Temperature reduction due to the application of phase change materials

Overheating is a major problem in many modern buildings due to the utilization of lightweight constructions with low heat storing capacity. A possible answer to this problem is the emplacement of phase change materials (PCM), thereby increasing the thermal mass of a building. These materials change their state of aggregation within a defined temperature range. Useful PCM for buildings show a phase transition from solid to liquid and vice versa. The thermal mass of the materials is increased by the latent heat. A modified gypsum plaster and a salt mixture were chosen as two materials for the study of their impact on room temperature reduction. For realistic investigations, test rooms were erected where measurements were carried out under different conditions such as temporary air change, alternate internal heat gains or clouding. The experimental data was finally reproduced by dint of a mathematical model.     

Optimal allocation of bioassays in the case of parametrized covariance functions: an application to Lung’s retention of radioactive particles

In this paper, we investigate the effect of employing a parametrized covariance function in a regression experiment on corresponding optimum designs. We demonstrate these effects in the framework of a real example for measuring the lung’s retention of radioactive particles. Also, two different covariance functions are considered, and it is shown that this choice can play a crucial role.      

Magnetically Controllable Silver Nanocomposite with Multifunctional Phosphotriazine Matrix and High Antimicrobial Activity

A recently developed multi‐functional phosphotriazine‐based polymer is used as a matrix for embedding γ‐Fe₂O₃ nanoparticles as well as a suitable chemical template for surface modification with silver nanoparticles. For the primary magnetic modification, maghemite nanoparticles are surface modified with oleic acid in order to render them organophilic and to prevent the aggregation of the nanoparticles. This aggregation could occur as the polymer synthesis, based on reaction of phosphonitrilic chlorine and 1,4‐phenylenediamine, takes place in toluene. The surface active amine units of the polymer structure enable the reduction of silver cations to silver nanoparticles, which are well attached and finely dispersed on its surface. The developed nanocomposite represents one of the few magnetically controllable antibacterial agents based on silver nanoparticles. Magnetic measurements reveal the completely suppressed interactions among maghemite nanoparticles because of their perfect surface coating with an organic surfactant and fine dispersion inside the polymer matrix. This magnetic nanocomposite exhibits a high antibacterial and antifungal activity as proven by tests with nine bacterial strains and four candida (yeast genus) species. For the majority of the tested species, the minimum‐inhibition concentrations are below 100 mg L^?1, which is comparable to their equivalent minimum‐inhibition concentrations in colloidal silver systems.     

Recent developments in cold plasma-based enzyme activity (browning,cell wall degradation,and antioxidant) in fruits and vegetables

According to the Food and Agriculture Organization of United Nations reports, approximately half of the total harvested fruits and vegetables vanish before they reach the end consumer due to their perishable nature. Enzymatic browning is one of the most common problems faced by fruit and vegetable processing. The perishability of fruits and vegetables is contributed by the various browning enzymes (polyphenol oxidase, peroxidase, and phenylalanine ammonia-lyase) and ripening or cell wall degrading enzyme (pectin methyl-esterase). In contrast, antioxidant enzymes (superoxide dismutase and catalase) assist in reversing the damage caused by reactive oxygen species or free radicals. The cold plasma technique has emerged as a novel, economic, and environmentally friendly approach that reduces the expression of ripening and browning enzymes while increasing the activity of antioxidant enzymes; microorganisms are significantly inhibited, therefore improving the shelf life of fruits and vegetables. This review narrates the mechanism and principle involved in the use of cold plasma technique as a nonthermal agent and its application in impeding the activity of browning and ripening enzymes and increasing the expression of antioxidant enzymes for improving the shelf life and quality of fresh fruits and vegetables and preventing spoilage and pathogenic germs from growing. An overview of hurdles and sustainability advantages of cold plasma technology is presented.     

