Celebrating the Physics in Geophysics

As 2005, the International Year of Physics, comes to an end, two physicists working primarily in geophysical research reflect on how geophysics is not an applied physics. Although geophysics has certainly benefited from progress in physics and sometimes emulated the reductionist program of mainstream physics, it has also educated the physics community about some of the generic behaviors of strongly nonlinear systems. Dramatic examples are the insights we have gained into the ``emergent'' phenomena of chaos, cascading instabilities, turbulence, self-organization, fractal structure, power-law variability, anomalous scaling, threshold dynamics, creep, fracture, and so on. In all of these examples, relatively simple models have been able to explain the recurring features of apparently very complex signals and fields. It appears that the future of the intricate relation between physics and geophysics will be as exciting as its past has been characterized by a mutual fascination. Physics departments in our universities should capitalize on this trend to attract and retain young talent motivated to address problems that really matter for the future of the planet. A pressing topic with huge impact on populations and that is challenging enough for both physics and geophysics communities to work together like never before is the understanding and prediction of extreme events.Comment: 6 pages, final version to appear in EOS-AGU Transactions in November 200

The various manifestations of collisionless dissipation in wave propagation

The propagation of an electrostatic wave packet inside a collisionless and initially Maxwellian plasma is always dissipative because of the irreversible acceleration of the electrons by the wave. Then, in the linear regime, the wave packet is Landau damped, so that in the reference frame moving at the group velocity, the wave amplitude decays exponentially with time. In the nonlinear regime, once phase mixing has occurred and when the electron motion is nearly adiabatic, the damping rate is strongly reduced compared to the Landau one, so that the wave amplitude remains nearly constant along the characteristics. Yet, we show here that the electrons are still globally accelerated by the wave packet, and, in one dimension, this leads to a non local amplitude dependence of the group velocity. As a result, a freely propagating wave packet would shrink, and, therefore, so would its total energy. In more than one dimension, not only does the magnitude of the group velocity nonlinearly vary, but also its direction. In the weakly nonlinear regime, when the collisionless damping rate is still significant compared to its linear value, this leads to an effective defocussing effect which we quantify, and which we compare to the self-focussing induced by wave front bowing.Comment: 23 pages, 6 figure

Deploying elastic routing capability in an SDN/NFV-enabled environment

SDN and NFV are two paradigms that introduce unseen flexibility in telecom networks. Where previously telecom services were provided by dedicated hardware and associated (vendor-specific) protocols, SDN enables to control telecom networks through specialized software running on controllers. NFV enables highly optimized packet-processing network functions to run on generic/multi-purpose hardware such as x86 servers. Although the possibilities of SDN and NFV are well-known, concrete control and orchestration architectures are still under design and few prototype validations are available. In this demo we demonstrate the dynamic up-and downscaling of an elastic router supporting NFV-based network management, for example needed in a VPN service. The framework which enables this elasticity is the UNIFY ESCAPE environment, which is a PoC following an ETSI NFV MANO-conform architecture. This demo is one of the first to demonstrate a fully closed control loop for scaling NFs in an SDN/NFV control and orchestration architecture

Thoracoscopic treatment of pulmonary sequestration

Objective: Pulmonary sequestration is a rare congenital malformation and may be the cause of recurrent infections or hemoptysis. It has been shown in case reports that resection by video-assisted thoracic surgery (VATS) is feasible despite the possible technical difficulties due to inflammatory changes, but its role has not been evaluated yet in a larger series of consecutively treated patients. Methods: Retrospective analysis of all consecutively thoracoscopically treated patients (between January 1991 and January 2005) with pulmonary sequestration in a single center. We included 14 patients in the study who fulfilled the criteria; seven were women. Median age was 33 years (20-64 years). The following data were analyzed for all patients: major symptoms, diagnostic procedures, treatment, and outcome. Operative parameters and findings including operating time, blood loss, anatomical location of the sequestration, and feeding vessels were evaluated. Results: Leading symptoms were recurrent infections (10), hemoptysis (3), and chest discomfort (1). The diagnosis was made by CT scan. Additionally, an arteriography or an angio-MRI was done in three patients and one patient, respectively. Thirteen intralobar (all lower lobes, eight on the right) and one left-sided extralobar pulmonary sequestration were resected. We performed eight lobectomies, four atypical segmentectomies, one extralobar resection, and one occlusion of the aberrant artery. One case had to be converted to a thoracotomy due to bleeding from the aberrant artery. There was no mortality. Complications included pneumonia in three cases, one hemothorax, one pneumothorax after removing the chest tube, and one wound infection. All were treated conservatively. Conclusion: Thoracoscopic treatment of pulmonary sequestration is feasible in experienced hands. The aberrant systemic artery can be freed and dissected safely despite the frequently occurring inflammatory changes. Conversion rate to thoracotomy is lo

Ultra-low phase noise all-optical microwave generation setup based on commercial devices

In this paper, we present a very simple design based on commercial devices for the all-optical generation of ultra-low phase noise microwave signals. A commercial, fibered femtosecond laser is locked to a laser that is stabilized to a commercial ULE Fabry-Perot cavity. The 10 GHz microwave signal extracted from the femtosecond laser output exhibits a single sideband phase noise $\mathcal{L}(f)=-104 \ \mathrm{dBc}/\mathrm{Hz}$ at 1 Hz Fourier frequency, at the level of the best value obtained with such "microwave photonics" laboratory experiments \cite{Fortier2011}. Close-to-the-carrier ultra-low phase noise microwave signals will now be available in laboratories outside the frequency metrology field, opening up new possibilities in various domains.Comment: 8 pages, 3 figures. To be published in Applied Optics, early posting version available at http://www.opticsinfobase.org/ao/upcoming_pdf.cfm?id=23114

Plaquette bond order wave in the quarter-filled extended Hubbard model on the checkerboard lattice

An extended Hubbard model (including nearest-neighbor repulsion and antiferromagnetic spin exchange) is investigated on the frustrated checkerboard lattice, a two-dimensional analog of the pyrochlore lattice. Combining Gutzwiller renormalized mean-field (MF) calculations, exact diagonalization (ED) techniques, and a weak-coupling renormalization group (RG) analysis we provide strong evidence for a crystalline valence bond plaquette phase at quarter-filling. The ground state is twofold degenerate and breaks translation symmetry. The bond energies show a staggering while the charge distribution remains uniform.Comment: 8 pages, 6 figures, published versio