Academic literature on the topic 'Metal nitrene species'
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Journal articles on the topic "Metal nitrene species"
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Balicka, Adrianna, and Jan Szadkowski. "Analysis of adsorption of heavy metals from water solutions by wood of selected domestic species using X-Ray Fluorescence (XRF)." Annals of WULS, Forestry and Wood Technology 111 (September 30, 2020): 73–82. http://dx.doi.org/10.5604/01.3001.0014.6773.
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Analysis of adsorption of heavy metals from water solutions by wood of selected domestic species using X-Ray Fluorescence (XRF).The aim of this study was to analyze the absorption of three specific heavy metals from model water solution by wood species from domestic Polish forests. This paper focuses on XRF method to determine metal content in samples. European aspen (Populus tremula L.) and Black locust (Robinia pseudoacacia L.) have been chosen. Firstly, shavings were prepared and soaked with standard solutions of lead (II) nitrate, cadmium nitrate and mercury (II) chloride for 7 days. Then, the material was dried and reduced to ashes using muffle furnace. Finally, content of absorbed metal was marked (XRF) and analyzed with a view to initial contents of metal ions in standard solutions. It was established, that the higher the concentration of mercury in standard solution is, the higher impulse counts is obtained for European aspen. This reversal of the dependence is noticeable for second analyzed species.
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Bahadori, Elnaz, Francesco Conte, Antonio Tripodi, Gianguido Ramis, and Ilenia Rossetti. "Photocatalytic Selective Oxidation of Ammonia in a Semi-Batch Reactor: Unravelling the Effect of Reaction Conditions and Metal Co-Catalysts." Catalysts 11, no. 2 (February 5, 2021): 209. http://dx.doi.org/10.3390/catal11020209.
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Photocatalysis has been used for the oxidation of ammonia/ammonium in water. A semibatch photoreactor was developed for this purpose, and nanostructured TiO2-based materials, either commercial P25 or prepared by flame spray pyrolysis (FSP), were used as catalysts. In the present work, we investigated the effect of (i) metal co-catalysts, (ii) pH, and (iii) ammonia concentration on the efficiency of oxidation and on the selectivity to the undesired overoxidation byproduct, i.e., nitrites and nitrates. Several metals were added to both titania samples, and the physicochemical properties of every sample were studied by XRD, BET, and UV-Vis spectroscopy. The pH, which was investigated in the range of 2.5–11.5, was the most important parameter. The optimum pH values, resulted as 11.5 and 4.8 for P25 and FSP respectively, matching the best compromise between an acceptable conversion and a limited selectivity toward nitrite and nitrate formation. For both titania samples (P25 and FSP), ammonia conversion vs. nitrite and nitrate formation were highly dependent on the pH. At pH ≥ 9, the initial rate of photooxidation was high, with selective formation of overoxidized byproducts, whereas, at a more acidic pH, the conversion was lower, but the selectivity toward nitrogen formation was higher. P25 samples added with noble metal co-catalysts (0.1 mol% Ag, Au, Pd, Pt) at pH = 11.5 remarkably increased the selectivity to nitrite and nitrate, while, in the case of FSP samples (pH = 4.8), the co-catalysts increased the selectivity toward N2 with respect to the unpromoted catalyst and also the conversion in the case of Au and Pt. Reactivity was discussed, leading to the proposing of a mechanism that correlates the activity with either surface adsorption (depending of the surface charge of the catalyst and on pH) or the homogeneous reactivity of oxidizing species.
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Papuc, Camelia, Corina Predescu, Valentin Nicorescu, Georgeta Stefan, and Isabela Nicorescu. "Antioxidant Properties of a Parsley (Petroselinum crispum) Juice Rich in Polyphenols and Nitrites." Current Research in Nutrition and Food Science Journal 4, Special-Issue-October (October 4, 2016): 114–18. http://dx.doi.org/10.12944/crnfsj.4.special-issue-october.15.
