Miller Indexes Research Articles

Microstructure Evolution of the Ti-46Al-8Nb-2.5V Alloy during Hot Compression and Subsequent Annealing at 900 °C.

TiAl alloys are high-temperature structural materials with excellent comprehensive properties, and their ideal service temperature range is about 700-950 °C. High-Nb containing the Ti-46Al-8Nb-2.5V alloy was subjected to hot compression and subsequent annealing at 900 °C. During hot compression, work-hardening and strain-softening occurred. The peak stresses during compression are positively correlated with the compressive strain rates and negatively correlated with the compression temperatures. The α2 phase exhibited a typical (0001)α2 basal plane texture after hot compression, while the β0 and γ phases did not show a typical strong texture. Subsequent annealing at 900 °C of the hot-compressed samples resulted in significant phase transformations, specifically the α2 → γ and β0 → γ phase transformations. After 30 min of annealing, the volume fraction of the α2 phase decreased from 39.0% to 4.6%. The microstructure characteristics and phase fraction after 60 min of annealing were similar to those after 30 min. According to the calculation of Miller indexes and texture evolution during annealing, the α2 → γ phase transformation did not follow the Blackburn orientation relationship. Multiple crystal-oriented α2 phases with nanoscale widths (20~100 nm) precipitate within the γ phase during the annealing process, which means the occurrence of γ → α2 phase transformation. Still, the γ → α2 phase transformation follows the Blackburn orientation relationship.

Facet type determination based on combined atomic force microscopy and electron backscatter diffraction.

The distribution of facet types affects the functionality of the surfaces of polycrystalline films. However, we are not aware of a previously published convenient method to determine their distribution. This work describes and demonstrates a process to determine and map the Miller indexes (hkl) of crystal facets exposed at the surfaces of polycrystalline films. To find facet types in non-trivial cases, one must know the orientation of the crystal and the direction in which the facet is facing. The method presented here combines the crystal orientations obtained with electron backscatter diffraction with the topography of the same sample area measured with atomic force microscopy. A challenging step is to transfer the data from the two instruments into a common coordinate system. The sequence of steps in the data processing is presented, with methods to verify the results. The process is illustrated with the analysis of an etched copper clad laminate (CCL) and an electroless Cu film deposited on the CCL. This example relates to facet selection in electroless and galvanic plating processes in printed circuit board production, where an uncontrolled transition from epitaxial to non-epitaxial growth can lead to surfaces with unacceptable roughness.

Computational Insights into Ru, Pd and Pt fcc Nano-Catalysts from Density Functional Theory Calculations: The Influence of Long-Range Dispersion Corrections

Ruthenium, palladium and platinum fall within the group of noble metals that are widely used in catalysis, especially for the electrocatalytic production of hydrogen. The dominant phase of the bulk Ru metal is hexagonal close-packed (hcp), which has been studied extensively. However, significantly less attention has been paid to the face-centred cubic (fcc) phases, which have been observed in nanoparticles. In this study, we have carried out density functional theory calculations with long-range dispersion corrections [DFT-D2, DFT-D3 and DFT-D3-(BJ)] to investigate the lattice parameters, surface energies and work functions of the (001), (011) and (111) surfaces of Ru, Pd and Pt in the fcc phase. When investigating the surface properties of the three metals, we observed that the DFT-D2 method generally underestimated the lattice parameters by up to 2.2% for Pt and 2.8% for Ru. The surface energies followed the observed trend (111) < (001) < (011) for both Ru and Pd with all three methods, which is comparable to experimental data. For Pt the same trend was observed with DFT-D2 and DFT-D3(BJ), but it deviated to Pt (111) < Pt (011) < Pt (001) for the DFT-D3 method. DFT-D2 overestimated the surface energies for all three Miller Indexes by 82%, 73%, and 60%, when compared to experimental values. The best correlation for the surface energies was obtained with the DFT-D3 and DFT-D3(BJ) methods, both of which have deviate by less than 15% deviation for all surfaces with respect to experiment. The work function followed the trend of Φ (111) < Φ (001) < Φ (011) for all three metals and calculated by all three methods. Five different types of Ru, Pd and Pt nanoparticles were considered, including icosahedral, decahedral, cuboctahedral, cubic and spherical particles of different sizes. The bulk, surface and nanoparticle calculations showed that the DFT-D2 method for Pt overestimated the exchange-correlation, leading to higher energy values that can be contributed erroneously to a more stable structure. The calculations showed that as soon as the surface-to-bulk ratio > 1, the energy per atom resembles bulk energy values.

