Modulation Of Na Research Articles

Phase stability, magnetic and elastic properties of Co2NiGa alloy: A first-principles calculation

The phase stability, magnetic and elastic properties of Co2NiGa high temperature shape memory alloy were systematically investigated by the first-principles calculations. A new configuration was proposed for the parent phase of the stoichiometric Co2NiGa alloy. The elastic constants of this new structure satisfy the criteria of mechanical stability. The formation energies of the stoichiometric Co2NiGa in the paramagnetic austenite (PA), ferromagnetic austenite (FA) and non-modulated (NM) martensite were calculated. The bulk modulus, Young’s modulus and shear modulus of Co2NiGa alloys are higher than those of the Ni2MnGa alloy, which can provide larger deformation resistance.

Laser powder bed fusion of Ni-Mn-Ga magnetic shape memory alloy

Additive manufacturing (AM) has gone through major developments in the past decade, enabling the rapid manufacture of complex geometries from traditional engineering materials. This study aims to facilitate the development and additive manufacturing of a new generation of fast and simple digital components with integrated magnetic shape memory (MSM) alloy sections that can be actuated by an external magnetic field. Here, we employ a systematic design of experiments (DoE) approach for investigating laser powder bed fusion (L-PBF) of a Ni-Mn-Ga based MSM alloy. The effects of the applied process parameters on the chemical composition and relative density are determined, and detailed investigations are conducted on the microstructural properties of the as-deposited material obtained using optimized parameters. The results show that although the L-PBF of Ni-Mn-Ga is characterized by an ever-present loss of Mn, deposition of Ni-Mn-Ga with a high relative density of 98.3% and a minimal loss of Mn at ∼1.1 at.% is feasible. The material produced in this manner was compositionally near homogenous and, in as-deposited condition, consisted of a mixture of 14 M and non-modulated (NM) martensites. However, combined measurements by the low-field ac magnetic susceptibility method (LFMS) and DSC revealed that the phase transformation of the as-deposited material from martensite to austenite, and vice versa, was broad and occurred in a paramagnetic state. Inspection by SEM revealed a layered microstructure with a stripe-like surface relief that originated from the presence of martensitic twins within the sample. Additionally, AFM and MFM measurements showed that in as-deposited Ni-Mn-Ga, there exists a weak MFM contrast that can be attributed to the twinned martensite having magnetic anisotropy. Overall, L-PBF shows high potential for the production of functional Ni-Mn-Ga based MSM alloys.

PKB is a central molecule in the modulation of Na+-ATPase activity by albumin in renal proximal tubule cells

Evidence points to a possible role of tubular sodium reabsorption in worsening renal injury. Proximal tubule (PT) albumin overload is a critical process in the development of tubule-interstitial injury (TII), and consequently in progression of renal disease. We studied the possible correlation between changes in albumin concentration in the lumen of PT with modification of Na+-ATPase activity. An albumin overload animal model and LLC-PK1 cells as a model of PT cells were used. Albumin overload was induced by intraperitoneal injection of BSA in 14-week-old male Wistar rats. An increase in sodium clearance, fractional excretion of sodium, proteinuria, ratio between urinary protein and creatinine, and albuminuria were observed. These observations indicate that there could be a correlation between an increase in albumin in the lumen of PTs and renal sodium excretion. We observed that the activity of both Na+-ATPase and (Na++K+)ATPase decreased in the renal cortex of an albumin overload animal model. Using LLC-PK1 cells as a model of PT cells, inhibition of Na+-ATPase activity was observed with higher albumin concentrations, similar to that observed in the animal model. The inhibition of protein kinase B by higher albumin concentration was found to be a critical step in the inhibition of Na+-ATPase activity. Interestingly, activation of the ERK1/2/mTORC1/S6K pathway was required for protein kinase B inhibition. This mechanism leads to a decrease in protein kinase C activity and, consequently to inhibition of Na+-ATPase activity. Taken together, our results indicate that the molecular mechanism underlying the modulation of PT Na+-ATPase activity by albumin overload involves activation of the ERK1/2/mTORC1/S6K pathway, which leads to inhibition of the mTORC2/PKB/PKC pathway. Our findings contribute to better understanding regarding handing of renal Na+ induced by albumin overload in the lumen of PTs and, consequently, in the progression of renal disease.

