Vertical gradient of needle ozone uptake within the canopy of Cryptomeria japonica.

Leaf ozone uptake through the stomata is an important index for the ozone risk assessments on trees. Stomatal conductance (gs) and ozone concentration ([O3]), determinants of the leaf ozone uptake, are known to show vertical gradients within a tree canopy. However, less is known about the within-canopy vertical gradient of leaf ozone uptake. This study was aimed to elucidate how the vertical gradient of [O3] and gs affect needle ozone uptake within a canopy of mature Cryptomeria japonica trees in a suburban forest at Tokyo, Japan. For this purpose, a multilayer gas exchange model was applied to estimate the vertical gradient of needle gs and the accumulated ozone uptake during the study period (POD1, Phytotoxic Ozone Dose above a threshold of 1 nmol m-2 s-1). In addition, we also tested several scenarios of vertical gradient of [O3] within the canopy for sensitivity analysis. The POD1 was declined from the top to the bottom of the canopy. This tendency strongly depended on the vertical gradient of gs and was hardly affected by the changes in simulated vertical reductions of the [O3]. We further assessed the photosynthesis of sunlit needles (needles absorbing both direct and diffuse light) and shaded needles (needles only absorbing diffuse light). The photosynthesis of shaded needles in the upper half of the canopy made a great contribution to the entire canopy photosynthesis. In addition, given that their POD1 was lower than that of sunlit needles, ozone may affect sunlit and shaded needles differently. We concluded that these considerations should be incorporated into modeling of the calculation of ozone uptake for mature trees to make accurate predictions of the ozone effects on trees at the canopy scale.

Anion recognition by silanetriol in acetonitrile.

The anion recognition ability of 2,4,6-triisopropylphenylsilanetriol 5 has been evaluated by 1H NMR titrations in MeCN-d3. The anion recognition ability of silanetriol 5 was greater than those of the structurally related silanediols and silanemono-ol, although less effective than those of 1,3-disiloxane-1,3-diol and 1,3-disiloxane-1,1,3,3-tetraol. From the comparison of the association constants and DFT calculations, all three silanol groups of 5 cooperatively hydrogen bonded to anionic species. The catalytic ability of silanetriol 5 for the addition of indole to ß-nitrostyrene in CH2Cl2 has also been evaluated. Silanetriol 5 acts as a more effective organocatalyst than the corresponding silanediol in this reaction.

On the origin and evolution of the asteroid Ryugu: A comprehensive geochemical perspective.

Presented here are the observations and interpretations from a comprehensive analysis of 16 representative particles returned from the C-type asteroid Ryugu by the Hayabusa2 mission. On average Ryugu particles consist of 50% phyllosilicate matrix, 41% porosity and 9% minor phases, including organic matter. The abundances of 70 elements from the particles are in close agreement with those of CI chondrites. Bulk Ryugu particles show higher δ18O, Δ17O, and ε54Cr values than CI chondrites. As such, Ryugu sampled the most primitive and least-thermally processed protosolar nebula reservoirs. Such a finding is consistent with multi-scale H-C-N isotopic compositions that are compatible with an origin for Ryugu organic matter within both the protosolar nebula and the interstellar medium. The analytical data obtained here, suggests that complex soluble organic matter formed during aqueous alteration on the Ryugu progenitor planetesimal (several 10's of km), <2.6 Myr after CAI formation. Subsequently, the Ryugu progenitor planetesimal was fragmented and evolved into the current asteroid Ryugu through sublimation.

Synthesis, Structures, and Thermal Properties of Symmetric and Janus "Lantern Cage" Siloxanes.

