Single Hydrogen Research Articles

Distribution and electronic structure of interstitial hydrogen atoms in β-SiC: a First-Principles study

Based on ab initio calculations, the interaction of multiple hydrogen atoms was considered with the “perfect” lattice of β-SiC as the interstitial in the neutral charge state. Starting from the single loading of hydrogen impurities on multi-atom H atoms in β-SiC, the most favorable configurations were established based on the energetic point by formation energies. The Tsc space manifests itself as the preferred option for a single hydrogen atom, and stable H2 can be available at the Tsi site. However, in the presence of H2, the subsequent loading hydrogen interstitials were expelled to the neighboring Tsc box and closed to the carbon pristine atom with C-H and Si-H bond formation at the expense of the Si-C bond cleavage. The calculated binding energy, which exhibits a pronounced increasing trend with the number of hydrogen atoms, opposes H-related cluster formation. Our results corroborate the experimental observation that no H bubbles are generated in a single crystal. Furthermore, the partial and total densities of states were calculated to facilitate the chemical characteristics and modifications of the electronic structures. The low-symmetry fields of hydrogen-related defects result in px, py, and pz orbital states of C and Si splitting, breaking away, and shifting towards the valence band, suggesting that some of the signals assigned to the impurity states appear in the pristine band gap near the new position of the Fermi level.

From Benzonitrile to Dicyanobenzenes: The Effect of an Additional CN Group on the Thermochemistry and Negative Ion Photoelectron Spectra of Dicyanobenzene Radical Anions.

The negative ion photoelectron spectra of 1,2-dicyanobenzene (o-DCNB), 1,3-dicyanobenzene (m-DCNB), and 1,4-dicyanobenzene (p-DCNB) radical anions (DCNB·-), acquired through the computation of Frack-Condon (FC) factors, are presented. The FC calculations utilize harmonic frequencies and normal mode vectors derived from density functional theory at the B3LYP/aug-cc-pVQZ basis set. All the totally symmetric vibrational modes are treated with Duschinsky rotations to yield neutral DCNBs in their singlet (So) and lowest triplet (T1) states, following an electron removal from the doublet anionic ground state. For the So state, the adiabatic electron affinities (EAs) for o-, m-, and p-DCNB are 1.179, 1.103, and 1.348 eV. The EAs for the lowest T1 state in o-, m-, and p-DCNB are 4.151, 4.185, and 4.208 eV, resulting in an So-T1 energy difference (ΔEST) of 2.973, 3.082, and 2.860 eV. A vibrational analysis reveals evidence of FC activity involving ring distortion, C-N bending, and ring C═C stretching vibrational progressions in both the So and T1 states. With the detection of cyanonaphthalene (C10H7CN) and cyanoindene (C9H7CN) in the interstellar medium (ISM), our results highlight the extent to which replacing a single hydrogen on an aromatic molecule with a cyano group, C≡N, can alter the vibrational structure of the molecule/radical anion. As such, dicyano-polyaromatic hydrocarbons may be reasonably robust in the ISM, making it appealing to search for them in future interstellar detection missions.

COCRYSTAL PREDICTION OF THE SALICYLIC ACIDNICOTINAMIDE

Salicylic acid-nicotinamide was used as a prediction model in the hydrogen bond interactions dominating a cocrystal structure. The combined conformation of the two molecules was analyzed at the B3LYP-D3BJ and WB97M-D3BJ theoretical level. The existing hydrogen bond dimer conformations were compared with putative conformations to determine the bond energy and stability. Some parameters were assessed for predictive descriptors, such as geometric parameters, total energy, interaction energy, single hydrogen bond energy, HOMO-LUMO gap, Laplacian Bond Order, and Natural Bond Orbital. An existing conformation, SACNIC1, produced intermolecular hydrogen bond energy which was quite higher than the other conformations, including the pure homomolecular conformations of either salicylic acid or nicotinamide. The cocrystal packing formation seems to be initiated with SACNIC1 as the basic structure conformation. Furthermore, the presence of the strongest intermolecular hydrogen bond energy in SACNIC1 suggests its potential utility as a predictive descriptor.

Nanoscale insights into the local structural rearrangements of amyloid-β induced by bexarotene.