Martensitic transformation and magnetocaloric effect in melt-spun Mn50Ni31.5Co8.5Ti10 all-3d-metal alloy ribbons

The martensitic transformation (MT) and magnetocaloric properties are investigated in melt-spun Mn50Ni31.5Co8.5Ti10 all-3d-metal alloy ribbons fabricated at different wheel speeds (WSs), 15, 20, and 25 m/s. All these ribbon samples reveal a coexistence of the predominant 5-layer modulated (5 M) (monoclinic, space group P2/m) martensite and a small amount of non-modulated (NM) L10 structure (tetragonal, space group P4/mmm) martensite at room temperature (RT), implying the MT temperature is above RT. With the increase of WSs from 15 to 25 m/s, the structural and magnetic parameters, such as average grain size, unit cell volume, MT temperature, and magnetic entropy change, decrease. However, it is worth noting that from 20 to 25 m/s, the reduction becomes much more sluggish or even almost stagnate in comparison with that from 15 to 20 m/s. Large effective refrigeration capacity ~79.4 J kg−1 is obtained in sample with 20 m/s under μ0ΔH = 0–5 T, indicating that these ribbons could be the potential candidate for magnetic refrigeration. The origins of manipulation in MT by WSs in these ribbon samples are discussed.

Photooxidative Destruction of Composites Based on Polyethylene and Montmorillonites Modified with Transition-Metal Salts

Metal-modified montmorillonites containing Ni2+, Co2+, Fe3+, Mn2+, and Cu2+ions are synthesized by interacting layered aluminosilicates Na+-montmorillonite and Cloisite 25A with transition-metal salts. The organomodified Cloisite 25A is saturated with ions of heavy metals Ni, Co, and Fe, retaining the organic modifier. The composition and structure of metal-modified aluminosilicates are studied by X-ray powder diffraction, X-ray fluorescence analysis, and FTIR spectroscopy. Montmorillonites of different degrees of intercalation are obtained depending on the particular transition-metal ion and silicate type. It is shown that metal-modified aluminosilicates being involved in the composition of LDPE-based composites considerably increase the rate of photooxidation of the polyethylene matrix. FTIR studies of the initial and irradiated films suggest that the photooxidation of polyethylene is accompanied by the formation of diverse oxygen-containing and unsaturated groups. According to the calculated carbonyl and vinyl indices, it is demonstrated that the efficiency of oxidation activation under UV irradiation depends on the particular transition metal and increases in the sequence Na < Co < Ni < Cu < Mn < Fe. The introduction of an iron-containing filler decreases the time of polyethylene matrix photooxidation by five to seven times. The irradiation of polyethylene films containing Fe-MMT and Mn-MMT for 250 h leads to the full loss of physicomechanical properties and destruction of the polymer. The activity of Cloisite 25A modified with transition-metal salts in sensitizing photochemical processes is higher than that of the fillers obtained by modification of Na+‑MMT; in this case, there is no destruction of the samples.

Effect of process parameters on non-modulated Ni-Mn-Ga alloy manufactured using powder bed fusion

Increasingly, metal parts made by additive manufacturing are produced using powder bed fusion (PBF). In this paper we report upon the combined effects of PBF parameters, including power and scan speed, in layer-by-layer manufacturing of gas atomized non-modulated (NM) Ni-Mn-Ga alloy. The effects of process parameters upon PBF is studied by applying nine different parameter sets in the as-printed state and after homogenization and ordering. The chemical composition of the samples is analyzed using EDX attached to an SEM, and the crystal structures are determined by X-ray diffraction. The phase transformation temperatures are measured using a low-field ac susceptibility measurement system and the magnetic properties are measured with a vibrating sample magnetometer (VSM). Before the heat-treatment, all as-printed samples showed paramagnetic behavior with low magnetization and no phase transformations could be observed in the susceptibility measurements. After annealing, the samples recovered the ferromagnetic behavior with comparable magnetization to annealed gas atomized powder. The as-printed samples were composed of a mixture of different crystal structures. However, after annealing the original NM structure with a = b = 5.47 Å and c = 6.66 Å with a c/a -ratio of 1.22 was recovered and crystallographic twins could be observed in an SEM.

