589 research outputs found
Predicting the impact of temperature dependent multi-phonon relaxation processes on the photon avalanche behavior in Tm3+: NaYF4 nanoparticles
No full textPhoton avalanche (PA) is an anti-Stokes process in which lanthanide-doped materials can emit upconverted luminescence in a highly non-linear manner. PA was recently demonstrated in thulium (III)-doped NaYF4 colloidal nanoparticles at room temperature, with reported nonlinearities (power factors) exceeding 30. Importantly, good rate-equations model agreement with experimental data was achieved, which enabled the derivation of the rates of energy transfer processes, providing a foundation for further developments and optimization of similar materials and their new applications. In order to apply PA to, for example, luminescent (nano)thermometry, we need to have a better understanding of the susceptibility of photon avalanche phenomenon to temperature variation. For this purpose, we study how the temperature and energy-gap-dependent multiphonon relaxation and inter-ionic energy transfer processes affect the photon avalanche behavior. As a result of these simulations, high susceptibility to temperature changes with relative sensitivity over 40 %⋅K−1 above 400 K (up to 15 %⋅K−1at room temperature) was noted. Moreover, by knocking-out the temperature dependences of the individual processes involved in the PA, we found the temperature dependence of the multiphonon relaxation of the intermediate F34 state to the ground state to be the primary one responsible for the simulated temperature dependence of PA emission. This process is observed to be more significant than temperature dependencies of energy looping and phonon assisted ground state non-resonant absorption. Although there are challenges with a single band technique, these results still show the great potential, especially when used ratiometrically with different excitation wavelengths.
Emory - M. J. Allen Emory
No full textA.B.; A.M., 1874; Phi Kappa Psi; Philomathaean; Divided Graeff Prize. Entered Preparatory, 1865. Law student at Easton, Pa. LL.B., Albany Law School, 1873. Born June 8, 1848 or 1850, West Newton, Westmoreland county, Pa. Parents, Rev. William S. and Martha. Residence, Palmyra, Pa. Practiced Law and studied along literary and artistic lines; modeled in clay. Author, Within White Walls; and short stories and plays. Discontinued practice of law and went West as a newspaper correspondent, engaged in gold and silver mining. Died Nov. 12, 1925, in West
Emory - M. J. Allen Emory
No full textA.B.; A.M., 1874; Phi Kappa Psi; Philomathaean; Divided Graeff Prize. Entered Preparatory, 1865. Law student at Easton, Pa. LL.B., Albany Law School, 1873. Born June 8, 1848 or 1850, West Newton, Westmoreland county, Pa. Parents, Rev. William S. and Martha. Residence, Palmyra, Pa. Practiced Law and studied along literary and artistic lines; modeled in clay. Author, Within White Walls; and short stories and plays. Discontinued practice of law and went West as a newspaper correspondent, engaged in gold and silver mining. Died Nov. 12, 1925, in West
Ligand-Assisted Direct Lithography of Upconverting and Avalanching Nanoparticles for Nonlinear Photonics
No full textUpconverting nanoparticles (UCNPs) exhibit unique nonlinear optical properties that can be harnessed in microscopy, sensing, and photonics. However, forming high-resolution nano- and micropatterns of UCNPs with large packing fractions is still challenging. Additionally, there is limited understanding of how nanoparticle patterning chemistries are affected by the particle size. Here, we explore direct patterning chemistries for 6-18 nm Tm3+-, Yb3+/Tm3+-, and Yb3+/Er3+-based UCNPs using ligands that form either new ionic linkages or covalent bonds between UCNPs under ultraviolet (UV), electron-beam (e-beam), and near-infrared (NIR) exposure. We study the effect of UCNP size on these patterning approaches and find that 6 nm UCNPs can be patterned with compact ionic-based ligands. In contrast, patterning larger UCNPs requires long-chain, cross-linkable ligands that provide sufficient interparticle spacing to prevent irreversible aggregation upon film casting. Compared to approaches that use a cross-linkable liquid monomer, our patterning method limits the cross-linking reaction to the ligands bound on UCNPs deposited as a thin film. This highly localized photo-/electron-initiated chemistry enables the fabrication of densely packed UCNP patterns with high resolutions (similar to 1 mu m with UV and NIR exposure; <100 nm with e-beam). Our upconversion NIR lithography approach demonstrates the potential to use inexpensive continuous-wave lasers for high-resolution 2D and 3D lithography of colloidal materials. The deposited UCNP patterns retain their upconverting, avalanching, and photoswitching behaviors, which can be exploited in patterned optical devices for next-generation UCNP applications.
