Fragmentation Mechanisms Research Articles

A holistic strategy for discovering structural analogues of drug residues in meat using characteristic structural fragments filtering by high-resolution Orbitrap mass spectrometry

ABSTRACT A holistic strategy for discovering structural analogs was established using characteristic structural fragments filtering by high-resolution Orbitrap mass spectrometry and successfully employed for discovering potential hazards in meat. The mass spectrometry fragmentation mechanisms of 113 compounds (including sulphonamides, tetracyclines, benzimidazoles, steroid hormones, cephalosporins, β-blockers) were investigated and a new strategy for screening of characteristic fragment ions was proposed. To process the data acquired by two scan modes, firstly an integrated filtering strategy was conducted to facilitate the characterisation of multi-class drugs. The integrated filtering strategy was applied to reduce interference in the raw data, which could help extracting the MS1 characteristics of the homolog-type chemical substances and expand the screening of the compounds as effectively as possible. This strategy was based on a combination of nitrogen rule, neutral loss and multiple characteristic fragment ions filtering. The method was validated by rapid screening and identification of targeted compounds in spiked samples. Particularly, the successful detection of several new compounds indicated that this strategy had significant advantages over individual filtration methods and could be a promising method for screening and identifying newly homolog-type drug residues in complex samples.

Metal-ion-assisted structural and anomeric analysis of Amadori compounds by electrospray ionization mass spectrometry.

The Maillard reaction plays an important role in food, physiology and traditional Chinese medicine, and its primary reaction products are formed through Amadori rearrangement by reducing sugars and amino acids. The analysis of the characteristic fragmentation and of the glycosidic bond configuration of Amadori compounds will promote their fast discovery and identification by mass spectrometry. Four Amadori compounds that reduce disaccharides and proline/tryptophan were used to investigate the fragmentation mechanisms via tandem mass spectrometry (MS/MS) with different alkali metal ion adducts. Cu2+ could be used to distinguish glycosidic bond configurations of the reducing disaccharides in the full-scan mass spectra. Quantum calculations were also conducted for a single Amadori compound with Cu2+ for analysis of the most optimized configurations and binding energies of metal complexes. MS/MS analysis of Amadori-alkali metal complexes revealed that the radius of the alkali metal ions had profound effects on the degree of fragmentation of such compounds, among which lithium-cationized ions produced the most extensive fragmentation. Amadori compounds with different glycosidic bonds formed differently proportioned metal complexes with Cu2+ , and the complexity of the copper complexes containing tryptophan moieties was higher than that of those containing proline moieties in the mass spectra. Quantum calculations showed that Amadori compounds with β-configurations can form more binding sites with Cu2+ than those with α-configurations, thus making the metal complex with a single ligand more stable. In addition, the chelation of tryptophan with copper ions increased the coordination binding energy, which showed that α-configured Amadori compounds were readily able to form multi-ligand copper complexes. Metal-ion-assisted analysis provides crucial information for structural and anomeric analysis of Amadori compounds by electrospray ionization mass spectrometry. Elucidation of binding sites and binding energies by quantum calculations has significantly improved the knowledge of metal complexes in the gas phase and provides background information for determining the glycosidic configuration of Amadori isomers.

Miocene long-runout debris-avalanche deposits in the Eastern Pamir foreland basin record cataclasis and fragmentation mechanisms

The Miocene Aertashi Debris-Avalanche Deposits at the southwestern Tarim Basin, the foreland basin of the Eastern Pamir (NW Tibetan Plateau), have an incredibly long-runout distance (much longer than 130 km) and provide critical constraints on the evolution of drainage patterns, tectonics, and geochronological framework of the region. To investigate when and how the deposits formed, we conducted extensive field and microstructural observations, as well as geochronologic analyses. The deposits are massive, poorly sorted, and matrix-supported, containing massive blocks, jigsaw-fractured clasts, and fluidal-shaped cataclastic lava bodies. Some cataclastic lava bodies up to ~25 m across are compact on the hand-specimen scale but are pervasively fragmented on the microscale. Microstructural observations of particles show abundant diagnostic features of highly-energetic collisions, such as conchoidal fractures and microcracks. Both field and microstructural observations indicate that the deposits were derived from a debris avalanche. Pervasive cataclasis of many fluidal-shaped lava bodies is interpreted to record intense shear of hot, semisolid lavas close to the glass-transition temperature, in which phenocrysts deformed brittlely while the glassy components mainly deformed plastically and controlled the rheology of the bodies as ductile material. The mechanical properties of clasts are important in controlling their deformation within debris avalanches. The presence of abundant hot, semisolid lavas in the studied deposits may be critical for the survival of megaclasts after a long-runout distance. The field and microstructural observations and geochronologic analyses show that debris-avalanche deposits can aid in constraining regional geochronologic framework. These results consistently confirm that the Aertashi Debris-Avalanche Deposits were deposited at ~11 Ma, during rather than long after the eruptive period.

