Plasma Electrolytic Modification of Zirconium and Its Alloys: Brief Review

The review focuses on the surface modification of Zr and its alloys, which is necessary to expand the applications of these kinds of materials. Data on the properties of pure zirconium and its alloys are presented. Since surface engineering and the operation of the above materials are in most cases associated with the formation of oxide coatings, information on the characteristics of ZrO2 is given. In addition, attention is paid to phasing in the zirconium-oxygen system. It is noted that the most effective method of surface engineering of Zr and its alloys is plasma electrolytic modification (PEM) technology. Specific examples and modes of modification are described, and the reached results are analyzed. The relevance, novelty and originality of the review are determined by the insufficient knowledge about a number of practical features concerning the formation of functional oxide coatings on Zr and some of its alloys by the technology of PEM. In particular, the information on the phase composition and possibilities of stabilization of the tetragonal and cubic modifications of ZrO2, the effects of the component composition of electrolyte solutions and electrolyte suspensions, and the specifics of the treatment of additive shaping and deformed materials are rather contradictory. This review aims to collect recent advances and provide insights into the trends in the modification of Zr and its alloys, promote the formulation of practical recommendations and assess the development prospects.

Electronic properties of single-crystalline Fe4O5

We synthesized single and polycrystals of iron oxide with an unconventional Fe₄O₅ stoichiometry under high-pressure high-temperature (HP-HT) conditions. The crystals of Fe₄O₅ had a CaFe₃O₅-type structure composed of linear chains of iron with octahedral and trigonal-prismatic oxygen coordinations. We investigated the electronic properties of this mixed-valence oxide using several experimental techniques, including measurements of electrical resistivity, the Hall effect, magnetoresistance, and thermoelectric power (Seebeck coefficient), X-ray absorption near edge spectroscopy (XANES), reflectance and absorption spectroscopy, and single-crystal X-ray diffraction. Under ambient conditions, the single crystals of Fe₄O₅ demonstrated a semimetal electrical conductivity with nearly equal partial contributions of electrons and holes (σ_n ≈ σ_p), in line with the nominal average oxidation state of iron as Fe^2.5+. This finding suggests that both the octahedral and trigonal-prismatic iron cations contribute to the electrical conductivity of Fe₄O₅via an Fe²⁺/Fe³⁺ polaron hopping mechanism. A moderate deterioration of crystal quality shifted the dominant electrical conductivity to n-type and considerably worsened the conductivity. Thus, alike magnetite, Fe₄O₅ with equal numbers of Fe²⁺ and Fe³⁺ ions can serve as a prospective model for other mixed-valence transition-metal oxides. In particular, it could help in the understanding of the electronic properties of other recently discovered mixed-valence iron oxides with unconventional stoichiometries, many of which are not recoverable to ambient conditions; it can also help in designing novel more complex mixed-valence iron oxides.

[Antibiotic resistance of strains of gram-positive cocci isolated from prostate secretion in men with chronic bacterial prostatitis]

OBJECTIVE

to characterize the antibiotic resistance of gram-positive cocci strains isolated from the prostate secretion in men with chronic bacterial prostatitis at the level of phenotype and genotype.

MATERIALS AND METHODS

Bacteria were isolated from the prostate secretion of men of reproductive age (20-45 years) with chronic bacterial prostatitis by conventional bacteriological method. The type of microorganisms was determined by MALDI-TOF mass spectrometry. Resistance to 16 antibiotics of 31 strains of E. faecalis and 91 cultures of coagulase-negative staphylococci (CoNS) was determined by the disk diffusion method. Antibiotic resistance genes (mecA; blaZ; aac(6)- aph (2); ant (4)-Ia; aph (3)-IIIa; gyrA, grlA) were detected using polymerase chain reaction (PCR ) using selected primers.

RESULTS

A high resistance of enterococci to antibacterial drugs was revealed: fluoroquinolones, carbapenens, cephalosporins (with the exception of cefoperazone), gentamicin and oxacillin. It has been established that CoNS are characterized by variable antibiotic resistance, while: isolates of S. epidermidis and S. haemolyticus are resistant to all studied fluoroquinolones and carbapenems; S. warneri to carbapenems and the vast majority of studied cephalosporins; S. saprophyticus - to aminoglycosides. Amoxiclav and cefoperazone are characterized by the highest activity against clinical isolates. Using PCR, the presence of genetic determinants of resistance to aminoglycosides and -lactams was established in the isolates, with a predominance of the studied genes in CoNS.

