Combustion, Chemistry, and Carbon Neutrality

Combustion is a reactive oxidation process that releases energy bound in chemical compounds used as fuels─energy that is needed for power generation, transportation, heating, and industrial purposes. Because of greenhouse gas and local pollutant emissions associated with fossil fuels, combustion science and applications are challenged to abandon conventional pathways and to adapt toward the demand of future carbon neutrality. For the design of efficient, low-emission processes, understanding the details of the relevant chemical transformations is essential. Comprehensive knowledge gained from decades of fossil-fuel combustion research includes general principles for establishing and validating reaction mechanisms and process models, relying on both theory and experiments with a suite of analytic monitoring and sensing techniques. Such knowledge can be advantageously applied and extended to configure, analyze, and control new systems using different, nonfossil, potentially zero-carbon fuels. Understanding the impact of combustion and its links with chemistry needs some background. The introduction therefore combines information on exemplary cultural and technological achievements using combustion and on nature and effects of combustion emissions. Subsequently, the methodology of combustion chemistry research is described. A major part is devoted to fuels, followed by a discussion of selected combustion applications, illustrating the chemical information needed for the future.

Transport properties in liquids from first-principles: The case of liquid water and liquid argon

Shear and bulk viscosities of liquid water and argon are evaluated from first-principles in the density functional theory (DFT) framework, by performing molecular dynamics simulations in the NVE ensemble and using the Kubo–Greenwood equilibrium approach. The standard DFT functional is corrected in such a way to allow for a reasonable description of van der Waals effects. For liquid argon, the thermal conductivity has been also calculated. Concerning liquid water, to our knowledge, this is the first estimate of the bulk viscosity and of the shear-viscosity/bulk-viscosity ratio from first-principles. By analyzing our results, we can conclude that our first-principles simulations, performed at a nominal average temperature of 366 to guarantee that the systems are liquid-like, actually describe the basic dynamical properties of liquid water at about 330 K. In comparison with liquid water, the normal, monatomic liquid Ar is characterized by a much smaller bulk-viscosity/shear-viscosity ratio (close to unity) and this feature is well reproduced by our first-principles approach, which predicts a value of the ratio in better agreement with experimental reference data than that obtained using the empirical Lennard-Jones potential. The computed thermal conductivity of liquid argon is also in good agreement with the experimental value.

Molecular modeling and simulation of aqueous solutions of alkali nitrates

A set of molecular models for the alkali nitrates (LiNO3, NaNO3, KNO3, RbNO3, and CsNO3) in aqueous solutions is presented and used for predicting the thermophysical properties of these solutions with molecular dynamics simulations. The set of models is obtained from a combination of a model for the nitrate anion from the literature with a set of models for the alkali cations developed in previous works of our group. The water model is SPC/E and the Lorentz–Berthelot combining rules are used for describing the unlike interactions. This combination is shown to yield fair predictions of thermophysical and structural properties of the studied aqueous solutions, namely the density, the water activity and the mean ionic activity coefficient, the self-diffusion coefficients of the ions, and radial distribution functions, which were studied at 298 K and 1 bar; except for the density of the solutions of all five nitrates and the activity properties of solutions of NaNO3, which were also studied at 333 K. For calculating the water the activity and the mean ionic activity coefficient, the OPAS ( osmotic pressure for the activity of selvents) method was applied. The new models extend an ion model family for the alkali halides developed in previous works of our group in a consistent way.

X-ray induced electron and ion fragmentation dynamics in IBr

Characterization of the inner-shell decay processes in molecules containing heavy elements is key to understanding x-ray damage of molecules and materials and for medical applications with Auger-electron-emitting radionuclides. The 1s hole states of heavy atoms can be produced by absorption of tunable x rays and the resulting vacancy decays characterized by recording emitted photons, electrons, and ions. The 1s hole states in heavy elements have large x-ray fluorescence yields that transfer the hole to intermediate electron shells that then decay by sequential Auger-electron transitions that increase the ion’s charge state until the final state is reached. In molecules, the charge is spread across the atomic sites, resulting in dissociation to energetic atomic ions. We have used x-ray/ion coincidence spectroscopy to measure charge states and energies of I q+ and Br q′+ atomic ions following 1s ionization at the I and Br K-edges of IBr. We present the charge states and kinetic energies of the two correlated fragment ions associated with core-excited states produced during the various steps of the cascades. To understand the dynamics leading to the ion data, we develop a computational model that combines Monte-Carlo/Molecular-Dynamics (MC/MD) simulations with a classical over-the-barrier model to track inner-shell cascades and redistribution of electrons in valence orbitals and nuclear motion of fragments.

Active layer dynamics drives a transition to biofilm fingering

The emergence of spatial organisation in biofilm growth is one of the most fundamental topics in biofilm biophysics and microbiology. It has long been known that growing biofilms can adopt smooth or rough interface morphologies, depending on the balance between nutrient supply and microbial growth; this 'fingering' transition has been linked with the average width of the 'active layer' of growing cells at the biofilm interface. Here we use long-time individual-based simulations of growing biofilms to investigate in detail the driving factors behind the biofilm-fingering transition. We show that the transition is associated with dynamical changes in the active layer. Fingering happens when gaps form in the active layer, which can cause local parts of the biofilm interface to pin, or become stationary relative to the moving front. Pinning can be transient or permanent, leading to different biofilm morphologies. By constructing a phase diagram for the transition, we show that the controlling factor is the magnitude of the relative fluctuations in the active layer thickness, rather than the active layer thickness per se. Taken together, our work suggests a central role for active layer dynamics in controlling the pinning of the biofilm interface and hence biofilm morphology.