Symmetric and asymmetric (Janus-type) new "lantern cage" siloxanes (PhSiO1.5 )4 (Me2 SiO)4 (RSiO1.5 )4 (R=Ph or iBu) were synthesized through reaction of all-cis-[PhSi(OSiMe2 Br)O]4 with all-cis-[RSi(OH)O]4 (R=Ph or iBu). These precursors were obtained by facile two or three-step reactions from commercially available compounds. The spectroscopic properties of the resulting products were fully characterized and they showed high thermal stability and sublimation without decomposition. The crystal structures clearly indicated that the internal vacancy volumes of the lantern cages are considerably larger than that of octaphenylsilsesquioxane (PhSiO1.5 )8 . DFT calculations of the lantern cage showed a distinctly different electronic state from that of octasilsesquioxane. These results suggest that lantern cage siloxanes have a characteristic "field" in the molecule.

Hypervelocity collision and water-rock interaction in space preserved in the Chelyabinsk ordinary chondrite.

A comprehensive geochemical study of the Chelyabinsk meteorite reveals further details regarding its history of impact-related fragmentation and melting, and later aqueous alteration, during its transit toward Earth. We support an ∼30 Ma age obtained by Ar-Ar method (Beard et al., 2014) for the impact-related melting, based on Rb-Sr isotope analyses of a melt domain. An irregularly shaped olivine with a distinct O isotope composition in a melt domain appears to be a fragment of a silicate-rich impactor. Hydrogen and Li concentrations and isotopic compositions, textures of Fe oxyhydroxides, and the presence of organic materials located in fractures, are together consistent with aqueous alteration, and this alteration could have pre-dated interaction with the Earth's atmosphere. As one model, we suggest that hypervelocity capture of the impact-related debris by a comet nucleus could have led to shock-wave-induced supercritical aqueous fluids dissolving the silicate, metallic, and organic matter, with later ice sublimation yielding a rocky rubble pile sampled by the meteorite.

Risk of secondary osteoporosis due to lobular cholestasis in non-cirrhotic primary biliary cholangitis.

BACKGROUND AND AIM: It remains unclear whether primary biliary cholangitis (PBC) represents a risk factor for secondary osteoporosis. METHODS: A case-control study was conducted to examine bone mineral density and bone turnover markers in middle-aged postmenopausal PBC patients without liver cirrhosis. We compared the incidence of low bone mineral density between propensity-score matched subgroups of PBC patients and healthy controls and investigated the mechanisms underlying unbalanced bone turnover in terms of the associations between bone turnover markers and PBC-specific histological findings. RESULT: Our analysis included 128 consecutive PBC patients, all postmenopausal women aged in their 50s or 60s, without liver cirrhosis or fragility fracture at the time of PBC diagnosis. The prevalence of osteoporosis was significantly higher in the PBC group than in the control group (26% vs 10%, P = 0.015, the Fisher exact probability test). In most PBC patients (95%), the level of bone-specific alkaline phosphatase was above the normal range, indicating increased bone formation. On the other hand, the urine type I collagen-cross-linked N-telopeptide showed variable levels among our PBC patients, indicating unbalanced bone resorption. Advanced fibrosis was associated with low bone turnover. Lobular cholestasis, evaluated as aberrant keratin 7 expression in hepatocytes, showed significant negative correlations with bone formation and resorption, indicating low bone turnover. CONCLUSION: Our results show that, compared with healthy controls, even non-cirrhotic PBC patients have significantly higher risk of osteoporosis. Moreover, lobular cholestasis was associated with low bone turnover, suggesting this feature of PBC may itself cause secondary osteoporosis in PBC patients.

Stereoselective synthesis and physicochemical properties of liquid-crystal compounds possessing a trans-2,5-disubstituted tetrahydropyran ring with negative dielectric anisotropy.

Three stereoselective syntheses and the physicochemical properties of trans,trans-5-(4-ethoxy-2,3-difluorophenyl)-2-(4-propylcyclohexyl)tetrahydropyran, which is an important liquid-crystal compound with a large negative dielectric anisotropy (Δε=-7.3), are described. The key step in the construction of the trans-2,5-disubstituted tetrahydropyran ring in the first approach involved a benzylic cation mediated intramolecular olefin cyclization of a 2-allyloxy-1-arylethanol derivative. The second method included the Et2 Zn-induced 1,2-aryl shift of a bromohydrin obtained from a hetero-Diels-Alder reaction, followed by stereoselective bromination. The third approach utilized the hetero-Diels-Alder reaction of trans-4-propylcyclohexanecarboxaldehyde and a 2-aryl-3-(trimethylsilyl)oxy-1,3-butadiene, followed by stereoselective protonation. From results obtained by using a quantum chemical calculation method, the reason why the target compound shows a large negative Δε value is discussed.

