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

Pharmacokinetic (Bioavailability) Studies of Magnesium Preparations

In order to obtain valid results when studying the bioavailability of medicinal products containing magnesium salts, it is necessary to take into account endogenous levels of the macroelement in the body. The aim of the study was to conduct a systematic review of the results of clinical studies on the bioavailability of medicinal products containing magnesium, to evaluate the methods used for determining the endogenous level of magnesium, and to establish the necessity for adjusting pharmacokinetic parameters according to the identified endogenous magnesium levels. The review includes data from clinical studies of magnesium bioavailability performed with healthy volunteers and published over the past 5 years. According to the literature review results, the most commonly chosen primary endpoint is urinary magnesium excretion analysis, and the most secondary endpoint is plasma or serum magnesium determination. Data sources for the review included Google’s search engine; PubMed, UpTodate®, ClinicalTrials.gov databases; and official websites of regulatory authorities (EFSA, EMA, and FDA). In most studies, endogenous magnesium levels were taken into account at all blood sampling points, and this provided an opportunity to avoid errors and misinterpretations of the results. Adjustments of pharmacokinetic parameters with regard to endogenous magnesium values were performed differently. Some studies treated endogenous magnesium values as independent variables and compared the values obtained after drug administration with them; other studies treated endogenous magnesium values as a covariate influencing the values obtained and requiring mandatory consideration; two studies involved a classical adjustment of pharmacokinetic parameters, the subtraction of endogenous values from the values obtained after drug administration. The evaluation of endogenous magnesium levels as part of bioavailability studies is necessary to adjust pharmacokinetic parameters and to obtain valid study results. It should be planned beforehand at the time of preparation of the study protocol

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

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