Functional clay nanotubes and composites

Tubular nanomaterials and their composites have been extensively studied in recent years in the fields of physics, chemistry, biology, and biomedicine. Carbon nanotube is the most commonly studied tubular nanomaterial; however, toxicity and high cost make it less attractive in industry and thus restricts its applications. Halloysite nanotubes, which are available in abundance in the United States as well as in other countries around the world, is a low-cost, unique and versatile aluminosilicate mineral with a chemical formula of Al4Si4O10(OH)8·nH2O. Basically, the halloysite tube diameter is around 50 nm and the length varies with different locations ranging from 0.4-1.5 μm. The hollow nanotubular structure in the submicrometer range and large specific surface area provide opportunities for advanced applications in the fields in electronics, catalysis, biological systems, drug delivery, absorbents and functional polymeric composites. This dissertation contains the applications of halloysite in functional nanocomposites: adsorbent for dyes removal, additive for phase change heat insulating composites related to the nanotube orientation phenomena were studied. Halloysite nanotubes aligned along a particular direction were formed both by shear force and casting methods in the droplet meniscus in the microchannels. Halloysite clay has a chemical structure similar to kaolinite, but it is rolled into tubes with external diameters of 50-60 nm, lumens of 12-15 nm and lengths of ca. 1000 nm. Halloysite exhibits higher adsorption capacity for both cationic and anionic dyes because it has negative SiO2 outermost and positive Al2O3 inner lumen surface; therefore, these clay nanotubes have a unique property of efficient bivalent absorbency. An adsorption study using cationic Rhodamine 6G and anionic Chrome azurol S has shown two times better dye removal for halloysite as compared to kaolin clay. Halloysite filters have been effectively regenerated up to 50 times by burning the adsorbed dyes at 350° C. Overall removal efficiency of anionic Chrome azurol S exceeded 99.9% for 5th regeneration cycle of halloysite. Chrome azurol S adsorption capacity decreases with the increase of ionic strength, temperature and pH. For cationic Rhodamine 6G, higher ionic strength, temperature and initial solution concentration were favorable to enhanced adsorption with optimal pH 8. The equilibrium adsorption data were described by Langmuir and Freundlich isotherms, showing that the Langmuir model describes the process better than the Freundlich model. The maximum adsorption capacity calculated from the Langmuir model is 43.6 mg/g for Rhodamine 6G and 38.7 mg/g for Chrome azurol S onto halloysite, and 21.4 mg/g for Rhodamine 6G and 36.7 mg/g for Chrome azurol S onto kaolinite. The halloysite surface modification with surfactants (dioctadecyldimethylammonium bromide) and polyelectrolytes (polyethyleneimine) allowed for varying the organic-inorganic nanocomposite adsorption properties. Electrically, bivalent halloysite tubule clay has a potential as a low-cost efficient adsorbent both for positively and negatively charged contaminant removal. Base or acid treatment of halloysite essentially increased its surface area from 40-50 to ca. 300 m2/g, which further improves the efficiency of the filtration. In order to further develop clay nanotube composites with organic materials, we developed phase change materials (PCMs), which have gained extensive attention in thermal energy storage. Wax can be used as a phase change material in solar energy storage but has low thermal conductivity and cannot sustain its shape at higher temperatures (above phase transition from solid to liquid at 55° C). Introducing 40-50% halloysite clay nanotubes into wax yields a stable and homogenous phase change composite (wax/halloysite) with thermal conductivity of 0.36 W/m-K and no leaking until 70° C (preserving layer-shape above the original wax melting point). To increase the base thermal conductivity, nanographite and carbon nanotubes were added to the phase change material composite. Thermal conductivity of wax/halloysite/graphite (45/45/10%) composite showed a six-fold conductivity increase to 1.4 W/m·K compared to pure wax and had no liquid wax leakage until 81° C. Wax/halloysite/graphite/carbon nanotubes (45/45/5/5%) composite showed thermal conductivity of 0.85 W/m·K while maintaining the original shape until 91 ° C. Vectorial thermal energy transfer for double layers of different composition was demonstrated: heat flux difference in the opposite directions differed by 25%. This variance in layer conductivity allows for smart building roof insulators with increased absorption during hot weather, but limited thermal losses during periods of cooler temperatures. The new wax-nanoclay composite is a promising heat storage material due to good heat capacity, high thermal conductivity, and the ability to preserve its shape during wax melting. We discovered clay nanotube orientation under shear force in clay nanotube-wax layered composites and analyzed this phenomenon in the following chapter. During drying, an aqueous suspension of charged halloysite clay nanotubes concentrates at the edge of the droplet ( coffee-ring effect) which provides alignment of the tubes along the liquid-substrate contact line. First, the surface charge of the nanotubes was enhanced by polyanion adsorption inside of the lumen to compensate for the internal positive charges. This increased the magnitude of the ξ-potential of the tubes from -36 to -81 mV and stabilized the colloids. Then, colloidal halloysite was dropped onto the substrate, dried at 65° C, and after a concentration of ~0.05 mg/mL was reached, the alignment of the nanotubes occurred starting from the droplet edges. We described the process with Onsager\u27s theory, in which longer nanorods, which have a higher surface charge, give better ordering after a critical concentration is reached. This study indicates a new application of halloysite clay nanotubes in polymeric composites with anisotropic properties, microchannel orientation, and production of coatings with aligned nanotubes

