Toughening of Semicrystalline and Amorphous Polylactide with Atactic Polyhydroxybutyrate

Biodegradable and biocompatible blends of polylactide with atactic poly([R,S]-3-hydroxybutyrate) were studied. Cold-crystallized blends exhibit lamellar–spherulitic morphology. Lamellae thickness and crystallinity, controlled by conditions of annealing, surprisingly do not depend on blend composition. In contrast, due to partial miscibility, the glass transition, cold crystallization, and melting temperatures depend on composition. Mechanical performance of polylactide, including drawability and toughness, is improved in both amorphous and semicrystalline blends. The main toughening mechanism identified was cavitation of atactic poly([R,S]-3-hydroxybutyrate), initiating multiple crazing of polylactide. A limited shear yielding was also observed. Activity of all these mechanisms brings brittle-to-ductile transformation in blends, above 10?wt% of atactic poly([R,S]-3-hydroxybutyrate).     

Diffusion of chromium,manganese, and iron in MnCr<Subscript>2</Subscript>O<Subscript>4</Subscript> spinel

As a result of the oxidation of chromium (Cr)-manganese (Mn) steels, a multilayer scale is formed. The intermediate layer of this scale is composed of MnCr₂O₄ spinel, and the outer layer is composed of MnO. The aim of the current study is to examine self-diffusion processes in MnCr₂O₄ spinel by a tracer method. In experiments, the radioisotopes ⁵⁴Mn, ⁵¹Cr, and ⁵⁹Fe were used. The serial sectioning method was applied for the simultaneous evaluation of diffusion rates of Cr, Mn, and iron (Fe) in MnCr₂O₄ spinel at 1173 K under a pressure of 10⁵ Pa in SO₂ containing 10 Pa O₂. This spinel was obtained by a modified sol-gel method from metal nitrates (R. Gajerski and Z. Zurek, personal communication, 14.04.2004). It was found that the dominant mechanism of Mn transport in the studied samples is a volume diffusion, while Cr and Fe are transported mainly through the high-diffusivity paths.     

Image simulation using Monte Carlo methods: Electron beam and detector characteristics

The rapid increase of computer speed allows using Monte Carlo simulation procedures for the analysis of complicated structures not only in a line scan mode but also in a three-dimensional approach similar to the scanning procedure in a scanning electron microscope. Simulation of image formation is a vital link in performing image analysis to obtain precise measurements, to provide the necessary connection between image parameters and structural dimensions, and to reflect important microscope beam and detector parameters. Monte Carlo simulation based on a single-scattering procedure was used for backscattered electron image simulation of three-dimensional multilayer and multielement structures. The procedure takes into account the effect of a solid state detector's electrical and angular characteristics and the effect of the electron beam dimensions on the image quality and artifacts.     

Methodological Aspects of Determining Apple Mechanical Properties During Impact

The influence of cylindrical sizes of samples and velocity of impact on its course and strength parameters for the “Braeburn” variety apples was studied. Three sample lengths of 17, 19, and 21 mm, three diameters of 10, 15, and 20 mm and four impact velocities of 0.25, 0.5, 0.75, and 1 ms^–1 were applied. Failure stress and strain, impact energy, absorbed energy as well as tissue stiffness and toughness were determined as dependent variables. The influence of the sample diameter on maximum force response, impact energy, absorbed energy, and tissue stiffness was studied. The other independent variables: Sample length and impact velocity did not show significant influence on the strength parameters of the apple tissue. The shock wave speed in the apple tissue was independent of both sample sizes and impact velocity. Its mean value amounted to 292 ms^–1. Under the experimental conditions the mean value of the absorbed energy contribution to the impact energy amounted to 9.9%. The experiment confirmed importance of a critical stress criterion as regards cylindrical samples of apples under impact conditions.     

Role of vanadium sites in NO and O2 adsorption processes over VOx/CeO2-ZrO2 catalysts – EPR and IR studies

The interaction of NO and O₂ with 5 mol.% of vanadia deposited on Ce_0.10Zr_0.90O₂ and Ce_0.69Zr_0.31O₂ supports by wet impregnation was studied by means of EPR and IR. The supports were structurally characterized by XRD and Raman spectroscopy. Influence of the phase composition of the support on vanadium speciation as well as on surface architecture of the oxovanadium entities was discussed. The NO forms adsorbed on vanadium-containing systems were compared to those observed on bare CeO₂-ZrO₂ supports. The main products appearing on the catalysts surface during the consecutive reaction with NO and O₂ were identified and their thermal evolution was observed. Changes in vanadium speciation accompanying redox processes related to NO and O₂ activation were also observed and discussed.     

