338 research outputs found

    Taxonomic Revision of the Obligate Plant-Ants of the Genus Crematogaster Lund (Hymenoptera, Formicidae, Myrmicinae), Associated with Macaranga Thouars (Euphorbiaceae) on Borneo and the Malay Peninsula

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    The taxonomy and natural history of ants of the genus Crematogaster Lund, 1831 (Crematogaster borneensis-group of the former subgenus Decacrema) obligately associated with myrmecophytic host-plants of the euphorb genus Macaranga are reviewed. Within this group of ants Crematogaster borneensis André, 1896 (with five subspecies and four varieties), Crematogaster captiosa Forel, 1910 as well as Crematogaster decamera Forel, 1910 have previously been described from SE Asia. Here we synonymise C. borneensis subsp. capax Forel, 1911, C. borneensis subsp. hosei Forel, 1911, C. borneensis subsp. sembilana Forel, 1911, and C. borneensis var. macarangae Viehmeyer, 1916 with C. borneensis André, 1896. Crematogaster borneensis var. harpyia Forel, 1911, C. borneensis var. insulsa Forel, 1911, C. borneensis subsp. symbia Forel, 1911, and C. borneensis subsp. novem Forel, 1911 are synonymised with C. captiosa Forel, 1910. In addition we describe five new species: C. claudiae sp. nov., C. hullettii sp. nov., C. linsenmairi sp. nov., C. maryatii sp. nov., and C. roslihashimi sp. nov.. Seven of these eight species are placed into two informal species subgroups based on queen morphology, life-history characters and a formerly published molecular phylogeny. Keys are provided for the identification of queens and workers, as well as natural history information on the eight ant species. The morphology of these Macaranga-associated Crematogaster (formerly Decacrema) species is compared to the only other three species described for this former subgenus in SE Asia, i.e. C. angulosa André, 1896, C. biformis André, 1892 and C. cephalotes Smith, 1857

    „Unternehmerische Kultur” an Universitäten: Voraussetzungen für erfolgreiche Kooperationen mit Unternehmen in der Weiterbildung?

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    Kooperationen zwischen Universitäten und Unternehmen habenin den letzten Jahren zunehmend an Bedeutung gewonnen,zeigen aber bei der Umsetzung erhebliche Schwierigkeiten.In dem folgenden Beitrag wird die These aufgestellt, dassdies insbesondere mit den hohen Transaktionskosten, dieaufgrund der sehr unterschiedlichen Organisationskulturenund dem damit verbundenen fehlendem Systemvertrauen entstehen,zu begründen ist. Auf Grundlage dieser Überlegungenwird der Frage nachgegangen, ob ähnliche Kulturen aufbeiden Seiten die Transaktionskosten verringern können bzw.ob es einer unternehmerischen Kultur in Hochschulen bedarf,um ein kooperationsförderndes Umfeld zu schaffen

    Assessment of Ground-Based Microwave Radiometer Calibration to Enable Investigation of Gas Absorption Models

