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In this paper we give a multi-scale analysis proof of the power-law localization for random operators on Z d for arbitrary d ≥ 1 .

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.

Ternary nickel-cobalt compounds with nano-arrayed structures can be used as promising electrodes to obtain high-performance electrochemical energy storage devices. Thus, ternary nickel-cobalt selenide, (NixCo1-x)0.85Se, nanosheet arrays are successfully synthesized via a two-step method consisting of hydrothermal and cation-exchange process, then directly used as binder-free electrodes for supercapacitors. Characterization results indicate that the morphologies and chemical composition of (NixCo1-x)0.85Se can be regulated by altering the reaction time. Electrochemical tests suggest that (Ni0.5Co0.5)0.85Se nanosheet arrays possess the best electrochemical properties, i.e.: a maximum specific capacity of 430.87 mA h g−1 at 1 A g−1 and good cycling stability with 85.25% capacity retention after 3000 cycles. In addition, hybrid supercapacitors based on (Ni0.5Co0.5)0.85Se nanosheet arrays and nitrogen-doped porous carbon can deliver a high energy density of 70.58 Wh kg−1 at power density of 320.02 W kg−1, as well as 91.88% capacitance retention after 8000 cycles, indicating that (Ni0.5Co0.5)0.85Se nanosheet arrays has higher applicable value in energy-storage fields.

Dopamine (DA), a typical catechol-containing monomer, which has been well reported for its excellent applications in biomedical research, was used to modify alginate (ALG) hydrogel for better gel formation and performance which are needed for drug delivery. By our design, Polydopamine (PDA) particles embedded ALG hydrogel (ALG-PDA), two types of DA and ALG co-polymerized hydrogels (ALG-DA-AS, ALG-DA-SP) which were initiated by ammonia aqueous solution (AS) and sodium periodate (SP), respectively, were successfully prepared. The status of incorporated DA/PDA and their interactions with hydrogel skeleton were investigated by chemical structure, morphology and rheology characterizations. Interestingly, a self-gelation process was discovered during ALG-DA-SP preparation, which is supposed to be the crosslinking formation via the aromatic interaction and hydrogen bonding between catechol or o-benzoquinone modified ALG molecules. Such self-crosslinked structure was proved helpful to improve the structural stability of gel even in saline environment. The effects of DA, SP concentration on the self-gelation process were discussed. The good biocompatibility of PDA material was also confirmed by a cytotoxicity test. In loading and release experiments, all the modified hydrogels were proved to have better adsorption ability to gatifloxacin (GFLX) and more steady in vitro release behavior than pristine ALG hydrogel.

To exploit a green way to produce polymer nanoparticles using biodegradable and renewable macromolecules instead of petroleum-based ones, we initiated a novel and facile method to synthesize lignin nanoparticles (LNPs). The LNPs, having a hydrodynamic diameter ranging from ca. 80 to 230 nm, were formed by self-assembly in a recyclable and non-toxic aqueous sodium p-toluenesulfonate (pTsONa) solution at room temperature, with a lowest concentration of up to 48 g/L. We eliminated the unfavorable factors of restricted processing pH and lignin species by taking advantage of the hydrotropic chemistry and the synergistic dissociation of the entrapped pTsONa and intrinsic phenolic hydroxyl and carboxylic acid moieties of the LNPs. Because of the hydrotropic system, various water-soluble or water-insoluble drugs can be dissolved and encapsulated in the LNPs with an encapsulation efficiency of up to 90%. The drug-encapsulated LNPs also showed great properties, with sustained drug-releasing capability and biocompatibility. Furthermore, the unloaded drugs and free pTsONa could be easily recycled for multiple use, thereby achieving environmental sustainability. This synthesis approach with broad processing window could realize the industrial scale-up production of LNPs and have wide potential applications, including but not limited to versatile drug/bioactive macromolecule loading in the biomedical field.

In this paper, it is proved that the full dimensional invariant tori obtained by Bourgain [J. Funct. Anal., 229 (2005), no. 1, 62–94] is stable in a very long time for 1D nonlinear Schrodinger equation with periodic boundary conditions.

