Different Degrees Of Structural Order Research Articles

Bioactive Glasses Enriched with Strontium or Zinc with Different Degrees of Structural Order as Components of Chitosan-Based Composite Scaffolds for Bone Tissue Engineering.

The development of innovative biomaterials with improved integration with bone tissue and stimulating regeneration processes is necessary. Here, we evaluate the usefulness of bioactive glasses from the SiO2-P2O5-CaO system enriched with 2 wt.% SrO or ZnO in the manufacturing of chitosan-based scaffolds. Bioglasses produced using the sol-gel method were subjected to thermal treatment in different regimes. Chitosan/bioglass composites were produced with a weight ratio. Bioglasses were evaluated via TG-DTA, FTIR, and SEM-EDS before and after incubation in simulated body fluid (SBF). The release of ions was tested. The cytocompatibility of the composites in contact with MG63 osteoblast-like cells was evaluated. The results showed that the presence of the crystalline phase decreased from 41.2-44.8% for nonmodified bioglasses to 24.2-24.3% for those modified with ZnO and 22.0-24.2% for those modified with SrO. The samples released Ca2+, Zn2+, and/or Sr2+ ions and were bioactive according to the SBF test. The highest cytocompatibility was observed for the composites containing nonmodified bioglasses, followed by those enriched with SrO bioglasses. The least cytocompatible were the composites containing ZnO bioglasses that released the highest amount of Zn2+ ions (0.58 ± 0.07 mL/g); however, those that released 0.38 ± 0.04 mL/g were characterised by acceptable cytocompatibility. The study confirmed that it is feasible to control the biological performance of chitosan/bioglass composites by adjusting the composition and heat treatment parameters of bioglasses.

Spatial distribution of organic functional groups in Ediacaran acritarchs from the Doushantuo Formation in South China as revealed by micro-FTIR spectroscopy

Raman and Fourier-transform infrared (FTIR) microspectroscopic analyses were performed to examine the chemical signatures and their spatial distribution of organic-walled microfossils together with organic matter (OM) in a black chert nodule from the Ediacaran (635–551 Ma) Doushantuo Formation in China. Raman spectral parameters (I-1350/1600 values) reveal that the acritarchs, bundled filaments, and OM have different degrees of structural order, and that there is no significant difference in I-1350/1600 values among the different portions of individual acritarchs (i.e., inner structure, inner membrane, and outer wall). The IR mapping reveals portion-specific chemical signatures within the individual acritarch specimens. The inner membrane of Tianzhushania contains aliphatic C-H bonds. The acritarchs, including Tianzhushania, show chemically four types of inner structures: (1) aromatic C-H-rich type, (2) aliphatic C-H-rich type, (3) aromatic/aliphatic C-H-poor type, or (4) heterogeneous. All of the examined acritarchs have aromatic C-H rich outer wall, irrespective of the presence/absence of processes. These features support a eukaryotic cyst origin, although it is difficult to determine whether the acritarchs correspond to the cysts of Protista or Metazoa. The bundled filaments also consist of an aromatic C-H bond, but its origin is uncertain. The OM shows a high degree of variation in Raman spectral I-1350/1600 values, as does the IR spectral intensity ratio of asymmetric aliphatic CH3/CH2, alongside a heterogeneous spatial distribution of aromatic and aliphatic C-H bands. This suggests the contribution of various precursors derived from dead microbial cell debris and extracellular organic compounds. Overall, these results confirm the presence of diverse microorganisms in the Doushantuo microbiota. Furthermore, the spatial distribution of organic functional groups in individual microfossils could provide clues about the taxonomy of microfossils of unknown origin.

Graphitic biogas-derived nanofibers as cathodes for sodium dual-ion batteries: Intercalation of PF6− anions

The electrochemical intercalation of PF6− anions into graphitic nanomaterials of renewable origin with different degrees of structural order to be subsequently used as cathodes for sodium dual-ion batteries is herein investigated for the first time. Overall, the electrochemical performance of the biogas-derived carbon nanofibers depends on their graphitic structure, specifically on crystallite height which was found to be the determining parameter for the scope of electrochemical intercalation of PF6− anions into these nanomaterials.

