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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,387 records · Page 77
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Sr{sub 1.98}Eu{sub 0.02}SiO{sub 4} luminescence whisker based on vapor-phase deposition: Facile synthesis, uniform morphology and enhanced luminescence properties

Highlights: • For the first time, it is possible to obtain Sr{sub 1.98}Eu{sub 0.02}SiO{sub 4} whisker. • The whiskers are smooth and uniform with L/D ratio over 50. • Durability and thermal stability of the whisker are enhanced. - Abstract: A high performance strontium silicate phosphor has been successfully synthesized though a facile vapor-phase deposition method. The product consists of single crystal whiskers which are smooth and uniform, and with a sectional equivalent diameter of around 5 μm; the aspect ratio is over 50 and no agglomeration can be observed. X-ray diffraction result confirmed that the crystal structure of the whisker was α’-Sr{sub 2}SiO{sub 4}. The exact chemical composition was Sr{sub 1.98}Eu{sub 0.02}SiO{sub 4} which was analyzed by energy dispersive spectrometer and inductively coupled plasma-mass spectrometer. The whisker shows broad green emission with peak at 523 nm ranging from 470 to 600 nm (excited at 370 nm). Compared with traditional Sr{sub 2}SiO{sub 4}:Eu phosphor, durability (at 85% humidity and 85 °C) and thermal stability of the whisker are obviously improved. Moreover, growth mechanism of the Sr{sub 1.98}Eu{sub 0.02}SiO{sub 4} whiskers is Vapor–Liquid–Solid. On a macro-scale, the product is still powder which makes it suitable for the current packaging process of WLEDs.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Facile solution-precipitation assisted synthesis and luminescence property of greenish-yellow emitting Ca{sub 6}Ba(PO{sub 4}){sub 4}O:Eu{sup 2+} phosphor

Highlights: • Ca{sub 6}Ba(PO{sub 4}){sub 4}O:Eu{sup 2+} phosphor was prepared by the solution-precipitation assisted route. • The phosphors have satisfactory smooth grain surface and particle size. • It shows greenish-yellow color emission (maximum at 540 nm) upon blue light excitation. • Eu{sup 2+} is coordinated with isolated oxygen atoms and those from PO{sub 4} polyhedra. - Abstract: Greenish-yellow emitting microcrystalline Ca{sub 6}Ba(PO{sub 4}){sub 4}O:Eu{sup 2+} phosphor was successfully prepared by a solution-precipitation assisted high temperature reaction method. Phase structure, morphology and/or luminescence properties of the precursor and the as-prepared phosphors were characterized. The phase-pure Ca{sub 6}Ba(PO{sub 4}){sub 4}O:Eu{sup 2+} phosphors were obtained with smooth grain surface and particle size of 2–8 μm. Ca{sub 6}Ba(PO{sub 4}){sub 4}O:Eu{sup 2+} exhibits bright greenish-yellow color emission with its maximum at 540 nm upon UV-blue light excitation. The maximum position of the broad emission band is independent on the calcination temperature. The emission intensity increases with increasing calcination temperature due to improved crystallinity. Besides, the presence of two Eu{sup 2+} emission centers in the Ca{sub 6}Ba(PO{sub 4}){sub 4}O crystal lattice was confirmed and the coordination effects are considered concerning the roles of isolated O atoms and those from the PO{sub 4} tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Fabrication of magnetic core PEI-silica shell particles

Highlights: • PEI-silica shell fabrication was developed for iron-carbonyl core material. • Magnetic separation of core-free by-product of the fabrication proved successful. • Varying fabrication method/concentration successfully tuned shell characteristics. • Sonication methods produced smooth coatings with a trend towards multicore particles. • Raspberry-like coatings were made by the slow addition, one- and two-pot methods. - Abstract: Magnetic core-silica shell particles combine the physico-chemical properties of the silica shell with the magnetic properties of the core. Seven possible particle coating methods utilizing the biomimetic polyamine polyethyleneimine (PEI) as the silication catalyst, have been identified and the objective of this study was to link the properties of the final PEI-silica coating with the methodology. The PEI-silica coated carbonyl iron particles were characterized via scanning electron microscopy, energy dispersive X-ray spectroscopy and Fourier transfer infrared spectroscopy. Varying the fabrication method and silane concentration successfully tuned the shell characteristics. Methods using sonication produced smooth more evenly distributed coatings with a tendency towards multicore particles. In contrast, raspberry-like coatings were produced via the slow addition, one- and two-pot methods. The magnetic separation process after synthesis achieved a degree of purification that makes these core–shell particles useful for potential applications that require specific surface interactions and the ease of magnetic separation.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Luminescence properties in relation to controllable morphologies of the InBO{sub 3}:Eu{sup 3+} phosphor

