Shear-induced phase transition in the aqueous solution of an imidazolium-based ionic liquid

An ionic liquid (IL) is a salt in the liquid state that consists of a cation and an anion, one of which possesses an organic component. Because of their non-volatile property, these solvents have a high recovery rate, and, hence, they are considered as environment-friendly green solvents. It is necessary to study the detailed physicochemical properties of these liquids for designing and processing techniques and find suitable operating conditions for IL-based systems. In the present work, the flow behavior of aqueous solutions of an imidazolium-based IL, 1-methyl-3-octylimidazolium chloride, is investigated, where the dynamic viscosity measurements indicate non-Newtonian shear thickening behavior in the solutions. Polarizing optical microscopy shows that the pristine samples are isotropic and transform into anisotropic after shear. These shear thickened liquid crystalline samples change into an isotropic phase upon heating, which is quantified by the differential scanning calorimetry. The small angle x-ray scattering study revealed that the pristine isotropic cubic phase of spherical micelles distort into non-spherical micelles. This has provided the detailed structural evolution of mesoscopic aggregates of the IL in an aqueous solution and the corresponding viscoelastic property of the solution.

Influence of Disorder on the Bad Metal Behavior in Polar Amalgams

The two new ternary amalgams K_1-xRb_xHg₁₁ [x = 0.472(7)] and Cs_3-xCa_xHg₂₀ [x = 0.20(3)] represent two different examples of how to create ternary compounds from binaries by statistical atom substitution. K_1-xRb_xHg₁₁ is a Vegard-type mixed crystal of the isostructural binaries KHg₁₁ and RbHg₁₁ [cubic, BaHg₁₁ structure type, space group Pm3̅m, a = 9.69143(3) Å, Rietveld refinement], whereas Cs_3-xCa_xHg₂₀ is a substitution variant of the Rb₃Hg₂₀ structure type [cubic, space group Pm3̅n, a = 10.89553(14) Å, Rietveld refinement] for which a fully substituted isostructural binary Ca phase is unknown. In K_1-xRb_xHg₁₁, the valence electron concentration (VEC) is not changed by the substitution, whereas in Cs_3-xCa_xHg₂₀, the VEC increases with the Ca content. Amalgams of electropositive metals form polar metal bonds and show "bad metal" properties. By thermal analysis, magnetic susceptibility and resistivity measurements, and density functional theory calculations of the electronic structures, we investigate the effect of the structural disorder introduced by creating mixed-atom occupation on the physical properties of the two new polar amalgam systems.

Unveiling the theoretical aspects of superelectrophilic activation in an inverse demand Diels-Alder reaction

The present computational study using B3LYP functional and 6-31+G(d) basis set has been accomplished to investigate the mechanism of the inverse demand Diels-Alder reaction between pyridyl imine and propene. The highly charged dicationic superelectrophilic diene with exceptionally low-lying LUMO makes the cycloaddition reaction with propene more favorable by significantly lowering the activation energy. The Wiberg bond indices are calculated in accordance with the formation and breaking processes of bonds. The synchronicity concept is also utilized to explain the global nature of the reaction. A potential outcome of this investigation is the utilization of propene as a C₂ building block in the industry.

Hybrid Molecular Magnets with Lanthanide- and Countercation-Mediated Interfacial Electron Transfer between Phthalocyanine and Polyoxovanadate

A series of {V₁₂}-nuclearity polyoxovanadate cages covalently functionalized with one or sandwiched by two phthalocyaninato (Pc) lanthanide (Ln) moieties via V-O-Ln bonds were prepared and fully characterized for paramagnetic Ln = Sm^III-Er^III and diamagnetic Ln = Lu^III, including Y^III. The LnPc-functionalized {V₁₂O₃₂} cages with fully oxidized vanadium centers in the ground state were isolated as (nBu₄N)₃[HV₁₂O₃₂Cl(LnPc)] and (nBu₄N)₂[HV₁₂O₃₂Cl(LnPc)₂] compounds. As corroborated by a combined experimental (EPR, DC and AC SQUID, laser photolysis transient absorption spectroscopy, and electrochemistry) and computational (DFT, MD, and model Hamiltonian approach) methods, the compounds feature intra- and intermolecular electron transfer that is responsible for a partial reduction at V(3d) centers from V^V to V^IV in the solid state and at high sample concentrations. The effects are generally Ln dependent and are clearly demonstrated for the (nBu₄N)₃[HV₁₂O₃₂Cl(LnPc)] representative with Ln = Lu^III or Dy^III. Intramolecular charge transfer takes place for Ln = Lu^III and occurs from a Pc ligand via the Ln center to the {V₁₂O₃₂} core of the same molecule, whereas for Ln = Dy^III, only intermolecular charge transfer is allowed, which is realized from Pc in one molecule to the {V₁₂O₃₂} core of another molecule usually via the nBu₄N⁺ countercation. For all Ln but Dy^III, two of these phenomena may be present in different proportions. Besides, it is demonstrated that (nBu₄N)₃[HV₁₂O₃₂Cl(DyPc)] is a field-induced single molecule magnet with a maximal relaxation time of the order 10^-3 s. The obtained results open up the way to further exploration and fine-tuning of these three modular molecular nanocomposites regarding tailoring and control of their Ln-dependent charge-separated states (induced by intramolecular transfer) and relaxation dynamics as well as of electron hopping between molecules. This should enable us to realize ultra-sensitive polyoxometalate powered quasi-superconductors, sensors, and data storage/processing materials for quantum technologies and neuromorphic computing.

