Effective generation mechanisms of tropical instability waves as represented by high-resolution coupled atmosphere-ocean prediction experiments.

Cusp-shaped fluctuations of the sea surface temperature (SST) front in the tropical Pacific, now known as tropical instability waves (TIWs), were discovered by remote sensing in the 1970s. Their discovery was followed by both theoretical and analytical studies, which, along with in situ observations, identified several possible generation mechanisms. Although modeling studies have shown that TIWs strongly influence the heat budget, their influence on local variations of realistically initialized predictions is not yet understood. We here evaluate a series of medium-range (up to ~ 10 days) coupled atmosphere-ocean predictions by a coupled model with different horizontal resolutions. Observational SST, surface wind stress, heat flux, and pressure data showed that representation of temporally and spatially local variations was improved by resolving fine-scale SST variations around the initialized coarse-scale SST front fluctuations of TIWs. Our study thus demonstrates the advantage of using high-resolution coupled models for medium-range predictions. In addition, analysis of TIW energetics showed two dominant sources of energy to anticyclonic eddies: barotropic instability between equatorial zonal currents and baroclinic instability due to intense density fronts. In turn, the eddy circulation strengthened both instabilities in the resolved simulations. This revealed feedback process refines our understanding of the generation mechanisms of TIWs.

Northward shift of the Kuroshio Extension during 1993-2021.

The Kuroshio Extension (KE) flows eastward at the northern boundary of the North Pacific subtropical gyre. By transporting large amounts of seawater with heat, the KE contributes significantly to the formation of sea surface temperature (SST) fields. Recently, poleward shifts of major ocean gyres in the world ocean, including the North Pacific subtropical gyre, have been highlighted based on basin-scale changes in SST and sea surface height (SSH) distributions. However, a detailed investigation of the long-term meridional KE movement has not been presented. Investigation of KE path changes helps provide insights into long-term changes in the physical fields in the western North Pacific. In this study, we identified the KE path from satellite-derived SSH and surface current velocity data using a front identification method and showed that the KE migrated northward by approximately 210 km during 1993-2021. We further explored the cause of the northward KE shift based on atmospheric reanalysis data and numerical experiments using a high-resolution ocean general circulation model. It was revealed that the northward KE shift is mostly caused by the trend of wind stress curl in the North Pacific during 1993-2021.

Cold- versus warm-season-forced variability of the Kuroshio and North Pacific subtropical mode water.

The ocean responds to atmospheric variations. Changes in sea surface winds, surface air temperature, and surface air humidity cause upper ocean variability by modulating air-sea momentum and heat exchanges. Upper ocean variability in the mid-latitudes on inter-annual and longer timescales has previously been considered to be attributable to atmospheric variations in the cold season, because atmospheric forcing is stronger in the cold season than in the warm season. However, this idea has not been sufficiently confirmed yet. Although the ocean model is a useful tool to evaluate the impact of the atmospheric forcing in each season, there are no past studies having examined ocean model responses respectively to the cold- and warm-season atmospheric forcing. In this study, we performed numerical experiments with an eddy-resolving ocean general circulation model and investigated oceanic responses to cold- and warm-season atmospheric forcing, focusing on the Kuroshio and North Pacific subtropical mode water (STMW) in the western mid-latitude North Pacific. We found that temporal variations of net Kuroshio transport and STMW distribution/temperature are dominantly controlled by atmospheric forcing in the cold season. These results suggest that cold-season atmospheric variations are key to obtaining insights into large-scale upper ocean variability in the North Pacific subtropical gyre.

CHOROIDAL VASCULAR DENSITY IN DIABETIC RETINOPATHY ASSESSED WITH SWEPT-SOURCE OPTICAL COHERENCE TOMOGRAPHY.

