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141.
Jos R. Ayala Gisela Montero Marcos A. Coronado Conrado García Mario A. Curiel-Alvarez Jos A. Len Carlos A. Sagaste Daniela G. Montes 《Molecules (Basel, Switzerland)》2021,26(5)
Annually, millions of tons of foods are generated with the purpose to feed the growing world population. One particular eatable is orange, the production of which in 2018 was 75.54 Mt. One way to valorize the orange residue is to produce bioethanol by fermenting the reducing sugars generated from orange peel. Hence, the objective of the present work was to determine the experimental conditions to obtain the maximum yield of reducing sugars from orange peel using a diluted acid hydrolysis process. A proximate and chemical analysis of the orange peel were conducted. For the hydrolysis, two factorial designs were prepared to measure the glucose and fructose concentration with the 3,5-DNS acid method and UV-Visible spectroscopy. The factors were acid concentration, temperature and hydrolysis time. After the hydrolysis, the orange peel samples were subjected to an elemental SEM-EDS analysis. The results for the orange peel were 73.530% of moisture, 99.261% of volatiles, 0.052% of ash, 0.687% of fixed carbon, 19.801% of lignin, 69.096% of cellulose and 9.015% of hemicellulose. The highest concentration of glucose and fructose were 24.585 and 9.709 g/L, respectively. The results highlight that sugar production is increased by decreasing the acid concentration. 相似文献
142.
Ayala P Grüneis A Kramberger C Rümmeli MH Solórzano IG Freire FL Pichler T 《The Journal of chemical physics》2007,127(18):184709
Single and multiwalled nitrogen-doped carbon nanotubes were grown by chemical vapor deposition varying the feedstock composition between pure acetonitrile and ethanol/acetonitrile mixtures. The advantage of using CN sources that develop close vapor pressure values has been used in order to elucidate the effects of the reaction atmosphere in the synthesis of N-doped nanotubes. Our findings show that the morphology of the nanotube material depends strongly on the composition of the reaction atmosphere. When carrying out the experiments in an atmosphere solely determined by the vapor pressure of the feedstock components, improved homogeneity is achieved with pure CN sources or low concentration of the foreign solute. Under these conditions the temperature has strong influence in the diameter distribution. 相似文献
143.
144.
David Ayala Angel E. Lozano Javier De Abajo Jos G. De La Campa 《Journal of polymer science. Part A, Polymer chemistry》1999,37(16):3377-3384
Polyimides derived from a new dianhydride with p-nitrophenyl pendant groups have been synthesized and their properties compared with those of a reference series, without side groups. The polymers were obtained by combination of the novel monomer with aromatic diamines, in a two-step procedure that involved the synthesis of poly(amic acid) or poly(amic silyl ester) intermediates and the cyclization of them to polyimides by thermal treatment. The introduction of the polar nitro groups caused significant increase of the Tgs. On the contrary, the thermal stability was reduced because of the breakdown of CAr—NO2 linkages around 400oC. A slight decrease in mechanical properties was observed, due to the bulkiness of the side groups, that also produced an important decrease in the strength of the β relaxation, as determined by dynamic mechanical analysis. The solubility of the current polyimides in organic solvents was as poor as that of the parent unsubstituted polymers. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3377–3384, 1999 相似文献
145.
David Ayala Angel E. Lozano Javier De Abajo Jos G. De La Campa 《Journal of polymer science. Part A, Polymer chemistry》1999,37(6):805-814
New dianhydrides containing t‐butyl and phenyl pendant groups have been synthesized and used as monomers, together with commercial diamines, to prepare novel polyimides. The influence of the chemical structure of the monomers on their reactivity has been studied by quantum semiempirical methods. The polyimides have been characterized by FTIR and by NMR in the case of soluble polymers. The presence of pendant groups and the method used to imidize polyimide precursors greatly affected polymer properties such as solubility, glass transition temperature, thermal stability, and mechanical properties. As a rule, the novel polyimides showed better solubility in organic solvents than the parent polyimides. Glass transition temperatures in the range 250–270°C and decomposition temperatures over 520°C were observed for the set of current polymers. Tensile strengths up to 135 MPa and mechanical moduli up to 3.0 GPa were measured on films of the current polyimides. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 805–814, 1999 相似文献
146.
The traditional analysis of electric quadrupole interaction in disordered materials can give hyperfine parameters that would
mask the actual values. As the relative distribution width δ increases, the correlation of this parameter with the rest produces
strong shifts in all of them. Motivated by the values δ ⩾ 0.4 fitted in BaTi1-xHfxO3 for 0 ⩽ x ⩽ 0.2 and other perovskites we extend previous calculations for Gaussian distribution function to the interval
0.3 ⩽ δ ⩽ 1. We also include the study of correlation between quadrupole parameters for Lorentzian distribution function in
the 0 ⩽ δ ⩽ 1 interval.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
147.
