Iron Salt Concentration Research Articles

Effect of EDTA and Citric Acid Additive on the Polymorph, Morphology, and Photocatalytic Activity of Iron Oxyhydroxide.

Iron oxyhydroxide [FeO(OH)] is a promising photocatalyst owing to its simple synthesis at mild temperatures and narrow band gap, which allows for the efficient harvesting of visible light. The selective production of FeO(OH) polymorphs and the modulation of their morphology by changing the iron salts, salt concentration, and additives have been widely reported. This study focuses on overcoming fast charge-carrier recombination by developing FeO(OH)-based heterostructure materials. The role of a chelating ligand (EDTA and citrate) in determining the polymorph type, morphology, and photocatalytic activity of FeO(OH) was studied. The findings revealed the additive produced of nanosized α-FeO(OH)/EDTA and layered γ-FeO(OH)/citrate with superior catalytic activities.

Copper and iron metal resistant rhizospheric bacteria boost the plant growth and bacoside A content in Bacopa monnieri under stress conditions.

Bacteria that enhance plant growth and development and are found in the vicinity of roots are referred to as plant growth-promoting rhizobacteria. Some beneficial bacteria help plant tolerance to many hazardous chemical elements. In this context, Cupriavidus basilensis, Novosphingobium humi, Bacillus zanthoxyli, Bacillus sp., Paenibacillus alvei, Ancylobacter aquaticus and Ralstonia syzygii metal-tolerant rhizospheric bacteria were isolated from rhizospheric soil associated with Bacopa monnieri. The beneficial effects of rhizospheric bacteria on B. monnieri plant physiology and biochemical responses were investigated under pot conditions at two levels (100μM and 500μM) of CuSO4 or FeCl3. N. humi, A. aquaticus and R. syzygii bacterial strains were associated with significantly increased height and biomass under normal and stress conditions. An assay for indole acetic acid in isolated rhizospheric bacteria found differential secretion except Bacillus zanthoxyli. Bacoside A is a major phytocompound in B. monnieri with medicinal value; maximum induction was observed in the R. syzygii treatment. High concentration of copper and iron salts negatively influenced height, biomass and photosynthetic pigments; however N. humi, A. aquaticus, Bacilllus sp. and R. syzygii beneficial bacterial helped plants under stress conditions. Moreover, a significant enhancement in chlorophyll a and b was noticed in C. basilensis, B. zanthoxyli, Bacilllus sp., P. alvei and R. syzygii treatments, without much influence on carotenoid levels. Therefore, the present study emphasises the importance of isolating plant growth-promoting rhizobacteria for use in bacopa plants exposed to metals such as copper and iron in soil.

Synthesis of Biocompatible Superparamagnetic Iron Oxide Nanoparticles (SPION) under Different Microfluidic Regimes.

Superparamagnetic iron oxide nanoparticles (SPION) have a great potential in both diagnostic and therapeutic applications as they provide contrast in magnetic resonance imaging techniques and allow magnetic hyperthermia and drug delivery. Though various types of SPION are commercially available, efforts to improve the quality of SPION are highly in demand. Here, we describe a strategy for optimization of SPION synthesis under microfluidics using the coprecipitation approach. Synthesis parameters such as temperature, pH, iron salt concentration, and coating materials were investigated in continuous and segmented flows. Continuous flow allowed synthesizing particles of a smaller size and higher stability than segmented flow, while both conditions improved the quality of particles compared to batch synthesis. The most stable particles were obtained at a synthesis condition of 6.5 M NH4OH base, iron salt (Fe2+/Fe3+) concentration ratio of 4.3/8.6, carboxymethyl dextran coating of 20 mg/mL, and temperature of 70 °C. The synthesized SPION exhibited a good efficiency in labeling of human platelets and did not impair cells. Our study under flow conditions provides an optimal protocol for the synthesis of better and biocompatible SPION that contributes to the development of nanoparticles for medical applications.

