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8 result(s) for "Okumura, Satsuki"
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Evaluation of the effect of gravity on the rotational loss of superconducting magnetic bearings for space applications
We study the relationship between the levitation gap change and losses in a superconducting magnetic bearing (SMB) system. We develop a polarization modulator bearing for a cosmic microwave background (CMB) polarization experiment. The heat generated by the polarization modulator needs to be kept very low. Therefore, it is essential to model the effect of the levitation gap change of a rotor due to gravity on the rotational loss. We have constructed a prototype small experimental platform of an axial-flux SMB with an array of high-temperature superconductors, YBCO, and a permanent magnet ring. In this system, the weight of the rotor can be set. We measured the effect of the change in the levitation gap of the rotor due to gravity on the loss. When the levitation force was 5.5 N and 16.0 N, the losses generated in the rotor were 9.1 × 10 −3 W and 1.6 × 10 −2 W, respectively. It was confirmed that the loss increases with the increase in the levitation force of the SMB.
Experimental characterization of the axial rotational instability of the cryogenic rotation mechanism using synchronous motor and superconducting magnetic bearing
We report the experimental characterization of the rotational instability of a cryogenic rotation mechanism, which uses a superconducting magnetic bearing (SMB) and a synchronous motor and operates at about 10 K in a vacuum environment. We conducted rotation tests: driving the rotor and reconstructing the rotational frequency of the rotor. We identified the rotational frequency oscillations and the damping of its amplitude around the target rotational frequency set by the motor drive electronics. The amplitude of the oscillation of about 0.005 Hz at the rotational frequency of 0.77 Hz with the damping coefficient of about 0.02 s −1 . We compared this damping coefficient to the energy loss by the rotational frequency spin down without any driving torque. We found that the two damping coefficients agree within a factor of two. Based on the analysis, we narrowed down the cause of the oscillation to the low-torque/low-friction rotation mechanism together with the high-purity copper wires used in drive motor coils as the source of eddy current.
Backward propagating quantum repeater protocol with multiple quantum memories
Quantum repeaters with multiple quantum memories provide high throughput, low latency, and high fidelity quantum state (qubit) transfer over long distances. However, conventional quantum repeater protocols require full connections among the multiple quantum memories in a repeater node, which is technically challenging. Here, we propose a quantum repeater protocol based on backward propagating photon emission and absorption, where the quantum memories are multiplexed in the time-domain to speed up a single transmission channel without requiring full connectivity, drastically facilitating physical implementation. Although the protocol is described with nitrogen-vacancy (NV) centers in diamond, it is applicable to various physical systems and opens up the possibility of high-speed high-fidelity quantum networks for distributed quantum computation and quantum Internet.
Prognostic impact of CRTC1/3‐MAML2 fusions in salivary gland mucoepidermoid carcinoma: A multiinstitutional retrospective study
Mucoepidermoid carcinoma (MEC) is rare, but the most common primary malignancy of the salivary gland and not infrequent in young individuals. CRTC1/3‐MAML2 fusions are frequently detected in MEC and are useful as a diagnostic biomarker. However, there has been debate as to whether the fusions have prognostic significance. In this study, we retrospectively collected 153 salivary gland MEC cases from 11 tertiary hospitals in Japan. As inclusion criteria, the MEC patients in this study had curative surgery as the initial treatment, received no preoperative treatment, and had no distant metastasis at the time of the initial surgery. The MEC diagnosis was validated by a central pathology review by five expert salivary gland pathologists. The CRTC1/3‐MAML2 fusions were detected using FISH and RT‐PCR. In 153 MEC cases, 90 (58.8%) were positive for CRTC1/3‐MAML2 fusions. During the follow‐up period, 28 (18.3%) patients showed tumor recurrence and 12 (7.8%) patients died. The presence of the fusions was associated with favorable tumor features. Of note, none of the fusion‐positive patients died during the follow‐up period. Statistical analysis showed that the presence of the fusions was a prognostic indicator of a better overall survival in the total and advanced‐stage MEC cohorts, but not in the early‐stage MEC cohort. In conclusion, CRTC1/3‐MAML2 fusions are an excellent biomarker for favorable overall survival of patients with salivary gland MEC. Debate exists as to whether CRTC1/3‐MAML2 fusions have a prognostic significance in salivary mucoepidermoid carcinoma (MEC). We undertook a multiinstitutional study including 153 MEC cases, and found that the fusions were an excellent biomarker for better overall survival in the total and advanced‐stage MEC cohorts.
