21 research outputs found
Correlation between magnetic and crystal structural sublattices in palladium-doped FeRh alloys: Analysis of the metamagnetic phase transition driving forces
FeRh alloys doped with the third element exhibit a change in the lattice and magnetic subsystems, which are manifested in antiferromagnetic- ferromagnetic (AFM-FM) first-order phase transition temperature, the shrinkage of the temperate hysteresis under transition, and the reduction of the saturation magnetization. All aforementioned parameters are crucial for practical applications. To control them it is quite important to determine the driving forces of the metamagnetic transition and its origins. In this manuscript ab initio calculations and experimental studies results are presented, which demonstrate the correlation between the structural and magnetic properties of the Fe50Rh50−xPdx alloys. The qualitative analysis of the metamagnetic phase transition driving forces in palladium-doped FeRh alloys was performed to determine their contribution to the evolution of magnetic and lattice subsystems. In addition, the impact of the impurities phases together with its magnetic behavior on the AFM-FM phase transition was considered.Fil: Komlev, Aleksei S.. Lomonosov Moscow State University; RusiaFil: Karpenkov, Dmitriy Y.. National University of Science and Technology; Rusia. Lomonosov Moscow State University; RusiaFil: Gimaev, Radel R.. Lomonosov Moscow State University; RusiaFil: Chirkova, Alisa. Institute for Materials Science; AlemaniaFil: Akiyama, Ayaka. Hirosaki University; JapónFil: Miyanaga, Takafumi. Hirosaki University; JapónFil: Hupalo, Marcio Ferreira. Universidade Estadual do Ponta Grossa; BrasilFil: Aguiar, D.J.M.. Universidade Federal do Paraná; BrasilFil: Carvalho, Alexandre Magnus G.. Universidade Estadual de Maringá; Brasil. Universidade Federal de Sao Paulo; BrasilFil: Jiménez, María Julia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; ArgentinaFil: Cabeza, Gabriela Fernanda. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; ArgentinaFil: Zverev, Vladimir I.. Lomonosov Moscow State University; RusiaFil: Perov, Nikolai S.. Lomonosov Moscow State University; Rusi
Peculiarities of the Phase Transformation Dynamics in Bulk FeRh Based Alloys from Magnetic and Structural Measurements
We analyze coexistence of antiferromagnetic and ferromagnetic phases in bulk iron-rhodium and its alloys with palladium, Fe50,4Rh49,6, Fe49,7Rh47,4Pd2,9 and Fe48,3Rh46,8Pd4,9, using neutron diffraction, magnetization and scanning Hall probe imaging. Temperature dependencies of the lattice parameters, AFM and FM phase weight fractions, and Fe magnetic moment values were obtained on cooling and heating across the AFM-FM transition. Substantial thermomagnetic hysteresis for the phases’ weight fractions and a relatively narrow one for the unit cell volume has been observed on cooling-heating. A clear dependence of hysteretic behavior on Pd concentration has been traced. Additional direct magnetic measurements of the spatial distribution of the phase transition are acquired using scanning Hall probe microscopy, which reveals the length scale of the phase coexistence and the spatial progression of the transition in the presence of external magnetic field. Also, the magnetic phase diagram has been constructed for a series of Pd-doped FeRh alloys. © 2020 Elsevier B.V.EL acknowledges funding from the UK EPSRC. LFC acknowledges funding from the EPSRC and InnovateUK: Project number: 105541. A portion of this research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. This work was partly supported by the state assignment of the Ministry of Science and Higher Education (themes “Flux” No. AAAA-A18-118020190112-8 and “Alloys” № AAAA-A19-119070890020-3)
The effect of cooling rate on magnetothermal properties of Fe49Rh51
We have investigated the effects of quenching rate on the thermal dependence of the magnetic entropy change ΔSM(T) and the magnetic field induced hysteresis loss through the antiferromagnetic (AFM) ↔ ferromagnetic (FM) transformation in bulk Fe49Rh51. Two nearly identical square-prism-shaped samples were subjected to two different temperature cooling regimes; one was rapidly quenched (FQ) in iced-water and another slow cooled (SC) to room temperature at a cooling rate of 2 K/min. The temperature of the AFM ↔ FM transition is similar for both samples, but the FQ sample shows much sharper temperature- and magnetic field-induced magnetization change; in addition, the total magnetization change is 14% larger. In FQ material, the magnetocaloric effect, i.e., ΔSM(T) quickly approaches saturation above 1 T and shows a large peak value at 2 T (13.9 versus 8.9 Jkg−1 K−1 in SC material), but a larger average hysteresis loss \u3cHL\u3eFWHM in the temperature range coinciding with of the full-width at half-maximum of the ΔSM(T) curve
A new class of glycomimetic drugs to prevent free fatty acid-induced endothelial dysfunction
