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371.
Marcelo Kobelnik Douglas Lopes Cassimiro Diógenes dos Santos Dias Clóvis Augusto Ribeiro Marisa Spirandeli Crespi 《Journal of Thermal Analysis and Calorimetry》2011,106(3):711-715
The jerivá is a well-known fruit, which belongs to the Arecaceae family, Syagrus romanzoffiana species frequently found in Brazil. Extraction of the jerivá oil was carried out, and the fatty acid profile of this oil
indicates the linoleic and oleic acid presence, around 29.35 and 28.89%, respectively. Thermogravimetry (TG), derivative thermogravimetry
(DTG), and differential scanning calorimetry (DSC) were used to characterize this oil. Additionally, this oil was evaluated
by DSC from 25 to −80 °C, and the crystallization behavior was verified. Details concerning the thermal behavior as well as
data of kinetic parameters of these stages have been described here. The obtained data were evaluated, and the values were
plotted in activation energy (E
a/kJ mol−1) in function of the conversion degree (α). 相似文献
372.
Sonia de Almeida Giseli Bernabé Marisa S. Crespi Clóvis A. Ribeiro Evaneide Nascimento Lima 《Journal of Thermal Analysis and Calorimetry》2011,105(2):461-465
The organic fraction of urban solid residues disposed of in sanitary landfills during the decomposition yields biogas and
leachate, which are sources of pollution. Leachate is a resultant liquid from the decomposition of substances contained in
solid residues and it contains in its composition organic and inorganic substances. Literature shows an increase in the use
of thermoanalytical techniques to study the samples with environmental interest, this way thermogravimetry is used in this
research. Thermogravimetric studies (TG curves) carried out on leachate and residues shows similarities in the thermal behavior,
although presenting complex composition. Residue samples were collected from landfills, composting plants, sewage treatment
stations, leachate, which after treatment, were submitted for thermal analysis. Kinetic parameters were determined using the
Flynn–Wall–Ozawa method. In this case they show little divergence between the kinetic parameter that can be attributed to
different decomposition reaction and presence of organic compounds in different phases of the decomposition with structures
modified during degradation process and also due to experimental conditions of analysis. 相似文献
373.
Voranuch Somsongkul Felix Lang Ah Reum Jeong Marin Rusu Marisa Arunchaiya Thomas Dittrich 《固体物理学:研究快报》2014,8(9):763-766
Modulated charge separation across (MO)/CH3NH3PbI3 and (MO)/PbI2/CH3NH3PbI3 (MO = TiO2, MoO3) interfaces was investigated by surface photovoltage (SPV) spectroscopy. Perovskite layers were deposited by solution‐based one‐step preparation and two‐step preparation methods. An unreacted PbI2 layer remained at the interface between the metal oxide and CH3NH3PbI3 for two‐step preparation. For the two‐step preparation on TiO2, the SPV signal related to absorption in CH3NH3PbI3 increased in comparison to the one‐step preparation due to electron transfer from CH3NH3PbI3 via PbI2 into TiO2 whereas the SPV signal related to defect transitions decreased. For the one‐step preparation on MoO3, holes photogenerated in CH3NH3PbI3 recombined with electrons in MoO3. In contrast, a hole transfer from CH3NH3PbI3 towards MoO3 was blocked by the PbI2 interlayer for the two‐step preparation on MoO3. (© 2014 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
374.
Dickstein JS Fennie MW Norman AL Paulose BJ Kozlowski MC 《Journal of the American Chemical Society》2008,130(47):15794-15795
The synthesis of alpha,alpha-disubstituted alpha-amino acids by means of a three component coupling is reported. The coupling occurs through umpolung addition of organometallic reagents to the nitrogen of alpha-iminoesters. The resulting enolate intermediates subsequently react with electrophiles (aldehydes, imines, alpha,beta-unsaturated nitro, alkyl halides, acyl cyanides) to form a quaternary center. Tethering of the electrophile and nucleophile components provides cyclic alpha,alpha-disubstituted alpha-amino acid derivatives. 相似文献
375.
