Double-layer Particles Research Articles

Electromagnetic wave absorbing behavior of nano-Fe1Co0.8Ni1@C single-layer core-shell and nano-Fe1Co0.8Ni1@SiO2 @C double-layer core-shell composite particles

To effectively explore the influence of nano core-shell structure on the absorption properties of Fe1Co0.8Ni1@X composite particles, three groups of Fe1Co0.8Ni1@C single-layer core-shell structures with varying C coating layer thicknesses and Fe1Co0.8Ni1@SiO2@C double-layer core-shell structure magnetic composite particles were prepared via chemical liquid phase deposition and high-temperature carbonization, and corresponding electromagnetic absorption properties were investigated. The study revealed that the prepared nano core-shell Fe1Co0.8Ni1@X composite particles exhibited a near-spherical shape with particle size of approximately 100 nanometers. The core of the FeCoNi alloy particles was FCC polycrystalline with C coating layer thicknesses ranging from 2 to 3 nm, 10–20 nm, to 30–50 nm, while Fe1Co0.8Ni1@SiO2@C composite particles with SiO2 coating layer thicknesses of 5–10 nm and C coating layer thicknesses of 2–3 nm. As the C coating layer thickness increased, the specific saturation magnetization intensity showed a decreasing trend while the coercivity exhibited an increasing trend, all composite particles presented soft magnetic properties. With the increase of the C coating layer thickness, the real and imaginary parts of the dielectric constant of composite particles continued to rise, while real part of the permeability showed minimal change and imaginary part of permeability exhibited significant variation. Polarization relaxation and electric conduction were observed as C layer thickness increased and magnetic loss primarily including eddy current loss and resonance loss. Additionally, the peak of the dielectric loss of the composite particles demonstrated a shift towards higher frequency with increasing C coating layer thickness, and the dielectric loss of the Fe1Co0.8Ni1@SiO2@C double-layer coating structure sample was lower than that of the Fe1Co0.8Ni1@C. The attenuation constant of Fe1Co0.8Ni1@C composite particles increased with C coating layer thickness and rising continuously with the electromagnetic wave frequency. The double-layer coating structure exhibited a lower attenuation constant than single-layer coating structure and FeCoNi alloy particles, which presented the best impedance matching. Compared with the Fe1Co0.8Ni1 alloy particles, the electromagnetic wave absorption performance of the Fe1Co0.8Ni1@C composite particles was enhanced in both high and low frequency bands, and with the increase of the C coating layer thickness the main absorption frequency band of the samples with the same thickness shifted towards lower frequency. Furthermore, the thickness of sample decreased from 1.5mm to 2.0 mm to 1–1.5 mm as the C coating layer thickness increased. Maximum reflection loss |RLmax| of 61.76 dB and effectively absorbed bandwidth of 4.64 GHz was obtained for Fe1Co0.8Ni1@C composite particle.

Double-layer coated particles formed by one-step method based on microfluidic technology

This study used a microfluidic device with a focus-wrapping structure to create double-layer calcium alginate hydrogel drug particles in a one-step process. We validated the double-layer structure of the particles using both a fluorescence and regular light microscope. Curcumin and catalase were distributed independently in each layer, and we expected that such structure could play a role in the slow release of drugs. This scheme greatly reduces the need of hydrophilic and hydrophobic modification treatment, therefore greatly simplifies the experimental process. In the meantime, the requirement for injecting drugs into osteoarthritis and other diseases is expected to be realized, expanding the use of hydrogel in the medical field, because the microsphere is easy to generate, inexpensive, and strong in internal drug substitutability.

Improvement in bioactive protein storage stability and colon-targeted release: a simple double-layer chitosan-based particle

Aim: To improve the long-term storage stability of a bioactive protein and the subsequent colon-targeted release, a double-layer chitosan (CS)-based particle was developed.Methods: To form the double-layer CS-based particle, the second layer was crosslinked onto the single-layer bovine serum albumin (BSA)-loaded CS-based particle. The structure and properties of particles were further investigated.Results: With the second layer, the double-layer particles became more compact, which was important for the inhibition of bioactive protein leakage during storage through strong electrostatic interactions and swelling of the hydrogels. After 30 d of storage, there was only 43.74–49.32% BSA leakage from the C15-TPP/C15-HMP double-layer particles. Moreover, the BSA release in subsequent colon-targeted delivery after storage was 44.02–48.59%.Conclusions: With double-layer shielding and a more compact arrangement, it was possible to reduce bioactive protein leakage over long periods storage and achieve subsequent colon-targeted delivery.

