Homogeneous Shape Research Articles

Strain Driven Shape Evolution of Stacked (In,Ga)N Quantum Disks Embedded in GaN Nanowires.

The fabrication of nanowires with axial multiquantum wells or disks presenting a homogeneous size and shape distribution along the whole stack is still an unresolved challenge, despite being essential for narrowing their light emission bandwidth. In this work we demonstrate that the commonly observed change in the shape of the disks along the stacking direction proceeds in a systematic, predictable way. High- resolution transmission electron microscopy of stacked (In,Ga)N quantum discs embedded in GaN nanowires with diameters of ∼40 nm and lengths of ∼700 nm and finite element method calculations show that, contrary to what is normally assumed, this change is not related to the radial growth of the nanowires, which is shown to be negligible, but to the strain relaxation of the whole active region. A simple model is proposed to account for the experimental observations. The model assumes that each disk reaches an equilibrium shape that minimizes the overall energy of the system, given by the sum of the surface and strain energies of the disk itself and the barrier below. The strain state of the barrier is affected by the presence of the disk buried directly below in a way that depends on its shape. This gives rise to a cumulative process, which makes the aspect ratio of each quantum disk to be smaller compared to the disk grown just before, in qualitative agreement with the experimental observations. The obtained results imply that strain relaxation is an important factor to bear in mind for the design of multiquantum disks with controlled shape along the stacking direction in any lattice mismatched nanowire system.

LLC «Rzhevkirpich» impact on the environment and environmental management of the territory

A sharp increase of anthropogenic impact on the environment has created a real threat to the ecological crisis. A huge variety of natural resources use in human activities led to the use of a systematic approach to the environmental management analysis, as well as to environmental management. This paper considers Rzhev brick factory impact on such environmental components as air, hydrosphere, soil and lithosphere. Currently, the production of bricks is one of the leading sectors of the building materials industry, accounting for more than 50% of the total production of wall materials. From the environmental point of pollution occurs at all stages of production: raw materials preparation (crushing, grinding, sifting, etc.), mixing of starting components into a homogeneous good shape commodity (preparation of press-powder with the use of emaciated and burnable additives, hydration, heating and mixing) and production with the help of various methods of pressing. As a result of the analysis the authors suggest a complex of measures to minimize negative impacts on the environment and health of workers and the public. As brick plants are widely distributed on the territory of the Russian Federation and as they are quite often located in urban areas, the market for brick production develops, the authors think that the subject is very relevant and important from a practical point of view.

Road Network Extraction from High-Resolution Remote Sensing Image Using Homogenous Property and Shape Feature

According to spectral homogeneity and ribbon-like shape of road, this letter presents a simple yet effective method of delineating road networks from high-resolution remote sensing images. The proposed method consists of three main steps. First, the mean shift algorithm is utilized to detect the modes of density of image points in spectral–spatial space which contain potential road center points and then detected mode points are classified into different classes by mean shift-based clustering on the basis of spectral information. Next, the combination of Gabor filtering and tensor encoding is used to identify the road class and to extract road center points. Lastly, road network is generated from detected road center points by means of tensor voting and connected component analysis. The experimental results demonstrate good performances of the proposed method in road network extraction from high-resolution remote sensing images.

Use of pillared clays in the preparation of washcoated clay honeycomb monoliths as support of manganese catalysts for the total oxidation of VOCs

Manganese catalysts supported by impregnation onto honeycomb monoliths extruded from commercial clay, previously coated with aluminium-pillared clay, were prepared and tested in the total combustion of propane and acetone. Samples characterization included chemical analysis, nitrogen physisorption, electron microscopies (SEM-EDS, HAADF and EELS), XRD, TPR and O2-TPD experiments. The active phase (around 5wt%), consisting of MnO2 particles as majority phase, with homogeneous size and shape, that tends to concentrate in some regions of the surface of the clay support, exhibited high efficiency to oxidize the two model VOCs investigated and stability in severe reaction conditions. Light-off temperatures as low as 225 and 330°C were found for the oxidation of acetone and propane respectively. The better performance observed in comparison to the monoliths without pillared clay was attributed to the higher active phase loading. Differences found as function of the VOC's nature and concentration were related to the different oxidation mechanisms proposed in literature, either just Mars-van Krevelen or this with also Eley-Rideal contribution, for acetone and propane respectively. These results combined with the intrinsic advantages of the honeycomb monolithic design open up new possibilities for using pillared clays as catalytic support in VOCs oxidation under more affordable conditions.

