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The aqueous zinc-ion batteries (ZIBs) have been considered as a promising energy storage device. However, the ion transfer at the Zn metal anode-electrolyte interface is limited by the sluggish kinetics resulting in high interface resistance. Herein, mesoporous TiO2 (m-TiO2) is coated on the Zn foil (Zn-TiO2) driving the ion's faster transfer to reduce interface resistance (70.1 Ω vs 799.3 Ω of bare Zn). The lower interface resistance is ascribed to shortening the ion transfer path provided by the mesoporous structure and the smaller Zn2+ absorption energy barrier of the surface of the Zn-TiO2 anode as well as the unobstructed ion transfer path at the crystal planes (100) of TiO2, which have been supported by the density functional theory (DFT) calculation and experiments. Therefore, the Zn-TiO2 anodes in the symmetrical cells display a low voltage hysteresis (36.5 mV) and long-term cycling stability (500 h at 4.4 mA cm-2). Especially, the Zn-TiO2/MnO2 full cells show superior cycling performance with a high capacity of 269.8 mAh g-1 after 50 cycles at 0.2 A g-1 and 210.9 mAh g-1 after 1000 cycles at 0.5 A g-1. The analysis of ion-transfer kinetics at the interface provides deep enlightenment and reference for the study of the metal anodes.

Multifunctional bismuth sulfide (Bi2S3) nanomaterials exhibit significant potential as nanomedicines for the diagnosis and treatment of cancer. These nanomaterials act as excellent photothermal agents and radiation sensitizers for the treatment of tumors, and they can also act as contrast agents for computed tomography (CT) imaging, photoacoustic imaging (PA), and other forms of imaging to provide real-time tumor monitoring and testing guidance. Compared with other nanomaterials, Bi2S3 nanomaterials can readily adapt to different applications by virtue of the fact that they can be easily functionalized. However, these nanomaterials have some limitations that cannot be ignored and need to be addressed, such as poor biocompatibility, toxicity, and low chemical stability. It is widely believed that appropriate functionalization of Bi2S3 nanomaterials could remedy such defects and significantly improve performance. This review summarizes the ways in which Bi2S3 nanomaterials can be functionalized and discusses their applications in cancer theranostics over the last few years, focusing particularly on imaging and therapy. We also discuss issues relating to how Bi2S3 nanomaterials can be analyzed, including how we might be able to use these systems to inhibit and treat tumors and how current limitations might be overcome to improve treatment efficacy. Finally, we hope to provide inspiration and guidance as to how we might create a more optimized multifunctional nano-system for the diagnosis and treatment of tumors.

High-entropy alloys containing multi-principal-element systems significantly expand the potential alloy design space, and offer the possibility of overcoming the strength-ductility trade-off in metallurgical research. However, the gain in ultra-high strength through traditional grain refinement and precipitation-strengthening mechanisms inevitably leads to a drastic loss of ductility. Here, we report on the design and fabrication of heterogeneous-lamella structured, aged bulk high-entropy alloy, which attains gigapascal tensile strength while retaining excellent ductility (UTS ~1.4 GPa, elongation ~30%; UTS ~1.7 GPa, elongation ~10%). Our work shows that the improved strength-ductility synergy arises due to various complementary strengthening mechanisms, including solid-solution, interfaces, precipitation and martensitic transformation, which influence the hardening and deformation processes at different strain levels. In particular, the hetero-deformation that is associated with the formation of microbands as well as the stress-induced martensite promotes additional hardening and hence high ductility. The strategy described here, that is leveraging the concept of heterogeneous microstructure design, provides a practical and novel method for fabricating high-performance structural materials.

Nanostructured materials with amorphous intergranular films (AIFs) have demonstrated superior strength and ductility. Their radiation tolerance is expected to be high as the large fraction of interfacial volume efficiently sinks radiation-induced defects. Here we demonstrate how a crystalline-amorphous system (nanocrystalline Cu with Zr-doped AIFs) responds to continuous irradiation with molecular dynamics simulations. We propose a diffusion model that well characterizes the cascade-driven mixing process, and reveal that the spread of Zr distribution scales linearly with the damage level. The exceptional radiation resistance is attributed to the interfaces acting as sustainable defect sinks, Zr mixing into the bulk to enhance local defect annihilation due to solute-interstitial dragging, and Zr impeding radiation-enhanced grain growth by restraining AIFs from migration and maintaining interface stiffness. These findings suggest that AIF-engineered systems hold promise as highly radiation-tolerant materials with strong structural stability and self-healing capability under radiation damage.

