Stability of casein micelles cross-linked with genipin: a physicochemical study as a function of pH

Chemical or enzymatic cross-linking of casein micelles (CMs) increases their stability against dissociating agents. In this paper, a comparative study of stability between native CMs and CMs cross-linked with genipin (CMs-GP) as a function of pH is described. Stability to temperature and ethanol were investigated in the pH range 2.0-7.0. The size and the charge ($\zeta$-potential) of the particles were determined by dynamic light scattering. Native CMs precipitated below pH 5.5, CMs-GP precipitated from pH 3.5 to 4.5, whereas no precipitation was observed at pH 2.0-3.0 or pH 4.5-7.0. The isoelectric point of CMs-GP was determined to be pH 3.7. Highest stability against heat and ethanol was observed for CMs-GP at pH 2, where visible coagulation was determined only after 800 s at 140 $^\circ$C or 87.5% (v/v) of ethanol. These results confirmed the hypothesis that cross-linking by GP increased the stability of CMs.Comment: 5 pages, 2 figures, International Dairy Journal, 201

Surface oxidation of a quasicrystalline Al–Cu–Fe alloy: No effect of surface orientation and grain boundaries on the final state

We have used x-ray photoelectron spectroscopy and Auger electron spectroscopy to examine the characteristics of oxides on two types of quasicrystalline Al–Cu–Fe samples. One type was formed by consolidation of powders, resulting in multiple grains with random surface orientations. The other was a single grain, oriented to expose a fivefold surface. Both were oxidized to saturation in a variety of environments at room temperature. We measured the elemental constituents that oxidized, the extent of oxygen-induced Al segregation, and the depth of the oxide. Under the conditions of our experiments, there was little, if any, significant difference between the two types of samples. Hence, surface orientation and bulk microstructure played little or no role on the final state of the oxide under these conditions

Correlation functions in the factorization approach of nonextensive quantum statistics

We study the long range behavior of a gas whose partition function depends on a parameter q and it has been claimed to be a good approximation to the partition function proposed in the formulation of nonextensive statistical mechanics. We compare our results, at large temperatures and at the critical point, with the case of Boltzmann-Gibbs thermodynamics for the case of a Bose-Einstein gas. In particular, we find that for all temperatures the long range correlations in a Bose gas decrease when the value of q departs from the standard value q=1.Comment: revtex file, 10 pages, two eps style figures, packaged as a single tar.gz fil

Electrochemical Pitting And Repassivation On Icosahedral AL-CU-FE, And A Comparison With Crystalline Phases

We report the electrochemical potentials at which localized pitting and repassivation occur on icosahedral Al-Cu-Fe, and on a series of related alloys and elemental metals. The electrochemistry occurs in a buffered NaCI solution, pH 8.4. Under these conditions, pitting and repassivation appear to be controlled mainly by the chemical composition of the alloy, although the quasicrystalline phase displays an anomalous resistance to repassivation. Corrosion of this phase proceeds by dissolution of Al and Fe, leaving behind pits which are Cu-enriched

Room Temperature Oxidation of Al-Cu-Fe and Al-Cu-Fe-Cr Quasicrystals

We have investigated formation of oxides on quasicrystalline and crystalline alloy surfaces of similar composition, in different oxidizing environments. This includes a comparison between a quaternary orthorhombic approximate of Al-Cu-Fe-Cr quasicrystal and the ternary Al-Cu-Fe quasicrystalline and crystalline phases. We noted that each sample showed the following common trends: preferential oxidation of the Al, enrichment in the concentration of Al present at the surface upon oxidation, water concentration is directly related to oxide thickness, and the oxide thickness displays a strong correlation with the bulk concentration of Al in the sample

Electronic structure of quasicrystalline surfaces: Effects of surface preparation and bulk structure

We elucidate the nature of the surface electronic properties of quasicrystalline Al-Pd-Mn. We do this by using photoelectron and Auger electron spectroscopies, and by making a variety of comparisons—across types of bulk samples, and across methods of surface preparation. The main conclusions are these: (i) The narrow Mn 2p3/2core-level line observed in the icosahedral phase is a fingerprint of a suppression in the density of states (a pseudogap) at the Fermi level and is not unique to the quasicrystalline phase. It is also independent of the symmetry of the quasicrystalline surface. The Auger line shape is also affected and may be used as a fingerprint of a pseudogap. (ii) A similarly narrow Fe 2p3/2 core-level line characterizes the icosahedral Al-Cu-Fe quasicrystal, consistent with the expectation that the electronic structure is of general importance in the stabilization of icosahedral phases. (iii) In icosahedral Al-Pd-Mn, the pseudogap of the bulk is not retained up to the surface immediately after fracture, but can be restored by annealing, or by sputter annealing to sufficiently high temperatures. Assuming that the pseudogap reflects an electronic stabilization of the atomic structure, these results suggest that the heat-treated surfaces are more stable than the surface obtained by fracturing at room temperature