Non-spherical Structures Research Articles

Chemical composition, structural properties, and source apportionment of organic macromolecules in atmospheric PM10 in a coastal city of Southeast China.

Particulate matter (PM10) associated with the fractions of organic macromolecules, including humic acid (HA), kerogen + black carbon (KB), and black carbon (BC), was determined during summer and winter at urban and suburban sites in a coastal city of southeast China. The organic macromolecules were characterized by elemental analysis (EA), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR), and their sources were identified by using stable carbon/nitrogen isotope (δ13C/δ15N) and the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) Model. The results showed that HA, kerogen (K), and BC accounted for the range of 3.89 to 4.55% in PM10, while they were the dominant fractions of total organic carbon (TOC), ranging from 64.70 to 84.99%. SEM analysis indicated that BC particles were porous/nonporous and consisted of spherical and non-spherical (i.e., cylindrical and elongate) structures. The FTIR spectra of HA, KB, and BC exhibited similar functional groups, but the difference of various sites and seasons was observed. HA in PM10 contained a higher fraction of aliphatic structures, such as long-chain fatty and carbohydrates with a carboxylic extremity. The C/N ratio, SEM, and δ13C/δ15N values provided reliable indicators of the sources of HA, K, and BC in PM10. The results suggested that HA and K majorly originated from terrestrial plants, and BC came from the mixture of combustion of terrestrial plants, fossil fuel, and charcoal. The air masses in winter originated from Mongolia (4%), the northern area of China (48%), and northern adjacent cities (48%), suggesting the influence of anthropogenic sources through long-range transport, while the air masses for the summer period came from South China Sea (34%) and Western Pacific Sea (66%), representing clean marine air masses with low concentrations of organic macromolecules.

Power of Modified Brown-Forsythe and Mixed-Model Approaches in Split-Plot Designs

Abstract. Low precision of the inferences of data analyzed with univariate or multivariate models of the Analysis of Variance (ANOVA) in repeated-measures design is associated to the absence of normality distribution of data, nonspherical covariance structures and free variation of the variance and covariance, the lack of knowledge of the error structure underlying the data, and the wrong choice of covariance structure from different selectors. In this study, levels of statistical power presented the Modified Brown Forsythe (MBF) and two procedures with the Mixed-Model Approaches (the Akaike’s Criterion, the Correctly Identified Model [CIM]) are compared. The data were analyzed using Monte Carlo simulation method with the statistical package SAS 9.2, a split-plot design, and considering six manipulated variables. The results show that the procedures exhibit high statistical power levels for within and interactional effects, and moderate and low levels for the between-groups effects under the different conditions analyzed. For the latter, only the Modified Brown Forsythe shows high level of power mainly for groups with 30 cases and Unstructured (UN) and Autoregressive Heterogeneity (ARH) matrices. For this reason, we recommend using this procedure since it exhibits higher levels of power for all effects and does not require a matrix type that underlies the structure of the data. Future research needs to be done in order to compare the power with corrected selectors using single-level and multilevel designs for fixed and random effects.

Nanopesticides: Synthesis and Application of Nanosphare Structures

Nanostructures are of great interest in many current emerging of technology. This review is devoted to the progress made in the last decade in synthesis and applications of nanostructures. We present an overview of synthetic strategies for hollow structures. These strategies are broadly categorized into four themes, which include sell-established approaches, such as conventional hard-templating and soft-templating methods, as well as newly emerging methods based on sacrificial templating and template-free synthesis. The Review therefore focuses on the fundamentals of each process, pointing out advantages and disadvantages where appropriate. Strategies for generating more complex hollow structures, such as nonspherical hollow structures, are also discussed and reviewed.

Theory and Experiment of Binary Diffusion Coefficient of n-Alkanes in Dilute Gases.

Binary diffusion coefficients were measured for n-pentane, n-hexane, and n-octane in helium and of n-pentane in nitrogen over the temperature range of 300 to 600 K, using reversed-flow gas chromatography. A generalized, analytical theory is proposed for the binary diffusion coefficients of long-chain molecules in simple diluent gases, taking advantage of a recently developed gas-kinetic theory of the transport properties of nanoslender bodies in dilute free-molecular flows. The theory addresses the long-standing question about the applicability of the Chapman-Enskog theory in describing the transport properties of nonspherical molecular structures, or equivalently, the use of isotropic potentials of interaction for a roughly cylindrical molecular structure such as large normal alkanes. An approximate potential energy function is proposed for the intermolecular interaction of long-chain n-alkane with typical bath gases. Using this potential and the analytical theory for nanoslender bodies, we show that the diffusion coefficients of n-alkanes in typical bath gases can be treated by the resulting analytical model accurately, especially for compounds larger than n-butane.