Reactive oxygen species (ROS) are by-products of aerobic metabolism and can also act as signaling molecules to participate in multiple regulation of biological and physiological processes. The occurrence, growth and metastasis of tumors, and even the apoptosis, necrosis and autophagy of tumor cells are all closely related to ROS. However, ROS levels in the body are usually maintained at a stable status. ROS produced by oxidative stress can cause damage to cell lipids, protein and DNA. In recent years, ROS have achieved satisfactory results on the treatment of tumors. Therefore, this review summarizes some research results of tumor treatments from the perspective of ROS in recent years, and analyzes how to achieve the mechanism of inhibition and treatment of tumors by ROS or how to affect the tumor microenvironment by influencing ROS. At the same time, the detection methods of ROS, problems encountered in the research process and solutions are also summarized. The purpose of this review is to provide a clearer understanding of the ROS role in tumor treatment, so that researchers might have more inspiration and thoughts for cancer prevention and treatment in the next stage.

Radiation-induced void swelling is a serious mode of degradation in nuclear structural materials. Much effort has been spent to predict swelling resistance, with the goal of increasing the void swelling incubation dose so as to postpone the consequences of radiation damage. However, this trial-and-error approach is highly inefficient due to the time- and resource-intensive nature of both experiments and physics-based multiscale simulations. In this work, as a first attempt, machine learning is applied to perform this prediction based on available experimental data. Of the multiple techniques applied, the gradient boosting ensemble method best predicts experimental onset doses for swelling in test datasets, and identifies the main contributing factors such as temperature, Fe and Cr content, and dose rate, which are consistent with established understanding. This work demonstrates the feasibility of machine learning to predict macroscale radiation effects based on material and environmental parameters, and has practical significance in guiding further material optimization for nuclear applications.

Atomistic simulations of radiation damage uncover how grain boundaries (GBs) migrate and coalesce under irradiation in bicrystalline Cu. Planar GB migration biased by defect cluster-mediated attraction first leads to slow and steady motion. Subsequently, adjoining GBs coalesce into curved surfaces, where curvature-driven migration with a velocity three orders of magnitude higher than that of a planar boundary dominates motion, triggering rapid grain growth. This study reveals the atomistic mechanisms of radiation-induced grain growth, and has practical implications towards engineering radiation-tolerant nanostructures.

Dynamic heterogeneity is an intrinsic characteristic of amorphous materials that is closely related to the mysterious glass transition. However, there is seldom an intuitive physical parameter characterizing the degree of dynamic heterogeneity and linking it quantitatively to the dynamic arrest phenomenon at the glass transition. Here, we propose a general theoretical protocol to explain the glass transition via a statistical parameter quantifying the dynamic heterogeneity of glass-forming systems. The parameter can be calculated using the concept of the Shannon information entropy associated with the variation in the activation barriers to local structural excitations on the underlying potential energy landscape, which can be explored extensively using the recently developed activation-relaxation technique in inherent structures spanning a wide range of configurational space. The concept is demonstrated successfully in a model of a prototypical glass-forming system ${\mathrm{Cu}}_{50}{\mathrm{Zr}}_{50}$. The Shannon entropy and statistical variation in the activation barriers are found to change dramatically at the glass-to-liquid transition and, therefore, can be treated as a novel signature of the glass transition, beyond the conventional thermodynamic indicators, such as the volume, potential energy, enthalpy, and heat capacity. The temperature-dependent Shannon entropy coincides with the evolution of the experimentally available stretching exponent during the glass-to-liquid transition and provides an intuitive explanation for the obscure decrease in dynamic heterogeneity from a metastable glass to an equilibrium liquid. Finally, possible relationships among structures, thermodynamics, and dynamics are discussed in terms of quantitative correlations among the structural Shannon entropy, excess total entropy, and dynamic Shannon entropy, respectively.

