Internal Hydrogen Research Articles

Optimization of an Inter-Plant Hydrogen Network: A Simultaneous Approach to Solving Multi-Period Optimization Problems

Inter-plant hydrogen integration can reduce the consumption of hydrogen utility in petrochemical parks. However, the fluctuation of operating conditions will lead to complex multi-period problems of hydrogen network integration. This work develops a simultaneous optimization approach to solving multi-period optimization problems for the inter-plant hydrogen network. To do this, we consider the inter-plant hydrogen integration and the fluctuation of operating conditions in each plant at the same time, and aim to minimize the total annualized cost of the entire hydrogen system of all plants involved. An industrial case study of a three-plant hydrogen network with seven subperiods was adopted to verify the effectiveness of the proposed method. Results show that the optimal structure and the corresponding scheduling scheme can be obtained when the lowest cost of the system is targeted. Compared with the stepwise methods, the proposed approach features taking the characteristics of all subperiods into account simultaneously and making the structure of the hydrogen network much more effective and economical. For the scheduling schemes, the utilization efficiency of the internal hydrogen sources is increased by hydrogen exchange among the plants.

The Influence of Carbon Nature on the Catalytic Performance of Ru/C in Levulinic Acid Hydrogenation with Internal Hydrogen Source.

The influence of the nature of carbon materials used as a support for Ru/C catalysts on levulinic acid hydrogenation with formic acid as a hydrogen source toward gamma-valerolactone was investigated. It has been shown that the physicochemical properties of carbon strongly affect the catalytic activity of Ru catalysts. The relationship between the hydrogen mobility, strength of hydrogen adsorption, and catalytic performance was established. The catalyst possessing the highest number of defects, stimulating metal support interaction, exhibited the highest activity. The effect of the catalyst grain size was also studied. It was shown that the decrease in the grain size resulted in the formation of smaller Ru crystallites on the catalyst surface, which facilitates the activity.

SPT analysis of hydrogen embrittlement in CrMoV welds

In this paper Small Punch Tests (SPT) are used to determine the mechanical properties of the heat affected zone (HAZ) of CrMoV welded joints and to evaluate the embrittlement caused by the presence of internal hydrogen. Hydrogen permeation tests were carried out to determine the effective diffusion coefficients of the different regions of welded joints, whose hydrogen contents were measured using a hydrogen analyser.The paper demonstrates that SPTs can be used to estimate the tensile properties and the toughness of small areas, such as the subzones of a welded joint which are not thick enough for machining standard specimens. In cases where it is not possible to determine the fracture toughness of brittle regions using standard SPT samples, tests using longitudinally notched SPT samples were conducted. The normalized energy at failure, W/t2, was selected as the most appropriate SPT parameter to estimate the fracture toughness regardless of the fracture behaviour of the material (ductile or brittle). It was seen that the fracture toughness of the fine grained HAZ (FG-HAZ) is similar to that of the Base Metal (BM), while the fracture toughness of the coarse grained HAZ (CG-HAZ) is more similar to that of the Weld Metal (WM). The effect of hydrogen on BM and FG-HAZ is low, with embrittlement indexes of about 20%. However, a strong effect of hydrogen was observed in CG-HAZs and WMs, with embrittlement indexes of 60–80%. and a clear change from ductile to brittle behaviour in their fracture surfaces.

Influence of Hydrogen Bonding on Low Critical Micellar Concentration Value and Formation of Giant Vesicle of Triazole‐Contained Amphiphile

AbstractAn amphiphile molecule consisting of triazole moiety has been thoroughly investigated using different approaches in its aqueous condition. The studies have discovered the explicit function of its heteroaromatic ability in molecular self‐assembling. From the fluorescence evidence, the triazole‐based amphiphile has shown that the aggregation‐induced emission behavior is mainly due to the triazolyl. It suggests that the triazole is directly involved in the self‐assembling mechanism through an intermolecular interaction. This interaction can be verified by the shifting of proton frequency of the triazole, which is clearly shown by the constant frequency of the proton above the critical micellar concentration (CMC) value. The frequency suggests the establishing hydrogen bond that occurred between the hydrogen and the second nitrogen of the adjacent triazole. These results are consistent with the micellization of the molecule which was determined at a very low CMC value (0.1 mM). The absorbance and optical polarizing microscopy results also support the evidence of the growth of giant vesicles produced from the neutralization of the amphiphile. The formation of stable giant vesicles at neutral pH demonstrates the immediate strong hydrogen bonding connections within the triazoles layer in the bilayer. The discovery reveals that internal hydrogen bonds formed from a heteroaromatic with the appropriate molecular arrangement can promote self‐aggregation and enhance overall stability.

