Interstitial Migration Research Articles

Theoretical study of Li-ion migration in perovskite­type AVO3 (A = Ca, La, Ce, and La0.75Ca0.25) with DFT+U methods

Density functional theory (DFT) simulations were carried out to investigate the Li­-ion migration characteristics in perovskite-type vanadium oxides AVO3 (A = Ca, La, Ce, and La0.75Ca0.25). The formation energies of interstitial Li ions in the bulk phase of AVO3 were calculated by DFT+U, followed by the comparative analysis of the electronic structures of pure AVO3 and AVO3 containing the interstitial Li-ion, and finally the Li­ion migration paths and energy barrier values in AVO3 were determined using the NEB method of the interstitial Li-ion migration mechanism. The results showed that 8d site and 4c site are occupied by the Li ions in the AVO3. For the average lithiation voltage, values of CaVO3 and La0.75Ca0.25VO3 were larger than the corresponding values for LaVO3 and CeVO3. LaVO3 with the interstitial Li(8d) ion displayed a minimal rate of change in cell volume. The DOS calculations showed that AVO3 with the interstitial Li ion had better electrical conductivity than pure AVO3, and the conductivity of La0.75Ca0.25VO3 was enhanced compared to LaVO3. There were two migration paths in this system, where the minimum migration energy barriers for Li ions in CaVO3, LaVO3, CeVO3, and La0.75Ca0.25VO3 were 0.930 eV, 1.917 eV, 1.787 eV, and 1.756 eV respectively.

Trap-limited diffusion of Zn in β−Ga2O3

Diffusion of Zn in (001)- and $(\overline{2}01)$-oriented $\ensuremath{\beta}\text{\ensuremath{-}}{\mathrm{Ga}}_{2}{\mathrm{O}}_{3}$ was studied using secondary-ion mass spectrometry and first-principles calculations based on hybrid and semilocal functionals. The $\ensuremath{\beta}\text{\ensuremath{-}}{\mathrm{Ga}}_{2}{\mathrm{O}}_{3}$ samples were sealed in quartz ampules together with a piece of metallic Zn and heated to temperatures of 900--1100 ${}^{\ensuremath{\circ}}\mathrm{C}$ for 1 h. The Zn concentration profiles as a function of depth were simulated by employing the trap-limited diffusion model. From this model the migration barrier for Zn diffusion was found to be ${E}_{m}=2.2\ifmmode\pm\else\textpm\fi{}0.2\phantom{\rule{4.pt}{0ex}}$ and $2.1\ifmmode\pm\else\textpm\fi{}0.1\phantom{\rule{4.pt}{0ex}}\phantom{\rule{0.28em}{0ex}}\mathrm{eV}$ in the (001) and ($\overline{2}01$) orientations of $\ensuremath{\beta}\text{\ensuremath{-}}{\mathrm{Ga}}_{2}{\mathrm{O}}_{3}$, respectively, with corresponding dissociation energies of ${E}_{d}$ = 3.5 $\ifmmode\pm\else\textpm\fi{}1.1$ and $3.2\ifmmode\pm\else\textpm\fi{}0.6\phantom{\rule{4.pt}{0ex}}\phantom{\rule{0.28em}{0ex}}\mathrm{eV}$. Results from the first-principles calculations predict an interstitialcy mechanism for the Zn diffusion when it is not in its trapped state. Using the nudged elastic band method, we obtain a barrier of 1.6 eV for migration of Zn split interstitials $({\mathrm{Zn}}_{i})$ in both the [001] and $[\overline{2}01]$ directions, in accordance with the results obtained from the trap-limited diffusion model. Interestingly, the Ga vacancy is found to be able to trap two Zn atoms forming a shallow donor complex labeled ${\mathrm{Zn}}_{i}{\mathrm{Zn}}_{\mathrm{Ga}}$. The energy needed for ${\mathrm{Zn}}_{i}$ to dissociate from this donor complex is estimated to be 2.99 eV, in reasonable agreement with the trap dissociation energies extracted from the diffusion model.

