We present a novel distributed-memory parallel implementation of the concurrent atomistic-continuum (CAC) method. Written mostly in Fortran 2008 and wrapped with a Python scripting interface, the CAC simulator in PyCAC runs in parallel using Message Passing Interface with a spatial decomposition algorithm. Built upon the underlying Fortran code, the Python interface provides a robust and versatile way for users to build system configurations, run CAC simulations, and analyze results. In this paper, following a brief introduction to the theoretical background of the CAC method, we discuss the serial algorithms of dynamic, quasistatic, and hybrid CAC, along with some programming techniques used in the code. We then illustrate the parallel algorithm, quantify the parallel scalability, and discuss some software specifications of PyCAC; more information can be found in the PyCAC user’s manual that is hosted on www.pycac.org.

3D printing has been shown to be a robust and inexpensive manufacturing tool for a range of applications within biomedical science. Here we report the design and fabrication of a 3D printer-enabled microfluidic device used to generate cell-laden hydrogel microspheres of tunable sizes. An inverse mold was printed using a 3D printer, and replica molding was used to fabricate a PDMS microfluidic device. Intersecting channel geometry was used to generate perfluorodecalin oil-coated gelatin methacrylate (GelMA) microspheres of varying sizes (35–250 μm diameters). Process parameters such as viscosity profile and UV cross-linking times were determined for a range of GelMA concentrations (7–15% w/v). Empirical relationships between flow rates of GelMA and oil phases, microspheres size, and associated swelling properties were determined. For cell experiments, GelMA was mixed with human osteosarcoma Saos-2 cells, to generate cell-laden GelMA microspheres with high long-term viability. This simple, inexpensive method does not require the use of traditional cleanroom facilities and when combined with the appropriate flow setup is robust enough to yield tunable cell-laden hydrogel microspheres for potential tissue engineering applications.

AgBr-modified Bi2WO6 nanosheets were successfully synthesized using a CTAB-assisted hydrothermal method followed by a facile deposition–precipitation procedure. The as-prepared photocatalysts were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), UV-vis diffuse reflectance spectroscopy (DRS), Brunauer–Emmett–Teller (BET), and photoluminescence emission spectroscopy (PL). AgBr nanoparticles were found evenly distributed on the surface of the Bi2WO6 nanosheets. The AgBr/Bi2WO6 nanocomposite demonstrated enhanced pollutant decolorization efficiency in eliminating Rhodamine B (RhB), methyl orange (MO), and phenol aqueous solutions under simulated solar light irradiation. It has been noticed that the adsorption performance of both Bi2WO6 nanosheets and AgBr-modified Bi2WO6 nanosheets played a more important role in the decolorization of pollutants, such as RhB and MO, than their photocatalytic ability. The high adsorption efficiency of the photocatalysts was mainly attributed to the increased surface area and the exposed reactive facets of the materials.

In this work, the negatively charged [NbMoO6]− nanosheets (NSs) were combined with positively charged [5,10,15,20-tetrakis (N-methylpyridinium-4-yl) porphyrinato cobalt] (CoTMPyP) to fabricate a sandwich-like CoTMPyP/[NbMoO6]− NSs intercalated material by a direct self-assembling process. The results confirmed that CoTMPyP cations formed an inclined monolayer between [NbMoO6]− NSs and the inclined angle was about 68°. The electrochemical properties of CoTMPyP/[NbMoO6]− NSs composite were also investigated by cyclic voltammetry and liner sweep voltammetry, which showed the enhanced electron transferred ability. The CoTMPyP/[NbMoO6]− NSs modified electrode displayed excellent electrocatalytic activity towards oxygen reduction with the reduction peak potential shifting from −0.681 to −0.235 V. And oxygen could be reduced to generate hydrogen peroxide with a two-electron process in neutral electrolytes. Moreover, the reduction peak current was linear relationship with the square root of scan rates, implying that the catalytic reaction depended on oxygen diffusion.

Al–12.6Si was annealed at both 500 and 560 °C for different lengths of time in this study. Additionally, the effects of annealing treatment on the spheroidization of eutectic Si and the mechanical properties of the Al–Si alloy have been investigated. The morphology of these particles was described using surface shape factor (φ), and it was found that the optimal annealing time of Al–12.6Si at 500 and 560 °C is seven hours and five hours, respectively. The average size of the Si particles in the Al–Si alloy annealed at 500 °C is less than that of the particles at 560 °C. The roundness of the Si particles within the Al–Si alloy annealed at 500 °C is slightly better than that at 560 °C. The elongation of the alloy apparently increases, while the tensile strength of the Al–Si alloy decreases. The tensile strength and elongation of the eutectic Al–Si alloy annealed at 500 °C is higher than that at 560 °C.

