Divalent Calcium Research Articles

Catalytic efficiency of copper nanoparticles modified silica-alginate hydrogel nanocomposite towards reduction of water pollutants and H2 generation

In the present study, a viscous solution of sodium alginate polymer (Alg) containing dispersed silica (Si) was prepared for the fabrication of hydrogel beads. It was added dropwise into a divalent calcium (Ca+2) ions solution which convert each drop into a hydrogel bead i.e, Si@AlgBD. In the next step, the outer surface of the Si@AlgBDs were modified with five different types of metal. As a result, it gives five types of metal coated M+n/Si@AlgBDs catalyst. These coated M+n [M+n = Ag+, Ni+2, Fe+3, Co+2, and Cu+2] were converted into zero-valent metal nanoparticles (MNPs) [M0 = Ag0, Ni0, Fe0, Co0, and Cu0] by NaBH4, which act as a strong reducing agent. Firstly, all catalysts were analyzed for the reduction of 4-NP to 4-AP to check out the efficiency of catalysts. Among which the reduction rate was higher for Cu0/Si@AlgBDs catalyst and was chosen for further study. Secondly, the Cu0/Si@AlgBDs catalyst was examined for the decolorization of 2-nitrophenol (2-NP), 2,6-dinitrophenol (2,6-DNP), methyl orange (MO), congo red (CR), and acridine orange (ArO). Additionally, its catalytic reduction was analyzed for the reduction of 4-NP to 4-AP in different quality of water sources. The highest reduction rate of 6.207 × 10−1 and 8.619 × 10−1 min−1 was calculated for CR and 4-NP, respectively. Beside its catalytic reduction, the same catalyst was evaluated for the generation of H2 gas from NaBH4 through methanolysis. Where, the lowest Ea energy of 25.9 kJ/mol was calculated at room temperature. In both experimental procedures i.e, catalytic reduction and H2 production, different parameters, such as, catalyst dosage, different amount of the NaBH4, initial concentration of the 4-NP, and temperature effect for the H2 production were studied in detail. Similarly, the hydrogel beads were characterized by SEM, EDX, and ICP-OES to identify and find out the successful incorporation of MNPs on Si@AlgBDs. Finally, the recyclability of the catalyst was also investigated.

A Study on the Effects of Calcium Lactate on the Gelling Properties of Large Yellow Croaker (Pseudosciaena crocea) Surimi by Low-Field Nuclear Magnetic Resonance and Raman Spectroscopy

Divalent calcium ions (Ca2+) are often used in surimi gels to improve their physicochemical characteristics. The present study aimed to investigate the effect of calcium lactate on the physicochemical properties, state distribution of water, and protein structure changes of surimi gels made from large yellow croaker. The results showed that the addition of calcium lactate (0%, 0.5%, 1.5%, 2.5%, 3.5%, and 4.5% on wet surimi) significantly (p < 0.05) increased gel strength and whiteness, while cooking loss decreased. The water-holding capacity increased first and then decreased. When calcium lactate was added to 1.5%, the water-holding capacity reached the best value. Using low-field nuclear magnetic resonance to study the distribution of water state, the bound water content first increased and then decreased with the addition of calcium lactate, reaching the highest at 1.5%. In addition, the relaxation time of immobilized water was shortest at the addition of 1.5% calcium lactate. Analyzing the protein structural changes by Raman spectroscopy showed that there was a significant decrease (p < 0.05) in the α-helix accompanied by an increase in β-sheets, turns, and random coils after the addition of calcium lactate. The above changes were due to the Ca2+ that was bound to the negatively charged myofibrils to form a protein-Ca2+-protein cross-linking. Therefore, the addition of calcium lactate had a significant positive effect on the gelling ability of surimi.

Differential effects of magnesium, calcium, and sodium on Listeria monocytogenes biofilm formation

Listeria monocytogenes is a gram-positive foodborne pathogen that causes outbreaks of listeriosis associated with a diverse range of foods. L. monocytogenes forms biofilms as a strategy to enhance its survival in the environment. These biofilms then provide a source of contamination in processing plant environments. Cations like magnesium, calcium, and sodium are commonly found in the environment and are important to bacteria to maintain their homeostasis. It is, therefore, valuable to understand the relationship between these cations and biofilm formation. In this study, four isolates of L. monocytogenes from seafood processing environments were used to investigate the influence of magnesium, calcium, and sodium (1, 10, and 50 mM) on biofilms. The isolates selected were defined as being either a low biofilm former, a high biofilm former, an outbreak isolate, and a persistent isolate from the seafood industry. The study showed that the divalent cations magnesium and calcium increased biofilm formation compared with the monovalent cation, sodium. Fifty mM concentrations of the divalent cations significantly enhanced biofilm formation. The cations did not have a significant effect on the initial stages of biofilm formation but appeared to influence the later stages of biofilm development.