Spatial inhomogeneity of point defect properties in refractory multi-principal element alloy with short-range order: A first-principles study

Short-range order can be developed in multi-principal element alloys and influences the point defect behavior due to the large variation of the local chemical environment. The effect of short-range order on vacancy and interstitial formation energy and migration behavior was studied in body-centered cubic multi-principal element alloy NbZrTi by first-principles calculations. Two short-range order structures created by density functional theory and Monte Carlo method at 500 and 800 K were compared with the structure of random solid solution. Both vacancy and interstitial formation energies increase with the degree of short-range order. Point defect formation energies tend to be higher in regions enriched in Nb and lower in regions enriched in Zr and Ti. Both vacancies and interstitials prefer to migrate toward Zr,Ti-rich regions and away from Nb-rich regions, suggesting that Zr,Ti-rich regions can potentially act as recombination centers for point defect annihilation. Compared to an ideal random solid solution, the short-range order increases the spatial inhomogeneity of point defect energy landscape. Tuning the degree of short-range order by different processing techniques can be a viable strategy to optimize the point defect behavior to achieve enhanced radiation resistance in multi-principal element alloys.

Neutrophils exhibit distinct migration phenotypes that are modulated by transendothelial migration.

Neutrophil extravasation, a critical component of the innate immune response, comprises two sequential processes: transendothelial migration (TEM) and interstitial migration. TEM requires intimate physical contact between leukocytes and vascular endothelial cells, triggering a cascade of biochemical and biomechanical interactions whose effect on leukocyte interstitial migration is currently unclear. To address this question, we culture human umbilical vascular endothelial cells on a fibronectin-treated transwell insert, mimicking the endothelium and basement membrane in vitro. Neutrophil-like differentiated HL60 (dHL-60) cells are loaded in the upper chamber of the insert, and cells that cross the membrane-supported monolayer are collected from the lower chamber. These cells are then seeded in a custom-built chemotaxis device containing a collagen gel matrix to study their 3D migration in the presence or absence of an fMLP gradient. dHL-60 cells that do not pass through the transwell insert serve as controls. Data collected from over 37,000 dHL-60 trajectories show two distinct migratory phenotypes conserved across treatment conditions: the high motility subpopulation is characterized by faster, more persistent cells undergoing fewer turning events; while the mid-motility subpopulation demonstrates lower speeds, increased incidence of large angle and 180o turns, and loitering periods in localized regions of the matrix. Changes in the relative proportion of subpopulations between conditions are correlated with changes in GRK2 expression levels. Our results suggest TEM may modulate GRK2 expression to prime neutrophils for a migration phenotype better suited for spatial exploration than highly persistent chemotaxis. In conjunction with previously presented TEM-induced changes in neutrophil ICAM-1 expression, associated with increased phagocytosis and neutrophil effector functions, this suggests a functional purpose underlying the shift in primary migration phenotype after TEM. These observations provide novel insight into the biophysical impacts of TEM that prime neutrophils to conduct sentinel functions.

Migration of Ga vacancies and interstitials in β−Ga2O3

The authors present a systematic and comprehensive theoretical study of Ga vacancy and interstitial migration in monoclinic gallium sesquioxide, based on hybrid functional calculations and the nudged elastic band technique. Notably, it is shown that the Ga vacancy can form a favorable three-split configuration, consisting of three Ga vacancies and two Ga interstitials, which enables migration with a dramatically lower migration barrier than previously calculated, further demonstrating the important role of split vacancies in this material.

Mechanisms for Radiation Resistance of InP Photovoltaic Cells: A First Principle Study

Herein, the mechanisms for radiation resistance of InP are investigated using first‐principle computational methods. It is found that the substantial recovery of post‐irradiated solar cells is attributed to the minority‐carrier‐injection‐enhanced annealing of the negative‐U defects, phosphorus vacancies, which produce the (0/−) and (+/0) level corresponding to the deep‐level transient spectroscopy signature H4 and E11, respectively. P vacancies can annihilate with P interstitials at low temperature, where by alternately capturing carrier with opposite sign P, interstitials become highly mobile upon minority‐carrier injection. By such Bourgoin diffusion mechanism, the calculated barrier for P interstitial migration and P Frenkel pair recombination are lowered to 0.04 and 0.16 eV, respectively. The results agree fairy well with experimental observations.

Approaches to Determine Nuclear Shape in Cells During Migration Through Collagen Matrices.