Optimized thermal conductivity of diamond/Cu composite prepared with tungsten-copper-coated diamond particles by vacuum sintering technique

Diamond/Cu composites with excellent thermal performance were fabricated by a novel method which coated diamond particles with tungsten as the inner layer through salt-bath plating and then deposited copper as the outer layer through electroless plating. After ultra-high cold pressing and vacuum sintering, these double-layer particles directly formed diamond/Cu composites without addition of copper powders. The thermal conductivity of 60 vol.% diamond/Cu composite reached maximum at 661 W m-1 K-1. The outstanding performance can be ascribed to strong interface bonding in the double-layer particles and uniform distribution of diamond particles in the composites when electroless plating was used to replace copper powder addition.

High thermal conductivity of diamond/copper composites produced with Cu–ZrC double-layer coated diamond particles

A new method was proposed to fabricate diamond/Cu composites. Double-layer diamond particles were directly compressed at ultra-high pressure to prepare the preform and then sintered in a vacuum equipment for densification. The raw diamond particles were coated with zirconium carbide by magnetron sputtering for the inner layer and then deposited with copper by chemical method for the outer layer. Prepared with these particles, the composites had good interface bonding and homogeneously distributed particles in the copper matrix. The thermal conductivity of 65 vol% diamond/Cu composite was as high as 720 W m−1 K−1. When the diamond content increased to 70 vol%, the coefficient of thermal expansion was extremely low (4.33 × 10−6/K). With superb thermal–physical performance, diamond/Cu composites are potentially applicable to electronic packaging.

Visible Light Communication Channel Models and Simulation of Coal Workface Energy Coupling

Due to their low energy consumption and small size, visible light communication systems have been widely used to eliminate communication-blind areas in coal workfaces. A workface visible light communication channel model and a mathematic model of energy coupling from the mining machine’s workspace to its footpath were established to investigate the characteristics of optical signal transmission on the workface. This paper studies the effects of coal dust (double-layer particles encapsulated by moisture) on optical signal degradation. Simulation results revealed the presence of an optimized transmitter location, which maximized the coupled energy of the two space signals due to the blocking effect of metal columns.

Characterization of Rotavirus RNAs That Activate Innate Immune Signaling through the RIG-I-Like Receptors

In mammalian cells, the first line of defense against viral pathogens is the innate immune response, which is characterized by induction of type I interferons (IFN) and other pro-inflammatory cytokines that establish an antiviral milieu both in infected cells and in neighboring uninfected cells. Rotavirus, a double-stranded RNA virus of the Reoviridae family, is the primary etiological agent of severe diarrhea in young children worldwide. Previous studies demonstrated that rotavirus replication induces a MAVS-dependent type I IFN response that involves both RIG-I and MDA5, two cytoplasmic viral RNA sensors. This study reports the isolation and characterization of rotavirus RNAs that activate IFN signaling. Using an in vitro approach with purified rotavirus double-layer particles, nascent single-stranded RNA (ssRNA) transcripts (termed in vitro ssRNA) were found to be potent IFN inducers. In addition, large RNAs isolated from rotavirus-infected cells six hours post-infection (termed in vivo 6 hr large RNAs), also activated IFN signaling, whereas a comparable large RNA fraction isolated from cells infected for only one hour lacked this stimulatory activity. Experiments using knockout murine embryonic fibroblasts showed that RIG-I is required for and MDA5 partly contributes to innate immune signaling by both in vitro ssRNA and in vivo 6 hr large RNAs. Enzymatic studies demonstrated that in vitro ssRNA and in vivo 6 hr large RNA samples contain uncapped RNAs with exposed 5’ phosphate groups. RNAs lacking 2’-O-methylated 5’ cap structures were also detected in the in vivo 6 hr large RNA sample. Taken together, our data provide strong evidence that the rotavirus VP3 enzyme, which encodes both guanylyltransferase and methyltransferase activities, is not completely efficient at either 5’ capping or 2’-O-methylation of the 5’ cap structures of viral transcripts, and in this way produces RNA patterns that activate innate immune signaling through the RIG-I-like receptors.

