Depressed 660-km discontinuity caused by akimotoite-bridgmanite transition.

The 660-kilometre seismic discontinuity is the boundary between the Earth's lower mantle and transition zone and is commonly interpreted as being due to the dissociation of ringwoodite to bridgmanite plus ferropericlase (post-spinel transition)1-3. A distinct feature of the 660-kilometre discontinuity is its depression to 750 kilometres beneath subduction zones4-10. However, in situ X-ray diffraction studies using multi-anvil techniques have demonstrated negative but gentle Clapeyron slopes (that is,  the ratio between pressure and temperature changes) of the post-spinel transition that do not allow a significant depression11-13. On the other hand, conventional high-pressure experiments face difficulties in accurate phase identification due to inevitable pressure changes during heating and the persistent presence of metastable phases1,3. Here we determine the post-spinel and akimotoite-bridgmanite transition boundaries by multi-anvil experiments using in situ X-ray diffraction, with the boundaries strictly based on the definition of phase equilibrium. The post-spinel boundary has almost no temperature dependence, whereas the akimotoite-bridgmanite transition has a very steep negative boundary slope at temperatures lower than ambient mantle geotherms. The large depressions of the 660-kilometre discontinuity in cold subduction zones are thus interpreted as the akimotoite-bridgmanite transition. The steep negative boundary of the akimotoite-bridgmanite transition will cause slab stagnation (a stalling of the slab's descent) due to significant upward buoyancy14,15.

Leaf optical properties and photosynthesis of fern species with a wide range of divergence time in relation to mesophyll anatomy.

BACKGROUND AND AIMS: For a comprehensive understanding of the mechanisms of changing plant photosynthetic capacity during plant evolutionary history, knowledge of leaf gas exchange and optical properties are essential, both of which relate strongly to mesophyll anatomy. Although ferns are suitable for investigating the evolutionary history of photosynthetic capacity, comprehensive research of fern species has yet to be undertaken in this regard. METHODS: We investigated leaf optical properties, gas exchange and mesophyll anatomy of fern species with a wide range of divergence time, using 66 ferns from natural habitats and eight glasshouse-grown ferns. We used a spectroradiometer and an integrating sphere to measure light absorptance and reflectance by the leaves. KEY RESULTS: The more newly divergent fern species had a thicker mesophyll, a larger surface area of chloroplasts facing the intercellular airspaces (Sc), thicker cell walls and large light absorptance. Although no trend with divergence time was obtained in leaf photosynthetic capacity on a leaf-area basis, when the traits were expressed on a mesophyll-thickness basis, trends in leaf photosynthetic capacity became apparent. On a mesophyll-thickness basis, the more newly divergent species had a low maximum photosynthesis rate, accompanied by a low Sc. CONCLUSIONS: We found a strong link between light capture, mesophyll anatomy and photosynthesis rate in fern species for the first time. The thick mesophyll of the more newly divergent ferns does not necessarily relate to the high photosynthetic capacity on a leaf-area basis. Rather, the thick mesophyll accompanied by thick cell walls allowed the ferns to adapt to a wider range of environments through increasing leaf toughness, which would contribute to the diversification of fern species.

Optimal probe position for precordial Doppler ultrasound in children.

BACKGROUND: Precordial Doppler ultrasound technology can be used to confirm correct peripheral intravenous access in children. Changes in precordial Doppler sound from the baseline after injecting normal saline are detected using a correct peripheral intravenous access. However, the location of the precordial Doppler probe has been inconsistent in previous studies. Our study aimed to determine whether the right or left parasternal border is the optimal location for precordial Doppler probe placement. METHODS: This single-center, prospective interventional study was conducted between July 2021 and January 2022 and included children aged 1-6 years. The Doppler probe was placed under general anesthesia at the most audible site on the right and left parasternal borders of patients. Baseline heartbeat was recorded by the Doppler for 10 s on the right and left parasternal borders. After randomizing the order of the recorded data, two blinded raters separately listened to the data and decided the audibility of the sounds. RESULTS: A total of 77 patients were enrolled in the study. The proportion of the audible baseline heartbeat was significantly higher on the left parasternal borders than on the right by both rater 1 (96.1%, 22.1%, p < 0.001) and rater 2 (96.1%, 27.3%, p < 0.001). Regarding inter-rater reproducibility, Cohen's kappa statistics for the left and right parasternal borders were significant (0.65 and 0.79, both p < 0.001). CONCLUSIONS: The baseline heartbeat was more audible on the left parasternal border than on the right parasternal border with acceptably high interrater reproducibility. This is inconsistent with the interpretations of previous reports.

