Relative Mobility Research Articles

The effect of chemical constitution on polyisoprene dynamics.

Polyisoprene (PI) melts have been studied, with most reports focusing on systems with high 1,4-cis content. In contrast, 1,4-trans PI homopolymers or random copolymers have seldom been examined, despite a handful of investigations suggesting a distinct dynamic behavior. Herein, we employ all-atom simulations to investigate the effect of chemical architecture on the dynamics of cis and trans-PI homopolymers, as well as copolymers. We examine the thermodynamic, conformational, and structural properties of the polymers and validate the performance of the models. We probe chain dynamics, revealing that cis-PI presents accelerated translation and reorientation modes relative to trans as recorded by the mean square displacement of the chain center-of-mass as well as by the characteristic times of the lower modes in a Rouse analysis. Interestingly, progressing to higher modes, we observe a reversal with trans units exhibiting faster dynamics. This was further confirmed by calculations of local carbon-hydrogen vector reorientation dynamics, which offer a microscopic view of segmental mobility. To obtain insight into the simulation trajectories, we evaluate the intermediate incoherent scattering function that supports a temperature-dependent crossover in relative mobility that extends over separations beyond the Kuhn-length level. Finally, we analyzed the role of non-Gaussian displacements, which demonstrate that cis-PI exhibits increased heterogeneity in dynamics over short-timescales in contrast to trans-PI, where deviations persist over times extending to terminal dynamics. Our all-atom simulations provide a fundamental understanding of PI dynamics and the impact of microstructure while providing important data for the design and optimization of PI-based materials.

The expression and correlation analysis of TOX and inhibitory receptors on peripheral blood CD8+T cells in patients with aplastic anemia

Objective: To investigate the expression levels of thymocyte selection related high mobility group proteins (TOX) and different inhibitory receptors in peripheral blood CD8+T cells of patients with aplastic anemia (AA), and to conduct correlation analysis. Methods: From September 2019 to November 2020, 27 AA patients in the Department of Hematology, General Hospital of Tianjin Medical University were retrospectively selected, including 21 males and 6 females, with a median age [M (Q1, Q3)] of 48 (30, 72) years. Thirty-three healthy controls, included 17 males and 16 females, with a median age of 46 (27, 69) years. The expression levels of TOX, programmed cell death receptor-1 (PD-1), T-cell immunoglobulin and mucin domain 3 (TIM-3), cytotoxic T-lymphocyte associated antigen-4 (CTLA-4), T-cell immune receptor with immunoglobulin (Ig) and immunoreceptor tyrosine-based inhibitory motif (ITIM) domain (TIGIT), perforin and granzyme B in peripheral blood CD8+T cells from AA patients and healthy controls were detected by flow cytometry. The correlation between TOX expression levels and different inhibitory receptors was analyzed using Pearson correlation analysis. Results: The expression levels of TOX, PD-1, TIM-3, CTLA-4, TIGIT, perforin, and granzyme B in peripheral blood CD8+T cells of AA patients were 47.33%(41.47%, 56.61%), (30.61±12.37)%, (39.94±10.84)%, (6.21±3.40)%, (51.45±20.21)%, (71.32±22.46)%, and (52.39±23.99)%, respectively, which were higher than those of healthy controls 27.32%(21.64%, 46.96%), (21.29±10.01)%, (21.11±3.00)%, (1.31±0.34)% (30.80±13.40)%, (46.72±22.53)%, (21.75±16.43)% (all P<0.05). The expression level of TOX in CD8+T cells was positively correlated with the expression levels of PD-1, TIM-3, CTLA-4, TIGIT, perforin, and granzyme B (r=0.49, 0.65, 0.70, 0.54, 0.58, 0.48, all P<0.05). Conclusion: The expression levels of TOX and different inhibitory receptors on peripheral blood CD8+T cells in AA patients are higher than those in the healthy control group, and the expression levels of TOX and different inhibitory receptors are positively correlated.

