Mott--Hubbard transition vs. Anderson localization of correlated, disordered electrons

The phase diagram of correlated, disordered electrons is calculated within dynamical mean--field theory using the geometrically averaged (''typical'') local density of states. Correlated metal, Mott insulator and Anderson insulator phases, as well as coexistence and crossover regimes are identified. The Mott and Anderson insulators are found to be continuously connected.Comment: 4 pages, 4 figure

Frequency-dependent transport through a quantum dot in the Kondo regime

We study the AC conductance and equilibrium current fluctuations of a Coulomb blockaded quantum dot. A relation between the equilibrium spectral function and the linear AC conductance is derived which is valid for frequencies well below the charging energy of the quantum dot. Frequency-dependent transport measurements can thus give experimental access to the Kondo peak in the equilibrium spectral function of a quantum dot. We illustrate this in detail for typical experimental parameters using the numerical renormalization group method in combination with the Kubo formalism.Comment: 4 pages, 4 figure

Josephson effect between superconducting nanograins with discrete energy levels

We investigate the Josephson effect between two coupled superconductors, coupled by the tunneling of pairs of electrons, in the regime that their energy level spacing is comparable to the bulk superconducting gap, but neglecting any charging effects. In this regime, BCS theory is not valid, and the notion of a superconducting order parameter with a well-defined phase is inapplicable. Using the density matrix renormalization group, we calculate the ground state of the two coupled superconductors and extract the Josephson energy. The Josephson energy is found to display a reentrant behavior (decrease followed by increase) as a function of increasing level spacing. For weak Josephson coupling, a tight-binding approximation is introduced, which illustrates the physical mechanism underlying this reentrance in a transparent way. The DMRG method is also applied to two strongly coupled superconductors and allows a detailed examination of the limits of validity of the tight-binding model

Unstructured mathematical model for biomass, lactic acid and bacteriocin productions by lactic acid bacteria in batch fermentation

6 páginas, 3 figuras, 2 tablasBACKGROUND: A simple macroscopical model was proposed to describe the fermentation kinetics of growth, bacteriocins and lactic acid production by Lactococcus lactis and Pediococcus acidilactici in a batch system. The equations used were: the logistic reparametrized for growth, the Luedeking–Piret model for bacteriocin production, the maintenance energy model for glucose consumption; and the homofermentative balance equation for lactic acid formation. RESULTS: In all the cultures, the mathematical models, consistents and robusts, adjusted, perfectly, the experimental kinetic profiles. Also, the corresponding kinetic parameters were significant, so much biological as statistically. CONCLUSIONS: The group of integrated equations used, besides showing high accuracy in predicting the studied bioproductions, established a useful tool for the control of lactic acid bacteria kinetics in bioreactors in terms of its statistical consistency. Copyright © 2007 Society of Chemical IndustryPeer reviewe

The Swiss chiropractic practice-based research network: a population-based cross-sectional study to inform future musculoskeletal research

The Swiss chiropractic practice-based research network (PBRN) is a nationwide project developed in collaboration with patients, clinicians, and academic stakeholders to advance musculoskeletal epidemiologic research. The aim of this study was to describe the clinician population recruited and representativeness of this PBRN to inform future collaboration. A population-based cross-sectional study was performed. PBRN clinician characteristics were described and factors related to motivation (operationalised as VAS score ≥ 70) to participate in a subsequent patient cohort pilot study were assessed. Among 326 eligible chiropractors, 152 enrolled in the PBRN (47% participation). The PBRN was representative of the larger Swiss chiropractic population with regards to age, language, and geographic distribution. Of those enrolled, 39% were motivated to participate in a nested patient cohort pilot study. Motivation was associated with age 40 years or older versus 39 years or younger (OR 2.3, 95% CI 1.0-5.2), and with a moderate clinic size (OR 2.4, 95% CI 1.1-5.7) or large clinic size (OR 2.8, 95% CI 1.0-7.8) versus solo practice. The Swiss chiropractic PBRN has enrolled almost half of all Swiss chiropractors and has potential to facilitate collaborative practice-based research to improve musculoskeletal health care quality.Trial registration: Swiss chiropractic PBRN (ClinicalTrials.gov identifier: NCT05046249); Swiss chiropractic cohort (Swiss ChiCo) pilot study (ClinicalTrials.gov identifier: NCT05116020)

Swiss chiropractic practice-based research network and musculoskeletal pain cohort pilot study: protocol of a nationwide resource to advance musculoskeletal health services research

