Cannabidiol Is a Novel Modulator of Bacterial Membrane Vesicles

Membrane vesicles (MVs) released from bacteria participate in cell communication and host-pathogen interactions. Roles for MVs in antibiotic resistance are gaining increased attention and in this study we investigated if known anti-bacterial effects of cannabidiol (CBD), a phytocannabinoid from Cannabis sativa, could be in part attributed to effects on bacterial MV profile and MV release. We found that CBD is a strong inhibitor of MV release from Gram-negative bacteria (E. coli VCS257), while inhibitory effect on MV release from Gram-positive bacteria (S. aureus subsp. aureus Rosenbach) was negligible. When used in combination with selected antibiotics, CBD significantly increased the bactericidal action of several antibiotics in the Gram-negative bacteria. In addition, CBD increased antibiotic effects of kanamycin in the Gram-positive bacteria, without affecting MV release. CBD furthermore changed protein profiles of MVs released from E. coli after 1 h CBD treatment. Our findings indicate that CBD may pose as a putative adjuvant agent for tailored co-application with selected antibiotics, depending on bacterial species, to increase antibiotic activity, including via MV inhibition, and help reduce antibiotic resistance

Analytical determination of coronal parameters using the period ratio P₁/2P₂

<p>Context. In transverse coronal loop oscillations, two periodicities have been measured simultaneously and are interpreted as the fundamental kink mode (with period P1) and the first harmonic (with period P2). Deviations of the period ratio P1/2P2 from unity provide information about the extent of longitudinal structuring within the loop.</p> <p>Aims. Here we develop an analytical approximation that describes the shift in P1/2P2 in terms of the ratio L/Λc of the length 2L of a coronal loop and the density scale height Λc.</p> <p>Methods. We study the MHD wave equations in a low β plasma using the thin tube approximation. Disturbances are described by a differential equation which may be solved for various equilibrium density profiles, obtaining dispersion relations in terms of Bessel functions. These dispersion relations may be used to obtain analytical approximations to the periods P1 and P2. We also present a variational approach to determining the period ratio and show how the WKB method may be used.</p> <p>Results. Analytical approximations to the period ratio P1/2P2 are used to shed light on the magnitude of longitudinal structuring in a loop, leading to a determination of the density scale height. We apply our formula to the observations in Verwichte et al. (2004) and Van Doorsselaere et al. (2007), obtaining the coronal density scale height.</p> <p>Conclusions. Our simple formula and approximate approaches highlight a useful analytical tool for coronal seismology. We demonstrate that P1/2P2 is linked to the density scale height, with no need for estimates of other external parameters. Given the accuracy of current observations, our formula provides a convenient means of determining density scale heights.</p&gt

The low-temperature sol-gel synthesis of metal-oxide films on polymer substrates and the determination of their optical and dielectric properties

Photoactive, optically transparent heterostructures from silver nanowires and titanium dioxide were obtained by the sol-gel method on the surface of a polyethylene terephthalate film. The characteristics of optical transmission on the wavelength and those of dielectric permittivity, conductivity and dissipation on frequency in the range of 25–1,000,000 Hz were investigated

The WITCH experiment: completion of a set-up to investigate the structure of weak interactions with a Penning trap

The WITCH experiment aims to study a possible admixture of a scalar or tensor type interaction in beta decay by determining the beta-neutrino angular correlation from the shape of the recoil energy spectrum. The installation period was completed and intensive commissioning of the set-up was performed already. The lay-out of the WITCH set-up and results of commissioning tests performed until now are described here, showing that the full set-up up to the spectrometer is now operational, although several efficiencies are still to be improved. Due to its feature of being able to measure the energy spectrum for recoil ions, the WITCH experiment also opens possibilities for other observables.Comment: 31 pages, 18 figures. International Journal of Mass Spectrometry, in pres

Multiwavelength observations of a giant flare on CN Leonis I. The chromosphere as seen in the optical spectra

Flares on dM stars contain plasmas at very different temperatures and thus affect a wide wavelength range in the electromagnetic spectrum. While the coronal properties of flares are studied best in X-rays, the chromosphere of the star is observed best in the optical and ultraviolet ranges. Therefore, multiwavelength observations are essential to study flare properties throughout the atmosphere of a star. We analysed simultaneous observations with UVES/VLT and XMM-Newton of the active M5.5 dwarf CN Leo (Gl 406) exhibiting a major flare. The optical data cover the wavelength range from 3000 to 10000 Angstrom. From our optical data, we find an enormous wealth of chromospheric emission lines occurring throughout the spectrum. We identify a total of 1143 emission lines, out of which 154 are located in the red arm, increasing the number of observed emission lines in this red wavelength range by about a factor of 10. Here we present an emission line list and a spectral atlas. We also find line asymmetries for H I, He I, and Ca II lines. For the last, this is the first observation of asymmetries due to a stellar flare. During the flare onset, there is additional flux found in the blue wing, while in the decay phase, additional flux is found in the red wing. We interpret both features as caused by mass motions. In addition to the lines, the flare manifests itself in the enhancement of the continuum throughout the whole spectrum, inverting the normal slope for the net flare spectrum.Comment: 15 pages, accepted by A&