Space environment of an asteroid preserved on micrograins returned by the Hayabusa spacecraft.

Records of micrometeorite collisions at down to submicron scales were discovered on dust grains recovered from near-Earth asteroid 25143 (Itokawa). Because the grains were sampled from very near the surface of the asteroid, by the Hayabusa spacecraft, their surfaces reflect the low-gravity space environment influencing the physical nature of the asteroid exterior. The space environment was examined by description of grain surfaces and asteroidal scenes were reconstructed. Chemical and O isotope compositions of five lithic grains, with diameters near 50 µm, indicate that the uppermost layer of the rubble-pile-textured Itokawa is largely composed of equilibrated LL-ordinary-chondrite-like material with superimposed effects of collisions. The surfaces of the grains are dominated by fractures, and the fracture planes contain not only sub-µm-sized craters but also a large number of sub-µm- to several-µm-sized adhered particles, some of the latter composed of glass. The size distribution and chemical compositions of the adhered particles, together with the occurrences of the sub-µm-sized craters, suggest formation by hypervelocity collisions of micrometeorites at down to nm scales, a process expected in the physically hostile environment at an asteroid's surface. We describe impact-related phenomena, ranging in scale from 10(-9) to 10(4) meters, demonstrating the central role played by impact processes in the long-term evolution of planetary bodies. Impact appears to be an important process shaping the exteriors of not only large planetary bodies, such as the moon, but also low-gravity bodies such as asteroids.

Determination of 17O-excess of terrestrial silicate/oxide minerals with respect to Vienna Standard Mean Ocean Water (VSMOW).

RATIONALE: Oxygen triple isotope compositions give key information for understanding physical processes during isotopic fractionation between the geo-, hydro-, bio-, and atmosphere. For detailed discussion of these topics, it is necessary to determine precise (17)O-excess values of terrestrial silicate/oxide minerals with respect to Vienna Standard Mean Ocean Water (VSMOW). METHODS: Water was fluorinated in an electrically heated Ni-metal tube into which water and BrF(5) were loaded for the quantitative extraction of oxygen. Silicate/oxide minerals were fluorinated by heating with a CO(2) laser in an atmosphere of BrF(5). The extracted oxygen was purified and isotope ratios of the oxygen triple isotope compositions were determined using a Finnigan MAT253 isotope ratio mass spectrometer. RESULTS: The oxygen triple isotope compositions of meteoric water and terrestrial silicate/oxide minerals fall on statistically distinguishable fractionation lines, defined as [ln(δ(17)O + 1) = λln(δ(18) O + 1) + Δ], where λ and Δ correspond to the slope and intercept, respectively. The fractionation line for meteoric water has λ = 0.5285 ± 0.0005 and Δ = 0.03 ± 0.02‰ and for terrestrial silicate/oxide minerals has λ = 0.5270 ± 0.0005 and Δ = -0.070 ± 0.005‰, at the 95% confidence limit. CONCLUSIONS: All the analyzed terrestrial silicate/oxide minerals including internationally accepted reference materials (NBS-28, UWG-2, and San Carlos olivine) have a negative (17)O-excess with respect to VSMOW. We propose that it is necessary to specify if the determined δ(17)O values of terrestrial and extraterrestrial samples are expressed as the difference from VSMOW or the terrestrial silicate mineral-corrected value.

Determination of mass-dependent chromium isotopic compositions in geological samples by double spike-total evaporation-thermal ionization mass spectrometry (DS-TE-TIMS).

