Petr Melnikov

Bio: Petr Melnikov is an academic researcher from Federal University of Mato Grosso do Sul. The author has contributed to research in topics: Thermal decomposition & Nitric acid. The author has an hindex of 17, co-authored 83 publications receiving 882 citations. Previous affiliations of Petr Melnikov include Sao Paulo State University & Moscow State University.

Clinical effects of cesium intake.

Abstract: The knowledge about cesium metabolism and toxicity is sparse. Oral intake of cesium chloride has been widely promoted on the basis of the hypothesis referred to as "high pH cancer therapy", a complimentary alternative medicine method for cancer treatment. However, no properly confirmed tumor regression was reported so far in all probability because of neither theoretical nor experimental grounds for this proposal. The aim of the present review was to resume and discuss the material currently available on cesium salts and their applications in medicine. The presence of cesium in the cell does not guarantee high pH of its content, and there is no clinical evidence to support the claims that cancer cells are vulnerable to cesium. Cesium is relatively safe; signs of its mild toxicity are gastrointestinal distress, hypotension, syncope, numbness, or tingling of the lips. Nevertheless, total cesium intakes of 6 g/day have been found to produce severe hypokalemia, hypomagnesemia, prolonged QTc interval, episodes of polymorphic ventricular tachycardia, with or without torsade de pointes, and even acute heart arrest. However, full information on its acute and chronic toxicity is not sufficiently known. Health care providers should be aware of the cardiac complications, as a result of careless cesium usage as alternative medicine.

Neodymium biosorption from acidic solutions in batch system

Abstract: Biosorption of neodymium in batch experiments took ∼2 h to achieve the equilibrium biosorbent-metal for all microorganisms tested. The best biosorption coefficient at a constant pH value of 1.5 was obtained using the microalgae Monoraphidium sp. (1511 mg g −1 cell), followed by Bakers’ yeast (313 mg g −1 cell), Penicillium sp. (178 mg g −1 cell), and activated carbon (61 mg g −1 cell). When compared to the biosorption of other metals, these results pointed out to the application of biosorption in neodymium recovery from acidic solutions.

Thermal decomposition mechanism of iron(III) nitrate and characterization of intermediate products by the technique of computerized modeling

Abstract: The nonahydrate of iron(III) nitrate shows no phase transitions in the range of −40 to 0 °C. Both hexahydrate Fe(NO3)3·6H2O and nonahydrate Fe(NO3)3·9H2O have practically the same thermal behavior. Thermal decomposition of iron nitrate is a complex process which has a different mechanism than those described for other trivalent elements. Thermolysis begins with the successive condensation of 4 mol of the initial monomer accompanied by the loss of 4 mol of nitric acid. At higher temperature, hydrolytic processes continue with the gradual elimination of nitric acid from resulting tetramer and dimeric iron oxyhydroxide Fe4O4(OH)4 is formed. After complete dehydration, oxyhydroxide is destroyed leaving behind 2 mol of Fe2O3. The molecular mechanics method provides a helpful insight into the structural arrangement of intermediate compounds.

Mechanism of thermal decomposition of yttrium nitrate hexahydrate, Y(NO3)3·6H2O and modeling of intermediate oxynitrates

Abstract: The thermal decomposition of yttrium nitrate hexahydrate Y(NO3)3·6H2O is a complex condensation process generating a tetramer arrangement Y4O4(NO3)4 formed by alternating yttrium and oxygen atoms. The anions NO3 − attach themselves to the yttrium atoms. The tetramer gradually loses N2O5 and, through the formation of Y4O5(NO3)2, is transformed into yttrium oxide. The bond lengths and bond angles of intermediate oxynitrates calculated using the molecular mechanics method rendered data compatible with the results of X-ray diffraction for related compounds.

