960 resultados para U-13C


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In this work, seven samples of humic acids extracted from gleysoils were investigated. These studies, using NMR CP/MAS 13C techniques, did not show significant correlation between the E4/E6 ratio and the degree of aromaticity. However, dipolar dephasing (DD) measurements of condensed aromatic or substituted carbons showed a negative correlation of 0.94. Also, there was a good correlation between the amount of semiquinone free radicals measured by the EPR technique and condensed aromatic rings measured by NMR CP/MAS 13C with the DD technique. The content of semiquinone free radicals was quantified by EPR spectroscopy and was correlated with the humification (degree of aromaticity) of the humic substances. The results indicated that the E4/E6 ratio identifies the degree of aromatic rings condensation. It was also found that the degree of aromaticity, measured by NMR, as frequently presented in the literature (by conventional CP/MAS), underestimates aromatic rings in condensed structures.

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We estimate the determinants of capital intensity in Japan and the US, characterized by striking different paths. We augment an otherwise standard Constant Elasticity of Substitution (CES) model with demand-side considerations, which we find especially relevant in the US. In this augmented setting, the elasticity of substitution between capital and labor is placed around 0.85 in Japan, and 0.30 in the US. We also find evidence of biased technical change, which is capital-saving in Japan but labor-saving in the US. These differences help us explain the diverse experience in the capital deepening process of these economies, and lead us to conclude that demand-side drivers may also be relevant to account for different growth experiences. A close look at the nature of technological change is also needed before designing one-size-fits-all industrial, economic growth, and/or labor market policies.

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Realitat de les dones que viuen a Girona que tenen en comú, per una banda, la seva condició de dona, i per una altra banda, la de viure en una societat marcada per una diferència sexual i de gènere que es tradueix en desigualtat social. La tipologia de dones és molt diversa i inclou les que treballen a casa, les que treballen fora de casa, les feministes, les que no ho són, etc

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Simulación es la creación de una situación donde experimentar un evento con el fin de practicar, evaluar o adquirir conocimientos de sistemas o actuaciones humanas.La simulación de alta fidelidad se introduce en el curso 2012-2013 como proyecto piloto en el grado de Enfermería de la UB, está dirigida a alumnos de 4º de grado de Enfermería, pretende reforzar contenidos de la asignatura “Pràcticum” en el entorno del aula de alta simulación, potenciando la toma de decisiones en equipo ante situaciones de riesgo vital. La experiencia permite analizar, evaluar y reflexionar sobre la práctica, posibilita la mejora o replanteamiento del aprendizaje sin riesgo para el paciente. Durante la observación, alumnos y docentes cumplimentan la plantilla del caso: reflexiones y chequeo de la práctica simulada. Terminada la simulación, la reflexión final o "debriefing" pone en común aspectos emocionales, de interrelación y formativos, susceptibles de mejorar. La metodología permite evaluar competencias básicas y específicas, utilizando un marco de valoración.

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The Steady-State Free Precession (SSFP) sequence has been widely used in low-field and low-resolution imaging NMR experiments to increase the signal-to-noise ratio (s/n) of the signals. Here, we analyzed the Scrambled Steady State - SSS and Unscrambled Steady State - USS sequences to suppress phase anomalies and sidebands of the 13C NMR spectrum acquired in the SSFP regime. The results showed that the application of the USS sequence allowed a uniform distribution of the time interval between pulses (Tp), in the established time range, allowing a greater suppression of phase anomalies and sidebands, when compared with the SSS sequence.

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The Annonaceae family is distributed throughout Neotropical regions of the world. In Brazil, it covers nearly all natural formations particularly Annona, Xylopia and Polyalthia and is characterized chemically by the production of sources of terpenoids (mainly diterpenes), alkaloids, steroids, polyphenols and, flavonoids. Studies from 13C NMR data of diterpenes related with their botanical occurrence were used to generate self-organizing maps (SOM). Results corroborate those in the literature obtained from morphological and molecular data for three genera and the model can be used to project other diterpenes. Therefore, the model produced can predict which genera are likely to contain a compound.

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A new triterpene, 1-epi-castanopsol, besides eleven known compounds: sitosterol, stigmasterol, campesterol, lupeol, lupenone, simirane B, syringaresinol, scopoletin, isofraxidin, 6,7,8-trimethoxycoumarin and harman, were isolated from the wood of Simira glaziovii. The structures of the known compounds were defined by 1D, 2D ¹H, 13C NMR spectra data analyses and comparison with literature data. The detailed spectral data analyses allowed the definition of the structure of the new 1-epi isomer of castanopsol and performance of ¹H and 13C NMR chemical shift assignments.