CONCLUSION

For effective antibiotic therapy in chronic bacterial prostatitis, it is necessary to conduct regional monitoring of the resistance of microorganisms to antibacterial drugs.

Giant Room-Temperature Power Factor in p-Type Thermoelectric SnSe under High Pressure

Materials that can efficiently convert heat into electricity are widely utilized in energy conversion technologies. The existing thermoelectrics demonstrate rather limited performance characteristics at room temperature, and hence, alternative materials and approaches are very much in demand. Here, it is experimentally shown that manipulating an applied stress can greatly improve a thermoelectric power factor of layered p-type SnSe single crystals up to ≈180 µW K^-2 cm^-1 at room temperature. This giant enhancement is explained by a synergetic effect of three factors, such as: band-gap narrowing, Lifshitz transition, and strong sample deformation. Under applied pressure above 1 GPa, the SnSe crystals become more ductile, which can be related to changes in the prevailing chemical bonding type inside the layers, from covalent toward metavalent. Thus, the SnSe single crystals transform into a highly unconventional crystalline state in which their layered crystal stacking is largely preserved, while the layers themselves are strongly deformed. This results in a dramatic narrowing in a band gap, from E_g = 0.83 to 0.50 eV (at ambient conditions). Thus, the work demonstrates a novel strategy of improving the performance parameters of chalcogenide thermoelectrics via tuning their chemical bonding type, stimulating a sample deformation and a band-structure reconstruction.

Synthesis of Ilmenite-type ε-Mn2O3 and Its Properties

In contrast to the corundum-type A₂X₃ structure, which has only one crystallographic site available for trivalent cations (e.g., in hematite), the closely related ABX₃ ilmenite-type structure comprises two different octahedrally coordinated positions that are usually filled with differently charged ions (e.g., in Fe²⁺Ti⁴⁺O₃ ilmenite). Here, we report a synthesis of the first binary ilmenite-type compound fabricated from a simple transition-metal oxide (Mn₂O₃) at high-pressure high-temperature (HP-HT) conditions. We experimentally established that, at normal conditions, the ilmenite-type Mn²⁺Mn⁴⁺O₃ (ε-Mn₂O₃) is an n-type semiconductor with an indirect narrow band gap of E_g = 0.55 eV. Comparative investigations of the electronic properties of ε-Mn₂O₃ and previously discovered quadruple perovskite ζ-Mn₂O₃ phase were performed using X-ray absorption near edge spectroscopy. Magnetic susceptibility measurements reveal an antiferromagnetic ordering in ε-Mn₂O₃ below 210 K. The synthesis of ε-Mn₂O₃ indicates that HP-HT conditions can induce a charge disproportionation in simple transition-metal oxides A₂O₃, and potentially various mixed-valence polymorphs of these oxides, for example, with ilmenite-type, LiNbO₃-type, perovskite-type, and other structures, could be stabilized at HP-HT conditions.

Structural Stability and Properties of Marokite-Type γ-Mn3O4

We synthesized single crystals of marokite (CaMn₂O₄)-type orthorhombic manganese (II,III) oxide, γ-Mn₃O₄, in a multianvil apparatus at pressures of 10-24 GPa. The magnetic, electronic, and optical properties of the crystals were investigated at ambient pressure. It was found that γ-Mn₃O₄ is a semiconductor with an indirect band gap E_g of 0.96 eV and two antiferromagnetic transitions (T_N) at ∼200 and ∼55 K. The phase stability of the γ-Mn₃O₄ crystals was examined in the pressure range of 0-60 GPa using single-crystal X-ray diffraction and Raman spectroscopy. A bulk modulus of γ-Mn₃O₄ was determined to be B₀ = 235.3(2) GPa with B' = 2.6(6). The γ-Mn₃O₄ phase persisted over the whole pressure range studied and did not transform or decompose upon laser heating of the sample to ∼3500 K at 60 GPa. This result seems surprising, given the high-pressure structural diversity of iron oxides with similar stoichiometries. With an increase in pressure, the degree of distortion of MnO₆ polyhedra decreased. Furthermore, there are signs indicating a limited charge transfer between the Mn³⁺ ions in the octahedra and the Mn²⁺ ions in the trigonal prisms. Our results demonstrate that the high-pressure behavior of the structural, electronic, and chemical properties of manganese oxides strongly differs from that of iron oxides with similar stoichiometries.