Nanocrystalline materials with a high density of grain boundaries have long been reported to alleviate radiation damage. However, a full mechanistic understanding of defect reduction, particularly the interaction mechanisms between grain boundaries and clustered defects during irradiation, remains an open question. Here we present atomistic simulations of prolonged radiation damage evolution in Cu bicrystals with increasing radiation dose. Our results reveal the atomic details of defect nucleation and migration, and the mechanisms for the annihilation of defect clusters during irradiation. Stacking fault tetrahedra formed due to radiation damage cascades show preferential migration to irradiated grain boundary. Interstitial-loaded grain boundaries are observed to be dynamically resilient, and persistently interact with the stacking fault tetrahedra, revealing a self-healing response to radiation damage. The results show a synergistic effect of grain boundaries on defect annihilation at small grain spacings of less than 6 nm, giving rise to a drastic decrease in the density of defect clusters. These findings, along with the mechanistic insights, present an integrated perspective on interface-mediated damage reduction in radiation-resistant nanomaterials.

Discrete stress relaxations (slip avalanches) in a model metallic glass under uniaxial compression are studied using a metadynamics algorithm for molecular simulation at experimental strain rates. The onset of yielding is observed at the first major stress drop, accompanied, upon analysis, by the formation of a single localized shear band region spanning the entire system. During the elastic response prior to yielding, low concentrations of shear transformation deformation events appear intermittently and spatially uncorrelated. During serrated flow following yielding, small stress drops occur interspersed between large drops. The simulation results point to a threshold value of stress dissipation as a characteristic feature separating major and minor avalanches consistent with mean-field modeling analysis and mechanical testing experiments. We further interpret this behavior to be a consequence of a nonlinear interplay of two prevailing mechanisms of amorphous plasticity, thermally activated atomic diffusion and stress-induced shear transformations, originally proposed by Spaepen and Argon, respectively. Probing the atomistic processes at widely separate strain rates gives insight to different modes of shear band formation: percolation of shear transformations versus crack-like propagation. Additionally a focus on crossover avalanche size has implications for nanomechanical modeling of spatially and temporally heterogeneous dynamics.

Understanding the time-dependent mechanical behavior of nanomaterials such as nanowires is essential to predict their reliability in nanomechanical devices. This understanding is typically obtained using creep tests, which are the most fundamental loading mechanism by which the time-dependent deformation of materials is characterized. However, due to existing challenges facing both experimentalists and theorists, the time-dependent mechanical response of nanowires is not well-understood. Here, we use atomistic simulations that can access experimental time scales to examine the creep of single-crystal face-centered cubic metal (Cu, Ag, Pt) nanowires. We report that both Cu and Ag nanowires show significantly increased ductility and superplasticity under low creep stresses, where the superplasticity is driven by a rate-dependent transition in defect nucleation from twinning to trailing partial dislocations at the micro- or millisecond time scale. The transition in the deformation mechanism also governs a corresponding transition in the stress-dependent creep time at the microsecond (Ag) and millisecond (Cu) time scales. Overall, this work demonstrates the necessity of accessing time scales that far exceed those seen in conventional atomistic modeling for accurate insights into the time-dependent mechanical behavior and properties of nanomaterials.

Understanding and predicting radiation damage is of central importance to develop radiation-tolerant structural materials for current and next-generation nuclear systems. Single-phase solid solution alloys constitute attractive choices due to their promising mechanical properties and radiation tolerance. Here, by examining radiation-induced defect production and evolution in single-phase Ni-Fe alloys, we show that radiation damage resistance directly correlates with thermodynamic mixing energy and heterogeneity of defect diffusion. We found that radiation damage in materials decreases linearly with lowering mixing energy, and the relationship holds true for all studied Ni-Fe compositions. The damage reduction with varying composition is further ascribed to the increasing heterogeneity of point defect migration across a complex potential energy landscape that enhances defect recombination. This new insight into the dynamical evolution of radiation defects points to a thermodynamic criterion for designing radiation-tolerant materials.