In this study, nano-hydroxyapatite (n-HAp) of average crystallite size ∼8.15 ± 4 nm of hexagonal geometry with size ranging between 14 and 50 nm was synthesized in laboratory at room temperature by using suitable sources of calcium and phosphate ions and using triethanolamine. Mesoporous bioactive glass (MBG) was synthesized by using cationic surfactant cetyl trimethyl ammonium bromide of the SiO2–CaO–P2O5 glass system. After calcination at 650 °C, MBG powders were having a zeta potential of −16.5 mV (pH ∼9.1), median particle size ∼75 nm, and specific surface area 473.2 m2/g. An aqueous suspension of DNA was used to disperse both n-HAp and MBG and further subjected for analysis including absorbance, circular dichroism spectroscopy, UV-melting, and isothermal titration calorimetry. Absorbance spectroscopy indicated that an equilibrium binding was obtained between both materials and DNA in solution phase. Due to the addition of the nanomaterial, molar ellipticity of DNA was changed revealing that the materials were interacted with DNA. From UV melting characterization, there is a shifting of the melting temperature of DNA in the presence of MBG and n-HAp, respectively, suggesting that the nanoparticles stabilized DNA helix to a considerable extent.

Porous carbon nanomaterials with significant capacitive performance were successfully prepared through a simple two-step process of thermal-polymerization and carbonization without an additional template. As a result, the as-prepared porous carbon nanomaterials of sample-A and sample-B exhibited an amorphous phase with low graphitization. And sample-A showed a moderate specific surface area of 476.39 m2/g, larger than that of sample-B (280.94 m2/g). The relatively high mass specific capacitance of 205.1 F/g at a scan rate of 5 mV/s and 211 F/g at a current density of 4 A/g was obtained by sample-A, which are higher than those of sample-B (82.6 F/g at 5 mV/s and 78.6 F/g at 4 A/g). Sample-A also showed excellent conductivity and superior cyclic stability with 94.19% capacitance retention after 5000 cycles, which are also higher than those of sample-B. This work proposed a cost-effective, green, and promising strategy for the large-scale preparation of porous carbon nanomaterial electrodes.

Molybdenum sulfide hydrotreating catalysts promoted with nickel over tridimensional mesoporous silica (KIT-6 post synthesis modified with alumina) were prepared with three different chelating agents. Citric acid and EDTA (ethylenediaminetetraacetic acid) were used as typical chelates and the new suggestion, polyacrylic acid as a polymeric agent. The catalysts were synthesized by the incipient wetness impregnation method, and two different activation methods were applied to determine the correlation between the chelating agent and activation conditions. The beneficial use of chelating agents was evaluated in their performance on HDS (hydrodesulfurization) of DBT (dibenzothiophene). To determine the properties of catalysts, nitrogen physisorption, X-ray diffraction, HRTEM (high-resolution transmission electron microscopy), and TGA (thermogravimetric analysis) were used. The beneficial effect of chelating Ni during impregnation to avoid NiSx formation and thus promoting NiMoS arrangement was clearly observed in the catalytic HDS performance, and the TGA analysis of Ni-chelate complexes also confirms this theory. The catalyst with the best performance in the HDS reaction of DBT was the synthesized with citric acid and a slow rate temperature sulfidation.

Direct ink writing of silicone elastomers enables printing with precise control of porosity and mechanical properties of ordered cellular solids, suitable for shock absorption and stress mitigation applications. With the ability to manipulate structure and feedstock stiffness, the design space becomes challenging to parse to obtain a solution producing a desired mechanical response. Here, we derive an analytical design approach for a specific architecture. Results from finite element simulations and quasi-static mechanical tests of two different parallel strand architectures were analyzed to understand the structure-property relationships under uniaxial compression. Combining effective stiffness-density scaling with least squares optimization of the stress responses yielded general response curves parameterized by resin modulus and strand spacing. An analytical expression of these curves serves as a reduced order model, which, when optimized, provides a rapid design capability for filament-based 3D printed structures. As a demonstration, the optimal design of a face-centered tetragonal architecture is computed that satisfies prescribed minimum and maximum load constraints.

A method for extracting the substrate-independent stress–strain curves of thin films was developed using spherical nanoindentation to investigate the yield behavior of diamond-like carbon (DLC) thin films with Young’s moduli of ∼73 GPa and ∼76 GPa. The resulting stress–strain curves showed that these films commence yielding at ∼13 GPa and ∼14 GPa, respectively. These yield strength values agree with the critical pressure necessary to initiate the transformation of sp 2-bonded carbon into significantly harder sp 3-bonded carbon, indicating that the yielding of the materials is associated with the sp 2-to-sp 3 phase transition. The ability of a DLC film to accommodate a progressively increasing contact stress with strain beyond the yield point while dissipating part of the accumulated strain energy, as evidenced in this work, implies a unique mechanism of the brittle material for passively mitigating contact deformation and fracture in tribological applications.

