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排序方式: 共有1133条查询结果,搜索用时 10 毫秒
81.
Rodolfo Daniel Velasco-Barraza Ricardo Vera-Graziano Eduardo Alberto López-Maldonado Mercedes Teresita Oropeza-Guzmán Syed G. Dastager Adriana Álvarez-Andrade 《国际聚合物材料杂志》2018,67(13):800-807
In recent times, electrospun nanofibers have been widely studied from several biotechnological approaches; in this work, poly(acrylic acid) (PAA) solutions mixed with chitosan and alginate were electrospun and characterized to determine the behavior of these fibers when used in combination with bacteria, different samples were incubated with the bacterial strains: Streptomyces spp., Micromonospora spp., and Escherichia coli and a OD600 test was performed. The formation of nanofibers via electrospinning and the physicochemical properties of the obtained fibers were evaluated. Results showed that the presence of chitosan enhanced the thermal stability of PAA, since PAA/alginate fibers lost 5% of their mass at 41°C, whereas PAA/chitosan lost this amount at around 125°C. The fibers demonstrated suitable characteristics to be used as a bacteria bioreactor. 相似文献
82.
This investigation presents the synthesis of simultaneous interpenetrating polymer networks based on dimethacrylic/epoxy resins with or without polyhedral oligomeric silsesquioxane (POSS) via in situ polymerization. The curing behavior was studied using differential scanning calorimetry (DSC). The influence of the organic groups from the POSS cages on the curing kinetics of the IPNs was also studied by FT-IR spectrometry. The homogeneous phase structure of the cured IPN was proved by DMA tests. Additionally the integrity of the IPN was also demonstrated by thermal decomposition which occurs in one single step. 相似文献
83.
Fabiana A. Lobo Danielle Goveia Adriana P. de Oliveira Edenir R. Pereira-Filho Newton L. Dias Filho 《Fuel》2009,88(10):1907-1914
Experimental design was used as a tool to define the optimum pyrolysis and atomization temperatures for four analytes (Cu, Pb, Ni and Cd) in biodiesel samples. Two chemical modifiers (Pd + Mg and W) and two distinct sample preparation procedures (microemulsion and wet digestion in a focused microwave system) were also investigated. The pyrolysis and atomization temperatures were optimized using 24 factorial design for Cu, Pb, Ni and Cd, with 16 assays carried out for each analyte. The results for Cu and Pb indicated that variables of sample preparation for digestion by focused microwave was the most important one for both analytes. The pyrolysis and atomization temperatures applied were 1000 °C and 2200 °C for Cu and 500 °C and 2000 °C for Pb. None of the variables analyzed here were important for Ni, and the pyrolysis and atomization temperatures chosen for this element were 800 °C and 2300 °C. A different factorial design was used for Cd. The variables of medium and modifier were not important for this element, and the lowest temperatures, Tp-500 °C and Ta-1400 °C, were chosen based on this second design. The importance of factorial design in the simultaneous optimization of several variables studied by GFAAS was confirmed, for it involves fewer experiments and hence, lower costs, greater speed and higher efficiency. 相似文献
84.
Spectrophotometric data followed by a suitable treatment of chemometric analysis were used for the simultaneous determination of monosodium glutamate (MSG), guanosine 5′-monophosphate (GMP) and inosine 5′-monophosphate (IMP) in stock cube samples, without any previous extraction step. By this way, the overlapping of the absorption spectra was resolved using a PLS-1 model. The concentration for experimental calibration matrix were varied between 5.03–34.2 μg mL−1 for IMP and GMP, and 448–1399 μg mL−1 for MSG. The relative errors of prediction (REPCV %) were 1.8, 2.8 and 3.1 for IMP, GMP and MSG, respectively. 相似文献
85.
Dora Angela Hoyos Adriana Echavarría Carlos Saldarriaga 《Journal of Materials Science》2001,36(22):5515-5518
A zinc vanadate with the formula Zn3(VO4)2·3H2O was synthesized by hydrothermal reaction of a gel of composition [(CH3CO2)2Zn·2H2O] : 0.5V2O5: 0.4 [1,3-diaminepropane] : 1.5 NaOH : 114 H2O, held at 170°C for 24 hours. The structure was determined ab initio by means of the EXPO direct methods program and refined with GSAS. The pale yellow solid crystallizes in the hexagonal space group P-6 with a= 6.07877(8), c= 7.1827(2) Å. The structure consists of vanadium tetrahedra bonded to distorted octahedral zinc atoms to create one dimensional columnar passageways for molecules. Though occupied by water in the as synthesized form, the passages could host other small molecules. 相似文献
86.