Graphical abstract: Four kinds of morphologies of Eu{sup 3+} doped indium borate of InBO{sub 3} phosphors have been prepared via a facile flux method only by adjusting the kinds of reaction boron source materials[(a)B{sub 2}O{sub 3}, (b)NH{sub 4}B{sub 5}O{sub 8}·4H{sub 2}O, (c)Li{sub 2}B{sub 4}O{sub 7}, (d)K{sub 2}B{sub 4}O{sub 7}·4H{sub 2}O], in which the monodisperse octahedral sample prepared with K{sub 2}B{sub 4}O{sub 7}·4H{sub 2}O as the boron source and Eu{sup 3+} doping concentration being 5% possesses the higher PL intensity and color purity, which can be used as a potential orange luminescent material. - Highlights: • InBO{sub 3}:Eu{sup 3+} phosphor with four morphologies were prepared by adjusting the boron source. • The doping concentration also has a great influence on the morphology. • The fluorescence performance is strongly correlated with morphology. • The smooth octahedral sample possesses the higher PL intensity and color purity. • InBO{sub 3}:Eu{sup 3+} smooth octahedra can be used as a potential orange luminescent material. - Abstract: Four kinds of morphologies of Eu{sup 3+} doped indium borate of the InBO{sub 3} phosphors have been prepared via a facile flux method only by adjusting the kinds of reaction boron source materials, which have been characterized by XRD, EDS and SEM. In addition, the doping concentration also has a great influence on the morphology of samples. Furthermore, the luminescence properties of the prepared InBO{sub 3}:Eu{sup 3+} samples have been investigated by photoluminescence (PL) spectra. The results show that the fluorescence performance is strongly correlated with morphologies. The prepared InBO{sub 3}:Eu{sup 3+} phosphors show strong orange emissions under ultraviolet excitation at 237 nm, in which the monodisperse octahedra sample prepared with K{sub 2}B{sub 4}O{sub 7}·4H{sub 2}O as the boron source and Eu{sup 3+} doping concentration being 5% possesses the higher PL intensity and color purity, which can be used as a potential orange luminescent material.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Structural and electrical properties of K{sub 3}Li{sub 2}Nb{sub 5}O{sub 15} thin film grown by pulsed laser deposition

Highlights: • (001)KLN tetragonal tungsten bronze thin film has been successfully deposited on MgO substrate using PLD. • Smooth and droplets-free surface has been obtained as evidenced by RHEED and AFM. • Impedance spectroscopy shows Debye type dielectric relaxation. • The ferroelectric character of the obtained (001)KLN film has been evidenced using capacitance voltage measurement. - Abstract: Potassium lithium niobate K{sub 3}Li{sub 2}Nb{sub 5}O{sub 15} (KLN) with tetragonal tungsten bronze-type structure (TTB) thin film was successfully deposited on MgO substrate by pulsed laser ablation method. The substrate was coated by a perovskite conductive layer of La{sub 0.5}Sr{sub 0.5}CoO{sub 3}. X-ray diffraction revealed (001) orientation with low mosaicity. The oriented film had smooth and droplets-free surface as evidenced by reflection high electron energy diffraction and atomic force microscopy. Using Pt top electrode, dielectric measurements indicated stable dielectric permittivity of about 400 up to 10{sup 5} Hz. A dielectric relaxation was also observed. Moreover, the capacitance voltage measurements of the obtained (001)KLN film show ferroelectric behavior. Our results provide useful insights into the growth of tetragonal tungsten and other complex materials. These results will be useful for the growth and integration of epitaxial TTB thin films on perovskite and Si substrates.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Study of magneto-optical characteristics of cerium incorporated yttrium iron garnet films

