Influence of finite size effect on magnetic and magnetotransport properties of La0.5Sr0.5CoO3 thin films

We present a comprehensive study of the thickness dependent structural, magnetic and magnetotransport properties of oriented La0.5Sr0.5CoO3 thin films grown on LaAlO3 by Pulsed Laser Deposition. We observe that these films undergo a reduction in Curie temperature (T-c) with a decrease in film thickness, and it is found to be primarily caused by the finite size effect since the finite scaling law [T-c(infinity) T-c(t)/T-c(infinity) = (c/t)lambda holds good over the studied thickness range. We rule out the contribution from the strain induced suppression of Curie temperature with decreasing film thickness since all the films exhibit a constant out of plane tensile strain (0.5%) irrespective of their varying thickness. However, we observe that the coercivity of the films is an order of magnitude higher than that of the bulk due to the tensile strain. In addition, we also observe an increase in the magneto resistance peak and a decrease in coercivity and electrical resistivity with an increase in film thickness. (C) 2010 Elsevier Ltd. All rights reserved.

With Good Reputation Size Does not Matter: Issue Frequency and the Determinants of Debt Maturity

This paper examines empirically the effect firm reputation has on the determinants of debt maturity. Utilising data from European primary bond market between 1999 and 2005, I find that the maturity choice of issuers with a higher reputation is less sensitive to macroeconomic conditions, market credit risk-premiums, prevailing firm credit quality and size of the debt issue. The annualised coupon payments are shown to be a significant factor in determining the debt maturity and reveal a monotonously increasing relationship between credit quality and debt maturity once controlled for. Finally, I show that issuers lacking a credit rating have an implied credit quality positioned between investment-grade and speculative-grade debt.

Overconfidence and investor size

Recent research documents that institutional or large investors act as antagonists to other investors by showing opposite behavior following disclosure of new information. Using an extremely comprehensive official transactions data set from Finland, we set out to explore the interrelation between investor size and behavior. More specifically, we test whether investor size is positively (negatively) correlated with investor reaction following positive (negative) news. We document robust evidence of that investor size affects investor behavior under new information, as larger investors on average react more positively (negatively) to good (bad) news than smaller investors. In the light of this study it seems increasingly feasible that several recent findings of heterogeneous investor behavior are functions of differences in overconfidence.

On the complexity of finding stopping set size in Tanner Graphs

The problem of determining whether a Tanner graph for a linear block code has a stopping set of a given size is shown to be NT-complete.

Interfacial coupling and its size dependence in PbTiO3 and PbMg1/3Nb2/3O3 multilayers

Multilayers of Pb(Mg1/3Nb2/3)O-3 (PMN)-PbTiO3 (PT) were deposited through pulsed laser ablation deposition with different periodicities (d=10, 20, 30, 40, 50, 60, and 70 nm) for a constant total thickness of the film. The presence of superlattice reflections in the x-ray diffraction pattern clearly showed the superlattice behavior of the fabricated structures over a periodicity range of 20-50 nm. Polarization hysteresis and the capacitance-voltage characteristics of these films show clear size dependent ferroelectric and antiferroelectric (AFE) characteristics. Presence of long-range coupling and strain in multilayers with lower periodicity (similar to 10 nm) exhibited a clear ferroelectric behavior similar to a solid solution of PMN and PT. Multilayers with higher periodicities (20-50 nm) exhibited antiferroelectric behavior, which could be understood from the energy arguments. On further increase of periodicity, they again exhibit ferroelectric behavior. The polarization studies were carried out beyond the Curie temperature T-c of PMN to understand the interlayer interaction. The interaction is changed to a ferroelectric-paraelectric interlayer and tends to lose its antiferroelectric behavior. The behavior of remnant polarization P-r and dP(r)/dT with temperature clearly proves that the AFE coupling of these superlattices is due to the extrinsic interfacial coupling and not an intrinsic interaction as in a homogeneous conventional AFE material. The evidence of an averaged behavior at a periodicity of similar to 10 nm, and the behavior of individual materials at larger periodicities were further confirmed through dielectric phase transition studies. The presence of AFE interfacial coupling was insignificant over the dielectric phase transition of the multilayers.

