Charge Content Research Articles

The separation of kreutzonit particles by cationic pullulan derivatives from model suspension

In the present work the flocculation properties of some cationic derivatives based on pullulan have been tested in a synthetic suspension of zirconium silicate (kreutzonit). The flocculants contain either quaternary ammonium salt groups (grafted chains, poly[(3-acrylamidopropyl)-trimethylammonium chloride] onto the pullulan (P-g-pAPTAC)) or tertiary amine groups (3-dimethylamino-1-propylamine-pullulan) (DMAPAX-P). The impact of polymer dose, the charge content and type (tertiary amine or quaternary ammonium salt groups), the grafted chains length and the suspension pH on the flocculation efficiency have been taken into consideration. The separation of mixtures consisting of kreutzonit, K-feldspar, kaolin, hematite (Fe2O3) particles by some of the above mentioned cationic derivatives was also followed. The addition of different doses of pullulan derivatives to kreutzonit dispersion as well as to particles mixture led to the increase of particles removal efficiency up to 95–99% in the optimum dose intervals. The charge patch and bridging mechanisms played an important role in the flocculation process, as revealed by zeta potential measurements. Flocs resulting from the flocculation process have been used successfully in removal of fungicide Bordeaux mixture particles from synthetic wastewater; a removal efficiency higher than 95% has been found for the optimum amount of flocs (10 g flocs per liter of fungicide suspension).

Protein primary structure correlates with calcium oxalate stone matrix preference.

Despite the apparent importance of matrix proteins in calcium oxalate kidney stone formation, the complexity of the protein mixture continues to elude explanation. Based on a series of experiments, we have proposed a model where protein aggregates formed from a mixture containing both strongly charged polyanions and strongly charged polycations could initiate calcium oxalate crystal formation and crystal aggregation to create a stone. These protein aggregates also preferentially adsorb many weakly charged proteins from the urine to create a complex protein mixture that mimics the protein distributions observed in patient samples. To verify essential details of this model and identify an explanation for phase selectivity observed in weakly charged proteins, we have examined primary structures of major proteins preferring either the matrix phase or the urine phase for their contents of aspartate, glutamate, lysine and arginine; amino acids that would represent fixed charges at normal urine pH of 6-7. We verified enrichment in stone matrix of proteins with a large number of charged residues exhibiting extreme isoelectric points, both low (pI<5) and high (pI>9). We found that the many proteins with intermediate isoelectric points exhibiting preference for stone matrix contained a smaller number of charge residues, though still more total charges than the intermediate isoelectric point proteins preferring the urine phase. While other sources of charge have yet to be considered, protein preference for stone matrix appears to correlate with high total charge content.

Hydrothermal treatments of aqueous cellulose nanocrystal suspensions: effects on structure and surface charge content

Hydrothermal treatments of aqueous cellulose nanocrystal suspensions: effects on structure and surface charge content

Macromolecular assembly and membrane activity of antimicrobial D,L-α-Cyclic peptides

Antimicrobial peptides are viewed as a promising alternative to conventional antibiotics, as their activity through membrane targeting makes them less prone to resistance development. Among them, antimicrobial D,L-α-cyclic peptides (CPs) have been proposed as an alternative, specially due to their cyclic nature and to the presence of D-α-amino acids that increases their resistance to proteases. In present work, second generation D,L-α-cyclic peptides with proven antimicrobial activity are shown to form complex macromolecular assemblies in the presence of membranes. We addressed the CPs:membrane interactions through a combination of experimental techniques (DSC and ATR-FTIR) with coarse-grained molecular dynamics (CG-MD) simulations, aiming at understanding their interactions, macromolecular assemblies and eventually unveil their mechanism of action. DSC shows that the interaction depends heavily on the negatively charge content of the membrane and on lipid/peptide ratio, suggesting different mechanisms for the different peptides and lipid systems. CG-MD proved that CPs can self-assemble at the lipid surface as nanotubes or micellar aggregates, depending on the peptide, in agreement with ATR-FTIR results. Finally, our results shed light into possible mechanisms of action of the peptides with pending hydrocarbon tail, namely membrane extensive segregation and/or membrane disintegration through the formation of disk-like lipid/peptide aggregates.

