Lamellar Formation Research Articles

Guest Exchange through Facilitated Transport in a Seemingly Impenetrable Hydrogen-Bonded Framework.

A new inclusion compound consisting of a guanidinium 1,3,5-tri(4-sulfophenyl)benzene (G3TSPHB) host framework containing isophorone guests that surround isolated and seemingly inaccessible pockets was amenable to guest exchange with hexafluorobenzene (HFB) through a single crystal-single crystal transformation (SCSCT). Single-crystal X-ray diffraction of intermediate transformation states, from the parent compound G3TSPHB·(isophorone)3.7·(methanol)5.4 to the final state G3TSPHB·(isophorone)3.1·(HFB)2·(methanol)2, indicated a crystal symmetry change from monoclinic to hexagonal prior to full incorporation of HFB. Optical microscopy during the SCSCT revealed the formation of lamellae, which expanded and then coalesced into a single crystal when the phase transformation was complete. In situ Raman microscopy revealed changes in the orientation of isophorone guests during the transformation that suggested a pathway for HFB entry into the host cavities. The SCSCT occurs more rapidly than expected on the basis of simple diffusion, consistent with facilitated transport along the lamellae interfaces and a reduction in the length scale for guest exchange.

Study of iron oxide magnetic nanoparticles obtained via pulsed laser ablation of iron in air

Magnetic nanoparticles were obtained using the nanosecond pulsed laser ablation (Nd:YAG laser, 1064 nm, 7 ns) of an iron target in air at atmospheric pressure. The particles obtained were further annealed at four different temperatures. The composition, structure and properties of all obtained powders were investigated using X-ray diffraction (XRD), DSC, attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR), Raman spectroscopy, TEM, SAED and other techniques. The initial sample was found to contain monoclinic magnetite and iron nitrides. Presumably, magnetite presents in the form of spherical particles with the distribution maximum of 12–15 nm, and nitrides take the form of lamellas and rolls. Thermal treatment of the sample led to particle enlargement and phase transformations, first, to cubic magnetite, then to a Fe3O4, α-Fe2O3 and γ-Fe2O3 mixture, and finally to the pure hematite phase. Zeta-potential, BET surface area and magnetic properties changed with the annealing as well. The obtained materials exhibited different properties that make them in demand in different fields, from biomedicine to technology.

The Difference of Lamellar Structure Formation between Ti-45Al-5.4V-3.6Nb-Y Alloy and Ti-44Al-4Nb-4V-0.3Mo-Y Alloy

In this study, the effect factors on the formation of lamellar structure for Ti-45Al-5.4V-3.6Nb-Y alloy and Ti-44Al-4Nb-4V-0.3Mo-Y alloy is discussed in detail. During heat treatment in different procedures, temperature was the common factor influencing the formation of lamellar structures of Ti-45Al-5.4V-3.6Nb-Y and Ti-44Al-4Nb-4V-0.3Mo-Y alloys. In the range of 1230 °C and 1300 °C, the volume fraction of lamellar structure in Ti-45Al-5.4V-3.6Nb-Y alloy was proportional to the annealing temperature. However, between 1210 °C and 1260 °C, the volume fraction of lamellar structure in Ti-44Al-4Nb-4V-0.3Mo-Y alloy deceased when temperature was located in the α + γ + β triple phase field and then increased when temperature was in the α + β binary phase field. Besides the influence of temperature, the lamellar structure formation of Ti-44Al-4Nb-4V-0.3Mo-Y alloy was also affected by the β-phase stabilizing element.

Inclusion Complexes of Non‐Granular Maize Starch with Fatty Acids and Ibuprofen. A Comparative Study of Their Morphology and Structure

Drum dried pregelatinized normal maize starch complexes with fatty acids (decanoic, myristic, palmitic, stearic, and oleic acid) and ibuprofen are studied by various techniques. The aim of the study is to investigate the structural and morphological characteristics of the starch complexes and assess whether any differences might exist between the starch‐fatty acid systems and the starch‐ibuprofen system. The complexes are prepared at 30, 50, or 70 °C. X‐ray diffraction analysis reveals the semicrystalline V‐type structure of all complexes regardless the temperature of their preparation. The degree of crystallinity (%) of complexes increases with the increase in the preparation temperature while the size of crystals decreases. The crystal size of ibuprofen complexes is smaller than that of the fatty acid ones. DSC thermal analysis shows that the dissociation temperature of the complexes ranged from 95 to 125 °C. The enthalpy of dissociation of ibuprofen complexes is much lower than that of the fatty acid ones. SEM microscopy reveales the formation of spherulites or lamellae in the matrix of the complexes. FTIR spectroscopy and light microscopy confirmed the formation of starch complexes with fatty acids and ibuprofen.