A better understanding of the abnormal protein aggregation and the effect of anti-aggregation agents on the fibrillation pathways and the secondary structure of aggregates can determine strategies for the early treatment of dementia. Herein, we present a combination of experimental and theoretical studies providing new insights into the influence of the anti-aggregation drug bexarotene on the secondary structure of individual amyloid-β aggregates and its primary aggregation. The molecular rearrangements and the spatial distribution of β-sheets within individual aggregates were monitored at the nanoscale with infrared nanospectroscopy. We observed that bexarotene limits the parallel β-sheets formation, known to be highly abundant in fibrils at later phases of the amyloid-β aggregation composed of in-register cross-β structure. Moreover, we applied molecular dynamics to provide molecular-level insights into the investigated system. Both theoretical and experimental results revealed that bexarotene slows down the protein aggregation process via steric effects, largely prohibiting the antiparallel to parallel β-sheet rearrangement. We also found that bexarotene interacts not only via the single hydrogen bond formation with the peptide backbone but also with the amino acid side residue via a hydrophobic effect. The studied model of the drug-amyloid-β interaction contributes to a better understanding of the inhibition mechanism of the amyloid-β aggregation by the small molecule drugs. However, our nanoscale findings need to meet in vivo research requiring different analytical approaches.

Experimental study on plasma generated by a tapered coaxial accelerator and its damage effects on a tungsten target at different angles

Plasma wall interaction inevitably occurs during the operation of tokamaks. The coaxial gun device has low operation cost and the parameters of plasma produced by the gun are close to those of type I edge localized mode (ELM); therefore, the coaxial gun is suitable in simulation experiments as a heat flux source of transient events such as type I ELM under the condition of H-mode in the International Thermonuclear Experimental Reactor. In this paper, the plasma generated by the discharge of a tapered coaxial accelerator thermal shock on a tungsten target is used to simulate the damage effect of the divertor. The plasma parameters are measured in the experiment. The velocity of the plasma is 41.7 km s−1, and the kinetic energy of a single hydrogen ion is 9.2 eV. The energy density at the center of the plasma can reach 1.5 MJ m−2, and the density can reach about 2.78 × 1015 cm−3. The reflection of plasma in the process of exposure at different angles is observed. It is observed that droplets of millimeter size splash from the target. Traces of liquid flow are observed on the surface of the target, which shows that there is a melting process on the surface of the target. The mass loss of the target is of the order of milligrams after 20 pulses. The ablation and residual stress of the target surface both decrease with a decrease in the angle. This is because the accumulated energy per unit area of the target surface decreases with a decrease in the angle. The results of the simulation experiment help us to understand the working state around the divertor target in tokamak devices.

Remarkable enhancement in durability of ZrCo alloy against hydrogen induced disproportionation by Ti and Nb co-substitution

Considering the thermodynamic stability of various hydrides, a strategy has been employed to improve the hydrogen isotope storage properties of ZrCo alloy which involves partial co-substitution of Zr with Ti and Nb. Herein, alloys of composition Zr0.8Ti0.2-xNbxCo (x = 0.05, 0.1, 0.15) is prepared, characterized and the effect of Ti and Nb doping on hydrogen storage properties of parent ZrCo alloy is investigated. XRD analysis confirmed the formation of desired pure cubic phase of all the synthesized alloys similar to ZrCo phase. The presence of a single plateau in hydrogen desorption pressure-composition isotherms confirms single step hydrogen absorption-desorption behavior in Zr0.8Ti0.2-xNbxCo alloys. The equilibrium pressure of hydrogen desorption decreases marginally with increasing Nb content in Zr0.8Ti0.2-xNbxCo alloys which is further corroborated by differential scanning calorimetry measurements. Investigation of hydrogen induced disproportionation behavior in ITER-simulating condition revealed substantial impact of co-substitution of Ti and Nb on anti-disproportionation properties of ZrCo alloy. These remarkable properties make the Ti and Nb co-substituted quaternary alloys a desirable material for hydrogen isotope storage and delivery application.

