Internalization of (bis)phosphonate-modified cellulose nanocrystals by human osteoblast cells

Covalent conjugation of (bis)phosphonate group-containing molecules, sodium Alendronate (Aln) and 3-AminoropylPhosphoric Acid (ApA), to Cellulose nanocrystals (CNCs) was performed via oxidation/Shiff-base reaction. Further fluorescent labelling with Rhodamine B Iso ThioCyanate (RBITC) was performed to follow CNCs interaction and potential internalization with/in human osteoblasts by confocal microscopy. Complementary analyses were applied to identify the conjugation (Atenuated Total Reflectance–Fourier Transform Infrared and UV–VIS spectroscopies), physico-chemical (Dynamic Light Scattering and Nanoparticle Tracking Analysis) and morphological (Transmission Electron Microscopy) features of native and ApA/Aln-modified CNCs in physiologically relevant environments (Phosphate Buffer Saline, Advanced Dulbecco’s Modified Eagle Medium). While conjugation did not affect the CNCs` size, the RBITC-labelling promotes their aggregation. Faster (1 h vs. 2 h) uptake by osteoblasts of RBITC-CNCoxAln, compared to RBITC-CNCoxApA, and no-internalization (in 24 h) of native RBITTC-CNC, indicate a higher affinity of Aln-modified CNCs to the cells, while all CNCs (in 0.25–0.06 wt%) promote the cell growth. Aln/Apa-modified CNCs shows high potential in drug-delivery for bone therapies, and theranostics.     

Laser microsampling and multivariate methods in provenance studies of obsidian artefacts

The provenance of obsidian artefacts and raw materials was studied by the multivariate statistical analysis of forty-five samples using elemental composition data obtained by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). One ICP-MS instrument equipped with a quadrupole mass filter and the other based on a time-of-flight analyser were coupled to the same type of laser ablation device (Nd:YAG 213 nm), thereby affording a comparison of the different mass spectrometers in terms of precision and verification of the consistency of the results. The influence of surface roughness (polished raw material vs artefact) and microinhomogeneity on the LA-ICP-MS signal was studied under the optimised working conditions of the laser ablation device. Principal component analysis, correspondence analysis, independent component analysis, multi-dimensional scaling, Sammon mapping and fuzzy cluster analysis were applied and compared in order to reveal statistically significant compositional differences between particular geological sites and to disclose the provenance of the raw materials used in manufacture of the artefacts. Twenty-seven artefacts and eighteen raw material samples from natural resources in the Czech Republic, Slovakia, Italy, Greece, Syria, Iraq, Turkey, Mexico and Nicaragua were examined with special attention focused on samples from Moravia (Czech Republic) and some Near East sites (Tell Arbid, Tell Asmar). The Carpathian origin of the obsidian artefacts was investigated in the Moravian samples using the Pb, Rb and U contents. The Near East samples were classified according to their Sr, Ba, Zr and REE contents as per-alkaline obsidians (Bingöl A/Nemrut Da?) originating from Southeast Anatolia.     

Heat transfer in a jacketed agitated vessel equipped with multistage impellers

In this work, heat transfer via the cylindrical part of the jacket in an agitated vessel has been investigated. Heat transfer coefficients were determined using the transient method based on measuring the temperature dependency of the liquid batch on time. A multistage impeller made of two impellers was used in a cylindrical vessel with dished bottom. The lower impeller was a curved blade turbine with the diameter of d = 100 mm and the upper impeller was either a pitched three-blade or pitched four-blade impeller with the diameter of d₁ = 67 mm. Three different impeller clearances in a multistage configuration, H₃/d₁ = 1, 1.5, and 2, were used in our measurements. The vessel was equipped with two baffles. Experimental results were evaluated using the Euler’s method and nonlinear regression procedure in the Matlab® software and they are summarized in form of Nusselt number correlations describing their dependency on the Reynolds number.     

Improvement of enzyme carbon paste-based biosensor using carbon nanotubes for determination of water-soluble analogue of vitamin E

The catalytic oxidation of a synthetic water-soluble analogue of vitamin E (α-tocopherol, Trolox) by tyrosinase enzyme in the presence of molecular oxygen was studied using electrochemical techniques. This specific enzymatic reaction was exploited for the preparation of a biosensor based on the amperometric reduction of the electroactive product (α-tocoquinone) formed. An electroactive surface of the transducers used was covered with a thin conductive layer of Nafion containing tyrosinase. Significant progress in sensitivity towards polyphenolic compounds such as Trolox was achieved at CPE with carbon nanotubes immobilised on its surface (CPE/CNTs) as electric transducers. The biosensor so developed can be used for the direct determination of total phenolic content (TPC). This important nutrition value can be expressed as the mass equivalent of Trolox, i.e. Trolox equivalent antioxidant capacity (TEAC), which could be used as an alternative to the evaluations currently used based on spectrophotometric methods such as total radical-trapping antioxidant parameter (TRAP), ferric reducing-antioxidant power (FRAP) or 1,1-diphenyl-2-picrylhydrazyl spectrometric assay (DPPH). The effects of the enzyme amount in the Nafion layer (3.0 µg), the influence of the nanoparticles present, the optimal pH value suitable for enzymatic activity (7.0), and the kinetics of enzymatic and electrochemical reactions were studied using cyclic voltammetry (CV). The determination of optimal conditions for amperometry in batch configuration (working potential, speed of stirring, volume of sample, calibration curve, etc.) was not a target of this electrochemical study.     

