Ozonolysis of oleic acid adsorbed to polar and nonpolar aerosol particles

Single-particle kinetic studies of the reaction between oleic acid and O 3 have been conducted on two different types of core particles: polystyrene latex (PSL) and silica. Oleic acid was found to adsorb to both particle types in multilayer islands that resulted in an adsorbed layer of a total volume estimated to be less than one monolayer. The rate of the surface reaction between surface-adsorbed oleic acid and O 3 has been shown for the first time to be influenced by the composition of the aerosol substrate in a mixed organic/inorganic particle. A Langmuir-Hinshelwood mechanism was applied to the observed dependence of the pseudo-first-order rate constant with [O 3], and the resulting fit parameters for the ozone partition coefficient ( K O 3 ) and maximum first order rate constant ( k 1,max ) suggest that the reaction proceeded faster on the less polar PSL core at lower [O 3] due to the increased residence time of O 3 on the PSL surface, but the reaction was ultimately more efficient on the silica surface at high [O 3]. Values for the uptake coefficient, gamma oleic , for reaction of oleic acid on PSL spheres decrease from 2.5 x 10 (-5) to 1 x 10 (-5) with increasing [O 3] from 4 to 25 ppm and overlap at high [O 3] with the estimated values for gamma oleic on silica, which decrease from 1.6 x 10 (-5) to 1.3 x 10 (-5). The relationship between gamma oleic and the more common expression for gamma O 3 is discussed.     

Entropic order quantity (EnOQ) model for deteriorating items

Jaber et al. [M.Y. Jaber, R.Y. Nuwayhid, M.A. Rosen, Price-driven economic order systems from a thermodynamic point of view, Int. J. Prod. Res. 42 (24) (2004) 5167–5184] suggested that it might be possible to improve production systems performance by applying the first and second laws of thermodynamics to reduce system entropy (or disorder). They then used these laws to modify the economic order quantity (EOQ) model to derive an equivalent entropic order quantity (EnOQ). The results suggested that larger quantities should be ordered than is suggested by the classical EOQ model.     

Mach stem hysteresis: Experiments addressing a novel explanation of clumpy astrophysical jet emission

Recent time-series observations of shock waves in stellar jets taken with the Hubble Space Telescope reveal localized bright knots that persist over nearly 15 years. While some of these features represent shock fronts caused by variable velocities in the flow, others appear at the intersection points between distinct bow shocks. Theoretically, when the angle between two intersecting shocks exceeds a certain critical value, a third shock (Mach stem) should form. Because Mach stems form perpendicular to the direction of flow, incoming particles encounter a normal shock instead of an oblique one, which results in brighter emission at this location. To study this phenomenon in a controlled laboratory setting, we have carried out experiments on the Omega laser aimed at understanding the formation, growth, and destruction of Mach stems in the warm dense plasma regime. Our experimental results indicate how the growth rate depends upon included angle, and numerical simulations indicate that it may be possible to stabilize an already-formed Mach stem below the critical angle when certain conditions are satisfied.     

A small molecule designed to bind to the adenine nucleotide pocket of Hsp90 causes Her2 degradation and the growth arrest and differentiation of breast cancer cells

BACKGROUND: The Hsp90s contain a conserved pocket that binds ATP/ADP and plays an important role in the regulation of chaperone function. Occupancy of this pocket by several natural products (geldanamycin (GM) and radicicol) alters Hsp90 function and results in the degradation of a subset of proteins (i.e. steroid receptors, Her2, Raf). We have used the structural features of this pocket to design a small molecule inhibitor of Hsp90. RESULTS: The designed small molecule PU3 competes with GM for Hsp90 binding with a relative affinity of 15-20 microM. PU3 induces degradation of proteins, including Her2, in a manner similar to GM. Furthermore, PU3 inhibits the growth of breast cancer cells causing retinoblastoma protein hypophosphorylation, G1 arrest and differentiation. CONCLUSIONS: PU3 is representative of a novel class of synthetic compounds that binds to Hsp90 and inhibits the proliferation of cancer cells. These reagents could provide a new strategy for the treatment of cancers.     

Understanding the relative affinity and specificity of the pleckstrin homology domain of protein kinase B for inositol phosphates

Protein kinase B (PKB) is a serine/threonine kinase that plays a key role in the phosphoinositide 3-kinase (PI3K) pathway-one of the most frequently activated proliferation pathways in cancer. In this pathway, PKB is recruited to the plasma membrane by direct interaction of its pleckstrin homology (PH) domain with the inositol phosphate head-group of phosphatidylinositol 3,4,5-trisphosphate [PtdIns(3,4,5)P(3)] or phosphatidylinositol 3,4-bisphosphate [PtdIns(3,4)P(2)]. This recruitment is a critical stage in the activation of PKB, whose downstream effectors play important roles in cell survival, proliferation and growth. It is therefore of great interest to understand PKB's mode of binding, as well as its specificity and affinity for different phosphoinositides. We have used a total of 3 μs of molecular dynamics (MD) simulations to better understand the interactions of the PKB PH domain with the inositol phosphate head-groups of phosphoinositides involved in the PI3K pathway. Our computational models successfully mirror PKB's in vivo selectivity for 3-phosphorylated phosphoinositides. Furthermore, the models also help to rationalize unexpected in vitro data in which inositol 1,4,5-trisphosphate [Ins(1,4,5)P(3)] binds with a relatively high affinity to the PKB PH domain, despite its parent lipid phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P(2)] being known not to bind in vivo. With the support of computational simulations, we propose that when not bonded to a phosphatidate tail Ins(1,4,5)P(3) binds in an orientation in which its inositol ring is flipped with respect to the 3-phosphorylated inositol phosphate ligands and its parent lipid.     

Effect of radiative cooling on collapsing charged grains

The effect of the radiative cooling of electrons on the gravitational collapse of cold dust grains with fluctuating electric charge is investigated. We find that the radiative cooling as well as the charge fluctuations, both, enhance the growth rate of the Jeans instability. However, the Jeans length, which is zero for cold grains and nonradiative plasma, becomes finite in the presence of radiative cooling of electrons and is further enhanced due to charge fluctuations of grains resulting in an increased threshold of the spatial scale for the Jeans instability.     

A parallel stochastic method for solving linearly constrained concave global minimization problems

A parallel stochastic algorithm is presented for solving the linearly constrained concave global minimization problem. The algorithm is a multistart method and makes use of a Bayesian stopping rule to identify the global minimum with high probability. Computational results are presented for more than 200 problems on a Cray X-MP EA/464 supercomputer.     

A neo-intuitive proposal for Kaluza-Klein unification

This paper addresses a central question of contemporary theoretical physics: Can a unified account be provided for the known forces of nature? The issue is brought into focus by considering the recently revived Kaluza-Klein approach to unification, a program entailing dimensional transformation through cosmogony. First it is demonstrated that, in a certain sence, revitalized Kaluza-Klein theory appears to undermine the intuitive foundations of mathematical physics, but that this implicit consequence has been repressed at a substantial cost. A fundamental reformulation of the Kaluza-Klein strategy is then undertaken, one that casts it within a new intuitive context. This is followed by a provisional application of the suggested approach to the specific problem of cosmological change. The paper concludes by exploring the far-reaching epistemological implications of the “neo-intuitive” proposal set forth.