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CaY is beta Np-derived structured and crystallizes in the orthorhombic Cmmm space group. The structure is three-dimensional. Ca is bonded in a 8-coordinate geometry to four equivalent Ca and four equivalent Y atoms. All Ca–Ca bond lengths are 3.54 Å. All Ca–Y bond lengths are 3.67 Å. Y is bonded in a 8-coordinate geometry to four equivalent Ca and four equivalent Y atoms. All Y–Y bond lengths are 3.54 Å.
CaY(CO4)2 crystallizes in the tetragonal P4_12_12 space group. The structure is three-dimensional. Ca is bonded in a 6-coordinate geometry to six O atoms. There are a spread of Ca–O bond distances ranging from 2.35–2.60 Å. Y is bonded in a 9-coordinate geometry to nine O atoms. There are a spread of Y–O bond distances ranging from 2.26–2.61 Å. There are two inequivalent C sites. In the first C site, C is bonded in a trigonal planar geometry to three O atoms. There are a spread of C–O bond distances ranging from 1.28–1.31 Å. In the second C site, C is bonded in a trigonal planar geometry to three O atoms. There are a spread of C–O bond distances ranging from 1.28–1.31 Å. There are eight inequivalent O sites. In the first O site, O is bonded in a distorted bent 120 degrees geometry to one Y and one C atom. In the second O site, O is bonded in a 1-coordinate geometry to one Ca, one Y, and one C atom. In the third O site, O is bonded in a water-like geometry to one Ca and one Y atom. In the fourth O site, O is bonded in a distorted single-bond geometry to one Ca, one Y, and one C atom. In the fifth O site, O is bonded in a 1-coordinate geometry to one Y and one C atom. In the sixth O site, O is bonded in a 1-coordinate geometry to two equivalent Ca, one Y, and one C atom. In the seventh O site, O is bonded in a 3-coordinate geometry to two equivalent Y and one O atom. The O–O bond length is 1.36 Å. In the eighth O site, O is bonded in a 3-coordinate geometry to one Ca, one Y, and one C atom.
Multi-component silicate garnet ceramics CaY{sub 2}MgMAlSi{sub 2}O{sub 12} comprising different cations M = Al, Ga or Sc in octahedral sites doped with Mn{sup 4+} ions have been synthesized and studied as novel red-emitting phosphors aiming at warm white pc-LED applications. All synthesized phosphors exhibit Mn{sup 4+} luminescence in rather deep red region, the shortest-wavelength spectrum of Mn{sup 4+} luminescence (peak wavelength at 668 nm) being obtained for the host with the largest cation M{sup 3+} = Sc{sup 3+} in the octahedral site. The effect of increasing the energy of the emitting Mn{sup 4+2}E level with the size of the host cation in octahedral sites is supposed to be the result of decrease of the covalence of the “Mn{sup 4+}-ligand” bonding with increase of the interionic Mn{sup 4+}–O{sup 2–} distance. All studied phosphors demonstrate rather poor thermal stability of Mn{sup 4+} photoluminescence with a thermal quenching temperature T{sub 1/2} below 200 K, the lowest value being observed for the host with M = Sc. As expected, the decrease of the energy of the O{sup 2–}–Mn{sup 4+} charge-transfer state is observed with the increase of the M{sup 3+} cation radius, i.e. with the increase of the O{sup 2–}–Mn{sup 4+} interionic distance. The thermal quenching temperature of Mn{sup 4+} luminescence in the studied phosphors correlates with the energy of the O{sup 2–}–Mn{sup 4+} charge transfer state which is supposed to serve as a quenching state for Mn{sup 4+} luminescence.