Thalassiosira pseudonana and Skeletonema costatum biomass optimization: Cultivation, harvesting, extraction of oils and biodiesel and pelletization of the residue

Microalgae are one of the most promising feedstocks for biofuel production that can solve the energy crisis, climate change, and the depletion of fossil fuels. Biorefineries have production capacity bottlenecks that prevent them from being economically profitable, without leaving aside the environmental safety of by-products. This research aims to analyze critical stages such as harvesting or lipid extraction from two microalgae species currently unknown, such as Thalassiosira pseudonana and Skeletonema costatum. Inorganic flocculation with a low concentration of iron or aluminum salts (FeCl3 and Al2(SO4)3) was achieved to recover >60% biomass in just 20 min in both cases. Lipids extractions through chloroform: methanol (solvent ratio 2:1) obtained low performance due to the ionic strength medium. The fatty acid composition of the algae extracts showed that stearic acid (C18:0) and palmitoleic acid (C16:1) were predominant in both species. In addition, residues from the lipid extraction process were used for the manufacture of pellets. The data collected showed that these solid biofuels should be combined with other biomass typologies if the end-use are biomass boilers. The development of these studies provides new information on different microalgae species and their potential to use their biomass through an integrated utilization.

Iron influences the expression of colonization factor CS6 of enterotoxigenic Escherichia coli.

Enterotoxigenic Escherichia coli (ETEC) is a major pathogen of acute watery diarrhoea. The pathogenicity of ETEC is linked to adherence to the small intestine by colonization factors (CFs) and secretion of heat-labile enterotoxin (LT) and/or heat-stable enterotoxin (ST). CS6 is one of the most common CFs in our region and worldwide. Iron availability functions as an environmental cue for enteropathogenic bacteria, signalling arrival within the human host. Therefore, iron could modify the expression of CS6 in the intestine. The objective of this study was to determine the effect of iron availability on CS6 expression in ETEC. This would help in understanding the importance of iron during ETEC pathogenesis. ETEC strain harbouring CS6 was cultured under increasing concentrations of iron salt to assess the effect on CS6 RNA expression by quantitative RT-PCR, protein expression by ELISA, promoter activity by β-galactosidase activity, and epithelial adhesion on HT-29 cells. RNA expression of CS6 was maximum in presence of 0.2 mM iron (II) salt. The expression increased by 50-fold, which also reduced under iron-chelation conditions and an increased iron concentration of 0.4 mM or more. The surface expression of CS6 also increased by 60-fold in presence of 0.2 mM iron. The upregulation of CS6 promoter activity by 25-fold under this experimental condition was in accordance with the induction of CS6 RNA and protein. This increased CS6 expression was independent of ETEC strains. Bacterial adhesion to HT-29 epithelial cells was also enhanced by five-fold in the presence of 0.2 mM iron salt. These findings suggest that CS6 expression is dependent on iron concentration. However, with further increases in iron concentration beyond 0.2 mM CS6 expression is decreased, suggesting that there might be a strong regulatory mechanism for CS6 expression under different iron concentrations.

Iron-pulsing, a novel seed invigoration technique to enhance crop yield in rice: A journey from lab to field aiming towards sustainable agriculture

Bulk fertilizer application is one of the easiest means of improving yield of crops however it comes with several environmental impediments and consumer health menace. In the wake of this situation, sustainable agricultural practices stand as pertinent agronomic tool to increase yield and ensure sufficient food supply from farm to fork. In the present study, efficacy of iron-pulsing in improving the rice yield has been elucidated. This technique involves seed treatment with different concentrations (2.5, 5 and 10 mM) of iron salts (FeCl3 and FeSO4) during germination. FeCl3 or FeSO4 was used to treat the sets and depending on the concentration of the salts, the sets were named as C2.5, C5, C10 and S2.5, S5, S10 (where C and S stands for FeCl3 and FeSO4 respectively and the numbers succeeding them denotes the concentration of salt in mM). Our investigation identified 72 h of treatment as ideal duration for iron-pulsing. At this time point, the seedling emergence attributes and activities of α-amylase and protease increased. The relative water uptake of the seeds also increased through upregulation of aquaporin expression. The treatment efficiently maintained the ROS balance with the aid of antioxidant enzymes and increased the iron content within the treated seeds. After transplantation in field, photosynthetic rate and chlorophyll content enhanced in the treated plants. Finally, the post-harvest agro-morphological traits (represented through panicle morphology, 1000 seed weight, harvest index) and yield showed significant improvement with treatment. Sets C5 and S5 showed optimum efficiency in terms of yield improvement. To our best knowledge, this study is the first report deciphering the efficacy of iron-pulsing as a safe, cost effective and promising technique to escalate the yield of rice crops without incurring an environmental cost. Thus, iron-pulsing is expected to serve as a potential tool to address global food security in years to come.