Precious metals can be green

In this chapter, a general view of metallic alloys nanoparticles from the atomic-scale view using advanced transmission electron microscopy techniques such as aberration-corrected electron microscopy (Cs-corrected) and high-resolution electron microscopy, is covered. It is well established that catalytic activity of metal nanoparticles is increased by roughness at the atomic scale. Indeed a flat smooth surface will be less active than its stepped counterpart. Metal nanoparticles have in most cases facets with different Miller indexes. However, the control of the shape and crystal structure is not easy to achieve. The possibility of passivizing the nanoparticle surface with organic molecules is a way to control the nanoparticle shape. Using separation techniques such as electrophoresis, it is possible to obtain a batch of particles with the same mass in average and hence the same number of atoms. Passivized particles still have enough free sites to allow catalytic activity. Then, it is possible by using aberration-corrected electron microscopy to obtain the structure and surface structure of nanoparticles. In this work, we will report those methods and demonstrate its application for mono- and multimetallic clusters. The surface of the metallic nanoparticles plays a crucial role in the catalytic activity and interaction between elements in the surface and in the core of the core-shell structures. In this way, the analysis of chemical composition and chemical bonding needs to be obtained using analytic techniques such as X-ray energy-dispersive spectroscopy and electron energy-loss spectroscopy. Herein, we also present quantitative analysis of particles with few atoms by atomic counting using a statistical method applied in Cs-corrected high-angle annular dark-field scanning transmission electron microscopy images.

Antioxidant, antimicrobial and cytotoxic activities of biosynthesized gold nanoparticles (AuNPs) from Chinese lettuce (CL) leave extract (Brassica rapa var. pekinensis)

In this study, a methodology to produce the high-quality gold nanoparticles (AuNPs) from aqueous Chinese lettuce (CL) leave extract as a reducing agent is presented. The effect of various parameters including Chinese lettuce (CL) leave extract, time, pH, temperature, and concentration of HAuCl4 in AuNPs synthesis was studied using the UV–vis spectroscopy. The synthesized AuNPs were recognized with XRD, FTIR spectroscopy and also TEM analysis. In addition, antibacterial activity, antifungal activity, DPPH radical scavenging, ABTS radical scavenging, MTT assay, DAPI staining and flow cytometry against the A549 cells were examined. AuNPs synthesis produced a color change in the colloidal solution from light yellow to wine, and spectrum absorption showed the maximum peak about 521 nm indicating AuNPs formation. The optimum condition for AuNPs synthesis was 2 mM HAuCl4.3H2O and 3 ml CL leave extract at pH 6. The particle sizes of AuNPs were about 25 nm due to TEM results. XRD structural analysis confirmed that the nanoparticles have a crystalline structure with miller indexes (1 1 1), (2 0 0), (2 2 0) and (3 1 1) in the cubic network. Due to the FTIR analysis, the high stability of AuNPs can be attributed to the existence of CL leave extract on particles’ surfaces. No significant differences were observed in the cell viability at AuNPs concentration ranging from 0 to 2 μg/ml; however, A549 cells proliferation was strongly suppressed in a dose-dependent manner at concentrations higher than 4 μg/ml. Cytotoxicity results indicated that the viability of cells was 90% after 48 h of treatment with AuNPs. Also, a healthy nucleus with less chromatin condensation after 48 h of treatment was observed. These findings suggested that AuNPs did not have adverse the effects on chromatin and DNA of A549 cells. The results of apoptosis assay indicated that AuNPs did induce necrosis and apoptosis in A549 cells. Although CL leave extract and AuNPs due to CL leave extract showed little antimicrobial activity, they indicated profound antioxidant activity against DPPH. The scavenging activity for DPPH and ABTS in AuNPs were more than CL leaves extract. This study indicated the promising potential of synthetized small sized and highly uniform AuNPs.