Understanding the magneto-structural coupling of Ni50Mn35.4In14.6 alloy from first-principles calculations

Abstract The magneto-structural coupling of non-stoichiometric Ni50Mn35.4In14.6 alloy is investigated by the first-principles calculations in view of phase stability and magnetic properties of the austenite, the six-layered modulated (6M) martensite, and the non-modulated (NM) martensite. The calculated martensitic phase transformation sequence of the Ni50Mn35.4In14.6 alloy is Paramagnetic Austenite (PA) → Ferromagnetic Austenite (FA) → Ferrimagnetic 6M (FIM 6M) → Ferrimagnetic NM (FIM NM) as a function of temperature. The Mn-Mn interatomic distance reduces significantly when the FA parent phase transforms to a 6M or NM martensitic phase. At the same time, magnetism of the alloy changes from ferromagnetic to ferrimagnetic; this is a typical magneto-structural coupling phenomenon. The Ni 3d state electrons play an important role in driving martensitic transformation for the Ni50Mn35.4In14.6 alloy.

Modelling the stress-induced multi-step martensite transformation of single crystal NiMnGa ferromagnetic shape memory alloys

Existing experimental results have shown that multi-step martensite transformation can be induced by the applied stress in single crystal NiMnGa ferromagnetic shape memory alloys (FSMAs) and the transformation property depends on the ambient temperature strongly. In this work, a crystal-plasticity based constitutive model is established to quantify such a phenomenon. Based on the crystallographic symmetry, the lattice structures and eigenstrains of austenite (A) and three different martensite phases, i.e., the modulated martensite phases with a periodicity of 5 lattice cells (5M) and a periodicity of 7 lattice cells (7M), and a non-modulated (NM) martensite phase are analyzed. A three-dimensional (3D) single crystal constitutive model is constructed in the framework of finite strain by considering five different martensite transformation processes, i.e., the transformations between A and 5M, A and 7M, A and NM, 5M and 7M, and 7M and NM phases. Thermodynamically consistent kinetic equations for the five different martensite transformation processes are proposed based on the constructed Helmholtz free energy and Clausius's dissipative inequality. The capability of the proposed model to describe the tensile stress-induced multi-step martensite transformation of single crystal NiMnGa FSMA in [100] crystallographic orientation is verified by comparing the predictions with corresponding experimental results. Further, the proposed model is used to predict the deformations of the single crystal under the tension and compression in various crystallographic orientations.

Stress-induced detwinning and martensite transformation in an austenite Ni-Mn-Ga alloy with martensite cluster under uniaxial loading.

Stress-induced martensitic detwinning and martensitic transformation during step-wise compression in an austenite Ni-Mn-Ga matrix with a martensite cluster under uniaxial loading have been investigated by electron backscatter diffraction, focusing on the crystallographic features of microstructure evolution. The results indicate that detwinning occurs on twins with a high Schmid factor for both intra-plate and inter-plate twins in the hierarchical structure, resulting in a nonmodulated (NM) martensite composed only of favourable variants with [001]NM orientation away from the compression axis. Moreover, the stress-induced martensitic transformation occurs at higher stress levels, undergoing a three-stage transformation from austenite to a twin variant pair and finally to a single variant with increasing compressive stress, and theoretical calculation shows that the corresponding crystallographic configuration is accommodated to the compression stress. The present research not only provides a comprehensive understanding of martensitic variant detwinning and martensitic transformation under compression stress, but also offers important guidelines for the mechanical training process of martensite.

Antiarrhythmic Activity of the Flavonoid Fraction of Plantago Major L. Extract

Antiarrhythmic activity of the flavonoid fraction of Plantago major L. extract (0.05 mg/mL) was studied. The studied fractions were found to lower the frequency of rat cardiac papillary muscle contractions with aconitine-induced (1 μM) arrythmia in vitro. An analysis of literature and experimental data suggested that the antiarrhythmic effects of the studied flavonoid fractions may have been related to functional modulation of Na+- and Ca2+-channels in cardiomyocytes.