PURPOSE: We aimed to assess choroidal vascularity by diabetic retinopathy (DR) stage using the choroidal vascular density (CVD) obtained from swept-source optical coherence tomography en-face images. METHODS: This prospective, cross-sectional, multicenter study included patients from Niigata City General Hospital and Saiseikai Niigata Hospital between October 2016 and October 2017. Choroidal vascular density was obtained by binarizing swept-source optical coherence tomography en-face images of patients with diabetes and those with DR, patients without DR, and healthy age-matched volunteers. RESULTS: Patients were allocated to the healthy control (n = 28), no DR (n = 23), nonproliferative DR (NPDR) without diabetic macular edema (DME) (n = 50), NPDR + DME (n = 38), and proliferative DR (PDR) or any previous treatment with panretinal photocoagulation (n = 26) groups. Investigation of the choriocapillaris slab level indicated that the no DR group had significantly high CVD values ( P < 0.05), and the PDR groups had significantly low CVD values ( P < 0.01). Investigation of the large choroidal vessel level indicated that the NPDR + DME and PDR groups had significantly lower CVD values than the control group ( P < 0.05 and P < 0.01, respectively). CONCLUSION: We found that at the choriocapillaris slab level, the no DR group had a higher CVD and the NPDR with DME and PDR groups had a lower CVD than the control group. At the level of the large choroidal vessels, the NPDR with DME and PDR groups had a lower CVD than the control group. There were significant differences in choroidal vasculature found using CVD obtained from swept-source optical coherence tomography en-face images of patients with diabetes and DR.

Synthesis of Si-Ge Nanosheets and Their Dispersion of Organic Solvents with Focus on the Hansen Solubility Parameters.

Two-dimensional (2D) materials combine the collective advantages of individual building blocks and synergistic properties and have spurred great interest as a new paradigm in materials science. Especially, exfoliation of 2D semiconductive materials into nanosheets is of significance for both fundamental and potential applications. In this report, silicon-germanium (Si-Ge) nanosheets were synthesized by sonication of porous Si-Ge powder. The raw material Si-Ge powder was obtained by leaching Li from Li13Si2Ge2 with ethanol; after that, it was crystallized by heat treatment at 500 °C. The thickness and the lateral size of the exfoliated Si-Ge nanosheets were about 3 nm and a few microns, respectively. The nanosheets were dispersed in 55 different organic solvents, and their Hansen solubility parameters were calculated and compared with those of the end member (Si and Ge) nanosheets and graphene.

Relationship between morphological changes in the foveal avascular zone of the epiretinal membrane and postoperative visual function.

OBJECTIVE: To investigate the relationship between the preoperative morphology of the foveal avascular zone (FAZ) and postoperative visual function in patients with idiopathic epiretinal membrane (ERM). METHODS AND ANALYSIS: This retrospective study enrolled 36 patients who underwent a unilateral internal limiting membrane peeling with vitrectomy for idiopathic ERM. We measured the area of superficial FAZ in the eyes with ERM and in the contralateral control eyes preoperatively and at 6 months postoperatively using optical coherence tomography (OCT) angiography. The ERM stage was measured using swept-source OCT. We evaluated the FAZ area ratio (preoperative FAZ of the ERM eye/FAZ of the control eye) to indicate the degree of FAZ contraction in the ERM eyes compared with the control eyes. The correlations between the FAZ area ratio and postoperative visual function and changes in macular morphology were assessed. RESULTS: Preoperative mean best-corrected visual acuity (BCVA) significantly improved from the logarithm of the minimum angle of resolution 0.20±0.24 to 0.01±0.13 at 6 months postoperatively (p<0.01). The mean area of the FAZ increased significantly from 0.06±0.07 mm2 preoperatively to 0.09±0.07 mm2 after vitrectomy (p<0.01). FAZ area ratio showed significant negative correlations with changes in BCVA (r=-0.44, p<0.01) and the ERM stages (r=-0.56, p<0.01). CONCLUSION: The FAZ is reduced as ERM progresses and enlarges after vitrectomy. The FAZ area ratio based on preoperative FAZ may predict postoperative visual acuity.

Choroid structure analysis following initiation of hemodialysis by using swept-source optical coherence tomography in patients with and without diabetes.

We aimed to evaluate choroid structural changes using swept-source optical coherence tomography (SS-OCT) following hemodialysis initiation in diabetic and nondiabetic patients with end-stage kidney disease (ESKD). In this multicenter, prospective, cross-sectional study, diabetic (DM group; 30 eyes; 16 patients) and nondiabetic patients (NDM group; 30 eyes; 15 patients) with ESKD were evaluated after hemodialysis initiation. SS-OCT findings were analyzed using a manual delineation technique and binarization method before the first and last hemodialysis sessions, conducted approximately 2 weeks apart. Subfoveal choroidal thickness changes and mean large choroidal vessel layer thickness were significantly greater in the DM group (-13.3% ± 2.5% and -14.5% ± 5.2%, respectively) than the NDM group (-9.5% ± 3.1% and -9.2% ± 3.4%, respectively; p = 0.049 and p = 0.02, respectively). Binarized SS-OCT analysis revealed that the mean subfoveal choroidal area was significantly larger in the DM group (-21.9% ± 6.5%) than the NDM group (-17.2% ± 5.9%; p = 0.032). The change ratio in mean luminal area values was significantly greater in the DM group (-27.7% ± 8.7%) than the NDM group (-17.7% ± 5.8%; p = 0.007). The DM group exhibited substantial changes in the choroidal layer, possibly reflecting choroidal vascular disorders caused by diabetes.

