Magnetic resonance study of the spin-reorientation transitions in the quasi-one-dimensional antiferromagnet BaCu2Si2O7

A quasi-one dimensional antiferromagnet with a strong reduction of the ordered spin component, BaCu2Si2O7, is studied by the magnetic resonance technique in a wide field and frequency range. Besides of conventional spin-flop transition at the magnetic field parallel to the easy axis of spin ordering, magnetic resonance spectra indicate additional spin-reorientation transitions in all three principal orientations of magnetic field. At these additional transitions the spins rotate in the plane perpendicular to the magnetic field keeping the mutual arrangement of ordered spin components. The observed magnetic resonance spectra and spin-reorientation phase transitions are quantitatively described by a model including the anisotropy of transverse susceptibility with respect to the order parameter orientation. The anisotropy of the transverse susceptibility and the strong reduction of the anisotropy energy due to the quantum spin fluctuations are proposed to be the reason of the spin reorientations which are observed.Comment: RevTeX, 9 pages, 7 figure

Constitutive and numerical modeling of chemical and mechanical phenomena in thermal barrier coatings for gas turbine blades of aircraft engines

Виконано моделювання хімічних і механічних явищ, та розроблені узагальнені визначальні співвідношення, які можуть бути використано для розрахунків залежних від часу розподілень напружень та пошкоджуваності термоізоляції лопаток газових турбін авіаційних двигунів. Розроблені визначальні співвідношення впроваджено в формі структурних моделей для аналізу пошкоджуваності в часі термоізоляції лопаток газових турбін авіаційних двигунів, для аналізу міцності та тривалої міцності, для забезпечення безпечної роботи лопаток газових турбін авіаційних двигунів

Sol-gel Synthesis, Photo- and Electrocatalytic Properties of Mesoporous TiO2 Modified with Transition Metal Ions

Abstract Mesoporous nanosized titania films modified with Co2+, Ni2+, Mn3+, and Cu2+ ions have been produced by templated sol-gel method and characterized by optical spectroscopy, X-ray diffraction (XRD), and Brunauer, Emmett, and Teller (BET) surface area measurement. Band gap energy and the position of flat band potentials were estimated by photoelectrochemical measurements. The films doped with transition metals possessed higher photocurrent quantum yield, as well as photo- and electrochemical activity compared to undoped samples. Mn+/TiO2 (M–Co, Ni, Mn, Cu) electrodes with low dopant content demonstrate high efficiency in electrocatalytic reduction of dissolved oxygen. Polarization curves of TiO2, TiO2/Ni2+, TiO2/Co2+/3+, and TiO2/Mn3+ electrodes contain only one current wave (oxygen reduction current). It means that reaction proceeds without the formation of an intermediate product H2O2

Application of a phase-measuring method in the inclinometric systems of geotechnical monitoring

The article considers the issue of the possibility of applying the phase-measuring method in inclinometric systems of geotechnical monitoring. The main problems with use of the inclinometric systems of geotechnical monitoring. The causes, causing the occurrence of angular measurement error

Laparoscopic retropubic extraurethral adenomectomy

Introduction. Existing methods of surgical treatment of benign prostatic hyperplasia are accompanied by the frequent development of postoperative complications, such as urinary incontinence, retrograde ejaculation, and urethral strictures. The method of preserving the prostatic urethra has been developed for a long time. At present, it is possible to use the operation technique and perform laparoscopic urethral-sparing adenomectomy.Objective. To assess the possibility of performing extraurethral adenomectomy with prostatic urethral preservation using the laparoscopic approach, its advantages and disadvantages.Materials and methods. Based on St. Luke’s Simferopol сlinical Multidisciplinary Medical Center, 35 successful laparoscopic operations were performed to remove benign prostate hyperplasia with the prostatic urethra preservation. The features of the operation are laparoscopic access, a transverse section of the capsule, alternate isolation of adenomatous nodes while preserving the prostatic urethra on the catheter without replacing it during the operation, suturing the capsule with a decrease in space from the removed adenomatous nodes. Urethral preservation provided accelerated epithelialization of the defect, in the absence of the formation of a “prevesical” space.Results. After the operation, it is possible to turn off the urinary bladder irrigation system earlier (up to 4 – 6 hours after the operation) and early removal of the catheter after surgery (2 – 3 days). The hospital stay averaged 5.7 days. Urination was restored immediately after catheter removal in 92% of the patients. There were no elements of dysuria, particularly urinary incontinence. Prostate volume measured throughout transrectal ultrasound after operation was 20 – 24 cm³.Conclusion. The technique of retropubic extraurethral adenomectomy with prostatic urethral preservation can be performed in laparoscopic technique. The advantages are early activation of the patient and discharge from the hospital, early removal of the catheter with restoration of independent urination, absence of dysuria, urinary incontinence, and postoperative complications. The results of our study demonstrate the effectiveness of the laparoscopic extraurethral adenomectomy technique, the further development of this technique, and the possibility of its application in practice

The Effect of Random Surface Inhomogeneities on Microresonator Spectral Properties: Theory and Modeling at Millimeter Wave Range