Morphological evolution of complex coacervate core micelles revealed by iPAINT microscopy

Structural characterization of polymeric micelles is important to understand the relation between micellar structure and properties for application in e.g. drug delivery, catalysis, and sensing. In this work we demonstrate the potential of iPAINT super-resolution microscopy for the imaging of complex coacervate core micelles (C3Ms). C3Ms are formed out of the flexible cationic diblock copolymer poly(N-methyl-2-vinyl pyridinium chloride)-b-poly(ethylene oxide) (P2MVP29-b-PEO204) and a stiff anionic polyfluorene derivative (PF22). We use iPAINT to ‘stain’ the C3Ms in a simple, non-covalent fashion to image the morphology of individual micelles. Spherical architectures are detected at low concentrations (< 0.07 mM), while more elongated, non-spherical structures with axial ratios υ ≤ 2.3 are adopted at higher concentrations (> 0.14 mM). The observed ellipsoid-like morphology is unusual and furthermore unexpected for C3Ms of copolymers with a considerably longer corona-forming hydrophilic block than the core-forming ionic block. We attribute the observed morphological transition from spherical to ellipsoidal micelles as concentration rises to the stiffness of the conjugated polyfluorene.

Hexagonal Hollow Mesoporous TiO2 Nanoparticles As an Advanced Anode Material for Lithium-Ion Batteries

Recently, TiO2 received tremendous attention due to its low cost, chemical stability, excellent rate performance, proper Li-intercalated potential and environmental friendliness1-3. However, the poor electronic conductivity and relatively low specific capacity lead to the major obstacles for large-scale application in the LIBs. To overcome these deficiencies, a series of efforts have been made to enhance the performance of TiO2 anode. It has been demonstrated that the morphology and nanostructure show significant impacts on the performance of electrochemical performance. However, most of the reported hollow structures have a spherical shape so far, non-spherical hollow structure might exhibit unusual propertioes when used as the anode materials.Hence, we explore the synthesis of the non-spherical hollow structures with favourable shell architectures, and used as the anode materials of LIBs. Here, we introduced an easy scale-up strategy for the fabrication of well-organized hexagonal hollow mesoporous TiO2(HHM-TiO2)materials by a facile, cost-effective template-engaged method at room temperature. We further introduce a conformal carbon coating layer on the hexagonal hollow mesoporous TiO2, and investigate the electrochemical performance. The hollow TiO2 is designed on the basis of the interplay and synergy of controlled hydtolysisi of Ti4+ and accompaning gradual etching of Cd(OH)2. During the process, interfacial reaction between (NH4)2TiF6 and Cd(OH)2 occurred simultaneously,TiO2 layer is deposited on the scaffold of Cd(OH)2 template through accelerated hydrolysis of [TiF6]2 - by consumption of H+.To evaluate the promising use of the TiO2 as an anode material for LIBs, a conformal carbon coating layer was introduced to coat on the porous TiO2 particles by hydrothermal method using glucose as the carbon source.Fig. 1 The morphology characterizations of HHM-TiO2 and HHM-TiO2/C. (a) SEM, (b) TEM and (c) HRTEM of HHM-TiO2, (d) TEM and (e)HRTEM of HHM-TiO2/C, (f) the SEAD pattern of HHM-TiO2 The morphology of the as-prepared HHM-TiO2 and HHM-TiO2/C were characterized by scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HR-TEM.). Fig. 1a indicated that the HHM-TiO2 is consisted of hexagonal particles with the particle-size range from 250 to 350 nm. Meanwhile, the hollow interior can be directly observed from the broken nanoparticle (inset in Fig. 1a) and TEM images (Fig. 1b), while the thickness of TiO2 shell is about 30 nm. A close examination (HRTEM images in Fig. 1c) of the sample reveals a highly porous shell that is consisted of small TiO2 nanoparticles with a size of several nanometers.After introducing the carbon coating layer, the feature of HHM-TiO2/C was analyzed in Fig. 1d-f. The TEM images of HHM-TiO2/C matching well with the pure HHM-TiO2 confirmed that the carbon coating process does not alter the structure of the HHM-TiO2. The selective area electron diffraction (SAED) pattern (Fig. 1f) showed bright diffraction rings indexed to (101), (004), (200), (211), and (204) planes of anatase TiO2, indicating its polycrystalline natureIn summary, a new structure and well-organizedhexagonal hollow mesoporous TiO2 was fabricated by a simple cost-effective method. After wrapping with an elastic carbon matrix, The HHM-TiO2/C electrode showed better rate, with a good rate capability of 175 mA h g-1 at 5 C, 152 mA h g-1 at 10 C and 126 mAh g-1 at 20 C. The higher capacity retention at higher current rates demonstrates a superior rate capability for the HHM-TiO2/C composite. Acknowledgements This work was supported by the Natural Science Foundation of China (21336003, 21333007).