Preparation of magnetic hydrochar derived from iron-rich Phytolacca acinosa Roxb. for Cd removal

Considering that hyperaccumulators can accumulate high concentrations of iron salt, they can successfully obtain magnetic hydrochar from iron-rich hyperaccumulators. In this study, iron-rich biomass was obtained by irrigating Phytolacca acinosa Roxb. using iron salt. Magnetic nano-Fe3O4 hydrochar was prepared from iron-rich Phytolacca acinosa Roxb. via hydrothermal carbonization to remove Cd. The characterization results showed that the synthesized magnetic nanoparticles had an average size of 2.62 ± 0.56 nm and N elements were doped into magnetic nano-Fe3O4 hydrochar with abundant oxygenic groups. Cd adsorption on magnetic nano-Fe3O4 hydrochar was better fitted using the Langmuir isotherm and the pseudo-second-order kinetic model. The maximum adsorption capacity was 246.6 mg g−1 of Cd. The research confirmed that Cd adsorption was controlled by multiple mechanisms from the jar test, transmission electron microscopy mapping, scanning electron microscopy-energy dispersive X-ray spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. CdCO3 crystals can be formed after adsorption, indicating that surface precipitation played an important role in Cd adsorption. The abundance of O atoms and the doping of N atoms on the hydrochar surface were conducive to Cd adsorption, indicating that the mechanisms were related to surface complexation and electrostatic attraction. In addition, the significant decrease in Na+ content after Cd adsorption illustrated that ion exchange had a non-negligible effect on Cd adsorption. This study not only provides a strategy for preparing magnetic nano-Fe3O4 hydrochar derived from iron-rich plants but also verifies multiple Cd adsorption mechanisms using magnetic nano-Fe3O4 hydrochar.

High Yield Synthesis and Application of Magnetite Nanoparticles (Fe3O4)

Magnetite nanoparticles (Fe3O4), average particle size of 12.9 nm, were synthesized de novo from ferrous and ferric iron salt solutions (total iron salt concentration of 3.8 mM) using steady-state headspace NH3(g), 3.3% v/v, at room temperature and pressure, without mechanical agitation, resulting in >99.9% yield. Nanoparticles size distributions were based on enumeration of TEM images and chemical compositions analyzed by: XRD, EDXRF, and FT-IR; super-paramagnetic properties were analyzed by magnetization saturation (74 emu/g). Studies included varying headspace [NH3(g)] (1.6, 3.3, 8.4% v/v), and total iron concentrations (1.0 mM, 3.8 mM, 10.0 mM, and >>10 mM). An application of the unmodified synthesized magnetite nanoparticles included analyses of tetracycline’s (50, 100, 200, 300, and 400 ppb) in aqueous, which was compared to the same tetracycline concentrations prepared in aqueous synthesis suspension with >97% extraction, analyzed with LC-MS/MS.

