Deposition Rate Research Articles

X-ray polarisation signatures in bombarded magnetar atmospheres

Abstract Magnetars are neutron stars that host huge, complex magnetic fields which require supporting currents to flow along the closed field lines. This makes magnetar atmospheres different from those of passively cooling neutron stars because of the heat deposited by backflowing charges impinging on the star surface layers. This particle bombardment is expected to imprint the spectral and, even more, the polarisation properties of the emitted thermal radiation. We present solutions for the radiative transfer problem for bombarded plane-parallel atmospheres in the high magnetic field regime. The temperature profile is assumed a priori, and selected in such a way to reflect the varying rate of energy deposition in the slab (from the impinging currents and/or from the cooling crust). We find that thermal X–ray emission powered entirely by the energy released in the atmosphere by the magnetospheric back–bombardment is linearly polarised and X-mode dominated, but its polarisation degree is significantly reduced (down to 10%–50%) when compared with that expected from a standard atmosphere heated only from the cooling crust below. By increasing the fraction of heat flowing in from the crust the polarisation degree of the emergent radiation increases, first at higher energies (∼10 keV) and then in the entire soft X-ray band. We use our models inside a ray-tracing code to derive the expected emission properties as measured by a distant observer and compare our results with recent IXPE observations of magnetar sources.

Fluidized Bed Chemical Vapor Deposition of Copper on Micronic Alumina Powders

AbstractUniformly coating micronic particles with metals is of main interest for a broad range of applications. This study demonstrates the feasibility of depositing pure copper on the surface of micronic alumina particles by the fluidized bed chemical vapor deposition process from the cheap and nontoxic copper acetylacetonate precursor. Thanks to the development of a preconditioning protocol, a complete fluidization of the particles organized as porous agglomerates was reached. The coating of the individual particles was favored by using conditions involving low deposition rates. The influence of key operating parameters on the process behavior and on the characteristics of the deposit was studied. The deposited copper was of cubic crystal structure without carbon nor oxide contamination.

Performance of Different Spray Nozzles in the Application of Defoliant on Cotton Plants (Gossypium hirsutum L.)

Defoliant spraying is an important link in the mechanized cotton harvest because adequate and uniform spraying can improve defoliation quality and reduce cotton trash content. In defoliant application, application volume and spraying technology are extremely important. In this study, the effectiveness of defoliant application to cotton plant that has come to harvest with two different application volumes and three different types of nozzles with a standard field crop sprayer was determined. Application rates were 250 and 400 L/ha and spraying nozzles were: (1) standard flat fan nozzle (TP8006), (2) air induction nozzle (AI 11002-VS) and (3) dual pattern nozzle (AI307003VP). A tracer (BSF) and defoliant were applied to mature cotton with approximately 60% open bolls and samplings for BSF deposition and spray coverage on cotton plant were done at two plant height (upper layer, lower layer) of plant. Before and after spraying, bolls open and leaves rate on cotton plants were calculated and filter papers were used to detect BSF deposition and water sensitive papers (WSP) were used to measure coverage rate of spraying methods used. Spectrofluorophotometer was used to detect the amount of tracer deposition on targets and an image process computer program was used to measure coverage rate on WSP. In analysis conclusions showed that air induction nozzle (AI 11002-VS), achieved better results than the dual pattern and standard flat fan nozzles in terms of higher depositions, coverages and leaf defoliations and boll opening rates. AI nozzles operating at 250 L/ha application rate provide the highest deposition and coverage rate on applications of defoliant, in addition, BSF as an indicator of the defoliant used reached on leaf beneath in merely this spray nozzle. After defoliation boll opining rate was 85-% on the 7th and 12th days after spraying and falling rate of leaves was 76-% at application rate of 250 L/ha with air induction (AI1102) nozzle.

