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Background Osteoarthritis (OA) is prevalent in postmenopausal women. Subchondral bone in ovariectomized (OVX) rats might play a more important role in cartilage degeneration compared with other types of OA. How subchondral osteoblast changes in OVX rats is still unclear. Understanding of osteoblast changes obtained from OVX subchondral bone might be helpful to clarify pathogenesis of OVX-OA. Methods Female Sprague-Dawley rats were randomly divided into two groups: Sham (n=20) and OVX (n=20). Serum levels of Alkaline phosphatase (ALP) and C-telopeptide of type I collagen (CTX-I) were measured every one or two weeks. All rats were executed at week 9 post surgery. The weight of rats and the wet weight of uterus were assessed. Micro-computed Tomography (micro-CT) was used to analyze the knee microstructure, and toluidine blue staining was employed to evaluate cartilage erosion. Subchondral osteoblast proliferation ability by cell counting kit-8 assay, osteogenic genes expressions by reverse transcription polymerase chain reaction (RT-PCR), differentiation and mineralization ability by ALP staining and alizarin red staining were evaluated and compared between Sham and OVX. Results Ovariectomy induced significant increases of serum ALP and CTX-I as early as at week 2. At week 9 after surgery, the body weight of OVX rats was significantly increased, and uterus weight of OVX rats was remarkably decreased. OVX rats demonstrated significant subchondral bone change and cartilage erosion compared with Sham rats. mRNA levels of early markers of osteogenic differentiation (ALP, type I collagen, Runx2) were enhanced in OVX rats, but the late marker (osteocalcin) was not significantly different. ALP activity of osteoblasts increased, but the mineralization capacity decreased in OVX rats. Conclusions Subchondral osteoblasts in OVX rats exhibited different proliferation, differentiation and mineralization abilities from normal counterparts.

A novel and simple method to directly assemble nanostructures onto plastic substrate via a quasi-2D electrodeposition approach was proposed. It was demonstrated that such synthetic method was feasible for flexible electronics, as exemplified by the fabrication of ZnO nanosheets film photoresponse devise onto flexible transparent, polyethylene terephthalate (PET) substrate that can withstand bending. This direct assembly strategy is general to other nanostructures onto plastic substrate which can be electrodeposited.

Nanoprint-based color display using either extrinsic structural colors or intrinsic emission colors is a rapidly emerging research field for high-density information storage. Nevertheless, advanced applications, e. g., dynamic full-color display and secure information encryption, call for demanding requirements on in situ color change, nonvacuum operation, prompt response, and favorable reusability. By transplanting the concept of electrical/chemical doping in the semiconductor industry, we demonstrate an in situ reversible color nanoprinting paradigm via photon doping, triggered by the interplay of structural colors and photon emission of lead halide perovskite gratings. It solves the aforementioned challenges at one go. By controlling the pumping light, the synergy between interlaced mechanisms enables color tuning over a large range with a transition time on the nanosecond scale in a nonvacuum environment. Our design presents a promising realization of in situ dynamic color nanoprinting and will empower the advances in structural color and classified nanoprinting.

Mid-infrared (IR) perfect absorbers have great potential in practical applications such as biomedical sensing and thermal energy and have been successfully demonstrated in a number of plasmonic metallic nanostructures. However, all the experimental realizations of perfect absorbers are strongly dependent on nanofabrication techniques, which usually require high costs and a long time to fabricate a wafer scale device. Here we propose and experimentally demonstrate a wafer scale, polarization independent, wide angle, and dual-band IR perfect absorber. By fabricating double "E"-shaped metallic structures on a ZnSe coated gold film, a dual-band metamaterial absorber has been uniformly realized on a 2'' silicon wafer. Two absorption peaks have been realized at 18 and 27 THz, which are well consistent with the designs. We believe that our research will boost the applications of metamaterial perfect absorbers.

Microstructural effects become important at regions of stress concentrators such as notches, cracks and contact surfaces. A multiscale model is presented that efficiently captures microstructural details at such critical regions. The approach is based on a multiresolution mesh that includes an explicit microstructure representation at critical regions where stresses are localized. At regions farther away from the stress concentration, a reduced order model that statistically captures the effect of the microstructure is employed. The statistical model is based on a finite element representation of the orientation distribution function (ODF). As an illustrative example, we have applied the multiscaling method to compute the stress intensity factor K I around the crack tip in a wedge-opening load specimen. The approach is verified with an analytical solution within linear elasticity approximation and is then extended to allow modeling of microstructural effects on crack tip plasticity.

