449 research outputs found
Auf Sand gebaut. Die Physik feuchter Granulate
No full textSicherlich hat jeder im Urlaub schon einmal eine Sandburg gebaut. Dabei mag manch einer sich gewundert haben, dass es für die Sandburg kaum eine Rolle spielt, wie feucht der Sand ist. Diese überraschende Eigenschaft lässt sich erklären, wenn man im Detail verfolgt, wie sich die Flüssigkeit zwischen den einzelnen Sandkörnern verteilt. Dort halten Kapillarbrücken die Körner zusammen
Auf Sand gebaut. Die Physik feuchter Granulate
No full textSicherlich hat jeder im Urlaub schon einmal eine Sandburg gebaut. Dabei mag manch einer sich gewundert haben, dass es für die Sandburg kaum eine Rolle spielt, wie feucht der Sand ist. Diese überraschende Eigenschaft lässt sich erklären, wenn man im Detail verfolgt, wie sich die Flüssigkeit zwischen den einzelnen Sandkörnern verteilt. Dort halten Kapillarbrücken die Körner zusammen
Influences of Central Bouquet Alterations on the Visual Outcome in Eyes Receiving Epiretinal Membrane Surgery
No full textBackground: Previous studies have shown that epiretinal membranes (ERMs) may be associated with abnormal outer retinal anatomy. However, long-term morphological and functional results of pars plana vitrectomy (PPV) with ERM and internal limiting membrane (ILM) peeling in eyes with central bouquet (CB) alterations have not yet been investigated. Methods: In a retrospective, consecutive study all patients underwent best corrected visual acuity (BCVA) testing and spectral domain optical coherence tomography (SD-OCT) before and after a mean of 20 months (range 3–70 months) postoperatively. CB abnormalities and ERMs were classified according to Govetto’s staging systems. Results: Of the 67 eyes, 22 (34%) showed CB abnormalities at baseline. The mean BCVA increased from 0.42 at baseline to 0.20 LogMAR at final follow-up (p < 0.001). Neither ERM stage (p = 0.06) nor CB stage (p = 0.939) at baseline were significant predictors of vision improvement following surgery. Conclusions: Our results show that baseline BCVA, but not classification of CB changes and ERM at baseline, seems to be a useful predictor for functional outcomes following PPV with ERM and ILM peeling in the long-term
Surface Hydrophobicity Causes SO₂ Tolerance in Lichens
No full textBackground and Aims: The superhydrophobicity of the thallus surface in one of the most SO2-tolerant lichen species, Lecanora conizaeoides, suggests that surface hydrophobicity could be a general feature of lichen symbioses controlling their tolerance to SO2. The study described here tests this hypothesis.
Methods: Water droplets of the size of a raindrop were placed on the surface of air-dry thalli in 50 lichen species of known SO2 tolerance and contact angles were measured to quantify hydrophobicity.
Key Results: The wettability of lichen thalli ranges from strongly hydrophobic to strongly hydrophilic. SO2 tolerance of the studied lichen species increased with increasing hydrophobicity of the thallus surface. Extraction of extracellular lichen secondary metabolites with acetone reduced, but did not abolish the hydrophobicity of lichen thalli.
Conclusions: Surface hydrophobicity is the main factor controlling SO2 tolerance in lichens. It presumably originally evolved as an adaptation to wet habitats preventing the depression of net photosynthesis due to supersaturation of the thallus with water. Hydrophilicity of lichen thalli is an adaptation to dry or humid, but not directly rain-exposed habitats. The crucial role of surface hydrophobicity in SO2 also explains why many markedly SO2-tolerant species are additionally tolerant to other (chemically unrelated) toxic substances including heavy metals
Decidability of the Brinkmann problems for endomorphisms of the free group
No full textThe version of record of this article, first published in Archiv der mathematik, is available online at Publisher’s website: http://dx.doi.org/10.1007/s00013-024-02029-2Building on the work of Brinkmann and Logan, we show that both the Brinkmann problem and the Brinkmann conjugacy problem are decidable for endomorphisms of the free group Fn.The first author is funded by national funds through the FCT - Fundação para a Ciência e a Tecnologia, I.P., under the scope of the projects UIDB/00297/2020 and UIDP/00297/2020 (Center for Mathematics and Applications).
The second author acknowledges support from the Spanish Agencia Estatal de Investigación through grant PID2021-126851NB-I00 (AEI/ FEDER, UE), as well as from the Universitat Politècnica de Catalunya in the form of a “María Zambrano” scholarshipPostprint (author's final draft
Mean curvature of spacelike submanifolds in a Brinkmann spacetime
No full textSeveral geometric properties of complete spacelike submanifolds, with codimension at least two, in a Brinkmann spacetime are shown from natural assumptions involving the mean curvature vector field \mcv of the spacelike submanifold. Especially, we get sufficient conditions that assure that a spacelike submanifold is contained in a leaf of the foliation of the Brinkmann spacetime defined by the orthogonal vectors to the parallel lightlike vector field. When this vector field is the gradient of a smooth function, a characterization of arbitrary codimension spacelike submanifolds contained in a leaf of this foliation is given. In the case of plane fronted wave spacetimes, relevant examples of Brinkmann spacetimes that generalize pp-waves spacetimes, several uniqueness results for codimension two spacelike submanifolds are obtained. In particular, it is proven that any compact codimension two spacelike submanifold with \mcv=0 in a plane fronted spacetime wave must be a (totally geodesic) front of wave.The first author has been partially supported by MINECO/FEDER project MTM2015-65430-P, Fundaci\'on S\'eneca project 19901/GERM/15 and research grant 19783/FPI/15 from Fundaci\'on S\'eneca, the second and the third authors by Spanish MINECO and ERDF project MTM2016-78807-C2-1-P and Andalusian and ERDF project A-FQM-494-UGR1
Prozessgericht-Vollstreckungsgericht-Insolvenzgericht-Überlegungen zur funktionellen Zuständigkeit
No full textProzessgericht-Vollstreckungsgericht-Insolvenzgericht-Überlegungen zur funktionellen Zuständigkeit
No full textThe unbearable speed of life. How to slow down in the world rushing around us. (S. Brinkmann)
No full textAutorka recenze shrnuje obsah úspěšné knihy Nesnesitelná rychlost života dánského psychologa Svenda Brinkmanna, který kritizuje pozitivní psychologii a nabízí alternativní přístup, založený na antické stoické filozofii.The author of the review summarises the content of the successful book, The unbearable speed of life, by Danish psychologist Svend Brinkmann who criticises the positive psychology and offers an alternative approach based on the antic stoic philosophy
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