Dispersed filler based on synthetic calcium carbonate – requirements for applications quality

The introduction of fillers into various materials improves its technological, physical and mechanical properties, and leads to a decrease in cost. The main areas of application of natural and synthetic calcium carbonate as highly dispersed fillers are: the construction industry, the production of Portland cement, mineral fertilizers, glass, paper, polymer composite materials, paints and varnishes, and rubbers. A promising direction at present is the use of production by-products as fillers, for example, conversion calcium carbonate - a waste product from the production of a complex mineral fertilizer - nitroammophoska. However, its use in the above areas is limited by the content of water-soluble nitrogen-containing impurities, impurities of heavy metals, strontium carbonate, phosphates, etc. The analysis of scientific, technical and patent literature on methods of purification of conversion calcium carbonate has been carried out. These methods are based on the extraction of impurities from the initial product of calcium carbonate production - a melt of calcium nitrate tetrahydrate by precipitation with various reagents, followed by the isolation of an insoluble precipitate (impurities) and processing of the purified melt into calcium carbonate and nitroammofoska. A method is proposed for the extraction of acid-tonic-soluble iron-containing impurities from the initial calcium nitrate melt in order to obtain a cleaner by-product - conversion calcium carbonate, which will expand the scope of its application. An effective method is to dilute the initial calcium nitrate melt with a 60% solution of ammonium nitrate to a calcium content of 12-13%, followed by the isolation of an acid-insoluble precipitate in a vacuum filter, conversion of the purified calcium nitrate solution with ammonium carbonate and separation of the resulting suspension in a drum filter. The described method can reduce the amount of iron-containing impurities by more than 50%.

Marine Microalgae Biomolecules and Their Adhesion Capacity to Salmonella enterica sv. Typhimurium

Different molecules have been tested as analog receptors due to their capacity to bind bacteria and prevent cell adhesion. By using in vitro assays, the present study characterized the aqueous and alkaline extracts from microalgae Pavlova lutheri and Pavlova gyrans and evaluated the capacity of these extracts to adhere to enterobacteria (Salmonella Typhimurium). The aqueous and alkaline extracts of both species were fractionated via freeze-thawing, giving rise to soluble and insoluble (precipitate) fractions in cold water. The obtained fractions were studied using thermogravimetric, methylation analyses, and using 1D and 2D NMR techniques. The cold-water-soluble fractions obtained from the aqueous extracts were mainly composed of highly branched (1→3),(1→6)-β-glucans, whereas the cold-water-precipitate fractions were constituted by (1→3)-β-glucans. The alkaline extract fractions showed similar compositions with a high protein content, and the presence of glycosides (sulfoquinovosylglycerol (SQG), digalactosylglycerol (DGG)), and free fatty acids. The linear (1→3)-β-glucans and the alkaline extract fractions showed an adhesion capacity toward Salmonella. The chemical composition of the active fractions suggested that the presence of three-linked β-glucose units, as well as microalgal proteins and glycosides, could be important in the adhesion process. Therefore, these microalgal species possess a high potential to serve as a source of anti-adhesive compounds.

Histochemical demonstration of neurotoxic esterase.

We developed a histochemical method for localizing neurotoxic esterase (NTE), defined as the phenylvalerate (PV)-hydrolyzing esterase that is resistant to 40 microM paraoxon (A) but inactivated by paraoxon plus 50 microM mipafox (B). NTE is considered to be the target enzyme in the production of organophosphorus ester-induced delayed neurotoxicity (OPIDN). Cryostat sections were incubated in a medium containing alpha-naphthyl valerate and 6-benzamido-4-methoxy-m-toluidine diazonium chloride (fast violet B) after treatment with the above-mentioned inhibitors, leading to formation of an aqueous insoluble precipitate at sites of enzymatic activity. NTE activity was estimated as staining detectable in A but not in B. In the central nervous system (CNS) of chicken, NTE appeared to be present primarily in the somata of most neurons, but at sites indistinguishable from those of the other inhibitor-resistant and -sensitive alpha-naphthyl valerate-hydrolyzing esterases. It could not be distinguished in the CNS of cat, probably because it constitutes less than 3% of the total PV-hydrolyzing activity in the CNS of that species.

Use of SEM, X-ray analysis and TEM to localize Fe3+ reduction in roots

In dicotyledons, Fe3+ must be reduced to Fe2+ before uptake and transport of this essential macronutrient can occur. Ambler et al demonstrated that reduction along the root could be observed by the formation of a stain, Prussian blue (PB), Fe4 [Fe(CN)6]3 n H2O (where n = 14-16). This stain, which is an insoluble precipitate, forms at the reduction site when the nutrient solution contains Fe3+ and ferricyanide. In 1972, Chaney et al proposed a model which suggested that the Fe3+ reduction site occurred outside the cell membrane; however, no physical evidence to support the model was presented at that time. A more recent study using the PB stain indicates that rapid reduction of Fe3+ occurs in a region of the root containing young root hairs. Furthermore the most pronounced activity occurs in plants that are deficient in Fe. To more precisely localize the site of Fe3+ reduction, scanning electron microscopy (SEM), x-ray analysis, and transmission electron microscopy (TEM) were utilized to examine the distribution of the PB precipitate that was induced to form in roots.

