We report on the observation of Bragg scattering at 1D atomic lattices. Cold atoms are confined by optical dipole forces at the antinodes of a standing wave generated by the two counter-propagating ...modes of a laser-driven high-finesse ring cavity. By heterodyning the Bragg-scattered light with a reference beam, we obtain detailed information on phase shifts imparted by the Bragg scattering process. Being deep in the Lamb-Dicke regime, the scattered light is not broadened by the motion of individual atoms. In contrast, we have detected signatures of global translatory motion of the atomic grating.
Recommender systems help users find relevant items of interest, for example on e-commerce or media streaming sites. Most academic research is concerned with approaches that personalize the ...recommendations according to long-term user profiles. In many real-world applications, however, such long-term profiles often do not exist and recommendations therefore have to be made solely based on the observed behavior of a user during an ongoing session. Given the high practical relevance of the problem, an increased interest in this problem can be observed in recent years, leading to a number of proposals for
session-based recommendation algorithms
that typically aim to predict the user’s immediate next actions. In this work, we present the results of an in-depth performance comparison of a number of such algorithms, using a variety of datasets and evaluation measures. Our comparison includes the most recent approaches based on recurrent neural networks like
gru4rec
, factorized Markov model approaches such as
fism
or
fossil
, as well as simpler methods based, e.g., on nearest neighbor schemes. Our experiments reveal that algorithms of this latter class, despite their sometimes almost trivial nature, often perform equally well or significantly better than today’s more complex approaches based on deep neural networks. Our results therefore suggest that there is substantial room for improvement regarding the development of more sophisticated session-based recommendation algorithms.
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Ion transport in plants is not only strictly regulated on a transcriptional level, but it is also regulated posttranslationally. Enzyme modifications such as phosphorylation provide rapid regulation ...of many plant ion transporters and channels. Upon exposure to high ammonium concentrations in the rhizosphere, the high-affinity ammonium transporters (AMTs) in Arabidopsis thaliana are efficiently inactivated by phosphorylation to avoid toxic accumulation of cytoplasmic ammonium. External ammonium stimulates the phosphorylation of a conserved threonine in the cytosolic AMT1 C terminus, which allosterically inactivates AMT1 trimers. Using a genetic screen, we found that CALCINEURIN B-LIKE INTERACTING PROTEIN KINASE23 (CIPK23), a kinase that also regulates the most abundant NO3
− transporter, NPF6;3, and activates the K+ channel AKT1, inhibits ammonium transport and modulates growth sensitivity to ammonium. Loss of CIPK23 increased root NH4
+ uptake after ammonium shock and conferred hypersensitivity to ammonium and to the transport analog methylammonium. CIPK23 interacts with AMT1;1 and AMT1;2 in yeast, oocytes, and in planta. Inactivation of AMT1;2 by direct interaction with CIPK23 requires kinase activity and the calcineurin B-like binding protein CBL1. Since K+, NO3
−, and NH4
+ are major ions taken up by plants, CIPK23 appears to occupy a key position in controlling ion balance and ion homeostasis in the plant cell.
A Fresh View on Lymph Node Organogenesis Onder, Lucas; Ludewig, Burkhard
Trends in immunology,
October 2018, 2018-10-00, 20181001, Letnik:
39, Številka:
10
Journal Article
Recenzirano
Lymph nodes (LNs) are strategically positioned outposts of the immune system that underpin regional immune surveillance. The current model describing LN formation in mice is based on a two cell-type ...interaction scheme with lymphoid tissue inducer cells regulating the activation of mesenchymal lymphoid tissue organizer cells. We highlight here the key role of lymphatic endothelial cells during the initiation of LN formation. The involvement of lymphatic endothelial cells as an additional organizer cell type in LN organogenesis unveils multiple control levels that govern the generation of lymphoid organs. Moreover, the linkage between lymphangiogenic and lymphvasculogenic processes and guidance of the accumulation and activation of lymphoid tissue inducer cells in the embryo suggests that LN formation may be driven on demand by developing organ systems.
Mammalian LN development is part of organ-specific lymphatic vasculature formation.
Embryonic lymphatic endothelial cells act as primary lymphoid tissue organizer (LTo) cells during the initiation of murine LN formation.
The trafficking of lymphoid tissue inducer (LTi) cells can be registered by lymphatic endothelial LTo cells at the main lymphatic vessel junctions in mice.
LN formation might potentially emerge as a consequence of the swarming behavior of LTi cells.
Enhanced lymphangiogenesis and elevated trafficking of lymphocytes may function to stimulate de novo generation of LNs in humans.
We use coarse index methods to prove that the Landau Hamiltonian on the hyperbolic half-plane, and even on much more general imperfect half-spaces, has no spectral gaps. Thus the edge states of ...hyperbolic quantum Hall Hamiltonians completely fill up the gaps between Landau levels, just like those of the Euclidean counterparts.
We construct a Clifford algebra bundle formed from the tangent bundle of the smooth loop space of a Riemannian manifold, which is a bundle of super von Neumann algebras on the loop space. We show ...that this bundle is in general non-trivial, more precisely that its triviality is obstructed by the transgressions of the second Stiefel-Whitney class and the first (fractional) Pontrjagin class of the manifold.
In this paper, we study Lagrangian correspondences between Hilbert spaces. A main focus is the question when the composition of two Lagrangian correspondences is again Lagrangian. Our answer leads in ...particular to a well-defined composition law in a category of Lagrangian correspondences respecting given polarizations of the Hilbert spaces involved. As an application, we construct a functorial field theory on geometric spin manifolds with values in this category of Lagrangian correspondences, which can be viewed as a formal Wick rotation of the theory associated to a free fermionic particle in a curved spacetime.
In chronic infection, inflammation and cancer, the tissue microenvironment controls how local immune cells behave, with tissue-resident fibroblasts emerging as a key cell type in regulating ...activation or suppression of an immune response. Fibroblasts are heterogeneous cells, encompassing functionally distinct populations, the phenotypes of which differ according to their tissue of origin and type of inciting disease. Their immunological properties are also diverse, ranging from the maintenance of a potent inflammatory environment in chronic inflammation to promoting immunosuppression in malignancy, and encapsulating and incarcerating infectious agents within tissues. In this Review, we compare the mechanisms by which fibroblasts control local immune responses, as well as the factors regulating their inflammatory and suppressive profiles, in different tissues and pathological settings. This cross-disease perspective highlights the importance of tissue context in determining fibroblast-immune cell interactions, as well as potential therapeutic avenues to exploit this knowledge for the benefit of patients with chronic infection, inflammation and cancer.
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