In Defense of the Ordinary / Extraordinary Distinction
No full textThe author, an assistant professor of philosophy at Emory and Henry College, Emory, Virginia, explains that his paper defends the traditional doctrine against a recent proposal by Robert M. Veatch inhis popular Death, Dying, and the Biological Revolution
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Introduction
No full textByline: Charles B. Nemeroff, Christopher M. O'Connor Author Affiliation: Atlanta, Ga, and Durham, NC From the Department of Psychiatry and Behavioral Sciences, Emory University School of Medicine, Atlanta; and Duke University Medical Center, Durham, NC Article Note: (footnote) [star] Reprint requests: Charles B. Nemeroff, MD, PhD, Psychiatry and Behavioral Sciences, Emory University School of Medicine,1639 Pierce Drive, Atlanta, GA 30322-4990. E-mail: [email protected], [star][star] Am Heart J 2000;140:S55-6.ProfessionalAcademi
John M. Rosenfield, Mynah Birds and Flying Rocks: Word and Image in the Art of Yosa Buson
No full textAuthor Institution: Emory Universit
Student Loan Discharge: Reevaluating Undue Hardship Under a Presumption of Consistent Usage
No full textAn increasing number of Americans are suffering from financial distress caused by educational debt. Some of those individuals seek relief from that distress through the bankruptcy system, where they must establish that repaying their educational debt would impose an undue hardship in order to obtain a discharge of such debt. The author focuses on § 523(a)(8) of the U.S. Bankruptcy Code, which sets forth educational debt as an exception to bankruptcy discharge unless the repayment of student loan obligations imposes an \u27undue hardship.\u27 The author concludes that the primary inquiry into a debtor\u27s undue hardship claim must focus on the debtor\u27s current financial circumstances without undue regard to pre-bankruptcy conduct or assurance of persisting financial distress
Infrared-to-ultraviolet upconverting nanoparticles for COVID-19-related disinfection applications
No full textIn light of the COVID-19 pandemic, the demand for better UV disinfection sources has increased drastically. Recent advances in Lanthanide-based upconverting nanoparticle (UCNP) designs have led to dramatic increases in efficiency – beyond what is possible in bulk upconverting material – for generating short-wavelength light from long-wavelength photons, pushing achievable upconversion into the UV regime. Such nanoparticles represent an ultimate source of ultra-local UV light, with applications in UV photocatalysis, 3D printing and manufacturing, and perhaps most importantly, health care. The goal of this article is to provide an assessment for the application of UCNPs as local UV sources for disinfection. We map out the potential for incorporation into personal protective equipment (PPE), focusing on N95 face masks as a model system. Performance and viability are evaluated based on recent UCNP findings and extrapolating cost trends following the recent example of commercialized semiconductor quantum dot nanoparticles.
A generalized approach to photon avalanche upconversion in luminescent nanocrystals
No full textPhoton avalanching nanoparticles (ANPs) exhibit extremely nonlinear
upconverted emission valuable for sub-diffraction imaging, nanoscale sensing,
and optical computing. Avalanching has been demonstrated with Tm3+, Nd3+ or
Pr3+-doped nanocrystals, but their emission is limited to 600 and 800 nm,
restricting applications. Here, we utilize Gd3+-assisted energy migration to
tune the emission wavelengths of Tm3+-sensitized ANPs and generate highly
nonlinear emission of Eu3+, Tb3+, Ho3+, and Er3+ ions. The upconversion
intensities of these spectrally discrete ANPs scale with the nonlinearity
factor s = 10-17 under 1064 nm excitation at power densities as low as 6
kW/cm2. This strategy for imprinting avalanche behavior on remote emitters can
be extended to fluorophores adjacent to ANPs, as we demonstrate with
CdS/CdSe/CdS core/shell/shell quantum dots. ANPs with rationally designed
energy transfer networks provide the means to transform conventional linear
emitters into a highly nonlinear ones, expanding the use of photon avalanching
in biological, chemical, and photonic applications.Comment: 13 pages, 5 figure
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