Implantation of silicon dioxide-based nanocrystalline hydroxyapatite and pure phase beta-tricalciumphosphate bone substitute granules in caprine muscle tissue does not induce new bone formation
Samuel E. Udeabor
Ines Bettina Anne Willershausen
Robert Alexander Sader
Charles James Kirkpatrick
- Background: Osteoinductive bone substitutes are defined by their ability to induce new bone formation even at heterotopic implantation sites. The present study was designed to analyze the potential osteoinductivity of two different bone substitute materials in caprine muscle tissue.
Materials and methods: One gram each of either a porous beta-tricalcium phosphate (β-TCP) or an hydroxyapatite/silicon dioxide (HA/SiO2)-based nanocrystalline bone substitute material was implanted in several muscle pouches of goats. The biomaterials were explanted at 29, 91 and 181 days after implantation. Conventional histology and special histochemical stains were performed to detect osteoblast precursor cells as well as mineralized and unmineralized bone matrix.
Results: Both materials underwent cellular degradation in which tartrate-resistant acid phosphatase (TRAP)-positive osteoclast-like cells and TRAP-negative multinucleated giant cells were involved. The ß-TCP was completely resorbed within the observation period, whereas some granules of the HA-groups were still detectable after 180 days. Neither osteoblasts, osteoblast precursor cells nor extracellular bone matrix were found within the implantation bed of any of the analyzed biomaterials at any of the observed time points.
Conclusions: This study showed that ß-TCP underwent a faster degradation than the HA-based material. The lack of osteoinductivity for both materials might be due to their granular shape, as osteoinductivity in goat muscle has been mainly attributed to cylindrical or disc-shaped bone substitute materials. This hypothesis however requires further investigation to systematically analyze various materials with comparable characteristics in the same experimental setting.
Measuring information-transfer delays
Joseph T. Lizier
- In complex networks such as gene networks, traffic systems or brain circuits it is important to understand how long it takes for the different parts of the network to effectively influence one another. In the brain, for example, axonal delays between brain areas can amount to several tens of milliseconds, adding an intrinsic component to any timing-based processing of information. Inferring neural interaction delays is thus needed to interpret the information transfer revealed by any analysis of directed interactions across brain structures. However, a robust estimation of interaction delays from neural activity faces several challenges if modeling assumptions on interaction mechanisms are wrong or cannot be made. Here, we propose a robust estimator for neuronal interaction delays rooted in an information-theoretic framework, which allows a model-free exploration of interactions. In particular, we extend transfer entropy to account for delayed source-target interactions, while crucially retaining the conditioning on the embedded target state at the immediately previous time step. We prove that this particular extension is indeed guaranteed to identify interaction delays between two coupled systems and is the only relevant option in keeping with Wiener’s principle of causality. We demonstrate the performance of our approach in detecting interaction delays on finite data by numerical simulations of stochastic and deterministic processes, as well as on local field potential recordings. We also show the ability of the extended transfer entropy to detect the presence of multiple delays, as well as feedback loops. While evaluated on neuroscience data, we expect the estimator to be useful in other fields dealing with network dynamics.
Jens Michael Breunig
- The crystal structure of the title salt, [Li(CH3CN)4][B(NCS)4], is composed of discrete cations and anions. Both the Li and B atoms show a tetrahedral coordination by four equal ligands. The acetonitrile and isothiocyanate ligands are linear. The bond angles at the B atom are close to the ideal tetrahedral value [108.92 (18)–109.94 (16)°], but the bond angles at the Li atom show larger deviations [106.15 (17)–113.70 (17)°].
CAST constraints on the axion-electron coupling
José Manuel Carmona
Juan I. Collar
Luigi Di Lella
J. A. García
Michael D. Hasinoff
Fritz Herbert Heinsius
Dieter H.H. Hoffmann
Igor Garcia Irastorza
David W. Miller
Mike J. Pivovaroff
Karl van Bibber
Joaquin D. Vieira
José A. Villar
Julia K. Vogel
- In non-hadronic axion models, which have a tree-level axion-electron interaction, the Sun produces a strong axion flux by bremsstrahlung, Compton scattering, and axiorecombination, the “BCA processes.” Based on a new calculation of this flux, including for the first time axio-recombination, we derive limits on the axion-electron Yukawa coupling gae and axion-photon interaction strength ga using the CAST phase-I data (vacuum phase). For ma <~ 10 meV/c2 we find ga gae < 8.1 × 10−23 GeV−1 at 95% CL. We stress that a next-generation axion helioscope such as the proposed IAXO could push this sensitivity into a range beyond stellar energy-loss limits and test the hypothesis that white-dwarf cooling is dominated by axion emission.