Effect of microstructural and environmental variables on ductility of austenitic stainless steels

Austenitic stainless steels are used extensively in harsh environments, including for high-pressure gaseous hydrogen service. However, the tensile ductility of this class of materials is very sensitive to materials and environmental variables. While tensile ductility is generally insufficient to qualify a material for hydrogen service, ductility is an effective tool to explore microstructural and environmental variables and their effects on hydrogen susceptibility, to inform understanding of the mechanisms of hydrogen effects in metals, and to provide insight to microstructural variables that may improve relative performance. In this study, hydrogen precharging was used to simulate high-pressure hydrogen environments to evaluate hydrogen effects on tensile properties. Several austenitic stainless steels were considered, including both metastable and stable alloys. Room temperature and subambient temperature tensile properties were evaluated with three different internal hydrogen contents for type 304L and 316L austenitic stainless steels and one hydrogen content for XM-11. Significant ductility loss was observed for both metastable and stable alloys, suggesting the stability of the austenitic phase is not sufficient to characterize the effects of hydrogen. Internal hydrogen does influence the character of deformation, which drives local damage accumulation and ultimately fracture for both metastable and stable alloys. While a quantitative description of hydrogen-assisted fracture in austenitic stainless steels remains elusive, these observations underscore the importance of the hydrogen-defect interactions and the accumulation of damage at deformation length scales.

Producing long afterglow by cellulose confinement effect: A wood-inspired design for sustainable phosphorescent materials

Embedding luminogens into a well-selected rigid matrix has been a particularly attractive way of preparing long afterglow materials. On this basis, seeking green, low-cost and sustainable materials or strategies, remains challenging but desirable. Prompted by the generation of wood fluorescence, a general strategy for preparing long afterglow materials successfully developed by embedding biomass-derived carbon dots into cellulose fibrils. Internal hydrogen bonding interactions between cellulose fibrils and carbon dots strongly erected a confinement effect for protecting the triplet exciton from quenching, leading to an increase of phosphorescence lifetime by seven orders of magnitude. These properties, which originated from such a green and convenient approach, were able to match most of reported long afterglow examples. Moreover, thanks to the humidity sensitivity of cellulose, the materials can behave a unique humidity-dependent phosphorescence property, showing superior potential application in advanced anti-counterfeiting and encryption.

Ni-Pd/γ-Al2O3 Catalysts in the Hydrogenation of Levulinic Acid and Hydroxymethylfurfural towards Value Added Chemicals

γ-Al2O3 supported Ni-Pd catalysts with different Ni:Pd ratios were studied in the hydrogenation of two industrially-relevant platform molecules derived from biomass, namely levulinic acid and hydroxymethylfurfural. The bimetallic catalysts showed better performances in both processes in comparison to the monometallic counterparts, for which a too strong interaction with the alumina support reduced the activity. The behavior of the bimetallic catalysts was dependent on the Ni:Pd ratio, and interestingly also on the targeted hydrogenation reaction. The Pd-modified Ni-rich system behaves like pure Ni catalyst, but with a strongly boosted activity due to a higher number of Ni active sites available, Pd being considered as a spectator. This high activity was manifested in the levulinic acid hydrogenation with formic acid used as an internal hydrogen source. This behavior differs from the case of the Pd-rich system modified by Ni, which displayed a much higher Pd dispersion on the support compared to the monometallic Pd catalyst. The higher availability of the Pd active sites while maintaining a high surface acidity allows the catalyst to push the HMF hydrodeoxygenation reaction forward towards the green biopolymer precursor 2,5-bis(hydroxymethyl)-tetrahydrofuran, and in consequence to strongly modify the selectivity of the reaction. In that case, residual chlorine was proposed to play a significant role, while Ni was considered as a spectator.

Simulation Study of the Plasticity of k-Turn Motif in Different Environments

The k-turn is a widespread and important motif in RNA. According to the internal hydrogen bond network, it has two stable states, called N1 and N3. The relative stability between the states changes with the environment. It is able to accept different conformations in different environments. This is called the “plasticity” of a molecule. In this work, we study the plasticity of k-turn by the mixing REMD method in explicit solvent. The results are concluded as follows. First, N1 and N3 are almost equally stable when k-turn is in the solvent alone. The molecule is quite flexible as a hinge. However, after binding to different proteins, such as the proteins L7Ae and L24e, k-turn falls into one global minimum. The preferred state could be either N1 or N3. On the contrary, the other nonpreferred state becomes unstable with a weaker binding affinity to the protein. It reveals that RNA-binding protein is able to modulate the representative state of k-turn at equilibrium. This is in agreement with the findings in experiments. Moreover, free energy calculations show that the free energy barrier between the N1 and N3 states of k-turn increases in the complexes. The state-to-state transition is greatly impeded. We also give a deep discussion on the mechanism of the high plasticity of k-turn in different environments.