Interpretable learning of voltage for electrode design of multivalent metal-ion batteries

Deep learning (DL) has indeed emerged as a powerful tool for rapidly and accurately predicting materials properties from big data, such as the design of current commercial Li-ion batteries. However, its practical utility for multivalent metal-ion batteries (MIBs), the most promising future solution of large-scale energy storage, is limited due to scarce MIB data availability and poor DL model interpretability. Here, we develop an interpretable DL model as an effective and accurate method for learning electrode voltages of multivalent MIBs (divalent magnesium, calcium, zinc, and trivalent aluminum) at small dataset limits (150–500). Using the experimental results as validation, our model is much more accurate than machine-learning models, which usually are better than DL in the small dataset regime. Besides the high accuracy, our feature-engineering-free DL model is explainable, which automatically extracts the atom covalent radius as the most important feature for the voltage learning by visualizing vectors from the layers of the neural network. The presented model potentially accelerates the design and optimization of multivalent MIB materials with fewer data and less domain-knowledge restriction and is implemented into a publicly available online tool kit in http://batteries.2dmatpedia.org/ for the battery community.

Chalcogenolato-bridged rhenium(I)-based ester functionalized flexible dinuclear metallacrown ethers: Cation binding, molecular recognition and docking studies

Chalcogenolato-bridged Re(I)-based dinuclear metallacrown ethers [{(CO)3Re(µ-ER)2Re(CO)3}(µ-L)] (E = S, Se; R = tolyl, benzyl) (1–4) were accomplished in a single-step process by the self-assembly of rudimentary dirhenium decacarbonyl, ditolyl disulfide/dibenzyl diselenide, and flexible ditopic polyether tethered ester functionalized pyridyl ligands [L = 4-pyridine carboxylic acid triethylene glycol diester (pcatrgd) and 4-pyridine carboxylic acid tetraethylene glycol diester (pcatgd)]. A series of chalcogenolato-bridged Re(I)-based dinuclear metallacrown ethers were synthesized via oxidative addition of RE−ER unit to the (CO)5Re−Re(CO)5 bond with simultaneous incorporation of flexible ditopic polyether tethered pyridyl linker in an orthogonal fashion. The dinuclear metallacrown ethers 1–4 were characterized by IR, UV−Vis, NMR, and ESI-Mass spectrometric techniques and elemental analysis. The molecular structural elucidation of 1 was carried out using single-crystal X-ray diffraction analysis. Furthermore, the metallacrown ethers 1–4 were investigated for the cation binding potential with monovalent (lithium, sodium, and potassium) and divalent (magnesium and calcium) cations using UV–vis absorption spectroscopic method. In addition, the molecular recognition studies of the metallacrown ethers 1 and 3 as hosts were performed with aromatic amine and alcohol as guests. Moreover, in silico molecular docking studies were carried out for the compounds 1–4 with KasA protein (PDB ID: 2WGD).

Rare‐earth Metal Substitution in Calcium Germanides with the Tetragonal Cr5B3 Type Structure

AbstractCalcium germanides with two mid‐late rare‐earth metals, Ca5−xGdxGe3 and Ca5−xTbxGe3 (x≈0.1−0.2), have been synthesized and structurally characterized. Additionally, a lanthanum‐rich germanide with calcium substitutions, La5−xCaxGe3 (x≈0.5) has also been identified. The three structures have been established from single‐crystal X‐ray diffraction methods and confirmed to crystallize with the Cr5B3‐type in the tetragonal space group I4/mcm (no. 140; Z=4; Pearson symbol tI32), where part of the germanium atoms are interconnected into Ge2‐dimers, formally [Ge2]6−. Rare‐earth metal and calcium atoms are arranged in distorted trigonal prisms, square‐antiprisms and cubes, centered by Ge or rare‐earth/calcium metal atoms. These studies show that the amount of trivalent rare‐earth metal atoms substituting divalent calcium atoms is in direct correlation with the lengths of the Ge−Ge bond within the Ge2‐dimers, with distance varying between 2.58 Å in Ca5−xGdxGe3 and 2.75 Å in La5−xCaxGe3. Such an elongation of the Ge−Ge bond is consistent with the notion that the parent Ca5Ge3 Zintl phase (e. g. (Ca2+)5[Ge2]6−[Ge4−]) is being driven out of the ideal valence electron count and further reduced. In this context, this work demonstrates the ability of the germanides with the Cr5B3 structure type to accommodate substitutions and wider valence electron count while maintaining their global structural integrity.

