Different Levels Of Mn Research Articles

Promoting nitrogen conversion in aerobic biotransformation of swine slurry with the co-application of manganese sulfate and biochar

This study aimed to explore the co-application of MnSO4 (Mn) and biochar (BC) in nitrogen conversion during the composting process. A 70-day aerobic composting was conducted using swine slurry, supplemented with different levels of Mn (0, 0.25%, and 0.5%) and 5% BC. The results demonstrated that the treatment with 0.5MnBC had the highest levels of NH4+-N (3.07 g kg−1), TKN (29.90 g kg−1), and NO3−-N (1.94 g kg−1) among all treatments. Additionally, the 0.5MnBC treatment demonstrated higher urease, protease, nitrate reductase, and nitrite reductase activities than the other treatments, with the peak values of 18.12, 6.96, 3.57, and 15.14 mg g−1 d−1, respectively. The addition of Mn2+ increased the total organic nitrogen content by 29.59%–47.82%, the acid hydrolyzed ammonia nitrogen (AN) content by 13.84%–57.86% and the amino acid nitrogen (AAN) content by 55.38%–77.83%. The richness of Chloroflexi and Ascomycota was also enhanced by the simultaneous application of BC and Mn. Structural equation modeling analysis showed that Mn2+ can promote the conversion of Hydrolyzed Unknown Nitrogen (HUN) into AAN, and there is a positive association between urease and NH4+-N according to redundancy analysis. Firmicutes, Basidiomycota, and Mortierellomycota showed significant positive correlations with ASN, AN, and NH4+-N, indicating their crucial roles in nitrogen conversion. This study sheds light on promoting nitrogen conversion in swine slurry composting through the co-application of biochar and manganese sulfate.

Impacts of Biosynthesized Manganese Dioxide Nanoparticles on Antioxidant Capacity, Hematological Parameters, and Antioxidant Protein Docking in Broilers.

Using green tomato extract, a green approach was used to synthesize manganese oxide nanoparticles (MnO2NPs). The synthesis of MnO2NPs was (20.93-36.85 nm) confirmed by energy-dispersive X-ray (EDX), scanning and transmission electron microscopy (SEM and TEM), Fourier transform infrared spectroscopy (FTIR), and UV-visible spectroscopy (UV-vis) analyses. One hundred fifty-day-old Arbor Acres broiler chicks were randomly divided into five groups. The control group received a diet containing 60 mg Mn/kg (100% NRC broiler recommendation). The other four groups received different levels of Mn from both bulk MnO2 and green synthesized MnO2NPs, ranging from 66 to 72 mg/kg (110% and 120% of the standard level). Each group comprised 30 birds, in three replicates of 10 birds each. Generally, the study's results indicate that incorporating MnO2NPs as a feed additive had no negative effects on broiler chick growth, antioxidant status, and overall physiological responses. The addition of MnO2NPs, whether at 66 or 72 mg/kg, led to enhanced superoxide dismutase (SOD) activity in both serum and liver tissues of the broiler chicks. Notably, the 72 mg MnO2NPs group displayed significantly higher SOD activity compared to the other groups. The study was further justified through docking. High throughput targeted docking was performed for proteins GHS, GST, and SOD with MnO2. SOD showed an effective binding affinity of -2.3 kcal/mol. This research sheds light on the potential of MnO2NPs as a safe and effective feed additive for broiler chicks. Further studies are required to explore the underlying mechanisms and long-term effects of incorporating MnO2NPs into broiler feed, to optimize broiler production and promote its welfare.

The effect of minor addition of Mn in AA7075 Al–Zn–Mg–Cu aluminum alloys on microstructural evolution and mechanical properties in warm forming and paint baking processes

