Organic Filaments Research Articles

Engineering Geobacter pili to produce metal:organic filaments

The organized self-assembly of conductive biological structures holds promise for creating new bioelectronic devices. In particular, Geobacter sulfurreducens type IVa pili have proven to be a versatile material for fabricating protein nanowire-based devices. To scale the production of conductive pili, we designed a strain of Shewanella oneidensis that heterologously expressed abundant, conductive Geobacter pili when grown aerobically in liquid culture. S. oneidensis expressing a cysteine-modified pilin, designed to enhance the capability to bind to gold, generated conductive pili that self-assembled into biohybrid filaments in the presence of gold nanoparticles. Elemental composition analysis confirmed the filament-metal interactions within the structures, which were several orders of magnitude larger than previously described metal:organic filaments. The results demonstrate that the S. oneidensis chassis significantly advances the possibilities for facile conductive protein nanowire design and fabrication.

Surface texture, mineralogy and stable isotope studies of nodular calcretes preserved in the YTT ash of Padang Terap river basin and lenggong valley, peninsular Malaysia: Implications in its origin and paleoclimatic reconstruction

Rounded to sub-rounded calcrete nodules, preserved in Youngest Toba Tuff (YTT, ~75 ka) ash, exposed at the Padang Terap river basin and Lenggong valley of Malaysia, have been investigated for their micromorphology, mineralogy and stable isotope compositions (δ18O and δ13C) with the aim to interpret their origin, climatic conditions and vegetational scenario in the studied areas. These nodules are associated with cylindrical, pipe-like, root calcretes and highly calcretized ant traces. The FESEM study shows dominance of sparry calcite and microsparite as groundmasses and presence of bacteria microfossils and microbial features. The microfossils are represented mainly by microcodium, calcified pedostructures and organic filaments, whereas, the microbial features as extracellular polymers substances (EPS) and bacillus type bacteria. Mineralogical compositions as reflected by X-ray diffractograms show dominant peaks of calcite followed by quartz, chlorite, illite and palygorskite. The δ18O and δ13C values suggest that the precipitation of calcium carbonate might have happened in in-situ manner that leached under the influence of meteoric water in presence of C4 dominated vegetation during the formations of the nodules. Presence of C4 vegetation in the area suggests that the same had revived after the YTT event. The study suggests that the CaCO3 would have been supplied to the host sediments by dust, rainwater and local geological set-ups during arid, semi-arid and humid climatic conditions.

Organic biomorphs may be better preserved than microorganisms in early Earth sediments

Abstract The Precambrian rock record contains numerous examples of microscopic organic filaments and spheres, commonly interpreted as fossil microorganisms. Microfossils are among the oldest traces of life on Earth, making their correct identification crucial to our understanding of early evolution. Yet, spherical and filamentous microscopic objects composed of organic carbon and sulfur can form in the abiogenic reaction of sulfide with organic compounds. Termed organic biomorphs, these objects form under geochemical conditions relevant to the sulfidic environments of early Earth. Furthermore, they adopt a diversity of morphologies that closely mimic a number of microfossil examples from the Precambrian record. Here, we tested the potential for organic biomorphs to be preserved in cherts; i.e., siliceous rocks hosting abundant microbial fossils. We performed experimental silicification of the biomorphs along with the sulfur bacterium Thiothrix. We show that the original morphologies of the biomorphs are well preserved through encrustation by nano-colloidal silica, while the shapes of Thiothrix cells degrade. Sulfur diffuses from the interior of both biomorphs and Thiothrix during silicification, leaving behind empty organic envelopes. Although the organic composition of the biomorphs differs from that of Thiothrix cells, both types of objects present similar nitrogen/carbon ratios after silicification. During silicification, sulfur accumulates along the organic envelopes of the biomorphs, which may promote sulfurization and preservation through diagenesis. Organic biomorphs possessing morphological and chemical characteristics of microfossils may thus be an important component in Precambrian cherts, challenging our understanding of the early life record.

Polyamide based amalgams in marine custom: History and forthcoming leanings

The increasing ecological concerns and the requirement to invent genuine substitutes to glass or strengthened fusions of carbon have improved the attention in polyamide amalgams filled with organic filaments, derivative of renewable and eco-friendly bases. The article’s scope is to endorse our attention towards the developed knowledge of science and technology in the field of green compound constituents to upkeep their grander application in numerous industries. Utilization of composites based on polymer and reinforced fibers (FRP) proposes numerous benefits for marine manufacturers to attain effective and dependable edifices. The trending applications of FRP in the maritime industry based on its materials, production techniques, and conservational disputes are projected to the attention of marine draftsmen, and also the potential exploration is concisely highlighted in this article.

