S-adenosyl-L-methionine: (S)-scoulerine 9-O-methyltransferase, a highly stereo- and regio-specific enzyme in tetrahydroprotoberberine biosynthesis

Suspension cultures of Berberis species are useful sources for the detection and isolation of a new enzyme which transfers the methyl group from S-adenosyl-L-methionine specifically to the 9-position of the (S)-enantiomer of scoulerine, producing (S)-tetrahydrocolumbamine. The enzyme was enriched 27-fold; it is not particle bound, has a pH optimum of 8.9, a molecular weight of 63 000 and shows a high degree of substrate specificity

Biosynthesis of the protoberberine alkaloid jatrorrhizine

Feeding experiments with distant single or doubly labelled precursors show that the methylene dioxy group of berberine is opened in the formation of jatrorrhizine

Double-spiral magnetic structure of the Fe/Cr multilayer revealed by nuclear resonance scattering

We have studied the magnetization depth profiles in a [57Fe(dFe)/Cr(dCr)]x30 multilayer with ultrathin Fe layers and nominal thickness of the chromium spacers dCr 2.0 nm using nuclear resonance scattering of synchrotron radiation. The presence of a broad pure-magnetic half-order (1/2) Bragg reflection has been detected at zero external field. The joint fit of the reflectivity curves and Mossbauer spectra of reflectivity measured near the critical angle and at the "magnetic" peak reveals that the magnetic structure of the multilayer is formed by two spirals, one in the odd and another one in the even iron layers, with the opposite signs of rotation. The double-spiral structure starts from the surface with the almost antiferromagnetic alignment of the adjacent Fe layers. The rotation of the two spirals leads to nearly ferromagnetic alignment of the two magnetic subsystems at some depth, where the sudden turn of the magnetic vectors by ~180 deg (spin-flop) appears, and both spirals start to rotate in opposite directions. The observation of this unusual double-spiral magnetic structure suggests that the unique properties of giant magneto-resistance devices can be further tailored using ultrathin magnetic layers.Comment: 9 pages, 3 figure

Current developments in SWIPPA ‘Space Weather Impact on Precise Positioning Applications of GNSS’

SWIPPA (Space Weather Impact on Precise Positioning Applications of GNSS) is a project, initiated by DLR, aiming at establishing a specific space weather (SW) service for improving current Global Navigation Satellite System (GNSS) applications. This activity is considered as being a substantial part of the preparations for the future European Space Weather Programme and GALILEO services. The SWIPPA project started with the definition of service, including user requirements, products, and related technical service definition. Following on the multiple discussions within the project consortium, all requirements of each user service have been carefully considered. It was important to obtain information on issues such as: which products are most needed and which should have higher priority than others, the optimal spatial and time resolution, products improvements, etc. The established information security and classification policy within the project is of primary importance and is strictly observed to protect the rights and interests of the SWIPPA customer. As a result of the user requirements, the final SWIPPA products list has been created. The products list include various nowcast and forecast maps, expert estimates, warning geophysical messages, etc. A sub-set of the listed products can become available to the SWENET (Space Weather European Network) and general public members following their interest and further discussions. Based on the user requirements and the products definition, the most adequate technical solutions have been sought and found considering the powerful technological base and rich experience available at DLR. All information will be operationally processed at the DLR premises, the products will be developed and placed on FTP server(s) providing near realtime access to the most recently generated data products. The ‘definition of service’ part has been successfully completed. The SWIPPA project continued recently with the establishment of service, including the built up of infrastructure and central processing facilities. Preliminary navigation data and products have been already transferred between DLR and its partners/users for testing purposes. In resume, the project is progressing well in time. The efforts are first in this field and require each space-weather service to be carefully adjusted to the specific needs of the SWIPPA users

On the relation between network RTK performance and ionospheric activity

GNSS RTK (Real-Time Kinematic) positioning techniques are based on precise but ambiguous carrier phase observations. The ambiguities can be resolved by properly modelling the ionospheric influence. However, under perturbed ionospheric conditions, the ionospheric modelling may become inaccurate and thus to lead to degraded network performance. The paper addresses the adverse space weather effects on GNSS-based positioning and discusses possible problems of reference network concepts that can be attributed to ionospheric interference in particular. For the purpose, analysed is the relation between the residual ionospheric error and the ionospheric activity. Generally, the ionospheric impact is noticeably stronger during ionospheric perturbations/storms, which raises the question of how the reference networks perform during such unfavourable conditions. Analysed also is the feasibility and effectivity of an operational space weather monitoring service for improving the performance and maintaining the integrity of network RTK