Direct Electrochemical Detection of Bisphenol A Using a Highly Conductive Graphite Nanoparticle Film Electrode.

We developed an accurate and sensitive sensor for electrochemical detection of bisphenol A (BPA) with a high-conductivity graphite nanoparticle (GN) film electrode. The GNs consisted of several stacked graphene sheets and showed a homogenous spherical shape, high conductivity, large surface area and good adsorption properties to BPA. The constructed GN film electrode exhibited improved amperometric current responses such as decreased impedance and lowered BPA oxidation potential compared with those of a pristine electrode, and also possessed a large surface area to allow fast electron transfer and BPA accumulation. A pre-accumulation process with BPA adsorption resulted in considerable current signal enhancement during BPA detection. The loading amount of GNs on the film electrode and the time for target BPA enrichment were optimized. The GN film electrode-based sensor showed high reproducibility and high selectivity for BPA over other reagents. Differential pulse voltammetry experiments revealed that the concentrations of BPA were linearly correlated with the current changes, and the lowest limit of detection of the sensor was 35 nM. Furthermore, the sensor showed great accuracy and reliability, as confirmed by high-performance liquid chromatography measurements. The sensor was also successfully used for BPA determination in groundwater samples, demonstrating its potential for real environmental analysis.

Adsorption of steroid micropollutants on polymer-based spherical activated carbon (PBSAC)

Removal and interaction mechanisms of four different steroid micropollutants, estrone (E1), estradiol (E2), progesterone (P) and testosterone (T) were determined for different types of polymer-based spherical activated carbon (PBSAC). Higher than 90% removal and significantly faster kinetics compared to conventional granular activated carbon (GAC) were observed, while performance was comparable with powdered activated carbon (PAC). No influence of pH in the range 2–12 was determined, while the presence of humic acid (HA) reduced both the removal and the kinetic by up to 20%.PBSAC was characterized in terms of morphology and material properties. The low oxygen content was identified as the main cause for the high performance observed. This was attributed to the enhancement of the hydrophobic effect between PBSAC and hormones and the reduced interactions between PBSAC and water. The ratio of micropollutant size (∼0.8nm) and average pore size (1–2nm) proved ideal for both micropollutant adsorption and HA exclusion.The homogenous size, spherical shape and surface smoothness of PBSAC did not influence adsorption negatively and make PBSAC a very promising sorbent for a vast range of applications, in particular for the removal of micropollutants in water treatment applications.

Triphenylphosphonium-modified poly(ethylene glycol)-poly(ε-caprolactone) micelles for mitochondria- targeted gambogic acid delivery

Mitochondria are important targets for the intracellular delivery of drugs and DNA. For mitochondria-targeted delivery, a mitochondriotropic molecule, triphenylphosphonium (TPP), was applied to the synthesis of amphiphilic TPP-poly(ethylene glycol)-poly(ε-caprolactone) (TPP-PEG-PCL) polymers. The TPP-PEG-PCL polymer was used to prepare micelles using a solvent evaporation method for the delivery of gambogic acid (GA) (GA-TPP). The micelles were obtained with a favorable particle size of 150.07±11.71nm and an encapsulation efficiency of 80.78±1.36%, and they displayed homogeneous spherical shapes. The GA-TPP micelles exerted enhanced cytotoxic and pro-apoptotic effect against A549 cells compared to free GA and GA-loaded PEG-PCL (GA-PP) micelles, due to the inhibition of the expression of apoptosis-related proteins and promotion of caspase 3/7 and caspase 9 activity. Notably, the mitochondria-targeting GA-TPP micelles selectively accumulated in the mitochondria, inducing the loss of mitochondrial membrane potential and the release of cytochrome c, thereby achieving improved mitochondria-targeting effects. In conclusion, the GA-TPP micelle system shows great promise for lung cancer treatment by inducing an apoptotic effect via the mitochondrial signaling pathway.

In vitro study of physical properties ofvarious embolization particles regarding morphology before, during and after catheter passage.