Synthesis of iron nanoparticles from aqueous extract of Eucalyptus robusta Sm and evaluation of antioxidant and antimicrobial activity

In this work we obtained iron nanoparticles (FeNP) from the aqueous extract of the leaves of E. robusta and to evaluate their antimicrobial activity on different pathogenic microorganisms. Different concentration of iron salt and leaf extract were used; the proportion of precursor to leaf extract was 1:1. The results reveled dependence on the particle size of FeNP and synthesis conditions. Subsequently, the antimicrobial activity was evaluated against the microorganisms Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus and Bacillus subtilis, being a close relationship between the conditions of synthesis and the increase or decrease of the antimicrobial activity. Finally, the quantification of flavonoids and total polyphenols was carried out and the antioxidant activity of the E. robusta extract was evaluated, which allowed associating the antimicrobial activity found in the FeNPs with the components present in the extract.

Mineral Waste Containing High Levels of Iron from an Environmental Disaster (Bento Rodrigues, Mariana, Brazil) is Associated with Higher Titers of Enteric Viruses.

Although the effects of heavy metals on the behavior, including infectivity, of bacteria have been studied, little information is available about their effects on enteric viruses. We report an investigation of effects on the biosynthesis of human adenoviruses (HAdV) and hepatitis A (HAV) of waters contaminated with mineral waste following an environmental disaster in Mariana City, Minas Gerais State, Brazil. The study area was affected on November 5, 2015, by 60million m3 of mud (containing very high concentrations of iron salts) from a mining reservoir (Fundão), reaching the Gualaxo do Norte River (sites evaluated in this study), the "Rio Doce" River and finally the Atlantic Ocean. We found substantial counts of infectious HAdV and HAV (by qPCR) in all sampled sites from Gualaxo do Norte River, indicating poor basic sanitation in this area. The effects of iron on viral infection processes were evaluated using HAdV-2 and HAV-175, as DNA and RNA enteric virus models, respectively, propagated in the laboratory and exposed to this contaminated water. Experiments in field and laboratory scales found that the numbers of plaque forming units (PFU) of HAdV and HAV were significantly higher in contaminated water with high iron concentrations than in waters with low iron concentration (< 20µg/L of iron). These findings indicate that iron can potentiate enteric virus infectivity, posing a potential risk to human and animal health, particularly during pollution disasters such as that described here in Mariana, Brazil.

Preparation conditions effect on the physico-chemical properties of magnetic–plasmonic core–shell nanoparticles functionalized with chitosan: Green route

We study the effect of temperatures and salt concentrations (two different points) on the physico-chemical and cytotoxicity properties of the core–shell magnetic–plasmonicnanoparticles functionalized with chitosan. This nano-composite core–shell has been produced through a green, facile, one-pot method using the fungal species Fuzarium oxyporium. The protocol of synthesis has been recorded as a patent in the Egyptian Academy of Science with no:2209/2017. We have proved the involvement of chitosan present in the fungal cell wall in the process of biosynthesis in addition to the decoration of the outer most layer of the nanocomposite by the chitosan functional groups. Characterization of the nanoparticles under selected conditions was performed by UV/visible, Fourier transform infrared spectroscopy (FTIR), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometer (VSM), and the dynamic light scattering (DLS). Furthermore, the cytotoxicity of the biosynthesized nanoparticles has been investigated for four different cell lines to identify the best condition for the biomedical applications. The data reveals that the 80 °C and the higher iron salt concentration yield the least particle size <2 nm and the best PDI ∼ 0.2, and least cytotoxicity 6% against liver cancer cell line and zero against other studied cell lines, additionally, it shows the best physico-chemical properties.

Magnetic targeting of smooth muscle cells in vitro using a magnetic bacterial cellulose to improve cell retention in tissue-engineering vascular grafts