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Parsley (Petroselinum crispum) is an herbaceous vegetable used as foodstuff, spice and medicinal plant because it provides antioxidants especially flavonoids (apigenin), vitamins (K, C and A), and volatile oils, among other compounds. Because parsley has important concentrations of nitrates and flavonoids, very little vegetal pigment and a mild flavour profile, it was chosen for this study. The aim of this study was to obtain parsley juice rich in nitrite and polyphenols and to assess its antioxidant activity. To obtain nitrite from nitrate by enzymatic reaction, Staphylococcus xylosus ATCC 29971 was used as nitrate reductase source. To obtain the vegetable juice, fresh roots were minced and homogenized in aqueous solution. The sterile juice was filtered and then inoculated with S. xylosus and incubated at 37°C. The nitrate and nitrite concentrations (mg/L) were determined using a colorimetric method using salicylic acid and Griess reagent, respectively. The total polyphenols content (TPC) was measured with Folin-Ciocalteu reagent and expressed as mg gallic acid equivalent / 100 mL (mg GAE / 100 mL). The total flavonoids content (TFC) was measured with aluminium chloride reagent, and expressed as mg catechin equivalent / 100 mL (mg CE / 100 mL). To determine the antioxidant activity of parsley juice, the ability to reduce DPPH synthetic radical, reducing power of Fe3+ ion and the capacity of chelating transition metal ions were assessed. Maximum concentration of nitrites was achieved for parsley juice in the presence of S. xylosus after 24 hours; TPC was 14.87 mg GAE / 100 mL and TFC was 11.21 mg CE / 100 mL. The ability of parsley fermented juice to reduce DPPH synthetic radical was 79.45%, while the capacity to reduce Fe3+ was 0.758 ± 0.14 (absorbance at 700 nm) and to chelate Fe2+ ion was 23.64%. Parsley juice represents an important source of natural nitrate and flavonoids, with important antioxidant capacity.
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Kodentsov, Alexander. "Diffusion-Limited Reactions of Non-Oxide Ceramics with Transition Metals." Diffusion Foundations 21 (March 2019): 85–126. http://dx.doi.org/10.4028/www.scientific.net/df.21.85.
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Thermodynamic and diffusion models are given to describe morphological evolution of the reaction zone during diffusion-limited interaction between non-oxide Si-containing ceramics (SiC and Si3N4) and transition metals (Cr, Mo, Ti, Ni, Co, Pt). In the case of diffusion-controlled process in the ternary metal-ceramic systems, reaction phenomena can be rationalized using chemical potential diagrams. However, in some cases, a periodic layered morphology is found in the transition zone, which is not fully understood, and it is difficult to predict a priori. Silicide formation in systems based on dense Silicon Nitride and non-nitride forming metals can be explained by assuming a nitrogen pressure build-up at the contact surface. This pressure determines the chemical potential of Silicon at the interface, and hence, the product phases in the diffusion zone. Traces of Oxygen in the ambient atmosphere might affect the interaction in non-oxide ceramic/transition metal systems. The thermodynamic stability of the condensed phases in the systems where volatile species may form can be interpreted using predominant area-type diagrams.
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Jasman, Siti Maryam, Hendrik Oktendy Lintang, Siew Ling Lee, and Leny Yuliati. "Photocatalytic oxidation of nitrite ion over carbon nitride." Malaysian Journal of Fundamental and Applied Sciences 14, no. 1-2 (April 30, 2018): 174–78. http://dx.doi.org/10.11113/mjfas.v14n1-2.987.
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Nitrite ion (NO2-) is a toxic inorganic contaminant, which is widely used in industry and agriculture as a food preservative and a fertilizing agent. One of the methods to reduce the toxicity of the NO2- is by oxidizing it into less hazardous compounds, such as nitrate ion (NO3-). In this study, we demonstrated that a simple and green photocatalytic process can be employed to oxidize the NO2- to NO3- over a metal free-carbon nitride photocatalyst under ultraviolet (UV) light irradiation. The carbon nitride was synthesized via pyrolysis of urea precursor by a thermal polymerization process at 823 K for 4 hours. The prepared carbon nitride was then characterized by using X-ray diffractometer (XRD), field emission scanning electron microscope (FESEM), diffuse reflectance UV-visible (DR UV-vis), fluorescence, and Fourier transform infrared (FTIR) spectrophotometers, as well as nitrogen adsorption-desorption isotherm analyzer. All the characterization results supported the successful synthesis of the carbon nitride. The carbon nitride was then used as the photocatalyst for oxidation of NO2- to NO3- under UV light irradiation for 3 h. The decrease of the NO2- and the formation of the NO3- were analyzed by using a high performance liquid chromatography (HPLC) equipped with Hypersil GoldTM PFP column. The mobile phase used was a mixture of methanol (MeOH) and water (H2O) with the ratio of MeOH:H2O was 30:70. The addition of orthophosphoric acid was required to set the pH at 2.5. The flow rate was fixed at 0.8 ml min-1 and the monitored wavelength was 220 nm. It was revealed that carbon nitride could oxidize NO2- to NO3- with a moderate conversion of 15%. Fluorescence quenching showed that there were good interactions between the emission sites of carbon nitride and the NO2- molecules. The good interactions would be one driving force for the carbon nitride to act as a good photocatalyst to oxidize the NO2- to NO3-. The oxidation pathway by the photogenerated species was also proposed.
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Percival, H. J., T. W. Speir, and A. Parshotam. "Soil solution chemistry of contrasting soils amended with heavy metals." Soil Research 37, no. 5 (1999): 993. http://dx.doi.org/10.1071/sr98055.
