Increase In Mn2 Research Articles

Effect of Mn2+ substitution on structural, magnetic, electric and dielectric properties of Mg–Zn ferrites

In this work, Mn substituted Mg–Zn spinel ferrites having general formula Zno.4Mg0.6−xMnxFe2O4 (0≤x≤0.30) have been synthesized by oxalate precursor chemical method and investigated their structural, magnetic and electric properties. X-ray diffraction (XRD) is used to study the crystal structure of synthesized materials. XRD study reveals the formation of polycrystalline cubic spinel lattice structure without any impurity phase having crystallite size in the range from 39.97nm to 45.62nm. Scanning electron micrographs revealed, increase in grain size (D) with increase in Mn2+ content up to x=0.10; then it decreases for x>0.10. Energy dispersive x-ray analysis (EDAX) confirms the presence of Mg2+, Mn2+, Fe3+, Zn2+ and O2− ions as per the stoichiometry. The magnetic moment (nB), with Mn2+ substitution is found to increase initially up to x=0.10 and then it deceases with further Mn2+ substitution. The observed variation in the magnetic moment (nB) is explained by considering the variation of saturation magnetization, anisotropy constant, density values and exchange interaction. The d.c. electrical resistivity decreased with increase in temperature in accordance with semiconducting behavior. Furthermore, the conductivity was found to obey the Arrhenius relation with a change in slope at critical temperature (i.e. the Curie temperature). The increase in d.c. resistivity is attributed to the hindering of Verwey mechanism between Fe2+⇔Fe3+ ions and Mn2+⇔Mn3+. The dielectric constant (ε′) measurement revealed the dielectric dispersion behavior in accordance with the Maxwell–Wagner model and Koops phenomenological theory, which is responsible for conduction and polarization. The dielectric characteristics (ε′, ε″ and tanδ) exhibit dispersion due to Maxwell–Wagner type interfacial polarization. The values of dielectric constant (ε′) and a.c. resistivity (ρac) exhibit highest magnitude at x=0.10 and decreases further with Mn2+ substitution.

Effect of Mn2+ doping and SiO2 coating on magneto-optical properties of CoFe2O4 nano-particles

Co1−xMnxFe2O4 (x = 0.2, 0.4, 0.6, 0.8, 1.0) magnetic nanoparticles were prepared using a modified citrate gel method and fired at 500 °C for 2 h. The modified Stöber method was used for coating the magnetic nanoparticles with a silica shell. The effects of Mn2+ substitution and the method of preparation on the formation of crystalline phases, particle size, morphology and the optical and magnetic properties of the synthesized materials were investigated by XRD, SAED, HR-TEM, EDX, UV/VIS double-beam spectrophotometry and vibrating sample magnetometry. The average crystallite size of the synthesized nanoparticles was 18.6–43.9 nm. The maximum value of saturation magnetization (Ms) achieved was 65.668 emu/g for Mn0.2Co0.8Fe2O4 nanoparticles. Diffuse reflectance increased with an increase of Mn2+content and SiO2 shell. These coated magnetic nanoparticles are promising materials for application to magnetic sensors and biomedical nanodevices.

Effect of Mn2+ ions on the enhancement red upconversion emission and energy transfer of Mn2+/Tm3+/Yb3+ tri-doped transparent glass-ceramics

The effects of Mn2+ ions on the enhancement red upconversion emission intensity of Mn2+/Tm3+/Yb3+ tri-doped transparent glass-ceramics were investigated. The ratio I698nm/I478nm significantly increases about ten-fold with the increase of Mn2+ concentrations up to 4.0mol.%. The red upconversion emission of Mn2+/Tm3+/Yb3+ tri-doped transparent glass-ceramics is greatly enhanced, due to constitution of the energy transfer bridge. The upconversion mechanism, the energy transfer and back energy transfer processes between the (1G4→3H6), (3F2→3H6) transitions of Tm3+ ions and the ∣2F7/2, 4T1〉→∣2F7/2, 6A1〉 transitions of Mn2+–Yb3+ dimer were discussed.