Rational design of in situ localization solid-state fluorescence probe for bio-imaging of intracellular endogenous cysteine

Fluorescence detection technology has been widely concerned for its advantages of low cost, simple operation, good sensitivity, real-time and non-destructive biological imaging. However, most fluorophores emit bright fluorescence in solution, and the fluorescence decreases significantly in the high concentration or solid/aggregated state, which is called aggregation-caused quenching (ACQ). Cysteine (Cys) is an important kind of amino-acid in the field of bio-medicine, whose main function is to participate in metabolism and protein synthesis, detoxification, but intracellular cysteine concentrations (30–200 μM) are much low, and direct detection of endogenous cysteine is hampered by interference with other thiols. To solve the above problems, based on solid-state fluorophore HPQ, we for the first time prepared a novel solid-state fluorescence probe MA-HPQ, for monitoring of endogenous Cys, operated by the mechanism of excited intramolecular proton transfer (ESIPT). MeO-HPQ is completely insoluble in water, has very strong solid-state fluorescence with the maximum emission wavelength of 510 nm and the maximum excitation wavelength of 365 nm. This special property makes it very suitable for confocal microscopy compared with ordinary water-soluble fluorescent dyes. Due to the large Stokes shift (145 nm), MA-HPQ has very desirable advantages: reduced interference of background fluorescence, increased sensitivity, and enhanced contrast of biological imaging. More importantly, by preventing it from establishing internal hydrogen bonds, which is between imine nitrogen and phenolic hydroxyl groups, it can be made insoluble in water and have strong fluorescence properties, and the process is reversible. The ESIPT process can be blocked by masking phenolic hydroxyl, which can inhibit fluorescence to a large extent. In the presence of Cys, the probe reacts, releasing free MeO-HPQ, and begins to form a precipitated solid. The precipitated solid emitted bright green solid-state fluorescence, which was enhanced 43 times more than MA-HPQ. These results indicate that the probe MA-HPQ can be suitable to real spatiotemporal imaging of endogenous cysteine in HeLa cells. The excellent performance of the probe makes it applying for the visualization detection of endogenous cysteine in living cells and tissues with obtaining satisfactory results.

Effect of internal hydrogen on the tensile properties of different CrMo(V) steel grades: Influence of vanadium addition on hydrogen trapping and diffusion

The influence of hydrogen on the mechanical behaviour of different quenched and tempered CrMo steels with or without vanadium were investigated by means of tensile tests. Smooth and circunferentially-notched round-bar specimens pre-charged with gaseous hydrogen in a high pressure hydrogen reactor were tested. The degradation of the tensile properties was correlated with the interaction between hydrogen atoms and microstructure, which was analysed by means of thermal desorption analysis (TDA) and permeation tests. A LECO DH603 hydrogen analyzer was used to study the activation energies of the different microstructural traps and also to study the hydrogen eggresion kinetics at room temperature. Moreover, electrochemical hydrogen permeation tests were also used to determine the apparent hydrogen diffusion coefficients and the density of traps present in the different steel grades.Hydrogen embrittlement measured in notched specimens was much greater than that observed in the smooth samples, being this effect more notable in the steel grades with higher yield strengths, tempered at the lowest temperatures, where a change in the fracture micromechanism from ductile in the absence of hydrogen to intermediate and brittle in the presence of internal hydrogen was clearly observed, especially in tests performed at the lowest displacement rates. Results were discussed through FEM simulations of local stresses acting on the process zone. On the other hand, the V-added steel grades were less sensitive to hydrogen embrittlement due to the effect of the submicrometric VC precipitated during the tempering treatment, which might be considered non-diffusible hydrogen-trapping sites, in view of their strong hydrogen-trapping capability (35–41 kJ/mol). In these steels (V-added grades), diffusible hydrogen and hydrogen accumulation in the process zone decrease, improving hydrogen embrittlement resistance.