Settled/unsettled blend nanofibers electrospun from photoactive polymeric/nonpolymeric constituents in PBDT‐DTNT:PCBM solar cells

ABSTRACTTo increase internal donor–acceptor interfaces and highlight the influence of ordering of donor–acceptor components inside fibers, novel blend fibrous structures comprising unsettled poly[benzodithiophene‐bis(decyltetradecyl‐thien) naphthothiadiazole] (PBDT‐DTNT):grafted‐reduced graphene oxide (rGO) nanofibers, settled PBDT‐DTNT/grafted‐rGO nanofibers including PBDT‐DTNT, and settled PBDT‐DTNT/grafted‐rGO nanofibers excluding PBDT‐DTNT were prepared and embedded in photovoltaics. Hence, three‐dimensional nonwoven network morphologies of triple electrospun fibers were acquired using electrospinning. Average diameter and conductivity of PBDT‐DTNT:grafted‐rGO, PBDT‐DTNT/grafted‐rGO:PBDT‐DTNT, and PBDT‐DTNT/grafted‐rGO fibers ranged in 200–250 and 1.1–1.6 × 10−9 S cm−1, 150–190 and 9.2–9.5 × 10−7 S cm−1, and 60–80 nm and 3.3–3.7 × 10−10 S cm−1, respectively. Photoluminescence quenching and thus donating–accepting characteristic of settled PBDT‐DTNT/grafted‐rGO nanofibers including PBDT‐DTNT were more intensified, resulting from greater internal interfaces. Through blending PBDT‐DTNT/grafted‐rGO supramolecules with PBDT‐DTNT chains and embedding them in PBDT‐DTNT:phenyl‐C71‐butyric acid methyl ester (PC71BM) thin films, the best results were obtained. Short‐circuit current density (Jsc), open circuit voltage (Voc), fill factor (FF), and power conversion efficiency (PCE) were 12.18 mA cm−2, 0.66 V, 65%, and 5.22%, respectively. Nanofiber template not only acted as guide path for charge transport but also increased interfacial area between donor and acceptor to induce more exciton dissociation. Inclusion of PBDT‐DTNT donor chains into blend nanofibers increased donor–acceptor interface in organic filaments. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47591.

Пеплы 2017 года с вулканов Ключевского и Камбального: сравнительный минералогогеохимический анализ

The results of the mineralogical and geochemical study of the ash of the Klyuchevskoy and Kambalnyy volcanoes located in different geological conditions (Klyuchevskoy – Central Kamchatskaya Depression, Kambalnyy - Southeast end Eastern Kamchatka Volcanic Ridge) were obtained in 2017, and allowed making following conclusions. The investigated ashes differ somewhat in chemical composition: the Klyuchevskoy volcano ash is close to andesibasalts, but that from Kambalnyy is close to andesites. According to the normative-mineral composition, they are composed of 65–87% basic plagioclases, 3–22% quartz, 6.5–14% Mg-Fe-Ca silicates (olivine, pyroxene, probably hornblende). In this case, the ashes from the volcano Kambalnyy are characterized by more acidic composition of plagioclase and higher content of quartz. The accessory minerals found in the ashes are presented by spinels (Ulviya magnetite, magnetite, and chromite), ilmenite, rutile, apatite, zircon, pyrite and native metallic-phase (Al, Cu, Fe). Pelitic (silty) fractions are enriched in quartz, but impoverished in Mg-Fe-Ca silicates. As a small admixture in the ash of the Cumulus volcano, titanite, andradite, kaolinite and gypsum are inherently resurgent. The fact of detecting the filamentous forms of abiogenic condensed organopolymer substance of CNO composition in the investigated ashes is of particular importance. It should be noted that, according to the isotope composition of carbon, these formations are identical to similar threads and particles identified in products of modern volcanism in the Kamchatka-Philippine island arc megabelt. Moreover, the analysis showed the presence in the ashes of the Kliuchevskoy and Kambalnyy volcanoes of the carbon substance, which carbon isotopic composition practically coincides with that in the organic filaments. Ashes contain 50 microelements divided into five groups: alkaline and alkaline earth, hydrolyzed, lanthanides, chalcoceridophiles, semi- and non-metals. The analysis leads to the conclusion that the predominantly plagioclase containing ash from both volcanoes show a 75% geochemical similarity to the deep source matter. According to the shape of the curves of chondritotropic concentrations of lanthanides, the ashes from both volcanoes are close to the basaltic lavas of TTI-50. The insignificance of the Eu anomaly on the most curves and the apparent moderate differentiation of the lanthanides indicate that the fractionation of plagioclases in the primary melts and the significant realization of the fractionation of olivine and pyroxenes are weak. Based on the granulometric and morphological homogeneity of particles and the presence of a significant content of fresh volcanic glass in ash from both volcanoes, it can be assumed that in both cases the ashes were predominantly or largely melt-formed, and primarily associated with deep magmatic chambers. It is supposed that the process of slow rise of magmatic melts with their fractionation and gravitational stratification into the lower Mg-Fe-silicate and upper aluminosilicate parts took place. Last eruption of the aluminosilicate substrate occurred in the ash form. Because of the viscosity and tendency to quick solidification, aluminum silicate magmatic magma plugged the channel thus preventing the eruption of the lava Hawaiian type.