pH-Sensitive Degradable Oxalic Acid Crosslinked Hyperbranched Polyglycerol Hydrogel for Controlled Drug Release

pH-sensitive degradable hydrogels are smart materials that can cleave covalent bonds upon pH variation, leading to their degradation. Their development led to many applications for drug delivery, where drugs can be released in a pH-dependent manner. Crosslinking hyperbranched polyglycerol (HPG), a biocompatible building block bearing high end-group functionality, using oxalic acid (OA), a diacid that can be synthesized from CO2 and form highly activated ester bonds, can generate this type of smart hydrogel. Aiming to understand the process of developing this novel material and its drug release for oral administration, its formation was studied by varying reactant stoichiometry, concentration and cure procedure and temperature; it was characterized regarding gel percent (%gel), swelling degree (%S), FTIR and thermal behavior; impregnated using ibuprofen, as a model drug, and a release study was carried out at pH 2 and 7. Hydrogel formation was evidenced by its insolubility, FTIR spectra and an increase in Td and Tg; a pre-cure step was shown to be crucial for its formation and an increase in the concentration of the reactants led to higher %gel and lower %S. The impregnation resulted in a matrix-encapsulated system; and the ibuprofen release was negligible at pH 2 but completed at pH 7 due to the hydrolysis of the matrix. A pH-sensitive degradable HPG-OA hydrogel was obtained and it can largely be beneficial in controlled drug release applications.

One-step removal of hexavalent chromium in wide pH range using thiourea dioxide: the role of reactive species

One-step removal of hexavalent chromium in a wide pH range is of great significance. In this paper, a single thiourea dioxide (TD) and two-components thiourea dioxide/ethanolamine (MEA) were used as a green reducing agent for the efficient removal of Cr(vi), respectively. The reduction of Cr(vi) and the precipitation of Cr(iii) were carried out simultaneously under this reaction system. The experimental results proved that TD was activated by amine exchange reaction with MEA. In other words, MEA promoted the generation of an active isomeride of TD by changing the equilibrium position of the reversible reaction. After adding MEA, the removal rate of Cr(vi) and total Cr could reach industrial water discharge standards in a wide pH range of 8-12. The change of pH, reduction potential and the decomposition rate of TD were investigated in the reaction processes. Meanwhile, reductive and oxidative reactive species were produced simultaneously during this reaction process. Further, oxidative reactive species (O₂˙^- and ¹O₂) were beneficial for the decomplexation of Cr(iii) complexes and the formation of Cr(iii) precipitation. The experimental results also demonstrated that TD/MEA was effective in practical industrial wastewater. Hence this reaction system has a significant industrial application prospect.

Combined effect of seawater and load on methacrylate adhesive

Although the shipbuilding industry is constantly demanding new advanced joining solutions, adhesive technology is not as developed in the marine as compared to other industries. The main reason is the lack of specific knowledge that guarantees the durability of the bonded joints in optimal conditions during the life cycle of a ship. This work simulates in the laboratory a marine-like environment by immersing an adhesive in seawater and subjecting it to constant loading. The objective is to characterize the seawater absorption behavior and its consequences on the mechanical, thermal, and chemical properties of the adhesive after this aging process. Seawater ingress was determined through gravimetric tests at several load conditions of the tensile strength of the adhesive. Besides, absorption process was studied using Fick's Law, determining the diffusion coefficients. The thermal behavior was monitored with differential scanning calorimetry (DSC) and the chemical degradation was analyzed using Fourier transform infrared spectroscopy (FTIR). Also, the mechanical properties were determined by tensile tests. The surface of the adhesive (dried) was studied by Scanning Electron Microscopy (SEM) technique and the porosity was measured by physisorption with a high-performance adsorption analyzer. A numerical simulation was developed using Darcy's Law combined with continuity equation. The results show that application of loads and immersion in seawater until full saturation of seawater improve the mechanical properties of the adhesive, but it affects negatively to the glass transition temperature. This should be considered when designing adhesive bonding joints on ships.

Consequence modeling and root cause analysis (RCA) of the real explosion of a methane pressure vessel in a gas refinery

Background

The present study aimed to consequence modeling and root cause analysis of the real explosion of a methane pressure vessel in separation unit of a gas refinery in Iran.

Method

ology: This study was performed in a gas refinery in the south of Iran. The studied scenario was the actual scenario that occurred in the studied pressure vessel. Modeling of possible consequences was performed using PHAST 7.2 software. Also, the root causes analysis of the accident was performed using experts' brainstorming.

Results

At radii of 15 and 45 m, the radiation level reaches 12.5 and 4 kW/m², respectively. In the late explosion worst-case, the vapor cloud explodes after reaching a distance of 20 m from the pressure vessel. At radii of 20 m, 25 m, and 150 m from the center of the explosion, the pressure reaches 0.2068, 0.1379, and 0.02068 bar, respectively. In the Early Explosion Overpressure, the acceptable pressure is obtained at a distance of 193 m. Moreover, in the Early Explosion Overpressure radiation, at radii of 28 m, 38 m, and 193 m, the pressure reaches 0.2068, 0.1379, and 0.02068 bar, respectively.

Conclusion

The findings revealed that creating an appropriate risk management algorithm with a focus on consequence modeling can be an effective step towards reducing losses in the process industry. This results can create a novel insight in comparing the two reactive and proactive approaches and also reveal the effectiveness of consequence modeling in reducing the severity of risks.

Investigation of substituent effect on O–C bond dissociation enthalpy of methoxy group in meta- and para-substituted anisoles

This paper is focused on the theoretical investigation of O-C Bond Dissociation Enthalpy (BDE) of methoxy OCH₃ group in 15 meta- and 15 para-substituted anisoles in gas phase, non-polar environment, and water. Density Functional Theory (DFT) calculations were carried out using M06-2X functional and 6-311++G(d,p) basis set. Obtained BDEs were correlated with Brown and Okamoto σ_p⁺ and Hammett σ_m constants representing commonly used descriptors of electron-donating or electron-withdrawing substituent effect. Obtained linear dependences allow the prediction of substituent effect on BDE using σ_p⁺ and σ_m constants. Calculated reaction enthalpies were also compared with available experimental and theoretical ab initio G4 values. Found results suggest that employed method may provide reliable thermochemistry data for demethylation of naturally occurring (poly)phenolic compounds, as well. In all studied environments, substituent induced changes in O-C BDE can be considered equal to those observed for the dissociation of phenolic O-H bond of substituted phenols.