3-D molecular stars with covalent axial bonding

In designing three-dimensional (3-D) molecular stars, it is very difficult to enhance the molecular rigidity through forming the covalent bonds between the axial and equatorial groups because corresponding axial groups will generally break the delocalized π bond over equatorial frameworks and thus break their star-like arrangement. In this work, exemplified by designing the 3-D stars Be₂ ©Be₅ E₅ ⁺ (E = Au, Cl, Br, I) with three delocalized σ bonds and delocalized π bond over the central Be₂ ©Be₅ moiety, we propose that the desired covalent bonding can be achieved by forming the delocalized σ bond(s) and delocalized π bond(s) simultaneously between the axial groups and equatorial framework. The covalency and rigidity of axial bonding can be demonstrated by the total Wiberg bond indices of 1.46-1.65 for axial Be atoms and ultrashort Be-Be distances of 1.834-1.841 Å, respectively. Beneficial also from the σ and π double aromaticity, these mono-cationic 3-D molecular stars are dynamically viable global energy minima with well-defined electronic structures, as reflected by wide HOMO-LUMO gaps (4.68-5.06 eV) and low electron affinities (4.70-4.82 eV), so they are the promising targets in the gas phase generation, mass-separation, and spectroscopic characterization.

Radiative Recombination Plasma Rate Coefficients for Multiply Charged Ions

Radiative recombination (RR) plasma rate coefficients are often applied to estimate electron densities and temperatures under quite different plasma conditions. Despite their frequent use, however, these rate coefficients are available only for selected (few-electron) ions and isoelectronic sequences, mainly because of the computational efforts required. To overcome this limitation, we report here a (relativistic) cascade model which helps compute fine-structure and shell-resolved as well as total RR plasma rate coefficients for many, if not most, elements of the periodic table. This model is based on Jac, the Jena Atomic Calculator, and supports studies on how the electron is captured in selected levels of the recombined ion, a relativistic (Maxwellian) electron distribution, or how the multipoles beyond the electric-dipole field in the electron-photon interaction affect the RR rate coefficients and, hence, the ionization and recombination dynamics of hot plasma. As a demonstration of this model, we compute, compare, and discuss different RR plasma rate coefficients for initially helium-like ions, with an emphasis especially on Fe24+ ions.

Direct Oral FXa Inhibitors Binding to Human Serum Albumin: Spectroscopic, Calorimetric, and Computational Studies

Direct FXa inhibitors are an important class of bioactive molecules (rivaroxaban, apixaban, edoxaban, and betrixaban) applied for thromboprophylaxis in diverse cardiovascular pathologies. The interaction of active compounds with human serum albumin (HSA), the most abundant protein in blood plasma, is a key research area and provides crucial information about drugs' pharmacokinetics and pharmacodynamic properties. This research focuses on the study of the interactions between HSA and four commercially available direct oral FXa inhibitors, applying methodologies including steady-state and time-resolved fluorescence, isothermal titration calorimetry (ITC), and molecular dynamics. The HSA complexation of FXa inhibitors was found to occur via static quenching, and the complex formation in the ground states affects the fluorescence of HSA, with a moderate binding constant of 10⁴ M^-1. However, the ITC studies reported significantly different binding constants (10³ M^-1) compared with the results obtained through spectrophotometric methods. The suspected binding mode is supported by molecular dynamics simulations, where the predominant interactions were hydrogen bonds and hydrophobic interactions (mainly π-π stacking interactions between the phenyl ring of FXa inhibitors and the indole moiety of Trp214). Finally, the possible implications of the obtained results regarding pathologies such as hypoalbuminemia are briefly discussed.