Effect of wire deposition rate on macro and microscopic characteristics of laser weld-brazed AA5083 aluminum alloy to galvanized steel joints and their corrosion response

ABSTRACT In this study, dissimilar metals, such as aluminium (AA5083) and galvanised interstitial free steel, were laser-brazed in a flange configuration using eutectic filler aluminium wire (4047, Al-12%Si). To investigate the effects of wire deposition rate on the characteristics of laser-brazed joints and to understand the factors contributing to corrosion in these joints. The wire deposition rates were varied while keeping other laser parameters constant. Changes in wire deposition rate were observed to affect the flow behaviour of molten metal leading to variations in the geometrical characteristics of the brazed joints and interfacial reactions as revealed by macroscopic examination. A series of corrosion tests, including electrochemical, immersion, and salt spray tests, were conducted on the laser-brazed joints. It was demonstrated by Immersion corrosion tests that the wire rate influenced the corrosion results for the laser-brazed joints. However, the salt spray test showed no substantial effect on corrosion with respect to different wire deposition rates. Furthermore, the electrochemical results indicated significant changes in the corrosion response of the brazed zone due to the presence of chemically dissimilar phases. A correlative discussion between laser parameters, observed microstructure, and their effects on the corrosion performance of the brazed samples is presented.

PSXIII-20 Impact of Aspergillus oryzae fermentation-derived prebiotic-like additive combined with monensin on feedlot performance in finishing steers

Abstract The aim of this study was to investigate the effects of supplementing a prebiotic-like action additive product derived from the fermentation of Aspergillus oryzae (AM; 2 g Amaferm/d) in combination with monensin throughout the entire feedlot period. The primary objective was to evaluate the impact of this dietary intervention on feedlot performance, focusing on parameters such as feed intake, feed-to-gain ratio, body weight (BW), average daily gain (ADG), and carcass quality. Steers (n = 1,200), aged approximately 18 mo with an initial BW of 307.8 ± 17 kg, were randomly assigned to 8 pens (150 steers per pen) and each pen was randomly assigned to two treatments: a control diet with monensin (M; monensin supplemented at 33 mg/kg DM) and a treatment diet with the addition of AM (M+AM; monensin supplemented at 33 mg/kg DM and 2 g Amaferm/d). The feedlot period comprised three steps, with daily feed delivery adjustments using a feed bunk management system. A multilevel model using the PROC MIXED procedure of SAS with pen as experimental unit, was employed to evaluate feed intake, feed to gain ratio, BW and ADG for each period, also including effects on carcass quality and growth measured by ultrasound (random sample of 45 animals per pen; 30% of each pen). No significant differences were observed in feed intake across the three diet steps (P > 0.10). During the adaptation period, steers fed AM had greater ADG (+0.168 kg/d; P = 0.003) and increased BW at d 20 (+5.5 kg; P < 0.001). Although ADG during the finishing phase was similar for both treatments, a trend was observed for greater BW at d 108 (+4.6 kg; P = 0.095) when supplemented with AM. The inclusion of AM showed no impact on feed-to-gain ratio for the entire period (P = 0.589). In the finishing period, a positive effect on ribeye area (REA) growth rate (+0.54 cm2/mo; P = 0.016) and a trend towards greater back fat deposition rate (+0.11 mm/mo; P = 0.069) were observed with AM supplementation. At the end of the finishing period, a trend towards greater REA (+1.39 cm2; P = 0.101) was noted with no differences in back fat. Overall, this study demonstrates that the addition of AM throughout the feedlot period positively influenced the productive response during the adaptation period, leading to improvements in carcass growth during the finishing period.

