Enhanced dielectronic recombination of lithium-like Ti19+ ions in external ExB fields

Dielectronic recombination(DR) of lithium-like Ti19+(1s2 2s) ions via 2s->2p core excitations has been measured at the Heidelberg heavy ion storage ring TSR. We find that not only external electric fields (0 <= Ey <= 280 V/cm) but also crossed magnetic fields (30 mT <= Bz <= 80 mT) influence the DR via high-n (2p_j nl)-Rydberg resonances. This result confirms our previous finding for isoelectronic Cl14+ ions [Bartsch T et al, PRL 82, 3779 (1999)] that experimentally established the sensitivity of DR to ExB fields. In the present investigation the larger 2p_{1/2}-2p_{3/2} fine structure splitting of Ti19+ allowed us to study separately the influence of external fields via the two series of Rydberg DR resonances attached to the 2s -> 2p_{1/2} and 2s -> 2p_{3/2} excitations of the Li-like core, extracting initial slopes and saturation fields of the enhancement. We find that for Ey > 80 V/cm the field induced enhancement is about 1.8 times stronger for the 2p_{3/2} series than for the 2p_{1/2} series.Comment: 10 pages, 3 figures, to be published in Journal of Physics B, see also http://www.strz.uni-giessen.de/~k

Interference effects in the photorecombination of argonlike Sc3+ ions: Storage-ring experiment and theory

Absolute total electron-ion recombination rate coefficients of argonlike Sc3+(3s2 3p6) ions have been measured for relative energies between electrons and ions ranging from 0 to 45 eV. This energy range comprises all dielectronic recombination resonances attached to 3p -> 3d and 3p -> 4s excitations. A broad resonance with an experimental width of 0.89 +- 0.07 eV due to the 3p5 3d2 2F intermediate state is found at 12.31 +- 0.03 eV with a small experimental evidence for an asymmetric line shape. From R-Matrix and perturbative calculations we infer that the asymmetric line shape may not only be due to quantum mechanical interference between direct and resonant recombination channels as predicted by Gorczyca et al. [Phys. Rev. A 56, 4742 (1997)], but may partly also be due to the interaction with an adjacent overlapping DR resonance of the same symmetry. The overall agreement between theory and experiment is poor. Differences between our experimental and our theoretical resonance positions are as large as 1.4 eV. This illustrates the difficulty to accurately describe the structure of an atomic system with an open 3d-shell with state-of-the-art theoretical methods. Furthermore, we find that a relativistic theoretical treatment of the system under study is mandatory since the existence of experimentally observed strong 3p5 3d2 2D and 3p5 3d 4s 2D resonances can only be explained when calculations beyond LS-coupling are carried out.Comment: 11 pages, 7 figures, 3 tables, Phys. Rev. A (in print), see also: http://www.strz.uni-giessen.de/~k

Design of a ring resonator-based optical beam forming network for phased array receive antennas

A novel squint-free ring resonator-based optical beam forming network (OBFN) for phased array antennas (PAA) is proposed. It is intended to provide broadband connectivity to airborne platforms via geostationary satellites. In this paper, we present the design of the OBFN and its control system. Our goal is to deliver large bandwidth Ku-band connectivity between antennas, mount conformal to the airplane fuselage and on a geostationary satellite, respectively.This way it would be possible to bring live DVB-S television to airplane passengers. In this paper, we present recent research conducted on a 4 × 1 ring resonator-based OBFN test set-up. This OBFN has four optical input ports and one optical output port. It is tuned to provide the desired signal combination with optimal constructive interference between the modulated input signals from the PAA. Therefore, combining circuitry and delay elements are required. The OBFN is tuned by electrically heating tunable true time delay (TTD) elements. These are built using optical ring resonators (ORRs). By cascading multiple ORRs with different resonance frequencies, it is possible to create a TTD with a large bandwidth. Optical beam forming is used because it provides advantages over traditional beam forming methods. These advantages are: large bandwidth, EMI resistance, and, when integrated onto a single chip, compactness and low costs. The OBFN is created using planar optical waveguide technology and consists of the following building blocks: waveguides, Mach-Zehnder interferometers, (MZIs) couplers and ORRs. The tuning of the OBFN is done by an electronic control system using a microcontroller. Communication with a PC is possible using USB. To our knowledge, this is the first integrated ORR-based OBFN circuit for PAA satellite reception