87.
César Valderrama Xavier Gamisans Jose L Cortina Adriana Farrán F Xavier de las Heras 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2009,84(2):236-245
BACKGROUND: Sorption of polycyclic aromatic hydrocarbons (PAHs) on activated carbon and the Macronet polymeric sorbent MN200 was investigated to determine the effectiveness of each sorbent for removal of pollutants from aqueous solution and their possible use as sorbent materials for groundwater. Experiments were carried out to determine the loading capacities of a family of PAHs (acenaphthene, anthracene, fluoranthene, fluorene, naphthalene and pyrene). RESULTS: Activated carbon was the more effective sorbent, with maximum loadings of PAHs between 90 and 230 g kg?1, while MN200 resin showed values of 25–160 g kg?1. Loading isotherms based on the Langmuir, Freundlich and Redlich–Peterson models were determined. The hydrophobic character of the pollutants appeared as an important parameter related to the sorption process. Equilibrium and kinetic parameters were used to determine the retardation factors for each PAH. CONCLUSION: The calculated values for the simulation of barrier thickness using both sorbents, taking into account EU requirements for PAHs in groundwater effluent, were perfectly reasonable as a first estimate. The better kinetic properties of MN200 are evident in lower hydraulic residence times and consequently in a lower barrier thickness. Copyright © 2008 Society of Chemical Industry 相似文献
88.
Joan Colón Julia Martínez‐Blanco Xavier Gabarrell Joan Rieradevall Xavier Font Adriana Artola Antoni Sánchez 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2009,84(8):1111-1117
BACKGROUND: Biofiltration is a suitable odor reduction technique for the treatment of gaseous emissions from composting processes, but little is known about the start‐up of full‐scale biofilters after material replacement and their performance after several years of operation. RESULTS: Biofilter material (wood chips used previously as bulking agent in a composting process) can effectively remove ammonia and most of the volatile organic compounds (VOCs) content, achieving removal efficiencies greater than 70% for VOCs and near 90% for ammonia immediately after material replacement. These removal efficiencies were maintained for several months after material replacement. In the studied full‐scale biofilter no lag phase was observed in the removal of ammonia whereas in the case of VOCs different patterns were detected during biofilter start‐up. For the old biofilter material, after 4 years of operation, a statistically significant decrease of removal efficiency for ammonia in comparison with the new material was detected. No statistically significant differences were found in the case of VOCs. CONCLUSIONS: Data on the emissions of several pollutants from biofilters treating composting exhaust gases have been systematically obtained. The tested filtering media presented adequate properties for biofiltration of gases emitted during the composting process. Copyright © 2009 Society of Chemical Industry 相似文献
89.
The effect of ammonium polymolybdate (APM) on the corrosion of carbon steel in a solution of 1 M HCl was studied by weight loss and Mössbauer spectrometry. Inhibition efficiencies (P) have been obtained from weight measurement. The inhibition efficiencies increased with increase APM concentration. Mössbauer spectrometry shows that a superficial compound is formed on the electrode surface as a result of corrosion. 相似文献
90.
Adriana W. Blom Shahriar Setoodeh Jan M.A.M. Hol Zafer Gürdal 《Computers & Structures》2008,86(9):870-878
Fiber-reinforced composite conical shells with given geometry and material properties are optimized for maximum fundamental frequency. The shells are assumed to be built using an advanced tow-placement machine, which allows in-plane steering of the fibers, resulting in a variable-stiffness structure. In this paper, different path definitions for variable-stiffness shells are provided and used to optimize conical shells for maximum fundamental frequency, while manufacturing constraints that apply for tow placement are taken into account in the process. The influence of manufacturing constraints on the performance is shown; and improvements of variable-stiffness conical shells over conventional, constant-stiffness shells are demonstrated. 相似文献