176 Works

Factors affecting the selectivity of the photocatalytic conversion of nitroaromatic compounds over TiO2 to valuable nitrogen-containing organic compounds

Amer Hakki, Ralf Dillert & Detlef W. Bahnemann
The photocatalytic conversion of various nitroaromatic compounds in alcohols employing four different types of TiO2 (Sachtleben Hombikat UV100 as anatase, Crystal Global R34 as rutile, Evonik-Degussa Aeroxide P25 as an anatase-rutile mixture, and home-made mesoporous anatase) has been studied. The effect of platinization of these different types of TiO2 on the reaction sequence has also been investigated. Upon irradiation of an ethanolic solution of m-nitrotoluene, as a model reaction, in the presence of the bare...

On the weak O-H⋯halogen hydrogen bond: A rotational study of CH 3CHClF⋯H2O

Gang Feng, Luca Evangelisti, Laura B. Favero, Jens-Uwe Grabow, Zhining Xia & Walther Caminati
We measured the molecular beam Fourier transform microwave spectra of six isotopologues of the 1:1 adduct of CH3CHClF with water. Water prefers to form an O-H⋯F rather than an O-H⋯Cl hydrogen bond. This is just the contrary of what was observed in the chlorofluoromethane-water adduct, where an O-H⋯Cl link was formed (W. Caminati, S. Melandri, A. Maris and P. Ottaviani, Angew. Chem., Int. Ed., 2006, 45, 2438). The water molecule is linked with an O-H⋯F...

Mesoporous silica coatings for controlled release of the antibiotic ciprofloxacin from implants

Nina Ehlert, Muhammad Badar, Anne Christel, Sven Jare Lohmeier, Tammo Luessenhop, Martin Stieve, Thomas Lenarz, Peter Paul Mueller & Peter Behrens
To generate bioactive coatings for medical implants, a novel procedure has been developed using a coating of mesoporous silica for controlled drug delivery. Plain glass slides were used as substrates. The mesoporous coatings were then loaded with the antibacterial drug ciprofloxacin. The drug release kinetics were investigated in a physiological buffered solution. The drug loading capacity of the unmodified mesoporous coatings was low but could be increased nearly ten-fold (to about 2 g cm-2 of...

Mesoporous silica films as a novel biomaterial: Applications in the middle ear

Nina Ehlert, Peter P. Mueller, Martin Stieve, Thomas Lenarz & Peter Behrens
In this tutorial review we present the process of the development of functional implants using mesoporous silica. The different steps from chemical synthesis and physicochemical characterization followed by in vitro testing in cell culture assays to clinically relevant in vivo animal studies are examined. Since the end of the 1990s, mesoporous silicas have been considered as biomaterials. Numerous investigations have demonstrated their non-toxic and biocompatible properties. These qualities in combination with the unique properties of...

Mesoporous TiO2 nanostructures: A route to minimize Pt loading on titania photocatalysts for hydrogen production

Tarek A. Kandiel, Adel A. Ismail & Detlef W. Bahnemann
Mesostructured TiO2 nanocrystals have been prepared using Pluronic F127 as the structure-directing agent. Platinum nanoparticles at different contents (0.1-1.0 wt%) have been photochemically deposited onto the mesoporous TiO2. TEM investigation of 0.2 wt% Pt/TiO2 calcined at 450 °C reveals that the TiO2 particles are quite uniform in size and shape with the particle sizes of TiO2 and Pt being 10 and 3 nm, respectively. The photocatalytic activities of the Pt loaded TiO2 have been assessed...

PAMAM-functionalized water soluble quantum dots for cancer cell targeting

M. Akin, Rebecca Bongartz, J.G. Walter, D.O. Demirkol, F. Stahl, S. Timur & Thomas Scheper
Herein, the phase-transfer reaction of quantum dots (QDs) with amine-terminated polyamidoamine (PAMAM) dendrimers with controllable ligand molar ratios was achieved. The unique properties of PAMAM allowed us to build up structurally and electrostatically stabilized water soluble QD complexes. Synthesized conjugates were characterized in terms of fluorescence and UV-Vis profiles, hydrodynamic size, number of surface dendrimer groups, and stability. Cytotoxic effects of conjugates for MCF-7, A-549 and HEP-G2 cancer cells were assessed based on cell viability...

Optimizing dirhodium(II) tetrakiscarboxylates as chiral NMR auxiliaries

Jens T. Mattiza, Joerg G.G. Fohrer, Helmut Duddeck, Michael G. Gardiner & Ashraf Ghanem
Thirteen enantiopure paddlewheel-shaped dirhodium(II) tetrakiscarboxylate complexes have been checked for their efficiency in the dirhodium method (differentiation of enantiomers by NMR spectroscopy); six of them are new. Their diastereomeric dispersion effects were studied and compared via so-called key numbers KN. Adducts of each complex were tested with five different test ligands representing all relevant donor properties from strong (phosphane) to very weak (ether). Only one of them, the dirhodium complex with four axial (S)-N-2,3-naphthalenedicarboxyl-tert-leucinate groups...

