Top PDF Change in lattice parameter of tantalum due to dissolved hydrogen

Change in lattice parameter of tantalum due to dissolved hydrogen

Change in lattice parameter of tantalum due to dissolved hydrogen

A unique combination of physical and chemical properties makes tantalum a valuable material for high temperature and advanced technological applications. These properties are high melting point, good heat and electrical conductivity, high ductility and corrosion re- sistance. It has various applications in the medical ield due to its good biocompatibility with the human body luids. It is also used in the construction of high tem- perature furnace components and as hardware in high temperature environments such as heat shielding of jet engines and vacuum furnaces. Tantalum crucibles are used for high temperature processes, like fusion, thin ilm deposition, distillation and as heat exchangers. In the electronic industry, tantalum is used in manufactur- ing of capacitors, coils and boats for resistive evapora- tion. Tantalum is also considered as a promising candi- date for the hydrogen separation membrane because of its superior mechanical strength compared to the pal- ladium or ceramic based hydrogen separation mem- branes. The surface oxidation and hydrogen embrit- tlement are two key issues to be resolved before its selection for any speciic application. Surface oxidation can be minimized by coating with thin palladium layer
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Effect of barium titanate seed particles on the sintering and lattice parameters in PbMg1/3Nb2/3O3 ceramics

Effect of barium titanate seed particles on the sintering and lattice parameters in PbMg1/3Nb2/3O3 ceramics

The PMN phases were quantified by XRD after the sin- tering process (Fig. 6). For the pure sample, the amount of perovskite phase visibly increased compared to the cal- cined sample, probably due to the higher temperature treatment. In Table I the results of the quantitative phase analysis are given together with unit cell parameter and volume for the sintered samples. The crystal structure parameters used for perovskite phase was given by the space group Pm3m, and the pyrochlore phase by Fd3m. In Table II the refinement indexes are given. We can observe that the amount of pyrochlore phase present in all samples, except for PMN10BT, does not change sig- nificantly as the amount of BT seeds increase, although the unit cell volume for both phases slightly decrease. These are indications that although Ba and Ti are incor- porated into the Pe and Py phases, their amounts are not enough to induce the formation of Pe phase as desired. For the case with 10% BT, the amount of Pe phase in- creased by 9%, and this behavior can be justified mainly due to the presence of more nucleus growth. Then only the addition of 10% of isostructural seed favors the for- mation of the perovskite phase to the detriment of the pyrochlore one in the sintered material.
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Anelastic relaxation due to hydrogen in Ti-35Nb-7Zr-5Ta alloy

Anelastic relaxation due to hydrogen in Ti-35Nb-7Zr-5Ta alloy

There were several studies of internal friction in the bcc ele- ments (as for example Nb, Ta, Zr, and Ti). Wipf et al. [22] studied polycrystalline samples of Ti and Zr containing hydrogen using mechanical spectroscopy data measured with the vibrating reed technique. In these metals, the hydrogen atoms occupy tetrahedral interstitials, forming a simple cubic lattice in the fcc ␦-phase. The jump rates follow an Arrhenius relation with activation enthalpies of 0.496 eV for the diffusion of hydrogen atoms in the titanium and zirconium metallic matrix. Yoshinari and Koiwa [23,24] studied polycrystalline samples of Nb and Ta containing hydrogen using the torsion pendulum technique, and obtained 0.114 eV and 0.084 eV for the activation enthalpies of the diffusion of hydrogen atoms by jumps into interstitial tetrahedral equivalent sites in the niobium and tantalum metallic matrix, respectively.The presence of substi- tutional atoms in Nb based alloys containing hydrogen and oxygen (or nitrogen) in solid solution increases the value of the activa- tion enthalpy [13,25,26]. In all of the studies, the heavy interstitial atoms acted as traps for hydrogen atoms. The interstitial solutes are located in octahedral sites near the substitutional solute atoms, and the activation energy for their reorientation jump was found to increase, so that the corresponding peak shifts towards a higher temperature [27].
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A CONTRIBUTION TO THE HYDROCHEMISTRY AND WATER TYPOLOGY OF THE AMAZON RIVER AND ITS TRIBUTARIES

