Polyvalent Metals Research Articles

Inelastic scattering effects on the inhomogeneous transverse conductivity of liquid metals and plasmas

Abstract On the basis of the quantum Wigner density operator formalism for multicomponent charged particle systems, the wavenumber (k)- and frequency (ω)- dependent transverse conductivity σ^T (k,ω) of simple liquid metals is presented for homogeneous (k = 0) and inhomogeneous (k≠0) electric fields separately. The theory takes into account correlated density fluctuations of electrons and ions, with their mutual inelastic scattering being described by the ionic dynamic structure factors. Since homogeneous and inhomogeneous fields perturb the diagonal and off-diagonal elements of the density matrix, respectively, the corresponding transport equations exhibit a dissimilarity in their collision terms. In both cases, approximate solutions to the transport equations yield a conductivity of generalized Drude form characterized by the k- and ω-dependent complex relaxation time. It is shown that the k→0 limit of the inhomogeneous conductivity, σ^T (k→0,ω), coincides with the homogeneous one in classical ion regime such that βℏω_i≪1, where β is the inverse temperature and ω_i is a characteristic frequency of ionic density fluctuation; this condition may be satisfied for metals well above melting. At lower temperatures, it is suggested that the (homogeneous) DC conductivity σ(0) can exceed the (inhomogeneous) optical conductivity extrapolated to zero frequency, σ^T (k→0,0). This trend is qualitatively consistent with earlier observations for liquid polyvalent metals.

Metal Polycation Adduction to Lipids Enables Superior Ion Mobility Separations with Ultrafast Ozone-Induced Dissociation.

Specific lipid isomers are functionally critical, but their structural rigidity and usually minute geometry differences make separating them harder than other biomolecules. Such separations by ion mobility spectrometry (IMS) were recently enabled by new high-definition methods using dynamic electric fields, but major resolution gains are needed. Another problem of identifying many isomers with no unique fragments in ergodic collision-induced dissociation (CID) was partly addressed by the direct ozone-induced dissociation (OzID) that localizes the double bonds, but a low reaction efficiency has limited the sensitivity, dynamic range, throughput, and compatibility with other tools. Typically lipids are analyzed by MS as singly charged protonated, deprotonated, or ammoniated ions. Here, we explore the differential IMS (FAIMS) separations with OzID for exemplary lipids cationized by polyvalent metals. These multiply charged adducts have much greater FAIMS compensation voltages (UC) than the 1+ ions, with up to 10-fold resolution gain enabling baseline isomer separations even at a moderate resolving power of the SelexION stage. Concomitantly OzID speeds up by many orders of magnitude, producing a high yield of diagnostic fragments already in 1 ms. These capabilities can be ported to the superior high-definition FAIMS and high-pressure OzID systems to take lipidomic analyses to the next level.

Participation of strong charge-assisted hydrogen bonds in interactions of dissolved organic matter represented by Suwannee River Humic Acid

Terrestrial dissolved organic matter (DOM) plays critical roles in many biotic and abiotic environmental reactions as well as in water treatment. Its structure is therefore of great interest. We examined dissolved Suwannee River Humic Acid (HA) to probe the potential participation of exceptionally strong, negative charge-assisted hydrogen bonds, (−)CAHB, in DOM cohesion and interaction with small weak acids using high performance size exclusion chromatography (HPSEC), transmission electron microscopy, zeta-pH curves, and pH drift experiments. The results support a previously proposed two-tier state of aggregation, in which tightly-knit primary particles (≤ ∼10 kDa) form larger secondary aggregates (up to micrometer in size). Evidence for (−)CAHB is gained through zeta potential changes and pH drift experiments. The primary particles interact with (−)CAHB-capable solutes (simple carboxylic acids and phosphate) but not (−)CAHB-incapable solutes. We identified disruption of intra-segmental and inter-molecular (−)CAHB leading to swelling and disaggregation, as well as formation of nouveau (−)CAHB with free groups on HA. The effects were solute-concentration dependent and greater at pH 5 than pH 6, consistent with CAHB theory. Phosphate induced the greatest shifts in the HPSEC molecular size distribution curves. The shifts were unaffected by prior stripping of innate polyvalent metals. We conclude that the (−)CAHB contributes to the cohesion of DOM, affecting its size and charge, and provides a means by which weak acid pollutants, nutrients, and natural compounds can interact with DOM. Such interactions have implications for the behavior of DOM in the environment, the fate and transport of anthropogenic pollutants, and the roles DOM play in water treatment technologies.

