Mobility of platinum and gold in the environment and the roles of microbes

Platinum (Pt) and gold (Au) are precious heavy metals that are widely used in the jewellery, automobile, chemical and medical industries. This increased use has resulted in their introduction into the environment at elevated concentrations which can adversely affect both ecosystem and human health. Currently, there is limited information available on the behaviour of Pt and Au in terrestrial environments and their impact on soil microorganisms. There is therefore a need to assess the environmental impacts of increased amounts of Pt and Au contamination. The aims of this study are to study the fate, transport and microbial interactions associated with Pt and Au in Australian soils. The first experimental investigation of this thesis was carried out using a bacterium Cupriavidus metallidurans (C. metallidurans), known to significantly biomineralize Au but with limited information available on its interactions with Pt. Therefore, the aim of this research was to assess the ability of C. metallidurans to biomineralize Pt. The results showed that both C. metallidurans and a control microorganism Escherichia coli (E. coli) tolerated platinum (IV) chloride (PtCl4). However, C. metallidurans had a higher tolerance to Pt, with the number of cells surviving at high PtCl4 concentration (10,000 µM) 300-fold more than that of E. coli. Both isolates formed Pt nanoparticles but C. metallidurans showed a higher Pt retention (87%) than E. coli (74%) in sand columns. C. metallidurans was tolerant of Pt and effective at its biomineralization, confirming its suitability for use for further studies on Pt and Au environmental behaviour. The interaction of Pt and Au with the biotic and abiotic components of Australian soils is largely unstudied, although metal transformation may lead to the nanoparticles formation. Importantly, little is known about the transportation of Pt and Au nanoparticles in soil. The second scientific investigation evaluated the movement of Pt and Au nanoparticles (AuNPs and PtNPs) in columns containing different matrices (sand only, sand-clay, sand-humic acids and sand-FeO) and soil types, including an organic rich soil, FoxLane (FLN) and an iron rich soil, Jamberoo (JBR). Nanoparticle aggregations with soil particles were observed and Transmission Electron Microscopy (TEM) showed that the nanoparticles formed both homo- and hetero-aggregates in columns. Gold NPs were more mobile (as shown by reduced retention in column) and more reactive (as determined by Fourier-transform infrared spectroscopy (FTIR) analysis) than PtNPs. The rate of movement of nanoparticles based on the breakthrough curves through the various matrices was, in decreasing order of mobility; sand (2 hours) > JBR soil (4 hours) > FLN soil (6 hours) > sand-clay (8-10 hours) >sand-FeO (8-12 hours) > sand-humic acids (12 hours). The aim of the third experimental investigation was to assess the effects of different Pt and Au concentrations (1, 25, 100, 500 and 2,000 mg kg-1) on soil respiration and activities of seven key soil enzymes (N-acetyl glucosaminidase, phosphatase, β-D-glucosidase, β-D-cellobiohydrolase, β-D-xylosidase, α-D-glucosidase and arylsulphatase) in a range of Australian soils. The findings from this study showed that the effects of Au and Pt application on the soil microbial activity were related to soil types; (1) a high pH (alkaline) soil (Minnipa, MNP), (2) a low pH (acidic) soil (BrnGrounds, BGR), (3) an iron rich soil (Jamberoo, JBR), (4) an organic matter rich soil (FxLane, FLN), and (5) a high metal/silt soil (Pinpinio, PPN). Platinum or Au at most of the concentrations evaluated (1-2,000 mg kg-1), generally resulted in significant reductions in soil respiration rates in BGR, JBR, MNP and PPN soils. Some reduction in soil respiration was also observed in FLN soils when Pt was applied, while the application of Au increased soil respiration in FLN soils at all concentrations (except 2,000 mg kg-1). The application of Pt inhibited the activities of most of or all the enzymes tested in BRG, FLN, JBR and PPN soils while enhancing the activities of most of the enzymes in MNP soils (1-100 mg kg-1). In contrast, the addition of Au resulted in a significant reduction in most enzyme activities in BGR, JBR and MNP soils while enhancing enzyme activities in FLN and PPN soils. The explanation for these differential results may be a combination of specific enzyme sensitivity, metal concentration and soil type. The aim of the final results chapter was to evaluate changes in the bacterial community of four soils (BGR, FLN, PPN and MNP) at three Au and Pt concentrations (1, 25 and 100 mg kg-1) using Next Generation Sequencing tools (NGS). The soil bacterial community was affected by both soil type and metal concentration. While no shift in the dominant groups (Class level) was observed in FLN and MNP soils following addition of Pt and Au with Proteobacteria and Actinobacteria being dominant, other bacterial Phyla/Classes such as Kazan-3B-28, Firmicutes and Caldithrix were selected in BGR and PPN soils. Amendments with Au significantly reduced bacterial community diversity in organic rich BRG soil while amendments with Pt substantially reduced bacterial diversity in the three other soil types. At the Family level, shifts in bacterial community structure were observed in all Pt- and Au- amended samples which were positively correlated with increasing metal concentrations. Bacteria that were selectively enriched only in Pt-amended samples (irrespective of soil type) were identified as belonging to the groups Burkholderiales, Burkholderiaceae, Alicyclobacillaceae, Rubrobacteraceae, Cytophagaceae and Oxalobacteraceae. In Au- amended samples, the bacterial groups that increased in Pt amended samples belonged to Sphingomonadaceae and Rhodospirillaceae. Generally, Au and Pt toxicity was concentration related with Au more toxic to soil bacterial communities at a lower concentration (25 mg kg-1). One key aim of this study was to assess the transportation of Pt complexes, Au- and Pt-NPs in different environmental media (soils). Overall, this research has demonstrated that Pt and Au have different rates of transportation in soils which affected their interactions with soil microorganisms and components. This research’s outcomes have important implications in the management (remediation) of Pt and Au-gold contaminated environments. Future research should include the application of NGS to assess Pt and Au effects on microbial function and assays to isolate metal resistant microorganisms for use in bioremediation