WITCH: a recoil spectrometer for weak interaction and nuclear physics studies

An experimental set-up is described for the precise measurement of the recoil energy spectrum of the daughter ions from nuclear beta decay. The experiment is called WITCH, short for Weak Interaction Trap for CHarged particles, and is set up at the ISOLDE facility at CERN. The principle of the experiment and its realization are explained as well as the main physics goal. A cloud of radioactive ions stored in a Penning trap serves as the source for the WITCH experiment, leading to the minimization of scattering and energy loss of the decay products. The energy spectrum of the recoiling daughter ions from the $\beta$--decays in this ion cloud will be measured with a retardation spectrometer. The principal aim of the WITCH experiment is to study the electroweak interaction by determining the beta--neutrino angular correlation in nuclear $\beta$--decay from the shape of this recoil energy spectrum. This will be the first time that the recoil energy spectrum of the daughter ions from $\beta$--decay can be measured for a wide variety of isotopes, independent of their specific properties

Progress at the WITCH experiment

The WITCH-experiment will measure the energy spectrum of the recoiling daughter ions in $\beta$-decay to search for non-standard scalar and tensor type interaction. To facilitate this a Penning trap is used to store the radioactive ions. Thus the recoil ions can leave the source without any energy loss and their energy can be probed by the subsequent retardation spectrometer. The experiment is being set up at present at ISOLDE/CERN. The principle and the status of the WITCH-experiment will be presented. (12 refs)

Some Like it Hot: The X-Ray Emission of The Giant Star YY Mensae

(Abridged abstract) We present an analysis of the X-ray emission of the rapidly rotating giant star YY Mensae observed by Chandra HETGS and XMM-Newton. Although no obvious flare was detected, the X-ray luminosity changed by a factor of two between the XMM-Newton and Chandra observations taken 4 months apart. The coronal abundances and the emission measure distribution have been derived from three different methods using optically thin collisional ionization equilibrium models. The abundances show an inverse first ionization potential (FIP) effect. We further find a high N abundance which we interpret as a signature of material processed in the CNO cycle. The corona is dominated by a very high temperature (20-40 MK) plasma, which places YY Men among the magnetically active stars with the hottest coronae. Lower temperature plasma also coexists, albeit with much lower emission measure. Line broadening is reported, which we interpret as Doppler thermal broadening, although rotational broadening due to X-ray emitting material high above the surface could be present as well. We use two different formalisms to discuss the shape of the emission measure distribution. The first one infers the properties of coronal loops, whereas the second formalism uses flares as a statistical ensemble. We find that most of the loops in the corona of YY Men have their maximum temperature equal to or slightly larger than about 30 MK. We also find that small flares could contribute significantly to the coronal heating in YY Men. Although there is no evidence of flare variability in the X-ray light curves, we argue that YY Men's distance and X-ray brightness does not allow us to detect flares with peak luminosities Lx <= 10^{31} erg/s with current detectors.Comment: Accepted paper to appear in Astrophysical Journal, issue Nov 10, 2004 (v615). This a revised version. Small typos are corrected. Figure 7 and its caption and some related text in Sct 7.2 are changed, without incidence for the conclusion

Review article: MHD wave propagation near coronal null points of magnetic fields

We present a comprehensive review of MHD wave behaviour in the neighbourhood of coronal null points: locations where the magnetic field, and hence the local Alfven speed, is zero. The behaviour of all three MHD wave modes, i.e. the Alfven wave and the fast and slow magnetoacoustic waves, has been investigated in the neighbourhood of 2D, 2.5D and (to a certain extent) 3D magnetic null points, for a variety of assumptions, configurations and geometries. In general, it is found that the fast magnetoacoustic wave behaviour is dictated by the Alfven-speed profile. In a $\beta=0$ plasma, the fast wave is focused towards the null point by a refraction effect and all the wave energy, and thus current density, accumulates close to the null point. Thus, null points will be locations for preferential heating by fast waves. Independently, the Alfven wave is found to propagate along magnetic fieldlines and is confined to the fieldlines it is generated on. As the wave approaches the null point, it spreads out due to the diverging fieldlines. Eventually, the Alfven wave accumulates along the separatrices (in 2D) or along the spine or fan-plane (in 3D). Hence, Alfven wave energy will be preferentially dissipated at these locations. It is clear that the magnetic field plays a fundamental role in the propagation and properties of MHD waves in the neighbourhood of coronal null points. This topic is a fundamental plasma process and results so far have also lead to critical insights into reconnection, mode-coupling, quasi-periodic pulsations and phase-mixing.Comment: 34 pages, 5 figures, invited review in Space Science Reviews => Note this is a 2011 paper, not a 2010 pape