First-principles investigation of the electronics, optical, mechanical, thermodynamics and thermoelectric properties of Na based Quaternary Heusler alloys (QHAs) NaHfXGe (X = Co, Rh, Ir).

In this study, we explored the electronic and thermoelectric (TE) properties of the Na-based Quaternary Heusler Alloys (QHAs) NaHfXGe (X = Co, Rh, Ir) using density functional theory (DFT). We performed the spin-polarized DFT calculations at the general gradient approximation (GGA) level and confirmed the ground state non-magnetic configuration of NaHfXGe. The mechanical and thermodynamical stabilities are analyzed and discussed to validate the stability by calculating the elastic constant and phonon dispersion curve. A thorough investigation on the electronic properties are carried out by performing the GGA, GGA+U, and GGA+SOC formalism where we report the semi-conducting characteristic of NaHfCoGe and NaHfRhGe QHAs. However, NaHfIrGe is predicted to be a non-magnetic metal. From the calculated optical properties we found that the most active optical absorption occurs within the vis-UV region withα>105 cm-1, therefore the studied QHAs are proposed to be a promising optoelectronic materials. The results of the thermodynamic properties have shown that NaHfXGe follows Debye's low-temperature specific heat law and the classical thermodynamics of the Dulong-Petit law at high temperatures. The calculated TE efficiency using GGA+SOC formalism atT= 1200 K are ZT∼1.22 and 0.57 for NaHfCoGe and NaHfRhGe, suggesting that these materials are potential TE materials to operate at high temperature.

Electronic, mechanical and piezoelectric properties of glass-like complex Na2Si1-x Ge x O3 (x = 0.0, 0.25, 0.50, 0.75, 1.0).

Motivated by our previous work on pristine Na2SiO3, we proceeded with calculations on the structural, electronic, mechanical and piezoelectric properties of complex glass-like Na2Si1-x Ge x O3 (x = 0.0, 0.25, 0.50, 0.75, 1.0) by using density functional theory (DFT). Interestingly, the optimized bond lengths and bond angles of Na2SiO3 and Na2GeO3 resemble each other with high similarity. On doping we report the negative formation energy and feasibility of transition of Na2SiO3 → Na2GeO3 while the structural symmetry is preserved. Analyzing the electronic profile, we have observed a reduced band gap on increasing x = Ge concentration at Si-sites. All the systems are indirect band gap (Z-Γ) semiconductors. The studied systems have shown mechanical stabilities by satisfying the Born criteria for mechanical stability. The calculated results have shown highly anisotropic behaviour and high melting temperature, which are a signature of glass materials. The piezoelectric tensor (both direct and converse) is computed. The results thus obtained predict that the systems under investigation are potential piezoelectric materials for energy harvesting.

Electronic, mechanical, optical and piezoelectric properties of glass-like sodium silicate (Na2SiO3) under compressive pressure.

The structural, mechanical, electronic, optical and piezoelectric properties of Na2SiO3 are studied under varying compressive unidirectional pressure (0-50 GPa with a difference of 10 GPa) using density functional theory (DFT). The calculated structural properties agree well with previously reported results. At 12 GPa, our calculation shows a structural phase transition from orthorhombic Cmc21 to triclinic P1. The mechanical profile of Na2SiO3 structures under different compressive unidirectional pressures are analysed by calculating the elastic moduli, Poisson's ratio and eigenvalues of stiffness matrix. Our study shows the mechanical stability of the system up to a pressure of 40 GPa. Herein, we have obtained an indirect band gap of 2.97 eV at 0 GPa. Between 0-50 GPa, the band gaps are within the range 2.62 to 3.46 eV. The system in our study possesses a wide band gap and high optical absorption in the UV-Vis range of electromagnetic radiation. The calculated static refractive indices η x,y,z (0) are close to unity suggesting its transparency. For piezoelectric properties, we have reported the total Cartesian polarization. Our calculations have revealed that Na2SiO3 is a promising candidate for optoelectronic devices while its application in ferroelectric and piezoelectric devices could be improved with further research.

[Prevention of ostial obstruction after microendoscopic endonasal dacryocystorhinostomy].

Ostial dilatator was created to prevent recurrence and improve efficacy of microendoscopic endonasal dacryocystorhinostomy. Proposed technique was for the first time used in 52 patients. Postoperative results were analyzed: recovery was achieved in 78% of cases, improvement - in 22%. In a control group (51 patients) we used conventional technique, recovery was achieved in 67% of patients and improvement in 28%, in 5% recurrence occurred. The use of ostial dilatator resulted in microendoscopic endonasal dacryocystorhinostomy efficacy improvement.

[Digital X-ray examination in diagnosis of lacrimal pathways disorders].

Digital radiological images of normal and patients with lacrimal pathways disorders were analyzed. Potentials of digital X-ray in diagnosis of lacrimal pathways disorders are demonstrated.

[Current potentials of endoscopic rhinosinusosurgery].

Information on current potentials of endoscopic rhinosinusosurgery are presented in this review. Potentials of miniinvasive endoscopic procedures as an alternative or adjuvant treatment option in surgery of ophthalmologic patients are discussed.

[Hydrodynamic method for diagnosing impaired patency of the lacrimal tract].

