Sum rules, plasma frequencies and Hall phenomenology in holographic plasmas

We study the AC optical and hall conductivities of Dp/Dq-branes intersections in the probe approximation and use sum-rules to study various associated transport coefficients. We determine that the presence of massive fundamental matter, as compared to massless fundamental matter described holographically by a theory with no dimensional defects, reduces the plasma frequency. We further show that this is not the case when the brane intersections include defects. We discuss in detail how to implement correctly the regularization of retarded Green's functions so that the dispersion relations are satisfied and the low energy behaviour of the system is physically realistic.Comment: 25 pages, 5 figures. v2.minor changes, published versio

Korarchaeota Diversity, Biogeography, and Abundance in Yellowstone and Great Basin Hot Springs and Ecological Niche Modeling Based on Machine Learning

Over 100 hot spring sediment samples were collected from 28 sites in 12 areas/regions, while recording as many coincident geochemical properties as feasible (>60 analytes). PCR was used to screen samples for Korarchaeota 16S rRNA genes. Over 500 Korarchaeota 16S rRNA genes were screened by RFLP analysis and 90 were sequenced, resulting in identification of novel Korarchaeota phylotypes and exclusive geographical variants. Korarchaeota diversity was low, as in other terrestrial geothermal systems, suggesting a marine origin for Korarchaeota with subsequent niche-invasion into terrestrial systems. Korarchaeota endemism is consistent with endemism of other terrestrial thermophiles and supports the existence of dispersal barriers. Korarchaeota were found predominantly in >55°C springs at pH 4.7–8.5 at concentrations up to 6.6×106 16S rRNA gene copies g−1 wet sediment. In Yellowstone National Park (YNP), Korarchaeota were most abundant in springs with a pH range of 5.7 to 7.0. High sulfate concentrations suggest these fluids are influenced by contributions from hydrothermal vapors that may be neutralized to some extent by mixing with water from deep geothermal sources or meteoric water. In the Great Basin (GB), Korarchaeota were most abundant at spring sources of pH<7.2 with high particulate C content and high alkalinity, which are likely to be buffered by the carbonic acid system. It is therefore likely that at least two different geological mechanisms in YNP and GB springs create the neutral to mildly acidic pH that is optimal for Korarchaeota. A classification support vector machine (C-SVM) trained on single analytes, two analyte combinations, or vectors from non-metric multidimensional scaling models was able to predict springs as Korarchaeota-optimal or sub-optimal habitats with accuracies up to 95%. To our knowledge, this is the most extensive analysis of the geochemical habitat of any high-level microbial taxon and the first application of a C-SVM to microbial ecology

Rule-Based Cell Systems Model of Aging using Feedback Loop Motifs Mediated by Stress Responses

Investigating the complex systems dynamics of the aging process requires integration of a broad range of cellular processes describing damage and functional decline co-existing with adaptive and protective regulatory mechanisms. We evolve an integrated generic cell network to represent the connectivity of key cellular mechanisms structured into positive and negative feedback loop motifs centrally important for aging. The conceptual network is casted into a fuzzy-logic, hybrid-intelligent framework based on interaction rules assembled from a priori knowledge. Based upon a classical homeostatic representation of cellular energy metabolism, we first demonstrate how positive-feedback loops accelerate damage and decline consistent with a vicious cycle. This model is iteratively extended towards an adaptive response model by incorporating protective negative-feedback loop circuits. Time-lapse simulations of the adaptive response model uncover how transcriptional and translational changes, mediated by stress sensors NF-κB and mTOR, counteract accumulating damage and dysfunction by modulating mitochondrial respiration, metabolic fluxes, biosynthesis, and autophagy, crucial for cellular survival. The model allows consideration of lifespan optimization scenarios with respect to fitness criteria using a sensitivity analysis. Our work establishes a novel extendable and scalable computational approach capable to connect tractable molecular mechanisms with cellular network dynamics underlying the emerging aging phenotype

Glycoprotein IV-independent adhesion of sickle red blood cells to immobilized thrombospondin under flow conditions

The abnormal adherence of red blood cells (RBC to the blood vessel wall is believed to contribute to the vascular occlusion observed in patients with sickle call anemia. The cell adhesion receptors GPIV (CD36) and integrin alpha 4 beta 1 (CD49d/CD29) were previously identified on circulating sickle reticulocytes, and shown to mediate sickle RBC adhesion to the endothelium. The presence of damaged endothelium in these patients suggests that exposed extracellular matrix proteins could provide a potential substrate for sickle RBC adhesion. To determine whether RBC adhesion receptors could mediate adhesion to extracellular matrix proteins, we tested their ability to adhere to a variety of immobilized, purified proteins under flow conditions. Neither sickle nor normal RBC adhered to fibronectin, vitronectin, fibrinogen, or collagen. In contrast, we observed substantial adhesion of sickle but not normal RBC to thrombospondin (TSP). The adhesion was not inhibited with known antagonists of the GPIV-TSP interaction, nor by inhibitors of several other known binding domains in TSP. Moreover, the adhesion was resistant to inhibition by soluble TSP, suggesting that immobilization of TSP exposes an adhesive site that is cryptic on TSP in solution. However, the glycosaminoglycans, chondroitin sulfate A, and dextran sulfate were potent inhibitors of this adhesion. These results suggest that a mechanism distinct from GPIV is responsible for sickle RBC adhesion to immobilized TSP under flow conditions.</jats:p