Steroid biosynthetic enzyme activities in leachate-exposed female perch (Perca fluviatilis) as biomarkers for endocrine disruption

Studies have shown that adult female perch in a freshwater lake, Molnbyggen, Sweden, have a reproductive disorder caused by unidentified endocrine disrupting compounds (EDCs) leaching from a local refuse dump. The adverse effects include shallow open sores, low ratio of sexually mature individuals, low gonadosomatic index and low circulating levels of androgens. We hypothesised that the low androgen levels could be a result of impaired production and/or stimulated excretion of androgens by EDCs. From October 2000 to November 2001, at time-points important in the perch reproductive cycle, adult female perch were collected in Molnbyggen and in the reference lake, Djursj?n. The activities of three key enzymes in androgen biosynthesis: 17alpha-hydroxylase (17OHlase), 17,20-lyase (lyase) and 17beta-hydroxysteroid dehydrogenase (17betaHSD) were determined in head kidney or ovary. The relationship between enzyme activities and plasma steroid concentrations was examined. Ovarian histopathology and the determination of brain aromatase activity were also included in the study. Similar 17OHlase, 17betaHSD and aromatase activities were found in Molnbyggen females and reference fish throughout the year. Head kidney 17OHlase showed a positive correlation to cortisol levels (r=0.754; p<0.001) but not to androgen levels. Molnbyggen females exhibited lower ovarian lyase activity during vitellogenesis than reference fish. Atretic oocytes were on most occasions more frequent in sexually immature than in sexually mature females. The results suggest that neither 17OHlase, 17betaHSD nor aromatase is the target for EDCs disrupting the androgen homeostasis of exposed female perch. Further investigation is needed to establish the role of decreased ovarian lyase activity in endocrine homeostasis, but the possibility of increased excretion of androgens should also be examined.     

Graphene based catalyst supports for high temperature PEM fuel cell application

In this study, the effect of graphene nanoplatelet (GNP) and graphene oxide (GO) based carbon supports on polybenzimidazole (PBI) based high temperature proton exchange membrane fuel cells (HT-PEMFCs) performances were investigated. Pt/GNP and Pt/GO catalysts were synthesized by microwave assisted chemical reduction support. X-ray diffraction (XRD), Thermogravimetric analysis (TGA), Brauner, Emmet and Teller (BET) analysis and high resolution transmission electron microscopy (HRTEM) were used to investigate the microstructure and morphology of the as-prepared catalysts. The electrochemical surface area (ESA) was studied by cyclic voltammetry (CV). The results showed deposition of smaller Pt nanoparticles with uniform distribution and higher ECSA for Pt/GNP compared to Pt/GO. The Pt/GNP and Pt/GO catalysts were tested in 25 cm² active area single HT-PEMFC with H₂/air at 160 °C without humidification. Performance evaluation in HT-PEMFC shows current densities of 0.28, 0.17 and 0.22 A/cm² for the Pt/GNP, Pt/C and Pt/GO catalysts based MEAs at 160 °C, respectively. The maximum power density was obtained for MEA prepared by Pt/GNP catalyst with H₂/Air dry reactant gases as 0.34, 0.40 and 0.46 W/cm² at 160 °C, 175 °C and 190 °C, respectively. Graphene based catalyst supports exhibits an enhanced HT-PEMFC performance in both low and high current density regions. The results indicate the graphene catalyst support could be utilized as the catalyst support for HT-PEMFC application.     

Estimation of functional dependency parameters at zero median value of noises in measurements

In the paper, we study a problem of estimating functional dependency parameters by empirical data with random noises. A specific feature of the formulation is a replacement of a traditional assumption of zero mathematical expectation of a noise by the condition of equality to zero of a median value of the noise. We represent an algorithm for constructing estimates of parameters minimizing a mathematical expectation of losses including the variant of spline approximation. We interpret such estimates. The results of the experiments are given.     