Recurrence patterns and progression-free survival after chemoradiotherapy with or without consolidation durvalumab for stage III non-small cell lung cancer
Chemoradiotherapy followed by consolidation durvalumab (CCRT+D) improves survival in patients with stage III non-small-cell lung cancer (NSCLC). We compared recurrence patterns and survival in the CCRT+D and CCRT cohorts. We conducted a multicenter, retrospective study in Japan. Patients who received CCRT for stage III NSCLC were included in this study. Of 178 eligible patients, 136 were in the CCRT+D and 42 were in the CCRT cohorts. Locoregional recurrence (LR), LR plus distant metastases (DM), and DM were observed in 20.6%, 8.8%, 27.9% of the CCRT+D, and 26.2%, 16.7% and 33.3% of the CCRT cohorts, respectively. In-field recurrence was the most common LR pattern in both cohorts. Squamous cell carcinoma and PD-L1 expression < 1%, and female sex and EGFR mutations were significantly associated with an increased risk of LR and DM. In patients with any risk factors for LR, the incidence of LR was similar in the CCRT+D and CCRT (39.5% vs 45.5%). The 24 month progression-free survival (PFS) and overall survival (OS) were 40.3% and 69.4% in the CCRT+D and 24.7% and 61.0% in the CCRT cohorts, respectively. Poor performance status and no consolidation durvalumab were significantly associated with shorter PFS. There was a significant difference in PFS between the CCRT+D and CCRT in the propensity score-matched cohort (HR = 0.51, P = 0.005). In conclusion, consolidation durvalumab decreased both LR and DM, and significantly improved PFS. However, in-field recurrence was still a major problem, as well as DM.
IMP dehydrogenase-2 drives aberrant nucleolar activity and promotes tumorigenesis in glioblastoma
In many cancers, high proliferation rates correlate with elevation of rRNA and tRNA levels, and nucleolar hypertrophy. However, the underlying mechanisms linking increased nucleolar transcription and tumorigenesis are only minimally understood. Here we show that IMP dehydrogenase-2 (IMPDH2), the rate-limiting enzyme for de novo guanine nucleotide biosynthesis, is overexpressed in the highly lethal brain cancer glioblastoma. This leads to increased rRNA and tRNA synthesis, stabilization of the nucleolar GTP-binding protein nucleostemin, and enlarged, malformed nucleoli. Pharmacological or genetic inactivation of IMPDH2 in glioblastoma reverses these effects and inhibits cell proliferation, whereas untransformed glia cells are unaffected by similar IMPDH2 perturbations. Impairment of IMPDH2 activity triggers nucleolar stress and growth arrest of glioblastoma cells even in the absence of functional p53. Our results reveal that upregulation of IMPDH2 is a prerequisite for the occurance of aberrant nucleolar function and increased anabolic processes in glioblastoma, which constitutes a primary event in gliomagenesis. Kofuji et al. demonstrate that upregulation of IMPDH2 promotes nucleostemin stabilization and nucleoli malformation, and its inactivation induces growth arrest in glioblastoma.
Perioperative serum and urine metabolome analyses in patients with hepatocellular carcinoma undergoing partial hepatectomy
•Metabolites in the serum and urine were analyzed after hepatectomy.•The Fischer ratio significantly decreased after liver resection in serum.•The changes in serum taurine levels were related to the white blood cell count after operation.•These findings highlight the usefulness of metabolome analysis for characterizing perioperative patterns. Perioperative nutritional management is essential for early recovery after liver surgery. The aim of this study was to assess changes in amino acid levels in serum and urine after hepatectomy. Serum samples were collected from 16 patients with hepatocellular carcinoma before and 1, 3, and 14 d after hepatectomy (S0, S1, S3, and S14, respectively). Spot urine samples were collected before and 3 d after the hepatectomy (U0 and U3). Metabolites in the serum and urine were analyzed. Compared with S0, insulin levels significantly increased in the S1 and S3 samples. Valine levels significantly decreased in S1 and S14, and leucine levels significantly decreased in S14. Phenylalanine levels significantly increased in S1 and S3, and tyrosine levels significantly increased in S1. The Fischer ratio (branched-chain/aromatic amino acids) significantly decreased in S1 and S3. In multiple regression analysis, changes in serum taurine levels were related to the white blood cell count in S1 and S3, and inversely related to alanine aminotransferase levels in S14. Changes in serum glutamine levels were negatively related to C-reactive protein levels in S3. Serum glutamine levels decreased in S3 and S14, and tended to increase in U3, suggesting a deficiency of glutamate resulting from the invasive surgical procedure. These findings highlight the usefulness of metabolome analysis for characterizing perioperative patterns after liver resection. The observed amino acid pattern, including the reduction in Fischer ratio, underscores the need for specialized nutritional support.
Mycophenolate Mofetil Is Effective and Well Tolerated in the Treatment of Refractory Acute and Chronic Graft-versus-Host Disease
We enrolled 11 patients with refractory graft-versus-host disease (GVHD) in a prospective trial evaluating the efficacy of mycophenolate mofetil (MMF). Four (67%) of the 6 patients with acute GVHD and all 5 patients with chronic GVHD responded to MMF. Ten (91%) of the 11 patients were able to decrease steroid use (median decrease, 86%; range, 25%-100%). After a median follow-up of 18 months (range, 1-65 months), 7 patients (64%) remained alive. The adverse events were infectious complications (36%), diarrhea (27%), and neutropenia (18%); the only patient discontinuing MMF did so because of grade 4 neutropenia. This preliminary study suggests that MMF is a well-tolerated agent and has a beneficial effect in the treatment of refractory acute and chronic GVHD.