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    Ground-based microwave radiometers are becoming more and more common for remotely sensing the atmospheric temperature and humidity profile, as well as path integrated cloud liquid water content. Several studies have been published, which compare radiosonde profiles with temperature profiles derived from microwave radiometer measurements and find biases of up to 1 K. The retrieved temperature profile is based on radiometric measurements and radiative transfer calculations. Once the accuracy of radiometer measurements is known, these can be used to validate existing gas absorption models. As the absolute accuracy of microwave radiometer measurements is determined by the quality of the calibration, this work investigates the uncertainty of two calibration techniques, which are commonly used with microwave radiometers. Namely, these are the liquid nitrogen calibration and the tipping curve calibration (Han and Westwater, 2000). Both methods are known to have open issues concerning systematic offsets and calibration repeatability. In this regard, this work focuses on the error assessment for the absolute calibration of the network suitable microwave radiometer HATPRO-G2 (Humidity And Temperature PROfiler - Generation 2), which makes up a significant part of the worldwide available systems (Rose et al., 2005). In order to capture dry high altitude conditions on the one side and mid-latitude, close to sea level conditions on the other side, the analysis is based on two deployments. Between August and October 2009, HATPRO-G2 was part of the Radiative Heating of Underexplored Bands Campaign - Part 2 (RHUBC-II) in Northern Chile (5320 m above mean sea level) conducted within the Atmospheric Radiation Measurement (ARM) program. Since 2010, it is part of the JOYCE (Jülich ObservatorY for Cloud Evolution) site located in Germany 92 m above mean sea level. For each of the deployments, a detailed error propagation for both techniques is performed. The uncertainty range of brightness temperature Tb measurements based on a single liquid nitrogen calibration is mainly caused by a reflective component from the liquid nitrogen surface of the cold calibration target. The overall calibration uncertainty is assessed for typical Tb values measured at each deployment. For RHUBC-II, the maximum uncertainty of TbT_b has been determined to +-1.6 K in the K-band and to +-1.0 K in the V-band. For JOYCE, the maximum uncertainty is assessed to be +-1.5 K in the K-band and +-0.6 K in the V-band. When a standing wave phenomena at the cold calibration point is eliminated by averaging several calibrations, the uncertainty in the K-band can be reduced to +-0.8 K for both deployments. In the V-band, the uncertainties are reduced to values less or equal +-0.7 K for both deployments. Furthermore, the analyses of the liquid nitrogen calibration has revealed, that the pressure dependent boiling point correction for liquid nitrogen, originally used by HATPRO-G2, is only exact for standard pressure conditions. Therefore, the boiling point correction has been modified and is now valid for all altitudes. At the low pressure conditions of RHUBC-II (530 hPa), the improved boiling point correction shifts the cold target temperature compared to the previously used formulation by more than 1 K. HATPRO-G2 has seven channels in the K-band and seven channels in the V-band. At standard pressure conditions, only the K-band channels are transparent enough to be calibrated by the tipping curve calibration. However, at 530 hPa, the technique can be applied to two low opacity channels in the V-band as well. This offers the unique opportunity of an independent validation of the liquid nitrogen calibration in the V-band. The analysis shows, that the uncertainty in the tipping curve calibration is mainly due to atmospheric inhomogeneities. For RHUBC-II, the total uncertainty is assessed to be +-0.1 K to +-0.2 K in the K-band and +-0.6 K and +-0.7 K for the two V-band channels at 51 GHZ and 52 GHz. For the low altitude deployment at JOYCE, the total uncertainties for K-band channels are +-0.2 K to +-0.6 K. Finally, the well-characterized radiometer measurements are used to investigate current absorption models. The profiles of temperature, humidity, and pressure from 62 clear sky radiosondes are used for Tb simulations at zenith and compared to HATPRO-G2 measurements. Biases, outside the uncertainty range of the calibration can be ascribed to errors within the gas absorption coefficients. It is found that the results of the Atmospheric Model (AM)(Paine, 2012), which uses the most recent oxygen absorption parameters (Tretyakov et al., 2005, Makarov et al., 2011), are closest to RHUBC-II measurements

    Finanzierung wissenschaftlicher Weiterbildung. Herausforderungen und Möglichkeiten bei der Implementierung und Umsetzung von weiterbildenden Angeboten an Hochschulen Thematischer Bericht der wissenschaftlichen Begleitung des Bundes-Länder-Wettbewerbs "Aufstieg durch Bildung: offene Hochschulen".

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    Die Finanzierung wissenschaftlicher Weiterbildung stellt aufgrund der besonderen Stellung der Weiterbildung an Hochschulen die damit befassten Akteure vor zentrale Herausforderungen. Deutlich zeigt sich hier der Widerspruch zwischen der Forderung Weiterbildung als Kernaufgabe an den Hochschulen zu etablieren und der gesonderten Finanzierungsmodelle, die aufgrund der notwendigen Kostendeckung über Gebühren entstehen. Die damit einhergehenden Herausforderungen werden in dem Thematischen Bericht auf Ebene der a) Trennungsrechnung, b) Vollkostenrechnung, c) Gebühren- und Entgeltberechnung und d) der Lehrendenvergütung skizziert, Umsetzungsmöglichkeiten dargelegt sowie Bundesländer übergreifende Lösungsansätze entwickelt. (DIPF/Orig.

    Investigation of ground-based microwave radiometer calibration techniques at 530 hPa

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    Ground-based microwave radiometers (MWR) are becoming more and more common for remotely sensing the atmospheric temperature and humidity profile as well as path-integrated cloud liquid water content. The calibration accuracy of the state-of-the-art MWR HATPRO-G2 (Humidity And Temperature Profiler – Generation 2) was investigated during the second phase of the Radiative Heating in Underexplored Bands Campaign (RHUBC-II) in northern Chile (5320 m above mean sea level, 530 hPa) conducted by the Atmospheric Radiation Measurement (ARM) program conducted between August and October 2009. This study assesses the quality of the two frequently used liquid nitrogen and tipping curve calibrations by performing a detailed error propagation study, which exploits the unique atmospheric conditions of RHUBC-II. Both methods are known to have open issues concerning systematic offsets and calibration repeatability. For the tipping curve calibration an uncertainty of ±0.1 to ±0.2 K (K-band) and ±0.6 to ±0.7 K (V-band) is found. The uncertainty in the tipping curve calibration is mainly due to atmospheric inhomogeneities and the assumed air mass correction for the Earth curvature. For the liquid nitrogen calibration the estimated uncertainty of ±0.3 to ±1.6 K is dominated by the uncertainty of the reflectivity of the liquid nitrogen target. A direct comparison between the two calibration techniques shows that for six of the nine channels that can be calibrated with both methods, they agree within the assessed uncertainties. For the other three channels the unexplained discrepancy is below 0.5 K. Systematic offsets, which may cause the disagreement of both methods within their estimated uncertainties, are discussed