Simplex-centroid design as innovative approach in the optimization of antimicrobial effect of Thymus satureioides, Myrtus communis and Artemisia herba alba essential oils against Escherichia coli, Staphylococcus aureus and Candidatropicalis

Essential Oils (EOs) known since Antiquity, and initially obtained by maceration of aromatic plants, are used as diseases' remedies because they contain valuable therapeutic components. Antimicrobial effect's evaluation of formulations established by an augmented centered mixing plan for three Moroccan medicinal and aromatic plants' essential oils (EOs): Thymus satureioides (T. satureioides), Myrtus communis (M. communis) and Artemisia herba alba (A. herba alba) against Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) and Candida tropicalis (C. tropicalis). The identification of E.Os chemical compounds was made using Gaz chromatography (GC) and Gaz chromatography coupled to Mass spectrometry (GC/MS).Whereas, the optimization of their antimicrobial effect was performed by experimental design methodology (mixture design) coupled to microdilution method based on Minimal Inhibitory Concentrations (MICs) determination. Results showed that the main components are borneol (34.26%) and α-pinene (31.21%); borneol (27.15%) and 1,8-cineole (21.33%); camphor (14.67%), chrysanthenone (14.10%), and β-thujone (12.60%) for T. satureioides, M. communis and A. herba alba respectively. Optimal mixtures composed of 60% and 40% of T. satureioides and M. communis E.Os; 72% and 28% of T. satureioides and A. Herba alba E.Os; 75% of thyme E.O and 25% of mugwort E.O; predicted the highest antimicrobial effect against E. coli, S. aureus and C. tropicalis, respectively. This study highlights the antimicrobial effect of EOs tertiary mixtures through using mixture design methodology, which may contribute to a successful application in pharmaceutical, food, or cosmetic industries.

Antimicrobial Photodynamic Inactivation: An Alternative for Group B Streptococcus Vaginal Colonization in a Murine Experimental Model

Background: Streptococcus agalactiae, referred to as Group B Streptococcus (GBS), is a prominent bacterium causing life-threatening neonatal infections. Although antibiotics are efficient against GBS, growing antibiotic resistance forces the search for alternative treatments and/or prevention approaches. Antimicrobial photodynamic inactivation (aPDI) appears to be a potent alternative non-antibiotic strategy against GBS. Methods: The effect of rose bengal aPDI on various GBS serotypes, Lactobacillus species, human eukaryotic cell lines and microbial vaginal flora composition was evaluated. Results: RB-mediated aPDI was evidenced to exert high bactericidal efficacy towards S. agalactiae in vitro (>4 log10 units of viability reduction for planktonic and >2 log10 units for multispecies biofilm culture) and in vivo (ca. 2 log10 units of viability reduction in mice vaginal GBS colonization model) in microbiological and metagenomic analyses. At the same time, RB-mediated aPDI was evidenced to be not mutagenic and safe for human vaginal cells, as well as capable of maintaining the balance and viability of vaginal microbial flora. Conclusions: aPDI can efficiently kill GBS and serve as an alternative approach against GBS vaginal colonization and/or infections.

Study on Estimation Method of Enthalpy of Evaporation Based on Elements and Chemical Bonds

A new Group Contribution Method based on elements and chemical bonds was proposed to predict the enthalpy of evaporation of organic compounds at their normal boiling points. A prediction model was built using 1266 experimental data points, and the accuracy of the model estimations was evaluated using 16 experimental data points. The new method has only 42 groups, a simple way of group splitting, and a wide range of predictions with an average relative error of 5.84%. Furthermore, the inclusion of silicon elements and their chemical bonds in the group library enables the effective prediction of silicon-containing compounds with an average relative error of 2.71%. By analyzing and comparing the other three commonly used methods, it can be concluded that the new method provides accurate and reliable estimation results and has a more comprehensive application range.

Sub-keV corrections to binary encounter cross section models for electron ionization of liquid water with application to the Geant4-DNA Monte Carlo code

INTRODUCTION

The electron ionization cross section of water is one of the most important input in Monte Carlo studies of cellular radiobiological effects. Analytical cross section models of the binary-encounter type have the potential of reducing simulation time and facilitate application to a variety of biological materials (other than water). The Binary-Encounter-Bethe (BEB) and Binary-Encounter-Dipole (BED) models of NIST are perhaps the most popular of such models giving reliable results for atoms and molecules in the gas-phase over a wide energy range. However, the use of such models to sub-keV electron energies in liquid water raises concerns due to the neglect of condensed phase effects that leads to a significant overestimation when compared to medium-specific dielectric models.

PURPOSE

To modify the BEB and BED models towards better agreement with the recommended low-energy dielectric model of Geant4-DNA (Option 4). To implement the new modifications to the existing BEB model of the Option 6 physics constructor of Geant4-DNA and re-evaluate fundamental transport quantities for sub-keV electrons.

METHODS

In analogy to a Yukawa potential a simple, yet physically-motivated, modification of the Burgess correction term is proposed to account for the reduction of the Coulomb interaction due to the polarizability of the target. The magnitude of the correction is guided by the dielectric-based ionization cross section implemented in Option 4.