Preparation and Characterization of Copper Borates as Lubricant Additives

The present study attempts the preparation of copper borate as a lubricating oil additive by the reaction of copper nitrate and borax solutions. Effects of borax/copper ratio, surface active agent （Span 60）, pH, temperature and mixing time on properties of the products were investigated. The obtained products were not pure form; therefore they were analyzed in detail. They were characterized by color measurement, X-ray diffraction, SEM, zeta sizer, ICP, EDX, TG, DSC, CHNS analysis and FTIR spectroscopy. Mainly Cu2（OH）3NO3 with nitrate ions partially substituted with borate ions was obtained at pH 3.7. There were borate ions equivalent to 0.32 tools of Cu（BO）2 per tool of CUE（OH）3NO3. The borate ions should have replaced partially the nitrate ions in Cu2（OH）3NO3 without changing its crystal structure. On the other hand, Cu （BO2）l 5（OH）074＇（H20）015 was produced at pH 10.2. It also contained 0.11 mol NO3- per tool. By mixing of dilute solutions at pH 8.2 and drying at room temperature nanopartieles of Cu（BO2）I 5（H20）6 having 0.05 NO3 per tool was obtained. The precipitates obtained at pH 10.1 and 8.2 were tested as lubricant additives. When they were added to lubricating oil with Span 60, the friction coefficient was reduced 28 % and 65 % for the precipitates prepared at pH 10.1 and 8.2, respectively.     

Practically achievable accuracy and reliability of the solution of inverse heat-conduction problems

We develop a method of solution of inverse heat-conduction problems which makes it possible to obtain a guaranteed minimum of reliable information in conditions of indeterminacy.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 52, No. 2, pp. 316–323, February, 1987.     

Amphiphilic conjugated block copolymers: synthesis and solvent-selective photoluminescence quenching

A novel, amphiphilic, conjugated block copolymer is described, which was prepared by a Suzuki-type cross-coupling of 2-bromo-[9,9-bis(2-ethylhexyl)fluorene]-7-pinacolato boronate as an AB-type monomer and monobromo-substituted poly[3-(6-bromohexyl)thiophene] (Br-P3BrHT) as a polymeric end capper in the key step. PF-P3PHT (P2; PF = poly(9,9-dialkylfluorene); P3PHT = poly[3-(6-diethylphosphonato-hexyl)thiophene]) as the amphiphilic target polymer was then generated in a polymer-analogous conversion of the alkyl bromide side chains of the PF-P3BrHT (P1) precursor into polar alkyl phosphonate groups by reaction with triethyl phosphite. P2 shows a strong influence of the solvent polarity on the optical spectra (absorption, emission). Treatment of solutions of P2 in tetrahydrofuran (THF), a nonselective solvent, with increasing amounts of solvents that are selective for the polar polythiophene blocks (water) or the nonpolar polyfluorene blocks (hexane), respectively, results in the formation of two different types of core-shell aggregates, which show rather different optical properties (photoluminescence quenching, excitation energy transfer).     

Semiquantitative method for the evaluation of grease barrier coatings

Many tests are known for testing the grease barrier performance of coatings in paper or paperboard. Some are manifested in standard procedures such as TAPPI, ASTM, or ISO, but as many procedures were developed and modified by companies and research groups. Mainly the test methods are based on visually detecting the amount of oil, which is in most cases dyed for better contrast, penetrating through the coating, meaning the procedures are based on a subjective visual evaluation and thus often not linked for instance to a statistical meaningful physical value. We found that by using a slightly modified ASTM D 722 test the L*a*b* color coordinates determined with a commercial handheld spectrophotometer are related to the grease barrier performance of an organic coating. By applying this new method the penetration time of an oil/dye mixture could be correlated to the lightness L* and chromaticity b* and fitted by an exponential function. Furthermore, the coating was slightly modified and an improvement or worsening of the grease barrier could be detected clearly outside of the statistical scatter of a control series. We call this method semiquantitative, since the level of grease barrier of a coating is not measured directly by a quantitative value, but color coordinates are correlated in a series to the effectiveness of the grease barrier.     

Hot-hole-induced degradation in depletion-mode n-channel MOSFETs

Injection and trapping of hot holes was studied in n-channel depletion-mode MOSFETs and compared to that in enhancement devices. The rate of device degradation was found to decrease with increasing channel doping. A model is proposed explaining this behaviour from the current transport in the buried channel and from the effect of the channel doping level on the field near the drain.