Hydrogen-assisted fatigue crack-propagation in a Ni-based superalloy 718, revealed via crack-path crystallography and deformation microstructures

Fatigue crack-growth (FCG) of Ni-based superalloy 718 was investigated under gaseous hydrogen environment (external hydrogen) and uniformly pre-charged state (internal hydrogen). Under external hydrogen, intergranular fracture predominated, whereas dislocation slip-band or twin boundary fracture were prevalent under internal hydrogen. This failure mode divergence encompassed unique characteristics of macroscale FCG response, leading to both cycle- and time-dependent cracking. The intergranular cracking was ascribed to short-circuit diffusion of hydrogen along grain boundaries. Meanwhile, the material’s inherently inhomogeneous deformation mode exerts harmfulness when hydrogen was uniformly distributed inside the specimen, causing slip-bands or twin boundaries to become the weakest links for fracture.

Co-precipitated poly(vinyl alcohol)/chitosan composites with excellent mechanical properties and tunable water-induced shape memory

The preparation of polymeric materials with high performance and functional performance remains a focus of extensive research. In this paper, a good dispersion of regenerated chitosan (RCS) in the poly(vinyl alcohol) (PVA) and a physical cross-linking network of molecular chain entanglements and hydrogen bonding were realized by unique co-precipitation to prepare composites. Dynamic mechanical analysis and tensile tests demonstrated that RCS achieved a significant increase in the mechanical properties. The storage modulus and tensile strength of composites containing 5% RCS were 5205 MPa and 105.7 MPa, which were significantly higher than the 3416 MPa and 60.2 MPa of the pure PVA. Intriguingly, the fabricated PVA/RCS composites exhibited good pH-sensitivity due to internal hydrogen bonding. Moreover, this achieved a tunable water-induced shape memory behavior at different pH environments. This study provides a promising strategy for the use of renewable polysaccharide to achieve high performance and functionality of polymer materials.

Hydrogen embrittlement of the coarse grain heat affected zone of a quenched and tempered 42CrMo4 steel

The coarse grain heat affected zone (CG-HAZ) of welds produced in a quenched and tempered 42CrMo4 steel was simulated by means of a laboratory heat treatment consisting in austenitizing at 1200 °C for 20 min, oil quenching and finally applying a post weld heat treatment at 700 °C for 2 h (similar to the tempering treatment previously applied to the base steel). A tempered martensite microstructure with a prior austenite grain size of 150 μm and a hardness of 230 HV, similar to the aforementioned CG-HAZ weld region, was produced. The effect of the prior austenite grain size on the hydrogen embrittlement (HE) behaviour of the steel was studied comparing this coarse-grained microstructure with that of the fine-grained base steel, with a prior austenite grain size of 20 μm.The specimens used in this study were charged with hydrogen gas in a reactor at 19.5 MPa and 450 °C for 21 h. Cylindrical specimens were used to determine hydrogen uptake and hydrogen desorption behaviour. Smooth and notched tensile specimens tested under different displacement rates were also used to evaluate HE.Embrittlement indexes, EI, were generally quite low in the case of hydrogen pre-charged tensile tests performed on smooth tensile specimens. However, very significant embrittlement indexes were obtained with notched tensile specimens. It was observed that these indexes always increase as the applied displacement rate decreases. Moreover, hydrogen embrittlement indexes also increase with increasing prior austenite grain size. In fact, the embrittlement index related to the reduction in area, EI(RA), reached values of over 20% and 50% for the fine and coarse grain size steels, respectively, when tested under the lowest displacement rates (0.002 mm/min).A comprehensive fractographic analysis was performed and the main operative failure micromechanisms due to the presence of internal hydrogen were determined at different test displacement rates. While microvoids coalescence (MVC) was found to be the typical ductile failure micromechanism in the absence of hydrogen in the two steels, brittle decohesion mechanisms (carbide-matrix interface decohesion, CMD, and martensitic lath interface decohesion, MLD) were observed under internal hydrogen. Intergranular fracture (IG) was also found to be operative in the case of the coarse-grained steel tested under the lowest displacement rate, in which hydrogen accumulation in the process zone ahead of the notch tip is maximal.