A CONTRIBUTION TO THE HYDROCHEMISTRY AND WATER TYPOLOGY OF THE AMAZON RIVER AND ITS TRIBUTARIES

3. Intermediate (mixed) rivers with waters ranging from slightly acidic to neutral during the dry and rainy season, these rivers are originated in the Precambrian shields, and they receive contributions from different areas along their courses. In this intermediate group are included the Içá, other rivers of the west part of the Amazon basin, the Tapajos and Trombetas rivers originated from the southern and northern parts of the basin (from the archaic Precambrian shields of the Central Brazil and Guianas. respectively). This group also includes rivers such as Jutaí, Tefé and Coari (RÍOS- VILLAMIZAR et al., 2014), considered before as black water rivers, belonging to the west and central Amazon region, according to the classification of Fittkau (1964).
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Eclet. Quím.  vol.34 número1

Eclet. Quím. vol.34 número1

by phenoxo or multidentate ligand with hetero donating groups. The most frequently used ligands are polydentate Schiff base. The nature of the mag- netic interaction between Cu(II) and Gd(III) ions within polynuclear species is, in most cases, ferro- magnetic, as in dinuclear complexes. From a mag- netic point of view, well isolated dinuclear com- plexes have a great advantage for they only contain the Cu–Gd interaction parameter. On the contrary, in complexes of higher nuclearity, as in trinulcear Cu 2 Gd complexes for example, we have to take into account the desired Cu–Gd interaction but also a possible Cu–Cu interaction (antiferromagnetic, ferromagnetic or equal to zero) [1-14].
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Hydrogen peroxide induces a specific DNA base change profile in the presence of the iron chelator 2,2' dipyridyl in Escherichia coli

Hydrogen peroxide induces a specific DNA base change profile in the presence of the iron chelator 2,2' dipyridyl in Escherichia coli

the G:C→A:T transition would be due to the mispairing of damaged cytosine, in this case 5-OHdC, with adenine. In the case of 5-OHdU we can speculate that it would be converted to an AP site, since Ung is active in nth fpg double mutants, leading to base substitu- tion of C to T as a consequence of the preference for adenine insertion during translesion synthesis at an AP site. The nature of base substitution in the nth, fpg and nth fpg background is presently under investigation by our group.
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J. Braz. Chem. Soc.  vol.25 número12

J. Braz. Chem. Soc. vol.25 número12

The identification of cobalt chemical states depends on the accurate determination of the binding energy lines. The flood gun technique was used to neutralize charge build-up on the sample surface. However, the flood gun may provide more electrons to the catalyst than those leaving it. As a result, the whole catalyst surface may charge up due to the energy of the flood gun beam. For this reason, the peak energies were corrected by reference to the C1s line at 284.8 eV. In our experiments, there was an excessive charge compensation making the peaks shift to lower binding energy at values of 0.5, 0.4, 0.3 and 0.2 eV for the catalysts with cobalt loadings of 1, 2, 3 and 4 wt.%, respectively. Other authors, such as Hilmen et al., 12 have
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Braz. j. oceanogr.  vol.62 número1

Braz. j. oceanogr. vol.62 número1

Another scenario considered is the influence of the intrusion of colder and nutrient rich waters on the shelf and mixing with TW to form a Shelf Water with slightly higher concentrations of major nutrients. Pereira et al (2005) also suggested a strong influence of tidally induced vertical displacements on the eastern Brazilian shelf, which can enhance vertical mixing at the shelf break and injects cold waters into the bottom layer on the continental shelf. Amorim et al. (2011) related the occurrence of resurgence at the eastern Brazilian shelf break (13ºS, southward of Todos os Santos Bay), during summer 2007. Prevailing East and Northeast winds associated with the topography of shelf canyons, promoted a southward narrow current inducing upwelling on the inner continental shelf. In the study area, two submarine canyons (in front of Contas and Almada rivers) reach the inner shelf (FREIRE; DOMINGUEZ, 2006). The narrow shelf in this region and the presence of these canyons can favor the TW intrusion onto the shelf, as well as cold water at the bottom on the shelf, inducing the composition of inner shelf waters, and in consequence, leading to the formation of a deep chlorophyll maximum (BRANDINI et al., 2013).
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An Advancement To The Security Level Through Galois Field In The Existing Password Based Technique Of Hiding Classified Information In Images

