On stable and explicit numerical methods for the advection–diffusion equation

In this paper two stable and explicit numerical methods to integrate the one-dimensional (1D) advection–diffusion equation are presented. These schemes are stable by design and follow the main general concept behind the semi-Lagrangian method by constructing a virtual grid where the explicit method becomes stable. It is shown that the new schemes compare well with analytic solutions and are often more accurate than implicit schemes. In particular, the diffusion-only case is explored in some detail. The error produced by the stable and explicit method is a function of the ratio between the standard deviation σ₀ of the initial Gaussian state and the characteristic virtual grid distance ΔS. Larger values of this ratio lead to very accurate results when compared to implicit methods, while lower values lead to less accuracy. It is shown that the σ₀/ΔS ratio is also significant in the advection–diffusion problem: it determines the maximum error generated by new methods, obtained with a certain combination of the advection and diffusion values. In addition, the error becomes smaller when the problem becomes more advective or more diffusive.     

Effects of extreme pressure and anti-wear additives on surface topography and tool wear during MQCL turning of AISI 1045 steel

The paper presents an original study of the influence of extreme pressure and anti-wear (EP/AW) additives on the surface topography of double-phase steel during turning with different cooling media and variable flow rates. The obtained surface topographies were compared using frequency and fractal analyses for dry, minimum quantity cooling lubrication (MQCL), and MQCL + EP/AW methods. Results showed that the addition of phosphate ester-based additives to an active medium caused the formation of tribofilm on the tool-chip interface and thus a change in the lubricating properties by reducing friction. The tool wear and the formation of the thin-layered tribofilm were also incorporated. The application of the MQCL method with the EP/AW additives led to a decrease in particular surface topography parameters from 8 % to 38 % in comparison with the effects of dry cutting and from 6 % to 35 % in comparison with the effects of machining under MQCL conditions. An exception was the result obtained for the surface roughness height parameter Sp, which was higher than that obtained after the MQCL + EP/AW process for the lowest investigated feed per revolution f = 0.1 mm/rev. This observation was correlated with the uneven formation of the tribofilm on the machined surface. The phosphate ester-based additive used in the MQCL + EP/AW method contributed to achieving tool wear that was less than that obtained by the processes conducted under dry and MQCL conditions.     

Postharvest Ozone Treatment of Cucumber as a Method for Prolonging the Suitability of the Fruit for Processing

Ground cucumber, as a nutrient, is a product highly valued by consumers in both fresh and processed form. The aim of the research was to develop a technology for extending the shelf life of ground cucumbers stored at room temperature before further processing. For this purpose, ozone treatment was utilized and the changes in the mesocarp and the peel puncture strength of the ozonated and the control cucumbers during storage were measured. Ozonation extended the shelf life of ground cucumber fruit making them useful for longer time for further processing.     

Porous structure of highly crosslinked styrene-divinylbenzene copolymers

Porous structure of two series of styrene (S)-divinylbenzene (DVB) copolymers has been studied. The copolymers were prepared by suspension copolymerization of the monomers (50 wt.-% of DVB) in the presence of heptane-toluene mixtures as inert diluents. The fraction of diluents in the polymerization system or heptane: toluene ratio was changed. Both the pore volume and specific surface area increase as does dilution or the fraction of heptane in diluents, but the measured values change depending on sample pretreatment. A mechanism of structure built up is discussed and the porosity changes explained in terms of a microsyneresis of inhomogeneous S-DVB copolymer gel.     

Fullerene C60 as an inhibitor of high temperature lipid oxidation

Non-isothermal oxidation of a model saturated lipid (stearic acid) in the bulk phase in the presence of fullerene C₆₀ at concentrations of 1–8 mM was monitored by differential scanning calorimetry in order to determine the kinetic parameters that describe the global first order oxidation process. The activation energies, pre-exponential factors, and rate constants calculated by the Ozawa–Flynn–Wall method for the first detectable exothermic effect of oxidation, indicate the antioxidant behavior of C₆₀ over a wide range of temperatures that makes it a non-corrosive agent effectively increasing the oxidative stability of lubricants and biolubricants.     

Increased Bioactive Lipids Content in Human Subcutaneous and Epicardial Fat Tissue Correlates with Insulin Resistance

Obesity is a risk factor for metabolic diseases. Intramuscular lipid accumulation of ceramides, diacylglycerols, and long chain acyl-CoA is responsible for the induction of insulin resistance. These lipids are probably implicated in obesity-associated insulin resistance not only in skeletal muscle but also in fat tissue. Only few data are available about ceramide content in human subcutaneous adipose tissue. However, there are no data on DAG and LCACoA content in adipose tissue. The aim of our study was to measure the lipids content in human SAT and epicardial adipose tissue we sought to determine the bioactive lipids content by LC/MS/MS in fat tissue from lean non-diabetic, obese non-diabetic, and obese diabetic subjects and test whether the lipids correlate with HOMA-IR. We found, that total content of measured lipids was markedly higher in OND and OD subjects in both types of fat tissue (for all p?<?0.001) as compared to LND group. In SAT we found positive correlation between HOMA-IR and C16:0-Cer (r?=?0.79, p?<?0.001) and between HOMA-IR and C16:0/18:2 DAG (r?=?0.56, p?<?0.001). In EAT we found a strong correlation between C16:0-CoA content and HOMA-IR (r?=?0.73, p?<?0.001). The study showed that in obese and obese diabetic patients, bioactive lipids content is greater in subcutaneous and epicardial fat tissue and the particular lipids content positively correlates with HOMA-IR.     

Computational spectroscopy and DFT investigations into nitrogen and oxygen bond breaking and bond making processes in model deNOx and deN2O reactions

Molecular DFT modeling combined with computational spectroscopy (EPR and IR) were applied for analysis of the NO bond breaking and NN and OO bond making in the context of deNO_x and deN₂O reactions. Interaction of NO, N₂O and NO₂ with cationic (transition metals) and anionic (surface O²⁻ ions) centers was explored at the molecular level. The elementary events such as reactant coordination, charge and spin redistributions, which are principal molecular constraints for efficient decomposition of the nitrogen oxides (N₂O and NO) were discussed. Particular attention was paid to dynamics of the NO bond cleavage in N₂O molecule through electron and oxygen atom transfer routes, evaluation of preferable coordination modes of NO, discrimination between inner- and outer-sphere mechanism of NN bond formation, and the influence of spin and electronic redistribution on the reaction course (spin catalysis). Owing to their simplicity and well known surface chemistry, model systems selected for studies of such processes include MoO_x/SiO₂, MgO and ZSM-5 zeolite exchanged with various transition metal ions (TMI) of different electron configuration and spin multiplicity: Mo⁵⁺ (d¹, ²D) Fe³⁺, Mn²⁺, Cr⁺ (d⁵, ⁶S), Fe²⁺ (d⁶, ⁵D), Co²⁺ (d⁷, ⁴F), Ni²⁺ (d⁸, ³F), Cu²⁺ (d⁹, ²D) and Cu⁺, Zn²⁺ (d¹⁰, ¹S).