According to the reliability and safety requirement for aircraft, fault detection and isolation (FDI) is essential to improve the fault tolerant performance of the navigation system. However, conventional principal component analysis (PCA) method does not consider the fault detection of the dynamic system and a high rate of false alarm rate. This paper proposes a modified method combined both superiority of generalized likelihood test (GLT)and principal component analysis (PCA). Firstly, this method through comparing the distribution of the projected points in the feature plane of the sensors data and historical normal navigation data detects the fault. Secondly, determines the time interval of failure by analyzing the length of each projection. Finally we compute the contribution of the variables to the statistic Q to carry out fault isolation. Monte Carlo simulation is carried out in order to verify the validity of the algorithm. Results show that this method can isolate the influence of the vehicle's own vibration on the sensors data effectively and can reduce the false alarm rate. Furthermore, this method can correctly detect and isolate the 2.4e — 4rad/ S amplitude of the fault while the noise level is 1e — 6. Consequently, this method can provide a new theoretical reference for the fault detection of aircraft redundant inertial measurement unit (RIMU).

Dark plasmonic resonances in metallic nanostructures are essential for many potential applications such as refractive index sensing, single molecule detection, nanolasers etc. However, it is difficult to excite the dark modes in optical experiments and thus the practical applications are severely limited. Herein, we demonstrate a simple method to experimentally excite the quadrupolar and higher-order plasmonic modes with normal incident light. By directionally depositing silver films onto the sidewalls of metal-covered one-dimensional grating, we have experimentally observed a series of asymmetrical resonances at the plasmonic ranges of silver gratings. Interestingly, both of the reflection and transmission coefficients of high-order plasmonic modes are reduced to around zero, demonstrating the perfect absorption very well. The corresponding numerical simulations show that these resonances are the well-known dark modes. Different from the conventional dark modes in plasmonic dimers, here the dark modes are the electric oscillations (as standing waves) within the silver sidewalls that are excited by charge accumulation via the bright plasmonic resonance of the top silver strips. In addition to the simple realization of perfect absorption, the dark modes are found to be quite sensitive to the environmental changes. The experimentally measured reflective index sensitivity is around 458 nm per RIU (refractive index unit), which is much higher than the sensitivity of the metal-covered grating without silver sidewalls. This research shall pave new routes to practical applications of dark surface plasmons.

Recently, color generation in resonant nanostructures have been intensively studied. Despite of their exciting progresses, the structural colors are usually generated by the plasmonic resonances of metallic nanoparticles. Due to the inherent plasmon damping, such plasmonic nanostructures are usually hard to create very distinct color impressions. Here we utilize the concept of metasurfaces to produce all-dielectric, low-loss, and high-resolution structural colors. We have fabricated TiO

All-dielectric, low-loss, and full-color structural color printing has been realized by TiO 2 -based all-dielectric metasurface. The highest recorded reflectance reached 64% and the full width at half maximum (FWHM) of reflection peak was around 30 nm.

Here we numerically and experimentally demonstrate the conversion of normally incident light into the guiding modes of distributed Bragg reflector (DBRs) mirror. By fabricating a gold grating onto a 7.5 pairs TiO2/SiO2 DBR mirror, a series of asymmetrical resonances have been formed at the bandgap range of the DBR mirror. The detailed numerical calculations show that these Fano resonances are attributed to the coupling of incident waves into guiding modes of the DBR mirror. Compared with the other resonances, this coupling mechanism can be simply realized and it has also been revealed to be quite robust to the environmental changes, making the conversion between propagating waves and guiding waves to be practically interesting for many applications.

