2,441 research outputs found
How FAIR can you get? Image Retrieval as a Use Case to calculate FAIR Metrics
A large number of services for research data management strive to adhere to
the FAIR guiding principles for scientific data management and stewardship. To
evaluate these services and to indicate possible improvements, use-case-centric
metrics are needed as an addendum to existing metric frameworks. The retrieval
of spatially and temporally annotated images can exemplify such a use case. The
prototypical implementation indicates that currently no research data
repository achieves the full score. Suggestions on how to increase the score
include automatic annotation based on the metadata inside the image file and
support for content negotiation to retrieve the images. These and other
insights can lead to an improvement of data integration workflows, resulting in
a better and more FAIR approach to manage research data.Comment: This is a preprint for a paper accepted for the 2018 IEEE conferenc
Non-volatile gated variable resistor based on doped La_{2}CuO_{4} and SrTiO_{3} heterostructures
Gated variable resistors were manufactured by depositing epitaxial
heterostructures of doped La_{2}CuO_{4} and SrTiO_{3} layers. Their conductance
change as function of write current I and write time t followed a simple
empirical law of the form {\Delta}G/G = CI^A t^B. This behavior is in agreement
with ionic transport that accelerates exponentially with electrical field
strength.Comment: Communicatio
The opilionid Amilenus aurantiacus from caves in Rhineland-Palatinate and Saarland/Germany (Arachnida: Opiliones: Phalangiidae)
Amilenus aurantiacus ist der in Rheinland-Pfalz/Saarland am häufigsten vorkommende Weberknecht in Höhlen und künstlichen Hohlraumen. Rund 1400 Objekte sind biospelaologisch (meist sporadisch) untersucht. Dabei konnte die Art in 25 Objekten nachgewiesen werden
Insulin-Like Growth Factor II (IGF-II) Is More Potent Than IGF-I in Stimulating Cortisol Secretion from Cultured Bovine Adrenocortical Cells: Interaction with the IGF-I Receptor and IGF-Binding Proteins
Although the stimulating effect of insulin-like growth factor I (IGF-I) on adrenal steroidogenesis has been well established, the role of IGF-II in the adult adrenal gland remains unknown. We, therefore, investigated the effect of recombinant human IGF-II on cortisol and cAMP synthesis from adult bovine adrenocortical cells. IGF-II, time and dose dependently, stimulated basal cortisol secretion maximally 3-fold. In combination with ACTH, IGF-II (13 nM) synergistically increased cortisol secretion from 1-fold (10(-8) M ACTH) to 28-fold of untreated control levels. In contrast, IGF-I at equimolar concentrations did not show an effect on basal cortisol secretion, and in combination with ACTH elicited a significant weaker stimulatory effect than IGF-II (22-fold increase). The synergistic effect of IGF-II on ACTH-promoted cortisol secretion was paralleled by accumulation of cAMP in the culture medium. Although both IGF receptors are present in adult bovine adrenocortical cells, the effect of IGF-II seems to be mediated through interaction with the IGF-I receptor, as [Arg54,55]IGF-II, which only binds to the IGF-I receptor, was equipotent to native IGF-II, whereas [Leu27]IGF-II, which preferentially binds to the type II IGF receptor, did not show any effect. By Western ligand blotting, four different molecular forms of IGF-binding proteins (IGFBPs) were identified in conditioned medium of bovine adrenocortical cells with apparent molecular masses of 39-44, 34, 29, and 24 kilodaltons. ACTH treatment increased the abundance of all binding proteins, on the average, 2.3-fold, except for the 29-kDa band, which was predominantly induced 6.8-fold. Additionally, [des1-3]IGF-I, a truncated IGF variant that exhibits only minimal binding to IGFBPs, was significant more potent than IGF-I and elicited the same maximum stimulatory effect on cortisol secretion as IGF-II and [des1-6]IGF-II. In conclusion, these results demonstrate that 1) IGF-II stimulates basal as well as ACTH-induced cortisol secretion from bovine adrenocortical cells more potently than IGF-I; 2) this effect is mediated through interaction of IGF-II with the IGF-I receptor; 3) bovine adrenocortical cells synthesize various IGFBPs that are induced differentially by ACTH; and 4) IGFBPs apparently play a modulatory role in IGF-induced stimulation of adrenal steroidogenesis. Therefore, bovine adult adrenocortical cells provide a useful tissue culture model in which the interactions among locally produced IGFs, IGFBPs, and the IGF-I receptor can be evaluated
Variable resistor made by repeated steps of epitaxial deposition and lithographic structuring of oxide layers by using wet chemical etchants
Variable resistors were constructed from epitaxial SrRuO3 (SRO),
La0.67Sr0.33MnO3 (LSMO) and SrTiO3 layers with perovskite crystal structure.
Each layer was patterned separately by lithographic methods. Optimized wet
chemical etchants and several polishing steps in organic solvents allowed good
epitaxy of subsequent layers, comparable to epitaxy on pristine substrates.
Periodate as the oxidizing agent for SRO and iodide with ascorbic acid as the
reducing agents for LSMO were used to attack these chemically resistant oxides.
