performance flexible all solid state supercapacitor based on the MnO2 sphere coated macro/mesoporous Ni/C electrode and ionic conducting electrolyte

    Science.gov (United States)

    Zhi, Jian; Reiser, Oliver; Wang, Youfu; Hu, Aiguo

    2016-06-01

    A high contact resistance between the active materials and the current collector, a low ionic conductivity of the gel electrolyte, and an impenetrable electrode structure are the three major barriers which greatly limit the capacitance of MnO2 in solid state supercapacitors. As a potential solution to these problems, in this work we report a novel electrode for solid state supercapacitors, based on a ternary system composed of hierarchical MnO2 spheres as the active material, macroporous Ni foam as gel penetrable skeletons and an ordered mesoporous carbon (OMC) membrane as the charge-transport accelerating layer. By employing butyl-3-methylimidazolium chloride (BMIMCl) modified gels as the ionic conducting electrolyte, the utilization efficiency of MnO2 on the specific capacitance was enhanced up to 88% of the theoretical value, delivering a volumetric capacitance of 81 F cm-3, which is the highest value among MnO2 based solid state supercapacitors. Moreover, such a flexible device exhibits exceptional volumetric energy and power density (6.6 Wh L-1 and 549 W L-1, based on the whole device volume) combined with a small capacity loss of 8.5% after 6000 cycles under twisting. These encouraging findings unambiguously overcome the energy bottleneck of MnO2 in solid state supercapacitors, and open up a new application of macro/mesoporous materials in flexible devices.A high contact resistance between the active materials and the current collector, a low ionic conductivity of the gel electrolyte, and an impenetrable electrode structure are the three major barriers which greatly limit the capacitance of MnO2 in solid state supercapacitors. As a potential solution to these problems, in this work we report a novel electrode for solid state supercapacitors, based on a ternary system composed of hierarchical MnO2 spheres as the active material, macroporous Ni foam as gel penetrable skeletons and an ordered mesoporous carbon (OMC) membrane as the charge-transport accelerating

  13. Prenatal exposure to integerrimine N-oxide enriched butanolic residue from Senecio brasiliensis affects behavior and striatal neurotransmitter levels of rats in adulthood.

    Science.gov (United States)

    Sandini, Thaísa M; Udo, Mariana S B; Reis-Silva, Thiago M; Sanches, Daniel; Bernardi, Maria Martha; Flório, Jorge Camilo; Spinosa, Helenice de S

    2015-12-01

    Pyrrolizidine alkaloids (PAs) are toxins that are exclusively biosynthesized by plants and are commonly present in foods and herbs. PAs are usually associated with poisoning events in livestock and human beings. The aim of the present study was to evaluate the behavioral and neurochemical effects of prenatal exposure to PA integerrimine N-oxide of rats in adulthood. Pregnant Wistar rats received integerrimine N-oxide from the butanolic residue of Senecio brasiliensis by gavage on gestational days 6-20 at doses of 3, 6 and 9 mg/kg. During adulthood of the offspring, the following behavioral tests were performed: open-field, plus-maze, forced swimming, catalepsy and stereotypy. Histological analyses and monoamine levels were measured. Male offspring from dams that were exposed to 9 mg/kg showed an increase in locomotion in the open-field test, an increased frequency of entries and time spent in open arms in elevated plus-maze test, as well as decreased swimming time. In the female offspring from dams that were exposed to 9 mg/kg, there was an increased time of climbing in forced swimming and intensity of stereotyped behavior. The histological study indicates an increase in the number of multinucleated cells in the liver (6 and 9 mg/kg). In neurotransmitter analysis, specifically in the striatum, we observed change in dopamine and serotonin levels in the middle dose. Thus, our results indicate that prenatal exposure to integerrimine N-oxide changed behavior in adulthood and neurotransmitter levels in the striatum. Our results agree with previous studies, which showed that integerrimine N-oxide impaired physical and neurobehavioral development in childhood that can persist until adulthood. Copyright © 2015 Elsevier Ltd. All rights reserved.

  14. Site-specific indolation of proline-based peptides via copper(II)-catalyzed oxidative coupling of tertiary amine N-oxides.

    Science.gov (United States)

    Wu, Xiaowei; Zhang, Dengyou; Zhou, Shengbin; Gao, Feng; Liu, Hong

    2015-08-14

    The first site-specific and purely chemical method for modifying proline-based peptides was developed via a convenient, copper-catalyzed oxidative coupling of tertiary amine N-oxides with indoles. This novel approach features high regioselectivity and diastereoselectivity, mild conditions, and compatibility with various functional groups. In addition, a simplified process was realized in one pot and two steps via in situ oxidative coupling of tertiary amine and indoles.

  15. New 1,4-di-N-oxide-quinoxaline-2-ylmethylene isonicotinic acid hydrazide derivatives as anti-Mycobacterieum tuberculosis agents

    OpenAIRE

    Torres, E; Moreno-Viguri, E. (Elsa); Ancizu, S. (Saioa); Barea, C. (Carlos); Aldana, I.; Monge, A; Perez-Silanes, S. (Silvia)

    2011-01-01

    The increase in the prevalence of drug-resistant tuberculosis cases demonstrates the need of discovering new and promising compounds with antimycobacterial activity. As a continuation of our research and with the aim of identifying new antitubercular drugs candidates, a new series of quinoxaline 1,4-di-N-oxide derivatives containing isoniazid was synthesized and evaluated for in vitro anti-tuberculosis activity against Mycobacterium tuberculosis H37Rv strain. Moreover, various drug-like prope...

  16. 1-(2-biphenyl)-3-methyltriazenide-N-oxide as a template for intramolecular copper(II)⋯arene-π interactions

    Science.gov (United States)

    Paraginski, Gustavo Luiz; Hörner, Manfredo; Back, Davi Fernando; Wohlmuth Alves dos Santos, Aline Joana Rolina; Beck, Johannes

    2016-01-01

    Deprotonated triazene N-oxides are able to chelate metal ions resulting in five-membered rings without carbon atoms. A new ligand 1-(2-biphenyl)-3-methyltriazenide-N-oxide (1) and its mononuclear Cu(II) complex (2) were synthesized to verify the capability of this ligand to promote Cu(II)⋯arene-π interactions. Ligand 1 and complex 2 have been characterized by elemental analysis, mass spectrometry (ESI(+)-TOF), IR, and UV-Vis spectroscopy. In addition, ligand 1 was characterized by 1H and 13C NMR and complex 2 by X-ray diffraction on single crystal. The crystal structure of complex 2 reveals a distorted tetrahedral geometry of Cu(II) in the first coordination sphere, which expands to a distorted octahedral environment by two symmetrically independent intramolecular metal⋯arene-π interactions. These interactions are provided by ortho-phenyl rings of both triazene N-oxide ligands 1. The aim of this work was to contribute to the architecture of new Cu(II)⋯arene-π complexes based on the synthesis of appropriated ligand for intramolecular interactions

  17. A MnO2/Graphene Oxide/Multi-Walled Carbon Nanotubes-Sulfur Composite with Dual-Efficient Polysulfide Adsorption for Improving Lithium-Sulfur Batteries.

    Science.gov (United States)

    Li, Yong; Ye, Daixin; Liu, Wen; Shi, Bin; Guo, Rui; Zhao, Hongbin; Pei, Haijuan; Xu, Jiaqiang; Xie, Jingying

    2016-10-12

    Lithium-sulfur batteries can potentially be used as a chemical power source because of their high energy density. However, the sulfur cathode has several shortcomings, including fast capacity attenuation, poor electrochemical activity, and low Coulombic efficiency. Herein, multi-walled carbon nanotubes (CNTs), graphene oxide (GO), and manganese dioxide are introduced to the sulfur cathode. A MnO2/GO/CNTs-S composite with a unique three-dimensional (3D) architecture was synthesized by a one-pot chemical method and heat treatment approach. In this structure, the innermost CNTs work as a conducting additive and backbone to form a conducting network. The MnO2/GO nanosheets anchored on the sidewalls of CNTs have a dual-efficient absorption capability for polysulfide intermediates as well as afford adequate space for sulfur loading. The outmost nanosized sulfur particles are well-distributed on the surface of the MnO2/GO nanosheets and provide a short transmission path for Li(+) and the electrons. The sulfur content in the MnO2/GO/CNTs-S composite is as high as 80 wt %, and the as-designed MnO2/GO/CNTs-S cathode displays excellent comprehensive performance. The initial specific capacities are up to 1500, 1300, 1150, 1048, and 960 mAh g(-1) at discharging rates of 0.05, 0.1, 0.2, 0.5, and 1 C, respectively. Moreover, the composite cathode shows a good cycle performance: the specific capacity remains at 963.5 mAh g(-1) at 0.2 C after 100 cycles when the area density of sulfur is 2.8 mg cm(-2).

  18. Improvement in the etching performance of the acrylonitrile-butadiene-styrene resin by MnO2-H3PO4-H2SO4 colloid.

    Science.gov (United States)

    Zhao, Wenxia; Ding, Jie; Wang, Zenglin

    2013-05-21

    The present study aimed to evaluate the surface etching of the acrylonitrile-butadiene-styrene (ABS) resin in the MnO2-H3PO4-H2SO4 colloid. To enhance the soluble Mn(IV) ion concentration and improve the etching performance of ABS resin, H3PO4 was added as a complexing agent into the MnO2-H2SO4 etching system. The effects of the H2SO4 concentration and etching time on the surface topography, surface roughness, adhesion strength, and the surface chemistry of the ABS substrates were investigated. The optimal oxidation potentials of MnO2 in the colloids decreased from 1.426 to 1.369 V with the addition of H3PO4. Though the etching conditions changed from 70 °C for 20 min to 60 °C for 10 min, the adhesion strength between the ABS substrates and electroless copper film increased from 1.19 to 1.33 KN/m after etching treatment. This could be attributed to the significant increase of the soluble Mn(IV) ion concentration in the MnO2-H3PO4-H2SO4 colloid. The surface chemistry results demonstrated that the oxidation reaction of -C═C- bonds in the polybutadiene phase was accelerated in the etching process by the addition of H3PO4, and the abundant -COOH and -OH groups were formed rapidly on the ABS surface with the etching treatment. These results were in agreement with the results of surface scanning electron microscopic observations and adhesion strength measurement. The results suggested that the MnO2-H3PO4-H2SO4 colloid was an effective surface etching system for the ABS surface roughness.

  19. Polyacrylamide Gel Preparation and Properties of La0.7Ca0.3MnO3 Nanoparticles%La0.7Ca0.3MnO3纳米颗粒的聚丙烯酰胺凝胶法制备及性能

    Institute of Scientific and Technical Information of China (English)

    朱彦虎; 杨华; 县涛; 魏智强; 马金元; 冯旺军

    2011-01-01

    采用聚丙烯酰胺凝胶法制备La0.7Ca0.3MnO3纳米颗粒。通过X射线衍射和扫描电镜研究不同pH值和不同络合剂对制备La0.7Ca0.3MnO3纳米颗粒形貌及性能的影响。结果表明:合成La0.7Ca0.3MnO3钙钛矿相的最佳pH=2;分别以醋酸、草酸、柠檬酸和乙二胺四乙酸为络合剂,在600℃煅烧温度制备的高纯La0.7Ca0.3MnO3纳米颗粒的形貌规整、呈类球形,尺寸分布较窄,平均粒径分别为30、37、45、50nm;以酒石酸为络合剂,在900℃煅烧制备的单相La0.7Ca0.3MnO3颗粒的形貌不甚规整,颗粒间出现明显的煅烧粘连现象,颗粒尺寸较大,平均粒径为170nm。磁滞回线测量结果表明:制得的La0.7Ca0.3MnO3颗粒在室温均表现为顺磁性,其顺磁磁化率随样品颗粒尺寸的减小而减小。%A polyacrylamide gel route was used to fabricate La0.7Ca0.3MnO3 nanoparticles. Influence of pH values and chelating agents on particle morphology and properties of the prepared La0.7Ca0.3MnO3 nanoparticles were investigated by X-ray diffraction and scanning electron microscopy. The optimal pH value for synthesis of perovskite La0.7Ca0.3MnO3 was obtained to be 2. Using acetic acid, oxalic acid, citric acid, and ethylenediamine-tetraacetic acid as chelating agents, single-phase La0.7Ca0.3MnO3 nanoparticles were prepared at a calcination temperature of 600 ℃. The particles prepared using the four chelating agents are uniform and regu- larly-shaped spheres, and have an average size of 30, 37, 45 nm, and 50 nm, respectively. When using tartaric acid as the chelating agent, a much higher calcination temperature at 900 ℃ was required to produce single-phase La0.7Ca0.3MnO3 particles. The obtained particles exhibit an irregular morphology and an obvious adhesive behavior, and have a relatively large average size of 170 nm. Mag- netic hysteresis loop measurements indicate that the prepared La0.7Ca0.3MnO3 samples exhibit paramagnetism at room temperature, but their

  20. Appearance of an inhomogeneous superconducting state in La0.67Sr0.33MnO3–YBa2Cu3O7–La0.67Sr0.33MnO3 trilayers

    Indian Academy of Sciences (India)

    K Senapati; R C Budhani

    2007-08-01

    An experimental study of proximity effect in La0.67Sr0.33MnO3–YBa2Cu3O7–La0.67Sr0.33MnO3 trilayers is reported. Transport measurements on these samples show clear oscillations in critical current (c) as the thickness of La0.67Sr0.33MnO3 layers (F) is scanned from ∼ 50 Å to ∼ 1100 Å. In the light of existing theories of ferromagnet–superconductor (FM–SC) heterostructures, this observation suggests a long range proximity effect in the manganite, modulated by its weak exchange energy (∼ 2 meV). The observed modulation of the magnetic coupling between the ferromagnetic LSMO layers as a function of F, also suggests an oscillatory behavior of the SC order parameter near the FM–SC interface.