Marisa A.A. Rocha Carlos F.R.A.C. Lima Luís M.N.B.F. Santos 《The Journal of chemical thermodynamics》2008,40(9):1458-1463
This work is focussed on the thermodynamics of phase transition for some naphthalene derivatives: 1-phenylnaphthalene, 2-phenylnaphthalene, 2-(biphen-3-yl)naphthalene, and 2-(biphen-4-yl)naphthalene.The Knudsen mass-loss effusion technique was used to measure the vapour pressures of the following compounds: 2-phenylnaphthalene (cr), between T= (333.11 and 353.19) K; 2-(biphen-4-yl)naphthalene (cr), between T = (405.17 and 437.19) K; 2-(biphen-3-yl)naphthalene (l), betweenT = (381.08 and 413.17) K. From the temperature dependence of the vapour pressure, the standard, (p = 105 Pa), molar enthalpies, entropies, and Gibbs free energies of sublimation for 2-phenylnaphthalene and 2-(biphen-4-yl)naphthalene were derived as well as the standard molar enthalpy, entropy, and Gibbs free energy of vaporization for 2-(biphen-3-yl)naphthalene at 298.15 K. The temperatures and the standard molar enthalpies of fusion were measured by differential scanning calorimetry and the standard molar entropies of fusion were derived. For 1-phenylnaphthalene the standard molar enthalpy of vaporization at 298.15 K was measured directly using the Calvet microcalorimetry drop method.The 1-phenylnaphthalene is liquid at room temperature, showing a remarkably low melting point when compared to the 2-phenylnaphthalene isomer and naphthalene. A regular decrease of volatility with the increase of a phenyl group in para position at the 2-naphthalene derivatives was observed. In 2-(biphen-3-yl)naphthalene, the meta substitution of the phenyl group results in a significantly higher volatility than in the respective para isomer. 相似文献
376.
Electrochemical study of a dendritic family at the water/1,2-dichloroethane interface 总被引:1,自引:0,他引:1
Calderon M Monzón LM Martinelli M Juarez AV Strumia MC Yudi LM 《Langmuir : the ACS journal of surfaces and colloids》2008,24(12):6343-6350
The transfer of six dendritric molecules, DMs, across the water/1,2-dichloroethane interface was investigated using cyclic voltammetry. From the variation of peak potential with pH, two different mechanisms of transfer were postulated depending on the nature of the molecules. Voltammetric parameters were employed to evaluate the hydrophilic/hydrophobic character and calculate the acid dissociation constant of these molecules. The results were explained taking into account the nature and multiplicity of functional surface groups. 相似文献
377.
By reacting thiosemicarbazides substituted on the aminic nitrogen with 5-formyluracil, several new 5-formyluracil thiosemicarbazones (H3ut) derivatives were synthesised and characterized. These ligands, treated with copper chloride and nitrate, afforded two different kinds of compounds. In the complexes derived from copper chloride the metal atom is pentacoordinated, being surrounded by the neutral ligand binding through SNO donor atoms and by two chlorines, while the nitrate derivatives consist of monocations and nitrate anions. The copper coordination (4 + 2) involves the SNO ligand atoms, two water oxygens and an oxygen atom of a monodentate nitrate group. On varying the substituents on the thiosemicarbazidic moiety, remarkable modifications of the coordination geometry are not observed for the complexes with the same counterion. For all the compounds, interactions with DNA (calf thymus) were studied using UV–Vis spectroscopy; the nuclease activity was verified on plasmid DNA pBR 322 by electrophoresis. 相似文献
378.
The antioxidant properties of extracts of Sybaris liquorice roots have been assessed using 2,2'-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity assay. The extracts, obtained by Soxhlet extraction (Et(2)O, AcOEt, MeOH and BuOH) of the yellow (inner part) and brown (cortex) root powders ensuing from decortication of the raw dry roots, followed by separation and powderisation, were analysed for their scavenging activity by evaluating the colourimetric decrease in the absorbance of DPPH. The highest antioxidant activity (98.39?±?0.56%) was observed in the case of the Et(2)O extract of the brown powder, at a concentration of 3.33?mg?mL(-1). Moreover, the total phenolic content of the extracts was determined using the Folin-Ciocalteu reagent and expressed as milligram gallic acid equivalent per gram of dry extract. Our results show that the Et(2)O extract of the liquorice root cortex could be used as an attractive natural source of antioxidant additives for food, cosmetic or pharmaceutical applications. 相似文献
379.
SE Allen J Mahatthananchai JW Bode MC Kozlowski 《Journal of the American Chemical Society》2012,134(29):12098-12103
The N-heterocyclic carbene catalyzed [4 + 2] cycloaddition has been shown to give γ,δ-unsaturated δ-lactones in excellent enantio- and diastereoselectivity. However, preliminary computational studies of the geometry of the intermediate enolate rendered ambiguous both the origins of selectivity and the reaction pathway. Here, we show that a concerted, but highly asynchronous, Diels-Alder reaction occurs rather than the stepwise Michael-type or Claisen-type pathways. In addition, two crucial interactions are identified that enable high selectivity: an oxyanion-steering mechanism and a CH-π interaction. The calculations accurately predict the enantioselectivity of a number of N-heterocyclic carbene catalysts in the hetero-Diels-Alder reaction. 相似文献
380.