Self-Assembly, Thermotropic, and Lyotropic Phase Behavior of Guerbet Branched-Chain Maltosides.

Five synthetic β-d-maltosides derived from Guerbet branched alcohols, whose total hydrocarbon chain length ranged from C8 to C24, were synthesized to a high anomeric purity, and their thermal properties, liquid-crystalline phases, and structures were characterized using differential scanning calorimetry, optical polarizing microscopy, and small-angle X-ray scattering. Thermal investigations of all anhydrous Guerbet maltosides showed that they do not form solid crystals but undergo a glass transition upon temperature change in the range of 35-53 °C. The glassy crystalline structure turns into the liquid-crystalline structure upon heating or addition of water. In thermotropic studies, the lamellar phase formation is prominent in shorter-chain-length analogues, whereas the longer-chain compounds exhibit a more frustrated form of self-assembly in the formation of a metastable state, polymorphism, and inverse bicontinuous cubic structure ( Ia3 d). The excess water conditions show that the phase formation is dominated by the lamellar phase for the longer-chain compounds. Normal micellar solution was observed in the shortest-chain-length maltosides because of the enlargement of hydrated maltose headgroups. The self-assembly of both dry and fully hydrated Guerbet maltosides, which exhibited glass-forming abilities and showed surface activity and also the ability to act as membrane-stabilizing compounds, makes them ideal candidates for practical use in industry as well as biomedical research.

Transcriptome analysis of sweet Sorghum inbred lines differing in salt tolerance provides novel insights into salt exclusion by roots

Sweet sorghum is an annual C4 crop with a high salt tolerance. However, little is known about the molecular mechanisms of salt exclusion in roots of sweet sorghum. In this study, the physiological parameters and transcript profiles of two inbred lines of sweet sorghum roots (salt-tolerant M-81E and salt-sensitive Roma) were analyzed in the presence of 0 or 150 mM NaCl in order to elucidate the molecular mechanisms of salt exclusion. We found that the Na+ concentrations in both shoots and roots of M-81E were lower than that of Roma. Moreover, we identified 2085 and 3172 differentially expressed genes between control plants and those subjected to salt stress in M-81E and Roma strains, respectively. The differentially expressed genes involved in pathways related to salt exclusion such as formation of root casparian bands and suberin lamellae, membrane-bound ion translocating proteins. Many of these genes underwent greater change in M-81E compared to Roma. These results revealed that the better ability of salt exclusion in M-81E may be caused by the combination of physical barrier effect of root apoplastic barriers and the transportation of Na+ out of the xylem by HKT1;5. Moreover, some genes encoding transcription factors were also differentially expressed, which may be involved in the regulation of genes related to salt exclusion. This RNA-seq dataset provide comprehensive insights into the transcriptomic landscape to reveal molecular mechanisms of salt exclusion in roots of sweet sorghum.

Новий тип розвитку нюхової розетки в анциструса звичайного Ancistrus dolichopterus