Gallium-containing hydroxyapatite for potential use in orthopedics

Abstract: A novel material that may be recommended for grafts and implants stimulating bone growth has been obtained by introducing gallium ions (up to 11.0 mass%) into crystalline lattice of hydroxyapatite. The doping was carried out using gallium nitrate and sodium gallate solutions. In both cases, lattice parameters of gallium-doped hydroxyapatite are identical to those of pure synthetic hydroxyapatite. Gallium does not replace calcium as a result of heterovalent substitution and consequently produces no distortions in the framework of hydroxyapatite matrix. It remains strongly fixed in the form of solid solution of intercalation. According to scanning electron microscopy images gallium insertion does not cause any morphological alterations in hydroxyapatite structure and the product developed meets physico-chemical criteria for biomaterial to be employed in orthopedic practice and local handling of traumatic injuries. Its future usage opens the opportunity to enhance osteosynthesis and calcium retention in loco.

The Pharmacological Basis of Therapeutics

Abstract: The Pharmacological Basis of Therapeutics A Textbook of Pharmacology, Toxicology and Therapeutics for Physicians and Medical Students. By Prof. Louis Goodman and Prof. Alfred Gilman. Pp. xiii + 1383. (New York: The Macmillan Company, 1941.) 50s. net.

Biosorbents for heavy metals removal and their future

Abstract: A vast array of biological materials, especially bacteria, algae, yeasts and fungi have received increasing attention for heavy metal removal and recovery due to their good performance, low cost and large available quantities. The biosorbent, unlike mono functional ion exchange resins, contains variety of functional sites including carboxyl, imidazole, sulphydryl, amino, phosphate, sulfate, thioether, phenol, carbonyl, amide and hydroxyl moieties. Biosorbents are cheaper, more effective alternatives for the removal of metallic elements, especially heavy metals from aqueous solution. In this paper, based on the literatures and our research results, the biosorbents widely used for heavy metal removal were reviewed, mainly focusing on their cellular structure, biosorption performance, their pretreatment, modification, regeneration/reuse, modeling of biosorption (isotherm and kinetic models), the development of novel biosorbents, their evaluation, potential application and future. The pretreatment and modification of biosorbents aiming to improve their sorption capacity was introduced and evaluated. Molecular biotechnology is a potent tool to elucidate the mechanisms at molecular level, and to construct engineered organisms with higher biosorption capacity and selectivity for the objective metal ions. The potential application of biosorption and biosorbents was discussed. Although the biosorption application is facing the great challenge, there are two trends for the development of the biosorption process for metal removal. One trend is to use hybrid technology for pollutants removal, especially using living cells. Another trend is to develop the commercial biosorbents using immobilization technology, and to improve the biosorption process including regeneration/reuse, making the biosorbents just like a kind of ion exchange resin, as well as to exploit the market with great endeavor.

Substituted hydroxyapatites for biomedical applications: A review

Abstract: This review summarizes recent and very recent work on preparing substituted hydroxyapatites. Ease of atomic doping or substitution in apatite opens this mineral up for a wide range of biomedical applications. It can be used for repairing and replacing diseased and damaged parts of musculoskeletal systems, and also as a drug or gene delivery agent, as a bioactive coating on metallic osseous implants, biomagnetic particles and fluorescent markers. First, the physicochemical properties of bioapatites are described and discussed. Then a general summary on substitution reaction for hydroxyapatite is made. Special attention is paid to describing anionic, cationic and multisubstituted hydroxyapatites used for various biomedical applications. Finally, conclusions are drawn and future perspectives are discussed.

Supramolecular Luminescent Sensors

Abstract: There is great need for stand-alone luminescence-based chemosensors that exemplify selectivity, sensitivity, and applicability and that overcome the challenges that arise from complex, real-world media. Discussed herein are recent developments toward these goals in the field of supramolecular luminescent chemosensors, including macrocycles, polymers, and nanomaterials. Specific focus is placed on the development of new macrocycle hosts since 2010, coupled with considerations of the underlying principles of supramolecular chemistry as well as analytes of interest and common luminophores. State-of-the-art developments in the fields of polymer and nanomaterial sensors are also examined, and some remaining unsolved challenges in the area of chemosensors are discussed.