Water-poor Conditions Research Articles

Heme-based aquareceptors

How cells sense water is of fundamental importance in biology. Hygrosensation has been demonstrated in specialized sensory cells that sense extracellular moisture. Even in microorganisms, osmosensors do not sense water per se. Water-sensing mechanisms would have been necessary for organisms to migrate and survive in water-poor conditions and to evolve into multicellular organisms. Due to the potential ability of water molecules to bind to gas-binding sites in the heme-based sensing domains of gasoreceptors, I suggest that some of them could have a parallel role as protein aquareceptors. Just as gasoreceptors function in almost every cell, aquareceptors must also function in almost every cell. I think that aquareceptors must be present in the cell membrane, cytoplasm, and every organelle. I also wonder if hemoglobin could also be considered a putative aquareceptor.

Aqueously altered igneous rocks sampled on the floor of Jezero crater, Mars.

The Perseverance rover landed in Jezero crater, Mars, to investigate ancient lake and river deposits. We report observations of the crater floor, below the crater's sedimentary delta, finding that the floor consists of igneous rocks altered by water. The lowest exposed unit, informally named Séítah, is a coarsely crystalline olivine-rich rock, which accumulated at the base of a magma body. Magnesium-iron carbonates along grain boundaries indicate reactions with carbon dioxide-rich water under water-poor conditions. Overlying Séítah is a unit informally named Máaz, which we interpret as lava flows or the chemical complement to Séítah in a layered igneous body. Voids in these rocks contain sulfates and perchlorates, likely introduced by later near-surface brine evaporation. Core samples of these rocks have been stored aboard Perseverance for potential return to Earth.

Electrical Conductivity of Eclogitic Omphacite and Garnet at Water-Rich Conditions

Electrical conductivity of water-rich omphacite and garnet in eclogite was measured at 1 GPa and 200–800°C in a piston cylinder press and by a Solartron-1260 impedance/gain-phase analyzer at 106-1 Hz frequency. The water content of pre-annealed omphacite and garnet was 775–2,000 and 705–1,460 ppm H2O, respectively. Sample chemistry and water contents remained unchanged during conductivity runs. At otherwise identical conditions, the conductivity of both minerals increases with both temperature and water content, and the water content exponent is ∼1.45 and 1.12 for omphacite and garnet, respectively. The activation enthalpy is ∼70 kJ/mol for omphacite and 84 kJ/mol for garnet and is broadly independent of sample water content. Combining with previous work, the conductivity dependence of omphacite on water content differs between water-rich and water-poor conditions, due to different types and mobility of water in samples that are closely related to its incorporation mechanism; in contrast, the conductivity dependence of garnet with a similar type of water is comparable over a wide range of water contents. The estimated bulk conductivity of eclogite at water-rich conditions is very high, up to ∼0.01–0.1 S/m at 600–900°C. Geophysically resolved high resistivity of subducting crusts at 70–120 km depth suggests extremely low water contents of omphacite and garnet in the eclogitized slab. The data provide support to the model based on omphacite and garnet conductivity at water-poor conditions that the amount of water recycled by crust subduction to the deep mantle is probably limited.

Electrical conductivity of omphacite and garnet indicates limited deep water recycling by crust subduction

It is usually stated that oceanic crust recycling at subduction zones introduces large quantities of water into Earth's interior. However, it remains clouded how much water is recycled to the deep mantle. This is largely due to the challenge in directly sampling, and analyzing the water content of, a deep subducting crust. The subducting crust below ∼30 km depth is dominated by omphacite and garnet in eclogite-facies rocks. Here we have determined the electrical conductivity of omphacite and garnet in representative subduction-related eclogites, each with varying contents of Fe and H2O that are key in electrical conduction. Considering the measured conductivity, the eclogite chemistry by geochemical investigations and the highly resistive property of subducting crusts by geophysical surveys, we demonstrate that, at 70-120 km depths in the subducting crust, the H2O contents of omphacite and garnet are strikingly small, with the maximum value being <400 and <80 ppm in the former and latter, respectively. The very small water contents indicate extremely water-poor conditions, or very low water activity, during the eclogite-facies metamorphism and in the system. This further implies the absence of appreciated amounts of hydrous phases such as amphibole and chlorite in the matrix, because of the strong ability of omphacite and garnet in hosting water as documented in natural samples. We suggest that the recycling of water to the deep mantle by oceanic crust subduction is probably very limited. The results are important for modeling the conductivity of subducting slabs and understanding the deep water circulation.

