Interest For Many Applications Research Articles

Light- and Metal Ion-Induced Self-Assembly and Reassembly Based on Block Copolymers Containing a Photoresponsive Polypeptide Segment

Because of the advantageous properties, the photoresponsive bioinspired polymers are of great interest for many applications. In this study, we synthesized a new family of photoresponsive poly(ethy...

Testing for Positive Quadrant Dependence

We develop an empirical likelihood (EL) approach to test independence of two univariate random variables X and Y versus the alternative that X and Y are strictly positive quadrant dependent (PQD). Establishing this type of ordering between X and Y is of interest in many applications, including finance, insurance, engineering, and other areas. Adopting the framework in Einmahl and McKeague, we create a distribution-free test statistic that integrates a localized EL ratio test statistic with respect to the empirical joint distribution of X and Y. When compared to well-known existing tests and distance-based tests we develop by using copula functions, simulation results show the EL testing procedure performs well in a variety of scenarios when X and Y are strictly PQD. We use three datasets for illustration and provide an online R resource practitioners can use to implement the methods in this article. Supplementary materials for this article are available online.

Raman spectroscopy of epitaxial InGaN/Si in the central composition range

InGaN alloys are of raising interest for many applications. The possibility of tuning their functional properties with the composition sets the importance of finding methods to characterize these materials in a fast and non-destructive way. Raman spectroscopy is one of these techniques, being able to yield information about the composition, strain, and other relevant parameters. However, the method of measuring the composition with a calibration of the maximum A1(LO) band is today limited to regions which are either rich in In or in Ga. The middle composition range still needs a calibration. By measuring the Raman spectra of different InxGa1-xN alloys grown epitaxially on Si and by comparing them with the results from X-ray diffraction, we investigated this missing region of compositions. Within the range of 30%–65%, we have found that the position of the maximum of A1(LO) scales with the In fraction x as ωx = 736 – 135x – 24x2 cm−1. With this calibration, it is possible to determine, by Raman spectroscopy, the composition of an unknown alloy with an uncertainty of 5%.

DETECTION OF BUILDING ROOFS AND FACADES FROM AERIAL LASER SCANNING DATA USING DEEP LEARNING

Abstract. In this work we test the power of prediction of deep learning for detection of buildings from aerial laser scanner point cloud information. Automatic extraction of built features from remote sensing data is of extreme interest for many applications. In particular latest paradigms of 3D mapping of buildings, such as CityGML and BIM, can benefit from an initial determination of building geometries. In this work we used a LiDAR dataset of urban environment from the ISPRS benchmark on urban object detection. The dataset is labelled with eight classes, two were used for this investigation: roof and facades. The objective is to test how TensorFlow neural network for deep learning can predict these two classes. Results show that for “roof” and “facades” semantic classes respectively, recall is 84% and 76% and precision is 72% and 63%. The number and distribution of correct points well represent the geometry, thus allowing to use them as support for CityGML and BIM modelling. Further tuning of the hidden layers of the DL model will likely improve results and will be tested in future investigations.

N-Hexanol Enhances the Cetyltrimethylammonium Bromide Stabilization of Small Gold Nanoparticles and Promotes the Growth of Gold Nanorods

Gold nanorods (AuNRs) are of interest for many applications, since their absorption in the regime of visible light can easily be tuned by their exact shape. To produce these AuNRs, a two-step synthesis that starts from small seed particles is used. These seed particles are stabilized by cetyltrimethylammonium bromide (CTAB), which forms micelles at the used concentration (0.1 mol/L). In this work, the influence of the micelle morphology on the stabilization of these seed particles and the consequences on the formation of AuNRs is reported. The elongation of CTAB micelles by the addition of n-hexanol leads to much more stable seed particle dispersions and thus less polydisperse AuNRs. In contrast, a higher number of micelles compared to pure CTAB dispersions result from the addition of n-pentanol. This promotes the formation of larger seed particles and leads to lower yields of AuNRs. The gold nanoparticles are characterized by UV–vis–NIR absorption spectroscopy, transmission electron microscopy, and small...

A straightforward procedure for the synthesis of silica@polyaniline core-shell nanoparticles

The synthesis of core-shell silica@polyaniline nanoparticles is of interest for many applications including electrorheology and inkjet printing. Formation of such structures by simple adsorption of aniline onto silica surfaces followed by polymerization is rather difficult. Chemical grafting of alkoxysilane monomers on silica surfaces followed by polymerization has been used to prepare silica@polyaniline microspheres but has never been applied to silica nanoparticles. Here, we report an efficient method to prepare silica@polyaniline nanoparticles of different sizes. This study goes far beyond the simple synthetic procedure. It also evidences a general law that can be applied by all to anticipate the efficient encapsulation of silica nanoparticles by polyaniline. Here, silica nanoparticles of different sizes (90–300 nm) were firstly synthesized by Stöber process and then functionalized with N-[3-(Trimethoxysilyl)propyl]aniline. The last step implied the room temperature polymerization of aniline in the presence of these functionalized-silica nanoparticles using ammonium persulfate as oxidant. Several sets of particles were prepared using different amounts of aniline monomers resulting in different polyaniline thicknesses. SEM, TEM, IR, TGA and XPS were then used to characterize thoroughly these core-shell particles.The highlight of this paper is that efficient encapsulation of silica particles by polyaniline occurred if, and only if, the ratio between the polyaniline thickness and the particle diameter was close to 10%. Higher ratio led to the presence of isolated polyaniline granules while lower ratio resulted in uncompleted encapsulation.