Insights into the Absorption of Hydrocarbon Gases in Phosphorus-Containing Ionic Liquids

The solubility of ethane, ethylene, propane, and propylene was measured in two phosphorus-containing ionic liquids, trihexyltetradecylphosphonium bis(2,4,4-trimethylpentyl)phosphinate, [P_6,6,6,14][DiOP], and 1-butyl-3-methylimidazolium dimethylphosphate, [C₄C₁Im][DMP], using an isochoric saturation method. The ionic liquid [C₄C₁Im][DMP] absorbed between 1 and 20 molecules of gas per 1000 ion pairs, at 313 K and 0.1 MPa, while [P_6,6,6,14][DiOP] absorbed up to 169 molecules of propane per 1000 ion pairs under the same conditions. [C₄C₁Im][DMP] had a higher capacity to absorb olefins than paraffins, while the opposite was true for [P_6,6,6,14][DiOP], with the former being slightly more selective than the later. From the analysis of the thermodynamic properties of solvation, we concluded that in both ionic liquids and for all of the studied gases the solvation is ruled by the entropy, even if its contribution is unfavorable. These results, together with density measurements, 2D NMR studies, and self-diffusion coefficients suggest that the gases' solubility is ruled mostly by nonspecific interactions with the ionic liquids and that the looser ion packing in [P_6,6,6,14][DiOP] makes it easier to accommodate the gases compared to [C₄C₁Im][DMP].

Rigorous Negative Ion Binding Energies in Low-Energy Electron Elastic Collisions with Heavy Multi-Electron Atoms and Fullerene Molecules: Validation of Electron Affinities

Dramatically sharp resonances manifesting stable negative ion formation characterize Regge pole-calculated low-energy electron elastic total cross sections (TCSs) of heavy multi-electron systems. The novelty of the Regge pole analysis is in the extraction of rigorous and unambiguous negative ion binding energies (BEs), corresponding to the measured electron affinities (EAs) of the investigated multi-electron systems. The measured EAs have engendered the crucial question: is the EA of multi-electron atoms and fullerene molecules identified with the BE of the attached electron in the ground, metastable or excited state of the formed negative ion during a collision? Inconsistencies in the meaning of the measured EAs are elucidated and new EA values for Bk, Cf, Fm, and Lr are presented.

Exploring the Effect of Different Reactivity Promoters on the Oxidation of Ammonia in a Jet-Stirred Reactor

The low reactivity of ammonia (NH₃) is the main barrier to applying neat NH₃ as fuel in technical applications, such as internal combustion engines and gas turbines. Introducing combustion promoters as additives in NH₃-based fuel can be a feasible solution. In this work, the oxidation of ammonia by adding different reactivity promoters, i.e., hydrogen (H₂), methane (CH₄), and methanol (CH₃OH), was investigated in a jet-stirred reactor (JSR) at temperatures between 700 and 1200 K and at a pressure of 1 bar. The effect of ozone (O₃) was also studied, starting from an extremely low temperature (450 K). Species mole fraction profiles as a function of the temperature were measured by molecular-beam mass spectrometry (MBMS). With the help of the promoters, NH₃ consumption can be triggered at lower temperatures than in the neat NH₃ case. CH₃OH has the most prominent effect on enhancing the reactivity, followed by H₂ and CH₄. Furthermore, two-stage NH₃ consumption was observed in NH₃/CH₃OH blends, whereas no such phenomenon was found by adding H₂ or CH₄. The mechanism constructed in this work can reasonably reproduce the promoting effect of the additives on NH₃ oxidation. The cyanide chemistry is validated by the measurement of HCN and HNCO. The reaction CH₂O + NH₂ ⇄ HCO + NH₃ is responsible for the underestimation of CH₂O in NH₃/CH₄ fuel blends. The discrepancies observed in the modeling of NH₃ fuel blends are mainly due to the deviations in the neat NH₃ case. The total rate coefficient and the branching ratio of NH₂ + HO₂ are still controversial. The high branching fraction of the chain-propagating channel NH₂ + HO₂ ⇄ H₂NO + OH improves the model performance under low-pressure JSR conditions for neat NH₃ but overestimates the reactivity for NH₃ fuel blends. Based on this mechanism, the reaction pathway and rate of production analyses were conducted. The HONO-related reaction routine was found to be activated uniquely by adding CH₃OH, which enhances the reactivity most significantly. It was observed from the experiment that adding ozone to the oxidant can effectively initiate NH₃ consumption at temperatures below 450 K but unexpectedly inhibit the NH₃ consumption at temperatures higher than 900 K. The preliminary mechanism reveals that adding the elementary reactions between NH₃-related species and O₃ is effective for improving the model performance, but their rate coefficients have to be refined.

