The use of DSC and FT-IR spectroscopy for evaluation of oxidative stability of interesterified fats

The aim of this paper was to assess the oxidative stability of structured lipids synthesized by enzymatic interesterification of a blend of lard and rapeseed oil with concentrates of n ? 3 fatty acids. Differential scanning calorimetry was used to evaluate the oxidation induction time of interesterified fats as a parameter assessing resistance of tested fats to their thermal-oxidative decomposition. Moreover, the IR spectra registered in the classic spectral range (4000–400 cm^?1) were used to differentiate the samples of interesterified fats. The results show that the interesterification process decreased the induction time. Increased content polar fraction in the interesterified fatty product can reduce its resistance to oxidation. FT-IR data of selected spectral ranges correlate with the value of induction time at a statistically significant level. This is a proof that chemical changes occurring during different treatments of the starting mixture can be monitored by FT-IR spectroscopy. Moreover, obtained correlations can be used for the evaluation of an induction value of an unknown oil sample.     

Fixed points of some nonlinear operators in spaces of multifunctions and the Ulam stability

We prove a fixed point theorem for nonlinear operators, acting on some function spaces (of set-valued maps), which satisfy suitable inclusions. We also show some applications of it in the Ulam type stability.     

Exact Confidence Intervals of the Extended Orey Index for Gaussian Processes

In this paper exact confidence intervals for the Orey index of Gaussian processes are obtained using concentration inequalities for Gaussian quadratic forms and discrete observations of the underlying process. The obtained result is applied to Gaussian processes with the Orey index which not necessarily have stationary increments.     

Preparation of nano-dispersed lithium niobate by mechanochemical route

Interaction in the system of lithium carbonate–niobium pentoxide during mechanochemical treatment in air and water has been studied. Prepared samples have been investigated with the help of DTA–TG, XRD, FTIR, Raman, and UV–Vis spectroscopy, adsorption–desorption of nitrogen and TEM. Activation of reagents and direct mechanochemical synthesis are observed at 600–850 and 1,000 rpm, respectively. Lithium metaniobate samples prepared via milling possess high dispersity, defective structure, and improved photocatalytic activity, including under visible illumination.     

L-argininato copper(II) complexes in solution exert significant selective anticancer and antimicrobial activities

A search for new drugs that overcome the multidrug resistance of microorganisms or are effective against cancer cells prompted us to investigate the binary and ternary Cu(II) complexes containing L-arginine, [CuCl(L-Arg)(phen)]Cl·2H₂O (phen = 1,10-phenanthroline) ( 1 ) and [Cu(L-Arg)₂(H₂O)]C₂O₄·6H₂O ( 2 ), for which crystal and molecular structures were characterized previously. In order to discuss the biological function, the complexes have been screened for their antitumor activity against A549 (human lung cancer cells), HepG2 (human liver hepatocellular carcinoma cells) and antimicrobial activity. To identify the complexes forms existing in the solutions of 1 and 2 crystals, the results obtained from EPR, NIR–Vis–UV and MS (mass spectrometry) measurements were correlated with those from analysis of potentiometric titration of Cu(II)―L-Arg and Cu(II)―L-Arg―phen systems. This comprehensive study indicated that the [Cu(L-Arg)(phen)]²⁺ and [Cu(L-Arg)₂]²⁺ species are dominant in the solution. Complexes 1 and 2 were found to present specific ligand-dependent cytotoxic and antiproliferative potential against cancer cells. They also show antibacterial activity against Gram-positive and Gram-negative bacteria as well as display antifungal properties.     

Bis(N‐Confused Porphyrin) as a Semirigid Receptor with a Chirality Memory: A Two‐Way Host Enantiomerization through Point‐to‐Axial Chirality Transfer

The adduct formation of protonated bis(N‐confused porphyrin) (BNCP, 3,3′‐bis(meso‐tetratolyl‐2‐aza‐21‐carbaporphyrin) with chiral anions, carboxylic acids, and alcohols was studied in solution by means of ¹H NMR and circular dichroism (CD) spectroscopic analysis and DFT methods. The addition of enantiopure guests to the acidified BNCP resulted in optical activity that vanished after neutralization. Pairs of the ¹H NMR‐distinguishable diastereomers were formed when enantiopure guests were applied, although a single form was observed upon the addition of the racemic mixtures in each case. Unidirectional configuration change that led to diastereomeric excess was observed in several instances. Such an excess was memorized by metalation of the adducts with AgBF₄, thus resulting in optically active silver(III) complexes of BNCP with some enantiomeric excess. Absolute configurations of BNCP cations and bis(zinc) and bis(silver(III)) complexes were determined on the basis of time‐dependent (TD)‐DFT calculations of their CD spectra. It was shown that some of the chiral carboxylates induced opposite directions of enantiomerization of di‐ and tetracations or di‐/tetracation and bis(zinc) complexes. The source of the optical activity of the equimolar diastereomeric mixture of adducts is discussed.     

The potential of biocarbon as CO2 adsorbent in VPSA unit

Journal of Thermal Analysis and Calorimetry - The pressure drop is one of the most important factors leading to the distribution of refrigerant in the micro-channel heat exchanger. The main...     

Electrochemical properties of exfoliated graphite affected by its two-step modification

Exfoliated graphite (EG) was modified by a two-stage process consisting of electrochemical oxidation followed by the thermal treatment. Within the former one, the process of re-intercalation of H₂SO₄ into the EG by linear sweep voltammetry was carried out. Thus, obtained re-intercalated EG underwent heat treatment at 800 °C in order to synthesize re-exfoliated EG (re-EG). The electrochemical features of the re-EG were examined in the model process of phenol electrooxidation carried out by cyclic voltammetry technique in alkaline solution with and without phenol addition. Taking into account the anodic charges as a main criterion of electrochemical activity, it was found that the modification of EG caused over twofold improvement of its electrochemical activity. This behavior is related with the changes within the chemical composition of modified EG surface and on much smaller scale with the modification of its structure. The degree of electrochemical activity improvement depends on the conditions under which the processes of re-intercalation and re-exfoliation were performed. The results of Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analysis supported by the data of the Brunauer-Emmett-Teller (BET) surface area and scanning electron microscope (SEM) observations allow an understanding of the physicochemical properties of re-exfoliated EG and enhancement of its electrochemical activity.