Borel singularities at small x

D.I.S. at small Bjorken $x$ is considered within the dipole cascade formalism. The running coupling in impact parameter space is introduced in order to parametrize effects that arise from emission of large size dipoles. This results in a new evolution equation for the dipole cascade. Strong coupling effects are analyzed after transforming the evolution equation in Borel ($b$) space. The Borel singularities of the solution are discussed first for the universal part of the dipole cascade and then for the specific process of D.I.S. at small $x$. In the latter case the leading infrared renormalon is at $b=1/\beta_0$ indicating the presence of $1/Q^2$ power corrections for the small-$x$ structure functions.Comment: 5 pages, Latex (Talk presented at DIS'97, Chicago, IL

Guided Elastic Waves in Pre-Stressed Solids for the Ultrasonic Characterization of Interfacial Zones

Towards a mechanical dynamic characterization of pre-stressed layered solids and a non-destructive ultrasonic evaluation of their interfacial bonds, it is necessary to examine the propagation of elastic interfacial waves along planar boundaries between finitely pre-strained incompressible solids. The effect of pre-stress on the propagation of Stoneley waves was first examined in [1,2] for two half-spaces of the same incompressible neo-hookean material subjected to different homogeneous pre-strains of common principal axes. In [3] propagation of Stoneley waves along a common principal axis of pre-strain of the two half-spaces which were taken as different incompressible materials having arbitrary strain energy functions was considered. The effect of pre-stress on Rayleigh waves was first studied in [4]. In [5] results were obtained for more general pre-stress conditions on an incompressible half-space of arbitrary strain energy function

Extracting the Groupwise Core Structural Connectivity Network: Bridging Statistical and Graph-Theoretical Approaches

Finding the common structural brain connectivity network for a given population is an open problem, crucial for current neuro-science. Recent evidence suggests there's a tightly connected network shared between humans. Obtaining this network will, among many advantages , allow us to focus cognitive and clinical analyses on common connections, thus increasing their statistical power. In turn, knowledge about the common network will facilitate novel analyses to understand the structure-function relationship in the brain. In this work, we present a new algorithm for computing the core structural connectivity network of a subject sample combining graph theory and statistics. Our algorithm works in accordance with novel evidence on brain topology. We analyze the problem theoretically and prove its complexity. Using 309 subjects, we show its advantages when used as a feature selection for connectivity analysis on populations, outperforming the current approaches

SRF role as a mechano-transductor in response to exercise in cancer cachexia

Introduction: Recent studies showed that physical activity increased survival in cancer patient and animal models of cancer cachexia. The underlying mechanisms, however, are still largely unknown. Methods: To identify signalling pathways involved in exercise-dependent maintenance of muscle mass and function in cachexia, we investigated the role of serum response factor (SRF)—a transcription factor playing a pivotal a role in muscular growth, differentiation and regeneration—in C26-bearing mice in the absence or presence of voluntary exercise (wheel running). Results: SRF levels are decreased at protein level in cachexia. Consistently, a decrease in the expression of SRF target genes such as MyoD and SK-actin occurs in C26-bearing mice, suggesting a decrease of SRF transcriptional activity. These tumour effects were counteracted by wheel running and associated to the rescue of muscle mass and function. However, a minimum amount of exercise (2 km/day) is necessary to keep SRF levels elevated in cachexia over a threshold which is necessary to exert beneficial effects. SRF levels inversely correlate with wasting in mice, suggesting that SRF play a role in maintaining body mass (mostly accounted for by muscle mass). We also observe the recruitment of nuclei within the muscle fibres in response to exercise, which could contribute to muscle homeostasis and is consistent with the previously observed opposite effects of tumour and exercise on MyoD and Pax7 expression. Conclusions: Our results suggest that physical activity rescues SRF expression as well as its transcriptional activity, highlighting the importance of genetic activation induced by skeletal muscle activity for muscle rescue and homeostasis. These effects could be extended to the fibre microenvironment, including myogenic stem cell activity

