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Recent work has demonstrated that, for bimetallic Au–Pd systems, the rate of catalytic alcohol and formyl dehydrogenation (DH) is intrinsically linked to the rate of oxygen reduction (ORR) within the same system.

If hydrogen evolution photocatalysis are to be deployed at industrial scale, the synthesis of these photocatalytic materials must be both economically and environmentally scalable.

In oxidation reactions catalysed by supported metal nanoparticles with oxygen as the terminal oxidant, the rate of the oxygen reduction can be a limiting factor. This is exemplified by the oxidative dehydrogenation of alcohols, an important class of reactions with modern commercial applications1–3. Supported gold nanoparticles are highly active for the dehydrogenation of the alcohol to an aldehyde4 but are less effective for oxygen reduction5,6. In contrast, supported palladium nanoparticles are less active than gold for dehydrogenation but offer high efficacy for oxygen reduction5,6. This imbalance can be overcome by alloying gold with palladium which gives enhanced activity to both reactions7,8; however, the electrochemical potential of the alloy is a compromise between that of the two metals meaning that although the oxygen reduction is improved in the alloy, the dehydrogenation activity is poorer. Here we show that by separating the gold and palladium components in bimetallic carbon-supported catalysts we can almost double the reaction rate beyond that achieved with a corresponding alloy catalyst. We demonstrate this using physical mixtures of carbon-supported monometallic gold and palladium and a bimetallic catalyst comprising separated gold and palladium regions. Furthermore, we demonstrate electrochemically that this enhancement is attributable to the coupling of separate redox processes occurring at isolated gold and palladium sites. The discovery of this novel catalytic effect, a cooperative redox enhancement (CORE), offers a new approach to the design of multi-component heterogeneous catalysts.

Choreographing nanocrystal biomineralization, cation exchange, and low-temperature annealing enables synthesis of ‘green’ functionalizable quantum dots suitable for bioimaging.

This paper investigates the determinants of participation and performance in post-compulsory education, controlling for the selection into post-compulsory education and prior attainment, using a unique primary dataset on pupils studying in the post-compulsory grade in 2011-2012 from one district of the Punjab province of Pakistan. The main findings of the paper show that participation and performance in post-compulsory education are two different processes, with participation being driven by availability of post-compulsory institutions within travel distance, while performance, once in post-compulsory education, is determined by ability. The results further highlight that distance reduces participation most for those living in rural areas.

We use longitudinal panel data from the EU-SILC for the period 2005-2011 to examine the micro and macro determinants, persistence and dynamics of overeducation. The key contribution in terms of the determinants of over-education is the inclusion of macro-level explanatory variables to control for both aggregate supply and\ud aggregate demand labour market conditions. Their effects are found to be strongly significant and to have the expected sign. The article also disentangles the effect of past over-education experience on the likelihood of current over-education. Results demonstrate that over-education is not only a long-run phenomenon for many workers\ud but also that current over-education is largely due to past circumstances of the individual with this state dependence present at all career stages.

The development of scalable, green, aqueous phase, nanomaterial synthesis routes that do not sacrifice the functional performance of the materials remains a persistent challenge. Bioinspired method...

CuZnSnS (CZTS) quantum dots (QDs) have potential application in quantum dot sensitized solar cells (QDSSCs); however, traditional synthesis approaches typically require elevated temperatures, expensive precursors, and organic solvents that can hinder large-scale application. Herein we develop and utilize an enzymatic, aqueous-phase, ambient temperature route to prepare CZTS nanocrystals with good compositional control. Nanoparticle synthesis occurs in a minimal buffered solution containing only the enzyme, metal chloride and acetate salts, and l-cysteine as a capping agent and sulfur source. Beyond isolated nanocrystal synthesis, we further demonstrate biomineralization of these particles within a preformed mesoporous TiO2 anode template where the formed nanocrystals bind to the TiO2 surface. This in situ biomineralization approach facilitates enhanced distribution of the nanocrystals in the anode and, through this, enhanced QDSSC performance.

CaTiO3-supported Pt is sometimes referred to as an “Intelligent” catalyst because Pt can reversibly leave or enter the perovskite lattice following high-temperature reduction or oxidation; however,...