Time–Temperature and Time–Water Superposition Principles Applied to Poly(allylamine)/Poly(acrylic acid) Complexes

The dynamic mechanical and rheological behavior of polyelectrolyte coacervates and complex precipitates is of interest for many applications ranging from health to personal care. Hydration is an im...

A Class of Alternating Linearization Algorithms for Nonsmooth Convex Optimization

We consider the problems of minimizing the sum of a continuously differentiable convex function and a nonsmooth convex function in this paper. These problems arise in many applications of practical interest. A class of alternating linearization methods is presented for solving these problems. The global convergence rate is also obtained under certain mild conditions. Numerical experiments validate the theoretical convergence analysis and verify the implementation of the proposed algorithm.

Consistent estimation of residual variance with random forest Out-Of-Bag errors

The issue of estimating residual variance in regression models with unknown and eventually complex link-function is still an open problem. Predictions of such outcomes are usually conducted by black-box procedures without seriously restricting the link-function class. However, quantifying uncertainty by means of residual variance estimators is of primary interest in many practical applications, e.g. as a primary step towards the construction of prediction intervals. Here, we consider this issue for the random forest. Therein, the functional relationship between covariates and response variable is modeled by a weighted sum of the latter. The dependence structure is, however, involved in the weights that are constructed during the tree construction process making the model complex in mathematical analysis. Restricting to L2-consistent random forest models, we provide random forest based residual variance estimators and prove their consistency.

Macro/Microporous Covalent Organic Frameworks for Efficient Electrocatalysis.

Covalent organic frameworks (COFs) are of interest for many applications originating from their mechanically robust architectures, low density, and high accessible surface area. Depending on their linkers and binding patterns, COFs mainly exhibit microporosity, even though COFs with small mesopores have been reported using extended linkers. For some applications, especially when fast mass transport is desired, hierarchical pore structures are an ideal solution, e.g., with small micropores providing large surface areas and larger macropores providing unhindered transport to and from the materials surface. Herein, we have developed a facile strategy for the fabrication of crystalline COFs with inherent microporosity and template-induced, homogeneously distributed, yet tunable, macroporous structures. This method has been successfully applied to obtain various β-ketoenamine-based COFs with interconnected macro-microporous structures. The as-synthesized macroporous COFs preserve high crystallinity with high specific surface area. When bipyridine moieties are introduced into the COF backbone, metals such as Co2+ can be coordinated within the hierarchical pore structure (macro-TpBpy-Co). The resulting macro-TpBpy-Co exhibits a high oxygen evolution reaction (OER) activity, which is much improved compared to the purely microporous COF with a competitive overpotential of 380 mV at 10 mA/cm2. This can be attributed to the improved mass diffusion properties in the hierarchically porous COF structures, together with the easily accessible active Co2+-bipyridine sites.

Chitosan/Thyme Oil Systems as Affected by Stabilizing Agent: Physical and Antimicrobial Properties

Antimicrobial biopolymer films and coatings are of great interest for many applications. Different chitosan systems were prepared and characterized to evaluate the effect of their composition on the physical and antimicrobial properties. Three types of emulsifiers (Tween 20, 80, and 85) were used as stabilizing agents, combined with thyme essential oil (from two producers) applied as an active substance. A predominant role of the applied stabilizer and its hydrophilic–lipophilic balance value was proven. The incorporation of thyme essential oil and surfactant into the chitosan matrix led to a significant decrease of particle size in film-forming solutions, as well as a thickness increase and the enhancement of the barrier properties in chitosan films. Antimicrobial effects were provided even at the lowest tested concentration of thyme essential oil. Hence, the prepared chitosan films represent promising candidates in antimicrobial packaging applications.