Platinum single crystal electrodes: Prediction of the surface structures of low and high Miller indexes faces

Platinum is widely used as electrode in electrocatalysis studies; however, the use of polycrystalline surfaces introduces a series of variables in the electrochemical system, due to the random contribution of all crystallographic orientations with different superficial packing of atoms. On the other hand, low Miller index platinum single crystal electrodes present surface structure with high regularity and serve as models for establishing the correlation between atomic arrangements and macroscopic properties, among which their electrochemical behavior. Here we predict the different contributions of each low Miller indexes planes in the size of terraces and number of steps of the high Miller indexes faces of platinum (called stepped surfaces), establish​ the correlation between the structural properties of these surfaces and their electrochemical behavior, and discuss the surface reconstruction process of each platinum low Miller index face.

SEM, XRD and FTIR analyses of both ultrasonic and heat generated activated carbon black microstructures

The microstructures of the activated carbon black microparticles (ACBMPs) generated through both treatments of 20 min ultrasonic and 400 °C thermal energy equivalent have been analyzed properly using scanning electron microscope (SEM), X-ray diffraction (XRD) and Fourier-transformed infrared (FTIR) spectroscopy methods. The research was aiming to generate binding or active sites points on the outer surface of the ACBMPs body of which commonly plays an important role in both adsorption and catalytic processes. It was observed that around 150 nm up to 400 nm in average diameter super macro voids with many various turns of nano-scale wells, and around 1.84 angstrom (Å) up to 15.98 Å intraparticle pores were generated. In addition, the parallel planes spacing of the carbonaceous framework sheets, namely dhkl in Miller indexes terminology, of about 4.44 Å up to 2.98 Å constructed the inner particles of the ACBMPs body. A new nomenclature method for the binding or active site shapes identification and classifying them into four categories based on the quadrants terminology, i.e. quadrant one (Q1), two (Q2), three (Q3) and four (Q4) is proposed. Each the quadrants contains four categories of turns types, i.e. sharp, semi sharp, obtuse and non-significant turns depending on the angle of the associated turn in radian angle, θ. Finally, it can be concluded that the combination of ultrasonic and thermal energy treatments in fabricating ACBMPs could generate binding or active site points with unique shapes as a transit terminal for any guest molecules, in this context is methyl red (MR) molecules to enter into the suitable intra-particles pores of the ACBMPs body.

Incipient plasticity and dislocation loop evolution in rock-salt vanadium nitride

Incipient plasticity and dislocation loop (DL) evolution are two important plastic behaviors of ceramic materials. In this work, we performed molecular dynamics simulations of the nanoindentation on vanadium nitride (VN) surfaces with different Miller indexes to investigate the incipient plasticity, dislocation reactions, and the evolution of the DLs. It was found that the plasticity of VN proceeds by the nucleation and glide of partial dislocations, forming {111} stacking fault (SF). However, dislocation patterns of nanoindentation along different crystallographic orientations are quite different, which to be specific are dislocation flower for {001}, SF tripyramid for {111}, and symmetric inclined SF for {110} indentions. There are two kinds of reactions between the primary defects, including the movement of two parallel partial dislocations forming an extended dislocation, and the intersection of two unparallel SFs forming a stair-rod dislocation. The Thompson tetrahedron was extended to the illustration of the evolution of the microstructures in B1 crystalline VN during the nano-indentations on differently oriented surfaces.

Stability, Structural, and Electronic Properties of Hausmannite (Mn3O4) Surfaces and Their Interaction with Water

Hausmannite (Mn3O4) is the stable phase of manganese oxides and has attracted interest due to its technological applications such as in molecular adsorption, ion exchange, catalysis, and water treatment. Hausmannite is a normal spinel structure that presents the formula A2+B23+O4, where the tetrahedral sites are occupied by Mn2+ and the octahedral sites by Mn3+ cations. The present work intends to fulfill the lack of information about the electronic and structural properties of hausmannite surfaces and their interaction with water. This is an important aspect for understanding the reaction mechanism occurring at the hausmannite–water interface. Density functional calculations have been employed to investigate the structural and electronic properties of hausmannite. Energy surfaces have been estimated for the low Miller indexes, and the water adsorption on the most favored surface was investigated in detail. The results indicate that the (001) cleavage surface is the most favored, in good agreement with th...

