Structural characterisation and luminescence properties of nanostructured lanthanide-doped Sc2O3 prepared by propellant synthesis

Nanocrystalline powders of undoped and lanthanide-doped scandium oxide were prepared by propellant synthesis and characterized by x-ray powder diffraction, electron microscopy, EDX spectroscopy and luminescence spectroscopy. The obtained material has the Sc2O3 cubic structure (space group ) with unit cell parameter increasing with the size of the dopant. The crystallite size is in the range 20-40 nm. The lanthanide-doped samples form Sc2-xLnxO3 solid solutions with x 480.2 (Ln = Eu or Er). No inhomogeneity was found by microanalysis on the micron scale. The emission spectrum of the Eu3+ doped Sc 2O3 sample shows strong bands in the visible region assigned to 4f-4f transitions of the lanthanide ion

Internal Jugular Vein Cross-Sectional Area and Cerebrospinal Fluid Pulsatility in the Aqueduct of Sylvius: A Comparative Study between Healthy Subjects and Multiple Sclerosis Patients

Objectives Constricted cerebral venous outflow has been linked with increased cerebrospinal fluid (CSF) pulsatility in the aqueduct of Sylvius in multiple sclerosis (MS) patients and healthy individuals. This study investigates the relationship between CSF pulsatility and internal jugular vein (IJV) cross-sectional area (CSA) in these two groups, something previously unknown. Methods 65 relapsing-remitting MS patients (50.8% female; mean age = 43.8 years) and 74 healthy controls (HCs) (54.1% female; mean age = 43.9 years) were investigated. CSF flow quantification was performed on cine phase-contrast MRI, while IJV-CSA was calculated using magnetic resonance venography. Statistical analysis involved correlation, and partial least squares correlation analysis (PLSCA). Results PLSCA revealed a significant difference (p<0.001; effect size = 1.072) between MS patients and HCs in the positive relationship between CSF pulsatility and IJV-CSA at C5-T1, something not detected at C2-C4. Controlling for age and cardiovascular risk factors, statistical trends were identified in HCs between: increased net positive CSF flow (NPF) and increased IJV-CSA at C5-C6 (left: r = 0.374, p = 0.016; right: r = 0.364, p = 0.019) and C4 (left: r = 0.361, p = 0.020); and increased net negative CSF flow and increased left IJV-CSA at C5-C6 (r = -0.348, p = 0.026) and C4 (r = -0.324, p = 0.039), whereas in MS patients a trend was only identified between increased NPF and increased left IJV-CSA at C5-C6 (r = 0.351, p = 0.021). Overall, correlations were weaker in MS patients (p = 0.015). Conclusions In healthy adults, increased CSF pulsatility is associated with increased IJV-CSA in the lower cervix (independent of age and cardiovascular risk factors), suggesting a biomechanical link between the two. This relationship is altered in MS patients

Endothelin-1 as a neuropeptide: neurotransmitter or neurovascular effects?

Endothelin-1 (ET-1) is an endothelium-derived peptide that also possesses potent mitogenic activity. There is also a suggestion the ET-1 is a neuropeptide, based mainly on its histological identification in both the central and peripheral nervous system in a number of species, including man. A neuropeptide role for ET-1 is supported by studies showing a variety of effects caused following its administration into different regions of the brain and by application to peripheral nerves. In addition there are studies proposing that ET-1 is implicated in a number of neural circuits where its transmitter affects range from a role in pain and temperature control to its action on the hypothalamo-neurosecretory system. While the effect of ET-1 on nerve tissue is beyond doubt, its action on nerve blood flow is often ignored. Here, we review data generated in a number of species and using a variety of experimental models. Studies range from those showing the distribution of ET-1 and its receptors in nerve tissue to those describing numerous neurally-mediated effects of ET-1

Nanocrystalline lanthanide-doped Lu3Ga5O12 garnets: interesting materials for light-emitting devices

Nanocrystalline Lu3Ga5O12, with average particle sizes of 40 nm, doped with a wide variety of luminescent trivalent lanthanide ions have been prepared using a sol\u2013gel technique. The structural and morphological properties of the powders have been investigated by x-ray powder diffraction, high resolution transmission electron microscopy and Raman spectroscopy. Structural data have been refined and are presented for Pr3+, Eu3+, Gd3+, Ho3+, Er3+ and Tm3+ dopants, while room temperature excited luminescence spectra and emission decay curves of Eu3+-, Tm3+- and Ho3+-doped Lu3Ga5O12 nanocrystals have been measured and are discussed. The Eu3+ emission spectrum shows typical bands due to 5D0 \u21927FJ (J = 0, 1, 2, 3, 4) transitions and the broadening of these emission bands with the non-exponential behaviour of the decay curves indicates the presence of structural disorder around the lanthanide ions. Lanthanide-doped nanocrystalline Lu3Ga5O12 materials show better luminescence intensities compared to Y2O3, Gd3Ga5O12 and Y3Al5O12 nanocrystalline hosts. Moreover, the upconversion emission intensity in the blue-green region for the Tm3+- and Ho3+-doped samples shows a significant increase upon 647.5 nm excitation with respect to other common oxide hosts doped with the same lanthanide ions

