Experimental investigation of peripheral-wall injection techniques in a water vortex tube

Effect of peripheral wall injection technique used to drive water vortex tube on structure and thickness of turbulent mixing region and on flow patterns in boundary layer

Experimental investigation of radial-inflow vortexes in jet-injection and rotating peripheral-wall water vortex tubes

Wall injection area and axial bypass effects on flow pattern of stagnation surface in radial inflow vortexe

The size of the nucleosome

The structural origin of the size of the 11 nm nucleosomal disc is addressed. On the nanometer length-scale the organization of DNA as chromatin in the chromosomes involves a coiling of DNA around the histone core of the nucleosome. We suggest that the size of the nucleosome core particle is dictated by the fulfillment of two criteria: One is optimizing the volume fraction of the DNA double helix; this requirement for close-packing has its root in optimizing atomic and molecular interactions. The other criterion being that of having a zero strain-twist coupling; being a zero-twist structure is a necessity when allowing for transient tensile stresses during the reorganization of DNA, e.g., during the reposition, or sliding, of a nucleosome along the DNA double helix. The mathematical model we apply is based on a tubular description of double helices assuming hard walls. When the base-pairs of the linker-DNA is included the estimate of the size of an ideal nucleosome is in close agreement with the experimental numbers. Interestingly, the size of the nucleosome is shown to be a consequence of intrinsic properties of the DNA double helix.Comment: 11 pages, 5 figures; v2: minor modification

Hardcore classification: identifying play styles in social games using network analysis

In the social network of a web-based online game, all players are not equal. Through network analysis, we show that the community of players in a online social game is an example of a scale free small world network and that the growth of the player-base obeys a power law. The community is centred around a minority group of ``hardcore" players who define the social environment for the game, and without whom the social network would collapse. Methods are discussed for identifying this critically important subset of players automatically through analysing social behaviours within the game

First-principles GW calculations for DNA and RNA nucleobases

On the basis of first-principles GW calculations, we study the quasiparticle properties of the guanine, adenine, cytosine, thymine, and uracil DNA and RNA nucleobases. Beyond standard G0W0 calculations, starting from Kohn-Sham eigenstates obtained with (semi)local functionals, a simple self-consistency on the eigenvalues allows to obtain vertical ionization energies and electron affinities within an average 0.11 eV and 0.18 eV error respectively as compared to state-of-the-art coupled-cluster and multi-configurational perturbative quantum chemistry approaches. Further, GW calculations predict the correct \pi -character of the highest occupied state, thanks to several level crossings between density functional and GW calculations. Our study is based on a recent gaussian-basis implementation of GW with explicit treatment of dynamical screening through contour deformation techniques.Comment: 5 pages, 3 figure

Platelet-Activating Factor-Induced Reduction in Contact Hypersensitivity Responses Is Mediated by Mast Cells via Cyclooxygenase-2-Dependent Mechanisms

Platelet-activating factor (PAF) stimulates numerous cell types via activation of the G protein-coupled PAF receptor (PAFR). PAFR activation not only induces acute proinflammatory responses, but it also induces delayed systemic immunosuppressive effects by modulating host immunity. Although enzymatic synthesis and degradation of PAF are tightly regulated, oxidative stressors, such as UVB, chemotherapy, and cigarette smoke, can generate PAF and PAF-like molecules in an unregulated fashion via the oxidation of membrane phospholipids. Recent studies have demonstrated the relevance of the mast cell (MC) PAFR in PAFR-induced systemic immunosuppression. The current study was designed to determine the exact mechanisms and mediators involved in MC PAFR-mediated systemic immunosuppression. By using a contact hypersensitivity model, the MC PAFR was not only found to be necessary, but also sufficient to mediate the immunosuppressive effects of systemic PAF. Furthermore, activation of the MC PAFR induces MC-derived histamine and PGE2 release. Importantly, PAFR-mediated systemic immunosuppression was defective in mice that lacked MCs, or in MC-deficient mice transplanted with histidine decarboxylase- or cyclooxygenase-2-deficient MCs. Lastly, it was found that PGs could modulate MC migration to draining lymph nodes. These results support the hypothesis that MC PAFR activation promotes the immunosuppressive effects of PAF in part through histamine- and PGE2-dependent mechanisms

Making the Most of Interim Assessment Data: Lessons from Philadelphia

Under No Child Left Behind, urban school districts have increasingly turned to interim assessments, administered at regular intervals, to help gauge student progress in advance of annual state exams. These assessments have spawned growing debate among educators, assessment experts, and the testing industry: are they worth the significant investment of money and time? In Making the Most of Interim Assessment Data: Lessons from Philadelphia, Research for Action (RFA) weighs in on this issue. The School District of Philadelphia (SDP) was an early adopter of interim assessments, implementing the exams in 2003. Unlike teachers in some other regions, Philadelphia elementary and middle grades teachers rated these 'Benchmark' assessments highly. However, the study found that enthusiasm did not necessarily correlate with higher rates of student achievement. What did predict student success were three factors -- instructional leadership, collective responsibility, and use of the SDP's Core Curriculum. The report underscores the value of investment in ongoing data interpretation that emphasizes teachers' learning within formal instructional communities, such as grade groups of teachers. This research was funded by the Spencer Foundation and the William Penn Foundation

Disordered, stretched, and semiflexible biopolymers in two dimensions

We study the effects of intrinsic sequence-dependent curvature for a two dimensional semiflexible biopolymer with short-range correlation in intrinsic curvatures. We show exactly that when not subjected to any external force, such a system is equivalent to a system with a well-defined intrinsic curvature and a proper renormalized persistence length. We find the exact expression for the distribution function of the equivalent system. However, we show that such an equivalent system does not always exist for the polymer subjected to an external force. We find that under an external force, the effect of sequence-disorder depends upon the averaging order, the degree of disorder, and the experimental conditions, such as the boundary conditions. Furthermore, a short to moderate length biopolymer may be much softer or has a smaller apparent persistent length than what would be expected from the "equivalent system". Moreover, under a strong stretching force and for a long biopolymer, the sequence-disorder is immaterial for elasticity. Finally, the effect of sequence-disorder may depend upon the quantity considered