Search results for "Small"

Bulk morphologies of polystyrene-block-polybutadiene-block-poly(tert-butyl methacrylate) triblock terpolymers

2015

Abstract The self-assembly of block copolymers in the bulk phase enables the formation of complex nanostructures with sub 100 nm periodicities and long-range order, both relevant for nanotechnology applications. Here, we map the bulk phase behavior of polystyrene-block-polybutadiene-block-poly(tert-butyl methacrylate) (SBT) triblock terpolymers on a series of narrowly distributed polymers with widely different block volume fractions, ϕS, ϕB and ϕT. In dependence of ϕ, we find the lamella–lamella, core-shell cylinder, cylinder-in-lamella and core-shell gyroid morphology, but also a rarely observed cylinder-in-lamella phase. The bulk morphologies are thoroughly characterized by transmission e…

Formation of α-ω(4,7,10,13-pentaoxa-16-azacyclooctadecane) hexadecane micelles in aqueous solution – effect of HCl addition

2003

The structure of aggregates of a new bolaform surfactant [α-ω (4,7,10,13-pentaoxa-16-azacyclooctadecane) hexadecane] in neat aqueous solution has been investigated by small-angle neutron scattering. Preliminary data analysis unequivocally indicates that globular micelles are formed. This finding has been confirmed by the analysis of data obtained upon addition of hydrochloric acid. The observed significant reduction of micelle aggregation number has been attributed to the peculiar complexing ability of the two aza-crown ether units in the surfactant molecule; this is in line with information inferred from the complexation of ions into the non alkylated azacrown ethers. As a consequence of h…

Investigating self-assembly and metal nanoclusters in aqueous di-block copolymers solutions

2002

Self-assembling properties of di-block copolymers/ surfactant hybrids in aqueous solution can be exploited to obtain metal nanoparticles stable dispersion. Results will be presented here for polystyrene-block-poly(ethylene oxide) solutions. A SANS structural investigation has been performed over different molecular weights of both hydrophilic and hydrophobic block, by varying temperature and concentration of the copolymer. A SAXS characterization of micellar systems containing Pt nanoparticles is reported.

Vitrification in restricted geometry: dry films of colloidal particles

2007

We prepared dry films of colloidal particles from surfactant co-stabilized polystyrene and poly(methyl methacrylate) latex spheres of moderate polydispersity. The film thickness was varied from monolayer to some 20 μm. The average structure and the influence of polydispersity was analyzed by small-angle X-ray scattering. An analysis of local microscopic structures was performed by force microscopy on the least polydisperse sample. Irrespective of the thickness, we observe the formation of only short-ranged order which is rather pronounced but changes its qualitative character in the vicinity of the substrate. The observations suggest a bulk structure of small, defect-rich and stacking fault…

Conformation of polyethylene molecules in the melt as revealed by small-angle neutron scattering

1975

1985

Samples of ring and open chain polystyrene in dilute perdeuterated toluene solution were measured by small angle neutron scattering up to a value of the scattering vector Q = 2 nm−1. The molar masses 12000 ≤ M/(g/mol) ≤ 22000, the mean square radii of gyration 〈R2〉 and the second virial coefficients A2 of the samples were determined. The results are compared to theories which describe the dependencies 〈R2〉 = f(M) and A2 = f(M) for both cyclic and linear chain molecules. A qualitative agreement between theory and experiment is obtained.

PCARE and WASF3 regulate ciliary F-actin assembly that is required for the initiation of photoreceptor outer segment disk formation

2020

Significance The photoreceptor outer segments are primary cilia, modified for phototransduction by incorporation of stacked opsin-loaded membrane disks that are continuously regenerated. This process is disrupted in several types of inherited retinal dystrophy, but the driving force remained unclear. We show that C2orf71/PCARE (photoreceptor cilium actin regulator), associated with inherited retinal dystrophy subtype RP54, efficiently recruits the Arp2/3 complex activator WASF3 to the cilium. This activates an actin dynamics-driven expansion of the ciliary tip, resembling membrane evagination in lamellipodia formation. Colocalization of this actin dynamics module to the base of the outer se…

Abitare in estensione

2014

Il saggio “Abitare in estensione” costituisce un’articolata premessa ai diversi contributi presenti nel volume esito delle attività dell’Unità di ricerca della Facoltà di Architettura di Palermo del Prin 2009 dal titolo Dalla campagna urbanizzata alla “città in estensione”: le norme compositive dell’architettura del territorio dei centri minori (Coordinatore nazionale Prof. Lugi Ramazzotti, responsabile dell’UDR locale Prof. Andrea Sciascia). Dalla stesura del modello B alla pubblicazione finale del Prin trascorrono in media tre anni. Anzi, qualche mese in meno, in considerazione dei tempi sempre più brevi imposti dalle nuove norme che regolano la rendicontazione finale. Durante questo peri…

Renewable Energy Technologies for Economic Development

2020

Indonesian villages are facing dangerous condition. Every year, young people are deserting the villages. To overcome this problem, Tangsi Jaya hamlet, West Java, has been provided with 18 kW micro-hydro to supply electricity both to the community and to Small Processing Center for ground coffee production. Results of cash flow analysis for ground coffee in Tangsi Jaya hamlet, with total investment of IDR 110 750 000 and discount rate of 18 % for 5 yr. Banyumeneng I hamlet, Yogyakarta with an investment cost IDR 95 000 000 and production cost of IDR 34 195 000 yr–1 and the interest rate of 14 % yr–1, the payback period was estimated to be 3 yr with ROI of 40 %. PEST analysics indicate that t…

From sustainability to sustainable development: the role of food banks in food security in Uganda : a case study of the hunger project food bank - Mb…

2014

Master thesis in development management - University of Agder 2014 The purpose of this study is to identify the role the food bank plays for food security, sustainable livelihoods and building resilience to climate change among smallholder farmers in Uganda. The aim is to investigate how the food bank in Uganda operates in relation to food security and smallholder farmers. Much of the studies on food banks reveal that food banks are merely institutions that offer emergency food supplies to the hungry and are not agencies aiming at food security. These studies have, however, been based on the context of developed countries and no study has been conducted to establish the role of food banks i…