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The first Phanerozoic bauxite appeared in the Early Cambrian in isolated areas of fold belts during their peneplenization. Commercial deposits of high-quality bauxite were formed in the Northern Urals during the Eifelian. In the Frasnian, bauxite accumulation expanded to the Central Timan. The number of known Devonian deposits does not exceed two dozen, and their total reserves are on the order of one billion tons. In the Early Carboniferous, bauxite accumulation shifted to the platforms of the Northern Hemisphere. Bauxite formation continued throughout the Middle Carboniferous on the Chinese and North American platforms, and up to the Early Permian in Korea. The number of deposits increased dramatically (hundreds), and their total reserves increased to four billion tons. Deposits of Mesozoic bauxite gravitate to fold belts and, within them, to the epi-Hercynian and epi-Kimmeridgian platforms of the Northern Hemisphere, the total number of known deposits being more than 1000. Most of them are small, but the bauxite quality is rather high. The total aluminum reserve of Mesozoic bauxites (3.3 billion tons) is less than those of the Paleozoic, while the number of Mesozoic deposits is greater. Bauxite accumulation in the Cenozoic took on a grandiose scale (85% of the world's total reserves of about 100 billion tons). It was caused by the expansion of areas of leveled land with a tropical climate, abundance of precipitation, and organic matter, which led to the formation of many large and super-large bauxite deposits. In general, the evolution of bauxite accumulation during the Phanerozoic occurred in increasing pulses, resulting in an uneven increase in the areas and capacity of bauxite deposits with time. [ABSTRACT FROM AUTHOR]

Purpose: Soil diaspore banks of bryophytes are poorly known in tundra grasslands, yet can be important for the maintenance of local bryophyte assemblages. We examined the effects of fertilization and grazing exclusion on above-ground bryophyte assemblages and soil diaspore banks in a tundra grassland. Methods: We collected soil diaspore samples and recorded the cover of above-ground bryophytes from a full-factorial experiment with NPK fertilization and grazing exclusion treatments (a Nutrient Network site in NW Finland). Soil diaspore samples were germinated on trays in a greenhouse. We analyzed the compositions of diaspore bank assemblages and of above-ground assemblages and assessed their responses to the experimental treatments. Results: The diaspore bank contained c. 50% of taxa found in above-ground assemblages; 26 bryophyte taxa germinated from the diaspore bank, while 40 taxa were found in the above-ground assemblages. These communities had distinct species compositions: the diaspore bank was dominated by Pohlia nutans, while above-ground assemblages were dominated by several species. NPK fertilization and grazing exclusion had negative effects on bryophyte richness and cover in above-ground assemblages, and weaker effects on these responses in the diaspore bank. Conclusion: Soil diaspore banks comprise about half of the bryophyte taxa encountered in above-ground assemblages. Bryophyte diaspore banks are more buffered against nutrient enrichment and grazing exclusion than above-ground assemblages, suggesting that diaspore banks may enhance persistence and recovery of local bryophyte assemblages from environmental changes. [ABSTRACT FROM AUTHOR]

The importance of many mutualistic interactions is poorly understood because information on their frequency and distribution at wide spatial scales is lacking. One such interaction is that between ants and plants bearing diaspores equipped with elaiosomes, which function as a reward for ants in exchange for dispersion. Our aim was to estimate the number of taxa having elaiosome-bearing diaspores in the Ibero-Balearic territory and its relationship to several factors. We estimated that at least 572 species and subspecies, almost one-third endemic, are present, which corresponds to ca. 5.1% of European angiosperms and 9% of Iberian ones. Because this number of elaiosome-bearing taxa is much higher than those given so far for the Northern Hemisphere, the Ibero-Balearic territory should be considered an important center of myrmecochory, with myrmecochorous species richness significantly positively correlated with ruggedness, latitude, and longitude. In contrast to other myrmecochorous territories (Australia and Cape Province), where numerous trees and shrubs develop on acid substrates, most myrmecochores in the Ibero-Balearic area are perennial herbs occupying basic substrates. Such perennial herbs are more frequent in the Eurosiberian floristic region, whereas annuals abound in the Mediterranean region. The enumerated taxa mainly inhabit forests, scrubs, and anthropized sites. Among them, 56.5% carry the elaiosome on seeds (especially strophiole and caruncle types). In 36.7%, the elaiosome is borne on indehiscent fruits, such as achenes in Asteraceae, where they are found either at the base of the style or the basal hilum, and at the base of nutlets (Boraginaceae and Lamiaceae). [ABSTRACT FROM AUTHOR]

Phenotypic plasticity has been studied in diaspore-dimorphic species, but no such study has been done on a diaspore-polymorphic species. Our aim was to determine the effects of abiotic and biotic factors on phenotypic plasticity of the diaspore-polymorphic cold desert annual Ceratocarpus arenarius. Plants produced from dispersal units near the soil surface (a, basicarps) and at the middle (c) and upper (f) parts of the plant canopy were subjected to different levels of soil moisture, nutrient supply and intramorph and intermorph densities. Different levels of these biotic and abiotic factors resulted in significant variation in total plant mass, diaspore mass, mass allocation to stem and reproductive organs and total number and proportion of morphs a, c and f on an individual. The effect of stress on number and mass of a dispersal unit morph varied by treatment, with dispersal unit f having the highest CV and dispersal unit a the lowest. The success of this diaspore polymorphic species in its rainfall-unpredictable environment likely is enhanced by plasticity in production of the different types of diaspores. [ABSTRACT FROM AUTHOR]

