bluuebunny/crossref_metadata_2025 huggingface dataset:
Hybrid systems of gold and silver nanoparticles generated on cellulose surfaces
Authors: Carapeto A.P. , Ferraria A.M. , Carvalho P.A. , Brogueira P. , Boufi S. , Botelho do Rego A.M.
Published: August 2013

Developing methods for immobilizing metallic nanoparticles (NP) onto different surfaces is a subject of fundamental interest, as nanometric structures enable the appearance of novel properties, absent in bulk or even in micrometric dimensions. In fact, the presence of NP with different size and shape on surfaces can induce substantial modifications on their electronic, optical, magnetic, physical or chemical proprieties. This will be very useful for many applications in different areas ranging from electronics to biomedicine.

In this work, we use a simple, reproducible and economic method to grow metallic gold and silver NP directly on cellulose surfaces. A prior chemical activation of the alcohol groups on the cellulose surface is needed for grafting amino functions, which will complex silver and gold ions. Therefore, NP nucleation is only allowed and selectively accomplished on these seed coordination sites. The growth of NP is achieved by the interaction of aqueous dilute solutions of AgNO3 or NaAuCl4 with the cellulose surface. The procedure limits the generation of NP only to the cellulose surface, keeping the dispersion medium completely exempt of them. The resulting NP are, consequently chemically immobilized on the cellulose surface. The chemical anchoring of the NP to the surface avoids particle desorption and extends the lifetime of the resulting hybrid materials. Following this procedure, silver and gold NP could be successfully created on cellulose and this was supported by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM).

The present AFM (Figure 1) study enabled to characterize the size and shape of silver NP: they are spherical and have a diameter of ~15 nm. SEM image of Ag NP (Figure 2) display the existence of NP agglomerates. Comparison of the two images suggests size and spatial distributions strongly non- uniform. It is now a challenge to deposit nanoparticles in an organized manner, achieving a regular surface functionalization of cellulose. In TEM (Figure 3) we see a sample where Ag and Au salts interacted simultaneously with the cellulose surface. Crossing the images with other information from analytical techniques, it seems that Ag NP and Au NP form mainly separately instead of presenting a core-shell structure. Also, there is evidence that larger NP are the ones made of silver which suggests that the final result is kinetically (and not thermodynamically) controlled.

The authors acknowledge FCT for A.M. Ferraria Grant SFRH/BPD/26239/2006, for A. P. Carapeto Grant SFRH/BD/75734/2011 and strategic projects PEst-OE/CTM/LA0024/2011 and PEst-OE/CTM-UI0084/2011.
Elemental interdiffusion in W-Ta composites developed for fusion applications
Authors: Mateus R. , Dias M. , Livramento V. , Nunes D. , Carvalho P.A. , Hanada K. , Correia J.B.
Published: August 2013

Tungsten (W) was select for an extensive use in nuclear fusion devices due to its low neutron activation, high melting point and sputtering threshold as well as low hydrogen inventory. Nevertheless, W is brittle at low and moderate temperatures, which results in abnormal thermal stress, component fracture and extra erosion under reactor operation due to inherent thermal cycling events. An attractive way to solve these problems involves the addition of other refractory metals in the W matrix and tantalum (Ta) is a natural candidate. It has a high ductility, toughness and radiation resistance relative to those of W and transmutes to W by high-energy neutron irradiation. Recently, IST proposed the production of W-Ta composite by mechanical synthesis.

The composite should reveal the individual properties of the pristine phases as long as the interdiffusion between the components is significantly avoided during the consolidation/sintering route of the final material. Sintering operations at temperatures higher than 1300ºC lead to significant improvements in the final densification and thermal conductivity of the composites, which is crucial for fusion applications. However, W and Ta interdiffusion can be relevant above 1300ºC, mainly due to diffusion of W into Ta, and the aim of the present work is to control the mechanism.

W-Taf composites presenting 10 and 20 at.% of Ta where produced by alloying W powders and Ta fibres with a planetary ball milling route (MA) and by consolidating the mixture with spark plasma sintering (SPS) in the 1300-1600ºC temperature range. The final densifications remain fairly constant in both composites after sintering at different temperatures (83 to 87%) and the elemental interdiffusion remained low at 1300ºC. Nevertheless, the diffusivity of W in Ta became significant at 1600ºC, leading to the formation of a solid solution zone with a stoichiometry close to W16Ta84. The mechanism was followed by scanning electron and energy-dispersive X-ray spectroscopies (SEM/EDS; Figures 1 and 2, Table 1). Fabrication routes yielding high densifications and low interdiffusion are currently under investigation.

The work has been supported by the Contract of Association between Euratom and IST and by the Fund. Ciência e a Tecnologia contracts PTDC/CTM/100163/2008, Pest-OE/SADG/LA0010/2011 and PEST-OE/CTM-UI0084/2011.
Studies on deuterium retention in W-Ta based materials
Authors: Dias M. , Mateus R. , Catarino N. , Livramento V. , Correia J.B. , Carvalho P.A. , Hanada K. , Pinhão N. , Barquinha P. , Alves E.
Published: August 2013

The high melting point, high sputtering threshold and low tritium inventory rendered W as a potentially suitable material in fusion devices. The major problem associated with presently available tungsten grades as structural materials is its brittleness at lower temperatures. This is further worsened by irradiation embrittlement. A strategy for ductility improvement is producing a composite, with the brittle W matrix being reinforced by short fibres of tantalum. As Ta is more ductile than W it can therefore divert or stop cracks propagating in the W matrix. In the present research Ta short fibres and powder were used as reinforcement component for W by alloying Ta short fibres or powder in a W powder matrix. The composites were subsequently irradiated with deuterium to assess the retention of this hydrogenic species in the materials.