  1. MnO_2纳米溶胶-甲醛化学发光体系及其分析应用研究%Chemiluminescence of Nano-Colloidal MnO2 with Formaldehyde and Its Analytical Application

    Institute of Scientific and Technical Information of China (English)

    杜建修; 王虹

    2012-01-01

    Water-soluble forms of colloidal MnO2 were prepared by the chemical reduction of KMnO4 with Na2S203 under neutral aqueous condition. The as-prepared colloidal MnO2 solution is dark-brown, trans- parent, stable, and possesses the maximum absorption peak at 375 nm and an average diameter of 40 nm. The as-prepared nano-colloidal MnO2 was found to react with formaldehyde to generate weak chemiluminescence (CL) under acidic condition. The effects of more than 30 pharmaceuticals on the nancolloidal MnO2-formaldehyde CL system were tested. Pharmaceuticals including phenothiazines and aminoethanethiols were observed to enhance the CL signal significantly. The experimental conditions were well optimized and the analytical figures for five phenothiazines and four aminoethanethiols were presented. The method was validated by the analysis of perphenazine in tablets and chlorpromazine hydrochloride in swine feed. The CL reaction mechanism was discussed by the study of CL spectra, fluorescence spectra, UV-vis absorption spectra, and other experiments. All of CL reactions had the same maximum emission wavelength about 640 nm, which suggested that the CL emitter was independent of analytes. The CL signal was inhibited obviously by single-state oxygen scavengers, sodium azide and 1,4-diazabicyclo[2,2,2]octane, indicating that single-state oxygen dimer was the potential CL emitter for the present CL reaction.%Na2S2O3在中性水溶液中还原KMnO4可制备得到暗棕色的可溶性MnO2溶胶.所制备的MnO2溶胶透明、稳定,最大吸收波长位于357 nm处,平均粒径约40 nm.研究发现,所制备的MnO2纳米溶胶在酸性介质中与甲醛反应可产生弱的化学发光.考察了近30种药物分子在MnO2纳米溶胶-甲醛体系中的化学发光行为.结果表明,吩噻嗪类药物、氨基硫醇类药物等对该体系的化学发光信号具有显著的增强作用.据此,建立了利用这一化学发光体系测定五种吩噻嗪类药物和四种氨基

  2. Betaine and Trimethylamine-N-Oxide as Predictors of Cardiovascular Outcomes Show Different Patterns in Diabetes Mellitus: An Observational Study.

    Directory of Open Access Journals (Sweden)

    Michael Lever

    Full Text Available Betaine is a major osmolyte, also important in methyl group metabolism. Concentrations of betaine, its metabolite dimethylglycine and analog trimethylamine-N-oxide (TMAO in blood are cardiovascular risk markers. Diabetes disturbs betaine: does diabetes alter associations between betaine-related measures and cardiovascular risk?Plasma samples were collected from 475 subjects four months after discharge following an acute coronary admission. Death (n = 81, secondary acute MI (n = 87, admission for heart failure (n = 85, unstable angina (n = 72 and all cardiovascular events (n = 283 were recorded (median follow-up: 1804 days.High and low metabolite concentrations were defined as top or bottom quintile of the total cohort. In subjects with diabetes (n = 79, high plasma betaine was associated with increased frequencies of events; significantly for heart failure, hazard ratio 3.1 (1.2-8.2 and all cardiovascular events, HR 2.8 (1.4-5.5. In subjects without diabetes (n = 396, low plasma betaine was associated with events; significantly for secondary myocardial infarction, HR 2.1 (1.2-3.6, unstable angina, HR 2.3 (1.3-4.0, and all cardiovascular events, HR 1.4 (1.0-1.9. In diabetes, high TMAO was a marker of all outcomes, HR 2.7 (1.1-7.1 for death, 4.0 (1.6-9.8 for myocardial infarction, 4.6 (2.0-10.7 for heart failure, 9.1 (2.8-29.7 for unstable angina and 2.0 (1.1-3.6 for all cardiovascular events. In subjects without diabetes TMAO was only significant for death, HR 2.7 (1.6-4.8 and heart failure, HR 1.9 (1.1-3.4. Adding the estimated glomerular filtration rate to Cox regression models tended to increase the apparent risks associated with low betaine.Elevated plasma betaine concentration is a marker of cardiovascular risk in diabetes; conversely low plasma betaine concentrations indicate increased risk in the absence of diabetes. We speculate that the difference reflects control of osmolyte retention in tissues. Elevated

  3. Interface-induced spontaneous positive and conventional negative exchange bias effects in bilayer La0.7Sr0.3MnO3/Eu0.45Sr0.55MnO3 heterostructures.

    Science.gov (United States)

    Murthy, J Krishna; Kumar, P S Anil

    2017-07-31

    We report zero-field-cooled spontaneous-positive and field-cooled conventional-negative exchange bias effects in epitaxial bilayer composed of La0.7Sr0.3MnO3 (LSMO) with ferromagnetic (FM) and Eu0.45Sr0.55MnO3 (ESMO) with A-type antiferromagnetic (AF) heterostructures respectively. A temperature dependent magnetization study of LSMO/ESMO bilayers grown on SrTiO3 (001) manifest FM ordering (TC) of LSMO at ~320 K, charge/orbital ordering of ESMO at ~194 K and AF ordering (TN) of ESMO at ~150 K. The random field Ising model has demonstrated an interesting observation of inverse dependence of exchange bias effect on AF layer thickness due to the competition between FM-AF interface coupling and AF domain wall energy. The isothermally field induced unidirectional exchange anisotropy formed at the interface of FM-LSMO layer and the kinetically phase-arrested magnetic phase obtained from the metamagnetic AF-ESMO layer could be responsible for the spontaneous exchange bias effect. Importantly, no magnetic poling is needed, as necessary for the applications. The FM-AF interface exchange interaction has been ascribed to the AF coupling with [Formula: see text] ([Formula: see text], coupling constant between AF spins) for the spontaneous positive hysteresis loop shift, and the field-cooled conventional exchange bias has been attributed to the ferromagnetically exchanged interface with [Formula: see text] (coupling constant between FM spins).

  4. Kinetics of Carbothermic Reduction of MnO2 and Catalytic Effect of La2O3

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Kinetics of carbothermic reduction of manganese oxide and the catalytic effect of La2O3 on the reduction have been studied by the measurement of mass loss in N2 atmosphere at different temperatures and followed by SEM analysis. It is concluded that the kinetics of carbothermic reduction of manganese oxide is divided into three stages: gas diffusion controlling stage, carbon gasification controlling stage and solid state diffusion controlling stage. La2O3 has catalytic effect on the reduction. The catalytic effect of La2O3 increases with the added amount of La2O3. SEM analysis shows that the catalytic mechanism is that Laa2O3 promotes the transfer of oxygen ions so that carbon gasifying is catalyzed and thus carbothermic reduction of MnO3 is catalyzed.

  5. Influence of La-dopant on the Material Characteristics and Supercapacitive Performance of MnO2 Electrodes

    Institute of Scientific and Technical Information of China (English)

    Lü Yanling; SHAO Guangjie; ZHAO Beilong; ZHANG Liuli

    2011-01-01

    Manganese dioxide was synthesized by electrodeposition method with Mn (CH3COO)2 · 4H2O as a raw material. La(NO3)3 · 6H2O was doped in electroyte during the preparing process to improve the performance of MnO2 electrodes. The micrographs, crystal structure and element content of electrodes were analyzed by SEM, XRD and atomic absorption spectroscopy, respectively. It is found that the La content ratio in the dioxide can be easily controlled by adjusting the composition of the plating solution. Appropriate amount of doped La can increase the surface area of Mn/La materials, resulting in the supercapacitive behavior enhancement. Electrochemical tests show that the specific capacitance is significantely increased from 198.72 F · g-1 to 276.60 F · g-1 by La-doping.

  6. Epitaxial Growth of Gd0.67Ca0.33MnO3 Thin Films by Laser Ablation

    Institute of Scientific and Technical Information of China (English)

    Ma Yanwei(马衍伟); Guilloux Viry; Barahona P; Pe(~n)a O; Moure C

    2004-01-01

    Gd0.67Ca0.33MnO3(GCMO)thin films grown by laser ablation on SrTiO3(100)(STO)substrates was studied. Films are highly crystallized, very well epitaxial and single-phased. The ordering magnetic temperature(Tc)of the films is much higher than the value of bulk samples of similar composition. It is found that the GCMO film exhibits a reversal of its magnetization at low temperature when cooled under a magnetic field. The negative magnetization is a consequence of the rapid increase(~1/T)with decreasing temperature of the magnetization of a sublattice aligned antiparallel to the local field, relative to the magnetic contribution of a second sublattice which is aligned parallel to the applied field.

  7. Efficient spin transfer torque in La2/3Sr1/3MnO3 nanostructures

    Science.gov (United States)

    Foerster, Michael; Peña, Luis; Vaz, C. A. F.; Heinen, Jan; Finizio, Simone; Schulz, Tomek; Bisig, André; Büttner, Felix; Eisebitt, Stefan; Méchin, Laurence; Hühn, Sebastian; Moshnyaga, Vasily; Kläui, Mathias

    2014-02-01

    We carry out low temperature magnetotransport measurements on nanostructured La2/3Sr1/3MnO3 wires to study the interaction between spin-polarized current and magnetization in this half metallic material. We selectively position domain walls by applying external fields. The domain wall resistance is found to be positive, in contrast to conventional 3d metals. The depinning field is reduced when current pulses are injected into the wire. By comparing measurements for both current polarities, we can disentangle heating and spin transfer torque effects. The determined spin transfer torque efficiency is of the order of 4 × 10-14 Tm2/A, which is significantly higher than in permalloy.

  8. Thermodynamic properties of nonstoichiometric oxygen in manganite Ca0.9Pr0.1MnO3-δ

    Science.gov (United States)

    Leonidov, I. A.; Konstantinova, E. I.; Patrakeev, M. V.; Kozhevnikov, V. L.

    2016-11-01

    The chemical potential of oxygen ΔμO relative to its standard state in the gas phase was calculated from the experimental dependences of the oxygen content in various polymorphic modifications of Ca0.9Pr0.1MnO3-δ on the partial pressure and temperature. The partial molar enthalpy Δ {overline H _O} and entropy Δ {overline S _O} of oxygen were obtained from the linear temperature dependences of ΔμO. Based on the ideal solution approximation, Δ {overline H _O} and Δ {overline S _O} were correlated with the enthalpies and entropies of the defect formation reactions, the concentrations of manganese cations, and the oxygen nonstoichiometry. The thermal excitation of Mn4+ cations was shown to substantially affect the thermodynamic functions of oxygen.

  9. Interface-dependent resistance switching in Nd0.7Sr0.3MnO3 ceramics

    Indian Academy of Sciences (India)

    S S Chen; C P Yang; C L Ren; R L Wang; H Wang; I V Medvedeva; K Baerner

    2011-07-01

    Interface-dependent electric-pulse-induced resistance switching effect (EPIR) in Nd0.7Sr0.3MnO3 ceramics was studied. The results reveal that the EPIR effect originates from the interface between the electrodes and the bulk, and the EPIR ratio as well as the high and low resistance states can be strongly influenced by applying a large electrical field on the sample for different intervals. Also, the pulse parameters have great effect on the stability of EPIR and the optimal pulse width, pulse amplitude and read bias are obtained. Based on the space charge limited current mechanism together with the theory of interfacial charge-trapped state, the interface-dependent resistance switching effect is discussed.

  10. Long-Term Charge/Discharge Cycling Stability of MnO2 Aqueous Supercapacitor under Positive Polarization

    KAUST Repository

    Ataherian, Fatemeh

    2011-01-01

    The long-term charge/discharge cycling stability of MnO 2 electrode under positive polarization in aqueous KCl electrolyte has been studied over different potential windows spanning from the open circuit potential to varied higher-end potential limited by O 2 evolution. Cycling up to 1.2 V (vs Ag/AgCl (aq)) causes partial (35) capacitance fading to a plateau value within the initial cycles, accompanied by morphological reconstruction, reduction of surface Mn ions and oxygen evolution. The surface Mn-ion reduction has been attributed to a two-step oxidation-reduction mechanism involving OH oxidation in electrolyte, based on electrochemical analysis. When cycling potential extends to 1.4 V, extensive oxygen evolution takes place. The combination of surface passivation of current collector and extensive gas bubbling, which deteriorates electrical contact among the constituent particles within the electrode, results in further monotonic capacitance reduction. © 2011 The Electrochemical Society.

  11. Hall effect of quinquevalent ion-doped La0.9Sb0.1MnO3 film

    Institute of Scientific and Technical Information of China (English)

    WANG Dengjing; WANG Mei; WANG Ruwu; LI Yunbao

    2013-01-01

    Hall effect of the quinquevalent ion-doped La0.gSb0.1MnO3 (LSbMO) film,with strong magnetic-resistive correlation,which was believed to be an electron-doped manganite,was experimentally studied,and a positive normal Hall coefficient was observed below the Curie temperature,which indicated that the system was hole doped.These observations might be attributed to the presence of excessive oxygen in the film.The resistivity of the film increased overall and the metal-semiconductor transition shifted to a lower temperature after removing excessive oxygen by vacuum annealing.These results implied that the magnetic-resistive correlation in the LSbMO film was attributed to the interaction between Mn3+ and Mn4+ ions,instead of that between Mn2+ and Mn3+ ions.