Multistep synthesis of non-spherical SnO2@SnO2 yolk-shell cuboctahedra with nanoparticle-assembled porous structure for toluene detection

A new type of nonspherical yolk-shell structures in the case of SnO2 has been successfully prepared by a simple anneal-etching strategy without employing any additional templates or capping agents. The morphological and structural characterization reveals that SnO2 yolk-shell particles have a hierarchical architecture with penetrable multi-walled surfaces and cuboctahedral shape, where the secondary building blocks are numerous nanoparticles. The synthetic step-dependent evolution process of SnO2 yolk-shell cuboctahedra is investigated and the possible formation mechanism is also discussed. To demonstrate the merit of unique structure for the fast mass transfer, sensor based on SnO2 products has been fabricated and the results exhibit excellent sensing performances for toluene detection. It is found that our SnO2 yolk-shell structures have a response of 28.6–20ppm toluene at the optimal working temperature of 250°C, and the response time and recovery time are within 1.8 and 4.1s, respectively.

Secondary growth synthesis of ZnSn(OH)6cube/Zn2SnO4nanowire yolk–shell hierarchical structures with enhanced lithium ion storage properties

Hierarchical ZnSn(OH)6/Zn2SnO4 yolk–shell nonspherical structures that are composed of self-supported nanowire arrays have been conveniently prepared via a simple secondary growth method. The XRD and TEM results indicate that the composition of the outer nanowire shell is the Zn2SnO4 (ZTO) phase, while the inner cubic core is the incomplete conversion ZnSn(OH)6 phase. Due to the synergistic effect of the low dimensional shell and stable yolk–shell structure, the as-obtained hierarchical ZnSn(OH)6/ZTO yolk–shell structures exhibit high stability and capacity for lithium ion batteries (LIBs).

Multiple nonspherical structures from the extrema of Szekeres scalars

We examine the spatial extrema (local maxima, minima and saddle points) of the covariant scalars (density, Hubble expansion, spatial curvature and eigenvalues of the shear and electric Weyl tensors) of the quasi-spherical Szekeres dust models. Sufficient conditions are obtained for the existence of distributions of multiple extrema in spatial comoving locations that can be prescribed through initial conditions. These distributions evolve without shell crossing singularities at least for ever expanding models (with or without cosmological constant) in the full evolution range where the models are valid. By considering the local maxima and minima of the density, our results allow for setting up elaborated networks of "pancake" shaped evolving cold dark matter over-densities and density voids whose spatial distribution and amplitudes can be controlled from initial data compatible with standard early Universe initial conditions. We believe that these results have an enormous range of potential application by providing a fully relativistic non-perturbative coarse grained modelling of cosmic structure at all scales.

Controlling the angular radiation of single emitters using dielectric patch nanoantennas

Dielectric nanoantennas have generated much interest in recent years owing to their low loss and optically induced electric and magnetic resonances. In this paper, we investigate the coupling between a single emitter and dielectric patch nanoantennas. For the coupled system involving non-spherical structures, analytical Mie theory is no longer applicable. A semi-analytical model is proposed instead to interpret the coupling mechanism and the radiation characteristics of the system. Based on the presented model, we demonstrate that the angular emission of the single emitter can be not only enhanced but also rotated using the dielectric patch nanoantennas.

