Energy allocation in a reef coral under varying resource availability

An organism's pattern of resource allocation to reproduction and growth over time critically impacts on its lifetime reproductive success. During times of low resource availability, there are two fundamental, mutually exclusive strategies of energy investment: maintenance of somatic tissues to support survival and later reproduction or investment into an immediate reproductive event at the risk of subsequent death. Here, we examine energy allocation patterns in the coral Montipora digitata to determine whether energy investment during periods of resource shortage favours growth or reproduction in a sessile, modular marine species. We manipulated light regimes (two levels of shading) on plots within a shallow reef flat habitat (Orpheus Island, Great Barrier Reef, Australia) and quantified energy uptake (rates of net photosynthesis), energy investment into reproduction (E R ), tissue growth per unit surface area (E T ) and energy channelled into calcification (E C ). With declining resource availability (i.e. reduced photosynthesis), relative energy investment shifted from high (~80%) allocation to tissue growth (E R :E T :E C =11:81:8%) to an increasing proportion channelled into reproduction and skeletal growth (20:31:49%). At the lowest light regime, calcification was maintained but reproduction was halted and thus energy content per unit surface area of tissue declined, although no mortality was observed. The changing hierarchy in energy allocation among life functions with increasing resource limitation found here for an autotrophic coral, culminating in cessation of reproduction when limitations are severe, stands in contrast to observations from annual plants. However, the strategy may be optimal for maximising fitness components (growth, reproduction and survival) through time in marine modular animal

Characterization and Thermal Behavior of the Iron Dietary Supplement Ferrous Glycine Sulfate Pentahydrate

Ferrous glycine sulfate pentahydrate [Fe(glycine)(SO4)·5H2O with glycine = C2H5NO2], contained in the supplement for treating iron deficiency anaemia, commercially known as ferro sanol duodenal®, was characterized by laboratory X‐ray powder diffraction (XRPD), scanning electron microscope (SEM), and infrared spectroscopy (IR). The thermal behavior was investigated by thermal analysis (TGA and DTA) and temperature‐dependent in situ XRPD measurements. Furthermore, the phase transitions to a less hydrated form [Fe(glycine)(SO4)·3H2O] and successively to the anhydrous form were demonstrated to occur in the crystalline solid state. Compared to the crystal structure of the pentahydrate, the trihydrate exhibits a different coordination environment of the iron sites where glycine ligands bridge iron forming a 1D polymeric chain structure. From detailed structural comparison, the mechanism of the phase transitions can be concluded

Is Reduced Strontium Titanate a Semiconductor or a Metal?

In recent decades, the behavior of SrTiO3 upon annealing in reducing conditions has been under intense academic scrutiny. Classically, its conductivity can be described using point defect chemistry and predicting n-type or p-type semiconducting behavior depending on oxygen activity. In contrast, many examples of metallic behavior induced by thermal reduction have recently appeared in the literature, challenging this established understanding. In this study, we aim to resolve this contradiction by demonstrating that an initially insulating, as-received SrTiO3 single crystal can indeed be reduced to a metallic state, and is even stable against room temperature reoxidation. However, once the sample has been oxidized at a high temperature, subsequent reduction can no longer be used to induce metallic behavior, but semiconducting behavior in agreement with the predictions of point defect chemistry is observed. Our results indicate that the dislocation-rich surface layer plays a decisive role and that its local chemical composition can be changed depending on annealing conditions. This reveals that the prediction of the macroscopic electronic properties of SrTiO3 is a highly complex task, and not only the current temperature and oxygen activity but also the redox history play an important role

crystal structure and de and rehydration behaviorof two new chloride containing zeolitic imidazolate frameworks

A previously unknown solid phase in the zinc-imidazole system relevant for the synthesis of ZIF-8 was obtained by adding a small excess of methylimidazole (Hmim) to a diluted zinc chloride solution. By chemical and thermal analyses, a composition of Zn3(mim)5ClH2O·xH2O with x = 0.74 was determined and the compound denoted as ZIF-yqt hydrate. The crystal structure was solved from laboratory X-ray powder diffraction (XRPD) data. ZIF-yqt hydrate crystallizes in a C-centered monoclinic unit cell with space group C2/c (15) and lattice parameters of a = 13.1574(3) A, b = 16.4959(3) A, c = 13.6403(3) A, and β = 119.166(2)°. The structure is built up from Zn(mim)4/2 and Zn(mim)3/2(Cl0.5H2O0.5)1/1 units forming a self-penetrating yqt1 type net. IR spectroscopy was employed to confirm the presence of water in the coordination sphere of zinc. In addition, noncoordinated water is situated in the voids of this net. By heating, ZIF-yqt hydrate can be completely dehydrated resulting in the formation of anhydrous Zn3(mim..