Formation of vacancy-type defects and hydride introduced by irradiation in pure titanium

The effect of hydrogen ion irradiation on the formation of hydride and vacancy-type defects in pure titanium was investigated by X-ray diffraction (XRD), Doppler broadening spectrum (DBS), and coincidence Doppler broadening spectrum (CDB) based on slow positron beam. The XRD results showed that γ-TiH was observed in single hydrogen ion-irradiated and hydrogen + deuterium (H + D) sequentially irradiated specimens but not in the single deuterium plasma-implanted sample. This finding indicates that the vacancy-type defects caused by H ion irradiation greatly promoted the formation of γ-TiH. The DBS results showed that for the single D plasma-implanted sample, the damage peak was closer to the surface region and lower compared to the other two samples containing γ-TiH, indicating that vacancy generated by lattice distortion didn't diffuse to the depth of the matrix, and the concentration of that was smaller, which was not conducive to the deuteride formation. For the H + D sequentially irradiated sample, the number of hydrogen-vacancy complexes (HmVn) further increased compared with the single H ion-irradiated sample. Thus, the effective volume of vacancy defects was reduced, which led to the decrease in the S parameter.

Enthalpic and entropic contributions to the activation free energy of single noncovalent bonds in molecular systems: A computational methodology

Insight into enthalpic and entropic contributions to the activation free energy of noncovalent bonds is crucial for understanding various phenomena in molecular systems, from formation of different molecular conformers to complex biophysical and biochemical processes. Standard experimental and computational methods provide only the average strength of noncovalent bonds. In this paper, we present a simple, formal, computational framework to determine both energy contributions for a single bond. Our approach is based on steered molecular dynamics simulations, the dynamic force spectroscopy method, and a modified theoretical model of force-induced bond rupture. To demonstrate the methodology, the enthalpic and entropic components for a single intramolecular hydrogen bond of a peptide helix were determined. The sum of the contributions is in agreement with the previously reported Gibbs energy for intramolecular hydrogen bonds. The proposed methodological framework is universal and can be applied to other noncovalent interactions in various molecular systems.

Hydrogen bubble growth in alkaline water electrolysis: An immersed boundary simulation study

Enhancing the efficiency of industrial water electrolysis for hydrogen production is important for the energy transition. In electrolysis, hydrogen is produced at the cathode, which forms bubbles due to the diffusion of dissolved hydrogen in the surrounding supersaturated electrolyte. Hydrogen (and oxygen) bubbles play an important role in the achievable electrolysis efficiency. The growth of the bubbles is determined by diffusive and convective mass transfer. In turn, the presence and the growth of the hydrogen bubbles affect the electrolysis process at the cathode.In the present study, we simulate the growth of a single hydrogen bubble attached to a vertical cathode in a 30 wt% KOH solution in a cathodic compartment represented by a narrow channel. We solve the Navier–Stokes equations, mass transport equations and potential equation for a tertiary current distribution. A sharp interface immersed boundary method with an artificial compressibility method for the pressure is employed. To verify the numerical accuracy of the method, we performed a grid refinement study and checked the global momentum and hydrogen mass balances. We investigate the effects of flow rate and operation pressure upon bubble growth behaviour, species concentrations, potential and current density. We compare different cases in two ways: for the same time and for the same bubble radius. We observe that increasing the flow velocity leads to a small increase in efficiency. Increasing the operation pressure causes higher hydrogen density which slows down the bubble growth. For a given bubble radius, increasing the pressure leads to a small decrease in efficiency.

Towards better survival: Modeling drivers for daily mortality in Norwegian Atlantic salmon farming

Mortality in the production of farmed salmonids is a major constraint to the sustainability of this form of animal husbandry. We have developed a model for the daily mortality in salmon farming over a full production cycle from stocking to harvest, considering different environmental and production factors. These factors included sea temperature, salinity, day within year, fish weight at stocking, stocking day, four types of lice treatments and the possible occurrence of pancreas disease (PD). We considered a generalized additive model following full production cycles, allowing for non-linear descriptions of how relevant factors relate to the daily mortality. We saw a high overall mortality rate immediately after stocking, which decreased the first three months in the cycle and thereafter increased. We found that the total mortality could be reduced by 21% if avoiding all lice treatments, and similarly reduced by 20% if no PD infections occurred. If avoiding jointly PD and all lice treatments, the accumulated mortality could be reduced by 34%. A single thermal or hydrogen peroxide treatment was associated with a mortality of around 1.6% and 1.3%, respectively. This modeling approach gave a unique opportunity to model how different factors interact on the overall global mortality and can easily be extended by other factors, such as additional fish diseases.