Nanowire-Intensified Metal-Enhanced Fluorescence in Hybrid Polymer-Plasmonic Electrospun Filaments.

Hybrid polymer-plasmonic nanostructures might combine high enhancement of localized fields from metal nanoparticles with light confinement and long-range transport in subwavelength dielectric structures. Here, the complex behavior of fluorophores coupling to Au nanoparticles within polymer nanowires, which features localized metal-enhanced fluorescence (MEF) with unique characteristics compared to conventional structures, is reported. The intensification effect when the particle is placed in the organic filaments is remarkably higher with respect to thin films of comparable thickness, thus highlighting a specific, nanowire-related enhancement of MEF effects. A dependence on the confinement volume in the dielectric nanowire is also indicated, with MEF significantly increasing upon reduction of the wire diameter. These findings are rationalized by finite element simulations, predicting a position-dependent enhancement of the quantum yield of fluorophores embedded in the fibers. Calculation of the ensemble-averaged fluorescence enhancement unveils the possibility of strongly enhancing the overall emission intensity for structures with size twice the diameter of the embedded metal particles. These new, hybrid fluorescent systems with localized enhanced emission, and the general nanowire-enhanced MEF effects associated to them, are highly relevant for developing nanoscale light-emitting devices with high efficiency and intercoupled through nanofiber networks, highly sensitive optical sensors, and novel laser architectures.

Electrospun Conjugated Polymer/Fullerene Hybrid Fibers: Photoactive Blends, Conductivity through Tunneling-AFM, Light Scattering, and Perspective for Their Use in Bulk-Heterojunction Organic Solar Cells.

Hybrid conjugated polymer/fullerene filaments based on MEH-PPV/PVP/PCBM were prepared by electrospinning, and their properties were assessed by scanning electron, atomic and lateral-force, tunneling, and confocal microscopies, as well as by attenuated-total-reflection Fourier transform infrared spectroscopy, photoluminescence quantum yield, and spatially resolved fluorescence. Highlighted features include the ribbon shape of the realized fibers and the persistence of a network serving as a template for heterogeneous active layers in solar cell devices. A set of favorable characteristics is evidenced in this way in terms of homogeneous charge-transport behavior and formation of effective interfaces for diffusion and dissociation of photogenerated excitons. The interaction of the organic filaments with light, exhibiting specific light-scattering properties of the nanofibrous mat, might also contribute to spreading incident radiation across the active layers, thus potentially enhancing photovoltaic performance. This method might be applied to other electron donor–electron acceptor material systems for the fabrication of solar cell devices enhanced by nanofibrillar morphologies embedding conjugated polymers and fullerene compounds.

