270 research outputs found
Measurement of the Temperature Dependence of the Casimir-Polder Force
We report on the first measurement of a temperature dependence of the
Casimir-Polder force. This measurement was obtained by positioning a nearly
pure 87-Rb Bose-Einstein condensate a few microns from a dielectric substrate
and exciting its dipole oscillation. Changes in the collective oscillation
frequency of the magnetically trapped atoms result from spatial variations in
the surface-atom force. In our experiment, the dielectric substrate is heated
up to 605 K, while the surrounding environment is kept near room temperature
(310 K). The effect of the Casimir-Polder force is measured to be nearly 3
times larger for a 605 K substrate than for a room-temperature substrate,
showing a clear temperature dependence in agreement with theory.Comment: 4 pages, 4 figures, published in Physical Review Letter
Automatic threshold determination for a local approach of change detection in long-term signal recordings
CUSUM (cumulative sum) is a well-known method that can be used to detect changes in a signal when the parameters of this signal are known. This paper presents an adaptation of the CUSUM-based change detection algorithms to long-term signal recordings where the various hypotheses contained in the signal are unknown. The starting point of the work was the dynamic cumulative sum (DCS) algorithm, previously developed for application to long-term electromyography (EMG) recordings. DCS has been improved in two ways. The first was a new procedure to estimate the distribution parameters to ensure the respect of the detectability property. The second was the definition of two separate, automatically determined thresholds. One of them (lower threshold) acted to stop the estimation process, the other one (upper threshold) was applied to the detection function. The automatic determination of the thresholds was based on the Kullback-Leibler distance which gives information about the distance between the detected segments (events). Tests on simulated data demonstrated the efficiency of these improvements of the DCS algorithm
Real-time lattice boltzmann shallow waters method for breaking wave simulations
We present a new approach for the simulation of surfacebased fluids based in a hybrid formulation of Lattice Boltzmann Method for Shallow Waters and particle systems. The modified LBM can handle arbitrary underlying terrain conditions and arbitrary fluid depth. It also introduces a novel method for tracking dry-wet regions and moving boundaries. Dynamic rigid bodies are also included in our simulations using a two-way coupling. Certain features of the simulation that the LBM can not handle because of its heightfield nature, as breaking waves, are detected and automatically turned into splash particles. Here we use a ballistic particle system, but our hybrid method can handle more complex systems as SPH. Both the LBM and particle systems are implemented in CUDA, although dynamic rigid bodies are simulated in CPU. We show the effectiveness of our method with various examples which achieve real-time on consumer-level hardware.Peer ReviewedPostprint (author's final draft
Recent progress in the discovery of macrocyclic compounds as potential anti-infective therapeutics
Novel therapeutic strategies are urgently needed for the treatment of serious diseases caused by viral, bacterial and parasitic infections, because currently used drugs are facing the problem of rapidly emerging resistance. There is also an urgent need for agents that act on novel pathogen-specific targets, in order to expand the repertoire of possible therapies. The high throughput screening of diverse small molecule compound libraries has provided only a limited number of new lead series, and the number of compounds acting on novel targets is even smaller. Natural product screening has traditionally been very successful in the anti-infective area. Several successful drugs on the market as well as other compounds in clinical development are derived from natural products. Amongst these, many are macrocyclic compounds in the 1-2 kDa size range. This review will describe recent advances and novel drug discovery approaches in the anti-infective area, focusing on synthetic and natural macrocyclic compounds for which in vivo proof of concept has been established. The review will also highlight the Protein Epitope Mimetics (PEM) technology as a novel tool in the drug discovery process. Here the structures of naturally occurring antimicrobial and antiviral peptides and proteins are used as starting points to generate novel macrocyclic mimetics, which can be produced and optimized efficiently by combinatorial synthetic methods. Several recent examples highlight the great potential of the PEM approach in the discovery of new anti-infective agents
Thermal heat radiation, near-field energy density and near-field radiative heat transfer of coated materials
We investigate the thermal radiation and thermal near-field energy density of
a metal-coated semi-infinite body for different substrates. We show that the
surface polariton coupling within the metal coating leads to an enhancement of