  12. Magnetoresistive memory in phase-separated La0.5Ca0.5MnO3

    Energy Technology Data Exchange (ETDEWEB)

    Sacanell, J. [Departamento de Fisica, Unidad de Actividad Fisica-Centro Atomico de Constituyentes, CNEA, Av. Gral. Paz 1499, San Martin 1650, Pcia. de Buenos Aires (Argentina)]. E-mail: sacanell@cnea.gov.ar; Parisi, F. [Departamento de Fisica, Unidad de Actividad Fisica-Centro Atomico de Constituyentes, CNEA, Av. Gral. Paz 1499, San Martin 1650, Pcia. de Buenos Aires (Argentina); Levy, P. [Departamento de Fisica, Unidad de Actividad Fisica-Centro Atomico de Constituyentes, CNEA, Av. Gral. Paz 1499, San Martin 1650, Pcia. de Buenos Aires (Argentina); Ghivelder, L. [Instituto de Fisica, UFRJ, Rio de Janeiro (Brazil)

    2004-12-31

    We have studied a non-volatile memory effect in the mixed valent compound La0.5Ca0.5MnO3 induced by magnetic field (H). In a previous work (Phys. Rev. B 65 (2002) 104403), it has been shown that the response of this system upon application of H strongly depends on the temperature range, related to three well-differentiated regimes of phase separation occurring below 220K. In this work we compare memory capabilities of the compound, determined following two different experimental procedures for applying H, namely zero-field cooling and field cooling the sample. These results are analyzed and discussed within the scenario of phase separation.

  13. Microwave study of Nd0.7Sr0.3MnO3 thin film resistivity

    Science.gov (United States)

    Claycomb, J. R.; Tralshawala, N.; Xie, L.-M.; Wosik, J.; Miller, J. H.

    1999-04-01

    We report on microwave studies of Nd0.7Sr0.3MnO3 thin film losses in a shielded TE011 dielectric cavity. The cavity quality (Q) factor and resonant frequency are measured as a function of temperature with the dielectric cavity loaded with a thin film on a LaAlO3 substrate. A reference Q measurement is then made without the film enabling the extraction of the film-Q factor Qfilm. Here the temperature dependence of the Q factor is discussed in terms of resistive losses in the thin film. A numerical finite difference time domain code is then used to extract the microwave resistivity as a function of temperature from the measured Q factors. The numerical method involves the discretization of Maxwell's equations on an axisymmetric space-time grid coupled to a discrete Fourier transform to determine the resonant frequency.

  14. Low-cost flexible supercapacitors with high-energy density based on nanostructured MnO2 and Fe2O3 thin films directly fabricated onto stainless steel

    National Research Council Canada - National Science Library

    Gund, Girish S; Dubal, Deepak P; Chodankar, Nilesh R; Cho, Jun Y; Gomez-Romero, Pedro; Park, Chan; Lokhande, Chandrakant D

    2015-01-01

    ...) methods have been employed in order to prepare manganese oxide (MnO2) and iron oxide (Fe2O3) thin films, respectively with the fine optimized nanostructures on highly flexible stainless steel sheet...

  15. Preparation of Li-rich layered-layered type xLi2MnO3·(1-x)LiMnO2 nanorods and its electrochemical performance as cathode material for Li-ion battery

    Science.gov (United States)

    Yang, Fan; Zhang, Qinggang; Hu, Xiaohong; Peng, Tianyou; Liu, Jianqiang

    2017-06-01

    Layered-layered type xLi2MnO3·(1-x)LiMnO2 (x = 0.91, 0.78, 0.67, 0.54, 0.42, and 0.32) nanorods with a diameter of 100-200 nm and length of 400-1000 nm are prepared through a pyrolysis reduction process of monoclinic Li2MnO3 (m-Li2MnO3) nanorods. All the synthesized xLi2MnO3·(1-x)LiMnO2 nanorods exhibit the main characteristic diffraction peaks of m-Li2MnO3 in addition to some weak peaks attributable to m-LiMnO2 especially for those composites with x window of 2.0-4.8 V. The m-LiMnO2 portion in those synthesized composites can significantly enhance the reversible capacity but lower the cyclic stability, while the m-Li2MnO3 portion can improve the cyclic stability due to its retardation effect of the layered-to-spinel transformation during the charge/discharge processes, and thus xLi2MnO3·(1-x)LiMnO2 nanorods with x = 0.54 exhibits the best cyclic and rate performance since it contains appropriate m-Li2MnO3/m-LiMnO2 contents to balance the reversible capacity and Jahn-Teller effect. The present findings demonstrate an effective strategy for the development of low-cost pure Mn-based Li-rich layered cathode materials with adjustable reversible capacity, cyclic and rate performance by tailoring the composition.

  16. Effect of MnO2 doping and temperature treatment on optical energy band gap properties in Zn-Bi-Ti-O varistor ceramics

    Science.gov (United States)

    Ghazali, M. S. M.; Abdullah, W. R. W.; Zakaria, A.; Kamari, H. M.; Rizwan, Z.

    2016-11-01

    In this study, the optical band-gap energy (Eg) was investigated with respect to MnO2 and sintering temperatures on ZnO based varistor ceramics. Eg of the ceramic (99-x) mol% ZnO + 0.5 mol% Bi2O3 + 0.5 mol% TiO2 + × MnO2 where × = 0, 0.2, 0.4, 0.6 and 0.8 mol%, were determined using UV-Vis spectrophotometer. The samples was prepared through solid-state route and sintered at the sintering temperature from 1110, 1140 and 1170 °C for 45 and 90 min in open air. At no doping of MnO2, the values of Eg are 2.991 ± 0.001, 2.989 ± 0.001 eV for 45 and 90 min sintering time; respectively. Eg was decreased to 2.192 ± 0.001 eV at 1140 °C at 45 min sintering time. Similar result of Eg was observed at longer heat treatment. Further addition of dopant causing the Eg decreases rapidly to 2.099 and 2.106 ± 0.001 eV at 45 and 90 min sintering time; respectively. XRD analysis indicates that there is hexagonal ZnO and secondary phases, Zn2MnO4, Bi4Ti3O12 and Zn2Ti3O8. The relative density of the sintered ceramics decreased or remain constant with the increase of MnO2 concentration for 45 min sintering time, however, further prolong sintering time; the relative density decreases form 90.25 to 88.35%. This indicates the pores are increasing with the increase of heat treatment. The variation of sintering temperatures to the optical band gap energy of based ZnO varistor doped with MnO2 due to the formation of interface states.

  17. Temperature and solvent structure dependence of VO2+ complexes of pyridine-N-oxide derivatives and their interaction with human serum transferrin.

    Science.gov (United States)

    Sanna, Daniele; Ugone, Valeria; Micera, Giovanni; Garribba, Eugenio

    2012-06-28

    The behaviour of the systems formed by VO(2+), 2-hydroxypyridine-N-oxide (Hhpo) and 2-mercaptopyridine-N-oxide (Hmpo) was studied both in solution and in the solid state through the combined application of spectroscopic (EPR and UV-Vis spectroscopy) and DFT methods. The geometry of solid bis-chelated complexes [VOL(2)], with L = hpo and mpo, is square pyramidal, but it can change to cis-[VOL(2)S], where S is a solvent molecule, when these are dissolved in a coordinating solvent. The equilibrium between the square pyramidal and cis-octahedral forms is strongly affected by solvent and temperature. At room temperature, the predominant species is [VOL(2)], which gives a pink colour to the solutions; at lower temperatures, the equilibrium is shifted--partially or completely--toward the formation of cis-[VOL(2)S], which is green. In an acidic environment and in the presence of an excess of ligand, [VOL(2)] can transform into the tris-chelated complex [VL(3)](+), in which vanadium loses the oxido ligand and adopts a hexa-coordinated geometry intermediate between octahedral and trigonal prismatic. 1-Methylimidazole (1-MeIm), which represents a model for His-N coordination, forms mixed complexes with stoichiometry cis-[VOL(2)(1-MeIm)], occupying an equatorial position. In the ternary systems VO(2+)-Hhpo-hTf and VO(2+)-Hmpo-hTf at room temperature and pH 7.4, besides (VO)hTf and (VO)(2)hTf, the mixed species cis-VO(hpo)(2)(hTf) and VO(mpo)(hTf) are observed, with the equatorial binding of an accessible histidine residue. Finally, the contribution of the N-oxide group to (51)V A(z) and A(iso) hyperfine coupling constants, which can be important in the characterisation of similar species, is discussed.

  18. CdTe quantum dots functionalized with 4-amino-2,2,6,6-tetramethylpiperidine-N-oxide as luminescent nanoprobe for the sensitive recognition of bromide ion

    Energy Technology Data Exchange (ETDEWEB)

    Adegoke, Oluwasesan [Department of Chemistry, Rhodes University, Grahamstown 6140 (South Africa); Hosten, Eric; McCleland, Cedric [Department of Chemistry, Nelson Mandela Metropolitan University (South Campus), Port Elizabeth 6031 (South Africa); Nyokong, Tebello, E-mail: t.nyokong@ru.ac.za [Department of Chemistry, Rhodes University, Grahamstown 6140 (South Africa)

    2012-04-06

    Graphical abstract: A bromide ion-selective modified nanoprobe sensor based on 4-amino-2,2,6,6-tetramethylpiperidine-N-oxide (4AT)-functionalized CdTe quantum dots (QDs-4AT) showed a high selectivity and sensitivity for the determination of bromide ion using fluorescence recovery. Highlights: Black-Right-Pointing-Pointer Water soluble CdTe quantum dots interact with tetramethylpiperidine-N-oxide. Black-Right-Pointing-Pointer Quantum dots fluorescence is quenched by the radical. Black-Right-Pointing-Pointer In the presence of bromide ions the fluorescence is restored. Black-Right-Pointing-Pointer The sensor is more selective to bromine ions than other common ions. - Abstract: A novel bromide ion-selective modified nanoprobe sensor based on 4-amino-2,2,6,6-tetramethylpiperidine-N-oxide (4AT)-functionalized CdTe quantum dots (QDs-4AT) has been developed. Fluorescence quenching of the QDs by 4AT was observed. The functionalized QDs-4AT nanoprobe allowed a highly sensitive determination of bromide ion via analyte-induced change in the photoluminescence (fluorescence recovery) of the modified QDs. A detection limit of 0.6 nM of bromide ion was obtained, while the interfering effect of other inorganic cations and anions was investigated to examine the selectivity of the nanoprobe. The linear range was between 0.01 and 0.13 {mu}M. Combined fluorescence lifetime and electron paramagnetic resonance measurements confirmed electron transfer processes between bromide ion and QDs-4AT.

  19. New 1,4-di-N-oxide-quinoxaline-2-ylmethylene isonicotinic acid hydrazide derivatives as anti-Mycobacterium tuberculosis agents.

    Science.gov (United States)

    Torres, Enrique; Moreno, Elsa; Ancizu, Saioa; Barea, Carlos; Galiano, Silvia; Aldana, Ignacio; Monge, Antonio; Pérez-Silanes, Silvia

    2011-06-15

    The increase in the prevalence of drug-resistant tuberculosis cases demonstrates the need of discovering new and promising compounds with antimycobacterial activity. As a continuation of our research and with the aim of identifying new antitubercular drugs candidates, a new series of quinoxaline 1,4-di-N-oxide derivatives containing isoniazid was synthesized and evaluated for in vitro anti-tuberculosis activity against Mycobacterium tuberculosis H37Rv strain. Moreover, various drug-like properties of new compounds were predicted. Taking into account the biological results and the promising drug-likeness profile of these compounds, make them valid leads for further experimental research.

  20. Emission spectra of the sol-gel glass doped with europium(III) complexes of picolinic acid N-oxide-A new UV-light sensor

    Energy Technology Data Exchange (ETDEWEB)

    Godlewska, P. [Department of Bioorganic Chemistry, Institute of Chemistry and Food Technology, Faculty of Engineering and Economics, Lower Silesian University of Economics, Wroclaw (Poland); Macalik, L. [Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Wroclaw (Poland); Hanuza, J. [Department of Bioorganic Chemistry, Institute of Chemistry and Food Technology, Faculty of Engineering and Economics, Lower Silesian University of Economics, Wroclaw (Poland); Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Wroclaw (Poland)], E-mail: j.hanuza@int.pan.wroc.pl

    2008-02-28

    New europium complexes of picolinic acid N-oxides have been synthesised and introduced into sol-gel matrices. Their application as UV-light sensors has been considered. The sequence of the electronic levels for Eu{sup 3+} ions has been determined from the absorption and emission studies and assigned to the respective electron transitions. The lifetimes of the excited states have been detected and analysed. The role of the CT transition inside the picolinic ligand and its influence on the ligand to metal charge transfer (LMCT) have been discussed.

  1. Simultaneous determination of ammonia, dimethylamine, trimethylamine and trimethylamine-N-oxide in fish extracts by capillary electrophoresis with indirect UV-detection

    DEFF Research Database (Denmark)

    Timm Heinrich, Maike; Jørgensen, Bo

    2002-01-01

    A capillary electrophoretic method with indirect UV detection is described for simultaneous determination of ammonia, dimethylamine (DMA), trimethylamine (TMA) and trimethylamine-N- oxide (TMAO) in aqueous extracts of fish, A buffer consisting of 4 mM formic acid, 5 mM copper(II)sulfate and 3 m......M. The detection limit for ammonia, DMA, TMA, and TMAO was less than 0.04 mM, corresponding to 2 mg nitrogen per 100 g fish. As an extra benefit, the method also provided a quantitative determination of potassium, sodium, calcium and magnesium ions. (C) 2002 Elsevier Science Ltd. All rights reserved....

  2. Magnetic and electronic transitions in charge-ordered Nd 0.50Ca 0.47Ba 0.03MnO 3 manganite

    Science.gov (United States)

    Mavani, K. R.; Paulose, P. L.

    The ABO 3 type charge-ordered antiferromagnetic Nd 0.50Ca 0.50MnO 3 (NCMO) manganite is doped at A-site by 3%of Ba 2+ for Ca 2+. The resulting system, Nd 0.50Ca 0.47Ba 0.03MnO 3 (NCBMO), is studied for the effects of Ba doping on the magnetic and electronic properties. On application of magnetic field to NCBMO, strongly correlated successive sharp metamagnetic and electronic transitions are observed from antiferromagnetic-insulating to ferromagnetic-metallic state at 2.5 K. The critical magnetic field ( Hc) required for metamagnetism is found to reduce drastically from 15 T for undoped NCMO to 3 T for NCBMO. On increasing the temperature, the Hc of NCBMO passes through a minimum. This behavior of Hc of NCBMO contrasts to that of NCMO. The results are discussed in context of A-site cation disorder and size.