Breakdown in p‐n junction diodes made on polycrystalline silicon of large grain size

This communication describes the voltage‐current characteristics in the breakdown region of p‐n junctions made on polycrystalline silicon of large grain size. The observed soft breakdown characteristics have been explained by taking into account the effect of curvature of the junction near the grain boundaries.

Size effect in self consolidating concrete beams with and without notches

The aim of this study is to obtain the fracture characteristics of low and medium compressive strength self consolidating concrete (SCC) for notched and un-notched plain concrete beams by using work of fracture G(F) and size effect model G(f) methods and comparing them with those of normal concrete and high performance concrete. The results show that; (i) with an increase in compressive strength, G(F) increases and G(f) decreases; (ii) with an increase in depth of beam, the decrease in nominal stress of notched beam is more when compared with that of a notchless beam.

Size-Dependent Melting of Finite-Length Nanowires

We report on the size-dependent melting of nanowires with finite length based on the thermodynamic as well as liquid drop model. It has been inferred that the length dependency cannot be ignored, unlike the case of infinite length nanowires. To validate the length dependency, we have analyzed a few experimental results reported in the literature.

Appropriate Institutions and Economic Growth - one size fits no-one

Modern-day economics is increasingly biased towards believing that institutions matter for growth, an argument that has been further enforced by the recent economic crisis. There is also a wide consensus on what these growth-promoting institutions should look like, and countries are periodically ranked depending on how their institutional structure compares with the best-practice institutions, mostly in place in the developing world. In this paper, it is argued that ”non-desirable” or “second-best” institutions can be beneficial for fostering investment and thus providing a starting point for sustained growth, and that what matters is the appropriateness of institutions to the economy’s distance to the frontier or current phase of development. Anecdotal evidence from Japan and South-Korea is used as a motivation for studying the subject and a model is presented to describe this phenomenon. In the model, the rigidity or non-rigidity of the institutions is described by entrepreneurial selection. It is assumed that entrepreneurs are the ones taking part in the imitation and innovation of technologies, and that decisions on whether or not their projects are refinanced comes from capitalists. The capitalists in turn have no entrepreneurial skills and act merely as financers of projects. The model has two periods, and two kinds of entrepreneurs: those with high skills and those with low skills. The society’s choice of whether an imitation or innovation – based strategy is chosen is modeled as the trade-off between refinancing a low-skill entrepreneur or investing in the selection of the entrepreneurs resulting in a larger fraction of high-skill entrepreneurs with the ability to innovate but less total investment. Finally, a real-world example from India is presented as an initial attempt to test the theory. The data from the example is not included in this paper. It is noted that the model may be lacking explanatory power due to difficulties in testing the predictions, but that this should not be seen as a reason to disregard the theory – the solution might lie in developing better tools, not better just better theories. The conclusion presented is that institutions do matter. There is no one-size-fits-all-solution when it comes to institutional arrangements in different countries, and developing countries should be given space to develop their own institutional structures that cater to their specific needs.

European aspen and hybrid aspen under changing environment : Leaf traits, growth and litter decomposition

