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111.
Anglica Serpa Guerra Catalina Gmez Hoyos Jorge Velsquez-Cock Lina Vlez Piedad Gan Robin Zuluaga 《Molecules (Basel, Switzerland)》2022,27(3)
Color is an important characteristic of food products. This characteristic is related to consumer acceptability. To use the entire rhizome of Curcuma longa (CL) as a food colorant, a novel gel alike stable suspension (CLS) was previously developed using cellulose nanofibers (CNFs). Therefore, the present study was conducted to evaluate the CLS as a color additive on a stirred yogurt. Three concentrations of CLS were studied (0.1, 0.125, and 0.15 wt. %) and compared to yogurt without CLS. The obtained yogurts were characterized through the determination of pH, titratable acidity, syneresis, color and curcumin content after 1, 7, 14, and 21 days of storage. Additionally, rheological and sensory measurements were performed on the samples after one day of storage. Results show that the addition of CLS does not affect the pH and titratable acidity of the samples, but all the yogurts showed an increase in their syneresis during the storage time, showing a breakdown of the gel structure. Furthermore, the CLS suspension has the ability to impart a yellow color to yogurts, a characteristic that was stable during storage. Finally, the addition of 1 wt. % or 1.25 wt. % of CLS allows the development of a yogurt with adequate sensory perception. 相似文献
112.
J. Solis C. Ortiz C. N. Afonso F. Catalina 《Applied Physics A: Materials Science & Processing》1992,54(3):279-283
Real time optical measurements are used to analyse two different kinds of phase changes which generate optical contrast in (In43Sb57)87Ge13 thin films. Amorphous to crystalline and amorphous to amorphous structural transformations are induced by pulsed laser irradiation in micron-sized regions. A two beam configuration is used to follow the evolution of the optical properties of the films in real time. It is shown that real time optical measurements provide a unique tool to analyse laser-induced fast structural transformations leading to optical contrast. Processes occurring via relaxation, solid state crystallization or melting-solidification are clearly distinguished. From the analysis of the optical transients the minimum transformation times are directly determined.On Sabbatical leave from IBM Almaden Research Center, San Jose, CA, USA 相似文献
113.
J. L. Mateo P. Bosch F. Catalina R. Sastre 《Journal of polymer science. Part A, Polymer chemistry》1993,31(1):153-157
The photochemical behavior of p-dimethylaminobenzoylated polystyrene (PS-MI) in benzene solution has been investigated, both in the presence and absence of methyl methacrylate (MMA). This behavior has been compared with that of the model compound, 4-isopropyl-4′-N,N-dimethylaminobenzophenone (CU-MI). PS-MI photoreduction takes place only through excimer formation due to the high local chromophore concentration, and therefore, PS-MI disappearance quantum yield is close to the previously calculated limiting value (0.02) and independent of chromophore concentration. Several parameters that characterize the polymerization process have been determined; it has been found that the obtained PMMA is photografted onto PS-MI backbone. This is in agreement with the proposed mechanism for radical generation. No homo-PMMA formation has been detected. © 1993 John Wiley & Sons, Inc. 相似文献
114.
115.
Catalina Arnau Ramn Carb Sigeru Huzinaga 《International journal of quantum chemistry》1972,6(5):843-847
The procedure proposed by Silverstone and others to modify virtual levels in SCF theory is extended as a technique to be used in any type of generalized secular equations. Some useful results are obtained. 相似文献
116.
Fernando Mendizábal Claudio Olea‐Azar Sebastian Miranda 《International journal of quantum chemistry》2007,107(6):1454-1458
Ab initio calculations suggest that a series of complexes of type [Pt(PH3)3? MPH3]+ (M = Au, Ag, Cu) are stable. We found that changes around the equilibrium distance Pt? M and in the interaction energies are sensitive to the electron correlation potential. This effect was evaluated using several levels of theory, including HF, MP2, and B3LYP. Both the magnitude of the interaction energies and distances Pt? M indicate a formal chemical bond, the latter being ratified by orbital diagram. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 相似文献
117.
[reaction: see text] Oxidative ring opening of 3-oxabicyclo[4.1.0]hept-4-enes, formed by the intramolecular Pt(II)-catalyzed cyclopropanation of enol ethers by alkynes, gives oxepane derivatives. Alternatively, the acid-catalyzed opening of the cyclopropane ring leads to dihydrobenzofurans or 3,4-dihydro-2H-chromenes. 相似文献
118.
J. L. Mateo P. Bosch F. Catalina R. Sastre 《Journal of polymer science. Part A, Polymer chemistry》1990,28(6):1445-1454
Several kinetics aspects of the methyl methacrylate (MMA) polymerization using 4-dimethylamino-4'-isopropylbenzophenone (PI) as photoinitiator have been studied. The order of the polymerization reaction with respect to monomer and initiator concentrations have been investigated, as well as the polymerization behavior under well-stirred and unstirred conditions; values of initiation quantum yield (?i) and kp/kt1/2 have also been determined. It has been found that the nature of the polymerization-initiating radicals depends on the type of solvent and the photoinitiator concentration ([PI]). In cyclohexane solution and at low [PI] (< 5 x 10-5M), the cyclohexyl radical is practically the only polymerization initiating radical, while at higher [PI] both radicals, cyclohexyl and the aminoalkyl derived from PI, participate in the initiation step, increasing the participation of the later as the [PI] increases. When benzene is used as solvent both phenyl and aminoalkyl radicals participate in the initiation step at any [PI] employed. Efficiencies of the radicals derived from solvent and photoinitiator have been determined. 相似文献
119.
A comparative study of the Mitsunobu reaction at C1 and C6 positions of mannose using bis(2,2,2-trifluoroethyl) malonate as nucleophile is disclosed. While C-alkylation was predominant at the C6 position, only O-alkylation occurred at the anomeric position of the carbohydrate. Some factors playing a role in the selectivity of the reaction are discussed and an inverse mechanism of the Mitsunobu reaction for the anomeric position is proposed. 相似文献
120.
Catalina MI van den Heuvel RH van Duijn E Heck AJ 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(3):960-968
Electrospray ionization mass spectrometry (ESI-MS) is a valuable tool in structural biology for investigating globular proteins and their biomolecular interactions. During the electrospray ionization process, proteins become desolvated and multiply charged, which may influence their structure. Reducing the net charge obtained during the electrospray process may be relevant for studying globular proteins. In this report we demonstrate the effect of a series of inorganic and organic gas-phase bases on the number of charges that proteins and protein complexes attain. Solution additives with very strong gas-phase basicities (GB) were identified among the so-called "proton sponges". The gas-phase proton affinities (PA) of the compounds that were added to the aqueous protein solutions ranged from 700 to 1050 kJ mol(-1). Circular dichroism studies showed that in these solutions the proteins retain their globular structures. The size of the proteins investigated ranged from the 14.3 kDa lysozyme up to the 800 kDa tetradecameric chaperone complex GroEL. Decharging of the proteins in the electrospray process by up to 60 % could be achieved by adding the most basic compounds rather than the more commonly used ammonium acetate additive. This decharging process probably results from proton competition events between the multiply protonated protein ions and the basic additives just prior to the final desolvation. We hypothesize that such globular protein species, which attain relatively few charges during the ionization event, obtain a gas-phase structure that more closely resembles their solution-phase structure. Thus, these basic additives can be useful in the study of the biologically relevant properties of globular proteins by using mass spectrometry. 相似文献