  3. High resistance modulation by the electric field based on La0.9Sr0.1MnO3/SrTiO3/Si structure

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    A field-effect configuration based on La0.9Sr0.1MnO3/SrTiO3/Si structure is fabricated on Si substrate by laser molecular-beam epitaxy. The resistance modulation by electric field of the La0.9Sr0.1MnO3/SrTiO3/Si structure is investigated in detail. An evident resistance modulation effect is observed at 80 K. The channel resistance modulation by field effect reaches 1.4×107% and 2.6×106% when VDS are -2 and -6.5 V, respectively. The ON/OFF ratio of approximately 4000 is obtained. The present results are worthy of further investigations for potential applications of resistance modulation by electrostatic field in the heterostructures consisting of perovskite oxides and Si.

  4. Preparation and magnetic properties of nanosized (La0.47Gd0.2 ) Sr0.33 MnO3

    Institute of Scientific and Technical Information of China (English)

    WANG Gui; WANG Zheng-de; ZHANG Li-de

    2005-01-01

    Nanosized (La0.47Gd0.2)Sr0.33MnO3 perovskite oxides were prepared at relatively low calcinating temperature of 600 ℃ and 800 ℃ for 10 h using amorphous complex precursor. Curie temperature (Tc) and magnetocaloric effects(MCE) were investigated. X-ray diffraction(XRD) and electron diffraction(ED) reveal that the resulting products are of pure single-phase rhombohedral perovskite structure. Transmission electron microscopy (TEM) observation finds that the particle sizes are about 40 - 50 nm and 80 - 100 nm, and the Tc are 285.1 K and with a broad peak around Curie temperature is observed in sample sintered at 800 ℃ for 10 h. This suggests that nanosized (La0.47Gd0.2)Sr0.33MnO3 is a suitable material as working substance in magnetic refrigeration in room temperature.

  5. The low temperature specific heat and electrical transport, magnetic properties of Pr0.65Ca0.35MnO3

    Science.gov (United States)

    Han, Zhiyong

    2017-02-01

    The magnetic properties, electrical transport properties, and low temperature specific heat of polycrystalline perovskite manganese oxide Pr0.65Ca0.35MnO3 have been investigated experimentally. It is found that there exists cluster glass state in the sample at low temperature besides the antiferromagnetic insulating state. With the increase of magnetic field, antiferromagnetic insulating state converts to ferromagnetic metal state and the Debye temperature decreases gradually. In addition, the low temperature electron specific heat in zero magnetic field is obviously larger than that of ordinary rare-earth manganites oxide and this phenomenon is related to the itinerant electrons in ferromagnetic cluster state and the disorder in Pr0.65Ca0.35MnO3.

  6. Superior Properties of Energetically Stable La2/3Sr1/3MnO3/Tetragonal BiFeO3 Multiferroic Superlattices

    KAUST Repository

    Feng, Nan

    2015-04-30

    The superlattice of energetically stable La2/3Sr1/3MnO3 and tetragonal BiFeO3 is investigated by means of density functional theory. The superlattice as a whole exhibits a half-metallic character, as is desired for spintronic devices. The interfacial electronic states and exchange coupling are analyzed in details. We demonstrate that the interfacial O atoms play a key role in controlling the coupling. The higher ferroelectricity of tetragonal BiFeO3 and stronger response to the magnetic moment in La2/3Sr1/3MnO3/BiFeO3 superlattice show a strongly enhanced electric control of the magnetism as compared to the rhombohedral one. Therefore, it is particularly practical interest in the magnetoelectric controlled spintronic devices.

  7. Broadening of the magnetic entropy change in La0.75Ca0.15Sr0.10MnO3

    DEFF Research Database (Denmark)

    Krishnan Venkatesh, Radha; Kuhn, Luise Theil; Pryds, Nini

    2012-01-01

    .15Sr0.10MnO3 is discussed in the light of magnetoelastic coupling between the magnetization and the lattice distortion. Application aspects of this unusual broad magnetocaloric effect with relative cooling power of 107 J kg−1 in an applied magnetic field of 1.6 T with an operating temperature range......A broad table-like entropy change (ΔS) at room temperature has been observed in the ferromagnetic compound La0.75Ca0.15Sr0.10MnO3, which is analyzed in the concept of Landau theory and with critical exponent analysis obtained from the magnetization measurements. The change in entropy in La0.75Ca0...

  8. MnO2 Nanofilms on Nitrogen-Doped Hollow Graphene Spheres as a High-Performance Electrocatalyst for Oxygen Reduction Reaction.

    Science.gov (United States)

    Yu, Qiangmin; Xu, Jiaoxing; Wu, Chuxin; Zhang, Jianshuo; Guan, Lunhui

    2016-12-28

    Platinum is commonly chosen as an electrocatalyst used for oxygen reduction reaction (ORR). In this study, we report an active catalyst composed of MnO2 nanofilms grown directly on nitrogen-doped hollow graphene spheres, which exhibits high activity toward ORR with positive onset potential (0.94 V vs RHE), large current density (5.2 mA cm(-2)), and perfect stability. Significantly, when it was used as catalyst for air electrode, a zinc-air battery exhibited a high power density (82 mW cm(-2)) and specific capacities (744 mA h g(-1)) comparable to that with Pt/C (20 wt %) as air cathode. The enhanced activity is ascribed to the synergistic interaction between MnO2 and the doped hollow carbon nanomaterials. This easy and cheap method paves a way of synthesizing high-performance electrocatalysts for ORR.

  9. Interface-related switching behaviors of amorphous Pr0.67Sr0.33MnO3-based memory cells

    Institute of Scientific and Technical Information of China (English)

    Zhang Ting; Bai Ying; Jia Cai-Hong; Zhang Wei-Feng

    2012-01-01

    The resistive switching properties in amorphous Pr0.67Sr0.33MnO3 films deposited by pulsed laser deposition are investigated. Reproducible and bipolar counter-8-shape and 8-shape switching behaviours of Au/Pr0.67Sr0.33MnOa/F:SnO2 junctions are obtained at room temperature. Dramatically,the coexistence of two switching polarities could be reversibly adjusted by an applied voltage range.The results allocated those two switching types to areas of different defect densities beneath the same electrode.The migration of oxygen vacancies and the trapping effect of electrons under an applied electric field play an important role.An interface-effect-related resistance switching is proposed in an amorphous Pr0.67Sr0.33MnO3-based memory cell.

  10. Pembuatan La0,8Ca0,2MnO3 sebagai Katoda pada Solid Oxide Fuel Cell (SOFC dan Karakteristiknya

    Directory of Open Access Journals (Sweden)

    Riska Ekawati

    2007-06-01

    Full Text Available The making of La0,8Ca0,2MnO3 cathode material of solid oxide fuel cell from lanthanum oxide (La2O3, calcium oxide (CaO, and manganese carbonate hydrate (MnCO3.H2O has been done using tape casting method. Time of firing the La0,8Ca0,2MnO3 varied. The values of t = 30 minutes, 60 minutes and 120 minutes. Microstructure of these materials was analyzed and characterized by means of their electric conductivity, XRD (x ray diffraction and SEM (scanning electron microscope. It is found that formulated micro structure is orthorhombic. The result of measurement shows that density is in linear (positive correlation with increasing of holding time of firing, porosity and coefficient of thermal expansion is negatively correlated with density and electric conductivity is in linear (positive correlation with increase density.

  11. Carbon-wrapped MnO nanodendrites interspersed on reduced graphene oxide sheets as anode materials for lithium-ion batteries

    Science.gov (United States)

    Liu, Boli; Li, Dan; Liu, Zhengjiao; Gu, Lili; Xie, Wenhe; Li, Qun; Guo, Pengqian; Liu, Dequan; He, Deyan

    2017-02-01

    Carbon-wrapped MnO nanodendrites interspersed on reduced graphene oxide sheets (C-MnO/rGO) were prepared on nickel foam by a facile vacuum filtration and a subsequent thermal treatment. As a binder-free anode of lithium-ion battery, the nanodendritic structure of C-MnO accommodates the huge volume expansion and shortens the diffusion length for lithium ion and electron, rGO sheets prevent C-MnO nanodendites from aggregation and offer a good electronic conduction. As a result, the electrode with such a novel architecture delivers superior electrochemical properties including high reversible capacity, excellent rate capability and cycle stability. Moreover, MnO nanodendrites change to nanoparticles wrapped in graphene sheets during the lithiation/delithiation process, which is a more beneficial microstructure to further increase the specific capacity and cycle life of the electrode.

  12. Lattice Effect on the Transport Properties in Double Doped La2/3(Ca1-xSrx)1/3MnO3 Films

    Institute of Scientific and Technical Information of China (English)

    Kexin JIN; Changle CHEN; Shenggui ZHAO; Yongcang WANG; Zhoumo SONG; Xiao YUAN

    2005-01-01

    The transport properties in the La2/3(Ca1-xSrx)1/3MnO3 (x=0, 1/3, 2/3) films prepared using the RF magnetron sputtering method were investigated. The effect of the Ca, Sr double-doping at the A position in the La2/3A1/3 MnO3 on the structure of the targets and transport of the films has been studied. With the increase of x, the structures of the targets transform from the rhombohedral phase to the cubic phase; the metal-insulator phase transition temperature(Tp) of the films increases; and the corresponding peak resistivity decreases. All the phenomena can be qualitatively explained by the lattice effect.

  13. Sign Change of Thermopower at Low Temperatures in Nd0.7(Ca,Sr,Ba)0.3MnO3

    Institute of Scientific and Technical Information of China (English)

    ZHOU Sheng-Ming; DONG Qiu-Zhao; ZHOU Gui-En; ZHANG Yu-Heng

    2000-01-01

    The temperature dependence of thermopower and resistivity for the series of Nd0.7(Ca,Sr, Ba)0.3MnO3 with a fixed average A-site cation radius have been measured. Infrared spectra revealed that the size differences between various A-site ions cause large local distortions of MnO6 octahedra. The thermopower is enhanced above metal-insulator transition temperature Tm and is reduced below Tm by increasing amount of A-site cation disorder.The sign change of thermopower induced by A-site cation disorder has been observed at low temperatures. The observed thermopower behaviors have been explained by Mott's formula and the effect of the spin disorder scattering.

  14. Magnetic, dielectric and magnetodielectric properties of PVDF-La0.7Sr0.3MnO3 polymer nanocomposite film

    Directory of Open Access Journals (Sweden)

    Ch. Thirmal

    2013-11-01

    Full Text Available We have investigated the structure, magnetic and dielectric properties of PVDF-La0.7Sr0.3MnO3 polymer nanocomposite thick film fabricated by dip coating technique along with the magnetodielectric effect. The structure and dielectric properties show the enhanced β phase in the composite compared to the PVDF film. The coupling between the ferroelectric and magnetic phases in the composite is revealed in the form of dielectric anomaly at the ferromagnetic Curie temperature. We observed 1.9% magnetodielectric effect at 300 K with the possibility of enhanced effect near the transition temperature. In addition, the analysis of the electric modulus indicates that the composite exhibits interfacial related relaxation and it follows Arrhenius Law. Our study suggests that the ac conductivity of the PVDF-La0.7Sr0.3MnO3 composite could be explained by correlated barrier hopping mechanism.

  15. 合成温度对La0.85K0.15MnO3纳米颗粒磁性能的影响%Effect of Synthesis Temperature on Magnetocaloric Properties of La0.85 K0.15MnO3 Nanoparticles

    Institute of Scientific and Technical Information of China (English)

    李丽荣; 赵娟; 王贵; 罗龙

    2012-01-01

    In this paper, the nanosized particles of La0.85Kg0.15MnO3 perovskite - type oxides were sucessfully synthesized at relatively low calcinated temperature by using amorphous heteronuclear complexing method. The relationship between mag-netocaloric properties and the calcined temperature of La0.85Kg0.15MnO3 MnO, nanoparticles was investigated systematically. The result of PPMS( Physical Property Measurement System) measurement shows that the Curie temperature Tc is 274.5 K and is independent of the calcined temperature within range of 600℃- 1000℃, the maximum magnetic entropy changes close to Tc(274 K ) of the samples calcined at 600℃ , 800℃ and 1000℃ are 2.02,3.06 and 3.56 J/kg · K at H = 2T. However, the Curie temperature of sample calcined at 1200℃ for 10h is 242.9K, which means that the magneticaloric property of the Lao.85 K0.15 MnO3 nanoparticles can be precisely controlled by adjusting the heat treatment process.%采用非晶态配合物前躯体法在比较低的烧结温度合成了钙钛矿结构氧化物La0.55K0.15MnO3纳米颗粒,系统的研究了烧结温度对Ia0.85K0.15 MnO3纳米颗粒磁性能的影响,用PPMS测量样品的居里温度和磁性能,结果表明烧结温度范围在600℃ ~ 1000℃之间,居里温度Tc为274.5 K,和烧结温度没有明显关系,在H=2T时,烧结温度分别为600℃,800℃,1000℃,对应的磁熵变△SM分别是2.02 J/(kg·K),3.06 J/(kg·K),3.56 J/(kg·K),当烧结温度升高到1200.C时,居里温度Tc为242.9K,通过控制烧结温度来调节La0.85K0.15MnO3纳米颗粒的磁性能.