Influence of phosphorus nutrition on seed yield and quality of pea (Pisum sativum L.) cultivars across different seasons

Due to the rapid shrinking of supply of mineral nutrients as well as observed weather fluctuations in throughout Europe in recent ten years, sustainable phosphorus fertilisation has become an important aspect of legume cultivation. There is a lack of knowledge about the effect of phosphorus (P) nutrition on the pea seed yield and quality in water poor conditions. This study was conducted to evaluate the seed yield and seed chemical composition of selected pea cultivars in response to the level of P fertilisation and weather conditions across three consecutive years. Redundancy analysis (RDA) was used to assess the proportion of variability of tested variables (seed quality traits) that could be explained by explanatory variables (year, cultivar, fertilisation). Temporary soil drought during flowering stage resulted in a significant increase in yield only after high level of phosphorus application (140 kg ha–1). This indicates that phosphorus significantly mitigated the effect of water shortage. In a dry year, pea had high concentration of fat and fibre in seeds, while in very humid year the opposite response was observed. RDA analysis proved that year effect explained over 50% variability, whereas cultivar and P fertilisation explained only 14.2% of variability. The effect of P fertilisation was only marginal (1.6%) in comparison with cultivar selection (12.6%). Interaction of pea cultivars with fertilisation shows a consistent tendency towards increase of crude protein under higher phosphorus doses for cultivars ‘Tarchalska’ and ‘Protecta’ whereas opposite tendency was observed for ‘Batuta’ and ‘Tinker’. It can be concluded that suitable cultivar selection gives a much greater opportunity to affect pea chemical composition than P fertilisation.

Study of the interaction of water with phospholipid bilayers by FTIR spectroscopy

The hydration of the dimyristoylphosphatidylcholine multi-bilayers has been studied by means of Fourier transform infrared spectroscopy. The structure of water confined in lipid membrane, under water-rich and water-poor conditions has been investigated by examining the OH stretching band region. We found that the structure of solvation water of lipid bilayer differs from bulk water. In addition, interaction of water molecules with carbonyl group and phosphate group of phosphatidylcholine have been observed through the downshift of the relative vibrational components representing hydrogen bonded groups. We infer that the disorder of the water network occurs especially in the interfacial region of phospholipids and it increases above the gel to liquid crystalline phase transition, giving rise to an increase of the absorption around 3600 cm -1 which indicates the presence of weakly hydrogen bonded water aggregates.

Biomass Allocation of Stoloniferous and Rhizomatous Plant in Response to Resource Availability: A Phylogenetic Meta-Analysis.

Resource allocation to different functions is central in life-history theory. Plasticity of functional traits allows clonal plants to regulate their resource allocation to meet changing environments. In this study, biomass allocation traits of clonal plants were categorized into absolute biomass for vegetative growth vs. for reproduction, and their relative ratios based on a data set including 115 species and derived from 139 published literatures. We examined general pattern of biomass allocation of clonal plants in response to availabilities of resource (e.g., light, nutrients, and water) using phylogenetic meta-analysis. We also tested whether the pattern differed among clonal organ types (stolon vs. rhizome). Overall, we found that stoloniferous plants were more sensitive to light intensity than rhizomatous plants, preferentially allocating biomass to vegetative growth, aboveground part and clonal reproduction under shaded conditions. Under nutrient- and water-poor condition, rhizomatous plants were constrained more by ontogeny than by resource availability, preferentially allocating biomass to belowground part. Biomass allocation between belowground and aboveground part of clonal plants generally supported the optimal allocation theory. No general pattern of trade-off was found between growth and reproduction, and neither between sexual and clonal reproduction. Using phylogenetic meta-analysis can avoid possible confounding effects of phylogeny on the results. Our results shown the optimal allocation theory explained a general trend, which the clonal plants are able to plastically regulate their biomass allocation, to cope with changing resource availability, at least in stoloniferous and rhizomatous plants.

