Evaluation of ozone difluoride as a liquid propellant additive Final report

Ozone difluoride evaluated as liquid propellant additiv

Computing Aggregate Properties of Preimages for 2D Cellular Automata

Computing properties of the set of precursors of a given configuration is a common problem underlying many important questions about cellular automata. Unfortunately, such computations quickly become intractable in dimension greater than one. This paper presents an algorithm --- incremental aggregation --- that can compute aggregate properties of the set of precursors exponentially faster than na{\"i}ve approaches. The incremental aggregation algorithm is demonstrated on two problems from the two-dimensional binary Game of Life cellular automaton: precursor count distributions and higher-order mean field theory coefficients. In both cases, incremental aggregation allows us to obtain new results that were previously beyond reach

A systems biology approach to invasive behavior: comparing cancer metastasis and suburban sprawl development

Background Despite constant progress, cancer remains the second leading cause of death in the United States. The ability of tumors to metastasize is central to this dilemma, as many studies demonstrate successful treatment correlating to diagnosis prior to cancer spread. Hence a better understanding of cancer invasiveness and metastasis could provide critical insight. Presentation of the hypothesis We hypothesize that a systems biology-based comparison of cancer invasiveness and suburban sprawl will reveal similarities that are instructive. Testing the hypothesis We compare the structure and behavior of invasive cancer to suburban sprawl development. While these two systems differ vastly in dimension, they appear to adhere to scale-invariant laws consistent with invasive behavior in general. We demonstrate that cancer and sprawl have striking similarities in their natural history, initiating factors, patterns of invasion, vessel distribution and even methods of causing death. Implications of the hypothesis We propose that metastatic cancer and suburban sprawl provide striking analogs in invasive behavior, to the extent that conclusions from one system could be predictive of behavior in the other. We suggest ways in which this model could be used to advance our understanding of cancer biology and treatment

Selective Cholesterol Dynamics between Lipoproteins and Caveolae/Lipid Rafts

Although low-density lipoprotein (LDL) receptor-mediated cholesterol uptake through clathrin-coated pits is now well understood, the molecular details and organizing principles for selective cholesterol uptake/efflux (reverse cholesterol transport, RCT) from peripheral cells remain to be resolved. It is not yet completely clear whether RCT between serum lipoproteins and the plasma membrane occurs primarily through lipid rafts/caveolae or from non-raft domains. To begin to address these issues, lipid raft/caveolae-, caveolae-, and non-raft-enriched fractions were resolved from purified plasma membranes isolated from L-cell fibroblasts and MDCK cells by detergent-free affinity chromatography and compared with detergent-resistant membranes isolated from the same cells. Fluorescent sterol exchange assays between lipoproteins (VLDL, LDL, HDL, apoA1) and these enriched domains provided new insights into supporting the role of lipid rafts/caveolae and caveolae in plasma membrane/lipoprotein cholesterol dynamics:  (i) lipids known to be translocated through caveolae were detected (cholesteryl ester, triacylglycerol) and/or enriched (cholesterol, phospholipid) in lipid raft/caveolae fractions; (ii) lipoprotein-mediated sterol uptake/efflux from lipid rafts/caveolae and caveolae was rapid and lipoprotein specific, whereas that from non-rafts was very slow and independent of lipoprotein class; and (iii) the rate and lipoprotein specificity of sterol efflux from lipid rafts/caveolae or caveolae to lipoprotein acceptors in vitro was slower and differed in specificity from that in intact cellsconsistent with intracellular factors contributing significantly to cholesterol dynamics between the plasma membrane and lipoproteins

Towards generalized measures grasping CA dynamics

In this paper we conceive Lyapunov exponents, measuring the rate of separation between two initially close configurations, and Jacobians, expressing the sensitivity of a CA's transition function to its inputs, for cellular automata (CA) based upon irregular tessellations of the n-dimensional Euclidean space. Further, we establish a relationship between both that enables us to derive a mean-field approximation of the upper bound of an irregular CA's maximum Lyapunov exponent. The soundness and usability of these measures is illustrated for a family of 2-state irregular totalistic CA

SCP-2/SCP-x gene ablation alters lipid raft domains in primary cultured mouse hepatocytes

Although reverse cholesterol transport from peripheral cell types is mediated through plasma membrane microdomains termed lipid rafts, almost nothing is known regarding the existence, protein/lipid composition, or structure of these putative domains in liver hepatocytes, cells responsible for the net removal of cholesterol from the body. Lipid rafts purified from hepatocyte plasma membranes by a nondetergent affinity chromatography method were

Photo-antagonism of the GABAA receptor

Neurotransmitter receptor trafficking is fundamentally important for synaptic transmission and neural network activity. GABAA receptors and inhibitory synapses are vital components of brain function, yet much of our knowledge regarding receptor mobility and function at inhibitory synapses is derived indirectly from using recombinant receptors, antibody-tagged native receptors and pharmacological treatments. Here we describe the use of a set of research tools that can irreversibly bind to and affect the function of recombinant and neuronal GABAA receptors following ultraviolet photoactivation. These compounds are based on the competitive antagonist gabazine and incorporate a variety of photoactive groups. By using site-directed mutagenesis and ligand-docking studies, they reveal new areas of the GABA binding site at the interface between receptor β and α subunits. These compounds enable the selected inactivation of native GABAA receptor populations providing new insight into the function of inhibitory synapses and extrasynaptic receptors in controlling neuronal excitation