Factors governing microalgae harvesting efficiency by flocculation using cationic polymers

This study aims to elucidate the mechanisms governing the harvesting efficiency of Chlorella vulgaris by flocculation using a cationic polymer. Flocculation efficiency increased as microalgae culture matured (i.e. 35–45, 75, and > 97% efficiency at early, late exponential, and stationary phase, respectively. Unlike the negative impact of phosphate on flocculation in traditional wastewater treatment; here, phosphorous residue did not influence the flocculation efficiency of C. vulgaris. The observed dependency of flocculation efficiency on growth phase was driven by changes in microalgal cell properties. Microalgal extracellular polymeric substances (EPS) in both bound and free forms at stationary phase were two and three times higher than those at late and early exponential phase, respectively. Microalgae cells also became more negatively charged as they matured. Negatively charged and high EPS content together with the addition of high molecular weight and positively charged polymer could facilitate effective flocculation via charge neutralisation and bridging.

Star Polymer Size, Charge Content, and Hydrophobicity Affect their Leaf Uptake and Translocation in Plants.

Determination of how the properties of nanocarriers of agrochemicals affect their uptake and translocation in plants would enable more efficient agent delivery. Here, we synthesized star polymer nanocarriers poly(acrylic acid)-block-poly(2-(methylsulfinyl)ethyl acrylate) (PAA-b-PMSEA) and poly(acrylic acid)-block-poly((2-(methylsulfinyl)ethyl acrylate)-co-(2-(methylthio)ethyl acrylate)) (PAA-b-P(MSEA-co-MTEA)) with well-controlled sizes (from 6 to 35 nm), negative charge content (from 17% to 83% PAA), and hydrophobicity and quantified their leaf uptake, phloem loading, and distribution in tomato (Solanum lycopersicum) plants 3 days after foliar application of 20 μL of a 1g L-1 star polymer solution. In spite of their property differences, ∼30% of the applied star polymers translocated to other plant organs, higher than uptake of conventional foliar applied agrochemicals (<5%). The property differences affected their distribution in the plant. The ∼6 nm star polymers exhibited 3 times higher transport to younger leaves than larger ones, while the ∼35 nm star polymer had over 2 times higher transport to roots than smaller ones, suggesting small star polymers favor symplastic unloading in young leaves, while larger polymers favor apoplastic unloading in roots. For the same sized star polymer, a smaller negative charge content (yielding ζ ∼ -12 mV) enhanced translocation to young leaves and roots, whereas a larger negative charge (ζ < -26 mV) had lower mobility. Hydrophobicity only affected leaf uptake pathways, but not translocation. This study can help design agrochemical nanocarriers for efficient foliar uptake and targeting to desired plant organs, which may decrease agrochemical use and environmental impacts of agriculture.

Efficacy of quaternary ammonium groups based polyelectrolytes for the reduction of various pesticide formulations content from synthetic wastewater

Cationic polyelectrolytes, synthetic (PCA) and dextran derivatives (D40-EtX) have been evaluated, for the first time, as flocculants for the separation of the commercial pesticides Novadim Progress -organophosphoric type (active ingredient Dimethoate), Decis and Karate Zeon - pyrethroid type (active ingredients Deltamethrin and lambda- Cyhalothrin, respectively) from synthetic wastewater. The investigated ionic polymer samples contain different amount of quaternary ammonium salts groups in the chain. The effects of settling time, polymer dose, ionic groups content, pesticides concentration on the separation efficacy have been investigated. The UV–Vis spectroscopy data indicate that the highest removal efficiency of pesticides (between 90 and 94% for Novadim Progress and between 86 and 94% for the pyrethroids insecticides) has been achieved by the polyelectrolytes with the highest charged groups content (higher than 90%). The charge neutralization mechanism had a noteworthy contribution to the pesticide removal as indicated by the zeta potential and particle size measurements. Slightly lower optimum polycation doses were found for lower pesticides concentrations.