An Advancement To The Security Level Through Galois Field In The Existing Password Based Technique Of Hiding Classified Information In Images

Such mediums are the best cover media to hide messages. Digital images are the most widespread cover files used for SG, due to their high embedding efficiency and the insensitivity of the human visual system (HVS) [3]. It is not necessary that the cover and message have a homogeneous structure. For example, it is possible to embed a recording of an audio stream message inside a digital image [4]. The simplest steganographic techniques embed the bits of the message directly into the least significant bit (LSB) plane of the cover image in a deterministic sequence [5, 6]. Different steganographic techniques focus on a variety of requirements such as robustness, tamper resistance, imperceptibility, security and capacity [7-10]. Our technique is focused on providing high security and high speed operation while maintaining imperceptibility. We are using here Galois Encoder to provide high operational speed while maintaining the security intensively. The 2BC (two bit code) technique is the basic steganography technique we are using with the Galois Operation. Galois field arithmetic has received considerable attention in recent years due to their application in public-key cryptography schemes and error correcting codes.[12] We are here using the 2BC(two bit code) and Galois Field algorithm to achieve the goal of the maximum reception of the original message signal while maintaining the losses and enhancing the speed of operation. Different steganographic techniques focus on a variety of requirements such as robustness, tamper resistance, imperceptibility, security and capacity. Our embedding technique is focused on providing security while maintaining imperceptibility. Our method can work in any transform domain, but we are illustrating the ideas in the spatial domain for convenience. The rest of the paper is divided among the following sections: section 2 explains the existing passcode based technique which involves the matching process and the embedding techniques, section 3 describes the Galois operation, section 4 and 5 explains the data transmission and retrieval process using the Galois Encoder and decoder, section 6 contains simulation result and section 7 summarizes the Conclusion.
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Boolean Representations of Simplicial Complexes and Matroids

Boolean Representations of Simplicial Complexes and Matroids

The class BR of boolean representable simplicial complexes is not closed under the most common operators, except for restriction and isomorphism, see Chapter 8. Those who seek closure under contraction and dual must restrict to matroids and use the representation theory for a fixed matroid. As it turns out, if all the contractions of a simplicial complex satisfy (PR), it must be a matroid (Proposition 8.3.6). Moreover, every simplicial complex is the contraction of a boolean representable simplicial complex (Proposition 8.3.7). Thus the concepts of minor and minor-closed subclass, so impor- tant in the contexts of graphs (Robertson-Seymour Theorem [15, Chapter 12]) and matroids (see [20]), cannot be directly applied in our generalized context. However, we can get away with restriction and isomorphism only, introducing the concept of prevariety of simplicial complexes: a class of simplicial complexes closed under restriction and isomorphism.
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Greenhouse gas emissions due to land use change in Brazil from 1990 to 2015: comparison of methodological approaches

Greenhouse gas emissions due to land use change in Brazil from 1990 to 2015: comparison of methodological approaches

ble Natural Resources (IBAMA) provided data for the years 2014, 2015, and 2016. This information was used for Cerrado. As for the other biomes, SE- EG utilizes data from the Monitoring of Deforesta- tion of Brazilian Biomes by Satellite project, which is run by IBAMA. Each forest typology is assigned a carbon stock value that considers all five IPCC pools. In order to complete the removal estimates, a reduction of 3.5% in total removals by protected areas (indigenous land or conservation unit) was adopted. This value was calculated from an estimate of the average deforestation found in the protected areas of the Amazon biome. Estimates of emissions from burning forest waste are also calculated sepa- rately from LUC GHG emissions (deforestation) considering non-CO 2 gases. SIRENE allows for emission analysis by the GWP and GTP metrics for SAR, AR4, and AR5. In this work, values given by the GWP-SAR procedure were adopted, and the emissions from waste burning were not disregarded to allow for comparison with other studies.
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Future flood risk estimates along the river Rhine