Structural investigation and Anti-Stokes emission of scandium oxide nanocrystals activated with trivalent erbium

The structural and emission (Stokes and anti-Stokes) properties of Sc2O3: Er3+ nanocrystals doped with 0.1, 1, and 10 mol % Er3+ were investigated. The nanocrystalline powders were characterized using X-ray scattering as well as transmission and scanning electron microscopy. The samples showed a very porous, open microstructure with the particles having a narrow distribution of sizes (10-60 nm). Furthermore, the mechanisms responsible for the anti-Stokes emission (lambda(exc) = 980 nm) were elucidated. We observed that the processes responsible for populating the green (H-2(11/2), S-4(3/2)) and red (F-4(9/2)) emitting states were dependent upon the concentration of the dopant ion. In 0.1 mol % nanocrystalline Sc2O3: Er3+, upconversion was determined to occur via excited state absorption while in the 10 mol % sample, energy transfer upconversion was the dominant mechanism. An enhancement of the red anti-Stokes emission from the F-4(9/2) --> I-4(15/2) transition was observed in Sc2O3: Er3+ nanocrystals as a function of Er3+ concentration. This was the result of two independent processes responsible for directly populating the F-4(9/2) state and bypassing the green emitting levels (H-2(11/2) and S-4(3/2)). Furthermore, the red enhancement was found to be more pronounced compared to identically doped Y2O3: Er3+ nanocrystals. An explanation for this phenomenon is presented and discussed

Best Practices for EdD Comprehensive Exams and Capstone Projects: Students\u27 Attitudes and Perspectives of Outcomes in an Online Program

This research was guided by a problem of practice experienced by an EdD program, which transitioned to a fully online modality during the pandemic and rapidly grew in enrollment. The problem evaluated was ensuring the redesigned program milestones – capstone and comprehensive exam – are feasible given the size of the program. The current study utilized descriptive research design to provide a comprehensive description of educational phenomena. The study was conducted at a large, public research university in the South. A total of 316 students enrolled in the program and were invited to complete the survey, of which 131 responses were analyzed. Results revealed differences in students’ attitudes toward capstone projects and comprehensive exams, with a strong correlation between students’ experiences with capstone projects and comprehensive exams and their overall academic self-efficacy while in the progra

guanosine 5'-triphosphate (GTP) en position 5'-terminale des RNA en cours de synthèse dans les cellules de HeLa et de foie de rat

info:eu-repo/semantics/publishe

Characterization of nanoporous Lanthanide-doped YAG powders obtained by propellant synthesis

In the present work, we explored the possibility of obtaining nanocrystalline powders of lanthanide-doped Y3Al5O12 (YAG, yttrium aluminum garnet) using solution propellant synthesis, a novel technique that has been proven to be capable of producing nanopowders of numerous oxides at relatively low temperatures and in a rapid way. A series of YAG samples containing a number of different trivalent lanthanide ions (Eu, Er, Ho, Tm) was produced. Samples were characterized by X-ray diffraction for phase identification and line broadening analysis, and by electron microscopy (SEM and HRTEM) for morphological and nanostructural investigation. The samples have a polycrystalline porous structure made up of particles in the nanometer range. Crystallites have a high degree of disorder; the ones doped with Eu3+ are characterized by an intense and well-resolved luminescence spectrum in the visible region

Characterization of nanoporous lanthanide-doped YAG powders obtained by propellant synthesis

In the present work, we explored the possibility of obtaining nanocrystalline powders of lanthanide-doped Y3Al5O12 (YAG, yttrium aluminum garnet) using solution propellant synthesis, a novel technique that has been proven to be capable of producing nanopowders of numerous oxides at relatively low temperatures and in a rapid way. A series of YAG samples containing a number of different trivalent lanthanide ions (Eu, Er, Ho, Tm) was produced. Samples were characterized by X-ray diffraction for phase identification and line broadening analysis, and by electron microscopy (SEM and HRTEM) for morphological and nanostructural investigation. The samples have a polycrystalline porous structure made up of particles in the nanometer range. Crystallites have a high degree of disorder; the ones doped with Eu3+ are characterized by an intense and well-resolved luminescence spectrum in the visible region