Tracking Improvement in Simulated Marine Biogeochemistry Between CMIP5 and CMIP6.

Purpose of Review: The changes or updates in ocean biogeochemistry component have been mapped between CMIP5 and CMIP6 model versions, and an assessment made of how far these have led to improvements in the simulated mean state of marine biogeochemical models within the current generation of Earth system models (ESMs). Recent Findings: The representation of marine biogeochemistry has progressed within the current generation of Earth system models. However, it remains difficult to identify which model updates are responsible for a given improvement. In addition, the full potential of marine biogeochemistry in terms of Earth system interactions and climate feedback remains poorly examined in the current generation of Earth system models. Summary: Increasing availability of ocean biogeochemical data, as well as an improved understanding of the underlying processes, allows advances in the marine biogeochemical components of the current generation of ESMs. The present study scrutinizes the extent to which marine biogeochemistry components of ESMs have progressed between the 5th and the 6th phases of the Coupled Model Intercomparison Project (CMIP).

Clinical Features of Patients with Exfoliation Glaucoma Requiring Surgical Intervention.

PURPOSE: To clarify the clinical features of patients with exfoliation glaucoma (XFG) requiring surgical intervention. Study Design. Retrospective study. METHODS: The study included 46 eyes from 36 XFG patients, 85 eyes from 53 primary open-angle glaucoma (POAG) patients, and 54 eyes from 35 normal-tension glaucoma (NTG) patients. Age, duration of previous glaucoma treatment, intraocular pressure, medication scores, visual function, and surgical procedure were compared among the three patient groups. RESULTS: The XFG group had the highest mean age (XFG: 75.7 ± 8.3 years, POAG: 65.8 ± 12.8 years, and NTG: 53.3 ± 12.8 years; p < 0.001) and the shortest mean duration of previous treatment with glaucoma medication (XFG: 5.1 ± 3.5 years, POAG: 8.9 ± 6.9 years, and NTG: 8.9 ± 5.9 years; p < 0.001). Intraocular pressure and medication scores were slightly higher in the XFG group than in the POAG group, although the differences were not significant. Among XFG patients, trabeculectomy was performed in 20 eyes from 16 patients (55.6%) and trabeculotomy was performed in 16 eyes from 14 patients (44.4%). Both trabeculectomy (3 eyes) and trabeculotomy (14 eyes) were performed in combination with cataract surgery. CONCLUSIONS: The XFG patients referred to our department for initial examination were older than the POAG and NTG patients, and their duration of treatment before referral was shorter. Moreover, intraocular pressure and the eye drop medication score were higher in the XFG patients. A significantly higher percentage of XFG patients required surgical intervention compared to patients with other disease types.

Precometary organic matter: A hidden reservoir of water inside the snow line.

The origin and evolution of solar system bodies, including water on the Earth, have been discussed based on the assumption that the relevant ingredients were simply silicates and ices. However, large amounts of organic matter have been found in cometary and interplanetary dust, which are recognized as remnants of interstellar/precometary grains. Precometary organic matter may therefore be a potential source of water; however, to date, there have been no experimental investigations into this possibility. Here, we experimentally demonstrate that abundant water and oil are formed via the heating of a precometary-organic-matter analog under conditions appropriate for the parent bodies of meteorites inside the snow line. This implies that H2O ice is not required as the sole source of water on planetary bodies inside the snow line. Further, we can explain the change in the oxidation state of the Earth from an initially reduced state to a final oxidized state. Our study also suggests that petroleum was present in the asteroids and is present in icy satellites and dwarf planets.

Photophysics and Inverted Solvatochromism of 7,7,8,8-Tetracyanoquinodimethane (TCNQ).