AFM and SEM Study on Crystallographic and Topographical Evolutions of Wet-Etched Patterned Sapphire Substrate (PSS): Part II. Cone-Shaped PSS Etched in H2SO4 and H3PO4 Mixture with Varying Volume Ratio at 230°C

Here we present a systematic study on crystallographic and topographical evolutions as well as etching rates of crystallographic planes of cone-shaped patterned sapphire substrate (PSS) etched in H2SO4 and H3PO4 mixture with a wide range of volume ratios (H2SO4:H3PO4 = 1:0, 5:1, 3:1, 1:1, 1:3, and 0:1) at 230°C. The Miller indexes of four major exposed crystallographic planes were determined as S1 {1 0 5}, S3 {4 1 38}, S4 {1 0 12}, and S6 {1 0 8}. The etching rates of crystallographic planes follow the order S1 > S3 > S4 > c plane for H2SO4 and H3PO4 mixtures as well as S1 > S6 > c plane for H3PO4. A larger volume ratio (higher H2SO4 concentration) favors a higher etching rate of c-plane and conversely lower etching rates of S1-, S3-, and S4-planes, thus causing a larger filling factor with the largest filling factor of 0.93 obtained at the volume ratio of 5:1. This work will contribute to revealing the etching mechanism and fabricating optimized PSS for enhanced performance of light-emitting diodes.

AFM and SEM Study on Crystallographic and Topographical Evolution of Wet-Etched Patterned Sapphire Substrates (PSS): I. Cone-Shaped PSS Etched in Sulfuric Acid and Phosphoric Acid Mixture (3:1) at 230°C

A thorough understanding about the crystallographic and topographical evolution of wet-etched patterned sapphire substrates (PSS) is essential for revealing the etching mechanism and critical for fabricating optimized PSS for enhanced performance of GaN-based LED devices. As the first one of a series of three papers, using complementary scanning electron microscope (SEM) and atomic force microscope (AFM), we carried out a systematic study on the crystallographic and topographical evolution of cone-shaped PSS etched with an ordinary etchant (H2SO4:H3PO4 = 3:1 at volume ratio, 230°C) which enables crystallographic specific etching. The topography of patterns was found to evolve from normal cones to truncated cones, to triangular pyramids with multiple families of exposed crystallographic planes, then to hexagonal and triangular pyramids with a single family of planes. The Miller indexes of three major exposed crystallographic planes, with decreasing slant angles, were determined to be {1 0 5}, {4 1 38} and {1 0 12} with the last two being reported for the first time to our best knowledge. It was clearly demonstrated that AFM, thanks to its 3D topography imaging capability compared to SEM and focused ion beam, can be an indispensable tool for fast and reliable characterization of routine PSS samples.

(Invited) Toward Selective Synthesis of Carbon Nanotubes: Paradoxes and Perspectives