Fibrillar collagen is an abundant extracellular matrix (ECM) component of interstitial tissues which supports the structure of many organs, including the skin and breast. Many different physiological processes, but also pathological processes such as metastatic cancer invasion, involve interstitial cell migration. Often, cell movement takes place through small ECM gaps and pores and depends upon the ability of the cell and its stiff nucleus to deform. Such nuclear deformation during cell migration may impact nuclear integrity, such as of chromatin or the nuclear envelope, and therefore the morphometric analysis of nuclear shapes can provide valuable insight into a broad variety of biological processes. Here, we describe a protocol on how to generate a cell-collagen model in vitro and how to use confocal microscopy for the static and dynamic visualization of labeled nuclei in single migratory cells. We developed, and here provide, two scripts that (Fidler, Nat Rev Cancer 3(6):453-458, 2003) enable the semi-automated and fast quantification of static single nuclear shape descriptors, such as aspect ratio or circularity, and the nuclear irregularity index that forms a combination of four distinct shape descriptors, as well as (Frantz et al., J Cell Sci 123 (Pt 24):4195-4200, 2010) a quantification of their changes over time. Finally, we provide quantitative measurements on nuclear shapes from cells that migrated through collagen either in the presence or the absence of an inhibitor of collagen degradation, showing the distinctive power of this approach. This pipeline can also be applied to cell migration studied in different assays, ranging from 3D microfluidics to migration in the living organism.

Effects of tungsten on vacancy aggregation behavior and its induction for interstitial and vacancy migration in tantalum–tungsten alloys: A first-principles study

Tantalum–tungsten (Ta–W) alloys have been considered candidates for plasma-facing materials (PFMs) in advanced nuclear fusion design due to their excellent thermal and mechanical properties. Herein, the effects of tungsten (W) on the clustering and migration of vacancies and interstitials in Ta are studied using first-principles calculations. We find that W can attract vacancies at the second nearest neighbor position, causing the original non-clustered W to gather around the vacancies, forming an octahedral cluster structure. However, as the number of W atoms increases, W exerts a progressive inhibitory effect on the formation of vacancy clusters. Furthermore, this work confirms that W induces the migration of vacancies, thus significantly improving the mobility and recombination ability of vacancies. Similarly, W also induces the migration of interstitial atoms in addition to reducing the interstitial rotation threshold energy, leading to an evolution of Ta–Ta interstitial to Ta–W interstitial. Therefore, it can be speculated that W not only plays a vital positive role in the combination between interstitials and vacancies, but also can effectively inhibit the formation of voids by adding W, and then improving the anti-irradiation ability of Ta–W alloy material under neutron irradiation.

The role of the cd99l2 gene on leukocyte interstitial migration in zebrafish.

Leukocytes play an essential role in ontogeny, tissue regeneration, and innate and adaptive immunity. The migration of leukocytes to the infected or traumatized areas is necessary for their immune response function. As an adhesion molecule, CD99L2 is crucial in the extravasation of leukocytes, however, its role in the interstitial migration of leukocytes remains unclear. In this study, the cd99l2 gene was knock-out by TALEN (transcription activator-like effector nuclease) in zebrafish and discovered that the deletion had no effect on zebrafish development. The number of granulocytes and macrophages recruited to the wounded tissue was significantly reduced in the cd99l2 mutants following caudal fin damage. Further research revealed that the expression of mfap4 was drastically decreased in the cd99l2 mutants, which may be one of the reasons that affect the migration of macrophages to the wound site. Moreover,transgenic lines with labeled vasculature, neutrophils and macrophages demonstrated that neutrophils and macrophages migrate throughout the interstitial space to the wound tissue in both wild-type and mutant zebrafish at 60 hours post-fertilization, indicating that the cd99l2 gene is involved in the interstitial migration of leukocytes. Finally, RNA transcription, protein folding, and the P450 pathway were enriched in cd99l2 mutants by RNA-seq analysis. Previous research had demonstrated that the regulation of transcription and signal transduction could be affected by adhesion molecules, which may suggest that the cd99l2 gene is involved in the cascade signaling pathway of leukocyte migration as an adhesion molecule. In conclusion, this study uncovered a novel function of the cd99l2 gene in the process of leukocyte migration in zebrafish, which is expected to provide a theoretical foundation for inflammatory and immune-related diseases.

