Heterogeneous Multilayer Research Articles

Polyarylene ether nitrile/boron nitride nanosheets thermally conductive films through heterogeneous multilayer electrostatic spinning

Thermal management materials with excellent thermal conductivity and electrical insulation are highly favorable in the modern integrated electronic areas. In present work, a novel polyarylene ether nitrile (PEN) composite film, integrating thermal conductivity, electrical insulation, and flexibility, was fabricated utilizing a hybrid approach combining heterogeneous multilayer electrostatic spinning with a subsequent hot pressing technique. BNNS acts as a thermally conductive filler which builds a good thermal conduction pathway, and PEN acts as a bonding agent which ensures the flexibility and insulation of the film. Heterogeneous multilayer electrostatic spinning ensures the formation of thermal conduction pathways. Compared to conventional composite film, heterogeneous multilayer film shows excellent thermal conductivity, increases by 83% in-plane, and 71% through-plane, respectively. Therefore, This work will provide a technological reserve for the preparation of thermally conductive and insulating flexible films.

Novel insights into crystal violet dye adsorption onto various macroalgae: Comparative study, recyclability and overview of chromium (VI) removal

In this study, effective biomaterials were prepared from marine macroalgae, namely Fucus spiralis (F.S), Ulva intestinalis (U.I), and Corallina officinalis (C.O). The ability to adsorb the hazardous organic dye crystal violet (CV) was examined, revealing different adsorptive properties for the three algae. The removal of CV dye occurred onto only a homogeneous monolayer for F.S, and both a homogeneous monolayer and a heterogeneous multilayer for U.I and C.O algae. The predicted monolayer capacities at 25 °C were approximately 53 mg/g, 55 mg/g, and 97 mg/g for F.S, C.O, and U.I, respectively. The adsorption of CV dye on all the algae was found to follow a pseudo-second-order rate. Ulva intestinalis algae, as a potential adsorbent of CV dye, were also tested in the adsorption of inorganic substances and demonstrated significant efficiency in the removal of chromium (VI). The findings highlight various adsorption properties and the relevance of macroalgae for wastewater treatment applications.

A three-dimensional active biochar for sintering in steel industry and remove methylene blue by synergistic activation of H3PO4 and ZnCl2

In the context of treating waste with waste, the development of three-dimensional biochar that may be used for sintering in the steel sector as well as successfully removing methylene blue from waste water is effective. The biochar activated by H3PO4 alone (DCP), ZnCl2 alone (DCZ) and H3PO4 cooperated with ZnCl2 (DCM) were prepared to investigate the mechanism of the synergism of H3PO4 and ZnCl2 at pyrolysis temperature 500 °C (selecting from 300 °C to 1000 °C). The SEM analysis indicates DCM possesses a stereoscopic porous network comparing agglomeration and stacking of the others, and the SEM and BET analysis indicate that DCM possesses a stereoscopic porous network and higher effective pore volume (VM/VT = 0.951) than DCP (VM/VT = 0.584) and DCZ (VM/VT = 0.812). EDS, XPS and FTIR analysis revealed that the surface heteroatom of P and Zn enhanced on DCM compared with that of DCP (P weight%=6.39 vs 3.26) and DCZ (Zn weight% = 5.93 vs 1.85) although the activator dosage was halved for DCM. The methylene blue isotherm adsorption curve of DCM fits well with Freundlich and Dual Langmuir adsorption isotherms, the adsorption kinetics is in line with the pseudo-second-order kinetic model. The results indicate that the adsorption process is based on a heterogeneous multilayer, that physisorption-chemisorption adsorption is the primary adsorption mechanism, and that the adsorption process is regulated by the combination of intra-particle and film diffusion. The DCM demonstrates to be a promising adsorbent for methylene blue removal, performing a high removal capacity at 576 mg/g. In this study, a feasible method to synergistically activate biochar from textile wastes was proposed, to deal with the removal of methylene blue.