Why the Car Is Not Always King in Global South Cities: Evidence From Ulaanbaatar

Access to a private car has established itself as a critical control on mobility and access to opportunities for residents living in a diverse range of settings, globally. Across cities of the Global South, the benefits of private car access are often intensified by the absence of viable alternative modes of travel. This article explores the influence of private car access and mobility in relation to residents living in “ger district” areas of Ulaanbaatar, Mongolia’s capital city. These peri-urban areas are informally created when rural migrants set up home on the edge of the city, initially using mobile felt dwellings called “ger” that become augmented or replaced by permanent structures over time. An absence of forward planning as well as unmade roads and hilly topography mean that the ger districts are often poorly served by public transport, while the low density of the built environment also means that informal transport services can be limited in coverage and relatively expensive. This article utilises a database of household questionnaires collected in 2020 to compare mobility patterns and accessibility between car-owning and non-car-owning households in three case study ger districts, capturing seasonal differences between the extreme cold of the wintertime and warmer summer conditions. The findings not only reveal stark mobility and access differences in relation to car ownership but also discrepancies between car ownership and actual car use for important and routine journeys. This indicates that despite a lack of public transport available, many households opt to use what public transport they can. This pattern provides a potentially important basis for future policies that aim to limit car use in order to reduce traffic congestion and broaden access to the city for non-car-owning households by providing more accessible public transport.

Transformation of dissolved organic matter and related arsenic mobility at a surface water-groundwater interface in the Hetao Basin, China

Porewater arsenic mobility above the groundwater table has been recognized as a potential cause of arsenic-rich groundwater, but the processing pathways of dissolved organic matter (DOM) in that hyporheic zone and their effect on porewater arsenic release remain poorly understood. To address these issues, two porewater profiles were sampled in a surface water-groundwater interaction zone from the Hetao Basin, China, to monitor the porewater geochemistry and DOM molecular characteristics. The results show that the porewater arsenic, Fe(II), and DOC concentrations were all significantly higher than those of the intruding pond water, and were located above the conservative mixing model lines. This indicates a net release of these solutes from the sediment. By comparing the porewater with pond water DOM, we found that the carboxyl-rich alicyclic molecules (CRAM) were selectively preserved, carbohydrates and aliphatics/proteins were preferentially consumed, and low O/C-ratio compounds with high bioproduction index (I_bioprod) and terrestrial index (I_terr) were produced. The transformation of CHO to CHOS compounds also represented a pathway of recalcitrant DOM production. The produced recalcitrant organic compounds mostly contributed to the elevated porewater DOC concentrations, but their contribution decreased along the filtration path. The consumption of labile DOM compounds would be responsible for Fe(III) hydroxide reduction and arsenic release. The generated recalcitrant DOM may also be a driver of porewater arsenic mobility by acting as electron shuttles. This study highlights the importance of the hyporheic zone in shaping shallow groundwater DOM composition and the potential contribution to arsenic enrichment.

UAV-Empowered IoT Network With Hardware Impairments and Shadowing

This letter investigates the performance of an unmanned aerial vehicle (UAV)-enabled communication network for energy-constrained Internet of Things devices (IoDs) in the presence of transceiver hardware impairments. Herein, a UAV operates as a radio frequency energy harvesting transmitter for several IoDs and employs the decode-and-forward protocol to relay the gathered information from the IoDs to the base station. We employ a first-order autoregressive method for modeling the relative mobility between the nodes. The log-normal distribution is used to characterize the shadowing components for modeling the composite fading channel. We leverage the Gauss-Hermite quadrature method to obtain accurate expressions for the outage probability, followed by system throughput and energy efficiency.

Acoustofluidic Properties of Polystyrene Microparticles.