The photosynthetic capacity in 35 ferns and fern allies: mesophyll CO2 diffusion as a key trait.

Ferns and fern allies have low photosynthetic rates compared with seed plants. Their photosynthesis is thought to be limited principally by physical CO2 diffusion from the atmosphere to chloroplasts. The aim of this study was to understand the reasons for low photosynthesis in species of ferns and fern allies (Lycopodiopsida and Polypodiopsida). We performed a comprehensive assessment of the foliar gas-exchange and mesophyll structural traits involved in photosynthetic function for 35 species of ferns and fern allies. Additionally, the leaf economics spectrum (the interrelationships between photosynthetic capacity and leaf/frond traits such as leaf dry mass per unit area or nitrogen content) was tested. Low mesophyll conductance to CO2 was the main cause for low photosynthesis in ferns and fern allies, which, in turn, was associated with thick cell walls and reduced chloroplast distribution towards intercellular mesophyll air spaces. Generally, the leaf economics spectrum in ferns follows a trend similar to that in seed plants. Nevertheless, ferns and allies had less nitrogen per unit DW than seed plants (i.e. the same slope but a different intercept) and lower photosynthesis rates per leaf mass area and per unit of nitrogen.

Rapid response of leaf photosynthesis in two fern species Pteridium aquilinum and Thelypteris dentata to changes in CO2 measured by tunable diode laser absorption spectroscopy.

We investigated stomatal conductance (g(s)) and mesophyll conductance (g(m)) in response to atmospheric CO2 concentration [CO2] in two primitive land plants, the fern species Pteridium aquilinum and Thelypteris dentata, using the concurrent measurement of leaf gas exchange and carbon isotope discrimination. [CO2] was initially decreased from 400 to 200 µmol mol(-1), and then increased from 200 to 700 µmol mol(-1), and finally decreased from 700 to 400 µmol mol(-1). Analysis by tunable diode laser absorption spectroscopy (TDLAS) revealed a rapid and continuous response in g m within a few minutes. In most cases, both ferns showed rapid and significant responses of g m to changes in [CO2]. The largest changes (quote % decrease) were obtained when [CO2] was decreased from 400 to 200 µmol mol(-1). This is in contrast to angiosperms where an increase in g(m) is commonly observed at low [CO2]. Similarly, fern species observed little or no response of g(s) to changes in [CO2] whereas, a concomitant decline of g(m) and g(s) with [CO2] is often reported in angiosperms. Together, these results suggest that regulation of g(m) to [CO2] may differ between angiosperms and ferns.

Efficacy of in-situ simulation training using evaluation checklists for sudden oxygen supply failure during general anesthesia: A preliminary report.

Introduction: Sudden oxygen supply failure (OSF) is a life-threatening consequence that may be triggered by natural disasters. Anesthesiologists are required to manage OSF promptly in such catastrophic situations. However, the current evidence regarding the efficacy of anesthesia training for sudden OSF is insufficient. This preliminary study aimed to introduce our in-situ simulation training utilizing evaluation checklists for a sudden OSF situation during general anesthesia and to evaluate the efficacy of the training program for anesthesia providers. Methods: This is a preliminary single-center, prospective study. We developed an OSF simulation scenario utilizing evaluation checklists with key actions to manage OSF. The training session comprised four components: orientation, benchmark evaluation (pre-test) according to the checklists, a short didactic lecture, and post-lecture evaluation (post-test). The scenario comprised two steps wherein the participants were supposed to utilize different oxygen supply sources immediately after OSF (Step 1) and minimize the amount of oxygen consumption (Step 2). Results: Fifteen anesthesia providers were enrolled. The score for all anesthesia providers in the post-test was significantly higher than that in the pre-test (median 8 [IQR: 8, 8], 3 [IQR: 3, 4], P < 0.001, respectively). The successful performance rates of all anesthesia providers in one key action of all the four in Step 1 and four of all the six in Step 2 were significantly higher in the post-test than in the pre-test. Conclusions: Our in-situ training method utilizing evaluation checklists for a sudden OSF situation improved overall performance of anesthesia providers.