3d oxidized alginate-porcine liver acellular collagen droplets for tumor microenvironment mimicking

The traditional 2d culture has been proved inferior to reproduce the subtle interaction between cell-to-cell and cell-to-extracellular matrix (ECM) in tumor microenvironment (TME) and collagen in ECM contributes to various malignancies of tumors. Hence, the 3d model contained with collagen may overcome the shortcomings of 2d culture. In this study, the in vitro TME mimicking matrix was prepared by coupling porcine liver-derived collagen (COL) and the dialdehyde group of partially oxidized alginate (OA), namely OA-COL, and the 3d OA-COL droplets were polymerized by divalent calcium ions. In the 3d OA-COL droplets, cancer cells displayed vigorous proliferation, and the cells grew in clusters and formed a unique spindle like clone. Quantitative analysis proved that various gene transcription and protein expression were up-regulated for the cells in the 3d OA-COL droplets, including F-actin reassembling, focal adhesion, pseudopodia formation, and the proteins involved in epithelial-to-mesenchymal transition (EMT). The 3d OA-COL droplets induced the cells with strengthened polarity, invasiveness, higher IC50, and manifested stronger tumorigenicity in vivo. The fabricated 3d OA-COL droplets reproduced a variety of TME parameters, constructed an in vitro model similar to the TME in vivo, and it may facilitate many investigations in cell biology and tumor biology.

Calcium Ion-Sodium Alginate-Piperine-Based Microspheres: Evidence of Enhanced Encapsulation Efficiency, Bio-Adhesion, Controlled Delivery, and Oral Bioavailability of Isoniazid.

Isoniazid (INH) is a first-line chemotherapeutic drug employed in the management of tuberculosis. However, its extensive first-pass metabolism, short-life life, and low oral bioavailability confined its medical application. Therefore, the calcium ion-alginate-piperine microspheres (INH-CaSP Ms) was prepared to enhance encapsulation efficiency, controlled delivery, and oral bioavailability of INH. The INH-CaSP Ms was developed using a modified emulsification method and optimized via Box-Behnken design (BBD). Optimized INH-CaSP Ms were characterized for encapsulation efficiency, differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FT-IR), bio-adhesion, in vitro dissolution, ex vivo permeation, and oral bioavailability studies. Characterization studies confirmed the formation of microspheres. The INH-CaSP Ms showed spherical microspheres with enhanced encapsulation efficiency (~ 93.03 ± 1.54% w/w). The optimized INH-CaSP Ms exhibited higher bio-adhesion around (~ 81.41 ± 1.31%). The INH-CaSP Ms enhanced the dissolution rate of INH (~ 57%) compared to pure INH (~ 57%) and INH-SA Ms (~ 81%) in simulated gastric fluid (SGF, pH 1.2) and simulated intestinal fluid (SIF, pH 7.4). The same formulations improved the permeation rate of INH (~ 90%) compared to pure INH (~ 55%) and INH-SA Ms (~ 80%). The oral bioavailability results indicated that INH-CaSP Ms appreciably improved the oral bioavailability of INH via increasing the Cmax, Tmax, t1/2, and AUC parameters compared to pure INH. The study demonstrates that the development of INH-CaSP Ms via cross-linked coordinate bond interaction between divalent cation calcium ion-alginate complex and anion piperine bio-enhancer is an effective approach for enhancing the encapsulation efficiency, bio-adhesion, controlled release, and oral bioavailability of INH.