Investigating the mechanism of enhancing interfacial adhesion of SiOx films on GaAs substrates through process optimization

In the manufacturing of GaAs-based quantum well (QW) lasers, the adhesion between the Silicon dioxide (SiOx) film layer and the Gallium arsenide (GaAs) substrate is crucial for the performance and durability of semiconductor devices. This study focused on depositing SiOx films on GaAs substrates using plasma-enhanced chemical vapor deposition (PECVD). The research aimed to investigate the impact of different coating processes on the deposition rate, properties, and composition of the coatings. The interfacial adhesion of various samples was assessed using nano-scratch tests. The results revealed that samples with lower SiH4 gas flow and RF power, or higher process pressure exhibited stronger adhesion strength. It's further observed that optimizing the process parameters reduced residual stresses in the film, thereby enhancing the GaAs-SiOx interfacial bonding. This work has the potential to significantly reduce the possibility of QW lasers malfunctions, improve the reliability of semiconductor devices and provide valuable insights for future studies on enhancing film-substrate adhesion.

Plasma PVD by small spiral Ta hollow cathodes

Spiral hollow cathodes represent interesting options for local PVD applications. Radio frequency powered small diameter spiral hollow cathodes made from 0.45 mm diameter Ta wire rolled around 0.5 mm diameter rod were tested in PVD regimes on silicon substrates at the gas pressure of 400 Pa (3 Torr). The PVD of Ta and reactive PVD of Ta-N resulted in deposition rates of about 130 nm/min with maximum thickness in the center of the coating spots. However, part of the coating spots can be heavily eroded. At higher RF powers droplets from the melted Ta tip of the spiral can damage the coating and melt the Si substrate. The PVD rates of Ta in argon were similar as those for TaN. However, lower number of droplets of the melted Ta were formed in argon. The heating of the spiral outlet and its effect on the coating was also more intense in nitrogen than in argon. The temperature of the Si substrate table reached about 500 °C in 20 min in the nitrogen plasma and up to 400 °C in argon. This heating was higher on electrically grounded substrates than on the floating substrates. The effect of sharp outlet on possible eroding of the sample was confirmed by a sharp ended 1 mm diameter stainless steel medical needle used as a hollow cathode.

Non-Oxidative Coupling of Methane via Plasma-Catalysis Over M/γ-Al2O3 Catalysts (M = Ni, Fe, Rh, Pt and Pd): Impact of Active Metal and Noble Gas Co-Feeding

Plasma-catalysis has attracted significant interest in recent years as an alternative for the direct upgrading of methane into higher-value products. Plasma-catalysis systems can enable the electrification of chemical processes; however, they are highly complex with many previous studies even reporting negative impacts on methane conversion. The present work focuses on the non-oxidative plasma-catalysis of pure methane in a Dielectric Barrier Discharge (DBD) reactor at atmospheric pressure and with no external heating. A range of transition and noble metals (Ni, Fe, Rh, Pt, Pd) supported on γ-Al2O3 are studied, complemented by plasma-only and support-only experiments. All reactor packings are investigated either with pure methane or co-feeding of helium or argon to assess the role of noble gases in enhancing methane activation via energy transfer mechanisms. Electrical diagnostics and charge characteristics from Lissajous plots, and electron temperature and collision rates calculations via BOLSIG+ are used to support the findings with the aim of elucidating the impact of both active metal and noble gas on the reaction pathways and activity. The optimal combination of Pd catalyst and Ar co-feeding achieves a substantial improvement over non-catalytic pure methane results, with C2+ yield rising from 30% to almost 45% at a concurrent reduction of energy cost from 2.4 to 1.7 \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:\ ext{M}\ ext{J}\\:{\ ext{m}\ ext{o}\ ext{l}}_{\ ext{C}{\ ext{H}}_{4}}^{-1}$$\\end{document} and from 9 to 4.7 \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:\ ext{M}\ ext{J}\\:\ ext{m}\ ext{o}{\ ext{l}}_{{\ ext{C}}_{2+}}^{-1}$$\\end{document}. Pd, along with Pt, further displayed the lowest coke deposition rates among all packings with overall stable product composition during testing.

