Nonlinear Sigma Model for Disordered Media: Replica Trick for Non-Perturbative Results and Interactions

In these lectures, given at the NATO ASI at Windsor (2001), applications of the replicas nonlinear sigma model to disordered systems are reviewed. A particular attention is given to two sets of issues. First, obtaining non-perturbative results in the replica limit is discussed, using as examples (i) an oscillatory behaviour of the two-level correlation function and (ii) long-tail asymptotes of different mesoscopic distributions. Second, a new variant of the sigma model for interacting electrons in disordered normal and superconducting systems is presented, with demonstrating how to reduce it, under certain controlled approximations, to known ``phase-only'' actions, including that of the ``dirty bosons'' model.Comment: 25 pages, Proceedings of the NATO ASI "Field Theory of Strongly Correlated Fermions and Bosons in Low - Dimensional Disordered Systems", Windsor, August, 2001; to be published by Kluwe

Socio-economic voter profile and motives for Islamist support in Morocco

Based on an original dataset of merged electoral and census data, this article is a study of electoral support for the Islamist Party in Morocco in the 2002 and 2007 elections. It differentiates between the clientelistic, grievance and horizontal network type of supporters. We disentangle these profiles empirically on the basis of the role of education, wealth and exclusion for Islamist votes. We find no evidence of the clientelistic profile, but a shift from grievance in 2002 to a horizontal network profile in 2007. World Values Survey individual level data are used as a robustness check, yielding similar results. Qualitative evidence on a changing mobilization pattern of the party between 2002 and 2007 supports our conclusions

A gentle introduction to the functional renormalization group: the Kondo effect in quantum dots

The functional renormalization group provides an efficient description of the interplay and competition of correlations on different energy scales in interacting Fermi systems. An exact hierarchy of flow equations yields the gradual evolution from a microscopic model Hamiltonian to the effective action as a function of a continuously decreasing energy cutoff. Practical implementations rely on suitable truncations of the hierarchy, which capture nonuniversal properties at higher energy scales in addition to the universal low-energy asymptotics. As a specific example we study transport properties through a single-level quantum dot coupled to Fermi liquid leads. In particular, we focus on the temperature T=0 gate voltage dependence of the linear conductance. A comparison with exact results shows that the functional renormalization group approach captures the broad resonance plateau as well as the emergence of the Kondo scale. It can be easily extended to more complex setups of quantum dots.Comment: contribution to Les Houches proceedings 2006, Springer styl

Pathologic response with neoadjuvant chemotherapy and stereotactic body radiotherapy for borderline resectable and locally-advanced pancreatic cancer

Background: Neoadjuvant stereotactic body radiotherapy (SBRT) has potential applicability in the management of borderline resectable and locally-advanced pancreatic adenocarcinoma. In this series, we report the pathologic outcomes in the subset of patients who underwent surgery after neoadjuvant SBRT. Methods: Patients with borderline resectable or locally-advanced pancreatic adenocarcinoma who were treated with SBRT followed by resection were included. Chemotherapy was to the discretion of the medical oncologist and preceded SBRT for most patients. Results: Twelve patients met inclusion criteria. Most (92%) received neoadjuvant chemotherapy, and gemcitabine/capecitabine was most frequently utilized (n = 7). Most were treated with fractionated SBRT to 36 Gy/3 fractions (n = 7) and the remainder with single fraction to 24 Gy (n = 5). No grade 3+ acute toxicities attributable to SBRT were found. Two patients developed post-surgical vascular complications and one died secondary to this. The mean time to surgery after SBRT was 3.3 months. An R0 resection was performed in 92% of patients (n = 11/12). In 25% (n = 3/12) of patients, a complete pathologic response was achieved, and an additional 16.7% (n = 2/12) demonstrated <10% viable tumor cells. Kaplan-Meier estimated median progression free survival is 27.4 months. Overall survival is 92%, 64% and 51% at 1-, 2-, and 3-years. Conclusions: This study reports the pathologic response in patients treated with neoadjuvant chemotherapy and SBRT for borderline resectable and locally-advanced pancreatic cancer. In our experience, 92% achieved an R0 resection and 41.7% of patients demonstrated either complete or extensive pathologic response to treatment. The results of a phase II study of this novel approach will be forthcoming. © 2013 Rajagopalan et al.; licensee BioMed Central Ltd