Background: Carbohydrates play a major role in cell signaling in many biological processes. We have developed a set of glycomimetic drugs that mimic the structure of carbohydrates and represent a novel source of therapeutics for endothelial dysfunction, a key initiating factor in cardiovascular complications. Purpose: Our objective was to determine the protective effects of small molecule glycomimetics against free fatty acidinduced endothelial dysfunction, focusing on nitric oxide (NO) and oxidative stress pathways. Methods: Four glycomimetics were synthesized by the stepwise transformation of 2,5dihydroxybenzoic acid to a range of 2,5substituted benzoic acid derivatives, incorporating the key sulfate groups to mimic the interactions of heparan sulfate. Endothelial function was assessed using acetylcholineinduced, endotheliumdependent relaxation in mouse thoracic aortic rings using wire myography. Human umbilical vein endothelial cell (HUVEC) behavior was evaluated in the presence or absence of the free fatty acid, palmitate, with or without glycomimetics (1µM). DAF2 and H2DCFDA assays were used to determine nitric oxide (NO) and reactive oxygen species (ROS) production, respectively. Lipid peroxidation colorimetric and antioxidant enzyme activity assays were also carried out. RTPCR and western blotting were utilized to measure Akt, eNOS, Nrf2, NQO1 and HO1 expression. Results: Ex vivo endotheliumdependent relaxation was significantly improved by the glycomimetics under palmitateinduced oxidative stress. In vitro studies showed that the glycomimetics protected HUVECs against the palmitateinduced oxidative stress and enhanced NO production. We demonstrate that the protective effects of preincubation with glycomimetics occurred via upregulation of Akt/eNOS signaling, activation of the Nrf2/ARE pathway, and suppression of ROSinduced lipid peroxidation. Conclusion: We have developed a novel set of small molecule glycomimetics that protect against free fatty acidinduced endothelial dysfunction and thus, represent a new category of therapeutic drugs to target endothelial damage, the first line of defense against cardiovascular disease
Rheological properties of crude oils with a high resin and asphaltene content. Effect of an electromagnetic field and modifiers
Magnetic and Electronic Properties of Heavy Lanthanides (Gd, Tb, Dy, Er, Ho, Tm)
Rare earth metals (REM) occupy a special and important place in our lives. This became especially noticeable during the rapid development of industry in the industrial era of the twentieth century. The tendency of development of the rare-earth metals market certainly remains in the XXI century. According to experts estimates the industry demand for chemical compounds based on them will tend to grow during the nearest years until it reaches the market balance. At the same time, the practical use of high-purity rare-earth metals requires the most accurate understanding of the physical properties of metals, especially magnetic ones. Despite a certain decline in interest in the study of high-purity REM single crystals during the last decade, a number of scientific groups (Ames Lab, Lomonosov Moscow State University (MSU), Baikov Institute of Metallurgy and Materials Science Russian Academy of Science (RAS)) are still conducting high-purity studies on high-purity metal samples. The present article is a combination of a review work covering the analysis of the main works devoted to the study of heavy REMs from gadolinium to thulium, as well as original results obtained at MSU. The paper considers the electronic properties of metals in terms of calculating the density of states, analyzes the regularities of the magnetic phase diagrams of metals, gives the original dependences of the Neel temperature and tricritical temperatures for Gd, Tb, Dy, Er, Ho, Tm, and also introduces a phenomenological parameter that would serve as an indicator of the phase transformation in heavy REMs
Structural and functional status of myocardium and signal-averaged electrocardiogram data in essential arterial hypertension patients
Aim. To study parameters of signal-averaged electrocardiography (SA-ECG) in patients with essential arterial hypertension (EAH), according to structural and functional cardiac disturbances. Material and methods. In total, 89 EAH patients were examined: 47 males and 39 females (mean age 51.5±7.2 years), including 24 patients with Stage I EAH, and 62 Р with Stage II EAH. Results. Late ventricular potentials (LVP) were registered in 29 EAH patients (33.7%). Patients with LVP had more advanced left ventricular and atrial dilatation (LV, LA). This resulted in increased LV end-systolic size, end-diastolic volume and size, LA size, compared to LVP-free participants. EAH patients with LVP had more progressed LV hypertrophy (LVH): increased thickness of interventricular septum, posterior wall, myocardial mass index. Assessing SA-ECG parameters in EAH patients with various LV remodeling types, the authors observed that LVP were more common for patients with eccentric LVH