Acoustophoresis has become a powerful tool to separate microparticles and cells, based on their material and biophysical properties, and is gaining popularity in clinical and biomedical research. One major application of acoustophoresis is to measure the compressibility of cells and small organisms, which is related to their contents. The cell compressibility can be extracted from the acoustic mobility, which is the main output of acoustic migration experiments, if the material properties and sizes of reference particles, the size of the cells, and the surrounding medium are known. Accurate methods to measure and calibrate the acoustic energy density in acoustophoresis systems are therefore critical. In this Perspective, polystyrene microparticles have become the most commonly used reference particles in acoustophoresis, due to their similar biophysical properties to cells. We utilized a two-step focusing method to measure the relative acoustic mobility of polystyrene beads of various sizes and colors and present a quantitative analysis of the variation in acousto-mechanical properties of polystyrene microparticles, showing a large spread in their material properties. A variation of more than 25% between different particle types was found. Thus, care is required when relying on polystyrene particles as a reference when characterizing acoustofluidics systems or acousto-mechanical properties of cells.

Evaluation of open access COVID-19 related mobile applications in India: An application store-based quantitative analysis

Purpose: To assess the features/functionalities and quality of the (open access) COVID-19 specific mobile application for India using the Mobile Application Rating Scale (MARS) and the quality of the reported COVID-19 data using the COVID-19 Data Reporting System (CDRS). Methods: We used an analytical, cross-sectional study in which we reviewed all open access (free) mobile phone-based applications across the application stores, namely Google Android Play Store, iTunes and Google search engine. We used MARS and CDRS to assess the mobile applications applicable to India. Results: We found a total of 247 applications through the iTunes store (n=176), android store (n=70) and Google search (n=1). Out of 247, 70 applications matched the inclusion criteria, and only 42 applications were accessible for detailed evaluation using MARS. The overall mean (SD) MARS score was 3.27 (0.59). The mean (SD) score for application mean quality, app subjective quality and app-specific quality domains were 3.43 (0.43), 2.95 (0.71), and 3.44 (0.82), respectively. Of the 20 applications evaluated using CDRS, Aarogya (Agra) Sarvam Setu and Odisha COVID had the highest normalized score (0.9), whereas Madhya Pradesh COVID response app and WHO Academy COVID-19 had the lowest (0.1). Conclusion: Though the overall quality of the mobile applications is good, the engagement aspect of the mobile application quality needs improvement. Applications providing comprehensive COVID-19 related services are still lacking. The necessity of the hour is to assess the user’s perspective and the impact of application features on COVID-19 prevention and control, either individually or in groups.

Research on the forward-modeling method of viscoelastic Chapman extension in partially saturated rocks

The propagation of seismic waves in fractured rocks is greatly influenced by the fracture system and fluid content. Seismic anisotropy varies with frequency and fluid saturation. Previous theories on frequency-dependent anisotropy (FDA) are mostly limited to the assumption of single-phase fluid, whereas almost all reservoirs are usually partially or fully saturated with one or more fluids. The inelasticity, heterogeneity, and anisotropy exhibited by real earth media seriously challenge the traditional theory of uniform fully elastic media. Therefore, based on the Chapman elastic theory, we consider the viscoelastic model, the relative mobility of saturated fluids, and the coupled effects of commonly independently considered squirt flow and patch effects on the frequency-dependent anisotropic seismic wave propagation in viscoelastic media. By calculating the frequency-dependent anisotropic elastic coefficients of two-phase immiscible fluid-saturated fractured rocks, a new viscoelastic Chapman extension model for FDA in partially saturated rocks, which includes the unified seismic wave propagation effects of squirt flow and patch effects, is constructed. The effect of relative permeability is significant, and compared to the case of complete saturation, the effective fluid mobility in partially saturated rocks may be lower, which may lead to nonmonotonic changes in elastic modulus and water saturation. Numerical experiments are conducted on our viscoelastic Chapman extension model to discuss the coupling effects of squirt flow and patch effects on the FDA of viscoelastic media in cracked rocks with partially saturated reservoirs, under the conditions of no fractures and the existence of fractures. The simulation results of the P-wave modulus, P-wave velocity, and anisotropy parameters confirm the validity of our method and model. We link the anisotropy of viscoelastic media with fluid flow parameters in fractures, which is conducive to improving the understanding of frequency-dependent seismic anisotropy in partially saturated rocks with fractures and the combination of seismology and reservoir engineering.

