Adaptive chemistry lookup tables for combustion simulations using optimal B-spline interpolants

Flamelet models, which enable the storing of precomputed detailed chemistry into lookup tables, are widely used in combustion simulations. They allow the computation of accurate results at low computational cost, but standard implementations can lead to numerical problems due to a non-smooth representation, and their applicability is limited by memory requirements. Here, the methods used by a newly developed and optimised lookup table generator based on B-spline interpolation are presented. The creation of smooth representations of flamelet solutions requiring less than one fifth of the number of points in each direction compared to the non-smooth representations of standard lookup tables based on linear interpolation is shown to be possible. The new B-spline interpolation based tables are also applied within a large-eddy simulation of the Swirling Methane/Hydrogen Flame 1 and the results are compared to simulations using lookup tables based on linear interpolation or optimised artificial neural networks. Better performance of the B-spline interpolation based tables with respect to physical accuracy and numerical performance is demonstrated.     

Quantitative top-down proteomics of SILAC labeled human embryonic stem cells

Human embryonic stem cells (hESCs) are self-renewing pluripotent cells with relevance to treatment of numerous medical conditions. However, a global understanding of the role of the hESC proteome in maintaining pluripotency or triggering differentiation is still largely lacking. The emergence of top-down proteomics has facilitated the identification and characterization of intact protein forms that are not readily apparent in bottom-up studies. Combined with metabolic labeling techniques such as stable isotope labeling by amino acids in cell culture (SILAC), quantitative comparison of intact protein expression under differing experimental conditions is possible. Herein, quantitative top-down proteomics of hESCs is demonstrated using the SILAC method and nano-flow reverse phase chromatography directly coupled to a linear-ion-trap Fourier transform ion cyclotron resonance mass spectrometer (nLC-LTQ-FT-ICR-MS). In this study, which to the best of our knowledge represents the first top-down analysis of hESCs, we have confidently identified 11 proteins by accurate intact mass, MS/MS, and amino acid counting facilitated by SILAC labeling. Although quantification is challenging due to the incorporation of multiple labeled amino acids (i.e., lysine and arginine) and arginine to proline conversion, we are able to quantitatively account for these phenomena using a mathematical model.     

Exotic components of SO(p,q) surface group representations,and their Higgs bundle avatars

For semisimple Lie groups, moduli spaces of Higgs bundles on a Riemann surface correspond to representation varieties for the surface fundamental group. In many cases, natural topological invariants label connected components of the moduli spaces. Hitchin representations into split real forms, and maximal representations into Hermitian Lie groups, are the only previously know cases where natural invariants do not fully distinguish connected components. In this note we announce the existence of new such exotic components in the moduli spaces for the groups $\mathrm{SO}(p,q)$ with $2<p<q$. These groups lie outside formerly know classes of groups associated with exotic components.     

Studies on the total synthesis of lactonamycin: construction of model ABCD ring systems

Model studies on the synthesis of the tetracyclic ABCD ring system of lactonamycin (1) are described. The key step involved the double Michael addition reaction of alcohol 8 to propynoate esters to produce the BCD units 13 and 14 of the target 1. Alternatively, double Michael addition of alcohol 8 to di-tert-butyl acetylenedcarboxylate gave the corresponding BCD ring systems 36 and 37. Acid-mediated hydrolysis of the dihydroquinone monoketal units of 13 and 14 and 36 and 37 in the presence of air gave the corresponding quinones 7 and 39. These were converted into the tetracyclic ABCD units 6, 26a, 40, and 42 of lactonamycin (1) by either dihydroxylation or epoxidation and acid-catalyzed lactonization.     

Cytotoxicity of Bacterial-Derived Toxins to Immortal Lung Epithelial and Macrophage Cells

Health risks associated with inhalation and deposition of biological materials have been a topic of great concern due to highly publicized cases of inhalation anthrax, of new regulations on the release of particulate matter, and to increased concerns on the hazards of indoor air pollution. Here, we present an evaluation of the sensitivity of two immortal cell lines (A549, human lung carcinoma epithelia) and NR8383 (rat alveolar macrophages) to a variety of bacterial-derived inhalation hazards and simulants including etoposide, gliotoxin, streptolysin O, and warfarin. The cell response is evaluated through quantification of changes in mitochondrial succinate dehydrogenase activity, release of lactate dehydrogenase, initiation of apoptosis, and through changes in morphology as determined by visible light microscopy and scanning electron microscopy. These cells display dose–response relations to each toxin, except for triton which has a step change response. The first observable responses of the epithelial cells to these compounds are changes in metabolism for one toxin (warfarin) and alterations in membrane permeability for another (gliotoxin). The other four toxins display a similar time course in response as gauged by changes in metabolism and loss of membrane integrity. Macrophages are more sensitive to most toxins; however, they display a lower level of stability. This information can be used in the design of cell-based sensors responding to these and similar hazards.