Association Between Plasma Fibrinogen Concentration After Cardiopulmonary Bypass and Postoperative Blood Loss in Children Undergoing Cardiac Surgery: A Retrospective Cohort Study.

Background Intraoperative hypofibrinogenemia is a major factor associated with increased postoperative blood loss in adult cardiac surgery. However, previous pediatric studies on this topic did not sufficiently adjust for potential confounders and variations in surgeons' techniques. Therefore, evidence for the association between hypofibrinogenemia and postoperative blood loss after cardiac surgery in children remains insufficient. In this study, we aimed to evaluate the association between postoperative blood loss and hypofibrinogenemia by adjusting for potential confounders and the effects of differences in surgeons' techniques. Methodology This single-center, retrospective, cohort study included children who underwent cardiac surgery with cardiopulmonary bypass from April 2019 to March 2022. Multilevel logistic regression models with mixed effects were used to evaluate the association of major blood loss in the first six hours postoperatively with fibrinogen concentration at the end of cardiopulmonary bypass. The difference in the surgeon's techniques was adjusted as a random effect for the model. The model included potential confounders identified as risk factors in previous studies. Results A total of 401 patients were included. A fibrinogen concentration ≤150 mg/dL (adjusted odds ratio (aOR) = 2.08; 95% confidence interval (CI) = 1.18-3.67; p = 0.011) and the presence of cyanotic disease (aOR = 2.34; 95% CI = 1.10-4.97; p = 0.027) were associated with major blood loss in the first six postoperative hours. Conclusions A fibrinogen concentration ≤150 mg/dL and the presence of cyanotic disease were associated with postoperative blood loss in pediatric cardiac surgery. Maintaining a fibrinogen concentration >150 mg/dL is recommended, especially for patients with cyanotic diseases.

Simultaneous generation of ultrahigh pressure and temperature to 50 GPa and 3300 K in multi-anvil apparatus.

We attempted to generate ultrahigh pressure and temperature simultaneously using a multi-anvil apparatus by combining the technologies of ultrahigh-pressure generation using sintered diamond (SD) anvils, which can reach 120 GPa, and ultrahigh-temperature generation using a boron-doped diamond (BDD) heater, which can reach 4000 K. Along with this strategy, we successfully generated a temperature of 3300 K and a pressure of above 50 GPa simultaneously. Although the high hardness of BDD significantly prevents high-pressure generation at low temperatures, its high-temperature softening allows for effective pressure generation at temperatures above 1200 K. High temperature also enhances high-pressure generation because of the thermal pressure. We expect to generate even higher pressure in the future by combining SD anvils and a BDD heater with advanced multi-anvil technology.

A strip-type boron-doped diamond heater synthesized by chemical vapor deposition for large-volume presses.

We have developed a high-pressure furnace assembly with a commercially available chemical-vapor-deposition synthesized boron-doped diamond heater consisting of four strips for large-volume multi-anvil presses (LVPs). This assembly successfully generated temperatures up to 2990 K at 15 GPa. It also has highly reproducible power-temperature relations, enabling us to estimate temperature from power reliably. It can be used for experiments above 9 GPa and is particularly useful for synchrotron x-ray experiments because of the x-ray transparency. It is also competitive in price. This technique is, thus, practical in various LVP experiments in the diamond-stability field.

Effect of sulfur on sound velocity of liquid iron under Martian core conditions.