FO Ayorinde BE Eribo JH Johnson E Elhilo 《Rapid communications in mass spectrometry : RCM》1999,13(12):1124-1128
Nonylphenol ethoxylates (NPEs) belong to a group of nonionic surfactants that are collectively referred to as alkylphenol ethoxylates (APEs). APEs find widespread use in heavy-duty commercial and household cleaning formulations, shampoos, and industrial processing, i.e. textile manufacture. Their environmental impact depends on the molecular distribution and the extent of their biodegradation in municipal sewage systems, waterways and rivers. We have established two sample preparation methods that have enabled the determination of the molecular distributions of six commercial nonylphenol ethoxylates using matrix-assisted laser desorption/ionization (MALDI) time-of-flight (TOF) mass spectrometry (MS). In both methods, alpha-cyano-4-hydroxycinnamic acid, dissolved in acetonitrile/tetrahydrofuran, was used as the matrix. In one set of experiments, the NPEs were dissolved in an acetonitrile/tetrahydrofuran solvent system prior to mixing with the matrix solution, and the resulting MALDI-TOF mass spectra produced mostly sodiated molecules [M + Na](+). The NPEs, all having the formula 4-(C(9)H(19))-C(6)H(4)-(OCH(2)CH(2))(n)-OH, are Surfonic (R)N-95, N-100, N-102, N-120, N-150 and N-300. Surfonic N-95 and N-100 gave n values of 5-20; Surfonic N-102, N-120, N-150, and N-300 gave n values of 5-21, 5-22, 8-25 and 15-40, respectively. In order to develop a sample preparation method that could be used with less polar NPEs, we dissolved the NPEs (except N-300) in pentane prior to mixing with the matrix solution, and found that the MALDI spectral quality was unaffected by the solvent systems. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
148.
Aurora Martín‐Calero Gracian Tejral Juan H. Ayala Venerando González Ana M. Afonso 《Journal of separation science》2010,33(2):182-190
The effects of several ionic liquids (ILs) as mobile‐phase additives in HPLC with fluorescence and UV–Vis detection for the determination of six heterocyclic aromatic amines were evaluated using two different C18 stationary phases with moderate silanol activity. The studied ILs were 1‐butyl‐3‐methylimidazolium tetrafluoroborate, 1‐hexyl‐3‐methylimidazolium tetrafluoroborate and 1‐methyl‐3‐octylimidazolium tetrafluoroborate. The optical behaviour of heterocyclic aromatic amines in presence of ILs was studied and the silanol‐suppressing potency of ILs was evaluated for the two stationary phases studied. Several chromatographic parameters were evaluated in the presence or absence of ILs, or using triethylamine, the most common mobile‐phase additive. The best results were achieved using 1 mM 1‐butyl‐3‐methylimidazolium tetrafluoroborate as mobile‐phase additive and NovaPak® column. In these conditions and with 18% of ACN in the mobile phase, analytical performance of the chromatographic methods using fluorescence and UV–Vis were evaluated, obtaining good precision in all cases (RSD lower than 6.6%) and low LOD (0.001–0.147 μg/mL with UV–Vis and 0.001–0.006 ng/mL with fluorescence detection). 相似文献
149.
Matthew A.J. Duncton Leticia Ayala Carl Kaub Satyanarayana Janagani William T. Edwards Nina Orike Krithika Ramamoorthy John Kincaid Michael G. Kelly 《Tetrahedron letters》2010,51(7):1009-823
Dibutyl-2-(trifluoromethyl)cyclopropylboronate 2, available in one step from commercially available reagents, serves as a useful (trifluoromethyl)cyclopropylating reagent by participating in a palladium-catalyzed Suzuki coupling. The use of boronate ester 2 in medicinal chemistry was exemplified by preparation of TRPV1 receptor antagonists. 相似文献
150.
In this work TiO2 thin films were modified with gold/palladium (Au/Pd) bimetallic paticles by sputtering method. TiO2 films were deposited on ITO (SnO2:In) by Doctor Blade method and post-anneling. The properties of the films were studied through measurements of XRD (X-ray diffraction) and AFM (atomic force microscopy). The degradation of methylene blue was studied by UV-irradiated pure TiO2 and Au/Pd-modified TiO2 in aqueous solution. Langmuir-Hinshelwood model was used to obtain kinetic information. Photocatalytic study indicated that Au/Pd-modified TiO2 photocatalytic activity was better than TiO2 pure; the best half-life time for Au/Pd-modified TiO2 in photodegradation was 2.8 times smaller than TiO2 pure; finally the efficiency in methylene blue photodegradation was improved from 23% to 43% when Au/Pd-modified TiO2 films were used. 相似文献