Removal behaviors of aerobic granular sludge on estrogens: Adsorption kinetics and removal mechanism

Aerobic granular sludge (AGS) has the advantages of high biomass and compact structure for withstanding the shocks and toxins. In this study, the removal behaviors of two typical endocrine disrupting chemicals (EDCs), 17β-estradiol (E2) and 17α-ethinylestradiol (EE2), by AGS were investigated. 93.5% of E2 and 84.8% of EE2 were removed at a concentration of 10 μg/L during 120 d operation, with the removal efficiencies of COD, NH4+-N and TP reaching the same level as those in the control group. Batch experimental results showed that the biodegradation was the dominant mechanism of E2 removal, while EE2 was more bio-refractory and mainly removed via adsorption. The adsorption of E2 and EE2 followed heterogeneous multilayer and chemical processes, owing to the active adsorption sites provided by amides, carboxylic groups, hydroxyl groups and polysaccharides on AGS. At the same time, Zoogloea, Sphingomonas, Pseudomonas and Brevundinomas were highly enriched under the pressure of estrogens, which assisted in the stability of AGS reactors by EPS secretion and estrogens degradation.

3D-thrust fault pattern control on negative inversion: An analogue modelling perspective on central Italy

During the last decades, central Italy has been struck by severe seismic sequences. Some authors have suggested that inherited thrust faults may have played an important role in controlling the recent-to active extensional deformation in the area, particularly during the 2016 Central Italy seismic sequence. To explore this hypothesis, we performed an analogue modelling study that addressed the structural evolution of a composite, heterogeneous multilayer affected by polyphase deformation. The overall three-dimensional geometry resulting from the modelling consists of a flat-ramp extensional fault system, with flats being localised along the weaker stratigraphic units, and ramps locally reactivating the pre-existing thrust ramps at depth. At shallower levels, deformation can localize at newly-formed short-cut faults depending on the geometry of deeper structures. The experimental results provide further support to the hypothesis of a link between Quaternary normal faults and inherited thrust faults during the 2016 seismic sequences. Specifically, analogue modelling results suggest that the Quaternary fault pattern may be controlled by the interaction between the active stress field and the pre-existing compressional structures. This scenario bears significant implications regarding the empirical relationship between the geometry of surface faulting and the magnitude of earthquakes, with considerable repercussions on seismic risk assessment.

Regulation of Microstructure, Static, and Microwave Magnetic Performance of NiFe/FeMn/NiFe Heterogeneous Multilayer Films Based on Thickness of FeMn Films

Ferromagnetic (FM)/antiferromagnetic (AFM) heterogeneous multilayer films have triggered tremendous interests for application in microwave/mm devices and components. However, with the development trend of miniaturization, high frequency, and lightweight of devices, the FM/AFM heterogeneous multilayers are desired to possess high saturation magnetization (4πMs), low coercivity (Hc), and low ferromagnetic resonance (FMR) linewidth (∆H). Herein, the Ni81Fe19 (50 nm)/Fe50Mn50 (t nm)/Ni81Fe19 (50 nm) films were fabricated by DC magnetron sputtering, and the effects of thickness of the Fe50Mn50 on the microstructure, static, and microwave properties were investigated in detail. With increasing the FeMn film thickness, the saturation magnetization firstly increased and then decreased from 7947 to 9448 Gs. The in-plane coercivity firstly decreased and then increased from 28.58 to 0.6115 Oe, and the out-of-plane exchange bias field undergoes a transition from a negative exchange bias to a positive exchange bias. Besides, the ferromagnetic resonance linewidth firstly decreased and then increased from 142 to 87 Oe. Remarkably, with a 15-nm Fe50Mn50 film, the heterogeneous multilayer films achieved optimum performance with high saturation magnetization (9448 Gs), low coercivity (1.02 Oe), and low FMR linewidth (94 Oe). The outstanding Ni81Fe19/Fe50Mn50/Ni81Fe19 heterogeneous multilayer films exhibit great potentials in radar remote sensing, communication, and electronic countermeasure fields.

