Fragmentation Model Research Articles

A highly sensitive fluorescence immunochromatography strip for thiacloprid in fruits and vegetables using recombinant antibodies

Thiacloprid (TCL) is a neonicotinoid insecticide. Its widespread use has led to high levels of residue in fruits and vegetables. Hence, it is important to detect TCL rapidly, accurately, and sensitively in fruits and vegetables. Recombinant antibodies (rAbs) can be synthesized rapidly with little batch-to-batch variation. In this study, recombinant single-chain variable fragment (scFv) antibody and full-length recombinant antibody against TCL were produced using three different expression systems (E. coli, yeast, and mammalian cell). The results of SDS-PAGE and non - competitive enzyme-linked immunosorbent assay (ELISA) indicated that the full-length rAb exhibited promising characteristics, and the IC50 value of indirect competitive ELISA (ic-ELISA) was 2.63 μg L−1. However, recombinant scFv antibody had little affinity for the antigen. To understand antibody recognition, the three-dimensional (3D) model of the variable fragment (Fv) was built via homologous modeling. The interaction between Fv and TCL was analyzed via molecular docking and the results of molecular docking showed that VAL-158, ALA-211, PHE-220, TRP-218, TRP-49, and ILE-100 were mainly responsible for antibody recognition. In addition, a time-resolved fluorescent microsphere-immunochromatographic test strip (TRFM-ICTS) was developed with a linear range and limit of detection of 0.01–10 ng mL−1 and 0.003 ng mL−1 within 15 min under optimal conditions. The IC50 value was 4.268 ng mL−1, and the recovery ranged between 79.4% and 118.6%, which was consistent with HPLC-MS. The TRFM-ICTS has great advantages in sensitivity and applicability.

Exploring the Regime of Fragmentation in Strongly Tilted Fermi-Hubbard Chains.

Intriguingly, quantum many-body systems may defy thermalization even without disorder. One example is so-called fragmented models, where the many-body Hilbert space fragments into dynamically disconnected subspaces that are not determined by the global symmetries of the model. In this Letter we demonstrate that the tilted one-dimensional Fermi-Hubbard model naturally realizes distinct effective Hamiltonians that are expected to support nonergodic behavior due to fragmentation, even at resonances between the tilt energy and the Hubbard on site interaction. We find that the effective description captures the observed dynamics in experimentally accessible parameter ranges of moderate tilt values. Specifically, we observe a pronounced dependence of the relaxation dynamics on the initial doublon fraction, which directly reveals the microscopic processes of the fragmented model. Our results pave the way for future studies of nonergodic behavior in higher dimensions.

Stress-dependent matrix crack opening in SiC/SiC composites: theory and analytical prediction

ABSTRACT In the present work, stress-dependent matrix crack opening behavior of SiC/SiC composites was analyzed considering stochastic fragmentation in fibers. The stochastic matrix multiple fragmentation model was adopted to determine the fragmentation lengths of three different types, the accompanying interface debonding process was assessed by the fracture mechanics theory, and stochastic fiber fragmentation was determined by the global load sharing (GLS) criterion. Considering the aforementioned multiple micro-damage mechanisms, matrix crack opening displacements (CODs) in different matrix fragmentation states were determined using a micromechanical technique. Relationships between CODs and the constituent properties of SiC/SiC composites with fiber fragmentation were established. The crack opening behavior of SiC/SiC composites was also analytically predicted. Effects of fiber stochastic fragmentation on crack opening-related damage parameters were examined.

Virtual endocast of late Paleocene Niptomomys (Microsyopidae, Euarchonta) and early primate brain evolution

Paleogene microsyopid plesiadapiforms are among the oldest euarchontans known from relatively complete crania. While cranial endocasts are known for larger-bodied Eocene microsyopine microsyopids, this study documents the first virtual endocast for the more diminutive uintasoricine microsyopids, derived from a specimen of Niptomomys cf. Niptomomys doreenae (USNM 530198) from the late Paleocene of Wyoming. Size estimates of smaller-bodied uintasoricines are similar to those inferred for the common ancestor of Primates, so the virtual endocast of Niptomomys may provide a useful model to study early primate brain evolution. Due to the broken and telescoped nature of the neurocranium of USNM 530198, a μCT scan of the specimen was used to create a 3D model of multiple bone fragments that were then independently isolated, repositioned, and merged to form a cranial reconstruction from which a virtual endocast was extracted. The virtual endocast of Niptomomys has visible caudal colliculi, suggesting less caudal expansion of the cerebrum compared to that of euprimates, but similar to that of several other plesiadapiforms. The part of the endocast representing the olfactory bulbs is larger relative to overall endocast volume in Niptomomys (8.61%) than that of other known plesiadapiforms (∼5%) or euprimates (<3.5%). The petrosal lobules (associated with visual stabilization) are relatively large for a Paleocene placental mammal (1.66%). The encephalization quotient of Niptomomys is relatively high (range = 0.35–0.85) compared to that of Microsyops (range = 0.32–0.52), with the upper estimates in the range of values calculated for early euprimates. However, this contrast likely relates in part to the small size of the taxon, and is not associated with evidence of neocortical expansion. These findings are consistent with a model of shifting emphasis in primate evolution toward functions of the cerebrum and away from olfaction with the origin of euprimates.