Understanding the responses of species and ecosystems to human-induced global environmental change has become a high research priority. The main aim of this thesis was to investigate how certain environmental factors that relate to global change affect European aspen (Populus tremula), a keystone species in boreal forests, and hybrid aspen (P. tremula × P. tremuloides), cultivated in commercial plantations. The main points under consideration were the acclimatization potential of aspen through changes in leaf morphology, as well as effects on growth, leaf litter chemistry and decomposition. The thesis is based on two experiments, in which young aspen (< 1 year) were exposed either to an atmospheric pollutant [elevated ozone (O3)] or variable resource availability [water, nitrogen (N)]; and two field studies, in which mature trees (> 8 years) were growing in environments exposed to multiple environmental stress factors (roadside and urban environments). The field studies included litter decomposition experiments. The results show that young aspen, especially the native European aspen, was sensitive to O3 in terms of visible leaf injuries. Elevated O3 resulted in reduced biomass allocation to roots and accelerated leaf senescence, suggesting negative effects on growth in the long term. Water and N availability modified the frost hardening of young aspen: High N supply, especially when combined with drought, postponed the development of frost hardiness, which in turn may predispose trees to early autumn frosts. This effect was more pronounced in European aspen. The field studies showed that mature aspen acclimatized to roadside and urban environments by producing more xeromorphic leaves. Leaf morphology was also observed to vary in response to interannual climatic variation, which further indicates the ability of aspen for phenotypic plasticity. Intraspecific variation was found in several of the traits measured, although intraspecific differences in response to the abiotic factors examined were generally small throughout the studies. However, some differences between clones were found in sensitivity to O3 and the roadside environment. Aspen leaf litter decomposition was retarded in the roadside environment, but only initially. By contrast, decomposition was found to be faster in the urban than the rural environment throughout the study. The higher quality of urban litter (higher in N, lower in lignin and phenolics), as well as higher temperature, N deposition and humus pH at the urban site were factors likely to promote decay. The phenotypic plasticity combined with intraspecific variation found in the studies imply that aspen has potential for withstanding environmental changes, although some global change factors, such as rising O3 levels, may adversely affect its performance. The results also suggest that the multiple environmental changes taking place in urban areas which correspond closely with the main drivers of global change can modify ecosystem functioning by promoting litter decomposition, mediated partly by alterations in leaf litter quality.

Approximate multipole coefficients of RF ion traps as functions of aperture size

In this study we present approximate analytical expressions for estimating the variation in multipole expansion coefficients as a function of the size of the apertures in the electrodes in axially symmetric (3D) and two-dimensional (2D) ion trap ion traps. Following the approach adopted in our earlier studies which focused on the role of apertures to fields within the traps, here too, the analytical expression we develop is a sum of two terms, A(n,noAperiure), the multipole expansion coefficient for a trap with no apertures and A(n,dueToAperture), the multipole expansion coefficient contributed by the aperture. A(n,noAperture) has been obtained numerically and A(n,dueToAperture) is obtained from the n th derivative of the potential within the trap. The expressions derived have been tested on two 3D geometries and two 2D geometries. These include the quadrupole ion trap (QIT) and the cylindrical ion trap (CIT) for 3D geometries and the linear ion trap (LIT) and the rectilinear ion trap (RIT) for the 2D geometries. Multipole expansion coefficients A(2) to A(12), estimated by our analytical expressions, were compared with the values obtained numerically (using the boundary element method) for aperture sizes varying up to 50% of the trap dimension. In all the plots presented, it is observed that our analytical expression for the variation of multipole expansion coefficients versus aperture size closely follows the trend of the numerical evaluations for the range of aperture sizes considered. The maximum relative percentage errors, which provide an estimate of the deviation of our values from those obtained numerically for each multipole expansion coefficient, are seen to be largely in the range of 10-15%. The leading multipole expansion coefficient, A(2), however, is seen to be estimated very well by our expressions, with most values being within 1% of the numerically determined values, with larger deviations seen for the QIT and the LIT for large aperture sizes. (C) 2010 Elsevier B.V. All rights reserved.

Effect of grain size and texture on the mechanical properties of warm worked cadmium-1.5 Pct zinc alloy

The structural changes occurring during warm working of Cd-1.5 pct Zn alloy and their effect on the subsequent mechanical properties are studied. It is observed that changes in grain size and preferred orientation are important to a large extent in controlling the mechanical strength. The Hall-Petch slope,R decreases in the warm worked material while the friction stress, σo increases. The lowerR values are attributed to the development of a (101l) texture and the higher σo values are interpreted on the basis of changes in the basal texture.