Future flood risk estimates along the river Rhine

Abstract. In Europe, water management is moving from flood defence to a risk management approach, which takes both the probability and the potential consequences of flooding into account. It is expected that climate change and socio-economic development will lead to an increase in flood risk in the Rhine basin. To optimize spatial planning and flood management measures, studies are needed that quantify future flood risks and estimate their uncertainties. In this paper, we estimated the current and future fluvial flood risk in 2030 for the entire Rhine basin in a scenario study. The change in value at risk is based on two land-use projections derived from a land-use model representing two different socio-economic scenarios. Potential damage was calculated by a damage model, and changes in flood probabilities were derived from two climate scenarios and hydrological modeling. We aggregated the results into seven sections along the Rhine. It was found that the annual expected damage in the Rhine basin may increase by between 54% and 230%, of which the major part (∼ three-quarters) can be accounted for by climate change. The highest current potential damage can be found in the Netherlands (110 billion C), compared with the second (80 billion C) and third (62 billion C) highest values in two areas in Germany. Results further show that the area with the highest fluvial flood risk is located in the Lower Rhine in Nordrhein- Westfalen in Germany, and not in the Netherlands, as is often perceived. This is mainly due to the higher flood protection standards in the Netherlands as compared to Germany.
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THE ICHTHYOFAUNA OF THE MARGINAL LAGOONS OF THE SOROCABA RIVER, SP, BRAZIL: COMPOSITION, ABUNDANCE AND EFFECT OF THE ANTHROPOGENIC ACTIONS

THE ICHTHYOFAUNA OF THE MARGINAL LAGOONS OF THE SOROCABA RIVER, SP, BRAZIL: COMPOSITION, ABUNDANCE AND EFFECT OF THE ANTHROPOGENIC ACTIONS

The fish population of the lagoons composed of small sized species, such as guaru (Phaloceros caudimaculatus), pequira (Cheirodon notomelas), canivete (Characidium fasciatum), cará (Geopha- gus brasiliensis), tilápia (Tilapia rendali) and the lambaris (Astyanax bimaculatus) usually inhabits the lagoons margins and uses macrophytes such as Salvínia sp., Elodea sp. and water lilies for feeding, shelter and egg laying. It was observed a predominance of Characiformes in relation to the number of species, and a balance in the number of individuals among the orders Characiformes, Cyprinodontiformes and Perciformes.
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Braz. J. Phys.  vol.37 número2B

Braz. J. Phys. vol.37 número2B

Recent results from lattice QCD [1], corroborated by exper- imental data from BNL-RHIC [2], indicate that strongly in- teracting matter under extreme conditions of temperature and pressure undergoes a phase transition to a deconfined plasma. Such extreme conditions are believed to have happened in the early universe, and might also be found in the core of neutron stars [3].

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Dynamics of ozone layer under Serbia and solar activity: Previous statement

Dynamics of ozone layer under Serbia and solar activity: Previous statement

Abstract: The aim of this paper is to identify ozone layer dynamics under Serbian area, as well as possible relations of change in stratospheric ozone concentration with some parameters of solar activity. During the period 1979-2005, the statistical decrease of ozone concentration was noticed under Serbian territory cumulatively for 24.5 DU (7.2%), apropos 9.4 DU (2.8%) by decade. These changes are consistent with the changes in surrounding countries. From absolute minimum 1993, flexible trend of ozone layer pentad values validate hypotheses of its recovery. Correspondence of ozone thickness extreme period with Wolf’s number and with the greatest volcanic eruptions shows that interannual variations of stratospheric ozone concentration are still in the function of natural factors above all, as are solar and volcanic activities. Investigation of larger number solar activity parameters shows statistically important antiphase synchronous between the number of polar faculae on the Sun and stratospheric ozone dynamics under Serbia. Respecting that relation between these two features until now isn’t depicted, some possible causal mechanisms are proposed.
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Braz. J. Phys.  vol.34 número2B

Braz. J. Phys. vol.34 número2B

We report ab-initio all electrons density- functional calculations for the electronic structure of the compounds MnAs and MnN, in the zinc-blende phase. They are potential materials for use in fabrication of new functional semiconductors taking advantage of the spin degree of freedom. The aim is the establishing of the semiconduc- tor spin electronics (spintronics) as a practical technology [H. Ohno, Semiconductor Science and Technology 17, 4 (2002).]. We compare results obtained using the theoretical approaches LDA (Local Density Approxi- mation) and GGA (Generalized Gradient Approximation). The calculations are spin-polarized and we follow the evolution of the band structures as a function of lattice parameter. We compare also the evolution of the density of states of the majority-spins and of the minority-spins. We conclude that, depending on the lattice parameter, both materials may be half-metallic, therefore showing conduction by charge carriers of one spin direction exclusively: the majority- spin band is continuous, while the minority-spin has a gap. Both materials reach a total magnetization of the order of 4 µ B . MnN changes from paramagnetic to ferromagnetic with the
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Dynamic reweighting of three modalities for sensor fusion.

