Kinetics and thermodynamics of U reduction by natural and simple organic matter

The hypothesized reaction mechanisms for U reduction by the dehydrogenation of hydroxyl groups and aliphatic hydrocarbonaceous moieties of lignite were verified by kinetic U reduction experiments using simple alcohols (1-octadecanol and 2-propanol) and aliphatic hydrocarbons (n-octacosane). The rate constants and activation energies for U reduction by these alcohols are similar to those obtained for U reduction by lignite. The rate-determining step for U reduction by both simple and natural organic matter is hypothesized to be controlled by oxygen diffusion through U oxides. The equilibria of the system lignite-aqueous uranyl have been used to calculate standard free energy changes ΔG° for lignite dehydrogenation. Their comparison with those for the dehydrogenation of simple organic molecules supports the proposed reactions thermodynamically.     

On modelling stratospheric positive ions

There has been a considerable improvement in the knowledge of stratospheric positive ion chemistry during the last decade. Results of several in-situ measurements of ion composition have been reported. Total ion density has also been measured with greater accuracy. In this work, theoretical study has been made to reproduce the main features of the above observations. Difficulties encountered in such studies are discussed. Finally models of total ion density and ion composition are given.     

熊本牡蛎(Crassostrea sikamea)多嵴和无嵴品系子二代生长性状的选择效应

为了进一步检查熊本牡蛎(Crassostrea sikamea)多嵴品系及无嵴品系的连续选择反应能力,以两个品系子一代上选组为材料,以壳高为指标,按照10%选择强度,开展了两个品系子二代混合上选研究,评估了两个品系子二代选择反应、现实遗传力,计算了两个品系的遗传改进量。结果表明:两个品系仍具有较高的现实遗传力,多嵴品系遗传参数均大于无嵴品系,表现出较好的遗传改良效果。多嵴和无嵴品系幼虫期的选择反应分别为0.47、0.34,稚贝期为0.65、0.40,养成期为0.82、0.56;幼虫期的现实遗传力分别为0.27、0.19,稚贝期为0.37、0.23,养成期为0.47、0.32;幼虫期的遗传改进量分别为4.83%、3.61%,稚贝期为7.55%、5.76%,养成期为9.95%、6.47%。经过一周年的养成,多嵴品系壳高显著大于无嵴品系,两个品系现实遗传力分别为0.50、0.35,遗传改进量分别为10.13%、6.61%。由此可见,多嵴品系具有较快的生长速度,遗传改良潜力较大。本研究为熊本牡蛎遗传改良和新品系培育奠定了坚实的基础。     

A New Index Developed for Fast Diagnosis of Meteorological Roles in Ground-Level Ozone Variations

China experienced worsening ground-level ozone(O₂) pollution from 2013 to 2019. In this study, meteorological parameters, including surface temperature(T₂), solar radiation(SW), and wind speed(WS), were classified into two aspects,(1) Photochemical Reaction Condition(PRC = T₂× SW) and(2) Physical Dispersion Capacity(PDC = WS). In this way, a Meteorology Synthetic Index(MSI = PRC/PDC) was developed for the quantification of meteorology-induced ground-level O₂pollution. The positive linear relationship between the 90 th percentile of MDA8(maximum daily 8-h average) O₂concentration and MSI determined that the contribution of meteorological changes to ground-level O-3 varied on a latitudinal gradient, decreasing from ~40% in southern China to 10%–20% in northern China. Favorable photochemical reaction conditions were more important for ground-level O₂pollution. This study proposes a universally applicable index for fast diagnosis of meteorological roles in ground-level O₂variability, which enables the assessment of the observed effects of precursor emissions reductions that can be used for designing future control policies.     

Deformation-enhanced reaction in experimentally deformed plagioclase-olivine aggregates

The effects of deformation on the kinetics of the net-transfer reaction anorthite + forsterite → cpx + opx + spinel ± gt were studied using static and shear deformation experiments. Experiments were performed on dry anorthite-olivine (An₉₂–Fo₉₃) samples at 900°C and pressures between 1,000 and 1,600 MPa in a Griggs apparatus. Deformed (‘non-hydrostatic’) and undeformed (‘static’) samples are compared in terms of phase petrology, reaction rate and reaction mechanisms. Anorthite + olivine reactions are diffusion-controlled as seen from reaction rim structures. In undeformed samples, delayed reaction onset and low reaction rates demonstrate sluggish nucleation of reaction products and slow rates of diffusion at dry conditions, even at 700–900 MPa confining pressure overstepping. The reaction rate is enhanced in deformed An–Fo samples. The higher rate is mainly attributed to a combination of high stresses and viscous deformation processes of the reactants and products, which cause an increase in the nucleation rate of products. The results imply that viscous deformation processes alone can be responsible for the initiation and localisation of metamorphic reactions in dry rocks in the absence of fluid infiltration. A. A. de Ronde was supported by the Swiss National Fond grants 2100-057092.99 and 2000-065041.01.     