The Covariance Matrix Adaptation Evolution Strategy (CMA-ES) algorithm is one of the most successful continuous black-box optimization algorithms widely used in many fields. However, the algorithm would be computationally unaffordable due to the sharp increase in dimension and complexity of problems. To improve the computational efficiency and global optimizing ability, a competitive variable-fidelity surrogate-assisted CMA-ES (CVFS-CMA-ES) algorithm using data mining techniques is proposed in this paper. In the first data mining of CVFS-CMA-ES, the establishment method of the competitive variable-fidelity model (VFM) based on the fuzzy clustering algorithm is developed, aiming at making full use of high-fidelity information and focusing more on potential areas of design space. In the second data mining of CVFS-CMA-ES, the Lower Confidence Bound (LCB) method is modified by introducing the step size of CMA-ES to control the uncertain term adaptively, and the sample points are screened in each generation of CMA-ES based on the modified LCB method, which can make a balance between exploration and exploitation in the optimization process. The performance of CVFS-CMA-ES is compared with four known black-box optimization algorithms. Firstly, ten numerical examples of 10-dimensional and 30-dimensional benchmark functions are carried out, respectively. Moreover, a 20-dimensional engineering example of the aerospace variable-stiffness composite shell under combined loadings is studied in detail. Results of benchmark functions and engineering examples verify the high efficiency, robustness and high global optimizing ability of the proposed CVFS-CMA-ES in comparison to other algorithms.

Strong interactions between loading drugs and nanocarriers contribute greatly to the high loading capacity while bringing about the problems on effective drug release. To solve this dilemma, we develop a density functional theory (DFT)-guided drug loading strategy to construct a dismountable nanoplatform for sensitized tumor-homing thermotherapy. DFT, a kind of computational method, is used to screen out a heat shock protein90 (HSP90) inhibitor, geldanamycin (GDM), that highly matched the structure of nanocarriers, thus providing a high drug loading efficiency (~ 42%). Of special note, GDM could be effectively released inside tumor cells because the isoelectric points of cancer cell membrane (CCM) and polydopamine (PDA) are both around pH 4.0 ~ 5.0, which could exactly match with the acidic environment of endo/lysosome. The CCM envelope enables self-targeting of PDA/GDM@CCM to the source cancer cells and homologous tumors while effectively inhibiting recognition and clearance by macrophages. Efficient photothermal ablation is attributed to the efficient suppression of tumor heat resistance by GDM and precise selection of the best matched tumor type by using The Cancer Genome Atlas (TCGA). This DFT-guided drug loading strategy points out a new avenue for optimization of drug-loading into nanocarriers, and ultimately contributes to the high drug availability and excellent curative effect.

Al2O3–SiO2 binary glasses with structural and chemical heterogeneities were prepared by consolidating glassy nanoparticles with different compositions using classical molecular dynamics simulations. Consolidated glasses show both excellent ductility and enhanced flow strength. It was found that the structural heterogeneities such as over-coordinated network formers and neighboring oxygen induced during consolidation serve as plasticity carriers to increase the ductility. On the other hand, the enhanced yield strength in consolidated glasses is due to the chemical heterogeneity inherited from the starting glassy nanoparticles, which does not compromise the ductility. Furthermore, apparent work hardening behavior appears upon cold work in the consolidated glasses, with an increase in yield strength from ~3.3 to ~6.4 GPa after 40% cold work. Consolidation with glassy nanoparticles could be a viable way to synthesize strong, damage resistant and transparent oxide glasses that cannot be obtained through the traditional melt-quench process.

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.

Metallic glasses, like many other glasses and ceramics, generally have zero tensile ductility. Distinct from common wisdom which seeks to toughen brittle glasses with ductile phases, we show that composites made from two brittle glasses can be ductile, strong and even harden under tension as a result of microstructure and stiffness contrast. Using molecular dynamics simulations, we designed and tested composites consisting of alternating wavy nanofilaments of two brittle glasses with different stiffness. The composites exhibit failure strain over 40% and strain hardening modulus over 2 GPa. The tensile ductility is determined by both the flexibility of nanofilaments and the propensity of crack deflection, with which a ductile composite design map can be constructed. The strain hardening is due to filament alignment analogous to linear polymer. The brittle-brittle composite design strategy proposed here is not material-specific and should be applicable to, for instance, ultra-hard materials as constituents in achieving new damage-resistance composites.

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.

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.

Nanocrystalline ultrathin metallic thin films have various applications for which mechanical properties and durability are important, such as electrodes and electrical interconnects. We investigated the effect of voids on mechanical behavior of thin nanocrystalline gold films using molecular dynamics. Different kinds of voids were considered. We found that the nature and geometry of the void was important for the mechanical properties in this model ductile material. It was found that in the half voids films the flow stress decreased following the decrease of mass density with a linear relation. For the full voids films, the strain–stress curve was different from that of voids-free film and half voids films. The plastic deformation could be activated with smaller amount of dislocations. Following the strain increase over the strain of ultimate tensile strength, the flow stress decreased. This implied that the voids which penetrated through the films would weaken the ductility of films. The deformation main mechanism was grain boundaries sliding with voids coalescence. On the contrary, if the void depth was less than the thickness of film, the ductility of film wasn’t influenced apparently, though the ultimate tensile strength decreased with the increase of voids size and decrease of mass density.