Nanocomposite photocatalysts offer a promising route to efficient and clean hydrogen production. However, the multistep, high-temperature, solvent-based syntheses typically utilized to prepare these photocatalysts can limit their scalability and sustainability. Biosynthetic routes to produce functional nanomaterials occur at room temperature and in aqueous conditions, but typically do not produce high-performance materials. We have developed a method to produce a highly efficient hydrogen evolution photocatalyst consisting of CdS quantum dots (QDs) supported on reduced graphene oxide (rGO) via enzyme-based syntheses combined with tuned ligand exchange-mediated self-assembly. All preparation steps are carried out in an aqueous environment at ambient temperature. Size-controlled CdS QDs and rGO are prepared through enzyme-mediated turnover of l-cysteine to HS

Photocatalysis is an attractive, sustainable, and potentially low-cost route to capture solar energy as fuel. However, current photocatalytic materials synthesis routes are not easily scaled-up to the magnitude required to impact our energy consumption due to both economic and environmental concerns. While the elements utilized are often earth abundant, typical synthetic routes utilize organic solvents at elevated temperatures with relatively expensive precursors. Herein, we demonstrate the fully biomineralized synthesis of a quantum confined CdS/reduced graphene oxide (CdS/rGO) photocatalyst catalyzed by the single enzyme cystathionine γ-lyase (CSE). The synthesis is performed at pH 9 in a buffered aqueous solution, under ambient conditions, and utilizes the low-cost precursors Cd acetate, L-cysteine, graphene oxide, and a poly-L-lysine linker molecule. CSE actively decomposes L-cysteine to generate reactive HS− in aqueous solution at pH 9. Careful selection and control of the synthesis conditions enable both reduction of graphene oxide to rGO, and control over the mean CdS nanocrystal size. The CdS is conjugated to the rGO via a poly-L-lysine crosslinker molecule introduced during rGO formation. The completed CdS/rGO photocatalyst is capable of producing H2, without the aid of a noble metal co-catalyst, at a rate of 550 μmol h−1 g−1 for an optimized CdS/rGO ratio. This rate is double that measured for unsupported CdS and is comparable to CdS/rGO photocatalysts produced using more typical chemical synthesis routes. Single enzyme biomineralization by CSE can produce a range of metal chalcogenides without altering the enzyme or benign approach, making this an easily adaptable procedure for the sustainable production of a wide variety of important photocatalyst systems.

CuZnSnS (CZTS) quantum dots (QDs) have potential application in quantum dot sensitized solar cells (QDSSCs); however, traditional synthesis approaches typically require elevated temperatures, expensive precursors, and organic solvents that can hinder large-scale application. Herein we develop and utilize an enzymatic, aqueous-phase, ambient temperature route to prepare CZTS nanocrystals with good compositional control. Nanoparticle synthesis occurs in a minimal buffered solution containing only the enzyme, metal chloride and acetate salts, and l-cysteine as a capping agent and sulfur source. Beyond isolated nanocrystal synthesis, we further demonstrate biomineralization of these particles within a preformed mesoporous TiO

Biomineralization is an intriguing route towards the low temperature, aqueous phase, green synthesis of inorganic functional nanomaterials. Herein we describe the biomineralization and optical properties of ZnxCd1−xS and ZnxCd1−xS–ZnS quantum confined nanocrystals that have potential application in optoelectronics. The reported biomineralization process is reduced to perhaps its simplest form wherein a single recombinant cystathionine γ-lyase (CSE) enzyme is responsible for catalyzing mineralization within an otherwise inert solution and plays a role in controlling the alloy composition. The biomineralized nanocrystals are sphalerite structured with average diameter below 3 nm. Biomineralization of a passivating ZnS shell on Zn0.73Cd0.27S core nanocrystals is achieved through subsequent addition of Zn precursor. This shell growth increases the photoluminescence quantum yield to 7% and increases the radiative decay time to 97.6 ns compared with 40.9 ns for the core materials.

