High-density Particles Research Articles

The formation of the complex oxide in Ni-based alloy powder during mechanical milling and heat treatment

Ni-based oxide dispersion strengthening (ODS) alloys fabricated by mechanical alloying (MA) and hot isostatic pressing (HIP) improve mechanical properties by adding yttria as a dispersoid. The evolution of the additive Y2O3 particles was studied by scanning electron microscope (SEM) for the powder milled for 5 h, 20 h, 40 h, and the un-milling powder. The samples of powders after the mechanical milling and the heat treatment at 1175 °C for 3 h corresponding to HIP were observed by high-resolution transmission electron microscopes (HRTEM). In the process of the mechanical alloying, the Y2O3 crystallites underwent dispersion, dissolution, and partly transformed into YCrO3 and Y2Ti2O7 particles. A small amount of the complex oxide particles could be produced in the process of mechanical milling. A high number density of complex oxide particles precipitated and coarsened in the powder after the heat treatment. Mechanical milling could induce the formation of complex oxide particles because of their formation energies. The difference in size of YCrO3 and Y2Ti2O7 particles in the powder after the heat treatment mainly attribute to diffusion coefficient, solubility, and the interfacial energy.

Bio efficacy of Cinnamaldehyde from <em>Cinnamomum verum</em> essential oil against <em>Culex quinquefasciatus</em> (Diptera: Culicidae)

This research aims to study the efficacy of Cinnamomum verum (Cv) extracts for ovicidal, larvicidal, and repellent activities against Culex quinquefasciatus mosquito vectors. The active components of C. verum or cinnamon oil by Gas Chromatography (GC) analysis showed the highest cinnamaldehyde at 83.53%. For ovicidal assay, C. verum essential oil at concentrations 12.5, 25 and 50 ppm at 72 h had 100% egg hatch inhibition and had a significant difference when compared to the control group (p<0.05). Larvicidal activity showed that concentrations of 25 and 50 ppm were highly effective in killing 100% mosquito larvae. Morphological changes in egg raft showed a faded color and eggs that seemed to have split from their raft while the larvae changed to a pale white wrinkled body with a destroyed inner tube of the body and were motionless. A Scanning electron microscope study showed that the eggshell and micropyle were wrinkled with the chitin peeled out. After treatment with cinnamon oil, larvae appeared to have a wrinkled body, the thorax and abdominal cuticle were also destroyed with high density of oil particles observed on mouth brushes and obstructing the spiracle. The repellent assay showed that cinnamon oil could repel both male and female mosquitos for up to 180 min. From the results, it was concluded that cinnamon oil had highly effective repellency against Culex quinquefasciatus adults and insecticidal activity on eggs and larvae stages evidenced by LC50 at 6.59±0.54, 9.07±0.67 and 36.91±7.56 ppm and its morphological changes indicated how the mosquito could not survive after cinnamon oil treatment hence this may be a useful alternative method that is green friendly for controlling mosquitoes in endemic areas.

High voltage pulse-enabled coal desulfurization and deashing – Part 1: Selective breakdown of mineral matter

Coal desulfurization and deashing are the common challenges that the coal industry worldwide is facing. A new technique is presented in this paper using high voltage pulse (HVP) selective breakdown of mineral matter that exhibits higher electric conductivity/permittivity than coal, followed by size-based separation to reject the pyritic sulfur-bearing and ash-bearing mineral matter. Part1 of this study demonstrates HVP selective breakdown of mineral matter, and Part 2 reports the optimization of the HVP treatment to minimize coal loss during the coal desulfurization and deashing process. Two coal samples, one bituminous and one anthracite, were collected from two coal mines in China and used to assess the viability of this new HVP technique for the coal industry. In the paired-particle tests with one low-density (<1.47 RD) particle and one high-density (greater than1.77 RD) particle in each batch subjected to one HVP discharge, over 75% of probabilities were observed that the high-density particles broken and the low-density particles remained intact, resulting in distinct product size distributions of the two density groups. In the multi-particle tests to treat the as-received Coal B sample without prior density-fractionation, the particles remaining on the parent size fraction (19–26.5 mm feed) after HVP treatment contained 0.49% sulfur, 13.4% ash, and 87.6% carbon, changing from 1.92% sulfur, 30.1% ash, and 78.5% carbon contents in the feed. The HVP treatment with <1 kWh/t specific energy (spark) resulted in 89.8% sulfur, 82.2% ash, and 55.6% carbon reporting to the −19 mm stream.