BACKGROUND: Chromium isotopes have been used to trace geochemical and cosmochemical processes in the past. However, the presence of multivalent Cr species has made it difficult to isolate Cr from geological samples, particularly for samples with a low Cr mass fraction. RESULTS: Here, a simple three-step ion exchange chromatography procedure is presented to separate Cr from various sample matrices, ranging from ultramafic to felsic rocks. Throughout each of the column chromatography step, 1 mL of cation exchange resin AG50W-X8 (200-400 mesh) was used as the stationary phase and oxalic acid as a chelating agent, was used in addition to the inorganic acids. This method yielded high recoveries of Cr [93 ± 8% (2SD, N = 7)] regardless of the lithology. The total procedural blank of Cr was <0.5 ng. We also developed a double spike-total evaporation-thermal ionization mass spectrometry (DS-TE-TIMS) technique that significantly reduced sample consumption to ∼20 ng of Cr per each measurement of mass-dependent 53Cr/52Cr. SIGNIFICANCE: This study achieved a 2SD external precision of 0.02‰ for the analysis of NIST NBS3112a and of 0.01-0.07‰ for the geological samples. This study enabled high-precision Cr isotope analysis in geological samples with various matrix and Cr compositions using relatively small sample volumes.

Stomatal ozone uptake of a Quercus serrata stand based on sap flow measurements with calibrated thermal dissipation sensors.

The amount of ozone absorbed by the tree leaves is a critical factor determining the ozone effects on forest trees. Stomatal ozone uptake of a forest canopy can be estimated from the ozone concentration and canopy conductance (gc) determined by the sap-flow-based method. This method measures sap flow as a metric of crown transpiration and then derives gc. The thermal dissipation method (TDM) has been used to measure sap flow in most studies adopting this approach. However, recent studies have indicated that TDM may underestimate sap flow, especially in ring-porous tree species. In the present study, the accumulated stomatal ozone uptake (AFST) of a stand of Quercus serrata, a typical ring-porous tree species in Japan, was estimated by measuring sap flow using species-specific calibrated TDM sensors. Laboratory calibration of the TDM sensors revealed that the parameters (α and ß) in an equation converting outputs from the sensors (K) to sap flux density (Fd) were substantially larger for Q. serrata than those originally proposed by Granier (1987). The Fd measured in the Q. serrata stand using calibrated TDM sensors were significantly larger than those obtained using non-calibrated sensors. The diurnal average of gc and daytime AFST (10.4 mm s-1 and 10.96 mmol O3 m-2 month-1) of the Q. serrata stand estimated by using calibrated TDM sensors in August 2020 were similar to those of forests dominated by Quercus species estimated by micrometeorological measurements in previous studies. In contrast, the gc and daytime AFST of the Q. serrata stand estimated by non-calibrated TDM sensors were remarkably lower than those estimated by micrometeorological measurements in previous studies, indicating severe underestimation. Therefore, it is strongly recommended that sap flow sensors are species-specifically calibrated when estimating the canopy conductance and ozone uptake of forests dominated by ring-porous trees based on sap flow measurements using TDM.

Organic Matter in the Asteroid Ryugu: What We Know So Far.

The Hayabusa2 mission was tasked with returning samples from the C-complex asteroid Ryugu (1999 JU3), in order to shed light on the formation, evolution and composition of such asteroids. One of the main science objectives was to understand whether such bodies could have supplied the organic matter required for the origin of life on Earth. Here, a review of the studies concerning the organic matter within the Ryugu samples is presented. This review will inform the reader about the Hayabusa2 mission, the nature of the organic matter analyzed and the various interpretations concerning the analytical findings including those concerning the origin and evolution of organic matter from Ryugu. Finally, the review puts the findings and individual interpretations in the context of the current theories surrounding the formation and evolution of Ryugu. Overall, the summary provided here will help to inform those operating in a wide range of interdisciplinary fields, including planetary science, astrobiology, the origin of life and astronomy, about the most recent developments concerning the organic matter in the Ryugu return samples and their relevance to understanding our solar system and beyond. The review also outlines the issues that still remain to be solved and highlights potential areas for future work.

Insights into the formation and evolution of extraterrestrial amino acids from the asteroid Ryugu.

