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61.
Carmela Tufano Gerrit W. M. Peters Peter Van Puyvelde Han E. H. Meijer 《Rheologica Acta》2009,48(3):343-358
The morphology evolution of two systems of partially immiscible polymers, differing in miscibility, is investigated by means of rheological experiments and optical microscopy. For each
system, two concentrations, 10% and 20%, are used. For immiscible systems, a hysteresis zone, defined by coalescence and breakup, exists where the average drop radius is not a unique function
of the shear rate. We investigate whether the findings also apply to partially immiscible polymers. The average radii at different shear rates, measured with rheology, are compared to model predictions. The hysteresis
zone, if present, is indeed affected by the polymeric system, the concentration and the flow history applied. Coalescence
evolution is measured for three different step-downs in shear rate. For both 10% systems, the resulting average radii show
a rather high scattering and do not match the theoretical predictions. For the 20% concentrations, the average experimental
drop sizes seem independent of the magnitude of the step-down, at least during a certain period of time. Thereafter, it experiences
a sudden, in the time scale of the experiments unbounded, increase in size that is more pronounced for the higher step-downs.
Deviations of the experimental data from theoretical predictions are attributed to the partially immiscible character of the
systems, yielding enhanced coalescence which, in turn, can induce confinement effects. 相似文献
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63.
Davide Collini Serena Fedi Cristina Femoni Francesco Kaswalder Maria Carmela Iapalucci Giuliano Longoni Piero Zanello 《Journal of Cluster Science》2005,16(3):455-476
The reaction of the [Ni6(CO)12]2− dianion with [Rh(COD)Cl]2 (COD = cyclooctadiene) in acetone affords a mixture of bimetallic Ni–Rh clusters, mainly consisting of the new [Ni7Rh3(CO)18]3− and [Ni8Rh(CO)18]3− trianions. A study of the reactivity of [Ni7Rh3(CO)18]3− led to isolation of the new [Ni3Rh3(CO)13]3− and [NiRh8(CO)19]2− anions. All these new bimetallic Ni–Rh carbonyl clusters have been isolated in the solid state as tetrasubstituted ammonium
salts and have been characterised by elemental analysis, X-ray diffraction studies, ESI-MS and electrochemistry. The unit
cell of the [NEt4]3[Ni7Rh3(CO)18] salt contains two orientationally-disordered ν2-tetrahedral [Ni7Rh3(CO)18]3− trianions with occupancy factors of 0.75 and 0.25. Besides, their inner Ni3Rh3 octahedral moieties show two cis sites purely occupied by Rh atoms, two trans sites purely occupied by Ni atoms and the remaining two cis sites are disordered Ni and Rh sites with respective occupancy fraction of 0.5. At difference from the parent [Ni7Rh3(CO)18]3−, the octahedral [Ni3Rh3(CO)13]3− displays an ordered distribution of Ni and Rh atoms in two staggered triangles. The [NiRh8(CO)19]2− dianion adopts an isomeric metal frame with respect to that of the [PtRh8(CO)19]2− congener. As a fallout of this work, new high-yield synthesis of the known [Ni6Rh3(CO)17]3− and [Ni6Rh5(CO)21]3−, as well as other currently-investigated bimetallic Ni–Rh clusters have been obtained. 相似文献
64.
A proteomic approach to study protein variation in GM durum wheat in relation to technological properties of semolina 总被引:1,自引:0,他引:1
Di Luccia A Lamacchia C Fares C Padalino L Mamone G La Gatta B Gambacorta G Faccia M Di Fonzo N La Notte E 《Annali di chimica》2005,95(6):405-414
Genetic manipulation of durum wheats by tobacco rab-1 genes influence the trafficking of gluten proteins through the secretory system by up- or down-regulating the transport step from the ER to the Golgi apparatus which may in turn modify functional performance of the grain. Gluten proteins were extracted from two genetically manipulated lines - Svevo B730 1-1 and Ofanto B688 1-2 - and their control lines and were analyzed by two dimensional gel electrophoresis. When the two-dimensional maps were compared by image analysis no significant differences between the GM line with an up-regulated trafficking containing the wild type tobacco rab1 (Svevo B730 1-1) and its control (Svevo control). By contrast, significant differences were found between the GM line with a down-regulated trafficking due to the tobacco rab1 mutant form (Ofanto B688 1-2) and its control (Ofanto control). Of the new protein spots detected in the down-regulated Ofanto B688 1-2 map, only a beta-amylase was identified. The remaining spots were susceptible to chymotripsin action but not to trypsin one, as in the case of the gluten protein. Rheological measurements showed that gluten quality was enhanced in the down-regulated Ofanto B688 1-2 without an increase in the amount of gluten. Proteomics is a useful and powerful tool for investigating protein changes in GMOs and in understanding events in food science and technology. 相似文献
65.