Highlights: • Ce:YIG films deposited by sol–gel method. • XRD results shows crystallite size of films decreases by Ce concentrations. • Morphological studies indicate of smooth and connected surface for all films. • Ce ions increased Faraday rotation of YIG films. - Abstract: In the current study, yttrium iron garnet films incorporated with cerium with the general formula of Ce{sub x}Y{sub 3-x}Fe{sub 5}O{sub 12} and values of (x = 0, 0.1, 0.3, 0.5, 0.7) were prepared through sol–gel method using spin coating technique and heating treatment on quartz substrates. Prepared samples were studied to check physical characteristics. X-ray diffraction analysis (XRD), scanning electron microscope (SEM), atomic force microscope (AFM) and vibrating sample magnetometer (VSM) were applied to study the impact of Ce impurities on the structural characteristic, surface morphology of films and magnetic properties, respectively. Faraday rotation values of samples were measured at the wavelength of 632 nm. The image of the atomic force microscope (AFM) of the prepared samples shows that the films have a continuous and smooth surface.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Nd3+ Doping effect on the optical and electrical properties of SnO2 thin films prepared by nebulizer spray pyrolysis for opto-electronic application

Highlights: • High quality, Nd:SnO{sub 2} thin films prepared using simple nebulizer spray pyrolysis technique. • Characterizations of the films confirmed good crystallinity and smooth surface morphology. • High optical transparency with low electrical resistivity in nebulizer spray pyrolysis prepared Nd: SnO{sub 2} thin films is presented. - Abstract: Neodymium doped tin oxide (Nd: SnO{sub 2}) thin films were deposited on heated glass substrates with different Nd concentrations (0, 2, 4 and 6 %) by nebulizer spray pyrolysis method. Effects of Nd doping on structural, optical and electrical properties of the prepared films were investigated. X-ray diffraction study confirmed that all the deposited Nd: SnO{sub 2} films are in polycrystalline tetragonal structure with (211) preferential orientation. FESEM images showed that the prepared SnO{sub 2} particles are in nano-size in spherical shape, completely covering the substrate. AFM topology showed smooth deposition of the films with minimum surface roughness. The films showed maximum optical transmittance 90 % in the visible region with a band gap value 3.67 eV, also showed low refractive index and extinction coefficients. Room temperature photoluminescence (PL) spectrum exhibited a strong UV emission peak at 356 nm for all the films. All the Nd: SnO{sub 2} films displayed n-type conductivity with low electrical resistivity 5.88 × 10{sup −4} (Ω cm) for 4 % Nd doping. As the films showed good figure of merit (ϕ) values, these Nd doped SnO{sub 2} thin films can perform better role in optoelectronic device.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

ICP etching of GaN microstructures in a Cl 2 –Ar plasma with subnanometer-scale sidewall surface roughness

In this work, substrate temperature, RF power, and ICP power were investigated for their effects on GaN micropillar sidewall roughness and etch characteristics. Elevated substrate temperature was shown to improve the sidewall etch morphology at low RF powers (reduced physical bombardment) and low ICP powers (lower plasma densities). Increased lateral etching is observed with both increased ICP power and substrate temperature, which both act to increase the chemical component of the etch. Etch conditions with a high chemical driving force resulted in faceting along the a-plane on the sidewalls. This faceting produced extremely smooth surfaces with root-meansquare roughness (R q ) as low as 0.20 nm which is comparable to typical epitaxy-ready surfaces and smaller than the a-plane lattice spacing of 0.3186 nm. The smooth surfaces produced in this study enable possibilities for laser facets or for new device structures that require high quality surfaces for GaN regrowth.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Infinitely rugged intra-cage potential energy landscape in metallic glasses caused by many-body interaction