Recently, perovskite lead halide semiconductors have attracted significant attention for their brilliant performances for optoelectronic applications. Here, we report a simple approach for the realization of highly uniform microlaser arrays on gold plasmonic grating. By placing a single crystalline CH 3 NH 3 PbBr 3 microribbon onto a gold grating, the lead halide perovskite microribbon has been divided into one-dimensional periodic segments. Each segment composes of one 770nm part on air gap and another 665nm part on gold. As the parts on of CH 3 NH 3 PbBr 3 microribbon on gold experience higher loss from the interband transition of bound electrons of gold, the corresponding laser thresholds are much higher than the ones above the air gaps. Consequently, only the suspended parts of the microribbon can generate laser emission and a microlaser array with density 697/mm has been achieved. Besides, the dimensions along the slits of the perovskite are almost the same resulting from the natural growth of crystals. And the spectra of the lasers from different subunits are found to be almost the same, indicating the nice uniformity of the microlaser array.

All-dielectric metamaterials offer a potential low-loss alternative to plasmonic metamaterials at optical frequencies. Here, we experimentally demonstrate a silicon based large-scale magnetic metamaterial, which is fabricated with standard photolithography and conventional reactive ion etching process. The periodically arrayed silicon sub-wavelength structures possess electric and magnetic responses with low loss in mid-infrared wavelength range. We investigate the electric and magnetic resonances dependencies on the structural parameters and demonstrate the possibility of obtaining strong dielectric-based magnetic resonance through a broad band range. The optical responses are quite uniform over a large area about 2 × 2 cm2. The scalability of this design and compatibility fabrication method with highly developed semiconductor devices process could lead to new avenues of manipulating light for low-loss, large-area and real integrated photonic applications.

EIT-like and Fano-like resonances can be obtained in a single hybrid plasmonic system under the excitation by different polarization light. The LSPs and the Bragg resonance from the plasmonic grating under different polarizations interference couple with the waveguide mode and contribute to the strong and weak couplings, respectively.

Lead halide perovskite based micro- and nano- lasers have been widely studied in past two years. Due to their long carrier diffusion length and high external quantum efficiency, lead halide perovskites have been considered to have bright future in optoelectronic devices, especially in the "green gap" wavelength region. However, the quality (Q) factors of perovskite lasers are unspectacular compared to conventional microdisk lasers. The record value of full width at half maximum (FWHM) at threshold is still around 0.22 nm. Herein we synthesized solution-processed, single-crystalline CH3NH3PbBr3 perovskite microrods and studied their lasing actions. In contrast to entirely pumping a microrod on substrate, we partially excited the microrods that were hanging in the air. Consequently, single-mode or few-mode laser emissions have been successfully obtained from the whispering-gallery like diamond modes, which are confined by total internal reflection within the transverse plane. Owning to the better light confinement and high crystal quality, the FWHM at threshold have been significantly improved. The smallest FWHM at threshold is around 0.1 nm, giving a Q factor over 5000., Comment: 7 pages, 4 figures

We have measured the Raman spectra of liquid CS2 at different volume concentrations in CHCl3 and CH2Cl2 solutions. With decreasing the volume concentration of CS2, a noticeable growth in the 2 ν 2 band frequency was observed, while the ν 1 band location remained practically unchanged. This asymmetric wavenumber shift phenomenon of the Fermi doublet ν 1 and 2 ν 2 of CS2 has been ascribed to weak, non-conventional hydrogen bonds formed between the CS2 and the solvent molecules. These weak hydrogen bonds were also responsible for significant decreases in the C–H bond symmetric stretching vibration band frequencies of CHCl3 and CH2Cl2. The values of the ν 1 - 2 ν 2 FR parameters of CS2 in CH2Cl2 and CHCl3 at different volume concentrations were calculated according to the FR theory. The magnitude of the FR coupling coefficient W of CS2 increases upon dilution with CH2Cl2 and CHCl3, indicating that the vibrational anharmonicity is relatively sensitive to variations in the weak hydrogen bonding. Compared with the changing tendencies of Fermi coupling coefficient W of CS2 in CH2Cl2 and CHCl3 at different volume concentrations, we discussed the effect of the weak hydrogen bond formation on the FR and the asymmetric wavenumber shift phenomenon of the Fermi doublet ν 1 and 2 ν 2 of CS2.