Ultrasensitive colorimetric detection of manganese(II) ions based on anti-aggregation of unmodified silver nanoparticles

We report a facile, selective, and sensitive colorimetric assay for Mn2+ ions based on the anti-aggregation of unmodified silver nanoparticles (AgNPs). In the absence of Mn2+ ions, the addition of l-arginine to the AgNPs dispersion caused the aggregation of AgNPs via Ag–N covalent interaction, and the color of the solution changed from yellow to colorless. While the presence of Mn2+ ions can prevent the aggregation of AgNPs due to the formation of the complex between Mn2+ ions and l-arginine, accompanying with a distinct color change from colorless to yellow with the increase of Mn2+ ions. Under the optimal experimental conditions, the absorbance at 390nm was linearly proportional to the Mn2+ ions concentration in the ranges from 0 to 700nM, and from 5μM to 70μM, with a detection limit of 20nM. Also, it was successfully used for the detection of Mn2+ ions in environmental water samples.

Investigation of structural and magnetic properties of co-precipitated Mn–Ni ferrite nanoparticles in the presence of α-Fe2O3 phase

A systematic study on structural and magnetic properties of co-precipitated MnxNi1−xFe2O4 (x=0.5, 0.6, 0.7) ferrite nanoparticles annealed at 800°C was carried out using XRD, FE-SEM, VSM and MÖSSBAUER techniques. Anti-ferromagnetic α-Fe2O3 phase was observed along with the magnetic spinel phase in the XRD patterns. It is observed that both lattice parameter and crystallite size of spinel phase increase with increase in concentration of Mn2+ along with the amount of α-Fe2O3 phase. The saturation magnetization (Ms) decreases while coercivity (Hc) increases with increase of Mn2+ ion concentration. Mössbauer spectra indicate that iron ions present in A and B sites are in the Fe3+ state and Fe2+ is absent. The results are interpreted in terms of observed anti-ferromagnetic α-Fe2O3 phase, core–shell interactions and cation redistribution.

Effect of Mn2+ ions on the enhancement upconversion emission and energy transfer of Mn2+/Tb3+/Yb3+ tri-doped transparent glass-ceramics

The effect of Mn2+ on the enhancement upconversion (UC) emission and energy transfer of Mn2+/Tb3+/Yb3+ tri-doped SiO2–AlF3–BaF2–TiO2–LaF3 transparent glass-ceramics under excitation 980nm LD were successfully investigated. The UC emission intensity bands centered at 493, 548, 593 and 622nm corresponding to (5D4→7FJ(J=6, 5, 4 and 3)) transitions of Tb3+ were significantly increased with the increase of the Mn2+ concentrations and reaches its maximum at 2.0mol%, then decreases due to the self-quenching effect. Particularly, the UC emission intensity bands centered at 656nm (5D4→7FJ(J=2, 1 and 0)) of Tb3+ was strongly increased about 15-fold with the increase of Mn2+ concentration up to 2.0mol%. The upconversion mechanism and the energy transfer processes from (4T1→6A1) transition of Mn2+ to 5D4→7FJ(J=6, 5, 4, 3, 2, 1 and 0) transitions of Tb3+ were discussed.

Studies on NO2 gas sensing properties of sprayed Co1−xMnxFe2O4 (0≤x≤0.5) spinel ferrite thin films

The Co1−xMnxFe2O4 (0≤x≤0.5) spinel ferrite thin films were deposited on quartz substrates by chemical spray pyrolysis technique. The effect of Mn substitution on to the structural, electrical, dielectric and NO2 gas sensing properties of cobalt ferrite thin films was studied. The X-ray diffraction analysis reveals that deposited films exhibit spinel cubic crystal structure. The lattice constant increases with the increase in Mn2+ content. The decrease in resistivity with increase in temperature suggests that the films have a semiconducting nature. The room temperature dielectric properties such as dielectric constant (ε′), loss tangent (tanδ), dielectric loss (ε′′) and AC conductivity have been studied in the frequency range 20Hz–1MHz. The film shows the highest sensor response at moderately low (150°C) operating temperature. The effect of operating temperature, gas concentration, film selectivity and substitution of Mn on to gas response is carefully studied. The manganese substituted cobalt ferrite films are extremely selective towards NO2 with a 20 times gas response compared with other gases. The gas response achieved nearly 92% of its initial value after 150 days, indicating good stability of the films.