The influence of random surface inhomogeneities on spectral properties of open microresonators is studied both theoretically and experimentally. To solve the equations governing the dynamics of electromagnetic fields the method of eigen-mode separation is applied previously developed with reference to inhomogeneous systems subject to arbitrary external static potential. We prove theoretically that it is the gradient mechanism of wave-surface scattering which is the highly responsible for non-dissipative loss in the resonator. The influence of side-boundary inhomogeneities on the resonator spectrum is shown to be described in terms of effective renormalization of mode wave numbers jointly with azimuth indices in the characteristic equation. To study experimentally the effect of inhomogeneities on the resonator spectrum, the method of modeling in the millimeter wave range is applied. As a model object we use dielectric disc resonator (DDR) fitted with external inhomogeneities randomly arranged at its side boundary. Experimental results show good agreement with theoretical predictions as regards the predominance of the gradient scattering mechanism. It is shown theoretically and confirmed in the experiment that TM oscillations in the DDR are less affected by surface inhomogeneities than TE oscillations with the same azimuth indices. The DDR model chosen for our study as well as characteristic equations obtained thereupon enable one to calculate both the eigen-frequencies and the Q-factors of resonance spectral lines to fairly good accuracy. The results of calculations agree well with obtained experimental data.Comment: 17+ pages, 5 figure

Laparoscopic radical prostatectomy with sparing of the proximal prostatic urethra

Introduction. The most common treatment option for prostate cancer is radical prostatectomy, which involves the removal of the prostate itself and the prostatic urethra in a single block, followed by the formation of a vesicourethral anastomosis. This approach is fraught with postoperative complications, such as urinary incontinence and strictures of anastomosis. In this sense, the clinic's staff faced the question of the possibility of a urethral-sparing variant of operative benefit for a certain category of patients.Objective. To assess the possibility of performing radical prostatectomy with sparing of the proximal prostatic urethra in the laparoscopic version, its advantages, and disadvantages.Materials & methods. From 2021 to 2022, 18 successful laparoscopic operations were performed using this technique at the St. Luke Clinical Multidisciplinary Medical Centre. Patients were selected according to the above criteria. In the preoperative period, patients underwent a standard examination in accordance with guidelines, including a blood test for prostate-specific antigen (PSA), ultrasound, magnetic resonance imaging (MRI) with 3D-modelling, data from a multifocal prostate biopsy, the International Prostate Symptom Score (IPSS), the International Index of Erectile Function (IIEF), the Quality of Life (QoL) index due to urinary disorders, assessment by the Partin’s nomogram. Intraoperative ratios, early and late postoperative complications, length of hospital stay, day of catheter removal, and time to complete urethral recovery were evaluated to study the effectiveness of this surgery type. PSA testing, uroflowmetry with post-void residual urine measurement and IPSS questionnaire were carried out one month after surgery.Results. There was an improvement in all measurements one month after surgery: median values of the mean urine flow rate increased by 1.7 ml/s, median values of the max urine flow rate increased by 3.7 ml/s, the IPSS decreased by 12 points.Conclusion. Based on the results of the study, clinical observations, and statistical analysis of the data obtained, it can be concluded that laparoscopic radical prostatectomy with sparing of the proximal prostatic urethra is the preferred surgical option for this pathology, due to its organ-preserving nature

Bimetallic gold/silver alloy nanoparticles prepared in the presence of tryptophan

The stable colloidal solutions of monometallic and bimetallic gold and silver nanoparticles (NPs) have been obtained in the presence of amino acid tryptophan. For the synthesis of bimetallic composition the metals were used in a molar ratio of Ag:Au = 3:1, 1:1 and 1:3. The only one plasmon resonance band in absorption spectra was located between the bands inherent to the individual metals and it was characteristic for “alloy” type bimetallic AgAu NPs. The position of its maximum strongly depends on the Ag:Au molar ratio. The surface of all synthesized nanoparticles carries a negative charge due to the stabilizing shell consisted of amino acid. In the paper we usedUV/visible spectroscopy and dynamic light scattering method to analyze the effect of experimental procedure on the properties of obtained NPs.Стабільні колоїдні розчини наночастинок (НЧ) срібла та золота та їх біметалічні композити зі співвідношенням металів Ag:Au = 3:1, 1:1, 1:3 синтезовані у присутності амінокислоти триптофану. В спектрах поглинання присутня лише одна смуга поглинання плазмонного резонансу НЧ, характерна для біметальних наночастинок сплаву AgAu, розташована між смугами індивідуальних металів. Положення максимуму поглинання дуже залежить від мольного співвідношення Ag:Au. Поверхня всіх синтезованих наночастинок має негативний заряд за рахунок стабілізуючою оболонки амінокислоти. Проаналізовано вплив експериментальних методик на властивості одержаних НЧ за допомогою УФ / видимої спектроскопії і методу динамічного світлорозсіювання.Стабильные коллоидные растворы наночастиц (НЧ) серебра и золота, а так же их биметаллические композиты с соотношением металлов Ag:Au = 3:1, 1:1, 1:3 синтезированы в присутствии аминокислоты триптофана. В спектрах поглощения присутствует только одна полоса плазмонного резонанса НЧ, характерная для биметаллических наночастиц сплава AgAu, находящаяся между полосами НЧ отдельных металлов. Положение ее максимума сильно зависит от мольного соотношения Ag:Au. Поверхность всех синтезированных наночастиц имеет отрицательный заряд за счёт стабилизирующей оболочки аминокислоты. Проанализировано влияние экспериментальных методик на свойства полученных НЧ с помощью УФ/видимой спестроскопии и метода динамического светорассеивания

Highly Dispersed Palladium on Carbon Nanofibers for Hydrogenation of Nitrocompounds to Amines

The effect of palladium dispersion and nature of the support on catalytic performance in hydrogenation of nitrobenzene to aniline was studied. It was shown that the type of the support and modification of palladium with phosphorus make it possible to stabilize highly dispersed (1.5-2 nm) palladium particles in the metallic state, thus increasing the efficiency of new catalysts