Brittle‐to‐Ductile Transition in Uniaxial Compression of Silicon Pillars at Room Temperature

Robust nanostructures for future devices will depend increasingly on their reliability. While great strides have been achieved for precisely evaluating electronic, magnetic, photonic, elasticity and strength properties, the same levels for fracture resistance have been lacking. Additionally, one of the self‐limiting features of materials by computational design is the knowledge that the atomistic potential is an appropriate one. A key property in establishing both of these goals is an experimentally‐determined effective surface energy or the work per unit fracture area. The difficulty with this property, which depends on extended defects such as dislocations, is measuring it accurately at the sub‐micrometer scale. In this Full Paper the discovery of an interesting size effect in compression tests on silicon pillars with sub‐micrometer diameters is presented: in uniaxial compression tests, pillars having a diameter exceeding a critical value develop cracks, whereas smaller pillars show ductility comparable to that of metals. The critical diameter is between 310 and 400 nm. To explain this transition a model based on dislocation shielding is proposed. For the first time, a quantitative method for evaluating the fracture toughness of such nanostructures is developed. This leads to the ability to propose plausible mechanisms for dislocation‐mediated fracture behavior in such small volumes.     

Polyurethane Composites Reinforced with Walnut Shell Filler Treated with Perlite,Montmorillonite and Halloysite

In the following study, polyurethane (PUR) composites were modified with 2 wt.% of walnut shell filler modified with selected mineral compounds–perlite, montmorillonite, and halloysite. The impact of modified walnut shell fillers on selected properties of PUR composites, such as rheological properties (dynamic viscosity, foaming behavior), mechanical properties (compressive strength, flexural strength, impact strength), dynamic-mechanical behavior (glass transition temperature, storage modulus), insulation properties (thermal conductivity), thermal characteristic (temperature of thermal decomposition stages), and flame retardant properties (e.g., ignition time, limiting oxygen index, heat peak release) was investigated. Among all modified types of PUR composites, the greatest improvement was observed for PUR composites filled with walnut shell filler functionalized with halloysite. For example, on the addition of such modified walnut shell filler, the compressive strength was enhanced by ~13%, flexural strength by ~12%, and impact strength by ~14%. Due to the functionalization of walnut shell filler with thermally stable flame retardant compounds, such modified PUR composites were characterized by higher temperatures of thermal decomposition. Most importantly, PUR composites filled with flame retardant compounds exhibited improved flame resistance characteristics-in all cases, the value of peak heat release was reduced by ~12%, while the value of total smoke release was reduced by ~23%.     

UVB Radiation and Selected Tryptophan-Derived AhR Ligands—Potential Biological Interactions in Melanoma Cells

Excessive UV exposure is considered the major environmental factor in melanoma progression. Human skin is constantly exposed to selected tryptophan-derived aryl hydrocarbon receptor (AhR) ligands, including kynurenine (KYN) and kynurenic acid (KYNA), as they are endogenously produced and present in various tissues and body fluids. Importantly, recent studies confirmed the biological activity of KYN and KYNA toward melanoma cells in vitro. Thus, in this study, the potential biological interactions between UVB and tryptophan metabolites KYN and KYNA were studied in melanoma A375, SK-MEL-3, and RPMI-7951 cells. It was shown that UVB enhanced the antiproliferative activity of KYN and KYNA in melanoma cells. Importantly, selected tryptophan-derived AhR ligands did not affect the invasiveness of A375 and RPMI-7951 cells; however, the stimulatory effect was observed in SK-MEL-3 cells exposed to UVB. Thus, the effect of tryptophan metabolites on metabolic activity, cell cycle regulation, and cell death in SK-MEL-3 cells exposed to UVB was assessed. In conclusion, taking into account that both UVB radiation and tryptophan-derived AhR ligands may have a crucial effect on skin cancer formation and progression, these results may have a significant impact, revealing the potential biological interactions in melanoma cells in vitro.     

Quantification of Dendritic Spines Remodeling under Physiological Stimuli and in Pathological Conditions

Numerous brain diseases are associated with abnormalities in morphology and density of dendritic spines, small membranous protrusions whose structural geometry correlates with the strength of synaptic connections. Thus, the quantitative analysis of dendritic spines remodeling in microscopic images is one of the key elements towards understanding mechanisms of structural neuronal plasticity and bases of brain pathology. In the following article, we review experimental approaches designed to assess quantitative features of dendritic spines under physiological stimuli and in pathological conditions. We compare various methodological pipelines of biological models, sample preparation, data analysis, image acquisition, sample size, and statistical analysis. The methodology and results of relevant experiments are systematically summarized in a tabular form. In particular, we focus on quantitative data regarding the number of animals, cells, dendritic spines, types of studied parameters, size of observed changes, and their statistical significance.     

Synthesis and characterization of Co5Cr2(P2O7)4 - New pyrophosphate as a colouring substance

A new pyrophosphate(V) of the formula Co₅Cr₂(P₂O₇)₄ was obtained in the system Co₂P₂O₇–Cr₄(P₂O₇)₃ as a result of solid-state reactions taking place between different reactants. The new compound crystallizes in the orthorhombic system and belongs to the family of pyrophosphates of the general formula M₅²⁺M₂³⁺(P₂O₇)₄ and is probably isostructural with Fe₅²⁺Fe₂³⁺(P₂O₇)₄. Powder diffraction pattern, infrared spectrum and SEM image of the new compound were presented. As a new potential inorganic pigment, Co₅Cr₂(P₂O₇)₄ was tested for its thermal stability, particle size distribution and colour properties, which were studied both for powder and after introduction into organic matrix and leadless ceramic glaze. The colour of Co₅Cr₂(P₂O₇)₄ powder was defined as deep grey with the colour coordinates L*/a*/b* = 60.63/-1.42/-3.41 and according to the hue angle (h° = 247.39°) it belongs to the blue region. Co₅Cr₂(P₂O₇)₄, with its relatively high thermal stability (t _m = 1230 ± 10 °C) and appropriate colour properties, is a good candidate to be used as inorganic pigment for colouring of acrylic paints. In the case of leadless glaze, the obtained compound acts as a dye.     