[Characteristics of the pathogenic potential of Escherichia coli isolated from patients with calculous pyelonephritis]

OBJECTIVE

Comparative phenotypic and genetic assessment of the pathogenic potential of E. coli strains isolated from patients with calculous pyelonephritis.

MATERIALS AND METHODS

78 strains of E. coli isolated from urine of patients with calculous pyelonephritis in the acute phase (n=58) and in the remission phase (n=20). Escherichia were investigated for the presence of virulence genes papA, pap EF, papGII; afa, bma E, iutA, fyuA, feoB, kspMTII, usp multiplex PCR using selected primers. Phenotypically determined the ability to biofilm formation, antilysozyme, antihemoglobin, anticytokine, adhesive and sIgA-protease activity E. coli.

RESULTS

The virulent potential of Escherichia coli at the pheno- and genotype levels was characterized. In strains of E. coli isolated from the urine of patients in the remission phase, the ability to form biofilms was more often and with high values of the trait; and in strains isolated in relapse - adhesive activity, the ability to inactivate pro- and anti-inflammatory cytokines, antihemoglobin activity, and genes encoding aphimbrial adhesin (afa), responsible for the synthesis of siderophore aerobactin (iutA), transporting bivalent iron (feoB).

CONCLUSION

The revealed differences in the pheno- and genotypic profiles between the cultures of Escherichia coli isolated from patients with calculous pyelonephritis in the phases of exacerbation and remission make it possible to differentiate the isolated strain and predict the course of the infectious-inflammatory process.

Controlling the thermoelectric power of silicon–germanium alloys in different crystalline phases by applying high pressure

Si–Ge crystals are promising materials for use in various stress-controlled electronic junctions for next-generation nanoelectronic devices.

Structural and Magnetic Transitions in CaCo3V4O12 Perovskite at Extreme Conditions

We investigated the structural, vibrational, magnetic, and electronic properties of the recently synthesized CaCo₃V₄O₁₂ double perovskite with the high-spin (HS) Co²⁺ ions in a square-planar oxygen coordination at extreme conditions of high pressures and low temperatures. The single-crystal X-ray diffraction and Raman spectroscopy studies up to 60 GPa showed a conservation of its cubic crystal structure but indicated a crossover near 30 GPa. Above 30 GPa, we observed both an abnormally high "compressibility" of the Co-O bonds in the square-planar oxygen coordination and a huge anisotropic displacement of HS-Co²⁺ ions in the direction perpendicular to the oxygen planes. Although this effect is reminiscent of a continuous HS → LS transformation of the Co²⁺ ions, it did not result in the anticipated shrinkage of the cell volume because of a certain "stiffing" of the bonds of the Ca and V cations. We verified that the oxidation states of all the cations did not change across this crossover, and hence, no charge-transfer effects were involved. Consequently, we proposed that CaCo₃V₄O₁₂ could undergo a phase transition at which the large HS-Co²⁺ ions were pushed out of the oxygen planes because of lattice compression. The antiferromagnetic transition in CaCo₃V₄O₁₂ at 100 K was investigated by neutron powder diffraction at ambient pressure. We established that the magnetic moments of the Co²⁺ ions were aligned along one of the cubic axes, and the magnetic structure had a 2-fold periodicity along this axis, compared to the crystallographic one.

Tuning the electronic and vibrational properties of Sn2P2Se6and Pb2P2S6crystals and their metallization under high pressure

Ferroelectric Sn₂P₂Se₆and paraelectric Pb₂P₂S₆demonstrate the remarkable responses of their electronic band structures to applied high pressures.

[Monitoring of influenza and other respiratory diseases causative agents in children, hospitalized with community-acquired pneumonia in 2012-2013 epidemic season]

AIM

Study the circulation of respiratory viruses in children with community-acquired pneumonia (CAP) during the period from October 2012 to May 2013.