Effects of Building Orientation on Fatigue Behavior of Ti-6Al-4V Alloy Produced by Selective Laser Melting

Addictive manufacturing (AM) allows for the layer-by-layer fabrication of components via sequential material deposition and it is of immediate interest in many applications, in particularly aviation field. This work is tackling the issue that the influence of the inner-defects and building orientations on the fatigue behavior of Ti-6Al-4V Alloys produced by Selective Laser Melting (SLM). Specimens were built in two orientations (horizontal and vertical to the substrate) in order to evaluate the impact of the induced anisotropy of fatigue properties. A series of fatigue tests at five stress ratios ranged from-1 to 0.8 are conducted at 400°C. Scanning Electron Microscopy (SEM) is used to examine the fracture surfaces of fatigue specimens to qualify the failure mechanism and crack initiation sites, which are most likely attached to the surface defects. The fracture surface analysis of HCF specimen tested at two temperatures reveals that near 85% of the crack initiates from the defect under subsurface. The results of this study imply that the fatigue properties at 400°C are highly dependent on the specimen orientations relative to build directions, as the defects close to surface are the mainly cause of the crack initiations.

Influence of silica architecture on the catalytic activity of immobilized glucose oxidase

Immobilizing enzymes on solid support materials is of great interest for many applications as it improves enzyme lifetime and enables its recycling. Synthetic mesoporous silica materials are widely used as supports for enzyme immobilization due to their high enzyme-loading capacity and their excellent mass transport properties through interconnected channels of mesopores. Much less is known about the enzyme support properties of naturally occurring mesoporous silica materials. These are readily available through the growth of diatoms, which biosynthesize hierarchically porous silica microshells with pore diameters ranging from 10 to 1000 nm. Here the authors investigated the performance as enzyme support materials of biosilica from three diatom species in comparison to synthetic silica materials. Using glucose oxidase (GOx) as a model enzyme, the authors determined the enzyme-loading capacities and the specific catalytic activities of the GOx-bearing (bio)silicas both under suspension conditions and in a flow-through setting. Remarkably, the specific activity of GOx was strongly dependent on the type of diatom biosilica material and in the best case was as high as on synthetic mesoporous silica. Porosity analysis of the materials points to an important role of large mesopores (diameters >20 nm) for supporting a high specific activity of (bio)silica-immobilized GOx.

Can we safely predict solvation Gibbs energies of pure and mixed solutes with a cubic equation of state?

Abstract Solvation Gibbs energies are basically defined as a chemical potential change when transferring a fixed molecule from a perfect gas to a real liquid mixture. This quantity is of special interest for many practical applications as it quantifies the degree of affinity of a solute for its solvent. Few methods are currently available in the literature for the prediction of solvation Gibbs energies. In this article, a new approach is proposed: the use of a predictive cubic equation of state (EoS). The UMR-PRU (Universal Mixing Rule Peng-Robinson UNIFAC) EoS has been selected for its known capacity to semi-predict behaviors of complex systems including polar and associating compounds (by semi-prediction, it is meant that the EoS predicts binary interaction parameters but requires pure-component properties as input parameters). UMR-PRU predictions have been compared to experimental data extracted from the extensive CompSol database (containing around 22 000 pure component data and 70 000 binary data). Accurate predictions were obtained (a mean absolute deviation of 0.36 kcal/mol was obtained for all the binary data). Finally, when using a fully-predictive approach (i.e. pure-component EoS parameters are predicted from group-contribution methods), the prediction accuracy is roughly preserved.

Ultra-Broadband Second-Harmonic Generation in ZnO Nano-Tetrapod With Over-One-Octave Bandwidth

Broadband nonlinear optical frequency conversion has attracted considerable interest in many applications, such as optical communication, frequency comb generation, and so on. In this letter, we report on the ultra-broadband second-harmonic generation (SHG) from the zinc oxide nano-tetrapod with less stringent phase-matching requirement. Using a super-continuum source together with an optical parametric oscillator as the excitation light, a broadband SHG with over-one-octave bandwidth spanning from the ultraviolet to near-infrared (375–1100 nm) is readily obtained. The SHG dependence of pump polarization and pump power is also characterized systematically. This nanoscale ultra-broadband optical converter may open a new way for various applications ranging from imaging to on-chip all-optical signal processing operations.

CVD Growth of Monolayer MoS2 on Sapphire Substrates by using MoO3 Thin Films as a Precursor for Co-Evaporation

ABSTRACTScalable synthesis of two-dimensional molybdenum disulfide (MoS2) via chemical vapor deposition (CVD) is of considerable interests for many applications in electronics and optoelectronics. Here, we investigate the CVD growth of MoS2 single crystals on sapphire substrates by using thermally evaporated molybdenum trioxide (MoO3) thin films as molybdenum (Mo) source instead of conventionally used MoO3 powder for co-evaporation synthesis. The MoO3 thin film source provides uniform Mo vapor pressure in the growth chamber resulting in clean and reproducible MoS2 triangles without any oxide or oxysulfide species. Scanning electron microscopy, Raman spectroscopy, photoluminescence spectroscopy and atomic force microscopy characterization were performed to characterize the growth results. Very high photoluminescence (PL) response was observed at 1.85 eV which is a good implication of high optical quality of these crystals directly grown on sapphire substrate.

