Molecular organization and viscosity of a thin film of molten polymer between two surfaces as probed by force measurements

Measurements are presented of the force between two molecularly smooth mica surfaces immersed in liquid poly(dimethylsiloxane) (Dow Corning 200 of nominal viscosity 50 cS) over a range of film thicknesses from 3 to 200 nm. There is a repulsion, attributed to conformational restrictions, when the polymer molecules are confined to a gap less than about 15 nm thick. In extremely thin films (<5 nm) the force is an oscillatory function of thickness with a repeat spacing corresponding to the width of the polymer molecule, which suggests that the polymer segments are arranged in layers near the solid surfaces. Dynamic force measurements show that the polymer has a viscosity equal to its bulk value even in very thin films, but a region next to each surface, only about one radius of gyration thick, does not flow. Saturation of the polymer with water destabilizes the film when it is very thin.

Quality of pre-school children's pretend play and subsequent development of semantic organization and narrative re-telling skills

Purpose: This study investigated if the quality of pre-school children's pretend play predicted their semantic organization and narrative re-telling ability when they were in early primary school. It was hypothesized that the elaborateness of a child's play and the child's use of symbols in play were predictors of their semantic organization and narrative re-tell scores of the School Age Oral Language Assessment. Method: Forty-eight children were assessed using the Child-Initiated Pretend Play Assessment when they were aged 4-5 years. Three-to-five years after this assessment their semantic organization and narrative re-telling skills were assessed. Results: Results indicate that the elaborateness of a child's play and their ability to use symbols was predictive of semantic organization skills. Use of symbols in play was the strongest play predictor of narrative re-telling skills. The quality of a pre-school child's ability to elaborate complex sequences in pretend play and use symbols predicted up to 20% of a child's semantic organization and narrative re-telling skills up to 5 years later. Conclusions: The study provides evidence that the quality of pretend play in 4-5 year olds is important for semantic organization and narrative re-telling abilities in the school-aged child.

Institutional processes and the production of gender inequalities: the case of Australian child support research and administration

This article analyses the administrative and research capture of child support data as a case study of how institutional data collection processes are performative in perpetuating gendered inequalities. We compare interviews with 19 low-income single mothers and their longitudinal survey responses from the same research to reveal how low-income women strategically or inadvertently ‘smoothed’ their experiences when responding to data collection processes. This directly resulted in material and symbolic costs in the form of reduced welfare benefits and limited evidence with which to lobby for policy reform. These processes in turn provided benefits to fathers and the state in the form of reduced child support liabilities and enforcement action, and welfare outlays, respectively. We conclude that current administrative and research data collection practices provide a limited and gendered evidence base for administrative justice and policy reform.

Materials Collection Creation and Administration: A New Role for Libraries (White Paper)

The Problem/Opportunity: To define, identify, and guide design-based materials collections in academic settings and foster community among those with existing collections and/or those considering creating and supporting one. Contents and topics: What is a materials collection? Why have a materials collection? Acquisition strategies Organizational approaches Programming possibilities Symposium summary Resources

Genomic organization and evolution of the 5S ribosomal DNA in Tilapiini fishes

5S rDNA sequences present an intense dynamism and have proved to be valuable as genetic markers to distinguish closed related species and also in the understanding of the evolutionary dynamic of repetitive sequences in the genomes. In order to identify patterns of 5S rDNA organization and their evolution in the genome of fish species, such genomic segment was investigated in the tilapias Oreochromis niloticus and Tilapia rendalli, and in the hybrid O. urolepis hornorum x O. mossambicus. A dual 5S rDNA system was identified in the three analyzed tilapia samples. Although each 5S rDNA class was conserved among the three samples, a distinct 5S rDNA genome organization pattern could be evidenced for each sample. The presence of a dual 5S rDNA system seems to be a general trait among non-related teleost fish orders, suggesting that evolutionary events of duplication have occurred before the divergence of the main groups of teleost fishes.