Simulations of magnetic capturing of drug carriers in the brain vascular system

The present paper reports on numerical simulations of blood flow and magnetic drug carrier distributions in a complex brain vascular system. The blood is represented as a non-Newtonian fluid by the generalised power law. The Lagrangian tracking of the double-layer spherical particles is performed to estimate particle deposition under influence of imposed magnetic field gradients across arterial walls. Two situations are considered: neutral (magnetic field off) and active control (magnetic field on) case. The double-layer spherical particles that mimic a real medical drug are characterised by two characteristic diameters - the outer one and the inner one of the magnetic core. A numerical mesh of the brain vascular system consisting of multi-branching arteries is generated from raw MRI scan images of a patient. The blood is supplied through four main inlet arteries and the entire vascular system includes more than 30 outlets, which are modelled by Murray’s law. The no-slip boundary condition is applied for velocity components along the smooth and rigid arterial walls. Numerical simulations revealed detailed insights into blood flow patterns, wall-shear-stress and local particle deposition efficiency along arterial walls. It is demonstrated that magnetically targeted drug delivery significantly increased the particle capturing efficiency in the pre-defined regions. This feature can be potentially useful for localised, non-invasive treatment of brain tumours.

Resonance scattering characteristics of double-layer spherical particles

Based on the principle of ultrasonic resonance scattering, sound-scattering characteristics of double-layer spherical particles in water were numerically studied in this paper. By solving the equations of the scattering matrix, the scattering coefficient determined by the boundary conditions can be obtained, thus the expression for the sound-scattering function of a single double-layer spherical particle can be derived. To describe the resonance scattering characteristics of a single particle, the reduced scattering cross section and reduced extinction cross section curves were found through numerical calculation. Similarly, the numerically calculated sound attenuation coefficient curves were used to depict the resonance scattering characteristics of monodisperse and polydisperse particles. The results of numerical calculation showed that, for monodisperse particles, the strength of the resonance was mainly related to the particle size and the total number of particles; while for polydisperse particles, it was primarily affected by the particle size, the coverage of the particle size distribution and the particle concentration.

A novel immunosensor for carcinoembryonic antigen based on poly(diallyldimethylammonium chloride) protected prussian blue nanoparticles and double-layer nanometer-sized gold particles

A highly sensitive amperometric immunosensor has been developed for the detection of carcinoembryonic antigen (CEA). It is based on (a) Prussian Blue nanoparticles coated with poly(diallyldimethylammonium chloride) (P-PB) and (b) double-layer gold nanocrystals. The sensor was obtained by first electrodepositing porous gold nanocrystals on the glassy carbon electrode (GCE), and then by modifying the electrode with the coated P-PB. Subsequently, colloidal gold nanoparticles (nano-Au) were adsorbed onto the GCE by electrostatic interactions between the negatively charged nano-Au and the positively charged P-PB to immobilize CEA antibodies. Finally, bovine serum albumin was employed to block possible remaining active sites and to prevent the non-specific adsorption on the nano-Au. This immunosensor was characterized by cyclic voltammetry and scanning electron microscopy. The working range was adjusted to two concentration ranges, viz. from 0.5 to 10 ng.mL−1, and from 10 to 120 ng.mL−1 of CEA, with a detection limit of 0.2 ng.mL−1 at three times the background noise.

Transverse optical trapping force of absorbing double-layer spherical particles in a Gaussian beam

In this paper, the transverse optical trapping of absorbing double-layer spherical particle is studied based on geometrical optics model. A model for double-layer spherical particle with optical absorption is presented. The transverse optical trapping force of a double-layer dielectric spherical particle with linear absorption in the outer layer illuminated by a focused Gaussian beam of TEM00 mode is simulated numerically. Our results show that the characteristicsof optical trapping, including the stable trapped positions, the peak intensityand the stiffness of stable trapping, greatly depend on by the absorption coefficient of the double-layer spherical particle. Besides, the ratio of the inner radius to the outer radius of the particle also has modulating influence on the properties of transverse trapping. It is possible to trap transversely the double-layer spherical particle with absorption on the axis of the incident Gaussian beam and on a circle centered at the optical axis for different axial offsets of sphere center from the beam waist as well.

Spike protein VP4 assembly with maturing rotavirus requires a postendoplasmic reticulum event in polarized caco-2 cells.

Rotavirus assembly is a multistep process that requires the successive association of four major structural proteins in three concentric layers. It has been assumed until now that VP4, the most external viral protein that forms the spikes of mature virions, associates with double-layer particles within the endoplasmic reticulum (ER) in conjunction with VP7 and with the help of a nonstructural protein, NSP4. VP7 and NSP4 are two glycosylated proteins. However, we recently described a strong association of VP4 with raft-type membrane microdomains, a result that makes the ER a highly questionable site for the final assembly of rotavirus, since rafts are thought to be absent from this compartment. In this study, we used tunicamycin (TM), a drug known to block the first step of protein N glycosylation, as a tool to dissect rotavirus assembly. We show that, as expected, TM blocks viral protein glycosylation and also decreases virus infectivity. In the meantime, viral particles were blocked as enveloped particles in the ER. Interestingly, TM does not prevent the targeting of VP4 to the cell surface nor its association with raft membranes, whereas the infectivity associated with the raft fractions strongly decreased. VP4 does not colocalize with the ER marker protein disulfide-isomerase even when viral particles were blocked by TM in this compartment. These results strongly support a primary role for raft membranes in rotavirus final assembly and the fact that VP4 assembly with the rest of the particle is an extrareticular event.

