Dendrite-like Structures Research Articles

The Novel Formation of Barium Titanate Nanodendrites

The barium titanate (BaTiO3) nanoparticles with novel dendrite‐like structures have been successfully fabricated via a simple coprecipitation method, the so‐called BaTiO3 nanodendrites (BTNDs). This method was remarkable, fast, simple, and scalable. The growth solution is prepared by barium chloride (BaCl2), titanium tetrachloride (TiCl4), and oxalic acid. The shape and size of BaTiO3 depend on the amount of added BaCl2 solvent. To investigate the influence of amount of BaCl2 on BTNDs, the amount of BaCl2 was varied in the range from 3 to 6 mL. The role of BaCl2 is found to have remarkable influence on the morphology, crystallite size, and formation of dendrite‐like structures. The thickness and length of the central stem of BTND were ~300 nm and ~20 μm, respectively. The branchings were found to occur at irregular intervals along the main stem. Besides, the formation mechanism of BTND is proposed and discussed.

An Efficient Rescaling Algorithm for Simulating the Evolution of Multiple Elastically Stressed Precipitates

AbstractIn this paper, we propose a space-time rescaling scheme for computing the long time evolution of multiple precipitates in an elastically stressed medium. The algorithm is second order accurate in time, spectrally accurate in space and enables one to simulate the evolution of precipitates in a fraction of the time normally used by fixed-frame algorithms. In particular, we extend the algorithm recently developed for single particle by Li et al. (Li, Lowengrub and Leo, J. Comput. Phys., 335 (2007), 554) to the multiple particle case, which involves key differences in the method. Our results show that without elasticity there are successive tip splitting phenomena accompanied by the formation of narrow channels between the precipitates. In presence of applied elastic field, the precipitates form dendrite-like structures with the primary arms aligned in the principal directions of the elastic field. We demonstrate that when the far-field flux decreases with the effective radius of the system, tip-splitting and dendrite formation can be suppressed, as in the one particle case. Depending on the initial position of the precipitates, we further observe that some precipitates grow while others may shrink, even when a positive far field flux is applied.

Evolution of the phase composition and defect substructure of rail steel subjected to high-intensity electron-beam treatment

The morphology, structure-phase states, and defect substructure of annealed rail steel subjected to electron-beam treatment in the surface-layer melting mode are studied by scanning and transmission electron microscopy methods. The formation of the lath martensite structure, as well as cellular and dendritelike structures, containing nanoscale martensite crystals, is revealed.

Lattice-Boltzmann Method with Dynamic Grid Refinement for Simulating Particle Deposition on a Single Fibre

In this work a numerical approach to predict the deposition behaviour of nano-scale particles on the surface of a single fibre by resolving the resulting dendrite-like particle structures in detail is presented. The gas flow simulation is carried out by a two-dimensional Lattice-Boltzmann method, which is coupled with a Lagrangian approach for the particle motion. To decrease calculation time and system requirements the Lattice-Boltzmann model is extended to allow for local grid refinement. Because of the a priori unknown location of deposition, the simulation procedure starts on a coarse mesh which is then locally refined in a fully adaptive way in regions of accumulated particles. After each deposition the fluid flow is recalculated in order to resolve the coupling of the flow with the growing particle structures correctly. For the purpose of avoiding unphysical blocking of flow by growing particle dendrites the Lattice-Boltzmann method is extended to permeable cells in these regions using the Brinkmann equation. This extended deposition model is compared to simpler approaches, where the deposit has no retroaction on the flow or is treated as a solid structure. It is clear that the permeable model is most realistic and allows considering the particle deposition on a fibre as two-dimensional problem. Comprehensive simulations were conducted for analysing the importance of different parameters, i.e. free-stream velocity and particle diameter on the deposit structure. The results of this sensitivity analysis agree qualitatively well with former published numerical and experimental results. Finally the structure of the particle deposit was quantitatively characterised by using a modified fractal dimension.

Approximate bilateral symmetry in evaporation-induced polycrystalline structures from droplets of wheat grain leakages and fluctuating asymmetry as quality indicator

The present paper reports on an observation that dendrite-like polycrystalline structures from evaporating droplets of wheat grain leakages exhibit bilateral symmetry. The exactness of this symmetry, measured by means of fluctuating asymmetry, varies depending on the cultivar and stress factor influence, and seems to correspond to the seed germination rate. In the bodies of plants, animals, and humans, the exactness of bilateral symmetry is known to reflect the environmental conditions of an organism's growth, its health, and its success in sexual selection. In polycrystalline structures, formed under the same conditions, the symmetry exactness depends on the properties of the crystallizing solution such as the composition and viscosity; however, it has never been associated with sample quality. We hypothesize here that, as in living nature, the exactness of approximate bilateral symmetry might be considered a quality indicator also in crystallographic methods applied to food quality analysis.