The irradiated composites, with Ta contents of 10 or 20 at%, were produced from pure elemental powders (W-Ta powder composites), and pure W powder and Ta fibre (W-Ta fibre composites) with 100 μm in diameter by low energy ball milling in argon atmosphere. These materials were consolidated via spark plasma sintering (SPS) in the temperature 1200 to 1600 ºC range. Pure W and Ta plates (controls) and W-Ta composites were irradiated with He+ ions (optional pre-implantation step) and D+ ion beams at room temperature with fluences in the 1020-1021 at/m2 range. Blistering and deuterium retention in W and Ta plates and in W-Ta composites were studied with scanning electron microscopy (SEM), X-ray diffraction and thermal desorption analysis. The deuterium concentration was evaluated trough nuclear reaction analysis (NRA) using 0.75 to 2.1 MeV 3He+ beam and the D(3He,p)α reaction.

The investigations showed that deuterium irradiation induced microstructural modifications producing blistering in Ta plates as well as in W-Ta composites (Figure 1). These effects increased substantially in the Ta and W-Ta materials with the He pre-implantation step, while blisters have not been observed in the W plates either for D+ or He+ plus D+ implantation. Higher deuterium retention was observed by thermal desorption for the composites than for the W plates. Moreover the present study revealed that D+ trapping in the composites is dependent on the microstructure with higher retention observed for fibers than for powder.

This work has been performed under the Contract of Association between EURATOM and Instituto Superior Tecnico. Financial support was also received from the Fundação para a Ciência Tecnologia (FCT) grants with references PTDC/CTM/100163/2008, Pest-OE/SADG/LA0010/2011 and PEST-OE/CTM-UI0084/2011. The authors wish to acknowledge Jorge Rocha the implantation in W-Ta samples.
TEM studies of the ThMn12–type and Th2Zn17–type phases in the Nd-Fe-Ti system
Authors: Nunes D. , Gonçalves A.P. , Carvalho P.A.
Published: August 2013

Rare-earth intermetallic compounds with high Fe concentrations and adopting the ThMn12–type and Th2Zn17-type structures have attracted considerable attention in the field of permanent magnets. A large number of experimental studies has been done on these compounds, which are usually measured on alloys structurally characterized only by powder X-ray diffraction (XRD). However, the materials are often multiphasic and their quenched or annealed microstructures evidence homogenization ranges, second phases (resulting from segregation) and on-going phase transformations that may not be easily detectable by XRD. Additional microstructural studies on these systems are therefore required.

Among the Fe-based systems, the ThMn12–type and Th2Zn17–type structures usually require stabilization by a third element, such as Ti. In the present work Nd:11Fe:Ti has been prepared by melting Nd, Fe and Ti in an arc furnace followed by subsequent splat-quenching and/or annealing treatments. The resulting materials have been characterized by XRD, scanning and transmission electron microscopy coupled with energy dispersive spectroscopy.

The results have shown that the presence of α-Fe(Ti) could not be avoided during the solidification of the Nd:11Fe:Ti alloy. Furthermore, the microstructure morphologies and elemental analyses showed that at moderate cooling rates a secondary crystallization phase of Th2Zn17–type appeared in the Nd:11Fe:Ti alloy as result of a peritectic reaction. This lower temperature phase was however not detected in the splat-quenched material, where the high cooling rate route suppressed its crystallization. Nevertheless during a subsequent heat-treatment at 800 ºC the following decomposition took place: NdFe11Ti → Nd2(Fe,Ti)17 + α-Fe(Ti) + Fe2Ti. This reaction had already been proposed by Jang and Stadelmaier, who suggested that the NdFe11Ti compound is unstable at temperatures below 1000 °C. The current study shows that this transformation results in the fine lamellar intergrowth of the Th2Zn17-type phase in ThMn12-type grains, displaying random distribution of planar defects (Figure 1). The reciprocal space of the combined parent and intergrown phases has been mapped through a series of 3-D microdiffraction experiments (Figure 2). This allowed to establish that the preferred orientation relation between the two phases is (020)1:12//(003)2:17 and [100]1:12//[110]2:17, with the invariant plane sitting at 1:12//(333)2:17 planes.

The work was supported by the Portuguese Science Foundation through the CTM/48617/2002, PEst-OE/CTM-UI0084/2011 and CFMC-PEst-OE/FIS/UI0261/2011 grants.
On the YFe11Mo intermetallic characterization
Authors: Nunes D. , Gonçalves A.P. , De Hosson J.Th.M. , Carvalho P.A.
Published: August 2013

Rare-earth intermetallic compounds adopting the tetragonal ThMn12–type structure and containing high Fe concentrations have attracted considerable attention in the field of permanent magnets. Among them, the Y-Fe-Mo series has been extensively investigated, especially by X-ray diffraction (XRD), but the microstructural characterization was very limited.

In the present work, Y:11Fe:Mo has been prepared by melting Y, Fe and Mo in an arc furnace followed by splat-quenching and/or annealing treatments. The structure, chemistry and magnetic domain configurations of the resulting polycrystalline aggregates have been investigated by XRD, scanning and transmission electron microscopies (SEM and TEM, respectively), energy dispersive X-ray spectroscopy (EDS) and Lorentz microscopy.

