Thermodynamic and Structural Properties of Sodium Lithium Niobate Solid Solutions

Thermodynamics of the Na_1−xLi _x NbO₃ system is investigated by high-temperature drop-solution calorimetry in molten 3Na₂O–4MoO₃ solvent at 973 K. Standard molar enthalpies of formation are derived. The estimated heats of transition between hypothetical and stable structures, lithium niobate and perovskite for NaNbO₃ and vice versa for LiNbO₃ are −6 kJ/mol and −10 kJ/mol, respectively. X-ray diffraction studies at room temperature showed for 0 ≤ x ≤ 0.14 there are three phases based on different ordering of the perovskite type lattice: orthorhombic with a quadrupled reduced perovskite cell at 0 ≤ x ≤ 0.02, orthorhombic with a doubled reduced perovskite cell at 0.015 ≤ x ≤ 0.14, and rhombohedral at 0.08 ≤ x ≤ 0.13. There are two two-phase (morphotropic) regions with coexistence of the two orthorhombic phases at 0.015 ≤ x ≤ 0.02 and with the second orthorhombic phase coexisting with the rhombohedral phase at 0.08 ≤ x ≤ 0.13. A reproducible anomaly in specific heat at ∼600 K, not reported previously, has been observed in pure NaNbO₃. Heat-capacity measurements confirm a phase transition at 553 K for 0.07 ≤ x ≤ 0.09. With increasing lithium concentration, a gradual disappearance of high-temperature phase transitions associated with tilting of oxygen octahedra has been observed.     

Structure Formation,Electrophysical and Mechanical Properties of an Electrically Conducting Ceramic Composite Based on Silicon and Boron Carbides

How the structure of electrically conducting ceramic composites in the SiC B₄C system is formed has been studied. The mechanical and electrophysical properties have been investigated as a function of the ratio of the components and the sintering conditions.     

Some Characteristics of Free Cell Population in the Airways of Rats after Intratracheal Instillation of Copper-Containing Nano-Scale Particles

We used stable water suspensions of copper oxide particles with mean diameter 20 nm and of particles containing copper oxide and element copper with mean diameter 340 nm to assess the pulmonary phagocytosis response of rats to a single intratracheal instillation of these suspensions using optical, transmission electron, and semi-contact atomic force microscopy and biochemical indices measured in the bronchoalveolar lavage fluid. Although both nano and submicron ultrafine particles were adversely bioactive, the former were found to be more toxic for lungs as compared with the latter while evoking more pronounced defense recruitment of alveolar macrophages and especially of neutrophil leukocytes and more active phagocytosis. Based on our results and literature data, we consider both copper solubilization and direct contact with cellular organelles (mainly, mitochondria) of persistent particles internalized by phagocytes as probable mechanisms of their cytotoxicity.     

The reliability and limits of the MTT reduction assay for carbon nanotubes-cell interaction

The unique physical and chemical properties of carbon nanotubes (CNTs) suggest enormous potential for many areas of research and application. The urgent need for toxicological studies on CNTs has arisen from the steadily increasing production volume. 2-(4,5-dimethyl-2-thiazolyl)-3,5-diphenyl-2H-tetrazolium bromide (MTT) assay is among the most versatile and popular assays used for in vitro toxicology. For particulate samples like CNTs the applicability and limits of various tests including the MTT assay have to be defined. Two MTT assays were applied to study the effect of single-walled CNTs (SWCNTs) on A549 cells. Both assays revealed significant and comparable loss of cell functionality that was confirmed by DNA assay. However, using a cell-free system, we have found that polyoxyethylene sorbitan monooleate-suspended SWCNTs interfere less with MTT assay than sodium dodecyl sulfate-suspended SWCNTs. Moreover, depending on the purification procedure of SWCNTs, they were able to convert MTT into its MTT-formazan insoluble form in the absence of any living system. In summary, a careful validation of MTT assay procedures is therefore suggested in experiments where CNTs are one of the constituents, to avoid a potential bias in concluding results of cytotoxicity studies.     

Direct synthesis of carbon nanofibers on the surface of copper powder

A novel approach to synthesize carbon nanofibers (CNFs) directly on the surface of metal μm-sized particles to evenly disperse the carbon nanomaterials in a composite material was proposed. As a metal matrix, 5–10 μm copper particles were utilized. As a carbon source, C₂H₂, CH₄ and CO were examined. The best conditions were found to be in C₂H₂ (30 cm³/min) and H₂ (260 cm³/min) atmosphere at the temperature of 750 °C. The composites based on copper and CNFs prepared by vacuum hot pressing showed the increase in hardness from 35 to 60 kg/mm² almost retaining pure copper electrical properties.     