Review of Opportunities and Challenges for Additive Manufacturing of Steels in the Construction Industry

Abstract Additive manufacturing (AM), or 3-D printing, encompasses a range of technologies that “print” material layer by layer to create the final part. Though there is significant interest in the AM of concrete in the construction sector, opportunities for the AM of steel still need to be explored. This review focuses on the AM of low-alloy steels, stainless steels, duplex stainless steels (DSSs), precipitation-hardened (PH) stainless steels, and tool steels, highlighting the challenges and opportunities of employing AM technology for construction applications. Fusion-based AM technologies, such as wire arc additive manufacturing (WAAM), laser powder bed fusion (LPBF), and laser-directed energy deposition (LDED), are the core technologies that have been tested in the industry so far. WAAM has seen the most exploration for construction applications because of its higher deposition rate, larger build volume, and lower cost than other AM technologies. The mechanical performance of low-alloy steel, stainless steel, and tool steel shows increased tensile strengths after AM processing compared with wrought counterparts. Although AM is not economical for geometrically simple metal components or geometries, there is potential for AM to fabricate unique structural connections or joints, optimized load-bearing columns, and even entire bridges, as highlighted in this paper. AM’s digital nature (i.e., using computer-aided design (CAD) to create G-code paths for printing) can increase structural efficiency if coupled with topology optimization methods and high-strength alloys. Currently, however, general applications of AM in the industry are limited because of barriers with structural codes and standards not incorporating AM parts and AM technology barriers (i.e., limited build volumes).

A New Approach to Single‐Step Fabrication of TiOx‐CeOx Nanoparticles

Mixed metal oxide (MMO) nanoparticles (NPs) are hybrids consisting of two or more nanoscale metal oxides. Advantages of MMO NPs over single metal oxides include improved catalytic activity, enhanced electrical and magnetic properties, and increased thermal stability due to the synergy of the different oxide components. This study presents a novel fabrication route for TiO2‐CeO2 NPs enriched with oxygen vacancies using a Haberland‐type gas aggregation cluster source. The NPs, deposited from different segmented Ti/Ce targets under varying O2 addition, were examined with respect to final composition, morphology, and Ti, Ce surface oxidation states. Particle formation mechanisms are proposed for the observed morphologies. Additionally, available O2 during deposition and its impact on the formation of defective sites were investigated. Defective sites in TiO2‐CeO2 NPs were analyzed using transfer to X‐ray photoelectron spectroscopy and transmission electron microscopy without contact to ambient oxygen. The incorporation of Ce to the target exhibits synergistic effects on the synthesis process. Segmented Ti/Ce targets enable the deposition of a broad range of mixed oxide NPs with diverse compositions and morphologies at considerably enhanced deposition rates, which is vital for practical applications. The presented fabrication approach is expected to be applicable for a broad variety of MMO NPs.

A multifunctional polyacrylonitrile fibers/alginate-based hydrogel loaded with chamomile extract and silver sulfadiazine for full-thickness wound healing

Most conventional wound dressings do not meet the clinical requisites owing to their limited multifunctionality. Herein, a bilayer wound dressing containing both hydrogel and fibrous structures with multifunctional features was developed for effective skin rehabilitation. Sodium alginate (SA)/gelatin (Gel) hydrogel comprising Matricaria chamomilla L extract and silver sulfadiazine (AgSD) drug as antibacterial agents was cross-linked using genipin and CaCl2. Then, the surface of the hydrogel was covered by electrospun polyacrylonitrile (PAN) nanofibers to fabricate a bilayer dressing. FESEM images revealed formation of continuous, smooth, and bead-free PAN nanofibers with excellent compatibility between hydrogel and fibers. The bilayer wound dressing exhibited satisfactory mechanical virtues including elastic modulus (2.4 ± 0.2 MPa), tensile strength (6.2 ± 0.5 MPa) and elongation at break (21.8 ± 1 %) as well as suitable swelling ratio. Such bilayer dressing revealed biodegradability, cytocompatibility and effective antibacterial performance against gram positive and gram negative strains. Release kinetics of AgSD drug followed a Fickian diffusion mechanism, ensuring sustained drug release. In vivo studies demonstrated bilayer dressing could promote rate of wound closure, re-epithelialization and collagen deposition, facilitating the replacement of damaged skin with healthy tissue. Such engineered wound dressing has a high potency for inducing skin repair and could be used in skin tissue engineering.