A physical method for investigating defect chemistry in solid metal oxides

The investigation of the defect chemistry of solid oxides is of central importance for the understanding of redox processes. This can be performed by measuring conductivity as a function of the oxygen partial pressure, which is conventionally established by using buffer gas mixtures or oxygen pumps based on zirconia. However, this approach has some limitations, such as difficulty regulating oxygen partial pressure in some intermediate-pressure regions or the possibility of influencing the redox process by gases that can also be incorporated into the oxide or react with the surface via heterogeneous catalysis. Herein, we present an alternative physical method in which the oxygen partial pressure is controlled by dosing pure oxygen inside an ultra-high vacuum chamber. To monitor the conductivity of the oxide under investigation, we employ a dedicated four-probe measurement system that relies on the application of a very small AC voltage, in combination with lock-in data acquisition using highly sensitive electrometers, minimizing the electrochemical polarization or electro-reduction and degradation effects. By analyzing the model material SrTiO3, we demonstrate that its characteristic redox behavior can be reproduced in good agreement with the theory when performing simultaneous electrical conductivity relaxation (ECR) and high-temperature equilibrium conductivity (HTEC) measurements. We show that the use of pure oxygen allows for a direct analysis of the characteristic oxygen dose, which opens up various perspectives for a detailed analysis of the surface chemistry of redox processes.Comment: 25 page

Total scattering reveals the hidden stacking disorder in a 2D covalent organic framework

Interactions between extended π-systems are often invoked as the main driving force for stacking and crystallization of 2D organic polymers. In covalent organic frameworks (COFs), the stacking strongly influences properties such as the accessibility of functional sites, pore geometry, and surface states, but the exact nature of the interlayer interactions is mostly elusive. The stacking mode is often identified as eclipsed based on observed high symmetry diffraction patterns. However, as pointed out by various studies, the energetics of eclipsed stacking are not favorable and offset stacking is preferred. This work presents lower and higher apparent symmetry modifications of the imine-linked TTI-COF prepared through high- and low-temperature reactions. Through local structure investigation by pair distribution function analysis and simulations of stacking disorder, we observe random local layer offsets in the low temperature modification. We show that while stacking disorder can be easily overlooked due to the apparent crystallographic symmetry of these materials, total scattering methods can help clarify this information and suggest that defective local structures could be much more prevalent in COFs than previously thought. A detailed analysis of the local structure helps to improve the search for and design of highly porous tailor-made materials

On the thermal dimorphy of the strontium perrhenate Sr[ReO4]2

Hygroscopic single crystals of a new hexagonal high‐temperature modification of Sr[ReO4]2 were prepared from a melt of Sr[ReO4]2 ⋅ H2O and SrCl2 ⋅ 6 H2O. The structure analysis of the obtained crystals by X‐ray diffraction revealed that the title compound crystallizes in the ThCd[MoO4]3‐type structure with the hexagonal space group P63/m and the lattice parameters a=1023.81(7) pm and c=646.92(4) pm (c/a=0.632) for Z=2 in its quenchable high‐temperature form. Two crystallographically independent Sr2+ cations are coordinated by oxygen atoms forming either octahedra or tricapped trigonal prisms, whereas the Re7+ cations are found in the centers of discrete tetrahedral meta‐perrhenate units [ReO4]-. Temperature‐dependent in‐situ PXRD studies of dry powder samples of Sr[ReO4]2 exhibited its thermal dimorphy with a phase‐transition temperature at 500-550 °C from literature‐known m‐Sr[ReO4]2 into the newly discovered h‐Sr[ReO4]2 (hexagonal).Federal State of Baden-Württemberg (Germany