The absence of translational symmetry in glassy materials poses a significant challenge in establishing effective structure-property relationships in real space. Consequently, the potential energy landscape (PEL) in phase space is widely utilized to comprehend the complex phenomena in glasses. The classical PEL features a two-scale profile comprising mega-basins and sub-basins, corresponding to α-relaxations (e.g. glass transition) and β-relaxations (e.g. local cage-breaking atomic rearrangements), respectively. Recent studies, however, reveal that sub-basins are not smooth and contain finer structures, the origins of which remain elusive. Here we probe the smoothness of sub-basin bottoms in glasses' PEL by introducing small intra-cage cyclic loading and then measuring the net changes in atomic-level stresses. Compared to glasses with pair interaction, glasses with many-body interaction exhibit orders-of-magnitude larger and loading-dependent stress changes even before the first cage-breaking event takes place, which reflect much more feature-rich sub-basins. We further demonstrate this stark contrast stems from the spatial distribution of individual atom's constraining force field. Specifically, at vanishing perturbations, many-body interactions disrupt the positive-definite synchrony in energy variations of the perturbed atom and the whole system, causing inherently less confined atomic responses and infinitely rugged sub-basins. The implications of these findings for the selective addition or removal of fine structures in the PEL and the subsequent tuning of glassy materials' responses to external stimuli are also explored.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Electropolishing parameters study for surface smoothening of low-$\beta$650 MHz five-cell niobium superconducting radio frequency cavity

Electropolishing (EP) is applied to niobium (Nb) superconducting radio frequency (SRF) cavities, which are used in particle accelerators for their surface treatment. The EP process for 1.3 GHz cavities has been extensively studied earlier. In this work, a parametric study on EP of low-β (0.61) 650 MHz Nb SRF cavities (LB650), which will be used in pre-production cryomodule for proton improvement plan-II (PIP-II) linear accelerator, was conducted to determine adequate EP conditions for attaining a smooth surface of the cavities. EP performed with the standard parameters and an initial cathode (cathode-I) having a cathode surface area of ~5% of the cavity surface area yielded a rough equator surface of the cavity. The grain step height on the equator weld position was measured to be ~ 32 μm. The rough surface was attributed to preferential grain etching confirmed by a polarization curve showing a linear relationship between the EP current and voltage and the absence of the current plateau region. The cathode was modified to make its surface area twice that of cathode-I. The modified cathode (cathode-M) provided a current plateau region in the corresponding I-V curves measured at different cavity temperatures. The onset voltage for the plateau was found to be higher at higher cavity temperatures. Here this study revealed that even with cathode-M, the standard 18 V was low for EP of such large-sized cavities when the cavity temperature was 18 °C. EP performed at a higher voltage of 22–24.5 V with cathode-M yielded a smooth surface with a grain step height of only 0.6 μm. The applied EP conditions also improved removal uniformity along the cavity length. In contrast to the cavity treated with cathode-I, the cavities treated with cathode-M achieved a significantly higher accelerating gradient (E acc ) in vertical tests conducted in a cryostat at 2 K. The modified EP was found efficient to produce the cavities that achieved E acc of 22.4 MV/m, required by PIP II project in the baseline RF tests, to qualify for further surface processing used to enhance their quality factors.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

An Open-Source Virtual Testbed for a Real Net-Zero Energy Community

Net zero energy communities (NZECs) are critical to ensure sustainability and resilience of modernized power systems. System modeling helps overcome technical challenges in designing and operating NZECs. In this paper, we present the modeling work based on a real NZEC. Two sets of models are developed: higher-fidelity physics-based models considering the interaction between subsystems of the studied NZEC and capturing fast-dynamics; and lower-fidelity data-driven models requiring less resource to establish and/or run. All models are validated against measurements from this real NZEC. In addition, we create a simulation framework which streamlines the processes for simulation and thus allows using developed models to form a virtual testbed. To demonstrate the usage of the virtual testbed, a case study is conducted where a building-to-grid integration control is evaluated via simulation. The evaluation results suggest that the tested control significantly smooths the power draw of the studied community and doesn’t sacrifice the thermal comfort to a great extent.

