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Selective carrier energy filtering effect is an important strategy to promote the power factor of a thermoelectrical materials, which requires an appropriate potential barrier and coherent interfaces between the secondary phase and the host matrix. Although the energy filtering effect has been realized in various bulk systems, its efficiency in promoting their thermoelectric performance is limited. Herein, simultaneously increased electrical conductivity and Seebeck coefficient are investigated in Ag-doped Bi 0.5 Sb 1.5 Te 3 films, leading to an increasement of the power factor up to 700%. Microstructure analysis reveals that the thin films prepared from magnetron sputtering consist of highly uniform nanocrystal domains, which construct coherent interfaces somewhere. Moreover, the local Ag doping might depress the Fermi level, providing the possibility to form a suitable potential barrier between the adjacent nanograins. This study suggests a facile method to significantly enhance the thermoelectric performance via energy filtering effect in high quality thin films. [ABSTRACT FROM AUTHOR]

Since the Industrial Revolution, increasing atmospheric CO 2 concentrations have had a substantial negative impact influence on coastal ecosystems because of direct effects including ocean acidification and indirect effects such as extreme rainfall events. Using a two-factor crossover indoor simulation experiment, this study examined the combined effects of acidification and hyposaline stress on Thalassia hemprichii. Seawater acidification increased the photosynthetic pigment content of T. hemprichii leaves and promoted seagrass growth rate. Hyposaline stress slowed down seagrass growth and had an impact on the osmotic potential and osmoregulatory substance content of seagrass leaves. Acidification and salinity reduction had significant interaction effects on the photosynthesis rate, photosynthetic pigment content, chlorophyll fluorescence parameters, and osmotic potential of T. hemprichii , but not on the growth rate. Overall, these findings have shown that the hyposaline stress inhibitory effect on the T. hemprichii physiological performance and growth may be reduced by acidification. • Thalassia hemprichii highly adapts to acidification and hyposalinity environments. • Acidification and hyposalinity had interaction effects on physiology of the seagrass. • Acidification and hyposalinity had no interaction effects on growth of the seagrass. • Acidification mitigates the inhibitory effects of hyposaline stress for the seagrass. [ABSTRACT FROM AUTHOR]

• Provides insights about how individual's aspirin use behaviors were affected by the information they got. • Reveals the interaction effect of information from health provider and internet on patients with different aspirin demand. • Shows the different risks and effectives of using aspirin in primary versus secondary CVD preventions. The internet has become an important source of health information for the general population. Previous research has shown that online health information seeking is associated with medication adherence. However, the direction of this relationship is still a matter of dispute. Even less is known about the factors that moderate such a relationship. To investigate the heterogeneous influences of online health information seeking on the use of aspirin in CVD prevention and the possible moderating factors among the applicable adult population in the U.S from 2016 to 2018. Respondents aged 40 or older, based on guidelines for aspirin use, were sampled from the 2016 to 2018 National Health Interview Survey. Linear probability models were used to test the association between patients' aspirin use behaviors and the variables of interest in four separate sub-populations. Aspirin use for CVD prevention was associated with online health information seeking in different ways. When patients received doctors' advice to use aspirin, online information seeking has a negative influence on aspirin use, depending on whether the individual has CVD risk factors. However, for patients without recommendations from providers, the effects of online information seeking on self-initiated aspirin use depend on the different types of prevention (i.e., primary vs. secondary) and CVD risk factors. Online health information might lead to both overuse and underuse of aspirin in CVD prevention. Online information seeking interacts with other information sources affecting consumers' decision making. Key consumer characteristics and risk factors may also moderate such a relationship. [ABSTRACT FROM AUTHOR]