A hydrodynamic method has been developed, which is based on measurement of the pressure of a certain amount of the fluid passing through the patient's lacrimal tract for a given period. Pressures were determined in 194 healthy volunteers (338 eyes). Three hundred and seventy-six patients (752 eyes) with impaired lacrimation were examined. The examinations have shown that the method provides a way of objectively defining the degree of dacryostenosis, which makes it possible to further use adequate therapy and to monitor its efficiency.

[The value of cytologic investigation for postoperative assessment in patients with nasolacrimal obstruction].

Cytologic investigation was performed in patients with dacryocystitis after microscopic endonasal dacryocystorhinostomy and in patients with lacrimal canaliculi orifice obstruction after microscopic endonasal canaliculocystorhinostomy. It allowed to monitor healing process, extubation time and to develop measures for prevention of dacryostoma cicatrisation.

[Morphological characteristics of actinomycotic dacryocanaliculitis].

The paper presents the results of pathohistological studies of the contents of the lacrimal canaliculi and the fragments of their walls, obtained at canaliculotomy in 25 patients. This permitted 14 cases of actinomycotic dacryocanaliculitis to be identified as drusens of the ray fungus Actinomyces israelii had been found. The reactive structural changes found in the wall of the lacrimal canaliculi due to the presence of fungal infection and foreign bodies in their lumen are described. A morphological study is shown to be effective in revealing the actinomycotic etiology of dacryocanaliculitis.

[Involvement of lacrimal organs in Wegener's granulomatosis].

Wegener's granulomatosis (WG) is a primary systemic vasculitis characterized by the development of granulomatous inflammation and necrotizing vasculitis of small- and middle-sized vessels. The clinical symptoms of the involvement of lacrimal organs in WG are of no specificity. Lacrimal tract lesion is encountered in prolonged Wegener's granulomatosis. Whether surgical intervention can and should be made in these patients remains to be debated. Successful surgical treatment for chronic dacryocystitis with recurrent lacrimal sac phlegmon in a female patient with WG has been used as an example to show that endoscopic endonasal dacryocystorhinostomy is the most sparing surgical treatment of dacryocystitis and therefore it is preferable in WG patients and effective at remission during systemic therapy with additional doses of corticosteroids in the pre- and postoperative periods. Lacrimal gland involvement (more commonly diffuse infiltration) is observed at the early stages of the disease and may be the first manifestation of WG so the latter should be excluded when long-term therapy for chronic dacryoadenitis fails.

[Inclusion of geothermal water in composition of nutrient medium for mycobacteria cultivation].

New effective nutrient medium for isolation and cultivation of mycobacteria was developed. Time of their growth on the developed medium decreased by 3 to 11 days compared with control media (Finn II, Levenstein-Jensen). Rate of mycobacteria isolation increased by 20 to 40% compared with control media.

[Modified nutrient medium for microbacterial isolation].

A new modified nutrient medium was obtained for mycobacterial isolation and cultivation. The medium proved to be more effective than the media traditionally used in phthisiobacteriology--Finn II medium and Löwenstein-Jensen medium.

[Magnetic resonance imaging in the diagnosis of lacrimal tract pathology].

Magnetic resonance imaging (MRI) was used to examine 45 patients (23 females and 22 males) aged 16-67 years with lacrimal tract pathology on a Sigma Gorizont magnetic resonance (MR) tomograph ("General Electric"). This yielded head MR scans in the frontal, axial, and sagittal projections. The thickness of MR sections was 2-3 mm. MRI provides direct images in 3 projections, permitting a full estimation of the lacrimal tract and its adjacent soft tissues. MRI is recommended for use in the examination of patients with complicates pathological processes after ineffective operations on the lacrimal tract, congenital lacrimatory disturbances, posttraumatic lesions, suspected tumors of the lacrimal duct and its adjacent soft tissues and paranasal sinuses.

[Morphological features of the mucosa of the nasal cavity and lacrimal sac in lacrimal passage obstruction].

A comprehensive morphological study of the mucosa of the nasal cavity and lacrimal sac was conducted, by using 160 biopsy specimens taken from 44 patients at endoscopic endonasal dacryocystorhinostomy. In all cases, different areas of the nasal cavity exhibited abnormal changes that were generalized and appeared as inflammatory, dystrophic, and sclerotic processes.

[A method for pre-seeding treatment of biomaterial for mycobacterial isolation].

Ethonium solutions were used as a detergent for the pretreatment of a biomaterial homogenate to isolate mycobacteria. The best results were obtained when 1% ethonium solution was used for these purposes for 30 minutes. The pretreatment of a biomaterial homogenate in this mode increases the rate of mycobacterial isolation and reduces the time of tests. The method may be also effective for the pretreatment of human sputum when it is bacteriologically tested for mycobacterial isolation.

[Endonasal micro-dacryocystorhinostomy in nasolacrimal obstruction]. / Endonazal'naia mikrodakriotsistostomiia pri neprokhodimosti slezno-nosovykh putei.

Disorders in lacrimal passage are often caused by anatomotopographic peculiarities of the nasolacrimal tract. Surgical treatments of such patients are reviewed. The authors made endoscopic endonasal dacryocystorhinostomy in 34 patients with good results. How to achieve good functional outcomes is described.