25 research outputs found
Spin-resolved electron waiting times in a quantum dot spin valve
We study the electronic waiting time distributions (WTDs) in a
non-interacting quantum dot spin valve by varying spin polarization and the
noncollinear angle between the magnetizations of the leads using scattering
matrix approach. Since the quantum dot spin valve involves two channels (spin
up and down) in both the incoming and outgoing channels, we study three
different kinds of WTDs, which are two-channel WTD, spin-resolved
single-channel WTD and cross-channel WTD. We analyze the behaviors of WTDs in
short times, correlated with the current behaviors for different spin
polarizations and noncollinear angles. Cross-channel WTD reflects the
correlation between two spin channels and can be used to characterize the spin
transfer torque process. We study the influence of the earlier detection on the
subsequent detection from the perspective of cross-channel WTD, and define the
influence degree quantity as the cumulative absolute difference between
cross-channel WTDs and first passage time distributions to quantitatively
characterize the spin flip process. The influence degree shows a similar
behavior with spin transfer torque and can be a new pathway to characterize
spin correlation in spintronics system.Comment: 9 pages, 7 figure
Optical Response of Terpyridine Ligands to Zinc Binding: A Close Look at the Substitution Effect by Spectroscopic Studies at Low Temperature
Terpyridine (tpy) ligands are popular
building blocks to bind metal
ions. Several tpy ligands with different substituents were synthesized
and examined for their binding with zinc cation. The study revealed
a large substituent effect on the zinc binding-induced fluorescence
quenching. With the aid of a liquid nitrogen Dewar, the tpy molecules
were frozen to their ground-state conformation, preventing (or minimizing)
molecular reorganization in the photoinduced excited state. This allowed
us to detect the fluorescence spectra from the locally excited state
(having a minimum of charge transfer interaction) and the temperature-dependent
fluorescence. The fluorescence response to low temperature provided
useful information about the intramolecular charge transfer (ICT)
interaction between the donor and acceptor groups. Furthermore, a
strong donor substituent (such as Me<sub>2</sub>N) played an essential
role in observed fluorescence quenching. The study also provides a
useful example to elucidate the ICT mechanism by using low-temperature
fluorescence spectroscopy
Change in stress scores according to age group (n = 812).
Change in stress scores according to age group (n = 812).</p
Phase 2 survey questions.
BackgroundOur previous study revealed that the COVID-19 pandemic posed mental health challenges to eye care professionals and students. The intent of this study was to identify the longitudinal impact of the COVID-19 pandemic on mental health among ophthalmic personnel and students. Additionally, the potential risk factors for mental health problems were investigated.MethodsA two-phase survey among eye care professionals and students in the USA and Canada was conducted. Phase 1 was administrated from June 23 to July 8, 2020, and has been published; Phase 2 was conducted from January 21 to February 2, 2021. A total of 824 eye care professionals and students participated in Phase 2, with a response rate of 44.1%. Symptoms of depression, anxiety, and stress were measured and calculated.ResultsCompared with Phase 1, stress scores in Phase 2 were significantly reduced (PP P = 0.20) and anxiety (P = 0.40) showed no change, comparing Phase 2 to Phase 1. Reduction of stress scores significantly differed among occupations (P = 0.005); students had less reduction of stress than other eye care professionals (all PP = 0.04).ConclusionsWith the continuing COVID pandemic, although stress level was reduced at 7-month follow-up, the mental health of eye care professionals was still impacted. In this population, COVID-19 vaccination was associated with fewer stress symptoms. These results indicate that the COVID-19 pandemic continues impacting mental health among eye care professionals, especially students. These study results warrant future interventions for eye care personnel and students to prevent or treat mental health disorders.</div
Changes in stress, depression, and anxiety scores according to vaccine status from Phase 1 (n = 812).
Changes in stress, depression, and anxiety scores according to vaccine status from Phase 1 (n = 812).</p
Demographic characteristics of the participants (n = 812).
Demographic characteristics of the participants (n = 812).</p
Change in stress scores according to occupation (n = 812).
Change in stress scores according to occupation (n = 812).</p
Large Fluorescence Response by Alcohol from a Bis(benzoxazole)–Zinc(II) Complex: The Role of Excited State Intramolecular Proton Transfer
The formation of a bisÂ(HBO) anion
is known to turn on the fluorescence
to give red emission, via controlling the excited-state intramolecular
proton transfer (ESIPT). The poor stability of the formed anion, however,
hampered its application. The anion stability is found to be greatly
improved by attaching the anion to Zn<sup>2+</sup> cation (i.e., forming
zinc complex), whose emission is at λ<sub>em</sub> ≈
550 and 760 nm. Interestingly, addition of methanol to the zinc complex
induces a remarkable red fluorescence (λ<sub>em</sub> ≈
630 nm, ϕ<sub>fl</sub> ≈ 0.8). With the aid of spectroscopic
studies (<sup>1</sup>H NMR, UV–vis, fluorescence, and mass
spectra), the structures of the zinc complexes are characterized.
The emission species is identified as a dimer-like structure. The
study thus reveals an effective fluorescence switching mechanism that
could further advance the application of ESIPT-based sensors
Flavone-Based ESIPT Ratiometric Chemodosimeter for Detection of Cysteine in Living Cells
We have designed and synthesized
a novel ratiometric fluorescent chemodosimeter <b>MHF</b>-based
ESIPT process for specific detection of cysteine among the biological
thiols. The probe <b>MHF</b> shows very weak blue fluorescence
under UV excitation. Upon addition of cysteine (Cys), the reaction
of Cys with <b>MHF</b> induces acrylate hydrolysis, thereby
enabling the ESIPT process to shift the weak blue emission to a strong
green emission with about 20-fold enhancement. We utilized <sup>1</sup>H NMR spectra to elucidate the fluorescence sensing mechanism. Moreover,
the cellular imaging experiment indicated the <b>MHF</b> possessed
excellent selectivity, low cytotoxicity, and desirable cell permeability
for biological applications
Biocompatible Flavone-Based Fluorogenic Probes for Quick Wash-Free Mitochondrial Imaging in Living Cells
Mitochondria, vital organelles existing
in almost all eukaryotic cells, play a crucial role in energy metabolism
and apoptosis of aerobic organisms. In this work, we report two new
flavone-based fluorescent probes, <b>MC-Mito1</b> and <b>MC-Mito2</b>, for monitoring mitochondria in living cells. These
two probes exhibit remarkably low toxicity, good cell permeability,
and high specificity; these probes complement the existing library
of mitochondrial imaging agents. The new dyes give nearly no background
fluorescence, and their application does not require tedious postwashing
after cell staining. The appreciable tolerance of <b>MC-Mito2</b> encourages a broader range of biological applications for understanding
the cell degeneration and apoptosis mechanism