Relics of Supersymmetry in Ordinary 1-flavor QCD: Hairpin Diagrams and Scalar-Pseudoscalar Degeneracy

The large-$N_c$ orientifold planar equivalence between $\mathcal{N}=1$ SUSY Yang-Mills theory and ordinary 1-flavor QCD suggests that low-energy quark-gluon dynamics in QCD should be constrained by the supersymmetry of the parent theory. One SUSY relic expected from orientifold equivalence is the approximate degeneracy of the scalar and pseudoscalar mesons in 1-flavor QCD. Here we study the role of the $q\bar{q}$ annihilation (hairpin) contributions to the meson correlators. These annihilation terms induce mass shifts of opposite sign in the scalar and pseudoscalar channels, making degeneracy plausible. Calculations of valence and hairpin correlators in quenched lattice QCD are consistent with approximate degeneracy, although the errors on the scalar hairpin are large. We also study the role of $q\bar{q}$ annihilation in the 1- and 2-flavor Nambu-Jona Lasinio model, where annihilation terms arise from the chiral field determinant representing the axial U(1) anomaly. Scalar-pseudoscalar degeneracy for the 1-flavor case reduces to a constraint on the relative size of the anomalous and non-anomalous 4-fermion couplings.Comment: 17 pages, 3 figure

Fractionally charged Wilson loops as a probe of θ\theta-dependence in CPN−1CP^{N-1} sigma models: Instantons vs. large N

The behavior of Wilson loops with fractional charge is used to study the $\theta$-dependence of the free energy density $\epsilon(\theta)$ for the $CP^1$, $CP^5$, and $CP^9$ sigma models in two spacetime dimensions. The function $\epsilon(\theta)$ is extracted from the area law for a Wilson loop of charge $q=\theta/2\pi$. For $CP^1$, $\epsilon(\theta)$ is smooth in the region $\theta\approx\pi$ and well-described by a dilute instanton gas throughout the range $0<\theta<2\pi$. For $CP^5$ and $CP^9$ the energy exhibits a clear cusp and evidence for discrete, degenerate vacua at $\theta = \pi$, as expected from large $N$ arguments. For $CP^9$ the $\theta$-dependence is in good quantitative agreement with the leading order large $N$ prediction $\epsilon(\theta)={1/2}\chi_t\theta^2$ throughout the range $0<\theta<\pi$.Comment: 16 pages, 10 figure

Modulation of p27/Cdk2 complex formation through 4D5-mediated inhibition of HER2 receptor signaling

The molecular mechanisms mediating the anti-proliferative effects of the murine anti-HER2 monoclonal antibody (4D5) were investigated in HER2-overexpressing human carcinoma cell lines. Treatment with 4D5 resulted in a dramatic accumulation of BT-474 breast carcinoma cells in Gl; concomitant with reduced expression of proteins involved in sequestration of the cyclin E/Cdk2 inhibitor protein p27, increased association of p27 with Cdk2 complexes and Cdk2 inactivation. No equivalent effects were observed in BT-474 cells treated with a control, non-inhibitory HER2 monoclonal antibody (FRP5) or in a HER2-overexpressing cell line insensitive to 4D5 treatment (MKN7 gastric carcinoma cells), confirming the relationship between these molecular changes and 4D5-mediated inhibition of proliferation. Increased p27 expression was also observed in 4D5-treated BT-474 cells; however an antisense approach demonstrated that this increase was not required for Cdk2 inactivation or establishment of the Gl block. These data suggest that 4D5 interferes with HER2 receptor signaling, resulting in downregulation of proteins involved in p27 sequestration. This causes release of p27, allowing binding and inhibition of cyclin E/Cdk2 complexes and inhibition of Gl/S progression. This model was confirmed using a second 4D5-sensitive, HER2-overexpressing breast tumor line (SKBR3), and suggests that the dependency of a given tumor cell on elevated HER2-receptor signaling for the maintenance of p27 sequestration proteins may determine the clinical response to treatment with the humanized anti-HER2 monoclonal antibody Herceptin® (trastuzumab

Le débit élément clé de la vie des cours d’eau : bilan des altérations et des possibilités de restauration