Student explorations of calcium alginate bead formation by varying pH and concentration of acidic beverage juices

Abstract Teaching experiments involving edible, biodegradable calcium alginate beads serve as an attractive model system to introduce upper secondary age students to core chemistry topics through innovations in sustainable consumer products. A teaching experiment is described that engages students with the synthesis of calcium alginate hydrogel beads from sodium alginate and calcium lactate, two food-safe and renewable materials. The beads’ outer membranes are a result of ionic interactions between carboxylate groups from alginate strands and the divalent calcium cations between them, thus forming cross-linked polymers. Protonation of the carboxylate groups on the alginate strands decreases crosslinking density affecting bead formation. First, various concentrations of citric acid are used to lower the pH of the sodium alginate solution and the effect on the calcium alginate bead formation is observed. A correlation between pH and bead shape and firmness is derived. This information is then used to explore juices with varying natural acidities. The experiment is amenable to implementation in the classroom or as an at-home activity. Learning outcomes include acid-base reactions, chemical bonding, polymer structures, and green chemistry concepts. Students consider the environmental challenges of traditional plastics used in packaging and how innovative new commercial products are attempting to provide solutions.

Calcium Substitution in Rare‐earth Metal Germanides with the Gd 5 Si 4 Type Structure

An extended series of rare-earth metal calcium germanides have been synthesized and structurally characterized. The compounds have the general formula RE5−xCaxGe4 (1.5<x<3.6; RE=rare-earth metal; Ce, Nd, Sm, Tb−Lu) and their structures have been established from single-crystal X-ray diffraction methods. They crystallize with the Gd5Si4-type in the orthorhombic space group Pnma (No. 62; Z=4; Pearson symbol oP36), where the germanium atoms are interconnected into two kinds of Ge2-dimers, formally [Ge2]6−. These studies show that Ca can be successfully incorporated into the host RE5Ge4 structure, whereby trivalent rare-earth metal atoms can be substituted by divalent calcium atoms. Rare-earth metal and calcium atoms are arranged in distorted trigonal prisms and cubes, centered by either Ge or Ca atoms. On one of the metal sites, the substitution is preferential and in 9 out of the 10 refined structures, the Wyckoff site 4c is found almost exclusively occupied by Ca. On the other two metal sites the substitution patterns appear to be governed by the mismatch between the size of the RE3+ and Ca2+ ions. This work further demonstrates the ability for the Gd5Si4 structure type to accommodate the substitution of a non-magnetic element while maintaining the global structural integrity.

Rhamnolipid Biosurfactants for Oil Recovery: Salt Effects on the Structural Properties Investigated by Mesoscale Simulations.

Rhamnolipids (RLs) are biosurfactants produced by Pseudomonas. The biodegradability and the variety of their functionality make them suitable for environmental remediation and oil recovery. We use dissipative particle dynamics simulations to investigate the aggregation behaviors of ionic RL congeners with nonane in various operating conditions. Under zero-salinity conditions, all RL congeners studied here form small ellipsoidal clusters with detectable free surfactants. When salt ions are present, the electrostatic repulsion between the ionized heads is overcome, resulting in the formation of larger aggregates of unique structures. RLs with C10-alkyl tails tend to form elongated wormlike micelles, while RLs with C16-alkyl tails tend to form clusters in spherical symmetry, including vesicles. Di-rhamnolipids (dRLs) require stronger solvation than monorhamnolipids (mRLs) to form clusters, and the resulting size of micelles is decreased. The morphology of the mixed dRL/mRL/oil systems is controlled based on the type of the congeners and the oil contents. In addition, the divalent calcium ions are found to be influential to the structure of the micelles through different mechanisms. For 5 wt % salinity, the ionic RLs can form oil-swollen micelles up to a 1:1 surfactant-to-oil ratio, suggesting that ionic RLs are superb to act as cleaning agents for petroleum hydrocarbons in the marine area. These key findings may guide the design for RL-based washing techniques in enhanced oil recovery.

The Electrostatic Basis of Diacylglycerol Pyrophosphate-Protein Interaction.