Fluoride removal by palm shell waste based powdered activated carbon vs. functionalized carbon with magnesium silicate: Implications for their application in water treatment

In this study, palm shell activated carbon powder (PSAC) and magnesium silicate (MgSiO3) modified PSAC (MPSAC) were thoroughly investigated for fluoride (F−) adsorption. F− adsorption isotherms showed that PSAC and MPSAC over-performed some other reported F− adsorbents with adsorption capacities of 116 mg g−1 and 150 mg g−1, respectively. Interestingly, the MgSiO3 impregnated layer changed the adsorption behavior of F− from monolayer to heterogeneous multilayer based on the Langmuir and Freundlich isotherm models verified by chi-square test (X2). Thermodynamic parameters indicated that the F− adsorption on PSAC and MPSAC was spontaneous and exothermic. PSAC and MPSAC were characterized using FESEM-EDX, XRD, FTIR and XPS to investigate the F− adsorption mechanism. Based on the regeneration tests using NaOH (0.01 M), PSAC exhibited poor regeneration (<20%) while MPSAC had steady adsorption efficiencies (∼70%) even after 5 regeneration cycles. This is due to highly polarized C–F bond was found on PSAC while Mg–F bond was distinguished on MPSAC, evidently denoting that the F− adsorption is mainly resulted from the exchange of hydroxyl (-OH) group. It was concluded that PSAC would be a potential adsorbent for in-situ F− groundwater remediation due to its capability to retain F− without leaching out in a wide range pH. MPSAC would be an alternative adsorbent for ex-situ F− water remediation because it can easily regenerate with NaOH solution. With the excellent F− adsorption properties, both PSAC and MPSAC offer as promising adsorbents for F− remediation in the aqueous phase.

Heterogeneous Multilayer Generalized Operational Perceptron

The traditional multilayer perceptron (MLP) using a McCulloch-Pitts neuron model is inherently limited to a set of neuronal activities, i.e., linear weighted sum followed by nonlinear thresholding step. Previously, generalized operational perceptron (GOP) was proposed to extend the conventional perceptron model by defining a diverse set of neuronal activities to imitate a generalized model of biological neurons. Together with GOP, a progressive operational perceptron (POP) algorithm was proposed to optimize a predefined template of multiple homogeneous layers in a layerwise manner. In this paper, we propose an efficient algorithm to learn a compact, fully heterogeneous multilayer network that allows each individual neuron, regardless of the layer, to have distinct characteristics. Based on the complexity of the problem, the proposed algorithm operates in a progressive manner on a neuronal level, searching for a compact topology, not only in terms of depth but also width, i.e., the number of neurons in each layer. The proposed algorithm is shown to outperform other related learning methods in extensive experiments on several classification problems.

Facile Biofabrication of Heterogeneous Multilayer Tubular Hydrogels by Fast Diffusion-Induced Gelation.

Multilayer (ML) hydrogels are useful to achieve stepwise and heterogeneous control over the organization of biomedical materials and cells. There are numerous challenges in the development of fabrication approaches toward this, including the need for mild processing conditions that maintain the integrity of embedded compounds and the versatility in processing to introduce desired complexity. Here, we report a method to fabricate heterogeneous multilayered hydrogels based on diffusion-induced gelation. This technique uses the quick diffusion of ions and small molecules (i.e., photoinitiators) through gel-sol or gel-gel interfaces to produce hydrogel layers. Specifically, ionically (e.g., alginate-based) and covalently [e.g., gelatin methacryloyl (GelMA-based)] photocross-linked hydrogels are generated in converse directions from the same interface. The ML (e.g., seven layers) ionic hydrogels can be formed within seconds to minutes with thicknesses ranging from tens to hundreds of micrometers. The thicknesses of the covalent hydrogels are determined by the reaction time (or the molecule diffusion time). Multiwalled tubular structures (e.g., mimicking branched multiwalled vessels) are mainly investigated in this study based on a removable gel core, but this method can be generalized to other material patterns. The process is also demonstrated to support the encapsulation of viable cells and is compatible with a range of thermally reversible core materials (e.g., gelatin and Pluronic F127) and covalently cross-linked formulations (e.g., GelMA and methacrylated hyaluronic acid). This biofabrication process enhances our ability to fabricate a range of structures that are useful for biomedical applications.