Synthesis of single wall carbon nanotubes (SWCNTs) with specific helicity, and thereby with particular properties, still remains one of the main challenges for scientific and engineering communities. Accumulated experimental results for the last two decades on preferential or helicity specific growth of nanotubes continue to fuel the field and suggest possible paths to overcome this obstacle [1-3].The common base that everybody agrees on is that the catalyst plays a key role, therefore a properly made catalyst can lead to the helicity controlled growth of nanotubes. Indeed, all efforts in recent years have been focused on manipulating catalyst properties such as size, composition, and structure [4]. Today, the role of a catalyst is more decisive, e.g. as a template that could not only control the diameter of grown tube, but also amend the structure of grown carbon layer via planar or perpendicular interactions between carbon sp2 network. More specifically, the dominant models rely on the epitaxial relationship between the structure of a nanotube and the corresponding facet of a catalyst. However, there are two paradoxes that need to be addressed: I) the structure of a carbon nanotube and circumference of its rims assume that its growth requires more than one facet i.e. 3D geometry. Moreover involvement of various facets (specifically with low Miller indexes) assumes the presence of steps/kinks with various structures on the catalyst surface, which are the most preferable carbon adsorption sites. Therefore, it is hard to picture van der Waals planar epitaxial relationship between one specific facet and carbon layer (nanotube wall) or between one specific catalyst step and carbon edge (nanotube rim); II) It is well established that a catalyst particle undergoes dynamic morphological reconstructions during nanotube nucleation due to the variation of surface energies of facets driven by carbon atoms adsorption. Therefore, it is hard to picture the mechanism that fulfills the correlation between the symmetry of growing carbon layer and the structure of the specific facet of catalyst that is continuously evolving. To address these problems we have carefully studied the nucleation of carbon nanotubes in very early stages by exploiting in situ environmental TEM technique [5]. We also used catalyst nanoparticles composition with a very high melting point that presumably remains stable during growth of carbon nanotubes. All the attempts, including variations of synthesis conditions, were futile to achieve helicial selectivity and resulted only in variation of the diameter range and of the yield of grown nanotubes. However, our studies [6] reveal that, as a function of morphology of a catalyst nanoparticle such as aspect ratio (L/D, where L-is the length and D-is the diameter) and interfacial angular distribution, there are two compatible scenarios for origination of helicity of a nanotube: 1) in the case of L>>D, the nucleation, the symmetry, and the growth direction of carbon layer along the tubular axis lead to a merging of grown flakes into a nanotube wall with perfect honeycomb lattice in the curved geometry. In this case, the structures of catalyst facets (along the tubular axis) amend the symmetry of grown carbon wall, which in turn defines the helicity of the grown tube. In the meantime, graphene embryo formation on the surface of catalyst nanoparticle with geometry L~D is accompanied by the introduction of the defects (polygons) into the honeycomb structure depending on the interfacial angular distributions. The configurations and the number of defects (pentagons) define the curvature and the helicity of the formed carbon cap and thereby of the grown nanotube. Hence, depending on catalyst morphology (aspect ratio and interfacial angular distribution), the nanotube helicity originates either by carbon wall symmetry or by carbon cap. Our ability to control these scenarios could lead to the helicity selective growth of SWNTs. A. R. Harutyunyan et al., Science 326, 116 (2009)F. Yang et al., Nature 510, 522 (2014)J. R. Sanchez-Valencia et al., Nature 512, 61 (2014)A. R. Harutyunyan J Nanosci. and Nanotechn. 9, 2480 (2009) R. Rao et al., Sci. Rep. 4, 6510 (2014)E. J. G Santos et al., J Phys. Chem. Lett. 6, 2232 (2015)

The effect of different annealing temperatures on the structure and luminescence properties of Y2O3:Bi3+ thin films fabricated by spin coating

This paper reports on the structural, morphology and optical properties of Y2−xO3:Bix=0.005 micro-and nanophosphors synthesized via the spin coating method. The influence of different annealing temperatures (900–1200°C) on the morphology, crystal structure and the photoluminescence (PL) properties of the synthesized films were studied in detail. The crystal structure of the films was investigated with X-ray diffraction. The presence of the three major diffraction peaks with Miller indexes (211), (222) and (400) indicated that the Y2−xO3:Bix=0.005 thin films were well-crystallized at 900°C, 1000°C, 1100°C and 1200°C. Additionally, extra diffraction peaks were observed for the sample that was annealed at 1200°C. Those extra peaks were due to the formation of the Y2Si2O7 phase owing to the annealing induced changes in the crystal structure and chemical composition of the Y2−xO3:Bix=0.005 thin film. This may also be attributed to inter diffusion of atomic species between the Si substrate and the Y2−xO3:Bix=0.005 thin film at the high annealing temperature. Due to structure-sensitive properties of the Bi3+ ions, a blue shift of the centre PL emission band from 495nm to 410nm was clearly observed and explained in detail. The time-of-flight secondary ion mass spectroscopy results show the Si diffusion from the Si substrate, whereas, the scanning electron microscopy and the atomic force microscopy were used for the morphology analysis.

