Stephan Schlemmer

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a r t i c l e i n f o a b s t r a c t The Virtual Atomic and Molecular Data Centre (VAMDC, http://www.vamdc.eu) is a European Union funded collaboration between groups involved in the generation, evaluation, and use of atomic and molecular data. VAMDC aims to build a secure, documented, flexible and interoperable e-science environment-based interface to(More)
Although the mechanisms of resistance to methotrexate (MTX) are known in experimental tumors made resistant to this drug, little information is available regarding acquired resistance to MTX in patients. A competitive displacement assay using the fluorescent lysine analogue of MTX, N-(4-amino-4-deoxy-N10-methylpteroyl)-N(More)
Context. The high degree of deuteration observed in some prestellar cores depends on the ortho-to-para H 2 ratio through the H + 3 fractionation. Aims. We want to constrain the ortho/para H 2 ratio across the L183 prestellar core. This is mandatory to correctly describe the deuter-ation amplification phenomenon in depleted cores such as L183 and to relate(More)
The Virtual Atomic and Molecular Data Centre (VAMDC, http://www.vamdc.eu/) is a European-Union-funded collaboration between groups involved in the generation, evaluation, and use of atomic and molecular data. VAMDC aims to build a reliable, open, flexible and interoperable e-science interface to existing atomic and molecular data. The project will cover(More)
Recent observations of H 2 and H + 3 in diffuse interstellar sightlines revealed a difference in the nuclear spin excitation temperatures of the two species. This discrepancy comes as a surprise, as H + 3 and H 2 should undergo frequent thermalizing collisions in molecular clouds. Non-thermal behavior of the fundamental H + 3 /H 2 collision system at low(More)
We present a novel chemical database for gas-phase astrochemistry. Named the KInetic Database for Astrochemistry (KIDA), this database consists of gas-phase reactions with rate coefficients and uncertainties that will be vetted to the greatest extent possible. Submissions of measured and calculated rate coefficients are welcome, and will be studied by(More)
The Virtual Atomic and Molecular Data Centre (VAMDC, http://www. vamdc.eu/) is a consortium between groups involved in the generation, evaluation, and use of atomic and molecular data, funded by the European Union. VAMDC aims to build a reliable, open, flexible and interoperable e-science interface to existing atomic and molecular data. The project will(More)
At the high densities and low temperatures found in star forming regions, all molecules other than H 2 should stick on dust grains on timescales shorter than the cloud lifetimes. Yet these clouds are detected in the millimeter lines of gaseous CO. At these temperatures, thermal desorption is negligible and hence a non-thermal desorption mechanism is(More)
We present laboratory data on pure, layered and mixed CO and O2 ices relevant for understanding the absence of gaseous O2 in space. Experiments have been performed on interstellar ice analogues under ultra high vacuum conditions by molecular deposition at 14 K on a gold surface. A combination of reflection absorption infrared spectroscopy (RAIRS) and(More)
Millimeter observations of pre-and protostellar cores show that the abundances of the gas-phase tracer molecules , C 18 O and N 2 H ϩ , anticorrelate with each other and often exhibit " holes " where the density is greatest. These results are reasonably reproduced by astrochemical models, provided that the ratio between the binding energies of N 2 and CO, ,(More)