RESULTS

Differential, total and stopping ionization cross sections for low-energy electrons in liquid water are presented. When combined with the Vriens correction (which is not included in Option 6), the proposed modification to the BEB and BED models brings the ionization and stopping cross sections in much better agreement against those used in the Option 4 dielectric model of Geant4-DNA, with up to 30% and 10% deviation, respectively. Implementation of the new correction to the Option 6 constructor of Geant4-DNA and re-evaluation of fundamental transport quantities, such as electron penetration ranges and dose-point-kernels, reduced the discrepancies from Option 4 at sub-keV energies from 20 to 100% (or more) to well below 10% in most cases.

CONCLUSIONS

A simple modification to the BEB and BED analytic models was found to improve their performance for sub-keV electrons in liquid water medium. Implementation of the new modification to the Option 6 constructor of Geant4-DNA significantly improved the agreement with the recommended low-energy Option 4 constructor for a variety of fundamental quantities related to electron transport.

Unexpected thermodynamic signature for the interaction of hydroxymethylated DNA with MeCP2

Hydroxymethylated cytosine (5hmC) is a stable DNA epigenetic mark recognized by methyl-CpG binding protein 2 (MeCP2), which acts as a transcriptional regulator and a global chromatin-remodeling element. Because 5hmC triggers a gene regulation response markedly different from that produced by methylated cytosine (5mC), both modifications must affect DNA structure and/or DNA interaction with MeCP2 differently. MeCP2 is a six-domain intrinsically disordered protein (IDP) with two domains responsible for dsDNA binding: methyl-CpG binding domain (MBD) and intervening domain (ID). Here we report the detailed thermodynamic characterization of the interaction of hmCpG-DNA with MeCP2. We find that hmCpG-DNA interacts with MeCP2 in a distinctly different mode with a particular thermodynamic signature, compared to methylated or unmethylated DNA. In addition, we find evidence for Rett syndrome-associated mutations altering the interaction of MeCP2 with dsDNA in a cytosine modification-specific manner which may correlate with disease onset time and clinical severity score.

Widespread detection of chlorine oxyacids in the Arctic atmosphere

Chlorine radicals are strong atmospheric oxidants known to play an important role in the depletion of surface ozone and the degradation of methane in the Arctic troposphere. Initial oxidation processes of chlorine produce chlorine oxides, and it has been speculated that the final oxidation steps lead to the formation of chloric (HClO₃) and perchloric (HClO₄) acids, although these two species have not been detected in the atmosphere. Here, we present atmospheric observations of gas-phase HClO₃ and HClO₄. Significant levels of HClO₃ were observed during springtime at Greenland (Villum Research Station), Ny-Ålesund research station and over the central Arctic Ocean, on-board research vessel Polarstern during the Multidisciplinary drifting Observatory for the Study of the Arctic Climate (MOSAiC) campaign, with estimated concentrations up to 7 × 10⁶ molecule cm^-3. The increase in HClO₃, concomitantly with that in HClO₄, was linked to the increase in bromine levels. These observations indicated that bromine chemistry enhances the formation of OClO, which is subsequently oxidized into HClO₃ and HClO₄ by hydroxyl radicals. HClO₃ and HClO₄ are not photoactive and therefore their loss through heterogeneous uptake on aerosol and snow surfaces can function as a previously missing atmospheric sink for reactive chlorine, thereby reducing the chlorine-driven oxidation capacity in the Arctic boundary layer. Our study reveals additional chlorine species in the atmosphere, providing further insights into atmospheric chlorine cycling in the polar environment.

Antimicrobial Mechanism of Salt/Acid Solution on Microorganisms Isolated from Trimmed Young Coconut

This study investigated the inhibitory activity of organic solutions containing 5, 10, 15, 20 and 30% (w/v) sodium chloride and citric acid solution and 15:10, 15:15, 15:20 and 15:30% (w/v) sodium chloride (NaCl) combined with citric acid (CA) solution (salt/acid solution) for 10 min against microorganisms isolated from trimmed young coconut: Bacillus cereus, B. subtilis, Staphylococcus aureus, S. epidermidis, Enterobacter aerogenes, Serratia marcescens, Candida tropicalis, Lodderromyces elongisporus, Aspergillus aculeatus and Penicillium citrinum. Commercial antimicrobial agents such as potassium metabisulfite and sodium hypochlorite (NaOCl) were used as the controls. Results showed that 30% (w/v) NaCl solution displayed antimicrobial properties against all microorganisms, with s reduction range of 0.00–1.49 log CFU/mL. Treatment of 30% (w/v) CA solution inhibited all microorganisms in the reduction range of 1.50–8.43 log CFU/mL, while 15:20% (w/v) salt/acid solution was the minimum concentration that showed a similar antimicrobial effect with NaOCl and strong antimicrobial effect against Gram-negative bacteria. The mode of action of this solution against selected strains including B. cereus, E. aerogenes and C. tropicalis was also determined by scanning electron microscopy and transmission electron microscopy. B. cereus and E. aerogenes revealed degradation and detachment of the outer layer of the cell wall and cytoplasm membrane, while cytoplasmic inclusion in treated C. tropicalis cells changed to larger vacuoles and rough cell walls. The results suggested that a 15:20% (w/v) salt/acid solution could be used as an alternative antimicrobial agent to eliminate microorganisms on fresh produce.

