X-ray computed micro tomography as complementary method for the characterization of activated porous ceramic preforms

X-ray computed micro tomography (CT) is an alternative technique to the classical methods such as mercury intrusion (MIP) and gas pycnometry (HP) to obtain the porosity, pore-size distribution, and density of porous materials. Besides the advantage of being a nondestructive method, it gives not only bulk properties, but also spatially resolved information. In the present work, uniaxially pressed porous alumina performs activated by titanium were analyzed with both the classical techniques and CT. The benefits and disadvantages of the applied measurement techniques were pointed out and discussed. With the generated data, development was proposed for an infiltration model under ideal conditions for the production of metal matrix composites (MMC) by pressureless melt infiltration of porous ceramic preforms. Therefore, the reliability of the results, received from different investigation techniques, was proved statistically and stereologicall

Ispitivanje koagulacione aktivnosti prirodnih koagulanata ekstrahovanih iz različitih sorti pasulja

Coagulation and flocculation by adding chemicals are the methods that are usually used for removal of water turbidity. This study is concerned with the coagulation activity of extracts of various strains of bean. The aim was to ascertain if bean varieties influence coagulation activity. Active components were extracted from 1 g of ground sample with 100 ml distilled water. Contents of dry matter and nitrogen were specified in the solid samples, and the content of soluble nitrogen was determined in the extracts. These data were used to calculate the efficiency of extraction of nitrogen-containing compounds. The coagulation activity was assessed by jar test using synthetic turbid water, of the initial pH 9 and turbidity 35 NTU. The jar test was carried out by adding different amounts of extracts to model water, and stirring the content. After sedimentation for 1 h, residual turbidity was determined by turbidimeter and coagulation activity was calculated. The increment of organic matter concentration after the coagulation was also determined. These experiments confirmed that extracts of all investigated strains of bean could be used successfully as natural coagulants.Koagulacija i flokulacija predstavljaju najčešće primenjivane metode za bistrenje vode, i uglavnom se izvode dodatkom hemijskih koagulanata. U ovom radu je ispitivana koagulaciona aktivnost ekstrakata dobijenih iz semena različitih sorti pasulja, a s ciljem da se utvrdi mogućnost njihove primene kao prirodnih koagulanata za uklanjanje mutnoće vode, i da se utvrdi uticaj sorte pasulja na koagulacionu aktivnost. Ekstrakcija aktivnih komponenti je izvedena sa 100 ml destilovane vode iz 1 g samlevenog uzorka. U čvrstim uzorcima je određen sadržaj suve materije i azota, a u ekstraktima sadržaj rastvorljivog azota, na osnovu čega je određena efikasnost ekstrakcije jedinjenja sa azotom. Za određivanje koagulacione aktivnosti ekstrakata izveden je džar-test, dodavanjem različitih doza ekstrakata model vodi, čiji je pH 9 i početna mutnoća 35 NTU. Nakon mešanja u određenom vremenskom intervalu, čaše su ostavljene da se njihov sadržaj istaloži, a zatim je u bistrom delu određivana mutnoća, i preko nje koagulaciona aktivnost. Takođe je utvrđen doprinos svakog od ekstrakata porastu sadržaja organskih materija u vodi nakon njenog bistrenja u odnosu na slepu probu, a preko permanganatnog broja. Ovim eksperimentima potvrđeno je da se ekstrakti svih ispitivanih sorti pasulja mogu uspešno primeniti kao prirodni koagulanti

THE INFLUENCE OF THE BERRY SIZE ON THE SKIN ANTHOCYANINS CONTENT OF SOME BLACK WINE VARIETIES

The influence of the berry size on the skin anthocyanins content of the black wine grape varieties Cabernet sauvignon (clone 169), Merlot (clone 348) and Pinot noir (clone 115) was studied. Research was conducted in vineyard of Experimental estate “Radmilovac” and  in the laboratory of  Faculty of Agriculture, University of Belgrade. The aim of the research was the determination of an anthocyanin of malvidin-3-glucoside on the berry skin. For all three varieties, berries were separated into three categories: small, medium and large. Based on the results, the goal was to compare the berry skin anthocyanin content of different sizes of berries. Determination of fertility coefficients, yield indicators, analysis of the composition and structure of clusters and berries and the content of sugars and total acids were performed regularly. The obtained results on the content anthocyanin of malvidin-3-glucoside were expressed in mg/g skin fresh weight. Varieties Cabernet sauvignon and Pinot noir had an expected result, meaning that the highest anthocyanin content was recorded in the smallest berries (diameter < 7.5 mm). For the Merlot variety, the highest anthocyanin content was observed in the medium berries (diameter 7.6 – 10 mm). The lowest anthocyanin content in varieties Cabernet sauvignon and Merlot was obtained in the largest berries (diameter > 10.1 mm), which was the expected result, while in the Pinot noir variety the lowest anthocyanin content was registered in the medium category (diameter 7.6 – 10 mm). Variety Cabernet sauvignon (clone 169) showed the highest anthocyanins content (average 6.871 mg/g fresh skin weigh), followed by Merlot variety, clone 348 (average 4.61 mg/g fresh skin weigh), whereas the lowest anthocyanin content was observed in Pinot noir, clone 115 (average 4.05 mg/g fresh skin weigh)