Characteristics and thermal cycling behavior of plasma-sprayed Ba(Mg1/3Ta2/3)O3 thermal barrier coatings

Abstract Ba(Mg 1/3 Ta 2/3 )O 3 (BMT) powders were synthesized by the solid state reaction method. BMT thermal barrier coatings (TBCs) were deposited by atmospheric plasma spraying (APS). The phase composition and microstructure of the BMT coatings were characterized. The thermal cycling behavior of the BMT coatings was investigated by the water quenching method from 1150 °C to room temperature. The results reveal that BMT powders have an ordered hexagonal perovskite structure, whereas the as-sprayed coating of BMT has a disordered cubic perovskite structure because of the different degree of structural order for different treatment conditions. During thermal cycling testing, the entire spalling of coatings occurred within the BMT coating near the bond coat. This is attributed to the following reasons: (1) the growth of a thermally grown oxides (TGO) layer, which leads to additional stresses in the coatings; (2) the coefficient of thermal expansion mismatch between the BMT coating and bond coat, which develops enormous stress in the coatings; (3) the precipitation of Ba 3 Ta 5 O 15 due to the evaporation of MgO during the spraying process, which changes the continuity of the coatings.

Graphitized stacked-cup carbon nanofibers as anode materials for lithium-ion batteries

The electrochemical performance as anodes in lithium-ion batteries (LIBs) of graphitized stacked-cup carbon nanofibers (CNFs) with different degree of structural order is investigated by galvanostatic cycling. To this end, two types of commercial CNFs (PR19 and PR24) bearing this microstructure were heat treated in the range of 1800-2800°C. The discharge capacity provided at the end of cycling, the capacity retention along cycling (cyclability) and the cycling efficiency (charge capacity/discharge capacity) of these nanomaterials improve significantly after heat treatment. Specifically, a progressive increase of the discharge capacity with the growth of the crystallites sizes (Lc, La) and the decrease of the structural defects (ID/It) is observed. All heat-treated CNFs exhibit cyclabilities > 80% after 50 cycles and efficiencies > 90%. Particularly outstanding is the performance of PR19-2800 which provides a discharge capacity of 295 mAh g−1 with capacity retention up to 88%. The CNFs heat treated at 2800°C also show good rate capabilities, keeping reversible capacities > 200 mAh g−1 at a 2C (744mA g−1) rate, and > 100 mAh g−1 after prolonged cycling (500 cycles) at a 1C rate, clearly outperforming synthetic graphite having micrometric particle size and much larger development of the crystalline structure.

Raman Microspectroscopy Performed on Extraterrestrial Particles

ABSTRACT Raman analyses have been performed on Interplanetary Dust Particles (IDPs) collected in the lower stratosphere by NASA high-flying aircrafts, dust from comet 81P/Wild2 collected by Stardust mission, and three particles collected in the upper stratosphere by the balloon-borne DUSTER instrument. All samples contain amorphous carbon (aC) with different degrees of structural order. Fe oxides were detected in the IDPs, aliphatic chains were found in comet grains, and three particles collected in the upper stratosphere are calcium carbonate (calcite or aragonite). Raman spectroscopy is a valuable tool for the nondestructive analyses of micrometer-scale constituents of complex natural materials.

Disorder-induced reversal of spin polarization in the Heusler alloy Co2FeSi

We study the spin polarization in the conduction band of Co${}_{2}$FeSi layers with a different degree of structural order. The injected spin polarization in Co${}_{2}$FeSi/(Al,Ga)As spin light-emitting diodes as well as the planar Hall effect measured for the Co${}_{2}$FeSi injectors exhibit a sign reversal between injectors crystallized in the ordered $L{2}_{1}$ phase and the Fe-Si disordered $B2$ phase. These results are explained by a disorder-induced change in the spin polarization at the Fermi energy of Co${}_{2}$FeSi. Support for the occurrence of such a striking change in the electronic band structure is obtained by first principles calculations.