Role of Mn2+ Doping on Structural, Morphological, and Opto-Magnetic Properties of Spinel Mn x Co1−x Fe2O4 (x = 0.0, 0.1, 0.2, 0.3, 0.4, and 0.5) Nanocatalysts

Spinel MnxCo1−x Fe2O4; x = 0.0, 0.1, 0.2, 0.3, 0.4, and 0.5) nanoparticles were synthesized by ureaassisted auto combustion method using nitrates of Co, Mn and Fe as the starting materials and urea as the fuel. X-ray diffraction (XRD) analysis showed that all composition was found to have a cubic spinel structure. The average crystallite size of the samples was estimated using the Debye-Scherrer formula and was found to be in the range of 22.62 and 36.45 nm. The lattice parameter increased from 8.432 to 8.457 A with increasing the Mn2+ content, which was determined by Rietveld analysis. High-resolution scanning electron microscopy (HR-SEM) and high-resolution transmission electron microscopy (HR-TEM) analyses were used to study the morphological variation, and the results showed a nanosized particle-like morphology. Energy-dispersive X-ray (EDX) results showed that the composition of the elements was relevant as expected from the synthesis. The bandgap energy of the pure CoFe2 O 4 was estimated to be 2.33 eV from UV-visible diffuse reflectance spectroscopy (DRS). With the increase of Mn2+ ion, the bandgap energy increased from 2.35 to 2.42 eV. The magnetic properties of the samples were investigated at room temperature by using a vibrating sample magnetometer (VSM). The magnetic hysteresis (M-H) loop confirmed the superparamagnetic nature of pure CoFe2 O 4 and a weak ferromagnetic behavior of Mn2+doped CoFe2 O 4 samples with specific saturation magnetization in the range of 55.16±24 and 66.92 ± 05 emu/g. All compositions of spinel Mn x Co1−x Fe2 O 4 samples were successfully tested as catalyst for the conversion of benzyl alcohol, which has resulted in 62.75 and 92.62 % conversion efficiency of CoFe2 O 4 and Mn0.5Co0.5Fe2 O 4, respectively.

Photoluminescence properties and energy transfer from Ce3+ to Mn2+ in Na2SrMg(PO4)2

Na2SrMg(PO4)2: Ce3+, Mn2+ phosphor was prepared by high temperature solid state reaction. Its luminescence properties and energy transfer from Ce3+ to Mn2+ were investigated. The emission bands of Ce3+ and Mn2+peaking at 334 nm and 617 nm were attributed to 5d→4f transition of Ce3+ and 4T1(4G)→6A1(6S) transition of Mn2+, respectively. Dependence of Ce3+ and Mn2+ luminescence properties on their concentrations was investigated as well. With the increase of Mn2+ content, the emission intensity of Ce3+ could be observed to decrease, however, the emission intensity of Mn2+ was found to increase. It is indicated that the luminescence of Mn2+ could be sensitized by energy transfer from Ce3+ to Mn2+ in Na2SrMg(PO4)2 host. According to the Dexter's energy transfer formula of multipolar interaction, it is demonstrated that the energy transfer between Ce3+ and Mn2+ is due to the electric dipole-quadripole interaction of the resonance transfer.

Sr3Bi(PO4)3:Eu2+, Mn2+: Single-phase and color-tunable phosphors for white-light LEDs

Sr3Bi(PO4)3:Eu2+, Sr3Bi(PO4)3:Mn2+, and Sr3Bi(PO4)3:Eu2+, Mn2+ phosphors were synthesized by solid state reaction. The structure and luminescent characteristics were investigated by X-ray powder diffraction and fluorescent spectrophotometer. All samples have the structural type of eulytine. The excitation and emission spectra of Sr3Bi(PO4)3:0.01Eu2+ sample show characteristic bands of Eu2+ ions. Also, the excitation and emission spectra of Sr3Bi(PO4)3:0.06Mn2+ sample show characteristic bands of Mn2+ ions. The emission color of Sr3Bi(PO4)3:Eu2+, Mn2+ sample could be tuned through tuning the co-dopant concentration of Mn2+ ions. The decay times for the Eu2+ ions decrease with the increase of Mn2+ dopant concentration, but the energy transfer efficiency increases with the increase of Mn2+ dopant concentration. On the basis of the luminescent spectra and fluorescence decay curves, we confirm that the energy transfer process from the Eu2+ to Mn2+ ions takes place in the co-doped Sr3Bi(PO4)3 phosphor. Sr3Bi(PO4)3:Eu2+, Mn2+ sample shows the good thermostability. The emission intensity of the sample at 400K is about 60% of the value at 300K. These results show Sr3Bi(PO4)3:Eu2+, Mn2+ phosphors could be anticipated for UV-pumped white-light-emitting diodes.

