Muon spin rotation and relaxation in the superconducting ferromagnet UCoGe

We report zero-field muon spin rotation and relaxation measurements on the superconducting ferromagnet UCoGe. Weak itinerant ferromagnetic order is detected by a spontaneous muon spin precession frequency below the Curie temperature $T_C = 3$ K. The $\mu^+$ precession frequency persists below the bulk superconducting transition temperature $T_{sc} = 0.5$ K, where it measures a local magnetic field $B_{loc} = 0.015$ T. The amplitude of the $\mu$SR signal provides unambiguous proof for ferromagnetism present in the whole sample volume. We conclude ferromagnetism coexists with superconductivity on the microscopic scale.Comment: 4 pages, 3 figures, accepted for publication in PR

Simultaneous suppression of ferromagnetism and superconductivity in UCoGe by Si substitution

We investigate the effect of substituting Si for Ge in the ferromagnetic superconductor UCoGe. Dc-magnetization, ac-susceptibility and electrical resistivity measurements on polycrystalline UCoGe$_{1-x}$Si$_x$ samples show that ferromagnetic order and superconductivity are progressively depressed with increasing Si content and simultaneously vanish at a critical concentration $x_{cr} \simeq 0.12$. The non-Fermi liquid temperature variation in the electrical resistivity near $x_{cr}$ and the smooth depression of the ordered moment point to a continuous ferromagnetic quantum phase transition. Superconductivity is confined to the ferromagnetic phase, which provides further evidence for magnetically mediated superconductivity.Comment: 5 pages, 4 figures, accepted for publication in PR

Conformal Invariance in Percolation, Self-Avoiding Walks and Related Problems

Over the years, problems like percolation and self-avoiding walks have provided important testing grounds for our understanding of the nature of the critical state. I describe some very recent ideas, as well as some older ones, which cast light both on these problems themselves and on the quantum field theories to which they correspond. These ideas come from conformal field theory, Coulomb gas mappings, and stochastic Loewner evolution.Comment: Plenary talk given at TH-2002, Paris. 21 pages, 9 figure

Vicinal Surfaces and the Calogero-Sutherland Model

A miscut (vicinal) crystal surface can be regarded as an array of meandering but non-crossing steps. Interactions between the steps are shown to induce a faceting transition of the surface between a homogeneous Luttinger liquid state and a low-temperature regime consisting of local step clusters in coexistence with ideal facets. This morphological transition is governed by a hitherto neglected critical line of the well-known Calogero-Sutherland model. Its exact solution yields expressions for measurable quantities that compare favorably with recent experiments on Si surfaces.Comment: 4 pages, revtex, 2 figures (.eps

M & L Jaargang 3/5

Roger Deneef De Demervallei tussen Aarschot en Werchter. Deel 1. [The Demer valley between Aarchot and Werchter (part 1).]R. Nijs en G. De Geyter Het kwartsiet van Tienen: petrografische kenmerken en gebruik als bouwsteen. [The quartzite of Tienen: petrographic characteristics and use as building stone.]Dirk Van Eenhooge Het Rood Kloosterken een archeologisch vooronderzoek. [The Rood Kloosterken (Red Monastery) a preliminary archaelogical inquiry.]Jos Vandenbreeden In Memoriam-Patrimonium [In Memoriam-Patrimonium (Decay of Brussels architectural heritage.]SummaryM&L Binnenkran

Connecting polymers to the quantum Hall plateau transition

A mapping is developed between the quantum Hall plateau transition and two-dimensional self-interacting lattice polymers. This mapping is exact in the classical percolation limit of the plateau transition, and diffusive behavior at the critical energy is shown to be related to the critical exponents of a class of chiral polymers at the $\theta$-point. The exact critical exponents of the chiral polymer model on the honeycomb lattice are found, verifying that this model is in the same universality class as a previously solved model of polymers on the Manhattan lattice. The mapping is obtained by averaging analytically over the local random potentials in a previously studied lattice model for the classical plateau transition. This average generates a weight on chiral polymers associated with the classical localization length exponent $\nu = 4/3$. We discuss the differences between the classical and quantum transitions in the context of polymer models and use numerical results on higher-moment scaling laws at the quantum transition to constrain possible polymer descriptions. Some properties of the polymer models are verified by transfer matrix and Monte Carlo studies.Comment: 9 pages, 2 figure