Trends in the Behavior of Point Defects in MB and MAB Phases

Binary and ternary transition metal borides exhibit many outstanding properties, such as high melting temperature, high temperature strength, and electrical and thermal conductivities. However, defect properties have been rarely studied so far. Here, using first-principles calculations, we investigate structural effects on defect recovery processes in MB and MAB phases focusing on how Al layers and the type of transition metal affect annihilation of defects. First, we find that metal interstitials cannot be accommodated in MAB phases that have two Al layers, but instead they form antisites, which are largely immobile and therefore detrimental for defect recovery processes. We also find that the absence of Al layers in MB phases that have B chains leads to faster migration of metal interstitials and lower recombination barriers of B Frenkel pairs and hence contributes to efficient defect recovery processes of those MB phases as compared to the corresponding MAB phases. In the other types of MB and MAB phases that have B rings, we find that the role of Al layers varies depending on the type of metal elements. Lastly, we find that a larger M–B bond strength, which depends on the type of transition metal in MAB phases, correlates with a higher recombination barrier of B Frenkel pairs. Based on the discovered trends, we provide insights into the selection of materials to help design diverse applications where defect recovery processes are important.

Aging is accompanied by T-cell stiffening and reduced interstitial migration through dysfunctional nuclear organization.

Age-associated changes in T-cell function play a central role in immunosenescence. The role of aging in the decreased T-cell repertoire, primarily because of thymic involution, has been extensively studied. However, increasing evidence indicates that aging also modulates the mechanical properties of cells and the internal ordering of diverse cell components. Cellular functions are generally dictated by the biophysical phenotype of cells, which itself is also tightly regulated at the molecular level. Based on previous evidence suggesting that the relative nuclear size contributes to variations of T-cell stiffness, here we examined whether age-associated changes in T-cell migration are dictated by biophysical parameters, in part through nuclear cytoskeleton organization and cell deformability. In this study, we first performed longitudinal analyses of a repertoire of 111 functional, biophysical and biomolecular features of the nucleus and cytoskeleton of mice CD4+ and CD8+ T cells, in both naive and memory state. Focusing on the pairwise correlations, we found that age-related changes in nuclear architecture and internal ordering were correlated with T-cell stiffening and declined interstitial migration. A similarity analysis confirmed that cell-to-cell variation was a direct result of the aging process and we applied regression models to identify biomarkers that can accurately estimate individuals' age. Finally, we propose a biophysical model for a comprehensive understanding of the results: aging involves an evolution of the relative nuclear size, in part through DNA-hypomethylation and nuclear lamin B1, which implies an increased cell stiffness, thus inducing a decline in cell migration.

First-principles calculations to study the metal-insulator transition of Al and Be doped RNiO3 (R = Pr, Nd, Sm, Gd, Tb, Dy, Ho and Er)

Rare earth nickelates (RNO) have been extensively studied in the past decades because of the metal-insulator phase transition. It was reported that the phase transition of RNO could be regulated with the electrons introduced by Li and H doping, but little is known about the multi-electrons (such as Be, Al) doping of RNO. In this paper, we applied the first-principles calculations to investigate the electronic structures, interstitial formation energies, migration behaviors and optical properties of Be and Al doped RNO. Results show that RNO would undergo a metal-insulator phase transition when the Be and Al doping concentrations respectively reach 50% and 25%. In addition, the migration of Be and Al along the [001] direction of RNO shows that as the radius of rare earth atoms decreases, the migration barrier generally shows a decreasing trend. As for optical properties, the absorption coefficient and reflectivity decrease in Be and Al doped RNO over the entire range of visible and infrared light. Generally, the transmissivity of RNO can be greatly improved by doping 50% of Be and Al.

Ibrutinib Does Not Impact CCR7-Mediated Homeostatic Migration in T-Cells from Chronic Lymphocytic Leukemia Patients.