N, S co-doped porous carbon derived from waste medical masks to support LaFexCo1-xO3 as highly effective peroxymonosulfate catalysts for degradation of tetracycline

N and S co-doped porous carbon was prepared by decorating the waste disposable medical masks (WDMM) with thioacetamide (TAA) as the N/S source and then carbonizing at high temperature, which was subsequently incorporated Co-doped LaFeO3 to obtain NSC@LaFexCo1-xO3 catalysts. The resulting catalysts were used to construct an advanced oxidation process (AOP) based on activation of peroxymonosulfate (PMS) to degrade tetracycline (TC) in water. The physicochemical properties of the as-obtained catalysts were characterized and environmental factors affecting the catalytic performances of NSC@LaFexCo1-xO3/PMS were systematically investigated. The results showed that N and S co-doped porous carbon derived from thioacetamide (TAA)-functionalized WDMM at high temperature could be used as good support for LaFexCo1-xO3. The synergistic effects between N/S co-doped carbon and polyvalent metals (Co2+/Co3+ and Fe3+/Fe2+) endowed NSC@LaFexCo1-xO3 with enhanced catalytic performances, in which nearly 100% of TC could be removed by NSC@LaFe0.95Co0.05O3/PMS system within 10 min under the conditions of 0.2 g/L of catalyst dose, 2.5 mmol/L of PMS concentration and 10 mg/L of initial TC concentration. Furthermore, the constructed NSC@LaFe0.95Co0.05O3/PMS system exhibited a wider pH adaptability (3.0 ∼ 10.0), good salt resistance and reusability as well as high mineralization. The mechanisms and possible pathways of TC degradation by NSC@LaFe0.95Co0.05O3/PMS system were proposed and the ecotoxicity of TC and its intermediates was also evaluated. This study demonstrated the feasible transformation of waste masks into porous carbon with high added value for water pollution control and remediation, accomplishing the dual purposes of recycling and resource utilization of waste masks and protecting the environment.

Theoretical investigation of collective motion in some liquid metals using pseudopotential approach

The collective motions are studied using a recently created pseudopotential and some elastic constants. This paper involves the calculations of the collective motions like phonon dispersion curves (PDCs) for longitudinal and transverse frequencies ([Formula: see text] and [Formula: see text]), longitudinal sound velocity ([Formula: see text]), transverse sound velocity ([Formula: see text]), isothermal bulk modulus (B), modulus of rigidity (G), Young’s modulus (Y), Poisson’s ratio [Formula: see text], Debye temperature ([Formula: see text]) of some monovalent (Na), divalent (Mg) and polyvalent liquid metals (Al, Pb, Bi). This investigation is based upon the theory of pseudopotential of second-order approach via the equations of Hubbard and Beeby (HB). [Formula: see text] The pair correlation function is calculated from the different mean spherical approximation (MSA), one-component plasma (OCP) and optimized random phase approximation (ORPA) structure factors employed in this work. Three different types of local field correction (screening) functions proposed by Hartree (H), Taylor (T) and Nagy (N) are utilized in this paper. The current findings are found to be in qualitative accord with experimental and theoretical data.