A special emphasis was given to Lorentz microscopy, where contrast is based on the Lorentz deflection imposed on electrons by the passage through a magnetic specimen. The magnetic domains have been imaged by the intermediate lens in Fresnel mode, with the objective lens switched off. In these conditions the intermediate lens is defocused so that out-of-focus images of the specimen are formed: the magnetic domain walls are imaged as alternate bright (convergent) and dark (divergent) lines. For the overfocused image, bright lines occur at the position of domain walls for which the magnetisation on either side is deflecting the electrons towards the wall, whereas dark lines are observed at the walls for which the magnetisation on either side is deflecting the electrons away from the wall. The opposite contrast is observed at the underfocused image.

The results have shown that the tetragonal YFe11-xMoy phase is predominant, with a cellular dendritic morphology (Figure 1), but a considerable presence of -Fe(Mo) could be inferred, forming a coarse intercellular eutectic mixture. Significant Fe segregation occurred during annealing. However, this composition variation corresponded to an extremely limited evolution of the lattice parameters, the Rietveld analysis pointing to Fe vacancies at the 8i sites on the annealed material. XRD and EDS results indicate that the fraction of point defects in the ThMn12-type structure adapts to the processing route and that the stable configuration depends on the temperature. The current study also showed that grain boundaries are usually associated with domain walls and that YFe11Mo grains present internal domain walls forming stripe/maze patterns characteristic of high anisotropy materials (Figure 2), while residual -Fe(Mo) grains exhibit vortex configurations (see arrows in Figures 2 (a-c)).

The work was supported by the Portuguese Science Foundation through the CTM/48617/2002 and PEst-OE/CTM-UI0084/2011 grants.
SEM characterization of two-dimensional patterns generated in titanium by femtosecond laser interferometry
Authors: Oliveira V. , Polushkin N.I. , Conde O. , Vilar R.
Published: August 2013

Laser ablation using ultrafast femtosecond lasers and holographic schemes has proven to be a powerful and versatile tool for surface and volume structuring. The principle of operation of this technique is simple: when two or more pulses overlap in time and space, an interference pattern is generated that can be used to create periodic surface structures. In addition, due to the extremely short pulse duration, a very high peak power is achieved leading to intense non-linear effects. As a result, almost any type of material can be processed without undesirable collateral thermal effects.

In this paper, characterization of two-dimensional (2D) patterns generated in titanium using femtosecond laser radiation has been carried out using scanning electron microscopy (SEM). The laser source is a commercial Yb:KYW laser system providing pulses with a duration of 560 fs at a central wavelength of >= 1030 nm. The surface topography was characterized using a Hitachi S2400 scanning electron microscope operated at an electron acceleration voltage of 25.0 kV. Laser processing was performed in air on polished grade 2 titanium samples, a material typically used in low load bearing medical devices.

One-dimensional (1D) gratings were created using a modified Michelson interferometer described in detail elsewhere (Oliveira et al., 2012). To create 2D gratings a double exposure method was used. First, 1D gratings were produced in linear tracks by translating the sample relatively to the stationary interfering laser beams with a fixed scanning velocity of 0.1 mm/s. As an example, Figure 1 depicts SEM pictures of horizontal and vertical 1D gratings with period of about 3.9 m, generated using a pulse energy and pulse repetition rate of 0.35 mJ and 100 Hz, respectively. The peak to valley distance of these patterns can be controlled either by changing the scanning velocity or the pulse repetition rate. By overlapping two linear tracks, different kinds of 2D structures can be created. Figure 2 depicts a square pattern obtained by overlapping two 1D gratings rotated by 90°. The dimensions of the squares depend on the one-dimensional gratings period, which in turn can be easily controlled by varying the distance between the interfering beams. Figure 3 depicts two other possibilities: i) trapezium-like patterns obtained by rotating the 1D gratings by 45°, and ii) rectangular patterns obtained using 1D gratings with different periods and rotated by 90°.

The proposed optical setup offers a simple method of texturing the surface of materials and, hence, to control surface properties such as wettability. In the case of titanium, this is particularly important because surface texturing enhances its osseointegration ability. For this purpose, when compared with the columns spontaneously formed on titanium surfaces treated with femtosecond laser radiation, these 2D gratings present the major advantage of being size and shape-controllable.
Morphological characterization by scanning electron microscopy of WC powder particles coated with Cu
Authors: Puga J.B. , Fernandes C.M. , Vieira M.T. , Senos A.M.R.
Published: August 2013

Cemented tungsten carbides (WC), are considered one of the oldest, most successful and commercialized powder metallurgy products. These materials are commonly composites of WC powder particles bonded with transition metals such as Co or Ni via liquid-phase sintering. WC-based composites have been used for decades in wide engineering applications, as cutting tools, components for oil and gas drilling, metal forming, among others. The conventional processing of the WC based composites initializes with powder preparation, performed by wet milling of all the powder components (WC and metallic binders). However, this process is high energy consuming, ecologically unfriendly and longstanding, thus new powder processing methods are welcome. In this work, copper (Cu) was selected as an alternative binder, due to its inability to form brittle carbides with WC at higher temperature, the superior ductility (compared with the traditional Co binder) and corrosion resistance. Nevertheless, melted Cu has low wettability on the WC surfaces, limiting the attained sintered density and, consequently, the final properties. Powder coating techniques, such as high energy ball milling (HEBM) and the sputter-coating technique (ST), improve the binder homogeneous distribution and nanostructuring enhancing the sinterability. WC-Cu composite powders (with 2 wt.% Cu) were prepared using the two methods mentioned above. The morphology of the particles was evaluated by scanning electron microscopy (SEM- Hitachi SU-70) and the distribution and chemical composition were assessed by energy dispersive spectroscopy (EDS- Bruker QUANTAX 400).