Flower heads in Asteraceae—recruitment of conserved developmental regulators to control the flower-like inflorescence architecture

Inflorescences in the Asteraceae plant family, flower heads, or capitula, mimic single flowers but are highly compressed structures composed of multiple flowers. This transference of a flower-like appearance into an inflorescence level is considered as the key innovation for the rapid tribal radiation of Asteraceae. Recent molecular data indicate that Asteraceae flower heads resemble single flowers not only morphologically but also at molecular level. We summarize this data giving examples of how rewiring of conserved floral regulators have led to evolution of morphological innovations in Asteraceae. Functional diversification of the highly conserved flower meristem identity regulator LEAFY has shown a major role in the evolution of the capitulum architecture. Furthermore, gene duplication and subsequent sub-and neofunctionalization of SEPALLATA and CYCLOIDEA-like genes in Asteraceae have been shown to contribute to meristem determinacy, as well as flower type differentiation-key traits that specify this large family. Future challenge is to integrate genomic, as well as evolutionary developmental studies in a wider selection of Asteraceae species to understand the detailed gene regulatory networks behind the elaborate inflorescence architecture, and to promote our understanding of how changes in regulatory mechanisms shape development.Peer reviewe

Robust Control Allocation among Overactuated Spacecraft Thrusters under Ellipsoidal Uncertainty

Spacecrafts with overactuated and redundant thrusters can work normally once some of them are out of work, which improves the reliability of spacecraft in orbit. In this way, the desired command of controller needs to be dynamically allocated among thrusters. Considering that uncertain factors may appear in forms of dynamics, installation errors, thrust deviations, or failures, this paper proposes a robust control allocation under ellipsoidal uncertainty. This method uses the uncertainty ellipsoid set to describe the uncertainty of the thrusters firstly and establish the thrust allocation robust reference model and then transforms it into a cone optimization model which can be solved as an optimized problem. Finally, this paper adopts the interior-point method for solving the optimization problem. In this way, difficulties of solving the problem caused by parameter uncertainties are avoided effectively. Finally, we take satellite rendezvous and docking as simulation scenarios; it is verified that the cumulative distribution error and maximum error can be reduced by more than 15% when the random error of control efficiency matrix is 5%–20%; also, precision of thruster allocation is improved

Regulation of Microglial Functions by Purinergic Mechanisms in the Healthy and Diseased CNS