We report a dynamic self-assembly system of ‘living’ polymeric chains sustained by chemistry using reactive molecular dynamics simulations. The linear polymeric chains consist of self-assembled nanoparticles connected by metastable linker molecules. As such, the polymeric chains, once assembled, undergo spontaneous dissociation driven by thermodynamics. However, with a continuous supply of linker molecules and the stored chemical energy therein, the polymeric chains can survive and maintain a steady state averaged chain length. These dynamically self-assembled polymeric chains are analogous to biological systems that both are thermodynamically metastable, yet dynamically stable upon continuous influx of matter and energy. [ABSTRACT FROM AUTHOR]

The diamond cutting of transition metal alloys, particularly steel, is severely hindered by accelerated chemical wear of the tool. Recent experimental findings show that the presence of graphene platelets mitigates this problem. However, the specific mechanisms responsible for this wear mitigation are currently unknown. In this paper, molecular dynamics techniques are successfully used to identify these diamond tool wear mitigation mechanisms. A modified embedded atom method force field is first evaluated for its ability to accurately simulate the catalyzed graphitization of diamond in the presence of steel. This force field is then used to simulate nanometric diamond cutting of steel in the presence of a 1 or 3 layered graphene platelet. Coordination analysis of these simulations shows that the presence of the graphene platelet results in 34%–96% reduction in tool wear, when compared to the graphene-free cutting condition. This is attributed to the graphene platelet serving as a physical barrier protecting the tool cutting edge, and also as a sacrificial source for carbon transfer into the workpiece. Other mechanisms, such as platelet cleaving and interlayer sliding, are also observed. The reduction in tool wear reported by the simulations is comparable to the trends observed in prior experiments. [ABSTRACT FROM AUTHOR]

Most existing particle-based polymeric models are non-reactive, and usually constructed to be monodisperse. This deficiency limits the utilization of these models to understand the dependency of polymer properties on polydispersity. Here we report a coarse-grained model with pairwise interactions, yet is reactive and capable of in silico synthesis of polydisperse polymers in a step-wise manner. The polymerization of linear, branched, cross-linked and network polymers can be described by this reactive model. The chain length distribution of the resulting linear polymer agrees well with the Flory-Schulz distribution. The importance of polydispersity in polymer behaviors is highlighted in terms of kinetic (self-diffusivities of linear polymer melts) and mechanical properties (stress-strain responses of linear polymer glasses under uniaxial tension). [ABSTRACT FROM AUTHOR]

Tensile fracture of metallic glasses due to shear-band-to-crack transition was studied by molecular dynamics. Such transition is difficult to characterize experimentally as it occurs within nanoseconds in the buried nanometer-thin shear band. We show that the sample fractures via shear band cavitation under high initial tensile stress, or with long sample length. The critical thermomechanical conditions for shear band cavitation, strongly influenced by shear, were identified. An analytical model was developed, leading to a length scale and a time scale for shear-band-to-crack transition. [ABSTRACT FROM AUTHOR]

This paper deals with the anti-triangular operator matrix M=(ABC0 with A2=A and CAπB=0). Using the resolvent expansion technique, we obtain the explicit representation of the Drazin inverse of M, in terms of its entries and the Drazin inverses of the entries and their compositions. The result extends the main results in Bu et al. (2011) [2] and Castro-González and Dopazo (2005) [6] and the results on group inverses in Bu et al. (2008) [3] and Liu and Yang (2012) [14]. As an application, a new additive result is given of the Drazin inverse for two matrices P, Q∈ Cn×n with P2=P and PQ2=0. [ABSTRACT FROM AUTHOR]

Abstract: Let be a complex Banach algebra with unit and let be two idempotents in . For , the authors obtain an explicit representation formula for the Drazin inverse of and give the upper bound of the corresponding Drazin index by using the presented method. As a consequence, the main previously published results on Drazin inverse of are corollaries of our theorem. Finally, the authors apply the theorem to an example which cannot be solved by previously known results. [Copyright &y& Elsevier]

