The Windermere perch and pike project: an historical review

This paper is an attempt to set the background, provide a brief history, review some of the Windermere perch and pike project's scientific achievements, note current developments and hopes for the future, and comment on some aspects of such long-term projects. The project was originally started in 1939 in order to provide fish in freshwater lakes which might be harvested to enhance the supplies of food in a country subject to blockade. Pike traps and gill-netting were trialed as fishing methods. Catch statistics are available from 1939 which can be used to study population dynamics or for modelling purposes. The author provides an overview of changes in the population dynamics of perch and pike but covers briefly other species like arctic charr and brown trout. Also covered are several aspects of the basic biology and ecology of the principal species involved

The Windermere perch and pike project: an historical review

When the Second World War began in September 1939, the first full-timeDirector of the FBA, Barton Worthington, wondered how the FBA might helpthe war effort, and decided that stocks of fish in freshwater lakes might beharvested to enhance the supplies of food in a country subject to blockade.This was the start of a project that has continued since then, and is stillcontinuing, sixty years later. The following account is an attempt to set thebackground, provide a brief history, review some of the project's scientificachievements, note current developments and hopes for the future, andcomment on some aspects of such long-term projects. I shall take some of thescientific results up to 1976, others up to 1998; several of the laterdevelopments are still being analysed and interpreted

A novel nib-like design for microfabricated nanospray tips

AbstractWe present here novel tips for nanoelectrosray ionization-mass spectrometry (ESI-MS) applications. These ionization sources have a planar geometry in the shape of a nib. Their functioning is based on a principle much akin to that of a fountain pen in that fluids are actuated by capillarity. Once a voltage is applied, an electrospray is formed at the nib tip. The nib fabrication relies on micromachining techniques using the epoxy-based negative photoresist SU-8 and a double exposure photolithographic process. Two types of nib-like sources were fabricated; they were made either conductive by metallization with a nickel layer or non-conductive but hydrophilic by covering them with a SiO2 layer. In the latter case, the HV was applied via a Pt wire inserted into the reservoir feature of the nib. The nib-like sources were tested on an ion trap mass spectrometer using Gramicidin S samples at concentrations as low as 1 μM and ionization voltages as low as 1.2 kV. We have observed a good overall stability of the spray during the tests with no marked decrease in the signal intensity even under extreme conditions

Microcavity-quality-factor enhancement using nonlinear effects close to the bistability threshold and coherent population oscillations

9 pagesInternational audienceWe analytically show that inserting a driven, two-level system inside a microcavity can improve its optical properties. In this approach, the strong dispersion induced by a pump via population oscillations increases the cavity lifetime experienced by a slightly detuned probe. We further predict that if the cavity is pumped through a resonant channel, optical absorptive or dispersive bistability can be combined with the population-oscillation-induced steep material dispersion to obtain a strong quality-factor enhancement. Moreover, differential amplification coming from the nonlinear feature of the pump transfer function can be used to drastically increase the probe transmission beyond intrinsic characteristics of the resonator. The Q-factor enhancement and the differential amplification can be advantageously combined with a frequency pulling effect to stabilize or readjust the microcavity resonance frequency

Characterization of Few Mode Fibers by OLCI Technique

International audienceAll LP modes of a few mode fiber are simultaneously characterized using phase-sensitive optical low-coherence interferometry. The differential modal group delay and absolute chromatic dispersion values of each mode are retrieved from a single measurement without spatial mode transformers

Controling the coupling properties of active ultrahigh-Q WGM microcavities from undercoupling to selective amplification

International audienceUltrahigh-quality (Q) factor microresonators have a lot of applications in the photonics domain ranging from low-threshold nonlinear optics to integrated optical sensors. Glass-based whispering gallery mode (WGM) microresonators are easy to produce by melting techniques, however they suffer from surface contamination which limits their long-term quality factor to a few 10^8 . Here we show that an optical gain provided by erbium ions can compensate for residual losses. Moreover it is possible to control the coupling regime of an ultrahigh Q-factor three port microresonator from undercoupling to spectral selective amplification by changing the pumping rate. The optical characterization method is based on frequency-swept cavity-ring-down- pectroscopy. This method allows the transmission and dispersive properties of perfectly transparent microresonators and intrinsic finesses up to 4.0x10^7 to be measured. Finally we characterize a critically coupled fluoride glass WGM microresonator with a diameter of 220 mm and a loaded Q-factor of 5.3x10^9 is demonstrated

Versatile Graded-Index Multi-Mode Fiber for High Capacity Single-and Multi-Mode Optical Home Network

International audienceA graded-index multi-mode fiber has been optimized to sustain a single excited mode when coupled with a standard single-mode fiber at 1310/1550nm while offering large effective modal bandwidth at 850nm under VCSEL excitations. Modeling and experimental results are presented

Imaging the Two Gaps of the High-TC Superconductor Pb-Bi2Sr2CuO6+x

The nature of the pseudogap state, observed above the superconducting transition temperature TC in many high temperature superconductors, is the center of much debate. Recently, this discussion has focused on the number of energy gaps in these materials. Some experiments indicate a single energy gap, implying that the pseudogap is a precursor state. Others indicate two, suggesting that it is a competing or coexisting phase. Here we report on temperature dependent scanning tunneling spectroscopy of Pb-Bi2Sr2CuO6+x. We have found a new, narrow, homogeneous gap that vanishes near TC, superimposed on the typically observed, inhomogeneous, broad gap, which is only weakly temperature dependent. These results not only support the two gap picture, but also explain previously troubling differences between scanning tunneling microscopy and other experimental measurements.Comment: 6 page