  16. Electron spin resonance study of a La sub 0 sub . sub 7 Ca sub 0 sub . sub 3 MnO sub 3 single crystal

    CERN Document Server

    Joh, K W; Lee, C E; Hur, N H; Ri, H C

    2003-01-01

    Comprehensive measurements of electron spin resonance were carried out on a La sub 0 sub . sub 7 Ca sub 0 sub . sub 3 MnO sub 3 single crystal over a wide temperature range covering the ferromagnetic as well as the paramagnetic phases. Our analysis of the asymmetric lineshapes indicates that the phase segregation of good and poor conducting regions persists far above the ferromagnetic-paramagnetic phase transition temperature.

  17. Magnetocaloric effect across the coupled structural and ferromagnetic transition in Pr0.1Ce0.4Sr0.5MnO3

    Indian Academy of Sciences (India)

    C Madhu; A Sundaresan

    2008-11-01

    We have investigated the magnetocaloric effect across a first order structural transition coupled to the ferromagnetic transition (C ∼ 270 K) in Pr0.1Ce0.4Sr0.5MnO3 using magnetization and heat capacity measurements. The adiabatic magnetic entropy change || obtained from magnetization measurements for a magnetic field change of 2 T is around 1.3 J/kg K. A similar value of || was obtained from the analysis of heat capacity data.

  18. Percolative Transition in the La_5/8Sr_3/8MnO_3/LuMnO3 Composite System

    Science.gov (United States)

    Park, Soonyong; Hur, Namjung; Guha, Sabyasachi; Cheong, Sang-Wook

    2003-03-01

    The interplay between ferromagnetism and ferroelectricity is an interesting, but underexplored problem in solid state physics. The La_5/8Sr_3/8MnO_3/LuMnO3 system offers a new playground in which to study this issue. Bulk samples are synthesized using the standard solid state reaction method. DC resitivity, magnetization, and magnetoresistance will be presented and discussed within the context of percolation.

  19. Signal-On Photoelectrochemical Immunoassay for Aflatoxin B1 Based on Enzymatic Product-Etching MnO2 Nanosheets for Dissociation of Carbon Dots.

    Science.gov (United States)

    Lin, Youxiu; Zhou, Qian; Tang, Dianping; Niessner, Reinhard; Knopp, Dietmar

    2017-05-16

    Aflatoxin B1 (AFB1) monitoring has attracted extensive attention because food safety is a worldwide public health problem. Herein, we design a novel simultaneously visual and photoelectrochemical (PEC) immunosensing system for rapid sensitive detection of AFB1 in foodstuff. The immunoreaction was carried out on anti-AFB1 antibody-modified magnetic beads by using glucose oxidase (GOx)-labeled AFB1-bovine serum albumin (AFB1-BSA) conjugates as the tags with a competitive-type immunoassay format, while the visual and PEC evaluation was performed via carbon quantum dots (CQDs)-functionalized MnO2 nanosheets. Accompanying the formation of immunocomplexes, the carried GOx initially oxidized the substrate (glucose) for the generation of H2O2, which reduced/etched MnO2 nanosheets into Mn(2+) ions, thereby resulting in the dissociation of CQDs from the electrode. Within the applied potentials, the photocurrent of MnO2-CQDs-modified electrode decreased with the increasing H2O2 level in the detection cell. Meanwhile, a visual detection could be performed according to the change in the color of MnO2-CQDs-coated electrode. To elaborate, this system was aggregated into a high-throughput microfluidic device to construct a semiautomatic detection cell. Under optimal conditions, the photocurrent increased with the increasing target AFB1 within a dynamic working range from 0.01 to 20 ng mL(-1) with a limit of detection (LOD) of 2.1 pg mL(-1) (ppt). The developed immunoassay exhibited good reproducibility and acceptable accuracy. In addition, the method accuracy relative to AFB1 ELISA kit was evaluated for analyzing naturally contaminated or spiked peanut samples, giving the well-matched results between two methods. Although our strategy was focused on the detection of target AFB1, it is easily extended to screen other small molecules or mycotoxins, thereby representing a versatile immunosensing scheme.

  20. The Effect of MnO2 Content and Sintering Atmosphere on The Electrical Properties of Iron Titanium Oxide NTC Thermistors using Yarosite

    Science.gov (United States)

    Wiendartun; Gustaman Syarif, Dani

    2017-02-01

    The effect of MnO2 content and sintering atmosphere on the characteristics of Fe2TiO5 ceramics for Negative Thermal Coefficient (NTC) thermistors by using Fe2O3 derived from yarosite has been studied. The ceramics were produced by pressing a homogeneous mixture of Fe2O3, TiO2 and MnO2 (0-2.0 w/o) powders in appropriate proportions to produce Fe2TiO5 based ceramics and sintering the pressed powder at 1100-1200°C for 3 hours in air, O2 and N2 gas. Electrical characterization was done by measuring electrical resistivity of the sintered ceramics at various temperatures from 30°C to 200°C. Microstructure and structural analyses were also carried out by using an scanning electron microscope (SEM) and x-ray diffraction (XRD). The XRD data showed that the pellets crystallize in orthorhombic. The presence of second phase could not be identified from the XRD analyses. The SEM images showed that the grain size of pellet ceramics increase with increasing of MnO2 addition, and the grains size of the ceramic sintered in oxygen gas is smaller than sintered in nitrogen gas. Electrical data showed that the value of room temperature resistance (RRT) tend to decrease with respect to the increasing of MnO2 addition and the pellet ceramics sintered in oxygen gas had the largest thermistor constant (B), activation energy (Ea), sensitivity (α) and room temperature resistance (RRT), compared to the sintered in nitrogen gas. From the electrical characteristics data, it was known that the electrical characteristics of the Fe2TiO5 pellet ceramics followed the NTC characteristic. The fabricated Fe2TiO5 ceramics have thermistor constants (B = 2207-7145K). This can be applied as temperature sensor, and will fulfill the market requirement.

  1. Spin-glass-like behaviour and positive magnetoresistance in oxygen deficient La2/3Ca1/3MnO3-δ thin films

    Institute of Scientific and Technical Information of China (English)

    Zhang Fu-Chang; Chen Wei-Ran; Gong Wei-Zhi; Xu Bo; Qiu Xiang-Gang; Zhao Bai-Ru

    2004-01-01

    The magnetism and magnetoresistance (MR) in a series of oxygen-deficient La2/3Ca1/3MnO3_δ (LCMO) thin films have been investigated. Compared with the films with stoichiometric oxygen concentration, the oxygen-deficient LCMO thin films show a spin-glass-like behaviour at low temperatures, and a positive MR effect above the metal-insulator transition temperature. The mechanism of such unusual phenomena is discussed.

  2. High loading MnO2 nanowires on graphene paper: facile electrochemical synthesis and use as flexible electrode for tracking hydrogen peroxide secretion in live cells.

    Science.gov (United States)

    Dong, Shuang; Xi, Jiangbo; Wu, Yanan; Liu, Hongwei; Fu, Chaoyang; Liu, Hongfang; Xiao, Fei

    2015-01-01

    Recent progress in flexible and lightweight electrochemical sensor systems requires the development of paper-like electrode materials. Here, we report a facile and green synthesis of a new type of MnO2 nanowires-graphene nanohybrid paper by one-step electrochemical method. This strategy demonstrates a collection of unique features including the effective electrochemical reduction of graphene oxide (GO) paper and the high loading of MnO2 nanowires on electrochemical reduced GO (ERGO) paper. When used as flexible electrode for nonenzymatic detection of hydrogen peroxide (H2O2), MnO2-ERGO paper exhibits high electrocatalytic activity toward the redox of H2O2 as well as excellent stability, selectivity and reproducibility. The amperometric responses are linearly proportional to H2O2 concentration in the range 0.1-45.4 mM, with a detection limit of 10 μM (S/N=3) and detection sensitivity of 59.0 μA cm(-2) mM(-1). These outstanding sensing performances enable the practical application of MnO2-ERGO paper electrode for the real-time tracking H2O2 secretion by live cells macrophages. Therefore, the proposed graphene-based nanohybrid paper electrode with intrinsic flexibility, tailorable shapes and adjustable properties can contribute to the full realization of high-performance flexible electrode material used in point-of-care testing devices and portable instruments for in-vivo clinical diagnostics and on-site environmental monitoring. Copyright © 2014 Elsevier B.V. All rights reserved.

  3. Resistivity and critical temperature of (La1-xPrx)0.7Ca0.3MnO3

    Institute of Scientific and Technical Information of China (English)

    Liu Zi-Xin; Bai Chun-Xu

    2006-01-01

    An empirical formula of the critical temperature that is concentration dependent for polycrystalline (La1-xPrx)0.7Ca0.3MnO3 is presented in this paper. With this formula, the temperature dependence of resistance is simulated for various values of x by using the random resistor network model and the Monte Carlo method. The hysteresis effect in ρ - T curves is reasonably explained. The simulation results are in good agreement with the relevant experimental measurements.

  4. Maxwell-Wagner relaxation and magnetodielectric properties of Bi0.5La0.5MnO3 ceramics

    Science.gov (United States)

    Turik, A. V.; Pavlenko, A. V.; Reznichenko, L. A.

    2016-08-01

    The complex permittivity ɛ = ɛ'- iɛ″ of manganite bismuth-lanthanum Bi0.5La0.5MnO3 ceramics has been measured at temperature T = 78 K in the frequency range f = 200-105 Hz and in the magnetic induction range B = 0-5 T. Dielectric relaxation and the pronounced magnetodielectric effect have been detected. The explanation based on the superposition of Maxwell-Wagner relaxation and the magnetoresistance effect has been proposed.

  5. Interface resistance of YBa2Cu3O7−δ/La0.67Sr0.33MnO3 ramp-type contacts

    NARCIS (Netherlands)

    Zalk, van M.; Brinkman, A.; Aarts, J.; Hilgenkamp, H.

    2010-01-01

    We fabricated and characterized YBa2Cu3O7−δ/La0.67Sr0.33MnO3 (YBCO/LSMO) ramp-type contacts and junctions. An interlayer technique was applied to repair the ramp stoichiometry after etching. It was found that, typically, the resistance of the YBCO/LSMO interface is high compared to the resistances o

  6. Interactive effects of MnO2, organic matter and pH on abiotic formation of N2O from hydroxylamine in artificial soil mixtures

    Science.gov (United States)

    Liu, Shurong; Berns, Anne E.; Vereecken, Harry; Wu, Di; Brüggemann, Nicolas

    2017-02-01

    Abiotic conversion of the reactive nitrification intermediate hydroxylamine (NH2OH) to nitrous oxide (N2O) is a possible mechanism of N2O formation during nitrification. Previous research has demonstrated that manganese dioxide (MnO2) and organic matter (OM) content of soil as well as soil pH are important control variables of N2O formation in the soil. But until now, their combined effect on abiotic N2O formation from NH2OH has not been quantified. Here, we present results from a full-factorial experiment with artificial soil mixtures at five different levels of pH, MnO2 and OM, respectively, and quantified the interactive effects of the three variables on the NH2OH-to-N2O conversion ratio (RNH2OH-to-N2O). Furthermore, the effect of OM quality on RNH2OH-to-N2O was determined by the addition of four different organic materials with different C/N ratios to the artificial soil mixtures. The experiments revealed a strong interactive effect of soil pH, MnO2 and OM on RNH2OH-to-N2O. In general, increasing MnO2 and decreasing pH increased RNH2OH-to-N2O, while increasing OM content was associated with a decrease in RNH2OH-to-N2O. Organic matter quality also affected RNH2OH-to-N2O. However, this effect was not a function of C/N ratio, but was rather related to differences in the dominating functional groups between the different organic materials.

  7. Structural and magnetic ordering in Pr0.65(CaySr1-y)0.35MnO3 : Quantum critical point versus phase segregation scenarios

    NARCIS (Netherlands)

    Blake, G.R.; Chapon, L.; Radaelli, P.G.; Argyriou, D.N.; Gutmann, M.J.; Mitchell, J.F.

    2002-01-01

    The phase diagram of Pr0.65(CaySr1–y)0.35MnO3, 0.6≤y≤0.8, has been determined by neutron diffraction, magnetization, and electrical conductivity measurements in order to investigate the nature of the transition between ferromagnetic metallic and charge-ordered insulating states near y = 0.75. Two po

  8. Photovoltaic Characteristic of La0.7Sr0.3MnO3/ZnO p-n Heterojunction

    Institute of Scientific and Technical Information of China (English)

    SUN Zhi-Hui; NING Ting-Yin; ZHOU Yue-Liang; ZHAO Song-Qing; CAO Ling-Zhu

    2008-01-01

    We report on the photovoltaic properties of La0.7Sr0.3MnO3/ZnO heterojunction fabricated by pulsed laser deposition methods.Nanosecond photovoltaic pulses are observed in this junction in the wavelength range from ultraviolet-visible to infrared.A qualitative explanation is presented,based on an analysis of the photovoltaic signals of p-n heterojunction.

  9. 多晶La0.49Sr0.51MnO3中的铁磁反共振%Ferromagnetic antiresonance in polycrystalline La0.49Sr0.51MnO3

    Institute of Scientific and Technical Information of China (English)

    舒启清; 柳文军; Bhagat S M; Lofladn S E; Troyanchuk I O

    2006-01-01

    采用谐振腔微扰技术测量了多晶La0.49Sr0.51MnO3的微波吸收(PMA),观察到在居里温度TC 或奈尔温度TN附近发生PMA呈现极小值即铁磁反共振(FMAR)现象. 基于朗道-利弗希茨-吉尔伯特模型,磁化强度μ0M对温度的依赖关系可以从FMAR得到. 发现当外加直流磁场μ0H = 0时,不同微波频率下得到的磁化强度μ0M对温度的依赖关系与标度律符合. 然而,当μ0H ≠ 0且μ0H<120 mT时,不同μ0H下得到的磁化强度μ0M对温度的依赖关系与标度律不符合. 在μ0H平行最大微波磁场hrf时,在TC 附近随μ0H增加发生FMAR的PMA值增加,且随μ0H增加发生FMAR的温度下降,但此时在TN 附近未观测到FMAR. 在μ0H垂直hrf时在TC 附近随μ0H增加发生FMAR的PMA值减少,且随μ0H增加发生FMAR的温度很少变化,但此时在TN 附近发生FMAR的PMA值和温度均几乎不随μ0H变化. 这些结果可归因为:①多晶La0.49Sr0.51MnO3是一种由铁磁(FM)和反铁磁(AFM)等多态微区组成的密切合物,是一个包含多个状态和取向互不相同的畴壁的复杂系统;②在μ0H增强或温度下降的过程中,都存在导致PMA增加或减少的两种机制的竞争.

