Localizing by Describing: Attribute-Guided Attention Localization for Fine-Grained Recognition

A key challenge in fine-grained recognition is how to find and represent discriminative local regions. Recent attention models are capable of learning discriminative region localizers only from category labels with reinforcement learning. However, not utilizing any explicit part information, they are not able to accurately find multiple distinctive regions. In this work, we introduce an attribute-guided attention localization scheme where the local region localizers are learned under the guidance of part attribute descriptions. By designing a novel reward strategy, we are able to learn to locate regions that are spatially and semantically distinctive with reinforcement learning algorithm. The attribute labeling requirement of the scheme is more amenable than the accurate part location annotation required by traditional part-based fine-grained recognition methods. Experimental results on the CUB-200-2011 dataset demonstrate the superiority of the proposed scheme on both fine-grained recognition and attribute recognition

Unidirectional orbital magnetoresistance in light metal/ferromagnet bilayers

We report the observation of a unidirectional magnetoresistance (UMR) that originates from the nonequilibrium orbital momentum induced by an electric current in a naturally oxidized Cu/Co bilayer. The orbital-UMR scales with the torque efficiency due to the orbital Rashba-Edelstein effect upon changing the Co thickness and temperature, reflecting their common origin. We attribute the UMR to orbital-dependent electron scattering and orbital-to-spin conversion in the ferromagnetic layer. In contrast to the spin-current induced UMR, the magnon contribution to the orbital-UMR is absent in thin Co layers, which we ascribe to the lack of coupling between low energy magnons and orbital current. The magnon contribution to the UMR emerges in Co layers thicker than about 5 nm, which is comparable to the orbital-to-spin conversion length. Our results provide insight into orbital-to-spin momentum transfer processes relevant for the optimization of spintronic devices based on light metals and orbital transport.Comment: 12 pages, 3 figure

Lineage-specific differences in the gp120 Inner Domain Layer 3 of Human and Simian Immunodeficiency Viruses

Binding of HIV-1 and SIV gp120 exterior envelope glycoprotein to CD4 triggers conformational changes in gp120 that promote its interaction with one of the chemokine receptors, usually CCR5, ultimately leading to gp41-mediated virus-cell membrane fusion and entry. We previously described that topological Layers (Layer 1, Layer 2 and Layer 3) in the gp120 inner domain contribute to gp120-trimer association in the unliganded state but also help secure CD4 binding. Relative to Layer 1 of HIV-1 gp120, the SIVmac239 gp120 Layer 1 plays a more prominent role in maintaining gp120-trimer association but is minimally involved in promoting CD4 binding, which could be explained by the existence of a well-conserved Tryptophan 375 (Trp 375) in HIV-2/SIVsmm. Here we investigated the role of SIV Layer 3 on viral entry, cell-to-cell fusion and CD4 binding. We observed that a network of interactions involving some residues of the β8-α5 region in SIVmac239 Layer 3 may contribute to CD4 binding by helping shape the nearby Phe 43 cavity which directly contacts CD4. In summary, our results suggest that SIV Layer 3 has a greater impact on CD4 binding than in HIV-1. This work defines lineage-specific differences in Layer 3 from HIV-1 and SIV

Lineage-specific differences in the gp120 Inner Domain Layer 3 of Human and Simian Immunodeficiency Viruses

Binding of HIV-1 and SIV gp120 exterior envelope glycoprotein to CD4 triggers conformational changes in gp120 that promote its interaction with one of the chemokine receptors, usually CCR5, ultimately leading to gp41-mediated virus-cell membrane fusion and entry. We previously described that topological Layers (Layer 1, Layer 2 and Layer 3) in the gp120 inner domain contribute to gp120-trimer association in the unliganded state but also help secure CD4 binding. Relative to Layer 1 of HIV-1 gp120, the SIVmac239 gp120 Layer 1 plays a more prominent role in maintaining gp120-trimer association but is minimally involved in promoting CD4 binding, which could be explained by the existence of a well-conserved Tryptophan 375 (Trp 375) in HIV-2/SIVsmm. Here we investigated the role of SIV Layer 3 on viral entry, cell-to-cell fusion and CD4 binding. We observed that a network of interactions involving some residues of the β8-α5 region in SIVmac239 Layer 3 may contribute to CD4 binding by helping shape the nearby Phe 43 cavity which directly contacts CD4. In summary, our results suggest that SIV Layer 3 has a greater impact on CD4 binding than in HIV-1. This work defines lineage-specific differences in Layer 3 from HIV-1 and SIV