Highlights: • K{sub 7}CaY{sub 2}(B{sub 5}O{sub 10}){sub 3} crystals were grown from new flux. • SHG efficiency for K{sub 7}CaY{sub 2}(B{sub 5}O{sub 10}){sub 3} crystals is comparable to that of KDP. • K{sub 7}CaY{sub 2}(B{sub 5}O{sub 10}){sub 3} crystals have UV cut off edge at 190 nm. - Abstract: Non-centrosymmetric borates K{sub 7}CaY{sub 2}(B{sub 5}O{sub 10}){sub 3} have been synthesized by solid state reaction and the crystals were successfully grown by the top seeded solution growth method using K{sub 2}O-B{sub 2}O{sub 3}-CaF{sub 2} flux. According to the single X-ray diffraction, the structure belongs to the R32 space group with lattice parameters a = 13.2516(2) Å and c = 14.9679(3) Å. IR, Raman, absorption spectra as well as data on melting temperature were obtained for the crystal. The short edge of UV absorption and SHG intensity comparable with KH{sub 2}PO{sub 4} (KDP) suggests that this crystal is a promising nonlinear-optical material.
Modern microbial mats are potential analogues of some of Earth’s earliest ecosystems. Excellent examples can be found in Shark Bay, Australia, with mats of various morphologies. To further our understanding of the functional genetic potential of these complex microbial ecosystems, we conducted for the first time shotgun metagenomic analyses. We assembled metagenomic nextgeneration sequencing data to classify the taxonomic and metabolic potential across diverse morphologies of marine mats in Shark Bay. The microbial community across taxonomic classifications using protein-coding and small subunit rRNA genes directly extracted from the metagenomes suggests that three phyla Proteobacteria, Cyanobacteria and Bacteriodetes dominate all marine mats. However, the microbial community structure between Shark Bay and Highbourne Cay (Bahamas) marine systems appears to be distinct from each other. The metabolic potential (based on SEED subsystem classifications) of the Shark Bay and Highbourne Cay microbial communities were also distinct. Shark Bay metagenomes have a metabolic pathway profile consisting of both heterotrophic and photosynthetic pathways, whereas Highbourne Cay appears to be dominated almost exclusively by photosynthetic pathways. Alternative non-rubisco-based carbon metabolism including reductive TCA cycle and 3-hydroxypropionate/4-hydroxybutyrate pathways is highly represented in Shark Bay metagenomes while not represented in Highbourne Cay microbial mats or any other mat forming ecosystems investigated to date. Potentially novel aspects of nitrogen cycling were also observed, as well as putative heavy metal cycling (arsenic, mercury, copper and cadmium). Finally, archaea are highly represented in Shark Bay and may have critical roles in overall ecosystem function in these modern microbial mats.
Single stranded DNA viruses have been previously shown to populate the oceans on a global scale, and are endemic in microbialites of both marine and freshwater systems. We undertook for the first time direct viral metagenomic shotgun sequencing to explore the diversity of viruses in the modern stromatolites of Shark Bay Australia. The data indicate that Shark Bay marine stromatolites have similar diversity of ssDNA viruses to that of Highbourne Cay, Bahamas. ssDNA viruses in cluster uniquely in Shark Bay and Highbourne Cay, potentially due to enrichment by phi29-mediated amplification bias. Further, pyrosequencing data was assembled from the Shark Bay systems into two putative viral genomes that are related to Genomoviridae family of ssDNA viruses. In addition, the cellular fraction was shown to be enriched for antiviral defense genes including CRISPR-Cas, BREX (bacteriophage exclusion), and DISARM (defense island system associated with restriction-modification), a potentially novel finding for these systems. This is the first evidence for viruses in the Shark Bay stromatolites, and these viruses may play key roles in modulating microbial diversity as well as potentially impacting ecosystem function through infection and the recycling of key nutrients.
A search for long-lived particles, which have come to rest within the ATLAS detector, is presented. The subsequent decays of these particles can produce high-momentum jets, resulting in large out-of-time energy deposits in the ATLAS calorimeters. These de- cays are detected using data collected during periods in the LHC bunch structure when collisions are absent. The analysed dataset is composed of events from proton-proton collisions produced by the Large Hadron Collider at a centre-of-mass energy of s = 13 TeV and recorded by the ATLAS experiment during 2017 and 2018. The dataset used for this search corresponds to a total live time of 579 hours. The results of this search are used to derive lower limits on the mass of gluino R -hadrons, assuming a branching fraction $ \mathcal{B}\left(\overset{\sim }{g}\to q\overline{q}{\chi}_1^0\right) $ B g ~ → q q ¯ χ 1 0 = 100%, with masses of up to 1 . 4 TeV excluded for gluino lifetimes of 10 - 5 to 10 3 s.