Stability of biological and inorganic hemimorphite: Implications for hemimorphite precipitation in non-sulfide Zn deposits

Hemimorphite, Zn4Si2O7(OH)2·H2O, one of the most common minerals in non-sulfide Zn deposits, together with smithsonite and hydrozincite, is one of the most abundant minerals in the “calamine” deposits in SW Sardinia. In spite of their importance for the development of ore genesis models, the stability properties of hemimorphite are poorly known. This paper presents solubility experiments on two different types of hemimorphite: a “geological” hemimorphite from a supergene non-sulfide Zn deposit, of supposed abiotic origin, and a hemimorphite precipitated by bacterial activity. Both specimens were characterized, before and after the experiment, by Synchrotron Radiation X-ray powder diffraction, Scanning Electron Microscopy, and X-ray Absorption Spectroscopy. The calculated solubility product constants (logKs) are similar for both “geological” and biogenic hemimorphite (30.3±0.4 and 30.5±0.1, respectively). During the solubility experiment, biological hemimorphite undergoes an amorphous to crystalline phase transition, and the distinctive features (mineralized bacterial sheaths and organic filaments), that allowed us to demonstrate its biological origin, are no longer recognizable by Scanning Electron Microscopy.The results of this study may be useful for developing ore genesis models, including evolution in a supergene environment, and in general for performing geochemical speciation and equilibrium calculations. Moreover, our findings open the way for a new interpretation of hemimorphite-forming processes, and suggest the possibility that bacteria may have played a role in the formation of this mineral in ore deposits.

Middle Ordovician acritarchs and problematic organic-walled microfossils from the Saq-Hanadir transitional beds in the QSIM-801 well, Saudi Arabia

Core samples from the QSIM-801 water well, drilled in central Saudi Arabia, cover a 93-foot interval spanning the transition between the Sajir Member of the Saq Formation, that consists mainly of sandstones of tidal sand flat environments, and the Hanadir Member of the Qasim Formation, characterized by argillaceous graptolitic mudstones, corresponding to a tidal delta front. The samples contain abundant, exceptionally well-preserved and diverse palynomorphs, which include cryptospores, acritarchs and chitinozoans, other problematic organic-walled microfossils as well as other organic particles such as cuticle-like fragments. The studied interval is biostratigraphically well constrained by the presence of chitinozoans of the formosa and pissotensis Zones of late-early to late Darriwilian age (Middle Ordovician) in the uppermost Saq Formation and Hanadir Member. The biostratigraphic age of the Sajir Member considered to span the Dapingian–Darriwilian boundary, is re-discussed based on the results herein. The uppermost part of the Sajir Member yielded the ichnofossil, Phycodes fusiforme. Acritarch assemblages from the Sajir Member of the Saq Formation are poorly diversified and dominated by sphaeromorphs. More diverse assemblages of acritarchs, associated with enigmatic forms, occur in the Hanadir Member of the Qasim Formation. The contact between the two formations and the transition between the palynomorph assemblages are sharp, suggesting a stratigraphic hiatus. A quantitative analysis allows us to discuss the paleoenvironmental changes and possibly climatic changes associated with an hypothesis of ice house conditions during this period. Among the diagnostic acritarch taxa observed are Frankea breviuscula, F. longiuscula, Baltisphaeridium ternatum, Dasydorus cirritus, Dicrodiacrodium ancoriforme, Poikilofusa ciliaris, Pterospermopsis colbathii and Uncinisphaera fusticula. These are associated with other typical forms known to range across the Lower–Middle Ordovician boundary, such as Aremoricanium rigaudae, Aureotesta clathrata, Barakella fortunata, B. rara, Baltisphaeridium klabavense, Glaucotesta latiramosa and Striatotheca spp. Galeate and peteinoid acritarchs are also well represented, as well as tiny forms of ultraplanctonic size. Three new species of acritarchs are proposed: Frankea longiuscula var. darriwilense var. nov, Micrhystridium regulum sp. nov, and Tyrannus proteus sp. nov. Repeated occurrences throughout the section of cryptospores, problematic microfossils such as organic filaments, cuticle-like tissues, striated and pigmented leiospheres frequently in clusters, are interpreted to reflect recurrent terrestrial and freshwater inputs in the depositional environment. Single-specimen, high-resolution analyses using Confocal Laser Scanning Microscopy on the enigmatic form Tyrannus proteus sp. nov. show fluorescence emission spectra and microstructural properties significantly different from those of typical marine acritarchs from the same levels.

Fresh Strange Music: Elizabeth Barrett Browning’s Language. Donald S. Hair. Montreal: McGill-Queen’s University Press, 2015. Pp. viii+301.