Залежно від умов існування в риб по-різному розвинені сенсорні системи, а особливо нюховий аналізатор. Здатність риб реагувати на запахи залежить від форми нюхової розетки та морфології нюхових ламел. Уважають, що найкраще розвинений нюховий аналізатор у видів із білатеральною видовженою нюховою розеткою. Зазвичай нюхові розетки зі схожою морфологією характерні для видів із близьких родин або видів, які існують в однакових умовах. Орган нюху риб під час розвитку проходить стадії нюхової плакоди, нюхової ямки та нюхової камери з нюховою розеткою. Проте залишається нез’ясованим механізм розвитку нюхових розеток. Недостатньо уваги звернено на особливості формування центрального шва в нюхових розетках, додавання нових ламел у різних видів костистих риб. Для вивчення розвитку нюхової розетки білатерального типу анциструса звичайного Ancistrus dolichopterus вирощували в лабораторії гістології та морфогенезу Східноєвропейського національного університету імені Лесі Українки. Гістологічні препарати виготовлено за стандартними гістологічними методиками. В анциструса звичайного формування розетки відбувається у чотири етапи. На першому етапі відбувається закладка першої ламели в середній частині нюхової камери та її зростання з ростральною стінкою нюхової камери під час подальшого розвитку. На другому етапі вперше закладаються латеральна й медіальна ламели. На третьому відбувається закладка четвертої ламели з медіального боку від центрального шва. На четвертому етапі проходить спочатку симетрична відносно центрального шва закладка ламел, а потім у парних ламел латеральні ламели залягають ростральніше від медіальних. В Ancistrus dolichopterus центральний шов розвивається з першої центральної ламели, яка зі збільшенням довжини нюхової камери видовжується. Потовщення шва відбувається за рахунок прикріплення до нього нових бічних пар нюхових ламел у ростральній частині нюхової камери. Під час розвитку дистальний кінець центральної ламели зміщується латерально й ламела втрачає осьове положення. Білатеральна нюхова розетка Ancistrus dolichopterus набуває дефінітивного стану внаслідок додавання нових ламел ростральніше від уже розвинутих ламел, як і в більшості костистих риб, навіть з іншими типами нюхових розеток. Під час закладки четвертої ламели простежуємо порушення симетрії й формування ламели в цей період відбувається лише з одного боку від центрального шва. Усі наступні ламели закладаються попарно.

Fibril microstructural changes of polyacrylonitrile fibers during the post-spinning process

Ultrathin sectioning and solvent etching were used to assess microstructural changes in polyacrylonitrile (PAN) fibrils following a dry-jet wet spinning process. Morphologic assessment revealed the coexistence of fibrils and lamellae within the PAN fibers, with a frill-like structure found on the fibrils. The size of the lamella-like layers was consistent with a crystal size of 13.2 nm as characterized by X-ray diffraction and microfibrils were composed of alternate dark lamella-like crystal layers and surrounded by bright amorphous chains. Further, fibril arrangement followed a weave-like pattern. During the post-spinning process, break-rearrangement of chain-folded lamellae had an important role in fibril structure evolution. The high stream stretching and heat treatment induced the breaking of lamellae and the formation of new lamellae through the molecular chains rotating and slipping, resulting in a decrease in voids and the coalescence of microfibrils. Consequently, the fibrils were arranged in a more orderly manner and interlinked more tightly, a process conducive for the preparation of high quality PAN fibers.

A General Approach for Estimating Lamella-Thickness Distribution in Polymers with Low-Frequency Raman Spectroscopy: Application to Lamella Formation in Crystallizing Polyethylene.

A general method for estimating lamella-thickness distribution in semicrystalline polymers has been developed and applied to polyethylene (PE). The longitudinal acoustic mode (LAM) of PE appears at very low frequencies (i.e., ν˜ 8-20 cm-1 ) in the Raman spectrum. It represents a distribution of lamellae of varying thicknesses. We propose a distribution function that converts a low-frequency LAM Raman band into the corresponding lamellae-thickness distribution. By using this distribution function, we can study lamella formation in crystallizing PE to elucidate the influence of supercooling and determine critical lamella thickness, the minimum chain length at which folding occurs, and the associated thermodynamic parameters accurately. This method has a general applicability toward the examination of polymer crystallization in an accurate and straightforward manner. Understanding the molecular details of polymer crystallization has applications, particularly in polymer thin-film photovoltaics and polymer processing, beyond its fundamental academic significance.