Power Scheduling Optimization Method of Wind-Hydrogen Integrated Energy System Based on the Improved AUKF Algorithm

With the proposal of China’s green energy strategy, the research and development technologies of green energy such as wind energy and hydrogen energy are becoming more and more mature. However, the phenomenon of wind abandonment and anti-peak shaving characteristics of wind turbines have a great impact on the utilization of wind energy. Therefore, this study firstly builds a distributed wind-hydrogen hybrid energy system model, then proposes the power dispatching optimization technology of a wind-hydrogen integrated energy system. On this basis, a power allocation method based on the AUKF (adaptive unscented Kalman filter) algorithm is proposed. The experiment shows that the power allocation strategy based on the AUKF algorithm can effectively reduce the incidence of battery overcharge and overdischarge. Moreover, it can effectively deal with rapid changes in wind speed. The wind hydrogen integrated energy system proposed in this study is one of the important topics of renewable clean energy technology innovation. Its grid-connected power is stable, with good controllability, and the DC bus is more secure and stable. Compared with previous studies, the system developed in this study has effectively reduced the ratio of abandoned air and its performance is significantly better than the system with separate grid connected fans and single hydrogen energy storage. It is hoped that this research can provide some solutions for the research work on power dispatching optimization of energy systems.

Numerical simulation of hydrogen bubble growth and mass transfer on horizontal microelectrode surface under electrode-normal magnetic field

Based on our previous visual experiments and the volume of fluid (VOF) multiphase model, the growth and detachment characteristics of a single hydrogen bubble on the horizontal microelectrode surface under the electrode-normal magnetic field have been numerically investigated. The mass transfer contributions of supersaturated dissolved hydrogen to the bubble growth from the liquid microlayer under the direct injection model and from the bulk bubble interface under the gas–liquid diffusion-controlled model are adopted. The bubble shapes and diameters predicted from the numerical investigation agree well with experimental results under the same conditions. The simulated results indicate that the supersaturated dissolved hydrogen concentration and the mass transfer source at the wedge-shaped areas adjacent to the bubble foot are obviously higher than those in the wider bulk bubble interface regions. The mass transfer contribution to the bubble growth from the liquid microlayer beneath the bubble base directly plays a dominant role. The higher current density and corresponding Lorentz force mainly appears in the wedge-shaped areas, while the higher rotational electrolyte flow velocity appear at oblique positions of the bubble equator. The bubble detachment behavior makes the rotational electrolyte flows is significantly more complex.

Analytical Approaches for Deriving Friction Coefficients for Selected α-Helical Peptides Based Entirely on Molecular Dynamics Simulations.

In this paper we derive analytically from molecular dynamics (MD) simulations the friction coefficients related to conformational transitions within several model peptides with α-helical structures. We study a series of alanine peptides with various length from ALA5 to ALA21 as well as their two derivatives, the (AAQAA)3 peptide and a 13-residue KR1 peptide that is a derivative of the (AAQAA)2 peptide with the formula GN(AAQAA)2G. We use two kinds of approaches to derive their friction coefficients. In the local approach, friction associated with fluctuations of single hydrogen bonds are studied. In the second approach, friction coefficients associated with a folding transitions within the studied peptides are obtained. In both cases, the respective friction coefficients differentiated very well the subtle structural changes between studied peptides and compared favorably to experimentally available data.