An engineered strain of Stenotrophomonas maltophilia (SMCD1) is capable of the direct extracellular biomineralization of CdS quantum dot nanocrystals from buffered aqueous solution of cadmium acetate and l-cysteine without the addition of a chemically reactive precursor. Nanocrystal synthesis is strongly influenced by both the l-cysteine/cadmium acetate ratio and pH of the solution. The observed trends are consistent with l-cysteine acting as both a sulfur source and nanocrystal capping agent. Enzymatic turnover of l-cysteine by a putative cystathionine γ-lyase forms reactive sulfur in solution, removing the requirement for addition of reactive sodium sulfide typical of most other biomineralization approaches. The utility of the biomineralized quantum dots is demonstrated by phase transfer from the aqueous to the organic phase and subsequent incorporation into a quantum dot sensitized solar cell and chemical growth of a ZnS shell onto the biomineralized CdS core.

The crystal structure and oxygen stoichiometry of the proposed double perovskite solid oxide fuel cell (SOFC) anode material PrBaMn2O5+δ were determined under SOFC anode conditions via in-situ neutron diffraction. Measurements were performed in reducing atmospheres between 692 K and 984 K. The structure was fit to a tetragonal (space group P4/mmm) layered double perovskite structure with alternating Pr and Ba A-site cation layers. Under all conditions examined, the oxygen sites in the Ba and Mn layers were fully occupied, while the sites in the Pr layer were close to completely vacant. The results of the neutron diffraction experiments are compared to previous thermogravimetric analysis experiments to verify the accuracy of both experiments. PrBaMn2O5+δ was shown to be stable over a wide range of reducing atmospheres similar to anode operating conditions in solid oxide fuel cells without significant structural changes.

Biomineralization utilizes biological systems to synthesize functional inorganic materials for application in diverse fields. In the current work, we enable biomineralization of quantum confined PbS and PbS–CdS core–shell nanocrystals and demonstrate their application in quantum dot sensitized solar cells (QDSSCs). An engineered strain of Stenotrophomonas maltophilia is utilized to generate a cystathionine γ-lyase that is active for the biomineralization of metal sulfide nanocrystals from a buffered aqueous solution of metal salts and L-cysteine. In the presence of lead acetate, this enzymatic route generates rock salt structured PbS nanocrystals. Controlling the growth conditions yields ∼4 nm PbS crystals with absorption and photoluminescence peaks at 910 nm and 1080 nm, respectively, consistent with the expected strong quantum confinement of PbS at this size. Quantum yields (QY) of the biomineralized PbS quantum dots, determined after phase transfer to the organic phase, range between 16 and 45%. These are the highest reported QY values for any biomineralized quantum dot materials to date and are comparable with QYs reported for chemically synthesized materials. Subsequent exposure to cadmium acetate results in the biomineralization of a thin CdS shell on the PbS core with a resultant blue-shift in optical properties. The photoluminescence peak shifts to 980 nm, consistent with the expected decrease in band gap energy of a PbS–CdS core–shell heterostructured quantum dot. HAADF-STEM imaging confirms the crystalline structure and size of the particles with complimentary XEDS analysis confirming the presence of Cd, Pb, and S in individual nanocrystals. Integration of these QDs into QDSSCs yields open circuit potentials of 0.43 V and 0.59 V for PbS and PbS–CdS, respectively, consistent with expectations for these materials and previously reported values for chemically synthesized QDs.

© 2015 The Authors. Active labour market policies are popular tools used by governments to help get unemployed people back into work. It is a common problem that interventions of this type are often established with no equivalent control group on which to base an evaluation of programme effectiveness. This study uses propensity score matching to evaluate the success of an active labour market policy (the Welsh Assembly's 'Want2Work' programme) that cannot otherwise be evaluated using standard parametric techniques. Using a range of matching and estimation methods, sub-samples and types of job, the scheme was successful. Our most conservative estimate indicates that participants were 7 percentage points more likely to find employment than a control group of non-treated job-seekers. The method adopted here is a useful addition to the real world policy evaluation tool kit, where programme effectiveness needs to be judged in the absence of an established control group. Our results provide evidence that even those who are currently out of the labour market and on health related benefits can find work with the help of appropriately designed support.