Determination of Pyrrolizidine Alkaloids in Honey with Sensitive Gas Chromatography-Mass Spectrometry Method

Pyrrolizidine alkaloids (PAs) are secondary metabolites produced by plants as a chemical defense against herbivores. Plants containing PAs are widely distributed in almost all geographical regions posing a risk of honey contamination. To provide safety of honey and decrease the potential risk for the consumers, a sensitive method based on gas chromatography-mass spectrometry enabling determination of a content of 1,2-unsaturated PAs in honey was developed. Honey samples were purified on MCX cartridges, and PAs were eluted with a solvent mixture consisting of ethyl acetate, methanol, ammonia, and triethylamine. Subsequently, 1,2-unsaturated alkaloids were reduced to their common backbone structures and derivatized with heptafluorobutyric anhydride. The method was validated according to SANTE 2015. All received parameters are in consistence with the document requirements as recovery ranged from 73.1 to 93.6%. The repeatability and reproducibility were calculated as relative standard deviation and ranged from 3.9 to 8.6% and from 10.6 to 17.8%, respectively. The limit of quantification was determined as 1 μg kg^?1. Good linearity of the method was obtained with the coefficient of determination R ²?>?0.99. The method was applied to 40 Polish and 14 Asian honey sample analyses.     

Structure of nanoconfined LiBH4 from first principles B NMR chemical shifts calculations

Nanoconfinement of metal borohydrides is a promising route for improvement of their kinetic and thermodynamic properties related to hydrogen storage. Since the atomic-scale properties of nanoconfined LiBH₄ remain under debate we propose a model of such a structure. Within extensive density functional theory calculations we consider continuous transformation of the lithium borohydride equilibrium structures from 3-dimensional to 1-dimensional. Such structures consist of single linear chains, linear ribbons and 3-dimensional chains, and together with the low temperature bulk phase they reproduce ¹¹B NMR spectra observed in LiBH₄ confined in porous carbon. The present model suggest that nanoconfined LiBH₄ consists of a dense bulk-like region and loosely distributed chains and ribbons of Li–BH₄. Even with the low effective density of loosely distributed LiBH₄ they occupy region with thickness as small as a quarter of a pore diameter.     

Increasing the security of the ping–pong protocol by using many mutually unbiased bases

In this paper we propose an extended version of the ping–pong protocol and study its security. The proposed protocol incorporates the usage of mutually unbiased bases in the control mode. We show that, by increasing the number of bases, it is possible to improve the security of this protocol. We also provide the upper bounds on eavesdropping average non-detection probability and propose a control mode modification that increases the attack detection probability.     

Optimization of Recording of Thermal-Wave Images in BDM Method

The beam displacement modulation (BDM) method is very difficult to implement and has a lot of features and parameters which require optimization to improve the effectiveness of detection of thermal non-uniformities. The most important parameters that have to be taken under consideration during the optimization process are the width of the excitation source, the displacement speed of the excitation source, and the distance between the excitation and measuring spots. The width of the excitation source (e.g., diameter of laser beam) and speed of beam dislocation, in relation to the surface of the object, influence the spectra of excitation’s energy. It allows examination and visualization of thermal properties of the object at varied depths. This article presents the general scheme of a thermal-wave microscope with the implemented BDM mode and describes the process of optimization for which the assignment is to find the microscope’s settings that guarantee the highest temperature contrast of non-uniformities at the surface of the examined object.     

The influence of calcination parameters on free calcium oxide content in natural hydroxyapatite

Effect of calcining temperature and time on the content of free CaO in hydroxyapatite of natural origin is presented. Hydroxyapatite was obtained from pork bones in the course of a three-stage process: hydrolysis with the application of lactic acid, pre-calcination at 600 °C and main calcination stage within the temperature range of 750-950 °C. Calcination was conducted in an electrically heated stationary chamber oven in air atmosphere and in a laboratory scale rotary kiln equipped with a gas burner. The FT-IR spectra confirmed that all organic substances were removed during the calcination process. An increase in free calcium oxide content in hydroxyapatite from 0.003% to 0.023% was caused by the increase of calcining temperature from 750 °C to 950 °C respectively. Calcining time at 950 °C gave a distinct impact upon free CaO content ranging from 0.014% (2 h) to 0.023% (3 h). Hydroxyapatite calcined in the rotary kiln contained the lowest amount of free calcium oxide: 0.002% (750 °C) and 0.003% (950 °C). A method of neutralizing of free calcium oxide, present in calcined hydroxyapatite powders of natural origin, through CaO transformation into hydroxyapatite by application of diluted thermic phosphoric acid has been developed.