Abstract: Nanoporous carbon (NPC) is structurally complex yet poorly understood, particularly the topological defects such as pentagon rings. Here we propose a computational approach that links the topological defects to structure factor S(q) measured from X-ray experiments. The essence of this method is to generate a large dataset of realistic NPC models by virtual synthesis procedures, from which both the population of topological defects and the S(q) can be calculated, and subsequently correlated. Three virtual synthesis procedures are utilized here to mimic high-energy electron irradiation, pyrolysis with rigid pentagon-rich precursors and pyrolysis with C60 molecules. The resulting population of topological defects is estimated based on an ensemble of NPC models, partially addressing the common non-uniqueness problem. As an example, we found that, in a low-density saccharose-based activated carbon sample, there should be fewer than one pentagon per 20 carbon atoms. Further analysis of this dataset of NPC model shows that the pore size distributions are insensitive to pentagon defects. Thus, adsorption experiments may not help directly characterize topological defects in NPC. On the other hand, as local curvature is sensitive to the ring defects, 3D tomography is likely to be capable of directly characterizing the population of topological defects. [Copyright &y& Elsevier]

Abstract: Porous nickel oxide (NiO) microflowers have been successfully synthesized by calcining a coordination microflower without any hard template, seed or using soft template. More importantly, porous NiO microflowers have been applied as effective electrochemical sensor of the tripeptide glutathione (GSH) and electrochemical supercapacitors. The effectively electrochemical GSH sensor of porous NiO microflowers in 0.1M HAc–NaAc (pH 5.0) solution was the first time evaluated. Moreover, the specific capacitance of porous NiO microflower was up to 1678.4Fg−1 at current density of 0.625Ag−1, and maintained about 99.7% at 6.25Ag−1 after 1000 cycles. [Copyright &y& Elsevier]

Abstract: A simple two-step strategy using phospholipid (PPL) to functionalize core/shell CdSe/ZnS quantum dots (QDs) has been described. The experimental data show that the use of S–H terminated PPL results not only in the high colloidal stability of core/shell CdSe/ZnS QDs in the aqueous phase, but also in the significant enhancement of photoluminescence. The degree of the enhancement is a function of the PPL–CdSe/ZnS QDs sample concentration. These results might be promising for future biological platform in new devices ranging from photovoltaic cells to biosensors and other devices. [Copyright &y& Elsevier]

Abstract: Simulations of a monatomic model amorphous matrix embedded with approximately 37% of a body-centered cubic phase demonstrate mechanisms by which nanocrystallites can alter the mechanical response of metallic glass. Three effects affect the resulting ductility: (i) the presence of weak amorphous–crystalline interfaces, (ii) the fraction of nanocrystallites oriented to prevent twinning relative to the loading stress, and (iii) the shear-induced growth and dissolution of the nanocrystallites when they are impinged by shear bands. While the first effect dominates in these simulations due to system size limitations, the third effect appears to be crucial for understanding the ductility of experimental samples. These simulations indicate that shear-induced growth of existing nanocrystallites, rather than nucleation of new crystalline regions, may account for the observed enhancement in ductility. [Copyright &y& Elsevier]

Abstract: Simulated nanoindentation tests on a three-dimensional model of a binary metallic glass-forming alloy reveal how the stress field and material structure interact to control deformation beneath the indenter. Initially, the stress field follows the Hertzian solution with fluctuations due to heterogeneities. Homogeneous or localized plastic deformation arises, depending on the processing history of the material. In the case of localized deformation, the first shear band initiates sub-surface, relaxing the local shear stress. The subsequent shear band morphology is observed to be rate-dependent. Deformation induced changes in material structure are characterized in terms of short-range ordering and free volume, with the former providing significantly greater signal-to-noise. [Copyright &y& Elsevier]