Paenibacillus polymyxa purified bacteriocin to control Campylobacter jejuni in chickens

Campylobacter spp. cause numerous foodborne diseases. Poultry is thought to be a significant source of this zoonosis. Although many interventions designed to control this agent have been researched, none have succeeded. We evaluated a bacteriocin-based treatment to reduce Campylobacter jejuni colonization in poultry. A previously described purified bacteriocin (class IIa; molecular mass, 3,864 Da), secreted by Paenibacillus polymyxa NRRL-B-30509, was microencapsulated in polyvinylpyrrolidone, and 0.25 g of the purified bacteriocin was incorporated into 1 kg of chicken feed. One-day-old chickens were orally challenged and colonized with one of four isolates of C. jejuni, then reared in isolation facilities. Birds were provided ad libitum access to standard broiler starter feed and water for 7 days until 3 days before sampling, when only the treated groups of birds were provided the bacteriocin-emended feed described. In each of the eight (four by two replicates) trials, significant reductions in colonization by C. jejuni were observed (P < or = 0.05). As an example of this highly consistent data, in the first trial, 10 untreated 10-day-old chickens were colonized at a mean log 7.2 + 0.3 CFU/g of feces, whereas none of the 10 bacteriocin-treated 10-day-old chickens were colonized with detectable numbers of C. jejuni. Bacteriocin treatment dramatically reduced both intestinal levels and frequency of chicken colonization by C. jejuni. Feeding bacteriocins before poultry slaughter appears to provide control of C. jejuni to effectively reduce human exposure. This advance is directed toward on-farm control of pathogens, as opposed to the currently used chemical disinfection of contaminated carcasses.     

Symmetric lithium-ion cell based on lithium vanadium fluorophosphate with ionic liquid electrolyte

Lithium vanadium fluorophosphate, LiVPO₄F, was utilized as both cathode and anode for fabrication of a symmetric lithium-ion LiVPO₄F//LiVPO₄F cell. The electrochemical evolution of the LiVPO₄F//LiVPO₄F cell with the commonly used organic electrolyte LiPF₆/EC-DMC has shown that this cell works as a secondary battery, but exhibits poor durability at room temperature and absolutely does not work at increased operating temperatures. To improve the performance and safety of this symmetric battery, we substituted a non-flammable ionic liquid (IL) LiBF₄/EMIBF₄ electrolyte for the organic electrolyte. The symmetric battery using the IL electrolyte was examined galvanostatically at different rates and operating temperatures within the voltage range of 0.01–2.8 V. It was demonstrated that the IL-based symmetric cell worked as a secondary battery with a Coulombic efficiency of 77% at 0.1 mA cm⁻² and 25 °C. It was also found that the use of the IL electrolyte instead of the organic one resulted in the general reduction of the first discharge capacity by about 20–25% but provided much more stable behavior and a longer cycle life. Moreover, an increase of the discharge capacity of the IL-based symmetric battery up to 120 mA h g⁻¹ was observed when the operating temperature was increased up to 80 °C at 0.1 mA cm⁻². The obtained electrochemical behavior of both symmetric batteries was confirmed by complex-impedance measurements at different temperatures and cycling states. The thermal stability of LiVPO₄F with both the IL and organic electrolytes was also examined.     

Involvement of Microglia in the Pathophysiology of Intracranial Aneurysms and Vascular Malformations—A Short Overview

Aneurysms and vascular malformations of the brain represent an important source of intracranial hemorrhage and subsequent mortality and morbidity. We are only beginning to discern the involvement of microglia, the resident immune cell of the central nervous system, in these pathologies and their outcomes. Recent evidence suggests that activated proinflammatory microglia are implicated in the expansion of brain injury following subarachnoid hemorrhage (SAH) in both the acute and chronic phases, being also a main actor in vasospasm, considerably the most severe complication of SAH. On the other hand, anti-inflammatory microglia may be involved in the resolution of cerebral injury and hemorrhage. These immune cells have also been observed in high numbers in brain arteriovenous malformations (bAVM) and cerebral cavernomas (CCM), although their roles in these lesions are currently incompletely ascertained. The following review aims to shed a light on the most significant findings related to microglia and their roles in intracranial aneurysms and vascular malformations, as well as possibly establish the course for future research.     

Synthesis and characterization of novel hydrophobically modified polybetaines as pour point depressants

A novel hydrophobic monomer was synthesized from the acetoacetic ester and dodecylamine by condensation reaction in mild conditions. The modification by the dodecyl groups monomer was involved in the Michael addition reaction with acrylic (or methacrylic) acid followed by radical polymerization. Both linear and crosslinked novel betaine‐type polyampholytes bearing hydrophobic “tail” and hydrophilic “head” were obtained. The linear polymer was characterized by viscometry, FTIR, and Raman spectroscopy. Swelling–shrinking behavior of linear and crosslinked samples was studied in water–DMF and water–DMSO mixtures. The applicability of hydrophobically modified polybetaines as pour point depressants (fluidity improvers) was also demonstrated. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1042–1048, 2004