VIRTIS emissivity of Alpha Regio, Venus, with implications for tessera composition

The composition of Venus tessera terrain is unknown. The Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) aboard Venus Express (VEx) collects data that yields the surface emissivity at ∼1μm, which contains information convolving a number of surface properties, including composition. We examine the variation of emissivity in the vicinity of Alpha Regio, which is the largest exposure of tessera terrain imaged by VIRTIS. We find that the emissivity of Alpha Regio tessera is lower than adjacent plains materials and the deposits and flows of Eve corona, both of which have previously been interpreted to be basaltic. The emissivity of the bulk of Alpha is also lower than its western boundary, which is interpreted to comprise plains structurally deformed to the same degree as tessera terrain. This suggests that the lower emissivity of Alpha is independent of structural elements, macroscale roughness, or local sedimentation processes, and is due to material properties like composition or grain size. The deviation of the emissivity of Alpha from that of the plains for which a bulk basaltic composition is well supported corresponds to a significant difference in rock type or surface mineral assemblage. The 1μm emissivity of Alpha is consistent with rocks with low ferrous iron content. This includes felsic igneous rocks like granitoids that form under either water-rich or water-poor conditions. A water-rich origin would require both a hydrosphere and a plate recycling mechanism and thus be limited to the lifetime of surface water on Venus. Alternatively, granitoids could form via the differentiation of basaltic melts. The production of all tessera terrain by this mechanism would require the accumulation and preservation of felsic melts from a volume of mafic magma that exceeds what is preserved in the currently observed plains. Both mechanisms of granitoid formation would require that tessera terrain be formed prior to the emplacement of the plains, consistent with their stratigraphic position. Anorthosites also satisfy the emissivity signature and can form from copious amounts of partial melting of a mafic source. Low emissivity values are also consistent with carbonates, sulfates, phyllosilicates and their dehydration products, which may have formed via weathering of basalts under conditions of higher atmospheric PH2O. All of these hypotheses suggest the mineralogy of Alpha tessera records an extinct era of Venus history and is a key target for future exploration.

Do aquatic macroinvertebrate communities respond to land-use effects in the Wilge River, Mpumalanga, South Africa?

Aquatic macroinvertebrate community responses to the effects of various land uses were investigated in 2010–2013 in the Wilge River, a tributary of the Olifants River, South Africa. The catchment area is characterised by agricultural, mining and industrial activities, which potentially contribute to the river's deteriorating water quality and poor in-stream habitat conditions. Agricultural activities comprise the predominant land use, causing major nutrient input into the Wilge River, resulting in eutrophic conditions. Thus it was expected that the functional feeding group (FFG) scraper/grazer populations would be the most abundant as they consume algae, but this was not the case. The primary FFGs present were predators and gathering collector populations, whilst shredders were the least abundant. The primary drivers responsible for separating the monitoring sites and their aquatic macroinvertebrate communities were differing in situ water quality, season and habitat availability. Therefore, land use was not a driving variable, probably owing to limited organic and inorganic water quality data.

Water adsorption on MnO:ZnO(001) — From single molecules to bilayer coverage

Improving photochemical water oxidation processes on sunlight absorbing materials requires understanding the photoelectrode-solution interface. We use ab initio density functional theory (DFT)+U to investigate the structure and energetics of water adsorbed on MnO:ZnO(001), a potential photoanode material we previously identified as having suitable band gaps and band edge placements for visible light induced water splitting. Our calculations show that there is a preference for molecular adsorption at water coverages of less than half a monolayer (ML). At higher coverages, cooperative water–water interactions facilitate water dissociation at the interface. We find that the work function is very sensitive to water dipole orientation and/or presence of hydroxyls on the surface. The computed phase diagram reveals the surface to be fairly hydrophilic with a preference for the first water ML to be 33% dissociated at 0.75ML, 50% dissociated at 1ML, and 50% dissociated at 2ML water coverage under various conditions away from water-poor conditions.