The starting WC powder has an average grain size of 9 µm, as depicted in Figures 1-a) and 2-a). In the WC coating by HEBM, the collisions of ball-to-ball and ball-to-wall with the entrapped powder particles cause at the same time severe binder plastic deformation and WC fragmentation, endorsing a high uniform distribution of Cu around WC particles, as is depicted in Figures 1-b) and c). On the other hand, the composite powders prepared by ST revealed a high uniformity of Cu coating on the WC particles (Figures 2-b) and c)), together with a columnar binder nanostructure, commonly observed on sputter–coated surfaces. In spite of the low binder content, the WC particles seem well covered, taking its rough morphology, in Figure 2-c), and the X- ray maps and the Cu, W concentration profiles presented in Figure 3. It can be, therefore, concluded that both powder coating techniques allow high uniform distribution of Cu coatings on WC particles and, furthermore, the ST technique presents a clear nanometric binder structure. The effect of the coating technique on the sinterability of WC-Cu powders will be evaluated on forthcoming studies.
Production and characterization of hypromellose phthalate nanoparticles containing levofloxacin for ophthalmic applications
Authors: Paradiso P. , Rodrigues M.A. , Colaço R. , Saramago B. , Serro A.P.
Published: August 2013

Although eyedrops are nowadays the most used administration form of ophthalmic drugs, they present several problems: they imply repeated applications, lead to significant drug losses, and may cause undesirable side effects, as a result of the rapid drug absorption into the blood stream. Several attempts have been made to develop new drug delivery systems, which increase the residence time of the drugs in the eye and improve its bioavailability. Therapeutic soft contact lenses (SCLs) seem to constitute a promising alternative due to the prolonged contact with the eye. Although drug soaked contact lenses have demonstrated to be more efficient than eyedrops, they still present limitations: maximum drug load is limited and diffusion is the only resistance to drug transport across the gel, which may lead to short release times. Designing an effective system for the treatment of ocular diseases is a challenging task, to which nanotechnologies may give a valuable contribution. The incorporation of drug-loaded nanostructures in the SCLs materials may help to control the drug release rates and to maintain drug therapeutic levels for longer periods of time.

The main objective of this work is to produce hypromellose phthalate (HPP 50) nanoparticles (NPs) containing levofloxacin (LOF) to incorporate in hydrogels for SCLs. LOF is an antibiotic which offers a broad spectrum against ocular infections and is used both in prophylaxis and treatment. The NPs were produced using a supercritical atomization process developed by the research team - Supercritical Enhanced Atomization (SEA) and were engineered in order to improve the release rate of LOF. Different working pressures, LOF concentrations and polymer+antibiotic starting solution concentrations were tested. The morphology and size of the obtained particles were analysed by scanning electron microscopy (SEM) (Figure 1). The release profiles of the drug were determined using a standard dissolution tester. The quantification of the drug in the supernatant was done by high performance liquid chromatography (HPLC). The particles which presented the best release rate were SEA 15 (Figure 2), containing 10% w/w of LOF and produced at 20 MPa with a concentration of polymer+antibiotic of 5 mg/mL. These particles were further characterized by dynamic light scattering (DLS) (Figure 3), which confirmed the wide size dispersion of the particles, and by zeta potential measurements, which gave a slightly negative potential, -10 mV.

Future work may involve both the optimization of the experimental conditions to decrease the size dispersion of the particles and their eventual coating with polyelectrolytes in order to extend the drug release time.

This study was financially supported by the project PEst- OE/QUI/UI0100/2011. Patrizia Paradiso acknowledges grant from the project SFRH/BD/71990/2010.
Characterization of Sc2O3&CeO2-Stabilized ZrO2 Powders Via Co-Precipitation or Hydrothermal Synthesis
Authors: Grzonka Justyna , Vereshchak Victor , Shevchenko Oleksiy , Vasylyev Oleksandr , Kurzydłowski Krzysztof J.
Published: August 2013

As the presence of Sc2O3 and CeO2 is known to largely enhance the ionic conductivity in the temperature range of 600–800°C, compared with the conventional yttria-stabilized ZrO2, Sc2O3&CeO2-stabilized ZrO2 provide its applicability as electrolytes in solid oxide fuel cells. The current study introduces the methodology to synthesize Sc2O3&CeO2-stabilized ZrO2 powders by using co-precipitation technique or high-temperature hydrothermal reaction, and further describes the structural characterization of the zirconia powders synthesized by the above-mentioned two methods. The co-precipitation technique was found to allow obtaining powders of cubic phase, whereas high-temperature hydrothermal synthesis results in the presence of a monoclinic phase as well. The scanning transmission electron microscope observations also confirm that the size of the synthesized ZrO2 powders in this study is found to be much smaller than that of commercially available powders.
The Mechanism of {113} Defect Formation in Silicon: Clustering of Interstitial–Vacancy Pairs Studied by In Situ High-Resolution Electron Microscope Irradiation
Authors: Fedina Ludmila I. , Song Se Ahn , Chuvilin Andrey L. , Gutakovskii Anton K. , Latyshev Alexander V.
Published: August 2013