Novel MOF-derived Fe/CoNHDC-400@GF cathode with improved in-situ catalytic degradation of chloroquine phosphate during heterogeneous electro-Fenton process

The preparation of stable and high-efficiency heterogeneous electro-Fenton cathodes for the treatment of pollutants is important for environmental remediation. Herein, a novel N-doped MOF-derived Fe/Co bimetallic catalyst was in-situ grown on graphite felt (GF) surface to yield a composite cathode Fe/CoNHDC-400@GF for use in electro-Fenton process. The introduction of cobalt accelerated electron transfer due to existing polyvalent metals. The synergistic effect between Co0, CoⅡ, CoШ, FeⅡ, and FeШ enabled the continuous generation of reactive oxygen species (•OH and •O2−). Under near-neutral conditions (pH=6.5), complete removal of 10 mg L−1 chloroquine phosphate (CQP) was achieved within 60 min. Additionally, efficient removal was also achievable over a wide pH range (pH=3–11). The mechanistic investigations indicated •OH as a major active oxygen species for CQP degradation. A combination of the experimental results with density functional theory calculations (DFT) clarified the degradation pathway and intermediate products of CQP. Moreover, the toxicity of degradation products significantly reduced. Overall, valuable insights on preparing composite cathodes grown in-situ for efficient removal of refractory pollutants from wastewater during the heterogeneous electro-Fenton process were provided, useful for future consideration.

Tannin-functionalized Mn3O4 as support for FeNiB alloy to construct sono-Fenton-like reaction for the degradation of antibiotic pollutants in water

In this paper, iron-based amorphous alloy (FeNiB) supported on Tannin-functionalized Mn3O4(Mn3O4-TA@FeNiB) were prepared and used as a heterogeneous catalyst to degrade ciprofloxacin (CIP) and norfloxacin (NOR) in aqueous solution by the ultrasound (US)-assisted Fenton-like process. The physicochemical properties of the resulting Mn3O4-TA@FeNiB were characterized by SEM, TEM, XRD, BET, FTIR, XPS and other techniques. The results showed that 92.04% and 90.34% of CIP and NOR at their initial concentration of 10 mg L−1 were removed by the sono-Fenton-like system after 60 min in comparison with 85.24% and 82.52% of CIP and NOR removal after 300 min by Mn3O4-TA@FeNiB alone and the rate constants of the former were 6.65 and 6.80 times higher than those of the latter, respectively. Excellent catalytic performances were benefited from synergistic interactions between US, H2O2 and Mn3O4-TA@FeNiB. Mn3O4-TA as a support and stabilizer could effectively load and disperse FeNiB, meanwhile providing reactive area and active sites (Mn2+/Mn3+). FeNiB was corroded to produce Fe2+ and Ni2+, thus forming reversible redox reactions between polyvalent metals, which ensured Fenton-like reaction to be effectively proceeded. While US accelerated the oxidation process to generate more reactive species, which resulted in higher catalytic efficiencies and reaction rates of CIP and NOR degradation. Metal leaching and cycling experiments showed that Mn3O4-TA@FeNiB exhibited good stability and reusability. Finally, the degradation intermediates of CIP were analyzed and the possible degradation mechanisms and pathways were proposed. These results indicated that Mn3O4-TA@FeNiB had great potential as an effective and low-cost catalyst in US-assisted Fenton-like process for removal of the emerging pollutants.

Synthesis of condensed phosphates of mono- and poly-valent metals, development of optimal methods for study of their properties and composition

Synthesis of condensed phosphates of mono- and polyvalent metals, development of optimal methods for study of their properties and composition. / M. Avaliani, G. Todradze, E. Shapakidze, V. Kveselava. / Nano Studies. – 2020. – # 20. – pp. 71-94. – geo. Work is a review and concern phosphorus and its various inorganic compounds, namely on first time synthesized by authors a number of condensed composites. Production of condensed compounds is based on high temperature (100 – 600 °C) synthesis in multi-component systems MI2O–MIII2O3–P2O5–Н2O (where MI – Ag and MIII – Ga and In) to receive new condensed compounds – inorganic polymers. The technology is based on the creation of new condensed forms – double inorganic oligomers, cyclic compounds and long chain polymeric composites via condensation of polyphosphosphoric acids. The problem that is solved through this work is the synthesis of a new, yet unknown double-condensed oligo-, poly- and cyclophosphates, analyzing their structure and composition, and the examination of properties. Over the last few years, numerous researchers has been paying serious attention to the careful synthesis and investigation of condensed phosphates – so-called inorganic polymers. It was possible afterward remarkable development of different fields of new technologies, as well as expanding the research area of nanotechnology and fundamental general researches. The study and analysis of the scientific literature both published online or printed were carried out. By analyzing the crystallization conditions and properties of polymers, the synthesis of new inorganic polymers with targeted properties will be possible, as well as identification of the optimal regimes for formation of monocrystals and in some cases – nanocomposites. To determine the composition of synthesized double condensed compounds, chemical analysis of these compounds has been conducted. The chemical analysis of these compounds has been compared to the existing methods of chemical researches and the optimal methods for determining phosphorus, mono- and trivalent metals in condensed compounds. During experiments, we synthesized scandium–silver, gallium–silver, indium–silver double cyclo-tetraphosphates and numerous condensed phosphates of trivalent and alkali metals’. With the synthesis of the obtained polymers and the analyzing of the crystallization conditions we can: enhance the fundamental research and create a database in an inorganic chemistry of polymer compounds, find parallels with other poly- and monovalent metals’ compounds. We determined: some inorganic oligomers and polymers can be used in practice whether they are new technology materials, binder and cementing compounds, fertilizers, or the ion exchange and substances with catalytic activity. Fig. 13, Tab. 10, Ref. 37.