Review of Hydrogen Embrittlement in Metals: Hydrogen Diffusion, Hydrogen Characterization, Hydrogen Embrittlement Mechanism and Prevention

Hydrogen dissolved in metals as a result of internal and external hydrogen can affect the mechanical properties of the metals, principally through the interactions between hydrogen and material defects. Multiple phenomena such as hydrogen dissolution, hydrogen diffusion, hydrogen redistribution and hydrogen interactions with vacancies, dislocations, grain boundaries and other phase interfaces are involved in this process. Consequently, several hydrogen embrittlement (HE) mechanisms have been successively proposed to explain the HE phenomena, with the hydrogen-enhanced decohesion mechanism, hydrogen-enhanced localized plasticity mechanism and hydrogen-enhanced strain-induced vacancies being some of the most important. Additionally, to reduce the risk of HE for engineering structural materials in service, surface treatments and microstructural optimization of the alloys have been suggested. In this review, we report on the progress of the studies on HE in metals, with a particular focus on steels. It focuses on four aspects: (1) hydrogen diffusion behavior; (2) hydrogen characterization methods; (3) HE mechanisms; and (4) the prevention of HE. The strengths and weaknesses of the current HE mechanisms and HE prevention methods are discussed, and specific research directions for further investigation of fundamental HE mechanisms and methods for preventing HE failure are identified.

Length-Dependent Structural Transformations of Huntingtin PolyQ Domain Upon Binding to 2D-Nanomaterials.

There is a strong negative correlation between the polyglutamine (polyQ) domain length (Q-length) in the intrinsically disordered Huntingtin protein (Htt) exon-1 and the age of onset of Huntington's disease (HD). PolyQ of Q-length longer than 40 has the propensity of forming very compact aggregate structures, leading to HD at full penetrance. Recent advances in nanobiotechnology provided a new platform for the development of novel diagnosis and therapeutics. Here, we explore the possibility of utilizing 2D-nanomaterials to inhibit the formation of supercompact polyQ structures through the so-called “folding-upon-binding” where the protein structure is dependent on the binding substrate. Using molecular dynamics simulations, we characterize two polyQ peptides with Q-length of 22 (Q22, normal length) and 46 (Q46, typical length causing HD) binding to both graphene and molybdenum disulfide (MoS2) nanosheets, which have been applied as antibacterial or anticancer agents. Upon binding, Q22 unfolds and elongates on both grapheme and MoS2 surfaces, regardless of its initial conformation, with graphene showing slightly stronger effect. In contrast, initially collapsed Q46 remains mostly collapsed within our simulation time on both nanosheets even though they do provide some “stretching” to Q46 as well. Further analyses indicate that the hydrophobic nature of graphene/MoS2 promotes the stretching of polyQ on nanosheets. However, there is strong competition with the intra-polyQ interactions (mainly internal hydrogen bonds) leading to the disparate folding/binding behaviors of Q22 and Q46. Our results present distinct Q-length specific behavior of the polyQ domain upon binding to two types of 2D-nanomaterials which holds clinical relevance for Huntington's disease.

Heterogeneous Catalytic Hydrogenation of Levulinic Acid to γ-Valerolactone with Formic Acid as Internal Hydrogen Source.

As one of the most promising biomass-based platform molecules, γ-valerolactone (GVL) can be synthesized from a variety of lignocellulosic feedstocks through different hydrogen supply pathways. Among these transformation routes, the hydrogenation of levulinic acid (LA) to GVL by using formic acid (FA) as the internal hydrogen source is regarded as a critical path for the sustainable development of renewable energy systems. Although a large number of studies on the synthesis of GVL have been reported, the FA/LA catalytic system has not been interpreted as thoroughly as it should be. In this Minireview, core concerns are focused on key issues and their effects in this FA/LA catalytic system. The catalytic mechanism, together with competitive adsorption behavior between FA and LA on heterogeneous catalysts, is presented. The effects of active metal species and catalyst supports on the overall catalytic performance are summarized, and the influences of key condition parameters, including the time, temperature, FA/LA molar ratios, and aqueous solvent, are discussed. In particular, impacts and improvements of coke deposition and metal leaching, which could greatly affect the catalyst stability, are analyzed in detail. Additionally, several feasible suggestions for the enhancement of the catalytic efficiency and stability are also proposed.