Sol-Gel Derived Strong Green Phosphor Zn<sub>2</sub>SiO<sub>4</sub>: Mn<sup>2+</sup> and the Luminescent Properties

Being added by H3BO3 as flux, the nanosize strong green phosphor Zn2SiO4: Mn2+ was prepared by an improved sol-gel method. The structure and the morphology of the samples were examined by XRD, UV-VL spectrophotometer and SEM. The photoluminescence properties were measured by fluorescence spectrometer. Results show that, when the samples were annealed at 850°C for 2 hours, the intensity of emission spectrum of the sample is not strictly followed the monotonically increasing with the increase of Mn2+ doping concentration. It appears in a fluctuated tendency with the increase of doping concentration. In the 4% Mn2+ doping concentration and annealing temperature 950°C, the most strong green emission spectrum can be obtained. The mechanism of luminescence properties of this kind of material is analyzed.

Role of Mn2+ in Doped Quantum Dot Solar Cell

In recent times, Mn doped quantum dot sensitized solar cells (QDSSCs) have shown a lot of interest as it provides a different strategy to improve the photovoltaic performances. In this work, we have systematically studied the effect of Mn2+ dopant concentration on the photovoltaic performances of CdS based QDSSCs. The open circuit potential increases systematically with increase in Mn2+ dopant concentration. The efficiency of the solar cell increases from 1.63% to 2.53% from undoped to 7.5% doped CdS. The role of Mn2+ in enhancing the photovoltaic performances was further probed by open circuit voltage decay and the energy levels were studied using transient absorption spectroscopy. Both spin and orbital forbidden Mn d-d transition (4T1 – 6A1) helps in reducing the recombination inside the solar cell, which improves the overall photovoltaic performances.

EDTA-assisted hydrothermal synthesis, characterization and photoluminescent properties of Mn2+-doped ZnS

In this paper, undoped ZnS and Mn2+-doped ZnS nanocrystals were synthesized through a facile EDTA-assisted hydrothermal method. The as-synthesized powder samples were systematically characterized by employing the following characterization technique such as X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), UV–visible optical absorption and photoluminescence (PL) spectroscopy. X-ray diffraction pattern revealed the presence of material in single phase with average crystallite size of about 3nm and the material remained cubic over the whole Mn solid solution range. Formation of ultrafine, spherical and homogeneous dispersed nanoparticles with size 4nm was confirmed by HRTEM analysis. Absorption shoulders of the samples were blue-shifted as compared to bulk ZnS (3.6eV) with decrease in the energy band gap as the Mn concentration increases. The room temperature photoluminescence (PL) spectra of Mn2+-doped ZnS nanocrystalline showed extra peaks in yellow–orange and red region in comparison of pure ZnS. Mn induced PL was suggested with the significant enhancement of the PL intensity in ZnS:Mn nanocrystalline due to Mn incorporation. The red shift in the yellow–orange emission peak can be attributed to the change in band structure due to the formation of ZnS:Mn alloy with increase in Mn2+ concentration. The yellow–orange emission peak corresponds to the 4T1(excited)–6A1(ground) transition of Mn2+ ion in Td symmetry in the ZnS host lattice. The emission peak in the red region may be due to Mn2+ d–d transitions in (Zn Mn)S matrix as some of the nearest neighbors of Mn2+ are now predominantly S atoms due to their random positioning nature in the nanocrystallite and Mn–Mn interaction at high Mn2+ concentration. This type of doped semiconductors with multi-band emission can be made bioactive when they are linked with suitable biomolecules.