Simple SummaryBruton’s tyrosine kinase inhibitor ibrutinib restores T-cell immunity and increases circulating T-cell numbers in chronic lymphocytic leukemia (CLL) patients. Recent evidence suggests T-cell enhanced expansion, rather than increased egress from secondary lymphoid organs (SLO), as a root cause for ibrutinib-induced lymphocytosis. However, this physiological change might reflect, as well, a forced retention in PB derived of impaired migration to SLO. With the aim to investigate the impact of ibrutinib on CCR7-mediated homeostasis in CLL T-cells, we have documented receptor expression in a large cohort of ibrutinib-treated patients, and performed different in vivo and in vitro migration models. We show that ibrutinib has no effect on CCR7 expression or receptor-mediated T-cell chemotaxis, homing to SLO, and interstitial migration. Together, these results indicate that ibrutinib T-lymphocytosis is not caused by accumulation in the blood stream, and therefore back the T-cell expansion as the most plausible cause.Bruton’s tyrosine kinase inhibitor ibrutinib has significantly changed treatment landscape in chronic lymphocytic leukemia (CLL). Growing evidence supports ibrutinib to work beyond the effect on tumor cells by means of, for example, restoring functionality of the T-cell compartment and increasing circulating T-cell numbers. Recent evidence suggests T-cell enhanced expansion, rather than increased egress from secondary lymphoid organs (SLO), as a root cause for ibrutinib-induced lymphocytosis. However, whether the latter physiological change is also a consequence of a forced retention in blood remains undisclosed. Since CCR7 is the main chemokine receptor taking over the homing of T-cells from peripheral compartments to lymph nodes and other SLO, we aimed to investigate the impact of ibrutinib on CCR7 functionality in T-cells. To this end, we documented receptor expression in T-cells from a large cohort of ibrutinib-treated CLL patients, and performed different in vivo and in vitro migration models. Overall, our data confirm that CCR7 expression or receptor-mediated migration in CLL T-cells is not affected by ibrutinib. Furthermore, it does not modulate CCR7-driven homing nor nodal interstitial migration. Together, our results support that ibrutinib-induced CLL T-cell accumulation in the blood stream is not derived from an impairment of CCR7-driven recirculation between the SLO and bloodstream, and therefore T-cell expansion is the most plausible cause.

Imaging Neutrophil Migration in the Mouse Skin to Investigate Subcellular Membrane Remodeling Under Physiological Conditions.

The study of immune cell recruitment and function in tissues has been a very active field over the last two decades. Neutrophils are among the first immune cells to reach the site of inflammation and to participate in the innate immune response during infection or tissue damage. So far, neutrophil migration has been successfully visualized using various in vitro experimental systems based on uniform stimulation, or confined migration under agarose, or micro-fluidic channels. However, these models do not recapitulate the complex microenvironment that neutrophils encounter in vivo. The development of multiphoton microscopy (MPM)-based techniques, such as intravital subcellular microscopy (ISMic), offer a unique tool to visualize and investigate neutrophil dynamics at subcellular resolutions under physiological conditions. In particular, the ear of a live anesthetized mouse provides an experimental advantage to follow neutrophil interstitial migration in real-time due to its ease of accessibility and lack of surgical exposure. ISMic provides the optical resolution, speed, and depth of acquisition necessary to track both cellular and, more importantly, subcellular processes in 3D over time (4D). Moreover, multi-modal imaging of the interstitial microenvironment (i.e., blood vessels, resident cells, extracellular matrix) can be readily accomplished using a combination of transgenic mice expressing select fluorescent markers, exogenous labeling via fluorescent probes, tissue intrinsic fluorescence, and second/third harmonic generated signals. This protocol describes 1) the preparation of neutrophils for adoptive transfer into the mouse ear, 2) different settings for optimal sub-cellular imaging, 3) strategies to minimize motion artifacts while maintaining a physiological response, 4) examples of membrane remodeling observed in neutrophils using ISMic, and 5) a workflow for the quantitative analysis of membrane remodeling in migrating neutrophils in vivo.

SCHISTOSOMA TURKESTANICA SKRJABIN, 1913: TOPOGRAPHY OF CERCARIAE EMISSION FROM A SPONTANEOUSLY INVADED OBLIGATE INTERMEDIATE HOST LYMNAEA AURICULARIA L., 1758