The final devices changed their conductance in a similar manner to previously
described variable resistors that were defined with shadow masks
Ein neues Verfahren zur Messung der radialen Temperaturverteilung in inhomogenen und instationären Plasmasäulen mit erheblicher Selbstabsorption
The complete lateral distributions of emitted intensity and optical thickness of the instationary plasma column are measured simultaneously by probing the plasma with its own radiation and recording both distributions on a single high-speed spectrum. From these lateral distributions the radial distributions of the coefficients of emission and absorption are calculated and by application of Kirchhoff’s law the radial temperature distribution is determined. This new technique has been applied to an exploding wire plasma with 37 000 K on the axis. The mean deviations of three temperature distributions obtained by independent measurements at different wavelengths are less than 3 per cent
Single Cs Atoms as Collisional Probes in a large Rb Magneto-Optical Trap
We study cold inter-species collisions of Caesium and Rubidium in a strongly
imbalanced system with single and few Cs atoms. Observation of the single atom
fuorescence dynamics yields insight into light-induced loss mechanisms, while
both subsystems can remain in steady-state. This significantly simplifies the
analysis of the dynamics, as Cs-Cs collisions are effectively absent and the
majority component remains unaffected, allowing us to extract a precise value
of the Rb-Cs collision parameter. Extending our results to ground state
collisions would allow to use single neutral atoms as coherent probes for
larger quantum systems.Comment: 6 pages, 4 figure
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A comparative time-resolved CW EPR and FT EPR investigation of the addition of 2-hydroxy-2-propyl radicals to acrylate and methacrylate monomers
The addition of 2-hydroxy-2-propyl radicals to n-butyl acrylate and n-butyl methacrylate has been investigated by time-resolved continuous wave electron paramagnetic resonance (TR CW EPR) and time-resolved Fourier transform electron paramagnetic resonance (TR FT EPR). The 2-hydroxy-2-propyl radicals were generated by the photolysis of acetone in propan-2-ol (through hydrogen abstraction) and by the photolysis of a ketone 5 (through α-cleavage). The TR CW and TR FT spectra were experimentally equivalent for the addition of 2-hydroxy-2-propyl radicals to n-butyl acrylate to produce 3a. However, there are distinct differences between the TR CW and TR FT spectra for the addition of 2-hydroxy-2-propyl radicals to n-butyl methacrylate which produces the radical adduct 4a. In particular, a number of hyperfine lines clearly present in the TR CW spectra are much weaker in, or are absent from, the TR FT spectra. The differences in the TR CW and TR FT spectra are attributed to hindered rotation, which is important in the spectrum of the adduct of 2-hydroxy-2-propyl radicals to n-butyl methacrylate (4a), but not in the spectrum of the adduct of 2-hydroxy-2-propyl radicals to n-butyl acrylate (3a). The hindered rotation is shown to selectively shorten the spin–spin relaxation time, T2, for certain hyperfine lines in the spectrum of 4a, resulting in broadening or disappearance of these lines and explaining the differences between the TR CW and TR FT spectra
Investigation of Gold-Vinyl Intermediates Opens New Avenues in Gold Catalysis
The mechanism of gold(I)-catalyzed intramolecular hydroarylation of allenes was studied in detail. While monitoring the reaction by NMR, an unexpected dinuclear gold-vinyl intermediate was observed, that was proposed to contain a geminally diaurated carbon center stabilized by an aurophilic interaction. Isolation of this intermediate was achieved by inhibiting catalytic turnover with a base. Addition of suitable ligands abstracted one gold unit and yielded a monogold-vinyl complex, which was structurally confirmed by X-ray diffraction analysis. The reactivity of both intermediates was studied. To better understand the formation of digold-vinyl intermediates, a variety of arylgold(I) model complexes were synthesized. A mixture of mono- and digold-aryl complexes revealed averaged proton signals by NMR. The chemical shift of these resonances could be used to determine the percentage of monogold bound as digold, which allowed for quantification of anion and ligand effects on digold formation. In addition, it was observed that Brønsted acids affected the coordinating ability of anions through homoconjugate acid/base pairs. Trends observed in model systems were confirmed by mechanistic studies on the intramolecular hydroalkoxylation of allenes. Depending on the reaction conditions a digold or a monogold resting state was observed. Kinetic isotope effect studies and isotope labeling experiments were conducted to identify the catalytic role of digold. Data suggested that the digold intermediate operated off cycle and acted as an inactive catalyst reservoir, which seemed inhibitory for efficient catalysis. Further mechanistic studies revealed that digold formation altered kinetic data as well, which complicated the interpretation of Hammett studies and the development of rate laws. It was also found that silver and palladium intercepted gold-vinyl intermediates as well. Silver affected the mechanism of the intramolecular hydroarylation of allenes, which could explain previously observed silver effects in gold catalysis. Organogold complexes could engage in cross-coupling chemistry by transmetallating their organic group to Pd. Further studies led to a palladium-catalyzed homo-coupling of gold-aryl model complexes was observed, which was driven by a bimetallic Au(I)/Pd(0) RedOx process. Other new avenues in gold catalysis include the Lewis acid mediated activation of silver-free catalyst precursors and a new mechanistic proposal for the origin of chirality in gold-catalyzed reactions.Doctor of Philosoph
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