This paper uses microdata for 19 African countries to examine the gender difference in maths test scores amongst primary school children. There is a significant difference in maths test scores in favour of boys, similar to that previously observed in developed countries. This difference cannot be explained by gender differences in school quality, home environment, or within-school gender discrimination in access to schooling inputs. However, the gender gap varies widely with characteristics of the regions in which the pupils live, and these regional characteristics are more predictive of the gender gap than parental education and school characteristics, including teacher gender. At the cross-country level, differences in fertility rates account for nearly half the variation in the gender gap, and this relationship is not due to the correlation between fertility and GDP nor to gender (in)equality as measured by the Gender Gap Index.

Nature provides powerful but as-yet largely unharnessed methods for low-cost, green synthesis of inorganic functional materials such as quantum dots. These materials have diverse applications from medicine to renewable energy. Harnessing nature's unique ability to achieve cost effective and scalable manufacturing solutions with reduced environmental impact is integral to realizing a future biomanufacturing economy. To address this challenge, a bacterial strain has been engineered to enable biosynthesis of CdS nanocrystals with extrinsic crystallite size control in the quantum confinement range. This strain yields extracellular, water-soluble quantum dots from low-cost precursors at ambient temperatures and pressure. The biomanufacturing approach demonstrated here produces CdS semiconductor nanocrystals with associated size-dependent band gap and photoluminescent properties.

Ruddlesden–Popper structured oxides, general form An+1BnO3n+1, consist of n-layers of the perovskite structure stacked in between rock-salt layers, and have potential application in solid oxide electrochemical cells and ion transport membrane reactors. Three materials with constant Co/Fe ratio, LaSrCo0.5Fe0.5O4−δ (n = 1), La0.3Sr2.7CoFeO7−δ (n = 2), and LaSr3Co1.5Fe1.5O10−δ (n = 3) were synthesized and studied via in situ neutron powder diffraction between 765 K and 1070 K at a pO2 of 10−1 atm. The structures were fit to a tetragonal I4/mmm space group, and were found to have increased total oxygen vacancy concentration in the order La0.3Sr2.7CoFeO7−δ > LaSr3Co1.5Fe1.5O10−δ > LaSrCo0.5Fe0.5O4−δ, following the trend predicted for charge compensation upon increasing Sr2+/La3+ ratio. The oxygen vacancies within the material were almost exclusively located within the perovskite layers for all of the crystal structures with only minimal vacancy formation in the rock-salt layer. Analysis of the concentration of these vacancies at each distinct crystallographic site and the anisotropic atomic displacement parameters for the oxygen sites reveals potential preferred oxygen transport pathways through the perovskite layers.

Given the UK finance sector is one of the largest in the world, it provides the perfect setting for a study into the nature of the finance sector wage premium. We reveal the pervasiveness of this premium, across all sub-sectors of finance, and across all occupations within finance, and with the very highest rewards going to 40-49 year old men working in London. Moreover, the UK premium has continued to rise despite the recent financial crisis. Consequently, this study uses rich data from the UK to investigate potential explanations. We find that the financial sector is more skill intensive but also that financial sector workers have higher childhood test scores vis-à-vis non-finance workers. So we investigate to what extent these higher qualifications and higher cognitive skills can explain the financial pay differential. We then go on to consider whether the financial premium is a consequence of differences in job characteristics and thus whether technological change can explain the growth in the premium. While each of these factors has some role to play, we find that none can fully explain the wage premium found in the financial sector, which we find to be pervasive across 17 OECD countries, including the US. We therefore attribute to this to rent-sharing.

This work demonstrates a bioenabled fully aqueous phase and room temperature route to the synthesis of CuInS

The surface oxygen exchange rates for NdBaCo 2 O 5 + d (NBCO), PrBaCo 2 O 5 + d (PBCO), and GdBaCo 2 O 5 + d (GBCO) were measured between 573 K and 973 K using an isotopic pulse exchange technique. Impedance spectroscopy was utilized to compare these surface rates with electrode performance. Both experiments showed NBCO to be the most active material, with both PBCO and GBCO approximately equal but with lower surface exchange rates and higher electrode area specific resistance. A discontinuity in both data sets was linked to a crystal phase transition in GBCO. It is proposed that the electrode performance is limited by the oxygen exchange rate.

