584 research outputs found
Dual-species quantum degeneracy of potassium-40 and rubidium-87 on an atom chip
In this article we review our recent experiments with a 40K-87Rb mixture. We
demonstrate rapid sympathetic cooling of a 40K-87Rb mixture to dual quantum
degeneracy on an atom chip. We also provide details on efficient BEC
production, species-selective magnetic confinement, and progress toward
integration of an optical lattice with an atom chip. The efficiency of our
evaporation allows us to reach dual degeneracy after just 6 s of evaporation -
more rapidly than in conventional magnetic traps. When optimizing evaporative
cooling for efficient evaporation of 87Rb alone we achieve BEC after just 4 s
of evaporation and an 8 s total cycle time.Comment: 8 pages, 4 figures. To be published in the Proceedings of the 20th
International Conference on Atomic Physics, 2006 (Innsbruck, Austria
Deformed Statistics Kullback-Leibler Divergence Minimization within a Scaled Bregman Framework
The generalized Kullback-Leibler divergence (K-Ld) in Tsallis statistics
[constrained by the additive duality of generalized statistics (dual
generalized K-Ld)] is here reconciled with the theory of Bregman divergences
for expectations defined by normal averages, within a measure-theoretic
framework. Specifically, it is demonstrated that the dual generalized K-Ld is a
scaled Bregman divergence. The Pythagorean theorem is derived from the minimum
discrimination information-principle using the dual generalized K-Ld as the
measure of uncertainty, with constraints defined by normal averages. The
minimization of the dual generalized K-Ld, with normal averages constraints, is
shown to exhibit distinctly unique features.Comment: 16 pages. Iterative corrections and expansion
Evaluation of a Fiber-Optic Based Pulsed Laser System for Fluorescence Spectroscopy
A fiber optic based continous wave laser setup has been developed to record the 5-aminolevulinic (5-ALA) induced Protoporfyrin IX (PpIX) fluorescence signals from cerebral gliomas. To reduce the energy delivered to the tissue as well as suppression of the ambient lamp artifact from the recorded spectra, a pulsed laser setup has been developed and evaluated. This setup has been calibrated and first evaluations were performed on the 5-ALA treated skin showing PpIX fluorescence peaks from the ALA treated skin at 635 and 704 nm wavelengths. The system controls laser pulses through a computer interface and labview software package. Pulses as short as 50 ms over a period time of 500 ms are generated and optimally detected. The results from primary measurements on skin show an effective suppression of room fluorescent lamp artifact from the recorded spectra
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Energy Flux Characterisation of Atmospheric Pressure Plasma Spray Torches with Passive Thermal Probes
Passive thermal probes were applied on two different plasma spraying devices to gain a detailed understanding of the energy flux towards the substrate under atmospheric pressure. The challenge of very high thermal load was solved by using an advanced time-resolved measuring and evaluation technique. The combination with a controlled movement of the jets allowed to obtain insightful radial profiles. The energy flux to the substrate changes linearly to the electrical input power. When adding diatomic gases (H2/N2) to the gas mixture the energy flux increases significantly, suggesting a more efficient energy transport. For increasing the axial distance, the energy flux shows a quadratic reduction. The obtained radial profiles are exemplarily utilized to show the inhomogeneous effect of powder injection on the energy flux distribution
Prospective cohort study of radiotherapy with concomitant and adjuvant temozolomide chemotherapy for glioblastoma patients with no or minimal residual enhancing tumor load after surgery
Survival of glioblastoma patients has been linked to the completeness of surgical resection. Available data, however, were generated with adjuvant radiotherapy. Data confirming that extensive cytoreduction remains beneficial to patients treated with the current standard, concomitant temozolomide radiochemotherapy, are limited. We therefore analyzed the efficacy of radiochemotherapy for patients with little or no residual tumor after surgery. In this prospective, non-interventional multicenter cohort study, entry criteria were histological diagnosis of glioblastoma, small enhancing or no residual tumor on post-operative MRI, and intended temozolomide radiochemotherapy. The primary study objective was progression-free survival; secondary study objectives were survival and toxicity. Furthermore, the prognostic value of O6-methylguanine-DNA methyltransferase (MGMT) promoter methylation was investigated in a subgroup of patients. One-hundred and eighty patients were enrolled. Fourteen were excluded by patient request or failure to initiate radiochemotherapy. Twenty-three patients had non-evaluable post-operative imaging. Thus, 143 patients qualified for analysis, with 107 patients having residual tumor diameters â€1.5 cm. Median follow-up was 24.0 months. Median survival or patients without residual enhancing tumor exceeded the follow-up period. Median survival was 16.9 months for 32 patients with residual tumor diameters >0 to â€1.5 cm (95% CI: 13.3â20.5, p = 0.039), and 13.9 months (10.3â17.5, overall p < 0.001) for 36 patients with residual tumor diameters >1.5 cm. Patient age at diagnosis and extent of resection were independently associated with survival. Patients with MGMT promoter methylated tumors and complete resection made the best prognosis. Completeness of resection acts synergistically with concomitant and adjuvant radiochemotherapy, especially in patients with MGMT promoter methylation
The Bregman chord divergence
Distances are fundamental primitives whose choice significantly impacts the
performances of algorithms in machine learning and signal processing. However
selecting the most appropriate distance for a given task is an endeavor.