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The soil solution chemistry of heavy metal amended soils is of great importance in assessing the bioavailability of heavy metals and their toxicity to the soil biota. Three contrasting soils were amended with Cd(II), Cu(II), Ni(II), Pb(II), Zn(II), and Cr(III) nitrate salts at rates of 10–100 mmol/kg. This concentration range was chosen to encompass a wide range of effects on sensitive soil biochemical properties as part of a larger project. Soil solutions were extracted and analysed for pH, and for concentrations of heavy metals, and major cations and anions. Heavy metal speciation was calculated with the GEOCHEM-PC model. Heavy metal concentrations in the soil solutions increased both in absolute terms and as a percentage of added heavy metal as amendment rates increased. This observation is due to decreasing specific adsorption (caused by decreasing pH induced by the amendments), and to increasing saturation of cation exchange sites. For all 3 soils, the percentage increase commonly follows the order Cr(III) < Pb < Cu < Ni < Cd < Zn. The percentage of each metal held in the soil solution increased from soil to soil as cation exchange capacity, and therefore sorptivity, decreased. Both the concentration and activity of free heavy metal ions were substantially lower than the corresponding total metal concentration. This was ascribed to ion-pairing of metal ions with anions, particularly nitrate introduced in the amending solutions, as well as to increases in ionic strength as a result of amendment. Metal-anion species were mainly inorganic but where Cu and Pb were relatively low in concentration because of strong adsorption by the soils, organic complexation was likely to be significant. Speciation trends were similar for the 3 soils but different in magnitude.
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Lebel, Hélène, and Henri Piras. "Stereoselective Synthesis of Chiral Sulfilimines from N-Mesyloxycarbamates: Metal-Nitrenes versus Metal-Nitrenoids Species." Journal of Organic Chemistry 80, no. 7 (March 18, 2015): 3572–85. http://dx.doi.org/10.1021/acs.joc.5b00256.
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Starkenburg, Shawn R., Frank W. Larimer, Lisa Y. Stein, Martin G. Klotz, Patrick S. G. Chain, Luis A. Sayavedra-Soto, Amisha T. Poret-Peterson, et al. "Complete Genome Sequence of Nitrobacter hamburgensis X14 and Comparative Genomic Analysis of Species within the Genus Nitrobacter." Applied and Environmental Microbiology 74, no. 9 (March 7, 2008): 2852–63. http://dx.doi.org/10.1128/aem.02311-07.
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ABSTRACT The alphaproteobacterium Nitrobacter hamburgensis X14 is a gram-negative facultative chemolithoautotroph that conserves energy from the oxidation of nitrite to nitrate. Sequencing and analysis of the Nitrobacter hamburgensis X14 genome revealed four replicons comprised of one chromosome (4.4 Mbp) and three plasmids (294, 188, and 121 kbp). Over 20% of the genome is composed of pseudogenes and paralogs. Whole-genome comparisons were conducted between N. hamburgensis and the finished and draft genome sequences of Nitrobacter winogradskyi and Nitrobacter sp. strain Nb-311A, respectively. Most of the plasmid-borne genes were unique to N. hamburgensis and encode a variety of functions (central metabolism, energy conservation, conjugation, and heavy metal resistance), yet ∼21 kb of a ∼28-kb “autotrophic” island on the largest plasmid was conserved in the chromosomes of Nitrobacter winogradskyi Nb-255 and Nitrobacter sp. strain Nb-311A. The N. hamburgensis chromosome also harbors many unique genes, including those for heme-copper oxidases, cytochrome b 561, and putative pathways for the catabolism of aromatic, organic, and one-carbon compounds, which help verify and extend its mixotrophic potential. A Nitrobacter “subcore” genome was also constructed by removing homologs found in strains of the closest evolutionary relatives, Bradyrhizobium japonicum and Rhodopseudomonas palustris. Among the Nitrobacter subcore inventory (116 genes), copies of genes or gene clusters for nitrite oxidoreductase (NXR), cytochromes associated with a dissimilatory nitrite reductase (NirK), PII-like regulators, and polysaccharide formation were identified. Many of the subcore genes have diverged significantly from, or have origins outside, the alphaproteobacterial lineage and may indicate some of the unique genetic requirements for nitrite oxidation in Nitrobacter.
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Yu, Guo Xian, Ji Bing Li, Xiao Long Zhou, Cheng Lie Li, Li Fang Chen, and Jin An Wang. "Adsorption of Dibenzothiophene on Transition Metals Loaded Activated Carbon." Advanced Materials Research 132 (August 2010): 141–48. http://dx.doi.org/10.4028/www.scientific.net/amr.132.141.
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Transition metal-modified carbon-based adsorbents were prepared by impregnating activated carbon with solutions of copper, cobalt or nickel chloride or nitrate. The mixtures were dried and then calcined under nitrogen stream. The surface metal species were analyzed by XRD technique and the surface oxygen-containing groups were characterized by FTIR. Their adsorption capacities for dibenzothiophene (DBT) were measured by using DBT-containing n-octane solution as model oil. Experimental results show that the metal species on the carbon surface could be controlled by the calcination process under nitrogen atmosphere. Both the transition metal precursors and kinds of metal species on the carbon surface have significant effects on DBT adsorption capacity.