Daily Dynamics of Resting-State Electroencephalographic Theta and Gamma Fluctuations Are Associated With Cognitive Performance in Healthy Aging.

Healthy age-related cognitive changes are highly heterogeneous across individuals. This variability is increasingly explained through the lens of spontaneous fluctuations of brain activity, now considered a powerful index of age-related changes. However, brain activity is a biological process modulated by circadian rhythms, and how these fluctuations evolve throughout the day is under investigation. We analyzed data from 101 healthy late middle-aged participants from the Cognitive Fitness in Aging study (68 women and 33 men; aged 50-69 years). Participants completed 5 electroencephalographic (EEG) recordings of spontaneous resting-state activity on the same day. We used weighted phase-lag index (wPLI) analyses as an index of the functional synchrony between brain regions couplings, and we computed daily global PLI fluctuation rates of the 5 recordings to assess the association with cognitive performance and β-amyloid and tau/neuroinflammation pathological markers. We found that theta and gamma daily fluctuations in the salience-control executive internetwork (SN-CEN) are associated with distinct mechanisms underlying cognitive heterogeneity in aging. Higher levels of SN-CEN theta daily fluctuations appear to be deleterious for memory performance and were associated with higher tau/neuroinflammation rates. In contrast, higher levels of gamma daily fluctuations are positively associated with executive performance and were associated with lower rate of β-amyloid deposition. Thus, accounting for daily EEG fluctuations of brain activity contributes to a better understanding of subtle brain changes underlying individuals' cognitive performance in healthy aging. Results also provide arguments for considering the time of day when assessing cognition for old adults in a clinical context.

Cannabis pollen dispersal across the United States

For the recently legalized US hemp industry (Cannabis sativa), cross-pollination between neighboring fields has become a significant challenge, leading to contaminated seeds, reduced oil yields, and in some cases, mandated crop destruction. As a step towards assessing hemp cross-pollination risk, this study characterizes the seasonal and spatial patterns in windborne hemp pollen dispersal spanning the conterminous United States (CONUS). By leveraging meteorological data obtained through mesoscale model simulations, we have driven Lagrangian Stochastic models to simulate wind-borne hemp pollen dispersion across CONUS on a county-by-county basis for five months from July to November, encompassing the potential flowering season for industrial hemp. Our findings reveal that pollen deposition rates escalate from summer to autumn due to the reduction in convective activity during daytime and the increase in wind shear at night as the season progresses. We find diurnal variations in pollen dispersion: nighttime conditions favor deposition in proximity to the source, while daytime conditions facilitate broader dispersal albeit with reduced deposition rates. These shifting weather patterns give rise to specific regions of CONUS more vulnerable to hemp cross-pollination.

Effect of Electrodeposition Time on the Growth Rate of Carbon Nanotubes (CNTs)

Carbon Nanotubes (CNTs) are nano-sized carbon that resembles tubes and has the potential to be used in various aspects of applications. Some of the CNT carbon capture methods include arc discharge, lasser ablation, CVD and electrodeposition. The advantage of the electrodeposition method is that the production cost is cheap and the preparation is easy. Electrodeposition is the precipitation of substances by using a direct electric current, with CO2 as the reactant. Factors that affect the growth rate of CNT are voltage, temperature, carbon source, electrode and time. The variation of the electorative time used was 60 minutes, 90 minutes, 120 minutes, 150 minutes, 180 minutes. The data collection process begins by shaping and measuring the weight of the electrode (Ni) with a diameter of 2 cm CNT deposition area. measuring the weight and melting Li2CO3 at a temperature of 750. then the CO2 flow rate setting, voltage setting 5V and time setting were then characterized by SEM-EDX and XRD. The results of the study showed that the optimal time obtained with a time of 120 minutes, the resulting CNT deposition rate was 1,618 g cm-2 h-1. Then based on the characterization of XRD and SEM, it shows that the longer the electrodeposition time, the less impurities are contained in the results obtained.

