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 Me₂N) 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

Change in stress scores according to occupation (n = 812).

Change in stress scores according to occupation (n = 812).</p

Demographic characteristics of the participants (n = 812).

Demographic characteristics of the participants (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 bis­(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 Zn²⁺ cation (i.e., forming zinc complex), whose emission is at λ_em ≈ 550 and 760 nm. Interestingly, addition of methanol to the zinc complex induces a remarkable red fluorescence (λ_em ≈ 630 nm, ϕ_fl ≈ 0.8). With the aid of spectroscopic studies (¹H 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 ¹H 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