Graphitized boron-doped carbon foams: Performance as anodes in lithium-ion batteries

The electrochemical performance as potential anodes in lithium-ion batteries of several boron-doped and non-doped graphitic foams with different degree of structural order was investigated by galvanostatic cycling. The boron-doped foams were prepared by the co-pyrolysis of a coal and two boron sources (boron oxide and a borane–pyridine complex), followed by heat treatment in the 2400–2800°C temperature interval. The extent of the graphitization process of the carbon foams depends on boron concentration and source. Because of the catalytic effect of boron, lightweight graphite-like foams were prepared. Boron in the foams was found to be present as carbide (B4C), in substitutional positions in the carbon lattice (B–C), bonded to nitrogen (B–N) and forming clusters. Larger reversible lithium storage capacities with values up to ∼310mAhg−1 were achieved by using the boron oxide-based carbon foams. Moreover, since the electrochemical anodic performance of these boron-doped foams with different degree of structural order is similar, the beneficial effect of the presence of the B–C boron phase was inferred. However, the bonding of boron with nitrogen in the pyridine borane-based has a negative effect on lithium intercalation.

Different degrees of structural order in distinct regions of the transcriptional repressor HES-1

HES-1 is a transcriptional repressor of the basic helix-loop-helix (bHLH) family and one of the main downstream effectors in Notch signaling. Its domain architecture is composed of a bHLH region, an Orange domain, and a poorly characterized C-terminal half. We show that different degrees of structural order are present in the different regions of HES-1. The isolated bHLH domain is only marginally stable in solution, and partially folds upon dimerization. Binding to DNA promotes folding, stabilization, and protection from proteolysis of the bHLH domain. The Orange domain, on the contrary, is well folded in all conditions, forms stable dimers, and greatly increases protein resistance to thermal denaturation. The isolated proline-rich C-terminal region is mainly disordered in solution, and remains unstructured also in the full length protein. Measurements of binding constants show that HES-1 recognizes dsDNA synthetic oligonucleotides corresponding to several functional DNA targets with high affinity, but with relatively little specificity. We propose that order/disorder transitions in the different domains are associated not only with binding to DNA, but also with protein homo- and hetero-dimerization.

Geminal Ionic Liquids: A Combined Approach to Investigate Their Three‐Dimensional Organisation

Different investigations, such as 1D and 2D NMR spectroscopy, resonance light scattering spectroscopy and molecular dynamics simulations, have been jointly used to achieve a deeper understanding of the degree of structural order in two geminal ionic liquids. In particular, 3,3'-di-n-butyl-1,1'-(1,3-phenylenedimethylene)diimidazolium and 3,3'-di-n-butyl-1,1'-(1,4-phenylenedimethylene)diimidazolium bis[bis(trifluoromethanesulfonyl)imide] have been studied. These geminal ionic liquids were chosen because of the presence of both a rigid phenylenedimethylene link between two imidazolium rings, which should give a high degree of order to the solvent system, and the different shapes of the two cations of the isomers, which could induce different properties and packing in the liquid state. Data collected here show that the two geminal ionic liquids are characterised by a different degree of structural order that induces, for example, a different sensitivity of the two solvent systems to temperature changes or to the presence of a co-solvent such as methanol.

Interplay between thermal percolation and jamming upon dimer adsorption on binary alloys

By means of Monte Carlo simulations we study jamming and percolation processes upon the random sequential adsorption of dimers on binary alloys with different degrees of structural order. The substrates are equimolar mixtures that we simulate using an Ising model with conserved order parameter. After an annealing at temperature T we quench the alloys to freeze the state of order of the surface at this temperature. The deposition is then performed neglecting thermal effects like surface desorption or diffusion. In this way, the annealing temperature is a continuous parameter that characterizes the adsorbing surfaces, shaping the deposition process. As the alloys undergo an order-disorder phase transition at the Onsager critical temperature (Tc), the jamming and percolating properties of the set of deposited dimers are subjected to nontrivial changes, which we summarize in a density-temperature phase diagram. We find that for T<T*=1.22Tc the occurrence of jamming prevents the onset of percolating clusters, while percolation is possible for T>T*. Particular attention is focused close to T*, where the interplay between jamming and percolation restricts fluctuations, forcing exponents seemingly different from the standard percolation universality class. By analogy with a thermal transition, we study the onset of percolation using the temperature T as a control parameter. We propose thermal scaling Ansätze to analyze the behavior of the percolation threshold and its thermally induced fluctuations. Also, the fractal dimension of the percolating cluster is determined. Based on these measurements and the excellent data collapse, we conclude that the universality class of standard percolation is preserved for all temperatures.