ApoE and ApoE Nascent-Like HDL Particles at Model Cellular Membranes: Effect of Protein Isoform and Membrane Composition.

Apolipoprotein E (ApoE), an important mediator of lipid transportation in plasma and the nervous system, plays a large role in diseases such as atherosclerosis and Alzheimer's. The major allele variants ApoE3 and ApoE4 differ only by one amino acid. However, this difference has major consequences for the physiological behaviour of each variant. In this paper, we follow (i) the initial interaction of lipid-free ApoE variants with model membranes as a function of lipid saturation, (ii) the formation of reconstituted High-Density Lipoprotein-like particles (rHDL) and their structural characterisation, and (iii) the rHDL ability to exchange lipids with model membranes made of saturated lipids in the presence and absence of cholesterol [1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) or 1-palmitoyl-2-oleoyl-glycero-3-phosphocholine (POPC) with and without 20 mol% cholesterol]. Our neutron reflection results demonstrate that the protein variants interact differently with the model membranes, adopting different protein conformations. Moreover, the ApoE3 structure at the model membrane is sensitive to the level of lipid unsaturation. Small-angle neutron scattering shows that the ApoE containing lipid particles form elliptical disc-like structures, similar in shape but larger than nascent or discoidal HDL based on Apolipoprotein A1 (ApoA1). Neutron reflection shows that ApoE-rHDL do not remove cholesterol but rather exchange saturated lipids, as occurs in the brain. In contrast, ApoA1-containing particles remove and exchange lipids to a greater extent as occurs elsewhere in the body.

Physical and thermo-chemical characterization of agricultural residues and municipal waste

Characteristics of crop residues such as size, angle of repose, colour and density, calorific value, percentage of moisture content and chemical composition affect the production of bio-fuels. These properties also affect drying and handling of biomass and the design of thermal conversion systems. These characteristics can vary noticeably from waste to waste. In this study, four local varieties of rice straw (Nabina, Tamapasara, Swarnaand NuaAchharmati), sugarcane bagasse, coconut coir and vegetable waste were characterized. Study revealed that the sugarcane bagasse has the darker color, higher particle density (384.66 kg.m-3) compared to others tested biomass. Sugarcane bagasse contained highest percentage 82.7% of volatile matter followed by coconut coir, vegetable waste and rice straw. Rice straw variety Nabina has shown the highest calorific value 22.98 MJ/kg compared to Tamapasara, Swarna and NuaAchharmati and can be utilized for biofuel production.

Orientation dependence of yield strength in a new single crystal-like FeCrAl oxide dispersion strengthened alloy

In the current study, new advanced oxidation-resistant FeCrAl oxide dispersion strengthened (ODS) alloys were developed via the control of composition-processing conditions for nuclear energy systems. For the first time, a single-crystal like recrystallized FeCrAl ODS alloy was achieved with a unique crystallographic texture of (110) 〈211〉 and a high number density of fine nanoscale oxide particles. Evaluation of yield strengths at different temperatures showed higher values in transverse direction than longitudinal direction. The orientation dependence of yield strength up to 800 °C was attributed to lower value of Schmid factor in transverse direction. Accordingly, the critical resolved shear stress of this practical class of advanced materials was calculated in various temperatures.