Diacylglycerol pyrophosphate (DGPP) is an anionic phospholipid formed in plants, yeast, and parasites under multiple stress stimuli. It is synthesized by the phosphorylation action of phosphatidic acid (PA) kinase on phosphatidic acid, a signaling lipid with multifunctional properties. PA functions in the membrane through the interaction of its negatively charged phosphomonoester headgroup with positively charged proteins and ions. DGPP, like PA, can interact electrostatically via the electrostatic-hydrogen bond switch mechanism but differs from PA in its overall charge and shape. The formation of DGPP from PA alters the physicochemical properties as well as the structural dynamics of the membrane. This potentially impacts the molecular and ionic binding of cationic proteins and ions with the DGPP enriched membrane. However, the results of these important interactions in the stress response and in DGPP’s overall intracellular function is unknown. Here, using 31P MAS NMR, we analyze the effect of the interaction of low DGPP concentrations in model membranes with the peptides KALP23 and WALP23, which are flanked by positively charged Lysine and neutral Tryptophan residues, respectively. Our results show a significant effect of KALP23 on the charge of DGPP as compared to WALP23. There was, however, no significant effect on the charge of the phosphomonoester of DGPP due to the interaction with positively charged lipids, dioleoyl trimethylammonium propane (DOTAP) and dioleoyl ethyl-phosphatidylcholine (EtPC). Divalent calcium and magnesium cations induce deprotonation of the DGPP headgroup but showed no noticeable differences on DGPP’s charge. Our results lead to a novel model for DGPP—protein interaction.

Managing CO2 levels through precipitation-based capture from seawater and electrochemical conversion

With the rise in global greenhouse gas emissions, many studies have sought methods to reduce the accumulation of carbon dioxide (CO2) in the atmosphere. Existing methodologies are primarily based on amine solvents such as monoethanolamine (MEA) and 2-amino-2-methylpropanol (AMP) due to their high carbon absorption capacity and good recyclability. As such, they are used for the capture of CO2 from sequestration sites and its subsequent electrochemical transformation. However, because amines have large enthalpies of reaction, this leads to expensive and energy-intensive processes that limit their capacity for large-scale application. Thus, this study seeks to develop an electrochemical device that can sustain efficient CO2 capture and conversion through precipitation. The dissolved inorganic divalent cation calcium (Ca,2+) reacts with carbon to form carbonate (CO32-) compounds that flow through a thin membrane, facilitating the filtration of the precipitate. We hypothesized that higher alkalinity will produce a greater quantity of CO2 capture, as measured by the change in seawater pH and the mass of precipitate formed. The CO32- compound is, in turn, converted to the industrial fuel formic acid (HCOOH). Through our experimentation, we found a statistically significant difference between the measured pH of seawater before and after CO2 capture (p &amp;lt; 0.001), thus suggesting this setup as a proof of concept for the effective reduction of ocean acidification. Additionally, we observed an upwards trend as higher concentrations of sodium hydroxide (NaOH) were generally associated with greater changes in pH.

Active site characterization and activity of the human aspartyl (asparaginyl) β-hydroxylase.

Human aspartyl/asparaginyl beta-hydroxylase (HAAH) is a member of the superfamily of nonheme Fe2+/α-ketoglutarate (αKG) dependent oxygenase enzymes with a noncanonical active site. HAAH hydroxylates epidermal growth factor (EGF) like domains to form the β-hydroxylated product from substrate asparagine or aspartic acid and has been suggested to have a negative impact in a variety of cancers. In addition to iron, HAAH also binds divalent calcium, although the role of the latter is not understood. Herein, the metal binding chemistry and influence on enzyme stability and activity have been evaluated by a combined biochemical and biophysical approach. Metal binding parameters for the HAAH active site were determined by use of isothermal titration calorimetry, demonstrating a high-affinity regulatory binding site for Ca2+ in the catalytic domain in addition to the catalytic Fe2+ cofactor. We have analyzed various active site derivatives, utilizing LC-MS and a new HPLC technique to determine the role of metal binding and the second coordination sphere in enzyme activity, discovering a previously unreported residue as vital for HAAH turnover. This analysis of the in vitro biochemical function of HAAH furthers the understanding of its importance to cellular biochemistry and metabolic pathways.

Calcium in Signaling: Its Specificity and Vulnerabilities toward Biogenic and Abiogenic Metal Ions.

Divalent calcium ion (Ca2+) plays an indispensable role as a second messenger in a myriad of signal transduction processes. Of utmost importance for the faultless functioning of calcium-modulated signaling proteins is their binding selectivity of the native metal cation over rival biogenic/abiogenic metal ion contenders in the intra/extracellular fluids. In this Perspective, we summarize recent findings on the competition between the cognate Ca2+ and other biogenic or abiogenic divalent cations for binding to Ca2+-signaling proteins or organic cofactors. We describe the competition between the two most abundant intracellular biogenic metal ions (Mg2+ and Ca2+) for Ca2+-binding sites in signaling proteins, followed by the rivalry between native Ca2+ and "therapeutic" Li+ as well as "toxic" Pb2+. We delineate the key factors governing the rivalry between the native and non-native cations in proteins and highlight key implications for the biological performance of the respective proteins/organic cofactors.