The mechanical properties and plastic deformation mechanisms of metal nanowires have been studied intensely for many years. One of the important yet unresolved challenges in this field is to bridge the gap in properties and deformation mechanisms reported for slow strain rate experiments (∼10–2 s–1), and high strain rate molecular dynamics (MD) simulations (∼108 s–1) such that a complete understanding of strain rate effects on mechanical deformation and plasticity can be obtained. In this work, we use long time scale atomistic modeling based on potential energy surface exploration to elucidate the atomistic mechanisms governing a strain-rate-dependent incipient plasticity and yielding transition for face centered cubic (FCC) copper and silver nanowires. The transition occurs for both metals with both pristine and rough surfaces for all computationally accessible diameters (

Molecular processes of creep in metallic glass thin films are simulated at experimental timescales using a metadynamics-based atomistic method. Space-time evolutions of the atomic strains and nonaffine atom displacements are analyzed to reveal details of the atomic-level deformation and flow processes of amorphous creep in response to stress and thermal activations. From the simulation results, resolved spatially on the nanoscale and temporally over time increments of fractions of a second, we derive a mechanistic explanation of the well-known variation of creep rate with stress. We also construct a deformation map delineating the predominant regimes of diffusional creep at low stress and high temperature and deformational creep at high stress. Our findings validate the relevance of two original models of the mechanisms of amorphous plasticity: one focusing on atomic diffusion via free volume and the other focusing on stress-induced shear deformation. These processes are found to be nonlinearly coupled through dynamically heterogeneous fluctuations that characterize the slow dynamics of systems out of equilibrium.

Since the initial discovery of applications of platinum complexes in the clinical treatment of many kinds of cancers, the efficiency of platinum complexes in inhibiting the proliferation of various types of tumors surprised researchers working on the development of anticancer drugs. Meanwhile, despite the potent clinical treatment patients get from platinum complexes, there are also disadvantages including limited solubility in aqueous media and side effects like ototoxicity, myelosuppression, nephrotoxicity, and poor selectivity toward healthy cells. For this reason, efforts have been made to search for novel solutions. Non-platinum complexes (like Fe, Pd, Ru, Cu, Bi, Zn, etc.) were found with potential anticancer activities. We here review the properties of five metal complexes as anticancer agents and make comparisons among them in biological features and cytotoxic activity. Seeking the interrelation between microstructure and mechanism of anticancer, we hope this review provides distinct insig...

Chromia (α-Cr2O3) is one of the most technologically important oxides, as it is the basis behind the passivation of many structural materials like stainless steel. It both resists oxygen ingress and slows the release of metals from its substrate by its high density and very low diffusivities. Were any further improvement to the protectiveness of chromia to be realized, no matter how small, it would have an enormous impact due to its ubiquitousness. Here we use molecular dynamics (MD) in conjunction with nudged elastic band (NEB) calculations to study the diffusion mechanisms of oxygen and chromium ions in α-Cr2O3. Significant anisotropic diffusion between the ab-plane and the c-axis is observed for both oxygen and chromium ions. We found that vacancy-mediated ion diffusion in the ab-plane is faster than diffusion along the c-axis, while interstitial-mediated diffusion along the c-axis is faster. Vacancy and interstitial defect migration paths unveil the atomistic mechanisms responsible for this anisotropic ion diffusion, as the most energetically favorable diffusion path accounts for the observed anisotropy. The results of this study have profound implications for the reduction and control of corrosion.

While glasses are ubiquitous in natural and manufactured materials, the atomic-level mechanisms governing their deformation and how these mechanisms relate to rheological behavior are still open questions for fundamental understanding. Using atomistic simulations spanning nearly 10 orders of magnitude in the applied strain rate we probe the atomic rearrangements associated with 3 characteristic regimes of homogeneous and heterogeneous shear flow. In the low and high strain-rate limits, simulation results together with theoretical models reveal distinct scaling behavior in flow stress variation with strain rate, signifying a nonlinear coupling between thermally activated diffusion and stress-driven motion. Moreover, we find the emergence of flow heterogeneity is closely correlated with extreme values of local strain bursts that are not readily accommodated by immediate surroundings, acting as origins of shear localization. The atomistic mechanisms underlying the flow regimes are interpreted by analyzing a distance matrix of nonaffine particle displacements, yielding evidence of various barrier-hopping processes on a fractal potential energy landscape (PEL) in which shear transformations and liquid-like regions are triggered by the interplay of thermal and stress activations.

Atomic-scale stick–slip friction of monolayer graphene on a copper substrate is computationally studied at a wide range of temperatures, which reveals strong temperature dependence of friction force and friction mode. The increase in temperature distorts regular stick–slip behavior and causes a nonlinear decrease of friction force, demonstrating a friction behavior transition from athermal friction to thermally activated. By analyzing atomic morphologies, the true contact area, defining the number of atoms interacting across the interface, shows a weak temperature dependence, yet the quality of interfacial contact substantially varies with temperature. Spatial distributions of atomic friction force uncover the significant effect of Moire superlattices, that act as strong pinning sites at low temperatures, partly change to pushing due to nonconcurrent atomic jumps at high temperatures, which leads to a chaotic friction mode with reduced lateral force. Additionally, we demonstrate the role of superlattices in strengthening friction and dictating the periodic stick–slip motion of interfacial sliding.