Radiation shielding properties of mortars containing heavyweight particles

Abstract In this study the radiation shielding properties of mortar samples were investigated. The samples were created by replacing heavyweight particles of iron, steel and chromium waste by calcareous sand in different volume percentages. Additionally, the effects of the physical properties of particles and samples on shielding properties is also discussed. In the scope of this work, the radiation shielding properties of mortar samples were measured by determining the values of mass attenuation coefficients by means of an experimental setup consisting of 133Ba, 137Cs and 60Co standard point sources and high purity germanium (HPGe) detector. It’s concluded that the highest mass attenuation coefficient values among the heavy particles were achieved by chromium particles. However, all the high-density particles used in the study improved the radiation shielding properties of the mortars considerably compared to ordinary mortars.

Motility-induced clustering and meso-scale turbulence in active polar fluids

Meso-scale turbulence was originally observed experimentally in various suspensions of swimming bacteria, as well as in the collective motion of active colloids. The corresponding large scale dynamical patterns were reproduced in a simple model of a polar fluid, assuming a constant density of active particles. Recent, more detailed studies in a variety of experimental realizations of active polar fluids revealed additional interesting aspects, such as anomalous velocity statistics and clustering phenomena. Those phenomena cannot be explained by currently available models for active polar fluids. Herein, we extend the continuum model suggested by Dunkel et al to include density variations and a local feedback between the local density and self-propulsion speed of the active polar particles. If the velocity decreases strong enough with the density, a linear stability analysis of the resulting model shows that, in addition to the short-wavelength instability of the original model, a long-wavelength instability occurs. This is typically observed for high densities of polar active particles and is analogous to the well-known phenomenon of motility-induced phase separation (MIPS) in scalar active matter. We determine a simple phase diagram indicating the linear instabilities and perform systematic numerical simulations for the various regions in the corresponding parameter space. The interplay between the well understood short-range instability (leading to meso-scale turbulence) and the long-range instability (associated with MIPS) leads to interesting dynamics and novel phenomena concerning nucleation and coarsening processes. Our simulation results display a rich variety of novel patterns, including phase separation into domains with dynamically changing irregularly shaped boundaries. Anomalous velocity statistics are observed in all phases where the system segregates into regions of high and low densities. This offers a simple explanation for their occurrence in recent experiments with bacterial suspensions.

Influence of rheocasting and rare earth metals on the 3D-microstructure of ZK60 Mg-alloy measured by multiscale X-ray computed tomography

Light weighting has been a key issue to meet stringent requirements on greenhouse gas emissions. One possible way of weight reduction is the substitution of heavier components with lighter metals like Magnesium. In this work, the internal architecture of cast and hot rolled ZK60 alloys with and without addition of 1.5 wt% rare earth metals (RE) has been investigated. The alloys were produced by permanent mould indirect chill cast (PMICC), while the material with 1.5 wt% RE was manufactured by additional rheocasting (RC). A multi-resolution procedure using X-ray computed tomography (XCT) was performed to investigate the alloys in size ranges from meso- (cast blocks) to micro-scale (microstructure). The voxel resolutions used were between (115 μm)3 down to (0.8 μm)3. Morphometric parameters such as volume, volume fraction, connectivity, structure separation, structure thickness etc. were calculated to characterize the 3D-microstructure of the various alloys. The alloys showed no detectable cracks in the as-cast condition, while macroscopic defects such as clusters of high-density Zr-rich particles as well as casting pores were identified. The Zr-rich particles as well as other primary intermetallic phases tended to agglomerate at the bottom of the ingots for all investigated alloys. The addition of RE increased the homogeneity of the microstructure in terms of spatial distribution as well as the global and local interconnectivities of intermetallic phases in the PMICC alloy. RC achieved a more homogeneous distribution of Zr-rich particles. Furthermore, RC led to changes of the solidification topology and increased the distance between the higher-density phases. Hot rolling reduced the fraction of pores formed during the casting process. However, pores were not detected in the ZK60 PMICC alloys after forming, while ZK60 + 1.5 wt% RE PMICC and RC showed the presence of voids that were not completely removed by hot rolling until the thickness was reduced about 60%.