Impact of fungicide applications for late blight management on huckleberry yields in Cameroon

The influence of late blight infections, caused by Phytophthora infestans, was evaluated on thirteen huckleberry (Solanum scabrum) varieties during the 2000 and 2001 cropping seasons in Dschang, Cameroon. A randomised split block design was used. Plants were sprayed four times with Ridomil Plus® (12% metalaxyl + 60% cuprous oxide) at 2.5 kg ha-1 on a 21-day schedule while control plots were not sprayed. Late blight intensity was recorded weekly and fresh shoot yields were evaluated six times at 14-day intervals. Fungicide applications significantly reduced late blight intensity and consequently increased huckleberry yields. Cumulative shoot yields varied with the variety and fungicide treatment, from 54.14 to 238.33 t ha-1. Yield losses due to late blight infection were estimated at up to 46%. Economic analyses indicated that fungicide sprays are necessary for a late blight protection programme in huckleberry. This spray regime based on fungicide application resulted in net profits of US$694 to$ 8,467 ha-1, depending on the variety used and the trial period. The results show that late blight infections if not controlled, decrease huckleberry yields, and consequently net farm incomes. High yielding resistant varieties or foliar applications of Ridomil Plus® may be incorporated in integrated pathogen management schemes against late blight in huckleberries with a view to minimise use of fungicides. Key Words: Integrated management, Phytophthora infestans, Solanum scabrum, yield loss Résumé L'influence du mildiou, causé par Phytophthora infestans, était évalué sur treize variétés de la morelle noire (Solanum scabrum) pendant les saisons culturalles de l'an 2000 et 2001 à Dschang, Cameroun. Les éssais étaient réalisés en split-blocs pris au hazard. Les plantes étaient traitées quatre fois avec Ridomil Plus (12% de métalaxyl + 60% oxyde cuivreux) à 21 jours d'intervalle à la dose de 2.5 kg ha-1. L'intensité du mildiou a été évalué hebdomadairement et les pousses fraiches ont été récoltées six fois à l'intervalle de 14 jours. Des traitements fongicides ont significativement réduit l'intensité du mildiou et par conséquent augmenté le rendement en pousses. Le rendement total en pousses fraiches a été variable. De 54, 14 à 238,33 t ha-1, selon la variété et le traitement fongicide. Des pertes en rendements associées aux attaques du mildiou ont atteint 46%. Des analyses économiques indiquent que quatre traitements au Ridomil plus"sont nécessaires dans un bon programme de protection de la morelle noire contre le mildiou. Ce régime de traitement a poduit des augmentations en revenu net de USS 694 à 8.467 ha-1, selon la variété utilisée et la période d'essai. Des résultats indiquent que le mildiou peut baisser le rendement de la morelle noire et par conséquent le bénéfice net des planteurs de la morelle noire si les actions appropriées ne sont pas menées pour rayer les effets néfastes de cette maladie. En outre, l'utilisation des variétés résistantes ou des traitements foliaires au Ridomil plus" peut etre incorporée dans des programmes de lutte intégrée contre le mildiou de la morelle noire. Mots Clés: Gestion intégrée, Phytophthora infestans, Solanum scabrum, perte de rendement (Af Crop Sci J 2003 Vol 11 No 3 pp163-170

Near--K-edge double and triple detachment of the F- negative ion: observation of direct two-electron ejection by a single photon

Double and triple detachment of the F-(1s2 2s2 2p6) negative ion by a single photon have been investigated in the photon energy range 660 to 1000 eV. The experimental data provide unambiguous evidence for the dominant role of direct photo-double-detachment with a subsequent single-Auger process in the reaction channel leading to F2+ product ions. Absolute cross sections were determined for the direct removal of a (1s+2p) pair of electrons from F- by the absorption of a single photon

Translating the Concept of Goal Setting into Practice -- What 'Else' does it Require than a Goal Setting Tool?

This conceptual paper reviews the current status of goal setting in the area of technology enhanced learning and education. Besides a brief literature review, three current projects on goal setting are discussed. The paper shows that the main barriers for goal setting applications in education are not related to the technology, the available data or analytical methods, but rather the human factor. The most important bottlenecks are the lack of students goal setting skills and abilities, and the current curriculum design, which, especially in the observed higher education institutions, provides little support for goal setting interventions.Comment: This paper has been accepted to be published in the proceedings of CSEDU 2020 by SciTePres