Topological Horseshoes of Traveling Waves for a Fast–Slow Predator–Prey System

We show the existence of a set of periodic traveling waves in a system of two scalar reaction diffusion equations, which is in one-to-one correspondence with a full shift on two symbols. We use a novel combination of rigorous numerical computations and the topological techniques of the Conley index theory. This approach is quite general, and this paper is intended as a demonstration of its usefulness and applicability.     

The Thermal Decomposition of Triple-Base Propellants

The thermal decompositions of a double-base propellant (DB), five triple-base propellants (TB) and nitroguanidine (NGV) were examined. The kinetic parameters were evaluated using the ASTM, Kissinger, Rogers-Morris, Freeman-Carroll and Borchardt-Daniels methods. The values of the orders of some of the chemical reactions (n), like some values of activation energies (E_a), do not have any physical meaning, but they represent the manner of propellant decomposition and prove that the mechanism of the reaction changes during the decomposition process. As a result of this fact, differences appear in the evaluated kinetic parameters between various methods. This revised version was published online in August 2006 with corrections to the Cover Date.     

The effect of a surface on the dynamic and thermodynamic properties of S=1 Heisenberg ferromagnet with biquadratic exchange

Properties of semi-infinite (S=1) Heisenberg ferromagnet with biquadratic exchange were studied in terms of surface exchange (=I_S/I) and biquadratic coupling (a). It was shown that a strict correlation exists, depending on , between the type of surface spin waves (acoustic or optical) and the mean-field (MF) critical temperature, bulk (T_c) and surface T_c^S>T_c (for ). Within the framework of the Landau–Ginsburg theory for semi-infinite simple cubic ferromagnet, a detailed study is presented of the critical behaviour of the system, in particular in the vicinity of the tricritical point which is the consequence of the biquadratic interaction. It is shown that tricritical exponents satisfy exactly the scaling relations for d=3. The analysis of the spin–spin correlation function within the framework of the same theory, shows that there occurs the critical magnetic scattering of low-energy electrons (LEED) from the surface in the case , when the ordering temperature T_c^S is approached from above (from paramagnetic phase). In the opposite case, , there occurs no surface critical scattering. It was also shown that in the vicinity of the tricritical point, the biquadratic interaction increases the range of validity of the MF approximation.     

Theoretical study of structure and properties of hexuronic acid and <Emphasis Type="SmallCaps">d</Emphasis>-glucosamine structural units of glycosaminoglycans

The Becke3LYP functional of DFT theory was used to investigate molecular structure and sodium affinity of the systems CH₃CO₂Na (1), CH₃–O–SO₃Na (2), CH₃–NH–SO₃Na (3), saccharide_1Na₂ (4), saccharide_2Na (5), saccharide_3Na₃ (6), saccharide_4Na₂ (7), and saccharide_5Na₂ (8), respectively, which are models of N- and O-sulfate glycosaminoglycans. Interaction enthalpies, entropies and Gibbs energies of the sodium-coordinated systems in the gas phase were determined with the B3LYP/6-311+G(d,p) and B3LYP/6-31+G(d) methods. The computed Gibbs energies, ΔG ^o , of model systems 1–3 are negative and span a rather broad energy interval (from −500 to −1,500 kJ mol⁻¹). Gibbs interaction energies for sodium acetate, sodium sulfate and sodium sulfamate functions of the five saccharides, systems 4–8 are always lower than those values found for the model compounds 1–3. The ionization of sodium salts of saccharides studied in gas phase is in most cases connected with considerable conformational rearrangement of the ionic species. This rearrangement causes an additional energetic stabilization of anionic species and is connected with the substantial release of entropy.     

More on betweenness-uniform graphs

We study graphs whose vertices possess the same value of betweenness centrality (which is defined as the sum of relative numbers of shortest paths passing through a given vertex). Extending previously known results of S. Gago, J. Hurajová, T. Madaras (2013), we show that, apart of cycles, such graphs cannot contain 2-valent vertices and, moreover, are 3-connected if their diameter is 2. In addition, we prove that the betweenness uniformity is satisfied in a wide graph family of semi-symmetric graphs, which enables us to construct a variety of nontrivial cubic betweenness-uniform graphs.     

Effect of waste tires addition on a low-temperature hydrovisbreaking process of vacuum residue

Most of the resources used for energy have a fossil origin and they are non-renewable materials. Using mixtures of waste materials with the currently used non-renewable materials can improve the renewability of the energy production. The goal of this work was to explore the effect of waste tire addition on a hydrovisbreaking process at low temperature. Four tests were carried out at 300 °C in H₂ with different feedstocks: (1) vacuum residue; (2) tires; (3) 37.5wt% tires + 62.5wt% vacuum residue; (4) 15wt% tires + 85wt% vacuum residue. Dynamic viscosity, simulated distillation, density, elemental analysis (C, H, N, S% content) by ICP and analysis of gaseous products by GC–MS were carried out for all products. Content of insoluble compounds in hexane was estimated for the products from test (1) and vacuum residue. TGA analyses of the tires were carried out. The addition of tires to the vacuum residue brought a positive effect to increasing the yield of lighter products in the final liquid product. Densities and composition determinated by elemental analyses were similar for feedstock and products. The dynamic viscosity (60 °C) decreased from 24,550 to 17,700 mPa s for test (1) and to 1640 mPa s for test (3).