What a little branching can do – Dissociative photoionization of two butanol isomers

The fragmentation processes of two internal energy-selected C4H10O+ isomers, 1-butanol and isobutanol cations, were investigated by imaging photoelectron photoion coincidence (iPEPICO) spectroscopy. The first dissociation channel leads to the formation of C4H8+ ions (m/z 56) by water loss in both isomers. Using statistical energy distribution and rate models including the isomerization of the parent ion, the 0 K appearance energies (E0) were determined to be 10.347 ± 0.015 eV and 10.57 ± 0.05 eV for 1-butanol and isobutanol, respectively. The second dissociation channel, the formation of CH3OH2+, quickly overtakes the water-loss channel in isobutanol with an E0 of 10.61 ± 0.02 eV. It appears only as a minor channel in 1-butanol with an E0 of 10.74 ± 0.09 eV. The methanol-loss channel, forming propylene ion, opens up at E0 = 10.94 ± 0.04 eV and 10.72 ± 0.02 eV in 1-butanol and isobutanol, respectively. The next two fragmentation pathways correspond to complementary pair formation of C3H7(+/o) and CH2OH(o/+). The former is assigned as the isopropyl (ion) in both butanol isomers. The channel corresponds to simple bond cleavage in isobutanol with the E0 difference corresponding to the ionization energy difference of the fragments at E0 = 10.97 ± 0.05 eV (C3H7+) and at E0 = 11.11 ± 0.20 eV (CH2OH+). However, there is an internal hydrogen shift necessary in 1-butanol and, therefore, the complementary ions appear at the same E0 = 11.10 ± 0.03 eV, which corresponds to a shared rate limiting transition state. The sequential dissociation product from m/z 56, C3H5+, appears above 11.6 eV as a minor channel in both isomers. Finally, we determined −279.1 ± 1.6 kJ mol−1 as the 298 K heat of formation of gaseous isobutanol. We also propose revised ionization energies for the two butanols isomers based on composite method calculations.

Atomic origin of the morphological evolution of aluminum hydride (AlH3) nanoparticles during oxidation using reactive force field simulations

Metal hydride nanoparticles exhibit different oxidation dynamic characteristics from bulk ones due to size effects as well as the existence of M-H bonds. We used ReaxFF-lg molecular dynamics to elucidate the dehydrogenation and oxidation mechanisms of aluminum hydride nanoparticle (AHNP). Results show that the morphological evolution of AHNP is induced by temperature and structure, and classified into four shapes: sphere, notched sphere, large branch, and small string. The surface dehydrogenation and oxidation are almost co-occurring. The initial dehydrogenation inhibits the rapid oxidation of the surface layer of AHNP. The increase in temperature induces the instability of the oxide shell and provides sufficient kinetic energy for the hydrogen bubbles. As a result, the oxidation shell ruptures, and the internal hydrogen bubbles physically escape from the nanoparticles. Some simultaneous notches appear in the shell, making its appearance to be branchy at 3000 K. AHNP explodes and ejects small strings of atoms at 3500 K. We also investigated the effect of different temperatures and initial oxygen densities on the morphologies of AHNP. Our results emphasize the complicated interplay between the structural evolution of nanoparticles and environmental conditions. It provides insights into the atomic-level dehydrogenation and oxidation mechanism of metal hydride nanoparticles.

Comparison of mode-Ⅰ crack propagation of tube subjected to internal hydrogen static and detonation loading

An elaborate numerical model with progressive damage and failure and fluid-structure coupling was developed to study the crack propagations of tubes under hydrogen static and detonation loads. The numerical model was verified with experiment in terms of crack behaviors and fracture patterns. The tube responses, crack propagations, pressure histories, crack lengths and speeds as well as the energy storages were obtained and analyzed in detailed. It was found the static load case has higher stored energy inside the tube, which causes the larger crack length and speed, as well as the severer bending deformation of tube. The forward crack first run faster under detonation load, but it will be caught up by the backward crack in the late period. The crack growths are incremental under both types of loads. However, the crack growth under detonation load has certain regular patterns, where the oscillating crack speed has a dominant frequency that can be calculated by the proposed formula. Moreover, the quantitative relationship between detonation load speed and the incremental crack growth length was revealed, which is fundamentally and practically useful.

Anilinopyrazines as potential mitochondrial uncouplers

Mitochondrial protonophores transport protons through the mitochondrial inner membrane into the matrix to uncouple nutrient oxidation from ATP production thereby decreasing the proton motive force. Mitochondrial uncouplers have beneficial effects of decrease reactive oxygen species generation and have the potential for treating diseases such as obesity, neurodegenerative diseases, non-alcoholic fatty liver disease (NAFLD), diabetes, and many others. In this study, we report the structure-activity relationship profile of the pyrazine scaffold bearing substituted aniline rings. Our work indicates that a trifluoromethyl group is best at the para position while the trifluoromethoxy group is preferred in the meta position of the aniline rings of 2,3-substituted pyrazines. As proton transport and cycling requires the formation of a negative charge that has to traverse the mitochondrial membrane, a stabilizing internal hydrogen bond is a key feature for efficient mitochondrial uncoupling activity.