Formation of dendrite domain structures in stoichiometric lithium niobate at elevated temperatures

Formation of the dendrite-type self-organized domain structures during polarization reversal at elevated temperatures (above 230 °C) has been revealed and studied in stoichiometric lithium niobate LiNbO3 single crystals. Optical, confocal Raman, scanning electron, and piezoelectric force microscopy have been used for domain visualization. It has been shown experimentally that formation of the dendrite-like structures has been attributed to correlated nucleation caused by a field distribution in the vicinity of the charged domain walls.

Drying dissipative structures of thermo-sensitive gel spheres of poly(N-isopropylacrylamide). Influence of degree of cross-linking of the gels

Drying dissipative patterns of de-ionized suspensions (colloidal crystal state above the critical concentrations of crystallization) of the thermo-sensitive gels of poly(N-isopropylacrylamide) with degrees of cross-linking of 10% and 2% (pNIPAm(200–10) and pNIPAm(200–2)) were observed at 20 °C and 45 °C on a cover glass, a watch glass, and a Petri glass dish. The broad rings were observed, and their size decreased as micro-gel concentration decreased. Formation of the monodispersed agglomerated particles and their ordered arrays were observed. Microscopic drying structures of (a) flickering ordered spoke-lines, (b) ordered rings, (c) net structure, and (d) lattice-like ordered structures of the agglomerated particles are observed. The net and lattice structures formed more favorably at high degrees of cross-linking, at high concentrations of the gels, and/or high temperatures. By the addition of sodium chloride, very large dendrite-like and net structures of the large agglomerated particles formed at 20 °C and 45 °C, respectively. Importance of the cooperated convectional flow of the agglomerated particles during the drying processes is supported for the ordered array formation. The role of the electrical double layers around the agglomerated particles and the interaction of the particles with the substrate surfaces during dryness are also important for the ordering. The microscopic drying patterns of gel spheres were different from those of linear type polymers and also from typical colloidal spheres, though the macroscopic patterns of gel system such as broad ring formation at the edges of the dried film were similar to other two systems.

Decitabine, independent of apoptosis, exerts its cytotoxic effects on cell growth in melanoma cells

Decitabine is a synthesized cytosine analog that is a potent inhibitor of DNA methylation. There have been a few reports on the in vitro anti-melanoma effect of decitabine or its functional mechanisms. We investigated the anti-proliferation effect of decitabine on the cultured murine melanoma cell line K1735M2. MTT assay showed that decitabine had strong inhibition on melanoma K1735M2 in a time- and dose-dependent manner in vitro. Morphological observation showed that decitabine could induce melanoma K1735M2 cells to produce dendrite-like structures with the increase of decitabine concentration and incubation time. Decitabine could effectively induce K1735M2 cells to differentiate in vitro. Additionally, decitabine could induce a dose-dependent G2/M cell cycle arrest in K1735M2 cells. We provided experimental evidences that the anti-proliferation effect of decitabine on murine K1735M2 melanoma cells was associated predominately with G2/M cell cycle arrest and the induction of differentiation rather than apopotosis.

The ethyl acetate extract of PGP (Phellinus linteus grown on Panax ginseng) suppresses B16F10 melanoma cell proliferation through inducing cellular differentiation and apoptosis

Phellinus linteus and Panax ginseng have been widely used as traditional herbal medicines to treat various diseases including cancer in East Asia. The present study sought to investigate the possible mechanism in anti-proliferative effect of Phellinus linteus that was grown on Panax ginseng (PGP) on B16F10 melanoma cells. The anti-proliferative effect of PGP on B16F10 was evaluated by CCK-8 assays. Apoptotic cells were detected by flow cytometry analysis. The proteins involved in apoptosis and cellular differentiation were assessed by immunoblot analysis. Ginsenosides contents of PG or PGP were analyzed using HPLC. The ethyl acetate fraction (EtOAc) of PGP exhibited the strongest anti-proliferative activity among PGP fractions (butanol or water) on B16F10 cells. PGP EtOAc extract showed stronger inhibitory effect than Panax ginseng (PG) or Phellinus linteus (PL) EtOAc extract on B16F10 melanoma cell proliferation. PGP EtOAc extract induced the dendrite-like structures and the melanin production in B16F10 cells. PGP EtOAc extract increased a sub-G1 cell population through inducing p53/p21 and activated caspase-8 protein expression in B16F10 cells. Notably, PGP EtOAc extract contained ginsenosides Rd, Rg3, Rb2, Rg1 and Rb1 more than PG EtOAc extract. Rd and Rg3 significantly inhibited B16F10 cell proliferation. Our data suggest that PGP EtOAc extract inhibits B16F10 cell proliferation through inducing apoptosis and cellular differentiation.