<i>Fresh Strange Music: Elizabeth Barrett Browning’s Language</i>. Donald S. Hair. Montreal: McGill-Queen’s University Press, 2015. Pp. viii+301.

Sublimation of ice–tholins mixtures: A morphological and spectro-photometric study

Sublimation, the direct transition from solid to gas phase, is a process responsible for shaping and changing the reflectance properties of many Solar System surfaces. In this study, we have characterized the evolution of the structure/texture and of the visible and near-infrared (VIS–NIR) spectral reflectance of surfaces made of water ice mixed with analogues of complex extraterrestrial organic matter, named tholins, under low temperature (<−70°C) and pressure (10−5mbar) conditions. The experiments were carried out in the SCITEAS simulation setup recently built as part of the Laboratory for Outflow Studies of Sublimating Materials (LOSSy) at the University of Bern (Pommerol, A. et al. [2015a]. Planet. Space Sci. 109–110, 106–122). As the water ice sublimated, we observed in situ the formation of a sublimation lag deposit made of a water-free porous (>90% porosity) network of organic filaments on top of the ice. The temporal evolution of the tholins and water ice spectral features (reflectance at the absorption bands wavelengths, red slope, from 0.40 to 1.90μm) are analyzed throughout the sublimation of the samples. We studied how different mixtures of tholins with water (0.1wt.% tholins as coating or inclusions within the water particles), and different ice particle sizes (4.5±2.5 or 67±31μm) influence the morphological and spectral evolutions of the samples. The sublimation of the ice below the mantle produces a gas flow responsible for the ejection of mm to cm-sized fragments of the deposit in outbursts-like events. The results show remarkable differences between these samples in term of mantle structure, speed of mantle building, rates and surface area of mantle ejections. These data provide useful references for interpreting remote-sensing observations of icy Solar System surfaces, in particular the activity of comet nuclei where sublimation of organic-rich ices and deposition of organic-dust particles likely play a major role. Consequently, the data presented here could be of high interest for the interpretation of Rosetta, and also New Horizons, observations.

Proteoglycans affect monomer infiltration in the etch-and-rinse bonding technique

ObjectivesTo identify proteoglycans (PGs) and collagen fibrils (CF) within human dentin by means of a dual immunofluorescent labeling technique and to investigate the monomer infiltration of two etch-and-rinse adhesives to tosyl-phenylalanine chloromethyl-ketone (TPCK)-treated trypsin (TRY)-pretreated dentin. MethodsThirty-micrometer sections of middle coronal dentin were obtained and etched with 37% phosphoric acid gel for 15s. After preconditioning with or without TRY digestion, the sections were subjected to dual immunofluorescent labeling and observed with a confocal laser scanning microscope (CLSM). Demineralized dentin matrixes treated with or without TRY were observed with field emission scanning electron microscope (FE-SEM). Two etch-and-rinse adhesives, Adper Single Bond 2 (SB) and Prime & Bond NT (PBNT), were applied to the dentin surfaces that were pretreated with or without TRY. The thickness of the hybrid layers was evaluated under confocal micro-Raman spectroscopy and analyzed with a two-way ANOVA. ResultsGreen and red fluorescence was used to represent the PGs and the CF that were colocalized in the same section with different distributions. PGs were localized in the lumens of the dentin tubules and in peritubular dentin, while the type-I collagen fibrils were localized in intertubular dentin and peritubular dentin. After preconditioning with TRY digestion, the red fluorescence decreased or disappeared, the organic filaments in the lumens of the dentin tubules disappeared, the tubules were enlarged, and the hybrid layer thickness for adhesives bonded to the TRY-pretreated dentin surfaces were significantly increased (p<0.001 for both SB and PBNT). SignificanceThe dual immunofluorescence labeling methodology can be used to study the human dentin matrix without decalcifying the entire dentin fragment. Proteoglycans were localized in the lumens of the dentin tubules and in peritubular dentin, which could depress the infiltration of the adhesive resin monomers. The use of TRY digestion increased the thickness of the hybrid layer created by the tested two-step etch-and-rinse adhesive.