Background Despite significant investments in health information technology (IT), the technology has not yielded the intended performance effects or transformational change. We describe activities that health systems are pursuing to better leverage health IT to improve performance. Methods We conducted semi-structured telephone interviews with C-suite executives from 24 U.S. health systems in four states during 2017–2019 and analyzed the data using a qualitative thematic approach. Results Health systems reported two broad categories of activities: laying the foundation to improve performance with IT and using IT to improve performance. Within these categories, health systems were engaged in similar activities but varied greatly in their progress. The most substantial effort was devoted to the first category, which enabled rather than directly improved performance, and included consolidating to a single electronic health record (EHR) platform and common data across the health system, standardizing data elements, and standardizing care processes before using the EHR to implement them. Only after accomplishing such foundational activities were health systems able to focus on using the technology to improve performance through activities such as using data and analytics to monitor and provide feedback, improving uptake of evidence-based medicine, addressing variation and overuse, improving system-wide prevention and population health management, and making care more convenient. Conclusions and implications Leveraging IT to improve performance requires significant and sustained effort by health systems, in addition to significant investments in hardware and software. To accelerate change, better mechanisms for creating and disseminating best practices and providing advanced technical assistance are needed.

Surface diffusion is an interesting and practically important phenomenon in many areas of chemistry and physics. One emerging problem is that of Li wetting on high-Z plasma-facing metals, especially tungsten, for application in tokamak reactors. We report construction of a Li-W binary force field to describe the interface between liquid Li and solid W. We show that this force field can simulate well the atomic processes of liquid Li diffusing across the W surface, as compared with results from first-principles calculations. We find that Li atoms have different wetting behaviors on different surfaces of W. Diffusion is the fastest on the (110) surface and the slowest on the (100) surface. Diffusion of second Li layer on the (110) surface is activated at relatively low temperatures above 262 K. In addition, the diffusion rate of single-layer Li changes with the coverage rate of Li on (110) surface. High diffusion coefficients at coverage rate of θ = 1/6, 1/3 and 1 are found to be related to the 2D phase transition of Li on the (110) surface.

Simulated nanoindentation tests on a model metallic glass reveal that the crack initiates inside a shear band via cavitation. The load-displacement curve was shown to be insensitive to the crack initiation but sensitive to subsequent crack propagation. The critical conditions for crack initiation were identified at both the macroscopic and microscopic levels. At the macroscopic level, the indenter geometry affects the overall critical load for crack initiation. Interestingly, the indentation volume at crack initiation appears to be a constant for different indenter geometries, based on which an analytical formula of the critical load as a function of the indenter geometry was derived. At the microscopic level, cavitation occurs once the normal stress perpendicular to the shear band exceeds a temperature-dependent critical cavitation stress. This critical cavitation stress was shown to reduce significantly upon shear deformation.

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).

The paradox of biomimetic research is to perform bio-functionality, usually associated with sophisticated structures optimized by nature, with minimal structural complexity for the ease of fabrication. Here we show that a three-particle trimer can exhibit kinesin-like autonomous walk on a track via reactive molecular dynamics simulations. The autonomous motion is due to imbalanced transitions resulting from exothermic catalytic reactions, and the spatial asymmetry from the track. This molecular design can be realized by reproducing the particle–particle interactions in functionalized nano- or colloidal particles. Our results open up the possibility of fabricating bio-mimetic nano-systems in a minimalist approach.

Background Multi-stakeholder alliances – groups of payers, purchasers, providers, and consumers that work together to address local health goals – are frequently used to improve health care quality within communities. Under the Aligning Forces for Quality (AF4Q) initiative, multi-stakeholder alliances were given funding and technical assistance to encourage the use of health information technology (HIT) to improve quality. We investigated whether HIT adoption was greater in AF4Q communities than in other communities. Methods Drawing upon survey data from 782 small and medium-sized physician practices collected as part of the National Study of Physician Organizations during July 2007 – March 2009 and January 2012—November 2013, we used weighted fixed effects models to detect relative changes in four measures representing three domains: use of electronic health records (EHRs), receipt of electronic information from hospitals, and patients’ online access to their medical records. Results Improvement on a composite EHR adoption measure was 7.6 percentage points greater in AF4Q communities than in non-AF4Q communities, and the increase in the probability of adopting all five EHR capabilities was 23.9 percentage points greater in AF4Q communities. There was no significant difference in improvement in receipt of electronic information from hospitals or patients’ online access to medical records between AF4Q and non-AF4Q communities. Conclusion By linking HIT to quality improvement efforts, AF4Q alliances may have facilitated greater adoption of EHRs in small and medium-sized physician practices, but not receipt of electronic information from hospitals or patients’ online access to medical records. Implications Multi-stakeholder alliances charged with promoting HIT to advance quality improvement may accelerate adoption of EHRs.