Ionic strength- and temperature-induced K(Ca) shifts in the uncoating reaction of rotavirus strains RF and SA11: correlation with membrane permeabilization.

The hydrodynamic diameters of native rotavirus particles, bovine RF and simian SA11 strains, were determined by quasielastic light scattering. By using this method and agarose gel electrophoresis, the Ca(2+) dissociation constant, K(Ca), governing the transition from triple-layer particles (TLPs) to double-layer particles (DLPs), was shown to increase, at constant pH, as the temperature and/or the ionic strength of the incubation medium increased. We report the novel observation that, under physiological conditions, K(Ca) values for both RF and SA11 rotaviruses were well above the intracytoplasmic Ca(2+) concentrations of various cells, which may explain why TLP uncoating takes place within vesicles (possibly endosomes) during the entry process. A correlation between TLP uncoating and cell membrane permeabilization was found, as shown by the release of carboxyfluorescein (CF) from CF-loaded intestinal brush-border membrane vesicles. Conditions stabilizing the virion in the TLP form inhibited CF release, whereas conditions favoring the TLP-to-DLP transformation activated this process. We conclude that membrane permeabilization must be preceded by the loss of the outer-capsid proteins from trypsinized TLP and that physiological ionic strength is required for permeabilization to take place. Finally, the paper develops an alternative explanation for the mechanism of rotavirus entry, compatible with the Ca(2+)-dependent endocytic pathway. We propose that there must be an iterative process involving tight coupling in time between the lowering of endosomal Ca(2+) concentration, virion decapsidation, and membrane permeabilization, which would cause the transcriptionally active DLPs to enter the cytoplasm of cells.

A new possibility of application of electron tunneling effects in electrochemical double layer structure investigations

Abstract A new method has been developed for studying in situ the dependence of the electroresistance of films on the electrolyte composition and potential. The method consists of measuring the contact electroresistance between two identical metallic specimens periodically contacted in electrolyte under potentiostatic control, in particular between the walls of a fatigue crack in a sample cyclically loaded below the corrosion fatigue crack growth threshold. The sensitivity of the method is 10 −9 Ω and it can be used for all conducting materials in any electrolytes at normal and high temperatures and pressures in a wide region of potentials including the potentials of the intensive evolution of hydrogen or oxygen. The method allows one to determine electroresistance of films on metals during adsorption of water and anions, formation and destruction of hydride and oxide films, electrodeposition of metals and electrochemical incorporation of cations, to study the kinetics of these processes and their dependence on potential, activators and inhibitors of corrosion. The water adsorption potentials for 16 metals are defined which are proposed to characterize the hydrophility of metals. The possibility of STM application in electrochemical double-layer structure investigations is briefly discussed in connection with the scan rate of STM and oscillation frequency of the double-layer particles. Electron tunneling between macrocontacts through thin electrolyte layers is proposed to be useful for the investigation of the processes in the double layer.

A new possibility of application of electron tunneling effects in electrochemical double layer structure investigations

A new method has been developed for studying in situ the dependence of the electroresistance of films on the electrolyte composition and potential. The method consists of measuring the contact electroresistance between two identical metallic specimens periodically contacted in electrolyte under potentiostatic control, in particular between the walls of a fatigue crack in a sample cyclically loaded below the corrosion fatigue crack growth threshold. The sensitivity of the method is 10 −9 Ω and it can be used for all conducting materials in any electrolytes at normal and high temperatures and pressures in a wide region of potentials including the potentials of the intensive evolution of hydrogen or oxygen. The method allows one to determine electroresistance of films on metals during adsorption of water and anions, formation and destruction of hydride and oxide films, electrodeposition of metals and electrochemical incorporation of cations, to study the kinetics of these processes and their dependence on potential, activators and inhibitors of corrosion. The water adsorption potentials for 16 metals are defined which are proposed to characterize the hydrophility of metals. The possibility of STM application in electrochemical double-layer structure investigations is briefly discussed in connection with the scan rate of STM and oscillation frequency of the double-layer particles. Electron tunneling between macrocontacts through thin electrolyte layers is proposed to be useful for the investigation of the processes in the double layer.

Energy distribution within double layer particles irradiated by a parallel light beam

Energy distribution within double layer particles irradiated by a parallel light beam