Ballast Contamination Mechanisms: A Criterial Review of Characterisation and Performance Indicators

Across the world, ballasted railway tracks are utilised extensively due to their cost efficiency, ease of drainage, and capacity to withstand cyclic imposed loadings from heavy trains. In spite of these benefits, the ballast is often considered as a flexible medium; as such, its continuous deterioration is largely disregarded. Geotechnical challenges such as ballast contamination in the form of particle fragmentation, deposition of weathered materials, upward pumping of clay and fines from underlayers, and coal intrusion have led to differential settlements and reduced drainability of tracks, thereby exacerbating track maintenance costs. This study reviews existing works of literature to expound on the mechanisms for ballast contamination and to highlight the fundamental parameters that guide the characterisation and performance evaluation of railway ballasts. The study shows that ballast fragmentation accounts for about 76% of commonly recorded contaminations, while it is also observed as the most critical to track stability. As such, a variety of indices and specifications for ballast gradation have been established worldwide to guide practice in ballast characterisation and performance evaluation. However, the mechanisms of ballast fragmentation and deterioration require further research to guide the improvement of contemporary guidelines, and mitigate the risk of abrupt track failures, especially in developing countries.

Revisiting the production of J/psi pairs at the LHC

We consider the prompt double J/psi production in pp collisions at the LHC in the framework of k_T-factorization QCD approach. Using the fragmentation mechanism, we evaluate the color octet contributions to the production cross sections taking into account the combinatorial effects of multiple gluon radiation in the initial state driven by the Ciafaloni–Catani–Fiorani–Marchesini evolution equation. We demonstrate the importance of these contributions in a certain kinematical region covered by the CMS and ATLAS measurements. On the other hand, the experimental data taken by the LHCb Collaboration at forward rapidities and moderate transverse momenta can be described well by {{{mathcal {O}}}}(alpha _s^4) color singlet terms and contributions from the double parton scattering mechanism. The extracted value of the effective cross section is compatible with many other estimations based on different final states.

Structure Transformation of Dispersionstrengthened Vanadium Alloys under Conditions of High-Pressure Torsion and Room-Temperature Tensile Deformation

A comparative study of the features of microstructure transformation in dispersion strengthened vanadium alloys of the V–Me(Cr, W)–Zr system under conditions of deformation by torsion under pressure and tension at room temperature is carried out. It is found out that suppression of dislocation plasticity in the high-strength state favors the formation of an anisotropic submicrocrystalline structure both during torsion deformation and in the region of strain localization in the case of tension at room temperature. It is shown that one of the main mechanisms of crystal fragmentation under these conditions is a dislocation-disclination mechanism, whose realization requires structural states with nonzero values of the curvature rotor or a high continual density of disclinations.

On the Plasma–Dust Processes Accompanying Meteor Showers

Plasma–dust processes in the Earth’s ionosphere related to transit of meteor bodies and spreading of meteor trail are analyzed. Processes that occur in the meteor trail itself and those taking place in the Earth’s atmosphere upon transit of a meteor body, along with their influence on observers and operation of various technical systems, are investigated. In particular, mechanisms explaining acoustic phenomena accompanying meteor transit during meteor showers are proposed. The mechanism of formation of dusty plasma in meteoroid trails is described. It is demonstrated that charging of dust particles of the meteoroid material creates conditions for the appearance of dust acoustic waves. Dust acoustic perturbations are driven as a result of development of modulation instability of electromagnetic waves emitted by the meteor trail and have frequencies typical of dust sound (0.003–60 Hz). The reports of witnesses revealed that observers on the Earth can hear low-frequency sounds appearing during meteor showers. It is suggested that the sound reaches the Earth’s surface as a result of transfer of oscillations from dust particles to neutrals the concentration of which in the atmosphere is high. The mechanisms of fragmentation of meteor bodies and charging of formed dust particles are analyzed. Characteristic charges of dust fragments for nano- and micrometer-scale particles are estimated. Particles of different shape are considered. The growth rates that give rise to modulation excitation of low-frequency dust acoustic perturbations are calculated. Conditions leading to development of a modulation instability are found.