Modulation of Na+/K+- ATPase activity by triterpene 3β, 6β, 16β-trihidroxilup-20 (29)-ene (TTHL) limits the long-term secondary degeneration after traumatic brain injury in mice

Traumatic brain injury (TBI) is a public health problem characterized by a combination of immediate mechanical dysfunction of the brain tissue, and secondary damage. Based on the hypothesis that selected targets, such as Na+ K+-ATPase are involved in the secondary damage after TBI and modulation of this enzyme activity by triterpene 3β, 6β, 16β-trihidroxilup-20 (29)-ene (TTHL) supports the ethnomedical applications of this plant, we decided to investigate whether previous TTHL treatment interrupts the progression of pathophysiology induced by TBI. Statistical analyses revealed that percussion fluid injury (FPI) increased Na+,K+-ATPase activity in all isoform (α1 and α2/3) 15 min after neuronal injury. The FPI protocol inhibited Na+,K+-ATPase activity total and α1 isoform, increased [3H]MK-801 binding but did not alter Dichloro-dihydro-fluorescein diacetate (DCFH-DA) oxidation, carbonylated proteins and free –SH groups 60 min after injury. The increase of immunoreactivity of protein PKC and state of phosphorylation of at Ser16 of Na+,K+-ATPase 60 min after FPI suggest the involvement of PKC on Na+,K+-ATPase activity oscillations characterized by inhibition of total and α1 isoform. Our experimental data also revealed that natural product rich in compounds such as triterpenes (TTHL; 30 mg/kg) attenuates [3H]MK-801 binding increase, phosphorylation of the PKC and the Na+,K+-ATPase alpha 1 subunit (Ser16) induced by FPI. The previous TTHL treatment had not effect on motor disability but protected against spatial memory deficit, BDNF, TrKB expression decrease, protein carbonylation and hippocampal cell death 7 days after FPI. These data suggest that TTHL-induced reduction on initial damage limits the long-term secondary degeneration and supports neural repair or behavioral compensation after neuronal injury.

L-Tyr-Induced Phosphorylation of Tyrosine Hydroxylase at Ser40: An Alternative Route for Dopamine Synthesis and Modulation of Na+/K+-ATPase in Kidney Cells

Background/Aims: Dopamine (DA) is a natriuretic hormone that inhibits renal sodium reabsorption, being Angiotensin II (Ang II) its powerful counterpart. These two systems work together to maintain sodium homeostasis and consequently, the blood pressure (BP) within normal limits. We hypothesized that L-tyrosine (L-tyr) or L-dihydroxyphenylalanine (L-dopa) could inhibit the Na⁺/K⁺-ATPase activity. We also evaluated whether L-tyr treatment modulates Tyrosine Hydroxylase (TH). Methods: Experiments involved cultured LLCPK₁ cells treated with L-tyr or L-dopa for 30 minutes a 37°C. In experiments on the effect of Dopa Descarboxylase (DDC) inhibition, cells were pre incubated for 15 minutes with 3-Hydroxybenzylhydrazine dihydrochloride (HBH), and them L-dopa was added for 30 minutes. Na⁺/K⁺-ATPase activity was quantified colorimetrically. We used immunoblotting and immunocytochemistry to identify the enzymes TH, DDC and the dopamine receptor D₁R in LLCPK₁ cells. TH activity was accessed by immunoblotting (increase in the phosphorylation). TH and DDC activities were also evaluated by the modulation of the Na⁺/K⁺-ATPase activity, which can be ascribed to the synthesis of dopamine. Results: LLCPK₁ cells express the required machinery for DA synthesis: the enzymes TH, and (DDC) as well as its receptor D₁R, were detected in control steady state cells. Cells treated with L-tyr or L-dopa showed an inhibition of the basolateral Na⁺/K⁺-ATPase activity. We can assume that DA formed in the cytoplasm from L-tyr or L-dopa led to inhibition of the Na⁺/K⁺-ATPase activity compared to control. L-tyr treatment increases TH phosphorylation at Ser⁴⁰ by 100%. HBH, a specific DDC inhibitor; BCH, a LAT2 inhibitor; and Sch 23397, a specific D₁R antagonist, totally suppressed the inhibition of Na⁺/K⁺-ATPase activity due to L-dopa or L-tyr administration, as indicated in the figures. Conclusion: The results indicate that DA formed mainly from luminal L-tyr or L-dopa uptake by LAT2, can inhibit the Na⁺/K⁺-ATPase. In addition, our results showed for the very first time that TH activity is also significantly increased when the cells were exposed to L-tyr.