Copper alginate surface for perpetual Self-Polishing and Anti-Biofouling compound release

Biofouling is a severe problem for many applied technical surfaces ranging from ships and piers to water inlets and medicine. Here we investigate the physical–chemical properties of divalent copper and divalent calcium alginate bulk films and their anti-biofouling properties on the example of Chlorella vulgaris and in a natural river water environment. Physical-chemical characterization includes mechanical characterization of different mixing ratios, oil contact angles, and equilibrium water contents, self-polishing properties and copper ion release of copper alginate and copper-calcium alginate compositions. The results prove highly composition dependent physical–chemical properties. This causes highly composition dependent antibiofouling properties against Chlorella vulgaris, which changes significantly over time due to copper ion release and self-polishing resulting into up to 100 times lower biofouling compared to glass slides. Extending the test to river water, less Chlorella vulgaris compared to pure Chlorella vulgaris solution were determined. The total biofouling, which reached however, saturation of 25% and 35% coverage for copper, and calcium alginate respectively, which is comparable to glass.

Assessment of enhanced oil recovery by osmotic pressure in unconventional reservoirs: Application to Niobrara chalk and Codell sandstone

The ultimate oil recovery from liquid-rich unconventional reservoirs is less than ten percent, thus a great interest in developing enhanced oil recovery (EOR) methods that can increase oil production from such reservoirs economically. Classical waterflooding in unconventional reservoirs is not plausible because of the small pore sizes and low permeability of shale reservoirs. However, when low-salinity water enters the stimulated reservoir micro-fractures an osmotic pressure gradient forms because of the salinity contrast between fracture and matrix and the nanometer size of pore throats (nano- and micro-fractures are a consequence of rock deformation instigated by hydraulic fracturing in shale reservoirs). Even in oil-wet shale reservoirs, osmotic pressure prevails—leading to brine imbibition into the matrix and generating a counter-current flow of oil from the matrix into the fractures. We also recognize that a fraction of the imbibition into the cores is due to capillary pressure while much of the imbibition results from capillary osmosis. In summary, we present a novel method to measure osmotic pressure in core samples. The method was applied to cores from Niobrara and Codell formations in the DJ basin. The osmotic pressure leads to EOR in laboratory cores and could impact EOR in shale reservoirs because of the large volume of low-salinity ‘slickwater’ fracturing fluid used for well completion.In the experiments, we used solvent-extracted clean cores, KCl brine (40,000 ppm), decane, an imbibition cell, and a high-speed centrifuge. It is important to know that we chose and used a pure hydrocarbon component (decane) for the oil, and a simple brine (KCl) for the water in our experiments so the increased low-salinity brine’s larger imbibition magnitude would not be attributed to the wettability alteration as shown by Haagh et al. [11]. For wettability alteration to take place, the oil should contain asphaltenes and some acidic components. Also, brine should contain divalent calcium, magnesium, and other specific ions which are beyond the scope of this study.Osmotic pressures, measured in low permeability shale cores, plus a precise thermodynamic calculation of the activity coefficients enabled us to calculate the ‘membrane efficiency’ of the cores. In our experiments, we used a high-speed centrifuge, first to saturate the cores with formation brine; second, we injected oil into the core to displace brine (1st drainage cycle); third, we allowed spontaneous imbibition of brine into the core; fourth, we conducted force imbibition displacement of the oil with brine until core reaches residual oil saturation. Because osmotic pressure is the difference between the high-salinity and low-salinity spontaneous imbibition capillary pressures, the experimental process was repeated using low-salinity brine. Lastly, we determined the produced oil during low-salinity experiments as a measure of the EOR. Finally, osmotic pressures measured in the low permeability shale cores, plus the calculated activity coefficients, enabled us to calculate ‘membrane efficiency’ of the cores. For the Codell sandstone, with permeability of 0.0085 to 0.0105 mD, the calculated membrane efficiency was 2.4%. Similarly, for the Niobrara B-chalk, with permeability of 0.0022 to 0.0099 mD, the membrane efficiency was 74.9%. This high recovery is attributed to the pore structure of Niobrara chalk vs. that of Codell sandstone.