We report the direct visualization of point defect clustering in {113} planes of silicon crystal using a transmission electron microscope, which was supported by structural modeling and high-resolution electron microscope image simulations. In the initial stage an accumulation of nonbonded interstitial–vacancy (I–V) pairs stacked at a distance of 7.68 Å along neighboring atomic chains located on the {113} plane takes place. Further broadening of the {113} defect across its plane is due to the formation of planar fourfold coordinated defects (FFCDs) perpendicular to chains accumulating I–V pairs. Closely packed FFCDs create a sequence of eightfold rings in the {113} plane, providing sites for additional interstitials. As a result, the perfect interstitial chains are built on the {113} plane to create an equilibrium structure. Self-ordering of point defects driven by their nonisotropic strain fields is assumed to be the main force for point defect clustering in the {113} plane under the existence of an energy barrier for their recombination.
Meso-Scale Transmission Electron Microscope Tomography Applied for Wax Distribution in Toner Particles
Authors: Yang Mino , Lee Jun-Ho , Kim Hee-Goo , Kim Euna , Kwon Young-Nam , Kim Jin-Gyu , Yang Cheol-Woong
Published: August 2013

Distribution of wax in laser printer toner was observed using an ultra-high-voltage (UHV) and a medium-voltage transmission electron microscope (TEM). As the radius of the wax spans a hundred to greater than a thousand nanometers, its three-dimensional recognition via TEM requires large depth of focus (DOF) for a volumetric specimen. A tomogram with a series of the captured images would allow the determination of their spatial distribution. In this study, bright-field (BF) images acquired with UHV-TEM at a high tilt angle prevented the construction of the tomogram. Conversely, the Z-contrast images acquired by the medium-voltage TEM produced a successful tomogram. The spatial resolution for both is discussed, illustrating that the image degradation was primarily caused by beam divergence of the Z-contrast image and the combination of DOF and chromatic aberration of the BF image from the UHV-TEM.
Precipitates in Nb and Nb–V Microalloyed X80 Pipeline Steel
Authors: Li Zhongyi , Liu Delu , Zhang Jianping , Tian Wenhuai
Published: August 2013

Precipitates in two X80 pipeline steels were studied by transmission electron microscopy equipped with an energy filtering system. The steels are microalloyed with niobium and niobium–vanadium (Nb–V), respectively, and produced by continuous hot rolling. Besides the precipitates TiN and (Ti, Nb) (C, N), which were 10–100 nm in size, a large number of precipitates smaller than 10 nm distributed in the two steels have been observed. In the Nb–V microalloyed steel, only a few titanium nitrides covered by vanadium compounds on the surface have been observed. It is inferred that the vanadium exists mainly in the matrix as a solid solution element. The fact has been accepted that there was no contribution to the precipitation strengthening of the X80 steel by adding 0.04–0.06% vanadium under the present production process. By contrast, the toughness of the Nb–V steel is deteriorated. Therefore, a better toughness property of the Nb microalloyed X80 results from the optimum microalloying composition design and the suitable accelerating cooling after hot rolling.
Detection and Determination of Solute Carbon in Grain Interior to Correlate with the Overall Carbon Content and Grain Size in Ultra-Low-Carbon Steel
Authors: Dong Jiling , He Yinsheng , Lee Chan-Gyu , Lee Byungho , Yoon Jeongbong , Shin Keesam
Published: August 2013

In this study, every effort was exerted to determine and accumulate data to correlate microstructural and compositional elements in ultra-low-carbon (ULC) steels to variation of carbon content (12–44 ppm), manganese (0.18–0.36%), and sulfur (0.0066–0.001%). Quantitative analysis of the ULC steel using optical microscope, scanning electron microscope, transmission electron microscope, and three-dimensional atom probe revealed the decrease of grain size and dislocation density with the increase of carbon contents and/or increase of the final delivery temperature. For a given carbon content, the grain interior carbon concentration increases as the grain size increases.
Effect of Creep Stress on the Microstructure of 9–12% Cr Steel for Rotor Materials
Authors: Dong Jiling , He Yinsheng , Kim Minsoo , Shin Keesam
Published: August 2013

High-chromium heat-resistant steel has been widely used as the key material to improve the condition of steam pressure and temperature in the modern high-efficiency power plants. Despite the use of the steel above 550°C for several decades, its major failure is owing to the creep fracture. In this study, the effect of creep stress on the microstructure in 9–12% Cr steel has been investigated microscopically, and it is clarified that the creep stress enhances precipitation of Laves phase and influences the lath width and dislocation density in lath interior.
Composition Fluctuation of In and Well-Width Fluctuation in InGaN/GaN Multiple Quantum Wells in Light-Emitting Diode Devices
Authors: Gu Gil Ho , Jang Dong Hyun , Nam Ki Bum , Park Chan Gyung
Published: August 2013