Deshelled Carica papaya Seeds as Natural Coagulant for Improvement Quality of River Water

This study evaluated the efficiency of deshelled papaya seeds as the natural coagulant in improving quality of river water. The deshelled papaya seeds biomass was mainly characterized for functional groups using FTIR, surface charge and protein content. Coagulation and flocculation tests were conducted using batch test for various dosages and pH values. The optimum dosage and pH were then tested in treating river of Class III to Class V. The functional groups in deshelled papaya seeds were O-H, C=O and C-O groups. The surface charge and protein content was +0.4 meq/g and 363 mg/g, respectively. The deshelled papaya seeds coagulant was able to remove turbidity up to 87.6 and 88.3% for river of Class III and Class IV, respectively, as well as 57.6 and 62.1% of total coliform and escherichia coli, respectively, from Class III river at dosage 196 mg/L and pH 4. This study demonstrated that the deshelled Carica papaya seeds-derived coagulant is capable in treating common pollutants of river and simultaneously shows antibacterial properties.

Adsorption of As(III) and As(V) by using the Fenton reaction modified kapok fiber

The hydrophilic kapok fiber was obtained by Fenton reaction via a cost-effective and controllable solution-dipping process. The adsorption performances of Fenton reaction modified kapok fiber (FRKF) were evaluated in terms of pH, time, pollutant concentration, temperature, co-existing anions, and reusability, so as to find the optimum adsorption conditions for removing As(III) and As(V) from the aqueous solution. The results showed that FRKF was stable at a relatively wide range of pH for As(III) and As(V), the optimal pH of As(III) and As(V) were 7.0 and 4.0, respectively, and the adsorption equilibrium time of As(III) was shorter than that of As(V). The effect of temperature on the adsorption of As(III) by FRKF was negligible, but it has an obvious effect on the adsorption of As(V). As the temperature increased from 293 K to 313 K, the adsorption uptakes of FRKF for As(V) increased from 18.7 mg g−1 to 30.0 mg g−1. Compared with NO3−, and SO42−, the co-existing anion of PO43− has a serious inhibitory effect on the adsorption of arsenic due to its high content of negative charge and a tetrahedral structure similar to As(V). Based on the XPS analysis, the functional groups of hydroxyl and/or carboxyl on FRKF play a major role by forming C-O-As bond with arsenic in the adsorption process. Finally, the adsorption-desorption experiments demonstrated that FRKF has good stability and reusability, thus FRKF can be used an effective and practical adsorbent for the treatment of arsenic or other heavy metals.

Twitter content analysis of the Australian bushfires disaster 2019-2020: futures implications

Purpose This paper aims to explore the themes and nature of sentiment of Twitter content that discussed the Australian bushfire disaster 2019–2020 and its associated wildlife devastation, with considerations for the future of Australia’s tourism industry. Design/methodology/approach A large, qualitative data set consisting of all publicly available Twitter posts during the period of the Australian bushfires from December 2019 to March 2020 that mentioned the bushfires and wildlife are explored. Findings The devastation of wildlife through the Australian bushfire disaster elicited emotionally charged Twitter content from both Australian and overseas users. Positive sentiment focused on offering support to areas impacted by wildlife devastation. Negative sentiment concentrated on linking the Australian bushfires disaster to global discussions surrounding the climate emergency, and a perceived lack of political action. Originality/value Despite the intensity of media attention directed towards the Australian bushfires disaster 2019–2020, there has been little scholarly research exploring social media content specifically focused on the wildlife devastation and its association with, and implications for, the tourism industry.