The fingerprints of weathering: Grain size distribution changes along weathering sequences in different lithologies

The weathering mechanisms that cause fragmentation of particles in the transition from bedrock to saprolite and regolith are little known. Yet, their quantification is an important missing link in the development of critical zones. To provide observational underpinning of mechanistic inference, we sampled and analysed the vertically changing particle size distribution in weathering profiles of varying lithology: quartzite, schist, gneiss and shale. The samples were studied for mineral composition by X-ray powder diffraction (XRD) and assessed whether these were consistent with the field identification. Then, simulations from twelve theoretical particle fragmentation models were confronted to the vertical particle size distribution measured. The models simulate different particle-size implications of physical and chemical weathering, but do not include surface effects on particle size distribution such as armouring. The results demonstrate that the lithology is an important determinant of the rock fragmentation mechanism. Furthermore, it is shown that the rock fragmentation models used here are a useful tool to identify geomorphological processes as soil redistribution or amouring. Further research will need to generate more data on weathering sequences in different environments.

In-situ investigation of coal particle fragmentation induced by thermal stress and numerical analysis of the main influencing factors

Particle fragmentation influences thermochemical coal conversion processes in different ways, which is of great significance for process design and control. Different mechanisms are proposed for fragmentation characterization, but direct and substantial optical evidence supporting these theories is rarely reported. In the present study, the fragmentation process of two anthracites with low volatiles is investigated in-situ with the aid of an optical system. The observed fragmentation phenomenon confirms that the thermal stress is the main driving force for the fragmentation of the investigated anthracite particles. Together with a model analysis, a fragmentation pattern different from previous reports is proposed. The tensile stress causes the particles to fragment from the center. Fine particles are produced by multiple tensile failure rather than by the spalling of particles’ outer shell caused by compressive stress. Based on the model, the impact of various process- and particle-related factors on the maximum thermal tensile stress and its appearance time are quantitatively evaluated, which significantly reduces the required time and effort in comparison to experimental analysis of the fragmentation. This study provides direct visual evidence and numerical validation of the fragmentation mechanism, which can be utilized to predict the coal particle behavior and the resulting particle size distribution.

Experimental Investigation and Mechanism Analysis on Rock Damage by High Voltage Spark Discharge in Water: Effect of Electrical Conductivity

High voltage spark discharge (HVSD) could generate strong pressure waves that can be combined with a rotary drill bit to improve the penetration rate in unconventional oil and gas drilling. However, there has been little investigation of the effect of electrical conductivity on rock damage and the fragmentation mechanism caused by HVSD. Therefore, we conducted experiments to destroy cement mortar, a rock-like material, in water with five conductivity levels, from 0.5 mS/cm to 20 mS/cm. We measured the discharge parameters, such as breakdown voltage, breakdown delay time, and electrical energy loss, and investigated the damage mechanism from stress waves propagation using X-ray computed tomography. Our study then analyzed the influence of conductivity on the surface damage of the sample by the pore size distribution and the cumulative pore area, as well as studied the dependence of internal damage on conductivity by through-transmission ultrasonic inspection technique. The results indicated that the increase in electrical conductivity decreased the breakdown voltage and breakdown delay time and increased the energy loss, which led to a reduction in the magnitude of the pressure wave and, ultimately, reduced the sample damage. It is worth mentioning that the relationship between the sample damage and electrical conductivity is non-linear, showing a two-stage pattern. The findings suggest that stress waves induced by the pressure waves play a significant role in sample damage where pores and two types of tensile cracks are the main failure features. Compressive stresses close horizontal cracks inside the sample and propagate vertical cracks, forming the tensile cracks-I. Tensile stresses generated at the sample–water interface due to the reflection of stress waves produce the tensile cracks-II. Our study is the first to investigate the relationship between rock damage and electrical conductivity, providing insights to guide the design of drilling tools based on HVSD.