Chemical structure and nanomechanics relevant electrochemistry of solid-phase humic acid along a typical forest-river-paddy landscape section in eastern China and its environmental implications

Solid-phase humic acid (HAsolid) plays a critical role in global carbon cycle and redox biogeochemistry of topsoil, because of its unique physicochemical properties, including electrochemical property. In this study, topsoil HAsolid along a typical forest-river-paddy landscape section in eastern China was investigated in the aspects of electrochemical property, chemical structure and nanomechanics, and their relationship. Nano-size HAsolid particles were extracted from topsoil of paddy soil (PS-HAsolid), forest soil (FS-HAsolid) and riverside sediment (RS-HAsolid). Results showed that all the HAsolid were conductive and played an important role in conductivity of topsoil suspension. HAsolid contained both reversible and irreversible redox peaks, with redox activity of PS-HAsolid > RS-HAsolid > FS-HAsolid. Owing to limited humification, electron exchange capacity (EEC) values of topsoil HAsolid suspensions were modest (3.18–4.45 μmol e−g−1 HAsolid). Compared with RS-HAsolid and FS-HAsolid, PS-HAsolid showed higher aromaticity and higher degree of humification with simple and even nanomechanical property. Long-term cultivation (human activities) as well as high content of polyvalent metals in paddy soil were supposed to facilitate formation of aromatic carbon and improve humification of HAsolid. The results suggested that aromatic carbon and high humification degree of PS-HAsolid contributed to simple and even nanomechanics, which further optimized its electrochemical property. This study not only provides novel insight into the mechanism of HAsolid mediating electron transfer, but also inspires ideas for soil and environmental management with different purposes based on regulation of HAsolid.

PECTIN SUBSTANCES

This article provides information about pectin substances. Information is given on the chemical structure of pectin macromolecules, their physiological activity and physicochemical properties. Clause contains the data, concerning applications of pectin in medicine and pharmacology. Pectin is effective detoksicant, possesses selective properties in relation to cations polyvalent, heavy and radioactive metals. It is used as plasmasubstitude of gemostatika.

Activated Carbon/Pectin Composite Enterosorbent for Human Protection from Intoxication with Xenobiotics Pb(II) and Sodium Diclofenac.