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Yoshie, S., N. Noda, T. Miyano, S. Tsuneda, A. Hirata, and Y. Inamori. "Characterization of microbial community in nitrogen removal process of metallurgic wastewater by PCR-DGGE." Water Science and Technology 46, no. 11-12 (December 1, 2002): 93–98. http://dx.doi.org/10.2166/wst.2002.0722.
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The metallurgic wastewater generated from the processes of recovering precious metals from industrial wastes contains high concentrations of nitrogen compounds such as ammonia and nitric acid and of salts such as sodium chloride and sodium sulfate. Biological nitrogen removal from this wastewater was attempted by a circulating bioreactor system equipped with an anoxic packed bed and an aerobic fluidized bed. The anoxic packed bed of this system was found to effectively remove nitrite and nitrate from the wastewater by denitrification at a removal ratio of 97%. As a result of denitrification activity tests at various NaCl concentrations, the sludge obtained from the anoxic packed bed exhibited accumulation of nitrite at 5.0 and 8.4% NaCl concentrations, suggesting that the reduction of nitrite is the key step in the denitrification pathway under hypersaline conditions. The microbial community analysis by denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S ribosomal DNA (rDNA) fragments revealed that the community diversity varied in accordance with water temperature, nitrate-loading rate and ionic strength. When particular major DGGE bands were excised, reamplified and directly sequenced, the dominant species in the anoxic packed bed were affiliated with the beta and gamma subclasses of the class Proteobacteria such as Alcaligenes defragrans and Pseudomonas spp., respectively.
Dissertations / Theses on the topic "Metal nitrene species"
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Bartholoméüs, Johan. "Réactions d’amination de liens C-H : synthèse d’amines propargyliques à partir de N-mésyloxycarbamates et études mécanistiques." Thèse, 2016. http://hdl.handle.net/1866/18430.
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Les composés aminés représentent une grande part des substances actives en chimie médicinale. Les travaux rapportés dans cette thèse décrivent les efforts consacrés au développement d’une nouvelle méthode d’amination de liens C-H propargyliques. Notre groupe de recherche a développé depuis quelques années un nouveau précurseur de nitrène métallique, les N-mésyloxycarbamates, permettant d’effectuer des réactions d’amination de liaisons C-H diversement activées. Au cours du développement de notre méthodologie, la synthèse du N-mésyloxycarbamate a fait l’objet de nombreuses optimisations, notamment en améliorant l’échelle globale de la synthèse ainsi que son efficacité. De même, des efforts ont été consacrés pour diminuer le nombre d’étapes nécessaires à la synthèse du réactif en développant la synthèse d’un des intermédiaires de manière énantiosélective. Enfin, la synthèse de ce réactif a également été envisagée à l’aide de la chimie en flux continu.
Au cours du développement de la méthode de synthèse d’amines propargyliques, nous avons constaté que l’acide acétique jouait un rôle déterminant dans la conservation de bonnes sélectivités et réactivités de la réaction. Ces différentes observations ont permis de mettre au point un procédé diastéréosélectif efficace permettant d’obtenir des amines propargyliques avec des rendements allant de moyens à bons et avec d’excellentes diastéréosélectivités.
A la suite de l’étude de l’étendue de notre procédé, nous avons tenté de déterminer les mécanismes réactionnels qui régissaient la réactivité et la sélectivité de celui-ci. Nous avons ainsi montré que l’espèce réactive du système catalytique était bel et bien un nitrène métallique, et que l’étape cinétiquement déterminante était celle d’insertion. Des expériences faites en oxydant l’espèce catalytique de rhodium ont suggéré que plusieurs états d’oxydation de cette espèce peuvent être présents et actifs dans le système catalytique.The nitrogen containing compounds represent a large portion of the active substances in medicinal chemistry. The work reported in this manuscript describe the efforts devoted to the development of a new method of amination of propargylic C-H bonds. Our research group has developed recently a new metal nitrene precursor, N-mesyloxycarbamates, to perform amination reactions on various C-H bonds. During the development of our methodology, the synthesis of N-mesyloxycarbamate has undergone many improvements, including improved global scale synthesis and effectiveness. Similarly, efforts were devoted to reduce the number of steps required for the synthesis of the reagent by developing the synthesis of an intermediate enantioselectively. Finally, the synthesis of this reagent was also considered using continuous flow chemistry. During development of the method of synthesis of propargylic amines, we have found that acetic acid plays a key role in the conservation of good selectivity and reactivity of the reaction. These observations allowed to develop an efficient diastereoselective process in order to obtain propargylic amines with moderate to good yields and with excellent diastereoselectivities. Following the study of the scope of our process, we tried to determine the reaction mechanisms governing the reactivity and selectivity. We have shown that the reactive species of the catalyst system was indeed a metal nitrene, and that the rate-determining step was the insertion. Experiments made by oxidizing the rhodium catalytic species suggested that several oxidation states of this species may be present and active in the catalytic system.