Free vibration solution of a free rectangular thin plate resting on multiple point supports has been a topic of fundamental importance in mechanical engineering. It is well known that various approximate/numerical methods have been developed to solve the problems, but exact analytic solutions, as the benchmarks, are rarely reported in the literature. This is attributed to the difficulty in seeking the solutions that satisfy the governing fourth-order partial differential equation (PDE) with the completely free boundary conditions as well as the support conditions. In this paper, we present a successful endeavor to address the issue with our recently developed symplectic superposition method for free vibration problems. A general set of equations are obtained for determining the natural frequencies and mode shapes of the plates with any point supports. Seventeen typical combinations of support locations are investigated for the plates with three or four point supports. The obtained solutions are all shown by the numerical results listed for comparison with those by the well-accepted finite element method (FEM), and very good agreement is observed. This study provides some useful benchmark solutions of the point-supported free rectangular plates, and demonstrates an effective analytic approach to solving similar boundary value problems which have not been well settled by other analytic methods.

We investigated the wear formation during a single-asperity sliding against a rigid substrate using molecular dynamics simulations. Two distinct wear mechanisms were observed: low-load atomic wear (isolated debris atoms or clusters) and high-load plastic wear (collective debris formation from plastic flow). The atomic wear rate depends on the normal stress exponentially, in agreement with the mechanically assisted bond-rupture theory. However, the plastic wear rate exhibits linear dependency on the normal stress. It was found that the asperity-substrate adhesion reduces the critical normal stress for the atomic-to-plastic wear transition, suppressing the atomic wear mode. Finally, a wear mechanism map of atomic/plastic wear was constructed in the domain of normal stress and adhesion, which is consistent with existing simulation and experimental results. This wear map could resolve the recent controversy on whether Archard׳s linear law is applicable for low-load tip wear.

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.

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 Fe3O4 nanocrystals (NCs). The FA-PEG-HPEI had FA targeting groups, low cytotoxicity and ideal gene transfection performance, while Fe3O4 NCs had superparamagnetic property, thus the resulting Fe3O4/FA-PEG-HPEI nanocomposites integrated the properties of FA-PEG-HPEI and Fe3O4 NCs together. As expected, the Fe3O4/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 Fe3O4/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.

Metallic glasses with secondary crystalline phase have been reported to either enhance or degrade the global plasticity. Here, we employed molecular dynamics simulation to investigate a generic glass-forming system, in which crystal-glass composites can be obtained via in situ crystallization. Ex situ composite samples were also constructed by embedding perfect crystals into monolithic glasses in order to delineate the precise influences of the composite microstructure. Our simulations demonstrate both toughening and embrittlement effects due to nanocrystallization. The double-edged-sword role of nanocrystals is mainly controlled by elasticity mismatch between the crystalline phase and the glass matrix. The effects of volume fraction and the size of nanocrystals can be understood in the perspective of cumulative probability of shear bands formation and propagation being interfered by the presence of nanocrystals.

Low-cycle fatigue fracture of metallic glass nanowires was investigated using molecular dynamics simulations. The nanowires exhibit work hardening or softening, depending on the applied load. The structural origin of the hardening/softening response was identified as the decrease/increase of the tetrahedral clusters, as a result of the non-hardsphere nature of the glass model. The fatigue fracture is caused by shear banding initiated from the surface. The plastic-strain-controlled fatigue tests show that the fatigue life follows the Coffin–Manson relation. Such power-law form originates from plastic-strain-dependent microscopic damage accumulation. Lastly, the effect of a notch on low-cycle fatigue of nanowires in terms of failure mode and fatigue life was also discussed.

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.

A novel enzyme-free hydrogen peroxide (H2O2) sensor was fabricated by coating graphene oxide (GO), branched polyethylenimine (PEI) and Pd particles in sequence on the surface of glassy carbon (GC) electrode (Pd-PEI/GO/GC). A layer-by-layer method was used, which involved π–π interactions, covalent bonding through 1-ethyl-3-[3-dimethylaminopropyl]carbodiimide/N-hydroxysulfosuccinimide (EDC/NHSS) chemistry, electrostatic adsorption and electroreduction. The Pd-PEI/GO/GC electrode exhibited high electrocatalytic activity, a low detection limit, and good stability for the detection of H2O2. The sensor’s practical application was tested via determination of H2O2 in real water samples.

