The Horizontal Component of Photospheric Plasma Flows During the Emergence of Active Regions on the Sun

The dynamics of horizontal plasma flows during the first hours of the emergence of active region magnetic flux in the solar photosphere have been analyzed using SOHO/MDI data. Four active regions emerging near the solar limb have been considered. It has been found that extended regions of Doppler velocities with different signs are formed in the first hours of the magnetic flux emergence in the horizontal velocity field. The flows observed are directly connected with the emerging magnetic flux; they form at the beginning of the emergence of active regions and are present for a few hours. The Doppler velocities of flows observed increase gradually and reach their peak values 4-12 hours after the start of the magnetic flux emergence. The peak values of the mean (inside the +/-500 m/s isolines) and maximum Doppler velocities are 800-970 m/s and 1410-1700 m/s, respectively. The Doppler velocities observed substantially exceed the separation velocities of the photospheric magnetic flux outer boundaries. The asymmetry was detected between velocity structures of leading and following polarities. Doppler velocity structures located in a region of leading magnetic polarity are more powerful and exist longer than those in regions of following polarity. The Doppler velocity asymmetry between the velocity structures of opposite sign reaches its peak values soon after the emergence begins and then gradually drops within 7-12 hours. The peak values of asymmetry for the mean and maximal Doppler velocities reach 240-460 m/s and 710-940 m/s, respectively. An interpretation of the observable flow of photospheric plasma is given.Comment: 20 pages, 10 figures, 3 tables. The results of article were presented at the ESPM-13 (12-16 September 2011, Rhodes, Greece, Abstract Book p. 102, P.4.12, http://astro.academyofathens.gr/espm13/documents/ESPM13_abstract_programme_book.pdf

Optimization of pharmacokinetic properties by modification of a carbazole-based cannabinoid receptor subtype 2 (CB2) ligand

Recently, the development of the fluorinated PET tracer [F-18]1a for imaging of CB2 receptors in the central nervous system was reported. [F-18]1a showed high CB2 affinity and selectivity over the CB1 subtype, but rapid biotransformation in mice. In addition to the amide hydrolysis, oxidative N-dealkylation and carbazole oxidation were postulated as main metabolic pathways. Based on these results, novel carbazole derivatives with additional 6-substituents (23a, 24a), modified hydrogenation state (26a) and enlarged fluoroalkyl substituent (13a, 13b) were synthesized and pharmacologically evaluated. The key step in the synthesis of substituted carbazoles 23a, 24a and 26a was a Fischer indole synthesis. Nucleophilic substitution of tosylated lactate 5 by carbazole anion provided the fluoroisopropyl derivatives 13a and 13b. Partial hydrogenation of the aromatic carbazole system (26a) was not tolerated by the CB2 receptor. A methylsulfonyl moiety in 6-position (24a) led to considerably reduced CB2 affinity, whereas a 6-methoxy moiety (23a) was well tolerated. An additional methyl moiety in the fluoroethyl side chain of la resulted in fluoroisopropyl derivatives 13 with unchanged high CB2 affinity and CB2: CB1 selectivity. Compared with the fluoroethyl derivative 1a, the carbazole N-atom of the fluoroisopropyl derivative 13a (K-i(CB2) = 2.9 nM) is better shielded against the attack of CYP enzymes as formation of N-oxides was not observed and N-dealkylation took place to a less amount. (C) 2017 Elsevier Masson SAS. All rights reserved.Medicinal Chemistr

The Relationship Between Plasma Flow Doppler Velocities and Magnetic Field Parameters During the Emergence of Active Regions at the Solar Photospheric Level

A statistical study has been carried out of the relationship between plasma flow Doppler velocities and magnetic field parameters during the emergence of active regions at the solar photospheric level with data acquired by the Michelson Doppler Imager (MDI) onboard the Solar and Heliospheric Observatory (SOHO). We have investigated 224 emerging active regions with different spatial scales and positions on the solar disc. The following relationships for the first hours of the emergence of active regions have been analysed: i) of peak negative Doppler velocities with the position of the emerging active regions on the solar disc; ii) of peak plasma upflow and downflow Doppler velocities with the magnetic flux growth rate and magnetic field strength for the active regions emerging near the solar disc centre (the vertical component of plasma flows); iii) of peak positive and negative Doppler velocities with the magnetic flux growth rate and magnetic field strength for the active regions emerging near the limb (the horizontal component of plasma flows); iv) of the magnetic flux growth rate with the density of emerging magnetic flux; v) of the Doppler velocities and magnetic field parameters for the first hours of the appearance of active regions with the total unsigned magnetic flux at the maximum of their development.Comment: 14 pages, 8 figures. The results of article were presented at the ESPM-13 (12-16 September 2011, Rhodes, Greece, Abstract Book p. 102-103, P.4.13, http://astro.academyofathens.gr/espm13/documents/ESPM13_abstract_programme_book.pdf

Helium identification with LHCb

The identification of helium nuclei at LHCb is achieved using a method based on measurements of ionisation losses in the silicon sensors and timing measurements in the Outer Tracker drift tubes. The background from photon conversions is reduced using the RICH detectors and an isolation requirement. The method is developed using pp collision data at √(s) = 13 TeV recorded by the LHCb experiment in the years 2016 to 2018, corresponding to an integrated luminosity of 5.5 fb-1. A total of around 105 helium and antihelium candidates are identified with negligible background contamination. The helium identification efficiency is estimated to be approximately 50% with a corresponding background rejection rate of up to O(10^12). These results demonstrate the feasibility of a rich programme of measurements of QCD and astrophysics interest involving light nuclei

Curvature-bias corrections using a pseudomass method

Momentum measurements for very high momentum charged particles, such as muons from electroweak vector boson decays, are particularly susceptible to charge-dependent curvature biases that arise from misalignments of tracking detectors. Low momentum charged particles used in alignment procedures have limited sensitivity to coherent displacements of such detectors, and therefore are unable to fully constrain these misalignments to the precision necessary for studies of electroweak physics. Additional approaches are therefore required to understand and correct for these effects. In this paper the curvature biases present at the LHCb detector are studied using the pseudomass method in proton-proton collision data recorded at centre of mass energy √(s)=13 TeV during 2016, 2017 and 2018. The biases are determined using Z→μ + μ - decays in intervals defined by the data-taking period, magnet polarity and muon direction. Correcting for these biases, which are typically at the 10-4 GeV-1 level, improves the Z→μ + μ - mass resolution by roughly 18% and eliminates several pathological trends in the kinematic-dependence of the mean dimuon invariant mass

Momentum scale calibration of the LHCb spectrometer

For accurate determination of particle masses accurate knowledge of the momentum scale of the detectors is crucial. The procedure used to calibrate the momentum scale of the LHCb spectrometer is described and illustrated using the performance obtained with an integrated luminosity of 1.6 fb-1 collected during 2016 in pp running. The procedure uses large samples of J/ψ → μ + μ - and B+ → J/ψ K + decays and leads to a relative accuracy of 3 × 10-4 on the momentum scale

Engineering lactococci for increased functionality

Various strategies have been employed to engineer lactic acid bacteria (LAB) to improve their functionality as cell-factory or in food fermentation applications. Lactococcus lactis has long served as a paradigm organism in genetic engineering of the LAB, and the analysis of gene-specific mutant strains and/or strains overexpressing specific functions has been crucial for our increased insight in gene-regulation and metabolism of these industrially important microbes. However, application of engineered strains in food fermentations is limited by the lack of consumer acceptance of genetically engineered foods. This has led to a renewed interest in natural mechanisms of gene transfer and has stimulated the use of experimental evolution to increase specific LAB functionalities