An efficient algorithm for computing the Baker-Campbell-Hausdorff series and some of its applications

We provide a new algorithm for generating the Baker--Campbell--Hausdorff (BCH) series Z = \log(\e^X \e^Y) in an arbitrary generalized Hall basis of the free Lie algebra $\mathcal{L}(X,Y)$ generated by $X$ and $Y$. It is based on the close relationship of $\mathcal{L}(X,Y)$ with a Lie algebraic structure of labeled rooted trees. With this algorithm, the computation of the BCH series up to degree 20 (111013 independent elements in $\mathcal{L}(X,Y)$) takes less than 15 minutes on a personal computer and requires 1.5 GBytes of memory. We also address the issue of the convergence of the series, providing an optimal convergence domain when $X$ and $Y$ are real or complex matrices.Comment: 30 page

Strain mapping at the nanoscale using precession electron diffraction in transmission electron microscope with off axis camera

International audiencePrecession electron diffraction is an efficient technique to measure strain in nanostructures by precessing the electron beam, while maintaining a few nanometre probe size. Here, we show that an advanced diffraction pattern treatment allows reproducible and precise strain measurements to be obtained using a default 512 x 512 DigiSTAR off-axis camera both in advanced or non-corrected transmission electron microscopes. This treatment consists in both projective geometry correction of diffraction pattern distortions and strain Delaunay triangulation based analysis. Precision in the strain measurement is improved and reached 2.7 x 10(-4) with a probe size approaching 4.2 nm in diameter. This method is applied to the study of the strain state in InGaAs quantum-well (QW) devices elaborated on Si substrate. Results show that the GaAs/Si mismatch does not induce in-plane strain fluctuations in the InGaAs QW region. (C) 2014 AIP Publishing LLC

Spherical Spectral Synthesis and Two-Radius Theorems on Damek-Ricci Spaces

We prove that spherical spectral analysis and synthesis hold in Damek-Ricci spaces and derive two-radius theorems

The probe beam linac in CTF3

JACoW web site http://accelconf.web.cern.ch/AccelConf/e06/The test facility CTF3, presently under construction at CERN within an international collaboration, is aimed at demonstrating the key feasibility issues of the multi-TeV linear collider CLIC. The objective of the probe beam linac is to "mimic" the main beam of CLIC in order to measure precisely the performances of the 30 GHz CLIC accelerating structures. In order to meet the required parameters of this 200 MeV probe beam, in terms of emittance, energy spread and bunch-length, the most advanced techniques have been considered: laser triggered photo-injector, velocity bunching, beam-loading compensation, RF pulse compression ... The final layout is described, and the selection criteria and the beam dynamics results are reviewed

What Is the Negative Predictive Value of Multiparametric Magnetic Resonance Imaging in Excluding Prostate Cancer at Biopsy? A Systematic Review and Meta-analysis from the European Association of Urology Prostate Cancer Guidelines Panel