Huang, Sen↗
DOE OSTI2016

TW-01, a piperazinedione-derived compound, inhibits Ras-mediated cell proliferation and angioplasty-induced vascular restenosis

Purpose: Vascular smooth muscle cell (VSMC) proliferation plays a critical role in the pathogenesis of atherosclerosis and restenosis. This study investigated piperazinedione derived compound TW-01-mediated inhibitory effects on VSMC proliferation and intimal hyperplasia. Methods: Cell proliferation was determined using [{sup 3}H]-thymidine incorporation and MTT assay; cell cycle distribution was measured using flow cytometry; proteins and mRNA expression were determined using western blotting and RT-PCR analyses; DNA binding activity of nuclear factor-κB (NF-κB), as measured using enzyme-linked immunosorbent assays (ELISA); in vivo effects of TW-01 were determined using balloon angioplasty in the rat. Results: TW-01 significantly inhibited cell proliferation. At the concentrations used, no cytotoxic effects were observed. Three predominant signaling pathways were inhibited by TW-01: (a) extracellular signal-regulated kinase (ERK)1/2 mitogen-activated protein kinase (MAPK) activation and its downstream effectors of c-fos, c-jun, and c-myc; (b) DNA binding activity of nuclear factor-κB (NF-κB); and, (c) Akt/protein kinase B (PKB) and cell cycle progression. Furthermore, TW-01 also inhibited Ras activation, a shared upstream event of each of these signaling cascades. In vascular injury studies, oral administration of TW-01 significantly suppressed intimal hyperplasia induced by balloon angioplasty. Conclusion: The present study suggests that TW-01 might be a potential candidate for atherosclerosis treatment. - Highlights: • TW-01significantly inhibits vascular smooth muscle cell proliferation. • TW-01 inhibits ERK, Akt and Ras pathway and DNA binding activity of NF-κB. • TW-01 significantly suppresses intimal hyperplasia induced by balloon angioplasty. • TW-01 might be a potential candidate for atherosclerosis treatment.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2014

EGF–FGF{sub 2} stimulates the proliferation and improves the neuronal commitment of mouse epidermal neural crest stem cells (EPI-NCSCs)

Epidermal neural crest stem cells (EPI-NCSCs), which reside in the bulge of hair follicles, are attractive candidates for several applications in cell therapy, drug screening and tissue engineering. As suggested remnants of the embryonic neural crest (NC) in an adult location, EPI-NCSCs are able to generate a wide variety of cell types and are readily accessible by a minimally invasive procedure. Since the combination of epidermal growth factor (EGF) and fibroblast growth factor type 2 (FGF{sub 2}) is mitogenic and promotes the neuronal commitment of various stem cell populations, we examined its effects in the proliferation and neuronal potential of mouse EPI-NCSCs. By using a recognized culture protocol of bulge whiskers follicles, we were able to isolate a population of EPI-NCSCs, characterized by the migratory potential, cell morphology and expression of phenotypic markers of NC cells. EPI-NCSCs expressed neuronal, glial and smooth muscle markers and exhibited the NC-like fibroblastic morphology. The treatment with the combination EGF and FGF{sub 2}, however, increased their proliferation rate and promoted the acquisition of a neuronal-like morphology accompanied by reorganization of neural cytoskeletal proteins βIII-tubulin and nestin, as well as upregulation of the pan neuronal marker βIII-tubulin and down regulation of the undifferentiated NC, glial and smooth muscle cell markers. Moreover, the treatment enhanced the response of EPI-NCSCs to neurogenic stimulation, as evidenced by induction of GAP43, and increased expression of Mash-1 in neuron-like cell, both neuronal-specific proteins. Together, the results suggest that the combination of EGF–FGF2 stimulates the proliferation and improves the neuronal potential of EPI-NCSCs similarly to embryonic NC cells, ES cells and neural progenitor/stem cells of the central nervous system and highlights the advantage of using EGF–FGF{sub 2} in neuronal differentiation protocols. - Highlights: • EPI-NCSCs express undifferentiated NC and lineage-specific markers. • EGF–FGF{sub 2} supports in vitro expansion of EPI-NCSCs. • EGF–FGF{sub 2} promotes acquisition of neuron-like morphology by EPI-NCSCs. • EGF–FGF{sub 2} up regulates the expression of the pan-neuronal marker βIII-tubulin. • EGF–FGF{sub 2} enhances the response of EPI-NCSCs to neurogenic stimulation in vitro.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Polymer microfiber meshes facilitate cardiac differentiation of c-kit{sup +} human cardiac stem cells

