Fayet-Iliopoulos Terms in AdS/CFT with Flavour

We construct the gravity dual of a field theory with flavour in which there are Fayet-Iliopoulos (FI) terms present. For this purpose we turn on a constant Kalb-Ramond B field in four internal space directions of AdS_5 x S^5 together with a D7 brane probe wrapping AdS_5 x S^3. The B field induces noncommutativity on the four internal directions of the D7 brane probe perpendicular to the AdS boundary. We argue on general grounds that the moduli space of the Higgs part of mixed Coulomb-Higgs states in the dual field theory at the boundary is described by the ADHM equations for noncommutative instantons on the four internal directions of the D7 brane probe. In particular, the global symmetries match. The FI term arises as the holographic dual of an anti-selfdual B field. We discuss possible applications for this construction.Comment: 31 pages, 2 figures, JHEP 3 style, v2: References added, final published versio

Phosphorus donors in highly strained silicon

The hyperfine interaction of phosphorus donors in fully strained Si thin films grown on virtual Si$_{1-x}$Ge$_x$ substrates with $x\leq 0.3$ is determined via electrically detected magnetic resonance. For highly strained epilayers, hyperfine interactions as low as 0.8 mT are observed, significantly below the limit predicted by valley repopulation. Within a Green's function approach, density functional theory (DFT) shows that the additional reduction is caused by the volume increase of the unit cell and a local relaxation of the Si ligands of the P donor.Comment: 12 pages, 3 figure

Vague promises. The school cloud as a means of technologising school and learning

Im Beitrag werden am Beispiel der digitalen Schul-Cloud die Transformation von Vermittlungswissen in Bildungsmedien und bildungspolitischer Steuerung sowie mögliche Effekte für schulisches Lernen kritisch beleuchtet. Es werden im Kern zwei Thesen vertreten: Zum einen die Verschmelzung von Lernen und Konsumieren in digitalisierten cloudgesteuerten Lernpraktiken und zum anderen die fortschreitende Kontrolle von Lernprozessen im Kontext von Learning Analytics, die mit einer umfassenden Produktion von Daten einhergeht und die eine Vorhersagbarkeit von SchülerInnenleistung versprechen. (DIPF/Orig.)The article uses the example of the digital Schul-Cloud (school-cloud) to analyse the transformation of knowledge in educational media and education policy control as well as the possible effects on school learning. Two main theses are put forward: first, that there is a fusion of learning and consumption in digitised cloud-driven learning practices and, secondly, that the progressive control of learning processes in the context of Learning Analytics, which involves a comprehensive production of data, implies the promise of predictability of student performance. (DIPF/Orig.

Prevention of M2 polarization and temporal limitation of differentiation in monocytes by extracellular ATP

BACKGROUND Elevated levels of extracellular adenosine triphosphate (ATP) modulate immunologic pathways and are considered to be a danger signal in inflammation, lung fibrosis and cancer. Macrophages can be classified into two main types: M1 macrophages are classically activated, pro-inflammatory macrophages, whereas M2 macrophages are alternatively activated, pro-fibrotic macrophages. In this study, we examined the effect of ATP on differentiation of native human monocytes into these macrophage subtypes. We characterized M1 and M2 like macrophages by their release of Interleukin-1beta (IL-1β) and Chemokine (C-C motif) ligand 18 (CCL18), respectively. RESULTS Monocytes were stimulated with ATP or the P2X7 receptor agonist Benzoylbenzoyl-ATP (Bz-ATP), and the production of various cytokines was analyzed, with a particular focus on CCL18 and IL-1β, along with the expression of different purinergic receptors. Over a 72 h period of cell culture, monocytes spontaneously differentiated to M2 like macrophages, as indicated by an increased release of CCL18. Immediate stimulation of monocytes with ATP resulted in a dose-dependent reduction in CCL18 release, but had no effect on the concentration of IL-1β. In contrast, delayed stimulation with ATP had no effect on either CCL18 or IL-1β release. Similar results were observed in a model of inflammation using lipopolysaccharide-stimulated human monocytes. Stimulation with the P2X7 receptor agonist Bz-ATP mimicked the effect of ATP on M2-macrophage differentiation, indicating that P2X7 is involved in ATP-induced inhibition of CCL18 release. Indeed, P2X7 was downregulated during spontaneous M2 differentiation, which may partially explain the ineffectiveness of late ATP stimulation of monocytes. However, pre-incubation of monocytes with PPADS, Suramin (unselective P2X- and P2Y-receptor blockers) and KN62 (P2X7-antagonist) failed to reverse the reduction of CCL18 by ATP. CONCLUSIONS ATP prevents spontaneous differentiation of monocytes into M2-like macrophages in a dose- and time-dependent manner. These effects were not mediated by P2X and P2Y receptors

Characterization of a short isoform of the kidney protein podocin in human kidney

BACKGROUND: Steroid resistant nephrotic syndrome is a severe hereditary disease often caused by mutations in the NPHS2 gene. This gene encodes the lipid binding protein podocin which localizes to the slit diaphragm of podocytes and is essential for the maintenance of an intact glomerular filtration barrier. Podocin is a hairpin-like membrane-associated protein that multimerizes to recruit lipids of the plasma membrane. Recent evidence suggested that podocin may exist in a canonical, well-studied large isoform and an ill-defined short isoform. Conclusive proof of the presence of this new podocin protein in the human system is still lacking. METHODS: We used database analyses to identify organisms for which an alternative splice variant has been annotated. Mass spectrometry was employed to prove the presence of the shorter isoform of podocin in human kidney lysates. Immunofluorescence, sucrose density gradient fractionation and PNGase-F assays were used to characterize this short isoform of human podocin. RESULTS: Mass spectrometry revealed the existence of the short isoform of human podocin on protein level. We cloned the coding sequence from a human kidney cDNA library and showed that the expressed short variant was retained in the endoplasmic reticulum while still associating with detergent-resistant membrane fractions in sucrose gradient density centrifugation. The protein is partially N-glycosylated which implies the presence of a transmembranous form of the short isoform. CONCLUSIONS: A second isoform of human podocin is expressed in the kidney. This isoform lacks part of the PHB domain. It can be detected on protein level. Distinct subcellular localization suggests a physiological role for this isoform which may be different from the well-studied canonical variant. Possibly, the short isoform influences lipid and protein composition of the slit diaphragm complex by sequestration of lipid and protein interactors into the endoplasmic reticulum

The von Hippel-Lindau tumor suppressor protein controls ciliogenesis by orienting microtubule growth

Cilia are specialized organelles that play an important role in several biological processes, including mechanosensation, photoperception, and osmosignaling. Mutations in proteins localized to cilia have been implicated in a growing number of human diseases. In this study, we demonstrate that the von Hippel-Lindau (VHL) protein (pVHL) is a ciliary protein that controls ciliogenesis in kidney cells. Knockdown of pVHL impeded the formation of cilia in mouse inner medullary collecting duct 3 kidney cells, whereas the expression of pVHL in VHL-negative renal cancer cells rescued the ciliogenesis defect. Using green fluorescent protein–tagged end-binding protein 1 to label microtubule plus ends, we found that pVHL does not affect the microtubule growth rate but is needed to orient the growth of microtubules toward the cell periphery, a prerequisite for the formation of cilia. Furthermore, pVHL interacts with the Par3–Par6–atypical PKC complex, suggesting a mechanism for linking polarity pathways to microtubule capture and ciliogenesis