Sulfonyl(thio)urea derivative induction of insulin secretion is mediated by potassium, calcium, and sodium channel signal transduction.

To investigate the mechanism of action of sulfonyl(thio)urea derivative (SD) on glycemia and on insulin secretion in pancreatic islets. Wistar rats were divided into hyperglycemic control group, rats received 4 g/kg body weight glucose plus sitagliptin 10 mg/kg (p.o.); hyperglycemic plus SD 10 mg/kg (p.o.); hyperglycemic plus SD plus sitagliptin. Blood was collected before glucose overloading (zero time), and at 15, 30, 60, and 180 min after glucose, from the afore mentioned groups for glycemia and glucagon-like peptide 1 (GLP-1) measurements and intestinal disaccharidases activity. Pancreatic islets were isolated for the calcium influx and insulin secretion in in vitro studies. SD reduced glycemia and increased GLP-1 secretion, while inhibited sucrase and lactase activity. This SD (1.0 and 10.0 µM) stimulated calcium influx in a similar percentile to that of glibenclamide, and in a nonsynergic manner. In addition, the trigger effect of SD on calcium influx was through the K+ -ATP-dependent channels, and partially by activating voltage-dependent K + channels and voltage-dependent calcium channels. Furthermore, SD-stimulated Na + and Ca 2+ entry, induced by the transient receptor potential ankyrin 1 and by modulation of Na + /Ca 2+ exchange. The activation of these pathways by SD culminated in in vitro insulin secretion, reinforcing the critical role of K + -ATP channels in the secretagogue effect of SD. SD diminish glycemia by inducing GLP-1 secretion and inhibiting disaccharidases. To our knowledge, this is the first report of an insulin secretagogue effect of SD that is mediated by potassium and calcium, as well as sodium, signal transduction.

Modulation of rat synaptosomal ATPases and acetylcholinesterase activities induced by chronic exposure to the static magnetic field

Purpose: It is considered that exposure to static magnetic fields (SMF) may have both detrimental and therapeutic effect, but the mechanism of SMF influence on the living organisms is not well understood. Since the adenosine triphosphatases (ATPases) and acetylcholinesterase (AChE) are involved in both physiological and pathological processes, the modulation of Na+/K+-ATPase, ecto-ATPases and AChE activities, as well as oxidative stress responses were followed in synaptosomes isolated from rats after chronic exposure toward differently oriented SMF.Material and methods: Wistar albino rats were randomly divided into three experimental groups (six animals per group): Up and Down group - exposed to upward and downward oriented SMF, respectively, and Control group. After 50 days, the rats were sacrificed, and synaptosomes were isolated from the whole rat brain and used for testing the enzyme activities and oxidative stress parameters.Results: Chronic exposure to 1 mT SMF significantly increased ATPases, AChE activities, and malondialdehyde (MDA) level in both exposed groups, compared to control values. The significant decrease in synaptosomal catalase activity (1.48 ± 0.17 U/mg protein) induced by exposure to the downward oriented field, compared to those obtained for Control group (2.60 ± 0.29 U/mg protein), and Up group (2.72 ± 0.21 U/mg protein).Conclusions: It could be concluded that chronic exposure to differently oriented SMF increases ATPases and AChE activities in rat synaptosomes. Since brain ATPases and AChE have important roles in the pathogenesis of several neurological diseases, SMF influence on the activity of these enzymes may have potential therapeutic importance

Beta-Dependent Modulation of Na+ Binding and Release of the Alpha-3 Na+K+Pump

Beta-Dependent Modulation of Na+ Binding and Release of the Alpha-3 Na+K+Pump

Detwinning process of martensite in Ni58Mn25Ga17 as a high temperature shape memory alloy under uniaxial compression

The Ni-rich Ni-Mn-Ga alloy as a high temperature shape memory alloy has been directionally solidified, which is consisted of non-modulated (NM) martensite with preferred orientation and γ precipitate with a three dimensional net structure. The detwinning process of Ni58Mn25Ga17 alloy was investigated under step-wise uniaxial compression with a cumulative strain of 2.5%, 5.5%, 12.9% and 30.2%, respectively. It has been captured how the hierarchically structured martensite variants reorient and the effect of the surrounding γ phase on detwinning process with the increase of compression strain. It can be found that the volume fraction of the original minor lamella gradually increases and then it occupies the whole plate. The detwinning of new microtwins is not observed during further compression. The results indicate that the move of the intra-plate boundaries is attributed to a higher Schmid factor of the nanotwins. The mobility of the new inter-plate boundary is mainly dependent on the preferred orientation of the lamella inside martensite variants. The present study provides useful insights for microstructure training in high temperature shape memory alloys including martensite and γ phase.