Observation of the pressure effect in simulations of droplets splashing on a dry surface

At atmospheric pressure, a drop of ethanol impacting on a solid surface produces a splash. Reducing the ambient pressure below its atmospheric value suppresses this splash. The origin of this so-called pressure effect is not well understood and this is the first study to present an in-depth comparison between various theoretical models that aim to predict splashing and simulations. In this work the pressure effect is explored numerically by resolving the Navier-Stokes equations at a 3-nm resolution. In addition to reproducing numerous experimental observations, it is found that different models all provide elements of what is observed in the simulations. The skating droplet model correctly predicts the existence and scaling of a gas film under the droplet, the lamella formation theory is able to correctly predict the scaling of the lamella ejection velocity as function of the impact velocity for liquids with different viscosity, and lastly, the dewetting theory's hypothesis of a lift force acting on the liquid sheet after ejection is consistent with our results.

Evolution of grain refinement mechanism in Cu-4wt.%Ti alloy during surface mechanical attrition treatment

This work reveals the grain refinement process of low-stacking fault energy Cu-4wt.%Ti alloy during surface mechanical attrition treatment (SMAT). Without phase transformations, the grain refinement process in Cu-4wt.%Ti alloy with a low stacking fault energy involves formation of planar dislocation arrays and twins in the small strain and low strain rate deformed region adjacent to the coarse grain matrix, twin-twin intersections leading to grain subdivision. The formation of lamellae, polygonal grains, and rotation recrystallization were induced by the large strain and high strain rate deformation near the treated surface. We also observed one distinct layer at the treated surface with the thickness about 15 μm, which is filled with equiaxed nanograins. The hardness of the treated surface was increased by 40% and attributed to the grain refinement according to the grain boundary strengthening mechanism.

Double-Layer Morphologies from a Silicon-Containing ABA Triblock Copolymer.

A combined experimental and self-consistent-field theoretical (SCFT) investigation of the phase behavior of poly(stryrene- b-dimethylsiloxane- b-styrene) (PS- b-PDMS- b-PS, or SDS32) thin films during solvent vapor annealing is presented. The morphology of the triblock copolymer is described as a function of the as-cast film thickness and the ratio of two different solvent vapors, toluene and heptane. SDS32 formed terraced bilayer morphologies even when the film thickness was much lower than the commensurate thickness. The morphology transitioned between bilayer cylinders, bilayer perforated lamellae, and bilayer lamellae, including mixed structures such as a perforated lamella on top of a layer of in-plane cylinders, as the heptane fraction during solvent annealing increased. SCFT modeling showed the same morphological trends as a function of the block volume fraction. In comparison with diblock PS- b-PDMS with the same molecular weight, the SDS32 offers a simple route to produce a diversity of well-ordered bilayer structures with smaller feature sizes, including the formation of bilayer perforated lamellae over a large process window.

Development of Novel 2D Composites of Silk Sericin and Rice Starch and Application as Bio‐Compatible Scaffold for Cell Culturing

Sericin and starch are waste materials of the silk and rice milling industries, respectively. Owing to their suitable physicochemical, mechanical and functional properties, the two materials are thermo‐mechanically conjugated and cast as films. Sericin forms a microfibrillar network structure which binds with gelatinized starch. Addition of crosslinkers, namely glycerol and polyethylene glycol results in smoother textured films, higher crystallinity, and thermal resistance as studied using XRD, FTIR, DSC, and TGA. Native crystalline patterns of both starch and sericin are lost during composite formation. Newer crystalline lamellae formation with enhanced crystallinity than the native materials is evident from XRD and DSC. Comparative analysis indicated polyethylene glycol to be a better cross linker than glycerol for the composite formation. Biocompatibility studies using L929 mice fibroblast cell lines demonstrated that the films supported normal growth and proliferation of cells without any toxic effect. This is well supported by fluorescence imaging and MTT assays. Enzymatic biodegradability using protease enzymes implied negligible weight loss of the films, strengthening their prospect to be manifested in cell culturing applications.

Intradomain phase transitions in flexible block copolymers with self-aligning segments.