A new statistical theory is introduced that takes into account the coupling between grain size, shape and crystallographic texture during deformation of polycrystalline microstructures. A “grain size orientation distribution function” (GSODF) is used to encode the probability density of finding a grain size D along a direction (given by unit vector n ) in grains with orientation g . The GSODF is sampled from the input microstructure and is represented in a finite element mesh. During elastoplastic deformation, the evolution of grain size D (in direction θ ) and the orientation g is tracked by directly updating the GSODF probabilities using a Lagrangian probability update scheme. The effect of grain shape (e.g. in high aspect ratio grains) is modeled by including the apparent grain size as seen by various different active slip systems in the grain within the constitutive law for the slip system resistance. The prediction of texture and strains achieved by the statistical approach is compared to Taylor aggregate and finite element deformation analysis of a planar polycrystalline microstructure. The role of grain shape and size in determining plastic response is investigated and a new adaptive GSODF model for modeling microstructures with multimodal grain shapes is proposed.

This Letter analyzed the hydrogen bond between pyridine and propionic acid using Raman and infrared spectra as a function of concentrations. The wavenumber shift and line width change were investigated to analyze the effects of hydrogen bond on the ring breathing mode and the triangle mode of pyridine. Density functional theory (DFT) at the B3LYP/6-31++G (d,p) level was performed on the binary solution. The simulated vibrational Raman spectra obtained the experimentally observed spectral features about the blue-shifted of the ring breathing mode. Furthermore, the effect of the hydrogen bond on Fermi Resonance (FR) was discussed.

According to the nonlinear, multivariable and multi-constraint features of the reentry trajectory optimization problem of airbreathing hypersonic vehicles, a suboptimal solution method is developed. The reentry trajectory generation is converted to a nonlinear programming (NLP) problem by using Gauss pseudospectral method (GPM). The state and control variables on Gauss nodes are chosen as parameters to be optimized and the minimum total heat absorption is chosen as the optimal performance index. Then the sequential quadratic programming (SQP) method is used to solve the NLP problem. The states of optimized trajectory are compared with the states obtained by the integral of kinetic equations. By simulating on an example of airbreathing hypersonic vehicles, it is demonstrated that the above method is not sensitive to the estimate of motion states and is easier to converge. And the method is effective to solve trajectory optimization problems.

This study investigates the influence of leaf surface water films on the deposition of ozone (O3) and peroxyacetyl nitrate (PAN) under controlled laboratory conditions. A twin cuvette system was used to simulate environmental variables. We observed a clear correlation between the O3 deposition on plants (Quercus ilex) and the relative humidity (RH) under both, light and dark conditions. During the light period the observed increase of the O3 deposition was mainly attributed to the opening of leaf stomata, while during the absence of light the liquid surface films were the reason for O3 deposition. This finding was supported by experimentally induced stomatal closure by the infiltration of abscisic acid. In the case of PAN, no relationship with RH was found during the dark period, which indicates that the non-stomatal deposition of PAN is not affected by the liquid surface films. Consequently, the ratio of the O3 and PAN deposition velocities is not constant when relative humidity changes, which is in contrast to assumptions made in many models. The flux partitioning ratio between non-stomatal and stomatal deposition as well as between non-stomatal and total deposition was found to be Rnsto/sto = 0.21 – 0.40, Rnsto/tot = 0.18 – 0.30 for O3 and Rnsto/sto = 0.26 – 0.29, Rnsto/tot = 0.21 – 0.23 for PAN. Furthermore, we demonstrate that the formation of the liquid surface film on leaves and the non-stomatal O3 deposition are depending on the chemical composition of the particles deposited on the leaf cuticles as proposed previously.

Nanowire based hybrid plasmonic structure plays an important role in achieving nanodevices, especially for the wide band-gap materials. However, the conventional schemes of nanowire based devices such as nano-resonators are usually isolated from the integrated nano-network and have extremely low quality (Q) factors. Here we demonstrate the transmission of waves across a gap in hybrid plasmonic waveguide, which is termed as “photon hopping”. Based on the photon hopping, we show that the emissions from nanodevices can be efficiently collected and conducted by additional nanowires. The collection ratio can be higher than 50% for a wide range of separation distance, transverse shift and tilt. Moreover, we have also explored the possibility of improving performances of individual devices by nano-manipulating the nanowire to a pseudo-ring. Our calculations show that both Q factor and Purcell factor have been increased by more than an order of magnitude. We believe that our researches will be essential to forming nanolasers and the following nano-networks.