Electrospun microfiber meshes have been shown to support the proliferation and differentiation of many types of stem cells, but the phenotypic fate of c-kit{sup +} human cardiac stem cells (hCSCs) have not been explored. To this end, we utilized thin (~5 µm) elastomeric meshes consisting of aligned 1.7 µm diameter poly (ester-urethane urea) microfibers as substrates to examine their effect on hCSC viability, morphology, proliferation, and differentiation relative to cells cultured on tissue culture polystyrene (TCPS). The results showed that cells on microfiber meshes displayed an elongated morphology aligned in the direction of fiber orientation, lower proliferation rates, but increased expressions of genes and proteins majorly associated with cardiomyocyte phenotype. The early (NK2 homeobox 5, Nkx2.5) and late (cardiac troponin I, cTnI) cardiomyocyte genes were significantly increased on meshes (Nkx=2.5 56.2±13.0, cTnl=2.9±0.56,) over TCPS (Nkx2.5=4.2±0.9, cTnl=1.6±0.5, n=9, p<0.05 for both groups) after differentiation. In contrast, expressions of smooth muscle markers, Gata6 and myosin heavy chain (SM-MHC), were decreased on meshes. Immunocytochemical analysis with cardiac antibody exhibited the similar pattern of above cardiac differentiation. We conclude that aligned microfiber meshes are suitable for guiding cardiac differentiation of hCSCs and may facilitate stem cell-based therapies for treatment of cardiac diseases. - Highlights: • First study to characterize c-kit{sup +} human cardiac stem cells on microfiber meshes. • Microfiber meshes seem reducing cell proliferation, but no effect on cell viability. • Microfiber meshes facilitate the elongation of human cardiac stem cells in culture. • Cardiac but not smooth muscle differentiation were enhanced on microfiber meshes. • Microfiber meshes may be used as cardiac patches in cell-based cardiac therapy.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Atractylenolide I restores HO-1 expression and inhibits Ox-LDL-induced VSMCs proliferation, migration and inflammatory responses in vitro

Pathogenesis of atherosclerosis is characterized by the proliferation and migration of vascular smooth muscle cells (VSMCs) and inflammatory lesions. The aim of this study is to elucidate the effect of atractylenolide I (AO-I) on smooth muscle cell inflammation, proliferation and migration induced by oxidized modified low density lipoprotein (Ox-LDL). Here, We found that atractylenolide I inhibited Ox-LDL-induced VSMCs proliferation and migration in a dose-dependent manner, and decreased the production of inflammatory cytokines and the expression of monocyte chemoattractant protein-1 (MCP-1) in VSMCs. The study also identified that AO-I prominently inhibited p38-MAPK and NF-κB activation. More importantly, the specific heme oxygenase-1 (HO-1) inhibitor zinc protoporphyrin (ZnPP) IX partially abolished the beneficial effects of atractylenolide I on Ox-LDL-induced VSMCs. Furthermore, atractylenolide I blocked the foam cell formation in macrophages induced by Ox-LDL. In summary, inhibitory roles of AO-I in VSMCs proliferation and migration, lipid peroxidation and subsequent inflammatory responses might contribute to the anti-atherosclerotic property of AO-I. - Highlights: • AO-I inhibited Ox-LDL-induced VSMCs proliferation and migration. • AO-I alleviated inflammatory response via inhibiting TNF-α, IL-6 and NO production. • AO-I restored HO-1 expression and down-regulated PCNA expression. • MCP-1 overexpression is potentially regulated by NF-κB and p38 MAPK pathway. • AO-I possesses strong anti-lipid peroxidation effect.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Mitochondria control acute and chronic responses to hypoxia