The shear-induced volumetric strain (SIS) of a set of model CuZr metallic glasses is studied for various deformation conditions characterized by different strain rates, temperatures and applied hydrostatic stress states. The various systems considered are obtained by quenching from the melt at different cooling rates. During shear deformation at constant pressure, the material reaches a steady state in which the sample volume remains constant. It is observed that the density of the glass during steady state deformation depends on temperature, pressure and shear strain rate, and is independent of the initial state of the sample. The SIS vanishes as the temperature of the shear test reaches the glass transition temperature. The SIS can become negative under compressive pressure since the instantaneous bulk modulus is lowered by the shear flow. The results suggest that the magnitude of the SIS is related to the difference in density between samples quenched with given finite rate and a fictitious sample quenched infinitely fast.

This paper deals with the anti-triangular operator matrix M = A B C 0 with A 2 = A and CA π B = 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-Gonzalez 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 ∈ C n × n with P 2 = P and PQ 2 = 0 .

Branched polyethylenimine (PEI) was covalently linked to graphene oxide (GO) pre-modified on glassy carbon (GC) electrode (PEI/GO/GC) via an amide bond with 1-ethyl-3-[3-dimethylaminopropyl]carbodiimide/N-hydroxysulfosuccinimide (EDC/NHS) chemistry, and gold nanoparticles was then assembled on the surface of the PEI/GO/GC electrode (Au-PEI/GO/GC) by the electro-reduction of absorbed AuCl4− through electrostatic interaction. The Au-PEI/GO/GC electrode exhibited high electrocatalytic activity toward nitrite oxidation and hydrogen peroxide (H2O2) reduction. The analytical performances of the Au-PEI/GO/GC electrode demonstrated low detection limit, wider linear range, and good stability for the determination of nitrite and H2O2, which make it a promising candidate for amperometric nitrite or enzymeless H2O2 sensor.

A novel poly(methacrylic acid) (PMAA) microcarriers coated with nanolayered chitosan(Cs) and carboxyl modified multi-walled carbon nanotubes (MWCNTs-COOH) via self-assembly method, has been successfully prepared for better loading and sustained release of gatifloxacin (GFLX). Due to the multi-loading and gradient release properties, PMAA/Cs/CNTs could adsorb a great amount of drug (84.89±9.63 μg mg −1 ), and 64.74±2.78% of its loading could slowly release in 24 h, which is important to delivery GFLX effectively and to reduce the risk of side effects.

We reported the deformation of close-cell nanoporous gold with grain size of 20 nm under tension using molecular dynamics. With the decrease of relative mass density and formation of close-cell nanoporous structures, mechanical properties of nanocrystal were found to be changed significantly. The Young's modulus decreases with the decrease of mass density and follows the similar rule to that of the open-cell nanoporous. While the strength of close-cell nanoporous is found to be much higher than that of the open-cell nanoporous. For pores in grain boundaries, grain boundary sliding is considered to be one of main mechanism of deformation. For the relative mass density less than 0.94, the pores control the deformation and Shockley partials are the main deformation source.

Let A be a complex Banach algebra with unit and let p , q be two idempotents in A . For α , β ∈ C \ { 0 } , the authors obtain an explicit representation formula for the Drazin inverse of α p + β q 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 α p + β q are corollaries of our theorem. Finally, the authors apply the theorem to an example which cannot be solved by previously known results.

Molecular dynamics simulations were carried out to investigate the wear formation of a truncated-cone-shaped tip sliding against a rigid flat substrate. Under a constant normal load, the worn volume of the tip increases sub-linearly with the sliding distance, which holds true for three distinct debris definitions (geometry-based, material-transfer-based and displacement-based). Under a constant normal stress, the tip height reduces linearly with the sliding distance, which can be conveniently used to calculate the wear rate. It was found that the tip height loss per sliding distance (ΔH/ΔL) is a function of the normal stress and the tapering angle of the tip, but independent of the sliding speed and the contact area. Above a critical stress, ΔH/ΔL increases linearly with the stress while the debris is generated from plastic flow. ΔH/ΔL is almost zero below the critical stress while the debris is generated from atom-by-atom attrition. Our results show that Archard's linear wear law is not applicable to single-asperity tip wear in the plastic wear regime. Finally, a new wear rate formula is given for tip wear as a function of the load, the contact area and the tapering angle of the tip.

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.