CFD–DEM–VDGM method for simulation of particle fluidization behavior in multi-ring inclined-hole spouted fluidized bed

The simulation of particle fluidization behavior in a complex geometry with a large number of particles is challenging owing to the complexity of unstructured computational grids and high computational intensity. In this study, a virtual dual-grid model (VDGM) is proposed to calculate the solid volume fraction in unstructured grids and speed up the calculation. The VDGM is coupled with a computational fluid dynamics–discrete element method model to simulate particle fluidization behavior in a multi-ring inclined-hole spouted fluidized bed with 4.2 million particles under a high temperature of 1423 K. A computational fluid dynamics–discrete element method–virtual dual-grid model (CFD–DEM–VDGM) coupling model is implemented based on commercial software Fluent and EDEM. The time step settings in Fluent and EDEM and the pattern of particle data transfer in Fluent are improved to speed up the calculation. It is discovered that the VDGM can calculate the solid volume fraction in unstructured grids of complex geometry and speed up the calculation effectively. The calculation speed increased by more than 10 times compared with that of the segmentation sampling method. The new pattern of particle data transfer in Fluent can reduce data transfer time by more than 90%. The fluidization behavior of 4.2 million high-density particles in the multi-ring inclined-hole spouted fluidized bed is obtained and analyzed in detail. The CFD–DEM–VDGM coupling method is validated for the bed expansion height and spouting cycle time in a spouted fluidized bed via experimental results.

3D Particle Localization in Living Cells by Deep Learning

Point spread function engineering techniques have extended the axial range accessible to fluorescence microscopy by simple modifications to the optical path of a microscope. A particularly promising engineered PSF is the double helix PSF (DHPSF), which provides an axial range of over 2 μm. This extended depth allows sub-diffraction localization of point sources in 3D across an axial range approaching the typical thickness of mammalian adherent cells. Thus, DHPSF is not only attractive for PALM-style superresolution experiments but also for tracking small punctate structures in cells. Still, data analysis of DHPSF images presents a challenge because no analytic form of the DHPSF exists. This difficulty has been addressed previously by using heuristic functions for fitting or interpolations of calibration scans of fluorescent beads. However, this approach is limiting for cellular particle tracking applications of DHPSF because of the heterogeneous signal background, high particle densities, and large variation in intensities of the target particles encountered in such experiments. Here, we present a data-driven and fast method based on deep learning (DL) to address these challenges. Specifically, we use the DL approach to analyze DHPSF data without the need to introduce heuristic fitting functions or interpolate calibration scans. We demonstrate the accuracy of the method on localizing simulated data in 3D, and test its efficacy in the presence of noisy, heterogeneous backgrounds. Finally, we localize and track in 3D puncta of human T-cell leukemia virus type 1 (HTLV-1) in live cells and present preliminary data on the mobilities of these particles measured in this noisy environment. This work has been supported by grants from the National Institutes of Health (R01 GM098550 and RO1 GM124279).

Investigation of groundwater contamination from leachate migration: a case study of Bowen University dumpsite, Nigeria

A microstudy of soil physical properties in combination with geoelectric delineation were adopted for the evaluation of groundwater contamination prospect from leachate migration at Bowen University dumpsite location. Samples of soil were collected from five different locations, with five locations within the dumpsite and one control sample which is 200 m far away from the dumpsite locations. A core sampler which is attached to the soil auger is used to obtain each sample within 60 cm depth. Each sample is collected into a sample bag and properly labeled for laboratory analysis. Schlumberger electrode configuration was employed for the survey spread to delineate total of four (4) Vertical electrical sounding (VES) points with electrode spacing varying 60 to 100 m. This was done to obtain resistivity, thickness and depth within the dumpsite location. The results of the average value of the soil properties between the control and the dumpsite are compared such that the soil properties for control site reveal a bulk density (BD) of 1.45 g/cm3, particle density (PD) of 2.63 g/cm3 and porosity (PO) of 44.90%, respectively. Whereas, the mean soil properties of the dumpsite show that BD is 1.35 g/cm3, PD is 2.93 g/cm3, and PO is 54.07%, respectively. This signifies that the control location has high BD, low PD and low PO, while the dumpsite reveals an inverse of the control results. Also, the results from the interpreted VES data reveal the prospect of migration of contaminants from the topsoil to the alluvium, which could further percolate to the aquifer with time. It could be concluded that groundwater contamination is feasible within the study area, since an alluvium and porous soils could permit leachate migration to the aquifer.