Energetic and Electronic Properties of NpH0/+/- and PuH0/+/

High-level correlated molecular orbital theory calculations have been performed to predict the thermodynamic and electronic properties of diatomic NpH^0/+/- and PuH^0/+/-. The excited states up to ∼10,000 cm^-1 were predicted for these molecules at the multireference SO-CASPT2 level. The inclusion of spin-orbit effects is fundamental to predict the low-lying state ordering. NpH is predicted to have a ⁵Π₀ ground state, and PuH has a ⁶Π_1/2 ground state at the SO-CASPT2 level. The adiabatic electron affinities (AEAs) and ionization energies (IEs) of NpH and PuH were calculated to be 0.389 and 6.156 and 0.396 and 6.296 eV, respectively, using the Feller-Peterson-Dixon approach. The AEA increases going from AcH (0.425 eV) to ThH (0.820 eV) and decreases from ThH to PuH. The IEs of Pa-Np hydrides are close to ∼6.2 eV followed by an increase of 0.14 eV to PuH (6.296 eV). The An-H bond dissociation energy (BDE) decreases from 276.4 (AcH) to 107.1 (PuH) kJ/mol; the BDE(NpH) is ∼80 kJ/mol higher than that of PuH. Natural bond orbital calculations show that the bond character for these molecules is mainly ionic, An⁺H^-. The additional electron in NpH^- and PuH^- populates the 6d orbital, and NpH⁺ and PuH⁺ are formed by the removal of a 7s electron. The current work in conjunction with prior work on the AcH to UH in different charge states provides insights into how these properties change across the actinide series.

Core-Shell, Critical-Temperature-Suppressed V Alloy-Pd Alloy Hydrides for Hydrogen Storage—A Technical Evaluation

Hydrogen storage for energy applications is of significant interest to researchers seeking to enable a transition to lower-pollution energy systems. Two of the key drawbacks of using hydrogen for energy storage are the low gas-phase storage density and the high energy cost of the gas-phase compression. Metal hydride materials have the potential to increase hydrogen storage density and decrease the energy cost of compression by storing the hydrogen as a solid solution. In this article, the technical viability of core-shell V90Al10-Pd80Ag20 as a hydrogen storage material is discussed. LaNi5, LaNi5/acrylonitrile-butadiene-styrene copolymer mixtures, core-shell V-Pd, and core-shell V90Al10-Pd80Ag20 are directly compared in terms of reversible hydrogen-storage content by weight and volume. The kinetic information for each of the materials is also compared; however, this work highlights missing information that would enable computational dynamics modelling. Results of this technical evaluation show that V90Al10-Pd80Ag20 has the potential to increase gravimetric and volumetric hydrogen capacity by 1.4 times compared to LaNi5/acrylonitrile-butadiene-styrene copolymer mixtures. In addition, the literature shows that Pd80Ag20 and V90Al10 both have similarly good hydrogen permeabilities, thermal conductivities, and specific heats. In summary, this evaluation demonstrates that core-shell V90Al10-Pd80Ag20 could be an excellent, less-expensive hydrogen storage material with the advantages of improved storage capacity, handleability, and safety compared to current AB5-polymer mixtures.

Solvent-Controlled Quadruple Catenation of Giant Chiral [8+12] Salicylimine Cubes Driven by Weak Hydrogen Bonding

Mechanically interlocked structures are fascinating synthetic targets and the topological complexity achieved through catenation offers numerous possibilities for the construction of new molecules with exciting properties. In the structural space of catenated organic cage molecules, only few examples have been realized so far, and control over the catenation process in solution is still barely achieved. Herein, we describe the formation of a quadruply interlocked catenane of giant chiral [8+12] salicylimine cubes. The formation could be controlled by the choice of solvent used in the reaction. The interlocked structure was unambiguously characterized by single crystal X-ray diffraction and weak hydrogen bonding was identified as a central driving force for the catenation. Furthermore, scrambling experiments using partially deuterated cages were performed, revealing that the catenane formation occurs through mechanical interlocking of preformed single cages.

Solvent Induced Conversion of a Self-Assembled Gyrobifastigium to a Barrel and Encapsulation of Zinc-Phthalocyanine within the Barrel for Enhanced Photodynamic Therapy

A rare gyrobifastigium architecture (GB) was constructed by self-assembly of a tetradentate donor (L) with Pd^II acceptor in DMSO. The GB was converted to its isomeric tetragonal barrel (MB) upon treatment with water. The hydrophobic cavity of MB has been explored for the encapsulation of zinc-phthalocyanine (ZnPc), which is an excellent photosensitizer for photodynamic therapy (PDT). However, the poor water-solubility and aggregation tendency are the main reasons for the suboptimal PDT performance of free ZnPc in the aqueous medium. Effective solubilization of ZnPc in an aqueous medium was achieved by encapsulating it in the cavity of MB. The inclusion complex (ZnPc⊂MB) showed enhanced singlet oxygen generation in water. Higher cellular uptake and anticancer activity of the ZnPc⊂MB compared to free ZnPc on HeLa cells indicate that encapsulation of ZnPc in an aqueous host is a potential strategy for enhancement of its PDT activity in water.

Interaction Effect of Operating Parameters during Oxidation of Different Dyes via the Fenton Process. Application of the Plackett-Burmann Design

The interaction effect of eight operating factors on the degradation of three organic dyes of different structures (Cibacron green, methylene blue and methyl orange) has been studied. Effect had been evaluated statistically using the Plackett-Burman screening design which ex-tracted valuable information on the most important parameters and their interactions. The goodness of the model fit was checked by the determination of the coefficient R2. The process factors, which affected the degradation efficiency of dyes, were then analyzed and illustrated; the most important valueі (p and F) for three dyes proved the validity of the model. The results of interactions between the factors allow to understand and study the impact of each parameter on the elimination of dyes and to distinguish the key factor to upgrade the efficiency of the Fenton process.