The use of enterosorbents—materials which can be administered orally and eliminate toxic substances from the gastrointestinal tract (GIT) by sorption—offers an attractive complementary protection of humans against acute and chronic poisoning. In this study, we report the results of developing a microgranulated binary biomedical preparation for oral use. It was designed with a core-shell structure based on pectin with low degree of esterification as the core, and nanoporous activated carbon produced from rice husk, AC-RH, as the shell, designated as AC-RH@pectin. The adsorption properties of the synthesized materials were studied in aqueous solutions for the removal of lead (II) nitrate as a representative of toxic polyvalent metals and sodium diclofenac as an example of a medicinal drug. The composite enterosorbent demonstrated high adsorption capacity for both adsorbates studied. Adsorption kinetics of lead and diclofenac adsorption by AC-RH, pectin, and AC-RH@pectin, fitted well a pseudo-second-order model. According to the Langmuir adsorption isotherm model, the best fitted isotherm model, the maximum adsorption capacity, qmax, of AC-RH@pectin for diclofenac and for lead (II) was 130.9 mg/g and 227.8 mg/g, respectively. Although qmax of AC-RH for diclofenac, 537.6 mg/g, and qmax of pectin for lead (II), 245.7 mg/g, were higher, the maximum adsorption capacity of AC-RH for lead (II), 52.7 mg/g, was much lower than that of the composite AC-RH@pectin and the adsorption capacity of pectin for diclofenac was negligible. Therefore, the composite material AC-RH@pectin demonstrated substantial efficiency of removing both species which potentially defines it as a more universal enterosorbent suitable for treating poisoning caused by substances of different chemical nature.

Complexation of 1,3-dihetaryl-5-phenyl-2-pyrazoline Derivatives with Polyvalent Metal Ions: Quantum Chemical Modeling and Experimental Investigation

1,3,5-Triaryl-2-pyrazoline derivatives with a pyridine ring in position 1 and 2-benzimidazolyl or 2-benzothiazolyl bicycles in position 3 were synthesized. Spectral properties in solvents of similar polarity, i.e. aprotic acetonitrile and in protic methanol, were studied, complexation with cadmium and mercury ions in acetonitrile was elucidated as well. Quantum-chemical modeling with application of the elements of Bader's atoms-in-molecules (AIM) theory of the title molecules conformational structure and 1:1 stoichiometry complexes formed with polyvalent metals of various nature (Mg, Zn, Cd, Pb, Hg, Ba) was conducted. The principal possibility of “nitrogen-sulfur” switching of the metal ions binding sites for the benzothiazole derivative was revealed, and makes possible to classify this compound as “smart ligand”.

Minimization of radioactive waste volume from nuclear power plants using precipitation-membrane technologies

The purpose of this study is the development and experimental testing on simulation solutions of a precipitation-membrane method for fractionation of liquid radioactive waste and sorption post-treatment of the filtrate. The choice of processing method is based on the analysis of factors affecting the efficiency of ion-exchange purification of solutions; properties of complex compounds of polyvalent metals; characteristics of commercially available membrane elements and economic aspects of the preparation and disposal of radioactive waste. The basic idea is to use the internal properties of solutions to isolate polyvalent cations and acidoligands in the form of poorly soluble compounds in the volume of an inert polypropylene element, which will increase the efficiency of ion-exchange post-treatment and reduce the amount of waste. The architecture and operating parameters of the experimental setup are designed to provide favorable conditions for the formation in solution of complexes (ion pairs) of polycharged cations with acid ligands of various nature.

Polyvalent Metal Ion Promoted Adsorption of DNA Oligonucleotides by Montmorillonite

Montmorillonite (MMT) is a two-dimensional (2D) clay material. Its abundance on the early earth has attracted studies for its role in prebiotic reactions, and adsorption of DNA to MMT is potentially important for understanding the origin of life. Although several possible models of DNA adsorption on MMT have been established, a consensus on the adsorption mechanism has yet to be formed, thereby a fundamental adsorption study is performed here. Adding up to 300 mM NaCl failed to promote DNA adsorption on MMT, Al2O3, or SiO2 nanoparticles. For polyvalent metals, DNA adsorption was achieved following the order Ce3+ > Cu2+ > Ni2+ > Zn2+. Among them, Ce3+ and Cu2+ inverted the surface charge of MMT to positive. In addition, using washing experiments, Cu2+- and Ce3+-mediated adsorption mainly depended on the DNA phosphate backbone, while Ni2+ and Zn2+ interacted with the backbone phosphate groups and adenine bases of DNA. Overall, these polyvalent metal ions promoted DNA adsorption via a cation bridge model. This research provides new insights into the surface interactions of MMT and DNA, which is conducive to future work on the interaction between clays and biopolymers.