Radiation damage of structural materials leads to mechanical property degradation, eventually inducing failure. Secondary-phase dispersoids or other defect sinks are often added to materials to boost their radiation resistance. We demonstrate that a metal composite made by adding 1D carbon nanotubes (CNTs) to aluminum (Al) exhibits superior radiation resistance. In situ ion irradiation with transmission electron microscopy (TEM) and atomistic simulations together reveal the mechanisms of rapid defect migration to CNTs, facilitating defect recombination and enhancing radiation tolerance. The origin of this effect is an evolving stress gradient in the Al matrix resulting from CNT transformation under irradiation, and the stability of resulting carbides. Extreme value statistics of large defect behavior in our simulations highlight the role of CNTs in reducing accumulated damage. This approach to controlling defect migration represents a promising opportunity to enhance the radiation resistance of nuclear materials without detrimental effects.

By mixing 5-bromo-2-furaldehyde, phenylthiosemicarbazide and Bi(CH3COO)3, a new amorphous bismuth-containing complex, BiL2Cl3, was synthesized under aqueous conditions via a one-pot method and characterized with some analytical techniques, where L was produced by dehydration between 5-bromo-2-furaldehyde, phenylthiosemicarbazide. The obtained complex effectively inhibited the proliferation and migration of A549 and H460 lung cancer cells, induced cell apoptosis and displayed fairly low cytotoxicity to normal human lung fibroblast (HLF). Compared with cisplatin, BiL2Cl3 displayed better anti-cancer activity against tumor cells and lower toxicity to normal cell. Therefore, BiL2Cl3 with potent anti-cancer activity may be a viable drug candidate in anti-cancer therapies.

We characterize the force-dependent unfolding pathways and intermediate configurations of the green fluorescence protein (GFP) using novel atomistic simulations based on potential energy surface exploration. By using this approach, we are able to unfold GFP to significantly longer end-to-end distances, i.e. 40 nm, as compared to that seen in previous atomistic simulation studies. We find that there are four intermediate states between 5 and 40 nm end-to-end distance, where the intermediate configurations and unfolding pathways are strongly force-dependent. We additionally calculate the force-dependent lifetime of the 14 nm α β 1 intermediate, and demonstrate that it obeys Bell’s formula.

6-Mercaptopurine (6-MP) is a clinically important antitumor drug and its commercially available form is provided as monohydrate, belonging to biopharmaceuticals classification system (BCS) class II category. The combination of bismuth(III) (Bi(III)) with 6-MP was proved to significantly improve the anticancer activity of 6-MP, leading to the discovery of a new amorphous complex ([Bi(MP)3(NO3)2]NO3). The prepared [Bi(MP)3(NO3)2]NO3 was characterized by the matrix assisted laser desorption-ionization time-of-flight (MALDI-TOF)-MS, etc. Noticeably, according to the in vitro evaluations of cytotoxicity, cellular apoptotic, colony formation as well as cell migration, the anticancer activity of amorphous [Bi(MP)3(NO3)2]NO3 was found to be of high therapeutic effect over 6-MP.

Nonohybrids of CeBi0.4O3.7 with feather-like structures (CeBi0.4O3.7 NFs) were synthesized by incorporating Bi into CeO2, and thereby exhibiting preferable conductivity and biocompatibility. The modification of gold nanoparticles (Au NPs) further enhanced both properties of the obtained Au@CeBi0.4O3.7 NFs without changing the crystal structure, thereby benefiting the efficient immobilization of the secondary antibody (Ab2). The prepared Au@CeBi0.4O3.7 NFs were then used as a probe to label the Ab2. The reduced graphene oxide (rGO) with Au NPs deposited on Au-rGO was selected to modify the electrode for the immobilization of the first antibody, forming a sandwich-type Au@CeBi0.4O3.7 NF based electrochemical immunosensor to detect carcinoembryonic antigen (CEA). Such a Au@CeBi0.4O3.7 NF based sandwich immunosensor was successfully applied to detect CEA and exhibited, as expected, a linear response to CEA in a wide range of concentrations from 0.01 ng/mL to 100 ng/mL with a detection limit as low as 0.121 pg/mL, comparable to many existing immunosensors. Moreover, the favorable selectivity and stability make this immunosensor potentially applicable for the detection of CEA in real samples and this work provides new insights into the early detection of CEA.