Luminescence of excitons in single-crystal garnets

Comparative studies of the luminescence of Y3Al5O12:Ce and Lu3Al5O12:Ce single-crystal films and their volume analogues—Y3Al5O12 and Y3Al5O12:Ce single crystals, excited by synchrotron radiation with energy E=120–150 eV, have been performed. The films were grown from melt-solution by liquid-phase epitaxy and the crystals were grown from melt. The single-crystal films and single crystals studied are characterized by different degrees of structural order, in particular, different concentrations of substitutional defects of the Y Al 3+ and LU Al 3+ types. It was ascertained that the bands at 260 and 250 nm in the intrinsic luminescence spectra of Y3Al5O12:Ce and Lu3Al5O12:Ce single-crystal films and single crystals are due to the emission of self-trapped excitons. The luminescence band with λmax=300 nm and τ=0.36 μs, which is present in the luminescence spectrum of single crystals and absent in the spectra of single-crystal films, is due to the recombination of electrons with holes localized at Y Al 3+ centers. It is shown that an efficient energy transfer by excitons to activator ions occurs in Y3Al5O12 and Lu3Al5O2 single-crystal films doped with Ce3+ ions.

Metamorphic grade of organic matter in six unequilibrated ordinary chondrites

Abstract— The thermal metamorphism grade of organic matter (OM) trapped in 6 unequilibrated ordinary chondrites (UOCs) (Semarkona [LL 3.0], Bishunpur [L/LL 3.1], Krymka [LL 3.1], Chainpur [LL 3.4], Inman [L/LL 3.4], and Tieschitz [H/L 3.6]) has been investigated with Raman spectroscopy in the region of the first‐order carbon bands. The carbonaceous chondrite Renazzo (CR2) was also investigated and used as a reference object for comparison, owing to the fact that previous studies pointed to the OM in this meteorite as being the most pristine among all chondrites. The results show that the OM thermal metamorphic grade: 1) follows the hierarchy Renazzo &lt;&lt; Semarkona &lt;&lt; other UOCs; 2) is well correlated to the petrographic type of the studied objects; and 3) is also well correlated with the isotopic enrichment δ15N. These results are strikingly consistent with earlier cosmochemical studies, in particular, the scenario proposed by Alexander et al. (1998). Thermal metamorphism in the parent body appears as the main evolution process of OM in UOCs, demonstrating that nebular heating was extremely weak and that OM burial results in the destabilization of an initial isotopic composition with high δD and δ15N. Furthermore, the clear discrimination between Renazzo, Semarkona, and other UOCs shows: 1) Semarkona is a very peculiar UOC—by far the most pristine; and 2) Raman spectroscopy is a valid and valuable tool for deriving petrographic sub‐types (especially the low ones) that should be used in the future to complement current techniques. We compare our results with other current techniques, namely, induced thermo‐luminescence and opaques petrography. Other results have been obtained. First, humic coals are not strictly valid standard materials for meteoritic OM but are helpful in the study of evolutionary trends due to thermal metamorphism. Second, terrestrial weathering has a huge effect on OM structure, particularly in Inman, which is a find. Finally, the earlier statement that fine‐grained chondrule rims and matrix in Semarkona could be the source of smectite‐rich IDPs is not valid, given the different degree of structural order of their OM.

Effect of the oxidation conditions on the maghemites produced by laser pyrolysis

AbstractPure γ − Fe2O3 particles were continuously prepared by a continuous wave CO2 laser‐induced pyrolysis of iron pentacarbonyl vapour in an oxidizing atmosphere. Two different oxidation procedures were investigated: (1) air–argon mixtures were employed to fill the apparatus; (2) air–ethylene mixtures were employed as carrier gas. The powders were identified by X‐ray diffraction. The grain size was measured using transmission electron microscopy and the degree of order was estimated by IR spectroscopy. The products obtained have grain sizes in the range 4 to 17 nm and different degrees of structural order depending on the synthesis conditions. The productivities attained are typically 0.05 gh−1. Finally, the magnetic properties of the maghemite powders are discussed. It seems that, for very small magnetic particles, the actual differences in the sizes of the particles are less important than differences in crystallinity with regard to the magnetic properties of the samples. Copyright © 2001 John Wiley &amp; Sons, Ltd.