Constitutive relation and particle size distribution model of rock fragments in the goaf.

Permeability is considered a key parameter used in goaf flow simulation. Particle size of caved rock fragments is an important factor that affects permeability. Current literature treats the particle sizes of rock fragments as a constant, which is something that will inevitably lead to great errors. The sigmoid function is introduced, based on the existing main roof subsidence displacement model, to establish a new main roof subsidence displacement model, which will reflect the characteristics of the natural accumulation zone, load-affected zone, and compacted zone in the goaf. The constitutive relationship of the rock fragments meanwhile is established from a mechanical perspective. Particle sizes of the rock fragments in the goaf are controlled by the maximum median particle size, with the minimum particle size calculated as 69.25% of the maximum median particle size. In addition, with the same mining height, the stronger the overlying strata is, the larger the particle size, while under the same geological conditions, the larger the mining height, the smaller the particle size of the rock fragments. This paper provides a constitutive relation and particle size distribution model of rock fragments which is more consistent with the actual coal mine's characteristics.

ЭКСПЕРИМЕНТАЛЬНЫЕ И ТЕОРЕТИЧЕСККИЕ ИССЛЕДОВАНИЯ ЖЕЛЕЗОБЕТОННЫХ ПЛОСКИХ ПЕРЕКРЫТИЙ ПРИ УДАЛЕНИИ ЦЕНТРАЛЬНОЙ ОПОРЫ

The paper experimentally and theoretically considers the issues of assessing the robustness of reinforced concrete structural systems with flat slabs in an accidental design situation. The methodolody of experimental studies for two scale models of a flat slab fragment in the case of removal of the central support under static (sample FS-1) and dynamic (sample FS-2) loading are presented. Based on the data obtained, the analysis of the main mechanisms of resistance of flat slabs to progressive collapse was carried out. The article presents a theoretical approach to a direct quantitative assessment of robustness, which is based on the provisions of the energy balance of a damaged structural system in an accidental design situation. The proposed solutions make it possible to determine the non-linear quasi-static "load-displacement" reaction and the ultimate dynamic resistance for reinforced concrete structural systems with flat slabs in the case of removal of the vertical key element.

Numerical modelling of rock fragmentation for TBM based on peridynamics

With the rapid development of tunnelling engineering construction, especially the deep buried long tunnels, the full-face hard rock tunnel boring machines (TBMs) have been widely used in excavation process because of its significant advantages including fast advance rate, excellent safety, low disturbance to surrounding rock, and so on. Figuring out clearly the rock fragmentation mechanism is very important for a tunnel project, which attracts extensive attention worldwide all the time. In this study, a 3D model of rock fragmentation induced by a disc cutter was established based on peridynamic theory (PD) to explore and comprehend it. Based on the reasonable values of the model parameters, a series of numerical simulation tests were implemented to investigate the evolution cracks with increase of the penetration. The simulation results shown that the entire process of rock breaking had a good agreement by comparing with results in existing literature. In this paper, the proposed model based on PD provided a novel approach to study further the rock fragmentation mechanism taking more complex conditions into consideration in the future.

Processo de trabalho em Clínicas Populares de Saúde na perspectiva de médicos

The objective of the study was to understand the perspective of doctors regarding the work process in Low-cost Health Clinics. To this end, we conducted qualitative research interviewing 8 young specialist doctors who work in these business firms in São Luís, Maranhão. We identified precarious working conditions, although presenting little resistance from the doctors, considering that these businesses are seen as spaces of projection in the local job market. Due to the limitations of the complaint-driven model of care, the interviewees activate an informal network, and the users of the Low-Cost Health Clinics are referred to the Brazilian National Health System (SUS). Thus, the physician’s work process is challenged by this fragmented care model, which blurs the boundaries in the public-private interfaces leading to a naturalized double gateway to the SUS.