The seeds of most plant species are dispersed by multiple mechanisms. Whether functional traits mediate positive correlations or negative correlations (trade-offs) between different dispersal mechanisms has important consequences for ecological and evolutionary dynamics. We investigate how traits affect wind-driven seed dispersal through the air and across the ground (primary and secondary wind dispersal, respectively). We hypothesized that primary and secondary wind dispersal were positively correlated because they should both decrease with the wing loading of seeds. We test this hypothesis with wind-tunnel experiments using different seed morphologies of Zygophyllum xanthoxylon (heterocarpous) and Calligonum species. We measured primary dispersal distance at varying wind speeds and release heights, and quantified secondary dispersal potential as the threshold wind speed for seed movement on four ground surfaces. Contrary to our expectation, we found a context-dependent trade-off between primary and secondary wind dispersal. The smoother the ground surface, the stronger this trade-off becomes. The trade-off results from a positive relationship between wing loading and the ratio of vertical to horizontal seed projection (v/h-ratio): an increasing v/h-ratio not only promotes secondary dispersal on smooth surfaces by increasing wind interception of seeds, but also decreases primary dispersal distance by increasing wing loading and terminal velocity of seeds. The trade-off contradicts the widespread assumption of a positive correlation between primary and secondary dispersal. A simple classification into poorly and well-dispersed seeds is thus not possible. The trade-off may affect dynamics of succession and the expansion of pioneer vegetation, while potentially slowing down evolutionary responses to selection on seed dispersal. [ABSTRACT FROM AUTHOR]

In-situ single-crystal and powder X-ray diffraction (XRD) experiments were performed on diaspore at high temperatures. The powder XRD experiments showed that the dehydration reaction from diaspore to corundum occurs between 703 and 733 K. The in-situ single-crystal XRD measurements of diaspore could successfully determine the cell parameters, fractional atomic coordinates and anisotropic displacement parameters at high temperatures, i.e., from 295 to 698 K. Temperature variations in the cell parameters indicate that thermal expansion of the a-axis is a little higher than those of the b-axis and the c-axis. However, the axial thermal expansivity is not as anisotropic as was previously suggested. The results of structure refinements indicate that such lattice expansion behavior is the result of thermal expansion of the tunnels through O2-H···O1 hydrogen-bond separation in the diaspore structure. To the best of our knowledge, this is the first time that the thermal expansion of diaspore has been investigated at an atomic level by in-situ single-crystal XRD experiments at high temperatures. [ABSTRACT FROM AUTHOR]

In this study, diasporic bauxite was mechanically activated for different durations (15, 30, 60, 90 and 120 min) by the planetary mono mill. The speed of the main disk and ball-to-mass ratio were kept constant at 600 rev min−1 and 25, respectively. The chemical composition of the ore was determined via X-ray fluorescence. Structural changes and thermal behavior were examined by X-ray diffraction analysis (XRD), Scanning electron microscopy (SEM), differential thermal analysis-thermogravimetry (DTA-TG) and Fourier transform infrared spectroscopy (FTIR). Diaspore, hematite and anatase were detected at XRD analysis, and with an increment in activation time, the intensity of the peaks decreased, and position and width of the peaks changed as well. In DTA analysis, with mechanical activation, the temperature of the endothermic peak that corresponds to dehydroxylation of the aluminum hydroxide was lowered and area of the peak was decreased. These results mean that the structure was disordered with mechanical activation. [ABSTRACT FROM AUTHOR]

Frugivory and dispersal can be influenced by the traits present in the frugivores and in the plant diaspores. We observed the frugivory process for one year, during dry and wet seasons, in tree species from the gallery forests located in Central Brazil. Traits of the visiting frugivores (morphology and behaviour) and of the diaspores (morphology) were associated with the quantity of fruit eaten. Quantitative components (e.g., the number of fruits eaten and the visit frequency) and qualitative components (e.g., treatment of the diaspore) were used to identify possible dispersers. The diaspore colour was crucial for frugivory in some species. Omnivores consumed more fruits during wet season, and the fruit pulp percentage was relevant for consume of fruits during dry season. Seasonality influenced the frugivore diversity and the number of fruits eaten. We found differences associated with the dispersal effectiveness (e.g., number of swallowed seeds) both among the tree species and among the frugivores; and that the potential of seed dispersal may vary between seasons. Responses to seasonality were related to species richness. The high frugivore richness at one of the gallery forests has made frugivory more crucial and dispersion more probable, independent of seasonality. [ABSTRACT FROM AUTHOR]

More than 0.5 billion tons of late Permian bauxite overlies the karstic topography of the Maokou Formation of western Guangxi in China. Here, we provide new mineralogical, geochemical, Sr-Nd-Pb isotopic, and pyrite S isotope and trace element compositional data for the Pingguo bauxite deposit, aiming to further our understanding of the genesis of Permian bauxite. The Pingguo bauxite contains three distinct layers: a lower layer dominated by ferric clay or weathered iron ore, a middle layer of cryptocrystalline and oolitic bauxite ore, and an upper layer dominated by argillaceous bauxite. The bauxite ore is mainly diaspore, pyrite, chamosite, and anatase, whereas the argillaceous bauxite contains diaspore, kaolinite, pyrophyllite, pyrite, and anatase. Two types of pyrite have been identified within the bauxite: fine-grained and framboidal pyrite (Py1) occurring in aggregates and coarse-grained and euhedral pyrite (Py2). Py1 is enriched in trace elements and is thought to have a diagenetic origin, whereas Py2 is deficient in trace elements and is considered to have formed by later recrystallization. The S isotopic composition of pyrite (−34.11 to −18.91‰) and visible ovoid microorganisms within the bauxite provide evidences of microbial activity during bauxite formation. The Sr-Nd-Pb isotopic composition of the bauxite indicates that these ores were generated by the weathering of basalts belonging to the Emeishan Large Igneous Province (LIP) and limestones of the Maokou Formation. Microorganisms were likely to have enhanced the dissolution and weathering of the parent rock and facilitated the precipitation of diaspore under near-surface conditions. [ABSTRACT FROM AUTHOR]