MATERIALS AND METHODS

136 children with CAP aged from 3 months to 16 years with ARI symptoms at the disease debut were studied. RNA/DNA of influenza A, B, parainfluenza (PI); adeno-, rhino-, RS-viruses, corona-, metapneumo- (MPV) and bocaviruses were detected in nasopharynx smears by PCR with hybridization-fluorescent detection in real time. Antibodies against influenza viruses A/H1N1/pdm09 California/07/09, epidemic reference strains of influenza viruses A/H1N1/Brisbane/59/07, A/ H3N2/Victoria/361/201 1, B/Wisconsin/1/10, against PI viruses type 1, 2, 3 were determined in paired sera by HAI.

RESULTS

In February-March 2013 the number of children protected by antibodies against influenza decreased, and circulation of influenza viruses A/H3N2 and A/H1N1/ pdm09 was detected. Rhinoviruses and PI viruses were determined throughout the epidemic season, bocavirus and adenoviruses--during the autumn-winter period, RS-virus and MPV--during winter-spring. Coronaviruses were not detected. The peak of virus detection was established in February when the threshold of influenza and ARI morbidity was exceeded. The main pathogens of children of the first 3 years of life are rhinoviruses, RS-virus, PI viruses and bocavirus. RS-virus infection at the debut of CAP in children younger than 3 years in 55.5% of cases is associated with the development of broncho-obstructive syndrome. Bocavirus infection in 50% of cases progresses with laryngo-tracheitis and bronchiolitis.

CONCLUSION

The fraction of viruses in etiologic structure ofARI in children varies depending on immune layer, season and age of children. Etiology of viral infection at the debut of CAP could only be proven using specialized laboratory studies.

A hard oxide semiconductor with a direct and narrow bandgap and switchable p-n electrical conduction

An oxide semiconductor (perovskite-type Mn2 O3 ) is reported which has a narrow and direct bandgap of 0.45 eV and a high Vickers hardness of 15 GPa. All the known materials with similar electronic band structures (e.g., InSb, PbTe, PbSe, PbS, and InAs) play crucial roles in the semiconductor industry. The perovskite-type Mn2 O3 described is much stronger than the above semiconductors and may find useful applications in different semiconductor devices, e.g., in IR detectors.

[Rate of identification and characteristic of Streptococcus pneumoniae isolated from carriers and ill children in Khabarovsk region]

AIM

To assess the role of nasopharyngeal and clinical strains of Streptococcus pneumoniae in respiratory disease of children.

MATERIALS AND METHODS

Two hundred and fifty-eight children attending and not-attending daycare as well as 1292 children with respiratory diseases admitted to clinic of Research Institute of Maternity and Childcare during 2001-2009 were studied. Materials for study were pharyngeal swabs and sputum. Identification was performed using optochin disks (bioMerieux), latex-agglutination (Slidex meningo-kit, bioMerieux) and agglutination on the glass. Fragment of S. pneumoniae genome was determined by PCR using diagnostic kits GenePac Spn (IsoGen Ltd., Moscow).

RESULTS

Level of nasopharyngeal carriage of pneumococci is increased in children with recurrent respiratory illnesses as well as in children closed communities of children. Strains isolated from nasopharynx were typical on morphological and tinctorial characteristics and have increased level of resistance to macrolides and decreased level of resistance to penicillin compared to clinical strains of which 15-20% were optochin-resistant.

CONCLUSION

Local serological spectrum of pneumococci circulating in Khabarovsk region was determined, which includes 13 serovariants with predominance of serotypes K1, K19, K6.

[Etiology of pulmonary diseases in children in Khabarovsk Region]

Microflora of upper respiratory tract in 658 children aged 1 month - 17 years hospitalized with acute pneumonia (AP), acute bronchitis (AB), recurrent obstructive bronchitis (ROB), malformation of lungs (ML) and broncho-alveolar dysplasia (BALD) were studied. Carriage rates of Streptococcus pneumoniae (up to 95%) and Haemophilus influenzae (up to 89%) in 240 children attending daycare centers and schools were determined. Etiology of infectious process was ascertained in 40% of cases. S. pneumoniae was isolated in 45% of acute cases (AP and AB) and in 25% of chronic cases (BALD). H. influenzae was isolated in 8 - 12% of acute cases and in 32% of chronic cases. In 23 - 29% of all cases of pulmonary pathology in children persistence of Enterococcus faecium was determined. There were 13 different serotypes among isolated pneumococci. In patients with pneumonia the rate of detection of S. pneumoniae and H. influenzae DNA fragments by PCR was significantly higher compared with rate of their isolation from sputum.