Tissue-engineered vascular grafts (TEVG) use biologically-active cells with or without supporting scaffolds to achieve tissue remodeling and regrowth of injured blood vessels. However, this process may take several weeks because the high hemodynamic shear stress at the damaged site causes cellular denudation and impairs tissue regrowth. We hypothesize that a material with magnetic properties can provide the force required to speed up re-endothelization at the vascular defect by facilitating high cell density coverage, especially during the first 24 h after implantation. To test our hypothesis, we designed a magnetic bacterial cellulose (MBC) to locally target cells in vitro under a pulsatile fluid flow (0.514 dynes cm−2). This strategy can potentially increase cell homing at TEVG, without the need of blood cessation. The MBC was synthesized by an in situ precipitation method of Fe3+ and Fe2+ iron salts into bacterial cellulose (BC) pellicles to form Fe3O4 nanoparticles along the BC’s fibrils, followed by the application of dextran coating to protect the embedded nanoparticles from oxidation. The iron salt concentration used in the synthesis of the MBC was tuned to balance the magnetic properties and cytocompatibility of the magnetic hydrogel. Our results showed a satisfactory MBC magnetization of up to 10 emu/g, which is above the value considered relevant for tissue engineering applications (0.05 emu/g). The MBC captured magnetically-functionalized cells under dynamic flow conditions in vitro. MBC magnetic properties and cytocompatibility indicated a dependence on the initial iron oxide nanoparticle concentration. Statement of SignificanceMagnetic hydrogels represent a new class of functional materials with great potential in TVEG because they offer a platform to (1) release drugs on demand, (2) speed up tissue regrowth, and (3) provide mechanical cues to cells by its deformability capabilities. Here, we showed that a magnetic hydrogel, the MBC, was able to capture and retain magnetically-functionalized smooth muscle cells under pulsatile flow conditions in vitro. A magnetic hydrogel with this feature can be used to obtain high-density cell coverage on sites that are aggressive for cell survival such as the luminal face of vascular grafts, whereas simultaneously can support the formation of a biologically-active cell layer that protects the material from restenosis and inflammation.

Degradation and initial mechanism pathway of chloramphenicol by photo-Fenton process at circumneutral pH

This paper describes the degradation of the antibiotic chloramphenicol by a photo-Fenton process under artificial and solar irradiation. Using artificial radiation, the role of different sources and concentrations of iron (salts of Fe2+ and Fe3+ and the iron complexes citrate (FeCit) and oxalate (FeOx)), initial pH, concentration of H2O2 and addition of oxalate at initial pH 6.0 were evaluated. The concentration of chloramphenicol was reduced to below the quantification limit of the equipment (<0.12 µmol L−1), as a result of 94% degradation after 40 min of reaction (equivalent to an accumulated UVA dose of 54 kJ m−2 furnished by two 8 W dark-light lamps). This occurred at pH 6.0, using 32 µmol L−1 FeOx and 44 µmol L−1 H2O2, and multiple additions of oxalate (before, and at 10 min of reaction, resulting in an excess of 192 µmol L−1). The same efficiency of chloramphenicol degradation was reached under solar irradiation using the same experimental conditions and accumulated UVA dose, but using a lower excess of oxalate (96 µmol L−1). In addition, three initial transformation products of chloramphenicol degradation were identified, one of them not yet being reported in the literature. These transformation products were probably formed by the attack of hydroxyl radicals on the aromatic ring or the benzylic carbon, according to a mechanism proposed in this study. Finally, on the basis of these results, the degradation under solar irradiation could represent a good alternative for degradation of chloramphenicol and its transformation products, since a solution with low toxicity in respect to the bacteria Vibrio fischeri was obtained, which is extremely advantageous due the reduction in energy costs.

Enhancing the ecological and operational characteristics of water treatment units at TPPs based on baromembrane technologies