Hydrogen blending in the Italian scenario: Effects on a real distribution network considering natural gas origin

Blending hydrogen into the natural gas network can help decarbonize the energy sector by supporting the penetration of renewables. Italy is an importer of natural gas whose composition and properties depend on its origin. Previous literature simulates gas networks using a set of hydrogen molar fractions regardless of the natural gas composition variability. Instead, this paper defines the maximum mixable percentage of hydrogen as a function of the gas composition underlining the importance of not adopting a single hydrogen limit. Furthermore, the paper investigates whether guaranteeing gas quality also guarantees compliance with fluid dynamic constraints on a real network. The test case consists of seven gases imported in Italy in 2019 and an urban distribution network, meshed and consisting of more than 2000 elements with medium and several low-pressure levels. A steady-state simulation of the network is performed using each of the seven gases for a winter day in the case of pure natural gas and natural gas blended with hydrogen. The results show that the highest hydrogen molar fraction mixable in these gases can range between 5.3% and 14.8% and considering the lowest percentage can reduce the decarbonization potential of the network by 1463 kg of CO2,eq. The simulations show that fluid-dynamic standards are not always met in the low-pressure networks and safety limits on pressure and velocity are exceeded at peak demand. The results also lead the authors to suggest that a modulation of pressure setpoints as a function of gas composition should be investigated.

Influence of Operating Parametres on PEM Based Ecmr for Hydrogen Production in Pressurised Condition

Hydrogen has the potential to promote the development of new, innovative and environmentally friendly solutions for future demands which would help for the smooth energy transition from fossil fuels. Though hydrogen has a high potential to replace fossil fuels, the challenges associated with the hydrogen value chain are in the production, storage, transportation and distribution stages.Electrolysis of water in PEM based system is a single step green hydrogen production process while integrated with renewable energy resources. However, this energy-intensive process makes the hydrogen production cost high and it is pave way for adopting the grey hydrogen or blue hydrogen production route as an intermediate stage for the transition from fossil fuel to hydrogen fuel economy. In this context PEM based Electrochemical Methanol Reformer (ECMR) technology has unique advantages such as low electrical energy consumption than water electrolysis and it can be easily integrated with renewable energy sources. Further, it can be operated at near ambient temperature and doesn’t require any hydrogen purification system, unlike a chemical reformer. Currently, PEM based water electrolyzer is producing pressurized hydrogen, which will eliminate the need for an external hydrogen compressor for its storage. Further, the influence of operating parameters on the operation of PEM water electrolyser under pressurised conditions is studied in the literature. However, this aspect of the study is not well studied and not much literature is available on PEM based ECMR systems. The present work, it is aimed to systematically study the effect of various operating parameters on the performance of ECMR under pressurised operation conditions and the obtained results are discussed. It shows the operation of ECMR under pressurised condition are promising and it will eliminate the need for an external H2 compressor system for hydrogen storage like PEM based water electrolyzer. Keywords: Hydrogen, PEM based Electrochemical reformer, pressurised hydrogen

Ligand Unbinding Pathway and Mechanism Analysis Assisted by Machine Learning and Graph Methods.

We present two methods to reveal protein-ligand unbinding mechanisms in biased unbinding simulations by clustering trajectories into ensembles representing unbinding paths. The first approach is based on a contact principal component analysis for reducing the dimensionality of the input data, followed by identification of unbinding paths and training a machine learning model for trajectory clustering. The second approach clusters trajectories according to their pairwise mean Euclidean distance employing the neighbor-net algorithm, which takes into account input data bias in the distances set and is superior to dendrogram construction. Finally, we describe a more complex case where the reaction coordinate relevant for path identification is a single intraligand hydrogen bond, highlighting the challenges involved in unbinding path reaction coordinate detection.

Energetics of carboxylic acid–pyridine heterosynthon revisited: A computational study of intermolecular hydrogen bond domination on phenylacetic acid–nicotinamide cocrystals

Abstract Carboxylic acid–pyridine heterosynthon (CPHS) is one of the most common synthons found in cocrystal packing. Phenylacetic acid (PYC)–nicotinamide (NIC) (PYCNIC) cocrystals were used as a computational model to assess the most important factor in the emergence of the synthon. Geometry optimization was carried out on every possible two molecules of PYC–NIC conformation based on B3LYP-D3BJ/6-311G (d,p). Various energetic parameters, including total energy, interaction energy, and hydrogen bond energy, were used to compare the existing conformation to the putative conformation. The conformation with CPHS has −53.87 kJ mol−1 of single intermolecular hydrogen bond energy (EHB), which is the strongest of all. It turns out that there is no other parameter better than EHB to describe the superiority of CPHS in PYCNIC.