Universal Properties of Self-Avoiding Walks from Two-Dimensional Field Theory

We use the recently conjectured exact $S$-matrix of the massive ${\rm O}(n)$ model to derive its form factors and ground state energy. This information is then used in the limit $n\to0$ to obtain quantitative results for various universal properties of self-avoiding chains and loops. In particular, we give the first theoretical prediction of the amplitude ratio $C/D$ which relates the mean square end-to-end distance of chains to the mean square radius of gyration of closed loops. This agrees with the results from lattice enumeration studies to within their errors, and gives strong support for the various assumptions which enter into the field theoretic derivation. In addition, we obtain results for the scaling function of the structure factor of long loops, and for various amplitude ratios measuring the shape of self-avoiding chains. These quantities are all related to moments of correlation functions which are evaluated as a sum over $m$-particle intermediate states in the corresponding field theory. We show that in almost all cases, the restriction to $m\leq2$ gives results which are accurate to at least one part in $10^3$. This remarkable fact is traced to a softening of the $m>2$ branch cuts relative to their behaviour based on phase space arguments alone, a result which follows from the threshold behaviour of the two-body $S$-matrix, $S(0)=-1$. Since this is a general property of interacting 2d field theories, it suggests that similar approximations may well hold for other models. However, we also study the moments of the area of self-avoiding loops,Comment: 48 pages, UCSBTH-93-12, ISAS-93-7

Randomized controlled study of pain education in patients receiving radiotherapy for painful bone metastases

BACKGROUND: Although short-course radiotherapy is an effective treatment for patients with painful bone metastases, pain is not always sufficiently controlled. We therefore investigated the additional effect of a nurse-led pain education program on pain control and quality of life (QoL).PATIENTS AND METHODS: In this multicenter study, patients with solid tumor bone metastases and a worst pain intensity of ≥5 on a 0-10 numeric rating scale (NRS) were randomized between care as usual (control-group) and care as usual plus the Pain Education Program (PEP-group). PEP consisted of a structured interview and personalized education with follow-up phone calls. Patients completed the Brief Pain Inventory, EORTC QLQ-C15-PAL and BM22 at week 0, 1, 4, 8 and 12. The primary outcome was pain control, defined as the number of patients whose worst pain intensity was &lt;5 on a 0-10 NRS after 12 weeks. Secondary outcomes were time to reach control of pain (NRS &lt; 5), mean worst pain and average pain, and QoL at weeks 1, 4, 8 and 12.RESULTS: Of 308 included patients, 182 (92 PEP-group) completed 12 weeks follow-up. At 12 weeks, more patients in the PEP-group (71%) compared to the control-group (52%) reported pain control (P =.008). In the PEP-group, pain control was reached earlier than in the control-group (median 29 days versus 56 days; P =.003). Mean worst and average pain decreased in both groups but decreased more in the PEP-group. QoL did not differ between the groups.CONCLUSION: The addition of PEP to care as usual for patients treated with radiotherapy for painful bone metastases resulted in less pain and faster pain control.</p

Individualized prediction of three- and six-year outcomes of psychosis in a longitudinal multicenter study:a machine learning approach

Schizophrenia and related disorders have heterogeneous outcomes. Individualized prediction of long-term outcomes may be helpful in improving treatment decisions. Utilizing extensive baseline data of 523 patients with a psychotic disorder and variable illness duration, we predicted symptomatic and global outcomes at 3-year and 6-year follow-ups. We classified outcomes as (1) symptomatic: in remission or not in remission, and (2) global outcome, using the Global Assessment of Functioning (GAF) scale, divided into good (GAF &gt;= 65) and poor (GAF &lt; 65). Aiming for a robust and interpretable prediction model, we employed a linear support vector machine and recursive feature elimination within a nested cross-validation design to obtain a lean set of predictors. Generalization to out-of-study samples was estimated using leave-one-site-out cross-validation. Prediction accuracies were above chance and ranged from 62.2% to 64.7% (symptomatic outcome), and 63.5-67.6% (global outcome). Leave-one-site-out cross-validation demonstrated the robustness of our models, with a minor drop in predictive accuracies of 2.3% on average. Important predictors included GAF scores, psychotic symptoms, quality of life, antipsychotics use, psychosocial needs, and depressive symptoms. These robust, albeit modestly accurate, long-term prognostic predictions based on lean predictor sets indicate the potential of machine learning models complementing clinical judgment and decision-making. Future model development may benefit from studies scoping patient's and clinicians' needs in prognostication.</p