Regular and chaotic dynamics of non-spherical bodies. Zeldovich’s pancakes and emission of very long gravitational waves

In this paper we review a recently developed approximate method for investigation of dynamics of compressible ellipsoidal figures. Collapse and subsequent behaviour are described by a system of ordinary differential equations for time evolution of semi-axes of a uniformly rotating, three-axis, uniform-density ellipsoid. First, we apply this approach to investigate dynamic stability of non-spherical bodies. We solve the equations that describe, in a simplified way, the Newtonian dynamics of a self-gravitating non-rotating spheroidal body. We find that, after loss of stability, a contraction to a singularity occurs only in a pure spherical collapse, and deviations from spherical symmetry prevent the contraction to the singularity through a stabilizing action of nonlinear non-spherical oscillations. The development of instability leads to the formation of a regularly or chaotically oscillating body, in which dynamical motion prevents the formation of the singularity. We find regions of chaotic and regular pulsations by constructing a Poincaré diagram. A real collapse occurs after damping of the oscillations because of energy losses, shock wave formation or viscosity. We use our approach to investigate approximately the first stages of collapse during the large scale structure formation. The theory of this process started from ideas of Ya. B. Zeldovich, concerning the formation of strongly non-spherical structures during nonlinear stages of the development of gravitational instability, known as ‘Zeldovich’s pancakes’. In this paper the collapse of non-collisional dark matter and the formation of pancake structures are investigated approximately. Violent relaxation, mass and angular momentum losses are taken into account phenomenologically. We estimate an emission of very long gravitational waves during the collapse, and discuss the possibility of gravitational lensing and polarization of the cosmic microwave background by these waves.

Shape-controlled synthesis and lithium storage properties of SnO2 nonspherical hollow structures

SnO2 hollow structures, such as peanuts, capsules and pseudocubes, have been controlled-synthesized by using SiO2 colloids with different shapes as templates, and show enhanced lithium storage performances.

Effect of Nanostructure on Thermal Conductivity of Nanofluids

The presence of colloidal particles is known to increase the thermal conductivity of base fluids. The shape and structure of the solid particles are important in determining the magnitude of enhancement. Spherical particles—the only shape for which analytic theories exist—produce the smallest enhancement. Nonspherical shapes, including clusters formed by colloidal aggregation, provide substantially higher enhancements. We conduct a numerical study of the thermal conductivity of nonspherical structures dispersed in a liquid at fixed volume fraction in order to identify structural features that promote the conduction of heat. We find that elongated structures provide high enhancements, especially if they are long enough to create a solid network (colloidal gel). Cross‐linking further enhances thermal transport by directing heat in multiple directions. The most efficient structure is the one formed by hollow spheres consisting of a solid shell and a core filled by the fluid. In both dispersed and aggregated forms, hollow spheres provide enhancements that approach the theoretical limit set by Maxwell’s theory.

Synthesis and properties study of the uniform nonspherical styrene/methacrylic acid copolymer latex particles.

A facile method to prepare the nonspherical amphiphilic random copolymer of poly(styrene-co-methacrylic acid) (poly(St-co-PMAA)) latex particles with well-defined shapes and high yields by one-step batch emulsifier-free polymerization was demonstrated. In our strategy, only varying the molar ratio of styrene (St) to methacrylic acid (MAA), no seed-particles, no cross-linker, and no multistep control procedures were needed. Due to the presence of carboxyl groups on the surface of (poly(St-co-PMAA) latex particles, these latex particles can be used as templates for fabricating core-shell nonspherical functional materials, such as poly(St-co-PMAA)@SiO2 and poly(St-co-PMAA)@polypyrrole). The corresponding nonspherical hollow structures (SiO2 and polypyrrole) could be obtained after removal of the templates. In addition, poly(St-co-PMAA) latex particles exhibit interesting morphologies in ethanol.

An Assembly Automation Approach to Alignment of Noncircular Projections in Electron Microscopy

In single-particle electron microscopy (EM), multiple micrographs of identical macromolecular structures or complexes are taken from various viewing angles to obtain a 3D reconstruction. A high-quality EM reconstruction typically requires several thousand to several million images. Therefore, an automated pipeline for performing computations on many images becomes indispensable. In this paper, we propose a modified cross-correlation method to align a large number of images from the same class in single-particle electron microscopy of highly nonspherical structures, and show how this method fits into a larger automated pipeline for the discovery of 3D structures. Our modification uses a probability density in full planar position and orientation, akin to the pose densities used in Simultaneous Localization and Mapping (SLAM) and Assembly Automation. Using this alignment and a subsequent averaging process, high signal-to-noise ratio (SNR) images representing each class of viewing angles are obtained for reconstruction algorithms. In the proposed method, first we coarsely align projection images, and then realign the resulting images using the cross correlation (CC) method. The coarse alignment is obtained by matching the centers of mass and the principal axes of the images. The distribution of misalignment in this coarse alignment is estimated using the statistical properties of the additive background noise. As a consequence, the search space for realignment in the CC method is reduced. Additionally, in order to overcome the false peak problems in the CC, we use artificially blurred images for the early stage of the iteration and segment the intermediate result from every iteration step. The proposed approach is demonstrated on synthetic noisy images of GroEL/ES.