Spin modulation instabilities and phase separation dynamics in trapped two-component Bose condensates
Nicolaas Jan van Druten
- n the study of trapped two-component Bose gases, a widely used dynamical protocol is to start from the ground state of a one-component condensate and then switch half the atoms into another hyperfine state. The slightly different intra-component and inter-component interactions can then lead to highly non-trivial dynamics, especially in the density mismatch between the two components, commonly referred to as 'spin' density. We study and classify the possible subsequent dynamics, over a wide variety of parameters spanned by the trap strength and by the inter- to intra-component interaction ratio. A stability analysis suited to the trapped situation provides us with a framework to explain the various types of dynamics in different regimes.
Multiple encoding in genetic editions: the case of "Faust"
- The aim of the present paper is to show how, and to what extent, the standards of critical genetic editions as applied to Goethe's Faust can be attained within a TEI framework. It proposes and argues for the introduction of two separate transcripts: documentary and textual. Despite the apparent disadvantages of multiple encoding, this approach recommends itself for practical reasons (e.g., avoidance of overlapping hierarchies), and it conveniently reflects the idea that any written document must be considered a material object on the one hand and a medium of textual transmission on the other. In the course of the paper, some aspects and problems of chapter 11 of version 2.0.0 of TEI P5 (the definition and use of the elements <line> and <mod> and related issues) will be discussed.
Die Sehnsucht nach Transzendenz : Zu ihrer Bedeutung im Werk von Botho Strauß
- Botho Strauß hat die Frage der Sehnsucht nach Transzendenz von verschiedenen Gesichtspunkten aus immer wieder in seinem Werk behandelt. Da ist zunächst der Punkt, wie Gesellschaftstheorien und Weltbilder, denen er ursprünglich selbst gefolgt ist, diese Sehnsucht in eine falsche Richtung gelenkt und die wirkliche Rolle von Technologie unbehandelt gelassen haben. Strauß' eigene Analyse, die Überlegungen vor allem aus den Naturwissenschaften aufnimmt, vernachlässigt aber die Bedeutung schöpferischer Aktivität. Ein weiterer Gesichtspunkt ergibt sich aus Strauß' Darstellung des unglücklichen Bewusstseins des modernen Individuums und den Versuchen, dieses zu transzendieren. In einem letzten Punkt wird dann Strauß' eigener Versuch erörtert, im Kunstwerk Transzendenz zu schaffen. Der Artikel macht hier erneut auf die unterbelichtete Rolle schöpferischer Aktivität aufmerksam.
Herta Müller e o ensaísmo autobiográfico na literatura contemporânea em língua alemã
Rosvitha Friesen Blume
- No presente artigo discute-se o ensaísmo poetológico de Herta Müller no contexto da escrita autobiográfica alemã contemporânea. A questão da referencialidade de seus ensaios receberá especial atenção; nesses textos também serão apontadas as diversas características estéticas da composição autobiográfica. No mais, demonstra-se em que medida o efeito de sua escrita ensaística não é somente estético mas também e, principalmente, político.
"Die Leiden des jungen Werthers" à luz da história do conceito de subjetividade
Felipe Vale da Silva
- O artigo analisa os paralelos entre o retrato do 'sujeito moderno em crise' visto no romance "Die Leiden des jungen Werthers" de Goethe e, por outro lado, o perfil psicossocial do 'homem do sentimento' do século XVIII, fruto da cultura da Empfindsamkeit. Defendo a perspectiva de que, no romance, Goethe não apenas se utiliza do formato literário mais tradicional da Empfindsamkeit (o do romance epistolar), como também se apropria de topói e técnicas discursivas que lhe são próprias em registro radicalmente heterodoxo. A argumentação nos ligará a uma dedução da visão do conceito de subjetividade moderna com que Goethe trabalha em sua fase final do Sturm und Drang, e que o situa como importante nome do discurso filosófico da modernidade.