Radiation-Tolerant, GaN-based Point of Load Converters for Small Spacecraft Missions

As computational loads for spacecraft continue to grow, the requirements levied on power-conversion electronics have become increasingly demanding. Designing for compute-intensive processing capabilities in the CubeSat form-factor further encourages the use of lightweight, compact, and efficient power-conversion electronics. However, the radiation-tolerant and radiation-hardened point-of-load converters available from existing vendors are large, expensive, and inefficient relative to their commercial counterparts. To alleviate this disparity, this paper presents the design, development, and testing of three radiation-tolerant, point-of-load (PoL) converters using Gallium Nitride (GaN) High-Electron Mobility Transistors (HEMT) and commercial controllers to enable the success of future small-satellite missions

SSIVP: Spacecraft Supercomputing Experiment for STP-H6

The Department of Defense Space Test Program (STP) provides spaceflight opportunities for conducting on-orbit research and technology demonstrations to advance the future of spacecraft. STP-H6, the next mission of the program to the International Space Station (ISS), will include a prototype spacecraft supercomputing experiment and framework, called Spacecraft Supercomputing for Image and Video Processing (SSIVP), developed at the National Science Foundation (NSF) Center for High-Performance Reconfigurable Computing (CHREC) at the University of Pittsburgh. SSIVP introduces scalable, high-performance computing (HPC) principles to a CubeSat form-factor to advance the state of the art in space computing. SSIVP adopts the CHREC Space Processor (CSP) concept, a multifaceted design philosophy for a hybrid system of commercial and radiation-hardened (rad-hard) components supplemented with fault-tolerant computing, and a hybrid processor combining fixed-logic CPU and reconfigurable-logic FPGA. SSIVP features five flight-qualified CSPv1 computers as compute nodes, to facilitate this supercomputing concept, and one μCSP smart module, for running a Gallium Nitride (GaN)-based power converter sub-experiment. SSIVP is a versatile, heterogenous platform capable of processing application workloads in the processor or on runtime-reconfigurable FPGA accelerators. In this paper, we present the flight hardware and software, frameworks for parallel and dependable computing, and mission objectives for SSIVP

Inflammation-induced formation of fat-associated lymphoid clusters

Fat-associated lymphoid clusters (FALCs) are a type of lymphoid tissue associated with visceral fat. Here we found that the distribution of FALCs was heterogeneous, with the pericardium containing large numbers of these clusters. FALCs contributed to the retention of B-1 cells in the peritoneal cavity through high expression of the chemokine CXCL13, and they supported B cell proliferation and germinal center differentiation during peritoneal immunological challenges. FALC formation was induced by inflammation, which triggered the recruitment of myeloid cells that expressed tumor-necrosis factor (TNF) necessary for signaling via the TNF receptors in stromal cells. Natural killer T cells (NKT cells) restricted by the antigen-presenting molecule CD1d were likewise required for the inducible formation of FALCs. Thus, FALCs supported and coordinated the activation of innate B cells and T cells during serosal immune responses

Ultralight vector dark matter search using data from the KAGRA O3GK run

Among the various candidates for dark matter (DM), ultralight vector DM can be probed by laser interferometric gravitational wave detectors through the measurement of oscillating length changes in the arm cavities. In this context, KAGRA has a unique feature due to differing compositions of its mirrors, enhancing the signal of vector DM in the length change in the auxiliary channels. Here we present the result of a search for U(1)B−L gauge boson DM using the KAGRA data from auxiliary length channels during the first joint observation run together with GEO600. By applying our search pipeline, which takes into account the stochastic nature of ultralight DM, upper bounds on the coupling strength between the U(1)B−L gauge boson and ordinary matter are obtained for a range of DM masses. While our constraints are less stringent than those derived from previous experiments, this study demonstrates the applicability of our method to the lower-mass vector DM search, which is made difficult in this measurement by the short observation time compared to the auto-correlation time scale of DM

Radiation-Tolerant, GaN-based Point of Load Converters for Small Spacecraft Missions

As computational loads for spacecraft continue to grow, the requirements levied on power-conversion electronics have become increasingly demanding. Designing for compute-intensive processing capabilities in the CubeSat form-factor further encourages the use of lightweight, compact, and efficient power-conversion electronics. However, the radiation-tolerant and radiation-hardened point-of-load converters available from existing vendors are large, expensive, and inefficient relative to their commercial counterparts. To alleviate this disparity, this paper presents the design, development, and testing of three radiation-tolerant, point-of-load (PoL) converters using Gallium Nitride (GaN) High-Electron Mobility Transistors (HEMT) and commercial controllers to enable the success of future small-satellite missions

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GPU-accelerated red blood cells simulations with transport dissipative particle dynamics

Mesoscopic numerical simulations provide a unique approach for the quantification of the chemical influences on red blood cell functionalities. The transport Dissipative Particles Dynamics (tDPD) method can lead to such effective multiscale simulations due to its ability to simultaneously capture mesoscopic advection, diffusion, and reaction. In this paper, we present a GPU-accelerated red blood cell simulation package based on a tDPD adaptation of our red blood cell model, which can correctly recover the cell membrane viscosity, elasticity, bending stiffness, and cross-membrane chemical transport. The package essentially processes all computational workloads in parallel by GPU, and it incorporates multi-stream scheduling and non-blocking MPI communications to improve inter-node scalability. Our code is validated for accuracy and compared against the CPU counterpart for speed. Strong scaling and weak scaling are also presented to characterizes scalability. We observe a speedup of 10.1 on one GPU over all 16 cores within a single node, and a weak scaling efficiency of 91% across 256 nodes. The program enables quick-turnaround and high-throughput numerical simulations for investigating chemical-driven red blood cell phenomena and disorders