Aluminous spinel, corundum and diaspore are reported from intensely altered parts of primitive troctolites recovered from IODP Site U1415 at the Hess Deep Rift. The spinel is green-colored, has an irregular shape, has low Cr concentrations, and is so distinct from primary igneous chromite. Corundum and diaspore occur mainly at the rims of green spinel grains with a texture suggesting a sequential replacement of spinel by corundum, and then corundum by diaspore. The green spinel is associated with anorthite and pargasite, which is overgrown by tremolite that forms coronitic aggregates with chlorite around olivine. These petrographic observations are supported by pressure-temperature pseudosections, which predict spinel + pargasite stability field, and tremolite/hornblende + chlorite field at lower temperature conditions. From these pseudosections and simplified system phase diagrams, estimated formation temperature conditions calculated at 2 kbar are 650-750 °C for spinel + pargasite, 410-690 °C for tremolite/hornblende + chlorite, 400-710 °C for corundum, and <400 °C for diaspore. Because the aluminous spinel occurs in the domains that were previously occupied by magmatic plagioclase, and because spinel-bearing rocks characteristically have high AlO/CaO and AlO/SiO ratios, it is likely that the stabilization of spinel was caused by the loss of Ca and SiO(aq) in high-temperature hydrothermal fluids. The results of this study suggest that (1) the concentrations of aluminous phases in the lower oceanic crust are presently underestimated, and (2) chemical modification of the lower oceanic crust due to high-temperature hydrothermal metasomatic reactions could be common near spreading axes. [ABSTRACT FROM AUTHOR]

An integrated technology is proposed for processing diaspore-boehmite bauxites and extracting their useful components. It is established that sintering bauxite with a caustic alkali increases the quantities of rare-earth metals that are recovered. Experiments showed that the sintering of bauxite with a caustic alkali must be done with no more than 10-15% moisture in the charge at the optimum temperature of 200°C. Leaching of the sinter cake with water or a dilute aluminate solution forms high-iron red mud with low concentrations of alkali and alkaline-earth metals. Leaching the mud with a dilute inorganic acid makes it possible to extract up to 90% of the rare-earth metals, including scandium oxide. [ABSTRACT FROM AUTHOR]

Algal mats in lakes and reservoirs can transport diaspores and carpological remains of plants, and thus may influence the creation of taphocoenoses. In 2012, I quantified carpological remains in two types of algal mats from a small reservoir in southern Poland. Mats formed by filamentous algae participate primarily in the original transport of diaspores, and can influence their concentration and facilitate their migration, mainly between the shores of the reservoir. Diatom mats partake primarily in diaspore redeposition, but can also cause their dispersal between the shore zone and the central part of the reservoir. This research demonstrates that mats built by diatoms contain far more remains and are more biologically diverse than filamentous algal mats. Movement of carpological remains observed in both types of algal mats points to their role in the formation of taphocoenoses and suggests that algal mats must be considered when interpreting macrofossil records. [ABSTRACT FROM AUTHOR]

Selective flocculation is a new method to solve the problem of China's bauxite de-silication besides flotation and reverse flotation. The method of selective flocculation of bauxite using hydrolyzed polyacrylamide as flocculant was experimented and evaluated. The results of diaspore and kaolinite single mineral settling tests show that the difference between settlement yield of kaolinite (settling 15 min) and diaspore (settling 3 min) increases from 16% to 60% by adding flocculant at pH=7. Results of selective flocculation experiment of bauxite show that the higher concentrate grade (65.75) and Al-Si ratio (7.34) could be obtained with sodium carbonate as dispersant compared with sodium hexametaphosphate; under the action of flocculating agent, the concentrate grade and Al-Si ratio increase to 67.99 and 9.01. These results could meet the requirements of Bayer production, and the simpler process was expected to cost far less than traditional flotation method and a promising de-silication method of bauxite. [ABSTRACT FROM AUTHOR]

The adsorption behaviors of three carboxyl hydroxamic acids on diaspore (010) and kaolinite (001) have been studied by density functional theory (DFT) and molecular dynamics (MD) method. The results indicated that carboxyl hydroxamic acids could adsorb on diaspore surface by ionic bonds and hydrogen bonds, and adsorb on kaolinite surface by hydrogen bonds. The models of carboxyl hydroxamic acids adsorbed on diaspore and kaolinite surfaces are proposed. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Bauxite resources are widely spread in the earth. However, the effective utilization of this mineral is still under infant. The conventional collector for diaspore mineral is oleic acid. It has three main drawbacks which are highly insoluble, large dosages in bauxite flotation, and low selectivity, which hinder its application in industry. In this research, octylic hydroxamic acid was synthesized, and its collecting ability toward two major minerals in bauxite-diaspore and kaolinite was investigated. The collecting power of various reagents for diaspore are shown as follows: oleic acid

In archaeobotanical studies, the taxonomic classification of diaspores has usually been done by simple morphological observation and visual comparison with ex situ collections of seeds, although the use of biometric indices has often proved to be a powerful approach in the taxonomic studies of the genus Vitis as well as for the species attribution of archaeological remains. Using image analysis techniques, seeds from two Sardinian archaeological sites, the pre-Nuragic and Nuragic complex of Sa Osa in central-western Sardinia, attested as the oldest Sardinian archaeological site with remains of Vitis seeds, and the Isola di Coltellazzo in southwest Sardinia, were selected and characterized on the basis of morphological features and Elliptic Fourier Descriptors. Moreover, seeds of five modern populations of V. vinifera ssp. sylvestris collected from southwest Sardinia and the seeds of 41 cultivars of V. vinifera ssp. vinifera mainly from southern and central-western Sardinia were also analysed by computer image analysis. The obtained data were used to implement a database of biometric parameters and to compare the unknown archaeological seeds with the characterized recent seeds, using Linear Discriminant Analysis. The similarity of the archaeological seeds to V. vinifera ssp. vinifera cultivars rather than to V. vinifera ssp. sylvestris populations could allow it to be stated that, between the Middle and Final Bronze Age, varieties very close to modern V. vinifera ssp. vinifera were already being used to produce wine and/or to be preserved for foodstuffs. Moreover, the better matching of the archaeological seeds to white grapes rather than black grape cultivars could indicate the origins of the traditional cultivation of white grapes in these regions of Sardinia. [ABSTRACT FROM AUTHOR]