Insights into the effect of Fe-Zn interaction on tunable reactivity in Fischer–Tropsch synthesis

In the Fischer–Tropsch synthesis (FTS) reaction, the intricate reaction conditions are prone to induce phase transitions in iron carbides, which markedly affect catalytic performance. Manipulating and stabilizing the active phase is paramount for ensuring the catalyst efficiency. In this study, we regulated the Fe-Zn interaction to investigate the influence of iron carbides and the characteristics of surface carbon species. The strong interaction significantly enhanced the adsorption and dissociation of CO on the catalyst surface, thereby facilitating the formation of carbon-rich Fe2(.2)C. Consequently, the FeZn-s catalyst exhibited the highest iron time yield (FTY) of 959 μmolCO·gFe-1·s-1. But meanwhile, the stronger Fe-Zn interaction also accelerated the carbon deposition rate and elevated the graphitization degree of the surface carbon, expediting the catalyst deactivation. These results provide an insight into the modulation and stabilization of iron carbides by adjusting the interaction between the Fe and supports, which inspires the further development of Fe-based catalysts for FTS applications.

Addressing Challenges of Membrane Clogging in AF4-UV-ICPMS Analysis for Size Determination of Trace Elements in Acidic, Organic-Rich Peat Bog Waters.

The analysis of colloid-associated trace elements (TEs) in acidic, organic-rich waters (pH 3.8-5.8) using AF4-UV-ICPMS often necessitates the use of neutral or weakly alkaline carriers (pH 7-8.6). Employing acidic mobile phases has been deemed impractical due to the substantial sorption of colloids onto a 0.3 kDa polyethersulfone (PES) membrane and greatly reduced separation performance. This has greatly restricted the determination of potentially bioavailable forms of TEs (i.e., < 1 kDa) in acidic, organic-rich waters. To address this issue, porewaters from Sphagnum moss and peat were investigated. Membrane clogging was more pronounced in peat porewaters, where a higher deposition rate of dissolved organic matter onto the membrane was observed compared to that in moss waters. This adsorption is driven by membrane-colloid interactions, with colloids in peat porewaters exhibiting weaker electrostatic repulsion due to their higher positive ζ-potentials. Considering the actual pore size and clogging tolerance of the membrane, it is advisable to employ a 5 kDa PES membrane for peat porewaters, while a 1 kDa PES membrane suits moss waters better. Employing the optimal method enables the separation of TEs within the 0.5-20 kDa size range. Operating within a metal-free, ultraclean laboratory, TEs are detectable at the ng·L-1 level. By enabling precise and accurate separation of dissolved TEs into their size species in these peat bog waters at an appropriate pH, this method addresses diverse size profiles. This information is crucial for comprehending the chemical forms, transformations, mobility, and potential bioavailability of TEs in peat bogs.

Simulating the Growth of TATA-Box Binding Protein-Associated Factor 15 Inclusions in Neuron Soma.