Vertebrate photoreceptors generate electrical signals across their cell membrane when they absorb light. Recent studies show, moreover, that the membrane potential of an individual photoreceptor may be also modified by illumination of its neighbors. Two types of lateral interactions have been described: a direct interaction mediated by electrical synapses between adjacent photoreceptors, and a recurrent interaction mediated by a feedback circuit involving horizontal cells. In the first mechanism, photoreceptors summate their responses over short retinal distances. In the feedback circuit photoreceptors may develop light responses of opposite polarity to those induced by direct illumination. In general, these 'antagonistic' responses are best elicited by large area retinal illumination. As a consequence of these photoreceptor interactions rather complex processing of visual information, in both spatial and chromatic domains, occurs at the first stage of the retinal network. 相似文献
66.
A portable dynamic air sampler and solid phase microextraction were used to simultaneously detect, identify, and quantify airborne sarin with immediate analysis of samples using a field portable gas chromatography-mass spectrometry system. A mathematical model was used with knowledge of the mass of sarin trapped, linear air velocity past the exposed sampling fiber, and sample duration allowing calculation of concentration estimates. For organizations with suitable field portable instrumentation, these methods are potentially useful for rapid onsite detection and quantification of high concern analytes, either through direct environmental sampling or through sampling of air collected in bags. 相似文献
67.
68.
69.
Maurizio Galimberti Fabrizio Piemontesi Laura Alagia Simona Losio Luca Boragno Paola Stagnaro Maria Carmela Sacchi 《Journal of polymer science. Part A, Polymer chemistry》2010,48(10):2063-2075
Ethene/1‐olefin blocky copolymers were obtained through nonliving insertion copolymerizations promoted by an isospecific single site catalyst. Propene or 4‐methyl‐1‐pentene were copolymerized with ethene with metallocenes endowed with different stereospecificity in propene polymerization: (i) aspecific “constrained geometry” half‐sandwich complex, {η1:η5‐([tert‐butyl‐amido)dimethylsilyl](2,3,4,5‐tetramethyl‐1‐cyclopentadienyl)}titanium dichloride [Me2Si(Me4Cp)(N‐tBu)TiCl2] ( CG ), (ii) moderately isospecific rac‐ethylenebis(indenyl)zirconium dichloride [rac‐(EBI)ZrCl2] ( EBI ), (iii) slightly more isospecific hydrogenated homologue, rac‐ethylenebis(tetrahydroindenyl)zirconium dichloride [rac‐(EBTHI)ZrCl2] ( EBTHI ), (iv) highly iso‐specific rac‐[methylenebis(3‐tert‐butyl‐1‐indenyl)]zirconium dichloride [rac‐H2C‐(3‐tBuInd)2ZrCl2] ( TBI ), (v) most isospecific rac‐[isopropylidene‐bis(3‐tert‐butyl‐cyclopentadienyl)]zirconium dichloride [rac‐Me2C‐(3‐tBuCp)2ZrCl2] ( TBC ). Copolymerizations were described by a 2nd order Markovian copolymerization model and data are proposed to correlate the formation of 1‐olefin sequences with catalytic site isospecificity, made by the cooperation of organometallic complex and growing chain. Blocky copolymers were prepared over wide ranges of compositions: with any of the isospecific metallocenes when 4‐methyl‐1‐pentene was the 1‐olefin and only with the highly isospecific ones ( TBI , TBC ) when propene was the comonomer. A penultimate unit effect was observed with TBI as the metallocene, whereas a 1st order Markov model described the ethene/propene copolymerization from TBC . A moderately isospecific metallocene, such as EBI , is shown to be able to prepare blocky ethene copolymers with 4‐methyl‐1‐pentene. These results pave the way for the synthesis of new ethene based materials. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2063–2075, 2010 相似文献
70.
Flavor is amongst the major personal satisfaction indicators for meat products. The aroma of dry cured meat products is generated under specific conditions such as long ripening periods and mild temperatures. In these conditions, the contribution of Maillard reactions to the generation of the dry cured flavor is unknown. The main purpose of this study was to examine mild curing conditions such as temperature, pH and aw for the generation of volatile compounds responsible for the cured meat aroma in model systems simulating dry fermented sausages. The different conditions were tested in model systems resembling dry fermented sausages at different stages of production. Three conditions of model system, labeled initial (I), 1st drying (1D) and 2nd drying (2D) and containing different concentrations of amino acid and curing additives, as well as different pH and aw values, were incubated at different temperatures. Changes in the profile of the volatile compounds were investigated by solid phase microextraction and gas chromatography mass spectrometry (SPME-GS-MS) as well as the amino acid content. Seventeen volatile compounds were identified and quantified in the model systems. A significant production of branched chain volatile compounds, sulfur, furans, pyrazines and heterocyclic volatile compounds were detected in the model systems. At the drying stages, temperature was the main factor affecting volatile production, followed by amino acid concentration and aw. This research demonstrates that at the mild curing conditions used to produce dry cured meat product volatile compounds are generated via the Maillard reaction from free amino acids. Moreover, in these conditions aw plays an important role promoting formation of flavor compounds. 相似文献