The Involvement of Xanthone and (E)-Cinnamoyl Chromophores for the Design and Synthesis of Novel Sunscreening Agents

Excessive UV exposure contributes to several pathological conditions like skin burns, erythema, premature skin aging, photodermatoses, immunosuppression, and skin carcinogenesis. Effective protection from UV radiation may be achieved with the use of sunscreens containing UV filters. Currently used UV filters are characterized by some limitations including systemic absorption, endocrine disruption, skin allergy induction, and cytotoxicity. In the research centers all over the world new molecules are developed to improve the safety, photostability, solubility, and absorption profile of new derivatives. In our study, we designed and synthesized seventeen novel molecules by combining in the structures two chromophores: xanthone and (E)-cinnamoyl moiety. The ultraviolet spectroscopic properties of the tested compounds were confirmed in chloroform solutions. They acted as UVB or UVA/UVB absorbers. The most promising compound 9 (6-methoxy-9-oxo-9H-xanthen-2-yl)methyl (E)-3-(2,4-dimethoxyphenyl)acrylate) absorbed UV radiation in the range 290–369 nm. Its photoprotective activity and functional photostability were further evaluated after wet milling and incorporation in the cream base. This tested formulation with compound 9 possessed very beneficial UV protection parameters (SPF_{in vitro} of 19.69 ± 0.46 and UVA PF of 12.64 ± 0.32) which were similar as broad-spectrum UV filter tris-biphenyl triazine. Additionally, compound 9 was characterized by high values of critical wavelength (381 nm) and UVA/UVB ratio (0.830) thus it was a good candidate for broad-spectrum UV filter and it might protect skin against UVA-induced photoaging. Compound 9 were also shown to be photostable, non-cytotoxic at concentrations up to 50 µM when tested on five cell lines, and non-mutagenic in Ames test. It also possessed no estrogenic activity, according to the results of MCF-7 breast cancer model. Additionally, its favorable lipophilicity (miLogP = 5.62) does not predispose it to penetrate across the skin after topical application.     

Strategies to improve the nutritional value of meat products: incorporation of bioactive compounds,reduction or elimination of harmful components and alternative technologies

Meat is an excellent source of protein with a good balance of amino acids. It is also rich in several minerals, vitamins and bioactive compounds, which play important roles in metabolism and are easily assimilated from meat compared with other foods. The nutritional value of meat is one of the factors that influence consumer acceptance. However, it can be significantly reduced during processing. Moreover, some operations, such as curing, smoking or fermentation, used for processing can lead to the formation of harmful components in meat, and hence, nutritionists associate high consumption of processed meat with an increased risk of several diseases such as cardiovascular disorders and cancers. This review deals with the distinctive aspects of the technological strategies that can be used to improve the nutritional value of meat products, including the incorporation of bioactive components, reduction or elimination of harmful components (e.g. nitrite/nitrate, fat) and alternative technologies (ultrasound).     

Digitising Teaching and Learning – Additional Perspectives for Chemistry Education

Chemistry requires and combines both observable and mental representations. Still we know that learners often struggle in combining these perspectives successfully, especially when experimental observations contradict the model‐based explanations, e. g. in interpreting the chemical equilibrium as dynamic processes while observing a static system without any visible changes. Digital media offer potentials that might not have been accessible to this degree until now. However, we do not know enough with regard to the degree and effects these media tools have in supporting learning processes but perhaps also in hindering them. This article presents four approaches on how to potentially make use of digital media in learning processes based on theoretical considerations and empirical investigations. The projects will explore applications of media as visualization, learning and investigation tools in chemistry education, embracing techniques from virtual realities to eye‐tracking.     

Twinned Growth of Metal‐Free,Triazine‐Based Photocatalyst Films as Mixed‐Dimensional (2D/3D) van der Waals Heterostructures

Design and synthesis of ordered, metal‐free layered materials is intrinsically difficult due to the limitations of vapor deposition processes that are used in their making. Mixed‐dimensional (2D/3D) metal‐free van der Waals (vdW) heterostructures based on triazine (C₃N₃) linkers grow as large area, transparent yellow‐orange membranes on copper surfaces from solution. The membranes have an indirect band gap (E _g,opt = 1.91 eV, E _g,elec = 1.84 eV) and are moderately porous (124 m² g^?1). The material consists of a crystalline 2D phase that is fully sp² hybridized and provides structural stability, and an amorphous, porous phase with mixed sp²–sp hybridization. Interestingly, this 2D/3D vdW heterostructure grows in a twinned mechanism from a one‐pot reaction mixture: unprecedented for metal‐free frameworks and a direct consequence of on‐catalyst synthesis. Thanks to the efficient type I heterojunction, electron transfer processes are fundamentally improved and hence, the material is capable of metal‐free, light‐induced hydrogen evolution from water without the need for a noble metal cocatalyst (34 µmol h^?1 g^?1 without Pt). The results highlight that twinned growth mechanisms are observed in the realm of “wet” chemistry, and that they can be used to fabricate otherwise challenging 2D/3D vdW heterostructures with composite properties.