Intramolecular and Lattice Melting in n-Alkane Monolayers: An Analog of Melting in Lipid Bilayers

URL:http://link.aps.org/doi/10.1103/PhysRevLett.83.2362 DOI:10.1103/PhysRevLett.83.2362Molecular dynamics (MD) simulations and neutron diffraction experiments have been performed on n-dotriacontane ( n-C32D66) monolayers adsorbed on a graphite basal- plane surface. The diffraction experiments show little change in the crystalline monolayer structure up to a temperature of ~350K above which a large thermal expansion and decrease in coherence length occurs. The MD simulations provide evidence that this behavior is due to a phase transition in the monolayer in which intramolecular and translational order are lost simultaneously. This melting transition is qualitatively similar to the gel-to-fluid transition found in bilayer lipid membranes.Acknowledgment is made to the U.S. National Science Foundation under Grants No. DMR-9314235 and No. DMR-9802476, the Missouri University Research Reactor, and to the donors of The Petroleum Research Fund, administered by the ACS, for partial support of this research. We thank L. Criswell for assistance with the figures

Molecular imaging of inflammation and intraplaque vasa vasorum: A step forward to identification of vulnerable plaques?

Current developments in cardiovascular biology and imaging enable the noninvasive molecular evaluation of atherosclerotic vascular disease. Intraplaque neovascularization sprouting from the adventitial vasa vasorum has been identified as an independent predictor of intraplaque hemorrhage and plaque rupture. These intraplaque vasa vasorum result from angiogenesis, most likely under influence of hypoxic and inflammatory stimuli. Several molecular imaging techniques are currently available. Most experience has been obtained with molecular imaging using positron emission tomography and single photon emission computed tomography. Recently, the development of targeted contrast agents has allowed molecular imaging with magnetic resonance imaging, ultrasound and computed tomography. The present review discusses the use of these molecular imaging techniques to identify inflammation and intraplaque vasa vasorum to identify vulnerable atherosclerotic plaques at risk of rupture and thrombosis. The available literature on molecular imaging techniques and molecular targets associated with inflammation and angiogenesis is discussed, and the clinical applications of molecular cardiovascular imaging and the use of molecular techniques for local drug delivery are addressed

The Sacks Density Theorem and S_2-Bounding

The Sacks Density Theorem (Sacks 1964) states that the Turing degrees of the recursively enumerable sets are dense. We show that the Density Theorem holds in every model of P \Gamma +B \Sigma 2 . The proof has two components: a lemma that in any model of P \Gamma +B \Sigma 2 , if B is recursively enumerable and incomplete then I \Sigma 1 holds relative to B and an adaptation of Shore's (1976) blocking technique in ff-recursion theory to models of arithmetic. 1 Introduction Proofs using the priority method are the trademark of recursion theory. In this paper, we continue the line of inquiry in which we use subsystems of first order arithmetic to calibrate priority methods and the theorems in whose proofs they appear. In the hierarchy of Groszek and Slaman (unpublished), we classify priority constructions according to the syntactic complexity of the outcomes in its most complicated families of strategies. In a \Pi 1 -priority construction the strategies have outcomes that are descri..