Particularly well-known among the many impacts of the invasive annual grass downy brome ( Bromus tectorum, Poaceae) is its ability to alter fire cycles and increase in abundance after fire. However, little is known about how fire influences B. tectorum dispersal. We quantified fire effects on B. tectorum dispersal using three recently burned areas in the western region of the Colorado Rocky Mountains by marking diaspores (seeds) with fluorescent powder, and then recovering them at night using ultraviolet lights. Diaspores were of two types: with and without sterile florets attached. We also characterized vegetation cover and near-surface wind speed in burned and unburned areas. Diaspores travelled much farther in burned areas than in nearby unburned areas (mean ± standard error at the end of the experiment: 209 ± 16 cm and 38 ± 1 cm, respectively; maximal distance at the end of the experiment: 2,274 cm and 150 cm, respectively), indicating an increase in dispersal distance after fire. Diaspores with sterile florets attached dispersed longer distances than those without sterile florets (mean ± standard error at the end of the experiment: 141 ± 14 cm and 88 ± 7 cm, respectively). Vegetation cover was lower and wind speeds were higher in the burned areas. Our results indicate that at least one of the mechanisms by which the spread of B. tectorum is promoted by fire is through increased seed dispersal distance. Preventing movement of seeds from nearby infestations into burned areas may help avoid the rapid population expansion often observed. [ABSTRACT FROM AUTHOR]

Elaiosomes of myrmecochorous plant seeds are known to enhance the attraction of diaspore-dispersing ants by serving as a nutritional reward. However, it remained unclear which (nutritional) compounds affect diaspore preferences of ants. We hypothesized that apart from elaiosome/seed-size ratio, volume, and physical surface of diaspores, the quantity and the composition of fatty acids, amino acids, and sugars strongly influence the diaspore preferences of different species. Chemical (nutritional) profiles as well as structural properties of seeds with and without elaiosomes were analyzed and correlated with observed seed choice behavior of ants. Cafeteria experiments in the field confirmed the enhanced attractiveness of elaiosome-bearing seeds for all three ant species tested ( Lasius fuliginosus, Myrmica ruginodis, and Temnothorax nylanderi), although seeds lacking elaiosomes also were transported. In multiple-choice cafeteria experiments with simultaneously offered diaspores of 16 plant species with and without elaiosome and with highly varying structural and chemical properties, all three ant species showed distinct preferences for certain diaspore species. Correlation analyses confirmed that the presence of an elaiosome represents the crucial factor that favors ant diaspore dispersal. In addition, the composition and the content of free amino acids, and to varying degrees fatty acids, were found to significantly affect preferences of each ant species, whereas the effect of single fatty acids acting as chemical triggers for diaspore transport by ants, as supposed by several studies, was not confirmed. In conclusion, although at least some diaspore species lacking elaiosomes attract ants for diaspore removal services by presenting nutritional seed coats, the production of elaiosomes seems to provide a worthwhile investment. Elaiosomes ensure rapid diaspore detection and removal due to chemical cue compounds and by offering a highly nutritional food supply, probably fitting the nutritional demands of ants. [ABSTRACT FROM AUTHOR]

The bauxites deposits of Kachchh area in Gujarat are investigated to characterize them based on mineralogical and petrographic studies. The major bauxitic mineral in these occurrences is gibbsite, with minor concentration of boehmite and diaspore. Apart from the bauxitic minerals, the other associate minerals are kaolin, calcite, alunite and the iron ore minerals such as hematite and goethite and titanium rich anatase. The iron ore minerals (hematite and goethite) are 10-50microns in size and are disseminated throughout the oolitic and pisolitic bauxitic minerals. At places the goethite exhibits colloform texture. The preservation of basaltic texture in some of the samples indicate that the insitu nature of these bauxites, which are formed by the alteration of calcic plagioclase from the parent basalt. Although, the basalt occurs as the main parent rock for these bauxites, the presence of calcite in some of the samples represent the possibility of having a limestone parent rock at least in some of the bauxite occurrences. [ABSTRACT FROM AUTHOR]

Vibrational properties of diaspore, α-AlOOH, have been re-investigated using room-temperature single-crystal Raman spectroscopy and low-temperature powder infrared (IR) transmission spectroscopy. First-principles harmonic calculations based on density functional theory provide a convincing assignment of the major Raman peaks and infrared absorption bands. The large width of the Raman band related to OH stretching modes is ascribed to mode-mode anharmonic coupling due to medium-strength H-bonding. Additional broadening in the powder IR spectrum arises from depolarization effects in powder particles. The temperature dependence of the IR spectrum provides a further insight into the anharmonic properties of diaspore. Based on their frequency and temperature behavior, narrow absorption features at ~2,000 cm and anti-resonance at ~2,966 cm in the IR spectrum are interpreted as overtones of fundamental bending bands. [ABSTRACT FROM AUTHOR]

Diaspore banks are crucial for the maintenance and resilience of plant communities, but diaspore banks of bryophytes remain poorly known, especially from tropical ecosystems. This is the first study to focus on the role of diaspore banks of bryophytes in tropical rain forests. Our aim was to test whether microhabitat (substrate type) and species traits (breeding system, phylum) are important in explaining the diaspore bank composition. Using samples cultivated in the laboratory, we assessed the number of species and shoots emerging from bark, decaying wood and soil from two sites of the Atlantic rain forest (montane and sea level) in Brazil by comparing the contribution of species by phylum (mosses, liverworts) and breeding system (monoicous, dioicous). More species emerged from bark (68) and decaying wood (55) than from soil (22). Similar numbers of species were found at both sites. Mosses were more numerous in terms of number of species and shoots, and monoicous species dominated over dioicous species. Substrate pH had only weak effects on shoot emergence. Species commonly producing sporophytes and gemmae had a high contribution to the diaspore banks. These superficial diaspore banks represented the extant vegetation rather well, but held more monoicous species (probably short-lived species) compared to dioicous ones. We propose that diaspore bank dynamics are driven by species traits and microhabitat characteristics, and that short-term diaspore banks of bryophytes in tropical rain forests contribute to fast (re)establishment of species after disturbances and during succession, particularly dioicous mosses investing in asexual reproduction and monoicous mosses investing in sexual reproduction. [ABSTRACT FROM AUTHOR]