Neutron powder diffraction (NPD) is a powerful tool for the characterization of oxides. Unlike X-ray diffraction where scattering occurs from the electron cloud, neutrons interact with the atomic nucleus enabling direct characterization of the oxygen sublattice. This reveals critical information related to the location, number, and mobility of oxygen anion vacancies and interstitials in hypo- and hyper-stoichiometric oxides. This review examines the growing use of in situ NPD to characterize materials for oxygen anion transport and oxygen storage in fuel cells, ion transport membranes, and as catalysts and catalyst supports. Typical measurement temperatures range between room temperature and 1200 °C, under vacuum or in controlled gas atmospheres from pure oxygen to dilute hydrogen.

The structure and oxygen stoichiometry of Ba 0.5 Sr 0.5 Co 0.5 Fe 0.5 O 3-δ (BSCF) between 793 K and 1100 K at an oxygen partial pressure of 0.1 atm were determined by in-situ neutron diffraction. Additional analysis at room temperature was conducted by synchrotron X-ray diffraction. BSCF has the cubic perovskite structure, space group Pm 3 ¯ m , for all investigated temperatures. The oxygen stoichiometry ranged from 2.26 (2) at 1100 K to 2.36 (2) at 793 K. The formation of secondary phases during long equilibration periods is suggested to be responsible for the discrepancy between oxygen stoichiometry values determined by neutron diffraction and those determined by thermogravimetry for this class of materials.

Reversible proton conducting solid oxide cells (SOCs) off a highly efficient route to matching supply from intermittent, renewable resources, with power demand by consumers. The cells would store excess electrical energy as chemical fuel during times of peak production, and operate in reverse during times of peak demand. In this study we examine the operation of anode supported proton conducting SOCs in electrolysis mode. The required overpotential for a given current density decreases with increasing humidity at the anode and increasing temperature. All of the V–I curves show distinct curvature. The electrode polarization resistance increases and electrolyte ohmic resistance decreases with increasing current density. This is accompanied by a deviation below the theoretical rate of hydrogen production. We interpret these changes as resulting from deviation away from pure proton conduction in the cell with increasing polarization.

La0.6Sr0.4CoxFe1−xO3−δ (LSCF), La0.6Sr0.4Cu0.2Fe0.8O3−δ, Ba0.5Sr0.4Co0.8Fe0.2O3−δ and LaFeO3−δ nanoparticles were synthesized by a reverse micelle procedure. Controlling the size of the micelles through the water:oil phase ratio enabled synthesis of phase pure perovskite particles with average sizes from 14 nm to 50 nm. Small amounts of an impurity phase, likely cobalt oxide, were detected in the XRD spectrum of high cobalt content samples of LSCF (x = 0.8). La0.6Sr0.4Co0.2Fe0.8O3−δ nanoparticles were utilized to coat the surface of a dense thin-film La0.6Sr0.4Co0.2Fe0.8O3−δ solid oxide fuel cell cathode. The polarization resistance of the nanoparticle coated electrode, measured at open circuit in air at 973 K, was 20% lower than an equivalent un-coated electrode.

There is growing interest in developing oxide materials for direct hydrocarbon solid oxide fuel cell anodes. In addition to electronic and ionic conductivities, the electrocatalytic activity of these materials is a critical requirement for a high performance anode. In this paper, we present evidence for the important role of variable lattice oxygen stoichiometry and anode geometry in dictating the activity and reaction mechanism of La 0.75 Sr 0.25 Cr 1 − x Mn x O 3 − δ -based anodes for CH 4 oxidation. Total oxidation of CH 4 is favored by low oxygen vacancy concentration and availability of reducible B-site cations. The non-linear dependence of electrode polarization resistance with current density is attributed to dynamic changes in lattice oxygen vacancy concentration. The relatively high open circuit potential of porous anodes compared with thin films is attributed to an increase in secondary reactions of the fuel within the porous anode.

Two decades ago, many campuses mobilized a major effort to deal with a clear problem; faculty and students needed access to desktop computing technologies. Now the situation is much more complex. Responding to the current challenges, like mobile computing and social networking, will be more difficult but equally important. There is a clear need for colleges to develop pilot projects and appropriate educational plans to prepare for these new learning environments.