The microstructures and mechanical properties in the peak ageing condition, warm forming process, and paint baking process of two Al–Zn–Mg–Cu aluminum alloys, which possessed the same base compositions but different levels of Mn (0 and 0.24 wt%), have been investigated. The results show that Mn addition can hardly refine the grain size (around 20 μm) in AA7075 aluminum alloy in warm forming and paint baking processes. Mn-free and Mn-containing alloys subjected to all three processes possess nano-precipitates of nearly the same size, indicating that Mn addition does not influence the nano-precipitate evolution in the aluminum matrix. Energy-dispersive X-ray spectroscopy (EDS) mapping results of dispersoids show that dispersoids in Mn-bearing specimens are enriched in Mn and depleted in Zn and Mg. The Zn and Mg expelled from dispersoids in Mn-containing specimens into the aluminum matrix presumably formed Zn- and Mg-rich zones around the dispersoids, which improved the precipitate transformation reation from GPII to η′ phase at the boundaries between aluminum matrix and dispersoids. Although the solid solution strengthening effect triggered by Mn addition might be less effective because of the formation of dispersoids, the slight enhancement of ultimate tensile strength (UTS) in Mn-containing specimens rather than in Mn-free specimens in all states can be attributed to the formation of nano-precipitates around the dispersoids.

Response of Wheat (Triticum aestivum L.) to Organic Manure and Manganese Levels Applications in Two Different Soil Orders

This study conducted to investigate the effect of organic manure and different levels of Mn on the wheat growth and yield at two different soil orders (Mollisols and Vertisol) in Sulaimani-Kurdistan Region of Iraq. Pot experiments was conducted during (November 12th, 2021 to May 10th, 2022), two rate of organic manure (0 and 2) % of (sheep manure) and five different levels of Mn (0,5,10,15 and 20) mg Kg-1 as MnSO4.H2O were used to the soil. The experiment was carried out using a factorial complete randomized design (CRD) in Triplicate. Growth characters, reproductive, and total dry matter were evaluated. The result showed that application organic manure and Mn were affected on the growth characters of wheat, except plant height (cm) and flag leaf area (cm2). While all reproductive characters were significantly affected with the fertilizer application. Total dry matter increased with application of organic manure and Mn levels in both soil orders. In Vertisol, total dry matter superior (40.813 %) from the most other application levels.

Multi-color materials NiMn LDH loaded on activated carbon as electrode for electrochemical performance investigation

Layered Double Hydroxide (LDH), as a typical two-dimensional electrochemical storage material, has shown great potential in the field of supercapacitors. Herein, three-dimensional (3D) multicolour NiMn LDH nanoparticles were prepared without substrate using a one-step formula using different levels of Mn and various N sources to assist the hydrothermal reaction. The appearance of the designed materials expressing different colors is owing to the Mn content of the reference playing an important role, where the electrochemical performance and structural stability also become more prominent. Adding a suitable Mn content to the G-NiMn LDH maintains the structural integrity and ultra-flake-like structure, revealing a uniform size of 2 μm compared with B-NiMn LDH. It provides abundant redox sites, enabling the green LDH to exhibit excellent electrochemical performance in appearance (1108F g−1@1 A g−1 in G-NiMn LDH). Furthermore, the in-situ growth of G-NiMn LDH nanomaterials (denoted as G-NiMn LDH/F-AC) on F-doped activated carbon material (F-AC) brought increased active sites, effectively inhibited the accumulation of nanosheets, revealing a good rate capability (78 %@15 A g−1). Moreover, the asymmetric supercapacitor's positive and negative electrodes are G-NiMn LDH/F-AC and biomass carbon, up to 73F g−1. This study methodology offers a novel viewpoint on the manufacture and discussion of LDH for understanding electrode materials' structural and surface chemical characteristics.

The effect of varying dietary manganese and selenium levels on the growth performance and manganese-superoxide dismutase activity in nursery pigs

