Backbone Can Not be Trained at Once: Rolling Back to Pre-trained Network for Person Re-Identification

In person re-identification (ReID) task, because of its shortage of trainable dataset, it is common to utilize fine-tuning method using a classification network pre-trained on a large dataset. However, it is relatively difficult to sufficiently fine-tune the low-level layers of the network due to the gradient vanishing problem. In this work, we propose a novel fine-tuning strategy that allows low-level layers to be sufficiently trained by rolling back the weights of high-level layers to their initial pre-trained weights. Our strategy alleviates the problem of gradient vanishing in low-level layers and robustly trains the low-level layers to fit the ReID dataset, thereby increasing the performance of ReID tasks. The improved performance of the proposed strategy is validated via several experiments. Furthermore, without any add-ons such as pose estimation or segmentation, our strategy exhibits state-of-the-art performance using only vanilla deep convolutional neural network architecture.Comment: Accepted to AAAI 201

Absorption of Transverse Spin Current in Ferromagnetic NiCu: Dominance of Bulk Dephasing over Spin-Flip Scattering

In ferromagnetic metals, transverse spin currents are thought to be absorbed via dephasing -- i.e., destructive interference of spins precessing about the strong exchange field. Yet, due to the ultrashort coherence length of $\approx$1 nm in typical ferromagnetic thin films, it is difficult to distinguish dephasing in the bulk from spin-flip scattering at the interface. Here, to assess which mechanism dominates, we examine transverse spin-current absorption in ferromagnetic NiCu alloy films with reduced exchange fields. We observe that the coherence length increases with decreasing Curie temperature, as weaker dephasing in the film bulk slows down spin absorption. Moreover, nonmagnetic Cu impurities do not diminish the efficiency of spin-transfer torque from the absorbed spin current. Our findings affirm that transverse spin current is predominantly absorbed by dephasing inside the nanometer-thick ferromagnetic metals, even with high impurity contents

Dephasing of Transverse Spin Current in Ferrimagnetic Alloys

It has been predicted that transverse spin current can propagate coherently (without dephasing) over a long distance in antiferromagnetically ordered metals. Here, we estimate the dephasing length of transverse spin current in ferrimagnetic CoGd alloys by spin pumping measurements across the compensation point. A modified drift-diffusion model, which accounts for spin-current transmission through the ferrimagnet, reveals that the dephasing length is about 4-5 times longer in nearly compensated CoGd than in ferromagnetic metals. This finding suggests that antiferromagnetic order can mitigate spin dephasing -- in a manner analogous to spin echo rephasing for nuclear and qubit spin systems -- even in structurally disordered alloys at room temperature. We also find evidence that transverse spin current interacts more strongly with the Co sublattice than the Gd sublattice. Our results provide fundamental insights into the interplay between spin current and antiferromagnetic order, which are crucial for engineering spin torque effects in ferrimagnetic and antiferromagnetic metals

Suppression of Spin Pumping at Metal Interfaces

An electrically conductive metal typically transmits or absorbs a spin current. Here, we report on evidence that interfacing two metal thin films can suppress spin transmission and absorption. We examine spin pumping in ferromagnet/spacer/ferromagnet heterostructures, in which the spacer -- consisting of metallic Cu and Cr thin films -- separates the ferromagnetic spin-source and spin-sink layers. The Cu/Cr spacer largely suppresses spin pumping -- i.e., neither transmitting nor absorbing a significant amount of spin current -- even though Cu or Cr alone transmits a sizable spin current. The antiferromagnetism of Cr is not essential for the suppression of spin pumping, as we observe similar suppression with Cu/V spacers where V is a nonmagnetic analogue of Cr. We speculate that diverse combinations of spin-transparent metals may form interfaces that suppress spin pumping, although the underlying mechanism remains unclear. Our work may stimulate a new perspective on understanding and engineering spin transport in metallic multilayers

Spermidine-induced recovery of human dermal structure and barrier function by skin microbiome.

An unbalanced microbial ecosystem on the human skin is closely related to skin diseases and has been associated with inflammation and immune responses. However, little is known about the role of the skin microbiome on skin aging. Here, we report that the Streptococcus species improved the skin structure and barrier function, thereby contributing to anti-aging. Metagenomic analyses showed the abundance of Streptococcus in younger individuals or those having more elastic skin. Particularly, we isolated Streptococcus pneumoniae, Streptococcus infantis, and Streptococcus thermophilus from face of young individuals. Treatment with secretions of S. pneumoniae and S. infantis induced the expression of genes associated with the formation of skin structure and the skin barrier function in human skin cells. The application of culture supernatant including Streptococcal secretions on human skin showed marked improvements on skin phenotypes such as elasticity, hydration, and desquamation. Gene Ontology analysis revealed overlaps in spermidine biosynthetic and glycogen biosynthetic processes. Streptococcus-secreted spermidine contributed to the recovery of skin structure and barrier function through the upregulation of collagen and lipid synthesis in aged cells. Overall, our data suggest the role of skin microbiome into anti-aging and clinical applications

Defective Localization With Impaired Tumor Cytotoxicity Contributes to the Immune Escape of NK Cells in Pancreatic Cancer Patients

Tumor-infiltrating lymphocytes (TILs), found in patients with advanced pancreatic ductal adenocarcinoma (PDAC), are shown to correlate with overall survival (OS) rate. Although majority of TILs consist of CD8+/CD4+ T cells, the presence of NK cells and their role in the pathogenesis of PDAC remains elusive. We performed comprehensive analyses of TIL, PBMC, and autologous tumor cells from 80 enrolled resectable PDAC patients to comprehend the NK cell defects within PDAC. Extremely low frequencies of NK cells (<0.5%) were found within PDAC tumors, which was attributable not to the low expression of tumor chemokines, but to the lack of chemokine receptor, CXCR2. Forced expression of CXCR2 in patients' NK cells rendered them capable of trafficking into PDAC. Furthermore, NK cells exhibited impaired cell-mediated killing of autologous PDAC cells, primarily due to insufficient ligation of NKG2D and DNAM-1, and failed to proliferate within the hypoxic tumor microenvironment. Importantly, these defects could be overcome by ex-vivo stimulation of NK cells from such patients. Importantly, when the proliferative capacity of NK cells in vitro was used to stratify patients on the basis of cell expansion, patients whose NK cells proliferated <250-fold experienced significantly lower DFS and OS than those with ≥250-fold. Ex-vivo activation of NK cells restored tumor trafficking and reactivity, hence provided a therapeutic modality while their fold expansion could be a potentially significant prognostic indicator of OS and DFS in such patients

Conservative Approach for Traumatic Anterior Crown–Root Fractured Teeth by Orthodontic Extrusion using Customized Mini-Tube Appliance: A Clinical Review

A complicated crown–root fracture is a fracture involving enamel, dentin, cementum, and pulp. Because crown fracture generally extends below the gingival margin, several options may be indicated to expose the margins before permanent restoration. Among them, orthodontic extrusion is the most non-invasive treatment option. In this case report, a case of traumatic crown–root fracture of the maxillary incisor was managed by root canal treatment with fiber-reinforced ceramic post-placement followed by orthodontic extrusion using a customized mini-tube appliance technique. Then, the porcelain fused zirconia crown was restored. Traumatized orthodontic extruded teeth have shown a reliable prognosis without inflammatory signs nor complications after a 15-month follow-up