New Forensic Insight into Carl Auer von Welsbach's 1910 Observation of Induced Radioactivity: Theoretical, Experimental and Historical Approaches

Georg Steinhauser, Roland Adunka, Dieter Hainz, Gerd Löffler & Andreas Musilek
In 1910, Carl Auer von Welsbach noted that he had made an observation of a radioactive substance inducing radioactivity to an inactive substance. From today's point of view, this could have been the first observation of neutron activation. Herein, we present new insights into our investigation of this ‘mysterious observation’ as Auer von Welsbach termed it. We believe that one of the activated objects was a platinum–iridium crucible. The dominating activation product of the crucible...

Enhanced grinding performance by means of patterned grinding wheels

Berend Denkena, Thilo Grove, Tim Göttsching, Eraldo Jannone Da Silva, Reginaldo Teixeira Coelho & Remo Filleti
In this paper, a new and innovative method for the patterning of grinding wheels is presented. The patterns are machined with a patterning tool by using fly-cutting kinematics. By changing the patterning process parameters, different pattern sizes and densities can be machined in a flexible way. Surface and cylindrical grinding experiments show that grinding with patterned grinding wheels can significantly reduce process forces, grinding burn, and grinding power. The surface roughness increases because less active...

Downstream processing of high chain length polysialic acid using membrane adsorbers and clay minerals for application in tissue engineering

Ismet Bice, Hilal Celik, Christopher Wolff, Sascha Beutel, Maria Zahid, Bernd Hitzmann, Ursula Rinas, Cornelia Kasper, Rita Gerardy-Schahn & Thomas Scheper
Polysialic acid (polySia) is a carbohydrate polymer of varying chain length. It is a promising scaffold material for tissue engineering. In this work, high chain length polySia was produced by an Escherichia coli K1 strain in a 10-L bioreactor in batch and fed-batch mode, respectively. A new downstream process for polySia is presented, based on membrane adsorber technology and use of inorganic anion exchanger. These methods enable the replacement of precipitation steps, such as acetone,...

Multi-Provider Service Chain Embedding With Nestor

David Dietrich, Ahmed Abujoda, Amr Rizk & Panagiotis Papadimitriou
Network function (NF) virtualization decouples NFs from the underlying middlebox hardware and promotes their deployment on virtualized network infrastructures. This essentially paves the way for the migration of NFs into clouds (i.e., NF-as-a-Service), achieving a drastic reduction of middlebox investment and operational costs for enterprises. In this context, service chains (expressing middlebox policies in the enterprise network) should be mapped onto datacenter networks, ensuring correctness, resource efficiency, as well as compliance with the provider's policy....

Instantons on sine-cones over Sasakian manifolds

S. Bunk, T.A. Ivanova, Olaf Lechtenfeld, Alexander D. Popov & M. Sperling
We investigate instantons on sine-cones over Sasaki-Einstein and 3-Sasakian manifolds. It is shown that these conical Einstein manifolds are Kähler with torsion (KT) manifolds admitting Hermitian connections with totally antisymmetric torsion. Furthermore, a deformation of the metric on the sine-cone over 3-Sasakian manifolds allows one to introduce a hyper-Kähler with torsion (HKT) structure. In the large-volume limit these KT and HKT spaces become Calabi-Yau and hyper-Kähler conifolds, respectively. We construct gauge connections on complex vector...

Orbifold instantons, moment maps, and Yang-Mills theory with sources

T.A. Ivanova, Olaf Lechtenfeld, Alexander D. Popov & R.J. Szabo
We revisit the problem of constructing instantons on ADE orbifolds R4/Γ and point out some subtle relations with the complex structure on the orbifold. We consider generalized instanton equations on R4/Γ which are BPS equations for the Yang-Mills equations with an external current. The relation between level sets of the moment maps in the hyper-Kähler quotient construction of the instanton moduli space and sources in the Yang-Mills equations is discussed. We describe two types of...

On the identification of weather avoidance routes in the terminal maneuvering area of Hong Kong International Airport

Manuela Sauer, Thomas Hauf, Ludmila Sakiew, Pak Wai Chan, Shuk-Mei Tse & Patrick Hupe
The safety and efficiency of air traffic are significantly affected by adverse weather. This holds especially in terminal maneuvering areas (TMA) where, in addition to the impact of weather itself, potential weather avoidance routes are strongly restricted by air traffic regulations. A weather avoidance model DIVMET has been developed which proposes a route through a field of developing thunderstorms. Air traffic control regulations have not been included in it at this stage. DIVMET was applied...

On the justification of the quasistationary approximation of several parabolic moving boundary problems - Part II

Friedrich Lippoth
We rigorously justify the quasistationary approximations of two moving boundary problems. We work out a systematic procedure to derive a priori estimates that allow to pass to the singular limit. The problems under our consideration are a one-phase osmosis model and the one-phase Stefan problem with Gibbs-Thomson correction and kinetic undercooling. © European Mathematical Society 2016.

Pragmatism, Ontology, and Philosophy of the Social Sciences in Practice

Simon Lohse
In this article, I will discuss two prominent views on the relevance and irrelevance of ontological investigations for the social sciences, namely, ontological foundationalism and anti-ontological pragmatism. I will argue that both views are unsatisfactory. The subsequent part of the article will introduce an alternative role for ontological projects in the philosophy of the social sciences that fares better in this respect by paying attention to the ontological assumptions of actual social scientific theories, models,...

