Selective Flocculation and H2O2-Free Oxidative Etching-Based Synthesis of Highly Monodisperse Ag Nanospheres for Uniform Quantum Dot Photoluminescence-Enhancing Plasmonic Cavity Applications.

Ag nanoparticles have garnered significant attention for their excellent plasmonic properties and potential use as plasmonic cavities, primarily because of their intrinsically low ohmic losses and optical properties in the visible range. These are particularly crucial in systems involving quantum dots that absorb light at low wavelengths, where the need for a high threshold energy of interband transitions necessitates the incorporation of Ag nanostructures. However, the synthesis of Ag nanoparticles still encounters challenges in achieving structural uniformity and monodispersity, along with chemical stability, consequentially inducing inconsistent and poorly reliable optical responses. Here, we present a two-step approach for synthesizing highly uniform spherical Ag nanoparticles involving depletion-induced flocculation and Cu(II)-mediated oxidative etching. We found that the selective flocculation of multitwinned Ag nanocrystals significantly enhances the uniformity of the resulting Ag nanostructures, leaving behind only single-crystalline and single-twinned nanostructures. Subsequent oxidative etching, in which cupric ions are directly involved in the reaction, was designed based on Pourbaix diagrams to proceed following thermodynamically favorable states and circumvent the generation of reactive chemical species such as H2O2. This leads to perfectly spherical shapes of final Ag nanoparticles with a synthetic yield of 99.5% and additionally reduces the overall reaction time. Furthermore, we explore the potential applications of these monodisperse Ag nanospheres as uniform plasmonic cavities. The fabricated Ag nanosphere films uniformly enhanced the photoluminescence of InP/ZnSe/ZnS quantum dots, showcasing their capabilities in exhibiting consistent plasmonic responses across a large area.

Factors Influencing Depression in Adolescents Focusing on the Degree of Appearance Stress.

This descriptive cross-sectional study examined the factors that affect depression in adolescents focusing on how stressed they are regarding their appearance (hereafter, degree of appearance stress). Data from 6493 adolescents from the 2020 Korean Youth Risk Behavior Survey were used. Using SPSS 25.0, a complex sample plan file was created, weighted, and analyzed. The frequency, chi-square test, independent t-test, and linear regression were used for the complex sample analysis. The results showed that among adolescents with low appearance stress, depression was significantly affected by the number of breakfast meals, weight control efforts, smoking, loneliness, subjective physical appearance, and smartphone overdependence. Among those with high appearance stress, depression was significantly affected by academic grades, weight control efforts, drinking habits, loneliness, subjective physical appearance, and smartphone overdependence. Furthermore, these factors differed according to the degree of appearance stress. Thus, while developing interventions for mitigating depression in adolescents, the degree of appearance stress should be considered, and a differentiated strategy should be used accordingly.

Plasmonic quenching and enhancement: metal-quantum dot nanohybrids for fluorescence biosensing.

Plasmonic metal nanoparticles and semiconductor quantum dots (QDs) are two of the most widely applied nanomaterials for optical biosensing and bioimaging. While their combination for fluorescence quenching via nanosurface energy transfer (NSET) or Förster resonance energy transfer (FRET) offers powerful ways of tuning and amplifying optical signals and is relatively common, metal-QD nanohybrids for plasmon-enhanced fluorescence (PEF) have been much less prevalent. A major reason is the competition between fluorescence quenching and enhancement, which poses important challenges for optimizing distances, orientations, and spectral overlap toward maximum PEF. In this feature article, we discuss the interplay of the different quenching and enhancement mechanisms (a mixed distance dependence of quenching and enhancement - "quenchancement") to better understand the obstacles that must be overcome for the development of metal-QD nanohybrid-based PEF biosensors. The different nanomaterials, their combination within various surface and solution based design concepts, and their structural and photophysical characterization are reviewed and applications toward advanced optical biosensing and bioimaging are presented along with guidelines and future perspectives for sensitive, selective, and versatile bioanalytical research and biomolecular diagnostics with metal-QD nanohybrids.