Martensitic transformation and detwinning in directionally solidified two-phase Ni-Mn-Ga alloys under uniaxial compression

A kind of Ni-Mn-Ga alloy consisting of orderly arrayed austenite and non-modulated (NM) martensite was designed and directionally solidified. The influences of step-wise uniaxial compression on martensitic transformation and detwinning processes of the above-mentioned sample were investigated by the electron backscatter diffraction (EBSD) tracing. Experimental results show that the stress has induced martensitic transformation at ambient temperature, which is completed after the three cycles (2%, 4% and 6% strain, respectively). This should be attributed to the increase of martensitic transformation temperature under compression. Moreover, the stress has caused detwinning of the twins with high Schmid factor, resulting in martensite only composed of favorable variants with 〈110〉M orientation parallel to the compression axis. The kernel average misorientation (KAM) maps reveal that the dislocation density decreases during stress-induced processes.

Proton-irradiation-induced structural and magnetic property changes in Ni–Mn–Ga high-temperature shape memory films

Ni51.90Mn28.86Ga19.24 alloy films were irradiated by 120keV protons at different fluences to investigate the effect of irradiation on their crystal structure, phase-transition temperature, and magnetic properties. The results show not only that a nanoscale amorphous layer may have been induced on the surface, but also that non-modulated (NM) martensite was produced. Moreover, differential scanning calorimetry peaks of the martensitic and austenitic transition temperatures are shifted to higher temperatures after irradiation; in particular, two endothermic and two exothermic peaks were observed for a proton fluence of 2.0×1016/cm2. Further, the formation of NM martensite could produce an extra shoulder on the M–T curves of the irradiated films. Regarding the magnetic properties, a gradual decrease in the Curie temperature TC can be caused by irradiation at a higher proton fluence. The changes in the saturation magnetization Ms with the proton fluence seem to be related to the reduction in TC.

Microstructural and crystallographic characteristics of modulated martensite, non-modulated martensite, and pre-martensitic tweed austenite in Ni-Mn-Ga alloys

A combinatorial approach using diffusion couples and TEM analyses was carried out to investigate the composition-dependent martensitic transformation in NiMnGa alloys. The compositions cover a large portion of the off-stoichiometric Ni2MnGa compositions and some Mn-rich compositions. Crystallographic variations of the martensitic phase, including non-modulated (NM) martensite, modulated (5M or 7M) martensite, and austenitic phase were identified in the diffusion couples and investigated with respect to their microstructure and crystallography. The 5M and 7M martensitic structures were only found near the interphase boundary between austenite and martensite, while the NM martensitic structures were found mostly away from the interphase boundary. The tetragonality ratio (c/a) for NM martensite generally increases with e/a ratio, but was also dependent on the composition. The habit plane and martensitic microstructure that consists of twinned variants with differing orientations were documented using electron diffraction. The pre-martensitic state was observed in the austenitic phase that was located near the interphase boundary between austenite and martensite, with distinctive tweed microstructure and a strain field originating from the local lattice distortions. The combinatorial approach proves to be efficient and systematic in studying the composition-dependent martensitic transformation in NiMnGa alloys and can be potentially applied to other shape memory alloys.

Elastic constants of non-modulated Ni-Mn-Ga martensite

Room temperature elastic constants of non-modulated (NM) tetragonal martensite of a Mn-rich Ni-Mn-Ga alloy were determined by ultrasonic methods. The results are in good qualitative agreement with ab-initio predictions and confirm that NM martensite exhibits strong elastic anisotropy with shear instability related to the soft acoustic phonons mediating the reverse transition. The geometric arrangement of the softest shearing modes is shown to be identical as for the stress-induced fct martensite of the Fe-31.2at.%Pd alloy. However, it markedly differs from the arrangement of the soft shearing modes in parent Ni-Mn-Ga austenite phase.