Discrete fragmentation equations with time-dependent coefficients

We examine an infinite, linear system of ordinary differential equations that models the evolution of fragmenting clusters, where each cluster is assumed to be composed of identical units. In contrast to previous investigations into such discrete-size fragmentation models, we allow the fragmentation coefficients to vary with time. By formulating the initial-value problem for the system as a non-autonomous abstract Cauchy problem, posed in an appropriately weighted $ \ell^1 $ space, and then applying results from the theory of evolution families, we prove the existence and uniqueness of physically relevant, classical solutions for suitably constrained coefficients.

(Gd3+) Complexation with oligopeptide (SFVG) and amyloid peptide (Aβ13–23) in aqueous solution by NMR spectroscopy

Gadolinium (III) ion, which belongs to the subgroup of transition metal ions, has practical importance for magnetic resonance imaging (MRI) with contrast. The accumulation of complexes of transition metal ions with amyloid peptides in the human body leads to the formation of insoluble plaques, which are presumably-one of the causes of Alzheimer's disease. This paper presents the results of studying the interaction of the gadolinium (III) ion with a fragment of amyloid protein Aβ40 in aqueous solutions using nuclear magnetic resonance spectroscopy. Tetrapeptide (SFVG) was used as the simplified model of metal-peptide interaction research. Beta-amyloid peptide (Aβ13-23) was chosen as the amyloid protein Aβ40 fragment model. Analysis of 1H NMR spectra revealed that the interaction exists for both types of molecules. It was also suggested the possible location of gadolinium (III) ion in the studied molecules.

Оценка траектории метеороидов по марсианским кластерам

Recently, about 1200 fresh meteoroid impact sites were discovered on Mars, they are single craters and crater fields with crater sizes up to 50 m. Atmosphere density on the surface of Mars corresponds to about 30 km height of the Earth's atmosphere. Thus, scattering fields of craters on Mars allow one to study fragmentation details, which are hidden in terrestrial conditions. Previously, data on 77 Martian clusters were analyzed. To estimate the trajectory of meteoroids, the scattering ellipses were constructed. The ellipse size determines the angle of the meteoroid entry into the atmosphere and provides information about the height of destruction and the density of a space object. For more than 70% of clusters, the obtained azimuth estimations are within 20° of those determined by independent evaluations. For some clusters, the flight direction can be specified from crater ejecta on Martian HiRISE images. Estimations of azimuth angles for 42 clusters coincide with previous results obtained for 70% of clusters, while the data on the flight direction fit only for 30%. The discrepancy between different estimations of azimuth angles requires the use of other approaches. Continuing on the topic, this work presents numerical modeling of the flight and fragmentation of a meteoroid in the atmospheres of two planets, Mars and Earth. It is assumed that the simulation results will allow one to determine meteoroid parameters, in particular, the trajectory parameters. The main purpose of the presented work is to demonstrate the efficiency of the fragmentation model, its applicability to Martian clusters, and the difference in the scattering fields on the Earth and Mars: the atmospheric sorting effect is weak on Mars, and the scattering field is mainly dependent on fragmentation and the lateral spreading of fragments. The area of the simulated cluster is described with an accuracy of about 10%; the size of the maximum crater, with an accuracy of about 35%. The ratios of crater diameters to the maximum crater diameter for the model and real cluster are close to each other. In the future, it is planned to implement a series of numerical simulations with different initial data and to compare the results with real clusters on Mars, which have already been analyzed in previous works. The aim is to propose the advanced methods for determining the direction of the flight of meteoroids and the properties of impactors such as density and strength.

Octanol/Air Partition Coefficient─A General-Purpose Fragment Model to Predict Log Koa from Molecular Structure.