All life on Earth contains amino acids and carbonaceous chondrite meteorites have been suggested as their source at the origin of life on Earth. While many meteoritic amino acids are considered indigenous, deciphering the extent of terrestrial contamination remains an issue. The Ryugu asteroid fragments (JAXA Hayabusa2 mission), represent the most uncontaminated primitive extraterrestrial material available. Here, the concentrations of amino acids from two particles from different touchdown sites (TD1 and TD2) are reported. The concentrations show that N,N-dimethylglycine (DMG) is the most abundant amino acid in the TD1 particle, but below detection limit in the other. The TD1 particle mineral components indicate it experienced more aqueous alteration. Furthermore, the relationships between the amino acids and the geochemistry suggest that DMG formed on the Ryugu progenitor body during aqueous alteration. The findings highlight the importance of aqueous chemistry for defining the ultimate concentrations of amino acids in primitive extraterrestrial samples.

New isolable dialkylsilylene and its isolable dimer that equilibrate in solution.

The new isolable dialkylsilylene 3 bearing a bidentate alkyl substituent was synthesized. Recrystallization of silylene 3 gave yellow crystals of 3 and orange-red crystals of tetraalkyldisilene 4, a dimer of 3. In the solid state, 3 exists as a monomer with a closest distance of 6.745 Å between dicoordinate silicon atoms, while disilene 4 has a remarkably long Si═Si double bond distance of 2.252 Å. An equilibrium between 3 and 4 in solution was observed by NMR and UV-vis spectroscopies, and the thermodynamic parameters of the equilibrium were estimated to be ΔH = -36 ± 3 kJ mol(-1) and ΔS = -170 ± 15 J mol(-1) K(-1). Analysis of the percent buried volume, a measure of the steric demand around the divalent silicon, showed that the flexible steric bulkiness of the alkyl substituent of 3 and 4 allows the reversible dimerization of silylene 3 to disilene 4 and the isolation of both species.

Novel nickel isolation procedure for a wide range of sample matrices without using dimethylglyoxime for isotope measurements using MC-ICP-MS.

Nickel isotope ratios have traditionally been used as an important tracer in cosmochemistry, and recently, it has gained attention in geochemistry, biochemistry, and environmental sciences with the development of MC-ICP-MS. Purification of Ni before isotope measurement is mandatory for obtaining precise data, which has been commonly achieved with ion-exchange chromatography, employing dimethylglyoxime (DMG) as a chelating agent for Ni. However, it has been pointed out that the use of DMG can adversely affect the isotope measurement due to insufficient Ni recovery and mass bias during measurement caused by the remaining DMG. Ni isolation procedures without the usage of DMG were innovated, but they have disadvantages such as the necessity of complex separation methods, high Ni blank, and matrix-dependent Ni recovery. Here, we present a simple Ni isolation procedure without using DMG but with the aid of oxalic acid along with common inorganic acids, achieving near-complete recovery of Ni with low blanks [0.7 ± 0.3 ng (2SD, n = 4)] only using three ion exchange column steps. To validate our method and strengthen the Ni isotope database of reference materials, 60Ni/58Ni of 20 geological reference materials, covering wide matrix compositions, were measured by MC-ICP-MS using the double-spike method. The results have shown that high recovery of Ni, independent of the sample matrix elements was achieved (98 ± 4%) and the 60Ni/58Ni was measured with a 2SD of 0.006-0.084‰ from samples containing 100-200 ng Ni.

The Albedo of Ryugu: Evidence for a High Organic Abundance, as Inferred from the Hayabusa2 Touchdown Maneuver.