Effect of Mn<sup>2+</sup> Additive on the Sinterability and Dielectric Properties of Ba<sub>0.55</sub>Sr<sub>0.4</sub>Ca<sub>0.05</sub>TiO<sub>3</sub>-MgO Composite Ceramics

Ba0.55Sr0.4Ca0.05TiO3-MgO (BSCTM) with Mn2+additive composite ceramics were prepared by the conventional solid state method with BaCO3, SrCO3, CaCO3, MgO and MnCO3as raw materials and B2O3and Li2CO3as sintering agent. The influence of the MnCO3additive on the sinterability and dielectric properties of BSCTM composite ceramics are investigated. The morphologies were analysized by scanning electron microscopy (SEM). The dielectric constant and dielectric loss of ceramics were measured by LCR meter at 1 kHz and 1 MHz. The temperature dependences of dielectric constant were measured by high-low temperature incubator tank and LCR meter at 1 MHz and a temperature range from-55 to 125 °C. The dielectric tunabilities were tested by C-T-V converter and LCR meter at 1 MHz and room temperature (25 °C). SEM results showed that BSCTM ceramics became more compact with the increase of Mn2+content, because Mn2+helped to form more oxygen vacancies for accelerating densification process. The addition of Mn2+largely reduced the dielectric loss while had little effect on dielectric constant. The dielectric constant and dielectric loss of 0.5mol% Mn2+doped BSCTM ceramics were 222 and 0.001, respectively. The dielectric tunability increased at first and then decreased with the increase of Mn2+content. The tunability of 0.5mol% Mn2+doped BSCTM ceramics were 4.04% under a DC electric field of 8.2 kV/cm.

Bi2O3 liquid phase assisted and Mn substituted permeability and magnetic properties of Ni-Cu-Zn ferrite for multilayer chip inductor application

In the present work, low-temperature fired MnxNi0.5−xCu0.25Zn0.25Fe2O4 + Bi2O3 (x = 0.0 to 0.45) was synthesized by the sol-gel auto combustion technique at a temperature of 1073 K. Bi2O3 (with 2 wt. %) was used as a sintering aid for improving the density, microstructure and lowering the sintering temperature of Mn-Ni-Cu-Zn ferrites. Synthesized samples were investigated for their structural, magnetic, and electrical properties such as density, porosity, saturation magnetization, and permeability as a function of Mn2+ substitution. Permeability and saturation magnetization were found to increase with the replacement of Ni2+ with Mn2+. Bulk density of 4.5 g/cm3 was observed for Mn-Ni-Cu-Zn ferrite with Bi2O3 additives which is greater than that of pure Mn-Ni-Cu-Zn ferrite (4.1 g/cm3). Saturation magnetization of NiCuZn ferrite increased from 37 to 63 emu/g with increase in Mn2+ substitution. Mn substituted NiCuZn ferrite shows higher complex permeability (μ′ = 672) than that of the pure NiCuZn ferrite (μ′ = 433). Curie temperature determined from temperature dependent permeability data shows that Tc attains maximum value of 707 K.

Low temperature combustion synthesis and magnetostructural properties of Co–Mn nanoferrites

In the present work, Co1−xMnxFe2O4 nanoparticles were synthesized by the low-temperature auto-combustion method. The thermal decomposition process was investigated by means of differential and thermal gravimetric analysis (TG-DTA) that showed the precursor yield the final product above 450°C. The phase purity and crystal lattice symmetry were estimated from X-ray diffraction (XRD). Microstructural features observed by scanning electron microscopy (SEM) demonstrates that the fine clustered particles were formed with an increase in average grain size with Mn2+ content. Fourier transform infrared spectroscopy (FTIR) study confirms the formation of spinel ferrite. Room temperature magnetization measurements showed that the magnetization Ms increases from 29 to 60emu/g and Hc increases from 13 to 28Oe with increase in Mn2+ content, which implies that these materials may be applicable for magnetic data storage and recording media.

The photoluminescence and magnetic properties of ZnAl2O4:Mn nanocrystals

The single-phase ZnAl2O4 phosphors with various components of Mn2+ dopant were fabricated by using hydrothermal method. The phosphors has been characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), photoluminescence (PL) spectra and vibrating sample magnetometer (VSM). The results of XRD and TEM measurements showed that the resultant nanoparticles were single crystal with octahedral and hexagonal shape, and after annealed, this shape had change. Green emission was observed from doped zinc aluminate with 427nm excitation. The temperature-dependant PL spectra revealed two emission peaks which exhibited different shifting tendency with a decrease in temperature. The room-temperature hysteresis loops of zinc aluminate nanoparticles showed magnetic behavior, and the magnetism disappeared gradually with the increase of Mn2+ doping contents.