[Alternative methods for prevention and treatment of dental caries using laser and magnetic laser exposure]

Alternative methods for prevention and treatment of dental caries are presented, based on the use of laser and magnetic laser exposure (patent No. 2053818, in Russia) with a new generation laser device with Optodan microprocessor monitoring (patent No. 2014107, Russia). The methods are intended for wide clinical application in children and adolescents in pedodontic departments and outpatient centers and particularly for group and individual use in dental rooms at school.

[Etiology, clinical manifestations, and epidemiology in community-acquired respiratory infection in children in the Khabarovsk region]

Clinico-epidemiological analysis and etiological verification of the outbreak of respiratory infection among school children in a rural district of the Khabarovsk territory, registered in spring 1997, were made. According to clinical signs, one-third of the patients had whooping cough, while the rest of the children exhibited the signs of respiratory infection with the symptoms of longering bronchitis. A half of the children had not been vaccinated against whooping cough, as they had been given injections of adsorbed DT vaccine with reduced antigen content. Etiologically, the diagnosis of whooping cough was confirmed in 57% of the patients with 47.4% of them having Bordetella pertussis monoinfection and 52.6% having mixed infection, mainly in combination with chlamydiosis. Whooping cough took an abnormal course under these circumstances. Treatment with erythromycin produced a good effect.

[Endobronchial use of low-frequency ultrasound and ultraviolet laser radiation in the complex treatment of patients with suppurative bronchial diseases]

The efficiency of endobronchial therapy with low-frequency ultrasound (LFUS) and ultraviolet laser radiation (UVLR) were studied in patients with pyoinflammatory diseases of the lung. A hundred and sixty two patients with chronic bronchitis (CB) and bronchoectatic disease (BD) were clinically followed up. The complex treatment of pyoinflammatory diseases of the bronchi was supplemented by endobronchial LFUS in 86 patients, by UVLR in 29. Routine bronchoscopy (without endobronchial application of LFUS and UVLR) was included into the treatment of 47 patients with CB and BD. Bronchoscopy with LFUS and UVLR was found to have a high efficiency in patients unresponsive to drug therapy. The number of bronchoscopies per treatment regimen could be reduced, the time of a remission and the interval of hospitalization were increased.

[Morphological changes in the primordia of the deciduous teeth during an exacerbated course of the antenatal period]

Histologic examination of 380 rudimentary deciduous teeth of 91 stillborn babies or corpses of newborns dead within 16 days after birth and comparison of the results with clinical data brought the authors to a conclusion that the diagnosis of enamel hypoplasia is erroneous because all dental tissues are involved during this condition. Pathohistologic changes in the enamel, dentin, and tissues adjacent to dental rudiment are described in detail, all these tissues developing under unfavorable conditions of antenatal odontogenesis.

[The deciduous teeth in children born to mothers with heart defects]

Stomatological examinations of infants aged 6 to 36 months, whose mothers suffer from heart diseases, have revealed that the number of infants with deciduous dental tissue abnormalities grows with the age of the infants, reaching the maximum in those aged 3 years: 63.88 percent. Caries and caries-complicated diseases were recorded in 3-year-old children. This permits regarding the presence of a heart disease in a mother as a risk factor in respect of developing deciduous teeth abnormalities and caries.

[Effect of local x-ray irradiation of the abdominal area on the amino acid content of the blood plasma and their urinary excretion in dogs and rats]

A study was made of the content of amino acids in blood plasma of dogs and rats and daily excretion thereof from rat body in urine after local X-irradiation of abdomen with a dose of 13.5 Gy. As the gastrointestinal syndrome developed the content and excretion of taurine increased, glucogenic amino acid content of plasma decreased, and the ratio of phenylalanine to tyrosine and branched-chain amino acids to aromatic amino acids changed. The ratio of arginine to ornithine and urea to ammonia sharply dropped in animals, which died later on, indicating that the urea-producing function of liver was impaired and hyperammonemia developed.