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Wang, Charles

Publications and source records attributed to Wang, Charles.

On the equivalence between SRS and PCO formulations of superstring perturbation theory

We establish the equivalence between two formulations of superstring perturbation theory, one based on integration over the supermoduli space of super Riemann surfaces (SRS), the other based on integration over the bosonic moduli space with insertions of picture changing operators (PCO) on the worldsheet and the vertical integration prescription, by showing how the latter arises from a specific construction of the supermoduli integration contour.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Structural variant analysis of a cancer reference cell line sample using multiple sequencing technologies

The cancer genome is commonly altered with thousands of structural rearrangements including insertions, deletions, translocation, inversions, duplications, and copy number variations. Thus, structural variant (SV) characterization plays a paramount role in cancer target identification, oncology diagnostics, and personalized medicine. As part of the SEQC2 Consortium effort, the present study established and evaluated a consensus SV call set using a breast cancer reference cell line and matched normal control derived from the same donor, which were used in our companion benchmarking studies as reference samples. We systematically investigated somatic SVs in the reference cancer cell line by comparing to a matched normal cell line using multiple NGS platforms including Illumina short-read, 10X Genomics linked reads, PacBio long reads, Oxford Nanopore long reads, and high-throughput chromosome conformation capture (Hi-C). We established a consensus SV call set of a total of 1788 SVs including 717 deletions, 230 duplications, 551 insertions, 133 inversions, 146 translocations, and 11 breakends for the reference cancer cell line. To independently evaluate and cross-validate the accuracy of our consensus SV call set, we used orthogonal methods including PCR-based validation, Affymetrix arrays, Bionano optical mapping, and identification of fusion genes detected from RNA-seq. We evaluated the strengths and weaknesses of each NGS technology for SV determination, and our findings provide an actionable guide to improve cancer genome SV detection sensitivity and accuracy. A high-confidence consensus SV call set was established for the reference cancer cell line. A large subset of the variants identified was validated by multiple orthogonal methods.

59 BASIC BIOLOGICAL SCIENCES↗

Mice Exposed to Combined Chronic Low-Dose Irradiation and Modeled Microgravity Develop Long-Term Neurological Sequelae

A combination of spaceflight-relevant factors (fluid-shift and radiation) created a different gene expression profile than either factor individually. Some gene pathways including reduced transcriptional machinery, increased neurogenesis and neuropeptide production, and dysregulated cell structure and cell signaling. Gene expression differences can persist for at least 4 months after a 21- day exposure to a combination of fluid-shift and radiation in the brain tissue of mice. Brain-related transcriptional changes are dynamic during readaptation phase from exposure to spaceflight-like conditions, which may lead to long-term neurological consequences.

Overbey, Eliah G.↗

Mice Exposed to Combined Chronic Low-Dose Irradiation and Modeled Microgravity Develop Long-Term Neurological Sequelae

Spaceflight poses many challenges for humans. Ground-based analogs typically focus on single parameters of spaceflight and their associated acute effects. This study assesses the long-term transcriptional effects following single and combination spaceflight analog conditions using the mouse model, simulated microgravity via hindlimb unloading (HLU) and/or low-dose irradiation (LDR) for 21-days, followed by 4 months of readaptation. Changes in gene expression and epigenetic modifications in whole brain samples during readaptation were analyzed by DESeq2 and reduced representation bisulfite sequencing (RRBS). The results showed minimal gene expression alterations at 4-months within single treatment conditions of HLU and LDR. Following combined HLU+LDR, gene ontology and methylation analyses showed multiple altered pathways involved in neurogenesis and neuroplasticity, regulation of neuropeptides and cellular signaling. In brief, neurological readaptation following combined chronic LDR and HLU is a dynamic process that impacts brain structure and function and may lead to late onset neurological sequelae

Overbey, Eliah G.↗

Microwave Propagation Attenuation due to Earth's Atmosphere and Weather at SHF Band