We study a model of flexible block copolymers (BCPs) in which there is an enlthalpic preference for orientational order, or local alignment, among like-block segments. We describe a generalization of the self-consistent field theory of flexible BCPs to include inter-segment orientational interactions via a Landau-de Gennes free energy associated with a polar or nematic order parameter for segments of one component of a diblock copolymer. We study the equilibrium states of this model numerically, using a pseudo-spectral approach to solve for chain conformation statistics in the presence of a self-consistent torque generated by inter-segment alignment forces. Applying this theory to the structure of lamellar domains composed of symmetric diblocks possessing a single block of "self-aligning" polar segments, we show the emergence of spatially complex segment order parameters (segment director fields) within a given lamellar domain. Because BCP phase separation gives rise to spatially inhomogeneous orientation order of segments even in the absence of explicit intra-segment aligning forces, the director fields of BCPs, as well as thermodynamics of lamellar domain formation, exhibit a highly non-linear dependence on both the inter-block segregation (χN) and the enthalpy of alignment (ε). Specifically, we predict the stability of new phases of lamellar order in which distinct regions of alignment coexist within the single mesodomain and spontaneously break the symmetries of the lamella (or smectic) pattern of composition in the melt via in-plane tilt of the director in the centers of the like-composition domains. We further show that, in analogy to Freedericksz transition confined nematics, the elastic costs to reorient segments within the domain, as described by the Frank elasticity of the director, increase the threshold value ε needed to induce this intra-domain phase transition.

Physics and hydraulics of the rhizosphere network

AbstractTake home messageMucilage secreted by roots and EPS produced by microorganisms alter the physical properties of the soil solution and impact the water dynamics in the rhizosphere. The high viscosity of mucilage and EPS is responsible for the formation of thin filaments and interconnected thin lamellae that span throughout the soil matrix maintaining the continuity of the liquid phase across the pore space even during severe drying. The impact of these mechanisms on plant and microorganisms needs to be explored.

Ecotoxicological impacts of exposure to copper oxide nanoparticles on the gill of the Swan mussel, Anodonta cygnea (Linnaeus, 1758)

ABSTRACTThis study was conducted to investigate the ecotoxicological effects of exposure to copper oxide nanoparticles (CuO NPs) on the gill of the swan mussel Anodonta cygnea using several approaches including qualitative and quantitative histopathology, ultra-morphology (scanning electron microscopy [SEM]) and measures of clearance rate (CR) and bioaccumulation of CuO NPs. Histological alterations in mussels exposed to 0.25 (T1), 2.5 (T2) and 25.0 µg L−1 (T3) CuO NPs for 12 days include changes in the length and form of gill lamellae, changes in inter-lamellar spaces, epithelial hyperplasia, atrophy and tissue rupture. Ultra-morphological changes following CuO NP exposure included epithelial hyperplasia and hypertrophy, epithelial lifting, tissue rupture (water channel fusion) and extensive necrosis of the gill surfaces. IGill (gill damage severity) index values for both histopathological and ultra-morphological data were significantly (P < 0.05) higher in T3. The CR of mussels was significantly (P < 0.05) lower in the highest exposure concentration (CR = 39.21 ± 16.85 [L min−1 g−1 dry weight]) in comparison to controls (CR = 108 ± 47.14 [L min−1 g−1 dry weight]). CuO NPs accumulated in exposed mussels at all exposure concentrations until day 4, but there was no further change in accumulation levels by the end of the exposure period. The accumulated content of CuO NPs was significantly (P < 0.05) lower in 25.0 µg L−1 exposure concentration. Based on these results, significant accumulation of CuO NPs in the gills of swan mussel could affect histological and ultra-structural characteristics of this organ and consequently have deleterious impacts on its filtration activity.

Light Microscopy of Development of the Olfactory Organ of European Weatherfish Misgurnus fossilis (Тeleostei: Cobitidae).

We studied the formation of the olfactory organ of European weatherfish Misgurnus fossilis (Linnaeus, 1758) from the formation of its placodes to the formation of lamellae using light microscopy. The aim of the present investigation was to determine which morphogenetic features of the olfactory organ ate associated with the demersal lifestyle. The olfactory organ of European weatherfish goes through such developmental stages as olfactory placode, olfactory pit, and olfactory chamber with lamellae. Formation of the olfactory pit occurs in prolarvae, but a considerable increase in size takes place during the switch to exogenous feeding. In late larva, lamellae are formed in the aboral part olfactory chamber as an outward fold at its bottom. At the same time, incurrent and excurrent nostrils start being formed as the result of approximation of lateral and medial margins in the rostal part above the olfactory cavity. In contrast to other fishes, the peculiarity of morphogenesis of olfactory organ of M. fossilis is its late formation followed by intensive postembryonic development.