Microglial cells, the resident macrophages of the central nervous system (CNS), exist in a process-bearing, ramified/surveying phenotype under resting conditions. Upon activation by cell-damaging factors, they get transformed into an amoeboid phenotype releasing various cell products including pro-inflammatory cytokines, chemokines, proteases, reactive oxygen/nitrogen species, and the excytotoxic ATP and glutamate. In addition, they engulf pathogenic bacteria or cell debris and phagocytose them. However, already resting/surveying microglia have a number of important physiological functions in the CNS; for example, they shield small disruptions of the blood–brain barrier by their processes, dynamically interact with synaptic structures, and clear surplus synapses during development. In neurodegenerative illnesses, they aggravate the original disease by a microglia-based compulsory neuroinflammatory reaction. Therefore, the blockade of this reaction improves the outcome of Alzheimer’s Disease, Parkinson’s Disease, multiple sclerosis, amyotrophic lateral sclerosis, etc. The function of microglia is regulated by a whole array of purinergic receptors classified as P2Y12, P2Y6, P2Y4, P2X4, P2X7, A2A, and A3, as targets of endogenous ATP, ADP, or adenosine. ATP is sequentially degraded by the ecto-nucleotidases and 5′-nucleotidase enzymes to the almost inactive inosine as an end product. The appropriate selective agonists/antagonists for purinergic receptors as well as the respective enzyme inhibitors may profoundly interfere with microglial functions and reconstitute the homeostasis of the CNS disturbed by neuroinflammation

Synergistic growth inhibition by sorafenib and vitamin K2 in human hepatocellular carcinoma cells

OBJECTIVE: Sorafenib is an oral multikinase inhibitor that has been proven effective as a single-agent therapy in hepatocellular carcinoma, and there is a strong rationale for investigating its use in combination with other agents. Vitamin K2 is nearly non-toxic to humans and has been shown to inhibit the growth of hepatocellular carcinoma. In this study, we evaluated the effects of a combination of sorafenib and vitamin K2 on the growth of hepatocellular carcinoma cells. METHODS: Flow cytometry, 3-(4,5-dimethyl-2-thiazolyl-2,5-diphenyl-2H-tetrazolium bromide) and nude mouse xenograft assays were used to examine the effects of sorafenib and vitamin K2 on the growth of hepatocellular carcinoma cells. Western blotting was used to elucidate the possible mechanisms underlying these effects. RESULTS: Assays for 3-(4,5-dimethyl-2-thiazolyl-2,5-diphenyl-2H-tetrazolium bromide) revealed a strong synergistic growth-inhibitory effect between sorafenib and vitamin K2. Flow cytometry showed an increase in cell cycle arrest and apoptosis after treatment with a combination of these two drugs at low concentrations. Sorafenib-mediated inhibition of extracellular signal-regulated kinase phosphorylation was promoted by vitamin K2, and downregulation of Mcl-1, which is required for sorafenib-induced apoptosis, was observed after combined treatment. Vitamin K2 also attenuated the downregulation of p21 expression induced by sorafenib, which may represent the mechanism by which vitamin K2 promotes the inhibitory effects of sorafenib on cell proliferation. Moreover, the combination of sorafenib and vitamin K2 significantly inhibited the growth of hepatocellular carcinoma xenografts in nude mice. CONCLUSIONS: Our results determined that combined treatment with sorafenib and vitamin K2 can work synergistically to inhibit the growth of hepatocellular carcinoma cells. This finding raises the possibility that this combined treatment strategy might be promising as a new therapy against hepatocellular carcinoma, especially for patients with poor liver tolerance

Listen to Minority: Encrypted Traffic Classification for Class Imbalance with Contrastive Pre-Training

Mobile Internet has profoundly reshaped modern lifestyles in various aspects. Encrypted Traffic Classification (ETC) naturally plays a crucial role in managing mobile Internet, especially with the explosive growth of mobile apps using encrypted communication. Despite some existing learning-based ETC methods showing promising results, three-fold limitations still remain in real-world network environments, 1) label bias caused by traffic class imbalance, 2) traffic homogeneity caused by component sharing, and 3) training with reliance on sufficient labeled traffic. None of the existing ETC methods can address all these limitations. In this paper, we propose a novel Pre-trAining Semi-Supervised ETC framework, dubbed PASS. Our key insight is to resample the original train dataset and perform contrastive pre-training without using individual app labels directly to avoid label bias issues caused by class imbalance, while obtaining a robust feature representation to differentiate overlapping homogeneous traffic by pulling positive traffic pairs closer and pushing negative pairs away. Meanwhile, PASS designs a semi-supervised optimization strategy based on pseudo-label iteration and dynamic loss weighting algorithms in order to effectively utilize massive unlabeled traffic data and alleviate manual train dataset annotation workload. PASS outperforms state-of-the-art ETC methods and generic sampling approaches on four public datasets with significant class imbalance and traffic homogeneity, remarkably pushing the F1 of Cross-Platform215 with 1.31%, ISCX-17 with 9.12%. Furthermore, we validate the generality of the contrastive pre-training and pseudo-label iteration components of PASS, which can adaptively benefit ETC methods with diverse feature extractors.Comment: Accepted by 2023 20th Annual IEEE International Conference on Sensing, Communication, and Networking, 9 pages, 6 figure