In this paper, we have observed an atomic-scale structure and compositional variation at the interface of the InGaN/GaN multi-quantum wells (MQW) by both scanning transmission electron microscopy (STEM) using high-angle annular dark-field mode and atom probe tomography (APT). The iso-concentration analysis of APT results revealed that the roughness of InGaN/GaN interface increased as the MQW layers were filled up, and that the upper interface of MQW (GaN/InGaN to the p-GaN side) was much rougher than that of the lower interface (InGaN/GaN tot he n-GaN side). On the basis of experimental results, it is suggested that the formation of interface roughness can affect the quantum efficiency of InGaN-based light-emitting diodes.
Microstructure Characterization of Defects in Cubic Silicon Carbide Using Transmission Electron Microscopy
Authors: Chayasombat Bralee , Kimata Yusuke , Tokunaga Tomoharu , Kuroda Kotaro , Sasaki Katsuhiro
Published: August 2013

Microstructures of 3C–SiC grown by chemical vapor deposition (CVD) technique on undulant silicon substrate and a further developed technique called switch-back epitaxy (SBE) were studied using transmission electron microscopy (TEM). In case of the CVD sample, the density of the stacking faults was found to be significantly decreasing along growth direction. Sites of collision of stacking faults were observed using high-resolution transmission electron microscopy. Some of the stacking faults were observed to have disappeared after colliding into each other. The stacking faults were identified to be on the same type of plane and had the same type of displacement vector not only in CVD and SBE but also in the epitaxial layer on the SBE SiC samples.
Spatial Distribution of Dislocations in Relation to a Substructure in High-Quality GaN Film
Authors: Yang Mino , Kim Chong-Don , Kim Hee-Goo , Yang Cheol-Woong
Published: August 2013

The dislocation distribution of high-quality single-crystal gallium nitride (GaN) films grown by the hybrid vapor phase epitaxy was analyzed. This study examined the domain structure of GaN from the dislocation distribution on the macroscale by optical microscopy. The surface structure of GaN consisted of domains with microcolumns as the substructure. The inner domains contained a lower density of dislocations but a large number of these dislocations were observed along the domain boundaries. The existence of a domain boundary structure doubly increased the total dislocation density.
Microstructural Characterization of High Indium-Composition InXGa1−XN Epilayers Grown on c-Plane Sapphire Substrates
Authors: Jeong Myoungho , Lee Hyo Sung , Han Seok Kyu , Eun-Jung-Shin  , Hong Soon-Ku , Lee Jeong Yong , Park Yun Chang , Yang Jun-Mo , Yao Takafumi
Published: August 2013

The growth of high-quality indium (In)-rich InXGa1−XN alloys is technologically important for applications to attain highly efficient green light-emitting diodes and solar cells. However, phase separation and composition modulation in In-rich InXGa1−XN alloys are inevitable phenomena that degrade the crystal quality of In-rich InXGa1−XN layers. Composition modulations were observed in the In-rich InXGa1−XN layers with various In compositions. The In composition modulation in the InXGa1−XN alloys formed in samples with In compositions exceeding 47%. The misfit strain between the InGaN layer and the GaN buffer retarded the composition modulation, which resulted in the formation of modulated regions 100 nm above the In0.67Ga0.33N/GaN interface. The composition modulations were formed on the specific crystallographic planes of both the {0001} and {0114} planes of InGaN.
A New Method for Measurement of the Vitrification Rate of Earthenware Texture by Scanning Electron Microscope
Authors: Moon Eun Jung , Kim Su Kyeong , Han Min Su , Lee Eun Woo , Heo Jun Su , Lee Han Hyoung
Published: August 2013

A new method for determining the vitrification rate of pottery depending on the firing temperature was devised using secondary electron images (SEI) of scanning electron microscope (SEM). Several tests were performed to establish the appropriate operating conditions of SEM and reproducibility as well as to examine the applicability of the method. The grayscale values converted from each pixel of SEI were used to determine the vitrification rate of pottery, which in our study were artificially fired specimens composed of three types of clay. A comparison between the vitrification rate value and appearance temperature of minerals shows that mullite formation starts at 1,100°C, during which the vitrification rate rapidly increases by over 10%. In consequence, the result presented here demonstrates that the new method can be applied to estimate the firing temperature of pottery.
Characterization of White and Black Deposits on the Surface of Korean Stone Cultural Heritages
Authors: Kim Jiyoung , Lee Chan Hee , Kim Ran Hee , Shin Eun Jeong
Published: August 2013

White and black deposits have been frequently observed on the surface of Korean stone cultural heritages, and they are considered as damage factors in both conservation and esthetic points of view. In order to set up the appropriate conservation remedy, it is important to know their origins, characteristics, and compositions. In this study, optical and scanning electron microscopes (SEMs) equipped with an energy-dispersive spectrometer (EDS) and X-ray diffractometer were employed to determine the white and black deposits. It was found that both deposits consisted mainly of calcium carbonate (calcite) and calcium sulfate (gypsum). The calcite and gypsum were characterized by bladed, rhombohedral, tabular, and amorphous morphologies under a SEM. The black deposit was not only composed of calcite or gypsum, but also accompanied amorphous and irregular matrix. SEM-EDS analysis revealed an abundance of silicon, aluminum, iron, phosphorus, and carbon on the matrix, which were major elements of soil, atmospheric deposits, and organisms. The white deposit, on the other hand, barely contained those coloring substances. These salts and deposited substances were caused by chemical reaction and physical adhesion between rock-forming minerals, lime mortar, sulfur in polluted air environment, soil dust, and microorganisms.
Three-Dimensional Imaging of Cerebellar Mossy Fiber Rosettes by Ion-Abrasion Scanning Electron Microscopy
Authors: Kim Hyun-Wook , Kim Namkug , Kim Ki Woo , Rhyu Im Joo
Published: August 2013