Integrated modifying zinc-containing additive for construction silicate compositions

Sodium silicate binders are a promising binder base for obtaining effective granular thermal insulation materials. Increasing water resistance, first of all, will expand the scope of their application in construction. At the same time, the features of the modification of sodium silicate binders by compounds of polyvalent metals have not been fully studied, the interaction with which leads to the formation of hardly soluble silicates. The purpose of this work was to develop a modifying complex based on a zinc-containing compound - zinc acetate to increase the water resistance and thermal characteristics of the porous granular material. The proposed modifying additive is a complex consisting of zinc acetate and an organic alcohol solvent. It is shown that the properties of porous granular material can be controlled by changing the composition of the zinc acetate solvent. Qualitative and quantitative dependences of the properties of porous granules (strength, water resistance, density, thermal conductivity) on the type of zinc-containing solution and its content in the compositions have been obtained. The concept of the mechanism of formation of sparingly soluble complexes during the modification of sodium silicate binders with zinc-containing aqueous-alcoholic solutions has been developed. X-ray phase analysis showed that the sodium silicate system modified with an aqueous alcohol solution of zinc acetate, in contrast to an aqueous solution of zinc acetate, is completely in an amorphous state. We believe that compounds of the Zn2SiO4H2O, ZnSiO3 type are in the amorphous state. The obtained research results made it possible to determine the rational composition of granular heat-insulating material with increased operational and functional characteristics (ρ = 200-280 kg / m3, λ = 0.052-0.063 W / (m °C), R = 1.3-1.8 MPa, Kr = 0.89-0.92, W = 16- 18 %).

INVESTIGATION OF THE PROCESS OF CHEMICAL CROSSLINKING OF NA-CMC POLYVALENT METAL IONS

This article is devoted to the study of the Na-CMC structuring process under various conditions: structuring with polyvalent metal ions, structuring with polyvalent metal ions in the presence of polybasic acids. Structuring in a Na-CMC solution was investigated by adding polyvalent metal ions to it at various ratios Me+p / COO-, pH, which allowed us to characterize the structuring process as a reaction of macromolecules with low molecular weight compounds.It was found that the probability of intermacromolecular crosslinking, responsible for gelation, increases with an increase in the initial concentration of Na-CMC solution and with the additional presence of polybasic acids. When salts of polyvalent metals interact with solutions of polybasic acids in the presence of a 2N NaOH solution, their complex salts are formed.Titration calculations and IR spectra of dried salts confirmed the conclusion made about the formation of salts of structure I, II, III, IV. Crosslinking of Na-CMC has been shown to occur via compounds of the M2+ (3+) - OOS-R-type. It has been established that strong, transparent jellies are formed by trivalent metal ions, divalent metal ions also form brittle, cloudy jellies that stratify during a day.A suggestion has been made that the main reaction during gelation of the Na-CMC solution is the interaction of -COOH groups along the chain of the Na-CMC macromolecule with the Al+3 salt and citric acid of structure III. The role of citric acid is that it is a transverse bridge in the binding of Na-CMC macromolecules. During the process of chemical crosslinking, the system turns from a fluid state into a non-fluid one, and the dynamic viscosity of the system increases from 3.548 Pa·s to 1585 Pa·s.

Insight into the mechanism of low molecular weight organic acids-mediated release of phosphorus and potassium from biochars

A crucial mechanism for the application of biochar in soil improvement is the direct release of nutrients from biochar. Low molecular weight organic acids (LMWOAs) ubiquitously exist in soil. However, the mechanism of LMWOAs-mediated release of nutrients from biochars remains little known. Ten biochars with different mineral element stoichiometric ratio were produced, and four LMWOAs [acetic (HAc), glycolic (GA), tartaric (TA), and citric acids (CA)] were employed, to enunciate the influence mechanism of LMWOAs on the release of phosphorus and potassium from biochar. The results showed that HAc suppressed the release of P from biochars, while TA and CA facilitated the release of P from biochars with high ratios of polyvalent metals to P. A new mechanism was proposed that the deprotonated HAc combined with the dissolved HPO42− or H2PO4− to form a complex through hydrogen bond and cation bridging. The hydrophobic methyl group of HAc was exposed outside of the complex, which decreased the water-solubility of phosphate. Meanwhile, a high ratio of polyvalent metals to P benefited more P to combine with polyvalent metals, which decreased the water-solubility of P, but the deprotonated TA and CA are polyvalent anions that could substitute this part of P by anion exchange. Also, LMWOAs promoted the release of K from biochars with low K/(P + S) ratios, possibly due to unionized carboxyl of LMWOAs served as a hydrogen bond donor to displace K out of biochars. This study gives a deep understanding of the fate of biochar originated nutrients response to LMWOAs.