Nonlinear Dynamics and Fragmentation Mechanism of Coastal Rocks Impacted by Ocean Waves

Wang, T.; Li, X.-H., and Zhu, Z.-W., 2020. Nonlinear dynamics and fragmentation mechanism of coastal rocks impacted by ocean waves. In: Wan, Z. (ed.), Coordinated Sustainable Development in Coastal Areas: Environment and Economy. Journal of Coastal Research, Special Issue No. 109, pp. 185–190. Coconut Creek (Florida), ISSN 0749-0208.A variable cross-section cantilever beam is established to describe coastal rocks. A new differential term is developed to interpret the rock's stress-strain curves. Ocean waves are treated as stochastic incentives. The dynamic model of the beam is built up, and its nonlinear dynamic characteristics is obtained. The results show that the large periodic vibrations will cause fragmentation of coastal rocks. These results will be available for the fragmentation mechanism of coastal rocks impacted by ocean waves.

Photoelectron and fragmentation dynamics of the H++H+ dissociative channel in NH3 following direct single-photon double ionization

We report measurements on the H$^{+}$ + H$^{+}$ fragmentation channel following direct single-photon double ionization of neutral NH$_{3}$ at 61.5 eV, where the two photoelectrons and two protons are measured in coincidence using 3-D momentum imaging. We identify four dication electronic states that contribute to H$^{+}$ + H$^{+}$ dissociation, based on our multireference configuration-interaction calculations of the dication potential energy surfaces. The extracted branching ratios between these four dication electronic states are presented. Of the four dication electronic states, three dissociate in a concerted process, while the fourth undergoes a sequential fragmentation mechanism. We find evidence that the neutral NH fragment or intermediate NH$^+$ ion is markedly ro-vibrationally excited. We also identify differences in the relative emission angle between the two photoelectrons as a function of their energy sharing for the four different dication states, which bare some similarities to previous observations made on atomic targets.

Determination of Fipronil and Four Metabolites in Foodstuffs of Animal Origin Using a Modified QuEChERS Method and GC–NCI–MS/MS

A sensitive, effective, and reliable method for the accurate determination of fipronil and four metabolites (fipronil carboxamide, fipronil sulfone, fipronil sulfide, and fipronil desulfinyl) in foodstuffs of animal origin (egg, milk, beef kidney, beef liver, chicken, and chicken liver) was developed by isotope dilution–gas chromatography–negative chemical ionization–tandem mass spectrometry (GC–NCI–MS/MS). Samples were purified by a modified QuEChERS method. Four isotopically labeled internal standards were added in the sample extraction process to compensate for the matrix effect. The average recoveries were 78.2–107.1% with RSD ≤ 8.5%. The limits of quantification (LOQs) were 0.2 μg kg−1 for fipronil carboxamide and fipronil sulfone and 0.1 μg kg−1 for fipronil, fipronil sulfide, and fipronil desulfinyl. At the same time, the fragmentation mechanism of the five target compounds was analyzed via mass spectral data to help identify the compounds.

Jet Fragmentation Characteristics During Molten Fuel and Coolant Interactions

Jet fragmentation greatly influences the possibility of steam explosion and the formation of a debris bed when a molten corium jet falls into subcooled coolant during a severe accident of a nuclear reactor—which is called fuel and coolant interaction (FCI). The characteristics of different jet fragmentation mechanisms and the conditions under which they play a major role are still in doubt. Experiments were carried out to investigate the fragmentation characteristics of melt jet interaction with water at medium temperature (~680°C) and high temperature (1800°C to 2150°C). Molten metal [tin or Type 304 stainless steel (304SS)], oxide (alumina), and their mixture (304SS-alumina) were used as melt materials to obtain different fragmentation mechanisms. In addition, the effects of melt temperature, water subcooling, and water depth on jet fragmentation were also studied. Through comprehensive analysis of high-speed photography, dynamic pressure, water temperature variation, and jet breakup length during interactions as well as the morphology and size of debris after interactions, it was found that the characteristics of jet fragmentation varied greatly at different melt temperatures and water subcooling due to competition between hydrodynamic fragmentation and thermodynamic fragmentation caused by boiling. In addition, under high-temperature conditions, fragmentation of alumina was much greater than 304SS due to the fracture of solidifying melt caused by thermal stress. Finally, five kinds of mechanisms of melt jet fragmentation under different conditions are summarized.

