Monte Carlo Study of the Inflation-Deflation Transition in a Fluid Membrane

We study the conformation and scaling properties of a self-avoiding fluid membrane, subject to an osmotic pressure $p$, by means of Monte Carlo simulations. Using finite size scaling methods in combination with a histogram reweighting techniques we find that the surface undergoes an abrupt conformational transition at a critical pressure $p^\ast$, from low pressure deflated configurations with a branched polymer characteristics to a high pressure inflated phase, in agreement with previous findings \cite{gompper,baum}. The transition pressure $p^{\ast}$ scales with the system size as $p^\ast \propto N^{-\alpha}$, with $\alpha = 0.69 \pm 0.01$. Below $p^\ast$ the enclosed volume scales as $V \propto N$, in accordance with the self-avoiding branched polymer structure, and for $p\searrow p^{\ast}$ our data are consistent with the finite size scaling form $V \propto N^{\beta_{+}}$, where $\beta_{+} = 1.43 \pm 0.04$. Also the finite size scaling behavior of the radii of gyration and the compressibility moduli are obtained. Some of the observed exponents and the mechanism behind the conformational collapse are interpreted in terms of a Flory theory.Comment: 20 pages + postscript-file, Latex + Postscript, IFA Report No. 94/1

A detector for continuous measurement of ultra-cold atoms in real time

We present the first detector capable of recording high-bandwidth real time atom number density measurements of a Bose Einstein condensate. Based on a two-color Mach-Zehnder interferometer, our detector has a response time that is six orders of magnitude faster than current detectors based on CCD cameras while still operating at the shot-noise limit. With this minimally destructive system it may be possible to implement feedback to stabilize a Bose-Einstein condensate or an atom laser.Comment: 3 pages, 3 figures, submitted to optics letter

Optical waveform sampling of a 320 Gbits/s serial data signal using a hydrogenated amorphous silicon waveguide

We propose using a hydrogenated amorphous silicon waveguide for ultra-high-speed serial data waveform sampling. 320 Gbit/s serial optical data sampling is experimentally demonstrated with +12 dB intrinsic four wave mixing conversion efficiency

Advancing projections of phytoplankton responses to climate change through ensemble modelling

A global trend of increasing health hazards associated with proliferation of toxin-producing cyanobacteria makes the ability to project phytoplankton dynamics of paramount importance. Whilst ensemble (multi-)modelling approaches have been used for a number of years to improve the robustness of weather forecasts this approach has until now never been adopted for ecosystem modelling. We show that the average simulated phytoplankton biomass derived from three different aquatic ecosystem models is generally superior to any of the three individual models in describing observed phytoplankton biomass in a typical temperate lake ecosystem, and we simulate a series of climate change projections. While this is the first multi-model ensemble approach applied for some of the most complex aquatic ecosystem models available, we consider it sets a precedent for what will become commonplace methodology in the future, as it enables increased robustness of model projections, and scenario uncertainty estimation due to differences in model structures

Optical switching and detection of 640 Gbits/s optical time-division multiplexed data packets transmitted over 50 km of fiber

We demonstrate 1×4 optical-packet switching with error-free transmission of 640¿Gbits/s single-wavelength optical time-division multiplexed data packets including clock distribution and short pulse generation for optical time demultiplexing based on a cavityless pulse source