Ligularia fischeri ethanol extract: An inhibitor of alpha-melanocyte-stimulating hormone-stimulated melanogenesis in B16F10 melanoma cells.

BACKGROUND: Ligularia fischeri is a perennial herb isolated from plants of the Asteraceae family. Ligularia fischeri is distributed throughout Korea, Japan, eastern Siberia, and China. AIMS: The aim of this study is to examine the intracellular inhibitory effect of Ligularia fischeri ethanol extract on melanin synthesis and expression of tyrosinase and tyrosinase-related protein 1 and 2. In addition, we analyzed the mitogen-activated protein kinase signaling pathway and microphthalmia-associated transcription factor in alpha-melanocyte-stimulating hormone-stimulated B16F10 melanoma cells. METHODS: To assess the inhibition of melanogenesis in alpha-melanocyte-stimulating hormone-stimulated B16F10 melanoma cells, the expression of melanogenesis-related genes was investigated by quantitative real-time polymerase chain reaction, while western blotting was performed to determine protein expression levels. RESULTS: We confirmed that the ethanol extract of Ligularia fischeri inhibited melanin synthesis in vitro by decreasing tyrosinase and tyrosinase-related protein 1 and 2 expression. Furthermore, we revealed that tyrosinase expression was regulated by the suppression of microphthalmia-associated transcription factor expression and activation of extracellular signal-regulated kinase phosphorylation. The ethanol extract of Ligularia fischeri inhibited melanogenesis by activating extracellular signal-regulated kinase phosphorylation and suppressing microphthalmia-associated transcription factor and tyrosinase expression. CONCLUSIONS: Ligularia fischeri ethanol extract may be used as an effective skin whitening agent in functional cosmetics.

Dual Mediating Effect of Electronic Device Utilization and Life Satisfaction on the Relationship between Instrumental Activities of Daily Living and Depression in Older Adults.

This study aimed to investigate the correlation between instrumental activities of daily living (IADL), depression, electronic device utilization (EDU) and life satisfaction in older adults and to evaluate the dual mediating effect of EDU and life satisfaction on the relationship between IADL and depression. A secondary data analysis of the 2020 Korean Elderly Survey was carried out with 9906 older adults. The dual mediating effect was analyzed using model 6 of PROCESS Macro for SPSS v. 4.1 (New York, NY, USA). EDU (B = -0.010, 95% CI [0.007, 0.013]) and life satisfaction (B = 0.071, 95% CI [0.064, 0.079]) each had a mediating effect on the relationship between IADL and depression in older adults, and in particular, these two variables were shown to dual mediate (B = 0.017, 95% CI [0.015, 0.019]). This study confirmed that life satisfaction can be increased and depression decreased by improving the ability to use electronic devices to combat the limitations in daily functioning due to aging. It is necessary to establish a strategy to increase EDU as a part of the intervention methods for managing depression in older adults.

Increasing the Energy Gap between Band-Edge and Trap States Slows Down Picosecond Carrier Trapping in Highly Luminescent InP/ZnSe/ZnS Quantum Dots.

Non-toxic InP-based nanocrystals have been developed for promising candidates for commercial optoelectronic applications and they still require further improvement on photophysical properties, compared to Cd-based quantum dots (QDs), for better device efficiency and long-term stability. It is, therefore, essential to understand the precise mechanism of carrier trapping even in the state-of-the-art InP-based QD with near-unity luminescence. Here, it is shown that using time-resolved spectroscopic measurements of systematically size-controlled InP/ZnSe/ZnS core/shell/shell QDs with the quantum yield close to one, carrier trapping decreases with increasing the energy difference between band-edge and trap states, indicating that the process follows the energy gap law, well known in molecular photochemistry for nonradiative internal conversion between two electronic states. Similar to the molecular view of the energy gap law, it is found that the energy gap between the band-edge and trap states is closely associated with ZnSe phonons that assist carrier trapping into defects in highly luminescent InP/ZnSe/ZnS QDs. These findings represent a striking departure from the generally accepted view of carrier trapping mechanism in QDs in the Marcus normal region, providing a step forward understanding how excitons in nanocrystals interact with traps, and offering valuable guidance for making highly efficient and stable InP-based QDs.

