Discrete simulation methods in combustion kinetics

A hybrid method, intermediate between diffential equation solution and Monte Carlo, is described for calculating the consequences of an assumed mechanism and set of rate constants. It is compared with standard methods as to simplicity, efficiency, stability, and other features. Situations in which it can replace or supplement other procedures are discussed. An example calculation is presented. It consists of a routine simulation of C₃H₈ oxidation with a 37-reaction mechanism and variable temperature, along with a comparison with results obtained with a collapsed mechanism, the latter simplication being one that is particularly facile when discrete stimulation is used.     

Neither Excessive Nitric Oxide Accumulation nor Acute Hyperglycemia Affects the N-Acetylaspartate Network in Wistar Rat Brain Cells

The N-acetylaspartate network begins in neurons with N-acetylaspartate production catalyzed by aspartate N-acetyltransferase from acetyl-CoA and aspartate. Clinical studies reported a significant depletion in N-acetylaspartate brain level in type 1 diabetic patients. The main goal of this study was to establish the impact of either hyperglycemia or oxidative stress on the N-acetylaspartate network. For the in vitro part of the study, embryonic rat primary neurons were treated by using a nitric oxide generator for 24 h followed by 6 days of post-treatment culture, while the neural stem cells were cultured in media with 25–75 mM glucose. For the in vivo part, male adult Wistar rats were injected with streptozotocin (65 mg/kg body weight, ip) to induce hyperglycemia (diabetes model) and euthanized 2 or 8 weeks later. Finally, the biochemical profile, NAT8L protein/Nat8l mRNA levels and enzymatic activity were analyzed. Ongoing oxidative stress processes significantly affected energy metabolism and cholinergic neurotransmission. However, the applied factors did not affect the N-acetylaspartate network. This study shows that reduced N-acetylaspartate level in type 1 diabetes is not related to oxidative stress and that does not trigger N-acetylaspartate network fragility. To reveal why N-acetylaspartate is reduced in this pathology, other processes should be considered.     

Electric and magnetic properties of lanthanum barium cobaltite

The cubic Ba_0.5La_0.5CoO_3-δ was synthesized using solid state reaction. The structural properties were determined by the simultaneous refinement of Synchrotron Powder X-ray Diffraction and Neutron Powder Diffraction data. Iodometric titration was used to examine the oxygen stoichiometry and average cobalt oxidation state. Low-temperature magnetic studies show soft ferromagnetic character of fully oxidized material, with θ_P = 198(3) K and µ_eff = 2.11(2) µ_B. Electric measurements show the thermally activated nature of conductivity at low temperatures, whereas, due to the variable oxidation and spin state of cobalt, a single charge transport mechanism cannot be distinguished. Around room temperature, a wide transition from thermally activated conductivity to semi-metallic behavior is observed. Under the inert atmosphere, the oxygen content lowers and the cation ordering takes place, leading to coexistence of two, ordered and disordered, phases. As a result of this change, thermally activated conductivity is observed also at high temperatures in inert atmosphere.     

Changes of Relative Crystallinity of Potato Starch Under Gamma Irradiation

Indices of relative crystallinity of starch samples after gamma irradiation in dry form or in potatoes have been determined by differential and integral methods and compared with those calculated for corresponding reference samples. In the case of dry samples, the diminution of relative crystallinity was observed after gamma ray irradiation. In the case of starch samples extracted from irradiated potatoes, the influence of drying conditions was additionally observed. The diminution of relative crystallinity seems to be accompanied by destruction of long-range ordering as observed by SAXS experiment.