Search results for "carbon"

Multifunctional hybrid nanocomposites based on carbon nanotubes and chemically modified graphene

2013

La Tesis trata del desarrollo de materiales híbridos multifuncionales basados en nanotubos de carbono y grafeno con interés en magnetismo molecular y electrónica molecular This Thesis deals with the chemistry and development of new hybrid multifunctional systems based on carbon nanotubes (CNTs) and graphene (G). To introduce both types of carbon nanoforms a brief historical overview of these systems has been briefly given at the Preface. Next and prior to the presentation of the results, two introductory chapters in which the principal aspects of the synthesis, properties and applications of carbon nanotubes (chapter 1) and graphene (chapter 2) are given. The results have been divided in th…

Imagining a “post-carbon” future? Climate change as represented by media and film industries

2020

This study explores current trends in representing and communicating climate change by media industries. It reviews the current literature on mainstream media narratives of climate change focusing on their naturalization of progress and their techno-optimism (e.g., as regards geoengineering). It provides insight on how the media industry’s commercial agenda is linked to the types of disseminated messages and dominant imaginaries. It compares respective codes inherent in news media and film/fictional representations of climate change on representative examples. It traces the evolution of disaster/dystopian genres that involve climate issues. It discusses the implications from such a comparat…

Comparison of different theory models and basis sets in the calculation of 13C NMR chemical shifts of natural products.

2004

The influence of the calculation method in mimicking experimental 13C NMR chemical shifts of 15 low-polarity natural products singularly containing 10–20 carbon atoms was investigated by employing different quantum chemistry approaches and basis sets, both in the preliminary geometry optimizations and in the following single-point 13C GIAO calculations of the NMR chemical shifts. The geometries of the involved species were optimized at the PM3, HF, B3LYP and mPW1PW91 levels whereas the 13C NMR parameters were determined at the HF, B3LYP and mPW1PW91 levels. Different combinations of basis sets were also tested. The consistency and efficiency of the considered combinations of geometry optimi…

Four-Component Relativistic DFT Calculations of C-13 Chemical Shifts of Halogenated Natural Substances

2015

We have calculated the (13) C NMR chemical shifts of a large ensemble of halogenated organic molecules (81 molecules for a total of 250 experimental (13) C NMR data at four different levels of theory), ranging from small rigid organic compounds, used to benchmark the performance of various levels of theory, to natural substances of marine origin with conformational degrees of freedom. Carbon atoms bonded to heavy halogen atoms, particularly bromine and iodine, are known to be rather challenging when it comes to the prediction of their chemical shifts by quantum methods, due to relativistic effects. In this paper, we have applied the state-of-the-art four-component relativistic density funct…

Sensitivity analysis in investment project of biogas plant

2017

The article shows the practical value of biogas as the second generation biofuel. All the projects dealing with biogas are subjected to external risks, such as the change of market condition, customer needs, governmental regulation, etc. In conditions of uncertainty it is necessary for administration to concentrate on decisionmaking. Fluctuations of sales volume, energy resources and raw material prices, etc. should be taken into account. Sensitivity analysis can predict the result of negative external pheno mena. We developed the economic-mathematical model for the analysis of biogas complexes sensitivity. The profitability index as a criterion for the effectiveness of investment projects …

Can differences in microbial abundances help explain enhanced N2O emissions in a permanent grassland under elevated atmospheric CO2?

2011

Acidity and basicity of primaryN-phenylnitramines: catalytic effect of protons on the nitramine rearrangement

2002

Para-substituted N-phenylnitramines were prepared either by oxidation of diazonium salts or by nitration under alkaline or acidic conditions. Isotopic [15N-NO2] labelling indicated that the bands characteristic of the N-nitro group appear in the 1318–1323 and 1585–1607 cm−1 regions. In the nitrogen NMR spectra, the nitramino group gives two resonances at −193 ± 3 (NH) and −32 ± 3 ppm (NO2). The chemical shifts in proton and carbon NMR spectra are predictable, based on increments and the additivity rule. The spectral data indicate the lack of conjugation between the nitramino group and another substituent bound to the ring. It seems to contradict the well-known fact that substituents strongl…

Comparison of oxidoreductive enzyme activities in three coal tar creosote-contaminated soils

2019

This study used laboratory experiments to compare the effects of coal tar creosote on the activity of oxidoreductive enzymes in sandy loam, loamy sand and sandy clay loam soils. Different amounts of coal tar creosote were added to soil samples as follows: 0 (control), 2, 10 or 50 g kg–1 dry matter. The activity of soil dehydrogenases (DHAs), o-diphenol oxidase (o-DPO), catalase (CAT), nitrate reductase (NR) and peroxidases (POX) was determined. Contamination of soil with coal tar creosote affected oxidoreductase activity. Oxidoreductive enzyme activity following soil contamination with coal tar creosote was in the following order: DHAs > CAT > NR > POX > o-DPO in…

El CO2 como disolvente y como reactivo

2016

Existen numerosas ventajas asociada con el uso de CO2 , tanto como disolvente que como reactivo, y todas se pueden resumir en cuatro categorías generales: beneficios ambiental, beneficios de salud y seguridad, beneficios en el procedimiento y beneficios químicos. Los procesos que implican el CO2 como disolvente no aumentaría las emisiones de CO2, más bien proporcionaría una oportunidad para el reciclaje de CO2 residual. Además, los esfuerzos para secuestrar el CO2 producido de los gases de combustión de las distintas industrias están rápidamente incrementando. En este contexto se ha decidido estudiar la reacción de hidrogenación de nitrilos utilizando el CO2sc como medio de reacción y CO2 a…

Apolar versus polar solvents: a comparison of the strength of some organic acids against different bases in toluene and in water

2010

The constants of ion-pair formation with 3-nitroaniline (3NO(2)A) for eight halogenoacetic acids (HAAs, 3a-h: TFA, TCA, TBA, DFA, DCA, DBA, MCA, and MBA), and five 2,2-dichloroalkanoic acids containing 3-8 carbon atoms (HAs, 5a-e: DCPA, DCBA, DCMBA, DCVA, and DCOA) have been determined in TOL at 298.1 K. The results obtained brought to evidence for HAAs the formation of ion-pairs with two different stoichiometries (base-acid, 1:1 or 1:2), while in contrast the HAs furnish only the 1:1 pairs. The different steric and electronic requirements of HAAs and HAs seem to be responsible for such an unlikely behavior. At the same time, the acid-catalyzed MRH of the (Z)-phenylhydrazone of 5-amino-3-be…