The detailed knowledge of the three-dimensional (3D) organization of the nervous tissue provides essential information on its functional elucidation. We used serial block-face scanning electron microscopy with focused ion beam (FIB) milling to reveal 3D morphologies of the mossy fiber rosettes in the mice cerebellum. Three-week-old C57 black mice were perfused with a fixative of 1% paraformaldehyde/1% glutaraldehyde in phosphate buffer; the cerebellum was osmicated and embedded in the Araldite. The block containing granule cell layer was sliced with FIB and observed by field-emission scanning electron microscopy. The contrast of backscattered electron image of the block-face was similar to that of transmission electron microscopy and processed using 3D visualization software for further analysis. The mossy fiber rosettes on each image were segmented and rendered to visualize the 3D model. The complete 3D characters of the mossy fiber rosette could be browsed on the A-Works, in-house software, and some preliminary quantitative data on synapse of the rosette could be extracted from these models. Thanks to the development of two-beam imaging and optimized software, we could get 3D information on cerebellar mossy fiber rosettes with ease and speedily, which would be an additive choice to explore 3D structures of the nervous systems and their networks.
Extraction of Three-Dimensional Information of Biological Membranous Tissue with Scanning Confocal Infrared Laser Microscope Tomography
Authors: Kwon Soonwook , Choi Se-Bum , Park Min Gyu , Yu Hyunung , Suh Seung-Woo , Rhyu Im Joo
Published: August 2013

The “LEXT” confocal laser scanning microscope has been used for the three-dimensional (3D) imaging of the surface of specimens, especially in materials science fields, by the penetration of near-infrared (NIR) light without mechanical cutting, deposition, or other specimen pretreatment. Noninvasive investigation of various biological tissues such as human spinal dura mater, rat aorta, and cornea without the dehydration process was successfully carried out with the “LEXT,” in order to access both surface and internal topographic images of the biological structures at a good status of the wet tissue such asin vivo, especially in measuring tissue thickness. The confocal NIR laser microscopy offers the viable means to visualize tissue architecture and its thickness in microdomain to integrate 3D images efficiently. We believe that the “LEXT” has a good application for biological researchers to study biomaterials, and it would be useful as a diagnostic tool in the near future.
Microscopic and Spectroscopic Analyses of Pt-Decorated Carbon Nanowires Formed on Carbon Fiber Paper
Authors: Jeong Namjo , Jang Cheol-yong , Kim Heeyeon , Jeong Hakgeun , Yeo Jeong-gu , Park Yun Chang , Hwang Kyo Sik
Published: August 2013

We report the synthesis of carbon nanowires (CNWs) via chemical vapor deposition using catalytic decomposition of ethanol on nanosized transition metals such as Co, Fe, and Ni. Dip-coating process was used for the formation of catalytic nanoparticles, inducing the growth of CNWs on the surface of the carbon fiber paper (CFP). The liquid ethanol used as carbon source was atomized by an ultrasonic atomizer and subsequently flowed into the reactor that was heated up to a synthesis temperature of 600–700°C. Microscopic images show that CNWs of <50 nm were densely synthesized on the surface of the CFP. Raman spectra reveal that a higher synthesis temperature leads to the growth of higher crystalline CNWs. In addition, we demonstrate the successful decoration of platinum nanoparticles on the surface of the prepared CNWs/CFP using the electrochemical deposition technique.
Features of the ISO-25498: Method of Selected Area Electron Diffraction Analysis in Transmission Electron Microscopy
Authors: Liu Delu
Published: August 2013

International standard ISO-25498 specifies the method of selected area electron diffraction (SAED) analysis in TEM. It is applicable to the acquisition of SAED patterns, indexing the patterns and calibration of diffraction constant. Several features of this standard are introduced. As an example of the applications, phosphide with nanometer scale in a low-carbon steel produced by compact strip production process was analyzed by SAED and EDX. The phosphide precipitates in the steel are identified as MxP, where x is 2–3 and M is Fe, Ti, Cr, or Ni. It possesses a hexagonal lattice with lattice parameter a = 0.609 nm and c = 0.351 nm.
Rapid In Vitro Corrosion Induced by Crack-Like Pathway in Biodegradable Mg–10% Ca Alloy
Authors: Jung Jae-Young , Kwon Sang-Jun , Han Hyung-Seop , Yang Gui Fu , Lee Ji-Young , Yang Seok-Jo , Cho Sung-Youn , Cha Pil-Ryung , Kim Young-Yul , Kim Yu-Chan , Seok Hyun-Kwang , Ahn Jae-Pyoung
Published: August 2013

The in vitro corrosion mechanism of the biodegradable cast Mg–10% Ca binary alloy in Hanks' solution was evaluated through transmission electron microscopy observations. The corrosion behavior depends strongly on the microstructural peculiarity of Mg2Ca phase surrounding the island-like primary Mg phase and the fast corrosion induced by the interdiffusion of O and Ca via the Mg2Ca phase of lamellar structure. At the corrosion front, we found that a nanosized crack-like pathway was formed along the interface between the Mg2Ca phase and the primary Mg phase. Through the crack-like pathway, O and Ca are atomically exchanged each other and then the corroded Mg2Ca phase was transformed to Mg oxides. The in vitro corrosion by the exchange of Ca and O at the nanosized pathway led to the rapid bulk corrosion in the Mg–Ca alloys.
Cyclic stabilizers and infinitely many hyperbolic orbits for pseudogroups
on
Authors: Rebelo Julio C. , Reis Helena
Published: August 2013