The Role of Ion Rotation in Ion Mobility: Ultrahigh-Precision Prediction of Ion Mobility Dependence on Ion Mass Distribution and Translational to Rotational Energy Transfer.

The role of ion rotation in determining ion mobilities is explored using the subtle gas phase ion mobility shifts based on differences in ion mass distributions between isotopomer ions that have been observed with ion mobility spectrometry (IMS) measurements. These mobility shifts become apparent for IMS resolving powers on the order of ∼1500 where relative mobilities (or alternatively momentum transfer collision cross sections; Ω) can be measured with a precision of ∼10 ppm. The isotopomer ions have identical structures and masses, differing only in their internal mass distributions, and their Ω differences cannot be predicted by widely used computational approaches, which ignore the dependence of Ω on the ion's rotational properties. Here, we investigate the rotational dependence of Ω, which includes changes to its collision frequency due to thermal rotation as well as the coupling of translational to rotational energy transfer. We show that differences in rotational energy transfer during ion-molecule collisions provide the major contribution to isotopomer ion separations, with only a minor contribution due to an increase in collision frequency due to ion rotation. Modeling including these factors allowed for differences in Ω to be calculated that precisely mirror the experimental separations. These findings also highlight the promise of pairing high-resolution IMS measurements with theory and computation for improved elucidation of subtle structural differences between ions.

Effect of Malathion (An Organophospahte) on Electrophoretic Banding Patterns of Esterase Isozymes in Gill, Liver, Brain Tissue of Fresh Water Fish Channa Punctatus (Bloch)

This investigation was conducted to compare the electrophoretetic banding patterns of esterase isozyme in the gill, liver, and brain tissues of the freshwater fish Channa punctatus (Bloch) at 24 hours, 48 hours, 72 hours, and 96 hours after exposure to Malathion (an Organophosphate) to those at the control group. Quantitative analysis of the esterase isozymes was performed using 7.5 native polyacrylamide gel electrophoresis (PAGE) stained with -naphthyl acetate as substrate. The relative mobilities of three esterase Isozyme bands in gill, liver, and brain tissue were determined to be 0.60.05, 0.40.05, and 0.30.05, respectively; these bands were designated Est-1, Est-2, and Est-3, respectively. Control samples from the gill, liver, and brain all had all three esterase bands. Both Est 2 and Est-3 Esterase Isozyme bands in gill and liver tissue were eliminated when fish were subjected to Malathion (an Organophosphate) for 72 and 96 hours, respectively. Malathion induced greater damage in Est-1 and Est-3 brain tissue than in Est-2.

A high resolution differential mobility analyzer for the study of large virus particles

The conical inner electrode of a recently described differential mobility analyzer (DMA), covering at resolution >50 the size range up to 60 nm, has been modified by increasing its radius at the outlet slit from 1 cm to 1.6 cm, and decreasing its convergence angle from 3° to 0.5°. The cylindrical outer electrode radius is maintained at 2 cm, while other critical dimensions are only slightly modified. The classification voltage for fixed flow rate of sheath gas and particle diameter decreases almost fourfold, extending the size range theoretically spanned at high resolution well beyond 120 nm. Tests with multiply charged polystyrene latex spheres 200 nm in diameter confirm the actual ability to cover this wide size range. A resolution above 100 (with no corrections for instrument or particle nonidealities) is demonstrated with rotavirus double-layered particles (DLP) whose mobility diameter is found to be near 60 nm. The DLP has several configurations that complicate its use for DMA characterization, but occasionally presents mainly one conformer, with singularly narrow relative mobility width FWHM < 1/150. Two broad range instruments with slightly different axial lengths have been developed and tested, both reaching resolving powers of 100.