Antioxidant activity in the weaned piglet is important for the developing animal at a cellular level. This study examined the impact of varying dietary levels of manganese and selenium on piglet growth performance and plasma manganese superoxide-dismutase (MnSOD) specific activity. Weaned piglets were blocked by weight (N = 216; 5.21 ± 1.17 kg; 21 ± 3 d) and sex (2 barrows and 2 gilts/pen). Pens (n = 9 pens/treatment) within a block were randomly assigned to dietary treatments in a 2 × 3 factorial design to examine the effect of adding different levels of Mn (0, 12, and 24 mg/kg added Mn from MnSO4 when pigs were fed diets containing 2 levels of Se (0.1 and 0.3 mg/kg added Se from Na2SeO3). Diets were fed in three phases (P1 = d 1–7, P2 = d 8–21, P3 = d 22–35). Pigs and orts were weighed weekly and blood collected on d 0, 7, 21, and 35 for analysis of red blood cell MnSOD. Data were analyzed via the GLM procedure of SAS. No Mn x Se interactions were observed. There was a linear response (P < 0.05) in overall average daily gain across dietary Mn levels. There was a linear trend (P < 0.10) in overall average daily feed intake across Mn levels. Gain to feed ratio (d 0–35) was not impacted by Mn or Se (P > 0.10). MnSOD activity in RBC increased from d 0–7, peaked at d 7, and decreased until d 35. On d 7, diets with 12 mg/kg Mn significantly increased (P < 0.05) MnSOD specific activity (0.91 IU/mg) compared to diets with 24 mg/kg Mn (0.67 IU/mg) but did not differ from diets with 0 mg/kg Mn (0.87 IU/mg). The dietary treatment that maintained specific MnSOD activity was 12 mg/kg Mn and 0.1 mg/kg Se supplemented, while ADG was maximized in diets with 24 mg/kg Mn supplemented.

Manganese Accumulation and Tissue-level Distribution in the Australian Hyperaccumulator Gossia Bidwillii (Myrtaceae)

The manganese (Mn) hyperaccumulator Gossia bidwillii is a tree species native to subtropical eastern Australia where it occurs on Mn-rich soils. Here, we conducted the first Mn accumulation and tissue-level distribution study on wild and experimentally grown G. bidwillii. Gossia bidwillii plants were subjected to different levels of Mn (250 µg g−1, 500 µg g−1, 1000 µg g−1) soil dosing treatments, whereas the wild G. bidwillii was sampled from growing on highly Mn-enriched natural soils. We used laboratory-based micro-X-ray Fluorescence (µXRF) elemental mapping to elucidate in situ distribution patterns of Mn and other elements in hydrated wild and Mn-dosed G. bidwillii leaves. The data from wild G. bidwillii revealed that it can be strongly Mn-hyperaccumulating with foliar Mn concentrations of 39 000 µg g−1 and 24 000 µg g−1 in old and young leaves, respectively. In the Mn dosing trial, G. bidwillii accumulated 24 400 µg g−1 in old leaves and 17 100 µg g−1 in young leaves in the highest treatment level. The laboratory based µXRF data revealed that Mn is uniformly enriched throughout the laminae and petioles of both young and old leaves in wild G. bidwillii; while in Mn-dosed G. bidwillii, the foliar Mn distribution was primarily concentrated at the leaf-tip and lamina. The approach employed by combining data from the field and controlled experiments was especially meaningful for investigating Mn accumulation in this species and gaining added insight into the phenomenon of Mn hyperaccumulation.

Blood concentrations of 50 elements in Eagle owl (Bubo bubo) at different contamination scenarios and related effects on plasma vitamin levels

Some metals and metalloids (e.g. Pb, Hg, Cd and As) are well-known for their bioaccumulation capacity and their toxic effects on birds, but concerns on other minor elements and rare earth elements (ME and REE) are growing due to their intensive use in modern technology and potential toxicity. Vitamins and carotenoids play essential roles in nestling growth and proper development, and are known to be affected by the metals classically considered as toxic. However, we are unaware of any attempts to evaluate the exposure to 50 elements and related effects in plasma vitamins and carotenoids in raptor species. The main goals of this study are: (i) to assess the exposure to 50 elements (i.e. classic toxic elements, trace elements, REE and ME) in nestling Eagle owls (Bubo bubo) inhabiting three differently polluted environments (mining, industrial and control areas) in southeastern Spain, and (ii) to evaluate how element exposure affects plasma vitamin and carotenoid levels, hematocrit and body measurements (mass and wing length) of the individuals. Our results show that local contamination in the mining area contributes to increased blood concentrations of Pb, As and Tl in nestlings, while diet differences between control and mining/industrial areas may account for the different levels of Mn, Zn, and Sr in blood, and lutein in plasma. Plasma tocopherol levels were increased in the mining-impacted environment, which may be a mechanism of protection to prevent toxic element-related oxidative stress. Plasma α-tocopherol was enhanced by 20% at blood Pb concentrations ≥8 ng/ml, and nestlings exhibited up to 56% increase in α-tocopherol levels when blood Pb concentrations reached 170 ng/ml. Tocopherol seems to be a sensitive biomarker under an exposure to certain toxic elements (e.g. Pb, As, Tl).

