New optical ceramics: High-entropy sesquioxide X2O3 multi-wavelength emission phosphor transparent ceramics

Highly transparent X₂O₃ sesquioxide ceramics were obtained from a solid solution of five different oxides (Lu₂O₃, Y₂O₃, Yb₂O₃, Gd₂O₃, and Dy₂O₃), mixed in an equal molar ratio according to the principle of high-entropy. The fabricated (Lu, Y, Yb, Gd, Dy)₂O₃ ceramics achieved 99.97 % of the relative density and exhibited a high degree of optical transparency with the in-line transmittance of almost 80 % in the visible wavelength range. Emissions of Gd³⁺ (⁶P_J → ⁸S_7/2 at 312 nm), Dy³⁺ (⁴F_9/2 → ⁶H_15/2 at 492 nm and ⁴F_9/2 → ⁶H_13/2 at 572 nm), and Yb³⁺ (²F_5/2 → ²F_7/2 at 1031 nm) suggested a potential application of the high-entropy ceramics as multi-wavelength emission phosphor transparent ceramics. High-entropy ceramics also exhibited lower specific heat and thermal conductivity compared to single-element sesquioxide ceramics. This work demonstrated that highly transparent oxide ceramics, with complex chemical compositions and good optical properties, could be obtained using the high-entropy principle.     

The Effect of Thermo-Mechanical Treatment on Structure of Ultrahigh Carbon PM Steel

The effects of thermo-mechanical treatment on selected properties related to the structure of Fe-0.85Mo-0.65i-1.4C powder metallurgy (PM) steel are reported. Three kinds of initial microstructure of specimens, i.e., pearlite + ferrite + cementite, martensite + retained austenite and α + spheroidized cementite were examined. Processing was carried out on a plastometer-dilatometer Bähr machine by compression cylindrical specimens at 775 °C at a strain rate of 0.001 s^?1. X-ray diffraction was carried out with symmetrical Bragg-Brentano and grazing incident angle methods on a D8-Advance diffractometer with filtered radiation of cobalt CoK _α . The following features were determined: texture, density of dislocations, density of vacancies, lattice parameter of Fe _α and mean size of crystallites. Significant differences in structure were observed, especially in quenched specimen, as a result of the thermo-mechanical treatment. Regardless of initial state of the specimens, the determined properties were on a similar level. Crystallite size was in the range 97-106 nm, crystallite texture (I{200}/I{110}) × 10 = 1.15-1.62 and density of vacancies I{110}/I{220} = 7.06-7.52.     

Thermal Stability and Coefficient of Friction of the Diamond Composites with the Titanium Compound Bonding Phase

In this paper, processes occurring during heat treatment of the diamond-Ti compound composites without Co addition were investigated and compared with commercial PCD. Three types of materials were prepared. The first material was sintered using the mixture containing diamond and 10 mass% of TiC, the second material was prepared using diamond powder and 10 mass% of Ti-Si-C, and the third composite was sintered using the addition of 10 mass% of TiB₂. During the research, it was proved that TiO₂ formation contributes to material swelling and WO₃ (W is present from the milling process) causes a significant increase in coefficient of friction. TiC and Ti-Si-C bonded materials are very susceptible to this process of oxidation; their hardness drops absolutely after wear test at 600 °C. The diamond composite with TiB₂ is the most resistant to oxidation from investigated materials.     

Application of zirconium (IV) acetylacetonate to the copolymerization of glycolide with ɛ-caprolactone and lactide

Summary A study on the copolymerization of glycolide with lactide and glycolide with ɛ-caprolactone was performed in the presence of zirconium (IV) acetylacetonate at moderate temperatures (100° and 150°C). Zirconium acetylacetonate appeared to be an efficient initiator of copolymerization. The obtained polymers were characterized by high molecular weights. Considerable influence of transesterification on the polymer chain microstructure was found. Received: 13 October 1998/Revised version: 4 January 1999/Accepted: 4 January 1999     

Comparison of antimicrobial resistance of Campylobacter jejuni and Campylobacter coli isolated from humans and chicken carcasses in Poland

Campylobacter-associated gastroenteritis remains an important cause of morbidity worldwide, and some evidence suggests that poultry is an important source of this foodborne infection in humans. This study was conducted to analyze the prevalence and genetic background of resistance of 149 Campylobacter jejuni and 54 Campylobacter coli strains isolated from broiler chicken carcasses and from stool samples of infected children in Poland from 2003 through 2005. Nearly all isolates were susceptible to macrolides and aminoglycosides. The highest resistance in both human and chicken strains was observed for ciprofloxacin (more than 40%), followed by ampicillin (13 to 21%), and tetracycline (8 to 29%). Resistance to ampicillin and tetracycline rose significantly between 2003 and 2005. Slight differences in resistance between human and chicken isolates indicate that although chicken meat is not the only source of Campylobacter infection in our population, it can be involved in the transmission of drug-resistant Campylobacter strains to humans.     