Bacteriophage endolysin powders for inhaled delivery against pulmonary infections

Endolysins are bacteriophage-encoded enzymatic proteins that have great potential to treat multidrug-resistant bacterial infections. Bacteriophage endolysins Cpl-1 and ClyJ-3 have shown promising antimicrobial activity against Streptococcus pneumoniae, which causes pneumonia in humans. This is the first study to investigate the feasibility of spray-dried endolysins Cpl-1 and ClyJ-3 with excipients to produce inhalable powders. The two endolysins were individually tested with leucine and sugar (lactose or trehalose) for spray drying method followed by characterization of biological and physico-chemical properties. A complete loss of ClyJ-3 bioactivity was observed after atomization of the liquid feed solution（before the drying process）, while Cpl-1 maintained its bioactivity in the spray-dried powders. Cpl-1 formulations containing leucine with lactose or trehalose showed promising physico-chemical properties (particle size, crystallinity, hygroscopicity, etc.) and aerosol performances (fine particle fraction values above 65%). The results indicated that endolysin Cpl-1 can be formulated as spray dried powders suitable for inhaled delivery to the lungs for the potential treatment of pulmonary infections.

Chromate Incarceration by Nanojars and Its Removal from Water by Liquid-Liquid Extraction

The unprecedented liquid-liquid extraction of the dinegative chromate ion (CrO₄^2-) from neutral aqueous solutions into aliphatic hydrocarbon solvents using nanojars as extraction agents is demonstrated. Transferring chromate from water into an organic solvent is extremely challenging due to its large hydration energy (ΔG_h° = -950 kJ/mol) and strong oxidizing ability. Owing to their highly hydrophilic anion binding pockets lined by a multitude of hydrogen bond donor OH groups, neutral nanojars of the formula [cis-Cu^II(μ-OH)(μ-4-Rpz)]_n (n = 27-33; pz = pyrazolate anion; R = H or n-octyl) strongly bind the CrO₄^2- ion and efficiently transfer it from water into n-heptane or C₁₁ - C₁₃ isoalkanes (when R = n-octyl). The extracted chromate can easily be recovered from the organic layer by stripping with an aqueous acid solution. Electrospray ionization mass spectrometric, UV-vis and paramagnetic ¹H NMR spectroscopic, X-ray crystallographic, and thermal stability studies in solution and chemical stability studies toward NH₃, methanol, and Ba²⁺ ions are employed to explore the binding of the CrO₄^2- ion by nanojars. Titration of carbonate nanojars [CO₃ ⊂ {Cu(OH)(pz)}_n]^2- with H₂CrO₄ leads to anion exchange and the formation of chromate nanojars [CrO₄ ⊂ {Cu(OH)(pz)}_n]^2-. Details of chromate binding by H-bonding based on single-crystal structures of (Bu₄N)₂[CrO₄ ⊂ {Cu(OH)(pz)}₂₈], four pseudopolymorphs of (Bu₄N)₂[CrO₄ ⊂ {Cu(OH)(pz)}₃₁], and also the methoxy-substituted derivative (Bu₄N)₂[CrO₄ ⊂ {Cu₃₁(OH)₃₀(OCH₃)(pz)₃₁}] are presented.

Self-Consistent Extraction of Spectroscopic Bounds on Light New Physics

Fundamental physical constants are determined from a collection of precision measurements of elementary particles, atoms, and molecules. This is usually done under the assumption of the standard model (SM) of particle physics. Allowing for light new physics (NP) beyond the SM modifies the extraction of fundamental physical constants. Consequently, setting NP bounds using these data, and at the same time assuming the Committee on Data of the International Science Council recommended values for the fundamental physical constants, is not reliable. As we show in this Letter, both SM and NP parameters can be simultaneously determined in a consistent way from a global fit. For light vectors with QED-like couplings, such as the dark photon, we provide a prescription that recovers the degeneracy with the photon in the massless limit and requires calculations only at leading order in the small new physics couplings. At present, the data show tensions partially related to the proton charge radius determination. We show that these can be alleviated by including contributions from a light scalar with flavor nonuniversal couplings.

A Robust, Divalent, Phosphaza-bicyclo[2.2.2]octane Connector Provides Access to Cage-Dense Inorganic Polymers and Networks

While polymers containing chain or ring motifs in their backbone are ubiquitous, those containing well-defined molecular cages are very rare and essentially unknown for the inorganic elements. We report that a rigid and dinucleophilic cage (PNSiMe₃)₂(NMe)₆, which is chemically robust and accessible on a multi-gram scale from commercial precursors, serves as a linear and divalent connector that forms cage-dense inorganic materials. Reaction of the cage with various ditopic P(III) dihalide comonomers proceeded via Me₃SiCl elimination to give high molecular weight (30 000-70 000 g mol^-1), solution-processable polymers that form free-standing films. The end groups of the polymers could be tuned to engender orthogonal reactivity and form block copolymers. Networked cage-dense materials could be accessed by using PCl₃ as a tritopic P(III) linker. Detailed mechanistic studies implicate a stepwise polycondensation that proceeds via phosphino-phosphonium ion intermediates, prior to Me₃SiCl loss. Thus, metathesis between the dinucleophilic cage and polyhalides represents a general strategy to making cage-dense polymers, setting the stage for systematically understanding the consequences of the three-dimensional microstructure on macroscopic material properties.

Effects of carbonated beverages on sustained swallowing behavior changes in older inpatients

Sensory stimulation, including stimulation with carbonated liquids, has been known to influence swallowing activity. The aim of this study is to determine the effect of sustained changes in the swallowing behavior of hospitalized patients without dysphagia using the cervical auscultatory recordings of swallowing sounds. The study participants were hospitalized older adults without dysphagia. The participants were asked to initially swallow water and then a carbonated beverage. The sustained effects of the carbonated beverage in relation to swallowing movements were evaluated by measuring the swallowing sounds at the following time periods: (1) immediately and (2) at 1 to 9 minutes with intervals of 2 minutes after swallowing the carbonated beverage. The swallowing sounds before and after swallowing the same volume of water were also measured and compared on a different day. Analysis was performed to calculate the time from a sound signal to the beginning of the swallowing sound. Significant shortening of the swallowing sound time of the late pharyngeal phase was observed up to 7 minutes after swallowing the carbonated beverage, except during the 3 minutes after swallowing. Shortening of the whole swallowing sound time was observed only immediately after swallowing the carbonated beverage. Regarding the shortening of the acoustic signal in the late pharyngeal period, the effect of cerebral excitability changes due to carbonic acid stimulation was considered.