Formation of eclogite, and reaction during exhumation to mid-crustal levels, Snowbird tectonic zone, western Canadian Shield

A re‐evaluation of the P–T history of eclogite within the East Athabasca granulite terrane of the Snowbird tectonic zone, northern Saskatchewan, Canada was undertaken. Using calculated pseudosections in combination with new garnet–clinopyroxene and zircon and rutile trace element thermometry, peak metamorphic conditions are constrained to ～16 kbar and 750 °C, followed by near‐isothermal decompression to ～10 kbar. Associated with the eclogite are two types of occurrences of sapphirine‐bearing rocks preserving a rich variety of reaction textures that allow examination of the retrograde history below 10 kbar. The first occurs as a 1–2 m zone adjacent to the eclogite body with a peak assemblage of garnet–kyanite–quartz interpreted to have formed during the eclogite facies metamorphism. Rims of orthopyroxene and plagioclase developed around garnet, and sapphirine–plagioclase and spinel–plagioclase symplectites developed around kyanite. The second variety of sapphirine‐bearing rocks occurs in kyanite veins within the eclogite. The veins involve orthopyroxene, garnet and plagioclase layers spatially organized around a central kyanite layer that are interpreted to have formed following the eclogite facies metamorphism. The layering has itself been modified, with, in particular, kyanite being replaced by sapphirine–plagioclase, spinel–plagioclase and corundum–plagioclase symplectites, as well as the kyanite being replaced by sillimanite. Petrological modelling in the CFMAS system examining chemical potential gradients between kyanite and surrounding quartz indicates that these vein textures probably formed during further essentially isothermal decompression, ultimately reaching ～7 kbar and 750 °C. These results indicate that the final reaction in these rocks occurred at mid‐crustal levels at upper amphibolite facies conditions. Previous geochronological and thermochronological constraints bracket the time interval of decompression to <5–10 Myr, indicating that ～25 km of exhumation took place during this interval. This corresponds to minimum unroofing rates of ～2–5 mm year^?1 following eclogite facies metamorphism, after which the rocks resided at mid‐crustal levels for 80–100 Myr.     

Flexural response of piles under liquefied soil conditions

The paper pertains to the development of a generalized procedure to analyze and predict the flexural behavior of axially and laterally loaded pile foundations under liquefied soil conditions. Pseudo-static analysis has been carried out taking into consideration the combined effect of axial load and lateral load. Based on the available literature effect of degradation on the modulus of subgrade reaction due to soil liquefaction has been incorporated in the analysis. The developed program was calibrated and validated by comparing the predicted behavior of the pile with theoretical and experimental results reported in literature. The predicted behavior has been found to be in excellent to very good agreement with the theoretical and observed values in the field, respectively. The present study highlights the importance of considering the axial load from the superstructure along with the inertia forces from the superstructure and the kinematic forces from the liquefied soil in the design of pile foundations in liquefiable areas. The significance of densification of the soil in the liquefiable areas and presence of an adequate top non-liquefied soil cover causing appreciable reduction in deflection and bending moment experienced by the piles has been highlighted.     

Variation of human perceptiveness of earthquakes during seismic sequences

This paper describes the variation of the human perception of earthquakes under the peculiar condition of seismic sequence occurrence. To this aim, we chose and have analyzed four seismic sequences that reflect the most common models of seismicity occurrence in the Italian territory. Our data always refer to the epicentral area, so that the contribution of the epicentral distance to the earthquake sensitiveness is considered constant. To search for recurrent behavior of people in the perception of earthquakes, we crossed seismological data to sensitivity data coming from the archives of the Italian Civil Protection. In each sequence, we individuate a number of “indicators”, such as the rate between felt and not-felt events and the minimum magnitude for which 100% of the events are felt. Such indicators are proportional to the energy released by the sequence and can be particularly affected by the time protraction of the sequence, and/or by the different familiarity with the seismic phenomenon, and/or by the intensity of the emotional impact of a seismic crisis. The observed trends of sensitiveness show a significant variation of the people perceptivity within the sequence development. From the analysis of the dataset, one can distinguish the variation of perceptivity due to emotional factors from those due to physical factors. An important observation, which is confirmed by a statistical analysis, is that the source depth does not affect the perceptiveness of earthquakes. Finally, we find important differences between on-sequence and off-sequence human perceptiveness that are connected with the different levels of alert.