The factors responsible for the patterns of niche differentiation and narrow endemism have rarely been investigated in annual Mediterranean plants. This topic was addressed here by performing comparative studies on realized niches, regional occupancy, global biogeographical distribution and seed traits of a set of Arenaria (Caryophyllaceae) species inhabiting southern Provence (SE France), focusing in particular on Arenaria provincialis, a narrow endemic restricted to the hills and modest calcareous mountains around the city of Marseille. Field studies were carried out from 2008 to 2009 at 624 sites in the limestone mountains where Arenaria species are likely to occur. The Arenaria species occurring in southern Provence vary greatly in their patterns of regional occupancy and their biogeographical distribution. Multivariate analysis of the realized niche showed that they have some similar limiting environmental factors in common, but they do not all occupy the same habitats. Studies on the fruits and seeds showed that the endemic A. provincialis has a larger seed than its congeners and a capsule that remains closed and falls from the plant at maturity. This well-differentiated diaspore specific to A. provincialis may be responsible for the limited dispersal capacity of this species. Phylogenetic analyses showed that A. provincialis is not closely related to the other taxa inhabiting southern Provence, but rather to Arenaria occurring in highland areas in the south of France. The restricted pattern of distribution of A. provincialis is probably due to the past isolation event from which it originated and to its limited dispersal capacity, rather than resulting from its ecological niche range. [ABSTRACT FROM AUTHOR]

We have measured the pressure-induced change in the lattice dynamics of diaspore, α-AlO(OH), by in situ Raman spectroscopy up to 25 GPa. The spectra are evaluated by density functional perturbation theory-based atomistic model calculations. The assignment of calculated to experimentally observed Raman bands is based on the calculation of Raman intensities. We discuss the accuracy of the approach employed for these calculations and explain the relative magnitudes of mode Grüneisen parameters. [ABSTRACT FROM AUTHOR]

Jajarm’s bauxite deposits are mainly diasporic, and they have a low mass ratio of Al2O3/SiO2. It is necessary to increase the run-of-mine mass ratio before feeding the material to the Bayer process. Chemical analysis indicated that the low-grade bauxite sample from Jajarm contained 43.9wt% Al2O3 and 13.35wt% SiO2, resulting in a mass ratio of 3.29. According to mineralogical studies, the presence of aluminosilicate minerals such as kaolinite, illite, and quartz was the main reason for the decrease of the mass ratio. Microscopic observations revealed that, with the size reduction from −1000+710 to −38 μm, the liberation degree of diaspore increased from 10% to 60%, and that of aluminosilicates increased from 20% to 85%. Heavy liquids with the densities of 2.8, 3.0, 3.2, and 3.4 g/cm3 were used to evaluate the heavy media separation in three sizes, i.e., −3350+710, −710+212, and −212+125 μm. Laboratory studies confirm that the density of 3.2 g/cm3 can produce the concentrates (in sunk fractions) with recoveries of 89.09%, 91.24%, and 84.68% with the Al2O3/SiO2 mass ratios of 5.03, 5.16, and 5.15 for the −3350+710, −710+212, and −212+125 μm sizes, respectively. [ABSTRACT FROM AUTHOR]

The contribution of morphological features of parent thalli, substrate and climatic factors, and their seasonal fluctuations to variation in the viability of vegetative diaspores has been studied on the model of epiphytic lichen Hypogymnia physodes. Seasonal trends in viability have been revealed only in certain types of biotopes. Hygrothermal conditions and substrate properties in the biotope have proved to have a significant effect on the viability of soredia. [ABSTRACT FROM AUTHOR]

Abstract  Several m-thick, karst-unconformity-type metabauxite horizons in the İlbir Mountains of SW Turkey host open-space mineralization of gem-quality diaspore (trademarked as zultanite), associated with muscovite, hematite, ilmenite, chloritoid, and younger calcite. The hydrothermal-metamorphogenic mineralization occurs in fracture zones (veins and open structures) that crosscut the metabauxite horizons, but does not extend into the marble host rocks. The white to dark gray marble sequence (over 2,000 m in thickness) is of Cretaceous depositional age and was affected by Alpine (Paleogene) tectonometamorphism which caused the hydrothermal remobilization of primary bauxite components into crosscutting structures. [ABSTRACT FROM AUTHOR]

Bryophyte diaspore banks are a potential source of reproductive propagules that may be able to colonize newly available habitat after forest harvesting. However, their role and the factors influencing the successful establishment of species remain poorly understood. To investigate these aspects of diaspore banks, we obtained mineral soil samples from mixed and coniferous stands of boreal mixed-wood forest in northern Alberta, Canada, which had recently experienced a range of harvesting intensities. Samples were germinated in growth cabinets under two light regimes. The composition of germinated bryophyte species was compared among forest types, harvesting intensities, and light levels, and also related to edaphic conditions and geographic location of the sample site. Germinated species composition was not related to forest type or harvesting intensity, but was associated with measured edaphic variables and geographic space, indicating that similarity in species composition reflected similarity in edaphic conditions and spatial proximity. This was partly because of spatial dependence of edaphic variables. Light intensity had a significant influence on the development of species assemblages and individual species responses. Richness and cover of acrocarpous mosses (fugitive, colonist, and shuttle life-history strategies) were significantly reduced under low light conditions, but pleurocarpous mosses (perennial strategy) were not affected. Shannon diversity and the frequency of reproduction were significantly greater with high light. Pleurocarpous mosses that are characteristic of intact forests germinated frequently, suggesting that diaspore banks may influence their recovery after disturbance. Diaspore banks are a repository of species at sites affected by forest harvesting; however, diaspore germination and establishment will be constrained by the local environment, including edaphic conditions and light intensity. [ABSTRACT FROM AUTHOR]

Comprehensive studies have established that ShPDM-45 refractory produced by OAO Zaporozhogneupor exhibits good anticorrosion properties towards the action of electrolysis bath corrosive extraneous components. The degree of degradation of ShPDM-45 refractory after two years of service is 10%. The average concentration of entry of Nag and Ftot into ShPDM-45 refractory through hearth blocks with 50% graphite is correspondingly 4.08 × 10–4 and 3.32 × 10–4 g-mole/day. It is established that ShPDM-45 refractory is a more reliable barrier material than unmolded aluminosilicate mixes. The penetration rate of corrosive components of the electrolysis bath into unmolded aluminosilicate materials is greater by a factor of 10 – 30 than for ShPDM-45 refractory. It is shown that the protective function of titanium-containing components and glass phase in an electrolyzer lining develops as a result of forming fluoride, subfluoride and oxyfluoride titanium compounds. Industrial approval of ShPDM-45 refractory under OAO Zaporozhe Aluminum Combine conditions has shown that it exhibits good operating properties in electrolyzers with hearth blocks with 50% graphite [ABSTRACT FROM AUTHOR]