Synthesis of far-red- and near-infrared-emitting Cu-doped InP/ZnS (core/shell) quantum dots with controlled doping steps and their surface functionalization for bioconjugation.

In this study, we designed and synthesized far-red- and near-infrared-emitting Cu-doped InP-based quantum dots (QDs), and we also demonstrated their highly specific and sensitive biological imaging ability. Cu-doped InP/ZnS (core/shell) QDs were prepared using the hot colloidal synthesis method in the organic phase. The ZnS shell passivates the surface and improves the photoluminescence (PL) intensity. However, the InP : Cu/ZnS (core : dopants/shell) QDs, which were obtained after the Cu dopant was incorporated into bare InP QDs, followed by ZnS shell coating, had relatively low PL intensities (maximum PL quantum yield (QY) was only ∼16%) presumably due to the formation of defect sites in the InP-core QDs caused by dopant migration from the InP core to the ZnS shell. We prepared high-quality InP/ZnS : Cu/ZnS (core/shell : dopant/outer-shell) QDs, where thin ZnS shell layers were grown on bare InP QDs prior to Cu ion doping to prevent dopant migration and obtained PL QYs as high as 40%. The native hydrophobic ligands of the as-synthesized Cu-doped QDs were replaced with hydrophilic ligands including dihydrolipoic acid and a zwitterionic ligand, which rendered the QDs water-soluble. These QDs exhibited remarkable colloidal stabilities over a wide pH range, with hydrodynamic diameters less than 10 nm. Modified QD surfaces can also be used in conjugation with other functional moieties to apply highly specific and sensitive imaging probes with very low background levels. As a proof-of-concept study, we successfully demonstrated the selective imaging of streptavidin beads with biotin-conjugated QDs. These decorated Cu-doped InP/ZnS (core/shell) QDs are promising biological-probe candidates for imaging and assaying with reduced concerns regarding toxicity.

A self-regulatory circuit of CIRCADIAN CLOCK-ASSOCIATED1 underlies the circadian clock regulation of temperature responses in Arabidopsis.

The circadian clock synchronizes biological processes to daily cycles of light and temperature. Clock components, including CIRCADIAN CLOCK-ASSOCIATED1 (CCA1), are also associated with cold acclimation. However, it is unknown how CCA1 activity is modulated in coordinating circadian rhythms and cold acclimation. Here, we report that self-regulation of Arabidopsis thaliana CCA1 activity by a splice variant, CCA1ß, links the clock to cold acclimation. CCA1ß interferes with the formation of CCA1α-CCA1α and LATE ELONGATED HYPOCOTYL (LHY)-LHY homodimers, as well as CCA1α-LHY heterodimers, by forming nonfunctional heterodimers with reduced DNA binding affinity. Accordingly, the periods of circadian rhythms were shortened in CCA1ß-overexpressing transgenic plants (35S:CCA1ß), as observed in the cca1 lhy double mutant. In addition, the elongated hypocotyl and leaf petiole phenotypes of CCA1α-overexpressing transgenic plants (35S:CCA1α) were repressed by CCA1ß coexpression. Notably, low temperatures suppressed CCA1 alternative splicing and thus reduced CCA1ß production. Consequently, whereas the 35S:CCA1α transgenic plants exhibited enhanced freezing tolerance, the 35S:CCA1ß transgenic plants were sensitive to freezing, indicating that cold regulation of CCA1 alternative splicing contributes to freezing tolerance. On the basis of these findings, we propose that dynamic self-regulation of CCA1 underlies the clock regulation of temperature responses in Arabidopsis.

Homocysteine and pulsatility index of cerebral arteries.