Surface Reconstruction of Hexagonal Y-doped HoMnO3 and LuMnO3 studied using low-energy electron diffraction

We have investigated the (0001) surfaces of several hexagonal manganite perovskites by low-energy electron diffraction (LEED) in order to determine if the surface periodicity is different from that of the bulk materials. These LEED studies were conducted using near-normal incidence geometry with a low energy electron microscope (LEEM)/LEED apparatus from room temperature to 1200 degrees Celsius and with an electron energy in the range of 15-50 eV. Diffraction patterns showed features of bulk-terminated periodicity as well as a 2\times2 surface reconstruction. Possible origins for this surface reconstruction structure are discussed and comparisons are made with surface studies of other complex oxides.Comment: 22 pages, 7 figure

Uticaj genotipa, đubrenja i mikroklimata na posetu polinatora i prinos suncokreta

Effects of genotype, fertilization and microclimate on visitation by pollinators and yield of sunflower were analyzed in the course of 2001 in a stationary field trial established at Rimski Šančevi experiment field. We analyzed four sunflower hybrids (Velja, NS-H-45, NS-H-111 and NS-H-702) grown in four fertilization variants. Bee visitation was monitored during flowering, making nine counts per day. Nectar content and weather parameters were observed at the same time. Seed yield per head measured after harvest. Significant yield differences were established among the hybrids as well as among the fertilization variants. Nectar content significantly differed among the hybrids (3.8 - 8.9 mg/20 flowers), and the fertilization variants (5.0 - 7.5 mg/20 flowers). Differences in bee visitation frequency observed among the hybrids and fertilization variants were in close association with the ranking of the hybrids for nectar content. Air temperature had a higher influence on bee visitation than relative air humidity. The influence of wind was insignificant. The daily dynamics of bee visitation showed one or two peaks, depending on the dynamics of flowering of individual hybrids.Izvršena je analiza uticaja genotipa, đubrenja i mikroklimata na posetu pčela i prinos suncokreta. Ispitivanja su obavljena na Rimskim Šančevima, na stacionarnom ogledu, u 2001. godini. Ispitivana su 4 hibrida suncokreta (Velja, NS-H-45, NS-H-111 i NS-H-702), na 4 varijante đubrenja. Praćenje posete pčela tokom perioda cvetanja, tokom dana vršeno je u 9 navrata. Utvrđen je sadržaj nektara i prinos semena po glavi kao i pojedini vremenski činioci u vreme opažanja. Utvrđene su značajne razlike u prinosu između hibrida, a takođe i između pojedinih varijanti đubrenja. Sadržaj nektara u cvetu značajno se razlikovao između pojedinih hibrida (3,8 - 8,9 mg/20 cvetova), i varijanti đubrenja (5,0 - 7,5 mg/20 cvetova). Poseta pčela se razlikovala između pojedinih hibrida i varijanti đubrenja, a rang hibrida bio je isti kao i kod sadržaja nektara. Temperatura vazduha pokazala je jači uticaj na posetu pčela od relativne vlažnosti vazduha dok vetar nije pokazao značajan uticaj. Dnevna dinamika posete imala je jedan ili dva maksimuma u zavisnosti od vremena cvetanja pojedinih hibrida

Do Political Attitudes Matter for Epistemic Decisions of Scientists?

The epistemic attitudes of scientists, such as epistemic tolerance and authoritarianism, play important roles in the discourse about rivaling theories. Epistemic tolerance stands for the mental attitude of an epistemic agent, e.g., a scientist, who is open to opposing views, while epistemic authoritarianism represents the tendency to uncritically accept views of authorities. Another relevant epistemic factor when it comes to the epistemic decisions of scientists is the skepticism towards the scientific method. However, the question is whether these epistemic attitudes are influenced by their sociopolitical counterparts, such as the researcher's degree of conservatism. To empirically investigate the interplay between epistemic and sociopolitical attitudes of scientists, we conducted a survey with researchers (N = 655) across different disciplines. We propose scales for measuring epistemic tolerance and epistemic authoritarianism, as well as a scale for detecting the participants' readiness to question the scientific method. Furthermore, we investigate the relationship between epistemic tolerance and epistemic authoritarianism on the one hand, and career stage and sociopolitical views on the other hand. Interestingly, our study found only small correlations between the participants' degree of conservatism and their epistemic attitudes. This suggests that political views, against common argumentation, actually do not play an important role in one's scientific decisions. Moreover, social scientists scored higher on the epistemic tolerance and lower on the epistemic authoritarianism scale than natural scientists. Finally, the results indicate that natural scientists question the scientific method less than social scientists

The influence of the electric field shape on the gas breakdown under low pressure and small inter-electrode gap conditions

The connection between nonhomogeneities of the electric field and the value of the breakdown voltage [direct current (dc), pulls] in gases (N-2, SF6) under low pressure and small inter-electrode gap was investigated in this paper. The obtained. results show that the values of. the breakdown voltages for nonhomogenous fields are considerably higher than the values for homogenous fields. It was also established that there is some disagreement between experimentally and theoretically (numerically) obtained values of the do breakdown voltages for nonhomogenous fields. These results could be explained by the small distance effect and by the combination of the gas and vacuum breakdown mechanisms