Abstract  Thermogravimetric analysis (TGA) testing was used to measure the change in weight of polished samples of Al–XSi (X = 0 and 1.2 mass%) alloys. The samples were heated at 843 K for 6 h in dry air or nitrogen gas. X-ray diffraction was used to monitor the formation of the oxide films on the surface of the samples. The surface oxide films were more compact after the Al alloy samples were heated in air, and the oxide films showed some cracks after being heated in nitrogen gas. The thermally formed surface oxide films on the Al–1.2 mass% Si alloy samples heated in air and in nitrogen gas possessed loose structures, which comprised mainly γ-alumina, diaspore, and gibbsite, along with metallic silicon and/or aluminum. The weight variation curve of the films appeared serrated; this can be attributed to chain reactions (3Si + 3O2 → 3SiO2 + 4Al → 3Si + 2Al2O3) that occurred within the film. [ABSTRACT FROM AUTHOR]

The adsorption of Cu(II) and Cr(VI) on diaspore was studied with the help of X-ray diffraction analysis, BE measurement, zeta potential measurement and atomic adsorption spectrometry. The adsorption equilibrium almost reaches within 60 min. The adsorption isotherms of Cu(II) and Cr(VI) could be well described by the Langmuir equation. The adsorption capacities o Cu(II) and Cr(VI) are 1.944 and 1.292 mg/g, respectively. The adsorption percentage of Cr(II) increases with the increment solution pH, but the adsorption percentage of Cr(VI) decreases. This could be explained by zeta potential theoretical and electrostatic attraction between metal ions and diaspore surface. [ABSTRACT FROM AUTHOR]

Tertiary amine was synthesized from fatty amine and formaldehyde. And then the synthesized tertiary amine was used to react with benzyl chloride to synthesize hexadecyl dimethyl benzyl ammonium chloride (1627) at ambient pressure. Using the synthesized 1627 as collector, the flotation properties of diaspore and kaolinite were investigated by single mineral and mixed mineral test. The flotation mechanism of diaspore, kaolinite and 1627 was discussed based on FTIR spectra. The results show that the mass ratio of aluminum to silicate achieves 15.02 and the recovery of alumina in concentrate is 43.07% using 1627 as a collector. The 1627 is found to be a more effective and a promising collector for reverse flotation to remove aluminum-silicate minerals from bauxite. [ABSTRACT FROM AUTHOR]

N, N-diethyl dodecyl amine(DEN12) was synthesized from dodecyl amine, formic acid and acetic aldehyde. The collecting property of DEN12 on diaspore, kaolinite and illite was investigated by flotation test and infrared spectrum. The results show that in the presence of 2.0×10−4 mol/L DEN12, the recoveries of kaolinite and illite are all higher than 78% and the recovery of diaspore is 50% in the pH range of 5.5–6.0. The mass ratio of Al2O3 to SiO2 in concentrate obtained from separation artificial mixture is higher than 10, suggesting that DEN12 can be used as a collector to separate the aluminosilicates from diaspore in bauxite ores at the pulp pH below 8. The measurements of the infrared spectrum approve that the action between aluminosilicates and tertiary amine collector is strong electrostatic adsorption and that of diaspore is weak electrostatic adsorption. [ABSTRACT FROM AUTHOR]

Reduced dispersability of species living on islands relative to mainland has been documented in both plants and animals. One evolutionary scenario explains this trend by strong selection against dispersal, once the species has reached the island, to reduce dispersal out to sea. In this study, we compare the dispersal ability of three wind dispersed plant species ( Cirsium arvense, Epilobium angustifolium, and E. hirsutum) from populations on mainland and three islands. Dispersal ability was estimated directly as drop time of diaspores, and indirectly using a morphological measure relating the weight of the diaspore to the size of the pappus ( Cirsium) or seed hairs ( Epilobium). Positive correlation between the morphological measure of dispersal ability and drop time of diaspores were found for all study species. Dispersal ability varied significantly among mainland and islands, and among species. C. arvense showed a significant reduction in dispersal ability on islands compared to mainland, whereas the reverse was found for the two Epilobium species. Overall Epilobium diaspores had a 2–4 times higher dispersability than C. arvense, indicating that degree of isolation of islands vary among study species. Significant differences in dispersability among plants within populations were detected in all species suggesting that this trait may have a genetic component. [ABSTRACT FROM AUTHOR]

Bryophytes disperse by small unicellular spores between 7 μm und usually less than 100 μm. A large percentage of species is sterile and propagates vegetatively either by special brood bodies or fragments of whole plants. It is shown that there is no difference in the effectiveness between generative and vegetative propagation. Size and weight of the diaspores suggest that both must easily be dispersed and the species must therefore have wide ranges. This does, however, not result in ubiquitous occurrence. This is only true for part of the species. Many, even sterile species show wide transcontinental ranges. On the other hand, there are many examples of limited to very limited distribution in spite of a rich production of diaspores. These are explained by narrow ecological niches, age of taxa, local extinction or historical events such as ice ages. Conspicuously, species can loose the ability for dispersal for unknown (perhaps genetic) reasons, which may ultimately lead to extinction. [ABSTRACT FROM AUTHOR]