Development of A-type olivine fabric in water-rich deep upper mantle

Water controls the activity of slip systems in olivine resulting in various types of olivine crystallographic preferred orientation (i.e., fabric) in mantle rocks. The A-type olivine fabric is the most commonly observed olivine fabric in natural peridotites. Development of A-type olivine fabric (developed by the (010)[100] slip system) is known to be limited to the water-poor conditions of the shallow upper mantle (<200km depth). We have performed simple-shear deformation experiments of olivine at 7.2–11.1GPa and 1400–1770 K. Here we show that A-type olivine fabric was developed under water-rich conditions (>2130ppm H/Si in olivine), while B-type fabric (by the (010)[001] slip system) was observed under moderately wet conditions (750–2130ppm H/Si). Developments of C-type (by the (100)[001] slip system) fabric was limited to water-poor conditions (<220ppm H/Si). We found that monotonic decrease in the seismic anisotropy VSH/VSV (the ratio of horizontally and vertically polarized shear waves) with depth in the global one-dimensional models is well explained by the olivine fabrics developed in the horizontal flow of a water-poor mantle. Only A-type olivine fabric can explain the vertical mantle flow which associates the seismic anisotropy of VSH/VSV<1 in the deep upper mantle (>200km depth). A strong anomaly of VSH/VSV<1 observed in the deep upper mantle beneath the East Pacific Rise is well explained by the distribution of water-rich regions (in which A-type olivine fabric is dominantly developed) in the deep upper mantle and upwelling mantle flows.

Abiotic Formation of Valine Peptides Under Conditions of High Temperature and High Pressure

We investigated the oligomerization of solid valine and the stabilities of valine and valine peptides under conditions of high temperature (150-200°C) and high pressure (50-150MPa). Experiments were performed under non-aqueous condition in order to promote dehydration reaction. After prolonged exposure of monomeric valine to elevated temperatures and pressures, the products were analyzed by liquid chromatography mass spectrometry comparing their retention times and masses. We identified linear peptides that ranged in size from dimer to hexamer, as well as a cyclic dimer. Previous studies that attempted abiotic oligomerization of valine in the absence of a catalyst have never reported valine peptides larger than a dimer. Increased reaction temperature increased the dissociative decomposition of valine and valine peptides to products such as glycine, β-alanine, ammonia, and amines by processes such as deamination, decarboxylation, and cracking. The amount of residual valine and peptide yields was greater at higher pressures at a given temperature, pressure, and reaction time. This suggests that dissociative decomposition of valine and valine peptides is reduced by pressure. Our findings are relevant to the investigation of diagenetic processes in prebiotic marine sediments where similar pressures occur under water-poor conditions. These findings also suggest that amino acids, such as valine, could have been polymerized to peptides in deep prebiotic marine sediments within a few hundred million years.

