Non-perturbative JpdJ_{pd} model and ferromagnetism in dilute magnets

We calculate magnetic couplings in the $J_{pd}$ model for dilute magnets, in order both to identify the relevant parameters which control ferromagnetism and also to bridge the gap between first principle calculations and model approaches. The magnetic exchange interactions are calculated non-perturbatively and disorder in the configuration of impurities is treated exacly, allowing us to test the validity of effective medium theories. Results differ qualitatively from those of weak coupling. In contrast to mean field theory, increasing $J_{pd}$ may not favor high Curie temperatures: $T_C$ scales primarily with the bandwidth. High temperature ferromagnetism at small dilutions is associated with resonant structure in the p-band. Comparison to diluted magnetic semiconductors indicate that Ga(Mn)As has such a resonant structure and thus this material is already close to optimality.Comment: 4 pages, 4 Figure

Celestial mechanics of elastic bodies

We construct time independent configurations of two gravitating elastic bodies. These configurations either correspond to the two bodies moving in a circular orbit around their center of mass or strictly static configurations.Comment: 16 pages, 2 figures, several typos removed, erratum appeared in MathZ.263:233,200

Analytical approximation of the exterior gravitational field of rotating neutron stars

It is known that B\"acklund transformations can be used to generate stationary axisymmetric solutions of Einstein's vacuum field equations with any number of constants. We will use this class of exact solutions to describe the exterior vacuum region of numerically calculated neutron stars. Therefore we study how an Ernst potential given on the rotation axis and containing an arbitrary number of constants can be used to determine the metric everywhere. Then we review two methods to determine those constants from a numerically calculated solution. Finally, we compare the metric and physical properties of our analytic solution with the numerical data and find excellent agreement even for a small number of parameters.Comment: 9 pages, 10 figures, 3 table

Sustaining entrepreneurial business: a complexity perspective on processes that produce emergent practice

This article examines the management practices in an entrepreneurial small firm which sustain the business. Using a longitudinal qualitative case study, four general processes are identified (experimentation, reflexivity, organising and sensing), that together provide a mechanism to sustain the enterprise. The analysis draws on concepts from entrepreneurship and complexity science. We suggest that an entrepreneur’s awareness of the role of these parallel processes will facilitate their approaches to sustaining and developing enterprises. We also suggest that these processes operate in parallel at multiple levels, including the self, the business and inter-firm networks. This finding contributes to a general theory of entrepreneurship. A number of areas for further research are discussed arising from this result

Cluster Dynamical Mean Field Theories

Cluster Dynamical Mean Field Theories are analyzed in terms of their semiclassical limit and their causality properties, and a translation invariant formulation of the cellular dynamical mean field theory, PCDMFT, is presented. The semiclassical limit of the cluster methods is analyzed by applying them to the Falikov-Kimball model in the limit of infinite Hubbard interaction U where they map to different classical cluster schemes for the Ising model. Furthermore the Cutkosky-t'Hooft-Veltman cutting equations are generalized and derived for non translation invariant systems using the Schwinger-Keldysh formalism. This provides a general setting to discuss causality properties of cluster methods. To illustrate the method, we prove that PCDMFT is causal while the nested cluster schemes (NCS) in general and the pair scheme in particular are not. Constraints on further extension of these schemes are discussed.Comment: 26 page

Randomised trial of once- or twice-daily MMX mesalazine for maintenance of remission in ulcerative colitis

AIM: Maintenance treatment in ulcerative colitis should be as convenient as possible, to increase the chance of compliance. MMX mesalazine is a once-daily, high-strength (1.2 g/tablet) formulation of 5-aminosalicylic acid. This study evaluated the safety and efficacy of MMX mesalazine dosed once or twice daily as maintenance therapy in patients with ulcerative colitis. METHODS: This multicentre, randomised, open-label trial enrolled patients with strictly defined clinical and endoscopic remission, immediately following an episode of mild to moderate ulcerative colitis. Patients were randomised to MMX mesalazine 2.4 g/day as a single (2x1.2 g tablet) or divided dose (1x1.2 g tablet twice daily) for 12 months. RESULTS: 174 patients (37.9%; safety population n = 459) experienced 384 adverse events, the majority of which were mild or moderate in intensity. Eighteen patients (3.9%), nine in each group, experienced a total of 22 serious adverse events (10 in the once-daily and 12 in the twice-daily group). Most serious adverse events were gastrointestinal, experienced by 5 patients in the once-daily and 4 in the twice-daily group. At month 12, 64.4% (efficacy population, n = 451) of patients in the once-daily and 68.5% of patients in the twice-daily group were in clinical and endoscopic remission (p = 0.351). At month 12, 88.9% and 93.2% in each group, respectively, had maintained clinical remission (were relapse free). CONCLUSIONS: MMX mesalazine 2.4 g/day administered as a single or divided dose demonstrated a good safety profile, was well tolerated and was effective as maintenance treatment. High clinical and endoscopic remission rates can be achieved with once-daily dosing. TRIAL REGISTRATION NUMBER: NCT00151944

Lung ultrasound: a new tool for the cardiologist

For many years the lung has been considered off-limits for ultrasound. However, it has been recently shown that lung ultrasound (LUS) may represent a useful tool for the evaluation of many pulmonary conditions in cardiovascular disease. The main application of LUS for the cardiologist is the assessment of B-lines. B-lines are reverberation artifacts, originating from water-thickened pulmonary interlobular septa. Multiple B-lines are present in pulmonary congestion, and may help in the detection, semiquantification and monitoring of extravascular lung water, in the differential diagnosis of dyspnea, and in the prognostic stratification of chronic heart failure and acute coronary syndromes