Genomic organization and comparative chromosome mapping of the U1 snRNA gene in cichlid fish, with an emphasis in Oreochromis niloticus

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Nucleotide sequence, genomic organization and chromosome localization of 5S rDNA in two species of Curimatidae (Teleostei, Characiformes)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Structural organization and thermal properties of the Sb2O3-SbPO4 glass system

The structural organization of Sb2O3-SbPO4 glasses has been studied by FTIR, Raman, P-31 MAS and spin echo NMR, Mossbauer and X-ray absorption spectroscopy (EXAFS and XANES at K and L-3,L-1-Sb edges). The combined results can be explained in terms of two potential mechanisms describing the change of the Sb(m) local environment upon incorporation of Q((4))-type phosphate. The formation of the latter species requires anionic compensation that may be adjusted by (a) formation of non bridging oxygen or (b) formation of SbO4E- groups (E = non-bonding electron pair). The second model is favored.

Complete nucleotide sequence, genomic organization and phylogenetic analysis of Citrus leprosis virus cytoplasmic type

The complete nucleotide sequence of the genomic RNA 1 (8745 nt) and RNA 2 (4986 nt) of Citrus leprosis virus cytoplasmic type (CiLV-C) was determined using cloned cDNA. RNA 1 contains two open reading frames (ORFs), which correspond to 286 and 29 kDa proteins. The 286 kDa protein is a polyprotein putatively involved in virus replication, which contains four conserved domains: methyltransferase, protease, helicase and polymerase. RNA 2 contains four ORFs corresponding to 15, 61, 32 and 24 kDa proteins, respectively. The 32 kDa protein is apparently involved in cell-to-cell movement of the virus, but none of the other putative proteins exhibit any conserved domain. The 5' regions of the two genomic RNAs contain a 'cap' structure and poly(A) tails were identified in the 3'-terminals. Sequence analyses and searches for structural and non-structural protein similarities revealed conserved domains with members of the genera Furovirus, Bromovirus, Tobravirus and Tobamovirus, although phylogenetic analyses strongly suggest that CiLV-C is a member of a distinct, novel virus genus and family, and definitely demonstrate that it does not belong to the family Rhabdoviridae, as previously proposed. Based on these results it was proposed that Citrus leprosis virus be considered as the type member of a new genus of viruses, Cilevirus.

Política económica, organización social y desarrollo regional: elementos para armar una teoría del desarrollo regional = Economic policy, social organization and regional development

Documento preparado para uso en los cursos de planificación ofrecidos por el ILPES

Chromosomal evolution of neotropical cichlids: The role of repetitive DNA sequences in the organization and structure of karyotype

Cichlids are important in the aquaculture and ornamental fish trade and are considered models for evolutionary biology. However, most studies of cichlids have investigated African species, and the South American cichlids remain poorly characterized. Studies in neotropical regions have focused almost exclusively on classical cytogenetic approaches without investigating physical chromosomal mapping of specific sequences. The aim of the present study is to investigate the genomic organization of species belonging to different tribes of the subfamily Cichlinae (Cichla monoculus, Astronotus ocellatus, Geophagus proximus, Acaronia nassa, Bujurquina peregrinabunda, Hoplarchus psittacus, Hypselecara coryphaenoides, Hypselecara temporalis, Caquetaia spectabilis, Uaru amphiacanthoides, Pterophyllum leopoldi, Pterophyllum scalare, and Symphysodon discus) and reexamine the karyotypic evolutionary patterns proposed for this group. Variations in some cytogenetic markers were observed, although no trends were found in terms of the increase, decrease, or maintenance of the basal diploid chromosome number 2n = 48 in the tribes. Several species were observed to have 18S rDNA genetic duplications, as well as multiple rDNA loci. In most of the taxa analyzed, the 5S rDNA was located in the interstitial region of a pair of homologous chromosomes, although variations from this pattern were observed. Interstitial telomere sites were also observed and appear to be involved in chromosomal rearrangement events and the accumulation of repeat-rich satellite DNA sequences. Our data demonstrated the karyotypic diversity that exists among neotropical cichlids, suggesting that most of this diversity is due to the repetitive sequences present in heterochromatic regions and that repeat sequences have greatly influenced the karyotypic evolution of these fishes. © 2012 Springer Science+Business Media B.V.

Antecedentes, organización y programas del Centro Latinoamericano de Documentación Económica y Social = Background, organization and programmes of the Latin American Centre for Economic and Social Documentation

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