Electrical conductivity relaxation (ECR) was utilized to determine the oxygen surface exchange coefficient, k chem , and bulk diffusion coefficient, D chem , for La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3 − δ (LSCF 6428) solid oxide fuel cell (SOFC) cathodes. Measurements were performed at 1073 K in the 100% to 3.3% p O 2 range. Both k chem and D chem were nearly one order of magnitude larger than previously reported values. This discrepancy is attributed to the low reliability, yet commonly utilized, two-parameter fit procedure that seeks to simultaneously determine k chem and D chem from a single measurement. The value of k chem is shown to vary by almost one order of magnitude depending on the number of terms chosen in the data fit, while the fit quality, S R , remained constant throughout. Polished LSCF 6428 samples were also individually surface-doped with La, Sr, Co, and Fe, as well as with LSCF 6428 nanoparticles (25–50 nm) to investigate trends in k chem and D chem . Fe surface doping caused a decrease in k chem , while La, Sr, Co and nanoparticle doping did not affect the oxygen surface exchange or bulk diffusion coefficients.

A pulse reactor technique was utilized to measure CH4 oxidation rates under solid oxide fuel cell (SOFC) anode conditions. La0.75Sr0.25Cr0.5Mn0.4X0.1O3−δ powders (LSCMX, X = Co, Fe, Mn and Ni) were synthesized and were found to be phase-pure perovskites, space group R3C. All compositions were determined by XRD to be stable up to 800 °C in dry 20% CH4/N2, at which point small amounts of a Ruddlesden-Poepper (RP) phase A2BO4-δ were detected. At higher temperatures, MnO and metallic Fe were observed, but no Ni and Co phases could be detected. Measurements of the CH4 reaction rates on LSCMX samples provided indirect evidence for the instability of Ni and Co containing perovskites at temperatures higher than 650 and 750 °C, respectively. At 600 and 650 °C, CH4 oxidation rates for LSCMCo and LSCMNi were similar to the rates on LSCM. At higher temperatures, CO2 and CO production on LSCMCo and LSCMNi samples was enhanced, which was ascribed to the exsolution of Co and Ni from the perovskite lattice. CO2 producti...

In this article, we explore whether an intergenerational relationship exists between the reading and mathematics test scores, taken at age 7, of a cohort of individuals born in 1958 and the equivalent test scores of their offspring measured in 1991. Our results suggest that how the parent performs in reading and mathematics during their childhood is positively related to the corresponding test scores of their offspring as measured at a similar age. The results further suggest that the effect of upbringing is mainly responsible for the intergenerational relationship in literacy, although genetic effects seem more relevant with respect to numeracy.

Cobalt doping between 2 and 10 at.% was utilized to lower the required sintering temperature of materials in the series BaCe 0.5 Zr 0.4 (Y,Yb) 0.1 − y Co y O 3 − δ to between 1373 and 1698 K. The required sintering temperature decreased with increasing Co content; however, significant electronic conductivity was observed in both oxidizing and reducing environments for materials with 10 at.% Co. This was accompanied by a loss of chemical stability in H 2 O/H 2 and CO 2 environments. BaCe 0.5 Zr 0.4 Yb 0.07 Co 0.03 O 3 − δ was stable in these environments and provided the highest proton conductivity of the materials tested, 1.98 × 10 − 3 S/cm at 923 K in humidified H 2 . Measurements in a hydrogen concentration cell indicated that the total ionic transference number for this material was between 0.86 and 1.00 with proton transference number between 0.84 and 0.75 at 773 and 973 K respectively. Under oxidizing conditions, the ionic transference number decreased to below 0.10. The grain boundary resistance dominated the total conductivity at low temperatures but was found to decrease with increased sintering temperature due to grain growth.

