Electromagnetic characteristics of biosilica from rice husk

Rice husk, being a widely available natural plant renewable agricultural resource, can be transformed into effective reinforcing fillers of special concrete and gypsum building materials. The samples of silica from rice husks were synthesized by thermal oxidative pyrolysis and their electromagnetic and microstructural characteristics were investigated. It was found that the rice husk itself is practically EM-wave transparent material in the frequency range of 0.1-7 GHz, while the products of its thermal oxidative pyrolysis have different microwave absorbing properties, depending on the amount of oxidizing agent used. The X-ray powder diffraction data showed the predominant presence of amorphous silica in the samples of rice husk ash with a small amount of α-quartz, α-cristobalite and α-tridymite. At a pyrolysis reaction temperature of rice husk of about 560 ± 20°C, the resulting product, in addition to amorphous silica and crystalline phases of silicon dioxide, contains traces of graphite particles, which leads to a sharp increase in dielectric characteristics and effective microwave absorption. When the temperature of the pyrolysis reaction of rice husk rises above 700°C the EM-wave absorption of such materials decreases. Thus, on the basis of the experiments carried out, the optimal ratios of rice husk and the used oxidizer of ammonium nitrate were revealed to obtain environmentally friendly ecological low-cost powder nanostructured biosilica additives for concrete and gypsum building compositions with increased effective radio absorption in the frequency range of the electromagnetic field above 1 GHz

Escaping a migrant metropolis: Post-Soviet urbanization through the art project Nasreddin in Russia

This article narrates the politics of escape from borders and labour discipline in a post-Soviet migrant metropolis drawing on the art-activism project Nasreddin in Russia. It explores the relation between control and autonomy in urban migrations through a trans-aesthetics: a set of visual and verbal stories weaving together experiences and outcomes of the art project with academic debates on late capitalist urbanization. The encounter of artistic practices and migrants’ embodied, everyday struggles to inhabit the city, it is suggested, has potential for disrupting the disciplinary and exclusionary effects of capitalist transformations and migration enforcement. This is made visible through transient spaces of escape in which the everyday lives and social worlds of migrants, constrained by the precarization of labour and by the multiplication and diversification of bordering practices, are reclaimed through laughter, mobility and care. This point is illustrated by focusing on three such spaces and practices: trickster politics in the housing market, acts of disidentification and care work on the city ‘as a body.’ The article offers a methodologically innovative contribution to ongoing debates on aesthetic political economy, cities and borders and artistic and activist interventions in global cities.Peer reviewe

Electromagnetic characteristics of biosilica from rice husk

Rice husk, being a widely available natural plant renewable agricultural resource, can be transformed into effective reinforcing fillers of special concrete and gypsum building materials. The samples of silica from rice husks were synthesized by thermal oxidative pyrolysis and their electromagnetic and microstructural characteristics were investigated. It was found that the rice husk itself is practically EM-wave transparent material in the frequency range of 0.1-7 GHz, while the products of its thermal oxidative pyrolysis have different microwave absorbing properties, depending on the amount of oxidizing agent used. The X-ray powder diffraction data showed the predominant presence of amorphous silica in the samples of rice husk ash with a small amount of α-quartz, α-cristobalite and α-tridymite. At a pyrolysis reaction temperature of rice husk of about 560 ± 20°C, the resulting product, in addition to amorphous silica and crystalline phases of silicon dioxide, contains traces of graphite particles, which leads to a sharp increase in dielectric characteristics and effective microwave absorption. When the temperature of the pyrolysis reaction of rice husk rises above 700°C the EM-wave absorption of such materials decreases. Thus, on the basis of the experiments carried out, the optimal ratios of rice husk and the used oxidizer of ammonium nitrate were revealed to obtain environmentally friendly ecological low-cost powder nanostructured biosilica additives for concrete and gypsum building compositions with increased effective radio absorption in the frequency range of the electromagnetic field above 1 GHz

Riforme agrarie e mutamenti sociali nell’Uzbekistan dell’era dell’Indipendenza

Cotton farming in Uzbekistan has been thoroughly reshaped by protracted decollectivization aimed at recovering agriculture from the post-Soviet crisis years. Based on a review of extant literature and on data collected over a socio-anthropological research in cotton-growing Khorezm region, this paper offers an overview over the Soviet-era cotton kolkhoz, post-Soviet agricultural reforms and agropolicies, and the transformations in rural society over the second post-Soviet decade. Agriculture in Uzbekistan is now resurfacing from difficult years, but old problems are perduring and prospects and burdens are more unequally distributed among stakeholders