Tailored polyelectrolyte thin film multilayers to modulate cell adhesion.

The layer-by-layer assembly of polyelectrolyte multilayers (PEMs) from natural or synthetic polyelectrolytes constitutes a very versatile and simple strategy to modify surfaces and modulate cell behavior. PEMs assembled from natural polyelectrolytes are very appealing for biological and medical applications due to their high biocompatibility. However, PEMs from natural polyelectrolytes display poor cell adhesion as they are soft materials with an elasticity modulus of a few kilopascal. In this report, the authors present results on the modulation of cell adhesion of different immortalized cell lines by PEMs. Two strategies are employed to vary cell adhesion: (1) a heterogeneous polyelectrolyte multilayer is assembled employing a rigid bottom block including a synthetic polyelectrolyte with a soft upper block of natural polyelectrolytes and (2) polyelectrolyte multilayers from natural polyelectrolytes are thermally annealed after assembly. The physicochemical characteristics of the PEMs change upon thermal treatment. Depending on the composition of the polyelectrolyte multilayer, cell adhesion may be enhanced or reduced. Based on the impact on PEM properties and cell adhesion caused by thermal annealing, a temperature gradient is applied to a PEM of poly-l-lysine/alginate to induce a spatial variation of PEM properties, resulting in a gradient in cell adhesion. The strategies shown here can be employed as simple alternatives to tailor PEM properties by means of fully biocompatible procedures.

Photoacoustic Signal Formation in Heterogeneous Multilayer Systems with Piezoelectric Detection

A new efficient model describing photoacoustic (PA) signal formation with piezoelectric detection is reported. Multilayer sandwich-like systems: heterogeneous studied structure—buffer layer—piezoelectric transducers are considered. In these systems, the buffer layer is used for spatial redistribution of thermoelastic force moments generated in the investigated structure. Thus, mechanical properties of this layer play a crucial role to ensure perfect control of the detected voltage formed on a piezoelectric transducer by contribution of different regions of the studied structure. In particular, formation of the voltage signal strongly depends on the point at which the thermoelastic source is applied. Therefore, use of relatively simple linear Green’s functions introduced in frames of the Kirchhoff–Love theory is chosen as an efficient approach for the PA signal description. Moreover, excellent agreement between the theoretical model and measured results obtained on a heterogeneous “porous silicon-bulk Si substrate” structure is stated. Furthermore, resolving of the inverse problem with fitting of the experimental curves by the developed model allows reliable evaluation of the thermal conductivity of the nanostructured porous silicon layer.

Magnetic Flocculant for High Efficiency Harvesting of Microalgal Cells

Magnetic flocculant was synthesized for the highly efficient recovery of microalgal cells. The highest flocculation was achieved using the magnetic flocculant synthesized with iron oxide and 0.1 mg/mL cationic polyacrylamide (CPAM). This resulted in a recovery efficiency of more than 95% within 10 min using a dosage of 25 mg/L for Botryococcus braunii and 120 mg/L for Chlorella ellipsoidea. For both species, the adsorption isotherm data fit the Freundlich model better than the Langmuir model, indicating that the adsorption process was a heterogeneous multilayer. The maximum adsorption capacity was 114.8 and 21.4 mg dry cells/mg-particles at pH 7 for B. braunii and C. ellipsoidea, respectively. The primary flocculation mechanism was bridging, which was assisted by the electrostatic interactions between the microalgal cells and the magnetic flocculant under acidic conditions. These results provide new opportunities and challenges for understanding and improving the harvesting of microalgae using magnetic separation.