Ni and Mn simultaneously doped ZnO nanoparticles under Ar ambiance: Structural and optical characterization

Ni and Mn simultaneously doped ZnO nanoparticles with different levels of Mn from 0–6% were prepared by sol–gel route. X-ray diffraction (XRD) pattern revealed the wurtzite hexagonal structure for the entire range of Mn concentrations without any impurity phases. The crystallite size obtained from Debye–Scherrer relation reduced from 23.1 nm to 16.6 nm due to the enhanced lattice disorder, defect density and strain induced by Mn substitution. The occurrence of Mn and Ni in ZnO was confirmed by energy dispersive X-ray (EDX) spectra. Merging of Fermi level into the conduction by enhanced carrier concentrations elevated the band gap from 3.92 eV (Mn = 0%) to 4.11 eV (Mn = 6%) based on Burstein–Moss (BM) effect. The simultaneous occurrence of the bands within 613–649 cm−1 and 457–462 cm−1 derived from Fourier transform infrared (FTIR) spectra were recognized to the stretching modes of Zn–O in the tetrahedral and octahedral sites, respectively.

Involvement of gap junctions in astrocyte impairment induced by manganese exposure

Glutamate excitotoxicity, characterized as excessive glutamate stress, is considered to be involved in cerebral ischaemia, brain trauma, and neurodegenerative diseases such as Parkinson’s disease and Alzheimer's disease. Glutamate homeostasis disruption was highlighted in Mn neurotoxicity caused by high levels of Mn. Astrocytes, accounting for approximately 50% of the neuronal cells in the central nervous system and maintain glutamate homeostasis, are sensitive to neurotoxicity induced by Mn exposure. Astrocytes are tightly coupled with gap junctions (GJ), which are comprised of connexins, mainly connexin43 (Cx43). The gap junctional intercellular communication (GJIC) pathway allows small signal molecules, such as glutamate, ATP (adenosine triphosphate, ATP) and tropic factors, etc., to transfer between adjacent cells. Evidence has shown that astrocytes execute the bystander effect during cell death through the GJIC pathway. However, the pathogenic mechanism of the gap junction underlying glutamate neurotoxicity induced by manganese exposure has not been elucidated yet. In the present study, primary astrocytes were cultured and then exposed to different levels of Mn (ranging from 0 to 1000 μM) for 4/16 h to investigate the function of the GJIC in apoptosis induced by Mn. The cellular toxicity was confirmed by cell viability and apoptotic percentage through MTT assay and flow cytometry (FC). The levels of intracellular/extracellular glutamate were measured by high-performance liquid chromatography (HPLC). The fluorescent dye, Lucifer Yellow (LY), was used to assess the status of gap junctions among astrocytes after Mn exposure. The protein/gene expression of major gap junctional forming protein, Cx43, was also investigated. Cell viability was distinctly reduced when exposed to 500 and 1000 μM MnCl2 compared with control cells at both time points. The percentage of apoptosis was significantly increased among all detected Mn levels (125, 500 and 1000 μM MnCl2) of exposure (p < 0.05) with a concentration-dependent manner at either time point. Mn administration for 4/16 h also caused a remarkable intracellular/extracellular glutamate increase in a concentration-dependent manner for extracellular glutamate levels (p < 0.01). Gap junctions were prominently inhibited by Mn with Cx43 protein shown as shortening of the LY dye transfer distance at both time points. In-cell western blot indicated that Mn caused a decrease in Cx43 protein/gene expression in a dose-dependent manner. These results suggested that the gap junction intercellular communication and its forming protein, Cx43, are likely involved in glutamate excitotoxicity induced by Mn exposure.