Facile electrochemical preparation of three-dimensional porous Cu films by potential perturbation

A 3-dimentional (3D) micro-nano hierarchical porous Cu film was fabricated by surface rebuilding of smooth Cu substrates in a blank solution of 1 M NaOH with square wave potential perturbation. The potential step from 0.4 to −2.5 V (vs. SCE) and a frequency of 50 Hz were chosen for the fabrication. The pore formation and Cu nanostructure evolution were characterized by scanning electron microscopy. The fabrication process involved fast Cu electrochemical oxidation–reduction and suitable rate of H 2 releasing. During the repeated Cu oxidation–reduction, the Cu atoms were removable, forming dendrite-like structures. At the same time, the formed H 2 bubbles acted as a dynamic template to shape the formation of micropores. The effect of H 2 bubble as a template on the size of the formed micropores was demonstrated by adding a small amount of surfactant (cetyltrimethylammonium bromide, CTAB) into the basic solution to adjust the size of the bubbles. The as-prepared 3D porous Cu showed high electrocatalytic activity toward the reduction of NO 3 − and H 2O 2. The present in situ preparation method was green, convenient and required neither Cu(II) species and additives in solution nor post-treatment for template removal.

Production and structure of exfoliated graphite/coke composites modified by ZrO 2 nanoparticles

Exfoliated graphite/coke composites modified by ZrO 2 nanoparticles were produced using two different techniques and characterized by means of X-ray diffraction, scanning and transmission electron microscopy. In the first, low-density exfoliated graphite/coke blocks were dipped repeatedly and alternately in ZrO(NO 3) 2 and NH 4OH solutions and subsequently heat treated at 1200°C in nitrogen to deposit thin layers of ZrO 2 nanoparticles on the free surfaces of the carbon matrix. In the second, a mixture of expandable graphite, phenol-formaldehyde resin powder, and ZrOC 2O 4-modified fibrous cellulose in a sealed container was submitted to thermal shock at 900 °C followed by heat treatment at 1 200 °C in nitrogen to obtain the modified composites. The ZrO 2 nanoparticles formed in the second technique were incorporated into the composites in three length scales: 6-30 nm-isolated nanoparticles and small blobs, 200-1000 nm-lengthy dendrite-like structures, and thin layer adhering to the surface of the 1-40 μm long cellulose carbon fibers.

NEURAL DIFFERENTIATION POTENTIAL OF RAT AMNIOTIC EPITHELIAL CELLS

Amniotic epithelial cells (AEC) are thought to represent a stem-like cell population and to be an attractive cell source for regenerative medicine, because abundant cells can be obtained noninvasively at delivery. The authors investigated the neural differentiation potential of rat AEC. Rat AEC expressed vimentin and nestin, but not c-kit, oct-4, or nanog. The expression of the neural lineage markers, including βIII-tubulin, neuron specific enolase (NSE), neurofilament-M, neuroD, glial fibrillary acidic protein (GFAP), myelin basic protein (MBP), tyrosine hydroxylase (TH), acetylcholinesterase (AChE), cholin acetyltransferase (ChAT), and mammalian achaete-scute homolog1 (MASH1), was detected by RT-PCR in the cultured rat AEC. After neural induction, rat AEC dramatically changed their shapes, projecting dendrite-like structures. Immunocytochemically, ∼20% of the induced cells expressed an immature neuronal marker, βIII-tubulin. Our findings suggested that rat AEC might be already committed to differentiate to various neural lineages and that they could differentiate to immature neurons in vitro.

Electrodeposition and Characterization of CoO/ZnO Composite Dendritic Structures Consisted of Hexagonal Nanoplatelets

Ferromagnetic–nonmagnetic heterogeneous alloy nanostructures are attracting growing interest because of their special physical properties, such as giant magnetoresistance effect and mixed magnetism produced by the change in structure, magnetism, or electrical transport. Here, we report a synthesis route for the preparation of CoO/ZnO alloy dendritelike structures consisting of orderly organized hexagonal nanoplatelets by electrochemical deposition in a solution of at . The main trunk and side branches of the CoO/ZnO alloy dendritelike structure are regularly angled, and each branch is made of periodic hexagonal nanoplatelets. The effects of electrodeposition parameters on the compositions of CoO/ZnO alloy dendritelike structures were studied. The morphologies of CoO/ZnO alloy dendritelike structures can be well controlled by changing deposition current densities or the concentration of . The formation process of the dendritelike arrangement of periodic CoO/ZnO alloy hexagonal nanoplatelets was investigated in this paper. A magnetization measurement indicates that these prepared CoO/ZnO alloy dendritelike structures have a soft ferromagnetic behavior at 120 K and a vortex magnetization at 215 K.