The influence of short chain branch on formation of shear induced crystals in bimodal polyethylene at high shear temperatures

The shear-induced crystallization of bimodal polyethylene with high molecular weight fraction having different content of short chain branch at low shear rate and high temperatures was investigated by in-situ small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) techniques. SAXS and WAXD results indicate that shish crystals form at different shear temperatures of 139 and 136 °C, subsequently kebab crystals and oriented lamellae form at the isothermal crystallization temperature of 121 °C. The presence of short chain branch significantly promotes the formation of shish-kebab crystals owing to the increase of the relaxation time, but overmuch short chain branch impedes the formation of shish-kebab crystals and form more oriented lamellae. These evidences clearly indicate that even though the existence of short chain branch impedes the crystallizability, it can still effectively promote the formation of shish-kebab crystals at high shear temperatures.

Investigations on the solidification microstructures and room temperature compression properties of Nb-doped NiAl-32Cr-6Mo hypereutectic alloy

Solidification microstructures and compression properties of NiAl-32Cr-6Mo hypereutectic alloys containing different contents of Nb were investigated. The addition of Nb did not change the basic phase constituents, though a new phase of Laves Nb(Cr1-x-yNixAly)2 was observed. However, the primary Cr(Mo) phase no longer showed obvious dendritic morphology, the formation of lamellae was disturbed and the eutectic cellular microstructure degenerated. When the Nb content was 5%, eutectic lamellae coarsened and became spherical and poorly aligned. Fully eutectic microstructures were obtained in the directionally solidified hypereutectic alloys grown at 6 µm/s regardless of the addition amount of Nb. With the increasing content of Nb addition, the volume fraction of Laves phase located at the NiAl/Cr(Mo) boundary became more. The yield strength of directionally solidified NiAl-32Cr-6Mo-3Nb alloy reached to 2072 MPa, which is the highest value in the NiAl-based eutectic alloy at present. Well-aligned microstructure and more strengthening phase are conducive to the improvement of properties. All the alloys exhibited brittle quasi-cleavage fracture mode, cleavage in the NiAl phase and debonding of the NiAl/Cr(Mo) interface accompanied by Cr(Mo) lamellae and Cr2Nb phase pulled out were observed in the fracture surface.

Probing the role of ceramide hydroxylation in skin barrier lipid models by 2H solid-state NMR spectroscopy and X-ray powder diffraction

In this work, we studied model stratum corneum lipid mixtures composed of the hydroxylated skin ceramides N-lignoceroyl 6-hydroxysphingosine (Cer[NH]) and α-hydroxylignoceroyl phytosphingosine (Cer[AP]). Two model skin lipid mixtures of the composition Cer[NH] or Cer[AP], N-lignoceroyl sphingosine (Cer[NS]), lignoceric acid (C24:0) and cholesterol in a 0.5:0.5:1:1 molar ratio were compared. Model membranes were investigated by differential scanning calorimetry and 2H solid-state NMR spectroscopy at temperatures from 25 °C to 80 °C. Each component of the model mixture was specifically deuterated for selective detection by 2H NMR. Thus, the exact phase composition of the mixture at varying temperatures could be quantified. Moreover, using X-ray powder diffraction we investigated the lamellar phase formation. From the solid-state NMR and DSC studies, we found that both hydroxylated Cer[NH] and Cer[AP] exhibit a similar phase behavior. At physiological skin temperature of 32 °C, the lipids form a crystalline (orthorhombic) phase. With increasing temperature, most of the lipids become fluid and form a liquid-crystalline phase, which converts to the isotropic phase at higher temperatures (65–80 °C). Interestingly, lignoceric acid in the Cer[NH]-containing mixture has a tendency to form two types of fluid phases at 65 °C. This tendency was also observed in Cer[AP]-containing membranes at 80 °C. While Cer[AP]-containing lipid models formed a short periodicity phase featuring a repeat spacing of d = 5.4 nm, in the Cer[NH]-based model skin lipid membranes, the formation of unusual long periodicity phase with a repeat spacing of d = 10.7 nm was observed.