[Display omitted] • Triethylamine-responsive QDs based on supramolecular self-assembly was synthesized. • Fluorescence of QD621/ZnS/HPEISA increased greatly after adding triethylamine. • QD621/ZnS/HPEISA supramolecular self-assembly was cleaved by excess triethylamine. • Released QDs/HPEI nanocomposites could easily be endocytosed by the L929 cells. A new strategy for the construction, release and cellular imaging application of triethylamine-responsive fluorescent quantum dots (QDs) based on supramolecular self-assembly has been described. The supramolecular self-assembly (HPEI/SA), which was constructed through the electrostatic interactions between terminal amine groups of hyperbranched polyethylenimines (HPEI) and carboxylic acid groups of stearic acid (SA), first captured aqueous Zn2+ ions into the hydrophilic dendritic core and subsequently encapsulated QDs/S2- by the complexation interactions and reactions between Zn2+ and S2- on QDs. Due to the pH-responsive property of the HPEI/SA supramolecular self-assembly, the fluorescence of encapsulated QDs is sensitive to the triethylamine/SA mole ratio, and the encapsulated QDs can be released to the aqueous phase by cleaving HPEI/SA. The resulting fluorescent QDs/HPEI nanocomposites show promising prospects in bioimaging. [ABSTRACT FROM AUTHOR]

• Nonviral gene vector with folate/magnetism targeting based on hyperbranched polymer. • FA-PEG-HPEI as nanoreactors to prepare superparamagnetic Fe 3 O 4 nanocrystals. • Fe 3 O 4 /FA-PEG-HPEI have higher luciferase expression level than HPEI. A new strategy for in situ preparation of non-viral gene vectors with folate/magnetism dual targeting based on hyperbranched polymers has been described. Folate-PEG-grafted-hyperbranched poly(ethylenimine)s (FA-PEG-HPEI) were synthesized and used as nanoreactors to prepare monodisperse Fe 3 O 4 nanocrystals (NCs). The FA-PEG-HPEI had FA targeting groups, low cytotoxicity and ideal gene transfection performance, while Fe 3 O 4 NCs had superparamagnetic property, thus the resulting Fe 3 O 4 /FA-PEG-HPEI nanocomposites integrated the properties of FA-PEG-HPEI and Fe 3 O 4 NCs together. As expected, the Fe 3 O 4 /FA-PEG-HPEI nanocomposites as non-viral gene vectors with folate/magnetism dual targeting had improved luciferase expression level in HEK 293T and Hela cells under a magnetic gradient field. The luciferase expression level mediated by Fe 3 O 4 /FA-PEG-HPEI nanocomposites in HEK 293T and Hela cells under a magnetic gradient field were 21 and 29 fold of that of standard HPEI transfection, respectively. [ABSTRACT FROM AUTHOR]

Silicon shows potential as an anode material in lithium ion batteries due to its high specific capacity, yet its considerable volume expansion during lithiation leads to fracture and pulverization. Unfortunately, neither the atomic-level structural evolution, nor the mechanical behavior of the anode during lithiation and delithiation cycles is well understood. Interestingly, the lithiation process of a-Si provides an interesting continuum from open-structured network glass to densely-packed atomic glass, which could be used to obtain useful insights regarding commonalities in glasses. Here atomic level simulation has been used to investigate one cycle of lithiation and delithiation of amorphous silicon electrode, using Grand Canonical Monte Carlo (GCMC) and molecular dynamics (MD) simulations. The atomic level structural transformation and damage accumulation of the anode during cycling has been systematically analyzed, as well as their mechanical responses in compact tension tests. There appears to be a ductile-brittle-ductile transition for the amorphous silicon anode during both the lithiation and delithiation cycle. In other words, amorphous silicon is particularly vulnerable at intermediate lithiation. The fracture behavior of lithiated silicon was found to correlate to the Poisson's ratio, due to variations in bond covalency and structural disorder. Image 1 [ABSTRACT FROM AUTHOR]