We report absorption, fluorescence, and Raman spectroscopy of 7,7,8,8-tetracyanoquinodimethane (TCNQ) in a variety of solvents. The fluorescence quantum yields (QYs) of linear alkane solutions are similar to one another, but QY is shown to acutely decrease in other solvents with increasing polarities. The slope of the solvatochromic plot of absorption maxima is inverted from negative to positive with an increase in solvent polarity. A significant change in the frequency of carbon-carbon double bond stretching modes is not observed in Raman spectra of TCNQ in different solvents. The molar absorption coefficient is determined to calculate the oscillator strength of the absorption band. The radiative decay rate constant calculated from the oscillator strength is approximately ten times larger than that elucidated from the fluorescence lifetime and QY. These spectroscopic parameters reveal that the relaxation occurs from a Franck-Condon excited state to a distinct fluorescence emissive state with a smaller transition dipole moment.

Hansen Solubility Parameters of Stacked Silicanes Derived from Porous Silicon.

Exfoliated nanomaterials could spur great interest as a new paradigm in materials science. Therefore, we have sought organic solvents to obtain high-quality two-dimensional nanomaterials and enable their adoption in large-scale applications. However, recent approaches in liquid-phase exfoliation are based on empirical trial-and-error strategies. Here, we show that the dispersibility of stacked silicanes is discussed on the basis of Hansen solubility parameters (HSPs). Using these parameters, we demonstrate that silicanes can be efficiently dispersed in bromonaphthalene and can be exfoliated as individual sheets (1-6 nm in thickness and up to 2 µm2 in area). During the exfoliation process, the oxidation state of the obtained sheets is affected by the nature of the solvents. Furthermore, HSPs of the stacked silicanes are compared with those of graphene and hydrogen-terminated germanane.

Mechano- and Photoresponsive Behavior of a Bis(cyanostyryl)benzene Fluorophore.

The mechanoresponsive behavior and photochemical response of a new bis(cyanostyryl)benzene fluorophore (CSB-5) were investigated. Green fluorescence with λem,max of 507 nm was found for CSB-5 in chloroform solution, mirroring the behavior of a previously reported similar dye (CSB-6). Alternatively, crystalline samples of CSB-5 exhibited orange fluorescence with λem,max of 620 nm, attributable to excimer emission. Although the emission color change was not clearly noticeable by naked eye, CSB-5 exhibited mechanochromic luminescence, due to transformation into the amorphous state upon grinding the crystalline powder. Interestingly, rubbed films of CSB-5 prepared on glass substrates exhibited a pronounced emission color change from orange to green when exposed to UV light. This response is the result of a photochemical reaction that occurs in the amorphous state and which causes a decrease of the excimer emission sites so that the emission color changes from excimer to monomer. The crystalline material did not display such a photoinduced emission color change and the difference in photochemical reactivity between crystalline and amorphous states was exploited to pattern the emission color of rubbed films.

Solid-State Electrochemistry of Copper(I) Coordination Polymers Containing Tetrafluoroborate Anions.

Host-guest materials based on coordination polymers (CPs) are currently emerging as potential candidates for battery applications. In this context, we describe the preparation of three-dimensional network structures containing BF4 anions and water molecules in the one-dimensional (1D) channels via hydrothermal reactions between Cu(BF4)2 and 4,4'-bipyridine or 1,2-di-4-pyridylethylene. A systematic characterization of the obtained CPs using single-crystal X-ray diffraction, X-ray absorption fine structure, and an electrochemical test was performed. The results showed that the BF4 anions were electrochemically reduced to BF3 in the cavities of the CPs, with concomitant elimination of a leaving fluoride at room temperature. Using this electrochemical property, a prototype battery, in which the CPs act as the anode and graphite as the cathode, was demonstrated. The cell exhibited a practical discharge potential of ∼1.5 V. This constitutes the first demonstration of CPs showing electrochemical B-F bond activation in the 1D channels and rocking-chair-type fluoride insertion and extraction by changes in the electric potential.

Photoinduced Shape Changes of Mixed Molecular Glass Particles Containing Azobenzene-Based Photochromic Amorphous Molecular Materials Fixed in Agar Gel.

It has been found that mixed molecular glass particles exhibit photoinduced shape changes, elongating their shapes to form stringlike structures similar to single molecular glass particles of azobenzene-based photochromic amorphous molecular materials. Furthermore, interestingly, the addition of 15 mol % photochemically inert 4,4',4″-tris[3-methylphenyl(phenyl)amino]triphenylamine enhanced the phenomenon relative to single particles of 4-[bis(4-methylphenyl)amino]azobenzene. The present mixed systems allowed to elucidate the effects of Tg and of the apparent photochromic reactivity independently by changing the mixing ratio of suitable materials. It has been clearly demonstrated that increase in the apparent photochromic reactivity enhanced monotonically the photomechanical elongation of the particles. On the other hand, it has been found that increase in Tg was favorable for the present photoinduced elongation of the particle, whereas the effect of Tg became saturated at sufficiently high Tg values.