Chronic osteomyelitis, a bone infection caused by bacteria, requires extensive parenteral treatments. With an aim to develop bioactive glass with antibacterial properties to resist such infections, bioactive glasses with bismuth oxide as the dopant in various amounts up to 8 wt% were prepared. X-ray diffraction patterns and Fourier-transform infrared spectra of glass samples after immersion in simulated body fluid showed the presence of hydroxyapatite (HAp) and hydroxyl carbonate apatite for all samples except with the one having Bi2O3 substitution of 8 wt%. In vitro cell proliferation by MTT assay studies using a mouse fibroblast cell line (NIH3T3) have also been carried out. Primary antimicrobial activity of the glass particles was analyzed against Escherichia coli (E. coli) using broth microdilution method which exhibited bacteriostatic effects and bactericidal properties in selected samples. The combination of bioactivity, cell proliferation, and antibacterial properties of selected Bismuth-containing bioactive glasses could be exploited in treating bone-related infections.

In fracture mechanics, established methods exist to model the stability of a crack tip or the kinetics of crack growth on both the atomic and the macroscopic scale. However, approaches to bridge the two scales still face the challenge in terms of directly converting the atomic forces at which bonds break into meaningful continuum mechanical failure stresses. Here we use two atomistic methods to investigate cleavage fracture of brittle materials: (i) we analyze the forces in front of a sharp crack and (ii) we study the bond breaking process during rigid body separation of half crystals without elastic relaxation. The comparison demonstrates the ability of the latter scheme, which is often used in ab initio density functional theory calculations, to model the bonding situation at a crack tip. Furthermore, we confirm the applicability of linear elastic fracture mechanics in the nanometer range close to crack tips in brittle materials. Based on these observations, a fracture mechanics model is developed to scale the critical atomic forces for bond breaking into relevant continuum mechanical quantities in the form of an atomistically informed scale-sensitive traction separation law. Such failure criteria can then be applied to describe fracture processes on larger length scales, e.g., in cohesive zone models or extended finite element models.

In this work, morphology, viability, and metabolism of the amniotic mesenchymal stem cells conditioned with different citric acid (CA)/media ratios were investigated using rhodamine-phalloidin/4′,6-diamidino-2-phenylindole staining, live/dead assay, proliferating cell nuclear antigen, and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL assay). The cells cultured in 25:75 CA/media displayed well spread actin filaments with a prominent nucleus and evidenced optimum viability. The gelation kinetics of chitosan solution in CA/media (25:75) was monitored via dynamic time sweep analysis on a rheometer. The chemical cross-linking of chitosan with CA was confirmed by nuclear magnetic resonance studies. Subsequently, chitosan solution was extruded in CA/media bath containing cells under benign conditions to form cell-laden fibers (living fibers). The prelabeled cells imaged immediately after fiber formation confirmed the attachment of the cells on the fibers. This approach has several advantages including instantaneous gelation, tunable mechanical properties, and adjustable biodegradability that can provide a platform technology for creating viable three dimensional (3D) building blocks for tissue engineering applications.

Mechanical properties of Pr (praseodymium)-doped ZnO thin films, deposited on a corning glass substrate and fused quartz at different deposition pressures using DC sputtering were investigated. Crystalline growth in Pr-doped ZnO thin films is more pronounced and improves at 10 mtorr deposition pressure. However, lower sputtering deposition pressure evoked deposition rates to the formation of polycrystalline films emerged in several crystal planes. Pr ions incorporated in the ZnO host lattice was examined by X-ray photoelectron spectroscopy (XPS), AFM, and FESEM. XPS spectroscopy revealed the presence of Pr3+ and Pr4+ at the ZnO surface layer and it was in tandem with EDS mapping. Nanoindentation prior to scratch testing is used for analyzing deformation characteristics. Pr-doped ZnO thin films exhibit better hardness (9.89 ± 0.14 GPa) and Young’s modulus (112.12 ± 3.45 GPa) on the glass substrate. The crack propagation resistance parameter of the films was evaluated using initial critical load, Lc1 ∼ 2250.5 µN for the crack initiation and upper critical load Lc2 ∼ 2754.5 µN for film failure. Better crack propagation resistance was observed for films deposited at 10 mtorr sputtering pressure on both substrates, attributed to better crystalline nature of the films.

We report the synthesis and optical properties of pure ZnS and Ag doped ZnS nanostructures. ZnS(Ag) was synthesized by using the hydrothermal technique and later annealed at different temperatures under vacuum conditions. It was observed that the photoluminescence (PL) emission from the ZnS(Ag) nanostructures can be easily tuned from the blue (445 nm) to green (530 nm) region of visible light by varying the annealing temperature. This tunability has been attributed to the introduction of excess sulfur vacancy states, which is evident from the PL excitation spectra. This observed change in the PL emission wavelength can be highly beneficial in the imaging screens where ZnS is regularly used and can be easily interfaced with the silicon photodiodes showing maximum sensitivity at 550 nm.

