Micro helical polymeric structures produced by variable voltage direct electrospinning

Direct near field electrospinning is used to produce very long helical polystyrene microfibers in water. The pitch length of helices can be controlled by changing the applied voltage, allowing to produce both micro springs and microchannels. Using a novel high frequency variable voltage electrospinning method we found the helix formation speed and compared the experimental buckling frequency to theoretical expressions for viscous and elastic buckling. Finally we showed that the newmethod can be used to produce new periodic micro and nano structures.Comment: accepted for publication in Soft Matte

Microspore embryogenesis: assignment of genes to embryo formation and green vs. albino plant production

Plant microspores can be reprogrammed from their normal pollen development to an embryogenic route in a process termed microspore embryogenesis or androgenesis. Stress treatment has a critical role in this process, inducing the dedifferentiation of microspores and conditioning the following androgenic response. In this study, we have used three barley doubled haploid lines with similar genetic background but different androgenic response. The Barley1 GeneChip was used for transcriptome comparison of these lines after mannitol stress treatment, allowing the identification of 213 differentially expressed genes. Most of these genes belong to the functional categories “cell rescue, defense, and virulence”; “metabolism”; “transcription”; and “transport”. These genes were grouped into clusters according to their expression profiles among lines. A principal component analysis allowed us to associate specific gene expression clusters to phenotypic variables. Genes associated with the ability of microspores to divide and form embryos were mainly involved in changes in the structure and function of membranes, efficient use of available energy sources, and cell fate. Genes related to stress response, transcription and translation regulation, and degradation of pollen-specific proteins were associated with green plant production, while expression of genes related to plastid development was associated with albino plant regeneration

The Influencing Factors on Population Growth in Metropolises from the Viewpoints of Experts: Case Study of Tehran

The present paper aims to find the factors influencing population growth in metropolises and thus provide a model for population growth in large cities based on expert opinions. Considering the fact that the multiple factors associated with life in the metropolis, affecting immigration, fertility and mortality, are from different fields, including economic, social, and cultural domains, this article is of an interdisciplinary nature. In the present article while the theoretical concepts are reviewed, the important factors affecting population growth are identified, and then grouped and studied as economic, cultural and social, geographical, infrastructural and urban facilities factors; following that a basic conceptual model is extracted. In this paper, a researcher-made questionnaire is distributed among thirty experts on demography, sociology, and economics. The analytic hierarchy process (AHP) applied in this study showed that the “economic factors” have the greatest impact on the population growth in the metropolis of Tehran; and socio-cultural, infrastructural and geographical factors and urban facilities have lesser impacts. Also, in the final prioritizing, of the eleven sub-factors, the sub-factors of occupation, income, lifestyle, individual values and the cost of living, which had the greatest weight, were analyzed. At the end, the final model of population growth in metropolises is provided

A multi-antenna coded caching scheme with linear subpacketization

Abstract Exponentially growing subpacketization is known to be a major issue for practical implementation of coded caching, specially in networks with multi-antenna communication setups. We provide a new coded caching scheme for such networks, which requires linear subpacketization and is applicable to any set of network parameters, as long as the multi-antenna gain L is larger than or equal to the global caching gain t. Our scheme includes carefully designed cache placement and delivery algorithms; which are based on circular shift of two generator arrays in perpendicular directions. It also achieves the maximum possible degrees of freedom of t+L, during any transmission interval

Subpacketization:beamformer interaction in multi-antenna coded caching

Abstract We study the joint effect of beamformer structure and subpacketization level on the achievable rate of cache-enabled multi-antenna communications. We use appropriate low-SNR approximations, to show that using simple zero-forcing (ZF) beamformers, increasing subpacketization degrades the achievable rate; in contrast to what has been shown in the literature for more complex, optimized beamformers. We also numerically analyze the probability distribution of symmetric rate terms, in order to confirm the validity of mathematical outputs. The results suggest that for improving the content delivery rate at low-SNR, subpacketization level and beamformer complexity should be jointly increased