Quantum Chemical Modeling of Propellant Degradation

An ab initio quantum chemical approach for the modeling of propellant degradation is presented. Using state-of-the-art bonding analysis techniques and composite methods, a series of potential degradation reactions are devised for a sample hydroxyl-terminated-polybutadiene (HTPB) type solid fuel. By applying thermochemical procedures and isodesmic reactions, accurate thermochemical quantities are obtained using a modified G3 composite method based on the resolution of the identity. The calculated heats of formation for the different structures produced presents an ∼2 kcal/mol average error when compared against experimental values.

R2022: A DFT/MRCI Ansatz with Improved Performance for Double Excitations

A reformulation of the combined density functional theory and multireference configuration interaction method (DFT/MRCI) is presented. Expressions for ab initio matrix elements are used to derive correction terms for a new effective Hamiltonian. On the example of diatomic carbon, the correction terms are derived, focusing on the doubly excited ¹Δ_g state, which was problematic in previous formulations of the method, as were double excitations in general. The derivation shows that a splitting of the parameters for intra- and interorbital interactions is necessary for a concise description of the underlying physics. Results for ¹L_a and ¹L_b states in polyacenes and ¹A_u and ¹A_g states in mini-β-carotenoids suggest that the presented formulation is superior to former effective Hamiltonians. Furthermore, statistical analysis reveals that all the benefits of the previous DFT/MRCI Hamiltonians are retained. Consequently, the here presented formulation should be considered as the new standard for DFT/MRCI calculations.

EUV Beam–Foil Spectra of Germanium and a Blind-Spot Problem in Spectroscopy

Beam–foil extreme-ultraviolet survey spectra of Ge (Z=32) are presented. The data have been garnered at the performance limit of the heavy-ion accelerator available, with a correspondingly limited statistical and calibrational reliability. However, the Ge spectra have been recorded at various delays after excitation, and this technique points to a possible blind spot in some other spectroscopic techniques, and thus in the literature coverage. A similarly patchy coverage can be noted in various atomic structure computations. The experimental and theoretical gaps seem to be correlated.

On pyridine chloronium cations

We present the first solid-state structural evidence of mono- and bis(pyridine)chloronium cations. The latter was synthesized from a mixture of pyridine, elemental chlorine and sodium tetrafluoroborate in propionitrile at low temperatures. The mono(pyridine) chloronium cation was realized with the less reactive pentafluoropyridine, using ClF, AsF₅, and C₅F₅N in anhydrous HF. During the course of this study, we also investigated pyridine dichlorine adducts and found a surprising disproportionation reaction of chlorine that depended on the substitutional pattern of the pyridine. Electron richer dimethylpyridine (lutidine) derivatives favor full disproportionation into a positively and a negatively charged chlorine atom which forms a trichloride monoanion, while unsubstituted pyridine forms a 1 : 1 py·Cl₂ adduct.

Organo-photocatalytic C-H bond oxidation: an operationally simple and scalable method to prepare ketones with ambient air

Oxidative C-H functionalization with O₂ is a sustainable strategy to convert feedstock-like chemicals into valuable products. Nevertheless, eco-friendly O₂-utilizing chemical processes, which are scalable yet operationally simple, are challenging to develop. Here, we report our efforts, via organo-photocatalysis, in devising such protocols for catalytic C-H bond oxidation of alcohols and alkylbenzenes to ketones using ambient air as the oxidant. The protocols employed tetrabutylammonium anthraquinone-2-sulfonate as the organic photocatalyst which is readily available from a scalable ion exchange of inexpensive salts and is easy to separate from neutral organic products. Cobalt(ii) acetylacetonate was found to be greatly instrumental to oxidation of alcohols and therefore was included as an additive in evaluating the alcohol scope. The protocols employed a nontoxic solvent, could accommodate a variety of functional groups, and were readily scaled to 500 mmol scale in a simple batch setting using round-bottom flasks and ambient air. A preliminary mechanistic study of C-H bond oxidation of alcohols supported the validity of one possible mechanistic pathway, nested in a more complex network of potential pathways, in which the anthraquinone form - the oxidized form - of the photocatalyst activates alcohols and the anthrahydroquinone form - the relevant reduced form of the photocatalyst - activates O₂. A detailed mechanism, which reflected such a pathway and was consistent with previously accepted mechanisms, was proposed to account for formation of ketones from aerobic C-H bond oxidation of both alcohols and alkylbenzenes.