Light absorption plays a key role in photovoltaic devices, especially in thin-film organic solar cells. Here we study the enhancement of optical absorption in a thin organic layer by embedding it into magnetic metamaterials. In a periodic metal-polymeric-metal sandwiched structure, the absorption of transverse magnetic polarized light has been significantly enhanced. The maximum enhancement is around 7 times, which is attributed to the strong local field enhancement in the organic thin film. Importantly, due to the coexistence of large electric resonance and magnetic resonance in magnetic metamaterials, the enhancement of light absorption has been obtained in a broadband from 350 nm to 750 nm, which is almost twice of that of the conventional plasmonic device and covers the strongest part of the solar spectrum. Moreover, such absorption enhancement is also valid for a wide range of incident angles. We believe that our finding can lead to a variety of important applications in solar cell technology.

We measured the Raman spectra of canthaxanthin which contains 9 CC conjugated double bonds in nonpolar solvent carbon disulfide under different pressures. The results showed that the Raman scattering cross section (RSCS) for C C and C C stretching vibration bands of canthaxanthin first increase and then decrease with the increase of pressure. We assume that the main mechanism of the RSCS values increasing can be attributed to the effect of steric hindrance. And the liquid–solid phase transition of carbon disulfide is occurred under the 0.5312 GPa, which lead to the decrease of RSCS values.

Lead halide perovskite microlasers have been intensively studied in the past few years. While a number of unique laser properties have been demonstrated, the main laser characteristics are determined by the crystal quality and the shapes of synthesized materials. Patterning the semiconductors with plasmonic nanostructures is an effective way to control light emission and absorption. However, due to the instability of perovskites, most of nanofabrication technologies of plasmonic nanostructures will significantly spoil the qualities of perovskite devices. Here the surface plasmon enhanced laser emissions from all-inorganic lead halide perovskites are experimentally demonstrated. Without using any mask or expensive pattern generations, relatively uniform aluminum nanoparticles (NPs) are deposited onto the top surface of CsPbBr3 perovskites with electron beam evaporation. After the deposition of optimized aluminum NPs, the thresholds of whispering-gallery-mode lasers in CsPbBr3 perovskite microrods are significantly reduced by more than 20% and the output intensities of perovskite microlasers are significantly enhanced by more than an order of magnitude via the plasmonic resonances. Considering the simple, controllable, and cost-effective fabrication process, this research shall route a new avenue to the control of perovskite microlasers and their applications.

We demonstrate a single crystal perovskite based, with grating-structured photoresist on top, highly polarized distributed feedback laser. A lower laser threshold than the Fabry–Perot mode lasers from the same single crystal CH3NH3PbBr3 microplate was obtained. Single crystal CH3NH3PbBr3 microplates was synthesized with one-step solution processed precipitation method. Once the photoresist on top of the microplate was patterned with electron beam, the device was realized. This one-step fabrication process utilized the advantage of single crystal to the greatest extend. The ultra-low defect density in single crystalline microplate offer an opportunity for lower threshold lasing action compare with poly-crystal perovskite films. In the experiment, the lasing action based on the distributed feedback grating design was found with lower threshold and higher intensity than the Fabry-Perot mode lasers supported by the flat facets of the same microplate.

Integrated optical power splitters are one of the fundamental building blocks in photonic integrated circuits. Conventional multimode interferometer-based power splitters are widely used as they have reasonable footprints and are easy to fabricate. However, it is challenging to realize arbitrary split ratios, especially for multi-outputs. In this Letter, an ultra-compact power splitter with a QR code-like nanostructure is designed by a nonlinear fast search method. The highly functional structure is composed of a number of freely designed square pixels with the size of 120×120 nm which could be either dielectric or air. The light waves are scattered by a number of etched squares with optimized locations, and the scattered waves superimpose at the outputs with the desired power ratio. We demonstrate 1×2 splitters with 1:1, 1:2, and 1:3 split ratios, and a 1×3 splitter with the ratio of 1:2:1. The footprint for all the devices is only 3.6×3.6 μm. Well-controlled split ratios are measured for all the cases. The measured transmission efficiencies of all the splitters are close to 80% over 30 nm wavelength range.