  10. A facile hydrothermal recovery of nano sealed MnO2 particle from waste batteries: An advanced material for electrochemical and environmental applications

    Science.gov (United States)

    Mylarappa, M.; Venkata Lakshmi, V.; Vishnu Mahesh, K. R.; Nagaswarupa, H. P.; Raghavendra, N.

    2016-09-01

    This work deliberates a method for manganese (Mn) recovery as manganese oxide obtained by leaching of waste batteries with 3M sulphuric acid. The Experimental test for the recovery of Mn present within the waste dry cell batteries were carried out by a reductive leachant. Elemental composition of leached sample was confirmed by Energy Dispersive X-ray analysis (EDAX), and Surface morphology of the recovered MnO2 was examined by using Scanning Electron microscopy (SEM). Phase composition was confirmed from X-ray Diffractro meter (XRD). The obtained leached solution was treated with 4M NaOH, yielded to Manganese Dioxide with high extraction degree, while it do not touches the Zn content within the solutions. The recovered samples were characterized using XRD, EDAX, SEM and Fourier transform infrared spectrometry (FTIR). The electrochemical properties of the as-recovered sample from leached solution was examined used cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Remarkably, the 80 wt.% MnO2 displays reversibility, diffusion constant, smaller equivalent series resistance and charge transfer resistance in 0.5M NaOH showed superior results as compared to alternative electrolytes. The ideal capacitive behaviour of MnO2 electrode and nano particle was applied to photocatalytic degradation of dyes.

  11. All-solid-state electrochemical capacitors using MnO2 electrode/SiO2-Nafion electrolyte composite prepared by the sol-gel process

    Science.gov (United States)

    Shimamoto, Kazushi; Tadanaga, Kiyoharu; Tatsumisago, Masahiro

    2014-02-01

    Electrode-electrolyte composites of MnO2 active material, acetylene black (AB), and SiO2-Nafion solid electrolyte were prepared using the sol-gel process to form good solid-solid interfaces. The composites were obtained by the addition of MnO2 and AB into a sol of hydrolyzed tetraethoxysilane with Nafion, and successive solidification of the precursor sol. Scanning electron microscope and energy dispersive X-ray spectroscopy measurements show that good solid-solid interface is formed between electrodes and solid electrolytes in the composites. All-solid-state hybrid capacitors were fabricated using the composites or the hand-grinding mixture of MnO2, AB and SiO2-Nafion powder as positive electrodes, activated carbon powder as a negative electrode, and phosphosilicate gel as a solid electrolyte. The all-solid-state hybrid capacitors using the composites exhibit larger capacitances and better rate performance than the capacitors using the electrode prepared by hand-mixing of powders. Specific discharge capacitances of the capacitor with the composite are 85 F g-1 for the one with the composite electrode and 48 F g-1 for the one with the hand-mixed electrode, at 1 mA cm-2. Moreover, the all-solid-state capacitors using the composite electrode can be operated at temperatures between -30 °C and 60 °C.

  12. Doping influence of spin dynamics and magnetoelectric effect in hexagonal Y0.7Lu0.3MnO3

    Science.gov (United States)

    Tian, Wei; Tan, Guotai; Liu, Liu; Zhang, Jinxing; Winn, Barry; Hong, Tao; Fernandez-Baca, Jaime; Zhang, Chenglin; Dai, Pengcheng

    2014-03-01

    Inelastic neutron scattering experiments were performed to study spin waves and their correlation with the magnetoelectric effect in Y0.7Lu0.3MnO3. The Mn trimerization distortion has been suggested to play a key role in determining the magnetic structure and the magnetoelectric effect in YMnO3 and LuMnO3. In Y0.7Lu0.3MnO3, our INS study reveals a much smaller in-plane (hexagonal ab-plane) anisotropy gap that coincides with a weaker in-plane dielectric anomaly at TN. Since both the smaller in-plane anisotropy gap and the weaker in-plane dielectric anomaly are coupled to a weaker Mn trimerization distortion in Y0.7Lu0.3MnO3 comparing to YMnO3 and LuMnO3, we conclude that the Mn trimerization is responsible for the magnetoelectric effect and multiferroic phenomenon in Y1-xLuxMnO3.

  13. Influence of doping on the spin dynamics and magnetoelectric effect in hexagonal Y0.7Lu0.3MnO3

    Science.gov (United States)

    Tian, W.; Tan, Guotai; Liu, Liu; Zhang, Jinxing; Winn, Barry; Hong, Tao; Fernandez-Baca, J. A.; Zhang, Chenglin; Dai, Pengcheng

    2014-04-01

    We use inelastic neutron scattering and dielectric constant measurements to study the doping influence on the spin dynamics and magnetoelectric (ME) effect in hexagonalY0.7Lu0.3MnO3. In undoped YMnO3 and LuMnO3, the Mn trimerization distortion has been suggested to play a key role in determining the magnetic structure and the magnetoelectric effect. In Y0.7Lu0.3MnO3, at the antiferromagnetic zone center, we observed a much smaller Δ12≈0.52 meV gap (which is ˜2.5 meV for both YMnO3 and LuMnO3) that coincides with a weaker in-plane dielectric anomaly at TN; both can be attributed to a weaker Mn trimerization distortion in Y0.7Lu0.3MnO3 compared to YMnO3 and LuMnO3. The results provide strong evidence that the magnitude of ME coupling is linked to the strength of the trimerization distortion, suggesting the Mn trimerization is responsible for the ME effect in Y1-yLuyMnO3.

  14. Europium substitution effects on structural, magnetic and magnetocaloric properties in La0.5Ca0.5MnO3

    Directory of Open Access Journals (Sweden)

    Boujelben W.

    2012-06-01

    Full Text Available We have investigated structural, magnetic and magnetocaloric properties of polycrystalline samples La0.5-xEuxCa0.5MnO3 (x=0 and 0.1. Rietveld refinement of the X-ray diffraction patterns show that our samples are single phase and crystallize in the orthorhombic structure with Pnma space group. Magnetization measurements versus temperature at a magnetic applied field of 500 Oe indicate that La0.4Eu0.1Ca0.5MnO3 sample exhibits a paramagnetic to ferromagnetic transition with decreasing temperature. Magnetic measurements reveal strong magnetocaloric effect in the vicinity of the Curie temperature TC. The parent compound shows a negative magnetic entropy change of ∆SM=−1.13Jkg−1K−1 at 220K and a positive magnetocaloric effects ∆SM=1Jkg−1K−1 at 150K under a magnetic applied field of 2T. La0.4Eu0.1Ca0.5MnO3 exhibits a maximum value of magnetic entropy change ∆SM=−1.15Jkg−1K−1 at 130K under an applied field of 2T and a large relative cooling power RCP with a maximum value of 72 J/kg.

  15. SUPPRESSED Tc OF La2/3Ca1/3MnO3/YBa2Cu4O8/La2/3Ca1/3MnO3 TRILAYER FILMS BY FACING-TARGET SPUTTERING TECHNIQUE%对靶溅射技术制备的La2/3Ca1/3MnO3/YBa2Cu4O8/La2/3Ca1/3MnO3薄膜中Tc的降低

    Institute of Scientific and Technical Information of China (English)

    赵昆; 黄康权

    2003-01-01

    本文用对靶溅射技术制备了La2/3Ca1/3MnO3/YBa2Cu4O8/La2/3Ca1/3MnO3薄膜.与YBCO单层薄膜相比,由于超导/铁磁系统中的磁性邻近效应,三层薄膜表现出较低的超导转变温度.薄膜的R~T测量曲线显示出超磁阻(CMR)效应和超导转变,预示着超导和铁磁特性共存于LCMO/YBCO/LCMO三文治结构.%Trilayer films in which a superconducting YBa2Cu4O8 (YBCO) layer is sandwiched between two ferromagnetic La2/3Ca1/3MnO3 (LCMO) layers are formed by facing-target sputtering technique. The difference of superconducting transition temperature (Tc) between YBCO single layer and LCMO/YBCO/LCMO trilayers as functions of YBCO thickness is described by the magnetic proximity effect in superconductor/ferromagnet structure. Colossal magnetoresistance (CMR) effect and superconducting transition are shown in R~T curve, indicating the coexistence of superconductivity and ferromagnetism in the LCMO/YBCO/LCMO sandwich structures.

  16. Enhanced simultaneous detection of ractopamine and salbutamol--Via electrochemical-facial deposition of MnO2 nanoflowers onto 3D RGO/Ni foam templates.

    Science.gov (United States)

    Wang, Ming Yan; Zhu, Wei; Ma, Lin; Ma, Juan Juan; Zhang, Dong En; Tong, Zhi Wei; Chen, Jun

    2016-04-15

    In this paper, we report a facile method to successfully fabricate MnO2 nanoflowers loaded onto 3D RGO@nickel foam, showing enhanced biosensing activity due to the improved structural integration of different electrode materials components. When the as-prepared 3D hybrid electrodes were investigated as a binder-free biosensor, two well-defined and separate differential pulse voltammetric peaks for ractopamine (RAC) and salbutamol (SAL) were observed, indicating the simultaneous selective detection of both β-agonists possible. The MnO2/RGO@NF sensor also demonstrated a linear relationship over a wide concentration range of 17 nM to 962 nM (R=0.9997) for RAC and 42 nM to 1463 nM (R=0.9996) for SAL, with the detection limits of 11.6 nM for RAC and 23.0 nM for SAL. In addition, the developed MnO2/RGO@NF sensor was further investigated to detect RAC and SAL in pork samples, showing satisfied comparable results in comparison with analytic results from HPLC.

  17. Raman scattering study of Nd sub 1 sub - sub x Sr sub x MnO sub 3 (x = 0.3, 0.5)

    CERN Document Server

    Choi, K Y; Güntherodt, G; Pattabiraman, M; Rangarajan, G; Gnezdilov, V P; Balakrishnan, G; Paul, D M; Lees, M R

    2003-01-01

    We report on polarized Raman scattering of single crystals of Nd sub 1 sub - sub x Sr sub x MnO sub 3 (x = 0.3, 0.5). Raman spectra of Nd sub 0 sub . sub 7 Sr sub 0 sub . sub 3 MnO sub 3 show a significant change through the metal-insulator transition. In the ferromagnetic metallic phase phonon modes grow in intensity and number while the electronic continuum becomes more pronounced. We suggest that these effects are due to the strong competition between the localization and the delocalization of carriers which is the origin of the largest colossal magnetoresistance effect ever reported for the manganites. Raman spectra of Nd sub 0 sub . sub 5 Sr sub 0 sub . sub 5 MnO sub 3 , upon cooling through the charge-ordering temperature T sub C sub O = 148 K, exhibit several new lines which undergo a substantial hardening. This hardening is interpreted as a freezing of the Jahn-Teller distortions with a gradual decrease of a fraction of the ferromagnetic phase in the CE-type charge/orbital ordered state.

  18. The unconventional doping in YBa2Cu3O7-x/La0.7Ca0.3MnO3 heterostructures by termination control

    Science.gov (United States)

    Tra, V. T.; Huang, R.; Gao, X.; Chen, Y.-J.; Liu, Y. T.; Kuo, W. C.; Chin, Y. Y.; Lin, H. J.; Chen, J. M.; Lee, J. M.; Lee, J. F.; Shi, P. S.; Jiang, M. G.; Duan, C. G.; Juang, J. Y.; Chen, C. T.; Jeng, H. T.; He, Q.; Chuang, Y.-D.; Lin, J.-Y.; Chu, Y.-H.

    2017-01-01

    In strongly correlated oxides, heterostructures provide a powerful route to manipulate the charge, spin, orbital, and lattice degrees of freedom to create distinctive functionalities. In this work, we have achieved atomically precise interface control in YBa2Cu3O7-x/La0.7Ca0.3MnO3 (YBCO/LCMO) heterostructures and find a hidden effective doping. This mechanism is responsible for higher Tc in the sample with the MnO2-terminated interface than in that with the La0.7Ca0.3O-terminated interface. The MnO2-terminated sample also shows a larger magnetic moment of Mn together with a lower valence state. For more than a decade, the control of Tc in these heterostructures prior to this work has been solely via the variation of YBCO or LCMO thickness. This work hints at an alternative way of exploiting and exploring the interactions between superconductivity and magnetism in this system.

  19. Nematicity in charge and orbital ordered structure: a new description of phase transitions in La0.33Ca0.67MnO3

    Science.gov (United States)

    Tao, Jing; Yin, W. G.; Zhu, Y.; Sun, K.

    2014-03-01

    Doped manganites have a well-known unidirectional superlattice modulation at low temperatures, although the origin of the modulation is still under debate. The phase transition of the modulation in this compound has been characterized by the superlattice reflections and the transition temperature was determined when the modulation becomes long-range. Here we report a new description of the phase transition in La0.33Ca0.67MnO3 from the aspect of symmetry by measuring anisotropy based on transmission electron microscopy results. Instead of one phase transition, we found that the electronic structures undergo smectic, nematic and isotropic behaviors upon warming. Comparing to previous characterizations of the phase transition in La0.33Ca0.67MnO3, this symmetry measurement enables a better unification between electronic structure and other properties such as the crystal lattice variation. Moreover, we directly observed the creation of dislocation pairs in the smectic phase, which is consistent with the dislocation-proliferation mechanism predicted by the nematicity theory in correlated systems. The defect observations also suggest the charge and orbital ordering nature of the modulation in La0.33Ca0.67MnO3.