Activities of olivine slip systems in the upper mantle

We investigated the effect of pressure (P) on olivine [100](001) and [001](100) dislocation slip systems by carrying out deformation experiments in the Deformation-DIA apparatus (D-DIA) on single crystals of Mg2SiO4 forsterite (Fo100) and San Carlos (SC) olivine (Fo89), at P ranging from 5.7 to 9.7GPa, temperature T=1473 and 1673K, differential stress σ in the range 140–1500MPa, and in water-poor conditions. Specimens were deformed in axisymmetry compression along the so-called [101]c crystallographic direction, which promotes the dual slip of [100] dislocations in (001) plane and [001] dislocations in (100) plane. Constant σ and specimen strain rates (ε˙) were monitored in situ by synchrotron X-ray diffraction and radiography, respectively. Comparison of the obtained high-P rheological data with room-P data, previously reported by Darot and Gueguen (1981) for Fo100 and Bai et al. (1991) for SC olivine, allowed quantifying the activation volume V* in classical creep power laws. We obtain V*=9.1±1.6 cm3/mol for Fo100. For SC olivine, we obtain V*=10.7±5.0cm3/mol taking into account the oxygen-fugacity uncertainty during the high-P runs. These results, combined with previous reports, provide complete sets of parameters for quantifying the activities of olivine dislocation slip systems. Extrapolation of the rheological laws obtained for SC olivine crystals to conditions representative of natural deformations show that [100](010) slip largely dominates deformation in the shallow upper mantle. At depths greater than ∼65km along a 20-Ma oceanic geotherm or ∼155km along a continental geotherm, the dual activity of [100](001) and [001](100) slips becomes comparable to that of [100](010) slip. At depths greater than ∼240km, [001](010) slip becomes dominant over all other investigated slip systems. Such changes in olivine dislocation-slips relative activity provide a straightforward explanation for the seismic anisotropy contrast and attenuation with depth observed in the Earth’s upper mantle.

Pressure effect on forsterite dislocation slip systems: Implications for upper-mantle LPO and low viscosity zone

In order to better constrained the effect of pressure ( P) on olivine dislocation slip-system activities, deformation experiments were carried out in a Deformation-DIA apparatus (D-DIA) on pure forsterite (Fo100) single crystals, at P ⩾ 5.7 GPa, temperature T ∼ 1675 K, differential stress σ < 350 MPa and in water-poor conditions. Constant σ and specimen strain rates ( ε ˙ ) were monitored in situ by synchrotron X-ray diffraction and radiography, respectively. Two compression directions were tested, promoting either [1 0 0] slip or [0 0 1] slip in (0 1 0) crystallographic plane. Comparison of the obtained high- P rheological data with room- P data previously reported by Darot and Gueguen (1981) shows that [1 0 0] slip is strongly inhibited by pressure while [0 0 1] slip is virtually P insensitive. This translates in creep power laws into a high activation volume V a ∗ = 15 ± 3 cm 3 / mol for [1 0 0](0 1 0) slip system, and V c ∗ = 0 ± 1.2 cm 3 / mol for [0 0 1](0 1 0) slip system. Using these laws along geotherms at natural σ condition shows that the [1 0 0] slip/[0 0 1] slip transition may occur at ∼200 km depth in the upper mantle, and be responsible for the observed lattice preferred orientation (LPO) transition. A rheological law for polycrystalline forsterite is deduced from the single-crystal rheological laws, assuming that individual grains are randomly oriented in the aggregate. Applying the aggregate law within a 2D geodynamic model of upper-mantle couette flow suggests that the pressure dependence of olivine dislocation-slip activities may partly explain the low viscosity zone (LVZ) observed underneath oceanic plates.

The Rehabilitation Project of Highland Road Tunnel

This paper presents the rehabilitation project of Dabanshan highland road tunnel. Cause analysis is carried by insight into the information of climate, geological, hydrological condition, tunnel defects type and parameters. Water leakage, low temperature and poor rock condition are considered to be source of tunnel defects, and the essential of rehabilitation of highland road tunnel are water leakage treatment and heat preservation system reinstatement. Measures taken to solve the problems of cracks, water leakage and frost are introduced in detail, and results show that measures taken are proved to be effective. Knowledge and experience gained are helpful for similar projects in future.