Preparation of degenerate n-type AlxGa1−xN (0 &amp;lt; x ≤ 0.81) with record low resistivity by pulsed sputtering deposition

Highly conductive AlGaN alloys hold a great technological potential, wherein the degenerate n-type doping is key in reducing parasitic resistances in electronic and opto-electronic devices. Nonetheless, AlxGa1−xN elaborated in conventional methods exhibits degraded electron concentration at high Al compositions. Here, we demonstrated the growth of degenerate n-type AlxGa1−xN (0 &amp;lt; x ≤ 0.81) with record high electron concentrations by using the pulsed sputtering deposition (PSD) method. The fabricated samples were investigated by cathodoluminescence and Hall-effect measurements in studying the related deep-level emission and electron mobility, respectively. Our findings showed that the PSD-grown heavily Si-doped AlxGa1−xN exhibits record low resistivity values: 2.5 × 10−3 Ω cm with an electron concentration of 1.2 × 1020 cm−3 for x = 0.60 and 1.7 × 10−2 Ω cm with an electron concentration of 3.2 × 1019 cm−3 for x = 0.81. Temperature-dependent Hall-effect measurements confirmed the degenerate nature of heavily Si-doped AlxGa1−xN up to x = 0.81. These results clearly show that the PSD n-type AlGaN is quite promising for reducing parasitic resistance in AlGaN based far UVC light-emitting devices and high breakdown voltage electron devices.

Controlled p-Type Doping of Pyrite FeS2.

Pyrite FeS2 has extraordinary potential as a low-cost, nontoxic, sustainable photovoltaic but has underperformed dramatically in prior solar cells. The latter devices focus on heterojunction designs, which are now understood to suffer from problems associated with FeS2 surfaces. Simpler homojunction cells thus become appealing but have not been fabricated due to the historical inability to understand and control doping in pyrite. While recent advances have put S-vacancy and Co-based n-doping of FeS2 on a firm footing, unequivocal evidence for bulk p-doping remains elusive. Here, we demonstrate the first unambiguous and controlled p-type transport in FeS2 single crystals doped with phosphorus (P) during chemical vapor transport growth. P doping is found to be possible up to at least ∼100 ppm, inducing ∼1018 holes/cm3 at 300 K, while leaving the crystal structure and quality unchanged. As the P doping is increased in crystals natively n-doped with S vacancies, the majority carrier type inverts from n to p near ∼25 and ∼55 ppm P, as detected by Seebeck and Hall effects, respectively. Detailed temperature- and P-doping-dependent transport measurements establish that the P acceptor level is 175 ± 10 meV above the valence band maximum, explain details of the carrier inversion, elucidate the relative mobility of electrons and holes, reveal mid-gap defect levels, and unambiguously establish that the inversion to p-type occurs in the bulk and is not an artifact of hopping conduction. Such controlled bulk p-doping opens the door to pyrite p-n homojunctions, unveiling new opportunities for solar cells based on this extraordinary semiconductor.

Is alumina suitable for solid phase extraction of catecholamines from brain tissue?

Occupational and environmental toxicology specialists find catecholamine fluctuations in brain tissue relevant for research of neurotoxicity, such as that induced by manganese or zinc, pesticides, industrial solvents, plastic, air pollution, or irradiation. Considering that catecholamine tissue concentrations are generally very low, their extraction requires a reliable and optimal method that will achieve maximum recovery and minimise other interferences. This study aimed to evaluate whether the aluminium (III) oxide (Al2O3, alumina) based cartridges designed for catecholamine isolation from plasma could be used for solid-phase extraction (SPE) of catecholamine from the brain tissue. To do that, we homogenised Wistar rat brain tissue with perchloric acid and compared three extraction techniques: SPE, the routine filtration through a 0.22 µm membrane filter, and their combination. In the extracts, we compared relative chromatographic catecholamine mobility measured with high performance liquid chromatography with electrochemical detection. Chromatographic patterns for norepinephrine and epinephrine were similar regardless of the extraction technique, which indicates that the alumina cartridge is good enough to isolate them from brain tissue. However, the dopamine pattern was unsatisfactory, and further experiments are needed to identify the issue and optimise the protocol.