Background Plant height and leaf angle are important determinants of yield in rice (Oryza sativa L.). Genes involved in regulating plant height and leaf angle were identified in previous studies; however, there are many remaining unknown factors that affect rice architecture. Results In this study, we characterized a dwarf mutant named ds1 with small grain size and decreased leaf angle,selected from an irradiated population of ssp. japonica variety Nanjing35. The ds1 mutant also showed abnormal floral organs. ds1 plants were insensitive to BL treatment and expression of genes related to BR signaling was changed. An F2 population from a cross between ds1 and indica cultivar 93–11 was used to fine map DS1 and to map-based clone the DS1 allele, which encoded an EMF1-like protein that acted as a transcriptional regulator. DS1 was constitutively expressed in various tissues, and especially highly expressed in young leaves, panicles and seeds. We showed that the DS1 protein interacted with auxin response factor 11 (OsARF11), a major transcriptional regulator of plant height and leaf angle, to co-regulate D61/OsBRI1 expression. These findings provide novel insights into understanding the molecular mechanisms by which DS1 integrates auxin and brassinosteroid signaling in rice. Conclusion The DS1 gene encoded an EMF1-like protein in rice. The ds1 mutation altered the expression of genes related to BR signaling, and ds1 was insensitive to BL treatment. DS1 interacts with OsARF11 to co-regulate OsBRI1 expression. Electronic supplementary material The online version of this article (10.1186/s12284-018-0239-9) contains supplementary material, which is available to authorized users.

GARS encodes an enzyme catalyzing the second step of purine nucleotide biosynthesis and plays an important role to maintain the development of chloroplasts in juvenile plants by affecting the expression of plastid-encoded genes. A series of rice white striped mutants were previously described. In this research, we characterized a novel gars mutant with white striped leaves at the seedling stage. By positional cloning, we identified the mutated gene, which encodes a glycinamide ribonucleotide synthetase (GARS) that catalyzes the second step of purine nucleotide biosynthesis. Thylakoid membranes were less abundant in the albinic sectors of mutant seedling leaves compared to the wild type. The expression levels of genes involved in chlorophyll synthesis and photosynthesis were changed. Contents of ATP, ADP, AMP, GTP and GDP, which are crucial for plant growth and development, were decreased in the mutant seedlings. Complementation and CrispR tests confirmed the role of the GARS allele, which was expressed in all rice tissues, especially in the leaves. GARS protein displayed a typical chloroplast location pattern in rice protoplasts. Our results indicated that GARS was involved in chloroplast development at early leaf development by affecting the expression of plastid-encoded genes.

WSL5 is crucial for the splicing of the chloroplast genes rpl2 and rps12 under cold stress, and affects the retrograde signaling from plastids to the nucleus., Chloroplasts play an essential role in plant growth and development, and cold conditions affect chloroplast development. Although many genes or regulators involved in chloroplast biogenesis and development have been isolated and characterized, many other components affecting chloroplast biogenesis under cold conditions have not been characterized. Here, we report the functional characterization of a white stripe leaf 5 (wsl5) mutant in rice. The mutant develops white-striped leaves during early leaf development and is albinic when planted under cold stress. Genetic and molecular analysis revealed that WSL5 encodes a novel chloroplast-targeted pentatricopeptide repeat protein. RNA sequencing analysis showed that expression of nuclear-encoded photosynthetic genes in the mutant was significantly repressed, and expression of many chloroplast-encoded genes was also significantly changed. Notably, the wsl5 mutation causes defects in editing of rpl2 and atpA, and splicing of rpl2 and rps12. wsl5 was impaired in chloroplast ribosome biogenesis under cold stress. We propose that the WSL5 allele is required for normal chloroplast development in maintaining retrograde signaling from plastids to the nucleus under cold stress.