Electrospray ionization with higher-energy collision dissociation tandem mass spectrometry toward characterization of ceramides as [M + Li]+ ions: Mechanisms of fragmentation and structural identification

Ceramide is a huge lipid family consisting of diversified structures in which various modifications are seen in the fatty acyl chain and the long chain base (LCB). In this contribution, a higher collision energy (HCD) linear ion-trap mass spectrometric method (LIT MSn) was applied to study the mechanisms underlying the fragmentation processes of ceramide molecules in 12 subclasses, which were desorbed by ESI as the [M + Li]+ ions. Multiple sets of fragment ions reflecting the fatty acyl chain and LCB were observed in the HCD MS2 spectra for all the ceramide classes, resulting in unambiguous definition of the ceramide structures, including the chain length and the modification (α-hydroxy-, β-hydroxy-, ω-hydroxy-FA) of the fatty acyl moiety, and the types of LCB (sphingosine, phytosphigosine, 6-hydroxy-sphingosine). Thereby, this approach permits differentiation of isomeric structures and ceramide species in the biological specimen can be unveiled in detail. By application of sequential MS3, the double bond position along the fatty acyl chain of the molecule can be located, and a complete structural characterization of ceramides can be achieved.

Structure Analysis and Characterization of Aminorex Analogue 4'-F-4-MAR

Objective To study the identification method for 4'-F-4-methylaminorex （4'-F-4-MAR） in samples without reference substance. Methods Gas chromatography-mass spectrometry （GC-MS）, ultra-high-performance liquid chromatography-quadrupole time-of-flight-mass spectrometry （UPLC-QTOF-MS）, nuclear magnetic resonance （NMR） and Fourier transform infrared （FTIR） were comprehensively used for the structure identification of 4'-F-4-MAR in samples. Results Under the positive electrospray ionization （ESI+） mode, quasi-molecular ion in the first order mass spectrometry of the unknown compound was 195.092 6 and its molecular formula was inferred to be C10H11FN2O. The fragment ions in the mass spectrometry of the unknown compound were compared with the related fragment ions of 4,4'-dimethylaminorex （4,4'-DMAR） in literature. It was found that the main fragment ions of the unknown compound were all 4 bigger than the corresponding fragment ions of 4,4'-DMAR. Therefore, the unknown compound was inferred to be a 4,4'-DMAR analogue with a methyl substituted by a fluorine in the benzene ring. The equivalent protons at δ=7.30 and δ=7.06 in 1H-nuclear magnetic resonance （1H-NMR） spectra and the characteristic spin-spin coupling constants （1JC-F=245.2 Hz, 2JC-F=21.3 Hz, 3JC-F=8.1 Hz） for 13C-19F interactions in carbon spectra, further proved that the fluorine substituted methyl at the para-position of the benzene ring. Finally, the unknown compound was determined as 4'-F-4-MAR. Conclusion A method that comprehensively used the identification materials 4'-F-4-MAR in GC-MS, UPLC-QTOF-MS, NMR and FTIR is established and the fragmentation mechanism of fragmentation ions of 4'-F-4-MAR created under the two modes -- electron impact （EI） and electrospray ionization under collision induced dissociation （ESI-CID） is deduced. The information will assist forensic science laboratories in identifying this compound or other substances with similar structure in their case work.

Influence of in-situ stress on rock fragmentation by TBM cutters and prediction of TBM performance for deep tunnels