The algorithm of ethology of cercariae (=furcocercariae) of the trematode Schistosoma turkestanica Skrjabin, 1913, when implementing the scenario of the emission process from the naturally invaded mollusk Lymnaea auricularia L., 1758, is constant and consists of two periods. In the first, preliminary, larvae migrate into the subepithelial tissue of the mollusk. In the second, final, consisting of two phases, furcocercariae pierce the epithelial tissue "from the inside out" and go out into the external environment. Initiation by cercariae of the process of exit from the body of the mollusk Lymnaea auricularia L., 1758, excludes the possibility of suspension or reverse development of the sequence of events. Anatomical and topographic areas of the body of the obligate intermediate host Lymnaea auricularia L., 1758, are not limiting factors for the realization of the final phases of the emission process of the cercariae of the trematode Schistosoma turkestanica Skrjabin, 1913. The resulting vector of interstitial migration of cercariae, stochastically oriented in the direction of the shell mouth of the mollusk Lymnaea auricularia L., 1758, brings the larva into the subepithelial tissue in any topographic area of the body of the intermediate host, where the integumentary epithelium borders with the external environment. To denote the anatomical topography of the apical part of the body of the cercarium trematode Schistosoma turkestanica Skrjabin, 1913, we propose to use the term "apical talus organ". The process of emission of cercariae of the trematode Schistosoma turkestanica Skrjabin, 1913, from the body of the mollusk Lymnaea auricularia L., 1758, is invasive for the latter.

Neural control of immune cell trafficking.

Leukocyte trafficking between blood and tissues is an essential function of the immune system that facilitates humoral and cellular immune responses. Within tissues, leukocytes perform surveillance and effector functions via cell motility and migration toward sites of tissue damage, infection, or inflammation. Neurotransmitters that are produced by the nervous system influence leukocyte trafficking around the body and the interstitial migration of immune cells in tissues. Neural regulation of leukocyte dynamics is influenced by circadian rhythms and altered by stress and disease. This review examines current knowledge of neuro-immune interactions that regulate leukocyte migration and consequences for protective immunity against infections and cancer.

Thiotetrelates Li2ZnXS4 (X = Si, Ge, and Sn) As Potential Li-Ion Solid-State Electrolytes.

A novel inorganic solid-state electrolyte (ISSE) with high ionic conductivity is a crucial part of all-solid-state lithium-ion (Li-ion) batteries (ASSLBs). Herein, we first report on Li2ZnXS4 (LZXS, X = Si, Ge, and Sn) semiconductor-based ISSEs, crystallizing in the corner-sharing tetrahedron orthorhombic space group, to provide valuable insights into the structure, defect chemistry, phase stability, electrochemical stability, H2O/CO2 chemical stability, and Li-ion conduction mechanisms. A key feature for the Li-ion transport and low migration barrier is the interconnected and corner-shared [LiS4] units along the a-axis, which allows Li-ion transport via empty or occupied tetrahedron sites. A major finding is the first indication that Li-ion migration in Li2ZnSiS4 (LZSiS) has lower energy barriers (∼0.24 eV) compared to Li2ZnGeS4 (LZGS) and Li2ZnSnS4 (LZSnS), whether through vacancy migration or interstitial migration. However, LZGS and LZSnS exhibit greater H2O/CO2 stability compared to LZSiS. The novel framework of LZXS with relatively low Li-ion migration barriers and moderate electrochemical stability could benefit the ASSLB communities.

Transendothelial migration alters subsequent neutrophil interstitial migration phenotype in 3D matrices

Neutrophil extravasation, a critical component of the innate immune response, comprises two sequential processes: transendothelial migration and interstitial migration. Transendothelial migration requires intimate physical contact between leukocytes and vascular endothelial cells, triggering a cascade of biochemical and biomechanical interactions that affect leukocyte interstitial migration in ways that are currently unclear.

Abnormal radiation resistance via direct-amorphization-induced defect recovery in HgTe

Understanding and mitigating effects of radiation are central to ensure reliable, long-term operation in space and strategic environments for compound semiconductor based electronics. A multiscale modeling approach has been employed to reveal the damage process and explore radiation resistance mechanisms in HgTe. Contrary to general belief, direct-amorphization and fast migration of interstitials within amorphous pockets provide a dominant driving force for rapid defect recovery, thus significantly enhancing radiation resistance. This study provides a precursor for developing predictive capabilities in designing and enabling radiation resistance with confidence for robust semiconductors.

Effects of Tungsten on Vacancy Aggregation Behavior and its Induction for Interstitial and Vacancy Migration in Tantalum–Tungsten Alloys: A First-Principles Study

Effects of Tungsten on Vacancy Aggregation Behavior and its Induction for Interstitial and Vacancy Migration in Tantalum–Tungsten Alloys: A First-Principles Study