Semiquantitative determination of trans-vacant and cis-vacant 2:1 layers in illites and illite-smectites by thermal analysis and X-ray diffraction

Other| December 01, 1998 Semiquantitative determination of trans-vacant and cis-vacant 2:1 layers in illites and illite-smectites by thermal analysis and X-ray diffraction Victor A. Drits; Victor A. Drits Russian Academy of Sciences, Institute of Geology, Moscow, Russian Federation Search for other works by this author on: GSW Google Scholar Holger Lindgreen; Holger Lindgreen Search for other works by this author on: GSW Google Scholar Alfred L. Salyn; Alfred L. Salyn Search for other works by this author on: GSW Google Scholar Robert Ylagan; Robert Ylagan Search for other works by this author on: GSW Google Scholar Douglas K. McCarty Douglas K. McCarty Search for other works by this author on: GSW Google Scholar American Mineralogist (1998) 83 (11-12_Part_1): 1188–1198. https://doi.org/10.2138/am-1998-11-1207 Article history first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Victor A. Drits, Holger Lindgreen, Alfred L. Salyn, Robert Ylagan, Douglas K. McCarty; Semiquantitative determination of trans-vacant and cis-vacant 2:1 layers in illites and illite-smectites by thermal analysis and X-ray diffraction. American Mineralogist 1998;; 83 (11-12_Part_1): 1188–1198. doi: https://doi.org/10.2138/am-1998-11-1207 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyAmerican Mineralogist Search Advanced Search Abstract Interstratified illite-smectites (I/S) and illite-smectite-vermiculites (ISV) representing both hydrothermal and diagenetic transformations and having different degrees of structural order were investigated for cis-trans occupancy in the octahedral sheet by X-ray diffraction (XRD) and by differential thermal analysis (DTA) in combination with evolved water analysis (EWA) using an infrared detector. By XRD, the amounts of cis (W cv ) and trans (W tv ) vacant 2:1 layers were determined for the three-dimensionally ordered samples using both the WILDFIRE simulation program and calculations based on positions of the 11l and 11l reflections. Based on the EWA curves, the I/S and ISV could be divided into three groups having (1) one strong and one or more weak EWA peaks; (2) two well-resolved peaks; and (3) a complex EWA curve. The amounts of cis- and trans-vacant sites were determined by peak fitting of the total dehydroxylation curve. The complex EWA curves were, however, in addition split into separate dehydroxylation processes during a step-heating technique. If the EWA peaks below and above 600 degrees C were attributed to trans vacant (tv) and cis vacant (cv) octahedra, respectively, the W cv values determined by XRD and by EWA were in agreement. For the three-dimensionally ordered minerals, both XRD and EWA should be used, whereas the EWA method can be applied to the structurally disordered samples having no diagnostic 11l reflections. Accordingly, a combination of XRD and EWA for the determination of W cv and W tv supports an evaluation of the mechanism of illitization in various geological environments. Thus, significant changes in W cv and W tv during illitization are likely due to a dissolution-precipitation, whereas almost constant values indicate a solid-state transformation. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Amorphous phase forming ability in(W–C)-based sputtered films

The effect of adding transition metals, Me, to the structure of (W–C)-based films obtained by sputtering has been studied by the means of electron probe microanalysis (EPMA), secondary ion mass spectrometry (SIMS), low angle X-ray diffraction (XRD), hot stage transmission electron microscopy (TEM), Mössbauer spectroscopy, extended X-ray absorption fine structure (EXAFS), magnetic measurements and differential thermal analysis (DTA). The results obtained for the films in the as-deposited conditions show two types of structures with different degrees of structural order. Films with Ti, Cr or Au are crystalline with a metastable structure of β-(W,Me)C 1- x with 1- x extending from near unity down to about 0.6. In opposition to these, films with Me=Group VIIIA transition metal, show crystalline→amorphous state transitions for Me percentages in the range 5–10 at.%. The structure of these films consists of small β-MC 1- x crystallites with a size of a few unity cells, surrounded by a disordered phase rich in element Me. Concerning the results obtained at increasing temperatures, the chemical and structural behaviour of the W–Me–C films depend on the affinity of carbon for the element Me. Strong or moderate carbide-forming elements (Ti or Cr) improve the stability of the crystalline phase at high temperatures; the films formed by W, C and a weak or non carbide-forming metal (Fe, Co, Ni, Pd or Au) change structurally in the temperature range studied.