Given non-trivial group G and a non-empty subset S of G such that not containing the identity element of G and S=S{sup −1}:={s"−"1∣s∈S}, the Cayley graph Γ=Cay(G,S) is the graph whose vertex set V(Γ) is G, and edge set E(Γ) is {{g,sg}∣g∈G,s∈S}. The Cayley graphs are presently being considered as models architecture for interconnection networks. When there is an uncertainty on vertices or edges, fuzzy graph has special importance. In this paper, we develop the concept of Cayley fuzzy graphs on the fuzzy groups and investigate some basic properties of Cayley fuzzy graphs. We introduce some sufficient conditions on the fuzzy graphs that under it’s, a fuzzy graph is a Cayley fuzzy graph and discuss some operations of the fuzzy graphs on the Cayley fuzzy graphs, prove that the product of two Cayley fuzzy graphs is a Cayley fuzzy graph, for some products. Also we provide an application of Cayley fuzzy graphs, and use Dijkstra’s Algorithm for finding the fuzzy shortest path in a Cayley fuzzy graph.
Vacuum pumps have been used for tritium processing since the 1940s following the isolation of pure tritium. The largest problem facing tritium vacuum pumps is the tritium radioactive decay. The beta particles, recoil energy, and subsequent radical formations are detrimental to most carbon-based materials. Carbon materials, such as plastics, elastomers, carbon fiber, activated carbon, etc., react with tritium to form methane and in the process strip material from the carbonbased material. Other reactions can be self-catalyzing, as is the case with nitrogen and tritium forming tritiated ammonia at room temperature and pressure. Tritium also readily isotopically exchanges with surface -OH groups, increasing the amount of protium in the gas stream while creating a tritium holdup on the surface. Metals are the preferred material when working with tritium, but tritium will permeate into and through almost all metals at some point. The entrapped tritium can decay inside the metal, creating local helium distortions that can impact the structural properties above and beyond the hydrogen embrittlement issue tritium can cause.
Using neutron powder diffraction and magnetic susceptibility measurements, we report on the preparation and characterization of the temperature- and field-dependent properties of CaY2ZrFe4O12, a composition closely related to the high-temperature ferrimagnet Y3Fe5O12. By diluting the concentration of paramagnetic ions on the octahedral sublattice of the garnet structure, we find temperature-dependent canting of the magnetic moments. This reflects the importance of the octahedral sublattice in mediating the magnetic interactions between the tetrahedral sites and offers insight into a large number of competing magnetic interactions in the garnet structure.
