Comparison of Yarrowia lipolytica and Pichia pastoris Cellular Response to Different Agents of Oxidative Stress

Yeast cells exposed to adverse conditions employ a number of defense mechanisms in order to respond effectively to the stress effects of reactive oxygen species. In this work, the cellular response of Yarrowia lipolytica and Pichia pastoris to the exposure to the ROS-inducing agents’ paraquat, hydrogen peroxide, and increased air pressure was analyzed. Yeast cells at exponential phase were exposed for 3 h to 1 mM paraquat, to 50 mM H₂O₂, or to increased air pressure of 3 or 5 bar. For both strains, the cellular viability loss and lipid peroxidation was lower for the cells exposed to increased air pressure than for those exposed to chemical oxidants. The glutathione induction occurred only in Y. lipolytica strain and reached the highest level as a response to PQ exposure. In general, antioxidant enzymes were more expressed in Y. lipolytica than in P. pastoris. The enzyme superoxide dismutase was induced in both strains under all the oxidant conditions but was dependent on the cellular growth phase, being undetectable in non-growing cells, whereas glutathione reductase was more induced in those conditions. Hydrogen peroxide was the most efficient inducer of catalase. Both yeast cultures underwent no cellular growth inhibition with increased air pressure, indicating that these yeast species were able to adapt to the oxidative stressful environment.     

An application of the monotone iterative method to a combustion problem in porous media

Problems related to combustion fronts in porous media have been studied by many authors recently, see e.g. [Y. Akkutlu, Y.C. Yortsos, The dynamics of in-situ combustion fronts in porous media, Combust. Flame 134 (2003) 239–247; J.C. da Mota, W. Dantas, D. Marchesin, Combustion fronts in porous media, SIAM J. Appl. Math. 62 (2002) 2175–2198; D.A. Schult, B.J. Matkowsky, V.A. Volpert, A.C. Fernandez-Pello, Forced forward smolder combustion, Combust. Flame 104 (1996) 1–26]. Most of this interest is due to the combustion process for oil recovery.In this paper we construct monotone iteractions for a Cauchy problem arising from a combustion model in a porous medium derived in [J.C. da Mota, S. Schecter, Combustion fronts in a porous medium with two layers, J. Dynam. Differential Equations 18 (3) (2006) 615–665]. We conclude that the monotone iteractions converge to a unique solution of this Cauchy problem, globally in time.     

Algebraic solutions of integrodifferential CRPA equations

We formulate a version of the collisional Random-Phase-Approximation obtained from the linearization of a general kinetic equation. The resulting equations are formally solved in three different situations depending on the way the previous history is considered. An application of the formalism here developed to a two level model is made.     

A simplified polarographic determination of dissolved Cd(II) at the 10?10 M level

Summary To simplify the determination of dissolved Cd(II) in water and sea water-like solutions at the 10^–10–10^–9 M level an automated concentration step was developed consisting of percolating about 21 of sample over a column with an immobilized reagent (ED₃A) and dissolving the trapped cadmium in 0.1 M nitric acid. A concentration factor of 50 or more is easily obtained. Recoveries are about 90%. With anodic stripping differential pulse polarography as a final determination technique overall standard deviations are in the range of 0.1–0.4·10^–10 Mol of Cd.On leave from Lisbon University, Portugal     

Nuclear dynamics with a wavelet representation

Fluctuation-dissipation aspects in heavy-ion reactions at intermediate energies are addressed in the framework of the DYWAN model. This new approach provides a strongly compressed representation of nuclear systems by expanding the corresponding wavefunctions in a basis of wavelets. Comparisons with the experimental results in nucleus—nucleus and nucleon—nucleus reactions are performed. These preliminary results provide a good test of working for the model and open new perspectives in the modeling of nuclear reactions.     

Topological self-dual configurations in a Maxwell–Higgs model with a CPT-odd and Lorentz-violating nonminimal coupling

We have studied the existence of topological self-dual configurations in a nonminimal CPT-odd and Lorentz-violating (LV) Maxwell–Higgs model, where the LV interaction is introduced by modifying the minimal covariant derivative. The Bogomol’nyi–Prasad–Sommerfield formalism has been implemented, revealing that the scalar self-interaction implying self-dual equations contains a derivative coupling. The CPT-odd self-dual equations describe electrically neutral configurations with finite total energy proportional to the total magnetic flux, which differ from the charged solutions of other CPT-odd and LV models previously studied. In particular, we have investigated the axially symmetrical self-dual vortex solutions altered by the LV parameter. For large distances, the profiles possess general behavior similar to the vortices of Abrikosov–Nielsen–Olesen. However, within the vortex core, the profiles of the magnetic field and energy can differ substantially from ones of the Maxwell–Higgs model depending if the LV parameter is negative or positive.     

A theoretical study of rate coefficients for the O + NO vibrational relaxation

Quasi-classical trajectories have been integrated to study the vibrational relaxation of the O + NO(v) process as a function of the initial vibrational quantum number for T = 298 K, 1500 K, and 3000 K. Two reliable potential energy surfaces have been employed for the A' and A' doublet states of NO2. The calculated vibrational relaxation rate constants show a nearly v-independent behavior at room temperature and a moderate increase with v for higher temperatures. Although deviating significantly from the recommended values, good agreement with recent experimental results has been obtained. The importance of multi-quantum transitions is also analyzed.     

Pyrolysis of petroleum fractions

Dynamic kinetic analyses were performed on different Brazilian petroleum fractions by thermogravimetry. The data were treated by a multiple heating rate methodology. The apparent activation energies for the light and middle fractions within the range of 62–74 kJ mol⁻¹ and for heavy distillation residues were within the range of 80–100 kJ mol⁻¹ at lower conversions and 100–240 kJ mol⁻¹ at higher conversions. The kinetic study can be a criterion for tells apart the main phenomena involved in the thermal behavior of the refinery feedstock.     

Two-column simulated moving-bed process for binary separation

A two-column simulated moving-bed system has been developed for binary separation. The system combines a flexible node design, robust pump configuration, and cyclic flow-rate modulation to exploit the benefits of simulated counter-current operation. The feasibility of the proposed two-column system is demonstrated on the linear separation of two nucleosides by reversed phase. Emphasis is given to the potentialities of the process compared to single-column batch chromatography with recycling for the same amount of stationary phase. The performance of the proposed two-column process is verified with laboratory-scale experiments and detailed simulations for different difficulties in separation and desorbent-to-feed ratios.     

HN2(2A') electronic manifold. I. A global ab initio study of first two states

A detailed ab initio multireference configuration interaction calculation with a standard aug-cc-pVTZ basis set is reported for the 1(2)A' and 2(2)A' states of the title system. The aim is to establish the dissociation scheme of all channels, while revealing the 2(2)A'/3(2)A' seam of conical intersections consistent with the crossings in the diatomic fragments. An ab initio mapping of linear NNH and T-shaped and linear NHN loci of conical intersections is also reported, jointly with a discussion of the topological features associated to a newly reported 2(2)A'/3(2)A' crossing seam.