We present a numerical simulation of second-harmonic generation (SHG) from a nonlinear magnetic metamaterial. By inserting a second-order nonlinear material in the high local field area of magnetic metamaterial, which consists of periodic arrays of paired thin silver strips, the convertion efficiency of SHG has been significantly enhanced by almost four orders of magnitude. The corresponding field patterns and further studies on dependance between SHG and symmetry of nonlinear crystal show that the increase of the conversion efficiency is attributed to the local field enhancement caused by the magnetic resonnance of the structure. Our researches provide an additional way to further improve the optical nonlinearity in nanostructures.

Chirality in microcavities has recently shown its bright future in optical sensing and microsized coherent light sources. The key parameters for such applications are the high quality (Q) factor and large chirality. However, the previous reported chiral resonances are either low Q modes or require very special cavity designs. Here we demonstrate a novel, robust and general mechanism to obtain the chirality in circular cavity. By placing a circular cavity and a spiral cavity in proximity, we show that ultra-high Q factor, large chirality and unidirectional output can be obtained simultaneously. The highest Q factors of the non-orthogonal mode pairs are almost the same as the ones in circular cavity. And the co-propagating directions of the non-orthogonal mode pairs can be reversed by tuning the mode coupling. This new mechanism for the combination of high Q factor and large chirality is found to be very robust to cavity size, refractive index and the shape deformation, showing very nice fabrication tolerance. And it can be further extended to microcavity chain and microcavity plane. We believe that our research will shed light on the practical applications of chirality and microcavities.

Here we demonstrate the impacts of emission mechanisms on the light confinements in open systems. Taking the oval-shaped cavities as examples, we show that the enhancements in quality (Q) factors are usually associated with the universal emissions. When the coupled resonances have similar far field patterns, the Q factor of the long-lived resonance has the possibility to be enhanced by the coherent destruction at the decay channels. Otherwise, the Q factors of long-lived resonances are usually reduced around the level crossings.

A visible absorption and Raman spectra of all-trans-beta-beta-carotene was measured in cyclohexanol solution in the temperature range from 68 degrees C to 26 degrees C. The results indicated that the visible absorption spectra are red-shifted, Raman scattering cross section increases, Huang-Ryes factor and electron-phonon coupling constants of CC bond vibration modes decreases with the temperature decreasing. The changes are interpreted using the theory of "coherent weakly damped electronic-lattice vibration model" and "effective conjugation length model". The red shift of the absorption spectra and intensity of the Raman active are attributed to the thermal conformational change-induced increase in the effective conjugation length in all-trans-beta-carotene chains. All-trans-beta-carotene has strong coherent weakly damped CC bonds vibrational properties, which lead to large Raman scattering cross section in the solvent of low temperature. The electron-phonon coupling constants with dimension are used, which can easily establish relation with the Huang-Rhys factor and calculate the electron-phonon coupling constants of CC bond vibration modes. Effective conjugation length, the pi-electron delocalization range and the Raman scattering cross section are described by the electron-phonon coupling constants.

In this study we report the set-up of a novel twin chamber technique that uses the comparative method and establishes an appropriate connection of atmospheric and laboratory methods to broaden the tools for investigations. It is designed to study the impact of certain parameters and gases on ambient processes, such as particle formation online, and can be applied in a large variety of conditions. The characterisation of both chambers proved that both chambers operate identically, with a residence time xT (COMPASS1) = 26.5 ± 0.3 min and xT (COMPASS2) = 26.6 ± 0.4 min, at a typical flow rate of 15 L min−1 and a gas leak rate of (1.6 ± 0.8) × 10−5 s−1. Particle loss rates were found to be larger (due to the particles' stickiness to the chamber walls), with an extrapolated maximum of 1.8 × 10−3 s−1 at 1 nm, i.e. a hundredfold of the gas leak rate. This latter value is associated with sticky non-volatile gaseous compounds, too. Comparison measurement showed no significant differences. Therefore operation under atmospheric conditions is trustworthy. To indicate the applicability and the benefit of the system, a set of experiments was conducted under different conditions, i.e. urban and remote, enhanced ozone and terpenes as well as reduced sunlight. In order to do so, an ozone lamp was applied to enhance ozone in one of two chambers; the measurement chamber was protected from radiation by a first-aid cover and volatile organic compounds (VOCs) were added using a small additional flow and a temperature-controlled oven. During the elevated ozone period, ambient particle number and volume increased substantially at urban and remote conditions, but by a different intensity. Protection of solar radiation displayed a clear negative effect on particle number, while terpene addition did cause a distinct daily pattern. E.g. adding β pinene particle number concentration rose by 13% maximum at noontime, while no significant effect was observable during darkness. Therefore, the system is a useful tool for investigating local precursors and the details of ambient particle formation at surface locations as well as potential future feedback processes.