The Hayabusa2 mission successfully collected samples from the asteroid Ryugu last year and will return these to Earth in December 2020. It is anticipated that the samples will enable the analysis of terrestrially uncontaminated organic matter and minerals. Such analyses are in turn expected to elucidate the evolution of organic matter through Solar System history, including the origination and processing of biogenically important molecules, which could have been utilized by the first organisms on Earth. In anticipation, studies have made predictions concerning the properties of Ryugu, including its composition. The spectral characteristics of Ryugu, such as albedo, have been employed to relate the asteroid to members of the carbonaceous chondrite group that have been identified on Earth. However, the recent Hayabusa2 touchdown highlights a disparity between the color of surfaces of displaced platy fragments, indicating a brightening trend for the surface exposed to space compared to that facing into the body. Here we present a mass balance calculation with reference to data from the literature, which indicates that Ryugu may contain a significantly higher abundance of organic matter (likely >50%) than the currently most accepted meteorite analogues. A high organic content may result in high levels of extractable organic matter for the second touchdown site, where the spacecraft sampled freshly exposed material. However, high abundances of insoluble aromatic/graphitic rich organic matter may be present in the first touchdown site, which sampled the surface of Ryugu that had been exposed to space. Moreover, we suggest that the potentially high organic abundance and the rubble-pile nature of Ryugu may originate from the capture of rocky debris by a comet nucleus and subsequent water-organic-mineral interactions and sublimation of water ice.

Origin of ocean island basalts in the West African passive margin without mantle plume involvement.

The geochemical variabilities in intraplate basalts (IB) from the West African passive margin (WAPM) region, have generally been employed to indicate the presence of recycled materials in an associated upwelling mantle plume. However, the absence of time-progressive linear hotspot tracks in WAPM-IB make it difficult to explain their genesis solely by the mantle plume hypothesis. Here, we show that the Sr-Nd-Hf-Pb isotopic variations in basalts from most of the WAPM-IB could have mainly attributed to the derivation from two types of fusible regions of the refertilized subcontinental lithospheric mantle (SCLM) and the sub-lithospheric mantle. The locations and magma genesis of WAPM-IB are strongly related to the distance from the Mesozoic rift axis and the structure of the rifted SCLM. The melting of the source region can possibly be attributed to small-scale mantle convection at the base of the SCLM without the involvement of a mantle plume.

Asian dust increases radiocesium retention ability of serpentine soils in Japan.

Radiocesium (RCs) is selectively adsorbed on interlayer sites of weathered micaceous minerals, which can reduce the mobility of RCs in soil. Therefore, soils developed from mica-deficient materials (e.g. serpentine soils) may have a higher risk of soil-to-plant transfer of RCs. Soils were collected from three serpentine soil profiles; Udepts in Oeyama, Japan, and Udepts and Udox in Kinabalu, Malaysia. Soil was sampled every 3 cm from 0 to 30 cm depth and sieved to isolate soil particles of ≤20 µm diameter for the assessment of radiocesium interception potential (RIP) after a series of pretreatments. One subset was treated with H2O2 to remove organic matter (OM). Another subset was further treated with hot sodium citrate to remove hydroxy-Al polymers (Al(OH)x). RIPuntreated was <0.4 mol kg-1 whereas mica-K content was <0.02% by weight for ≤20-µm soil particles from Udepts and Udox in Kinabalu, Malaysia, values as low as those of non-micaceous minerals (e.g. kaolinite and smectite). Neither OM nor Al(OH)x removal resulted in a large increase in RIP value for these soils. These results clearly indicated that serpentine soils in Malaysia have very few RCs selective adsorption sites due to the absence of micaceous minerals. In contrast, soil from Udepts in Oeyama, Japan showed average RIPuntreated of 5.6 mol kg-1 and mica-K content of 0.72% by weight for the ≤20-µm particles. Furthermore, the RIP value was significantly increased to an average of 22.5 mol kg-1 after removing both OM and Al(OH)x. These results strongly suggest that weathered micaceous minerals primarily control the ability to retain RCs. These micaceous minerals cannot originate from serpentine minerals, and are probably incorporated as an exotic material, such as Asian dust. This hypothesis is supported by the δ18O value of quartz isolated from the ≤20-µm soil particles from Oeyama, Japan (+16.13‰±0.11‰), very similar to that of Asian dust. In conclusion, serpentine soils in Japan may exhibit a reduced risk of soil-to-plant transfer of RCs due to the historical deposition of Asian dust.