Particle encapsulation techniques for atom probe tomography of precipitates in microalloyed steels

Atom probe tomography (APT) provides sub-nm resolution in the analysis of complex industrial steels. It can resolve the carbonitride precipitates in Nb-Ti microalloyed high-strength low-alloy (HSLA) steels that strongly affect material performance and illuminate the complex precipitation sequence before and during the thermo-mechanical controlled process (TMCP). However, the precipitate concentration is low in HSLA steels during austenite conditioning, especially at temperatures > 850 °C, so that the probability of detecting precipitates via APT is below 5%. Here, we demonstrate two encapsulation-based approaches that increase the precipitate concentration in the APT sample volume sufficiently to enable the analysis of sparse precipitates. The first method is based on metallographic etching and direct targeting of precipitates in the steel. A focused ion beam was used to mark precipitation sites. Encapsulation with nickel-phosphorus (Ni-P) enabled localized APT and increased the yield by a factor of 10. The second method relies on the chemical extraction of precipitates and subsequent encapsulation in a silicon oxide (SiOx) network at a very high particle density. Analysis of tips cut from the encapsulated particles increased the yield by a factor of >15. We discuss and compare the spatial and chemical accuracy obtained in the analysis of pure Nb-, Ti- and mixed Nb-Ti carbonitrides.

Echogenic particles in the amniotic fluid of term low-risk pregnant women: does it have a clinical significance?

In this study, we aimed to analyse the clinical features of the third-trimester pregnant women, with echogenic amniotic fluid and to compare their obstetric and neonatal outcomes with pregnant women with normal amniotic fluid echogenicity. This case-control study was conducted in a tertiary antenatal care centre. A total of 560 term (37–42 weeks of gestation) singleton women; 280 with echogenic particles in amniotic fluid and 280 with clear amniotic fluid, who delivered within 24 h after the ultrasound scan were evaluated. The women in the two groups were similar in terms of age, parity, body mass index, foetal birth weight, and gestational age. More patients in the particulate amnion group had lower Apgar scores (<7) in 1st and 5th minutes than controls (p = .006, p = .031 respectively) however the rate of admission to neonatal intensive care was similar. Vernix stained amniotic fluid was more common in the study group (48.8%, p = .031), the rate of meconium-stained amniotic fluid was similar in the study and control groups (9.6–9.2%, p = .881). The primary caesarean section rate was higher in women with particulate amnion (18.4%, p = .037). Echogenic particles in the amniotic fluid in the third trimester could not be attributed to meconium, however, higher rates of primary caesarean section may require further attention. IMPACT STATEMENT What is already known on this subject? Previous studies showed that high-density intra-amniotic particles were possibly related to vernix caseosa, intra-amniotic bleeding, and meconium. The number of study groups in these studies was also limited. What do the results of this study add? Additional to other previous studies, we found an increased rate of intra-amniotic echogenic particles in male foetuses. What are the implications of these findings for clinical practice and/or further research? The presence of echogenic particles on ultrasound was not related to increased risk for the presence of meconium. Significantly more neonates born to mothers with intra-amniotic echogenic particles tended to have lower Apgar scores (<7), however, this significant difference did not affect the need for NICU admission. The presence of echogenic particles in the amniotic fluid of the third-trimester pregnant women could not be attributed to meconium and adverse perinatal outcomes, however, the higher rates of primary caesarean section may require further attention.