Diversity of algae and lichens in biological soil crusts of Ardley and King George islands, Antarctica

Nadine Borchhardt, Ulf Schiefelbein, Nelida Abarca, Jens Boy, Tatiana Mikhailyuk, Harrie J.M. Sipman & Ulf Karsten
In the present study the biodiversity of the most abundant phototrophic organisms forming biological soil crust communities were determined, which included green algae, diatoms, yellow-green algae and lichens in samples collected on Ardley and King George islands, Maritime Antarctic. The species were identified by their morphology using light microscopy, and for lichen identification thin layer chromatography as also used to separate specific secondary metabolites. Several sources of information were summarized in an algae catalogue. The...

Epiphytic biomass of a tropical montane forest varies with topography

F.A. Werner, J. Homeier, M. Oesker & J. Boy
The spatial heterogeneity of tropical forest epiphytes has rarely been quantified in terms of biomass. In particular, the effect of topographic variation on epiphyte biomass is poorly known, although forests on ridges and ravines can differ drastically in stature and exposure. In an Ecuadorian lower montane forest we quantified epiphytic biomass along two gradients: (1) the twig-branch-trunk trajectory, and (2) the ridge-ravine gradient. Twenty-one trees were sampled in each of three forest types (ridge, slope,...

Executive Agencies, Ministers, and Departments: Can Policy and Management Ever be Separated?

B. Verschuere & T. Bach
The creation of executive agencies outside core departments has been a major element of administrative reforms throughout Europe during the past two decades, driven by a managerial logic, which also has been at the core of most academic works on "agencification." In this article, the authors take a different perspective by focusing on executive agencies' influence in the policy process. The authors analyze the policy influence of a large executive agency with service delivery tasks...

Lithium Diffusion in Ion-Beam Sputtered Amorphous LiAlO2

Johanna Rahn, Elena Witt, Paul Heitjans & Harald Schmidt
We investigated lithium self-diffusion in amorphous lithium aluminate (LiAlO2) layers between room temperature and 473 K. For the experiments, amorphous 6LiAlO2 (30 nm)/7LiAlO2 (1200 nm) isotope hetero-structures were deposited by ion-beam sputtering on sapphire substrates. Diffusion profiles were analysed by secondary ion mass spectrometry (SIMS). The results show that the diffusivities obey the Arrhenius law with an activation enthalpy of (0.94 ± 0.02) eV. This is not much different to the activation enthalpy of 1.14 eV found for LiAlO2 single crystals by...

Impacts of salinity parameterizations on temperature simulation over and in a hypersaline lake

Lijuan Wen, Nidhi Nagabhatla, Lin Zhao, Zhaoguo Li & Shiqiang Chen
In this paper, we introduced parameterizations of the salinity effects (on heat capacity, thermal conductivity, freezing point and saturated vapor pressure) in a lake scheme integrated in the Weather Research and Forecasting model coupled with the Community Land Model (WRF-CLM). This was done to improve temperature simulation over and in a saline lake and to test the contributions of salinity effects on various water properties via sensitivity experiments. The modified lake scheme consists of the...

Meta-Synthesis of Qualitative Case Studies: An Approach to Theory Building

Christina Hoon
The purpose of this article is to provide the research design of a meta-synthesis of qualitative case studies. The meta-synthesis aims at building theory out of primary qualitative case studies that have not been planned as part of a unified multisite effect. By drawing on an understanding of research synthesis as the interpretation of qualitative evidence from a postpositivistic perspective, this article proposes eight steps of synthesizing existing qualitative case study findings to build theory....

Of 'true professionals' and 'ethical hero warriors': A gender-discourse analysis of private military and security companies

Jutta Joachim & Andrea Schneiker
Private military and security companies (PMSCs) have gained increasingly in importance over the course of the past two decades. Yet, given the intransparency of the industry and the heterogeneity of the companies that comprise it, we thus far know little about the actors involved. In this article, we offer preliminary insights into the self-representation of PMSCs, based on a gender-discourse analysis of the homepages of select companies and their main professional associations. We argue that...

Condillacs \"Essai\" - Experiment der Einbildungskraft

Anneke Meyer
Mit dem "Essai sur l'origine des connoissances humaines, ouvrage où l'on réduit à un seul principe tout ce qui concerne l'entendement" begann Etienne Bonnot de Condillac 1746 seine philosophische Karriere. Bis zu seinem Tode 1780 veröffentlichichte er regelmäßig weitere Schriften: 1749 den "Traité des systèmes", 1754 den "Traité des sensations", 1755 den "Traité des animaux" und 1775 den mehrteiligen "Cours d'etudes pour l'instruction du Prince de Parme". Seine letzte Schrift "La Langue des Calculs" erschien...

Historische und philosophische Notizen über das Kontinuum

Thomas Bedürftig & Roman Murawski
The final publication is available at Springer via http://dx.doi.org/10.1007/s00591-017-0179-2

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