Initial yield of hydrated electron production from water radiolysis based on first-principles calculation

Many scientific insights into water radiolysis have been applied for developing life science, including radiation-induced phenomena, such as DNA damage and mutation induction or carcinogenesis. However, the generation mechanism of free radicals due to radiolysis remains to be fully understood. Consequently, we have encountered a crucial problem in that the initial yields connecting radiation physics to chemistry must be parameterized. We have been challenged in the development of a simulation tool that can unravel the initial free radical yields, from physical interaction by radiation. The presented code enables the first-principles calculation of low energy secondary electrons resulting from the ionization, in which the secondary electron dynamics are simulated while considering dominant collision and polarization effects in water. In this study, using this code, we predicted the yield ratio between ionization and electronic excitation from a delocalization distribution of secondary electrons. The simulation result presented a theoretical initial yield of hydrated electrons. In radiation physics, the initial yield predicted from parameter analysis of radiolysis experiments in radiation chemistry was successfully reproduced. Our simulation code helps realize a reasonable spatiotemporal connection from radiation physics to chemistry, which would contribute to providing new scientific insights for precise understanding of underlying mechanisms of DNA damage induction.

Destabilization of Pickering emulsions by interfacial transport of mutually soluble solute

HYPOTHESIS

Pickering emulsions (PEs) once formed are highly stable because of very high desorption energies (∼10⁷ k_BT) associated with particles adsorbed to the interfaces. The destabilization of PEs is required in many instances for recovery of valuable chemicals, products and active compounds. We propose to exploit interfacial instabilities develop by the addition of different types of solutes to PEs as a route to engineer their destabilization.

EXPERIMENTS

PEs stabilized by (i) spherical particles, (ii) non-spherical particles, (iii) oppositely charged particle-particle mixtures, and (iv) oppositely charged particle-polyelectrolyte mixtures are formulated. Different types of solutes are added to these highly stable PEs and the macroscopic as well as microscopic changes induced in the PEs is recorded by visual observation and bright field optical microscopy.

FINDINGS

Our results point to a simple yet robust method to induce destabilization of PEs by transiently perturbing the oil-water interface by transport of a mutually soluble solute across the interface. The generality of the method is demonstrated for different kind of solutes and stabilizers including particles of different sizes (nm to µm), shapes (sphere, spheroids, spherocylinders) and types (polystyrene, metal oxides). The method works for both oil-in-water (o/w) and water-in-oil (w/o) PEs with different kinds of non-polar solvents as oil-phase. However, the method fails when the solute is insoluble in one of the phases of PEs. The study opens up a new approach to destabilization of particle stabilized emulsions.

Utilization of delactosed whey permeate for the synthesis of ethyl acetate with Kluyveromyces marxianus

Ethyl acetate is an important organic solvent and currently produced from fossil carbon resources. Microbial synthesis of this ester from sugar-rich waste could be an interesting alternative. Therefore, synthesis of ethyl acetate by Kluyveromyces marxinanus DSM 5422 from delactosed whey permeate (DWP) was studied in an aerated stirred bioreactor at 40 °C. DWP is mainly composed of residual lactose and minerals. The minerals inhibited yeast growth, as witnessed by an increased lag period, a reduced growth rate, and an extended process duration. All experiments were therefore carried out with diluted DWP. In a series of batch experiments, the pH of iron-deficient DWP medium varied between 4.8 and 5.9. The pH of the cultivation medium significantly influenced cell growth and product syntheses, with the highest ethyl acetate yield of 0.347 g g^-1 and lowest by-product formation achieved at pH 5.1. It is likely that this effect is due to pH-dependent iron chelation, which affects the iron bioavailability and the intracellular iron content, thus affecting growth and metabolite synthesis. The viability of yeast cells was always high despite the harsh conditions in DWP medium, which enabled extended usage of the biomass in repeated-batch and fed-batch cultivations. These two culture techniques increased the volume of DWP processed per time by 32 and 84% for the repeated-batch and the fed-batch cultivation, respectively, without a drop of the ester yield. KEY POINTS: • Delactosed whey permeate was converted to ethyl acetate with a high rate and yield. • The formation of ethyl acetate in DWP medium at iron limitation is pH-dependent. • Highly active yeasts from batch processes enabled extension as fed and repeated batch.

Nanodiamond-promoted white light emission in Eu, Dy, and Cu-containing phosphate glass: quantitative analysis and colorimetric study

A thorough analysis of glass containing Eu₂ O₃ and Dy₂ O₃ , or Eu₂ O₃ , Dy₂ O₃ , and CuO melted together with nanodiamond powder was pursued based on measurements of optical absorption, photoluminescence (PL) emission and excitation spectra, and colorimetry. Nanodiamond facilitated the stabilization of Cu⁺ and Eu²⁺ ions with blue-emitting characteristics that, along with yellow-emitting Dy³⁺ and red-emitting Eu³⁺ led to the white light-emitting glass. Novel intensity notations implemented in intensity-based spectral ratios, and difference intensity correlation analysis were proposed for the assessment of PL properties. The chromaticity and correlated colour temperature of the emission were ultimately investigated as a two-parametric problem based on: (1) the different ionic components; and (2) the various excitation wavelengths employed. The optical analysis approach adds to the characterization methods to further fundamental understanding and provide helpful analytical tools for designing materials for tunable white light-emitting devices.