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Four goyazensolide-type sesquiterpene lactones - lychnofolide, centratherin, goyazensolide and goyazensolide acetate - were thoroughly studied by NMR experimental techniques. ¹H NMR, 13C NMR {¹H}, COSY, HMQC, HMBC, J-res. and NOE experiments were performed to provide the needed structural information. Complete and unequivocal assignment, including the determination of all multiplicities, was obtained for each structure and the data collections are presented in tables.

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This manuscript describes an update review with up to 285 references concerning the occurrence of amides from a variety of species of the genus Piper (Piperaceae). Besides addressing occurrence, this review also describes the biological activities attributed to extracts and pure compounds, a compiled 13C NMR data set, the main correlations between structural and NMR spectroscopic data of these compounds, and employment of hyphened techniques such as LC-MS, GC-MS and NMR for analysis of amides from biological samples and crude Piper extracts.

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The aim of the study was to synthesize the urea (13CO(NH2)2), with 99% 13C atoms, and to perform a quality analysis for the diagnosis (breath test) of Helicobacter pylori. Furthermore, the process was submitted to economic analysis. The reaction was performed in a stainless steel reactor, lined with polytetrafluoroethylene, under low pressure and temperature. The synthesis method was shown to be appropriate (2.35 g; 81.9% yield), evidenced by physico-chemical and microbiological results, according to Brazilian legislation. The production and diagnosis costs were competitive compared with national and international market values, rendering this a valuable tool in clinical medicine.

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In a continuing investigation for potentially bioactive natural products, flavonoids were isolated from Lonchocarpus araripensis (Leguminoseae) and identified as 3-methoxy-6-O-prenyl-6'',6''-dimethylchromene-[7,8,2'',3'']-flavone (1), 3,6-dimethoxy-6'',6''-dimethylchromene-[7,8,2'',3'']-flavone (2) and 3,5,8-trimethoxy-[6,7,2",3"]-furanoflavone (3). This is the first time compound 3 has been described. Compound 2 has been previously isolated from roots while this is the first time 1 is reported in this species. Complete NMR assignments are given for1 ,2 and 3 together with the determination of conformation for 1.

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The chemical study of the orchid Maxillaria picta resulted in the isolation of the bioactive stilbenes phoyunbene B and phoyunbene C, in addition to four phenolic acids, one xanthone, steroidal compounds and two triterpenes. Crude extract, fractions, subfractions and the isolated xanthone were evaluated for anticancer activity against human tumor cell lines and against evolutionary forms of T. cruzi and L. amazonensis. The structures of the compounds were determined by GC-MS, and ¹H NMR, 13C NMR spectral methods as well as bidimensional techniques.

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Venäjän Euroopan puoleisen pohjoisosan kartta, jossa Suomen alue näkyy Venäjän luoteisena naapurina. - 1 kartta : vär. ; 47,8 x 58,5 cm, lehti 50,5 x 62,7 cm. - Mittakaava [N. 1: 3350000]. - Myös teoksessa: Atlas Universel, Par M. Robert Geographe ordinaire du Roy, et Par M. Robert De Vaugondy son fils Geographe ord. du Roy, et de S. M. Polonoise, Duc de Lorraine et de Bar, et Associe de L’Academie Royale des Sciences et belles Lettres de Nancy ... 1757. A Paris, Chez Les Auteurs ... Boudet Libraire Imprimeur du Roi

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Von Wrightin taitelijaveljeksistä Wilhelm v. Wright (1810-1887) muutti Ruotsiin 18-vuotiaana avustaakseen vanhempaa veljeään Magnusta SKANDINAVIENS FÅGLAR -teoksen (ks. kohde 258) valmistamisessa. Wilhelm jäi pysyvästi Ruotsiin ja ryhtyi työskentelemään Kuninkaallisen tiedeakatemian piirtäjänä. Vuonna 1836 alkoi ilmestyä laaja kalakuvasto SKANDINAVIENS FISKAR, johon hän oli laatinut kuvat ja eläintieteilijät C. U. Ekström, B. F. Fries ja C. J. Sundevall kirjoittaneet tekstit. Tästä teoksesta tuli v. Wrightin kuvitustöistä merkittävin ja korkeatasoisin. Myöhemmin v. Wright toimi Bohuslänin kalastuksentarkastajan virassa, mutta halvaantui loppuelämäkseen yli kolmenkymmenen vuoden ajaksi.