The trade-off between COVID-19 and mental diseases burden during a lockdown: Mathematical modeling of control measures.

During the COVID-19 pandemic, many countries used lockdowns as a containment measure. While lockdowns successfully contributed to slowing down the contagion, the related mobility restrictions were reportedly associated with an increased risk of major depressive and anxiety disorders. We aimed to quantify the trade-off between the quality-adjusted life years (QALY) gain due to lower COVID-19 incidence as a result of a lockdown and QALY loss due to lockdown-induced mental disorders. We developed an agent-based model of COVID-19 epidemic and coupled mental disorder development in the population of a large city. We used data sources on the places of living, studying and working, public health and census surveys. Modeling of mental disorders was based on diathesis-stress concept. We quantified mental and physical health burden in terms of QALY taking into account major depressive and anxiety disorder episodes, lethal and non-lethal cases of COVID-19, and immunization. We evaluated the dynamics of new major depressive disorder (MDD) and anxiety disorder (AD) cases during the period between September 2020 and December 2021 in Moscow, Russia. We found that lockdown imposition increases the daily chances of getting MDD or ADD by a vulnerable person by 16.79% (95% CI [12.36%, 21.23%]). The QALY loss associated with COVID-19-induced and lockdown-induced mental disorders was estimated to be 18.93% (95% CI [16.94%, 19.73%]) of the total QALY loss caused by COVID-19, immunization, and all kinds of mental disorders. For a synthetic "strong" lockdown, it had been shown that QALY loss is minimized when about 70% of the population are isolated. The burden associated with mental disorders amounts to a considerable part of COVID-19-related losses. Our findings demonstrate that cost-benefit analysis of mobility restriction should include a forecast of mental disorder development in the population.

Eddy-Current Actuator for Attraction and Repulsion of Non-Ferromagnetic, Conductive Spacecraft

This paper introduces a propellant-free approach to mobility of an inspection or servicing vehicle. The approach is suitable for motion near the surface of non-ferromagnetic, conductive objects in orbit. This work considers the specifics of eddy-current interactions between a translating permanent magnet and the aluminum surfaces of spacecraft. Such an actuator moves within the body of an inspection vehicle, requiring that its motion remains limited if the vehicle is to continuously interact with the client spacecraft. Experimental verification on a low-friction air track verifies a model for attraction–repulsion dynamics at millimeter-scale initial separations in one dimension. Results show good agreement between the simulated and tested conditions and motivate extension of the model to more general cases. To bound the design space and relative distances at which this actuator is effective, this work identifies the required size, mass, and trajectories for repulsion that restores the actuator to its initial configuration. Results support the utility of eddy-current actuation for microsatellites at separations of millimeters to centimeters from their conductive clients. For such clients the actuator may enable relative mobility and achieve other objectives key to proximity operations.

The Adriatic Catholic Marian Pilgrimage in Nin near Zadar as a Maritime Pilgrimage

Following the general approach to pilgrimage as established by anthropologists and other scientists, the paper analyses the pilgrimage in Nin to Our Lady of Zečevo. More specifically, this pilgrimage will be observed as a maritime pilgrimage, following relevant recent research. Based on the oral story about the apparition of Virgin Mary to a widow, the statue of Mary is transported from Nin in a boat procession via sea to a mediaeval church on the nearby uninhabited island of Zečevo. Pilgrimage practices include many sensorial and symbolic practices, so it will be analysed from several points of view and more than one theoretical approach, including the relational approach and mobility turn, applied also to maritime pilgrimage with a reflection on influence of tourism on pilgrimage activities, especially in the Mediterranean. The paper relies on the field research from 2020–2023 in Nin near Zadar in Croatia which has been supported in part by the Croatian Science Foundation under the project ‘PILGRIMAR’ (UIP-2019-04-8226).