Improvement of Superplasticity in High-Mg Aluminum Alloys by Sacrifice of Some Room Temperature Formability

The mechanical properties of fully annealed Al-4.6 wt pct Mg alloys with different levels of Mn and Fe have been characterized at room and superplastic forming (SPF) temperatures. The effects of Mn and Fe on the intermetallic phase, grain structure, and cavitation were investigated and correlated to the formability at different temperatures. Although both Mn and Fe contribute to the formation of Al6(Mn,Fe) phase, which refines the grain structure by particle-stimulated nucleation and Zener pinning, their effects are different. An increasing Mn reduces the room temperature formability due to the increasing number of intermetallic particles, but significantly improves the superplasticity by fine grain size-induced grain boundary sliding. Meanwhile, the Fe makes the constituent particles very coarse, resulting in reduced formability at all temperatures due to extensive cavitation. A combination of high Mn and low Fe is therefore beneficial to SPF, while low levels of both elements are good for cold forming. Consequently, the superplasticity of high-Mg aluminum alloys can be significantly improved by modifying the chemical composition with sacrifice of some room temperature formability.

Plant growth and N2 fixation in Cyclopia longifolia (Vogel L.) supplied with mineral nutrients in pot and field experiments

Cyclopia longifolia Vogel L. is indigenous to the Cape fynbos, and widely grown for the production of Honeybush tea, a beverage with health benefits and economic potential in the cosmetic and nutraceutical industries. The aim of this study was to assess plant growth and symbiotic performance of Cyclopia longifolia in field and pot experiments. Field plants were supplemented with different levels of P, Mg and Ca at Kanetberg mountains using 0, 5, 25 and 50mM of K2HPO4, MgCl2·6H2O and CaCl2·2H2O in split application, while P, Ca and Mg were applied as Supergrow (20.3% P), CaMg·(CO3)2, and MgSO4·7H2O) at 0, 10, 20 and 50kg·ha−1 to potted plants. Shoots were harvested at 240 and 300days after last fertilisation for pot and field experiments respectively, and analyzed for nodulation and N2 fixation. The data revealed significantly increased nodule number, nodule dry weight, root and shoot biomass in the pot experiment with P, Ca and Mg supply. Shoot dry matter, N content, amount of N-fixed, soil N uptake and tea yield of C. longifolia was significantly increased with increasing supply of P, Mg and Ca to field plants, and was highest at 50mM level of each element. Applying different levels of Mn, Cu, Zn and Mo to field plants of C. longifolia also markedly increased shoot biomass, N content, δ15N, amount of N-fixed, soil N uptake and tea yield. The increase in δ15N values, and hence reduced %Ndfa, of Cyclopia longifolia plants supplied with P, Mg, Ca, Mn, Cu, Zn and Mo suggests that the endogenous soil concentration of these nutrients were more limiting for plant growth than for nodule functioning. As a result, supplying P, Mg, Ca, Mn, Cu, Zn and Mo increased plant growth and biomass, but not %N derived from fixation.

Development of Al-Mg Alloys with Different Levels of Mn and Fe for Super-Plastic Forming

New Al-Mg alloys have been developed for super-plastic forming (SPF) based on commercial AA5083/AA5086 alloys, but with an increased Mn content from 0.5 to 1.5 wt.% and a decreased impurity Fe level from 0.25 to 0.05 wt.%.The effects of Mn and Fe levels on super-plasticity have been investigated by high temperature tensile testing of cold rolled H18 sheets at 425 to 525°C with a strain rate of 2×10-3 s-1. The microstructure evolution during different processing stages, grain size and grain size stability were investigated by optical microscopy and scanning electron microscopy. Both Mn and Fe showed a similar and significant contribution to grain size control in recrystallization, but their effect on high temperature sheet formability was different. An increase in Mn level led to an improvement in high temperature tensile elongation, while an increase in Fe content reduced the sheet formability. A new alloy with 1.5 wt.% Mn and 0.05 wt.% Fe, when processed to H18 temper, was able to reach more than 400% tensile elongation at 450 - 500°C with a strain rate of 2×10-3 s-1.