Predicting Detection Performance on Security X-Ray Images as a Function of Image Quality.

Developing methods to predict how image quality affects the task performance is a topic of great interest in many applications. While such studies have been performed in the medical imaging community, little work has been reported in the security X-ray imaging literature. In this paper, we develop models that predict the effect of image quality on the detection of the improvised explosive device components by bomb technicians in images taken using portable X-ray systems. Using a newly developed NIST-LIVE X-Ray Task Performance Database, we created a set of objective algorithms that predict bomb technician detection performance based on the measures of image quality. Our basic measures are traditional image quality indicators (IQIs) and perceptually relevant natural scene statistics (NSS)-based measures that have been extensively used in visible light image quality prediction algorithms. We show that these measures are able to quantify the perceptual severity of degradations and can predict the performance of expert bomb technicians in identifying threats. Combining NSS- and IQI-based measures yields even better task performance prediction than either of these methods independently. We also developed a new suite of statistical task prediction models that we refer to as quality inspectors of X-ray images (QUIX); we believe this is the first NSS-based model for security X-ray images. We also show that QUIX can be used to reliably predict conventional IQI metric values on the distorted X-ray images.

Phonon Transmission Across Silicon Grain Boundaries by Atomistic Green's Function Method

Nanostructured materials are of great interest for many applications because of their special properties. Understanding the effect of grain boundaries on phonon transport in polycrystals is important for engineering nanomaterials with desired thermal transport properties. The phonon transport properties of Σ3 grain boundaries in silicon are investigated by employing atomistic Green’s function method. Results show that similar to electron transport, the perfect grain boundary does not significantly reduce the thermal conductance, while defective grain boundaries can dramatically reduce the thermal conductance. This work may be helpful for the understanding of the underlying thermal transport mechanism with grain boundaries and the design of grain boundaries for energy applications.

Copper- and Cobalt-Codoped CeO2 Nanospheres with Abundant Oxygen Vacancies as Highly Efficient Electrocatalysts for Dual-Mode Electrochemical Sensing of MicroRNA.

Oxide materials with redox properties have aroused growing interest in many applications. Introducing dopants into crystal lattices provides an effective way to optimize the catalytic activities of the oxides as well as their redox properties. Herein, CeO2 nanospheres codoped with Cu and Co (CuCo-CeO2 NSs) were first synthesized and exploited as efficient electrocatalysts for dual-mode electrochemical sensing of microRNA (miRNA). With the doping of Cu and Co into the CeO2 lattice, large amounts of extra oxygen vacancies were generated, remarkably enhancing the redox and electrocatalytic properties of the CeO2 material. The abundant oxygen vacancies of the CuCo-CeO2 NSs were further identified by X-ray photoelectron spectroscopy (XPS), H2 temperature-programmed reduction (H2-TPR), and electron-energy-loss spectroscopy (EELS). Moreover, Mg2+-induced DNAzyme-assisted target recycling was introduced for ultrasensitive determination. The dual-mode sensing with generality was conducted as follows: First, the CuCo-CeO2 NSs acted as a direct redox mediator to generate a differential-pulse-voltammetry (DPV) signal, which was then greatly amplified by the efficient electrocatalysis of CuCo-CeO2 NSs toward H2O2 decomposition. Second, under the electrocatalysis of CuCo-CeO2 NSs, 3,3-diaminobenzidine (DAB) was oxidized to form nonconductive insoluble precipitates (IPs), leading to great amplification of the electrochemical-impedimetric-spectroscopy (EIS) signal. The dual-mode electrochemical sensor showed a wide linear range (0.1 fM to 10 nM) with a low detection limit (33 aM), paving a new way for constructing ultrasensitive electrochemical sensors.

Time scale based analysis of in-situ crystal formation in droplet undergoing rapid dehydration

The surface structure of crystalline particles affects the functionality of the particles in drug delivery. Prediction of the final structure of particles that crystallize easily within the spray drying process is of interests for many applications. A theoretical framework was developed for the prediction of crystal structure precipitating on the surface of the particle. This model was based on the dimensionless Damkohler number (Da), to be an indicator of final particle morphology. Timescales of evaporation and reaction were required for calculation of the Damkohler number. The modified evaporation time scale was estimated based on the time that is available for the crystal to precipitate after supersaturation. The reaction time scale was estimated based on the time scale for induction time. Mannitol was produced under different processing conditions in order to validate the theoretical model. Results showed for the high Damkohler numbers, the surface structure of the particle was rough, while smaller Damkohler numbers led to relatively smooth particle surfaces. Additionally, although the beta polymorph was dominant in all of the experiments, alpha polymorph was precipitated in the experiments with a large Damkohler number. The theoretical framework developed will be a useful predictive tool to guide the manipulation of particle crystallization in spray dryers.