Platinum single crystal electrodes for the electrocatalysis of methane oxidation

The main objective of this paper is to characterize the voltammetric profiles of platinum single crystals of low Miller indexes Pt(100) and Pt(110) and study their catalytic activities on the oxidation of methane. In this way, it was developed a metallic surface modified by presence of other metal oxide, which presents catalytic activity for this reaction. It is well known that the electrooxidation of methane (CH4) leads mainly to the formation of CO2 and H2O, however, the oxidation can also lead to the formation of CO, a reaction intermediate that has strong interaction with metal surfaces, such as platinum. This molecule tends to accumulate on the platinum surface and to passive it, due to the self-poisoning, decreasing its catalytic activity. Therefore, the main aim of this work was the development of a platinum electrode modified by deposition of titanium oxide, which presented electrocatalytic properties for the oxidation of methane.

Rheolytic thrombectomy in patients with massive and submassive acute pulmonary embolism

To appraise the impact of AngioJet rheolytic thrombectomy (RT) on angiographic and clinical endpoints in patients with acute pulmonary embolism (PE). The management of patients with acute PE and hemodynamic compromise, based mainly on anticoagulant and thrombolytic therapies, is challenging and still suboptimal in many patients. In such a setting, mechanical removal of thrombus from pulmonary circulation holds the promise of significant clinical benefits, albeit remains under debate. We retrospectively report on 51 patients referred to our catheterization laboratory and treated with AngioJet RT. Patients were classified according to the degree of hemodynamic compromise (shock, hypotension, and right ventricular dysfunction) to explore thoroughly the degree of angiographic pulmonary involvement (angiographic massive PE was defined as the presence of a Miller index >or= 17) and the impact on angiographic (obstruction, perfusion, and Miller indexes) and clinical (all-cause death, recurrence of PE, bleeding, renal failure, and severe thrombocytopenia) endpoints of AngioJet RT. Angiographic massive PE was present in all patients with shock, whereas patients with right ventricular dysfunction and hypotension showed a similar substantial pulmonary vascular bed involvement. Technical success was obtained in 92.2% of patients, with a significant improvement in obstruction, perfusion and Miller indexes in each subgroup (all P < 0.0001). Four patients reported major bleedings and eight (15.7%) died in-hospital. Laboratory experience was significantly associated to a lower rate of major bleedings. All survivors were alive at long-term follow-up (35.5 +/- 21.7 months) except three who expired due to cancer and acute myocardial infarction. In experienced hands AngioJet RT can be operated safely and effectively in most patients with acute PE, either massive or submassive, and substantial involvement of pulmonary vascular bed.

On the Determination of Si(110) Convex Corner Undercut Planes by the Zoning Model

The etching behavior and emerging facets of Si(110) convex corner anisotropically etched in alcohol (IPA) solutions are investigated. A two-dimensional (2-D) zoning model, in which the undercut planes arising at a masked convex corner are presumed to be at the same zone of the sidewalls forming that convex corner, is employed in conjunction with the use of the Si(110) stereogram, Wulff net, and analytical geometry to determine the Miller indexes of the undercut planes. The theoretical results are verified by experimental measurement. With the two mask openings (one is the top-inverted of the other) being the same, the stereographically projected poles of the undercut planes of one masked corner etched in KOH plus IPA solution are mirror-symmetric in the 2-D Si(110) stereogram to those of the other masked corners. While the pure KOH aqueous solution produces the undercut planes of the two masked corners with poles being inversely symmetric, this discrepancy can be interpreted successfully by the proposed zoning-model theory. Although the atom-packing density of silicon of (110) orientation is less dense than that of (100) orientation, the zoning behavior of the undercut planes for Si(110) is the same as that of Si(100).

Early and Long-Term Clinical Results of AngioJet Rheolytic Thrombectomy in Patients With Acute Pulmonary Embolism

