Partial nonlinear reciprocity breaking through ultrafast dynamics in a random photonic medium

We demonstrate that ultrafast nonlinear dynamics gives rise to reciprocity breaking in a random photonic medium. Reciprocity breaking is observed via the suppression of coherent backscattering, a manifestation of weak localization of light. The effect is observed in a pump-probe configuration where the pump induces an ultrafast step-change of the refractive index during the dwell time of the probe light in the material. The dynamical suppression of coherent backscattering is reproduced well by a multiple scattering Monte Carlo simulation. Ultrafast reciprocity breaking provides a distinct mechanism in nonlinear optical media which opens up avenues for the active manipulation of mesoscopic transport, random lasers, and photon localization.Comment: 5 pages, 4 figure

Voorspelfouten bij de toepassing van Markov-modellen in de personeelsplanning

Markov-modellen, zoals deze bij de personeelsplanning worden gebruikt, leveren geen exacte voorspellingen voor de toekomstige bezetting van de rangen binnen een te beschouwen organisatie. Een reden hiervoor is, dat bijvoorbeeld schommelingen in het personeelsverloop nooit exact kunnen worden voorspeld uit beschikbare historische gegevens over het personeelssysteem. In dit rapport zullen de statistische aspecten van de toepassing van Markovmodellen in de personeelsplanning worden belicht. Fouten tengevolge onnauwkeurige schattingen van overgangswaarschijnlijkheden zullen worden beschouwd en worden vergeleken met de variantie in de schattingen tengevolge van het stochastische karakter van het model. Daarnaast zullen schattingen voor de verwachte kwadratische fout in de voorspellingen worden gegeven. Voorts zullen de gevolgen voor de kwaliteit van de voorspellingen van het clusteren van toestanden in het Markov-model, waarbij binnen één cluster historische promotie- en verloopgegevens worden geaggregeerd, worden besproken

Melting of regular and decoupled vortex lattices in BSCCO crystals

The angular dependence of the first-order phase transition (FOT) in the vortex lattice in Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8}$ crystals was investigated by a low frequency AC shielding technique (with the AC field $\parallel c$), in which the static-field component parallel to $c$- ($H_{\perp}$) was varied with the in-plane field $H_{\parallel}$ held constant. The linear decrease of the FOT field $H_{\perp}^{FOT}$ with increasing $H_{\parallel}$ ends at a temperature--dependent critical value of $H_{\parallel}$. A new transition, marked by the abrupt drop of the $ab$-plane shielding current, appears at this point. We draw a new phase diagram with $H_{\parallel}$ and $H_{\perp}$ field components as coordinates; this features at least two distinct regions in the vortex solid phase, that are determined by the different interplay between the pancake vortex-- and Josephson vortex lattice.Comment: 2 pages, 2 figures Paper submitted to the conference proceedings of M2S-2000 Houston, T

Magnetization Decay due to Vortex Phase Boundary Motion in BSCCO

We identify a new regime of decay of the irreversible magnetization in clean Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8}$ crystals, at induction values close to the ``second peak field'' at which the bulk critical current density steeply increases. A time window is identified during which the decay of the induction is controlled by the slow propagation of the phase transformation front across the sample.Comment: 2 pages, 3 figures Paper submitted to the conference proceedings of M2S-2000 Houston T

Vortex Solid-Liquid Transition in Bi2_{2}Sr2_{2}CaCu2_{2}O8+δ_{8+\delta} with a High Density of Strong Pins

The introduction of a large density of columnar defects in %underdoped Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$ crystals does not, at sufficiently low vortex densities, increase the irreversibility line beyond the first order transition (FOT) field of pristine crystals. At such low fields, the flux line wandering length $r_{w}$ behaves as in pristine %Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$ crystals. Next, vortex positional correlations along the $c$--axis in the vortex Bose glass at fields above the FOT are smaller than in the low--field vortex solid. Third, the Bose-glass-to-vortex liquid transition is signaled by a rapid decrease in c-axis phase correlations. These observations are understood in terms of the ``discrete superconductor'' model.Comment: 4 pages, 4 figures Submitted to Phys. Rev. B Rapid Comm. 16-1-2004 Revised version 18-3-200

The BAPRAS screening tool for reimbursement in a postbariatric population

Introduction: Reimbursement of body-contouring surgery (BCS) is a worldwide problem: there is no objective instrument to decide which postbariatric patients should qualify for reimbursement. The British Association of Plastic, Reconstructive and Aesthetic Surgeons (BAPRAS) has developed a screening tool for this purpose. In this study, we used a modified version of this screening tool in a postbariatric population and describe which patients would qualify for reimbursement using this tool. Methods: In this cross-sectional study postbariatric patients were asked to fill in an online questionnaire based on the BAPRAS screening tool with questions regarding complaints of overhanging skin and medical history. Weight loss data were extracted from a prospective database. The BODY-Q was added to assess patient-reported outcomes. Results: Patients who wanted to undergo BCS (n = 90) had higher screening tool scores and lower BODY-Q scores compared to patients who did not want BCS (n = 24). In total, 25 patients (26%) qualified for reimbursement, these patients had higher weight loss (33.5% versus 29.2%, p = 0.008), lower BMI (27.3 kg/m2 versus 30.4 kg/m2, p = 0.014) and more medical (4.0 versus 2.0, p = 0.004) and psychological complaints (88% versus 61%, p = 0.009). There was a significant, negative correlation between the screening tool scores and almost all BODY-Q scales. Conclusions: Patients with a desire for BCS have more complaints of excess skin, which negatively impacts their well-being. With the modified BAPRAS screening tool, patients with the best weight (loss) and most medical and psychological complaints of excess skin qualified for referral and reimbursement of BCS

Defect-unbinding and the Bose-glass transition in layered superconductors

The low-field Bose-glass transition temperature in heavy-ion irradiated Bi_2Sr_2CaCu_2O_8+d increases progressively with increasing density of irradiation-induced columnar defects, but saturates for densities in excess of 1.5 x10^9 cm^-2. The maximum Bose-glass temperature corresponds to that above which diffusion of two-dimensional pancake vortices between different vortex lines becomes possible, and above which the ``line-like'' character of vortices is lost. We develop a description of the Bose-glass line that is in excellent quantitative agreement with the experimental line obtained for widely different values of track density and material parameters.Comment: 4 pages, 4 figures, submitted to Phys. Rev. Let