359 research outputs found
Effects of polymer polydispersity on the phase behaviour of colloid-polymer mixtures
We study the equilibrium behaviour of a mixture of monodisperse hard sphere
colloids and polydisperse non-adsorbing polymers at their -point, using
the Asakura-Oosawa model treated within the free-volume approximation. Our
focus is the experimentally relevant scenario where the distribution of polymer
chain lengths across the system is fixed. Phase diagrams are calculated using
the moment free energy method, and we show that the mean polymer size at which gas-liquid phase separation first occurs decreases with increasing
polymer polydispersity . Correspondingly, at fixed mean polymer size,
polydispersity favours gas-liquid coexistence but delays the onset of
fluid-solid separation. On the other hand, we find that systems with different
but the same {\em mass-averaged} polymer chain length have nearly
polydispersity-independent phase diagrams. We conclude with a comparison to
previous calculations for a semi-grandcanonical scenario, where the polymer
chemical potentials are imposed, which predicted that fluid-solid coexistence
was over gas-liquid in some areas of the phase diagram. Our results show that
this somewhat counter-intuitive result arose because the actual polymer size
distribution in the system is shifted to smaller sizes relative to the polymer
reservoir distribution.Comment: Changes in v2: sketch in Figure 1 corrected, other figures improved;
added references to experimental work and discussion of mapping from polymer
chain length to effective radiu
Evolucao historica dos precos do suino, insumos e suas relacoes de troca na Regiao Oeste de Santa Catarina.
bitstream/item/67828/1/CUsersPiazzonDocumentsProntosCPATC-DOCUMENTOS-29-EVOLUCAO-HISTORICA-DOS-PRECOS-DO-SUINO-INSUMOS-E-SUAS-RELACOES-DE-TROCA-NA-RE.pd
Caracterização química, física e mineralógica de solos intermediários entre latossolos brunos e latossolos roxos.
Levantamento de reconhecimento dos solos da região sudeste do Estado do Paraná (áreas 4, 5 e 6).
bitstream/item/63300/1/BPD-13-2002-Parana-Sudeste-areas-4-5-6.pd
Guia para identificação dos principais solos do Estado do Paraná.
Conceitos e definições; Principais solos do Estado do Paraná.bitstream/item/36228/1/Guia-para-identificacao.pd
Caracterização dos solos do Município de Castro, PR.
O município de Castro, com uma superfície aproximada de 2.030km2, situa-se no Primeiro Planalto Paranaense, com uma pequena porção, a oeste da sede municipal, localizada no Segundo Planalto. O clima é do tipo Cfb, com precipitação da ordem de 1.400-1.600mm e com chuvas bem distribuídas durante o ano. O material de origem do solo está relacionado ao intemperismo de diferentes litologias, compreendendo desde granitos referidos ao Proterozóico/Paleozóico até arenitos da Formação Furnas, do Devoniano. Na porção sudeste da área, onde o relevo é mais vigoroso, a vegetação original predominante é do tipo floresta subtropical perenifólia, enquanto no restante da área predominava a vegetação de campo subtropical úmido. Ao todo foram estabelecidas 23 unidades de mapeamento, distribuídas pelas seguintes classes: Latossolos Brunos (13,77%), Latossolos Vermelhos (2,75%), Latossolos Vermelho-Amarelos (0,26%), Nitossolos Háplicos (25,39%), Cambissolos Háplicos (23,97%), Cambissolos Húmicos (2,71%), Organossolos Mésicos (15,14%) e Neossolos Litólicos + Afloramentos Rochosos (16,01%).bitstream/item/63306/1/BPD-09-2002-Parana-Castro.pd
Classificação e caracterização dos solos de testes de progenies de erva-mate (Ilex paraguariensis St. Hil.).
bitstream/CNPF-2009-09/16608/1/com_tec29.pd
Caracterização dos solos do Município de Piraí do Sul, PR.
bitstream/item/104763/1/Parana-Pirai.pd
Avaliacao genetica da massa foliar e sobrevivencia de progenies de erva-mate em duas classes de solos na regiao de Ponta Grossa, PR.
Equilibrium phase behavior of polydisperse hard spheres
We calculate the phase behavior of hard spheres with size polydispersity,
using accurate free energy expressions for the fluid and solid phases. Cloud
and shadow curves, which determine the onset of phase coexistence, are found
exactly by the moment free energy method, but we also compute the complete
phase diagram, taking full account of fractionation effects. In contrast to
earlier, simplified treatments we find no point of equal concentration between
fluid and solid or re-entrant melting at higher densities. Rather, the fluid
cloud curve continues to the largest polydispersity that we study (14%); from
the equilibrium phase behavior a terminal polydispersity can thus only be
defined for the solid, where we find it to be around 7%. At sufficiently large
polydispersity, fractionation into several solid phases can occur, consistent
with previous approximate calculations; we find in addition that coexistence of
several solids with a fluid phase is also possible
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