Scale without Conformal Invariance: Theoretical Foundations

We present the theoretical underpinnings of scale without conformal invariance in quantum field theory. In light of our results the gradient-flow interpretation of renormalization-group (RG) flow is challenged, due to deep connections between scale-invariant theories and recurrent behaviors in the RG. We show that, on scale-invariant trajectories, there is a redefinition of the dilatation current that leads to generators of dilatations that generate dilatations. Finally, we develop a systematic algorithm for the search of scale-invariant trajectories in perturbation theory.Comment: 18 pages. Added note to make clear that the results of arXiv:1106.2540 do not imply the existence of unitary theories with scale but without conformal invariance in perturbation theory in $d=4-\epsilon$ spacetime dimension

Visual Dependency and Dizziness after Vestibular Neuritis

Symptomatic recovery after acute vestibular neuritis (VN) is variable, with around 50% of patients reporting long term vestibular symptoms; hence, it is essential to identify factors related to poor clinical outcome. Here we investigated whether excessive reliance on visual input for spatial orientation (visual dependence) was associated with long term vestibular symptoms following acute VN. Twenty-eight patients with VN and 25 normal control subjects were included. Patients were enrolled at least 6 months after acute illness. Recovery status was not a criterion for study entry, allowing recruitment of patients with a full range of persistent symptoms. We measured visual dependence with a laptop-based Rod-and-Disk Test and severity of symptoms with the Dizziness Handicap Inventory (DHI). The third of patients showing the worst clinical outcomes (mean DHI score 36–80) had significantly greater visual dependence than normal subjects (6.35° error vs. 3.39° respectively, p = 0.03). Asymptomatic patients and those with minor residual symptoms did not differ from controls. Visual dependence was associated with high levels of persistent vestibular symptoms after acute VN. Over-reliance on visual information for spatial orientation is one characteristic of poorly recovered vestibular neuritis patients. The finding may be clinically useful given that visual dependence may be modified through rehabilitation desensitization techniques

Citrullination facilitates cross-reactivity of rheumatoid factor with non-IgG1 Fc epitopes in rheumatoid arthritis

Rheumatoid factor (RF) and anti-citrullinated protein antibodies (ACPAs) are the two most prevalent autoantibodies in rheumatoid arthritis (RA), and are thought to have distinct autoantigen targets. Whilst RF targets the Fc region of antibodies, ACPAs target a far broader spectrum of citrullinated peptides. Here we demonstrate significant sequence and structural homology between proposed RF target epitopes in IgG1 Fc and the ACPA target fibrinogen. Two of the three homologous sequences were susceptible to citrullination, and this modification, which occurs extensively in RA, permitted significant cross-reactivity of RF+ patient sera with fibrinogen in both western blots and ELISAs. Crucially, this reactivity was specific to RF as it was absent in RF− patient and healthy control sera, and could be inhibited by pre-incubation with IgG1 Fc. These studies establish fibrinogen as a common target for both RF and ACPAs, and suggest a new mechanism in RF-mediated autoimmune diseases wherein RF may act as a precursor from which the ACPA response evolves

Combining tractography and cortical measures to test system-specific hypotheses in multiple sclerosis

The objective was to test three motor system-specific hypotheses in multiple sclerosis patients: (i) corticospinal tract and primary motor cortex imaging measures differ between multiple sclerosis patients and controls; (ii) in patients, these measures correlate with disability; (iii) in patients, corticospinal tract measures correlate with measures of the ipsilateral primary motor cortex