Characterization of Mn-resistant endophytic bacteria from Mn-hyperaccumulator Phytolacca americana and their impact on Mn accumulation of hybrid penisetum

Three hundred Mn-resistant endophytic bacteria were isolated from the Mn-hyperaccumulator, Phytolacca americana, grown at different levels of Mn (0, 1, and 10mM) stress. Under no Mn stress, 90%, 92%, and 11% of the bacteria produced indole acetic acid (IAA), siderophore, and 1-aminocyclopropane-1-carboxylate (ACC) deaminase, respectively. Under Mn stress, 68–94%, 91–92%, and 21–81% of the bacteria produced IAA, siderophore, and ACC deaminase, respectively. Greater percentages of ACC deaminase-producing bacteria were found in the Mn-treated P. americana. Furthermore, the ratios of IAA- and siderophore-producing bacteria were significantly higher in the Mn treated plant leaves, while the ratio of ACC deaminase-producing bacteria was significantly higher in the Mn treated-roots. Based on 16S rRNA gene sequence analysis, Mn-resistant bacteria were affiliated with 10 genera. In experiments involving hybrid penisetum grown in soils treated with 0 and 1000mgkg−1 of Mn, inoculation with strain 1Y31 was found to increase the root (ranging from 6.4% to 18.3%) and above-ground tissue (ranging from 19.3% to 70.2%) mass and total Mn uptake of above-ground tissues (64%) compared to the control. Furthermore, inoculation with strain 1Y31 was found to increase the ratio of IAA-producing bacteria in the rhizosphere and bulk soils of hybrid penisetum grown in Mn-added soils. The results showed the effect of Mn stress on the ratio of the plant growth-promoting factor-producing endophytic bacteria of P. americana and highlighted the potential of endophytic bacterium as an inoculum for enhanced phytoremediation of Mn-polluted soils by hybrid penisetum plants.

Phase fraction mapping in the as-cast microstructure of extrudable 6xxx aluminum alloys

Abstract The mapping of Mg2Si and β-AlFeSi phase fractions in the as-cast microstructure of Al–Mg–Si–Fe–Mn (6xxx series) alloys has been performed over the useful composition range (0–1.2 mass%) of the principal alloying elements Mg and Si. The calculations were based on the Scheil–Gulliver assumption of infinite diffusion in the liquid and limited diffusion in the solid state. The computed phase fractions were validated with experimental measurements of phase fractions. The mapping procedure allows the control of intermetallic phases in the as-cast microstructure, the minimization of the β-AlFeSi phase in particular, which is a significant prerequisite in obtaining enhanced extrudability, combined with high strength in this alloy series. Construction of maps for different levels of Mn has shown that addition of Mn could allow for higher alloying with Mg and Si, in order to obtain higher amounts of Mg2Si, without at the same time increasing the β-AlFeSi phase in the as-cast microstructure.

Interaction Effects of Zinc and Manganese on Growth, Uptake Response and Chlorophyll Content of Sweet Corn (Zea mays var. saccharata)

Manganese (Mn) and Zinc (Zn) interact with each other and this interaction can result in impacts on the yield of corn plants. This study was conducted to examine the effect of different levels of Mn and Zn on the yield, Mn and Zn concentration, root growth parameters and chlorophyll contents of corn plants. Sweet corn was grown in nutrient culture containing all combinations of Zn and Mn at levels of 0.0, 0.1, 1.0 and 10.0 mg L-1 as ZnSO4.7H2O and MnSO4.H2O, respectively and harvested at 28 days after transplanting. Mn and Zn concentrations in roots and shoots increased with increasing Mn and Zn concentration in nutrient solution. Zn concentration in both roots and shoots enhanced with increasing Mn levels. Mn concentration in shoots did not show any correlation with Zn concentration in nutrient solution, but Mn concentration in roots decreased with increasing levels of Zn. Zn0Mn1 treatment produced the highest yield. The lowest dry weight of young corn plants was recorded under Zn10Mn0 treatment due to Mn deficiency. Chlorophyll content decreased with high Zn application and this can be attributed to the interaction of Zn with iron in the growth medium. Different levels of Zn and Mn in nutrient solution did not have any significant effect on root parameters.