Origin and palaeo-environmental significance of the Berrazales carbonate spring deposit, North of Gran Canaria Island, Spain

The Berrazales carbonate spring deposit is a small outcrop constituted mainly by cascade-like geometries. Four main facies have been identified: fibrous dense macrocrystalline formed by rapid degassing under high-flow conditions; framestones of coated plant moulds formed in moderate energy flow favoured by the presence of biogenic support; micrite/microsparite are primary precipitates in which crystalline aggregates nucleated on organic filaments and/or EPS; banded micrite-coarse crystalline were the result of alternating physically, chemically and biologically induced precipitation in areas of varying flow-velocities. Most facies underwent different degrees of micritization processes. Micrite is distributed as thin lines penetrating the crystals, as irregular patches or as micrite layers. In the first case organic filaments penetrate crystals, suggesting that micritization is mainly biogenically driven. In the latter cases micritization is caused mostly by partial dissolution. Microbe participation in micrite formation increased micrite MgCO3 content in comparison with coarse crystalline facies.Isotopic analyses show positive δ13C values (+2.63 and +4.29‰ VPDB) and negative δ18O (−5.65 and −4.48‰ VPDB) values. Positive δ13C values clearly indicate “deep-sourced” fluids.The Berrazales spring deposit studied here very probably is a small part of a larger carbonate building that was largely eroded by fluvial incision. Calculations of spring water temperature give a range from 20°C to 35°C, characteristic of a cold to warm spring favouring precipitation of calcite and important biogenic activity (framestones). Although the study deposit has textural characteristics of tufas, proving that the CO2 sourced from deep fluids, it should be considered as thermogene travertine, being one more example of the difficulty of using those terms for ancient sedimentary deposits. Carbonate spring deposits, very rare in the Canary Islands, are good archives of recent volcanic activity, fluvial processes and vegetation regimes prevailing in the islands in recent times.

Recent analog of gypsified microbial laminites and stromatolites in solar salt works and the Miocene gypsum deposits of Saudi Arabia and Egypt

Accumulation of microbial mats and stromatolites dominate in the crystallization ponds of solar salt works west of Alexandria, Egypt. These microbial mats are laminar in the permanent submerged part of the ponds. The microbial mats commonly form sites for growth of gypsum crystals during periods having higher salinity. In the dominant submerged part of the pond, domal stromatolites are common around groundwater seepage holes. In the shallow, intermittent margin of the ponds, the laminated microbial structure forms laterally close-linked hemispheroidal stromatolite type, with unidirectional and multidirectional ripple mark-like morphology on their surface. The microbial laminite and stromatolite types in the modern solar salt works are similar to the organic-rich Miocene gypsum beds of El-Barqan (west Alexandria, Egypt) and Rabigh (north Jeddah, Saudi Arabia). The Miocene organic-rich beds consist of interlayered dark-colored microbial laminae and light-colored gypsum laminae. These beds may have three different variations: regular even lamination, laterally closed-linked hemispheroidal stromatolites, and/or discrete hemispheroidal stromatolites. Petrographic examination of the microbial laminites and stromatolites in the solar salt works and the Miocene gypsum beds indicate that the dark-colored, organic-rich laminae are composed of micritized microbial laminae and/or brown organic filaments. In El-Barqan area, the light-colored gypsum-rich laminae are composed of either gypsum crystal fragments, or lenticular and prismatic gypsum. These gypsum crystals are either entrapped within the microbial filaments or are nucleated at the surface of the microbial laminae to form a radial pattern, whereas in Rabigh area, the light-colored gypsum-rich laminae are composed of secondary porphyrotopic, poikilotopic, or granular gypsum crystals. By comparison of the microbial structure in the Miocene gypsum beds with the recent occurrence of the microbial laminites and stromatolites in the solar salt works, it is demonstrated that the organic-rich Miocene gypsum beds were formed in a very shallow salina with slightly fluctuating brine levels.

Bacterial symbiosis forming laminated iron‐rich deposits in Okuoku‐hachikurou hot spring, Akita Prefecture, Japan