Preparation and staining of hard seed tissue for backscatter imaging

Hard seed coat material is extremely difficult to prepare for observation at the EM level. Seed coat segments are usually removed for embedding and sectioning, which results in loss of tissue juxtaposition. Observation and monitoring reactions of the intact seed coat under experimental procedures such as tracking dye penetration into seeds make seed coat dissection unfeasible. Efforts to apply analytical EM methods such as STEM/EDS analysis, are restricted by the limiting effect of section thickness on X-ray signal. We investigated the ultrastructure of dry seeds by treating them with various metallic staining solutions and observing the trimmed block faces with the SEM in backscatter mode. Good structural information was obtained as well as visualization of a specific tissue layer that accumulates lead.Intact seeds were incubated in several aqueous solutions including: 2% w/v uranyl acetate; 1% w/v OsO4; 2% ferrous chloride (Followed by 5% potassium ferricyanide to form an insoluble precipitate) ; and various lead solutions including Reynolds lead citrate.

Mechanisms of Actinide Isotope Leaching from Monazite

The remarkable geological stability of the actinide-containing rare-earth orthophosphate mineral monazite has led to consideration of synthetic analogs of this material as the wasteform for high-level nuclear wastes (1). Monazite is resistant to metamictization in spite of the alpha radiation from decaying actinides to which it has been subjected during its lifetime. This material is also very insoluble in most groundwaters. Consequently, dissolution of the mineral and leaching of its constituent actinides are very small. However, leaching experiments on natural monazite specimens, presented here, show that radioactive decay and radiation damage produce significant differences in the release rates of several isotopes into aqueous solutions. Within the duration of the present experiments, 6.3 to 6.8 years, these effects are particularly prominent in the nuclides in the decay chain of 232-Th. This series includes the alpha-recoil 228-Ra atom (a 5.8-year fT emitter formed directly by 232-Th decay), and its daughter 228-Th (a 1.9-year a emitter, produced by 3 decay). The present experiments exhibit preferential release into solution of 228-Th relative to 232-Th by a factor of 1.3 to 21. This highly enhanced 228-Th release is explained by four different isotope incongruency effects that operate during leaching. One mechanism involves the preferential etching of alpha-recoil tracks. The three other mechanisms depend upon the behaviour of 228-Ra. In particular, dissolution-released, recoil-released and diffusion-released 228-Ra atoms (the latter process is applicable to a high-temperature anneal) are observed to remain with the solid as an insoluble precipitate, possibly loosely attached to the mineral surface. Subsequent decay of this released insoluble 228-Ra immediately leads to the formation of readily dissolved 226-Th. The phenomena may be quite general, so potential wasteforms should be examined for these isotope fractionation effects in order to insure satisfactory prediction of the long-term leaching of actinides from the material.

Dimethylplatinum(IV) Complexes With Cyanide: Thermal and Photoassisted Substitution Reactions, and Characterization of Products by N.M.R.

Reactions of cyanide with the dimethylplatinum (IV) complexes, [PtMe2(OH) (H20)1.5 n, [PtMe2Br2]n and fac-PtMe2Br(H2O)3+, have been studied, principally by 1H, 13C and 195Pt n.m.r. Cyanide rapidly displaces the ligands trans to the methyl groups. Subsequent reactions cis to the methyl groups occur more slowly with heating, or, for bromo complexes, on ultraviolet irradiation. These substitution reactions compete with reductive elimination of groups from the platinum(IV) compounds to produce platinum(II) products. All attempts to prepare solutions of fac-PtMe2(CN)(H2O)3+ were unsuccessful. Oxidative addition of ICN to cis-PtMe2( py )2 ( py = pyridine) gave PtMe2I(CN)( py )2, from which a solution of fac-PtMe2(CN)( MeOH )3+ in methanol could be obtained. Addition of water or aqueous acid to this solution gave a very insoluble precipitate of [PtMe2(CN)(OH)n. The cis and trans influences on Jpt -C and δC of the cyanide ligands have been evaluated.

Heparin interferes with albumin determination by dye-binding methods.

Heparin, when added in vitro at rather high concentrations (400--1000 kilounits/L) as an anticoagulant, interferes with albumin determination by bromcresol green by forming an insoluble precipitate with this dye. The interference is much less with bromcresol purple. It can be abolished by addition of hexadimethrine bromide.