There are numerous mechanisms by which mammals respond to hypoxia. These include acute changes in pulmonary arterial tone due to smooth muscle cell contraction, acute increases in respiration triggered by the carotid body chemosensory cells, and chronic changes such as induction of red blood cell proliferation and angiogenesis by hypoxia inducible factor targets erythropoietin and vascular endothelial growth factor, respectively. Mitochondria account for the majority of oxygen consumption in the cell and have recently been appreciated to serve as signaling organelles required for the initiation or propagation of numerous homeostatic mechanisms. Mitochondria can influence cell signaling by production of reactive oxygen species and metabolites. Here we review recent evidence that mitochondrial signals can imitate acute and chronic hypoxia responses. - Highlights: • Mitochondrial electron transport chain function plays a key role in organismal hypoxia sensing. • ETC Complex III ROS are necessary for acute hypoxic contraction of pulmonary smooth muscle cells. • ETC Complex I function is essential for acute glomus cell sensing of hypoxemia in the carotid body. • mROS are required for HIF stabilization and organismal adaptation to hypoxia.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

NF-κB mediated miR-130a modulation in lung microvascular cell remodeling: Implication in pulmonary hypertension

Pulmonary arterial hypertension (PAH) is a progressive pulmonary vascular disease which is associated with pulmonary arterial endothelial cells (PAEC) dysfunction and pulmonary arterial smooth muscle cells proliferation. Moreover, inflammation is contributing a critical role in EC dysfunction and remains elusive. Nuclear factor-kappa B (NF-κB) is a master transcriptional regulator in various cardiovascular pathologies; but, NF-κB's role in EC dysfunction in unknown. Our previous study using cardiac and lung specific IκBα mutant mice (3 M and IKBM) showed that PAH induced right ventricular hypertrophy (RVH) was prevented in monocrotaline (MCT) treated 3 M and IKBM mice, compared to the wild-type mice. Recently, microRNAs (miRNAs) have emerged as a new class of post-transcriptional regulators in vascular remodeling; but, NF-κB regulated miRNA modulation in EC dysfunction is unknown. Using miRNA array analysis, we identified miR-130a which is upregulated in MCT-induced PAH mouse model, as a possible candidate to study. We showed that overexpressing miR-130a in lung microvascular endothelial cells (MVEC) promoted activation of α-smooth muscle actin, a critical component in endothelial-to-mesenchymal transition in EC remodeling. In this study, we demonstrated that bone morphogenetic protein receptor 2 (BMPR2) was a target for miR-130a and miR-130a was regulated by NF-κB which controlled apoptosis and vascular genes in MVEC. The findings reveal that NF-κB-mediated miR-130a modulation is critical in lung vascular remodeling. - Highlights: • Demonstrates a positive feedback regulation of miR-130a with NF-κB in lung MVEC. • MiR-130a targets BMPR2 and modulates EndMT in lung MVEC. • Both NF-κB and miR-130a contribute a primary role in the pathogenesis of PAH.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2021

Dexamethasone reduces the formation of thoracic aortic aneurysm and dissection in a murine model

Highlights: • Dexamethasone attenuated thoracic aortic aneurysm and dissection in a mouse model. • Dexamethasone reduced infiltration of inflammatory cell and apoptosis of vascular smooth muscle cell and fibroblast. • Dexamethasone partly alleviated degradation of collagen and phenotype switch. • DEX might ameliorate thoracic aortic aneurysm and dissection by suppressing NF-κB signaling pathway. Thoracic aortic aneurysm and dissection (TAAD) is a life-threatening vascular disease with no effective pharmaceutical therapies currently available. Inflammation plays a key role in the progression of aneurysms. Dexamethasone (DEX), a synthetic glucocorticoid, has showed alleviating effects on cells in vitro from TAAD patients. Here we performed a study aiming at investigating the protective role of DEX in a β-aminopropionitrile monofumarate (BAPN)-induced TAAD mouse model. DEX (dose: 0.04 mg/kg/day) treatment significantly reduced the aortic diameter and inhibited TAAD formation. DEX reduced infiltration of macrophages and neutrophils, apoptosis of vascular smooth muscle cells (VSMCs), expression of metalloproteinase 2/9, and extracellular matrix degradation in BAPN-treated TAAD mice. Furthermore, DEX therapy downregulated the expression of p-p65 in macrophages and VSMCs, which suggested that DEX might ameliorate BAPN-induced TAAD by suppressing NF-κB signaling. Therefore, DEX therapy attenuates the progression of BAPN-induced TAAD murine model and could be used as an effective adjuvant therapy for treating TAAD.

60 APPLIED LIFE SCIENCES↗