Direct mesoscale measurements of radiation-induced changes in the mechanical properties of bulk materials remain difficult to perform. Most widely used characterization techniques are either macro- or microscale in nature, focusing on overall properties or overly small areas for analysis. Linking the atomic structure of irradiated materials directly with their radiation-affected properties remains one of the largest unmet challenges in radiation materials science. By measuring the change in surface acoustic wave speed as a function of relative orientation on metallic single crystals, we demonstrate that transient grating (TG) spectroscopy experiments have the sensitivity necessary to detect radiation-induced material property changes. We also show that classical molecular dynamics (MD) simulations can be used to accurately simulate orientation-based changes in surface acoustic wave speed in TG experiments, by comparing with experimental measurements and theoretical predictions. The agreement between theory, simulation, and experiment gives confidence in classical MD as a predictive tool to simulate defect-based changes in elastic properties, which cannot yet be fully treated by theory. This ability is of critical importance for the informed use of TG spectroscopy to measure material property changes induced by radiation damage, which may vary by amounts formerly too small for reliable in situ detection. Finally, our MD simulation framework is used to study the effect of an imposed vacancy population on the acoustic response of several materials. The results of these studies indicate that TG experiments are well suited to the ex situ and in situ study of radiation-induced material property changes., National Science Foundation (U.S.) (Grant 1122374), National Science Foundation (U.S.) (Grant CHE-1111557), Transatomic Power (Award 023875-001), U.S. Nuclear Regulatory Commission (MIT Nuclear Education Faculty Development Program. Grant NRC-HQ- 84-15-G-0045)

The aim of this work is experimental study of an interesting bismuth(III) complex derived from pentadentate 2,6-pyridinedicarboxaldehyde bis(4N-methylthiosemicarbazone), [BiL(NO3)2]NO3 {L=2,6-pyridinedicarboxaldehyde bis(4N-methylthiosemicarbazone)}. A series of in vitro biological studies indicate that the newly prepared [BiL(NO3)2]NO3 greatly suppressed colony formation, migration and significantly induced apoptosis of human lung cancer cells A549 and H460, but did not obviously decrease the cell viability of non-cancerous human lung fibroblast (HLF) cell line, showing much higher anticancer activities than its parent ligands, especially with half maximum inhibitory concentration (IC50)

The objective of this paper is to examine the instability characteristics of both a bulk FCC crystal and a (100) surface of an FCC crystal under uniaxial stretching along a 〈100〉 direction using an atomistic-based nonlocal instability criterion. By comparison to benchmark atomistic simulations, we demonstrate that for both the FCC bulk and (100) surface, about 5000–10,000 atoms are required in order to obtain an accurate converged value for the instability strain and a converged instability mode. The instability modes are fundamentally different at the surface as compared to the bulk, but in both cases a strong dependence of the instability mode on the number of atoms that are allowed to participate in the instability process is observed. In addition, the nonlocal instability criterion enables us to determine the total number of atoms, and thus the total volume occupied by these atoms, that participate in the defect nucleation process for both cases. We find that this defect participation volume converges as the number of atoms increases for both the bulk and surface, and that the defect participation volume of the surface is smaller than that of the bulk. Overall, the present results demonstrate both the necessity and utility of nonlocal instability criteria in predicting instability and subsequent failure of both bulk and surface-dominated nanomaterials.

Novel bismuth nanoparticle-modified mesoporous carbon (MPC) was successfully prepared on a glassy carbon electrode (Bi@MPC/GCE) for the adsorptive stripping voltammetric determination of nickel by complexing with dimethylglyoxime (DMG). The presence of MPC obviously improved the properties of Bi particles like the electron transfer ability, particle size and hydrophicility, important parameters to achieve preferable analytical performances of Bi@MPC/GCE toward Ni(II). The best electrochemical behaviors of Bi@MPC/GCE was obtained for the stripping determination of Ni(II), compared with electrodes individually modified with Bi and MPC. The synergic effect between metallic Bi and ordered MPC (forming a 3D array like Bi microelectrodes) made major contribution to such improved electrochemical properties of Bi@MPC/GCE for Ni(II) sensing. The good linear analytical curve was achieved in a Ni(II) concentration range from 0.1[Formula: see text][Formula: see text]M to 5.0[Formula: see text][Formula: see text]M with a correlation coefficient of 0.9995. The detection limit and sensitivity were calculated to be 1.2[Formula: see text]nM ([Formula: see text]) and 1410[Formula: see text][Formula: see text]A[Formula: see text]mM[Formula: see text][Formula: see text]cm[Formula: see text], respectively. The new method was successfully applied to Ni(II) determination in soybean samples with recoveries higher than 99% and proved to be a simple, efficient alternative for Ni(II) monitoring in real samples.