In this article, we report the synthesis of highly packed graphene oxide-based electrodes (1.25 g/cm3) with a three-dimensional multiscale porous structure (denoted as MPGP) through the ZnO nanodisk (100–500 nm) template and subsequent H2O2 treatment. Consequently, MPGP with a macropore diameter of 100 nm and a mesopore diameter of 2–3 nm was fabricated as the electrode for supercapacitors (SCs). Significantly, the MPGP achieves a high-volumetric capacitance of 327 F/cm3 (262 F/g) at a current density of 1 A/g and retains 240 F/cm3 (192 F/g) at a current density of 16 A/g in 3 M KOH solution. More importantly, it was also capable of delivering a high-volumetric energy density as well as power density in a SC device. Our work shows that the capability of preparing highly packed graphene-based electrodes with high-volumetric as well as specific capacitance is critical for the application of SCs.

High-entropy alloys (HEAs), originally introduced to the literature due to their ability to stabilize a single phase across large temperature ranges, have recently demonstrated to display multiphase systems undergoing a variety of strengthening mechanisms. Previous reports have focused on solid solution strengthening and precipitation hardening; however, other hardening mechanisms such as twinning and martensite formation have been reported to play a key role in controlling their mechanical behavior. Such deformation mechanisms display significant variations with temperature and strain rate. The present contribution provides an outline of the various hardening mechanisms reported in the literature for HEAs. For each mechanism, a modeling strategy is proposed to describe the associated mechanical behavior. The mechanisms are combined into a single framework to discover new HEAs of improved mechanical behavior. A strategy for HEA design is presented, and the advantages of adopting additive layer manufacturing to improve mechanical behavior are discussed.

The self-learning kinetic Monte Carlo method has been shown to be suitable for examining the temporal and spatial evolution of adatom islands on the (111) surface of several fcc metals, unbiased by diffusion processes chosen a priori. A pattern-recognition scheme and a diffusion path finder scheme enable collection of a large database of diffusion processes and their energetics. A variety of mechanisms involving single and multiple atoms, and concerted island motion are uncovered in long-time simulations. In this contribution, after reviewing the methodology, we present results comparing the diffusion kinetics of two sets of homo-epitaxial and hetero-epitaxial systems: small (2–8 atom) Pd and Ag islands on the respective (111) surfaces and small Cu islands on Ni(111) and Ni islands on Cu(111). We trace the dominance of concerted motion in Pd/Pd(111) and Ni/Cu(111) and competition among concerted, multiatom and single-atom processes in Ag/Ag(111) and Cu/Ni(111) to the strength of the lateral interaction among adatoms in these systems.

Luminescent biolabels are being eagerly investigated as a means of detecting cancer cells by bioimaging. Upconversion nanoparticles are a promising option to be used as biolabels for cancer cell detection. This process uses a near infrared beam (NIR λ = 980 nm) as the excitation source to upconvert the energy into light in the visible region. The present study, used Y2O3:Yb3+, Er3+ (1%, 10% mol) and Gd2O3:Yb3+, Er3+ (1%, 10% mol) capable of emitting red photons of λ = 660 nm. The nanoparticles were previously functionalized with aminosilanes and folic acid (UCNP-NH2-FA). Folic acid binds to the folate receptor on the surface of MCF-7 breast cancer cells, and this binding promotes internalization of the UCNPs via endocytosis. The UCNPs were characterized by TEM, EDS, and Fourier transform infrared. Cytotoxicity was also analyzed using the MTT (methy-134 thiazolyltetrazolium) colorimetric assay. The UCNPs-NH2-FA was noncytotoxic to the studied cancer cells and they were clearly localizable within the cell cytoplasm via confocal microscope.

In this project, we described the production of chrysin-loaded L-phenyl alanine (Phe)-coated iron oxide magnetic nanoparticles (chrysin@Phe@IOMNs). chrysin@Phe@IOMNs were characterized by X-ray diffraction, thermogravimetric analysis, fourier transform infrared spectroscopy, vibrating sample magnetometer, and transmission electron microscopy techniques. Next, hemocompatibility and biocompatibility of Phe-coated IOMNs were determined by hemolysis and MTT assays on HFF-2 and HEK-293 cell lines, respectively. Finally, the anticancer activity of chrysin@Phe@IOMNs was examined on MCF-7 cell line. The outcomes direct that as-prepared nanocarriers are nontoxic and biocompatible and also chrysin@Phe@IOMNs are appropriate for chrysin delivery and other hydrophobic therapeutic agents.