  20. Redox Active Cation Intercalation/Deintercalation in Two-Dimensional Layered MnO2 Nanostructures for High-Rate Electrochemical Energy Storage.

    Science.gov (United States)

    Xiong, Pan; Ma, Renzhi; Sakai, Nobuyuki; Bai, Xueyin; Li, Shen; Sasaki, Takayoshi

    2017-02-22

    Two-dimensional (2D) layered materials with a high intercalation pseudocapacitance have long been investigated for Li(+)-ion-based electrochemical energy storage. By contrast, the exploration of guest ions other than Li(+) has been limited, although promising. The present study investigates intercalation/deintercalation behaviors of various metal ions in 2D layered MnO2 with various interlayer distances, K-birnessite nanobelt (K-MnO2), its protonated form (H-MnO2), and a freeze-dried sample of exfoliated nanosheets. Series of metal ions, such as monovalent Li(+), Na(+), and K(+) and divalent Mg(2+), exhibit reversible intercalation during charge/discharge cycling, delivering high-rate pseudocapacitances. In particular, the freeze-dried MnO2 of exfoliated nanosheets restacked with the largest interlayer spacing and a less compact 3D network exhibits the best rate capability and a stable cyclability over 5000 cycles. Both theoretical calculation and kinetic analysis reveal that the increased interlayer distance facilitates the fast diffusion of cations in layered MnO2 hosts. The results presented herein provide a basis for the controllable synthesis of layered nanostructures for high-rate electrochemical energy storage using various single- and multivalent ions.

  1. MnO Nanoparticle@Mesoporous Carbon Composites Grown on Conducting Substrates Featuring High-performance Lithium-ion Battery, Supercapacitor and Sensor

    Science.gov (United States)

    Wang, Tianyu; Peng, Zheng; Wang, Yuhang; Tang, Jing; Zheng, Gengfeng

    2013-01-01

    We demonstrate a facile, two-step coating/calcination approach to grow a uniform MnO nanoparticle@mesoporous carbon (MnO@C) composite on conducting substrates, by direct coating of the Mn-oleate precursor solution without any conducting/binding reagents, and subsequent thermal calcination. The monodispersed, sub-10 nm MnO nanoparticles offer high theoretical energy storage capacities and catalytic properties, and the mesoporous carbon coating allows for enhanced electrolyte transport and charge transfer towards/from MnO surface. In addition, the direct growth and attachment of the MnO@C nanocomposite in the supporting conductive substrates provide much reduced contact resistances and efficient charge transfer. These excellent features allow the use of MnO@C nanocomposites as lithium-ion battery and supercapacitor electrodes for energy storage, with high reversible capacity at large current densities, as well as excellent cycling and mechanical stabilities. Moreover, this MnO@C nanocomposite has also demonstrated a high sensitivity for H2O2 detection, and also exhibited attractive potential for the tumor cell analysis. PMID:24045767

  2. Simultaneous observation of positive and negative giant magnetoresistances in composite (La0.83Sr0.17MnO3) 1-x(ITO)x

    Institute of Scientific and Technical Information of China (English)

    Wang Miao; Zhang Ning

    2006-01-01

    We have studied the transport property of the composites (La0.83Sr0.17 MnO3)l-x(ITO)x[ITO=(In2O3) 0.95 (SnO2)0.05],which were fabricated by mechanically mixing La0.83Sr0.17MnO3 and ITo grains. A giant positive magnetoresistance (PMR) has been observed above the Curie temperature Tc for samples with x around 0.40,in addition to the negative magnetoresistance related to spin-dependent interfacial tunnelling below Tc.Fbr (La0.83Sr0.17MnO3) 0.6(ITO)0.4,the magnetoresistive ratio for the PMR can reach 39.3% under a magnetic field H=2.24x105A/m.Theoretical analysis suggests that the magnetic-field-induced broadening of the p-n barrier between both kinds of grains and the density of the p-n heterostructures should be responsible for the PMR behaviour.

  3. Influence of BiFeO3 Additions on the Electrical and Magnetic Properties of La0.7Ca0.3MnO3 Ceramics

    Science.gov (United States)

    Luo, B. C.; Dong, H. J.

    2016-07-01

    (1 - x) La0.7Ca0.3MnO3- xBiFeO3 (0 ≤ x ≤ 0.1) ceramics were prepared by a solid state reaction method, and the structural, magnetic, electrical and thermoelectric power properties have been investigated. The single-phase (1 - x) La0.7Ca0.3MnO3- xBiFeO3 solid solutions with orthorhombic structure are achieved for x ≤ 0.1, and the lattice parameters of La0.7Ca0.3MnO3 ceramics keep equivalence with BiFeO3 additions. In contrast, both the ferromagnetic-paramagnetic transition temperature and the metal-insulator transition temperature monotonically shift towards lower temperature, and the thermoelectric power is enhanced for all the measured temperatures with increasing BiFeO3 content. In combination with resistivity and Seebeck coefficient data, the small polaron hopping is demonstrated to be responsible for the transport phenomena above the metal-insulator transition temperature.

  4. Effect of iron doping on electrical, electronic and magnetic properties of La0.7Sr0.3MnO3

    Science.gov (United States)

    Deshmukh, Alka V.; Patil, S. I.; Bhagat, S. M.; Sagdeo, P. R.; Choudhary, R. J.; Phase, D. M.

    2009-09-01

    The effect of 5% Fe doping at Mn site, on the valence band structure of La0.7Sr0.3MnO3 has been investigated. Polycrystalline samples of La0.7Sr0.3MnO3 and La0.7Sr0.3Mn0.95Fe0.05O3 have been prepared by the solid-state reaction route. The phase purity of these samples was confirmed using x-ray diffraction. Core-level x-ray photoelectron spectroscopy measurements were performed to study the changes in the chemical composition. The valence band spectroscopy measurements on these samples, using a synchrotron radiation source, show a considerable change in the density of states (DOSs) at the Fermi level with 5% Fe doping. The results are correlated with room temperature resistivity and magnetization data on these samples. These results suggest that though the DOSs at the Fermi level increase on Fe doping, the conduction in LSMO gets hampered. This may be a result of changes in the hybridization of the orbitals due to Fe doping which modifies the MnO6 octahedra and hence the Mn3+-O-Mn4+ network.

  5. Polyethylenimine-Mediated Electrostatic Assembly of MnO2 Nanorods on Graphene Oxides for Use as Anodes in Lithium-Ion Batteries.

    Science.gov (United States)

    Chae, Changju; Kim, Ki Woong; Yun, Young Jun; Lee, Daehee; Moon, Jooho; Choi, Youngmin; Lee, Sun Sook; Choi, Sungho; Jeong, Sunho

    2016-05-11

    In recent years, the development of electrochemically active materials with excellent lithium storage capacity has attracted tremendous attention for application in high-performance lithium-ion batteries. MnO2-based composite materials have been recognized as one of promising candidates owing to their high theoretical capacity and cost-effectiveness. In this study, a previously unrecognized chemical method is proposed to induce intra-stacked assembly from MnO2 nanorods and graphene oxide (GO), which is incorporated as an electrically conductive medium and a structural template, through polyethylenimine (PEI)-derived electrostatic modulation between both constituent materials. It is revealed that PEI, a cationic polyelectrolyte, is capable of effectively forming hierarchical, two-dimensional MnO2-RGO composites, enabling highly reversible capacities of 880, 770, 630, and 460 mA·h/g at current densities of 0.1, 1, 3, and 5 A/g, respectively. The role of PEI in electrostatically assembled composite materials is clarified through electrochemical impedance spectroscopy-based comparative analysis.

  6. The electronic, structural and magnetic properties of La(1-1/3)Sr(1/3)MnO3 film with oxygen vacancy: a first principles investigation.

    Science.gov (United States)

    Li, Jia

    2016-03-01

    We have systematically investigated the influence of oxygen vacancy defects on the structural, electronic and magnetic properties of La(1-x)Sr(x)MnO3 (x = 1/3) film by means of ab initio calculations using bare GGA as well as GGA+U formalism, in the latter of which, the on-site Coulombic repulsion parameter U for Mn 3d orbital has been determined by the linear response theory. It is revealed that the introduction of the vacancy defects causes prominent structural changes including the distortion of MnO6 octahedra and local structural deformation surrounding the oxygen vacancy. The GGA+U formalism yields a significantly larger structural change than the bare GGA method, surprisingly in contrast with the general notion that the inclusion of Hubbard U parameter exerts little influence on structural properties. The distortion of MnO6 octahedra leads to a corresponding variation in the hybridization between Mn 3d and O 2p, which gets strengthened if the Mn-O distance becomes smaller and vice versa. The magnetic moments of the Mn atoms located in three typical sites of the vacancy-containing supercell are all larger than those in the pristine system. We have characterized the O-vacancy defect as a hole-type defect that forms a negative charge center, attracting electrons.

  7. Synthesis and magnetic structure of the layered manganese oxide selenide Sr2MnO2Ag1.5Se2

    Science.gov (United States)

    Blandy, Jack N.; Boskovic, Jelena C.; Clarke, Simon J.

    2017-01-01

    The synthesis of a high-purity sample of the layered oxide selenide Sr2MnO2Ag1.5Se2 is reported. At ambient temperature it crystallises in the space group I4/mmm with two formula units in the unit cell and lattice parameters a=4.08771(1) Å, c=19.13087(8) Å. The compound displays mixed-valent manganese in a formal oxidation state close to +2.5 and powder neutron diffraction measurements reveal that below the Néel temperature of 63(1) K this results in an antiferromagnetic structure which may be described as A-type, modelled in the magnetic space group PI4/mnc (128.410 in the Belov, Neronova and Smirnova (BNS) scheme) in which localised Mn moments of 3.99(2) μB are arranged in ferromagnetic layers which are coupled antiferromagnetically. In contrast to the isostructural compound Sr2MnO2Cu1.5S2, Sr2MnO2Ag1.5Se2 does not display long range ordering of coinage metal ions and vacancies, nor may significant amounts of the coinage metal readily be deintercalated using soft chemical methods.

  8. Inhibition of Tapeworm Thioredoxin and Glutathione Pathways by an Oxadiazole N-Oxide Leads to Reduced Mesocestoides vogae Infection Burden in Mice

    Directory of Open Access Journals (Sweden)

    Vivian Pasquet

    2015-06-01

    Full Text Available Parasitic flatworms cause serious infectious diseases that affect humans and livestock in vast regions of the world, yet there are few effective drugs to treat them. Thioredoxin glutathione reductase (TGR is an essential enzyme for redox homeostasis in flatworm parasites and a promising pharmacological target. We purified to homogeneity and characterized the TGR from the tapeworm Mesocestoides vogae (syn. M. corti. This purification revealed absence of conventional TR and GR. The glutathione reductase activity of the purified TGR exhibits a hysteretic behavior typical of flatworm TGRs. Consistently, M. vogae genome analysis revealed the presence of a selenocysteine-containing TGR and absence of conventional TR and GR. M. vogae thioredoxin and glutathione reductase activities were inhibited by 3,4-bis(phenylsulfonyl-1,2,5-oxadiazole N2-oxide (VL16E, an oxadiazole N-oxide previously identified as an inhibitor of fluke and tapeworm TGRs. Finally, we show that mice experimentally infected with M. vogae tetrathyridia and treated with either praziquantel, the reference drug for flatworm infections, or VL16E exhibited a 28% reduction of intraperitoneal larvae numbers compared to vehicle treated mice. Our results show that oxadiazole N-oxide is a promising chemotype in vivo and highlights the convenience of M. vogae as a model for rapid assessment of tapeworm infections in vivo.

  9. Synthesis and anticancer activity evaluation of new 2-alkylcarbonyl and 2-benzoyl-3-trifluoromethyl-quinoxaline 1,4-di-N-oxide derivatives.

    Science.gov (United States)

    Zarranz, Belén; Jaso, Andrés; Aldana, Ignacio; Monge, Antonio

    2004-07-01

    As a continuation of our research in quinoxaline 1,4-di-N-oxide and with the aim of obtaining new anticancer agents, which can improve the current chemotherapeutic treatments, new series of 2-alkylcarbonyl and 2-benzoyl-3-trifluoromethylquinoxaline 1,4-di-N-oxide derivatives have been synthesized and evaluated for in vitro antitumor activity against a 3-cell line panel, consisting of MCF7 (breast), NCI-H460 (lung), and SF-268 (CNS). These active compounds were then evaluated in the full panel of 60 human tumor cell lines derived from nine cancer cell types. The results have shown that, in general, anticancer activity depends on the substituents in the carbonyl group, improving in the order: ethyl

  10. Theoretical studies on the structure, thermochemical and detonation properties of amino and nitroso substituted 1,2,4-triazol-5-one-N-oxides.

    Science.gov (United States)

    Ravi, P; Venkatesan, V; Tewari, Surya P

    2013-11-01

    DFT calculations at the B3LYP/aug-cc-pVDZ level have been carried out to explore the structure, stability, electron density, heat of formation, detonation velocity and detonation pressure of substituted amino- and nitroso-1,2,4-triazol-5-one-N-oxides. Heats of formation of substituted triazol-5-one-N-oxides have been computed at the B3LYP/aug-cc-pVDZ level via isodesmic reaction procedure. Materials Studio 4.1 package was used to predict the crystal density of model compounds. Kamlet-Jacob equations were used to calculate detonation properties based on the calculated heat of explosion and crystal density. The designed compounds 4, 6, 7 and 8 have shown higher performance compared with those of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane and octanitrocubane. Atoms-in-molecule (AIM) analyses have also been carried out to understand the nature of intramolecular interactions in the designed molecules.

