JCMmode: An Adaptive Finite Element Solver for the Computation of Leaky Modes

We present our simulation tool JCMmode for calculating propagating modes of an optical waveguide. As ansatz functions we use higher order, vectorial elements (Nedelec elements, edge elements). Further we construct transparent boundary conditions to deal with leaky modes even for problems with inhomogeneous exterior domains as for integrated hollow core Arrow waveguides. We have implemented an error estimator which steers the adaptive mesh refinement. This allows the precise computation of singularities near the metal's corner of a Plasmon-Polariton waveguide even for irregular shaped metal films on a standard personal computer.Comment: 11 page

Mid-infrared observations of the SGR 1900+14 error box

We report on mid-infrared observations of the compact stellar cluster located in the proximity of SGR 1900+14, and the radio/X-ray position of this soft-gamma repeater. Observations were performed in May and June of 2001 when the bursting source was in an active state. At the known radio and X-ray position of the SGR we did not detect transient mid-IR activity, although the observations were performed only hours before and after an outburst in the high-energy band.Comment: 4 pages, 3 figures, to appear in "Gamma-Ray Burst and Afterglow Astronomy 2001", Woods Hole; 5-9 Nov, 200

In Situ Diffuse Reflectance IR Spectroscopic Investigation of n-Butane Isomerization on Promoted Sulfated Zirconia Catalysts

Introduction Sulfated zirconia (SZ) is an attractive catalyst for low temperature butane isomerization [1]. Its activity can be improved by 1–2 orders of magnitude through addition of promoters such as iron or manganese in cationic form [2,3]. The state of these promoters has been characterized, and depending on the method of preparation, a major fraction is found to form a solid solution with zirconia [4]. It has been proposed that promoters facilitate reaction initiation via oxidative dehydrogenation to butenes, which may be converted into the reaction carriers, viz. carbenium ions. Only indirect evidence such as better activity after activation in oxidizing than in inert atmosphere has been presented [5]. Reaction profiles recorded under moderate reaction conditions (e.g. 323 K, 1 kPa n-butane) show an induction period and zero conversion in the extrapolation to zero time on stream. Either the catalyst becomes active only in the feed, or intermediates accumulate on the surface. We have focused on manganese as a promoter and have used in situ diffuse reflectance IR spectroscopy (DRIFTS) to reveal the effects of activation or regeneration in inert gas or O2, and to monitor the events during the induction period. References 1. Hino, M., Arata, K., J. Am. Chem. Soc. 101, 6439 (1979). 2. Hsu, C.-Y., Heimbuch, C.R., Armes, C.T., Gates, B.C., Chem. Commun. 1645 (1992). 3. Lange, F.C., Cheung, T.-K., Gates, B.C., Catal. Lett. 41, 95 (1996). 4. Jentoft, F.C., Hahn, A., Kröhnert, J., Lorenz, G., Jentoft, R.E., Ressler, T., Wild, U., Schlögl, R., J. Catal. 224, 124 (2004). 5. Wan, K.T., Khouw, C.B., Davis, M.E., J. Catal. 158, 311 (1996)

On the Origin of the Dark Gamma-Ray Bursts

The origin of dark bursts - i.e. that have no observed afterglows in X-ray, optical/NIR and radio ranges - is unclear yet. Different possibilities - instrumental biases, very high redshifts, extinction in the host galaxies - are discussed and shown to be important. On the other hand, the dark bursts should not form a new subgroup of long gamma-ray bursts themselves.Comment: published in Nuovo Ciment

The Balance Between Reactivity and Stability of Modified Oxide Surfaces Illustrated by the Behavior of Sulfated Zirconia Catalysts

The stability of a series of sulfated zirconia catalysts, promoted with up to 2 wt% iron or manganese, in their calcined state was investigated. Phase composition, nature of surface sulfate species, degree of hydroxylation, and butane isomerization activity changed during aging over months in various atmospheres and during milling. The metastability of small oxide particles is discussed, including literature data on alumina, titania and other oxides. Catalytically active fractions of a material easily transition into more stable, less active forms

The environment of the SN-less GRB 111005A at z = 0.0133

The collapsar model has proved highly successful in explaining the properties of long gamma-ray bursts (GRBs), with the most direct confirmation being the detection of a supernova (SN) coincident with the majority of nearby long GRBs. Within this model, a long GRB is produced by the core-collapse of a metal-poor, rapidly rotating, massive star. The detection of some long GRBs in metal-rich environments, and more fundamentally the three examples of long GRBs (GRB 060505, GRB 060614 and GRB 111005A) with no coincident SN detection down to very deep limits is in strong contention with theoretical expectations. In this paper we present MUSE observations of the host galaxy of GRB 111005A, which is the most recent and compelling example yet of a SN-less, long GRB. At z=0.01326, GRB 111005A is the third closest GRB ever detected, and second closest long duration GRB, enabling the nearby environment to be studied at a resolution of 270 pc. From the analysis of the MUSE data cube, we find GRB 111005A to have occurred within a metal-rich environment with little signs of ongoing star formation. Spectral analysis at the position of the GRB indicates the presence of an old stellar population (tau > 10 Myr), which limits the mass of the GRB progenitor to M_ZAMS<15 Msolar, in direct conflict with the collapsar model. Our deep limits on the presence of any SN emission combined with the environmental conditions at the position of GRB 111005A necessitate the exploration of a novel long GRB formation mechanism that is unrelated to massive stars.Comment: Now accepted by A&A. Manuscript replaced to match accepted version. Some additional discussion added, and velocity map of the host galaxy now include