Adsorption of ferric ions onto natural feldspar: kinetic modeling and adsorption isotherm

The removing of ferric ions (Fe3+) from aqueous solution using natural feldspar (NF) has been studied in a batch operation mode. The factors affecting of the sorption equilibrium, such as contact time, initial concentration of the ferric ions (Fe3+), feldspar dosage concentration and temperature, were investigated. The maximum removal is 93 % (approx.) using low-level concentration of Fe3+ ions (30 mg L−1) and high dosage concentration (40 g L−1). The adsorption equilibrium is achieved during the first 90 min. Freundlich model has successfully analyzed the equilibrium of isotherms with R 2 = 1. The adsorption mechanism of aqueous ferric ion on NF follows Freundlich isotherm models (R 2 = 0.997). The capacity (K f) and intensity (1/n) of Freundlich adsorption are 1.70 and 0.621, respectively. The results reveal that the adsorption mechanism of ferric ion on NF is chemisorptions, heterogeneous multilayer and spontaneous in nature (ΔG = −19.778 kJ mol−1). Adsorption reaction kinetic models, such as pseudo-first order and pseudo-second order, and adsorption diffusion model, such as Weber–Morris intraparticle diffusion model, have been used to describe the adsorption rate and mechanism of the ferric ion onto NF surface. Adsorption of ferric ion on the NF has achieved Lagergren pseudo-second-order model (R 2 = 1.0 approx.) more than Lagergren pseudo-first-order model. The kinetic parameters, rate constant and sorption capacities have been calculated. The new information in this study suggests that NF could be used as a novel filtering materials for removing ferric ions from water.

Loading and Release Behaviors of Compressed Polyelectrolyte Multilayers for Small Dye Molecules

Loading and release behaviors of compressed polyelectrolyte multilayers composed of poly(styrenesulfonate sodium salt) and poly(diallyldimethylammonium chloride) were investigated using fluorescein and rhodamine 6G as indicators by confocal laser scanning microcopy, fluorescence spectroscopy, and UV-vis spectroscopy. Compression of the multilayers resulted in a more densely packed microstructure, leading to the decrease of fluorescence intensity of the incorporated probes to 80% of its initial value, and much slower releasing rate as well as smaller releasing amount regardless of the types of the probes and the presence of salt. Utilizing the difference of loading and release rates between the compressed and the uncompressed regions, arrays of dye reservoirs have been fabricated on a chemical homogeneous but physical heterogeneous multilayer film.

Determining Radiative Heat Transfer Through Heterogeneous Multilayer Nonwoven Materials

A theoretical equation of the combined thermal conductive, convective, and radiative heat flow through heterogeneous multilayer fibrous materials is presented. Samples whose properties are analyzed by this equation were constructed from glass and ceramic webs and used in an earlier work to experimentally determine their thermal conductivities. In that experimental work, overall effective thermal conductivities were determined using a guarded hot plate instrument with temperatures ranging from 430 to 480°C. In the theoretical equation presented here, thermal convective heat flow is ignored because of fabric structural conditions, and the conduction component of the overall conductivity is determined by Fricke's equation. Furthermore, the results of Fricke's equation and the overall effective thermal conductivity are used to estimate the radiative thermal conduc tivity of the samples.

Dihydrofolate reductase gene amplification-associated shift of differentiation in methotrexate-adapted HT-29 cells.

Postconfluent cultures of HT-29 cells form a heterogeneous multilayer of which greater than 95% of the cells are undifferentiated. In contrast, when stably adapted to normally lethal concentrations of methotrexate (10(-6)-10(-5) M), they form a monolayer of gobletlike cells (Lesuffleur et al., 1990) which secrete large quantities of mucins and display a discrete brush border with the presence of villin, dipeptidylpeptidase-IV, and carcinoembryonic antigen. When adapted to even higher concentrations of methotrexate (10(-4) and 10(-3) M) there is a shift in the pattern of differentiation from gobletlike to dome-forming absorptive-like cells. These cells still display an apical brush border which expresses villin and dipeptidylpeptidase-IV, but no longer express significant levels of mucins and carcinoembryonic antigen. This shift of differentiation coincides with a sudden amplification of the gene coding for dihydrofolate reductase and an increased activity of the enzyme.