Anticoagulant and thrombolytic therapies are a mainstay in the management of acute pulmonary embolism (PE), especially when hemodynamic compromise is present. However, systemic drugs cannot achieve timely and effective treatment of acute PE in all patients. In such a setting, mechanical removal of thrombus from the pulmonary circulation holds the promise of significant clinical benefits, although it remains untested. We report early and long-term outcome of patients with massive or submassive acute PE treated with rheolytic thrombectomy by means of the 6Fr Xpeedior AngioJet device at our institution. Three main groups were defined pre hoc: subjects with severe (i.e., shock), moderate, or mild hemodynamic compromise. Technical and procedural successes, obstruction, perfusion and Miller indexes, and clinical events were appraised. In total 25 patients were treated with thrombectomy (8 in severe, 12 in moderate, and 5 in mild hemodynamic compromise). Technical and procedural successes were obtained in all patients, as confirmed by the significant improvement in obstruction, perfusion and Miller indexes overall, and in each subgroup (all p values <0.001). Improvement in obstruction, perfusion, and Miller indexes at the end of the procedure could also be confirmed in patients (n = 8) treated with local fibrinolysis and in the absence of concomitant thrombolysis (n = 17, p <0.05). Four patients died in hospital, all other patients but 1 were safely discharged after an appropriate hospital stay, and all were alive at long-term follow-up (median 61 months). In conclusion, this study supports at early and long-term follow-up the effectiveness and safety of rheolytic thrombectomy for PE.

Growth ofβ-FeSi2 single crystals by the chemical vapor transport method

In order to grow β-FeSi2 single crystals by the chemical vapor transport (CVT) method, the growth conditions, including density of iodine transport agent and growth duration, were examined. An iodine density of 8.9 mg cm–3 was thought to be optimum in the present experiment. It was found that the growth duration should be over 4 weeks for growing β-FeSi2 single crystals. X-ray structural analysis revealed that the growth direction of the β-FeSi2 crystals was The growth rate along the directions with lower Miller indexes was slower than that along the directions with higher Miller indexes. The measured lattice constants were a = 0.986 nm, b = 0.780 nm, and c = 0.781 nm. These values are consistent with the previously reported values. Hall measurements showed that the electron mobility was over 350 cm2 V–1 s–1 at 10 K. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Islanding mechanism and band edges in InAs/GaAs [formula omitted] nanostructures

Within the continuum elasticity theory, we investigate the substrate orientation effects on the Stranski–Krastanov (SK) growth mode and the band edges in InAs/GaAs (11n) nanostructures. Attending to the first part of the study, we estimate the transition thickness and the accumulated stress for substrate orientations (113) and (115) and we compare with the values obtained previously in InAs/GaAs (001) nanostructures. Assuming a coherent behavior at the substrate/film interface in the investigated substrate orientations, we consider a sigmoidal-type function for the dependence of the lattice parameter on the height. To evaluate the transition thickness, a minimization of the total free energy density with the slope is made. Similar to the orientation (001), in (113) and (115)-oriented substrates, two different stability regimes for the total free-energy density as well as for the accumulated stress are obtained. These regimes are directly related to the two stages of the SK growth mode. Although the relief strain mechanisms seem similar in all orientations, a delay in the 2D–3D phase transition is induced for high Miller indexes of the substrate. The non-rigid substrate approximation applied in InAs/GaAs (11n) nanostructures yields successful results for the transition thicknesses; the fraction of strained substrate being greater in InAs/GaAs (113). On the other hand, within our model, quantum dots formation is predicted for InAs/GaAs (111) heterostructures. Attending to the second, we find for all substrate orientations investigated, the strain-induced shifts lower the energies of the conduction band edges, while they raise the energies of the heavy- and light-holes band edges. In addition, the energy shifts are less significant for orientation (113), where the compressive stresses are smaller.

Surface Structures and Crystal Morphology of ZnS: Computational Study

Both cubic and hexagonal phases of ZnS are modeled using interatomic potential based simulations and density functional theory. A new set of potential parameters is derived, showing improved behavior compared with the previous ones. Results obtained with this new potential model show very good agreement with those obtained with density functional theory calculations and with experimental results when available. To calculate crystal morphologies for both phases, we perform an extensive study of the surface energies. In the cubic phase we take into account all the nonpolar surfaces with Miller indexes 0, 1, 2, 3, and 4, and all the polar surfaces with indexes 0, 1, and 2. The nonpolar (110) surface is the most stable surface in this phase and entirely dominates the crystal morphology, which is a dodecahedron showing only the (110) surface and its equivalents. In the hexagonal phase we find that it is necessary to take into account polar surfaces to obtain the crystal morphology, which has a highly anisotrop...