ZnS:Mn2+ nanoparticles as compact layer to enhance the conversion efficiency of CdS QD-sensitized solar cells

The CdS quantum dots sensitized ZnO nanorods solar cells with ZnS:Mn2+ nanoparticles as compact layer were fabricated. The effects of Mn2+ doping concentration on the photovoltaic performance of ZnO/ZnS:Mn2+ photoanode were investigated. Besides the suppression of the back transfer of photoelectrons by ZnS:Mn2+ compact layer, with the increase of Mn2+ doping concentration, the energy level of conduction band of ZnS:Mn2+ nanoparticles turned lower, which is beneficial for the charge transfer from the conduction band of CdS. Thus, the photoelectric conversion efficiency of the cell with ZnS:Mn2+ (5%) exhibited ∼3.6 folds increments of as-synthesized bare ZnO solar cell.

Nox2-Dependent Redox Regulation of Calcium Influx in Dystrophic Skeletal Muscle

Duchenne Muscular Dystrophy (DMD) is an X-linked, muscle-wasting disease caused by deletions in the gene that encodes dystrophin, an integral muscle membrane protein that links the contractile proteins to the muscle membrane. Recent studies have suggested that increased Ca2+ influx into the muscle and increased production of free radicals (or reactive oxygen species, ROS) are essential for increased susceptibility of mdx muscle to damage. However, the source of the ROS, the Ca2+ channels affected, and the mechanism(s) of how mechanical stress results in altered regulation of these signaling pathways have yet to be determined. We hypothesis that NADPH oxidase (Nox2) drives excessive ROS production, increased Ca2+ influx, and muscle damage. Manganes (Mn2+) quench was used to assess the role of Nox2 dependent ROS on sarcolemmal Ca2+ influx in response to a physiological stretch and depolarization. Our results show that stretch-activated Ca2+ entry in mdx is significantly increased 4.2-fold (p<0.001) compared to WT, while K+-induced depolarization results in 20-fold (p<0.001) increase in Mn2+ quench in mdx skeletal muscle. Administration of either gp91ds-TAT, an inhibitor of Nox2, or reduced glutathione ethyl ester, a glutathione analogue, in mdx muscle reduces the Mn2+ quench rates back to the WT levels for both passive stretch and K+depolarization. Addition of BTP2, a calcium release activated calcium channel inhibitor, also significantly attenuates Mn2+ quench rates in mdx compared to WT. Our data supports a model in which Nox2 dependent redox modifications of stretch and depolarization activated Ca2+ channels leads to exuberant Ca2+ influx. Our results identify Nox2 as a potential therapeutic approach to minimize or delay the progressive DMD disease.

TRPC1 and Orai1 interact with STIM1 and Mediate Capacitative Calcium Entry Activated by Acute Hypoxia in Mouse Pulmonary Arterial Smooth Muscle Cells

The present study aimed to determine if TRPC1 and Orai1 interact with STIM1 and mediate CCE caused by acute hypoxia in mouse PASMCs. In primary cultured PASMCs loaded with fura‐2, acute hypoxia caused a transient followed by a sustained rise in intracellular Ca2+ concentration ([Ca2+]i). Acute hypoxia also increased the rate of Mn2+ quench of fura‐2 fluorescence that was inhibited by SKF 96365, Ni2+, La3+ and Gd3, exhibiting pharmacological properties characteristic of CCE. The nifedipine‐insensitive rise in [Ca2+]i and the increase in Mn2+ quench rate were both inhibited in cells treated with TRPC1 antibody, in cells transfected with STIM1 siRNA and cells transfected with Orai1 siRNA. Moreover, overexpression of STIM1 resulted in a marked increase in [Ca2+]i and Mn2+ quench rate caused by acute hypoxia, and they were reduced in cells treated with TRPC1 antibody and cells treated with Orai1 siRNA. Furthermore, TRPC1 and Orai1 co‐immunoprecipitate with STIM1 and the precipitation levels of TRPC1 and Orai1 were increased in cells exposed to acute hypoxia. Immunostaining showed co‐localizations of TRPC1‐STIM1 and Orai1‐STIM1, and the co‐localizations of these proteins were more apparent in acute hypoxia. These data provide direct evidence that TRPC1 and Orai1 channels mediate CCE through activation of STIM1 in mouse PASMCs in acute hypoxia. [Supported by HL49254 (JR Hume) and AHA Scientist Development Grant (LC Ng)]