We developed a reactive coarse-grained model for chain-growth polymerization to study the chain length distribution of polymers grafted from a surface as compared to those grown in solution. The surface-initiated polymer chains exhibit a markedly broader distribution of chain lengths (larger dispersity) and slower chain growth kinetics as compared to the solution phase process. Two key factors that cause deviation from ideal grafting are identified: (1) the formation of chain “loops” with both termini attached to the substrate via recombination and (2) the “starvation” effect, in which the live chain ends of short polymers are sterically shielded from monomers by the presence of longer neighboring chains. Both effects are markedly amplified with increasing initiator surface density, thus limiting the density of high molecular weight chains grafted from the surface. Whereas the “loop” effect is absent in systems that are very strictly “living” (no termination), the starvation effect is likely operative in most real systems. Taken together, these results suggest a theoretical limit on the density of polymer brushes that can form on surfaces by a “grafting-from” technique, based on the kinetics of the chain-growth polymerization process. [ABSTRACT FROM AUTHOR]

Understanding the dynamics of shear band propagation in metallic glasses remains elusive due to the limited temporal and spatial scales accessible in experiments. In micron-scale molecular dynamics simulations on two model metallic glasses, we studied the propagation of a dominant shear band under uniaxial tension with a macroscopic strain of 3-5%. For both materials, the shear band can be intersonic with a propagation speed exceeding their respective shear wave speeds. The propagation exhibits intrinsic instability that manifests itself as microbranching and considerable fluctuations in velocity. The shear strain singularity ahead of propagating shear band tip scales as 1/ r (r is the distance away from the tip), independent of the macroscopic tensile strain. In addition, we studied the intersection of two shear bands under uniaxial tension, during which path deflection, speed slowing-down, and temperature rise at the junction region were observed. The dynamics of propagating shear band shown here indicate that shear band in metallic glasses can be viewed as shear crack under the framework of weakly nonlinear fracture mechanics theory. [Display omitted] [ABSTRACT FROM AUTHOR]

Metallic glasses (MGs) usually suffer brittle fracture under uniaxial tension due to size-dependent shear band cavitation. Here we developed a concurrent multi-scale simulation method to describe the uniaxial tension of a binary Lennard-Jones (BLJ) model glass up to 88 microns in length. No cavitation or brittle fracture was found even for the longest BLJ sample. As the length increases, the shear band temperature increases, then saturates, while the elastic unloading from shear-off diminishes. We conjecture that the shear band of a BLJ sample, even with a macroscopic length, cannot reach the herein estimated critical cavitation conditions. Thus, BLJ samples appear to be free of size-induced tensile brittleness. Based on the shear band evolution and the critical cavitation conditions, we propose three classes of MGs in terms of tensile ductility: brittle-MGs (brittle for all lengths), normal-MGs (ductile for short samples, brittle for long samples), cohesive-MGs (ductile for all lengths). Our simulation results illustrate limitations of existing molecular models, and suggest that certain experimental metallic glasses may be free of size-induced tensile brittleness. [ABSTRACT FROM AUTHOR]

Abstract: N-doped TiO2 nanooctahedra, nanoparticles and nanospheres were successfully synthesized through nitrification of the corresponding TiO2 nanostructures in the presence of ammonia gas at 700°C for 30min. The crystal phase and compositions of N-doped TiO2 samples were confirmed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. The product morphology was characterized with scanning microscopy (SEM) and transmission electron microscopy (TEM). UV–vis absorption results show that all the as-synthesized N-doped TiO2 samples present red-shift absorption up to ∼410nm, which can be ascribed to the addition energy level between TiO2 valence and conducion band. Surface areas of all samples were measured through nitrogen absorption–desorption isothermal. In order to evaluate the photocatalytic activity of N-doped TiO2 samples, photodecomposition for methyl orange (MO) was performed under UV–vis light irradiation for 30min, indicating that N-doped TiO2 nanooctahedra with the exposed {101} crystallized surfaces show good photocatalytic behavior in comparison with other samples. [Copyright &y& Elsevier]