Synthesis and characterization of hafnium carbide fine powders

Hafnium carbide powder was synthesized by sol–gel polycondensation of hafnium chloride with citric acid. The starting materials were dissolved in water and mixed homogeneously on a hot plate until precursor gel was formed. Pyrolysis of this gel resulted in monoclinic hafnia which after subsequent heat treatment transformed into hafnium carbide. The obtained materials were analyzed by means of X-ray diffraction and scanning electron microscopy. The results showed that the obtained carbide powders were composed of nearly equiaxed particles with narrow size distribution. Characterization by nitrogen adsorption showed that the obtained powders were micro- and mesoporous materials with high specific surface area.     

A Sulfur–Limonene‐Based Electrode for Lithium–Sulfur Batteries: High‐Performance by Self‐Protection

The lithium–sulfur battery is considered as one of the most promising energy storage systems and has received enormous attentions due to its high energy density and low cost. However, polysulfide dissolution and the resulting shuttle effects hinder its practical application unless very costly solutions are considered. Herein, a sulfur‐rich polymer termed sulfur–limonene polysulfide is proposed as powerful electroactive material that uniquely combines decisive advantages and leads out of this dilemma. It is amenable to a large‐scale synthesis by the abundant, inexpensive, and environmentally benign raw materials sulfur and limonene (from orange and lemon peels). Moreover, owing to self‐protection and confinement of lithium sulfide and sulfur, detrimental dissolution and shuttle effects are successfully avoided. The sulfur–limonene‐based electrodes (without elaborate synthesis or surface modification) exhibit excellent electrochemical performances characterized by high discharge capacities (≈1000 mA h g^?1 at C/2) and remarkable cycle stability (average fading rate as low as 0.008% per cycle during 300 cycles).     

Human experience and product usability: principles to assist the design of user-product interactions

This paper introduces research that investigates how human experience influences people's understandings of product usability. It describes an experiment that employs visual representation of concepts to elicit participants' ideas of a product's use. Results from the experiment lead to the identification of relationships between human experience, knowledge, and context-of-use - relationships that influence designers' and users' concepts of product usability. These relationships are translated into design principles that inform the design activity with respect to the aspects of experience that trigger people's understanding of a product's use. A design tool (ECEDT) is devised to aid designers in the application of these principles. This tool is then trialled in the context of a design task in order to verify applicability of the findings.     

New technique for effective dose estimation using Monte Carlo simulation for the patients undergoing radioiodine therapy

We presume that radioiodine capsule, used for therapy, stays in stomach for 15 min before the absorption starts when large amount of radioactivity needlessly expose a part of stomach and several surrounding organs. Investigations were performed at Institute of Pathophysiology and Nuclear Medicine, Faculty of Medicine, Ss. Cyril and Methodius University, Skopje, Macedonia. Eighty-seven patients were reviewed, age between 21 and 73. Patients were divided in 20 groups receiving average dose per group from 1813 MBq to 6105 MBq. We used Monte Carlo MCNP 4b code and gave the results only for administrated activity of 6105 MBq. Calculated results are given for imparted energy per transformation, dose equivalent and effective doses for different organs. The effective doses were between 9.17 nSv (for bone surface) to 122.4 mSv (for stomach). As the total dose is estimated to be 126.73 mSv it is obvious that the highest part is received by stomach.     

Second order derivative spectrophotometric method for determination of vitamin C content in fruits,vegetables and fruit juices

A second-order derivative UV spectrophotometric method for determination of vitamin C [ascorbic acid (AA)] content in a variety of natural samples is described. The method is based on the measurement of a peak–baseline amplitude in the second derivative of the AA spectrum at 267.5 nm. The following corresponding regression equation was obtained within the concentration range 2×10^-5 to 1×10^-4 M AA (3.5–17.6 g/cm³ AA) in 1.0 M HCl solution: ²D_267.5=2.420×10⁴ c+0.025; the correlation coefficient was 0.9993 and the detection limit 4.2×10^-6 M. The results obtained by analysing 21 different species of fruits, vegetables and juices indicated a possibility for a more extensive application of the proposed method. This method is rapid, simple and requires no pretreatment of the analysed material, which makes it suitable for routine analyses. The reliability of the method was confirmed by comparative determinations with the generally accepted 2,6-dichloroindophenol method.     

Kinetics of struvite to newberyite transformation in the precipitation system MgCl2-NH4H2PO4NaOH-H2O

The influence of the initial reactant concentrations on the composition of the solid phases formed in the precipitation system MgCl(2)-NH(4)H(2)PO(4)-NaOH-H(2)O was investigated. The precipitation diagram constructed shows the approximate concentration regions within which struvite, newberyite, and their mixtures exist at 25 degrees C and an aging time of 60 min. It was found that immediately after mixing the reactant solutions, struvite (MgNH(4)PO(4).6H(2)O) precipitated in nearly the whole concentration area, while newberyite (MgHPO(4).3H(2)O) appeared mostly within the region of the excess of magnesium concentration. It was also found that after aging time of 60 min the precipitation domain of struvite alone is much broader than that of newberyite or the domain of their coexistence, and shows that struvite is more abundant in the systems in which the initial concentration of ammonium phosphate is higher than that of magnesium. The kinetics of struvite to newberyite transformation (conversion) was systematically studied under the conditions of different initial reactant concentrations and different initial pH in the systems in which a mixture of both phases precipitated spontaneously. The struvite to newberyite conversion period was found to be strongly related to the ratio of initial supersaturations, S(N)/S(S), rather than to the any particular physical quantity that can describe and predict the behavior of the precipitation system. Experimental data suggest a solution-mediated process as a most possible transformation mechanism. Along with a continuous monitoring of the changes in the liquid phase, the content of struvite in the solid phase was estimated by means of a Fourier transform infrared (FT-IR) method, developed for this particular precipitation system.     

Antioxidant activity of medicinal plant extracts in cookies

The antioxidant activity of ethanolic extracts of parsley, buckthorn, mint, caraway, and their mixture "Vitalplant" was evaluated, and the potential of "Vitalplant" mixture extract to retard the process of lipid oxidation in cookies was tested. The antioxidant activity was estimated by 2 direct (ESR) and 4 indirect (spectrophotometric) tests and correlated with the total phenolic and flavonoid content. The potential of "Vitalplant" mixture extract to retard the process of lipid oxidation in cookies was measured by thiobarbituric acid (TBA)-reactive-substances assay (TBARS) and DPPH˙ (1,1-diphenyl-2-picryl-hydrazyl) test. Significantly different (P < 0.05) amounts of total phenolics were found among extracts in the following order: mint > buckthorn > "Vitalplant" > parsley > caraway. Total flavonoid content varied from 0.510% (parsley) to 2.05% ("Vitalplant"). A statistically significant correlation was found between IC(50) values on DPPH˙ and total flavonoid content of the samples (r=- 0.94, P < 0.05) and between IC(50) values on DPPH˙ and IC(50) values on O(2) (·-) scavenging activity (r= 0.89, P < 0.05). A correlation between reducing activity and total phenolic content was found to be positive and statistically significant (r= 0.94, P < 0.05). "Vitalplant" mixture exhibited a relatively high antioxidant activity in most of the tests, which can be explained by synergistic effects of the ingredients of which it is composed. Finally, "Vitalplant" extract addition (2%, 4%, and 6%) improved antioxidant activity and oxidative stability of the cookies in dose-dependent manner. PRACTICAL APPLICATION: Supplementation of cookies with a mixture of Petroselini fructus, Frangulae cortex, Mentha piperitae folium, Carvi fructus can retard the process of lipid oxidation and elevate antioxidant activity of the final product.