Synthesis of ordered mesostructured TiO x thin films from tetrahydrofuran–water solutions

The co-self-assembly of hybrid mesostructured TiO x -based films from water-deficient tetrahydrofuran (THF) solutions, including a titania precursor species and ethylene oxide structure-directing agents (SDA), is reported. A variety of TiO x mesostructures could be obtained, evident from small angle X-ray scattering and electron microscopy measurements, depending on the chemical composition and concentration of the SDA, and the concentration of water in the precursor solution. We find that the TiO x mesostructured phase evolution with increasing SDA concentration in the THF-based solution follows the cubic → hexagonal → lamellar sequence reported for mesostructured TiO x films deposited from the conventional aqueous/ethanol evaporation induced self-assembly (EISA) process. However, the unavailability of water molecules and the limited hydrolysis of the titania precursor due to the water-poor conditions in the THF-based solution, effectively reduce the concentration of hydrophilic species in the solution and their interactions with the SDA. As a result, directing a specific TiO x mesostructure from a THF-based precursor solution requires SDA concentrations lower than that known to direct the same TiO x mesostructure from the conventional, well studied aqueous/ethanol process. Furthermore, SDAs with very long ethylene oxide hydrophilic segments, which require high overall hydrophilic species concentration to promote self-assembly, are extremely sensitive to the concentration of water and hydrolyzed titania precursor concentrations in the solution, showing sharp mesophase transitions as a function of minute changes in water concentration.

Electrical conductivity of wadsleyite at high temperatures and high pressures

The electrical conductivity of wadsleyite aggregates has been determined under the broad range of thermodynamic conditions using the impedance spectroscopy for a frequency range of 10 − 2 to 10 6 Hz. Two branches are observed in the complex impedance, one (at high frequency range) showing a half circle originated at Z′ (real part of impedance) = Z″ (imaginary part of impedance) = 0 in the Z′– Z″ plot, and another branch in the low frequency range. The results from high frequency semi-circles correspond to the electric properties of a sample, whereas the results from a low frequency branch correspond to the electrode effects. From the analysis of the results from the semi-circles, we have identified two distinct mechanisms of electrical conduction having different activation enthalpies and different sensitivity to oxygen fugacity and water content. One mechanism dominating at water-poor condition has a high activation enthalpy (~ 147 kJ/mol) and the conductivity increases with oxygen fugacity. We suggest that electrical conduction in this regime is due to charge transfer involving ferric iron (“polaron” conduction). Under water-rich conditions, electrical conductivity increases with water content but decreases with oxygen fugacity, and the activation enthalpy is smaller (~ 88 kJ/mol). We infer that electrical conduction in this regime is due to protons. The activation enthalpy in this regime is insensitive to water content and the conductivity is proportional to water content, C W, as σ ∝ C w r with r~ 0.72. The value of r is smaller than one suggests that minority defects such as H M′ or H ● are responsible for electrical conduction. Our results show that a completely dry transition zone is incompatible with most of the geophysical observations on the mantle transition zone, and some water (~ 0.1–0.3 wt.% in the Pacific) is required to explain the observed electrical conductivity.

Thermally Stable Nanocrystalline TiO2 Photocatalysts Synthesized via Sol−Gel Methods Modified with Ionic Liquid and Surfactant Molecules

Recently, sol−gel methods employing ionic liquids (ILs) have shown significant implications for the synthesis of well-defined nanostructured inorganic materials. Herein, we synthesized nanocrystalline TiO2 particles via an alkoxide sol−gel method employing a water-immiscible room temperature IL (1-butyl-3-methylimidazolium hexafluorophosphate, [bmim][PF6]) as a new solvent medium and further modified with nonionic surfactant (polyoxyethylenesorbitan monooleate) as a pore templating material. Detailed information on the preparative method, synthesis route and mechanism, crystallographic and structural properties, and photocatalytic activity of the TiO2 particles is described. The possible rationale for the formation of nanocrystalline TiO2 particles with high surface area and activity is discussed with respect to the special characteristics of [bmim][PF6] as well as the role of the surfactant self-assembly in the sol−gel network. Due to its capping effect and water immiscibility, the use of [bmim][PF6] in sol−gel synthesis of TiO2 induces controlled hydrolysis of titanium alkoxide precursor, resulting in a stable sol−gel network with an ordered array, and localized water-poor conditions, resulting in the formation of completely condensed and directly crystalline systems at ambient condition. The low surface energy and adaptability of [bmim][PF6] facilitate the generation of very small nanocrystalline TiO2 particles and then it also acts as a particles aggregation inhibitor. The ensuing TiO2 particles have good thermal stability to resist pore collapse and anatase-to-rutile crystal phase transformation during thermal treatment.