10.1007/s11454-008-2023-0

The pulsed-periodic regime of a negative corona (Trichel pulses) in atmospheric-pressure air, which leads to explosion emission mechanisms (ecton generation) of pointed cathode erosion, is investigated. The jet erosion process at the copper cathode is discovered, and micrometer dendritelike structures formed by erosion products returning to the cathode are detected.

The Study of Ordered Melanin Films

Two types of melanin films: self-arranged ordered films and amorphous films have been studied in the present paper. The structure, absorption spectra, spectra of photovoltage, and spectra of time-resolved photoluminescence have been investigated for both types of melanin films. Time-resolved photoluminescence was measured at room temperature at different delay times. The reason for the difference in the electronic properties of structurized and amorphous films of melanin is attributed to the structural features of the films related to ordered dendrite-like structures and amorphous disordered ones, respectively.

Erosion of a copper cathode in a negative corona discharge

The pulsed-periodic regime of a negative corona (Trichel pulses) in atmospheric-pressure air, which leads to explosion emission mechanisms (ecton generation) of pointed cathode erosion, is investigated. The jet erosion process at the copper cathode is discovered, and micrometer dendritelike structures formed by erosion products returning to the cathode are detected.

A model of Internet topology using k -shell decomposition

We study a map of the Internet (at the autonomous systems level), by introducing and using the method of k -shell decomposition and the methods of percolation theory and fractal geometry, to find a model for the structure of the Internet. In particular, our analysis uses information on the connectivity of the network shells to separate, in a unique (no parameters) way, the Internet into three subcomponents: ( i ) a nucleus that is a small (≈100 nodes), very well connected globally distributed subgraph; ( ii ) a fractal subcomponent that is able to connect the bulk of the Internet without congesting the nucleus, with self-similar properties and critical exponents predicted from percolation theory; and ( iii ) dendrite-like structures, usually isolated nodes that are connected to the rest of the network through the nucleus only. We show that our method of decomposition is robust and provides insight into the underlying structure of the Internet and its functional consequences. Our approach of decomposing the network is general and also useful when studying other complex networks.

Three-phase-boundary dynamics at Pt/YSZ microelectrodes

Strong electrode activation, inductive hysteresis and non-linearity are well-known phenomena on model Pt-YSZ cathodes, and recently also a regular current fluctuation pattern have been reported. The oxygen electrode reaction with YSZ as electrolyte is studied at Pt microelectrodes prepared by electrochemical etching of platinum wire. The result is a well-defined contact area of ∼ 25 μm in diameter. Due to the small size and a favourable ratio between the three-phase-boundary (TPB) length and the contact area, microelectrodes should have an increased sensitivity to local events at the TPB compared to larger point electrodes normally applied. The electrode processes are studied by potential sweep, step and impedance techniques. Investigation of the YSZ and Pt surfaces afterwards reveals the growth of dendrite-like Pt structures from the TPB. The formation of these structures can explain the observed regular current fluctuation pattern and contributes to the explanation of the activation phenomena of the model Pt-YSZ and SOFC cathodes.

The effects of oridonin on cell growth, cell cycle, cell migration and differentiation in melanoma cells

Oridonin, a diterpenoid isolated from Rabdosia rubescens (Hemsl.) Hara, is currently one of the most important traditional Chinese herbal medicines. We investigated the anti-proliferation effect of oridonin on the cultured murine melanoma cell line K1735M2. The growth inhibition activity of oridonin for K1735M2 cells occurred in a time- and dose-dependent manner (IC50 was 7.4 ± 0.6 μM). Further studies showed that these inhibition effects were associated with dose-dependent G2/M phase arrest and differentiation induction. Detection of morphological observation showed that oridonin could induce K1735M2 cells to produce dendrite-like structures. The results of the migration indicated that oridonin affected motility of K1735M2 cells in a dose-dependent manner. These results suggested that oridonin is a potential candidate for melanoma cancer therapy.

MECHANISMS OF NANO-SHORTS IN THE ELECTRICAL BREAKDOWN OF FERROELECTRIC THIN FILMS

ABSTRACT Micro-Raman, SEM and electron nano-probe techniques are used to show that bismuth titanate thin films undergoes a local phase transformation from layered-perovskite structure to pyrochlore-like structure during filamentary electrical breakdown, with the loss of Bi and oxygen. In PZT, dendrite-like structures (precursors of electrical shorts) of a few microns diameter, produced by bipolar voltage cycling (i.e. fatigue), exhibit almost pure regions of α -PbO, β -PbO and rutile-TiO2. Note that β -PbO is not the stable ambient phase.