Study of the Electrodeposition of Silver Nanoparticles on Glassy Carbon by Galvanostatic Control

In this work, nucleation and growth processes under galvanostatic control are studied, taking silver as a reference system. The methodology proposed allows electrodeposition to be carried out in areas of 5 mm2 and with a reagent volume of 10 μL, using a capillary droplet cell built for this purpose. Silver nuclei were generated by transfer of the same charge but varying the intensity of the applied current density and the pulse duration. It was found that pulses with a current density of 1.70 mA/cm2 generate a high density of particles with low variability. The comparison between the galvanostatic and potentiostatic methods shows that the galvanostatic control generates smaller particles with high density. In contrast, the potentiostatic pulse result in a better spatial distribution of the particles on the electrode area limited by the droplet.

Characterization and quality analysis of wood pellets: effect of pelletization and torrefaction process variables on quality of pellets

A lab-scale single-channel press was employed for producing pellets and the effect of pressure, die temperature, moisture content (MC), particle size, and binding agent on pellet quality was investigated. Meanwhile, torrefaction subsequent to pelletization was performed and the quality of pellets was evaluated under different torrefaction conditions. From the analysis of variance (at p < 0.05), temperature (70–200 °C), pressure (70–160 MPa), and MC (5.5–28%) were found most significant factors for density, strength, and compression energy of pellets. Particle density and strength of raw wood pellets were significantly affected by temperature and pressure. The highest particle density and strength (1.307 g/cm3, 11.8 N/mm2) for particles of 0.25–0.5 mm and (1.300 g/cm3 and 10.7 N/mm2) for particles of 0.5–1.41 mm were found at a temperature of 200 °C (pressure ≥ 100 MPa and MC 5.5%), indicating that pelletization at a temperature of 200 °C was beneficial. The relaxed density of pellets remained the same as of particle initial density after storage time of 2 weeks. The expansion ratio of the pellet was found lower. Use of synthetic resin as a binder in the proportion of 1:9 was found optimum, the particle density increased from 1.19 to 1.24 g/cm3 (0.25–0.5 mm) and from 1.17 to 1.22 g/cm3 (0.5–1.41 mm) and energy consumption reduced by 9.39% (0.25–0.5 mm) and 8.7% (0.5–1.41 mm). Pellets made at a temperature of 200 °C were found water-resistive as compared to those made at other temperatures. The highest lower heating value, i.e., 26.76 MJ/kg of torrefied pellets (TOPs) was achieved at 300 °C and 120 min. Torrefaction process parameters adversely affected the particle density, volumetric energy density, strength, and durability of TOPs. The highest true density (1.85 g/cm3) and porosity (65 v %) for TOPs were achieved at 300 °C and 120 min, much higher than those of raw pellets. Moisture uptake of TOPs at 300 °C was 2.0–2.8 wt.%, showing strong water-resistant ability. From the results of FTIR, O–H bond was destroyed after torrefaction.

A novel torque analysis method for drilling deep lunar soil by DEM

In order to solve the torque design problem of deep lunar soil sampling using drilling, a novel torque analysis method was presented based on discrete element model (DEM). This method includes three stages: drilling simulation of the bit and stem segment, resultant torque calculation, and predicted curve fitting. First, special drilling models were designed for a bit and stem separately. A high-density equivalent particle group, boundary vibration control, pre-drilling simulation and constant pressure surface control were designed for the bit and stem drilling modelling at different depths to ensure the rationality of the model. An example of the torque synthesis process was given, and the simulation time was analyzed. Finally, the simulation predicted torque curve was plotted and compared with the experimental curve. The experimental and simulation curves show that as the drilling depth increases, the torque increases approximately linearly first and then flattens out gradually after a depth of 1 m. The consistency between the two results indicated that the proposed method was validated. Using this method, engineers can take short time to analyze the torque and design basic parameters of the drill mechanism. The problem of high experimental cost and long simulation time in torque design is solved.