Gendered intergenerational educational mobility patterns converge in the cohort sequence: evidence from Switzerland using administrative data.

In many societies, educational attainment determines social inequality in terms of life chances, and at the same time there is a strong link between social origin and educational success. Therefore, analysis of educational mobility patterns is a central concern for sociologists. In the context of societal changes, such as trend of modernization, educational expansion and significantly increased female participation in education, we use administrative data from different sources (N = 556,112) to examine the extent to which absolute and relative intergenerational educational mobility has changed in Switzerland for women and men from the 1951-1990 birth cohorts. We show that there is significantly more upward than downward mobility, while a large proportion of individuals are laterally mobile. By looking at absolute mobility patterns by cohort and gender separately, we extend previous research and show that the decreasing absolute mobility rates are due to the changing educational composition of the parental generations. Following on from previous studies, we reveal that the observed trend toward less relative social mobility continues in the youngest cohorts. It is also worth noting that, while the father's educational attainment has a higher predictive power for children's education in all cohorts, the impact of the mother's education approaches that of the father. Overall, the mobility patterns of men and women converge very strongly over the cohort sequence. Beyond these substantive points, our study demonstrates the potential of using administrative data for social stratification research.

Controls of local grain size distribution, bed structure and flow conditions on sediment mobility

AbstractSteep, boulder bed streams often contain sediment patches, which are areas of the bed with relatively well‐defined boundaries that are occupied by distinct grain size distributions (GSD). In sediment mixtures, the underlying GSD affects the critical Shields stress for a given grain size, which is commonly predicted using hiding functions. Hiding functions may vary with reach‐wide bed GSD, but the effect of local GSD on relative sediment mobility between sediment patches is poorly understood. We explore the effects of patch‐scale GSD on sediment mobility using tracer particles combined with local shear stresses to develop hiding functions for different patch classes within a steep stream. Hiding functions for all tested patch classes were similar, which indicates that the same hiding function can be used for different patches. However, the critical Shields stress for a given grain size generally decreased with lower patch median grain size (D50) suggesting that patches control the relative mobility of each size through both the underlying GSD and local shear stresses. The effects of the underlying GSD partly depend on grain protrusion, which we measured for all grain sizes present on each patch class. Protrusion was generally greater for larger grains regardless of patch class, but for a given grain size, protrusion was increased with smaller patch D50. For a given grain size, higher protrusion results in greater applied fluid forces and reduced resisting forces to partly explain our lower critical Shields stresses in finer patches. Patches therefore can importantly modulate relative sediment mobility through bed structure and may need to be included in reach‐scale sediment transport and channel stability estimates.

The impact of overqualification on the intention of urban withdrawal from the perspective of talent crowding

Talent agglomeration greatly promotes the development of cities as a special form of talent allocation. However, excessive agglomeration of talent also leads to talent crowding and overqualification, which undermines the effectiveness of employing human resources and stimulates talent urban withdrawal. Based on the data from 327 questionnaires, data analysis was performed using Mplus 8.0 and HLM 6.08, this study explores the internal mechanism between overqualification and talent's intention of urban withdrawal from the perspective of talent crowding. The following conclusions were drawn: (1) Overqualification is positively correlated with talents' intention of urban withdrawal. (2) Psychological contract breach plays a mediating effect between overqualification and the talents' intention of urban withdrawal. (3) Relational mobility is negatively correlated with talents' intention of urban withdrawal. (4) Relational mobility plays a moderating role in the relationship between overqualification and talents' intention of urban withdrawal. (5) Urban livability is negatively correlated with talents' intention of urban withdrawal. (6) Urban livability plays a moderating role in the relationship between overqualification and talents' intention of urban withdrawal. The results can further improve the human resource management theory and serve as a foundation for developing and implementing population management policies in cities.