To evaluate various embolization particles on their physical properties with special regard on morphological variability and elasticity. 8 embolization particles (EmboCept®, Contour SE® Microspheres, Embosphere® Micorspheres 400 μm, 500 μm, 1300 μm, Embozene® Microspheres, DC Beads®, Embozene Tandem®) were evaluated and graduated from 1-6 microscopically due to morphologic changes in vitro before, during and after their catheter passage by 4 blinded reviewers. To facilitate comparison, microscopic images were provided with a scale. All tested particles showed a homogenous shape and morphology before passage through the simulation catheter. During the passage all particles were elastically deformable, where necessary. After the catheter passage no loss of basic shape was seen. Changes in size were found in 5/8 particles. Grading of morphologic changes varied between mean value of 1.0 and 3.0. No complete destruction or loss of function was seen. All tested embolization particles are, regarding their morphological properties in sense of homogenous shape and deformation after catheter passage, a safe treatment option. Tested in vitro no less of functionality regarding physical properties should be expected.

Green synthesis of silver nanoparticles using Datura stramonium leaf extract and assessment of their antibacterial activity

Abstract Silver nanoparticles of 15–20 nm size with spherical shape were synthesized from green synthesis method using Datura stramonium leaf extract. Synthesized Ag NPs were studied for their optical, structural, surface morphological and antibacterial properties. The optical study shows that the appearance of SPR peak at 444 nm in the absorption spectrum is affirming the formation of Ag NPs and its high intensity with narrowed width indicating the homogenous size and shape of the Ag NPs. Structural studies reveal the good crystalline nature of face center cubic structure of Ag crystal and preferentially oriented along (111) plane with average crystallite size of 18 nm. FTIR analysis exhibits the possible reducing bio-molecules within the leaf extract. The well defined homogenous spherical shape of the Ag NPs is clearly observed from the TEM studies and lattice fringes spacing of 0.23 nm shows the high crystalline nature of the synthesized Ag NPs. EDAX profile affirms the Ag crystal by the presence of energy peak at 3 eV. The synthesized Ag NPs showed antibacterial activity against E. coli and S. aureus bacteria. However, well pronounced activity was observed against E. coli .

Synthesis of silica-core gold nanoshells and some modifications/variations

Gold nanoshells are particles usually composed of a spherical silica core coated with a thin gold layer. Their chemical and optical properties make them suitable and attractive for medical applications, namely cancer treatment and diagnosis, as they have been studied for biosensing, imaging, and photothermal ablation. For their synthesis, most of the reported methods are based on the first reported by Oldenburg et al. In this method, silica nanoparticles are first produced and then modified to incorporate amino groups aimed to adsorb small gold clusters, which in turn act as the nucleation sites for the reduction of additional gold until complete gold shells are formed. In this review, we examine some common conditions to synthesize gold nanoshells based on this process, along with important aspects that need to be followed to ensure the production of gold nanoshells having homogeneous size and shape that render suspensions with consistent properties in the near-infrared region of the electromagnetic spectrum. Since the customary method is laborious and time-consuming, three additional processes intended to simplify or reduce some steps are described as well. Finally, fundamental aspects on the chemistry of the synthesis and their variations involved in all the revised processes are also presented. Figures from our own findings are included to support these descriptions. Please notice that this review focuses on the synthesis; other reviews focus in optical properties and applications.

The effects of synthesis conditions on the magnetic properties of zinc ferrite spinel nanoparticles

Zinc ferrite nanocrystals were synthesized from metal chloride precursors via chemical co-precipitation method, using different synthesis conditions. Characterization measurements including X-ray diffraction (XRD), transmission electron microscopy (TEM) and super conductiong quantum device (SQUID) were used to study the influence of precursor's concentration and reaction time on the crystalline structure, average sizes and magnetic properties of zinc ferrite nanoparticles. The transmission images show spherical, homogenous shape and particle size ranging from 16 to 22 nm. DC magnetization (2-300 K) measurements reveal a superparamagnetic behavior for the ZnFe2O4 samples with a blocking temperature in the range of 18-24 K. Our results demonstrate that magnetic properties of magnetic particles can be largely modified by just changing the reaction condition such as concentration and reaction time, which might be a useful way to design novel magnetic materials.