Prediction of osteoporotic degradation of tibia human bone at trabecular scale

A theoretical numerical model is proposed to predict patient dependent osteoporotic bone degradation. The model parameters are identified through a particle swarm optimization algorithm and based on individual patient high resolution peripherical quantitative computer tomography (HRpQCT) scan data. The degradation model is based on cellular activity initiated by the elastic strain energy developed in the bone microstructure through patient's body weight. The macro (organ scale) and meso (trabecular scale) scale analyses are carried out and predicted bone volume fraction and microstructure evolution are compared with in-vivo experimental bone degradation for four elderly women over a period of 10 years. A significant correlation (r > 0.9) is observed between the model predictions and in-vivo experiments in all cases with an average deviation error of 1.46%. The model can easily be extended to other patients and provide good predictions for different population categories such as ethnicity, gender, age, etc.

A Review: Aeration Efficiency of Hydraulic Structures in Diffusing DO in Water

This paper contemplates the review of aeration efficiency with commonly used different aeration systems such as Venturi flumes, Weirs, Conduits, Stepped channels, In Venturi Aeration, the SAE value grows fast with the number of air holes. In Weir Aeration, it was found that among all the different labyrinth weir structure, triangular notch weirs are known for the optimum results for air entrainment. The ANN model was developed with parameters discharge (Q) and tail water depth (T_w) which showed that Q is more influential parameter than T_w. In conduits structure, it was found that circular high head gated conduits have better aeration performance than other conduits. Aeration efficiency in Stepped channels cascades may range from 30% to 70%. The sensitivity analysis with ANN model showed that discharge (Q) followed by number of steps (N) was the most influential parameter in E₂₀. Bubble size was the important parameter to undertake when using bubble diffuser. The oxygen transfer efficiency (OTE) in jet diffusers was predicted developing an ANN model. It was found in sensitivity analysis that the input of 'velocity' is highly sensitive to OTE. According to literature, jets can provide OTE in the range of 1.91- 21.53kgO₂/kW-hr.

Measurement and Prediction of Molar Volumes of Bivalent Metal Sulfates and Their Mixtures in Aqueous Solution

Densities of aqueous solutions of MnSO$$_4$$ 4 , CoSO$$_4$$ 4 , NiSO$$_4$$ 4 and CuSO$$_4$$ 4 have been measured by vibrating tube densimetry up to near-saturation concentrations over the temperature range 293.15 $$\le T/$$ ≤ T / K $$\le $$ ≤ 343.15 at 5 K intervals and at 0.1 MPa pressure. Apparent molar volumes, $$V_\phi $$ V ϕ , calculated from the densities revealed close similarities among all four electrolytes, with their $$V_\phi $$ V ϕ values essentially differing by constant concentration-independent addends for each salt at each temperature. It was found that there is an almost linear relationship between $$V_\phi $$ V ϕ (MSO$$_4$$ 4 ,aq) and the M–O bond length of the hydrated cations obtained from structural studies. This relationship can be used to predict values of $$V_\phi $$ V ϕ (MSO$$_4$$ 4 ,aq) for other sulfate salts over wide ranges of concentration and temperature, providing that the requisite structural data are available. Measurements of selected ternary, quaternary and quinary mixtures of these electrolytes at constant total concentrations showed that their $$V_\phi $$ V ϕ values almost always exhibit linear mixing (Young’s rule) behavior at all temperatures investigated. This finding can be exploited to predict the volumetric properties of solutions containing complex mixtures of bivalent metal sulfates.

Dramatic effect of the nature of R on the intrinsic acidity and basicity of potential astrochemical R–C≡COH and R–C≡CSH compounds

The effect of changing the nature of the R substituent from the first row (H, Li, BeH, BH2, CH3, NH2, OH and F) to second row (Na, MgH, AlH2, SiH3, PH2, SH and Cl) on the intrinsic acidity and basicity of R–C≡COH and R–C≡CSH compounds was investigated through the use of G4 high-level ab initio calculation. The variation of the acidity and basicity of the R–C≡CSH derivatives as a function of R is practically parallel to that found for the corresponding R–C≡COH analogs; though the basicities of the former are 9–14% higher than those of the latter, the acidity gap being very small (~ 2%). When this analysis is extended to the derivatives in which the triple CC bond is replaced by a double or single bond, it is found that the acidity gap increases systematically as the CC bond goes from triple to single; whereas, as expected for the basicity, the trend is the opposite. Quite surprisingly, however, the variation of the basicity of R–C≡CX (X = OH, SH) compounds with the nature of the first-row substituents, R, is remarkably different from that produced by the second-row analogs. The same is observed as far as intrinsic acidities are concerned. These dissimilarities reflect the rather different changes in the strength of the CC and the CX (X = OH, SH) bonds when a first-row substituent is replaced by the second-row analog, as reflected in the atoms in molecules (AIM), natural bond orbital (NBO) and the electron localization function (ELF) analyses of the corresponding species.