The innovative baromembrane technologies for water demineralization were introduced at Russian TPPs more than 25 years ago. While being used in the power engineering industry of Russia, these technologies demonstrated certain advantages over the traditional ion-exchange and thermal technologies of makeup water treatment for steam boilers. Water treatment units based on the baromembrane technology are compact, easy to operate, and highly automated. The experience gained from the use of these units shows that their reliability depends directly on preliminary water treatment. The popular water pretreatment technology with coagulation by aluminum oxychloride proved to be inefficient during the seasonal changes of source water quality that occurs at some stations. The use of aluminum coagulant at pH 8 and higher does not ensure the stable and qualitative pretreatment regime: soluble aluminum forms slip on membranes of the ultrafiltration unit, thereby causing pollution and intoxication as well as leading to structural damages or worsening of mechanical properties of the membranes. The problem of increased pH and seasonal changes of the source water quality can be solved by substitution of the traditional coagulant into a new one. To find the most successful coagulant for water pretreatment, experiments have been performed on both qualitative and quantitative analysis of the content of natural organic matters in the Volga water and their structure. We have developed a software program and measured the concentrations of soluble aluminum and iron salts at different pH values of the source water. The analysis of the obtained results has indicated that iron sulfate at pH 6.0−10.2, in contrast to aluminum oxychloride, is not characterized by increased solubility. Thus, the basic process diagrams of water pretreatment based on baromembrane technologies with pretreatment through coagulation by iron salts and wastewater amount reducing from 60–40 to 5–2% have been introduced for thermal power stations.

Effect of the synthesis conditions on the size of magnetite nanoparticles produced by high-temperature reductive hydrolysis

A study was made into the effect of the conditions (synthesis temperature, water content, iron salt(III) concentration, and nature of precipitant) of the synthesis of magnetite nanoparticles by high-temperature reductive hydrolysis of iron(III) salts in an ethylene glycol medium on their size and morphology. It was shown that is basically possible to carry out the direct synthesis of spherical particles with an average size of 55–170 nm while varying synthesis conditions. The obtained particles were characterized by X-ray powder diffraction analysis, and their magnetic properties were explored. The synthesized particles are ferrimagnets. The magnetic moments, numbers, and sizes of domains in magnetite particles of various sizes were found.

Synthesis and characterization of nanometric magnetite coated by oleic acid and the surfactant CTAB

Nanometric magnetite (nm-Fe3O4) particles were prepared by the reverse co-precipitation synthesis method, obtaining particle sizes that ranged from 4 to 8.5 nm. In their synthesis, the concentration of iron salts of ferric nitrate, Fe(NO3)3⋅9H2O, and ferrous sulfate, FeSO4⋅7H2O, were varied relative to the chemical reaction volume and by using different surfactants such as oleic acid (OA) and hexadecyltrimethylammonium bromide (CTAB). The nm-Fe3O4 particles were characterized by transmission electron microscopy (TEM), Mossbauer spectroscopy (MS), magnetic and X-ray diffraction (XRD) measurements. Typical asymmetrical and/or broad lines shapes appeared in all Mossbauer spectra of the as prepared samples suggesting strong magnetic inter-particle interactions, reducing these interactions to some extent by gentle mechanical grinding. For the smallest particles, maghemite instead of magnetite was the main preparation product as low temperature Mossbauer and magnetic measurements indicated. For the intermediate and largest particles a mixture of magnetite and maghemite phases were produced as the saturation magnetization values of MS ∼ 60 emu/g indicated; these values were measured for most samples, independently of the coating surfactant concentration, and according to the ZFC-FC curves the blocking temperatures were 225K and 275K for the smallest and largest magnetite nanoparticles, respectively. The synthesis method was highly reproducible.

A Simple and “Green” Method for Synthesis of Magnetic Hollow Silica Spheres and Its &amp;lt;sup&amp;gt;99&amp;lt;/sup&amp;gt;Tc&amp;lt;sup&amp;gt;m&amp;lt;/sup&amp;gt; Labeled Targeting Studies

The magnetic hollow silica spheres (MHSS) with uniform cavity size and shell thickness were prepared by a simple and “green” method using functionalized SiO2 spheres as templates. Magnetic particles (Fe3O4) were deposited on the SiO2 surface by varying the molar ratio of [Fe2+]/[Fe3+] and the molar concentration of iron salts. The obtained magnetic hollow silica spheres exhibited a super-paramagnetic behavior at room temperature. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray powder scattering (XRD) were applied to characterize the MHSS. Besides, their unit cell parameters are calculated according to results indexing to XRD, the MHSS sample prepared at 0.10 M iron salts and 2:1 molar ratio of [Fe2+]/[Fe3+] has a largest cell angle (β) of unit cell. Due to large hollow cavity space and super-paramagnetic characteristics, the inner amino-functionalized MHSS could be labeled with radioisotope 99Tcm to study the MHSS’s magnetic targeting distribution in vivo. These results indicate that the MHSS has potential in the magnetic targeted drug delivery system which reduces the damage to normal cells and improves the therapeutic effect of cancer.

