gHRV: Heart rate variability analysis made easy

In this paper, the gHRV software tool is presented. It is a simple, free and portable tool developed in python for analysing heart rate variability. It includes a graphical user interface and it can import files in multiple formats, analyse time intervals in the signal, test statistical significance and export the results.     

Composition and Properties of Biodegradable Materials

The important possibility of fabricating biodegradable materials by incorporating different bio- and photodegradable additives in the polymer is demonstrated. Changes were found in the structure and properties of degradable materials during exposure to soil microorganisms, air, and UV radiation for different times. The results obtained can serve as the basis for a more in-depth investigation of the mechanism of degradation of PCM.     

Mechanism of growth of silicon nitride crystals in combustion of ferrosilicon in nitrogen

The process of nitride formation in burning of iron-silicon melt in gaseous nitrogen was investigated. It was found that silicon nitride is synthesized at temperatures (2100°C) which are much higher than the temperature of appearance of the liquid phase (1206°C). Silicon is in the liquid state during synthesis in the form of an iron-silicon melt and a gaseous melt. The electron-microscopic studies showed that silicon nitride crystals grow according to two mechanisms: vapor-liquid-crystal and crystallization from iron-silicon melt. The ratio of the contributions of these mechanisms to structural formation of silicon nitride is determined by the conditions of synthesis. __________ Translated from Steklo i Keramika, No. 8, pp. 18–21, August, 2007.     

Use of mesoporous SBA-15 for nanostructuring titania for photocatalytic applications

SBA15–TiO₂ samples prepared by introducing titanium with a grafting method and having TiO₂ loadings below 15 wt.% have been characterized by XRF, XRD, IR, porosimetry, SEM, HRTEM, and UV–Visible diffuse reflectance. Differently from the samples reported in the literature characterized by a high TiO₂ loading, no evidences have been found for the presence of titania particles inside or outside the mesopores of SBA-15. Three different titanium species were instead evidenced to be present. The first two derive from the reaction of titanium with silanol groups in the corona area of inner SBA-15 walls leading to the formation of either TiO₄ tetrahedral sites (by reaction by hydroxyl nests of surface defect sites) and/or pseudo-octahedral surface sites anchored by two (or more) Si or Ti ions through bridging oxygens. The third species derives from the reaction of titanium in the regions with high sylanol density, e.g. in the micropores located in the corona of SBA-15 channels, leading to the formation of TiO₂-like nanoareas (probably Si-doped) with dimensions of around 1–2 nm maximum. The potential interest of these materials as photocatalysts, for the presence of a TiO₂-like nanoareas highly accessible by reactants, is discussed.     

Suitability of commercial cottonseed for producing edible high protein flours by liquid classification

The 1976 and 1977 crops of glanded cottonseed from oil mills located in 7 major U.S. cottonbelt growing areas were evaluated as to their suitability for processing into edible, high-protein flours. Both the physical and chemical characteristics of fuzzy seed samples were studied. Ginned seed samples were hulled, dried, comminuted, slurried with hexane and liquid classified by both a laboratory differential settling test (DST) and pilot plant liquid cyclone process (LCP). Liquid cyclone operating data and extensive analytical data of the kernels, flour and meals produced are shown. A free gossypol level of 1.10% or less in full fat kernels was the determining factor for producing edible flours from glanded seed by the LCP. The Lower Rio Grande Valley area was the only area from which liquid classified cottonseed flour consistently exceeded the current maximal free gossypol standard of 450 ppm. Ca. 94% of the total U.S. cottonseed production is suitable for producing edible, high-protein flours by liquid classification.     

Softening and melting mechanisms of polyamides interfering with sliding stability under adhesive conditions

The thermal stability of polymers is a main issue when used as friction elements under dry sliding. Cast polyamide grades processed with either natrium or magnesium catalysors are slid on a small-scale and a large-scale test configuration to reveal the effect of softening or degradation on the sliding stability and to investigate possibilities for extrapolation of friction and wear rates between both testing scales. The combination of softening and afterwards transition into the glassy state is detrimental for the sliding stability of natrium catalysed polyamides, characterised by heavy noise during sliding. A transfer film formed under continuous softening also provides high friction. Melting during initial sliding is necessary for stabilisation in both friction and wear, and eventual softening of a molten film near the end of the test then not deteriorates the sliding stability. Softening of magnesium catalysed polyamides is favourable for the formation of a coherent transfer film resulting in more stable sliding than natrium catalysed polyamides. The differences in softening mechanisms of both polyamide grades is correlated to structural changes investigated by thermal analysis and Raman spectroscopy: the γ crystalline structure prevails in magnesium catalysed samples and the α crystalline structure is predominant in natrium catalysed samples. For internal oil lubricated polyamides, a time dependent degradation of the polyamide bulk deteriorates the supply of internal oil lubricant to the sliding interface, resulting in high friction and wear under overload conditions. As the degradation mechanisms during sliding are strongly correlated to the test set-up, extrapolation is only possible for friction in a limited application range, while wear rates cannot be extrapolated.     

Formation mechanism and ceramic process of the ferroelectric perovskites: Pb (Mg13Nb23)O3 and Pb (Fe12Nb12)O3

The formation of the $\text{Pb}\text{(}\text{Mg}{}_{\mathrm{<mtext>1</mtext><mtext>3</mtext>}}\text{Nb}{}_{\mathrm{<mtext>2</mtext><mtext>3</mtext>}}\text{)}\text{O}{}_3$ and Pb $\text{(}\text{Fe}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$$\text{Nb}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{)}\text{O}{}_3$ phases with a perovskite type structure is directly dependent on the reactivity of magnesium and ferric oxides to other phases belonging to the binary system PbO  Nb₂O₅. Moreover, it is shown that the ceramic process influences the proportion of perovskite phases in comparison with parasite phases and also the densification of the samples. The optimization of the ceramic process allows to obtain a pure $\text{Pb(Fe}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{Nb}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{O}{}_3$ phase, but as far as $\text{Pb(Mg}{}_{\mathrm{<mtext>1</mtext><mtext>3</mtext>}}\text{Nb}{}_{\mathrm{<mtext>2</mtext><mtext>3</mtext>}}\text{)}\text{O}{}_3$ is concerned, a parasite phase is never entirely eliminated.     

Polyelectrolyte swelling of polyamidobenzimidazole

Conclusions An extreme character of the swelling of PABI fibres in DMAc-water mixtures has been detected. The maximum is observed in the region of a 10% water content.The peculiarity in swelling has been explained by the manifestation of a polyelectrolyte nature of the polymer.Translated from Khimicheskie Volokna, No. 5, pp. 34–35, September–October, 1987.