Sulfur has been considered to be a predominant light element in the Martian core, and thus the sound velocity of Fe-S alloys at relevant high pressure and temperature is of great importance to interpret its seismological data. Here we measured the compressional sound velocity (VP) of liquid Fe, Fe80S20 and Fe57S43 using ultrasonic pulse-echo overlap method combined with a Kawai-type multi-anvil apparatus up to 20 GPa, likely corresponding to the condition at the uppermost core of Mars. The results demonstrate that the VP of liquid iron is least sensitive to its sulfur concentration in the Mars' whole core pressure range. The comparison of seismic wave speeds of Fe-S liquids with future observations will therefore tell whether the Martian core is molten and contains impurity elements other than sulfur.

Submillimetre Network Formation by Light-induced Hybridization of Zeptomole-level DNA.

Macroscopic unique self-assembled structures are produced via double-stranded DNA formation (hybridization) as a specific binding essential in biological systems. However, a large amount of complementary DNA molecules are usually required to form an optically observable structure via natural hybridization, and the detection of small amounts of DNA less than femtomole requires complex and time-consuming procedures. Here, we demonstrate the laser-induced acceleration of hybridization between zeptomole-level DNA and DNA-modified nanoparticles (NPs), resulting in the assembly of a submillimetre network-like structure at the desired position with a dramatic spectral modulation within several minutes. The gradual enhancement of light-induced force and convection facilitated the two-dimensional network growth near the air-liquid interface with optical and fluidic symmetry breakdown. The simultaneous microscope observation and local spectroscopy revealed that the assembling process and spectral change are sensitive to the DNA sequence. Our findings establish innovative guiding principles for facile bottom-up production via various biomolecular recognition events.

Stability of the Liquid State of Imidazolium-Based Ionic Liquids under High Pressure at Room Temperature.

To understand the stability of the liquid phase of ionic liquids under high pressure, we investigated the phase behavior of a series of 1-alkyl-3-methylimidazolium tetrafluoroborate ([Cnmim][BF4]) homologues with different alkyl chain lengths for 2 ≤ n ≤ 8 up to ∼7 GPa at room temperature. The ionic liquids exhibited complicated phase behavior, which was likely due to the conformational flexibility in the alkyl chain. The present results reveal that [Cnmim][BF4] falls into superpressed state around 2-3 GPa range upon compression with an implication of multiple phase or structural transitions to ∼7 GPa. Remarkably, a characteristic nanostructural organization in ionic liquids largely diminishes at the superpressed state. The behaviors of imidazolium-based ionic liquids can be classified into, at least, three patterns: (1) pressure-induced crystallization, (2) superpressurization upon compression, and (3) decompression-induced crystallization from the superpressurized glass. Interestingly, the high-pressure phase behavior was relevant to the glass transition behavior at low temperatures and ambient pressure. As n increases, the glass transition pressure (pg) decreases (from 2.8 GPa to ∼2 GPa), and the glass transition temperature increases. The results indicate that the p-T range of the liquid phase is regulated by the alkyl chain length of [Cnmim][BF4] homologues.

Selective optical assembly of highly uniform nanoparticles by doughnut-shaped beams.

A highly efficient natural light-harvesting antenna has a ring-like structure consisting of dye molecules whose absorption band changes through selective evolutionary processes driven by external stimuli, i.e., sunlight depending on its territory and thermal fluctuations. Inspired by this fact, here, we experimentally and theoretically demonstrate the selective assembling of ring-like arrangements of many silver nanorods with particular shapes and orientations onto a substrate by the light-induced force of doughnut beams with different colours (wavelengths) and polarizations in conjunction with thermal fluctuations at room temperature. Furthermore, the majority of nanorods are electromagnetically coupled to form a prominent red-shifted collective mode of localized surface plasmons resonant with the wavelength of the irradiated light, where a spectral broadening also appears for the efficient broadband optical response. The discovered principle is a promising route for "bio-inspired selective optical assembly" of various nanomaterials that can be used in the wide field of nanotechnology.