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21.
Rheological aspects of the rejuvenation of aged bitumen 总被引:1,自引:0,他引:1
Ramón Romera Anton Santamaría Juan José Peña Maria Eugenia Muñoz Marisol Barral Esteban García Victorio Jañez 《Rheologica Acta》2006,45(4):474-478
Rheological techniques are used to investigate the rejuvenation of aged bitumen. The thermal transition associated with the collapse of the compact structure constituted by asphaltene is determined by Dynamic Mechanical Thermal Analysis. For aged bitumen, this transition shifts to a higher temperature but when rejuvenating agents are added, the transition returns to its original value. The “rutting factor,” G*/sin δ allows to define the maximum temperature the binder can reach without permanent deformation. The employed rejuvenating agents are suitable because permanent deformation is postponed. Viscosity results reveal that aged bitumen needs a high mixing temperature (>200°C) to behave like a fluid material able to wet, adhere, and envelop aggregates. The addition of rejuvenating agents considerably reduces mixing and compaction temperatures. The mixture of 80% aged bitumen—20% recycled motor oil, obtained exclusively from waste materials is an apt binder that can compete satisfactorily with new 60/70 bitumen.Paper presented at the AERC2005. This paper will be part of a special issue of AERC2005. 相似文献
22.
The first detailed examination of flow injection-capillary electrophoresis (FI-CE) active parameters and their interactions via response surface methodology (RSM) is presented. Specifically, RSM in the form of a Box-Behnken design was implemented to effectively predict the significance of capillary length, voltage and injection volume on the optimization of an in-house built FI-CE analyzer. Initial studies were performed assessing peak height and peak shape of the model compound N,N-dimethylformamide. Optimum model conditions were then derived and used in the model separation of two small molecules, nicotinamide adenine dinucleotide, reduced form (NADH) and benzenesulfonamide. By implementing the RSM approach, detailed examination of active FI-CE parameters was possible, including the ability to reveal a significant interactive effect. This work is not only highly significant for advancing FI-CE developments, but instructive for investigators actively exploring other coupled analytical techniques and associated experimental parameters. 相似文献
23.
Development of analytical method for determination of Sb(V), Sb(III) and TMSb(V) in occupationally exposed human urine samples by HPLC-HG-AFS 总被引:1,自引:0,他引:1
In the present paper, we develop a methodology for antimony speciation in occupationally exposed human urine samples by high-performance liquid chromatography with hydride generation atomic fluorescence spectrometry (HPLC-HG-AFS). The methodology was applied to the determination of Sb(V), Sb(III) and (CH3)3SbCl2 (TMSb(V)). Retention time of Sb(V), Sb(III) and TMSb(V) species were 0.88, 2.00 and 3.61 and the detection limits were 0.18, 0.19 and 0.12 μg L− 1, for 100 μL loop injection respectively which is considered useful for elevated/occupationally exposed urine samples. Studies on the stability of antimony species in urine samples on the function of the elapsed time of preservation (4 °C) and storage (− 70 °C) were performed. Results revealed that antimony species are highly unstable at − 70 °C, probably due to co-precipitation reaction. In this kind of matrix transformation during preservation time may occur, such as oxidation of Sb(III) to Sb(V) and transformation into species that do not elute from the column. EDTA shows that it is able to stabilize Sb(III) for more than one week of preservation time at 4 °C avoiding co-precipitation during storage at − 70 °C. Finally the methodology was applied to occupationally exposed human urine samples. 25% of specimens present antimony levels (Sb(V)) of more than 5 μg L− 1. 相似文献
24.
Marisol Ibarra‐Rodríguez H. V. Rasika Dias Dr. Víctor M. Jiménez‐Pérez Blanca M. Muñoz‐Flores Angelina Flores‐Parra Sonia Sánchez 《无机化学与普通化学杂志》2012,638(10):1486-1490
The reaction of the di‐lithiated oxamide of 1 with two equivalents of SnCl2 provided the tin trans‐oxamide 3 . In solution, spectroscopic analysis suggests exclusively the formation of a trans‐oxamide (trans‐ 3 ). However, the solid state shows an atypical cis‐oxamide (cis‐ 3 ), where the oxamide fragment acts as an anti‐Janus head ligand. An 119Sn‐NMR variable temperature experiment ([D8]THF) of the trans‐oxamide (trans‐ 3 ) was performed however, at lower temperature no additional signal was observed, which confirmed the absence of a dynamic equilibrium. Dispersion‐corrected density functional calculations revealed that the cis conformation of this tin(II) oxamide complex is more stable than the trans isomer by 1.4 kcal · mol–1. 相似文献
25.