the TM-mode part of the thermal near-field energy density when a polar
substrate is used. In this case the result obtained for a free standing metal
film is retrieved. In contrast, in the case of a metal substrate there is no
enhancement in the TM-mode part, as can also be explained within the framework
of surface plasmon coupling within the coating. Finally, we discuss the
influence of the enhanced thermal energy density on the near-field radiative
heat transfer between a simple semi-infinite and a coated semi-infinite body
for different material combinations
A trapped-ion local field probe
We introduce a measurement scheme that utilizes a single ion as a local field
probe. The ion is confined in a segmented Paul trap and shuttled around to
reach different probing sites. By the use of a single atom probe, it becomes
possible characterizing fields with spatial resolution of a few nm within an
extensive region of millimeters. We demonstrate the scheme by accurately
investigating the electric fields providing the confinement for the ion. For
this we present all theoretical and practical methods necessary to generate
these potentials. We find sub-percent agreement between measured and calculated
electric field values
Towards surface quantum optics with Bose-Einstein condensates in evanescent waves
We present a surface trap which allows for studying the coherent interaction
of ultracold atoms with evanescent waves. The trap combines a magnetic Joffe
trap with a repulsive evanescent dipole potential. The position of the magnetic
trap can be controlled with high precision which makes it possible to move
ultracold atoms to the surface of a glass prism in a controlled way. The
optical potential of the evanescent wave compensates for the strong attractive
van der Waals forces and generates a potential barrier at only a few hundred
nanometers from the surface. The trap is tested with Rb Bose-Einstein
condensates (BEC), which are stably positioned at distances from the surfaces
below one micrometer
Diffuse reflection of a Bose-Einstein condensate from a rough evanescent wave mirror
We present experimental results showing the diffuse reflection of a
Bose-Einstein condensate from a rough mirror, consisting of a dielectric
substrate supporting a blue-detuned evanescent wave. The scattering is
anisotropic, more pronounced in the direction of the surface propagation of the
evanescent wave. These results agree very well with theoretical predictions.Comment: submitted to J Phys B, 10 pages, 6 figure
Casimir force on amplifying bodies
Based on a unified approach to macroscopic QED that allows for the inclusion
of amplification in a limited space and frequency range, we study the Casimir
force as a Lorentz force on an arbitrary partially amplifying system of
linearly locally responding (isotropic) magnetoelectric bodies. We demonstrate
that the force on a weakly polarisable/magnetisable amplifying object in the
presence of a purely absorbing environment can be expressed as a sum over the
Casimir--Polder forces on the excited atoms inside the body. As an example, the
resonant force between a plate consisting of a dilute gas of excited atoms and
a perfect mirror is calculated
Buildings LCA and digitalization: Designers\u27 toolbox based on a survey
In a context of digitalization and increasing quality requirements, the building sector is facing an increasing level of complexity regarding its design process. This results in a growing number of involved actors from different domains, a multitude of tasks to be completed and a higher degree of needed expertise. New buildings are also required to reach higher performances in terms of environmental quality. To that regard, the exploitation of the full potential of digital tools can facilitate the integration of environmental aspects in the planning process, limit productivity shortcomings and reduce environmental impacts, which can result from an unaware decision making. Building environmental assessment can be performed through several Life Cycle Assessment (LCA)-based tools. “Pure calculation” tools quantify final buildings\u27 environmental potential, while “complex tools” additionally support decision making during the planning process. It is often difficult to choose the best suitable tool, which strongly depends on the user\u27s needs. Within the IEA EBC Annex 72, a survey was realized with the main objective of creating a comprehensive overview of the existing tools dedicated to buildings LCA. The questionnaire included the usability, functionality, compliance, data reliability and interoperability of the analysed tools. Lastly, based on the survey outcomes and their critical assessment, a procedure for the identification and selection of a tool has been proposed based on user\u27s needs. As a result, this work outlines main features of currently available building LCA tools, for which there is a harmonized status in terms of usability and overall applied LCA methodology. Despite the need for more automatized workflows, tools\u27 embedding is mostly not yet applicable in system chains or limited to a restricted number of tools
- …