In-situ stress is a significant factor influencing TBM tunneling for deep tunnels, especially for the construction of deep repository for radioactive waste disposal. Beishan area of Gansu Province is the first preferred area for high-level radioactive waste disposal repository in China, and the feasibility of using TBM technology in Beishan area is investigated in recent years. In this paper, six levels of in-situ stress related to different depths from ground to 500m at Beishan area were selected and the influence of in-situ stress on rock fragmentation was investigated by linear cutting test. The rock samples were collected from the Jijicao site in Beishan area, with uniaxial compressive strength of 105.6MPa. The test results show that: 1) there is a clear power function correlation between the penetration and the normal cutter force for each stressed condition, and the higher the confining stress, the smaller the gradient of the power function curve, which means slower increase of penetration rate under the same cutterhead thrust; 2) the required normal cutter force increases with the increase of overburden as the corresponding in-situ stress increases. Based on the laboratory testing, the Specific Rock Mass Boreability Index model was modified and further used in the prediction of TBM performance at different depths on Jijicao site. This paper helps better understanding of rock fragmentation mechanism in TBM tunneling in stressed ground, and also provides reference on parameter selection for TBM operation in deep tunnel tunnelling.

Quarkonium TMD fragmentation functions in NRQCD

We study the transverse-momentum spectrum of quarkonium production from single light-parton fragmentation mechanism. In the case of semi-inclusive deep inelastic scattering, we observe that there are two possible initiating processes, namely photon-gluon fusion and light-quark fragmentation. For the second case we derive the factorization theorem, which involves a new hadronic quantity: the quarkonium transverse-momentum-dependent fragmentation functions in NRQCD. We calculate their matching onto the non-perturbative long distance matrix elements at the lowest order in the strong-coupling constant, mathcal{O}left({alpha}_s^2right) . Focusing on the case of the electron-ion collider, we make a comparative phenomenological study of the two production mechanisms and find the regions of the phase space where one is dominant over the other.

Assessing sleep-wake survival dynamics in relation to sleep quality in a placebo-controlled pharmacological intervention study with people with insomnia and healthy controls

RationaleThe mechanisms underlying impaired sleep quality in insomnia are not fully known, but an important role for sleep fragmentation has been proposed.ObjectivesThe aim of this study is to explore potential mechanisms of sleep fragmentation influencing alterations of perceived sleep quality.MethodsWe analyzed polysomnography (PSG) recordings from a double-blind crossover study with zopiclone 7.5 mg and placebo, in elderly participants with insomnia complaints and age-matched healthy controls. We compared survival dynamics of sleep and wake across group and treatment. Subsequently, we used a previously proposed model to estimate the amount of sleep onset latency (SOL) misperception from PSG-defined sleep fragmentation. Self-reported and model-estimated amount of SOL misperception were compared across group and treatment, as well as model prediction errors.ResultsIn the zopiclone night, the average segment length of NREM sleep was increased (group F = 1.16, p = 0.32; treatment F = 8.89, p< 0.01; group x treatment F = 0.44, p = 0.65), while the segment length of wake was decreased (group F = 1.48, p = 0.23; treatment F = 11.49, p< 0.01; group x treatment F = 0.36, p = 0.70). The self-reported and model-estimated amount of SOL misperception were lower during the zopiclone night (self-reported group F = 6.08, p< 0.01, treatment F = 10.8, p< 0.01, group x treatment F = 2.49, p = 0.09; model-estimated F = 1.70, p = 0.19, treatment F = 16.1, p< 0.001, group x treatment F = 0.60, p = 0.55). The prediction error was not altered (group F = 1.62, p = 0.20; treatment F = 0.20, p = 0.65; group x treatment F = 1.01, p = 0.37).ConclusionsImpaired subjective sleep quality is associated with decreased NREM stability, together with increased stability of wake. Furthermore, we conclude that zopiclone-induced changes in SOL misperception can be largely attributed to predictable changes of sleep architecture.

Studying the plasma‐assisted polymerization at atmospheric pressure in Ar/TEOS by active laser diagnostics

AbstractThe key processes in an atmospheric‐pressure plasma jet containing Ar and tetraethyl orthosilicate (TEOS) are studied by means of two‐dimensional imaging of the important discharge radicals: OH, CH, and atomic O. The kinetics of the species generation is investigated by laser‐induced fluorescence spectroscopy. The work is focused on the behavior of the ground‐state radicals' density as a function of the applied voltage and of the Ar/TEOS mixing ratio. First insights on the physicochemical mechanisms of precursor fragmentation are provided. The influence of precursor admixture and precursor fragmentation on the OH, CH radicals, and atomic oxygen kinetics is revealed. The dominant role of gas‐phase oxidation processes in CH radical formation and polymerization is discussed and analyzed.