Directionally asymmetric self-assembly of cadmium sulfide nanotubes using porous alumina nanoreactors: Need for chemohydrodynamic instability at the nanoscale

We explore nanoscale hydrodynamical effects on synthesis and self-assembly of cadmium sulfide nanotubes oriented along one direction. These nanotubes are synthesized by horizontal capillary flow of two different chemical reagents from opposite directions through nanochannels of porous anodic alumina which are used primarily as nanoreactors. We show that uneven flow of different chemical precursors is responsible for directionally asymmetric growth of these nanotubes. On the basis of structural observations using scanning electron microscopy, we argue that chemohydrodynamic convective interfacial instability of multicomponent liquid-liquid reactive interface is necessary for sustained nucleation of these CdS nanotubes at the edges of these porous nanochannels over several hours. However, our estimates clearly suggest that classical hydrodynamics cannot account for the occurrence of such instabilities at these small length scales. Therefore, we present a case which necessitates further investigation and understanding of chemohydrodynamic fluid flow through nanoconfined channels in order to explain the occurrence of such interfacial instabilities at nanometer length scales.Comment: 26 pages, 6 figures; http://www.iiserpune.ac.in/researchhighlight

The effect of electrodeposition conditions on morphology and composition of sn-snsb deposits

Sn-SnSb films were electrochemically deposited on the Cu and Cu/Au substrates by simple galvanostatic electrodeposition from a chloride-based solution. Dense, adherent and quite homogeneous deposits were obtained and the effect of current density on morphology and composition of as synthesized materials was investigated. It was found that with increasing current density the size of particles decreases and deposits become smoother and more homogeneous. Moreover, antimony content in the deposit decreases with increasing current density independently of the type of substrate. Both, Sn and SnSb metallic compound phases were identified in the samples by XRD analysis.Sn-SnSb пленки были осаждены электрохимически на Cu и Cu/Au субстраты простым гальваностатическим методом из хлоридных растворов. Были получены плотные, прочные и достаточно гомогенные покрытия и исследовано влияние плотности тока на морфологию и состав синтезированных материалов. Было показано, что с повышением плотности тока размер частиц уменьшается и осадки становятся более гладкими и гомогенными. Кроме того, с повышением плотности тока содержание сурьмы в осадке уменьшается независимо от типа субстрата. Наличие металлических фаз Sn и SnSb в образцах была идентифицирована методом рентгеновского анализа.Sn-SnSb плівки були осаджені електрохімічно на Cu та Cu/Au субстрати простим гальваностатичним методом з хлоридних розчинів. Були отримані щільні, міцні та достатньо гомогенні покриття та досліджений вплив густини струму на морфологію та склад синтезованих матеріалів. Було показано, що з підвищенням густини струму розмір частинок зменшується і осади стають більш гладкими та гомогенними. Крім того, з підвищенням густини струму вміст сурми в осаді зменшується незалежно від типу субстрату. Наявність металевих фаз Sn та SnSb в зразках була ідентифікована методом рентгенівського аналізу

‘Albania: €1’ or the story of ‘big policies, small outcomes’: how Albania constructs and engages its diaspora

Since the fall of the communist regime in the early 1990s, Albania has experienced one of the most significant emigrations in the world as a share of its population. By 2010 almost half of its resident population was estimated to be living abroad – primarily in neighbouring Greece and Italy, but also in the UK and North America. This chapter discusses the emergence and establishment of the Albanian diaspora, its temporal and geographical diversity, and not least its involvement with Albania itself. Albania’s policymaking and key institutions are considered, with a focus on matters of citizenship; voting rights; the debate on migration and development; and not least the complex ways in which kin-state minority policies – related to ethnic Albanians living in Kosovo, Montenegro, southern Serbia, Macedonia and Greece – are interwoven with Albania’s emigration policies

A Dynamic View of Domain-Motif Interactions

Many protein-protein interactions are mediated by domain-motif interaction, where a domain in one protein binds a short linear motif in its interacting partner. Such interactions are often involved in key cellular processes, necessitating their tight regulation. A common strategy of the cell to control protein function and interaction is by post-translational modifications of specific residues, especially phosphorylation. Indeed, there are motifs, such as SH2-binding motifs, in which motif phosphorylation is required for the domain-motif interaction. On the contrary, there are other examples where motif phosphorylation prevents the domain-motif interaction. Here we present a large-scale integrative analysis of experimental human data of domain-motif interactions and phosphorylation events, demonstrating an intriguing coupling between the two. We report such coupling for SH3, PDZ, SH2 and WW domains, where residue phosphorylation within or next to the motif is implied to be associated with switching on or off domain binding. For domains that require motif phosphorylation for binding, such as SH2 domains, we found coupled phosphorylation events other than the ones required for domain binding. Furthermore, we show that phosphorylation might function as a double switch, concurrently enabling interaction of the motif with one domain and disabling interaction with another domain. Evolutionary analysis shows that co-evolution of the motif and the proximal residues capable of phosphorylation predominates over other evolutionary scenarios, in which the motif appeared before the potentially phosphorylated residue, or vice versa. Our findings provide strengthening evidence for coupled interaction-regulation units, defined by a domain-binding motif and a phosphorylated residue

Motif co-regulation and co-operativity are common mechanisms in transcriptional, post-transcriptional and post-translational regulation

A substantial portion of the regulatory interactions in the higher eukaryotic cell are mediated by simple sequence motifs in the regulatory segments of genes and (pre-)mRNAs, and in the intrinsically disordered regions of proteins. Although these regulatory modules are physicochemically distinct, they share an evolutionary plasticity that has facilitated a rapid growth of their use and resulted in their ubiquity in complex organisms. The ease of motif acquisition simplifies access to basal housekeeping functions, facilitates the co-regulation of multiple biomolecules allowing them to respond in a coordinated manner to changes in the cell state, and supports the integration of multiple signals for combinatorial decision-making. Consequently, motifs are indispensable for temporal, spatial, conditional and basal regulation at the transcriptional, post-transcriptional and post-translational level. In this review, we highlight that many of the key regulatory pathways of the cell are recruited by motifs and that the ease of motif acquisition has resulted in large networks of co-regulated biomolecules. We discuss how co-operativity allows simple static motifs to perform the conditional regulation that underlies decision-making in higher eukaryotic biological systems. We observe that each gene and its products have a unique set of DNA, RNA or protein motifs that encode a regulatory program to define the logical circuitry that guides the life cycle of these biomolecules, from transcription to degradation. Finally, we contrast the regulatory properties of protein motifs and the regulatory elements of DNA and (pre-)mRNAs, advocating that co-regulation, co-operativity, and motif-driven regulatory programs are common mechanisms that emerge from the use of simple, evolutionarily plastic regulatory modules