A Revised Checklist of Mongolian Mammal Species

A revised annotated checklist of Mongolian mammals is presented, supplemented with comments on modifications in species- and genus-level taxonomy introduced over the last 30 years. The checklist includes 140 species compared to 124 species recognized three decades ago by SOKOLOV & ORLOV (1980). Since then, four species were newly described; seven species were registered for the first time on Mongolian territory. Names for more than 20 taxa have changed, on most occasions this change occurred not for purely nomenclatural reasons but rather as a result of taxonomic revisions at the species level which have elevated the rank of many nominal taxa treated previously as subspecies. Recent molecular studies have shown that many widespread Central Asian species, in fact, consist of several highly divergent phylogenetic lineages the taxonomic status of which is yet unclear. Therefore, further updates to our knowledge of mammal biodiversity in Mongolia are expected

Offline diagnostika rotoru asynchronního motoru

Asynchronous machines are widely used in various industrial applications, and their reliable operation is essential to maintain the production process. Rotor faults are one of the most common types of faults in asynchronous machines and can lead to a significant decrease in the machine's efficiency and lifespan. Offline diagnostic methods have been developed to detect rotor faults in asynchronous machines, including vibration analysis, current signature analysis, and motor current signature analysis. This research paper presents an overview of offline diagnostic methods for detecting rotor faults in asynchronous machines, their principles, advantages, and limitations. The paper also includes case studies of rotor fault diagnosis in asynchronous machines using Finite Element Method (FEM) and FFT analysis for Maxwell 2D electromagnetic FEM model.Asynchronní stroje jsou široce používány v různých průmyslových aplikacích a jejich spolehlivý provoz je nezbytný pro zachování výrobního procesu. Poruchy rotoru jsou jedním z nejčastějších typů poruch asynchronních strojů a mohou vést k výraznému snížení účinnosti a životnosti stroje. Pro detekci poruch rotoru asynchronních strojů byly vyvinuty offline diagnostické metody, včetně analýzy vibrací, analýzy proudové signatury a analýzy proudové signatury motoru. Tento výzkumný článek uvádí přehled offline diagnostických metod pro detekci poruch rotoru asynchronních strojů, jejich principy, výhody a omezení. Článek rovněž obsahuje případové studie diagnostiky poruch rotoru asynchronních strojů pomocí metody konečných prvků (MKP) a analýzy FFT pro Maxwellův 2D elektromagnetický model MKP.410 - Katedra elektroenergetikyvelmi dobř

Micro-alloying and surface texturing of Ti-6Al-4V alloy by embedding nanoparticles using gas tungsten arcwelding

YesTitanium alloy Ti-6Al-4V is known for both its excellent mechanical properties and its low surface hardness. This study explores a two-step process for depositing a hard nanocrystalline coating onto the surface of the Ti-alloy, followed by surface melting, which embeds hard nanoparticles into a thin surface layer of the alloy. The treated surface layer was studied using X-ray diffraction, scanning electron microscopy, and Vicker's micro-hardness testing. The results of the study show that the surface of the Ti-6Al-4V alloy can be successfully hardened by embedding nanosized Al2O3 particles into the surface using gas tungsten arc welding to melt the surface of the material. Surface melting the Ti-6Al-4V alloy with a 50A welding current produced the maximum microhardness of 701 HV0.2kg. The micro-hardness of the treated surface layer decreased with the increasing size of the nanoparticles, while the roughness of the surface increased with the increasing welding current. The heat input into the surface during the surface melting process resulted in the formation of various intermetallic compounds capable of further increasing the hardness of the Ti-6Al-4V surface