Consider a pseudogroup on $( \mathbb{C} , 0)$ generated by two local diffeomorphisms having analytic conjugacy
classes a priori fixed in $\mathrm{Diff} \hspace{0.167em} ( \mathbb{C} , 0)$. We show that a generic pseudogroup as above is such that every
point has a (possibly trivial) cyclic stabilizer. It also follows that these generic
groups possess infinitely many hyperbolic orbits. This result possesses several
applications to the topology of leaves of foliations, and we shall explicitly
describe the case of nilpotent foliations associated to Arnold’s singularities of
type ${A}^{2n+ 1} $.
Experience of anxiety among patients with severe COPD: A qualitative, in-depth interview study
Authors: Strang Susann , Ekberg-Jansson Ann , Henoch Ingela
Published: August 2013

Objectives:

Anxiety often arises in conjunction with dyspnoea in patients with severe COPD. Considering the provoking symptomatology and the high mortality rate for COPD, it is reasonable to believe that these conditions trigger death-related and existential anxiety. Although anxiety causes considerable distress and reduces quality of life, people's experience of anxiety has been studied relatively little. The aim of this study was to explore severely ill COPD patients’ experience of anxiety and their strategies to alleviate anxiety.

Methods:

This qualitative, in-depth interview study explored perceptions of anxiety and the alleviation strategies that are adopted. Interviews were analyzed using a thematic content analysis approach, involving interpretive coding and identification of themes. People suffering from COPD (stage III or IV) were recruited from a pulmonary outpatient clinic in the west of Sweden. Purposive sampling was used, and thirty-one (31) patients were included.

Results:

Most of the patients had experienced anxiety associated with COPD. Analyses revealed three major themes, death anxiety, life anxiety, and counterweights to anxiety. Death anxiety included fear of suffocation, awareness of death, fear of dying and separation anxiety. Life anxiety included fear of living and fear of the future. Counterweights to anxiety concerned coping with suffocation, avoiding strategy, and a sense of joy that defied their vulnerable situation.

Significance of results:

The majority of patients experienced anxiety, which limited their lives. Although the patients experienced both life anxiety and death anxiety, they were able to cope with the situation and find a defiant joy to some extent.
Maize silage and Italian ryegrass silage as high-energy forages in organic dairy cow diets: Differences in feed intake, milk yield and quality, and nitrogen efficiency
Authors: Baldinger L. , Zollitsch W. , Knaus W.F.
Published: August 2013

During the winter feeding period in organic dairy production systems in the alpine and pre-alpine regions of Austria and its neighboring countries, maize silage is an energy-rich forage that is regularly included in grass-silage-based diets to improve the energy supply of the cows. Italian ryegrass (Lolium multiflorumLam.) is also a high-energy fodder grass popular as forage for dairy cows, but it is rarely cultivated in Austrian organic agriculture. The two crops differ in their cultivation demands and characteristics. Italian ryegrass establishes rapidly and may reduce the risk of soil erosion. Italian ryegrass would be a beneficial addition to crop rotation, which is an essential tool in successful organic farming. In a 15-week feeding trial, Italian ryegrass silage and maize silage were fed to 22 lactating Holstein dairy cows. Organically produced Italian ryegrass silage and maize silage were included at a rate of 40% [of dry matter (DM)] in grass-silage-based mixed basal diets. The mixed basal diets were supplemented with modest amounts of additional concentrates (2.7–3.0 kg DM day−1). Owing to the higher energy content of maize silage as compared to Italian ryegrass silage, the maize diet provided more energy [6.3 MJ net energy for lactation (NEL) kg−1DM] than the ryegrass diet (6.15 MJ NEL kg−1DM). The protein supply of the maize diet and the ryegrass diet was intended to be equal, but in fact the protein content of the maize diet was significantly lower (122 g crude protein kg−1DM) than that of the ryegrass diet (141 g kg−1DM). When the maize diet was fed, feed intake, milk yield and milk protein content were significantly higher as compared to the ryegrass diet. Also, intake of crude protein was significantly lower when feeding the maize diet, and in combination with the higher milk protein yield, this enabled an efficiency of gross nitrogen (N) utilization as high as 0.304. This level of N efficiency can be considered as above average and was significantly and considerably higher than the level of 0.259 observed when the ryegrass diet was fed. Therefore, maize silage upholds its reputation as an ideal energy-rich component in grass-silage-based dairy cow diets.
CATULLUS 61: EPITHALAMIUM AND COMPARISON
Authors: Feeney Denis
Published: August 2013

Similes are a prominent feature of epithalamia, with poets comparing the bride and groom to characters from myth or to elements of the natural world. Catullus wrote two epithalamia (61 and 62), together with two other poems with marked epithalamian characteristics (64 and 68). This paper examines the question of why similes are so important to the genre of epithalamium, concentrating on Catullus 61, which is particularly rich in its deployment of comparison. The paper argues that comparison is crucial to the themes of Roman marriage: similes locate the human institution of marriage between the poles of myth and nature, and they afford a vehicle for considering the way marriage links together the disparate terms of male and female.