Perovskite-structured La0.75Sr0.25CrxMn1−xO3−δ (LSCM, x = 0 , 0.25, 0.50, 0.75, and 1) is a potential anode material for direct hydrocarbon solid oxide fuel cells (SOFCs). A pulse reactor system was used to determine the catalytic activity and selectivity of LSCM toward methane total oxidation f between 700 and 900 °C in the absence of gas-phase oxygen. This replicates the SOFC anode environment, in which oxidation occurs through reduction of the oxide lattice. Activity and selectivity were characterized as a function of lattice oxygen stoichiometry, 3 − δ . As 3 − δ decreased, the selectivity toward total oxidation decreased for all compositions due to either a change toward partial oxidation or increased dry-reforming activity. The reaction rate and range of oxygen stoichiometry favoring total oxidation increased with increasing Mn content. This was accompanied by a decrease in both carbon formation and oxide stability. These measurements suggest that more-active catalysts are required for SOFC applications.

This paper uses data from the Labour Force Survey over the period 1996–2002 to investigate the returns to a detailed list of academic and vocational qualifications. In particular, the analysis focuses on how these returns have varied over the time period considered, how the returns vary over an individual's lifetime using a pseudo cohort analysis, and how the returns vary according to the highest level of qualification obtained at school.

This paper reviews recent work on SOFC anode fabrication at the University of Pennsylvania. In this work, anode fabrication is based on the preparation of a porous YSZ matrix, into which electronic and catalytic components are added by impregnation of the appropriate metal salts. First, the methods used to prepare porous YSZ are described, along with a description of the structures that are obtained. Next, it is demonstrated that cell performance is strongly affected by the methods used to impregnate and pretreat ceria that is added to the porous YSZ. Third, the role of carbonaceous deposits within the anode is discussed. These deposits can lead to improved electronic conductivity that results in improved performance. Finally, the effect of precious-metal dopants, added to ceria to improve the catalytic properties of the anode, is discussed. Pd, Pt, and Rh are shown to give large increases in the performance of the cells, particularly in CH4.

Cathodic and anodic overpotentials were measured using current interruption and AC impedance spectroscopy for two separate solid oxide fuel cells (SOFCs). The fuel cells used yttria-stabilized zirconia (YSZ) as the electrolyte, strontium-doped lanthanum manganite (LSM) as the cathode, and a porous YSZ layer impregnated with copper and ceria as the anode. The Cu/CeO2/YSZ anode is active for the direct conversion of hydrocarbon fuels. Overpotentials measured using both current interruption and impedance spectroscopy for the fuel cell operating at 700 °C on both hydrogen and n-butane fuels are reported. In addition to providing the first electrode overpotential measurements for direct conversion fuel cells with Cu-based anodes, the results demonstrate that there may be significant uncertainties in measurements of electrode overpotentials for systems where there is a large difference between the characteristic frequencies of the anode and cathode processes and/or complex electrode kinetics.

Cet article se propose d'analyser la repartition de l'emploi a differents niveaux de competences. L'auteur tente de repondre a trois questions majeures. D'abord, il tente d'etudier la proportion de la population active qui a un faible niveau de qualification dans chaque pays et de degager l'evolution de ces proportions. Ensuite, il s'agit de porter un regard sur l'impact de ces changements sur le marche du travail. Enfin, l'auteur s'interesse a la facon d'augmenter la production d'un travail qualifie.

Dans cet article, l'auteur discute de la chute de la demande pour des travailleurs non qualifies sur le marche du travail. Il identifie et explique la cause de cette baisse par l'apparition de nouvelles competences liees aux nouvelles technologies. Il se fait egalement l'echo de recherches qui examinent les chances d'integration professionnelle par categories d'emploi pour les personnes les moins qualifiees.

This study seeks to explain changes in the proportion of 16 year olds, 17 year olds and 18 year olds who decide to participate in post-compulsory education. Four countries are considered; Germany, the Netherlands, Sweden and England, over as much of the period from 1960 to the present day as data will allow. An initial inspection of the data reveals non-stationarity in virtually all of the series under consideration, so that a cointegration framework is appropriate. The analysis therefore proceeds using the two-stage procedure proposed by Engle and Granger. The results suggest that the key variable that explains the growth in post-compulsory education participation is the increase in prior academic attainment before the end of compulsory schooling. This is the case particularly for females, males being also influenced by the returns available to offering a higher level of education, and the level of real income available to 'spend' on education. The level of youth unemployment seems to play only a small part in the decision as to whether to remain in education.