Crack propagation in polycrystalline grains is analyzed using a novel multiscale polycrystalline model. The approach combines reduced order descriptors of microstructures with explicit representation of polycrystals at critical areas (eg. crack tips). For the critical areas, refined meshes are employed to discretize each crystal. The crack propagation in the microstructure is calculated using the variational multiscale method which allows for arbitrary transgranular and intergranular crack paths. The computational load is reduced substantially by combining probabilistic representation of the macroscale problem with exact resolution of the crystals at the crack tips. One example of grain boundary failure is demonstrated in this paper, showing exceptional mesh convergence and efficiency of the numerical approach.

We have measured the Raman spectra of liquid CS(2) at different volume concentrations in CHCl(3) and CH(2)Cl(2) solutions. With decreasing the volume concentration of CS(2), a noticeable growth in the 2ν(2) band frequency was observed, while the ν(1) band location remained practically unchanged. This asymmetric wavenumber shift phenomenon of the Fermi doublet ν(1) and 2ν(2) of CS(2) has been ascribed to weak, non-conventional hydrogen bonds formed between the CS(2) and the solvent molecules. These weak hydrogen bonds were also responsible for significant decreases in the C-H bond symmetric stretching vibration band frequencies of CHCl(3) and CH(2)Cl(2). The values of the ν(1)-2ν(2) FR parameters of CS(2) in CH(2)Cl(2) and CHCl(3) at different volume concentrations were calculated according to the FR theory. The magnitude of the FR coupling coefficient W of CS(2) increases upon dilution with CH(2)Cl(2) and CHCl(3), indicating that the vibrational anharmonicity is relatively sensitive to variations in the weak hydrogen bonding. Compared with the changing tendencies of Fermi coupling coefficient W of CS(2) in CH(2)Cl(2) and CHCl(3) at different volume concentrations, we discussed the effect of the weak hydrogen bond formation on the FR and the asymmetric wavenumber shift phenomenon of the Fermi doublet ν(1) and 2ν(2) of CS(2).

In this article, we report a broadband, isotropic three-dimensional metamaterial design with extremely high refractive index in the terahertz region. Two peaks of refractive index, 67.9 at 2.14 THz and 66.9 at 2.16 THz, are observed under TE and TM mode polarizations, respectively. The high refractive index metamaterial maintains low loss with figure of merit as high as 15 under both polarizations. Moreover, the refractive index does not decrease sharply at higher frequencies, and shows a very broadband behavior with a full-width at half-maximum (FWHM) of 2 THz.

This paper presents the first application of peridynamics theory for crystal plasticity simulations. A state-based theory of peridynamics is used (Silling et al., 2007) where the forces in the bonds between particles are computed from stress tensors obtained from crystal plasticity. The stress tensor at a particle, in turn, is computed from strains calculated by tracking the motion of surrounding particles. We have developed a quasi-static implementation of the peridynamics theory. The code employs an implicit iterative solution procedure similar to a non-linear finite element implementation. Peridynamics results are compared with crystal plasticity finite element (CPFE) analysis for the problem of plane strain compression of a planar polycrystal. The stress, strain field distribution and the texture formation predicted by CPFE and peridynamics were found to compare well. One particular feature of peridynamics is its ability to model fine shear bands that occur naturally in deforming polycrystalline aggregates. Peridynamics simulations are used to study the origin and evolution of these shear bands as a function of strain and slip geometry.