(Invited) Silicon Nano-Tip Pattern Approach for Surface and Interface Engineering of Fully Coherent, High Ge Content Nanostructure Arrays for High Performance Photodetection

Defects in form of dislocations at the interface and threading arms in the film as well as SiGe intermixing are the main mechanisms to release the crystallographic misfit strain in Germanium (Ge) heterostructures grown on the mature Silicon (Si) wafer platform, severely deteriorating thereby the superior optoelectronic properties of Ge for device applications. We demonstrate here a novel technique, enabling fully coherent, high Ge content islands on nano-tip patterned Si (001) substrates by the suppression of plastic relaxation as well as SiGe intermixing. The Si-tip patterned substrate, fabricated by complementary metal-oxide-semiconductor (CMOS) compatible nanotechnology, features ~50 nm wide Si tips emerging from a SiO2 matrix and arranged in an ordered lattice. Molecular beam epitaxy (MBE) growths result in Ge nano-islands with high selectivity and having homogeneous shape and size. The ~850°C growth temperature required for ensuring selective growth has been shown to lead to the formation of Ge islands of high crystalline quality without extensive Si intermixing (with 91 at.% Ge). Nano-tip patterned wafers result in geometric, kinetic diffusion barrier intermixing hindrance (in particular surface diffusion suppression) confining the major intermixing to the pedestal region of Ge islands where kinetic diffusion barriers are however high. Theoretical calculations suggest that the self-assembled thin SiGe layer at the interface plays nevertheless a significant role in realizing fully coherent Ge nano-islands free from extended defects especially dislocations. Finally, single layer graphene (SLG)/Ge/Si-tip Schottky junctions were fabricated and thanks to the absence of extended defects and SiGe intermixing in the Ge islands, high performance photodetection characteristics with responsivity and Ion/Ioff ratio of ~45 mA/W and ~103, respectively, are demonstrated.

New quality control phantom for stereotactic body radiation therapy using radiochromic EBT3 film

Introduction Stereotactic Body Radiation Therapy (SBRT) is an increasingly used technique. Due to its particular characteristics a patient specific quality control (QC) is mandatory to ensure an accurate dose delivery. Purpose To develop a dosimetry system consisting of a phantom for insertion of radiochromic films positioned in orthogonal directions for dose measurements. Materials and methods A full film characterization was performed, evaluating megavoltage radiation response, scanning symmetry, angle positioning, after radiation time dependence. Sensitometric curves were performed for a high dose range (1–40 Gy) with 6 MV photons. A PMMA homogeneous and spherical shape phantom was developed, divided in four identical pieces allowing the positioning of the radiochromic films in an orthogonal disposal. Several SBRT treatment plans (conformal, IMRT and VMAT) were measured for validation purpose. The comparison between the calculated and measured doses was made using the gamma index criteria (3%/3 mm) in an in-house software and compared with the results of a commercial system. Results Optimal conditions for film transmission scanning were obtained as well as the correction factors for high uniformity achievement. The spherical shape of the phantom revealed to be advantageous allowing several non-coplanar irradiation angles. Due to the homogeneity of this phantom, heterogeneities problems associated to other commercial systems are not relevant. The passing rate for the gamma index was >95% for the total points analyzed. Conclusions The developed phantom and the system characterization result in a suitable phantom/radiochromic system for SBRT plan dose QC. With a single irradiation, dose distribution in orthogonal planes is obtained, with the characteristic high spatial resolution of these films. Disclosure The authors have no relevant financial or non-financial relationships to disclose.

Preparation and characterization of functional material based on hybrid polymer composites

The microstructures and properties of hybrid polymer composites based on polyaniline (PANi)/γ-Fe2O3 nanoparticles/TiO2/carbon have been investigated for multifunctional applications such as heavy metal removal and initial study for radar absorbing material application. γ-Fe2O3 nanoparticles with spherical shape were synthetized by a coprecipitation method from iron sand. By activating the polyethylene glycol (PEG-400) coated carbon of coconut shell, the homogenous shape and size of carbon was achieved. Then, γ- Fe2O3, TiO2, and carbon were mixed with PANi by an in situ polymerization method at low temperature 0-5 oC. Characterization process involved XRD, SEM, FTIR, VSM, and DC conductivity measurements. For radar absorber application, the functionalized polymer composites showed good electrical conductivity 0.45 S/cm to absorb the incoming electromagnetic energy. An efficient and effective reduction of Pb2+ ion from the water has been achieved by using this material.