Dynamics and hydrodynamic efficiency of diving beetle while swimming

Diving beetle, an excellent biological prototype for bionic underwater vehicles, can achieve forward swimming, backward swimming, and flexible cornering by swinging its two powerful hind legs. An in-depth study of the propulsion performance of them will contribute to the micro underwater vehicles. In this paper, the kinematic and dynamic parameters, and the hydrodynamic efficiency of the diving beetle are studied by analysis of swimming videos using Motion Capture Technology, combined with CFD simulations. The results show that the hind legs of diving beetle can achieve high propulsion force and low return resistance during one propulsion cycle at both forward and backward swimming modes. The propulsion efficiencies of forward and backward swimming are 0.47 and 0.30, respectively. Although the efficiency of backward swimming is lower, the diving beetle can reach a higher speed in a short time at this mode, which can help it avoid natural enemies. At backward swimming mode, there is a long period of passive swing of hind legs, larger drag exists at higher speed during the recovery stroke, which reduces the propulsion efficiency to a certain extent. Reasonable planning of the swing speed of the hind legs during the power stroke and the recovery stroke can obtain the highest propulsion efficiency of this propulsion method. This work will be useful for the development of a bionic propulsion system of micro underwater vehicle.

Needles to Spheres: Evaluation of inkjet printing as a particle shape enhancement tool

Active pharmaceutical ingredients (APIs) often reveal shapes challenging to process, e.g. acicular structures, and exhibit reduced bioavailability induced by slow dissolution rate. Leveraging the API particles' surface and bulk properties offers an attractive pathway to circumvent these challenges. Inkjet printing is an attractive processing technique able to tackle these limitations already in initial stages when little material is available, while particle properties are maintained over the entire production scale. Additionally, it is applicable to a wide range of formulations and offers the possibility of co-processing with a variety of excipients to improve the API's bioavailability. This study addresses the optimization of particle shapes for processability enhancement and demonstrates the successful application of inkjet printing to engineer spherical lacosamide particles, which are usually highly acicular. By optimizing the ink formulation, adapting the substrate-liquid interface and tailoring the heat transfer to the particle, spherical particles in the vicinity of 100 µm, with improved flow properties compared to the bulk material, were produced. Furthermore, the particle size was tailored reproducibly by adjusting the deposited ink volume per cycle and the number of printing cycles. Therefore, the present study shows a novel, reliable, scalable and economical strategy to overcome challenging particle morphologies by co-processing an API with suitable excipients.

Emissions and fate of organophosphate esters in outdoor urban environments

Cities are drivers of the global economy, containing products and industries that emit many chemicals. Here, we use the Multimedia Urban Model (MUM) to estimate atmospheric emissions and fate of organophosphate esters (OPEs) from 19 global mega or major cities, finding that they collectively emitted ~81,000 kg yr^-1 of ∑₁₀OPEs in 2018. Typically, polar "mobile" compounds tend to partition to and be advected by water, while non-polar "bioaccumulative" chemicals do not. Depending on the built environment and climate of the city considered, the same compound behaves like either a mobile or a bioaccumulative chemical. Cities with large impervious surface areas, such as Kolkata, mobilize even bioaccumulative contaminants to aquatic ecosystems. By contrast, cities with large areas of vegetation fix and transform contaminants, reducing loadings to aquatic ecosystems. Our results therefore suggest that urban design choices could support policies aimed at reducing chemical releases to the broader environment without increasing exposure for urban residents.