BACKGROUND AND PURPOSE: A pulsatility index (PI) represents vascular resistance distal to an examined artery. The purpose of the present study was to evaluate an association between plasma total homocysteine (tHcy) and PIs of the cerebral arteries in patients with ischemic stroke. METHODS: Consecutive patients with ischemic stroke referred to a neurovascular ultrasound laboratory were evaluated from March 2007 to February 2008. PI was defined as (peak systolic velocity-end-diastolic velocity)/mean flow velocity as recommended. Transcranial Doppler was examined in both middle cerebral arteries and vertebral arteries, and basilar arteries. All patients with ischemic stroke were subdivided according to the presence of proximal internal carotid arterial steno-occlusion (ICS). RESULTS: The numbers of patients enrolled for the present analysis as ischemic stroke without and with ICS were 272 and 92, respectively. PIs measured in the cerebral arteries did not show a significant difference in the two groups, in spite of the fact that mean flow velocities of both basilar arteries and vertebral arteries were significantly elevated in the patients with ICS. Plasma tHcy was found to be independently associated with graded increases of PIs in all cerebral arteries in the patients without ICS, even adjusted for the potential confounders. However, there was no association between tHcy and PI in the patients with ICS. CONCLUSION: Plasma tHcy was directly associated with increased cerebral arterial resistance. But in clinical situations when the cerebral arterial hemodynamics were altered as in the patients with ICS, the effect of tHcy on arterial remodeling could be obscured.

A membrane-bound NAC transcription factor regulates cell division in Arabidopsis.

Controlled release of membrane-tethered, dormant precursors is an intriguing activation mechanism that regulates diverse cellular functions in eukaryotes. An exquisite example is the proteolytic activation of membrane-bound transcription factors. The proteolytic cleavage liberates active transcription factors from the membranes that can enter the nucleus and evokes rapid transcriptional responses to incoming stimuli. Here, we show that a membrane-bound NAC (for NAM, ATAF1/2, CUC2) transcription factor, designated NTM1 (for NAC with transmembrane motif1), is activated by proteolytic cleavage through regulated intramembrane proteolysis and mediates cytokinin signaling during cell division in Arabidopsis thaliana. Cell proliferation was greatly reduced in an Arabidopsis mutant with retarded growth and serrated leaves in which a transcriptionally active NTM1 form was constitutively expressed. Accordingly, a subset of cyclin-dependent kinase (CDK) inhibitor genes (the KIP-related proteins) was induced in this mutant with a significant reduction in histone H4 gene expression and in CDK activity. Consistent with a role for NTM1 in cell cycling, a Ds element insertional mutant was morphologically normal but displayed enhanced hypocotyl growth with accelerated cell division. Interestingly, cytokinins were found to regulate NTM1 activity by controlling its stability. These results indicate that the membrane-mediated activation of NTM1 defines a molecular mechanism by which cytokinin signaling is tightly regulated during cell cycling.

A new Arabidopsis gene, FLK, encodes an RNA binding protein with K homology motifs and regulates flowering time via FLOWERING LOCUS C.

Posttranscriptional RNA metabolism plays versatile roles in the regulation of gene expression during eukaryotic growth and development. It is mediated by a group of RNA binding proteins with distinct conserved motifs. In this study, an Arabidopsis (Arabidopsis thaliana) gene, designated FLK, was identified and shown to encode a putative RNA binding protein with K homology motifs. A mutant in which FLK was inactivated by T-DNA insertion exhibited a severe late flowering phenotype both in long and short days. The late flowering phenotype was reversed by gibberellin and vernalization treatments. The FLOWERING LOCUS C (FLC) transcription was greatly upregulated, whereas those of FLOWERING LOCUS T and SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 decreased in the mutant. These observations demonstrate that FLK regulates the autonomous flowering pathway via FLC. It is now evident that a battery of different RNA binding proteins are involved in the posttranscriptional regulation of flowering time in Arabidopsis.