We perform a systematic study of the characteristics of shear transformation zones (STZs) that nucleate at free surfaces of two-dimensional amorphous solids subject to tensile loading using two different atomistic simulation methods, the standard athermal, quasistatic (AQ) approach and our recently developed self-learning metabasin escape (SLME) method, to account for the finite temperature and strain-rate effects. In the AQ, or strain-driven limit, the nonaffine displacement fields of surface STZs decay exponentially away from their centers at similar decay rates as their bulk counterparts, though the direction of maximum nonaffine displacement is tilted away from the tensile axis due to surface effects. Using the SLME method at room temperature and at the high strain rates that are seen in classical molecular dynamics simulations, the characteristics for both bulk and surface STZs are found to be identical to those seen in the AQ simulations. However, using the SLME method at room temperature and experimentally relevant strain rates, we find a transition in the surface STZ characteristics where a loss in the characteristic angular tensile-compression symmetry is observed. Finally, the thermally activated surface STZs exhibit a slower decay rate in the nonaffine displacement field than do strain-driven surface STZs, which is characterized by a larger drop in potential energy resulting from STZ nucleation that is enabled by the relative compliance of the surface as compared to the bulk.

We couple the recently developed self-learning metabasin escape algorithm, which enables efficient exploration of the potential energy surface (PES), with shear deformation to elucidate strain-rate and temperature effects on the shear transformation zone (STZ) characteristics in two-dimensional amorphous solids. In doing so, we report a transition in the STZ characteristics that can be obtained through either increasing the temperature or decreasing the strain rate. The transition separates regions having two distinct STZ characteristics. Specifically, at high temperatures and high strain rates, we show that the STZs have characteristics identical to those that emerge from purely strain-driven, athermal quasistatic atomistic calculations. At lower temperatures and experimentally relevant strain rates, we use the newly coupled PES $+$ shear deformation method to show that the STZs have characteristics identical to those that emerge from a purely thermally activated state. The specific changes in STZ characteristics that occur in moving from the strain-driven to thermally activated STZ regime include a 33% increase in STZ size, faster spatial decay of the displacement field, a change in the deformation mechanism inside the STZ from shear to tension, a reduction in the stress needed to nucleate the first STZ, and finally a notable loss in characteristic quadrupolar symmetry of the surrounding elastic matrix that has previously been seen in athermal, quasistatic shear studies of STZs.

Modeling physical phenomena with atomistic fidelity and at laboratory timescales is one of the holy grails of computational materials science. Conventional molecular dynamics (MD) simulations enable the elucidation of an astonishing array of phenomena inherent in the mechanical and chemical behavior of materials. However, conventional MD, with our current computational modalities, is incapable of resolving timescales longer than microseconds (at best). In this short review article, we briefly review a recently proposed approach—the so-called autonomous basin climbing (ABC) method—that in certain instances can provide valuable information on slow timescale processes. We provide a general summary of the principles underlying the ABC approach, with emphasis on recent methodological developments enabling the study of mechanically-driven processes at slow (experimental) strain rates and timescales. Specifically, we show that by combining a strong physical understanding of the underlying phenomena, kinetic Monte Carlo, transition state theory and minimum energy pathway methods, the ABC method has been found to be useful in a variety of mechanically-driven problems ranging from the prediction of creep-behavior in metals, constitutive laws for grain boundary sliding, void nucleation rates, diffusion in amorphous materials to protein unfolding. Aside from reviewing the basic ideas underlying this approach, we emphasize some of the key challenges encountered in our own personal research work and suggest future research avenues for exploration.

We utilize density functional theory to calculate the edge energy and edge stress for monolayer MoS$_{2}$ nanoribbons. In contrast to previous reports for graphene, for both armchair and zigzag chiralities, the edge stresses for MoS$_{2}$ nanoribbons are found to be tensile, indicating that their lowest energy configuration is one of compression in which Mo-S bond lengths are shorter than those in a bulk, periodic MoS$_{2}$ monolayer. The edge energy and edge stress is found to converge for both chiralities for nanoribbon widths larger than about 1 nm., Comment: 10 pages, 4 figures