Chemical modification of group IV graphene analogs.

Mono-elemental two-dimensional (2D) crystals (graphene, silicene, germanene, stanene, and so on), termed 2D-Xenes, have been brought to the forefront of scientific research. The stability and electronic properties of 2D-Xenes are main challenges in developing practical devices. Therefore, in this review, we focus on 2D free-standing group-IV graphene analogs (graphene quantum dots, silicane, and germanane) and the functionalization of these sheets with organic moieties, which could be handled under ambient conditions. We highlight the present results and future opportunities, functions and applications, and novel device concepts.

Stark Spectroscopy of Rubrene. I. Electroabsorption Spectroscopy and Molecular Parameters.

Electroabsorption spectroscopy investigation and the determination of molecular parameters for rubrene dispersed in a poly(methyl methacrylate) (PMMA) matrix are reported. The features of the band system in the absorption spectrum in PMMA are analogous to those in solutions. The changes in the electric dipole moment and the polarizability between the excited and ground states are determined from analysis of the Stark effect in the absorption band. The change in the transition dipole moment in the presence of an external electric field is also observed. Although rubrene is predicted to be classified as a nonpolar molecule, there is a contribution of the difference in the electric dipole moment between the excited and ground states to the electroabsorption spectrum. The origin of the nonzero difference in the electric dipole moment is argued. Stark fluorescence spectroscopy investigation is reported in Part II of this series.

Monolayer-to-bilayer transformation of silicenes and their structural analysis.

Silicene, a two-dimensional honeycomb network of silicon atoms like graphene, holds great potential as a key material in the next generation of electronics; however, its use in more demanding applications is prevented because of its instability under ambient conditions. Here we report three types of bilayer silicenes that form after treating calcium-intercalated monolayer silicene (CaSi2) with a BF4(-) -based ionic liquid. The bilayer silicenes that are obtained are sandwiched between planar crystals of CaF2 and/or CaSi2, with one of the bilayer silicenes being a new allotrope of silicon, containing four-, five- and six-membered sp(3) silicon rings. The number of unsaturated silicon bonds in the structure is reduced compared with monolayer silicene. Additionally, the bandgap opens to 1.08 eV and is indirect; this is in contrast to monolayer silicene which is a zero-gap semiconductor.

Isolation of Hypervalent Group-16 Radicals and Their Application in Organic-Radical Batteries.

Using a newly prepared tridentate ligand, we isolated hypervalent sulfur and selenium radicals for the first time and characterized their structures. X-ray crystallography, electron spin resonance spectroscopy, and density functional theory calculations revealed a three-coordinate hypervalent structure. Utilizing the reversible redox reactions between hypervalent radicals and the corresponding anions bearing Li(+), we developed organic radical batteries with these compounds as cathode-active materials. Furthermore, an all-radical battery, with these compounds as the cathode and a silyl radical as the anode, was developed that exhibited a practical discharge potential of ∼ 1.8 V and stable cycle performance, demonstrating the potential of these materials for use in metal-free batteries that can replace conventional Li-ion batteries where Li is used in the metal form.

Improving Powder Magnetic Core Properties via Application of Thin, Insulating Silica-Nanosheet Layers on Iron Powder Particles.

A thin, insulating layer with high electrical resistivity is vital to achieving high performance of powder magnetic cores. Using layer-by-layer deposition of silica nanosheets or colloidal silica over insulating layers composed of strontium phosphate and boron oxide, we succeeded in fabricating insulating layers with high electrical resistivity on iron powder particles, which were subsequently used to prepare toroidal cores. The compact density of these cores decreased after coating with colloidal silica due to the substantial increase in the volume, causing the magnetic flux density to deteriorate. Coating with silica nanosheets, on the other hand, resulted in a higher electrical resistivity and a good balance between high magnetic flux density and low iron loss due to the thinner silica layers. Transmission electron microscopy images showed that the thickness of the colloidal silica coating was about 700 nm, while that of the silica nanosheet coating was 30 nm. There was one drawback to using silica nanosheets, namely a deterioration in the core mechanical strength. Nevertheless, the silica nanosheet coating resulted in nanoscale-thick silica layers that are favorable for enhancing the electrical resistivity.