Mathematical optimization of a supply chain for the production of fuel pellets from residual biomass

One of the main concerns of humankind in the last years is the availability of energy sources. Research has been focused on finding clean and renewable ways to satisfy the energy demand worldwide. In the particular case of the state of Guanajuato, Mexico, clay industry burns each year about 15,000 m3 of fuel oil and residual oils, and 96,000 t of wood derivatives. As a way to reduce the environmental impact of clay industry, the use of solid fuel pellets, obtained from vegetable residual material, is proposed. The raw material for the pellets is obtained from agribusiness and from the cities of the state. The solid biofuel has high density, low content of humidity, a homogeneous shape and high energy density. Nevertheless, special care must be taken about the location of the production facility and hubs, in order to make the production of the biofuel economically feasible. Furthermore, to have an environmentally friendly fuel, the supply chain and the production process must minimize the global environmental impact. In this work, a mathematical programming model is proposed to determinate the optimal location of the production facilities, the hubs, and the best distribution logistics. The problem is modelled using a general disjunctive programming approach, and then relaxed into a mixed-integer non-linear programming (MINLP) problem. It has been determined that the main plant should be located in the city of Irapuato, while secondary plants must be established in the cities of Leon, Irapuato, Abasolo and Salamanca. Moreover, it has been estimated that, when the residual biomass is converted into pellets, about 72,548 t/year of equivalent CO2 are avoided in the main plant, together with 24,182 of equivalent CO2 avoided per secondary facility.

Analysis of the static magnetic field-dependent optical transmission of Ni nanorod colloidal suspensions

The magnetic field-dependent optical transmission of dilute Ni nanorod aqueous suspensions was investigated. A series of four samples of nanorods were synthesized using the AAO template method and processed to stable colloids. The distributions of their length and diameter were characterized by analysis of TEM images and revealed average diameters of ∼25 nm and different lengths in the range of 60 nm–1100 nm. The collinear magnetic and optical anisotropy was studied by static field-dependent transmission measurements of linearly polarized light parallel and perpendicular to the magnetic field direction. The experimental results were modelled assuming the field-dependent orientation distribution function of a superparamagnetic ensemble for the uniaxial ferromagnetic nanorods in liquid dispersion and extinction cross sections for longitudinal and transversal optical polarization derived from different approaches, including the electrostatic approximation and the separation of variables method, both applied to spheroidal particles, as well as finite element method simulations of spheroids and capped cylindrical particles. The extinction cross sections were compared to reveal the differences associated with the approximations of homogeneous polarization and/or particle shape. The consequences of these approximations for the quantitative analysis of magnetic field-dependent optical transmission measurements were investigated and a reliable protocol derived. Furthermore, the changes in optical cross sections induced by electromagnetic interaction between two nanorods in parallel end-to-end and side-by-side configuration as a function of their separation were studied.

A robust synthesis and characterization of superparamagnetic CoFe2O4 nanoparticles as an efficient and reusable catalyst for green synthesis of some heterocyclic rings

A robust synthesis for magnetic CoFe2O4 nanoparticles via a hydrothermal technique was investigated. The prepared magnetic nanoparticles were characterized using powder X‐ray diffraction, scanning, transmission and high‐resolution transmission electron microscopies, energy‐dispersive X‐ray and infrared spectroscopies, thermogravimetric analysis and vibrating sample magnetometry. Based on the obtained data, the prepared powder was composed of ultrafine particles in nanometer size range with highly homogeneous spherical shape and elemental composition. Moreover, the prepared magnetic CoFe2O4 nanoparticles were used as an efficient catalyst for green synthesis of tetrahydropyridines and pyrrole derivatives in excellent yields, with easy work‐up and purification of products by non‐chromatographic methods. The catalyst can be recovered for subsequent reactions and reused without any appreciable loss of activity. Copyright © 2016 John Wiley & Sons, Ltd.