To the best of the author's knowledge, this paper presents the first attempt to develop a mathematical model of the formation and growth of inclusions containing misfolded TATA-box binding protein associated factor 15 (TAF15). It has recently been shown that TAF15 inclusions are involved in approximately 10% of cases of frontotemporal lobar degeneration (FTLD). FTLD is the second most common neurodegenerative disease after Alzheimer's disease (AD). It is characterized by a progressive loss of personality, behavioral changes, and a decline in language skills due to the degeneration of the frontal and anterior temporal lobes. The model simulates TAF15 monomer production, nucleation and autocatalytic growth of free TAF15 aggregates, and their deposition into TAF15 inclusions. The accuracy of the numerical solution of the model equations is validated by comparing it with analytical solutions available for limiting cases. Physiologically relevant parameter values were used to predict TAF15 inclusion growth. It is shown that the growth of TAF15 inclusions is influenced by two opposing mechanisms: the rate at which free TAF15 aggregates are deposited into inclusions and the rate of autocatalytic production of free TAF15 aggregates from monomers. A low deposition rate slows inclusion growth, while a high deposition rate hinders the autocatalytic production of new aggregates, thus also slowing inclusion growth. Consequently, the rate of inclusion growth is maximized at an intermediate deposition rate of free TAF15 aggregates into TAF15 inclusions.

Microplastics in the Atmospheric Deposited Dust Collected from Different Traffic Intersections in Dhaka City

Plastic particles less than 5 mm in size, known as microplastics, can infiltrate the environment from a variety of sources. This study aimed to assess the presence of microplastics (MPs) in the atmosphere at fifteen major traffic intersections in the greater Dhaka city from July to August 2022.The deposition rate (DP) of MPs was calculated and the observed DPs value ranged from 1.11×106 MPs/m2/day to 5.78×106 MPs/m2/day with a portion of microplastics exhibiting fluorescence activity. Fourier Transform Infrared (FTIR) spectroscopy was used to analyze the functional groups present in microplastics. The identified polymer compositions of MPs were polyethylene (PE), Nylon-6 and natural polymers (cellulose and rubber). The current study highlights the data and knowledge gaps on the atmospheric transport of microplastics and their impact to the deterioration of overall urban air quality. Dhaka Univ. J. Sci. 72(2): 07-14, 2024 (July)

Dynamic Complexity of a Discrete-time Prey-Predator Model with Mixed Functional Responses

Plastic particles less than 5 mm in size, known as microplastics, can infiltrate the environment from a variety of sources. This study aimed to assess the presence of microplastics (MPs) in the atmosphere at fifteen major traffic intersections in the greater Dhaka city from July to August 2022.The deposition rate (DP) of MPs was calculated and the observed DPs value ranged from 1.11×106 MPs/m2/day to 5.78×106 MPs/m2/day with a portion of microplastics exhibiting fluorescence activity. Fourier Transform Infrared (FTIR) spectroscopy was used to analyze the functional groups present in microplastics. The identified polymer compositions of MPs were polyethylene (PE), Nylon-6 and natural polymers (cellulose and rubber). The current study highlights the data and knowledge gaps on the atmospheric transport of microplastics and their impact to the deterioration of overall urban air quality. Dhaka Univ. J. Sci. 72(2): 15-24, 2024 (July)

Recent Progress on Atmospheric Corrosion of Field-Exposed Magnesium Alloys

It is well known that the poor corrosion resistance of magnesium alloys is a key factor limiting their application. Field exposure is the most reliable means to evaluate the atmospheric corrosion performance of magnesium alloys. This article reviews the field exposure corrosion behavior of magnesium alloys in typical atmospheric environments (including the marine atmosphere, industrial atmosphere, etc.) in recent years. According to the literature review, it was found that there are significant regional differences in the atmospheric corrosion behavior of magnesium alloys, which is the result of the coupling of multiple factors in the atmospheric environment. By investigating the corrosion rate and corrosion products of different types of magnesium alloys in different environments, the corrosion mechanism of magnesium alloys in different environments was summarized. Specifically, environmental parameters such as atmospheric temperature, relative humidity, CO2, and chloride ion deposition rates in the marine atmospheric environment can affect the corrosion behavior of magnesium alloys. The corrosion of magnesium alloys in different industrial atmospheric environments is mainly affected by atmospheric temperature and relative humidity, as well as atmospheric pollutants (such as SO2, CO2, NO2) and dust. This review provides assistance to the development of new corrosion-resistant magnesium alloys.