The octanol/air partition coefficient Koa is important for assessing the bioconcentration of airborne xenobiotics in foliage and in air-breathing organisms. Moreover, Koa informs about compound partitioning to aerosols and indoor dust, and complements the octanol/water partition coefficient Kow and the air/water partition coefficient Kaw for multimedia fate modeling. Experimental log Koa at 25 °C has been collected from literature for 2161 compounds with molecular weights from 16 to 959 Da. The curated data set covers 18.2 log units (from -1.0 to 17.2). A newly developed fragment model for predicting log Koa from molecular structure outperforms COSMOtherm, EPI-Suite KOAWIN, OPERA, and linear solvation energy relationships (LSERs) regarding the root-mean-squared error (rms) and the maximum negative and positive errors (mne and mpe) (rms: 0.57 vs 0.86 vs 1.09 vs 1.19 vs 1.05-1.53, mne: -2.55 vs -3.95 vs -7.51 vs -7.54 vs (-5.63) - (-7.34), mpe: 2.91 vs 5.97 vs 7.54 vs 4.24 vs 6.89-10.2 log units). The prediction capability, statistical robustness, and sound mechanistic basis are demonstrated through initial separation into a training and prediction set (80:20%), mutual leave-50%-out validation, and target value scrambling in terms of temporarily wrong compound-Koa allocations. The new general-purpose model is implemented in a fully automatized form in the ChemProp software available to the public. Regarding Koa indirectly determined through Kow and Kaw, a new approach is developed to convert from wet to dry octanol, enabling higher consistency in experimental (and thus also predicted) Koa.

Temperature Behavior of Precursor Clusters at the Pre-Crystallization Phase of K(H2PO4) Studied by SAXS

Elementary building blocks for the growth of KDP crystals were established. The solution of potassium dihydrogen phosphate (KH2PO4–KDP) has been experimentally studied by the small-angle X-ray scattering (SAXS) method. The analysis of SAXS data in the temperature range of 2.5–90 °C using a set of models of 3D fragments of the crystal structure showed that the saturated solution contains above K+, H2PO4− and KH2PO4 monomers, as well as mainly octamers. The 3D model of the octamer isolated from the crystal structure has dimensions of 17.443 Å along the [001] axis and 5.963 Å along the [100] and [010] axes. As the temperature is decreased, starting from the saturation temperature of the solution, the volume fraction of octamers sharply increases while the volume fraction of monomers decreases. The results indicate that the monomers and octamers represent major components in the solution with the presence of minor populations of other oligomers. The significant dominance of octamers in the supersaturated solution indicates that they are elementary building blocks for the growth of KDP crystals of tetragonal modification.

Improved accuracy and convergence of homotopy‐based solutions for aggregation–fragmentation models

We discuss the formulation of a numerical scheme based on the homotopy method to solve different aggregation–fragmentation models including the simultaneous event. Several test cases are considered and analyzed qualitatively and quantitatively to ascertain the improved accuracy and efficiency of the proposed model over the existing semi‐analytical models. The generalized solution of the truncated problem is obtained for some test cases, which in the limiting sense tends to the exact solution. A detailed convergence analysis of the scheme is also studied.

Henry's Law Constant─A General-Purpose Fragment Model to Predict Log Kaw from Molecular Structure.

Henry's law constant is important for assessing the environmental fate of organic compounds, including polar accumulation, indoor contamination, and the impact of airborne predominance on persistence. Moreover, it can be used in the context of alternative 3R bioassays to inform about the compound loss through volatilization as a confounding factor. For 2636 compounds, curated experimental log Kaw (air/water partition coefficient) data at 25° covering 23.6 orders of magnitude (from -18.6 to 5.0) have been collected from the literature. Subsequently, a new fragment model for predicting log Kaw from molecular structures has been developed. According to the root-mean-squared error (rms) and the maximum negative and positive errors (mne and mpe), this general-purpose model outperforms COSMOtherm, EPISuite HENRYWIN, OPERA, and LSER with calculated input parameters significantly (rms 0.50 vs 0.92 vs 1.25 vs 1.28 vs 1.38, mne -2.74 vs -6.78 vs -9.11 vs -6.24 vs -6.27, mpe 2.25 vs 6.22 vs 8.27 vs 11.5 vs 7.69 log units). Initial separation into a training and prediction set (80%:20%), mutual leave-50%-out validation, and target value scrambling (temporarily wrong compound-Kaw allocations) demonstrate the prediction capability, statistical robustness, and mechanistically sound basis of the fragment scheme. The new model is available to the public in fully computerized form through the ChemProp software, and can be combined with a separate existing model to extend the log Kaw prediction to temperatures different from 25 °C.

