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  • 1
    Electronic Resource
    Electronic Resource
    Gas chromatographic separation of isomeric dienestrol diacetates and analyses of industrial products
    Amsterdam : Elsevier
    Journal of Chromatography A 42 (1969), S. 452-456 
    Details
    ISSN: 0021-9673
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/S0021-9673(01)80653-1
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Purity evaluation of dipyridamole by high-performance liquid chromatography
    Amsterdam : Elsevier
    Journal of Chromatography A 280 (1983), S. 181-187 
    Details
    ISSN: 0021-9673
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/S0021-9673(00)91557-7
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    HPLC determination of papaveraldine and papaverinol in papaverine injection
    Amsterdam : Elsevier
    Journal of Pharmaceutical and Biomedical Analysis 5 (1987), S. 493-499 
    Details
    ISSN: 0731-7085
    Keywords: HPLC. ; Papaverine injection ; papaveraldine ; papaverinol
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0731-7085(87)80058-4
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  • 4
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    Hot and dense water in the inner 25 au of SVS13-A (2016)
    Oxford University Press
    Details
    Publication Date: 2016-07-22
    Description: In the context of the ASAI (Astrochemical Surveys At IRAM) project, we carried out an unbiased spectral survey in the millimetre window towards the well known low-mass Class I source SVS13-A. The high sensitivity reached (3–12 mK) allowed us to detect at least six HDO broad (full width at half-maximum ~4–5 km s –1 ) emission lines with upper level energies up to E u = 837 K. A non-local thermodynamic equilibrium Large Velocity Gradient (LVG) analysis implies the presence of very hot (150–260 K) and dense (≥3  x  10 7  cm –3 ) gas inside a small radius (~25 au) around the star, supporting, for the first time, the occurrence of a hot corino around a Class I protostar. The temperature is higher than expected for water molecules are sublimated from the icy dust mantles (~100 K). Although we cannot exclude we are observing the effects of shocks and/or winds at such small scales, this could imply that the observed HDO emission is tracing the water abundance jump expected at temperatures ~220–250 K, when the activation barrier of the gas phase reactions leading to the formation of water can be overcome. We derive X ( HDO ) ~ 3  x  10 –6 , and a H 2 O deuteration ≥1.5  x  10 –2 , suggesting that water deuteration does not decrease as the protostar evolves from the Class 0 to the Class I stage.
    Print ISSN: 1745-3925
    Electronic ISSN: 1745-3933
    Topics: Physics
    Published by Oxford University Press
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  • 5
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    Widespread deuteration across the IRDC G035.39-00.33 (2016)
    Oxford University Press
    Details
    Publication Date: 2016-03-23
    Description: Infrared Dark Clouds (IRDCs) are cold, dense regions that are usually found within Giant Molecular Clouds. Ongoing star formation within IRDCs is typically still deeply embedded within the surrounding molecular gas. Characterizing the properties of relatively quiescent IRDCs may therefore help us to understand the earliest phases of the star formation process. Studies of local molecular clouds have revealed that deuterated species are enhanced in the earliest phases of star formation. In this paper, we test this towards IRDC G035.39–00.33. We present an 80 arcsec by 140 arcsec map of the J = 2 -〉 1 transition of N 2 D + , obtained with the Institut de Radioastronomie Millimétrique 30 m telescope telescope. We find that N 2 D + is widespread throughout G035.39–00.33. Complementary observations of N 2 H + (1 – 0) are used to estimate the deuterium fraction, D $_\mathrm{frac}^\mathrm{N_2H^+}$    N (N 2 D + )/ N (N 2 H + ). We report a mean D $_\mathrm{frac}^\mathrm{N_2H^+}$  = 0.04 ± 0.01, with a maximum of D $_\mathrm{frac}^\mathrm{N_2H^+}$  = 0.09 ± 0.02. The mean deuterium fraction is ~3 orders of magnitude greater than the interstellar [D]/[H] ratio. High angular resolution observations are required to exclude beam dilution effects of compact deuterated cores. Using chemical modelling, we find that the average observed values of D $_\mathrm{frac}^\mathrm{N_2H^+}$ are in agreement with an equilibrium deuterium fraction, given the general properties of the cloud. This implies that the IRDC is at least ~3 Myr old, which is ~8 times longer than the mean free-fall time of the observed deuterated region.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 6
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    Gravity or turbulence? - III. Evidence of pure thermal Jeans fragmentation at ~0.1 pc scale (2015)
    Oxford University Press
    Details
    Publication Date: 2015-09-13
    Description: We combine previously published interferometric and single-dish data of relatively nearby massive dense cores that are actively forming stars to test whether their ‘fragmentation level’ is controlled by turbulent or thermal support. We find no clear correlation between the fragmentation level and velocity dispersion, nor between the observed number of fragments and the number of fragments expected when the gravitationally unstable mass is calculated including various prescriptions for ‘turbulent support’. On the other hand, the best correlation is found for the case of pure thermal Jeans fragmentation, for which we infer a core formation efficiency around 13 per cent, consistent with previous works. We conclude that the dominant factor determining the fragmentation level of star-forming massive dense cores at 0.1 pc scale seems to be thermal Jeans fragmentation.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 7
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    Gravity or turbulence? - III. Evidence of pure thermal Jeans fragmentation at ~0.1 pc scale (2015)
    Oxford University Press
    Details
    Publication Date: 2015-09-27