La gestion quantitative de la ressource en eau constitue l’un des principaux enjeux mondiaux tant du point de vue environnemental, économique que sociologique. Les besoins en eau continuent de croître et la ressource est déjà fortement utilisée. Les régimes de débits de la majorité des grands cours d’eau sont modifiés par des aménagements. Ces modifications ont des conséquences fortes sur le fonctionnement écologique des eaux courantes. Les régimes hydrologiques sont en effet reconnus comme la clé de voûte des hydrosystèmes. Leur variabilité est la base du fonctionnement morphologique des rivières, du renouvellement des habitats et donc de la richesse écologique. Les altérations de ces régimes dues aux usages directs de l’eau (irrigation, eau potable, hydroélectricité) ou aux modifications des bassins versants, touchent à la fois les valeurs de bas débits, les crues et les fréquences de variations. Les enjeux de la restauration concernent non pas seulement le maintien de valeur de débit minimum mais la définition de véritables régimes hydrologiques réservés assurant les grandes fonctionnalités des eaux courante au travers du respect d’un certain degré de variabilité des débits. Actuellement, peu d’expériences de restauration hydrologique de cours d’eau sont conduites. Ces expériences doivent à la fois s’appuyer sur l’identification des enjeux, sur des outils d’aide à la décision mais également sur des suivis à long terme de l’ensemble des compartiments de l’écosystème

Distribution and abundance of fish and crayfish in a Waikato stream in relation to basin area

The aim of this study was to relate the longitudinal distribution of fish and crayfish to increasing basin area and physical site characteristics in the Mangaotama Stream, Waikato region, North Island, New Zealand. Fish and crayfish were captured with two-pass removal electroshocking at 11 sites located in hill-country with pasture, native forest, and mixed land uses within the 21.6 km2 basin. Number of fish species and lineal biomass of fish increased with increasing basin area, but barriers to upstream fish migration also influenced fish distribution; only climbing and non-migratory species were present above a series of small waterfalls. Fish biomass increased in direct proportion to stream width, suggesting that fish used much of the available channel, and stream width was closely related to basin area. Conversely, the abundance of crayfish was related to the amount of edge habitat, and therefore crayfish did not increase in abundance as basin area increased. Densities of all fish species combined ranged from 17 to 459 fish 100 m-2, and biomass ranged from 14 to 206 g m-2. Eels dominated the fish assemblages, comprising 85-100% of the total biomass; longfinned eels the majority of the biomass at most sites. Despite the open access of the lower sites to introduced brown trout, native species dominated all the fish communities sampled

Exploring the Levinthal limit in protein folding

According to the thermodynamic hypothesis, the native state of proteins is uniquely defined by their amino acid sequence. On the other hand, according to Levinthal, the native state is just a local minimum of the free energy and a given amino acid sequence, in the same thermodynamic conditions, can assume many, very different structures that are as thermodynamically stable as the native state. This is the Levinthal limit explored in this work. Using computer simulations, we compare the interactions that stabilize the native state of four different proteins with those that stabilize three non-native states of each protein and find that the nature of the interactions is very similar for all such 16 conformers. Furthermore, an enhancement of the degree of fluctuation of the non-native conformers can be explained by an insufficient relaxation to their local free energy minimum. These results favor Levinthal's hypothesis that protein folding is a kinetic non-equilibrium process.FCT - Foundation for Science and Technology, Portugal [UID/Multi/04326/2013]; Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP); Conselho Nacional de Desenvolvimento Cientia co e Tecnologico (CNPq

Pleasure and pedagogy: the consumption of DVD add-ons among Irish teenagers

This article addresses the issue of young people and media use in the digital age, more specifically the interconnection between new media pleasures and pedagogy as they relate to the consumption of DVD add-ons. Arguing against the view of new media as having predominantly detrimental effects on young people, the authors claim that new media can enable young people to develop media literacy skills and are of the view that media literacy strategies must be based on an understanding and legitimating of young people's use patterns and pleasures. The discussion is based on a pilot research project on the use patterns and pleasures of use with a sample of Irish teenagers. They found that DVDs were used predominantly in the home context, and that, while there was variability in use between the groups, overall they developed critical literacy skills and competences which were interwoven into their social life and projects of identity construction. The authors suggest that these findings could be used to develop DVDs and their add-on features as a learning resource in the more formal educational setting and they go on to outline the potential teaching benefits of their use across a range of pedagogical areas