15,091,986 research outputs found

    Thermotropic and structural effects of poly(malic acid) on fully hydrated multilamellar DPPC鈥搘ater systems

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    The thermotropic and structural effects of low molecular weight poly(malic acid) (PMLA) on fully hydrated multilamellar dipalmitoylphosphatidylcholine (DPPC)-water systems were investigated using differential scanning calorimetry (DSC), small-angle X-ray scattering (SAXS), and freeze-fracture transmission electron microscopy (FFTEM). Systems of 20 wt% DPPC concentration and 1 and 5 wt% PMLA to lipid ratios were studied. The PMLA derivatives changed the thermal behavior of DPPC significantly and caused a drastic loss in correlation between lamellae in the three characteristic thermotropic states (i.e., in the gel, rippled gel and liquid crystalline phases). In the presence of PBS or NaCl, the perturbation was more moderate. The structural behavior on the atomic level was revealed by FTIR spectroscopy. The molecular interactions between DPPC and PMLA were simulated via modeling its measured infrared spectra, and their peculiar spectral features were interpreted. Through this interpretation, the poly(malic acid) is inferred to attach to the headgroups of the phospholipids through hydrogen bonds between the free hydroxil groups of PMLA and the phosphodiester groups of DPPC

    Interweaving Chiral Spirals

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    We elaborate how to construct interweaving chiral spirals in (2+1) dimensions, defined as a superposition of chiral spirals oriented in different directions. We divide a two-dimensional Fermi sea into distinct wedges, characterized by the opening angle 2Theta and depth Q ~ pF, where pF is the Fermi momentum. In each wedge, the energy is lowered by forming a single chiral spiral. The optimal values for Theta and Q are chosen by balancing this gain in energy versus the cost of deforming the Fermi surface (which dominates at large Theta) and patch-patch interactions (dominant at small Theta). Using a non-local four-Fermi interaction model, we estimate the gain and cost in energy by expanding in terms of 1/Nc (where Nc is the number of colors), lqcd/Q, and Theta. Due to a form factor in our non-local model, at small 1/Nc the mass gap (chiral condensate) is large, and the interaction among quarks and the condensate local in momentum space. Consequently, interactions between different patches are localized near their boundaries, and it is simple to embed many chiral spirals. We identify the dominant and subdominant terms at high density and categorize formulate an expansion in terms of lqcd/Q or Theta. The kinetic term in the transverse directions is subdominant, so that techniques from (1+1)-dimensional systems can be utilized. To leading order in 1/Nc and lqcd/Q, the total gain in energy is ~ pF lqcd^2 with Theta ~ (lqcd/pF)^{3/5}. Since Theta decreases with increasing pF, there should be phase transitions associated with the change in the wedge number. We also argue the effects of subdominant terms at lower density where the large-Nc approximation is more reliable.Comment: 54 pages, 21 figures, published versio

    Nonlocal SU(3) chiral quark models at finite temperature: the role of the Polyakov loop

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    We analyze the role played by the Polyakov loop in the description of the chiral phase transition within the framework of nonlocal SU(3) chiral models with flavor mixing. We show that its presence provides a substantial enhancement of the predicted critical temperature, bringing it to a better agreement with the most recent results of lattice calculations.Comment: 9 pages, 1 figur

    A general purpose programming framework for ubiquitous computing environments

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    It is important to note that the need to support ad-hoc and potentially mobile arrangements of devices in ubiquitous environments does not fit well within the traditional client/server architecture. We believe peer-to-peer communication offers a preferable alternative due to its decentralised nature, removing dependence on individual nodes. However, this choice adds to the complexity of the developers task. In this paper, we describe a two-tiered approach to address this problem: A lower tier employing peer-to-peer interactions for managing the network infrastructure and an upper tier providing a mobile agent based programming framework. The result is a general purpose framework for developing ubiquitous applications and services, where the underlying complexity is hidden from the developer. This paper discusses our on-going work; presenting our design decisions, features supported by our framework, and some of the challenges still to be addressed in a complex programming environment

    Will anyone vote? Prospects for turnout in the general election

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    One of the most notable features of the last two general elections was the low level of turnout. Before 2001 turnout at general elections was always at least 70% (and often far higher). But in 2001 it fell to just 59% and, at 61%, the figure in 2005 was little better. Over 17 million people eligible to vote that year chose not to do so, seven million more than voted for the winning Labour party. Britain found itself almost at the bottom of the turnout league among established European democracies. The failure of large sections of the public to go to the polls has led to considerable concern about the health of Britain鈥檚 democracy and stimulated many a suggestion as to how the country鈥檚 politicians might be able to reconnect with the electorate

    Sinking or swimming in the New Zealand mainstream: Four young Asian learners in a new languaculture

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    New Zealand schools are increasingly diverse in terms of language and culture, and many immigrant school children are faced with the 鈥榣anguacultural鈥 (Agar, 1994) challenge of learning not only a new language but a new culture of learning 鈥 to learn new classroom interaction skills (Barnard, 2005) as a route from Basic Interpersonal Communication Skills to Cognitive Academic Language Proficiency (Cummins 1981, 2000). This paper explores the challenges by referring to four young Asian learners in an upper primary school classroom (Barnard 2002, 2003, 2007). Brief profiles of each of these children are given and then transcript data of their classroom interactions are presented and interpreted. In conclusion, questions are raised about the respective responsibilities of teachers and school and parents and students, to ensure that new immigrant learners swim rather than sink in the mainstrea