Impact of the Force Field on the Calculation of Density and Surface Tension of Epoxy-Resins

The molecular simulation of interfacial systems is a matter of debate because of the choice of many input parameters that can affect significantly the performance of the force field of reproducing the surface tension and the coexisting densities. After developing a robust methodology for the calculation of the surface tension on a Lennard-Jones fluid, we apply it with different force fields to calculate the density and surface tension of pure constituents of epoxy resins. By using the model that best reproduces the experimental density and surface tension, we investigate the impact of composition in mass fraction on uncured epoxy resins and the effects of degree of cross-linking on cured resins.

Confocal LiDAR for remote high-resolution imaging of auto-fluorescence in aquatic media

Spatially resolved in situ monitoring of plankton can provide insights on the impacts of climate change on aquatic ecosystems due to their vital role in the biological carbon pump. However, high-resolution underwater imaging is technically complex and restricted to small close-range volumes with current techniques. Here, we report a novel inelastic scanning confocal light detection and ranging (LiDAR) system for remote underwater volumetric imaging of fluorescent objects. A continuous wave excitation beam is combined with a pinhole in a conjugated detection plane to reject out-of-focus scattering and accomplish near-diffraction limited probe volumes. The combination of bi-directional scanning with remote focusing enables the acquisition of three-dimensional data. We experimentally determine the point spread and axial weighting functions, and demonstrate selective volumetric imaging of obstructed layers through spatial filtering. Finally, we spatially resolve in vivo autofluorescence from sub-millimeter Acocyclops royi copepods to demonstrate the applicability of our novel instrument in non-intrusive morphological and spectroscopic studies of aquatic fauna. The proposed system constitutes a unique tool e.g. for profiling chlorophyll distributions and for quantitative studies of zooplankton with reduced interference from intervening scatterers in the water column that degrade the the performance of conventional imaging systems currently in place.

Ultrafast Imaging of the Jahn-Teller Topography in Carbon Tetrachloride

We report the direct time-domain observation of ultrafast dynamics driven by the Jahn-Teller effect. Using time-resolved photoelectron spectroscopy with a vacuum-ultraviolet femtosecond source to prepare high-lying Rydberg states of carbon tetrachloride, our measurements reveal the local topography of a Jahn-Teller conical intersection. The pump pulse prepares a configurationally mixed superposition of the degenerate ¹T₂ 4p-Rydberg states, which then distorts through spontaneous symmetry breaking that we identify to follow the t₂ bending motion. Photoionization of these states to three cationic states ²T₁, ²T₂, and ²E reveals a shift in the center-of-mass of the photoelectron peaks associated with the ²T_n states which reveals the local topography of the Jahn-Teller conical intersection region prepared by the pump pulse. Time-dependent density functional theory calculations confirm that the dominant nuclear motion observed in the spectrum is the CCl₄ t₂ bending mode. The large density of states in the VUV spectral region at 9.33 eV of carbon tetrachloride and strong vibronic coupling result in ultrafast decay of the excited-state signal with a time constant of 75(4) fs.

Microhydration of the Pyrrole Cation (Py+) Revealed by IR Spectroscopy: Ionization-Induced Rearrangement of the Hydrogen-Bonded Network of Py+(H2O)2

Microhydration of heterocyclic aromatic molecules can be an appropriate fundamental model to shed light on intermolecular interactions and functions of macromolecules and biomolecules. We characterize herein the microhydration process of the pyrrole cation (Py⁺) by infrared photodissociation (IRPD) spectroscopy and dispersion-corrected density functional theory calculations (B3LYP-D3/aug-cc-pVTZ). Analysis of IRPD spectra of mass-selected Py⁺(H₂O)₂ and its cold Ar-tagged cluster in the NH and OH stretch range combined with geometric parameters of intermolecular structures, binding energies, and natural atomic charge distribution provides a clear picture of the growth of the hydration shell and cooperativity effects. Py⁺(H₂O)₂ is formed by stepwise hydration of the acidic NH group of Py⁺ by a hydrogen-bonded (H₂O)₂ chain with NH···OH···OH configuration. In this linear H-bonded hydration chain, strong cooperativity, mainly arising from the positive charge, strengthens both the NH···O and OH···O H-bonds with respect to those of Py⁺H₂O and (H₂O)₂, respectively. The linear chain structure of the Py⁺(H₂O)₂ cation is discussed in terms of the ionization-induced rearrangement of the hydration shell of the neutral Py(H₂O)₂ global minimum characterized by the so-called "σ-π bridge structure" featuring a cyclic NH···OH···OH···π H-bonded network. Emission of the π electron from Py by ionization generates a repulsive interaction between the positive π site of Py⁺ and the π-bonded OH hydrogen of (H₂O)₂, thereby breaking this OH···π hydrogen bond and driving the hydration structure toward the linear chain motif of the global minimum on the cation potential.