  11. Structural and spectroscopic characterization of methyl isocyanate, methyl cyanate, methyl fulminate, and acetonitrile N-oxide using highly correlated ab initio methods

    Science.gov (United States)

    Dalbouha, S.; Senent, M. L.; Komiha, N.; Domínguez-Gómez, R.

    2016-09-01

    Various astrophysical relevant molecules obeying the empirical formula C2H3NO are characterized using explicitly correlated coupled cluster methods (CCSD(T)-F12). Rotational and rovibrational parameters are provided for four isomers: methyl isocyanate (CH3NCO), methyl cyanate (CH3OCN), methyl fulminate (CH3ONC), and acetonitrile N-oxide (CH3CNO). A CH3CON transition state is inspected. A variational procedure is employed to explore the far infrared region because some species present non-rigidity. Second order perturbation theory is used for the determination of anharmonic frequencies, rovibrational constants, and to predict Fermi resonances. Three species, methyl cyanate, methyl fulminate, and CH3CON, show a unique methyl torsion hindered by energy barriers. In methyl isocyanate, the methyl group barrier is so low that the internal top can be considered a free rotor. On the other hand, acetonitrile N-oxide presents a linear skeleton, C3v symmetry, and free internal rotation. Its equilibrium geometry depends strongly on electron correlation. The remaining isomers present a bend skeleton. Divergences between theoretical rotational constants and previous parameters fitted from observed lines for methyl isocyanate are discussed on the basis of the relevant rovibrational interaction and the quasi-linearity of the molecular skeleton.

  12. Transport properties in La0.7-xGdxSr0.3MnO3 system

    Institute of Scientific and Technical Information of China (English)

    GAO; Guizhen; (

    2003-01-01

    [1]Helmolt, R. V., Wecker, J., Holzapfel, B. et al., Giant negative magnetoresistance in perovskitelike La2/3Ba1/3MnOx ferromagnetic films, Phys. Rev. Lett., 1993, 71: 2331-2333.[2]Jin, S., Tiefel, T. H., McCormack, M. et al., Thousandfold change in resistivity in magnetoresistive La-Ca-Mn-O films, Science, 1994, 264: 413-415.[3]Xiong, G. C. et al., Giant magnetoresistance in epitaxial Nd0.7Sr0.3MnO3-Delta thin-films, Appl. Phys. Lett., 1995, 66: 1427-1429.[4]Zener, C., Interaction between the d-shells in the transition metals (II)-- Ferromagnetic compounds of manganese with perovskite structure, Phys. Rev., 1951, 82: 403-409.[5]Millis, A. J., Littlewood, P. B., Shraiman, B. I., Double exchange alone does not explain the resistivity of La1-xSrxMnO3, Phys. Rev. Lett., 1995, 74: 5144-5147.[6]Hwang, H. Y., Cheong, S. W., Radaelli, P. G., Lattice effect on the magnetoresistance in doped LaMnO3 , Phys. Rev. Lett., 1995, 77: 914-917.[7]Zhou, J. S., Goodenough, J. B., Phonon-assisted double exchange in perovskite manganites, Phys. Rev. Lett., 1998 , 80: 2665-2668.[8]Moreo, A., Yunoki, S., Dagotto, E., Phase separation scenario for manganese oxides and related materials, Science, 1999, 283: 2034-2040.[9]Fath, M., Freisem. S., Menovsky, A. A. et al., Spatially inhomogeneous metal-insulator transition in doped manganites, Science, 1999, 285: 1540-1542.[10]Uehara, M., Mori, S., Chen, C. H. et al., Percolative phase separation underlies colossal magnetoresistance in mixed- valent manganites, Nature, 1999, 399: 560-563.[11]Liu, N., Sun, Y., Zhang, Y. H., Mechanism of insulator-metal transition in La2/3Ca1/3MnO3: Collapse of small polaron, China Phys. Lett., 2001, 7: 957-959.

  13. Hydrostatic pressure effect on the spin reorientation transition of ferromagnetic Sm0.7-xLaxSr0.3MnO3 (x = 0, 0.1) polycrystals

    Science.gov (United States)

    Thiyagarajan, R.; Arumugam, S.; Sivaprakash, P.; Kannan, M.; Saravanan, C.; Yang, Wenge

    2017-06-01

    The hydrostatic pressure effect on the resistivity and magnetization of the narrow band gap manganite Sm0.7-xLaxSr0.3MnO3 (x = 0, 0.1) systems has been investigated. At ambient pressure measurements, the parent compound Sm0.7Sr0.3MnO3 showed a ferromagnetic-insulating nature, whereas the 10% La-doped compound Sm0.6La0.1Sr0.3MnO3 showed a ferromagnetic-metallic nature. Furthermore, both samples showed a spin-reorientation transition (TSR) below Curie temperature, which originated from the Mn sublattice and was supported by an antiferromagnetic Sm(4f)-Mn(3d) interaction. Both samples exhibited a normal and inverse magnetocaloric effect as a result of these two different magnetic transitions. Magnetization measurements on Sm0.7Sr0.3MnO3 under pressure did not show an appreciable change in the Curie temperature, but enhanced TSR, whereas an insulator-metallic transition was observed during resistivity measurements under pressure. On the other hand, for Sm0.6La0.1Sr0.3MnO3, TC increased and TSR reduced upon the application of pressure. The metallic nature which is observed at ambient pressure resistivity measurement was further enhanced with 97% of piezoresistance. The pressure did not change the normal magnetocaloric effect of Sm0.7Sr0.3MnO3, but increased it in Sm0.6La0.1Sr0.3MnO3. However, there was not much change in the inverse magnetocaloric effect of both compounds. These studies were analyzed based on the pressure effect on the activation energy and scattering interaction factors.

  14. Electrical transport in epitaxial La0.7Ca0.3MnO3 thin films

    Science.gov (United States)

    El Helali, S.; Daoudi, K.; Oumezzine, M.; Oueslati, M.

    2017-02-01

    We investigated the electrical transport properties of epitaxial La0.7Ca0.3MnO3 thin films grown by metal organic deposition process on LaAlO3 single crystalline substrates. To explain the coexistence of ferromagnetic (FM)-metallic and paramagnetic (PM) -insulator phases in the same specimen, the temperature dependence of resistivity was simulated by the phenomenological percolation model which is based on the phase segregation of FM-metallic to PM-insulator. The temperature dependence of resistivity (ρ (T)) curves can be well fitted by ρ (T) = ρFM f + ρPM (1 - f) with ρFM is the resistivity of the FM phase below the Curie temperature (TC), ρPM is the resistivity of the PM phase above TC and "f" is the FM volume fraction. The obtained fitting parameters have been correlated to the change in the strain in the films having various thicknesses. The ferromagnetic volume fraction (f(T)) and the reduced magnetization m(T) show monotonic and "similar" behaviors.

  15. Invar effect accompanying charge order in La0.25Ca0.75MnO3

    Science.gov (United States)

    Trotsenko, V. G.; Mikheykin, A. S.; Shirokov, V. B.; Razumnaya, A. G.; El Marssi, M.; Gorshunov, B. P.; Bush, A. A.; Torgashev, V. I.

    2017-10-01

    To determine the role of the Jahn-Teller effect in the orbital and charge ordering of mixed crystals of the strongly correlated La1-xCaxMnO3 system, we have used the diffraction of synchrotron radiation and the subsequent Rietveld analysis of diffraction patterns in order to obtain structural data for La0.25Ca0.75MnO3 compound in the temperature range from 90 to 325 K with a step of ∼2 K. For the first time for this compound, an Invar effect was observed below the charge-order temperature. In the entire temperature range, atomic displacements were analyzed and correlations between charge ordering and deformational modes were made, on the basis of which the secondary role of the Jahn-Teller effect in observed structure distortions was established. A hypothesis of a spin crossover in the vicinity of the charge-ordering temperature is proposed that describes adequately both the obtained structural data and the results of measurements of the macroscopic magnetic and elastic properties of the studied compound as well as related materials with charge ordering.

  16. Anomalous magnetostrictive effects in (Lal-xTbx)2/3Sr1/3MnO3

    Institute of Scientific and Technical Information of China (English)

    吴坚; 张世远

    2003-01-01

    A series of (La1-xTbx)2/3Srl/3MnO3 polycrystalline samples has been studied by means of x-ray diffraction,magnetostriction, and thermal expansion measurements. It has been found that this series undergoes a phase transition from a rhombohedral to an orthorhombic form at the doping level x≈0.20 at room temperature accompanied by an anisotropic magnetostriction up to -50×10-6 under a magnetic field of 1T. The linear and volume magnetostrictions vary with chemical composition, even change sign. At T=80K, the magnetostrictions for the samples of x=0.20 and 0.40 exhibit different behaviours. The sample of x=0.20 has positive volume and linear magnetostrictions and a negative anisotropic magnetostriction, while the sample of x=0.40 has an opposite behaviour. The magnitude of volume magnetostriction for both the samples is essential (-10-4) at T=80K under a magnetic field of 4T. We conclude that these anomalous effects are due to the charge delocalization and the structural phase transition between orthorhombic and rhombohedral forms induced by the applied magnetic field.

  17. Nanoscratch behaviors of La0.7Sr0.3MnO3+δ thin films

    Institute of Scientific and Technical Information of China (English)

    JIANG Shaoqun; MA Xinxin; TANG Guangze; SUN Mingren; WANG Gang

    2008-01-01

    The nanoscratch behaviors of La0.7Sr0.3MnO3+δ films, which were deposited with ratio of O2/(O2+Ar), ranging from 4.4% to 45.6%, by DC magnetron sputter, were investigated by a nanoindentation technique. The results indicated that the friction coefficient between the films and the diamond tip depended on the loading critical load. The friction coefficient was about 0.08-0.12 when the loading normal load was less than the loading critical load. The films displayed excellent elastic recovery after unloading. When the loading load was larger than the loading critical load, plastic deformation and ploughing appeared for the films. The friction coefficient was about 0.43 when the film was damaged completely. The suitable decrease in ratio of O2/(O2+Ar) could improve the nanoscratch resistance of the films. The film deposited with O2/(O2+Ar)=25% possessed better scratch resistance due to good elastic recovery, high nanohardness, and critical load. The loading critical load of the film was larger than 80 mN.

  18. Electronic structure and chemical bonding in La1-x Sr x MnO3 perovskite ceramics

    Science.gov (United States)

    Thenmozhi, N.; Sasikumar, S.; Sonai, S.; Saravanan, R.

    2017-04-01

    This study reports on the synthesis of La1-x Sr x MnO3 (x  =  0.3, 0.4 and 0.5) manganites by high temperature solid state reaction method using lanthanum oxide, strontium carbonate and manganese oxide as starting materials. The synthesized samples were characterized by XRD, UV-vis, SEM/EDS and VSM. Structural characterization shows that all the prepared samples have the perovskite rhombohedral structure. Influence of Sr doping on electron density distributions in the lattice structure of LaMnO3 were analyzed through maximum entropy method (MEM). Cell parameters are found to be decreasing with the addition of Sr content. The qualitative and quantitative analysis by MEM reveals that, incorporation of Sr into LaMnO3 lattice enhances the ionic nature between La and O ions and decreases the covalent nature between Mn and O ions. Optical band gap values are determined from the UV-visible absorption spectra. Particles with polygonal form are observed from the SEM micrographs. The elemental compositions of the synthesized samples are confirmed by EDS. The magnetic properties studied from the M-H plot taken at room temperature indicated that, the prepared samples are exhibited ferromagnetic behavior.

  19. Top-Down Strategy to Synthesize Mesoporous Dual Carbon Armored MnO Nanoparticles for Lithium-Ion Battery Anodes.

    Science.gov (United States)

    Zhang, Wei; Li, Jiannian; Zhang, Jie; Sheng, Jinzhi; He, Ting; Tian, Meiyue; Zhao, Yufeng; Xie, Changjun; Mai, Liqiang; Mu, Shichun

    2017-04-12

    To overcome inferior rate capability and cycle stability of MnO-based materials as a lithium-ion battery anode associated with the pulverization and gradual aggregation during the conversion process, we constructed robust mesoporous N-doped carbon (N-C) protected MnO nanoparticles on reduced graphene oxide (rGO) (MnO@N-C/rGO) by a simple top-down incorporation strategy. Such dual carbon protection endows MnO@N-C/rGO with excellent structural stability and enhanced charge transfer kinetics. At 100 mA g(-1), it exhibits superior rate capability as high as 864.7 mAh g(-1), undergoing the deep charge/discharge for 70 cycles and outstanding cyclic stability (after 1300 cyclic tests at 2000 mA g(-1); 425.0 mAh g(-1) remains, accompanying merely 0.004% capacity decay per cycle). This facile method provides a novel strategy for synthesis of porous electrodes by making use of highly insulating materials.

  20. KINETIC TRANSFORMATION OF SPINEL TYPE LiMnLiMn2O4 INTO TUNNEL TYPE MnO2

    Directory of Open Access Journals (Sweden)

    Daud K Walanda

    2010-06-01

    Full Text Available Lithiated phase LiMn2O4 is a potential cathode material for high-energy batteries because it can be used in conjunction with suitable carbon anode materials to produce so-called lithium ion cells. The kinetic transformation of LiMn2O4 into manganese dioxide (MnO2 in sulphuric acid has been studied. It is assumed that the conversion of LiMn2O4 into R-MnO2 is a first order autocatalytic reaction. The transformation actually proceeds through the spinel l-MnO2 as an intermediate species which is then converted into gamma phase of manganese dioxide. In this reaction LiMn2O4 whose structure spinel type, which is packing between tetrahedral coordination and octahedral coordination, is converted to form octahedral tunnel structure of manganese dioxide, which is probably regarded as a reconstructive octahedral-coordination transformation. Therefore, it is a desire to investigate the transformation of manganese oxides in solid state chemistry by analysing XRD powder patterns. Due to the reactions involving solids, concentrations of reactant and product are approached with the expression of peak areas.   Keywords: high-energy battery, lithium ion cells, kinetic transformation