A Tool for Predicting Heating Uniformity in Industrial Radio Frequency Processing

Radio frequency energy is utilised for heating in a wide range of applications, particularly in the food industry. A major challenge of RF processing is non-uniform heating in loads of variable and angular geometry, leading to reduced quality and product damage. In the study, the specific effects of geometry on the heating profiles of a range of geometrically variable loads in an industrial scale RF system are analysed, and the understanding used to derive a general tool to predict heating uniformity. Potato was selected as a test material for experimental work; dielectric properties were measured using a 44mm coaxial probe. Analysis of simulated and experimental surface temperature profiles and simulated power uniformity indices indicates that the presence of vertices and edges on angular particles, and their proximity to faces perpendicular to the RF electrodes increases localised heating; faces parallel to the electrodes heated less than those faces perpendicular to them. Comparison of the same geometrical shape in different orientations indicates that overall power absorption uniformity can be better even when localised heating of edges is greater. It is suggested, for the first time, that the rotation of angular shapes within a parallel plate electric field can improve heating uniformity, and that this can be achieved through the design of bespoke electrode systems. A Euler characteristic based shape factor is proposed, again for the first time, that can predict heating uniformity for solid, dielectrically homogenous shapes. This provides industry with a tool to quickly determine the feasibility for uniform RF heating of different three dimensional shapes based on geometry alone. This provides a screening method for food technologists developing new products, allowing rapid assessment of potential heating uniformity and reducing the need for early stage specialist computational modelling.

Vitamin E succinate-conjugated F68 micelles for mitoxantrone delivery in enhancing anticancer activity.

Mitoxantrone (MIT) is a chemotherapeutic agent with promising anticancer efficacy. In this study, Pluronic F68-vitamine E succinate (F68-VES) amphiphilic polymer micelles were developed for delivering MIT and enhancing its anticancer activity. MIT-loaded F68–VES (F68–VES/MIT) micelles were prepared via the solvent evaporation method with self-assembly under aqueous conditions. F68–VES/MIT micelles were found to be of optimal particle size with the narrow size distribution. Transmission electron microscopy images of F68–VES/MIT micelles showed homogeneous spherical shapes and smooth surfaces. F68–VES micelles had a low critical micelle concentration value of 3.311 mg/L, as well as high encapsulation efficiency and drug loading. Moreover, F68–VES/MIT micelles were stable in the presence of fetal bovine serum for 24 hours and maintained sustained drug release in vitro. Remarkably, the half maximal inhibitory concentration (IC50) value of F68–VES/MIT micelles was lower than that of free MIT in both MDA-MB-231 and MCF-7 cells (two human breast cancer cell lines). In addition, compared with free MIT, there was an increased trend of apoptosis and cellular uptake of F68–VES/MIT micelles in MDA-MB-231 cells. Taken together, these results indicated that F68–VES polymer micelles were able to effectively deliver MIT and largely improve its potency in cancer therapy.

Magnetic NiFe2O4 nanoparticles: efficient, heterogeneous and reusable catalyst for synthesis of acetylferrocene chalcones and their anti‐tumour activity

A robust synthesis of magnetic NiFe2O4 nanoparticles via a hydrothermal technique was investigated. The prepared magnetic NiFe2O4 nanoparticles were characterized using powder X‐ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy (TEM), high‐resolution TEM, energy‐dispersive X‐ray spectroscopy, thermogravimetric analysis, infrared spectroscopy and vibrating sample magnetometry. XRD and TEM analyses confirmed the formation of single‐phase ultrafine nickel ferrite nanoparticles with highly homogeneous cubic shape and elemental composition. Moreover, the prepared magnetic NiFe2O4 nanoparticles were used as an efficient, cheap and eco‐friendly catalyst for the Claisen–Schmidt condensation reaction between acetylferrocene and various aldehydes (aromatic and/or heterocyclic) yielding acetylferrocene chalcones in excellent yields, with easy work‐up and reduced reaction time. The products were purified via crystallization. The structures of the produced compounds were elucidated using various spectroscopic analyses (1H NMR, 13C NMR, GC–MS). The catalyst is readily recovered by simple magnetic decantation and can be recycled several times with no discernible loss of catalytic activity. Furthermore, the prepared chalcone derivatives were evaluated for their anti‐tumour activity against three human tumour cell lines, namely HCT116 (colon cancer), MCF7 (breast cancer) and HEPG2 (liver cancer), and showed a good activity against colon cancer. Copyright © 2016 John Wiley & Sons, Ltd.