7,635 research outputs found
Towards a unification of HRT and SCOZA
The Hierarchical Reference Theory (HRT) and the Self-Consistent
Ornstein-Zernike Approximation (SCOZA) are two liquid state theories that both
furnish a largely satisfactory description of the critical region as well as
phase separation and the equation of state in general. Furthermore, there are a
number of similarities that suggest the possibility of a unification of both
theories. As a first step towards this goal we consider the problem of
combining the lowest order gamma expansion result for the incorporation of a
Fourier component of the interaction with the requirement of consistency
between internal and free energies, leaving aside the compressibility relation.
For simplicity we restrict ourselves to a simplified lattice gas that is
expected to display the same qualitative behavior as more elaborate models. It
turns out that the analytically tractable Mean Spherical Approximation is a
solution to this problem, as are several of its generalizations. Analysis of
the characteristic equations shows the potential for a practical scheme and
yields necessary conditions any closure to the Ornstein Zernike relation must
fulfill for the consistency problem to be well posed and to have a unique
differentiable solution. These criteria are expected to remain valid for more
general discrete and continuous systems, even if consistency with the
compressibility route is also enforced where possible explicit solutions will
require numerical evaluations.Comment: Minor changes in accordance with referee comment
Self-Consistent Ornstein-Zernike approximation for the Yukawa fluid with improved direct correlation function
Thermodynamic consistency of the Mean Spherical Approximation as well as the
Self-Consistent Ornstein-Zernike Approximation (SCOZA) with the virial route to
thermodynamics is analyzed in terms of renormalized gamma-ordering. For
continuum fluids this suggests the addition of a short-range contribution to
the usual SCOZA direct correlation function, and the shift of the adjustable
parameter from the potential term to this new term. The range of this
contribution is fixed by imposing consistency with the virial route at the
critical point. Comparison of the results of our theory for the hard-core
Yukawa potential with simulation data show very good agreement for cases where
the liquid-vapor transition is stable or not too far into the metastable region
with respect to the solid state. In the latter case for extremely short-ranged
interactions discrepancies arise.Comment: Minimal changes due to referee's comments. Accepted for publication
in J. Chem. Phys
Self-consistent Ornstein-Zernike approximation for molecules with soft cores
The Self-Consistent Ornstein-Zernike Approximation (SCOZA) is an accurate
liquid state theory. So far it has been tied to interactions composed of hard
core repulsion and long-range attraction, whereas real molecules have soft core
repulsion at short distances. In the present work, this is taken into account
through the introduction of an effective hard core with a diameter that depends
upon temperature only. It is found that the contribution to the configurational
internal energy due to the repulsive reference fluid is of prime importance and
must be included in the thermodynamic self-consistency requirement on which
SCOZA is based. An approximate but accurate evaluation of this contribution
relies on the virial theorem to gauge the amplitude of the pair distribution
function close to the molecular surface. Finally, the SCOZA equation is
transformed by which the problem is reformulated in terms of the usual SCOZA
with fixed hard core reference system and temperature-dependent interaction
Leishmania promastigotes evade interleukin 12 (IL-12) induction by macrophages and stimulate a broad range of cytokines from CD4+ T cells during initiation of infection.
Leishmania major are intramacrophage parasites whose eradication requires the induction of T helper 1 (Th1) effector cells capable of activating macrophages to a microbicidal state. Interleukin 12 (IL-12) has been recently identified as a macrophage-derived cytokine capable of mediating Th1 effector cell development, and of markedly enhancing interferon gamma (IFN-gamma) production by T cells and natural killer cells. Infection of macrophages in vitro by promastigotes of L. major caused no induction of IL-12 p40 transcripts, whereas stimulation using heat-killed Listeria or bacterial lipopolysaccharide induced readily detectable IL-12 mRNA. Using a competitor construct to quantitate a number of transcripts, a kinetic analysis of cytokine induction during the first few days of infection by L. major was performed. All strains of mice examined, including susceptible BALB/c and resistant C57BL/6, B10.D2, and C3H/HeN, had the appearance of a CD4+ population in the draining lymph nodes that contained transcripts for IL-2, IL-4, and IFN-gamma (and in some cases, IL-10) that peaked 4 d after infection. In resistant mice, the transcripts for IL-2, IL-4, and IL-10 were subsequently downregulated, whereas in susceptible BALB/c mice, these transcripts were only slightly decreased, and IL-4 continued to be reexpressed at high levels. IL-12 transcripts were first detected in vivo by 7 d after infection, consistent with induction by intracellular amastigotes. Challenge of macrophages in vitro confirmed that amastigotes, in contrast to promastigotes, induced IL-12 p40 mRNA. Reexamination of the cytokine mRNA at 4 d revealed expression of IL-13 in all strains analyzed, suggesting that IL-2 and IL-13 may mediate the IL-12-independent production of IFN-gamma during the first days after infection. Leishmania have evolved to avoid inducing IL-12 from host macrophages during transmission from the insect vector, and cause a striking induction of mRNAs for IL-2, IL-4, IL-10, and IL-13 in CD4+ T cells. Each of these activities may favor survival of the organism
Internship with the Women's Institute for Housing and Economic Development
This report describes the author's experience as an intern working with two community development organizations. (Library-derived description)Reiner, R. S. (1993). Internship with the Women's Institute for Housing and Economic Development. Retrieved from http://academicarchive.snhu.eduMaster of Science (M.S.)School of Community Economic Developmen
Capture and release of a conditional state of a cavity QED system by quantum feedback
Detection of a single photon escaping an optical cavity QED system prepares a nonclassical state of the electromagnetic field. The evolution of the state can be modified by changing the drive of the cavity. For the appropriate feedback, the conditional state can be captured (stabilized) and then released. This is observed by a conditional intensity measurement that shows suppression of vacuum Rabi oscillations for the length of the feedback pulse and their subsequent return
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