Book chapters on the topic "Metal nitrene species"
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Sudhir Kumar Sinha, Akhoury, and Umaprasana Ojha. "Recent Trends in Development of Metal Nitride Nanocatalysts for Water Electrolysis Application." In Electrocatalysis [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.95748.
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Nanocatalysts for sustainable water electrolysis is strongly desirable to promote the commercialization of H2 as the alternate clean energy source for the future. The goal is cheaper hydrogen production from sea and low grade water by minimizing the energy consumption and using low cost cell components & non-noble metal catalysts. The conductivity of metal nitrides and their ability to carry out Hydrogen Evolution Reaction and Oxygen Evolution Reaction at relatively low overpotential render these one of the frontline candidates to be potentially utilized as the catalyst for low cost H2 production via electrolysis. In this chapter, the potential of metal nitride catalyst towards fulfilling the above objective is discussed. The synthesis of various metal nitride catalysts, their efficiency towards electrode half reactions and the effectiveness of these class of nanocatalyst for electrolysis of sea water is elaborated. A review of recent literature with special reference to the catalyst systems based on non-noble metals will be provided to assess the likelihood of these nanocatalyst to serve as a commercial grade electrode material for sea water electrolysis.
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Schweitzer, George K., and Lester L. Pesterfield. "The Nitrogen Group." In The Aqueous Chemistry of the Elements. Oxford University Press, 2010. http://dx.doi.org/10.1093/oso/9780195393354.003.0011.
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The Nitrogen Group of the Periodic Table contains the elements nitrogen N, phosphorus P, arsenic As, antimony Sb, and bismuth Bi. The outer electron structure ns2np3 characterizes all five of the elements, with n representing principal quantum numbers 2, 3, 4, 5, and 6, respectively. The ns2np3 indicates the possibility of oxidation states V, III, and -III. As one goes down the group, the metallic character increases, with N and P being distinctly non-metals, As a metalloid, and Sb and Bi metals. However, the major bonding in most of the compounds of the group is covalent, aqueous cationic species being formed only by Sb and Bi. A covalency of 5 is exhibited by all the elements except N, this being assignable to the considerable energy required to place 10 electrons around the atom. The pentavalent state is the most stable for P, with its stability falling off down the group, as the trivalent state stability increases. Covalent radii in pm are as follows: N (75), P (110), As(122), and Sb(143). Ionic radii (most hypothetical) in pm are these: Sb+3 (90), Sb+5 (74), Bi+3 (117), and Bi+5 (90). a. E–pH diagram. Figure 9.1 depicts the E–pH diagram for N with the soluble species (except H+) at 10−1.0 M. Equations for the lines that separate the species are displayed in the legend. The colorless strong acid nitric acid HNO3, its colorless anion nitrate NO3−, the colorless weak acid nitrous acid HNO2, its colorless anion NO2−, the colorless ammonium ion NH4+, and the colorless hypothetical compound ammonium hydroxide NH4OH are involved.
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Taber, Douglass F. "Metal-Mediated C–C Ring Construction: The Lei Synthesis of (−)-Huperzine Q." In Organic Synthesis. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780190646165.003.0076.
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Following the Szymoniak protocol, Morwenna S. M. Pearson-Long and Philippe Bertus of the Université du Maine added (Synthesis 2015, 47, 992) the Grignard reagent 2 to the nitrile 1 to give the cyclopropyl amine 3. Chen-Guo Feng of the Shanghai Institute of Organic Chemistry prepared (Chem. Commun. 2015, 51, 8773) the cyclobutane 6 by enantioselective conjugate addition of 5 to the unsaturated ester 4. Martin Kotora of Charles University showed (Eur. J. Org. Chem. 2015, 2868) that the zirconacycle from the eneyne 7 reacted with the aldehyde 8 to give, after iodination, the alcohol 9. Xiaoming Feng of Sichuan University used (Angew. Chem. Int. Ed. 2015, 54, 1608) a scandium catalyst to effect the intramolecular Roskamp cyclization of 10 to 11. Celia Dominguez of CHDI observed (Org. Lett. 2015, 17, 1401) that the double alkylation of the ester 12 with the dibromide 13 proceeded with high diastereoselectivity, to give 14. Hirokazu Tsukamoto of Tohoku University cyclized (Chem. Commun. 2015, 51, 8027) 15 to 16 in high ee. Daniel J. Weix of the University of Rochester found (J. Am. Chem. Soc. 2015, 137, 3237) that under the influence of an enantiomerically-pure Ti catalyst, the organonickel species derived from 18 opened the prochiral epoxide 17 to give 19 in high ee. John F. Bower of the University of Bristol optimized (J. Am. Chem. Soc. 2015, 137, 463) conditions for the highly diastereoselective Rh-mediated cyclocarbonylation of 20 to 21. Margaret A. Brimble of the University of Auckland initiated (J. Org. Chem. 2015, 80, 2231) the construction of the cyclohexenone 24 by the diastereoselective addition of 23 to the unsaturated ester 22. Olivier Baslé and Marc Maduit of ENSC Rennes devised (Chem. Eur. J. 2015, 21, 993) conditions for the preparation of 26 by enantioselective conjugate addition to the cyclohexenone 25. Yoshito Kishi of Harvard University demonstrated (Tetrahedron Lett. 2015, 56, 3220) that the carbenoid generated from the epoxide 27 cyclized to 28 with high diastereoselectivity. Wenjun Tang, also of the Shanghai Institute of Organic Chemistry, developed (Angew. Chem. Int. Ed. 2015, 54, 3033) a Pd catalyst for the diastereoselective (because it is enantioselective) cyclization of 29 to 30.
