NiO/CaAl2O4 as active oxygen carrier for low temperature chemical looping applications

The implementation of CO2 capture systems in conventional processes has been proposed by the IPCC as an effective way to reduce anthropogenic CO2 emissions. However, these capture systems may represent an important decrease in the global efficiency for conventional processes. Chemical Looping has already been demonstrated as a promising technology for more efficient CO2 capture. Novel reactor concepts have been proposed in the literature, in which the reactions take place at lower temperatures with increased overall energy efficiency. However, few investigations have been carried out regarding the behaviour of oxygen carriers at relatively low operating temperatures. In this work, an active Ni-based oxygen carrier supported on CaAl2O4 inert material has been tested and characterized. The oxygen carrier has shown a promising behaviour for low temperature applications. However, it has been demonstrated that the oxygen carrier has to be pre-treated because of an interesting activation process which takes place only at high reduction temperatures. Oxygen carrier activation is caused by a reorganization of superficial nickel. Fresh oxygen carrier is covered by a layer of nickel with a strong interaction with the support. However, once the sample is reduced at high temperatures Ni is reorganized into small grains with reduced interaction with the support. This results in an enhancement in the reactivity and a higher oxygen transport capacity. After about 200 redox cycles, a small decrease in the solid conversion is observed due to agglomeration of the NiO grains. Nevertheless, the redox kinetics is still sufficiently fast for low temperature applications, provided that the oxygen carrier is pre-activated. The kinetics rates for the gas–solid reactions and gas-phase catalytic reactions have been determined, which can be used to predict the performance of the activated NiO/CaAl2O4 oxygen carrier for low temperature chemical looping applications

Dissipative Dynamics of a Josephson Junction In the Bose-Gases

The dissipative dynamics of a Josephson junction in the Bose-gases is considered within the framework of the model of a tunneling Hamiltonian. The effective action which describes the dynamics of the phase difference across the junction is derived using functional integration method. The dynamic equation obtained for the phase difference across the junction is analyzed for the finite temperatures in the low frequency limit involving the radiation terms. The asymmetric case of the Bose-gases with the different order parameters is calculated as well

An early Cambrian greenhouse climate

The oceans of the early Cambrian (~541 to 509 million years ago) were the setting for a marked diversification of animal life. However, sea temperatures — a key component of the early Cambrian marine environment — remain unconstrained, in part because of a substantial time gap in the stable oxygen isotope (delta 18 O) record before the evolution of euconodonts. We show that previously overlooked sources of fossil biogenic phosphate have the potential to fill this gap. Pristine phosphatic microfossils from the Comley Limestones, UK, yield a robust delta 18 O signature, suggesting sea surface temperatures of 20° to 25°C at high southern paleolatitudes (~65°S to 70°S) between ~514 and 509 million years ago. These sea temperatures are consistent with the distribution of coeval evaporite and calcrete deposits, peak continental weathering rates, and also our climate model simulations for this interval. Our results support an early Cambrian greenhouse climate comparable to those of the late Mesozoic and early Cenozoic, offering a framework for exploring the interplay between biotic and environmental controls on Cambrian animal diversification

Electrochemical behavior of Ti/Al2O3 interfaces produced by diffusion bonding

In the field of biomedical applications a special interest exists regarding the study of the physicochemical and mechanical behaviour of materials, with special focus on the electrochemical degradation of metal/ceramic interfaces. In fact, etal/ceramic interfaces may be present in several biomedical devices, ranging from external or implantable sensors, to dental implants. Diffusion bonding represents an important technique since, in opposition to other production technologies, such as active metal brazing, avoid the possible liberation of certain chemical components harmful to health. The aim of this work is to study the electrochemical degradation of the interface formed between commercially pure Ti and Al2O3 produced by diffusion bonding, in contact with a physiological solution. The present approach included the evaluation of the contribution of individual and pairs of interfacial layers on the global degradation processes. For this propose d.c. electrochemical techniques were used to monitor the open-circuit potential, and to perform potentiodynamic polarization and galvanic corrosion evaluation. Also, electrochemical impedance spectroscopy was used as a complementary technique of the corrosion behaviour of the interface. Chemical composition and morphology of samples and corrosion products were evaluated by SEM and EDS analysis. According to experimental results, two principal reaction layers were formed in the interface: TiAl and Ti3Al. The TiAl layer appears to be the responsible for the strong increase in corrosion rate of the interface.Fundação para a Ciência e Tecnologia -POCTI/CTM/33384/2000; SFRH/BPD/ 5518/2001

Resonances in the three-neutron system

A study of 3-body resonances has been performed in the framework of configuration space Faddeev equations. The importance of keeping a sufficient number of terms in the asymptotic expansion of the resonance wave function is pointed out. We investigated three neutrons interacting in selected force components taken from realistic nn forces.Comment: 38 pages, 11 tables, 4 figure

An attempt to understand exclusive pi+ electroproduction

Hard exclusive pi+ electroproduction is investigated within the handbag approach. The prominent role of the pion-pole contribution is demonstrated. It is also shown that the experimental data require a twist-3 effect which ensues from the helicity-flip generalized parton distribution H_T and the twist-3 pion wave function. The results calculated from this handbag approach are compared in detail with the experimental data on cross sections and spin asymmetries measured with a polarized target. It is also commented on consequences of this approach for exclusive \pi^0 and vector-meson electroproduction.Comment: 35 pages, 12 figures, using Latex, a number of additional comments have been included in the text, e.g. in paragraph above (3) or at end of sect.

Assessing the appropriateness of the management of upper respiratory tract infection in Australian children: a population-based sample survey

OBJECTIVE:To assess the proportion of Australian children aged 0-15 years that received care in line with clinical practice guidelines (CPGs) for upper respiratory tract infections (URTIs). DESIGN:Retrospective medical record review using a multistage sampling strategy. SETTING:General practices, hospital emergency departments and hospital inpatient service providers in three Australian states. PARTICIPANTS:Children aged up to 15 years who received care for URTI in 2012 and 2013. PRIMARY AND SECONDARY OUTCOME MEASURES:The primary assessment was estimated adherence with 14 indicators of appropriate care as documented in medical records. Indicators were extracted from national and international CPGs and ratified by experts. Secondary assessment was adherence to two bundles of indicators (diagnostic symptoms and medical history taking), where all indicators must be adherent for the bundle to be scored as adherent. RESULTS:There were 1653 children with one or more assessments of URTI care to CPG adherence. Over half of the children were under 3 years of age, with roughly equal numbers of males and females. Three indicators had fewer than 25 visits so were not reported. Overall adherence ranged from 0.5% for 'documented advice around antibiotics' to 88.3% for 'documentation of medical history'. Adherence with Bundle A (documentation of all three definitive symptoms) was 43.1% (95% CI 32.8% to 54.0%) and Bundle B (documentation of all four indicators of medical history) was 30.2% (95% CI 20.9% to 40.9%). CONCLUSIONS:URTIs in children are common, usually self-limiting, conditions that are allocated considerable resources. The results suggest that there may be a need for more thorough holistic assessment of the patient and improved documentation. Since inappropriate prescription of antibiotics for URTIs is still a known problem in Australia, there is a need for consistent, clear communication around antibiotics' lack of impact on symptoms and a high association with undesirable side effects.Janet C Long, Helena M Williams, Shefali Jani, Gaston Arnolda, Hsuen P Ting, Charlotte J Molloy ... et al