Cross-Linked Chitosan-Glyoxal/Kaolin Clay Composite: Parametric Optimization for Color Removal and COD Reduction of Remazol Brilliant Blue R Dye

Kaolin clay (KN) was employed as an inorganic filler to modify a cross-linked chitosan-glyoxal as Schiff’s-based chitosan composite derivative (CTS-GLY). The resulting (CTS-GLY/KN) was found to be a promising composite synthetic biopolymer that can be potentially utilized for color removal as well as COD reduction of an industrial anionic dye (remazol brilliant blue R, RBBR). The surface porosity, crystallinity, morphology, functionality, charge, and amine content of the CTS-GLY/KN were studied using BET, XRD, SEM, FTIR, pHpzc and pH-potentiometric titration analyses, respectively. Response surface methodology-Box-Behnken design (RSM-BBD) was used to optimize the impact of the main input factors on the color removal and COD reduction of RBBR. The adsorptive performance CTS-GLY/KN towards RBBR was well-defined by both Langmuir and Freundlich isotherm models with highest adsorption capacity of 447.1 mg/g at 30 °C. This finding reveals that CTS-GLY/KN can be utilized as a promising, feasible, and environmentally friendly composite-biosorbent for color removal and COD reduction of textile dyes from aqueous medium.

Complex effect of sulfur and phosphorus on the characteristics of wheel steel of KP-T brand before and after modification

The object of the research is KP-2 wheel steel modified by the Al-Mg-Si-Fe-C-Ca-Ti-Ce system. One of the most problematic places in the smelting of modern steel is the stability of the chemical composition due to the use of uncontrolled content of scrap, charge and standard modifiers, which are made by the fused method. To eliminate this problem, multifunctional modifiers were used during the study. This is due to the fact that the KP-2 steel modification method proposed in this article, has a number of features. In this case, the influence modifiers of multifunctional action on the installation of vacuum processing of steel on desulfurization of wheel steel KP-2, obtained under the conditions of the open joint-stock company Interpipe NTRP (Dnipro, Ukraine), was established. In particular, when treating a steel melt with multifunctional modifiers, not only a refining effect occurs, but also an increase in the stability of the chemical composition and level of mechanical characteristics of the KP-2 wheel steel. This is confirmed by the coefficients of variation and interfusion difference presented in the article (span), obtained by statistical processing of a large data set – 442 serial smeltings and 1 modified (6 wheels). Thanks to the multifunctional modification, the level of mechanical characteristics and the quality of the finished wheels really increases. Compared with similar mass-produced materials, such as FeSi, FeCa, FeMn, SiCa, the use of new multifunctional modifiers in KP-2 wheel steel provides a significant reduction in the mass fraction of sulfur than in the same metal that is processed in the traditional way. It has been established that the use of multifunctional modifiers changes the shape of non-metallic inclusions to globular and reduces their number, which also increases the level of mechanical properties of KP-2 wheel steel. The obtained coefficients of variation prove that the mechanical characteristics of KP-2 modified steel are more stable than in serial melts of the same steel. This will increase the demand and quality of these railway wheels.

Affective Affordances: Exploring Facebook Reactions as Emotional Responses to Hyperpartisan Political News

This research examines the key characteristics of hyperpartisan news pages on Facebook and how audiences interact with politically polarized content through the visual-emotional shorthand of Facebook Reactions. Through a quantitative content analysis of 4,236 posts shared by the most popular hyperpartisan U.S. Facebook pages before, during, and after the 2016 U.S. Presidential Election, the researchers introduce the concept of affective affordances to analyse emotional reactions elicited through Facebook Reactions in response to right- and left-leaning Facebook news posts, as well as the political topics, rhetorical devices, stylistic devices and emotionally charged content that are most likely to elicit emotional responses and inspire shares and comments from audiences in reaction to liberal and conservative content. The results are interpreted in light of the theory of affective intelligence.

Extraction, characterization and chemical functionalization of phosphorylated cellulose derivatives from Giant Reed Plant