English

Microorganisms are known to be highly sensitive to the presence of heavy metals and some of the early attempts to control microorganisms had used copper sulphate as plant fungicide and mercury salts for some infectious diseases; but, the order of toxicity varies among different organisms and in general mercury and silver are more toxic than manganese and zinc. It has been seen that responses of organisms to heavy metal occur at concentration considerably below those at which they response to alkali and alkaline earth metal occur. Here an attempt has been made to study the susceptibility and resistance pattern of three common pathogenic bacteria, Klebsiella pneumonia, Escherichia coli and Staphylococcus aureus against heavy metals. The inhibitory effect of different concentrations of five metal salts, namely chromium, nickel, iron, cobalt and zinc on microbial growth were studied using gel diffusion method. Results show that all three study organisms were completely resistant for all concentrations of chromium and iron salts. E. coli and S. aureus were most susceptible for zinc and nickel salts as compared to K. pneumonia. In all salts, zones of inhibition were increased along with increasing concentrations of salts and maximum inhibition was seen at 150 mM concentration. All the three microbes were highly susceptible for zinc. Key words: Chromium, iron, metal salts, resistant.

Establishment of new monoxenic culture systems for root-knot nematodes, Meloidogyne spp., on axenic water spinach roots

To establish optimal monoxenic culture systems for Meloidogyne spp., in vitro axenic culture methods of water spinach and tomato roots and monoxenic reproduction of the nematodes were assessed on six different media (MS-I to MS-VI), based on the standard Murashige and Skoog (MS) medium. The concentrations of the major elements of MS medium were amended, and the main differences among these media were concentrations of iron salts, hormone and ammonium nitrate in the macroelements. Both water spinach and tomato successfully produced roots on MS-I to MS-V media (with ammonium nitrate), but not on MS-VI (without ammonium nitrate). Water spinach produced many more roots than tomato, especially on MS-I (without hormones). Meloidogyne incognita was successfully established on in vitro roots of the two plants on MS-I to MS-V media. It was also possible to culture M. javanica and M. arenaria on water spinach root on MS-I medium. In addition, water spinach root tissues could be maintained for 8 months on MS-II and MS-V media.

Influencing factors in the CO-precipitation process of superparamagnetic iron oxide nano particles: A model based study

The study, presented here, focuses on the impact of synthesis parameters on the co-precipitation process of superparamagnetic iron oxide nanoparticles. Particle diameters between 3 and 17 nm and saturation magnetizations from 26 to 89 Am 2 kg −1 were achieved by variation of iron salt concentration, reaction temperature, ratio of hydroxide ions to iron ions and ratio of Fe 3+ /Fe 2+ . All synthesis assays were conceived according to the “design of experiments” method. The results were fitted to significant models. Subsequent validation experiments could confirm the models with an accuracy>95%. The characterization of the chemical composition, as well as structural and magnetic properties was carried out using powder X-ray diffraction, transmission electron microscopy , Raman and Mössbauer spectroscopy and superconducting quantum interference device magnetometry. The results reveal that the particles' saturation magnetization can be enhanced by the employment of high iron salt concentrations and a molar ratio of Fe 3+ /Fe 2+ below 2:1. Furthermore, the particle size can be increased by higher iron salt concentrations and a hyperstoichiometric normal ratio of hydroxide ions to iron ions of 1.4:1. Overall results indicate that the saturation magnetization is directly related to the particle size. • We model the impact of synthesis parameters in the Massart process. • Optimization of synthesis parameters according to particle size and magnetization. • Particles are fully characterized with XRD, TEM and SQUID magnetometry.