AbstractBanded iron formations are the most characteristic of Archean–Paleoproterozoic sediment records. Laminated textures resembling banded iron formations can be observed in modern hot‐spring environments. Using sedimentological and microbiological techniques, we investigated the processes of laminar formation and considered the origin of lamination textures. An iron‐rich deposit at the Okuoku‐hachikurou hot spring in Japan exhibits sub‐millimeter laminations consisting of bacteria‐induced ferrihydrite and aragonite. The ferrihydrite particles are spherical and exhibit fine lamination, up to 100 µm thick in ferrihydrite‐rich parts. In aragonite‐rich parts, ferrihydrite particles form filamentous textures with diameters of 10–30 µm, but not laminations. Textural analysis using scanning electron microscopy and phylotype analysis using 16S rRNA indicated the bacterial contribution to ferrihydrite precipitation. A sheath‐like fabric showing a meshwork of nanometer‐order organic filaments, and sheath‐forming bacteria were observed in the deposit specimen etched by citric acid. Phylotype analysis detected in the iron‐rich deposits some bacterial types related to cyanobacteria, purple bacteria, and iron‐oxidizing bacteria. Iron‐oxidizing bacteria probably were responsible for precipitation of the ferrihydrite. Chemolithoautotrophic iron‐oxidizing bacteria are microaerophilic and thrive on Fe(II) in a redox gradient, but dissolved oxygen was not detected in the Okuoku‐hachikurou hot spring. Thus, a certain supply of oxygen is needed for metabolism of the microaerophilic iron‐oxidizing bacteria. The distribution of photosynthetic pigments in the iron‐rich parts indicates that the most likely source of oxygen is photosynthesis by cyanobacteria. This symbiotic relationship between cyanobacteria and iron‐oxidizing bacteria can explain the laminated texture of iron‐rich deposits in the Okuoku‐hachikurou hot spring. These laminations may reflect changes in photosynthetic intensity. There is presently some debate about the bacterial groups that may have played roles in precipitation of banded iron formations. This study presents a new bacterial model for iron precipitation and may provide a mechanism for sub‐millimeter laminations in banded iron formations deposited in shallow water.

The importance of microscopic examinations of eggshells: Discrimination of bioalteration and diagenetic overprints from biological features

Although fossilization usually favors the preservation of calcium carbonate biominerals, diagenetic alterations might still produce erratic patterns that overprint the original biological structures. This investigation tries to discriminate in the fossil record “pathological” eggshells from diagenetic induced features as well as determine their origin, and aims, when possible, to provide alternative parsimonious interpretations to the origin of some of these rare and erratic features. In the past, most dinosaur eggshell studies failed to combine cathodoluminescence, scanning electron microscopy, transmitted and polarized light microscopic observations and were limited to only one or several of these examinations, which might have contributed to misinterpretations by lack of thorough observations. Sauropod eggshells from Faidella (Spain) and Auca Mahuevo (Argentina) provide ideal proxies to perform this research, as they display aberrant crystallographic features that have been or could be considered pathological. Under cathodoluminescence, the specimens fluoresce tremendously, indicating a strong diagenetic component in their make up. Guide by this information, further transmitted and polarized light microscopic examinations reveal microscopic dissolution fronts, which otherwise would have been left unnoted. The proposed hypothesis for the Faidella specimens in that organic filaments, which represent up to 2% of the shell composition, were exposed on the internal wall surfaces of pore canals where the calcium carbonate had been dissolved during a first diagenetic event. As such, the exposed extremities of the organic filaments likely triggered the formation of pseudo cores that mimic those in the membrana testacea during oogenesis. Observations based on the Argentinean specimens indicate that an added extra external structural layer is also separated from the original biological eggshell by a dissolution and recrystallization front. In addition to this abiotic process, artifact formations induced by bacterial mediation, a topic treated in an earlier publication, was also common at Auca Mahuevo. Without combined microscopic and cathodoluminiscence observations, the Faidella and Auca Mahuevo megaloolithid eggshells could be easily considered pathological eggshells. This would bias ensuing phylogenetic, paleobiological, and paleoenvironmental interpretations.

Use of Polyelectrolyte Complexes as a Binding Agent in the Granulation Process of Titania Particles

The process of powder granulation by the colloidal way allows to shape millimetric ceramic spheres with a homogeneous distribution in terms of size and shape. This process is based on the coalescence of agglomerates in diluted media. This occurs because grains are partially covered by a “binding” agent. The system studied is based on a titania (anatase) powder granulated by a mixed system of a polyanion, the poly(sodium 4‐styrenesulfonate), and a polycation, the chitosan. The reaction of condensation between the two polyelectrolytes leads to in situ formation of filaments acting as efficient binding agents. By selecting the suitable ratio between the two polymers, this formulation makes it possible to granulate the titania powder while retaining its purity. Organic filaments favor the coalescence step and also prevent the formation of cracks within the granules. The microstructural arrangement results from a “snowball” growth mechanism and from the migration of the grains due to the capillary forces occurring during the drying stage.