Cytotoxic effects of extracts and isolated compounds from Ifloga spicata (forssk.) sch. bip against HepG-2 cancer cell line: Supported by ADMET analysis and molecular docking.

The purpose of this study was to determine the anticancer potential of Ifloga spicata (I. spicata) against HepG-2 cell line. To assess I. spicata cytoxicity, brine shrimp lethality and MTT assays were performed. In the brine shrimp bioassay, the ethyl acetate fraction had a significant impact with an IC50 of 10 μg/ml. The ethyl acetate and chloroform fractions inhibited HepG-2 cell line effectively (IC50 values 5.54 and 6.52 μg/ml, respectively). The isolated compound, heptadecyl benzoate inhibited growth significantly (IC50, 8.92 μg/ml) while methyl dihydroxybenzoate had modest activity (25.66 μg/ml) against the cell line. Both compounds displayed acceptable pharmacokinetic parameters in the ADME study. In the docking study, the methyl dihydroxybenzoate was involved in two hydrogen bonds with two different residues Thr830 and Asp831. The heptadecyl benzoate carbonyl oxygen exhibited a single hydrogen bond with Lys692. Both showed good interactions with the active site of the (EGFR) tyrosine kinase. Our findings suggest that I. spicata might be a viable source of anticancer natural agents. This discovery raises the prospect of the future development of a new medication for the treatment of liver cancer.

The effect of surface functional groups on the wettability of graphene oxide coated alumina substrate: Molecular dynamics simulations

In this article, molecular dynamic simulation was used to simulate the wetting process of graphene oxide coated alumina substrate. By changing the density of hydroxyl and epoxy groups on the surface of graphene oxide, the influence mechanism of two functional groups on the wetting process of water molecules was explored. From the simulation results, the increase of hydroxyl density can enhance the wettability of the substrate and reduce the wettability angle from 64.32° to 54.20°. By calculating the formation of the hydrogen bond in the wetting process, it is found that hydroxyl can significantly raise the hydrogen bond lifetime in the system. This increasing effect is particularly prominent in the observation of the hydrogen bond between water molecules and graphene oxide. The hydrogen bond lifetime increases from 2.20 ps to 12.77 ps. The result also reflects the reason why hydroxyl increases the wettability of the substrate. In addition, the increase of hydroxyl density also brings changes in hydrogen bond behavior and the number of hydrogen bonds. Under the condition of high epoxy density, most of the hydrogen bonds between water molecules and the substrate exist in the form of single hydrogen bonds, and the number is small. When the hydroxyl density increases, double-hydrogen bond, triple-hydrogen bond and single hydrogen bond appear in the model. In this process, the number of hydrogen bonds between the water droplet and the substrate is also increasing. Temperature is an important influence on the formation and lifetime of the hydrogen bond. High temperatures can promote the formation of the hydrogen bond between alumina and water molecules. In addition, it can also decrease the lifetime of all types of hydrogen bonds. Through the free energy perturbation theory, we get the free energy of different models in the wetting process. The results show that high hydroxyl density can improve the free energy of the wetting process, reduce the ability of spontaneous desorption and increase the stability of wetting. High temperatures can reduce the free energy and lead to the occurrence of desorption behavior. This article reveals the wetting mechanism of water molecules on graphene oxide coated alumina substrate, mainly reveals the influence of hydrogen bond and the change of free energy in the wetting process, which lays a theoretical foundation for the application of graphene oxide wetted coating on the aluminum alloy surface.

Flame structure and NOx emission characteristics in a single hydrogen combustor

In this study, the effects of fuel-induced swirl number on the flame structure and NOx emissions are observed. A tube-type nozzle with four fuel injection holes is used. The fuel injection holes are located away from the centerline of the nozzle to induce a low swirl effect in the flow. First, the flame structure changes with the fuel-induced swirl number, separating into four small flames in the high-swirl region; the flames are classified into three types. Subsequently, NOx emissions decrease with an increase in the fuel-induced swirl number. However, this shows a stepwise discontinuous change rather than a gradual change. The NOx emission is linearly proportional to the residence time of the combustion gas, which is calculated using the flame volume and flame structure. In conclusion, the change in the flame structure by the fuel-induced swirl is a decisive factor in the reduction of the NOx.