Sr2(MgMo)2O6−δ and materials of nominal compositions with increased and decreased Mo content were synthesized and their stability and catalytic activity towards CH4 oxidation characterized under solid oxide fuel cell (SOFC) anode conditions. Sr2(MgMo)2O6−δ was synthesized as a double perovskite. Materials with increased Mo content formed a mixture of the double perovskite Sr2MgMoO6−δ and the single perovskite SrMoO3, after synthesis in H2, with the amount of SrMoO3 increasing with increasing Mo content. SrMoO3 is unstable in air and slowly oxidized to the scheelite-structured impurity SrMoO4. All compositions decomposed to Mo, MgO and SrO in dry 20% CH4/N2 at temperatures ≥ 850 °C. CH4 reaction rates were catalytically limited with measured rates significantly lower than for La0.75Sr0.25Cr0.5Mn0.5O3-δ. Rates increased by 1–2 orders of magnitude when 2 wt-% of Pt was added to the surface.

Dense La 0.8 Sr 0.2 MnO 3 (LSM) film electrodes with an average thickness of 600 nm were fabricated on yttria-stabilized zirconia and cerium gadolinium oxide by ultrasonic spray pyrolysis. LSM was studied for initial nonstationary behavior by activating with current density for short duration (5 min) and long duration (16 h). The polarization resistance at zero dc bias was reduced upon activation irrespective of the electrolyte, with the reduction more significant after long-duration activation. Short-duration activation was removed by deliberate introduction of La 2 Zr 2 O 7 impurities into the LSM phase or by surface doping with La 0.6 Sr 0.4 FeO 3 nanoparticles. However, long-duration activation still occurred in these samples. Scanning electron micrographs of short-duration-activated films showed no changes in morphology while long-duration activation resulted in a significant bulk pore formation in the LSM phase. Two distinct mechanisms for LSM activation in a solid oxide fuel cell (SOFC) are proposed. Short-duration activation results in changes in the film surface chemistry while long-duration activation leads to the reconstruction of the LSM phase.

La 0.8 Sr 0.2 MnO 3-δ (LSM) film electrodes of thickness 100, 450, 650, and 700 nm were fabricated on yttria-stabilized zirconia (YSZ) electrolyte pellets by ultrasonic spray pyrolysis. In addition, 650 nm thick LSM electrodes with a surface doped with La-, Sr-, or Mn-nitrate were studied. Electrodes were deposited on both sides of the YSZ pellets in a symmetric arrangement. The individual electrode impedance spectra were measured at 973 K in laboratory air using a reference electrode placed on the free electrolyte surface. The open-circuit polarization resistance of the pure LSM and Sr and Mn surface-doped electrodes decreased significantly after initial application of cathodic current. In contrast, the La-doped sample showed no activation, with an initial polarization resistance similar to the activated, undoped LSM film. This indicates that surface La species play an important role in LSM electrode activation. All of the electrodes showed a strong, nonlinear decrease in polarization resistance accompanied by a linear decrease in ohmic resistance with increasing applied cathodic current. These changes are attributed to the introduction of a bulk-ion-transport path in the LSM film due to reduction of LSM under polarization. A minimum polarization resistance of 0.17 Ω cm 2 was measured for the La surface-doped 650 nm thick electrode at 250 mA/cm 2 .

Increasing participation in Higher Education, and the rising number of graduates in the labour markets of most developed countries, are likely to alter graduate wage distributions. Increasing wage inequality amongst graduates has been observed in a number of countries. This paper takes as an example the UK, where the increase in inequality has been amongst the highest, to investigate any potential link between these two phenomena of participation and inequality. Dividing graduates by subject of degree to provide more variation, we show that most of the increase in graduate wage inequality has occurred within subjects. We investigate two potential explanations, specifically the increase in the variance of childhood cognitive test scores amongst graduates in the same subject, and the widening variety of jobs performed by graduates with degrees in the same subject. The paper shows that both of these factors have played a role in explaining growing graduate wage inequality within subjects, though the largest is by far from the increased variance of test scores. The results also show that mean test scores are falling over time within every subject to a greater or lesser extent, suggesting that the widening variance of test scores is due to universities accepting individuals from lower in the ability distribution, as Higher Education participation has expanded.