In this paper, we report inelastic neutron scattering experiments in Ca 2 Y 2 Cu 5 O 10 and map out the full one-magnon dispersion which extends up to a record value of 53 meV for frustrated ferromagnetic (FM) edge-sharing CuO 2 chain (FFESC) cuprates. A homogeneous spin-1/2 chain model with a FM nearest-neighbor (NN), an antiferromagnetic (AFM) next-nearest-neighbor (NNN) inchain, and two diagonal AFM interchain couplings (ICs) analyzed within linear spin-wave theory (LSWT) reproduces well the observed strong dispersion along the chains and a weak one perpendicularly. The ratio α=| J a 2 / J a 1 | of the FM NN and the AFM NNN couplings is found as ~0.23, close to the critical point α c =1/4 which separates ferromagnetically and antiferromagnetically correlated spiral magnetic ground states in single chains, whereas α c >0.25 for coupled chains is considerably upshifted even for relatively weak IC. Although the measured dispersion can be described by homogeneous LSWT, the scattering intensity appears to be considerably reduced at ~11.5 and ~28 meV. The gaplike feature at 11.5 meV is attributed to magnon-phonon coupling whereas based on density matrix renormalization group simulations of the dynamical structure factor the gap at 28 meV is considered to stem partly from quantum effects due to the AFM IC. Another contribution to that gap is ascribed to the intrinsic superstructure from the distorting incommensurate pattern of CaY cationic chains adjacent to the CuO 2 ones. It gives rise to nonequivalent CuO 4 units and Cu-O-Cu bond angles Φ and a resulting distribution of all exchange integrals. The J 's fitted by homogeneous LSWT are regarded as average values. The record value of the FM NN integral J 1 =24 meV among FFESC cuprates can be explained by a nonuniversal Φ(≠90°) and Cu-O bond length dependent anisotropic mean direct FM Cu-O exchange $\overline{K}_{pd}$~120 meV, similar to a value of 105 meV for Li 2 CuO 2 , in accord with larger values for La 2 CuO 4 and CuGeO 3 (~110 meV) reported by Braden et al . [Phys. Rev. B 54, 1105 (1996)] phenomenologically. Lastly, enhanced $K_{pd}$ values are also needed to compensate a significant AFM J dd ≥ 6 meV from the dd channel, generic for FFESC cuprates but ignored so far.
A new species of panopeid crab from shallow coastal waters of Belize is formally described and named based upon comparative study of three small specimens obtained in the course of a regional biodiversity survey of decapod crustaceans. The herein designated holotype of Hexapanopeus klausruetzleri n. sp. is a specimen previously included in a comparative molecular phylogenetic analysis that showed it to be closely related to, but genetically distinct from, the western Atlantic species Hexapanopeus angustifrons (Benedict & Rathbun, 1891). Hexapanopeus klausruetzleri n. sp. differs from this widely reported warm-temperate species in both its smoother carapace and pereopod surfaces and its generally more lobiform anterolateral teeth. The unique male first gonopod of the new species also strongly supports its morphological separation from all known congeners and other superficially similar western Atlantic panopeids with which it might be confused. To date, mature females have not been found, and the limited available collections are restricted to the vicinity of Carrie Bow Cay and nearby waters. Fourteen additional species of small panopeid and pseudorhombilid crabs, similar to Hexapanopeus klausruetzleri n. sp. in size and general habitus, were taken in the course of our studies in Belize. Most have not been previously reported from these waters, and several warrant further study to confirm their identifications.
Coastal environments like mangrove forests are increasingly recognized as potential hotspots for organic carbon burial, giving them a crucial and yet poorly constrained role in the global carbon cycle. Mangrove sediments are frequently anoxic, which facilitates elevated organic matter (OM) burial via several mechanisms, including sulfurization – abiotic reactions between dissolved (poly)sulfide and OM that decrease its lability. Although sulfurization was estimated to account for roughly half of OM preservation in a Bermuda mangrove forest, both its mechanisms and its global significance remain poorly understood. In this study, we investigate S cycling in mangrove forest sediments from Little Ambergris Cay, Turks and Caicos Islands, an environment with predominantly microbial OM inputs and no major source of terrestrial iron. We characterize the S- and C-isotope composition and organic S speciation of sedimentary OM fractions with varying degrees of resistance to acid hydrolysis, along with other inorganic S phases. Near the surface of a 3-mm-diameter, O 2 -releasing root, abundant organic and elemental S with a 34 S-depleted composition indicates microbial sulfur cycling and OM sulfurization. A mixture of pyrite, elemental S, and organic S form a plaque within the outer 50 μm of the root, which also contains strongly 34 S-depleted sulfate in its xylem. OM sulfurization products in the sediments include both the alkyl sulfides and disulfides associated with the root plaque and more oxidized forms, especially sulfonates. Hydrolysis-resistant organic S in the sediments is consistently 3–5‰ more 34S-enriched than coexisting elemental S, matching the reported kinetic isotope fractionation factor for OM sulfurization via reaction with polysulfides. These sediments also contain a substantial pool of solid-phase, hydrolyzable organic S with a seawater sulfate-like isotope composition, largely in the form of sulfate esters, which may represent excretions from abundant gastropods. The coexistance of sulfurized OM and aerobic macrofauna highlights how understanding spatial scales and/or temporal cycles in local redox state is critical for predicting net OM preservation, especially in dynamic, coastal environments. Future attempts to mechanistically predict changes in carbon storage in coastal systems will benefit from incorporating OM sulfurization as both a sink for microbially produced sulfide and a mechanism for enhanced carbon sequestration.
