Strange nonchaotic stars

The unprecedented light curves of the Kepler space telescope document how the brightness of some stars pulsates at primary and secondary frequencies whose ratios are near the golden mean, the most irrational number. A nonlinear dynamical system driven by an irrational ratio of frequencies generically exhibits a strange but nonchaotic attractor. For Kepler's "golden" stars, we present evidence of the first observation of strange nonchaotic dynamics in nature outside the laboratory. This discovery could aid the classification and detailed modeling of variable stars.Comment: 5 pages, 4 figures, published in Physical Review Letter

Lopsided Schumpeterian Competition and the Superstar Firm Phenomenon

In many industries worldwide, gains from technological innovation have increasingly accrued only to the largest and most resource-endowed companies, while most companies lag in implementation of vital new technologies. As a result, the phenomenon of so-called “superstar” firms that outdistance industry rivals has become a major topic in technology management.https://dc.suffolk.edu/ciclseries/1000/thumbnail.jp

Toll-Like Receptor Gene Expression in Cecum and Spleen of Chicks Challenged with Salmonella Enterica Serovar Enteritidis

Toll-like receptors (TLR) recognize pathogenassociated molecular patterns (PAMP) of infectious microbes. Activation of TLR with PAMP can result in immune response by modulation of innate and adoptive immune system. This study aimed to investigate the acute effect of Salmonella challenge on TLR RNA expression in cecum and spleen of birds from different genetic lines. Chicks from broiler, Leghorn, and Fayoumi lines were challenged or mock challenged with Salmonella. The RNA expression levels of TLR2, TLR4 and TLR5 genes were assessed by quantitative RT-PCR in cecum and spleen tissue harvested at 2 or 18 h post-challenge. The results demonstrate a significant genetic line effect on TLR expression in the spleen of Salmonella infected birds, which may partly explain the genetic variability in immune response to Salmonella enterica serovar Enteritidis. The higher level of TLR2 and TLR4 RNA expression observed in the spleen of Fayoumi line compare to Leghorn and broiler lines in Salmonella enterica serovar Enteritidis challenged birds may be associated with the stronger immune response to the infection and might be useful characteristics to be considered in breeding immunocompetent chickens

Boron Nitride Nanotubes: Force Field Parameterization, Epoxy Interactions, and Comparison with Carbon Nanotubes for High-Performance Composite Materials

Boron nitride nanotubes (BNNTs) are a very promising reinforcement for future high-performance composites because of their excellent thermo-mechanical properties. To take full advantage of BNNTs in composite materials, it is necessary to have a comprehensive understanding of the wetting characteristics of various high-performance resins. Molecular dynamics (MD) simulations provide an accurate and efficient approach to establish the contact angle values of engineering polymers on reinforcement surfaces, which offers a measure for the interaction between the polymer and reinforcement. In this research, MD simulations and experiments are used to determine the wettability of various epoxy systems on BNNT surfaces. The reactive interface force field (IFF-R) is parameterized and utilized in the simulations to accurately describe the interaction of the epoxy monomers with the BNNT surface. The effect of the epoxy monomer type, hardener type, local atomic charges, and temperature on the contact angle is established. The results show that contact angles decrease with increases in temperature for all the epoxy/hardener systems. The bisphenol-A-based epoxy system demonstrates better wettability with the BNNT surface than the bisphenol-F based epoxy system. Furthermore, the MD predictions demonstrate that these observations are validated with experimental results, wherein the same contact angle trends are observed for macroscopic epoxy drops on nonwoven nanotube papers. As wetting properties drive the resin infusion in the reinforcement materials, these results are important for the future manufacturing of high-quality BNNT/epoxy nanocomposites for high-performance applications such as aerospace and aeronautical vehicles

Heat Induced Grafting of Poly(glycidyl methacrylate) on Polybutylene Terephthalate Nonwovens for Bioseparations

Polybutylene terephthalate (PBT) nonwovens were successfully grafted with poly(glycidyl methacrylate) (polyGMA) using a heat induced grafting approach with the thermal initiator benzoyl peroxide (Bz2O2). This grafting method resulted in complete, uniform, and conformal grafted layers around the PBT fibers that could be further functionalized as ion exchangers for protein capture. Protein binding capacities as high as 200 mg/g were achieved for ion exchange PBT nonwovens grafted to 20% weight gain using this heat induced grafting method. Compared to UV grafted polyGMA PBT nonwovens, the rates of protein adsorption are several times faster for the heat grafted polyGMA PBT nonwoven, reaching equilibrium within minutes; UV grafted polyGMA ion exchange PBT nonwovens require hours to reach equilibrium. This indicates that polyGMA grafts formed by heat induced grafting are thinner, and therefore more dense, than UV grafted layers with the same % weight gain. To further investigate the structural differences between the two grafting methods, targets of various molecular weights (ATP, lysozyme, BSA, hIgG) were adsorbed to the materials. Increasing the target size resulted in a decrease of target molecules bound for both grafting methods. However, the heat grafted nonwovens exhibited a much stronger dependence of protein molecular weight on protein capture, indicating that heat induced grafting results in a polyGMA layer that has a smaller free volume between chains available for protein binding compared to the UV grafting method. Protein adsorption isotherms for the two grafting methods confirmed that both methods resulted in similar strengths of protein binding, with dissociation constants on the order of Kd = 10-6 M which is consistent with ion exchange binding on polymer brush networks. Heat grafted polyGMA ion exchange PBT nonwovens showed excellent protein binding and elution

From pre-ceramic polymer to high-toughness ceramic: An SLA 3D printing approach

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Large scale structure around a z=2.1 cluster

The most prodigious starburst galaxies are absent in massive galaxy clusters today, but their connection with large scale environments is less clear at $z\gtrsim2$. We present a search of large scale structure around a galaxy cluster core at $z=2.095$ using a set of spectroscopically confirmed galaxies. We find that both color-selected star-forming galaxies (SFGs) and dusty star-forming galaxies (DSFGs) show significant overdensities around the $z=2.095$ cluster. A total of 8 DSFGs (including 3 X-ray luminous active galactic nuclei, AGNs) and 34 SFGs are found within a 10 arcmin radius (corresponds to $\sim$15 cMpc at $z\sim2.1$) from the cluster center and within a redshift range of $\Delta z=0.02$, which leads to galaxy overdensities of $\delta_{\rm DSFG}\sim12.3$ and $\delta_{\rm SFG}\sim2.8$. The cluster core and the extended DSFG- and SFG-rich structure together demonstrate an active cluster formation phase, in which the cluster is accreting a significant amount of material from large scale structure while the more mature core may begin to virialize. Our finding of this DSFG-rich structure, along with a number of other protoclusters with excess DSFGs and AGNs found to date, suggest that the overdensities of these rare sources indeed trace significant mass overdensities. However, it remains puzzling how these intense star formers are triggered concurrently. Although an increased probability of galaxy interactions and/or enhanced gas supply can trigger the excess of DSFGs, our stacking analysis based on 850 $\mu$m images and morphological analysis based on rest-frame optical imaging do not show such enhancements of merger fraction and gas content in this structure.Comment: 11 pages, 4 figures, ApJ accepte