INTRODUCTION Musculoskeletal (MSK) pain conditions, a leading cause of global disability, are usually first managed in primary care settings such as medical, physiotherapy, and chiropractic community-based practices. While chiropractors often treat MSK conditions, there is limited real-world evidence on the topic of health service outcomes among patients receiving this type of care. A nationwide Swiss chiropractic practice-based research network (PBRN) and MSK pain patient cohort study will have potential to monitor the epidemiological trends of MSK pain conditions and contribute to healthcare quality improvement. The primary aims of this protocol are to (1) describe the development of an MSK-focused PBRN within the Swiss chiropractic setting, and (2) describe the methodology of the first nested study to be conducted within the PBRN-an observational prospective patient cohort pilot study. METHODS AND ANALYSIS This initiative is conceptualised with two distinct phases. Phase I focuses on the development of the Swiss chiropractic PBRN, and will use a cross-sectional design to collect information from chiropractic clinicians nationwide. Phase II will recruit consecutive patients aged 18 years or older with MSK pain from community-based chiropractic practices participating in the PBRN into a prospective chiropractic cohort pilot study. All data collection will occur through electronic surveys offered in the three Swiss official languages (German, French, Italian) and English. Surveys will be provided to patients prior to their initial consultation in clinics, 1 hour after initial consultation, and at 2, 6 and 12 weeks after initial consultation. ETHICS AND DISSEMINATION Ethics approval has been obtained from the independent research ethics committee of Canton Zurich (BASEC-Nr: 2021-01479). Informed consent will be obtained electronically from all participants. Findings will be reported to stakeholders after each study phase, presented at local and international conferences, and disseminated through peer-reviewed publications. STUDY PRE-REGISTRATION Phase I-Swiss chiropractic PBRN (ClinicalTrials.gov identifier: NCT05046249); Phase 2-Swiss chiropractic cohort (Swiss ChiCo) pilot study (ClinicalTrials.gov identifier: NCT05116020)

SU(4) Fermi Liquid State and Spin Filtering in a Double Quantum Dot System

We study a symmetrical double quantum dot (DD) system with strong capacitive inter-dot coupling using renormalization group methods. The dots are attached to separate leads, and there can be a weak tunneling between them. In the regime where there is a single electron on the DD the low-energy behavior is characterized by an SU(4)-symmetric Fermi liquid theory with entangled spin and charge Kondo correlations and a phase shift $\pi/4$. Application of an external magnetic field gives rise to a large magneto-conductance and a crossover to a purely charge Kondo state in the charge sector with SU(2) symmetry. In a four lead setup we find perfectly spin polarized transmission.Comment: 4 pages, 4 figures, ReVTe

Kondo quantum dot coupled to ferromagnetic leads: Numerical renormalization group study

We systematically study the influence of ferromagnetic leads on the Kondo resonance in a quantum dot tuned to the local moment regime. We employ Wilson's numerical renormalization group method, extended to handle leads with a spin asymmetric density of states, to identify the effects of (i) a finite spin polarization in the leads (at the Fermi-surface), (ii) a Stoner splitting in the bands (governed by the band edges) and (iii) an arbitrary shape of the leads density of states. For a generic lead density of states the quantum dot favors being occupied by a particular spin-species due to exchange interaction with ferromagnetic leads leading to a suppression and splitting of the Kondo resonance. The application of a magnetic field can compensate this asymmetry restoring the Kondo effect. We study both the gate-voltage dependence (for a fixed band structure in the leads) and the spin polarization dependence (for fixed gate voltage) of this compensation field for various types of bands. Interestingly, we find that the full recovery of the Kondo resonance of a quantum dot in presence of leads with an energy dependent density of states is not only possible by an appropriately tuned external magnetic field but also via an appropriately tuned gate voltage. For flat bands simple formulas for the splitting of the local level as a function of the spin polarization and gate voltage are given.Comment: 18 pages, 18 figures, accepted for publication in PR

Flow equation approach to the sine-Gordon model

A continuous sequence of infinitesimal unitary transformations is used to diagonalize the quantum sine-Gordon model for \beta^2\in(2\pi,\infty). This approach can be understood as an extension of perturbative scaling theory since it links weak- to strong-coupling behavior in a systematic expansion: a small expansion parameter is identified and this parameter remains small throughout the entire flow unlike the diverging running coupling constant of perturbative scaling. Our approximation consists in neglecting higher orders in this small parameter. We find very accurate results for the single-particle/hole spectrum in the strong-coupling phase and can describe the full crossover from weak to strong-coupling. The integrable structure of the sine-Gordon model is not used in our approach. Our new method should be of interest for the investigation of nonintegrable perturbations and for other strong-coupling problems.Comment: 38 pages, 7 figure

The relationship between quality of life (EORTC QLQ-C30) and survival in patients with gastro-oesopohageal cancer

It remains unclear whether any aspect of quality of life has a role in predicting survival in an unselected cohort of patients with gastro-oesophageal cancer. Therefore the aim of the present study was to examine the relationship between quality of life (EORTC QLQ-C30), clinico-pathological characteristics and survival in patients with gastro-oesophageal cancer. Patients presenting with gastric or oesophageal cancer, staged using the UICC tumour node metastasis (TNM) classification and who received either potentially curative surgery or palliative treatment between November 1997 and December 2002 (n=152) participated in a quality of life study, using the EORTC QLQ-C30 core questionnaire. On univariate analysis, age (P < 0.01), tumour length (P < 0.0001), TNM stage (P<0.0001), weight loss (P<0.0001), dysphagia score (P<0.001), performance status (P<0.1) and treatment (P<0.0001) were significantly associated with cancer-specific survival. EORTC QLQ-C30, physical functioning (P<0.0001), role functioning (P<0.001), cognitive functioning (P<0.01), social functioning (P<0.0001), global quality of life (P<0.0001), fatigue (P<0.0001), nausea/vomiting (P<0.01), pain (P<0.001), dyspnoea (P<0.0001), appetite loss (P<0.0001) and constipation (P<0.05) were also significantly associated with cancer-specific survival. On multivariate survival analysis, tumour stage (P<0.0001), treatment (P<0.001) and appetite loss (P<0.0001) were significant independent predictors of cancer-specific survival. The present study highlights the importance of quality of life (EORTC QLQ-C30) measures, in particular appetite loss, as a prognostic factor in these patients