The transport of diaspores on animal hairs depends on the ability of a diaspore to attach to the hair and to be retained in it over longer periods of time. Whereas several studies of diaspore retention on animal hairs have been conducted recently, the process of diaspore attachment to the hair has not yet been studied systematically. We describe a new method to quantify the attachment potential (AtP) of plant diaspores. Attachment potential was measured as the proportion of diaspores of a given species that attached to pieces of an animal coat in a standardised experiment. The experiment was conducted for 58 plant species (herbs and grasses) and three different coat types: sheep wool, cattle and roe deer hair. Attachment potentials differed widely between the three coat types, but also between plant species. We found diaspore surface structure (a quantitative measure of diaspore morphology) and diaspore exposition (describing the morphology of the infructescence) to be the most important plant traits regulating AtP. An influence of seed mass on attachment potential could not be detected. For sheep wool, a general linear model (with diaspore exposure as a factor and diaspore surface structure as covariate) explained 77% of the variation in AtPs. To validate this model, we predicted AtPs for 27 additional species and compared these to the measured Atps; the predicted and measured AtPscorrelated significantly with r s = 0.68. A comparison of attachment and retention potentials to sheep wool for 127 randomly selected plant species showed that attachment and retention are only very weakly correlated, indicating that both processes act rather independently of each other. Since many diaspores seem to perform well in only one of these processes, attachment can be considered to be as equally as decisive as retention in terms of epizoochorous dispersal. [ABSTRACT FROM AUTHOR]

Abstract  The structural compression mechanism and compressibility of diaspore, AlO(OH), were investigated by in situ single-crystal synchrotron X-ray diffraction at pressures up to 7 GPa using the diamond-anvil cell technique. Complementary density functional theory based model calculations at pressures up to 40 GPa revealed additional information on the pressure-dependence of the hydrogen-bond geometry and the vibrational properties of diaspore. A fit of a second-order Birch–Murnaghan equation of state to thep–Vdata resulted in the bulk modulusB 0 = 150(3) GPa andB 0 = 150.9(4) GPa for the experimental and theoretical data, respectively, while a fit of a third-order Birch–Murnaghan equation of state resulted inB 0 = 143.7(9) GPa with its pressure derivativeB′ = 4.4(6) for the theoretical data. The compression is anisotropic, with thea-axis being most compressible. The compression of the crystal structure proceeds mainly by bond shortening, and particularly by compression of the hydrogen bond, which crosses the channels of the crystal structure in the (001) plane, in a direction nearly parallel to thea-axis, and hence is responsible for the pronounced compression of this axis. While the hydrogen bond strength increases with pressure, a symmetrisation is not reached in the investigated pressure range up to 40 GPa and does not seem likely to occur in diaspore even at higher pressures. The stretching frequencies of the O–H bond decrease approximately linearly with increasing pressure, and therefore also with increasing O–H bond length and decreasing hydrogen bond length. [ABSTRACT FROM AUTHOR]

Dispersal limitation was studied in a species-rich meadow (53-65 species of vascular plants per 1.1 m²) to which a mixture of weeds was accidentally sown. Even if none of the sown species belonged to the local species pool, five species successfully established. Of them one persisted for 7 years, however declined from 41 individuals in 1995 to 1 individual recorded in 2001. These results can be interpreted as an evidence for short-term diaspore limitation. In contrast, long-term data indicate no diaspore limitation. Establishment of weeds in subplots with a lower number of species and individuals was higher than in other subplots, indicating that plant establishment in the studied open-canopy grassland is affected by the spatial pattern of present plants. [ABSTRACT FROM AUTHOR]

It has been hypothesized that the relative role of species dispersal in determining plant community composition and species richness changes along primary productivity and disturbance intensity gradients. Manipulative experiments with either diaspore addition or prevention are needed to validate this hypothesis. Due to methodological constraints, diaspore prevention experiments are rarely used. In the case of diaspore addition experiments, there are some potential sources of error. (1) Experiments may be confounded since patchiness of microbial communities is not considered and techniques equalizing microbial communities over study plots are not used. (2) The length of the period of observation may not be sufficient to understand whether the establishment of sown individuals was really successful. (3) The effect of the sowing treatment and the theoretical context of the whole experiment depends on the number and identity of species sown. When addressing the role of long-distance dispersal, it is almost impossible to say what the appropriate number and composition of species to be used for the experiment should be. (4) Until now, most of the attention has been on dispersal in space, while the role of "dispersal in time" (seed bank) has rarely been addressed. We conclude that stepwise accumulation of experimental studies, addressing the role of dispersal in shaping plant communities, will sooner or later reveal general patterns, given the experiments are well planned and aim to avoid the sources of errors described above. [ABSTRACT FROM AUTHOR]

Species pool theory claims that diaspore and microsite availability limit species richness in plant communities. Wet meadows (Calthion) and litter meadows (Molinion, Caricion davallianae) belonging to the most species-rich meadows in the foothills of the Alps have suffered from a strong decrease since the 1970s. Restoration efforts including nutrient impoverishment and rewetting management after drainage and fertilization did not result in the re-establishment of the former species richness although the abiotic filter would have been appropriate for the re-colonization of many locally extinct species. In our experiment at four sites in the largest fen of Southwest-Germany we tested if the restoration success was seed- and gap-limited. We applied sowing and hay spreading (hay seed) as treatments to make seeds available and harrowing to increase gap availability. Sowing seeds or hay seed of species of the former meadow types increased species richness immediately. The proportion of re-established species was higher when additional harrowing was applied. Species richness could be increased not only in vascular plants but also in bryophytes when hay spreading was applied. The strongest re-development towards the target communities (defined through the abiotic filter and the species richness before drainage and fertilization) took place on those sites where hay spreading and harrowing were applied. Sowing seeds and hay seed were traditional techniques to establish e.g. litter meadows, both techniques have been applied for centuries. Even harrowing was described as early as the 19th century to increase the chance of establishing certain species. Therefore, the "application of the knowledge coming from the species pool theory" (although not named during this time) has been common practice since at least the 19th century. [ABSTRACT FROM AUTHOR]

A series of abrasives with various hardness values including monocrystalline and polycrystalline diamond, α- and γ-alumina, zirconia, ceria, and silica were used to examine the concept of chemical-assisted polishing for finishing the (0001), c-plane (basal plane), of sapphire. Diaspore, a monohydrate of alumina, was also evaluated. Atomic force microscopy suggested that the hydrated layer of the c-plane surface was about 1 nm thick. Polishing experiments were designed to determine whether the chemically modified surface hydration layer forms on the basal plane in water. The results indicate that harder abrasives do not necessarily cause faster material removal and better surface finish for similar abrasive particle size. Abrasives with hardness equal to or less than sapphire such as α-Al2O3 and γ-Al2O3 achieved the best surface finish and greatest efficiency of material removal. It is proposed that the (0001) c-plane sapphire surface was modified by water to form a thin hydration layer with structure and hardness close to diaspore. This reaction layer can be removed by an abrasive that is softer than sapphire but harder than the reaction layer, α-Al2O3 was particularly effective. This result is attributed to adhesion between identical reaction layers on the basal planes of the alumina abrasive and the sapphire. This demonstrates that high removal rates and good surface finish can be achieved without costly diamond polishing. [ABSTRACT FROM AUTHOR]