We present first-principles calculations of the vibrational density of states (VDOS), the specific heat and the mean-squared displacement of the five lowest-energy isomers of Au(13) and of two low-energy FeAu(12) nanoparticles. We find that the vibrational contributions to the Helmholtz energy do not affect the energy ordering of the isomers. As expected, for nanoparticles the vibrational density of states differs dramatically from the function proposed by the Debye model. We demonstrate that, for the nanoclusters we studied, the alternative calculations of the 'Debye temperature' yield significantly inconsistent results. We conclude that T(D) obtained from a particular thermodynamic property is neither applicable for deriving conclusions about other thermodynamic properties nor correlated with atomic bond strengths. Instead, in order to describe the temperature dependence of a nanoparticle's mean-squared displacement and its specific-heat capacity, what is necessary is its discrete phonon spectrum. 相似文献
26.
The motion of a colloid induced by a temperature gradient is simulated by means of multiparticle collision dynamics, a mesoscale simulation technique. Two algorithms to quantify the thermophoretic behavior are employed and contrasted. The validity of the methods is verified as a function of the temperature gradient, system size, and algorithm parameters. The variation of the solvent-colloid interaction from attractive to purely repulsive interestingly results in the change of the colloid behavior from thermophobic to thermophilic. 相似文献
27.
Teresa Mancilla Percino Roxana Magaly Flores Ancona Marisol Lpez Martínez 《Polyhedron》2009,28(13):2771-2775
A new, mild and friendly method for the synthesis of (N → B) phenyl[N-alkyliminodiacetate-O,O′,N]boranes 2–7 is reported. All compounds were identified by 1H, 11B, 13C NMR and their high resolution mass spectra (HRMS) are reported. The structure of the compounds 2, 4 and 5 were established by single crystal X-ray. Compounds 2 and 4 crystallized with two independent molecules 2A, 2B and 4A, 4B, respectively in the asymmetric unit. These molecular structures established the bicyclic structure showing a N → B bond length of 1.666 (2) Å for 2A, 1.675 (2) Å for 2B, 1.675 (3) Å for 4A, 1.663 (3) Å for 4B and 1.679 (2) Å for 5, as well as different torsion angles of the junction, 28.70 (2)° (C11–B1–N6–C17) for 2A, 21.50 (2)° (C11a–B1a–N6a–C17a) for 2B, 25.76 (0.26)° (C11–B1–N6–C17) for 4A, 21.96 (0.28)° (C11a–B1a–N6a–C17a) for 4B and −29.22 (0.20)° (C5–N1–B1–C13) for 5. 相似文献
28.
Noé Zúñiga-Villarreal Juan Manuel Germán-Acacio Ana Adela Lemus-Santana Marisol Reyes-Lezama Rubén A. Toscano 《Journal of organometallic chemistry》2004,689(17):2827-2832
The halocarbonyls BrM(CO)5, M = Mn and Re, were reacted with the KN(SePPh2)2 salt in equimolar amounts; the reactions were thermally carried out and resulted in the generation of the hexacoordinated isostructural complexes [M(CO)4{Ph2P(Se)NP(Se)Ph2-Se,Se′}] with a twist MSePNPSe ring conformation. Complexes’ characterizations were achieved by IR, mass, NMR (1H, 13C, 31P, 77Se) spectroscopies, and by single-crystal X-ray diffraction. 相似文献
29.
Paul Chiy Miguel de la Fuente Enrique Barrado Marisol Vega C. Phillips 《Fresenius' Journal of Analytical Chemistry》1998,361(4):343-348
The optimum conditions for microwave digestion of herbage and faeces to determine mineral concentrations were obtained by
varying sample mass, reagent and heating programme, and it was confirmed that the resulting element concentrations were the
same as for certified reference material. The effects of feeding cadmium to sheep at a level that is typical of polluted
regions (1 mg/kg) for ten days were investigated, as well as the possible amelioration of cadmium effects by adding 30 mg/kg
Zn to the diet. Cadmium in the feed increased the cadmium balance and produced several mineral disturbances, in particular
a reduction in sodium balance which is typical of renal tubular disorders. Including zinc in the diet as well as cadmium reduced
the cadmium balance to a level similar to that of sheep that did not receive cadmium or zinc, which suggests that the zinc
status is critical in determining whether cadmium in feed increases the cadmium balance in sheep.
Received: 1 August 1997 / Revised: 8 December 1997 / Accepted: 10 December 1997 相似文献
30.
Fernando Hung-Low Gabriela C. Uzcátegui Juan Alvarez Marisol C. Ortega Alvaro J. Pardey Clementina Longo 《Reaction Kinetics and Catalysis Letters》2006,88(1):143-148
Summary The complex, [Rh(COD)(4-picoline)2](PF6) (COD = 1,5-cyclooctadiene), immobilized on poly(4-vinylpyridine) in contact with methanol catalyzes the hydroesterification
and hydroformylation-acetalization of 1-hexene to methylheptanoate, heptanal and 1,1-dimethoxyheptane, respectively. The by-product,
1,1-dimethoxyheptane comes from the nucleophilic addition of methanol over the heptanal formed. Also, H2 and CO2 from the water gas shift reaction (WGSR) are observed. The catalytic activity for the hydroformylation and the WGSR proved
to be non-linear in the rhodium total concentration range 0.9-5.0 wt.%. 相似文献