Adsorption of CH4/CO2/N2 by different functional groups in coal

To explore the microscopic mechanism of gas adsorption by different functional groups in coal and provide theoretical support for the prevention and control of coal mine gas disasters, a slit-pore model and fragment model modified by different functional groups were built using Materials Studio software, based on density functional theory and the Monte Carlo method. The adsorption characteristics of seven different functional group models on the gas were analyzed, and the microscopic mechanism of adsorption performance of different functional groups on CH4/CO2/N2 was revealed. The results showed that the order of the electrophilic ability of each functional group fragment followed benzene ring > –OH > –CO > –O–CH3 > –COOH > –CH3 > –CH2–CH3, and the order of nucleophilic ability was benzene ring > –CH2–CH3 > –CH3 > –COOH > –OH > –CO > –O–CH3. After adding different functional groups to the surface of the complete activated carbon, the electrophilic ability and nucleophilic ability decreased. The adsorption capacity was affected by both gas properties and functional group structure. The adsorption heat was not only affected by the adsorption amount but also by the non-uniformity of the adsorbent surface. The oxygen-containing functional groups were beneficial to the adsorption of CO2 gas, and the aliphatic functional groups were committed to the adsorption of CH4 and N2.

Fragmentation modeling of gas-phase ionic liquid clusters in high-voltage electric field

Cluster fragmentation subjected to a high-voltage electric field may play an important role in controlling the novel ionic liquid (IL) electrospray propulsion but has received little attention. In this work, the micro-fragmentation mechanisms of three kinds of IL clusters are numerically investigated using both static and dynamic approaches based on the quantum mechanical principles. Firstly, it reveals that the Coulomb interaction dominates the total inter-fragment energy for all three IL dimers, whereas the hydrogen-bonding interaction is identified as the main cause for the much slower break-up rate of the 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM-BF4]) dimer. In addition to the electrostatic interaction, the van der Waals interaction is a secondary energy component to which only a small fraction of atoms contribute significantly, regardless of IL cluster type. We find, only when the applied electric field is larger than 1 V/nm, the total inter-fragment energies of all three IL clusters start to dramatically reduced, indicating the possible occurrence of massive break-up. Secondly, ab initio molecular dynamics simulation further confirms that the [EMIM-BF4] negatively charged dimer is the most stable of three IL clusters under the identical conditions. As far as the high-voltage electric field is concerned, the one-parameter exponential function of break-up ratio versus time, routinely used in the field-free region, is not valid. Finally, on the basis of simulated results, a compound exponential-decay model is proposed, and the derived differential-sum equations from constant electric fields can be further applied to the non-uniform electric field.

Polyurea-coated ceramic-aluminum composite plates subjected to low velocity large fragment impact

Research on high-velocity bullet impact resistance of composite plates has been widely used in bulletproof material field, but limited studies have focused on the response of composite plate under low velocity and large fragment impact. In this paper, the impact response of polyurea-coated ceramic-aluminum composite plate to low velocity and large mass fragment was experimentally and numerically studied. The fragments were launched using a self-designed launcher, which can realize the free flip impact test of low velocity and large mass fragments with flight speed of 100–300 m/s and the mass of 0–100 g. Based on finite element method and smooth particle hydrodynamics, the impact model of low-velocity large fragments on composite plates was established to study fragment deformation and composite plate damage and compared with the experimental results to verify the effectiveness of the model. The multi-angle impact response of the fragment on the composite plate was studied. Results indicated that unlike the high-velocity impact of traditional bullets, low-velocity and large-mass fragments will flip in varying degrees after hitting the target accompanied by the deformation of the fragments, which remarkably influence the impact penetration ability of the fragments. Moreover, with the increase of biting angle, the composite plates show enhanced energy absorption capacity.

Mathematical Modeling of Fragmentation Under Plastic Deformation in Alloys with the L12 Structure

Mathematical Modeling of Fragmentation Under Plastic Deformation in Alloys with the L12 Structure

Microplastics in the first-year sea ice of the Novik Bay, Sea of Japan.

Sea ice is heavily contaminated with microplastics particles (MPs, <5mm). First-year sea ice cores (38-41cm thick) were taken in the beginning of spring in a narrow populated bay of the Sea of Japan. Two ice cores were examined (layer-by-layer, excluding surface) for MPs content: one using μ-FTIR for 25-300μm (SMPs), and another one - with visual+Raman identification for 300-5000μm particles (LMPs). The integral (25-5000μm) bulk mean abundance of MPs was found to be 428 items/L of meltwater, with fibers making 19% in SMPs size range and 59% in LMPs. Integral mean mass of MPs was estimated in 34.6mg/L, with 99.6% contribution from fragments of LMPs. Comparison with simple fragmentation models confirms deficit of SMPs (especially of fibers in size range 150-300μm), suggested to result from their leakage with brine. Multivariate statistical analysis indicates strong positive correlation of large fiber (>300μm) counts and ice salinity.