Synthesis of novel silica-gel-supported thiosemicarbazide and its properties for solid phase extraction of mercury

A new thiosemicarbazidе-modi?ed silica gel (SG-THSC) sorbent was prepared. The sorbent was quantified by adsorption of mercury ions on silica gel, desorption and then spectrophotometry detection of mercury ions. The retention parameters (sample flow rate, eluent type, sample volume, presence of foreign ions, shaking time, sample flow rate and volume, eluent condition, interfering substances) were investigated. The quantitative recovery (>95%) of Hg(II) ions could be obtained by use of 5 mL of 6 mol L^?1 HCl. The adsorption capacity of SG-THSC was found to be 98.3 mg g^–1 at optimum pH. The maximum preconcentration factor was 400. The technique detection limit was 70 ng L^–1, and the relative standard deviation was lower than 4.0% (n = 6). The studied sorbent was applied to preconcentrate the trace Hg(II) from the mineralised residues of fish and seawater samples.     

Refined model of elastic nanoindentation of a half-space by the blunted Berkovich indenter accounting for tangential displacements on the contact surface

Elastic contact between a non-ideal Berkovich indenter and a half-space is investigated. The derived mathematical model of the contact allows for tangential displacements of the boundary points of the half-space. The tip of the blunted indenter is simulated as a smooth surface. The boundary element method is implemented in the model for numerical simulation of nanoindentation. The relative deviation function is introduced and calculated to quantify the influence of the tangential displacements on the load–displacement curves. A simple expression is derived for the impact of the tangential displacements on the values of the reduced Young’s modulus determined due to nanoindentation studies. The refined model was successfully applied to simulate the experimental load–displacement curves gained by elastic nanoindentations of flat LiF and KCl samples. Such values of the indenter bluntness (the varying parameter) were found that the simulated load–displacement curves coincided with those of the experimental data at displacements higher than 7.5 nm. The model neglecting tangential displacements gives slightly differing values for the parameter of the indenter bluntness.

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Experimental Evaluation of Food-Grade Semi-Refined Carrageenan Toxicity

The safety of food additives E407 and E407a has raised concerns in the scientific community. Thus, this study aims to assess the local and systemic toxic effects of the common food additive E407a in rats orally exposed to it for two weeks. Complex evaluations of the effects of semi-refined carrageenan (E407a) on rats upon oral exposure were performed. Local effects of E407a on the intestine were analyzed using routine histological stains and CD68 immunostaining. Furthermore, circulating levels of inflammatory markers were assessed. A fluorescent probe O1O (2- (2′-OH-phenyl)-5-phenyl-1,3-oxazole) was used for evaluating the state of leukocyte cell membranes. Cell death modes of leukocytes were analyzed by flow cytometry using Annexin V and 7-aminoactinomycin D staining. Oral administration of the common food additive E407a was found to be associated with altered small and large intestinal morphology, infiltration of the lamina propria in the small intestine with macrophages (CD68⁺ cells), high systemic levels of inflammation markers, and changes in the lipid order of the phospholipid bilayer in the cell membranes of leukocytes, alongside the activation of their apoptosis. Our findings suggest that oral exposure to E407a through rats results in the development of intestinal inflammation.     

Scattering and reflective properties of ordered mesoporous silica films

Ordered mesoporous and nonporous silica films were studied by analysis of reflection spectra and hemispherical elastic light scattering (HELS). The real and imaginary parts of the index of the films were estimated from the reflection spectra. The HELS angular distribution of the mesoporous film shows a minimum, which has been interpreted as an interference pattern coming from the beams scattered by the mesopores.     

Evaluation of Aluminium Alloys Degradation in Aging Aircraft

The specimens of D16ATHB and B95T1 aluminum alloys (like 2024T3 and 7075T6 alloys, respectively) cut out from lower and upper wing skins of AN-12 aircraft after 40 years exploitation are investigated. The dependencies between mechanical characteristics and electrical conductivity obtained for long-term exploited alloys show a radically different trend in comparison with known for alloys in as-received state after various heat treatments. Such data are explained by results of materials fine structure study. Nondestructive eddy current (EC) method and instrument for aluminum alloys degradation monitoring in aging aircraft are analyzed.     

Laser‐Assisted Strain Engineering of Thin Elastomer Films to Form Variable Wavy Substrates for Cell Culture

Endothelial and epithelial cells usually grow on a curved environment, at the surface of organs, which many techniques have tried to reproduce. Here a simple method is proposed to control curvature of the substrate. Prestrained thin elastomer films are treated by infrared laser irradiation in order to rigidify the surface of the film. Wrinkled morphologies are produced upon stress relaxation for irradiation doses above a critical value. Wrinkle wavelength and depth are controlled by the prestrain, the laser power, and the speed at which the laser scans the film surface. Stretching of elastomer substrates with a “sand clock”‐width profile enables the generation of a stress gradient, which results in patterns of wrinkles with a depth gradient. Thus, different combinations of topography changes on the same substrate can be generated. The wavelength and the depth of the wrinkles, which have the characteristic values within a range of several tens of µm, can be dynamically regulated by the substrate reversible stretching. It is shown that these anisotropic features are efficient substrates to control polarization of cell shapes and orientation of their migration. With this approach a flexible tool is provided for a wide range of applications in cell biophysics studies.     

Microstructure Evolution and Pinning of Boundaries by Precipitates in a 9 pct Cr Heat Resistant Steel During Creep

Structural changes in a 9 pct Cr martensitic steel during a creep test at 923 K (720 °C) under the applied stress of 118 MPa were examined. The tempered martensite lath structure (TMLS) was characterized by M₂₃C₆-type carbide particles with an average size of about 110 nm and MX-type carbonitrides with a size of 40 nm. The M₂₃C₆ particles were located on the packet/block/lath boundaries, whereas the MX precipitates were distributed homogeneously throughout TMLS. TMLS in the grip portion of the crept specimen changed scarcely during the tests. In contrast, the structural changes in the gauge section of the samples were characterized by the evolution of relatively large subgrains with remarkably lowered density of interior dislocations within former martensite laths. The formation of a well-defined subgrain structure in the gauge section was accompanied by the coarsening of M₂₃C₆ carbides and precipitations of Laves phase during creep. The most pronounced structural changes occurred just at the beginning of the tertiary creep regime, which was interpreted as a result of the change in the mechanism of grain boundary pinning by precipitates.