An investigation of metallurgical bonding in Al–7Si/gray iron bimetal composites

Abstract

Evolution in microstructure and mechanical properties during back-annealing of AlMnFeSi alloy

An Al–Mn–Fe–Si model alloy was subjected to two homogenization treatments, to achieve materials with different levels of Mn in solid solution and dispersoid densities, followed by cold rolling and back-annealing. Characterization of homogenization and deformation structures with respect to the effect of different microchemistries and strains on the structures was performed. Time-temperature-transformation (TTT) diagram with respect to precipitation and recrystallisation as a basis for analysis of the degree of concurrent precipitation was established. The TTT-diagram shows a strong effect of Mn concentration in solid solution and dispersoid density on the softening behavior. Recrystallization which finishes without the effect of concurrent precipitation results in an even, fine and equiaxed grain structure. Precipitation prior to or during recrystallization (concurrent) does retard the softening kinetics and leads to a coarse grain structure. However, the effect also depends on the duration of recrystallization and amount of precipitation. Recrystallization proceeding over a long time combined with a large amount of concurrent precipitation has a strong effect, otherwise the effect will be limited. Pre-existing fine and dense dispersoids (mean size 0.1 μm) before back-annealing do also lead to a coarse grain structure after recrystallization no matter whether additional concurrent precipitation occurs.

Systemic immune cell response in rats after pulmonary exposure to manganese-containing particles collected from welding aerosols

Welding fume inhalation affects the immune system of exposed workers. Manganese (Mn) in welding fume may induce immunosuppressive effects. The goal was to determine if Mn in welding fume alters immunity by reducing the number of circulating total leukocytes and specific leukocyte sub-populations. Sprague-Dawley rats were treated by intratracheal instillation (ITI) with either a single dose (2.00 mg/rat) or repeated doses (0.125 or 2.00 mg/rat for 7 weeks) with welding fumes that contained different levels of Mn. Additional rats were treated by ITI once a week for 7 weeks with the two doses of manganese chloride (MnCl2). Bronchoalveolar lavage was performed to assess lung inflammation. Also, whole blood was recovered, and the number of circulating total leukocytes, as well as specific lymphocyte subsets, was determined by flow cytometry. The welding fume highest in Mn content significantly increased lung inflammation, injury, and production of inflammatory cytokines and chemokines compared to all other treatment groups. In addition, the same group expressed significant decreases in the number of circulating CD4+ and CD8+ T-lymphocytes after a single exposure, and significant reductions in the number of circulating total lymphocytes, primarily CD4+ and CD8+ T-lymphocytes, after repeated exposures (compared to control values). Repeated MnCl2 exposure led to a trend of a reduction (but not statistically significant) in circulating total lymphocytes, attributable to the changes in the CD4+ T-lymphocyte population levels. The welding fume with the lower concentration of Mn had no significant effect on the numbers of blood lymphocytes and lymphocyte subsets compared to control values. Evidence from this study indicates that pulmonary exposure to certain welding fumes cause decrements in systemic immune cell populations, specifically circulating T-lymphocytes, and these alterations in immune cell number are not dependent exclusively on Mn, but likely a combination of other metals present in welding fume.

The effect of Fe, Mn and Sr on the microstructure and tensile properties of A356–10% SiC composite

This study investigates the formation of Fe containing intermetallic compounds on the microstructure and tensile properties of A356–10% SiC composite in the Mn- and Sr-modified conditions. The composite ingots were made by stir casting process and iron was added to the remelted composites at different concentrations varied from 0.5 to 2%. For 2 wt.% Fe, different levels of Mn were added to identify the optimum Mn:Fe ratio for eliminating harmful β-phase and obtaining microstructure with well distributed and fine intermetallics. 300 ppm Sr was added to the Mn-modified composite to investigate the effect of Sr and Mn on the microstructure and tensile properties of A356–10% SiC. T6 heat treatment was applied for all specimens. It was found that the addition of Mn changes the morphology of Fe-rich intermetallics from plate-like β- to α-phase. The tensile test results demonstrated that the addition of iron considerably reduces both UTS and elongation values while, modification by Mn and Sr improves tensile properties of the composite with 1 and 2 wt.% Fe. Fractographic examination of iron containing composites also showed that large β-Fe intermetallics are responsible for fracture behavior in unmodified condition.