Order and chaos in the rotation and revolution of two massive line segments.

As a generalization of Newton's two body problem, we explore the dynamics of two massive line segments interacting gravitationally. The extension of each line segment or slash (/) provides extra degrees of freedom that enable the interplay between rotation and revolution in an especially simple example. This slash-slash (//) body problem can thereby elucidate the dynamics of nonspherical space structures, from asteroids to space stations. Fortunately, as we show, Newton's laws imply exact algebraic expressions for the force and torque between the slashes, and this greatly facilitates analysis. The diverse dynamics include a stable synchronous orbit, families of unstable periodic orbits, generic chaotic orbits, and spin-orbit coupling that can unbind the slashes. In particular, retrograde orbits where the slashes spin opposite to their orbits are stable, with regular dynamics and smooth parameter spaces, while prograde orbits are unstable, with chaotic dynamics and fractal parameter spaces.

ChemInform Abstract: Anisotropic Gold Nanoparticles: Synthesis, Properties, Applications, and Toxicity

AbstractReview: 429 refs.

Facile Synthesis and Properties of Hierarchical Double-Walled Copper Silicate Hollow Nanofibers Assembled by Nanotubes

The hierarchical assembly of multilevel, nonspherical hollow structures remains a considerable challenge. Here, we report a facile approach for synthesizing copper silicate hollow nanofibers with an ultrasmall nanotube-assembled, double-walled structure. The as-prepared hollow fibers possess a tailored complex wall structure, high length-to-diameter ratio, good structural stability, and a high surface area, and they exhibit excellent performance as an easily recycled adsorbent for wastewater treatment and as an ideal support for noble metal catalysts. In addition, this strategy can be extended as a general approach to prepare other double-walled, hollow, fibrous silica-templated materials.

One-Step Carbonization Synthesis of Hollow Carbon Nanococoons with Multimodal Pores and Their Enhanced Electrochemical Performance for Supercapacitors

Hollow carbon capsules with multimodal pores are highly promising for developing novel electrode materials for high-performance electrochemical devices due to their more active sites for ion and electron transfer. However, at present, most of the previous efforts are focused on the multistep process for the synthesis of hollow carbon nanostructures with individual pores. Herein, hollow carbon nanococoons (HCNCs) with non-spherical cavity and multimodal hierarchical pores have been facilely synthesized via a one-step carbonization of a Fe2O3/carbon precursor core/shell nanospindle at 850 °C. We interestingly found that during the carbonization, Fe2O3 was automatically "escaped" from the inside nanospindle, leading to the formation of new HCNCs. Most importantly, the spindle-shaped cavity of the obtained HCNCs with high conductivity can offer a multimodal ion diffusion pathway, which can facilitate the reaction kinetics in a supercapacitor. As a result, the HCNCs-based supacapacitor exhibits the capacitance of 220.0 F g(-1) at a given scan rate of 5 mV s(-1), 3.5 times higher than that of hollow carbon spheres, high stability with 98% of the initial capacity maintained even after 1000 cycles, and high rate capability. This work provides a new and facile avenue for enhancing performance of a HCNCs-based supercapacitor by using the non-spherical hollow structures with multimodal pores.

Anisotropic Gold Nanoparticles: Synthesis, Properties, Applications, and Toxicity

Anisotropic gold nanoparticles (AuNPs) have attracted the interest of scientists for over a century, but research in this field has considerably accelerated since 2000 with the synthesis of numerous 1D, 2D, and 3D shapes as well as hollow AuNP structures. The anisotropy of these nonspherical, hollow, and nanoshell AuNP structures is the source of the plasmon absorption in the visible region as well as in the near-infrared (NIR) region. This NIR absorption is especially sensitive to the AuNP shape and medium and can be shifted towards the part of the NIR region in which living tissue shows minimum absorption. This has led to crucial applications in medical diagnostics and therapy ("theranostics"), especially with Au nanoshells, nanorods, hollow nanospheres, and nanocubes. In addition, Au nanowires (AuNWs) can be synthesized with longitudinal dimensions of several tens of micrometers and can serve as plasmon waveguides for sophisticated optical devices. The application of anisotropic AuNPs has rapidly spread to optical, biomedical, and catalytic areas. In this Review, a brief historical survey is given, followed by a summary of the synthetic modes, variety of shapes, applications, and toxicity issues of this fast-growing class of nanomaterials.