Dynamic reweighting of three modalities for sensor fusion.

in anterior-posterior direction (i.e., sagittal plane). The visual stimulus was presented at different amplitudes (0.2 deg and 0.8 deg rotation about ankle axis) at 0.2 Hz to measure: the change in gain (weighting) to vision, an intramodal effect; and a change in gain to vibration and galvanic stimulation, both intermodal effects. For the proprioceptive sensory perturbation, bilateral vibration of Achilles tendons was applied through two 20 mm vibrator motors, driven at 80 Hz and 1 mm amplitude displacement. While vibration is a common technique, it is typically used in an always-on or always-off manner (e.g., Capicikova et al, 2006) [25]. For this study, we designed the vibrator to turn on and off quickly to approximate a square-wave periodic stimulus of a specified frequency with equal on and off time durations. The vibrators are enclosed in a hollow rectangular PVC container (3.563.863.5 cm) with a flexible recessed surface mounted on the contact face for comfortable fitting around the Achilles tendon. The enclosure was held in place by an elastic strap. The proprioceptive sensory perturbation was applied to different conditions (standing with vibration or standing without vibration) at 0.28 Hz. For the vestibular sensory perturbation, two linear isolated stimulators (Biopac Systems, Inc., Goleta, California, USA) were used as a binaural-monopolar galvanic vestibular stimulation (GVS). Independent stimuli were delivered to each side via a pair of circular electrodes secured over the mastoid
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The modification process of AlSi21CuNi silumin and its effect on change of mechanical properties of the alloy

The modification process of AlSi21CuNi silumin and its effect on change of mechanical properties of the alloy

Pouring temperature belongs to very important factors in obtainment of correct results of the modification. Hypereutectoid silumins are characteristic of good castability even in temperatures close to liquidus curve, what suggests implementation of low temperature of casting. However, such method of casting creates conditions to easy coarsening of primary crystals of silicon and their non-uniform distribution on microstructure of the casting. Rate of cooling of the alloy poured into mould has also an effect on results of the modification.
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Analysis of Water in the Chicken Eggshell Using the 1H Magic Angle Spinning Nuclear Magnetic Resonance Spectroscopy

Analysis of Water in the Chicken Eggshell Using the 1H Magic Angle Spinning Nuclear Magnetic Resonance Spectroscopy

NMR (proton Magic Angle Spinning Nuclear Magnetic Resonance spectroscopy) allows differentiating the different types of water present in the human bone. According to their study, water has three structural roles in the bone, and a few types of water reservoirs. Solid state NMR is a highly selective structural technique that can be applied for the study of the nanostructure of different biomaterials, including CE. The magnetic spin properties of the nuclei are very sensitive to the surroundings. The bonding environment, distance and abundance of other magnetic nuclei and order or disorder of the material all have an influence on the NMR proprieties in the solid state.
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COMPOSITION AND MICROSTRUCTURE OF MgAl2O4–W COMPOSITE OBTAINED BY ALUMINOTHERMIC REACTION UNDER COKE PROTECTION

COMPOSITION AND MICROSTRUCTURE OF MgAl2O4–W COMPOSITE OBTAINED BY ALUMINOTHERMIC REACTION UNDER COKE PROTECTION

(1) where x = 0, 0.4, 0.8, 1.4, 2.1 mol, respectively and mgO content kept unchanged in the process. the starting mixed powders were weighed separately according to the predetermined ratio and then dry mixed in a qmS planetary mill for 60 min. then the mixed powder was uniaxially pressed into pellets of 20 mm diameter and 12-20 mm height under the pressure of 100mpa. Samples were dried for 24 h at 110°C and calcined at various iring temperatures for 3h under coke protection. The specimens were separated from coke granules by fused spinel powder to eliminate the inluence of carbon and CO. Coke protection is a common and low cost method for carbon containing refractories from oxidization than inert atmosphere.
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