Control of Luminescence by Tuning of Crystal Symmetry and Local Structure in Mn4+‐Activated Narrow Band Fluoride Phosphors

Mn⁴⁺‐doped fluoride phosphors have been widely used in wide‐gamut backlighting devices because of their extremely narrow emission band. Solid solutions of Na₂(Si_xGe_1?x)F₆:Mn⁴⁺ and Na₂(Ge_yTi_1?y)F₆:Mn⁴⁺ were successfully synthesized to elucidate the behavior of the zero‐phonon line (ZPL) in different structures. The ratio between ZPL and the highest emission intensity υ₆ phonon sideband exhibits a strong relationship with luminescent decay rate. First‐principles calculations are conducted to model the variation in the structural and electronic properties of the prepared solid solutions as a function of the composition. To compensate for the limitations of the Rietveld refinement, electron paramagnetic resonance and high‐resolution steady‐state emission spectra are used to confirm the diverse local environment for Mn⁴⁺ in the structure. Finally, the spectral luminous efficacy of radiation (LER) is used to reveal the important role of ZPL in practical applications.     

Gold three dimensional film electrode prepared from oppositely charged nanoparticles

Nanoparticulate gold film electrodes were prepared from oppositely charged gold nanoparticles (c.a. 6 nm diameter) by a layer-by-layer approach without application of linker molecules. This was done by alternative immersion of indium tin oxide plates into suspensions of positively and negatively charged particles. The thickness of the film and the magnitude of the characteristic surface plasmon band are proportional to the number of immersion and withdrawal steps. Up to nine double immersions and withdrawal steps can be used to systematically increase the amount of nanoparticulate gold material. The capacitive current density and current density of hydrogen peroxide reduction are proportional to the number of immersion and withdrawal steps. Highly efficient and low overpotential glucose electrooxidation in alkaline solution is demonstrated.     

Multiple periodic solutions for a nonlinear suspension bridge equation

We investigate nonlinear oscillations in a fourth-order partialdifferential equation which models a suspension bridge. Previouswork establishes multiple periodic solutions when a parameterexceeds a certain eigenvalue. In this paper, we use Leray-Schauderdegree theory to prove that if the parameter is increased further,beyond a second eigenvalue, then additional solutions are created.     

Experimental Procedures for Sensitive and Reproducible In Situ EPR Tooth Dosimetry

In vivo electron paramagnetic resonance (EPR) tooth dosimetry provides a means for non-invasive retrospective assessment of personal radiation exposure. While there is a clear need for such capabilities following radiation accidents, the most pressing need for the development of this technology is the heightened likelihood of terrorist events or nuclear conflicts. This technique will enable such measurements to be made at the site of an incident, while the subject is present, to assist emergency personnel as they perform triage for the affected population. At Dartmouth Medical School this development is currently being tested with normal volunteers with irradiated teeth placed in their mouths and with patients who have undergone radiation therapy. Here we describe progress in practical procedures to provide accurate and reproducible in vivo dose estimates.     

The smooth cohomology ofN=2 supersymmetric Landau-Ginzburg field theories

We compute the smooth cohomology (both unrestricted and compactly supported) of the supercharge of an ultraviolet cutoffN=2 supersymmetric Landau-Ginzburg field theory.Supported in part by the National Science Foundation under grant DMS-9206936.Supported in part by the Department of Energy under grant DE-FG02-88ER25065.     

Equivariant entire cyclic cohomology: I. Finite groups

We extend the framework of entire cyclic cohomology to the equivariant context.Supported in part by the Department of Energy under Grant DE-FG02-88ER25065.     

Chern character in equivariant entire cyclic cohomology

We construct the Chern character in the equivariant entire cyclic cohomology. We prove a general index theorem for theG-invariant Dirac operator.Supported in part by the Department of Energy under Grant DE-FG02-88ER25065.     

Effective action for the Yukawa2 quantum field theory

Using a rigorous version of the renormalization group we construct the effective action for theY ₂ model. The construction starts with integrating out the bosonic field which eliminates the large fields problem. Studying the soobtained purely fermionic theory proceeds by a series of convergent perturbation expansions. We show that the continuum limit of the effective action exists and its perturbation expansion is Borel summable.     

Progranulin is expressed within motor neurons and promotes neuronal cell survival

Background

Progranulin is a secreted high molecular weight growth factor bearing seven and one half copies of the cysteine-rich granulin-epithelin motif. While inappropriate over-expression of the progranulin gene has been associated with many cancers, haploinsufficiency leads to atrophy of the frontotemporal lobes and development of a form of dementia (frontotemporal lobar degeneration with ubiquitin positive inclusions, FTLD-U) associated with the formation of ubiquitinated inclusions. Recent reports indicate that progranulin has neurotrophic effects, which, if confirmed would make progranulin the only neuroprotective growth factor that has been associated genetically with a neurological disease in humans. Preliminary studies indicated high progranulin gene expression in spinal cord motor neurons. However, it is uncertain what the role of Progranulin is in normal or diseased motor neuron function. We have investigated progranulin gene expression and subcellular localization in cultured mouse embryonic motor neurons and examined the effect of progranulin over-expression and knockdown in the NSC-34 immortalized motor neuron cell line upon proliferation and survival.

Results

In situ hybridisation and immunohistochemical techniques revealed that the progranulin gene is highly expressed by motor neurons within the mouse spinal cord and in primary cultures of dissociated mouse embryonic spinal cord-dorsal root ganglia. Confocal microscopy coupled to immunocytochemistry together with the use of a progranulin-green fluorescent protein fusion construct revealed progranulin to be located within compartments of the secretory pathway including the Golgi apparatus. Stable transfection of the human progranulin gene into the NSC-34 motor neuron cell line stimulates the appearance of dendritic structures and provides sufficient trophic stimulus to survive serum deprivation for long periods (up to two months). This is mediated at least in part through an anti-apoptotic mechanism. Control cells, while expressing basal levels of progranulin do not survive in serum free conditions. Knockdown of progranulin expression using shRNA technology further reduced cell survival.

Conclusion

Neurons are among the most long-lived cells in the body and are subject to low levels of toxic challenges throughout life. We have demonstrated that progranulin is abundantly expressed in motor neurons and is cytoprotective over prolonged periods when over-expressed in a neuronal cell line. This work highlights the importance of progranulin as neuroprotective growth factor and may represent a therapeutic target for neurodegenerative diseases including motor neuron disease.