Effects of divalent cations on Schaffer collateral axon function.

Previously, we reported that distal Schaffer collaterals undergo biphasic changes in excitability during high-frequency stimulation (HFS), with an early hyper-excitability period followed by an excitability depression period. The extracellular divalent cations calcium and magnesium can regulate membrane excitability in neuronal tissue. Therefore, we hypothesized that altering the concentrations of extracellular calcium and magnesium would alter the biphasic excitability changes. We tested this hypothesis by recording distal Schaffer collateral fiber volleys in stratum radiatum of hippocampal area CA1 during 100Hz HFS in artificial cerebral spinal fluid (ACSF) containing normal and altered concentrations of extracellular divalent cations. Our normal ACSF contained 2.0mM calcium and 2.0mM magnesium. We examined four solutions with altered divalent cation concentrations: (1) high-calcium/low-magnesium (3.8mM/0.2mM), (2) low-calcium/high-magnesium (0.2mM/3.8mM), (3) high-calcium/normal-magnesium (3.8mM/2.0mM), or (4) normal-calcium/high-magnesium (2.0mM/10.0mM), and assessed the effects on Schaffer collateral responses. Increasing or decreasing extracellular calcium enhanced or reduced (respectively) the early hyper-excitable period whereas increasing extracellular magnesium reduced the later excitability depression. Because these results might be explained by altered calcium influx through voltage-gated calcium (CaV) channels, we tested CaV blockers (ω-agatoxin IVA, ω-conotoxin-GVIA, cadmium), but observed no effects on responses during HFS. Some of the effects of altered divalent cation concentration may be explained by altered membrane surface charge. Although this mechanism does not completely explain our findings, calcium influx through CaV channels is not required.

Effect of charge balancing cations on the viscoelastic and thermal properties of welan

Welan is a branched polymer in the gellan family of polysaccharides. It has good compatibility with divalent calcium ions with a potential use in cementing applications. It is also been utilized as an anti-washout material for underwater concrete placement. Herein, influence of divalent cations Ca2+, Ni2+, Mg2+, Zn2+ and Sr2+ on the gelling and thermal properties of welan have been investigated. The viscoelastic properties reveal strong gelation behavior that are stable up to 80 °C. Among all the five cations Ni2+, Ca2+, Zn2+ and Sr2+ are suited well, compared to Mg2+ ions, to promote favorable interactions among the welan chains leading to stronger junction zones and elastic moduli. The melting peak and enthalpy are dependent on the nature and size of the divalent cation. The outcome is deemed to aid to expand the welan utility in food and non-food applications.

Inhaled Water and Salt Suppress Respiratory Droplet Generation and COVID-19 Incidence and Death on US Coastlines

Dry air alters salt and water balance in the upper airways and increases the risks of COVID-19 among other respiratory diseases. We explored whether such upper airway variations in salt and water balance might alter respiratory droplet generation and potentially contribute to observed impacts of airway hydration on respiratory disease. In a randomized 4-arm study of 21 healthy human subjects we found that the breathing of humid air, the wearing of cotton masks, and the delivery of (sodium, calcium, and magnesium chloride) salt droplets sized to deposit in the nose, trachea, and main bronchi similarly reduce the exhalation of respiratory droplets by approximately 50% ([Formula: see text] &lt; 0.05) within 10 minutes following hydration. Respiratory droplet generation returns to relatively high baseline levels within 60–90 minutes on return to dry air in all cases other than on exposure to divalent (calcium and magnesium) salts, where suppression continues for 4–5 hours. We also found via a preliminary ecological regression analysis of COVID-19 cases in the United States between January 2020 and March 2021 that exposure to elevated airborne salt on (Gulf and Pacific) US coastlines appears to suppress by approximately 25%–30% ([Formula: see text] &lt; 0.05) COVID-19 incidence and deaths per capita relative to inland counties — accounting for ten potential confounding environmental, physiological, and behavioral variables including humidity. We conclude that the hydration of the upper airways by exposure to humidity, the wearing of masks, or the breathing of airborne salts that deposit in the upper airways diminish respiratory droplet generation and may reduce the risks of COVID-19 incidence and symptoms.