    Description: We combine previously published interferometric and single-dish data of relatively nearby massive dense cores that are actively forming stars to test whether their ‘fragmentation level’ is controlled by turbulent or thermal support. We find no clear correlation between the fragmentation level and velocity dispersion, nor between the observed number of fragments and the number of fragments expected when the gravitationally unstable mass is calculated including various prescriptions for ‘turbulent support’. On the other hand, the best correlation is found for the case of pure thermal Jeans fragmentation, for which we infer a core formation efficiency around 13 per cent, consistent with previous works. We conclude that the dominant factor determining the fragmentation level of star-forming massive dense cores at 0.1 pc scale seems to be thermal Jeans fragmentation.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 8
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    DNC/HNC and N2D+/N2H+ ratios in high-mass star-forming cores (2014)
    Oxford University Press
    Details
    Publication Date: 2014-04-02
    Description: Chemical models predict that the deuterated fraction (the column density ratio between a molecule containing D and its counterpart containing H) of N 2 H + , D frac (N 2 H + ), high in massive pre-protostellar cores, is expected to rapidly drop by an order of magnitude after the protostar birth, while that of HNC, D frac (HNC), remains constant for much longer. We tested these predictions by deriving D frac (HNC) in 22 high-mass star-forming cores divided in three different evolutionary stages, from high-mass starless core candidates (HMSCs, eight) to high-mass protostellar objects (HMPOs, seven) to ultracompact H  ii regions (UCHIIs, seven). For all of them, D frac (N 2 H + ) was already determined through IRAM 30 m Telescope observations, which confirmed the theoretical rapid decrease of D frac (N 2 H + ) after protostar birth. Therefore, our comparative study is not affected by biases introduced by the source selection. We have found average D frac (HNC) of 0.012, 0.009 and 0.008 in HMSCs, HMPOs and UCHIIs, respectively, with no statistically significant differences among the three evolutionary groups. These findings confirm the predictions of the chemical models, and indicate that large values of D frac (N 2 H + ) are more suitable than large values of D frac (HNC) to identify cores on the verge of forming high-mass stars, likewise what was found in the low-mass regime.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 9
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    The dynamical properties of dense filaments in the infrared dark cloud G035.39-00.33 (2014)
    Oxford University Press
    Details
    Publication Date: 2014-04-14
    Description: Infrared dark clouds (IRDCs) are unique laboratories to study the initial conditions of high-mass star and star cluster formation. We present high-sensitivity and high-angular-resolution Institut de Radioastronomie Millimétrique (IRAM) Plateau de Bure Interferometer observations of N 2 H + (1–0) towards IRDC G035.39–00.33. It is found that G035.39–00.33 is a highly complex environment, consisting of several mildly supersonic filaments ($\sigma _{\rm NT}/c_{{\rm s}}$ ~ 1.5), separated in velocity by 〈1 km s –1 . Where multiple spectral components are evident, moment analysis overestimates the non-thermal contribution to the line-width by a factor of ~2. Large-scale velocity gradients evident in previous single-dish maps may be explained by the presence of substructure now evident in the interferometric maps. Whilst global velocity gradients are small (〈0.7 km s –1  pc –1 ), there is evidence for dynamic processes on local scales (~1.5–2.5 km s –1  pc –1 ). Systematic trends in velocity gradient are observed towards several continuum peaks. This suggests that the kinematics are influenced by dense (and in some cases, starless ) cores. These trends are interpreted as either infalling material, with accretion rates ~(7 ± 4)  x 10 –5  M  yr –1 , or expanding shells with momentum ~24 ± 12 M  km s –1 . These observations highlight the importance of high-sensitivity and high-spectral-resolution data in disentangling the complex kinematic and physical structure of massive star-forming regions.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 10
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    A high-resolution study of complex organic molecules in hot cores (2014)
    Oxford University Press
    Details
    Publication Date: 2014-08-09
    Description: We present the results of a line identification analysis using data from the IRAM Plateau de Bure Plateau de Bure Interferometer, focusing on six massive star-forming hot cores: G31.41+0.31, G29.96–0.02, G19.61–0.23, G10.62–0.38, G24.78+0.08A1 and G24.78+0.08A2. We identify several transitions of vibrationally excited methyl formate (HCOOCH 3 ) for the first time in these objects as well as transitions of other complex molecules, including ethyl cyanide (C 2 H 5 CN), and isocyanic acid (HNCO). We also postulate a detection of one transition of glycolaldehyde (CH 2 (OH)CHO) in two new hot cores. We find G29.96–0.02, G19.61–0.23, G24.78+0.08A1 and G24.78+0.08A2 to be chemically very similar. G31.41+0.31, however, is chemically different: it manifests a larger chemical inventory and has significantly larger column densities. We suggest that it may represent a different evolutionary stage to the other hot cores in the sample, or it may surround a star with a higher mass. We derive column densities for methyl formate in G31.41+0.31, using the rotation diagram method, of 4 10 17  cm –2 and a T rot of ~170 K. For G29.96–0.02, G24.78+0.08A1 and G24.78+0.08A2, glycolaldehyde, methyl formate and methyl cyanide, all seem to trace the same material and peak at roughly the same position towards the dust emission peak. For G31.41+0.31, however, glycolaldehyde shows a different distribution to methyl formate and methyl cyanide and seems to trace the densest, most compact inner part of hot cores.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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