Effect of water and stress on the lattice-preferred orientation of olivine

The influence of water and stress on the lattice-preferred orientation (LPO) of olivine aggregates was investigated through large strain, shear deformation experiments at high pressures and temperatures ( P = 0.5–2.1 GPa, T = 1470–1570 K) under both water-poor and water-rich conditions. The specimens are hot-pressed synthetic olivine aggregates or single crystals of olivine. Water was supplied to the sample by decomposition of a mixture of talc and brucite. Deformation experiments were conducted up to γ (shear strain) ∼ 6 using the Griggs apparatus where water fugacity was up to ∼ 13 GPa at the pressure of 2 GPa. The water content in olivine saturated with water increases with increasing pressure and the solubility of water in olivine at P = 0.5–2 GPa was ∼ 400–1200 ppm H/Si. Several new types of LPO in olivine are found depending on water content and stress. Samples deformed in water-poor conditions show a conventional LPO of olivine where the olivine [100] axis is subparallel to the shear direction, the (010) plane subparallel to the shear plane (type-A). However, we identified three new types (type-B, C, and E) of LPO of olivine depending on the water content and stress. The type-B LPO of olivine which was found at relatively high stress and/or under moderate to high water content conditions is characterized by the olivine [001] axis subparallel to the shear direction, the (010) plane subparallel to the shear plane. The type-C LPO which was found at low stress and under water-rich conditions is characterized by the olivine [001] axis subparallel to the shear direction, the (100) plane subparallel to the shear plane. The type-E LPO which was found under low stress and moderate water content is characterized by the olivine [100] axis subparallel to the shear direction, the (001) plane subparallel to the shear plane. Observations by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) show that the dislocations in water-poor samples (type-A) are curved and both b = [100] and b = [001] dislocations have a similar population. Numerous subgrains are seen in water-poor samples in backscattered electron images. In contrast, water-rich samples (both type-B and type-C) contain mostly b = [001] dislocations and dislocations are straight and sub-grain boundaries are rare compared to those in water-poor samples. These observations suggest that (1) dominant slip systems in olivine change with water fugacity (and stress) and (2) grain boundary migration is enhanced in the presence of water. Seismic anisotropy corresponding to the fabrics under water-rich condition is significantly different from that under water-poor condition. Consequently, the relationship between seismic anisotropy and flow geometry in water-rich regions is expected to be different from that in water-poor regions in which type-A fabric dominates (i.e., the lithosphere). A few cases are discussed including anisotropy in the subduction zone and in the deep upper mantle.

Influence of Water Content on the Self-Assembly of Metal−Organic Frameworks Based on Pyridine-3,5-dicarboxylate

A 0D discrete molecule [Co(3,5-pdc)(H2O)5].2H2O (1) was obtained in quantitative yield from the reaction of CoCl2.6H2O and pyridine-3,5-dicarboxylate (3,5-pdc) in pure water solvent at ambient temperature. While a 1D zigzag chain species, [{Co(3,5-pdc)(H2O)4}.H2O]n (2), was produced in a water-rich environment, a 2D layer compound, [Co(3,5-pdc)(H2O)2]n (3), with a 6(3) topology was generated under a water-reduced condition and a 2D sheet structure, [{Cu(3,5-pdc)(py)2}.H2O.EtOH]n (4), was formed under a water-poor condition. Compounds 1, 2, and 4 were characterized by single-crystal X-ray diffraction analysis. The 1D zigzag chain 2 shows a recoverable collapsing property. Compound 4 adopts a 2D sheet structure with a 4.8(2) topology, observed for the first time for the 3,5-pdc-related metal-organic frameworks. Water content was found to be an important factor in determining the topologies of the products in the self-assembly of divalent metal ions (Co2+, Cu2+) and pyridine-3,5-dicarboxylate under mild conditions.