Electromagnetic Wave Scattering by Small Impedance Particles of an Arbitrary Shape

Scattering of electromagnetic (EM) waves by one and many small ($ka\ll 1$) impedance particles $D_m$ of an arbitrary shape, embedded in a homogeneous medium, is studied. Analytic formula for the field, scattered by one particle, is derived. The scattered field is of the order $O(a^{2-\kappa})$, where $\kappa \in [0,1)$ is a number. This field is much larger than in the Rayleigh-type scattering. An equation is derived for the effective EM field scattered by many small impedance particles distributed in a bounded domain. Novel physical effects in this domain are described and discussed

Bioactive secondary metabolites from Schizogyne sericea (Asteraceae) endemic to Canary Islands

Schizogyne sericea (Asteraceae) is a species endemic to the Canary Islands and traditionally employed as analgesic, astringent, anti-inflammatory and vulnerary. A comprehensive phytochemical investigation was conducted on the flowering aerial parts by analyzing both essential oil constituents and polar compounds. The essential oil was dominated by p-cymene, with the noteworthy occurrence of β-pinene and thymol esters. From the ethanolic extract eight compounds were isolated and structurally elucidated. Essential oil, polar fractions and isolates (2), (4) and (5) were separately in vitro assayed for antiproliferative activity on human tumor cell lines (A375, MDA-MB 231, HCT 116) by MTT assay, for antioxidant potential by DPPH, ABTS and FRAP assays, and for antimicrobial activity by the agar disc diffusion method. Results revealed that essential oil and compounds 1 and 2 exert a strong inhibition on tumor cells, in some cases higher than that of cisplatin. Fractions containing thymol derivatives (1 and 2) and compounds 4 and 5 displayed antioxidant activity comparable to that of Trolox, making S. sericea extract an interesting natural product with potential applications as preservative or in the treatment of diseases in which oxidative stress plays an important role

Governing effective and legitimate smart grid developments

Smart grids which use Information and Communication Technologies to augment energy network management have been developed in several locations including London and Stockholm. Common rationales for smart grids include: de-carbonising energy supply, maintaining security of supply and promoting affordability. However, beyond these general abstractions, smart grids seem to exhibit considerable diversity in terms of their characteristics and rationales for development. Thus, while the term smart grid may imply abstract notions of what smart grids are and might do, they are developed in response to local contingencies and diverse. In this paper we therefore explore the governance processes through which smart grids are constructed. The paper suggests that standardising smart grids through definitions and best practices that fix both problems and solutions should be avoided. Rather governance processes should be promoted in which local contingencies can be articulated and more legitimate smart grids developed in response to these

Multilevel seismic demand prediction for acceleration-sensitive non-structural components

Existing methods to predict the seismic demand of non-structural components in current seismic design guidelines do not generally consider the intensity of the design earthquake and the expected performance level of the lateral load bearing system. This limitation is especially important in performance-based design of buildings and industrial facilities in seismic regions. In this study, a novel multilevel approach is proposed to predict the seismic demand of acceleration-sensitive non-structural components using two new parameters obtained based on site seismicity and seismic capacity of the lateral load carrying system. The main advantage of the new method is to take into account the seismic hazard level and the expected performance level of structure in the calculation of the seismic demand of non-structural components. Based on the results of a comprehensive reliability study on 5 and 10-storey steel frame structures, the efficiency of the proposed approach is demonstrated compared to the conventional seismic design methods. The results, in general, indicate that the current standards may provide inaccurate predictions and lead to unsafe design solutions for acceleration-sensitive non-structural components, especially in the case of higher seismic intensity or medium performance levels. It is shown that the estimated accelerations by NIST and ASCE suggested equations are up to 50% and 80% lower than the minimum demand accelerations calculated for the studied structures, respectively, under the selected design conditions. Based on the results of this study, a simple but efficient design equation is proposed to estimate the maximum acceleration applied to non-structural components for different earthquake intensity levels and performance targets

Mechanical Properties of High and Very-High Strength Steel at Elevated Temperatures and After Cooling Down

High-strength steels (HSS) are produced using special chemical composition or/and manufacturing processes. Both aspects affect their mechanical properties at elevated temperatures and after cooling down, and particularly the residual strength and the ductility of the structural members. As HSS equates the design of lighter structural elements, higher temperatures are developed internally compared to the elements designed with conventional carbon steel. Therefore, the low thickness members, along with the severe effect of high temperature on the mechanical properties of the HSS, constitute to the increased vulnerability of such structures in fire. Moreover, the re-use and reinstatement of these structures are more challenging due to the lower residual mechanical properties of HSS after the cooling down period. This paper presents a review of the available experimental studies of the mechanical properties of HSS at elevated temperatures and after cooling down. The experimental results are collected and compared with the proposed material model (reduction factors) of EN1993–1-2. Based on these comparisons, modified equations describing the effect of elevated temperatures on the mechanical properties of HSS are proposed. Also, the post-fire mechanical properties of HSS are examined. A comprehensive discussion on the effect of influencing parameters, such as manufacturing process, microstructure, loading conditions, maximum temperature, and others is further explored