This profile provides a snapshot of the electricity generation or reduction technologies, including solar hot water heating, available to the Commonwealth of the Bahamas - a country consisting of more than 700 islands, cays, and islets - of which only 30 are actually inhabited. Heating and transportation fuels are not addressed.
This fact sheet provides a snapshot of the energy landscape of the Commonwealth of the Bahamas — a country consisting of more than 700 islands, cays, and islets— of which only 28 are populated. The Bahamaas is located north of Cuba, with the Turks and Caicos Islands to the southeast. Like many island nations, the Bahamas is almost 100% reliant on imported fossil fuels.
Thin-film nanocomposite (TFN) membranes are emerging water-purification membranes that could provide enhanced water permeance with similar solute removal over traditional thin-film composite (TFC) membranes. However, the effects of nanofiller incorporation on active layer physico-chemical properties have not been comprehensively studied. Accordingly, we aimed to understand the correlation between nanofillers, active layer physico-chemical properties, and membrane performance by investigating whether observed performance differences between TFN and control TFC membranes correlated with observed differences in physico-chemical properties. Throughout this work, the effects of nanofiller loading, surface area, and size on membrane performance, along with active layer physico-chemical properties, were characterized in TFN membranes incorporated with Linde Type A (LTA) zeolite and zeolitic imidazole framework-8 (ZIF-8). Results show that nanofiller incorporation up to ~0.15 wt% resulted in higher water permeance and unchanged salt rejection, above which salt rejection decreased 0.9–25.6 % and 26.1–48.3 % for LTA-TFN and ZIF-8-TFN membranes, respectively. Observed changes in active layer physico-chemical properties were generally unsubstantial and did not explain observed changes in TFN membrane performance. Therefore, increased water permeance in TFN membranes could be due to preferential water transport through porous structures of nanofillers or along polymer-nanofiller interfaces. These findings offer new insights into the development of high-performance TFN membranes for water/ion separations.
Silver (Ag) layers were deposited by remote plasma enhanced atomic layer deposition (PALD) using Ag(fod)(PEt{sub 3}) (fod = 2,2-dimethyl-6,6,7,7,8,8,8-heptafluorooctane-3,5-dionato) as precursor and hydrogen plasma on silicon substrate covered with thin films of SiO{sub 2}, TiN, Ti/TiN, Co, Ni, and W at different deposition temperatures from 70 to 200 °C. The deposited silver films were analyzed by x-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) with energy dispersive x-ray spectroscopy, four point probe measurement, ellipsometric measurement, x-ray fluorescence (XRF), and x-ray diffraction (XRD). XPS revealed pure Ag with carbon and oxygen contamination close to the detection limit after 30 s argon sputtering for depositions made at 120 and 200 °C substrate temperatures. However, an oxygen contamination was detected in the Ag film deposited at 70 °C after 12 s argon sputtering. A resistivity of 5.7 × 10{sup −6} Ω cm was obtained for approximately 97 nm Ag film on SiO{sub 2}/Si substrate. The thickness was determined from the SEM cross section on the SiO{sub 2}/Si substrate and also compared with XRF measurements. Polycrystalline cubic Ag reflections were identified from XRD for PALD Ag films deposited at 120 and 200 °C. Compared to W surface, where poor adhesion of the films was found, Co, Ni, TiN, Ti/TiN and SiO{sub 2} surfaces had better adhesion for silver films as revealed by SEM, TEM, and AFM images.