Pressure-induced effects in the spectra of collective excitations in pure liquid metals

Collective dynamics of metallic melts at high pressures is one of the open issues of condensed matter physics. By means of ab initio molecular dynamics simulations, we examine features of dispersions of collective excitations through transverse current spectral functions, as a function of pressure. Typical metallic melts, such as Li and Na monovalent metals as well as Al, Pb and In polyvalent metals are considered. We firmly establish the emergence of a second branch of high-frequency transverse modes with pressure in these metals, that we associate with the pronounced high-frequency shoulder in the vibrational density of states. Similar correlation also exist with the low frequency modes. The origin of the pressure-induced evolution of transverse excitations in liquid metals is discussed.

Beyond Charge Balance: Counter-Cations in Polyoxometalate Chemistry.

Polyoxometalates (POMs) are molecular metal‐oxide anions applied in energy conversion and storage, manipulation of biomolecules, catalysis, as well as materials design and assembly. Although often overlooked, the interplay of intrinsically anionic POMs with organic and inorganic cations is crucial to control POM self‐assembly, stabilization, solubility, and function. Beyond simple alkali metals and ammonium, chemically diverse cations including dendrimers, polyvalent metals, metal complexes, amphiphiles, and alkaloids allow tailoring properties for known applications, and those yet to be discovered. This review provides an overview of fundamental POM–cation interactions in solution, the resulting solid‐state compounds, and behavior and properties that emerge from these POM–cation interactions. We will explore how application‐inspired research has exploited cation‐controlled design to discover new POM materials, which in turn has led to the quest for fundamental understanding of POM–cation interactions.

Alternative Approaches in Direct Microscobic Examination of Fresh Fecal Samples

Aim of the present study was to identify protozoones which are difficult to define through wet slide in fresh fecal samples by using different fixatives with modified Trichrome stain within five minutes. Two different fixatives prepared for the alternative approach. The slides were fixed by two different fixatives, one of them (fixative-1) was based ethylalcohol, formalin, acetic acid, distilled water and the other one (fixative-2) based ethylalcohol, formalin, citric acid, distilled water included a mordant [divalent or polyvalent metals which make coordination complex with some dyes] consisted copper sulphate pentahydrate (CuSO4 .5H2 O). Slides prepared by the two different fixatives were stained by a different modification of Gomori's trichrome stain that we made. Samples fixed by Schaudinn fixative including mercury chloride were stained by Wheatley modification of Gomori's trichrome stain as a gold standard for control and comparison. We worked with 50 fecal samples which we thought included human intestinal protozoones after the wet slide examination. Comparing the methods, slides prepared with the method including citric acid gave almost similar results with the classical method excluded Entamoeba coli cystes. Slides prepared with the methode including acetic acid gave low performance compared with the classical method especially E.coli cystes and Blastocystis spp., Endolimax nana, Iodamoeba bütschlii, E.hartmanni. Both new fixatives gave superior performance at the slides included Dientamoeba fragilis and approximately shorten the procedure process ten times than the classical method. When the both alternative methods compared in each other, the slides prepared with fixative-2 exposed better performance for the protozoones Blastocystis spp., E.nana, I.bütschlii and E.hartmanni while the fixative-1 displayed minimal superiority for D.fragilis including criterias that we based. The fixative-2 and modified stain methode that we used in our study, makes available the diagnostic phase ten times faster than the classical method in human stool parasitological tests excluding the E.coli cystes at parasitology and microbiolgy laboratories. It seems to be a good option to the classical method for routine usage.