Thermal inactivation of Byssochlamys nivea in pineapple nectar combined with preliminary high pressure treatments

Byssochlamys nivea is a thermal resistant filamentous fungi and potential micotoxin producer. Recent studies have verified the presence of ascospores of such microorganism in samples of pineapple nectars. Although the majority of filamentous fungi have limited heat resistance and are easily destroyed by heat, Byssochlamys nivea ascospores have shown high thermal resistance. The aim of this work was to evaluate the application of linear and Weibull models on thermal inactivation (70, 80 and 90ºC) of Byssochlamys nivea ascospores in pineapple nectar after pretreatment with high pressure (550MPa or 650MPa during 15min). Following the treatments, survival curves were built up for each processing temperature and adjusted for both models. It was observed that survival curves at 90°C after high pressure pretreatment at 550 MPa/15 min did not fit well to linear and Weibull models. For all the other treatments, the Weibull model presented a better fit. At 90ºC without pressure treatment, the Weibull model also showed a better adjustment, having a larger R2 and a smaller RMSE. Regarding the process effectiveness, a 5-log reduction (t5), as recommended for pasteurization, was only achieved for Byssochlamys nivea ascospores presented in pineapple nectar at 90ºC/10.7 min with previous high pressure treatment of 650 MPa for 15 min. Considering the high intensity and energy demanding process with possibly product damage, other preventive and alternative treatments are being investigated

The Heme Protein P450 from Adrenal Cortex: Its Reactivities in Ferric and Ferrous Forms

In the course of this reaction cycle the heme protein undergoes a series of changes of its coordination around the Fe (on reduction to its »unliganded~ Fe2+ state, on binding of the 0 2 molecule, and upon introduction of the second reducing equivalent, as the heme protein returns to its original Fe3+ state}. Steroid substrates, inhibitors, and a variety of agents bind to the heme protein P450(Fe3+), isolated in a S = 1/2 form from bovine adrenal glands, with high affinities at sites near the heme group, but do not as a rule enter the coordination sphere of the Fe. This leads to perturbations of the electronic structure which can be followed by spectroscopic techniques (optical absorption, EPR spectroscopy) in combination with suitable chemical methods. Direct replacement of a ligand can also be achieved. The ferrous heme protein P450(Fe2+), in its unliganded and liganded forms, was also investigated. P450(Fe2•) combines readily with small ligands such as 0 2 (418 nm), CO (448 nm), and nitric oxide. Larger lipophilic molecules (e. g. pyridine derivatives, other heterocyclic compounds, haloalkanes, or hydroperoxides) also bind readily to P450(Fe2+), often with high affinities. They tend to enter the coordination sphere of the Fe and form stable complexes often with distinct optical absorption (440-470 nm); additional unspecific binding is frequently observed. Representative examples of the results for the various cases of interactions are presented and are discussed in relation to a hypothetical structure of P450(Fe3• ), S = 1/2, as a protoheme IX complex, with a thiol-group and a N-containing group as axial ligands; the observations are further related to the required changes in coordination in the course of the hydroxylation reaction

The Heme Protein P450 from Adrenal Cortex: Its Reactivities in Ferric and Ferrous Forms

In the course of this reaction cycle the heme protein undergoes a series of changes of its coordination around the Fe (on reduction to its »unliganded~ Fe2+ state, on binding of the 0 2 molecule, and upon introduction of the second reducing equivalent, as the heme protein returns to its original Fe3+ state}. Steroid substrates, inhibitors, and a variety of agents bind to the heme protein P450(Fe3+), isolated in a S = 1/2 form from bovine adrenal glands, with high affinities at sites near the heme group, but do not as a rule enter the coordination sphere of the Fe. This leads to perturbations of the electronic structure which can be followed by spectroscopic techniques (optical absorption, EPR spectroscopy) in combination with suitable chemical methods. Direct replacement of a ligand can also be achieved. The ferrous heme protein P450(Fe2+), in its unliganded and liganded forms, was also investigated. P450(Fe2•) combines readily with small ligands such as 0 2 (418 nm), CO (448 nm), and nitric oxide. Larger lipophilic molecules (e. g. pyridine derivatives, other heterocyclic compounds, haloalkanes, or hydroperoxides) also bind readily to P450(Fe2+), often with high affinities. They tend to enter the coordination sphere of the Fe and form stable complexes often with distinct optical absorption (440-470 nm); additional unspecific binding is frequently observed. Representative examples of the results for the various cases of interactions are presented and are discussed in relation to a hypothetical structure of P450(Fe3• ), S = 1/2, as a protoheme IX complex, with a thiol-group and a N-containing group as axial ligands; the observations are further related to the required changes in coordination in the course of the hydroxylation reaction

Mars rover sample return: An exobiology science scenario

A mission designed to collect and return samples from Mars will provide information regarding its composition, history, and evolution. At the same time, a sample return mission generates a technical challenge. Sophisticated, semi-autonomous, robotic spacecraft systems must be developed in order to carry out complex operations at the surface of a very distant planet. An interdisciplinary effort was conducted to consider how much a Mars mission can be realistically structured to maximize the planetary science return. The focus was to concentrate on a particular set of scientific objectives (exobiology), to determine the instrumentation and analyses required to search for biological signatures, and to evaluate what analyses and decision making can be effectively performed by the rover in order to minimize the overhead of constant communication between Mars and the Earth. Investigations were also begun in the area of machine vision to determine whether layered sedimentary structures can be recognized autonomously, and preliminary results are encouraging

Resource Competition on Integral Polymatroids

We study competitive resource allocation problems in which players distribute their demands integrally on a set of resources subject to player-specific submodular capacity constraints. Each player has to pay for each unit of demand a cost that is a nondecreasing and convex function of the total allocation of that resource. This general model of resource allocation generalizes both singleton congestion games with integer-splittable demands and matroid congestion games with player-specific costs. As our main result, we show that in such general resource allocation problems a pure Nash equilibrium is guaranteed to exist by giving a pseudo-polynomial algorithm computing a pure Nash equilibrium.Comment: 17 page

NEAR-SURFACE EFFECTS IN MODELLING OSCILLATIONS OF ETA BOO

Following the report of solar-like oscillations in the G0 V star eta Boo (Kjeldsen et al. 1995, AJ 109, 1313), a first attempt to model the observed frequencies was made by Christensen-Dalsgaard et al. (1995, ApJ Letters, in press). This attempt succeeded in reproducing the observed frequency separations, although there remained a difference of about 10 microHz between observed and computed frequencies. In those models, the near-surface region of the star was treated rather crudely. Here we consider more sophisticated models that include non-local mixing-length theory, turbulent pressure and nonadiabatic oscillations.Comment: uuencoded and compressed Postscript (2 pages, including figure); To appear in Proceedings of IAU Colloquium 155, "Astrophysical Applications of Stellar Pulsation", Cape Town, South Afric