The importance of microscopic examinations of eggshells: Discrimination of bioalteration and diagenetic overprints from biological features

Although fossilization usually favors the preservation of calcium carbonate biominerals, diagenetic alterations might still produce erratic patterns that overprint the original biological structures. This investigation tries to discriminate in the fossil record “pathological” eggshells from diagenetic induced features as well as determine their origin, and aims, when possible, to provide alternative parsimonious interpretations to the origin of some of these rare and erratic features. In the past, most dinosaur eggshell studies failed to combine cathodoluminescence, scanning electron microscopy, transmitted and polarized light microscopic observations and were limited to only one or several of these examinations, which might have contributed to misinterpretations by lack of thorough observations. Sauropod eggshells from Faidella (Spain) and Auca Mahuevo (Argentina) provide ideal proxies to perform this research, as they display aberrant crystallographic features that have been or could be considered pathological. Under cathodoluminescence, the specimens fluoresce tremendously, indicating a strong diagenetic component in their make up. Guide by this information, further transmitted and polarized light microscopic examinations reveal microscopic dissolution fronts, which otherwise would have been left unnoted. The proposed hypothesis for the Faidella specimens in that organic filaments, which represent up to 2% of the shell composition, were exposed on the internal wall surfaces of pore canals where the calcium carbonate had been dissolved during a first diagenetic event. As such, the exposed extremities of the organic filaments likely triggered the formation of pseudo cores that mimic those in the membrana testacea during oogenesis. Observations based on the Argentinean specimens indicate that an added extra external structural layer is also separated from the original biological eggshell by a dissolution and recrystallization front. In addition to this abiotic process, artifact formations induced by bacterial mediation, a topic treated in an earlier publication, was also common at Auca Mahuevo. Without combined microscopic and cathodoluminiscence observations, the Faidella and Auca Mahuevo megaloolithid eggshells could be easily considered pathological eggshells. This would bias ensuing phylogenetic, paleobiological, and paleoenvironmental interpretations.

Quaternary sandstones, northeast Jordan: Age, depositional environments and climatic implications

OSL dating of weakly consolidated, root-bound, non-calcareous quartz arenites in northeast Jordan, currently assigned to the Plio–Pleistocene Azraq Formation, suggests a Middle Pleistocene (652 ± 47 ka) age. The sandstones are up to 15.5 m thick and overlain by a 2.5 m thick Holocene gypcrete caprock. Facies and textural analyses suggest that the sandstones are predominantly aeolian in origin, mainly derived from Tertiary sediments exposed close to the depositional site. The sands were transported by the prevailing NW winds and deposited in a broad, relatively flat sand sheet environment. Rhizoliths occur throughout the sandstones, mainly as long, downward tapering, vertical tap roots, rarely branched and with few laterals. Microscopic examination of root cores replaced by carbonate reveals the presence of alveolar fabrics, possible needle fibre calcite, calcified organic filaments of fungal, root vessel and root hair origins, characteristic of low magnesium beta calcretes, typical of humid climates. Morphologically the roots resemble modern shrub-like species typical of desert environments where water availability at the surface and in the subsurface was sufficient to support an effective vegetation cover. Plots of stratigraphic variations in root length, root spacing and root frequency reflect temporal variations in the water table level and precipitation during sand deposition. All three parameters show a similar crude cyclicity consistent with fluctuations in the level of the water table with the most moist phase beneath the predominantly waterlain Holocene gypcrete when trees appeared for the first time. The gypcrete signifies a change to temporary wetter conditions and may mark the boundary between the Pleistocene and Holocene in this area. Although pedogenic horizonation is poorly developed, especially in desert sands, the beta calcretes and rhizocretions typically form within active soil zones. Soils do not form where rainfall is < 150 mm per year, and above 350 mm complete leaching of the edaphon occurs. However, above 300 mm per year shrubs are replaced by grassland, hence rainfall is inferred to have been 150–300 mm per year, much higher than the < 50 mm in the area today. The age of the sandstones may correlate with isotopic event 17, dated at 659 ka, when the Pleistocene climate in Jordan was characterised by arid to semi-arid phases interrupted by shorter more humid phases, when the water table was higher and the precipitation/evaporation balance greater than today.