In this work, cellulose microfibers (CMFs) and cellulose nanocrystals (P-CNCs) having phosphoric groups on their surfaces were prepared by phosphorylation of cellulose extracted from Giant Reed plant, using ammonium dihydrogen phosphate (NH4H2PO4) in a water-based urea system and phosphoric acid (H3PO4) without urea as phosphorous agents, respectively. Phosphorylated samples were studied in terms of their charge content, chemical structure, crystallinity, morphology, and thermal stability using several characterization techniques. Conductometric titration results showed higher charge content after phosphorylation with urea for P-CMFs about 3133 mmol kg−1, while without urea P-CNCs exhibited 254 mmol kg−1. FTIR analysis confirmed the total removal of non-cellulosic compounds from microfibers’ surface and their partial oxidation after phosphorylation. XRD analysis proved that the P-CMFs and P-CNCs exhibited cellulose I structure, with a crystallinity index of 70 and 83%, respectively. SEM and AFM observations showed micro-sized and needle-like morphologies for P-CMFs and P-CNCs with an average diameter of 15 µm and 20.5 nm, respectively. The thermal properties of P-CMFs indicate early dehydration with high char formation, while the high thermal stability of P-CNCs (Tmax = 352 °C) was similar to that of microcrystalline cellulose. The present work showed new routes for preparing phosphorylated micro- and nano-cellulose from a new natural source, having new functions that benefit various applications.

Reduction-sensitive polymeric micelles as amplifying oxidative stress vehicles for enhanced antitumor therapy

Chemotherapy-photodynamic therapy (PDT)-based combination therapy is a currently frequently used means in cancer treatment that photosensitizer was able to generate reactive oxygen species (ROS) for improving chemotherapy, owing to the high oxidative stress of the tumor microenvironment (TME). Whereas, cancer cells were accustomed to oxidative stress by overexpression of antioxidant such as glutathione (GSH), which would consume the damage of ROS, as well as it could result in ineffective treatment. Herein, amplification of oxidative stress preferentially in tumor cells by consuming GSH or generating ROS is a reasonable treatment strategy to develop anticancer drugs. To achieve excellent therapeutic effects, we designed a GSH-scavenging and ROS-generating polymeric micelle mPEG-S-S-PCL-Por (MSLP) for amplifying oxidative stress and enhanced anticancer therapy. The amphiphilic polymer of methoxy poly(ethylene glycol) (mPEG)-S-S-poly(ε-caprolactone) (PCL)-Protoporphyrin (Por) was self-assembled into polymeric micelles with the anticancer drug doxorubicin (DOX) for treatment and tracking via FRET. Spherical DOX/MSLP micelles with the average size of 88.76 ± 3.52 nm was procured with negatively charged surface, reduction sensitivity and high drug loading content (17.47 ± 1.53 %). The intracellular ROS detection showed that the MSLP could deplete glutathione and regenerate additional ROS. The cellular uptake of DOX/MSLP micelles was grabbed real-time monitoring by the Fluorescence resonance energy transfer (FRET) effect between DOX and MSLP. The reduction-sensitive polymeric micelles MSLP as amplifying oxidative stress vehicles combined chemotherapy and PDT exhibited significant antitumor activity both in vitro (IC50 = 0.041 μg/mL) and much better antitumor efficacy than that of mPEG-PCL-Por (MLP) micelles in vivo.

Chloroaluminate Gel Electrolytes Prepared with Copolymers Based on Imidazolium Ionic Liquids and Deep Eutectic Solvent AlCl3:Urea.

Polymer gel electrolytes (PGEs) have been prepared with copolymers based on imidazolium ionic liquids and the deep eutectic mixture of AlCl3:urea (uralumina) as liquid electrolyte. The copolymers were synthesized by photopolymerization of vinylpirrolidone or methylmethacrylate with imidazolium bis (trifluoromethane sulfonyl) imide (TFSI) ionic liquid monomer and mixed in an increasing range of wt.% with uralumina. The rheology and electrochemical activity of PGEs were highly dependent on the molar ratio of charged groups and copolymer content. Structure of the PGEs was studied by FTIR and Raman spectroscopy and a correlation between interactions polymer/uralumina and changes in speciation of uralumina was established. Despite the low molecular weight of the copolymers, the resulting polymer electrolytes develop elastomeric character associated with the binding ionic species. Although there is room to improve the electrochemical activity, in this study these new gels provide sufficient electroactivity to make them feasible alternatives as electrolytes in secondary aluminum batteries.