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Dalton, David R. "The Soil." In The Chemistry of Wine. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780190687199.003.0012.
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The widespread practices of viniculture (the study of production of grapes for wine) and oenology (the study of winemaking) affirm the generalization that grapevines have fewer problems with mineral deficiency than many other crops. Only occasionally is the addition of iron (Fe), phosphorus (P), magnesium (Mg), and manganese (Mn) supplements to the soil needed. Addition of potassium (K), zinc (Zn), and boron (B) to the soil is more common. And, of course, nitrogen (N) is critical for the production of proteins. Over the years, various transition metals (metals in groups three through twelve [3– 12] of the periodic table, Appendix 1) have been shown to be generally important. These groups include iron (Fe), magnesium (Mg), manganese (Mn), zinc (Zn), and copper (Cu). Many metals are bound to organic molecules that are important for life. Some of the metals, such as copper (Cu) and iron (Fe), are important in electron transport while others, including manganese (Mn) and iron (Fe), inhibit reactive oxygen (O) species (ROSs) that can destroy cells. Metals serve both to cause some reactions to speed up, called positive catalysis while caus¬ing others (e.g., unwanted oxidation) to slow down (negative catalysis). It is not uncommon to add nitrogen (N), in the form of ammonium salts such as ammonium nitrate (NH4NO3), as fertilizer to the soil in which the vines are growing. It is also common to increase the nitrogen (N) content in the soil by planting legumes (legumes have roots that are frequently colonized by nitrogen-fixing bacteria). Nitrogen- fixing bacteria convert atmospheric nitrogen (N2), which plants cannot use, to forms, such as ammonia (NH3) or its equivalent, capable of absorption by plants. Nitrogen, used in plant proteins, tends to remain in the soil after harvest or decomposition. With sufficient nitrogen present in the soil the growth cycle can begin again in the following season without adding too much fertilizer. In a more general sense, however, it is clear (as mentioned earlier) that the soil must be capable of good drainage so the sub-soil parts of the plant do not rot and it must be loose enough to permit oxygen to be available to the growing roots.
Conference papers on the topic "Metal nitrene species"
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Won, Hui Jun, Byambatseren Baigalmaa, Jei Kwon Moon, Chong Hun Jung, and Kune Woo Lee. "Decontamination of Metal Surfaces Artificially Contaminated With Cs+ Ions by a Laser Ablation." In 17th International Conference on Nuclear Engineering. ASMEDC, 2009. http://dx.doi.org/10.1115/icone17-75535.
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A Q-switched Nd:YAG laser with a 1064 nm and 450 mJ/pulse was employed to study the decontamination characteristics of Type 304 stainless steel specimens artificially contaminated with Cs+ ions. The specimens were treated with KCl and KNO3, respectively. The optimum number of laser shots for the system was determined at a given fluence of 57.3 J/cm2. The relative atomic molar ratio of a metal surface was determined by EPMA. For all the test specimens, more than 95% of the Cs+ ions were removed by the application of 42 laser shots. Cs+ ion removal efficiency could be improved by the addition of nitrate ions to the contaminated metal surface. A specimen treated with a KCl solution was more difficult to decontaminate in the experimental range. Before and after the laser irradiation, the morphology of the metal surfaces was investigated by SEM and XPS. Dusts generated during the laser irradiation were found to accumulate around a crater of the specimen treated with the KCl solution. By analyzing the XPS spectra of the KCl system, it was found that the ablated Cs+ ions formed an oxide in air. The higher decontamination efficiency of the KNO3 system could be attributed to the decomposition of the nitrate ions at a relatively low temperature and the easy reaction of the Cs+ ions with the oxygen generated from the decomposition of nitrate ions.
