Design of Magnesium Phosphate Cement Based Composite for High Performance Bipolar Plate of Fuel Cells

In this work, we report a comprehensive study on a magnesium phosphate cement (MPC) based composite as the construction material for high performance bipolar plates of fuel cells. MPC with partial replacement of fly ash was employed as the binding matrix. Some carbon-based materials, such as graphite, carbon black, carbon fiber, and multi-walled carbon nanotubes were used to construct the conductive phase. A simple hot-press process was applied to produce the composite. The formula and the structure of the composite was modified and adjusted to optimize the properties of the composite to meet the US DOE 2015 technical targets, including the introducing of a reinforcement support. Finally, all the technical targets such as electrical conductivity (\u3e100 S cm-1), the flexural strength (\u3e25 MPa), the corrosion resistance ( \u3c 1 μA cm-2), and gas permeability ( \u3c 10-5 cm3 (s cm2)-1) were achieved as well as low cost ( \u3c 5 $ per kW). The optimized formula and the detailed procedures to fabricate the MPC based composite were concluded

Towards artificial general intelligence via a multimodal foundation model

The fundamental goal of artificial intelligence (AI) is to mimic the core cognitive activities of human. Despite tremendous success in the AI research, most of existing methods have only single-cognitive ability. To overcome this limitation and take a solid step towards artificial general intelligence (AGI), we develop a foundation model pre-trained with huge multimodal data, which can be quickly adapted for various downstream cognitive tasks. To achieve this goal, we propose to pre-train our foundation model by self-supervised learning with weak semantic correlation data crawled from the Internet and show that promising results can be obtained on a wide range of downstream tasks. Particularly, with the developed model-interpretability tools, we demonstrate that strong imagination ability is now possessed by our foundation model. We believe that our work makes a transformative stride towards AGI, from our common practice of "weak or narrow AI" to that of "strong or generalized AI".Comment: Published by Nature Communications, see https://www.nature.com/articles/s41467-022-30761-

Yersinia pestis Interacts With SIGNR1 (CD209b) for Promoting Host Dissemination and Infection

Yersinia pestis, a Gram-negative bacterium and the etiologic agent of plague, has evolved from Yersinia pseudotuberculosis, a cause of a mild enteric disease. However, the molecular and biological mechanisms of how Y pseudotuberculosis evolved to such a remarkably virulent pathogen, Y pestis, are not clear. The ability to initiate a rapid bacterial dissemination is a characteristic hallmark of Y pestis infection. A distinguishing characteristic between the two Yersinia species is that Y pseudotuberculosis strains possess an O-antigen of lipopolysaccharide (LPS) while Y pestis has lost the O-antigen during evolution and therefore exposes its core LPS. In this study, we showed that Y pestis utilizes its core LPS to interact with SIGNR1 (CD209b), a C-type lectin receptor on antigen presenting cells (APCs), leading to bacterial dissemination to lymph nodes, spleen and liver, and the initiation of a systemic infection. We therefore propose that the loss of O-antigen represents a critical step in the evolution of Y pseudotuberculosis into Y pestis in terms of hijacking APCs, promoting bacterial dissemination and causing the plague.Peer reviewe

Metasurface holograms reaching 80% efficiency

Surfaces covered by ultrathin plasmonic structures—so-called metasurfaces—have recently been shown to be capable of completely controlling the phase of light, representing a new paradigm for the design of innovative optical elements such as ultrathin flat lenses, directional couplers for surface plasmon polaritons and wave plate vortex beam generation. Among the various types of metasurfaces, geometric metasurfaces, which consist of an array of plasmonic nanorods with spatially varying orientations, have shown superior phase control due to the geometric nature of their phase profile. Metasurfaces have recently been used to make computer-generated holograms, but the hologram efficiency remained too low at visible wavelengths for practical purposes. Here, we report the design and realization of a geometric metasurface hologram reaching diffraction efficiencies of 80% at 825 nm and a broad bandwidth between 630 nm and 1,050 nm. The 16-level-phase computer-generated hologram demonstrated here combines the advantages of a geometric metasurface for the superior control of the phase profile and of reflectarrays for achieving high polarization conversion efficiency. Specifically, the design of the hologram integrates a ground metal plane with a geometric metasurface that enhances the conversion efficiency between the two circular polarization states, leading to high diffraction efficiency without complicating the fabrication process. Because of these advantages, our strategy could be viable for various practical holographic applications

The Effects of the Low-molecular-weight Component on Banded Spherulites of Poly(L-lactic acid).

In this study, blends of low- and high-molecular-weight (Mw) poly(l-lactic acid) (PLLA) were prepared. High-Mw PLLA films that were crystallized at 125 A degrees C for 7 h showed no clear-banded structures at film thicknesses less than approximately 40 mu m. However, banded structures were observed in 1- mu m-thick films of high- and low-Mw PLLA blends with as little as 1 wt% low-Mw PLLA. Our results revealed that the formation of banded structures in pure PLLA was mainly due to the low-Mw component

The Ecological Service Function Development of Urban Modern Agriculture in Tianjin City and Corresponding Countermeasures

Based on the current situation of ecological environment of agriculture in Tianjin City, we divide the ecological service function of urban modern agriculture in Tianjin City into seven types: air regulation, climate regulation, water conservation, soil formation and protection, waste disposal, biodiversity conservation, and ecological entertainment. According to the method for assessing the value of natural ecosystem, coupled with the ecological service value equivalency factor table of China's ecosystem formulated by domestic scholars, we estimate the ecological value in Tianjin City. The results show that the actual ecological value of agriculture in Tianjin City was 30.752 billion yuan in 2010, close to the agricultural economic value (31.733 billion yuan) in 2010. Finally we put forth the following countermeasures for the ecological function development of urban modern agriculture in Tianjin City: strictly protecting arable land, and raising the standards of compensation for agricultural land requisition; actively and prudently developing facility agriculture, and preventing the blind scale expansion of facility agriculture to better give play to its ecological function; strengthening the construction of ecological agriculture, and promoting the market conversion of the ecological service value of agriculture; improving the environment, to form relatively complete agro-ecological system