Optimisation of puffing naked barley

The expansion of volume (the puffing index) of naked barley was investigated at various operating conditions of the puffing process. The purpose was to optimise the manufacture of expanded grains of the naked barley cultivars that have exceptional nutritional value for humans. The influence of the following parameters on the puffing index was investigated: the mass and the moisture content of the charge of the puffing barrel, pressure and temperature during the puffing process, the cultivar of barley, pre-processing of the grain (grinding and polishing), adding water into the barrel and the sensory quality of the product.

A regression equation was established for the calculation of the puffing index as a function of the operating parameters. The puffing index is influenced especially by the operating temperature and pressure. There was no influence found of mass of the charge, the cultivar of barley, the degree of grinding of barley, washing of the grains and adding water on the puffing index. The puffing index is not the sole indicator of the quality of the expanded product. It is necessary to take into account the sensory evaluation. A quality expanded naked barley was obtained at the operating temperature of 550 °C and pressure from 0.9 to 1.0 MPa with the moisture content of the charge around 16.5%.     

Influence of temperature of thermal treatment on surface densification of spruce

Spruce (Picea abies L. Karst) wood lamellae, thermally treated at 170, 190, 210 and 230 °C were surface densified by compression at a temperature of 150 °C to three degrees of compression. Immediate springback, set recovery, mechanical properties in 3-point flexure, Brinell hardness and density profiles measurements were used to determine the effect of thermal treatment on the properties of surface densified wood. The highest immediate springback occurred in wood specimens thermally treated at the highest temperature (230 °C) and decreased with decreasing thermal treatment temperature. The untreated samples had the highest set recovery, which decreased with the temperature of thermal treatment. The surface densification increased hardness and bending strength. The highest increase was in the case of untreated wood and decreased with the temperature of thermal treatment. The modulus of elasticity (MOE) and modulus of rupture (MOR) of surface densified wood decreased with increasing thermal treatment temperature. The trend was similar for specimens which were thermally treated but not surface densified. Surface densification increased the density of the specimens in the first few millimetres below the surface. The highest density was achieved in untreated specimens and the lowest in specimens thermally treated at the highest temperature.     

Nanoindentation,AFM and tribological properties of thin nc-WC/a-C Coatings

Instrumented indentation, AFM (atomic force microscopy) and tribological studies were performed on PE CVD (Plasma Enhanced Chemical Vapor Deposition) nanocomposite WC–C coatings to investigate the effects of surface roughness on the reliability of nanoindentation data and the possibilities of different AFM modes in nanomechanical testing, which can be used as a feedback to optimize deposition technology from the viewpoint of their mechanical properties. It was confirmed that surface roughness below 30 nm is necessary to keep the scatter of indentation modulus, E_IT, and hardness, H_IT, below 15%. PF QNM (Peak Force Quantitative NanoMechanical) mode was successfully applied for qualitative mapping of the elastic modulus of coatings with the stiffness above 300 GPa. LFM (lateral force microscopy) mode showed only weak contrast and quantitative measurements in both AFM modes require precise calibration. Coefficients of friction of the studied WC–C coatings were below 0.2 at RT, but increased to 0.7–0.8 at 450 °C due to the formation of a transfer film. Optimization of the deposition conditions based on nanoindentation resulted in the increase of E_IT from ～220 GPa to 350 GPa and H_IT from ～17 GPa to ～29 GPa.     

PARTITIONING OF π-ELECTRONS IN RINGS OF POLYCYCLIC conjugated HYDROCARBONS. PART 1: CATACONDENSED BENZENOIDS

Recently a novel view on Kekulé valence structures (or resonance structures) was reported in which their standard geometrical representation was replaced by a numerical representation obtained by assigning π-electrons associated with CC double bonds to individual benzenoid rings. In the present article, we examine in more detail the partitioning of π-electrons to benzenoid rings for cata-condensed benzenoid hydrocarbons. For special families of cata-condensed benzenoids, we offer formulas which allow one to obtain the average π-electron ring content for individual benzenoid rings of polycyclic conjugated hydrocarbons. We also show that the average π-electron ring content for individual benzenoid rings can be calculated from Pauling bond orders without a need to examine all Kekulé resonance structures of a molecule.