In this study we have estimated radio wave propagation losses at super high frequency (SHF) band by applying available propagation models into several Air Force benchmark scenarios. The study shows that dominantly additional losses over the free space loss are atmospheric absorption, clouds, fog, and precipitation, as well as scintillation /multipath at low elevation angles. The free space loss equation has been modified to include all atmospheric attenuation and fading effects that cannot be neglected over the range of frequency of interest. Terrain profiles along all directions of interest within the coastal areas and inland areas for four benchmark cases have been analyzed in detail. We find that while the atmospheric gaseous absorption plays a significant role under a clear weather, heavy rainfalls can cause several tens of dB loss for a 100- km path through the rain. At very low elevation angles (< 5 deg), atmospheric scintillation/multipath fading becomes a very important factor. There are significant differences in the feature of anomalous mode (ducting) propagation between the east and the west coastal receiving stations.

atmospheric absorption↗

Global Interoperability of High Definition Video Streams Via ACTS and Intelsat

In 1993, a proposal at the Japan.-U.S. Cooperation in Space Program Workshop lead to a subsequent series of satellite communications experiments and demonstrations, under the title of Trans-Pacific High Data Rate Satellite Communications Experiments. The first of which is a joint collaboration between government and industry teams in the United States and Japan that successfully demonstrated distributed high definition video (HDV) post-production on a global scale using a combination of high data rate satellites and terrestrial fiber optic asynchronous transfer mode (ATM) networks. The HDV experiment is the first GIBN experiment to establish a dual-hop broadband satellite link for the transmission of digital HDV over ATM. This paper describes the team's effort in using the NASA Advanced Communications Technology Satellite (ACTS) at rates up to OC-3 (155 Mbps) between Los Angeles and Honolulu, and using Intelsat at rates up to DS-3 (45 Mbps) between Kapolei and Tokyo, with which HDV source material was transmitted between Sony Pictures High Definition Center (SPHDC) in Los Angeles and Sony Visual Communication Center (VCC) in Shinagawa, Tokyo. The global-scale connection also used terrestrial networks in Japan, the States of Hawaii and California. The 1.2 Gbps digital HDV stream was compressed down to 22.5 Mbps using a proprietary Mitsubishi MPEG-2 codec that was ATM AAL-5 compatible. The codec: employed four-way parallel processing. Improved versions of the codec are now commercially available. The successful post-production activity performed in Tokyo with a HDV clip transmitted from Los Angeles was predicated on the seamless interoperation of all the equipment between the sites, and was an exciting example in deploying a global-scale information infrastructure involving a combination of broadband satellites and terrestrial fiber optic networks. Correlation of atmospheric effects with cell loss, codec drop-out, and picture quality were made. Current efforts in the Trans-Pacific series plan to examine the use of Internet Protocol (IP)-related technologies over such an infrastructure. The use of IP allows the general public to be an integral part of the exciting activities, helps to examine issues in constructing the solar-system internet, and affords an opportunity to tap the research results from the (reliable) multicast and distributed systems communities. The current Trans- Pacific projects, including remote astronomy and digital library (visible human) are briefly described.

Hsu, Eddie↗

Performance of DA/FDMA architecture proposed for MSS

The system architecture proposed for the Mobile Satellite Service (MSS) by the National Aeronautics and Space Administration (NASA)/JPL is presented. The demand assigned Frequency Division Multiple Access (FDMA) scheme is described, and results for the associated network access protocol developed by JPL are presented. Both the total number of users that the system can support and the system spectral efficiency are given for a variety of traffic conditions, including those postulated for the Mobile Satellite System Architectures and Multiple Access Techniques Workshop. The results are given for both first- and second-generation one- and two-satellite systems.

Wang, Charles↗

An operational open-end file transfer protocol for mobile satellite communications

This paper describes an operational open-end file transfer protocol which includes the connecting procedure, data transfer, and relinquishment procedure for mobile satellite communications. The protocol makes use of the frame level and packet level formats of the X.25 standard for the data link layer and network layer, respectively. The structure of a testbed for experimental simulation of this protocol over a mobile fading channel is also introduced.

Wang, Charles↗