Context: It remains unclear whether patients with a suspicion of prostate cancer (PCa) and negative multiparametric magnetic resonance imaging (mpMRI) can safely obviate prostate biopsy. Objective: To systematically review the literature assessing the negative predictive value (NPV) of mpMRI in patients with a suspicion of PCa. Evidence acquisition: The Embase, Medline, and Cochrane databases were searched up to February 2016. Studies reporting prebiopsy mpMRI results using transrectal or transperineal biopsy as a reference standard were included. We further selected for meta-analysis studies with at least 10-core biopsies as the reference standard, mpMRI comprising at least T2-weighted and diffusion-weighted imaging, positive mpMRI defined as a Prostate Imaging Reporting Data System/Likert score of ≥3/5 or ≥4/5, and results reported at patient level for the detection of overall PCa or clinically significant PCa (csPCa) defined as Gleason ≥7 cancer. Evidence synthesis: A total of 48 studies (9613 patients) were eligible for inclusion. At patient level, the median prevalence was 50.4% (interquartile range [IQR], 36.4–57.7%) for overall cancer and 32.9% (IQR, 28.1–37.2%) for csPCa. The median mpMRI NPV was 82.4% (IQR, 69.0–92.4%) for overall cancer and 88.1% (IQR, 85.7–92.3) for csPCa. NPV significantly decreased when cancer prevalence increased, for overall cancer (r = –0.64, p < 0.0001) and csPCa (r = –0.75, p = 0.032). Eight studies fulfilled the inclusion criteria for meta-analysis. Seven reported results for overall PCa. When the overall PCa prevalence increased from 30% to 60%, the combined NPV estimates decreased from 88% (95% confidence interval [95% CI], 77–99%) to 67% (95% CI, 56–79%) for a cut-off score of 3/5. Only one study selected for meta-analysis reported results for Gleason ≥7 cancers, with a positive biopsy rate of 29.3%. The corresponding NPV for a cut-off score of ≥3/5 was 87.9%. Conclusions: The NPV of mpMRI varied greatly depending on study design, cancer prevalence, and definitions of positive mpMRI and csPCa. As cancer prevalence was highly variable among series, risk stratification of patients should be the initial step before considering prebiopsy mpMRI and defining those in whom biopsy may be omitted when the mpMRI is negative. Patient summary This systematic review examined if multiparametric magnetic resonance imaging (MRI) scan can be used to reliably predict the absence of prostate cancer in patients suspected of having prostate cancer, thereby avoiding a prostate biopsy. The results suggest that whilst it is a promising tool, it is not accurate enough to replace prostate biopsy in such patients, mainly because its accuracy is variable and influenced by the prostate cancer risk. However, its performance can be enhanced if there were more accurate ways of determining the risk of having prostate cancer. When such tools are available, it should be possible to use an MRI scan to avoid biopsy in patients at a low risk of prostate cancer

ASTERIX and 2.0 Knowledge Management : exploring the appropriation of 2.0 KMS via the Myth of the Gaulish village

International audienceKnowledge Management Systems (KMS) in companies have profoundly changed in recent years. They have become KMS 2.0 that aim to transform the firm and are driven by a new relationship to knowledge in line with 2.0 organisations. These 2.0 KMS have implemented modes of organisation that disrupt those that previously guided firms’ performance. This can sometimes lead to paradoxical organizational dysfunctions as witnessed by the difficulties faced by some traditionally hierarchical French companies. Through a case study of Constructor and a theoretical background on IS appropriation in organizations and myths in management, we show how the Asterix myth contributes to understanding how 2.0. KMS are appropriated in such companies. We find evidence of similarities regarding knowledge and Knowledge Management between the Asterix’ myth and the behaviours and practices concerning knowledge management within Constructor. As a result, the Asterix’ myth may be a relevant perspective for understanding the obstacles, advantages and appropriations of 2.0. KMS within French organizations

Conversion of Iodide to Hypoiodous Acid and Iodine in Aqueous Microdroplets Exposed to Ozone

Halides are incorporated into aerosol sea spray, where they start the catalytic destruction of ozone (O3) over the oceans and affect the global troposphere. Two intriguing environmental problems undergoing continuous research are (1) to understand how reactive gas phase molecular halogens are directly produced from inorganic halides exposed to O3 and (2) to constrain the environmental factors that control this interfacial process. This paper presents a laboratory study of the reaction of O3 at variable iodide (I–) concentration (0.010–100 μM) for solutions aerosolized at 25 °C, which reveal remarkable differences in the reaction intermediates and products expected in sea spray for low tropospheric [O3]. The ultrafast oxidation of I– by O3 at the air–water interface of microdroplets is evidenced by the appearance of hypoiodous acid (HIO), iodite (IO2–), iodate (IO3–), triiodide (I3–), and molecular iodine (I2). Mass spectrometry measurements reveal an enhancement (up to 28%) in the dissolution of gaseous O3 at the gas–liquid interface when increasing the concentration of NaI or NaBr from 0.010 to 100 μM. The production of iodine species such as HIO and I2 from NaI aerosolized solutions exposed to 50 ppbv O3 can occur at the air–water interface of sea spray, followed by their transfer to the gas-phase, where they contribute to the loss of tropospheric ozone