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Tateno, Masayoshi, and Takahiro Miura. "Effects of Metal Thickness on Bonding Strength in Bonded Dissimilar Materials." In ASME 2014 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/pvp2014-29021.
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This study provides effects of metal thickness on bonding tensile strength of ceramic to metal joint based on numerical and experimental analyses. Thermal elastoplastic FEA was carried out to clarify effects of the metal side thickness on the stress distribution near the edge of the interface on ceramic side by changing metal side thickness each bonded silicon nitride to nickel joint system. It was confirmed the stress distribution on the ceramic of the joint system depends on the metal side thickness based on the FEM results. Decreasing of metal thickness reduces the intensity of the stress near the edge of the interface on ceramics side. It can be effective for reduction of the residual stress near the edge of the interface to use thin metal layer in the ceramic to metal joint. Reduction effects on the residual stress were confirmed by using two stages of bonding processing. This process used in this experiment consists of two stages, first bonding process as the ceramic are bonded to thin layer metal at high temperature, and secondary process as thick metal are bonded to the thin metal layer of the joint specimen at lower temperature than first stage. The bonding tensile strength of the joint specimens manufactured from the two stages bonding processe was evaluated experimentally. It appears that setting a ratio of metal thickness to length of the interface to approximate tm/W=0.08 achieves maximum bonding tensile strength. Effects of metal thickness on bonding tensile strength of ceramic to metal joint are confirmed based on numerical and experimental results.
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Tateno, Masayoshi, and Eiichiro Yokoi. "Dependence of Bonding Temperature Conditions on Metal Thickness Effects in Bonded Dissimilar Materials." In ASME 2015 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/pvp2015-45822.
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This study provides information on the dependence of bonding temperature conditions on metal thickness effects in bonded dissimilar materials as a composite material system. Effects of metal thickness on the bonding strength were confirmed each bonding temperature condition by using silicon-nitride and nickel to confirm for each joint manufactured by a bonding method, two stages bonding process. This process used in this experiment consists of two stages, first bonding process as the ceramic is bonded to thin layer metal at high temperature, and secondary process as thick metal is bonded to the thin metal layer of the joint at lower temperature than first stage’s one. Bonding tensile strength of the joint specimen was evaluated experimentally. The bonding strength was dominated by the residual stress near the edge of the interface on ceramic side. The maximum bonding strength appears at optimum metal thickness. It shows that the optimum metal thickness depends on the first temperature condition. Reduction of the residual stress was considered based on the experimental and numerical results. Two stages bonding process can be applied for high strength bonded dissimilar materials as useful engineering application by setting optimum metal thickness each bonding temperature condition.
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Neuburger, André L., and Gilles Carrier. "Design and Test of Non-Rotating Ceramic Gas Turbine Components." In ASME 1988 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1988. http://dx.doi.org/10.1115/88-gt-146.
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This paper deals with elements of an on-going ceramics research and development program at a major manufacturer of turbine engines for general aviation and commuter aircraft. The program comprises design and test of non-rotating, ceramic components for two widely used turboprop engines. The design, analysis and test of three components are discussed: a simple ceramic turbine shroud, a metal and ceramic turbine shroud, and an all ceramic nozzle vane assembly. Fabrication and assembly of these components are described. A discussion of non-destructive evaluation and component prooftesting includes a prooftest strategy that seeks to retain the stronger half of a sample of specimens. Candidate ceramics, silicon carbide and silicon nitride, are assessed and chosen as the shroud and vane materials. The paper also includes assessment of improvements in fuel efficiency, specific power and operating cost, some based on test results and some on analysis.
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Lee, Cheng-Chang, and Wensyang Hsu. "A New Surface Modification Method to Alleviate Stiction of Microstructures." In ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-39299.
Full textAbstract:
Modification on surface roughness has been shown effectively to alleviate both release and in-use stiction in the previous literatures. However, the modified materials in the previously reported methods were limited to polysilicon or single crystalline silicon with special properties. Here, the proposed modification method not only can apply to silicon without extra property requirements, but also has potential to modify other materials, such as oxide, nitride, and some metals. The process combined spin-on photoresist and reactive ion etching (RIE). The proposed low temperature process is simple, and no extra mask is needed. Consequently, there is more flexibility to add the roughness modification to the original fabrication process of micro devices. In this study, polysilicon and silicon nitride are demonstrated as the modified materials. Then the anti-stiction effect is characterized by calibrating the detachment lengths of released cantilevers and water contact angle on the modified surface. The experimental results show that the detachment length is almost twice longer than the cantilevers without modified substrate, where the interfacial surface energy between solids is reduced about fifteen times. Besides, polysilicon with a nearly hydrophobic surface is obtained after the modification process.
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Adinberg, R., and D. Zvegilsky. "Thermal Measurement System for Phase Change Materials." In ASME 2012 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/imece2012-86844.