Wide-angle elastic scattering and color randomization

Baryon-baryon elastic scattering is considered in the independent scattering (Landshoff) mechanism. It is suggested that for scattering at moderate energies, direct and interchange quark channels contribute with equal color coefficients because the quark color is randomized by soft gluon exchange during the hadronization stage. With this assumption, it is shown that the ratio of cross sections $R_{\overline{p} p/ p p}$ at CM angle $\theta = 90^0$ decreases from a high energy value of R_{\pbar p / pp} \approx 1/2.7, down to R_{\pbar p / pp} \approx 1/28, compatible with experimental data at moderate energies. This sizable fall in the ratio seems to be characteristic of the Landshoff mechanism, in which changes at the quark level have a strong effect precisely because the hadronic process occurs via multiple quark scatterings. The effect of color randomization on the angular distribution of proton-proton elastic scattering and the cross section ratio $R_{np/pp}$ is also discussed.Comment: 18 pages, latex2e, 4 uuencoded figures, include

Red cell distribution width and mortality in acute heart failure patients with preserved and reduced ejection fraction.

Elevated red blood cell distribution width (RDW) is a valid predictor of outcome in acute heart failure (AHF). It is unknown whether elevated RDW remains predictive in AHF patients with either preserved left ventricular ejection fraction (LVEF) ≥50% or reduced LVEF (<50%). Prospective local registry including 402 consecutive hospitalized AHF patients without acute coronary syndrome or need of intensive care. The primary outcome was all-cause mortality (ACM) at 1 year after admission. Demographic and clinical data derive from admission, echocardiographic examinations (n = 269; 67%) from hospitalization. The Cox proportional hazard model including all patients (P < 0.001) was adjusted for age, gender, and RDW quartiles. Independent predictors of 1-year ACM were cardiogenic shock (HR 2.86; CI: 1.3-6.4), male sex (HR 1.9; CI: 1.2-2.9), high RDW quartile (HR 1.66; CI: 1.02-2.8), chronic HF (HR 1.61; CI: 1.05-2.5), valvular heart disease (HR 1.61; CI: 1.09-2.4), increased diastolic blood pressure (HR 1.02 per mmHg; CI: 1.01-1.03), increasing age (HR 1.04 by year; CI: 1.02-1.07), platelet count (HR 1.002 per G/l; CI: 1.0-1.004), systolic blood pressure (HR 0.99 per mmHg; CI: 0.98-0.99), and weight (HR 0.98 per kg; CI: 0.97-0.99). A total of 114 patients (28.4%) died within the first year; ACM of all patients increased with quartiles of rising RDW (χ(2) 18; P < 0.001). ACM was not different between RDW quartiles of patients with reduced LVEF (n = 153; χ(2) 6.6; P = 0.084). In AHF with LVEF ≥50% the probability of ACM increased with rising RDW (n = 116; χ(2) 9.9; P = 0.0195). High RDW is associated with increased ACM in AHF patients with preserved but not with reduced LVEF in this study population

New anomalous trajectory in Regge theory

We show that a new Regge trajectory with \alpha_{f_1} (0) \approx 1 and slope \alpha_{f_1}'(0) \approx 0 explains the features of hadron-hadron scattering and photoproduction of the rho and phi mesons at large energy and momentum transfer. This trajectory with quantum numbers P = C = +1 and odd signature can be considered as a natural partner of the Pomeron which has even signature. The odd signature of the new exchange leads to contributions to the spin-dependent cross sections, which do not vanish at large energy. The links between the anomalous properties of this trajectory, the axial anomaly and the flavor singlet axial vector f_1 (1285) meson are discussed.Comment: 20 pages, REVTeX, 8 figures (9 eps files), version to appear in Phys. Rev.

Bi-local baryon interpolating fields with two flavours

We construct bi-local interpolating field operators for baryons consisting of three quarks with two flavors, assuming good isospin symmetry. We use the restrictions following from the Pauli principle to derive relations/identities among the baryon operators with identical quantum numbers. Such relations that follow from the combined spatial, Dirac, color, and isospin Fierz transformations may be called the (total/complete) Fierz identities. These relations reduce the number of independent baryon operators with any given spin and isospin. We also study the Abelian and non-Abelian chiral transformation properties of these fields and place them into baryon chiral multiplets. Thus we derive the independent baryon interpolating fields with given values of spin (Lorentz group representation), chiral symmetry ($U_L(2) \times U_R(2)$ group representation) and isospin appropriate for the first angular excited states of the nucleon.Comment: 15 pages, 4 tables, accepted by EPJ