Enhancing the creep resistance of a dilute Mg-1.5 wt%Nd alloy plate via pre-compression and subsequent peak-aging

Both static precipitation and dynamic precipitation could hardly enhance the creep resistance of dilute Mg-Nd alloys. To solve this problem, the present paper proposed a practical method, which was combining pre-compression and subsequent peak-aging. A binary Mg-1.5 wt%Nd alloy plate, was prepared for researching the tensile creep behaviors at 523 K. Due to the aging hardening was weak, the directly aged sample was not studied. The pre-compressed sample was named PC sample, and the pre-compressed with subsequent peak-aged sample was named PC-AA sample, while the sample without any pre-compression or aging was named NPC sample. The PC-AA sample had the best creep resistance, followed by the NPC sample, and the PC sample had the poorest. For the NPC sample, twinning and dislocation slip (including basal slip, cross-slip and pyramidal<c+a>slip) jointly controlled the creep behavior. Various creep mechanisms led to the easy creep strain increment and the poor creep resistance. In regard to the PC sample, the thermal stability of the preset twins was inferior and twin widening happened, resulting in a faster increment in the creep strain and a poorer creep resistance. With respect to the PC-AA sample, the dominant creep mechanisms were basal slip and dislocation climb. The high-density particles inside the preset twins successfully delayed cross-slip and twin widening, leading to the enhanced creep resistance. Thus, the twins induced by the pre-compression and the particles inside the twins induced by the subsequent peak-aging successfully enhanced the creep resistance of the dilute Mg-Nd alloys.

Influence of organic particle addition on nitrification rates and ammonium oxidiser abundances in Baltic seawater

Nitrification is a key microbial process in the nitrogen cycle of the ocean that largely determines the pool sizes of nitrite, nitrate and ammonium but hardly affects the total pool of inorganic nitrogen (except through N2O losses to the atmosphere). This study explored the regulation of nitrification and its dependency on particle and ammonium concentrations. Incubation experiments were conducted in which particles of different origin were added to Baltic seawater, followed by 15NH4+-labelling and droplet digital PCR. Both nitrification rates according to particle size (&gt;3 µm and 0.22-3 µm) and archaeal and betaproteobacterial ammonia monooxygenase α-subunit gene (amoA) abundances were determined in order to assess the impact of high particle concentrations found in coastal areas of the Baltic Sea. The data show that the addition of particulate organic matter enhanced the nitrification rates in bulk (~805 nmol l-1 d-1) but not in the &lt;3 µm fraction (&lt;100 nmol l-1 d-1), indicative of a strong influence of the added particles on nitrification rates. The regulation of nitrification rates by the substrate ammonium was suggested by the inverse correlation between these 2 variables. Measurements of amoA gene abundances showed the dominance of ammonium-oxidising bacteria over ammonium-oxidising archaea during most of the 41 d experiment. Abundances of amoA were highest in the particle-associated fraction of the bacteria (≤6.9 × 106 amoA copies l-1). These findings demonstrate the importance of particle-associated ammonium-oxidising bacteria in the nitrification processes of coastal and estuarine waters containing high particle densities.

Repair of Turbine Components by Abrasive-Jet Machining

In the operation of modern gas and steam turbines, the amount of deposits on the aggregate surfaces inevitably increases (mainly in the form of amorphous silicon), which leads to metal corrosion and erosion damage. The relevance of solving the problem of removing technological pollution in the process of repairing gas and steam turbines in order to restore the design capacity of the equipment is shown in this paper. The efficiency of using hydroabrasive treatment for performing repair operations on turbine components (rotors, blades, etc.) has been established. The method developed is an alternative to the chemical cleaning processes and mechanical surface abrasion. The technology does not have a negative effect on the environment and has an isolated system of using technological components. The technology (composition of the technological medium) and equipment (high speed and density of particles) provide cleaning of deposits from the gas and steam turbine components, in particular, turbine blades, with a high quality of the resulting surface and the required productivity.