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A lab scale set-up designed based on reflux heat transfer is used for studying latent heat storage for concentrating solar power systems. Phase change materials (PCM) with temperature of fusion range between 300 and 400°C are being tested using this system, including metal alloys and inorganic salts. In the present configuration, the system provides thermal measurements of PCM specimens of about 1000 g under heating temperature up to 450°C and enables simultaneous studying calorimetric properties of the loaded materials and heat transfer effects developed in the thermal storage process composed of charge and discharge phases. The measurement technique includes a thermal analysis model aimed at evaluating the experimental data. Results of the thermal measurements conducted with a thermal storage medium composed of potassium nitrate KNO3 (m.p. 334°C) as PCM and Diphyl (synthetic thermal oil, max working temperature 400°C) as the heat transfer fluid are presented and discussed in this study.
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Shareef, Iqbal, Manikandan Natarajan, and Oyelayo O. Ajayi. "Dry Machinability of Aluminum Alloys." In World Tribology Congress III. ASMEDC, 2005. http://dx.doi.org/10.1115/wtc2005-64098.
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Adverse effects of the use of cutting fluids and environmental concerns with regard to cutting fluid disposability is compelling industry to adopt Dry or near Dry Machining, with the aim of eliminating or significantly reducing the use of metal working fluids. Pending EPA regulations on metal cutting, dry machining is becoming a hot topic of research and investigation both in industry and federal research labs. Although the need for dry machining may be apparent, most of the manufacturers still consider dry machining to be impractical and even if possible, very expensive. This perception is mainly due to lack of appropriate cutting tools that can withstand intense heat and Built-up-Edge (BUE) formation during dry machining. The challenge of heat dissipation without coolant requires a completely different approach to tooling. Special tooling utilizing high-performance multi-layer, multi-component, heat resisting, low friction coatings could be a plausible answer to the challenge of dry machining. In pursuit of this goal Argonne National Labs has introduced Nano-crystalline near frictionless carbon (NFC) diamond like coatings (DLC), while industrial efforts have led to the introduction of composite coatings such as titanium aluminum nitride (TiAlN), tungsten carbide/carbon (WC/C) and others. Although, these coatings are considered to be very promising, they have not been tested either from tribological or from dry machining applications point of view. As such a research program in partnership with federal labs and industrial sponsors has started with the goal of exploring the feasibility of dry machining using the newly developed coatings such as Near Frictionless Carbon Coatings (NFC), Titanium Aluminum Nitride (TiAlN), and multi-layer multicomponent nano coatings such as TiAlCrYN and TiAlN/YN. Although various coatings are under investigation as part of the overall dry machinability program, this extended abstract deals with a systematic investigation of dry machinability of Aluminum 6061 and 2024 using uncoated carbide, TiN coated carbide, and TiAlN coated carbide inserts. Central Composite Design (CCD) is used to study the effect of speed, feed, depth of cut, workpiece material, and cutting tool material on the resulting forces, surface finish, temperature, chip morphology and tool wear. Each of the machining responses is measured and compared under 15 different machining conditions. Results from CCD experiments have been used to develop linear and logarithmic models for forces (Fx, Fy, Fz, & Fr) surface finish (Ra), and temperature. Furthermore, chip morphology and tool wear have also been compared. From the comparison of forces, surface finish, temperature, chip morphology, tool wear and the corresponding statistical models, it is clear that in general TiAlN results in lower forces, better surface finish, greater fragmented chips, and lesser tool wear.
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Joel, J., and M. Anthony Xavior. "Enhancing the Frictional Behaviour of H-BN Reinforced Nanocomposites Through Laser Shock Peening." In ASME 2019 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/imece2019-10162.
Full textAbstract:
Abstract In this research work, LM6 Aluminum alloy based metal matrix composites reinforced with varying amounts (0.2, 0.4, 0.6 and 0.8 wt%) of boron nitride (BN) having 10 to 30 nanometers average size were developed by using powder metallurgy and squeeze casting routes. The mechanical and tribological properties are analyzed for the samples developed through the two different routes and the influence of the process on the properties is discussed. Thus developed nano composite is studied for the effect of weight percentage addition of nano H-BN particle on the bulk and surface properties. Mechanical testing and advanced characterization methods are used to study the effect of the nano H-BN addition to the matrix material and to evaluate the composite for its suitability as a potential friction material used in strategic sectors. It has been inferred that the presence of nano H-BN have improved the bulk and surface properties. Further, it has been established that the powder metallurgy route has some favorable results when compared to squeeze casting in terms of certain properties. Thus fabricated composites were subjected to laser shock peening process to study its impact on the surface and wear characteristics. The 0.6 wt% H-BN reinforced composites fabricated separately by Powder metallurgy and Squeeze casting method are exposed to laser shock peening process and it was inferred that there is a significant improvement on the surface and wear properties when compared to normal specimen.