Self-compacting concrete blended with fly ash and ground granulated blast furnace slag

This research study was performed on the self-compacting concrete (SCC) mixture blended with 5%, 10%, 15%, and 20% of fly ash (FA) and 5%, 10%, 15%, and 20% of ground granulated blast furnace slag (GGBFS) individually and with a combination of FA and GGBFS, that is, 5% (2.5% FA and 2.5% GGBFS), 10% (5% FA and 5% GGBFS), 15% (7.5% FA and 7.5% GGBFS), and 20% (10% FA and 10% GGBFS) by the weight of Portland cement. The main theme of this research work is to determine the fresh properties in terms of filling ability (slump flow, V�Funnel and T50 flow), passing ability (J-Ring and L-box), and sieve segregation test of SCC mixture and hardened properties in terms of compressive, split tensile, and flexural strengths and permeability of SCC mixture. However, the concrete specimens were prepared at 0.40 water– cement ratio, and these specimens were tested at 28 and 90 days. The results showed that the fresh properties of SCC mixture blended with FA and GGBFS provide better results with addition of a superplasticizer and hardened properties of SCC mixture are enhanced while utilizing 5% of GGBFS and 5% of FA by the weight of PC at 28 and 90 days, respectively

Solar-powered direct contact membrane distillation system: performance and water cost evaluation

YesFresh water is crucial for life, supporting human civilizations and ecosystems, and its production is one of the global issues. To cope with this issue, we evaluated the performance and cost of a solar-powered direct contact membrane distillation (DCMD) unit for fresh water production in Karachi, Pakistan. The solar water heating system (SWHS) was evaluated with the help of a system advisor model (SAM) tool. The evaluation of the DCMD unit was performed by solving the DCMD mathematical model through a numerical iterative method in MATLAB software®. For the SWHS, the simulation results showed that the highest average temperature of 55.05 ◦C and lowest average temperature of 44.26 ◦C were achieved in May and December, respectively. The capacity factor and solar fraction of the SWHS were found to be 27.9% and 87%, respectively. An exponential increase from 11.4 kg/m2 ·h to 23.23 kg/m2 ·h in permeate flux was observed when increasing the hot water temperatures from 44 ◦C to 56 ◦C. In the proposed system, a maximum of 279.82 L/day fresh water was produced in May and a minimum of 146.83 L/day in January. On average, the solar-powered DCMD system produced 217.66 L/day with a levelized water cost of 23.01 USD/m3This research was funded by the Researcher’s Supporting Project Number (RSP-2021/269), King Saud University, Riyadh, Saudi Arabia

Beaver Research in the Uvs Nuur Region

In 1985, 1988, and 2002 Castor fiber birulai was introduced to the Tes Gol of the Uvs Nuur basin in North-western Mongolia. The beavers migrated through the Republic of Tyva and settled in the middle part of Tes Gol near the Tyvinian-Mongolian border. About 10 colonies were recorded in this region in 2002. Strict protection of Castor fiber birulai has to be ensured in Mongolia and the Republic of Tyva in future

First Report of the Herb Field Mouse , \u3ci\u3eApodemus uralensis\u3c/i\u3e (Pallas, 1811) from Mongolia

The herb fi eld mouse, Apodemus uralensis (Pallas, 1811) is recorded for the fi rst time in Mongolia, from western part of the Mongolian Altai and the adjacent Mongolian part of the Dzungarian Gobi. In addition, we discovered several additional fi ndings of this species recorded as early as 1976 from diff erent scientifi c collections. Body and skull measurements are presented along with a molecular genetic analysis of one specimen

Structure of nanoparticles embedded in micellar polycrystals

We investigate by scattering techniques the structure of water-based soft composite materials comprising a crystal made of Pluronic block-copolymer micelles arranged in a face-centered cubic lattice and a small amount (at most 2% by volume) of silica nanoparticles, of size comparable to that of the micelles. The copolymer is thermosensitive: it is hydrophilic and fully dissolved in water at low temperature (T ~ 0{\deg}C), and self-assembles into micelles at room temperature, where the block-copolymer is amphiphilic. We use contrast matching small-angle neuron scattering experiments to probe independently the structure of the nanoparticles and that of the polymer. We find that the nanoparticles do not perturb the crystalline order. In addition, a structure peak is measured for the silica nanoparticles dispersed in the polycrystalline samples. This implies that the samples are spatially heterogeneous and comprise, without macroscopic phase separation, silica-poor and silica-rich regions. We show that the nanoparticle concentration in the silica-rich regions is about tenfold the average concentration. These regions are grain boundaries between crystallites, where nanoparticles concentrate, as shown by static light scattering and by light microscopy imaging of the samples. We show that the temperature rate at which the sample is prepared strongly influence the segregation of the nanoparticles in the grain-boundaries.Comment: accepted for publication in Langmui