Unraveling the initial steps of the ignition chemistry of the hypergolic ionic liquid 1-ethyl-3-methylimidazolium cyanoborohydride ([EMIM][CBH]) with nitric acid (HNO3) exploiting chirped pulse triggered droplet merging

The composition of the products and the mechanistic routes for the reaction of the hypergolic ionic liquid (HIL) 1-ethyl-3-methylimidazolium cyanoborohydride ([EMIM][CBH]) and nitric acid (HNO₃) at various concentrations from 10% to 70% were explored using a contactless single droplet merging within an ultrasonic levitation setup in an inert atmosphere of argon to reveal the initial steps that cause hypergolicity. The reactions were initiated through controlled droplet-merging manipulation triggered by a frequency chirp pulse amplitude modulation. Utilizing the high-speed optical and infrared cameras surrounding the levitation process chamber, intriguing visual images were unveiled: (i) extensive gas release and (ii) temperature rises of up to 435 K in the merged droplets. The gas development was validated qualitatively and quantitatively with Fourier Transform Infrared Spectroscopy (FTIR) indicating the major gas-phase products to be hydrogen cyanide (HCN) and nitrous oxide (N₂O). The merged droplet was also probed by pulsed Raman spectroscopy which deciphered features for key functional groups of the reaction products and intermediates (-BH, -BH₂, -BH₃, -NCO); reaction kinetics revealed that the reaction was initiated by the interaction of the [CBH]^- anion of the HIL with the oxidizer (HNO₃) through proton transfer. Computations indicate the formation of a van-der-Waals complex between the [CBH]^- anion and HNO₃ initially, followed by proton transfer from the acid to the anion and subsequent extensive isomerization; these rearrangements were found to be essential for the formation of HCN and N₂O. The exoergicity observed during the merging process provides a molar enthalpy change up to 10 kJ mol^-1 to the system, which could be sufficient for a significant fraction of the reactants of about 11% to overcome the reaction barriers in the individual steps of the computationally determined minimum energy pathways.

Colloidal aspects of calcium carbonate scaling in water-in-oil emulsions: A fundamental study using droplet-based microfluidics

HYPOTHESIS

As a mainstream process in the extraction and recovery of crude oil, water is injected into reservoirs in the so-called waterflooding process to facilitate the oil displacement through the wellbore, typically generating water-in-oil (W/O) emulsions. Based on economic considerations, sea water is used in the flooding process; however, the ionic incompatibility between the injected water and the formation water inside the reservoir may precipitate sparingly-soluble inorganic salts (scale). We hypothesize that calcium carbonate (CaCO₃) scale dynamically interacts with cationic surfactants in W/O emulsions, resulting in (i) scale growth retardation and (ii) emulsion destabilization.

EXPERIMENTS

We developed stable W/O emulsions via combining droplet-based microfluidics with multifactorial optimizations to investigate the influence of emulsion properties, such as surfactant type and concentrations, temperature, and pH, as well as calcium ions on the CaCO₃ scaling kinetics and emulsion stability. The CaCO₃ scale was characterized based on particle size and charge, lattice structure, interactions with the surfactant, and time-dependent effects on emulsion stability.

FINDINGS

The interfacial interactions between the cationic surfactant (cetyltrimethylammonium bromide, CTAB) and CaCO₃ retarded scale growth rate, decreased crystal size, and destabilized emulsion within hours as a result of surfactant depletion at the water-oil interface. The surfactant did not affect the crystal structure of scale, which was formed as the most thermodynamically stable crystalline polymorph, calcite, at the ambient condition. This fundamental study may open new opportunities for engineering stable W/O emulsions, e.g., for enhanced oil recovery (EOR), and developing scale-resistant multiphase flows.

Effects of incoming particle energy and cluster size on the G-value of hydrated electrons

In hydrated electron (e^-_aq) dosimetry, absorbed radiation dose to water is measured by monitoring the concentration of radiation-induced e^-_aq. However, to obtain accurate dose, the radiation chemical yield of e^-_aq, G(e^-_aq), is needed for the radiation quality/setup under investigation. The aim of this study was to investigate the time-evolution of the G-values for the main generated reactive species during water radiolysis using GEANT4-DNA. The effects of cluster size and linear energy transfer (LET) on G(e^-_aq) were examined. Validity of GEANT4-DNA for calculation of G(e^-_aq) for clinically relevant energies was studied. Three scenarios were investigated with different phantom sizes and incoming electron energies (1 keV to 1 MeV). The time evolution of G(e^-_aq) was in good agreement with published data and did not change with decreasing phantom size. The time-evolution of the G-values increases with increasing LET for all radiolytic species. The particle tracks formed with high-energy electrons are separated and the resulting reactive species develop independently in time. With decreasing energy, the mean separation distance between reactive species decreases. The particle tracks might not initially overlap but will overlap shortly thereafter due to diffusion of reactive species, increasing the probability of e^-_aq recombination with other species. This also explains the decrease of G(e^-_aq) with cluster size and LET. Finally, if all factors are kept constant, as the incoming electron energy increases to clinically relevant energies, G(e^-_aq) remains similar to its value at 1 MeV, hence GEANT4-DNA can be used for clinically relevant energies.