Instanton effects and linear-chiral duality

We discuss duality between the linear and chiral dilaton formulations, in the presence of super-Yang-Mills instanton corrections to the effective action. In contrast to previous work on the subject, our approach appeals directly to explicit instanton calculations and does not rely on the introduction of an auxiliary Veneziano-Yankielowicz superfield. We discuss duality in the case of an axion that has a periodic scalar potential, and find that the bosonic fields of the dual linear multiplet have a modified interpretation. We note that symmetries of the axion potential manifest themselves as symmetries of the equations of motion for the linear multiplet. We also make some brief remarks regarding dilaton stabilization. We point out that corrections recently studied by Dijkgraaf and Vafa can be used to stabilize the axion in the case of a single super-Yang-Mills condensate.Comment: 1+18 pages, 1 figure, comments and references adde

Cosmological Rescaling through Warped Space

We discuss a scenario where at least part of the homogeneity on a brane world can be directly related to the hierarchy problem through warped space. We study the dynamics of an anti-D3-brane moving toward the infrared cut-off of a warped background. After a region described by the DBI action, the self-energy of the anti-D3-brane will dominate over the background. Then the world-volume scale of the anti-D3-brane is no longer comoving with the background geometry. After it settles down in the infrared end, the world-volume inhomogeneity will appear, to a Poincare observer, to be stretched by an exponentially large ratio. This ratio is close to that of the hierarchy problem between the gravitational and electroweak scales.Comment: 12 pages, 2 figures; v2, PRD version, comments and references adde

On supersymmetric Minkowski vacua in IIB orientifolds

Supersymmetric Minkowski vacua in IIB orientifold compactifications based on orbifolds with background fluxes and non-perturbative superpotentials are investigated. Especially, microscopic requirements and difficulties to obtain such vacua are discussed. We show that orbifold models with one and two complex structure moduli and supersymmetric 2-form flux can be successfully stabilized to such vacua. By taking additional gaugino condensation on fixed space-time filling D3-branes into account also models without complex structure can be consistently stabilized to Minkowski vacua.Comment: 17 pages, 2 figures; More detailed proof for absence of complex flat directions in susy AdS vacua given; Footnotes and reference adde

The effect of B and Si additions on the structural and magnetic behavior of Fe-Co-Ni alloy prepared by high-energy mechanical milling

Nanocrystalline Fe50Co25Ni15X10 (X = Bamorphous, Bcrystalline, and Si) powdered alloys were prepared by mechanical alloying process. Morphological, microstructural, and structural characterizations of the powders milled several times were investigated by scanning electron microscopy and X-ray diffraction. The final crystallographic state strongly depends on the chemical composition and the grinding time; it can be single-phase or two-phase. The crystallite size reduction down the nanometer scale is accompanied by the introduction of high level of lattice strains. The dissolution of Co, Ni, B (amorphous and crystalline), and Si into the α-Fe lattice leads to the formation of highly disordered Fe-based solid solutions. Coercivity (Hc) and the saturation magnetization (Ms) of alloyed powders were measured at room temperature by a vibration sample magnetization. The magnetic measurements show a contrasting Ms and (Hc) in all alloy compositions. Conclusively, soft magnetic properties of nanocrystalline alloys are related to various factors such as metalloid addition, formed phases, and chemical compositions

Moduli potentials in string compactifications with fluxes: mapping the Discretuum

We find de Sitter and flat space solutions with all moduli stabilized in four dimensional supergravity theories derived from the heterotic and type II string theories, and explain how all the previously known obstacles to finding such solutions can be removed. Further, we argue that if the compact manifold allows a large enough space of discrete topological choices then it is possible to tune the parameters of the four dimensional supergravity such that a hierarchy is created and the solutions lie in the outer region of moduli space in which the compact volume is large in string units, the string coupling is weak, and string perturbation theory is valid. We show that at least two light chiral superfields are required for this scenario to work, however, one field is sufficient to obtain a minimum with an acceptably small and negative cosmological constant. We discuss cosmological issues of the scenario and the possible role of anthropic considerations in choosing the vacuum of the theory. We conclude that the most likely stable vacuua are in or near the central region of moduli space where string perturbation theory is not strictly valid, and that anthropic considerations cannot help much in choosing a vacuum.Comment: 34 pages, no figure