The influence of biochar on the content of carbon and the chemical transformations of fallow and grassland humic acids

There is limited information regarding the effect of biochar (BioC) on the fertility of fallow and grassland soils, as well as on the properties of their humic acids (HAs). The objective of this study was to evaluate with a 3-year field experiment the influence of BioC on the organic matter (OM) in Haplic Luvisol. BioC (obtained via wood waste pyrolysis at 650 °C) was applied to the soil of subplots under fallow and grassland at doses of 0, 1, 2 and 3 kg m−2. The soil samples were collected eight times. The physicochemical properties were determined for the soil and BioC by analysing the density, pH, surface charge, ash, and organic carbon content. Based on the changes in the structure of the HAs and their quantity in the soils, the chemical properties of the HAs were determined. The maximum BioC dose caused an increase in the content of Corg and HAs. BioC did not influence the humification degree coefficients of the HAs originated from fallow, whereas in the grassland, there were significant changes observed in these coefficient values, indicating that BioC may stimulate and accelerate the humification process of soil HAs. Increasing the BioC doses caused an increase in the soil’s HA content, suggesting an increase in soil sorption capacity. The fluorescence data showed BioC addition to the soil caused an increase in the number of structures characterised by low molecular weight and a low degree of humification.

Detecting fake news on Facebook: The role of emotional intelligence.

The proliferation of fake news on social media is now a matter of considerable public and governmental concern. In 2016, the UK EU referendum and the US Presidential election were both marked by social media misinformation campaigns, which have subsequently reduced trust in democratic processes. More recently, during the COVID-19 pandemic, the acceptance of fake news has been shown to pose a threat to public health. Research on how to combat the false acceptance of fake news is still in its infancy. However, recent studies have started to focus on the psychological factors which might make some individuals less likely to fall for fake news. Here, we adopt that approach to assess whether individuals who show high levels of ‘emotional intelligence’ (EQ) are less likely to fall for fake news items. That is, are individuals who are better able to disregard the emotionally charged content of such items, better equipped to assess the veracity of the information. Using a sample of UK participants, an established measure of EQ and a novel fake news detection task, we report a significant positive relationship between individual differences in emotional intelligence and fake news detection ability. We also report a similar effect for higher levels of educational attainment, and we report some exploratory qualitative fake news judgement data. Our findings are discussed in terms of their applicability to practical short term (i.e. current Facebook user data) and medium term (i.e. emotional intelligence training) interventions which could enhance fake news detection.

Exploring the Effects of Increased Charge Content on the Phase Behavior of a Protein Low Complexity Domain

Exploring the Effects of Increased Charge Content on the Phase Behavior of a Protein Low Complexity Domain

Hidden Complexities in the Phase Behavior of Low-Complexity Disordered Proteins

Liquid-liquid phase separation (LLPS) is the underlying driving force for membrane-less compartmentalization in cells. LLPS plays key roles in fundamental cell biological processes and is often mediated by disordered low-complexity domains (LCDs). How the driving forces for LLPS are encoded in LCDs and how the phase behavior can be predicted from their sequence is incompletely understood. We are using the stickers-and-spacers framework to reconstruct the full phase behavior. Stickers form non-covalent inter- and intramolecular crosslinks, whereas spacers either enable or suppress the formation of these crosslinks. We have previously shown that aromatic residues are the stickers in the polar prion-like LCD of hnRNPA1. However, the balance of tyrosine and phenylalanine residues varies across LCDs and charged residues may contribute to LLPS in sequences with higher charge content. Herein we (i) extend the stickers-and-spacers model to account for interactions of charged residues and (ii) disentangle the interaction strength of phenylalanine and tyrosine for themselves and for each other. We demonstrate that tyrosine is a stronger sticker than phenylalanine and negatively charged residues are solubilizing spacers. Arginines act as stickers through pairwise interactions with aromatic residues. Importantly, low or high values of the net charge per residue weaken the driving force for LLPS via mean-field electrostatic effects. We further demonstrate that the phase behavior correlates well with the single-chain dimensions of LCD variants with different fractions of aromatic residues, but that this correlation can be broken by mean-field electrostatic effects. Our results support that the stickers-and-spacers model can be adapted for LCDs with a wide range of sequence characteristics, promising precise prediction of phase behavior from the sequence alone.