The Stacking Faulted Nature of the Narrow Gap Semiconductor Sc2_{2}Si2_{2}Te6_{6}

Crystals of Sc$_{2}$Si$_{2}$Te$_{6}$ have been grown and its crystal, micro- and electronic structures were investigated. The layered character of the title compound exhibits stacking faults that impede a full structural characterization by single crystal X-ray diffraction due to diffuse scattering. Based on high resolution transmission electron micrographs and diffraction patterns, the stacking faulted nature of the real structure of Sc$_{2}$Si$_{2}$Te$_{6}$ has been revealed. Different stacking models were derived from the idealized, faultless structure and the stacking disorder was quantitatively analyzed by Rietveld refinement of powder X-ray diffraction patterns. An energetic comparison of the stacking models by density functional theory is in line with the experimental observations. Further, the bonding situation was investigated by electronic structure calculations. Sc$_{2}$Si$_{2}$Te$_{6}$ is a narrow gap semiconductor with an indirect band gap of 0.65 eV

Is reduced strontium titanate a semiconductor or a metal?

In recent decades, the behavior of SrTiO3 upon annealing in reducing conditions has been under intense academic scrutiny. Classically, its conductivity can be described using point defect chemistry and predicting n-type or p-type semiconducting behavior depending on oxygen activity. In contrast, many examples of metallic behavior induced by thermal reduction have recently appeared in the literature, challenging this established understanding. In this study, we aim to resolve this contradiction by demonstrating that an initially insulating, as-received SrTiO3 single crystal can indeed be reduced to a metallic state, and is even stable against room temperature reoxidation. However, once the sample has been oxidized at a high temperature, subsequent reduction can no longer be used to induce metallic behavior, but semiconducting behavior in agreement with the predictions of point defect chemistry is observed. Our results indicate that the dislocation-rich surface layer plays a decisive role and that its local chemical composition can be changed depending on annealing conditions. This reveals that the prediction of the macroscopic electronic properties of SrTiO3 is a highly complex task, and not only the current temperature and oxygen activity but also the redox history play an important role

Li4Ln[PS4]2Cl : chloride-containing lithium thiophosphates with lanthanoid participation (Ln = Pr, Nd and Sm)

The synthesis and structural analysis of three new chloride-containing lithium thiophosphates(V) Li4Ln[PS4]2Cl with trivalent lanthanoids (Ln = Pr, Nd and Sm) are presented and discussed. Single crystals of Li4Sm[PS4]2Cl were obtained and used for crystal structure determination by applying X-ray diffraction. The other compounds were found to crystallize isotypically in the monoclinic space group C2/c. Thus, Li4Sm[PS4]2Cl (a = 2089.31(12) pm, b = 1579.69(9) pm, c = 1309.04(8) pm, β = 109.978(3)°, Z = 12) was used as a representative model to further describe the crystal structure in detail since Li4Pr[PS4]2Cl and Li4Nd[PS4]2Cl were confirmed to be isotypic using powder X-ray diffraction measurements (PXRD). In all cases, a trigonal structure in the space group R3̲ (e.g., a = 1579.67(9) pm, c = 2818.36(16) pm, c/a = 1.784, Z = 18, for Li4Sm[PS4]2Cl) displaying almost identical building units worked initially misleadingly. The structure refinement of Li4Sm[PS4]2Cl revealed bicapped trigonal prisms of sulfur atoms coordinating the two crystallographically distinct (Sm1)3+ and (Sm2)3+ cations, which are further coordinated by four anionic [PS4]3- tetrahedra. The compounds also contain chloride anions residing within channel-like pores made of [PS4]3- units. Eight different sites for Li+ cations were identified with various coordination environments (C.N. = 4-6) with respect to chlorine and sulfur. EDXS measurements supported the stoichiometric formula of Li4Ln[PS4]2Cl, and diffuse reflectance spectroscopy revealed optical band gaps of 2.69 eV, 3.52 eV, and 3.49 eV for Li4Sm[PS4]2Cl, Li4Nd[PS4]2Cl, and Li4Pr[PS4]2Cl, respectively. The activation energy for Li+-cation mobility in Li4Sm[PS4]2Cl was calculated as Ea(Li+) = 0.88 eV using BVEL, which indicates potential as a Li+-cation conductor