Instead of testing one by one the entries of an ever-expanding dictionary of
{\em ad hoc} distances, one rather prefers to consider parametric classes of
distances that are exhaustively characterized by axioms derived from first
principles. Bregman divergences are such a class. However fine-tuning a Bregman
divergence is delicate since it requires to smoothly adjust a functional
generator. In this work, we propose an extension of Bregman divergences called
the Bregman chord divergences. This new class of distances does not require
gradient calculations, uses two scalar parameters that can be easily tailored
in applications, and generalizes asymptotically Bregman divergences.Comment: 10 page
A time-dependent model for improved biogalvanic tissue characterisation
Measurement of the passive electrical resistance of biological tissues through biogalvanic characterisation has been proposed as a simple means of distinguishing healthy from diseased tissue. This method has the potential to provide valuable real-time information when integrated into surgical tools. Characterised tissue resistance values have been shown to be particularly sensitive to external load switching direction and rate, bringing into question the stability and efficacy of the technique. These errors are due to transient variations observed in measurement data that are not accounted for in current electrical models. The presented research proposes the addition of a time-dependent element to the characterisation model to account for losses associated with this transient behaviour. Influence of switching rate has been examined, with the inclusion of transient elements improving the repeatability of the characterised tissue resistance. Application of this model to repeat biogalvanic measurements on a single ex vivo human colon tissue sample with healthy and cancerous (adenocarcinoma) regions showed a statistically significant difference (p 0.05) between tissue types was found when measurements were subjected to the current model, suggesting that the proposed model may allow for improved biogalvanic tissue characterisation
Physics Beyond Colliders:The Conventional Beams Working Group
The Physics Beyond Colliders initiative aims to exploit the full scientific potential of the CERN accelerator complex and its scientific infrastructure for particle physics studies, complementary to current and future collider experiments. Several experiments have been proposed to fully utilize and further advance the beam options for the existing fixed target experiments present in the North and East Experimental Areas of the CERN SPS and PS accelerators. We report on progress with the RF-separated beam option for the AMBER experiment, following a recent workshop on this topic. In addition we cover the status of studies for ion beams for the NAâ¶â°âș experiment, as well as of those for high intensity beams for Kaon physics and feebly interacting particle searches. With first beams available in 2021 after a CERN-wide long shutdown, several muon beam options were already tested for the NA64mu, MUonE and AMBER experiments
Rapid sympathetic cooling to Fermi degeneracy on a chip
Neutral fermions present new opportunities for testing many-body condensed
matter systems, realizing precision atom interferometry, producing ultra-cold
molecules, and investigating fundamental forces. However, since their first
observation, quantum degenerate Fermi gases (DFGs) have continued to be
challenging to produce, and have been realized in only a handful of
laboratories. In this Letter, we report the production of a DFG using a simple
apparatus based on a microfabricated magnetic trap. Similar approaches applied
to Bose-Einstein Condensation (BEC) of 87Rb have accelerated evaporative
cooling and eliminated the need for multiple vacuum chambers. We demonstrate
sympathetic cooling for the first time in a microtrap, and cool 40K to Fermi
degeneracy in just six seconds -- faster than has been possible in conventional
magnetic traps. To understand our sympathetic cooling trajectory, we measure
the temperature dependence of the 40K-87Rb cross-section and observe its
Ramsauer-Townsend reduction.Comment: 5 pages, 4 figures (v3: new collision data, improved atom number
calibration, revised text, improved figures.
Evaluation of the third- and fourth-generation GOCE Earth gravity field models with Australian terrestrial gravity data in spherical harmonics
In March 2013 the fourth generation of ESAâs (European Space Agency) global gravity field models, DIR4 (Bruinsma et al, 2010b) and TIM4 (Pail et al, 2010), generated from the GOCE (Gravity field and steady-state Ocean Circulation Explorer) gravity observation satellite were released. We evaluate the models using an independent ground truth data set of gravity anomalies over Australia. Combined with GRACE (Gravity Recovery and Climate Experiment) satellite gravity, a new gravity model is obtained that is used to perform comparisons with GOCE models in spherical harmonics. Over Australia, the new gravity model proves to have significantly higher accuracy in the degrees below 120 as compared to EGM2008 and seems to be at least comparable to the accuracy of this model between degree 150 and degree 260. Comparisons in terms of residual quasi-geoid heights, gravity disturbances, and radial gravity gradients evaluated on the ellipsoid and at approximate GOCE mean satellite altitude (h=250 km) show both fourth generation models to improve significantly w.r.t. their predecessors.Relatively, we find a root-mean-square improvement of 39 % for the DIR4 and 23 % for TIM4 over the respective third release models at a spatial scale of 100 km (degree 200). In terms of absolute errors TIM4 is found to perform slightly better in the bands from degree 120 up to degree 160 and DIR4 is found to perform slightly better than TIM4 from degree 170 up to degree 250. Our analyses cannot confirm the DIR4 formal error of 1 cm geoid height (0.35 mGal in terms of gravity) at degree 200. The formal errors of TIM4, with 3.2 cm geoid height (0.9 mGal in terms of gravity) at degree 200, seem to be realistic. Due to combination with GRACE and SLR data, the DIR models, at satellite altitude, clearly show lower RMS values compared to TIM models in the long wavelength part of the spectrum (below degree and order 120). Our study shows different spectral sensitivity of different functionals at ground level and at GOCE satellite altitude and establishes the link among these findings and the Meissl scheme (Rummel and van Gelderen in Manuscripta Geodaetica 20:379â385, 1995)
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