Essential Oils Distilled from Colombian Aromatic Plants and Their Constituents as Penetration Enhancers for Transdermal Drug Delivery

The study aimed to determine the enhanced effects of essential oils (EOs) and plant-derived molecules (PDMs) as penetration enhancers (PEs) for transdermal drug delivery (TDD) of caffeine. A 1% w/w solution of eight EOs and seven PDMs was included in the 1% caffeine carbopol hydrogel. Franz diffusion cell experiments were performed using mice with full-thickness skin. At various times over 24 h, 300 μL of the receptor were withdrawn and replaced with fresh medium. Caffeine was analyzed spectrophotometrically at 272 nm. The skin irritation effects of the hydrogels applied once a day for 21 days were investigated in mice. The steady-state flux (J_SS) of the caffeine hydrogel was 30 ± 19.6 µg cm^-2 h^-1. An increase in caffeine J_SS was induced by Lippia origanoides > Turnera diffusa > eugenol > carvacrol > limonene, with values of 150 ± 14.1, 130 ± 47.6, 101 ± 21.7, 90 ± 18.4, and 86 ± 21.0 µg cm^-2 h^-1, respectively. The Kp of caffeine was 2.8 ± 0.26 cm h^-1, almost 2-4 times lower than that induced by Lippia origanoides > Turnera diffusa > limonene > eugenol > carvacrol, with Kp values of 11 ± 1.7, 8.8 ± 4.2, 6.8 ± 1.7, 6.3 ± 1.2, and 5.15 ± 1.0 cm h^-1, respectively. No irritating effects were observed. Lippia origanoides, Turnera diffusa, eugenol, carvacrol, and limonene improved caffeine's skin permeation. These compounds may be as effective as the PE in TDD systems.

Surface species in direct liquid phase synthesis of dimethyl carbonate from methanol and CO2: an MCR-ALS augmented ATR-IR study

The reaction mechanism of dimethyl carbonate (DMC) production over ZrO₂ from CO₂ and CH₃OH is well-known, but the level of understanding has not improved in the last decade. Most commonly, the reaction mechanism has been explored in the gas phase, whilst DMC production occurs in the liquid phase. To overcome this contradiction, we exploited in situ ATR-IR spectroscopy to study DMC formation over ZrO₂ in the liquid phase. A multiple curve resolution-alternate least square (MCR-ALS) approach was applied to spectra collected during the CO₂/CH₃OH interaction with the catalyst surface, leading to the identification of five pure components with their respective concentration profiles. CO₂ and CH₃OH activation to carbonates and methoxide species was found to strongly depend on the reaction temperature. Low temperature prevents methanol dissociation leaving a catalyst covered with stable carbonates, whilst higher temperature decreases the stability of the carbonates and enhances the formation of methoxides. A reaction path involving the methoxide/carbonate interaction at the surface was observed at low temperature (≤50 °C). We propose that a different reaction path, independent of carbonate formation and involving the direct CO₂/methoxide interplay, occurs at 70 °C.

Protonation of serine: conformers, proton affinities and gas-phase basicities at the "gold standard" and beyond

The potential energy surfaces (PESs) of serine and its protonated counterparts are investigated to determine the structures of the minima. A total of 95 neutral serine, 15 N-(amino-) and 46 O-(carbonyl-)protonated serine conformers are found. Their relative energies, geometries and harmonic vibrational frequencies are determined at the MP2/aug-cc-pVDZ level of theory. To obtain highly accurate thermodynamic values, further computations are performed: the ten conformers with the lowest relative energies from each molecule type (neutral, N- and O-protonated) are further optimized using the explicitly correlated CCSD(T)-F12a/cc-pVDZ-F12 method (for neutral serine, harmonic vibrational frequencies were also computed). In addition, auxiliary corrections were determined: basis-set effects up to CCSD(T)-F12b/cc-pVQZ-F12, electron correlation effects up to CCSDT(Q), core correlation and second-order Douglas-Kroll relativistic effects along with zero-point energy contributions. Two important thermodynamic parameters (at 298.15 K), proton affinity (PA)/gas-phase basicity (GB) are calculated considering the two different protonation sites: 218.05 ± 0.2/209.86 ± 0.6 kcal mol^-1 and 205.87 ± 0.2/196.36 ± 0.3 kcal mol^-1 for the amino and carbonyl sites, respectively. The uncertainty of the determined values was approximated based on various sources including auxiliary corrections, basis-set effects, harmonic vibrational frequencies.

Prediction of the structures and heats of formation of MO2, MO3, and M2O5 for M = V, Nb, Ta, Pa

Structures for the mono-, di-, and tri-bridge isomers of M₂O₅ as well as those for the MO₂ and MO₃ fragments for M = V, Nb, Ta, and Pa were optimized at the density functional theory (DFT) level. Single point CCSD(T) calculations extrapolated to the complete basis set (CBS) limit at the DFT geometries were used to predict the energetics. The lowest energy dimer isomer was the di-bridge for M = V and Nb and the tri-bridge for M = Ta and Pa. The di-bridge isomers were predicted to be composed of MO₂⁺ and MO₃^- fragments, whereas the mono- and tri-bridge are two MO₂⁺ fragments linked by an O^2-. The heats of formation of M₂O₅ dimers, as well as MO₂ and MO₃ neutral and ionic species were predicted using the Feller-Peterson-Dixon (FPD) approach. The heats of formation of the MF₅ species were calculated to provide additional benchmarks. Dimerization energies to form the M₂O₅ dimers are predicted to become more negative going down group 5 and range from -29 to -45 kcal mol^-1. The ionization energies (IEs) for VO₂ and TaO₂ are essentially the same at 8.75 eV whereas the IEs for NbO₂ and PaO₂ are 8.10 and 6.25 eV, respectively. The predicted adiabatic electron affinities (AEAs) range from 3.75 eV to 4.45 eV for the MO₃ species and vertical detachment energies from 4.21 to 4.59 eV for MO₃^-. The calculated MO bond dissociation energies increase from 143 kcal mol^-1 for M = V to ∼170 kcal mol^-1 for M = Nb and Ta to ∼200 kcal mol^-1 for M = Pa. The M-O bond dissociation energies are all similar ranging from 97 to 107 kcal mol^-1. Natural bond analysis provided insights into the types of chemical bonds in terms of their ionic character. Pa₂O₅ is predicted to behave like an actinyl species dominated by the interactions of approximately linear PaO₂⁺ groups.