    INTEGRATION OF SCALE INSECTS (HEMIPTERA: COCCIDAE) IN THE SOUTH-EAST ASIAN ANT-PLANT (CREMATOGASTER (FORMICIDAE)- MACARANGA (EUPHORBIACEAE)) SYSTEM.

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    INTEGRATION OF SCALE INSECTS (HEMIPTERA: COCCIDAE) IN THE SOUTH-EAST ASIAN ANT-PLANT (CREMATOGASTER (FORMICIDAE)-MACARANGA (EUPHORBIACEAE)) SYSTEM. The coccid colonisers of myrmecophytic Macaranga were tested for their trophic integration into the mutualistic Crematogaster-Macaranga ant-plant system. Honeydew secretion by these mostly endophytic scale insects was observed in Coccus caviramicolus Morrison, C. penangensis Morrison, C. secretus Morrison, C. tumuliferus Morrison, C. tumuliferus var. C.84 and in two other Macaranga coccid species. However, the use of coccids as protein-rich food by ants under normal and starvation conditions was not observed. Key words: trophobiosis, ant nutrition, Myzolecaniinae, survival, dumping areas, C. macarangae, food-bodies, Pseudococcidae, Malaysia, Macaranga bancana, M. hypoleuca, M. hullettii, M. winkleri, M. triloba

    Performance Characterization of ESA's Tropospheric Delay Calibration System for Advanced Radio Science Experiments

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    Media propagation noises are amongst the main error sources of radiometric observables for deep space missions, with fluctuations of the tropospheric excess path length representing a relevant contributor to the Doppler noise budget. Microwave radiometers currently represent the most accurate instruments for the estimation of the tropospheric delay and delay rate along a slant direction. A prototype of a tropospheric delay calibration system (TDCS), using a 14 channel Ka/V band microwave radiometer, has been developed under a European Space Agency contract and installed at the deep space ground station in Malargüe, Argentina, in February 2019. After its commissioning, the TDCS has been involved in an extensive testbed campaign by recording a total of 44 tracking passes of the Gaia spacecraft, which were used to perform an orbit determination analysis. This work presents the first statistical characterization of the end-to-end performance of the TDCS prototype in an operational scenario. The results show that using TDCS-based calibrations instead of the standard GNSS-based calibrations leads to a significant reduction of the residual Doppler noise and instability

    Phylogeography of three closely related myrmecophytic pioneer tree species in SE Asia: implications for species delimitation

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    Members of the Euphorbiaceae are ecologically important elements of Southeast Asian forests. Species of the pioneer tree genus Macaranga, which is also known for its association with ants, are often abundant in disturbed areas. Phylogenetic studies suggested a recent radiation of section Pachystemon which comprises the majority of obligate myrmecophytes within Macaranga. In the present study, we analyzed the genetic structure of three closely related species of this section (M. constricta, M. griffithiana, and M. motleyana) with the aim of resolving their controversial taxonomy and historical biogeography. Chloroplast DNA haplotypes proved to be species-specific and showed a strong phylogeographic pattern. Nuclear microsatellite data supported the taxonomic distinctness of M. griffithiana and M. motleyana, but gave ambiguous results for M. constricta. Genetic differentiation was stronger each within M. griffithiana and M. motleyana than between M. constricta and M. griffithiana, highlighting problems of defining species boundaries. We found no indication for introgression or hybridization events. The high intraspecific morphological variation of the Bornean endemic M. motleyana was partly reflected by similar patterns of genetic variation. The pronounced genetic structure indicates a comparatively long diversification for this species. In contrast, the weak genetic differentiation within M. griffithiana, as well as the widespread distribution of its most common chloroplast haplotype from peninsular Malaysia up to Indochina, indicates a recent expansion in this area. Despite their morphological similarity and close relatedness, all species possess their own specific ant-partners with a corresponding distribution pattern
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