River fragmentation in the northern Sandomierz Basin (SE Poland)

River fragmentation is a process highly detrimental for fish survival by impeding their migrations. Although fragmentation by big dams has been studied, there is still a big deficiency of data related to small barriers. This study was designed as a detailed, local-scale analysis of several chosen river stretches in the Sandomierz Basin, Poland. It aimed to: (1) map all natural and artificial barriers in the study area, (2) assess the impacts of these barriers on fish migration, (3) compare findings to existing databases, and (4) make recommendations for improved barrier management. Ten lowland rivers covering a total 424 km length were surveyed by river walkovers and kayak surveys, with all the barriers mapped and all the artificial structures assessed for fish migration using the ICE protocol protocol for ecological continuity. There were 67 beaver dams and 89 artificial barriers recorded, with only 24% of the latter being included in national databases. The average artificial barrier density in all the surveyed rivers was 0.2 barriers/km and varied from 0.75 barriers/km in first order streams to 0.01 barriers/km in sixth order river. The findings revealed that 18% of the barriers were passable for all fish species, with 35% totally impassable. The analysis of specific barrier parameters indicated that water depth at the barrier had a greater influence on fish passability than the barrier height. Several barriers were proposed for removal to specifically improve the potential for fish migration.     

Thermodynamic analysis of afterburning of detonation products in confined explosions

Abstract

In the paper, an attempt is undertaken to apply the thermodynamic theory of closed combustion, proposed by A. K. Oppenheim and co-workers, to analyse the process of afterburning of the detonation products of condensed explosives in a chamber filled with air. The principal assumptions of the theory are presented and the problem of combustion of fuel in a closed volume is formulated. The relations between thermodynamic parameters and fuel consumption are determined from the laws of conservation of volume, mass and energy. These relations are used to estimate the rate and heat effect of afterburning of the detonation products of some explosives in a steel chamber of 150 dm³ volume. The influence of assumed degree of mixing of the combustion products and air on the mean pressure in the chamber is discussed.     

Selection of yeast strains for alcoholic fermentation of sugar beet thick juice and green syrup

Presented work aimed at determination of effect of various strains of yeast Saccharomyces cerevisiae and concentration of fermentation worts on dynamics and efficiency of alcoholic fermentation. Fermentation worts contained either thick juice or green syrup.It was found that yeast strains designated as M₁, M₂ and D-2 most efficiently fermented thick juice worts inoculated with yeast cream at a rate of 2 kg m⁻³ of wort. Fermentation processes lasted for approximately 2 days and ethanol yield approached 92-94% of the theoretical yield. Fermentations of green syrup worts were most efficient (ethanol yield reached 90-92% of the theoretical yield) when these processes were carried out by yeast strains M₁, M₂, D-2 and As4 (inoculum - 2 kg m⁻³ of wort).S. cerevisiae strains M₁ and M₂ dynamically and efficiently fermented thick juice worts with extract of 200 g kg⁻¹ and 250 g kg⁻¹ (89-94% of the theoretical yield) while strain D-2 preferred less dense worts (extract of 200 g kg⁻¹) and produced ethanol with the yield of over 92% of the theoretical yield. The optimum green syrup worts extract was 200 g kg⁻¹.     

Identification and characterization of surface lipid components of the dried-bean beetle Acanthoscelides obtectus (Say) (Coleoptera: Bruchidae)

The dried-bean beetle Acanthoscelides obtectus is a major post-harvest pest, which can cause up to 30% losses from dry-stored beans. For the use of microbial agents for biocontrol of A. obtectus, it is of importance to identify cuticular lipids of this pest, if we are to understand the factors responsible for preferential adhesion or selective repulsion of entomopathogenic fungi that are potentially useful for biocontrol.The cuticular lipids of adult A. obtectus of both sexes were found to consist of hydrocarbons, aldehydes, methyl- and ethyl-esters of fatty acids, triacylglycerols, free fatty acids, alcohols and sterols. All the fatty acids identified in this study were found in both ether extracts and dichloromethane extracts. The dominant fraction of all the lipids isolated from this species consisted of C_16:0, C_18:0, C_18:1, C_18:2 and C_18:3 compounds. Males and females contained similar amounts of hexadecanoic acid, but there was a significant difference between the total amounts of C_18:0, C_18:1 and C_18:2 acids in the two groups. We have also successfully identified one of the sesquiterpenes present in the cuticle as α-farnesene.     

The influence of porous silicon on junction formation in silicon solar cells

In this work the results of a structural investigation by SEM of porous silicon (PS) before and after diffusion processes are reported. The formation of PS n⁺/p structures were carried out on PS p/p silicon wafers with two methods: from POCl₃ in a conventional furnace and from a phosphorous doped paste in an infrared furnace. Sheet resistance was found to be a strong function of PS structure. Further details on sheet resistance distribution are reported. The electrical contacts in prepared solar cells were obtained by screen printing process, with a Du Ponte photovoltaic silver paste for front contacts and home-prepared silver with 3% aluminium paste for the back ones. Metallization was done in the infrared furnace. Solar cell current–voltage characteristics were measured under an AM 1.5 global spectrum sun simulator. The average results for multi-crystalline silicon solar cells without antireflection coating are: I_sc=720 (mA), V_oc=560 (mV), FF=69%, Eff=10.6% (area 25 cm²).