High-grade gneisses from the Pulur complex in NE Turkey bear evidence for biotite-dehydration melting at ≥820 °C and 0.7-0.8GPa, melt segregation and near-isothermal decompression to 0.4-0.5GPa. During further exhumation, the rocks underwent secondary pervasive rehydration at temperatures between ∼400 and 230 °C and fluid pressures between ∼0.3 and 0.1 GPa. Metamorphic peak conditions are dated at 331-327 Ma, while hydrothermal retrogression occurred significantly later at 315-310Ma under static conditions. During the rehydration event, primary high-grade mineral assemblages including garnet, cordierite, sillimanite, spinel, biotite, plagioclase and ilmenite were extensively replaced by muscovite, paragonite, margarite, corundum, diaspore, chlorite, kaolinite, pumpellyite, prehnite, epidote, titanite, anatase, pyrite and chalcopyrite. Secondary mineral assemblages indicate that the infiltrating fluids were characterized by low fO2, very low XCO2 (<0.002), variable activities of Ca2+, K+, Na+ and H+ and relatively high activities of H2S and CH4. Quartz veins that might have acted as pathways for the fluids are rare. Ubiquitous veinlets consisting of (i) albite, (ii) chlorite + calcite + quartz or (iii) K-feldspar + calcite + quartz were formed after the pervasive rehydraton event by precipitation from aqueous solutions that were somewhat richer in CO2. [ABSTRACT FROM AUTHOR]

The possibilities of mechanical activation for extraction of alumina from low-grade bauxites are investigated on the example of the Bokson deposit ores. It is established that the effective acid opening results from combination of mechanical activation and acid processing of activated product. The two-stage method of bauxite decomposition is considered. [ABSTRACT FROM AUTHOR]

The luminescence of Cr3+ in natural and calcined diaspore is applied to probe structural properties of the phases. Steady-state luminescence spectra of the natural diaspore [α-AlO(OH)] are typical of ²E→4A2 transitions of Cr3+ luminescence centers (R-lines) substituting for Al3+ in six-fold coordination. The dehydroxylated phase of the diaspore is characterized by a low degree of crystallinity. This phase is not detectable by XRD and Raman spectroscopy up to 900°C. The time-resolved luminescence spectra of the diaspore treated at 900°C showed two variations: the first is an R-line of Cr3+ luminescence in octahedral sites with a strong crystal field in a very disordered environment, and the second is a broad band of Cr3+ luminescence in weaker crystal field sites. The crystalline phase of corundum [a-Al2O3] is detected by XRD and Raman spectroscopy after treating the diaspore at 1000°C and above (up to 1300°C). The lines in the spectrum of the diaspore treated at this temperature are typical of Cr3+ luminescence centers (R-lines) in Cr-corundum (ruby) structure. [ABSTRACT FROM AUTHOR]

Structural and chemical modifications of the essential Al-containing minerals of bauxite ores - boehmite and diaspore - are examined in the processes of mechanochemical preparation for opening. It is established that the violations changing the character of hydroxide bond and the reactivity of mineralogical bauxite components decrease under mechanical activation in the agrAl(OH)3- ggrAlOOH- agrAlOOH series. The possibilities are considered for intensifying Al2O3 extraction in leaching. [ABSTRACT FROM AUTHOR]

Periclase-carbon linings made from objects supplied by OAO Borovichi Refractory Combine have been tested under operating conditions of converter workshop No. 2 at OAO NLMK in 2007–2008. There is comparative analysis of linings and directions for improving refractory composition are determined. [ABSTRACT FROM AUTHOR]

Seed dispersal by ants (myrmecochory) is mediated by the presence of a lipid-rich appendage (elaiosome) on the seed that induces a variety of ants to collect the diaspores. When seeds mature or fall onto the ground, these ant species transport them to their nest. After eating the elaiosome, the seed is discarded in nest galleries or outside, in the midden or farther away, where seeds can potentially germinate. The final location of seeds with their elaiosomes removed was evaluated to assess the importance of possible handles (structures that ants can grasp to carry) in transporting ants during re-dispersal experiments of seeds from nests of six species of ants. The results indicate that seeds remained within the nest because the ants were not able to transport them out of the nest. As a consequence of the elaiosome being removed, small ant species could not take Euphorbia characias seeds out of their nests. Only large ant species could remove E. characias seeds from their nests. Attaching an artificial handle to E. characias seeds allowed small ant species to redistribute the seeds from their nests. On the other hand, Rhamnus alaternus seeds that have a natural handle after the elaiosome removal were removed from the nests by both groups of ant species. If a seed has an element that acts as a handle, it will eventually get taken out of the nest. The ants’ size and their mandible gap can determine the outcome of the interaction (i.e. the pattern of the final seed shadow) and as a consequence, could influence the events that take place after the dispersal process. [ABSTRACT FROM AUTHOR]

Diaspore (α-AlOOH) was heated at various temperatures from 300 to 1 000 °C for 2 h. The alteration of diaspore by thermal treatment was investigated by differential thermal analysis, thermogravimetric analysis and X-ray diffraction. The mechanism of thermal decomposition of diaspore was discussed according to the Coats-Redfern equation. It is found that after thermal treatment at 500 °C, diaspore is transformed entirely to corundum (α-Al2O3). Combined with the mass loss ratio obtained from the thermogravimetric analysis data, the activation energies for the thermal treatment of diaspore are calculated as E a=10.4 kJ/mol below 400 °C and E b=47.5 kJ/mol above 400 °C, respectively, which is directly related to the structural alteration of diaspore during the thermal treatment. The results indicate that the thermal decomposition of diaspore is conducted primarily by means of an interfacial reaction. [ABSTRACT FROM AUTHOR]