An Effect of α′\alpha' Corrections on Racetrack Inflation

We study the effects of $\alpha '$ corrections to the K\"ahler potential on volume stabilisation and racetrack inflation. In a region where classical supergravity analysis is justified, stringy corrections can nevertheless be relevant for correctly analyzing moduli stabilisation and the onset of inflation.Comment: 13 pages, 4 figures. Typos corrected, references added, this version to appear in JHE

The DNA damage and the DNA replication checkpoints converge at the MBF transcription factor

In fission yeast cells, Cds1 is the effector kinase of the DNA replication checkpoint. We previously showed that when the DNA replication checkpoint is activated, the repressor Yox1 is phosphorylated and inactivated by Cds1, resulting in activation of MluI-binding factor (MBF)-dependent transcription. This is essential to reinitiate DNA synthesis and for correct G1-to-S transition. Here we show that Cdc10, which is an essential part of the MBF core, is the target of the DNA damage checkpoint. When fission yeast cells are treated with DNA-damaging agents, Chk1 is activated and phosphorylates Cdc10 at its carboxy-terminal domain. This modification is responsible for the repression of MBF-dependent transcription through induced release of MBF from chromatin. This inactivation of MBF is important for survival of cells challenged with DNA-damaging agents. Thus Yox1 and Cdc10 couple normal cell cycle regulation in unperturbed conditions and the DNA replication and DNA damage checkpoints into a single transcriptional complex

Development and validation of a questionnaire to evaluate lifestyle-related behaviors in elementary school children

Background: The SI! Program promotes cardiovascular health through a multilevel school-based intervention on four lifestyle-related components: diet, physical activity, understanding the body and heart, and management of emotions. We report here the development and validation of the KAH (knowledge, attitudes and habits)-questionnaire adapted for elementary school children (6-7 years old) as a tool for the forthcoming evaluation of the SI! Program, where the KAH scoring will be the primary outcome. The efficacy of such an intervention will be based on the improvements in children's KAH towards a healthy lifestyle. Methods: The questionnaire validation process started with a pool of items proposed by the pedagogical team who developed the SI! Program for elementary school. The questionnaire was finalized by decreasing the number of items from 155 to 48 using expert panels and statistical tests on the responses from 384 children (ages 6-7). A team of specialized psychologists administered the questionnaire at schools providing standard directions for the final administration. The internal consistency was assessed using Cronbach's a coefficients. Reliability was measured through the split-half method, and problematic items were detected applying the item response theory. Analysis of variance and Tukey's test of additivity were used for multiple comparisons. Results: The final KAH-questionnaire for elementary school children should be administered to children individually by trained staff. The 48 items-questionnaire is divided evenly between the 4 components of the intervention, with an overall Cronbach's a = 0.791 (a = 0.526 for diet, a = 0.537 for physical activity, a = 0.523 for human body and heart, and a = 0.537 for management of emotions). Conclusions: The KAH-questionnaire is a reliable instrument to assess the efficacy of the SI! Program on instilling healthy lifestyle-related behaviors in elementary school children.This work is supported by the SHE Foundation (Foundation for Science, Health and Education) and the Daniel and Nina Carasso Foundation.S

Influence of a Large Image Watermarking Scheme Parallelization on Possible Attacks

Digital data representation provides an efficient and fast way to access to information and to exchange it. In many situations though ownership or copyright protection mechanisms are desired. For still images and video, one possible way to achieve this is through watermarking. Watermarking consists of an imperceptible information embedded within a given media. Parallel ProcessingWatermarking Embedding Schemes have demonstrated to be efficient from a computational and memory usage point of view for very large images. These schemes consist in dividing the image into tiles and watermarking each independently. The processing allows the use of a parallel computation scheme. The watermarking method used in the scope of this work is a parallel variant of an approach known as self-referenced Spread Spectrum signature pattern. Since the watermarking scheme has been modified through tiling, the extra references due to signature replication can be used in the retrieval. This work describes the above mentioned approach to watermark images and provides an analysis of its performance