M2-polarized macrophages promote metastatic behavior of Lewis lung carcinoma cells by inducing vascular endothelial growth factor-C expression

OBJECTIVES: Tumor-associated macrophages that generally exhibit an alternatively activated (M2) phenotype have been linked to tumor progression and metastasis. However, the role of M2-polarized macrophages in the growth and metastasis of lung adenocarcinoma remains enigmatic. The aim of this study was to explore the effect of M2 macrophages on the proliferation and migration of mouse Lewis lung carcinoma cells and tumor-induced lymphangiogenesis. METHODS: Trypan blue staining and the Transwell migration assay were performed to evaluate the effects of activated (M1 or M2) macrophages on the proliferation and migration of Lewis cells. Furthermore, vascular endothelial growth factor-C expression in Lewis cells and nitric oxide secretion from activated macrophages were detected during the co-culture assay. Following treatment with activated macrophages, lymphatic endothelial cells differentiated into capillary-like structures, and the induction of Lewis cell migration was assessed using a twodimensional Matrigel-based assay. RESULTS: In the co-culture Transwell system, the proliferation and migration of Lewis cells were promoted by M2 macrophages. Moreover, the co-culture significantly increased the expression of vascular endothelial growth factor-C by Lewis cells and reduced the secretion of nitric oxide from M2 macrophages, which subsequently led to the capillary morphogenesis of lymphatic endothelial cells. Interestingly, following co-culture with Lewis cells, the function of RAW264.7 cells was polarized toward that of the M2 macrophage phenotype. CONCLUSION: M2-polarized macrophages promoted the metastatic behavior of Lewis cells by inducing vascular endothelial growth factor-C expression. Thus, the interruption of signaling between M2 macrophages and Lewis cells may be considered to be a new therapeutic strategy

Geographical Distribution Characteristics of Ethnic-Minority Villages in Fujian and Their Relationship with Topographic Factors

The geographical distribution characteristics of villages characterised by ethnic minorities are determined by the selection of the site when the village was initially established. The location of inherited and well-preserved minority villages must be exceptionally compatible with the natural terrain, with a logical relationship. Nonetheless, the issue of village location, which is directly related to the development of the features of the geographical distribution, has received little attention from scholars. The average nearest proximity index, Voronoi, kernel density analysis, proximity analysis, and the Geographical Detector (GeoDetector) were used to analyse the geographic distribution characteristics of villages and their correlation with terrain, as well as the difference between the influence of each terrain factor. The findings indicated the following. (1) The geographical distribution of minority villages in Fujian Province is of the agglomeration type, with a significant “mononuclear” feature, and the topography has a facilitating effect on the clustering distribution of villages. (2) The geographical distribution of minority villages in each city of Fujian Province coexisted with the agglomeration type and the dispersion type, and the role of topography in promoting the agglomeration-type distribution of villages was not affected by the distribution density of villages. (3) The site selection of Fujian-minority villages is characterised by medium altitude, moderate slope, sun exposure, and no obvious hydrophilicity. Minority villages are mainly located in areas with an elevation of 202–647 m; a slope of 6–15°; a flat land aspect with a south slope, southeast slope, or southwest slope; and distance of 500–1500 m from 5–20 m wide rivers of level 2. (4) The site selection of Fujian minority villages is influenced by various topographic factors, such as elevation, slope, aspect, river buffer, river width, and river level, among which river width has the most substantial effect. (5) All topographic factors have a two-factor enhancing relationship with each other, aspect and slope have the most substantial effect and play a dominant role in site selection. The research findings illuminate the internal logic of the geographical distribution differentiation of villages characterised by ethnic minorities, which is critical for promoting the protection of modern ethnic-minority villages